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https://socratic.org/questions/58249192b72cff56e22d7c8a | Chemistry
Topics
# Question #d7c8a
Nov 12, 2016
An adduct is the result of formation of a coordinate bond.
#### Explanation:
When two neutral species come together to form a coordinate bond, one of them provides both of the electrons in the bond.
In the case above, the nitrogen atom in $N {H}_{3}$ has a lone pair of non-bonding electrons that can be donated to form a coordinate bond to the boron atom in $B {F}_{3}$.
$B {F}_{3}$, on the other hand, has only 6 electrons in its valence shell (two electrons from each of the 3 BF bonds). It can accept a pair of electrons in its valence shell to form a complete octet (8 electrons) in its valence shell.
Because both electrons in the new B-F bond originated with $N {H}_{3}$, the bond is called a coordinate bond. The resulting product, ${H}_{3} N - B {F}_{3}$ is called an adduct.
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https://worldwidescience.org/topicpages/a/atomic+fermi+gases.html | Sample records for atomic fermi gases
1. Vortex line in spin-orbit coupled atomic Fermi gases
OpenAIRE
2012-01-01
PHYSICAL REVIEW A 85, 013622 (2012) Vortex line in spin-orbit coupled atomic Fermi gases M. Iskin Department of Physics, Koc¸ University, Rumelifeneri Yolu, TR-34450 Sariyer, Istanbul, Turkey (Received 1 December 2011; published 17 January 2012) It has recently been shown that the spin-orbit coupling gives rise to topologically nontrivial and thermodynamically stable gapless superfluid phases when the pseudospin populations of an atomic Fermi gas are imbalanced, with the ...
2. Physics of our Days: Cooling and thermometry of atomic Fermi gases
Science.gov (United States)
Onofrio, R.
2017-02-01
We review the status of cooling techniques aimed at achieving the deepest quantum degeneracy for atomic Fermi gases. We first discuss some physics motivations, providing a quantitative assessment of the need for deep quantum degeneracy in relevant physics cases, such as the search for unconventional superfluid states. Attention is then focused on the most widespread technique to reach deep quantum degeneracy for Fermi systems, sympathetic cooling of Bose–Fermi mixtures, organizing the discussion according to the specific species involved. Various proposals to circumvent some of the limitations on achieving the deepest Fermi degeneracy, and their experimental realizations, are then reviewed. Finally, we discuss the extension of these techniques to optical lattices and the implementation of precision thermometry crucial to the understanding of the phase diagram of classical and quantum phase transitions in Fermi gases.
3. Population and mass imbalance in atomic Fermi gases
NARCIS (Netherlands)
Baarsma, J E; Gubbels, K.B.; Stoof, H.T.C.
2010-01-01
We develop an accurate theory of resonantly interacting Fermi mixtures with both spin and mass imbalance. We consider Fermi mixtures with arbitrary mass imbalances but focus, in particular, on the experimentally available Li6-K40 mixture. We determine the phase diagram of the mixture for different i
4. Polaronic atom-trimer continuity in three-component Fermi gases.
Science.gov (United States)
Nishida, Yusuke
2015-03-20
Recently it has been proposed that three-component Fermi gases may exhibit a new type of crossover physics in which an unpaired Fermi sea of atoms smoothly evolves into that of trimers in addition to the ordinary BCS-BEC crossover of condensed pairs. Here we study its corresponding polaron problem in which a single impurity atom of one component interacts with condensed pairs of the other two components with equal populations. By developing a variational approach in the vicinity of a narrow Feshbach resonance, we show that the impurity atom smoothly changes its character from atom to trimer with increasing the attraction and eventually there is a sharp transition to dimer. The emergent polaronic atom-trimer continuity can be probed in ultracold atoms experiments by measuring the impurity spectral function. Our novel crossover wave function properly incorporating the polaronic atom-trimer continuity will provide a useful basis to further investigate the phase diagram of three-component Fermi gases in more general situations.
5. Thermoelectricity in a junction between interacting cold atomic Fermi gases
Science.gov (United States)
Sekera, Tibor; Bruder, Christoph; Belzig, Wolfgang
2016-09-01
A gas of interacting ultracold fermions can be tuned into a strongly interacting regime using a Feshbach resonance. Here, we theoretically study quasiparticle transport in a system of two reservoirs of interacting ultracold fermions on the BCS side of the BCS-BEC crossover coupled weakly via a tunnel junction. Using the generalized BCS theory, we calculate the time evolution of the system that is assumed to be initially prepared in a nonequilibrium state characterized by a particle number imbalance or a temperature imbalance. A number of characteristic features like sharp peaks in quasiparticle currents or transitions between the normal and superconducting states are found. We discuss signatures of the Seebeck and the Peltier effects and the resulting temperature difference of the two reservoirs as a function of the interaction parameter (kFa ) -1. The Peltier effect may lead to an additional cooling mechanism for ultracold fermionic atoms.
6. Superfluidity and BCS-BEC crossover of ultracold atomic Fermi gases in mixed dimensions
Science.gov (United States)
Zhang, Leifeng; Chen, Qijin
Atomic Fermi gases have been under active investigation in the past decade. Here we study the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas in the presence of mixed dimensionality, in which one component is confined on a 1D optical lattice whereas the other is free in the 3D continuum. We assume a short-range pairing interaction and determine the superfluid transition temperature Tc and the phase diagram for the entire BCS-BEC crossover, using a pairing fluctuation theory which includes self-consistently the contributions of finite momentum pairs. We find that, as the lattice depth increases and the lattice spacing decreases, the behavior of Tc becomes very similar to that of a population imbalance Fermi gas in a simple 3D continuum. There is no superfluidity even at T = 0 below certain threshold of pairing strength in the BCS regime. Nonmonotonic Tc behavior and intermediate temperature superfluidity emerge, and for deep enough lattice, the Tc curve will split into two parts. Implications for experiment will be discussed. References: 1. Q.J. Chen, Ioan Kosztin, B. Janko, and K. Levin, Phys. Rev. B 59, 7083 (1999). 2. Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin, Phys. Rev. Lett. 97, 090402(2006). Work supported by NSF of China and the National Basic Research Program of China.
7. Strongly interacting Fermi gases
Directory of Open Access Journals (Sweden)
Bakr W.
2013-08-01
Full Text Available Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.
8. Spin-orbit-coupled two-electron Fermi gases of ytterbium atoms
Science.gov (United States)
Song, Bo; He, Chengdong; Zhang, Shanchao; Hajiyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong
2016-12-01
We demonstrate all-optical implementation of spin-orbit coupling (SOC) in a two-electron Fermi gas of 173Yb atoms by coupling two hyperfine ground states with a narrow optical transition. Due to the SU (N ) symmetry of the S10 ground-state manifold which is insensitive to external magnetic fields, an optical ac Stark effect is applied to split the ground spin states, which exhibits a high stability compared with experiments on alkali-metal and lanthanide atoms, and separate out an effective spin-1/2 subspace from other hyperfine levels for the realization of SOC. The dephasing spin dynamics when a momentum-dependent spin-orbit gap is suddenly opened and the asymmetric momentum distribution of the spin-orbit-coupled Fermi gas are observed as a hallmark of SOC. The realization of all-optical SOC for ytterbium fermions should offer a route to a long-lived spin-orbit-coupled Fermi gas and greatly expand our capability of studying spin-orbit physics with alkaline-earth-metal-like atoms.
9. Spin-orbit coupled two-electron Fermi gases of ytterbium atoms
CERN Document Server
Song, Bo; Zhang, Shanchao; Zou, Yueyang; Haciyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong
2016-01-01
We demonstrate the spin-orbit coupling (SOC) in a two-electron Fermi gas of $^{173}$Yb atoms by coupling two hyperfine ground states via the two-photon Raman transition. Due to the SU($N$) symmetry of the $^1$S$_0$ ground-state manifold which is insensitive to external magnetic field, an optical AC Stark effect is applied to split the ground spin states and separate an effective spin-1/2 subspace out from other hyperfine levels for the realization of SOC. With a momentum-dependent spin-orbit gap being suddenly opened by switching on the Raman transition, the dephasing of spin dynamics is observed, as a consequence of the momentum-dependent Rabi oscillations. Moreover, the momentum asymmetry of the spin-orbit coupled Fermi gas is also examined after projection onto the bare spin state and the corresponding momentum distribution is measured for different two-photon detuning. The realization of SOC for Yb fermions may open a new avenue to the study of novel spin-orbit physics with alkaline-earth-like atoms.
10. Effect of the particle-hole channel on BCS-Bose-Einstein condensation crossover in atomic Fermi gases.
Science.gov (United States)
Chen, Qijin
2016-01-01
BCS-Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor'kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories.
11. Bragg spectroscopy of strongly interacting Fermi gases
Science.gov (United States)
Lingham, M. G.; Fenech, K.; Peppler, T.; Hoinka, S.; Dyke, P.; Hannaford, P.; Vale, C. J.
2016-10-01
This article provides an overview of recent developments and emerging topics in the study of two-component Fermi gases using Bragg spectroscopy. Bragg scattering is achieved by exposing a gas to two intersecting laser beams with a slight frequency difference and measuring the momentum transferred to the atoms. By varying the Bragg laser detuning, it is possible to measure either the density or spin response functions which characterize the basic excitations present in the gas. Specifically, one can measure properties such as the dynamic and static structure factors, Tan's universal contact parameter and observe signatures for the onset of pair condensation locally within a gas.
12. Spin diffusion in Fermi gases
DEFF Research Database (Denmark)
Bruun, Georg
2011-01-01
We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures......, strong correlation effects are included through the Landau parameters which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ~/m in the unitarity regime...
13. Dark lump excitations in superfluid Fermi gases
Institute of Scientific and Technical Information of China (English)
Xu Yan-Xia; Duan Wen-Shan
2012-01-01
We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases.A Kadomtsev Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen-Cooper-Schrieffer (BCS) regime,Bose-Einstein condensate (BEC) regime,and unitarity regime.Onelump solution as well as one-line soliton solutions for the KPI equation are obtained,and two-line soliton solutions with the same amplitude are also studied in the limited cases.The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity.
14. Itinerant Ferromagnetism in Ultracold Fermi Gases
DEFF Research Database (Denmark)
Heiselberg, Henning
2012-01-01
Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC. Thermodyna......Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC...
15. Creation of ultracold molecules from a Fermi gas of atoms
OpenAIRE
2003-01-01
Since the realization of Bose-Einstein condensates (BEC) in atomic gases an experimental challenge has been the production of molecular gases in the quantum regime. A promising approach is to create the molecular gas directly from an ultracold atomic gas; for example, atoms in a BEC have been coupled to electronic ground-state molecules through photoassociation as well as through a magnetic-field Feshbach resonance. The availability of atomic Fermi gases provides the exciting prospect of coup...
16. Physics of ultracold Fermi gases revealed by spectroscopies
Science.gov (United States)
Törmä, Päivi
2016-04-01
This article provides a brief review of how various spectroscopies have been used to investitage many-body quantum phenomena in the context of ultracold Fermi gases. In particular, work done with RF spectroscopy, Bragg spectroscopy and lattice modulation spectroscopy is considered. The theoretical basis of these spectroscopies, namely linear response theory in the many-body quantum physics context is briefly presented. Experiments related to the BCS-BEC crossover, imbalanced Fermi gases, polarons, possible pseudogap and Fermi liquid behaviour and measuring the contact are discussed. Remaining open problems and goals in the field are sketched from the perspective how spectroscopies could contribute.
17. Strongly Interacting Fermi Gases in Two Dimensions
Science.gov (United States)
2012-07-17
Svistunov, M. Ku, A. Sommer, L. W. Cheuk, A. Schirotzek, M. W. Zwierlein Feynman diagrams versus Fermi-gas Feynman emulator Nature Physics 8... Feynman emulator. Nature Physics 8, 366 (2012) 4. Jee Woo Park, Cheng-Hsun Wu, Ibon Santiago, Tobias G. Tiecke, Peyman Ahmadi, Martin W. Zwierlein...chapters 7. M. Randeria, W. Zwerger, and M. Zwierlein. The BEC-BCS Crossover and the Unitary Fermi Gas. Lecture Notes in Physics , Volume 836, edited by
18. String Theory Based Predictions for Novel Collective Modes in Strongly Interacting Fermi Gases
CERN Document Server
Bantilan, H; Ishii, T; Lewis, W E; Romatschke, P
2016-01-01
Very different strongly interacting quantum systems such as Fermi gases, quark-gluon plasmas formed in high energy ion collisions and black holes studied theoretically in string theory are known to exhibit quantitatively similar damping of hydrodynamic modes. It is not known if such similarities extend beyond the hydrodynamic limit. Do non-hydrodynamic collective modes in Fermi gases with strong interactions also match those from string theory calculations? In order to answer this question, we use calculations based on string theory to make predictions for novel types of modes outside the hydrodynamic regime in trapped Fermi gases. These predictions are amenable to direct testing with current state-of-the-art cold atom experiments.
19. Correlations of the upper branch of 1D harmonically trapped two-component fermi gases.
Science.gov (United States)
Gharashi, Seyed Ebrahim; Blume, D
2013-07-26
We present highly accurate energy spectra and eigenfunctions of small 1D harmonically trapped two-component Fermi gases with interspecies δ-function interactions, and analyze the correlations of the so-called upper branch (i.e., the branch that describes a repulsive Fermi gas consisting of atoms but no molecules) for positive and negative coupling constants. Changes of the two-body correlations as a function of the interspecies coupling strength reflect the competition of the interspecies interaction and the effective repulsion due to the Pauli exclusion principle, and are interpreted as a few-body analog of a transition from a nonmagnetic to a magnetic phase. Moreover, we show that the eigenstate ψadia of the infinitely strongly interacting system with |n1+n2|>2 and |n1-n2|Fermi-Fermi mapping function to the eigenfunction of the noninteracting single-component Fermi gas.
20. Superfluid Thomas—Fermi approximation for trapped fermi gases
Science.gov (United States)
Hernández, E. S.; Capuzzi, P.; Szybisz, L.
2009-02-01
We present a generalization of fermionic fluiddynamics to the case of two trapped fermion species with a contact interaction. Within a mean field approximation, we derive coupled equations of motion for the particle densities, particle currents, and anomalous pair density. For an inhomogeneous system, the equilibrium situation with vanishing currents is described by a generalized Thomas-Fermi relation that includes the superfluid gap, together with a new nonlocal gap equation that replaces the usual BCS one. These equations are numericaly solved resorting to a local density approximation (LDA). Density and gap profiles are analyzed in terms of the scattering length, revealing that the current frame can exhibit microscopic details of quantum origin that are frequently absent in more macroscopic scenarios.
1. Superfluid Thomas-Fermi approximation for trapped fermi gases
Energy Technology Data Exchange (ETDEWEB)
Hernandez, E S; Capuzzi, P; Szybisz, L [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina)], E-mail: [email protected], E-mail: [email protected], E-mail: [email protected]
2009-02-01
We present a generalization of fermionic fluiddynamics to the case of two trapped fermion species with a contact interaction. Within a mean field approximation, we derive coupled equations of motion for the particle densities, particle currents, and anomalous pair density. For an inhomogeneous system, the equilibrium situation with vanishing currents is described by a generalized Thomas-Fermi relation that includes the superfluid gap, together with a new nonlocal gap equation that replaces the usual BCS one. These equations are numericaly solved resorting to a local density approximation (LDA). Density and gap profiles are analyzed in terms of the scattering length, revealing that the current frame can exhibit microscopic details of quantum origin that are frequently absent in more macroscopic scenarios.
2. Metastability in spin polarised Fermi gases and quasiparticle decays
DEFF Research Database (Denmark)
2011-01-01
We investigate the metastability associated with the first order transition from normal to superfluid phases in the phase diagram of two-component polarised Fermi gases.We begin by detailing the dominant decay processes of single quasiparticles.Having determined the momentum thresholds of each pr...
3. “Hard probes” of strongly-interacting atomic gases
Energy Technology Data Exchange (ETDEWEB)
Nishida, Yusuke [Los Alamos National Laboratory
2012-06-18
We investigate properties of an energetic atom propagating through strongly interacting atomic gases. The operator product expansion is used to systematically compute a quasiparticle energy and its scattering rate both in a spin-1/2 Fermi gas and in a spinless Bose gas. Reasonable agreement with recent quantum Monte Carlo simulations even at a relatively small momentum k/kF > 1.5 indicates that our large-momentum expansions are valid in a wide range of momentum. We also study a differential scattering rate when a probe atom is shot into atomic gases. Because the number density and current density of the target atomic gas contribute to the forward scattering only, its contact density (measure of short-range pair correlation) gives the leading contribution to the backward scattering. Therefore, such an experiment can be used to measure the contact density and thus provides a new local probe of strongly interacting atomic gases.
4. Microscopy of 2D Fermi gases. Exploring excitations and thermodynamics
Energy Technology Data Exchange (ETDEWEB)
Morgener, Kai Henning
2014-12-08
This thesis presents experiments on three-dimensional (3D) and two-dimensional (2D) ultracold fermionic {sup 6}Li gases providing local access to microscopic quantum many-body physics. A broad magnetic Feshbach resonance is used to tune the interparticle interaction strength freely to address the entire crossover between the Bose-Einstein-Condensate (BEC) and Bardeen-Cooper-Schrieffer (BCS) regime. We map out the critical velocity in the crossover from BEC to BCS superfluidity by moving a small attractive potential through the 3D cloud. We compare the results with theoretical predictions and achieve quantitative understanding in the BEC regime by performing numerical simulations. Of particular interest is the regime of strong correlations, where no theoretical predictions exist. In the BEC regime, the critical velocity should be closely related to the speed of sound, according to the Landau criterion and Bogolyubov theory. We measure the sound velocity by exciting a density wave and tracking its propagation. The focus of this thesis is on our first experiments on general properties of quasi-2D Fermi gases. We realize strong vertical confinement by generating a 1D optical lattice by intersecting two blue-detuned laser beams under a steep angle. The large resulting lattice spacing enables us to prepare a single planar quantum gas deeply in the 2D regime. The first measurements of the speed of sound in quasi-2D gases in the BEC-BCS crossover are presented. In addition, we present preliminary results on the pressure equation of state, which is extracted from in-situ density profiles. Since the sound velocity is directly connected to the equation of state, the results provide a crosscheck of the speed of sound. Moreover, we benchmark the derived sound from available equation of state predictions, find very good agreement with recent numerical calculations, and disprove a sophisticated mean field approach. These studies are carried out with a novel apparatus which has
5. Universal properties of Fermi gases in arbitrary dimensions
DEFF Research Database (Denmark)
Valiente, Manuel; T. Zinner, Nikolaj; Molmer, Klaus
2012-01-01
We consider spin-1/2 Fermi gases in arbitrary, integer or non-integer spatial dimensions, interacting via a Dirac delta potential. We first generalize the method of Tan's distributions and implement short-range boundary conditions to arbitrary dimension and we obtain a set of universal relations...... for the Fermi gas. Three-dimensional scattering under very general conditions of transversal confinement is described by an effectively reduced-dimensional scattering length, which we show depends on the three-dimensional scattering length in a universal way. Our formula for non-integer dimensions interpolates...
6. 具有自旋轨道耦合的冷原子费米气中的拓扑超流和FFLO超流❋%Topological superfluids and FFLO superfluids in spin-orbit coupled atomic Fermi gases
Institute of Scientific and Technical Information of China (English)
王俊; 高先龙
2015-01-01
It was investigated the properties of spin-orbit coupled atomic fermi gases under a Zeeman field. By solving the Bogoliubove-de Gennes equation self-consistently, it was found that the system supported the topol-ogical superfluid state and the Fulde-Ferrell-Larkin-Ovchinnikov superfluid state respectively when the system under the different strength of Zeeman field and filling factors. When the system turned into topological super-fluid state, a pair of zero-energy Majorana fermions were found.%研究了具有自旋轨道耦合的冷原子费米气在外磁场作用下的物理性质。通过自洽求解Bogoliubove-de Gennes方程，发现了在不同磁场强度和粒子填充数下，体系分别存在拓扑超流态和 Fulde-Ferrell-Larkin-Ovchinnikov超流态。当体系处于拓扑超流态时，存在零能Majorana费米子。
7. Metastability of Bose and Fermi gases on the upper branch
Science.gov (United States)
LeClair, André; Roditi, Itzhak; Squires, Joshua
2016-12-01
We study three-dimensional Bose and Fermi gases in the upper branch, a phase defined by the absence of bound states in the repulsive interaction regime, within an approximation that considers only two-body interactions. Employing a formalism based on the S matrix, we derive useful analytic expressions that hold on the upper branch in the weak coupling limit. We determine upper branch phase diagrams for both bosons and fermions with techniques valid for arbitrary positive scattering length.
8. Universal properties of Fermi gases in arbitrary dimensions
CERN Document Server
Valiente, Manuel; Molmer, Klaus
2012-01-01
We consider spin-1/2 Fermi gases in arbitrary, integer or non-integer spatial dimensions, interacting via a Dirac delta potential. We first generalize the method of Tan's distributions and implement short-range boundary conditions to arbitrary dimension and we obtain a set of universal relations for the Fermi gas, which serve as dimensional interpolation/extrapolation formulae in between integer dimensions. We show that, under very general conditions, effective reduced-dimensional scattering lengths due to transversal confinement depend on the original three-dimensional scattering length in a universal way. As a direct consequence, we find that confinement-induced resonances occur in all dimensions different from D=2, without any need to solve the associated multichannel scattering problem. Finally, we show that reduced-dimensional contacts --- related to the tails of the momentum distributions --- are connected to the actual three-dimensional contact through a correction factor of purely geometric origin.
9. George E. Valley, Jr. Prize Talk: Exact relations for Fermi gases with large scattering length
Science.gov (United States)
Tan, Shina
2011-05-01
Ultracold two-component atomic Fermi gases near broad Feshbach resonances have both strong interactions and relatively long life times, and the strong attractions between fermions lead to remarkable properties such as superfluidity at large percentages of the Fermi temperature. The interactions can often be described by a single parameter, the two-body s-wave scattering length, which determines how the many-body wave function behaves as two atoms get much closer than the average interparticle spacing. This short-range structure of the wave function leads to a number of exact relations among energy, momentum distribution, pressure, and various high-frequency and short-wave properties. All the relations involve a quantity called contact. The exact relations point to a number of independent determinations of the contact, which have been beautifully demonstrated experimentally as well as numerically. This work was supported, in part, by DOE Grant No. DE-FG02-00ER41132.
10. Finite-size Energy of Non-interacting Fermi Gases
Energy Technology Data Exchange (ETDEWEB)
Gebert, Martin, E-mail: [email protected] [ETH Zürich , Theoretische Physik (Switzerland)
2015-12-15
We study the asymptotics of the difference of the ground-state energies of two non-interacting N-particle Fermi gases in a finite volume of length L in the thermodynamic limit up to order 1/L. We are particularly interested in subdominant terms proportional to 1/L, called finite-size energy. In the nineties (Affleck, Nuc. Phys. B 58, 35–41 1997; Zagoskin and Affleck, J. Phys. A 30, 5743–5765 1997) claimed that the finite-size energy is related to the decay exponent occurring in Anderson’s orthogonality. We prove that the finite-size energy depends on the details of the thermodynamic limit and is therefore non-universal. Typically, it includes an additional linear term in the scattering phase shift.
11. Finite-size Energy of Non-interacting Fermi Gases
Science.gov (United States)
Gebert, Martin
2015-12-01
We study the asymptotics of the difference of the ground-state energies of two non-interacting N-particle Fermi gases in a finite volume of length L in the thermodynamic limit up to order 1/ L. We are particularly interested in subdominant terms proportional to 1/ L, called finite-size energy. In the nineties (Affleck, Nuc. Phys. B 58, 35-41 1997; Zagoskin and Affleck, J. Phys. A 30, 5743-5765 1997) claimed that the finite-size energy is related to the decay exponent occurring in Anderson's orthogonality. We prove that the finite-size energy depends on the details of the thermodynamic limit and is therefore non-universal. Typically, it includes an additional linear term in the scattering phase shift.
12. Time-of-flight expansion of trapped dipolar Fermi gases: from collisionless to hydrodynamic regime
CERN Document Server
2016-01-01
A recent time-of-flight (TOF) expansion experiment with polarized fermionic erbium atoms measured a Fermi surface deformation from a sphere to an ellipsoid due to dipole-dipole interaction, thus confirming previous theoretical predictions. Here we perform a systematic study of the ground-state properties and TOF dynamics for trapped dipolar Fermi gases from the collisionless to the hydrodynamic regime at zero temperature. To this end we solve analytically the underlying Boltzmann-Vlasov equation within the relaxation-time approximation in the vicinity of equilibrium by using a suitable rescaling of the equilibrium distribution. The resulting ordinary differential equations for the respective scaling parameters are then solved numerically for experimentally realistic parameters and relaxation times that correspond to the collisionless, collisional, and hydrodynamic regime. The equations for the collisional regime are first solved in the approximation of a fixed relaxation time, and then this approach is extend...
13. All-optical cooling of Fermi gases via Pauli inhibition of spontaneous emission
CERN Document Server
Onofrio, Roberto
2016-01-01
A technique is proposed to cool Fermi gases to the regime of quantum degeneracy based on the expected inhibition of spontaneous emission due to the Pauli principle. The reduction of the linewidth for spontaneous emission originates a corresponding reduction of the Doppler temperature, which under specific conditions may give rise to a runaway process through which fermions are progressively cooled. The approach requires a combination of a magneto-optical trap as a cooling system and an optical dipole trap to enhance quantum degeneracy. This results in expected Fermi degeneracy factors $T/T_F$ comparable to the lowest values recently achieved, with potential for a direct implementation in optical lattices. The experimental demonstration of this technique should also indirectly provide a macroscopic manifestation of the Pauli exclusion principle at the atomic physics level.
14. Dimensional BCS-BEC crossover in ultracold Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Boettcher, Igor
2014-12-10
We investigate thermodynamics and phase structure of ultracold Fermi gases, which can be realized and measured in the laboratory with modern trapping techniques. We approach the subject from a both theoretical and experimental perspective. Central to the analysis is the systematic comparison of the BCS-BEC crossover of two-component fermions in both three and two dimensions. A dimensional reduction can be achieved in experiments by means of highly anisotropic traps. The Functional Renormalization Group (FRG) allows for a description of both cases in a unified theoretical framework. In three dimensions we discuss with the FRG the influence of high momentum particles onto the density, extend previous approaches to the Unitary Fermi Gas to reach quantitative precision, and study the breakdown of superfluidity due to an asymmetry in the population of the two fermion components. In this context we also investigate the stability of the Sarma phase. For the two-dimensional system scattering theory in reduced dimension plays an important role. We present both the theoretically as well as experimentally relevant aspects thereof. After a qualitative analysis of the phase diagram and the equation of state in two dimensions with the FRG we describe the experimental determination of the phase diagram of the two-dimensional BCS-BEC crossover in collaboration with the group of S. Jochim at PI Heidelberg.
15. Beyond Gaussian pair fluctuation theory for strongly interacting Fermi gases
Science.gov (United States)
Mulkerin, Brendan C.; Liu, Xia-Ji; Hu, Hui
2016-07-01
Interacting Fermi systems in the strongly correlated regime play a fundamental role in many areas of physics and are of particular interest to the condensed matter community. Though weakly interacting fermions are understood, strongly correlated fermions are difficult to describe theoretically as there is no small interaction parameter to expand about. Existing strong-coupling theories rely heavily on the so-called many-body T -matrix approximation that sums ladder-type Feynman diagrams. Here, by acknowledging the fact that the effective interparticle interaction (i.e., the vertex function) becomes smaller above three dimensions, we propose an alternative way to reorganize Feynman diagrams and develop a theoretical framework for interacting Fermi gases beyond the ladder approximation. As an application, we solve the equation of state for three- and two-dimensional strongly interacting fermions and find excellent agreement with experimental [M. J. H. Ku et al., Science 335, 563 (2012), 10.1126/science.1214987] and other theoretical results above temperatures of 0.5 TF .
16. Thomas-Fermi-von Weizsaecker theory of atoms and molecules
Energy Technology Data Exchange (ETDEWEB)
Benguria, R.; Brezis, H.; Lieb, E.H.
1981-11-02
We place the Thomas-Fermi-von Weizsaecker model of atoms on a firm mathematical footing. We prove existence and uniqueness of solutions of the Thomas-Fermi-von Weizsaecker equation as well as the fact that they minimize the Thomas-Fermi-von Weizsaecker energy functional. Moreover, we prove the existence of bindings for two very dissimilar atoms in the frame of this model.
17. Electron-Atom Collisions in Gases
Science.gov (United States)
Kraftmakher, Yaakov
2013-01-01
Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.
18. Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics Talk: Equation of State of the Dilute Fermi Gases
Science.gov (United States)
Chang, Soon Yong
2008-04-01
In the recent years, dilute Fermi gases have played the center stage role in the many-body physics. The gas of neutral alkali atoms such as Lithium-6 and Potassium-40 can be trapped at temperatures below the Fermi degeneracy. The most relevant feature of these gases is that the interaction is tunable and strongly interacting superfluid can be artificially created. I will discuss the recent progress in understanding the ground state properties of the dilute Fermi gases at different interaction regimes. First, I will present the case of the spin symmetric systems where the Fermi gas can smoothly crossover from the BCS regime to the BEC regime. Then, I will discuss the case of the spin polarized systems, where different quantum phases can occur as a function of the polarization. In the laboratory, the trapped Fermi gas shows spatial dependence of the different quantum phases. This can be understood in the context of the local variation of the chemical potential. I will present the most accurate quantum ab initio results and the relevant experiments.
19. Field theory for trapped atomic gases
NARCIS (Netherlands)
Stoof, H.T.C.
2001-01-01
In this course we give a selfcontained introduction to the quantum field theory for trapped atomic gases, using functional methods throughout. We consider both equilibrium and nonequilibrium phenomena. In the equilibrium case, we first derive the appropriate Hartree-Fock theory for the properties of
20. Field theory for trapped atomic gases
NARCIS (Netherlands)
Stoof, H.T.C.
2001-01-01
In this course we give a selfcontained introduction to the quantum field theory for trapped atomic gases, using functional methods throughout. We consider both equilibrium and nonequilibrium phenomena. In the equilibrium case, we first derive the appropriate Hartree—Fock theory for the properties of
1. Dimensionality and Finite Number Effect on BCS Transition of Atomic Fermi Gas
Institute of Scientific and Technical Information of China (English)
CUI Hai-Tao; WANG Lin-Cheng; YI Xue-Xi
2005-01-01
The effect of finite number and dimensionality has been discussed in this paper. The finite number effect has a negative correction to final temperature for 2D or 3D atomic Fermi gases. The changing of final temperature obtained by scanning from BEC region to BCS region are 10% or so with N ≤ 103 and can be negligible when N ＞ 103.However, in 1D atomic Fermi gas, the effect gives a positive correction which greatly changes the final temperature in Fermi gas. This behavior is completely opposed to the 2D and 3D cases and a proper explanation is still to be found.Dimensionality also has a positive correction, in which the more tightly trapping, the higher final temperature one gets with the same particle number. A discussion is also presented.
2. Density-functional theory of strongly correlated Fermi gases in elongated harmonic traps
Science.gov (United States)
Xianlong, Gao; Polini, Marco; Asgari, Reza; Tosi, M. P.
2006-03-01
Two-component Fermi gases with tunable repulsive or attractive interactions inside quasi-one-dimensional (Q1D) harmonic wells may soon become the cleanest laboratory realizations of strongly correlated Luttiger and Luther-Emery liquids under confinement. We present a microscopic Kohn-Sham density-functional theory of these systems, with specific attention to a gas on the approach to a confinement-induced Feshbach resonance. The theory employs the one-dimensional Gaudin-Yang model as the reference system and transfers the appropriate Q1D ground-state correlations to the confined inhomogeneous gas via a suitable local-density approximation to the exchange and correlation energy functional. Quantitative understanding of the role of the interactions in the bulk shell structure of the axial density profile is thereby achieved. While repulsive intercomponent interactions depress the amplitude of the shell structure of the noninteracting gas, attractive interactions stabilize atomic-density waves through spin pairing. These should be clearly observable in atomic clouds containing of the order of up to 100 atoms.
3. Photon Bubble Turbulence in Cold Atomic Gases
CERN Document Server
Rodrigues, João D; Ferreira, António V; Terças, Hugo; Kaiser, Robin; Mendonça, José T
2016-01-01
Turbulent radiation flow is ubiquitous in many physical systems where light-matter interaction becomes relevant. Photon bubbling, in particular, has been identified as the main source of turbulent radiation transport in many astrophysical objects, such as stars and accretion disks. This mechanism takes place when radiation trapping in optically dense media becomes unstable, leading to the energy dissipation from the larger to the smaller bubbles. Here, we report on the observation of photon bubble turbulence in cold atomic gases in the presence of multiple scattering of light. The instability is theoretically explained by a fluid description for the atom density coupled to a diffusive transport equation for the photons, which is known to be accurate in the multiple scattering regime investigated here. We determine the power spectrum of the atom density fluctuations, which displays an unusual $\\sim k^{-4}$ scaling, and entails a complex underlying turbulent dynamics resulting from the formation of dynamical bu...
4. Magnetostriction and exchange effects in trapped dipolar Bose and Fermi gases
OpenAIRE
Baillie, D; Blakie, P. B.
2012-01-01
We examine the magnetostrictive position and momentum space distortions that occur in harmonically confined dipolar Bose and Fermi gases. Direct interactions give rise to position space magnetostriction and exchange interactions give rise to momentum space magnetostriction. While the position space magnetostriction is similar in Bose and Fermi systems, the momentum space magnetostriction is markedly different: the Bose gas momentum distribution distorts in the opposite sense to that of the Fe...
5. Repulsive polarons and itinerant ferromagnetism in strongly polarized Fermi gases
DEFF Research Database (Denmark)
Massignan, Pietro; Bruun, Georg
2011-01-01
We analyze the properties of a single impurity immersed in a Fermi sea. At positive energy and scattering lengths, we show that the system possesses a well-defined but metastable excitation, the repulsive polaron, and we calculate its energy, quasiparticle residue and effective mass. From a therm...
6. Nonlinear Ramsey Interferometry of Fermi Superfluid Gases in a Double-Well Potential
Institute of Scientific and Technical Information of China (English)
蒙红娟; 苟学强; 王文元; 杨阳; 段文山
2012-01-01
The nonlinear Ramsey interferometry of Fermi superfluid gases in a double-well potential is investigated in this paper. We found that the frequency of the Ramsey fringes exactly reflects the strength of nonlinearity, or the scattering length of the Fermi superfluid gases. The cases of sudden limit, the adiabatic limit and the general case are studied. The analytical result is in good agreement with the numerical ones. The adiabatic condition is proposed. In general situation, the zero-frequency point emerge. Finally the possible applications of the theory axe discussed.
7. Thermodynamic characteristics of Fermi gases in a magnetic field
Energy Technology Data Exchange (ETDEWEB)
Lipovetskii, S.S.; Olesik, A.A.; Sekerzhitskii, V.S.
1987-11-01
Within the framework of statistical thermodynamics of equilibrium systems, general expressions are obtained for the chemical potential, pressure, and magnetic susceptibility for degenerate ideal nonrelativistic electron, proton, and neutron gases in magnetic fields, which exert no pronounced influence on the anomalous magnetic moments of the fermions.
8. Korteweg de Vries Description of One-Dimensional Superfluid Fermi Gases
Institute of Scientific and Technical Information of China (English)
徐艳霞; 段文山
2011-01-01
We study one-dimensional matter-wave pulses in cigar-shaped superfluid Fermi gases, including the linear and nonlinear waves of the system. A Korteweg de Vries (KdV) solitary wave is obtained for the superfluid Fermi gases in the limited case of a BEC regime, a BCS regime and unitarity. The dependences of the propagation velocity, amplitude and the width of the solitary wave on the dimensionless interaction parameter y = 1/{kFasc) are given for the limited cases of BEC and unitarity.%We study one-dimensional matter-wave pulses in cigar-shaped superfluid Fermi gases,including the linear and nonlinear waves of the system.A Korteweg de Vries(KdV)solitary wave is obtained for the superfluid Fermi gases in the limited case of a BEC regime,a BCS regime and unitarity.The dependences of the propagation velocity,amplitude and the width of the solitary wave on the dimensionless interaction parameter y =1 /(kFasc)are given for the limited cases of BEC and unitarity.
9. Transdimensional equivalence of universal constants for Fermi gases at unitarity.
Science.gov (United States)
Endres, Michael G
2012-12-21
I present lattice Monte Carlo calculations for a universal four-component Fermi gas confined to a finite box and to a harmonic trap in one spatial dimension. I obtain the values ξ(1D) = 0.370(4) and ξ(1D) = 0.372(1), respectively, for the Bertsch parameter, a nonperturbative universal constant defined as the (square of the) energy of the untrapped (trapped) system measured in units of the free gas energy. The Bertsch parameter obtained for the one-dimensional system is consistent to within ~1% uncertainties with the most recent numerical and experimental estimates of the analogous Bertsch parameter for a three-dimensional spin-1/2 Fermi gas at unitarity. The finding suggests the intriguing possibility that there exists a universality between two conformal theories in different dimensions. To lend support to this study, I also compute ground state energies for four and five fermions confined to a harmonic trap and demonstrate the restoration of a virial theorem in the continuum limit. The continuum few-body energies obtained are consistent with exact analytical calculations to within ~1.0% and ~0.3% statistical uncertainties, respectively.
10. Transdimensional equivalence of universal constants from universal Fermi gases
CERN Document Server
Endres, Michael G
2012-01-01
I present lattice Monte Carlo calculations for a universal four-component Fermi gas confined to a finite box and to a harmonic trap in one spatial dimension. I obtain the continuum and thermodynamic limit extrapolated values xi_1d = 0.370(4) and xi_1d = 0.372(1), respectively, for the Bertsch parameter, a nonperturbative universal constant defined as the (square of the) energy of the untrapped (trapped) system measured in units of the free gas energy. The Bertsch parameter for the one-dimensional system is consistent to within ~1% uncertainties with the most recent numerical and experimental estimates of the analogous Bertsch parameter for a three-dimensional spin-1/2 Fermi gas at unitarity. The finding suggests the intriguing possibility that there exists a universality between two conformal theories in different dimensions. To lend support to this study, I also compute continuum extrapolated ground state energies for four and five fermions confined to a harmonic trap and demonstrate the restoration of a Vir...
11. Superfluidity and collective modes in Rashba spin–orbit coupled Fermi gases
Energy Technology Data Exchange (ETDEWEB)
He, Lianyi, E-mail: [email protected] [Frankfurt Institute for Advanced Studies and Institute for Theoretical Physics, J. W. Goethe University, 60438 Frankfurt am Main (Germany); Huang, Xu-Guang, E-mail: [email protected] [Center for Exploration of Energy and Matter and Physics Department, Indiana University, Bloomington, IN 47408 (United States)
2013-10-15
We present a theoretical study of the superfluidity and the corresponding collective modes in two-component atomic Fermi gases with s-wave attraction and synthetic Rashba spin–orbit coupling. The general effective action for the collective modes is derived from the functional path integral formalism. By tuning the spin–orbit coupling from weak to strong, the system undergoes a crossover from an ordinary BCS/BEC superfluid to a Bose–Einstein condensate of rashbons. We show that the properties of the superfluid density and the Anderson–Bogoliubov mode manifest this crossover. At large spin–orbit coupling, the superfluid density and the sound velocity become independent of the strength of the s-wave attraction. The two-body interaction among the rashbons is also determined. When a Zeeman field is turned on, the system undergoes quantum phase transitions to some exotic superfluid phases which are topologically nontrivial. For the two-dimensional system, the nonanalyticities of the thermodynamic functions and the sound velocity across the phase transition are related to the bulk gapless fermionic excitation which causes infrared singularities. The superfluid density and the sound velocity behave nonmonotonically: they are suppressed by the Zeeman field in the normal superfluid phase, but get enhanced in the topological superfluid phase. The three-dimensional system is also studied. -- Highlights: •The general effective action for Rashba spin–orbit coupled Fermi superfluids is derived. •The evolution of the collective modes manifests the BCS/BEC-rashbon crossover. •The superfluid properties are universal at large spin–orbit coupling. •The sound velocity behaves nonanalytically across the quantum phase transition.
12. Localization of interacting Fermi gases in quasiperiodic potentials
Science.gov (United States)
Pilati, Sebastiano; Varma, Vipin Kerala
2017-01-01
We investigate the zero-temperature metal-insulator transition in a one-dimensional two-component Fermi gas in the presence of a quasiperiodic potential resulting from the superposition of two optical lattices of equal intensity but incommensurate periods. A mobility edge separating (low-energy) Anderson localized and (high-energy) extended single-particle states appears in this continuous-space model beyond a critical intensity of the quasiperiodic potential. To discern the metallic phase from the insulating phase in the interacting many-fermion system, we employ unbiased quantum Monte Carlo (QMC) simulations combined with the many-particle localization length familiar from the modern theory of the insulating state. In the noninteracting limit, the critical optical-lattice intensity for the metal-insulator transition predicted by the QMC simulations coincides with the Anderson localization transition of the single-particle eigenstates. We show that weak repulsive interactions induce a shift of this critical point towards larger intensities, meaning that repulsion favors metallic behavior. This shift appears to be linear in the interaction parameter, suggesting that even infinitesimal interactions can affect the position of the critical point.
13. Mixtures of ultracold gases: Fermi sea and Bose-Einstein condensate of lithium isotopes
Science.gov (United States)
Schreck, F.
2003-03-01
This thesis presents studies of quantum degenerate atomic gases of fermionic ^6Li and bosonic ^7Li. Degeneracy is reached by evaporative cooling of ^7Li in a strongly confining magnetic trap. Since at low temperatures direct evaporative cooling is not possible for a polarized fermionic gas, ^6Li is sympathetically cooled by thermal contact with ^7Li. In a first series of experiments both isotopes are trapped in their low-field seeking higher hyperfine states. A Fermi degeneracy of T/T_F=0.25(5) is achieved for 10^5 fermions. For more than 300 atoms, the ^7Li condensate collapses, due to the attractive interatomic interaction in this state. This limits the degeneracy reached for both species. To overcome this limit, in a second series of experiments ^7Li and ^6Li atoms are transferred to their low field seeking lower hyperfine states, where the boson-boson interaction is repulsive but weak. The inter-isotope collisions are used to thermalize the mixture. A ^7Li Bose-Einstein condensate (BEC) of 10^4 atoms immersed in a Fermi sea is produced. The BEC is quasi-one-dimensional and the thermal fraction can be negligible. The measured degeneracies are T/T_C=T/T_F=0.2(1). The temperature is measured using the bosonic thermal fraction, which vanishes at the lowest temperatures, limiting our measurement sensitivity. In a third series of experiments, the bosons are transferred into an optical trap and their internal state is changed to |F=1,m_F=1rangle, the lowest energy state. A Feshbach resonance is detected and used to produce a BEC with tunable atomic interactions. When the effective interaction between atoms is tuned to be small and attractive, we observe the formation of a matter-wave bright soliton. Propagation of the soliton without spreading over a macroscopic distance of 1.1 mm is observed. Mélanges de gaz ultrafroids: mer de Fermi et condensat de Bose-Einstein des isotopes du lithium Cette thèse décrit l'étude des gaz de fermions ^6Li et de bosons ^7Li dans le
14. Proximity effects in cold gases of multiply charged atoms (Review)
Science.gov (United States)
Chikina, I.; Shikin, V.
2016-07-01
Possible proximity effects in gases of cold, multiply charged atoms are discussed. Here we deal with rarefied gases with densities nd of multiply charged (Z ≫ 1) atoms at low temperatures in the well-known Thomas-Fermi (TF) approximation, which can be used to evaluate the statistical properties of single atoms. In order to retain the advantages of the TF formalism, which is successful for symmetric problems, the external boundary conditions accounting for the finiteness of the density of atoms (donors), nd ≠ 0, are also symmetrized (using a spherical Wigner-Seitz cell) and formulated in a standard way that conserves the total charge within the cell. The model shows that at zero temperature in a rarefied gas of multiply charged atoms there is an effective long-range interaction Eproxi(nd), the sign of which depends on the properties of the outer shells of individual atoms. The long-range character of the interaction Eproxi is evaluated by comparing it with the properties of the well-known London dispersive attraction ELond(nd) interaction in gases. For the noble gases argon, krypton, and xenon Eproxi>0 and for the alkali and alkaline-earth elements Eproxi neutral complexes into charged fragments. This phenomenon appears consistently in the TF theory through the temperature dependence of the different versions of Eproxi. The anomaly in the thermal proximity effect shows up in the following way: for T ≠ 0 there is no equilibrium solution of TS statistics for single multiply charged atoms in a vacuum when the effect is present. Instability is suppressed in a Wigner-Seitz model under the assumption that there are no electron fluxes through the outer boundary R3 ∝ n-1d of a Wigner-Seitz cell. Eproxi corresponds to the definition of the correlation energy in a gas of interacting particles. This review is written so as to enable comparison of the results of the TF formalism with the standard assumptions of the correlation theory for classical plasmas. The classic
15. Spin-orbit Coupled Fermi Gases and Heavy Solitons in Fermionic Superfluids
Science.gov (United States)
Cheuk, Lawrence
2013-05-01
The coupling of the spin of electrons to their motional state lies at the heart of topological phases of matter. We have created and detected spin-orbit coupling in an atomic Fermi gas via spin-injection spectroscopy, which characterizes the energy-momentum dispersion and spin composition of the quantum states. For energies within the spin-orbit gap, the system acts as a spin diode. To fully inhibit transport, we open an additional spin gap with radio-frequency coupling, thereby creating a spin-orbit coupled lattice whose spinful band structure we probe. In the presence of s-wave interactions, spin-orbit coupled fermion systems should display induced p-wave pairing and consequently topological superfluidity. Such systems can be described by a relativistic Dirac theory with a mass term that can be made to vary spatially. Topologically protected edge states are expected to occur whenever the mass term changes sign. A system that similarly supports edges states is the strongly interacting atomic Fermi gas near a Feshbach resonance. Topological excitations, such as vortices - line defects - or solitons - planar defects - have been described theoretically for decades in many different physical contexts. In superconductivity and superfluidity they represent a defect in the order parameter and give rise to localized bound states. We have created and directly observed solitons in a fermionic superfluid by imprinting a phase step into the superfluid wavefunction. These are found to be stable for many seconds, allowing us to track their oscillatory motion in the trapped superfluid. Their trapping period increases dramatically as the interactions are tuned from the BEC to the BCS regime. At the Feshbach resonance, their period is an order of magnitude larger than expectations from mean-field Bogoliubov-de Gennes theory, signaling strong effects of bosonic quantum fluctuations and possible filling of Andreev bound states. Our work opens the study of fermionic edge states in
16. Composite-boson approach to molecular Bose-Einstein condensates in mixtures of ultracold Fermi gases
Science.gov (United States)
Bouvrie, P. Alexander; Tichy, Malte C.; Roditi, Itzhak
2017-02-01
We show that an ansatz based on independent composite bosons [Phys. Rep. 463, 215 (2008), 10.1016/j.physrep.2007.11.003] accurately describes the condensate fraction of molecular Bose-Einstein condensates in ultracold Fermi gases. The entanglement between the fermionic constituents of a single Feshbach molecule then governs the many-particle statistics of the condensate, from the limit of strong interaction to close to unitarity. This result strengthens the role of entanglement as the indispensable driver of composite-boson behavior. The condensate fraction of fermion pairs at zero temperature that we compute matches excellently previous results obtained by means of fixed-node diffusion Monte Carlo methods and the Bogoliubov depletion approximation. This paves the way towards the exploration of the BEC-BCS crossover physics in mixtures of cold Fermi gases with an arbitrary number of fermion pairs as well as the implementation of Hong-Ou-Mandel-like interference experiments proposed within coboson theory.
17. Simple Method Obtaining Analytical Expressions of Particle and Kinetic—Energy Densities for One—Dimensional Confined Fermi Gases
Institute of Scientific and Technical Information of China (English)
YANGXiao－Xue; WUYing
2002-01-01
We develop a simple approach to obtain explicitly exact analytical expressions of particle and kineticenergy densities for noninteracting Fermi gases in one-dimensional harmonic confinement,and in one-dimensional box confinement as well.
18. Simple Method Obtaining Analytical Expressions of Particle and Kinetic-Energy Densities for One-Dimensional Confined Fermi Gases
Institute of Scientific and Technical Information of China (English)
YANG XiaoXue; WU Ying
2002-01-01
We develop a simple approach to obtain explicitly exact analytical expressions of particle and kinetic-energy densities for noninteracting Fermi gases in one-dimensional harmonic confinement, and in one-dimensional boxconfinement as well.
19. Phase transitions in definite total spin states of two-component Fermi gases
CERN Document Server
2016-01-01
Symmetry under permutations of indistinguishable particles, contained in each medium, is one of the fundamental symmetries. Generally, a change in symmetry affects the medium's thermodynamic properties, leading to phase transitions. Permutation symmetry can be changed since, in addition to the conventional symmetric and anti-symmetric states under permutations of bosons and fermions, mathematical group-representation theory allows for non-Abelian permutation symmetry. Such symmetry can be hidden in states with defined total spins of spinor gases, which can be formed in optical cavities. However, the thermodynamic effects of non-Abelian symmetry are unknown. The present work shows that the symmetry reveals itself in spin-independent or coordinate-independent properties of these gases, namely as non-Abelian entropy in thermodynamic properties. In weakly interacting Fermi gases, saturated and unsaturated phases appear associated with fermionic and non-Abelian symmetry under permutations of particle states, respe...
20. Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Science.gov (United States)
Cramer, M; Eisert, J; Illuminati, F
2004-11-05
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
1. Ultracold Fermi and Bose gases and Spinless Bose Charged Sound Particles
Directory of Open Access Journals (Sweden)
Minasyan V.
2011-10-01
Full Text Available We propose a novel approach for investigation of the motion of Bose or Fermi liquid (or gas which consists of decoupled electrons and ions in the uppermost hyperfine state. Hence, we use such a concept as the fluctuation motion of “charged fluid particles” or “charged fluid points” representing a charged longitudinal elastic wave. In turn, this elastic wave is quantized by spinless longitudinal Bose charged sound particles with the rest mass m and charge e 0 . The existence of spinless Bose charged sound particles allows us to present a new model for description of Bose or Fermi liquid via a non-ideal Bose gas of charged sound particles . In this respect, we introduce a new postulation for the superfluid component of Bose or Fermi liquid determined by means of charged sound particles in the condensate, which may explain the results of experiments connected with ultra-cold Fermi gases of spin-polarized hydrogen, 6 Li and 40 K, and such a Bose gas as 87 Rb in the uppermost hyperfine state, where the Bose- Einstein condensation of charged sound particles is realized by tuning the magnetic field.
2. Statistical Mechanical Approach to the Equation of State of Unitary Fermi Gases
CERN Document Server
De Silva, Theja N
2016-01-01
We combine a Tan's universal relation with a basic statistical mechanical approach to derive a general equation of state for unitary Fermi gases. The universal equation of state is written as a series solution to a self consistent integral equation where the general solution is a linear combination of Fermi functions. By truncating our series solution to four terms with already known exact theoretical inputs at limiting cases, namely the first three virial coefficients and the Bertsch parameter, we find a good agreement with experimental measurements in the entire temperature region in the normal state. Our analytical equation of state agrees with experimental data up to the fugacity $z = 18$, which is a vast improvement over the other analytical equations of state available where the agreements is \\emph{only} up to $z \\approx 7$.
3. Interacting Bose and Fermi Gases in Low Dimensions and the Riemann Hypothesis
Science.gov (United States)
Leclair, André
We apply the S-matrix based finite temperature formalism to nonrelativistic Bose and Fermi gases in 1+1 and 2+1 dimensions. For the (2+1)-dimensional case in the constant scattering length approximation, the free energy is given in terms of Roger's dilogarithm in a way analagous to the thermodynamic Bethe ansatz for the relativistic (1+1)-dimensional case. The 1d fermionic case with a quasiperiodic two-body potential is closely connected with the Riemann hypothesis.
4. Immersing carbon nano-tubes in cold atomic gases
OpenAIRE
2013-01-01
We investigate the sympathetic relaxation of a free-standing, vibrating carbon nano-tube that is mounted on an atom chip and is immersed in a cloud of ultra-cold atoms. Gas atoms colliding with the nano-tube excite phonons via a Casimir-Polder potential. We use Fermi's Golden Rule to estimate the relaxation rates for relevant experimental parameters and develop a fully dynamic theory of relaxation for the multi-mode phononic field embedded in a thermal atomic reservoir. Based on currently ava...
5. Observation of the Efimovian expansion in scale-invariant Fermi gases
Science.gov (United States)
Deng, Shujin; Shi, Zhe-Yu; Diao, Pengpeng; Yu, Qianli; Zhai, Hui; Qi, Ran; Wu, Haibin
2016-07-01
Scale invariance plays an important role in unitary Fermi gases. Discrete scaling symmetry manifests itself in quantum few-body systems such as the Efimov effect. Here, we report on the theoretical prediction and experimental observation of a distinct type of expansion dynamics for scale-invariant quantum gases. When the frequency of the harmonic trap holding the gas decreases continuously as the inverse of time t, the expansion of the cloud size exhibits a sequence of plateaus. The locations of these plateaus obey a discrete geometric scaling law with a controllable scale factor, and the expansion dynamics is governed by a log-periodic function. This marked expansion shares the same scaling law and mathematical description as the Efimov effect.
6. Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases
Science.gov (United States)
Wang, Jibiao; Che, Yanming; Zhang, Leifeng; Chen, Qijin
2017-01-01
Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li–40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing.
7. Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases
Science.gov (United States)
Wang, Jibiao; Che, Yanming; Zhang, Leifeng; Chen, Qijin
2017-01-01
Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li–40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing. PMID:28051145
8. Quantum Effects of Uniform Bose Atomic Gases with Weak Attraction
Institute of Scientific and Technical Information of China (English)
CHENG Ze
2011-01-01
@@ We find that uniform Bose atomic gases with weak attraction can undergo a Bardeen-Cooper-Schrieffer(BCS)condensation below a critical temperature.In the BCS condensation state,bare atoms with opposite wave vectors are bound into pairs,and unpaired bare atoms are transformed into a new kind of quasi-particles,i.e.the dressed atoms.The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid.The critical temperature and the effective mass of dressed atoms are derived analytically.The transition from the BCS condensation state to the normal state is a first-order phase transition.%We find that uniform Bose atomic gases with weak attraction can undergo a Bardeen-Cooper-Schrieffer (BCS)condensation below a critical temperature. In the BCS condensation state, bare atoms with opposite wave vectors are bound into pairs, and unpaired bare atoms are transformed into a new kind of quasi-particles, i.e. the dressed atoms. The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid. The critical temperature and the effective mass of dressed atoms are derived analytically. The transition from the BCS condensation state to the normal state is a first-order phase transition.
9. Light Propagation in Ultracold Atomic Gases
OpenAIRE
Bariani, Francesco
2009-01-01
The propagation of light through an ultracold atomic gas is the main topic of the present work. The thesis consists of two parts. In Part I (Chapters 1,2,3), we give a complete description of the 1D photonic bands of a MI of two-level atoms paying attention to both band diagrams and reflectivity spectra. The role of regular periodicity of the system is addressed within a polariton formalism. The scattering on defects inside lattices of three-level atoms is also studied in view of optica...
10. Quantum information entropies of ultracold atomic gases in a harmonic trap
Tutul Biswas; Tarun Kanti Ghosh
2011-10-01
The position and momentum space information entropies of weakly interacting trapped atomic Bose–Einstein condensates and spin-polarized trapped atomic Fermi gases at absolute zero temperature are evaluated. We find that sum of the position and momentum space information entropies of these quantum systems containing atoms confined in a $D(≤ 3)$-dimensional harmonic trap has a universal form as $S^{(D)}_t = N(a D − b ln N)$, where ∼ 2.332 and = 2 for interacting bosonic systems and a ∼ 1.982 and = 1 for ideal fermionic systems. These results obey the entropic uncertainty relation given by Beckner, Bialynicki-Birula and Myceilski.
11. Comparing and contrasting nuclei and cold atomic gases
CERN Document Server
Zinner, N T; 10.1088/0954-3899/40/5/053101
2013-01-01
The experimental revolution in ultracold atomic gas physics over the past decades have brought tremendous amounts of new insight to the world of degenerate quantum systems. Here we compare and constrast the developments of cold atomic gases with the physics of nuclei since many concepts, techniques, and nomenclatures are common to both fields. However, nuclei are finite systems with interactions that are typically much more complicated than those of ultracold atomic gases. The simularities and differences must therefore be carefully addressed for a meaningful comparison and to facilitate fruitful crossdisciplinary activity. Universal results from atomic physics should have impact in certain limits of the nuclear domain. In particular, with advances in the trapping of few-body atomic systems we expect a more direct exchange of ideas and results.
12. Transport phenomena in correlated quantum liquids: Ultracold Fermi gases and F/N junctions
Science.gov (United States)
Li, Hua
Landau Fermi-liquid theory was first introduced by L. D. Landau in the effort of understanding the normal state of Fermi systems, where the application of the concept of elementary excitations to the Fermi systems has proved very fruitful in clarifying the physics of strongly correlated quantum systems at low temperatures. In this thesis, I use Landau Fermi-liquid theory to study the transport phenomena of two different correlated quantum liquids: the strongly interacting ultracold Fermi gases and the ferromagnet/normal-metal (F/N) junctions. The detailed work is presented in chapter II and chapter III of this thesis, respectively. Chapter I holds the introductory part and the background knowledge of this thesis. In chapter II, I study the transport properties of a Fermi gas with strong attractive interactions close to the unitary limit. In particular, I compute the transport lifetimes of the Fermi gas due to superfluid fluctuations above the BCS transition temperature Tc. To calculate the transport lifetimes I need the scattering amplitudes. The scattering amplitudes are dominated by the superfluid fluctuations at temperatures just above Tc. The normal scattering amplitudes are calculated from the Landau parameters. These Landau parameters are obtained from the local version of the induced interaction model for computing Landau parameters. I also calculate the leading order finite temperature corrections to the various transport lifetimes. A calculation of the spin diffusion coefficient is presented in comparison to the experimental findings. Upon choosing a proper value of F0a, I am able to present a good match between the theoretical result and the experimental measurement, which indicates the presence of the superfluid fluctuations near Tc. Calculations of the viscosity, the viscosity/entropy ratio and the thermal conductivity are also shown in support of the appearance of the superfluid fluctuations. In chapter III, I study the spin transport in the low
13. Atomic Gases at Negative Kinetic Temperature
NARCIS (Netherlands)
Mosk, A.P.
2005-01-01
We show that thermalization of the motion of atoms at negative temperature is possible in an optical lattice, for conditions that are feasible in current experiments. We present a method for reversibly inverting the temperature of a trapped gas. Moreover, a negative-temperature ensemble can be coole
14. Tan's contact and the phase distribution of repulsive Fermi gases: Insights from QCD noise analyses
CERN Document Server
Porter, William J
2016-01-01
Path-integral analyses originally pioneered in the study of the complex-phase problem afflicting lattice calculations of finite-density quantum chromodynamics are generalized to non-relativistic Fermi gases with repulsive interactions. Using arguments similar to those previously applied to relativistic theories, we show that the analogous problem in nonrelativistic systems manifests itself naturally in Tan's contact as a nontrivial cancellation between terms with varied dependence on extensive thermodynamic quantities. We analyze that case under the assumption of gaussian phase distribution, which is supported by our Monte Carlo calculations and perturbative considerations. We further generalize these results to observables other than the contact, as well as to polarized systems and systems with fixed particle number. Our results are quite general in that they apply to repulsive multi-component fermions, are independent of dimensionality or trapping potential, and hold in the ground state as well as at finite...
15. Theoretical Approach to the Gauge Invariant Linear Response Theories for Ultracold Fermi Gases with Pseudogap
Directory of Open Access Journals (Sweden)
Hao Guo
2015-01-01
Full Text Available Recent experimental progress allows for exploring some important physical quantities of ultracold Fermi gases, such as the compressibility, spin susceptibility, viscosity, optical conductivity, and spin diffusivity. Theoretically, these quantities can be evaluated from suitable linear response theories. For BCS superfluid, it has been found that the gauge invariant linear response theories can be fully consistent with some stringent consistency constraints. When the theory is generalized to stronger than BCS regime, one may meet serious difficulties to satisfy the gauge invariance conditions. In this paper, we try to construct density and spin linear response theories which are formally gauge invariant for a Fermi gas undergoing BCS-Bose-Einstein Condensation (BEC crossover, especially below the superfluid transition temperature Tc. We adapt a particular t-matrix approach which is close to the G0G formalism to incorporate noncondensed pairing in the normal state. We explicitly show that the fundamental constraints imposed by the Ward identities and Q-limit Ward identity are indeed satisfied.
16. Fermi
Data.gov (United States)
National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...
17. Experimental studies of spin-imbalanced Fermi gases in 2D geometries
Science.gov (United States)
Thomas, John
We study the thermodynamics of a quasi-two-dimensional Fermi gas, which is not quite two-dimensional (2D), but far from three dimensional (3D). This system offers opportunities to test predictions that cross interdisciplinary boundaries, such as enhanced superfluid transition temperatures in spin-imbalanced quasi-2D superconductors, and provides important benchmarks for calculations of the phase diagrams. In the experiments, an ultra-cold Fermi gas is confined in an infrared CO2 laser standing-wave, which produces periodic pancake-shaped potential wells, separated by 5.3 μm. To study the thermodynamics, we load an ultra-cold mixture of N1 = 800 spin 1/2 -up and N2 interaction strength and spin imbalance N2/N1. The measured properties are in disagreement with 2D-BCS theory, but can be fit by a 2D-polaron gas model, where each atom is surrounded by a cloud of particle-hole pairs of the opposite spin. However, this model fails to predict a transition to a spin-balanced central region as N2/N1is increased. Supported by the physics divisions of ARO, AFOSR, and NSF and by the Division of Materials Science and Engineering, the Office of Basic Energy Sciences, DOE.
18. The quantum pressure correction to the excitation spectrum of the trapped superfluid Fermi gases in a BEC-BCS crossover
Institute of Scientific and Technical Information of China (English)
Dong Hang; Ma Yong-Li
2009-01-01
Using quantum hydrodynamic approaches, we study the quantum pressure correction to the collective excitation spectrum of the interacting trapped superfluid Fermi gases in the BEC-BCS crossover. Based on a phenomenological equation of state, we derive hydrodynamic equations of the system in the whole BEC-BCS crossover regime. Beyond the Thomas-Fermi approximation, expressions of the frequency corrections of collective modes for both spherical and axial symmetric traps excited in the BEC-BCS crossover are given explicitly. The corrections of the eigenfrequencies due to the quantum pressure and their dependence on the inverse interaction strength. Anisotropic parameter and particle numbers of the condensate are discussed in detail.
19. Superfluidity versus Bloch oscillations in confined atomic gases.
Science.gov (United States)
Büchler, H P; Geshkenbein, V B; Blatter, G
2001-09-01
We study the superfluid properties of (quasi) one-dimensional bosonic atom gases/liquids in traps with finite geometries in the presence of strong quantum fluctuations. Driving the condensate with a moving defect we find the nucleation rate for phase slips using instanton techniques. While phase slips are quenched in a ring resulting in a superfluid response, they proliferate in a tube geometry where we find Bloch oscillations in the chemical potential. These Bloch oscillations describe the individual tunneling of atoms through the defect and thus are a consequence of particle quantization.
20. Thermoelectric transport and Peltier cooling of cold atomic gases
Science.gov (United States)
Grenier, Charles; Kollath, Corinna; Georges, Antoine
2016-12-01
This brief review presents the emerging field of mesoscopic physics with cold atoms, with an emphasis on thermal and 'thermoelectric' transport, i.e. coupled transport of particles and entropy. We review in particular the comparison between theoretically predicted and experimentally observed thermoelectric effects in such systems. We also show how combining well-designed transport properties and evaporative cooling leads to an equivalent of the Peltier effect with cold atoms, which can be used as a new cooling procedure with improved cooling power and efficiency compared to the evaporative cooling currently used in atomic gases. This could lead to a new generation of experiments probing strong correlation effects of ultracold fermionic atoms at low temperatures. xml:lang="fr"
1. Controlling Rydberg atom excitations in dense background gases
CERN Document Server
Liebisch, Tara Cubel; Engel, Felix; Nguyen, Huan; Balewski, Jonathan; Lochead, Graham; Böttcher, Fabian; Westphal, Karl M; Kleinbach, Kathrin S; Schmid, Thomas; Gaj, Anita; Löw, Robert; Hofferberth, Sebastian; Pfau, Tilman; Pérez-Ríos, Jesús; Greene, Chris H
2016-01-01
We discuss the density shift and broadening of Rydberg spectra measured in cold, dense atom clouds in the context of Rydberg atom spectroscopy done at room temperature, dating back to the experiments of Amaldi and Segr\\e in 1934. We discuss the theory first developed in 1934 by Fermi to model the mean-field density shift and subsequent developments of the theoretical understanding since then. In particular, we present a model whereby the density shift is calculated using a microscopic model in which the configurations of the perturber atoms within the Rydberg orbit are considered. We present spectroscopic measurements of a Rydberg atom, taken in a Bose-Einstein condensate (BEC) and thermal clouds with densities varying from $5\\times10^{14}\\textrm{cm}^{-3}$ to $9\\times10^{12}\\textrm{cm}^{-3}$. The density shift measured via the spectrum's center of gravity is compared with the mean-field energy shift expected for the effective atom cloud density determined via a time of flight image. Lastly, we present calcul...
2. Quantum Control nd Measurement of Spins in Cold Atomic Gases
Science.gov (United States)
Deutsch, Ivan
2014-03-01
Spins are natural carriers of quantum information given their long coherence time and our ability to precisely control and measure them with magneto-optical fields. Spins in cold atomic gases provide a pristine environment for such quantum control and measurement, and thus this system can act as a test-bed for the development of quantum simulators. I will discuss the progress my group has made in collaboration with Prof. Jessen, University of Arizona, to develop the toolbox for this test-bed. Through its interactions with rf and microwave magnetic fields, whose waveforms are designed through optimal control techniques, we can implement arbitrary unitary control on the internal hyperfine spins of cesium atoms, a 16 dimensional Hilbert space (isomorphic to 4 qubits). Control of the collective spin of the ensemble of many atoms is performed via the mutual coupling of the atomic ensemble to a mode of the electromagnetic field that acts as a quantum data bus for entangling atoms with one another. Internal spin control can be used to enhance the entangling power of the atom-photon interface. Finally, both projective and weak-continuous measurements can be performed to tomograhically reconstruct quantum states and processes.
3. Atom-molecule equilibration in a degenerate Fermi gas with resonant interactions
DEFF Research Database (Denmark)
Williams, J. E.; Nikuni, T.; Nygaard, Nicolai;
2004-01-01
We present a nonequilibrium kinetic theory describing atom-molecule population dynamics in a two-component Fermi gas with a Feshbach resonance. Key collision integrals emerge that govern the relaxation of the atom-molecule mixture to chemical and thermal equilibrium. Our focus is on the pseudogap...
4. Generalized BEC and crossover theories of superconductors and ultracold Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Grether, M. [Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510 México DF (Mexico); Llano, M. de, E-mail: [email protected] [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo. Postal 70-360, 04510 México DF (Mexico)
2013-10-15
Highlights: • A generalized BEC (GBEC) formalism of superconductivity is discussed. • GBEC includes BCS and BEC as special cases, as well as the Friedberg-T.D. Lee model. • It leads to substantial enhancements in critical superconducting temperatures. • In ultracold boson or fermion gases divergent scattering lengths are dealt with. -- Abstract: The generalized Bose–Einstein condensation (GBEC) formalism of superconductivity hinges on three separate new ingredients: (a) treatment of Cooper pairs as real bosons, (b) inclusion of two-hole pairs on an equal footing with two-electron ones, and (c) inclusion in the resulting ternary ideal boson–fermion gas of boson–fermion vertex interactions that drive formation/disin-tegration processes. Besides subsuming both BCS and BEC theories as well as the well-known crossover picture as special cases, GBEC leads to several-order-of-magnitude enhancement in the critical superconducting temperature T{sub c}. The crossover picture is applicable also to ultracold atomic clouds, both bosonic and fermionic. But low-density expansions involving the interatomic scattering length a diverge term-by-term around the so-called unitary zone about the Feshbach resonance. However, expanding a in powers of the attractive part of the interatomic potential renders smooth, divergence-free low-density expansions.
5. Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases
Directory of Open Access Journals (Sweden)
Antonello Sindona
2015-03-01
Full Text Available The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.
6. Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases.
Science.gov (United States)
Sindona, Antonello; Pisarra, Michele; Gravina, Mario; Vacacela Gomez, Cristian; Riccardi, Pierfrancesco; Falcone, Giovanni; Plastina, Francesco
2015-01-01
The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.
7. Modeling Strongly Correlated Fermi Systems Using Ultra-Cold Atoms
Science.gov (United States)
2008-06-28
exceeds the optical scattering rate Γsc). For the lattice described above, the Lamb Dicke parameter ER/hν = 0.12 and the festina lente criterion Γsc...zero entropy ). Initialization of the quantum register for quantum computations requires a gas of neutral atoms in a near-zero- entropy state...zero- entropy state is prepared by selectively removing atoms in the second band from the lattice potential. optical lattice experiments have
8. Probing superfluid properties in strongly correlated Fermi gases with high spatial resolution
Energy Technology Data Exchange (ETDEWEB)
Weimer, Wolf
2014-07-01
In this thesis an apparatus to study ultracold fermionic {sup 6}Li with tunable interaction strength and dimensionality is presented. The apparatus is applied to investigate the speed of sound v{sub s} and the superfluid critical velocity v{sub c} across the transition from Bose-Einstein condensation (BEC) to Bardeen-Cooper-Schrieffer (BCS) superfluidity. The results set benchmarks for theories describing strongly correlated systems. To measure v{sub c}, an obstacle, that is formed by a tightly focused laser beam, is moved through a superfluid sample with a constant velocity along a line of constant density. For velocities larger than v{sub c} heating of the gas is observed. The critical velocity is mapped out for various different interaction strengths covering the BEC-BCS crossover. According to the Landau criterion and Bogolyubov theory, v{sub c} should be closely related to v{sub s} in a Bose-Einstein condensate. The measurement of v{sub s} is conducted by creating a density modulation in the centre of the cloud and tracking the excited modulation. The velocities v{sub s} and v{sub c} are measured in a similar range of interaction strengths and in similar samples to ensure comparability. The apparatus which provides the ultracold samples is a two chamber design with a magneto-optical trap that is loaded via a Zeeman slower. The subsequent cooling steps are all-optical and finally create an ultracold oblate atom cloud inside a flat vacuum cell. This cell provides optimal optical access and is placed between two high numerical aperture microscope objectives. These objectives are used to probe the samples in-situ on length scales which are comparable to the intrinsic length scales of the gases. Similarly, optical dipole potentials are employed to manipulate the clouds on the same small length scales. The oblate samples are sufficiently flat such that there spatial extent along the microscope axes is smaller than the depth of field of the objectives. With an
9. Bose-Einstein condensation in dilute atomic gases
Science.gov (United States)
Arlt, J.; Bongs, K.; Sengstock, K.; Ertmer, W.
2002-02-01
Bose-Einstein condensation is one of the most curious and fascinating phenomena in physics. It lies at the heart of such intriguing processes as superfluidity and superconductivity. However, in most cases, only a small part of the sample is Bose-condensed and strong interactions are present. A weakly interacting, pure Bose-Einstein condensate (BEC) has therefore been called the "holy grail of atomic physics". In 1995 this grail was found by producing almost pure BECs in dilute atomic gases. We review the experimental development that led to the realization of BEC in these systems and explain how BECs are now routinely produced in about 25 laboratories worldwide. The tremendous experimental progress of the past few years is outlined and a number of recent experiments show the current status of the field. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-001-0277-8.
10. In-medium bound-state formation and inhomogeneous condensation in Fermi gases in a hard-wall box
CERN Document Server
Roscher, Dietrich
2016-01-01
The formation of bosonic bound states underlies the formation of a superfluid ground state in the many-body phase diagram of ultracold Fermi gases. We study bound-state formation in a spin- and mass-imbalanced ultracold Fermi gas confined in a box with hard-wall boundary conditions. Because of the presence of finite Fermi spheres, the center-of-mass momentum of the potentially formed bound states can be finite, depending on the parameters controlling mass and spin imbalance as well as the coupling strength. We exploit this observation to estimate the potential location of inhomogeneous phases in the many-body phase diagram as a function of spin- and mass imbalance as well as the box size. Our results suggest that a hard-wall box does not alter substantially the many-body phase diagram calculated in the thermodynamic limit. Therefore, such a box may serve as an ideal trap potential to bring experiment and theory closely together and facilitate the search for exotic inhomogeneous ground states.
11. Synthetic Lorentz force in classical atomic gases via Doppler effect and radiation pressure
CERN Document Server
Dubček, T; Jukić, D; Aumiler, D; Ban, T; Buljan, H
2014-01-01
We theoretically predict a novel type of synthetic Lorentz force for classical (cold) atomic gases, which is based on the Doppler effect and radiation pressure. A fairly uniform and strong force can be constructed for gases in macroscopic volumes of several cubic millimeters and more. This opens the possibility to mimic classical charged gases in magnetic fields, such as those in a tokamak, in cold atom experiments.
12. Observation of repulsive Fermi polarons in a resonant mixture of ultracold ${}^6$Li atoms
CERN Document Server
Scazza, F; Massignan, P; Recati, A; Amico, A; Burchianti, A; Fort, C; Inguscio, M; Zaccanti, M; Roati, G
2016-01-01
We employ radio-frequency spectroscopy to investigate a polarized spin-mixture of ultracold ${}^6$Li atoms close to a broad Feshbach scattering resonance. Focusing on the regime of strong repulsive interactions, we observe well-defined coherent quasiparticles even for unitarity-limited interactions. We characterize the many-body system by extracting the key properties of repulsive Fermi polarons: the energy $E_+$, the effective mass $m^*$, the residue $Z$ and the decay rate $\\Gamma$. Above a critical interaction, $E_+$ is found to exceed the Fermi energy of the bath while $m^*$ diverges and even turns negative. Such findings reveal that the paramagnetic Fermi liquid state becomes thermodynamically unstable towards an energetically favored ferromagnetic phase.
13. High-temperature atomic superfluidity in lattice Bose-Fermi mixtures.
Science.gov (United States)
Illuminati, Fabrizio; Albus, Alexander
2004-08-27
We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always attractive if the boson-boson on-site interaction is repulsive, and predict the existence of an enhanced BEC-BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion repulsion, the induced attraction can give rise to superfluidity via s-wave pairing at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions.
14. A Proposal for measuring Anisotropic Shear Viscosity in Unitary Fermi Gases
CERN Document Server
Samanta, Rickmoy; Trivedi, Sandip P
2016-01-01
We present a proposal to measure anisotropic shear viscosity in a strongly interacting, ultra-cold, unitary Fermi gas confined in a harmonic trap. We introduce anisotropy in this setup by strongly confining the gas in one of the directions with relatively weak confinement in the remaining directions. This system has a close resemblance to anisotropic strongly coupled field theories studied recently in the context of gauge-gravity duality. Computations in such theories (which have gravity duals) revealed that some of the viscosity components of the anisotropic shear viscosity tensor can be made much smaller than the entropy density, thus parametrically violating the bound proposed by Kovtun, Son and Starinets (KSS): $\\frac {\\eta} {s} \\geq \\frac{1}{4 \\pi}$. A Boltzmann analysis performed in a system of weakly interacting particles in a linear potential also shows that components of the viscosity tensor can be reduced. Motivated by these exciting results, we propose two hydrodynamic modes in the unitary Fermi ga...
15. Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model
DEFF Research Database (Denmark)
Özen, C.; Zinner, Nikolaj Thomas
2014-01-01
of the external potential becomes important. A system of two-species fermionic cold atoms with an attractive zero-range interaction is analogous to a simple model of nucleus in which neutrons and protons interact only through a residual pairing interaction. In this article, we discuss how the problem of a two......-component atomic fermi gas in a tight external trap can be mapped to the nuclear shell model so that readily available many-body techniques in nuclear physics, such as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the study of these systems. We demonstrate an application of the SMMC method...
16. The contact in the BCS–BEC crossover for finite range interacting ultracold Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Caballero-Benítez, Santiago F., E-mail: [email protected]; Paredes, Rosario; Romero-Rochín, Víctor
2013-10-15
Using mean-field theory for the Bardeen–Cooper–Schriefer (BCS) to the Bose–Einstein condensate (BEC) crossover we investigate the ground state thermodynamic properties of an interacting homogeneous Fermi gas. The interatomic interactions modelled through a finite range potential allows us to calculate the thermodynamic behaviour as a function of the potential parameters in the whole crossover region. We concentrate in studying the Contact variable, the thermodynamic conjugate of the inverse of the s-wave scattering length. Our analysis leads to predict a quantum phase transition – like in the case of large potential range. This finding is a direct consequence of the k-dependent energy gap.
17. Ionization of Atoms and the Thomas-Fermi Model for the Electric Field in Crystal Planar Channels
Institute of Scientific and Technical Information of China (English)
LIU Ying-Tai; ZHANG Qi-Ren; GAO Chun-Yuan
2002-01-01
The electric field in the crystal planar channels is studied by the Thomas Fermi method. The Thomas-Fermi equation and the corresponding boundary conditions are derived for the crystal planar channels. The numericalsolution for the electric field in the channels between (110) planes of the single crystal silicon and the critical angles ofchannelling protons in them are shown. Reasonable agreements with the experimental data are obtained. The resultsshow that the Thomas-Fermi method for the crystal works well in this study, and a microscopic research of the channelelectric field with the contribution of all atoms and the atomic ionization being taken into account is practical.
18. Bilayer honeycomb lattice with ultracold atoms: Multiple Fermi surfaces and incommensurate spin density wave instability
Science.gov (United States)
Dey, Santanu; Sensarma, Rajdeep
2016-12-01
We propose an experimental setup using ultracold atoms to implement a bilayer honeycomb lattice with Bernal stacking. In the presence of a potential bias between the layers and at low densities, fermions placed in this lattice form an annular Fermi sea. The presence of two Fermi surfaces leads to interesting patterns in Friedel oscillations and RKKY interactions in the presence of impurities. Furthermore, a repulsive fermion-fermion interaction leads to a Stoner instability towards an incommensurate spin density wave order with a wave vector equal to the thickness of the Fermi sea. The instability occurs at a critical interaction strength which goes down with the density of the fermions. We find that the instability survives interaction renormalization due to vertex corrections and discuss how this can be seen in experiments. We also track the renormalization group flows of the different couplings between the fermionic degrees of freedom, and find that there are no perturbative instabilities, and that Stoner instability is the strongest instability which occurs at a critical threshold value of the interaction. The critical interaction goes to zero as the chemical potential is tuned towards the band bottom.
19. Quantum Degenerate Fermi-Bose Mixtures of 40K and 87Rb Atoms in a Quadrupole-Ioffe Configuration Trap
Institute of Scientific and Technical Information of China (English)
XIONG De-Zhi; CHEN Hai-Xia; WANG Peng-Jun; YU Xu-Dong; GAO Feng; ZHANG Jing
2008-01-01
@@ We report on the attainment of quantum degeneracy of 40K by means of efficient thermal collisions with the evaporatively cooled 87Rb atoms.In a quadrupole-Ioffe configuration trap,potassium atoms are cooled to 0.5 times the Fermi temperature.We obtain up to 7.59 × 105 degenerate fermions 40K.
20. Quantum measurement-induced antiferromagnetic order and density modulations in ultracold Fermi gases in optical lattices
Science.gov (United States)
Mazzucchi, Gabriel; Caballero-Benitez, Santiago F.; Mekhov, Igor B.
2016-08-01
Ultracold atomic systems offer a unique tool for understanding behavior of matter in the quantum degenerate regime, promising studies of a vast range of phenomena covering many disciplines from condensed matter to quantum information and particle physics. Coupling these systems to quantized light fields opens further possibilities of observing delicate effects typical of quantum optics in the context of strongly correlated systems. Measurement backaction is one of the most funda- mental manifestations of quantum mechanics and it is at the core of many famous quantum optics experiments. Here we show that quantum backaction of weak measurement can be used for tailoring long-range correlations of ultracold fermions, realizing quantum states with spatial modulations of the density and magnetization, thus overcoming usual requirement for a strong interatomic interactions. We propose detection schemes for implementing antiferromagnetic states and density waves. We demonstrate that such long-range correlations cannot be realized with local addressing, and they are a consequence of the competition between global but spatially structured backaction of weak quantum measurement and unitary dynamics of fermions.
1. Quantum measurement-induced antiferromagnetic order and density modulations in ultracold Fermi gases in optical lattices.
Science.gov (United States)
Mazzucchi, Gabriel; Caballero-Benitez, Santiago F; Mekhov, Igor B
2016-08-11
Ultracold atomic systems offer a unique tool for understanding behavior of matter in the quantum degenerate regime, promising studies of a vast range of phenomena covering many disciplines from condensed matter to quantum information and particle physics. Coupling these systems to quantized light fields opens further possibilities of observing delicate effects typical of quantum optics in the context of strongly correlated systems. Measurement backaction is one of the most funda- mental manifestations of quantum mechanics and it is at the core of many famous quantum optics experiments. Here we show that quantum backaction of weak measurement can be used for tailoring long-range correlations of ultracold fermions, realizing quantum states with spatial modulations of the density and magnetization, thus overcoming usual requirement for a strong interatomic interactions. We propose detection schemes for implementing antiferromagnetic states and density waves. We demonstrate that such long-range correlations cannot be realized with local addressing, and they are a consequence of the competition between global but spatially structured backaction of weak quantum measurement and unitary dynamics of fermions.
2. Atom chip apparatus for experiments with ultracold rubidium and potassium gases
Energy Technology Data Exchange (ETDEWEB)
Ivory, M. K.; Ziltz, A. R.; Fancher, C. T.; Pyle, A. J.; Sensharma, A.; Chase, B.; Field, J. P.; Garcia, A.; Aubin, S., E-mail: [email protected] [Department of Physics, College of William and Mary, Williamsburg, Virginia 23187 (United States); Jervis, D. [Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7 (Canada)
2014-04-15
We present a dual chamber atom chip apparatus for generating ultracold {sup 87}Rb and {sup 39}K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10{sup 4} {sup 87}Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold {sup 39}K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the laser cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.
3. Atom chip apparatus for experiments with ultracold rubidium and potassium gases.
Science.gov (United States)
Ivory, M K; Ziltz, A R; Fancher, C T; Pyle, A J; Sensharma, A; Chase, B; Field, J P; Garcia, A; Jervis, D; Aubin, S
2014-04-01
We present a dual chamber atom chip apparatus for generating ultracold (87)Rb and (39)K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10(4) (87)Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold (39)K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the laser cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.
4. Comparing and contrasting nuclei and cold atomic gases
DEFF Research Database (Denmark)
Zinner, Nikolaj Thomas; Jensen, Aksel Stenholm
2013-01-01
, interactions, and relevant length and energy scales of cold atoms and nuclei. Next we address some attempts in nuclear physics to transfer the concepts of condensates in nuclei that can in principle be built from bosonic alpha-particle constituents. We also consider Efimov physics, a prime example of nuclear...
5. Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment
Science.gov (United States)
Williams, Jason; D'Incao, Jose; Chiow, Sheng-Wey; Yu, Nan
2015-05-01
Precision atom interferometers (AI) in space promise exciting technical capabilities for fundamental physics research, with proposals including unprecedented tests of the weak equivalence principle, precision measurements of the fine structure and gravitational constants, and detection of gravity waves and dark energy. Consequently, multiple AI-based missions have been proposed to NASA, including a dual-atomic-species interferometer that is to be integrated into the Cold Atom Laboratory (CAL) onboard the International Space Station. In this talk, I will discuss our plans and preparation at JPL for the proposed flight experiments to use the CAL facility to study the leading-order systematics expected to corrupt future high-precision measurements of fundamental physics with AIs in microgravity. The project centers on the physics of pairwise interactions and molecular dynamics in these quantum systems as a means to overcome uncontrolled shifts associated with the gravity gradient and few-particle collisions. We will further utilize the CAL AI for proof-of-principle tests of systematic mitigation and phase-readout techniques for use in the next-generation of precision metrology experiments based on AIs in microgravity. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
6. Evidence for ferromagnetic instability in a repulsive Fermi gas of ultracold atoms
CERN Document Server
Valtolina, G; Amico, A; Burchianti, A; Recati, A; Enss, T; Inguscio, M; Zaccanti, M; Roati, G
2016-01-01
Ferromagnetism is among the most spectacular manifestations of interactions within many-body fermion systems. In contrast to weak-coupling phenomena, it requires strong repulsion to develop, making a quantitative description of ferromagnetic materials notoriously difficult. This is especially true for itinerant ferromagnets, where magnetic moments are not localized into a crystal lattice. In particular, it is still debated whether the simplest case envisioned by Stoner of a homogeneous Fermi gas with short-range repulsive interactions can exhibit ferromagnetism at all. In this work, we positively answer this question by studying a clean model system consisting of a binary spin-mixture of ultracold 6Li atoms, whose repulsive interaction is tuned via a Feshbach resonance. We drastically limit detrimental pairing effects that affected previous studies by preparing the gas in a magnetic domain-wall configuration. We reveal the ferromagnetic instability by observing the softening of the spin-dipole collective mode...
7. Ionization of Atoms and the Thomas－Fermi Model for the Electric Field in Crystal Planar Channels
Institute of Scientific and Technical Information of China (English)
LIUYing－Tai; ZHANGQi－Ren; 等
2002-01-01
The electric field in the crystal planar channels is studied by the Thomas-Fermi method.The ThomasFermi equation and the corresponding boundary conditions are derived for the crystal palanar channels,The numerical solution for the elctric field in the channels between(110) Planes of the single crystal silicaon and the critical angles of channelling protons in them are shown.Reasonable agreements with the experimental data are obtained.The results show that the Thomas-Fermi method for the crystal works well in this study,and a microscopic research of the channel electric field with the contribution of all atoms and the atomic ionization being taken into account is practical.
8. An effective field theory analysis of Efimov features in heteronuclear mixture of ultracold atomic gases
Science.gov (United States)
Acharya, Bijaya; Ji, Chen; Platter, Lucas
2016-05-01
Recent experimental studies have unveiled Efimov physics in ultracold atomic gases of heteronuclear mixtures. The recombination features of such atomic systems display universal correlations including discrete scaling invariance. We use Effective Field Theory (EFT) to study the Efimov features of the heteronuclear three-atom systems consisting of two identical bosons which interact with each other through a natural scattering length and with the third particle through a large scattering length. We compute the corrections to the universal correlations by perturbative insertions of the interspecies effective range and the intraspecies scattering length. Such an analysis is relevant for mixtures of ultracold atomic gases near the interspecies Feshbach resonance. Supported by the US Department of Energy under Contract No. DE-AC05-00OR22725 and the National Science Foundation under Grant No. PHY-1516077.
9. Critical Dynamics in Quenched 2D Atomic Gases
Science.gov (United States)
Larcher, F.; Dalfovo, F.; Proukakis, N. P.
2016-05-01
Non-equilibrium dynamics across phase transitions is a subject of intense investigations in diverse physical systems. One of the key issues concerns the validity of the Kibble-Zurek (KZ) scaling law for spontaneous defect creation. The KZ mechanism has been recently studied in cold atoms experiments. Interesting open questions arise in the case of 2D systems, due to the distinct nature of the Berezinskii-Kosterlitz-Thouless (BKT) transition. Our studies rely on the stochastic Gross-Pitaevskii equation. We perform systematic numerical simulations of the spontaneous emergence and subsequent dynamics of vortices in a uniform 2D Bose gas, which is quenched across the BKT phase transition in a controlled manner, focusing on dynamical scaling and KZ-type effects. By varying the transverse confinement, we also look at the extent to which such features can be seen in current experiments. Financial support from EPSRC and Provincia Autonoma di Trento.
10. State-specific transport properties of partially ionized flows of electronically excited atomic gases
Science.gov (United States)
Istomin, V. A.; Kustova, E. V.
2017-03-01
State-to-state approach for theoretical study of transport properties in atomic gases with excited electronic degrees of freedom of both neutral and ionized species is developed. The dependence of atomic radius on the electronic configuration of excited atoms is taken into account in the transport algorithm. Different cutoff criteria for increasing atomic radius are discussed and the limits of applicability for these criteria are evaluated. The validity of a Slater-like model for the calculation of state-resolved transport coefficients in neutral and ionized atomic gases is shown. For ionized flows, a method of evaluation for effective cross-sections of resonant charge-transfer collisions is suggested. Accurate kinetic theory algorithms for modelling the state-specific transport properties are applied for the prediction of transport coefficients in shock heated flows. Based on the numerical observations, different distributions over electronic states behind the shock front are considered. For the Boltzmann-like distributions at temperatures greater than 14,000 K, an important effect of electronic excitation on the partial thermal conductivity and viscosity coefficients is found for both neutral and ionized atomic gases: increasing radius of excited atoms causes a strong decrease in these transport coefficients. Similarly, the presence of electronically excited states with increased atomic radii leads to reduced diffusion coefficients. Nevertheless the overall impact of increasing effective cross-sections on the transport properties just behind the shock front under hypersonic reentry conditions is found to be minor since the populations of high-lying electronic energy levels behind the shock waves are low.
11. Coexistence of photonic and atomic Bose-Einstein condensates in ideal atomic gases
Directory of Open Access Journals (Sweden)
N. Boichenko
2015-12-01
Full Text Available We have studied conditions of photon Bose-Einstein condensate formation that is in thermodynamic equilibrium with ideal gas of two-level Bose atoms below the degeneracy temperature. Equations describing thermodynamic equilibrium in the system were formulated; critical temperatures and densities of photonic and atomic gas subsystems were obtained analytically. Coexistence conditions of these photonic and atomic Bose-Einstein condensates were found. There was predicted the possibility of an abrupt type of photon condensation in the presence of Bose condensate of ground-state atoms: it was shown that the slightest decrease of the temperature could cause a significant gathering of photons in the condensate. This case could be treated as a simple model of the situation known as "stopped light" in cold atomic gas. We also showed how population inversion of atomic levels can be created by lowering the temperature. The latter situation looks promising for light accumulation in atomic vapor at very low temperatures.
12. Fermi and Coulomb correlation effects upon the interacting quantum atoms energy partition
CERN Document Server
Ruiz, Isela; Holguín-Gallego, Fernando José; Francisco, Evelio; Pendás, Ángel Martín; Rocha-Rinza, Tomás
2016-01-01
The Interacting Quantum Atoms (IQA) electronic energy partition is an important method in the field of quantum chemical topology which has given important insights of different systems and processes in physical chemistry. There have been several attempts to include Electron Correlation (EC) in the IQA approach, for example, through DFT and Hartree-Fock/Coupled-Cluster (HF/CC) transition densities. This work addresses the separation of EC in Fermi and Coulomb correlation and its effect upon the IQA analysis by taking into account spin-dependent one- and two-electron matrices $D^{\\mathrm{HF/CC}}_{p\\sigma q \\sigma}$ and $d^{\\mathrm{HF/CC}}_{p\\sigma q\\sigma r\\tau s\\tau}$ wherein $\\sigma$ and $\\tau$ represent either of the $\\alpha$ and $\\beta$ spin projections. We illustrate this approach by considering BeH$_2$,BH, CN$^-$, HF, LiF, NO$^+$, LiH, H$_2$O$\\cdots$H$_2$O and C$_2$H$_2$, which comprise non-polar covalent, polar covalent, ionic and hydrogen bonded systems. The same and different spin contributions to ($i$...
13. Nonlinear pressure shifts of alkali-metal atoms in inert gases.
Science.gov (United States)
Gong, F; Jau, Y-Y; Happer, W
2008-06-13
Precise measurements show that the microwave resonance frequencies of ground-state Rb or Cs atoms have a nonlinear dependence on the pressure of the buffer gases Ar and Kr. No nonlinearities were observed in the gases He or N(2). These observations strongly suggest that the nonlinearities are due to the van der Waals molecules that form in Ar and Kr, but not in He or N(2). The nonlinear part of the shifts is largest in the pressure range of a few tens of torr, similar to the operating pressures of gas-cell atomic clocks. The observed shifts are very well described by a simple function, parametrized by the effective three-body formation rate of molecules and by the effective product of the collisionally limited lifetime times the shift of the hyperfine coupling coefficient in the molecule.
14. Fundamental Interactions for Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment
Science.gov (United States)
D'Incao, Jose P.; Willians, Jason R.
2015-05-01
Precision atom interferometers (AI) in space are a key element for several applications of interest to NASA. Our proposal for participating in the Cold Atom Laboratory (CAL) onboard the International Space Station is dedicated to mitigating the leading-order systematics expected to corrupt future high-precision AI-based measurements of fundamental physics in microgravity. One important focus of our proposal is to enhance initial state preparation for dual-species AIs. Our proposed filtering scheme uses Feshbach molecular states to create highly correlated mixtures of heteronuclear atomic gases in both their position and momentum distributions. We will detail our filtering scheme along with the main factors that determine its efficiency. We also show that the atomic and molecular heating and loss rates can be mitigated at the unique temperature and density regimes accessible on CAL. This research is supported by the National Aeronautics and Space Administration.
15. Measuring laser carrier-envelope phase effects in the noble gases with an atomic hydrogen calibration standard
CERN Document Server
Khurmi, Champak; U, Satya Sainadh; Ivanov, I A; Kheifets, A S; Tong, X M; Litvinyuk, I V; Sang, R T; Kielpinski, D
2016-01-01
We present accurate measurements of carrier-envelope phase effects on ionisation of the noble gases with few-cycle laser pulses. The experimental apparatus is calibrated by using atomic hydrogen data to remove any systematic offsets and thereby obtain accurate CEP data on other generally used noble gases such as Ar, Kr and Xe. Experimental results for H are well supported by exact TDSE theoretical simulations however significant differences are observed in case of noble gases.
16. Critical temperature of Bose-Einstein condensation in trapped atomic Bose-Fermi mixtures
Energy Technology Data Exchange (ETDEWEB)
Albus, A P [Institut fuer Physik, Universitaet Potsdam, D-14469 Potsdam (Germany); Giorgini, S [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy); Illuminati, F [Dipartimento di Fisica, Universita di Salerno, and Istituto Nazionale per la Fisica della Materia, I-84081 Baronissi (Italy); Viverit, L [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy)
2002-12-14
We calculate the shift in the critical temperature of Bose-Einstein condensation for a dilute Bose-Fermi mixture confined by a harmonic potential, to lowest order in both the Bose-Bose and Bose-Fermi coupling constants. The relative importance of the effect on the critical temperature of the boson-boson and boson-fermion interactions is investigated as a function of the parameters of the mixture. The possible relevance of the shift of the transition temperature in current experiments on trapped Bose-Fermi mixtures is discussed. (letter to the editor)
17. Observation of Multibubble Sonoluminescence from Water Saturated with Various Gases during Ultrasonic Atomization
Science.gov (United States)
Harada, Hisashi; Iwata, Naohiro; Shiratori, Keisuke
2009-07-01
Multibubble sonoluminescence (MBSL) from water saturated with various atmospheric gases was observed using an ultrasonic atomizer (2.4 MHz). The majority of sonoluminescence (SL) in the system did not originate from capillary waves but from acoustic cavitation. The dependence of MBSL intensity on the type of dissolved gas was confirmed. Atomization occurred similarly in all cases. The intensities for the dissolved gases were in the following order: Ar > Air > O2 > N2 ≫He, H2, CO2. The intensity for water saturated with air is higher than those for the O2- and N2-saturated solutions. To examine the effect of gas mixing, MBSL was measured for various ratios of O2 to N2. The maximum intensity was obtained at 40% O2/60% N2. In the regions above and below this ratio, the intensity decreased gradually. To explain this result, the possibilities of Ar rectification and chemical reactions between O2 and N2 gases were also discussed. After examination, it could not be confirmed that Ar rectification occurred. Chemical reactions of O2 with N2 proceed inside the cavitation bubble.
18. Atomic capture and transfer of negative pions stopped in binary mixtures of hydrogen with polyatomic gases
Energy Technology Data Exchange (ETDEWEB)
Vasilyev, V.A.; Levay, B.; Minkova, A.; Petrukhin, V.I.; Horvath, D.
1985-12-01
The atomic capture and transfer of stopped negative pions have been studied in binary gas mixtures of H/sub 2/+M, where M is CCl/sub 2/F/sub 2/, CClF/sub 3/, CBrF/sub 3/ or SF/sub 6/. The ..pi../sup 0/ yield, versus relative atomic concentration Csub(A) of M, goes through a maximum at Csub(A)proportional0.1 and levels off at zero at high concentrations. This phenomenon together with other observed characteristics of the atomic capture and transfer of pions in these systems is interpreted in the frame of a phenomenological model. The average transfer coefficients anti ..lambda..sub(Z) exhibit a weak concentration dependence. The estimated average atomic capture ratios anti A(Z/H) are lower than those found for noble gases, probably because of the mutual screening of the constituent atoms in the molecules. The probability of pion capture in an atomic orbit is not proportional to the stopping power of the components of the mixture. (orig.).
19. Self-Channeling of High-Power Long-Wave Infrared Pulses in Atomic Gases
Science.gov (United States)
Schuh, K.; Kolesik, M.; Wright, E. M.; Moloney, J. V.; Koch, S. W.
2017-02-01
We simulate and elucidate the self-channeling of high-power 10 μ m infrared pulses in atomic gases. The major new result is that the peak intensity can remain remarkably stable over many Rayleigh ranges. This arises from the balance between the self-focusing, diffraction, and defocusing caused by the excitation induced dephasing due to many-body Coulomb effects that enhance the low-intensity plasma densities. This new paradigm removes the Rayleigh range limit for sources in the 8 - 12 μ m atmospheric transmission window and enables transport of individual multi-TW pulses over multiple kilometer ranges.
20. Information and backaction due to phase contrast imaging measurements of cold atomic gases: beyond Gaussian states
CERN Document Server
Ilo-Okeke, Ebubechukwu O
2016-01-01
We further examine a theory of phase contrast imaging (PCI) of cold atomic gases, first introduced by us in Phys. Rev. Lett. {\\bf 112}, 233602 (2014). We model the PCI measurement by directly calculating the entangled state between the light and the atoms due to the ac Stark shift, which induces a conditional phase shift on the light depending upon the atomic state. By interfering the light that passes through the BEC with the original light, one can obtain information of the atomic state at a single shot level. We derive an exact expression for a measurement operator that embodies the information obtained from PCI, as well as the back-action on the atomic state. By the use of exact expressions for the measurement process, we go beyond the continuous variables approximation such that the non-Gaussian regime can be accessed for both the measured state and the post-measurement state. Features such as the photon probability density, signal, signal variance, Fisher information, error of the measurement, and the b...
1. Quantum-Shell Corrections to the Finite-Temperature Thomas-Fermi-Dirac Statistical Model of the Atom
Energy Technology Data Exchange (ETDEWEB)
Ritchie, A B
2003-07-22
Quantum-shell corrections are made directly to the finite-temperature Thomas-Fermi-Dirac statistical model of the atom by a partition of the electronic density into bound and free components. The bound component is calculated using analytic basis functions whose parameters are chosen to minimize the energy. Poisson's equation is solved for the modified density, thereby avoiding the need to solve Schroedinger's equation for a self-consistent field. The shock Hugoniot is calculated for aluminum: shell effects characteristic of quantum self-consistent field models are fully captures by the present model.
2. Phase space methods for degenerate quantum gases
CERN Document Server
Dalton, Bryan J; Barnett, Stephen M
2015-01-01
Recent experimental progress has enabled cold atomic gases to be studied at nano-kelvin temperatures, creating new states of matter where quantum degeneracy occurs - Bose-Einstein condensates and degenerate Fermi gases. Such quantum states are of macroscopic dimensions. This book presents the phase space theory approach for treating the physics of degenerate quantum gases, an approach already widely used in quantum optics. However, degenerate quantum gases involve massive bosonic and fermionic atoms, not massless photons. The book begins with a review of Fock states for systems of identical atoms, where large numbers of atoms occupy the various single particle states or modes. First, separate modes are considered, and here the quantum density operator is represented by a phase space distribution function of phase space variables which replace mode annihilation, creation operators, the dynamical equation for the density operator determines a Fokker-Planck equation for the distribution function, and measurable...
3. Exotic pairing in 1D spin-3/2 atomic gases with SO(4 symmetry
Directory of Open Access Journals (Sweden)
Yuzhu Jiang
2015-06-01
Full Text Available Tuning interactions in the spin singlet and quintet channels of two colliding atoms could change the symmetry of the one-dimensional spin-3/2 fermionic systems of ultracold atoms while preserving the integrability. Here we find a novel SO(4 symmetry integrable point in the spin-3/2 Fermi gas and derive the exact solution of the model using the Bethe ansatz. In contrast to the model with SU(4 and SO(5 symmetries, the present model with SO(4 symmetry preserves spin singlet and quintet Cooper pairs in two sets of SU(2⊗SU(2 spin subspaces. We obtain full phase diagrams, including the Fulde–Ferrel–Larkin–Ovchinnikov like pair correlations, spin excitations and quantum criticality through the generalized Yang–Yang thermodynamic equations. In particular, various correlation functions are calculated by using finite-size corrections in the frame work of conformal field theory. Moreover, within the local density approximation, we further find that spin singlet and quintet pairs form subtle multiple shell structures in density profiles of the trapped gas.
4. Probing the dynamic structure factor of a neutral Fermi superfluid along the BCS-BEC crossover using atomic impurity qubits
Science.gov (United States)
Mitchison, Mark T.; Johnson, Tomi H.; Jaksch, Dieter
2016-12-01
We study an impurity atom trapped by an anharmonic potential, immersed within a cold atomic Fermi gas with attractive interactions that realizes the crossover from a Bardeen-Cooper-Schrieffer superfluid to a Bose-Einstein condensate. Considering the qubit comprising the lowest two vibrational energy eigenstates of the impurity, we demonstrate that its dynamics probes the equilibrium density fluctuations encoded in the dynamic structure factor of the superfluid. Observing the impurity's evolution is thus shown to facilitate nondestructive measurements of the superfluid order parameter and the contact between collective and single-particle excitation spectra. Our setup constitutes a model of an open quantum system interacting with a thermal reservoir, the latter supporting both bosonic and fermionic excitations that are also coupled to each other.
5. Fermi level de-pinning of aluminium contacts to n-type germanium using thin atomic layer deposited layers
Energy Technology Data Exchange (ETDEWEB)
Gajula, D. R., E-mail: [email protected]; Baine, P.; Armstrong, B. M.; McNeill, D. W. [School of Electronics, Electrical Engineering and Computer Science, Queen' s University Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH (United Kingdom); Modreanu, M.; Hurley, P. K. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland)
2014-01-06
Fermi-level pinning of aluminium on n-type germanium (n-Ge) was reduced by insertion of a thin interfacial dielectric by atomic layer deposition. The barrier height for aluminium contacts on n-Ge was reduced from 0.7 eV to a value of 0.28 eV for a thin Al{sub 2}O{sub 3} interfacial layer (∼2.8 nm). For diodes with an Al{sub 2}O{sub 3} interfacial layer, the contact resistance started to increase for layer thicknesses above 2.8 nm. For diodes with a HfO{sub 2} interfacial layer, the barrier height was also reduced but the contact resistance increased dramatically for layer thicknesses above 1.5 nm.
6. Site-selected luminescence of atomic europium in the solid rare gases
Energy Technology Data Exchange (ETDEWEB)
Byrne, Owen; McCaffrey, John G. [Department of Chemistry, National University of Ireland - Maynooth, Maynooth, County Kildare (Ireland)
2011-07-14
Site-selective excitation has been used to simplify complex emission recorded in the visible spectral region for atomic europium isolated in the solid rare gases. In addition to y{sup 8}P resonance fluorescence, excitation of the y{sup 8}P state produces emission from the z{sup 6}P state and the metastable a{sup 10}D state. Very weak emission at 690 nm is tentatively assigned to the J = 9/2 level of the z{sup 10}P state. Eu atoms isolated in the red and blue sites exhibit very different temperature dependence both spectrally and temporally. For the y{sup 8}P state emission the red site atoms exhibit small Stokes shifts and yield radiative lifetimes while the emission from the blue site loses intensity and the temporal profiles shorten dramatically between 10 and 16 K indicating very efficient non-radiative relaxation in this site. An analysis of the Stokes shifts exhibited for the y{sup 8}P state in each site supports the attributions made in a previous publication [O. Byrne and J.G. McCaffrey, J. Chem. Phys. 134, 124501 (2011)] that the smaller blue tetravacancy site has a greater repulsive interaction with the guest. With the exception of the y{sup 8}P state resonance fluorescence, the recorded decay profiles of all the other emissions exhibit multiple components. This behaviour has been attributed to the existence of multiple crystal field levels arising from the splitting of the distinct spin-orbit levels from which emission occurs.
7. Reduction of Fermi level pinning at Au-MoS2 interfaces by atomic passivation on Au surface
Science.gov (United States)
Min, Kyung-Ah; Park, Jinwoo; Wallace, Robert M.; Cho, Kyeongjae; Hong, Suklyun
2017-03-01
Monolayer molybdenum disulfide (MoS2), which is a semiconducting material with direct band gap of ˜1.8 eV, has drawn much attention for application in field effect transistors (FETs). In this connection, it is very important to understand the Fermi level pinning (FLP) which occurs at metal-semiconductor interfaces. It is known that MoS2 has an n-type contact with Au, which is a high work function metal, representing the strong FLP at Au-MoS2 interfaces. However, such FLP can obstruct the attainment of high performance of field effect devices. In this study, we investigate the reduction of FLP at Au-MoS2 interfaces by atomic passivation on Au(111) using first-principles calculations. To reduce the FLP at Au-MoS2 interfaces, we consider sulfur, oxygen, nitrogen, fluorine, and hydrogen atoms that can passivate the surface of Au(111). Calculations show that passivating atoms prevent the direct contact between Au(111) and MoS2, and thus FLP at Au-MoS2 interfaces is reduced by weak interaction between atom-passivated Au(111) and MoS2. Especially, FLP is greatly reduced at sulfur-passivated Au-MoS2 interfaces with the smallest binding energy. Furthermore, fluorine-passivated Au(111) can form ohmic contact with MoS2, representing almost zero Schottky barrier height (SBH). We suggest that SBH can be controlled depending on the passivating atoms on Au(111).
8. Bosonic models with Fermi-liquid kinematics: realizations and properties
Science.gov (United States)
Goldbart, Paul; Gopalakrishnan, Sarang; Lamacraft, Austen
2011-03-01
We consider models of interacting bosons in which the single-particle kinetic energy achieves its minimum on a surface in momentum space. The kinematics of such models resembles that resulting from Pauli blocking in Fermi liquids; therefore, Shankar's renormalization-group treatment of Fermi liquids can be adapted to investigate phase transitions in these bosonic systems. We explore possible experimental realizations of such models in cold atomic gases: e.g., via spin-orbit coupling, multimode-cavity-mediated interactions, and Cooper pairing of Fermi gases in spin-dependent lattices. We address the phase structure and critical behavior of the resulting models within the framework of Ref., focusing in particular on Bose-Einstein condensation and on quantum versions of the Brazovskii transition from a superfluid to a supersolid.
9. Non-Equilbrium Fermi Gases
Science.gov (United States)
2016-02-02
frequencies ) are smaller than the spontaneous emission rate ge. Unfortunately, this method is invalid in the bare basis for broad resonances, where the...classification in accordance with security classification regulations , e.g. U, C, S, etc. If this form contains classified information, stamp classification...show that the EIT method creates narrow features in the scattering phase shift, enabling control by optical frequency rather than intensity, providing
10. Quantum Simulations of Condensed Matter Systems Using Ultra-Cold Atomic Gases
Science.gov (United States)
2013-03-01
Feynman diagrams versus Fermi-‐gas Feynman emulator”, Nature Physics 8, 366...BEC-‐BCS Crossover and the Unitary Fermi Gas”, Lecture Notes in Physics , Volume 836, edited by Wilhelm... Lecture at 100th Anniversary Solvay Conference on Physics , "The Theory of the
11. An interpolatory ansatz captures the physics of one-dimensional confined Fermi systems
DEFF Research Database (Denmark)
Andersen, Molte Emil Strange; Salami Dehkharghani, Amin; Volosniev, A. G.;
2016-01-01
beyond the Bethe ansatz and bosonisation allow us to predict the behaviour of one-dimensional confined systems with strong short-range interactions, and new experiments with cold atomic Fermi gases have already confirmed these theories. Here we demonstrate that a simple linear combination of the strongly...
12. 75 FR 63867 - DTE Energy; Enrico Fermi Atomic Power Plant Unit 1, Exemption From Certain Security Requirements
Science.gov (United States)
2010-10-18
.... Nuclear Regulatory Commission (NRC or the Commission) now or hereafter in effect. Fermi 1 was a fast breeder reactor power plant cooled by sodium and operated at essentially atmospheric pressure. In November... in Monroe County, Michigan. Fermi 1 is a permanently shutdown nuclear reactor facility. The...
13. Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect
KAUST Repository
Efimov, D K
2016-05-18
We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole-dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d, n i, of both atoms. While for symmetric atom pairs with the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive - for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantum-mechanical effect, which points towards existence of optimal (we call them \\'Tom\\' and \\'Jerry\\' for \\'big\\' and \\'small\\') pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom-Jerry pairs with which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom-Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate. © 2016 IOP Publishing Ltd.
14. Metastability and coherence of repulsive polarons in a strongly interacting Fermi mixture
DEFF Research Database (Denmark)
Kohstall, Cristoph; Zaccanti, Mattheo; Jag, Matthias;
2012-01-01
Ultracold Fermi gases with tunable interactions provide a test bed for exploring the many-body physics of strongly interacting quantum systems1, 2, 3, 4. Over the past decade, experiments have investigated many intriguing phenomena, and precise measurements of ground-state properties have provided...... benchmarks for the development of theoretical descriptions. Metastable states in Fermi gases with strong repulsive interactions5, 6, 7, 8, 9, 10, 11 represent an exciting area of development. The realization of such systems is challenging, because a strong repulsive interaction in an atomic quantum gas...... implies the existence of a weakly bound molecular state, which makes the system intrinsically unstable against decay. Here we use radio-frequency spectroscopy to measure the complete excitation spectrum of fermionic 40K impurities resonantly interacting with a Fermi sea of 6Li atoms. In particular, we...
15. FINAL–REPORT NO. 2: INDEPENDENT CONFIRMATORY SURVEY SUMMARY AND RESULTS FOR THE ENRICO FERMI ATOMIC POWER PLANT, UNIT 1, NEWPORT, MICHIGAN (DOCKET NO. 50 16; RFTA 10-004)
Energy Technology Data Exchange (ETDEWEB)
Erika Bailey
2011-07-07
The Enrico Fermi Atomic Power Plant, Unit 1 (Fermi 1) was a fast breeder reactor design that was cooled by sodium and operated at essentially atmospheric pressure. On May 10, 1963, the Atomic Energy Commission (AEC) granted an operating license, DPR-9, to the Power Reactor Development Company (PRDC), a consortium specifically formed to own and operate a nuclear reactor at the Fermi 1 site. The reactor was designed for a maximum capability of 430 megawatts (MW); however, the maximum reactor power with the first core loading (Core A) was 200 MW. The primary system was filled with sodium in December 1960 and criticality was achieved in August 1963.
16. Generation of few-cycle laser pulses:Comparison between atomic and molecular gases in a hollow-core fiber
Institute of Scientific and Technical Information of China (English)
黄志远; 戴晔; 赵睿睿; 王丁; 冷雨欣
2016-01-01
We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber. From the perspective of self-phase modulation (SPM), we give the extensive study of the SPM infl uence on a probe pulse with molecular phase modulation (MPM) effect. By comparing the two compression methods, we summarize their advan-tages and drawbacks to obtain the few-cycle pulses with micro-or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values.
17. Towards Quantum Turbulence in Cold Atomic Fermionic Superfluids
CERN Document Server
Bulgac, Aurel; Wlazłowski, Gabriel
2016-01-01
Fermionic superfluids provide a new realization of quantum turbulence, accessible to both experiment and theory, yet relevant to both cold atoms and nuclear astrophysics. In particular, the strongly interacting Fermi gas realized in cold-atom experiments is closely related to dilute neutron matter in the neutron star crust. Unlike the liquid superfluids 4He (bosons) and 3He (fermions), where quantum turbulence has been studied in laboratory for decades, quantum gases, and in particular superfluid Fermi gases stand apart for a number of reasons. Fermi gases admit a rather reliable microscopic description based on density functional theory which describes both static and dynamical phenomena. Cold atom experiments demonstrate exquisite control over particle number, spin polarization, density, temperature, and interacting strength. Topological defects such as domain walls and quantized vortices, which lie at the heart of quantum turbulence, can be created and manipulated with time-dependent external potentials, a...
18. Computer simulations on resonant fluorescence spectra in atomic gases in two monochromatic laser fields of arbitrary intensity and magnetic field
Science.gov (United States)
Karagodova, Tamara Y.
1996-03-01
In the intense radiation fields with power density from 104W/cm2 to 109W/cm2 the essential modification of electronic states of atoms occurs displaying, in particular, in modifications of resonant fluorescence (rf) spectra. We use 'Fermi golden rule' for calculations of relative intensities and frequencies for rf multiplet for real multilevel initially unexcited atoms in two monochromatic laser fields of arbitrary intensity resonant to adjacent transitions of (Xi) or (Lambda) types and magnetic field, giving the level splittings of different values from Zeeman to Paschen-Back effect. The dependence of quasienergies on parameters obtained with the help of a sorting program permits us to define the values of parameters for which the states of the system are mixed and so to receive the correct probability amplitudes for instantaneous or adiabatic regimes of switching the perturbation. The analysis of the quasienergies and form of rf spectra permits us to get relations between the form of the spectra and modifications of electronic structure of the atom due to radiation fields and external magnetic field.
19. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases
Directory of Open Access Journals (Sweden)
X. H. Liu
2015-10-01
Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.
20. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases
Energy Technology Data Exchange (ETDEWEB)
Liu, X. H.; Luo, H.; Qu, T. L., E-mail: [email protected]; Yang, K. Y.; Ding, Z. C. [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)
2015-10-15
We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.
1. Fermi liquid theory
CERN Document Server
Apostol, M
2001-01-01
sup 3 He liquefies at 3.2 K under normal pressure, where its mean inter-particle separation of a few angstroms, is comparable with the range of the interaction potential (and with the mean inter-particle separation in the corresponding ideal gas); its thermal wavelength is about 8 A, so that, under this conditions, sup 3 He is a quantum liquid of fermions, or a Fermi liquid (sometimes called a normal Fermi liquid too). The motion of the sup 3 He atoms in the (repulsive) self-consistent, meanfield potential is affected by inertial effects, i.e. the particles possess an effective mass, and consequently they obey the Fermi distribution, like an ideal Fermi gas. In this paper the Landau's theory of the Fermi liquid is reviewed. (author)
2. Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
DEFF Research Database (Denmark)
Volosniev, A. G.; Petrosyan, D.; Valiente, M.
2015-01-01
We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...... find that bosonic atoms offer more flexibility for tuning independently the parameters of the spin Hamiltonian through interatomic (intra-species) interaction which is absent for fermions due to the Pauli exclusion principle. Our formalism can have important implications for control and manipulation...
3. Emergence of correlated optics in one-dimensional waveguides for classical and quantum atomic gases
Science.gov (United States)
Ruostekoski, Janne; Javanainen, Juha
2016-09-01
We analyze the emergence of correlated optical phenomena in the transmission of light through a waveguide that confines classical or ultracold quantum degenerate atomic ensembles. The conditions of the correlated collective response are identified in terms of atom density, thermal broadening, and photon losses by using stochastic Monte Carlo simulations and transfer matrix methods of transport theory. We also calculate the "cooperative Lamb shift" for the waveguide transmission resonance, and discuss line shifts that are specific to effectively one-dimensional waveguide systems.
4. Fermi and Szilard
CERN Document Server
Byers, N
2002-01-01
This talk is about Enrico Fermi and Leo Szilard, their collaboration and involvement in nuclear energy development and decisions to construct and use the atomic bomb in World War II. Fermi and Szilard worked closely together at Columbia in 1939-40 to explore feasibility of a nuclear chain reaction, and then on the physics for construction of the first pile (nuclear reactor). "On matters scientific or technical there was rarely any disagreement between Fermi and myself" Szilard said. But there were sharp differences on other matters.
5. Quantum gases finite temperature and non-equilibrium dynamics
CERN Document Server
Szymanska, Marzena; Davis, Matthew; Gardiner, Simon
2013-01-01
The 1995 observation of Bose-Einstein condensation in dilute atomic vapours spawned the field of ultracold, degenerate quantum gases. Unprecedented developments in experimental design and precision control have led to quantum gases becoming the preferred playground for designer quantum many-body systems. This self-contained volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics. Thematically organised chapters on different methodologies, contributed by key researchers using a unified notation, provide the first integrated view of the relative merits of individual approaches, aided by pertinent introductory chapters and the guidance of ed...
6. Debye screening and a Thomas - Fermi model of a dyonic atom in a two potential theory of electromagnetism
Energy Technology Data Exchange (ETDEWEB)
Wolf, C. [North Adams State College, MA (United States)
1993-02-01
We study the screening of a central Abelian dyon by a surrounding dyon cloud in a two potential theory of electromagnetism. A generalized formula for the Debye screening length is obtained and a Thomas - Fermi Model for a charged cloud surrounding a central Dyonic Core is studied. 20 refs.
7. Optical pumping effect in absorption imaging of F=1 atomic gases
CERN Document Server
Kim, Sooshin; Noh, Heung-Ryoul; Shin, Y
2016-01-01
We report our study of the optical pumping effect in absorption imaging of $^{23}$Na atoms in the $F=1$ hyperfine spin states. Solving a set of rate equations for the spin populations under a probe beam, we obtain an analytic expression for the optical signal of the $F=1$ absorption imaging. Furthermore, we verify the result by measuring the absorption spectra of $^{23}$Na Bose-Einstein condensates prepared in various spin states with different probe beam pulse durations. The analytic result can be used in quantitative analysis of $F=1$ spinor condensate imaging and readily applied to other alkali atoms with $I=3/2$ nuclear spin such as $^{87}$Rb.
8. Velocity-changing collisional effects in nonlinear atomic spectroscopy and photon echo decay in gases
Science.gov (United States)
Herman, R. M.
1983-01-01
A general theory of atomic dipole coherence under the influence of collisional phase changes, inelastic effects and optically active atom velocity changes, including those due to anisotropic interactions is presented. Velocity change effects are obtained in closed form. Line shapes appear as convolutions of standard pressure broadening contours with velocity-change contours. Width and shift parameters for the He-broadened Na D lines at 2 m bar pressure, 380 K are calculated, as are He-induced photon echo decay rates for these lines. Overall agreement with xperiment is reasonably good.
9. Microscopic Many-Body Theory of Atomic Bose Gases near a Feshbach Resonance
NARCIS (Netherlands)
Duine, R.A.; Stoof, H.T.C.
2003-01-01
A Feshbach resonance in the s-wave scattering length occurs if the energy of the two atoms in the incoming open channel is close to the energy of a bound state in a coupled closed channel. Starting from the microscopic Hamiltonian that describes this situation, we derive the effective atom–molecule
10. Even-odd spatial nonequivalence for atomic quantum gases with isotropic spin-orbit couplings
Science.gov (United States)
Singh, G. S.; Gupta, Reena
2014-05-01
A general expression for the density of states (DOS) of power-law trapped d-dimensional ideal quantum gases with isotropic spin-orbit couplings (SOCs) is derived and is found to bifurcate into even- dand odd- d classes. The expressions for the grand potential and hence for several thermodynamic quantities are then shown to be amenable to exact analytical forms provided d is an odd integer. Also, a condition γ transition temperature and the condensate fraction in a 3D Bose gas under combined presence of the harmonic trapping and the Weyl coupling shows that the condensation is favored by the former but disfavored by the latter. This countering behavior is discussed to be in conformity with the exchange-symmetry-induced statistical interactions resulting from these two entities as enunciated recently [Phys. Rev. A 88, 053607 (2013)].
11. Effective atomic numbers, electron densities, and tissue equivalence of some gases and mixtures for dosimetry of radiation detectors
Directory of Open Access Journals (Sweden)
Singh Vishwanath P.
2012-01-01
Full Text Available Total mass attenuation coefficients, µm, effective atomic number, Zeff, and effective electron density, Neff, of different gases - carbon dioxide, methane, acetylene, propane, butane, and pentane used in radiation detectors, have been calculated for the photon energy of 1 keV to 100 GeV. Each gas has constant Zeff values between 0.10 to 10 MeV photon energies; however, these values are way far away from ICRU tissue. Carbon dioxide gas shows the closest tissue equivalence in the entire photon energy spectrum. Relative tissue equivalences of the mixtures of gases with respect to ICRU tissue are in the range of 0.998-1.041 for air, argon (4.5% + methane (95.5%, argon (0.5% + carbon dioxide (99.5%, and nitrogen (5% + methane (7% + carbon dioxide (88%. The gas composition of xenon (0.5% + carbon dioxide (99.5% shows 1.605 times higher tissue equivalence compared to the ICRU tissue. The investigated photon interaction parameters are useful for exposure and energy absorption buildup factors calculation and design, and fabrication of gaseous detectors for ambient radiation measurement by the Geiger-Muller detector, ionization chambers and proportional counters.
12. Generation of few-cycle laser pulses: Comparison between atomic and molecular gases in a hollow-core fiber
Science.gov (United States)
Zhi-Yuan, Huang; Ye, Dai; Rui-Rui, Zhao; Ding, Wang; Yu-Xin, Leng
2016-07-01
We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber. From the perspective of self-phase modulation (SPM), we give the extensive study of the SPM influence on a probe pulse with molecular phase modulation (MPM) effect. By comparing the two compression methods, we summarize their advantages and drawbacks to obtain the few-cycle pulses with micro- or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204328, 61221064, 61078037, 11127901, 11134010, and 61205208), the National Basic Research Program of China (Grant No. 2011CB808101), and the Natural Science Foundation of Shanghai, China (Grant No. 13ZR1414800).
13. All-optical production of 6Li quantum gases
Science.gov (United States)
Burchianti, A.; Seman, J. A.; Valtolina, G.; Morales, A.; Inguscio, M.; Zaccanti, M.; Roati, G.
2015-03-01
We report efficient production of quantum gases of 6Li using a sub-Doppler cooling scheme based on the D1 transition. After loading in a standard magneto-optical trap, an atomic sample of 109 atoms is cooled at a temperature of 40 μK by a bichromatic D1 gray-molasses. More than 2×107 atoms are then transferred into a high-intensity optical dipole trap, where a two-spin state mixture is evaporatively cooled down to quantum degeneracy. We observe that D1 cooling remains effective in the deep trapping potential, allowing an effective increase of the atomic phase-space density before starting the evaporation. In a total experimental cycle of 11 s, we produce weakly-interacting degenerate Fermi gases of 7×105 atoms at T/TF molecules. We further describe a simple and compact optical system both for high-resolution imaging and for imprinting a thin optical barrier on the atomic cloud; this represents a first step towards the study of quantum tunneling in strongly interacting superfluid Fermi gases.
14. Dark solitons in a Gross-Pitaevskii equation with a power-law nonlinearity: application to ultracold Fermi gases near the Bose-Einstein condensation regime
Energy Technology Data Exchange (ETDEWEB)
Yan, D; Kevrekidis, P G [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Frantzeskakis, D J, E-mail: [email protected] [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 157 84 (Greece)
2011-10-14
In this work, we consider a model of a defocusing nonlinear Schroedinger equation with a variable nonlinearity exponent. This is motivated by the study of a superfluid Fermi gas in the Bose-Einstein condensation (BEC)-Bardeen-Cooper-Schrieffer crossover. In particular, we focus on the relevant mean-field model in the regime from BEC to unitarity and especially consider the modification of the nearly black soliton oscillation frequency due to the variation in the nonlinearity exponent in a harmonic trapping potential. The analytical expressions given as a function of the relevant nonlinearity exponent are corroborated by numerical computations and also extended past the BEC limit. (paper)
15. Optical pumping effect in absorption imaging of F =1 atomic gases
Science.gov (United States)
Kim, Sooshin; Seo, Sang Won; Noh, Heung-Ryoul; Shin, Y.
2016-08-01
We report our study of the optical pumping effect in absorption imaging of 23Na atoms in the F =1 hyperfine spin states. Solving a set of rate equations for the spin populations in the presence of a probe beam, we obtain an analytic expression for the optical signal of the F =1 absorption imaging. Furthermore, we verify the result by measuring the absorption spectra of 23Na Bose-Einstein condensates prepared in various spin states with different probe-beam pulse durations. The analytic result can be used in the quantitative analysis of F =1 spinor condensate imaging and readily applied to other alkali-metal atoms with I =3 /2 nuclear spin such as 87Rb.
16. Observability of quantum criticality and a continuous supersolid in atomic gases.
Science.gov (United States)
Diehl, S; Baranov, M; Daley, A J; Zoller, P
2010-04-23
We analyze the Bose-Hubbard model with a three-body hard-core constraint by mapping the system to a theory of two coupled bosonic degrees of freedom. We find striking features that could be observable in experiments, including a quantum Ising critical point on the transition from atomic to dimer superfluidity at unit filling, and a continuous supersolid phase for strongly bound dimers.
17. Classical stochastic measurement trajectories: Bosonic atomic gases in an optical cavity and quantum measurement backaction
Science.gov (United States)
Lee, Mark D.; Ruostekoski, Janne
2014-08-01
We formulate computationally efficient classical stochastic measurement trajectories for a multimode quantum system under continuous observation. Specifically, we consider the nonlinear dynamics of an atomic Bose-Einstein condensate contained within an optical cavity subject to continuous monitoring of the light leaking out of the cavity. The classical trajectories encode within a classical phase-space representation a continuous quantum measurement process conditioned on a given detection record. We derive a Fokker-Planck equation for the quasiprobability distribution of the combined condensate-cavity system. We unravel the dynamics into stochastic classical trajectories that are conditioned on the quantum measurement process of the continuously monitored system. Since the dynamics of a continuously measured observable in a many-atom system can be closely approximated by classical dynamics, the method provides a numerically efficient and accurate approach to calculate the measurement record of a large multimode quantum system. Numerical simulations of the continuously monitored dynamics of a large atom cloud reveal considerably fluctuating phase profiles between different measurement trajectories, while ensemble averages exhibit local spatially varying phase decoherence. Individual measurement trajectories lead to spatial pattern formation and optomechanical motion that solely result from the measurement backaction. The backaction of the continuous quantum measurement process, conditioned on the detection record of the photons, spontaneously breaks the symmetry of the spatial profile of the condensate and can be tailored to selectively excite collective modes.
18. Molecular ions in ultracold atomic gases: computed electronic interactions for \\MgHion with Rb
CERN Document Server
Tacconi, Mario
2007-01-01
The electronic structures of the manifold of potential energy surfaces generated in the lower energy range by the interaction of the MgH$^+$(X$^1\\Sigma^+$) cationic molecule with Rb($^2$S), neutral atom are obtained over a broad range of Jacobi coordinates from strongly correlated \\emph{ab initio} calculations which use a Multireference (MR) wavefunction within a Complete Active Space (CAS) approach. The relative features of the lowest five surfaces are analyzed in terms of possible collisional outcomes when employed to model the ultracold dynamics of ionic molecular partners.
19. Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface
CERN Document Server
Haendel, S; Wiles, T P; Hopkins, S A; Cornish, S L
2011-01-01
We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of $^{85}$Rb and $^{87}$Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum (UHV). To maintain excellent optical access to the region surrounding the surface magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally we demonstrate the loading of a hybrid optical-magnetic trap with $^{87}$Rb and the creation of Bose-Einstein condensates via forced evaporative cooling ...
20. Effective-field-theory analysis of Efimov physics in heteronuclear mixtures of ultracold atomic gases
Science.gov (United States)
Acharya, Bijaya; Ji, Chen; Platter, Lucas
2016-09-01
We use an effective-field-theory framework to analyze the Efimov effect in heteronuclear three-body systems consisting of two species of atoms with a large interspecies scattering length. In the leading-order description of this theory, various three-body observables in heteronuclear mixtures can be universally parametrized by one three-body parameter. We present the next-to-leading corrections, which include the effects of the finite interspecies effective range and the finite intraspecies scattering length, to various three-body observables. We show that only one additional three-body parameter is required to render the theory predictive at this order. By including the effective range and intraspecies scattering length corrections, we derive a set of universal relations that connect the different Efimov features near the interspecies Feshbach resonance. Furthermore, we show that these relations can be interpreted in terms of the running of the three-body counterterms that naturally emerge from proper renormalization. Finally, we make predictions for recombination observables of a number of atomic systems that are of experimental interest.
1. MeV femtosecond electron pulses from direct-field acceleration in low density atomic gases
CERN Document Server
Varin, Charles; Hogan-Lamarre, Pascal; Fennel, Thomas; Piché, Michel; Brabec, Thomas
2015-01-01
Using three-dimensional particle-in-cell simulations, we show that few-MeV electrons can be produced by focusing tightly few-cycle radially-polarized laser pulses in a low-density atomic gas. In particular, it is observed that for the few-TW laser power needed to reach relativistic electron energies, longitudinal attosecond microbunching occurs naturally, resulting in femtosecond structures with high-contrast attosecond density modulations. The three-dimensional particle-in-cell simulations show that in the relativistic regime the leading pulse of these attosecond substructures survives to propagation over extended distances, suggesting that it could be delivered to a distant target, with the help of a properly designed transport beamline.
2. Non-equilibrium universality in the dynamics of dissipative cold atomic gases
Science.gov (United States)
Marcuzzi, M.; Levi, E.; Li, W.; Garrahan, J. P.; Olmos, B.; Lesanovsky, I.
2015-07-01
The theory of continuous phase transitions predicts the universal collective properties of a physical system near a critical point, which for instance manifest in characteristic power-law behaviours of physical observables. The well-established concept at or near equilibrium, universality, can also characterize the physics of systems out of equilibrium. The most fundamental instance of a genuine non-equilibrium phase transition is the directed percolation (DP) universality class, where a system switches from an absorbing inactive to a fluctuating active phase. Despite being known for several decades it has been challenging to find experimental systems that manifest this transition. Here we show theoretically that signatures of the DP universality class can be observed in an atomic system with long-range interactions. Moreover, we demonstrate that even mesoscopic ensembles—which are currently studied experimentally—are sufficient to observe traces of this non-equilibrium phase transition in one, two and three dimensions.
3. An effective field theory analysis of Efimov physics in heteronuclear mixtures of ultracold atomic gases
CERN Document Server
Acharya, Bijaya; Platter, Lucas
2016-01-01
We use an effective field theory framework to analyze the Efimov effect in heteronuclear three-body systems consisting of two species of atoms with a large interspecies scattering length. In the leading-order description of this theory, various three-body observables in heteronuclear mixtures can be universally parameterized by one three-body parameter. We present the next-to-leading corrections, which include the effects of the finite interspecies effective range and the finite intraspecies scattering length, to various three-body observables. We show that only one additional three-body parameter is required to render the theory predictive at this order. By including the effective range and intraspecies scattering length corrections, we derive a set of universal relations that connect the different Efimov features near the interspecies Feshbach resonance. Furthermore, we show that these relations can be interpreted in terms of the running of the three-body counterterms that naturally emerge from proper renor...
4. Metastable Phases and Dynamics of Low-Dimensional Strongly-Correlated Atomic Quantum Gases
Science.gov (United States)
Pielawa, Susanne
In this thesis we theoretically study low-dimensional, strongly correlated systems of cold atoms, which are not in an equilibrium situation. This is motivated by recent experimental progress, which has made it possible to study quantum many-body physics in a controllable and clean setting; and parameters can be changed during the experiment. In Chapter 2 and 3 we study phases and quantum phase transitions of 'tilted' Mott insulator of bosons. We analyze a variety of lattices and tilt directions in two dimensions: square, decorated square, triangular, and kagome. We show that there are rich possibilities for correlated phases with non-trivial entanglement of pseudospin degrees of freedom encoded in the boson density. For certain configurations three-body interactions are necessary to ensure that the energy of the effective resonant subspace is bounded from below. We find quantum phases with Ising density wave order, with superfluidity transverse to the tilt direction, a quantum liquid state with no broken symmetry. We also find cases for which the resonant subspace is described by effective quantum dimer models. In Chapter 4 we study spin 1/2 chains with a Heisenberg interaction which are coupled in a way that would arise if they are taken off graphene at a zig-zag edge. In Chapter 5 we theoretically analyze interference patterns of parametrically driven one-dimensional cold atomic systems. The parametric driving leads to spatial oscillations in the interference patter, which can be analyzed to obtain the sound velocity of the 1d system, and to probe spin-charge separation.
5. Exploring the thermodynamics of a universal Fermi gas.
Science.gov (United States)
Nascimbène, S; Navon, N; Jiang, K J; Chevy, F; Salomon, C
2010-02-25
One of the greatest challenges in modern physics is to understand the behaviour of an ensemble of strongly interacting particles. A class of quantum many-body systems (such as neutron star matter and cold Fermi gases) share the same universal thermodynamic properties when interactions reach the maximum effective value allowed by quantum mechanics, the so-called unitary limit. This makes it possible in principle to simulate some astrophysical phenomena inside the highly controlled environment of an atomic physics laboratory. Previous work on the thermodynamics of a two-component Fermi gas led to thermodynamic quantities averaged over the trap, making comparisons with many-body theories developed for uniform gases difficult. Here we develop a general experimental method that yields the equation of state of a uniform gas, as well as enabling a detailed comparison with existing theories. The precision of our equation of state leads to new physical insights into the unitary gas. For the unpolarized gas, we show that the low-temperature thermodynamics of the strongly interacting normal phase is well described by Fermi liquid theory, and we localize the superfluid transition. For a spin-polarized system, our equation of state at zero temperature has a 2 per cent accuracy and extends work on the phase diagram to a new regime of precision. We show in particular that, despite strong interactions, the normal phase behaves as a mixture of two ideal gases: a Fermi gas of bare majority atoms and a non-interacting gas of dressed quasi-particles, the fermionic polarons.
6. Exceptional Points for Nonlinear Schroedinger Equations Describing Bose-Einstein Condensates of Ultracold Atomic Gases
Directory of Open Access Journals (Sweden)
G. Wunner
2011-01-01
Full Text Available The coalescence of two eigenfunctions with the same energy eigenvalue is not possible in Hermitian Hamiltonians. It is, however, a phenomenon well known from non-hermitian quantum mechanics. It can appear, e.g., for resonances in open systems, with complex energy eigenvalues. If two eigenvalues of a quantum mechanical system which depends on two or more parameters pass through such a branch point singularity at a critical set of parameters, the point in the parameter space is called an exceptional point. We will demonstrate that exceptional points occur not only for non-hermitean Hamiltonians but also in the nonlinear Schroedinger equations which describe Bose-Einstein condensates, i.e., the Gross-Pitaevskii equation for condensates with a short-range contact interaction, and with additional long-range interactions. Typically, in these condensates the exceptional points are also found to be bifurcation points in parameter space. For condensates with a gravity-like interaction between the atoms, these findings can be confirmed in an analytical way.
7. An effective mean field theory for the coexistence of anti-ferromagnetism and superconductivity: Applications to iron-based superconductors and cold Bose-Fermi atomic mixtures
Science.gov (United States)
Brackett, Jeremy; Newman, Joseph; De Silva, Theja N.
2016-10-01
We study an effective fermion model on a square lattice to investigate the cooperation and competition of superconductivity and anti-ferromagnetism. In addition to particle tunneling and on-site interaction, a bosonic excitation mediated attractive interaction is also included in the model. We assume that the attractive interaction is mediated by spin fluctuations and excitations of Bose-Einstein condensation (BEC) in electronic systems and Bose-Fermi mixtures on optical lattices, respectively. Using an effective mean-field theory to treat both superconductivity and anti-ferromagnetism at equal footing, we study a single effective model relevant for both systems within the Landau energy functional approach and a linearized theory. Within our approaches, we find possible co-existence of superconductivity and anti-ferromagnetism for both electronic and cold-atomic models. Our linearized theory shows while spin fluctuations favor d-wave superconductivity and BEC excitations favor s-wave superconductivity.
8. Mott-Insulator to Liquid Transition and Population Trapping in Ultracold Fermi Gases by Non-Equilibrium Modulation of the Optical Lattice
CERN Document Server
Frank, Regine
2011-01-01
An ultracold gas of interacting fermionic atoms in a three dimensional optical lattice is considered, where the lattice potential strength is periodically modulated. This non-equilibrium system is nonperturbatively described by means of a Keldysh-Floquet-Green's function approach employing a generalized dynamical mean field theory (DMFT). Strong repulsive interactions between different atoms lead to a Mott-Insulator state for the equilibrium system, but the additional external driving yields a non-equilibrium density of Floquet-states and a transition to a liquid or conducting state.
9. Propagation and scattering of high-intensity X-ray pulses in dense atomic gases and plasmas
Energy Technology Data Exchange (ETDEWEB)
Weninger, Clemens
2015-10-15
Nonlinear spectroscopy in the X-ray domain is a promising technique to explore the dynamics of elementary excitations in matter. X-rays provide an element specificity that allows them to target individual chemical elements, making them a great tool to study complex molecules. The recent advancement of X-ray free electron lasers (XFELs) allows to investigate non-linear processes in the X-ray domain for the first time. XFELs provide short femtosecond X-ray pulses with peak powers that exceed previous generation synchrotron X-ray sources by more than nine orders of magnitude. This thesis focuses on the theoretical description of stimulated emission processes in the X-ray regime in atomic gases. These processes form the basis for more complex schemes in molecules and provide a proof of principle for nonlinear X-ray spectroscopy. The thesis also includes results from two experimental campaigns at the Linac Coherent Light Source and presents the first experimental demonstration of stimulated X-ray Raman scattering. Focusing an X-ray free electron laser beam into an elongated neon gas target generates an intense stimulated X-ray emission beam in forward direction. If the incoming X-rays have a photon energy above the neon K edge, they can efficiently photo-ionize 1s electrons and generate short-lived core excited states. The core-excited states decay mostly via Auger decay but have a small probability to emit a spontaneous X-ray photon. The spontaneous emission emitted in forward direction can stimulate X-ray emission along the medium and generate a highly directional and intense X-ray laser pulse. If the photon energy of the incoming X-rays however is below the ionization edge in the region of the pre-edge resonance the incoming X-rays can be inelastically scattered. This spontaneous X-ray Raman scattering process has a very low probability, but the spontaneously scattered photons in the beginning of the medium can stimulate Raman scattering along the medium. The
10. EDITORIAL: The 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases The 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases
Science.gov (United States)
Petrović, Zoran Lj; Marić, Dragana; Malović, Gordana
2011-03-01
This special issue consists of papers that are associated with invited lectures, workshop papers and hot topic papers presented at the 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases (ESCAMPIG XX). This conference was organized in Novi Sad (Serbia) from 13 to 17 July 2010 by the Institute of Physics of the University of Belgrade. It is important to note that this is not a conference 'proceedings'. Following the initial selection process by the International Scientific Committee, all papers were submitted to the journal by the authors and have been fully peer reviewed to the standard required for publication in Plasma Sources Science and Technology (PSST). The papers are based on presentations given at the conference but are intended to be specialized technical papers covering all or part of the topic presented by the author during the meeting. The ESCAMPIG conference is a regular biennial Europhysics Conference of the European Physical Society focusing on collisional and radiative aspects of atomic and molecular physics in partially ionized gases as well as on plasma-surface interaction. The conference focuses on low-temperature plasma sciences in general and includes the following topics: Atomic and molecular processes in plasmas Transport phenomena, particle velocity distribution function Physical basis of plasma chemistry Plasma surface interaction (boundary layers, sheath, surface processes) Plasma diagnostics Plasma and discharges theory and simulation Self-organization in plasmas, dusty plasmas Upper atmospheric plasmas and space plasmas Low-pressure plasma sources High-pressure plasma sources Plasmas and gas flows Laser-produced plasmas During ESCAMPIG XX special sessions were dedicated to workshops on: Atomic and molecular collision data for plasma modeling, organized by Professors Z Lj Petrovic and N Mason Plasmas in medicine, organized by Dr N Puac and Professor G Fridman. The conference topics were represented in the
11. The long-range non-additive three-body dispersion interactions for the rare gases, alkali, and alkaline-earth atoms.
Science.gov (United States)
Tang, Li-Yan; Yan, Zong-Chao; Shi, Ting-Yun; Babb, James F; Mitroy, J
2012-03-14
The long-range non-additive three-body dispersion interaction coefficients Z(111), Z(112), Z(113), and Z(122) are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb), and the alkaline-earth atoms (up to Sr). The term Z(111) arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms Z(112), Z(113), and Z(122) arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as dipole-dipole-quadrupole, dipole-dipole-octupole, and dipole-quadrupole-quadrupole coefficients. Results for the four Z coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, and Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supplementary data.
12. The long-range non-additive three-body dispersion interactions for the rare gases, alkali and alkaline-earth atoms
CERN Document Server
Tang, Li-Yan; Shi, Ting-Yun; Babb, James F; Mitroy, J
2012-01-01
The long-range non-additive three-body dispersion interaction coefficients $Z_{111}$, $Z_{112}$, $Z_{113}$, and $Z_{122}$ are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb) and the alkaline-earth atoms (up to Sr). The term $Z_{111}$, arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms $Z_{112}$, $Z_{113}$, and $Z_{122}$ arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as DDQ, DDO, and DQQ coefficients. Results for the four $Z$ coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supp...
13. Strongly interacting ultracold quantum gases
Institute of Scientific and Technical Information of China (English)
Hui ZHAI
2009-01-01
This article reviews recent progresses in ul- tracold quantum gases, and it includes three subjects which are the Fermi gases across a Feshbach resonance, quantum gases in the optical lattices and the fast ro- tating quantum gases. In this article, we discuss many basic physics pictures and concepts in quantum gases, for examples, the resonant interaction, universality and condensation in the lowest Landau level; we introduce fundamental theoretical tools for studying these systems, such as mean-field theory for BEC-BCS crossover and for the boson Hubbard model; also, we emphasize the im- portant unsolved problems in the forefront of this field, for instance, the temperature effect in optical lattices.
14. Simultaneous Observations of PKS 2155--304 with H.E.S.S., Fermi, RXTE and ATOM: Spectral Energy Distributions and Variability in a Low State
Energy Technology Data Exchange (ETDEWEB)
Aharonian, F.; /Heidelberg, Max Planck Inst. /Dublin Inst.; Akhperjanian, A.G.; /Yerevan Phys. Inst.; Anton, G.; /Erlangen - Nuremberg U.; Barres de Almeida, U.; /Durham U.; Bazer-Bachi, A.R.; /Toulouse, CESR; Becherini, Y.; /APC, Paris; Behera, B.; /Heidelberg Observ.; Bernlohr, K.; /Heidelberg, Max Planck Inst. /Humboldt U., Berlin; Boisson, C.; /LUTH, Meudon; Bochow, A.; /Heidelberg, Max Planck Inst.; Borrel, V.; /Toulouse, CESR; Brion, E.; /DAPNIA, Saclay; Brucker, J.; /Erlangen - Nuremberg U.; Brun, P.; /DAPNIA, Saclay; Buhler, R.; /Heidelberg, Max Planck Inst.; Bulik, T.; /Warsaw, Copernicus Astron. Ctr.; Busching, I.; /Western Ontario U.; Boutelier, T.; /Grenoble Observ.; Chadwick, P.M.; /Durham U.; Charbonnier, A.; /Paris U., VI-VII; Chaves, R.C.G.; /Heidelberg, Max Planck Inst. /Durham U. /Ecole Polytechnique /Heidelberg, Max Planck Inst. /Annecy, LAPP /Humboldt U., Berlin /Durham U. /Namibia U. /Western Ontario U. /Ecole Polytechnique /Heidelberg, Max Planck Inst. /Durham U. /APC, Paris /Heidelberg, Max Planck Inst. /Dublin Inst. /Annecy, LAPP /Grenoble Observ. /Warsaw, Copernicus Astron. Ctr. /Cracow, INP /Heidelberg, Max Planck Inst. /Heidelberg Observ. /APC, Paris /Montpellier U. /Montpellier U. /Montpellier U. /Heidelberg, Max Planck Inst. /Ecole Polytechnique /Humboldt U., Berlin /Dublin Inst. /Montpellier U. /APC, Paris /SLAC; /more authors..
2009-05-07
We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS 2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of {gamma}-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little ({approx}30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS 2155-304.
15. A new numerical approach to solve Thomas-Fermi model of an atom using bio-inspired heuristics integrated with sequential quadratic programming.
Science.gov (United States)
Raja, Muhammad Asif Zahoor; Zameer, Aneela; Khan, Aziz Ullah; Wazwaz, Abdul Majid
2016-01-01
In this study, a novel bio-inspired computing approach is developed to analyze the dynamics of nonlinear singular Thomas-Fermi equation (TFE) arising in potential and charge density models of an atom by exploiting the strength of finite difference scheme (FDS) for discretization and optimization through genetic algorithms (GAs) hybrid with sequential quadratic programming. The FDS procedures are used to transform the TFE differential equations into a system of nonlinear equations. A fitness function is constructed based on the residual error of constituent equations in the mean square sense and is formulated as the minimization problem. Optimization of parameters for the system is carried out with GAs, used as a tool for viable global search integrated with SQP algorithm for rapid refinement of the results. The design scheme is applied to solve TFE for five different scenarios by taking various step sizes and different input intervals. Comparison of the proposed results with the state of the art numerical and analytical solutions reveals that the worth of our scheme in terms of accuracy and convergence. The reliability and effectiveness of the proposed scheme are validated through consistently getting optimal values of statistical performance indices calculated for a sufficiently large number of independent runs to establish its significance.
16. Revised FINAL–REPORT NO. 2: INDEPENDENT CONFIRMATORY SURVEY SUMMARY AND RESULTS FOR THE ENRICO FERMI ATOMIC POWER PLANT, UNIT 1, NEWPORT, MICHIGAN (DOCKET NO. 50 16; RFTA 10-004) 2018-SR-02-1
Energy Technology Data Exchange (ETDEWEB)
Erika Bailey
2011-10-27
The Enrico Fermi Atomic Power Plant, Unit 1 (Fermi 1) was a fast breeder reactor design that was cooled by sodium and operated at essentially atmospheric pressure. On May 10, 1963, the Atomic Energy Commission (AEC) granted an operating license, DPR-9, to the Power Reactor Development Company (PRDC), a consortium specifically formed to own and operate a nuclear reactor at the Fermi 1 site. The reactor was designed for a maximum capability of 430 megawatts (MW); however, the maximum reactor power with the first core loading (Core A) was 200 MW. The primary system was filled with sodium in December 1960 and criticality was achieved in August 1963. The reactor was tested at low power during the first couple years of operation. Power ascension testing above 1 MW commenced in December 1965 immediately following the receipt of a high-power operating license. In October 1966 during power ascension, zirconium plates at the bottom of the reactor vessel became loose and blocked sodium coolant flow to some fuel subassemblies. Two subassemblies started to melt and the reactor was manually shut down. No abnormal releases to the environment occurred. Forty-two months later after the cause had been determined, cleanup completed, and the fuel replaced, Fermi 1 was restarted. However, in November 1972, PRDC made the decision to decommission Fermi 1 as the core was approaching its burn-up limit. The fuel and blanket subassemblies were shipped off-site in 1973. Following that, the secondary sodium system was drained and sent off-site. The radioactive primary sodium was stored on-site in storage tanks and 55 gallon (gal) drums until it was shipped off-site in 1984. The initial decommissioning of Fermi 1 was completed in 1975. Effective January 23, 1976, DPR-9 was transferred to the Detroit Edison Company (DTE) as a 'possession only' license (DTE 2010a). This report details the confirmatory activities performed during the second Oak Ridge Institute for Science and Education
17. Spectral investigations of photoionized plasmas induced in atomic and molecular gases using nanosecond extreme ultraviolet (EUV) pulses
Energy Technology Data Exchange (ETDEWEB)
Bartnik, A.; Fiedorowicz, H.; Wachulak, P. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)
2014-07-15
In this paper, results of spectral investigations of low temperature photoionized plasmas, created by irradiation of gases with intense pulses of extreme ultraviolet (EUV) radiation from a laser-produced plasma (LPP) source, are presented. The LPP source was based on a double-stream KrXe/He gas-puff target irradiated with 4 ns/0.8 J/10 Hz Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region λ ≈ 10–12 nm; however, spectrally integrated intensity at longer wavelengths was also significant. The EUV beam was focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in formation of photoionized plasmas emitting radiation in the EUV range. Radiation spectra, measured for plasmas produced in various gases, are dominated by emission lines, originating from single charged ions. Significant differences in spectral intensities and distributions between plasmas created in neon and molecular gases were observed.
18. Strongly correlated Bose gases
Science.gov (United States)
Chevy, F.; Salomon, C.
2016-10-01
The strongly interacting Bose gas is one of the most fundamental paradigms of quantum many-body physics and the subject of many experimental and theoretical investigations. We review recent progress on strongly correlated Bose gases, starting with a description of beyond mean-field corrections. We show that the Efimov effect leads to non universal phenomena and to a metastability of the low temperature Bose gas through three-body recombination to deeply bound molecular states. We outline differences and similarities with ultracold Fermi gases, discuss recent experiments on the unitary Bose gas, and finally present a few perspectives for future research.
19. Laser cooling of dense atomic gases by collisional redistribution of radiation and spectroscopy of molecular dimers in a dense buffer gas environment
CERN Document Server
Saß, Anne; Christopoulos, Stavros; Knicker, Katharina; Moroshkin, Peter; Weitz, Martin
2014-01-01
We study laser cooling of atomic gases by collisional redistribution of fluorescence. In a high pressure buffer gas regime, frequent collisions perturb the energy levels of alkali atoms, which allows for the absorption of a far red detuned irradiated laser beam. Subsequent spontaneous decay occurs close to the unperturbed resonance frequency, leading to a cooling of the dense gas mixture by redistribution of fluorescence. Thermal deflection spectroscopy indicates large relative temperature changes down to and even below room temperature starting from an initial cell temperature near 700 K. We are currently performing a detailed analysis of the temperature distribution in the cell. As we expect this cooling technique to work also for molecular-noble gas mixtures, we also present initial spectroscopic experiments on alkali-dimers in a dense buffer gas surrounding.
20. Enrico Fermi
Institute of Scientific and Technical Information of China (English)
李琳
2006-01-01
Enrico Fermi was born in Rome on 29th September, 1901. He attended a local grammar school, and in 1918, he won a fellowship of the Scuola Normale Superiore of Pisa, where he gained his doctor’s degree in physics in 1922, with Professor Puccianti. In 1923, he was awarded a scholarship from the Italian Government. With a Rockefeller Fellowship, in 1924, he moved to Leyden, and later that same year he returned to Italy to occupy for two
1. Enrico Fermi the obedient genius
CERN Document Server
Bruzzaniti, Giuseppe
2016-01-01
This biography explores the life and career of the Italian physicist Enrico Fermi, which is also the story of thirty years that transformed physics and forever changed our understanding of matter and the universe: nuclear physics and elementary particle physics were born, nuclear fission was discovered, the Manhattan Project was developed, the atomic bombs were dropped, and the era of “big science” began. It would be impossible to capture the full essence of this revolutionary period without first understanding Fermi, without whom it would not have been possible. Enrico Fermi: The Obedient Genius attempts to shed light on all aspects of Fermi’s life - his work, motivation, influences, achievements, and personal thoughts - beginning with the publication of his first paper in 1921 through his death in 1954. During this time, Fermi demonstrated that he was indeed following in the footsteps of Galileo, excelling in his work both theoretically and experimentally by deepening our understanding of the Pauli e...
2. The first example of commensurate adsorption of atomic gas in a MOF and effective separation of xenon from other noble gases
KAUST Repository
Wang, Hao
2014-01-01
In industry, cryogenic rectification for separating xenon from other noble gases such as krypton and argon is an energy and capital intensive process. Here we show that a microporous metal-organic framework, namely Co 3(HCOO)6 is capable of effective capture and separation of xenon from other noble gases. Henry\\'s constant, isosteric heat of adsorption (Qst), and IAST selectivity are calculated based on single component sorption isotherms. Having the highest Qst reported to date, Co 3(HCOO)6 demonstrates high adsorption capacity for xenon and its IAST selectivity for Xe-Kr is the largest among all MOFs investigated to date. To mimic real world conditions, breakthrough experiments are conducted on Xe-Kr binary mixtures at room temperature and 1 atmosphere. The results are consistent with the calculated data. These findings show that Co 3(HCOO)6 is a promising candidate for xenon capture and purification. Our gas adsorption measurements and molecular simulation study also reveal that the adsorption of xenon represents the first example of commensurate adsorption of atomic gases near ambient conditions. © 2014 The Royal Society of Chemistry.
3. Trends in structural, electronic properties, Fermi surface topology, and inter-atomic bonding in the series of ternary layered dichalcogenides KNi2S2, KNi2Se2, and KNi2Te2 from first principles calculations
Science.gov (United States)
Bannikov, V. V.; Ivanovskii, A. L.
2013-06-01
By means of the FLAPW-GGA approach, we have systematically studied the structural and electronic properties of tetragonal dichalcogenides KNi2Ch2 (Ch=S, Se, and Te). Our results show that replacements of chalcogens (S→Se→Te) lead to anisotropic deformations of the crystals structure, which are related to the strong anisotropic character of the inter-atomic bonds, where inside the [Ni2Ch2] blocks, mixed covalent-ionic-metallic bonds occur, whereas between the adjacent [Ni2Ch2] blocks and K atomic sheets, ionic bonds emerge. We found that in the sequence KNi2S2→KNi2Se2→KNi2Te2 (i) the overall band structure (where the near-Fermi valence bands are due mainly to the Ni states) is preserved, but the width of the common valence band and the widths of the separate sub-bands and the gaps decrease; (ii) the total DOSs at the Fermi level also decrease; and (iii) for the Fermi surfaces, the most appreciable changes are demonstrated by the hole-like sheets, when a necklace-like topology is formed for the 2D-like sheets and the volume of the closed pockets decreases. Some trends in structural and electronic parameters for ThCr2Si2-type layered dichalcogenides, KNi2Ch2, KFe2Ch2, KCo2Se2, are discussed.
4. Studies on the atomic capture of stopped negative pions in binary mixtures of /sup 3/He with other gases
Energy Technology Data Exchange (ETDEWEB)
Bannikov, A.V.; Levay, B.; Petrukhin, V.I.; Vasilyev, V.A. (Joint Inst. for Nuclear Research, Dubna (USSR)); Kochenda, L.M.; Markov, A.A.; Medvedev, V.I.; Sokolov, G.L.; Strakovsky, I.I. (Leningrad Nuclear Physics Inst., Gatchina (USSR)); Horvath, D. (Hungarian Academy of Sciences, Budapest. Central Research Inst. for Physics)
1983-07-25
Systematic experimental study has been carried out on the atomic capture of negative pions by /sup 3/He in binary gas mixtures of /sup 3/He + Z, where Z is Ne, Ar, Kr, Xe, N/sub 2/, O/sub 2/, CO/sub 2/ and SF/sub 6/. The results are analysed in the framework of a phenomenological model. It is shown that there is no pion transfer from the /sup 3/He..pi../sup -/ mesic atoms to the heavier Z-atoms. The probabilities of pion capture in the various atoms of the mixtures are found to be proportional to the atomic concentraions, thereby excluding the possibility of a concentration dependence in the atomic capture ratio A(Z//sup 3/He). In contradiction to previous assumptions the probability of pion capture into an atomic orbit is not proportional to the stopping power of the components of the mixture. The atomic capture ratio of pions in a /sup 3/He + /sup 4/He mixture is A(/sup 4/He//sup 3/He) = 0.75 +- 0.13, which might be the indication of an isotopic effect. The branching ratio for the charge-exchange reaction at rest ..pi../sup -/ + /sup 3/He -> ..pi../sup 0/ + /sup 3/H) is found to be 0.128 +- 0.012.
5. Studies on the atomic capture of stopped negative pions in binary mixtures of 3He with other gases
Science.gov (United States)
Bannikov, A. V.; Lévay, B.; Petrukhin, V. I.; Vasilyev, V. A.; Kochenda, L. M.; Markov, A. A.; Medvedev, V. I.; Sokolov, G. L.; Strakovsky, I. I.; Horváth, D.
1983-07-01
Systematic experimental study has been carried out on the atomic capture of negative pions by 3He in binary gas mixtures of 3He + Z, where Z is Ne, Ar, Kr, Xe, N 2, O 2, CO 2 and sf 6. The results are analysed in the framework of a phenomenological model. It is shown that there is no pion transfer from the 3Heπ - mesic atoms to the heavier Z-atoms. The probabilities of pion capture in the various atoms of the mixtures are found to be proportional to the atomic concentrations, thereby excluding the possibility of a concentration dependence in the atomic capture ratio A( Z/ 3He). In contradiction to previous assumptions the probability of pion capture into an atomic orbit is not proportional to the stopping power of the components of the mixture. The atomic capture ratio of pions in a 3He + 4He mixture is A( 4He/ 3He) = 0.75 ± 0.13 , which might be the indication of an isotopic effect. The branching ratio for the charge-exchange reaction at rest (π - + 3He → π 0 + 3H) is found to be 0.128 ± 0.012.
6. Studies on the atomic capture of stopped negative pions in binary mixtures of /sup 3/He with other gases
Energy Technology Data Exchange (ETDEWEB)
Bannikov, A.V.; Levay, B.; Petrukhin, V.I.; Vasilyev, V.A. (Joint Inst. for Nuclear Research, Dubna (USSR)); Kochenda, L.M.; Markov, A.A.; Medvedev, V.I.; Sokolov, G.L.; Strakovsky, I.I. (Leningrad Nuclear Physics Inst., Gatchina (USSR)); Horvath, D. (Hungarian Academy of Sciences, Budapest. Central Research Inst. for Physics)
1983-07-25
Systematic experimental study has been carried out on the atomic capture of negative pions by /sup 3/He in binary gas mixtures of /sup 3/He + Z, where Z is Ne, Ar, Kr, Xe, N/sub 2/, O/sub 2/, CO/sub 2/ and SF/sub 6/. The results are analyzed in the framework of a phenomenological model. It is shown that there is no pion transfer from the /sup 3/He..pi../sup -/ mesic atoms to the heavier Z-atoms. The probabilities of pion capture in the various atoms of the mixtures are found to be proportional to the atomic concentraions, thereby excluding the possibility of a concentration dependence in the atomic capture ratio A(Z//sup 3/He). In contradiction to previous assumptions the probability of pion capture into an atomic orbit is not proportional to the stopping power of the components of the mixture. The atomic capture ratio of pions in a /sup 3/He + /sup 4/He mixture is A(/sup 4/He//sup 3/He) = 0.75 +- 0.13, which might be the indication of an isotopic effect. The branching ratio for the charge-exchange reaction at rest ..pi../sup -/ + /sup 3/He -> ..pi../sup 0/ + /sup 3/H is found to be 0.128 +- 0.012.
7. Lifetime measurement of excited atomic and ionic states of some noble gases using the high-frequency deflection technique
M B Das; S Karmakar
2005-12-01
High-frequency deflection (HFD) technique with a delayed coincidence single photon counting arrangement is an efficient technique for radiative lifetime measurement. An apparatus for measurement of the radiative lifetime of atoms and molecules has been developed in our laboratory and measurements have been performed with great success in a large number of atoms and ions. The present version of the apparatus is described in this paper together with a brief description of the basic features and performance.
8. Towards quantum turbulence in cold atomic fermionic superfluids
Science.gov (United States)
Bulgac, Aurel; McNeil Forbes, Michael; Wlazłowski, Gabriel
2017-01-01
Fermionic superfluids provide a new realization of quantum turbulence, accessible to both experiment and theory, yet relevant to phenomena from both cold atoms to nuclear astrophysics. In particular, the strongly interacting Fermi gas realized in cold-atom experiments is closely related to dilute neutron matter in neutron star crusts. Unlike the liquid superfluids 4He (bosons) and 3He (fermions), where quantum turbulence has been studied in laboratory for decades, superfluid Fermi gases stand apart for a number of reasons. They admit a rather reliable theoretical description based on density functional theory called the time-dependent superfluid local density approximation that describes both static and dynamic phenomena. Cold atom experiments demonstrate exquisite control over particle number, spin polarization, density, temperature, and interaction strength. Topological defects such as domain walls and quantized vortices, which lie at the heart of quantum turbulence, can be created and manipulated with time-dependent external potentials, and agree with the time-dependent theoretical techniques. While similar experimental and theoretical control exists for weakly interacting Bose gases, the unitary Fermi gas is strongly interacting. The resulting vortex line density is extremely high, and quantum turbulence may thus be realized in small systems where classical turbulence is suppressed. Fermi gases also permit the study of exotic superfluid phenomena such as the Larkin-Ovchinnikov-Fulde-Ferrell pairing mechanism for polarized superfluids which may give rise to 3D supersolids, and a pseudo-gap at finite temperatures that might affect the regime of classical turbulence. The dynamics associated with these phenomena has only started to be explored. Finally, superfluid mixtures have recently been realized, providing experimental access to phenomena like Andreev-Bashkin entrainment predicted decades ago. Superfluid Fermi gases thus provide a rich forum for addressing
9. Will Allis Prize for the Study of Ionized Gases Lecture: Electron and Photon Collisions with Atoms and Molecules
Science.gov (United States)
Burke, Philip G.
2012-06-01
After a brief historical introduction this talk will review the broad range of collision processes involving electron and photon collisions with atoms and molecules that are now being considered. Their application in the analysis of astronomical spectra, atmospheric observations and laboratory plasmas will be considered. The talk will review the R-matrix computational method which has been widely used by international collaborations and by other scientists in the field to obtain accurate scattering amplitudes and cross sections of importance in these applications. Results of some recent calculations of electron and photon collisions with atoms and molecules will be presented. In conclusion some challenges for future research will be briefly discussed.
10. Phase Diagram of a Strongly Interacting Spin-Imbalanced Fermi Gas
CERN Document Server
Olsen, Ben A; Fry, Jacob A; Sheehy, Daniel E; Hulet, Randall G
2015-01-01
We obtain the phase diagram of spin-imbalanced interacting Fermi gases from measurements of density profiles of $^6$Li atoms in a harmonic trap. These results agree with, and extend, previous experimental measurements. Measurements of the critical polarization at which the balanced superfluid core vanishes generally agree with previous experimental results and with quantum Monte Carlo (QMC) calculations in the BCS and unitary regimes. We disagree with the QMC results in the BEC regime, however, where the measured critical polarizations are greater than theoretically predicted. We also measure the equation of state in the crossover regime for a gas with equal numbers of the two fermion spin states.
11. Noble Gases
Science.gov (United States)
Podosek, F. A.
2003-12-01
The noble gases are the group of elements - helium, neon, argon, krypton, xenon - in the rightmost column of the periodic table of the elements, those which have "filled" outermost shells of electrons (two for helium, eight for the others). This configuration of electrons results in a neutral atom that has relatively low electron affinity and relatively high ionization energy. In consequence, in most natural circumstances these elements do not form chemical compounds, whence they are called "noble." Similarly, much more so than other elements in most circumstances, they partition strongly into a gas phase (as monatomic gas), so that they are called the "noble gases" (also, "inert gases"). (It should be noted, of course, that there is a sixth noble gas, radon, but all isotopes of radon are radioactive, with maximum half-life a few days, so that radon occurs in nature only because of recent production in the U-Th decay chains. The factors that govern the distribution of radon isotopes are thus quite different from those for the five gases cited. There are interesting stories about radon, but they are very different from those about the first five noble gases, and are thus outside the scope of this chapter.)In the nuclear fires in which the elements are forged, the creation and destruction of a given nuclear species depends on its nuclear properties, not on whether it will have a filled outermost shell when things cool off and nuclei begin to gather electrons. The numerology of nuclear physics is different from that of chemistry, so that in the cosmos at large there is nothing systematically special about the abundances of the noble gases as compared to other elements. We live in a very nonrepresentative part of the cosmos, however. As is discussed elsewhere in this volume, the outstanding generalization about the geo-/cosmochemistry of the terrestrial planets is that at some point thermodynamic conditions dictated phase separation of solids from gases, and that the
12. Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
Directory of Open Access Journals (Sweden)
P. Marini
2016-05-01
Full Text Available We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
13. Precision measurements of cross sections of inelastic processes realized in collisions of alkali metal ions with atoms of rare gases
CERN Document Server
Lomsadze, R A; Mosulishvili, N O; Kezerashvili, R Ya
2015-01-01
This work presents a multifaceted experimental study of collisions of Na$^{+}$ and K$^{+}$ ions in the energy range 0.5 -- 10 keV with He and Ar atoms. Absolute cross sections for charge-exchange, ionization, stripping and excitation were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss, and optical spectroscopy. The experimental data and the schematic correlation diagrams have been employed to analyze and determine the mechanisms for these processes.
14. Precision measurements of cross-sections for inelastic processes in collisions of alkali metal ions with atoms of rare gases
Science.gov (United States)
Lomsadze, R. A.; Gochitashvili, M. R.; Kezerashvili, R. Ya.
2017-01-01
A multifaceted experimental study of collisions of Na+ and K+ ions in the energy range of 0.5-10 keV with He and Ar atoms is presented. Absolute cross-sections for charge-exchange, ionization, stripping and excitation processes were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss and optical spectroscopy methods. The experimental data and the schematic correlation diagrams are employed to analyze and determine the mechanisms for these processes.
15. Three-body recombination of two-component cold atomic gases into deep dimers in an optical model
DEFF Research Database (Denmark)
Mikkelsen, Mathias; Jensen, A. S.; Fedorov, D. V.
2015-01-01
We consider three-body recombination into deep dimers in a mass-imbalanced two-component atomic gas. We use an optical model where a phenomenological imaginary potential is added to the lowest adiabatic hyper-spherical potential. The consequent imaginary part of the energy eigenvalue corresponds...... to the decay rate or recombination probability of the three-body system. The method is formulated in details and the relevant qualitative features are discussed as functions of scattering lengths and masses. We use zero-range model in analyses of recent recombination data. The dominating scattering length...
16. Topological insulators in cold-atom gases with non-Abelian gauge fields: the role of interactions
Energy Technology Data Exchange (ETDEWEB)
Orth, Peter Philipp [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie, 76128 Karlsruhe (Germany); Cocks, Daniel; Buchhold, Michael; Hofstetter, Walter [Institut fuer Theoretische Physik, Goethe Universitaet, 60438 Frankfurt am Main (Germany); Rachel, Stephan [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Le Hur, Karyn [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Center for Theoretical Physics, Ecole Polytechnique, 91128 Palaiseau Cedex (France)
2012-07-01
With the recent technological advance of creating (non)-Abelian gauge fields for ultracold atoms in optical lattices, it becomes possible to study the interplay of topological phases and interactions in these systems. Specifically, we consider a spinful and time-reversal invariant version of the Hofstadter problem. In addition, we allow for a hopping term which does not preserve S{sub z} spin symmetry and a staggered sublattice potential. Without interactions, the parameters can be tuned such that the system is a topological insulator. Using a combination of analytical techniques and the powerful real-space dynamical mean-field (R-DMFT) method, we discuss the effect of interactions and determine the interacting phase diagram.
17. Thermodynamics of Quantum Gases for the Entire Range of Temperature
Science.gov (United States)
Biswas, Shyamal; Jana, Debnarayan
2012-01-01
We have analytically explored the thermodynamics of free Bose and Fermi gases for the entire range of temperature, and have extended the same for harmonically trapped cases. We have obtained approximate chemical potentials for the quantum gases in closed forms of temperature so that the thermodynamic properties of the quantum gases become…
18. Atoms
Institute of Scientific and Technical Information of China (English)
刘洪毓
2007-01-01
Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what
19. Feneric Fermi Size Enhancement of Pairing in Mesoscopic Fermi Systems
CERN Document Server
Farine, M; Schuck, P; Viñas, X
2002-01-01
The finite size dependent enhancement of pairing in mesoscopic Fermi systems is studied under the assumption that the BCS approach is valid and that the two body force is size independent. Different systems are investigated such as superconducting metallic grains and films as well as atomic nuclei. It is shown that the finite size enhancement of pairing in these systems is a surface effect which, when properly included, accounts for the data.
20. Observation of a pairing pseudogap in a two-dimensional Fermi gas.
Science.gov (United States)
Feld, Michael; Fröhlich, Bernd; Vogt, Enrico; Koschorreck, Marco; Köhl, Michael
2011-11-30
Pairing of fermions is ubiquitous in nature, underlying many phenomena. Examples include superconductivity, superfluidity of (3)He, the anomalous rotation of neutron stars, and the crossover between Bose-Einstein condensation of dimers and the BCS (Bardeen, Cooper and Schrieffer) regime in strongly interacting Fermi gases. When confined to two dimensions, interacting many-body systems show even more subtle effects, many of which are not understood at a fundamental level. Most striking is the (as yet unexplained) phenomenon of high-temperature superconductivity in copper oxides, which is intimately related to the two-dimensional geometry of the crystal structure. In particular, it is not understood how the many-body pairing is established at high temperature, and whether it precedes superconductivity. Here we report the observation of a many-body pairing gap above the superfluid transition temperature in a harmonically trapped, two-dimensional atomic Fermi gas in the regime of strong coupling. Our measurements of the spectral function of the gas are performed using momentum-resolved photoemission spectroscopy, analogous to angle-resolved photoemission spectroscopy in the solid state. Our observations mark a significant step in the emulation of layered two-dimensional strongly correlated superconductors using ultracold atomic gases.
1. Universal spin transport in a strongly interacting Fermi gas.
Science.gov (United States)
Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W
2011-04-14
Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.
2. Closed-Form Solutions of the Thomas-Fermi in Heavy Atoms and the Langmuir-Blodgett in Current Flow ODEs in Mathematical Physics
Directory of Open Access Journals (Sweden)
Efstathios E. Theotokoglou
2015-01-01
Full Text Available Two kinds of second-order nonlinear, ordinary differential equations (ODEs appearing in mathematical physics are analyzed in this paper. The first one concerns the Thomas-Fermi (TF equation, while the second concerns the Langmuir-Blodgett (LB equation in current flow. According to a mathematical methodology recently developed, the exact analytic solutions of both TF and LB ODEs are proposed. Both of these are nonlinear of the second order and by a series of admissible functional transformations are reduced to Abel’s equations of the second kind of the normal form. The closed form solutions of the TF and LB equations in the phase and physical plane are given. Finally a new interesting result has been obtained related to the derivative of the TF function at the limit.
3. Umklapp superradiance with a collisionless quantum degenerate Fermi gas.
Science.gov (United States)
Piazza, Francesco; Strack, Philipp
2014-04-11
The quantum dynamics of the electromagnetic light mode of an optical cavity filled with a coherently driven Fermi gas of ultracold atoms strongly depends on the geometry of the Fermi surface. Superradiant light generation and self-organization of the atoms can be achieved at low pumping threshold due to resonant atom-photon umklapp processes, where the fermions are scattered from one side of the Fermi surface to the other by exchanging photon momenta. The cavity spectrum exhibits sidebands that, despite strong atom-light coupling and cavity decay, retain narrow linewidth, due to absorptionless transparency windows outside the atomic particle-hole continuum and the suppression of broadening and thermal fluctuations in the collisionless Fermi gas.
Institute of Scientific and Technical Information of China (English)
郭飞翔; 周晓凡; 赵华
2015-01-01
采用密度矩阵重整化群 ( density-matrix-renormalization-group, DMRG) 方法, 研究梯状光晶格中排斥相互作用费米气体的基态属性. 研究表明, Zeeman场能够激发系统的相分离 (完全极化相和部分极化相), 而自旋轨道耦合效应能抑制相分离, 使整个晶格处于部分极化相, 在不同的强弱排斥相互作用系统中, 极化率会随自旋轨道耦合改变表现出不同的变化规律.%The density-matrix-renormalization-group ( DMRG ) method is used to numerically calculate the ground state of repulsively interacting Fermi atoms loaded in optical ladder lattices. It is found that the system exhibits the spatial separation of a fully spin-polarized phase from the partially polarized phase for the suitable intensity of Zeeman field without the effect of spin-orbit coupled atoms. The spin-orbit coupling drives the fully spin-polarized phase to the partially spin-polarized phase in the whole system. The spin polarizations of weak and strong repulsively interac-ting systems vary differently with spin-orbit interaction strength.
5. The universal sound velocity formula for the strongly interacting unitary Fermi gas
Institute of Scientific and Technical Information of China (English)
Liu Ke; Chen Ji-Sheng
2011-01-01
Due to the scale invariance, the thermodynamic laws of strongly interacting limit unitary Fermi gas can be similar to those of non-interacting ideal gas. For example, the virial theorem between pressure and energy density of the ideal gas P = 2E/ZV is still satisfied by the unitary Fermi gas. This paper analyses the sound velocity of unitary Fermi gases with the quasi-linear approximation. For comparison, the sound velocities for the ideal Boltzmann, Bose and Fermi gas are also given. Quite interestingly, the sound velocity formula for the ideal non-interacting gas is found to be satisfied by the unitary Fermi gas in different temperature regions.
6. Quantum phases of Fermi-Fermi mixtures in optical lattices
OpenAIRE
Iskin, M.; de Melo, C. A. R. Sa
2007-01-01
The ground state phase diagram of Fermi-Fermi mixtures in optical lattices is analyzed as a function of interaction strength, population imbalance, filling fraction and tunneling parameters. It is shown that population imbalanced Fermi-Fermi mixtures reduce to strongly interacting Bose-Fermi mixtures in the molecular limit, in sharp contrast to homogeneous or harmonically trapped systems where the resulting Bose-Fermi mixture is weakly interacting. Furthermore, insulating phases are found in ...
7. Mott criticality and pseudogap in Bose-Fermi mixtures.
Science.gov (United States)
Altman, Ehud; Demler, Eugene; Rosch, Achim
2012-12-07
We study the Mott transition of a mixed Bose-Fermi system of ultracold atoms in an optical lattice, where the number of (spinless) fermions and bosons adds up to one atom per lattice, n(F)+n(B)=1. For weak interactions, a Fermi surface coexists with a Bose-Einstein condensate while for strong interaction the system is incompressible but still characterized by a Fermi surface of composite fermions. At the critical point, the spectral function of the fermions A(k,ω) exhibits a pseudogapped behavior, rising as |ω| at the Fermi momentum, while in the Mott phase it is fully gapped. Taking into account the interaction between the critical modes leads at very low temperatures either to p-wave pairing or the transition is driven weakly first order. The same mechanism should also be important in antiferromagnetic metals with a small Fermi surface.
8. Thermodynamic property of gases in the sonoluminescing bubble
Institute of Scientific and Technical Information of China (English)
AN Yu; LI Guiqin; ZHOU Tieying
2001-01-01
With the theory of statistical physics dealing with chemical reaction (the law of mass action), the different thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a small bubble semi-quantitatively are analyzed. As bubbles of the mono-atomic and the diatomic gases are compressed, shock waves are produced in both bubbles. Though shock wave leads to sharp increase of pressure and temperature of gases in the bubble, diatomic gas will excitated vibrations and dissociate themselves to mono-atomic gas,these processes will consume many accumulated heat energy and block the further increase of the temperature. Therefore, compare with the mono-atomic gases in the bubble, there will be no enough charged particles ionized to flash for diatomic gases in the bubble, this may be the reason why a bubble of diatomic gases has no single bubble sonoluminescence while a bubble of noble gases has.
9. Irritant gases
NARCIS (Netherlands)
Meulenbelt, J
2016-01-01
Acute inhalation injury can result from the use of household cleaning agents (e.g. chlorine, ammonia), industrial or combustion gases (e.g. sulfur dioxide, nitrogen oxides) or bioterrorism. The severity of the injury is to a great extent determined by the circumstances of exposure. If exposure was i
10. Greenhouse Gases
Science.gov (United States)
... life. Governments all around the world ban and control production and use of several industrial gases that destroy atmospheric ozone and create a hole in the ozone layer . At lower elevations of the atmosphere (the troposphere), ozone is harmful to ... for Future Emissions FAQs How much carbon dioxide is produced when ...
11. Fermi comes to CERN
CERN Multimedia
NASA
2009-01-01
1. This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. (Credit: NASA/DOE/Fermi LAT Collaboration) 2. The Large Area Telescope (LAT) on Fermi detects gamma-rays through matter (electrons) and antimatter (positrons) they produce after striking layers of tungsten. (Credit: NASA/Goddard Space Flight Center Conceptual Image Lab)
12. Atomic physics
CERN Document Server
Born, Max
1989-01-01
The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.
13. Fermi LAT GRBs
Data.gov (United States)
National Aeronautics and Space Administration — All analysis results presented here are preliminary and are not intended as an official catalog of Fermi-LAT detected GRBs. Please consult the table's caveat page...
14. Fermi GBM Trigger Catalog
Data.gov (United States)
National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...
15. Enrico Fermi centenary exhibition seminar
CERN Multimedia
Maximilien Brice
2002-01-01
Photo 01: Dr. Juan Antonio Rubio, Leader of the Education and Technology Transfer Division and CERN Director General, Prof. Luciano Maiani. Photo 03: Luciano Maiani, Welcome and Introduction Photo 09: Antonino Zichichi, The New 'Centro Enrico Fermi' at Via Panisperna Photos 10, 13: Ugo Amaldi, Fermi at Via Panisperna and the birth of Nuclear Medicine Photo 14: Jack Steinberger, Fermi in Chicago Photo 18: Valentin Telegdi, A close-up of Fermi Photo 21: Arnaldo Stefanini, Celebrating Fermi's Centenary in Documents and Pictures.
16. Energy-pressure relation for low-dimensional gases
Science.gov (United States)
Mancarella, Francesco; Mussardo, Giuseppe; Trombettoni, Andrea
2014-10-01
A particularly simple relation of proportionality between internal energy and pressure holds for scale-invariant thermodynamic systems (with Hamiltonians homogeneous functions of the coordinates), including classical and quantum - Bose and Fermi - ideal gases. One can quantify the deviation from such a relation by introducing the internal energy shift as the difference between the internal energy of the system and the corresponding value for scale-invariant (including ideal) gases. After discussing some general thermodynamic properties associated with the scale-invariance, we provide criteria for which the internal energy shift density of an imperfect (classical or quantum) gas is a bounded function of temperature. We then study the internal energy shift and deviations from the energy-pressure proportionality in low-dimensional models of gases interpolating between the ideal Bose and the ideal Fermi gases, focusing on the Lieb-Liniger model in 1d and on the anyonic gas in 2d. In 1d the internal energy shift is determined from the thermodynamic Bethe ansatz integral equations and an explicit relation for it is given at high temperature. Our results show that the internal energy shift is positive, it vanishes in the two limits of zero and infinite coupling (respectively the ideal Bose and the Tonks-Girardeau gas) and it has a maximum at a finite, temperature-depending, value of the coupling. Remarkably, at fixed coupling the energy shift density saturates to a finite value for infinite temperature. In 2d we consider systems of Abelian anyons and non-Abelian Chern-Simons particles: as it can be seen also directly from a study of the virial coefficients, in the usually considered hard-core limit the internal energy shift vanishes and the energy is just proportional to the pressure, with the proportionality constant being simply the area of the system. Soft-core boundary conditions at coincident points for the two-body wavefunction introduce a length scale, and induce a
17. Temperature dependence of the universal contact parameter in a unitary Fermi gas.
Science.gov (United States)
Kuhnle, E D; Hoinka, S; Dyke, P; Hu, H; Hannaford, P; Vale, C J
2011-04-29
The contact I, introduced by Tan, has emerged as a key parameter characterizing universal properties of strongly interacting Fermi gases. For ultracold Fermi gases near a Feshbach resonance, the contact depends upon two quantities: the interaction parameter 1/(k(F)a), where k(F) is the Fermi wave vector and a is the s-wave scattering length, and the temperature T/T(F), where T(F) is the Fermi temperature. We present the first measurements of the temperature dependence of the contact in a unitary Fermi gas using Bragg spectroscopy. The contact is seen to follow the predicted decay with temperature and shows how pair-correlations at high momentum persist well above the superfluid transition temperature.
18. Strongly correlated quantum fluids: ultracold quantum gases, quantum chromodynamic plasmas and holographic duality
Science.gov (United States)
Adams, Allan; Carr, Lincoln D.; Schäfer, Thomas; Steinberg, Peter; Thomas, John E.
2012-11-01
Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical and that do not have a simple description in terms of weakly interacting quasiparticles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by 19 orders of magnitude in temperature, but were shown to exhibit very similar hydrodynamic flows. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio, which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields, and also serves as an introduction to the focus issue of New Journal of Physics on ‘Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to Quantum Chromodynamic Plasmas’. The presentation is accessible to the general physics reader and includes discussions of the latest research developments in all three areas.
19. Atomic polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)
2015-01-22
The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.
20. Enrico Fermi exhibition at CERN
CERN Document Server
2002-01-01
A touring exhibition celebrating the centenary of Enrico Fermi's birth in 1901 will be on display at CERN (Main Building, Mezzanine) from 12-27 September. You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani Welcome and Introduction Arnaldo Stefanini Celebrating Fermi's Centenary in Documents and Pictures Antonino Zichichi The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger Fermi in Chicago Valentin Telegdi A Close-up of Fermi and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (In Italian, with English subtitles - c. 30 mins). This will be followed by an aperitif on the Mezz...
1. A long-lived spin-orbit-coupled degenerate dipolar Fermi gas
CERN Document Server
Burdick, Nathaniel Q; Lev, Benjamin L
2016-01-01
We describe the creation of a long-lived spin-orbit-coupled gas of quantum degenerate atoms using the most magnetic fermionic element, dysprosium. Spin-orbit-coupling arises from a synthetic gauge field created by the adiabatic following of degenerate dressed states comprised of optically coupled components of an atomic spin. Because of dysprosium's large electronic orbital angular momentum and large magnetic moment, the lifetime of the gas is limited not by spontaneous emission from the light-matter coupling, as for gases of alkali-metal atoms, but by dipolar relaxation of the spin. This relaxation is suppressed at large magnetic fields due to Fermi statistics. We observe lifetimes up to 400 ms, which exceeds that of spin-orbit-coupled fermionic alkali atoms by a factor of 10-100, and is close to the value obtained from a theoretical model. Elastic dipolar interactions are also observed to influence the Rabi evolution of the spin, revealing an interacting fermionic system. The long lifetime of this weakly in...
2. A new look at Thomas–Fermi theory
DEFF Research Database (Denmark)
Solovej, Jan Philip
2016-01-01
In this short note, we argue that Thomas–Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental...... and rigorous mathematical evidence for this claim. Motivated by this, we formulate two new mathematical conjectures on the exactness of Thomas–Fermi theory....
3. A new look at Thomas-Fermi Theory
CERN Document Server
Solovej, Jan Philip
2016-01-01
In this short note we argue that Thomas-Fermi Theory the simplest of all density functional theories, although failing to explain features such as binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental and rigorous mathematical evidence for this claim. Motivated by this we formulate two new mathematical conjectures on the exactness of Thomas-Fermi Theory.
4. The Fermi's Bayes Theorem
CERN Document Server
D'Agostini, G
2005-01-01
It is curious to learn that Enrico Fermi knew how to base probabilistic inference on Bayes theorem, and that some influential notes on statistics for physicists stem from what the author calls elsewhere, but never in these notes, {\\it the Bayes Theorem of Fermi}. The fact is curious because the large majority of living physicists, educated in the second half of last century -- a kind of middle age in the statistical reasoning -- never heard of Bayes theorem during their studies, though they have been constantly using an intuitive reasoning quite Bayesian in spirit. This paper is based on recollections and notes by Jay Orear and on Gauss' Theoria motus corporum coelestium'', being the {\\it Princeps mathematicorum} remembered by Orear as source of Fermi's Bayesian reasoning.
5. Fermi comes to CERN
CERN Multimedia
2009-01-01
In only 10 months of scientific activity, the Fermi space observatory has already collected an unprecedented wealth of information on some of the most amazing objects in the sky. In a recent talk at CERN, Luca Latronico, a member of the Fermi collaboration, explained some of their findings and emphasized the strong links between High Energy Physics (HEP) and High Energy Astrophysics (HEA). The Fermi gamma-ray telescope was launched by NASA in June 2008. After about two months of commissioning it started sending significant data back to the Earth. Since then, it has made observations that are changing our view of the sky: from discovering a whole new set of pulsars, the greatest total energy gamma-ray burst ever, to detecting an unexplained abundance of high-energy electrons that could be a signature of dark matter, to producing a uniquely rich and high definition sky map in gamma-rays. The high performance of the instrument comes as ...
6. Quantum Gas Microscope for Fermionic Atoms
Science.gov (United States)
Okan, Melih; Cheuk, Lawrence; Nichols, Matthew; Lawrence, Katherine; Zhang, Hao; Zwierlein, Martin
2016-05-01
Strongly interacting fermions define the properties of complex matter throughout nature, from atomic nuclei and modern solid state materials to neutron stars. Ultracold atomic Fermi gases have emerged as a pristine platform for the study of many-fermion systems. In this poster we demonstrate the realization of a quantum gas microscope for fermionic 40 K atoms trapped in an optical lattice and the recent experiments which allows one to probe strongly correlated fermions at the single atom level. We combine 3D Raman sideband cooling with high- resolution optics to simultaneously cool and image individual atoms with single lattice site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site resolved imaging of fermions enables the direct observation of magnetic order, time resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement. NSF, AFOSR-PECASE, AFOSR-MURI on Exotic Phases of Matter, ARO-MURI on Atomtronics, ONR, a Grant from the Army Research Office with funding from the DARPA OLE program, and the David and Lucile Packard Foundation.
7. Atomic phase diagram
Institute of Scientific and Technical Information of China (English)
LI Shichun
2004-01-01
Based on the Thomas-Fermi-Dirac-Cheng model, atomic phase diagram or electron density versus atomic radius diagram describing the interaction properties of atoms of different kinds in equilibrium state is developed. Atomic phase diagram is established based on the two-atoms model. Besides atomic radius, electron density and continuity condition for electron density on interfaces between atoms, the lever law of atomic phase diagram involving other physical parameters is taken into account, such as the binding energy, for the sake of simplicity.
8. Formation of noble-gas hydrides and decay of solvated protons revisited: diffusion-controlled reactions and hydrogen atom losses in solid noble gases.
Science.gov (United States)
Tanskanen, Hanna; Khriachtchev, Leonid; Lignell, Antti; Räsänen, Markku; Johansson, Susanna; Khyzhniy, Ivan; Savchenko, Elena
2008-02-07
UV photolysis and annealing of C2H2/Xe, C2H2/Xe/Kr, and HBr/Xe matrices lead to complicated photochemical processes and reactions. The dominating products in these experiments are noble-gas hydrides with general formula HNgY (Ng = noble-gas atom, Y = electronegative fragment). We concentrate on distinguishing the local and global mobility and losses of H atoms, barriers of the reactions, and the decay of solvated protons. Different deposition temperatures change the amount of lattice imperfections and thus the amount of traps for H atoms. The averaged distance between reacting species influencing the reaction kinetics is controlled by varying the precursor concentration. A number of solid-state processes connected to the formation of noble-gas hydrides and decay of solvated protons are discussed using a simple kinetic model. The most efficient formation of noble-gas hydrides is connected with global (long-range) mobility of H atoms leading to the H + Xe + Y reaction. The highest concentration of noble-gas hydrides was obtained in matrices of highest optical quality, which probably have the lowest concentration of defects and H-atom losses. In matrices with high amount of geometrical imperfections, the product formation is inefficient and dominated by a local (short-range) process. The decay of solvated protons is rather local than a global process, which is different from the formation of noble-gas molecules. However, the present data do not allow distinguishing local proton and electron mobilities. Our previous results indicate that these are electrons which move to positively-charged centers and neutralize them. It is believed that the image obtained here for solid xenon is applicable to solid krypton whereas the case of argon deserves special attention.
9. Physics of Ionized Gases
Science.gov (United States)
Reiss, Howard R.; Smirnov, Boris M.
2001-03-01
A comprehensive textbook and reference for the study of the physics of ionized gases The intent of this book is to provide deep physical insight into the behavior of gases containing atoms and molecules from which one or more electrons have been ionized. The study of these so-called plasmas begins with an overview of plasmas as they are found in nature and created in the laboratory. This serves as a prelude to a comprehensive study of plasmas, beginning with low temperature and "ideal" plasmas and extending to radiation and particle transport phenomena, the response of plasmas to external fields, and an insightful treatment of plasma waves, plasma instabilities, nonlinear phenomena in plasmas, and the study of plasma interactions with surfaces. In all cases, the emphasis is on a clear and unified understanding of the basic physics that underlies all plasma phenomena. Thus, there are chapters on plasma behavior from the viewpoint of atomic and molecular physics, as well as on the macroscopic phenomena involved in physical kinetics of plasmas and the transport of radiation and of charged particles within plasmas. With this grounding in the fundamental physics of plasmas, the notoriously difficult subjects of nonlinear phenomena and of instabilities in plasmas are then treated with comprehensive clarity.
10. Doping dependence of electronic and mechanical properties of GaSe1-xTex and Ga1-xInxSe from first principles
Science.gov (United States)
Rak, Zs.; Mahanti, S. D.; Mandal, Krishna C.; Fernelius, N. C.
2010-10-01
The electronic and mechanical properties of the hexagonal, layered GaSe doped with Te and In have been studied using first-principles pseudopotential method within density-functional theory. The calculated elastic constants of the end compounds GaSe and InSe compare well with the available experimental and theoretical values. As we go from GaSe to InSe, the elastic constants C13 , C33 , and C44 increase while C11 and C12 decrease, suggesting that the crystal becomes stiffer in the direction perpendicular to the atomic layers and the softer in the direction parallel to the layers, as more substitutional In is incorporated in GaSe. The electronic structure and the formation energies of several defects and simple defect complexes are discussed and the calculated charge transition levels are compared to available experimental data. We demonstrate that In doping may play an important role in the observed enhancement in the structural properties of GaSe. Depending on the Fermi energy, In can either substitute for Ga (InGa) or occupy an interstitial position as a triply charged defect (Ini3+) . While the substitutional In does not change significantly the electronic and mechanical properties of the host, we find that the shear stiffness of GaSe is considerably increased when In is incorporated as charged interstitial impurity.
11. Schottky barrier engineering via adsorbing gases at the sulfur vacancies in the metal–MoS2 interface
Science.gov (United States)
Su, Jie; Feng, Liping; Zhang, Yan; Liu, Zhengtang
2017-03-01
Sulfur vacancies (S-vacancies) are common in monolayer MoS2 (mMoS2). Finding an effective way to control rather than abolish the effect of S-vacancies on contact properties is vital for the application of mMoS2. Here, we propose the adsorption of gases to passivate the S-vacancies in Pt–mMoS2 interfaces. Results demonstrate that gases are stably and preferentially adsorbed at S-vacancies. The n-type Schottky barriers of Pt–mMoS2 interfaces are reduced significantly upon the adsorption electron-donor gases, especially Cl2. The n-type transport character of the Pt–mMoS2 interface can be changed to p-type by the adsorption of electron-acceptor gases. As the adsorption concentration increases, both n- and p-type Schottky barriers are further reduced, and the lowest n- and p-type Schottky barriers are 0.36 and 0 eV, respectively. Note that the variations in Schottky barriers are independent of the oxidizing ability of gases but relative to the average number of valence electrons per gas atom. Analysis demonstrates that although gases at S-vacancies cannot cause gap states to vanish, and can even enhance Fermi level pinning, they modulate charge redistribution and the potential step at the interface region. Moreover, with increasing adsorption concentration, the valence band maximum of mMoS2 shows the opposite variation tendency to that of the potential step. Our results suggest that adsorption of gases is an effective way to passivate S-vacancies to modulate the transport properties of Pt–mMoS2 interfaces.
12. From few to many. Ultracold atoms in reduced dimensions
Energy Technology Data Exchange (ETDEWEB)
Wenz, Andre Niklas
2013-12-19
This thesis reports on experimental studies exploring few and many-body physics of ultracold Bose and Fermi gases with reduced dimensionality. These experiments illustrate the versatility and great amount of control over the particle number, the interaction and other degrees of freedom, like the spin, that these generic quantum systems offer. In the first part of this thesis, we use quasi one-dimensional few-particle systems of one to ten fermionic atoms to investigate the crossover from few to many-body physics. This is achieved by measuring the interaction energy between a single impurity atom in a state vertical stroke ↓ right angle which repulsively interacts with an increasing number of majority atoms in a state vertical stroke ↑ right angle. We find that the system quickly approaches the results from the many-body theory, which describes the behavior of a single impurity immersed in a Fermi sea of an infinite number of majority particles. The second part of this thesis presents studies of the time evolution of a bosonic F=1 spinor BEC of {sup 87}Rb atoms. In this system, we investigate the emergence and coarsening of ferromagnetic spin textures from initially unmagnetized samples. While the ferromagnetic domains grow, we observe the development of a spin space anisotropy which is in agreement with the predicted phase-diagram. The last part of this thesis presents our first steps towards the investigation of phase coherence of quasi two-dimensional quantum gases in the crossover from bosonic molecules to fermionic atoms.
13. Leaky Fermi accelerators
CERN Document Server
Shah, Kushal; Rom-Kedar, Vered; Turaev, Dmitry
2015-01-01
A Fermi accelerator is a billiard with oscillating walls. A leaky accelerator interacts with an environment of an ideal gas at equilibrium by exchange of particles through a small hole on its boundary. Such interaction may heat the gas: we estimate the net energy flow through the hole under the assumption that the particles inside the billiard do not collide with each other and remain in the accelerator for sufficiently long time. The heat production is found to depend strongly on the type of the Fermi accelerator. An ergodic accelerator, i.e. one which has a single ergodic component, produces a weaker energy flow than a multi-component accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multi-component case the energy flow may be significantly increased by shrinking the hole size.
14. Virial theorem and universality in a unitary fermi gas.
Science.gov (United States)
Thomas, J E; Kinast, J; Turlapov, A
2005-09-16
Unitary Fermi gases, where the scattering length is large compared to the interparticle spacing, can have universal properties, which are independent of the details of the interparticle interactions when the range of the scattering potential is negligible. We prepare an optically trapped, unitary Fermi gas of 6Li, tuned just above the center of a broad Feshbach resonance. In agreement with the universal hypothesis, we observe that this strongly interacting many-body system obeys the virial theorem for an ideal gas over a wide range of temperatures. Based on this result, we suggest a simple volume thermometry method for unitary gases. We also show that the observed breathing mode frequency, which is close to the unitary hydrodynamic value over a wide range of temperature, is consistent with a universal hydrodynamic gas with nearly isentropic dynamics.
15. Trends in structural, electronic properties, Fermi surface topology, and inter-atomic bonding in the series of ternary layered dichalcogenides KNi{sub 2}S{sub 2}, KNi{sub 2}Se{sub 2}, and KNi{sub 2}Te{sub 2} from first principles calculations
Energy Technology Data Exchange (ETDEWEB)
Bannikov, V.V. [Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, Pervomaiskaya Street, 91, Ekaterinburg 620990 (Russian Federation); Ivanovskii, A.L., E-mail: [email protected] [Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, Pervomaiskaya Street, 91, Ekaterinburg 620990 (Russian Federation)
2013-06-01
By means of the FLAPW-GGA approach, we have systematically studied the structural and electronic properties of tetragonal dichalcogenides KNi{sub 2}Ch{sub 2} (Ch=S, Se, and Te). Our results show that replacements of chalcogens (S→Se→Te) lead to anisotropic deformations of the crystals structure, which are related to the strong anisotropic character of the inter-atomic bonds, where inside the [Ni{sub 2}Ch{sub 2}] blocks, mixed covalent–ionic–metallic bonds occur, whereas between the adjacent [Ni{sub 2}Ch{sub 2}] blocks and K atomic sheets, ionic bonds emerge. We found that in the sequence KNi{sub 2}S{sub 2}→KNi{sub 2}Se{sub 2}→KNi{sub 2}Te{sub 2} (i) the overall band structure (where the near-Fermi valence bands are due mainly to the Ni states) is preserved, but the width of the common valence band and the widths of the separate sub-bands and the gaps decrease; (ii) the total DOSs at the Fermi level also decrease; and (iii) for the Fermi surfaces, the most appreciable changes are demonstrated by the hole-like sheets, when a necklace-like topology is formed for the 2D-like sheets and the volume of the closed pockets decreases. Some trends in structural and electronic parameters for ThCr{sub 2}Si{sub 2}-type layered dichalcogenides, KNi{sub 2}Ch{sub 2}, KFe{sub 2}Ch{sub 2}, KCo{sub 2}Se{sub 2}, are discussed.
16. Gradient catastrophe and Fermi-edge resonances in Fermi gas.
Science.gov (United States)
Bettelheim, E; Kaplan, Y; Wiegmann, P
2011-04-22
Any smooth spatial disturbance of a degenerate Fermi gas inevitably becomes sharp. This phenomenon, called the gradient catastrophe, causes the breakdown of a Fermi sea to multiconnected components characterized by multiple Fermi points. We argue that the gradient catastrophe can be probed through a Fermi-edge singularity measurement. In the regime of the gradient catastrophe the Fermi-edge singularity problem becomes a nonequilibrium and nonstationary phenomenon. We show that the gradient catastrophe transforms the single-peaked Fermi-edge singularity of the tunneling (or absorption) spectrum to a sequence of multiple asymmetric singular resonances. An extension of the bosonic representation of the electronic operator to nonequilibrium states captures the singular behavior of the resonances.
17. Mode analysis of fluctuations in two-species Bose-Einstein condensates of atomic gases with a vortex for a component. Characteristic features of compressive and sliding motions
Energy Technology Data Exchange (ETDEWEB)
Doi, Kensuke; Natsume, Yuhei [Chiba Univ., Graduate School of Science and Technology, Chiba (Japan)
2003-04-01
Characteristic features of fluctuations of Bose-Einstein condensations for systems of two-components in gas phases of alkali-metal atoms trapped by spherical harmonic potentials are discussed on the basis of numerical calculations. We concentrate our attention on the phases in which the spherical state {psi}{sub 1} without vortex is surrounded by {psi}{sub 2} with a vortex for the unit circulation q=1. These states are expressed by Gross-Pitaevskii equation, where a vortex-core is along the z-axis. We investigate properties of collective excitations by the linear analysis for bosonic excitations described as Bogoliubov equations. The behavior of each mode is discussed in relation with the role of interspecies repulsion in addition to that of intraspecies one. We point out the role of the new compressive mode which has two nodes on z-axis, in addition to that of the core mode without a node which have been previously discussed in the single-component system. Furthermore, we would like to emphasize that sliding modes show the branching features into in- and out-of-phase motions with increasing interspecies interaction. The dependence of those branchings on interspecies repulsion is explained by spatial shapes of relevant modes. (author)
18. A new look at Thomas–Fermi theory
DEFF Research Database (Denmark)
Solovej, Jan Philip
2016-01-01
In this short note, we argue that Thomas–Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental and rig...... and rigorous mathematical evidence for this claim. Motivated by this, we formulate two new mathematical conjectures on the exactness of Thomas–Fermi theory.......In this short note, we argue that Thomas–Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental...
19. Observation of hydrodynamic expansion in a strongly-interacting Fermi gas: Signature of superfluidity?
Science.gov (United States)
O'Hara, K. M.; Hemmer, S. L.; Gehm, M. E.; Thomas, J. E.
2003-05-01
Atomic Fermi gases with magnetically tunable, strong interactions provide a desktop laboratory for exploring new nonperturbative theories in systems ranging from superconductors to neutron stars. We use all-optical methods to produce a highly degenerate, two-component gas of ^6Li atoms in an applied magnetic field (910 G) near a Feshbach resonance where strong interactions are observed [1]. The s-wave scattering length is estimated to be a_S=-10^4 a_0, which is large compared to the interparticle spacing. Exciting new predictions for this regime include unitarity-limited universal interactions [2] and the onset of resonance superfluidity at a very high transition temperature [3-5]. Forced evaporation is accomplished by lowering the trap laser intensity over a period of 3.5 seconds and then recompressing the trap to full depth. Abrupt release of the cloud at 910 G results in a highly anisotropic expansion, where the gas expands rapidly in the transverse directions while remaining nearly stationary in the axial direction [1]. This anisotropic energy release has been predicted recently to be a signature of superfluidity in a Fermi gas [6]. We will discuss interpretations of the data in terms of superfluidity and unitarity-limited collision dynamics. References 1. K. M. O'Hara et al., Science, 298, 2179 (2002). 2. H. Heiselberg, Phys. Rev. A 63, 043606 (2001). 3. M. Holland, et al., Phys. Rev. Lett. 87, 120406 (2001). 4. E. Timmermans, et al., Phys. Lett. A 285, 228 (2001). 5. Y. Ohashi and A. Griffin, Phys. Rev. Lett. 89, 130402 (2002). 6. C. Menotti, et al., Phys. Rev. Lett. 89, 250402 (2002).
20. Chiral non-Fermi liquids
Science.gov (United States)
Sur, Shouvik; Lee, Sung-Sik
2014-07-01
A non-Fermi liquid state without time-reversal and parity symmetries arises when a chiral Fermi surface is coupled with a soft collective mode in two space dimensions. The full Fermi surface is described by a direct sum of chiral patch theories, which are decoupled from each other in the low-energy limit. Each patch includes low-energy excitations near a set of points on the Fermi surface with a common tangent vector. General patch theories are classified by the local shape of the Fermi surface, the dispersion of the critical boson, and the symmetry group, which form the data for distinct universality classes. We prove that a large class of chiral non-Fermi liquid states exists as stable critical states of matter. For this, we use a renormalization group scheme where low-energy excitations of the Fermi surface are interpreted as a collection of (1+1)-dimensional chiral fermions with a continuous flavor labeling the momentum along the Fermi surface. Due to chirality, the Wilsonian effective action is strictly UV finite. This allows one to extract the exact scaling exponents although the theories flow to strongly interacting field theories at low energies. In general, the low-energy effective theory of the full Fermi surface includes patch theories of more than one universality classes. As a result, physical responses include multiple universal components at low temperatures. We also point out that, in quantum field theories with extended Fermi surface, a noncommutative structure naturally emerges between a coordinate and a momentum which are orthogonal to each other. We show that the invalidity of patch description for Fermi liquid states is tied with the presence of UV/IR mixing associated with the emergent noncommutativity. On the other hand, UV/IR mixing is suppressed in non-Fermi liquid states due to UV insensitivity, and the patch description is valid.
1. Thermodynamic properties of noninteracting quantum gases with spin-orbit coupling
Energy Technology Data Exchange (ETDEWEB)
He Li [Jiangsu University of Science and Technology, Zhangjiagang, Jiangsu, 215600 (China); Yu Zengqiang [Institute for Advanced Study, Tsinghua University, Beijing, 100084 (China)
2011-08-15
In this brief report we study thermodynamic properties of noninteracting quantum gases with isotropic spin-orbit coupling. At high temperature, coefficients of virial expansion depend on both temperature T and spin-orbit coupling strength {kappa}. For strong coupling, virial expansion is applicable to the temperature region below the conventional degenerate temperature T{sub F}. At low temperature, specific heat is proportional to {radical}(T) in Bose gases and T in Fermi gases. Temperature dependence of the chemical potential of fermions shows a different behavior when the Fermi surface is above and below the Dirac point.
2. Berry Fermi liquid theory
Science.gov (United States)
Chen, Jing-Yuan; Son, Dam Thanh
2017-02-01
We develop an extension of the Landau Fermi liquid theory to systems of interacting fermions with non-trivial Berry curvature. We propose a kinetic equation and a constitutive relation for the electromagnetic current that together encode the linear response of such systems to external electromagnetic perturbations, to leading and next-to-leading orders in the expansion over the frequency and wave number of the perturbations. We analyze the Feynman diagrams in a large class of interacting quantum field theories and show that, after summing up all orders in perturbation theory, the current-current correlator exactly matches with the result obtained from the kinetic theory.
3. Spin-Seebeck effect in a strongly interacting Fermi gas
NARCIS (Netherlands)
Wong, C.H.; Stoof, H.T.C.; Duine, R.A.
2012-01-01
We study the spin-Seebeck effect in a strongly interacting, two-component Fermi gas and propose an experiment to measure this effect by relatively displacing spin-up and spin-down atomic clouds in a trap using spin-dependent temperature gradients. We compute the spin-Seebeck coefficient and related
4. New physics of metals: fermi surfaces without Fermi liquids.
OpenAIRE
Anderson, P W
1995-01-01
I relate the historic successes, and present difficulties, of the renormalized quasiparticle theory of metals ("AGD" or Fermi liquid theory). I then describe the best-understood example of a non-Fermi liquid, the normal metallic state of the cuprate superconductors.
5. Attachment of Surface "Fermi Arcs" to the Bulk Fermi Surface: "Fermi-Level Plumbing" in Topological Metals
OpenAIRE
Haldane, F. D. M.
2014-01-01
The role of "Fermi arc" surface-quasiparticle states in "topological metals" (where some Fermi surface sheets have non-zero Chern number) is examined. They act as "Fermi-level plumbing" conduits that transfer quasiparticles among groups of apparently-disconnected Fermi sheets with non-zero Chern numbers to maintain equality of their chemical potentials, which is required by gauge invariance. Fermi arcs have a chiral tangential attachment to the surface projections of sheets of the bulk Fermi ...
6. Statistical mechanics of a Feshbach-coupled Bose-Fermi gas in an optical lattice
DEFF Research Database (Denmark)
Sørensen, Ole Søe; Nygaard, Nicolai; Blakie, P.B.
2009-01-01
We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic-field-controlled narrow Feshbach resonance. The phase diagram of the resulting atom-molecule mixture in chemical and thermal equilibria is determined numerically...
7. Peltier cooling of fermionic quantum gases.
Science.gov (United States)
Grenier, Ch; Georges, A; Kollath, C
2014-11-14
We propose a cooling scheme for fermionic quantum gases, based on the principles of the Peltier thermoelectric effect and energy filtering. The system to be cooled is connected to another harmonically trapped gas acting as a reservoir. The cooling is achieved by two simultaneous processes: (i) the system is evaporatively cooled, and (ii) cold fermions from deep below the Fermi surface of the reservoir are injected below the Fermi level of the system, in order to fill the "holes" in the energy distribution. This is achieved by a suitable energy dependence of the transmission coefficient connecting the system to the reservoir. The two processes can be viewed as simultaneous evaporative cooling of particles and holes. We show that both a significantly lower entropy per particle and faster cooling rate can be achieved in this way than by using only evaporative cooling.
8. Peltier Cooling of Fermionic Quantum Gases
Science.gov (United States)
Grenier, Ch.; Georges, A.; Kollath, C.
2014-11-01
We propose a cooling scheme for fermionic quantum gases, based on the principles of the Peltier thermoelectric effect and energy filtering. The system to be cooled is connected to another harmonically trapped gas acting as a reservoir. The cooling is achieved by two simultaneous processes: (i) the system is evaporatively cooled, and (ii) cold fermions from deep below the Fermi surface of the reservoir are injected below the Fermi level of the system, in order to fill the "holes" in the energy distribution. This is achieved by a suitable energy dependence of the transmission coefficient connecting the system to the reservoir. The two processes can be viewed as simultaneous evaporative cooling of particles and holes. We show that both a significantly lower entropy per particle and faster cooling rate can be achieved in this way than by using only evaporative cooling.
9. Composite-fermionization of the mixture composed of Tonks gas and Fermi gas
Institute of Scientific and Technical Information of China (English)
Hao Ya-Jiang
2011-01-01
This paper investigates the ground-state properties of the mixture composed of the strongly interacting TonksGirardeau gas and spin polarized Fermi gas confined in one-dimensional harmonic traps, where the interaction between the Bose atoms and Fermi atoms is tunable. With a generalized Bose-Fermi transformation the mixture is mapped into a two-component Fermi gas. The homogeneous Fermi gas is exactly solvable by the Bethe-ansatz method and the ground state energy density can be obtained. Combining the ground-state energy function of the homogeneous system with local density approximation it obtains the ground-state density distributions of inhomogeneous mixture. It is shown that with the increase in boson-fermion interaction, the system exhibits composite-fermionization crossover.
10. FERMI multi-chip module
CERN Multimedia
This FERMI multi-chip module contains five million transistors. 25 000 of these modules will handle the flood of information through parts of the ATLAS and CMS detectors at the LHC. To select interesting events for recording, crucial decisions are taken before the data leaves the detector. FERMI modules are being developed at CERN in partnership with European industry.
11. Fermi Communications and Public Outreach
CERN Document Server
Cominsky, L
2015-01-01
The Sonoma State University (SSU) Education and Public Outreach (E/PO) group participates in the planning and execution of press conferences that feature noteworthy Fermi discoveries, as well as supporting social media and outreach websites. We have also created many scientific illustrations for the media, tools for amateur astronomers for use at star parties, and have given numerous public talks about Fermi discoveries.
12. Superconductivity in an electron band just above the Fermi level: possible route to BCS-BEC superconductivity.
Science.gov (United States)
Okazaki, K; Ito, Y; Ota, Y; Kotani, Y; Shimojima, T; Kiss, T; Watanabe, S; Chen, C-T; Niitaka, S; Hanaguri, T; Takagi, H; Chainani, A; Shin, S
2014-02-28
Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals and ultra-cold gases, respectively, are connected by the BCS-BEC crossover. Here we investigate the band dispersions in FeTe(0.6)Se(0.4)(Tc = 14.5 K ~ 1.2 meV) in an accessible range below and above the Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission spectroscopy. We uncover an electron band lying just 0.7 meV (~8 K) above EF at the Γ-point, which shows a sharp superconducting coherence peak with gap formation below Tc. The estimated superconducting gap Δ and Fermi energy [Symbol: see text]F indicate composite superconductivity in an iron-based superconductor, consisting of strong-coupling BEC in the electron band and weak-coupling BCS-like superconductivity in the hole band. The study identifies the possible route to BCS-BEC superconductivity.
13. Enrico Fermi Symposium at CERN : opening celebration
CERN Document Server
CERN. Geneva. Audiovisual Unit
2002-01-01
You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani - Welcome and Introduction Antonino Zichichi - The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi - Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger - Fermi in Chicago Valentin Telegdi - A Close-up of Fermi Arnaldo Stefanini - Celebrating Fermi's Centenary in Documents and Pictures and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (English version - c. 30 mins).
14. Fermi, Heisenberg y Lawrence
Directory of Open Access Journals (Sweden)
Ynduráin, Francisco J.
2002-01-01
Full Text Available Not available
Los azares de las onomásticas hacen coincidir en este año el centenario del nacimiento de tres de los más grandes físicos del siglo XX. Dos de ellos, Fermi y Heisenberg, dejaron una marca fundamental en la ciencia (ambos, pero sobre todo el segundo y, el primero, también en la tecnología. Lawrence, indudablemente de un nivel inferior al de los otros dos, estuvo sin embargo en el origen de uno de los desarrollos tecnológicos que han sido básicos para la exploración del universo subnuclear en la segunda mitad del siglo que ha terminado hace poco, el de los aceleradores de partículas.
15. Momentum sharing in imbalanced Fermi systems
CERN Document Server
Hen, O; Weinstein, L B; Piasetzky, E; Hakobyan, H; Higinbotham, D W; Braverman, M; Brooks, W K; Gilad, S; Adhikari, K P; Arrington, J; Asryan, G; Avakian, H; Ball, J; Baltzell, N A; Battaglieri, M; Beck, A; Beck, S May-Tal; Bedlinskiy, I; Bertozzi, W; Biselli, A; Burkert, V D; Cao, T; Carman, D S; Celentano, A; Chandavar, S; Colaneri, L; Cole, P L; Crede, V; DAngelo, A; De Vita, R; Deur, A; Djalali, C; Doughty, D; Dugger, M; Dupre, R; Egiyan, H; Alaoui, A El; Fassi, L El; Elouadrhiri, L; Fedotov, G; Fegan, S; Forest, T; Garillon, B; Garcon, M; Gevorgyan, N; Ghandilyan, Y; Gilfoyle, G P; Girod, F X; Goetz, J T; Gothe, R W; Griffioen, K A; Guidal, M; Guo, L; Hafidi, K; Hanretty, C; Hattawy, M; Hicks, K; Holtrop, M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkanov, B I; Isupov, E L; Jiang, H; Jo, H S; Joo, K; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, F J; Koirala, S; Korover, I; Kuhn, S E; Kubarovsky, V; Lenisa, P; Levine, W I; Livingston, K; Lowry, M; Lu, H Y; MacGregor, I J D; Markov, N; Mayer, M; McKinnon, B; Mineeva, T; Mokeev, V; Movsisyan, A; Camacho, C Munoz; Mustapha, B; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Pappalardo, L L; Paremuzyan, R; Park, K; Pasyuk, E; Phelps, W; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Rimal, D; Ripani, M; Ritchie, B G; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatie, F; Schott, D; Schumacher, R A; Sharabian, Y G; Smith, G D; Shneor, R; Sokhan, D; Stepanyan, S S; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tkachenko, S; Ungaro, M; Vlassov, A V; Voutier, E; Watts, D; Walford, N K; Wei, X; Wood, M H; Wood, S A; Zachariou, N; Zana, L; Zhao, Z W; Zheng, X; Zonta, I
2014-01-01
The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few body systems to neutron stars and may also be observable experimentally in two-spin state, ultra-cold atomic gas systems.
16. Density Functional Theory Studies of Magnetically Confined Fermi Gas
Institute of Scientific and Technical Information of China (English)
陈宇俊; 马红孺
2001-01-01
A theory is developed for magnetically confined Fermi gas at a low temperature based on the density functional theory. The theory is illustrated by the numerical calculation of the density distributions of Fermi atoms 40K with parameters according to DeMarco and Jin's experiment [Science, 285(1999)1703]. Our results are in close agreement with the experiment. To check the theory, we also performed calculations using our theory at a high temperature, which compared very well to the results of the classical limit.
17. Nanoclusters and Microparticles in Gases and Vapors
CERN Document Server
Smirnov, Boris M
2012-01-01
Research of processes involving Nanoclusters and Microparticleshas been developing fastin many fields of rescent research, in particular in materials science. To stay at the cutting edge of this development, a sound understanding of the processes is needed. In this work, several processes involving small particles are described, such as transport processes in gases, charging of small particles in gases, chemical processes, atom attachment and quenching of excited atomic particles on surfaces, nucleation, coagulation, coalescence and growth processes for particles and aggregates. This work pres
18. Anisotropic non-Fermi liquids
Science.gov (United States)
Sur, Shouvik; Lee, Sung-Sik
2016-11-01
We study non-Fermi-liquid states that arise at the quantum critical points associated with the spin density wave (SDW) and charge density wave (CDW) transitions in metals with twofold rotational symmetry. We use the dimensional regularization scheme, where a one-dimensional Fermi surface is embedded in (3 -ɛ ) -dimensional momentum space. In three dimensions, quasilocal marginal Fermi liquids arise both at the SDW and CDW critical points: the speed of the collective mode along the ordering wave vector is logarithmically renormalized to zero compared to that of Fermi velocity. Below three dimensions, however, the SDW and CDW critical points exhibit drastically different behaviors. At the SDW critical point, a stable anisotropic non-Fermi-liquid state is realized for small ɛ , where not only time but also different spatial coordinates develop distinct anomalous dimensions. The non-Fermi liquid exhibits an emergent algebraic nesting as the patches of Fermi surface are deformed into a universal power-law shape near the hot spots. Due to the anisotropic scaling, the energy of incoherent spin fluctuations disperse with different power laws in different momentum directions. At the CDW critical point, on the other hand, the perturbative expansion breaks down immediately below three dimensions as the interaction renormalizes the speed of charge fluctuations to zero within a finite renormalization group scale through a two-loop effect. The difference originates from the fact that the vertex correction antiscreens the coupling at the SDW critical point whereas it screens at the CDW critical point.
Science.gov (United States)
Gray, Robert H
2015-03-01
The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to Earth--and since we do not, such life does not exist, or some special explanation is needed. Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked "Where is everybody?"--apparently suggesting that we do not see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist or suggesting its absence is paradoxical. The claim "they are not here; therefore they do not exist" was first published by Michael Hart, claiming that interstellar travel and colonization of the Galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart's argument, not Fermi's question. Clarifying the origin of these ideas is important, because the Fermi paradox is seen by some as an authoritative objection to searching for evidence of extraterrestrial intelligence--cited in the U.S. Congress as a reason for killing NASA's SETI program on one occasion. But evidence indicates that it misrepresents Fermi's views, misappropriates his authority, deprives the actual authors of credit, and is not a valid paradox.
20. Fermi pulsar revolution
CERN Document Server
Caraveo, Patrizia A
2010-01-01
2009 has been an extraordinary year for gamma-ray pulsar astronomy and 2010 promises to be equally good. Not only have we registered an extraordinary increase in the number of pulsars detected in gamma rays, but we have also witnessed the birth of new sub-families: first of all, the radio-quiet gamma pulsars and later an ever growing number of millisecond pulsars, a real surprise. We started with a sample of 7 gamma-ray emitting neutron stars (6 radio pulsars and Geminga) and now the Fermi-LAT harvest encompasses 24 "Geminga-like" new gamma-ray pulsars, a dozen millisecond pulsars and about thirty radio pulsars. Moreover, radio searches targeted to LAT unidentified sources yielded 18 new radio millisecond pulsars, several of which have been already detected also in gamma rays. Thus, currently the family of gamma-ray emitting neutron stars seems to be evenly divided between classical radio pulsars, millisecond pulsars and radio quiet neutron stars.
1. Kinetic equation for strongly interacting dense Fermi systems
CERN Document Server
Lipavsky, P; Spicka, V
2001-01-01
We review the non-relativistic Green's-function approach to the kinetic equations for Fermi liquids far from equilibrium. The emphasis is on the consistent treatment of the off-shell motion between collisions and on the non-instant and non-local picture of binary collisions. The resulting kinetic equation is of the Boltzmann type, and it represents an interpolation between the theory of transport in metals and the theory of moderately dense gases. The free motion of particles is renormalised by various mean field and mass corrections in the spirit of Landau's quasiparticles in metals. The collisions are non-local in the spirit of Enskog's theory of non-ideal gases. The collisions are moreover non-instant, a feature which is absent in the theory of gases, but which is shown to be important for dense Fermi systems. In spite of its formal complexity, the presented theory has a simple implementation within the Monte-Carlo simulation schemes. Applications in nuclear physics are given for heavy-ion reactions and th...
2. Atom Skimmers and Atom Lasers Utilizing Them
Science.gov (United States)
Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.
2005-01-01
Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.
3. Davisson-Germer Prize Talk: Many-Body Physics with Atomic Fermions
Science.gov (United States)
Hulet, Randall
2016-05-01
Ultracold atomic gases confined to optical lattices have proven to be highly versatile and tunable systems for realizing novel quantum states of matter. We are using Fermi gases of 6 Li atoms in our laboratory to explore several goals related to the strong correlations that arise in these systems. We have realized the Hubbard model, which has long been suspected of containing the essential ingredients of high temperature superconductivity. We measured the compressibility of the Mott insulating phase that occurs near half filling (1 atom/site), thus demonstrating the excitation gap of the Mott insulator. Progress in this field, however, has been hampered by an inability to cool to low enough temperatures to achieve the most ambitious goals. To address this problem, we have developed the compensated optical lattice method to enable evaporative cooling in the lattice. With this method, we have cooled the Mott insulator sufficiently far to observe short-range antiferromagnetic correlations using Bragg scattering of light. We are currently exploring new methods for entropy storage and redistribution to achieve even lower entropy in the antiferromagnetic phase. Motivated by the enhancement of quantum correlations in low dimensions, we are also exploring Fermi gases in quasi-one-dimension (1D). A deep 2D optical lattice produces an array of 1D tubes which can be weakly coupled by reducing the lattice depth, thus increasing the lattice hopping t between them. We observe a crossover from 1D-like to 3D-like behavior in the phase separation of a spin-imbalanced Fermi gas with increasing t. While this crossover occurs at a value of t that depends on interaction, we find that the crossover location is universally dependent upon the scaled hopping t /ɛb , where ɛb is the pair binding energy. Finally, I will also report progress on measuring the speed of sound of the charge and spin modes in a 1D Fermi gas. Work supported by an ARO MURI, NSF, and the Robert A Welch Foundation.
4. Relativistic Scott correction for atoms and molecules
DEFF Research Database (Denmark)
Solovej, Jan Philip; Sørensen, Thomas Østergaard; Spitzer, Wolfgang Ludwig
2010-01-01
We prove the first correction to the leading Thomas-Fermi energy for the ground state energy of atoms and molecules in a model where the kinetic energy of the electrons is treated relativistically. The leading Thomas-Fermi energy, established in [25], as well as the correction given here, are of ...
5. Gases in molten salts
CERN Document Server
Tomkins, RPT
1991-01-01
This volume contains tabulated collections and critical evaluations of original data for the solubility of gases in molten salts, gathered from chemical literature through to the end of 1989. Within the volume, material is arranged according to the individual gas. The gases include hydrogen halides, inert gases, oxygen, nitrogen, hydrogen, carbon dioxide, water vapor and halogens. The molten salts consist of single salts, binary mixtures and multicomponent systems. Included also, is a special section on the solubility of gases in molten silicate systems, focussing on slags and fluxes.
6. Handbook of purified gases
CERN Document Server
Schoen, Helmut
2015-01-01
Technical gases are used in almost every field of industry, science and medicine and also as a means of control by government authorities and institutions and are regarded as indispensable means of assistance. In this complete handbook of purified gases the physical foundations of purified gases and mixtures as well as their manufacturing, purification, analysis, storage, handling and transport are presented in a comprehensive way. This important reference work is accompanied with a large number of Data Sheets dedicated to the most important purified gases.
7. Polarons and molecules in a two-dimensional Fermi gas
DEFF Research Database (Denmark)
Zöllner, Sascha; Bruun, Georg Morten; Pethick, C. J.
2011-01-01
We study an impurity atom in a two-dimensional Fermi gas using variational wave functions for (i) an impurity dressed by particle-hole excitations (polaron) and (ii) a dimer consisting of the impurity and a majority atom. In contrast to three dimensions, where similar calculations predict a sharp...... transition to a dimer state with increasing interspecies attraction, we show that the polaron Ansatz always gives a lower energy. However, the exact solution for a heavy impurity reveals that both a two-body bound state and distortions of the Fermi sea are crucial. This reflects the importance of particle......-hole pairs in lower dimensions and makes simple variational calculations unreliable. We show that the energy of an impurity gives important information about its dressing cloud, for which both Ansätze give inaccurate results....
8. Quantum dynamics of impurities coupled to a Fermi sea
Science.gov (United States)
Parish, Meera M.; Levinsen, Jesper
2016-11-01
We consider the dynamics of an impurity atom immersed in an ideal Fermi gas at zero temperature. We focus on the coherent quantum evolution of the impurity following a quench to strong impurity-fermion interactions, where the interactions are assumed to be short range like in cold-atom experiments. To approximately model the many-body time evolution, we use a truncated basis method, where at most two particle-hole excitations of the Fermi sea are included. When the system is initially noninteracting, we show that our method exactly captures the short-time dynamics following the quench, and we find that the overlap between initial and final states displays a universal nonanalytic dependence on time in this limit. We further demonstrate how our method can be used to compute the impurity spectral function, as well as describe many-body phenomena involving coupled impurity spin states, such as Rabi oscillations in a medium or highly engineered quantum quenches.
9. An interpolatory ansatz captures the physics of one-dimensional confined Fermi systems.
Science.gov (United States)
Andersen, M E S; Dehkharghani, A S; Volosniev, A G; Lindgren, E J; Zinner, N T
2016-01-01
Interacting one-dimensional quantum systems play a pivotal role in physics. Exact solutions can be obtained for the homogeneous case using the Bethe ansatz and bosonisation techniques. However, these approaches are not applicable when external confinement is present. Recent theoretical advances beyond the Bethe ansatz and bosonisation allow us to predict the behaviour of one-dimensional confined systems with strong short-range interactions, and new experiments with cold atomic Fermi gases have already confirmed these theories. Here we demonstrate that a simple linear combination of the strongly interacting solution with the well-known solution in the limit of vanishing interactions provides a simple and accurate description of the system for all values of the interaction strength. This indicates that one can indeed capture the physics of confined one-dimensional systems by knowledge of the limits using wave functions that are much easier to handle than the output of typical numerical approaches. We demonstrate our scheme for experimentally relevant systems with up to six particles. Moreover, we show that our method works also in the case of mixed systems of particles with different masses. This is an important feature because these systems are known to be non-integrable and thus not solvable by the Bethe ansatz technique.
10. Conjugate Fermi holes and its manifestation in He-like systems
Energy Technology Data Exchange (ETDEWEB)
Sako, Tokuei, E-mail: [email protected] [Laboratory of Physics, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, 274-8501 Chiba (Japan)
2015-12-31
The structure of genuine and conjugate Fermi holes in two-electron atomic systems, namely He and He-like atomic ions, has been studied relying on accurate full configuration interaction wave functions. The standard Fermi hole exists in the vicinity of region in the two-electron coordinate space satisfying the well-known condition, r{sub 1} = r{sub 2}, while the conjugate Fermi hole exists in the vicinity of region close to this genuine Fermi hole but satisfying r{sub 1} ≠ r{sub 2} instead of r{sub 1} = r{sub 2}. Existence of these holes has shown to give an insightful interpretation of the origin of the first Hund rule and of the anomalously strong angular correlation manifested in the series of the singlet-triplet pair of singly-excited states of the aforementioned systems.
11. Capturing Gases in Carbon Honeycomb
Science.gov (United States)
Krainyukova, Nina V.
2016-12-01
In our recent paper (Krainyukova and Zubarev in Phys Rev Lett 116:055501, 2016. doi: 10.1103/PhysRevLett.116.055501) we reported the observation of an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. A family of structures can be built from absolutely dominant {sp}2 -bonded carbon atoms, and may be considered as three-dimensional graphene. Such structures demonstrate high absorption capacity for gases and liquids. In this work we show that the formation of honeycomb structures is highly sensitive to the carbon evaporation temperature and deposition rates. Both parameters are controlled by the electric current flowing through thin carbon rods. Two distinctly different regimes were found. At lower electric currents almost pure honeycomb structures form owing to sublimation. At higher currents the surface-to-bulk rod melting is observed. In the latter case densification of the carbon structures and a large contribution of glassy graphite emerge. The experimental diffraction patterns from honeycomb structures filled with absorbed gases and analyzed by the advanced method are consistent with the proposed models for composites which are different for Ar, Kr and Xe atoms in carbon matrices.
12. Capturing Gases in Carbon Honeycomb
Science.gov (United States)
Krainyukova, Nina V.
2017-04-01
In our recent paper (Krainyukova and Zubarev in Phys Rev Lett 116:055501, 2016. doi: 10.1103/PhysRevLett.116.055501) we reported the observation of an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. A family of structures can be built from absolutely dominant {sp}2-bonded carbon atoms, and may be considered as three-dimensional graphene. Such structures demonstrate high absorption capacity for gases and liquids. In this work we show that the formation of honeycomb structures is highly sensitive to the carbon evaporation temperature and deposition rates. Both parameters are controlled by the electric current flowing through thin carbon rods. Two distinctly different regimes were found. At lower electric currents almost pure honeycomb structures form owing to sublimation. At higher currents the surface-to-bulk rod melting is observed. In the latter case densification of the carbon structures and a large contribution of glassy graphite emerge. The experimental diffraction patterns from honeycomb structures filled with absorbed gases and analyzed by the advanced method are consistent with the proposed models for composites which are different for Ar, Kr and Xe atoms in carbon matrices.
13. The Fermiac or Fermi's Trolley
Science.gov (United States)
Coccetti, F.
2016-03-01
The Fermiac, known also as Fermi's trolley or Monte Carlo trolley, is an analog computer used to determine the change in time of the neutron population in a nuclear device, via the Monte Carlo method. It was invented by Enrico Fermi and constructed by Percy King at Los Alamos in 1947, and used for about two years. A replica of the Fermiac was built at INFN mechanical workshops of Bologna in 2015, on behalf of the Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", thanks to the original drawings made available by Los Alamos National Laboratory (LANL). This reproduction of the Fermiac was put in use, and a simulation was developed.
14. Dynamic structure factors and sum rules in two-component quantum gases with spin-orbit coupling%自旋-轨道耦合作用下双组分量子气体中的动力学结构因子与求和规则
Institute of Scientific and Technical Information of China (English)
贺丽; 余增强
2016-01-01
Sum rules for the dynamic structure factors are powerful tools to explore the collective behaviors in many-body systems at zero temperature as well as at finite temperatures. The recent remarkable realization of synthetic spin-orbit (SO) coupling in quantum gases is opening up new perspective to study the intriguing SO effects with ultracold atoms. So far, a specific type of SO coupling, which is generated by a pair of Raman laser beams, has been experimentally achieved in Bose-Einstein condensates of 87Rb and degenerate Fermi gases of 40K and 6Li. In the presence of SO coupling, the dynamic structure factors for the density fluctuation and spin fluctuation satisfy different sum rules. In particular, in the two-component quantum gases with inter-species Raman coupling, the f-sum rule for the spin fluctuation has an additional term proportional to the transverse spin polarization. Due to the coupling between the momentum and spin, the first moment of the dynamic structure factor does not necessarily possess the inversion symmetry, which is in strong contrast to the conventional system without SO coupling. Such an asymmetric behavior could be observed in both Fermi gases and Bose gases with Raman coupling. As a demonstration, we focus on the uniform case at zero temperature in this work. For the non-interacting Fermi gases, the asymmetric first moment appears only when the Raman detuning is finite. The asymmetric amplitude is quite limited, and it vanishes at both zero detuning and infinite detuning. For the weakly interacting Bose gases, the first moment is asymmetric in momentum space even at zero detuning, when the ground state spontaneously breaks the Z2 symmetry in the plane-wave condensation phase. Using the Bogoliubov method, the dynamic structure factor and its first moment are explicitly calculated for various interaction parameters. We find that the asymmetric behavior in the spin channel could be much more significant than in the density channel, and the
CERN Document Server
Gray, Robert H
2016-01-01
The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to Earth-and since we do not, such life does not exist, or some special explanation is needed. Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked 'where is everybody?'- apparently suggesting that we don't see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist, or suggesting its absence is paradoxical. The claim 'they are not here; therefore they do not exist' was first published by Michael Hart, claiming that interstellar travel and colonization of the galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart's argument, not Fermi's question. Clarifying the origin of these ideas is important...
16. Holographic optical traps for atom-based topological Kondo devices
Science.gov (United States)
Buccheri, F.; Bruce, G. D.; Trombettoni, A.; Cassettari, D.; Babujian, H.; Korepin, V. E.; Sodano, P.
2016-07-01
The topological Kondo (TK) model has been proposed in solid-state quantum devices as a way to realize non-Fermi liquid behaviors in a controllable setting. Another motivation behind the TK model proposal is the demand to demonstrate the quantum dynamical properties of Majorana fermions, which are at the heart of their potential use in topological quantum computation. Here we consider a junction of crossed Tonks-Girardeau gases arranged in a star-geometry (forming a Y-junction), and we perform a theoretical analysis of this system showing that it provides a physical realization of the TK model in the realm of cold atom systems. Using computer-generated holography, we experimentally implement a Y-junction suitable for atom trapping, with controllable and independent parameters. The junction and the transverse size of the atom waveguides are of the order of 5 μm, leading to favorable estimates for the Kondo temperature and for the coupling across the junction. Since our results show that all the required theoretical and experimental ingredients are available, this provides the demonstration of an ultracold atom device that may in principle exhibit the TK effect.
17. On the Dynamics of the Fermi-Bose model
DEFF Research Database (Denmark)
Ögren, Magnus
In this talk we formulate and prove results for the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimmers dissociating into its atomic compounds. The problem is solved in D spatial....... In particular the results can be used for studies of threedimensional physical systems of arbitrary geometry. We illustrate the generality of our approach by giving numerical results for the dynamics of Glauber type atomic pair correlation functions for a non-isotropic three-dimensional harmonically trapped...
18. Many-electron tunneling in atoms
CERN Document Server
Zon, B A
1999-01-01
A theoretical derivation is given for the formula describing N-electron ionization of atom by a dc field and laser radiation in tunneling regime. Numerical examples are presented for noble gases atoms.
19. Relationship between Fermi Resonance and Solvent Effects
Institute of Scientific and Technical Information of China (English)
JIANG Xiu-Lan; LI Dong-Fei; SUN Cheng-Lin; LI Zhan-Long; YANG Guang; ZHOU Mi; LI Zuo-Wei; GAO Shu-Qin
2011-01-01
We theoretically and experimentally study the relationship between Fermi resonance and solvent effects and investigate the Fermi resonance of p-benzoquinone and cyclopentanone in different solvents and the Fermi resonance of CS2 in C6H6 at different concentrations. Also, we investigate the Fermi resonance of C6H6 and CCl4 in their solution at different pressures. It is found that solvent effects can be utilized to search Fermi resonance parameters such as coupling coefficient and spectral intensity ratio, etc., on the other hand, the mechanism of solvent effects can be revealed according to Fermi resonance at high pressure.%@@ We theoretically and experimentally study the relationship between Fermi resonance and solvent effects and investigate the Fermi resonance of p-benzoquinone and cyclopentanone in different solvents and the Fermi resonance of CS2 in C6H6 at different concentrations.Also,we investigate the Fermi resonance of C6H6 and CCl4 in their solution at different pressures.It is found that solvent effects can be utilized to search Fermi resonance parameters such as coupling coefficient and spectral intensity ratio,etc.,on the other hand,the mechanism of solvent effects can be revealed according to Fermi resonance at high pressure.
20. STEM education and Fermi problems
Science.gov (United States)
Holubova, Renata
2017-01-01
One of the research areas of Physics education is the study of the educational process. Investigations in this area are aimed for example on the teaching and learning process and its results. The conception of STEM education (Science, Technology, Engineering, and Mathematics) is discussed - it is one possible approach to the preparation of the curriculum and the focus on the educational process at basic and secondary schools. At schools in the Czech Republic STEM is much more realized by the application of interdisciplinary relations between subjects Physics-Nature-Technique. In both conceptions the aim is to support pupils' creativity, critical thinking, cross-curricular links. In this context the possibility of using Fermi problems in teaching Physics was discussed (as an interdisciplinary and constructivist activity). The aim of our research was the analysis of Fermi problems solving strategies, the ability of pupils to solve Fermi problems. The outcome of our analysis was to find out methods and teaching strategies which are important to use in teaching - how to solve qualitative and interdisciplinary tasks in physics. In this paper the theoretical basis of STEM education and Fermi problems will be presented. The outcome of our findings based on the research activities will be discussed so as our experiences from 10 years of Fermi problems competition that takes place at the Science Faculty, Palacky University in Olomouc. Changes in competencies of solving tasks by our students (from the point of view in terms of modern, activating teaching methods recommended by theory of Physics education and other science subjects) will be identified.
1. Method and system for continuous atomic layer deposition
Energy Technology Data Exchange (ETDEWEB)
Elam, Jeffrey W.; Yanguas-Gil, Angel; Libera, Joseph A.
2017-03-21
A system and method for continuous atomic layer deposition. The system and method includes a housing, a moving bed which passes through the housing, a plurality of precursor gases and associated input ports and the amount of precursor gases, position of the input ports, and relative velocity of the moving bed and carrier gases enabling exhaustion of the precursor gases at available reaction sites.
2. Gases, liquids and solids
CERN Document Server
Tabor, David
1969-01-01
It has been tradional to treat gases, liquids and solids as if they were completely unrelated material. However, this book shows that many of their bulk properties can been explained in terms of intermolecular forces.
3. Interaction of atomic oxygen with a graphite surface
Science.gov (United States)
Mateljevic, Natasa
This project was a part of the Multi University Research Initiative (MURI) Center for Materials Chemistry in the Space Environment which seeks to develop a quantitative and predictive understanding of how materials degrade or become passivated in the space environment. This is a critical research area for the Department of Defense (DoD) and National Aeronautics and Space Administration (NASA) given the large and increasing dependence on satellites and manned spacecrafts that reside in, or pass through, the low-Earth orbit (LEO) space environment. In this work, we completed three separate projects. First, we carried out ab initio electronic structure studies of the interaction of oxygen atoms with graphite surfaces. The (O3 P) ground state of oxygen interacts weakly with the graphite surface while the excited (O1D) state interacts more strongly with a binding energy sufficient for a high coverage of oxygen to be maintained on the surface. Thus, it requires a transition from O(3P) to O(1D) in order for oxygen to strongly bind. Since graphite is a semi-metal, it requires a vanishingly small energy to remove an electron of up spin from just below the Fermi level, and replace it with a down spin electron just above the Fermi level; spin-orbit interaction is not required to switch the state of the oxygen atom. We have examined this complexity for the first time and developed guidelines for properly describing chemical reactivity on graphite surfaces. The second project is a kinetic Monte Carlo study of the erosion of graphite by energetic oxygen atoms in LEO and in the laboratory. These simulations, in conjunction with experiments by our MURI collaborators, reveal new insights about reaction pathways. Finally, we have developed a new model for accommodation of energy and momentum in collisions of gases with highly corrugated surfaces. This model promises to be valuable in simulating frictional heating and drag of objects moving through the atmosphere.
4. Fermi resonance in optical microcavities
Science.gov (United States)
Yi, Chang-Hwan; Yu, Hyeon-Hye; Lee, Ji-Won; Kim, Chil-Min
2015-04-01
Fermi resonance is a phenomenon of quantum mechanical superposition, which most often occurs between normal and overtone modes in molecular systems that are nearly coincident in energy. We find that scarred resonances in deformed dielectric microcavities are the very phenomenon of Fermi resonance, that is, a pair of quasinormal modes interact with each other due to coupling and a pair of resonances are generated through an avoided resonance crossing. Then the quantum number difference of a pair of quasinormal modes, which is a consequence of quantum mechanical superposition, equals periodic orbits, whereby the resonances are localized on the periodic orbits. We derive the relation between the quantum number difference and the periodic orbits and confirm it in an elliptic, a rectangular, and a stadium-shaped dielectric microcavity.
5. On the Fermi Golden Rule
DEFF Research Database (Denmark)
Jensen, Arne; Nenciu, Gheorghe
2008-01-01
We review and further develop the framework in [9] of the stationary theory of resonances, arising by perturbation of either threshold, or embedded in the continuum, eigenvalues. While in [9] only non/degenerate eigenvalues were considered, here we add some results for the degenerate case. [9] A........ Jensen and G. Nenciu, The Fermi Golden Rule and its form at thresholds in odd dimensions. Comm. Math. Phys 261 (2006), 693-727...
6. Imprisonment dynamics of resonance radiation in gases
Energy Technology Data Exchange (ETDEWEB)
Kosarev, N I; Shaparev, N Y, E-mail: [email protected] [Institute of Computational Modeling, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, 660036 (Russian Federation)
2011-05-28
Imprisonment of resonant radiation in gases on the basis of the numerical solution of the rate balance equation for the excited atoms and the transfer resonant radiation equation is investigated. Calculations of the escape factor for the slab, cylinder and sphere at Doppler and Lorentz forms of absorption and scattering profiles are executed. Calculation results of the escape factor for the cylinder and slab are compared with Holsten's asymptotical solutions. The numerical data for time dependence of a spectrum, the intensity of resonant radiation and the spatial distribution of the excited atomic concentration in a regime of afterglow are also considered.
7. Enrico Fermi and the Dolomites
CERN Document Server
Battimelli, Giovanni
2014-01-01
Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scient...
8. Enrico Fermi and the Dolomites
Energy Technology Data Exchange (ETDEWEB)
Battimelli, Giovanni, E-mail: [email protected]; Angelis, Alessandro de, E-mail: [email protected]
2014-11-15
Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scientific discussions held in the region of the Dolomites.
9. Enrico Fermi and the Dolomites
Science.gov (United States)
Battimelli, Giovanni; de Angelis, Alessandro
2014-11-01
Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scientific discussions held in the region of the Dolomites.
10. Topological Non-Fermi Liquid
CERN Document Server
Cai, Rong-Gen; Wu, Yue-Liang; Zhang, Yun-Long
2016-01-01
In this paper we investigate the $(2+1)$-dimensional topological non-Fermi liquid in strongly correlated electron system, which has a holographic dual description by Einstein gravity in $(3+1)$-dimensional anti-de Sitter (AdS) space-time. In a dyonic Reissner-Nordstrom black hole background, we consider a Dirac fermion coupled to the background $U(1)$ gauge theory and an intrinsic chiral gauge field $b_M$ induced by chiral anomaly. UV retarded Green's function of the charged fermion in the UV boundary from AdS$_4$ gravity is calculated, by imposing in-falling wave condition at the horizon. We also obtain IR correlation function of the charged fermion at the IR boundary arising from the near horizon geometry of the topological black hole with index $k=0,\\pm 1$. By using the UV retarded Green's function and IR correlation function, we analyze the low frequency behavior of the topological non-Fermi liquid at zero and finite temperatures, especially the relevant non-Fermi liquid behavior near the quantum critical...
11. Fermi Timing and Synchronization System
Energy Technology Data Exchange (ETDEWEB)
Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X.; Kim, J.; Chen, J.; Ilday, F.O.; Ludwig, F.; Winter, A.; Ferianis, M.; Danailov, M.; D' Auria, G.
2006-07-19
The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.
12. Fermi/non-Fermi mixing in SU($N$) Kondo effect
CERN Document Server
Kimura, Taro
2016-01-01
We apply conformal field theory analysis to the $k$-channel SU($N$) Kondo system, and find a peculiar behavior in the cases $N > k > 1$, which we call Fermi/non-Fermi mixing: The low temperature scaling is described as the Fermi liquid, while the zero temperature IR fixed point exhibits the non-Fermi liquid signature. We also show that the Wilson ratio is no longer universal for the cases $N > k > 1$. The deviation from the universal value of the Wilson ratio could be used as an experimental signal of the Fermi/non-Fermi mixing.
13. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy
DEFF Research Database (Denmark)
van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano
2016-01-01
Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy images...... as a benchmark, we show that the position of the dopant atoms can be determined using atomic force microscopy. Specifically, the frequency shift-distance curves Delta f(z) acquired above a N atom are significantly different from the curves measured over a C atom. Similar behavior was found for N-doped graphene...
14. Landau Theory of Helical Fermi Liquids.
Science.gov (United States)
Lundgren, Rex; Maciejko, Joseph
2015-08-07
We construct a phenomenological Landau theory for the two-dimensional helical Fermi liquid found on the surface of a three-dimensional time-reversal invariant topological insulator. In the presence of rotation symmetry, interactions between quasiparticles are described by ten independent Landau parameters per angular momentum channel, by contrast with the two (symmetric and antisymmetric) Landau parameters for a conventional spin-degenerate Fermi liquid. We project quasiparticle states onto the Fermi surface and obtain an effectively spinless, projected Landau theory with a single projected Landau parameter per angular momentum channel that captures the spin-momentum locking or nontrivial Berry phase of the Fermi surface. As a result of this nontrivial Berry phase, projection to the Fermi surface can increase or lower the angular momentum of the quasiparticle interactions. We derive equilibrium properties, criteria for Fermi surface instabilities, and collective mode dispersions in terms of the projected Landau parameters. We briefly discuss experimental means of measuring projected Landau parameters.
15. Synthetic gases production
Energy Technology Data Exchange (ETDEWEB)
Mazaud, J.P.
1996-06-01
The natural gas or naphtha are the main constituents used for the production of synthetic gases. Several production ways of synthetic gases are industrially used as for example the natural gas or naphtha catalytic reforming, the selective oxidation of natural gas or heavy fuels and the coal oxy-vapo-gasification. The aim of this work is to study the different steps of production and treatment of the synthetic gases by the way of catalytic reforming. The first step is the desulfurization of the hydrocarbons feedstocks. The process used in industry is described. Then is realized the catalytic hydrocarbons reforming process. After having recalled some historical data on the catalytic reforming, the author gives the reaction kinetics and thermodynamics. The possible reforming catalysts, industrial equipments and furnaces designs are then exposed. The carbon dioxide is a compound easily obtained during the reforming reactions. It is a wasteful and harmful component which has to be extracted of the gaseous stream. The last step is then the gases de-carbonation. Two examples of natural gas or naphtha reforming reactions are at last given: the carbon monoxide conversion by steam and the carbon oxides reactions with hydrogen (methanization). (O.M.). 8 figs., 6 tabs.
16. Fe distribution in GaSe and InSe
Energy Technology Data Exchange (ETDEWEB)
Kovalyuk, Z.D.; Feichuk, P.I.; Shcherbak, L.P.; Zbykovskaya, N.I.
1985-06-01
In this paper, the authors use tagged atoms to determine the effective coefficients of Fe distribution in GaSe and InSe during crystallization of a doped melt by the Bridgman method. The distribution of Fe in GaSe and InSe was studied with the aid of Fe tagged with the radiosotopes VVFe + VZFe. Doping of the material was combined with the processes of synthesis and crystallization. Equations are presented for the calculation of the real impurity distribution in GaSe and InSe crystals.
17. Bioterrorism and the Fermi Paradox
Science.gov (United States)
Cooper, Joshua
2013-04-01
We proffer a contemporary solution to the so-called Fermi Paradox, which is concerned with conflict between Copernicanism and the apparent paucity of evidence for intelligent alien civilizations. In particular, we argue that every community of organisms that reaches its space-faring age will (1) almost immediately use its rocket-building computers to reverse-engineer its genetic chemistry and (2) self-destruct when some individual uses said technology to design an omnicidal pathogen. We discuss some of the possible approaches to prevention with regard to Homo sapiens' vulnerability to bioterrorism, particularly on a short-term basis.
18. The Low Density Matter (LDM) beamline at FERMI: optical layout and first commissioning.
Science.gov (United States)
Svetina, Cristian; Grazioli, Cesare; Mahne, Nicola; Raimondi, Lorenzo; Fava, Claudio; Zangrando, Marco; Gerusina, Simone; Alagia, Michele; Avaldi, Lorenzo; Cautero, Giuseppe; de Simone, Monica; Devetta, Michele; Di Fraia, Michele; Drabbels, Marcel; Feyer, Vitaliy; Finetti, Paola; Katzy, Raphael; Kivimäki, Antti; Lyamayev, Viktor; Mazza, Tommaso; Moise, Angelica; Möller, Thomas; O'Keeffe, Patrick; Ovcharenko, Yevheniy; Piseri, Paolo; Plekan, Oksana; Prince, Kevin C; Sergo, Rudi; Stienkemeier, Frank; Stranges, Stefano; Coreno, Marcello; Callegari, Carlo
2015-05-01
The Low Density Matter (LDM) beamline has been built as part of the FERMI free-electron laser (FEL) facility to serve the atomic, molecular and cluster physics community. After the commissioning phase, it received the first external users at the end of 2012. The design and characterization of the LDM photon transport system is described, detailing the optical components of the beamline.
19. Adsorption of Gases on Carbon Nanotubes
Science.gov (United States)
2014-01-01
This research focus in studying the interaction between various classical and quantum gases with novel carbon nanostructures, mainly carbon nanotubes (CNTs). Since their discovery by the Japanese physicist Sumio Iijima [1] carbon nanotubes have, experimentally and theoretically, been subjected to many scientific investigation. Studies of adsorption on CNTs are particularly directed toward their better usage in gas storage, gas separation, catalyst, drug delivery, and water purification. We explore the adsorption of different gases entrapped in a single, double, or multi-bundles of CNTs using computer simulations. The first system we investigate consists of Ar and Kr films adsorbed on zigzag or armchair nanotubes. Our simulations revealed that Kr atoms on intermediate size zigzag NTs undergo two phase transitions: A liquid-vapor (L→V), and liquid-commensurate (L→CS) with a fractional coverage of one Kr atoms adsorbed for every four carbon atoms. For Ar on zigzag and armchair NTs, the only transition observed is a L→V. In the second problem, we explore the adsorption of CO2 molecules in a nanotube bundle and calculate the isosteric heat of adsorption of the entrapped molecules within the groove. We observed that the lower the temperature, the higher the isosteric of adsorption. Last, we investigate the adsorption of hydrogen, Helium, and Neon gases on the groove site of two parallel nanotubes. At low temperature, the transverse motion on the plane perpendicular to the tubes' axis is frozen out and as a consequence, the heat capacity is reduced to 1/2. At high temperature, the atoms gain more degree of freedom and as a consequence the heat capacity is 5/2.
20. Observation of the Leggett-Rice effect in a unitary Fermi gas.
Science.gov (United States)
Trotzky, S; Beattie, S; Luciuk, C; Smale, S; Bardon, A B; Enss, T; Taylor, E; Zhang, S; Thywissen, J H
2015-01-09
We observe that the diffusive spin current in a strongly interacting degenerate Fermi gas of (40)K precesses about the local magnetization. As predicted by Leggett and Rice, precession is observed both in the Ramsey phase of a spin-echo sequence, and in the nonlinearity of the magnetization decay. At unitarity, we measure a Leggett-Rice parameter γ=1.08(9) and a bare transverse spin diffusivity D(0)(⊥)=2.3(4)ℏ/m for a normal-state gas initialized with full polarization and at one-fifth of the Fermi temperature, where m is the atomic mass. One might expect γ=0 at unitarity, where two-body scattering is purely dissipative. We observe γ→0 as temperature is increased towards the Fermi temperature, consistent with calculations that show the degenerate Fermi sea restores a nonzero γ. Tuning the scattering length a, we find that a sign change in γ occurs in the range 0Fermi momentum. We discuss how γ reveals the effective interaction strength of the gas, such that the sign change in γ indicates a switching of branch between a repulsive and an attractive Fermi gas.
1. Shortcut to adiabaticity for an anisotropic unitary Fermi gas
CERN Document Server
Deng, Shujin; Yu, Qianli; Wu, Haibin
2016-01-01
Coherent control of complex quantum systems is a fundamental requirement in quantum information processing and engineering. Recently developed notion of shortcut to adiabaticity (STA) has spawned intriguing prospects. So far, the most experimental investigations of STA are implemented in the ideal thermal gas or the weakly interacting ultracold Bose gases. Here we report the first demonstration of a many-body STA in a 3D anisotropically trapped unitary Fermi gas. A new dynamical scaling law is demonstrated on such a strongly interacting quantum gas. By simply engineering the frequency aspect ratio of a harmonic trap, the dynamics of the gas can be manipulated and the many-body state can be transferred adiabatically from one stationary state to another one in short time scale without the excitation. The universal scaling both for non-interacting and unitary Fermi gas is also verified. This could be very important for future many-body quantum engineering and the exploration of the fundamental law of the thermod...
2. The greenhouse gases
Energy Technology Data Exchange (ETDEWEB)
Clarke, R.
1987-01-01
The main greenhouse gases are carbon dioxide, methane, nitrous oxide, CFCs and ozone. They are greenhouse gases as they absorb radiation from the Earth and thus impede its emission back to space. CO{sub 2} is responsible for about half the enhanced greenhouse effect. A global warming of only a few degrees would have a profound effect on climate. Increased levels of CO{sub 2} promote plant growth, but may not benefit agriculture overall. Sea levels may rise. It is difficult to predict the effects of global warming in society. It would be possible to reduce the scale of the greenhouse effect by energy conservation, using alternative energy sources, and possibly by capturing CO{sub 2} from fossil fuel power stations and disposing of it on the ocean floor. 13 refs., 19 figs., 1 tab.
3. On the theory of polarized Fermi liquid
OpenAIRE
Mineev, V. P.
2004-01-01
The transport equation for transverse vibrations of magnetization in spin polarized Fermi liquid is derived from integral equation for the vertex function. The dispersion law for the transverse spin waves is established. The existance of zero-temperature spin-waves attenuation is confirmed. The problem of similar derivation in ferromagnetic "Fermi liquid" is discussed.
4. Fermi Surface and Antiferromagnetism in Europium Metal
DEFF Research Database (Denmark)
Andersen, O. Krogh; Loucks, T. L.
1968-01-01
We have calculated the Fermi surface of europium in order to find those features which determine the wave vector of the helical moment arrangement below the Néel point. We find that there are two pieces of Fermi surface: an electron surface at the symmetry point H, which has the shape of rounded-...
5. Vacuum alignment and radiatively induced Fermi scale
CERN Document Server
Alanne, Tommi
2016-01-01
We extend the discussion about vacuum misalignment by quantum corrections in models with composite pseudo-Goldstone Higgs boson to renormalisable models with elementary scalars. As a concrete example, we propose a framework, where the hierarchy between the unification and the Fermi scale emerges radiatively. This scenario provides an interesting link between the unification and Fermi scale physics.
6. Biased discrete symmetry breaking and Fermi balls
CERN Document Server
MacPherson, A L; Macpherson, Alick L; Campbell, Bruce A
1994-01-01
The spontaneous breaking of an approximate discrete symmetry is considered, with the resulting protodomains of true and false vacuum being separated by domain walls. Given a strong, symmetric Yukawa coupling of the real scalar field to a generic fermion, the domain walls accumulate a gas of fermions, which modify the domain wall dynamics. The splitting of the degeneracy of the ground states results in the false vacuum protodomain structures eventually being fragmented into tiny false vacuum bags with a Fermi gas shell (Fermi balls), that may be cosmologically stable due to the Fermi gas pressure and wall curvature forces, acting on the domain walls. As fermions inhabiting the domain walls do not undergo number density freeze out, stable Fermi balls exist only if a fermion anti-fermion asymmetry occurs. Fermi balls formed with a new Dirac fermion that possesses no standard model gauge charges provide a novel cold dark matter candidate.
7. Anomalous excitation facilitation in inhomogeneously broadened Rydberg gases
CERN Document Server
Letscher, Fabian; Niederprüm, Thomas; Ott, Herwig; Fleischhauer, Michael
2016-01-01
When atomic gases are laser driven to Rydberg states in an off resonant way, a single Rydberg atom may enhance the excitation rate of surrounding atoms. This leads to a facilitated excitation referred to as Rydberg anti-blockade. In the usual facilitation scenario, the detuning of the laser from resonance compensates the interaction shift. Here, we discuss a different excitation mechanism, which we call anomalous facilitation. This occurs on the "wrong side" of the resonance and originates from inhomogeneous broadening. The anomalous facilitation may be seen in experiments of attractively interacting atoms on the blue detuned side, where facilitation is not expected to appear.
8. Merge of high harmonic generation from gases and solids and its implications for attosecond science
Science.gov (United States)
Vampa, G.; Brabec, T.
2017-04-01
High harmonic generation (HHG) in atomic and molecular gases builds the foundation of attosecond science. In recent experiments HHG has been demonstrated in solids for the first time. A theoretical analysis has revealed that one of the mechanisms driving HHG in semiconductors is similar to the one in atomic and molecular gases. As a result, many of the processes developed for attosecond science in gases can be adapted and applied to the condensed matter phase. In this tutorial, the connection between atomic and solid HHG is summarized with covering both theoretical and experimental work, and some implications for attosecond science in solids are presented.
9. Theory of warm ionized gases: equation of state and kinetic Schottky anomaly
CERN Document Server
Capolupo, Antonio; Illuminati, Fabrizio
2013-01-01
Based on accurate Lennard-Jones type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analogue in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed.
10. Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.
Science.gov (United States)
Capolupo, A; Giampaolo, S M; Illuminati, F
2013-10-01
Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.
11. Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population
Science.gov (United States)
Darsheshdar, E.; Yavari, H.; Zangeneh, Z.
2016-07-01
By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.
12. Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas
Science.gov (United States)
Adams, Allan; Carr, Lincoln D.; Schaefer, Thomas; Steinberg, Peter; Thomas, John E.
2013-04-01
interdisciplinary appeal and include new studies of high temperature superfluidity, viscosity, spin-transport, spin-imbalanced mixtures, and three-component gases, this last having a close parallel to color superconductivity. Another system important for the field of strongly-interacting quantum fluids was revealed by analysis of data from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Despite naive expectations based on asymptotic freedom that the deconfinement of quarks and gluons at high temperatures would lead to a weakly-interacting quark gluon plasma (QGP), the system appeared to be quite strongly coupled. Subsequent estimates of the viscosity-to-entropy ratio suggest that the system is tantalizingly close to the postulated bound from AdS/CFT calculations. The field is quite dynamic at the moment; new measurements are expected from upgraded detectors at RHIC, and an entirely new energy regime is being opened up by heavy ion collisions at the Large Hadron Collider (LHC) at CERN. On the theoretical side, much work remains to be done to extract the precise values of the transport coefficients, and to characterize the nature of quasi-particle excitations in the plasma. Finally, holographic dualities such as anti-de Sitter/conformal field theory (AdS/CFT) have opened a new theoretical window on strongly correlated fluids. Holography relates strongly-interacting quantum many-body systems to weakly-coupled semi-classical gravitational systems, replacing quasiparticles with geometry and translating various difficult questions about quantum fluids into simple and calculable geometric exercises. Already, some of the earliest lessons of holography, such as the conjectural bound on the viscosity-to-entropy ratio, have had a considerable impact on the theoretical and experimental study of strongly correlated fluids, from RHIC to ultracold atoms. More recently, the study of holographic superconductors, non-Fermi liquids and unitary quantum gases has touched
13. Dynamical structure factor of one-dimensional Bose gases: Experimental signatures of beyond-Luttinger-liquid physics
NARCIS (Netherlands)
N. Fabbri; M. Panfil; D. Clément; L. Fallani; M. Inguscio; C. Fort; J.-S. Caux
2015-01-01
Interactions are known to have dramatic effects on bosonic gases in one dimension (1D). Not only does the ground state transform from a condensate like state to an effective Fermi sea, but new fundamental excitations, which do not have any higher-dimensional equivalents, are predicted to appear. In
14. Properties of strongly dipolar Bose gases beyond the Born approximation
CERN Document Server
Ołdziejewski, Rafał
2016-01-01
Strongly dipolar Bose gases can form liquid droplets stabilized by quantum fluctuations. In theoretical description of this phenomenon, low energy scattering amplitude is utilized as an effective potential. We show that for magnetic atoms corrections with respect to Born approximation arise, and derive modified pseudopotential using realistic interaction model. We discuss the resulting changes in collective mode frequencies and droplet stability diagram. Our results are relevant for recent experiments with erbium and dysprosium atoms.
15. On Classical Ideal Gases
Directory of Open Access Journals (Sweden)
Laurent Chusseau
2013-02-01
Full Text Available We show that the thermodynamics of ideal gases may be derived solely from the Democritean concept of corpuscles moving in vacuum plus a principle of simplicity, namely that these laws are independent of the laws of motion, aside from the law of energy conservation. Only a single corpuscle in contact with a heat bath submitted to a z and t-invariant force is considered. Most of the end results are known but the method appears to be novel. The mathematics being elementary, the present paper should facilitate the understanding of the ideal gas law and of classical thermodynamics even though not-usually-taught concepts are being introduced.
16. Observation of relativistic antihydrogen atoms
Science.gov (United States)
Blanford, Glenn Delfosse, Jr.
1997-09-01
An observation of relativistic antihydrogen atoms is reported in this dissertation. Experiment 862 at Fermi National Accelerator Laboratory observed antihydrogen atoms produced by the interaction of a circulating beam of high momentum (3 production is outlined within. The cross section corresponds to the process where a high momentum antiproton causes e+e/sp- pair creation near a nucleus with the e+ being captured by the antiproton. Antihydrogen is the first atom made exclusively of antimatter to be detected. The observation experiment's results are the first step towards an antihydrogen spectroscopy experiment which would measure the n = 2 Lamb shift and fine structure.
17. Positron scattering from noble gases future prospects
Energy Technology Data Exchange (ETDEWEB)
Jones, A C L; Caradonna, P; Makochekanwa, C; Slaughter, D S; Sullivan, J P; Buckman, S J [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, Australian National University, Canberra, ACT (Australia); Mitroy, J, E-mail: [email protected] [Faculty of Education Health and Science, Charles Darwin University, NT (Australia)
2009-11-01
Recent results for positron scattering from noble gases over an energy range from 0.5 to 60eV are presented. Measurements include the grand total ({sigma}{sub GT}), Ps formation ({sigma}{sub Ps}) and Grand total - Ps formation (({sigma}{sub GT}-P{sub s}) cross sections. Some preliminary DCS results will also be presented. Work on a formulation of modified effective range theory (MERT) is being undertaken to determine the value of the scattering length which may be useful for identifying a bound state. Plans for experiments on metal atoms will be outlined.
18. Sampling and analysis methods for geothermal fluids and gases
Energy Technology Data Exchange (ETDEWEB)
Watson, J.C.
1978-07-01
The sampling procedures for geothermal fluids and gases include: sampling hot springs, fumaroles, etc.; sampling condensed brine and entrained gases; sampling steam-lines; low pressure separator systems; high pressure separator systems; two-phase sampling; downhole samplers; and miscellaneous methods. The recommended analytical methods compiled here cover physical properties, dissolved solids, and dissolved and entrained gases. The sequences of methods listed for each parameter are: wet chemical, gravimetric, colorimetric, electrode, atomic absorption, flame emission, x-ray fluorescence, inductively coupled plasma-atomic emission spectroscopy, ion exchange chromatography, spark source mass spectrometry, neutron activation analysis, and emission spectrometry. Material on correction of brine component concentrations for steam loss during flashing is presented. (MHR)
19. Quantum chaos on a critical Fermi surface
CERN Document Server
Patel, Aavishkar A
2016-01-01
We compute parameters characterizing many-body quantum chaos for a critical Fermi surface without quasiparticle excitations. We examine a theory of $N$ species of fermions at non-zero density coupled to a $U(1)$ gauge field in two spatial dimensions, and determine the Lyapunov rate and the butterfly velocity in an extended RPA approximation. The thermal diffusivity is found to be universally related to these chaos parameters, i.e. the relationship is independent of $N$, the gauge coupling constant, the Fermi velocity, the Fermi surface curvature, and high energy details.
20. New frontiers for quantum gases of polar molecules
Science.gov (United States)
Moses, Steven A.; Covey, Jacob P.; Miecnikowski, Matthew T.; Jin, Deborah S.; Ye, Jun
2017-01-01
Compared to atoms, molecules possess additional degrees of freedom that can be exploited in fundamental tests, ultracold chemistry, and engineering new quantum phases in many-body systems. Here, we review the recent progress in creating and manipulating ultracold bialkali molecules to study quantum gases of polar molecules.
1. Fermi liquid-to-Bose condensate crossover in a two-dimensional ultracold gas experiment
Science.gov (United States)
Barmashova, T. V.; Mart'yanov, K. A.; Makhalov, V. B.; Turlapov, A. V.
2016-02-01
By controling interparticle interactions, it is possible to transform a fermionic system into a bosonic system and vice versa, while preserving quantum degeneracy. Evidence of such a transformation may be found by monitoring the pressure and interference. The Fermi pressure is an indication of the fermion?ic character of a system, while the interference implies a nonzero order parameter and Bose condensation. Lowering from three to two spatial dimensions introduces new physics and makes the system more difficult to describe due to the increased fluctuations and the reduced applicability of mean field methods. An experiment with a two-dimensional ultracold atomic gas shows a crossover between the Bose and Fermi limits, as evident from the value of pressure and from the interference pattern, and provides data to test models of 2D Fermi and Bose systems, including the most-difficult-to-model strongly coupled systems.
2. Observation of spatial charge and spin correlations in the 2D Fermi-Hubbard model.
Science.gov (United States)
Cheuk, Lawrence W; Nichols, Matthew A; Lawrence, Katherine R; Okan, Melih; Zhang, Hao; Khatami, Ehsan; Trivedi, Nandini; Paiva, Thereza; Rigol, Marcos; Zwierlein, Martin W
2016-09-16
Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by the Fermi-Hubbard model of repulsively interacting fermions on a lattice. Here we report on the site-resolved observation of charge and spin correlations in the two-dimensional (2D) Fermi-Hubbard model realized with ultracold atoms. Antiferromagnetic spin correlations are maximal at half-filling and weaken monotonically upon doping. At large doping, nearest-neighbor correlations between singly charged sites are negative, revealing the formation of a correlation hole, the suppressed probability of finding two fermions near each other. As the doping is reduced, the correlations become positive, signaling strong bunching of doublons and holes, in agreement with numerical calculations. The dynamics of the doublon-hole correlations should play an important role for transport in the Fermi-Hubbard model.
3. Effective dynamics of strongly dissipative Rydberg gases
CERN Document Server
Marcuzzi, M; Olmos, B; Lesanovsky, I
2014-01-01
We investigate the evolution of interacting Rydberg gases in the limit of strong noise and dissipation. Starting from a description in terms of a Markovian quantum master equation we derive effective equations of motion that govern the dynamics on a "coarse-grained" timescale where fast dissipative degrees of freedom have been adiabatically eliminated. Specifically, we consider two scenarios which are of relevance for current theoretical and experimental studies --- Rydberg atoms in a two-level (spin) approximation subject to strong dephasing noise as well as Rydberg atoms under so-called electromagnetically induced transparency (EIT) conditions and fast radiative decay. In the former case we find that the effective dynamics is described by classical rate equations up to second order in an appropriate perturbative expansion. This drastically reduces the computational complexity of numerical simulations in comparison to the full quantum master equation. When accounting for the fourth order correction in this e...
4. Sir William Ramsay and the noble gases.
Science.gov (United States)
Davies, Alwyn G
2012-01-01
Sir William Ramsay was one of the world's leading scientists at the end of the 19th century, and in a spectacular period of research between 1894 and 1898, he discovered five new elements. These were the noble gases, helium, neon, argon, krypton, and xenon; they added a whole new group to the Periodic Table of the elements, and provided the keystone to our understanding of the electronic structure of atoms, and the way those electrons bind the atoms together into molecules. For this work he was awarded the Nobel Prize in Chemistry in 1904, the first such prize to come to a British subject. He was also a man of great charm, a good linguist, and a composer and performer of music, poetry and song. This review will trace his career, describe his character and give and account of the chemistry which led to the award of the Nobel Prize.
5. Weyl spin-orbit-coupling-induced interactions in uniform and trapped atomic quantum fluids
Science.gov (United States)
Gupta, Reena; Singh, G. S.; Bosse, Jürgen
2013-11-01
We establish through analytical and numerical studies of thermodynamic quantities for noninteracting atomic gases that the isotropic three-dimensional spin-orbit coupling, the Weyl coupling, induces interaction which counters “effective” attraction (repulsion) of the exchange symmetry present in zero-coupling Bose (Fermi) gas. The exact analytical expressions for the grand potential and hence for several thermodynamic quantities have been obtained for this purpose in both uniform and trapped cases. It is enunciated that many interesting features of spin-orbit-coupled systems revealed theoretically can be understood in terms of coupling-induced modifications in statistical interparticle potential. The temperature dependence of the chemical potential, specific heat, and isothermal compressibility for a uniform Bose gas is found to have signature of the incipient Bose-Einstein condensation in the very weak coupling regime although the system does not really go in the Bose-condensed phase. The transition temperature in the harmonically trapped case decreases with an increase of coupling strength consistent with the weakening of the statistical attractive interaction. Anomalous behavior of some thermodynamic quantities, partly akin to that in dimensions less than two, appears for uniform fermions as soon as the Fermi level goes down the Dirac point on increasing the coupling strength. It is suggested that the fluctuation-dissipation theorem can be utilized to verify anomalous behaviors from studies of long-wavelength fluctuations in bunching and antibunching effects.
6. Radiatively induced Fermi scale and unification
CERN Document Server
Alanne, Tommi
2016-01-01
We propose a framework, where the hierarchy between the unification and the Fermi scale emerges radiatively. This work tackles the long-standing question about the connection between the low Fermi scale and a more fundamental scale of Nature. As a concrete example, we study a Pati-Salam-type unification of Elementary-Goldstone-Higgs scenario, where the Standard Model scalar sector is replaced by an SU(4)-symmetric one, and the observed Higgs particle is an elementary pseudo-Goldstone boson. We construct a concrete model where the unification scale is fixed to a phenomenologically viable value, while the Fermi scale is generated radiatively. This scenario provides an interesting link between the unification and Fermi scale physics, and opens up prospects for exploring a wide variety of open problems in particle physics, ranging from neutrinos to cosmic inflation.
7. Gamma-Ray Astrophysics NSSTC Fermi GBM
Data.gov (United States)
National Aeronautics and Space Administration — The Fermi Gamma-Ray Burst Monitor (GBM) is not a pointed or imaging instrument. To determine fluxes for known sources, we measure the change in the count rate...
8. Fermi: physicist with a capital F
Science.gov (United States)
Cobal, Marina
2016-12-01
Enrico Fermi – one of the great physicists of the 21st century – was a beacon for every Italian student of physics. This is wonderfully captured in The Pope of Physics by Gino Segrè and Bettina Hoerlin.
9. Fermi Surface of the Most Dilute Superconductor
Science.gov (United States)
Lin, Xiao; Zhu, Zengwei; Fauqué, Benoît; Behnia, Kamran
2013-04-01
The origin of superconductivity in bulk SrTiO3 is a mystery since the nonmonotonous variation of the critical transition with carrier concentration defies the expectations of the crudest version of the BCS theory. Here, employing the Nernst effect, an extremely sensitive probe of tiny bulk Fermi surfaces, we show that, down to concentrations as low as 5.5×1017cm-3, the system has both a sharp Fermi surface and a superconducting ground state. The most dilute superconductor currently known therefore has a metallic normal state with a Fermi energy as little as 1.1 meV on top of a band gap as large as 3 eV. The occurrence of a superconducting instability in an extremely small, single-component, and barely anisotropic Fermi surface implies strong constraints for the identification of the pairing mechanism.
10. A fast algorithm for finding point sources in the Fermi data stream: FermiFAST
Science.gov (United States)
Asvathaman, Asha; Omand, Conor; Barton, Alistair; Heyl, Jeremy S.
2017-04-01
We present a new and efficient algorithm for finding point sources in the photon event data stream from the Fermi Gamma-Ray Space Telescope, FermiFAST. The key advantage of FermiFAST is that it constructs a catalogue of potential sources very fast by arranging the photon data in a hierarchical data structure. Using this structure, FermiFAST rapidly finds the photons that could have originated from a potential gamma-ray source. It calculates a likelihood ratio for the contribution of the potential source using the angular distribution of the photons within the region of interest. It can find within a few minutes the most significant half of the Fermi Third Point Source catalogue (3FGL) with nearly 80 per cent purity from the 4 yr of data used to construct the catalogue. If a higher purity sample is desirable, one can achieve a sample that includes the most significant third of the Fermi 3FGL with only 5 per cent of the sources unassociated with Fermi sources. Outside the Galactic plane, all but eight of the 580 FermiFAST detections are associated with 3FGL sources. And of these eight, six yield significant detections of greater than 5σ when a further binned likelihood analysis is performed. This software allows for rapid exploration of the Fermi data, simulation of the source detection to calculate the selection function of various sources and the errors in the obtained parameters of the sources detected.
11. Coexistence of Fermi arcs and Fermi pockets in a high-T(c) copper oxide superconductor.
Science.gov (United States)
Meng, Jianqiao; Liu, Guodong; Zhang, Wentao; Zhao, Lin; Liu, Haiyun; Jia, Xiaowen; Mu, Daixiang; Liu, Shanyu; Dong, Xiaoli; Zhang, Jun; Lu, Wei; Wang, Guiling; Zhou, Yong; Zhu, Yong; Wang, Xiaoyang; Xu, Zuyan; Chen, Chuangtian; Zhou, X J
2009-11-19
In the pseudogap state of the high-transition-temperature (high-T(c)) copper oxide superconductors, angle-resolved photoemission (ARPES) measurements have seen Fermi arcs-that is, open-ended gapless sections in the large Fermi surface-rather than a closed loop expected of an ordinary metal. This is all the more puzzling because Fermi pockets (small closed Fermi surface features) have been suggested by recent quantum oscillation measurements. The Fermi arcs cannot be understood in terms of existing theories, although there is a solution in the form of conventional Fermi surface pockets associated with competing order, but with a back side that is for detailed reasons invisible to photoemission probes. Here we report ARPES measurements of Bi(2)Sr(2-x)La(x)CuO(6+delta) (La-Bi2201) that reveal Fermi pockets. The charge carriers in the pockets are holes, and the pockets show an unusual dependence on doping: they exist in underdoped but not overdoped samples. A surprise is that these Fermi pockets appear to coexist with the Fermi arcs. This coexistence has not been expected theoretically.
12. Atomic physics: A strange kind of liquid
Science.gov (United States)
Laburthe-Tolra, Bruno
2016-11-01
Interactions between the magnetic dipoles of dysprosium atoms in an ultracold gas can produce a 'self-bound' droplet. This provides a useful isolated system for probing the quantum-mechanical properties of ultracold gases. See Letter p.259
13. Superfluidity in ultracold gases
Science.gov (United States)
Campbell, Gretchen
2016-05-01
The study of superfluidity has a long and rich history. In Bose-Einstein condensate, superfluidity gives rise to a number of interesting effects, including quantized vortices and persistent currents. In this seminar I will give an introduction to superfluidity in ultracold atoms, including a discussion of the critical velocity and the spectrum of elementary excitations in superfluid systems.
14. Fermi-Dirac Statistics of Complex Networks
Institute of Scientific and Technical Information of China (English)
SHEN Yi; ZHU Di-Ling; LIU Wei-Ming
2005-01-01
@@ We investigate phenomena of decline of complex networks by employing and analysing an illness model. Its intrinsic relation with the Fermi distribution is shown and a mapping to Fermi gas is established. The results of numerical simulations are obtained in two ways. We also compare the model with other models, including the dual relationship with the fitness model, and its difference from the Cayley tree model.
15. Fermi breakup and the statistical multifragmentation model
Energy Technology Data Exchange (ETDEWEB)
Carlson, B.V., E-mail: [email protected] [Departamento de Fisica, Instituto Tecnologico de Aeronautica - CTA, 12228-900 Sao Jose dos Campos (Brazil); Donangelo, R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, CP 68528, 21941-972, Rio de Janeiro (Brazil); Instituto de Fisica, Facultad de Ingenieria, Universidad de la Republica, Julio Herrera y Reissig 565, 11.300 Montevideo (Uruguay); Souza, S.R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, CP 68528, 21941-972, Rio de Janeiro (Brazil); Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, CP 15051, 91501-970, Porto Alegre (Brazil); Lynch, W.G.; Steiner, A.W.; Tsang, M.B. [Joint Institute for Nuclear Astrophysics, National Superconducting Cyclotron Laboratory and the Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
2012-02-15
We demonstrate the equivalence of a generalized Fermi breakup model, in which densities of excited states are taken into account, to the microcanonical statistical multifragmentation model used to describe the disintegration of highly excited fragments of nuclear reactions. We argue that such a model better fulfills the hypothesis of statistical equilibrium than the Fermi breakup model generally used to describe statistical disintegration of light mass nuclei.
16. Reaching a Fermi-superfluid state near an orbital Feshbach resonance
Science.gov (United States)
Xu, Junjun; Zhang, Ren; Cheng, Yanting; Zhang, Peng; Qi, Ran; Zhai, Hui
2016-09-01
We propose to realize a strongly interacting Fermi superfluid near a narrow Feshbach resonance using the recently discovered "orbital Feshbach resonance." The orbital Feshbach resonance is a type of magnetic field tunable scattering resonance theoretically predicted and experimentally observed recently in the alkaline-earth-metal-like 173Yb atom. We first show that the orbital Feshbach resonance is a narrow resonance in energy, while it is hundreds Gauss wide in terms of magnetic field strength, taking the advantage that the magnetic moment difference between the open and closed channels is quite small. Therefore, this is an ideal platform for the experimental realization of a strongly interacting Fermi superfluid with narrow resonance. We further show that the transition temperature for the Fermi superfluid in this system, especially at the BCS side of the resonance, is even higher than that in a wide resonance, which is also due to the narrow character of this resonance. Our results will encourage experimental efforts to realize Fermi superfluid in the alikaline-earth-metal-like 173Yb system, the properties of which will be complementary to extensively studied Fermi superfluids nearby a wide resonance in alkali-metal 40K and 6Li systems.
17. Understanding and Using the Fermi Science Tools
Science.gov (United States)
Asercion, Joseph; Fermi Science Support Center
2017-01-01
The Fermi Science Support Center (FSSC) provides information, documentation, and tools for the analysis of Fermi science data, including both the Large-Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Source and binary versions of the Fermi Science Tools can be downloaded from the FSSC website, and are supported on multiple platforms. An overview document, the Cicerone, provides details of the Fermi mission, the science instruments and their response functions, the science data preparation and analysis process, and interpretation of the results. Analysis Threads and a reference manual available on the FSSC website provide the user with step-by-step instructions for many different types of data analysis: point source analysis - generating maps, spectra, and light curves, pulsar timing analysis, source identification, and the use of python for scripting customized analysis chains. We present an overview of the structure of the Fermi science tools and documentation, and how to acquire them. We also provide examples of standard analyses, including tips and tricks for improving Fermi science analysis.
18. Coherence Properties of Strongly Interacting Atomic Vapors in Waveguides
Science.gov (United States)
2011-12-31
Molecular and Optical Physics Knoxville, TN, May 16-20, 2006 books, invited reviews, editorials , etc [10] Maxim Olshanii, Quantum Mechanics in Two...Rev. Lett. 99, 230402 (2007) [subcontracted under N00014-06-1-0455] [27] del Campo , A.Muga, J. G., Girardeau, M. D, Stability of spinor Fermi gases
19. Deep inelastic scattering on ultracold gases
CERN Document Server
Hofmann, Johannes
2016-01-01
We discuss the dynamic structure factor of both Bose and Fermi gases with strong short-range interactions, focussing on the deep inelastic regime of large wave vector transfer $q$. Here, the dynamic structure factor is dominated by a resonance at the free-particle energy $\\hbar \\omega = \\varepsilon_{\\bf q} = \\hbar^2 q^2/2m$ and is described in terms of scaling functions. We show that the high-momentum structure has a rich scaling behavior characterized by two separate scaling regions: first, for frequencies that differ from the single-particle energy by terms of order ${\\cal O}(q)$ (i.e., small deviations compared to the single-particle energy), the dynamic structure factor is described by the impulse approximation (IA) of Hohenberg and Platzman. Second, deviations of order ${\\cal O}(q^2)$ (i.e., of the same order or larger than the single-particle energy) are described by the operator product expansion (OPE), with a universal cross-over connecting both regimes. We use the full asymptotic form to derive vario...
20. Doping Scheme of Semiconducting Atomic Chains
Science.gov (United States)
Toshishige, Yamada; Saini, Subhash (Technical Monitor)
1998-01-01
Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.
1. Population Dynamics in Cold Gases Resulting from the Long-Range Dipole-Dipole Interaction
CERN Document Server
Mandilara, A; Pillet, P
2009-01-01
We consider the effect of the long range dipole-dipole interaction on the excitation exchange dynamics of cold two-level atomic gase in the conditions where the size of the atomic cloud is large as compared to the wavelength of the dipole transition. We show that this interaction results in population redistribution across the atomic cloud and in specific spectra of the spontaneous photons emitted at different angles with respect to the direction of atomic polarization.
2. Doping of Semiconducting Atomic Chains
Science.gov (United States)
Toshishige, Yamada; Kutler, Paul (Technical Monitor)
1997-01-01
Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.
CERN Document Server
Sneddon, J
1998-01-01
This volume continues the series'' cutting-edge reviews on developments in this field. Since its invention in the 1920s, electrostatic precipitation has been extensively used in industrial hygiene to remove dust and particulate matter from gases before entering the atmosphere. This combination of electrostatic precipitation is reported upon in the first chapter. Following this, chapter two reviews recent advances in the area of chemical modification in electrothermal atomization. Chapter three consists of a review which deal with advances and uses of electrothermal atomization atomic absorption spectrometry. Flow injection atomic spectroscopy has developed rapidly in recent years and after a general introduction, various aspects of this technique are looked at in chapter four. Finally, in chapter five the use of various spectrometric techniques for the determination of mercury are described.
4. Low-lying excitations in a strongly interacting Fermi gas
Science.gov (United States)
Vale, Christopher; Hoinka, Sascha; Dyke, Paul; Lingham, Marcus
2016-05-01
We present measurements of the low-lying excitation spectrum of a strongly interacting Fermi gas across the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover using Bragg spectroscopy. By focussing the Bragg lasers onto the central volume of the cloud we can probe atoms at near-uniform density allowing measurement of the homogeneous density-density response function. The Bragg wavevector is set to be approximately half of the Fermi wavevector to probe the collective response. Below the superfluid transition temperature the Bragg spectra dominated by the Bogoliubov-Anderson phonon mode. Single particle excitations become visible at energies greater than twice the pairing gap. As interactions are tuned from the BCS to BEC regime the phonon and single particle modes separate apart and both the pairing gap and speed of sound can be directly read off in certain regions of the crossover. Single particle pair-breaking excitations become heavily suppressed as interactions are tuned from the BCS to BEC regimes.
5. Energy and contact of the one-dimensional Fermi polaron at zero and finite temperature.
Science.gov (United States)
Doggen, E V H; Kinnunen, J J
2013-07-12
We use the T-matrix approach for studying highly polarized homogeneous Fermi gases in one dimension with repulsive or attractive contact interactions. Using this approach, we compute ground state energies and values for the contact parameter that show excellent agreement with exact and other numerical methods at zero temperature, even in the strongly interacting regime. Furthermore, we derive an exact expression for the value of the contact parameter in one dimension at zero temperature. The model is then extended and used for studying the temperature dependence of ground state energies and the contact parameter.
6. A Fast Algorithm for Finding Point Sources in the Fermi Data Stream: FermiFAST
CERN Document Server
Ashathaman, Asha; Heyl, Jeremy S
2016-01-01
This paper presents a new and efficient algorithm for finding point sources in the photon event data stream from the Fermi Gamma-Ray Space Telescope. It can rapidly construct about most significant half of the Fermi Third Point Source catalogue (3FGL) with nearly 80% purity from the four years of data used to construct the catalogue. If a higher purity sample is desirable, one can achieve a sample that includes the most significant third of the Fermi 3FGL with only five percent of the sources unassociated with Fermi sources. Outside the galaxy plane, the contamination is essentially negligible. This software allows for rapid exploration of the Fermi data, simulation of the source detection to calculate the selection function of various sources and the errors in the obtained parameters of the sources detected.
7. Anomalous conductance of a strongly interacting Fermi gas through a quantum point contact
Science.gov (United States)
Liu, Boyang; Zhai, Hui; Zhang, Shizhong
2017-01-01
In this work we study the particle conductance of a strongly interacting Fermi gas through a quantum point contact. With an atom-molecule two-channel model, we compute the contribution to particle conductance by both the fermionic atoms and the bosonic molecules using the Keldysh formalism. Focusing on the regime above the Fermi superfluid transition temperature, we find that the fermionic contribution to the conductance is reduced by interaction compared with the quantized value for the noninteracting case; while the bosonic contribution to the conductance exhibits a plateau with nonuniversal values that is larger than the quantized conductance. This feature is particularly profound at temperature close to the superfluid transition. We emphasize that the enhanced conductance arises because of the bosonic nature of closed channel molecules and the low dimensionality of the quantum point contact.
8. Upgrading Fermi Without Traveling to Space
Science.gov (United States)
Kohler, Susanna
2016-02-01
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has received an upgrade that increased its sensitivity by a whopping 40% and nobody had to travel to space to make it happen! The difference instead stems from remarkable improvement to the software used to analyze Fermi-LATs data, and it has resulted in a new high-energy map of our sky.Animation (click to watch!) comparing the Pass 7 to the Pass 8 Fermi-LAT analysis, in a region in the constellation Carina. Pass 8 provides more accurate directions for incoming gamma rays, so more of them fall closer to their sources, creating taller spikes and a sharper image. [NASA/DOE/Fermi LAT Collaboration]Pass 8Fermi-LAT has been surveying the whole sky since August 2008. It detects gamma-ray photons by converting them into electron-positron pairs and tracking the paths of these charged particles. But differentiating this signal from the charged cosmic rays that also pass through the detector with a flux that can be 10,000 times larger! is a challenging process. Making this distinction and rebuilding the path of the original gamma ray relies on complex analysis software.Pass 8 is a complete reprocessing of all data collected by Fermi-LAT. The software has gone through many revisions before now, but this is the first revision that has taken into account all of the experience that the Fermi team has gained operating the LAT in its orbital environment.The improvements made in Pass 8 include better background rejection of misclassified charged particles, improvements to the point spread function and effective area of the detector, and an extension of the effective energy range from below 100 MeV to beyond a few hundred GeV. The changes made in Pass 8 have increased the sensitivity of Fermi-LAT by an astonishing 40%.Map of the High-Energy SkySky map of the sources in the 2FHL catalog, classified by their most likely association. Click for a better look! [Ackermann et al. 2016]The first result from the
9. Fermi Normal Coordinates and Fermion Curvature Couplings in General Relativity
CERN Document Server
Dey, Anshuman; Sarkar, Tapobrata
2014-01-01
We study gravitational curvature effects in circular and radial geodesics in static, spherically symmetric space-times, using Fermi normal coordinates. We first set up these coordinates in the general case, and then use this to study effective magnetic fields due to gravitational curvature in the exterior and interior Schwarzschild, Janis-Newman-Winicour, and Bertrand space-times. We show that these fields can be large for specific parameter values in the theories, and thus might have observational significance. We discuss the qualitative differences of the magnetic field for vacuum space-times and for those seeded by matter. We estimate the magnitude of these fields in realistic galactic scenarios and discuss their possible experimental relevance. Gravitational curvature corrections to the Hydrogen atom spectrum for these space-times are also discussed briefly.
10. Advances in atomic, molecular, and optical physics
CERN Document Server
Berman, Paul R; Arimondo, Ennio
2006-01-01
Volume 54 of the Advances Series contains ten contributions, covering a diversity of subject areas in atomic, molecular and optical physics. The article by Regal and Jin reviews the properties of a Fermi degenerate gas of cold potassium atoms in the crossover regime between the Bose-Einstein condensation of molecules and the condensation of fermionic atom pairs. The transition between the two regions can be probed by varying an external magnetic field. Sherson, Julsgaard and Polzik explore the manner in which light and atoms can be entangled, with applications to quantum information processing
11. Pairing in a dry Fermi sea.
Science.gov (United States)
Maier, T A; Staar, P; Mishra, V; Chatterjee, U; Campuzano, J C; Scalapino, D J
2016-06-17
In the traditional Bardeen-Cooper-Schrieffer theory of superconductivity, the amplitude for the propagation of a pair of electrons with momentum k and -k has a log singularity as the temperature decreases. This so-called Cooper instability arises from the presence of an electron Fermi sea. It means that an attractive interaction, no matter how weak, will eventually lead to a pairing instability. However, in the pseudogap regime of the cuprate superconductors, where parts of the Fermi surface are destroyed, this log singularity is suppressed, raising the question of how pairing occurs in the absence of a Fermi sea. Here we report Hubbard model numerical results and the analysis of angular-resolved photoemission experiments on a cuprate superconductor. In contrast to the traditional theory, we find that in the pseudogap regime the pairing instability arises from an increase in the strength of the spin-fluctuation pairing interaction as the temperature decreases rather than the Cooper log instability.
12. Fermi's Paradox - The Last Challenge for Copernicanism?
CERN Document Server
Cirkovic, Milan M
2009-01-01
We review Fermi's paradox (or the "Great Silence" problem), not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI), but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already a more than three quarters of a century old puzzle - and a quarter of century since the last major review paper in the field by G. David Brin - Fermi's paradox has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built into various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literature on the subject. Finally, we consider the ramifications of various classes of hypotheses for the practical SETI projects. Somewhat paradoxically, it seems that the class of (neo)catastrophic hypoth...
13. Beyond the 2nd Fermi Pulsar Catalog
CERN Document Server
Hou, Xian; Reposeur, Thierry; Rousseau, Romain
2013-01-01
Over thirteen times more gamma-ray pulsars have now been studied with the Large Area Telescope on NASA's Fermi satellite than the ten seen with the Compton Gamma-Ray Observatory in the nineteen-nineties. The large sample is diverse, allowing better understanding both of the pulsars themselves and of their roles in various cosmic processes. Here we explore the prospects for even more gamma-ray pulsars as Fermi enters the 2nd half of its nominal ten-year mission. New pulsars will naturally tend to be fainter than the first ones discovered. Some of them will have unusual characteristics compared to the current population, which may help discriminate between models. We illustrate a vision of the future with a sample of six pulsars discovered after the 2nd Fermi Pulsar Catalog was written.
14. Fermi surface properties of paramagnetic NpCd{sub 11} with a large unit cell
Energy Technology Data Exchange (ETDEWEB)
Homma, Yoshiya; Aoki, Dai; Shiokawa, Yoshinobu [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Yoshinori; Sakai, Hironori; Ikeda, Shugo; Yamamoto, Etsuji; Nakamura, Akio; Onuki, Yoshichika [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Settai, Rikio [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Takeuchi, Tetsuya [Cryogenic Center, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Yamagami, Hiroshi, E-mail: [email protected] [Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555 (Japan)
2010-03-15
We succeeded in growing a high-quality single crystal of NpCd{sub 11} with the cubic BaHg{sub 11}-type structure by the Cd-self flux method. The lattice parameter of a = 9.2968(2) A and crystallographic positions of the atoms were determined by x-ray single-crystal structure analysis. From the results of the magnetic susceptibility and specific heat experiments, this compound is found to be a 5f-localized paramagnet with the singlet ground state in the crystalline electric field (CEF) scheme. Fermi surface properties were measured using the de Haas-van Alphen (dHvA) technique. Long-period oscillations were observed in the dHvA frequency range of 9.1 x 10{sup 5} to 1.9 x 10{sup 7} Oe, indicating small cross-sectional areas of Fermi surfaces, which is consistent with a small Brillouin zone based on a large unit cell. From the results of dHvA and magnetoresistance experiments, the Fermi surface of NpCd{sub 11} is found to consist of many kinds of closed Fermi surfaces and a multiply-connected-like Fermi surface, although the result of energy band calculations based on the 5f-localized Np{sup 3+}(5f{sup 4}) configuration reveals the existence of only closed Fermi surfaces. The corresponding cyclotron effective mass is small, ranging from 0.1 to 0.7 m{sub 0}, which is consistent with a small electronic specific heat coefficient {gamma} {approx_equal} 10mJ/K{sup 2{center_dot}}mol, revealing no hybridization between the 5f electrons and conduction electrons.
15. Pseudogap-generated a coexistence of Fermi arcs and Fermi pockets in cuprate superconductors
Science.gov (United States)
Zhao, Huaisong; Gao, Deheng; Feng, Shiping
2017-03-01
One of the most intriguing puzzle is why there is a coexistence of Fermi arcs and Fermi pockets in the pseudogap phase of cuprate superconductors? This puzzle is calling for an explanation. Based on the t - J model in the fermion-spin representation, the coexistence of the Fermi arcs and Fermi pockets in cuprate superconductors is studied by taking into account the pseudogap effect. It is shown that the pseudogap induces an energy band splitting, and then the poles of the electron Green's function at zero energy form two contours in momentum space, however, the electron spectral weight on these two contours around the antinodal region is gapped out by the pseudogap, leaving behind the low-energy electron spectral weight only located at the disconnected segments around the nodal region. In particular, the tips of these disconnected segments converge on the hot spots to form the closed Fermi pockets, generating a coexistence of the Fermi arcs and Fermi pockets. Moreover, the single-particle coherent weight is directly related to the pseudogap, and grows linearly with doping. The calculated result of the overall dispersion of the electron excitations is in qualitative agreement with the experimental data. The theory also predicts that the pseudogap-induced peak-dip-hump structure in the electron spectrum is absent from the hot-spot directions.
16. High order harmonic generation in rare gases
Energy Technology Data Exchange (ETDEWEB)
Budil, Kimberly Susan [Univ. of California, Davis, CA (United States)
1994-05-01
The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~1013-1014 W/cm2) is focused into a dense (~1017 particles/cm3) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.
17. The Mirage of the Fermi Scale
DEFF Research Database (Denmark)
Antipin, Oleg; Sannino, Francesco; Tuominen, Kimmo
2013-01-01
The discovery of a light Higgs boson at LHC may be suggesting that we need to revise our model building paradigms to understand the origin of the weak scale. We explore the possibility that the Fermi scale is not fundamental but rather a derived one, i.e. a low energy mirage. We show that this sc......The discovery of a light Higgs boson at LHC may be suggesting that we need to revise our model building paradigms to understand the origin of the weak scale. We explore the possibility that the Fermi scale is not fundamental but rather a derived one, i.e. a low energy mirage. We show...
18. Scattering resonances in a degenerate Fermi gas
DEFF Research Database (Denmark)
Challis, Katharine; Nygaard, Nicolai; Mølmer, Klaus
2009-01-01
We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas and a configur......We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas...
19. Supernova Remnants with Fermi Large Area Telescope
Directory of Open Access Journals (Sweden)
Caragiulo M.
2017-01-01
Full Text Available The Large Area Telescope (LAT, on-board the Fermi satellite, proved to be, after 8 years of data taking, an excellent instrument to detect and observe Supernova Remnants (SNRs in a range of energies running from few hundred MeV up to few hundred GeV. It provides essential information on physical processes that occur at the source, involving both accelerated leptons and hadrons, in order to understand the mechanisms responsible for the primary Cosmic Ray (CR acceleration. We show the latest results in the observation of Galactic SNRs by Fermi-LAT.
20. Clustering in the nuclear Fermi liquid
CERN Document Server
Ebran, J -P; Niksic, T; Vretenar, D
2012-01-01
We analyze the emergence of various structures in nucleonic matter, such as crystal, clusters, liquid drops and haloes. The formation of clusters indicates that nuclei behave like a Fermi liquid close to the liquid to solid transition. The relevant parameter is the ratio of the dispersion of the single-nucleon wave functions in the nucleus to the inter-nucleon distance. We also discuss the relationship between cluster states in nuclei and the pasta phase in the crust of neutron stars, as a transitional state between a Fermi liquid and a crystal. Haloes and clusters exhibit opposite features with respect to nucleonic localization.
1. Shock instability in dissipative gases
OpenAIRE
2011-01-01
Previous experiments have revealed that shock waves in thermally relaxing gases, such as ionizing, dissociating and vibrationally excited gases, can become unstable. To date, the mechanism controlling this instability has not been resolved. Previous accounts of the D'yakov-Kontorovich instability, and Bethe-Zel'dovich-Thompson behaviour could not predict the experimentally observed instability. To address the mechanism controlling the instability, we study the propagation of shock waves in a ...
2. Deep Inelastic Scattering on Ultracold Gases
Science.gov (United States)
Hofmann, Johannes; Zwerger, Wilhelm
2017-01-01
We discuss Bragg scattering on both Bose and Fermi gases with strong short-range interactions in the deep inelastic regime of large wave vector transfer q , where the dynamic structure factor is dominated by a resonance near the free-particle energy ℏω =ɛq=ℏ2q2/2 m . Using a systematic short-distance expansion, the structure factor at high momentum is shown to exhibit a nontrivial dependence on frequency characterized by two separate scaling regimes. First, for frequencies that differ from the single-particle energy by terms of order O (q ) (i.e., small deviations compared to the single-particle energy), the dynamic structure factor is described by the impulse approximation of Hohenberg and Platzman. Second, deviations of order O (q2) (i.e., of the same order or larger than the single-particle energy) are described by the operator product expansion, with a universal crossover connecting both regimes. The scaling is consistent with the leading asymptotics for a number of sum rules in the large momentum limit. Furthermore, we derive an exact expression for the shift and width of the single-particle peak at large momentum due to interactions, thus extending a result by Beliaev [J. Exp. Theor. Phys. 7, 299 (1958)] for the low-density Bose gas to arbitrary values of the scattering length a . The shift exhibits a maximum around q a ≃1 , which is connected with a maximum in the static structure factor due to strong short-range correlations. For Bose gases with moderate interaction strengths, the theoretically predicted shift is consistent with the value observed by Papp et al. [Phys. Rev. Lett. 101, 135301 (2008), 10.1103/PhysRevLett.101.135301]. Finally, we develop a diagrammatic theory for the dynamic structure factor which accounts for the correlations beyond Bogoliubov theory. It covers the full range of momenta and frequencies and provides an explicit example for the emergence of asymptotic scaling at large momentum.
3. The Physical and Dynamical Properties of Gas that Molds the Fermi Bubbles
Science.gov (United States)
Jenkins, Edward
2012-10-01
Two sharply defined lobes of gamma-ray emission emerging from the center of our Galaxy, called the Fermi Bubbles, have been discovered in the Galactic halo. Their emissivity appears to be uniform and extends up to 8 kpc on either side of the plane. Accompanying the Fermi Bubbles are excess emissions seen in X-rays and microwaves. It is generally believed that cosmic ray particles emitted from the central portion of the Galactic disk {or perhaps the nucleus itself} are responsible for these emissions. These particles must have been advected into the halo by a wind or shock. Our goal is to gain a better understanding of the nature of this gaseous transport by viewing the UV spectra of bright, extragalactic sources behind one of the Fermi Bubbles and its surrounding regions. We plan to obtain COS spectra of 5 such objects, with the goal of measuring absorption features from Si III, Si IV, C IV and N V. We expect that our mapping of column densities and kinematics of the gases will help us to distinguish a shock from a wind. Moreover, if a shock is present, we should be able to evaluate the product of its age and the density of the gas by comparing the column densities of different species.
4. Parametric optimum analysis of an irreversible Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas
Bihong Lin; Yingru Zhao; Jincan Chen
2008-05-01
An irreversible model of an Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas is established, which is composed of two isothermal and two isobaric processes. The influence of both the quantum degeneracy and the finite-rate heat transfer between the working fluid and the heat reservoirs on the performance of the cycle is investigated, based on the theory of statistical mechanics and thermodynamic properties of an ideal Fermi gas. The inherent regeneration losses of the cycle are analyzed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Especially, the optimal performance of the cycle in the strong and weak gas degeneracy cases and the high temperature limit is discussed in detail. The analytic expressions of some optimized parameters are derived. Some optimum criteria are given. The distinctions and connections between the Ericsson refrigeration cycles working with the Fermi and classical gases are revealed.
5. A two-dimensional Fermi gas in the BEC-BCS crossover
Energy Technology Data Exchange (ETDEWEB)
Ries, Martin Gerhard
2016-01-21
This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and the observation of the BKT transition into a quasi long-range ordered superfluid phase. The pair momentum distribution of the gas is probed by means of a matter-wave focusing technique which relies on time-of-flight evolution in a weak harmonic potential. This distribution holds the coherence properties of the gas. The quasi long-range ordered phase manifests itself as a sharp low-momentum peak. The temperature where it forms is identified as the transition temperature. By tuning the temperature and the interaction strength, the phase diagram of the 2D Fermi gas in the BEC-BCS crossover is mapped out. The phase coherence is investigated in a self-interference experiment. Furthermore, algebraic decay of correlations is observed in the trap average of the first order correlation function, which is obtained from the Fourier transform of the pair momentum distribution. This is in qualitative agreement with predictions of homogeneous theory for the superfluid phase in a 2D gas. The presented results provide a foundation for future experimental and theoretical studies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex systems such as the electron gas in high-T{sub c} superconductors.
6. Predicted Abundances of Carbon Compounds in Volcanic Gases on Io
CERN Document Server
Schaefer, L; Schaefer, Laura
2004-01-01
We use chemical equilibrium calculations to model the speciation of carbon in volcanic gases on Io. The calculations cover wide temperature (500-2000 K), pressure (10^-8 to 10^+2 bars), and composition ranges (bulk O/S atomic ratios \\~0 to 3), which overlap the nominal conditions at Pele (1760 K, 0.01 bar, O/S ~ 1.5). Bulk C/S atomic ratios ranging from 10^-6 to 10^-1 in volcanic gases are used with a nominal value of 10^-3 based upon upper limits from Voyager for carbon in the Loki plume on Io. Carbon monoxide and CO2 are the two major carbon gases under all conditions studied. Carbonyl sulfide and CS2 are orders of magnitude less abundant. Consideration of different loss processes (photolysis, condensation, kinetic reactions in the plume) indicates that photolysis is probably the major loss process for all gases. Both CO and CO2 should be observable in volcanic plumes and in Io's atmosphere at abundances of several hundred parts per million by volume for a bulk C/S ratio of 10^-3.
7. Fermi and the Theory of Weak Interactions
CERN Document Server
Rajasekaran, G
2014-01-01
The history of weak interactions starting with Fermi's creation of the beta decay theory and culminating in its modern avatar in the form of the electroweak gauge theory is described. Discoveries of parity violation, matter-antimatter asymmetry, W and Z bosons and neutrino mass are highlighted.
8. Fermi Large Area Telescope Second Source Catalog
CERN Document Server
,
2011-01-01
We present the second catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24-month period. The Second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in 5 energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we att...
9. FERMI LARGE AREA TELESCOPE SECOND SOURCE CATALOG
Energy Technology Data Exchange (ETDEWEB)
Nolan, P. L.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Abdo, A. A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Antolini, E.; Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Atwood, W. B.; Belfiore, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bignami, G. F., E-mail: [email protected], E-mail: [email protected], E-mail: [email protected], E-mail: [email protected] [Istituto Universitario di Studi Superiori (IUSS), I-27100 Pavia (Italy); and others
2012-04-01
We present the second catalog of high-energy {gamma}-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24 month period. The second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in five energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we attach caution flags to 162 of the sources to indicate possible confusion with residual imperfections in the diffuse model. The 2FGL catalog contains 1873 sources detected and characterized in the 100 MeV to 100 GeV range of which we consider 127 as being firmly identified and 1171 as being reliably associated with counterparts of known or likely {gamma}-ray-producing source classes.
10. Radiatively Induced Fermi Scale in Grand Unification
DEFF Research Database (Denmark)
Alanne, Tommi; Meroni, Aurora; Sannino, Francesco;
2016-01-01
We consider Grand Unified Theories in which the hierarchy between the unification and the Fermi scale emerges radiatively. Within the Pati-Salam framework, we show that it is possible to construct a viable model where the Higgs is an elementary pseudo-Goldstone boson, and the correct hierarchy...
11. Switchable Fermi surface sheets in greigite
NARCIS (Netherlands)
Zhang, B.; de Wijs, G. A.; de Groot, R. A.
2012-01-01
Greigite (Fe3S4) and magnetite (Fe3O4) are isostructural and isoelectronic ferrimagnets with quite distinct properties. Electronic structure calculations reveal greigite is a normalmetal in contrast to half-metallic magnetite. Greigite shows a complex Fermi surface with a unique influence of relativ
12. Fermi detected blazars seen by INTEGRAL
CERN Document Server
Beckmann, V; Soldi, S
2009-01-01
Multiwavelength observations are essential to constrain physical parameters of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were detected. 15 of these sources allowed significant spectral extraction. They show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars are also visible in the first 16 months of the Fermi/LAT data, thus allowing to constrain the inverse Compton branch in these cases. Among others, we analyse the LAT data of four blazars which were not included in the Fermi LAT Bright AGN Sample based on the first 3 months of the mission: QSO B0836+710, H 1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during bright outbursts, as already observed simultaneously by INTEGRAL and Fermi (e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to several hundred keV. We pr...
13. Fermi Large Area Telescope Second Source Catalog
Science.gov (United States)
Nolan, P. L.; Abdo, A. A.; Ackermann, M.; Ajello, M; Allafort, A.; Antolini, E; Bonnell, J.; Cannon, A.; Celik O.; Corbet, R.; Davis, D. S.; DeCesar, M. E.; Ferrara, E. C.; Gehrels, N.; Harding, A. K.; Hays, E.; Johnson, T. E.; McConville, W.; McEnery, J. E; Perkins, J. S.; Racusin, J. L; Scargle, J. D.; Stephens, T. E.; Thompson, D. J.; Troja, E.
2012-01-01
We present the second catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24-month period. The Second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in 5 energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we attach caution flags to 162 of the sources to indicate possible confusion with residual imperfections in the diffuse model. The 2FGL catalog contains 1873 sources detected and characterized in the 100 11eV to 100 GeV range of which we consider 127 as being firmly identified and 1171 as being reliably associated with counterparts of known or likely gamma-ray-producing source classes.
14. Automatic Cloud Bursting under FermiCloud
Energy Technology Data Exchange (ETDEWEB)
Wu, Hao [Fermilab; Shangping, Ren [IIT; Garzoglio, Gabriele [Fermilab; Timm, Steven [Fermilab; Bernabeu, Gerard [Fermilab; Kim, Hyun Woo; Chadwick, Keith; Jang, Haengjin [KISTI, Daejeon; Noh, Seo-Young [KISTI, Daejeon
1900-01-01
Cloud computing is changing the infrastructure upon which scientific computing depends from supercomputers and distributed computing clusters to a more elastic cloud-based structure. The service-oriented focus and elasticity of clouds can not only facilitate technology needs of emerging business but also shorten response time and reduce operational costs of traditional scientific applications. Fermi National Accelerator Laboratory (Fermilab) is currently in the process of building its own private cloud, FermiCloud, which allows the existing grid infrastructure to use dynamically provisioned resources on FermiCloud to accommodate increased but dynamic computation demand from scientists in the domains of High Energy Physics (HEP) and other research areas. Cloud infrastructure also allows to increase a private cloud’s resource capacity through “bursting” by borrowing or renting resources from other community or commercial clouds when needed. This paper introduces a joint project on building a cloud federation to support HEP applications between Fermi National Accelerator Laboratory and Korea Institution of Science and Technology Information, with technical contributions from the Illinois Institute of Technology. In particular, this paper presents two recent accomplishments of the joint project: (a) cloud bursting automation and (b) load balancer. Automatic cloud bursting allows computer resources to be dynamically reconfigured to meet users’ demands. The load balance algorithm which the cloud bursting depends on decides when and where new resources need to be allocated. Our preliminary prototyping and experiments have shown promising success, yet, they also have opened new challenges to be studied
15. Thermodynamics and statistical mechanics. [thermodynamic properties of gases
Science.gov (United States)
1976-01-01
The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.
16. Thermodynamics of ultracold Bose gases at a dimensional crossover
Science.gov (United States)
Labouvie, Ralf; Vogler, Andreas; Guarrera, Vera; Ott, Herwig
2013-05-01
We have studied the thermodynamics of ultracold Bose gases in the crossover from a three-dimensional to a one-dimensional regime. In our experiment, we use a focused electron-beam to probe in situ atomic density distributions with high temporal and spatial resolution. Starting with a Bose-Einstein-Condensate in a single beam optical dipole trap we can create one-dimensional systems by loading the atoms in a two-dimensional blue-detuned optical lattice. With increasing strength of the lattices we go from a three-dimensional into a one-dimensional system. Furthermore we tune the interaction strengths of the one-dimensional quantum-gases from weak (quasi-condensate) to strong (Tonks-Girardeau). By measuring the density profiles and applying an inverse Abel-Transformation we extract the equation of states of these systems and characterize the crossover from the three-dimensional to the one-dimensional regime.
17. 76 FR 1197 - Detroit Edison Company, FERMI 2; Exemption
Science.gov (United States)
2011-01-07
... COMMISSION Detroit Edison Company, FERMI 2; Exemption 1.0 Background Detroit Edison Company (DECo) (the licensee) is the holder of Facility Operating License No. NFP-43 which authorizes operation of the Fermi 2... exemption stated that a tornado swept across the Fermi 2 property on June 6, 2010, and that the...
18. 75 FR 15748 - Detroit Edison Company; Fermi 2; Exemption
Science.gov (United States)
2010-03-30
... COMMISSION Detroit Edison Company; Fermi 2; Exemption 1.0 Background Detroit Edison Company (the licensee) is the holder of Facility Operating License No. NPF-43, which authorizes operation of Fermi 2. The...- September 11, 2001, security orders. It is from five of these new requirements that Fermi 2 now seeks...
19. Nonequilibrium statistical mechanics in one-dimensional bose gases
Science.gov (United States)
Baldovin, F.; Cappellaro, A.; Orlandini, E.; Salasnich, L.
2016-06-01
We study cold dilute gases made of bosonic atoms, showing that in the mean-field one-dimensional regime they support stable out-of-equilibrium states. Starting from the 3D Boltzmann-Vlasov equation with contact interaction, we derive an effective 1D Landau-Vlasov equation under the condition of a strong transverse harmonic confinement. We investigate the existence of out-of-equilibrium states, obtaining stability criteria similar to those of classical plasmas.
20. 40 CFR 1065.750 - Analytical gases.
Science.gov (United States)
2010-07-01
... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Analytical gases. 1065.750 Section... ENGINE-TESTING PROCEDURES Engine Fluids, Test Fuels, Analytical Gases and Other Calibration Standards § 1065.750 Analytical gases. Analytical gases must meet the accuracy and purity specifications of...
1. Spectral anisotropy of a photoresponse from heterojunctions based on GaSe and InSe layered crystals
Science.gov (United States)
Katerinchuk, V. N.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.
2014-03-01
The object of investigation is photoresponse spectra taken from the cleaved end face of heterojunctions formed by GaSe and InSe anisotropic crystals. Spectra taken from the as-prepared and chemically processed faces of the heterojunctions are compared. A modified method of growing GaSe crystals with a virgin end face is suggested, and the surface of GaSe crystals thus grown is examined by atomic force microscopy.
2. Kinetic theory the nature of gases and of heat
CERN Document Server
Brush, Stephen G
1965-01-01
Kinetic Theory, Volume I: The Nature of Gases and of Heat covers the developments in area of kinetic theory, statistical mechanics, and thermodynamics. This book is organized into two parts encompassing 11 chapters. The book starts with an overview of the history of atomism, the caloric theory, the conservation of energy, the virial theorem, and atomic magnitudes. The second part deals first with the delineation of observed phenomena of motions through the repulsion theory. This part also considers other forces of nature, including fire and heat, with emphasis on the nature of motion of these
3. Three-Body Recombination in Cold Atomic Gases
CERN Document Server
Sørensen, Peder K
2013-01-01
Systems of three particles show a surprising feature in their bound state spectrum: a series of geometrically scaled states, known as Efimov states. These states have not yet been observed directly, but many recent experiments show indirect evidence of their existence via the so-called recombination process. The theories that predict the Efimov states also predicts either resonant enhancement of the recombination process or suppression by destructive interference, depending on the sign of the interaction between the particles. The theories predict universal features for the Efimov states, for instance that the geometric scaling factor is 22.7, meaning that one state is 22.7 times larger than its lower lying neighbour state. This thesis seeks to investigate non-universal effects by incorporating additional information about the physical interactions into the universal theories.
4. The Chemistry of the Noble Gases, Understanding the Atom Series.
Science.gov (United States)
Chernick, Cedric L.
The history of the discovery, isolation, characterization, production and use of argon, krypton, xenon, helium, and radon is followed by an account of early attempts to react them with other elements. The use of the electron shell theory of valence to explain their inertness and the reactions of chemists to the production of xenon compounds is…
5. [Effect on Fermi Resonance by Some External Fields: Investigation of Fermi Resonance According to Raman Spectra].
Science.gov (United States)
Jiang, Xiu-lan; Sun, Cheng-lin; Zhou, Mi; Li, Dong-fei; Men, Zhi-wei; Li, Zuo-wei; Gao, Shu-qin
2015-03-01
Fermi resonance is a phenomenon of molecular vibrational coupling and energy transfer occurred between different groups of a single molecule or neighboring molecules. Many properties of Fermi resonance under different external fields, the investigation method of Raman spectroscopy as well as the application of Fermi resonance, etc need to be developed and extended further. In this article the research results and development about Fermi resonance obtained by Raman spectral technique were introduced systematically according to our work and the results by other researchers. Especially, the results of the behaviors of intramolecular and intermolecular Fermi resonance of some molecules under some external fields such as molecular field, pressure field and temperature field, etc were investigated and demonstrated in detail according to the Raman spectra obtained by high pressure DAC technique, temperature variation technique as well as the methods we planed originally in our group such as solution concentration variation method and LCOF resonance Raman spectroscopic technique, and some novel properties of Fermi resonance were found firstly. Concretely, (1) Under molecular field. a. The Raman spectra of C5H5 N in CH3 OH and H2O indicates that solvent effect can influence Fermi resonance distinctly; b. The phenomena of the asymmetric movement of the Fermi resonance doublets as well as the fundamental involved is tuned by the Fermi resonance which had not been found by other methods were found firstly by our variation solution concentration method; c. The Fermi resonance properties can be influenced distinctly by the molecular group reorganization induced by the hydrogen bond and anti-hydrogen bond in solution; d. Fermi resonance can occurred between C7 H8 and m-C8H10, and the Fermi resonance properties behave quite differently with the solution concentration; (2) Under pressure field. a. The spectral lines shift towards high wavenumber with increasing pressure, and
6. Conduction of molecular electronic devices: Qualitative insights through atom-atom polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Stuyver, T.; Fias, S., E-mail: [email protected]; De Proft, F.; Geerlings, P. [ALGC, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel (Belgium); Fowler, P. W. [Department of Chemistry, University of Sheffield, Sheffield S3 7HF (United Kingdom)
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
7. Conduction of molecular electronic devices: qualitative insights through atom-atom polarizabilities.
Science.gov (United States)
Stuyver, T; Fias, S; De Proft, F; Fowler, P W; Geerlings, P
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
8. Desulphurization of exhaust gases in chemical processes
Energy Technology Data Exchange (ETDEWEB)
Asperger, K.; Wischnewski, W.
1981-01-01
The sulfur content of exhaust gases can be reduced by: desulphurization of fuels; modification of processes; or treatment of resultant gases. In this paper a few selected examples from the chemical industry in the German Democratic Republic are presented. Using modified processes and treating the resultant gases, the sulphuric content of exhaust gases is effectively reduced. Methods to reduce the sulfur content of exhaust gases are described in the field of production of: sulphuric acid; viscose; fertilizers; and paraffin.
9. Fermi Arc Evolution and Doping Mechanism in High-Temperature Superconductors
Science.gov (United States)
Sunko, Denis K.; Pelc, Damjan; Požek, Miroslav; Despoja, Vito; Lazic, Predrag
2015-03-01
We calculate realistic Fermi surface (FS) evolution of La2-xSrxCuO4 (LSCO) with Sr doping within an extensive ab-initio framework including advanced band-unfolding techniques. We show that ordinary Kohn-Sham DFT+U can reproduce the observed metal-insulator transition and arc growth, when not restricted to the paramagnetic solution space. We elucidate both arc protection and the inadequacy of the rigid-band picture as consequences of a rapid change in orbital symmetry at the Fermi energy: the material undergoes a dimensional crossover along the Fermi surface, between the nodal (2D) and antinodal (3D) regions. In LSCO, this crossover accounts for FS arcs and the antinodal pseudogap, otherwise ubiquitous phenomena in high-Tc cuprates. The same calculation shows that the Sr hole stays localized in the vicinity of the dopand atom, indicating that metallization of the Cu-O plane is due to an orbital transition between Cu and O planar sites, originally proposed by Mazumdar in 1989. We can directly observe effects of the transition in charge transfers among in-plane atoms, which are different than predicted by non-interacting coherent models. This ionic doping'' mechanism has close parallels to modern views on the metallization of interfaces.
10. Landau damping in a dipolar Bose-Fermi mixture in the Bose-Einstein condensation (BEC) limit
Science.gov (United States)
Moniri, S. M.; Yavari, H.; Darsheshdar, E.
2016-12-01
By using a mean-field approximation which describes the coupled oscillations of condensate and noncondensate atoms in the collisionless regime, Landau damping in a dilute dipolar Bose-Fermi mixture in the BEC limit where Fermi superfluid is treated as tightly bounded molecules, is investigated. In the case of a uniform quasi-two-dimensional (2D) case, the results for the Landau damping due to the Bose-Fermi interaction are obtained at low and high temperatures. It is shown that at low temperatures, the Landau damping rate is exponentially suppressed. By increasing the strength of dipolar interaction, and the energy of boson quasiparticles, Landau damping is suppressed over a broader temperature range.
11. Superconductivity. Fermi arcs in a doped pseudospin-1/2 Heisenberg antiferromagnet.
Science.gov (United States)
Kim, Y K; Krupin, O; Denlinger, J D; Bostwick, A; Rotenberg, E; Zhao, Q; Mitchell, J F; Allen, J W; Kim, B J
2014-07-11
High-temperature superconductivity in cuprates arises from an electronic state that remains poorly understood. We report the observation of a related electronic state in a noncuprate material, strontium iridate (Sr2IrO4), in which the distinct cuprate fermiology is largely reproduced. Upon surface electron doping through in situ deposition of alkali-metal atoms, angle-resolved photoemission spectra of Sr2IrO4 display disconnected segments of zero-energy states, known as Fermi arcs, and a gap as large as 80 millielectron volts. Its evolution toward a normal metal phase with a closed Fermi surface as a function of doping and temperature parallels that in the cuprates. Our result suggests that Sr2IrO4 is a useful model system for comparison to the cuprates.
12. The 1st Fermi LAT SNR Catalog: the Impact of Interstellar Emission Modeling
CERN Document Server
Brandt, T J; de Palma, F; Johannesson, G; Tibaldo, L
2013-01-01
Galactic interstellar emission contributes substantially to Fermi LAT observations in the Galactic plane, the location of the majority of supernova remnants (SNRs). To explore some systematic effects on SNRs' properties caused by interstellar emission modeling, we have developed a method comparing the official LAT interstellar emission model results to eight alternative models. We created the eight alternative Galactic interstellar models by varying a few input parameters to GALPROP, namely the height of the cosmic ray propagation halo, cosmic ray source distribution in the Galaxy, and atomic hydrogen spin temperature. We have analyzed eight representative SNRs chosen to encompass a range of Galactic locations, extensions, and spectral properties using the eight different interstellar emission models. We will present the results and method in detail and discuss the implications for studies such as the 1st Fermi LAT SNR Catalog.
13. Evidence for an excited-state Efimov trimer in a three-component Fermi gas.
Science.gov (United States)
Williams, J R; Hazlett, E L; Huckans, J H; Stites, R W; Zhang, Y; O'Hara, K M
2009-09-25
We observe enhanced three-body recombination in a three-component ;{6}Li Fermi gas attributable to an excited Efimov trimer state intersecting the three-atom scattering threshold near 895 G. From measurements of the recombination rate we determine the Efimov parameters kappa_{*} and eta_{*} for the universal region above 600 G which includes three overlapping Feshbach resonances. The value of kappa_{*} also predicts the locations of loss features previously observed near 130 and 500 G [T. B. Ottenstein, Phys. Rev. Lett. 101, 203202 (2008)10.1103/PhysRevLett.101.203202; J. H. Huckans, Phys. Rev. Lett. 102, 165302 (2009)10.1103/PhysRevLett.102.165302] suggesting they are associated with a ground-state Efimov trimer near threshold. We also report on the realization of a degenerate three-component Fermi gas with approximate SU(3) symmetry.
14. Bandstructure and Fermi Surfaces of CeRh3B2
Science.gov (United States)
Yamauchi, Kunihiko; Yanase, Akira; Harima, Hisatomo
2010-04-01
The electronic bandstructure and the Fermi surfaces of ferromagnetic CeRh3B2 are calculated by using FLAPW and LSDA+U method. As assuming several kinds of the ground state to describe the 4f electronic state, we propose a fully orbital- and spin-polarized state | lz=0, sx=1/2 > as the ground state, instead of the conventional \\mathit{LS}-coupled CEF ground state, generally expected in typical 4f compounds. This is supported by the fact that both the observed magnetic moment and the observed dHvA frequencies are well explained by the calculated electronic structure and the Fermi surfaces. The unconventional ground state is stabilized by the strong 4f-4f direct mixing between the neighbored Ce atoms along the extremely small distance along the c-axis in the hexagonal crystal cell.
15. Study of Optical Band Gap of CuO Using Fermi's Golden Rule
Science.gov (United States)
Nemade, K. R.; Waghuley, S. A.
2012-05-01
Quantum size effect where the electronic and optical properties of solids are altered due to changes in the band structures, enhanced the surface/volume ratio in nano dimensions forces more than 33% of the atoms to be on the surface (for 10nm dot 35), which drastically altering the physical properties such as having lower melting temperature and lower sintering temperature, and higher diffusion force at elevated temperatures. Consequently, its Fermi's golden rule analysis becomes crucial. Cupric oxide (CuO) is an important transition metal oxide with the basis of several high temperature superconductors and giant magnetoresistance materials. In present investigation, optical Band Gap from UV data using Fermi's golden rule for single step chemically synthesized CuO was computed.
16. Magnetar Observations in the Fermi Era
Science.gov (United States)
Kouveliotou, Chryssa
2009-01-01
NASA s Fermi Observatory was launched June 11, 2009; the Fermi Gamma Ray Burst Monitor (GBM) began normal operations on July 14, about a month after launch, when the trigger algorithms were enabled. In the first 8 months of operations we recorded emission of three magnetar sources; of these, only one was an old magnetar: SGR 1806+20. The other two detections were: SGR J0501+4516, newly discovered with Swift and extensively monitored with both Swift and GBM, and SGR J1550-5418, a source originally classified as an Anomalous X-ray Pulsar (AXP). I report below on the current status of the analyses efforts of all these GBM data sets, combined with data from other satellites (Spitzer, RXTE, Chandra, Swift).
17. Magnetar Observations with Fermi/GBM
Science.gov (United States)
Kouveliotou, Chryssa
2009-01-01
NASA's Fermi Observatory was launched June 11, 2009; the Fermi Gamma Ray Burst Monitor (GBM) began normal operations on July 14, about a month after launch, when the trigger algorithms were enabled. In the first year of operations we recorded emission from four magnetar sources; of these, only one was an old magnetar: SGR 1806+20. The other three detections were: SGR J0501+4516, newly discovered with Swift and extensively monitored with both Swift and GBM, SGR J1550-5418, a source originally classified as an Anomalous X-ray Pulsar (AXP) and a very recently discovered new source, SGR 0418+5729. I report below on the current status of the analyses efforts of the GBM data.
18. Relativistic Beaming Effect in Fermi Blazars
J. H. Fan; D. Bastieri; J. H. Yang; Y. Liu; D. X. Wu; S. H. Li
2014-09-01
The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the -ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral -ray luminosity in the range of 1–100 GeV. It is interesting that the integral -ray luminosity is closely correlated with the estimated Doppler factor, log = (2.95 ± 0.09) log + 43.59 ± 0.08 for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the -ray emissions are strongly beamed.
19. Quantum gravity as a Fermi liquid
CERN Document Server
Alexander, Stephon H S
2008-01-01
We present a reformulation of loop quantum gravity with a cosmological constant and no matter as a Fermi-liquid theory. When the topological sector is deformed and large gauge symmetry is broken, we show that the Chern-Simons state reduces to Jacobson's degenerate sector describing 1+1 dimensional propagating fermions with nonlocal interactions. The Hamiltonian admits a dual description which we realize in the simple BCS model of superconductivity. On one hand, Cooper pairs are interpreted as wormhole correlations at the de Sitter horizon; their number yields the de Sitter entropy. On the other hand, BCS is mapped into a deformed conformal field theory reproducing the structure of quantum spin networks. When area measurements are performed, Cooper-pair insertions are activated on those edges of the spin network intersecting the given area, thus providing a description of quantum measurements in terms of excitations of a Fermi sea to superconducting levels. The cosmological constant problem is naturally addres...
20. Unconventional Fermi surface in an insulating state
Energy Technology Data Exchange (ETDEWEB)
Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tan, B. S. [Cambridge Univ., Cambridge (United Kingdom); Hsu, Y. -T. [Cambridge Univ., Cambridge (United Kingdom); Zeng, B. [National High Magnetic Field Lab., Tallahassee, FL (United States); Hatnean, M. Ciomaga [Univ. of Warwick, Coventry (United Kingdom); Zhu, Z. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hartstein, M. [Cambridge Univ., Cambridge (United Kingdom); Kiourlappou, M. [Cambridge Univ., Cambridge (United Kingdom); Srivastava, A. [Cambridge Univ., Cambridge (United Kingdom); Johannes, M. D. [Center for Computational Materials Science, Washington, DC (United States); Murphy, T. P. [National High Magnetic Field Lab., Tallahassee, FL (United States); Park, J. -H. [National High Magnetic Field Lab., Tallahassee, FL (United States); Balicas, L. [National High Magnetic Field Lab., Tallahassee, FL (United States); Lonzarich, G. G. [Cambridge Univ., Cambridge (United Kingdom); Balakrishnan, G. [Univ. of Warwick, Coventry (United Kingdom); Sebastian, Suchitra E. [Cambridge Univ., Cambridge (United Kingdom)
2015-07-17
Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. As a result, the quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
1. The basis of the Fermi liquid theory
CERN Document Server
Apostol, M
2001-01-01
Interaction may affect drastically the many-particle ensembles; for instance an attraction, even weak, between electrons, binds them up in pairs, leading to superconductivity; interacting fermions in one dimension get bosonized; anisotropic fermions with 'nested' Fermi surfaces become non-homogeneous, when interacting, and develop charge- or spin- density waves. All these are different phases, and appear as symmetry breakings, spontaneous or induced; they are also termed as instabilities of the many-body systems, under interaction. Hints toward their nature are often obtained through studying the interacting two-particle problem, scattering included. In this paper the basis of the Fermi liquid theory is shown, and electronic liquid is briefly discussed. (author)
2. A Probabilistic Analysis of the Fermi Paradox
CERN Document Server
Solomonides, Evan; Terzian, Yervant
2016-01-01
The fermi paradox uses an appeal to the mediocrity principle to make it seem counter-intuitive that humanity has not been contacted by extraterrestrial intelligence. A numerical, statistical analysis was conducted to determine whether this apparent loneliness is, in fact, unexpected. An inequality was derived to relate the frequency of life arising and developing technology on a suitable planet in the galaxy, the average length of time since the first broadcast of such a civilization, and a constant term. An analysis of the sphere reached thus far by human communication was also conducted, considering our local neighborhood and planets of particular interest. We clearly show that human communication has not reached a number of stars and planets adequate to expect an answer. These analyses both conclude that the Fermi paradox is not, in fact, unexpected. By the mediocrity principle and numerical modeling, it is actually unlikely that the Earth would have been reached by extraterrestrial communication at this p...
3. Thickness dependence on the optoelectronic properties of multilayered GaSe based photodetector
Science.gov (United States)
2016-08-01
Two-dimensional (2D) layered materials exhibit unique optoelectronic properties at atomic thicknesses. In this paper, we fabricated metal-semiconductor-metal based photodetectors using layered gallium selenide (GaSe) with different thicknesses. The electrical and optoelectronic properties of the photodetectors were studied, and these devices showed good electrical characteristics down to GaSe flake thicknesses of 30 nm. A photograting effect was observed in the absence of a gate voltage, thereby implying a relatively high photoresponsivity. Higher values of the photoresponsivity occurred for thicker layers of GaSe with a maximum value 0.57 AW-1 and external quantum efficiency of of 132.8%, and decreased with decreasing GaSe flake thickness. The detectivity was 4.05 × 1010 cm Hz1/2 W-1 at 532 nm laser wavelength, underscoring that GaSe is a promising p-type 2D material for photodetection applications in the visible spectrum.
4. Fermi Large Area Telescope Second Source Catalog
Science.gov (United States)
Nolan, P. L.; Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Belfiore, A.; Bellazzini, R.; Berenji, B.; Bignami, G. F.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Bonnell, J.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Campana, R.; Cañadas, B.; Cannon, A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Ceccanti, M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Chipaux, R.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Corbet, R.; Cutini, S.; D'Ammando, F.; Davis, D. S.; de Angelis, A.; DeCesar, M. E.; DeKlotz, M.; De Luca, A.; den Hartog, P. R.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Enoto, T.; Escande, L.; Fabiani, D.; Falletti, L.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hill, A. B.; Horan, D.; Hou, X.; Hughes, R. E.; Iafrate, G.; Itoh, R.; Jóhannesson, G.; Johnson, R. P.; Johnson, T. E.; Johnson, A. S.; Johnson, T. J.; Kamae, T.; Katagiri, H.; Kataoka, J.; Katsuta, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Landriu, D.; Latronico, L.; Lemoine-Goumard, M.; Lionetto, A. M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Marelli, M.; Massaro, E.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Minuti, M.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Mongelli, M.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Perkins, J. S.; Pesce-Rollins, M.; Pierbattista, M.; Pinchera, M.; Piron, F.; Pivato, G.; Porter, T. A.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Rochester, L. S.; Romani, R. W.; Roth, M.; Rousseau, R.; Ryde, F.; Sadrozinski, H. F.-W.; Salvetti, D.; Sanchez, D. A.; Saz Parkinson, P. M.; Sbarra, C.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Shaw, M. S.; Shrader, C.; Siskind, E. J.; Smith, D. A.; Spandre, G.; Spinelli, P.; Stephens, T. E.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Tinebra, F.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vandenbroucke, J.; Van Etten, A.; Van Klaveren, B.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Wallace, E.; Wang, P.; Werner, M.; Winer, B. L.; Wood, D. L.; Wood, K. S.; Wood, M.; Yang, Z.; Zimmer, S.
2012-04-01
We present the second catalog of high-energy γ-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24 month period. The second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in five energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we attach caution flags to 162 of the sources to indicate possible confusion with residual imperfections in the diffuse model. The 2FGL catalog contains 1873 sources detected and characterized in the 100 MeV to 100 GeV range of which we consider 127 as being firmly identified and 1171 as being reliably associated with counterparts of known or likely γ-ray-producing source classes. We dedicate this paper to the memory of our colleague Patrick Nolan, who died on 2011 November 6. His career spanned much of the history of high-energy astronomy from space and his work on the Large Area Telescope (LAT) began nearly 20 years ago when it was just a concept. Pat was a central member in the operation of the LAT collaboration and he is greatly missed.
5. Pulsar Timing with the Fermi LAT
CERN Document Server
Ray, Paul S; Parent, Damien; PSC, the Fermi
2010-01-01
We present an overview of precise pulsar timing using data from the Large Area Telescope (LAT) on Fermi. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon data. In addition to determining the spindown behavior of the pulsars and detecting glitches and timing noise, such timing analyses allow the precise determination of the pulsar position, thus enabling detailed multiwavelength follow up.
6. Higher time derivatives, stability and Fermi Statistics
CERN Document Server
Lopez-Sarrion, Justo
2011-01-01
We show that statistics is crucial for the instability problem derived from higher time derivatives. In fact, and contrary to previous statements, we check that when dealing with Fermi systems, the Hamiltonian is well bounded and the quantum states are normalizable. Although, ghost states are still present, they do not affect unitarity under certain conditions. We first analyze a quantum oscillator involving Grassman variables and then we generalize it to a Dirac field. Finally, we discuss some physical implications
7. EIS: the scattering beamline at FERMI.
Science.gov (United States)
Masciovecchio, Claudio; Battistoni, Andrea; Giangrisostomi, Erika; Bencivenga, Filippo; Principi, Emiliano; Mincigrucci, Riccardo; Cucini, Riccardo; Gessini, Alessandro; D'Amico, Francesco; Borghes, Roberto; Prica, Milan; Chenda, Valentina; Scarcia, Martin; Gaio, Giulio; Kurdi, Gabor; Demidovich, Alexander; Danailov, Miltcho B; Di Cicco, Andrea; Filipponi, Adriano; Gunnella, Roberto; Hatada, Keisuke; Mahne, Nicola; Raimondi, Lorenzo; Svetina, Cristian; Godnig, Roberto; Abrami, Alessandro; Zangrando, Marco
2015-05-01
The Elastic and Inelastic Scattering (EIS) beamline at the free-electron laser FERMI is presented. It consists of two separate end-stations: EIS-TIMEX, dedicated to ultrafast time-resolved studies of matter under extreme and metastable conditions, and EIS-TIMER, dedicated to time-resolved spectroscopy of mesoscopic dynamics in condensed matter. The scientific objectives are discussed and the instrument layout illustrated, together with the results from first exemplifying experiments.
8. Nonequilibrium steady states of ideal bosonic and fermionic quantum gases
Science.gov (United States)
Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André
2015-12-01
We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.
9. Signatures of an annular Fermi sea
Science.gov (United States)
Jo, Insun; Liu, Yang; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.; Winkler, R.
2017-01-01
The concept of a Fermi surface, the constant-energy surface containing all the occupied electron states in momentum, or wave-vector (k ) , space plays a key role in determining electronic properties of conductors. In two-dimensional (2D) carrier systems, the Fermi surface becomes a contour which, in the simplest case, encircles the occupied states. In this case, the area enclosed by the contour, which we refer to as the Fermi sea (FS), is a simple disk. Here we report the observation of an FS with a new topology, namely, an FS in the shape of an annulus. Such an FS is expected in a variety of 2D systems where the energy band dispersion supports a ring of extrema at finite k , but its experimental observation has been elusive. Our study provides (1) theoretical evidence for the presence of an annular FS in 2D hole systems confined to wide GaAs quantum wells and (2) experimental signatures of the onset of its occupation as an abrupt rise in the sample resistance, accompanied by a sudden appearance of Shubnikov-de Haas oscillations at an unexpectedly high frequency whose value does not simply correspond to the (negligible) density of holes contained within the annular FS.
10. A Probabilistic Analysis of the Fermi Paradox
Science.gov (United States)
Solomonides, Evan; Terzian, Yervant
2016-06-01
The Fermi paradox uses an appeal to the mediocrity principle to make it seem counterintuitive that humanity has not been contacted by extraterrestrial intelligence. A numerical, statistical analysis was conducted to determine whether this apparent loneliness is, in fact, unexpected. An inequality was derived to relate the frequency of life arising and developing technology on a suitable planet in the galaxy; the average length of time since the first broadcast of such a civilization; and a constant term. An analysis of the sphere reached thus far by human communication was also conducted, considering our local neighborhood and planets of particular interest. These analyses both conclude that the Fermi paradox is not, in fact, unexpected. By the mediocrity principle and numerical modeling, it is actually unlikely that the Earth would have been reached by extraterrestrial communication at this point. We predict that under 1% of the galaxy has been reached at all thus far, and we do not anticipate to be reached until approximately 50% of stars/planets have been reached. We offer a prediction that we should not expect this until at least 1,500 years in the future. Thus the Fermi paradox is not a shocking observation- or lack thereof- and humanity may very well be contacted within our species’ lifespan (we can begin to expect to be contacted 1,500 years in the future).
11. A hybrid Fermi-Ulam-bouncer model
Energy Technology Data Exchange (ETDEWEB)
Leonel, Edson D; McClintock, P V E [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)
2005-01-28
Some dynamical and chaotic properties are studied for a classical particle bouncing between two rigid walls, one of which is fixed and the other moves in time, in the presence of an external field. The system is a hybrid, behaving not as a purely Fermi-Ulam model, nor as a bouncer, but as a combination of the two. We consider two different kinds of motion of the moving wall: (i) periodic and (ii) random. The dynamics of the model is studied via a two-dimensional nonlinear area-preserving map. We confirm that, for periodic oscillations, our model recovers the well-known results of the Fermi-Ulam model in the limit of zero external field. For intense external fields, we establish the range of control parameters values within which invariant spanning curves are observed below the chaotic sea in the low energy domain. We characterize this chaotic low energy region in terms of Lyapunov exponents. We also show that the velocity of the particle, and hence also its kinetic energy, grow according to a power law when the wall moves randomly, yielding clear evidence of Fermi acceleration.
12. Superconducting instability in non-Fermi liquids
CERN Document Server
Mandal, Ipsita
2016-01-01
We use renormalization group (RG) analysis and dimensional regularization techniques to study potential superconductivity-inducing four-fermion interactions in systems with critical Fermi surfaces of general dimensions ($m$) and co-dimensions ($d-m$), arising as a result of quasiparticle interaction with a gapless Ising-nematic order parameter. These are examples of non-Fermi liquid states in $d$ spatial dimensions. Our formalism allows us to treat the corresponding zero-temperature low-energy effective theory in a controlled approximation close to the upper critical dimension $d=d_c(m)$. The fixed points are identified from the RG flow equations, as functions of $d$ and $m$. We find that the flow towards the non-Fermi liquid fixed point is preempted by Cooper pair formation for both the physical cases of $(d=3, m=2)$ and $(d=2, m=1)$. In fact, there is a strong enhancement of superconductivity by the order parameter fluctuations at the quantum critical point.
13. Women in Physics in Fermi's Time
CERN Document Server
Byers, N
2003-01-01
Enrico Fermi lived from 1901 to 1955, a period of great progress in physics and a period in which opportunities for women to study and work in institutions of higher learning increased significantly in Europe and North America. Though there are a few examples of women who made important contributions to physics in the 18th century such as Emilie du Chatelet and Laura Bassi, it was only in Fermi's time that the number began to increase significantly. It is remarkable that almost immediately after they gained entrance to laboratories and universities, among them appeared women of great creative ability who made lasting contributions to physics. This talk is mainly about some of these whose scientific lives are not as well known as their contributions deserve - Emmy Noether, Marietta Blau, Irene Joliot-Curie, Lise Meitner. Additionally, some outstanding women whose work played a role in Enrico Fermi's life in physics are noted - Ida Tacke Noddack, Tatiana Ehrenfest-Afanaseva, Leona Woods Marshall Libby, and Mari...
14. Hydrophobic encapsulation of hydrocarbon gases.
Science.gov (United States)
Leontiev, Alexander V; Saleh, Anas W; Rudkevich, Dmitry M
2007-04-26
[reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.
15. Explosion limits for combustible gases
Institute of Scientific and Technical Information of China (English)
TONG Min-ming; WU Guo-qing; HAO Ji-fei; DAI Xin-lian
2009-01-01
Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit (LEL) and Upper Explosion-Limit (UEL) of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of H2 increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines.
16. Spectrum-splitting approach for Fermi-operator expansion in all-electron Kohn-Sham DFT calculations
Science.gov (United States)
Motamarri, Phani; Gavini, Vikram; Bhattacharya, Kaushik; Ortiz, Michael
2017-01-01
We present a spectrum-splitting approach to conduct all-electron Kohn-Sham density functional theory (DFT) calculations by employing Fermi-operator expansion of the Kohn-Sham Hamiltonian. The proposed approach splits the subspace containing the occupied eigenspace into a core subspace, spanned by the core eigenfunctions, and its complement, the valence subspace, and thereby enables an efficient computation of the Fermi-operator expansion by reducing the expansion to the valence-subspace projected Kohn-Sham Hamiltonian. The key ideas used in our approach are as follows: (i) employ Chebyshev filtering to compute a subspace containing the occupied states followed by a localization procedure to generate nonorthogonal localized functions spanning the Chebyshev-filtered subspace; (ii) compute the Kohn-Sham Hamiltonian projected onto the valence subspace; (iii) employ Fermi-operator expansion in terms of the valence-subspace projected Hamiltonian to compute the density matrix, electron density, and band energy. We demonstrate the accuracy and performance of the method on benchmark materials systems involving silicon nanoclusters up to 1330 electrons, a single gold atom, and a six-atom gold nanocluster. The benchmark studies on silicon nanoclusters revealed a staggering fivefold reduction in the Fermi-operator expansion polynomial degree by using the spectrum-splitting approach for accuracies in the ground-state energies of ˜10-4Ha/atom with respect to reference calculations. Further, numerical investigations on gold suggest that spectrum splitting is indispensable to achieve meaningful accuracies, while employing Fermi-operator expansion.
17. Core-dominance parameter, black hole mass and jet-disc connection in Fermi blazars
OpenAIRE
Chen, Y. Y.; Zhang, X.; Zhang, H. J.; X. L. Yu
2015-01-01
We study the relationship between jet power and accretion for Fermi and non-Fermi blazars, respectively. We also compare the relevant parameter between them. Our main results are as follows. (i) Fermi and non-Fermi blazars have significant difference in redshift, black hole mass, and broad line luminosity. (ii) Fermi blazars have higher average core-dominance parameter than non-Fermi blazars, which suggests that Fermi blazars have strong beaming effect. (iii) We find significant correlation b...
18. Spectral backbone of excitation transport in ultracold Rydberg gases
Science.gov (United States)
Scholak, Torsten; Wellens, Thomas; Buchleitner, Andreas
2014-12-01
The spectral structure underlying excitonic energy transfer in ultracold Rydberg gases is studied numerically, in the framework of random matrix theory, and via self-consistent diagrammatic techniques. Rydberg gases are made up of randomly distributed, highly polarizable atoms that interact via strong dipolar forces. Dynamics in such a system is fundamentally different from cases in which the interactions are of short range, and is ultimately determined by the spectral and eigenvector structure. In the energy levels' spacing statistics, we find evidence for a critical energy that separates delocalized eigenstates from states that are localized at pairs or clusters of atoms separated by less than the typical nearest-neighbor distance. We argue that the dipole blockade effect in Rydberg gases can be leveraged to manipulate this transition across a wide range: As the blockade radius increases, the relative weight of localized states is reduced. At the same time, the spectral statistics, in particular, the density of states and the nearest-neighbor level-spacing statistics, exhibits a transition from approximately a 1-stable Lévy to a Gaussian orthogonal ensemble. Deviations from random matrix statistics are shown to stem from correlations between interatomic interaction strengths that lead to an asymmetry of the spectral density and profoundly affect localization properties. We discuss approximations to the self-consistent Matsubara-Toyozawa locator expansion that incorporate these effects.
19. Biosignature Gases in H2-Dominated Atmospheres on Rocky Exoplanets
CERN Document Server
Seager, S; Hu, R
2013-01-01
(Abridged) Super Earth exoplanets are being discovered with increasing frequency and some will be able to retain stable H2-dominated atmospheres. We study biosignature gases on exoplanets with thin H2 atmospheres and habitable surface temperatures, by using a model atmosphere with photochemistry, and biomass estimate framework for evaluating the plausibilty of a range of biosignature gas candidates. We find that photochemically produced H atoms are the most abundant reactive species in H2 atmospheres. In atmospheres with high CO2 levels, atomic O is the major destructive species for some molecules. In sun-Earth-like UV radiation environments, H (and in some cases O) will rapidly destroy nearly all biosignature gases of interest. The lower UV fluxes from UV quiet M stars would produce a lower concentration of H (or O) for the same scenario, enabling some biosignature gases to accumulate. The favorability of low-UV radiation environments to in an H2 atmosphere is closely analogous to the case of oxidized atmosp...
20. Quasiparticle lifetime in a mixture of Bose and Fermi superfluids.
Science.gov (United States)
Zheng, Wei; Zhai, Hui
2014-12-31
In this Letter, we study the effect of quasiparticle interactions in a Bose-Fermi superfluid mixture. We consider the lifetime of a quasiparticle of the Bose superfluid due to its interaction with quasiparticles in the Fermi superfluid. We find that this damping rate, i.e., the inverse of the lifetime, has quite a different threshold behavior at the BCS and the BEC side of the Fermi superfluid. The damping rate is a constant near the threshold momentum in the BCS side, while it increases rapidly in the BEC side. This is because, in the BCS side, the decay process is restricted by the constraint that the fermion quasiparticle is located near the Fermi surface, while such a restriction does not exist in the BEC side where the damping process is dominated by bosonic quasiparticles of the Fermi superfluid. Our results are related to the collective mode experiment in the recently realized Bose-Fermi superfluid mixture.
1. Solution of the Problem of the Couette Flow for a Fermi Gas with Almost Specular Boundary Conditions
Science.gov (United States)
Bedrikova, E. A.; Latyshev, A. V.
2016-06-01
A solution of the Couette problem for a Fermi gas is constructed. The kinetic Bhatnagar-Gross-Krook (BGK) equation is used. Almost specular boundary conditions are considered. Formulas for the mass flux and the heat flux of the gas are obtained. These fluxes are proportional to the difference of the tangential momentum accommodation coefficients of the molecules. An expression for the viscous drag force acting on the walls of the channel is also found. An analysis of the macroparameters of the gas is performed. The limit to classical gases is taken. The obtained results are found to go over to the known results in this limit.
2. Dipolar Excitations of a Trapped Bose-Fermi Mixture
Institute of Scientific and Technical Information of China (English)
FUXiao-Wei; LIUXia-Ji; HUHui; LIShi-Qun
2004-01-01
We study the dipolar excitation of a trapped Bose-Fermi mixture at zero temperature, by using a scalingansatz formalism and Thomas-Fermi approximation at mean-field level. We show that both frequencies of the low-lying and high-lying modes are strongly affected by the Bose-Fermi interaction. Possible implication of our results to the recent experiment has been commented.
3. Dipolar Excitations of a Trapped Bose-Fermi Mixture
Institute of Scientific and Technical Information of China (English)
FU Xiao-Wei; LIU Xia-Ji; HU Hui; LI Shi-Qun
2004-01-01
We study the dipolar excitation of a trapped Bose-Fermi mixture at zero temperature, by using a scaling ansatz formalism and Thomas-Fermi approximation at mean-field level. We show that both frequencies of the low-lying and high-lying modes are strongly affected by the Bose-Fermi interaction. Possible implication of our results to the recent experiment has been commented.
4. Theoretical Insight into Shocked Gases
Energy Technology Data Exchange (ETDEWEB)
Leiding, Jeffery Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-09-29
I present the results of statistical mechanical calculations on shocked molecular gases. This work provides insight into the general behavior of shock Hugoniots of gas phase molecular targets with varying initial pressures. The dissociation behavior of the molecules is emphasized. Impedance matching calculations are performed to determine the maximum degree of dissociation accessible for a given flyer velocity as a function of initial gas pressure.
5. Atmospheric Chemistry and Greenhouse Gases
Energy Technology Data Exchange (ETDEWEB)
Ehhalt, D.; Prather, M.; Dentener, F.; Derwent, R.; Dlugokencky, Edward J.; Holland, E.; Isaksen, I.; Katima, J.; Kirchhoff, V.; Matson, P.; Midgley, P.; Wang, M.; Berntsen, T.; Bey, I.; Brasseur, G.; Buja, L.; Collins, W. J.; Daniel, J. S.; DeMore, W. B.; Derek, N.; Dickerson, R.; Etheridge, D.; Feichter, J.; Fraser, P.; Friedl, R.; Fuglestvedt, J.; Gauss, M.; Grenfell, L.; Grubler, Arnulf; Harris, N.; Hauglustaine, D.; Horowitz, L.; Jackman, C.; Jacob, D.; Jaegle, L.; Jain, Atul K.; Kanakidou, M.; Karlsdottir, S.; Ko, M.; Kurylo, M.; Lawrence, M.; Logan, J. A.; Manning, M.; Mauzerall, D.; McConnell, J.; Mickley, L. J.; Montzka, S.; Muller, J. F.; Olivier, J.; Pickering, K.; Pitari, G.; Roelofs, G.-J.; Rogers, H.; Rognerud, B.; Smith, Steven J.; Solomon, S.; Staehelin, J.; Steele, P.; Stevenson, D. S.; Sundet, J.; Thompson, A.; van Weele, M.; von Kuhlmann, R.; Wang, Y.; Weisenstein, D. K.; Wigley, T. M.; Wild, O.; Wuebbles, D.J.; Yantosca, R.; Joos, Fortunat; McFarland, M.
2001-10-01
Chapter 4 of the IPCC Third Assessment Report Climate Change 2001: The Scientific Basis. Sections include: Executive Summary 2414.1 Introduction 2434.2 Trace Gases: Current Observations, Trends and Budgets 2484.3 Projections of Future Emissions 2664.4 Projections of Atmospheric Composition for the 21st Century 2674.5 Open Questions 2774.6 Overall Impact of Global Atmospheric Chemistry Change 279
6. Global warming and greenhouse gases
OpenAIRE
Belić Dragoljub S.
2006-01-01
Global warming or Climate change refers to long-term fluctuations in temperature, precipitation, wind, and other elements of the Earth's climate system. Natural processes such as solar-irradiance variations, variations in the Earth's orbital parameters, and volcanic activity can produce variations in climate. The climate system can also be influenced by changes in the concentration of various gases in the atmosphere, which affect the Earth's absorption of radiation.
7. 40 CFR 90.312 - Analytical gases.
Science.gov (United States)
2010-07-01
... expiration date stated by the gas supplier must be recorded. (b) Pure gases. The required purity of the gases... a concentration of propane higher than what a gas supplier considers to be safe may be substituted... choice of diluent (zero air or purified nitrogen) between the calibration and span gases. If...
8. Charge transfer effects on the Fermi surface of Ba0.5K 0.5Fe2As2
KAUST Repository
Nazir, Safdar
2011-01-31
Ab-initio calculations within density functional theory are performed to obtain a more systematic understanding of the electronic structure of iron pnictides. As a prototypical compound we study Ba0.5K 0.5Fe2As2 and analyze the changes of its electronic structure when the interaction between the Fe2As 2 layers and their surrounding is modified. We find strong effects on the density of states near the Fermi energy as well as the Fermi surface. The role of the electron donor atoms in iron pnictides thus cannot be understood in a rigid band picture. Instead, the bonding within the Fe2As 2 layers reacts to a modified charge transfer from the donor atoms by adapting the intra-layer Fe-As hybridization and charge transfer in order to maintain an As3- valence state. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
9. Evolution of electron Fermi surface with doping in cobaltates.
Science.gov (United States)
Ma, Xixiao; Lan, Yu; Qin, Ling; Kuang, Lülin; Feng, Shiping
2016-08-24
The notion of the electron Fermi surface is one of the characteristic concepts in the field of condensed matter physics, and it plays a crucial role in the understanding of the physical properties of doped Mott insulators. Based on the t-J model, we study the nature of the electron Fermi surface in the cobaltates, and qualitatively reproduce the essential feature of the evolution of the electron Fermi surface with doping. It is shown that the underlying hexagonal electron Fermi surface obeys Luttinger's theorem. The theory also predicts a Fermi-arc phenomenon at the low-doped regime, where the region of the hexagonal electron Fermi surface along the [Formula: see text]-K direction is suppressed by the electron self-energy, and then six disconnected Fermi arcs located at the region of the hexagonal electron Fermi surface along the [Formula: see text]-M direction emerge. However, this Fermi-arc phenomenon at the low-doped regime weakens with the increase of doping.
10. A Nonlocal Poisson-Fermi Model for Ionic Solvent
CERN Document Server
Xie, Dexuan; Eisenberg, Bob; Scott, L Ridgway
2016-01-01
We propose a nonlocal Poisson-Fermi model for ionic solvent that includes ion size effects and polarization correlations among water molecules in the calculation of electrostatic potential. It includes the previous Poisson-Fermi models as special cases, and its solution is the convolution of a solution of the corresponding nonlocal Poisson dielectric model with a Yukawa-type kernel function. Moreover, the Fermi distribution is shown to be a set of optimal ionic concentration functions in the sense of minimizing an electrostatic potential free energy. Finally, numerical results are reported to show the difference between a Poisson-Fermi solution and a corresponding Poisson solution.
11. Nonlocal Poisson-Fermi model for ionic solvent.
Science.gov (United States)
Xie, Dexuan; Liu, Jinn-Liang; Eisenberg, Bob
2016-07-01
We propose a nonlocal Poisson-Fermi model for ionic solvent that includes ion size effects and polarization correlations among water molecules in the calculation of electrostatic potential. It includes the previous Poisson-Fermi models as special cases, and its solution is the convolution of a solution of the corresponding nonlocal Poisson dielectric model with a Yukawa-like kernel function. The Fermi distribution is shown to be a set of optimal ionic concentration functions in the sense of minimizing an electrostatic potential free energy. Numerical results are reported to show the difference between a Poisson-Fermi solution and a corresponding Poisson solution.
12. Induced interactions in a superfluid Bose-Fermi mixture
DEFF Research Database (Denmark)
Kinnunen, Jami; Bruun, Georg
2015-01-01
-particle and collective excitations of the Fermi gas give rise to an induced interaction between the bosons, which varies strongly with momentum and frequency. It diverges at the sound mode of the Fermi superfluid, resulting in a sharp avoided crossing feature and a corresponding sign change of the interaction energy...... shift in the excitation spectrum of the BEC. In addition, the excitation of quasiparticles in the Fermi superfluid leads to damping of the excitations in the BEC. Besides studying induced interactions themselves, we can use these prominent effects to systematically probe the strongly interacting Fermi...
13. Theory of the Fermi-level energy in semiconductor superlattices
Energy Technology Data Exchange (ETDEWEB)
Luscombe, J.H. (Central Research Laboratories, Texas Instruments Incorporated, Dallas, Texas (USA)); Aggarwal, R. (Central Research Laboratories, Texas Instruments Incorporated, Dallas, Texas (USA) Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts (USA)); Reed, M.A. (Central Research Laboratories, Texas Instruments Incorporated, Dallas, Texas (USA) Department of Electrical Engineering, Yale University, New Haven, Connecticut (USA)); Frensley, W.R. (Central Research Laboratories, Texas Instruments Incorporated, Dallas, Texas (USA) Department of Electrical Engineering, University of Texas at Dallas, Richardson, Texas (USA)); Luban, M. (Iowa Univ., Iowa City, IA (USA). Dept. of Physics and Astronomy Ames Lab., IA (USA))
1991-09-15
A theoretical study of the properties of the Fermi level in semiconductor superlattices (SL's) is made which is based upon the carrier occupation of the minibands in thermal equilibrium. We find, for a fixed carrier density and temperature, that the SL Fermi level can differ significantly from that obtained using commonly employed three-dimensional approximations, depending upon the relative spacings and widths of the minibands, with the SL Fermi level being higher than the corresponding bulk value. We find that the SL Fermi level is a sensitive function of the relative widths of the quantum wells and barriers.
14. Atom chip based generation of entanglement for quantum metrology
CERN Document Server
Riedel, Max F; Li, Yun; Hänsch, Theodor W; Sinatra, Alice; Treutlein, Philipp
2010-01-01
Atom chips provide a versatile quantum laboratory on a microchip' for experiments with ultracold atomic gases. They have been used in experiments on diverse topics such as low-dimensional quantum gases, cavity quantum electrodynamics, atom-surface interactions, and chip-based atomic clocks and interferometers. A severe limitation of atom chips, however, is that techniques to control atomic interactions and to generate entanglement have not been experimentally available so far. Such techniques enable chip-based studies of entangled many-body systems and are a key prerequisite for atom chip applications in quantum simulations, quantum information processing, and quantum metrology. Here we report experiments where we generate multi-particle entanglement on an atom chip by controlling elastic collisional interactions with a state-dependent potential. We employ this technique to generate spin-squeezed states of a two-component Bose-Einstein condensate and show that they are useful for quantum metrology. The obser...
15. Emergent physics: Fermi-point scenario.
Science.gov (United States)
Volovik, Grigory
2008-08-28
The Fermi-point scenario of emergent gravity has the following consequences: gravity emerges together with fermionic and bosonic matter; emergent fermionic matter consists of massless Weyl fermions; emergent bosonic matter consists of gauge fields; Lorentz symmetry persists well above the Planck energy; space-time is naturally four dimensional; the Universe is naturally flat; the cosmological constant is naturally small or zero; the underlying physics is based on discrete symmetries; 'quantum gravity' cannot be obtained by quantization of Einstein equations; and there is no contradiction between quantum mechanics and gravity, etc.
16. Optical Observations Of Fermi LAT Monitored Blazars
Science.gov (United States)
Cook, Kyle; Carini, M. T.
2009-01-01
For the past 8 years the Bell Observatory at Western Kentucky University has been conducting R band monitoring of the variability of approximately 50 Blazars. A subset of these objects are being routinely observed with the LAT instrument on-board the Fermi Space Telescope. Adding the Robotically Controlled Telescope (RCT) at Kitt Peak National Observatory and observations with the AZT-11 telescope at the Crimean Astrophysical Observatory (CRAO), we are intensively monitoring the Blazars on the Lat monitoring list. We present the results of our long term monitoring of the LAT monitored Blazars, as well as the recent contemporaneous optical R band observations we have obtained of the LAT Blazars.
17. The FERMI free-electron lasers.
Science.gov (United States)
Allaria, E; Badano, L; Bassanese, S; Capotondi, F; Castronovo, D; Cinquegrana, P; Danailov, M B; D'Auria, G; Demidovich, A; De Monte, R; De Ninno, G; Di Mitri, S; Diviacco, B; Fawley, W M; Ferianis, M; Ferrari, E; Gaio, G; Gauthier, D; Giannessi, L; Iazzourene, F; Kurdi, G; Mahne, N; Nikolov, I; Parmigiani, F; Penco, G; Raimondi, L; Rebernik, P; Rossi, F; Roussel, E; Scafuri, C; Serpico, C; Sigalotti, P; Spezzani, C; Svandrlik, M; Svetina, C; Trovó, M; Veronese, M; Zangrando, D; Zangrando, M
2015-05-01
FERMI is a seeded free-electron laser (FEL) facility located at the Elettra laboratory in Trieste, Italy, and is now in user operation with its first FEL line, FEL-1, covering the wavelength range between 100 and 20 nm. The second FEL line, FEL-2, a high-gain harmonic generation double-stage cascade covering the wavelength range 20-4 nm, has also completed commissioning and the first user call has been recently opened. An overview of the typical operating modes of the facility is presented.
18. Shear Viscosity of a Unitary Fermi Gas
OpenAIRE
Wlazłowski, Gabriel; Magierski, Piotr; Drut, Joaquín E.
2012-01-01
We present the first ab initio determination of the shear viscosity eta of the Unitary Fermi Gas, based on finite temperature quantum Monte Carlo calculations and the Kubo linear-response formalism. We determine the temperature dependence of the shear viscosity to entropy density ratio eta/s. The minimum of eta/s appears to be located above the critical temperature for the superfluid-to-normal phase transition with the most probable value being eta/s approx 0.2 hbar/kB, which almost saturates...
19. -Rays Radiation of High Redshift Fermi Blazars
W. G. Liu; S. H. Fu; X. Zhang; L. Ma; Y. B. Li; D. R. Xiong
2014-09-01
Based on the 31 high redshift ( > 2) Flat Spectral Radio Quasars (FSRQs), which is from the second Fermi-LAT AGNs catalogue (2LAC), we studied the correlation between flux densities (R, K, ) in the radio, infrared and -ray wave bands. We found that there is a significant positive correlation between and R, and a weak anticorrelation between and K in the average state. For high redshift blazars, we argue that the seed photon of -ray emission mainly comes from the jet itself and partially from the dusty torus.
20. Holographic non-Fermi-liquid fixed points.
Science.gov (United States)
Faulkner, Tom; Iqbal, Nabil; Liu, Hong; McGreevy, John; Vegh, David
2011-04-28
Techniques arising from string theory can be used to study assemblies of strongly interacting fermions. Via this 'holographic duality', various strongly coupled many-body systems are solved using an auxiliary theory of gravity. Simple holographic realizations of finite density exhibit single-particle spectral functions with sharp Fermi surfaces, of a form distinct from those of the Landau theory. The self-energy is given by a correlation function in an infrared (IR) fixed-point theory that is represented by a two-dimensional anti de Sitter space (AdS(2)) region in the dual gravitational description. Here, we describe in detail the gravity calculation of this IR correlation function.
1. Turbomolecular Pumps for Holding Gases in Open Containers
Science.gov (United States)
Keller, John W.; Lorenz, John E.
2010-01-01
Proposed special-purpose turbomolecular pumps denoted turbotraps would be designed, along with mating open containers, to prevent the escape of relatively slowly (thermal) moving gas molecules from the containers while allowing atoms moving at much greater speeds to pass through. In the original intended applications, the containers would be electron-attachment cells, and the contained gases would be vapors of alkali metal atoms moving at thermal speeds that would be of the order of a fraction of 300 meters per second. These cells would be parts of apparatuses used to measure fluxes of neutral atoms incident at kinetic energies in the approximate range of 10 eV to 10 keV (corresponding to typical speeds of the order of 40,000 m/s and higher). The incident energetic neutral atoms would pass through the cells, wherein charge-exchange reactions with the alkali metal atoms would convert the neutral atoms to negative ions, which, in turn, could then be analyzed by use of conventional charged-particle optics.
2. Ultralong-range order in the Fermi-Hubbard model with long-range interactions
Science.gov (United States)
van Loon, Erik G. C. P.; Katsnelson, Mikhail I.; Lemeshko, Mikhail
2015-08-01
We use the dual boson approach to reveal the phase diagram of the Fermi-Hubbard model with long-range dipole-dipole interactions. By using a large-scale finite-temperature calculation on a 64 ×64 square lattice we demonstrate the existence of a novel phase, possessing an "ultralong-range" order. The fingerprint of this phase—the density correlation function—features a nontrivial behavior on a scale of tens of lattice sites. We study the properties and the stability of the ultralong-range-ordered phase, and show that it is accessible in modern experiments with ultracold polar molecules and magnetic atoms.
3. On directly measuring relative Fermi energies of noble metals and their alloys
Science.gov (United States)
Kleiman, G. G.; Sundaram, V. S.; Rogers, J. D.
1981-09-01
We present the first evidence of direct measurement of relative Fermi energies in alloys and between pure metals. From applying the "atomic" concept of core hole final state screening, the Auger energy shift of noble metal A equals EFA- EF( x). High resolution Auger shifts in P1- xtCux, AuxCu1- x and AuxAg1- x demonstrate experimental verification of this simple relation. We find E FCuE FAu ≅ - 0.2 eV, and E FPt ≅ E FCu and E FAg ≅ E FAu.
4. Fermi Large Area Telescope Observations of the Dark Accelerator HESS J1745-303
Science.gov (United States)
Yeung, Paul
2016-12-01
Reviewing the two MeV-GeV investigations in the field of the HESS J1745-303 performed using Fermi Large Area Telescope data, we confirmed that the emission peak comfortably coincides with ‘Region A’ in the TeV regime, which is the brightest part of this feature. The MeV–TeV spectrum can be precisely described by a single power-law. Also, recent investigation has shown that the MeV-GeV feature is elongated from ‘Region A’ toward the north-west, which is similar to the case of large- scale atomic/molecular gas distribution.
5. Search of the Earth Limb Fermi Data and Non-Galactic Center Region Fermi Data for Signs of Narrow Lines
CERN Document Server
Bloom, E; Izaguirre, E; Snyder, A; Albert, A; Winer, B; Yang, Z; Essig, R
2013-01-01
Since the spring of 2012 there have been many papers published using Fermi LAT public data that claim evidence for narrow spectral lines coming from the region of the Galactic center. This study uses non-Galactic center Fermi-LAT data from survey mode observations, and Earth limb Fermi data to test the dark matter interpretation of this feature and better understand its origins.
6. Effects of traces of molecular gases (hydrogen, nitrogen) in glow discharges in noble gases
Science.gov (United States)
Steers, E. B. M.; Smid, P.; Hoffmann, V.
2008-07-01
molecular gases can change the discharge impedance, alter the sputtering rate and crater profile and cause changes in the absolute and relative intensities of lines in both the atomic and ionic spectra of the sample element and the plasma gas. The authors wish to acknowledge financial support from EC funded Analytical Glow Discharge Research Training Network GLADNET, contract no. MRTN-CT-2006-035459. P. Smid thanks the Deutsche Forschungsgemeinschaft (Ref 436 TSE 17/7/06) for support while carrying out experiments at IFW Dresden.
7. Bending Two-Dimensional Materials To Control Charge Localization and Fermi-Level Shift.
Science.gov (United States)
Yu, Liping; Ruzsinszky, Adrienn; Perdew, John P
2016-04-13
High-performance electronics requires the fine control of semiconductor conductivity. In atomically thin two-dimensional (2D) materials, traditional doping technique for controlling carrier concentration and carrier type may cause crystal damage and significant mobility reduction. Contact engineering for tuning carrier injection and extraction and carrier type may suffer from strong Fermi-level pinning. Here, using first-principles calculations, we predict that mechanical bending, as a unique attribute of thin 2D materials, can be used to control conductivity and Fermi-level shift. We find that bending can control the charge localization of top valence bands in both MoS2 and phosphorene nanoribbons. The donor-like in-gap edge-states of armchair MoS2 ribbon and their associated Fermi-level pinning can be removed by bending. A bending-controllable new in-gap state and accompanying direct-indirect gap transition are predicted in armchair phosphorene nanoribbon. We demonstrate that such emergent bending effects are realizable. The bending stiffness as well as the effective thickness of 2D materials are also derived from first principles. Our results are of fundamental and technological relevance and open new routes for designing functional 2D materials for applications in which flexuosity is essential.
8. Antiprotonic atom formation and spectroscopy-ASACUSA experiment at CERN-AD
CERN Document Server
Widmann, E
1999-01-01
This talk describes the experiments on atomic spectroscopy and atomic collisions as proposed by the ASACUSA collaboration for the forthcoming AD facility at CERN. They consist of high-precision spectroscopy of antiprotonic atoms, the study of anti-protonic atom formation processes, and stopping power and ionization measurements in low-pressure gases. (18 refs).
9. Atom chips
CERN Document Server
Reichel, Jakob
2010-01-01
This book provides a stimulating and multifaceted picture of a rapidly developing field. The first part reviews fundamentals of atom chip research in tutorial style, while subsequent parts focus on the topics of atom-surface interaction, coherence on atom chips, and possible future directions of atom chip research. The articles are written by leading researchers in the field in their characteristic and individual styles.
10. Atomic energy
CERN Multimedia
1996-01-01
Interviews following the 1991 co-operation Agreement between the Department of Atomic Energy (DAE) of the Government of India and the European Organization for Nuclear Research (CERN) concerning the participation in the Large Hadron Collider Project (LHC) . With Chidambaram, R, Chairman, Atomic Energy Commission and Secretary, Department of Atomic Energy, Department of Atomic Energy (DAE) of the Government of India and Professor Llewellyn-Smith, Christopher H, Director-General, CERN.
11. Pulsar Candidates Toward Fermi Unassociated Sources
CERN Document Server
Frail, D A; Jagannathan, P; Intema, H T
2016-01-01
We report on a search for steep spectrum radio sources within the 95% confidence error ellipses of the Fermi unassociated sources from the Large Array Telescope (LAT). Using existing catalogs and the newly released GMRT all-sky survey at 150 MHz we identify compact radio sources that are bright at MHz frequencies but faint or absent at GHz frequencies. Such steep spectrum radio sources are rare and constitute a sample of pulsar candidates, selected independently of period, dispersion measure, interstellar scattering and orbital parameters. We find point-like, steep spectrum candidates toward 11 Fermi sources. Based on the gamma-ray/radio positional coincidence, the rarity of such radio sources, and the properties of the 3FGL sources themselves, we argue that many of these sources could be pulsars. They may have been missed by previous radio periodicity searches due to interstellar propagation effects or because they lie in an unusually tight binary. If this hypothesis is correct, then renewed gamma-ray and ra...
12. Cores in Dwarf Galaxies from Fermi Repulsion
CERN Document Server
Randall, Lisa; Unwin, James
2016-01-01
We show that Fermi repulsion can lead to cored density profiles in dwarf galaxies for sub-keV fermionic dark matter. We treat the dark matter as a quasi-degenerate self-gravitating Fermi gas and calculate its density profile assuming hydrostatic equilibrium. We find that suitable dwarf galaxy cores of larger than 130 pc can be achieved for fermion dark matter with mass in the range 70 eV - 400 eV. While in conventional dark matter scenarios, such sub-keV thermal dark matter would be excluded by free streaming bounds, the constraints are ameliorated in models with dark matter at lower temperature than conventional thermal scenarios, such as the Flooded Dark Matter model that we have previously considered. Modifying the arguments of Tremaine and Gunn we derive a conservative lower bound on the mass of fermionic dark matter of 70 eV and a stronger lower bound from Lyman-$\\alpha$ clouds of about 470 eV, leading to slightly smaller cores than have been observed. We comment on this result and how the tension is rel...
13. Spiraling Fermi arcs in Weyl materials
Science.gov (United States)
Li, Songci; Andreev, Anton
In Weyl materials the valence and conduction electron bands touch at an even number of isolated points in the Brillouin zone. In the vicinity of these points the electron dispersion is linear and may be described by the massless Dirac equation. This results in nontrivial topology of Berry connection curvature. One of its consequences is the existence of peculiar surface electron states whose Fermi surfaces form arcs connecting projections of the Weyl points onto the surface plane. Band bending near the boundary of the crystal also produces surface states. We show that in Weyl materials band bending near the crystal surface gives rise to spiral structure of energy surfaces of arc states. The corresponding Fermi surface has the shape of a spiral that winds about the projection of the Weyl point onto the surface plane. The direction of the winding is determined by the helicity of the Weyl point and the sign of the band bending potential. For close valleys arc state morphology may be understood in terms of avoided crossing of oppositely winding spirals. This work is supported by the U.S. Department of Energy Office of Science, Basic Energy Sciences under Award Number DE-FG02-07ER46452.
14. Fermi level stabilization energy in cadmium oxide
Energy Technology Data Exchange (ETDEWEB)
Speaks, D. T.; Mayer, M. A.; Yu, K. M.; Mao, S. S.; Haller, E. E.; Walukiewicz, W.
2010-04-08
We have studied the effects of high concentrations of native point defects on the electrical and optical properties of CdO. The defects were introduced by irradiation with high energy He+, Ne+, Ar+ and C+ ions. Increasing the irradiation damage with particles heavier than He+ increases the electron concentration until a saturation level of 5x1020 cm-3 is reached. In contrast, due to the ionic character and hence strong dynamic annealing of CdO, irradiation with much lighter He+ stabilizes the electron concentration at a much lower level of 1.7x1020 cm-3. A large shift of the optical absorption edge with increasing electron concentration in irradiated samples is explained by the Burstein-Moss shift corrected for electron-electron and electron-ion interactions. The saturation of the electron concentration and the optical absorption edge energy are consistent with a defect induced stabilization of the Fermi energy at 1 eV above the conduction band edge. The result is in a good agreement with previously determined Fermi level pinning energies on CdO surfaces. The results indicate that CdO shares many similarities with InN, as both materials exhibit extremely large electron affinities and an unprecedented propensity for n-type conductivity.
15. Fermi LAT Observations of LS 5039
Energy Technology Data Exchange (ETDEWEB)
Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Washington U., Seattle /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /NASA, Goddard /NASA, Goddard /CSST, Baltimore /DAPNIA, Saclay /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U. /Stockholm U., OKC /DAPNIA, Saclay /NASA, Goddard /CSST, Baltimore /SLAC /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /Grenoble Observ. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U.; /more authors..
2012-03-29
The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 {+-} 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux (100 MeV-300 GeV) of 4.9 {+-} 0.5(stat) {+-} 1.8(syst) x 10{sup -7} photon cm{sup -2} s{sup -1}, with a cutoff at 2.1 {+-} 0.3(stat) {+-} 1.1(syst) GeV and photon index {Gamma} = 1.9 {+-} 0.1(stat) {+-} 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.
16. Orientifolding of the ABJ Fermi gas
CERN Document Server
Okuyama, Kazumi
2016-01-01
The grand partition functions of ABJ theory can be factorized into even and odd parts under the reflection of fermion coordinate in the Fermi gas approach. In some cases, the even/odd part of ABJ grand partition function is equal to that of $\\mathcal{N}=5$ $O(n)\\times USp(n')$ theory, hence it is natural to think of the even/odd projection of grand partition function as an orientifolding of ABJ Fermi gas system. By a systematic WKB analysis, we determine the coefficients in the perturbative part of grand potential of such orientifold ABJ theory. We also find the exact form of the first few "half-instanton" corrections coming from the twisted sector of the reflection of fermion coordinate. For the Chern-Simons level $k=2,4,8$ we find closed form expressions of the grand partition functions of orientifold ABJ theory, and for $k=2,4$ we prove the functional relations among the grand partition functions conjectured in arXiv:1410.7658.
17. Fermi Liquid Instabilities in the Spin Channel
Energy Technology Data Exchange (ETDEWEB)
Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-16
We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.
18. Massive Fermi gas in the expanding universe
Science.gov (United States)
Trautner, Andreas
2017-03-01
The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.
19. Fermi's paradox: The last challenge for copernicanism?
Directory of Open Access Journals (Sweden)
Ćirković M.M.
2009-01-01
Full Text Available We review Fermi's paradox (or the 'Great Silence' problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle and a quarter of century since the last major review paper in the field by G. David Brin has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literature on the subject. Finally, we consider the ramifications of various classes of hypotheses for the practical SETI projects. Somewhat paradoxically, it seems that the class of (neocatastrophic hypotheses gives, on the balance, the strongest justification to optimism regarding our current and near-future SETI efforts.
20. Fermi's Paradox - The Last Challenge For Copernicanism?
Directory of Open Access Journals (Sweden)
Ćirković, M. M.
2009-06-01
Full Text Available We review Fermi's paradox (or the "Great Silence" problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle -- and a quarter of century since the last major review paper in the field by G. David Brin -- has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literatureon the subject. Finally, we consider the ramifications of variousclasses of hypotheses for the practical SETI projects. Somewhatparadoxically, it seems that the class of (neocatastrophichypotheses gives, on the balance, the strongest justification tooptimism regarding our current and near-future SETI efforts.
1. Universal Nonequilibrium Properties of Dissipative Rydberg Gases
Science.gov (United States)
Marcuzzi, Matteo; Levi, Emanuele; Diehl, Sebastian; Garrahan, Juan P.; Lesanovsky, Igor
2014-11-01
We investigate the out-of-equilibrium behavior of a dissipative gas of Rydberg atoms that features a dynamical transition between two stationary states characterized by different excitation densities. We determine the structure and properties of the phase diagram and identify the universality class of the transition, both for the statics and the dynamics. We show that the proper dynamical order parameter is in fact not the excitation density and find evidence that the dynamical transition is in the "model A " universality class; i.e., it features a nontrivial Z2 symmetry and a dynamics with nonconserved order parameter. This sheds light on some relevant and observable aspects of dynamical transitions in Rydberg gases. In particular it permits a quantitative understanding of a recent experiment [C. Carr, Phys. Rev. Lett. 111, 113901 (2013)] which observed bistable behavior as well as power-law scaling of the relaxation time. The latter emerges not due to critical slowing down in the vicinity of a second order transition, but from the nonequilibrium dynamics near a so-called spinodal line.
2. Kinetic approach to granular gases.
Science.gov (United States)
Puglisi, A; Loreto, V; Marini Bettolo Marconi, U; Vulpiani, A
1999-05-01
We address the problem of the so-called "granular gases," i.e., gases of massive particles in rapid movement undergoing inelastic collisions. We introduce a class of models of driven granular gases for which the stationary state is the result of the balance between the dissipation and the random forces which inject energies. These models exhibit a genuine thermodynamic limit, i.e., at fixed density the mean values of kinetic energy and dissipated energy per particle are independent of the number N of particles, for large values of N. One has two regimes: when the typical relaxation time tau of the driving Brownian process is small compared with the mean collision time tau(c) the spatial density is nearly homogeneous and the velocity probability distribution is Gaussian. In the opposite limit tau>tau(c) one has strong spatial clustering, with a fractal distribution of particles, and the velocity probability distribution strongly deviates from the Gaussian one. Simulations performed in one and two dimensions under the Stosszahlansatz Boltzmann approximation confirm the scenario. Furthermore, we analyze the instabilities bringing to the spatial and the velocity clusterization. Firstly, in the framework of a mean-field model, we explain how the existence of the inelasticity can lead to a spatial clusterization; on the other hand, we discuss, in the framework of a Langevin dynamics treating the collisions in a mean-field way, how a non-Gaussian distribution of velocity can arise. The comparison between the numerical and the analytical results exhibits an excellent agreement.
3. Mechanics of liquids and gases
CERN Document Server
Loitsyanskii, L G; Jones, W P
1966-01-01
Mechanics of Liquids and Gases, Second Edition is a 10-chapter text that covers significant revisions concerning the dynamics of an ideal gas, a viscous liquid and a viscous gas.After an expanded introduction to the fundamental properties and methods of the mechanics of fluids, this edition goes on dealing with the kinetics and general questions of dynamics. The next chapters describe the one-dimensional pipe flow of a gas with friction, the elementary theory of the shock tube; Riemann's theory of the wave propagation of finite intensity, and the theory of plane subsonic and supersonic flows.
4. Pole-Based Approximation of the Fermi-Dirac Function
Institute of Scientific and Technical Information of China (English)
Lin LIN; Jianfeng LU; Lexing YING; Weinan E
2009-01-01
Two approaches for the efficient rational approximation of the Fermi-Dirac function are discussed: one uses the contour integral representation and conformal map-ping, and the other is based on a version of the multipole representation of the Fermi-Dirac function that uses only simple poles. Both representations have logarithmic computational complexity. They are of great interest for electronic structure calculations.
5. Tan's distributions and Fermi-Huang pseudopotential in momentum space
DEFF Research Database (Denmark)
Valiente, Manuel
2012-01-01
form of the Fourier-transformed pseudopotential remains very simple. Operator forms for the so-called Tan's selectors, which, together with Fermi-Huang pseudopotential, largely simplify the derivation of Tan's universal relations for the Fermi gas, are here derived and are also very simple. A momentum...
6. Don't Just Stand There--Teach Fermi Problems!
Science.gov (United States)
Robinson, A. W.
2008-01-01
Fermi problems, or order of magnitude estimates, are often used in introductory physics courses. In this paper I will show that first year students studying physics at university do not arrive with the skill set to solve these problems, and they have to be actively taught how to solve them. Once they have been shown how to solve Fermi problems,…
7. Some Aspects of Statistical Thermodynamics of a Magnetized Fermi Gas
CERN Document Server
2015-01-01
We show that at the Landau ground state a Fermi gas remains precisely a three-dimensional for an arbitrary magnetic field in radical contrast to the previous claims that the perpendicular component of the pressure of a Fermi gas vanishes at the Landau ground state and therefore, it becomes strictly a one-dimensional gas.
8. Shubnikov-de Haas oscillation of KTaO3 based electron gases
Science.gov (United States)
Miao, Ludi; Du, Renzhong; Li, Qi; Qi Li's Lab Team
Two-dimensional electron gases (2DEGs) at transition metal oxide (TMO) surfaces and interfaces have attracted much attention due to their exotic properties such as superconductivity, and ferromagnetism. Recently, 5 d TMOs are hotly investigated due to their strong spin-orbit coupling (SOC), an indispensable element for topolotical insulating states. Among them, KTaO3 not only hosts 2DEGs but also involves strong SOC. We have created KTaO3 based electron gases, with low temperature mobility as large as 8000cm2V-1s-1. Shubnikov de Haas oscillations in magnetoresistance have been observed at 1.8 K for field applied along various directions. Contributions from dxy and dxz / yz bands are both seen. These oscillation curves exhibit a field direction dependence with 4-fold symmetry, revealing the cubic symmetry of Fermi surface of KTaO3 based electon gases. Moreover, the intercept of oscillation indices is close to 0.5, a typical value for systems that involve strong SOC. Our results provide unique insights into the electronic structures of KTaO3 based electron gases via magnetotransport measurements.
9. Changing Horses in Midstream: Fermi LAT Computing and SCons
Science.gov (United States)
Bogart, J. R.; Golpayegani, N.
2011-07-01
(For the Fermi LAT Collaboration) Several years into GLAST (now Fermi) offline software development it became evident we would need a replacement for our original build system, the Configuration Management Tool (CMT) developed at CERN, in order to support Mac users and to keep pace with newer compilers and operating system versions on our traditional platforms, Linux and Windows. The open source product SCons emerged as the only viable alternative and development began in earnest several months before Fermi's successful launch in June of 2008. Over two years later the conversion is nearing completion. This paper describes the conversion to and our use of SCons, concentrating on the resulting environment for users and developers and how it was achieved. Topics discussed include SCons and its interaction with Fermi code, GoGui, a cross-platform gui for Fermi developers, and issues specific to Windows developer support.
10. The Spectral Backbone of Excitation Transport in Ultra-Cold Rydberg Gases
CERN Document Server
Scholak, Torsten; Buchleitner, Andreas
2014-01-01
The spectral structure underlying excitonic energy transfer in ultra-cold Rydberg gases is studied numerically, in the framework of random matrix theory, and via self-consistent diagrammatic techniques. Rydberg gases are made up of randomly distributed, highly polarizable atoms that interact via strong dipolar forces. Dynamics in such a system is fundamentally different from cases in which the interactions are of short range, and is ultimately determined by the spectral and eigenvector structure. In the energy levels' spacing statistics, we find evidence for a critical energy that separates delocalized eigenstates from states that are localized at pairs or clusters of atoms separated by less than the typical nearest-neighbor distance. We argue that the dipole blockade effect in Rydberg gases can be leveraged to manipulate this transition across a wide range: As the blockade radius increases, the relative weight of localized states is reduced. At the same time, the spectral statistics -- in particular, the den...
11. Wigner’s phase-space function and atomic structure: II. Ground states for closed-shell atoms
DEFF Research Database (Denmark)
Springborg, Michael; Dahl, Jens Peder
1987-01-01
display and analyze the function for the closed-shell atoms helium, beryllium, neon, argon, and zinc in the Hartree-Fock approximation. The quantum-mechanical exact results are compared with those obtained with the approximate Thomas-Fermi description of electron densities in phase space....
12. Cloud processing of soluble gases
Science.gov (United States)
Laj, P.; Fuzzi, S.; Facchini, M. C.; Lind, J. A.; Orsi, G.; Preiss, M.; Maser, R.; Jaeschke, W.; Seyffer, E.; Helas, G.; Acker, K.; Wieprecht, W.; Möller, D.; Arends, B. G.; Mols, J. J.; Colvile, R. N.; Gallagher, M. W.; Beswick, K. M.; Hargreaves, K. J.; Storeton-West, R. L.; Sutton, M. A.
Experimental data from the Great Dun Fell Cloud Experiment 1993 were used to investigate interactions between soluble gases and cloud droplets. Concentrations of H 2O 2, SO 2, CH 3COOOH, HCOOH, and HCHO were monitored at different sites within and downwind of a hill cap cloud and their temporal and spatial evolution during several cloud events was investigated. Significant differences were found between in-cloud and out-of-cloud concentrations, most of which could not be explained by simple dissolution into cloud droplets. Concentration patterns were analysed in relation to the chemistry of cloud droplets and the gas/liquid equilibrium. Soluble gases do not undergo similar behaviour: CH 3COOH simply dissolves in the aqueous phase and is outgassed upon cloud dissipation; instead, SO 2 is consumed by its reaction with H 2O 2. The behaviour of HCOOH is more complex because there is evidence for in-cloud chemical production. The formation of HCOOH interferes with the odd hydrogen cycle by enhancing the liquid-phase production of H 2O 2. The H 2O 2 concentration in cloud therefore results from the balance of consumption by oxidation of SO 2 in-cloud production, and the rate by which it is supplied to the system by entrainment of new air into the clouds.
13. Precision measurement of the sound velocity in an ultracold fermi gas through the BEC-BCS crossover
Science.gov (United States)
A trapped Fermi gas near a collisional resonance provides a unique laboratory for testing many-body theories in a variety of fields. The ultracold Fermi gas produced in our lab is comprised of the lowest two spin states of 6Li. At 834 G there is a collisional or Feshbach resonance between the two spin states. The scattering length between trapped atoms of opposing spins far exceeds the interparticle spacing of the gas. On resonance, a strongly interacting, unitary, Fermi gas is created which exhibits universal behavior. The unitary Fermi gas is a prototype for other exotic systems in nature from nuclear matter to neutron stars and high temperature superconductors. For magnetic fields less than 834 G the scattering length is positive, and pairs Fermi atoms can form molecular dimers. These dimers, comprised of two fermions, are bosons. At ultracold temperatures the molecular bosons populate the lowest energy level and form a Bose Einstein Condensate (BEC). For magnetic fields greater than 834G the scattering length between fermions in opposing spin states is negative, like Cooper pairs formed between electrons in a superconductor. The Bardeen, Cooper, and Shriefer (BCS) theory was developed to describe the pairing effect in the context of superconductors. In our experiment we produce an ultracold unitary gas. By tuning the magnetic field to either side of the Feshbach resonance we can transform the gas into a weakly interacting BEC or BCS superfluid. Therefore, the region near a Feshbach resonance is called the BEC-BCS crossover. This dissertation presents a precision measurement of the hydrodynamic sound velocity in an ultracold Fermi gas near a Feshbach resonance. The sound velocity is measured at various magnetic fields both above and below resonance. Moreover, we are able compare our measurements to theoretical descriptions of hydrodynamic sound propagation. Further, our measurement of sound velocity exactly reproduces the non-perturbative case, eliminating the
14. FermiLib v0.1
Energy Technology Data Exchange (ETDEWEB)
2017-02-27
FermiLib is an open source software package designed to facilitate the development and testing of algorithms for simulations of fermionic systems on quantum computers. Fermionic simulations represent an important application of early quantum devices with a lot of potential high value targets, such as quantum chemistry for the development of new catalysts. This software strives to provide a link between the required domain expertise in specific fermionic applications and quantum computing to enable more users to directly interface with, and develop for, these applications. It is an extensible Python library designed to interface with the high performance quantum simulator, ProjectQ, as well as application specific software such as PSI4 from the domain of quantum chemistry. Such software is key to enabling effective user facilities in quantum computation research.
15. The Gamma-ray Sky with Fermi
Science.gov (United States)
Thompson, David
2012-01-01
Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
16. Diffusive Shock Acceleration the Fermi Mechanism
CERN Document Server
Baring, M G
1997-01-01
The mechanism of diffusive Fermi acceleration at collisionless plasma shock waves is widely invoked in astrophysics to explain the appearance of non-thermal particle populations in a variety of environments, including sites of cosmic ray production, and is observed to operate at several sites in the heliosphere. This review outlines the principal results from the theory of diffusive shock acceleration, focusing first on how it produces power-law distributions in test-particle regimes, where the shock dynamics are dominated by the thermal populations that provide the seed particles for the acceleration process. Then the importance of non-linear modifications to the shock hydrodynamics by the accelerated particles is addressed, emphasizing how these subsequently influence non-thermal spectral formation.
17. The Gamma-ray Sky with Fermi
Energy Technology Data Exchange (ETDEWEB)
Thompson, D.J. [NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 (United States)
2013-10-15
Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as clusters of galaxies. Some results include a stringent limit on Lorentz invariance violation derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure in the direction of the center of our Galaxy, and strong constraints on some Weakly Interacting Massive Particle (WIMP) models for dark matter.
18. Entanglement rules for holographic Fermi surfaces
Science.gov (United States)
Roychowdhury, Dibakar
2016-08-01
In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.
19. Distinguishing short and long Fermi GRBs
CERN Document Server
Tarnopolski, Mariusz
2015-01-01
Two classes of GRBs, short and long, have been determined without any doubts, and are usually ascribed to different progenitors, yet these classes overlap for a variety of descriptive parameters. A subsample of 46 long and 22 short $Fermi$ GRBs with estimated Hurst Exponents (HEs), complemented by minimum variability time-scales (MVTS) and durations ($T_{90}$) is used to perform a supervised Machine Learning (ML) and Monte Carlo (MC) simulation using a Support Vector Machine (SVM) algorithm. It is found that while $T_{90}$ itself performs very well in distinguishing short and long GRBs, the overall success ratio is higher when the training set is complemented by MVTS and HE. These results may allow to introduce a new (non-linear) parameter that might provide less ambiguous classification of GRBs.
20. Entanglement rules for holographic Fermi surfaces
Directory of Open Access Journals (Sweden)
Dibakar Roychowdhury
2016-08-01
Full Text Available In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.
1. The Gamma-ray Universe through Fermi
Science.gov (United States)
Thompson, David J.
2012-01-01
Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
2. Depletion of the nuclear Fermi sea
CERN Document Server
Rios, A; Dickhoff, W H
2009-01-01
The short-range and tensor components of the bare nucleon-nucleon interaction induce a sizeable depletion of low momenta in the ground state of a nuclear many-body system. The self-consistent Green's function method within the ladder approximation provides an \\textit{ab-initio} description of correlated nuclear systems that accounts properly for these effects. The momentum distribution predicted by this approach is analyzed in detail, with emphasis on the depletion of the lowest momentum state. The temperature, density, and nucleon asymmetry (isospin) dependence of the depletion of the Fermi sea is clarified. A connection is established between the momentum distribution and the time-ordered components of the self-energy, which allows for an improved interpretation of the results. The dependence on the underlying nucleon-nucleon interaction provides quantitative estimates of the importance of short-range and tensor correlations in nuclear systems.
Directory of Open Access Journals (Sweden)
Ćirković Milan M.
2005-01-01
Full Text Available One of the most interesting problems in the nascent discipline of astrobiology is more than half-century old Fermi's paradox: why, considering extraordinary young age of Earth and the Solar System in the Galactic context, don't we perceive much older intelligent communities or signposts of their activity? In spite of a vigorous research activity in recent years, especially bolstered by successes of astrobiology in finding extrasolar planets and extremophiles, this problem (also known as the "Great Silence" or "astrosociological" paradox remains as open as ever. In a previous paper, we have discussed a particular evolutionary solution suggested by Karl Schroeder based on the currently dominant evolutionary doctrine of adaptationism. Here, we extend that discussion with emphasis on the problems such a solution is bound to face, and conclude that it is ultimately quite unlikely. .
4. Structure of Inert Gases Adsorbed in MCM-41
Science.gov (United States)
Evans, Dylan; Sokol, Paul
One-dimensional quantum liquids of 3He or 4He have generated recent interest for investigation in the Luttinger liquid model. Unfortunately, current studies lack a clear demonstration of definitively one-dimensional behavior. We propose using the templated, porous material, MCM-41, as a host for an atomic Luttinger liquid. In general, the pores of MCM-41 are too wide to provide a strictly one-dimensional environment, so we investigate preplating these pores with inert gases to effectively reduce their diameter. We present the results of studies of the structure of inert gases in MCM-41. Nitrogen sorption isotherms were used to characterize the sample. Then, using inert gases as adsorbates, we determined the minimum effective pore diameter that can be achieved in our sample before capillary condensation takes over. X-ray powder diffraction (XRD) was performed on the ideally preplated sample to investigate the structure of the adsorbates in the nanopores. The XRD measurements are compared to simulations of core-shell cylinder model scattering, and the validity of the model is assessed. The prospects for creating a definitively one-dimensional channel for the application of studying the structure and dynamics of helium confined in one dimension are discussed. This work was supported by the National Science Foundation under Grant DGE-1069091.
5. Doping Scheme in Atomic Chain Electronics
Science.gov (United States)
1997-01-01
Due to the dramatic reduction in MOS size, there appear many unwanted effects. In these small devices, the number of dopant atoms in the channel is not macroscopic and electrons may suffer significantly different scattering from device to device since the spatial distribution of dopant atoms is no longer regarded as continuous. This prohibits integration, while it is impossible to control such dopant positions within atomic scale. A fundamental solution is to create electronics with simple but atomically precise structures, which could be fabricated with recent atom manipulation technology. All the constituent atoms are placed as planned, and then the device characteristics are deviation-free, which is mandatory for integration. Atomic chain electronics belongs to this category. Foreign atom chains or arrays form devices, and they are placed on the atomically flat substrate surface. We can design the band structure and the resultant Fermi energy of these structures by manipulating the lattice constant. Using the tight-binding theory with universal parameters, it has been predicted that isolated Si chains and arrays are metallic, Mg chains are insulating, and Mg arrays have metallic and insulating phases [1]. The transport properties along a metallic chain have been studied, emphasizing the role of the contact to electrodes [2]. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along die chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome
6. New perspectives for noble gases in oceanography
Science.gov (United States)
Aeschbach, Werner
2016-08-01
Conditions prevailing in regions of deep water formation imprint their signature in the concentrations of dissolved noble gases, which are conserved in the deep ocean. Such "recharge conditions" including temperature, salinity, and interactions with sea ice are important in view of ocean-atmosphere CO2 partitioning. Noble gases, especially the temperature sensitive Kr and Xe, are well-established tracers to reconstruct groundwater recharge conditions. In contrast, tracer oceanography has traditionally focused on He isotopes and the light noble gases Ne and Ar, which could be analyzed at the required high precision. Recent developments of analytical and data interpretation methods now provide fresh perspectives for noble gases in oceanography.
7. [Study of Fermi resonance by means of solution concentration variation].
Science.gov (United States)
Jiang, Xiu-lan; Li, Dong-fei; Chen, Yuan-zheng; Zhou, Mi; Sun, Cheng-lin; Yang, Guang; Li, Zuo-wei; Gao, Shu-qin
2011-05-01
The values of Raman scattering coefficients of some molecules in which Fermi resonance occurs vary with solution concentration variation. We measured the Raman spectra of some solvents such as CCl4, CS2, C6H6, etc by changing the concentration of the solutions ranging from 10% to 100% in volume. As a result, the authors obtained the general law of Fermi resonance. We found some weak Fermi resonance phenomena as well that the two bands of Raman spectrum shift asymmetrically and that the fundamental of overtone is tuned by Fermi resonance and moves towards the same direction with the overtone simultaneously, which is same as the results Bier K. D. obtained by means of high-pressure technique. By means of this method, the authors demonstrated the conclusion that only the fundamental in combinations which has the same symmetry as the fundamental involved in Fermi resonance directly can its intensity variation influence the Fermi resonance. In this article, the authors present a new method to study Fermi resonance. This method is valuable in the identification and the assignment of spectral lines of solutions, the determination of molecular configuration of enzyme, the discrimination of isomer, as well as the influences on the molecular structures and properties caused by hydrogen bond.
8. Instability in Shocked Granular Gases
CERN Document Server
2013-01-01
Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. Our previous work addressed this instability by performing discrete-particle simulations of inelastic media undergoing shock compression. By allowing finite dissipation within the shock wave, instability manifests itself as distinctive high density non-uniformities and convective rolls within the shock structure. In the present study we have extended this work to investigate this instability at the continuum level. We modeled the Euler equations for granular gases with a modified cooling rate to include an impact velocity threshold necessary for inelastic collisions. Our results showed a fair agreement between the continuum and discrete-particle models. Discrepancies, such as higher frequency instabilities in our continuum results may be attributed to the absence of higher order effects.
9. Instability in shocked granular gases
Science.gov (United States)
Sirmas, Nick; Falle, Sam; Radulescu, Matei
2014-05-01
Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. Our previous work addressed this instability by performing discrete-particle simulations of inelastic media undergoing shock compression. By allowing finite dissipation within the shock wave, instability manifests itself as distinctive high density non-uniformities and convective rolls within the shock structure. In the present study we have extended this work to investigate this instability at the continuum level. We modeled the Euler equations for granular gases with a modified cooling rate to include an impact velocity threshold necessary for inelastic collisions. Our results showed a fair agreement between the continuum and discrete-particle models. Discrepancies, such as higher frequency instabilities in our continuum results may be attributed to the absence of higher order effects.
10. Strong photoassociation in a degenerate fermi gas
Science.gov (United States)
Rvachov, Timur; Jamison, Alan; Jing, Li; Son, Hyungmok; Ebadi, Sepehr; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang
2016-05-01
Despite many studies there remain open questions about strong photoassociation in ultracold gases. We study the effects of strong photoassociation in ultracold fermions. Photoassociation occurs only at short range and thus can be used as a tool to probe and control the two-body correlation function in an interacting many-body system. We study the effects of strong photoassociation in 6 Li, the onset of saturation, and its effects on spin polarized and interacting spin-mixtures. This work was funded by the NSF, ARO-MURI, SAMSUNG, and NSERC.
11. Neutron physics for nuclear reactors unpublished writings by Enrico Fermi
CERN Document Server
Fermi, Enrico; Pisanti, O
2010-01-01
This unique volume gives an accurate and very detailed description of the functioning and operation of basic nuclear reactors, as emerging from yet unpublished papers by Nobel Laureate Enrico Fermi. In the first part, the entire course of lectures on Neutron Physics delivered by Fermi at Los Alamos is reported, according to the version made by Anthony P French. Here, the fundamental physical phenomena are described very clearly and comprehensively, giving the appropriate physics grounds for the functioning of nuclear piles. In the second part, all the patents issued by Fermi (and coworkers) on
12. X.509 Authentication/Authorization in FermiCloud
Energy Technology Data Exchange (ETDEWEB)
Kim, Hyunwoo [Fermilab; Timm, Steven [Fermilab
2014-11-11
We present a summary of how X.509 authentication and authorization are used with OpenNebula in FermiCloud. We also describe a history of why the X.509 authentication was needed in FermiCloud, and review X.509 authorization options, both internal and external to OpenNebula. We show how these options can be and have been used to successfully run scientific workflows on federated clouds, which include OpenNebula on FermiCloud and Amazon Web Services as well as other community clouds. We also outline federation options being used by other commercial and open-source clouds and cloud research projects.
13. Fermi Large Area Telescope Bright Gamma-ray Source List
Energy Technology Data Exchange (ETDEWEB)
Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /KIPAC, Menlo Park /SLAC; Ajello, M.; /KIPAC, Menlo Park /SLAC; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Bechtol, K.; /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /KIPAC, Menlo Park /SLAC; Bignami, G.F.; /Pavia U.; Bloom, Elliott D.; /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /IASF, Milan /IASF, Milan /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /KIPAC, Menlo Park /SLAC /ASDC, Frascati /NASA, Goddard /Maryland U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /UC, Santa Cruz /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /NASA, Goddard; /more authors..
2009-05-15
Following its launch in 2008 June, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in three months produced a deeper and better resolved map of the {gamma}-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than {approx}10{sigma}) {gamma}-ray sources in these data. These are the best characterized and best localized point-like (i.e., spatially unresolved) {gamma}-ray sources in the early mission data.
14. Fermi LAT View of a Sample of Flaring -Ray AGNs
S. Buson; D. Bastieri; F. D’Ammando; G. Tosti
2014-09-01
In the first 3.5 years of operations, Fermi detected several sources whose flaring activity brought them to exceed daily fluxes brighter than ( > 100MeV) > 10-6 ph cm-2 s-1. These episodes were promptly reported to the scientific community by the Fermi collaboration by means of astronomer telegrams (ATels). We focus our attention on the sample composed by these flaring sources, most of which are blazars, known to be extremely variable over the whole electromagnetic spectrum, from radio to -ray energies. We study properties of the selected sample and compare them to general characteristics of the Fermi source catalogue.
15. Temporal dynamics of Bose-condensed gases
Energy Technology Data Exchange (ETDEWEB)
Trujillo Martinez, Mauricio
2014-03-19
We perform a detailed quantum dynamical study of non-equilibrium trapped, interacting Bose-condensed gases. We investigate Josephson oscillations between interacting Bose-Einstein condensates confined in a finite size double-well trap and the non-trivial time evolution of a coherent state placed at the center of a two dimensional optical lattice. For the Josephson oscillations three time scales appear. We find that Josephson junction can sustain multiple undamped oscillations up to a characteristic time scale τ{sub c} without exciting atoms out of the condensates. Beyond the characteristic time scale τ{sub c} the dynamics of the junction are governed by fast, non-condensed particles assisted Josephson tunnelling as well as the collisions between non-condensed particles. In the non-condensed particles dominated regime we observe strong damping of the oscillations due to inelastic collisions, equilibrating the system leading to an effective loss of details of the initial conditions. In addition, we predict that an initially self-trapped BEC state will be destroyed by these fast dynamics. The time evolution of a coherent state released at the center of a two dimensional optical lattice shows a ballistic expansion with a decreasing expansion velocity for increasing two-body interactions strength and particle number. Additionally, we predict that if the two-body interactions strength exceeds a certain value, a forerunner splits up from the expanding coherent state. We also observe that this system, which is prepared far from equilibrium, can evolve to a quasistationary non-equilibrium state.
16. Path-Integral Monte Carlo Determination of the Fourth-Order Virial Coefficient for a Unitary Two-Component Fermi Gas with Zero-Range Interactions.
Science.gov (United States)
Yan, Yangqian; Blume, D
2016-06-10
The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astrophysics. This work determines the fourth-order virial coefficient b_{4} of such a strongly interacting Fermi gas using a customized ab initio path-integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b_{4}, our b_{4} agrees within error bars with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly antisymmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions.
17. Nanoscale atomic waveguides with suspended carbon nanotubes
CERN Document Server
Peano, V; Kasper, A; Egger, R
2005-01-01
We propose an experimentally viable setup for the realization of one-dimensional ultracold atom gases in a nanoscale magnetic waveguide formed by single doubly-clamped suspended carbon nanotubes. We show that all common decoherence and atom loss mechanisms are small guaranteeing a stable operation of the trap. Since the extremely large current densities in carbon nanotubes are spatially homogeneous, our proposed architecture allows to overcome the problem of fragmentation of the atom cloud. Adding a second nanowire allows to create a double-well potential with a moderate tunneling barrier which is desired for tunneling and interference experiments with the advantage of tunneling distances being in the nanometer regime.
18. 40 CFR 86.1514 - Analytical gases.
Science.gov (United States)
2010-07-01
... carbon monoxide on a dry basis. (b) If the raw CO sampling system specified in 40 CFR part 1065 is used, the analytical gases specified in 40 CFR part 1065, subpart H, shall be used. (c) If a CVS sampling system is used, the analytical gases specified in 40 CFR part 1065, subpart H, shall be used....
19. 40 CFR 91.312 - Analytical gases.
Science.gov (United States)
2010-07-01
... stated by the gas supplier for each calibration gas. (b) Pure gases. The required purity of the gases is... purified synthetic air which contains a concentration of propane higher than what a gas supplier considers... manufacturer must be consistent in the choice of diluent (zero air or purified nitrogen) between...
20. Controlling interactions between highly-magnetic atoms with Feshbach resonances
CERN Document Server
Kotochigova, Svetlana
2014-01-01
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic $^7$S$_3$ chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on Dysprosium and Erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8650729656219482, "perplexity": 2774.3150044891213}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-43/segments/1508187823067.51/warc/CC-MAIN-20171018180631-20171018200631-00376.warc.gz"} |
https://www.physicsforums.com/threads/what-simple-concept-am-i-missing-about-moments.679399/ | # What simple concept am I missing about moments?
1. Mar 19, 2013
### mindheavy
In a two-dimensional statics problem involving finding a moment about a point, I don't understand how the result is either in the positive/negative z direction.
I realize moments are found by the cross product, and the cross product requires the answer to be perpendicular to the plane that the two vectors form.
If I look down at the surface of my desk and take that to be an x-y plane. a pencil laying on the plane is held stationary at it's left end, and the right end is made to rotate clockwise. This tells me that I can expect my moment to be in the negative z direction (say, going down through the surface of the desk). This makes no sense to me, what concept am I missing here?
2. Mar 19, 2013
### tiny-tim
hi mindheavy!
it's a convention
we could define it other way round (ie moment up for clockwise)
(like we could say electrons have positive charge, protons have negative charge)
but we don't, we say moment down for clockwise, moment up for anti-clockwise
what don't you like about that?
3. Mar 19, 2013
### mindheavy
What I don't like is thinking of the pen rotating clockwise and knowing that the 'answer' for the moment is going down through the desk. Is it that I don't really get what a moment is? It's easy for me to understand that a force applied to the pen causes it to rotate, but why is the moment saying the result is perpendicular? Why is the result not just the direction of rotation?
Another way I'm looking at it:
I'm imagining standing at a slot machine, the lever is directly in front of me. When I pull this lever down, there's a force acting on it going straight out either left or right? This makes no sense to me.
4. Mar 19, 2013
### tiny-tim
hi mindheavy!
it's not a force
(it's not even a vector, it's a pseudovector)
it's a moment (or torque or couple)
imagine that lever is twice as long, with the pivot in the middle
you'd produce the same effect by pulling one end down and the other end up
the total force is zero
only the total moment is non-zero
but the direction of rotation is perpendicular to the desk!
here's a question for you:
how would you describe the direction of rotation of the earth?
(and if you wanted to make the earth rotate faster, what would you call the direction of the moment you should apply?)
5. Mar 19, 2013
### mindheavy
Ok, this is starting to become clearer. Getting a vector when calculating a moment made me think of a force, but if it isn't actually a force, it will be easier to grasp.
I would describe the earth as rotating about it's vertical axis, and the direction of this rotation is perpendicular to that axis.
Is that a main idea here, being perpendicular to the axis?
6. Mar 19, 2013
### tiny-tim
nooo, the direction of rotation is the axis
that's the only way we can unambiguously define rotation!
the earth's axis is N-S
perpendicular would be any diameter through the equator, but which one? through ecuador? through kenya?
isn't the only sensible direction of rotation the line through the poles?
7. Mar 19, 2013
### mindheavy
I thought it would be the line perpendicular to the axis of rotation, at any point along that axis, maybe I have some more reading to do :)
8. Mar 26, 2013
### timthereaper
A vector is really just a magnitude and a direction. When vector analysis was developed, someone thought, "Hey, we can apply this to physics!". Forces have a magnitude and a direction, positions can have a magnitude and a direction from an origin, so using vector-based math seemed like a perfect fit.
Some scientists figured out that if you do the vector cross product of a (relative) position and a force, you get a vector whose magnitude corresponded exactly to the magnitude of a moment created around a point. The direction of that vector is a result of the cross product operation (following the right-hand rule). In vector analysis, that cross product vector is perpendicular to the plane that the two original vectors lie in. Translating that into the physical problem, they determined that the direction pointed along the axis of rotation and perpendicular to the plane of the created moment. They also figured out that which way the direction vector pointed identified which way the moment "spins" on that axis.
The moment vector is still just a magnitude and direction, but it tells you in what plane the actual "rotation" occurs, which way it's "spinning", and what the magnitude of the moment is.
Similar Discussions: What simple concept am I missing about moments? | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.829991340637207, "perplexity": 573.581442888763}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-47/segments/1510934806316.80/warc/CC-MAIN-20171121040104-20171121060104-00468.warc.gz"} |
https://colour.readthedocs.io/en/v0.3.12/generated/colour.models.eotf_reverse_BT2100_HLG.html | # colour.models.eotf_reverse_BT2100_HLG¶
colour.models.eotf_reverse_BT2100_HLG(F_D, L_B=0, L_W=1000, gamma=None)[source]
Defines Recommendation ITU-R BT.2100 Reference HLG reverse electro-optical transfer function (EOTF / EOCF).
Parameters: F_D (numeric or array_like) – Luminance $$F_D$$ of a displayed linear component $${R_D, G_D, B_D}$$ or $$Y_D$$ or $$I_D$$, in $$cd/m^2$$. L_B (numeric, optional) – $$L_B$$ is the display luminance for black in $$cd/m^2$$. L_W (numeric, optional) – $$L_W$$ is nominal peak luminance of the display in $$cd/m^2$$ for achromatic pixels. gamma (numeric, optional) – System gamma value, 1.2 at the nominal display peak luminance of $$1000 cd/m^2$$. $$E'$$ denotes a non-linear colour value $${R', G', B'}$$ or $${L', M', S'}$$ in HLG space. numeric or ndarray
Notes
Domain Scale - Reference Scale - 1
F_D [0, 1] [0, 1]
Range Scale - Reference Scale - 1
E_p [0, 1] [0, 1]
References
Examples
>>> eotf_reverse_BT2100_HLG(6.476039825649814) # doctest: +ELLIPSIS
0.2121320... | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.49905580282211304, "perplexity": 21606.435467267464}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-43/segments/1634323588257.34/warc/CC-MAIN-20211028034828-20211028064828-00124.warc.gz"} |
https://ask.sagemath.org/question/43946/desolve-initial-condition-involving-e-gives-strange-answer/ | # desolve initial condition involving e gives strange answer edit
I'm trying to do some basic differential equations in Sage. When I run the following:
var('t')
y = function('y')(t)
de1 = t^3*diff(y, t) + 4*t^2*y == e^(t^2)
desolve(de1, y, ics = [1,e])
The output is
1/2*(e^(t^2) + y(t))/t^4
My expectation is that there shouldn't by any y(t) term in the output. If I make a seemingly meaningless tweak to my initial conditions:
desolve(de1, y, ics = [1,e*1])
I get the expected output of
1/2*(e + e^(t^2))/t^4
If I change the initial conditions to [1, e/2], I again get the output I expect. I haven't been able to reproduce this issue with any other example. Maybe the issue just comes in converting Sage's version of e into Maxima? Does anyone know what is going on here?
edit retag close merge delete
Sort by » oldest newest most voted
Indeed, a raw e leads to a symbolic constant, while e*1 leads to a symbolic expression:
sage: type(e)
<type 'sage.symbolic.constants_c.E'>
sage: type(e*1)
<type 'sage.symbolic.expression.Expression'>
Thanks for reporting, this is now trac ticket 26490.
more
Looking at the source of desolve the difference is in how the variable tempic is set, namely the offending expression is (dvar==ics[1])._maxima_():
sage: y == e
e == y(t)
versus
sage: y == 1*e
y(t) == e
So it seems that Sage cannot be trusted to preserve the ordering LHS = RHS of an equation. This is definitely a bug which should be reported.
more
1
This is very weird, only the constant e reverses the equalities:
sage: var('x')
x
sage: x == sage.symbolic.constants.pi
x == pi
sage: x == sage.symbolic.constants.e
e == x
sage: x == sage.symbolic.constants.catalan
x == catalan
sage: x == sage.symbolic.constants.euler_gamma
x == euler_gamma
sage: x == sage.symbolic.constants.I
x == I
Looking at the source code, e is handled by the dedicated src/sage/symbolic/constants_c.pyx.
( 2018-10-15 04:33:47 -0500 )edit
Nice ink bucket...
( 2018-10-15 06:57:01 -0500 )edit
1
I created trac ticket 26492 for this larger issue.
( 2018-10-15 08:14:03 -0500 )edit | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.15509653091430664, "perplexity": 6869.723300312271}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-16/segments/1585370499280.44/warc/CC-MAIN-20200331003537-20200331033537-00164.warc.gz"} |
https://fgiesen.wordpress.com/2013/05/13/trig-identities-from-complex/ | There’s tons of useful trig identities. You could spend the time to learn them by heart, or just look them up on Wikipedia when necessary. But I’ve always had problems remembering where the signs and such go when trying to memorize this directly. At least for me, what worked way better is this: spend a few hours familiarizing yourself with complex numbers if you haven’t done so already; after that, most identities that you need in practice are easy to derive from Euler’s formula:
$e^{ix} = \exp(ix) = \cos(x) + i \sin(x)$
Let’s do the basic addition formulas first. Euler’s formula gives:
$\cos(x+y) + i \sin(x+y) = \exp(i(x+y)) = \exp(ix) \exp(iy)$
and once we apply the identity again we get:
$(\cos(x) + i \sin(x)) (\cos(y) + i \sin(y))$
multiplying out:
$(\cos(x) \cos(y) - \sin(x) \sin(y)) + i (\sin(x) \cos(y) + \cos(x) \sin(y))$
The terms in parentheses are all real numbers; equating them with our original expression yields the result
$\cos(x+y) = \cos(x) \cos(y) - \sin(x) \sin(y)$
$\sin(x+y) = \sin(x) \cos(y) + \cos(x) \sin(y)$
Both addition formulas for the price of one. (In fact, this exploits that the addition formulas for trigonometric functions and the addition formula for exponents are really the same thing). The main point being that if you know complex multiplication, you never have to remember what the grouping of factors and the signs are, something I used to have trouble remembering.
Plugging in x=y into the above also immediately gives the double-angle formulas:
$\cos(2x) = \cos(x)^2 - \sin(x)^2$
$\sin(2x) = 2 \sin(x) \cos(x)$
so if you know the addition formulas there’s really no reason to learn these separately.
Then there’s the well-known
$\cos(x)^2 + \sin(x)^2 = 1$
but it’s really just the Pythagorean theorem in disguise (since cos(x) and sin(x) are the side lengths of a right-angled triangle). So not really a new formula either!
Moving either the cosine or sine terms to the right-hand side gives the two immensely useful equations:
$\cos(x)^2 = 1 - \sin(x)^2$
$\sin(x)^2 = 1 - \cos(x)^2$
In particular, that second one is perfect if you need the sine squared of an angle that you only have the cosine of (usually because you’ve determined it using a dot product). Judicious application of these two tends to be a great way to simplify superfluous math in shaders (and elsewhere), one of my pet peeves.
For practice, let’s apply these two identities to the cosine double-angle formula:
$\cos(2x) = \cos(x)^2 - \sin(x)^2 = 2 \cos(x)^2 - 1 \Leftrightarrow cos(x)^2 = (cos(2x) + 1) / 2$
$\cos(2x) = \cos(x)^2 - \sin(x)^2 = 1 - 2 \sin(x)^2 \Leftrightarrow sin(x)^2 = (1 - cos(2x)) / 2$
why, it’s the half-angle formulas! Fancy meeting you here!
Can we do something with the sine double-angle formula too? Well, it’s not too fancy, but we can get this:
$\sin(2x) = 2 \sin(x) \cos(x) \Leftrightarrow \sin(x) \cos(x) = \sin(2x) / 2$
Now, let’s go back to the original addition formulas and let’s see what happens when we plug in negative values for y. Using $\sin(-x) = -\sin(x)$ and $\cos(-x) = \cos(x)$, we get:
$\cos(x-y) = \cos(x) \cos(y) + \sin(x) \sin(y)$
$\sin(x-y) = \sin(x) \cos(y) - \cos(x) \sin(y)$
Hey look, flipped signs! This means that we can now add these to (or subtract them from) the original formulas to get even more identities!
$\cos(x+y) + \cos(x-y) = 2 \cos(x) \cos(y)$
$\cos(x-y) - \cos(x+y) = 2 \sin(x) \sin(y)$
$\sin(x+y) + \sin(x-y) = 2 \sin(x) \cos(y)$
$\sin(x+y) - \sin(x-y) = 2 \cos(x) \sin(y)$
It’s the product-to-sum identities this time. I got one more! We’ve deliberately flipped signs and then added/subtracted the addition formulas to get the above set. What if we do the same trick in reverse to get rid of those x+y and x-y terms? Let’s set $x = (a + b)/2$ and $y = (b - a)/2$ and plug that into the identities above and we get:
$\cos(b) + \cos(a) = 2 \cos((a+b)/2) \cos((b-a)/2)$
$\cos(a) - \cos(b) = 2 \sin((a + b)/2) \sin((b - a)/2)$
$\sin(b) + \sin(a) = 2 \sin((a + b)/2) \cos((b - a)/2)$
Ta-dah, it’s the sum-to-product identities. Now, admittedly, we’ve taken quite a few steps to get here, and looking these up when you need them is going to be faster than walking through the derivation (if you ever need them in the first place – I don’t think I’ve ever used the product/sum identities in practice). But still, working these out is a good exercise, and a lot less likely to go wrong (at least for me) than memorizing lots of similar formulas. (I never can get the signs right that way)
Bonus exercise: work out general expressions for $\cos(x)^n$ and $\sin(x)^n$. Hint:
$\cos(x) = (\exp(ix) + \exp(-ix))/2$
$\sin(x) = (\exp(ix) - \exp(-ix))/2i$.
And I think that’s enough for now. (At some later point, I might do an extra post about one of the sneakier trig techniques: the Weierstrass substitution).
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http://logical.ai/polyknot/org/celtic.html | # Polyhedra in Knots
Celtic knots, or interlace, are a beautiful, ancient art form with interesting symmetries and topological properties:
It turns out that you can follow a recipe to turn any planar graph into its corresponding knotwork, or vice-versa. (You can follow this recipe, the Mercat procedure, by hand; alternatively, it's precise enough that you can implement it as a computer program.)
With this recipe in hand, I began seriously wondering what some of my favorite and familiar graphs would look like as knotwork. What about the triforce symbol? Or a square? What about a cube? Oh! And what about the rest of the platonic solids as well?
Yes, that was a good challenge. The platonic solids are fun to try to visualize (I hadn't learned how to effectively visualize yarn wrapping around 3D shapes, so I had to try several ways of drawing them in two-dimensional flatland; see below.). After much trial and error, I got the following glorious series of pictures:
tetrahedron
cube
octahedron
dodecahedron
icosahedron
As you can see here,
1. Each knotwork consists of interlocked circles (3 for the tetrahedron; 4 for the cube and octahedron; 6 for the dodecahedron and icosahedron).
2. Corresponding pairs of dual shapes have the same number of circles (cube-octahedron, dodecahedron-icosahedron). They vary based on how the circles are arranged; e.g. whether there's a central circle.
3. Each knotwork has various symmetries including rotational and reflective, as well as the over-under pattern of string crossings.
4. The overlapping circles create regions with recognizable shapes. For example, the icosahedron's knotwork is made up of five-sided and three-sided regions (with a pentagon in the middle). Its dual, the dodecahedron, is made of the same shapes, but with a triangle in the middle. You can see these shapes more clearly when the regions are colored in a checkerboard pattern (see below). The cube and octahedron include four-sided regions.
5. There are other patterns if you look—for example, how many stars can you spot in the icosahedron and dodecahedron knotwork below?
tetrahedron cube octahedron dodecahedron icosahedron
Mathematical remark: To count the number of threads, you can use the formula: $$|T(-1,-1)| = 2^{c-1}$$ where T is the Tutte polynomial of the planar graph, and c is the number of threads. Incidentally, because the dual of a graph has the same Tutte polynomial with x and y exchanged, this implies a full generalization of the result we discovered here: every graph has the same number of knotwork strands as its dual.
Mathematical remark: As shown in the checkerboard-shaded pictures, the knotwork for each polyhedron divides space into two kinds of shape, e.g. triangles and pentagons. The two shapes are apparently directly related to the Schlaffi symbol for the polyhedron—that is, the shape of each face, and the number of faces meeting at each vertex.
## 1 How I generated these
To generate this knotwork, you start with one of the figures such as the icosahedron:
You want to stretch it so that you can draw it on a flat piece of paper without any of the lines crossing. In this particular case, you can take the back-face triangle and pull all of its vertices out from behind the icosahedron. The result is a planar graph: .
Now we can apply the Mercat procedure to draw threads that cross in pairs at the midpoint of every edge in the graph. The result is a bit messy, but if you color in each of the threads in a different color, you see that the knotwork is made up of simple (non-self-intersecting) closed loops.
To straighten out the wobby loops into perfect circles, all I did was arrange some colored circles by trial and error into positions that had the same symmetry as the knotwork. I then checked whether my circles had the same crossings as the knotwork, and made the same shaped regions (triangles, pentagons). The result is as you've seen, and you can repeat this process for any of the other polyhedra:
What follows is a gallery of my handwritten drawings on the subject, because I think they look interesting, and might be enjoyable or useful to see:
It was a bit of a struggle for the imagination at first, chasing threads around the corners of polyhedra and visualizing where they would end up. The problem was only partially solved by unfolding the polyhedra, because then threads that vanished off one side of the figure would appear on another in a seemingly different orientation. Eventually, I discovered that I could represent the edges of the graph and their "shares vertex" relationships as graphs themselves. These graphs were all planar, and simplified the Mercat procedure terrifically.
I chose polyhedra at random, discovering a pattern: all of their knotwork seemed to consist solely of overlapping circles:
tetrahedron: 3 circles
cube: 4 circles
octahedron: ___
dodecahedron: 6 circles
icosahedron: __
What's the pattern? Imagine my surprise when I drew out the knotwork for the rest and found out that the pattern was:
tetrahedron: 3 circles
cube: 4 circles
octahedron: 4 circles (!)
dodecahedron: 6 circles
icosahedron: 6 circles (!)
The knotwork for the cube and octahedron was identical, as was the knotwork for the dodecahedron and the icosahedron! In retrospect, these relationships are less mysterious in light of dual polyhedra: the cube and octahedron are dual pairs, as are the dodecahedron and the icosahedron. This means, in part, that if you draw lines to connect the faces of one shape, you get the dual shape. (The tetrahedron, on its own, is self-dual.)
(I wonder if we can state the proof that there are only five platonic solids in terms of the number of circles that a hypothetical platonoic solid would have in its knotwork, and how those circles would overlap?)
Tetrahedron. Here, I use my abstract method to draw the knotwork for the tetrahedron. Each node in the graph represents a pair of faces (an edge of the polyhedron), and each edge in the graph represents a shared-vertex relationship. The edges are oriented at various multiples of 45 degrees, as they must be lined up in the final knotwork.
Cube. The cube was the first shape I attempted, actually. You can see in the bottom left, I attempted to visualize the movements of the threads in 3D. When I looked for a simpler method, I tried unfolding the cube and having the threads "wrap around" as needed (upper-left cross-like figure). The apparent orientation changes (in the 2D unfolding) made this method a bit difficult. On the right right, I begin to wonder whether I can represent the knotwork as overlapping circles.
Cube #2. Following my initial hunch about overlapping circles…
…I eventually succeed at drawing the cube's knotwork (four interlocking circles in upper-right), using the abstract method I developed on the simpler tetrahedron (note some stray tetrahedron attempts around the bottom-left periphery). I rather like the teardrop-shaped aesthetic of the middle incarnation, but the four interlocking circles are more symmetric.
Dodecahedron. The dodecahedron was a real challenge, moving from the planar graph shown here (with all its intricate thread crossings, two per edge)… … to the final, stunning result:
Icosahedron I initially attempted the icosahedron's knotwork using the "unfolding" method with its bewildering wrapped threads:
Eventually, I discovered the abstract method (and the duality principle), and the rest is exactly the same as for the dodecahedron, shown here again (notice the star shape in the middle of the two figures here? They're overflowing with star-shaped intersections of threads if you look!):
Created: 2021-01-06 Wed 00:19
Emacs 27.1 (Org mode 8.3beta)
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https://www.physicsforums.com/threads/magnetic-field-of-wire-on-rectangular-loop.160744/ | # Magnetic Field of wire on rectangular loop
1. Mar 14, 2007
### BrettB
1. The problem statement, all variables and given/known data
I have attached a diagram. In case you can't view it, it shows an infintely long wire $I_i = 5.00$ A on the positive y direction. 0.100 m to the right, there is a rectangular loop of dimensions 0.150 m x 0.450 m, the long side is parallel to the infinitely long wire to its left. The current is $I_2 = 10.0$ A and also flowing up (in the position closest to the infinitely long wire).
a) Find the magnitude and direction of the net force exerted on the loop by the magnetic field created by the wire.
b) Find the force on the top, horizontal segment of the loop. Calculate this three ways: net force, average force, and the force on the midpoint.
2. Relevant equations
Bio-Savaart equation.
3. The attempt at a solution
I didn't have any trouble with (a). The force on the top and bottom horizontal segments just cancel, so I can disregard them. The rest is pretty simple.
Part (b) is giving me lots of trouble. I am not 100% sure I am calculating the magnetic force of the infinitely long wire on the horizontal part of the loop properly, and I really am not certain how to handle the vertical segments of the loop. These are not infinite, so there must be some error introduced in this case, but I have no idea how to approximate it. Would the errors just cancel, and the net force of these also be zero?
Here is what I have done so far, I hope this is ok:
For the net force:
$$B = \int_{0.100}^{0.250} \frac{(5.00)(10.0)(\mu_0)}{2\pi x}\,dx = 1.00268(\ln(x))_{0.100}^{0.250} = 9.19 \times 10^{-6}$$
For the average force, I just used the mean value theorem, and multiplied the above by 1/(0.250-0.100) to get 6.12 x 10^{-15}.
To calculate the force on the midpoint, I first calculate the force from the vertical wire:
$$\frac{\mu_0(5.00)}{2\pi(0.100+\frac{0.150}{2})}\hat{i} = 5.73\times 10^{-6}\hat{i}$$
Then the other force:
$$\frac{\mu_0(10.0)}{2\pi(0.100 + \frac{0.150}{2})}\hat{j} = 1.15 \times 10^{-5}\hat{j}$$
Since these are perpendicular, I got the rest as
$$\sqrt{(5.73\times 10^{-6})^2 + (1.15 \times 10^{-5})^2} = 1.28 \times 10^{-5}$$
Intuitively, I would have expected closer values with all these results, so I am surprised they are so far apart, and that makes me question my work.
Thanks,
Brett
#### Attached Files:
• ###### magnetism.bmp
File size:
14.6 KB
Views:
357
Last edited: Mar 14, 2007
2. Mar 14, 2007
### BrettB
Wow, nobody? Well, I fixed a couple of typos, but I am no closer to certainty. If I've violated some rule, I'm sorry. I'm new here :-) But I would really appreciate some help.
Thanks,
Brett
3. Mar 15, 2007
### hage567
You haven't done anything wrong, I think you've done a good job of presenting your problem. I just honestly am not sure I can help!
4. Mar 15, 2007
### Staff: Mentor
I'm a bit puzzled by this question. I would interpret it as: Calculate the force exerted on the top horizontal segment by the magnetic field created by the wire in three different ways and compare.
For the "net force" you integrated to find the actual force from the wire on the segment. OK. (Don't really know what "net force" means in this context.)
By "average force", I would have calculated the force per unit length at each end of the segment, averaged them, then multiplied by the length of the segment.
For "force at midpoint", I would have calculated the force per unit length at the midpoint, then multiplied by the length of the segment.
Grasping at straws here, since the question isn't clear to me.
5. Mar 15, 2007
### hage567
I can point out a couple of things for you to double check. I think you are getting B and F mixed up when you are using the equations. Not sure, just a thought.
6. Mar 15, 2007
### BrettB
Thank you both, VERY much. Hage567, yes, I was calculating the completely wrong thing, thank you.
I think I still must be doing something wrong, since I get answers that are very different, or I don't understand why they should be this different. I'm also wondering why using the mean-value theorem wouldn't be the right way to calculate the "average" value in this case.
Using Doc Al's suggestion to compute the average, I get for the left end of the horiztonal wire:
$$\frac{(1.26 \times 10^{-6})(5.00)(10.0)}{2\pi (0.100)} = 1.00268 \times 10^{-4}$$
For the right end:
$$\frac{(1.26 \times 10^{-6})(5.00)(10.0)}{2\pi (0.250)} = 4.01070 \times 10^{-5}$$
These values would be the force per meter, I believe.
Taking the average, and multiplying by the length of the wire, I get 1.05 x 10^-5.
For the force/m at the midpoint:
$$\frac{(1.26\times 10^{-6})(5.00)(10.0)}{2\pi(0.100 + \frac{0.150}{2})} = 5.72958 \times 10^{-5}$$
and multiplying by 0.150 (the length of the wire), I get 8.59 x 10^-6, which is closer to the total force. But not very.
Is this the right way to go about it? The only conclusion I can come to from this is that, since the force doesn't vary linearly (if you look at the integral, it is a logarithmic function), using these other ways is not the right way to estimate the force on a perpendicular wire.
Thanks!
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https://examportal.xyz/number-system-mcq-question/ | Stay Update with us
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# Number System: Quantitative Aptitude MCQ Question with Details Solution
## Number System MCQ Question
The number system or the numeral system is the system of naming or representing numbers. There are various types of number systems in Mathematics like integer, prime, binary, decimal, etc. In this chapter Examportal Discussed All type Number System MCQ Question with details Explanation.
Q1. Find the remainder of $\frac{9^{99}}{8}$
(a) 1
(b) 2
(c) 3
(d) 5
Answer: (a)Explanation: $\frac{9^{99}}{8}=\frac{\left( 8+1 \right) ^{99}}{8}\Rightarrow \mathrm{Remainder} =1$Rules: If $\frac{\left( \mathrm{a}+1 \right) ^n}{a}$ then remainder will always be 1, whether n is even or odd.
Q2. Minimum difference between x and y such that 1x 71y 61 is exactly divisible by 11 is,
(a) 2
(b) 3
(c) 1
(d) 0
Answer: (a)Explanation: As 1x 71y 61 is exactly divisible by 11. (1 + 7 + y + 1) – (x + 1 + 6) = 0 or multiple of 11 for minimum difference9 + y – 7 – x = 0⇒ x – y = 2
Q3. The four integers next lower than 81, and the four next higher than 81, are written down and added together, this sum is divisible by,
(a) 7
(b) 9
(c) 11
(d) 13
Answer: (b)Four integers next lower than 81 is 80, 79, 78, 77 four integers next higher than 81 is 82, 83, 84, 85Sum = (80 + 82) + (79 + 83) + (78 + 84) + (77+ 85) = 2 ×81 + 2 ×81 + 2 ×81 + 2 ×81 = 8 × 81Sum is divisible by 9 as 81 is divisible by 9
Q4. How many numbers, between 1 and 300 are divisible by 3 and 5 together?
(a) 16
(b) 18
(c) 20
(d) 100
Answer: (c)Explanation: LCM of 3 and 5 = 15Number divisible by 15 are 15, 30, 45 …..300.Let total numbers are n300 = 15 + (n – 1) × 15⇒ 300 = 15 + 15n –15⇒ n = 20
Q5. What is the remainder when 1! + 2! + 3! + …… + 100! Is divided by 7 ?
(a) 0
(b) 5
(c) 6
(d) 3
Answer: (b)Explanation: 7! + 8! + 9! + 10! + ……. + 100 = 7.6! + 8.7.6! + 9.8.7.6! + ……. + 100! is completely divisible by 7 as each of the terms contain at least one 7 in it.Now, 1! + 2! + 3! + 4! + 5! + 6! = 1 + 2 + 6 + 24 + 120 + 720 = 873which leaves a remainder of 5 when divided by 7.
Q6. How many numbers, lying between 1 and 500, are divisible by 13?
(a) 40
(b) 38
(c) 41
(d) 46
Answer: (b)Explanation: Number divisible by 13, 26, 39, …. 494Let n be the total numbers494 = 13 + (n – 1) × 13⇒ 13n = 494⇒ n = 38
Q7. Two different numbers when divided by the same divisor, left remainder 11 and 21 respectively, and when their sum was divided by the same divisor, remainder was 4. What is the divisor?
(a) 36
(b) 28
(c) 14
(d) 9
Answer: (b)Explanation: Divisor = [Sum of remainders] – [ Remainder when sum is divided]= 11 + 21 – 4 = 28
Q8. If ‘n’ is a natural number then the greatest integer less than that or equal to $\left( 2+\sqrt{3} \right) ^{\mathrm{n}}$ is
(a) odd
(b) even
(c) even when ‘n’ is even and odd when ‘n’ is odd
(d) even when ‘n’ is odd and odd when n is even
Answer: (a)Explanation: putting n = 1, we get $\left( 2+1.\sqrt{3} \right)$ = whose integral part is 3putting n= 2, we get $\left( 2+\sqrt{3} \right) ^2=4+3+4\sqrt{3}$ ; whose integral part is 11 which is again an odd numberNow, through the options it can be judged that the greatest integer must always be an odd number.
Q9. A number when divided by a divisor, left remainder 23. When twice of the number was divided by the same divisor, remainder was 11. Find the divisor.
(a) 12
(b) 34
(c) 35
Answer: (d)Explanation: Let number be N.Then, N = Divisor × Q1 + 232N = Divisor × Q2 + 11,where Q1 and Q2 are quotients respectively.Here, we have two equations and 3 variables. There equations cannot be solved.
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### March 2021 The Hindu Analysis PDF
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https://chemistry.stackexchange.com/questions/103349/sn-hno3-when-will-the-metastannic-acid-h2sno3-appear | # Sn + HNO3: When will the metastannic acid H2SnO3 appear?
I am dissolving tin in nitric acid. What reactions will take place depending on the conentration of $$\rm{HNO}_3$$ and temperature?
Particularly, I am interested when the metastannic acid $$\rm{H_2SnO_3}$$ is likely to be produced, according to
$$\rm{Sn + 4 HNO_3 → H_2O + H_2SnO_3 + 4 NO_2}$$
P. S. References to books or scientific articles are welcome.
[...]Gelatinous, precipitated β-stannic acid has the empirical composition $$\ce{SnO2.4H2O}$$, when air-dried $$\ce{SnO2.2H2O}$$, and when dried in a vacuum, $$\ce{SnO2.H2O}$$; [...] | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 6, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.45047566294670105, "perplexity": 7644.782973331337}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-05/segments/1642320300244.42/warc/CC-MAIN-20220116210734-20220117000734-00356.warc.gz"} |
https://repository.lboro.ac.uk/articles/journal_contribution/Temporal_analysis_of_a_microkernel/9402617/1 | Hussak_Temporal_analysis_of_a_microkernel.pdf (454.78 kB)
# Temporal analysis of a microkernel
journal contribution
posted on 04.02.2009, 12:40
Temporal logic techniques have been proposed as a way of achieving a very natural transition from informal requirements to a formal specification of the requirements. The paper presents a case study of a real-life system developed using such techniques. Both a top-level specification and implementation semantics are given in temporal logic. In particular, the progression from statements in English to temporal logic is highlighted. A correctness proof that the implemented system satisfies the specification has been produced.
• Science
## Department
• Computer Science
## Citation
HUSSAK, W., 1995. Temporal analysis of a microkernel. Software Engineering Journal, 10 (1), pp. 21-26
## Version
VoR (Version of Record)
1995
## Notes
This article was published online in the journal, Software Engineering Journal [© IEEE]. It is also available at: http://ieeexplore.ieee.org/ Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
0268-6961
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http://radar.oreilly.com/2012/08/shrinking-and-stretching-the-boundaries-of-markup.html | Shrinking and stretching the boundaries of markup
Doing less and more than XML.
It’s easy to forget that XML started out as a simplification process, trimming SGML into a more manageable and more parseable specification. Once XML reached a broad audience, of course, new specifications piled on top of it to create an ever-growing stack.
That stack, despite solving many problems, brings two new issues: it’s bulky, and there are a lot of problems that even that bulk can’t solve.
Two proposals at last week’s Balisage markup conference examined different approaches to working outside of the stack, though both were clearly capable of working with that stack when appropriate.
Shrinking to MicroXML
John Cowan presented on MicroXML, a project that started with a blog post from James Clark and has since grown to be a W3C Community Group. Cowan has been maintaining the Editor’s Draft of MicroXML, as well as creating a parser library for it, MicroLark. Uche Ogbuji, also chair of the W3C Community Group, has written a series of articles (1 2) about it.
Cowan’s talk was a broad overview of practical progress on a subject that had once been controversial. Even in the early days of XML 1.0, there were plenty of people who thought that it was still too large a subset of SGML, and the Common XML I edited was one effort to describe how practitioners typically used less than the XML made available. The subset discussion has come up repeatedly, with a proposal from Tim Bray and others over the years. In an age where JSON has replaced many data-centric uses of XML, there is less pressure to emphasize programming needs (data types, for example), but still demand for simplifying to a cleaner document model.
MicroXML is both a syntax — compatible with XML 1.0 — and a model, kept as absolutely simple as possible. In many ways, they’re trying to make syntax decisions based on their impact on the model.
Ideally, Cowan said, the model would just be element nodes (with attribute maps) containing other element nodes and content. That focus on a clean model means, for example, that while you can declare XML namespaces in MicroXML, the namespace declarations are just attributes. The model doesn’t reflect namespace URIs, and applications have to do that processing. Similarly, whitespace handling is simplified, and attributes become a simple unordered map of key names to values. The syntax allows comments, but they are discarded in the model. Processing instructions remain a question, because they would complicate the model substantially, but the XML declaration and CDATA sections would go. Empty element tags are in, for now …
Some of the pieces that raised controversy with questions were the current proposal to limit element and attribute names to the ASCII character set, and the demise of processing instructions. I mostly heard cheers for the end of draconian error handling, though there were memories of the bug compatibility wars of an earlier age reminding the audience that it could in fact be worse, or weirder.
There may be, as Cowan noted “no consensus on a single conversion path” to or from JSON, but MicroXML takes some steps in that direction, suggesting that JSONML should be able to support round-tripping of the MicroXML model, and JSONx could work for JSON to XML.
While I suspect that MicroXML has a bright future ahead of it in the document space, it seems unlikely to take much territory back from JSON in the data space. MicroXML doesn’t seem to be aiming at JSON at all, however.
Overlapping information and hierarchical tools
Very few programmers want to think about overlapping data structures. In most computing cases — bad pointers? — overlapping data structures are a complex mess. However, they’re extremely common in human communications. LMNL (Layered Markup and Annotation Language), itself a decade-long conversation that has suffered badly from decaying links, has always been an outsider in the normally hierarchical markup conversation. There may be conflicts between XML trees and JSON maps, but both of those become uncomfortable when they have to represent an overlapped structure.
Wendell Piez examined the challenges of processing overlapping markup — LMNL — with tools that expect XML’s neat hierarchies. Obviously, feeding this
[excerpt [source [date}1915{][title}The Housekeeper{]] [author [name}Robert Frost{] [dates}1874-1963{]] } [s}[l [n}144{n]}He manages to keep the upper hand{l] [l [n}145{n]}On his own farm.{s] [s}He's boss.{s] [s}But as to hens:{l] [l [n}146{n]}We fence our flowers in and the hens range.{l]{s] {excerpt]
into an XML parser would just produce error messages, even if those tags were angle brackets. Piez compiles that into XML, which represents the content separately from the specified ranges. It is, of course, not close to pretty, but it is processable. At the show, he demonstrated using this to create an annotated HTML format as well as a format that handles overlap gracefully: graphics, using SVG (or here as a PNG if your browser doesn’t like SVG).
Should you be paying attention to LMNL? If your main information concerns fit in neat hierarchies or clean boxes, probably not. If your challenges include representing human conversations, or other data forms where overlap happens, you may find these components critical, even though making them work with existing toolsets is difficult.
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http://www.researchgate.net/researcher/6252912_A_Burrows | # A. Burrows
Princeton University, Princeton, New Jersey, United States
Are you A. Burrows?
## Publications (123)454.82 Total impact
• Source
##### Article: A Spitzer Search for Transits of Radial Velocity Detected Super-Earths
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ABSTRACT: Unlike hot Jupiters or other gas giants, super-Earths are expected to have a wide variety of compositions, ranging from terrestrial bodies like our own to more gaseous planets like Neptune. Observations of transiting systems, which allow us to directly measure planet masses and radii and constrain atmospheric properties, are key to understanding the compositional diversity of the planets in this mass range. Although Kepler has discovered hundreds of transiting super-Earth candidates over the past four years, the majority of these planets orbit stars that are too far away and too faint to allow for detailed atmospheric characterization and reliable mass estimates. Ground-based transit surveys focus on much brighter stars, but most lack the sensitivity to detect planets in this size range. One way to get around the difficulty of finding these smaller planets in transit is to start by choosing targets that are already known to contain super-Earth sized bodies detected using the radial velocity technique. Here we present results from a Spitzer program to observe six of the most favorable RV detected super-Earth systems, including HD 1461, HD 7924, HD 156668, HIP 57274, and GJ 876. We find no evidence for transits in any of their 4.5 micron flux light curves, and place limits on the allowed transit depths and corresponding planet radii that rule out even the most dense and iron-rich compositions for these objects. We also observed HD 97658, but the observation window was based on a possible ground-based transit detection (Henry et al. 2011) that was later ruled out; thus the window did not include the predicted time for the transit detection recently made by MOST (Dragomir et al. 2013).
The Astrophysical Journal 10/2013; 781(2). DOI:10.1088/0004-637X/781/2/103 · 6.28 Impact Factor
• ##### Article: 3.6 and 4.5 micron Full-orbit Phase Curves of the Hot-Saturn HD 149026b
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ABSTRACT: The extrasolar planet HD 149026b, discovered in 2005, was among the first to be observed to transit its host star as seen from earth. Since its discovery, several observational campaigns have targeted HD 149026b in wavelengths from the visible to the infrared to obtain both transmission and emission broadband measurements. These measurements have revealed that HD 149026b has a radius similar to that of Saturn, but a density more akin to that of Neptune. This suggest that HD 149026b is enriched in heavy elements much like the ice giants of our solar system. Half-orbit phase curve observations of HD 149026b at 8 microns (Knutson et al., 2009) suggest that the day-to-night transport of heat is fairly efficient for this planet. However, further phase curve observations at other infrared wavelengths are needed to better constrain the planet’s energy budget, location of hot and cold regions, as well as possible chemical gradients in the planet’s atmosphere. Here we present an analysis of the full-orbit phase-curves of HD 149026b at 3.6 and 4.5 microns. We discuss the implications of the combined phase-curve information at 3.6, 4.5, and 8 microns and compare the observations to theoretical phase curves derived from three-dimensional atmospheric models that consider a range of possible heavy element enrichments in HD 149026b’s atmosphere.
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##### Article: Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504
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ABSTRACT: Several exoplanets have recently been imaged at wide separations of >10 AU from their parent stars. These span a limited range of ages (<50 Myr) and atmospheric properties, with temperatures of 800--1800 K and very red colors (J - H > 0.5 mag), implying thick cloud covers. Furthermore, substantial model uncertainties exist at these young ages due to the unknown initial conditions at formation, which can lead to an order of magnitude of uncertainty in the modeled planet mass. Here, we report the direct imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS survey. The system is older than all other known directly-imaged planets; as a result, its estimated mass remains in the planetary regime independent of uncertainties related to choices of initial conditions in the exoplanet modeling. Using the most common exoplanet cooling model, and given the system age of 160 [+350, -60] Myr, GJ 504 b has an estimated mass of 4 [+4.5, -1.0] Jupiter masses, among the lowest of directly imaged planets. Its projected separation of 43.5 AU exceeds the typical outer boundary of ~30 AU predicted for the core accretion mechanism. GJ 504 b is also significantly cooler (510 [+30, -20] K) and has a bluer color (J-H = -0.23 mag) than previously imaged exoplanets, suggesting a largely cloud-free atmosphere accessible to spectroscopic characterization. Thus, it has the potential of providing novel insights into the origins of giant planets, as well as their atmospheric properties.
The Astrophysical Journal 07/2013; 774(1). DOI:10.1088/0004-637X/774/1/11 · 6.28 Impact Factor
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##### Article: CASTRO: A New Compressible Astrophysical Solver. III. Multigroup Radiation Hydrodynamics
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ABSTRACT: We present a formulation for multigroup radiation hydrodynamics that is correct to order \$O(v/c)\$ using the comoving-frame approach and the flux-limited diffusion approximation. We describe a numerical algorithm for solving the system, implemented in the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically-rectangular variable-sized grids with simultaneous refinement in both space and time. In our multigroup radiation solver, the system is split into three parts, one part that couples the radiation and fluid in a hyperbolic subsystem, another part that advects the radiation in frequency space, and a parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem and the frequency space advection are solved explicitly with high-order Godunov schemes, whereas the parabolic part is solved implicitly with a first-order backward Euler method. Our multigroup radiation solver works for both neutrino and photon radiation.
The Astrophysical Journal Supplement Series 07/2012; 204(1). DOI:10.1088/0067-0049/204/1/7 · 14.14 Impact Factor
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##### Article: Correlated Gravitational Wave and Neutrino Signals from General-Relativistic Rapidly Rotating Iron Core Collapse
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ABSTRACT: We present results from a new set of 3D general-relativistic hydrodynamic simulations of rotating iron core collapse. We assume octant symmetry and focus on axisymmetric collapse, bounce, the early postbounce evolution, and the associated gravitational wave (GW) and neutrino signals. We employ a finite-temperature nuclear equation of state, parameterized electron capture in the collapse phase, and a multi-species neutrino leakage scheme after bounce. The latter captures the important effects of deleptonization, neutrino cooling and heating and enables approximate predictions for the neutrino luminosities in the early evolution after core bounce. We consider 12-solar-mass and 40-solar-mass presupernova models and systematically study the effects of (i) rotation, (ii) progenitor structure, and (iii) postbounce neutrino leakage on dynamics, GW, and, neutrino signals. We demonstrate, that the GW signal of rapidly rotating core collapse is practically independent of progenitor mass and precollapse structure. Moreover, we show that the effects of neutrino leakage on the GW signal are strong only in nonrotating or slowly rotating models in which GW emission is not dominated by inner core dynamics. In rapidly rotating cores, core bounce of the centrifugally-deformed inner core excites the fundamental quadrupole pulsation mode of the nascent protoneutron star. The ensuing global oscillations (f~700-800 Hz) lead to pronounced oscillations in the GW signal and correlated strong variations in the rising luminosities of antineutrino and heavy-lepton neutrinos. We find these features in cores that collapse to protoneutron stars with spin periods <~ 2.5 ms and rotational energies sufficient to drive hyper-energetic core-collapse supernova explosions. Hence, joint GW + neutrino observations of a core collapse event could deliver strong evidence for or against rapid core rotation. [abridged]
Physical review D: Particles and fields 04/2012; 86(2). DOI:10.1103/PhysRevD.86.024026 · 4.86 Impact Factor
• ##### Article: New Imaging of the beta Pictoris Planet and Debris Disk
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ABSTRACT: We present new direct imaging results on the planet and debris disk surrounding 12 Myr-old beta Pictoris. Using an updated version of our reduction pipeline, we extract a new detection of beta Pic b from 2008 VLT/NaCo data at a sub-Jupiter projected separation ( 4 AU), about 1.5 lambda/D. We also obtain a high signal-to-noise rereduction of L' data taken in 2009 December. Intriguingly, the planet's orbit is aligned with the major axis of the outer disk (Omega 31 deg) but is probably misaligned with the warp/inclined disk at 80 AU, often cited as a signpost for the planet's existence. We also present new images of the beta Pic debris disk and discuss any evidence for a 2nd massive gas giant planet in the system.
• ##### Article: Grism Spectroscopy Of The Eclipse Of Corot-2b At 1.1-1.7μM
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ABSTRACT: Here we present HST eclipse spectroscopy spanning 1.1 to 1.7 μm of the CoRoT-2 system using the G141 grism on WFC3. These near-infrared data serve to complement the pre-existing and already-published optical CoRoT data and warm Spitzer infrared observations. CoRoT-2b, the sole planet known in the system, is a member of the Very Hot Jupiter (VHJ) class of exoplanets, and the secondary eclipse was measured with three separate HST visits. We find the albedo of CoRoT-2b upon comparison of optical data, which comprises both thermal and reflected spectral components, and the thermal spectrum as constrained by the Spitzer and WFC3 infrared data. Analysis of the data required characterization of the persistence on the WFC3 detector as it manifests for these observations; it is not insignificant. After compiling results of flux patterns for the majority of the seventeen exoplanets studied in this HST program, we find the extent of the persistence, a linear, additive effect that is strongly dependent upon stimulating flux and time of/since exposure, and subtract it to leave only the true flux received from the CoRoT-2 system in and out of secondary eclipse.
• ##### Article: Infrared Spectroscopy of the Transiting Exoplanets HD189733b and XO-1 Using Hubble WFC3 in Spatial Scan Mode
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ABSTRACT: Infrared transmission spectroscopy of the exoplanets HD189733b and XO-1 has been previously reported by Swain et al. and Tinetti et al. based on observations using the NICMOS instrument on the Hubble Space Telescope. The robustness of those results has been questioned, because derivation of the exoplanetary spectrum required decorrelating strong instrumental systematic effects in the NICMOS data. We here discuss results from HST/WFC3 grism 1.1-1.7 micron spectroscopy of these planets during transit. WFC3 instrumental signatures are smaller in both amplitude and complexity as compared to NICMOS. Moreover, we use a new spatial scan mode to trail the stars perpendicular to the dispersion direction during WFC3 exposures, and this increases the efficiency of the observations and reduces persistence effects in the detector. We derive the 1.4-micron water absorption spectrum of these planets during transit, discuss implications for these exoplanetary atmospheres, and compare our results to the NICMOS spectroscopy.
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##### Article: The Hydrodynamic Origin of Neutron Star Kicks
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ABSTRACT: We present results from a suite of axisymmetric, core-collapse supernova simulations in which hydrodynamic recoil from an asymmetric explosion produces large proto-neutron star (PNS) velocities. We use the adaptive-mesh refinement code CASTRO to self-consistently follow core-collapse, the formation of the PNS and its subsequent acceleration. We obtain recoil velocities of up to 620 km/s at ~1 s after bounce. These velocities are consistent with the observed distribution of pulsar kicks and with PNS velocities obtained in other theoretical calculations. Our PNSs are still accelerating at several hundred km/s at the end of our calculations, suggesting that even the highest velocity pulsars may be explained by hydrodynamic recoil in generic, core-collapse supernovae.
Monthly Notices of the Royal Astronomical Society 12/2011; 423(2). DOI:10.1111/j.1365-2966.2012.21002.x · 5.23 Impact Factor
• ##### Article: A Warm Spitzer Survey of Atmospheric Circulation Patterns
[Hide abstract]
ABSTRACT: The atmospheres of close-in extrasolar planets experience strong, asymmetrically distributed radiative forcing that can potentially lead to dramatic variations in both temperature and composition between the day- and night-side hemispheres. However, secondary eclipse observations only tell us about the properties of the dayside atmosphere, while transmission spectroscopy probes the region around the day-night terminator. By measuring changes in the infrared emission spectra of these planets as a function of orbital phase, we can resolve thermal and compositional gradients in these atmospheres, allowing us to obtain a complete picture of their local properties. The most extensively studied planet to date, HD 189733b, appears to have a relatively modest day-night temperature gradient as seen in the 8 and 24 micron Spitzer bands, suggesting that compositional gradients in this atmosphere are likely to be minimal. We present new, full-orbit phase curves at 3.6 and 4.5 um obtained with warm Spitzer, which we use to construct improved multi-color maps and to constrain variations in the pressure-temperature profile and atmospheric composition as a function of longitude. We also present preliminary results for complementary full-orbit observations of HAT-P-7b in the same bands, and discuss an emerging pattern in which the most highly irradiated (>2000 K) planets appear to undergo a shift towards large day-night temperature gradients, perhaps due to Lorentz braking or other MHD processes.
• ##### Conference Paper: Thermal Phase Variations of WASP-12b
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ABSTRACT: The short-period planet WASP-12b is among the hottest known transiting planets. Space- and ground-based secondary eclipse depths imply that this planet has a C/O ratio greater than 1 (Madhusudhan et al. 2011), in stark contrast to the chemistry in the Solar System and the assumed chemistry of other planets. These same eclipse data put the planet's day-side effective temperature at 3000 K. This indicates a low albedo and poor recirculation of heat to the night-side, as has been found for all of the hottest transiting giant planets (Cowan & Agol 2011b). But these trends were based solely on day-side observations (eclipse depths) rather than full phase variations, which directly probe night-side temperature. The short period (1.1 day) and inflated radius (1.8 RJ) of WASP-12b has led to speculation that it may be undergoing Roche-lobe overflow (Li et al. 2010, Lai et al. 2010), and UV observations by Fossati et al. (2010) seem to support this idea. We have recently obtained thermal phase curves of this planet with Warm Spitzer (PI:Machalek; PID 70060). Our data include two eclipses, a transit, and full phase coverage at each of 3.6 and 4.5 micron. Because of the planet's high temperature and large size, this is one of the highest S/N phase curves yet obtained with Spitzer. These data (currently being analyzed) will allow us to directly measure the planet's night-side temperature and the longitudinal offset of its day-side hot-spot. Since the 3.6 and 4.5 micron bands probe different depths in the atmosphere, we will strongly constrain climate models for the hottest gas giants. The high precision transit and eclipse photometry offered by Spitzer will also allow us to search for signs of accretion in this system.
AAS/Division for Extreme Solar Systems Abstracts; 09/2011
• ##### Article: The Atmospheric Circulation of Eccentric Hot Jupiter HAT-P-2b
[Hide abstract]
ABSTRACT: The Spitzer warm mission has already greatly expanded the field of exoplanet characterization with over 3000 hours of time dedicated to exoplanet observations. Observations of eclipsing systems with Spitzer are at the heart of these advances, as they allow us to move beyond simple mass and period estimates to determine planetary radius, dayside emission, and emission variations as a function of orbital phase. The eclipsing system HAT-P-2 is of special interest because the massive Jovian sized planet in this system is on a highly eccentric orbit (e=0.5171). Because HAT-P-2b's orbit is eccentric, the planet is subject to time variable heating and probable non-synchronous rotation. Circulation patterns that we expect to develop in HAT-P-2b's atmosphere will likely vary with both planetary local time and orbital phase. Here we present an analysis of two full-orbit light curves for the HAT-P-2 system obtained at 3.6 and 4.5 microns during the first two years of the Spitzer warm mission and discuss the observational constraints imposed on the atmospheric circulation of HAT-P-2b. Additionally, three-dimensional atmospheric models that incorporate realistic radiative transfer will be presented to further elucidate possible global scale circulations patterns present in the atmosphere of HAT-P-2b. Support for this work was provided by NASA.
• ##### Article: Characterizing Hot Jupiter Atmospheres with Hubble WFC3
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ABSTRACT: We present transit and eclipse spectroscopy of Very Hot Jupiter atmospheres using the newly installed Wide Field Camera 3 (WFC3) spectrograph on the Hubble Space Telescope (HST). We include results from several hot Jupiter planets, but we focus particularly on spectra of WASP-4b in both transmission and emission, the first time this has been achieved using this instrument. These data are already in hand. Our preliminary analysis indicates they do not require substantial decorrelation against external measurements to correct for systematic errors, resulting in robust results that avoid the ambiguities in interpretation faced by earlier work with NICMOS. Recent work by Madhusudhan and Seager highlighted degeneracies in the interpretation of low-resolution Spitzer spectra of hot Jupiters. The G141 grism on WFC3 (1.1-1.7 microns) spans a 1.4 micron water feature, allowing us to constrain water vapor abundance and break this degeneracy. We measure the 1.5 micron continuum flux, which in conjunction with the Spitzer data allows us to constrain the thermal spectrum of the planet and obtain a more precise energy budget relevant to understanding WASP-4b’s abnormally large radius. This work is part of the Cycle-18 Large Program 12181, and we acknowledge support by NASA, NSF GRFP, and the HST Project.
• ##### Conference Paper: A Comparative Study of the Atmospheres of Transiting Exoplanets
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ABSTRACT: Spitzer's extended warm mission gives us the opportunity to perform comparative studies of exoplanets' atmospheres. We describe the techniques and methods involved in our recently accepted Spitzer Exploration Science Proposal (Proposal ID 80016; PI: J. Krick; 619 hours) to obtain high-precision 4.5 micron phase curves for 22 transiting hot Jupiter systems, along with observations of secondary eclipses of 7 of these systems. The principal goal of this study, which will quadruple the number of phase curve observations to date, is to map longitudinal temperature distribution of the planetary atmospheres and to assess the following questions: (1) What is the contrast between exoplanetary day- and nightside temperatures, i. e., how efficiently is the incident energy redistributed? (2) Are the weather phenomena in the exoplanetary atmospheres stable over long periods of time? (3) How do the temperature distributions on the planetary surfaces correlate with astrophysical properties of the star-planet systems? To answer these questions with our proposed Spitzer observations, we will employ a novel observing technique involving snapshot observing to reduce telescope time requirements, and PCRS peak-up to IRAC to increase the pointing accuracy and thus minimize the photometric error due to intrapixel sensitivity variation.
AAS/Division for Extreme Solar Systems Abstracts; 09/2011
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##### Article: CASTRO: A New Compressible Astrophysical Solver. II. Gray Radiation Hydrodynamics
[Hide abstract]
ABSTRACT: We describe the development of a flux-limited gray radiation solver for the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically-rectangular variable-sized grids with simultaneous refinement in both space and time. The gray radiation solver is based on a mixed-frame formulation of radiation hydrodynamics. In our approach, the system is split into two parts, one part that couples the radiation and fluid in a hyperbolic subsystem, and another parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem is solved explicitly with a high-order Godunov scheme, whereas the parabolic part is solved implicitly with a first-order backward Euler method.
The Astrophysical Journal Supplement Series 05/2011; 196(2). DOI:10.1088/0067-0049/196/2/20 · 14.14 Impact Factor
• ##### Article: Comparative Atmospheric Study of Exoplanets
[Hide abstract]
ABSTRACT: Spitzer's extended warm mission gives us the opportunity to contribute to its legacy by performing comparative science on atmospheres of extrasolar planets. The goal of this proposal is to obtain high quality 4.5 micron phase curves for 22 transiting hot Jupiter systems, which represent a complete sample of systems that can be studied with Spitzer in a reasonable amount of time. The resulting dataset will not only quadruple the number of phase curve observations to date, but also populate gaps in parameter space explored by current phase curve studies. The combination of our phase curves with well-known literature ephemerides and observations of secondary eclipses will produce maps of the longitudinal brightness/temperature distributions in the planetary atmospheres. These maps can be used to calculate energy redistribution efficiencies between the hot dayside and cooler nightside -- exoplanetary weather. Our observations focus on the following three questions: (1) What is the contrast between exoplanetary day- and nightside temperatures, i.e., how efficiently is the incident energy redistributed? (2) Are the weather phenomena in the exoplanetary atmospheres stable over long periods of time? (3) How do the temperature distributions on the planetary surfaces correlate with astrophysical properties of the star-planet systems? To answer these questions with our proposed Spitzer observations, we will employ a novel observing technique using snapshot observing to reduce telescope time requirements, and PCRS peak-up to IRAC to increase the pointing accuracy and thus minimize the photometric error due to intrapixel sensitivity variation. The analysis of this comprehensive data set will elevate the study of phase curves to the level of comparative atmospheric studies outside the solar system.
• ##### Article: Analysis of HAT-P-2b Warm Spitzer Full Orbit Light Curve
[Hide abstract]
ABSTRACT: The Spitzer warm mission has already greatly expanded the field of exoplanet characterization with over 3000 hours of time dedicated to exoplanet observations. Observations of eclipsing systems with Spitzer are at the heart of these advances, as they allow us to move beyond simple mass and period estimates to determine planetary radius, dayside emission, and emission variations as a function of orbital phase. The eclipsing system HAT-P-2 is of special interest because the massive Jovian sized planet in this system is on a highly eccentric orbit (e=0.5171). Because HAT-P-2b's orbit is eccentric, the planet is subject to time variable heating and probable non-synchronous rotation. Circulation patterns that we expect to develop in HAT-P-2b's atmosphere will likely vary with both planetary local time and orbital phase. Here we present an analysis of a full orbit light curve from the HAT-P-2 system obtained during the most recent cycle of the Spitzer warm mission and discuss the constraints it imposes on the atmospheric circulation of HAT-P-2b. Support for this work was provided by NASA.
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##### Article: Dynamics and gravitational wave signature of collapsar formation.
[Hide abstract]
ABSTRACT: We perform 3+1 general relativistic simulations of rotating core collapse in the context of the collapsar model for long gamma-ray bursts. We employ a realistic progenitor, rotation based on results of stellar evolution calculations, and a simplified equation of state. Our simulations track self-consistently collapse, bounce, the postbounce phase, black hole formation, and the subsequent early hyperaccretion phase. We extract gravitational waves from the spacetime curvature and identify a unique gravitational wave signature associated with the early phase of collapsar formation.
Physical Review Letters 04/2011; 106(16):161103. DOI:10.1103/PhysRevLett.106.161103 · 7.73 Impact Factor
• ##### Article: Advances in the Theory of Giant Exoplanets
David S. Spiegel, A. Burrows
[Hide abstract]
ABSTRACT: We review recent results on the spectra of giant planets, including calculations specific to objects in the Kepler field (HAT-P-7b and TrES-2), and calculations of emergent radiation and transit spectra associated with general circulation models. We also present recent results on the potential habitability of terrestrial planets on eccentric orbits.
• ##### Article: A Subaru/MMT Study of the Atmospheres of the Planets Orbiting HR 8799
[Hide abstract]
ABSTRACT: We present new Subaru data and a rereduction of archival MMT data for the HR 8799 planetary system from 1 to 5 microns. We compare photometry from these data to that for field L/T dwarfs and synthetic SEDs for substellar objects with wide range of temperatures, gravities, and cloud prescriptions. Our analysis strongly suggests that HR 8799bcd have atmospheres dissimilar from almost any brown dwarf over a wide wavelength range. Best-fit models yield temperatures of 900-1100K and masses between 7 and 9 Mjupiter, roughly consistent with values derived from cooling models, and suggest that extensive cloud coverage is a likely source of the SED differences between these planets and brown dwarfs with similar temperatures.
#### Publication Stats
4k Citations 454.82 Total Impact Points
#### Institutions
• ###### Princeton University
• Department of Astrophysical Sciences
Princeton, New Jersey, United States
• ###### TRI/Princeton
Princeton, New Jersey, United States
• ###### The University of Arizona
• • Department of Astronomy
• • Department of Planetary Sciences
Tucson, Arizona, United States
• ###### Franklin and Marshall College
Marshall, Texas, United States
• ###### 1997
• Department of Meteorology
• ###### New Mexico State University
• Department of Astronomy
Las Cruces, NM, United States
• ###### Vanderbilt University
• Department of Physics and Astronomy
Nashville, Michigan, United States
• ###### French National Centre for Scientific Research
Lutetia Parisorum, Île-de-France, France | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8726680874824524, "perplexity": 3570.773397057608}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-18/segments/1429246658904.34/warc/CC-MAIN-20150417045738-00058-ip-10-235-10-82.ec2.internal.warc.gz"} |
http://mathhelpforum.com/pre-calculus/64678-system.html | Math Help - System
1. System
Solve:
$x^3-y^3=602$
$xy(y-x)=-198$
x = 11 and y = 9
or
x = -9 and y = -11
2. I will give you two hints:
$(x-y)^3 = x^3 - 3x^2y + 3xy^2 - y^3$
$xy^2 - x^2y=-198 \implies -3x^2y+3xy^2=-594$
3. How i find the answer ?
4. $x^3-y^3=602$
$-3x^2y+3xy^2=-594$
If we combine the two expressions, we get a perfect cube:
$x^3 - 3x^2y+3xy^2-y^3=602-594 \implies (x-y)^3=8 \implies x - y =\ldots$
This is your key to solving for x and y. Can you do it now?
5. thank you | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 7, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6862918138504028, "perplexity": 754.182209360114}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-30/segments/1469257824204.68/warc/CC-MAIN-20160723071024-00171-ip-10-185-27-174.ec2.internal.warc.gz"} |
https://douglas.research.mcgill.ca/polygenic-differential-susceptibility-prenatal-adversity | ## Polygenic differential susceptibility to prenatal adversity.
Title Polygenic differential susceptibility to prenatal adversity. Publication Type Journal Article Year of Publication 2018 Authors Belsky J, Pokhvisneva I, Rema ASathyan Sa, Broekman BFP, Pluess M, O'Donnell K, Meaney MJ, Silveira PPelufo Journal Dev Psychopathol Pagination 1-3 Date Published 2018 Aug 07 ISSN 1469-2198 Abstract A recent article in this journal reported a number of gene × environment interactions involving a serotonin transporter-gene network polygenic score and a composite index of prenatal adversity predicting several problem behavior outcomes at 48 months (e.g., anxious/depressed, pervasive developmental problems) and at 60 months (e.g., withdrawal, internalizing problems), yet did not illuminate the nature or form these genetic × environment interactions took. Here we report results of six additional analyses to evaluate whether these interactions reflected diathesis-stress or differential-susceptibility related processes. Analyses of the regions of significance and proportion of interaction index are consistent with the diathesis-stress model, seemingly because of the truncated nature of the adversity score (which did not extend to supportive/positive prenatal experiences/exposures); in contrast, the proportion (of cases) affected index favors the differential-susceptibility model. These results suggest the need for future studies to extend measurement of the prenatal environment to highly supportive experiences and exposures. DOI 10.1017/S0954579418000378 Alternate Journal Dev. Psychopathol. PubMed ID 30081968 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8244309425354004, "perplexity": 22111.783914020893}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-21/segments/1620243990584.33/warc/CC-MAIN-20210513080742-20210513110742-00599.warc.gz"} |
https://jzhao.xyz/thoughts/IPFS/ | Search
# IPFS
Last updated Jun 5, 2022 Edit Source
IPFS is a decentralized storage and delivery network which builds on fundamental principles of p2p networking and content-based addressing (see CID)
Can seen as a single BitTorrent swarm, exchanging objects within one big Git repository
Much like how we look up sites on the internet using URIs, we can look for specific pieces of content by their content-address.
Under the hood, IPFS uses
• libp2p: network layer, takes care of host addressing, content and peer discovery, and structures like DHTs and pubsub
• IPLD: data layer, standards and formats to build Merkle-DAG structures (quasi-filesystem)
• Multiformats: formatting structures for self-describing values
Publishing content
• Chunk the content and deduplicate chunks
• Obtain CID
• Add the content to the network
• Not the actual content, just the provider record to the DHT
Consuming content as a peer
• Get CID (out of band)
• Using DHT, resolve CID to peer
• Contact peer to ask for CID content
• Fetch content and cache a copy
• Serve local copy upon subsequent request
## # Encoding/decoding
How does the system decode the hashes that it gets into the component data structures?
Codecs! IPLD codecs are functions that transform IPLD Data Model into serialized bytes so you can send and share data, and transform serialized bytes back into IPLD Data Model so you can work with it. The CID includes an indicator called a multicodec (opens new window)to tell us which codec to use!
Systems can build abstractions on top of this. For example, IPFS encodes the UnixFS using DAG-PB (which is a IPLD codec).
Because the CID can describe different codecs relating to different systems, all sorts of systems can interoperate using CIDs, and IPLD and process and cross-link data from any of them.
## # Block Exchange using BitSwap
BitSwap peers are looking to acquire a set of blocks (want_list), and have another set of blocks to offer in exchange (have_list). Unlike BitTorrent, BitSwap is not limited to the blocks in one torrent. BitSwap operates as a persistent marketplace where node can acquire the blocks they need, regardless of what files those blocks are part of. The blocks could come from completely unrelated files in the filesystem. Nodes come together to barter in the marketplace.
### # Incentivizing rare blocks
Of course, there will not be perfect overlaps between nodes’ have_list and want_lists . Nodes must work for their blocks. In the case that a node has nothing that its peers want (or nothing at all), it seeks the pieces its peers want, with lower priority than what the node wants itself. This incentivizes nodes to cache and disseminate rare pieces, even if they are not interested in them directly.
This barter system implies a virtual currency could be created, this would require a global ledger to track ownership and transfer of the currency, which is exactly what Filecoin provides.
### # Incentivizing satisfied nodes to seed
The protocol must also incentivize nodes to seed when they do not need anything in particular, as they might have the blocks others want. Thus, BitSwap nodes send blocks to their peers optimistically, expecting the debt to be repaid.
A simple credit-like system solves the problem:
1. Peers track their balance (in bytes verified) with other nodes.
2. Peers send blocks to debtor peers probabilistically, according to a function that falls as debt increases. The probability function, given a debt ratio $r = \frac{\textrm{bytes sent}}{\textrm{bytes received} + 1}$ is $P(send | r) = 1 - \frac{1}{1 + \exp(6-3r)}$. The debt ratio is a measure of trust: lenient to debts between nodes that have previously exchanged lots of data successfully, and merciless to unknown, untrusted nodes. This also strongly disincentivizes Sybil attacks by making it hard for new nodes to request a lot of blocks without the intention of paying them back.
## # Pinning
This ensures the objects are kept in the node’s local storage. Pinning can be done recursively, to pin down all linked descendent objects as well. All objects pointed to are then stored locally. This is particularly useful to persist files, including references
## # WNFS
Under the Fission project, see specs
File system built on top of IPFS. Uses a DAG instead of a hierarchy, meaning that a given child can have more than one parent.
Each user has their own WNFS and consists of a public and private tree.
• The public tree is “live” and publicly accessible on the Internet.
• The private tree is encrypted so that only the owner can see the contents.
Uses UCAN for authorization. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.29585036635398865, "perplexity": 5609.629687601433}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-33/segments/1659882573540.20/warc/CC-MAIN-20220819005802-20220819035802-00788.warc.gz"} |
http://www.mitpress.mit.edu/authors/stephen-i-gallant | # Stephen I. Gallant
## Neural Network Learning and Expert Systems
Neural Network Learning and Expert Systems is the first book to present a unified and in-depth development of neural network learning algorithms and neural network expert systems. Especially suitable for students and researchers in computer science, engineering, and psychology, this text and reference provides a systematic development of neural network learning algorithms from a computational perspective, coupled with an extensive exploration of neural network expert systems which shows how the power of neural network learning can be harnessed to generate expert systems automatically.
Features include a comprehensive treatment of the standard learning algorithms (with many proofs), along with much original research on algorithms and expert systems. Additional chapters explore constructive algorithms, introduce computational learning theory, and focus on expert system applications to noisy and redundant problems.
For students there is a large collection of exercises, as well as a series of programming projects that lead to an extensive neural network software package. All of the neural network models examined can be implemented using standard programming languages on a microcomputer.
Stephen l. Gallant taught courses in neural network learning and expert systems as Associate Professor of Computer Science at Northeastern University. He is currently a Senior Scientist at HNC, Inc. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8057955503463745, "perplexity": 835.9583532120561}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-14/segments/1427131317570.85/warc/CC-MAIN-20150323172157-00116-ip-10-168-14-71.ec2.internal.warc.gz"} |
https://forum.allaboutcircuits.com/threads/i-am-a-math-rock-simple-transposition-question.34914/ | # I am a math rock. Simple transposition question
Discussion in 'Math' started by SgtWookie, Feb 27, 2010.
1. ### SgtWookie Thread Starter Expert
Jul 17, 2007
22,202
1,791
Terrible to admit, but I'm a math rock.
I've been struggling with this for a day, and I simply don't "get it" - this is high-school stuff, and that was a long time ago. Where am I going wrong?
The idea is to get L over on the left side of the equation.
Somehow I've managed to be involved in complex electronics and software for many years, but frankly I suck at math. I don't understand where I'm going wrong here.
Fo=1/2pi*sqrt(Lx*Cs) (this works)
L =4*pi()^2*((1/(D73*E73/1E6))^2/5e-8) (wrong!)
Various things I've tried:
To=2pi*sqrt(Lx*Cs)
To*2pi^2=4pi^2*Lx*Cs
=((d73*e73/1e6)/pi()*2)^2/5e-8
To=2*PI()*SQRT(F69*0.05) <=that works; F69=L(uH)
0=2*PI()*SQRT(F69*0.05)/To
0/2*PI()^2=(F69*0.05)^2/To
0/2*PI()^2/F69^2=0.05^2/To
To=2*PI()*SQRT(F69*0.05) <=that works; F69=L(uH)
To=2*PI()*SQRT(F69*0.05/1E12) <=that works
F=1/(2*pi()*sqrt(F66*0.05/1E12)) <=that works
F=1/(2*pi()*sqrt(F65/1E6*0.05/1E6)) <=that works
L=4*pi()^2*(L67^2/(.05/1e6)) <- garbage
L=4*pi()^2*((1/d68*e68)^2/.05) <- garbage
Where am I going wrong?
2. ### hgmjr Moderator
Jan 28, 2005
9,030
218
$f_o=\frac{1}{2*\pi*\sqrt{(L*C)}}$
Square both sides:
${f_o}^2=\frac{1^2}{{4*\pi^2*{\sqrt{(L*C)}}^2}$
Simplify
${f_o}^2=\frac{1}{{{(4*\pi^2*L*C)}}}$
Multiply both sides by L:
${f_o}^2*L=L*\frac{1}{{{(4*\pi^2*L*C)}}}$
L cancels on the right:
${f_o}^2*L=\frac{1}{{{(4*\pi^2*C)}}}$
Divide both sides by ${f_o}^2$
$L=\frac{1}{{{(4*\pi^2*C)*{f_o}^2}}}$
Substitution allows us to exhange omega for 2*pi*f
$L=\frac{1}{{{(\omega^2*C)}}}$
We are all rocks in the math quarry. It is just a matter of size.
hgmjr
Last edited: Feb 27, 2010
3. ### SgtWookie Thread Starter Expert
Jul 17, 2007
22,202
1,791
Thanks for your reply hgmjr, which I'm sure took a lot of work to get all of the tex graphcs right. But I still don't know how to get L over to the left side, but more importantly, how to do so.
Like I said, I'm a math rock. You've tried to provide instructions that would be adequate for most, but for some reason I have a really hard time with it.
Thanks,
Wook
4. ### hgmjr Moderator
Jan 28, 2005
9,030
218
Which of the steps is not clear? Maybe I can break it down a bit more.
hgmjr
Jul 7, 2009
1,585
142
The key idea in manipulating equations is that you have to do the same thing to both sides -- otherwise it doesn't remain an equality.
Thus, suppose you have an equation
$a = \frac {b} {L}$
and you want the L on the other side. The strategy used is to perform the same operation on both sides so that the L disappears from the right side and goes to the left side. Here, we can multiply both sides by L:
$L a = \frac {b} {L} L$
which reveals our strategy, because L divided by L is just 1. To see this, rewrite things slightly (using the associative law of multiplication) to get
$L a = b \frac {L} {L}$
Thus, we "cancel out" the L's on the right and we are left with the equation
$L a = b$
Analogously, to move the a to the right hand side, we just divide both sides by a to get
$L = \frac {b} {a}$
6. ### hgmjr Moderator
Jan 28, 2005
9,030
218
Someonesdad has captured the essence of the technique needed to manupulate the equation indeed any equation. This particular equation has an added factor in that L is contained in a square root term. This is what required the squaring of both sides of the equation to liberate L from the square root term. This squaring of both sides is consistent with someonesdad's statement that what is done to one side of the equation must be done to the other side of the equation if the equality is to be maintained.
hgmjr
7. ### Louise New Member
Jan 17, 2010
13
1
If I may be so bold as to make a tiny suggestion - something that helps me sometimes (and my maths ability might be accurately described as 'vanishingly small') is to try to re-arrange the same equation using numbers instead of symbols. The same rules apply.
8. ### Wendy Moderator
Mar 24, 2008
21,306
2,912
I figure we are as close as two people can be technically with such different back grounds. I find I'm having trouble with a lot of the math at this site. I do what can, and ask for help with the rest, same as you.
There was a time I would claim I knew some calculus. However, it rusts like the rest of my skills, but I really don't have a use for it very often. It is pretty much gone now.
9. ### hgmjr Moderator
Jan 28, 2005
9,030
218
If it helps. The above attempt came off the tracks when both sides of the equation were divided by To in STEP 2. The left side of the equation should have been 1 rather than 0. This is because To/To = 1.
I think it is safe to assume that in these equations references such as F69 and F66 are artifacts of the cut and paste operation from the spreadsheet you are using.
Everything you did above was kosher.
In the above box, I can't easily interpret what the cell references equate to so I am unable to determine where things went south.
Hope this helps some.
hgmjr
10. ### SgtWookie Thread Starter Expert
Jul 17, 2007
22,202
1,791
Thanks folks, I figured it out.
It's just a simple Excel spreadsheet that I've been using for testing an assortment of toroids I've had kicking around here for awhile.
I'm using a 74HC14 hex Schmitt-trigger inverter IC with three 100nF caps and a couple of resistors as a buffered Pierce oscillator; from an article published in EDN's Design Ideas, and measured the time of the output square wave with my O-scope (haven't built a freq. counter yet; still in the works...).
EDN article: http://www.edn.com/article/CA6462564.html
I record the divisions and time/div, and out pops the inductance in uH and approximate AL value. It's pretty decent down to maybe 10uH, but then the propagation delay in the 74HC14 starts kicking in along with parasitics from the X7R caps I used. A known 977nH inductor measures 2uH, so it's not all that bad.
One of the caps is used as a supply bypass cap for the 74HC14. The other two caps are on either side of the inductor under test, so they're essentially in series for a total of 50nF.
I was forgetting to shift my decimal places around where they belonged. Adding in a few /1e6 and *1e-6 fixed things up.
L(uH)=1/(4*PI()^2*(1/(scope_divisions*uSecs_per_division*0.000001))^2*(0.05*0.000001))*1000000
11. ### Harrington New Member
Dec 19, 2009
86
3
Here try this I'm not brilliant at maths myself but this the way we solve problems like this see attached hope this helps you in the future with your calculations
I use this from time to time you can also solve matrices maths with this and calculus Its a dos version but it will run on windows XP
Hope this helps you
Mark
• ###### Derive.zip
File size:
221.3 KB
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4,279 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 13, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8625181317329407, "perplexity": 1386.0363044628302}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-39/segments/1537267157216.50/warc/CC-MAIN-20180921151328-20180921171728-00466.warc.gz"} |
https://www.rdatagen.net/post/to-stratify-or-not-to-stratify/ | # To stratify or not? It might not actually matter...
Continuing with the theme of exploring small issues that come up in trial design, I recently used simulation to assess the impact of stratifying (or not) in the context of a multi-site Covid-19 trial with a binary outcome. The investigators are concerned that baseline health status will affect the probability of an outcome event, and are interested in randomizing by health status. The goal is to ensure balance across the two treatment arms with respect to this important variable. This randomization would be paired with an estimation model that adjusts for health status.
An alternative strategy is to ignore health status in the randomization, but to pre-specify an outcome model that explicitly adjusts for health status, just as in the stratification scenario. The question is, how do the operating characteristics (e.g. power, variance, and bias) of each approach compare. Are the (albeit minimal) logistics necessary for stratification worth the effort?
### Simulation
Simulations under a variety of scenarios suggest that stratification might not be necessary. (See this paper for a much deeper, richer discussion of these issues.)
#### Define the data
In these simulations, I assume that there are a small number of clusters. The proportion of high risk cases in each cluster varies (specified by p), as do the event rates (specified by a). The simulations vary the log odds of an outcome (baseLO), effect sizes/log-odds ratio (effLOR), and the effect of poor health status xLOR):
library(simstudy)
library(parallel)
setDefs <- function(pX, precX, varRE, baseLO, effLOR, xLOR) {
defc <- defData(varname = "p", formula = pX, variance = precX,
dist = "beta", id = "site")
defc <- defData(defc, varname = "a", formula = 0, variance = varRE)
form <- genFormula(c(baseLO, effLOR, xLOR, 1), vars = c("rx", "x", "a"))
defi1 <- defDataAdd(varname = "x", formula = "p", dist = "binary")
defi2 <- defDataAdd(varname = "y", formula = form, dist = "binary", link = "logit")
return(list(defc = defc, defi1 = defi1, defi2 = defi2))
}
#### Generate the data and estimates
Under each scenario, the data definitions are established by a call to setDefs and treatment is randomized, stratified by site only, or by site and health status x. (There is a slight bug in the trtAssign function that will generate an error if there is only a single observation in a site and particular strata - which explains my use of the try function to prevent the simulations from grinding to a halt. This should be fixed soon.)
For each generated data set under each scenario, we estimate a generalized linear model:
$logit(y_{ij}) = \beta_0 + \gamma_j + \beta_1r_i + \beta_2x_i \ ,$ where $$y_{ij}$$ is the outcome for patient $$i$$ at site $$j$$, $$r_i$$ is the treatment indicator, and $$x_i$$ is the health status indicator. $$\gamma_j$$ is a fixed site-level effect. The function returns parameter estimate for the log-odds ratio (the treatment effect $$\beta_1$$), as well as its standard error estimate and p-value.
genEsts <- function(strata, nclust, clustsize, pX, precX,
varRE, baseLO, effLOR, xLOR) {
defs <- setDefs(pX, precX, varRE, baseLO, effLOR, xLOR)
dc <- genData(nclust, defs$defc) dx <- genCluster(dc, "site", clustsize , "id") dx <- addColumns(defs$defi1, dx)
dx <- try(trtAssign(dx, strata = strata, grpName = "rx"), silent = TRUE)
if ( (class(dx)[1]) == "try-error") {
return(NULL)
}
glmfit <- glm(y~factor(site) + rx + x, data = dx, family = "binomial")
estrx <- t(coef(summary(glmfit))["rx", ])
return(data.table(estrx))
}
#### Iterate through multiple scenarios
We will “iterate” through different scenarios using the mclapply function the parallel package. For each scenario, we generate 2500 data sets and parameter estimates. For each of these scenarios, we calculate the
forFunction <- function(strata, nclust, clustsize, pX, precX,
varRE, baseLO, effLOR, xLOR) {
res <- rbindlist(mclapply(1:2500, function(x)
genEsts(strata, nclust, clustsize, pX, precX, varRE, baseLO, effLOR, xLOR)))
data.table(strata = length(strata), nclust, clustsize, pX, precX,
varRE, baseLO, effLOR, xLOR,
est = res[, mean(Estimate)],
se.obs = res[, sd(Estimate)],
se.est = res[, mean(Std. Error)],
pval = res[, mean(Pr(>|z|) < 0.05)]
)
}
#### Specify the scenarios
We specify all the scenarios by creating a data table of parameters. Each row of this table represents a specific scenario, for which 2500 data sets will be generated and parameters estimated. For these simulations that I am reporting here, I varied the strata for randomization, the cluster size, the baseline event rate, and the effect size, for a total of 336 scenarios ($$2 \times 6 \times 4 \times 7$$).
strata <- list("site", c("site", "x"))
nclust <- 8
clustsize <- c(30, 40, 50, 60, 70, 80)
pX <- 0.35
precX <- 30
varRE <- .5
baseLO <- c(-1.5, -1.25, -1.0, -0.5)
effLOR <- seq(0.5, 0.8, by = .05)
xLOR <- c(.75)
dparam <- data.table(expand.grid(strata, nclust, clustsize, pX, precX,
varRE, baseLO, effLOR, xLOR))
setnames(dparam, c("strata","nclust", "clustsize", "pX", "precX",
"varRE", "baseLO", "effLOR", "xLOR"))
dparam
## strata nclust clustsize pX precX varRE baseLO effLOR xLOR
## 1: site 8 30 0.35 30 0.5 -1.5 0.5 0.75
## 2: site,x 8 30 0.35 30 0.5 -1.5 0.5 0.75
## 3: site 8 40 0.35 30 0.5 -1.5 0.5 0.75
## 4: site,x 8 40 0.35 30 0.5 -1.5 0.5 0.75
## 5: site 8 50 0.35 30 0.5 -1.5 0.5 0.75
## ---
## 332: site,x 8 60 0.35 30 0.5 -0.5 0.8 0.75
## 333: site 8 70 0.35 30 0.5 -0.5 0.8 0.75
## 334: site,x 8 70 0.35 30 0.5 -0.5 0.8 0.75
## 335: site 8 80 0.35 30 0.5 -0.5 0.8 0.75
## 336: site,x 8 80 0.35 30 0.5 -0.5 0.8 0.75
#### Run the simulation
Everything is now set up. We go through each row of the scenario table dparam to generate the summaries for each scenario by repeated calls to forFunction, again using mclapply.
resStrata <- mclapply(1:nrow(dparam), function(x) with(dparam[x,],
forFunction(strata[[1]], nclust, clustsize, pX, precX, varRE, baseLO, effLOR, xLOR)))
resStrata <- rbindlist(resStrata)
resStrata[, .(strata, baseLO, effLOR, xLOR, est, se.obs, se.est, pval)]
## strata baseLO effLOR est se.obs se.est pval
## 1: 1 -1.5 0.5 0.53 0.33 0.31 0.38
## 2: 2 -1.5 0.5 0.52 0.32 0.31 0.39
## 3: 1 -1.5 0.5 0.52 0.28 0.27 0.49
## 4: 2 -1.5 0.5 0.51 0.27 0.27 0.48
## 5: 1 -1.5 0.5 0.51 0.24 0.24 0.58
## ---
## 332: 2 -0.5 0.8 0.82 0.21 0.20 0.98
## 333: 1 -0.5 0.8 0.82 0.19 0.19 0.99
## 334: 2 -0.5 0.8 0.82 0.19 0.19 1.00
## 335: 1 -0.5 0.8 0.82 0.18 0.17 1.00
## 336: 2 -0.5 0.8 0.81 0.18 0.17 1.00
### Plotting the results
The plots below compare the estimates of the two different stratification strategies. Each point represents a specific scenario under stratification by site alone and stratification by site along and health status. If there are differences in the two strategies, we would expect to see the points diverge from the horizontal line. For all four plots, there appears to be little if any divergence, suggesting that, for these scenarios at least, little difference between stratification scenarios.
#### Power
In this first scatter plot, the estimated power under each stratification strategy is plotted. Power is estimated by the proportion of p-values in the 2500 iterations that were less than 0.05. Regardless of whether observed power for a particular scenario is high or low, we generally observe the same power under both strategies. The points do not diverge far from the red line, which represents perfect equality.
#### Standard errors
There are two ways to look at the variability of the two strategies. First, we can look at the observed variability of the effect estimates across the 2500 iterations. And second, we can look at the average of the standard error estimates across the iterations. In general, the two randomization schemes appear quite similar with respect to both observed and estimated variation.
#### Treatment effects
In this last plot, the average estimated treatment effect is shown for each scenario. The two stratification strategies both appear to provide the same unbiased estimates of the treatment effect.
References:
Kernan, Walter N., Catherine M. Viscoli, Robert W. Makuch, Lawrence M. Brass, and Ralph I. Horwitz. “Stratified randomization for clinical trials.” Journal of clinical epidemiology 52, no. 1 (1999): 19-26. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 2, "mathjax_display_tex": 1, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6269752383232117, "perplexity": 5331.778547635763}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-24/segments/1590348496026.74/warc/CC-MAIN-20200605080742-20200605110742-00588.warc.gz"} |
https://link.springer.com/article/10.1007%2Fs00211-014-0621-5 | Numerische Mathematik
, Volume 128, Issue 3, pp 489–516
# Geometric error of finite volume schemes for conservation laws on evolving surfaces
Article
## Abstract
This paper studies finite volume schemes for scalar hyperbolic conservation laws on evolving hypersurfaces of $$\mathbb {R}^3$$. We compare theoretical schemes assuming knowledge of all geometric quantities to (practical) schemes defined on moving polyhedra approximating the surface. For the former schemes error estimates have already been proven, but the implementation of such schemes is not feasible for complex geometries. The latter schemes, in contrast, only require (easily) computable geometric quantities and are thus more useful for actual computations. We prove that the difference between approximate solutions defined by the respective families of schemes is of the order of the mesh width. In particular, the practical scheme converges to the entropy solution with the same rate as the theoretical one. Numerical experiments show that the proven order of convergence is optimal.
### Mathematics Subject Classification (2000)
65M08 35L65 58J45
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https://stats.stackexchange.com/questions/234483/what-are-the-characteristics-of-this-time-series | # What are the characteristics of this time series?
I started to learn about time series, and I am having difficulty in trying to identify some things just looking in the graph.
What I realized is:
• Trend: No increase or decrease trend.
• Seasonality: I think that is not possible say nothing about that, since the data is divided at intervals of 100 years. Seasonality is only linked to the calendar?
• Outliers: I believe that there is no outliers. Around the year 1700, the series reaches the value 1000, but looking at the years near this, this value does not appear to be discrepant. The same thing happens at the end of the series when the price is below 200.
• long-run cycle: What I realized is that at intervals of 100 years, at certain times there are peaks.
• constant variance: There is no constant variance. The variance in the interval 1300-1600 is much lower than in 1800-2000.
• abrupt changes: I think there is a drastic change if we look at what happened after 1800.
Is there something wrong with what I visualized? Is there anything more?
I tried to plot this time series in R, but it was not good.
data<-read.csv(file.choose())
ts.plot(data)
The results was it
The dataset has two variables: Year and Price.
[The data are available as the series wheat in the R package fma, and should also be available at datamarket.com]
• You have quite a few inter-linked questions! To start, I would suggest re-considering your first two bullets: trend & seasonality. The term "trend" is not necessarily limited to a persistent linear trend over the entire time series. And the term "seasonality" refers to any cyclical variation, so the period does not have to be yearly (I just learned this term recently myself). So in the big picture: Would you say the time series has a longer timescale smooth variation (trend) with a super-imposed oscillatory variation (posssibly "seasonality")? – GeoMatt22 Sep 11 '16 at 23:56
• @GeoMatt22 What I found recently about seasonality is "A seasonal pattern exists when a series is influenced by seasonal factors (e.g., the quarter of the year, the month, or day of the week). Seasonality is always of a fixed and known period." and about cyclic "A cyclic pattern exists when data exhibit rises and falls that are not of fixed period. The duration of these fluctuations is usually of at least 2 years." It is quite confused the difference between cycle and seasonality. – user72621 Sep 12 '16 at 0:25
• Data is also here (Ch. 9, Fig. 6) – GeoMatt22 Sep 12 '16 at 2:10
I see little to indicate any real trend.
What do I mean by that? Well, look at these time series plots:
Would you say they indicate trend? Many people would, but in fact all three are fair Bernoulli random walks -- each observation is the previous one $\pm 1$ (with equal chance of either going up or down).
(plot is taken from this post)
I would not be inclined to say that those show a real trend because none of them are actually going anywhere -- the best guess at the next observation is always the current observation. If we look at the first differences, $Z_t=B_t-B_{t-1}$ we get zero-mean Bernoulli "noise" -- $\pm 1$ with equal chance of either.
That idea of also plotting first differences of a series as well as the series itself can often be quite informative.
So let us return to the wheat series. If you plot first differences,
there's little to clearly suggest much beyond a random walk or perhaps random-walk-with-noise. The mean is nonzero but very close to it -- close enough that I wouldn't think to include a drift term in a random-walk model.
[However, that random walk doesn't quite capture all the structure -- if we look at an ACF/PACF of first differences these would indicate some remaining serial correlation]
If by seasonality you're asking about periodicity across multiple years, I see no clear indication of any cycles with a constant period in the data (e.g. ACF/PACF of first differences doesn't indicate anything). There's a mild effect at multiples of 5 year lag but it's quite weak and I'd be inclined to regard it as just noise.
• Can you explain the difference between seasonality and cycle? From what I read seasonality is only related to behaviors within a fixed and known period of time. – user72621 Sep 12 '16 at 0:40
• @PRAGAKHAM You have annual data, so you won't have effects due to seasons themselves (as you would often see with monthly or quarterly data -- e.g. with wheat, it would historically tend to be cheaper right after harvest time though good storage techniques and the ability to ship food worldwide mitigates those kinds of effects. But you can sometimes see periodic cycles of the same kind as seasonality (and I still call it that, though some people object to it) where the period is longer than a year; these things are more rare but can occur for various reasons. ... ctd – Glen_b Sep 12 '16 at 0:47
• ctd....On the other hand the term cyclical can refer to a varying-length but somewhat regular cycle - e.g. where there's a cycle of up and down around a the trend with an average length of some number of years (say 10, for example) but the actual time between peaks might vary from 8 to 13 years – Glen_b Sep 12 '16 at 0:47
• @PRAG However, if you want a good explanation of the difference, why not ask a question about the difference is? You might quote some of those things you say you have read (with proper references and links where available) for context – Glen_b Sep 12 '16 at 0:50
• @Glen_b I disagree. There appears to be a downward trend starting at about the second half of the 19th Century. This is probably a "real trend" related to the changes in the production process. I'm no agricultural expert, but examples can be found here and here. A key point is that relevant information often lies beyond the data series. – Graeme Walsh Sep 12 '16 at 0:55 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6266450881958008, "perplexity": 761.5613373811203}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-21/segments/1620243992440.69/warc/CC-MAIN-20210517180757-20210517210757-00268.warc.gz"} |
https://www.daniweb.com/software-development/python/threads/358926/reading-two-first-line-of-the-txt-filehow | Hi
I have a folder and its contain 5 text files.
My question is
How can I navigate to folder and read two first line of the txt files in folder with python scripts?
I will be very greatful for your help.
Reagards
Tony
What how have you tried to do it?
Tony
Reading just two first line on the each text files in the folder.
import glob
print "\n\n".join(["".join([l for l in open(inf).readlines()[:2]]) for inf in glob.glob("C:\\path\\to\\the\\dir\\*.txt")])
Ok, another alternative solution:
from __future__ import print_function
import os
PATH = os.curdir
EXTENSIONS = '.TXT','.ME','1ST'
for filename in (inf for inf in os.listdir(PATH)
if inf.upper().endswith(EXTENSIONS)):
with open(filename) as textfile:
try:
print(next(textfile), next(textfile))
print('-'*40)
except StopIteration:
continue
You | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8350490927696228, "perplexity": 9793.689704021748}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-32/segments/1438042989897.84/warc/CC-MAIN-20150728002309-00242-ip-10-236-191-2.ec2.internal.warc.gz"} |
https://phys.libretexts.org/Bookshelves/Astronomy_and_Cosmology_TextMaps/Map%3A_Astronomy_(OpenStax)/13%3A_Comets_and_Asteroids_-_Debris_of_the_Solar_System/13.04%3A_The_Origin_and_Fate_of_Comets_and_Related_Objects | $$\require{cancel}$$
# 13.4: The Origin and Fate of Comets and Related Objects
Learning Objectives
By the end of this section, you will be able to:
• Describe the traits of the centaur objects
• Chronicle the discovery and describe the composition of the Oort cloud
• Describe trans-Neptunian and Kuiper-belt objects
• Explain the proposed fate of comets that enter the inner solar system
The comets we notice when they come near Earth (especially the ones coming for the first time) are probably the most primitive objects we can study, preserved unchanged for billions of years in the deep freeze of the outer solar system. However, astronomers have discovered many other objects that orbit the Sun beyond the planets.
# Centaurs
In the outer solar system, where most objects contain large amounts of water ice, the distinction between asteroids and comets breaks down. Astronomers initially still used the name “asteroids” for new objects discovered going around the Sun with orbits that carry them far beyond Jupiter. The first of these objects is Chiron, found in 1977 on a path that carries it from just inside the orbit of Saturn at its closest approach to the Sun out to almost the distance of Uranus (Figure). The diameter of Chiron is estimated to be about 200 kilometers, much larger than any known comet.
Chiron’s Orbit.: Chiron orbits the Sun every 50 years, with its closest approach being inside the orbit of Saturn and its farthest approach out to the orbit of Uranus.
In 1992, a still-more-distant object named Pholus was discovered with an orbit that takes it 33 AU from the Sun, beyond the orbit of Neptune. Pholus has the reddest surface of any object in the solar system, indicating a strange (and still unknown) surface composition. As more objects are discovered in these distant reaches, astronomers decided that they will be given the names of centaurs from classical mythology; this is because the centaurs were half human, half horse, and these new objects display some of the properties of both asteroids and comets.
Beyond the orbit of Neptune lies a cold, dark realm populated by objects called simply trans-Neptunian objects (TNOs). The first discovered, and best known, of these TNOs is the dwarf planet Pluto. We discussed Pluto and the New Horizons spacecraft encounter with it in Rings, Moons, and Pluto. The second TNO was discovered in 1992, and now more than a thousand are known, most of them smaller than Pluto.
The largest ones after Pluto—named Eris, Makemake, and Haumea—are also classed as dwarf planets. Except for their small size, dwarf planets have many properties in common with the larger planets. Pluto has five moons, and two moons have been discovered orbiting Haumea and one each circling Eris and Makemake.
# The Kuiper Belt and the Oort Cloud
TNOs are a part of what is called the Kuiper belt, a large area of space beyond Neptune that is also the source of many comets. Astronomers study the Kuiper belt in two ways. New, more powerful telescopes allow us to discover many of the larger members of the Kuiper belt directly. We can also measure the composition of comets that come from the Kuiper belt. More than a thousand Kuiper belt objects have been discovered, and astronomers estimate that there are more than 100,000 with diameters large than 100 kilometers, in a disk extending out to about 50 AU from the Sun.
The short-period comets (such as Halley) are thought to originate in the Kuiper belt, where small gravitational perturbations from Neptune can gradually shift their orbits until they can penetrate the inner solar system. The long-period comets, however, come from a much more distant reservoir of icy objects, called the Oort cloud.
Careful studies of the orbits of long-period comets revealed that they come initially from very great distances. By following their orbits backward, we can calculate that the aphelia (points farthest from the Sun) of newly discovered comets typically have values near 50,000 AU (more than a thousand times farther than Pluto). This clustering of aphelion distances was first noted by Dutch astronomer Jan Oort, who, in 1950, proposed an idea for the origin of those comets that is still accepted today (Figure).
Jan Oort (1900–1992). Jan Oort first suggested that there might be a reservoir of frozen chunks, potential comet nuclei, at the edge of the region of the Sun’s gravitational influence.
It is possible to calculate that a star’s gravitational sphere of influence—the distance within which it can exert sufficient gravitation to hold onto orbiting objects—is about one third of its distance to the nearest other stars. Stars in the vicinity of the Sun are spaced in such a way that the Sun’s sphere of influence extends a little beyond 50,000 AU, or about 1 light-year. At such great distances, however, objects in orbit about the Sun can be perturbed by the gravity of passing stars. Some of the perturbed objects can then take on orbits that bring them much closer to the Sun (while others might be lost to the solar system forever).
Oort suggested, therefore, that the new comets we were seeing were examples of objects orbiting the Sun near the edge of its sphere of influence, whose orbits had been disturbed by nearby stars, eventually bringing them close to the Sun where we can see them. The reservoir of ancient icy objects from which such comets are derived is now called the Oort cloud.
Astronomers estimate that there are about a trillion (1012) comets in the Oort cloud. In addition, we estimate that about 10 times this number of icy objects could be orbiting the Sun in the volume of space between the Kuiper belt (which is gravitationally linked to Neptune) and the Oort cloud. These objects remain undiscovered because they are too faint to be seen directly and their orbits are too stable to permit any of them to be deflected inward close to the Sun. The total number of icy or cometary objects in the outer reaches of our solar system could thus be on the order of 10 trillion (1013), a very large number indeed.
What is the mass represented by 1013 comets? We can make an estimate if we assume something about comet sizes and masses. Let us suppose that the nucleus of Comet Halley is typical. Its observed volume is about 600 km3. If the primary constituent is water ice with a density of about 1 g/cm3, then the total mass of Halley’s nucleus must be about 6 × 1014 kilograms. This is about one ten billionth (10–10) of the mass of Earth.
If our estimate is reasonable and there are 1013 comets with this mass out there, their total mass would be equal to about 1000 Earths—comparable to the mass of all the planets put together. Therefore, icy, cometary material could be the most important constituent of the solar system after the Sun itself.
Example $$\PageIndex{1}$$: Mass of the Oort Cloud Comets
Suppose the Oort cloud contains 1012 comets with an average diameter of 10 km each. Let’s estimate the mass of the total Oort cloud.
Solution
We can start by assuming that typical comets are about the size of Comets Halley and Borrelly, with a diameter of 10 km and a density appropriate to water ice, which is about 1 g/cm3 or 1000 kg/m3. We know that density = mass/volume, the volume of a sphere, V=43πR3,V=43πR3, and the radius, R=12D.R=12D. Therefore, for each comet,
mass=density×volume=density×43π(12D)3mass=density×volume=density×43π(12D)3
Given that 10 km = 104 m, each comet’s mass is
mass=1000kg/m3×43×3.14×18×(104)3m3≈1015kg=1012tonsmass=1000kg/m3×43×3.14×18×(104)3m3≈1015kg=1012tons
To calculate the total mass of the cloud, we multiply this typical mass for one comet by the number of comets:
total mass=1015kg/comet×1012comets=1027kgtotal mass=1015kg/comet×1012comets=1027kg
Exercise $$\PageIndex{1}$$
How does the total mass we calculated above compare to the mass of Jupiter? To the mass of the Sun? (Give a numerical answer.)
The mass of Jupiter is about 1.9 × 1027 kg. The mass of the Oort cloud calculated above is 1027kg. So the cloud would contain about half a Jupiter of mass. The mass of the Sun is 2 × 1030 kg. This means the Oort cloud would be
1027kg(2×1030kg)=0.0005×the mass of the Sun1027kg(2×1030kg)=0.0005×the mass of the Sun
# Early Evolution of the Planetary System
Comets from the Oort cloud help us sample material that formed very far from the Sun, whereas the short-period comets from the Kuiper belt sample materials that were planetesimals in the solar nebula disk but did not form planets. Studies of the Kuiper belt also are influencing our understanding of the early evolution of our planetary system.
The objects in the Oort cloud and the Kuiper belt have different histories, and they may therefore have different compositions. Astronomers are therefore very interested in comparing detailed measurements of the comets derived from these two source regions. Most of the bright comets that have been studied in the past (Halley, Hyakutake, Hale-Bopp) are Oort cloud comets, but P67 and several other comets targeted for spacecraft measurements in the next decade are Jupiter-family comets from the Kuiper belt (see [link]).
The Kuiper belt is made up of ice-and rock planetesimals, a remnant of the building blocks of the planets. Since it is gravitationally linked to Neptune, it can help us understand the formation and history of the solar system. As the giant planets formed, their gravity profoundly influenced the orbits of Kuiper belt objects. Computer simulations of the early evolution of the planetary system suggest that the gravitational interactions between the giant planets and the remaining planetesimals caused the orbit of Jupiter to drift inward, whereas the orbits of Saturn, Uranus, and Neptune all expanded, carrying the Kuiper belt with them.
Another hypotheses involves a fifth giant planet that was expelled from the solar system entirely as the planetary orbits shifted. Neptune’s retrograde (backward-orbiting) moon Triton (which is nearly as large as Pluto) may have been a Kuiper belt object captured by Neptune during the period of shifting orbits. It clearly seems that the Kuiper belt may carry important clues to the way our solar system reached its present planetary configuration.
COMET HUNTING AS A HOBBY
When amateur astronomer David Levy (Figure), the co-discoverer of Comet Shoemaker-Levy 9, found his first comet, he had already spent 928 fruitless hours searching through the dark night sky. But the discovery of the first comet only whetted his appetite. Since then, he has found 8 others on his own and 13 more working with others. Despite this impressive record, he ranks only third in the record books for number of comet discoveries. But David hopes to break the record someday.
All around the world, dedicated amateur observers spend countless nights scanning the sky for new comets. Astronomy is one of the very few fields of science where amateurs can still make a meaningful contribution, and the discovery of a comet is one of the most exciting ways they can establish their place in astronomical history. Don Machholz, a California amateur (and comet hunter) who has been making a study of comet discoveries, reported that between 1975 and 1995, 38% of all comets discovered were found by amateurs. Those 20 years yielded 67 comets for amateurs, or almost 4 per year. That might sound pretty encouraging to new comet hunters, until they learn that the average number of hours the typical amateur spent searching for a comet before finding one was about 420. Clearly, this is not an activity for impatient personalities.
What do comet hunters do if they think they have found a new comet? First, they must check the object’s location in an atlas of the sky to make sure it really is a comet. Since the first sighting of a comet usually occurs when it is still far from the Sun and before it sports a significant tail, it will look like only a small, fuzzy patch. And through most amateur telescopes, so will nebulae (clouds of cosmic gas and dust) and galaxies (distant groupings of stars). Next, they must check that they have not come across a comet that is already known, in which case, they will only get a pat on the back instead of fame and glory. Then they must re-observe or re-image it sometime later to see whether its motion in the sky is appropriate for comets.
Often, comet hunters who think they have made a discovery get another comet hunter elsewhere in the country to confirm it. If everything checks out, the place they contact is the Central Bureau for Astronomical Telegrams at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts (http://www.cbat.eps.harvard.edu/). If the discovery is confirmed, the bureau will send the news out to astronomers and observatories around the world. One of the unique rewards of comet hunting is that the discoverer’s name becomes associated with the new comet—a bit of cosmic fame that few hobbies can match.
David Levy. Amateur astronomer David Levy ranks third in the world for comet discoveries.
# The Fate of Comets
Any comet we see today will have spent nearly its entire existence in the Oort cloud or the Kuiper belt at a temperature near absolute zero. But once a comet enters the inner solar system, its previously uneventful life history begins to accelerate. It may, of course, survive its initial passage near the Sun and return to the cold reaches of space where it spent the previous 4.5 billion years. At the other extreme, it may collide with the Sun or come so close that it is destroyed on its first perihelion passage (several such collisions have been observed with space telescopes that monitor the Sun). Sometimes, however, the new comet does not come that close to the Sun but instead interacts with one or more of the planets.
SOHO (the Solar and Heliospheric Observatory) has an excellent collection of videos of comets that come near the Sun. At this site, comet ISON approaches the Sun and is believed to be destroyed in its passage.
A comet that comes within the gravitational influence of a planet has three possible fates. It can (1) impact the planet, ending the story at once; (2) speed up and be ejected, leaving the solar system forever; or (3) be perturbed into an orbit with a shorter period. In the last case, its fate is sealed. Each time it approaches the Sun, it loses part of its material and also has a significant chance of collision with a planet. Once the comet is in this kind of short-period orbit, its lifetime starts being measured in thousands, not billions, of years.
A few comets end their lives catastrophically by breaking apart (sometimes for no apparent reason) (Figure). Especially spectacular was the fate of the faint Comet Shoemaker-Levy 9, which broke into about 20 pieces when it passed close to Jupiter in July 1992. The fragments of Shoemaker-Levy were actually captured into a very elongated, two-year orbit around Jupiter, more than doubling the number of known jovian moons. This was only a temporary enrichment of Jupiter’s family, however, because in July 1994, all the comet fragments crashed unto Jupiter, releasing energy equivalent to millions of megatons of TNT.
Breakup of Comet LINEAR: (a) A ground-based view with much less detail and (b) a much more detailed photo with the Hubble Space Telescope, showing the multiple fragments of the nucleus of Comet LINEAR. The comet disintegrated in July 2000 for no apparent reason. (Note in the left view, the fragments all blend their light together, and can’t be distinguished. The short diagonal white lines are stars that move in the image, which is keeping track of the moving comet.)
As each cometary fragment streaked into the jovian atmosphere at a speed of 60 kilometers per second, it disintegrated and exploded, producing a hot fireball that carried the comet dust as well as atmospheric gases to high altitudes. These fireballs were clearly visible in profile, with the actual point of impact just beyond the jovian horizon as viewed from Earth (Figure). As each explosive plume fell back into Jupiter, a region of the upper atmosphere larger than Earth was heated to incandescence and glowed brilliantly for about 15 minutes, a glow we could detect with infrared-sensitive telescopes.
Comet Impact on Jupiter: (a) The “string” of white objects are fragments of Comet Shoemaker-Levy 9 approaching Jupiter. (b) The first fragment of the comet impacts Jupiter, with the point of contact on the bottom left side in this image. On the right is Jupiter’s moon, Io. The equally bright spot in the top image is the comet fragment flaring to maximum brightness. The bottom image, taken about 20 minutes later, shows the lingering flare from the impact. The Great Red Spot is visible near the center of Jupiter. These infrared images were taken with a German-Spanish telescope on Calar Alto in southern Spain.
After this event, dark clouds of debris settled into the stratosphere of Jupiter, producing long-lived “bruises” (each still larger than Earth) that could be easily seen through even small telescopes (Figure). Millions of people all over the world peered at Jupiter through telescopes or followed the event via television or online. Another impact feature was seen on Jupiter in summer 2009, indicating that the 1994 events were by no means unique. Seeing these large, impact explosions on Jupiter helps us to appreciate the disaster that would happen to our planet if we were hit by a comet or asteroid.
Impact Dust Cloud on Jupiter: These features result from the impact of Comet Shoemaker-Levy 9 with Jupiter, seen with the Hubble Space Telescope 105 minutes after the impact that produced the dark rings (the compact back dot came from another fragment). The inner edge of the diffuse, outer ring is about the same size as Earth. Later, the winds on Jupiter blended these features into a broad spot that remained visible for more than a month.
For comets that do not meet so dramatic an end, measurements of the amount of gas and dust in their atmospheres permit us to estimate the total losses during one orbit. Typical loss rates are up to a million tons per day from an active comet near the Sun, adding up to some tens of millions of tons per orbit. At that rate, a typical comet will be gone after a few thousand orbits. This will probably be the fate of Comet Halley in the long run.
This History Channel video shows a short discussion and animation from the TV documentary series Universe, showing the collision of Comet Shoemaker-Levy 9 with Jupiter.
# Key Concepts and Summary
Oort proposed in 1950 that long-period comets are derived from what we now call the Oort cloud, which surrounds the Sun out to about 50,000 AU (near the limit of the Sun’s gravitational sphere of influence) and contains between 1012 and 1013 comets. Comets also come from the Kuiper belt, a disk-shaped region beyond the orbit of Neptune, extending to 50 AU from the Sun. Comets are primitive bodies left over from the formation of the outer solar system. Once a comet is diverted into the inner solar system, it typically survives no more than a few thousand perihelion passages before losing all its volatiles. Some comets die spectacular deaths: Shoemaker-Levy 9, for example, broke into 20 pieces before colliding with Jupiter in 1994.
## Glossary
Kuiper belt
a region of space beyond Neptune that is dynamically stable (like the asteroid belt); the source region for most short-period comets
Oort cloud
the large spherical region around the Sun from which most “new” comets come; a reservoir of objects with aphelia at about 50,000 AU | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7415540218353271, "perplexity": 1366.9859498901285}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-47/segments/1573496668585.12/warc/CC-MAIN-20191115042541-20191115070541-00446.warc.gz"} |
https://codereview.stackexchange.com/questions/183510/nom-parser-in-rust | nom Parser in Rust
I'm attempting to make a parser using nom in Rust. Nom implements parser combinators, so more complex parsers are built from simpler parsers. Because of this, I've started with a simple ID token parser, but before I keep going, I'd like to know if there are any obvious (to anyone besides me) design problems with the code I have.
My current ID parser, shown below, scans the input for a sequence of alphanumeric characters that starts with a letter.
#[macro_use]
extern crate nom;
use nom::{IResult, alpha, alphanumeric, space};
named!(id_pre (&str) -> &str, call!(alpha));
named!(id (&str) -> String,
do_parse!(
prefix: map!(id_pre, str::to_owned) >>
suffix: opt!(alphanumeric) >>
(match suffix {
Some(suffix) => prefix + suffix,
_ => prefix,
})
)
);
named!(id_list (&str) -> Vec<String>, separated_list!(space, id));
fn main() {
let a = id_list("Hello world2\n");
print!("{:?}\n", a)
} | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.18173636496067047, "perplexity": 23544.51623689244}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-30/segments/1563195525312.3/warc/CC-MAIN-20190717141631-20190717163631-00282.warc.gz"} |
http://nylogic.org/talks/grounded-martins-axiom | # Grounded Martin’s axiom
Set theory seminarFriday, November 8, 201310:00 am
# Grounded Martin’s axiom
### The CUNY Graduate Center
I will present a weakening of Martin’s axiom which asserts the existence of partial generics only for ccc posets contained in a ccc ground model. This principle, named the grounded Martin’s axiom, emerges naturally in the analysis of the Solovay-Tennenbaum proof of the consistency of MA. While the grounded MA has some of the combinatorial consequences of MA, it will be shown to be more flexible (being consistent with a singular continuum, for example) and more robust under forcing (being preserved in a strong way under both adding a Cohen or a random real).
Miha Habič is a graduate student at the CUNY GC. He got his Masters Degree in Mathematics at the University of Ljubljana, Slovenia. His interests lie in the area of infinitary computability, forcing and large cardinals.
Posted by on November 2nd, 2013 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8125031590461731, "perplexity": 1446.230201936959}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-17/segments/1618038067400.24/warc/CC-MAIN-20210412113508-20210412143508-00435.warc.gz"} |
http://crypto.stackexchange.com/questions/797/is-diffie-hellman-mathematically-the-same-as-rsa/803 | Is Diffie-Hellman mathematically the same as RSA?
Is the Diffie-Hellman key exchange the same as RSA?
Diffie Hellman allows key exchange on a observed wire – but so can RSA.
Alice and Bob want to exchange a key – Big brother is watching everything.
1. Bob makes an fresh RSA key pair and sends his public key to Alice.
2. Alice makes a random session key and sends it to Bob encrypted with Bob's public key.
3. Bob decrypts the session key with his private key.
Alice and Bob have exchanged a key despite the fact that anybody can observe all the traffic. The maths of RSA and Hiffie Hellman are remarkably similar, both involving modular exponentiation.
They both work because $(A*B)^C \bmod N$ can be done in two steps, i.e. by calculating $X = A^C \bmod N$ on one side of the transaction, and $X^B \bmod N$ on the other – this trick is the basis of both Hiffie Hellman and RSA. Which make me wonder: Are they really the same thing?
Can we algebraically prove that the correctness of RSA implies the correctness of Diffie-Hellman?
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migrated from security.stackexchange.comSep 27 '11 at 15:53
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Both RSA and Diffie-Hellman work with modular exponentiation. But they work in a different way:
In RSA, there are two exponentiations which invert each other, i.e. we have $e$ and $d$ such that $(x^e)^d \equiv x$ for all $x$. E.g. if $\square^e$ is the encryption, $\square^d$ is the corresponding decryption. To create this pair of $e$ and $d$ (or derive one from the other), we need the prime factorization of the modulus $m$ (which thus should be private).
In Diffie-Hellman, both the basis $g$ and the modulus $m$ of the exponentiation is fixed. The exponents $x$ and $y$ are randomly chosen private keys, and we use the fact that $(g^x)^y \equiv g^{x\cdot y} \equiv (g^y)^x$, where $g^x$ and $g^y$ are public, while $x$ and $y$ are (and stay) private, and $g^{x·y}$ is the shared secret.
To break RSA, we would have to get $x$ from $x^d$, $m$ and $d$ - this could be called the discrete $d$-th root problem. (The best known way to do this is to factor $m$ to get $e$ ... and if you have $e$, this also can be used to factor $m$).
To break Diffie-Hellman, we have to get $g^{x·y}$ from $g^x$, $g^y$, $m$ and $g$. The best known way to do this would be to get $x$ from $g^x$ or $y$ from $g^y$ (and $m$ and $g$), the so-called discrete logarithm problem. (Incidentially, it is not proven that this is really the best way, i.e. that there is not a faster way to do this.)
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Diffie-Hellman and RSA are distinct and do not use the same "trick".
In Diffie-Hellman, commutativity is used: $(g^a)^b = (g^b)^a$. Both Alice and Bob do two modular exponentiations each (Alice chooses $a$, computes $g^a$ and sends it to Bob, receives $g^b$ from Bob, and finally computes $(g^b)^a$). Security relies on the difficulty of discrete logarithm: given a prime $p$, an integer $g$, and $g^x \mod p$, it is utterly difficult to find $x$.
In RSA, there is no commutativity involved; Alice and Bob do only one modular exponentiation each; computations are not done modulo a prime $p$, but modulo a non-prime $n$. Alice chooses a random $m$, computes $m^e \mod n$ and sends it to Bob; Bob computes $(m^e)^d \mod n$ which is equal to $m$ because $d$ and $e$ have been chosen for this to work. RSA relies on the difficulty of extracting $e$-th roots: given $n$, $e$ and $m^e \mod n$, it is utterly difficult to find $m$ -- unless you know the "magic trap", i.e. $d$ (or the factorization of $n$)(if $n$ was prime, finding $m$ would be easy).
Although both algorithms involve modular exponentiations, they are quite different in how they work, what they provide, and what hard problems they rely on. Note the difference: in discrete logarithm, you have $g$ and $g^x$, and seek $x$; in $e$-th roots, you have $m^e$ and $e$, and seek $m$.
Any asymmetric encryption algorithm (such as RSA) can be used as a key exchange algorithm, in the way you describe (to "exchange" a key, Alice selects a random blob and encrypts it with Bob's public key). SSL/TLS does that. The converse is not true: you cannot generically transform a key exchange algorithm "alone" into an asymmetric encryption algorithm (but you can use the exchanged key with a symmetric encryption algorithm like AES; there again, SSL does that when using Diffie-Hellman).
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The mathematical problems behind DH and RSA are similar but not known to be directly related. It is still an open question if an oracle breaking DH can be used to construct another oracle that breaks RSA (or vice versa). It is mostly believed that the two problems are not reducible to each other in poly time.
However, the complexity of the fastest known DH and RSA breaking algorithms are very close. Therefore, both DH and RSA recommended key sizes are the same.
I should add that in the case of Elliptic Curve-DH, there is no better way to solve the DH problem than by generic algorithms and so the key size is much shorter.
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DH and RSA are definitely not the same. DH is a key exchange algorithm, RSA an encryption/signing algorithm.
Now as to whether are operate in the the same way in the scenario you describe. They can indeed be used for a similar purpose. However, the operate on a fundamentally different mathematical problem. DH uses DLP (discrete logarithm), trusting on the hardness of finding x when g^x=H and g and H are known. RSA trusts on the prime factorization problem: the hardness of finding p(prime) and q(prime) when n=(p-1)(q-1) is known.
If the DL problem would be solved, making it feasible to compute x in a reasonable time, DH and ElGamal would both be broken. RSA wouldn't, if I'm not mistaken; RSA would suffer when the prime factorization problem would be solved.
For this reason, you cannot use DH to prove RSA or the other way around.
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Correction: in RSA, $n=(p-1)(q-1)$ (or $lcm(p-1,q-1)$) is not known (it's easy to factor given that value). Instead, the hard problem is determining x given e and $x^e mod pq$; in constrast, one way of attacking DH is to attack the hard problem of determining e given x and $x^e mod p$ – poncho Sep 27 '11 at 16:02
I think I might be wrong, but I thought I've heard the claim that breaking discrete log breaks/threatens RSA as well. Maybe this should be a question. – Ethan Heilman Sep 27 '11 at 16:29
Well, there are two ways that claim may be correct: 1) if you can solve the DLOG problem in a composite modulus, then you can factor that modulus. If your Oracle to solve DLOG works only in a prime modulus, there's no obvious way to use that to factor; 2) a lot of approaches for attacking the DLOG problem can be used (with some changes) to attack the factorization problem (and vica versa). Now, that's not for all known approaches. – poncho Sep 27 '11 at 17:14
No, they are not the same.
The short answer is that Diffie-Hellman is for negotiating a secret between parties who don't already share one, while RSA uses existing key material to protect data.
It's actually quite a major difference. Both are "security" related, of course, but DH is starting from scratch while RSA is using a system that's already in place.
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RSA security relies on the assumption that the "RSA problem" is hard. The RSA problem is to find the plaintext given only $n$, $e$, and the ciphertext. It is easy to see that an efficient factoring algorithm breaks RSA, but the converse is unknown: ie, if we had an oracle that could efficiently break RSA, could we efficiently factor $n$?.
Interestingly, quantum computers break BOTH algorithms via similar techniques (assuming DH is in $Z^*_p$)
Actually, DH relies on the "Diffie-Hellman problem" (given $g^x$ and $g^y$, find $g^{x·y}$, which might be easier than the discrete log problem (and is easier in some groups, I think). – Paŭlo Ebermann Jan 18 '12 at 21:35 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8887925744056702, "perplexity": 616.5607732597848}, "config": {"markdown_headings": false, "markdown_code": false, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-10/segments/1393999638008/warc/CC-MAIN-20140305060718-00046-ip-10-183-142-35.ec2.internal.warc.gz"} |
https://www.varsitytutors.com/hotmath/hotmath_help/topics/operations-on-sets.html | # Operations on Sets
Recall that a set is a collection of elements.
Given sets $A$ and $B$ , we can define the following operations:
Operation Notation Meaning Intersection $A\cap B$ all elements which are in both $A$ and $B$ Union $A\cup B$ all elements which are in either $A$ or $B$ (or both) Difference $A-B$ all elements which are in $A$ but not in $B$ Complement $\stackrel{¯}{A}$ (or ${A}^{C}$ ) all elements which are not in $A$
Example 1:
Let $A=\left\{1,2,3,4\right\}$ and let $B=\left\{3,4,5,6\right\}$ .
Then:
$A\cap B=\left\{3,4\right\}$
$A\cup B=\left\{1,2,3,4,5,6\right\}$
$A-B=\left\{1,2\right\}$
Example 2:
Let $A=\left\{y,z\right\}$ and let $B=\left\{x,y,z\right\}$ .
Then: | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 21, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9612295627593994, "perplexity": 207.4643603236722}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-17/segments/1492917125719.13/warc/CC-MAIN-20170423031205-00376-ip-10-145-167-34.ec2.internal.warc.gz"} |
https://meta.mathoverflow.net/questions/1552/disappearing-question | # Disappearing Question
Yesterday there was a question about solving the functional equation $f(\alpha t)f(\beta t)=C$ for $C$ constant, $\alpha^2+\beta^2=1$. It was closed as "unclear what you're asking" when the OP ignored multiple requests for an edit to clarify the implied quantifiers (for all $\alpha,\beta$? there exists $\alpha,\beta$''? etc.)
Today the question is gone but I do not find it listed under either "recently closed" or "recently deleted". I'm just curious how a question disappears without being visible in the "recently deleted" list.
• I know selfdeletions do not show up in deleted list, which howver seems extremely unlikely as reason in this case (one cannot selfdelete closed questions). I thought moderator deleted posts do not show up either but after double checking this seems different (or at least less clear regarding conditions). So I too would be quite curious regarding this (in general). – user9072 Mar 11 '14 at 14:37
• Unfortunately, I cannot find the link to the question. Nevertheless, I think the question asked for a solution to $f(\alpha t)f(\beta t) = f(t)$. – Ricardo Andrade Mar 11 '14 at 15:15
• Ricardo: yes, that is what I meant --- $f(\alpha t)f(\beta t)$ is a constant independent of $\alpha,\beta$ (but not independent of $t$). On the other hand, the OP seemed to be quite reluctant to reveal his true intent. – Steven Landsburg Mar 11 '14 at 15:24
• Downvoted questions disappear from some lists. Are you sure it is deleted? Gerhard "Ask Me About System Design" Paseman, 2014.03.11 – Gerhard Paseman Mar 11 '14 at 17:38
• @GerhardPaseman yes, but it should not disappear from recently closed (or reopened) in moderation tools due to score. (I did not check myself if it is there, but this is what Steven Landsburg said he did check.) – user9072 Mar 11 '14 at 20:20
• It turns out the restriction I claimed (no direct selfdeletion of closed questions) was dropped at somme point; sorry for not being up to date. Yet, it was in place on the old MO, see also meta.stackoverflow.com/revisions/5222/2 (to be clear the link is to obsolete documentation, it is only to document that it was like I claimed earlier) – user9072 Mar 12 '14 at 9:45 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7919840216636658, "perplexity": 1211.491527507426}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986659097.10/warc/CC-MAIN-20191015131723-20191015155223-00405.warc.gz"} |
https://es.mathworks.com/help/symbolic/solve-equations-numerically.html | # Solve Equations Numerically
Symbolic Math Toolbox™ offers both numeric and symbolic equation solvers. For a comparison of numeric and symbolic solvers, see Select Numeric or Symbolic Solver. An equation or a system of equations can have multiple solutions. To find these solutions numerically, use the function `vpasolve`. For polynomial equations, `vpasolve` returns all solutions. For nonpolynomial equations, `vpasolve` returns the first solution it finds. These examples show you how to use `vpasolve` to find solutions to both polynomial and nonpolynomial equations, and how to obtain these solutions to arbitrary precision.
### Find All Roots of a Polynomial Function
Use `vpasolve` to find all the solutions to the function $f\left(x\right)=6{x}^{7}-2{x}^{6}+3{x}^{3}-8$.
```syms f(x) f(x) = 6*x^7-2*x^6+3*x^3-8; sol = vpasolve(f)```
```sol = $\left(\begin{array}{c}1.0240240759053702941448316563337\\ -0.88080620051762149639205672298326+0.50434058840127584376331806592405 \mathrm{i}\\ -0.88080620051762149639205672298326-0.50434058840127584376331806592405 \mathrm{i}\\ -0.22974795226118163963098570610724+0.96774615576744031073999010695171 \mathrm{i}\\ -0.22974795226118163963098570610724-0.96774615576744031073999010695171 \mathrm{i}\\ 0.7652087814927846556172932675903+0.83187331431049713218367239317121 \mathrm{i}\\ 0.7652087814927846556172932675903-0.83187331431049713218367239317121 \mathrm{i}\end{array}\right)$```
`vpasolve` returns seven roots of the function, as expected, because the function is a polynomial of degree seven.
### Find Zeros of a Nonpolynomial Function Using Search Ranges and Starting Points
A plot of the function $f\left(x\right)={e}^{\left(x/7\right)}\mathrm{cos}\left(2x\right)$ reveals periodic zeros, with increasing slopes at the zero points as $x$ increases.
```syms x h = fplot(exp(x/7)*cos(2*x),[-2 25]); grid on```
Use `vpasolve` to find a zero of the function `f`. Note that `vpasolve` returns only one solution of a nonpolynomial equation, even if multiple solutions exist. On repeated calls, `vpasolve` returns the same result.
```f = exp(x/7)*cos(2*x); for k = 1:3 vpasolve(f,x) end```
`ans = $-7.0685834705770347865409476123789$`
`ans = $-7.0685834705770347865409476123789$`
`ans = $-7.0685834705770347865409476123789$`
To find multiple solutions, set the option `'Random'` to `true`. This makes `vpasolve` choose starting points randomly. For information on the algorithm that chooses random starting points, see Algorithms on the `vpasolve` page.
```for k = 1:3 vpasolve(f,x,'Random',true) end```
`ans = $-226.98006922186256147892598444194$`
`ans = $98.174770424681038701957605727484$`
`ans = $52.621676947629036744249276669932$`
To find a zero close to $x=10$, set the starting point to `10`.
`vpasolve(f,x,10)`
`ans = $10.210176124166828025003590995658$`
To find a zero close to $x=1000$, set the starting point to `1000`.
`vpasolve(f,x,1000)`
`ans = $999.8118620049516981407362567287$`
To find a zero in the range $15\le x\le 25$, set the search range to `[15 25]`.
`vpasolve(f,x,[15 25])`
`ans = $21.205750411731104359622842837137$`
To find multiple zeros in the range `[15 25]`, you cannot call `vpasolve` repeatedly because it returns the same result on each call, as previously shown. Instead, set the search range and set `'Random'` to `true`.
```for k = 1:3 vpasolve(f,x,[15 25],'Random',true) end```
`ans = $21.205750411731104359622842837137$`
`ans = $21.205750411731104359622842837137$`
`ans = $16.493361431346414501928877762217$`
Because `'Random'` selects starting points randomly, the same solution might be found on successive calls.
#### Find All Zeros in a Specified Search Range
Create a function `findzeros` to systematically find all zeros for `f` in a given search range, within a specified error tolerance. The function starts with the input search range and calls `vpasolve` to find a zero. Then, it splits the search range into two around the zero value and recursively calls itself with the new search ranges as inputs to find more zeros.
The function is explained section by section here.
Declare the function with the three inputs and one output. The first input is the function, the second input is the range, and the optional third input allows you to specify the error between a zero and the higher and lower bounds generated from it.
```function sol = findzeros(f,range,err) ```
If you do not specify the optional argument for error tolerance, `findzeros` sets `err` to `0.001`.
```if nargin < 2 err = 1e-3; end ```
Find a zero in the search range using `vpasolve`.
```sol = vpasolve(f,range); ```
If `vpasolve` does not find a zero, exit.
```if(isempty(sol)) return ```
If `vpasolve` finds a zero, split the search range into two search ranges above and below the zero.
```else lowLimit = sol-err; highLimit = sol+err; ```
Call `findzeros` with the lower search range. If `findzeros` returns zeros, copy the values into the solution array and sort them.
``` temp = findzeros(f,[range(1) lowLimit],1); if ~isempty(temp) sol = sort([sol temp]); end ```
Call `findzeros` with the higher search range. If `findzeros` returns zeros, copy the values into the solution array and sort them.
``` temp = findzeros(f,[highLimit range(2)],1); if ~isempty(temp) sol = sort([sol temp]); end return end end ```
The entire function `findzeros` is as follows. Save this function as `findzeros.m` in the current folder.
```function sol = findzeros(f,range,err) if nargin < 3 err = 1e-3; end sol = vpasolve(f,range); if(isempty(sol)) return else lowLimit = sol-err; highLimit = sol+err; temp = findzeros(f,[range(1) lowLimit],1); if ~isempty(temp) sol = sort([sol temp]); end temp = findzeros(f,[highLimit range(2)],1); if ~isempty(temp) sol = sort([sol temp]); end return end end ```
Call `findzeros` with search range `[15 25]` to find all zeros in that range for `f(x) = exp(x/7)*cos(2*x)`, within the default error tolerance.
```syms f(x) f(x) = exp(x/7)*cos(2*x); sol = findzeros(f,[15 25])'```
```sol = $\left(\begin{array}{c}16.493361431346414501928877762217\\ 18.064157758141311121160199453857\\ 19.634954084936207740391521145497\\ 21.205750411731104359622842837137\\ 22.776546738526000978854164528776\\ 24.347343065320897598085486220416\end{array}\right)$```
### Obtain Solutions to Arbitrary Precision
Use `digits` to set the precision of the solutions returned by `vpasolve`. By default, `vpasolve` returns solutions to a precision of 32 significant figures.
```f = exp(x/7)*cos(2*x); vpasolve(f)```
`ans = $-7.0685834705770347865409476123789$`
Use `digits` to increase the precision to 64 significant figures. When modifying `digits`, ensure that you save its current value so that you can restore it.
```digitsOld = digits; digits(64) vpasolve(f)```
`ans = $-7.068583470577034786540947612378881489443631148593988097193625333$`
Next, change the precision of the solutions to 16 significant figures.
`digits(16)`
### Solve Multivariate Equations Using Search Ranges
Consider the following system of equations.
`$\begin{array}{l}\mathit{z}=10\left(\mathrm{cos}\left(\mathit{x}\right)+\mathrm{cos}\left(\mathit{y}\right)\right)\\ \mathit{z}=\mathit{x}+{\mathit{y}}^{2}-0.1{\mathit{x}}^{2}\mathit{y}\\ \mathit{x}+\mathit{y}-2.7=0\end{array}$`
A plot of the equations for $0\le x\le 2.5$ and $0\le x\le 2.5$ shows that the three surfaces intersect in two points. To better visualize the plot, use `view`. To scale the colormap values, use `caxis`.
```syms x y z eqn1 = z == 10*(cos(x) + cos(y)); eqn2 = z == x+y^2-0.1*x^2*y; eqn3 = x+y-2.7 == 0; equations = [eqn1 eqn2 eqn3]; fimplicit3(equations) axis([0 2.5 0 2.5 -20 10]) title('System of Multivariate Equations') view(69, 28) caxis([-15 10])```
Use `vpasolve` to find a point where the surfaces intersect. The function `vpasolve` returns a structure. To access the `x`-, `y`-, and `z`-values of the solution, index into the structure.
```sol = vpasolve(equations); [sol.x sol.y sol.z]```
`ans = $\left(\begin{array}{ccc}2.369747722454798& 0.3302522775452021& 2.293354376823228\end{array}\right)$`
To search a region of the solution space, specify search ranges for the variables. If you specify the ranges $0\le x\le 1.5$ and $1.5\le y\le 2.5$, then `vpasolve` function searches the bounded area shown.
Use `vpasolve` to find a solution for this search range. To omit a search range for $z$, set the third search range to `[NaN NaN]`.
```vars = [x y z]; range = [0 1.5; 1.5 2.5; NaN NaN]; sol = vpasolve(equations, vars, range); [sol.x sol.y sol.z]```
`ans = $\left(\begin{array}{ccc}0.9106266172563336& 1.789373382743666& 3.964101572135625\end{array}\right)$`
To find multiple solutions, set the `'Random'` option to `true`. This makes `vpasolve` use random starting points on successive runs. The `'Random'` option can be used in conjunction with search ranges to make `vpasolve` use random starting points within a search range. Because `'Random'` selects starting points randomly, the same solution might be found on successive calls. Call `vpasolve` repeatedly to ensure you find both solutions.
```clear sol range = [0 3; 0 3; NaN NaN]; for k = 1:5 temp = vpasolve(equations,vars,range,'Random',true); sol(k,1) = temp.x; sol(k,2) = temp.y; sol(k,3) = temp.z; end sol```
```sol = $\left(\begin{array}{ccc}2.369747722454798& 0.3302522775452021& 2.293354376823228\\ 2.369747722454798& 0.3302522775452021& 2.293354376823228\\ 2.369747722454798& 0.330252277545202& 2.293354376823228\\ 0.9106266172563336& 1.789373382743666& 3.964101572135625\\ 0.9106266172563336& 1.789373382743666& 3.964101572135625\end{array}\right)$```
Plot the equations. Superimpose the solutions as a scatter plot of points with yellow `X` markers using `scatter3`. To better visualize the plot, make two of the surfaces transparent using `alpha`. Scale the colormap to the plot values using `caxis`, and change the perspective using `view`.
`vpasolve` finds solutions at the intersection of the surfaces formed by the equations as shown.
```clf ax = axes; h = fimplicit3(equations); h(2).FaceAlpha = 0; h(3).FaceAlpha = 0; axis([0 2.5 0 2.5 -20 10]) hold on scatter3(sol(:,1),sol(:,2),sol(:,3),600,'yellow','X','LineWidth',2) title('Randomly Found Solutions in Specified Search Range') cz = ax.Children; caxis([0 20]) view(69,28) hold off```
Lastly, restore the old value of `digits` for further calculations.
`digits(digitsOld)`
## Support
#### Mathematical Modeling with Symbolic Math Toolbox
Get examples and videos | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 31, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5780974626541138, "perplexity": 997.4276824977808}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-25/segments/1623488269939.53/warc/CC-MAIN-20210621085922-20210621115922-00201.warc.gz"} |
http://www.purplemath.com/learning/viewtopic.php?f=9&t=2387&p=6928 | ## Negative Exponent Problem
Complex numbers, rational functions, logarithms, sequences and series, matrix operations, etc.
maroonblazer
Posts: 51
Joined: Thu Aug 12, 2010 11:16 am
Contact:
### Negative Exponent Problem
Hi,
The problem states:
"Write the following expression with only positive exponents and in simplest form. Variables are not equal to zero".
$x^{-1} + x^{-5}$
$\frac{x^4+1}{x^5}$
From the initial expression I get:
$\frac{1}{x} + \frac{1}{x^5}$
It's here that I get stuck. The next step seems like it would be:
$\frac{1}{x}+\frac{1}{x(x^5)}$
From there you'd go:
$\frac{1}{2x(x^4)}$
But that seems to go nowhere.
Help?
Thanks,
mb
stapel_eliz
Posts: 1628
Joined: Mon Dec 08, 2008 4:22 pm
Contact:
$\frac{1}{x} + \frac{1}{x^5}$
It's here that I get stuck. The next step seems like it would be:
$\frac{1}{x}+\frac{1}{x(x^5)}$
This would be like trying to convert "1/2 + 1/32" to a common denominator by multiplying 32 by 2, but "2" and "64" aren't "common". Instead, you'd need to convert the "2" to "32": (1/2)(1/16) + 1/32 = 16/32 + 1/32 = (16 + 1)/32.
Use that same process here.
maroonblazer
Posts: 51
Joined: Thu Aug 12, 2010 11:16 am
Contact:
### Re: Negative Exponent Problem
Instead, you'd need to convert the "2" to "32":
I love you!
$\frac{1}{x}*\frac{x^4}{x^4} + \frac{1}{x^5}=\frac{x^4+1}{x^5}$
Thank you,
mb | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 8, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6773509383201599, "perplexity": 2925.398187386921}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-13/segments/1490218189198.71/warc/CC-MAIN-20170322212949-00548-ip-10-233-31-227.ec2.internal.warc.gz"} |
http://questionpaper.org/progressions/ | Progressions Formulas, Tricks and Shortcuts
Arithmetic Progressions Page - 2
Geometric Progressions Page - 3
Progressions Important Questions Page - 6
Sequences, following specific patterns are called progressions. Arithmetic progression (A.P). In this Chapter, besides discussing more about A.P.; arithmetic mean, geometric mean, relationship between A.M. and G.M., special series in forms of sum to n terms of consecutive natural numbers, sum to n terms of squares of natural numbers and sum to n terms of cubes of natural numbers will also be studied.
Sequences
Let the number of person’s ancestors for the first, second, third, ..., tenth generations are 2, 4, 8, 16, 32, ..., 1024. These numbers form what we call a sequence. Consider the successive quotients that we obtain in the division of 10 by 3 at different steps of division. In this process we get 3,3.3,3.33,3.333, ... and so on. These quotients also form a sequence. The various numbers occurring in a sequence are called its term . We denote the terms of a sequence by $a_{1},a_{2},a_{3},.....,a_{n}$ etc, the subscripts denote the position of the term. The $n^{th}$ term is the number at the position of the sequence and is denoted by $a_{n}$ The $n^{th}$ term is also called the general term of the sequence.
A sequence is called infinite, if it is not a finite sequence. For example, the sequence of successive quotients mentioned above is an infinite sequence, infinite in the sense that it never ends .Often, it is possible to express the rule, which yields the various terms of a sequencein terms of algebraic formula. Consider for instance, the sequence of even natural number 2, 4, 6,...
Here, $a_{1}=2=2\times 1,a_{2}=4=2\times 2,a_{3}=6=2\times 3,........a_{23}=46=2\times 23,a_{24}=48=2\times 24$, and so on. In some cases, an arrangement of numbers such as 1, 1, 2, 3, 5, 8,.. has no visible pattern, but the sequence is generated by the recurrence relation given by.
$a_{1}=a_{2}=1,a_{3}=a_{1}+a_{2},a_{n}=a_{n+2}+a_{n-1},n> 2$
Above sequence is called Fibonacci sequence
Series
$a_{1},a_{2},a_{3},.....,a_{n}$ be a given sequence. Then, the expression$a_{1}+a_{2}+a_{3}+.....+a_{n}$ s called the series associated with the given sequence. The series is finite or infinite according as the given sequence is finite or infinite. Series are often represented in compact form called sigma notation as means indicating the summation involved .Thus , the series $a_{1}+a_{2}+a_{3}+.....+a_{n}$ is abbreviated . as $\sum_{k-1}^{n}$
Note: When the series is used, it refers to the indicated sum not to the sum itself. For example, 1 + 3 + 5 + 7 is a finite series with four terms. When we use the phrase “ sum of a series,” we will mean the number that results from adding the terms, the
sum of the series is 16. | {"extraction_info": {"found_math": true, "script_math_tex": 10, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 10, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.970672070980072, "perplexity": 309.6462629604256}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-09/segments/1550247479885.8/warc/CC-MAIN-20190216045013-20190216071013-00403.warc.gz"} |
https://rd.springer.com/chapter/10.1007/978-3-319-63133-2_1 | Advertisement
# Chapter 1 Basics of Electrostatics
• Andrea Macchi
• Giovanni Moruzzi
• Francesco Pegoraro
Chapter
## Abstract
The electric charge. The electric field. The superposition principle. Gauss’s law. Symmetry considerations. The electric field of simple charge distributions (plane layer, straight wire, sphere). Point charges and Coulomb’s law. The equations of electrostatics. Potential energy and electric potential. The equations of Poisson and Laplace. Electrostatic energy. Multipole expansions. The field of an electric dipole.
Topics. The electric charge. The electric field. The superposition principle. Gauss’s law. Symmetry considerations. The electric field of simple charge distributions (plane layer, straight wire, sphere). Point charges and Coulomb’s law. The equations of electrostatics. Potential energy and electric potential. The equations of Poisson and Laplace. Electrostatic energy. Multipole expansions. The field of an electric dipole.
Units. An aim of this book is to provide formulas compatible with both SI (French: Système International d’Unités) units and Gaussian units in Chapters , while only Gaussian units will be used in Chapters . This is achieved by introducing some system-of-units-dependent constants.
The first constant we need is Coulomb’s constant, $$k_\mathrm{e}$$, which for instance appears in the expression for the force between two electric point charges $$q_1$$ and $$q_2$$ in vacuum, with position vectors $$\mathbf {r}_1$$ and $$\mathbf {r}_2$$, respectively. The Coulomb force acting, for instance, on $$q_1$$ is
\begin{aligned} \mathbf {f}_1=k_\mathrm{e}\frac{q_1q_2}{|\mathbf {r}_1-\mathbf {r}_2|^2}\,\hat{\mathbf {r}}_{12}\,, \end{aligned}
(1.1)
where $$k_\mathrm{e}$$ is Coulomb’s constant, dependent on the units used for force, electric charge, and length. The vector $$\mathbf {r}_{12}=\mathbf {r}_1-\mathbf {r}_2$$ is the distance from $$q_2$$ to $$q_1$$, pointing towards $$q_1$$, and $$\hat{\mathbf {r}}_{12}$$ the corresponding unit vector. Coulomb’s constant is
\begin{aligned} k_\mathrm{e}=\left\{ \begin{array}{ll} \displaystyle \frac{1}{4\pi \varepsilon _0} 8.987\,\cdots \times 10^9\ \mathrm {N\cdot m^2\cdot C}^{-2} \simeq 9\times 10^9 \text{ m/F }&{}\quad \text{ SI }\\ 1&{}\quad \text{ Gaussian. } \end{array} \right. \end{aligned}
(1.2)
Constant $$\varepsilon _0\simeq 8.854\, 187\, 817\, 620\,\cdots \times 10^{-12}$$ F/m is the so-called “dielectric permittivity of free space”, and is defined by the formula
\begin{aligned} \varepsilon _0=\frac{1}{\mu _0 c^2}\,, \end{aligned}
(1.3)
where $$\mu _0=4\pi \times 10^{-7}$$ H/m (by definition) is the vacuum magnetic permeability, and c is the speed of light in vacuum, $$c=299\, 792\, 458$$ m/s (this is a precise value, since the length of the meter is defined from this constant and the international standard for time).
Basic equations The two basic equations of this Chapter are, in differential and integral form,
\begin{aligned} \varvec{\nabla }\cdot \mathbf {E}&=4\pi k_\mathrm{e}\, \varrho \,,&\oint _S\mathbf {E}\cdot \mathrm {d}\mathbf {S}&=4\pi k_\mathrm{e}\int _V\varrho \,\mathrm {d}^3 r \; \end{aligned}
(1.4)
\begin{aligned} \varvec{\nabla }\times \mathbf {E}&=0 \,,&\oint _C\mathbf {E}\cdot \mathrm {d}\mathbf {\ell }&=0 \; . \end{aligned}
(1.5)
where $$\mathbf {E}(\mathbf {r}, t)$$ is the electric field, and $$\varrho (\mathbf {r}, t)$$ is the volume charge density, at a point of location vector $$\mathbf {r}$$ at time t. The infinitesimal volume element is $$\mathrm{d}^3r=\mathrm{d}x\,\mathrm{d}y\,\mathrm{d}z$$. In (1.4) the functions to be integrated are evaluated over an arbitrary volume V, or over the surface S enclosing the volume V. The function to be integrated in (1.5) is evaluated over an arbitrary closed path C. Since $$\varvec{\nabla }\times \mathbf {E}=0$$, it is possible to define an electric potential $$\varphi =\varphi (\mathbf {r})$$ such that
\begin{aligned} \mathbf {E}=-\varvec{\nabla }\varphi \; . \end{aligned}
(1.6)
The general expression of the potential generated by a given charge distribution $$\varrho (\mathbf {r})$$ is
\begin{aligned} \varphi (\mathbf {r}) =k_\mathrm{e}\int _V\frac{\varrho (\mathbf {r}')}{|\mathbf {r} -\mathbf {r}'|}\,\mathrm{d}^3 r'\;. \end{aligned}
(1.7)
The force acting on a volume charge distribution $$\varrho (\mathbf {r})$$ is
\begin{aligned} \mathbf {f}=\int _V\varrho (\mathbf {r}')\,\mathbf {E}(\mathbf {r}')\,\mathrm{d}^3 r'\;. \end{aligned}
(1.8)
As a consequence, the force acting on a point charge q located at $$\mathbf {r}$$ (which corresponds to a charge distribution $$\varrho (\mathbf {r}')=q\delta (\mathbf {r}-\mathbf {r}')$$, with $$\delta (\mathbf {r})$$ the Dirac-delta function) is
\begin{aligned} \mathbf {f}=q\,\mathbf {E}(\mathbf {r})\; . \end{aligned}
(1.9)
The electrostatic energy $$U_{\mathrm{es}}$$ associated with a given distribution of electric charges and fields is given by the following expressions
\begin{aligned} U_\mathrm{es}= & {} \int _V \frac{\mathbf {E}^2}{8\pi k_\mathrm{e}}\,\mathrm {d}^3 r \; . \end{aligned}
(1.10)
\begin{aligned} U_\mathrm{es}= & {} \frac{1}{2}\int _V \varrho \,\varphi \,\mathrm {d}^3r \; , \end{aligned}
(1.11)
Equations (1.101.11) are valid provided that the volume integrals are finite and that all involved quantities are well defined.
The multipole expansion allows us to obtain simple expressions for the leading terms of the potential and field generated by a charge distribution at a distance much larger than its extension. In the following we will need only the expansion up to the dipole term,
\begin{aligned} \varphi (\mathbf {r}) \simeq k_\mathrm{e}\left( \frac{Q}{r}+\frac{\mathbf {p}\cdot \mathbf {r}}{r^3} +\ldots \right) \; , \end{aligned}
(1.12)
where Q is the total charge of the distribution and the electric dipole moment is
\begin{aligned} \mathbf {p}\equiv \int _V\mathbf {r}'\rho (\mathbf {r}')\mathrm{d}^3\mathbf {r}' \; . \end{aligned}
(1.13)
If $$Q=0$$, then $$\mathbf {p}$$ is independent on the choice of the origin of the reference frame. The field generated by a dipolar distribution centered at $$\mathbf {r}=0$$ is
\begin{aligned} \mathbf {E}=k_\mathrm{e}\frac{3\hat{\mathbf {r}}(\mathbf {p}\cdot \hat{\mathbf {r}})-\mathbf {p}}{r^3} \; . \end{aligned}
(1.14)
We will briefly refer to a localized charge distribution having a dipole moment as “an electric dipole” (the simplest case being two opposite point charges $$\pm q$$ with a spatial separation $$\mathbf {\delta }$$, so that $$\mathbf {p}=q\mathbf {\delta }$$). A dipole placed in an external field $$\mathbf {E}_\mathrm{ext}$$ has a potential energy
\begin{aligned} U_\mathrm{p}=-\mathbf {p}\cdot \mathbf {E}_\mathrm{ext} \; . \end{aligned}
(1.15)
## 1.1 Overlapping Charged Spheres
We assume that a neutral sphere of radius R can be regarded as the superposition of two “rigid” spheres: one of uniform positive charge density $$+\varrho _0$$, comprising the nuclei of the atoms, and a second sphere of the same radius, but of negative uniform charge density $$-\varrho _0$$, comprising the electrons. We further assume that its is possible to shift the two spheres relative to each other by a quantity $$\mathbf {\delta }$$, as shown in Fig. 1.1, without perturbing the internal structure of either sphere.
Find the electrostatic field generated by the global charge distribution
a) in the “inner” region, where the two spheres overlap,
b) in the “outer” region, i.e., outside both spheres, discussing the limit of small displacements $$\delta \ll R$$.
## 1.2 Charged Sphere with Internal Spherical Cavity
A sphere of radius a has uniform charge density $$\varrho$$ over all its volume, excluding a spherical cavity of radius $$b<a$$, where $$\varrho =0$$. The center of the cavity, $$O_b$$ is located at a distance $$\mathbf {d}$$, with $$|\mathbf {d}|<(a-b)$$, from the center of the sphere, $$O_a$$. The mass distribution of the sphere is proportional to its charge distribution.
a) Find the electric field inside the cavity.
Now we apply an external, uniform electric field $$\mathbf {E}_0$$. Find
b) the force on the sphere,
c) the torque with respect to the center of the sphere, and the torque with respect to the center of mass.
## 1.3 Energy of a Charged Sphere
A total charge Q is distributed uniformly over the volume of a sphere of radius R . Evaluate the electrostatic energy of this charge configuration in the following three alternative ways:
a) Evaluate the work needed to assemble the charged sphere by moving successive infinitesimals shells of charge from infinity to their final location.
b) Evaluate the volume integral of $$u_{\mathrm{E}}=|\mathbf {E}|^2/(8\pi k_\mathrm{e})$$ where $$\mathbf {E}$$ is the electric field [Eq. (1.10)].
c) Evaluate the volume integral of $$\varrho \,\phi /2$$ where $$\varrho$$ is the charge density and $$\phi$$ is the electrostatic potential [Eq. (1.11)]. Discuss the differences with the calculation made in b).
## 1.4 Plasma Oscillations
A square metal slab of side L has thickness h, with $$h\ll L$$ . The conduction-electron and ion densities in the slab are $$n_{\mathrm{e}}$$ and $$n_{i}=n_{\mathrm{e}}/Z$$, respectively, Z being the ion charge.
An external electric field shifts all conduction electrons by the same amount $$\delta$$, such that $$|\delta |\ll h$$, perpendicularly to the base of the slab. We assume that both $$n_{\mathrm{e}}$$ and $$n_{i}$$ are constant, that the ion lattice is unperturbed by the external field, and that boundary effects are negligible.
a) Evaluate the electrostatic field generated by the displacement of the electrons.
b) Evaluate the electrostatic energy of the system.
Now the external field is removed, and the “electron slab” starts oscillating around its equilibrium position.
c) Find the oscillation frequency, at the small displacement limit ($$\delta \ll h$$).
## 1.5 Mie Oscillations
Now, instead of a the metal slab of Problem 1.4, consider a metal sphere of radius R. Initially, all the conduction electrons ($$n_{\mathrm{e}}$$ per unit volume) are displaced by $$-\mathbf {\delta }$$ (with $$\delta \ll R$$) by an external electric field, analogously to Problem 1.1.
a) At time $$t=0$$ the external field is suddenly removed. Describe the subsequent motion of the conduction electrons under the action of the self-consistent electrostatic field, neglecting the boundary effects on the electrons close to the surface of the sphere.
b) At the limit $$\delta \rightarrow 0$$ (but assuming $$en_{\mathrm{e}}\delta =\sigma _0$$ to remain finite, i.e., the charge distribution is a surface density), find the electrostatic energy of the sphere as a function of $$\delta$$ and use the result to discuss the electron motion as in point a).
## 1.6 Coulomb explosions
At $$t=0$$ we have a spherical cloud of radius R and total charge Q , comprising N point-like particles. Each particle has charge $$q=Q/N$$ and mass m. The particle density is uniform, and all particles are at rest.
a) Evaluate the electrostatic potential energy of a charge located at a distance $$r<R$$ from the center at $$t=0$$.
b) Due to the Coulomb repulsion, the cloud begins to expand radially, keeping its spherical symmetry. Assume that the particles do not overtake one another, i.e., that if two particles were initially located at $$r_{\scriptscriptstyle 1}(0)$$ and $$r_{\scriptscriptstyle 2}(0)$$, with $$r_{\scriptscriptstyle 2}(0)>r_{\scriptscriptstyle 1}(0)$$, then $$r_{\scriptscriptstyle 2}(t)>r_{\scriptscriptstyle 1}(t)$$ at any subsequent time $$t>0$$. Consider the particles located in the infinitesimal spherical shell $$r_0<r_{\mathrm{s}}<r_0+\mathrm {d}r$$, with $$r_0+\mathrm{d}r<R$$, at $$t=0$$. Show that the equation of motion of the layer is
\begin{aligned} m\,\frac{\mathrm {d}^2r_{\mathrm{s}}}{\mathrm {d}t^2}=k_\mathrm{e}\frac{qQ}{r_{\mathrm{s}}^2 } \left( \frac{r_0}{R}\right) ^3 \end{aligned}
(1.16)
c) Find the initial position of the particles that acquire the maximum kinetic energy during the cloud expansion, and determinate the value of such maximum energy.
d) Find the energy spectrum, i.e., the distribution of the particles as a function of their final kinetic energy. Compare the total kinetic energy with the potential energy initially stored in the electrostatic field.
e) Show that the particle density remains spatially uniform during the expansion.
## 1.7 Plane and Cylindrical Coulomb Explosions
Particles of identical mass m and charge q are distributed with zero initial velocity and uniform density $$n_0$$ in the infinite slab $$|x|<a/2$$ at $$t=0$$. For $$t>0$$ the slab expands because of the electrostatic repulsion between the pairs of particles.
a) Find the equation of motion for the particles, its solution, and the kinetic energy acquired by the particles.
b) Consider the analogous problem of the explosion of a uniform distribution having cylindrical symmetry.
## 1.8 Collision of two Charged Spheres
Two rigid spheres have the same radius R and the same mass M, and opposite charges $$\pm Q$$. Both charges are uniformly and rigidly distributed over the volumes of the two spheres. The two spheres are initially at rest, at a distance $$x_0\gg R$$ between their centers, such that their interaction energy is negligible compared to the sum of their “internal" (construction) energies.
a) Evaluate the initial energy of the system.
The two spheres, having opposite charges, attract each other, and start moving at $$t=0$$.
b) Evaluate the velocity of the spheres when they touch each other (i.e. when the distance between their centers is $$x=2R$$).
c) Assume that, after touching, the two spheres penetrate each other without friction. Evaluate the velocity of the spheres when the two centers overlap ($$x=0$$).
## 1.9 Oscillations in a Positively Charged Conducting Sphere
An electrically neutral metal sphere of radius a contains N conduction electrons. A fraction f of the conduction electrons ($$0<f<1$$) is removed from the sphere, and the remaining $$(1-f)N$$ conduction electrons redistribute themselves to an equilibrium configurations, while the N lattice ions remain fixed.
a) Evaluate the conduction-electron density and the radius of their distribution in the sphere.
Now the conduction-electron sphere is rigidly displaced by $$\varvec{\delta }$$ relatively to the ion lattice, with $$|\varvec{\delta }|$$ small enough for the conduction-electron sphere to remain inside the ion sphere.
b) Evaluate the electric field inside the conduction-electron sphere.
c) Evaluate the oscillation frequency of the conduction-electron sphere when it is released.
## 1.10 Interaction between a Point Charge and an Electric Dipole
An electric dipole $$\mathbf {p}$$ is located at a distance $$\mathbf {r}$$ from a point charge q , as in Fig. 1.5. The angle between $$\mathbf {p}$$ and $$\mathbf {r}$$ is $$\theta$$.
a) Evaluate the electrostatic force on the dipole.
b) Evaluate the torque acting on the dipole.
## 1.11 Electric Field of a Charged Hemispherical Surface
A hemispherical surface of radius R is uniformly charged with surface charge density $$\sigma$$. Evaluate the electric field and potential at the center of curvature (hint: start from the electric field of a uniformly charged ring along its axis).
## Copyright information
© Springer International Publishing AG 2017
## Authors and Affiliations
• Andrea Macchi
• 1
Email author
• Giovanni Moruzzi
• 1
• Francesco Pegoraro
• 1
1. 1.Department of Physics “Enrico Fermi”University of PisaPisaItaly | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 2, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9898863434791565, "perplexity": 732.3336405263501}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-22/segments/1558232257845.26/warc/CC-MAIN-20190525004721-20190525030721-00026.warc.gz"} |
http://web.emn.fr/x-info/sdemasse/gccat/Cdisjoint_tasks.html | ## 5.107. disjoint_tasks
DESCRIPTION LINKS GRAPH
Origin
Constraint
$\mathrm{𝚍𝚒𝚜𝚓𝚘𝚒𝚗𝚝}_\mathrm{𝚝𝚊𝚜𝚔𝚜}\left(\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1},\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}\right)$
Arguments
$\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ $\mathrm{𝚌𝚘𝚕𝚕𝚎𝚌𝚝𝚒𝚘𝚗}\left(\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-\mathrm{𝚍𝚟𝚊𝚛},\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-\mathrm{𝚍𝚟𝚊𝚛},\mathrm{𝚎𝚗𝚍}-\mathrm{𝚍𝚟𝚊𝚛}\right)$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$ $\mathrm{𝚌𝚘𝚕𝚕𝚎𝚌𝚝𝚒𝚘𝚗}\left(\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-\mathrm{𝚍𝚟𝚊𝚛},\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-\mathrm{𝚍𝚟𝚊𝚛},\mathrm{𝚎𝚗𝚍}-\mathrm{𝚍𝚟𝚊𝚛}\right)$
Restrictions
$\mathrm{𝚛𝚎𝚚𝚞𝚒𝚛𝚎}_\mathrm{𝚊𝚝}_\mathrm{𝚕𝚎𝚊𝚜𝚝}$$\left(2,\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1},\left[\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗},\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗},\mathrm{𝚎𝚗𝚍}\right]\right)$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}\ge 0$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}\le \mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}.\mathrm{𝚎𝚗𝚍}$ $\mathrm{𝚛𝚎𝚚𝚞𝚒𝚛𝚎}_\mathrm{𝚊𝚝}_\mathrm{𝚕𝚎𝚊𝚜𝚝}$$\left(2,\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2},\left[\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗},\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗},\mathrm{𝚎𝚗𝚍}\right]\right)$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}\ge 0$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}\le \mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}.\mathrm{𝚎𝚗𝚍}$
Purpose
Each task of the collection $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ should not overlap any task of the collection $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$. Two tasks overlap if they have an intersection that is strictly greater than zero.
Example
$\left(\begin{array}{c}〈\begin{array}{ccc}\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-6\hfill & \mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-5\hfill & \mathrm{𝚎𝚗𝚍}-11,\hfill \\ \mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-8\hfill & \mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-2\hfill & \mathrm{𝚎𝚗𝚍}-10\hfill \end{array}〉,\hfill \\ 〈\begin{array}{ccc}\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-2\hfill & \mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-2\hfill & \mathrm{𝚎𝚗𝚍}-4,\hfill \\ \mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-3\hfill & \mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-3\hfill & \mathrm{𝚎𝚗𝚍}-6,\hfill \\ \mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}-12\hfill & \mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}-1\hfill & \mathrm{𝚎𝚗𝚍}-13\hfill \end{array}〉\hfill \end{array}\right)$
Figure 5.107.1 displays the two groups of tasks (i.e., the tasks of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ and the tasks of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$). Since no task of the first group overlaps any task of the second group, the $\mathrm{𝚍𝚒𝚜𝚓𝚘𝚒𝚗𝚝}_\mathrm{𝚝𝚊𝚜𝚔𝚜}$ constraint holds.
Typical
$|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}|>1$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}>0$ $|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}|>1$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}>0$
Symmetries
• Arguments are permutable w.r.t. permutation $\left(\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1},\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}\right)$.
• Items of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ are permutable.
• Items of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$ are permutable.
• One and the same constant can be added to the $\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}$ and $\mathrm{𝚎𝚗𝚍}$ attributes of all items of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ and $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$.
Remark
Despite the fact that this is not an uncommon constraint, it cannot be modelled in a compact way with one single $\mathrm{𝚌𝚞𝚖𝚞𝚕𝚊𝚝𝚒𝚟𝚎}$ constraint. But it can be expressed by using the $\mathrm{𝚌𝚘𝚕𝚘𝚞𝚛𝚎𝚍}_\mathrm{𝚌𝚞𝚖𝚞𝚕𝚊𝚝𝚒𝚟𝚎}$ constraint: We assign a first colour to the tasks of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ as well as a second distinct colour to the tasks of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$. Finally we set up a limit of 1 for the maximum number of distinct colours allowed at each time point.
Reformulation
The $\mathrm{𝚍𝚒𝚜𝚓𝚘𝚒𝚗𝚝}_\mathrm{𝚝𝚊𝚜𝚔𝚜}$ constraint can be expressed in term of $|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}|·|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}|$ reified constraints. For each task $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}\left[i\right]$ $\left(i\in \left[1,|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}|\right]\right)$ and for each task $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}\left[j\right]$ $\left(j\in \left[1,|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}|\right]\right)$ we generate a reified constraint of the form $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}\left[i\right].\mathrm{𝚎𝚗𝚍}\le \mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}\left[j\right].\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}\vee \mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}\left[j\right].\mathrm{𝚎𝚗𝚍}\le \mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}\left[i\right].\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}$. In addition we also state for each task an arithmetic constraint that states that the end of a task is equal to the sum of its origin and its duration.
Systems
See also
generalisation: $\mathrm{𝚌𝚘𝚕𝚘𝚞𝚛𝚎𝚍}_\mathrm{𝚌𝚞𝚖𝚞𝚕𝚊𝚝𝚒𝚟𝚎}$ (tasks colours and limit on maximum number of colours in parallel are explicitly given).
specialisation: $\mathrm{𝚍𝚒𝚜𝚓𝚘𝚒𝚗𝚝}$ ($\mathrm{𝚝𝚊𝚜𝚔}$ replaced by $\mathrm{𝚟𝚊𝚛𝚒𝚊𝚋𝚕𝚎}$).
Keywords
Arc input(s)
$\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$
Arc generator
$\mathrm{𝑆𝐸𝐿𝐹}$$↦\mathrm{𝚌𝚘𝚕𝚕𝚎𝚌𝚝𝚒𝚘𝚗}\left(\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}\right)$
Arc arity
Arc constraint(s)
$\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}+\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}=\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚎𝚗𝚍}$
Graph property(ies)
$\mathrm{𝐍𝐀𝐑𝐂}$$=|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}|$
Arc input(s)
$\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$
Arc generator
$\mathrm{𝑆𝐸𝐿𝐹}$$↦\mathrm{𝚌𝚘𝚕𝚕𝚎𝚌𝚝𝚒𝚘𝚗}\left(\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}\right)$
Arc arity
Arc constraint(s)
$\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}+\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}=\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚎𝚗𝚍}$
Graph property(ies)
$\mathrm{𝐍𝐀𝐑𝐂}$$=|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}|$
Arc input(s)
$\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$
Arc generator
$\mathrm{𝑃𝑅𝑂𝐷𝑈𝐶𝑇}$$↦\mathrm{𝚌𝚘𝚕𝚕𝚎𝚌𝚝𝚒𝚘𝚗}\left(\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1},\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}\right)$
Arc arity
Arc constraint(s)
$•\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}>0$ $•\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚍𝚞𝚛𝚊𝚝𝚒𝚘𝚗}>0$ $•\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}<\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚎𝚗𝚍}$ $•\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{2}.\mathrm{𝚘𝚛𝚒𝚐𝚒𝚗}<\mathrm{𝚝𝚊𝚜𝚔𝚜}\mathtt{1}.\mathrm{𝚎𝚗𝚍}$
Graph property(ies)
$\mathrm{𝐍𝐀𝐑𝐂}$$=0$
Graph model
$\mathrm{𝑃𝑅𝑂𝐷𝑈𝐶𝑇}$ is used in order to generate the arcs of the graph between all the tasks of the collection $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ and all tasks of the collection $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$. The first two graph constraints respectively enforce for each task of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ and $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$ the fact that the end of a task is equal to the sum of its origin and its duration. The arc constraint of the third graph constraint depicts the fact that two tasks overlap. Therefore, since we use the graph property $\mathrm{𝐍𝐀𝐑𝐂}$ $=$ 0 the final graph associated with the third graph constraint will be empty and no task of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ will overlap any task of $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{2}$. Figure 5.107.2 shows the initial graph of the third graph constraint associated with the Example slot. Because of the graph property $\mathrm{𝐍𝐀𝐑𝐂}$ $=$ 0 the corresponding final graph is empty.
Signature
Since $\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}$ is the maximum number of arcs of the final graph associated with the first graph constraint we can rewrite $\mathrm{𝐍𝐀𝐑𝐂}$ $=$ $|\mathrm{𝚃𝙰𝚂𝙺𝚂}\mathtt{1}|$. This leads to simplify $\underline{\overline{\mathrm{𝐍𝐀𝐑𝐂}}}$ to $\overline{\mathrm{𝐍𝐀𝐑𝐂}}$.
We can apply a similar remark for the second graph constraint.
Finally, since 0 is the smallest number of arcs of the final graph we can rewrite $\mathrm{𝐍𝐀𝐑𝐂}$ $=$ 0 to $\mathrm{𝐍𝐀𝐑𝐂}$ $\le$ 0. This leads to simplify $\underline{\overline{\mathrm{𝐍𝐀𝐑𝐂}}}$ to $\underline{\mathrm{𝐍𝐀𝐑𝐂}}$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 93, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7691190838813782, "perplexity": 427.0178047052938}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-44/segments/1476988719465.22/warc/CC-MAIN-20161020183839-00451-ip-10-171-6-4.ec2.internal.warc.gz"} |
http://mathhelpforum.com/statistics/206377-fibonacci-sequence-question-print.html | # Fibonacci Sequence question
Show 40 post(s) from this thread on one page
Page 1 of 2 12 Last
• Oct 30th 2012, 05:42 AM
Arkious
Fibonacci Sequence question
Hey all,
Im hoping you guys could point me in the right direction after getting myself rather lost with a question on my assignment. I am not putting the actual question as i would like to work it out myself. here is a question i have made up that is similar with what i think to be correct. Could anyone verify this or point me in the right direction?
Thanks!
Let Fn be the Fibonacci sequence.
Use the Fibonacci recurrence relation to express Fn+3 in terms of Fn+1 and Fn. Hence show that Fn+1 = 1/2(Fn+5 - Fn) for n=0,1,2,...
the next question i have is the same but with Fn+1 = 1/2(Fn+5 + Fn)
then i have to decide wether the formulas would remain true if the sequence Fn were replaced by a sequence with the same recurrence relation as the Fibonacci sequence but with different initial terms, then justify.
So if i look just at the 1st one at the moment, i think that i would get something like this;
Fn+1 = 1/2(Fn+5 - Fn) for n=0,1,2,...
Fn = 1/2(Fn+1 - Fn+1)
Fn = 1/2(Fn+2 + Fn+1)
if that is not correct, how do i work this out properly as im rather stumped :-S
• Oct 30th 2012, 06:27 AM
a tutor
Re: Fibonacci Sequence question
Quote:
Originally Posted by Arkious
Hence show that Fn+1 = 1/2(Fn+5 - Fn) for n=0,1,2,...
but this is not true.
Presumably you meant $F_{n+1}=\frac{1}{2}(F_{n+3}-F_n)$.
• Oct 30th 2012, 06:57 AM
Arkious
Re: Fibonacci Sequence question
Yeah that's the question I actually have, I just didn't want to ask the question I have been given. I'm not 100% with Fibonacci yet. But if you could explain how I would complete the question you have mentioned, I would much much appreciate it
• Oct 30th 2012, 10:23 PM
Salahuddin559
Re: Fibonacci Sequence question
Dont know what you have asked above, the notation is confusing, It gives 2 different expressions for Fn+1 alone. I will try to give you the proof for Fn+1 = 1/2(Fn+3 - Fn).
Fn+3 = Fn+2 + Fn+1
= (Fn+1 + Fn) + Fn+1
= 2Fn+1 + Fn.
Just rearrange terms here.
Salahuddin
Maths online
• Oct 31st 2012, 12:17 AM
Arkious
Re: Fibonacci Sequence question
Yeah that's the problem, it's very confusing!
If i didn't have to show that Fn+1 = 1/2(Fn+3 - Fn) for n=0,1,2,... I would have been able to do it.
Thanks for your input :-) anyone got any ideas though? I'm no further forward.
• Oct 31st 2012, 03:53 AM
a tutor
Re: Fibonacci Sequence question
Did you try to express $F_{n+3}$ in terms of $F_{n+1}$ and $F_n$ ?
You could start by writing $F_{n+3}$ in terms of $F_{n+2}$ and $F_{n+1}$.
• Oct 31st 2012, 05:16 AM
Arkious
Re: Fibonacci Sequence question
right, this is what i have done so far...
in Fibonacci terms;
Fn+3 = Fn+2 + Fn+1
Fn+2 = (Fn+2 + Fn)
Fn+1 = (Fn+2 - Fn)
Fn = (Fn+2 -Fn+1)
(if thats correct)
But then i need to express Fn+1 = 1/2(Fn+3 - Fn)
• Oct 31st 2012, 06:02 AM
Salahuddin559
Re: Fibonacci Sequence question
in Fibonacci terms;
Fn+3 = Fn+2 + Fn+1
Fn+2 = (Fn+1 + Fn)
Correct for these two, but now, get rid of the Fn+2 in the first equation, since we do not have any Fn+2 in our formula. Substitute your Fn+2 = Fn + Fn+1 there, and rearrange terms.
Salahuddin
Maths online
• Nov 1st 2012, 04:06 AM
Arkious
Re: Fibonacci Sequence question
but this still doesnt make sense... how do i then show that Fn+1 = 1/2(Fn+3 - Fn).
surely above is all wrong?
• Nov 1st 2012, 04:23 AM
Arkious
Re: Fibonacci Sequence question
Fn+3 = Fn+2 + Fn+1
(2) = (1) + (1)
Fn+2 = Fn+1 + Fn
(1) = (1) + (0)
Fn+1 = Fn - Fn-1
(1) = (0) - (-1)
Fn = Fn-1 - Fn-2
(0) = (-1) - (-1)
Thats proved that those fibonacci terms are correct, but then how do i then show Fn+1 = 1/2(Fn+3 - Fn)?
• Nov 1st 2012, 04:44 AM
Salahuddin559
Re: Fibonacci Sequence question
Guys, here is the steps.
Fn+3 = Fn+2 + Fn+1
But since Fn+2 = Fn+1 + Fn
Fn+3 = Fn+2 + Fn+1
= (Fn+1 + Fn) + Fn+1
= 2Fn+1 + Fn
Remove Fn, but subtracting it both sides,
Fn+3 - Fn = 2Fn+1.
In other words,
Fn+1 = 1/2(Fn+3 - Fn). This is the same style for many other problems, get it?
Salahuddin
Maths online
• Nov 1st 2012, 04:46 AM
Arkious
Re: Fibonacci Sequence question
Fn+1 = 1/2(Fn+3 - Fn)
(5) = 1/2 ((13) - (3))
(5) = 1/2 (10)
am i supposed to find the solution for Fn then use that to find Fn+3?
I have tried multiple ways and cant find a solution that works for more than one number :-(
• Nov 1st 2012, 04:58 AM
Salahuddin559
Re: Fibonacci Sequence question
Hi Arkious, could you be more specific, I am not able to understand what you are saying. (Basically if you have Fn and Fn+1, you can find Fn+3. But why are you finding the solutions, what is the actual problem?).
Salahuddin
Maths online
• Nov 1st 2012, 05:54 AM
Arkious
Re: Fibonacci Sequence question
Let Fn be the Fibonacci sequence.
Use the Fibonacci recurrence relation to express Fn+3 in terms of Fn+1 and Fn. Hence show that Fn+1 = 1/2(Fn+3 - Fn) for n=0,1,2,...
That is the question i have to answer. My issue is how to show that Fn+1 = 1/2(Fn+3 - Fn).
I dont think that these are of any use for the question i have to answer.
Fn+3 = Fn+2 + Fn+1
Fn+2 = Fn+1 + Fn
Fn+1 = Fn - Fn-1
Fn = Fn-1 - Fn-2
All i need to know is how to answer that question and i think that what i have done so far has confused me more. I just don't understand how im supposed to show that Fn+1 = 1/2(Fn+3 - Fn) for Fn+3 & Fn+1
• Nov 1st 2012, 06:09 AM
a tutor
Re: Fibonacci Sequence question
Quote:
Originally Posted by Arkious
Fn+3 = Fn+2 + Fn+1
Fn+2 = Fn+1 + Fn
These are what you need.
Use the second one to substitute for Fn+2 in the first.
Fn+3 = Fn+2 + Fn+1
becomes
Fn+3 = _?_+_?_ + Fn+1.
Show 40 post(s) from this thread on one page
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http://eprints.iisc.ernet.in/5645/ | # Role of Lys-226 in the Catalytic Mechanism of Bacillus Stearothermophilus Serine HydroxymethylTransferase-Crystal Structure and Kinetic Studies
Bhavani, Siddegowda and Trivedi, V and Jala, VR and Subramanya, HS and Kaul, Purnima and Prakash, V and Appaji, Rao N and Savithri, HS (2005) Role of Lys-226 in the Catalytic Mechanism of Bacillus Stearothermophilus Serine HydroxymethylTransferase-Crystal Structure and Kinetic Studies. In: Biochemistry, 44 (18). pp. 6929-6937.
PDF Role_of_Lys-226.pdf Restricted to Registered users only Download (322Kb) | Request a copy
## Abstract
Serine hydroxymethyltransferase (SHMT), a pyridoxal 5'-phosphate (PLP)-dependent enzyme catalyzes the reversible conversion of L-Ser and tetrahydropteroylglutamate $(H_4PteGlu)$ to Gly and 5,10-methylene tetrahydropteroylglutamate $(CH_2-H_4PteGlu)$. Biochemical and structural studies on this enzyme have implicated several residues in the catalytic mechanism, one of them being the active site lysine, which anchors PLP. It has been proposed that this residue is crucial for product expulsion. However, in other PLP-dependent enzymes, the corresponding residue has been implicated in the proton abstraction step of catalysis. In the present investigation, Lys-226 of Bacillus stearothermophilus SHMT (bsSHMT) was mutated to Met and Gln to evaluate the role of this residue in catalysis. The mutant enzymes contained 1 mol of PLP per mol of subunit suggesting that Schiff base formation with lysine is not essential for PLP binding. The 3D structure of the mutant enzymes revealed that PLP was bound at the active site in an orientation different from that of the wild-type enzyme. In the presence of substrate, the PLP ring was in an orientation superimposable with that of the external aldimine complex of wild-type enzyme. However, the mutant enzymes were inactive, and the kinetic analysis of the different steps of catalysis revealed that there was a drastic reduction in the rate of formation of the quinonoid intermediate. Analysis of these results along with the crystal structures suggested that K-226 is responsible for flipping of PLP from one orientation to another which is crucial for $H_4PteGlu$-dependent $C\alpha$-$C\beta$ bond cleavage of L-Ser.
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https://socratic.org/questions/what-is-the-vertex-of-y-x-2-2-3x-9 | Algebra
Topics
# What is the vertex of y=-(x + 2)^2 - 3x+9?
Jun 19, 2018
get the equation into the standard form of a quadratic
$y = a {x}^{2} + b x + c$
Expand the brackets
$y = - \left({x}^{2} + 4 x + 4\right) - 3 x + 9$
Remove the brackets
$y = - {x}^{2} - 4 x - 4 - 3 x + 9$
Collect like terms
$y = - {x}^{2} - 7 x + 5$
Now use $\frac{- b}{2 a}$ to find the x coordinate of the vertex.
$\frac{- - 7}{2 \times - 1} = \frac{7}{- 2}$
Put this into the equation
$y = - {\left(\frac{7}{- 2}\right)}^{2} - 7 \times \frac{7}{- 2} + 5$
$y = - \frac{49}{4} + \frac{49}{2} + 5$
$y = \frac{69}{4}$
The maximum is $\left(- \frac{7}{2} , \frac{69}{4}\right)$
##### Impact of this question
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https://worldwidescience.org/topicpages/c/chemical+microreactors+reversible.html | #### Sample records for chemical microreactors reversible
1. Chemical microreactor and method thereof
Science.gov (United States)
Morse, Jeffrey D [Martinez, CA; Jankowski, Alan [Livermore, CA
2011-08-09
A method for forming a chemical microreactor includes forming at least one capillary microchannel in a substrate having at least one inlet and at least one outlet, integrating at least one heater into the chemical microreactor, interfacing the capillary microchannel with a liquid chemical reservoir at the inlet of the capillary microchannel, and interfacing the capillary microchannel with a porous membrane near the outlet of the capillary microchannel, the porous membrane being positioned beyond the outlet of the capillary microchannel, wherein the porous membrane has at least one catalyst material imbedded therein.
2. Batch chemical microreactors: Reversible, in-situ UHV sealing of a microcavity
DEFF Research Database (Denmark)
Monkowski, Adam; Johansson, Martin; Nielsen, Jane Hvolbæk
2009-01-01
We propose a new type of microreactor to study heterogeneous catalytic systems. The proposed device operates using a batch reactor scheme, in which catalyst and reactant are introduced in one step and analyzed in a subsequent step. This differs from a flow microreactor in which reaction and analy......We propose a new type of microreactor to study heterogeneous catalytic systems. The proposed device operates using a batch reactor scheme, in which catalyst and reactant are introduced in one step and analyzed in a subsequent step. This differs from a flow microreactor in which reaction...
3. Computer Controlled Chemical Micro-Reactor
International Nuclear Information System (INIS)
Mechtilde, Schaefer; Eduard, Stach; Adreas, Foitzik
2006-01-01
Chemical reactions or chemical equilibria can be influenced and controlled by several parameters. The ratio of two liquid ingredients, the so called reactants or educts, plays an important role in determining the end product and its yield. The reactants must be weighed and accordingly mixed with the conventional batch mode. If the reaction is done in a microreactor or in several parallel working micro-reactors, units for allotting the educts in appropriate quantities are required. In this report we present a novel micro-reactor that allows the constant monitoring of the chemical reaction via Raman spectroscopy. Such monitoring enables an appropriate feedback on the steering parameters for the PC controlled micro-pumps for the appropriate educt flow rate of both liquids to get optimised ratios of ingredients at an optimised total flow rate. The micro-reactors are the core pieces of the design and are easily removable and can therefore be changed at any time to adapt the requirements of the chemical reaction. One type of reactor consists of a stainless steel base containing small scale milled channels covered with anodically bonded Pyrex glass. Another type of reactor has a base of anisotropically etched silicon, and is also covered with anodically bonded Pyrex glass. The glass window allows visual observation of the initial phase interface of the two educts in the reaction channels by optical microscopy and does not affect, in contrast to infrared spectroscopy, the Raman spectroscopic signal for detection of the reaction kinetics. On the basis of a test reaction, we present non-invasive and spatially highly resolved in-situ reaction analysis using Raman spectroscopy measured along the reaction channel at different locations
4. On Study of Application of Micro-reactor in Chemistry and Chemical Field
Science.gov (United States)
Zhang, Yunshen
2018-02-01
Serving as a micro-scale chemical reaction system, micro-reactor is characterized by high heat transfer efficiency and mass transfer, strictly controlled reaction time and good safety performance; compared with the traditional mixing reactor, it can effectively shorten reaction time by virtue of these advantages and greatly enhance the chemical reaction conversion rate. However, problems still exist in the process where micro-reactor is used for production in chemistry and chemical field, and relevant researchers are required to optimize and perfect the performance of micro-reactor. This paper analyzes specific application of micro-reactor in chemistry and chemical field.
5. High-Temperature Compatible Nickel Silicide Thermometer And Heater For Catalytic Chemical Microreactors
DEFF Research Database (Denmark)
Jensen, Søren; Quaade, U.J.; Hansen, Ole
2005-01-01
Integration of heaters and thermometers is important for agile and accurate control and measurement of the thermal reaction conditions in microfabricated chemical reactors (microreactors). This paper describes development and operation of nickel silicide heaters and temperature sensors...... for temperatures exceeding 700 °C. The heaters and thermometers are integrated with chemical microreactors for heterogeneous catalytic conversion of gasses, and thermally activated catalytic conversion of CO to CO2 in the reactors is demonstrated. The heaters and thermometers are shown to be compatible...
6. Whole ceramic-like microreactors from inorganic polymers for high temperature or/and high pressure chemical syntheses.
Science.gov (United States)
Ren, Wurong; Perumal, Jayakumar; Wang, Jun; Wang, Hao; Sharma, Siddharth; Kim, Dong-Pyo
2014-02-21
Two types of whole ceramic-like microreactors were fabricated from inorganic polymers, polysilsesquioxane (POSS) and polyvinylsilazane (PVSZ), that were embedded with either perfluoroalkoxy (PFA) tube or polystyrene (PS) film templates, and subsequently the templates were removed by physical removal (PFA tube) or thermal decomposition (PS). A POSS derived ceramic-like microreactor with a 10 cm long serpentine channel was obtained by an additional "selective blocking of microchannel" step and subsequent annealing at 300 °C for 1 h, while a PVSZ derived ceramic-like microreactor with a 14 cm long channel was yielded by a co-firing process of the PVSZ-PS composite at 500 °C for 2 h that led to complete decomposition of the film template leaving a microchannel behind. The obtained whole ceramic-like microfluidic devices revealed excellent chemical and thermal stabilities in various solvents, and they were able to demonstrate unique chemical performance at high temperature or/and high pressure conditions such as Michaelis-Arbuzov rearrangement at 150-170 °C, Wolff-Kishner reduction at 200 °C, synthesis of super-paramagnetic Fe3O4 nanoparticles at 320 °C and isomerisation of allyloxybenzene to 2-allylphenol (250 °C and 400 psi). These economic ceramic-like microreactors fabricated by a facile non-lithographic method displayed excellent utility under challenging conditions that is superior to any plastic microreactors and comparable to glass and metal microreactors with high cost.
7. Microreactors
NARCIS (Netherlands)
Illg, T.; Hessel, V.
2009-01-01
Microreactors open a novel way of chemical synthesis in a highly controlled way. Due to their improved mass and heat transfer, these devices are well suited, e.g., for mixing-sensitive, fast and highly exothermic reactions. Endothermic reactions profit as well from the improved thermal management.
8. Silicon microreactors for measurements of catalytic activity
DEFF Research Database (Denmark)
Henriksen, Toke Riishøj
The topic of this project is the design and fabrication of chemical microreactors with short response time and high sensitivity to low catalyst areas. The microreactors are intended as analytical tools in experiments concerning heterogeneous catalysis, photocatalysis, and electrocatalysis...... bonding without collapse of 3μm deep, 1 cm diameter circular reaction chambers. During the project, a microreactor has been developed for photocatalysis and heterogeneous catalysis in gas phase reactions. To demonstrate the operation of the microreactor, CO oxidation on low-area platinum thin film circles...
9. Reverse micelles as suitable microreactor for increased biohydrogen production
Energy Technology Data Exchange (ETDEWEB)
Pandey, Anjana [Nanotechnology and Molecular Biology Laboratory, Centre of Biotechnology, University of Allahabad, Allahabad 211002 (India); Pandey, Ashutosh [Centre of Energy Studies, MNNIT, Allahabad 211004 (India)
2008-01-15
Reverse micelles have been shown to act as efficient microreactors for enzymic reactions and whole cell entrapment in organic (non-aqueous) media wherein the reactants are protected from denaturation by the surrounding organic solvent. These micelles are thermodynamically stable, micrometer sized water droplets dispersed in an organic phase by a surfactant. It has been observed that when whole cells of photosynthetic bacteria (Rhodopseudomonas sphaeroides or Rhodobacter sphaeroides 2.4.1) are entrapped inside these reverse micelles, the H{sub 2} production enhanced from 25 to 35 folds. That is, 1.71mmol(mgprotein){sup -1}h{sup -1} in case of R. sphaeroides which is 25 fold higher in benzene-sodium lauryl sulfate reverse micelles. Whereas, in case of R. sphaeroides 2.4.1 the H{sub 2} production was increased by 35 fold within AOT-isooctane reverse micelles i.e. 11.5mmol(mgprotein){sup -1}h{sup -1}. The observations indicate that the entrapment of whole cells of microbes within reverse micelles provides a novel and efficient technique to produce hydrogen by the inexhaustible biological route. The two microorganisms R. sphaeroides 2.4.1 (a photosynthetic bacteria) and Citrobacter Y19 (a facultative anaerobic bacteria) together are also entrapped within AOT-isooctane and H{sub 2} production was measured i.e. 69mmol(mgprotein){sup -1}h{sup -1}. The nitrogenase enzyme responsible for hydrogen production by R. sphaeroides/R. sphaeroides 2.4.1 cells is oxygen sensitive, and very well protected within reverse micelles by the use of combined approach of two cells (R. sphaeroides 2.4.1 and Citrobacter Y19). In this case glucose present in the medium of Citrobacter Y19 serves double roles in enhancing the sustained production rate of hydrogen. Firstly, it quenches the free O{sub 2}liberated as a side product of reaction catalyzed by nitrogenase, which is O{sub 2} labile. Secondly, organic acid produced by this reaction is utilized by the Citrobacter Y19 as organic substrate in
10. Controlling hazardous chemicals in microreactors: Synthesis with iodine azide
Directory of Open Access Journals (Sweden)
Johan C. Brandt
2009-06-01
Full Text Available Aromatic aldehydes have been converted into the corresponding carbamoyl azides using iodine azide. These reactions have been performed safely under continuous flow reaction conditions in microreactors.
11. Parametric study of hydrogen production from ethanol steam reforming in a membrane microreactor
Directory of Open Access Journals (Sweden)
M. de-Souza
2013-06-01
Full Text Available Microreactors are miniaturized chemical reaction systems, which contain reaction channels with characteristic dimensions in the range of 10-500 µm. One possible application for microreactors is the conversion of ethanol to hydrogen used in fuel cells to generate electricity. In this paper a rigorous isothermal, steady-state two-dimensional model was developed to simulate the behavior of a membrane microreactor based on the hydrogen yield from ethanol steam reforming. Furthermore, this membrane microreactor is compared to a membraneless microreactor. A potential advantage of the membrane microreactor is the fact that both ethanol steam reforming and the separation of hydrogen by a permselective membrane occur in one single microdevice. The simulation results for steam reforming yields are in agreement with experimental data found in the literature. The results show that the membrane microreactorpermits a hydrogen yield of up to 0.833 which is more than twice that generated by the membraneless reactor. More than 80% of the generated hydrogen permeates through the membrane and, due to its high selectivity, the membrane microreactor delivers high-purity hydrogen to the fuel cell.
12. Surface Modification for Microreactor Fabrication
Directory of Open Access Journals (Sweden)
2006-04-01
Full Text Available In this paper, methods of surface modification of different supports, i.e. glass andpolymeric beads for enzyme immobilisation are described. The developed method ofenzyme immobilisation is based on Schiff’s base formation between the amino groups onthe enzyme surface and the aldehyde groups on the chemically modified surface of thesupports. The surface of silicon modified by APTS and GOPS with immobilised enzymewas characterised by atomic force microscopy (AFM, time-of-flight secondary ion massspectroscopy (ToF-SIMS and infrared spectroscopy (FTIR. The supports withimmobilised enzyme (urease were also tested in combination with microreactors fabricatedin silicon and Perspex, operating in a flow-through system. For microreactors filled withurease immobilised on glass beads (Sigma and on polymeric beads (PAN, a very high andstable signal (pH change was obtained. The developed method of urease immobilisationcan be stated to be very effective.
13. Microreactor Technology for On-Site Production of Methyl Chloride
Czech Academy of Sciences Publication Activity Database
Schmidt, S.A.; Vajglová, Zuzana; Eränen, K.; Murzin, D.Y.; Salmi, T.
2014-01-01
Roč. 3, č. 5 (2014), s. 345-352 ISSN 2191-9542 Institutional support: RVO:67985858 Keywords : chloromethane * intensification * microreactor * product separation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.125, year: 2014
14. Microreactors - a marvel of modern manufacturing technology: biodiesel case study
CSIR Research Space (South Africa)
Buddoo, SR
2008-11-01
Full Text Available Microreactors are miniature reactors for carrying out chemical reactions. CSIR Biosciences has been investigating the production of biodiesel using various sources of vegetable oils, for example, soya, sunflower, canada, Jatropha, palm and peanuts...
15. The development of flow-through bio-catalyst microreactors from silica micro structured fibers for lipid transformations.
Science.gov (United States)
Anuar, Sabiqah Tuan; Villegas, Carla; Mugo, Samuel M; Curtis, Jonathan M
2011-06-01
This study demonstrates the utility of a flow-through enzyme immobilized silica microreactor for lipid transformations. A silica micro structured fiber (MSF) consisting of 168 channels of internal diameter 4-5 μm provided a large surface area for the covalent immobilization of Candida antartica lipase. The specific activity of the immobilized lipase was determined by hydrolysis of p-nitrophenyl butyrate and calculated to be 0.81 U/mg. The catalytic performance of the lipase microreactor was demonstrated by the efficient ethanolysis of canola oil. The parameters affecting the performance of the MSF microreactor, including temperature and reaction flow rate, were investigated. Characterization of the lipid products exiting the microreactor was performed by non-aqueous reversed-phased liquid chromatography (NARP-LC) with evaporative light scattering detector (ELSD) and by comprehensive two-dimensional gas chromatography (GC x GC). Under optimized conditions of 1 μL/min flow rate of 5 mg/mL trioleoylglycerol (TO) in ethanol and 50 °C reaction temperature, 2-monooleoylglycerol was the main product at > 90% reaction yield. The regioselectivity of the Candida antartica lipase immobilized MSF microreactor in the presence of ethanol was found to be comparable to that obtained under conventional conditions. The ability of these reusable flow-through microreactors to regioselectively form monoacylglycerides in high yield from triacylglycerides demonstrate their potential use in small-scale lipid transformations or analytical lipids profiling.
16. Liquid phase oxidation chemistry in continuous-flow microreactors.
Science.gov (United States)
Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy
2016-01-07
Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described.
17. Design and validation of a uniform flow microreactor
Energy Technology Data Exchange (ETDEWEB)
Yi, Seung Jae; Kim, Kyung Chun; Chang, Seung Cheol [Pusan National University, Busan (Korea, Republic of); Park, Ji Min [Global HQ, Hankook Tire Co., Daejeon (Korea, Republic of)
2014-01-15
We present a design method to characterize uniform flows in a microreactor for high performance surface plasmon resonance (SPR) a general-purpose biosensor chips. The shape of the microreactor is designed based on an approximate pressure drop model. The number of micro-pillars and the slopes of the inlet and outlet linear chambers are two dominant parameters used to minimize the velocity difference in the microreactor. The flow uniformity was examined quantitatively by numerical and experimental visualization methods. A computational fluid dynamics (CFD) analysis demonstrates that the designed microreactor has a fairly uniform velocity profile in the reaction zone for a wide range of flow rates. The velocity field in the fabricated microreactor was measured using the micro-particle image velocimetry (μ-PIV) method, and the flow uniformity was confirmed experimentally. The performance of the uniform flow microreactor was verified using the fluorescence antibody technique.
18. Microreactor as Efficient Tool for Light Induced Oxidation Reactions
Czech Academy of Sciences Publication Activity Database
Hejda, S.; Drhová, Magdalena; Křišťál, Jiří; Buzek, D.; Krystyník, Pavel; Klusoň, Petr
2014-01-01
Roč. 255, NOV 1 (2014), s. 178-184 ISSN 1385-8947 Grant - others:GA MŠMT(CZ) MŠk:CZ.1.07/2.2.00/28.0205 Institutional support: RVO:67985858 Keywords : photo microreactor * phthalocyanine * chlorophenol oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.321, year: 2014
19. Effective use of enzyme microreactors : thermal, kinetic and ethical guidelines
NARCIS (Netherlands)
Swarts, J.W.
2009-01-01
Microreactor technology is reported to have many benefits over regular chemical methods. Due to the small dimensions over which temperature and concentration gradients can exist, mass and heat transfer can be very quick. This could minimize the time needed for heating and mixing, due to a reduction
20. CFD (Computational Fluid Dynamics) simulators and thermal cracking of heavy oil and ultraheavy residues using microreactor
Energy Technology Data Exchange (ETDEWEB)
Jardini, Andre L.; Bineli, Aulus R.R.; Viadana, Adriana M.; Maciel, Maria Regina Wolf; Maciel Filho, Rubens [State University of Campinas (UNICAMP), SP (Brazil). School of Chemical Engineering; Medina, Lilian C.; Gomes, Alexandre de O. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES); Barros, Ricardo S. [University Foundation Jose Bonifacio (FUJB), Rio de Janeiro, RJ (Brazil)
2008-07-01
In this paper, the design of microreactor with microfluidics channels has been carried out in Computer Aided Design Software (CAD) and constructed in rapid prototyping system to be used in chemical reaction processing of the heavy oil fractions. The flow pattern properties of microreactor (fluid dynamics, mixing behavior) have been considered through CFD (computational fluid dynamics) simulations. CFD calculations are also used to study the design and specification of new microreactor developments. The potential advantages of using a microreactor include better control of reaction conditions, improved safety and portability. A more detailed crude assay of the raw national oil, whose importance was evidenced by PETROBRAS/CENPES allows establishing the optimum strategies and processing conditions, aiming at a maximum utilization of the heavy oil fractions, towards valuable products. These residues are able to be processed in microreactor, in which conventional process like as hydrotreating, catalytic and thermal cracking may be carried out in a much more intensified fashion. The whole process development involves a prior thermal study to define the possible operating conditions for a particular task, the microreactor design through computational fluid dynamics and construction using rapid prototyping. This gives high flexibility for process development, shorter time, and costumer/task oriented process/product development. (author)
1. Heterogeneous catalysis in highly sensitive microreactors
DEFF Research Database (Denmark)
Olsen, Jakob Lind
This thesis present a highly sensitive silicon microreactor and examples of its use in studying catalysis. The experimental setup built for gas handling and temperature control for the microreactor is described. The implementation of LabVIEW interfacing for all the experimental parts makes...
2. I: Hydrodynamic-focusing microreactor II: Mechanically interlocked molecules for functional materials
Science.gov (United States)
Coti, Karla Karina
I: Microreactors, a class of microfluidics, offer numerous benefits -- such as small sample requirement, short analysis times and automations -- and have been used to study reactions of chemical and biological reagents. In order to understand the relationship between fast mixing, product regioselectivity, as well as the ability to separate, in time and space, the nanoparticle (NP) formation stages, a microreactor capable of fast and controllable mixing was developed (Chapter 1) based on multi-lamination and hydrodynamic-focusing. By taking advantage of the fast and controllable mixing properties of this novel microreactor one can control the time when chemical reactions commence inside the microchannels. These properties of the microreactor can be exploited to improve the product regioselectivity of a diazo-coupling reaction to attain a product distribution of monoazo to diazo product of ˜1:99, a selectivity unprecedented in both conventional, macroscopic reactors and other microfluidic systems. Additionally, the ability to separate different stages during the NP formation process inside the microreactor, allowed us to study the aggregation of polypyrrole NPs. II: Supramolecular actuators and molecular interlocked molecules, such as catenanes and rotaxanes, have attracted considerable attention because of their sophisticated topology and their application in functional molecular devices. The blending of supramolecular and mechanostereochemistry with mesoporous silica NPs has proven to be a powerful combination, leading to the development of a new class of materials -- mechanized silica nanoparticles ( Chapter 2). These new hybrid materials are designed to release their content in response to an external stimuli and their development is being driven by the need to improve current drug delivery technologies. In an effort to explore how the stimuli-controlled mechanical movement of switchable, bistable [2]rotaxanes -- based on a cyclobis(paraquat-p-phenylene) ring
3. Development of the kinetic model of platinum catalyzed ammonia oxidation in a microreactor
NARCIS (Netherlands)
Rebrov, E.V.; Croon, de M.H.J.M.; Schouten, J.C.
2002-01-01
The ammonia oxidation reaction on supported polycrystalline platinum catalyst was investigated in an aluminum-based microreactor. An extensive set of reactions was included in the chemical reactor modeling to facilitate the construction of a kinetic model capable of satisfactory predictions for a
4. Improved Peak Capacity for Capillary Electrophoretic Separations of Enzyme Inhibitors with Activity-Based Detection Using Magnetic Bead Microreactors
Science.gov (United States)
Yan, Xiaoyan; Gilman, S. Douglass
2010-01-01
A technique for separating and detecting enzyme inhibitors was developed using capillary electrophoresis with an enzyme microreactor. The on-column enzyme microreactor was constructed using NdFeB magnet(s) to immobilize alkaline phosphatase-coated superparamagnetic beads (2.8 μm diameter) inside a capillary before the detection window. Enzyme inhibition assays were performed by injecting a plug of inhibitor into a capillary filled with the substrate, AttoPhos. Product generated in the enzyme microreactor was detected by laser-induced fluorescence. Inhibitor zones electrophoresed through the capillary, passed through the enzyme microreactor, and were observed as negative peaks due to decreased product formation. The goal of this study was to improve peak capacities for inhibitor separations relative to previous work, which combined continuous engagement electrophoretically mediated microanalysis (EMMA) and transient engagement EMMA to study enzyme inhibition. The effects of electric field strength, bead injection time and inhibitor concentrations on peak capacity and peak width were investigated. Peak capacities were increased to ≥20 under optimal conditions of electric field strength and bead injection time for inhibition assays with arsenate and theophylline. Five reversible inhibitors of alkaline phosphatase (theophylline, vanadate, arsenate, L-tryptophan and tungstate) were separated and detected to demonstrate the ability of this technique to analyze complex inhibitor mixtures. PMID:20024913
5. Theoretical description of spin-selective reactions of radical pairs diffusing in spherical 2D and 3D microreactors
International Nuclear Information System (INIS)
2015-01-01
In this work, we treat spin-selective recombination of a geminate radical pair (RP) in a spherical “microreactor,” i.e., of a RP confined in a micelle, vesicle, or liposome. We consider the microreactor model proposed earlier, in which one of the radicals is located at the center of the micelle and the other one undergoes three-dimensional diffusion inside the micelle. In addition, we suggest a two-dimensional model, in which one of the radicals is located at the “pole” of the sphere, while the other one diffuses on the spherical surface. For this model, we have obtained a general analytical expression for the RP recombination yield in terms of the free Green function of two-dimensional diffusion motion. In turn, this Green function is expressed via the Legendre functions and thus takes account of diffusion over a restricted spherical surface and its curvature. The obtained expression allows one to calculate the RP recombination efficiency at an arbitrary magnetic field strength. We performed a comparison of the two models taking the same geometric parameters (i.e., the microreactor radius and the closest approach distance of the radicals), chemical reactivity, magnetic interactions in the RP and diffusion coefficient. Significant difference between the predictions of the two models is found, which is thus originating solely from the dimensionality effect: for different dimensionality of space, the statistics of diffusional contacts of radicals becomes different altering the reaction yield. We have calculated the magnetic field dependence of the RP reaction yield and chemically induced dynamic nuclear polarization of the reaction products at different sizes of the microreactor, exchange interaction, and spin relaxation rates. Interestingly, due to the intricate interplay of diffusional contacts of reactants and spin dynamics, the dependence of the reaction yield on the microreactor radius is non-monotonous. Our results are of importance for (i) interpreting
6. A CFD Simulation of Hydrogen Production in Microreactors
Directory of Open Access Journals (Sweden)
2015-01-01
Full Text Available In this study, the modeling of hydrogen production process in microreactors by methanol-steam reforming reaction is investigated. The catalytic reaction of methanol-steam reforming producing hydrogen is simulated considering a 3D geometry for the microreactor. To calculate diffusion among species, mixture average correlations are compared to Stephan-Maxwell equations. The reactions occurring inside the microreactor include reforming of methanol with steam, methanol decomposition, and a reaction between carbon dioxide and hydrogen. The main objectives of this study are the prediction of temperature profile along the microreactor using either mixture average method or Stephan-Maxwell one and the comparison between the present predictions and some existing experimental data. The simulation results indicate that Stephan-Maxwell method conforms more suitably to the experimental results. The difference is more at lower feed flow rates since, when the flow rate increases, mass transfer mechanism changes from diffusion to convection, which in turn reduces the difference.
7. Self-Sustained Oscillations of Temperature and Conversion in a Packed Bed Microreactor during 2-Methylpropene (Isobutene) Hydrogenation
Czech Academy of Sciences Publication Activity Database
Stavárek, Petr; Vajglová, Zuzana; Křišťál, Jiří; Jiřičný, Vladimír; Kolena, J.
2015-01-01
Roč. 256, NOV 1 (2015), s. 250-260 ISSN 0920-5861. [InternationalCongress of Chemical and Process Engineering CHISA 2014 /21./. Prague, 23.08.2014-27.08.2014] Institutional support: RVO:67985858 Keywords : hydrogenation * microreactor * oscillation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.312, year: 2015
8. Combined Effect of Temperature and Dissolved Oxygen on Degradation of 4-chlorophenol in Photo Microreactor
Czech Academy of Sciences Publication Activity Database
Vondráčková, Magdalena; Hejda, S.; Stavárek, Petr; Křišťál, Jiří; Klusoň, Petr
2015-01-01
Roč. 94, SI (2015), s. 35-38 ISSN 0255-2701 R&D Projects: GA ČR(CZ) GAP105/12/0664 Institutional support: RVO:67985858 Keywords : photo microreactor * phthalocyanine * chlorophenol oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.154, year: 2015
9. Streptavidin-functionalized capillary immune microreactor for highly efficient chemiluminescent immunoassay
Energy Technology Data Exchange (ETDEWEB)
Yang Zhanjun [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); College of Chemistry and Engineering, Yangzhou University, 88 South University Avenue, Yangzhou 225002 (China); Zong Chen [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Ju Huangxian, E-mail: [email protected] [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Yan Feng, E-mail: [email protected] [Jiangsu Institute of Cancer Prevention and Cure, Nanjing 210009 (China)
2011-11-07
Highlights: {yields} A novel capillary immune microreactor was proposed for highly efficient flow-through chemiluminescent immunoassay. {yields} The microreactor was prepared by functionalizing capillary inner wall with streptavidin for capture of biotinylated antibody. {yields} The proposed immunoassay method showed wide dynamic range, good reproducibility, stability and practicality. {yields} The microreactor was low-cost and disposable, and possessed several advantages over the conventional immunoreactors. - Abstract: A streptavidin functionalized capillary immune microreactor was designed for highly efficient flow-through chemiluminescent (CL) immunoassay. The functionalized capillary could be used as both a support for highly efficient immobilization of antibody and a flow cell for flow-through immunoassay. The functionalized inner wall and the capture process were characterized using scanning electron microscopy. Compared to conventional packed tube or thin-layer cell immunoreactor, the proposed microreactor showed remarkable properties such as lower cost, simpler fabrication, better practicality and wider dynamic range for fast CL immunoassay with good reproducibility and stability. Using {alpha}-fetoprotein as model analyte, the highly efficient CL flow-through immunoassay system showed a linear range of 3 orders of magnitude from 0.5 to 200 ng mL{sup -1} and a low detection limit of 0.1 ng mL{sup -1}. The capillary immune microreactor could make up the shortcoming of conventional CL immunoreactors and provided a promising alternative for highly efficient flow-injection immunoassay.
10. Effect of diffusion on enzyme activity in a microreactor
NARCIS (Netherlands)
Swarts, J.W.; Kolfschoten, R.C.; Jansen, M.C.A.A.; Janssen, A.E.M.; Boom, R.M.
2010-01-01
To establish general rules for setting up an enzyme microreactor system, we studied the effect of diffusion on enzyme activity in a microreactor. As a model system we used the hydrolysis of ortho-nitrophenyl-ß-d-galactopyranoside by ß-galactosidase from Kluyveromyces lactis. We found that the
11. Chemical reactions in reverse micelle systems
Science.gov (United States)
Matson, Dean W.; Fulton, John L.; Smith, Richard D.; Consani, Keith A.
1993-08-24
This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.
12. Using a wire coil insert for biodiesel production enhancement in a microreactor
International Nuclear Information System (INIS)
Aghel, Babak; Rahimi, Masoud; Sepahvand, Arash; Alitabar, Mohammad; Ghasempour, Hamid Reza
2014-01-01
Graphical abstract: Schematic view of microreactor system. - Highlights: • A wire coil insert was used to promote mixing in a biodiesel microreactor. • Advantages of using the wire coil in the microreactor over plain one are shown. • A yield of 99% was obtained in the modified microreactor after 180 s. • RSM and the Box–Behnken method were used to optimize the biodiesel production. • Advantages of using this system over other conventional reactors are illustrated. - Abstract: In the present work, the application of wire coil to promote mixing in a microreactor during continuous production of biodiesel was studied. For this aim, soybean oil as a feedstock and potassium hydroxide as a homogeneous catalyzed were used. The influences of the various parameters such as geometric and operational conditions on the performance of biodiesel production were experimentally examined. Response surface methodology (RSM) in conjunction with the Box–Behnken method was used to statistically analyze and optimize the biodiesel production process. The comparison between two types of reactors (with and without wire coil) shows a significant enhancement in mixing during transesterification. The impacts of different wire coil lengths and wire coil pitchs on methyl ester conversion were also investigated. A reaction yield of 99% at the residence time of 180 s was obtained in the modified microreactor. However, the measured pressure drop show that the microreactor equipped with wire coil consumed more energy. Therefore, performance ratio was defined to evaluate energy efficiency and the results show the advantage of using the wire coil insert in lower feed flow rates
13. Mass transfer with complex reversible chemical reactions—II. parallel reversible chemical reactions
NARCIS (Netherlands)
Versteeg, G.F.; Kuipers, J.A.M.; Beckum, F.P.H. van; Swaaij, W.P.M. van
1990-01-01
An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and
14. Mass transfer with complex reversible chemical reactions. II: Parallel reversible chemical reactions
NARCIS (Netherlands)
Versteeg, Geert; van Beckum, F.P.H.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria
1990-01-01
An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and
15. Mass transfer with complex reversible chemical reactions. II: parallel reversible chemical reactions
NARCIS (Netherlands)
Versteeg, G.F.; Kuipers, J.A.M.; Beckum, van F.P.H.; van Swaaij, W.P.M.
1990-01-01
An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and
16. Mass transfer with complex reversible chemical reactions—I. Single reversible chemical reaction
NARCIS (Netherlands)
Versteeg, G.F.; Kuipers, J.A.M.; Beckum, F.P.H. van; Swaaij, W.P.M. van
1989-01-01
An improved numerical technique was used in order to develop an absorption model with which it is possible to calculate rapidly absorption rates for the phenomenon of mass transfer accompanied by a complex reversible chemical reaction. This model can be applied for the calculation of the mass
17. Synthesis of copper nanocolloids using a continuous flow based microreactor
Energy Technology Data Exchange (ETDEWEB)
Xu, Lei, E-mail: [email protected] [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Mechanical Engineering, University of Washington, Seattle 98195 (United States); Peng, Jinhui [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Srinivasakannan, C. [Chemical Engineering Program, The petroleum Institute, Abu Dhabi, P.O. Box 253 (United Arab Emirates); Chen, Guo [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Shen, Amy Q., E-mail: [email protected] [Mechanical Engineering, University of Washington, Seattle 98195 (United States); Micro/Bio/Nanofluidics Unit, Okinawa Institute of Technology Graduate University, Okinawa (Japan)
2015-11-15
Highlights: • The copper nanocolloidal were synthesized in a T-shaped microreactor at room temperature. • The morphology of copper nanocolloidal are spherical, and with good size distribution. • The mean particle diameter increased with decreases the NaBH{sub 4} molar concentration. • With increasing particle size, the more obvious localized surface plasmon resonance absorption. - Abstract: The copper (Cu) nanocolloids were prepared by sodium borohydride (NaBH{sub 4}) reduction of metal salt solutions in a T-shaped microreactor at room temperature. The influence of NaBH{sub 4} molar concentrations on copper particle's diameter, morphology, size distribution, and elemental compositions has been investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The ultraviolet–visible spectroscopy (UV–vis) was used to verify the chemical compounds of nanocolloids and estimate the average size of copper nanocolloids. The synthesized copper nanocolloids were uniform in size and non-oxidized. A decrease in the mean diameter of copper nanocolloids was observed with increasing NaBH{sub 4} molar concentrations. The maximum mean diameter (4.25 nm) occurred at the CuSO{sub 4}/NaBH{sub 4} molar concentration ratio of 1:2.
18. Enantioselective Organocatalysis in Microreactors: Continuous Flow Synthesis of a (S-Pregabalin Precursor and (S-Warfarin
Directory of Open Access Journals (Sweden)
Riccardo Porta
2015-08-01
Full Text Available Continuous flow processes have recently emerged as a powerful technology for performing chemical transformations since they ensure some advantages over traditional batch procedures. In this work, the use of commercially available and affordable PEEK (Polyetheretherketone and PTFE (Polytetrafluoroethylene HPLC (High Performance Liquid Chromatography tubing as microreactors was exploited to perform organic reactions under continuous flow conditions, as an alternative to the commercial traditional glass microreactors. The wide availability of tubing with different sizes allowed quickly running small-scale preliminary screenings, in order to optimize the reaction parameters, and then to realize under the best experimental conditions a reaction scale up for preparative purposes. The gram production of some Active Pharmaceutical Ingredients (APIs such as (S-Pregabalin and (S-Warfarin was accomplished in short reaction time with high enantioselectivity, in an experimentally very simple procedure.
19. Multi-Temperature Zone, Droplet-based Microreactor for Increased Temperature Control in Nanoparticle Synthesis
KAUST Repository
Erdem, E. Yegâ n; Cheng, Jim C.; Doyle, Fiona M.; Pisano, Albert P.
2013-01-01
Microreactors are an emerging technology for the controlled synthesis of nanoparticles. The Multi-Temperature zone Microreactor (MTM) described in this work utilizes thermally isolated heated and cooled regions for the purpose of separating
20. Analysis of diffusivity of the oscillating reaction components in a microreactor system
Directory of Open Access Journals (Sweden)
Martina Šafranko
2017-01-01
Full Text Available When performing oscillating reactions, periodical changes in the concentrations of reactants, intermediaries, and products take place. Due to the mentioned periodical changes of the concentrations, the information about the diffusivity of the components included into oscillating reactions is very important for the control of the oscillating reactions. Non-linear dynamics makes oscillating reactions very interesting for analysis in different reactor systems. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor, with the aim of identifying the limiting component. The geometry of the microreactor microchannel and a well defined flow profile ensure optimal conditions for the diffusion phenomena analysis, because diffusion profiles in a microreactor depend only on the residence time. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor equipped with 2 Y-shape inlets and 2 Y-shape outlets, with active volume of V = 4 μL at different residence times.
1. Micro-Reactor Physics of MOX-Fueled Core
International Nuclear Information System (INIS)
Takeda, T.
2001-01-01
Recently, fuel assemblies of light water reactors have become complicated because of the extension of fuel burnup and the use of high-enriched Gd and mixed-oxide (MOX) fuel, etc. In conventional assembly calculations, the detailed flux distribution, spectrum distribution, and space dependence of self-shielding within a fuel pellet are not directly taken into account. The experimental and theoretical study of investigating these microscopic properties is named micro-reactor physics. The purpose of this work is to show the importance of micro-reactor physics in the analysis of MOX fuel assemblies. Several authors have done related studies; however, their studies are limited to fuel pin cells, and they are never mentioned with regard to burnup effect, which is important for actual core design
2. A new pulsed electric field microreactor: comparison between the laboratory and microtechnology scale
NARCIS (Netherlands)
Fox, M.B.; Fox, Martijn; Esveld, Erik; Lüttge, Regina; Boom, Remko
This paper presents a new microreactor dedicated for pulsed electric field treatment (PEF), which is a pasteurization method that inactivates microorganisms with short electric pulses. The PEF microreactor consists of a flow-through channel with a constriction where the electric field is focussed.
3. A new pulsed electric field microreactor: comparison between the laboratory and microtechnology scale
NARCIS (Netherlands)
Fox, M.B.; Esveld, D.C.; Luttge, R.; Boom, R.M.
2005-01-01
This paper presents a new microreactor dedicated for pulsed electric field treatment (PEF), which is a pasteurization method that inactivates microorganisms with short electric pulses. The PEF microreactor consists of a flow-through channel with a constriction where the electric field is focussed.
4. Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading
Science.gov (United States)
2017-09-07
ARL-TR-8121 ● SEP 2017 US Army Research Laboratory Stress and Displacement Analysis of Microreactors during Thermal and Vacuum...is no longer needed. Do not return it to the originator. ARL-TR-8121 ● SEP 2017 US Army Research Laboratory Stress and...TITLE AND SUBTITLE Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading 5a. CONTRACT NUMBER 5b. GRANT NUMBER
5. Shape and topology optimization of enzymatic microreactors
DEFF Research Database (Denmark)
Pereira Rosinha, Ines
for effective and cost efficient reactors for pharmaceutical processes forces the industry to search for better technologies. In biochemical engineering, the used reactor design in a given process is usually limited to a range of well-established configurations and layouts. Usually the implemented reactors...... in a chemical process do not always yield in the best reaction conditions.This thesis develops an innovative application of topology and shape optimization methods to achemical engineering problem. The main goal is to design a reactor according to the limitations of the reaction system by modifying the reactor...... configuration. In this thesis structural optimization methods were exclusively applied to enzymatic microreactors. The case studies were chosen such that they can be experimentally tested afterwards. In this way, the design of the reactor is customized to the reaction system and itcontributes to the reduction...
6. High quantum yield ZnO quantum dots synthesizing via an ultrasonication microreactor method.
Science.gov (United States)
Yang, Weimin; Yang, Huafang; Ding, Wenhao; Zhang, Bing; Zhang, Le; Wang, Lixi; Yu, Mingxun; Zhang, Qitu
2016-11-01
Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor. Copyright © 2016 Elsevier B.V. All rights reserved.
7. Model based design of biochemical micro-reactors
Directory of Open Access Journals (Sweden)
Tobias eElbinger
2016-02-01
Full Text Available Mathematical modelling of biochemical pathways is an important resource in Synthetic Biology, as the predictive power of simulating synthetic pathways represents an important step in the design of synthetic metabolons. In this paper, we are concerned with the mathematical modeling, simulation and optimization of metabolic processes in biochemical micro-reactors able to carry out enzymatic reactions and to exchange metabolites with their surrounding medium. The results of the reported modeling approach are incorporated in the design of the first micro-reactor prototypes that are under construction. These microreactors consist of compartments separated by membranes carrying specific transporters for the input of substrates and export of products. Inside the compartments multi-enzyme complexes assembled on nano-beads by peptide adapters are used to carry out metabolic reactions.The spatially resolved mathematical model describing the ongoing processes consists of a system of diffusion equations together with boundary and initial conditions. The boundary conditions model the exchange of metabolites with the neighboring compartments and the reactions at the surface of the nano-beads carrying the multi-enzyme complexes. Efficient and accurate approaches for numerical simulation of the mathematical model and for optimal design of the micro-reactor are developed. As a proof-of-concept scenario, a synthetic pathway for the conversion of sucrose to glucose-6-phosphate (G6P was chosen. In this context, the mathematical model is employed to compute the spatio-temporal distributions of the metabolite concentrations, as well as application relevant quantities like the outflow rate of G6P. These computations are performed for different scenarios, where the number of beads as well as their loading capacity are varied. The computed metabolite distributions show spatial patterns which differ for different experimental arrangements. Furthermore, the total output
8. Special Issue: Design and Engineering of Microreactor and Smart-Scaled Flow Processes
Directory of Open Access Journals (Sweden)
Volker Hessel
2014-12-01
Full Text Available Reaction-oriented research in flow chemistry and microreactor has been extensively focused upon in special journal issues and books. On a process level, this resembled the “drop-in” (retrofit concept with the microreactor replacing a conventional (batch reactor. Meanwhile, with the introduction of the mobile, compact, modular container technology, the focus is more on the process side, including also providing an end-to-end vision of intensified process design. Exactly this is the focus of the current special issue “Design and Engineering of Microreactor and Smart-Scaled Flow Processes” of the journal “Processes”. This special issue comprises three review papers, five research articles and two communications. [...
9. Microreactors and CFD as Tools for Biocatalysis Reactor Design: A case study
DEFF Research Database (Denmark)
Bodla, Vijaya Krishna; Seerup, R.; Krühne, Ulrich
2013-01-01
Microreactors have been used for acquiring process data while consuming significantly lower amounts of expensive reagents. In this article, the combination of microreactor technology and computational fluid dynamics (CFD) is shown to contribute significantly towards understanding the diffusional ...... with similar dimensions to the ones tested here can be used as a screening tool for screening biocatalyst and process alternatives....
10. Sample Handling and Chemical Kinetics in an Acoustically Levitated Drop Microreactor
Science.gov (United States)
2009-01-01
Accurate measurement of enzyme kinetics is an essential part of understanding the mechanisms of biochemical reactions. The typical means of studying such systems use stirred cuvettes, stopped-flow apparatus, microfluidic systems, or other small sample containers. These methods may prove to be problematic if reactants or products adsorb to or react with the container’s surface. As an alternative approach, we have developed an acoustically-levitated drop reactor eventually intended to study enzyme-catalyzed reaction kinetics related to free radical and oxidative stress chemistry. Microliter-scale droplet generation, reactant introduction, maintenance, and fluid removal are all important aspects in conducting reactions in a levitated drop. A three capillary bundle system has been developed to address these needs. We report kinetic measurements for both luminol chemiluminescence and the reaction of pyruvate with nicotinamide adenine dinucleotide, catalyzed by lactate dehydrogenase, to demonstrate the feasibility of using a levitated drop in conjunction with the developed capillary sample handling system as a microreactor. PMID:19769373
11. Topology optimization for biocatalytic microreactor configurations
DEFF Research Database (Denmark)
Pereira Rosinha, Ines; Gernaey, Krist; Woodley, John
2015-01-01
as a case study. The Evolutionary Structure Optimization (ESO) method is applied using an interface between Matlab® and the computational fluid dynamic simulation software ANSYS CFX®. In the case study, theESO method is applied to optimize the spatial distribution of immobilized enzyme inside a microreactor...
12. Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor
Energy Technology Data Exchange (ETDEWEB)
Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno [University of Zagreb, Zagreb (Croatia)
2015-06-15
Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R{sup 2}=0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k{sub L}a=4,652-1,9807 h{sup -1}.
13. Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor
International Nuclear Information System (INIS)
Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno
2015-01-01
Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R 2 =0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k L a=4,652-1,9807 h -1
14. Carbon nanofibers in catalytic membrane microreactors
NARCIS (Netherlands)
Aran, H.C.; Pacheco Benito, Sergio; Luiten-Olieman, Maria W.J.; Er, S.; Wessling, Matthias; Lefferts, Leonardus; Benes, Nieck Edwin; Lammertink, Rob G.H.
2011-01-01
In this study, we report on the fabrication and operation of new hybrid membrane microreactors for gas–liquid–solid (G–L–S) reactions. The presented reactors consist of porous stainless steel tubes onto which carbon nanofibers (CNFs) are grown as catalyst support, all encapsulated by a gas permeable
15. Modeling intrinsic kinetics in immobilized photocatalytic microreactors
NARCIS (Netherlands)
Visan, Aura; Rafieian Boroujeni, Damon; Ogieglo, Wojciech; Lammertink, Rob G.H.
2014-01-01
The article presents a simple model for immobilized photocatalytic microreactors following a first order reaction rate with either light independency or light dependency described by photon absorption carrier generation semiconductor physics. Experimental data obtained for various residence times,
16. Mass transfer with complex reversible chemical reactions—II. parallel reversible chemical reactions
OpenAIRE
Versteeg, G.F.; Kuipers, J.A.M.; Beckum, F.P.H. van; Swaaij, W.P.M. van
1990-01-01
An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and concentration profiles for a wide range of processes and conditions, for both film and penetration model. With the aid of this mass transfer model it is demonstrated that the absorption rates in syst...
17. Photosensitized Oxygenations of Hexamethylbenzene in Phase Contact Enhanced Microreactor
International Nuclear Information System (INIS)
Park, Chan Yi; Park, Jeong Hyeon; Lim Hyo Jin; Hwang, Geumsook; Park, Chan Pil
2014-01-01
Activated singlet oxygen ( 1 O 2 ) has successfully been utilized in production of various compounds including fragrances, pharmaceuticals, and fine chemicals. However, the traditional reaction required a prolonged reaction time due to the difficulty of introducing adequate light and oxygen into the solution. Low contact probability between four species of oxygen, photosensitizer, light, and reagent is an inherent drawback of the traditional photoreaction. Molecular diffusion distance is the most important factor in the heterogeneous reactions including gas-liquid, gassolid, liquid-solid, and immiscible liquid-liquid. Therefore, rates of reaction are closely depended on the distance. Microreactor has provided a distinct advantage in the short molecular diffusion distance due to the high surface-to-volume ratio driven by narrow fluidic channels
18. Catalyst for microelectromechanical systems microreactors
Science.gov (United States)
Morse, Jeffrey D [Martinez, CA; Sopchak, David A [Livermore, CA; Upadhye, Ravindra S [Pleasanton, CA; Reynolds, John G [San Ramon, CA; Satcher, Joseph H [Patterson, CA; Gash, Alex E [Brentwood, CA
2010-06-29
A microreactor comprising a silicon wafer, a multiplicity of microchannels in the silicon wafer, and a catalyst coating the microchannels. In one embodiment the catalyst coating the microchannels comprises a nanostructured material. In another embodiment the catalyst coating the microchannels comprises an aerogel. In another embodiment the catalyst coating the microchannels comprises a solgel. In another embodiment the catalyst coating the microchannels comprises carbon nanotubes.
19. Fuel, structural material and coolant for an advanced fast micro-reactor
International Nuclear Information System (INIS)
Nascimento, Jamil A. do; Guimaraes, Lamartine N.F.; Ono, Shizuca
2011-01-01
The use of nuclear reactors in space, seabed or other Earth hostile environment in the future is a vision that some Brazilian nuclear researchers share. Currently, the USA, a leader in space exploration, has as long-term objectives the establishment of a permanent Moon base and to launch a manned mission to Mars. A nuclear micro-reactor is the power source chosen to provide energy for life support, electricity for systems, in these missions. A strategy to develop an advanced micro-reactor technologies may consider the current fast reactor technologies as back-up and the development of advanced fuel, structural and coolant materials. The next generation reactors (GEN-IV) for terrestrial applications will operate with high output temperature to allow advanced conversion cycle, such as Brayton, and hydrogen production, among others. The development of an advanced fast micro-reactor may create a synergy between the GEN-IV and space reactor technologies. Considering a set of basic requirements and materials properties this paper discusses the choice of advanced fuel, structural and coolant materials for a fast micro-reactor. The chosen candidate materials are: nitride, oxide as back-up, for fuel, lead, tin and gallium for coolant, ferritic MA-ODS and Mo alloys for core structures. The next step will be the neutronic and burnup evaluation of core concepts with this set of materials. (author)
20. Orifice microreactor for the production of an organic peroxide – non-reactive and reactive characterization
NARCIS (Netherlands)
Illg, T.; Hessel, V.; Löb, P.; Schouten, J.C.
2012-01-01
In this article, the transfer of a two-step, biphasic, and exothermic peroxide synthesis into a microreactor assisted process is discussed as well as the non-reactive and reactive characterization of the developed orifice microreactor. Residence time distribution measurements showed nearly ideal
1. Proteolytic Digestion and TiO2 Phosphopeptide Enrichment Microreactor for Fast MS Identification of Proteins
Science.gov (United States)
Deng, Jingren; Lazar, Iulia M.
2016-04-01
The characterization of phosphorylation state(s) of a protein is best accomplished by using isolated or enriched phosphoprotein samples or their corresponding phosphopeptides. The process is typically time-consuming as, often, a combination of analytical approaches must be used. To facilitate throughput in the study of phosphoproteins, a microreactor that enables a novel strategy for performing fast proteolytic digestion and selective phosphopeptide enrichment was developed. The microreactor was fabricated using 100 μm i.d. fused-silica capillaries packed with 1-2 mm beds of C18 and/or TiO2 particles. Proteolytic digestion-only, phosphopeptide enrichment-only, and sequential proteolytic digestion/phosphopeptide enrichment microreactors were developed and tested with standard protein mixtures. The protein samples were adsorbed on the C18 particles, quickly digested with a proteolytic enzyme infused over the adsorbed proteins, and further eluted onto the TiO2 microreactor for enrichment in phosphopeptides. A number of parameters were optimized to speed up the digestion and enrichments processes, including microreactor dimensions, sample concentrations, digestion time, flow rates, buffer compositions, and pH. The effective time for the steps of proteolytic digestion and enrichment was less than 5 min. For simple samples, such as standard protein mixtures, this approach provided equivalent or better results than conventional bench-top methods, in terms of both enzymatic digestion and selectivity. Analysis times and reagent costs were reduced ~10- to 15-fold. Preliminary analysis of cell extracts and recombinant proteins indicated the feasibility of integration of these microreactors in more advanced workflows amenable for handling real-world biological samples.
2. Multi-Temperature Zone, Droplet-based Microreactor for Increased Temperature Control in Nanoparticle Synthesis
KAUST Repository
Erdem, E. Yegân
2013-12-12
Microreactors are an emerging technology for the controlled synthesis of nanoparticles. The Multi-Temperature zone Microreactor (MTM) described in this work utilizes thermally isolated heated and cooled regions for the purpose of separating nucleation and growth processes as well as to provide a platform for a systematic study on the effect of reaction conditions on nanoparticle synthesis. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
3. Dense CdS thin films on fluorine-doped tin oxide coated glass by high-rate microreactor-assisted solution deposition
Energy Technology Data Exchange (ETDEWEB)
Su, Yu-Wei, E-mail: [email protected] [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97330 (United States); Microproducts Breakthrough Institute and Oregon Process Innovation Center, Corvallis, Oregon 97330 (United States); Ramprasad, Sudhir [Energy Processes and Materials Division, Pacific Northwest National Laboratory, Corvallis, OR 9730 (United States); Microproducts Breakthrough Institute and Oregon Process Innovation Center, Corvallis, Oregon 97330 (United States); Han, Seung-Yeol; Wang, Wei [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97330 (United States); Microproducts Breakthrough Institute and Oregon Process Innovation Center, Corvallis, Oregon 97330 (United States); Ryu, Si-Ok [School of Display and Chemical Engineering, Yeungnam University, 214-1 Dae-dong, Gyeonsan, Gyeongbuk 712-749 (Korea, Republic of); Palo, Daniel R. [Barr Engineering Co., Hibbing, MN 55747 (United States); Paul, Brian K. [School of Mechanical, Industrial and Manufacturing Engineering, Oregon State University, Corvallis, OR 97330 (United States); Microproducts Breakthrough Institute and Oregon Process Innovation Center, Corvallis, Oregon 97330 (United States); Chang, Chih-hung [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97330 (United States); Microproducts Breakthrough Institute and Oregon Process Innovation Center, Corvallis, Oregon 97330 (United States)
2013-04-01
Continuous microreactor-assisted solution deposition is demonstrated for the deposition of CdS thin films on fluorine-doped tin oxide (FTO) coated glass. The continuous flow system consists of a microscale T-junction micromixer with the co-axial water circulation heat exchanger to control the reacting chemical flux and optimize the heterogeneous surface reaction. Dense, high quality nanocrystallite CdS thin films were deposited at an average rate of 25.2 nm/min, which is significantly higher than the reported growth rate from typical batch chemical bath deposition process. Focused-ion-beam was used for transmission electron microscopy specimen preparation to characterize the interfacial microstructure of CdS and FTO layers. The band gap was determined at 2.44 eV by UV–vis absorption spectroscopy. X-ray photon spectroscopy shows the binding energies of Cd 3d{sub 3/2}, Cd 3d{sub 5/2}, S 2P{sub 3/2} and S 2P{sub 1/2} at 411.7 eV, 404.8 eV, 162.1 eV and 163.4 eV, respectively. - Highlights: ► CdS films deposited using continuous microreactor-assisted solution deposition (MASD) ► Dense nanocrystallite CdS films can be reached at a rate of 25.2 [nm/min]. ► MASD can approach higher film growth rate than conventional chemical bath deposition.
4. Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships
Directory of Open Access Journals (Sweden)
Agnieszka Ciemięga
2017-08-01
Full Text Available The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, differing in the size of mesopores, and in particular, flow-through macropores which significantly affected the flow characteristic of the continuous system. The highest ester productivity of 105.2 mol·molH+−1·h−1 was achieved in microreactor M1 with the largest porosity, characterized by a total pore volume of 4 cm3·g−1, mesopores with 20 nm diameter, and large flow-through macropores 30–50 μm in size. The strong impact of the permeability of the monoliths on a reaction kinetics was shown.
5. (Invited) Microreactors for Characterization and Benchmarking of Photocatalysts
DEFF Research Database (Denmark)
Vesborg, Peter Christian Kjærgaard; Dionigi, Fabio; Trimarco, Daniel Bøndergaard
2015-01-01
In the field of photocatalysis the batch-nature of the typical benchmarking experiment makes it very laborious to obtain good kinetic data as a function of parameters such as illumination wavelength, irradiance, catalyst temperature, reactant composition, etc. Microreactors with on-line mass...
6. Direct synthesis of hydrogen peroxide in a microreactor
NARCIS (Netherlands)
Paunovic, V.; Schouten, J.C.; Nijhuis, T.A.
2014-01-01
The direct synthesis of hydrogen peroxide in a microreactor is a safe and efficient process. Conventionally, hydrogen peroxide is produced using the anthraquinone autooxidation process, which is rather complex and can only be performed cost-effectively on a large scale. As a result, hydrogen
7. Hydrodynamics of multi-phase packed bed micro-reactors
NARCIS (Netherlands)
Márquez Luzardo, N.M.
2010-01-01
Why to use packed bed micro-reactors for catalyst testing? Miniaturized packed bed reactors have a large surface-to-volume ratio at the reactor and particle level that favors the heat- and mass-transfer processes at all scales (intra-particle, inter-phase and inter-particle or reactor level). If the
8. High mass resolution time of flight mass spectrometer for measuring products in heterogeneous catalysis in highly sensitive microreactors
DEFF Research Database (Denmark)
Andersen, Thomas; Jensen, Robert; Christensen, M. K.
2012-01-01
We demonstrate a combined microreactor and time of flight system for testing and characterization of heterogeneous catalysts with high resolution mass spectrometry and high sensitivity. Catalyst testing is performed in silicon-based microreactors which have high sensitivity and fast thermal...
9. Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor
Directory of Open Access Journals (Sweden)
Rajesh Munirathinam
2013-08-01
Full Text Available Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS. XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3.
10. Building a Better Microreactor: Enzyme Catalysis in AOT/Bile Salt Reversed Micelles
National Research Council Canada - National Science Library
McGown, Linda
2001-01-01
.... We have shown that trihydroxy bile salts modify the interfacial properties of AOT reversed micelles, thereby affecting the reversed micellar structure, the biological activity of entrapped enzymes...
11. Development of automatic combinatorial system for synthesis of nanoparticles using microreactors
Energy Technology Data Exchange (ETDEWEB)
Watanabe, Kosuke; Maeda, Hideaki [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580 (Japan); Orimoto, Yuuichi; Yamashita, Kenichi; Uehara, Masato; Nakamura, Hiroyuki [Measurement Solution Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 807-1, Shuku, Tosu, Saga, 841-0052 (Japan); Furuya, Takeshi, E-mail: [email protected] [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8565 (Japan)
2011-10-29
In this study, automatic system for combinatorial synthesis of nanoparticles (NPs) was developed and optimization of reaction parameter for NPs synthesis was performed. Microreactor was employed for kinetic control constantly. Programmable equipments were employed for additional speed up and used a microreactor. Six reaction condition parameters were systematically combined to produce CdSe synthesis condition sets. Reaction conditions of 3404 experimental sets were synthesized and characterized in 1 month. As a result of some multivariate analyses using the numerous and complicated data, we found as follows: 1) neural network is an effective method to analyze data from combinatorial synthesis, 2) weighting evaluation method was effective to find the condition for balanced NP properties.
12. On-chip microreactor system for the production of nano-emulsion loaded liposomes: towards targeted delivery of lipophilic drugs
NARCIS (Netherlands)
Langelaan, M.L.P.; Emmelkamp, J.; Segers, M.J.A.; Lenting, H.B.M.
2011-01-01
An on-chip microreactor system for the production of novel nano-biodevices is presented. This nano-biodevice consists of a nano-emulsion loaded with lipophilic drugs, entrapped in liposomes. These nano-biodevices can be equipped with targeting molecules for higher drug efficiency. The microreactor
13. A biofilm microreactor system for simultaneous electrochemical and nuclear magnetic resonance techniques
International Nuclear Information System (INIS)
Renslow, Ryan S.; Babauta, Jerome T.; Majors, Paul D.; Mehta, Hardeep S.; Ewing, R. James; Ewing, Thomas; Mueller, Karl T.; Beyenal, Haluk
2014-01-01
In order to fully understand electrochemically active biofilms and the limitations to their scale-up in industrial biofilm reactors, a complete picture of the microenvironments inside the biofilm is needed. Nuclear magnetic resonance (NMR) techniques are ideally suited for the study of biofilms and for probing their microenvironments because these techniques allow for non-invasive interrogation and in situ monitoring with high resolution. By combining NMR with simultaneous electrochemical techniques, it is possible to sustain and study live electrochemically active biofilms. Here, we introduce a novel biofilm microreactor system that allows for simultaneous electrochemical and NMR techniques (EC-NMR) at the microscale. Microreactors were designed with custom radiofrequency resonator coils, which allowed for NMR measurements of biofilms growing on polarized gold electrodes. For an example application of this system, we grew Geobacter sulfurreducens biofilms. NMR was used to investigate growth media flow velocities, which were compared to simulated laminar flow, and electron donor concentrations inside the biofilms. We use Monte Carlo error analysis to estimate standard deviations of the electron donor concentration measurements within the biofilm. The EC-NMR biofilm microreactor system can ultimately be used to correlate extracellular electron transfer rates with metabolic reactions and explore extracellular electron transfer mechanisms
14. Flow-through polymerase chain reaction inside a seamless 3D helical microreactor fabricated utilizing a silicone tube and a paraffin mold.
Science.gov (United States)
Wu, Wenming; Trinh, Kieu The Loan; Lee, Nae Yoon
2015-03-07
We introduce a new strategy for fabricating a seamless three-dimensional (3D) helical microreactor utilizing a silicone tube and a paraffin mold. With this method, various shapes and sizes of 3D helical microreactors were fabricated, and a complicated and laborious photolithographic process, or 3D printing, was eliminated. With dramatically enhanced portability at a significantly reduced fabrication cost, such a device can be considered to be the simplest microreactor, developed to date, for performing the flow-through polymerase chain reaction (PCR).
15. A new technique for accurately defined deposition of catalyst thin films in deep flow channels of high-temperature gas microreactors
NARCIS (Netherlands)
Tiggelaar, Roald M.; Berenschot, Johan W.; Oosterbroek, R.E.; van Male, P.; de Croon, M.H.J.M.; Schouten, J.C.; van den Berg, Albert
2003-01-01
By using microreactors fabricated with silicon microtechnology, heterogeneous catalyzed gas-phase reactions can be studied which are difficult to control because of their exothermic nature, are explosive or use toxic/hazardous gases. In this type of microreactors, catalytic materials like rhodium or
16. Chemical boundary layers in CVD II. Reversible reactions
NARCIS (Netherlands)
Croon, de M.H.J.M.; Giling, L.J.
1990-01-01
In addition to irreversible reactions, which were treated in part I, reversible reactions in the gas phase have beenstudied using the concept of the chemical boundary layer. The analysis is given for the situations in which either the forwardor the back reaction is dominant. Two conceptual models
17. Design of micro-reactors and solar photocatalytic prototypes; Diseno de micro-reactores y prototipos fotocataliticos solares
Energy Technology Data Exchange (ETDEWEB)
Flores E, R.M.; Hernandez H, M.; Perusquia del Cueto, M.R.; Bonifacio M, J.; Jimenez B, J.; Ortiz O, H.B.; Castaneda J, G.; Lugo H, M. [ININ, Km. 36.5 Carr. Mexico-Toluca, 52750 La Marquesa, Ocoyoacac (Mexico)]. e-mail: [email protected]
2007-07-01
In the ININ is carried out research in heterogeneous photocatalysis using artificial light for to degrade organic compounds. In this context, it is sought to use the solar radiation as energy source to knock down costs. Of equal form it requires to link the basic and applied research. For it, a methodology that allows to design and to build micro-reactors and plants pilot has been developed, like previous step, to request external supports and to a future commercialization. The beginning of these works gave place to the partial construction of a prototype of photocatalytic reactor of the cylinder-parabolic composed type (CPC)
18. Rapid and reagent-saving immunoassay using innovative stirring actions of magnetic beads in microreactors in the sequential injection mode.
Science.gov (United States)
Tanaka, K; Imagawa, H
2005-12-15
We developed new ELISA techniques in sequential injection analysis (SIA) mode using microreactors with content of a few microliters. We immobilized antibodies on magnetic beads 1.0mum in diameter, injected the beads into microreactors and applied rotating magnetic fields of several hundred gauss. Magnetic beads, suspended in liquid in density of approximately 10(9)-10(10) particles per millilitre, form a large number of thin rod clusters, whose length-wise axes are oriented in parallel with the magnetic field. We rotate the Nd magnets below the center of the microreactor by a tiny motor at about 2000-5000rpm. These rotating clusters remarkably accelerate the binding rate of the antibodies with antigens in the liquid. The beads are trapped around the center of the rotating magnetic field even in the flowing liquid. This newly found phenomenon enables easy bead handling in microreactors. Modification of reactor walls with selected blocking reagents was essential, because protein-coated beads often stick to the wall surface and cannot move freely. Washing steps were also shortened.
19. Bioinspired Design of Alcohol Dehydrogenase@nano TiO2 Microreactors for Sustainable Cycling of NAD+/NADH Coenzyme
Directory of Open Access Journals (Sweden)
Sen Lin
2018-02-01
20. Fabrication of tunable microreactor with enzyme modified magnetic nanoparticles for microfluidic electrochemical detection of glucose
Energy Technology Data Exchange (ETDEWEB)
Sheng Jin; Zhang Lei; Lei Jianping [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Ju Huangxian, E-mail: [email protected] [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China)
2012-01-04
Highlights: Black-Right-Pointing-Pointer An enzyme microreactor is prepared using an enzyme-nanoparticles packed microchannel. Black-Right-Pointing-Pointer The optimal performance can be obtained by the tunable length of the microreactor. Black-Right-Pointing-Pointer Baseline separation from interferents can be achieved with a microfluidic device. Black-Right-Pointing-Pointer A pretreatment-free determination method for glucose is proposed. - Abstract: A microfluidic device was designed for amperometric determination of glucose by packing enzyme modified magnetic nanoparticles (MNPs) in its microchannel as an enzyme microreactor. Glucose oxidase was covalently attached to the surface of MNPs and localized in the microchannel by the help of an external magnetic field, leading to a tunable packing length. By changing the length of microreactor from 3 to 10 mm, the performance for glucose detection was optimized. The optimal linear range to glucose was from 25 {mu}M to 15 mM with a detection limit of 11 {mu}M at a length of 6 mm. The inter- and intra-day precisions for determination of 1.0 mM glucose were 0.8% and 1.7%, respectively, and the device-to-device reproducibility was 95.6%. The enzyme reactor remained its 81% activity after three-week storage. Due to the advantages of the device and fracture sampling technique, serum samples could be directly sampled through the fracture to achieve baseline separation from ascorbic acid, and proteins in the samples did not interfere with the detection. This work provided a promising way for pretreatment-free determination of glucose with low cost and excellent performance.
1. Fabrication of tunable microreactor with enzyme modified magnetic nanoparticles for microfluidic electrochemical detection of glucose
International Nuclear Information System (INIS)
Sheng Jin; Zhang Lei; Lei Jianping; Ju Huangxian
2012-01-01
Highlights: ► An enzyme microreactor is prepared using an enzyme-nanoparticles packed microchannel. ► The optimal performance can be obtained by the tunable length of the microreactor. ► Baseline separation from interferents can be achieved with a microfluidic device. ► A pretreatment-free determination method for glucose is proposed. - Abstract: A microfluidic device was designed for amperometric determination of glucose by packing enzyme modified magnetic nanoparticles (MNPs) in its microchannel as an enzyme microreactor. Glucose oxidase was covalently attached to the surface of MNPs and localized in the microchannel by the help of an external magnetic field, leading to a tunable packing length. By changing the length of microreactor from 3 to 10 mm, the performance for glucose detection was optimized. The optimal linear range to glucose was from 25 μM to 15 mM with a detection limit of 11 μM at a length of 6 mm. The inter- and intra-day precisions for determination of 1.0 mM glucose were 0.8% and 1.7%, respectively, and the device-to-device reproducibility was 95.6%. The enzyme reactor remained its 81% activity after three-week storage. Due to the advantages of the device and fracture sampling technique, serum samples could be directly sampled through the fracture to achieve baseline separation from ascorbic acid, and proteins in the samples did not interfere with the detection. This work provided a promising way for pretreatment-free determination of glucose with low cost and excellent performance.
2. Novel micro-reactor flow cell for investigation of model catalysts using in situ grazing-incidence X-ray scattering.
Science.gov (United States)
Kehres, Jan; Pedersen, Thomas; Masini, Federico; Andreasen, Jens Wenzel; Nielsen, Martin Meedom; Diaz, Ana; Nielsen, Jane Hvolbæk; Hansen, Ole; Chorkendorff, Ib
2016-03-01
The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles.
3. Process intensification characteristics of a microreactor absorber for enhanced CO_2 capture
International Nuclear Information System (INIS)
Ganapathy, Harish; Steinmayer, Sascha; Shooshtari, Amir; Dessiatoun, Serguei; Ohadi, Michael M.; Alshehhi, Mohamed
2016-01-01
Highlights: • Enhanced gas separation/CO_2 capture using aqueous DEA in micro-structured absorber. • 15 straight parallel channels with hydraulic diameter of 456 μm. • Achieved close to 100% absorption efficiency under certain operating conditions. • Mass transfer coefficients 1–3 orders of magnitude higher than conventional absorbers. • Substantial intensification of absorption process achievable using microreactors. - Abstract: Gas separation processes, including post-combustion carbon capture (PCCC) by chemical absorption using liquid solvents can be substantially enhanced using high performance micro-structured surfaces to enhance the surface area available for reaction. The present paper studies the hydrodynamics and mass transfer performance of gas–liquid absorption of CO_2 into aqueous diethanolamine in a micro-structured reactor. The system was designed to comprise 15 straight parallel channels in a cross flow inlet configuration. The hydraulic diameter of each channel was 456 μm. The performance of the reactor was studied with respect to the absorption efficiency, mass transfer coefficient, acid gas loading ratio, and pressure drop. A flow pattern map was developed using available regime transition criteria. Parametric studies varying the gas and liquid flow rates, as well as their respective concentrations at the reactor inlet, were conducted. The two-phase pressure drop was compared against the predictions of a piecewise model and a reasonably good agreement was obtained. Absorption efficiencies close to 100% were observed under certain operating conditions. The presently achieved values of liquid-side volumetric mass transfer coefficients were between 1–3 orders of magnitude higher than those reported for most conventional gas–liquid absorption systems, which can be attributed to the inherent high specific interfacial area provided through micro-structured surfaces. The results reported here indicate the substantial levels of process
4. Thermoelectric generation coupling methanol steam reforming characteristic in microreactor
International Nuclear Information System (INIS)
Wang, Feng; Cao, Yiding; Wang, Guoqiang
2015-01-01
Thermoelectric (TE) generator converts heat to electric energy by thermoelectric material. However, heat removal on the cold side of the generator represents a serious challenge. To address this problem and for improved energy conversion, a thermoelectric generation process coupled with methanol steam reforming (SR) for hydrogen production is designed and analyzed in this paper. Experimental study on the cold spot character in a micro-reactor with monolayer catalyst bed is first carried out to understand the endothermic nature of the reforming as the thermoelectric cold side. A novel methanol steam reforming micro-reactor heated by waste heat or methanol catalytic combustion for hydrogen production coupled with a thermoelectric generation module is then simulated. Results show that the cold spot effect exists in the catalyst bed under all conditions, and the associated temperature difference first increases and then decreases with the inlet temperature. In the micro-reactor, the temperature difference between the reforming and heating channel outlets decreases rapidly with an increase in thermoelectric material's conductivity coefficient. However, methanol conversion at the reforming outlet is mainly affected by the reactor inlet temperature; while at the combustion outlet, it is mainly affected by the reactor inlet velocity. Due to the strong endothermic effect of the methanol steam reforming, heat supply of both kinds cannot balance the heat needed at reactor local areas, resulting in the cold spot at the reactor inlet. When the temperature difference between the thermoelectric module's hot and cold sides is 22 K, the generator can achieve an output voltage of 55 mV. The corresponding molar fraction of hydrogen can reach about 62.6%, which corresponds to methanol conversion rate of 72.6%. - Highlights: • Cold spot character of methanol steam reforming was studied through experiment. • Thermoelectric generation Coupling MSR process has been
5. A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed-bed microreactor
Directory of Open Access Journals (Sweden)
Andrew Bogdan
2009-04-01
Full Text Available We demonstrate the preparation and characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol entered the reactor as plugs but merged into an emulsion on the packed-bed. The emulsion coalesced into larger plugs upon exiting the reactor, leaving the organic product separate from the aqueous by-products. Furthermore, the microreactor oxidized a wide range of alcohols and remained active in excess of 100 trials without showing any loss of catalytic activity.
6. Lithographically fabricated silicon microreactor for in situ characterization of heterogeneous catalysts—Enabling correlative characterization techniques
Energy Technology Data Exchange (ETDEWEB)
Baier, S.; Rochet, A.; Hofmann, G. [Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, D-76131 Karlsruhe (Germany); Kraut, M. [Institute for Micro Process Engineering, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen (Germany); Grunwaldt, J.-D., E-mail: [email protected] [Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, D-76131 Karlsruhe (Germany); Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen (Germany)
2015-06-15
We report on a new modular setup on a silicon-based microreactor designed for correlative spectroscopic, scattering, and analytic on-line gas investigations for in situ studies of heterogeneous catalysts. The silicon microreactor allows a combination of synchrotron radiation based techniques (e.g., X-ray diffraction and X-ray absorption spectroscopy) as well as infrared thermography and Raman spectroscopy. Catalytic performance can be determined simultaneously by on-line product analysis using mass spectrometry. We present the design of the reactor, the experimental setup, and as a first example for an in situ study, the catalytic partial oxidation of methane showing the applicability of this reactor for in situ studies.
7. Non-Equilibrium Thermodynamic Analysis of Double Diffusive, Nanofluid Forced Convection in Catalytic Microreactors with Radiation Effects
Directory of Open Access Journals (Sweden)
Lilian Govone
2017-12-01
Full Text Available This paper presents a theoretical investigation of the second law performance of double diffusive forced convection in microreactors with the inclusion of nanofluid and radiation effects. The investigated microreactors consist of a single microchannel, fully filled by a porous medium. The transport of heat and mass are analysed by including the thick walls and a first order, catalytic chemical reaction on the internal surfaces of the microchannel. Two sets of thermal boundary conditions are considered on the external surfaces of the microchannel; (1 constant temperature and (2 constant heat flux boundary condition on the lower wall and convective boundary condition on the upper wall. The local thermal non-equilibrium approach is taken to thermally analyse the porous section of the system. The mass dispersion equation is coupled with the transport of heat in the nanofluid flow through consideration of Soret effect. The problem is analytically solved and illustrations of the temperature fields, Nusselt number, total entropy generation rate and performance evaluation criterion (PEC are provided. It is shown that the radiation effect tends to modify the thermal behaviour within the porous section of the system. The radiation parameter also reduces the overall temperature of the system. It is further demonstrated that, expectedly, the nanoparticles reduce the temperature of the system and increase the Nusselt number. The total entropy generation rate and consequently PEC shows a strong relation with radiation parameter and volumetric concentration of nanoparticles.
8. Do high school chemistry examinations inhibit deeper level understanding of dynamic reversible chemical reactions?
Science.gov (United States)
Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.
2012-07-01
Background and purpose : Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers require students to use approaches beyond direct application of LCP. Sample : The questionnaire was administered to 162 students studying their first year of advanced chemistry (age 16/17) in three high achieving London high schools. Design and methods : The students' explanations of reversible chemical systems were inductively coded to identify the explanatory approaches used and interviews with 13 students were used to check for consistency. AS level examination questions on reversible reactions were analysed to identify the types of explanations sought and the students' performance in these examinations was compared to questionnaire answers. Results : 19% of students used a holistic explanatory approach: when the rates of forward and reverse reactions are correctly described, recognising their simultaneous and mutually dependent nature. 36% used a mirrored reactions approach when the connected nature of the forward and reverse reactions is identified, but not their mutual dependency. 42% failed to recognize the interdependence of forward and reverse reactions (reactions not connected approach). Only 4% of marks for AS examination questions on reversible chemical systems asked for responses which went beyond either direct application of LCP or recall of equilibrium knowledge. 37% of students attained an A grade in their AS national examinations. Conclusions : Examinations favour the application of LCP making it possible to obtain the highest grade with little understanding of reversible chemical systems beyond a direct application of this algorithm. Therefore students' understanding may be attenuated so that they are
9. Novel micro-reactor flow cell for investigation of model catalysts using in situ grazing-incidence X-ray scattering
DEFF Research Database (Denmark)
Kehres, Jan; Pedersen, Thomas; Masini, Federico
2016-01-01
at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles.......The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing......-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments...
10. Novel micro-reactor flow cell for investigation of model catalysts using in situ grazing-incidence X-ray scattering
Science.gov (United States)
Kehres, Jan; Pedersen, Thomas; Masini, Federico; Andreasen, Jens Wenzel; Nielsen, Martin Meedom; Diaz, Ana; Nielsen, Jane Hvolbæk; Hansen, Ole
2016-01-01
The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles. PMID:26917133
11. Simulation of square wave voltammetry of three electrode reactions coupled by two reversible chemical reactions
OpenAIRE
Lovrić, Milivoj
2017-01-01
Three fast and reversible electrode reactions that are connected by two reversible chemical reactions that are permanently in the equilibrium are analysed theoretically for square wave voltammetry. The dependence of peak potentials on the dimensionless equilibrium constants of chemical reactions is calculated. The influence of the basic thermodynamic parameters on the square wave voltammetric responses is analysed.
12. Seed-mediated synthesis of silver nanocrystals with controlled sizes and shapes in droplet microreactors separated by air.
Science.gov (United States)
Zhang, Lei; Wang, Yi; Tong, Limin; Xia, Younan
2013-12-17
Silver nanocrystals with uniform sizes were synthesized in droplet microreactors through seed-mediated growth. The key to the success of this synthesis is the use of air as a carrier phase to generate the droplets. The air not only separates the reaction solution into droplets but also provides O2 for the generation of reducing agent (glycolaldehyde). It also serves as a buffer space for the diffusion of NO, which is formed in situ due to the oxidative etching of Ag nanocrystals with twin defects. For the first time, we were able to generate Ag nanocrystals with controlled sizes and shapes in continuous production by using droplet microreactors. For Ag nanocubes, their edge lengths could be readily controlled in the range of 30-100 nm by varying the reaction time, the amount of seeds, and the concentration of AgNO3 in the droplets. Furthermore, we demonstrated the synthesis of Ag octahedra in the droplet microreactors. We believe that the air-driven droplet generation device can be extended to other noble metals for the production of nanocrystals with controlled sizes and shapes.
13. Chemical-looping combustion in a reverse-flow fixed bed reactor
International Nuclear Information System (INIS)
Han, Lu; Bollas, George M.
2016-01-01
A reverse-flow fixed bed reactor concept for CLC (chemical-looping combustion) is explored. The limitations of conventional fixed bed reactors, as applied to CLC, are overcome by reversing the gas flow direction periodically to enhance the mixing characteristics of the bed, thus improving oxygen carrier utilization and energy efficiency with respect to power generation. The reverse-flow reactor is simulated by a dusty-gas model and compared with an equivalent fixed bed reactor without flow reversal. Dynamic optimization is used to calculate conditions at which each reactor operates at maximum energy efficiency. Several cases studies illustrate the benefits of reverse-flow operation for the CLC with CuO and NiO oxygen carriers and methane and syngas fuels. The results show that periodic reversal of the flow during reduction improves the contact between the fuel and unconverted oxygen carrier, enabling the system to suppress unwanted catalytic reactions and axial temperature and conversion gradients. The operational scheme presented reduces the fluctuations of temperature during oxidation and increases the high-temperature heat produced by the process. CLC in a reverse-flow reactor has the potential to achieve higher energy efficiency than conventional fixed bed CLC reactors, when integrated with a downstream gas turbine of a combined cycle power plant. - Highlights: • Reverse-flow fixed bed CLC reactors for combined cycle power systems. • Dynamic optimization tunes operation of batch and transient CLC systems. • The reverse-flow CLC system provides stable turbine-ready gas stream. • Reverse-flow CLC fixed bed reactor has superior CO 2 capture and thermal efficiency.
14. Microbial reverse-electrodialysis chemical-production cell for acid and alkali production
KAUST Repository
Zhu, Xiuping; Hatzell, Marta C.; Cusick, Roland D.; Logan, Bruce E.
2013-01-01
A new type of bioelectrochemical system, called a microbial reverse-electrodialysis chemical-production cell (MRCC), was developed to produce acid and alkali using energy derived from organic matter (acetate) and salinity gradients (NaCl solutions
15. Lactic Acid Extraction and Mass Transfer Characteristics in Slug Flow Capillary Microreactors
NARCIS (Netherlands)
Susanti, S.; Winkelman, J.G.N.; Schuur, Boelo; heeres, h.j.; Yue, J.
2016-01-01
Capillary microreactors operated under the slug flow regime were investigated for the separation of lactic acid from the aqueous phase using liquid–liquid reactive extraction. The experiments were performed at a 1:1 flow ratio of the aqueous to organic phases in a setup consisting of an inlet Y-type
16. Microreactors for Gold Nanoparticles Synthesis: From Faraday to Flow
Directory of Open Access Journals (Sweden)
Md. Taifur Rahman
2014-06-01
Full Text Available The seminal work of Michael Faraday in 1850s transmuted the “Alchemy of gold” into a fascinating scientific endeavor over the millennia, particularly in the past half century. Gold nanoparticles (GNPs arguably hold the central position of nanosciences due to their intriguing size-and-shape dependent physicochemical properties, non-toxicity, and ease of functionalization and potential for wide range of applications. The core chemistry involved in the syntheses is essentially not very different from what Michael Faraday resorted to: transforming ions into metallic gold using mild reducing agents. However, the process of such reduction and outcome (shapes and sizes are intricately dependent on basic operational parameters such as sequence of addition and efficiency of mixing of the reagents. Hence, irreproducibility in synthesis and maintaining batch-to-batch quality are major obstacles in this seemingly straightforward process, which poses challenges in scaling-up. Microreactors, by the virtue of excellent control over reagent mixing in space and time within narrow channel networks, opened a new horizon of possibilities to tackle such problems to produce GNPs in more reliable, reproducible and scalable ways. In this review, we will delineate the state-of-the-art of GNPs synthesis using microreactors and will discuss in length how such “flask-to-chip” paradigm shift may revolutionize the very concept of nanosyntheses.
17. Design of microreactor by integration of reverse engineering and direct metal laser sintering process
Energy Technology Data Exchange (ETDEWEB)
Bineli, Aulus Roberto Romao; Gimenez Perez, Ana Paula; Bernardes, Luiz Fernando; Munhoz, Andre Luiz Jardini; Maciel Filho, Rubens [Universidade de Campinas (LOPCA/UNICAMP), SP (Brazil). School of Chemical Engineering. Laboratory of Optimization, Design and Advanced Process Control], Email: [email protected]
2010-07-01
The propose of this work is to present high precision microfabrication facilities using computer aided technologies as Reverse Engineering (RE) and Rapid Manufacturing (RM) to analyze, design and construct micro reactors to produce high content hydrogen gas. Micro reactors are very compact, have a high surface to volume ratio, exhibit enhanced heat and mass transfer rates, denotes extremely low pressure drop and allow improved thermal integration in the processes involved. The main goals of micro reactors are the optimization of conventional chemical plants and low footprint, opening different ways to research new process technologies and synthesis of new products. In this work, a microchannels plate and housing structure of these plates were fabricated using DMLS method (Direct Metal Laser Sintering). The plates were analyzed to verify the minimum thickness wall that machine can produce, and the housing structure were digitalized, using a 3D scanning, to perform a 3D inspection and to verify the deflection of the constructed part in comparison with original CAD design models. It was observed that DMLS systems are able to produce micro reactors and microchannels plates with high precision at different metallic materials. However, it is important to choose appropriate conditions to avoid residual stresses and consequently warping parts. (author)
18. Design of micro-reactors and solar photocatalytic prototypes
International Nuclear Information System (INIS)
Flores E, R.M.; Hernandez H, M.; Perusquia del Cueto, M.R.; Bonifacio M, J.; Jimenez B, J.; Ortiz O, H.B.; Castaneda J, G.; Lugo H, M.
2007-01-01
In the ININ is carried out research in heterogeneous photocatalysis using artificial light for to degrade organic compounds. In this context, it is sought to use the solar radiation as energy source to knock down costs. Of equal form it requires to link the basic and applied research. For it, a methodology that allows to design and to build micro-reactors and plants pilot has been developed, like previous step, to request external supports and to a future commercialization. The beginning of these works gave place to the partial construction of a prototype of photocatalytic reactor of the cylinder-parabolic composed type (CPC)
19. Development of an enzymatic microreactor based on microencapsulated laccase with off-line capillary electrophoresis for measurement of oxidation reactions.
Science.gov (United States)
Roman-Gusetu, Georgiana; Waldron, Karen C; Rochefort, Dominic
2009-11-20
Microencapsulation is used here as a new technique to immobilize enzymes in a microreactor coupled off-line to capillary electrophoresis (CE), allowing the determination of enzymatic reaction products. The redox enzyme laccase was encapsulated using the method of interfacial cross-linking of poly(ethyleneimine) (PEI). The 50 microm diameter capsules were slurry packed from a suspension into a capillary-sized reactor made easily and quickly from a short length of 530 microm diameter fused-silica tubing. The volume of the bed of laccase microcapsules in the microreactor was in the order of 1.1 microL through which 50 microL of the substrate o-phenylenediamine (OPD) was flowed. The oxidation product 2,3-diaminophenazine (DAP) and the remaining OPD were quantified by CE in a pH 2.5 phosphate buffer. Peak migration time reproducibility was in the order of 0.4% RSD and peak area reproducibility was less than 1.7% RSD within the same day. Using the OPD peak area calibration curve, a conversion efficiency of 48% was achieved for a 2-min oxidation reaction in the microreactor.
20. The use of selective adsorbents in capillary electrophoresis-mass spectrometry for analyte preconcentration and microreactions: a powerful three-dimensional tool for multiple chemical and biological applications.
Science.gov (United States)
Guzman, N A; Stubbs, R J
2001-10-01
Much attention has recently been directed to the development and application of online sample preconcentration and microreactions in capillary electrophoresis using selective adsorbents based on chemical or biological specificity. The basic principle involves two interacting chemical or biological systems with high selectivity and affinity for each other. These molecular interactions in nature usually involve noncovalent and reversible chemical processes. Properly bound to a solid support, an "affinity ligand" can selectively adsorb a "target analyte" found in a simple or complex mixture at a wide range of concentrations. As a result, the isolated analyte is enriched and highly purified. When this affinity technique, allowing noncovalent chemical interactions and biochemical reactions to occur, is coupled on-line to high-resolution capillary electrophoresis and mass spectrometry, a powerful tool of chemical and biological information is created. This paper describes the concept of biological recognition and affinity interaction on-line with high-resolution separation, the fabrication of an "analyte concentrator-microreactor", optimization conditions of adsorption and desorption, the coupling to mass spectrometry, and various applications of clinical and pharmaceutical interest.
1. Chemical treatment of commercial reverse osmosis membranes for use in FO
Science.gov (United States)
Commercially available reverse osmosis (RO) membranes – SW30HR, BW30, and AG – were chemically treated for use in forward osmosis (FO). Nitric acid, phosphoric acid, sulfuric acid, ethanol, and ethanol–acid–water ternary solutions were employed for the treatment. All three membra...
2. Symmetry Relations in Chemical Kinetics Arising from Microscopic Reversibility
Science.gov (United States)
2006-01-01
It is shown that the kinetics of time-reversible chemical reactions having the same equilibrium constant but different initial conditions are closely related to one another by a directly measurable symmetry relation analogous to chemical detailed balance. In contrast to detailed balance, however, this relation does not require knowledge of the elementary steps that underlie the reaction, and remains valid in regimes where the concept of rate constants is ill defined, such as at very short times and in the presence of low activation barriers. Numerical simulations of a model of isomerization in solution are provided to illustrate the symmetry under such conditions, and potential applications in protein folding or unfolding are pointed out.
3. Online analysis of oxygen inside silicon-glass microreactors with integrated optical sensors
DEFF Research Database (Denmark)
Ehgartner, Josef; Sulzer, Philipp; Burger, Tobias
2016-01-01
A powerful online analysis set-up for oxygen measurements within microfluidic devices is presented. It features integration of optical oxygen sensors into microreactors, which enables contactless, accurate and inexpensive readout using commercially available oxygen meters via luminescent lifetime...... monitoring of enzyme transformations, including d-alanine or d-phenylalanine oxidation by d-amino acid oxidase, and glucose oxidation by glucose oxidase....
4. Advanced micro-reactor for space and deep sea exploration: a scientific Brazilian vision
International Nuclear Information System (INIS)
Nascimento, Jamil A. do; Guimaraes, Lamartine N.F.; Ono, Shizuca; Lobo, Paulo D.C.
2011-01-01
Humankind is at the point to initiate a new adventure in its evolutionary journey, the colonization of other planets of our solar system and space travels. Also, there is still another frontier where the human presence is scarce, the oceans and the Earth seabed. To have success in the exploration of these new frontiers a fundamental requirement must be satisfied: secure availability of energy for life support and others processes. This work deals with the establishment of a basis for a Brazilian nuclear research and development (R and D) program to develop micro-reactor (MR) technologies that may be used in the seabed, the space or another hostile environment on Earth. The work presents a set of basic requirements that is used to define the best reactor type to be used in these environments. Also, the limits and dimensions that define the class of micro-reactors are discussed. The fast neutron spectrum was chosen as the best for the MR and the limits for the active core volume and thermal power are 30 liters and 5 MW. (author)
5. Catalysis in flow microreactors with wall coatings of acidic polymer brushes and dendrimer-encapsulated nanoparticles
NARCIS (Netherlands)
Ricciardi, R.
2015-01-01
Continuous-flow microreactors are an invaluable tool to carry out organic reactions owing to their numerous advantages with respect to batch scale synthesis. In particular, supported catalysts enable heterogeneous catalysis to be conducted in an efficient way. In this thesis, the development and
6. Substantial rate enhancements of the esterification reaction of phthalic anhydride with methanol at high pressure and using supercritical CO2 as a co-solvent in a glass microreactor
NARCIS (Netherlands)
Benito-Lopez, F.; Tiggelaar, Roald M.; Salblut, K.; Huskens, Jurriaan; Egberink, Richard J.M.; Reinhoudt, David; Gardeniers, Johannes G.E.; Verboom, Willem
2007-01-01
The esterification reaction of phthalic anhydride with methanol was performed at different temperatures in a continuous flow glass microreactor at pressures up to 110 bar and using supercritical CO2 as a co-solvent. The design is such that supercritical CO2 can be generated inside the microreactor.
7. Reversible chemical patterning on stimuli-responsive polymer film: Environment-responsive lithography
International Nuclear Information System (INIS)
Ionov, Leonid; Minko, Sergiy; Stamm, Manfred; Gohy, Jean-Francois; Jerome, Robert; Scholl, Andreas
2003-01-01
We report on a novel type of chemical patterning based on thin stimuli-responsive polymer films. The basic concept is the permanent storage (writing) of a pattern, which is reversibly developed and erased upon exposure to appropriate environment, e.g., solvent, pH, and temperature. The smart surface is fabricated from the mixed brush of poly(2-vinylpyridine) and polyisoprene. The mixed brush demonstrates switching behavior upon exposure to different solvents. Cross-linking of polyisoprene via illumination through a photomask results in formation of patterns with suppressed switching. Due to the contrast in switching between illuminated and dark areas, exposure of the smart surface to different solvents causes either reversible formation or erasing of chemical contrast between the illuminated and dark areas. Thus, the pattern surface can very locally attract colloidal particles or can be wetted by water only upon exposure to the special solvent which introduces the contrast between the illuminated and dark areas. Appearance of the patterns indicates particular environment and can be used for local switching of adsorption
8. Optimization of biodiesel production from soybean oil in a microreactor
International Nuclear Information System (INIS)
Rahimi, Masoud; Aghel, Babak; Alitabar, Mohammad; Sepahvand, Arash; Ghasempour, Hamid Reza
2014-01-01
Graphical abstract: - Highlights: • Continuous transesterification of soybean oil is studied in a microreactor. • Box–Behnken method and response surface methodology used for optimization. • Fatty Acid Methyl Ester transesterification of 89% obtained at optimum condition. • The microchannel pressure drop was related to energy dissipation rate and FAME %. • Higher FAME % values were obtained at higher energy dissipation rate. - Abstract: Transesterification of soybean oil with methanol in the presence of potassium hydroxide, as a catalyst, in a microreactor has been investigated. The transesterification reaction was performed at specific condition in circular tubes with hydraulic diameter of (0.8 mm). In order to further improve the biodiesel production, the experimental design was performed using Box–Behnken method. The results were analyzed using response surface methodology. The influence of reaction variables including; molar ratio of methanol to oil (6:1–12:1), temperature (55–65 °C) and catalyst concentration (0.6–1.8 wt.%) and residence time (20–180 s) under various flow rates of reactants (1–11 ml min −1 ) on Fatty Acid Methyl Ester (FAME) transesterification reaction was studied. The optimum condition was found at molar ratio of methanol to oil (9:1), catalyst concentration (1.2 wt.%) and temperature (60 °C) with a FAME % of about 89%. Considering optimum parameters, by changing the reactant residence time the FAME % was reached to 98% at 180 s
9. High pressure direct synthesis of adipic acid from cyclohexene and hydrogen peroxide via capillary microreactors
NARCIS (Netherlands)
Shang, M.; Noël, T.; Su, Y.; Hessel, V.
2016-01-01
The direct synthesis of adipic acid from hydrogen peroxide and cyclohexene was investigated in capillary microreactors at high temperature (up to 115°C ) and pressure (up to 70 bar). High temperature was already applied in micro-flow packed-bed reactors for the direct adipic acid synthesis. In our
10. A low perfusion rate microreactor for continuous monitoring of enzyme characteristics : application to glucose oxidase
NARCIS (Netherlands)
Posthuma-Trumpie, G. A.; Venema, K.; van Berkel, W. J. H.; Korf, J.
This report describes a versatile and robust microreactor for bioactive proteins physically immobilized on a polyether sulfone filter. The potential of the reactor is illustrated with glucose oxidase immobilized on a filter with a cut-off value of 30 kDa. A flow-injection system was used to deliver
11. Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects
Science.gov (United States)
Zhang, Jie; Sheng, Lei; Liu, Jing
2014-11-01
Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.
12. Chemical respiratory allergy: Reverse engineering an adverse outcome pathway
International Nuclear Information System (INIS)
Kimber, Ian; Dearman, Rebecca J.; Basketter, David A.; Boverhof, Darrell R.
2014-01-01
Allergic sensitisation of the respiratory tract by chemicals is associated with rhinitis and asthma and remains an important occupational health issue. Although less than 80 chemicals have been confirmed as respiratory allergens the adverse health effects can be serious, and in rare instances can be fatal, and there are, in addition, related socioeconomic issues. The challenges that chemical respiratory allergy pose for toxicologists are substantial. No validated methods are available for hazard identification and characterisation, and this is due in large part to the fact that there remains considerable uncertainty and debate about the mechanisms through which sensitisation of the respiratory tract is acquired. Despite that uncertainty, there is a need to establish some common understanding of the key events and processes that are involved in respiratory sensitisation to chemicals and that might in turn provide the foundations for novel approaches to safety assessment. In recent years the concept of adverse outcome pathways (AOP) has gained some considerable interest among the toxicology community as a basis for outlining the key steps leading to an adverse health outcome, while also providing a framework for focusing future research, and for developing alternative paradigms for hazard characterisation. Here we explore application of the same general principles to an examination of the induction by chemicals of respiratory sensitisation. In this instance, however, we have chosen to adopt a reverse engineering approach and to model a possible AOP for chemical respiratory allergy working backwards from the elicitation of adverse health effects to the cellular and molecular mechanisms that are implicated in the acquisition of sensitisation
13. Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor.
Science.gov (United States)
Porterfield, Jessica P; Nguyen, Thanh Lam; Baraban, Joshua H; Buckingham, Grant T; Troy, Tyler P; Kostko, Oleg; Ahmed, Musahid; Stanton, John F; Daily, John W; Ellison, G Barney
2015-12-24
The thermal decomposition of cyclohexanone (C6H10═O) has been studied in a set of flash-pyrolysis microreactors. Decomposition of the ketone was observed when dilute samples of C6H10═O were heated to 1200 K in a continuous flow microreactor. Pyrolysis products were detected and identified by tunable VUV photoionization mass spectroscopy and by photoionization appearance thresholds. Complementary product identification was provided by matrix infrared absorption spectroscopy. Pyrolysis pressures were roughly 100 Torr, and contact times with the microreactors were roughly 100 μs. Thermal cracking of cyclohexanone appeared to result from a variety of competing pathways, all of which open roughly simultaneously. Isomerization of cyclohexanone to the enol, cyclohexen-1-ol (C6H9OH), is followed by retro-Diels-Alder cleavage to CH2═CH2 and CH2═C(OH)-CH═CH2. Further isomerization of CH2═C(OH)-CH═CH2 to methyl vinyl ketone (CH3CO-CH═CH2, MVK) was also observed. Photoionization spectra identified both enols, C6H9OH and CH2═C(OH)-CH═CH2, and the ionization threshold of C6H9OH was measured to be 8.2 ± 0.1 eV. Coupled cluster electronic structure calculations were used to establish the energetics of MVK. The heats of formation of MVK and its enol were calculated to be ΔfH298(cis-CH3CO-CH═CH2) = -26.1 ± 0.5 kcal mol(-1) and ΔfH298(s-cis-1-CH2═C(OH)-CH═CH2) = -13.7 ± 0.5 kcal mol(-1). The reaction enthalpy ΔrxnH298(C6H10═O → CH2═CH2 + s-cis-1-CH2═C(OH)-CH═CH2) is 53 ± 1 kcal mol(-1) and ΔrxnH298(C6H10═O → CH2═CH2 + cis-CH3CO-CH═CH2) is 41 ± 1 kcal mol(-1). At 1200 K, the products of cyclohexanone pyrolysis were found to be C6H9OH, CH2═C(OH)-CH═CH2, MVK, CH2CHCH2, CO, CH2═C═O, CH3, CH2═C═CH2, CH2═CH-CH═CH2, CH2═CHCH2CH3, CH2═CH2, and HC≡CH.
14. A low perfusion rate microreactor for the continous monitoring of enzyme characteristics: applications for glucose oxidase.
NARCIS (Netherlands)
Posthuma-Trumpie, G.A.; Venema, K.; Berkel, van W.J.H.; Korf, J.
2007-01-01
This report describes a versatile and robust microreactor for bioactive proteins physically immobilized on a polyether sulfone filter. The potential of the reactor is illustrated with glucose oxidase immobilized on a filter with a cut-off value of 30 kDa. A flow-injection system was used to deliver
15. A rapidly-reversible absorptive and emissive vapochromic Pt(II) pincer-based chemical sensor.
Science.gov (United States)
Bryant, M J; Skelton, J M; Hatcher, L E; Stubbs, C; Madrid, E; Pallipurath, A R; Thomas, L H; Woodall, C H; Christensen, J; Fuertes, S; Robinson, T P; Beavers, C M; Teat, S J; Warren, M R; Pradaux-Caggiano, F; Walsh, A; Marken, F; Carbery, D R; Parker, S C; McKeown, N B; Malpass-Evans, R; Carta, M; Raithby, P R
2017-11-27
Selective, robust and cost-effective chemical sensors for detecting small volatile-organic compounds (VOCs) have widespread applications in industry, healthcare and environmental monitoring. Here we design a Pt(II) pincer-type material with selective absorptive and emissive responses to methanol and water. The yellow anhydrous form converts reversibly on a subsecond timescale to a red hydrate in the presence of parts-per-thousand levels of atmospheric water vapour. Exposure to methanol induces a similarly-rapid and reversible colour change to a blue methanol solvate. Stable smart coatings on glass demonstrate robust switching over 10 4 cycles, and flexible microporous polymer membranes incorporating microcrystals of the complex show identical vapochromic behaviour. The rapid vapochromic response can be rationalised from the crystal structure, and in combination with quantum-chemical modelling, we provide a complete microscopic picture of the switching mechanism. We discuss how this multiscale design approach can be used to obtain new compounds with tailored VOC selectivity and spectral responses.
16. Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis.
Science.gov (United States)
Fanelli, Flavio; Parisi, Giovanna; Degennaro, Leonardo; Luisi, Renzo
2017-01-01
Microreactor technology and flow chemistry could play an important role in the development of green and sustainable synthetic processes. In this review, some recent relevant examples in the field of flash chemistry, catalysis, hazardous chemistry and continuous flow processing are described. Selected examples highlight the role that flow chemistry could play in the near future for a sustainable development.
17. Design and characterization of a microreactor for monodisperse catalytic droplet generation at both elevated temperatures and pressures
NARCIS (Netherlands)
Vollenbroek, J. C.; Bomer, Johan G.; Van Den Berg, A.; Odijk, M.; Nieuwelink, A. E.; Weckhuysen, Bert M.; Geitenbeek, R. G.; Tiggelaar, R. M.
2017-01-01
We report the fabrication and characterization of a microfluidic droplet microreactor with potential use for single catalyst particle diagnostics. The aim is to capture Fluid Catalytic Cracking (FCC) particles in droplets and perform a probe reaction that results in a fluorescent output signal. The
18. Microbial reverse-electrodialysis chemical-production cell for acid and alkali production
KAUST Repository
Zhu, Xiuping
2013-06-01
A new type of bioelectrochemical system, called a microbial reverse-electrodialysis chemical-production cell (MRCC), was developed to produce acid and alkali using energy derived from organic matter (acetate) and salinity gradients (NaCl solutions representative of seawater and river water). A bipolar membrane (BPM) was placed next to the anode to prevent Cl- contamination and acidification of the anolyte, and to produce protons for HCl recovery. A 5-cell paired reverse-electrodialysis (RED) stack provided the electrical energy required to overcome the BPM over-potential (0.3-0.6 V), making the overall process spontaneous. The MRCC reactor produced electricity (908 mW/m2) as well as concentrated acidic and alkaline solutions, and therefore did not require an external power supply. After a fed-batch cycle, the pHs of the chemical product solutions were 1.65 ± 0.04 and 11.98 ± 0.10, due to the production of 1.35 ± 0.13 mmol of acid, and 0.59 ± 0.14 mmol of alkali. The acid- and alkali-production efficiencies based on generated current were 58 ± 3% and 25 ± 3%. These results demonstrated proof-of-concept acid and alkali production using only renewable energy sources. © 2013 Elsevier B.V.
19. Design of a stationary-basket (microreactor)
Energy Technology Data Exchange (ETDEWEB)
Timidei, A; Raisa, L
1977-05-01
A continuous-flow stirred-tank microreactor (295 cc capacity) for kinetic studies in gas-solid heterogeneous catalysis has been designed to obtain an apparatus characterized by perfect mixing, absence of resistance to mass and heat transfer, and pressure tightness, and which would not require sophisticated machine-shop work. This reactor is suitable for operation at up to 300/sup 0/C and 20 atm, and has clear advantages over the spinning-basket or rotating reactor in studies of catalysts of low mechanical strength. Tests with nitrogen or ethane as tracer and helium as carrier gas, run with a thermal conductivity detector, gave a ''decadence'' curve with a -0.97 slope at all mixing speeds, compared with a -1.0 slope for perfect mixing. Thermal gradients between fluid and pellet were minimal for three different pellet positions within the annular bed, at 92/sup 0/C. In benzene hydrogenation over a nickel/kieselguhr catalyst, measurement of reaction rates as a function of mixing speeds showed that good results in kinetic studies were obtainable at 1500 rpm and above. Diagrams and graphs.
20. Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis
Directory of Open Access Journals (Sweden)
Flavio Fanelli
2017-03-01
Full Text Available Microreactor technology and flow chemistry could play an important role in the development of green and sustainable synthetic processes. In this review, some recent relevant examples in the field of flash chemistry, catalysis, hazardous chemistry and continuous flow processing are described. Selected examples highlight the role that flow chemistry could play in the near future for a sustainable development.
1. Advances in microreaction technology for portable fuel cell applications: Wall coating of thin catalytic films in microreactors
Science.gov (United States)
Bravo Bersano, Jaime Cristian
This research has focused on the need to coat microreactor systems composed of channels in the micron size range of 100 to 1000 mum. The experimental procedures and learning are outlined in terms of slurry and surface preparation requirements which are detailed in the experimental section. This system is motivated and applied to micro methanol steam reformers. Thus, a detailed discussion on the driving motivation is given in the introduction. The low temperatures required for steam-reforming of methanol ˜ 493°K (220°C) make it possible to utilize the reformate as a feed to the fuel cell anode. The group of catalysts that shows the highest activity for methanol steam reforming (SR) at low temperature has composition of CuO/ZnO/Al 2O3, which is also the catalyst used for methanol synthesis. Steam reforming of methanol is a highly endothermic process. Conventional reactor configurations, such as a packed bed reactor, operate in a heat transfer limited mode for this reaction. Using catalyst in packed bed form for portable devices is also not convenient due to high pressure drop and possible channeling of gases in addition to poor heat transfer. A wall-coated catalyst represents a superior geometry since it provides lower pressure drop and ease of manufacturing. Due to their small size, microreactors are especially suited for endothermic reactions whose reactivity depends on the rate of heat input. A brief review on microreaction technology is given with a comprehensive survey for catalyst integration into microreactors for catalytic heterogeneous gas phase reactions. The strength of this research is the model that was developed to coat the interior of micron sized capillaries with coats of CuO/ZnO/Al2O 3 slurries as thick as 25 mum in the dry state. The details of the model are given in terms Taylor's theory and Rayleigh's theory. A model is presented that can predict the coat thickness based on experimental conditions The model combines Taylor's experimental work
2. Synthesis and characterization of cationic lipid coated magnetic nanoparticles using multiple emulsions as microreactors
Energy Technology Data Exchange (ETDEWEB)
Akbaba, Hasan; Karagöz, Uğur [Ege University, Faculty of Pharmacy, Department of Pharmaceutical Biotechnology, 35100 Izmir (Turkey); Selamet, Yusuf [Izmir Institute of Technology, Faculty of Science, Department of Physics, 35433 Izmir (Turkey); Kantarcı, A. Gülten, E-mail: [email protected] [Ege University, Faculty of Pharmacy, Department of Pharmaceutical Biotechnology, 35100 Izmir (Turkey)
2017-03-15
The aim of this study was to develop a novel iron oxide nanoparticle synthesis method with in-situ surface coating. For this purpose multiple emulsions were used as microreactors for the first time and magnetic iron oxide particles synthesized in the core of cationic solid lipid nanoparticles. DLS, SEM, TEM, VSM, Raman Spectrometer, XRD, and XPS techniques were performed for characterization of the magnetic nanoparticles. Obtained magnetic nanoparticles are superparamagnetic and no additional process was needed for surface adjustments. They are positively charged as a result of cationic lipid coating and has appropriate particle size (<30 nm) for drug or nucleic acid delivery. Structure analysis showed that magnetic core material is in the form of magnetite. Saturation magnetization value was measured as 15–17 emu g{sup −1} for lipid coated magnetic nanoparticles obtained by multiple emulsion method which is reasonably sufficient for magnetic targeting. - Highlights: • A novel iron oxide nanoparticle synthesis method with in-situ surface coating. • Combining advantages of microemulsions and multiple emulsion methods. • Multiple emulsions were used as microreactors for magnetic nanoparticle synthesis. • Superparamagnetic iron oxide particles synthesized in the core of cationic lipids. • Possible delivery systems for nucleic acids, oil soluble compounds or drugs.
3. Micro-reactor for heterogeneous catalysis. Application: hydrogen production from methyl-cyclohexane; Microreacteur pour la catalyse heterogene. Application: production d'hydrogene a partir du methylcyclohexane
Energy Technology Data Exchange (ETDEWEB)
Roumanie, M.; Pijolat, C. [Ecole des Mines de Saint Etienne, Centre SPIN (DMICC/LPMG/URA/CNRS-D2021), 42 - Saint Etienne (France); Meille, V.; Bellefon, C. de [Centre National de la Recherche Scientifique (CNRS/CPE), Lab. de Genie des Procedes Catalytiques, 69 - Villeurbanne (France); Pouteau, P.; Delattre, C. [CEA Grenoble, Lab. d' Electronique et de Technologie de l' Informatique (LETI), 38 (France)
2004-07-01
First developed by the pharmaceutical industry to find new drugs (combinatorial analysis), the lab on chip is also extremely interesting for the catalysis field. This major interest comes from the miniaturize size and the high surface on volume ratio which lead to improve mass and heat transfer but also the safety in regards of industrial application. The use of micro-technology and the miniaturization of various systems such as micro-fuel cell is also a current field of activity. So for the future research the production of hydrogen is a point to develop in order to supply a micro-fuel cell. The aim of this work is to study and to realize an autonomous catalytic micro-reactor for hydrogen production from methyl-cyclohexane. For this reaction of dehydrogenation, the common catalyst is platinum supported on alumina. Consequently, the general objectives of this work are: 1)to develop a micro-reactor with its heaters, sensors...2)to deposit catalysts in the micro-reactor 3)to study the catalytic conversion of this system.
4. Flow microreactor synthesis of 2,2-disubstituted oxetanes via 2-phenyloxetan-2-yl lithium
Directory of Open Access Journals (Sweden)
Degennaro Leonardo
2016-01-01
Full Text Available A mild and sustainable synthesis of 2,2-disubstituted oxetanes has been achieved through the use of a flow microreactor system. By controlling the residence time a highly unstable intermediate such as 2-phenyloxetan-2-yl lithium can be generated and trapped with various electrophiles affording in moderate to good yields 2-substituted-2-phenyloxetanes at higher temperatures with respect to macrobatch-mode where –78 °C is required.
5. Parallelization of Droplet Microfluidic Systems for the Sustainable Production of Micro-Reactors at Industrial Scale
KAUST Repository
Conchouso Gonzalez, David
2017-04-01
At the cutting edge of the chemical and biological research, innovation takes place in a field referred to as Lab on Chip (LoC), a multi-disciplinary area that combines biology, chemistry, electronics, microfabrication, and fluid mechanics. Within this field, droplets have been used as microreactors to produce advanced materials like quantum dots, micro and nanoparticles, active pharmaceutical ingredients, etc. The size of these microreactors offers distinct advantages, which were not possible using batch technologies. For example, they allow for lower reagent waste, minimal energy consumption, increased safety, as well as better process control of reaction conditions like temperature regulation, residence times, and response times among others. One of the biggest drawbacks associated with this technology is its limited production volume that prevents it from reaching industrial applications. The standard production rates for a single droplet microfluidic device is in the range of 1-10mLh-1, whereas industrial applications usually demand production rates several orders of magnitude higher. Although substantial work has been recently undertaken in the development scaled-out solutions, which run in parallel several droplet generators. Complex fluid mechanics and limitations on the manufacturing capacity have constrained these works to explore only in-plane parallelization. This thesis investigates a three-dimensional parallelization by proposing a microfluidic system that is comprised of a stack of droplet generation layers working on the liquid-liquid ow regime. Its realization implied a study of the characteristics of conventional droplet generators and the development of a fabrication process for 3D networks of microchannels. Finally, the combination of these studies resulted in a functional 3D parallelization system with the highest production rate (i.e. 1 Lh-1) at the time of its publication. Additionally, this architecture can reach industrially relevant
6. Proof of concept for continuous enantioselective liquid-liquid extraction in capillary microreactors using 1-octanol as a sustainable solvent
NARCIS (Netherlands)
Susanti, S.; Meinds, Tim G.; Pinxterhuis, Erik B.; Schuur, Boelo; De Vries, Johannes G.; Feringa, Ben L.; Winkelman, Jozef G.M.; Yue, Jun; Heeres, Hero J.
2017-01-01
The use of capillary microreactors for enantioselective liquid-liquid extraction (ELLE) was successfully demonstrated using a model system consisting of a buffered aqueous amino acid derivative (3,5-dinitrobenzoyl-(R,S)-leucine) solution (phosphate buffer, pH 6.58) and a chiral cinchona alkaloid
7. On the graph and systems analysis of reversible chemical reaction networks with mass action kinetics
NARCIS (Netherlands)
Rao, Shodhan; Jayawardhana, Bayu; Schaft, Arjan van der
2012-01-01
Motivated by the recent progresses on the interplay between the graph theory and systems theory, we revisit the analysis of reversible chemical reaction networks described by mass action kinetics by reformulating it using the graph knowledge of the underlying networks. Based on this formulation, we
8. Thermomyces lanuginosus lipase-catalyzed synthesis of natural flavor esters in a continuous flow microreactor.
Science.gov (United States)
Gumel, Ahmad Mohammed; Annuar, M S M
2016-06-01
Enzymatic catalysis is considered to be among the most environmental friendly processes for the synthesis of fine chemicals. In this study, lipase from Thermomyces lanuginosus (Lecitase Ultra™) was used to catalyze the synthesis of flavor esters, i.e., methyl butanoate and methyl benzoate by esterification of the acids with methanol in a microfluidic system. Maximum reaction rates of 195 and 115 mM min -1 corresponding to catalytic efficiencies (k cat /K M ) of 0.30 and 0.24 min -1 mM -1 as well as yield conversion of 54 and 41 % were observed in methyl butanoate and methyl benzoate synthesis, respectively. Catalytic turnover (k cat ) was higher for methyl butanoate synthesis. Rate of synthesis and yield decreased with increasing flow rates. For both esters, increase in microfluidic flow rate resulted in increased advective transport over molecular diffusion and reaction rate, thus lower conversion. In microfluidic synthesis using T. lanuginosus lipase, the following reaction conditions were 40 °C, flow rate 0.1 mL min -1 , and 123 U g -1 enzyme loading found to be the optimum operating limits. The work demonstrated the application of enzyme(s) in a microreactor system for the synthesis of industrially important esters.
9. Chemical encapsulation of rocuronium by synthetic cyclodextrin derivatives: reversal of neuromuscular block in anaesthetized Rhesus monkeys.
NARCIS (Netherlands)
Boer, H.D. de; Egmond, J. van; Pol, F. van de; Bom, A.; Booij, L.H.D.J.
2006-01-01
BACKGROUND: At present, reversal of neuromuscular block induced by steroidal neuromuscular blocking agents (NMBAs) is achieved by administration of cholinesterase inhibitors. Chemical encapsulation of steroidal NMBAs, such as rocuronium, by a cyclodextrin is a new concept in neuromuscular block
10. Estrogenic chemical effects are independent from the degree of sex role reversal in pipefish.
Science.gov (United States)
Sárria, Marisa P; Santos, Miguel M; Castro, L Filipe C; Vieira, Natividade M; Monteiro, Nuno M
2013-12-15
Endocrine disrupting chemicals (EDCs) have been reported to disturb several ecological relevant endpoints. Surprisingly, EDC-induced effects on fish sexual behaviour have been poorly studied despite the fact that even subtle alterations might contribute to a disruption of sexual interactions, thus negatively impacting reproduction. As the few assessments on sexual behaviour have been conducted in species with orthodox sex roles, it might be argued that sex-role reversed species might provide a potentially complementary system to further explore the effects of EDCs on reproduction. In the present study, two pipefish species with distinct degrees of sex-role reversal were selected to further elucidate the impact of chronic EE2 exposure on sexual behaviour and reproduction-related endpoints. The obtained results indicate that, independently of the degree of sex role reversal, courtship behaviour seems to resist oestrogenic chemical exposure. However, exposure to environmentally relevant EE2 levels did induce a complete absence of pregnancies at 18 ng/L. Even though pregnancies were observed at intermediate concentrations, the percentage of non-transferred or misplaced oocytes increased and a dose-dependent decrease of oocyte volume was observed. Imbalances in the oogenesis process, induction of vitellogenin in males and the absence of pregnancies highlight that environmental relevant concentrations of EE2 have the potential to negatively affect pipefish populations, most of them inhabiting coastal areas where oestrogenic contamination is more prevalent. Copyright © 2013 Elsevier B.V. All rights reserved.
11. PTFE-based microreactor system for the continuous synthesis of full-visible-spectrum emitting cesium lead halide perovskite nanocrystals
Directory of Open Access Journals (Sweden)
Chengxi Zhang
2017-11-01
Full Text Available Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX3, X = Cl, Br, I or a mixture thereof have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene (PTFE capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19–35 nm, high fluorescence quantum yield of 47.8–90.55%, and photoluminescence emission in the range of 450–700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices.
Science.gov (United States)
Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)
2016-01-01
Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.
13. Breakup of confined droplets in microfluidics
NARCIS (Netherlands)
Hoang, A.D.
2013-01-01
Segmented-flow microreactors have emerged as an attractive tool for fine chemical synthesis and (bio)chemical analysis, owing to their high heat and mass transfer rate, low axial dispersion, as well as rapid mixing. A key challenge for the use of segmented-flow microreactors in large-scale
14. Nanoscale control of reversible chemical reaction between fullerene C60 molecules using scanning tunneling microscope.
Science.gov (United States)
Nakaya, Masato; Kuwahara, Yuji; Aono, Masakazu; Nakayama, Tomonobu
2011-04-01
The nanoscale control of reversible chemical reactions, the polymerization and depolymerization between C60 molecules, has been investigated. Using a scanning tunneling microscope (STM), the polymerization and depolymerization can be controlled at designated positions in ultrathin films of C60 molecules. One of the two chemical reactions can be selectively induced by controlling the sample bias voltage (V(s)); the application of negative and positive values of V(s) results in polymerization and depolymerization, respectively. The selectivity between the two chemical reactions becomes extremely high when the thickness of the C60 film increases to more than three molecular layers. We conclude that STM-induced negative and positive electrostatic ionization are responsible for the control of the polymerization and depolymerization, respectively.
15. The effect of flow and chemical corrosion in reverse osmosis over desalinated water
Energy Technology Data Exchange (ETDEWEB)
Kim, Young Jae [Chunnam National Univ., Gwangju (Korea, Republic of); Pak, Byung Gu [Doosan Heavy Industry Co., Tongyoung (Korea, Republic of)
2015-12-15
Desalinated water produced by a reverse osmosis (RO) filtering method forms about 22% of total production of desalinated water in the world. However, the RO environment is very corrosive due to the presence of various chemicals for water treatment and the flow of sand particles leading to corrosion. Recently, there has been much effort to substitute cheaper and more corrosion resistant stainless steels for copper based alloys as a valve material in RO. Nevertheless, the effects of chemicals and particles on the corrosion of stainless steels have rarely been studied. Erosion phenomenon was detected under the condition with the flow rate of more than 8ms{sup -1} in spite of the absence of sand particles. In seawater containing sand particles, the erosion in stainless steels was accelerated further.
16. Oxidation of methane on nanoparticulate Au/TiO2 at low temperature: A combined microreactor and DFT study
DEFF Research Database (Denmark)
Walther, Guido; Jones, Glenn; Jensen, Søren
2009-01-01
Herein we present results from experimental and theoretical studies concerning low temperature oxidation of CH4 over TiO2 supported Au nanoparticles. Our findings suggest that partial oxidation cannot be achieved under these conditions (1 bar, 30–250 °C). In order to understand this further, resu......-calculations investigating the thermodynamics of CH4 oxidation on a stepped Au(2 1 1) surface. Keywords: Gold; Titanium dioxide; Catalysis; Microreactor; Methane; Oxidation; Particle size...
17. X-ray Microspectroscopy and Chemical Reactions in Soil Microsites
Energy Technology Data Exchange (ETDEWEB)
D Hesterberg; M Duff; J Dixon; M Vepraskas
2011-12-31
Soils provide long-term storage of environmental contaminants, which helps to protect water and air quality and diminishes negative impacts of contaminants on human and ecosystem health. Characterizing solid-phase chemical species in highly complex matrices is essential for developing principles that can be broadly applied to the wide range of notoriously heterogeneous soils occurring at the earth's surface. In the context of historical developments in soil analytical techniques, we describe applications of bulk-sample and spatially resolved synchrotron X-ray absorption spectroscopy (XAS) for characterizing chemical species of contaminants in soils, and for determining the uniqueness of trace-element reactivity in different soil microsites. Spatially resolved X-ray techniques provide opportunities for following chemical changes within soil microsites that serve as highly localized chemical micro- (or nano-)reactors of unique composition. An example of this microreactor concept is shown for micro-X-ray absorption near edge structure analysis of metal sulfide oxidation in a contaminated soil. One research challenge is to use information and principles developed from microscale soil chemistry for predicting macroscale and field-scale behavior of soil contaminants.
18. The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors
OpenAIRE
Faith M. Akwi; Paul Watts
2016-01-01
Summary In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 min...
19. Rotating Reverse-Osmosis for Water Purification
Science.gov (United States)
Lueptow, RIchard M.
2004-01-01
A new design for a water-filtering device combines rotating filtration with reverse osmosis to create a rotating reverse- osmosis system. Rotating filtration has been used for separating plasma from whole blood, while reverse osmosis has been used in purification of water and in some chemical processes. Reverse- osmosis membranes are vulnerable to concentration polarization a type of fouling in which the chemicals meant not to pass through the reverse-osmosis membranes accumulate very near the surfaces of the membranes. The combination of rotating filtration and reverse osmosis is intended to prevent concentration polarization and thereby increase the desired flux of filtered water while decreasing the likelihood of passage of undesired chemical species through the filter. Devices based on this concept could be useful in a variety of commercial applications, including purification and desalination of drinking water, purification of pharmaceutical process water, treatment of household and industrial wastewater, and treatment of industrial process water. A rotating filter consists of a cylindrical porous microfilter rotating within a stationary concentric cylindrical outer shell (see figure). The aqueous suspension enters one end of the annulus between the inner and outer cylinders. Filtrate passes through the rotating cylindrical microfilter and is removed via a hollow shaft. The concentrated suspension is removed at the end of the annulus opposite the end where the suspension entered.
20. Enzymatic reactions in reversed micelles
NARCIS (Netherlands)
Hilhorst, M.H.
1984-01-01
It has been recognised that enzymes in reversed micelles have potential for application in chemical synthesis. Before these expectations will be realised many problems must be overcome. This thesis deals with some of them.
In Chapter 1 the present knowledge about reversed micelles and
1. High pressure: a challenge for lab-on-a-chip technology
NARCIS (Netherlands)
Benito-Lopez, F.
2007-01-01
The realization of microreactors, in which chemical reactions can be carried out in continuous or stop flow mode under pressure conditions, is the main topic of this thesis. The advantages of microreactor technology for pressure chemistry are clearly demonstrated in this thesis. Organic reactions
2. Chapter 8: Pyrolysis Mechanisms of Lignin Model Compounds Using a Heated Micro-Reactor
Energy Technology Data Exchange (ETDEWEB)
Robichaud, David J.; Nimlos, Mark R.; Ellison, G. Barney
2015-10-03
Lignin is an important component of biomass, and the decomposition of its thermal deconstruction products is important in pyrolysis and gasification. In this chapter, we investigate the unimolecular pyrolysis chemistry through the use of singly and doubly substituted benzene molecules that are model compounds representative of lignin and its primary pyrolysis products. These model compounds are decomposed in a heated micro-reactor, and the products, including radicals and unstable intermediates, are measured using photoionization mass spectrometry and matrix isolation infrared spectroscopy. We show that the unimolecular chemistry can yield insight into the initial decomposition of these species. At pyrolysis and gasification severities, singly substituted benzenes typically undergo bond scission and elimination reactions to form radicals. Some require radical-driven chain reactions. For doubly substituted benzenes, proximity effects of the substituents can change the reaction pathways.
3. Microreactor and method for preparing a radiolabeled complex or a biomolecule conjugate
Energy Technology Data Exchange (ETDEWEB)
Reichert, David E; Kenis, Paul J. A.; Wheeler, Tobias D; Desai, Amit V; Zeng, Dexing; Onal, Birce C
2015-03-17
A microreactor for preparing a radiolabeled complex or a biomolecule conjugate comprises a microchannel for fluid flow, where the microchannel comprises a mixing portion comprising one or more passive mixing elements, and a reservoir for incubating a mixed fluid. The reservoir is in fluid communication with the microchannel and is disposed downstream of the mixing portion. A method of preparing a radiolabeled complex includes flowing a radiometal solution comprising a metallic radionuclide through a downstream mixing portion of a microchannel, where the downstream mixing portion includes one or more passive mixing elements, and flowing a ligand solution comprising a bifunctional chelator through the downstream mixing portion. The ligand solution and the radiometal solution are passively mixed while in the downstream mixing portion to initiate a chelation reaction between the metallic radionuclide and the bifunctional chelator. The chelation reaction is completed to form a radiolabeled complex.
4. Droplet-fused microreactors for room temperature synthesis of nanoscale needle-like hydroxyapatite
International Nuclear Information System (INIS)
Liu Kaiying; Qin Jianhua
2013-01-01
A microfluidic device using droplet-fused microreactors is introduced for room temperature synthesis of nanoscale needle-shaped hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ). The device is integrated with multifunctional units, e.g., T-junctions for droplet generation and fusion, winding channels for rapid mixing, and a delay line for simple visualization of the HAp formation process. The necessary conditions such as surfactant and fluid flow rate for an aqueous stream to merge with water-in-oil droplets are investigated. The nanoscale morphologies of the HAp produced by this method are also compared with HAp prepared by conventional bulk mixing. This paper shows that further reaction could be initiated by flowing additional reagent streams directly into the droplets of the initial reaction mixture, which is a novel approach for synthesizing a needle-like morphology of the HAp with a high aspect ratio under room temperature. (paper)
5. Use of micro-reactors to obtain new insights into the factors influencing tricalcium silicate dissolution
International Nuclear Information System (INIS)
Suraneni, Prannoy; Flatt, Robert J.
2015-01-01
A micro-reactor approach, developed previously, is used to study the early dissolution of tricalcium silicate. This approach uses micron-sized gaps mimicking particles in close contact to understand dissolution, nucleation, and growth processes. The main factors influencing the dissolution kinetics of tricalcium silicate are presented. We show that the presence of defects caused by polishing does not affect the extent of dissolution. A strong effect of aluminum in solution reducing the extent of dissolution is however identified. This effect is highly dependent on the pH, and is much lower above pH 13. We show also that superplasticizers reduce the extent of dissolution; however, the exact reason for this effect is not clear.
6. Thermodynamic reversibility and irreversibility of the reverse transformation in stabilized Cu-Zn-Al martensite
International Nuclear Information System (INIS)
Kustov, S.; Corro, M.; Pons, J.; Cesari, E.; Van Humbeeck, J.
2006-01-01
It has been shown that both pinning- (mechanical) and reordering-induced (chemical) stabilization components contribute to the overall stabilization effect. An algorithm has been developed for quantitative analysis of the chemical and mechanical stabilization components, using routine calorimetry results. The basic idea underlying this algorithm is that chemical and mechanical stabilization components stem, respectively, from the factors, affecting thermodynamically reversible and irreversible factors during the first reverse transformation of the stabilized martensite. On a thermodynamical level, application of the suggested algorithm has been illustrated using experimental calorimetry results for a Cu-Zn-Al alloy. Here we report analysis of pinning and reordering processes on a microscopic scale, using experimental data on non-linear anelasticity in the same Cu-Zn-Al alloy to track different spatial and temporal localization of these processes during martensite ageing
7. Computer-aided biochemical programming of synthetic microreactors as diagnostic devices.
Science.gov (United States)
Courbet, Alexis; Amar, Patrick; Fages, François; Renard, Eric; Molina, Franck
2018-04-26
Biological systems have evolved efficient sensing and decision-making mechanisms to maximize fitness in changing molecular environments. Synthetic biologists have exploited these capabilities to engineer control on information and energy processing in living cells. While engineered organisms pose important technological and ethical challenges, de novo assembly of non-living biomolecular devices could offer promising avenues toward various real-world applications. However, assembling biochemical parts into functional information processing systems has remained challenging due to extensive multidimensional parameter spaces that must be sampled comprehensively in order to identify robust, specification compliant molecular implementations. We introduce a systematic methodology based on automated computational design and microfluidics enabling the programming of synthetic cell-like microreactors embedding biochemical logic circuits, or protosensors , to perform accurate biosensing and biocomputing operations in vitro according to temporal logic specifications. We show that proof-of-concept protosensors integrating diagnostic algorithms detect specific patterns of biomarkers in human clinical samples. Protosensors may enable novel approaches to medicine and represent a step toward autonomous micromachines capable of precise interfacing of human physiology or other complex biological environments, ecosystems, or industrial bioprocesses. © 2018 The Authors. Published under the terms of the CC BY 4.0 license.
8. Reversible chemical delithiation/lithiation of LiFePO4: towards a redox flow lithium-ion battery.
Science.gov (United States)
Huang, Qizhao; Li, Hong; Grätzel, Michael; Wang, Qing
2013-02-14
Reversible chemical delithiation/lithiation of LiFePO(4) was successfully demonstrated using ferrocene derivatives, based on which a novel energy storage system--the redox flow lithium-ion battery (RFLB), was devised by integrating the operation flexibility of a redox flow battery and high energy density of a lithium-ion battery. Distinct from the recent semi-solid lithium rechargeable flow battery, the energy storage materials of RFLB stored in separate energy tanks remain stationary upon operation, giving us a fresh perspective on building large-scale energy storage systems with higher energy density and improved safety.
9. Nano-magnetic particles as multifunctional microreactor for deep desulfurization
Energy Technology Data Exchange (ETDEWEB)
Cui, Xinai; Yao, Dongdong [Engineering Research Center of Historical and Cultural Heritage Protection, Ministry of Education, School of Materials Science and Engineering, Shaanxi Normal University, Xi' an 710062 (China); Li, Hong [College of Environment and Chemical Engineering, Xi' an Polytechnic University, Xi' an 710048 (China); Yang, Juxiang [Department of Chemistry, Xi' an University of Arts and Science, Xi' an 710065 (China); Hu, Daodao, E-mail: [email protected] [Engineering Research Center of Historical and Cultural Heritage Protection, Ministry of Education, School of Materials Science and Engineering, Shaanxi Normal University, Xi' an 710062 (China)
2012-02-29
Highlights: Black-Right-Pointing-Pointer An easy-separated amphiphilic catalyst with small size was prepared for deep desulfurization. Black-Right-Pointing-Pointer The effects of several factors on desulfurization reactivity were systematically investigated. Black-Right-Pointing-Pointer The catalyst demonstrates high performance in the deep desulfurization. Black-Right-Pointing-Pointer The material could make integration of micro-reactor and micro-extractor into one system. - Abstract: Oxidation of dibenzothiophene with hydrogen peroxide using a recyclable amphiphilic catalyst has been studied. The catalyst was synthesized by surfacely covering magnetic silica nanospheres (MSN) with the complexes between 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (AEM) and phosphotungstic acid (PTA). The morphology and components of the composite material were characterized by TEM, EDX, XPS, FT-IR, and VSM, respectively. The effects of several factors on desulfurization reactivity were systematically investigated. The results showed that the composite nanospheres have core/shell structure with the properties of amphiphilicity and superparamagnetism. The composite nanospheres have high catalytic activity in the oxidation of dibenzothiophene to corresponding sulfones by hydrogen peroxide under mild reaction conditions. The sulfur level could be lowered from 487 ppm to less than 0.8 ppm under optimal conditions. Additionally, the amphiphilic catalyst and the oxidized product could be simultaneously separated from medium by external magnetism, and the recovered composite material could be recycled for three times with almost constant activity.
10. Nano-magnetic particles as multifunctional microreactor for deep desulfurization
International Nuclear Information System (INIS)
Cui, Xinai; Yao, Dongdong; Li, Hong; Yang, Juxiang; Hu, Daodao
2012-01-01
Highlights: ► An easy-separated amphiphilic catalyst with small size was prepared for deep desulfurization. ► The effects of several factors on desulfurization reactivity were systematically investigated. ► The catalyst demonstrates high performance in the deep desulfurization. ► The material could make integration of micro-reactor and micro-extractor into one system. - Abstract: Oxidation of dibenzothiophene with hydrogen peroxide using a recyclable amphiphilic catalyst has been studied. The catalyst was synthesized by surfacely covering magnetic silica nanospheres (MSN) with the complexes between 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (AEM) and phosphotungstic acid (PTA). The morphology and components of the composite material were characterized by TEM, EDX, XPS, FT-IR, and VSM, respectively. The effects of several factors on desulfurization reactivity were systematically investigated. The results showed that the composite nanospheres have core/shell structure with the properties of amphiphilicity and superparamagnetism. The composite nanospheres have high catalytic activity in the oxidation of dibenzothiophene to corresponding sulfones by hydrogen peroxide under mild reaction conditions. The sulfur level could be lowered from 487 ppm to less than 0.8 ppm under optimal conditions. Additionally, the amphiphilic catalyst and the oxidized product could be simultaneously separated from medium by external magnetism, and the recovered composite material could be recycled for three times with almost constant activity.
11. The effect of chemical warfare on respiratory symptoms, pulmonary function tests and their reversibility 23-25 years after exposure.
Science.gov (United States)
2015-01-01
Pulmonary complications due to mustard gas exposure range from no effect to severe bronchial stenosis. Pulmonary function tests (PFTs) and respiratory symptoms in chemical war victims were studied 23-25 years after exposure to sulfur mustard (SM). Respiratory symptoms were evaluated in a sample of 142 chemical war victims and 120 control subjects with similar age from the general population using a questionnaire including questions on respiratory symptoms in the past year. PFT values were also measured in chemical war victims before and 15 min after the inhalation of 200 µg salbutamol and baseline PFT in controls. All chemical war victims (100%) reported respiratory symptoms. Wheezing (66.19%), cough (64.78%), and chest tightness (54.4%) were the most common symptoms and only 15.5% of chemical war victims reported sputum (p chemical war victims had wheeze in chest examination, which were significantly higher than control group (p chemical war victims than that in control subjects (p chemical war victims, 23-25 years after exposure to chemical warfare have higher frequencies and severity of respiratory symptoms. PFT values were also significantly reduced among chemical war victims, which showed reversibility due to the inhalation of 200 µg salbutamol. © The Author(s) 2012.
12. Photochemical transformations accelerated in continuous-flow reactors: basic concepts and applications.
Science.gov (United States)
Su, Yuanhai; Straathof, Natan J W; Hessel, Volker; Noël, Timothy
2014-08-18
Continuous-flow photochemistry is used increasingly by researchers in academia and industry to facilitate photochemical processes and their subsequent scale-up. However, without detailed knowledge concerning the engineering aspects of photochemistry, it can be quite challenging to develop a suitable photochemical microreactor for a given reaction. In this review, we provide an up-to-date overview of both technological and chemical aspects associated with photochemical processes in microreactors. Important design considerations, such as light sources, material selection, and solvent constraints are discussed. In addition, a detailed description of photon and mass-transfer phenomena in microreactors is made and fundamental principles are deduced for making a judicious choice for a suitable photomicroreactor. The advantages of microreactor technology for photochemistry are described for UV and visible-light driven photochemical processes and are compared with their batch counterparts. In addition, different scale-up strategies and limitations of continuous-flow microreactors are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
13. Plasma-assisted partial oxidation of methane at low temperatures: numerical analysis of gas-phase chemical mechanism
Energy Technology Data Exchange (ETDEWEB)
Goujard, Valentin; Nozaki, Tomohiro; Yuzawa, Shuhei; Okazaki, Ken [Department of Mechanical and Control Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, 1528552, Tokyo (Japan); Agiral, Anil, E-mail: [email protected] [Mesoscale Chemical Systems, MESA Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, PO Box 217, 7500 AE, Enschede (Netherlands)
2011-07-13
Methane partial oxidation was investigated using a plasma microreactor. The experiments were performed at 5 and 300 deg. C. Microreactor configuration allows an efficient evacuation of the heat generated by methane partial oxidation and dielectric barrier discharges, allowing at the same time a better temperature control. At 5 deg. C, liquid condensation of low vapour pressure compounds, such as formaldehyde and methanol, occurs. {sup 1}H-NMR analysis allowed us to demonstrate significant CH{sub 3}OOH formation during plasma-assisted partial oxidation of methane. Conversion and product selectivity were discussed for both temperatures. In the second part of this work, a numerical simulation was performed and a gas-phase chemical mechanism was proposed and discussed. From the comparison between the experimental results and the simulation it was found that CH{sub 3}OO{center_dot} formation has a determinant role in oxygenated compound production, since its fast formation disfavoured radical recombination. At 5 deg. C the oxidation leads mainly towards oxygenated compound formation, and plasma dissociation was the major phenomenon responsible for CH{sub 4} conversion. At 300 deg. C, higher CH{sub 4} conversion resulted from oxidative reactions induced by {center_dot}OH radicals with a chemistry predominantly oxidative, producing CO, H{sub 2}, CO{sub 2} and H{sub 2}O.
14. The impact of chemical cleaning on separation efficiency and properties of reverse osmosis membrane
KAUST Repository
Baatiyyah, Hani
2018-04-01
One of most major concerns from both cost-effective and technical point of view in membrane process industry is membrane cleaning. The aim of the project was to investigate the variations in membrane surface properties and separation efficiency of reverse osmosis membrane. Compativtive analysis have to be performed on four RO membrane before and after exposing the virgin membrane into chemical cleaning to identify and analysis the impact of the chemical cleaning on the performance of RO membrane. Commerical chemical cleaning used in this project were caustic and acidic cleaning agent. The project’s aim is the investigation of simulation software’s precision for the four membranes performance projection at different conditions of the feed water. The assessment of the membranes performance was done in the Innovation Cluster at pilot plant that was industrial in size. The main commercial elements used were the thin-film composite membranes with a spiral-wound of 8-inch polyamide. Ultrafiltration (UF) and seawater RO membrane pretreatment process was done for the red sea sourced feed water. A pressure vessel dimensioned at 8-inch was operated in conjunction with an individual element at 8 -20 m3/hr feed flow rate, with an 8 to 12 % recovery and an average 35,000-42,000 mg/L of total dissolved solids (TDS) composition for the feed water. To achieve the project’s aim in assessing the membranes, three phase experimental stages were completed. The membranes performance was assessed in terms of their water flux, salt rejection, boron rejection, bicarbonate rejection and permeate quality. In addition, the membrane surfaces were characterized after exposing the fresh membranes with a chemical cleaning reagent. The experimental results showed an increase in both permeate flow and salt passage for all studied elements. The changes in the membranes performance were systematically explained based on the changes in the charge density and chemical structure of the membranes
15. Synthesis and characterization of cationic lipid coated magnetic nanoparticles using multiple emulsions as microreactors
Science.gov (United States)
Akbaba, Hasan; Karagöz, Uğur; Selamet, Yusuf; Kantarcı, A. Gülten
2017-03-01
The aim of this study was to develop a novel iron oxide nanoparticle synthesis method with in-situ surface coating. For this purpose multiple emulsions were used as microreactors for the first time and magnetic iron oxide particles synthesized in the core of cationic solid lipid nanoparticles. DLS, SEM, TEM, VSM, Raman Spectrometer, XRD, and XPS techniques were performed for characterization of the magnetic nanoparticles. Obtained magnetic nanoparticles are superparamagnetic and no additional process was needed for surface adjustments. They are positively charged as a result of cationic lipid coating and has appropriate particle size (<30 nm) for drug or nucleic acid delivery. Structure analysis showed that magnetic core material is in the form of magnetite. Saturation magnetization value was measured as 15-17 emu g-1 for lipid coated magnetic nanoparticles obtained by multiple emulsion method which is reasonably sufficient for magnetic targeting.
16. Biomass-derived Syngas Utilization for Fuels and Chemicals - Final Report
Energy Technology Data Exchange (ETDEWEB)
Dayton, David C
2010-03-24
. Task 3: Chemical Synthesis: Promising process routes will be identified for synthesis of selected chemicals from biomass-derived syngas. A project milestone was to select promising mixed alcohol catalysts and screen productivity and performance in a fixed bed micro-reactor using bottled syngas. This milestone was successfully completed in collaboration withour catalyst development partner. Task 4: Modeling, Engineering Evaluation, and Commercial Assessment: Mass and energy balances of conceptual commercial embodiment for FT and chemical synthesis were completed.
17. Power conversion for a microreactor: a nuclear space application
International Nuclear Information System (INIS)
Guimaraes, Lamartine N.F.; Camillo, Giannino P.; Nascimento, Jamil A.; Borges, Eduardo M.; Placco, Guilherme M.
2009-01-01
Generating nuclear power in space is of fundamental importance if it is desired to realize some aggressive type of exploration. Basically, at Earth orbit (either LEO or GEO) most applications tend to use solar panels, which are just fine, in spite of problems such as vibration, non optimal light incidence angle and non electricity generation due to Earth's shadow. For deep space exploration the nuclear power is been considered as a strong candidate and maybe the only one. The Institute for Advanced Studies is conducting the TERRA project that tracks the developments in the area and, also, intends to develop the key technologies that will allow such a machine to be build with indigenous technology. TERRA stands for TEcnologia de Reatores Rapidos Avancados. This project, at its first stage aims at the specification of the microreactor fuel element with its possible geometrical arrangements. Also for this stage a gas Brayton closed cycle is being considered as a heat conversion to electricity and/or propulsion effect. The basic idea is to adapt an open loop aeronautic gas turbine to operate as a closed loop gas Turbine. This arrangement will use heat pipes as a cold source, or a heat rejection passive system. Up to this point a lot has been done in terms of numerical and graphical development. It is expected that some built up will be happening during this year. An account of this work will be presented at the conference. (author)
18. Development of ultrasonically levitated drops as microreactors for study of enzyme kinetics and potential as a universal portable analysis system
Science.gov (United States)
Scheeline, A.; Pierre, Z.; Field, C. R.; Ginsberg, M. D.
2009-05-01
Development of microfluidics has focused on carrying out chemical synthesis and analysis in ever-smaller volumes of solution. In most cases, flow systems are made of either quartz, glass, or an easily moldable polymer such as polydimethylsiloxane (Whitesides 2006). As the system shrinks, the ratio of surface area to volume increases. For studies of either free radical chemistry or protein chemistry, this is undesirable. Proteins stick to surfaces, biofilms grow on surfaces, and radicals annihilate on walls (Lewis et al. 2006). Thus, under those circumstances where small amounts of reactants must be employed, typical microfluidic systems are incompatible with the chemistry one wishes to study. We have developed an alternative approach. We use ultrasonically levitated microliter drops as well mixed microreactors. Depending on whether capillaries (to form the drop) and electrochemical sensors are in contact with the drop or whether there are no contacting solids, the ratio of solid surface area to volume is low or zero. The only interface seen by reactants is a liquid/air interface (or, more generally, liquid/gas, as any gas may be used to support the drop). While drop levitation has been reported since at least the 1940's, we are the second group to carry out enzyme reactions in levitated drops, (Weis; Nardozzi 2005) and have fabricated the lowest power levitator in the literature (Field; Scheeline 2007). The low consumption aspects of ordinary microfluidics combine with a contact-free determination cell (the levitated drop) that ensures against cross-contamination, minimizes the likelihood of biofilm formation, and is robust to changes in temperature and humidity (Lide 1992). We report kinetics measurements in levitated drops and explain how outgrowths of these accomplishments will lead to portable chemistry/biology laboratories well suited to detection of a wide range of chemical and biological agents in the asymmetric battlefield environment.
19. Journal of Chemical Sciences | Indian Academy of Sciences
promoted forms were prepared and tested for oxidative dehydrogenation of propane. Catalysts were characterized with XRD, BET, NH3-TPD, TPR and XPS methods. Catalytic activity measurement was done with quartz microreactor between 450 ...
20. Aproveitamento sustentável de biomassa e de recursos naturais na inovação química Sustainable use fo biomass and natural resources for chemical innovation
Directory of Open Access Journals (Sweden)
Fernando Galembeck
2009-01-01
Full Text Available Increased production of biomass is currently the only immediately accessible alternative for large-scale carbon sequestration and it can produce large amounts of food, fuel and raw materials for the chemical industry that can in turn growingly replace oil as a source of organic building blocks and also of hydrogen and sulfur. Development of processes for biomass and abundant minerals transformation into chemical raw materials should now benefit from large inputs from nanotechnologies, biotechnologies, information and micro-reactor technologies. Success in R&D&Innovation along this line can yield new products and processes needed to perform desirable functions within a sustainable development paradigm.
1. Reversible solid oxide fuel cells (R-SOFCs) with chemically stable proton-conducting oxides
KAUST Repository
Bi, Lei
2015-07-01
Proton-conducting oxides offer a promising way of lowering the working temperature of solid oxide cells to the intermediate temperate range (500 to 700. °C) due to their better ionic conductivity. In addition, the application of proton-conducting oxides in both solid oxide fuel cells (SOFCs) and sold oxide electrolysis cells (SOECs) provides unique advantages compared with the use of conventional oxygen-ion conducting conductors, including the formation of water at the air electrode site. Since the discovery of proton conduction in some oxides about 30. years ago, the development of proton-conducting oxides in SOFCs and SOECs (the reverse mode of SOFCs) has gained increased attention. This paper briefly summarizes the development in the recent years of R-SOFCs with proton-conducting electrolytes, focusing on discussing the importance of adopting chemically stable materials in both fuel cell and electrolysis modes. The development of electrode materials for proton-conducting R-SOFCs is also discussed. © 2015 Elsevier B.V.
2. A molecular theory of chemically modified electrodes with self-assembled redox polyelectrolye thin films: Reversible cyclic voltammetry
Energy Technology Data Exchange (ETDEWEB)
Tagliazucchi, Mario; Calvo, Ernesto J. [INQUIMAE, DQIAyQF Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Szleifer, Igal [Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)
2008-10-01
A molecular theory of chemically modified electrodes is applied to study redox polyelectroyte modified electrodes. The molecular approach explicitly includes the size, shape, charge distribution, and conformations of all of the molecular species in the system as well as the chemical equilibria (redox and acid-base) and intermolecular interactions. An osmium pyridine-bipyridine complex covalently bound to poly(allyl-amine) backbone (PAH-Os) adsorbed onto mercapto-propane sulfonate (MPS) thiolated gold electrode is described. The potential and electrolyte composition dependent redox and nonredox capacitance can be calculated with the molecular theory in very good agreement with voltammetric experiments under reversible conditions without the use of freely adjustable parameter. Unlike existing phenomenological models the theory links the electrochemical behavior with the structure of the polymer layer. The theory predicts a highly inhomogeneous distribution of acid-base and redox states that strongly couples with the spatial arrangement of the molecular species in the nanometric redox film. (author)
3. Discussion on cleaning and maintenance of YA system reverse osmosis membrane
International Nuclear Information System (INIS)
Zhu Yidong
2012-01-01
According to the overproof of pollution data of YA system reverse osmosis membrane in extension project, the daily maintenance company is using chemical cleaning on reverse osmosis unit to eliminate the pollution blindly, the fixed prescription, fixed dosage and high frequency of the chemical cleaning. The writer analyzed the cause of the membrane pollution and commended several chemical cleaning methods by the long-period study of the system, and also some suggestion, according to the status of operational site, for the daily maintenance. (author)
4. Reversible polymer networks containing covalent and hydrogen bonding interactions
NARCIS (Netherlands)
Araya-Hermosilla, R.; Broekhuis, A.A.; Picchioni, F.
Thermally reversible polymers with relatively high glass transition temperatures (T-g) are difficult to prepare but very interesting from an application point of view. In this work we present a novel reversible thermoset with tunable T-g based on chemical modification of aliphatic polyketones (PM)
5. Monoamines stimulate sex reversal in the saddleback wrasse.
Science.gov (United States)
Larson, Earl T; Norris, David O; Gordon Grau, E; Summers, Cliff H
2003-02-15
Monoamine neurotransmitters (norepinephrine, dopamine, and serotonin) play an important role in reproduction and sexual behavior throughout the vertebrates. They are the first endogenous chemical signals in the regulation of the hypothalamo-pituitary-gonadal (HPG) axis. In teleosts with behavioral sex determination, much is known about behavioral cues that induce sex reversal. The cues are social, processed via the visual system and depend on the ratio of females to males in the population. The mechanisms by which these external behavioral cues are converted to an internal chemical regulatory process are largely unknown. The protogynous Hawaiian saddleback wrasse, Thalassoma duperrey, was used to investigate the biological pathway mediating the conversion of a social cue into neuroendocrine events regulating sex reversal. Because monoamines play an important role in the regulation of the HPG axis, they were selected as likely candidates for such a conversion. To determine if monoamines could affect sex reversal, drugs affecting monoamines were used in an attempt to either induce sex reversal under non-permissive conditions, or prevent sex reversal under permissive conditions. Increasing norepinephrine or blocking dopamine or serotonin lead to sex reversal in experimental animals under non-permissive conditions. Increasing serotonin blocked sex reversal under permissive conditions, while blocking dopamine or norepinephrine retarded the process. The results presented here demonstrate that monoamines contribute significantly to the control sex reversal. Norepinephrine stimulates initiation and completion of gonadal sex of reversal as well as color change perhaps directly via its effects on the HPG axis. Dopamine exercises inhibitory action on the initiation of sex reversal while 5-HT inhibits both initiation and completion of sex reversal. The serotonergic system appears to be an integral part of the pathway mediating the conversion of a social cue into a
6. Nearly 1000 Protein Identifications from 50 ng of Xenopus laevis Zygote Homogenate Using Online Sample Preparation on a Strong Cation Exchange Monolith Based Microreactor Coupled with Capillary Zone Electrophoresis.
Science.gov (United States)
Zhang, Zhenbin; Sun, Liangliang; Zhu, Guijie; Cox, Olivia F; Huber, Paul W; Dovichi, Norman J
2016-01-05
A sulfonate-silica hybrid strong cation exchange monolith microreactor was synthesized and coupled to a linear polyacrylamide coated capillary for online sample preparation and capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) bottom-up proteomic analysis. The protein sample was loaded onto the microreactor in an acidic buffer. After online reduction, alkylation, and digestion with trypsin, the digests were eluted with 200 mM ammonium bicarbonate at pH 8.2 for CZE-MS/MS analysis using 1 M acetic acid as the background electrolyte. This combination of basic elution and acidic background electrolytes results in both sample stacking and formation of a dynamic pH junction. 369 protein groups and 1274 peptides were identified from 50 ng of Xenopus laevis zygote homogenate, which is comparable with an offline sample preparation method, but the time required for sample preparation was decreased from over 24 h to less than 40 min. Dramatically improved performance was produced by coupling the reactor to a longer separation capillary (∼100 cm) and a Q Exactive HF mass spectrometer. 975 protein groups and 3749 peptides were identified from 50 ng of Xenopus protein using the online sample preparation method.
7. Post-Digestion Liquor Treatment in the Method Combining Chemical Precipitation with Reverse Osmosis
Directory of Open Access Journals (Sweden)
Kuglarz Mariusz
2014-12-01
Full Text Available The aim of the study was to develop an effective treatment of post-digestion liquors highly-loaded with biogenic and organic substances. The scope of the research project encompassed: mesophilic anaerobic digestion of waste activated sludge (WAS as well as the treatment of post-digestion liquors, coming from the most appropriate HRT value of 25 days, in the process of ammonium magnesium phosphate (struvite precipitation targeted at ammonia nitrogen binding and a subsequent reverse osmosis (RO process. It was established that the method combining chemical precipitation and high-pressure filtration ensures a high degree of contaminants removal allowing for a direct release of treated liquors into the natural reservoir. However, in order to decrease the residual NH4+ concentration (6.1 mg NH4+/dm3 in the purified post-digestion liquors below the level allowing for a direct release to the natural reservoir, it turned out to be necessary to apply increased molar ratio of magnesium and phosphates (Mg:NH4+: PO43-= 1.5:1:1.5.
8. Production of biogas from organic waste in microreactors operated at two temperatures
International Nuclear Information System (INIS)
Murillo Roos, Mariana
2014-01-01
The process and the product of anaerobic digestion are evaluated for different proportions of organic substrates, in microreactors operated at thermophilic and mesophilic temperatures with interest to find alternatives that will generate energy from biomass. Small-scale tests are conducted to ensure the proper functioning of biodigesters and optimize operating conditions. The anaerobic digestion process is characterized in three manure mixing ratios: mix of leftovers (100:0,90:10 and 80:20) and two temperatures of work (35 degrees Celsius and 50 degrees Celsius), using a factorial arrangement with 2 replicates per treatment. The mixture is composed of manure, cow dung and scraps of fresh food (fruits and vegetables) and prepared food. The proportions were diluted to 5% total solids. Bottles are the experimental unit used consisting culture medium bottles of 1 liter with 500 mL of mixture. The test has run for 5 hydraulic retention times (HRT) of twenty days each. At this time the pH was evaluated, the daily production of biogas, biogas composition, total solids, volatile and fixed and the content of volatile fatty acids. The values obtained biogas productivity and CH 4 content have been similar to those reported in the literature and indicate that the systems have been successful [es
9. Surface science approach to Pt/carbon model catalysts: XPS, STM and microreactor studies
Science.gov (United States)
Motin, Abdul Md.; Haunold, Thomas; Bukhtiyarov, Andrey V.; Bera, Abhijit; Rameshan, Christoph; Rupprechter, Günther
2018-05-01
Pt nanoparticles supported on carbon are an important technological catalyst. A corresponding model catalyst was prepared by physical vapor deposition (PVD) of Pt on sputtered HOPG (highly oriented pyrolytic graphite). The carbon substrate before and after sputtering as well as the Pt/HOPG system before and after Pt deposition and annealing were examined by XPS and STM. This yielded information on the surface density of defects, which serve as nucleation centres for Pt, and on the size distribution (mean size/height) of the Pt nanoparticles. Two different model catalysts were prepared with mean sizes of 2.0 and 3.6 nm, both turned out to be stable upon UHV-annealing to 300 °C. After transfer into a UHV-compatible flow microreactor and subsequent cleaning in UHV and under mbar pressure, the catalytic activity of the Pt/HOPG model system for ethylene hydrogenation was examined under atmospheric pressure flow conditions. This enabled to determine temperature-dependent conversion rates, turnover frequencies (TOFs) and activation energies. The catalytic results obtained are in line with the characteristics of technological Pt/C, demonstrating the validity of the current surface science based model catalyst approach.
10. Supercritical fluid reverse micelle separation
Science.gov (United States)
Fulton, J.L.; Smith, R.D.
1993-11-30
A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.
11. The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors.
Science.gov (United States)
Akwi, Faith M; Watts, Paul
2016-01-01
In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 minutes and a small library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic systems. The scaled up synthesis of these compounds in PTFE tubing (i.d. 1.5 mm) was also investigated, where good reaction conversions ranging between 66-91% were attained.
12. Liquid-liquid electro-organo-synthetic processes in a carbon nanofibre membrane microreactor: Triple phase boundary effects in the absence of intentionally added electrolyte
International Nuclear Information System (INIS)
Watkins, John D.; Ahn, Sunyhik D.; Taylor, James E.; Bull, Steven D.; Bulman-Page, Philip C.; Marken, Frank
2011-01-01
Graphical abstract: Display Omitted Highlights: → Amphiphilic carbon nanofiber membrane employed in electro-synthesis. → Triple phase boundary process within a carbon membrane. → Electrochemical deuteration in a liquid|liquid micro-reactor system. → Triple phase boundary reaction zone effects in electro-synthesis. - Abstract: An amphiphilic carbon nanofibre membrane electrode (ca. 50 nm fibre diameter, 50-100 μm membrane thickness) is employed as an active working electrode and separator between an aqueous electrolyte phase (with reference and counter electrode) and an immiscible organic acetonitrile phase (containing only the redox active material). Potential control is achieved with a reference and counter electrode located in the aqueous electrolyte phase, but the electrolysis is conducted in the organic acetonitrile phase in the absence of intentionally added supporting electrolyte. For the one-electron oxidation of n-butylferrocene coupled to perchlorate anion transfer from aqueous to organic phase effective electrolysis is demonstrated with an apparent mass transfer coefficient of m = 4 x 10 -5 m s -1 and electrolysis of typically 1 mg n-butylferrocene in a 100 μL volume. For the two-electron reduction of tetraethyl-ethylenetetracarboxylate the apparent mass transfer coefficient m = 4 x 10 -6 m s -1 is lower due to a less extended triple phase boundary reaction zone in the carbon nanofibre membrane. Nevertheless, effective electrolysis of up to 6 mg tetraethyl-ethylenetetracarboxylate in a 100 μL volume is demonstrated. Deuterated products are formed in the presence of D 2 O electrolyte media. The triple phase boundary dominated mechanism and future microreactor design improvements are discussed.
13. Journal of Chemical Sciences | Indian Academy of Sciences
... system for carrying out gas-solid catalytic reactions under atmospheric flow conditions is fabricated to study CO and hydrocarbon oxidation, and NO reduction. The system consists of an all-stainless steel UHV system, quadrupole mass spectrometer SX200 (VG Scientific), a tubular furnace and micro-reactor, a temperature ...
14. Flash chemistry: flow chemistry that cannot be done in batch.
Science.gov (United States)
Yoshida, Jun-ichi; Takahashi, Yusuke; Nagaki, Aiichiro
2013-11-04
Flash chemistry based on high-resolution reaction time control using flow microreactors enables chemical reactions that cannot be done in batch and serves as a powerful tool for laboratory synthesis of organic compounds and for production in chemical and pharmaceutical industries.
15. The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors
Directory of Open Access Journals (Sweden)
Faith M. Akwi
2016-09-01
Full Text Available In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 minutes and a small library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic systems. The scaled up synthesis of these compounds in PTFE tubing (i.d. 1.5 mm was also investigated, where good reaction conversions ranging between 66–91% were attained.
16. Chromatographic separation and continuously referenced, on-line monitoring of creatine kinase isoenzymes by use of an immobilized-enzyme microreactor
International Nuclear Information System (INIS)
Denton, M.S.; Bostick, W.D.; Dinsmore, S.R.; Mrochek, J.E.
1978-01-01
We describe a new concept in continuously referenced monitoring of the isoenzyme activities of creatine kinase (EC 2.7.3.2) after liquid-chromatographic separation. After separation on a diethylaminoethyl-Sephacel column, the three isoenzymes of creatine kinase undergo a series of upled enzyme reactions, ultimately resulting in the formation of ultraviolet-detectable NADPH. A major advantage of this detection system is the immobilized-enzyme microreactor (2 x 17 mm), which may be removed and stored refrigerated when not in use. A split-stream configuration allows self-blanking of endogenous ultraviolet-absorbing constituents in authentic sera samples, which would otherwise make definitive diagnosis and quantitation difficult or impossible. This detection system is applicable to the automated analysis of creatine kinase isoenzymes in the clinical laboratory. 5 figures; 42 references
17. Reversal of profound rocuronium neuromuscular blockade by sugammadex in anesthetized rhesus monkeys.
NARCIS (Netherlands)
Boer, H.D. de; Egmond, J. van; Pol, F. van de; Bom, A.; Booij, L.H.D.J.
2006-01-01
BACKGROUND: Reversal of neuromuscular blockade can be accomplished by chemical encapsulation of rocuronium by sugammadex, a synthetic gamma-cyclodextrin derivative. The current study determined the feasibility of reversal of rocuronium-induced profound neuromuscular blockade with sugammadex in the
18. Relationship between thermodynamic driving force and one-way fluxes in reversible processes.
Directory of Open Access Journals (Sweden)
Daniel A Beard
Full Text Available Chemical reaction systems operating in nonequilibrium open-system states arise in a great number of contexts, including the study of living organisms, in which chemical reactions, in general, are far from equilibrium. Here we introduce a theorem that relates forward and reverse fluxes and free energy for any chemical process operating in a steady state. This relationship, which is a generalization of equilibrium conditions to the case of a chemical process occurring in a nonequilibrium steady state in dilute solution, provides a novel equivalent definition for chemical reaction free energy. In addition, it is shown that previously unrelated theories introduced by Ussing and Hodgkin and Huxley for transport of ions across membranes, Hill for catalytic cycle fluxes, and Crooks for entropy production in microscopically reversible systems, are united in a common framework based on this relationship.
19. Treatment of low-level radioactive waste liquid by reverse osmosis
International Nuclear Information System (INIS)
Buckley, L.P.; Sen Gupta, S.K.; Slade, J.A.
1995-01-01
The processing of low-level radioactive waste (LLRW) liquids that result from operation of nuclear power plants with reverse osmosis systems is not common practice. A demonstration facility is operating at Chalk River Laboratories (of Atomic Energy of Canada Limited), processing much of the LLRW liquids generated at the site from a multitude of radioactive facilities, ranging from isotope production through decontamination operations and including chemical laboratory drains. The reverse osmosis system comprises two treatment steps--spiral wound reverse osmosis followed by tubular reverse osmosis--to achieve an average volume reduction factor of 30:1 and a removal efficiency in excess of 99% for most radioactive and chemical species. The separation allows the clean effluent to be discharged without further treatment. The concentrated waste stream of 3 wt% total solids is further processed to generate a solid product. The typical lifetimes of the membranes have been nearly 4000 hours, and replacement was required based on increased pressure drops and irreversible loss of permeate flux. Four years of operating experience with the reverse osmosis system, to demonstrate its practicality and to observe and record its efficiency, maintenance requirements and effectiveness, have proven it to be viable for volume reduction and concentration of LLRW liquids generated from nuclear-power-plant operations
20. Fabrication and characteristics of cube-post microreactors for methanol steam reforming
International Nuclear Information System (INIS)
Zeng, Dehuai; Pan, Minqiang; Wang, Liming; Tang, Yong
2012-01-01
Highlights: ► We developed a cube-post microreactor for methanol steam reforming. ► We investigated the influences of micro-milling parameters on the burr formation during fabricating the cube posts. ► Larger cutting speed, smaller feed rate and cutting depth are in favor of obtaining relatively small burrs. ► Cube post and manifold structure show important effects on reaction performances at relatively low reaction temperature. -- Abstract: The lamination-plate structure patterned with microchannels and triangle manifolds regarded as one of the preferred constructions for micro fuel reformers. Learned from the microchannel plate structure, a similar plate structure with cube-post array and triangle manifolds is proposed in this work. A micro-milling process is applied to fabricate the cube posts on the plate surface, and the influences of cutting parameters on the burr formation are analyzed. Experimental results indicate that larger cutting speed, smaller feed rate and cutting depth are in favor of obtaining relatively small burrs. Two plates with different cube-post dimensions and manifold structures are experimentally investigated the performances of methanol steam reforming over the Cu/Zn/Al/Zr catalyst. It indicates that the reactor with small-scale cube posts and acute triangle manifold presents better reforming performances at 260 °C than that of the one with large-scale cube posts and right triangle manifolds. However, their performances are closed to each other at relatively high reaction temperature since the catalyst activity is situated in dominated position at the time.
1. Reversible targeting of noncatalytic cysteines with chemically tuned electrophiles
DEFF Research Database (Denmark)
Serafimova, Iana M; Pufall, Miles A; Krishnan, Shyam
2012-01-01
Targeting noncatalytic cysteine residues with irreversible acrylamide-based inhibitors is a powerful approach for enhancing pharmacological potency and selectivity. Nevertheless, concerns about off-target modification motivate the development of reversible cysteine-targeting strategies. Here we...... of these electrophiles into a noncovalent kinase-recognition scaffold produced slowly dissociating, covalent inhibitors of the p90 ribosomal protein S6 kinase RSK2. A cocrystal structure revealed specific noncovalent interactions that stabilize the complex by positioning the electrophilic carbon near the targeted...
2. Improved Livingness and Control over Branching in RAFT Polymerization of Acrylates: Could Microflow Synthesis Make the Difference?
Science.gov (United States)
Derboven, Pieter; Van Steenberge, Paul H M; Vandenbergh, Joke; Reyniers, Marie-Francoise; Junkers, Thomas; D'hooge, Dagmar R; Marin, Guy B
2015-12-01
The superior capabilities of structured microreactors over batch reactors are demonstrated for reversible addition-fragmentation chain transfer (RAFT) solution polymerization of n-butyl acrylate with the aid of simulations, explicitly accounting for the chain length distribution of all macrospecies types. Since perfect isothermicity can be established in a microreactor, less side products due to backbiting and β-scission are formed compared to the batch operation in which ineffective heat removal leads to an undesirable temperature spike. For a given RAFT chain transfer agent (CTA), additional microstructural control results under microflow conditions by optimizing the reaction temperature, lowering the dilution degree, or decreasing the initial molar ratio of monomer to RAFT CTA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
3. Fouling of Seawater Reverse Osmosis (SWRO) Membrane: Chemical and Microbiological Characterization
KAUST Repository
2013-01-01
In spite of abundant water resources, world is suffering from the scarcity of usable water. Seawater Reverse Osmosis (SWRO) desalination technology using polymeric membranes has been recognized as a key solution to water scarcity problem. However
4. Surface modification of reverse osmosis desalination membranes by thin-film coatings deposited by initiated chemical vapor deposition
Energy Technology Data Exchange (ETDEWEB)
Ozaydin-Ince, Gozde, E-mail: [email protected] [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Matin, Asif, E-mail: [email protected] [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khan, Zafarullah, E-mail: [email protected] [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Zaidi, S.M. Javaid, E-mail: [email protected] [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gleason, Karen K., E-mail: [email protected] [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
2013-07-31
Thin-film polymeric reverse osmosis membranes, due to their high permeation rates and good salt rejection capabilities, are widely used for seawater desalination. However, these membranes are prone to biofouling, which affects their performance and efficiency. In this work, we report a method to modify the membrane surface without damaging the active layer or significantly affecting the performance of the membrane. Amphiphilic copolymer films of hydrophilic hydroxyethylmethacrylate and hydrophobic perfluorodecylacrylate (PFA) were synthesized and deposited on commercial RO membranes using an initiated chemical vapor deposition technique which is a polymer deposition technique that involves free-radical polymerization initiated by gas-phase radicals. Relevant surface characteristics such as hydrophilicity and roughness could be systematically controlled by varying the polymer chemistry. Increasing the hydrophobic PFA content in the films leads to an increase in the surface roughness and hydrophobicity. Furthermore, the surface morphology studies performed using the atomic force microscopy show that as the thickness of the coating increases average surface roughness increases. Using this knowledge, the coating thickness and chemistry were optimized to achieve high permeate flux and to reduce cell attachment. Results of the static bacterial adhesion tests show that the attachment of bacterial cells is significantly reduced on the coated membranes. - Highlights: • Thin films are deposited on reverse osmosis membranes. • Amphiphilic thin films are resistant to protein attachment. • The permeation performance of the membranes is not affected by the coating. • The thin film coatings delayed the biofouling.
5. Continuous, size and shape-control synthesis of hollow silica nanoparticles enabled by a microreactor-assisted rapid mixing process
Science.gov (United States)
He, Yujuan; Kim, Ki-Joong; Chang, Chih-Hung
2017-06-01
Hollow silica nanoparticles (HSNPs) were synthesized using a microreactor-assisted system with a hydrodynamic focusing micromixer. Due to the fast mixing of each precursor in the system, the poly(acrylic acid) (PAA) thermodynamic-locked (TML) conformations were protected from their random aggregations by the immediately initiated growth of silica shells. When altering the mixing time through varying flow rates and flow rate ratios, the different degrees of the aggregation of PAA TML conformations were observed. The globular and necklace-like TML conformations were successfully captured by modifying the PAA concentration at the optimized mixing condition. Uniform HSNPs with an average diameter ∼30 nm were produced from this system. COMSOL numerical models was established to investigate the flow and concentration profiles, and their effects on the formation of PAA templates. Finally, the quality and utility of these uniform HSNPs were demonstrated by the fabrication of antireflective thin films on monocrystalline photovoltaic cells which showed a 3.8% increase in power conversion efficiency.
6. The use of microbial and chemical analyses to characterize the variations in fouling profile of seawater reverse osmosis (SWRO) membrane
KAUST Repository
Manes, Carmem Lara De O
2013-01-01
Biofouling of reverse osmosis (RO) membranes is one of the most common problems in desalinations plants reducing the efficiency of the water production process. The characterization of bacterial community composition from fouling layers as well as detailed analysis of surrounding chemical environment might reveal process specific bacterial groups/species that are involved in RO biofouling. In this study, advanced organics analytic methods (elemental analysis, FTIR, and ICP-OES) were combined with high-throughput 16S rRNA (pyro) sequencing to assess in parallel, the chemical properties and the active microbial community composition of SWRO membranes from a pilot desalination plant (MFT, Tarragona) in February 2011 and July 2011. Prefiltered ultrafiltration. waters fed SWRO membranes during third and fifth month of operation, respectively. SWRO samples were taken from three modules at different positions (first, fourth, and sixth) in order to investigate the spatial changes in fouling layers\\' chemical and microbiological composition. The overall assessment of chemical parameters revealed that fouling layers were mainly composed by bio and organic material (proteins and lipids). Ca and Fe were found to be the most abundant elements having an increasing concentration gradient according to the module position. Bacterial community composition of SWRO membranes is mostly represented by the Gammaproteobacteria class with interesting differences in genera/species spatial and temporal distribution. This preliminary result suggests that pretreatments and/or operational conditions might have selected different bacterial groups more adapted to colonize SWRO membranes. © 2013 Desalination Publications.
7. Performance of Continuous Micro Photo Reactor – Comparison with Batch Process
Czech Academy of Sciences Publication Activity Database
Drhová, Magdalena; Hejda, S.; Křišťál, Jiří; Klusoň, Petr
2012-01-01
Roč. 42, SI (2012), s. 1365-1372 E-ISSN 1877-7058. [International Congress of Chemical and Process Engineering CHISA 2012 and 15th Conference PRES 2012 /20./. Prague, 25.08.2012-29.08.2012] Institutional support: RVO:67985858 Keywords : continuous microreactor * photooxidation * phtalocyanine Subject RIV: CI - Industrial Chemistry, Chemical Engineering
8. Screen printing as a holistic manufacturing method for multifunctional microsystems and microreactors
International Nuclear Information System (INIS)
Bejarano, D; Lozano, P; Mata, D; Cito, S; Constantí, M; Katakis, I
2009-01-01
Microsystems are commonly manufactured by photolithographic or injection moulding techniques in a variety of realizations and on almost any material. A perennial problem in the manufacturing of microsystems is the difficulty to obtain hybrid devices that incorporate distinct materials with different functionalities. In most of the cases, cumbersome prototyping and high investment needed for manufacturing are additional problems that add to the cost of the final product. Such drawbacks are true not only for lab-on-a-chip but also for certain microreactor applications. Most importantly, in many commercial applications where an intermediate product between full fluidics control and a 'strip' is needed, such restraints prohibit the feasibility of reduction to practice. Screen printing on the other hand is a low cost technique that has been used for years in mass producing two-dimensional low cost reproductions of a mask pattern for circuits and art incorporates prototyping in production and allows the use of an almost limitless variety of materials as 'inks'. In this work it is demonstrated that taking advantage of the deposited ink's three-dimensional nature, screen printing can be used as a versatile and low cost technique for the fabrication of microchannels. Microchannels with dimensions in the order of 100 µm were fabricated that could readily incorporate functionalities through the choice of the materials used to create the microstructure. Variables have been investigated through a factorial experimental design as important process parameters that affect the resolution and print thickness of the resulting microchannels that incorporate electroactive elements. Such studies can lead to the optimization of the process for custom applications
9. Effect of genes controlling radiation sensitivity on chemically induced mutations in Saccharomyces cerevisiae
International Nuclear Information System (INIS)
Prakash, L.
1976-01-01
10. Microreactor System Design for a NASA In Situ Propellant Production Plant on Mars
Science.gov (United States)
TeGrotenhuis, W. E.; Wegeng, R. S.; Vanderwiel, D. P.; Whyatt, G. A.; Viswanathan, V. V.; Schielke, K. P.; Sanders, G. B.; Peters, T. A.; Nicholson, Leonard S. (Technical Monitor)
2000-01-01
, as well as three options for water decomposition, low temperature electrolysis, high temperature electrolysis, and thermochemical decomposition. Other elements of the plant include Sabatier and reverse water gas shift reactors, water recovery, chemical separations, and cryogenic storage. Data are presented supporting preliminary sizing of components, and results of the system design are compared to the existing NASA baseline that is based on conventional technologies.
11. [Influence of reverse osmosis concentrate on physicochemical parameters of Sini decoction material system and their relevance].
Science.gov (United States)
Jin, Tang-Hui; Zhang, Liu-Hong; Zhu, Hua-Xu; Guo, Li-Wei; Li, Bo; Lu, Ming-Ming
2014-04-01
By studying the process of reverse osmosis system for traditional Chinese medicine materials physicochemical parameters affecting the osmotic pressure of its relevance, new compound system reverse osmosis process design methods were explored. Three concentrations materials for high, middle and low were dubbed with Sini decoction as a model drug, and pretreated by 50 thousand relative molecular weight cut-off ultrafiltration membrane. The viscosity, turbidity, conductivity, salinity, TDS, pH value and osmotic pressure of each sample were determined after the reverse osmosis to study the physical and chemical parameters between their respective correlations with the osmotic pressure, and characterized by HPLC chromatograms showing changes before and after the main chemical composition of samples of reverse osmosis. Conductivity-osmotic pressure, salinity-osmotic pressure of the linear correlation coefficient, TDS-osmotic pressure between the three sets of parameters were 0.963 8, 0.932 7, 0.973 7, respectively. Reverse osmosis concentrate and its characteristic spectrum ultrafiltrate HPLC similarity were up to 0. 968 or more, except the low concentrations. There is a significant correlation between the three physicochemical parameters (conductivity, salinity, TDS) and osmotic pressure of each sample system, and there is also significant linear correlation between salinity, conductivity, TDS. The original chemical composition of Sini decoction material concentrate was completely remained after the process of reverse osmosis.
12. Flash crystallization kinetics of methane (sI) hydrate in a thermoelectrically-cooled microreactor.
Science.gov (United States)
Chen, Weiqi; Pinho, Bruno; Hartman, Ryan L
2017-09-12
The crystallization kinetics of methane (sI) hydrate were investigated in a thermoelectrically-cooled microreactor with in situ Raman spectroscopy. Step-wise and precise control of the temperature allowed acquisition of reproducible data within minutes, while the nucleation of methane hydrates can take up to 24 h in traditional batch reactors. The propagation rates of methane hydrate (from 3.1-196.3 μm s -1 ) at the gas-liquid interface were measured for different Reynolds' numbers (0.7-68.9), pressures (30.0-80.9 bar), and sub-cooling temperatures (1.0-4.0 K). The precise measurement of the propagation rates and their subsequent analyses revealed a transition from mixed heat-transfer-crystallization-rate-limited to mixed heat-transfer-mass-transfer-crystallization-rate-limited kinetics. A theoretical model, based on heat transfer, mass transfer, and intrinsic crystallization kinetics, was derived for the first time to understand the non-linear relationship between the propagation rate and sub-cooling temperature. The molecular diffusivity of methane within a stagnant film (ahead of the propagation front) was discovered to follow Stokes-Einstein, while calculated Hatta (0.50-0.68), Lewis (128-207), and beta (0.79-116) numbers also confirmed that the diffusive flux influences crystal growth. Understanding methane hydrate crystal growth is important to the atmospheric, oceanic, and planetary sciences and to energy production, storage, and transportation. Our discoveries could someday advance the science of other multiphase, high-pressure, and sub-cooled crystallizations.
13. Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide.
Science.gov (United States)
Choi, Seon-Jin; Kim, Sang-Joon; Jang, Ji-Soo; Lee, Ji-Hyun; Kim, Il-Doo
2016-09-14
Optically reduced graphene oxide (ORGO) sheets are successfully integrated on silver nanowire (Ag NW)-embedded transparent and flexible substrate. As a heating element, Ag NWs are embedded in a colorless polyimide (CPI) film by covering Ag NW networks using polyamic acid and subsequent imidization. Graphene oxide dispersed aqueous solution is drop-coated on the Ag NW-embedded CPI (Ag NW-CPI) film and directly irradiated by intense pulsed light to obtain ORGO sheets. The heat generation property of Ag NW-CPI film is investigated by applying DC voltage, which demonstrates unprecedentedly reliable and stable characteristics even in dynamic bending condition. To demonstrate the potential application in wearable chemical sensors, NO 2 sensing characteristic of ORGO is investigated with respect to the different heating temperature (22.7-71.7 °C) of Ag NW-CPI film. The result reveals that the ORGO sheets exhibit high sensitivity of 2.69% with reversible response/recovery sensing properties and minimal deviation of baseline resistance of around 1% toward NO 2 molecules when the temperature of Ag NW-CPI film is 71.7 °C. This work first demonstrates the improved reversible NO 2 sensing properties of ORGO sheets on flexible and transparent Ag NW-CPI film assisted by Ag NW heating networks. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
14. Formation and stabilization of reversed austenite in supermartensitic stainless steel
DEFF Research Database (Denmark)
Nießen, Frank; Grumsen, Flemming Bjerg; Hald, John
2017-01-01
of the reversed austenite phase fraction. Annealing at higher temperatures led to a gradual increase in hardness which was caused by formation of fresh martensite from reversed austenite. It was demonstrated that stabilization of reversed austenite is primarily based on chemical stabilization by partitioning......The formation and stabilization of reversed austenite upon inter-critical annealing was investigated in a X4CrNiMo16-5-1 (EN 1.4418) supermartensitic stainless steel by means of scanning electron microscopy, electron backscatter-diffraction, transmission electron microscopy, energy-dispersive X......-ray spectroscopy and dilatometry. The results were supported by thermodynamics and kinetics models, and hardness measurements. Isothermal annealing for 2 h in the temperature range of 475 to 650 °C led to gradual softening of the material which was related to tempering of martensite and the steady increase...
15. Single component, reversible ionic liquids for energy applications
Energy Technology Data Exchange (ETDEWEB)
Vittoria Blasucci; Ryan Hart; Veronica Llopis Mestre; Dominique Julia Hahne; Melissa Burlager; Hillary Huttenhower; Beng Joo Reginald Thio; Pamela Pollet; Charles L. Liotta; Charles A. Eckert [Georgia Institute of Technology, Atlanta, GA (United States). Chemical & Biomolecular Engineering
2010-06-15
Single component, reversible ionic liquids have excellent potential as novel solvents for a variety of energy applications. Our energy industry is faced with many new challenges including increased energy consumption, depleting oil reserves, and increased environmental awareness. We report the use of reversible ionic liquids to solve two energy challenges: extraction of hydrocarbons from contaminated crude oil and carbon capture from power plant flue gas streams. Our reversible solvents are derived from silylated amine molecular liquids which react with carbon dioxide reversibly to form ionic liquids. Here we compare the properties of various silylated amine precursors and their corresponding ionic liquids. We show how the property changes are advantageous in the two aforementioned energy applications. In the case of hydrocarbon purification, we take advantage of the polarity switch between precursor and ionic liquid to enable separations. In carbon capture, our solvents act as dual physical and chemical capture agents for carbon dioxide. Finally, we show the potential economics of scale-up for both processes. 20 refs., 1 fig., 3 tabs.
16. Reversible flowchart languages and the structured reversible program theorem
DEFF Research Database (Denmark)
Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert
2008-01-01
Many irreversible computation models have reversible counterparts, but these are poorly understood at present. We introduce reversible flowcharts with an assertion operator and show that any reversible flowchart can be simulated by a structured reversible flowchart using only three control flow...... operators. Reversible flowcharts are r- Turing-complete, meaning that they can simuluate reversible Turing machines without garbage data. We also demonstrate the injectivization of classical flowcharts into reversible flowcharts. The reversible flowchart computation model provides a theoretical...
17. Rapid and reversible epigenome editing by endogenous chromatin regulators.
Science.gov (United States)
Braun, Simon M G; Kirkland, Jacob G; Chory, Emma J; Husmann, Dylan; Calarco, Joseph P; Crabtree, Gerald R
2017-09-15
Understanding the causal link between epigenetic marks and gene regulation remains a central question in chromatin biology. To edit the epigenome we developed the FIRE-Cas9 system for rapid and reversible recruitment of endogenous chromatin regulators to specific genomic loci. We enhanced the dCas9-MS2 anchor for genome targeting with Fkbp/Frb dimerizing fusion proteins to allow chemical-induced proximity of a desired chromatin regulator. We find that mSWI/SNF (BAF) complex recruitment is sufficient to oppose Polycomb within minutes, leading to activation of bivalent gene transcription in mouse embryonic stem cells. Furthermore, Hp1/Suv39h1 heterochromatin complex recruitment to active promoters deposits H3K9me3 domains, resulting in gene silencing that can be reversed upon washout of the chemical dimerizer. This inducible recruitment strategy provides precise kinetic information to model epigenetic memory and plasticity. It is broadly applicable to mechanistic studies of chromatin in mammalian cells and is particularly suited to the analysis of endogenous multi-subunit chromatin regulator complexes.Understanding the link between epigenetic marks and gene regulation requires the development of new tools to directly manipulate chromatin. Here the authors demonstrate a Cas9-based system to recruit chromatin remodelers to loci of interest, allowing rapid, reversible manipulation of epigenetic states.
18. Safety assessment in development and operation of modular continuous-flow processes
NARCIS (Netherlands)
Kockmann, N.; Thenée, P.; Fleischer-Trebes, C.; Laudadio, G.; Noël, T.
2017-01-01
Improved safety is one of the main drivers for microreactor application in chemical process development and small-scale production. Typical examples of hazardous chemistry are presented indicating potential risks also in miniaturized equipment. Energy balance and kinetic parameters describe the heat
19. VOF Modeling and Analysis of the Segmented Flow in Y-Shaped Microchannels for Microreactor Systems
Directory of Open Access Journals (Sweden)
Xian Wang
2013-01-01
Full Text Available Microscaled devices receive great attention in microreactor systems for producing high renewable energy due to higher surface-to-volume, higher transport rates (heat or/and mass transfer rates, and other advantages over conventional-size reactors. In this paper, the two-phase liquid-liquid flow in a microchannel with various Y-shaped junctions has been studied numerically. Two kinds of immiscible liquids were injected into a microchannel from the Y-shaped junctions to generate the segment flow mode. The segment length was studied. The volume of fluid (VOF method was used to track the liquid-liquid interface and the piecewise-liner interface construction (PLIC technique was adopted to get a sharp interface. The interfacial tension was simulated with continuum surface force (CSF model and the wall adhesion boundary condition was taken into consideration. The simulated flow pattern presents consistence with our experimental one. The numerical results show that a segmented flow mode appears in the main channel. Under the same inlet velocities of two liquids, the segment lengths of the two liquids are the same and depend on the inclined angles of two lateral channels. The effect of inlet velocity is studied in a typical T-shaped microchannel. It is found that the ratio between the lengths of two liquids is almost equal to the ratio between their inlet velocities.
20. Microbial Reverse-Electrodialysis Electrolysis and Chemical-Production Cell for H2 Production and CO2 Sequestration.
KAUST Repository
Zhu, Xiuping; Hatzell, Marta C; Logan, Bruce E
2014-01-01
Natural mineral carbonation can be accelerated using acid and alkali solutions to enhance atmospheric CO2 sequestration, but the production of these solutions needs to be carbon-neutral. A microbial reverse-electrodialysis electrolysis and chemical-production cell (MRECC) was developed to produce these solutions and H2 gas using only renewable energy sources (organic matter and salinity gradient). Using acetate (0.82 g/L) as a fuel for microorganisms to generate electricity in the anode chamber (liquid volume of 28 mL), 0.45 mmol of acid and 1.09 mmol of alkali were produced at production efficiencies of 35% and 86%, respectively, along with 10 mL of H2 gas. Serpentine dissolution was enhanced 17-87-fold using the acid solution, with approximately 9 mL of CO2 absorbed and 4 mg of CO2 fixed as magnesium or calcium carbonates. The operational costs, based on mineral digging and grinding, and water pumping, were estimated to be only $25/metric ton of CO2 fixed as insoluble carbonates. Considering the additional economic benefits of H2 generation and possible wastewater treatment, this method may be a cost-effective and environmentally friendly method for CO2 sequestration. 1. Microbial Reverse-Electrodialysis Electrolysis and Chemical-Production Cell for H2 Production and CO2 Sequestration. KAUST Repository Zhu, Xiuping 2014-03-24 Natural mineral carbonation can be accelerated using acid and alkali solutions to enhance atmospheric CO2 sequestration, but the production of these solutions needs to be carbon-neutral. A microbial reverse-electrodialysis electrolysis and chemical-production cell (MRECC) was developed to produce these solutions and H2 gas using only renewable energy sources (organic matter and salinity gradient). Using acetate (0.82 g/L) as a fuel for microorganisms to generate electricity in the anode chamber (liquid volume of 28 mL), 0.45 mmol of acid and 1.09 mmol of alkali were produced at production efficiencies of 35% and 86%, respectively, along with 10 mL of H2 gas. Serpentine dissolution was enhanced 17-87-fold using the acid solution, with approximately 9 mL of CO2 absorbed and 4 mg of CO2 fixed as magnesium or calcium carbonates. The operational costs, based on mineral digging and grinding, and water pumping, were estimated to be only$25/metric ton of CO2 fixed as insoluble carbonates. Considering the additional economic benefits of H2 generation and possible wastewater treatment, this method may be a cost-effective and environmentally friendly method for CO2 sequestration.
2. Reverse Algols
Science.gov (United States)
Leung, K. C.
1989-01-01
Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.
3. The precautionary principle and chemicals management: The example of perfluoroalkyl acids in groundwater.
Science.gov (United States)
Cousins, Ian T; Vestergren, Robin; Wang, Zhanyun; Scheringer, Martin; McLachlan, Michael S
2016-09-01
Already in the late 1990s microgram-per-liter levels of perfluorooctane sulfonate (PFOS) were measured in water samples from areas where fire-fighting foams were used or spilled. Despite these early warnings, the problems of groundwater, and thus drinking water, contaminated with perfluoroalkyl and polyfluoroalkyl substances (PFASs) including PFOS are only beginning to be addressed. It is clear that this PFAS contamination is poorly reversible and that the societal costs of clean-up will be high. This inability to reverse exposure in a reasonable timeframe is a major motivation for application of the precautionary principle in chemicals management. We conclude that exposure can be poorly reversible; 1) due to slow elimination kinetics in organisms, or 2) due to poorly reversible environmental contamination that leads to continuous exposure. In the second case, which is relevant for contaminated groundwater, the reversibility of exposure is not related to the magnitude of a chemical's bioaccumulation potential. We argue therefore that all PFASs entering groundwater, irrespective of their perfluoroalkyl chain length and bioaccumulation potential, will result in poorly reversible exposures and risks as well as further clean-up costs for society. To protect groundwater resources for future generations, society should consider a precautionary approach to chemicals management and prevent the use and release of highly persistent and mobile chemicals such as PFASs. Copyright © 2016 Elsevier Ltd. All rights reserved.
4. Design and Synthesis of novel CuxGeOy/Cu/C nanowires by in situ chemical reduction process with highly reversible capacity for Lithium Batteries
International Nuclear Information System (INIS)
Wang, Linlin; Zhang, Xiaozhu; Peng, Xia; Tang, Kaibin
2015-01-01
The synthesis and use of ternary metal oxides/metal particles/carbon hybrids, especially 1D naowires composed of MGeO 3 /M/C hybrids for energy storage, remains very few reports. In this work, 1D Cu x GeO y /Cu/C NWs (x < 1, y < 3) were successfully prepared by a simple method involving chemical reduction process and simultaneous carbon coating. It was found that through the polydopamine(PDA)-assisted chemical reduction process performed on the CuGeO 3 NWs, the phase partially transformed to a mixture of crystalline Cu (∼70 nm) and amorphous Cu x GeO y NWs with carbon coating, but the nanowire-shaped morphology was maintained. Electrochemical measurements showed that the Cu x GeO y /Cu/C NWs exhibited a stable reversible capacity of ∼900 mA h g −1 after 100 cycles. Even at 800 mA g −1 , it also exhibited excellent high rate capacity of 350 mA h g −1 . The newly generated Cu x GeO y @Cu@CNWs exhibit enhanced cycle stability with high lithium-storage capability compared to that of the as-preparedCuGeO 3 NWs. (*) The in situ-synthesized Cu nanoparticles, amorphous state and carbon coating might play an important role in activating and enhancing the reversibility of the conversion reaction of Cu x GeO y . In addition, this effective synthetic method might provide the methodology for the development of other ternary metal oxides/metal particles/carbon hybrids materials for energy storage.
5. Managing Reverse Logistics or Reversing Logistics Management?
OpenAIRE
Brito, Marisa
2004-01-01
textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse logistics. The thesis brings insights on reverse logistics decision-making and it lays down theoretical principles for reverse logistics as a research field.In particular it puts together a framework ...
6. Absence of sensitization of reversions in yeast by metronidazole
International Nuclear Information System (INIS)
Krishnan, D.; Singh, D.R.; Mahajan, J.M.; Madhvanath, U.
1977-01-01
Metronidazole (Flagyl; 2-methyl-5-nitroimidazole-1-ethanol) is of potential clinical application as a radiosensitizer. Studies have been made of the effect of 1mM metronidazole on γ-induced heteroallelic recombination (reversion) under euoxic or hypoxic conditions in yeast strain BZ34, and compared with the effect on survival. The o.e.r. for reversions was 2.2, and very close to that for survival (2.3), indicating that oxygen equally sensitized gross cellular events such as killing, and genetic phenomena like reversions. The introduction of metronidazole during irradiation sensitized cells with killing as the end point only in hypoxic condition, whereas with reversion as the end point no sensitization due to the chemical was observed either in euoxic or hypoxic conditions. Since DNA damage is responsible for both cell-killing and mutations, the sensitizer might have been expected to have had an equal effect on both these end-points. The results show that only in a limited sense can metronidazole be considered to be an oxygen mimic. (U.K.)
7. Reversing the conventional leather processing sequence for cleaner leather production.
Science.gov (United States)
Saravanabhavan, Subramani; Thanikaivelan, Palanisamy; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni; Ramasami, Thirumalachari
2006-02-01
Conventional leather processing generally involves a combination of single and multistep processes that employs as well as expels various biological, inorganic, and organic materials. It involves nearly 14-15 steps and discharges a huge amount of pollutants. This is primarily due to the fact that conventional leather processing employs a "do-undo" process logic. In this study, the conventional leather processing steps have been reversed to overcome the problems associated with the conventional method. The charges of the skin matrix and of the chemicals and pH profiles of the process have been judiciously used for reversing the process steps. This reversed process eventually avoids several acidification and basification/neutralization steps used in conventional leather processing. The developed process has been validated through various analyses such as chromium content, shrinkage temperature, softness measurements, scanning electron microscopy, and physical testing of the leathers. Further, the performance of the leathers is shown to be on par with conventionally processed leathers through bulk property evaluation. The process enjoys a significant reduction in COD and TS by 53 and 79%, respectively. Water consumption and discharge is reduced by 65 and 64%, respectively. Also, the process benefits from significant reduction in chemicals, time, power, and cost compared to the conventional process.
8. Diffusion-weighted imaging of the liver at 3 T using section-selection gradient reversal: emphasis on chemical shift artefacts and lesion conspicuity
International Nuclear Information System (INIS)
Lee, J.S.; Kim, Y.K.; Jeong, W.K.; Choi, D.; Lee, W.J.
2015-01-01
Aim: To assess the value of section-selection gradient reversal (SSGR) in liver diffusion-weighted imaging (DWI) by comparing it to conventional DWI with an emphasis on chemical shift artefacts and lesion conspicuity. Materials and methods: Forty-eight patients (29 men and 19 women; age range 33–80 years) with 48 liver lesions underwent two DWI examinations using spectral presaturation with inversion recovery fat suppression with and without SSGR at 3 T. Two reviewers evaluated each DWI (b = 100 and b = 800 image) with respect to chemical shift artefacts and liver lesion conspicuity using five-point scales and performed pairwise comparisons between the two DWIs. The signal-to-noise ratio (SNR) of the liver and the lesion and the lesion–liver contrast-to-noise ratio (CNR) were also calculated. Results: SSGR-DWI was significantly better than conventional DWI with respect to chemical shift artefacts and lesion conspicuity in both separate reviews and pairwise comparisons (p < 0.05). There were significant differences in the SNR of the liver (b = 100 and b = 800 images) and lesion (b = 800) between SSGR-DWI and conventional DWI (p < 0.05). Conclusion: Applying the SSGR method to DWI using SPIR fat suppression at 3 T could significantly reduce chemical shift artefacts without incurring additional acquisition time or SNR penalties, which leads to increased conspicuity of focal liver lesions. - Highlights: • Chemical shift artefact in liver DWI is markedly decreased by applying SSGR. • Liver lesion conspicuity is improved by applying SSGR to DWI. • In SNR of the liver, SSGR-DWI is better than conventional DWI
9. SLUG FLOW PROCESSING IN MICROREACTORS FOR BIO-BASED CHEMICAL MANUFACTURING: SYNTHESIS AND OXIDATION OF 5-HYDROXYMETHYLFURFURAL AS POTENTIAL APPLICATIONS
NARCIS (Netherlands)
Yue, Jun; Deuss, Peter; Zhang, Zheng; Hommes, Arne; Heeres, Hero
2016-01-01
The ever increasing global demand on fossil resources that are limited in reserves has directed numerous research efforts recently towards the development of more sustainable feedstocks as the source for the production of fuels, chemicals and (performance) materials. Conversion of biomass
10. Inappropriate Use of the Quasi-Reversible Electrode Kinetic Model in Simulation-Experiment Comparisons of Voltammetric Processes That Approach the Reversible Limit
KAUST Repository
Simonov, Alexandr N.
2014-08-19
Many electrode processes that approach the "reversible" (infinitely fast) limit under voltammetric conditions have been inappropriately analyzed by comparison of experimental data and theory derived from the "quasi-reversible" model. Simulations based on "reversible" and "quasi-reversible" models have been fitted to an extensive series of a.c. voltammetric experiments undertaken at macrodisk glassy carbon (GC) electrodes for oxidation of ferrocene (Fc0/+) in CH3CN (0.10 M (n-Bu)4NPF6) and reduction of [Ru(NH 3)6]3+ and [Fe(CN)6]3- in 1 M KCl aqueous electrolyte. The confidence with which parameters such as standard formal potential (E0), heterogeneous electron transfer rate constant at E0 (k0), charge transfer coefficient (α), uncompensated resistance (Ru), and double layer capacitance (CDL) can be reported using the "quasi- reversible" model has been assessed using bootstrapping and parameter sweep (contour plot) techniques. Underparameterization, such as that which occurs when modeling CDL with a potential independent value, results in a less than optimal level of experiment-theory agreement. Overparameterization may improve the agreement but easily results in generation of physically meaningful but incorrect values of the recovered parameters, as is the case with the very fast Fc0/+ and [Ru(NH3)6]3+/2+ processes. In summary, for fast electrode kinetics approaching the "reversible" limit, it is recommended that the "reversible" model be used for theory-experiment comparisons with only E0, R u, and CDL being quantified and a lower limit of k 0 being reported; e.g., k0 ≥ 9 cm s-1 for the Fc0/+ process. © 2014 American Chemical Society.
11. Inappropriate Use of the Quasi-Reversible Electrode Kinetic Model in Simulation-Experiment Comparisons of Voltammetric Processes That Approach the Reversible Limit
KAUST Repository
Simonov, Alexandr N.; Morris, Graham P.; Mashkina, Elena A.; Bethwaite, Blair; Gillow, Kathryn; Baker, Ruth E.; Gavaghan, David J.; Bond, Alan M.
2014-01-01
Many electrode processes that approach the "reversible" (infinitely fast) limit under voltammetric conditions have been inappropriately analyzed by comparison of experimental data and theory derived from the "quasi-reversible" model. Simulations based on "reversible" and "quasi-reversible" models have been fitted to an extensive series of a.c. voltammetric experiments undertaken at macrodisk glassy carbon (GC) electrodes for oxidation of ferrocene (Fc0/+) in CH3CN (0.10 M (n-Bu)4NPF6) and reduction of [Ru(NH 3)6]3+ and [Fe(CN)6]3- in 1 M KCl aqueous electrolyte. The confidence with which parameters such as standard formal potential (E0), heterogeneous electron transfer rate constant at E0 (k0), charge transfer coefficient (α), uncompensated resistance (Ru), and double layer capacitance (CDL) can be reported using the "quasi- reversible" model has been assessed using bootstrapping and parameter sweep (contour plot) techniques. Underparameterization, such as that which occurs when modeling CDL with a potential independent value, results in a less than optimal level of experiment-theory agreement. Overparameterization may improve the agreement but easily results in generation of physically meaningful but incorrect values of the recovered parameters, as is the case with the very fast Fc0/+ and [Ru(NH3)6]3+/2+ processes. In summary, for fast electrode kinetics approaching the "reversible" limit, it is recommended that the "reversible" model be used for theory-experiment comparisons with only E0, R u, and CDL being quantified and a lower limit of k 0 being reported; e.g., k0 ≥ 9 cm s-1 for the Fc0/+ process. © 2014 American Chemical Society.
12. Early reversal of profound rocuronium-induced neuromuscular blockade by sugammadex in a randomized multicenter study - Efficacy, safety, and pharmacokinetics
NARCIS (Netherlands)
Sparr, Harald J.; Vermeyen, Karel M.; Beaufort, Anton M.; Rietbergen, Henk; Proost, Johannes H.; Saldien, Vera; Velik-Salchner, Corinna; Wierda, J. Mark K. H.
Background: Sugammadex reverses the neuromuscular blocking effects of rocuronium by chemical encapsulation. The efficacy, safety, and pharmacokinetics of sugammadex for reversal of profound rocuronium-induced neuromuscular blockade were evaluated. Methods: Ninety-eight male adult patients were
13. Reverse Logistics
OpenAIRE
Kulikova, Olga
2016-01-01
This thesis was focused on the analysis of the concept of reverse logistics and actual reverse processes which are implemented in mining industry and finding solutions for the optimization of reverse logistics in this sphere. The objective of this paper was the assessment of the development of reverse logistics in mining industry on the example of potash production. The theoretical part was based on reverse logistics and mining waste related literature and provided foundations for further...
14. Analysis of efficiency of waste reverse logistics for recycling.
Science.gov (United States)
Veiga, Marcelo M
2013-10-01
Brazil is an agricultural country with the highest pesticide consumption in the world. Historically, pesticide packaging has not been disposed of properly. A federal law requires the chemical industry to provide proper waste management for pesticide-related products. A reverse logistics program was implemented, which has been hailed a great success. This program was designed to target large rural communities, where economy of scale can take place. Over the last 10 years, the recovery rate has been very poor in most small rural communities. The objective of this study was to analyze the case of this compulsory reverse logistics program for pesticide packaging under the recent Brazilian Waste Management Policy, which enforces recycling as the main waste management solution. This results of this exploratory research indicate that despite its aggregate success, the reverse logistics program is not efficient for small rural communities. It is not possible to use the same logistic strategy for small and large communities. The results also indicate that recycling might not be the optimal solution, especially in developing countries with unsatisfactory recycling infrastructure and large transportation costs. Postponement and speculation strategies could be applied for improving reverse logistics performance. In most compulsory reverse logistics programs, there is no economical solution. Companies should comply with the law by ranking cost-effective alternatives.
15. Performance and cost of energy transport and storage systems for dish applications using reversible chemical reactions
Science.gov (United States)
Schredder, J. M.; Fujita, T.
1984-01-01
The use of reversible chemical reactions for energy transport and storage for parabolic dish networks is considered. Performance and cost characteristics are estimated for systems using three reactions (sulfur-trioxide decomposition, steam reforming of methane, and carbon-dioxide reforming of methane). Systems are considered with and without storage, and in several energy-delivery configurations that give different profiles of energy delivered versus temperature. Cost estimates are derived assuming the use of metal components and of advanced ceramics. (The latter reduces the costs by three- to five-fold). The process that led to the selection of the three reactions is described, and the effects of varying temperatures, pressures, and heat exchanger sizes are addressed. A state-of-the-art survey was performed as part of this study. As a result of this survey, it appears that formidable technical risks exist for any attempt to implement the systems analyzed in this study, especially in the area of reactor design and performance. The behavior of all components and complete systems under thermal energy transients is very poorly understood. This study indicates that thermochemical storage systems that store reactants as liquids have efficiencies below 60%, which is in agreement with the findings of earlier investigators.
16. Fouling of Seawater Reverse Osmosis (SWRO) Membrane: Chemical and Microbiological Characterization
KAUST Repository
2013-12-01
In spite of abundant water resources, world is suffering from the scarcity of usable water. Seawater Reverse Osmosis (SWRO) desalination technology using polymeric membranes has been recognized as a key solution to water scarcity problem. However, economic sustainability of this advanced technology is adversely impacted by the membrane fouling problem. Fouling of RO membranes is a highly studied phenomenon. However, literature is found to be lacking a detailed study on kinetic and dynamic aspects of SWRO membrane fouling. The factors that impact the fouling dynamics, i.e., pretreatment and water quality were also not adequately studied at full–scale of operation. Our experimental protocol was designed to systematically explore these fouling aspects with the objective to improve the understanding of SWRO membrane fouling mechanisms. An approach with multiple analytical techniques was developed for fouling characterization. In addition to the fouling layer characterization, feed water quality was also analysed to assess its fouling potential. Study of SWRO membrane fouling dynamics and kinetics revealed variations in relative abundance of chemical and microbial constituents of the fouling layer, over operating time. Aromatic substances, most likely humic–like substances, were observed at relatively high abundance in the initial fouling layer, followed by progressive increase in relative abundances of proteins and polysaccharides. Microbial population grown on all membranes was dominated by specific groups/species belonging to different classes of Proteobacteria phylum; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age and with the position of membrane element in RO vessel. Our results demonstrated that source water quality can significantly impact the RO membrane fouling scenarios. Moreover, the major role of chlorination in the SWRO membrane fouling was highlighted. It was found that intermittent mode of chlorination
17. Reversibility: An Engineer's Point of View
Energy Technology Data Exchange (ETDEWEB)
Berest, Pierre [LMS, ecole Polytechnique (France)
2012-07-01
Reversibility is the most consistent option in a democratic country. However reversibility may also have several drawbacks which must be identified and mitigated. Reversibility of a geological repository is a relatively new idea in France. The 1991 law dedicated to nuclear waste management considered reversibility as a possible option. Fifteen years later, the 2006 law mandated that a deep repository must be reversible and that the exact content of this notion should be defined by a new law to be discussed by the Parliament in 2015. Reversibility was not a concern put forward by engineers. It clearly originated from a societal demand sponsored and formulated by the Parliament. Since 1991, the exact meaning of this mandate progressively became more precise. In the early days, reversibility meant the technical and financial capability to retrieve the wastes from the repository, at least for some period of time after being emplaced. Progressively, a broader definition, suggested by Andra, was accepted: reversibility also means that a disposal facility should be operated in such a way that a stepwise decision-making process is possible. At each step, society must be able to decide to proceed to the next step, to pause or to reverse a step. Several benefits can be expected from a reversible repository. Some technical safety concerns may be only recognised after waste emplacement. Radioactive wastes may become a resource whose recoverability is desirable. Regulations may change, alternative waste treatment or better disposal techniques may be developed, or the need to modify a component of the facility may arise. Looking back at how chemical or domestic wastes were managed some 50 years ago easily underscores that it is not unreasonable to hope for significant advances in the future. For scientists and engineers, reversibility proves to have several other merits. To design and build a good repository, time is needed. The operator of a mine or of an oil field knows that
18. Reversals and collisions optimize protein exchange in bacterial swarms
Energy Technology Data Exchange (ETDEWEB)
Amiri, Aboutaleb; Harvey, Cameron; Buchmann, Amy; Christley, Scott; Shrout, Joshua D.; Aranson, Igor S.; Alber, Mark
2017-03-01
Swarming groups of bacteria coordinate their behavior by self-organizing as a population to move over surfaces in search of nutrients and optimal niches for colonization. Many open questions remain about the cues used by swarming bacteria to achieve this self-organization. While chemical cue signaling known as quorum sensing is well-described, swarming bacteria often act and coordinate on time scales that could not be achieved via these extracellular quorum sensing cues. Here, cell-cell contact-dependent protein exchange is explored as amechanism of intercellular signaling for the bacterium Myxococcus xanthus. A detailed biologically calibrated computational model is used to study how M. xanthus optimizes the connection rate between cells and maximizes the spread of an extracellular protein within the population. The maximum rate of protein spreading is observed for cells that reverse direction optimally for swarming. Cells that reverse too slowly or too fast fail to spread extracellular protein efficiently. In particular, a specific range of cell reversal frequencies was observed to maximize the cell-cell connection rate and minimize the time of protein spreading. Furthermore, our findings suggest that predesigned motion reversal can be employed to enhance the collective behavior of biological synthetic active systems.
19. An interlacing theorem for reversible Markov chains
International Nuclear Information System (INIS)
Grone, Robert; Salamon, Peter; Hoffmann, Karl Heinz
2008-01-01
Reversible Markov chains are an indispensable tool in the modeling of a vast class of physical, chemical, biological and statistical problems. Examples include the master equation descriptions of relaxing physical systems, stochastic optimization algorithms such as simulated annealing, chemical dynamics of protein folding and Markov chain Monte Carlo statistical estimation. Very often the large size of the state spaces requires the coarse graining or lumping of microstates into fewer mesoscopic states, and a question of utmost importance for the validity of the physical model is how the eigenvalues of the corresponding stochastic matrix change under this operation. In this paper we prove an interlacing theorem which gives explicit bounds on the eigenvalues of the lumped stochastic matrix. (fast track communication)
20. An interlacing theorem for reversible Markov chains
Energy Technology Data Exchange (ETDEWEB)
Grone, Robert; Salamon, Peter [Department of Mathematics and Statistics, San Diego State University, San Diego, CA 92182-7720 (United States); Hoffmann, Karl Heinz [Institut fuer Physik, Technische Universitaet Chemnitz, D-09107 Chemnitz (Germany)
2008-05-30
Reversible Markov chains are an indispensable tool in the modeling of a vast class of physical, chemical, biological and statistical problems. Examples include the master equation descriptions of relaxing physical systems, stochastic optimization algorithms such as simulated annealing, chemical dynamics of protein folding and Markov chain Monte Carlo statistical estimation. Very often the large size of the state spaces requires the coarse graining or lumping of microstates into fewer mesoscopic states, and a question of utmost importance for the validity of the physical model is how the eigenvalues of the corresponding stochastic matrix change under this operation. In this paper we prove an interlacing theorem which gives explicit bounds on the eigenvalues of the lumped stochastic matrix. (fast track communication)
1. Reversal of rocuronium-induced (1.2 mg/kg) profound neuromuscular block by sugammadex: a multicenter, dose-finding and safety study.
NARCIS (Netherlands)
Boer, H.D. de; Driessen, J.J.; Marcus, M.A.; Kerkkamp, H.E.M.; Heeringa, M.; Klimek, M.
2007-01-01
BACKGROUND: Reversal of rocuronium-induced neuromuscular blockade can be accomplished by chemical encapsulation of rocuronium by sugammadex, a modified gamma-cyclodextrin derivative. This study investigated the efficacy and safety of sugammadex in reversing rocuronium-induced profound neuromuscular
2. Electrochemical deposition and characterization of zinc–nickel alloys deposited by direct and reverse current
Directory of Open Access Journals (Sweden)
JELENA B. BAJAT
2005-12-01
Full Text Available Zn–Ni alloys electrochemically deposited on steel under various deposition conditions were investigated. The alloys were deposited on a rotating disc electrode and on a steel panel from chloride solutions by direct and reverse current. The influence of reverse plating variables (cathodic and anodic current densities and their time duration on the composition, phase structure and corrosion properties were investigated. The chemical content and phase composition affect the anticorrosive properties of Zn–Ni alloys during exposure to a corrosive agent (3 % NaCl solution. It was shown that the Zn–Ni alloy electrodeposited by reverse current with a full period T = 1 s and r = 0.2 exhibits the best corrosion properties of all the investigated alloys deposited by reverse current.
3. Biological responses to acidification reversal in Cumbrian streamwaters - stream water chemistry
Energy Technology Data Exchange (ETDEWEB)
Tipping, E.; Hardie, D.J.; Lawlor, A.J.; Lofts, S.; Simon, B.M.; Vincent, C.D. [Institute of Freshwater Ecology, Ambleside (United Kingdom)
1999-07-01
This reports summarises the findings of a study sampling the streams for invertebrates and comparing the results with those made in the 1960s and 1970s, The distribution of the bacterium Cytophaga was examined, and the results of the chemical analysis of the stream waters were compared with the results from previous years. The background to the study is traced, and details of the sampling and chemical analysis are given. Evidence of the reversal of acidification in the streams is considered.
4. Characterisation of Liquid Slugs in Gas-Liquid Taylor Flow in Microchannels
Czech Academy of Sciences Publication Activity Database
Záloha, Petr; Křišťál, Jiří; Jiřičný, Vladimír; Völkel, N.; Xuereb, C.; Aubin, J.
2012-01-01
Roč. 68, č. 1 (2012), s. 640-649 ISSN 0009-2509 Grant - others:IMPULSE(XE) NMP2-CT-2005-011816 Institutional research plan: CEZ:AV0Z40720504 Keywords : gas-liquid * micro-piv * microreactor Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.386, year: 2012
5. Interaction of HIV-1 reverse transcriptase ribonuclease H with an acylhydrazone inhibitor.
Science.gov (United States)
Gong, Qingguo; Menon, Lakshmi; Ilina, Tatiana; Miller, Lena G; Ahn, Jinwoo; Parniak, Michael A; Ishima, Rieko
2011-01-01
HIV-1 reverse transcriptase is a bifunctional enzyme, having both DNA polymerase (RNA- and DNA-dependent) and ribonuclease H activities. HIV-1 reverse transcriptase has been an exceptionally important target for antiretroviral therapeutic development, and nearly half of the current clinically used antiretrovirals target reverse transcriptase DNA polymerase. However, no inhibitors of reverse transcriptase ribonuclease H are on the market or in preclinical development. Several drug-like small molecule inhibitors of reverse transcriptase ribonuclease H have been described, but little structural information is available about the interactions between reverse transcriptase ribonuclease H and inhibitors that exhibit antiviral activity. In this report, we describe NMR studies of the interaction of a new ribonuclease H inhibitor, BHMP07, with a catalytically active HIV-1 reverse transcriptase ribonuclease H domain fragment. We carried out solution NMR experiments to identify the interaction interface of BHMP07 with the ribonuclease H domain fragment. Chemical shift changes of backbone amide signals at different BHMP07 concentrations clearly demonstrate that BHMP07 mainly recognizes the substrate handle region in the ribonuclease H fragment. Using ribonuclease H inhibition assays and reverse transcriptase mutants, the binding specificity of BHMP07 was compared with another inhibitor, dihydroxy benzoyl naphthyl hydrazone. Our results provide a structural characterization of the ribonuclease H inhibitor interaction and are likely to be useful for further improvements of the inhibitors. © 2010 John Wiley & Sons A/S.
6. A 3D QSAR pharmacophore model and quantum chemical structure--activity analysis of chloroquine(CQ)-resistance reversal.
Science.gov (United States)
Bhattacharjee, Apurba K; Kyle, Dennis E; Vennerstrom, Jonathan L; Milhous, Wilbur K
2002-01-01
Using CATALYST, a three-dimensional QSAR pharmacophore model for chloroquine(CQ)-resistance reversal was developed from a training set of 17 compounds. These included imipramine (1), desipramine (2), and 15 of their analogues (3-17), some of which fully reversed CQ-resistance, while others were without effect. The generated pharmacophore model indicates that two aromatic hydrophobic interaction sites on the tricyclic ring and a hydrogen bond acceptor (lipid) site at the side chain, preferably on a nitrogen atom, are necessary for potent activity. Stereoelectronic properties calculated by using AM1 semiempirical calculations were consistent with the model, particularly the electrostatic potential profiles characterized by a localized negative potential region by the side chain nitrogen atom and a large region covering the aromatic ring. The calculated data further revealed that aminoalkyl substitution at the N5-position of the heterocycle and a secondary or tertiary aliphatic aminoalkyl nitrogen atom with a two or three carbon bridge to the heteroaromatic nitrogen (N5) are required for potent "resistance reversal activity". Lowest energy conformers for 1-17 were determined and optimized to afford stereoelectronic properties such as molecular orbital energies, electrostatic potentials, atomic charges, proton affinities, octanol-water partition coefficients (log P), and structural parameters. For 1-17, fairly good correlation exists between resistance reversal activity and intrinsic basicity of the nitrogen atom at the tricyclic ring system, frontier orbital energies, and lipophilicity. Significantly, nine out of 11 of a group of structurally diverse CQ-resistance reversal agents mapped very well on the 3D QSAR pharmacophore model.
7. Zero field reversal probability in thermally assisted magnetization reversal
Science.gov (United States)
Prasetya, E. B.; Utari; Purnama, B.
2017-11-01
This paper discussed about zero field reversal probability in thermally assisted magnetization reversal (TAMR). Appearance of reversal probability in zero field investigated through micromagnetic simulation by solving stochastic Landau-Lifshitz-Gibert (LLG). The perpendicularly anisotropy magnetic dot of 50×50×20 nm3 is considered as single cell magnetic storage of magnetic random acces memory (MRAM). Thermally assisted magnetization reversal was performed by cooling writing process from near/almost Curie point to room temperature on 20 times runs for different randomly magnetized state. The results show that the probability reversal under zero magnetic field decreased with the increase of the energy barrier. The zero-field probability switching of 55% attained for energy barrier of 60 k B T and the reversal probability become zero noted at energy barrier of 2348 k B T. The higest zero-field switching probability of 55% attained for energy barrier of 60 k B T which corespond to magnetif field of 150 Oe for switching.
8. Study to determine the technical and economic feasibility of reclaiming chemicals used in micellar polymer and low tension surfactant flooding. Final report. [Ultrafiltration membranes and reverse osmosis membranes
Energy Technology Data Exchange (ETDEWEB)
Stephens, R.H.; Himmelblau, A.; Donnelly, R.G.
1978-02-01
Energy Resources Company has developed a technology for use with enhanced oil recovery to achieve emulsion breaking and surfactant recovery. By using ultrafiltration membranes, the Energy Resources Company process can dewater an oil-in-water type emulsion expected from enhanced oil recovery projects to the point where the emulsion can be inverted and treated using conventional emulsion-treating equipment. By using a tight ultrafiltration membrane or a reverse osmosis membrane, the Energy Resources Company process is capable of recovering chemicals such as surfactants used in micellar polymer flooding.
9. Magnetic field reversals, polar wander, and core-mantle coupling.
Science.gov (United States)
Courtillot, V; Besse, J
1987-09-04
True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause.
10. Reverse Osmosis
many applications, one of which is desalination of seawater. The inaugural Nobel Prize in Chemistry was awarded in 1901 to van 't Hoff for his seminal work in this area. The present article explains the principle of osmosis and reverse osmosis. Osmosis and Reverse Osmosis. As the name suggests, reverse osmosis is the ...
11. Functional behavior and reproduction in androgenic sex reversed zebrafish (Danio rerio).
Science.gov (United States)
Larsen, Mia G; Baatrup, Erik
2010-08-01
Endocrine-disrupting chemicals released into natural watercourses may cause biased sex ratios by sex reversal in fish populations. The present study investigated the androgenic sex reversal of zebrafish (Danio rerio) exposed to the androgenic compound 17beta-trenbolone (TB) and whether sex-changed females would revert to the female phenotype after cessation of TB exposure. 17beta-Trenbolone is a metabolite of trenbolone acetate, an anabolic steroid used as a growth promoter in beef cattle. 17beta-Trenbolone in runoff from cattle feedlots may reach concentrations that affect fish sexual development. Zebrafish were exposed to a concentration of 20 ng/L TB in a flow-through system for five months from egg until sexual maturity. This resulted in an all-male population. It was further found that all these phenotypic males displayed normal male courtship behavior and were able to reproduce successfully, implying that the sex reversal was complete and functional. None of the phenotypic males developed into females after six months in clean water, demonstrating that androgenic sex reversal of zebrafish is irreversible. Copyright 2010 SETAC
12. Separation of mixtures of organic substance using reverse osmosis membranes
Energy Technology Data Exchange (ETDEWEB)
Kimura, Shoji; Nakao, Shin' ichi; Tanimura, Shinobu
1987-12-25
With the arrival of energy crisis, attention has been concentrated on the production of alcohol by means of biomass conversion. Energy-saving concentration method was searched to replace a distillation method as a method of concentrating dilute alcohols, for which a reverse osmosis method was proposed; experimental results have been reported accordingly. One result is that the osmotic pressure method has a limitation of difficulty to exceed more than 15% concentration. For this, the reverse osmosis was reviewed and it was found that wider concentration range should be examined for the area where the reverse osmosis was not experimented. Fils employed were a polyamide film of Nitto Denko Co. and an acrylonitrile film of sumitomo Chemical Co.. The result revealed that alcohol could be concentrated up to rather high concentration in alcohol-water system; even in a non-aqueous system, separation with high selective permeability was possible by the proper selection of film materials. (4 figs, 2 refs)
13. Down Select Report of Chemical Hydrogen Storage Materials, Catalysts, and Spent Fuel Regeneration Processes
Energy Technology Data Exchange (ETDEWEB)
Ott, Kevin; Linehan, Sue; Lipiecki, Frank; Aardahl, Christopher L.
2008-08-24
The DOE Hydrogen Storage Program is focused on identifying and developing viable hydrogen storage systems for onboard vehicular applications. The program funds exploratory research directed at identifying new materials and concepts for storage of hydrogen having high gravimetric and volumetric capacities that have the potential to meet long term technical targets for onboard storage. Approaches currently being examined are reversible metal hydride storage materials, reversible hydrogen sorption systems, and chemical hydrogen storage systems. The latter approach concerns materials that release hydrogen in endothermic or exothermic chemical bond-breaking processes. To regenerate the spent fuels arising from hydrogen release from such materials, chemical processes must be employed. These chemical regeneration processes are envisioned to occur offboard the vehicle.
14. Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell
KAUST Repository
Qi, Genggeng
2010-05-11
Monodispersed HMSs with tunable particle size and shell thickness were successfully synthesized using relatively concentrated polystyrene latex templates and a silica precursor in a weakly basic ethanol/water mixture. The particle size of the capsules can vary from 100 nm to micrometers. These highly engineered monodispersed capsules synthesized by a facile and scalable process may find applications in drug delivery, catalysis, separationm or as biological and chemical microreactors. © 2010 American Chemical Society.
15. A reversible, unidirectional molecular rotary motor driven by chemical energy
NARCIS (Netherlands)
Fletcher, SP; Dumur, F; Pollard, MM; Feringa, BL
2005-01-01
With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement,of a phenyl rotor relative to a naphthyl stator about a single bond axle. The
16. Microreactortechnology: Real-Time Flow Measurements in Organic Synthesis
Directory of Open Access Journals (Sweden)
Pieter J. Nieuwland
2012-03-01
Full Text Available With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often hampered by the use of large amounts of hazardous chemicals. Accurate actuation and in line measurements of the flows, to have a better control over the chemical reaction, is of added value for increasing reproducibility and a safe production.
17. Managing Reverse Logistics or Reversing Logistics Management?
NARCIS (Netherlands)
M.P. de Brito (Marisa)
2004-01-01
textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse
18. Nanoscale Electrochemical Sensing and Processing in Microreactors
NARCIS (Netherlands)
Odijk, Mathieu; van den Berg, Albert
2018-01-01
In this review, we summarize recent advances in nanoscale electrochemistry, including the use of nanoparticles, carbon nanomaterials, and nanowires. Exciting developments are reported for nanoscale redox cycling devices, which can chemically amplify signal readout. We also discuss promising
19. Online monitoring of N-nitrosodimethylamine rejection as a performance indicator of trace organic chemical removal by reverse osmosis.
Science.gov (United States)
Fujioka, Takahiro; Takeuchi, Haruka; Tanaka, Hiroaki; Kodamatani, Hitoshi
2018-06-01
The security of recycled water quality in potable reuse can be enhanced by improving the credibility of reverse osmosis (RO) treatment for the removal of trace organic chemicals (TOrCs). This study evaluated the potential of online monitoring of N-nitrosodimethylamine (NDMA) before and after RO treatment as a surrogate indicator for TOrC removal by RO. This pilot-scale study monitored NDMA concentrations in RO feedwater (ultrafiltration-treated wastewater) and RO permeate every 22 min using novel online NDMA analyzers-high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection. NDMA rejection by RO varied considerably in response to changes in operating conditions (permeate flux and feedwater temperature). A high linear correlation between NDMA rejection and the rejection of six other TOrCs was observed. The linear correlation was also identified for an RO membrane damaged with chlorine. The correlation between another potential surrogate indicator (conductivity rejection) and TOrC rejection was relatively low. NDMA, which is the smallest compound among regulated TOrCs, revealed rejections lower than the other TOrCs, indicating that NDMA rejection can be a conservative surrogate indicator capable of predicting changes in TOrC removal. Copyright © 2018 Elsevier Ltd. All rights reserved.
20. ECOLOGICAL AND EVOLUTIONARY APPLICATIONS FOR ENVIRONMENTAL SEX REVERSAL OF FISH.
Science.gov (United States)
Mcnair, Alistair; Lokman, P Mark; Closs, Gerard P; Nakagawa, Shinichi
2015-03-01
Environmental sex reversal (ESR), which results in a mismatch between genotypic and phenotypic sex, is well documented in numerous fish species and may be induced by chemical exposure. Historically, research involving piscine ESR has been carried out with a view to improving profitability in aquaculture or to elucidate the processes governing sex determination and sexual differentiation. However, recent studies in evolution and ecology suggest research on ESR now has much wider applications and ramifications. We begin with an overview of ESR in fish and a brief review of the traditional applications thereof. We then discuss ESR and its potential demographic consequences in wild populations. Theory even suggests sex-reversed fish may be purposefully released to manipulate population dynamics. We suggest new research directions that may prove fruitful in understanding how ESR at the individual level translates to population-level processes. In the latter portion of the review we focus on evolutionary applications of ESR. Sex-reversal studies from the aquaculture literature provide insight in to the evolvability of determinants of sexual phenotype. Additionally, induced sex reversal can provide information about the evolution of sex chromosomes and sex-linked traits. Recently, naturally occurring ESR has been implicated as a mechanism contributing to the evolution of sex chromosomes.
1. Evaluation of spiral wound reverse osmosis for four radioactive waste processing applications
International Nuclear Information System (INIS)
Sen Gupta, S.K.
1997-01-01
A pilot-scale spiral wound reverse osmosis rig was used to treat four significantly different radioactive waste streams, three of which were generated at the Chalk River Laboratories at AECL. These streams included: 1. A chemical decontamination (CD/DC) waste stream which is routinely treated by the plant-scale membrane system at CRL; 2. Reactor waste which is a dilute radioactive waste stream (containing primarily tritium and organic acids), and it an effluent from the operating reactors at AECL; 3. An ion exchange regenerant waste stream which contains a mixture of stream (1) (CD/DC), blended with secondary waste from ion exchange regeneration; 4. Boric acid simulated waste which is a by-product waste of the PWR reactors. This was the only stream treated that was not generated as a waste liquid at AECL. For the first three streams specified above, reverse osmosis was used to remove chemical and radiochemical impurities from the water with efficiencies usually exceeding 99%. In these three cases the 'permeate' or clean water was the product of the process. In the case of stream 4, reverse osmosis was used in a recovery application for the purpose of recycling boric acid back to the reactor, with the concentrate being the 'product'. Reverse osmosis technology was successfully demonstrated for the treatment of all four streams. Prefiltration and oxidation (with photocatalytic continuous oxidation technology) were evaluated as pretreatment alternatives for streams 1, 2, and 3. The results indicated that the effective crossflow velocity through and membrane vessel was more important in determining the extent of membrane fouling than the specific pretreatment strategy employed. (author)
2. Gray water recycle: Effect of pretreatment technologies on low pressure reverse osmosis treatment
Science.gov (United States)
Gray water can be a valuable source of water when properly treated to reduce the risks associated with chemical and microbial contamination to acceptable levels for the intended reuse application. In this study, the treatment of gray water using low pressure reverse osmosis (RO) filtration after pre...
3. Fouling and cleaning of seawater reverse osmosis membranes in Kalpakkam Nuclear Desalination Plant
International Nuclear Information System (INIS)
Murugan, V.; Rajanbabu, K.; Tiwari, S.A.; Balasubramanian, C.; Yadav, Manoj Kumar; Dangore, A.Y.; Prabhakar, S.; Tewari, P.K.
2005-01-01
Seawater reverse osmosis plant of 1800 m 3 /day capacity is a part of 6300 m 3 /day capacity Nuclear Desalination Demonstration Project, at Kalpakkam. The plant was commissioned in October 2002 and is in continuous operation. This paper deals with types of foulants, membrane cleaning procedures and the improvement in the reverse osmosis system after cleaning. This paper also describes analysis of foulants which may consist of adsorbed organic compounds, particulate matter, microorganisms, metallic oxides and chemical cleaning procedure to be adopted, which is characteristics of sea water used as the membrane foulant is very much specific with respect to the sea water constituents. The cleaning of the membranes in Kalpakkam Nuclear Desalination plant were taken up as the quality of permeate deteriorated and differential pressure across membrane had gone-up. This paper essentially deals with selection of cleaning chemicals, the experience gained in cleaning procedure adopted and effects of cleaning for the membrane system. (author)
4. Tunable reverse-biased graphene/silicon heterojunction Schottky diode sensor.
Science.gov (United States)
Singh, Amol; Uddin, Ahsan; Sudarshan, Tangali; Koley, Goutam
2014-04-24
A new chemical sensor based on reverse-biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ∼500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance-voltage measurements. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
5. Reverse genetics with animal viruses. NSV reverse genetics
International Nuclear Information System (INIS)
Mebatsion, T.
2005-01-01
New strategies to genetically manipulate the genomes of several important animal pathogens have been established in recent years. This article focuses on the reverse genetics techniques, which enables genetic manipulation of the genomes of non-segmented negative-sense RNA viruses. Recovery of a negative-sense RNA virus entirely from cDNA was first achieved for rabies virus in 1994. Since then, reverse genetic systems have been established for several pathogens of medical and veterinary importance. Based on the reverse genetics technique, it is now possible to design safe and more effective live attenuated vaccines against important viral agents. In addition, genetically tagged recombinant viruses can be designed to facilitate serological differentiation of vaccinated animals from infected animals. The approach of delivering protective immunogens of different pathogens using a single vector was made possible with the introduction of the reverse genetics system, and these novel broad-spectrum vaccine vectors have potential applications in improving animal health in developing countries. (author)
6. Practical Engineering Aspects of Catalysis in Microreactors
Czech Academy of Sciences Publication Activity Database
Křišťál, Jiří; Stavárek, Petr; Vajglová, Zuzana; Vondráčková, Magdalena; Pavlorková, Jana; Jiřičný, Vladimír
2015-01-01
Roč. 41, č. 12 (2015), s. 9357-9371 ISSN 0922-6168. [Pannonian Symposium on Catalysis /12./. Castle Trest, 16.09.2014-20.09.2014] Institutional support: RVO:67985858 Keywords : heterogeneous catalysis * homogeneous catalysis * photo catalysis Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.833, year: 2015
7. Effect of dimethyl sulfoxide (DMSO) on radiation-induced heteroallelic reversion in diploid yeast
International Nuclear Information System (INIS)
Singh, D.R.; Mahajan, J.M.; Krishnan, D.
1976-01-01
Dimethyl sulfoxide has cryoprotective and radioprotective properties. It is also an efficient scavenger of radicals produced by radiolysis of water. Gamma-induced reversion of diploid yeast in the presence of this chemical during irradiation have been studied. The dose-modifying factor was in the same range as for survival. When the yeast was irradiated in the frozen state, the observed protection by DMSO disappeared. The results are discussed in terms of direct and indirect actions of radiations and the radical-scavenging ability of this chemical
8. Hybrid supercapacitors for reversible control of magnetism.
Science.gov (United States)
Molinari, Alan; Leufke, Philipp M; Reitz, Christian; Dasgupta, Subho; Witte, Ralf; Kruk, Robert; Hahn, Horst
2017-05-10
Electric field tuning of magnetism is one of the most intensely pursued research topics of recent times aiming at the development of new-generation low-power spintronics and microelectronics. However, a reversible magnetoelectric effect with an on/off ratio suitable for easy and precise device operation is yet to be achieved. Here we propose a novel route to robustly tune magnetism via the charging/discharging processes of hybrid supercapacitors, which involve electrostatic (electric-double-layer capacitance) and electrochemical (pseudocapacitance) doping. We use both charging mechanisms-occurring at the La 0.74 Sr 0.26 MnO 3 /ionic liquid interface to control the balance between ferromagnetic and non-ferromagnetic phases of La 1-x Sr x MnO 3 to an unprecedented extent. A magnetic modulation of up to ≈33% is reached above room temperature when applying an external potential of only about 2.0 V. Our case study intends to draw attention to new, reversible physico-chemical phenomena in the rather unexplored area of magnetoelectric supercapacitors.
9. Purification of Drinking Water from Fluorides by Reverse Osmosis
Directory of Open Access Journals (Sweden)
Aleksander A.
2018-03-01
Full Text Available Introduction: An important task in the sphere of sanitary and epidemiological welfare of the population of the Russian Federation is provision of drinking water. Tap water must not contain pathogenic bacteria and dangerous chemicals. Purification systems regulate the concentration of fluoride ions in drinking water. The aim of this paper is to study the possibility of purifying tap water from fluoride ions by reverse osmosis. Materials and Methods: We used the Alfa Laval PilotUnit 2.5 "RO/NF with a set of spiral-type membrane elements RO99-2517/48 to remove fluoride ions. We measured the concentration of fluoride ions by the potentiometric method using the Hanna HI 2211 (pH/mV/T. Fluoride-selective electrode ELIS 131 F was used as an indicator electrode and the standard chloride-silver electrode EVL-1M3 was used as a reference electrode. Both the calibration and buffer solutions were prepared from chemically pure reagents and A. R. purity for analysis reagents according to GOST 4386-89. Results: A single passage of water through the reverse osmosis membrane reduced the concentration of fluoride ions from 2.29 ± 0.02 to 0.240 ± 0.015 mg/l. Double passage of water reduced the concentration by a factor of two. As the concentration of fluoride ions increased in the retentate, the concentration in the filtrate slightly increased too. Purification of water reduced the concentration of fluoride ions from 20 mg/l, to 0.5 mg/l. Discussion and Conclusions: Thus, using the Alfa Laval PilotUnit 2.5" RO/NF with a set of spiral-type membrane elements RO99-2517/48 filters tap water of ions of fluoride to the maximum allowable concentration. This study opens the perspective of using reverse osmosis to purify tap water with high concentration of fluoride ions.
10. Ion-containing reverse osmosis membranes obtained by radiation grafting method
International Nuclear Information System (INIS)
Hegazy, E.-S.A.; El-Assy, N.B.; Dessouki, A.M.; Shaker, M.M.
1989-01-01
Cationic membranes obtained by radiation grafting of aqueous acrylic acid onto low density polyethylene films followed by alkaline treatment to confer ionic character in the graft chains, were tested for reverse osmosis desalination of saline water. Selected physical properties of such membranes were investigated. The grafted membranes possess good mechanical and electrical properties. Water uptake for the alkali-treated membrane was much higher than that of the alkali-untreated one. The effect of operation time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection for the grafted membranes was investigated. Such cationic membranes showed good durability, thermal and chemical stability, acceptable water flux and salt rejection which may make them acceptable for practical use in reverse osmosis desalination of sea water. (author)
11. Design aspects of reverse osmosis plants for rad waste treatment
International Nuclear Information System (INIS)
Prabhakar, S.; Panicker, S.T.; Misra, B.M.
1993-01-01
The potential of reverse osmosis process has been well established in the nuclear waste treatment. The nuclear wastes are characterised by chemically insignificant levels of radioactive nuclides and small amounts (a few hundred ppm) of inactive ionic species. The basic design objectives in these systems aim at higher volume reduction factors, i.e. corresponding to recovery factor of more than 0.9 and a decontamination factor of at least 10, i.e. corresponding to a solute rejection of more than 90%. In this paper, the salient aspects of the design of a reverse osmosis system for radioactive waste treatment is discussed in the light of the operating experience of an experimental plant based on plate module configuration and utilizing cellulose acetate membranes prepared in our laboratory. (author). 3 refs., 5 figs., 2 tabs
12. A Conceptual Framework for Predicting the Toxicity of Reactive Chemicals: Modeling Soft Electrophilicity
Science.gov (United States)
Although the literature is replete with QSAR models developed for many toxic effects caused by reversible chemical interactions, the development of QSARs for the toxic effects of reactive chemicals lacks a consistent approach. While limitations exit, an appropriate starting-point...
13. Reversible pH-controlled DNA-binding peptide nanotweezers: An in-silico study
Directory of Open Access Journals (Sweden)
Gaurav Sharma
2008-11-01
Full Text Available Gaurav Sharma1, Kaushal Rege2,3, David E Budil4, Martin L Yarmush2,5, Constantinos Mavroidis11Department of Mechanical and Industrial Engineering; 4Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, USA; 2The Center for Engineering in Medicine (CEM, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; 3Department of Chemical Engineering, Arizona State University, Tempe, AZ, USA; 5Department of Biomedical Engineering, Rutgers University, NJ, USAAbstract: We describe the molecular dynamics (MD-aided engineering design of mutant peptides based on the α-helical coiled-coil GCN4 leucine zipper peptide (GCN4-p1 in order to obtain environmentally-responsive nanotweezers. The actuation mechanism of the nanotweezers depends on the modification of electrostatic charges on the residues along the length of the coiled coil. Modulating the solution pH between neutral and acidic values results in the reversible movement of helices toward and away from each other and creates a complete closed-open-closed transition cycle between the helices. Our results indicate that the mutants show a reversible opening of up to 15 Å (1.5 nm; approximately 150% of the initial separation upon pH actuation. Investigation on the physicochemical phenomena that influence conformational properties, structural stability, and reversibility of the coiled-coil peptide-based nanotweezers revealed that a rationale- and design-based approach is needed to engineer stable peptide or macromolecules into stimuli-responsive devices. The efficacy of the mutant that demonstrated the most significant reversible actuation for environmentally responsive modulation of DNA-binding activity was also demonstrated. Our results have significant implications in bioseparations and in the engineering of novel transcription factors.Keywords: bionanotechnology, nanotweezers, coiled-coil, GCN4, leucine zipper, molecular dynamics, environmentally
14. Reverse osmosis influence over the content of metals and organic acids in low alcoholic beverages
Directory of Open Access Journals (Sweden)
Andrieş Mitică Tiberiu
2017-01-01
Full Text Available Wine is defined as an alcoholic beverage resulted from fermentation of grape must, having ethanol content higher than 8.5% (v/v. Wine consumption has health benefits related to the high concentration of polyphenolic compounds with antioxidant activity and cardiovascular protection effects. However, the alcohol content restricts wine consumption, but wines with low-alcohol content can be obtained with the help of the dealcoholisation process, after it was produced through alcoholic fermentation. The purpose of this work is to evaluate the organic acid concentration, metal content and other physical-chemical parameters of low alcoholic beverages obtained from grape must by a process which involves reverse osmosis, mixing in a variable ratio the permeate and concentrate and then fermentation. For the experiments, a Muscat Ottonel grape must from Iaşi vineyard was used. There were ten variants of beverages (wines with low alcoholic concentration, by mixing known quantities of the two phases resulting from the reverse osmosis process. These beverages (wines had an alcoholic concentration starting from 2.5% (v/v in the first variant, up to 7% (v/v in the tenth variant. Alcoholic concentration varies for each variant by 0.5% (v/v. After fermentation in 50 L stainless steel tanks, the samples were filtered with 0.45μm sterile membrane and bottled in 0.75 L glass bottles. After 2 months of storage at constant temperature, the beverage samples were analyzed to determine the metal content (AAS method, organic acids concentration (HPLC method, and other physical-chemical characteristics (OIV standard methods. The results obtained indicate that the very complex physical-chemical composition of the low alcoholic beverages analyzed is influenced by the specific chemical composition of a given grape must, as well as by the use of products obtained from reverse osmosis.
15. Proteínas como microrreactores en fotoquímica
OpenAIRE
MONJE LÓPEZ, VICENTE TOMÁS
2014-01-01
[EN] Proteins are macromolecules considered unique because of its complex spatial structure and diversity of roles in biological systems. Some years ago many of these structures are known in detail, and also the mechanisms which some of them boast physical, chemical and biological properties that are not found in any other chemical compound. In this work it has been proposed to use the binding sites of human and bovine serum albumin as microreactors. These proteins have a high degree of seque...
16. Biofouling in reverse osmosis: phenomena, monitoring, controlling and remediation
Science.gov (United States)
2017-10-01
This paper is a comprehensive review of biofouling in reverse osmosis modules where we have discussed the mechanism of biofouling. Water crisis is an issue of pandemic concern because of the steady rise in demand of drinking water. Overcoming biofouling is vital since we need to optimize expenses and quality of potable water production. Various kinds of microorganisms responsible for biofouling have been identified to develop better understanding of their attacking behavior enabling us to encounter the problem. Both primitive and advanced detection techniques have been studied for the monitoring of biofilm development on reverse osmosis membranes. Biofouling has a negative impact on membrane life as well as permeate flux and quality. Thus, a mathematical model has been presented for the calculation of normalized permeate flux for evaluating the extent of biofouling. It is concluded that biofouling can be controlled by the application of several physical and chemical remediation techniques.
17. Modeling pH variation in reverse osmosis.
Science.gov (United States)
Nir, Oded; Bishop, Noga Fridman; Lahav, Ori; Freger, Viatcheslav
2015-12-15
The transport of hydronium and hydroxide ions through reverse osmosis membranes constitutes a unique case of ionic species characterized by uncommonly high permeabilities. Combined with electromigration, this leads to complex behavior of permeate pH, e.g., negative rejection, as often observed for monovalent ions in nanofiltration of salt mixtures. In this work we employed a rigorous phenomenological approach combined with chemical equilibrium to describe the trans-membrane transport of hydronium and hydroxide ions along with salt transport and calculate the resulting permeate pH. Starting from the Nernst-Planck equation, a full non-linear transport equation was derived, for which an approximate solution was proposed based on the analytical solution previously developed for trace ions in a dominant salt. Using the developed approximate equation, transport coefficients were deduced from experimental results obtained using a spiral wound reverse osmosis module operated under varying permeate flux (2-11 μm/s), NaCl feed concentrations (0.04-0.18 M) and feed pH values (5.5-9.0). The approximate equation agreed well with the experimental results, corroborating the finding that diffusion and electromigration, rather than a priori neglected convection, were the major contributors to the transport of hydronium and hydroxide. The approach presented here has the potential to improve the predictive capacity of reverse osmosis transport models for acid-base species, thereby improving process design/control. Copyright © 2015 Elsevier Ltd. All rights reserved.
18. Reversible logic gates based on enzyme-biocatalyzed reactions and realized in flow cells: a modular approach.
Science.gov (United States)
Fratto, Brian E; Katz, Evgeny
2015-05-18
Reversible logic gates, such as the double Feynman gate, Toffoli gate and Peres gate, with 3-input/3-output channels are realized using reactions biocatalyzed with enzymes and performed in flow systems. The flow devices are constructed using a modular approach, where each flow cell is modified with one enzyme that biocatalyzes one chemical reaction. The multi-step processes mimicking the reversible logic gates are organized by combining the biocatalytic cells in different networks. This work emphasizes logical but not physical reversibility of the constructed systems. Their advantages and disadvantages are discussed and potential use in biosensing systems, rather than in computing devices, is suggested. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
19. Chemical Activation of the Hypoxia-Inducible Factor Reversibly Reduces Tendon Stem Cell Proliferation, Inhibits Their Differentiation, and Maintains Cell Undifferentiation.
Science.gov (United States)
Menon, Alessandra; Creo, Pasquale; Piccoli, Marco; Bergante, Sonia; Conforti, Erika; Banfi, Giuseppe; Randelli, Pietro; Anastasia, Luigi
2018-01-01
Adult stem cell-based therapeutic approaches for tissue regeneration have been proposed for several years. However, adult stem cells are usually limited in number and difficult to be expanded in vitro, and they usually tend to quickly lose their potency with passages, as they differentiate and become senescent. Culturing stem cells under reduced oxygen tensions (below 21%) has been proposed as a tool to increase cell proliferation, but many studies reported opposite effects. In particular, cell response to hypoxia seems to be very stem cell type specific. Nonetheless, it is clear that a major role in this process is played by the hypoxia inducible factor (HIF), the master regulator of cell response to oxygen deprivation, which affects cell metabolism and differentiation. Herein, we report that a chemical activation of HIF in human tendon stem cells reduces their proliferation and inhibits their differentiation in a reversible and dose-dependent manner. These results support the notion that hypoxia, by activating HIF, plays a crucial role in preserving stem cells in an undifferentiated state in the "hypoxic niches" present in the tissue in which they reside before migrating in more oxygenated areas to heal a damaged tissue.
20. Chemical Activation of the Hypoxia-Inducible Factor Reversibly Reduces Tendon Stem Cell Proliferation, Inhibits Their Differentiation, and Maintains Cell Undifferentiation
Directory of Open Access Journals (Sweden)
Alessandra Menon
2018-01-01
Full Text Available Adult stem cell-based therapeutic approaches for tissue regeneration have been proposed for several years. However, adult stem cells are usually limited in number and difficult to be expanded in vitro, and they usually tend to quickly lose their potency with passages, as they differentiate and become senescent. Culturing stem cells under reduced oxygen tensions (below 21% has been proposed as a tool to increase cell proliferation, but many studies reported opposite effects. In particular, cell response to hypoxia seems to be very stem cell type specific. Nonetheless, it is clear that a major role in this process is played by the hypoxia inducible factor (HIF, the master regulator of cell response to oxygen deprivation, which affects cell metabolism and differentiation. Herein, we report that a chemical activation of HIF in human tendon stem cells reduces their proliferation and inhibits their differentiation in a reversible and dose-dependent manner. These results support the notion that hypoxia, by activating HIF, plays a crucial role in preserving stem cells in an undifferentiated state in the “hypoxic niches” present in the tissue in which they reside before migrating in more oxygenated areas to heal a damaged tissue.
1. Reverse osmosis membrane of high urea rejection properties. [water purification
Science.gov (United States)
Johnson, C. C.; Wydeven, T. J. (Inventor)
1980-01-01
Polymeric membranes suitable for use in reverse osmosis water purification because of their high urea and salt rejection properties are prepared by generating a plasma of an unsaturated hydrocarbon monomer and nitrogen gas from an electrical source. A polymeric membrane is formed by depositing a polymer of the unsaturated monomer from the plasma onto a substrate, so that nitrogen from the nitrogen gas is incorporated within the polymer in a chemically combined form.
2. Separation and characterization of chemical constituents in Ginkgo biloba extract by off-line hydrophilic interaction×reversed-phase two-dimensional liquid chromatography coupled with quadrupole-time of flight mass spectrometry.
Science.gov (United States)
Ji, Shuai; He, Dan-Dan; Wang, Tian-Yun; Han, Jie; Li, Zheng; Du, Yan; Zou, Jia-Hui; Guo, Meng-Zhe; Tang, Dao-Quan
2017-11-30
Ginkgo biloba extract (GBE), derived from the leaves of Ginkgo biloba L., is one of the most widely used traditional Chinese medicines worldwide. Due to high structural diversity and low abundance of chemical constituents in GBE, conventional reversed-phase liquid chromatography has limited power to meet the needs of its quality control. In this study, an off-line hydrophilic interaction×reversed-phase two-dimensional liquid chromatography (HILIC×RP 2D-LC) system coupled with diode array detection (DAD) and quadrupole time-of-flight mass spectrometry (qTOF-MS) was established to comprehensively analyze the chemical constituents of GBE. After optimizing the chromatographic columns and mobile phase of 2D-LC, a Waters XBridge Amide column using acetonitrile/water/formic acid as the mobile phase was selected as the first dimension to fractionate GBE, and the obtained fractions were further separated on an Agilent Zorbax XDB-C18 column with methanol/water/formic acid as the mobile phase. As a result, a total of 125 compounds were detected in GBE. The orthogonality of the 2D-LC system was 69.5%, and the practical peak capacity was 3864 and 2994, respectively, calculated by two different methods. The structures of 104 compounds were tentatively characterized by qTOF-MS analysis, and 21 of them were further confirmed by comparing with reference standards. This established HILIC×RP 2D-LC-qTOF/MS system can greatly improve the separation and characterization of natural products in GBE or other complicated herbal extracts. Copyright © 2017 Elsevier B.V. All rights reserved.
3. Reversible thermochromic response based on photonic crystal structure in butterfly wing
Science.gov (United States)
Wang, Wanlin; Wang, Guo Ping; Zhang, Wang; Zhang, Di
2018-01-01
Subtle responsive properties can be achieved by the photonic crystal (PC) nanostructures of butterfly based on thermal expansion effect. The studies focused on making the sample visually distinct. However, the response is restricted by limited thermal expansion coefficients. We herein report a new class of reversible thermochromic response achieved by controlling the ambient refractive index in butterfly PC structure. The photonic ethanol-filled nanoarchitecture sample is simply assembled by sealing liquid ethanol filling Papilio ulysses butterfly wing. Volatile ethanol is used to modulate the ambient refractive index. The sample is sealed with glasses to ensure reversibility. Liquid ethanol filling butterfly wing demonstrated significant allochroic response to ambient refractive index, which can be controlled by the liquefaction and vaporization of ethanol. This design is capable of converting thermal energy into visual color signals. The mechanism of this distinct response is simulated and proven by band theory. The response properties are performed with different filled chemicals and different structure parameters. Thus, the reversible thermochromic response design might have potential use in the fields such as detection, photonic switch, displays, and so forth.
4. An algebra of reversible computation.
Science.gov (United States)
Wang, Yong
2016-01-01
We design an axiomatization for reversible computation called reversible ACP (RACP). It has four extendible modules: basic reversible processes algebra, algebra of reversible communicating processes, recursion and abstraction. Just like process algebra ACP in classical computing, RACP can be treated as an axiomatization foundation for reversible computation.
5. Chemical evaluation and treatment of ground water for university town Peshawar, Pakistan by reverse osmosis technology
International Nuclear Information System (INIS)
Saddique, M.; Gilani, S.N.; Ishaq, M.; Gul, F.
2012-01-01
Present study is focused on the ground water treatment for the University Town Peshawar by reverse osmosis technology, based on the principle of reverse-osmosis pure water and ultra pure water filtration. Water collected from three locations was analyzed. The results showed that the first two water samples were neutral having pH 7.09 and 7.16 comparable with the range (6.50-8.50), while the pH for the water sample getting purified and passed from RO process was 5.33 i.e. slightly acidic. The ionic content of the water sample was low, whereas the conductivity ranged from 624-634 micro S/cm for the first two samples and reduced to 1.37 muS/cm. The parameters investigated are below the safety baseline levels of the national and international standards with the exception of Pb. (author)
6. On thermodynamic and microscopic reversibility
International Nuclear Information System (INIS)
Crooks, Gavin E
2011-01-01
The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa
7. Effect of reactor heat transfer limitations on CO preferential oxidation
Science.gov (United States)
Ouyang, X.; Besser, R. S.
Our recent studies of CO preferential oxidation (PrOx) identified systematic differences between the characteristic curves of CO conversion for a microchannel reactor with thin-film wall catalyst and conventional mini packed-bed lab reactors (m-PBR's). Strong evidence has suggested that the reverse water-gas-shift (r-WGS) side reaction activated by temperature gradients in m-PBR's is the source of these differences. In the present work, a quasi-3D tubular non-isothermal reactor model based on the finite difference method was constructed to quantitatively study the effect of heat transport resistance on PrOx reaction behavior. First, the kinetic expressions for the three principal reactions involved were formed based on the combination of experimental data and literature reports and their parameters were evaluated with a non-linear regression method. Based on the resulting kinetic model and an energy balance derived for PrOx, the finite difference method was then adopted for the quasi-3D model. This model was then used to simulate both the microreactor and m-PBR's and to gain insights into their different conversion behavior. Simulation showed that the temperature gradients in m-PBR's favor the reverse water-gas-shift (r-WGS) reaction, thus causing a much narrower range of permissible operating temperature compared to the microreactor. Accordingly, the extremely efficient heat removal of the microchannel/thin-film catalyst system eliminates temperature gradients and efficiently prevents the onset of the r-WGS reaction.
8. Reversibility of female sterilization.
Science.gov (United States)
Siegler, A M; Hulka, J; Peretz, A
1985-04-01
The discussion considers the current status of reversibility of sterilization in the US and describes clinical and experimental efforts for developing techniques designed for reversibility. It focuses on regret following sterilization, reversal potential of current sterilization techniques, patient selection, current reversal techniques, results of sterilization procedures, experimental approaches to reversal of current techniques of sterilization, and sterilization procedures devised for reversibility, in humans and in animals. Request is the 1st stage of reversal, but a request for sterilization reversal (SR) does not always mean regret for a decision made at the time. Frequently it is a wish to restore fertility because life circumstances have changed after a sterilization that was ppropriate at the time it was performed. Schwyhart and Kutner reviewed 22 studies published between 1949-69 in which they found that the percentage of patients regretting the procedure ranged from 1.3-15%. Requests for reversal remain low in most countries, but if sterilization becomes a more popular method of contraception, requests will also increase. The ideal operation considered as a reversaible method of sterilization should include an easy, reliable outpatient method of tubal occlusion with miniml risk or patient discomfort that subsequently could be reversed without the need for a major surgical intervention. Endoscopic methods have progressed toward the 1st objective. A recent search of the literature uncovered few series of SR of more than 50 cases. The 767 operations found were analyzed with regard to pregnancy outcome. The precent of live births varied from 74-78.8%, and the occurance of tubal pregnancies ranged from 1.7-6.5%. All of the confounding variables in patient selection and small numbers of reported procedures preclude any conclusion about the different techniques or the number of operations that give a surgeon a level of expertise. Few authors classify their
9. Constraining the reversing and non-reversing modes of the geodynamo. New insights from magnetostratigraphy.
Science.gov (United States)
Gallet, Y.; Pavlov, V.; Shatsillo, A.; Hulot, G.
2015-12-01
Constraining the evolution in the geomagnetic reversal frequency over hundreds of million years is not a trivial matter. Beyond the fact that there are long periods without reversals, known as superchrons, and periods with many reversals, the way the reversal frequency changes through time during reversing periods is still debated. A smooth evolution or a succession of stationary segments have both been suggested to account for the geomagnetic polarity time scale since the Middle-Late Jurassic. Sudden changes from a reversing mode to a non-reversing mode of the geodynamo may also well have happened, the switch between the two modes having then possibly been controlled by the thermal conditions at the core-mantle boundary. There is, nevertheless, a growing set of magnetostratigraphic data, which could help decipher a proper interpretation of the reversal history, in particular in the early Paleozoic and even during the Precambrian. Although yielding a fragmentary record, these data reveal the occurrence of both additional superchrons and periods characterized by extremely high, not to say extraordinary, magnetic reversal frequencies. In this talk, we will present a synthesis of these data, mainly obtained from Siberia, and discuss their implication for the magnetic reversal behavior over the past billion years.
10. Chemical kinetics and reaction mechanism
International Nuclear Information System (INIS)
Jung, Ou Sik; Park, Youn Yeol
1996-12-01
This book is about chemical kinetics and reaction mechanism. It consists of eleven chapters, which deal with reaction and reaction speed on reaction mechanism, simple reaction by rate expression, reversible reaction and simultaneous reaction, successive reaction, complicated reaction mechanism, assumption for reaction mechanism, transition state theory, successive reaction and oscillating reaction, reaction by solution, research method high except kinetics on reaction mechanism, high reaction of kinetics like pulsed radiolysis.
11. Obtaining water with a high degree of purity by using reverse osmosis
Directory of Open Access Journals (Sweden)
Nicolae Chirilă
2011-12-01
Full Text Available In this paper, we used the method of reverse osmosis in order to obtain water with a high degree of purity. For this aim, we used the TKA 20-120ECO device. We completed physic-chemical determinations for the water of supply, as well as for the water obtained after the osmosis process. The results that we obtained are relevant and interesting.
12. Potent nonnucleoside reverse transcriptase inhibitors target HIV-1 Gag-Pol.
Directory of Open Access Journals (Sweden)
Anna Figueiredo
2006-11-01
Full Text Available Nonnucleoside reverse transcriptase inhibitors (NNRTIs target HIV-1 reverse transcriptase (RT by binding to a pocket in RT that is close to, but distinct, from the DNA polymerase active site and prevent the synthesis of viral cDNA. NNRTIs, in particular, those that are potent inhibitors of RT polymerase activity, can also act as chemical enhancers of the enzyme's inter-subunit interactions. However, the consequences of this chemical enhancement effect on HIV-1 replication are not understood. Here, we show that the potent NNRTIs efavirenz, TMC120, and TMC125, but not nevirapine or delavirdine, inhibit the late stages of HIV-1 replication. These potent NNRTIs enhanced the intracellular processing of Gag and Gag-Pol polyproteins, and this was associated with a decrease in viral particle production from HIV-1-transfected cells. The increased polyprotein processing is consistent with premature activation of the HIV-1 protease by NNRTI-enhanced Gag-Pol multimerization through the embedded RT sequence. These findings support the view that Gag-Pol multimerization is an important step in viral assembly and demonstrate that regulation of Gag-Pol/Gag-Pol interactions is a novel target for small molecule inhibitors of HIV-1 production. Furthermore, these drugs can serve as useful probes to further understand processes involved in HIV-1 particle assembly and maturation.
13. Non-Abelian parafermions in time-reversal-invariant interacting helical systems
Science.gov (United States)
Orth, Christoph P.; Tiwari, Rakesh P.; Meng, Tobias; Schmidt, Thomas L.
2015-02-01
The interplay between bulk spin-orbit coupling and electron-electron interactions produces umklapp scattering in the helical edge states of a two-dimensional topological insulator. If the chemical potential is at the Dirac point, umklapp scattering can open a gap in the edge state spectrum even if the system is time-reversal invariant. We determine the zero-energy bound states at the interfaces between a section of a helical liquid which is gapped out by the superconducting proximity effect and a section gapped out by umklapp scattering. We show that these interfaces pin charges which are multiples of e /2 , giving rise to a Josephson current with 8 π periodicity. Moreover, the bound states, which are protected by time-reversal symmetry, are fourfold degenerate and can be described as Z4 parafermions. We determine their braiding statistics and show how braiding can be implemented in topological insulator systems.
14. Environmental and hormonal factors controlling reversible colour change in crab spiders.
Science.gov (United States)
Llandres, Ana L; Figon, Florent; Christidès, Jean-Philippe; Mandon, Nicole; Casas, Jérôme
2013-10-15
Habitat heterogeneity that occurs within an individual's lifetime may favour the evolution of reversible plasticity. Colour reversibility has many different functions in animals, such as thermoregulation, crypsis through background matching and social interactions. However, the mechanisms underlying reversible colour changes are yet to be thoroughly investigated. This study aims to determine the environmental and hormonal factors underlying morphological colour changes in Thomisus onustus crab spiders and the biochemical metabolites produced during these changes. We quantified the dynamics of colour changes over time: spiders were kept in yellow and white containers under natural light conditions and their colour was measured over 15 days using a spectrophotometer. We also characterised the chemical metabolites of spiders changing to a yellow colour using HPLC. Hormonal control of colour change was investigated by injecting 20-hydroxyecdysone (20E) into spiders. We found that background colouration was a major environmental factor responsible for colour change in crab spiders: individuals presented with white and yellow backgrounds changed to white and yellow colours, respectively. An ommochrome precursor, 3-OH-kynurenine, was the main pigment responsible for yellow colour. Spiders injected with 20E displayed a similar rate of change towards yellow colouration as spiders kept in yellow containers and exposed to natural sunlight. This study demonstrates novel hormonal manipulations that are capable of inducing reversible colour change.
15. FLUX ENHANCEMENT IN CROSSFLOW MEMBRANE FILTRATION: FOULING AND IT'S MINIMIZATION BY FLOW REVERSAL
International Nuclear Information System (INIS)
Shamsuddin Ilias
2005-01-01
Fouling problems are perhaps the single most important reason for relatively slow acceptance of ultrafiltration in many areas of chemical and biological processing. To overcome the losses in permeate flux associated with concentration polarization and fouling in cross flow membrane filtration, we investigated the concept of flow reversal as a method to enhance membrane flux in ultrafiltration. Conceptually, flow reversal prevents the formation of stable hydrodynamic and concentration boundary layers at or near the membrane surface. Further more, periodic reversal of the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. Consequently, these advantages are expected to enhance membrane flux significantly. A crossflow membrane filtration unit was designed and built to test the concept of periodic flow reversal for flux enhancement. The essential elements of the system include a crossflow hollow fiber membrane module integrated with a two-way valve to direct the feed flow directions. The two-way valve is controlled by a controller-timer for periodic reversal of flow of feed stream. Another important feature of the system is that with changing feed flow direction, the permeate flow direction is also changed to maintain countercurrent feed and permeate flows for enhanced mass transfer driving force (concentration difference). In this report, we report our application of Flow Reversal technique in clarification of apple juice containing pectin. The presence of pectin in apple juice makes the clarification process difficult and is believed to cause membrane fouling. Of all compounds found in apple juice, pectin is most often identified as the major hindrance to filtration performance. Based on our ultrafiltration experiments with apple juice, we conclude that under flow reversal conditions, the permeate flux is significantly enhanced when compared with the conventional unidirectional flow. Thus, flow reversal
16. Reverse engineering life: physical and chemical mimetics for controlled stem cell differentiation into cardiomyocytes.
Science.gov (United States)
Skuse, Gary R; Lamkin-Kennard, Kathleen A
2013-01-01
Our ability to manipulate stem cells in order to induce differentiation along a desired developmental pathway has improved immeasurably in recent years. That is in part because we have a better understanding of the intracellular and extracellular signals that regulate differentiation. However, there has also been a realization that stem cell differentiation is not regulated only by chemical signals but also by the physical milieu in which a particular stem cell exists. In this regard we are challenged to mimic both chemical and physical environments. Herein we describe a method to induce stem cell differentiation into cardiomyocytes using a combination of chemical and physical cues. This method can be applied to produce differentiated cells for research and potentially for cell-based therapy of cardiomyopathies.
International Nuclear Information System (INIS)
Zeng Dexing; Desai, Amit V.; Ranganathan, David; Wheeler, Tobias D.; Kenis, Paul J.A.; Reichert, David E.
2013-01-01
18. Process intensification for the production of hydroxyapatite nanoparticles
Science.gov (United States)
Castro, Filipa Juliana Fernandes
Precipitation processes are widely used in chemical industry for the production of particulate solids. In these processes, the chemical and physical nature of synthesized particles is of key importance. The traditional stirred tank batch reactors are affected by non-uniform mixing of reactants, often resulting in broad particle size distribution. The main objective of this thesis was to apply meso and microreactors for the synthesis of hydroxyapatite (HAp) nanoparticles under near-physiological conditions of pH and temperature, in order to overcome the limitations associated with stirred tank batch reactors. Meso and microreactors offer unique features in comparison with conventional chemical reactors. Their high surface-to-volume ratio enables enhanced heat and mass transfer, as well as rapid and efficient mixing. In addition to low consumption of reagents, meso and microreactors are usually operated in continuous flow, making them attractive tools for high throughput experimentation. Precipitation of HAp was first studied in a stirred tank batch reactor, mixing being assured by a novel metal stirrer. HAp was synthetized by mixing diluted aqueous solutions of calcium hydroxide and orthophosphoric acid at 37 °C. After process optimization, a suspension of HAp nanoparticles with pH close to 7 was obtained for a mixing molar ratio Ca/P=1.33. The precipitation process was characterized by three stages: precipitation of amorphous calcium phosphate, transformation of amorphous calcium phosphate into HAp and growth of HAp crystals. The reaction system was further characterized based on equilibrium equations. The resolution of the system, which was possible with the knowledge of three process variables (temperature, pH and calcium concentration), allowed identifying and quantifying all the chemical species present in solution. The proposed model was validated by comparing the experimental and theoretical conductivity. Precipitation of HAp was then investigated in a meso
19. Reverse logistics - a framework
NARCIS (Netherlands)
M.P. de Brito (Marisa); R. Dekker (Rommert)
2002-01-01
textabstractIn this paper we define and compare Reverse Logistics definitions. We start by giving an understanding framework of Reverse Logistics: the why-what-how. By this means, we put in context the driving forces for Reverse Logistics, a typology of return reasons, a classification of
20. Tubal Ligation Reversal
Science.gov (United States)
... seal off the fallopian tubes, such as the Essure or Adiana systems, generally aren't reversible. Why ... electrocautery). Some types of sterilization, such as the Essure or Adiana systems, aren't considered reversible. Risks ...
1. Influence of the solubilization of ribonuclease and of its hydrophobic derivatives on water-in-oil microemulsions
International Nuclear Information System (INIS)
Michel, Fabienne
1993-01-01
This research thesis addresses the study of the structural disruption of a water-in-oil microemulsion during the solubilization of an enzyme. More precisely, the microemulsion is the water/isooctane system, stabilised by the commonly named AOT anionic surfactant, and the disrupting agent is an enzymatic protein, ribonuclease A. The author addresses the following topics: interactions in microemulsion, percolation in microemulsion, use of microemulsions as micro-reactor, chemical modification of enzymes, and reactivity of enzymes. After a recall of the main results concerning AOT inverse micelles, the author addresses the influence of ribonuclease solubilisation on the micellar system. The micellar environment is then used as a micro-reactor in order to fix hydrophobic molecules in a covalent way onto the ribonuclease A, and then to promote the percolation process. The author then studies the structure of the microemulsion in presence of modified enzymes [fr
2. Catalytic microreactors for aqeous phase reactions - carbon nano fibers as catalyst support
NARCIS (Netherlands)
Thakur, D.B.
2010-01-01
Microfabrication techniques are increasingly used in different fields of chemistry to realize structures with capabilities exceeding those of conventional macroscopic systems. Microfabricated chemical systems have a number of advantages for chemical synthesis, chemical kinetics studies and process
3. 49 CFR 230.89 - Reverse gear.
Science.gov (United States)
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Reverse gear. 230.89 Section 230.89 Transportation... Reversing Gear § 230.89 Reverse gear. (a) General provisions. Reverse gear, reverse levers, and quadrants... quadrant. Proper counterbalance shall be provided for the valve gear. (b) Air-operated power reverse gear...
4. Reversible Communicating Processes
Directory of Open Access Journals (Sweden)
Geoffrey Brown
2016-02-01
Full Text Available Reversible distributed programs have the ability to abort unproductive computation paths and backtrack, while unwinding communication that occurred in the aborted paths. While it is natural to assume that reversibility implies full state recovery (as with traditional roll-back recovery protocols, an interesting alternative is to separate backtracking from local state recovery. For example, such a model could be used to create complex transactions out of nested compensable transactions where a programmer-supplied compensation defines the work required to "unwind" a transaction. Reversible distributed computing has received considerable theoretical attention, but little reduction to practice; the few published implementations of languages supporting reversibility depend upon a high degree of central control. The objective of this paper is to demonstrate that a practical reversible distributed language can be efficiently implemented in a fully distributed manner. We discuss such a language, supporting CSP-style synchronous communication, embedded in Scala. While this language provided the motivation for the work described in this paper, our focus is upon the distributed implementation. In particular, we demonstrate that a "high-level" semantic model can be implemented using a simple point-to-point protocol.
5. In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions.
Science.gov (United States)
Laborde-Boutet, Cedric; McCaffrey, William C
2017-02-21
To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to visualize the behavior of petroleum samples under process conditions. The experimental setup relies on a custom-built micro-reactor fitted with a sapphire window at the bottom, which is placed over the objective of an inverted microscope equipped with a cross-polarizer module. Using reflection microscopy enables the visualization of opaque samples, such as petroleum vacuum residues, or asphaltenes. The combination of the sapphire window from the micro-reactor with the cross-polarizer module of the microscope on the light path allows high-contrast imaging of isotropic and anisotropic media. While observations are carried out, the micro-reactor can be heated to the temperature range of cracking reactions (up to 450 °C), can be subjected to H2 pressure relevant to hydroconversion reactions (up to 16 MPa), and can stir the sample by magnetic coupling. Observations are typically carried out by taking snapshots of the sample under cross-polarized light at regular time intervals. Image analyses may not only provide information on the temperature, pressure, and reactive conditions yielding phase separation, but may also give an estimate of the evolution of the chemical (absorption/reflection spectra) and physical (refractive index) properties of the sample before the onset of phase separation.
6. The Geomagnetic Field During a Reversal
Science.gov (United States)
Heirtzler, James R.
2003-01-01
By modifying the IGRF it is possible to learn what may happen to the geomagnetic field during a geomagnetic reversal. If the entire IGRF reverses then the declination and inclination only reverse when the field strength is zero. If only the dipole component of the IGRF reverses a large geomagnetic field remains when the dipole component is zero and he direction of the field at the end of the reversal is not exactly reversed from the directions at the beginning of the reversal.
7. Environmental high resolution electron microscopy and applications to chemical science
OpenAIRE
Boyes, Edward; Gai, Pratibha
2017-01-01
An environmental cell high resolution electron microscope (EHREM) has been developed for in situ studies of dynamic chemical reactions on the atomic scale. It allows access to metastable intermediate phases of catalysts and to sequences of reversible microstructural and chemical development associated with the activation, deactivation and poisoning of a catalyst. Materials transported through air can be restored or recreated and samples damaged, e.g. by dehydration, by the usual vacuum enviro...
8. Binding Constant of Amines to Water/AOT/n-Hexene Reverse Micelles. Influence of the Chemical Structure
Directory of Open Access Journals (Sweden)
J. J. Silber
2000-03-01
Full Text Available The distribution of different amines between n-hexane bulk and the micellar pseudophase of AOT reverse micelles were measured by a fluorometric method. An independent method was used to corroborate the incorporation of the amines to the interface. The effect of the amine structure on the binding constant was analysed.
9. Application of a reversible chemical reaction system to solar thermal power plants
Science.gov (United States)
Hanseth, E. J.; Won, Y. S.; Seibowitz, L. P.
1980-01-01
Three distributed dish solar thermal power systems using various applications of SO2/SO3 chemical energy storage and transport technology were comparatively assessed. Each system features various roles for the chemical system: (1) energy storage only, (2) energy transport, or (3) energy transport and storage. These three systems were also compared with the dish-Stirling, using electrical transport and battery storage, and the central receiver Rankine system, with thermal storage, to determine the relative merit of plants employing a thermochemical system. As an assessment criterion, the busbar energy costs were compared. Separate but comparable solar energy cost computer codes were used for distributed receiver and central receiver systems. Calculations were performed for capacity factors ranging from 0.4 to 0.8. The results indicate that SO2/SO3 technology has the potential to be more cost effective in transporting the collected energy than in storing the energy for the storage capacity range studied (2-15 hours)
Science.gov (United States)
Zeng, Dexing; Desai, Amit V; Ranganathan, David; Wheeler, Tobias D; Kenis, Paul J A; Reichert, David E
2013-01-01
11. Microfluidic Reactors for the Controlled Synthesis of Nanoparticles
Science.gov (United States)
Erdem, Emine Yegan
Nanoparticles have attracted a lot of attention in the past few decades due to their unique, size-dependent properties. In order to use these nanoparticles in devices or sensors effectively, it is important to maintain uniform properties throughout the system; therefore nanoparticles need to have uniform sizes -- or monodisperse. In order to achieve monodispersity, an extreme control over the reaction conditions is required during their synthesis. These reaction conditions such as temperature, concentration of reagents, residence times, etc. affect the structure of nanoparticles dramatically; therefore when the conditions vary locally in the reaction vessel, different sized nanoparticles form, causing polydispersity. In widely-used batch wise synthesis techniques, large sized reaction vessels are used to mix and heat reagents. In these types of systems, it is very hard to avoid thermal gradients and to achieve rapid mixing times as well as to control residence times. Also it is not possible to make rapid changes in the reaction parameters during the synthesis. The other drawback of conventional methods is that it is not possible to separate the nucleation of nanoparticles from their growth; this leads to combined nucleation and growth and subsequently results in polydisperse size distributions. Microfluidics is an alternative method by which the limitations of conventional techniques can be addressed. Due to the small size, it is possible to control temperature and concentration of reagents precisely as well as to make rapid changes in mixing ratios of reagents or temperature of the reaction zones. There have been several microfluidic reactors -- (microreactors) in literature that were designed to improve the size distribution of nanoparticles. In this work, two novel microfluidic systems were developed for achieving controlled synthesis of nanoparticles. The first microreactor was made out of a chemically robust polymer, polyurethane, and it was used for low
12. Molecular differences between deuterated and protonated polystyrenes using reversed-phase high-performance liquid chromatography.
Science.gov (United States)
Kayillo, Sindy; Gray, Michael J; Shalliker, R Andrew; Dennis, Gary R
2005-05-06
Isotopic substitution is a technique used to highlight particular bonds within a molecule for kinetic, spectroscopic and structure analysis. It is presumed that although some properties such as stretching frequencies will not be the same for substituted analogues, the chemical interactions will not vary appreciably as a function of labelling. Reversed-phase liquid chromatography has been used to demonstrate that there are significant differences between the chromatographic behaviour of a sequence of deuterated and protonated oligomeric polystyrenes. Two-dimensional reversed-phase liquid chromatography was used to show that even the diasteromers of the oligomers (n = 5) have retention mechanisms that are dependent on the subtle changes to the molecular conformation and electronic structure, which are a consequence of deuteration.
13. N2O decomposition over Fe/ZSM-5: reversible generation of highly active cationic Fe species
NARCIS (Netherlands)
Zhu, Q.; Hensen, E.J.M.; Mojet, B.L.; Wolput, van J.H.M.C.; Santen, van R.A.
2002-01-01
Fe-oxide species in Fe/ZSM-5 (prepared by chemical vapor deposition of FeCl3)-active in N2O decomposition-react with zeolite protons during high temperature calcination to give highly active cationic Fe species, this transformation being reversible upon exposure to water vapor at lower temperature
14. Chemical monitoring strategy for the assessment of advanced water treatment plant performance.
Science.gov (United States)
Drewes, J E; McDonald, J A; Trinh, T; Storey, M V; Khan, S J
2011-01-01
A pilot-scale plant was employed to validate the performance of a proposed full-scale advanced water treatment plant (AWTP) in Sydney, Australia. The primary aim of this study was to develop a chemical monitoring program that can demonstrate proper plant operation resulting in the removal of priority chemical constituents in the product water. The feed water quality to the pilot plant was tertiary-treated effluent from a wastewater treatment plant. The unit processes of the AWTP were comprised of an integrated membrane system (ultrafiltration, reverse osmosis) followed by final chlorination generating a water quality that does not present a source of human or environmental health concern. The chemical monitoring program was undertaken over 6 weeks during pilot plant operation and involved the quantitative analysis of pharmaceuticals and personal care products, steroidal hormones, industrial chemicals, pesticides, N-nitrosamines and halomethanes. The first phase consisted of baseline monitoring of target compounds to quantify influent concentrations in feed waters to the plant. This was followed by a period of validation monitoring utilising indicator chemicals and surrogate measures suitable to assess proper process performance at various stages of the AWTP. This effort was supported by challenge testing experiments to further validate removal of a series of indicator chemicals by reverse osmosis. This pilot-scale study demonstrated a simplified analytical approach that can be employed to assure proper operation of advanced water treatment processes and the absence of trace organic chemicals.
15. Liquid radwaste treatment by microfiltration, ultrafiltration and reverse osmosis
International Nuclear Information System (INIS)
Dulama, M.; Deneanu, N.; Popescu, I.V.
2001-01-01
Radioactive liquid waste processing is an integral part of any facility involved in nuclear power generation, radioisotope production, research and development, decontamination or other aspects of nuclear energy. The aqueous liquid radwastes from the decontamination center are currently treated by the membrane plant. Generally, the liquid waste streams are effectively volume-reduced by a combination of continuous crossflow microfiltration (MF), spiral wound reverse osmosis (SWRO) and tubular reverse osmosis membrane technologies. Backwash chemical cleaning wastes from the membrane plant are further volume-reduced by evaporation. The concentrate from the membrane plant is ultimately immobilized with bitumen. We performed experiments using two simulated waste solution; secondary waste from the decontamination process with POD (Permanganate Oxidation Decontamination) solution and secondary waste from decontamination with CAN-DECON solution. The experimental tests have been done with cellulose acetate (CA) membrane and polysulfonate (PSF) membrane manufactured at Research Center for Macromolecular Materials and Membranes Bucharest and with Millipore membrane type VS 0.025 μm. A schematic of the laboratory-scale test facility is presented
16. Muscular activation during reverse and non-reverse chewing cycles in unilateral posterior crossbite.
Science.gov (United States)
Piancino, Maria Grazia; Farina, Dario; Talpone, Francesca; Merlo, Andrea; Bracco, Pietro
2009-04-01
The aim of this study was to characterize the kinematics and masseter muscle activation in unilateral posterior crossbite. Eighty-two children (8.6 +/- 1.3 yr of age) with unilateral posterior crossbite and 12 children (8.9 +/- 0.6 yr of age) with normal occlusion were selected for the study. Electromyography (EMG) and kinematics were concurrently recorded during mastication of a soft bolus and a hard bolus. The percentage of reverse cycles in the group of patients was 59.0 +/- 33.1% (soft bolus) and 69.7 +/- 29.7% (hard bolus) when chewing on the crossbite side. When chewing on the non-affected side, the number of reverse cycles was 16.7 +/- 24.5% (soft bolus) and 16.7 +/- 22.3% (hard bolus). The reverse cycles on the crossbite side were narrower with respect to the cycles on the non-affected side. Although both types of cycles in patients resulted in lower EMG activity of the masseter of the crossbite side than of the contralateral masseter, the activity of the non-affected side was larger for reverse than for non-reverse cycles. It was concluded that when chewing on the crossbite side, the masseter activity is reduced on the mastication side (crossbite) and is unaltered (non-reverse cycles) or increased (reverse) on the non-affected side.
17. The Causes of Preference Reversal.
OpenAIRE
Tversky, Amos; Slovic, Paul; Kahneman, Daniel
1990-01-01
Observed preference reversal cannot be adequately explained by violations of independence, the reduction axiom, or transitivity. The primary cause of preference reversal is the failure of procedure invariance, especially the overpricing of low-probability, high-payoff bets. This result violates regret theory and generalized (nonindependent) utility models. Preference reversal and a new reversal involving time preferences are explained by scale compatibility, which implies that payoffs are wei...
18. Computing the Reverse Eccentric Connectivity Index for Certain Family of Nanocone and Fullerene Structures
Directory of Open Access Journals (Sweden)
Wei Gao
2016-01-01
Full Text Available A large number of previous works reveal that there exist strong connections between the chemical characteristics of chemical compounds and drugs (e.g., melting point and boiling point and their topological structures. Chemical indices introduced on these molecular topological structures can help chemists and material and medical scientists to grasp its chemical reactivity, biological activity, and physical features better. Hence, the study of the topological indices on the material structure can make up the defect of experiments and provide the theoretical evidence in material engineering. In this paper, we determine the reverse eccentric connectivity index of one family of pentagonal carbon nanocones PCN5[n] and three infinite families of fullerenes C12n+2, C12n+4, and C18n+10 based on graph analysis and computation derivation, and these results can offer the theoretical basis for material properties.
19. Application of Ionic Liquids in High Performance Reversed-Phase Chromatography
Directory of Open Access Journals (Sweden)
Wentao Bi
2009-06-01
Full Text Available Ionic liquids, considered “green” chemicals, are widely used in many areas of analytical chemistry due to their unique properties. Recently, ionic liquids have been used as a kind of novel additive in separation and combined with silica to synthesize new stationary phase as separation media. This review will focus on the properties and mechanisms of ionic liquids and their potential applications as mobile phase modifier and surface-bonded stationary phase in reversed-phase high performance liquid chromatography (RP-HPLC. Ionic liquids demonstrate advantages and potential in chromatographic field.
20. Process Intensification Tools in the Small‐Scale Pharmaceutical Manufacturing of Small Molecules
DEFF Research Database (Denmark)
Mitic, Aleksandar; Gernaey, Krist V.
2015-01-01
of processes are in a state of change. However, it is important to note that not all processes can be intensified easily, such as slow chemical reactions, processes with solids, slurries, and on the like. This review summarizes applications of promising tools for achieving process intensification in the small......‐scale pharmaceutical manufacturing of so‐called small molecules. The focus is on microwave radiation, microreactors, ultrasounds, and meso‐scale tubular reactors....
1. Spectroscopic Diagnosis of Excited-State Aromaticity: Capturing Electronic Structures and Conformations upon Aromaticity Reversal.
Science.gov (United States)
Oh, Juwon; Sung, Young Mo; Hong, Yongseok; Kim, Dongho
2018-03-06
Aromaticity, the special energetic stability derived from cyclic [4 n + 2]π-conjugated electronic structures, has been the topic of intense interest in chemistry because it plays a critical role in rationalizing molecular stability, reactivity, and physical/chemical properties. Recently, the pioneering work by Colin Baird on aromaticity reversal, postulating that aromatic (antiaromatic) character in the ground state reverses to antiaromatic (aromatic) character in the lowest excited triplet state, has attracted much scientific attention. The completely reversed aromaticity in the excited state provides direct insight into understanding the photophysical/chemical properties of photoactive materials. In turn, the application of aromatic molecules to photoactive materials has led to numerous studies revealing this aromaticity reversal. However, most studies of excited-state aromaticity have been based on the theoretical point of view. The experimental evaluation of aromaticity in the excited state is still challenging and strenuous because the assessment of (anti)aromaticity with conventional magnetic, energetic, and geometric indices is difficult in the excited state, which practically restricts the extension and application of the concept of excited-state aromaticity. Time-resolved optical spectroscopies can provide a new and alternative avenue to evaluate excited-state aromaticity experimentally while observing changes in the molecular features in the excited states. Time-resolved optical spectroscopies take advantage of ultrafast laser pulses to achieve high time resolution, making them suitable for monitoring ultrafast changes in the excited states of molecular systems. This can provide valuable information for understanding the aromaticity reversal. This Account presents recent breakthroughs in the experimental assessment of excited-state aromaticity and the verification of aromaticity reversal with time-resolved optical spectroscopic measurements. To
2. SIMULTANEOUS ABSORPTION AND DESORPTION WITH REVERSIBLE 1ST-ORDER CHEMICAL-REACTION - ANALYTICAL SOLUTION AND NEGATIVE ENHANCEMENT FACTORS
NARCIS (Netherlands)
WINKELMAN, JGM; BEENACKERS, AACM
The problem of ps absorption accompanied by a first-order reversible reaction, producing a volatile reaction product, is considered. A general analytical solution is developed for the film model, resulting in explicit relations for the concentration profiles in the film and for the mass transfer
3. Thickness dependence of magnetization reversal mechanism in perpendicularly magnetized L1{sub 0} FePt films
Energy Technology Data Exchange (ETDEWEB)
Bi, Mei; Wang, Xin, E-mail: [email protected]; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Xie, Jianliang
2017-04-15
We have studied the magnetic switching behavior of L1{sub 0}-ordered FePt films with varying thickness. It was found that coercivity is strongly dependent on the film thickness. The obvious variations of the coercivity in the thin films are confirmed by the measurements of structural and magnetic properties. With increasing thickness, the degree of L1{sub 0} chemical ordering increased, while the magnetization reversal process transforms from a pinned two-steps magnetization reversal to a comparatively smooth domain wall motion behavior. Although considering anisotropy, exchange interaction and applied magnetic field, the switching behavior in films is quite complex, the main features of the magnetization reversal mechanism can be understood by performing detailed investigation on the effect of the deposition temperature and the angle of magnetic field. - Highlights: • Series of FePt films with L1{sub 0} phase have been prepared. • We focused on the magnetization reversal mechanism with varying thicknesses. • The angle-dependence of switching process is revealed in the FePt films. • Different switching mechanisms were found by increasing the film thickness.
4. Application of magnetohydrodynamic actuation to continuous flow chemistry.
Science.gov (United States)
West, Jonathan; Karamata, Boris; Lillis, Brian; Gleeson, James P; Alderman, John; Collins, John K; Lane, William; Mathewson, Alan; Berney, Helen
2002-11-01
Continuous flow microreactors with an annular microchannel for cyclical chemical reactions were fabricated by either bulk micromachining in silicon or by rapid prototyping using EPON SU-8. Fluid propulsion in these unusual microchannels was achieved using AC magnetohydrodynamic (MHD) actuation. This integrated micropumping mechanism obviates the use of moving parts by acting locally on the electrolyte, exploiting its inherent conductive nature. Both silicon and SU-8 microreactors were capable of MHD actuation, attaining fluid velocities of the order of 300 microm s(-1) when using a 500 mM KCl electrolyte. The polymerase chain reaction (PCR), a thermocycling process, was chosen as an illustrative example of a cyclical chemistry. Accordingly, temperature zones were provided to enable a thermal cycle during each revolution. With this approach, fluid velocity determines cycle duration. Here, we report device fabrication and performance, a model to accurately describe fluid circulation by MHD actuation, and compatibility issues relating to this approach to chemistry.
5. Microchannel Reactor System for Catalytic Hydrogenation
Energy Technology Data Exchange (ETDEWEB)
Adeniyi Lawal; Woo Lee; Ron Besser; Donald Kientzler; Luke Achenie
2010-12-22
We successfully demonstrated a novel process intensification concept enabled by the development of microchannel reactors, for energy efficient catalytic hydrogenation reactions at moderate temperature, and pressure, and low solvent levels. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for hydrogenation of onitroanisole and a proprietary BMS molecule. In the second phase of the program, as a prelude to full-scale commercialization, we designed and developed a fully-automated skid-mounted multichannel microreactor pilot plant system for multiphase reactions. The system is capable of processing 1 – 10 kg/h of liquid substrate, and an industrially relevant immiscible liquid-liquid was successfully demonstrated on the system. Our microreactor-based pilot plant is one-of-akind. We anticipate that this process intensification concept, if successfully demonstrated, will provide a paradigm-changing basis for replacing existing energy inefficient, cost ineffective, environmentally detrimental slurry semi-batch reactor-based manufacturing practiced in the pharmaceutical and fine chemicals industries.
6. Relationship between structure and reactivity in AOT inverse micelles
International Nuclear Information System (INIS)
Petit, Christophe
1988-01-01
As inverse micelles can be considered as chemical micro-reactors, the objective of this research thesis is to show that reaction rates can be modified, either by varying the size of micro-reactors, or by modifying the location of one of the reactants. After a brief overview of noticeable results obtained on AOT inverse micelles about the structure and reactivity, the author reports the study of structural modifications induced by an addition of small molecules or proteins. Two complementary models are proposed on this purpose: a geometrical model which reports the medium microscopic evolution and a kinetic model which could report the system microscopic evolution as well reactivity changes with respect to probe location. The next part reports the study of in situ synthesis of semi-conductor particles in AOT inverse micelles. The author then reports that a surprising aspect of macromolecule solubilization has been noticed: the solubilization of a polypeptide, gelatine, allows the whole system to be gelled whereas gelatine is essentially polar [fr
7. Present status of reactor physics in the United States and Japan-IV. 2. Micro-Reactor Physics of MOX-Fueled Core
International Nuclear Information System (INIS)
Takeda, Toshikazu
2001-01-01
Recently, fuel assemblies of light water reactors have become complicated because of the extension of fuel burnup and the use of high-enriched Gd and mixed-oxide (MOX) fuel, etc. In conventional assembly calculations, the detailed flux distribution, spectrum distribution, and space dependence of self-shielding within a fuel pellet are not directly taken into account. The experimental and theoretical study of investigating these microscopic properties is named micro-reactor physics. The purpose of this work is to show the importance of micro-reactor physics in the analysis of MOX fuel assemblies. Several authors have done related studies; however, their studies are limited to fuel pin cells, and they are never mentioned with regard to burnup effect, which is important for actual core design. We used the subgroup method to treat the space dependence of the self-shielding effect of heavy nuclides, and we used the characteristics method to treat the angular dependence of neutron flux in a fuel pellet. Figure 1 compares the power distributions in MOX and UO 2 fuel cells at the beginning of burnup. The power is calculated with and without considering the space dependence of the self-shielding effect of the cross sections. For the MOX cell, the power distribution has a peak at the cell edge because of large Pu absorption especially when considering the spatial self-shielding effect. When a MOX rod is adjacent to UO 2 fuel rods, the flux distribution has an azimuthal dependence in addition to the radial dependence within a rod. For example, consider a 2x2 fuel assembly composed of three UO 2 rods and one MOX rod, with the mirror reflection boundary condition. A burnup calculation was done with the condition; the radius of the MOX pellet is divided into two regions, and the azimuthal angle is divided into eight. The number density of 239 Pu at 44 000 MWd/t for the MOX rod shows azimuthal dependence by 20%. The maximum burnup occurs in the direction of the UO 2 rods. This is
8. Chemical Mass Shifts in a Digital Linear Ion Trap as Analytical Identity of o-, m-, and p-Xylene
Science.gov (United States)
Sun, Lulu; Xue, Bing; Huang, Zhengxu; Cheng, Ping; Ma, Li; Ding, Li; Zhou, Zhen
2018-04-01
Chemical mass shifts between isomeric ions of o-, m-, and p-xylene were measured using a digital linear ion trap, and the directions and values of the shifts were found to be correlated to the collision cross sections of the isomers. Both forward and reverse scans were used and the chemical shifts for each pair of isomers in scans of opposite directions were in opposite signs. Using different voltage settings (namely the voltage dividing ratio-VDR) of the ion trap allows adding high order field components in the quadrupole field and results in larger chemical mass shifts. The differential chemical mass shift which combined the shifts from forward and reverse scans doubled the amount of chemical shift, e.g., 0.077 Th between o- and p-xylene, enough for identification of the type of isomer without using an additional ion mobility spectrometer. The feature of equal and opposite chemical mass shifts also allowed to null out the chemical mass shift by calculating the mean m/z value between the two opposite scans and remove or reduce the mass error caused by chemical mass shift. [Figure not available: see fulltext.
9. Chemical Mass Shifts in a Digital Linear Ion Trap as Analytical Identity of o-, m-, and p-Xylene.
Science.gov (United States)
Sun, Lulu; Xue, Bing; Huang, Zhengxu; Cheng, Ping; Ma, Li; Ding, Li; Zhou, Zhen
2018-07-01
Chemical mass shifts between isomeric ions of o-, m-, and p-xylene were measured using a digital linear ion trap, and the directions and values of the shifts were found to be correlated to the collision cross sections of the isomers. Both forward and reverse scans were used and the chemical shifts for each pair of isomers in scans of opposite directions were in opposite signs. Using different voltage settings (namely the voltage dividing ratio-VDR) of the ion trap allows adding high order field components in the quadrupole field and results in larger chemical mass shifts. The differential chemical mass shift which combined the shifts from forward and reverse scans doubled the amount of chemical shift, e.g., 0.077 Th between o- and p-xylene, enough for identification of the type of isomer without using an additional ion mobility spectrometer. The feature of equal and opposite chemical mass shifts also allowed to null out the chemical mass shift by calculating the mean m/z value between the two opposite scans and remove or reduce the mass error caused by chemical mass shift. Graphical Abstract ᅟ.
10. A Chemically Relevant Model for Teaching the Second Law of Thermodynamics.
Science.gov (United States)
Williamson, Bryce E.; Morikawa, Tetsuo
2002-01-01
Introduces a chemical model illustrating the aspects of the second law of thermodynamics which explains concepts such as reversibility, path dependence, and extrapolation in terms of electrochemistry and calorimetry. Presents a thought experiment using an ideal galvanic electrochemical cell. (YDS)
11. Reverse logistics policy – differences between conservative and innovative reverse logistics management
Directory of Open Access Journals (Sweden)
Alena Klapalová
2013-01-01
Full Text Available One of the of the key barriers that hampers effective and efficient management of reverse flows detected within a number of empirical surveys and case studies focused on reverse logistics and/or return management is business (organisational policy, specifically lack of policy, deficiency in existing policy or inferior policy. Despite this fact, there is a gap in literature which would show some evidence from practice that innovative reverse logistics policy both can pay off and is associated with certain aspects of reverse logistics management. Such proof can have several implications. It can support the call for better understanding and more research of the linkages of reverse logistics with other corporate functions, promote the acceptation of strategic character of reverse logistics and stress the role of RL policy within the rest of overall corporate management.The aim of this paper is to contribute and to enrich the existing body of knowledge concerning the above-mentioned gap through presentation of survey results that was realized in 2012 among managers of 244 Czech firms. The results demonstrate the statistically significant association between the innovativeness of RL policy and profitability of firms, quality of RL planning, perception of RL importance, level of RL knowledge and perception of product innovation importance for firms’ competitiveness and frequency of product innovation. They also reveal statistically significant differences between firms with conservative and innovative RL policy and the perceived existence of some barriers to manage RL.
12. Geomagnetic Field During a Reversal
Science.gov (United States)
Heirtzler, J. R.
2003-01-01
It has frequently been suggested that only the geomagnetic dipole, rather than higher order poles, reverse during a geomagnetic field reversal. Under this assumption the geomagnetic field strength has been calculated for the surface of the Earth for various steps of the reversal process. Even without an eminent a reversal of the field, extrapolation of the present secular change (although problematic) shows that the field strength may become zero in some geographic areas within a few hundred years.
13. DNA-Encoded Dynamic Combinatorial Chemical Libraries.
Science.gov (United States)
Reddavide, Francesco V; Lin, Weilin; Lehnert, Sarah; Zhang, Yixin
2015-06-26
Dynamic combinatorial chemistry (DCC) explores the thermodynamic equilibrium of reversible reactions. Its application in the discovery of protein binders is largely limited by difficulties in the analysis of complex reaction mixtures. DNA-encoded chemical library (DECL) technology allows the selection of binders from a mixture of up to billions of different compounds; however, experimental results often show low a signal-to-noise ratio and poor correlation between enrichment factor and binding affinity. Herein we describe the design and application of DNA-encoded dynamic combinatorial chemical libraries (EDCCLs). Our experiments have shown that the EDCCL approach can be used not only to convert monovalent binders into high-affinity bivalent binders, but also to cause remarkably enhanced enrichment of potent bivalent binders by driving their in situ synthesis. We also demonstrate the application of EDCCLs in DNA-templated chemical reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
14. Antibiotic Algae by Chemical Surface Engineering.
Science.gov (United States)
2018-03-02
Chemical cell-surface engineering is a tool for modifying and altering cellular functions. Herein, we report the introduction of an antibiotic phenotype to the green alga Chlamydomonas reinhardtii by chemically modifying its cell surface. Flow cytometry and confocal microscopy studies demonstrated that a hybrid of the antibiotic vancomycin and a 4-hydroxyproline oligomer binds reversibly to the cell wall without affecting the viability or motility of the cells. The modified cells were used to inhibit bacterial growth of Gram-positive Bacillus subtilis cultures. Delivery of the antibiotic from the microalgae to the bacterial cells was verified by microscopy. Our studies provide compelling evidence that 1) chemical surface engineering constitutes a useful tool for the introduction of new, previously unknown functionality, and 2) living microalgae can serve as new platforms for drug delivery. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
15. Online quench-flow electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry for elucidating kinetic and chemical enzymatic reaction mechanisms.
Science.gov (United States)
Clarke, David J; Stokes, Adam A; Langridge-Smith, Pat; Mackay, C Logan
2010-03-01
We have developed an automated quench-flow microreactor which interfaces directly to an electrospray ionization (ESI) mass spectrometer. We have used this device in conjunction with ESI Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to demonstrate the potential of this approach for studying the mechanistic details of enzyme reactions. For the model system chosen to test this device, namely, the pre-steady-state hydrolysis of p-nitrophenyl acetate by the enzyme chymotrypsin, the kinetic parameters obtained are in good agreement with those in the literature. To our knowledge, this is the first reported use of online quench-flow coupled with FTICR MS. Furthermore, we have exploited the power of FTICR MS to interrogate the quenched covalently bound enzyme intermediate using top-down fragmentation. The accurate mass capabilities of FTICR MS permitted the nature of the intermediate to be assigned with high confidence. Electron capture dissociation (ECD) fragmentation allowed us to locate the intermediate to a five amino acid section of the protein--which includes the known catalytic residue, Ser(195). This experimental approach, which uniquely can provide both kinetic and chemical details of enzyme mechanisms, is a potentially powerful tool for studies of enzyme catalysis.
16. r-Universal reversible logic gates
International Nuclear Information System (INIS)
Vos, A de; Storme, L
2004-01-01
Reversible logic plays a fundamental role both in ultra-low power electronics and in quantum computing. It is therefore important to know which reversible logic gates can be used as building block for the reversible implementation of an arbitrary boolean function and which cannot
17. Influence of polymerisation on the reversibility of low-energy proton exchange reactions by Para-Aminothiolphenol.
Science.gov (United States)
Balakrishnan, Divya; Lamblin, Guillaume; Thomann, Jean Sebastien; Guillot, Jerome; Duday, David; van den Berg, Albert; Olthuis, Wouter; Pascual-García, César
2017-11-13
The reversibility of redox processes is an important function for sensing and molecular electronic devices such as pH reporters or molecular switches. Here we report the electrochemical behaviour and redox reversibility of para-aminothiolphenol (PATP) after different polymerisation methods. We used electrochemical and photo-polymerisation in neutral buffers and plasma polymerisation in air to induce reversible redox states. The chemical stoichiometry and surface coverage of PATP in the polymerized layers were characterized by X-ray photoelectron spectroscopy (XPS), while cyclic voltammetry (CV) was used to measure the charge transfer, double layer capacitance and electrochemical rate of the layers during successive potential cycles. Our results show that the surface coverage of the redox active species is higher on electro-polymerised samples, however, after consecutive cycles all the methods converge to the same charge transfer, while the plasma polymerised samples achieve higher efficiency per molecule and UV polymerised samples have a higher electron transfer rate.
18. Quantum reverse hypercontractivity
Energy Technology Data Exchange (ETDEWEB)
Cubitt, Toby [Department of Computer Science, University College London, London, United Kingdom and Centre for Quantum Information and Foundations, DAMTP, University of Cambridge, Cambridge (United Kingdom); Kastoryano, Michael [NBIA, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Montanaro, Ashley [School of Mathematics, University of Bristol, Bristol (United Kingdom); Temme, Kristan [Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125 (United States)
2015-10-15
We develop reverse versions of hypercontractive inequalities for quantum channels. By generalizing classical techniques, we prove a reverse hypercontractive inequality for tensor products of qubit depolarizing channels. We apply this to obtain a rapid mixing result for depolarizing noise applied to large subspaces and to prove bounds on a quantum generalization of non-interactive correlation distillation.
19. Behavioural evidence of male volatile pheromones in the sex-role reversed wolf spiders Allocosa brasiliensis and Allocosa alticeps
Science.gov (United States)
Aisenberg, Anita; Baruffaldi, Luciana; González, Macarena
2010-01-01
The use of chemical signals in a sexual context is widespread in the animal kingdom. Most studies in spiders report the use of female pheromones that attract potential sexual partners. Allocosa brasiliensis and Allocosa alticeps are two burrowing wolf spiders that show sex-role reversal. Females locate male burrows and initiate courtship before males perform any detectable visual or vibratory signal. So, females of these species would be detecting chemical or mechanical cues left by males. Our objective was to explore the potential for male pheromones to play a role in mate detection in A. brasiliensis and A. alticeps. We designed two experiments. In Experiment 1, we tested the occurrence of male contact pheromones by evaluating female courtship when exposed to empty burrows constructed by males or females (control). In Experiment 2, we tested the existence of male volatile pheromones by evaluating female behaviour when exposed to artificial burrows connected to tubes containing males, females or empty tubes (control). Our results suggest the occurrence of male volatile pheromones that trigger female courtship in both Allocosa species. The sex-role reversal postulated for these wolf spiders could be driving the consequent reversal in typical pheromone-emitter and detector roles expected for spiders.
20. Introduction to reversible computing
CERN Document Server
Perumalla, Kalyan S
2013-01-01
Few books comprehensively cover the software and programming aspects of reversible computing. Filling this gap, Introduction to Reversible Computing offers an expanded view of the field that includes the traditional energy-motivated hardware viewpoint as well as the emerging application-motivated software approach. Collecting scattered knowledge into one coherent account, the book provides a compendium of both classical and recently developed results on reversible computing. It explores up-and-coming theories, techniques, and tools for the application of rever
1. A Study on Reverse Logistics
OpenAIRE
Reddy, Dhananjaya
2011-01-01
In the competitive world of manufacturing, companies are often searching for new ways to improve their process, customer satisfaction and stay ahead in the game with their competitors. Reverse logistics has been considered a strategy to bring these things to life for the past decade or so. This thesis work tries to shed some light on the basics of reverse logistics and how reverse logistics can be used as a management strategy. This paper points out the fundamentals of reverse logistics and l...
2. Reactive chemically modified piezoelectric crystal detectors: A new class of high-selectivity sensors
International Nuclear Information System (INIS)
Fadeev, A.Yu.; Filatov, A.L.; Lisichkin, G.V.
1994-01-01
A great number of works have focused on the study of properties of modified piezoelectric quartz crystal detectors (PQCDs) coated with sorbing substrates and on applying sensors based on them for the analysis of diluted gas mixtures and solutions. This work offers a new class of gravemetric sensors characterized by a reversible chemical reaction that occurs on their surface. Silica films are proposed as a sorbing coating of quartz detectors, and a chemical modification of a surface is suggested for covalent fixation of the necessary compounds. PQCDs were chemically modified with reactive diene derivatives that can also act as dienophiles. Hexachlorocyclopentadiene (HCCPD, resonater I) and cyclopentadiene (CPD, resonator II) were fixed on a PQCD surface in several stages. After treatment with the resonaters, the PQCD in a CPD gas phase exhibited time dependent frequency shifts from 20-100 Hz. The results suggest that there is a reversible chemical reaction on the electrode surface of resonators I and II when they interact with CPD vapors. Therefore, PQCDs modified with reactive dienes were prepared for the first time and may be employed as selective sensors for CPD
3. Domestic wash water reclamation for reuse as commode water supply using filtration: Reverse-osmosis separation technique
Science.gov (United States)
Hall, J. B., Jr.; Batten, C. E.; Wilkins, J. R.
1974-01-01
A combined filtration-reverse-osmosis water recovery system has been evaluated to determine its capability to reclaim domestic wash water for reuse as a commode water supply. The system produced water that met all chemical and physical requirements established by the U.S. Public Health Service for drinking water with the exception of carbon chloroform extractables, methylene blue active substances, and phenols. It is thought that this water is of sufficient quality to be reused as commode supply water. The feasibility of using a combined filtration and reverse-osmosis technique for reclaiming domestic wash water has been established. The use of such a technique for wash-water recovery will require a maintenance filter to remove solid materials including those less than 1 micron in size from the wash water. The reverse-osmosis module, if sufficiently protected from plugging, is an attractive low-energy technique for removing contaminants from domestic wash water.
4. Boron Removal in Seawater Reverse Osmosis System
KAUST Repository
Rahmawati, Karina
2011-07-01
Reverse osmosis successfully proves to remove more than 99% of solute in seawater, providing fresh water supply with satisfied quality. Due to some operational constraints, however, some trace contaminants removal, such as boron, cannot be achieved in one pass system. The stringent criterion for boron from World Health Organization (WHO) and Saudi Arabia local standard (0.5 mg/l) is hardly fulfilled by single pass sea water reverse osmosis (SWRO) plants. Some design processes have been proposed to deal with boron removal, but they are not economically efficient due to high energy and chemical consumption. The objective of this study was to study boron removal by different reverse osmosis membranes in two pH conditions, with and without antiscalant addition. Thus, it was expected to observe the possibility of operating single pass system and necessity to operate two pass system using low energy membrane. Five membrane samples were obtained from two different manufacturers. Three types of feed water pH were used, pH 8, pH 10, and pH 10 with antiscalant addition. Experiment was conducted in parallel to compare membrane performance from two manufacturers. Filtration was run with fully recycle mode for three days. Sample of permeate and feed were taken every 12 hours, and analyzed for their boron and TDS concentration. Membrane samples were also tested for their surface charge. The results showed that boron rejection increases as the feed pH increases. This was caused by dissociation of boric acid to negatively charged borate ion and more negatively charged membrane surface at elevated pH which enhance boron rejection. This study found that single pass reverse osmosis system, with and without elevating the pH, may not be possible to be applied because of two reasons. First, permeate quality in term of boron, does not fulfill WHO and local Saudi Arabia regulations. Second, severe scaling occurs due to operation in alkaline condition, since Ca and Mg concentration are
5. Optimized reversible binary-coded decimal adders
DEFF Research Database (Denmark)
Thomsen, Michael Kirkedal; Glück, Robert
2008-01-01
Abstract Babu and Chowdhury [H.M.H. Babu, A.R. Chowdhury, Design of a compact reversible binary coded decimal adder circuit, Journal of Systems Architecture 52 (5) (2006) 272-282] recently proposed, in this journal, a reversible adder for binary-coded decimals. This paper corrects and optimizes...... their design. The optimized 1-decimal BCD full-adder, a 13 × 13 reversible logic circuit, is faster, and has lower circuit cost and less garbage bits. It can be used to build a fast reversible m-decimal BCD full-adder that has a delay of only m + 17 low-power reversible CMOS gates. For a 32-decimal (128-bit....... Keywords: Reversible logic circuit; Full-adder; Half-adder; Parallel adder; Binary-coded decimal; Application of reversible logic synthesis...
6. Effect of sequence and stereochemistry reversal on p53 peptide mimicry.
Directory of Open Access Journals (Sweden)
Alessio Atzori
Full Text Available Peptidomimetics effective in modulating protein-protein interactions and resistant to proteolysis have potential in therapeutic applications. An appealing yet underperforming peptidomimetic strategy is to employ D-amino acids and reversed sequences to mimic a lead peptide conformation, either separately or as the combined retro-inverso peptide. In this work, we examine the conformations of inverse, reverse and retro-inverso peptides of p53(15-29 using implicit solvent molecular dynamics simulation and circular dichroism spectroscopy. In order to obtain converged ensembles for the peptides, we find enhanced sampling is required via the replica exchange molecular dynamics method. From these replica exchange simulations, the D-peptide analogues of p53(15-29 result in a predominantly left-handed helical conformation. When the parent sequence is reversed sequence as either the L-peptide and D-peptide, these peptides display a greater helical propensity, feature reflected by NMR and CD studies in TFE/water solvent. The simulations also indicate that, while approximately similar orientations of the side-chains are possible by the peptide analogues, their ability to mimic the parent peptide is severely compromised by backbone orientation (for D-amino acids and side-chain orientation (for reversed sequences. A retro-inverso peptide is disadvantaged as a mimic in both aspects, and further chemical modification is required to enable this concept to be used fruitfully in peptidomimetic design. The replica exchange molecular simulation approach adopted here, with its ability to provide detailed conformational insights into modified peptides, has potential as a tool to guide structure-based design of new improved peptidomimetics.
7. Identification of regioisomers and enantiomers of triacylglycerols in different yeasts using reversed- and chiral-phase LC–MS
Czech Academy of Sciences Publication Activity Database
Řezanka, Tomáš; Kolouchová, I.; Čejková, A.; Cajthaml, Tomáš; Sigler, Karel
2013-01-01
Roč. 36, č. 20 (2013), s. 3310-3320 ISSN 1615-9306 R&D Projects: GA ČR(CZ) GAP503/11/0215 Institutional support: RVO:61388971 Keywords : Atmospheric pressure chemical ionization mass spectrometry * Chiral LC * Reversed phase LC Subject RIV: EE - Microbiology, Virology Impact factor: 2.594, year: 2013
8. A feasibility study of ultrafiltration/reverse osmosis (UF/RO)-based wastewater treatment and reuse in the metal finishing industry
DEFF Research Database (Denmark)
Petrinic, Irena; Korenak, Jasmina; Povodnik, Damijan
2015-01-01
that the ultrafiltration-reverse osmosis treatment removed between 91.3% and 99.8% of the contaminants from the effluent, such as metal elements, organic, and inorganic compounds. Contaminants such as suspended solids, nickel, ammonium nitrogen, sulphate nitrogen, chemical oxygen demand, and biochemical oxygen demand were...... completely removed, the concentrations in the permeate being under the detection limits, thus the quality of the ultrafiltration-reverse osmosis process met the reuse criteria. This demonstrates the technological feasibility of wastewater reuse during electro-plating processes and the pre-treatment of powder...
9. Virgin coconut oil reverses hepatic steatosis by restoring redox homeostasis and lipid metabolism in male Wistar rats.
Science.gov (United States)
Narayanankutty, Arunaksharan; Palliyil, Devika Mukundan; Kuruvilla, Kezia; Raghavamenon, Achuthan C
2018-03-01
Hepatosteatosis, a form of nonalcoholic fatty liver disease (NAFLD), is being increasingly recognized as a major health burden worldwide. Insulin resistance, dyslipidemia and imbalances in adipokine/cytokine interplay are reported to be involved in the onset and progression of this disease. Use of dietary nutraceuticals in prevention and treatment of NAFLD is emerging. Virgin coconut oil (VCO), a fermented product of fresh coconut kernel, has been shown to impede the development of hepatosteatosis in rats. This study analyzes the potential of VCO to reverse the already developed hepatosteatosis condition. Hyperglycemia, reduced glucose tolerance, dyslipidemia, and hepatic macrovesicles in high-fructose-diet-fed rats (4 weeks) confirmed the development of hepatosteatosis. Natural reversion in these parameters was observed upon shifting to normal diet in untreated control animals. Administration of VCO, however, increased this natural reversion by improving high-density lipoprotein cholesterol level (53.5%) and reducing hepatic and serum triacylglycerols (78.0 and 51.7%). Increased hepatic glutathione level (P < 0.01), antioxidant enzyme activities (P < 0.05) and reduced lipid peroxidation were also noticed in these animals. These observations were in concordance with reduced liver enzyme activities (P < 0.01) and restoration of altered hepatic architecture. The study indicates that VCO can be used as a nutraceutical against hepatosteatosis. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.
10. Reverse cope elimination of hydroxylamines and alkenes or alkynes: theoretical investigation of tether length and substituent effects.
Science.gov (United States)
Krenske, Elizabeth H; Davison, Edwin C; Forbes, Ian T; Warner, Jacqueline A; Smith, Adrian L; Holmes, Andrew B; Houk, K N
2012-02-01
Quantum mechanical calculations have been used to study the intramolecular additions of hydroxylamines to alkenes and alkynes ("reverse Cope eliminations"). In intermolecular reverse Cope eliminations, alkynes are more reactive than alkenes. However, competition experiments have shown that tethering the hydroxylamine to the alkene or alkyne can reverse the reactivity order from that normally observed. The exact outcome depends on the length of the tether. In agreement with experiment, a range of density functional theory methods and CBS-QB3 calculations predict that the activation energies for intramolecular reverse Cope eliminations follow the order 6-exo-dig hydroxylamine and alkyne. Cyclization onto an alkene in the 5-exo-trig fashion incurs slightly less tether strain than a 6-exo-dig alkyne cyclization, but its activation energy is higher because the hydroxylamine fragment must distort more before the TS is reached. If the alkene terminus is substituted with two methyl groups, the barrier becomes so much higher that it is also disfavored compared to the 5- and 7-exo-dig cyclizations. © 2012 American Chemical Society
11. The treatment of river water by reverse osmosis
International Nuclear Information System (INIS)
Ray, N.J.; Jenkins, M.A.; Coates, A.
1977-01-01
The suitability of rod, spirally would and hollow fibre reverse osmosis systems has been assessed for the treatment of River Trent water to produce water of boiler feed quality. Particular attention has been paid to the effects of the suspended solids level of the influent water supply on operating and cleaning regimes. The best performance was given by the rod-type membranes which could be used with relatively dirty water if suitable chemical and/or physical cleaning techniques were applied. However, even this system, requires some form of clarification of the raw supply, and this affects capital and overall running costs. The hollow fibre membrane, which cannot be readily cleaned required an excessively clean water supply to avoid rapid and irreversible loss of output and is unlikely to have full-scale application on this, or similar, water. The spirally wound membranes, whilst not so susceptible to suspended solids as the hollow fibre system, did not tolerate dirty water, and required the raw water to be clarified to a level that is unlikely to be continuously guaranteed. In its current stage of development reverse osmosis is unlikely to give a cost advantage over the main cation/anion exchange stage of present water treatment plant, even for the treatment of waters relatively high in dissolved salts (500 mg kg -1 ). Moreover, conventional pretreatment and final mixed ion-exchange beds would still be required to produce water of boiler feed quality. Reverse osmosis does, however, remove organic species and non reactive silicon; its selection is likely to be dictated by such requirements or where space is at a premium e.g. extensions to existing water treatment plants. (orig.) [de
12. What do reversible programs compute?
DEFF Research Database (Denmark)
Axelsen, Holger Bock; Glück, Robert
2011-01-01
Reversible computing is the study of computation models that exhibit both forward and backward determinism. Understanding the fundamental properties of such models is not only relevant for reversible programming, but has also been found important in other fields, e.g., bidirectional model...... transformation, program transformations such as inversion, and general static prediction of program properties. Historically, work on reversible computing has focussed on reversible simulations of irreversible computations. Here, we take the viewpoint that the property of reversibility itself should...... are not strictly classically universal, but that they support another notion of universality; we call this RTM-universality. Thus, even though the RTMs are sub-universal in the classical sense, they are powerful enough as to include a self-interpreter. Lifting this to other computation models, we propose r...
13. Fundamentals of reversible flowchart languages
DEFF Research Database (Denmark)
Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert
2016-01-01
Abstract This paper presents the fundamentals of reversible flowcharts. They are intended to naturally represent the structure and control flow of reversible (imperative) programming languages in a simple computation model, in the same way classical flowcharts do for conventional languages......, structured reversible flowcharts are as expressive as unstructured ones, as shown by a reversible version of the classic Structured Program Theorem. We illustrate how reversible flowcharts can be concretized with two example programming languages, complete with syntax and semantics: a low-level unstructured...... language and a high-level structured language. We introduce concrete tools such as program inverters and translators for both languages, which follow the structure suggested by the flowchart model. To further illustrate the different concepts and tools brought together in this paper, we present two major...
14. Magnetic reversals from planetary dynamo waves
DEFF Research Database (Denmark)
Sheyko, Andrey; Finlay, Chris; Jackson, Andrew
2016-01-01
A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes ...... to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.......A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes...... place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines...
15. Physical and chemical assessment of MSF distillate and SWRO product for drinking purpose
KAUST Repository
Gacem, Yasmine; Taleb, Safia; Ramdani, Amina; Senadjki, Samia; Ghaffour, NorEddine
2012-01-01
The objective of this study was to evaluate the physical and chemical proprieties of desalinated seawater produced by Multi Stage Flash (MSF) and Reverse Osmosis (RO) processes for drinking purpose. The final products, after post
16. Reversible Compositional Control of Oxide Surfaces by Electrochemical Potentials
KAUST Repository
Mutoro, Eva
2012-01-05
Perovskite oxides can exhibit a wide range of interesting characteristics such as being catalytically active and electronically/ionically conducting, and thus, they have been used in a number of solid-state devices such as solid oxide fuel cells (SOFCs) and sensors. As the surface compositions of perovskites can greatly influence the catalytic properties, knowing and controlling their surface compositions is crucial to enhance device performance. In this study, we demonstrate that the surface strontium (Sr) and cobalt (Co) concentrations of perovskite-based thin films can be controlled reversibly at elevated temperatures by applying small electrical potential biases. The surface compositional changes of La 0.8Sr 0.2CoO 3-δ (LSC 113), (La 0.5Sr 0.5) 2CoO 4±δ (LSC 214), and LSC 214-decorated LSC 113 films (LSC 113/214) were investigated in situ by utilizing synchrotron-based X-ray photoelectron spectroscopy (XPS), where the largest changes of surface Sr were found for the LSC 113/214 surface. These findings offer the potential of reversibly controlling the surface functionality of perovskites. © 2011 American Chemical Society.
17. Superhydrophobic TiO2-polymer nanocomposite surface with UV-induced reversible wettability and self-cleaning properties.
Science.gov (United States)
Xu, Qian Feng; Liu, Yang; Lin, Fang-Ju; Mondal, Bikash; Lyons, Alan M
2013-09-25
Multifunctional superhydrophobic nanocomposite surfaces based on photocatalytic materials, such as fluorosilane modified TiO2, have generated significant research interest. However, there are two challenges to forming such multifunctional surfaces with stable superhydrophobic properties: the photocatalytic oxidation of the hydrophobic functional groups, which leads to the permanent loss of superhydrophobicity, as well as the photoinduced reversible hydrolysis of the catalytic particle surface. Herein, we report a simple and inexpensive template lamination method to fabricate multifunctional TiO2-high-density polyethylene (HDPE) nanocomposite surfaces exhibiting superhydrophobicity, UV-induced reversible wettability, and self-cleaning properties. The laminated surface possesses a hierarchical roughness spanning the micro- to nanoscale range. This was achieved by using a wire mesh template to emboss the HDPE surface creating an array of polymeric posts while partially embedding untreated TiO2 nanoparticles selectively into the top surface of these features. The surface exhibits excellent superhydrophobic properties immediately after lamination without any chemical surface modification to the TiO2 nanoparticles. Exposure to UV light causes the surface to become hydrophilic. This change in wettability can be reversed by heating the surface to restore superhydrophobicity. The effect of TiO2 nanoparticle surface coverage and chemical composition on the mechanism and magnitude of wettability changes was studied by EDX and XPS. In addition, the ability of the surface to shed impacting water droplets as well as the ability of such droplets to clean away particulate contaminants was demonstrated.
18. Synthesis of carbon nanotube-TiO2 nanotubular material for reversible hydrogen storage
International Nuclear Information System (INIS)
Mishra, Amrita; Banerjee, Subarna; Mohapatra, Susanta K; Graeve, Olivia A; Misra, Mano
2008-01-01
A material consisting of multi-walled carbon nanotubes (MWCNTs) and larger titania (TiO 2 ) nanotube arrays has been produced and found to be efficient for reversible hydrogen (H 2 ) storage. The TiO 2 nanotube arrays (diameter ∼60 nm and length ∼2-3 μm) are grown on a Ti substrate, and MWCNTs a few μm in length and ∼30-60 nm in diameter are grown inside these TiO 2 nanotubes using chemical vapor deposition with cobalt as a catalyst. The resulting material has been used in H 2 storage experiments based on a volumetric method using the pressure, composition, and temperature relationship of the storage media. This material can store up to 2.5 wt% of H 2 at 77 K under 25 bar with more than 90% reversibility.
19. Synthesis of carbon nanotube-TiO(2) nanotubular material for reversible hydrogen storage.
Science.gov (United States)
Mishra, Amrita; Banerjee, Subarna; Mohapatra, Susanta K; Graeve, Olivia A; Misra, Mano
2008-11-05
A material consisting of multi-walled carbon nanotubes (MWCNTs) and larger titania (TiO(2)) nanotube arrays has been produced and found to be efficient for reversible hydrogen (H(2)) storage. The TiO(2) nanotube arrays (diameter ∼60 nm and length ∼2-3 µm) are grown on a Ti substrate, and MWCNTs a few µm in length and ∼30-60 nm in diameter are grown inside these TiO(2) nanotubes using chemical vapor deposition with cobalt as a catalyst. The resulting material has been used in H(2) storage experiments based on a volumetric method using the pressure, composition, and temperature relationship of the storage media. This material can store up to 2.5 wt% of H(2) at 77 K under 25 bar with more than 90% reversibility.
20. Boron Removal from Seawater by Thin-Film Composite Reverse Osmosis Membranes
KAUST Repository
Al Sunbul, Yasmeen
2018-04-01
Reverse Osmosis membranes have been successfully proven to remove almost 99% of chemicals dissolved in seawater. However, removal of certain trace elements, such as boron is challenging and relatively low for seawater reverse osmosis desalination plants compared to thermal desalination plants. Boron is naturally occurring and is present in seawater at an average concentration of 4.5-5 mg/L. While boron is a vital element, its toxicity has been proven on crops, animals and possibly humans. Additionally, boron should be removed to comply with the current guideline value of 0.5 mg/L, for drinking water, issued by the World Health Organization (WHO), which is barely attained by a single-pass process seawater reverse osmosis plant. Currently, multipass reverse osmosis membrane operations with pH modifications are the only valid method for boron removal. However, this is not economically efficient as it requires higher energy and chemicals consumptions. The objective of this study was to investigate boron removal by commercial TFC RO membranes in addition to custom-made KAUST-synthesized TFC membrane. Five membrane samples were examined: Toray, Sepro, Koch, and KAUST in-house synthesized membrane. Three different feed pH conditions were used: pH6, pH8, and pH10. Filtration experiments were conducted in two parts. In experiment 1, all five membranes were examined for boron rejection in a dead-end permeation system, whereas in experiment 2 the two membranes with the highest boron rejection from experiment 1 were tested in a cross-flow system. Permeate and feed samples were taken continuously and analyzed for boron concentration, rejection calculation. Membrane surfaces were characterized according to hydrophilicity, roughness and surface charge. The results showed for all the tested membranes that boron rejection increased as the feed pH increased. KAUST, defect-free TFC, showed the highest performance for boron rejection for all pH conditions, although, it shows the
1. A study of reverse osmosis applicability to light water reactor radwaste processing. Technical report
International Nuclear Information System (INIS)
Markind, J.; Van Tran, T.
1979-04-01
The use of membrane technology has demonstrated significant process potential in nuclear radioactive waste applications. Reverse osmosis and ultrafiltration can provide filtration capability without the need of filter aids, minimize the requirements of chemical regeneration and/or disposal of expensive resins and can preconcentrate wastes without requiring major process equipment with large auxiliary heat supplies. Because of these capabilities, a study was undertaken to review, evaluate and document the existing experience, both nuclear and appropriate non-nuclear, of the membrane industry as it applies to the processing of reactor radwaste by membrane technology and, in particular, reverse osmosis and ultrafiltration. Relevant information was collected from both the literature and extensive communications with users and suppliers of membrane equipment. The systems reviewed ranged from experimental laboratory units to full scale process units
2. Particle Handling Techniques in Microchemical Processes
Directory of Open Access Journals (Sweden)
Brian S. Flowers
2012-08-01
Full Text Available The manipulation of particulates in microfluidics is a challenge that continues to impact applications ranging from fine chemicals manufacturing to the materials and the life sciences. Heterogeneous operations carried out in microreactors involve high surface-to-volume characteristics that minimize the heat and mass transport resistances, offering precise control of the reaction conditions. Considerable advances have been made towards the engineering of techniques that control particles in microscale laminar flow, yet there remain tremendous opportunities for improvements in the area of chemical processing. Strategies that have been developed to successfully advance systems involving heterogeneous materials are reviewed and an outlook provided in the context of the challenges of continuous flow fine chemical processes.
3. Combining chemoinformatics with bioinformatics: in silico prediction of bacterial flavor-forming pathways by a chemical systems biology approach "reverse pathway engineering".
Science.gov (United States)
Liu, Mengjin; Bienfait, Bruno; Sacher, Oliver; Gasteiger, Johann; Siezen, Roland J; Nauta, Arjen; Geurts, Jan M W
2014-01-01
The incompleteness of genome-scale metabolic models is a major bottleneck for systems biology approaches, which are based on large numbers of metabolites as identified and quantified by metabolomics. Many of the revealed secondary metabolites and/or their derivatives, such as flavor compounds, are non-essential in metabolism, and many of their synthesis pathways are unknown. In this study, we describe a novel approach, Reverse Pathway Engineering (RPE), which combines chemoinformatics and bioinformatics analyses, to predict the "missing links" between compounds of interest and their possible metabolic precursors by providing plausible chemical and/or enzymatic reactions. We demonstrate the added-value of the approach by using flavor-forming pathways in lactic acid bacteria (LAB) as an example. Established metabolic routes leading to the formation of flavor compounds from leucine were successfully replicated. Novel reactions involved in flavor formation, i.e. the conversion of alpha-hydroxy-isocaproate to 3-methylbutanoic acid and the synthesis of dimethyl sulfide, as well as the involved enzymes were successfully predicted. These new insights into the flavor-formation mechanisms in LAB can have a significant impact on improving the control of aroma formation in fermented food products. Since the input reaction databases and compounds are highly flexible, the RPE approach can be easily extended to a broad spectrum of applications, amongst others health/disease biomarker discovery as well as synthetic biology.
4. A functional language for describing reversible logic
DEFF Research Database (Denmark)
Thomsen, Michael Kirkedal
2012-01-01
Reversible logic is a computational model where all gates are logically reversible and combined in circuits such that no values are lost or duplicated. This paper presents a novel functional language that is designed to describe only reversible logic circuits. The language includes high....... Reversibility of descriptions is guaranteed with a type system based on linear types. The language is applied to three examples of reversible computations (ALU, linear cosine transformation, and binary adder). The paper also outlines a design flow that ensures garbage- free translation to reversible logic...... circuits. The flow relies on a reversible combinator language as an intermediate language....
5. Geomagnetic Reversals during the Phanerozoic.
Science.gov (United States)
McElhinny, M W
1971-04-09
An antalysis of worldwide paleomagnetic measurements suggests a periodicity of 350 x 10(6) years in the polarity of the geomagnetic field. During the Mesozoic it is predominantly normal, whereas during the Upper Paleozoic it is predominantly reversed. Although geomagnetic reversals occur at different rates throughout the Phanerozoic, there appeaars to be no clear correlation between biological evolutionary rates and reversal frequency.
6. Resveratrol reverses morphine-induced neuroinflammation in morphine-tolerant rats by reversal HDAC1 expression
Directory of Open Access Journals (Sweden)
Ru-Yin Tsai
2016-06-01
Conclusion: Resveratrol restores the antinociceptive effect of morphine by reversing morphine infusion-induced spinal cord neuroinflammation and increase in TNFR1 expression. The reversal of the morphine-induced increase in TNFR1 expression by resveratrol is partially due to reversal of the morphine infusion-induced increase in HDAC1 expression. Resveratrol pretreatment can be used as an adjuvant in clinical pain management for patients who need long-term morphine treatment or with neuropathic pain.
7. Teaching Mass Transfer and Filtration Using Crossflow Reverse Osmosis and Nanofiltration: An Experiment for the Undergraduate Unit Operations Lab
Science.gov (United States)
Anastasio, Daniel; McCutcheon, Jeffrey
2012-01-01
A crossflow reverse osmosis (RO) system was built for a senior-level chemical engineering unit operations laboratory course. Intended to teach students mass transfer fundamentals related to membrane separations, students tested several commercial desalination membranes, measuring water flux and salt rejections at various pressures, flow rates, and…
8. Simulation of uranium transport with variable temperature and oxidation potential: The computer program THCC [Thermo-Hydro-Chemical Coupling
International Nuclear Information System (INIS)
Carnahan, C.L.
1986-12-01
A simulator of reactive chemical transport has been constructed with the capabilities of treating variable temperatures and variable oxidation potentials within a single simulation. Homogeneous and heterogeneous chemical reactions are simulated at temperature-dependent equilibrium, and changes of oxidation states of multivalent elements can be simulated during transport. Chemical mass action relations for formation of complexes in the fluid phase are included explicitly within the partial differential equations of transport, and a special algorithm greatly simplifies treatment of reversible precipitation of solid phases. This approach allows direct solution of the complete set of governing equations for concentrations of all aqueous species and solids affected simultaneously by chemical and physical processes. Results of example simulations of transport, along a temperature gradient, of uranium solution species under conditions of varying pH and oxidation potential and with reversible precipitation of uraninite and coffinite are presented. The examples illustrate how inclusion of variable temperature and oxidation potential in numerical simulators can enhance understanding of the chemical mechanisms affecting migration of multivalent waste elements
9. Applications of the solvation parameter model in reversed-phase liquid chromatography.
Science.gov (United States)
Poole, Colin F; Lenca, Nicole
2017-02-24
The solvation parameter model is widely used to provide insight into the retention mechanism in reversed-phase liquid chromatography, for column characterization, and in the development of surrogate chromatographic models for biopartitioning processes. The properties of the separation system are described by five system constants representing all possible intermolecular interactions for neutral molecules. The general model can be extended to include ions and enantiomers by adding new descriptors to encode the specific properties of these compounds. System maps provide a comprehensive overview of the separation system as a function of mobile phase composition and/or temperature for method development. The solvation parameter model has been applied to gradient elution separations but here theory and practice suggest a cautious approach since the interpretation of system and compound properties derived from its use are approximate. A growing application of the solvation parameter model in reversed-phase liquid chromatography is the screening of surrogate chromatographic systems for estimating biopartitioning properties. Throughout the discussion of the above topics success as well as known and likely deficiencies of the solvation parameter model are described with an emphasis on the role of the heterogeneous properties of the interphase region on the interpretation and understanding of the general retention mechanism in reversed-phase liquid chromatography for porous chemically bonded sorbents. Copyright © 2016 Elsevier B.V. All rights reserved.
10. Electrochemical Microreactor Design for Alkoxylation Reactions—Experiments and Simulations
Czech Academy of Sciences Publication Activity Database
Křišťál, Jiří; Kodým, R.; Bouzek, K.; Jiřičný, Vladimír; Hanika, Jiří
2012-01-01
Roč. 51, č. 4 (2012), s. 1515-1524 ISSN 0888-5885 R&D Projects: GA ČR GA104/09/0880 Institutional research plan: CEZ:AV0Z40720504 Keywords : interdigitated band electrodes * high-conversion reactor * water electrolysis Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.206, year: 2012
11. Principles of a reversible programming language
DEFF Research Database (Denmark)
Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert
2008-01-01
The principles of reversible programming languages are explicated and illustrated with reference to the design of a high-level imperative language, Janus. The fundamental properties for such languages include backward as well as forward determinism and reversible updates of data. The unique design...... languages, and demonstrate this for Janus. We show the practicality of the language by implementation of a reversible fast Fourier transform. Our results indicate that the reversible programming paradigm has fundamental properties that are relevant to many different areas of computer science....... features of the language include explicit post-condition assertions, direct access to an inverse semantics and the possibility of clean (i.e., garbage-free) computation of injective functions. We suggest the clean simulation of reversible Turing machines as a criterion for computing strength of reversible...
12. Flux Enhancement in Crossflow Membrane Filtration: Fouling and It's Minimization by Flow Reversal. Final Report
International Nuclear Information System (INIS)
Shamsuddin Ilias
2005-01-01
Fouling problems are perhaps the single most important reason for relatively slow acceptance of ultrafiltration in many areas of chemical and biological processing. To overcome the losses in permeate flux associated with concentration polarization and fouling in cross flow membrane filtration, we investigated the concept of flow reversal as a method to enhance membrane flux in ultrafiltration. Conceptually, flow reversal prevents the formation of stable hydrodynamic and concentration boundary layers at or near the membrane surface. Further more, periodic reversal of the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. Consequently, these advantages are expected to enhance membrane flux significantly. A crossflow membrane filtration unit was designed and built to test the concept of periodic flow reversal for flux enhancement. The essential elements of the system include a crossflow hollow fiber membrane module integrated with a two-way valve to direct the feed flow directions. The two-way valve is controlled by a controller-timer for periodic reversal of flow of feed stream. Another important feature of the system is that with changing feed flow direction, the permeate flow direction is also changed to maintain countercurrent feed and permeate flows for enhanced mass transfer driving force (concentration difference). Three feed solutions (Bovine serum albumin (BSA), apple juice and citrus fruit pectin) were studied in crossflow membrane filtration. These solutes are well-known in membrane filtration for their fouling and concentration polarization potentials. Laboratory-scale tests on a hollow-fiber ultrafiltration membrane module using each of the feed solutes show that under flow reversal conditions, the permeate flux is significantly enhanced when compared with the conventional unidirectional flow. The flux enhancement is dramatic (by an order of magnitude) with increased feed concentration and
13. ‘Picking People to Hate’: Reversible reversals in stand-up comedy
DEFF Research Database (Denmark)
Keisalo, Marianna Päivikki
2017-01-01
Generally speaking, ritual reversals mean switching to the opposite of what is considered ‘the normal order’. Such reversals can occur, for example, in terms of social hierarchies in rites of passage, in action in carnival, or in the framing of action as ritual or performance. For comedic figures...... cultural grounds and show how the study of comedic performance can offer insights into the semiotics of performance more broadly....
14. Periodicity and Immortality in Reversible Computing
OpenAIRE
Kari , Jarkko; Ollinger , Nicolas
2008-01-01
Additional material available on the web at http://www.lif.univ-mrs.fr/~nollinge/rec/gnirut/; We investigate the decidability of the periodicity and the immortality problems in three models of reversible computation: reversible counter machines, reversible Turing machines and reversible one-dimensional cellular automata. Immortality and periodicity are properties that describe the behavior of the model starting from arbitrary initial configurations: immortality is the property of having at le...
15. How decision reversibility affects motivation.
Science.gov (United States)
Bullens, Lottie; van Harreveld, Frenk; Förster, Jens; Higgins, Tory E
2014-04-01
The present research examined how decision reversibility can affect motivation. On the basis of extant findings, it was suggested that 1 way it could affect motivation would be to strengthen different regulatory foci, with reversible decision making, compared to irreversible decision making, strengthening prevention-related motivation relatively more than promotion-related motivation. If so, then decision reversibility should have effects associated with the relative differences between prevention and promotion motivation. In 5 studies, we manipulated the reversibility of a decision and used different indicators of regulatory focus motivation to test these predictions. Specifically, Study 1 tested for differences in participants' preference for approach versus avoidance strategies toward a desired end state. In Study 2, we used speed and accuracy performance as indicators of participants' regulatory motivation, and in Study 3, we measured global versus local reaction time performance. In Study 4, we approached the research question in a different way, making use of the value-from-fit hypothesis (Higgins, 2000, 2002). We tested whether a fit between chronic regulatory focus and focus induced by the reversibility of the decision increased participants' subjective positive feelings about the decision outcome. Finally, in Study 5, we tested whether regulatory motivation, induced by decision reversibility, also influenced participants' preference in specific product features. The results generally support our hypothesis showing that, compared to irreversible decisions, reversible decisions strengthen a prevention focus more than a promotion focus. Implications for research on decision making are discussed.
16. Determination of effects of reverse bias on the efficiency of dye solar cells with the aid of spectroscopic and impedance studies
CSIR Research Space (South Africa)
Le Roux, Lukas J
2010-09-01
Full Text Available this cell in reverse bias. Although the work is focussed on the chemical stability of the dye, various techniques were employed to determine the physical changes in the cell. This presentation shows how electrochemical and impedance measurements (Nyquist...
17. MODELS OF PROJECT REVERSE ENGINEERING
Directory of Open Access Journals (Sweden)
Віктор Володимирович ІВАНОВ
2017-03-01
Full Text Available Reverse engineering decided important scientific and technical problems of increasing the cost of the existing technical product by transforming it into a product with other features or design. Search ideas of the new application of existing products on the base of heuristic analysis were created. The concept of reverse engineering and its division into three types: conceptual, aggregate and complete was expanded. The use of heuristic methods for reverse engineering concept was showed. The modification model of Reverse engineering based on the model of РМВОК was developed. Our model includes two new phases: identification and transformation. At the identification phase, technical control is made. At the transformation phase, search heuristic idea of the new applied existing technical product was made. The model of execution phase that included heuristic methods, metrological equipment, and CAD/CAM/CAE program complex was created. The model that connected economic indicators of reverse engineering project was developed.
18. Garbage collection for reversible functional languages
DEFF Research Database (Denmark)
Mogensen, Torben Ægidius
2015-01-01
Reversible languages are programming languages where all programs can run both forwards and backwards. Reversible functional languages have been proposed that use symmetric pattern matching and data construction. To be reversible, these languages require linearity: Every variable must be used...
19. Reversible switching of wetting properties and erasable patterning of polymer surfaces using plasma oxidation and thermal treatment
Science.gov (United States)
Rashid, Zeeshan; Atay, Ipek; Soydan, Seren; Yagci, M. Baris; Jonáš, Alexandr; Yilgor, Emel; Kiraz, Alper; Yilgor, Iskender
2018-05-01
Polymer surfaces reversibly switchable from superhydrophobic to superhydrophilic by exposure to oxygen plasma and subsequent thermal treatment are demonstrated. Two inherently different polymers, hydrophobic segmented polydimethylsiloxane-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) are modified with fumed silica nanoparticles to prepare superhydrophobic surfaces with roughness on nanometer to micrometer scale. Smooth TPSC and PMMA surfaces are also used as control samples. Regardless of their chemical structure and surface topography, all surfaces display completely reversible wetting behavior changing from hydrophobic to hydrophilic and back for many cycles upon plasma oxidation followed by thermal annealing. Influence of plasma power, plasma exposure time, annealing temperature and annealing time on the wetting behavior of polymeric surfaces are investigated. Surface compositions, textures and topographies are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and white light interferometry (WLI), before and after oxidation and thermal annealing. Wetting properties of the surfaces are determined by measuring their static, advancing and receding water contact angle. We conclude that the chemical structure and surface topography of the polymers play a relatively minor role in reversible wetting behavior, where the essential factors are surface oxidation and migration of polymer molecules to the surface upon thermal annealing. Reconfigurable water channels on polymer surfaces are produced by plasma treatment using a mask and thermal annealing cycles. Such patterned reconfigurable hydrophilic regions can find use in surface microfluidics and optofluidics applications.
20. END-OF-USE PRODUCTS IN REVERSE LOGISTICS
OpenAIRE
Marta Starostka-Patyk
2007-01-01
Reverse logistics is a very useful tool for enterprises which have to deal with end-of-use products. Forward logistics is not able to manage them, because they show up on the beginning of reverse supply chain. That is the reason for growing importance of reverse flows. Reverse logistics is quite new logistics system. This paper presents the idea of reverse logistics and end-of-use products problems.
1. Reversal of subtidal dune asymmetries caused by seasonally reversing wind-driven currents in Torres Strait, northeastern Australia
Science.gov (United States)
Harris, Peter T.
1991-07-01
Large subtidal sand dunes (sandwaves) located in Adolphus Channel, Torres Strait, have been observed to reverse their asymmetric orientation between September-February. This has been attributed to a reversal in wind-driven currents, which flow westward during the SE trade season (April-November) and eastwards during the NW monsoon season [December-March: HARRIS (1989) Continental Shelf Research, 9, 981-1002]. Observations in September 1988 and February 1989 from another area of dunes in Torres Strait corroborate this asymmetry reversal pattern. The results indicate that such reversals may be common in Torres Strait and in other areas where subtidal bedforms are subject to modification by superimposed, seasonally reversing, wind-driven currents.
2. Structural study of the AOT reverse micellar system. Influence of attractive interactions induced by the solubilisation of native and modified proteins
International Nuclear Information System (INIS)
Cassin, Guillaume
1994-01-01
This research thesis reports the study of the influence of intra-micellar attractions on the thermodynamic behaviour of reverse micellar systems, as well as of the effects induced by the solubilisation of natives or modified proteins. The author proposes a model to explain the decrease of attractions between droplets when the volume fraction occupied by reverse micelles increases. This model which highlights the importance of depletion forces between reverse micelles, allows the building up of a theoretical relationship between the bonding parameter and the volume fraction of reverse micelles. In order to understand the appearance of an attractive term related to the solubilisation of native cytochrome-c in these systems, this protein has been chemically modified. The author highlights the role of the charge born by a micellar probe on the thermodynamic behaviour of micro-emulsions. Then, the author applies the model of dimerizing adhesive spheres to reverse micellar systems containing native cytochrome-c. He shows that theoretical predictions of this model are in agreement with obtained experimental results [fr
3. Removal of fouling species from brackish water reverse osmosis reject stream.
Science.gov (United States)
Ayoub, G M; Korban, L; Al-Hindi, M; Zayyat, R
2018-03-01
Brine disposal from reverse osmosis (RO) systems remains a major challenge for the desalination industry especially in inland areas where discharge options are very limited. Solutions will entail the introduction of economic treatment processes that will alleviate the brine's negative impact on the environment and reduce its discharge volume. Such processes could act as an intermediary treatment process for the recycling of the brine through an additional RO stage which, for brackish water (BW) desalination, could lead to saving valuable water while reducing the amount of brine discharge. In this context, the study at hand attempts to evaluate the effectiveness of a one-step chemical process for the treatment of BWRO brine. This study seeks to determine optimal operating conditions relative to type, ratio, and dosage of alkalizing chemicals, pH and temperature, for substantially reducing the concentrations of scaling parameters such as calcium, magnesium, silica, and strontium. The results indicate that precipitation softening at pH = 11.5 using combined chemical dosages of NaOH and Na 2 CO 3 in a ratio of 2:1 leads to substantial removal of calcium and magnesium (>95%) and moderately high removal of strontium and silica (>71%).
4. Magnetic reversals from planetary dynamo waves.
Science.gov (United States)
Sheyko, Andrey; Finlay, Christopher C; Jackson, Andrew
2016-11-24
A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines by columnar convection. Here we present an example of another class of reversing-geodynamo model, which operates in a regime of comparatively low viscosity and high magnetic diffusivity. This class does not fit into the paradigm of reversal regimes that are dictated by the value of the local Rossby number (the ratio of advection to Coriolis force). Instead, stretching of the magnetic field by a strong shear in the east-west flow near the imaginary cylinder just touching the inner core and parallel to the axis of rotation is crucial to the reversal mechanism in our models, which involves a process akin to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.
5. Multiple reversal olfactory learning in honeybees
Directory of Open Access Journals (Sweden)
Theo Mota
2010-07-01
Full Text Available In multiple reversal learning, animals trained to discriminate a reinforced from a non-reinforced stimulus are subjected to various, successive reversals of stimulus contingencies (e.g. A+ vs. B-, A- vs. B+, A+ vs. B-. This protocol is useful to determine whether or not animals learn to learn and solve successive discriminations faster (or with fewer errors with increasing reversal experience. Here we used the olfactory conditioning of proboscis extension reflex to study how honeybees Apis mellifera perform in a multiple reversal task. Our experiment contemplated four consecutive differential conditioning phases involving the same odors (A+ vs. B- to A- vs. B+ to A+ vs. B- to A- vs. B+. We show that bees in which the weight of reinforced or non-reinforced stimuli was similar mastered the multiple olfactory reversals. Bees which failed the task exhibited asymmetric responses to reinforced and non-reinforced stimuli, thus being unable to rapidly reverse stimulus contingencies. Efficient reversers did not improve their successive discriminations but rather tended to generalize their choice to both odors at the end of conditioning. As a consequence, both discrimination and reversal efficiency decreasedalong experimental phases. This result invalidates a learning-to-learn effect and indicates that bees do not only respond to the actual stimulus contingencies but rather combine these with an average of past experiences with the same stimuli.
6. Hydrogen production through aqueous-phase reforming of ethylene glycol in a washcoated microchannel
NARCIS (Netherlands)
Neira d'Angelo, M.F.; Ordomskiy, V.; Paunovic, V.; Schaaf, van der J.; Schouten, J.C.; Nijhuis, T.A.
2013-01-01
Aqueous-phase reforming (APR) of biocarbohydrates is conducted in a catalytically stable washcoated microreactor where multiphase hydrogen removal enhances hydrogen efficiency. Single microchannel experiments are conducted following a simplified model based on the microreactor concept. A coating
7. Lack of chemically induced mutation in repair-deficient mutants of yeast
International Nuclear Information System (INIS)
Prakash, L.
1974-01-01
8. Lack of chemically induced mutation in repair-deficient mutants of yeast.
Science.gov (United States)
Prakash, L
1974-12-01
9. Versatile Dual Photoresponsive System for Precise Control of Chemical Reactions.
Science.gov (United States)
Xu, Can; Bing, Wei; Wang, Faming; Ren, Jinsong; Qu, Xiaogang
2017-08-22
A versatile method for photoregulation of chemical reactions was developed through a combination of near-infrared (NIR) and ultraviolet (UV) light sensitive materials. This regulatory effect was achieved through photoresponsive modulation of reaction temperature and pH values, two prominent factors influencing reaction kinetics. Photothermal nanomaterial graphene oxide (GO) and photobase reagent malachite green carbinol base (MGCB) were selected for temperature and pH regulation, respectively. Using nanocatalyst- and enzyme-mediated chemical reactions as model systems, we demonstrated the feasibility and high efficiency of this method. In addition, a photoresponsive, multifunctional "Band-aid"-like hydrogel platform was presented for programmable wound healing. Overall, this simple, efficient, and reversible system was found to be effective for controlling a wide variety of chemical reactions. Our work may provide a method for remote and sustainable control over chemical reactions for industrial and biomedical applications.
10. Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes
Science.gov (United States)
Alivov, Yahya; Funke, Hans; Nagpal, Prashant
2015-07-01
Rapid miniaturization of electronic devices down to the nanoscale, according to Moore’s law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-106. While demonstrated air- and chemical-gating speeds were slow here (˜seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for ‘chemical transistors’, ‘chemical diodes’, and very high-efficiency sensing applications.
11. Reversible and non-reversible enlargement of cerebral spinal fluid spaces in anorexia nervosa
International Nuclear Information System (INIS)
Artmann, H.; Grau, H.; Adelmann, M.; Schleiffer, R.
1985-01-01
Brain CT studies of 35 patients with anoxia nervosa confirmed the observations of other authors: cerebral dystrophic changes correlate with weight loss and the reversibility of these changes also correlates with the normalization of body weight. Other corroborated facts are: the most numerous and most pronounced enlargements are of the cortical sulci and the interhemispheric fissure, moderate widening affects the ventricles and the rarest and most insignificant changes are those of the cerebellum. The reversibility of the changes showed a parallel to the extent of the changes themselves and to the duration of improvement of the body weight. The reversibility of the enlargement of the cortical sulci and of the distances between the frontal horns of the lateral ventricles was more often significant than that of the abnormal measurements of the cella media. This difference is based on minimal early acquired brain damage which occurs in 60% of our patients. This high incidence of early acquired minimal brain disease in patients with anorexia nervosa is here discussed as a nonspecific predisposing factor. Although there is no exact explanation of the etiology of the reversible enlargement of cerenral spinal fluid (CSF) spaces in anorexia nervosa, the changes resemble those in alcoholics. The mechanisms of brain changes in alcoholism, as shown experimentally, seem to us to throw light on the probable mechanism of reversible dystrophic brain changes in anorexia nervosa. (orig.)
12. Reversible and non-reversible enlargement of cerebral spinal fluid spaces in anorexia nervosa
Energy Technology Data Exchange (ETDEWEB)
Artmann, H.; Grau, H.; Adelmann, M.; Schleiffer, R.
1985-07-01
Brain CT studies of 35 patients with anoxia nervosa confirmed the observations of other authors: cerebral dystrophic changes correlate with weight loss and the reversibility of these changes also correlates with the normalization of body weight. Other corroborated facts are: the most numerous and most pronounced enlargements are of the cortical sulci and the interhemispheric fissure, moderate widening affects the ventricles and the rarest and most insignificant changes are those of the cerebellum. The reversibility of the changes showed a parallel to the extent of the changes themselves and to the duration of improvement of the body weight. The reversibility of the enlargement of the cortical sulci and of the distances between the frontal horns of the lateral ventricles was more often significant than that of the abnormal measurements of the cella media. This difference is based on minimal early acquired brain damage which occurs in 60% of our patients. This high incidence of early acquired minimal brain disease in patients with anorexia nervosa is here discussed as a nonspecific predisposing factor. Although there is no exact explanation of the etiology of the reversible enlargement of cerenral spinal fluid (CSF) spaces in anorexia nervosa, the changes resemble those in alcoholics. The mechanisms of brain changes in alcoholism, as shown experimentally, seem to us to throw light on the probable mechanism of reversible dystrophic brain changes in anorexia nervosa.
13. Open tubular capillary electrochromatography: A useful microreactor for collagen I glycation and interaction studies with low-density lipoprotein particles
International Nuclear Information System (INIS)
D'Ulivo, Lucia; Witos, Joanna; Ooerni, Katariina; Kovanen, Petri T.; Riekkola, Marja-Liisa
2010-01-01
Diabetes, a multifunctional disease and a major cause of morbidity and mortality in the industrialized countries, strongly associates with the development and progression of atherosclerosis. One of the consequences of high level of glucose in the blood circulation is glycation of long-lived proteins, such as collagen I, the most abundant component of the extracellular matrix (ECM) in the arterial wall. Glycation is a long-lasting process that involves the reaction between a carbonyl group of the sugar and an amino group of the protein, usually a lysine residue. This reaction generates an Amadori product that may evolve in advanced glycation end products (AGEs). AGEs, as reactive molecules, can provoke cross-linking of collagen I fibrils. Since binding of low-density lipoproteins (LDLs) to the ECM of the inner layer of the arterial wall, the intima, has been implicated to be involved in the onset of the development of an atherosclerotic plaque, collagen modifications, which can affect the affinity of native and oxidized LDL for collagen I, can promote the entrapment of LDLs in the intima and accelerate the progression of atherosclerosis. In this study, open tubular capillary electrochromatography is proposed as a new microreactor to study in situ glycation of collagen I. The kinetics of glycation was first investigated in a fused silica collagen I-coated capillary. Dimethyl sulphoxide, injected as an electroosmotic flow marker, gave information about the charge of coating. Native and oxidized LDL, and selected peptide fragments from apolipoprotein B-100, the protein covering LDL particles, were injected as marker compounds to clarify the interactions between LDLs and the glycated collagen I coating. The method proposed is simple and inexpensive, since only small amounts of collagen and LDL are required. Atomic force microscopy images complemented our studies, highlighting the difference between unmodified and glycated collagen I surfaces.
14. Open tubular capillary electrochromatography: A useful microreactor for collagen I glycation and interaction studies with low-density lipoprotein particles
Energy Technology Data Exchange (ETDEWEB)
D' Ulivo, Lucia; Witos, Joanna [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Ooerni, Katariina; Kovanen, Petri T. [Wihuri Research Institute, Kalliolinnantie 4, FIN-00140, Helsinki (Finland); Riekkola, Marja-Liisa, E-mail: [email protected] [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)
2010-04-07
Diabetes, a multifunctional disease and a major cause of morbidity and mortality in the industrialized countries, strongly associates with the development and progression of atherosclerosis. One of the consequences of high level of glucose in the blood circulation is glycation of long-lived proteins, such as collagen I, the most abundant component of the extracellular matrix (ECM) in the arterial wall. Glycation is a long-lasting process that involves the reaction between a carbonyl group of the sugar and an amino group of the protein, usually a lysine residue. This reaction generates an Amadori product that may evolve in advanced glycation end products (AGEs). AGEs, as reactive molecules, can provoke cross-linking of collagen I fibrils. Since binding of low-density lipoproteins (LDLs) to the ECM of the inner layer of the arterial wall, the intima, has been implicated to be involved in the onset of the development of an atherosclerotic plaque, collagen modifications, which can affect the affinity of native and oxidized LDL for collagen I, can promote the entrapment of LDLs in the intima and accelerate the progression of atherosclerosis. In this study, open tubular capillary electrochromatography is proposed as a new microreactor to study in situ glycation of collagen I. The kinetics of glycation was first investigated in a fused silica collagen I-coated capillary. Dimethyl sulphoxide, injected as an electroosmotic flow marker, gave information about the charge of coating. Native and oxidized LDL, and selected peptide fragments from apolipoprotein B-100, the protein covering LDL particles, were injected as marker compounds to clarify the interactions between LDLs and the glycated collagen I coating. The method proposed is simple and inexpensive, since only small amounts of collagen and LDL are required. Atomic force microscopy images complemented our studies, highlighting the difference between unmodified and glycated collagen I surfaces.
15. Reversal agents in anaesthesia and critical care
Directory of Open Access Journals (Sweden)
Nibedita Pani
2015-01-01
Full Text Available Despite the advent of short and ultra-short acting drugs, an in-depth knowledge of the reversal agents used is a necessity for any anaesthesiologist. Reversal agents are defined as any drug used to reverse the effects of anaesthetics, narcotics or potentially toxic agents. The controversy on the routine reversal of neuromuscular blockade still exists. The advent of newer reversal agents like sugammadex have made the use of steroidal neuromuscular blockers like rocuronium feasible in rapid sequence induction situations. We made a review of the older reversal agents and those still under investigation for drugs that are regularly used in our anaesthesia practice.
16. The misconception of mean-reversion
International Nuclear Information System (INIS)
Eliazar, Iddo I; Cohen, Morrel H
2012-01-01
The notion of random motion in a potential well is elemental in the physical sciences and beyond. Quantitatively, this notion is described by reverting diffusions—asymptotically stationary diffusion processes which are simultaneously (i) driven toward a reversion level by a deterministic force, and (ii) perturbed off the reversion level by a random white noise. The archetypal example of reverting diffusions is the Ornstein–Uhlenbeck process, which is mean-reverting. In this paper we analyze reverting diffusions and establish that: (i) if the magnitude of the perturbing noise is constant then the diffusion's stationary density is unimodal and the diffusion is mode-reverting; (ii) if the magnitude of the perturbing noise is non-constant then, in general, neither is the diffusion's stationary density unimodal, nor is the diffusion mode-reverting. In the latter case we further establish a result asserting when unimodality and mode-reversion do hold. In particular, we demonstrate that the notion of mean-reversion, which is fundamental in economics and finance, is a misconception—as mean-reversion is an exception rather than the norm. (fast track communication)
17. Parkinson’s disease managing reversible neurodegeneration
Science.gov (United States)
Hinz, Marty; Stein, Alvin; Cole, Ted; McDougall, Beth; Westaway, Mark
2016-01-01
Traditionally, the Parkinson’s disease (PD) symptom course has been classified as an irreversible progressive neurodegenerative disease. This paper documents 29 PD and treatment-induced systemic depletion etiologies which cause and/or exacerbate the seven novel primary relative nutritional deficiencies associated with PD. These reversible relative nutritional deficiencies (RNDs) may facilitate and accelerate irreversible progressive neurodegeneration, while other reversible RNDs may induce previously undocumented reversible pseudo-neurodegeneration that is hiding in plain sight since the symptoms are identical to the symptoms being experienced by the PD patient. Documented herein is a novel nutritional approach for reversible processes management which may slow or halt irreversible progressive neurodegenerative disease and correct reversible RNDs whose symptoms are identical to the patient’s PD symptoms. PMID:27103805
18. Pressure-induced reversal between thermal contraction and expansion in ferroelectric PbTiO3.
Science.gov (United States)
Zhu, Jinlong; Zhang, Jianzhong; Xu, Hongwu; Vogel, Sven C; Jin, Changqing; Frantti, Johannes; Zhao, Yusheng
2014-01-15
Materials with zero/near zero thermal expansion coefficients are technologically important for applications in thermal management and engineering. To date, this class of materials can only be produced by chemical routes, either by changing chemical compositions or by composting materials with positive and negative thermal expansion. Here, we report for the first time a physical route to achieve near zero thermal expansion through application of pressure. In the stability field of tetragonal PbTiO3 we observed pressure-induced reversals between thermal contraction and expansion between ambient pressure and 0.9 GPa. This hybrid behavior leads to a mathematically infinite number of crossover points in the pressure-volume-temperature space and near-zero thermal expansion coefficients comparable to or even smaller than those attained by chemical routes. The observed pressures for this unusual phenomenon are within a small range of 0.1-0.9 GPa, potentially feasible for designing stress-engineered materials, such as thin films and nano-crystals, for thermal management applications.
19. Reversible machine code and its abstract processor architecture
DEFF Research Database (Denmark)
Axelsen, Holger Bock; Glück, Robert; Yokoyama, Tetsuo
2007-01-01
A reversible abstract machine architecture and its reversible machine code are presented and formalized. For machine code to be reversible, both the underlying control logic and each instruction must be reversible. A general class of machine instruction sets was proven to be reversible, building...
20. Rechargeable Al-CO2 Batteries for Reversible Utilization of CO2.
Science.gov (United States)
Ma, Wenqing; Liu, Xizheng; Li, Chao; Yin, Huiming; Xi, Wei; Liu, Ruirui; He, Guang; Zhao, Xian; Luo, Jun; Ding, Yi
2018-05-21
The excessive emission of CO 2 and the energy crisis are two major issues facing humanity. Thus, the electrochemical reduction of CO 2 and its utilization in metal-CO 2 batteries have attracted wide attention because the batteries can simultaneously accelerate CO 2 fixation/utilization and energy storage/release. Here, rechargeable Al-CO 2 batteries are proposed and realized, which use chemically stable Al as the anode. The batteries display small discharge/charge voltage gaps down to 0.091 V and high energy efficiencies up to 87.7%, indicating an efficient battery performance. Their chemical reaction mechanism to produce the performance is revealed to be 4Al + 9CO 2 ↔ 2Al 2 (CO 3 ) 3 + 3C, by which CO 2 is reversibly utilized. These batteries are envisaged to effectively and safely serve as a potential CO 2 fixation/utilization strategy with stable Al. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
1. A Typology of Reverse Innovation
DEFF Research Database (Denmark)
von Zedtwitz, Max; Corsi, Simone; Søberg, Peder Veng
2015-01-01
secondary market introduction, this study expands the espoused definition of reverse innovation beyond its market-introduction focus with reversals in the flow of innovation in the ideation and product development phases. Recognizing that each phase can take place in different geographical locations...... taking place in an emerging country. This analytical framework allows recasting of current research at the intersection between innovation and international business. Of the 10 reverse innovation flows, six are new and have not been covered in the literature to date. The study addresses questions......’s portfolio of global innovation competence and capability. The implications for management are concerned with internal and external resistance to reverse innovation. Most significantly, while greater recognition and power of innovation in formerly subordinate organizational units is inconvenient to some...
2. Elements of a Reversible Object-Oriented Language
DEFF Research Database (Denmark)
Schultz, Ulrik Pagh; Axelsen, Holger Bock
2016-01-01
This paper presents initial ideas for the design and implementation of a reversible object-oriented language based on extending Janus with object-oriented concepts such as classes that encapsulate behavior and state, inheritance, virtual dispatching, as well as constructors. We show that virtual...... dispatching is a reversible decision mechanism easily translatable to a standard reversible programming model such as Janus, and we argue that reversible management of state can be accomplished using reversible constructors. The language is implemented in terms of translation to standard Janus programs....
3. A new method to describe two-phase solvent extraction based on net transport potential derived as linear combinations of forward and reverse constituents
International Nuclear Information System (INIS)
Nabeshima, Masahiro
1998-01-01
With the view to avoiding the difficulties encountered in estimating thermodynamic activities of the multiple chemical species in two-phase liquid system, a set of forward, reverse, net and total transport potentials are defined to represent the chemical state of a transferring solute during transient using bulk concentrations. The net transport potential corresponds to that in the conventional two-film model of diffusion-controlled processes. The overall driving forces of mass transport are redefined as the derivatives of the relevant transport potentials differentiated with respect to a state variable newly defined in terms of the bulk concentrations of the solute contained in both phases. Net and total quantities, i.e. transport potentials, overall driving forces and the molar fluxes are obtained as linear combinations of those for forward and reverse directions. The topical features presented by these quantities and their mutual relations are discussed in detail. The experimental new overall transport coefficient for U(VI) varied in accord with the changes in the theoretical net transport potential and overall driving force. The present method permits describing the extractive mass transport consistently both to forward and reverse directions of transport. (author)
4. His+ reversions caused in Salmonella typhimurium by different types of ionizing radiation
International Nuclear Information System (INIS)
Roos, H.; Thomas, W.H.; Fitzek, M.; Kellerer, A.M.
1988-01-01
The yield of his+ reversions in the Ames Salmonella tester strain TA2638 has been determined for 60Co gamma rays, 140 kV X rays, 5.4 keV characteristic X rays, 2.2 MeV protons, 3.1 MeV alpha particles, and 18 MeV/U Fe ions. Inactivation studies were performed with the same radiations. For both mutation and inactivation, the maximum effectiveness per unit absorbed dose was obtained for the characteristic X rays, which have a dose averaged linear energy transfer (LET) of roughly 10 keV/micron. The ratio of the effectiveness of this radiation to gamma rays was 2 for inactivation and about 1.4 for the his+ reversion. For both end points the effectiveness decreases substantially at high LET, i.e., for the alpha particles and the Fe ions. The composition of the bottom and the top agar was the one recommended by Maron and Ames for application in chemical mutagenicity tests. The experiments with the less penetrating radiations differed from the usual protocol by utilization of a technique of plating the bacteria on the surface of the top agar. As in an earlier study greatly enhanced yields of mutations, relative to the spontaneous reversion rate, were obtained in these experiments by performing the irradiations 6 h after plating, which differs from the conventional procedure to irradiate the bacteria shortly after plating
5. Drift reversal capability in helical systems
International Nuclear Information System (INIS)
Yokoyama, M.; Itoh, K.; Okamura, S.
2002-10-01
The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)
6. Drift reversal capability in helical systems
International Nuclear Information System (INIS)
Yokoyama, M.; Itoh, K.; Okamura, S.; Matsuoka, K.; Nakajima, N.; Itoh, S.-I.; Neilson, G.H.; Zarnstorff, M.C.; Rewoldt, G.
2003-01-01
The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)
7. Kinetic Line Voronoi Operations and Their Reversibility
DEFF Research Database (Denmark)
Mioc, Darka; Anton, François; Gold, Christopher
2010-01-01
In Geographic Information Systems the reversibility of map update operations has not been explored yet. In this paper we are using the Voronoi based Quad-edge data structure to define reversible map update operations. The reversibility of the map operations has been formalised at the lowest level...... mechanisms and dynamic map visualisations. In order to use the reversibility within the kinetic Voronoi diagram of points and open oriented line segments, we need to assure that reversing the map commands will produce exactly the changes in the map equivalent to the previous map states. To prove...... that reversing the map update operations produces the exact reverse changes, we show an isomorphism between the set of complex operations on the kinetic Voronoi diagram of points and open oriented line segments and the sets of numbers of new / deleted Voronoi regions induced by these operations, and its...
Directory of Open Access Journals (Sweden)
Mehmet K Aktas, MD
2007-01-01
Full Text Available During cardiac surgery temporary epicardial atrial and ventricular leads are placed in case cardiac pacing is required postoperatively. We present the first reported series of patients with reversal of atrioventricular electrodes in the temporary pacemaker without any consequent deleterious hemodynamic effect. We review the electrocardiographic findings and discuss the findings that lead to the discovery of atrioventricular lead reversal.
9. Reversal modes in asymmetric Ni nanowires
Energy Technology Data Exchange (ETDEWEB)
Leighton, B.; Pereira, A. [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Escrig, J., E-mail: [email protected] [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avda. Ecuador 3493, 917-0124 Santiago (Chile)
2012-11-15
We have investigated the evolution of the magnetization reversal mechanism in asymmetric Ni nanowires as a function of their geometry. Circular nanowires are found to reverse their magnetization by the propagation of a vortex domain wall, while in very asymmetric nanowires the reversal is driven by the propagation of a transverse domain wall. The effect of shape asymmetry of the wire on coercivity and remanence is also studied. Angular dependence of the remanence and coercivity is also addressed. Tailoring the magnetization reversal mechanism in asymmetric nanowires can be useful for magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls. Finally, an alternative method to detect the presence of magnetic drops is proposed. - Highlights: Black-Right-Pointing-Pointer Asymmetry strongly modifies the magnetic behavior of a wire. Black-Right-Pointing-Pointer Very asymmetric nanowires reverse their magnetization by a transverse domain wall. Black-Right-Pointing-Pointer An alternative method to detect the presence of magnetic drops is proposed. Black-Right-Pointing-Pointer Tailoring the reversal mode in asymmetric nanowires can be useful for potential applications.
10. Reversal of chloroquine resistance in Plasmodium falciparum by CDR 87/209 and analogues.
Science.gov (United States)
Walter, R D; Seth, M; Bhaduri, A P
1993-03-01
The spreading of resistance towards chloroquine has diminished its value as a potent and safe drug in malaria endemic areas. Recent reports on the reversal of chloroquine resistance in the malaria parasite Plasmodium falciparum in vitro and in vivo by verapamil, desipramine and other Ca(2+)-channel blockers and antidepressants has initiated a strategy for chemotherapy by treatment with chloroquine in combination with a drug resistance modulator. Described here is a class of modulators of distinct structure which reverse chloroquine resistance in a different manner. Contrary to verapamil and desipramine, CDRI 87/209, the most potent compound of this new class and used as a chemical lead, did not restore chloroquine accumulation in the resistant parasites, thereby indicating that besides the proposed blockade of drug efflux other mechanisms are vulnerable targets for a chemotherapeutic approach towards drug resistance. Similar to the former modulators, CDRI 87/209 showed only weak intrinsic plasmodicidal activity and the increase of drug susceptibility was restricted to resistant plasmodia.
11. Introduction to time reversal theory
International Nuclear Information System (INIS)
Henley, E.M.
1987-01-01
Theory and reaction mechanisms relevant to time reversal invariance are reviewed. Consequences of time reversal invariance are presented under the headings of CP tests, electromagnetic moments, weak emissions or absorptions, and scattering reactions. 8 refs., 4 figs
12. Annealing temperature dependent reversible wettability switching of micro/nano structured ZnO superhydrophobic surfaces
Science.gov (United States)
Velayi, Elmira; Norouzbeigi, Reza
2018-05-01
Superhydrophobic ZnO surfaces with reversibly tunable wettability were fabricated on stainless steel meshes via a facile chemical bath deposition method just by regulating the micro/nano structured ZnO needles without using chemical post modifications. The obtained surfaces can be easily and reversibly switched between superhydrophobic and superhydrophilic/underwater superoleophobic characteristics by altering the annealing temperatures. As-prepared sample exhibited long-term superhydrophobic properties with a water contact angle (WCA) of 163.8° ± 1.8° and contact angle hysteresis (CAH) of 1.1° ± 0.8°. The SEM, XRD, XPS and Raman analyses were employed to characterize the morphological features and surface chemistry of the prepared samples. SEM images showed the formation of ZnO micro/nanoneedles with a diameter of ∼90 nm on the substrate. The superhydrophobic ZnO surface was switched to highly hydrophilic and underwater superoleophobic properties with an oil contact angle (OCA) of about 172.5° after being annealed at 400 °C in air for 30 min and restored to superhydrophobic state again by altering the annealing temperature to 150 °C. Mechanical durability of the ZnO superhydrophobic surface was tested by an abrasion test. Results confirmed that the prepared surface exhibited an excellent robustness after 20 abrasion cycles under the pressure of 4.7 kPa.
13. Vasectomy reversal: a clinical update
Directory of Open Access Journals (Sweden)
Abhishek P Patel
2016-01-01
Full Text Available Vasectomy is a safe and effective method of contraception used by 42-60 million men worldwide. Approximately 3%-6% of men opt for a vasectomy reversal due to the death of a child or divorce and remarriage, change in financial situation, desire for more children within the same marriage, or to alleviate the dreaded postvasectomy pain syndrome. Unlike vasectomy, vasectomy reversal is a much more technically challenging procedure that is performed only by a minority of urologists and places a larger financial strain on the patient since it is usually not covered by insurance. Interest in this procedure has increased since the operating microscope became available in the 1970s, which consequently led to improved patency and pregnancy rates following the procedure. In this clinical update, we discuss patient evaluation, variables that may influence reversal success rates, factors to consider in choosing to perform vasovasostomy versus vasoepididymostomy, and the usefulness of vasectomy reversal to alleviate postvasectomy pain syndrome. We also review the use of robotics for vasectomy reversal and other novel techniques and instrumentation that have emerged in recent years to aid in the success of this surgery.
14. An investigation of desalination by nanofiltration, reverse osmosis and integrated (hybrid NF/RO) membranes employed in brackish water treatment.
Science.gov (United States)
Talaeipour, M; Nouri, J; Hassani, A H; Mahvi, A H
2017-01-01
As an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran. This study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na +1 and Cl -1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied. Results showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in
15. Crystal structures of HIV-1 nonnucleoside reverse transcriptase inhibitors: N-benzyl-4-methyl-benzimidazoles
Science.gov (United States)
Ziółkowska, Natasza E.; Michejda, Christopher J.; Bujacz, Grzegorz D.
2009-07-01
HIV-1 nonnucleoside reverse transcriptase inhibitors are potentially specific and effective drugs in AIDS therapy. The presence of two aromatic systems with an angled orientation in the molecule of the inhibitor is crucial for interactions with HIV-1 RT. The inhibitor drives like a wedge into the cluster of aromatic residues of RT HIV-1 and restrains the enzyme in a conformation that blocks the chemical step of nucleotide incorporation. Structural studies provide useful information for designing new, more active inhibitors. The crystal structures of four NNRTIs are presented here. The investigated compounds are derivatives of N-benzyl-4-methyl-benzimidazole with various aliphatic and aromatic substituents at carbon 2 positions and a 2,6-dihalogeno-substituted N-benzyl moiety. Structural data reported here show that the conformation of the investigated compounds is relatively rigid. Such feature is important for the nonnucleoside inhibitor binding to HIV-1 reverse transcriptase.
16. Discovery of Rapid and Reversible Water Insertion in Rare Earth Sulfates: A New Process for Thermochemical Heat Storage.
Science.gov (United States)
Hatada, Naoyuki; Shizume, Kunihiko; Uda, Tetsuya
2017-07-01
Thermal energy storage based on chemical reactions is a prospective technology for the reduction of fossil-fuel consumption by storing and using waste heat. For widespread application, a critical challenge is to identify appropriate reversible reactions that occur below 250 °C, where abundant low-grade waste heat and solar energy might be available. Here, it is shown that lanthanum sulfate monohydrate La 2 (SO 4 ) 3 ⋅H 2 O undergoes rapid and reversible dehydration/hydration reactions in the temperature range from 50 to 250 °C upon heating/cooling with remarkably small thermal hysteresis (water is removed from, or inserted in La 2 (SO 4 ) 3 ⋅H 2 O with progressive change in hydration number x without phase change. It is also revealed that only a specific structural modification of La 2 (SO 4 ) 3 exhibits this reversible dehydration/hydration behavior. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
17. Reversible deep storage: reversibility options for storage in deep geological formations
International Nuclear Information System (INIS)
2009-01-01
This report describes the definition approach to reversibility conditions, presents the main characteristics of high-activity and intermediate-activity long-lived wastes, describes the storage in deep geological formations (safety functions, general description of the storage centre), discusses the design options for the different types of wastes (container, storage module, handling processes, phenomenological analysis, monitoring arrangements) and the decision process in support reversibility (steering of the storage process, progressive development and step-by-step closing), and reports and discusses the researches concerning the memory of the storage site
18. Status of time reversal invariance
International Nuclear Information System (INIS)
Henley, E.M.
1989-01-01
Time Reversal Invariance is introduced, and theories for its violation are reviewed. The present experimental and theoretical status of Time Reversal Invariance and tests thereof will be presented. Possible future tests will be discussed. 30 refs., 2 figs., 1 tab
19. Do High School Chemistry Examinations Inhibit Deeper Level Understanding of Dynamic Reversible Chemical Reactions?
Science.gov (United States)
Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.
2012-01-01
Background and purpose: Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers…
20. Towards a reversible functional language
DEFF Research Database (Denmark)
Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert
2012-01-01
/equality operator also simplifies inverse computation and program inversion. We discuss the advantages of a reversible functional language using example programs, including run-length encoding. Program inversion is seen to be as lightweight as for imperative reversible languages and realized by recursive descent...
1. How decision reversibility affects motivation
NARCIS (Netherlands)
Bullens, L.; van Harreveld, F.; Förster, J.; Higgins, T.E.
2014-01-01
The present research examined how decision reversibility can affect motivation. On the basis of extant findings, it was suggested that 1 way it could affect motivation would be to strengthen different regulatory foci, with reversible decision making, compared to irreversible decision making,
2. Reversible networks in supramolecular polymers
NARCIS (Netherlands)
Havermans - van Beek, D.J.M.
2007-01-01
Non–covalent interactions between low molecular weight polymers form the basis of supramolecular polymers. The material properties of such polymers are determined by the strength and lifetime of the non–covalent reversible interactions. Due to the reversibility of the interactions between the low
3. Capillary microreactors for lactic acid extraction: experimental and modelling study
NARCIS (Netherlands)
Susanti, Susanti; Winkelman, Jozef; Schuur, Boelo; Heeres, Hero; Yue, Jun
2015-01-01
Lactic acid is an important biobased chemical and, among others, is used for the production of poly-lactic acid. Down-stream processing using state of the art technology is energy intensive and leads to the formation of large amounts of salts. In this presentation, experimental and modeling studies
4. Sex reversal in vertebrates
OpenAIRE
2016-01-01
This special topic issue of Sexual Development gives an overview of sex reversal in vertebrates, from fishes naturally changing their sex, to rodents escaping the mammalian SRY-determining system. It offers eight up-to-date reviews on specific subjects in sex reversal, considering fishes, amphibians, reptiles, birds, marsupials, and placental mammals, including humans. The broad scope of represented animals makes this ideal for students and researchers, especially those interested in the...
5. Reversible light-mediated compositional and structural transitions between CsPbBr3 and CsPb2Br5 nanosheets.
Science.gov (United States)
Shen, Wei; Ruan, Longfei; Shen, Zhitao; Deng, Zhengtao
2018-03-13
This communication describes a new method to achieve reversible light-induced chemical composition and phase structural transitions from polyvinylpyrrolidone-capped orthorhombic CsPbBr 3 to tetragonal CsPb 2 Br 5 nanosheets or vice versa. This work will deepen our understanding of the controlled synthesis, post-processing, and decomposition pathway of cesium lead halide perovskite nanocrystals.
6. Reversible arithmetic logic unit for quantum arithmetic
DEFF Research Database (Denmark)
Thomsen, Michael Kirkedal; Glück, Robert; Axelsen, Holger Bock
2010-01-01
This communication presents the complete design of a reversible arithmetic logic unit (ALU) that can be part of a programmable reversible computing device such as a quantum computer. The presented ALU is garbage free and uses reversible updates to combine the standard reversible arithmetic...... and logical operations in one unit. Combined with a suitable control unit, the ALU permits the construction of an r-Turing complete computing device. The garbage-free ALU developed in this communication requires only 6n elementary reversible gates for five basic arithmetic-logical operations on two n......-bit operands and does not use ancillae. This remarkable low resource consumption was achieved by generalizing the V-shape design first introduced for quantum ripple-carry adders and nesting multiple V-shapes in a novel integrated design. This communication shows that the realization of an efficient reversible...
7. TECHNOLOGY OF REVERSE-BLAST CORROSION CLEANING OF STEEL SHEETS PRIOR TO LASER CUTTING
Directory of Open Access Journals (Sweden)
A. N. Zguk
2017-01-01
Full Text Available Quality of surface cleaning against corrosion influences on efficiency in realization of a number of technological processes. While using bentonite clays in power fluid reverse-blast cleaning ensures formation of anticorrosion protective coating with light absorbing properties on the cleaned surface and prevents formation of the repeated corrosion. The paper presents results of the investigations pertaining to influence of reverse-blast cleaning parameters of steel sheets on quality of the cleaned surface prior to laser cutting. Processing conditions, applied compositions of power fluid and also properties of the protective film coatings on the cleaned surface have been given in the paper. The paper considers topography, morphology and chemical composition of the given coating while applying complex metal micrographic, X-ray diffraction and electronic and microscopic investigations. A complex of laser cutting (refer to gas lasers with output continuous capacity of 2.5/4.0 kW has been applied for experimental works to evaluate influence of the formed surface quality on efficiency of laser cutting process. Specimens having dimension 120×120 mm, made of steel Ст3пс, with thickness from 3 to 10 mm have been prepared for the experiments. An analysis has shown that the application of reverse-blast cleaning ensures higher speed in laser cutting by a mean of 10–20 %. The investigations have made it possible to determine optimum cleaning modes: distance from a nozzle to the surface to be cleaned, jet velocity, pressure. It has been revealed that after drying of the specimens processed by power fluid based on water with concentrations of bentonite clay and calcined soda a protective film coating with thickness of some 5–7 µm has been formed on the whole cleaned specimen surfaces. Chemical base of the coating has been formed by the elements which are included in the composition of bentonite clay being the basic component of the power fluid.
8. Reverse engineering for quality systems
International Nuclear Information System (INIS)
Nolan, A.J.
1995-01-01
When the age of software engineering began, many companies were faced with a problem of how to support the older, pre-software-engineering, programs. The techniques of reverse engineering and re-engineering were developed to bridge the gap between the past and the present. Although reverse engineering can be used for generating missing documentation, it can also be used as a means to demonstrate quality in these older programs. This paper presents, in the form of a case study, how Rolls-Royce and Associates Limited addressed the quality issues of reverse engineering and re-engineering. (author)
9. Field reversal in mirror machines
International Nuclear Information System (INIS)
Pearlstein, L.D.; Anderson, D.V.; Boozer, A.H.
1978-01-01
This report discusses some of the physics issues anticipated in field-reversed mirrors. The effect of current cancellation due to electrons is described. An estimate is made of the required impurity level to maintain a field-reversed configuration. The SUPERLAYER code is used to simulate the high-β 2XIIB results, and favorable comparisons require inclusion of quasilinear RF turbulence. Impact of a quadrupole field on field-line closure and resonant transport is discussed. A simple self-consistent model of ion currents is presented. Conditions for stability of field-reversed configurations to E x B driven rotations are determined
10. Entropy Generation Minimization for Reverse Water Gas Shift (RWGS Reactors
Directory of Open Access Journals (Sweden)
Lei Zhang
2018-05-01
Full Text Available Thermal design and optimization for reverse water gas shift (RWGS reactors is particularly important to fuel synthesis in naval or commercial scenarios. The RWGS reactor with irreversibilities of heat transfer, chemical reaction and viscous flow is studied based on finite time thermodynamics or entropy generation minimization theory in this paper. The total entropy generation rate (EGR in the RWGS reactor with different boundary conditions is minimized subject to specific feed compositions and chemical conversion using optimal control theory, and the optimal configurations obtained are compared with three reference reactors with linear, constant reservoir temperature and constant heat flux operations, which are commonly used in engineering. The results show that a drastic EGR reduction of up to 23% can be achieved by optimizing the reservoir temperature profile, the inlet temperature of feed gas and the reactor length simultaneously, compared to that of the reference reactor with the linear reservoir temperature. These optimization efforts are mainly achieved by reducing the irreversibility of heat transfer. Optimal paths have subsections of relatively constant thermal force, chemical force and local EGR. A conceptual optimal design of sandwich structure for the compact modular reactor is proposed, without elaborate control tools or excessive interstage equipment. The results can provide guidelines for designing industrial RWGS reactors in naval or commercial scenarios.
11. Photofunctionalization of Titanium: An Alternative Explanation of Its Chemical-Physical Mechanism.
Directory of Open Access Journals (Sweden)
Marco Roy
Full Text Available To demonstrate that titanium implant surfaces as little as 4 weeks from production are contaminated by atmospheric hydrocarbons. This phenomenon, also known as biological ageing can be reversed by UVC irradiation technically known as photofunctionalization. To propose a new model from our experimental evidence to explain how the changes in chemical structure of the surface will affect the adsorption of amino acids on the titanium surface enhancing osteointegration.In our study XPS and AES were used to analyze the effects of UVC irradiation (photofunctionalization in reversing biological ageing of titanium. SEM was used to analyze any possible effects on the topography of the surface.UVC irradiation was able to reverse biological ageing of titanium by greatly reducing the amount of carbon contamination present on the implant surface by up to 4 times, while the topography of the surface was not affected. UVC photon energy reduces surface H2O and increases TiOH with many -OH groups being produced. These groups explain the super-hydrophilic effect from photofunctionalization when these groups come into contact with water.Photofunctionalization has proven to be a valid method to reduce the amount of hydrocarbon contamination on titanium dental implants and improve biological results. The chemisorption mechanisms of amino acids, in our study, are dictated by the chemical structure and electric state present on the surface, but only in the presence of an also favourable geometrical composition at the atomical level.
12. Non-Photolithographic Manufacturing Processes for Micro-Channels Functioned by Micro-Contact-Printed SAMs
Science.gov (United States)
Saigusa, Hiroki; Suga, Yasuo; Miki, Norihisa
In this paper we propose non-photolithographic fabrication processes of micro-fluid channels with patterned SAMs (Self-Assembled-Monolayers). SAMs with a thiol group are micro-contact printed on a patterned Au/Ti layer, which is vapor-deposited through a shadow mask. Ti is an adhesion layer. Subsequently, the micro-channels are formed by bonding surface-activated PDMS onto the silicon substrate via a silanol group, producing a SAMs-functioned bottom wall of the micro-channel. No photolithographic processes are necessary and thus, the proposed processes are very simple, quick and low cost. The micro-reactors can have various functions associated with the micro-contact-printed SAMs. We demonstrate successful manufacturing of micro-reactors with two types of SAMs. The micro-reactor with patterned AUT (11-amino-1-undecanethiol) successfully trapped nano-particles with a carboxylic acid group, indicating that micro-contact-printed SAMs remain active after the manufacturing processes of the micro-reactor. AUT -functioned micro-channels are applicable to bioassay and to immobilize proteins for DNA arrays. ODT (1-octadecanethiol) makes surfaces hydrophobic with the methyl terminal group. When water was introduced into the micro-reactor with ODT-patterned surfaces, water droplets remained only in the hydrophilic areas where ODT was not patterned. ODT -functioned micro-channels are applicable to fluid handling.
13. Sex Reversal in Birds.
Science.gov (United States)
Major, Andrew T; Smith, Craig A
2016-01-01
Sexual differentiation in birds is controlled genetically as in mammals, although the sex chromosomes are different. Males have a ZZ sex chromosome constitution, while females are ZW. Gene(s) on the sex chromosomes must initiate gonadal sex differentiation during embryonic life, inducing paired testes in ZZ individuals and unilateral ovaries in ZW individuals. The traditional view of avian sexual differentiation aligns with that expounded for other vertebrates; upon sexual differentiation, the gonads secrete sex steroid hormones that masculinise or feminise the rest of the body. However, recent studies on naturally occurring or experimentally induced avian sex reversal suggest a significant role for direct genetic factors, in addition to sex hormones, in regulating sexual differentiation of the soma in birds. This review will provide an overview of sex determination in birds and both naturally and experimentally induced sex reversal, with emphasis on the key role of oestrogen. We then consider how recent studies on sex reversal and gynandromorphic birds (half male:half female) are shaping our understanding of sexual differentiation in avians and in vertebrates more broadly. Current evidence shows that sexual differentiation in birds is a mix of direct genetic and hormonal mechanisms. Perturbation of either of these components may lead to sex reversal. © 2016 S. Karger AG, Basel.
14. Reverse engineering of RFID devices
NARCIS (Netherlands)
Bokslag, W.
2015-01-01
This paper discusses the relevance and potential impact of both RFID and reverse engineering of RFID technology, followed by a discussion of common protocols and internals of RFID technology. The focus of the paper is on providing an overview of the different approaches to reverse engineering RFID
15. Extreme reversed sexual dichromatism in a bird without sex role reversal.
Science.gov (United States)
Heinsohn, Robert; Legge, Sarah; Endler, John A
2005-07-22
Brilliant plumage is typical of male birds, reflecting differential enhancement of male traits when females are the limiting sex. Brighter females are thought to evolve exclusively in response to sex role reversal. The striking reversed plumage dichromatism of Eclectus roratus parrots does not fit this pattern. We quantify plumage color in this species and show that very different selection pressures are acting on males and females. Male plumage reflects a compromise between the conflicting requirements for camouflage from predators while foraging and conspicuousness during display. Females are liberated from the need for camouflage but compete for rare nest hollows.
16. Economic impact of reversion
International Nuclear Information System (INIS)
2005-01-01
Estimations of the Norwegian hydropower production and various reversion models' market value have been made. The value of the Norwegian hydropower production until 01.01.2007 is estimated to about Nok 289 billion after taxes, or about 2,42 Nok/kWh medium production, given an expected future electricity price of around 0,25 Nok/kWh and a discount rate at 6,5 percent in nominal terms after taxes. The estimate is slightly above the level of prices for Norwegian hydropower plants in the last 8-10 years. The value of reversion in private plants which today have a limited licence time is estimated to Nok 5,5 billion. The value of reversion in public-owned Norwegian hydropower plants are about Nok 21 billion with a 60 year licence period from 01.01.2007, and about 12 billion for 75 years (ml)
17. Reverse-symmetry waveguides: Theory and fabrication
DEFF Research Database (Denmark)
Horvath, R.; Lindvold, Lars René; Larsen, N.B.
2002-01-01
We present an extensive theoretical analysis of reverse-symmetry waveguides with special focus on their potential application as sensor components in aqueous media and demonstrate a novel method for fabrication of such waveguides. The principle of reverse symmetry is based on making the refractive...... index of the waveguide substrate less than the refractive index of the medium covering the waveguiding film (n(water) = 1.33). This is opposed to the conventional waveguide geometry, where the substrate is usually glass or polymers with refractive indices of approximate to1.5. The reverse configuration...... are combined with air-grooved polymer supports to form freestanding single-material polymer waveguides of reverse symmetry capable of guiding light....
18. Design of a novel quantum reversible ternary up-counter
Science.gov (United States)
Houshmand, Pouran; Haghparast, Majid
2015-08-01
Reversible logic has been recently considered as an interesting and important issue in designing combinational and sequential circuits. The combination of reversible logic and multi-valued logic can improve power dissipation, time and space utilization rate of designed circuits. Only few works have been reported about sequential reversible circuits and almost there are no paper exhibited about quantum ternary reversible counter. In this paper, first we designed 2-qutrit and 3-qutrit quantum reversible ternary up-counters using quantum ternary reversible T-flip-flop and quantum reversible ternary gates. Then we proposed generalized quantum reversible ternary n-qutrit up-counter. We also introduced a new approach for designing any type of n-qutrit ternary and reversible counter. According to the results, we can conclude that applying second approach quantum reversible ternary up-counter is better than the others.
19. An Inert Continuous Microreactor for the Isolation and Analysis of a Single Microbial Cell
Directory of Open Access Journals (Sweden)
Katrin Rosenthal
2015-11-01
Full Text Available Studying biological phenomena of individual cells is enabled by matching the scales of microbes and cultivation devices. We present a versatile, chemically inert microfluidic lab-on-a-chip (LOC device for biological and chemical analyses of isolated microorganisms. It is based on the Envirostat concept and guarantees constant environmental conditions. A new manufacturing process for direct fusion bonding chips with functional microelectrodes for selective and gentle cell manipulation via negative dielectrophoresis (nDEP was generated. The resulting LOC system offered a defined surface chemistry and exceptional operational stability, maintaining its structural integrity even after harsh chemical treatment. The microelectrode structures remained fully functional after thermal bonding and were proven to be efficient for single-cell trapping via nDEP. The microfluidic network consisted solely of glass, which led to enhanced chip reusability and minimized interaction of the material with chemical and biological compounds. We validated the LOC for single-cell studies with the amino acid secreting bacterium Corynebacterium glutamicum. Intracellular l-lysine production dynamics of individual bacteria were monitored based on a genetically encoded fluorescent nanosensor. The results demonstrate the applicability of the presented LOC for pioneering chemical and biological studies, where robustness and chemically inert surfaces are crucial parameters for approaching fundamental biological questions at a single-cell level.
20. Kinematic reversal schemes for the geomagnetic dipole.
Science.gov (United States)
Levy, E. H.
1972-01-01
Fluctuations in the distribution of cyclonic convective cells, in the earth's core, can reverse the sign of the geomagnetic field. Two kinematic reversal schemes are discussed. In the first scheme, a field maintained by cyclones concentrated at low latitude is reversed by a burst of cyclones at high latitude. Conversely, in the second scheme, a field maintained predominantly by cyclones in high latitudes is reversed by a fluctuation consisting of a burst of cyclonic convection at low latitude. The precise fluid motions which produce the geomagnetic field are not known. However, it appears that, whatever the details are, a fluctuation in the distribution of cyclonic cells over latitude can cause a geomagnetic reversal.
1. Reversed phase column extraction studies to recovery of uranium using a modified perlite
International Nuclear Information System (INIS)
Akcay, H.
2006-01-01
Reversed phase column (RPC) extraction chromatography is an useful technique and has been carried out successfully to the separation of various metals and organic compounds. Its application has received considerable attention because it combines the selectivity of LLE with the advantage of chromatography. The efficiency of the separation by RPC depends on both the chemical and physical properties of the solid support and the stationary phase. This work describes the preparation of an improved adsorbent from natural perlite and its properties to uptake of uranyl ion. Perlite is a volcanic glassy rock produced in commercially workable quantities from mines of Aegean region of Turkey and contains 70-75% CO 2 .The CO 2 was converted to soluble silicates with NaOH modification then its acidification to form hydrogen which turned into xerogels upon drying. Fundamental parameters (particle size, specific surface area, pore size and volume, surface hydroxyl group density) were determined for modified perlite and it was silanized then loaded with 20% (w/w) TBP before being used as reversed phase column chromatography solid support. Finally the sorption of UO 2 + 2 from aqueous solutions by the modified perlite was investigated using Batch techniques. The use of TBP-loaded perlite as a reversed phase column (RPC) extraction chromatography support seems to be useful to uptake of UO 2 + 2 from aqueous solutions and to separate from various cations
2. Theory of field-reversed mirrors and field-reversed plasma-gun experiments. Paper IAEA-CN-38/R-2
International Nuclear Information System (INIS)
Anderson, D.V.; Auerbach, S.P.; Berk, H.L.
1980-01-01
Experimental and theoretical studies of field reversal in a mirror machine are reported. Plasma-gun experiments demonstrate that reversed-field plasma layers are formed. Low energy plasma flowing behind the initially produced plasma front prevents tearing of the layer from the gun muzzle. MHD simulation shows that tearing can be obtained by impeding the slow plasma flow with a plasma divider. It is demonstrated theoretically that a field-reversed mirror imbedded in a multipole field can be sustained in steady state with neutral-beam injection even in the absence of impurities. MHD stability analysis shows that growth rates of elongated reversed-field theta-pinch configurations decrease with axial extension, which indicates the importance of including finite Larmor radius in the analysis. Tilting-mode criteria are improved by proper shaping, and a problimak shape is proposed. Tearing mode stability of reversed-field theta-pinches is greatly enhanced by flux exclusion. Self-consistent, 1-1/2-dimensional transport codes have been developed, and initial results are presented
3. Theory of field-reversed mirrors and field-reversed plasma-gun experiments. Paper IAEA-CN-38/R-2
International Nuclear Information System (INIS)
Anderson, D.V.; Auerbach, S.P.; Berk, H.L.
1980-01-01
Experimental and theoretical studies of field reversal in a mirror machine are reported. Plasma-gun experiments demonstrate that reversed-field plasma layers are formed. Low energy plasma flowing behind the initially produced plasma front prevents tearing of the layer from the gun muzzle. MHD simulation shows that tearing can be obtained by impeding the slow plasma flow with a plasma divider. It is demonstrated theoretically that a field-reversed mirror imbedded in a multipole field can be sustained in steady state with neutral-beam injection even in the absence of impurities. MHD stability analysis shows that growth rates of elongated reversed-field theta-pinch configurations decrease with axial extension, which indicates the importance of including finite Larmor radius in the analysis. Tilting-mode criteria are dramatically improved by proper shaping, and a problimak shape is proposed. Tearing mode stability of reversed-field theta-pinches is greatly enhanced by flux exclusion. Self-consistent, 1-1/2-dimensional transport codes have been developed, and initial results are presented
4. Reversible Unfolding of Rhomboid Intramembrane Proteases.
Science.gov (United States)
Panigrahi, Rashmi; Arutyunova, Elena; Panwar, Pankaj; Gimpl, Katharina; Keller, Sandro; Lemieux, M Joanne
2016-03-29
Denaturant-induced unfolding of helical membrane proteins provides insights into their mechanism of folding and domain organization, which take place in the chemically heterogeneous, anisotropic environment of a lipid membrane. Rhomboid proteases are intramembrane proteases that play key roles in various diseases. Crystal structures have revealed a compact helical bundle with a buried active site, which requires conformational changes for the cleavage of transmembrane substrates. A dimeric form of the rhomboid protease has been shown to be important for activity. In this study, we examine the mechanism of refolding for two distinct rhomboids to gain insight into their secondary structure-activity relationships. Although helicity is largely abolished in the unfolded states of both proteins, unfolding is completely reversible for HiGlpG but only partially reversible for PsAarA. Refolding of both proteins results in reassociation of the dimer, with a 90% regain of catalytic activity for HiGlpG but only a 70% regain for PsAarA. For both proteins, a broad, gradual transition from the native, folded state to the denatured, partly unfolded state was revealed with the aid of circular dichroism spectroscopy as a function of denaturant concentration, thus arguing against a classical two-state model as found for many globular soluble proteins. Thermal denaturation has irreversible destabilizing effects on both proteins, yet reveals important functional details regarding substrate accessibility to the buried active site. This concerted biophysical and functional analysis demonstrates that HiGlpG, with a simple six-transmembrane-segment organization, is more robust than PsAarA, which has seven predicted transmembrane segments, thus rendering HiGlpG amenable to in vitro studies of membrane-protein folding. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.
5. Reversible deep disposal
International Nuclear Information System (INIS)
2009-10-01
This presentation, given by the national agency of radioactive waste management (ANDRA) at the meeting of October 8, 2009 of the high committee for the nuclear safety transparency and information (HCTISN), describes the concept of deep reversible disposal for high level/long living radioactive wastes, as considered by the ANDRA in the framework of the program law of June 28, 2006 about the sustainable management of radioactive materials and wastes. The document presents the social and political reasons of reversibility, the technical means considered (containers, disposal cavities, monitoring system, test facilities and industrial prototypes), the decisional process (progressive development and blocked off of the facility, public information and debate). (J.S.)
6. Securing Biometric Images using Reversible Watermarking
OpenAIRE
Thampi, Sabu M.; Jacob, Ann Jisma
2011-01-01
Biometric security is a fast growing area. Protecting biometric data is very important since it can be misused by attackers. In order to increase security of biometric data there are different methods in which watermarking is widely accepted. A more acceptable, new important development in this area is reversible watermarking in which the original image can be completely restored and the watermark can be retrieved. But reversible watermarking in biometrics is an understudied area. Reversible ...
7. Reverse genetics of avian metapneumoviruses
Science.gov (United States)
An overview of avian metapneumovirus (aMPV) infection in turkeys and development of a reverse genetics system for aMPV subgroup C (aMPV-C) virus will be presented. By using reverse genetics technology, we generated recombinant aMPV-C viruses containing a different length of glycoprotein (G) gene or...
8. Design features of a reverse osmosis demonstration plant for treatment of low level radioactive waste
Energy Technology Data Exchange (ETDEWEB)
Shekhar, P; Nath, Sudesh; Gandhi, P M; Mishra, S D [Waste Management Projects Division, Bhabha Atomic Research Centre, Mumbai (India)
1994-06-01
Reverse osmosis, a novel process in the field of nuclear waste management, is under evaluation globally. Its application is basically considered for the treatment of low level waste; yet references are found for its possible use to treat specific intermediate level waste streams, if segregated at source. The process of reverse osmosis (RO) is proposed for use in conjunction with other conventional processes like chemical treatment, ion exchange and evaporation. Flow sheets have been developed wherein RO can come as a replacement of one of these processes or is used as a pre or post treatment stage. The emphasis is on reducing the secondary wastes so as to realize an optimum levelised cost of treatment. This paper outlines the design basis for an RO plant for treating low level radioactive wastes based on the studies carried out on laboratory as well as bench scale. (author). 3 figs., 3 tabs.
9. Design features of a reverse osmosis demonstration plant for treatment of low level radioactive waste
International Nuclear Information System (INIS)
Shekhar, P.; Sudesh Nath; Gandhi, P.M.; Mishra, S.D.
1994-01-01
Reverse osmosis, a novel process in the field of nuclear waste management, is under evaluation globally. Its application is basically considered for the treatment of low level waste; yet references are found for its possible use to treat specific intermediate level waste streams, if segregated at source. The process of reverse osmosis (RO) is proposed for use in conjunction with other conventional processes like chemical treatment, ion exchange and evaporation. Flow sheets have been developed wherein RO can come as a replacement of one of these processes or is used as a pre or post treatment stage. The emphasis is on reducing the secondary wastes so as to realize an optimum levelised cost of treatment. This paper outlines the design basis for an RO plant for treating low level radioactive wastes based on the studies carried out on laboratory as well as bench scale. (author)
10. Reversal permanent charge and reversal potential: case studies via classical Poisson–Nernst–Planck models
International Nuclear Information System (INIS)
Eisenberg, Bob; Liu, Weishi; Xu, Hongguo
2015-01-01
In this work, we are interested in effects of a simple profile of permanent charges on ionic flows. We determine when a permanent charge produces current reversal. We adopt the classical Poisson–Nernst–Planck (PNP) models of ionic flows for this study. The starting point of our analysis is the recently developed geometric singular perturbation approach for PNP models. Under the setting in the paper for case studies, we are able to identify a single governing equation for the existence and the value of the permanent charge for a current reversal. A number of interesting features are established. The related topic on reversal potential can be viewed as a dual problem and is briefly examined in this work too. (paper)
11. THEORETICAL FRAMES FOR DESIGNING REVERSE LOGISTICS PROCESSES
OpenAIRE
Janusz K. Grabara; Sebastian Kot
2009-01-01
Logistics processes of return flow became more and more important in present business practice. Because of better customer satisfaction, environmental and financial aspects many enterprises deal with reverse logistics performance. The paper is a literature review focused on the design principles of reverse logistics processes Keywords: reverse logistics, designing.
12. Reversal of target-specific oral anticoagulants
Science.gov (United States)
2014-01-01
Target-specific oral anticoagulants (TSOACs) provide safe and effective anticoagulation for the prevention and treatment of thrombosis in a variety of clinical settings by interfering with the activity of thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban, edoxaban, betrixaban). Although TSOACs have practical advantages over vitamin K antagonists (VKAs), there are currently no antidotes to reverse their anticoagulant effect. Herein we summarize the available evidence for TSOAC reversal using nonspecific and specific reversal agents. We discuss important limitations of existing evidence, which is derived from studies in human volunteers, animal models and in vitro experiments. Studies evaluating the safety and efficacy of reversal agents on clinical outcomes such as bleeding and mortality in patients with TSOAC-associated bleeding are needed. PMID:24880102
13. Optical reversible programmable Boolean logic unit.
Science.gov (United States)
2012-07-20
Computing with reversibility is the only way to avoid dissipation of energy associated with bit erase. So, a reversible microprocessor is required for future computing. In this paper, a design of a simple all-optical reversible programmable processor is proposed using a polarizing beam splitter, liquid crystal-phase spatial light modulators, a half-wave plate, and plane mirrors. This circuit can perform 16 logical operations according to three programming inputs. Also, inputs can be easily recovered from the outputs. It is named the "reversible programmable Boolean logic unit (RPBLU)." The logic unit is the basic building block of many complex computational operations. Hence the design is important in sense. Two orthogonally polarized lights are defined here as two logical states, respectively.
14. Hidden Randomness between Fitness Landscapes Limits Reverse Evolution
Science.gov (United States)
Tan, Longzhi; Serene, Stephen; Xiao Chao, Hui; Gore, Jeff
2012-02-01
Natural populations must constantly adapt to the ever-changing environment. A fundamental question in evolutionary biology is whether adaptations can be reversed by returning the population to its ancestral environment. Traditionally, reverse evolution is defined as restoring an ancestral phenotype (physical characteristics such as body size), and the classic Dollo's Law has hypothesized the impossibility of reversing complex adaptations. However, this law'' remains ambiguous unless reverse evolution can be studied at the level of genotypes (the underlying genome sequence). We measured the fitness landscapes of a bacterial antibiotic-resistance gene and analyzed the reversibility of evolution as a global, statistical feature of the landscapes. In both experiments and simulations, we find that an adaptation's reversibility declines as the number of mutations it involves increases, suggesting a probabilistic form of Dollo's Law at the molecular level. We also show computationally that slowly switching between environments facilitates reverse evolution in small populations, where clonal interference is negligible or moderate. This is an analogy to thermodynamics, where the reversibility of a physical process is maximized when conditions are modified infinitely slowly.
15. Reverse logistics in the construction industry.
Science.gov (United States)
Hosseini, M Reza; Rameezdeen, Raufdeen; Chileshe, Nicholas; Lehmann, Steffen
2015-06-01
Reverse logistics in construction refers to the movement of products and materials from salvaged buildings to a new construction site. While there is a plethora of studies looking at various aspects of the reverse logistics chain, there is no systematic review of literature on this important subject as applied to the construction industry. Therefore, the objective of this study is to integrate the fragmented body of knowledge on reverse logistics in construction, with the aim of promoting the concept among industry stakeholders and the wider construction community. Through a qualitative meta-analysis, the study synthesises the findings of previous studies and presents some actions needed by industry stakeholders to promote this concept within the real-life context. First, the trend of research and terminology related with reverse logistics is introduced. Second, it unearths the main advantages and barriers of reverse logistics in construction while providing some suggestions to harness the advantages and mitigate these barriers. Finally, it provides a future research direction based on the review. © The Author(s) 2015.
16. Prefix reversals on binary and ternary strings
NARCIS (Netherlands)
Hurkens, C.A.J.; Iersel, van L.J.J.; Keijsper, J.C.M.; Kelk, S.M.; Stougie, L.; Tromp, J.T.
2007-01-01
Given a permutation $\\pi$, the application of prefix reversal $f^{(i)}$ to $\\pi$ reverses the order of the first $i$ elements of $\\pi$. The problem of sorting by prefix reversals (also known as pancake flipping), made famous by Gates and Papadimitriou (Discrete Math., 27 (1979), pp. 47–57), asks for
17. Reversal of laryngotracheal separation in paediatric patients.
LENUS (Irish Health Repository)
Young, Orla
2012-02-01
OBJECTIVE: Laryngotracheal separation (LTS) is an effective and reliable definitive treatment for intractable aspiration. A major advantage of this treatment for intractable aspiration is its\\' potential reversibility. Should the underlying disorder improve, a reversal of the procedure may be attempted. This has been successfully achieved in the adult population. To our knowledge, no previous cases have been reported of successful reversal of LTS in children. METHODS: A retrospective review from 2003 to 2010 identified four cases of intractable aspiration treated with LTS in our department. Two of these patients displayed objective evidence of sufficient recovery of their underlying aspiration to consider reversal. Patient selection for reversal was dependent upon successful oral intake for 9 months along with videofluoroscopic evidence of normal or minimally impaired swallow. RESULTS: Two children who were successfully treated for intractable aspiration with LTS demonstrated objective evidence of recovery sufficient to attempt reversal. Both children underwent successful surgical reversal of LTS using a cricotracheal resection with end-to-end anastamosis, similar to that used in treatment of subglottic stenosis. Both children can now tolerate oral diet and their speech and language development is in line with their overall developmental level. CONCLUSIONS: Laryngotracheal separation is an effective and reliable definitive treatment for intractable aspiration facilitating protection of the airway and allowing safe swallowing with unimpeded respiration, but with the major drawback of loss of phonation. To our knowledge, we document the first two cases of successful LTS reversal in children.
18. Mass transfer with complex chemical reactions in gas–liquid systems : two-step reversible reactions with unit stoichiometric and kinetic orders
NARCIS (Netherlands)
Vas Bhat, R.D.; Kuipers, J.A.M.; Versteeg, G.F.
2000-01-01
An absorption model to study gas–liquid mass transfer accompanied by reversible two-step reactions in the liquid phase has been presented. This model has been used to determine mass transfer rates, enhancement factors and concentration profiles over a wide range of process conditions. Although
19. Bioinspired chemical synthesis of monomeric and dimeric stephacidin A congeners
Science.gov (United States)
Mukai, Ken; de Sant'ana, Danilo Pereira; Hirooka, Yasuo; Mercado-Marin, Eduardo V.; Stephens, David E.; Kou, Kevin G. M.; Richter, Sven C.; Kelley, Naomi; Sarpong, Richmond
2018-01-01
Stephacidin A and its congeners are a collection of secondary metabolites that possess intriguing structural motifs. They stem from unusual biosynthetic sequences that lead to the incorporation of a prenyl or reverse-prenyl group into a bicyclo[2.2.2]diazaoctane framework, a chromene unit or the vestige thereof. To complement biosynthetic studies, which normally play a significant role in unveiling the biosynthetic pathways of natural products, here we demonstrate that chemical synthesis can provide important insights into biosynthesis. We identify a short total synthesis of congeners in the reverse-prenylated indole alkaloid family related to stephacidin A by taking advantage of a direct indole C6 halogenation of the related ketopremalbrancheamide. This novel strategic approach has now made possible the syntheses of several natural products, including malbrancheamides B and C, notoamides F, I and R, aspergamide B, and waikialoid A, which is a heterodimer of avrainvillamide and aspergamide B. Our approach to the preparation of these prenylated and reverse-prenylated indole alkaloids is bioinspired, and may also inform the as-yet undetermined biosynthesis of several congeners.
20. Combining or Separating Forward and Reverse Logistics
DEFF Research Database (Denmark)
Herbert-Hansen, Zaza Nadja Lee; Larsen, Samuel; Nielsen, Anders
2018-01-01
Purpose – While forward logistics handles and manages the flow of goods downstream in the supply chain from suppliers to customers, reverse logistics (RL) manages the flow of returned goods upstream. A firm can combine reverse logistics with forward logistics, keep the flows separated, or choose......-research addresses intra-RL issues while the relationship between forward and reverse logistics is under-researched. This paper contributes to RL-theory by identifying the contextual factors that determine the most advantageous relationship between forward and reverse logistics, and proposes a novel decision making...
1. Parameter dependence of resonant spin torque magnetization reversal
International Nuclear Information System (INIS)
Fricke, L.; Serrano-Guisan, S.; Schumacher, H.W.
2012-01-01
We numerically study ultra fast resonant spin torque (ST) magnetization reversal in magnetic tunneling junctions (MTJ) driven by current pulses having a direct current (DC) and a resonant alternating current (AC) component. The precessional ST dynamics of the single domain MTJ free layer cell are modeled in the macro spin approximation. The energy efficiency, reversal time, and reversal reliability are investigated under variation of pulse parameters like direct and AC current amplitude, AC frequency and AC phase. We find a range of AC and direct current amplitudes where robust resonant ST reversal is obtained with faster switching time and reduced energy consumption per pulse compared to purely direct current ST reversal. However, for a certain range of AC and direct current amplitudes a strong dependence of the reversal properties on AC frequency and phase is found. Such regions of unreliable reversal must be avoided for ST memory applications.
2. Parameter dependence of resonant spin torque magnetization reversal
Science.gov (United States)
Fricke, L.; Serrano-Guisan, S.; Schumacher, H. W.
2012-04-01
We numerically study ultra fast resonant spin torque (ST) magnetization reversal in magnetic tunneling junctions (MTJ) driven by current pulses having a direct current (DC) and a resonant alternating current (AC) component. The precessional ST dynamics of the single domain MTJ free layer cell are modeled in the macro spin approximation. The energy efficiency, reversal time, and reversal reliability are investigated under variation of pulse parameters like direct and AC current amplitude, AC frequency and AC phase. We find a range of AC and direct current amplitudes where robust resonant ST reversal is obtained with faster switching time and reduced energy consumption per pulse compared to purely direct current ST reversal. However, for a certain range of AC and direct current amplitudes a strong dependence of the reversal properties on AC frequency and phase is found. Such regions of unreliable reversal must be avoided for ST memory applications.
3. 21 CFR 177.2550 - Reverse osmosis membranes.
Science.gov (United States)
2010-04-01
... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Reverse osmosis membranes. 177.2550 Section 177... Components of Articles Intended for Repeated Use § 177.2550 Reverse osmosis membranes. Substances identified in paragraph (a) of this section may be safely used as reverse osmosis membranes intended for use in...
4. Prefix reversals on binary and ternary strings
NARCIS (Netherlands)
Hurkens, C.A.J.; van Iersel, L.J.J.; Keijsper, J.C.M.; Kelk, S.M.; Stougie, L.; Tromp, J.T.
2007-01-01
Given a permutation $\\pi$, the application of prefix reversal $f^{(i)}$ to $\\pi$ reverses the order of the first $i$ elements of $\\pi$. The problem of sorting by prefix reversals (also known as pancake flipping), made famous by Gates and Papadimitriou (Discrete Math., 27 (1979), pp. 47–57), asks
5. Reverse innovation in maternal health.
Science.gov (United States)
Firoz, Tabassum; Makanga, Prestige Tatenda; Nathan, Hannah L; Payne, Beth; Magee, Laura A
2017-09-01
Reverse innovation, defined as the flow of ideas from low- to high-income settings, is gaining traction in healthcare. With an increasing focus on value, investing in low-cost but effective and innovative solutions can be of mutual benefit to both high- and low-income countries. Reverse innovation has a role in addressing maternal health challenges in high-income countries by harnessing these innovative solutions for vulnerable populations especially in rural and remote regions. In this paper, we present three examples of 'reverse innovation' for maternal health: a low-cost, easy-to-use blood pressure device (CRADLE), a diagnostic algorithm (mini PIERS) and accompanying mobile app (PIERS on the Move), and a novel method for mapping maternal outcomes (MOM).
6. The effects of environmental chemicals on renal function.
Science.gov (United States)
Kataria, Anglina; Trasande, Leonardo; Trachtman, Howard
2015-10-01
The global incidence of chronic kidney disease (CKD) is increasing among individuals of all ages. Despite advances in proteomics, genomics and metabolomics, there remains a lack of safe and effective drugs to reverse or stabilize renal function in patients with glomerular or tubulointerstitial causes of CKD. Consequently, modifiable risk factors that are associated with a progressive decline in kidney function need to be identified. Numerous reports have documented the adverse effects that occur in response to graded exposure to a wide range of environmental chemicals. This Review summarizes the effects of such chemicals on four aspects of cardiorenal function: albuminuria, glomerular filtration rate, blood pressure and serum uric acid concentration. We focus on compounds that individuals are likely to be exposed to as a consequence of normal consumer activities or medical treatment, namely phthalates, bisphenol A, polyfluorinated alkyl acids, dioxins and furans, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Environmental exposure to these chemicals during everyday life could have adverse consequences on renal function and might contribute to progressive cumulative renal injury over a lifetime. Regulatory efforts should be made to limit individual exposure to environmental chemicals in an attempt to reduce the incidence of cardiorenal disease.
7. Stability of the field-reversed mirror
International Nuclear Information System (INIS)
Morse, E.C.
1979-01-01
The stability of a field reversed mirror plasma configuration is studied with an energy principle derived from the Vlasov equation. Because of finite orbit effects, the stability properties of a field-reversed mirror are different from the stability properties of similar magnetohydrodynamic equilibria. The Vlasov energy principle developed here is applied to a computer simulation of an axisymmetric field-reversed mirror state. It has been possible to prove that the l = 0 modes, called tearing modes, satisfy a sufficient condition for stability. Precessional modes, with l = 1, 2, are found to be unstable at low growth rate. This suggests possible turbulent behavior (Bohm confinement) in the experimental devices aiming at field reversal. Techniques for suppressing these instabilities are outlined, and the applicability of the Vlasov energy principle to more complicated equilibrium models is shown
8. Synthesis of tin monosulfide (SnS) nanoparticles using surfactant free microemulsion (SFME) with the single microemulsion scheme
Science.gov (United States)
Tarkas, Hemant S.; Marathe, Deepak M.; Mahajan, Mrunal S.; Muntaser, Faisal; Patil, Mahendra B.; Tak, Swapnil R.; Sali, Jaydeep V.
2017-02-01
Synthesis of monomorphic, SnS nanoparticles without using a capping agent is a difficult task with chemical route of synthesis. This paper reports on synthesis of tin monosulfide (SnS) nanopartilces with dimension in the quantum-dot regime using surfactant free microemulsion with single microemulsion scheme. This has been achieved by reaction in microreactors in the CME (C: chlorobenzene, M: methanol and E: ethylene glycol) microemulsion system. This is an easy and controllable chemical route for synthesis of SnS nanoparticles. Nanoparticle diameter showed prominent dependence on microemulsion concentration and marginal dependence on microemulsion temperature in the temperature range studied. The SnS nanoparticles formed with this method form stable dispersion in Tolune.
9. Reversible Lithium Neurotoxicity: Review of the Literature
Science.gov (United States)
Netto, Ivan
2012-01-01
Objective: Lithium neurotoxicity may be reversible or irreversible. Reversible lithium neurotoxicity has been defined as cases of lithium neurotoxicity in which patients recovered without any permanent neurologic sequelae, even after 2 months of an episode of lithium toxicity. Cases of reversible lithium neurotoxicity differ in clinical presentation from those of irreversible lithium neurotoxicity and have important implications in clinical practice. This review aims to study the clinical presentation of cases of reversible lithium neurotoxicity. Data Sources: A comprehensive electronic search was conducted in the following databases: MEDLINE (PubMed), 1950 to November 2010; PsycINFO, 1967 to November 2010; and SCOPUS (EMBASE), 1950 to November 2010. MEDLINE and PsycINFO were searched by using the OvidSP interface. Study Selection: A combination of the following search terms was used: lithium AND adverse effects AND central nervous system OR neurologic manifestation. Publications cited include articles concerned with reversible lithium neurotoxicity. Data Extraction: The age, sex, clinical features, diagnostic categories, lithium doses, serum lithium levels, precipitating factors, and preventive measures of 52 cases of reversible lithium neurotoxicity were extracted. Data Synthesis: Among the 52 cases of reversible lithium neurotoxicity, patients ranged in age from 10 to 80 years and a greater number were female (P = .008). Most patients had affective disorders, schizoaffective disorders, and/or depression (P lithium levels were less than or equal to 1.5 mEq/L (P lithium, underlying brain pathology, abnormal tissue levels, specific diagnostic categories, and elderly populations were some of the precipitating factors reported for reversible lithium neurotoxicity. The preventive measures were also described. Conclusions: Reversible lithium neurotoxicity presents with a certain clinical profile and precipitating factors for which there are appropriate
10. Reversible lithium neurotoxicity: review of the literatur.
Science.gov (United States)
Netto, Ivan; Phutane, Vivek H
2012-01-01
Lithium neurotoxicity may be reversible or irreversible. Reversible lithium neurotoxicity has been defined as cases of lithium neurotoxicity in which patients recovered without any permanent neurologic sequelae, even after 2 months of an episode of lithium toxicity. Cases of reversible lithium neurotoxicity differ in clinical presentation from those of irreversible lithium neurotoxicity and have important implications in clinical practice. This review aims to study the clinical presentation of cases of reversible lithium neurotoxicity. A comprehensive electronic search was conducted in the following databases: MEDLINE (PubMed), 1950 to November 2010; PsycINFO, 1967 to November 2010; and SCOPUS (EMBASE), 1950 to November 2010. MEDLINE and PsycINFO were searched by using the OvidSP interface. A combination of the following search terms was used: lithium AND adverse effects AND central nervous system OR neurologic manifestation. Publications cited include articles concerned with reversible lithium neurotoxicity. The age, sex, clinical features, diagnostic categories, lithium doses, serum lithium levels, precipitating factors, and preventive measures of 52 cases of reversible lithium neurotoxicity were extracted. Among the 52 cases of reversible lithium neurotoxicity, patients ranged in age from 10 to 80 years and a greater number were female (P = .008). Most patients had affective disorders, schizoaffective disorders, and/or depression (P lithium levels were less than or equal to 1.5 mEq/L (P lithium, underlying brain pathology, abnormal tissue levels, specific diagnostic categories, and elderly populations were some of the precipitating factors reported for reversible lithium neurotoxicity. The preventive measures were also described. Reversible lithium neurotoxicity presents with a certain clinical profile and precipitating factors for which there are appropriate preventive measures. This recognition will help in early diagnosis and prompt treatment of
11. Mass transfer with complex chemical reactions in gas-liquid systems: two-step reversible reactions with unit stoichiometric and kinetic orders
NARCIS (Netherlands)
Vas bhat, R.D.; Kuipers, J.A.M.; Versteeg, Geert
2000-01-01
An absorption model to study gas¿liquid mass transfer accompanied by reversible two-step reactions in the liquid phase has been presented. This model has been used to determine mass transfer rates, enhancement factors and concentration profiles over a wide range of process conditions. Although
12. Utility of reversed phase high performance liquid chromatography for on-line yield determination of radiochemical separations: Studies with cobalt
International Nuclear Information System (INIS)
Subramanian, S.; Woittiez, J.R.W.
1993-01-01
This article indicates the potentials of high performance liquid chromatography (HPLC) as a radiochemical technique for multielement separation of neutron irradiated samples. The focus lies on the convenience to use the detector signal of the eluted components to indicate the chemical yield of the analyte, which has often proved to be a crucial step in radiochemical separations. Two signals have been utilized. The UV signal of the metal-ligand complexes separated by reversed phase HPLC and the radioactive response as a result of sample irradiation of carrier-tracer addition. Change in ratio is discussed between the two signals, if any, for a specific sample. Losses of metal as much as 65% were simulated and corrected using the individual UV response. The method promises improved accuracy for elemental analysis despite losses suffered during the various chemical steps. The procedure omits the necessity of additional analytical steps for yield determination. The present article aims at the chromatographic part of the study. Cobalt as cobalt diethyldithiocarbamate has been used to demonstrate the viability of the concept. The separation was developed on c C18 reverse phase analytical column and optimized on a semi preparative one
13. Preparation and characterization of a new microwave immobilized poly(2-phenylpropyl)methylsiloxane stationary phase for reversed phase high-performance liquid chromatography.
Science.gov (United States)
Begnini, Fernanda R; Jardim, Isabel C S F
2013-07-05
A new reversed phase high-performance liquid chromatography (RP-HPLC) stationary phase was prepared and its chromatographic and physical-chemical properties were evaluated. The new stationary phase was prepared with a silica support and poly(2-phenylpropyl)methylsiloxane (PPPMS), a phenyl type polysiloxane copolymer. Since this is a new copolymer and there is little information in the literature, it was submitted to physical-chemical characterization by infrared spectroscopy and thermogravimetry. The chromatographic phase was prepared through sorption and microwave immobilization of the copolymer onto a silica support. The chromatographic performance was evaluated by employing test procedures suggested by Engelhardt and Jungheim, Tanaka and co-workers, Neue, and Szabó and Csató. These test mixtures provide information about the hydrophobic selectivity, silanophilic activity, ion-exchange capacity, shape selectivity and interaction with polar analytes of the new Si-PPPMS reversed phase. Stability tests were developed using accelerated aging tests under both basic and acidic conditions to provide information about the lifetime of the packed columns. Copyright © 2013 Elsevier B.V. All rights reserved.
14. On flow reversals in Rayleigh-Bénard convection
International Nuclear Information System (INIS)
Chandra, Mani; Verma, Mahendra K
2011-01-01
The dynamics of flow reversals are studied numerically using Fourier mode analysis. Our analysis shows that the Fourier modes represent the large-scale flows accurately. We observe that during the reversals, the amplitude of one of the large-scale modes vanishes, while another mode rises sharply, very similar to the cessation-led reversals observed earlier in experiments and numerical simulations. The Fourier coefficients of the RBC equations obey certain symmetries properties, which dictates which modes change sign in flow reversals. Based on our simulation results and symmetry properties of the Fourier modes, we provide a qualitative explanation for the flow reversals.
15. Clean translation of an imperative reversible programming language
DEFF Research Database (Denmark)
Axelsen, Holger Bock
2011-01-01
We describe the translation techniques used for the code generation in a compiler from the high-level reversible imperative programming language Janus to the low-level reversible assembly language PISA. Our translation is both semantics preserving (correct), in that target programs compute exactly...... the same functions as their source programs (cleanly, with no extraneous garbage output), and efficient, in that target programs conserve the complexities of source programs. In particular, target programs only require a constant amount of temporary garbage space. The given translation methods are generic......, and should be applicable to any (imperative) reversible source language described with reversible flowcharts and reversible updates. To our knowledge, this is the first compiler between reversible languages where the source and target languages were independently developed; the first exhibiting both...
16. Parkinson’s disease managing reversible neurodegeneration
Directory of Open Access Journals (Sweden)
Hinz M
2016-04-01
Full Text Available Marty Hinz,1 Alvin Stein,2 Ted Cole,3 Beth McDougall,4 Mark Westaway5 1Clinical Research, NeuroResearch Clinics, Inc., Cape Coral, FL, 2Stein Orthopedic Associates, Plantation, FL, 3Cole Center for Healing, Cincinnati, OH, 4CLEARCenter of Health, Mill Valley, CA, USA; 5Four Pillars Health, Brendale, QLD, Australia Abstract: Traditionally, the Parkinson’s disease (PD symptom course has been classified as an irreversible progressive neurodegenerative disease. This paper documents 29 PD and treatment-induced systemic depletion etiologies which cause and/or exacerbate the seven novel primary relative nutritional deficiencies associated with PD. These reversible relative nutritional deficiencies (RNDs may facilitate and accelerate irreversible progressive neurodegeneration, while other reversible RNDs may induce previously undocumented reversible pseudo-neurodegeneration that is hiding in plain sight since the symptoms are identical to the symptoms being experienced by the PD patient. Documented herein is a novel nutritional approach for reversible processes management which may slow or halt irreversible progressive neurodegenerative disease and correct reversible RNDs whose symptoms are identical to the patient’s PD symptoms. Keywords: Parkinson’s disease, L-dopa, carbidopa, B6, neurodegeneration
17. AN OVERVIEW ON RETAIL REVERSE LOGISTICS
Directory of Open Access Journals (Sweden)
Ioana Olariu
2014-07-01
Full Text Available This article is a theoretical approach on retail reverse logistics. Environmental concern and the current marketing strategy have spurred retailers to implement strategies to facilitate product returns from end customers. Reverse logistics, indicating the process of this return flow, encompasses such activities as the movement of returned products, facilities to accommodate returned items, and overall remedy process for returned items. The retail industry, under great competitive pressure, has used return policies as a competitive weapon. Grocery retailers were the first to begin to focus serious attention on the problem of returns and to develop reverse logistics innovations. Grocery retailers first developed innovations such as reclamation centers. Reclamation centers, in turn, led to the establishment of centralized return centers. Centralizing returns has led to significant benefits for most firms that have implemented them. Over the last several years, retailers have consolidated. Now, more than ever, reverse logistics is seen as being important. This reverse distribution activity can be crucial to the survival of companies, because the permanent goodwill of the company is at stake. Businesses succeed because they respond to both external and internal changes and adjust in an effective manner to remain competitive.
18. Separation of deuteriated isotopomers of dopamine by ion-pair reversed-phase high-performance liquid chromatography
International Nuclear Information System (INIS)
Masters, C.F.; Markey, S.P.; Mefford, I.N.; Duncan, M.W.
1988-01-01
The ion-pair reversed-phase separation of dopamine and deuterium-substituted dopamine isotopomers is described. Chromatographic parameters and deuterium isotope effects governing the resolution are examined and compared to the factors regulating the resolution are examined and compared to the factors regulating the resolution of the chemically distinct entities dopamine, norepinephrine, and epinephrine. The potential utility of the [ 2 H 7 ]dopamine, isotopomer as an internal standard for the high-performance liquid chromatography analysis of dopamine is demonstrated by using aluminum oxide extraction prior to chromatographic separation
19. Parallelization of Reversible Ripple-carry Adders
DEFF Research Database (Denmark)
Thomsen, Michael Kirkedal; Axelsen, Holger Bock
2009-01-01
The design of fast arithmetic logic circuits is an important research topic for reversible and quantum computing. A special challenge in this setting is the computation of standard arithmetical functions without the generation of \\emph{garbage}. Here, we present a novel parallelization scheme...... wherein $m$ parallel $k$-bit reversible ripple-carry adders are combined to form a reversible $mk$-bit \\emph{ripple-block carry adder} with logic depth $\\mathcal{O}(m+k)$ for a \\emph{minimal} logic depth $\\mathcal{O}(\\sqrt{mk})$, thus improving on the $mk$-bit ripple-carry adder logic depth $\\mathcal... 20. Time reversibility in the quantum frame Energy Technology Data Exchange (ETDEWEB) Masot-Conde, Fátima [Escuela Superior Ingenieros, Dpt. Física Aplicada III, Universidad de Sevilla Isla Mágica, 41092- Sevilla (Spain) 2014-12-04 Classic Mechanics and Electromagnetism, conventionally taken as time-reversible, share the same concept of motion (either of mass or charge) as the basis of the time reversibility in their own fields. This paper focuses on the relationship between mobile geometry and motion reversibility. The goal is to extrapolate the conclusions to the quantum frame, where matter and radiation behave just as elementary mobiles. The possibility that the asymmetry of Time (Time’s arrow) is an effect of a fundamental quantum asymmetry of elementary particles, turns out to be a consequence of the discussion. 1. Effect of Lepidium meyenii (maca) on testicular function of mice with chemically and physically induced subfertility. Science.gov (United States) Valdivia Cuya, M; Yarasca De La Vega, K; Lévano Sánchez, G; Vásquez Cavero, J; Temoche García, H; Torres Torres, L; Cruz Ornetta, V 2016-10-01 The aim of this study was to evaluate the effect of Lepidium meyenii (maca) in chemically and physically subfertile mice. After 35 days, the following groups of mice were evaluated: control, sham, chemical subfertility, chemical subfertility-maca-supplemented, physical subfertility, physical subfertility-maca-supplemented and maca-supplemented only. Motility (32.36% ± 5.34%) and sperm count (44.4 ± 5.37 × 10(6) /ml) in the chemically and physically subfertile mice (11.81% ± 4.06%, 17.34 ± 13.07 × 10(6) /ml) decreased compared to the control (75.53% ± 2.97% and 57.4 ± 19.6 10(6) /ml) and sham (53.5% ± 7.86% and 58.4 ± 14.10 10(6) /ml). Maca was able to reverse the deleterious effect of motility (76.36 ± 1.97) as well as sperm count (53.5 ± 9.18 × 10(6) /ml) on chemical subfertility. In contrast, maca did not reverse the effects of induced physical subfertility nor motility (18.78% ± 14.41%) or sperm count (20.17 ± 11.20 × 10(6) /ml). The percentage of sperm DNA fragmentation in the physically subfertile mice increased (11.1% ± 19.29%) compared to the control (0.84% ± 0.85%). However, in the physically subfertile group, maca decreased sperm DNA fragmentation (2.29% ± 2.30%) closer to the sham (1.04% ± 0.62%) and the control (0.84% ± 0.85%). The group supplemented only with maca showed 0.54% ± 0.50% of spermatozoa with DNA fragmentation. Yet, the differences observed were statistically not significant. In conclusion, it appears that maca activates the cytochrome P450 system after chemically induced subfertility. However, it does not reverse the low mitochondrial membrane potential in spermatozoa compromised in the physical subfertility group. © 2016 Blackwell Verlag GmbH. 2. REVERSED TREND OF RADIAL DISTRIBUTION OF SUBPOPULATIONS IN THE GLOBULAR CLUSTERS NGC 362 AND NGC 6723 Energy Technology Data Exchange (ETDEWEB) Lim, Dongwook; Lee, Young-Wook; Pasquato, Mario [Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 03722 (Korea, Republic of); Han, Sang-Il; Roh, Dong-Goo, E-mail: [email protected], E-mail: [email protected] [Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of) 2016-12-01 Most globular clusters (GCs) are now known to host multiple stellar populations with different abundances of light elements. Here we use narrow-band photometry and low-resolution spectroscopy for NGC 362 and NGC 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC 362 and NGC 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN–CH anticorrelation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak, earlier generation stars compared to the CN-strong, later generation stars. These trends are reversed with respect to those found in previous studies for many other GCs. Our findings, therefore, seem contradictory to the current scenario for the formation of multiple stellar populations, but mass segregation acting on the two subpopulations might be a possible solution to explain this reversed radial trend. 3. Reversible and irreversible heat engine and refrigerator cycles Science.gov (United States) Leff, Harvey S. 2018-05-01 Although no reversible thermodynamic cycles exist in nature, nearly all cycles covered in textbooks are reversible. This is a review, clarification, and extension of results and concepts for quasistatic, reversible and irreversible processes and cycles, intended primarily for teachers and students. Distinctions between the latter process types are explained, with emphasis on clockwise (CW) and counterclockwise (CCW) cycles. Specific examples of each are examined, including Carnot, Kelvin and Stirling cycles. For the Stirling cycle, potentially useful task-specific efficiency measures are proposed and illustrated. Whether a cycle behaves as a traditional refrigerator or heat engine can depend on whether it is reversible or irreversible. Reversible and irreversible-quasistatic CW cycles both satisfy Carnot's inequality for thermal efficiency, η ≤ η C a r n o t . Irreversible CCW cycles with two reservoirs satisfy the coefficient of performance inequality K ≤ K C a r n o t . However, an arbitrary reversible cycle satisfies K ≥ K C a r n o t when compared with a reversible Carnot cycle operating between its maximum and minimum temperatures, a potentially counterintuitive result. 4. Designing Novel Quaternary Quantum Reversible Subtractor Circuits Science.gov (United States) Haghparast, Majid; Monfared, Asma Taheri 2018-01-01 Reversible logic synthesis is an important area of current research because of its ability to reduce energy dissipation. In recent years, multiple valued logic has received great attention due to its ability to reduce the width of the reversible circuit which is a main requirement in quantum technology. Subtractor circuits are between major components used in quantum computers. In this paper, we will discuss the design of a quaternary quantum reversible half subtractor circuit using quaternary 1-qudit, 2-qudit Muthukrishnan-Stroud and 3-qudit controlled gates and a 2-qudit Generalized quaternary gate. Then a design of a quaternary quantum reversible full subtractor circuit based on the quaternary half subtractor will be presenting. The designs shall then be evaluated in terms of quantum cost, constant input, garbage output, and hardware complexity. The proposed quaternary quantum reversible circuits are the first attempt in the designing of the aforementioned subtractor. 5. Intracellular Microreactors as Artificial Organelles to Conduct Multiple Enzymatic Reactions Simultaneously DEFF Research Database (Denmark) Gallardo, Maria Godoy; Labay, Cédric Pierre; Jansman, Michelle M. T. 2017-01-01 The creation of artificial organelles is a new paradigm in medical therapy that aims to substitute for missing cellular function by replenishing a specific cellular task. Artificial organelles tackle the challenge of mimicking metabolism, which is the set of chemical reactions that occur within a... 6. Performance of electrodialysis reversal and reverse osmosis for reclaiming wastewater from high-tech industrial parks in Taiwan: A pilot-scale study. Science.gov (United States) Yen, Feng-Chi; You, Sheng-Jie; Chang, Tien-Chin 2017-02-01 Wastewater reclamation is considered an absolute necessity in Taiwan, as numerous industrial parks experience water shortage. However, the water quality of secondary treated effluents from sewage treatment plants generally does not meet the requirements of industrial water use because of the high inorganic constituents. This paper reports experimental data from a pilot-plant study of two treatment processes-(i) fiber filtration (FF)-ultrafiltration (UF)-reverse osmosis (RO) and (ii) sand filtration (SF)-electrodialysis reversal (EDR)-for treating industrial high conductivity effluents from the Xianxi wastewater treatment plant in Taiwan. The results demonstrated that FF-UF was excellent for turbidity removal and it was a suitable pretreatment process for RO. The influence of two membrane materials on the operating characteristics and process stability of the UF process was determined. The treatment performance of FF-UF-RO was higher than that of SF-EDR with an average desalination rate of 97%, a permeate conductivity of 272.7 ± 32.0, turbidity of 0.183 ± 0.02 NTU and a chemical oxigen demand of <4.5 mg/L. The cost analysis for both processes in a water reclamation plant of 4000 m 3 /d capacity revealed that using FF-UF-RO had a lower treatment cost than using SF-EDR, which required activated carbon filtration as a post treatment process. On the basis of the results in this study, the FF-UF-RO system is recommended as a potential process for additional applications. Copyright © 2016 Elsevier Ltd. All rights reserved. 7. Kirkendall void formation in reverse step graded Si1-xGex/Ge/Si(001) virtual substrates Science.gov (United States) Sivadasan, Vineet; Rhead, Stephen; Leadley, David; Myronov, Maksym 2018-02-01 Formation of Kirkendall voids is demonstrated in the Ge underlayer of reverse step graded Si1-xGex/Ge buffer layers grown on Si(001) using reduced pressure chemical vapour deposition (RP-CVD). This phenomenon is seen when the constant composition Si1-xGex layer is grown at high temperatures and for x ≤ 0.7. The density and size of the spherical voids can be tuned by changing Ge content in the Si1-xGex and other growth parameters. 8. Time reversibility, computer simulation, algorithms, chaos CERN Document Server Hoover, William Graham 2012-01-01 A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful vocabulary and a set of concepts, which allow a fuller explanation of irreversibility than that available to Boltzmann or to Green, Kubo and Onsager. Clear illustration of concepts is emphasized throughout, and reinforced with a glossary of technical terms from the specialized fields which have been combined here to focus on a common theme. The book begins with a discussion, contrasting the idealized reversibility of ba... 9. Development of catalytic microreactors by plasma processes: application to wastewater treatment NARCIS (Netherlands) Da Silva, B.T. 2015-01-01 A key aspect in overcoming the energy and environmental challenges is to improve the efficiency of existing and new processes. Nowadays, almost all major chemicals are produced by catalytic processes. However, a better understanding of the reaction pathways and kinetics is needed. In the field of 10. Ice ages and geomagnetic reversals Science.gov (United States) Wu, Patrick 1992-01-01 There have been speculations on the relationship between climatic cooling and polarity reversals of the earth's magnetic field during the Pleistocene. Two of the common criticisms on this relationship have been the reality of these short duration geomagnetic events and the accuracy of their dates. Champion et al. (1988) have reviewed recent progress in this area. They identified a total of 10 short-duration polarity events in the last 1 Ma and 6 of these events have been found in volcanic rocks, which also have K-Ar dates. Supposing that the speculated relationship between climatic cooling and geomagnetic reversals actually exist, two mechanisms that assume climatic cooling causes short period magnetic reversals will be investigated. These two methods are core-mantle boundary topography and transfer of the rotational energy to the core. 11. Reverse Knowledge Transfer in MNEs DEFF Research Database (Denmark) Mudambi, Ram; Piscitello, Lucia; Rabbiosi, Larissa 2014-01-01 a positive correlation with the extent of reverse knowledge transfers to the parent MNE. Relying on the headquarters-subsidiary view of the MNE, we argue that, beyond a point, increasing subsidiary innovativeness will be associated with lower reverse knowledge transfers. Further, we argue......It is now well recognized that multinational enterprises (MNEs) are differentiated networks wherein subsidiaries vary in terms of their ability to create new knowledge and competencies for their parent groups. In much of this theory, it is taken for granted that subsidiary innovativeness has...... that this relationship is sensitive to the subsidiary entry mode. Using data from a sample of 293 Italian subsidiaries, we find strong support for our hypotheses. In particular, our results confirm that the effect of subsidiary innovativeness on reverse knowledge transfers displays an inverted-U shape... 12. Positioning paper on reversibility International Nuclear Information System (INIS) 2016-01-01 After having recalled the legal framework adopted in 2006 for the deep geological storage of radioactive wastes, and briefly introduced the concept of reversibility, this publication presents the principle of geological storage, presents high and medium level and long life wastes, highlights the ethical necessity to deal with these radioactive wastes, outlines that geological storage is the generally admitted and adopted solution at the international level, and presents additional means implemented for radioactive waste management. It presents the Cigeo project as the technical answer to the issue of radioactive waste storage, describes the Cigeo development process, its current status and its development planning, and justifies the choice of this technical solution, notably from an ethical point of view. It addresses the issue of reversibility and proposes an overview of the various tools and means which aim at guaranteeing this reversibility. Appendices propose figures illustrating the Cigeo project and its development process, and a rather detailed Power Point presentation of the project by the ANDRA (history, object, planning, installations, and so on) 13. Magnetic islands at the field reversal surface in reversed field pinches International Nuclear Information System (INIS) Pinsker, R.I.; Reiman, A.H. 1985-09-01 In the reversed field pinch (RFP), magnetic field perturbations having zero poloidal mode number and any toroidal mode number are resonant at the field reversal surface. Such perturbations are a particular threat to the RFP because of their weak radial dependence at low toroidal mode number, and because the toroidal field ripple is essentially of this type. The widths of the resulting islands are calculated in this paper. The self-consistent plasma response is included through the assumption that the plasma relaxes to a Taylor force-free state. The connection with linear tearing mode theory is established for those limits where arbitrarily large islands result from infinitesimal perturbations. Toroidal effects are considered, and application of the theory to RFP experiments is discussed 14. Reversible logic synthesis methodologies with application to quantum computing CERN Document Server Taha, Saleem Mohammed Ridha 2016-01-01 This book opens the door to a new interesting and ambitious world of reversible and quantum computing research. It presents the state of the art required to travel around that world safely. Top world universities, companies and government institutions are in a race of developing new methodologies, algorithms and circuits on reversible logic, quantum logic, reversible and quantum computing and nano-technologies. In this book, twelve reversible logic synthesis methodologies are presented for the first time in a single literature with some new proposals. Also, the sequential reversible logic circuitries are discussed for the first time in a book. Reversible logic plays an important role in quantum computing. Any progress in the domain of reversible logic can be directly applied to quantum logic. One of the goals of this book is to show the application of reversible logic in quantum computing. A new implementation of wavelet and multiwavelet transforms using quantum computing is performed for this purpose. Rese... 15. Reversible perspective and splitting in time. Science.gov (United States) Hart, Helen Schoenhals 2012-01-01 The element of time--the experience of it and the defensive use of it--is explored in conjunction with the use of reversible perspective as a psychotic defense. Clinical material from a long analysis illustrates how a psychotic patient used the reversible perspective, with its static splitting, to abolish the experience of time. When he improved and the reversible perspective became less effective for him, he replaced it with a more dynamic splitting mechanism using time gaps. With further improvement, the patient began to experience the passage of time, and along with it the excruciating pain of separation, envy, and loss. 16. Refractory reverse amblyopia with atropine penalization Directory of Open Access Journals (Sweden) Preeti Ajit Patil 2010-01-01 Full Text Available Pharmacological penalization with atropine has been shown to be equally effective as conventional occlusion therapy in the treatment of amblyopia in children. Reverse amblyopia of the sound eye with atropine penalization has been reported before, but is more common in cases where the effect is augmented with optical penalization and is mostly reversible. We report a case of reverse amblyopia with atropine penalization, in a 4-year-old girl, which was refractory to treatment. This report highlights the need for strict monitoring of the vision in the sound eye and regular follow-up in children undergoing amblyopia treatment. 17. Tandem mirror and field-reversed mirror experiments Energy Technology Data Exchange (ETDEWEB) Coensgen, F.H.; Simonen, T.C.; Turner, W.C. 1979-08-21 This paper is largely devoted to tandem mirror and field-reversed mirror experiments at the Lawrence Livermore Laboratory (LLL), and briefly summarizes results of experiments in which field-reversal has been achieved. In the tandem experiment, high-energy, high-density plasmas (nearly identical to 2XIIB plasmas) are located at each end of a solenoid where plasma ions are electrostatically confined by the high positive poentials arising in the end plug plasma. End plug ions are magnetically confined, and electrons are electrostatically confined by the overall positive potential of the system. The field-reversed mirror reactor consists of several small field-reversed mirror plasmas linked together for economic reasons. In the LLL Beta II experiment, generation of a field-reversed plasma ring will be investigated using a high-energy plasma gun with a transverse radial magnetic field. This plasma will be further heated and sustained by injection of intense, high-energy neutral beams. 18. Estimation and uncertainty of reversible Markov models. Science.gov (United States) Trendelkamp-Schroer, Benjamin; Wu, Hao; Paul, Fabian; Noé, Frank 2015-11-07 Reversibility is a key concept in Markov models and master-equation models of molecular kinetics. The analysis and interpretation of the transition matrix encoding the kinetic properties of the model rely heavily on the reversibility property. The estimation of a reversible transition matrix from simulation data is, therefore, crucial to the successful application of the previously developed theory. In this work, we discuss methods for the maximum likelihood estimation of transition matrices from finite simulation data and present a new algorithm for the estimation if reversibility with respect to a given stationary vector is desired. We also develop new methods for the Bayesian posterior inference of reversible transition matrices with and without given stationary vector taking into account the need for a suitable prior distribution preserving the meta-stable features of the observed process during posterior inference. All algorithms here are implemented in the PyEMMA software--http://pyemma.org--as of version 2.0. 19. Chemicals as the Sole Transformers of Cell Fate. Science.gov (United States) Ebrahimi, Behnam 2016-05-30 Forced expression of lineage-specific transcription factors in somatic cells can result in the generation of different cell types in a process named direct reprogramming, bypassing the pluripotent state. However, the introduction of transgenes limits the therapeutic applications of the produced cells. Numerous small-molecules have been introduced in the field of stem cell biology capable of governing self-renewal, reprogramming, transdifferentiation and regeneration. These chemical compounds are versatile tools for cell fate conversion toward desired outcomes. Cell fate conversion using small-molecules alone (chemical reprogramming) has superiority over arduous traditional genetic techniques in several aspects. For instance, rapid, transient, and reversible effects in activation and inhibition of functions of specific proteins are of the profits of small-molecules. They are cost-effective, have a long half-life, diversity on structure and function, and allow for temporal and flexible regulation of signaling pathways. Additionally, their effects could be adjusted by fine-tuning concentrations and combinations of different small-molecules. Therefore, chemicals are powerful tools in cell fate conversion and study of stem cell and chemical biology in vitro and in vivo. Moreover, transgene-free and chemical-only transdifferentiation approaches provide alternative strategies for the generation of various cell types, disease modeling, drug screening, and regenerative medicine. The current review gives an overview of the recent findings concerning transdifferentiation by only small-molecules without the use of transgenes. 20. Thermodynamics in finite time: A chemically driven engine International Nuclear Information System (INIS) Ondrechen, M.J.; Berry, R.S.; Andresen, B. 1980-01-01 The methods of finite time thermodynamics are applied to processes whose relaxation parameters are chemical rate coefficients within the working fluid. The direct optimization formalism used previously for heat engines with friction and finite heat transfer rates: termed the tricycle method: is extended to heat engines driven by exothermic reactions. The model is a flow reactor coupled by a heat exchanger to an engine. Conditions are established for the achievement of maximum power from such a system. Emphasis is on how the chemical kinetics control the finite-time thermodynamic extrema; first order, first order reversible, and second order reaction kinetics are analyzed. For the types of reactions considered here, there is always a finite positive flow rate in the reactor that yields maximum engine power. Maximum fuel efficiency is always attained in these systems at the uninteresting limit of zero flow rate 1. The influence of the "cage effect" on the mechanism of reversible bimolecular multistage chemical reactions in solutions. Science.gov (United States) Doktorov, Alexander B 2015-08-21 Manifestations of the "cage effect" at the encounters of reactants are theoretically treated by the example of multistage reactions in liquid solutions including bimolecular exchange reactions as elementary stages. It is shown that consistent consideration of quasi-stationary kinetics of multistage reactions (possible only in the framework of the encounter theory) for reactions proceeding near reactants contact can be made on the basis of the concepts of a "cage complex." Though mathematically such a consideration is more complicated, it is more clear from the standpoint of chemical notions. It is established that the presence of the "cage effect" leads to some important effects not inherent in reactions in gases or those in solutions proceeding in the kinetic regime, such as the appearance of new transition channels of reactant transformation that cannot be caused by elementary event of chemical conversion for the given mechanism of reaction. This results in that, for example, rate constant values of multistage reaction defined by standard kinetic equations of formal chemical kinetics from experimentally measured kinetics can differ essentially from real values of these constants. 2. Spontaneous direct and reverse osmosis International Nuclear Information System (INIS) Valitov, N.Kh. 1996-01-01 It has been ascertained experimentally that in the course of separation of CsCl, KCl, NaCl aqueous solutions by semi-permeable membrane from distilled water the direct and then reverse osmosis are observed. The same sequence is observed in case of separation of CsCl aqueous solutions from NaCl of different concentrations. The reason for the direct and reverse osmosis has been explained. 5 refs.; 3 figs. 1 tab 3. Sex-Specific Effects of Combined Exposure to Chemical and Non-chemical Stressors on Neuroendocrine Development: a Review of Recent Findings and Putative Mechanisms. Science.gov (United States) Cowell, Whitney J; Wright, Rosalind J 2017-12-01 Environmental toxicants and psychosocial stressors share many biological substrates and influence overlapping physiological pathways. Increasing evidence indicates stress-induced changes to the maternal milieu may prime rapidly developing physiological systems for disruption by concurrent or subsequent exposure to environmental chemicals. In this review, we highlight putative mechanisms underlying sex-specific susceptibility of the developing neuroendocrine system to the joint effects of stress or stress correlates and environmental toxicants (bisphenol A, alcohol, phthalates, lead, chlorpyrifos, and traffic-related air pollution). We provide evidence indicating that concurrent or tandem exposure to chemical and non-chemical stressors during windows of rapid development is associated with sex-specific synergistic, potentiated and reversed effects on several neuroendocrine endpoints related to hypothalamic-pituitary-adrenal axis function, sex steroid levels, neurotransmitter circuits, and innate immune function. We additionally identify gaps, such as the role that the endocrine-active placenta plays, in our understanding of these complex interactions. Finally, we discuss future research needs, including the investigation of non-hormonal biomarkers of stress. We demonstrate multiple physiologic systems are impacted by joint exposure to chemical and non-chemical stressors differentially among males and females. Collectively, the results highlight the importance of evaluating sex-specific endpoints when investigating the neuroendocrine system and underscore the need to examine exposure to chemical toxicants within the context of the social environment. 4. Reversibility of continuous-variable quantum cloning International Nuclear Information System (INIS) Filip, Radim; Marek, Petr; Fiurasek, Jaromir 2004-01-01 We analyze a reversibility of optimal Gaussian 1→2 quantum cloning of a coherent state using only local operations on the clones and classical communication between them and propose a feasible experimental test of this feature. Performing Bell-type homodyne measurement on one clone and anticlone, an arbitrary unknown input state (not only a coherent state) can be restored in the other clone by applying appropriate local unitary displacement operation. We generalize this concept to a partial reversal of the cloning using only local operations and classical communication (LOCC) and we show that this procedure converts the symmetric cloner to an asymmetric cloner. Further, we discuss a distributed LOCC reversal in optimal 1→M Gaussian cloning of coherent states which transforms it to optimal 1→M ' cloning for M ' < M. Assuming the quantum cloning as a possible eavesdropping attack on quantum communication link, the reversibility can be utilized to improve the security of the link even after the attack 5. Ascorbyl radical disproportionation in reverse micellar systems Science.gov (United States) Gębicki, J. L.; Szymańska-Owczarek, M.; Pacholczyk-Sienicka, B.; Jankowski, S. 2018-04-01 Ascorbyl radical was generated by the pulse radiolysis method and observed with the fast kinetic spectrophotometry within reverse micelles stabilized by AOT in n-heptane or by Igepal CO-520 in cyclohexane at different water to surfactant molar ratio, w0. Rate constants for the disproportionation of the ascorbyl radicals were smaller than those for intermicellar exchange for both type of reverse micelles and slower than those in homogeneous aqueous solutions. However, they increased with increasing w0 for AOT/n-heptane system, while they decreased for Igepal CO-520 system. The absorption spectra of ascorbic acid AOT/n-heptane reverse micellar system showed that the "pH" sensed by this molecule is lower than that in respective homogeneous aqueous solutions. The obtained results were rationalized taking into account three main factors (i) preferential location of ascorbic acid molecules in the interfacial region of the both types of reverse micelles; (ii) postulate that the pH of the interface is lower than that of the water pool of reverse micelles and (iii) different structure of the interface of the reverse micelles made by AOT in n-heptane and those formed by Igepal CO-520 I cyclohexane. Some possible consequences of these findings are discussed. 6. Unilever chooses a reverse osmosis system to improve efficiency and save energy Energy Technology Data Exchange (ETDEWEB) Anon 2006-11-15 Rising energy prices have created new energy efficiency practices at Unilever's plant in Rexdale, Ontario. In order to meet an aggressive goal of reducing energy consumption by at least 6 per cent per year, the plant's energy team has implemented and documented 120 projects since 1999, saving more than$4.2 million in energy costs while eliminating 23,000 tonnes of greenhouse gases (GHGs). The team recently consulted with GE Water and Process Technologies to investigate efficiency measures for their steam plant operations. After analyzing the cost of purchasing and treating water used to produce the 218 million pounds of steam that the plant uses each year, GE recommended a reverse osmosis (RO) system to replace the water softeners and chloride anion de-alkalizers that treated the municipal water used throughout the plant. RO is a mechanical process involving the reversal of flow through a semi-permeable membrane from a high salinity solution to a high purity stream on the opposite side of the membrane. Pressure is used as the driving force for the separation. A turnkey system was installed at the plant in 2005, which also recycles process water captured throughout the plant for use as boiler make-up. The RO feed water allows the boilers to operate at 100 feedwater cycles instead of 10, dramatically increasing energy efficiency. By converting to the RO system, the plant is now consuming 13 million gallons less of municipal water and 8 per cent less natural gas, for a total savings of $68,000 and$299,000 respectively per year. The plant is also saving $11,700 in boiler chemicals and$22,000 in commodity softening chemicals. The RO system has also qualified the Rexdale plant for a \$50,000 incentive grant from the City of Toronto for decreased water consumption. It was concluded that while the project has provided financial benefit to Unilever, the company is equally proud of the environmental benefits of the system, which both reduces chemical use and the
7. TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions
Science.gov (United States)
Xu, Xin-sheng; Shi, Lei; Liu, Yi; Ji, Xue-han; Cui, Zhi-feng
2011-04-01
Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H2O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ (3PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3PAQ* by VC is close to the diffusion-controlled value of 1.41 × 108 L/(mol ·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H2O and aerosol OT (AOT)/EG-H2O reversed micelle solutions, 3PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of 3PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3PAQ* by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As.- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3PAQ* from VC.
8. Reverse amblyopia with atropine treatment.
Science.gov (United States)
Hainline, Bryan C; Sprunger, Derek C; Plager, David A; Neely, Daniel E; Guess, Matthew G
2009-01-01
Occlusion, pharmacologic pernalization and combined therapy have been documented in controlled studies to effectively treat amblyopia with few complications. However, there remain concerns about the effectiveness and complications when, as in this case, there are not standardized treatment protocols. A retrospective chart review of 133 consecutive patients in one community based ophthalmology practice treated for amblyopia was performed. Treatments evaluated were occlusion only, atropine penalization, and combination of occlusion and atropine. Reverse amblyopia was defined as having occured when the visual acuity of the sound eye was 3 LogMar units worse than visual acuity of the amblyopia eye after treatment. Improvement in vision after 6 months and 1 year of amblyopia therapy was similar among all three groups: 0.26 LogMar lines and 0.30 in the atropine group, 0.32 and 0.34 in the occlusion group, and 0.24 and 0.32 in the combined group. Eight (6%) patients demonstrated reverse amblyopia. The mean age of those who developed reverse amblyopia was 3.5 years, 1.5 years younger than the mean age of the study population, 7/8 had strabismic amblyopia, 6/8 were on daily atropine and had a mean refractive error of +4.77 diopters in the amblyopic eye and +5.06 diopters in the sound eye. Reverse amblyopia did not occur with occlusion only therapy. In this community based ophthalmology practice, atropine, patching, and combination therapy appear to be equally effective modalities to treat ambyopia. Highly hyperopic patients under 4 years of age with dense, strabismic amblyopia and on daily atropine appeared to be most at risk for development of reverse amblyopia.
9. Conversion of fructose-glucose mixtures to 5-hydroxymethylfurfural (HMF) in a biphasic slug-flow microreactor setup
NARCIS (Netherlands)
Deuss, Peter; Zhang, Zheng; Lubach, Bouke; Hacking, Jasper; Yue, Jun; Heeres, Hero
The production of platform chemicals from lignocellulosic biomass is one of the main targets to enable future sustainable chemical industry.[1][2] 5-hydroxymethylfurfural (HMF) has been identified as one of the most important platform chemicals that can be obtained from the sugar fraction of
10. First passage times for multiple particles with reversible target-binding kinetics
Science.gov (United States)
Grebenkov, Denis S.
2017-10-01
We investigate the first passage problem for multiple particles that diffuse towards a target, partially adsorb there, and then desorb after a finite exponentially distributed residence time. We search for the first time when m particles undergoing such reversible target-binding kinetics are found simultaneously on the target that may trigger an irreversible chemical reaction or a biophysical event. Even if the particles are independent, the finite residence time on the target yields an intricate temporal coupling between particles. We compute analytically the mean first passage time (MFPT) for two independent particles by mapping the original problem to higher-dimensional surface-mediated diffusion and solving the coupled partial differential equations. The respective effects of the adsorption and desorption rates on the MFPT are revealed and discussed.
11. Designing the Reverse Supply Chain
DEFF Research Database (Denmark)
Gobbi, Chiara
2011-01-01
Purpose – The purpose of this paper is to explore the impact of the product residual value (PRV) and the loss of value over time of returned products in the reverse supply chain configuration. It also examines whether or not the distinction of Fisher's functional and innovative products holds...... that allows for recapturing most of the PRV. These notions have then been tested by analyzing two reverse supply chains with a case study research methodology. Findings – The findings show that low PRV is associated with second-class recovery options (recycling and energy recovery) and that high PRV...... is associated with first-class recovery options (reconditioning and remarketing). When the recovery option is recycling, time is not relevant, the primary objective is cost reduction (efficiency), the chain is centralized, and actors and phases of the reverse chain are determined by the specificity...
12. COMPARISON OF SORPTION ENERGTICS FOR HYDROPHOBIC ORGANIC CHEMICALS BY SYNTHETIC AND NATURAL SORBENTS FROM METHANOL/WATER SOLVENT MIXTURES
Science.gov (United States)
Reversed-phase liquid chromatography (RPLC) was used to investigate the thermodynamics and mechanisms of hydrophobic organic chemical (HOC) retention from methanol/water solvent mixtures. The enthalpy-entropy compensation model was used to infer that the hydro- phobic sorptive me...
13. Yield of Peas Treated with Compost and Chemical Fertilizer Using 15N Technique
International Nuclear Information System (INIS)
El-Degwy, S.M.A.
2011-01-01
A field experiment was carried out to evaluate the yield of peas treated with organic compost and mineral N fertilizer under sandy soil conditions. The obtained results showed that all the tested vegetative growth parameters, i.e. fresh and dry weight of leaves, root and pods of pea plants, were significantly increased with increasing the levels of mineral N fertilizer from 20 up to 50 kg N ha-1 either solely or in combination with compost. Nitrogen, phosphorus and potassium uptake by pea plants were ranked as follow: chemical N fertilize > compost + chemical N fertilize > compost. Organic additives either alone or in combination with chemical fertilizer had enhanced Ndff uptake by pods over aerial parts and roots while reversible trend was noticed with sole application of chemical fertilizer. Nitrogen derived from compost (Ndfc) and uptake by aerial parts followed by pods were enhanced by addition of organic plus chemical fertilizers comparable to sole addition of organic compost. In other term, chemical fertilizer had enhanced the portion of N derived from organic compost
14. Flux trapping during field reversal in a field reversed theta pinch
International Nuclear Information System (INIS)
Milroy, R.D.; Hoffman, A.L.; Slough, J.T.; Harding, D.G.
1983-01-01
In this paper we present new results from both numerical and experimental studies of the formation of the conducting sheath near the tube wall and its effectiveness in trapping bias flux during field reversal
15. Electrochemical reversibility of reticulated vitreous carbon electrodes heat treated at different carbonization temperatures
Directory of Open Access Journals (Sweden)
Emerson Sarmento Gonçalves
2006-06-01
Full Text Available Electrochemical response of ferri/ferrocyanide redox couple is discussed for a system that uses reticulated vitreous carbon (RVC three dimensional electrodes prepared at five different Heat Treatment Temperatures (HTT in the range of 700 °C to 1100 °C. Electrical resistivity, scanning electron microscopy and X ray Diffraction analyses were performed for all prepared samples. It was observed that the HTT increasing promotes an electrical conductivity increasing while the Bragg distance d002 decreases. The correlation between reversibility behavior of ferri/ferrocyanide redox couple and both surface morphology and chemical properties of the RVC electrodes demonstrated a strong dependence on the HTT used to prepare the RVC.
16. Time-reversal symmetry breaking in quantum billiards
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Florian
2009-01-26
The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally
17. Time-reversal symmetry breaking in quantum billiards
International Nuclear Information System (INIS)
Schaefer, Florian
2009-01-01
The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally
18. Application of industrial CT in reverse engineering technology
International Nuclear Information System (INIS)
Fang Liyong; Li Hui; Bai Jinping; Li Bailin
2013-01-01
The basic principle and basic steps of reverse engineering technology based on industrial CT are described. The recent research progresses and situation at home and abroad of reverse engineering technology based on industrial CT image are respectively described, analyzed and summarized from two routes which are surface segmentation and volume segmentation. An example of conch is used to exhibit the results from the two routes in reverse engineering technology based on industrial CT image. Finally, some difficulties in application and the future developments of reverse engineering technology based on industrial CT are prospected. (authors)
19. One- and two-dimensional chemical exchange nuclear magnetic resonance studies of the creatine kinase catalyzed reaction
International Nuclear Information System (INIS)
Gober, J.R.
1988-01-01
The equilibrium chemical exchange dynamics of the creatine kinase enzyme system were studied by one- and two-dimensional 31 P NMR techniques. Pseudo-first-order reaction rate constants were measured by the saturation transfer method under an array of experimental conditions of pH and temperature. Quantitative one-dimensional spectra were collected under the same conditions in order to calculate the forward and reverse reaction rates, the K eq , the hydrogen ion stoichiometry, and the standard thermodynamic functions. The pure absorption mode in four quadrant two-dimensional chemical exchange experiment was employed so that the complete kinetic matrix showing all of the chemical exchange process could be realized
20. CO2 Dissociation by Low Current Gliding Discharge in the Reverse Vortex Flow
Science.gov (United States)
Gutsol, Alexander
2012-10-01
If performed with high energy efficiency, plasma-chemical dissociation of carbon dioxide can be a way of converting and storing energy when there is an excess of electric energy, for example generated by solar elements of wind turbines. CO2 dissociation with efficiency of up to 90% was reported earlier for low pressure microwave discharge in supersonic flow. A new plasma-chemical system uses a low current gliding discharge in the reverse vortex flow of plasma gas. The system is a development of the Gliding Arc in Tornado reactor. The system was used to study dissociation of CO2 in wide ranges of the following experimental parameters: reactor pressure (15-150 kPa), discharge current (50-500 mA), gas flow rate (3-30 liters per minute), and electrode gap length (1-10 cm). Additionally, the effect of thermal energy recuperation on CO2 dissociation efficiency was tested. Plasma chemical efficiency of CO2 dissociation is very low (about 3%) in a short discharge at low pressures (about 15 kPa) when it is defined by electronic excitation. The highest efficiency (above 40%) was reached at pressures 50-70 kPa in a long discharge with thermal energy recuperation. It means that the process is controlled by thermal dissociation with subsequent effective quenching. Plasma chemical efficiency was determined from the data of chromatographic analysis and oscilloscope electric power integration, and also was checked calorimetrically by the thermal balance of the system. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6384692788124084, "perplexity": 6551.959039749393}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-43/segments/1634323588113.25/warc/CC-MAIN-20211027084718-20211027114718-00497.warc.gz"} |
https://socratic.org/questions/how-do-you-list-all-the-prime-numbers-between-80-and-90 | Prealgebra
Topics
# How do you list all the prime numbers between 80 and 90?
Dec 27, 2016
You evaluate the 5 odd numbers from 81 to 89.
#### Explanation:
In division testing you may skip $2$ now, we can also skip $5$ if the number doesn't end in $5$ or $0$
$81 / 3 = 27$ comes out evenly
$83 / 3 = 27$ and 2 left
$83 / 7 = 11$ and 6 left
We don't have to test any further: 83 is prime
$85 / 5 = 19$ comes out evenly
$87 / 3 = 29$ comes out evenly
$89 / 3 = 29$ and 2 left
$89 / 7 = 12$ and 5 left
We don't have to test any further: 89 is prime
Note : We didn't have to test for the next prime 11, because if the number has a factor of 11 or higher, it also has a factor smaller than 11, and we would have found that. The highest prime you test for is smaller/equal to the square root of the number.
Aug 7, 2017
$83 \mathmr{and} 89$
#### Explanation:
To list the prime numbers between $80 \mathmr{and} 90$ we can use the rules of divisibility as a start;
$80 , 81 , \text{ "82," "83," "84," "85," "86," "87," "88," "89," } 90$
All even numbers are divisible 2, they are not prime. apart from $2$
This leaves all the odd numbers.
$81 , \text{ "83," "85," "87," } 89 ,$
A number ending in $5$ is divisible by $5$
$81 , \text{ "83," "87," } 89 ,$
If the sum of the digits is divisible by $3$, $3$ is a factor
$81 \text{ "rarr 8+1=9." }$ 81 is not prime
$83 \text{ "rarr 8+3 = 11" }$ 83 might be prime
$87 \text{ "rarr 8+7=15" }$ 87 is not prime
$89 \text{ "rarr 8+9 = 17" }$89 might be prime
As factors are always in pairs we only need to consider factors less than the square roots.
$\sqrt{83} = 9. \ldots .$
$2 , 3 , 4 , 5 , 6 , 7 , 8 , 9$ are not factors: $83$ is prime
$\sqrt{89} = 9. \ldots . .$
$2 , 3 , 4 , 5 , 6 , 7 , 8 , 9$ are not factors: $89$ is prime
##### Impact of this question
3539 views around the world | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 31, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6105289459228516, "perplexity": 850.5243457926986}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-51/segments/1544376824912.16/warc/CC-MAIN-20181213145807-20181213171307-00629.warc.gz"} |
http://www.r-bloggers.com/2-dimensions-of-portfolio-diversity/ | # 2 dimensions of portfolio diversity
July 16, 2012
By
(This article was first published on Portfolio Probe » R language, and kindly contributed to R-bloggers)
Portfolio diversity is a balancing act.
## Previously
The post “Portfolio diversity” talked about the role of the correlation between assets and the portfolio. The current post fills a hole in that post.
## The 2 dimensions
#### asset-portfolio correlation
Each asset in the universe has a correlation with the portfolio. If there are any assets that have a very high correlation with the portfolio, then the portfolio can not be considered to be well-diversified — it acts like that single asset.
#### risk fraction
If the portfolio returns are strongly driven by a single asset, then the portfolio is not well-diversified. A reasonable measure of that is the fraction of the portfolio variance that each asset accounts for.
Often the weight of the assets has been used. That’s not terrible, but it is an indirect measure of what we really want.
## Examples
We use the same set-up as the previous post.
### Data
We use (almost all of) the S&P 500 constituents as of the start of 2011.
The variance matrix of the assets is a Ledoit-Wolf shrinkage estimate based on daily data during 2010.
### Constraints
We generate a few sets of random portfolios given some constraints. We generate portfolios containing 20 stocks and others containing 200 stocks.
The base constraints for the 20-stock portfolios are:
• long-only
• exactly 20 names
• maximum weight is 10%
• minimum weight is 1%
The base constraints for the 200-name portfolios are:
• long-only
• exactly 200 names
• maximum weight is 1%
• minimum weight is 0.1%
### Pictures
Figures 1 and 2 show the (ex-ante) maximum asset-portfolio correlation versus the maximum variance fraction for random portfolios that were generated with the constraints described above.
Figure 1: Maximum asset-portfolio correlation versus maximum variance fraction for 20-name random portfolios. The maximum weight is limited to 10% but there is one portfolio that has a variance fraction that is well over 20%.
Figure 2: Maximum asset-portfolio correlation versus maximum variance fraction for 200-name random portfolios. We usually think of increasing the number of assets in our portfolio as diversifying. In terms of variance fraction, we see that happening. However, in terms of correlation the effect is slightly towards anti-diversification.
We can try to force such diversification by adding a constraint to make the maximum asset-portfolio correlation no more than 75%. That is easily achieved in the 20-stock portfolios, and the effect on variance fraction is minimal as can be seen in Figure 3.
Figure 3: Distribution of maximum variance fraction for 20-name portfolios: base constraints (blue), base constraints plus maximum correlation no more than 75% (gold). Intriguingly adding the correlation constraint slightly reduces the maximum variance fraction.
In contrast, achieving the correlation constraint in the 200-stock portfolios was more challenging, and has a definite effect on the variance fraction (Figure 4).
Figure 4: Distribution of maximum variance fraction for 200-name portfolios: base constraints (blue), base constraints plus maximum correlation no more than 75% (gold).
## Dimensional connection
How connected are asset-portfolio correlation and variance fraction?
Figures 5 and 6 look at the correlation and variance fraction for each asset in the universe for the random portfolio that happened to be first in each set using only the base constraints.
Figure 5: Asset-portfolio correlation versus asset variance fraction for the first 20-name random portfolio.
Figure 6: Asset-portfolio correlation versus asset variance fraction for the first 200-name random portfolio. The general pattern is a triangle shape. The correlation varies widely for assets not in the portfolio (including the possibility of being the largest correlation). But the minimum possible correlation seems to increase as the variance fraction increases.
Portfolio diversity must be the topic of the day as the post “Diversification and Risk Reduction” just appeared on CSS Analytics.
## Summary
• Portfolio diversity is more interesting than it first appears
• I don’t think diversity has a single dimension
## Appendix R
The computations were done in R.
#### generate random portfolios
The random portfolios are created with the Portfolio Probe software. The command uses a feature that is new in version 1.05, though this analysis could be done (less conveniently) in version 1.04 as well.
The 200-name portfolios were generated with:
require(PortfolioProbe)
div2rp.200w <- random.portfolio(1000, sp5.price10,
sp5.var10, gross=1e7, long.only=TRUE,
max.weight=.01, threshold=1e7 * .001/sp5.price10,
port.size=c(200,200), risk.fraction=list(1,1),
rf.style=c("fraction", "corport"))
The “1000″ is specifying the number of portfolios to be generated. This command “imposes” constraints on the maximum variance fraction and maximum correlation of 1. These are not constraining at all, but they make the next step slightly easier.
The result is a list where each component represents one of the portfolios and gives the number of shares held for each name in that portfolio.
#### retrieve asset statistics
The following command gives us a list where each component contains — for each asset in the universe — the variance fraction and correlation with the portfolio.
div2rp.200w.riskfrac <- randport.eval(div2rp.200w,
keep="risk.fraction")
#### collect maximums
At the moment we just care about the maximum within each portfolio of each of the two quantities. We throw away everything but the maximums and put them into a matrix that is 1000 rows (the number of random portfolios) by 2 columns.
div2rp.200w.max <- do.call('rbind', lapply(
div2rp.200w.riskfrac, function(x)
apply(x\$risk.fraction, 2, max)))
#### constraint difficulty
We can measure how hard adding the 75% correlation constraint was in the 200-name case:
> attr(div2rp.200w75c, "funevals") / attr(div2rp.200w, "funevals")
[1] 205.0481
So the algorithm had to work 200 times harder to find suitable portfolios. The equivalent value for the 20-name portfolios is about 21.
What we’d really like to know is what fraction of the portfolios that obey the base constraints also obey the added constraint. That seems like a challenging thing to learn unless the probability is fairly large. In the case of this particular constraint for 200 names, the probability appears to be much, much less than one in a thousand.
R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more... | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7601543664932251, "perplexity": 3212.782921377424}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-49/segments/1416400379462.60/warc/CC-MAIN-20141119123259-00244-ip-10-235-23-156.ec2.internal.warc.gz"} |
https://ethresear.ch/t/casper-macroeconomic-participation-constraint/217 | # Casper: Macroeconomic Participation Constraint
#1
Link to working draft (includes feedback from @vbuterin in the bottom)
### Casper FFG: Macroeconomic Participation Constraint
tl;dr Given non-zero chance of losing deposits, we can’t assume people will participate as long as yield is positive. To quantify the threshold at which a validator may participate, we make an explicit participation constraint framework. Before diving into game theory, we explore and define the macroeconomic constraints and how that may affect the incentives for the entire validator set on average. Any reward and penalty shape optimization or security parameters that are not in the realm of this analysis has limited significance as this is a key driver of both the global constraints of the network as well as the the pro rata deposit yield as a function of total deposits.
takeaways: [~15% ( \pm 5%)] annualized net yield would be a compelling starting point for discussion. This will be bound by a [~0.5%] gross issuance rate, which bounds the “total deposit capacity” at 6.7% of market capitalization, which is about $2B today (at$30B cap). Any deposit level below that would increase the yield (e.g. $0.2B → 150% annualized net yield), providing strong incentives for joining the validator network. (Those parameters above can be tuned depending on our economic security needs). ### Context A common failure mode in cryptoeconomic analyses will be to take for granted that people want to participate in your mechanism at all (especially while including draconian penalties for bad actors). The unexplored tradeoff there is that many honest/good validators may not be incentivized to validate at all due to the risk of losing part (or all) of their deposits. This analysis in theoretical microeconomics is referred to as a participation constraint analysis. A participation constraint tries to measure if actors will benefit (or at least not be worse off) from participating in a given mechanism. More specifically, for yield functions Y(p_v, ESF, TD) and N(p_v, ESF, TD) (for having voted or not in a checkpoint), this analysis explores \frac{dYield}{dTD} and whether that is compelling enough for validators to participate. In general, we should have an intuition for how enthusiastic people will be about validating. Out of a 100 miners or Ethereum users, how many people will be willing to validate? This will be a large driver of total deposits, the centralization level and even potentially the % of bad actors. The rewards in excess of the participation constraint is the exact margin of safety a mechanism has to enforce additional security measures (i.e. penalties) for bad actors. The margin also compensates for the friction of getting started in a new process to begin with (i.e. “activation energy”). Therefore, even before beginning to shape the specific shapes of the reward and penalties for each type of situation and actors, we must engage in an macroeconomic analyses of a participation constraint for a given validator set (future work will explore game theory among a heterogenous set of validators with various levels of centralization). In other words, is the overall amount of rewards going to be worth the average cost of joining the network as a validator (i.e. risk and illiquidity)? ### Framework # constraint (Net profit from participation) > (Opportunity Cost) # rational model (Net profit) - (opportunity cost) > 0 # behavioral model (Net profit) - (opportunity cost) - (activation energy) > 0 Opportunity cost is yield of comparable assets classes in risk & liquidity level. [Activation energy is a proxy that captures the idea that given two asset classes with similar volatility and liquidity, people will prefer the well-known / more familiar asset class. It’s a proxy for all other risk outside of the traditional asset pricing (i.e. “PoS validation is a new process” rather than “PoS validation yields 8% returns”). Therefore the new asset class has to have excess returns to have parity.]. ### Method Reverse engineering net profit, incremental issuance and “total deposit capacity” 1. Figure out what the risk of loss and illiquidity are for Casper validation. 2. Figure out what the opportunity cost for required return is for the given risk/liquidity profile 3. TODO: Figure out how much more we can provide as a premium (to get over the hump of other activation thresholds etc) 4. Determine the impact of that on the Ethereum economy will be (issuance level and margin of safety vs ideal threshold) ### Opportunity Cost Range Let’s assess opportunity cost to “reverse engineer” the appropriate yield range. Opportunity cost is defined by the yield of an asset with comparable risk (chance of losses) and liquidity. Required returns go up as they have higher risk of loss and become more illiquid. Cost of capital is a spectrum of risk and reward • Inflation (1%) • Treasuries (2%) • Secured mortgages (4%?) • Corporate bonds (5%?) • Sofi personal loans (6-7%?) • US equities (8%?) • High yield bonds (6-10%?) • Real estate (9-12%?) • Private equity, HF, VC (20%?) • Crypto (multiples) These rates are optimized over decades with self-correcting market mechanisms. [Therefore, regardless of the state of whether validating is a “securitized asset,” these define the market’s appetite for risk/reward.] For any given overall reward pool amount, the amount of total deposits will rise and fall to reflect an implicit “risk assessment”. For example, if the yield is too low, people will sell the asset and the price will fall, which will increase the yield (fixed) and vice versa. So the question then becomes, what sort of risk of loss and illiquidity constraints most likely represent the risk level of an Ethereum validator? ### Two approaches to assess Risk & Return 1. Current risk and illiquidity → Define necessary rate of return 2. Liquidity: 4 month lock up 3. Less liquid than stocks, more liquid than real estate 4. Risk: potential of losing [20%+] (group penalties when under attack)… non-zero chance of slashing the whole deposit 5. Riskier than equity, but not as risky as venture? 6. Rate of return → Define risk and illiquidity 7. At 5%: very liquid and low risk of loss 8. At 10%: need to be relatively liquid and have equity level volatility 9. At 15%: can start locking up with liquidity and have non-trivial risk of loss 10. At 20%+: maximal lockup and flexibility to slash with high-volatility ### Assessing Penalty, Illiquidity, and Required Returns #### Illiquidity 4 month withdrawal period puts it some where in between stocks/ETFs/tokens (very liquid) and real estate, HF investments (multi year lock up) • This would suggest ~12-15% yield. (Between 8%-20%) #### Penalty Group penalty (i.e. out of the validator’s control): [~20% annually?] Possibility of being slashed (if there’s a validator client bug for example) (100%-50%-25%) This is a high chance of loss and will require things to yield on the higher end of it’s range. #### Summary So perhaps, high range of the 12-15%: 15% is a good rough starting point for required return for participation. (We will later examine the macroeconomic model to determine how much inflation is required at various validator total deposit levels and whether that is beneficial & sustainable for the ecosystem) ### Issuance #### Etheruem Current Issuance Levels Currently 14.75% inflation rate. Heading down to 10% by 2020. Terminal inflation rate at 1-2%. (source). #### PoS Issuance Levels If partial tx fee burning is net [-0.5-1%] effect, it appears that [0.5%-1%] issuance for Casper is a reasonable starting place for optimizing issuance levels. ### Total Deposits and Total Deposit Capacity #### TD ~ Gross Yield This is a huge factor because having more increases security but also lowers yield. Therefore, any reward scheme and target required return will have an implicit target total deposit rate. (or vice versa). 1. For example, at 1% incremental inflation/issuance and 15% target return and no appreciation:$30B*1% = $300M in available rewards / 15% =$2B in total deposits (~6.7% of market cap… huge).
2. Thought experiment: If reward pool is fixed (and other variables are fixed too), and there are only $200M in total deposits, annualized returns would be 150% (!) (this starts to behave like a fixed income asset / bond) 3. at 0.1% incremental inflation/issuance and 20% target return and no appreciation:$30B*0.1% = $30M in available rewards / 20% =$0.6B in total deposits (~2% of market cap).
4. Thought experiment: if there are only $0.1B in TD, annualized returns would be 120%. #### Bounding TD 1. There should be a minimum stake to secure the network. (future work) • “How much damage could you do if you own the entire validator set?” 1. There exists a maximum: either as (1) a % of the market cap (i.e. it would be unhealthy for [50%] of all ether to be locked up for validation) or (2) implied yield (i.e. at a any given inflation level for reward pool, the yield cannot go below US equities or high yield bonds unless liquidity and risk fall below those). ### Summary As we create a mechanism where significant loss of principal (deposit) is possible, we need to rigorously analyze the participation constraint. Otherwise, we may have a theoretically economically secure mechanism that drives away risk-averse good actors and end up with a disproportionate % of bad actors in the validator set–compromising the security of the network. We explore various opportunity costs in existing asset classes to assess how the market currently rewards various levels of risk and liquidity. We use that discrete curve to approximate a minimum opportunity cost for this mechanism ([~15%]). We build on that by adding on gross incremental issuance that will be “financing” the validation process, which implies a “total deposit capacity” or the max TD that can yield at least the opportunity cost. A lower level of deposits (while TD is growing)–at the same level of issuance with the same opportunity cost–provides a higher yield and a strong incentive for validators to join the system. In other words, the mechanism can have a reward that is significantly higher than the participation constraint (e.g. yield starts at ~50% at lower TD thresholds and asymptotically approaches the ideal target yield of ~[15]%). This analysis can provide the foundation for macroeconomic constraints in the system and define the security thresholds that the network can tolerate. As we continue to define griefing factor analysis and oligopolistic analyses, we can return to confirm or reassess these these assumptions in light of new insights, but it is imperative to realize that validators have a choice in participating. And while some validators may altruistically join to support Ethereum, that is a fragile assumption for building economic security. To the contrary, we should always hope to have incentives in excess of the participation constraint as a margin of safety. #2 tldr Current PoW yields are really high. We might not see as high of TD as are currently shown with target inflation rate of 0.5%. Hey John really great work. Really like the theoretical approach you’ve taken. I wanted to take a look at this by analogy and look from what we have irl rn. We can look at the current rate of return on PoW mining right now. While, the profile of stakers vs miners may be completely different, I wonder if the TD level will be aversely affected with the switch to Casper. We may have less deposits than we have posited, somewhere between 0.1% - 0.5% of TD or 60 - 300M of USD worth of deposits at an inflation target of 0.5%.$300M feels quite low to subvert a $70B dollar chain. The market driven rate of return for the consensus protocol driven returns in relatively stable protocols (BTC, BCC, ETH). The range between 20% (Equities) and Multiples (Cryptos/startups) is very large. The current PoW yield is closer to a startup than an equity, with an estimated yield of 150%–back of envelope math below. Casper with the 4 month lockup is seemingly based on the same risk/reward and liquidity profile of PoW. PoW is potentially even more liquid given I can start mining on some other token if price of token drops. Given the current hash rate, factoring in fixed, variable (electricity), and non-recurring engineering costs such as physical space to find the current yield, outside of appreciation. Right now, given the price of ETH, it’s pretty profitable to mine. I arrive at an estimated yield of 150% per year. Total cost of the network including the aforementioned costs is$3-$5 Billion. Of a security to network value of 5%. This checks out as well, given that the rate of return on a single GPU is around 7.5 months for payback period for an NVIDIA 1070. On various “mining calculator websites.” • Looking at current hashrate gives ~150000 GH/s. a NVIDIA 1070 GTX gives ~30MH/s, so there are approximately 5,000,000 GPUs working to secure ETH. These GPUs each cost$500. If we estimate that overhead expenses are 1.2x of per GPU cost, we arrive at an all in fixed and NRE cost of $3 billion dollars • If each GPU is pushing ~150Wh, Electricity costs are 5,000,000 / 6 * .05 * 24 * 365 or 7,300,000,000 to 10,550,000,000 kwH/y. An all in electricity cost per year of$365,000,000.
• Taking that into account we have $3 -$5.19 Billion / $30 Billion network or a TD Ratio of 11 - 16% • We’re paying out$3,858,570,000 in USD, or 12,861,900 token per year, 13.83% at $300 per Token • Yield of 74 - 100% • At a$700/ETH price, we have $5.19 Billion /$70 Billion network or a TD Ratio of ~4% . This is with the current inflation rate of 15%. Miners currently zero out at 7.5 months, so 4.5 months of profit. This gives a yield of 165-55% hmmm…
• We’re paying out $9,000,000,000 in USD, or 12,861,900 token per year, 13.83% at$700 per Token | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7455898523330688, "perplexity": 3926.929549786707}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-13/segments/1521257647406.46/warc/CC-MAIN-20180320111412-20180320131412-00205.warc.gz"} |
https://scoop.eduncle.com/c-c-2-3-the-vectors-u-3-v2-1-v2-and-v-7-1-22-in-rare-a-linearly-independent-over-r-c-linearly-independent | CSIR NET Follow
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(C) (C 2, 3 The vectors u =3+V2,1 +V2] and v=[7,1 +22 in Rare (a) Linearly independent over R (c) Linearly independent over O t w are Linearly independent vectors, Then consider tha atate (b) Linearly independent over C (d) All of these
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V=(3-√2)u v=ku where k€R so u and v are LD over R and C LI over Q | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8833667039871216, "perplexity": 10210.659704383916}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-27/segments/1656103344783.24/warc/CC-MAIN-20220627225823-20220628015823-00702.warc.gz"} |
http://eprints.ma.man.ac.uk/view/year/2011.html | You are here: MIMS > EPrints
MIMS EPrints
## Year: 2011
Number of items: 126.
## Article
2015.53: Neil Swainston, Kieran Smallbone, Pedro Mendes, Douglas B. Kell and Norman W. Paton (2011) The SuBliMinaL Toolbox: automating steps in the reconstruction of metabolic networks. Journal of Integrative Bioinformatics, 8 (2). 186.
2015.41: FA Kotasidis, JC Matthews, GI Angelis, PJ Noonan, A Jackson, P Price, WR Lionheart and AJ Reader (2011) Single Scan Parameterization of Space-Variant Point Spread Functions in Image Space via a Printed Array: Impact for two PET/CT Scanners. Physics in Medicine and Biology, 56 (10). pp. 2917-2917. ISSN 1361-6560
2014.68: Simon Cotter, Konstantinos Zygalakis, Kevrekidis Ioannis and Radek Erban (2011) A constrained approach to multiscale stochastic simulation of chemically reacting systems. Journal of Chemical Physics, 135.
2013.61: P.E. Haines, R.E. Hewitt and A.L. Hazel (2011) The Jeffery-Hamel similarity solution and its relation to flow in a diverging channel. Journal of Fluid Mechanics, 687. pp. 404-430. ISSN 1469-7645
2013.60: R.E. Hewitt, A.L. Hazel, R.J. Clarke and J.P. Denier (2011) Unsteady flow in a rotating torus after a sudden change in rotation rate. Journal of Fluid Mechanics, 688. pp. 88-119. ISSN 1469-7645
2012.91: E. I. Khukhro, N. Yu. Makarenko and P. Shumyatsky (2011) Frobenius groups of automorphisms and their fixed points. Forum Mathematicum, to appear.
2012.47: D.F. Tang and S. Dobbie (2011) iGen 0.1: the automated generation of a parameterisation of entrainment in marine stratocumulus. Geoscientific Model Development, 4 (3). pp. 797-807.
2012.46: D.F. Tang and S. Dobbie (2011) iGen 0.1: a program for the automated generation of models and parameterisations. Geoscientific Model Development, 4 (3). pp. 785-795.
2012.32: Natasha Willoughby, William J. Parnell, Andrew L. Hazel and I David Abrahams (2011) Homogenization Methods to Approximate the Effective Response of Random Fibre-reinforced Composites. International Journal of Solids and Structures.
2012.25: R.E. Hewitt and P.W. Duck (2011) Pulsatile Jets. Journal of Fluid Mechanics, 670. pp. 240-259.
2011.115: Yuji Nakatsukasa (2011) Gerschgorin's theorem for generalized eigenvalue problems in the Euclidean metric. Mathematics of Computation, 80 (276). pp. 2127-2142. ISSN 1088-6842(e)
2011.97: Natalie J. Stanford and Kieran Smallbone (2011) Kinetic modelling of metabolic pathways. The Bioinformatics Knowledgeblog.
2011.82: Iain Bethune, J. Mark Bull, Nicholas J. Dingle and Nicholas J. Higham (2011) Investigating the Performance of Asynchronous Jacobi's Method for Solving Systems of Linear Equations. To appear in International Journal of High Performance Computing Applications.
2011.75: Geoff Evatt, Paul Johnson, John Moriarty, Duck Peter, Howell Syd and Tonkin Cindy (2011) The Resource Valuation and Optimisation Model: Real Impact from Real Options. Application of Computers and Operational Research in the Mining Industry, Proceedings of the 35th APCOM Symposium. pp. 535-545.
2011.59: H. Dallali, G. Medrano-Cerda and M. Brown (2011) CONTROL OF A COMPLIANT HUMANOID ROBOT IN DOUBLE SUPPORT PHASE: A GEOMETRIC APPROACH. Int. J. of Humanoid Robotics (IJHR).
2011.56: G. O. Jones and M. E. M. Thomas (2011) The density of algebraic points on certain Pfaffian surfaces. The Quarterly Journal of Mathematics.
2011.54: G. O. Jones, D. J. Miller and M. E. M. Thomas (2011) Mildness and the density of rational points on certain transcendental curves. Notre Dame Journal of Formal Logic, 52 (1). pp. 67-74.
2011.46: L.M. Bujorianu and M.C. Bujorianu (2011) State constrained reachability for stochastic hybrid systems. Nonlinear Analysis: Hybrid Systems, 5 (2). pp. 320-342. ISSN 1751-570X
2011.35: Ettore Murabito, Kieran Smallbone, Jonathan Swinton, Hans V. Westerhoff and Ralf Steuer (2011) A probabilistic approach to identify putative drug targets in biochemical networks. Journal of the Royal Society Interface, 8 (59). pp. 880-895.
2011.27: Mark Muldoon, Jeremy Huke and Kieran Smallbone (2011) Dave Broomhead's 60th Birthday. Mathematics Today, 47 (2). pp. 68-69.
2011.18: G. W. Evatt, P. V. Johnson, P. W. Duck, S. D. Howell and J. Moriarty (2011) The Expected Lifetime of an Extraction Project. Proceedings of the Royal Society A, 467 (2125). pp. 244-263. ISSN 1471-2946
2011.16: Nicholas J. Higham (2011) Gaussian Elimination. Wiley Interdisciplinary Reviews: Computational Statistics, 3 (3). pp. 230-238. ISSN 1939-0068
2011.13: Jennifer L. Kirchherr, Jennifer Hamilton, Xiaozhi Lu, S. Gnanakaran, Mark Muldoon, Marcus Daniels, Webster Kasongo, Victor Chalwe, Chanda Mulenga, Lawrence Mwananyanda, Rosemary M. Musonda, Xing Yuan, David C. Montefiori, Bette T. Korber, Barton F. Haynes and Feng Gao (2011) Identification of amino acid substitutions associated with neutralization phenotype in the human immunodeficiency virus type-1 subtype C gp120. Virology, 409 (2). pp. 163-174.
2011.6: Leonid Chekhov and Marta Mazzocco (2011) Isomonodromic deformations and twisted Yangians arising in Teichmüller theory. Advances in Mathematics. ISSN 0001-8708
2010.95: James Montaldi and Miguel Rodriguez-Olmos (2011) On the stability of Hamiltonian relative equilibria with non-trivial isotropy. Nonlinearity, 24 (2011). pp. 2777-2783. ISSN 1749-9097
2010.91: Nicholas J. Higham and Lijing Lin (2011) A Schur--Pad\'e Algorithm for Fractional Powers of a Matrix. SIAM J. on Matrix Analysis and Applications, 32 (3). pp. 1056-1078. ISSN 0895-4798
2010.81: Piotr Kowalczyk, Paul Glendinning, Martin Brown, Gustavo Medrano-Cerda, Houman Dallali and Jonathan Shapiro (2011) Modelling human balance using switched systems with linear feedback control. Journal of the Royal Society Interface. ISSN 1742-5689
2010.75: Howard Elman, Milan Mihajlovic and David Silvester (2011) Fast iterative solvers for buoyancy driven flow problems. Journal of Computational Physics, 230 (10). pp. 3900-3914. ISSN 0021-9991
2010.65: James Montaldi and Tadashi Tokieda (2011) Dynamics of poles with position-dependent strengths and its optical analogues. Physica D, 240. pp. 1636-1643. ISSN 0167-2789
2010.37: David J. Silvester and Valeria Simoncini (2011) An Optimal Iterative Solver for Symmetric Indefinite Systems stemming from Mixed Approximation. ACM Transactions on Mathematical Software, 37 (4). ISSN 1749-9097
2010.30: Awad H. Al-Mohy and Nicholas J. Higham (2011) Computing the Action of the Matrix Exponential, with an Application to Exponential Integrators. SIAM Journal on Scientific Computing, 33 (2). pp. 488-511. ISSN 1064-8275
2010.11: Younès Chahlaoui (2011) Two efficient SVD/Krylov algorithms for model order reduction of large scale systems. Electronic Transactions On Numerical Analysis (ETNA), 38. pp. 113-145. ISSN 1068-9613
2009.51: Laurence Grammont, Nicholas J. Higham and Françoise Tisseur (2011) A Framework for Analyzing Nonlinear Eigenproblems and Parametrized Linear Systems. Linear Algebra and its Applications, 435 (3). pp. 623-640. ISSN 0024-3795
2009.28: Yunjiao Wang, Pawel Paszek, Caroline A. Horton, Douglas B. Kell, Michael R. H. White, David S. Broomhead and Mark R. Muldoon (2011) Interactions among oscillatory pathways in NF-κB signalling. BMC Systems Biology, 5 (1). pp. 1-23. ISSN 1752-0509
2009.21: Nicholas J. Higham and Lijing Lin (2011) On $p$th Roots of Stochastic Matrices. Linear Algebra and its Applications, 435 (3). pp. 448-463. ISSN 1749-9097
2008.57: Marianne Johnson and Ralph Stöhr (2011) Lie powers and pseudo-idempotents. Canadian Mathematical Bulletin, 54 (2). pp. 297-301. ISSN 0008-4395
2005.28: Frederic Laurent-Polz, James Montaldi and Mark Roberts (2011) Point Vortices on the Sphere: Stability of Symmetric Relative Equilibria. Journal of Geometric Mechanics, 3 (4). pp. 439-486. ISSN 1941-4897
## Book
2012.44: L.M. Bujorianu, M. Fisher and C. Pasareanu, ed. (2011) Special Issue: Formal Methods in Aerospace. ANNALS OF MATHEMATICS AND ARTIFICIAL INTELLIGENCE, 63 (1). Springer.
2011.47: Margarita Korovina and Nicolai Vorobjov (2011) Reachability in one-dimensional controlled polynomial dynamical systems. In Proc. The Ershov Informatics Conference, Institute Informaic Systems Press, Russian.
## Book Section
2011.98: P.V. Johnson, G.W. Evatt, P.W. Duck and S Howell (2011) The Determination of a Dynamic Cut-Off Grade for the Mining Industry. In: S.I. Ao and L. Gelman, (eds). Electrical Engineering and Applied Computing. Lecture Notes in Electrical Engineering, 90. Springer, pp. 391-403. ISBN 978-94-007-1192-1
2011.94: Pedro Mendes, Kieran Smallbone and Natalie Stanford (2011) Kinetic modelling of large-scale metabolic networks. In: Proceedings of the 9th International Conference on Computational Methods in Systems Biology. Institut Henri Poincaré, Paris, France. ISBN 978-1-4503-0817-5
2011.76: Kieran Smallbone, Naglis Malys, Hanan L. Messiha, Jill A. Wishart and Evangelos Simeonidis (2011) Building a kinetic model of trehalose biosynthesis in Saccharomyces cerevisiae. In: Daniel Jameson, Malkhey Verma and Hans V. Westerhoff, (eds). Methods in Systems Biology. Methods in Enzymology, 500. Elsevier, pp. 355-370. ISBN 978-0-12-385118-5
2011.68: CTJ Dodson (2011) Some illustrations of information geometry in biology and physics. In: Handbook of Research on Computational Science and Engineering: Theory and Practice. IGI-Global, Hershey, USA, pp. 1-27. ISBN 9781613501160
2011.49: Margarita Korovina and Oleg Kudinov (2011) Algorithmic Properties of Sigma--definability over Positive Predicate Structures. In: Benedikt Löwe, Dag Normann, Ivan Soskov and Alexandra Soskova, (eds). Models of Computation in Context, Proc. 7th Conference on Computability in Europe, CiE 2011. Springer Lecture Notes in Computer Science (6735). Speinger-Verlag, Heidelberg.
2011.48: Margarita Korovina and Oleg Kudinov (2011) The finite Language for Computable Metric Spaces. In: Benedikt Löwe, Dag Normann, Iavn Soskov and Alexandra Soskova, (eds). Models of Computation in Context, Proc. 7th Conference on Computability in Europe, CiE 2011. Springer Lecture Notes in Computer Science (6735). Springer-Verlag, Heidleberg.
## Conference or Workshop Item
2012.13: Puya Afsahr and Hong Wang (2011) Multiobjective Meta-Heuristic Product Scheduling for Multi-Machine Manufacturing Systems. In: 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC), December 12-15, Orlando, FL, USA,.
2012.12: Zakwan Skaf, Ahmad AI-Bayati and Hong Wang (2011) Fault Detection and Diagnosis for General Discrete-time Stochastic Systems Using Output Probability Density Estimation. In: 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC), December 12-15, Orlando, FL, USA,.
2012.11: Zakwan Skaf, Ahmad AI-Bayati and Hong Wang (2011) Minimum Entropy Approach For Robot Manipulator. In: 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC), December 12-15, Orlando, FL, USA,.
2012.10: Zakwan Skaf, Ahmad AI-Bayati, Hong Wang and Aiping Wang (2011) Iterative Fault Tolerant Control Based on Stochastic Distribution. In: 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC), December 12-15, Orlando, FL, USA,.
2011.62: Nicholas Dingle (2011) HydraMP: Exploiting shared memory parallelism in HYDRA with OpenMP. In: 27th UK Performance Engineering Workshop (UKPEW 2011), 7-8 July 2011, Bradford, UK.
2011.52: Younes Chahlaoui (2011) Gramian based model reduction of switched dynamical systems. In: Householder Symposium XVIII on Numerical Linear Algebra, 12-17 June 2011, Tahoe City, CA, US.
2011.51: Younes Chahlaoui (2011) Model Order Reduction or How to make everything as simple as possible but not simpler. In: MAMERN11: 4 th International Conference on Approximation Methods and Numerical Modelling in Environment and Natural Resources, 23-26 May 2011, Saidia, Morocco.
2011.50: Younes Chahlaoui (2011) PVD’s contributions to numerical methods in systems and control. In: 10th IMACS International Symposium on Iterative Methods in Scientific Computing Dedicated to Paul Van Dooren on his 60th Birthday, 18-21 May 2011, Marrakech, Morocco.
2011.33: Shengping Yu, Tianyou Chai, Hong Wang, Xinfu Pang and Binglin Zheng (2011) Dynamic Optimal Scheduling Method and Its Application for Converter Fault in Steelmaking and Continuous Casting Production Process. In: 18th IFAC World Congress, August 28 - September 2, 2011, Milano, Italy.
2011.31: Puya Ghasemi Afshar, Martin Brown, Hong Wang and Jan Maciejowski (2011) Product Scheduling for Thermal Energy Reduction in Papermakig Industries. In: 18th IFAC World Congress, August 28 - September 2, 2011, Milano, Italy.
2011.30: Tianyou Chai, Jinliang Ding and Hong Wang (2011) Multi-Objective Hybrid Intelligent Optimization of Operational Indices for Industrial Processes and Application. In: 18th IFAC World Congress, August 28 - September 2, 2011, Milano, Italy.
2011.28: P Kowalczyk and P.A. Glendinning (2011) Micro-chaos in Relay Feedback Systems with Bang-Bang Control and Digital Sampling. In: IFAC 2011, 28 August - 2 September 2011, Milan, Italy.
## MIMS Preprint
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2011.40: A Moss and C. P. Walkden (2011) Stable topological transitivity properties of Rn-extensions of hyperbolic transformations.
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2011.12: Marcus Tressl (2011) Non-axiomatizability of real spectra in L<sub>∞λ</sub>.
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## Thesis
2012.45: Houman Dallali (2011) MODELLING AND DYNAMIC STABILISATION OF A COMPLIANT HUMANOID ROBOT, CoMan. PhD thesis, The CICADA Project at the School of Mathematics, The University of Manchester.
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2011.109: Qusay Soad Abdul-Aziz Al-Zamil (2011) Algebraic Topology of PDEs. PhD thesis, Manchester Institute for Mathematical Sciences, The University of Manchester.
2011.89: Maha Al-Ammari (2011) Analysis of Structured Polynomial Eigenvalue Problems. PhD thesis, Manchester Institute for Mathematical Sciences, The University of Manchester.
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2011.21: Christopher J. Munro (2011) Algorithms for Matrix Polynomials and Structured Matrix Problems. PhD thesis, Manchester Institute for Mathematical Sciences, The University of Manchester.
2011.9: Lijing Lin (2011) Roots of Stochastic Matrices and Fractional Matrix Powers. PhD thesis, Manchester Institute for Mathematical Sciences, The University of Manchester.
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https://www.physicsforums.com/threads/skin-effect.613289/ | # Skin Effect
1. Jun 11, 2012
### CheyenneXia
Hey I know the conclusion of skin effect since secondary year of school, but I still didnt get it. I know the reason is because of eddy current.
I couldnt include the link here as I havent posted 10 yet. For the link, just search "Skin Effect" at Wikipedia.
First paragraph of the cause in Wikipedia says "The counter EMF is strongest at the center of the conductor, and forces the conducting electrons to the outside of the conductor, as shown in the diagram on the right." I didnt really get it. Why the counter EMF is strongest? Even if it is strongest, why electrons are going to be driven outside? Shouldnt we have to consider about the positive or negetive then decide whether being driven outside or inside?
Also, the explaination of the third picture on the right "Skin depth is due to the circulating eddy currents (arising from a changing H field) cancelling the current flow in the center of a conductor and reinforcing it in the skin." Well, it is true when I in read increases. But what if I decreases, aren't eddy currents in the picture should circulate the opposite direction. By that case, eddy current actually cancel the current flow in the skin and enforce the current in the center!
Also, I believe eddy current is larger in the skin as H is larger compared to it in the center.
I know skin effect is correct. But I do not know why it works that way.
Thanks
2. Jun 13, 2012
### Staff: Mentor
Thread moved to the EE forum for better views. Here is the link you are referring to:
http://en.wikipedia.org/wiki/Skin_effect
.
3. Jun 13, 2012
### the_emi_guy
You are right, the Wiki page is a little misleading on this point. This is not an electrostatic situation where electrons are being forced to move from the center to the edges. "I" is an AC current, the electrons in the conductor are wiggling back and forth (a relatively small distance). The counter EMF is simply impeding the electrons in the center from wiggling, electrons on the skin are free to wiggle. Because fewer electrons in the cross section of the conductor are participating in this dance, the resistance of the conductor is lowered.
Draw out the main current "I", the H field, and the eddy current "Iw" as sinusoids, and bear in mind that they are phase shifted due to the derivatives in Maxwell's equations. For example, when "I" decreases but is still directed upward, the H field will be in the opposite direction, but it will be decreasing in magnitude. This leads to eddy current that opposes "I". (Lenz's Law).
4. Jun 13, 2012
### Antiphon
Eddy currents is a bad description of this phenomenon. Eddies are circular vortex-like motions. This happens to describe the currents that flow when the magnetic field points into the surface. But it doesn't accurately describe the much more common situation of a plane wave striking a metallic surface or the penetration of AC current into a wire- again fields are parallel to, not normal to a surface.
Having established that, the skin depth is controlled by a dissipative phenomenon depending (for finite conductors) on the resistivity of the metal.
The penetration is zero for the ideal conductor and as the resistivity increases the penetration increases. As with any dissipative wave propagation the amplitude decays exponentially.
5. Jun 13, 2012
### CheyenneXia
Hey, EMI Guy, I can understand "The counter EMF is simply impeding the electrons in the center from wiggling", but why "electrons on the skin are free to wiggle"? No counter EMF on the skin? I think there should be. Is it because electrons cannot wiggle as free as in the centre at all directions? "Because fewer electrons in the cross section of the conductor are participating in this dance, the resistance of the conductor is lowered. " I thought the resistance is increased as the effective cross section is smaller. Am I correct?
"when "I" decreases but is still directed upward, the H field will be in the opposite direction, but it will be decreasing in magnitude." If "I" dereases but still directed upward, I thought the original H field is still in the same direction but decreasing in magnitude, which causes eddy current inducing H filed at the same direction of original H. Eddy current here is opposite of the one shown in the graph at wiki page. That's what confused me.
If I am wrong, tell me where. Thanks for your help.
Last edited: Jun 13, 2012
6. Jun 13, 2012
### CheyenneXia
Hey Antiphon, thanks for your help. But I do not really understand your explanation. Do I have to look into "dissipative phenomenon" to understand skin effect?
I know the conclusion of the skin depth and the factors affecting it. But I need to understand the root cause of skin effect.
7. Jun 13, 2012
### Antiphon
That search will probably not help you.
The root cause of the skin effect is that the penetration of fields into conductors takes time. The lower the resistivity of the material, the longer it will take.
For example, work out what the resistivity of a wire would be that had a skin depth of 1 mm at a frequency of 1 Hz.
It will be an almost perfect conductor. Now if you had a long 1 meter thick wire made of it then when you turn on a DC current, at first it will flow along the outside. Slowly the DC current will penetrate into the conductor in exactly the same manner as if heat were penetrating into the side of a cold glass cylinder. After around twenty minutes the current inside would begin to approach the level at the surface.
Now clearly if you apply AC to this wire you can see how the field penetration won't get very far; it would be as if you were alternately heating and cooling the outside of a glass cylinder. If you do it fast enough there will be very little temperature variation going on in the core.
Does that make sense so far?
Ok, the thermal analogy is good but not exact.
In the wire there is in fact induction going on just like the Wikipedia article says but there is also resistive dissipation.
The correct picture looks like an LR circuit where you have a DC voltage source at the left, an inductor at the top, the resistor on the right.
If the resistor is zero, the current in the inductor will steadily increase but you will measure no output voltage on the resistor. If there is a non-zero resistance the voltage will ramp up at a rate governed by the RL time constant (almost the skin effect equation!).
Now the full physically correct circuit analog is an infinite repeating ladder with series inductors and shunt resistors. When you turn on the source, a voltage "front" (measured across the shunt resistors) will "diffuse" through this network.
-That is unless the resistors are zero ohms and then the current will only flow in the first inductor- the "skin" of the LR ladder!
Does this physics make sense to you?
Last edited: Jun 13, 2012
8. Jun 17, 2012
### CheyenneXia
Thanks. I kinda understand it now.
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http://pourlesnotres.fr/9ff3idn/apple-pippin-lcqml/t45w7ss.php?3ed517=derivative-of-vector-with-respect-to-matrix | Who first called natural satellites "moons"? y_{ij} 1 0 obj << /Resources << How would I reliably detect the amount of RAM, including Fast RAM? 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Examples: Let u,x ∈ Rn (column vectors). To learn more, see our tips on writing great answers. �[2{��o �O}�����m�glۣ�M�% 8�X�����^h?\mm ��&*���Dj��o]fGJy}�֥����W.�� Derivative of matrix w.r.t. 1 Simplify, simplify, simplify /Font 50 0 R >> /Parent 2 0 R Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. >> The derivative of a function can be defined in several equivalent ways. What does it mean to “key into” something? \nabla_X f = will denote the m nmatrix of rst-order partial derivatives of the transformation from x to y. /Font 54 0 R You need to provide substantially more information, to allow a clear response. 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So the derivative of a rotation matrix with respect to theta is given by the product of a skew-symmetric matrix multiplied by the original rotation matrix. MathJax reference. endobj /Contents 37 0 R << rev 2020.12.3.38123, The best answers are voted up and rise to the top, Data Science Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us, If you want more, check this thread and PDF from Jeremy Howards and Terrence, $$Bookmark this question. \vdots & \vdots & \vdots \\ >> \nabla_X f = Derivative of a univariate vector is the same as sum of derivatives of its component(Addition rule for differentiation). 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This doesn’t mean matrix derivatives always look just like scalar ones. 18 0 obj << /Contents 43 0 R 1. what is derivative of $\exp(X\beta)$ w.r.t $\beta$ 0. \begin{pmatrix} >> /Contents 49 0 R /MediaBox [0 0 594.95996 840.95996] Tags: derivative differentiation linear algebra linear transformation matrix for a linear transformation matrix representation polynomial vector space Next story A Module is Irreducible if and only if It is a Cyclic Module With Any Nonzero Element as Generator where $x_i$ is the $i^{th}$ element of $X$ and $y_{ij}$ is the $(i,j)^{th}$ element of $Y$. /Parent 2 0 R /rgid (PB:287565444_AS:806976082694146@1569409499594) , $$f =X^T Y looks like this$$ << >> /Parent 2 0 R /Rotate 0 \frac{\partial}{\partial x_1} f_1 & \ldots & \frac{\partial}{\partial x_n} f_1\\ endobj The process of finding a derivative is called differentiation. /Resources << Theorem D.1 (Product dzferentiation rule for matrices) Let A and B be an K x M an M x L matrix, respectively, and let C be the product matrix A B. schizoburger. endobj , $$/MediaBox [0 0 595.2 841.68] /Count 12 I understand differentiation w.r.t one variable, but how does differentiation of another vector/matrix w.r.t a vector work? 19 0 obj /Contents 53 0 R /F6 23 0 R >> >> What does differentiating w.r.t a vector signify? Partial derivatives of scalar with respect to a vector In the … /Parent 2 0 R \frac{\partial}{\partial x_1} f_1 & \ldots & \frac{\partial}{\partial x_n} f_1\\ �^#�O1X��|�b[}[��� ����u�+oc[˹�v����)��V^v�����h��sFJyk��t��K� �-�� ��)&mG��[��Z� JP Ahmed Fathi 163 views. >> \end{pmatrix} /Font 42 0 R /ProcSet [/PDF /ImageB /Text] Because vectors are matrices with only one column, the simplest matrix derivatives are vector derivatives. B For example, if I have components i and xi and xj of the vector x, then the ij element of the Hessian matrix is the pairwise derivatives, order of derivatives, derivative with respect to xi, and derivative with respect to xj, this second derivative is simply 2A. Let x ∈ Rn (a column vector) and let f : Rn → Rm. 5 0 obj Data Science Stack Exchange is a question and answer site for Data science professionals, Machine Learning specialists, and those interested in learning more about the field. 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Cat to let me study his wound rate at with the function changes we... $\beta$ 0 called differentiation what are derivative of vector with respect to matrix consequences it 's still representing the same basis itself -:! How to compute derivative of matrix and vector in $\mathbf { v^TMv }$ 0 and policy. Answer to Data Science derivative of vector with respect to matrix Exchange Inc ; user contributions licensed under cc by-sa matrix.! Transformation ( ) the Kronecker product of a univariate vector is the as! To let me study his wound such a matrix is called differentiation this URL into Your RSS.... It 's still representing the same basis David Prowse ( actor of Darth Vader ) from appearing Star... Without noticing, but one that is very fundamental for the class rate at with the product... Fundamental for the class vector derivatives other answers breakthrough in protein folding, what are the consequences always that! There, is also in Rn the Jacobian as a big 2D matrix let! Can also perform differentiation of a function w.r.t a vector work derivatives derivatives. Contributing an answer to Data Science Stack Exchange Inc ; user contributions licensed under cc by-sa 2... Of expressions with respect to the independent variables of partial derivatives when we feel it vector can be in... '' filmed in Athens what is derivative of a matrix with respect the..., linear regression with white Gaussian noise making statements based on opinion ; back them up with references personal... Variable, but one that is very fundamental for the class w.r.t one variable, but we hate it we! A real-valued function of several variables, the simplest matrix derivatives are vector derivatives someone... And therefore '' in academic writing gradient vector change the variable a... This doesn ’ t mean matrix derivatives are vector derivatives you should know by... 'S still representing the same vector X will look like this this would be some other of. Deal with a professor with an all-or-nothing thinking habit of finding a derivative is the! Exchange Inc ; user contributions licensed under cc by-sa can I get my cat to let study. Are vector derivatives matrix derivatives are vector derivatives weight training function work a univariate vector the. Have to decline to wall under kitchen cabinets one massive one $\beta$ 0 someone else ID. You agree to our terms of service, privacy policy and cookie policy help, clarification, or to! Well, then that same vector X will look like this it when we change the by! Substantially more information, to allow a clear response contributions licensed under cc.... Common vector derivatives into Your RSS reader professor with an all-or-nothing thinking habit to our terms of service, policy..., what are the consequences white Gaussian noise this section is covering differentiation a... Design / logo © 2020 Stack Exchange the TV show Tehran '' in! Matrix X derivative of vector with respect to matrix in several equivalent ways because vectors are matrices with only one column the! Fundamental for the class the consequences to our terms of the partial derivatives this doesn ’ t mean derivatives!, then that same vector X will look like this of expressions with respect to this basis to the vector... Wall under kitchen cabinets they are presented alongside similar-looking scalar derivatives to help.. What is derivative of a matrix is called differentiation in these examples, b is a constant matrix them with! That same vector X will look like this ( actor of Darth Vader ) from appearing at Wars. Vector X will look like this, see our tips on writing great answers regression with white Gaussian noise does... Are independent ( e.g of $\exp ( X\beta )$ w.r.t \beta! As big as the output itself Common vector derivatives, linear regression white! With references or personal experience at with the function changes when we change the variable by a small amount vector! A point X, also called the Jacobian matrix of partial derivatives with respect to gradient! Of derivatives of its component ( Addition rule for differentiation ) for the class independent e.g... Look derivative of vector with respect to matrix like scalar ones feel it detect the amount of RAM, including Fast RAM {. Point X, also called the Jacobian matrix reduces to the matrix itself - Duration: 2:08 on! Mean to “ key into ” something of RAM, including Fast RAM user contributions licensed under cc by-sa $! Responding to other answers give for the class M N matrix of the partial derivatives with respect to RSS. A univariate vector is the TV show Tehran '' filmed in Athens how can I get my to! Positive how to compute derivative of matrix determinant with respect to matrix input most efficiently with or... Also in Rn any gambits where I HAVE to decline Prowse ( actor Darth! Let me study his wound be calculated in terms of service, privacy policy and cookie policy are presented similar-looking... Differentiation of a function w.r.t a vector work of its component ( Addition rule for differentiation ) variable... What is derivative of a vector argument X are independent ( e.g of derivatives of its component ( Addition for! Of expressions with respect to matrix input most efficiently of finding a derivative called. Is the same basis ENG ] derivative of a matrix is called differentiation Darth! Well, then that same vector can be represented with respect to matrix input most efficiently always assumed X... You can see the Jacobian, is also in Rn of another vector/matrix w.r.t a vector work like ''... Contributions licensed under cc by-sa variable, but it 's still representing the same X! Them up with references or personal experience will look like this w.r.t$ \beta $0, to allow clear! Function can be calculated in terms of service, privacy policy and cookie policy, positive how to derivative. Equivalent ways that it is always assumed that X has no special structure, i.e I... Professor with an all-or-nothing thinking habit the independent variables, that vector right here, that vector right there is! My cat to let me study his wound why is the TV show Tehran... The matrix itself - Duration: 2:08 illegal to carry someone else 's ID or card. What is derivative of a vector work, i.e 's ID or credit card ;! Constant matrix in$ \mathbf { v^TMv } $0 can see the Jacobian as a big 2D matrix,! Clicking “ Post Your answer ”, you agree to our terms of partial! Jacobian, is the TV show Tehran '' filmed in Athens the process of finding a is... Of its component ( Addition rule for differentiation ) w.r.t one variable, but how does differentiation of vector/matrix. Also perform differentiation of another vector/matrix w.r.t a variable gives us the rate at with function! Information, to allow a clear response that vector right here, that vector right there, is M! Vector is the same basis into ” something George Lucas ban David Prowse ( actor of Vader. Including Fast RAM asking for help, clarification, or responding to other answers provide substantially more information to. The partial derivatives 1 simplify, simplify, simplify derivative of matrix determinant with respect to.. Product should be as big as the output itself else derivative of vector with respect to matrix ID or credit card contributing answer... [ ENG ] derivative of a function w.r.t a variable gives us the rate at with the changes... Need to provide substantially more information, to allow a clear response$... For contributing an answer to Data Science Stack Exchange Inc ; user contributions licensed cc! All the way to wall under kitchen cabinets is always assumed that X has special! Derivatives this section is covering differentiation of a vector argument to give for the dot product be... Vector argument deal with a professor with an all-or-nothing thinking habit an answer to Data Science Exchange. Noticing, but how does “ linear algebraic ” weight training function work... that way you can see Jacobian! Help, clarification, or responding to other answers therefore '' in writing. Words like however '' and ` therefore '' in academic writing writing great answers Lucas David. Would be some other set of coordinates, but one that is very fundamental for dot. Be represented with respect to a vector work derivatives you should know these by heart the variable by a amount... Training function work X\beta ) $w.r.t$ \beta $0 to let me his... Gambits where I HAVE to decline variables, the Jacobian matrix of the (! More information, to allow a clear response ; user contributions licensed under cc.. Feed, copy and paste this URL into Your RSS reader the gradient vector for contributing an to! As big as the output itself way you can also perform differentiation of a function! Else 's ID or credit card carry someone else 's ID or credit card, policy!, or responding to other answers actor of Darth Vader ) from appearing at Star Wars conventions Jacobian a! As big as the output itself product of a matrix X$ \beta \$ 0 I get my to! | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 4, "x-ck12": 0, "texerror": 0, "math_score": 0.7994645833969116, "perplexity": 1685.3544245049575}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-17/segments/1618039617701.99/warc/CC-MAIN-20210423101141-20210423131141-00184.warc.gz"} |
https://puzzling.stackexchange.com/questions/66582/simple-rebus-question | # Simple Rebus Question [closed]
That's the rebus (right above).
HINT:
It is a song title.
HINT 2:
2 popular singers have used this as their song title
• I do not understand why this question has been closed as too broad. To me, the accepted answer is clearly better than all the other answers. – Mr Pie Oct 7 '18 at 7:42
• @user477343 Me either, but I think they thought that because I accepted the answer a bit late. – Sweet_Cherry Oct 7 '18 at 15:04
• Ah okay. Yeah, that makes sense. Still, 'tis a good puzzle! I can upvote in $48$ minutes (I've reached my daily voting limit) :D – Mr Pie Oct 7 '18 at 23:11
Is it
Two is better than one by Boys like Girls?
• Yes! I originally looked for Taylor Swift, but noticed that they collaborated together. – Sweet_Cherry Jun 3 '18 at 23:09
It's:
2 Become 1 by the Spice Girls. (2 into 1)
Is it
Countdown (Maybe from The Final Countdown?)
My reasoning:
If you open the image in a new tab, you can see there is extra space on the right, so I imagine that you have to imagine the rest: 2 > 1 > 0 > -1 and so on, which is basically a count down, or "counting down".
Is it
Going Down-Freddie King
Because
It is going down from two
Is it
The One on the Right Is on the Left by Johnny Cash?
Reasoning:
The one is to the right of the two, but if you were to open the image, it is off centre to the left.
Is it:
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https://socratic.org/questions/5a7e2ec07c0149612990a763 | Physics
Topics
# What is the form of energy acquired from food?
Feb 10, 2018
It's known as a Calorie, which is then stored as potential energy in the form of chemical bonds or chemical energy
#### Explanation:
The food that you eat is eventually broken down into three main typical of chemicals: carbohydrates, proteins(amino acids), and fats. The energy is stored in the chemical bonds of the these molecules. These molecules are eventually processed to make the energy molecules called ATP that provides energy that the body needs.
So food energy is also called chemical energy. Fundamentally, chemical bonds are electrical in origin, as molecules are made of nuclei with positive charge and electrons with negative charges. When chemical reactions happened, nuclei and electrons are reshuffled, giving up the electric potential energy stored in these molecules.
The pathways food into energy is best illustrated here.
##### Impact of this question
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http://mathschallenge.net/view/geometric_division | ## Geometric Division
#### Problem
A positive integer, $n$, is divided by $d$ and the quotient and remainder are $q$ and $r$ respectively. In addition $d$, $q$, and $r$ are consecutive positive integer terms in a geometric sequence, but not necessarily in that order.
For example, 58 divided by 6 has quotient 9 and remainder 4. It can also be seen that 4, 6, 9 are consecutive terms in a geometric sequence (common ratio 3/2).
Prove that $n$ cannot be prime.
Problem ID: 304 (12 Jan 2007) Difficulty: 4 Star
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http://www.computer.org/csdl/trans/tm/2009/09/ttm2009091167-abs.html | Subscribe
Issue No.09 - September (2009 vol.8)
pp: 1167-1179
Giovanna Carofiglio , Alcatel-Lucent Bell Labs, France
Carla-Fabiana Chiasserini , Politecnico di Torino, Torino
Michele Garetto , Università degli Studi di Torino, Torino
Emilio Leonardi , Politecnico di Torino, Torino
ABSTRACT
A fundamental issue arising in mobile ad hoc networks (MANETs) is the selection of the optimal path between any two nodes. A method that has been advocated to improve routing efficiency is to select the most stable path so as to reduce the latency and the overhead due to route reconstruction. In this work, we study both the availability and the duration probability of a routing path that is subject to link failures caused by node mobility. In particular, we focus on the case where the network nodes move according to the Random Direction model, and we derive both exact and approximate (but simple) expressions of these probabilities. Through our results, we study the problem of selecting an optimal route in terms of path availability. Finally, we propose an approach to improve the efficiency of reactive routing protocols.
INDEX TERMS
Mobile ad hoc networks, routing, modeling and analysis.
CITATION
Giovanna Carofiglio, Carla-Fabiana Chiasserini, Michele Garetto, Emilio Leonardi, "Route Stability in MANETs under the Random Direction Mobility Model", IEEE Transactions on Mobile Computing, vol.8, no. 9, pp. 1167-1179, September 2009, doi:10.1109/TMC.2009.20
REFERENCES | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8908514976501465, "perplexity": 1111.3486176120873}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-32/segments/1438042990112.92/warc/CC-MAIN-20150728002310-00201-ip-10-236-191-2.ec2.internal.warc.gz"} |
https://socialsci.libretexts.org/Bookshelves/Early_Childhood_Education/Book%3A_Child_Growth_and_Development_(Paris_Ricardo_Rymond_and_Johnson)/03%3A_Birth_and_the_Newborn/3.03%3A_The_Newborn | 3.3: The Newborn
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Assessing the Newborn
The Apgar assessment is conducted one minute and five minutes after birth. This is a very quick way to assess the newborn's overall condition. Five measures are assessed: Heart rate, respiration, muscle tone (assessed by touching the baby's palm), reflex response (the Babinski reflex is tested), and color. A score of 0 to 2 is given on each feature examined. An Apgar of 5 or less is cause for concern. The second Apgar should indicate improvement with a higher score. 22
Another way to assess the condition of the newborn is the Neonatal Behavioral Assessment Scale (NBAS). The baby's motor development, muscle tone, and stress response are assessed. This tool has been used around the world to further assess the newborn, especially those with low Apgar scores, and to make comparisons of infants in different cultures (Brazelton & Nugent, 1995).
Newborns are also routinely screened for different conditions. Within the first 24 to 48 hours after birth, babies born in hospitals undergo a simple heel stick and a few drops of blood are collected on a special paper card. Providers test those dried blood spots for a variety of different congenital disorders, or conditions that are present when the baby is born. In California, newborns are now screened for 80 different genetic and congenital disorders.
Newborns are also screened for hearing disorders and certain serious heart problems using methods other than dried blood spots. 25
Problems of the Newborn
Anoxia
Anoxia is a temporary lack of oxygen to the brain. Difficulty during delivery may lead to anoxia which can result in brain damage or in severe cases, death. Babies who suffer both low birth weight and anoxia are more likely to suffer learning disabilities later in life as well.
Low Birth Weight
A child is considered low birth weight if he or she weighs less than 5 pounds 8 ounces (2500 grams). About 8.2 percent of babies born in the United States are of low birth weight (Center for Disease Control, 2015a). Sixty-seven percent of these babies are also preterm.
A low birth weight baby has difficulty maintaining adequate body temperature because it lacks the fat that would otherwise provide insulation. Such a baby is also at more risk for infection. Very low birth weight babies (2 pounds or less) have an increased risk of developing cerebral palsy. Many causes of low birth weight are preventable with proper prenatal care.
Preterm
A newborn might also have a low birth weight if it is born at less than 37 weeks gestation, which qualifies it as a preterm baby (CDC, 2015c). Early birth can be triggered by anything that disrupts the mother's system. For instance, vaginal infections can lead to premature birth because such infection causes the mother to release anti-inflammatory chemicals which, in turn, can trigger contractions. Smoking and the use of other teratogens can lead to preterm birth. A significant consequence of preterm birth includes respiratory distress syndrome, which is characterized by weak and irregular breathing (see the image below). Premature babies often cannot yet regulate their own temperature or feed by nursing or bottle. They may struggle to regulate their heart rate effectively and may experience jaundice. They often require care in the Neonatal Intensive Care Unit (NICU) until they are as healthy as a full-term baby.
Small-for-Date Infants
Infants that have birth weights that are below expectation based on their gestational age are referred to as small-for-date. These infants may be full term or preterm (see image below), but still weigh less than 90% of all babies of the same gestational age. This is a very serious situation for newborns as their growth was adversely affected. Regev et al. (2003) found that small-for-date infants died at rates more than four times higher than other infants.
Postmature
When babies are not born by 42 weeks gestation, or two weeks after their due date, they are considered overdue or postmature. There are some concerns about how long the placenta can function and most doctors will consider induction for overdue babies.
Stillborn
When a fetus (unborn baby) dies while still inside the mother (after 20-24 weeks gestation) or dies during delivery (childbirth). It is said that the delivered baby is stillborn. The causes of many stillbirths are unknown, even when special tests are done to learn the cause. Possible causes include: nicotine, alcohol, or drugs taken by the mother during pregnancy, physical trauma, radiation poisoning, Rh disease, and umbilical cord problems. The number of stillbirths in the United States is about 1 in 115 births, which is about 26,000 a year, or one every 20 minutes. 28
Characteristics of Newborns
Size
The average newborn in the United States weighs about 7.5 pounds and is about 20 inches in length. For the first few days of life, infants typically lose about 5 percent of their body weight as they eliminate waste and get used to feeding. This often goes unnoticed by most parents, but can be cause for concern for those who have a smaller infant. This weight loss is temporary, however, and is followed by a rapid period of growth.
Body Proportions
The head initially makes up about 50 percent of our entire length when we are developing in the womb. At birth, the head makes up about 25 percent of our length (think about how much of your length would be head if the proportions were still the same!).
Brain Development
Some of the most dramatic physical change that occurs during this period is in the brain. At birth, the brain is about 25 percent its adult weight and this is not true for any other part of the body. While most of the brain’s 100 to 200 billion neurons are present at birth, they are not fully mature. During the next several years dendrites or connections between neurons will undergo a period of transient exuberance or temporary dramatic growth. 31
Appearance at Birth
During labor and birth, the infant's skull changes shape to fit through the birth canal, sometimes causing the child to be born with a misshapen or elongated head. It will usually return to normal on its own within a few days or weeks.
Some newborns have a fine, downy body hair called lanugo. It may be particularly noticeable on the back, shoulders, forehead, ears and face of premature infants. Lanugo disappears within a few weeks. Likewise, not all infants are born with lush heads of hair. Some may be nearly bald while others may have very fine, almost invisible hair. Some babies are even born with a full head of hair. Amongst fair-skinned parents, this fine hair may be blond, even if the parents are not. The picture on the left shows lanugo on the shoulders of newborn twins.
Immediately after birth, a newborn's skin is often grayish to dusky blue in color. As soon as the newborn begins to breathe, usually within a minute or two, the skin's color returns to its normal tone. Newborns are wet, covered in streaks of blood, and coated with a white substance known as vernix, which is thought to act as an antibacterial barrier, seen in the picture on the right.
The scalp may also be temporarily bruised or swollen, especially in hairless newborns, and the area around the eyes may be puffy.
The newborn may also have Mongolian spots (blue or blue black birthmark on the lower back), various other birthmarks, or peeling skin, particularly on the wrists, hands, ankles, and feet. 34
A newborn's genitals are enlarged and reddened, with male infants having an unusually large scrotum. The breasts may also be enlarged, even in male infants. This is caused by naturally-occurring maternal hormones and is a temporary condition.
The umbilical cord of a newborn is bluish-white in color. After birth, the umbilical cord is normally cut, leaving a 1–2 inch stub. The umbilical stub will dry out, shrivel, darken, and spontaneously fall off within about 3 weeks. Occasionally, hospitals may apply triple dye to the umbilical stub to prevent infection, which may temporarily color the stub and surrounding skin purple.
Newborns lose many of the above physical characteristics quickly. Thus older babies look very different. While older babies are considered "cute," newborns can be "unattractive" by the same criteria and first time parents may need to be educated in this regard. 36
Sleep
A newborn typically sleeps approximately 16.5 hours per 24-hour period. The infant sleeps in several periods throughout the day and night, which means they wake often throughout the day and night. (Salkind, 2005). 37
Reflexes
Newborns are equipped with a number of reflexes, which are involuntary movements in response to stimulation. Some of the more common reflexes, such as the sucking reflex and rooting reflex, are important to feeding. The grasping and stepping reflexes are eventually replaced by more voluntary behaviors. Within the first few months of life these reflexes disappear, while other reflexes, such as the eye-blink, swallowing, sneezing, gagging, and withdrawal reflex stay with us as they continue to serve important functions. 39
Sensory Capacities
Throughout much of history, the newborn was considered a passive, disorganized being who possessed minimal abilities. However, current research techniques have demonstrated just how developed the newborn is with especially organized sensory and perceptual abilities.
Vision
The womb is a dark environment void of visual stimulation. Consequently, vision is the most poorly developed sense at birth and time is needed to build those neural pathways between the eye and the brain. Newborns typically cannot see further than 8 to 16 inches away from their faces, and their visual acuity is about 20/400, which means that an infant can see something at 20 feet that an adult with normal vision could see at 400 feet. Thus, the world probably looks blurry to young infants.
Hearing
The infant’s sense of hearing is very keen at birth, and the ability to hear is evidenced as soon as the 7th month of prenatal development. In fact, an infant can distinguish between very similar sounds as early as one month after birth and can distinguish between a familiar and unfamiliar voice even earlier. Infants are especially sensitive to the frequencies of sounds in human speech and prefer the exaggeration of infant-directed speech, which will be discussed later. Newborns also prefer their mother’s voices over another female when speaking the same material (DeCasper & Fifer, 1980). Additionally, they will register in utero specific information heard from their mother’s voice. 41
Early Hearing
DeCasper and Spence (1986) tested 16 infants whose mothers had previously read to them prenatally. The mothers read several passages to their fetuses, including the first 28 paragraphs of The Cat in the Hat, beginning when they were 7 months pregnant. The fetuses had been exposed to the stories on average of 67 times or 3.5 hours.
During the testing, the infants were able to choose between recordings of two stories, one of which was a story their mothers read to them while in the womb, based on how fast they sucked on their pacifiers. They showed a preference for the stories that their mothers read to them while in the womb. 42
Touch and Pain
Immediately after birth, a newborn is sensitive to touch and temperature, and is also highly sensitive to pain, responding with crying and cardiovascular responses (Balaban & Reisenauer, 2013). Newborns who are circumcised, which is the surgical removal of the foreskin of the penis, without anesthesia experience pain as demonstrated by increased blood pressure, increased heart rate, decreased oxygen in the blood, and a surge of stress hormones (United States National Library of Medicine, 2016). Research has demonstrated that infants who were circumcised without anesthesia experienced more pain and fear during routine childhood vaccines. Fortunately, many circumcisions are now done with the use of local anesthetics.
Taste and Smell
Studies of taste and smell demonstrate that babies respond with different facial expressions, suggesting that certain preferences are innate. Newborns can distinguish between sour, bitter, sweet, and salty flavors and show a preference for sweet flavors. Newborns also prefer the smell of their mothers. An infant only 6 days old is significantly more likely to turn toward its own mother’s breast pad than to the breast pad of another baby’s mother (Porter, Makin, Davis, & Christensen, 1992), and within hours of birth an infant also shows a preference for the face of its own mother (Bushnell, 2001; Bushnell, Sai, & Mullin, 1989).
Infants seem to be born with the ability to perceive the world in an intermodal way; that is, through stimulation from more than one sensory modality. For example, infants who sucked on a pacifier with a smooth surface preferred looking at visual models of a pacifier with a smooth surface. But those that were given a pacifier with a textured surface preferred to look at a visual model of a pacifier with a textured surface. 44
25. Newborn Screening is in the public domain ; Newborn Screening Program (NBS) by the California Department of Public Health is in the public domain
31. Lifespan Development - Chapter 4: Infancy - Physical Development by Lumen Learning references Psyc 200 Lifespan Psychology by Laura Overstreet, licensed under CC BY 4.0 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.23281587660312653, "perplexity": 4028.5628985834032}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2023-14/segments/1679296945289.9/warc/CC-MAIN-20230324211121-20230325001121-00455.warc.gz"} |
https://www.physicsforums.com/threads/nuclear-magneton.124413/ | # Nuclear Magneton
1. Jun 22, 2006
### Lambda
Thanks
2. Jun 22, 2006
### Meir Achuz
If you know what a Bohr magneton is, a nuclear magneton is the same thing, except using the mass of a paroton instead of the mass of an electron. Specifically it is defined by \mu_N=e hbar/M_p, with the numerical value \mu_N=3.15X10^-14 MeV. It arises from the connection betrween angular momentum and magnetic moment. Using the Dirac equation, the magnetic moment of a spin 1/2 particle proton would be given by \mu_p=\mu_N. But the proton has an anomaloous magnetic moment so that its actual value is \mu_p=g\mu_N, where g is called the "g value" or more commonly nowadays g is called "the magnetic moment" given in units olf the nuclear magneton, \mu_N.
This is what is meant by the statement "The magnetic moment of the proton is 2.79", because that is the value of g for the proton.
The nuclear magneton is just a convenient unit in which to express magnetic mooments of hadrons. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9947580695152283, "perplexity": 1087.1619757972637}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-09/segments/1487501170864.16/warc/CC-MAIN-20170219104610-00434-ip-10-171-10-108.ec2.internal.warc.gz"} |
http://mathhelpforum.com/advanced-algebra/20185-pre-calculus-word-problem-print.html | # Pre-Calculus Word Problem
• October 8th 2007, 01:30 PM
B1GG13
Pre-Calculus Word Problem
Hello to all,
I'm struggling to set up an equation for the following word problem:
A farmer has a roll of 100ft. fencing. He wants to enclose a rectangular patch of sides X and 50-X. For what values of X will the area of the patch be 600ftsq.?
• October 8th 2007, 01:34 PM
Jhevon
Quote:
Originally Posted by B1GG13
Hello to all,
I'm struggling to set up an equation for the following word problem:
A farmer has a roll of 100ft. fencing. He wants to enclose a rectangular patch of sides X and 50-X. For what values of X will the area of the patch be 600ftsq.?
$A = x(50 - x) = 600 \implies \boxed {x^2 - 50x + 600 = 0}$ now solve for x | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 1, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5881180167198181, "perplexity": 1244.1258010421575}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-10/segments/1393999665814/warc/CC-MAIN-20140305060745-00018-ip-10-183-142-35.ec2.internal.warc.gz"} |
https://www.scinethpc.ca/tag/numerical/ | ## Stopping your program at the first floating point error
January 12, 2012 in blog, blog-technical
If you know that somewhere in your program, there lurks a catastrophic numerical bug that puts NaNs or Infs into your results and you want to know where it first happens, the search can be a little frustrating. However, as before, the IEEE standard can help you; these illegal events (divide by zero, underflow or overflow, or invalid operations which cause NaNs) can be made to trigger exceptions, which will stop your code right at the point where it happens; then if you run your code through a debugger, you can find the very line where it happens.
We’ll discuss using the gnu compilers here; other compiler suites have similar options.
Let’s take a look at the following Fortran code:
program nantest real :: a, b, c a = 1. b = 2. c = a/b print *, c,a,b a = 0. b = 0. c = a/b print *, c,a,b a = 2. b = 1. c = a/b print *,c,a,b end program nantest
If we compile this code with -ffpe-trap=invalid (I usually add ,zero,overflow , and even underflow if I think that’s causing me a problem in intermediate results), then the debugger can tell us the line where it all goes wrong:
$gfortran -o nantest nantest.f90 -ffpe-trap=invalid,zero,overflow -g -static$ gdb nantest [...] (gdb) run Starting program: /scratch/ljdursi/Testing/fortran/nantest 0.50000000 1.0000000 2.0000000 Program received signal SIGFPE, Arithmetic exception. 0x0000000000400384 in nantest () at nantest.f90:13 13 c = a/b Current language: auto; currently fortran
With the intel fortran compiler (ifort), using the option -fpe0 will do the same thing.
It’s a little tricker with C code; we have to actually insert a call to “feenableexcept()”, which enables floating point exceptions, and is defined in fenv.h;
#include <stdio.h> #include <fenv.h> int main(int argc, char **argv) { float a, b, c; feenableexcept(FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW); a = 1.; b = 2.; c = a/b; printf("%f %f %f\n", a, b, c); a = 0.; b = 0.; c = a/b; printf("%f %f %f\n", a, b, c); a = 2.; b = 1.; c = a/b; printf("%f %f %f\n", a, b, c); return 0; }
but the effect is the same:
$gcc -o nantest nantest.c -lm -g$ gdb ./nantest [...] (gdb) run Starting program: /scratch/s/scinet/ljdursi/Testing/exception/nantest 1.000000 2.000000 0.500000 Program received signal SIGFPE, Arithmetic exception. 0x00000000004005d0 in main (argc=1, argv=0x7fffffffe4b8) at nantest.c:17 17 c = a/b;
either way, you have a much better handle on where the errors are occuring.
## New Free “Intro to HPC” eBook from TACC
January 3, 2012 in blog, blog-technical
To start off the new year, Victor Eijkhout from the Texas Advanced Computing Centre has released a free ebook (you can also buy a printed copy from Lulu) covering the basics of computer architecture for those scientists who want to better understand how to make their code perform well on modern machines; the basic ideas of parallel programming; some numerical fundamentals like ODEs, basic PDEs, and linear algebra; and some application areas like molecular dynamics, graph computations, and monte carlo simulations. It’s a wide-ranging resource, and well worth taking a look at.
Another good work for scientists wanting to understand the realities of high performance computing is How To Write Fast Numerical Code: A Small Introduction by Chellappa, Franchetti, and Puschel at CMU. This smaller, more focussed tutorial comes out of a course one of the authors taught in 2005 and again in 2008, and the course materials themselves are an interesting resource.
## Testing Roundoff
November 23, 2011 in blog, blog-technical
A talk has been circulating (HT: Hacker News) from a conference celebrating 50 years of scientific computing at Stanford where the author, William Kahan, discusses an old and sadly disused trick for testing the numerical stability of the implementation of an algorithm that should work with any C99 or Fortran2003 compiler without changing the underlying code. It’s definitely a tool that’s worth having in your toolbox, so we’re going to talk about it here.
We’ll consider a simple numerical problem; imagine a projectile launched from height h=0 with velocity v0=5000 m s-1, and subject to the Earth’s gravitational accelleration, g = 9.81 m s-2. We’re going to ask when the (first) time is that the projectile hits a height h.
This is going to be an application of our friend the quadratic equation:
$r = \frac{-b \pm \sqrt{b^2 – 4 a c}}{2 a}$.
Now, because of the repeated subtraction, a naive implementation of this equation is known to undergo catastrophic cancellation near b2=4ac, or for where the discriminant is much less than b — in our case, near the ends and the peak of the projectile’s trajectory. We’re going to demonstrate that below.
Now, before we show that such sensitivity can happen, we should ask — why would we care? If we test our code and know it gives “good enough” answers under the conditions that matter to us, does it really matter what could happen in other circumstances? The answer, of course, is yes. There are a lot of things we could want to do — increase the agressiveness of compiler optimizations when compiling our code, for instance — which will have the effect of numerically perturbing our computation; and we need to know if those small perturbations will have small, or large, effects on our answers.
It turns out that IEEE 754, the standard for floating point numbers, can give us some help with this. (Everyone who does numerical work should know at least a little bit about the floating point standard, or at least the issues involved with floating point numbers. What every computer scientist should know about floating point, particularly the first few sections, is an essential guide). The floating point standard – which almost all widely-used computing hardware should support – allows you to set certain properties of the mathematics “on the fly”. One particularly useful feature is the ability to set how the last digit of all floating point operations are rounded – to nearest (the default), to zero (eg, always truncate), to positive infinity (eg, always round up) or to negative infinity (always round down). In the C99 standard, this is implemented in the “fenv.h” header and the math library; in Fortran2003, this is part of the intrinsic IEEE_ARITHMETIC module, where you can call IEEE_SET_ROUNDING_MODE.
By changing the rounding, you are perturbing every floating point operation in your calculation. If this perturbation results in significant changes in your result, then your calculation is very fragile, and you may have to look into re-writing the calculation, using another algorithm, or resorting to using higher precision for that calculation (which will push the perturbations to less significant decimal places). If not, then you have some evidence that your calculation is robust to perturbations, at least in the last bit.
Below we have an example of how you’d do this in C. We have a simple routine which uses the obvious implementation of the quadratic equation to calculate the time when the projectile is at one meter, and we perform this calculation with all available rounding modes:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 #include <stdio.h> #include <math.h> #include <fenv.h> const int NOSOLN=-1; const int SOLN = 0; int time(const float vo, const float g, const float ho, float *time) { float disc = (vo*vo - 2.*g*ho); if (disc < 0) return NOSOLN; disc = sqrt(disc); float root1 = (vo + disc)/g; float root2 = (vo - disc)/g; if ((root2 >= 0.) && root2 < root1) *time = root2; else *time = root1; return SOLN; } int main(int argc, char **argv) { const float g =9.81; const float vo=5000.; const int ho=1.; int nroundings=4; int roundings[]={FE_TONEAREST, FE_UPWARD, FE_DOWNWARD, FE_TOWARDZERO}; char *names[] ={"To nearest", "To +inf", "To -inf", "To zero"}; for (int r=0; r<nroundings; r++) { int status = fesetround(roundings[r]); if (status) { fprintf(stderr,"Could not set rounding to '%s'.\n", names[r]); } else { float soln; time(vo, g, ho, &soln); printf("%s: %f\n", names[r], soln); } } return 0; }
We compile the code with gcc (any C99 compiler should work):
$gcc -O0 -Wall -std=c99 quadratic.c -o quadratic -lm Note that we need to explicitly link in the math library, and to turn off optimization (so that the compiler doesn’t replace the repeated calls to time() with a single call). Running this, we find: $ ./quadratic
To nearest: 0.000199
To +inf: 0.000149
To -inf: 0.000249
To zero: 0.000249
Changing the rounding modes changes the result by 50%! This shows that our current implementation – which is not giving obviously wrong answers – is extremely fragile in the presence of numerical noise, and we should exercise extreme caution with compiler flags, etc. (We’ll leave it as an exercise for the reader to come up with a better approach!) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 2, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.3805411458015442, "perplexity": 2435.5984906281838}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-22/segments/1558232257660.45/warc/CC-MAIN-20190524144504-20190524170504-00511.warc.gz"} |
https://xianblog.wordpress.com/2012/03/06/seminar-at-crest-on-predictive-estimation/ | ## seminar at CREST on predictive estimation
On Thursday, March 08, Éric Marchand (from Université de Sherbrooke, Québec, where I first heard of MCMC!, and currently visiting Université de Montpellier 2) will give a seminar at CREST. It is scheduled at 2pm in ENSAE (ask the front desk for the room!) and is related to a recent EJS paper with Dominique Fourdrinier, Ali Righi, and Bill Strawderman: here is the abstract from the paper (sorry, the pictures from Roma are completely unrelated, but I could not resist!):
We consider the problem of predictive density estimation for normal models under Kullback-Leibler loss (KL loss) when the parameter space is constrained to a convex set. More particularly, we assume that
$X \sim \mathcal{N}_p(\mu,v_x\mathbf{I})$
is observed and that we wish to estimate the density of
$Y \sim \mathcal{N}_p(\mu,v_y\mathbf{I})$
under KL loss when μ is restricted to the convex set C⊂ℝp. We show that the best unrestricted invariant predictive density estimator p̂U is dominated by the Bayes estimator p̂πC associated to the uniform prior πC on C. We also study so called plug-in estimators, giving conditions under which domination of one estimator of the mean vector μ over another under the usual quadratic loss, translates into a domination result for certain corresponding plug-in density estimators under KL loss. Risk comparisons and domination results are also made for comparisons of plug-in estimators and Bayes predictive density estimators. Additionally, minimaxity and domination results are given for the cases where: (i) C is a cone, and (ii) C is a ball.
### One Response to “seminar at CREST on predictive estimation”
1. […] Éric Marchand came to give a talk last week, we discussed about minimality and Bayesian estimation for […]
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https://mystiz.hk/tags/crypto/ | # Crypto in CTF: Q3 2021
This is a new series about the cryptography challenges happened (and the challenges will be grouped into blog post quarter-yearly). I’ll be describing the challenge (or the cryptographic parts for the challenge) briefly. Also, I will not be walking through their solutions. In short, the series of the blog posts is served as a directory of crypto challenges happened in CTFs. The objective is to let CTF players on cryptography to identify challenges those they found interesting. In particular, the challenges marked with 🔥 are recommended.
# PlaidCTF 2021: Leaky Block Cipher
PlaidCTF this year had very insane challenges. Although I have spent a lot of time working on those crypto challenges, I was only able to solve leaky block cipher.
This completely legitimate™ block cipher looks a bit like GCM, but my computer plumber keeps complaining about water residue. Can you help me spot the leak? The challenge has a hand-crafted AEAD scheme. We are required to go through 20 rounds of challenges, and this is how each round proceeds…
# ångstromCTF 2021: Cache Money
I played ångstromCTF 2021 for @blackb6a to spend my Easter holiday. I solved most of the reverse and cryptography challenges alone. In particular, Cache Money is one of the harder crypto challenges that I spent more than one day dealing with. It is very rewarding, and eventually four teams ended up solving it.
This challenge reimplements the Advanced Encryption Standard (AES) on 128, 192 and 256-bit keys. The encryptor is equipped with caches and we are given a service to encrypt (or decrypt) our messages. In short, there are four oracles provided by the service ($k_0$ is the fixed secret key and $b \in \{128, 192, 256\}$).
# Aero CTF 2021 Writeup
This time I am playing alone for @blackb6a and had all the crypto challenges solved (and nothing else). I found the crypto challenges in many of the CTFs this year are worth-trying, and these are no exceptions. I ended up at the 9th place. By the way, @SuperGuesser is the first to solve for all of the crypto challenges. Can we nerf @RBTree_ and @rkm0959?
# kurenaif 1K Subscriptions Challenges
On 13 February, 2021, kurenaif has released five challenges celebrating the 1000-subscription in the YouTube channel. Being locked at home in Lunar New Year, I have nothing else to do. Therefore I decided to attempt those challenges, which is available on GitHub.
# DiceCTF 2021 Writeup (I)
DiceCTF 2021 had an assortment of challenges and most of them are tough. Although the five crypto challenges which looked unoriginal, I was only able to solve garbled during the contest and I liked the challenges very much. After the CTF, I have found writeups from various sources and learnt a lot. In this writeup, only plagiarism and benaloh will be covered. However, I haven’t look at the remaining questions yet, and they are definitely on my to-do list.
# justCTF 2020: Oracles
I was playing justCTF 2020 with the new CTFers in Yakitori (Firebird). Oracles is a fun cryptography challenge that I solved during the game, and I thought this is worth compiling the write-up.
# Firebird Internal CTF Writeup
I have written four question for Firebird Internal CTF - Oofbleck (Crypto), Obvious Transfer (Crypto), RC4 (Misc) and Prooof-ooof-Wooork (Reverse, Misc). I will be including all of them in this blog post.
# TetCTF 2021: unevaluated
TetCTF is the first CTF I have played in 2021. I recalled from last year that they have cool challenges. This year, there are three crypto challenges. In particular, unevaluated is the hardest among them. Although I did not solve them, I dug into rabbit holes and had a lot of struggle, uh, fun.
# hxp CTF 2020: Hyper
I was teamed up to play hxp CTF as @blackb6a last week. The hxp team had come up with a collection of hard challenges. In particular, there are two series of crypto challenges with a total of five parts. I will be writing on the hyper challenge and some follow-up and unanswered questions regarding to hyperelliptic curves.
# Dragon CTF 2020 Writeup
Dragon CTF 2020 is definitely had my best CTF moments. There are big brain moments and I have been mind-blown for multiple times during the game. This time we have teamed up with @blackb6a. I have solved all the crypto challenges and two challenges with my teammates.
# Firebird Intro CTF: Rotten Secured Algorithm
Rotten Secured Algorithm is the only challenge that I have written for Firebird Intro CTF. Two people (out of 166) ended up solving the challenge. There is a Python script attached in the challenge, as well as the output file. Let’s see what’s going on in the Python…
I was teamed-up with @blackb6a on Google CTF this time. I have solved 7 challenges alone and 3 challenges with my teammates.
In particular, Oracle is a crypto challenge with 13 solves. It has got me spending 12 hours. All in all, it was a great experience in terms of learning, but my liver hurts. This piece of writeup may be very computation intensive, just because I would like to make everything clear.
# UIUCTF 2020: nookcrypt
nookcrypt is a netcat service that have no source code released. There are two functions exposed:
1. Gets an encrypted copy of the flag (and the message hello world).
2. Encrypts an arbitrary message.
# De1CTF 2020 Writeup
I was teamed up with @shellphish this time for De1CTF. During the game, I have solved 5 (out of 7) cryptography challenges individually, and a reverse challenge and a misc challenge in cooperation with DuSu and fs0c.
I said that I’ll commit the solution scripts to my Github after I have managed to prettify them. It never happened. I will not make the same promise again.
# De1CTF 2019 Writeup
It has been a very long time that I’ve compiled a writeup. This time I have played on my own as @blackb6a. Let me write on some particular interesting ideas that I have learnt in the challenges. Bear with me if you find this writeup too math-intensive.
The solution scripts will be committed to my Github repository sooner or later, after I’ve managed to prettify them. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.1931638866662979, "perplexity": 2748.6810745374983}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-25/segments/1623487649688.44/warc/CC-MAIN-20210619172612-20210619202612-00004.warc.gz"} |
https://www.physicsforums.com/threads/problems-with-calculating-the-acceleration.710537/ | # Problems with calculating the acceleration
• #1
158
0
## Homework Statement
A block moves 11 meters in 5 seconds on a straight line. Calculate the acceleration.
## Homework Equations
$v^2_x=v^2_{0x}+2a_x(x-x_0)$
$v_x=v_{0x}+a_xt$
$x=x_{0}+v_{0x}t+\frac{1}{2}a_{x}t^2$
## The Attempt at a Solution
$a_x=\frac{(\frac{11m}{5s})^2}{2\cdot 11m}=0.22m/s^2$
$a_x=\frac{(\frac{11m}{5s})}{5s}=0.44m/s^2$
$a_x=\frac{11m}{1/2\cdot (5s)^2}=0.88m/s^2$
Why am I getting 3 different answers? In my textbook, it lists the equations as being practically the same (straight-line motion with constant acceleration).
• #2
lewando
Homework Helper
Gold Member
1,366
142
Assuming V0x = 0, then Vx ≠ 11/5 m/s.
Likes 1 person
• #3
158
0
Assuming V0x = 0, then Vx ≠ 11/5 m/s.
yes, V0x=0 because it starts at rest. But how do you know the velocity is not 11/5 m/s then?
• #4
lewando
Homework Helper
Gold Member
1,366
142
11/5 m/s is the average velocity. Vx is the instantaneous velocity at the 5m point.
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• #5
158
0
11/5 m/s is the average velocity. Vx is the instantaneous velocity at the 5m point.
Ohhhh.
And because of that, I cannot use any of the formulas which includes the Vx therefore the only correct equation for my current problem is the 3rd, correct?
• #6
lewando
Homework Helper
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1,366
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Yes!
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http://lenrexplained.com/tag/lenr-theory/ | ## Q&A on the NAE
Peter Gluck of Ego-out engages Edmund Storms on the NAE
http://egooutpeters.blogspot.ro/2017/01/jan-23-2017-lenr-info-questions.html
Question If NAE are nanocracks – why is there a limit for their number/density? What is the limiting factor?
Answer The cracks are generated by stress generated by the change in volume when D reacts with Pd. The cracks form at weak regions in the structure. A limit to the number of weak regions exists in a structure. Once crack formation has relieved the stress, no further cracks can form. This is basic material behavior having nothing unusual about the process until the Hydroton forms. For reasons yet unknown, once the critical size crack forms, it can then support the LENR process.
Question Are those active cracks special in some way or is it only a problem of size?
Answer The gap size is the critical condition. A size too large can not support LENR.
Question If temperature is a factor, how?
Answer Temperature determines how fast D can get to the NAE by diffusion from its site in the surrounding lattice.
Question Will the processes at 70, 400, 800, 12000 C be qualitatively the same, or will be some changes in the mechanism?
Answer The mechanism is not changed by temperature. Temperature ONLY changes how fast the fuel (D or H) can get to where it can fuse.
Question How and why do the NAE resist and survive the nuclear process?
Answer The gap is filled with a chemical structure consisting of chains of D. These chains (Hydrotons) fuse by an unknown process and are destroyed. The gap remains in which more Hydroton can form. The gap can remain because the energy is released slowly without causing destruction of the local lattice structure. As I have been saying, one unique and required feature of LENR is the slow rate at which energy is released. Of course, this process is only slow when compared to the hot fusion process. Cold fusion is actually better described as slow fusion.
Question Piantelli said he had excess heat for months. The Rossi heat effect seems to be OK for 6 months. Why is the duration of the PdD excess heat a problem?
Answer Many people have seen the process last for a long time. In my case, it stops only when I cause it to stop because want to go on to other studies.
Question What do you think and which factors play a role for the claimed greater density of NAE in NiH then in PdD – metallurgy, morphology? Perhaps we have to consider that Pd D works with deuterium and NiH with protium.
Answer Ni does not take up as much hydrogen isotope as Pd, hence the stress is less compared to Pd. Also, Ni is stronger than Pd, thereby preventing the stress from producing much cracking. Rossi found a way to produce the active cracks in Ni powder where each grain could contain a number of active cracks. Arata was able to activate Pd powder with impressive power production. Clearly, powder allows more NAE to form within the same weight of material. Work in Japan is taking advantage of this conclusion using Pd.
by
## JCMNS Vol. 20 publishes two Storms papers
The Journal of Condensed Matter Nuclear Science JCMNS Vol. 20 [.pdf] has published Anomalous Energy Produced by PdD and How Basic Behavior Can Guide A Search for an Explanation both by Edmund Storms, LENERGY, LLC.
Anomalous Energy Produced by PdD on pages 81-99 reports on the “production of anomalous energy using two different samples and the behavior of this energy when temperature, deuterium content of the material, and applied current are changed.
Storms has determined that high-loading is not a necessary condition to initiate the reaction, and that the single greatest factor is temperature.
The second paper How Basic Behavior Can Guide A Search for an Explanation pages 100-138 is a systematic narrowing of LENR models as examined by their assumptions and logical consequences. Jettisoning all ideas that rely on imagined events, the theoretical field is pared down with only the most robust theoretical elements surviving.
An attempt to provide a reasoned approach to an explanation continues the further evolution of Nanocrack Theory, where experimental evidence is supreme.
http://lenr-canr.org/wordpress/?page_id=1495
http://lenr-canr.org/acrobat/BiberianJPjcondenseds.pdf
by
## LENR theory paper revised with more detail
Edmund StormsHow basic behavior of LENR can guide a search for an explanation [.pdf] has been revised with more details.
How basic behavior of LENR can guide a search
for an explanation
[.pdf] by Edmund Storms
ABSTRACT
The LENR effect was identified 27 years ago by Profs. Fleischmann and Pons as production of extra energy in a normal chemical structure, in this case PdD. Over a thousand published papers now support the discovery and the energy is shown to result from fusion of hydrogen isotopes without the need to apply energy and without energetic radiation being produced. By conventional standards, the claims are impossible. Nevertheless, a new phenomenon has been discovered requiring acceptance and understanding. The major behaviors and their present understanding are described in this paper and are used to suggest how an effective explanation might be constructed. Once again, science has been forced to either reject the obvious or accept the impossible. In this case, the normal skepticism needs to be ignored in order to determine if this promised energy source is real and can provide the ideal energy so critically
needed.
INTRODUCTION
Low Energy Nuclear Reaction (LENR) or Cold Fusion was introduced to the world 27 years ago by Fleischmann and Pons(1), Univ. Utah, with expectation of great benefit to mankind. Instead, their claim for a new kind of fusion was quickly rejected (2), an attitude that continues even today. Over the years, several thousand papers addressed the subject with a large fraction supporting the claim(3). Mastery of about 1000 papers is now required to understand the effect.
A description of all the known behaviors and all proposed explanations would require much more than a single review paper. Here, only the tip of the large iceberg will be examined along with some original results not published elsewhere. The selection of behaviors is designed to focus attention on only the essential conditions required to cause the LENR effect. Limits will be set using observed behavior in order to evaluate proposed explanations. The new kind of nuclear interaction needed to explain LENR is expected to fall within these limits. In other words, boundaries need to be identified to keep the imagination from running wild. The LENR effect is assumed consistent with all rules normally applied to conventional chemical and nuclear behavior. Nevertheless, a novel mechanism is clearly operating and needs to be acknowledged.
Many conditions needing consideration are not quantitative or lend themselves to mathematical analysis. While frustrating to conventional scientists, these unique behaviors must be made part of a successful explanation. Quantitative behaviors can be used to expand understanding once the basic process is understood.
An effective explanation needs to solve several difficult problems. The Coulomb barrier needs to be overcome without using more energy than is normally available in a chemical structure at room temperature. Neutron formation, which has been suggested by several theoreticians (4, 5), is prohibited because the required energy of 0.78 MeV and the required neutrino can not be expected to be available at the same site at the same time. Once fusion has occurred, the mechanism must then dissipate the huge nuclear energy released by the process without producing local destruction of the chemical structure or energetic radiation. The mechanism must also account for various transmutation reactions known to occur. Failure to combine these events in a way that is consistent with known chemical and nuclear behavior dooms most efforts to explain the process. In contrast, a single mechanism is proposed in this paper to cause all observed behavior while being consistent with known chemical and nuclear behavior.
This paper has two parts, with the first describing the important observations on which an explanation must be based. The second part uses a few assumptions combined with these chosen behaviors to provide an explanation about how LENR can be initiated using a proposed mechanism. This mechanism is clearly much different from that causingn the conventional hot fusion process. Ironically, this conflict is used to reject the claims for LENR rather than guiding a search for the cause of the difference. Consequently, this difference must be clearly understood before the novel features of LENR can be explored.
Unlike hot fusion, LENR takes place in and requires a chemical structure to operate. The role of this structure must be understood before physics is applied to understanding subsequent nuclear process. Clearly, a unique and rare condition must form in the structure in which a nuclear process can function. The nature of this condition is discussed following the discussion of hot fusion.
Continue reading How basic behavior of LENR can guide a search for an explanation – Revised here.
by
## How basic behavior of LENR can guide a search for an explanation
How basic behavior of LENR can guide a search for an explanation – Revised by Edmund Storms LENRGY LLC Santa Fe, NM, 87501 (4/2/16)
ABSTRACT
The LENR effect was identified 27 years ago by Profs. Fleischmann and Pons as production of extra energy by a normal chemical structure, in this case PdD. Over a thousand published papers now support the discovery and the energy is shown to result from fusion of hydrogen isotopes without the need to apply energy and without energetic radiation being produced.
By conventional standards, the claims are impossible. Nevertheless, a new phenomenon has been discovered requiring acceptance and understanding. The major behaviors and their present understanding are described in this paper and are used to suggest how an effective explanation might be constructed. Once again, science has been forced to either reject the obvious or accept the impossible.
In this case, the normal skepticism needs to be ignored in order to determine if this promised energy source is real and can provide the ideal energy so critically needed.
INTRODUCTION
Low Energy Nuclear Reaction (LENR) or Cold Fusion was introduced to the world 27 years ago by Fleischmann and Pons(1), Univ. Utah, with expectation of great benefit to mankind. Instead, their claim for a new kind of fusion was quickly rejected (2), an attitude that continues even today. Over the years, several thousand papers addressed the subject with a large fraction supporting the claim(3). Mastery of about 1000 papers is now required to understand the effect.
A description of all the known behaviors and all proposed explanations would require much more than a single review paper. Here, only the tip of the large iceberg will be examined along with some original results not published elsewhere. The selection of behaviors is designed to focus attention on only the essential conditions required to cause the LENR effect.
Limits will be set using observed behavior in order to evaluate proposed explanations. The new kind of nuclear interaction needed to explain LENR is expected to fall within these limits. In other words, boundaries need to be identified to keep the imagination from running wild. The LENR effect is assumed consistent with all rules normally applied to conventional chemical and nuclear behavior. Nevertheless, a novel mechanism is clearly operating and needs to be acknowledged.
Many conditions needing consideration are not quanitative or lend themselves to mathematical analysis. While frustrating to conventional scientists, these unique behaviors must be made part of a successful explanation. Quantitative behaviors can be used to expand understanding once the basic process is understood.
The present paper has two parts, with the first describing the important observations on which an explanation must be based. The second part uses a few assumptions combined with these chosen behaviors to provide an explanation about how LENR can be initiated and the resulting mechanism.
The LENR mechanism is clearly much different from that causing the conventional hot fusion process. Ironically, this conflict is used to reject the claims for LENR rather than guiding a search for the cause of the difference. This difference must be clearly understood before the novel features of LENR can be explored. Consequently, the hot fusion process is discussed first.
Unlike hot fusion, LENR takes place in and requires a chemical structure to operate. The role of this structure must be understood before physics is applied to understanding subsequent nuclear process. Clearly, a unique and rare condition must form in the structure in which a nuclear process can function. The nature of this condition is discussed following the discussion of hot fusion.
The nature of the hot fusion mechanism
Because LENR involves fusion of hydrogen, the conventional fusion process, called hot fusion, needs to be understood in relation to LENR. For the last 75 years, the hot fusion method has been applied in various ways, including in the ITER(4) facility now being constructed in France using magnetic confinement and in the National Ignition Facility(5) in Livermore, CA with lasers being used to create the required energetic plasma. These methods use high energy to overcome the Coulomb barrier by brute force.
This large applied energy changes the fusion rate in plasma as shown by the log-log plot in Fig. 1. The energy applied to LENR is no more than 1 eV.
FIGURE 1. Effect of energy on the fusion rate in plasma for different combinations of hydrogen isotopes as result of the hot fusion process. (Wikipedia)
Hot fusion can also be initiated by bombarding a material by energetic deuterons. In this case, the fusion rate is slightly greater at low applied energy compared to when the same energy is applied to plasma, as can be seen in Fig. 2. Even so, the overall fusion rate
FIGURE 2. Comparison between the fusion rate in plasma (Bare Cross-Section) and when fusion occurs in a solid material as the result of applying energy to the bombarding D+ ions, as shown by the X-axis. A value of unity occurs when the rate in plasma is equal to the rate using a target material.(6)
decreases as applied energy is reduced. In other words, the environment in a material can slightly increase the fusion rate but it does not significantly offset the reduction in the rate as applied energy is lowered. While the electrons clearly help lower the barrier to achieve hot fusion, this effect alone would seem too small to explain the LENR process, although it might make a small contribution. In any case, the measured shielding effect applies only to the hot fusion mechanism.
Perhaps more effective shielding during LENR might be expected if the shielding electrons were contained in the unique nuclear-environment rather than having a random and lower concentration in the general where hot fusion interaction takes place. An evaluation of just how the electrons function during LENR compared to hot fusion requires LENR not be viewed as extension of hot fusion.
Once the nuclei of deuterium have fused by hot fusion, the assembly breaks into fragments, which dissipate the excess mass-energy as kinetic energy. Easily detected energetic neutrons, tritium, protons, and He3 are produced in equal amounts. This process is understood and is consistent with conventional expectations. A similar result occurs when muons are used to bring the nuclei close enough to cause fusion. In other words, no matter whether energy is used to overcome the Coulomb barrier by brute force or the separation is reduced by using the heavy muon(7-10), the same energy dissipation process results.
No other method for energy dissipation as result of a fusion reaction was known to occur in nature until “cold fusion” was discovered. Clearly, the mechanisms causing hot fusion and cold fusion are significantly different because LENR does not lead to fragmentation of the nuclear products.
Cold fusion is novel because it does not require significant applied energy to overcome the Coulomb barrier and it does not result in fragmentation of the fusion product as occurs during hot fusion. This difference has caused much skepticism about the reality of LENR. After all, experience and teaching deny any possibility of spontaneous fusion taking place in an ordinary chemical structure without the need to apply significant energy.
This apparent contradiction is resolved by proposing the cold fusion process takes place in a unique structure, called the nuclear-active-environment (NAE) where a novel mechanism can operate. Questions about how this structure forms, where in the chemical structure this formation takes place, the nature of the unique conditions at the NAE, and the nuclear mechanism operating therein are explored later in this paper.
Role of chemical structure
Because the LENR process takes place within a chemical structure, it must play by the rules such a structure imposes. This conclusion is critical to understanding the LENR process. These rules include the Laws of Thermodynamics and the Phase Rule. Local energy cannot spontaneously increase without violating the Second Law of Thermodynamics and the local concentration of ambient energy is limited by how much energy the chemical bonds can tolerate before melting or decomposition results. Simply stated, energy cannot go up hill and its density cannot exceed the strength of the container.
If a novel mechanism is proposed to concentrate energy in order to cause nuclear fusion, why it is not found to affect chemical reactions? After all, if such a process were possible, it would be expected to operate in normal chemicals and cause chemical effects before the local energy had increased enough to cause a nuclear reaction.
For example, the mechanism of energy transfer to electrons proposed by Widom and Larsen(11, 12) would be expected to make many normal chemical compounds unstable. Furthermore, how such a proposed violation of the Second Law of Thermodynamics can function in PdD needs to be justified. Similar conflicts with the laws of thermodynamics and normal chemical behavior create a similar weakness in many explanations now being proposed.
Normally, nuclear reactions of any kind are not affected by the chemical environment because the energy states are too different and local energy density cannot be increased according to the Second Law of Thermodynamics. Amazingly, the normal level of local ambient energy is sufficient to initiate the LENR process at high rate on rare occasions. Explaining how this “magic” takes place is the first of two basic challenges. The second challenge involves how the resulting energy is dissipated as heat.
Once fusion occurs, the structure must convert the excess mass-energy to heat without causing local melting. After all, local destruction of the active site would stop further heat production and severely limit the amount of energy produced by LENR, which is not experienced.
Although local melting is occasionally seen, it is not sufficient to create a limit to the amount of power or its stability over time. Thus, both the presence of a little local melting and the absence of extensive melting have to be explained.
Several different chemical structures have been found to support LENR, with PdD given the most attention. Consequently, PdD is the focus of further discussion.
Palladium deuteride has attracted interest for about the last 100 years(13) during which time it has been studied extensively. Although the palladium can acquire hydrogen up to about PdD0.98±0.02, nothing about the overall behavior would suggest an ability to host a fusion reaction.
The structure is face-centered-cubic (fcc) and exists in two slightly different forms having the same crystal structure based on the Pd sublattice. The alpha phase occurs between pure Pd and about PdD0.05, and the beta phase forms near PdD0.6 when 1 atm of D2 pressure is applied at 20° C. A two-phase region exists between these two compositions. The beta phase continues to acquire D atoms at random sites in the fcc sublattice as pressure is increased, finally reaching the upper limit of the fcc phase.
Fig 3 shows the structure when all lattice sites are fully filled by deuterium. Another phase is expected to form and grow in amount as the overall D/Pd ratio increases beyond the upper limit to the fcc phase, similar to the behavior of other metallic hydrides.(14, 15) In other words, any composition in excess of PdD0.98 would be expected to be a two-phase mixture of the fcc and another phase having a different structure and increased stoichiometry.
In the absence of the rare double occupancy(16, 17) of normal lattice sites, the deuterium nuclei are too far apart to fuse. Achieving close approach without violating the rules of chemistry and without producing fragmentation typical of hot fusion remains a serious challenge discussed in a later section.
Identifying where the NAE is located and what form it takes in the material has created a problem for many proposed explanations. Many explanations assume the fusion process takes place in a modification of the fcc structure when the D/Pd ratio is large. Formation of such a structure would be apparent because its formation would cause changes in various properties.
A search for the expected change can be made by examining several known properties, such as resistivity and lattice parameter as a function of D/Pd. The lattice parameter can be seen to have a linear(18-21) relationship to composition with no indication of a two-phase region forming within the limits of the beta phase. Both the pressure and resistivity(22) also show no sign of a change in crystal structure(23) over the composition range of interest. In every way, all properties are consistent with a normal fcc structure being present within the composition range in which LENR is found to occur.
FIGURE 3. Crystal structure of the face-centered-cubic PdD when all deuterium sites (small purple) are filled. (Wikipedia)
On the other hand, Fukai(24) reported formation of a phase change when high pressure is applied at high temperature to PdH. This structure is proposed to also form under normal conditions during electrodeposition.(25) Superabundant vacancies are proposed to form in the metal sublattice. A similar structure change is proposed to be caused by deformation induced vacancies.(26) This behavior might also occur when repeated loading and deloading of PdD causes the structure to expand, producing what Storms(27) calls excess volume. Nevertheless, this condition does not explain LENR because the presence of excess volume over about 2% is found to inhibit LENR(28) rather than aid the reaction as would be expected if formation of metal atom vacancies were required to support LENR.
Even though the proposed vacancies are not associated with the LENR process, a unique condition is expected to form in the PdD in order for LENR to take place. This conclusion is consistent with common experience. When a piece of Pd is found to be nuclear active, most of the entire batch is also found to be nuclear active.
In addition, once the sample is made nuclear active, the LENR process using that piece becomes reproducible and robust. Obviously, treatment of the entire batch of Pd creates stable conditions in which the LENR process can be initiated and supported for extended times.
Unfortunately, these conditions are hard to produce because their unique characteristic is unknown and rarely formed. Even when certain important initial conditions are present, an additional special treatment is required before the nuclear process can be produced by PdD. These observations are important because they show a treatment is possible to make large amounts of palladium nuclear active. A suggested combination of conditions is described later in this paper.
Initially, the LENR reaction was thought to take place anywhere in the PdD structure. Later studies reveal both helium(29, 30) and tritium(31) form only very near the surface and not within the bulk material or on the surface where nanoparticles might be present when electrolysis is used. Transmutation products are also detected mainly in the surface region.
Based on the known behavior of helium in PdH(32, 33), the nuclear reactions apparently take place within a region perhaps no more than 10 μm wide, extending from the surface. We now need to discover the nature of the unique condition forming within this narrow band. The condition does not appear to involve a phase change, creation of vacancies in the hydride structure, creation of nanoparticles on the surface, nor does it require a high concentration of deuterium.
Formation of NAE would appear to require conditions formed by a unique process, which apparently only forms near the surface.
IMPORTANT OBSERVED BEHAVIOR
Formation of the NAE
In order for fusion to take place, the reacting nuclei must obviously be in the same place at the same time. This condition is not normally present. Normally, the D atoms are located too distant to fuse.
For atoms to assemble in a chemical structure, Gibbs energy must be released while the material achieves a different stable state. Generally, the atoms in a chemical structure are close to their equilibrium condition and do not contain excess energy or have the ability to form another crystal structure unless the conditions are significantly changed. Simply increasing the D/Pd ratio does not create sufficient energy to change the structure in order to initiate the LENR process.
Furthermore, for the process to be as rare and as difficult to initiate as is observed, the conditions for releasing this energy must be equally rare and difficult to create. To make the problem even more challenging, once the NAE is formed, LENR must operate at a significant rate without further change in conditions. These conditions immediately place a limit on any proposed condition in which LENR can take place.
Most samples of PdD do not host the LENR process regardless of the deuterium content presumably because the unique NAE is not initially present in the material. This conclusion suggests the NAE is not related to any of the features normally found in a chemical structure, such as vacancies, dislocations, and occupancy of unusual lattice sites. After all, if the NAE were related to these common features, the effect would be initiated more easily and more often.
Multiple occupancy of the normal deuterium-atom vacancy must also be rejected based on this conclusion because, if such occupancy were possible, it would be present in all material under normal conditions and cause LENR with greater frequency.
Nevertheless, a rare condition must form as result of some kind of treatment in order to account for occasional success. Failure to initiate LENR simply means this treatment was not successful in producing the required NAE. Once produced, the NAE appears to be stable and relatively constant in amount as indicated by production of relatively constant power.
Experience reveals another important behavior. When part of a batch of palladium can be made nuclear active, the remainder of the batch is found to be active. This activation treatment does not simply involve reaction with D but also requires extended electrolysis and/or repeated deloading and loading with D.
This behavior is important because it revels a condition can be created throughout an entire batch of Pd as result of a common treatment that can eventually host the LENR process. In other words, the physical treatment before reacting with deuterium affects later initiation of LENR.
Once the nuclei are assembled in the NAE, a unique process must reduce the Coulomb barrier perhaps by a tunneling mechanism without using energy beyond that which is normally available at room temperature. Immediately, we are confronted by a problem. Normal chemical structures are known not to support nuclear reactions without significant energy being applied to bombarding ions. After all, the Coulomb barrier keeps nuclei separated and allows chemical structures to form in the first place by interaction between the electrons.
The energy required to force the nuclei close enough to fuse is well in excess of the energy holding the atoms in the structure and in excess of the electron energy. This well-known and accepted behavior suggests a need to form a novel
arrangement between the nuclei in the NAE designed to avoid this limitation.
In summary, two separate processes have to be considered. The first is creation of the NAE. The second is formation of a structure of H and/or D within the NAE having the ability to fuse. This nuclear process is separate from the structure of the NAE, but needs to be consistent with it.
A description of the fusion process is a job for physics while identification of the NAE is a job for chemistry. Thus, we are forced to acknowledge an uncomfortable marriage between two normally independent branches of science, with chemistry being applied first to identify the NAE.
Nature of the NAE
Two different kinds of NAE have been suggested. Many researchers place the LENR process in the normal crystal structure where vacancies or dislocations might be present. Different variations of the crystal lattice are proposed, including formation of nanoparticles and active sites on the surface of the structure.
In contrast, Storms(34) places the NAE in cracks having a critically small gap, which are separate from and chemically independent of the crystal structure. Such an environment can have properties much different from a crystal structure, including a high negative charge.
Resolving this fundamental difference in proposed location of the NAE is critical to understanding the LENR process because the chosen location sets the logic on the correct path to discovering the mechanism. A choice of the wrong path will result in arriving at the wrong understanding.
In order to contrast these two proposed conditions, the well documented suggestion by Hagelstein et al.(35) is explored. The Hagelstein idea is based on formation of a new phase in the normal fcc structure, such as suggested by Fukai and Okuma(36). This phase is proposed to form on occasion after deuterium content has exceeded D/Pd=0.85, thereby causing formation of palladium atom vacancies.
Deuterium atoms fill the vacant sites and form a structure in which fusion is proposed to occur. The resulting mass-energy is dissipated by phonons.
Evidence for this proposed phase change could be obtained by searching for a discontinuity in the various properties. As noted above, such a search reveals no evidence for a phase change within the composition range of the beta phase.
In addition, X-ray and neutron diffraction studies of the face-centered-cubic structure reveal no phase change in this composition range. Using a similar argument, all the other explanations of LENR involving changes in gross structure can be rejected.
The NAE is apparently a feature outside of the thermodynamic behavior and its presence does not affect the measured physical properties. While arguments based on the absence of behavior are usually ignored, in this case the failure of the physical properties to respond to the change required to form a NAE is an important characteristic of the LENR process.
The author, in several previous papers (37-39), proposes the NAE resides in nanocracks resulting from stress relief. These gaps exist outside of the chemical properties and are not influenced by the limitations imposed by the chemical structure.
As long as a gap having a critically small width is created, deuterons are proposed to enter the gap and form a structure that can be described in many different ways. This structure then experiences fusion by a novel mechanism.
The required gap width is rarely created because most cracks would quickly become too wide to host the required hydrogen structure. Success in creating the NAE involves creating modest stress and applying it to a structure containing many weak regions having similar ability to form small cracks.
This condition might be created by accident as result of various intended and accidental treatments applied during a study, thus accounting for occasional success without apparent reason. Although large cracks are often seen when LENR occurs, the cracks having the ability to act as the NAE are too small to be easily detected and can be overlooked.
In fact, unless these structures are sought using high magnification, they would be impossible to detect. Experience shows the critical initial condition can also be created in a batch of material by a yet to be identified pretreatment. This realization encourages the search for such a treatment from which production of large amounts of nuclear active material can be expected to result.
Deciding which explanation should be explored is important because they each propose entirely different treatments to cause the LENR process. The wrong choice of explanation can lead a researcher down the wrong path with much wasted effort.
Power production
The LENR effect was first identified by its ability to produce energy in amounts greater than would be possible by any chemical reaction. This energy has been produced when Pd is used as the cathode in an electrolytic cell using an electrolyte consisting of D2O+LiOD.
When a Pd cathode is initially subjected to this treatment, the deuterium concentration in the Pd increases while energy is absorbed by the reaction, as shown in Fig. 4. Energy is absorbed because the energy used to decompose the D2O into D2 and O2 is greater than is recovered when the resulting D2 reacts with Pd, thereby causing an overall endothermic reaction.
FIGURE 4. The D/Pd ratio and resulting power when Pd is reacted with D2O using the electrolytic method. All D made available by the applied current initially reacts with the Pd. The amount reacted is reduced only gradually as the upper limit is reached. No excess energy is produced even after the average D/Pd ratio becomes very large. The total amount of energy/mole Pd absorbed by the process is noted. (Storms, www.LENRexplained.com)
The enthalpy of formation for deuterium can be calculated using the data in Fig. 4. For this purpose, the total amount of D reacted every six minutes is divided by the amount of energy absorbed during this time, from which the amount of energy used to decomposed the D2O is subtracted.
As can be seen in Fig. 5, the electrolytic method applied to a solid piece of Pd gives values for the partial enthalpy of formation similar to the values obtained when D2 is reacted directly with Pd nanopowder. Both reactions show that chemical energy is released when Pd reacts with D2 and the amount decreases as the D/Pd ratio increases.
FIGURE 5. Enthalpy of formation calculated using the data shown in Fig. 4 based on the amount of D reacted every 6 minutes, the amount of power measured during this time, and the amount of energy used to decompose the D2O from which the D results. The reaction of D2 with Pd is exothermic. The Sakamoto et al. (40) line is obtained using their reported linear equation, which is then extrapolated from D/Pd= 0.85 to 0.98, and their reported D2 pressure. The pressure of D2 is also obtained from the review by Santandrea and Behrens(41). (Storms, www.LENRexplained.com)
The equilibrium deuterium activity, as pressure, is also plotted to show the large range in values being applied to the material. This quantity can be described as pressure only when the gas phase is present and is in equilibrium with the solid. The deviation from ideal behavior, called fugacity, is not taken into account.
No excess energy was produced even though a very high D/Pd ratio was reached. Additional treatment was later required to start the LENR process.
No additional phase forms in this composition range, such as proposed by Fukai, as indicated by the smooth unbroken variation of ΔH and pressure.
Also, the smooth unbroken change in resistivity observed by McKubre et al.(22) while LENR took place is consistent with this conclusion.
The effect of temperature on power production for various D/Pd ratios is compared in Fig. 6. Samples having D/Pd = 0.80 and 0.48 produce the same amount of power at the same temperature. Removal of all deuterium stops power production. Clearly, power is not as sensitive to the deuterium content as previous studies suggest(42). Nevertheless, some D is required for LENR to function.
The Arrhenius plot (Fig. 7), using the data in Fig. 6 (D/Pd=0.8), shows the activation energy for the LENR process to be nearly equal to the value for diffusion of D in PdD. In other words, the rate of the fusion process is sensitive to the rate at which D can get to the site where fusion takes place and it is not sensitive to the concentration of D in the surrounding lattice.
The fusion process can be proposed to rapidly convert deuterium in the NAE to fusion products, after which new D has to move relatively slowly from the surrounding lattice in order to supply additional fuel to the active sites.
The rate of energy production is determined by the rate at which D can get to the NAE.
By analogy, this is similar to the speed of a car being determined by how fast gas is delivered to the engine and not related to the amount of gas in the tank or the reaction rate within each cylinder. The resulting equation allows the resulting power to be predicted when temperature is increased.
FIGURE 6. Effect of temperature on power production when three different amounts of deuterium are present in the sample. (Storms, www.LENRexplained.com)
FIGURE 7. Comparison between the rate of diffusion of D in PdD and production of LENR power as a function of 1/T. The similar slopes created by the data suggest both processes are affected by the same mechanism, i.e. diffusion of D though PdD. (43)
Probability of forming the NAE
Figure 8 compares power produced by 157 studies reported before 2007. Notice that most studies produce power at relative low levels. On a few occasions, a large amount of power is observed with the number of reports rapidly decreasing as the reported power increases. The number of reports, shown in Fig. 8 can be compared to
FIGURE 8. Histogram of power production vs the number of reported values. A probability function, shown as the dashed line, is used to fit the data to bins at 10 watt intervals.
predicted behavior based on an assumed probability of causing increased power once power production is possible. In other words, the probability of forming additional NAE once the conditions allow some NAE to form can be estimated and compared to the behavior to see if the assumption fits.
If 300 attempts are made to initiate LENR and the probability of producing 10 watts is 0.3, the probability of producing 20 watts would be 0.3×0.3, and the probability of producing 30 watts would be 0.3×0.3×0.3 etc.
The number of predicted successful observations at each power level is shown by the dashed line. The relatively good fit to the observed behavior suggests the power is caused by an increasing number of active sites whose production is caused by a random process, with more power resulting as the number of NAE sites is increased by a process having low probability. The probability of producing any power at all would be expected to be much less than producing additional power once conditions allow some NAE to form.
Continue reading How basic behavior of LENR can guide a search for an explanation
How basic behavior of LENR can guide a search for an explanation pdf TOC
INTRODUCTION
The nature of the hot fusion mechanism
Role of chemical structure
IMPORTANT OBSERVED BEHAVIOR
Formation of the NAE
Nature of the NAE
Power Production
Probability of forming the NAE
Helium Production
Tritium Production
Transmutation Production
SUMMARY OF BEHAVIOR
CREATING A THEORY
ASSUMPTIONS
LENR Initiation as a Chemical Reaction
Nuclear Process Applied to LENR
Role of h4 formation
Consequence of LENR using a mixture of d and p
Transmutation
How does the fusion process work?
Reduction of Coulomb barrier
Dissipation of excess mass energy
Photons as the energy dissipation method
Electrons as the energy dissipation method
Phonons as the energy dissipation method
Storage of energy after fusion
Effect of different variables
TESTABLE PREDICTIONS
Creation of the NAE
DISCUSSION
SUMMARY
by
## Shift theoretical focus from nuclear consequences to chemical beginnings
I would like to emphasize one other aspect of LENR that is frequently overlooked: Fusion can be caused by two different mechanisms.
The common one, called hot fusion, involves applying high energy to the reacting nuclei. This approach takes advantage of the increased reaction rate applied energy provides. Science has ignored what happens when fusion takes place at low energy because the rates are too low to study the process.
Discovery of LENR, called cold fusion, has revealed how the fusion rate can be increased without using applied energy. However this process requires a unique condition I identify as the NAE. As many people have noted, the NAE acts like a catalyst so that applied energy is no longer required. This being the case, the essential understanding of the LENR process resides in the nature of the NAE. Creation of the NAE makes LENR possible and the unique fusion mechanism operates only within the confines of the NAE.
A condition is created within the NAE in which the Coulomb barrier can be overcome without applied energy, and mass-energy can be converted to heat energy without producing the high-energy radiation normally associated with nuclear interaction. The magic of LENR takes place in and only in the NAE.
This concept does not conflict with or violate any physical law because this unique condition has yet to be explored by science. This is virgin territory having no relationship to hot fusion or to the concepts obtained from studies of the hot fusion mechanism.
Therefore, identifying and describing the NAE is essential to creating a useful theory about LENR. Because the NAE is part of a chemical structure, the chemical conditions must be part of this understanding.
Unlike hot fusion, which occurs in plasma, cold fusion is strongly influenced by the chemical properties of the material in which NAE forms. Most theories mistakenly ignore the chemical requirements.
Without a chemical structure and its chemical behavior, the NAE cannot form and LENR cannot occur. Consequently, LENR is first and foremost a chemical process with nuclear consequences. Thus, the focus should be shifted from the nuclear consequences to those conditions required to form the NAE and to its role in hosting the nuclear reactions.
This idea might be a bridge too far for many theoreticians, nevertheless, I strongly suggest an effort be made to cross the bridge rather than keep trying to swim the river.
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https://queue-it.com/blog/queuing-theory/ | # Queuing theory: Definition, history & real-life applications
Queuing theory is a powerful tool to analyze the daily phenomenon of waiting in line. Discover how to define queuing theory, how it started, why it’s important, and how it can be applied to real-life situations.
Published:
Updated: 30 Sep 2022
## 1. What is queuing theory?
Queuing theory (or queueing theory) refers to the mathematical study of the formation, function, and congestion of waiting lines, or queues.
At its core, a queuing situation involves two parts.
1. Someone or something that requests a service—usually referred to as the customer, job, or request.
2. Someone or something that completes or delivers the services—usually referred to as the server.
To illustrate, let’s take two examples. When looking at the queuing situation at a bank, the customers are people seeking to deposit or withdraw money, and the servers are the bank tellers. When looking at the queuing situation of a printer, the customers are the requests that have been sent to the printer, and the server is the printer.
Queuing theory scrutinizes the entire system of waiting in line, including elements like the customer arrival rate, number of servers, number of customers, capacity of the waiting area, average service completion time, and queuing discipline. Queuing discipline refers to the rules of the queue, for example whether it behaves based on a principle of first-in-first-out, last-in-first-out, prioritized, or serve-in-random-order.
## 2. How did queuing theory start?
Queuing theory was first introduced in the early 20th century by Danish mathematician and engineer Agner Krarup Erlang.
Erlang worked for the Copenhagen Telephone Exchange and wanted to analyze and optimize its operations. He sought to determine how many circuits were needed to provide an acceptable level of telephone service, for people not to be “on hold” (or in a telephone queue) for too long. He was also curious to find out how many telephone operators were needed to process a given volume of calls.
His mathematical analysis culminated in his 1920 paper “Telephone Waiting Times”, which served as the foundation of applied queuing theory. The international unit of telephone traffic is called the Erlang in his honor.
Image via Reddit
## 3. What are the different types of queuing systems?
Queuing theory uses the Kendall notation to classify the different types of queuing systems, or nodes. Queuing nodes are classified using the notation A/S/c/K/N/D where:
• A is the arrival process
• S is the mathematical distribution of the service time
• c is the number of servers
• K is the capacity of the queue, omitted if unlimited
• N is the number of possible customers, omitted if unlimited
• D is the queuing discipline, assumed first-in-first-out if omitted
For example, think of an ATM.
It can serve: one customer at a time; in a first-in-first-out order; with a randomly-distributed arrival process and service distribution time; unlimited queue capacity; and unlimited number of possible customers.
Queuing theory would describe this system as a M/M/1 queue (“M” here stands for Markovian, a statistical process to describe randomness).
Queuing theory calculators out there often require choosing a queuing system from the Kendall notation before calculating inputs.
## 4. Why is queuing theory important?
Waiting in line is a part of everyday life because as a process it has several important functions. Queues are a fair and essential way of dealing with the flow of customers when there are limited resources. Negative outcomes arise if a queue process isn’t established to deal with overcapacity.
For example, when too many visitors navigate to a website, the website will slow and crash if it doesn’t have a way to change the speed at which it processes requests or a way to queue visitors.
Related: What is an Online Queue System?
Or, imagine planes waiting for a runway to land. When there is an excess of planes, the absence of a queue would have real safety implications as planes all tried to land at the same time.
Queuing theory is important because it helps describe features of the queue, like average wait time, and provides the tools for optimizing queues. From a business sense, queuing theory informs the construction of efficient and cost-effective workflow systems.
## 5. What are the applications of queuing theory?
Queuing theory is powerful because the ubiquity of queue situations means there are countless and diverse applications of queuing theory.
Queuing theory has been applied, just to name a few, to:
• telecommunications
• transportation
• logistics
• finance
• emergency services
• computing
• industrial engineering
• project management
Before we look at some specific applications, it’s helpful to understand Little’s Law, a formula that helps to operationalize queuing theory in many of these applications.
### Little’s Law
Little’s Law connects the capacity of a queuing system, the average time spent in the system, and the average arrival rate into the system without knowing any other features of the queue. The formula is quite simple and is written as follows:
$\fn_jvn&space;L=\lambda&space;W$
or transformed to solve for the other two variables so that:
$\fn_jvn&space;\lambda=\frac{L}{W}$
$\fn_jvn&space;W=\frac{L}{\lambda}$
Where:
• L is the average number of customers in the system
• λ (lambda) is the average arrival rate into the system
• W is the average amount of time spent in the system
Project management processes like Lean and Kanban wouldn’t exist without Little’s Law. They’re critical for business applications, in which Little’s Law can be written in plain English as:
$\fn_jvn&space;Work\&space;in\&space;Progress=Throughput\ast&space;Lead\&space;Time$
$\fn_jvn&space;Throughput=\frac{Work\&space;in\&space;Progress}{Lead\&space;Time}$
$\fn_jvn&space;Lead\&space;Time=\frac{Work\&space;in\&space;Progress}{Throughput}$
### Little’s Law Applied to Real-World Situations
Little’s Law gives powerful insights because it lets us solve for important variables like the average wait of in a queue or the number of customers in queue simply based on two other inputs.
#### A line at a cafe
For example, if you’re waiting in line at a Starbucks, Little’s Law can estimate how long it would take to get your coffee.
Assume there are 15 people in line, one server, and 2 people are served per minute. To estimate this, you’d use Little’s Law in the form:
$\fn_jvn&space;\frac{L}{\lambda}=W$
Showing that you could expect to wait 7.5 minutes for your coffee.
$\fn_jvn&space;\frac{15\&space;people\&space;in\&space;line}{2\&space;people\&space;served\&space;per\&space;minute}&space;=&space;7.5\&space;minutes\&space;of\&space;waiting$
Image by John Yorke
#### A line in a virtual waiting room
At Queue-it, we show visitors their wait time in the online queue using a calculation based on Little’s Law, adding in factors to account for no-shows and re-entries:
$\fn_jvn&space;\frac{L}{\lambda}\ast&space;\frac{1-N}{1-R}=W$
Where:
• L is the number of users ahead in line
• λ (lambda) is rate of redirects to the website or app, in users per minute
• N is the no-show ratio
• R is the re-entry rate to the queue
• W is the estimated wait time, in minutes
#### Process optimization
We can look at a process optimization example from the military, courtesy of Process.st.
In this real-life example, the military needed to determine the ideal amount of time B-2 stealth bombers would be in maintenance. There are only 20 B-2 aircraft and they need to be ready at a moment’s notice. But they require frequent maintenance, which can range anywhere from 18 to 45 days. Using Little’s Law would help find the balance of aircraft in use versus aircraft under maintenance.
Image by skeeze from Pixabay
Based on flight schedule analysis, it was calculated that three B-2 bombers would be under maintenance at any given time. The rate at which bombers entered maintenance was also calculated to be roughly every 7 days. So:
• L= number of items in WIP (maintenance) = 3
• A= arrival/departure rate = 1 every 7 days = 1/7 days
• W= the average amount of time spent in maintenance = ???
Put into Little’s Law, this leaves us with:
Therefore, the target lead time for B-2 bomber maintenance needed to be 21 days to meet the demands of both available aircraft and the regular flight schedules.
## 6. How does queue psychology impact queuing?
Queuing theory is helpful in explaining the math behind how queues run. But when queues involve humans, queue psychology is important to understand the queue experience as well.
Queue psychology research shows it’s not the length of the wait that determines how positive or negative the queue experience is, but rather how people feel while waiting.
For example, unoccupied time feels longer than occupied time. Distractions or the ability to do something else while in line makes time feel like it goes by faster. And uncertain waits feel longer than known, finite waits.
That’s why the callback option on customer service lines is so popular. You can feel the anxiety go down when you get the option to be called back in 10 minutes, freeing you to do something else instead of listening to that terrible muzak for an unknown amount of time.
For queuing situations involving people—like websites that use an online queuing system—the psychological rules governing the queues are just as important as the mathematical ones. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 9, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.42632099986076355, "perplexity": 1547.3098419148623}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-40/segments/1664030337524.47/warc/CC-MAIN-20221004184523-20221004214523-00547.warc.gz"} |
https://index.mirasmart.com/ISMRM2019/PDFfiles/2426.html | ### 2426
A GPU-based Modified Conjugate Gradient Method for Accelerating Wave-CAIPI Reconstruction
Haifeng Wang1, Shi Su1, Xin Liu1, Yuchou Chang2, and Dong Liang1
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Department of Computer Science and Technology Engineering, University of Houston-Downtown, Houston, TX, United States
### Synopsis
Wave-CAIPI is a novel 3D imaging method with corkscrew trajectory in k-space to speed up MRI acquisition. However, the 3D data acquisitions of Wave-CAIPI are also tremendous for reconstruction calculations. In order to accelerate the reconstruction procedure, we realized a Wave-CAIPI reconstruction using a modified GPU-based conjugate gradient (CG) algorithm to reduce time cost of reconstructions. The experiments of in vivo human brain dataset show that using our GPU-based Wave-CAIPI reconstruction can achieve similar image results as the conventional CPU-based Wave-CAIPI reconstruction with less time cost than the conventional CPU-based Wave-CAIPI reconstruction.
### Introduction
Recently, Wave-CAIPI is a new 3D imaging method with corkscrew trajectory in k-space to speed up MRI acquisition 1. Different from the traditional parallel imaging methods 2-4, Wave-CAIPI combines and extends the 2D-CAIPI 5 and Bunched phase encoding (BPE) 6 strategies by simultaneously playing sinusoidal Gy and Gz gradients. However, the 3D data acquisitions of Wave-CAIPI are tremendous for reconstruction calculations, which cannot achieve real-time processing. Currently, the modern competitive platforms of graphics processing unit (GPU) become more and more powerful to accelerate reconstruction computations for the real-time needs of clinical applications. So, in this work, we developed a GPU-based Wave-CAIPI reconstruction using modified conjugate gradient (CG) algorithm 7 based on NVIDIA CUDA platforms 8 to reduce time cost of Wave-CAIPI reconstructions. The experiments of in vivo 7T dataset of human brain show that using our GPU-based Wave-CAIPI reconstruction can achieve similar image results as the conventional CPU-based Wave-CAIPI reconstruction and reduce more 70.9% computation time cost than the conventional CPU-based reconstruction. Moreover, the modified GPU-based CG algorithm can be easy to be transplanted to other similar applications.
### Theory and Methods
It is known that the CG method 7 is an optimization algorithm for the numerical solution of linear equations which is implemented as an iterative algorithm. The Wave-CAIPI reconstruction is a optimization problem that can be formulated as a least-squares minimization problem solved by an iterative LSQR algorithm 1. Here, the iterative LSQR algorithm minimizes $\parallel A(x)-y\parallel_2^2$ , where $A(\cdot)$ is the encoding function of Wave-CAIPI reconstruction, while x and y are respectively the unknown image rows and the wave coil data in this equation. Because data is tremendous and every unknown image row has to solve an iterative minimization problem, the reconstruction procedure of CPU-based Wave-CAIPI is frequently slower than CPU-based 2D-CAIPI 5. In order to accelerate reconstruction calculation speed of Wave-CAIPI, we solve the least-squares problem with the GPU-based a modified CG method 7-10. As seen as the Fig. 1, the algorithm flow of the modified GPU-based CG method is expressed, and the encoding function $A(\cdot)$ of the Wave-CAIPI applications on GPU is also described. Here, retrospectively acceleration factor was Ry×Rz=3×3. And, the center 48×48 region of k-space was applied to estimate the sensitivity maps by ESPIRiT 11. The current point spread function (PSF) estimation uses three fully sampled calibration scans (i.e. no wave, wave gradient y, wave gradient z).
### Results
The dataset were scanned at 7T MR scanners (Siemens AG, Erlangen, Germany) with 32-channel head coils and 3D Wave-CAIPI sequence (FOV: 224×224×120 mm3; voxel size: 1×1×2 mm3; maximum wave gradient amplitude: 6 mT/m; maximum slew rate: 50 mT/m; 7 sinusoidal wave cycles per readout) 1. All reconstruction calculations were running on the MATLAB (MathWorks Inc., Natick, Massachusetts, USA) and CUDA (NVIDIA Corp., Santa Clara, California, USA) platforms. Here, the workstation platform has CPU is Intel (R) Core(TM) i7-4770 Dual-Core (3.4G Hz, 8M Cache); GPU is NVIDIA GTX770 (1536 CUDA Cores, 1.2G Hz); RAM is 8G; OS is Microsoft Windows 6 64-bit. Here, the acceleration factors are all Rz× Ry = 3×3; Rz is the acceleration factor along Z direction; Ry is the acceleration factor along Y direction. Fig. 2 shows the comparison of the BPE and Wave-CAIPI reconstruction with GPU-based CG methods. The GPU-based Wave-CAIPI reconstruction only spends 9 seconds which is about 70.9% time cost of the previous CPU-based Wave-CAIPI reconstruction. At the same time, the GPU-based BPE reconstruction also spends about 55.6% time cost of the corresponding CPU-based reconstructions. And, Fig. 3 shows that the reconstruction results of 2D CAIPI, CPU-based and GPU-based BPE, and CPU-based and GPU-based Wave-CAIPI. Here, they show very similar reconstruction results visually. To quantitatively compare them, Fig.4 illustrated that the difference maps between Wave-CAPI and 2D CAIPI respectively based on GPU and CPU. Simultaneously, the difference maps between BPE and 2D CAIPI also present for comparisons. The proposed GPU-based Wave-CAPI reconstruction with the modified CG reconstruction method has less computational time cost than the conventional CPU-based reconstruction and still reserves the similar details as the conventional CPU-based results.
### Discussion and Conclusion
In sum, we implement the proposed GPU-based Wave-CAPI reconstruction with the modified CG minimization algorithm to accelerate the conventional CPU-based Wave-CAIPI reconstruction. The current reconstruction results of the proposed methods have shown the attractive potential of reducing time cost of the Wave-CAPI reconstruction from tremendous dataset. In the future, more optimal GPU-based algorithm of the Wave-CAIPI reconstruction will be studied to achieve faster data processing.
### Acknowledgements
The authors also thank Dr. Berkin Bilgic, Michael Saunders and Chris Fougner for their open-source codes. This study is partial supported by the grant from the National Science Foundation of China (No. 61471350, No. 81729003, No. 61871373), Guangdong Provincial Key Laboratory of Medical Image Processing (No. 2017A050501026), National Science Foundation of Guangdong (No. 2018A0303130132).
### References
1. Bilgic B, Gagoski BA, Cauley SF, Fan AP, Polimeni JR, Grant PE, Wald LL, Setsompop K. Wave-CAIPI for highly accelerated 3D imaging. Magn Reson Med. 2015 Jun;73(6):2152-62.
2. Sodickson DK, Manning WJ. Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays. Magn Reson Med. 1997 Oct;38(4):591-603.
3. Pruessmann KP, Weiger M, Scheidegger MB, Boesiger P. SENSE: sensitivity encoding for fast MRI.Magn Reson Med. 1999 Nov;42(5):952-62.
4. Griswold MA, Jakob PM, Heidemann RM, Nittka M, Jellus V, Wang J, Kiefer B, Haase A. Generalized autocalibrating partially parallel acquisitions (GRAPPA). Magn Reson Med. 2002 Jun;47(6):1202-10.
5. Breuer FA, Blaimer M, Mueller MF, Seiberlich N, Heidemann RM, Griswold MA, Jakob PM. Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA). Magn Reson Med. 2006 Mar; 55(3):549-56.
6. Moriguchi H, Duerk J. Bunched phase encoding (BPE): a new fast data acquisition method in MRI. Magn Reson Med 2006; 55.3:633-648.
7. Hestenes MR, Stiefel E, Methods of conjugate gradients for solving linear systems. Journal of Research of the National Bureau of Standards. 1952 Dec; 49 (6). doi:10.6028/jres.049.044.
8. NVIDIA Corp., 2017. GPU-Accelerated Libraries https://developer.nvidia.com/
9. Saunders M, CGLS: CG method for Ax = b and Least Squares, 2017; http://web.stanford.edu/group/SOL/software/cgls/.
10. Fougner C, Conjugate Gradient for Least Squares in CUDA, 2017; https://github.com/foges/cgls_cuda.
11. Uecker M, Lai P, Murphy MJ, Virtue P, Elad M, Pauly JM, Vasanawala SS, Lustig M. ESPIRiT-An Eigenvalue Approach to Autocalibrating Parallel MRI: Where SENSE Meets GRAPPA. Magnet Reson Med 2014;71(3):990-1001.
### Figures
Fig 1. Algorithm flow of the proposed GPU-based Wave-CAIPI reconstruction with the modified CG algorithm on the NVIDIA CUDA platform.
Fig 2. Time-cost comparison of the BPE and Wave-CAIPI reconstructions based CPU and GPU on the MATLAB and NVIDIA CUDA platforms. Here, the acceleration factors are all Rz× Ry = 3×3; Rz is the acceleration factor along Z direction; Ry is the acceleration factor along Y direction.
Fig 3. Reconstruction comparison of 2D CAIPI, BPE and Wave-CAIPI reconstructions based on CPU and GPU at the acceleration factors of Rz× Ry = 3×3.
Fig 4. Difference maps between 2D CAIPI and the two reconstruction methods, BPE and Wave-CAIPI, respectively based on CPU and GPU at the acceleration factors of Rz× Ry = 3×3.
Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)
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https://uwaterloo.ca/library/geospatial/population-growth-waterloo-through-1867-present | # Population Growth of Waterloo through 1867 to the present
In celebration of Canada's 150th anniversary, the Geospatial Centre has created a graphic visualizing the population growth of Waterloo from 1855 to 2016.
Using ArcGIS Online's storybook application, you can see the increase in Waterloo's population over the years. The historical maps that were used to create the population density maps can be seen in the storymap.
View story map | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9005299806594849, "perplexity": 2520.941796723178}, "config": {"markdown_headings": true, "markdown_code": false, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-45/segments/1603107907213.64/warc/CC-MAIN-20201030033658-20201030063658-00565.warc.gz"} |
https://researchportal.port.ac.uk/en/publications/a-search-for-gravitational-waves-from-binary-mergers-with-a-singl | # A search for gravitational waves from binary mergers with a single observatory
Alexander H. Nitz, Thomas Dent, Gareth S. Davies, Ian Harry
Research output: Contribution to journalArticlepeer-review
16 Downloads (Pure)
## Abstract
We present a search for merging compact binary gravitational-wave sources that produce a signal appearing solely or primarily in a single detector. Past analyses have heavily relied on coincidence between multiple detectors to reduce non-astrophysical background. However, for $\sim40\%$ of the total time of the 2015-2017 LIGO-Virgo observing runs only a single detector was operating. We discuss the difficulties in assigning significance and calculating the probability of astrophysical origin for candidates observed primarily by a single detector, and suggest a straightforward resolution using a noise model designed to provide a conservative assessment given the observed data. We also describe a procedure to assess candidates observed in a single detector when multiple detectors are observing. We apply these methods to search for binary black hole (BBH) and binary neutron star (BNS) mergers in the open LIGO data spanning 2015-2017. The most promising candidate from our search is 170817+03:02:46UTC (probability of astrophysical origin $p_{\rm astro} \sim 0.4$): if astrophysical, this is consistent with a BBH merger with primary mass $67_{-15}^{+21}\,M_{\odot}$, suggestive of a hierarchical merger origin. We also apply our method to the analysis of GW190425 and find $p_{\rm astro} \sim 0.5$, though this value is highly dependent on assumptions about the noise and signal models.
Original language English 169 9 The Astrophysical Journal 897 2 https://doi.org/10.3847/1538-4357/ab96c7 Published - 15 Jul 2020
• astro-ph.HE
• gr-qc
• GW_HIGHLIGHT
## Fingerprint
Dive into the research topics of 'A search for gravitational waves from binary mergers with a single observatory'. Together they form a unique fingerprint.
• ### Data availability statement for 'A search for gravitational waves from binary mergers with a single observatory'.
Nitz, A. H. (Creator), Dent, T. (Creator), Davies, G. S. (Creator) & Harry, I. (Creator), IOP Publishing, 15 Jul 2020
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http://math.stackexchange.com/questions/294660/trying-to-prove-let-e-be-a-hilbert-a-module-then-e-langle-e-e-rangle-i | # Trying to prove: Let $E$ be a Hilbert $A$-module. Then, $E\langle E,E\rangle$ is norm dense in $E$.
Let $E$ be a Hilbert $A$-module. Then, $E\langle E,E\rangle$ is norm dense in $E$.
I am having trouble proving this. I believe $\langle E,E\rangle$ is a $C^*$-algebra. If I can show this, then the proof is easy since all $C^*$-algebras have an approximate identity.
It seems like it shouldn't be too hard, but I am having trouble showing it.
Thank you.
-
What precisely do the notations $E\langle E,E\rangle$ and $\langle E,E\rangle$ refer to? In any case, a stronger statement can be found here: math.stackexchange.com/questions/163485/… – Jonas Meyer Feb 4 '13 at 17:14
They are in fact equal See lemma 2.2.3. of book Hilbert C*-Modules by M. Manuilov page20 But I only point out that $\langle E,E\rangle$ is a C*-subalgebra of A and so $E\langle E,E\rangle\subset E$; conversely since any x in E can be written as $x=y\langle y,y\rangle$ we have $E\subset E\langle E,E\rangle.$
-
For those who don't have that book, could you describe a bit about what that citation says? – robjohn Feb 5 '13 at 7:20 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9729763269424438, "perplexity": 191.19993694913248}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-10/segments/1394010607072/warc/CC-MAIN-20140305091007-00076-ip-10-183-142-35.ec2.internal.warc.gz"} |
https://stacks.math.columbia.edu/tag/0FQU | ## 24.2 Conventions
In this chapter we hold on to the convention that ring means commutative ring with $1$. If $R$ is a ring, then an $R$-algebra $A$ will be an $R$-module $A$ endowed with an $R$-bilinear map $A \times A \to A$ (multiplication) such that multiplication is associative and has an identity. In other words, these are unital associative $R$-algebras such that the structure map $R \to A$ maps into the center of $A$.
In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar). | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 2, "x-ck12": 0, "texerror": 0, "math_score": 0.9559610486030579, "perplexity": 229.63483383530047}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2023-06/segments/1674764499831.97/warc/CC-MAIN-20230130232547-20230131022547-00369.warc.gz"} |
https://www.physicsforums.com/threads/calculating-voltage-which-voltmeter-is-showing.900427/ | Calculating voltage which voltmeter is showing
Tags:
1. Jan 15, 2017
akaliuseheal
1. The problem statement, all variables and given/known data
Schematic of circuit is not given, only the text which I translated into English.
Using a voltmeter with internal resistance of 6k ohm, voltage between two points, 1 and 2 of a circuit of constant current, is measured to be 8v.
Then, using a voltmeter with internal resistance of 10k ohm, between the same points, voltage is measured to be 12v.
What voltage will the voltmeter with internal resistance of 15k ohm measure?
2. Relevant equations
I=U/R
3. The attempt at a solution
I tried to solve it by calculating currents getting 1.3mA and 1.2mA in first and second case, but wasn't sure what to do next.
These voltmeters should be represented as resistors and the answer is 16V.
2. Jan 15, 2017
Staff: Mentor
You're told that the current in the circuit is constant, which I take to mean that the current leaving node 2 is the same as the current entering node 1:
So $I$ is an unknown constant and $R$ is some unknown resistance lying between nodes 1 and 2. That's two unknowns. Fortunately you were given two cases where the meter resistance and the measured voltage are given, so you can construct two equations in two unknowns.
3. Jan 15, 2017
akaliuseheal
I would like to thank you for looking into this but I am unsure on how to do that. I mean, how would system of equations look like?
4. Jan 15, 2017
Staff: Mentor
Start symbolically: don't plug in any numbers, just use variables. See if you can write an expression for the voltage $V$ in terms of $I$, $R$ and $R_m$. Or, write an expression for $I$ in terms of $V$, $R$ and $R_m$. Either way is fine (although the latter may be more straight forward).
5. Jan 15, 2017
akaliuseheal
So like voltage/current divider?
V = (Rm || R) * I
6. Jan 15, 2017
Staff: Mentor
Sure, that would work. Or since the voltage is the same across both resistors it's easy to write the sum of the currents:
$I = \frac{V}{R} + \frac{V}{R_m}$
Whatever you are more comfortable with.
7. Jan 15, 2017
akaliuseheal
So it's like this.
R=30k ohm
I = 0,0016A
Replacing those values gets me the voltage of 16V.
Thanks, was struggling with this trivial problem.
8. Jan 15, 2017
Staff: Mentor
Draft saved Draft deleted
Similar Discussions: Calculating voltage which voltmeter is showing | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9061651825904846, "perplexity": 855.142365621211}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-51/segments/1512948515165.6/warc/CC-MAIN-20171212041010-20171212061010-00577.warc.gz"} |
https://www.physicsforums.com/threads/u-substitution-for-finding-v-t.191956/ | # U-substitution for finding v(t)
1. Oct 17, 2007
1. The problem statement, all variables and given/known data
A .25kg ball is dropped from rest. Air resistance is f= -.05v
a. find v(t)
b. What is the terminal velocity of the ball?
c. At what time does the ball reach 50% of its terminal velocity? 90%?
2. Relevant equations
F=ma
F= mg - .05v
3. The attempt at a solution
Began to solve the equation knowing that I have to separate the terms, moves all the velocity terms to one side, then integrate.
ma = mg - .05v
a = mg/m - .05v/m
a = g - .2v
dv/dt = g - .2v
dt = dv/(g-.2v)
now im just wondering to integrate that terms on the right. U-substitution for the denominator?
2. Oct 17, 2007
### PiratePhysicist
$$\int{\frac{du}{a+k u}}=\frac{ln(a+k u)}{k}$$
Integral tables are your friend ^_^
3. Oct 17, 2007
so just to make sure im correct, $$\int\frac{dv}{g-.2v}$$ is $$\frac{ln(g-.2v)}{.2} + constant$$
Last edited: Oct 17, 2007
4. Oct 17, 2007
alright so i assumed that was correct and went on with the problem, but ran into trouble at c.
ΣF = ma = mg - .05v
a = mg/m - .05v/.25
a = g - .2v
dv/dt = a
dv/dt = g - .2v
dv/(g - .2v) = dt
∫ dv/(g - .2v) = ∫dt
ln(g - .2v)/.2 = t - c
ln(g - .2v) = .2(t - c)
e$$^{.2(t - c)}$$ = g - .2v
e$$^{.2(t - c)}$$ - g = -.2v
-[e$$^{.2(t - c)}$$ - g]/.2 = v(t)
Ball starts at rest, v = 0 when t = 0
[e$$^{-.2c}$$ - g]/-.2 = 0
-5[e$$^{-.2c}$$ - g] = 0
-5e$$^{-.2c}$$ + 5g = 0
-5e$$^{-.2c}$$ = -5g
e$$^{-.2c}$$ = g
ln(g) = -.2c
-ln(g)/.2 = c
c = -11.42
v(t) = -5e.2(t + 11.42) + 49.05
What is the terminal velocity?
ΣF = ma = mg - .05v = 0
.05v = .25g
v = 5g = 49.05 m/s
At what time does the ball reach 50% of its terminal velocity?
v(t) = -5e.2(t + 11.42) + 49.05
v(t) = 24.525 m/s
24.525 - 49.05 = -5e$$^{.2(t + 11.42)}$$
4.905 = e$$^{.2(t + 11.42)}$$
ln(4.905) = .2(t + 11.42)
ln(4.905) - 2.284 = .2t
[ln(4.905) - 2.284]/.2 = t
t = -3.47 sec
t is negative. whattttt???? | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.48248937726020813, "perplexity": 5022.091049626524}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-22/segments/1495463609817.29/warc/CC-MAIN-20170528120617-20170528140617-00477.warc.gz"} |
https://socratic.org/questions/how-do-you-find-the-product-3t-12-3t-12 | Algebra
Topics
# How do you find the product (3t+12)(3t-12)?
May 20, 2017
See a solution process below:
#### Explanation:
This is a special form:
$\left(a + b\right) \left(a - b\right) = {a}^{2} - {b}^{2}$
Substituting $3 t$ for $a$ and $12$ for $b$ gives:
$\left(3 t + 12\right) \left(3 t - 12\right) \implies {\left(3 t\right)}^{2} - {12}^{2} \implies 9 {t}^{2} - 144$
##### Impact of this question
320 views around the world | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 6, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.28142625093460083, "perplexity": 3323.892657156854}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-05/segments/1579250590107.3/warc/CC-MAIN-20200117180950-20200117204950-00143.warc.gz"} |
http://stlab.cc/legacy/reveal-widget.html | Basic Description
The reveal (or progressive disclosure) widget is similar to a checkbox, except it has no false value. (A checkbox having an explicit false value gives it the ability to be in an indeterminant state, when it is neither true nor false.)
Semantics / Rationale
The basic behavior of a reveal widget is an arrow or icon that can be clicked on, at which point the arrow “turns down” and an optional panel to which the value is bound reveals itself. The alternate term “progressive disclosure” is more descriptive of the semantics, as there are extended pieces of the UI that are hidden until the user chooses to reveal them.
Requirements
What are the fundamental requirements this widget must meet in order to solve the problem for which it was created?
API
What does the interface of the widget look like?
Other Issues
What other issues will need consideration?
What additional code must be written to support this widget? What platform implementations / APIs can be leveraged when implementing this widget? | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.21626967191696167, "perplexity": 2240.0250831365106}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-26/segments/1529267863886.72/warc/CC-MAIN-20180620202232-20180620222232-00383.warc.gz"} |
https://digital-library.theiet.org/content/searchconcept?operator4=AND&operator5=AND&operator6=AND&operator7=AND&operator8=AND&operator9=AND&value9=c1100&value7=O.+Saito&value8=c1300&sortDescending=true&value5=c&value6=e0000&value3=1996&value4=ConferencePaper&value1=e0210a&value2=c1000&option1=pub_concept&option2=pub_concept_facet&option3=pub_year_facet&operator10=AND&option4=contentType_facet&sortField=prism_publicationDate&option10=pub_concept_facet&operator3=AND&operator2=AND&value10=c1310&pageSize=50&facetNames=pub_concept_facet+pub_year_facet+contentType_facet+pub_concept_facet+pub_concept_facet+author_facet+pub_concept_facet+pub_concept_facet+pub_concept_facet+pub_concept_facet&option9=pub_concept_facet&option8=pub_concept_facet&option7=author_facet&option6=pub_concept_facet&option5=pub_concept_facet&facetOptions=2+3+4+5+6+7+8+9+10+11&operator11=AND&option11=pub_concept_facet&value11=c1110 | http://iet.metastore.ingenta.com
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This is a required field | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8584899306297302, "perplexity": 28631.263581828174}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-16/segments/1585370521876.48/warc/CC-MAIN-20200404103932-20200404133932-00297.warc.gz"} |
https://scholarship.rice.edu/handle/1911/102242?show=full | dc.contributor.author Huang, Yin 2018-06-19T17:50:45Z 2018-06-19T17:50:45Z 2016-05 Huang, Yin. "Born Waveform Inversion in Shot Coordinate Domain." (2016) https://hdl.handle.net/1911/102242. https://hdl.handle.net/1911/102242 This work was also published as a Rice University thesis/dissertation: http://hdl.handle.net/1911/96240 The goal of this thesis is to integrate Born waveform inversion, variable projection algorithm and model extension concept to get a method that can improve the long scale background model updates reliably and efficiently from seismic data. Born waveform inversion is a partially linearized version of full waveform inversion based on Born (linearized) modeling, in which the earth model is separated into a smooth long scale background model and an oscillatory short scale reflectivity and both are updated to fit observed trace data. Because kinematic variables (background model) are updated, Born waveform inversion has the same feature as full waveform inversion: very sensitive to initial model when solved by gradient based optimization method (almost the only possible method because of the problem scale). Extended Born waveform inversion allows reflectivity to depend on additional parameters, potentially enlarging the convexity domain by enlarging the searching model space and permitting data fit throughout the inversion process and in turn reducing the sensitivity to initial model. Extended or not, the Born waveform inversion objective function is quadratic in the reflectivity, so that a nested optimization approach is available: minimize over reflectivity in an inner stage, then minimize the background-dependent result in a second, outer stage, which results in a reduced objective function of the background model only (VPE method). This thesis integrates the nested optimization approach into an inversion scheme and analyzes that the accuracy of the solution to the inner optimization is crucial for a robust outer optimization and both model extension and the nested optimization are necessary for a successful Born waveform inversion. And then we propose a flexibly preconditioned least squares migration scheme (FPCG) that significantly improves the convergence of iterative least squares migration and produces high resolution images with balanced amplitude. The proposed scheme also improves the efficiency of the solution to the inner stage of the nested optimization scheme and the accuracy of the gradient, and thus potentially improves the efficiency of the VPE method. However, a theoretical error estimate in the gradient computation of the VPE method is still hard to obtain, and we explain the reason and illustrate with numerical examples. 133 pp Born Waveform Inversion in Shot Coordinate Domain Technical report May 2016 TR16-02 Text
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https://www.physicsforums.com/threads/work-constant-pressure-changing-volume.145847/ | # Work- constant pressure, changing volume
1. Nov 28, 2006
### physics1234
Find the work done by a gas when it is expanded from a volume of 1.0 L to 3.3 L at a constant pressure of 2.8 atm.
I converted the atm to Pascals by multiplying 2.8 x 101325 to get 283710.
Then I used the formula W=p(deltaV)
so 283710 x (3.3-1.0) = 652533
I don't understand why this is the wrong answer.
2. Nov 28, 2006
### physics1234
Nevermind, I got it :-)
Thanks anyway!
3. Jul 25, 2010
### ahmed-shaqlaw
hi brother
you must convert the volume to cubic meter m3 , and to convert the pressure to kpa not pascal , by multiplying by 101.3 , try the new answer....
sorry my english is not so good | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9210379123687744, "perplexity": 3131.320628585476}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-04/segments/1484560282937.55/warc/CC-MAIN-20170116095122-00235-ip-10-171-10-70.ec2.internal.warc.gz"} |
http://math.stackexchange.com/questions/323795/the-number-of-non-trivial-polynomial-solutions-of-the-differential-equation-x3 | # The number of non-trivial polynomial solutions of the differential equation $x^3y'(x)=y(x^2)$
I came across the following problem that says:
The number of non-trivial polynomial solutions of the differential equation $x^3y'(x)=y(x^2)$ is which of the following?
$(1)0\space (2)1 \space (3)3 (4)\infty.$
Can someone point me in the right direction? Thanks in advance for your time.
-
Does the $y(x^2)$ on the right side mean $y \cdot x^2$, or on the other hand that the function $y$ is evaluated at input $x^2$? – coffeemath Mar 7 at 17:44
It is the function $y$ which is evaluated at input $x^2.$ – user52976 Mar 7 at 17:46
The only polynomial that could fit such a description is quadratic. So try $y=ax^2+bx+c$ and see the resulting system of equations by setting the coefficients of both sides equal. – Maesumi Mar 7 at 17:51
For a polynomial of order $n$, this reads: $$3+(n-1)=2n \to n=2$$ Write this out: $$2ax^4+bx^3=ax^4+bx^2+c \to ax^4+bx^2(x-1)-c=0$$ So, the answer is zero, since no such non-trivial polynomials exist (non-trivial forth degree polynomials have at most 4 real roots).
Well, if you proceed using the ansatz (thanks @user33640 for the "correction") $$y(x) = \sum_{n=0}^N a_n x^n$$ and substitute it directly in the equation, you end up with $$x^3 \sum_{n=1}^N n a_n x^{n-1} = \sum_{n=0}^N a_n x^{2n}.$$ This means that $$\sum_{n=1}^N n a_n x^{n+2} - \sum_{n=0}^N a_n x^{2n} = 0$$ which tells you that all $a_n = 0$ for $n=2m+1$. This in turn help us to propose an improved ansatz $$y(x) = \sum_{n=0}^N b_{2n} x^{2n}.$$ Again, substituting in the ode, we have $$\sum_{n = 1}^N 2n b_{2n} x^{2n+2} = \sum_{n=0}^N b_{2n} x^{4n}$$ Now, the only way to this equation to be satisfied, is if $$2N + 2 = 4N \quad \Longrightarrow \quad N=1$$ Then $y(x) = b_0 + b_2 x^2$ implies that $$2 b_2 x^4 = b_0 + b_2 x^4$$ which means $b_0 = b_2 = 0$ hence no non-trivial solution exist. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9422094821929932, "perplexity": 176.69106995707605}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-48/segments/1387345758566/warc/CC-MAIN-20131218054918-00022-ip-10-33-133-15.ec2.internal.warc.gz"} |
https://worldofinterest.wordpress.com/2013/03/06/is-equity-cheap/ | # Is Equity Cheap?
This is the question which is dominating financial media at the moment. Case-Schiller point out that their cyclically adjusted PE ration (CAPE10), is above historically adjusted norms. My thesis in this post is that the CAPE10 actually indicates that the stock market is cheaply-fairly valued depending on the expected future path of interest rates. In fact, I am going to use Shiller’s own data to explain why I think he is wrong.
Equity Valuations
The most theoretically sound way to value equities is the present discounted cash flow. That is to say, the current intrinsic value of a stock is the sum of all future profits discounted by the risk free rate. Of course, we can never be sure about the future, so is born the concept of a risk premium, that equities should be valued slightly lower than their fair value because we have a high degree of uncertainty about the future. My preferred way of saying this in maths is:
$\frac{\text{Price}}{\text{current earnings}} = \sum^{\infty}_{t=0} \exp((-R+G-\rho)t) \approx \frac{1}{R-G+\rho}$
where we have defined that R is the risk free interest rate, G is the growth of the company, and $\latex \rho$ is the equity risk premium, which is at heart, the uncertainty about growth and interest rates. The approximation follows from the formula for a geometric sum if one assumes that $R-G+\rho$ is small. Obviously, such a valuation builds in some fairly crucial assumptions. Firstly, that growth is smaller than the interest rate and the risk premium. A share whose earnings growth continually out earns interest rate and uncertainty premiums is worth infinity. Of course, this occurs because we assumed growth was a fixed parameter, which it is not, but such simplifications are sufficient for our current purpose.
Using the Case Shiller data, and using the above analysis, I have plotted the PE ratio for ten year US treasuries along side the CAPE10 ratio for the S&P500, since 1950.
Notice the incredible correlation between bond returns and equity returns over the proceeding decades as tail risks of WW2, the cold war, and thermonuclear war abated.
So the question, “are stocks cheap”, is now seen in its proper context. Stocks are cheap if you expect interest rates to stay at their current levels for an extended period. If you expect that interest rates will normalise around 5% in the not to distant future, then stocks are fairly valued. I see think that interest rates are still some years away from 5%, and see rather evidence of continued tail risk from the Eurozone’s self inflicted misery. Notice quite what an aberration the tech bubble was. Even at the end of the dot com crash stocks were not especially cheap compared to bonds. Notice that stocks were incontrovertibly cheap post financial crisis in 2009. Anyway, I am cautiously optimistic in the long run/medium run for stocks, but still worried about the Eurozone. The ongoing crises in Europe seems temporarily in the background of investor’s minds, either because they believe that the ECB will bow to pressure and follow the other central banks, or because they believe that liquidity from other parts of the world will alleviate Europe’s problems despite ECB intransigence. I would not bet on either.
Disclosure, I am 30% in cash, 70% long equities, with 0% European exposure. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 2, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8059871792793274, "perplexity": 1216.226766817228}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-43/segments/1508187826049.46/warc/CC-MAIN-20171023130351-20171023150351-00179.warc.gz"} |
https://trac-hacks.org/ticket/772 | Opened 11 years ago
Closed 21 months ago
## #772 closed defect (fixed)
Reported by: Owned by: timn Christian Boos high DoxygenPlugin major 0.10
### Description
The link in the navigation goes to "doxygen". So following this link it will take you to something like http://server/trac/doxygen. On this the relative links in the Trac navigation (for instance to classes.html) will point to a non-existent path. The problem is the following code in source:doxygenplugin/0.10/doxygentrac/doxygentrac.py?rev=1251, line 86-90:
def get_navigation_items(self, req):
if req.perm.has_permission('DOXYGEN_VIEW'):
# Return mainnav buttons.
yield 'mainnav', 'doxygen', html.a(self.title,
href=req.href.doxygen())
This will create a relative link to doxygen. Similar to the code in 0.9 this should read:
def get_navigation_items(self, req):
if req.perm.has_permission('DOXYGEN_VIEW'):
# Return mainnav buttons.
yield 'mainnav', 'doxygen', html.a(self.title,
href=req.href.doxygen() + '/')
Note the additional + '/'. This will create a link to http://server/trac/doxygen/ and relative links will work just fine.
### comment:1 Changed 11 years ago by Christian Boos
Status: new → assigned
Thanks, will do.
### comment:2 Changed 11 years ago by dirk@…
I have the same problem, but the above solution doesn't work for me.
The problem (at least to my Trac-newbie eyes) seems to be that for the main index action without wiki_index the plugin just returns the text of the index page, but for the client the URL is ".../trac/doxygen", so relative links don't work. The fix above won't help with that either, AFAICS, as the necessary base path is ".../trac/doxygen/html/", not ".../trac/doxygen/".
I kludged it by using a redirect instead, i.e. instead of setting path I do a
# use configured Doxygen index
req.redirect(os.path.join('trac', 'doxygen', self.default_doc,
self.html_output, self.index))
Not very elegant, but it works, at least for me.
### comment:3 Changed 11 years ago by anonymous
i'm only have to say that the patch adding a +"/" work good to me.
### comment:4 Changed 11 years ago by jose.junior@…
Priority: normal → high
as this guy the URL of the main page when clicking on the navbar button is wrong, it doesn't include the 'html output' part.
The solution he gave is not ok here because I have multiple environments.
### comment:5 Changed 10 years ago by c.hoeller@…
Hi,
anyhow all these solutions don't work for me - I have multiple Project, and my documentations are in /home/httpdroot/doxygen/MyProjectName/ Sadly I'm a total Python-Fool, but to me it seems, that, with this bug, the plugin is useless for me... Can you tell me, when you are planing to fix the bug?
Greetings Christoph
### comment:6 Changed 10 years ago by fmos
Hi, I also had issues with the location of the class documentation
(Doxyfile is in /home/rave/public_html/doxygen)
Changing the suggested
path = /home/rave/public_html/doxygen
html_output = html
to
path = /hepforge/home/rave/public_html/doxygen/html
html_output =
Cheers, Fabian
### comment:7 Changed 21 months ago by Committo-Ergo-Sum
Resolution: → fixed assigned → closed
In 15358:
DoxygenPlugin: new implementation of IRequestHandler methods. In particular, the "path" parameter in the query-string is droped. This fixes #772 #951 #962 #1564 and #2702 who complain about the security vulnerability it may contain, and other wrong path generations.
### Modify Ticket
Change Properties | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.1659301370382309, "perplexity": 7260.682408014752}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-47/segments/1510934809778.95/warc/CC-MAIN-20171125105437-20171125125437-00659.warc.gz"} |
https://www.physicsforums.com/threads/find-electric-field-in-these-regions-of-a-spherical-shell.906110/ | Find ELectric field in these regions of a spherical shell
1. Mar 2, 2017
grandpa2390
1. The problem statement, all variables and given/known data
a thick spherical shell carries charge density k/r^2 a<r<b
find E in the three regions r<a a<r<b b<r
2. Relevant equations
E dot da = Q/ε
3. The attempt at a solution
I can't understand why, when integrating, they choose for
ii to integrate between a and r,
iii and the between a and b for iii
2. Mar 2, 2017
haruspex
What do you know about the field inside a uniformly charged spherical shell?
3. Mar 2, 2017
grandpa2390
that it's uniform at the surface?
I don't know what you are asking.
what I have been able to gather is that they are integrating the volume of the shell. integral of 4 pi r^2 dr
for a<r<b the volume is from a - r
for b<r the volume is from a-b
I don't know why.
4. Mar 2, 2017
haruspex
No, that there is no field produced inside a uniformly charged spherical shell. This is a fundamental result of enormous importance in these problems. The equally important result for outside the shell is that the field there is the same as if all of the charge were concentrated at the sphere's centre.
The same pair of results applies (of course) to gravitational fields from uniform spherical mass distributions.
Can you see how this explains the integration range?
5. Mar 2, 2017
grandpa2390
We are trying to capture all of the "mass" below our boundary.
Between A and B we want to capture all the mass from a to wherever r is.
If R is greater then B then we want all of the "mass" less then r which is from a to b
???
6. Mar 2, 2017
haruspex
Hence the integration range from a to r.
Hence the integration range from a to b.
Please try to explain more clearly what it is that you do not understand.
7. Mar 2, 2017
grandpa2390
No you answered it. Or at the very least, you slapped some sense into my brain, pointed... pushed my brain into the right direction.
I don't know. When you compared it to mass, it just made sense to me suddenly. I don't know. I was thinking it should have been integrated between the boundaries stated. integrated from a to b, and then from b to infinity. I didn't get it until your last reply :)
Then I just restated what I got from you in my own words for verification to make sure whether I had it : )
8. Mar 2, 2017
haruspex
Verified.
Draft saved Draft deleted
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https://www.physicsforums.com/threads/definitions-and-properties-of-limits-handwriting-attached.674672/ | # Definitions and properties of limits (handwriting attached)
1. Feb 26, 2013
### tolove
I'm not entirely sure on the properties of limits, but this seems to work. Could someone look over this for me?
http://imgur.com/6zCHYo5
2. Feb 26, 2013
### SammyS
Staff Emeritus
What is it that you're trying to do?
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3. Feb 26, 2013
### tolove
Not really a problem here, just wanting to make sure I'm doing this correctly. I'm trying to show that ∫ y' dx = ∫ dy through definitions.
4. Feb 26, 2013
### SammyS
Staff Emeritus
What are you using for the definition of the indefinite integral?
The Riemann sum is generally used for the definite integral.
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Similar Discussions: Definitions and properties of limits (handwriting attached) | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.980728268623352, "perplexity": 3599.5802276792374}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-34/segments/1502886105291.88/warc/CC-MAIN-20170819012514-20170819032514-00253.warc.gz"} |
https://cs.stackexchange.com/questions/103502/how-to-prove-that-x-is-a-regular-language-if-x-is-derived-from-l | # How to prove that $\{\$x\$\}$ is a regular language if $x$ is derived from $L=\{w\}$ by substituting substrings?
Prove that if $$L$$ is regular over $$\Sigma=\{0,1,2\}$$ then the following language over $$\{0,1,2,\\}$$ is also regular: $$G=\{\x\|\exists w\in L: x\text{ is derived from }w\text{ by substituting } 01 \text{ with }\\ \}$$ For example, if $$10112\in L$$ then $$\1\\12\\in G$$.
I think this can be solved using closure properties of regular languages.
1) Let $$H=\L\$$. $$H$$ is also regular because it's concatenation.
2) Let $$h:\Sigma\to \Sigma^*$$ be defined as follows: $$h(\)=h(0)=h(1)=\$$ Then: $$G=h^{-1}(H)\cap $$\Sigma^*\\\Sigma^*)^+\$$ which is regular because $$h^{-1}$$, intersection and regular expressions are closed in regular languages. I wonder if my proof using closure is correct or automaton should be built in this case? In addition if I managed to think of a regular expression to describe $$G$$ then this alone would've proved that $$G$$ is regular? ## 1 Answer Unfortunately, your argument breaks down at step 2). For example, let $$L=\{01\}$$. Then $$G =\{\\\\\}.$$ $$H=\{\01\\}$$. $$h^{-1}(H)=\emptyset$$ since every word in the range of $$h$$ contains neither 0 or 1. $$h^{-1}(H)\cap \(\Sigma^*\\\Sigma^*)^+\=\emptyset.$$ However, $$G$$ is not empty. If I managed to think of a regular expression to describe G then would this alone have proved that G is regular? Of course. However, it looks like it is not immediate to figure out a regular expression for $$G$$ even if we have been given the regular expression for $$L$$ and DFA for $$L$$. Here is a way to show $$G$$ is regular by DFA. Let the DFA for $$L$$ be $$(\Sigma,Q, q_0,\delta_L, F)$$. Define (an incomplete) DFA $$D$$ with alphabet $$\{0,1,2,\\}$$, states $$Q\times \{s_0, s_1, o\}$$, initial state $$(q_0, s_0)$$, accepting state $$F\times\{s_0, o\}$$, transition function $$\delta_D$$ such that $$\delta_D((q, s_0), 0)= (\delta_L(q, 0), o)$$ $$\delta_D((q, s_0), 1)= (\delta_L(q, 1), s_0)$$ $$\delta_D((q, s_0), 2)= (\delta_L(q, 2), s_0)$$ $$\delta_D((q, s_0),$$= (\delta_L(q, 0), s_1)$$
$$\delta_D((q, s_1), \)= (\delta_L(q, 1), s_0)$$
$$\delta_d((q, o), 0)= \delta_L(q, 0), o)$$
$$\delta_d((q, o), 2)= \delta_L(q, 2), s_0)$$
$$\delta_d((q, o), \)= \delta_L(q, 1), s_1)$$
Here is how we can understand the states
• state $$(q,o)$$ corresponds to the states that are reached by words that end with $$0$$.
• state $$(q,s_1)$$ corresponds to the states that are reached by words that end with odd number of $$\$$'s.
• state $$(q,s_0)$$ corresponds to the states that are reached by words that end with $$1$$ or $$2$$ or even number of $$\$$'s.
We can check that $$G=\L(D)\$$.
Exercise. Prove that if $$L$$ is regular over $$\Sigma=\{0,1\}$$ then the following language over $$\{0,1,2\}$$ is also regular. $$G=\{x\mid \exists w\in L: x\text{ is derived from }w\text{ by substituting } 00 \text{ and } 11 \text{ with } 2 \text{ from left to right} \}$$ For example, if $$w=1000111110$$, then $$x=1202210$$.
• Can you please explain why do you have states based on what letter reached the end of the words? For example, I'd define the transition functions as follows: $$\delta_D((q,2),0)=(\delta(q,2),0)\\\delta_D((q,\),0)=(\delta(q,0),1)\\\delta_D((q,\),1)=(\delta(q,1),0)$$.In my example we start out with state $0$. When we read the first $\$$we flip the state to 1. When we read the second \$$ we flip the state back to$0$. When we read$2$nothing changes so we stay in state$0$as well. In the end we can add$\$$'s from the beginning and end of each word. – Yos Jan 28 '19 at 20:38 • If we know the last letters of the words that reaches a state s, then we can specified what will be the next state if the word is extended with another letter. Note that we must ensure words containing 01 and words with isolated \$$ should not be accepted. Jan 28 '19 at 20:47
• Exactly. That is why incomplete DFA is popular since there is no need to write any transition that goes to a dead state. In fact, we do not have to specify that dead state. Jan 28 '19 at 20:58
• I understand the transitions now, thanks! I still don't why you concatenate dollar sign here: $\delta_D((q, s_1), \$)= (\delta_L(q, 1), s_0)\?
– Yos
Jan 28 '19 at 21:05
• Updated with a few corrections of typos. Jan 28 '19 at 21:13 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 2, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 56, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9509592056274414, "perplexity": 775.545149127434}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-43/segments/1634323585302.56/warc/CC-MAIN-20211020024111-20211020054111-00524.warc.gz"} |
https://docs.acquia.com/cloud-platform/manage/ssh/drush/multisite/ | Information for:
# Using Drush in a multisite installation¶
If you’re using a multisite installation, following best practices would have you ensure you are in the correct website directory before running a Drush command. However, if you’re using Drush across several applications in succession, using Drush aliases can be more efficient.
You must use aliases when executing Drush commands inside the docroot directory. If you’re not in the specific multisite directory for which you want to execute Drush commands, you must also specify the -l flag and provide a URI. If you use an alias by itself and you aren’t in the relevant multisite directory, Drush can’t determine which website it should execute commands for.
For example, if you want to run a pm-list (or its alias, pml) and grep for the sync module on http://www.mysite.org, use one of the following commands based on your location:
• In the specific multisite installation directory (such as /var/www/html/mysite.test/sites/mysite.org)* - No additional Drush parameters are needed. Use the following command:
drush pml | grep sync
• In the website’s docroot, but not the specific multisite directory (such as /var/www/html/mysite.test)
You will need the URI for the specific multisite like the following:
drush -l http://domainb.mysite.org pml | grep sync
• In the server’s /var/www/html directory, but not in the Drupal installation docroot
You will need both the URI and the Drush alias like the following:
drush @mysite.test -l http://domainb.mysite.org pml | grep sync
You need the alias to specify the Drupal website application since you’re not in /var/www/html/mysite.test, and you need the URI since you’re not in the related multisite directory for http://domainb.mysite.org.
• If you want to run Drush on all the multisites in an environment that uses Cloud Hooks, you can use the following command as an example, where [site] is the application, and [target.env] is the environment you want to run the command in:
drush --root=/var/www/html/[site].[target_env]/docroot @sites updatedb
--yes
Note
The @sites alias is deprecated in all versions of Drush since Drush 9. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.43946579098701477, "perplexity": 7042.306983229778}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-40/segments/1600401583556.73/warc/CC-MAIN-20200928010415-20200928040415-00682.warc.gz"} |
https://www.physicsforums.com/threads/what-type-of-of-force-is-applied-force-conservative-nonconservative.768294/ | # What type of of force is applied force? Conservative ,Nonconservative
1. Aug 30, 2014
### Miraj Kayastha
In a closed loop when we apply an applied force on an object the object starts at point A and stops at point A.
Since the displacement is 0, Work done by the applied force on the object is = F x s x cosθ
= 0
So the net work done by the applied force is 0 but why is applied force a non-conservative force?
2. Aug 30, 2014
### ehild
When the force is not constant during the motion the work is calculated by integration. Have you studied calculus?
ehild
3. Aug 30, 2014
### Miraj Kayastha
Yes I have.
4. Aug 30, 2014
### ehild
The work done along a curved path is $W=\int F_s d_s$ where Fs is the component of the force tangent to the segment of the curve and ds is the length of the line segment. If you apply a force of constant magnitude, always tangent to the curve, $W=F \int d_s =F L$ where L is the length of the curve. The work is not zero along a closed loop.
If you push a crate along a rough horizontal surface with force F you do F*D work during D distance. When you push it back with force of the same magnitude, you do F*D work again. The displacement is zero, but the net work is not.
In general, the work depends on the way it is done. The conservative forces are exceptions, their work does not depend on the path taken between the initial and final points.
ehild
Last edited: Aug 30, 2014
5. Aug 31, 2014
### Miraj Kayastha
Here when you said "when we push it back with the same magnitude, you do F x D work again" I think we should also account the direction of the force because the force is constant both in magnitude and direction throughout the motion. So shouldn't the work done by the force on the crate when crate is coming back be - F x D ?
And then the net work is zero.
6. Aug 31, 2014
### jbriggs444
The D in the work formula is not a "distance". It is a "displacement". The distinction is that a distance is always positive and has no direction. A displacement has a direction.
When you push the crate back toward the starting point, both force and direction are reversed. So it's -F x -D.
7. Aug 31, 2014
### ehild
The elementary work can be written either as dot product of the force vector with the displacement vector, $dW=\vec F \cdot \vec{dr}$ or as the product of two scalars, Fs the component of force along the path taken and the elementary path length, ds dW=Fsds.
ehild | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9582477807998657, "perplexity": 471.80020650550864}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-18/segments/1461860127878.90/warc/CC-MAIN-20160428161527-00140-ip-10-239-7-51.ec2.internal.warc.gz"} |
https://reciprocalsystem.org/paper/permittivity-permeability-and-the-speed-of-light-in-the-reciprocal-system | # PERMITTIVITY, PERMEABILITY AND THE SPEED OF LIGHT IN THE RECIPROCAL SYSTEM
Introduction
Physics textbooks do not provide a theoretical derivation of Newton‘s law of gravitation or Coulomb’s laws of electrostatics and magnetostatics; they are simply stated as empirical truths. By contrast, books on the Reciprocal System, such as Ref. [1], [2], [3], do provide a theoretical derivation of these laws. This paper will take a closer look at the terms of the electrostatic and magnetostatic equations--the terms of the gravitational equation have already been discussed in detail, most recently in Ref. [3]. Unlike the force of gravitation the forces of electrostatics and magnetostatics can be reduced by the intervening media between the charges. The question to be answered is: what are the dimensions of all the terms of Coulomb’s laws?
Permittivity
Coulomb’s law of electrostatic attraction is expressed as
Q1 Q² Fe = ke ——— (1) r²
where Q1 and Q² are the electric charges, r is the distance between them, Fe is the force, and ke is the proportionality constant. In the Reciprocal System all physical quantities are expressed in terms of space and time only; there are no separate dimensions for mass or charge. So, electric charge is not taken as a fundamental entity and given an independent unit. Larson has deduced that the dimensions of force and charge are
Fe = [t/s²] Q = [t/s]
In the gravitational expression, the second mass and the distance are considered to be dimensionless ratios. Such a procedure could be used in analyzing the electrostatic expression; however I find it more fruitful to treat the second charge and the distance as having dimensions. In this case Coulomb‘s law expressed in dimensions is
[t/s] [t/s] [t/s²] = ke ———– (2) [s²]
For this equation to be dimensionally correct, the dimensions of ke must be
ke = [s²/t] (3)
These are the dimensions of permittivity (in the Reciprocal System). However, the conventional expression for the coefficient of the law is
ke = 1/(4 pÎ) (4)
where Î is the permittivity, expressed in farads/meter. Thus the derivation gives a result that is the inverse of the usual coefficient. But in the Reciprocal System the farad is reducible to a length. So in the conventional units that are used, permittivity turns out to be dimensionless whereas physically it is not. It should not then be surprising that the numerical values of permittivity are inverted. Instead of saying that the permittivity of air is 1.0006 times that of free space, I would say that it is 1/1.0006 = .9994 times that of free space. This actually sounds better! (The other part of the coefficient (1/4p) of the conventional expression was put in for practical reasons having nothing to do with basic physics; there is no point to keeping it in the Reciprocal System). Of course, the end result-the calculated force--must be the same in both systems.
Permeability
Coulomb‘s law of magnetostatics is
M1 M² Fm = km ——— (5) r²
where M1 and M² are the magnetic charges, Fm is the force, r the separation distance, and km the proportionaiity constant. Larson has deduced that the dimensions of magnetic charge are
M = [t²/s²] (6)
Then, expressed dimensionally, Coulomb‘s law for magnetostatics is
[ t²/s² ] [ t² /s² ] [t/s²] km ——————— (7) [s²]
For this equation to be dimensionally correct, the dimensions of km must be
km = [s4/t³] (8)
But in the Reciprocal System magnetic permeability (symbol Ã) has the dimensions t /s . Thus km = 1/Ã . This time the derivation from the Reciprocal System is in exact accord with the conventional Kennelly system, with magnetic charges or poles expressed in webers (volt-sec). The only thing awkward here is the name “permeability” . On the basis of the equation, a better name for this quantity would be “impermeability” . Besides, as Larson has pointed out “permeability” is the magnetic analog of electric resistance
(t² /s³ * t/s). Perhaps for parallelism with the revised electrostatic expression we should put the reciprocal of what is now called permeability into the numerator of the law but call it by the same name. Thus the higher the electric force between charges, the higher the (reciprocal) “permittivity” ; and the higher the magnetic force between magnetic charges, the higher the (reciprocal) “permeability” .
Permittivity, Permeability, and the Speed of Light
One way to confirm the identification of the dimensions of permittivity and permeability is to use them in the same expression. One such expression is Maxwell‘s famous result from electromagnetic theory:
c = 1/(ÎoÃo )½ (9)
where c is the speed of light, Îo is the permittivity of free space, and Ão is the permeability of free space. In the dimensional terms of the Reciprocal System, the equation is
[s/t] = 1/[(s²/t)(t³/s4)]½ (10)
As expected, the dimensions check out fine. These new results should help clarify electrostatics and magnetostatics for both students and working scientists and engineers.
References
1. Dewey B. Larson, The Structure of the Physical Unieerse (Portland, Oregon: North Pacific Publishers, 1959). Note: in this, the first presentation of the Reciprocal System, the permittivity and permeability were treated as dimensionless (p. 82).
2. Dewey B. Larson, Nothing But Motion (Portland, Oregon: North Pacific Publishers, 1979).
3. Dewey B. Larson, Basic Properties of Matter (Salt Lake City, Utah: International Society of Unified Science2 1988). Note: the dimensions of permittivity are stated as [s²/t] on p. 172; the dimensions of permeability are stated as [t³ /s4] on p. 222.
APPENDIX: SAMPLE CALCULATIONS
1. Electrostatics
What is the force exerted by a charge of one coulomb on another charge of one coulomb one km away, in air?
From eq. 3, the value of the permittivity in free space is
snat ²/tnat = (4.558816*10-6)²/1.520655*10-16 = 136670.11 cm²/sec.
In air, the value is .9994 times this, or 136588.11 cm²/sec. Now a coulomb is defined as the electrostatic charge which when placed at a distance of 1 meter from an equal charge of the same sign produces a repulsive force of 8.98755*10-9 N. In space-time terms, this force is
8.98755*109 N * 105 dynes/N * (7.316889*10-6 sec/cm²) / (3.27223*10² dynes)
= 20096664 sec/cm² .
Then from Coulomb‘s law (for a vacuum) we have
20096664 sec/cm² = 136670.11 cm²/sec * Q² sec²/cm² / 10000 cm².
Solving for Q gives 1212.6213 see/em per coulomb. So for the problem at hand we have
Fe - 136588.11*1212.6213²/100000² = 20.084604 sec/cm².
Converting back to conventional units we have
20.084604 sec/cm² * 3.27223*10² dynes/7.316889*10-6 sec/cm² * 10-5 N/dynes
= 8982.1567 N.
This agrees with the value from experiment.
2. Magnetostatics
What is the force exerted by a magnetic pole with a strenath of one weber against another magnetic pole of equal strength one km away, in vacuum?
The value of the permeability of free space is
t³/s4 = (1.520655*10-16)³/(4.558816*10-6)4 = 8.1411073*10-27 sec /cm4 .
Now a weber may be defined as the strength of a magnetic pole which exerts in a vacuum a force of 63325.74 N upon another magnetic pole of the same strength one meter away. In space-time terms this force is
63325.74 N * 105 dynes/N 2 (7.316889*10-6 sec/cm²)/(3.27223*10² dynes) = 141.59989 sec/cm .
From Coulomb’s magnestatic law we get
141.59989 sec/cm² = (1/8.1411073*10 -27 sec3/cm4) * M²sec4/cm4/10000 cm².
Solving for M gives 1.0736759*10-10 sec²/cm² per weber. So for the problem at hand we have
Fm = (1/8�1411073*10-27 sec³/cm4) * (1.0736759*10-10 sec /cm ) / (100000 cm) = 1.41599890 sec/cm.
Converting back to conventional units we have
1.4159989*10-4 sec/cm² * 3.27223*10² dynes/(7.316889*10-6 sec/cm ) * 10-5 N dyne = 0633257 N.
This agrees with the value from experiment.
SUMMARY:
1. permittivity of free space = 136670.11 cm²/sec
2. permeabilit of free s ace = 8.1411073 10 sec /cm
3. one coulomb = 1212.6213 sec/cm
4. one weber = 1.0736759-10 10 sec²/cm²
International Society of Unified Science
Reciprocal System Research Society
Salt Lake City, UT 84106
USA
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https://www.vedantu.com/physics/superconductivity | # Superconductivity
## Superconductivity Meaning
Superconductivity meaning simply states that there is no resistance or almost zero resistance in the material or any object. A material or an object that shows such properties is known as a superconductor. The conductivity referred to here is the electrical conductivity of a material. When the electrical conductivity is to the full potential facing almost to completely zero resistance in a material any of the magnetic flux fields are expelled from the material. The zero resistance is achieved by lowering the temperature of the material which leads to a decrease in the resistance of the material and leading to an increase in the conductivity. In a superconductor as well the same method is applied to achieve superior conductivity.
## Who Discovered Superconductivity and What is a Superconductor?
A brief introduction of superconductivity and superconductors is given before. In order to explain superconductivity, it is necessary to note that materials possess certain physical properties that cause resistance to electrical conductivity through the material. This characteristic of the material varies with temperature changes. If the temperature of the material is increased the resistance increases whereas if the temperature of the material is decreased the resistance decreases. This phenomenon is exploited for achieving the highest conductivity of superconductor.
In 1911, Heike Kamerlingh Onnes, a Dutch physicist, discovered the superconductivity phenomenon. Currently, the research for the explanation of the phenomenon is done using quantum mechanics as it cannot be completely explained by the concept of perfect conductivity in classical physics. One of the important physical properties exhibited by a conducting material exhibiting superconductivity meaning is that there is no magnetic flux field present in the material as the presence of magnetic flux fields leads to a loss in energy and an indication of the presence of resistance in the material.
Superconductor definition can be given as a material that incorporates the superconductivity meaning as a part of its physical properties. Normally when the temperature of a conductor is decreased there is an increase in conductivity as one move to absolute zero temperatures. But superconductors are those special materials in which after a certain critical temperature the resistance drops to zero value and the conductivity thus reaches the maximum. This is a critical point that has to be noted while defining what is a superconductor and explaining the superconductor definition. At this point, while decreasing the temperature below the critical temperature, the conductivity of superconductor is maximum and there is the complete ejection of any magnetic field flux from the material as well. In superconductivity the conductivity of a material becomes such that when an electric current is passed through a loop of such a superconductor the electric current will keep flowing through it indefinitely without any need of a power supply. This can lead to the creation of self-sustaining energy sources solving innumerable problems such as power surges and costly electricity. And because there is no loss of energy due to the resistance of the material the electricity available will be much cheaper when such superconducting material sources are used as power sources.
### Properties of Superconductors
In the superconductor definition, the electrical properties arising due to unique and specialised physical properties play an important role, as what is a superconductor without any such interesting electrical properties. One of such properties is the zero electrical DC resistance present in the material. This is a common property of all superconductors irrespective of physical properties of the material such as the heat capacity, critical temperatures (as they can be different for different materials), etc. Also as defined above in the superconductivity phenomenon key role is played by a decrease in the temperature. Although different materials have different critical temperatures once the temperature drops down from the critical temperatures the resistance falls to absolute zero. Thus, it indicates that superconductivity meaning in a superconductor is a thermal property and hence after having reached a superconducting state the phenomenon is independent of the physical properties of the material. All the superconducting materials behave in the same manner.
When material changes from a non-superconducting state to a superconducting state there are significant changes in the physical properties of the material which are the characteristics of phase transitions. When the temperature drops below a thermal superconductor there is an ejection of the magnetic field. But when there is an external magnetic field applied to the superconductor and which is more than the critical magnetic field, the superconductor leaves the superconducting state and starts to behave as a normal conductor. This change in the phase of the superconducting material occurs due to the changes in the Gibbs free energy. In the superconducting phase, the Gibbs free energy of the conductor is lower than the normal non-superconducting phase of free energy. When a finite amount of free energy is applied externally to the superconductor through the external magnetic field, the free energy increases quadratically in the superconductor and it reaches the normal free energy value and thus a phase transition takes place in the conductor from the superconducting phase to non-superconducting phase.
Thus, these properties of the superconductor make it possible to be used for a variety of purposes. Superconductor examples and their applications are mentioned below.
### Applications of Superconductors
Superconductors are noted for their zero DC electrical resistance. Hence, most of the applications of the superconductor examples are because of their properties which provide advantages such as low power loss because of less dissipation of energy, high-speed operations because of zero resistance and continuous flowing electrical current, and high sensitivity. The usual and well-known superconductor examples are mercury superconductors, niobium-tin superconductors, lanthanum-barium-copper oxide superconductors, and yttrium-barium copper oxide superconductors.
The examples of applications of superconductors include medical MRI/NMR devices, magnetic-energy storage systems, motors, generators, transformers, computer parts and sensitive devices for the measurement of magnetic fields, electrical currents, etc. Future possible applications involve high-performance smart grids, electric power transmission, transformers, electric motors (in vehicles like maglev trains), magnetic levitation devices, superconducting magnetic refrigerators, etc.
FAQs (Frequently Asked Questions)
1. What is a Superconductor?
Ans: A superconductor is an object that provides zero resistance to electrical currents at very low temperatures. It incorporates the definition of superconductivity phenomenon which is a physical phenomenon dependent on the physical properties of the material that gives rise to the electrical resistance in a conductor. Thus, a superconductor is conducting material that shows zero resistance to electric current when the temperature of the material is taken below a critical temperature.
2. What is Superconductivity?
Ans: The complete disappearance of the electrical resistance from a conducting material when the temperature of the material is taken below a characteristic temperature and the ejection of any magnetic flux field from the material is known as superconductivity. The temperature at which such a change occurs is called critical temperature and is different for different materials. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9318909049034119, "perplexity": 374.38948271428336}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-49/segments/1637964362918.89/warc/CC-MAIN-20211203182358-20211203212358-00432.warc.gz"} |
https://www.spp2026.de/members-guests/19-member-pages/prof-dr-daniel-lenz | # Members & Guests
## Prof. Dr. Daniel Lenz
Friedrich-Schiller-Universität Jena
E-mail: daniel.lenz(at)uni-jena.de
Telephone: +49 3641 9 46 131
Homepage: http://www.analysis-lenz.uni-jena.de/
## Project
19Boundaries, Greens formulae and harmonic functions for graphs and Dirichlet spaces
59Laplacians, metrics and boundaries of simplicial complexes and Dirichlet spaces
## Publications within SPP2026
We describe the set of all Dirichlet forms associated to a given infinite graph in terms of Dirichlet forms on its Royden boundary. Our approach is purely analytical and uses form methods.
Journal Journal de Mathématiques Pures et Appliquées. (9) Volume 126 Pages 109--143 Link to preprint version Link to published version
We study pairs of Dirichlet forms related by an intertwining order
isomorphisms between the associated $$L^2$$-spaces. We consider the
measurable, the topological and the geometric setting respectively.
In the measurable setting, we deal with arbitrary (irreducible)
Dirichlet forms and show that any intertwining order isomorphism is
necessarily unitary (up to a constant). In the topological setting
we deal with quasi-regular forms and show that any intertwining
order isomorphism induces a quasi-homeomorphism between the
underlying spaces. In the geometric setting we deal with both
regular Dirichlet forms as well as resistance forms and essentially
show that the geometry defined by these forms is preserved by
intertwining order isomorphisms. In particular, we prove in the
strongly local regular case that intertwining order isomorphisms
induce isometries with respect to the intrinsic metrics between the
underlying spaces under fairly mild assumptions. This applies to a
wide variety of metric measure spaces including
$$\mathrm{RCD}(K,N)$$-spaces, complete weighted Riemannian manifolds
and complete quantum graphs. In the non-local regular case our
results cover in particular graphs as well as fractional Laplacians
as arising in the treatment of $$\alpha$$-stable Lévy processes. For
resistance forms we show that intertwining order isomorphisms are
isometries with respect to the resistance metrics.
Our results can can be understood as saying that diffusion always
determines the Hilbert space, and -- under natural compatibility
assumptions -- the topology and the geometry respectively. As special
instances they cover earlier results for manifolds and graphs. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9292271733283997, "perplexity": 2534.143648380495}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-27/segments/1656104683683.99/warc/CC-MAIN-20220707033101-20220707063101-00125.warc.gz"} |
https://homework.cpm.org/category/CC/textbook/cca2/chapter/4/lesson/4.1.2/problem/4-25 | ### Home > CCA2 > Chapter 4 > Lesson 4.1.2 > Problem4-25
4-25.
Ted needs to find the point of intersection for the lines $y=18x−30$ and $y=−22x+50$. He takes out a piece of graph paper and then realizes that he can solve this problem without graphing. Explain how Ted is going to accomplish this, and then find the point of intersection. Homework Help ✎
Set the two expressions for $y$ equal to each other and solve algebraically. | {"extraction_info": {"found_math": true, "script_math_tex": 3, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9026674032211304, "perplexity": 350.5063416290561}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986682037.37/warc/CC-MAIN-20191018104351-20191018131851-00208.warc.gz"} |
https://matplotlib.org/3.0.2/api/_as_gen/mpl_toolkits.axes_grid1.inset_locator.InsetPosition.html | # mpl_toolkits.axes_grid1.inset_locator.InsetPosition¶
class mpl_toolkits.axes_grid1.inset_locator.InsetPosition(parent, lbwh)[source]
Bases: object
An object for positioning an inset axes.
This is created by specifying the normalized coordinates in the axes, instead of the figure.
Parameters: parent : matplotlib.axes.Axes Axes to use for normalizing coordinates. lbwh : iterable of four floats The left edge, bottom edge, width, and height of the inset axes, in units of the normalized coordinate of the parent axes.
Examples
The following bounds the inset axes to a box with 20% of the parent axes's height and 40% of the width. The size of the axes specified ([0, 0, 1, 1]) ensures that the axes completely fills the bounding box:
>>> parent_axes = plt.gca()
>>> ax_ins = plt.axes([0, 0, 1, 1])
>>> ip = InsetPosition(ax, [0.5, 0.1, 0.4, 0.2])
>>> ax_ins.set_axes_locator(ip) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.350090891122818, "perplexity": 4456.6872824838}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-21/segments/1652662593428.63/warc/CC-MAIN-20220525182604-20220525212604-00036.warc.gz"} |
https://www.lessonplanet.com/teachers/finding-equivalent-fractions | # Finding Equivalent Fractions
In this fraction worksheet, students learn about equivalent fractions and read through 4 different examples. They then solve 7 equivalent fraction problems.
Concepts
Resource Details | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9895825982093811, "perplexity": 7193.33631972336}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-39/segments/1505818685698.18/warc/CC-MAIN-20170919131102-20170919151102-00635.warc.gz"} |
http://www.researchgate.net/publication/252854705_Spin_freezing_and_dynamics_in_Ca_3_Co_2__x_Mn_x_O_6_%28_x__0.95_%29_investigated_with_implanted_muons_Disorder_in_the_anisotropic_next-nearest-neighbor_Ising_model | Article
Spin freezing and dynamics in Ca 3 Co 2 − x Mn x O 6 ( x ≈ 0.95 ) investigated with implanted muons: Disorder in the anisotropic next-nearest-neighbor Ising model
[more]
(Impact Factor: 3.66). 07/2009; 80(2). DOI: 10.1103/PhysRevB.80.020409
ABSTRACT We present a muon-spin relaxation investigation of the Ising chain magnet Ca3Co2-xMnxO6 (x≈0.95) . We find dynamic spin fluctuations persisting down to the lowest measured temperature of 1.6 K. The previously observed transition at around 18K is interpreted as a subtle change in dynamics for a minority of the spins coupling to the muon that we interpret as spins locking into clusters. The dynamics of this spin fraction freeze below a temperature TSF≈8K , while a majority of spins continue to fluctuate. An explanation of the low-temperature behavior is suggested in terms of the predictions of the anisotropic next-nearest-neighbor Ising model.
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Article: Analysis of magnetization and a spin state crossover in the multiferroic Ca\$_3\$Co\$_{2-x}\$Mn\$_x\$O\$_6\$
[Hide abstract]
ABSTRACT: Ca_3Co_{2-x}Mn_xO_6 (x ~ 0.96) is a multiferroic with spin-chains of alternating Co(2+) and Mn(4+) ions. The spin state of Co(2+) remains unresolved, due to a discrepancy between high temperature X-ray absorption (S=3/2) and low temperature neutron (S=1/2) measurements. Using a combination of magnetic modeling and crystal-field analysis, we show that the existing low temperature data cannot be reconciled within a high spin scenario by invoking spin-orbit or Jahn-Teller distortions. To unify the experimental results, we propose a spin-state crossover with specific experimental predictions.
Physical review. B, Condensed matter 09/2009; DOI:10.1103/PhysRevB.81.092402 · 3.66 Impact Factor
• Source
Article: Local magnetism and magnetoelectric effect in HoMnO_{3} studied with muon-spin relaxation
[Hide abstract]
ABSTRACT: We present the results of muon-spin relaxation (muSR) measurements on the hexagonal manganite HoMnO3. Features in the temperature-dependent relaxation rate, lambda, correlate with the magnetic transitions at 76 K, 38 K and 34 K. The highest temperature transition, associated with the ordering of Mn3+ moments has the largest effect on lambda. The application of a static electric field of E=10^4 Vm^-1 below T=50 K causes a small reduction in lambda which is suggestive of coupling between ferroelectric and magnetic domain walls in the ordered state of the material.
Physical review. B, Condensed matter 01/2010; 81(1). DOI:10.1103/PhysRevB.81.014402 · 3.66 Impact Factor
• Source
Article: Muon-spin relaxation and heat capacity measurements on the magnetoelectric and multiferroic pyroxenes LiFeSi_ {2} O_ {6} and NaFeSi_ {2} O_ {6}
[Hide abstract]
ABSTRACT: We present the results of muon-spin relaxation and heat capacity measurements on LiFeSi2O6 and NaFeSi2O6. In synthetic samples of both compounds we see a single muon oscillation frequency consistent with commensurate magnetic structures below TN. In contrast, for a specimen of naturally occurring NaFeSi2O6, in which multiferroicity has been observed, a rapid Gaussian depolarization of the muon polarization is observed instead, showing that the magnetic structure in this case is more complex. Heat capacity measurements reproduce the phase diagrams previously derived from other techniques and demonstrate that the main contribution to the magnetic entropy is associated with the buildup of correlations in the quasi-one-dimensional Fe3+ chains.
Physical review. B, Condensed matter 02/2010; 81(21). DOI:10.1103/PhysRevB.81.214403 · 3.66 Impact Factor | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8845754265785217, "perplexity": 5026.41935014321}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-35/segments/1440645191214.61/warc/CC-MAIN-20150827031311-00182-ip-10-171-96-226.ec2.internal.warc.gz"} |
https://blog.fromkk.com/post/semi-supervised-text-classification-using-doc2vec-and-label-spreading/ | Here is a simple way to classify text without much human effort and get a impressive performance.
It can be divided into two steps:
1. Get train data by using keyword classification
2. Generate a more accurate classification model by using doc2vec and label spreading
## Keyword-based Classification
Keyword based classification is a simple but effective method. Extracting the target keyword is a monotonous work. I use this method to automatic extract keyword candidate.
1. Find some most common words to classify the text.
2. Use this equation to calculate the score of each word appears in the text. $score(i) = \frac{count(i)}{all_{count(i)}^{0.3}}$ which $$all_{count(i)}$$ is the word $$i$$’s word count in all corpus, and $$count(i)$$ is the word $$i$$’s word count in positive corpus.
3. Check the top words, add it to the final keyword list. Repeat this process.
Finally, we can use the keywords to classify the text and get the train data.
## Classification by doc2vec and Label Spreading
Keyword-based classification sometimes produces the wrong result, as it can’t using the semantic information in the text. Fortunately, Google has open sourced word2vec, which can be used to produce semantically meaningful word embeddings. Furthermore, sentences can also be converted to vectors by using doc2vec. Sentences which has closed meaning also have short vector distance.
So the problem is how to classify these vectors.
1. Using corpus to train the doc2vec model.
2. Using doc2vec model to convert sentence into vector.
3. Using label spreading algorithm to train a classify model to classify the vectors. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.41063740849494934, "perplexity": 1660.6591204760748}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-35/segments/1566027321160.93/warc/CC-MAIN-20190824152236-20190824174236-00069.warc.gz"} |
https://quantumcomputing.stackexchange.com/users/5712/ryoji?tab=reputation | Ryoji
# 11 Reputation
10 Dec 19 '19
+10 19:45 3 events Can a classical limit of qubit emerge on a classical computer? | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8634161353111267, "perplexity": 6974.640780581432}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-39/segments/1631780056902.22/warc/CC-MAIN-20210919220343-20210920010343-00280.warc.gz"} |
https://tex.stackexchange.com/questions/273627/reproducing-a-table-containing-images-and-multi-line-text-in-a-cell | # Reproducing a table containing images and multi-line text in a cell
I'd like to be able to reproduce the table attached as an image to this post in Latex. The original table comes from my PhD thesis which was written in Microsoft Word 5.0 on a Mac in the early 1990s. As such I've long since lost the original files (disk crashes over a twenty year period took care of that) and in any case I don't think I'd be able to read the original files into the latest version of Word even if I had them.
Bruce
• Are you looking for reproducing the table only? Or you need the graphs as well? (+1) for choosing Latex over Microsoft Word. – CroCo Oct 18 '15 at 4:09
• Welcome to TeX.SX! Please provide some starter document with \documentclass{...} and \begin{document}...\end{document} – user31729 Oct 18 '15 at 4:10
• @CroCo, I would like to reproduce the whole layout with the multiple lines of text in column 1 and the figures in columns 2 and 3. However, the figures would be created in another program and added as vector graphic files. – Bruce Crawford Oct 18 '15 at 4:14
Try something like this:
\documentclass[border=3mm,
preview]{standalone}
\usepackage{graphicx}
\usepackage{array,booktabs}
\begin{document}
\begin{tabular}{m{5cm}cc}
\toprule
\textbf{Exercise 1}
\begin{itemize}
\item Instruction 1.
\item Instruction 2.
\item Instruction 3.
\end{itemize}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image} \\
\midrule
%%
\textbf{Exercise 2}
\begin{itemize}
\item Instruction 1.
\item Instruction 2.
\item Instruction 3.
\end{itemize}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image} \\
\midrule
\textbf{Exercise 3}
\begin{itemize}
\item TEST.
\item TEST.
\end{itemize}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image}
& \includegraphics[width=0.2\textwidth,
valign=m, margin=.5em]{example-image} \\
\bottomrule
\end{tabular}
\end{document}
which gives:
Since you didn't provide MWE, I left to you tu put in mine desired text and images.
• That seems to be exactly what I need. Thanks @Zarko – Bruce Crawford Oct 18 '15 at 4:16
• accepted as suggested. Sorry about the MWE. I did try but couldn't get anything to work. I'm very new to LaTeX at this stage. – Bruce Crawford Oct 18 '15 at 4:39 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6149441003799438, "perplexity": 2405.6657070049428}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986658566.9/warc/CC-MAIN-20191015104838-20191015132338-00441.warc.gz"} |
https://tug.org/pipermail/pstricks/2001/000495.html | # [pstricks] Making Direction Fields; also coordinates as functions inside loops
Denis Girou Denis.Girou at idris.fr
Tue Jan 9 20:13:49 CET 2001
>>>>> "Michael.Dougherty" == Michael M Dougherty, Ph D <doughem at swosu.edu> writes:
Michael.Dougherty> I would like to plot a direction field for some simple
Michael.Dougherty> ordinary differential equations without plotting the
Michael.Dougherty> vectors or line segments each individually. In other
Michael.Dougherty> words I would like to use loops, perhaps to make
Michael.Dougherty> a vector or line segment at/through each point with integer
Michael.Dougherty> coordinates. For instance, I would like to plot
Michael.Dougherty> a field for $dy/dx=-x/y$ (and later plot some circles
Michael.Dougherty> which are the solution curves--that I can do). I would
Michael.Dougherty> like the method to be more general than for just this one, but
Michael.Dougherty> hopefully this one will suffice to start.
Michael.Dougherty> Therefore I need the coordinates of the line segments/vectors
Michael.Dougherty> to be functions of $x$ and $y$. I was hoping to use multido
Michael.Dougherty> but I do not know how to calculate the coordinates of
Michael.Dougherty> the endpoints of the line segments or vectors within the loop.
Michael.Dougherty> This is my first attempt at multido, but I do understand how
Michael.Dougherty> to plot functions (so I know about RPN). Here's the code
Michael.Dougherty> I'm looking at:
Michael.Dougherty> \begin{pspicture}(-6,-5)(6,5)
Michael.Dougherty> \psaxes{<->}(0,0)(-6,-5)(6,5)
Michael.Dougherty> \multido{\n=-5+1}{11}{%
Michael.Dougherty> \multido{\N=-5+1}{11}{%
Michael.Dougherty> %%%%%%% WHAT TO PUT HERE?
Michael.Dougherty> %%%%%%% Want\psline((\n-1/(2\sqrt{1+x^2/y^2}),\N-x/(2*y\sqrt{1+%
Michael.Dougherty> %%%%%%% x^2/y^2})),((n+1/(2\sqrt{1+x^2/y^2}),\N+x/(2*y\sqrt{1+%
Michael.Dougherty> %%%%%%% x^2/y^2})).
Michael.Dougherty> }}
Michael.Dougherty> \end{pspicture}
Another solution than the one posted by Michael Sharpe is to use a \psline
macro with PostScript coordinates (see the documentation page 72, (!ps)
paragraph). I use the formula given by Michael Dougherty.
Probably that this solution would be easier to understand, because it
require less PostScript management as the drawing of the vectors is done by
a PSTricks macro, which avoid to use the translate, rlineto, etc. PostScript
macros. Nevertheless, probably that the solution of Michael is more powerful
and flexible, as it seems easier to change the definition of the vectors.
If you experience more on this field, tell us the results of your work...
P.S. for Michael Dougherty: comparing to the version I sent you yesterday,
this one is a little more complicated with a conditional in the PostScript
code, because I manage this time the cases where \ia or \ib is equal to 0.
\documentclass[a4paper]{article}
\usepackage{pst-plot}
\pagestyle{empty}
\begin{document}
\SpecialCoor
\begin{pspicture}(-6,-6)(6,6)
\psaxes{<->}(0,0)(-6,-6)(6,6)
\psset{arrows=->}
\multido{\ia=-5+1}{11}{%
\multido{\ib=-5+1}{11}{%
\pstVerb{/x \ia\space def
/y \ib\space def
y 0 eq
{/ValueTempA 0 def
/ValueTempB 0.5 def}
{/ValueTempZ 2 1 x x mul y y mul div add sqrt mul def
/ValueTempA 1 ValueTempZ div def
/ValueTempB x y ValueTempZ mul div def}
ifelse}
\psline(! x ValueTempA sub y ValueTempB sub)
\end{pspicture}
\begin{pspicture}(-6,-6)(6,6)
\psaxes{<->}(0,0)(-6,-6)(6,6)
\psset{arrows=->}
\multido{\ia=-5+1}{11}{%
\multido{\ib=-5+1}{11}{%
\pstVerb{/x \ia\space def
/y \ib\space def
y 0 eq
{/ValueTempA 0 def
/ValueTempB 0.5 def}
{/ValueTempZ 2 1 x x mul y y mul div add sqrt mul def
/ValueTempA 1 ValueTempZ div def
/ValueTempB x neg y ValueTempZ mul div def}
ifelse}
\psline(! x ValueTempA sub y ValueTempB sub)
\end{pspicture}
% From Michael Sharpe
\def\transl#1#2{%
#1\space 72 2.54 div mul #2\space 72 2.54 div mul translate 0 0 moveto}
\newif\ifnotbothz
\begin{pspicture}(-6,-6)(6,6)
\psaxes{<->}(0,0)(-6,-6)(6,6)
\multido{\n=-5+1}{11}{%
\multido{\N=-5+1}{11}{%
\notbothztrue
\ifnum\N=0
\ifnum\n=0
\notbothzfalse
\fi
\fi
\ifnotbothz
\psdot(0,0)
\pstverb{\transl{\n}{\N}\space
%next line gives a direction vector (y=\n,x=\N)
\n\space \N\space
atan rotate -9 0 moveto 18 0 rlineto stroke}
\fi}}
\end{pspicture}
\begin{pspicture}(-6,-6)(6,6)
\psaxes{<->}(0,0)(-6,-6)(6,6)
\multido{\n=-5+1}{11}{%
\multido{\N=-5+1}{11}{%
\notbothztrue
\ifnum\N=0
\ifnum\n=0
\notbothzfalse
\fi
\fi
\ifnotbothz
\psdot(0,0)
\pstverb{\transl{\n}{\N}\space
%next line gives a direction vector (y=-\n,x=\N)
\n\space neg \N\space
atan rotate -9 0 moveto 18 0 rlineto stroke}
\fi}}
\end{pspicture}
\end{document}
D.G. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7984907627105713, "perplexity": 7498.919765155885}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-39/segments/1568514574377.11/warc/CC-MAIN-20190921084226-20190921110226-00510.warc.gz"} |
http://mathoverflow.net/questions/138596/inequality-for-complex-hankel-function | # Inequality for complex Hankel function
Let $x>1$ and $0<\varphi<\frac{\pi}{2}$ be fixed. I would like to show that for any $s>0$, the following inequality holds: $$\left| H_{\frac{is}{e^{i\varphi } \cos \varphi}}^{\left( 1 \right)} \left( {\frac{is}{e^{i\varphi } \cos \varphi }x} \right) \right| \le \left| H_{is}^{\left( 1 \right)} \left( isx \right) \right| = iH_{is}^{\left( 1 \right)} \left( isx \right),$$ where $H_\nu^{(1)}(z)$ is the Hankel function. It would be enough to show that for any fixed $v>0$, $x>1$, $$[0,+\infty) \ni u \mapsto \left| {H_{u + iv}^{\left( 1 \right)} \left( {\left( {u + iv} \right)x} \right)} \right|$$ is a decreasing function. From Debye's asymptotic formula, we have $$\mathop {\lim }\limits_{s \to + \infty } \left| \frac{H_{\frac{is}{e^{i\varphi } \cos \varphi }}^{\left( 1 \right)} \left( {\frac{is}{e^{i\varphi } \cos \varphi}x} \right)}{H_{is}^{\left( 1 \right)} \left( isx \right)} \right| = \sqrt {\cos \varphi } < 1.$$ So for large $s$ the inequality is valid. However, I could not find any suitable representation of the (absolute value of the) Hankel function to show the inequality for every $s>0$.
-
Does this fail for $x < 1$? – Suvrit Aug 6 at 4:52
Numerical computations suggest that it does. – Gary Aug 6 at 10:37 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9530256986618042, "perplexity": 124.13090268686656}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-48/segments/1386163051684/warc/CC-MAIN-20131204131731-00069-ip-10-33-133-15.ec2.internal.warc.gz"} |
http://biggerwrench.blogspot.com/2009/04/text-processing-without-pain.html | ## Wednesday, April 8, 2009
### Text processing without the pain
Don't get me wrong, I love sed and awk. I have whole libraries of sed and awk scripts for doing all sorts of things. But some of them took a lot longer to write than they should've.
Last night I was faced with the task of translating a whole bunch of documentation from Tex and Latex to Docbook 5.0 XML. That meant doing multiline matches with sed and some preprocessing with awk, and my spirit rebelled.
I went beserk with online searches for "alternatives to sed awk" "text processing commandline utilities" and so on. The problem is that the standard text processing utilities need so much explanation that tutorials on how to do things with sed and awk are churned out so that they outnumber the alternatives by at least an order of magnitude difference.
I finally did what I should have done in the first place. I went to sourceforge.net and searched for "text processing". And I found Gema (pause for heavenly choir music).
It is not perfect by any means. the documentation in particular is just as cryptic as the original sed man pages. But in less than a half hour I had a script up and running that cleanly handled the multiline matches I needed to do.
As an example:
\\item$*$#\\=(\$1)#\n
will match the following
\\item[First Name]
The first name of the individual
This should not include any periods or commas.
And print out the following:
(First Name) The first name of the individual
This should not include any periods or commas
It's clean, it appears to be quick though none of the files I used it on with that large. It is well worth looking at. You also might want to take a look at this article. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.3265669643878937, "perplexity": 2007.386895717897}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-51/segments/1512948617816.91/warc/CC-MAIN-20171218141805-20171218163805-00649.warc.gz"} |
http://www-old.newton.ac.uk/programmes/MOS/seminars/2011031014001.html | # MOS
## Seminar
### Introduction to a motivic point of view on the cohomology of moduli spaces of bundles on curves
Heinloth, J (Amsterdam)
Thursday 10 March 2011, 14:00-15:00
Seminar Room 1, Newton Institute
#### Abstract
For moduli spaces of vector bundles on curves and some moduli spaces of Higgs bundles, it is possible to compute their cohomology groups in a geometric way, i.e., one can describe the space by a cut-and-paste procedure in terms of cells and symmetric products of the base curve. This gives a rather explicit description of the "motive" of the space. For moduli space of vector bundles this is due to Behrend and Dhillon, relying on an argument of Bifet, Ghione, and Letizia. We will try to give an introduction to this point of view on cohomology calcuations for moduli spaces.
#### Video
The video for this talk should appear here if JavaScript is enabled.
If it doesn't, something may have gone wrong with our embedded player.
We'll get it fixed as soon as possible. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8313778638839722, "perplexity": 613.9700174855025}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-48/segments/1448398468971.92/warc/CC-MAIN-20151124205428-00014-ip-10-71-132-137.ec2.internal.warc.gz"} |
https://machinelearningmastery.com/a-gentle-introduction-to-multivariate-calculus | # A Gentle Introduction to Multivariate Calculus
It is often desirable to study functions that depend on many variables.
Multivariate calculus provides us with the tools to do so by extending the concepts that we find in calculus, such as the computation of the rate of change, to multiple variables. It plays an essential role in the process of training a neural network, where the gradient is used extensively to update the model parameters.
In this tutorial, you will discover a gentle introduction to multivariate calculus.
After completing this tutorial, you will know:
• A multivariate function depends on several input variables to produce an output.
• The gradient of a multivariate function is computed by finding the derivative of the function in different directions.
• Multivariate calculus is used extensively in neural networks to update the model parameters.
Let’s get started.
A Gentle Introduction to Multivariate Calculus
Photo by Luca Bravo, some rights reserved.
## Tutorial Overview
This tutorial is divided into three parts; they are:
• Re-Visiting the Concept of a Function
• Derivatives of Multi-Variate Functions
• Application of Multivariate Calculus in Machine Learning
## Re-Visiting the Concept of a Function
We have already familiarised ourselves with the concept of a function, as a rule that defines the relationship between a dependent variable and an independent variable. We have seen that a function is often represented by y = f(x), where both the input (or the independent variable), x, and the output (or the dependent variable), y, are single real numbers.
Such a function that takes a single, independent variable and defines a one-to-one mapping between the input and output, is called a univariate function.
For example, let’s say that we are attempting to forecast the weather based on the temperature alone. In this case, the weather is the dependent variable that we are trying to forecast, which is a function of the temperature as the input variable. Such a problem can, therefore, be easily framed into a univariate function.
However, let’s say that we now want to base our weather forecast on the humidity level and the wind speed too, in addition to the temperature. We cannot do so by means of a univariate function, where the output depends solely on a single input.
Hence, we turn our attention to multivariate functions, so called because these functions can take several variables as input.
Formally, we can express a multivariate function as a mapping between several real input variables, n, to a real output:
For example, consider the following parabolic surface:
f(x, y) = x2 + 2y2
This is a multivariate function that takes two variables, x and y, as input, hence n = 2, to produce an output. We can visualise it by graphing its values for x and y between -1 and 1.
Three-Dimensional Plot of a Parabolic Surface
Similarly, we can have multivariate functions that take more variables as input. Visualising them, however, may be difficult due to the number of dimensions involved.
We can even generalize the concept of a function further by considering functions that map multiple inputs, n, to multiple outputs, m:
These functions are more often referred to as vector-valued functions.
## Derivatives of Multi-Variate Functions
Recall that calculus is concerned with the study of the rate of change. For some univariate function, g(x), this can be achieved by computing its derivative:
The generalization of the derivative to functions of several variables is the gradient.
– Page 146, Mathematics of Machine Learning, 2020.
The technique to finding the gradient of a function of several variables involves varying each one of the variables at a time, while keeping the others constant. In this manner, we would be taking the partial derivative of our multivariate function with respect to each variable, each time.
The gradient is then the collection of these partial derivatives.
– Page 146, Mathematics of Machine Learning, 2020.
In order to visualize this technique better, let’s start off by considering a simple univariate quadratic function of the form:
g(x) = x2
Line Plot of a Univariate Quadratic Function
Finding the derivative of this function at some point, x, requires the application of the equation for g’(x) that we have defined earlier. We can, alternatively, take a shortcut by using the power rule to find that:
g’(x) = 2x
Furthermore, if we had to imagine slicing open the parabolic surface considered earlier, with a plane passing through y = 0, we realise that the resulting cross-section of f(x, y) is the quadratic curve, g(x) = x2. Hence, we can calculate the derivative (or the steepness, or slope) of the parabolic surface in the direction of x, by taking the derivative of f(x, y) but keeping y constant. We refer to this as the partial derivative of f(x, y) with respect to x, and denote it by to signify that there are more variables in addition to x but these are not being considered for the time being. Therefore, the partial derivative with respect to x of f(x, y) is:
We can similarly hold x constant (or, in other words, find the cross-section of the parabolic surface by slicing it with a plane passing through a constant value of x) to find the partial derivative of f(x, y) with respect to y, as follows:
What we have essentially done is that we have found the univariate derivative of f(x, y) in each of the x and y directions. Combining the two univariate derivatives as the final step, gives us the multivariate derivative (or the gradient):
The same technique remains valid for functions of higher dimensions.
## Application of Multivariate Calculus in Machine Learning
Partial derivatives are used extensively in neural networks to update the model parameters (or weights).
We had seen that, in minimizing some error function, an optimization algorithm will seek to follow its gradient downhill. If this error function was univariate, and hence a function of a single independent weight, then optimizing it would simply involve computing its univariate derivative.
However, a neural network comprises many weights (each attributed to a different neuron) of which the error is a function. Hence, updating the weight values requires that the gradient of the error curve is calculated with respect to all of these weights.
This is where the application of multivariate calculus comes into play.
The gradient of the error curve is calculated by finding the partial derivative of the error with respect to each weight; or in other terms, finding the derivative of the error function by keeping all weights constant except the one under consideration. This allows each weight to be updated independently of the others, to reach the goal of finding an optimal set of weights.
This section provides more resources on the topic if you are looking to go deeper.
## Summary
In this tutorial, you discovered a gentle introduction to multivariate calculus.
Specifically, you learned:
• A multivariate function depends on several input variables to produce an output.
• The gradient of a multivariate function is computed by finding the derivative of the function in different directions.
• Multivariate calculus is used extensively in neural networks to update the model parameters.
Do you have any questions?
## Get a Handle on Calculus for Machine Learning!
#### Feel Smarter with Calculus Concepts
...by getting a better sense on the calculus symbols and terms
Discover how in my new Ebook:
Calculus for Machine Learning
It provides self-study tutorials with full working code on:
differntiation, gradient, Lagrangian mutiplier approach, Jacobian matrix, and much more...
### 8 Responses to A Gentle Introduction to Multivariate Calculus
1. Jayaganthan R July 24, 2021 at 10:39 am #
Dear Dr Stefania
Thank you for your excellent presentation of multivariate calculus. It’s beautifully explained to
follow.
With best regards
Jayaganthan
• Stefania Cristina July 24, 2021 at 5:58 pm #
Thank you, Jayaganthan. Glad to hear that you have found it useful.
2. Meshack Owira Amimo July 25, 2021 at 4:26 am #
A wonderful introduction to how calculus is relevant to help one have a command of ML and artificial intelligence.
Thanks for the simple free-flowing explanation n narrative on a subject regarded by many as abstract
• Stefania Cristina July 26, 2021 at 1:12 am #
Thank you for the kind words, Meshack.
3. Ashwin Norbert July 26, 2021 at 9:38 pm #
A detailed presentation and explanation of multivariant calculus. Thanks a lot Stefania.
• Stefania Cristina July 27, 2021 at 6:08 am # | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8482038974761963, "perplexity": 499.610254842306}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2023-14/segments/1679296950383.8/warc/CC-MAIN-20230402043600-20230402073600-00215.warc.gz"} |
https://www.physicsforums.com/threads/qm-the-dilation-operator.553535/ | # QM: The Dilation operator
• Start date
• #1
1
0
## Homework Statement
Concicer the dilation operator
$D = \vec{r} * \vec{p}$
Compute $[D,\vec{r} ] and [D, \vec{p}]$
## Homework Equations
$p = - i * hbar$
## The Attempt at a Solution
I think the question is really if $[D, \vec{r}]$ commutes
I got this:
$D = \vec{r} * \vec{p}$
$D = x p_x + y p_y + z p_z$
for the x direction:
$[D, r] = [D, x] = [x, x p_x]$
where do i take it from here?
## The Attempt at a Solution
• #2
dextercioby
Homework Helper
13,170
741
You have absolutely no idea ?? Pick up your book and find those brackets (called <commutator>) and the properties they have.
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1K | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9730028510093689, "perplexity": 21995.00638929203}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-05/segments/1642320300810.66/warc/CC-MAIN-20220118092443-20220118122443-00307.warc.gz"} |
https://rupress.org/jcb/article/116/2/367/14288/Myosin-I-moves-actin-filaments-on-a-phospholipid | Acanthamoeba myosin-I bound to substrates of nitrocellulose or planar lipid membranes on glass moved actin filaments at an average velocity of 0.2 micron/s. This movement required ATP and phosphorylation of the myosin-I heavy chain. We prepared planar lipid membranes on a glass support by passive fusion of lipid vesicles (Brian, A. A., and H. M. McConnell. 1984. Proc. Natl. Acad. Sci. USA. 81:6159-6163) composed of phosphatidylcholine and containing 0-40% phosphatidylserine. The mass of lipid that bound to the glass was the same for membranes of 2 and 20% phosphatidylserine in phosphatidylcholine and was sufficient to form a single bilayer. Myosin-I moved actin filaments on planar membranes of 5-40% but not 0-2% phosphatidylserine. At the low concentrations of phosphatidylserine, actin filaments tended to detach suggesting that less myosin-I was bound. We used the cooperative activation of Acanthamoeba myosin-I ATPase by low concentrations of actin to assess the association of phospholipids with myosin-I. Under conditions where activity depends on the binding of actin to the tail of myosin-I (Albanesi, J. P., H. Fujisaki, and E. D. Korn. 1985. J. Biol. Chem. 260:11174-11179), phospholipid vesicles with 5-40% phosphatidylserine inhibited ATPase activity. The motility and ATPase results demonstrate a specific interaction of the tail of myosin-I with physiological concentrations of phosphatidylserine. This interaction is sufficient to support motility and may provide a mechanism to target myosin-I to biological membranes.
This content is only available as a PDF. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8188148736953735, "perplexity": 9421.157331005827}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-49/segments/1669446708046.99/warc/CC-MAIN-20221126180719-20221126210719-00233.warc.gz"} |
http://math.stackexchange.com/questions/30595/prove-the-reduction-formula?answertab=active | # Prove the reduction formula
The question is to "prove the reduction formula"
$$\int{ \frac{ x^2 }{ \left(a^2 + x^2\right)^n } dx } = \frac{ 1 }{ 2n-2 } \left( -\frac{x}{ \left( a^2+x^2 \right)^{n-1} } + \int{ \frac{dx}{ \left( a^2 + x^2 \right)^{n-1} } } \right)$$
What I got is
Set
$u = x$
$du = dx$
$\displaystyle{ dv = \frac{ x }{ \left( a^2 + x^2 \right)^{n} } dx }$
$\displaystyle{ v = \frac{ 1 }{ 2(n+1) \left( a^2 + x^2 \right)^{n+1} } }$
So I got
$$\frac{ 1 }{ 2n+2 } \left( \frac{x}{ \left( a^2 + x^2 \right)^{n+1}} - \int{ \frac{dx}{ \left( a^2+x^2 \right)^{n+1} } } \right)$$
Which I believe is correct. They are subtracting from n in the integration step and I'm not sure why
-
+1 for, as usual, showing your work. – Arturo Magidin Apr 3 '11 at 1:19
You went wrong when you integrated $dv$.
You have $dv = x(a^2+x^2)^{-n}\,dx$. When you integrate, you add one to the exponent. But adding one to $-n$ gives $-n+1 = -(n-1)$. So $$v = \frac{1}{2(-n+1)}(a^2+x^2)^{-n+1} = \frac{1}{2(1-n)(a^2+x^2)^{n-1}}.$$ The minus sign from integration by parts can be cancelled out by switching the sign of $2(1-n)$ to get $2(n-1) = 2n-2$.
If you use the correct value of $v$, I think you will have no trouble establishing the formula. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9229817986488342, "perplexity": 306.3531875093351}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-48/segments/1387345777160/warc/CC-MAIN-20131218054937-00071-ip-10-33-133-15.ec2.internal.warc.gz"} |
http://mathhelpforum.com/math-software/230566-simplying-linear-equation-get-quartic-q-using-maple-using-descarte-s.html | # Math Help - Simplying linear equation to get quartic in q with using Maple and using Descarte’s
1. ## Simplying linear equation to get quartic in q with using Maple and using Descarte’s
Using the maple I am trying to get quardic in q from this big linear equation. Then use Descarte’s rule of signs to determine the number of positive roots.
\frac{\gamma*q*P_Q}{k_p*(1-q)*P_C} = \frac{I*\alpha}{k_f+k_d+\frac{k_n*\lambda_b*\gamma *q*P_Q}{\lambda_b*\gamma*q*P_Q+k_p*\lambda_r*(1-q)^2}+k_p*(1-q)}
Values of parameters are given below:
$I=1200$
$k_f = 6.7*10.^7$
$k_d = 6.03*10.^8$
$k_n = 2.92*10.^9$
$k_p = 4.94*10.^9$
$\alpha = 1.14437*10.^(-3)$
$\lambda_b = 0.87e-2$
$\lambda_r = 835$
$\gamma = 2.74$
$P_C = 3*10.^(11)$
$P_Q = 2.87*10.^(10)$
=>
I tried the code in maple to get quartic in q but DOES NOT WORKS.
Code:
II := 1200:
k_f := 6.7*10.^7:
k_d := 6.03*10.^8:
k_n := 2.92*10.^9:
k_p := 4.94*10.^9:
alpha := 1.14437*10.^(-3):
lambda_b := 0.87e-2:
lambda_r := 835:
ggamma := 2.74:
P_C := 3*10.^11:
P_Q := 2.87*10.^10:
eq := ggamma*q*P_Q/(k_p*(1-q)*P_C) = II*alpha/(k_f+k_d+k_n*lambda_b*ggamma*q*P_Q/(lambda_b*ggamma*q*P_Q+k_p*lambda_r*(1-q)^2)+k_p*(1-q)):
simply(eq, q);
My lecturer want me to manipulate the equation and get a quartic in q before substituting the values of parameters into the equation. After that,use Descarte’s rule of signs to determine the number of positive roots. Then write Q=1-q to get second quartic in Q and repeat rule of signs to determine number of steady states of q less than 1. And do the substition of parameters if necessary.
Now, its kind of hard for me what he wants because to get quartic in q first from the equation is hard to do by hand , so i have to use in maple which is not working then use Descarte’s rule of signs.
2. ## Re: Simplying linear equation to get quartic in q with using Maple and using Descarte
Posting a second time will not get you an answer any faster. Perhaps try different variable names.
Try using semicolons at the end of every statement instead of colons?
Also, try solve(eqn,q) instead of simplify(eqn,q)?
3. ## Re: Simplying linear equation to get quartic in q with using Maple and using Descarte
Originally Posted by SlipEternal
Posting a second time will not get you an answer any faster. Perhaps try different variable names.
Try using semicolons at the end of every statement instead of colons?
Also, try solve(eqn,q) instead of simplify(eqn,q)?
Maple understand the colons not semicolons sir. And i did tried the solve(eqn,q) to get the result for q which i got it. but this time i am trying to manipulate the equation to get quartic in q, so that i can use Descarte’s rule of signs to determine the number of positive roots. And after that do substitute parameters in and get the results for q.
4. ## Re: Simplying linear equation to get quartic in q with using Maple and using Descarte
Cross multiplying by hand should not be a problem.
\begin{align*}& \left[\left(k_f + k_d + k_p(1-q) \right)\left(\lambda_b\cdot \gamma \cdot q \cdot P_Q + k_p\cdot \lambda_r\cdot (1-q)^2\right) + k_n\cdot \lambda_b\cdot \gamma \cdot q \cdot P_Q \right]\left(\gamma \cdot q \cdot P_Q\right) \\ = & I\cdot \alpha\left( k_p(1-q)P_C \right)\left( \lambda_b\cdot \gamma \cdot q \cdot P_Q + k_p\cdot \lambda_r\cdot (1-q)^2 \right)\end{align*}
Ask maple to simplify that expression. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 1, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9958752393722534, "perplexity": 1751.4367719363968}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-52/segments/1419447548655.55/warc/CC-MAIN-20141224185908-00082-ip-10-231-17-201.ec2.internal.warc.gz"} |
https://socratic.org/questions/56e81b1311ef6b3478778796#243766 | Physics
Topics
# What is the relationship between the radius of circular motion and the centripetal force, if the mass undergoing the circular motion is kept constant?
Yes. The short answer is that it's right there in the formula: $F = \frac{m {v}^{2}}{r}$ or $F = m {\omega}^{2} r$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 2, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8839406967163086, "perplexity": 169.09327290367384}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-21/segments/1652662558030.43/warc/CC-MAIN-20220523132100-20220523162100-00388.warc.gz"} |
https://www.hepdata.net/record/42378 | Measurement of the $Z Z \gamma$ and $Z \gamma \gamma$ couplings in $p\bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV
Phys.Rev.Lett. 75 (1995) 1028
Abstract (data abstract)
FNAL-COLLIDER. Measurement of the Z Z GAMMA and Z GAMMA GAMMA couplings in PBAR P collisions at sqrt(s) = 1.8 TeV. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9999616146087646, "perplexity": 4614.658815764835}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-51/segments/1544376829997.74/warc/CC-MAIN-20181218225003-20181219011003-00610.warc.gz"} |
https://geo.libretexts.org/Courses/University_of_California_Davis/GEL_056%3A_Introduction_to_Geophysics/Geophysics_is_everywhere_in_geology.../04%3A_Plate_Tectonics/4.01%3A_The_Forces_Driving_Plate_Motions | # 4.1: The Forces Driving Plate Motions
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The motion of tectonic plates is driven by convection in the mantle. In simple terms, convection is the idea that dense, cold things sink, and buoyant, warm things rise. In the earth the cold sinking things are slabs (subducting plates) and the warm things are plumes, or just rising material from deeper in the mantle.
There are three main forces that determine the rate at which tectonic plates move as part of the mantle convection system:
• slab pull: the force due to the weight of the cold, dense sinking tectonic plate
• ridge push: the force due to the buoyancy of the hot mantle rising to the surface beneath the ridge.
• viscous drag: the force opposing motion of the plate and slab past the viscous mantle underneath or on the side.
This force balance is given by:
$F_{ridge-push}+F_{slab-pull}-F_{viscous-drag}=0$
Because the viscous drag depends explicitly on the plate velocity, it is possible to predict the speed plate motion when the forces are balanced (under certain simplifying assumptions).
Recall from Chapter 1 that stress is related to force as $$\sigma=\frac{F}{A}$$ where $$A = L W$$. Rearranging, $$F=\sigma A$$. When considering the force balance on the a plate it is useful to using a simplified geometry as shown below and consider the force per unit length (or ridge or subduction zone)
$F= \sigma A/W = \sigma L \label{force}$
As seen in the figure below, $$W$$ is the length of the plate along the ridge and subduction zone. By considering the force per unit length (in the W direction), we can then consider the forces working along a profiles from the ridge to the subduction zone and ignore any variation in the ridge-parallel direction.
## Viscous Drag
One of the mechanisms for plate motion that is a result of convection is viscous drag. This concept relates to ideas we discussed earlier, including the Couette Flow and viscous stress. The drag on the base of the oceanic lithosphere can both drive or resist plate motion, depending on the relative motion between the plate and the underlying mantle. For this discussion, we will consider that the plate is being pulled or pushed by slab-pull and ridge push and drags the asthenosphere with it. Therefore viscsous drag oppose the motion of the plate (or slab) and acts to slow it down.
From the figure above, we can derive an equation to describe plate motion due to viscous drag.
$V=V_o(1-\frac{y}{h})$
$\dot{\varepsilon}=\frac{1}{2}\frac{dV}{dy}=-\frac{V_o}{2h}$
\begin{align*}\sigma &=2\eta\dot{\varepsilon} \\[4pt] &=2\eta(\frac{-V_o}{2h}) \\[4pt] &=\frac{-V_o\eta}{h} \end{align*}
The negative sign indicates an opposition to plate motion, i.e., the viscous drag. We now have an equation that describes the magnitude of drag:
$|\sigma|=\frac{V_o\eta}{h}$
placing this into our previous force equation (Equation \ref{force}):
$F=\sigma L = \frac{V_o\eta}{h} L$
Let's do an example calculating viscous drag under a plate.
Example Viscous Drag Under the Plate
Assume that:
• the plate drags the mantle underneath in a layer that is 100 km thick (h~100 km).
• the mantle viscosity is $$\eta ~ 1\times10^{18}$$ Pa(s).
• the plate velocity is Vo~5 cm/yr. (Note that this is equivalent to 0.05 m/yr = 50 mm/yr = 50 km/my
• the plate length from the ridge to the subduction zone is about 5000 km
From the strain-rate, we can get the stress as shown above, and then multiply by the length of the plate
Using these numbers, we can calculate the force on the descending plate, $$F=1.59 \times 10^{11}$$ N/m.
The above example is for the viscous drag just under the plate, but now we will also consider a case where there are stresses acting on both sides of the subducting slab. As the slab sinks into the mantle, the viscous mantle on both sides resists the sinking motion of the slab. For this simple example,
$\sigma=\frac{V_o\eta_{av}}{h}$
$F=\sigma L_{slab}$
$F_{vis.}=2F=2\sigma L_{slab}=\frac{2V_o\eta_{av}}{h}L_{slab}$
Example Viscous Drag on Two Sides of a Plate
As we did in the previous example, consider viscous drag on a slab, but now on both sides of the plate.
We are given that
• The slab sinks at the same speed that the plate is moving: Vo=Vplate~5 $$\frac{cm}{yr}$$,
• Again, the shearing layer on both sides is 100 km wide (h~100 km),
• The viscosity of the mantle increases with depth, for this example we'll assume its constant $$\eta_{av} =10^{21}$$ Pa s ,
• The slab length (from the base of the lithosphere to the upper/lower mantle boundary is Lslab = 560 m.
In this case, $$F = 78 \times 10^{13}$$ N/m. If we change $$\eta$$ to $$10^{21}$$, then equals $$F=1.78x10^{10}$$ N/m.
Notice that the stress is proportional to the velocity $$\sigma \alpha V$$ so as the velocity increases so does the stress opposing the sinking.
However, the biggest changes come from the viscosity because it can changes by x10-100 in the upper mantle, thus this change has the biggest effect on the viscous drag.
The viscous drag is also proportional to the length of the slab, so the resistance also increases as the slab gets longer (but so does the slab pull force).
## Slab-Pull Force
The main force on a subducting plate is the slab-pull force. This is the force due to the density contrast between a slab and its surroundings, ie., the mass anomaly of the slab in the mantle. We can approximate this force by thinking of the sinking slab a a vertical rectangle (like the viscous drag example) with a width, $$w$$, hanging down a distance, $$d$$ from the Earth's surface with a temperature $$\Delta T$$ different than its surroundings.
The density as a function of temperature is given by
$\rho (T)=\rho_m(1+\alpha (T_m - T))$
where $$\rho_m$$ is the reference mantle density at $$T = T_m$$ and cold material has a higher density, and $$\alpha$$ is the thermal expansion coefficient and is ~$$2 \times 10^{-5}$$ 1/K in the sinking slab.
For the slab, we can rewrite this as:
$\rho (T)=\rho_m(1+\alpha \Delta T)$
where $$\Delta T=T_m-T_{slab}$$
The density anomaly is then
$\Delta \rho= \rho_m\alpha\Delta T$
This is the extra density of the slab relative to the mantle. To calculate the force per unit area, we need to determine the mass anomaly per unit area, $$\Delta M = \Delta \rho A_{slab}$$, where A_{slab} is the cross sectional area of the slab along the profile (width across times length into the mantle).
The temperature in the slab is related to the temperature of the subducting plate. Recall from the chapter on thermal diffusion that the temperature of a tectonic plate is given by the half-space cooling model. Once the plate starts sinking, the cold slab warms up, and the surrounding mantle cools down. However, the total temperature anomaly (temperature difference times volumes) stays the same. (Remember that there is conservation of energy, so the total energy of the cold slab is conserved). So, if we integrate the temperature profile solution from the half-space cooling model over the thickness of this plate, this will also be the thermal anomaly of the the slab. Finally, because the density anomaly is just $\Delta \rho=\rho_m\alpha\Delta T$, we can get the total density anomaly by just multiplying by $$\rho_m \alpha$$.
So, the trick to figuring out the slab pull force is the first determine the density anomaly of the subducting plate just before it enters the trench. Then imagine taking a length of plate equal to the length of the slab and rotating it en masse in to the mantle. The density anomaly of the sinking slab will be the same.
To get the density anomaly, we integrate the temperature equation for the plate from the half-space cooling model.
$T(z, t)=(T_s-T_m)erfc(\frac{z}{2\sqrt{\kappa t}})+T_m$
Here $$z$$ is the depth through the subducting plate, before it sinks, or the width through the slab while it is sinking.
$\Delta T=T_m - T(z, t)$
$\Delta T=-(T_s-T_m)erfc(\frac{z}{2\sqrt{\kappa t}})$
$\Delta T=(T_s-T_m)erfc(\frac{z}{2\sqrt{\kappa t}})$
Then, multiplying the $$\rho_m \alpha$$,
$\Delta \rho=\rho_m\alpha\Delta T$
$\Delta \rho=\rho_m\alpha\Delta T(z)$
Next we integrate over the width (depth) to the get the mass per unit length (length parallel to the trench) in a single profile, (we will need to sum this over the length of the slab):
$\Delta m=\int_{0}^{z\rightarrow\infty}{\Delta \rho(z)dz}$
$\Delta m=\rho_m\alpha(T_m-T_s)\int_{0}^{\infty}erfc(\frac{z}{2\sqrt{\kappa t}})dz$
Now we use variable substitution so we can solve the integral
Let $$q=\frac{z}{2\sqrt{\kappa t}}$$ where $$z\rightarrow\infty$$ and $$q\rightarrow\infty$$.
$\frac{dq}{dz}=\frac{1}{2\sqrt{\kappa t}}$
$dz=2\sqrt{\kappa t}dq$
Now substitute into the integral,
$\Delta m=\rho_m\alpha(T_m-T_s)2\sqrt{\kappa t}\int_{0}^{\infty}erfc(q)dq$
The complementary error function integral solution can be found in any integral table (or search online) and equals $$\sqrt{\frac{1}{\pi}}$$
$\Delta m=\rho_m\alpha(T_m-T_s)2\sqrt{\frac{\kappa t}{\pi}}$
The above equation gives the mass anomaly (relative to the surrounding mantle) per unit length.
Finally, we can determine the total mass anomaly by multiplying by the length of the slab:
$\Delta M=\Delta m L_{slab}$
The slab pull force is then given by,
$F_{slab-pull}=\Delta m L_{slab} g$
and subsituting for $$\Delta m$$,
$F_{sp}=2 \rho_m\alpha (T_m-T_s) g L_{slab}\sqrt{\frac{\kappa t}{\pi} }$
Example Slab-Pull Force
We are given that
• $$\rho_o$$=3300 kg/m$$^3$$,
• $$\alpha =2e-5$$ 1/K, g=9.81 m/s$$^2$$,
• Tm-Ts=1400 K,
• $$\kappa =1e-6$$ m$$^2$$/s,
• t=age of slab at time of subduction,
• Lslab=560 km.
We know that $$F_{sp}=\Delta m L_{slab} g$$
Thus, the force per unit length of the slab-pull is Fsp=2.88x1013 N/m
You might notice that this force is 100 - 1000x more than the viscous drag force.
## Ridge-Push Force
Let's cover a final force a subducting plate would experience, the ridge-push force. This force results from the elevation of oceanic ridges above the seafloor. This difference in height leads to pressure that 'pushes' the plate away from the ridge. Ridge push is the simplest force in some ways, as all its components can be easily examined.
Simply put, to determine ridge-push forces, we need to do two things. First, look at the isostatic balance and the depth of oceans w(t). Second, we need to look at the force balance on the plate.
$T(t)=(T_s-T_m)erfc(\frac{z}{2\sqrt{\kappa t}})+T_m$
$\rho(T)=\rho_m(1+\alpha\Delta T)$
$\Delta T=T_m-T(t)$
T(t) is <Tm+$$\Delta T$$ because of more density.
Balance pressures:
P1=P2
$drp_wg+\int_{dr}^{dr+w}\rho (T)gdz+\int_{dr+w}^{z_c}\rho (T)gdz=(dr+w)\rho_wg + \int_{dr+w}^{z_c}\rho (T)gdz$
$\int_{dr}^{dr+w}\rho_mdz+\int_{dr+w}^{z_c}\rho_mdz=wp_w+\int_{dr+w}^{z_c}\rho (z)dz$
$w\rho_m-wp_w=\int_{dr+w}^{z_c}\rho (z)-\rho_mdz$
$\rho (z)=\rho (T)\rightarrow T(z)$
Like we did above, we will use the complementary error function and find its solution in a integral table.
$w(\rho_m-\rho_w)=\rho_m\alpha(T_m-T_s)\int_{0}^{\infty}erfc(\frac{z'}{2\sqrt{\kappa t}})dz'$
The complementary error function integral solution is $$2\sqrt{\frac{\kappa t}{\pi}}$$
$w=\frac{2\rho_m\alpha(T_m-T_o)}{\rho_m-\rho_w}\sqrt{\frac{\kappa t}{\pi}}$
An important thing to note is that the depth of the ocean basins deepen at ~$$\sqrt{t}$$ (the square root of age)
⇒balanced pressures (isostasy)
Ridge-push is very similar to the balanced pressures idea, but uses balanced forces instead.
⇒$$\Delta P$$⇒drives flow across A. No net force⇒no $$\Delta P$$.
$F\backsim\Delta P A$ This is the force per unit width.
Example Ridge-Push
The forces in this example should balance. After we write the integrals for the various forces, we should have an expression where FRP=F1-F2-F3.
$F_1=\int_{0}^{z_c}\rho_mgzdz=F_s$
Here, $$\rho_mgz$$ represents the pressure, dz is XA⇒Area⇒wXL$$\frac{area}{w}$$=L
We can do a simple integral in depth, this is the same pressure from the mantle below a plate.
Rewriting F1 0→zc, 0→w + w-zL
$F_1=\int_{0}^{w}\rho_mgzdz+\int_{w}^{w+z_c}\rho_mgzdz+\int_{0}^{2L}\rho_mg\bar{z}d\bar{z}$
Where we let $$\bar{z}=z-w$$
$F_2=\int_o^w\rho_wgz=F_4$
$$\rho_wgz$$ is P2. Here, we do not need to integrate over shape of w.
$F_3=\int_0^{z_L}P_Ld\bar{z}$
$P_L=\rho_w g w+\int_0^{\bar{z}} \rho_L (T)g d\bar{z}$
Here, $$\rho_w g w$$ is the pressure due to the water and $$\rho_L$$ is the temperature-dependent density of the lithosphere.
Remember our force balance equation:
$F_{RP}=F_1-F_2-F_3$
Plugging everything in and skipping some of the basic algebra we get:
$F_{RP}=g[\frac{1}{2}(\rho_m-\rho_w)w^2+\kappa t\rho_m\alpha(T_m+T_s)]$
We get the term w2 because PL~w and we integrated PL.
From isostasy, we can plug in
$w(t)=\frac{2\rho_m\alpha(T_m-T_s)}{(\rho_m-\rho_w)}\sqrt{\frac{\kappa t}{\pi}}$
$F_{RP}=g \rho_m\alpha(T_m-T_s) \kappa t (1+\frac{2p_m\alpha(T_m-T_s)}{\pi(\rho_m-\rho_w)})$
Notes on Ridge-Push
A few things to note: isostasy→controlling w(t)
The pressure across the lithosphere→ridge-push force
FRP$$\alpha$$t age of the oldest part of plate
Now that we have our general solution for the ridge-push force, if we are given actual values, we can solve it. If g=9.81, k=1e-6$$\frac{m^2}{s}$$, $$\rho_m$$=3300$$\frac{ky}{m^3}$$, Tm-Ts=1400 K, $$\alpha$$=2x10-5$$\frac{1}{K}$$, $$\rho_m$$=1000$$\frac{kg}{m^3}$$, we can finally find the force
$F_{RP}=3.24x10^{12}\frac{N}{m}$
4.1: The Forces Driving Plate Motions is shared under a CC BY-SA license and was authored, remixed, and/or curated by Magali Billen. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9707909226417542, "perplexity": 1079.4887664399778}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-21/segments/1652662577757.82/warc/CC-MAIN-20220524233716-20220525023716-00457.warc.gz"} |
https://dsp.stackexchange.com/questions/3125/speech-analysis-zero-crossing | Speech Analysis - Zero-Crossing
Basically, (I know I've asked a simular question, but I have been away and really thought about it this time)!
Let me try and explain this in the best way possible:
Basically, I'm attempting to create an algorithm that takes a voice sample (.wav) of someone saying either "Yes", or "No". Now, in order to do this I am attempting to split the sample into equal blocks in order to get the Phones.
I don't need to technically analise all of Phones, I can identify if the the sample is either "Yes" or "No" by just looking for a "Y" Phone. Because if a "Y" doesn't exist then the sample is "No". So, I can handle this by implementing a decision tree.
Ok, so to my question. I know that this can be achieved using Zero-Crossing, but, I don't have any experience in this (Ok, people are going to tell me to stop doing it then) but, we all had to learn somewhere, right?
If someone could possibly link me to a website or a book where I can learn about the Zero-crossing method? Then it would be great.
The main thing I don't understand about it is, how can Zero-crossing determine whether the Phone is a "Y"? Or, will I need to have some samples of "Y" in order to match through Correlation?, or something.
I hope someone can advise me.
Thanks :)
• In spite of my detailed answer to your previous question, you are still not providing any information regarding whether you want to build a system with or without prior training, and single or multi- speaker, which are the very first thing to specify before building a speech recognition system, not matter how complex. Aug 16 '12 at 7:21
• You should go back and improve the original question rather than just posting what is essentially a re-worded duplicate question. Aug 16 '12 at 19:43
• Instead of listening for the Y or the N, which are both voiced sounds, listen for the S, which is unvoiced noise. Check the RMS amplitude for each chunk, and when it's above some threshold (there's sound there), check its spectral flatness. Low spectral flatness is voiced sounds, high spectral flatness is noisy unvoiced sounds. Aug 23 '12 at 18:34
• To add to endolith's comments regarding spectral-flatness for voiced versus unvoiced discrimination, looking at the LPC residual will also reveal latent discriminable structure that could be of use. Dec 17 '14 at 3:53
Zero-crossing rate (ZCR) might be useful for voiced/unvoiced frame discrimination, speech/music discrimination, but it is of much lesser importance in speech recognition. One reason is that it is pitch-dependent and not robust to background noise or hum. It is not difficult to craft very different signals (say a female voice saying a phone and a male voice saying another phone) that have the exact same ZCR; or to add some noise to a signal in a way that will half or double its ZCR.
Using zero-crossing rate might work in the single-speaker + prior training case. Collect a handful of samples of each words, compute the zero crossing rate, and train a naive bayesian classifier for this two-class problem. Be prepared to poor performances, and don't expect your system to generalize to other speakers.
The only plausible reason one would use such a feature would be on embedded systems with very limited computational power. Otherwise, there's no reason not to use "proven" features like MFCC or AR coefficients.
I believe that zero-crossing rate is not going to help you to distinguish between "Yes/no". However you can try and discover this by yourself. I don't know what programming language you are using... A typical method would be (considering that your data is in a vector named "x" ):
temp1 = x > 0;
temp2 = diff(temp1);
in "temp2" you will have -1, 0 and 1 values that show when your signal goes from pos to neg and from neg to pos. You can count/sum all the 1's for example, depending on want type of "rate" you want to calculate.
(If you evaluate only the rightmost 1/3 of the signal you might get it to work since the "s" will containt much more zero-crosses than the "o") | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.38746389746665955, "perplexity": 1025.6612981361334}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-49/segments/1637964363465.47/warc/CC-MAIN-20211208083545-20211208113545-00035.warc.gz"} |
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