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Relatively few bacteria have been comprehensively studied for their protein–protein interactions. However, none of these interactomes are complete in the sense that they captured all interactions. In fact, it has been estimated that none of them covers more than 20% or 30% of all interactions, primarily because most of these studies have only employed a single method, all of which discover only a subset of interactions. Among the published bacterial interactomes (including partial ones) are
The E. coli and Mycoplasma interactomes have been analyzed using large-scale protein complex affinity purification and mass spectrometry (AP/MS), hence it is not easily possible to infer direct interactions. The others have used extensive yeast two-hybrid (Y2H) screens. The Mycobacterium tuberculosis interactome has been analyzed using a bacterial two-hybrid screen (B2H).
Note that numerous additional interactomes have been predicted using computational methods (see section above). | 1 | Applied and Interdisciplinary Chemistry |
In nature, pyruvate oxidase employs two cofactors thiamine pyrophosphate (ThDP) and Flavin adenine dinucleotide (FAD) to catalyze a conversion of pyruvate to acetyl phosphate. First, ThDP mediates a decarboxylation of pyruvate and generates an active aldehyde as a product. The aldehyde is then oxidized by FAD and is subsequently attacked by phosphate to yield acetyl phosphate.
Diederich and coworkers mimicked this system with a supramolecular catalyst based on cyclophane. The catalyst has thiazolium ion, a reactive part of ThDP and flavin, a bare-bones core of FAD, in close proximity and near the substrate binding site. The catalytic cycle is almost the same as that in nature, except the substrate is an aromatic aldehyde rather than pyruvate. First, the catalyst binds the substrate within its cyclophane ring. Then, it uses thiazolium ion to condense with the substrate generating an active aldehyde. This aldehyde is oxidized by flavin and then attacked by methanol to yield a methyl ester. | 0 | Theoretical and Fundamental Chemistry |
In July 1914—shortly before the outbreak of World War I—Hahn was recalled to active duty with the army in a Landwehr regiment. They marched through Belgium, where the platoon he commanded was armed with captured machine guns. He was awarded the Iron Cross (2nd Class) for his part in the First Battle of Ypres. He was a joyful participant in the Christmas truce of 1914, and was commissioned as a lieutenant. In mid-January 1915, he was summoned to meet chemist Fritz Haber, who explained his plan to break the trench deadlock with chlorine gas. Hahn raised the issue that the Hague Convention banned the use of projectiles containing poison gases, but Haber explained that the French had already initiated chemical warfare with tear gas grenades, and he planned to get around the letter of the convention by releasing gas from cylinders instead of shells.
Habers new unit was called Pioneer Regiment 35. After brief training in Berlin, Hahn, together with physicists James Franck and Gustav Hertz, was sent to Flanders again to scout for a site for a first gas attack. He did not witness the attack because he and Franck were off selecting a position for the next attack. Transferred to Poland, at the Battle of Bolimów on 12 June 1915, they released a mixture of chlorine and phosgene gas. Some German troops were reluctant to advance when the gas started to blow back, so Hahn led them across No Mans land. He witnessed the death agonies of Russians they had poisoned, and unsuccessfully attempted to revive some with gas masks. He was transferred to Berlin as a human guinea pig testing poisonous gases and gas masks. On their next attempt on 7 July, the gas again blew back on German lines, and Hertz was poisoned. This assignment was interrupted by a mission at the front in Flanders and again in 1916 by a mission to Verdun to introduce shells filled with phosgene to the Western Front. Then once again he was hunting along both fronts for sites for gas attacks. In December 1916 he joined the new gas command unit at Imperial Headquarters.
Between operations, Hahn returned to Berlin, where he was able to slip back to his old laboratory and work with Meitner, continuing with their research. In September 1917 he was one of three officers, disguised in Austrian uniforms, sent to the Isonzo front in Italy to find a suitable location for an attack, utilising newly developed rifled minenwerfers that simultaneously hurled hundreds of containers of poison gas onto enemy targets. They selected a site where the Italian trenches were sheltered in a deep valley so that a gas cloud would persist. The following Battle of Caporetto broke the Italian lines, and the Central Powers overran much of northern Italy. In 1918 the German offensive in the west smashed through the Allies' lines after a massive release of gas from their mortars. That summer Hahn was accidentally poisoned by phosgene while testing a new model gas mask. At the end of the war he was in the field in mufti on a secret mission to test a pot that heated and released a cloud of arsenicals. | 0 | Theoretical and Fundamental Chemistry |
The abundance of total alpha elements in stars is usually expressed in terms of logarithms, with astronomers customarily using a square bracket notation:
where is the number of alpha elements per unit volume, and is the number of iron nuclei per unit volume. It is for the purpose of calculating the number that which elements are to be considered "alpha elements" becomes contentious. Theoretical galactic evolution models predict that early in the universe there were more alpha elements relative to iron. | 0 | Theoretical and Fundamental Chemistry |
In quantum mechanics, the Hellmann–Feynman theorem relates the derivative of the total energy with respect to a parameter to the expectation value of the derivative of the Hamiltonian with respect to that same parameter. According to the theorem, once the spatial distribution of the electrons has been determined by solving the Schrödinger equation, all the forces in the system can be calculated using classical electrostatics.
The theorem has been proven independently by many authors, including Paul Güttinger (1932), Wolfgang Pauli (1933), Hans Hellmann (1937) and Richard Feynman (1939).
The theorem states
where
* is a Hermitian operator depending upon a continuous parameter ,
*, is an eigenstate (eigenfunction) of the Hamiltonian, depending implicitly upon ,
* is the energy (eigenvalue) of the state , i.e. .
Note that there is a breakdown of the Hellmann-Feynman theorem close to quantum critical points in the thermodynamic limit. | 0 | Theoretical and Fundamental Chemistry |
For incident photon energies E larger than two times the rest mass of the electron (1.022 MeV), pair production can occur. The resulting positron annihilates with one of the surrounding electrons, typically producing two photons with 511 keV. In a real detector (i.e. a detector of finite size) it is possible that after the annihilation:
* Both photons deposit their energy in the detector. This results in a 511 keV peak.
* One of the two photons escapes the detector and only one of the photons deposits its energy in the detector, resulting in a peak with E − 511 keV, the single escape peak.
* Both photons escape the detector, resulting in a peak with E − 2 × 511 keV, the double escape peak.
The above Am-Be-source spectrum shows an example of single and double escape peak in a real measurement. | 0 | Theoretical and Fundamental Chemistry |
By conservation of mass, the inverse-square law requires that the radially outward velocity must be inversely proportional to the square of the distance from the origin (the center of the bubble). Therefore, letting be some function of time,
In the case of zero mass transport across the bubble surface, the velocity at the interface must be
which gives that
In the case where mass transport occurs, the rate of mass increase inside the bubble is given by
with being the volume of the bubble. If is the velocity of the liquid relative to the bubble at , then the mass entering the bubble is given by
with being the surface area of the bubble. Now by conservation of mass , therefore . Hence
Therefore
In many cases, the liquid density is much greater than the vapor density, , so that can be approximated by the original zero mass transfer form , so that | 1 | Applied and Interdisciplinary Chemistry |
The PCP protein has been identified in dinoflagellate genomes in at least two forms, a homodimeric form composed of two 15-kD monomers, and a monomeric form of around 32kD believed to have evolved from the homodimeric form via gene duplication. The monomeric form consists of two pseudosymmetrical eight-helix domains in which the helices are packed in a complex topology resembling that of the beta sheets in a jelly roll fold. The three-dimensional arrangement of helices forms a boat-shaped molecule with a large central cavity in which the pigments and lipids are bound. Each eight-helix segment typically binds four peridinin molecules, one chlorophyll a molecule, and one lipid molecule such as digalactosyl diacyl glycerol; however, this stoichiometry varies among species and among PCP isoforms. The most common 4:1 peridinin:chlorophyll ratio was predicted by spectroscopy in the 1970s, but was unconfirmed until the crystal structure of the Amphidinium carterae PCP complex was solved in the 1990s. Whether formed from a protein monomer or dimer, the assembled protein-pigment complex is sometimes known as bPCP (for "building block") and is the minimal stable unit. In at least some PCP forms, including that from A. carterae, these building blocks assemble into a trimer thought to be the biologically functional state.
When the X-ray crystallography structure of PCP was solved in 1997, it represented a novel protein fold, and its topology remains unique among known proteins. The structure is referred to by the CATH database, which systematically classifies protein structures, as an "alpha solenoid" fold; however, elsewhere in the literature the term alpha solenoid is used for open and less compact helical protein structures. | 0 | Theoretical and Fundamental Chemistry |
Canadian Reference Materials (CRM) are certified reference materials of high-quality and reliability produced by the National Metrology Institute of Canada – the National Research Council Canada. The NRC Certified Reference Materials program is operated by the Measurement Science and Standards portfolio and provides CRMs for environmental, biotoxin, food, nutritional supplement, and stable isotope analysis. The program was established in 1976 to produce CRMs for inorganic and organic marine environmental analysis and remains internationally recognized producer of CRMs. | 1 | Applied and Interdisciplinary Chemistry |
On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides.
* Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes. Primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long (>100 million years) that they have not yet completely decayed. Some radionuclides have half-lives so long (many times the age of the universe) that decay has only recently been detected, and for most practical purposes they can be considered stable, most notably bismuth-209: detection of this decay meant that bismuth was no longer considered stable. It is possible decay may be observed in other nuclides, adding to this list of primordial radionuclides.
* Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238, and uranium-235. Examples include the natural isotopes of polonium and radium.
* Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays.
Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare. For example, polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10). Further radionuclides may occur in nature in virtually undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions. | 0 | Theoretical and Fundamental Chemistry |
The Ames process is a process by which pure uranium metal is obtained. It can be achieved by mixing any of the uranium halides (commonly uranium tetrafluoride) with magnesium metal powder or aluminium metal powder. | 1 | Applied and Interdisciplinary Chemistry |
Initiation involves the small subunit of the ribosome binding to the 5 end of mRNA with the help of initiation factors (IF). In bacteria and a minority of archaea, initiation of protein synthesis involves the recognition of a purine-rich initiation sequence on the mRNA called the Shine–Dalgarno sequence. The Shine–Dalgarno sequence binds to a complementary pyrimidine-rich sequence on the 3 end of the 16S rRNA part of the 30S ribosomal subunit. The binding of these complementary sequences ensures that the 30S ribosomal subunit is bound to the mRNA and is aligned such that the initiation codon is placed in the 30S portion of the P-site. Once the mRNA and 30S subunit are properly bound, an initiation factor brings the initiator tRNA–amino acid complex, f-Met-tRNA, to the 30S P site. The initiation phase is completed once a 50S subunit joins the 30S subunit, forming an active 70S ribosome. Termination of the polypeptide occurs when the A site of the ribosome is occupied by a stop codon (UAA, UAG, or UGA) on the mRNA, creating the primary structure of a protein. tRNA usually cannot recognize or bind to stop codons. Instead, the stop codon induces the binding of a release factor protein (RF1 & RF2) that prompts the disassembly of the entire ribosome/mRNA complex by the hydrolysis of the polypeptide chain from the peptidyl transferase center of the ribosome. Drugs or special sequence motifs on the mRNA can change the ribosomal structure so that near-cognate tRNAs are bound to the stop codon instead of the release factors. In such cases of translational readthrough, translation continues until the ribosome encounters the next stop codon. | 1 | Applied and Interdisciplinary Chemistry |
The naming of polycyclic alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (e.g., "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane which consists of a six-member ring and a four-member ring, which share two adjacent carbon atoms which form a shared edge, is [4.2.0]-bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons. | 0 | Theoretical and Fundamental Chemistry |
Sprinkler systems are intended to either control the fire or to suppress the fire. Control mode sprinklers are intended to control the heat release rate of the fire to prevent building structure collapse, and pre-wet the surrounding combustibles to prevent fire spread. The fire is not extinguished until the burning combustibles are exhausted or manual extinguishment is effected by firefighters. Suppression mode sprinklers, also known as Early Suppression Fast Response (ESFR) sprinklers, are intended to result in a severe sudden reduction of the heat release rate of the fire, prior to manual intervention.
Control mode sprinkler systems are designed using an area and density approach. The building use and contents are analyzed to determine the level of fire hazard. The hazard is classified as light hazard, ordinary hazard group 1, ordinary hazard group 2, extra hazard group 1, or extra hazard group 2. After determining the hazard classification, a design area and density can be determined by referencing tables in the 13 National Fire Protection Association standard. The design area is a theoretical area of the building representing the worst case area where a fire could burn. The design density is a measurement of how much water per square foot of floor area should be applied to the design area.
For example, in an office building classified as light hazard, a typical design area would be and the design density would be per or a minimum of applied over the design area. Another example would be a manufacturing facility classified as ordinary hazard group 2 where a typical design area would be and the design density would be per or a minimum of applied over the design area.
After the design area and density have been determined, calculations are performed to prove that the system can deliver the required amount of water over the required design area. These calculations account for all of the pressure that is lost or gained between the water supply source and the sprinklers that would operate in the design area. This includes pressure losses due to friction inside the piping and losses or gains due to elevational differences between the source and the discharging sprinklers. Sometimes momentum pressure from water velocity inside the piping is also calculated. Typically these calculations are performed using computer software, but before the advent of computer systems these sometimes complicated calculations were performed by hand. This skill of calculating sprinkler systems by hand is still required training for a sprinkler system design technologist who seeks senior level certification from engineering certification organizations such as the National Institute for Certification in Engineering Technologies (NICET).
Sprinkler systems in residential structures are becoming more common, as the cost of such systems becomes more practical and the benefits become more obvious. Residential sprinkler systems usually fall under a residential classification separate from the commercial classifications mentioned above. A commercial sprinkler system is designed to protect the structure and the occupants from a fire. Most residential sprinkler systems are primarily designed to control a fire for a sufficient time to allow for the safe escape of the building occupants. While these systems will often also protect the structure from major fire damage, this is a secondary consideration. In residential structures, sprinklers are often omitted from closets, bathrooms, balconies, garages and attics because a fire in these areas would not usually impact the occupant's escape route. | 1 | Applied and Interdisciplinary Chemistry |
Matrix-assisted inlet ionization (MAII) has shown that the laser is not necessary for the ionization process. Ions are formed when matrix-analyte is introduced to the vacuum of a mass spectrometer through an inlet aperture. LSI is a subset of MAII and is now called laserspray inlet ionization (LSII). Laser spray inlet ionization and matrix-assisted inlet ionization can be coupled to a fourier transform ion cyclotron resonance (FT-ICR) mass analyzer to improve detection of peptides and proteins. | 0 | Theoretical and Fundamental Chemistry |
Its physiological function is unknown. It is a member of the C1Q domain proteins which have important signalling roles in inflammation and in adaptive immunity. | 1 | Applied and Interdisciplinary Chemistry |
The second of these was developed by Lea and Nurse. The bed is 25 mm in diameter and 10 mm thick. The desired porosity (which may vary in the range 0.4 to 0.6) is obtained by using a calculated weight of sample, pressed to precisely these dimensions. The required weight is given by:
A flowmeter consisting of a long capillary is connected in series with the powder bed. The pressure drop across the flowmeter (measured by a manometer) is proportional to the flowrate, and the proportionality constant can be measured by direct calibration. The pressure drop across the bed is measured by a similar manometer. Thus the required pressure/flow ratio can be obtained from the ratio of the two manometer readings, and when fed into the Carman equation, yields an "absolute" value of the air permeability surface area. The apparatus is maintained at a constant temperature, and dry air is used so that the air viscosity can be obtained from tables. | 1 | Applied and Interdisciplinary Chemistry |
Helium is in the same category as alkaline earths with respect to spectroscopy, as it has two electrons in the S subshell as do the other alkaline earths.
Helium has a diffuse series of doublet lines with wavelengths 5876, 4472 and 4026 Å. Helium when ionised is termed He and has a spectrum very similar to hydrogen but shifted to shorter wavelengths. This has a diffuse series as well with wavelengths at 6678, 4922 and 4388 Å. | 0 | Theoretical and Fundamental Chemistry |
ScerTF is a comprehensive database of position weight matrices for the transcription factors of Saccharomyces. | 1 | Applied and Interdisciplinary Chemistry |
;closo-
:The boron atoms lie on each vertex of the octahedron and are sp hybridized. One sp-hybrid radiates away from the structure forming the bond with the hydrogen atom. The other sp-hybrid radiates into the center of the structure forming a large bonding molecular orbital at the center of the cluster. The remaining two unhybridized orbitals lie along the tangent of the sphere like structure creating more bonding and antibonding orbitals between the boron vertices. The orbital diagram breaks down as follows:
::The 18 framework molecular orbitals, (MOs), derived from the 18 boron atomic orbitals are:
::*1 bonding MO at the center of the cluster and 5 antibonding MOs from the 6 sp-radial hybrid orbitals
::*6 bonding MOs and 6 antibonding MOs from the 12 tangential p-orbitals.
:The total skeletal bonding orbitals is therefore 7, i.e. . | 0 | Theoretical and Fundamental Chemistry |
Instead of collecting onto a greased substrate or agar plate, impingers have been developed to impact bioaerosols into liquids, such as deionized water or phosphate buffer solution. Collection efficiencies of impingers are shown by Ehrlich et al. (1966) to be generally higher than similar single stage impactor designs. Commercially available impingers include the AGI-30 (Ace Glass Inc.) and Biosampler (SKC, Inc). | 0 | Theoretical and Fundamental Chemistry |
Levofloxacin is a third-generation fluoroquinolone, being one of the isomers of ofloxacin, which was a broader-spectrum conformationally locked analog of norfloxacin; both ofloxacin and levofloxaxin were synthesized and developed by scientists at Daiichi Seiyaku. The Daiichi scientists knew that ofloxacin was racemic, but tried unsuccessfully to separate the two isomers; in 1985 they succeeded in separately synthesizing the pure levo form and showed that it was less toxic and more potent than the other form.
It was first approved for marketing in Japan in 1993, for oral administration, and Daiichi marketed it there under the brand name Cravit. Daiichi, working with Johnson & Johnson as it had with ofloxacin, obtained FDA approval in 1996 under the brand name Levaquin to treat bacterial sinusitus, bacterial exacerbations of bronchitis, community-acquired pneumonia, uncomplicated skin infections, complicated urinary tract infections, and acute pyelonephritis.
Levofloxacin is marketed by Sanofi-Aventis under a license agreement signed with Daiichi in 1993, under the brand name "Tavanic".
Levofloxacin had reached blockbuster status by this time; combined worldwide sales of levofloxacin and ofloxacin for J&J alone were in 2009.
The term of the levofloxacin United States patent was extended by the U.S. Patent and Trademark Office 810 days under the provisions of the Hatch Waxman Amendment so that the patent would expire in 2010 instead of 2008. This extension was challenged by generic drug manufacturer Lupin Pharmaceuticals, which did not challenge the validity of the patent, but only the validity of the patent extension, arguing that the patent did not cover a "product" and so Hatch-Waxman was not available for extensions. The federal patent court ruled in favor of J&J and Daiichi, and generic versions of levofloxacin did not enter the U.S. market until 2009. | 0 | Theoretical and Fundamental Chemistry |
The Bragg condition is correct for very large crystals. Because the scattering of X-rays and neutrons is relatively weak, in many cases quite large crystals with sizes of 100 nm or more are used. While there can be additional effects due to crystal defects, these are often quite small. In contrast, electrons interact thousands of times more strongly with solids than X-rays, and also lose energy (inelastic scattering). Therefore samples used in transmission electron diffraction are much thinner. Typical diffraction patterns, for instance the Figure, show spots for different directions (plane waves) of the electrons leaving a crystal. The angles that Braggs law predicts are still approximately right, but in general there is a lattice of spots which are close to projections of the reciprocal lattice that is at right angles to the direction of the electron beam. (In contrast, Braggs law predicts that only one or perhaps two would be present, not simultaneously tens to hundreds.) With low-energy electron diffraction where the electron energies are typically 30-1000 electron volts, the result is similar with the electrons reflected back from a surface. Also similar is reflection high-energy electron diffraction which typically leads to rings of diffraction spots.
With X-rays the effect of having small crystals is described by the Scherrer equation. This leads to broadening of the Bragg peaks which can be used to estimate the size of the crystals. | 0 | Theoretical and Fundamental Chemistry |
radioisotope - radioisotopic labelling - Raman spectroscopy - random coil - Ras gene - Ras protein - reading frame - receptor (biochemistry) - receptor antagonist - receptor protein-tyrosine kinase - recombinant fusion protein - recombinant interferon-gamma - recombinant protein - recombination - redox - redox reaction - redox system - reflux - replication origin - replicon - repressor - repressor protein - respiration (physiology) - restriction enzyme - retinoblastoma protein - retinoic acid receptor - retinol-binding protein - retroelement - retroviridae protein - retrovirus - Reverse transcriptase - RFLP - rho factor - rhodopsin - ribonucleoprotein - ribose - ribosomal protein - ribosomal protein S6 kinase - ribosome - RNA - RNA virus - RNA-binding protein - RNA-directed DNA polymerase - rod outer segment - rough ER | 1 | Applied and Interdisciplinary Chemistry |
Concern about the increasing discoveries of bay pollution problems, and of the institutional challenges of organizing bay restoration programs over a large geographical area, led to Congress directing the US Environmental Protection Agency (EPA) to take a greater role in studying the scientific and technical aspects of the problems beginning in the late 1970s. The agency conducted its research over a seven-year period and published a major report in 1983. The report stated that the bay was an "ecosystem in decline" and cited numerous instances of declines in the populations of oysters, crabs, freshwater fish and other wildlife.
The growing concerns about pollution also prompted the legislatures of Maryland and Virginia to establish the Chesapeake Bay Commission, an advisory body, in 1980. The commission consults with the state legislatures and executive agencies, as well as Congress, about environmental, economic and social issues related to the bay.
As an initial follow-up to the EPA report, the Chesapeake Bay Commission and EPA developed the Chesapeake Bay Agreement in 1983. The agreement was signed by the governors of Maryland, Virginia and Pennsylvania; the Mayor of the District of Columbia; and the EPA Administrator. The parties agreed to:
* Creation of an "Executive Council" consisting of cabinet-level appointees from each state and Washington, D.C., and the EPA Regional Administrator
* The council's creation of an implementation committee to coordinate technical issues and development management plans for bay restoration
* The establishment of the Chesapeake Bay Program as a liaison office for all of the participating organizations. The program's office, based in Annapolis, is partially funded by EPA and staffed by experts from the member states, EPA and other federal agencies, and academic institutions.
Concurrent with the 1983 agreement EPA began providing matching grants to the bay states for research and restoration projects.
In 1987 the parties agreed to set a goal of reducing the amount of nutrients that enter the bay by 40 percent by 2000. In 1992, the bay program partners agreed to continue the 40 percent reduction goal beyond 2000 and to attack nutrients at their source: upstream, in the bay tributaries. | 1 | Applied and Interdisciplinary Chemistry |
Optical transitions must preserve the total spin and occur only between levels of the same total spin. Specifically, transitions between the ground and excited states (with equal spin) can be induced using a green laser with a wavelength of 546 nm. Transitions E→A and E→A are non-radiative, while A →E has both a non-radiative and infrared decay path.
The diagram on the right shows the multi-electronic states of the NV center labeled according to their symmetry (E or A) and their spin state (3 for a triplet (S=1) and 1 for a singlet (S=0)). There are two triplet states and two intermediate singlet states. | 0 | Theoretical and Fundamental Chemistry |
In this technique a square or rectangular paper is used. Here the sample is applied to one of the corners and development is performed at a right angle to the direction of the first run. | 0 | Theoretical and Fundamental Chemistry |
The Plateau–Rayleigh instability is named for Joseph Plateau and Lord Rayleigh. In 1873, Plateau found experimentally that a vertically falling stream of water will break up into drops if its length is greater than about 3.13 to 3.18 times its diameter, which he noted is close to Pi|. Later, Rayleigh showed theoretically that a vertically falling column of non-viscous liquid with a circular cross-section should break up into drops if its length exceeded its circumference, which is indeed times its diameter. | 1 | Applied and Interdisciplinary Chemistry |
The first approved gene therapy clinical research in the US took place on 14 September 1990, at the National Institutes of Health (NIH), under the direction of William French Anderson. Four-year-old Ashanti DeSilva received treatment for a genetic defect that left her with adenosine deaminase deficiency (ADA-SCID), a severe immune system deficiency. The defective gene of the patients blood cells was replaced by the functional variant. Ashantis immune system was partially restored by the therapy. Production of the missing enzyme was temporarily stimulated, but the new cells with functional genes were not generated. She led a normal life only with the regular injections performed every two months. The effects were successful, but temporary.
Cancer gene therapy was introduced in 1992/93 (Trojan et al. 1993). The treatment of glioblastoma multiforme, the malignant brain tumor whose outcome is always fatal, was done using a vector expressing antisense IGF-I RNA (clinical trial approved by NIH protocol no.1602 24 November 1993, and by the FDA in 1994). This therapy also represents the beginning of cancer immunogene therapy, a treatment which proves to be effective due to the anti-tumor mechanism of IGF-I antisense, which is related to strong immune and apoptotic phenomena.
In 1992, Claudio Bordignon, working at the Vita-Salute San Raffaele University, performed the first gene therapy procedure using hematopoietic stem cells as vectors to deliver genes intended to correct hereditary diseases. In 2002, this work led to the publication of the first successful gene therapy treatment for ADA-SCID. The success of a multi-center trial for treating children with SCID (severe combined immune deficiency or "bubble boy" disease) from 2000 and 2002, was questioned when two of the ten children treated at the trial's Paris center developed a leukemia-like condition. Clinical trials were halted temporarily in 2002, but resumed after regulatory review of the protocol in the US, the United Kingdom, France, Italy, and Germany.
In 1993, Andrew Gobea was born with SCID following prenatal genetic screening. Blood was removed from his mothers placenta and umbilical cord immediately after birth, to acquire stem cells. The allele that codes for adenosine deaminase (ADA) was obtained and inserted into a retrovirus. Retroviruses and stem cells were mixed, after which the viruses inserted the gene into the stem cell chromosomes. Stem cells containing the working ADA gene were injected into Andrews blood. Injections of the ADA enzyme were also given weekly. For four years T cells (white blood cells), produced by stem cells, made ADA enzymes using the ADA gene. After four years more treatment was needed.
In 1996, Luigi Naldini and Didier Trono developed a new class of gene therapy vectors based on HIV capable of infecting non-dividing cells that have since then been widely used in clinical and research settings, pioneering lentivirals vector in gene therapy.
Jesse Gelsinger's death in 1999 impeded gene therapy research in the US. As a result, the FDA suspended several clinical trials pending the reevaluation of ethical and procedural practices. | 1 | Applied and Interdisciplinary Chemistry |
Several sources have reported that Fraser-Reid was nominated in 1998 for a Nobel Prize in chemistry for his work on oligosaccharides and immune responses. This statement cannot be verified since the names of the nominees are never publicly announced, and neither are they told that they have been considered for the Prize. Nomination records are sealed for fifty years.
The Institute of Jamaica awarded Fraser-Reid the 2007 Musgrave Medal (Gold) for his work in chemistry, noting that during his career he co-authored over 330 peer-reviewed publications and supervised 85 post-doctoral fellows and 55 PhD students. | 0 | Theoretical and Fundamental Chemistry |
Protein interaction networks have been used to predict the function of proteins of unknown functions. This is usually based on the assumption that uncharacterized proteins have similar functions as their interacting proteins (guilt by association). For example, YbeB, a protein of unknown function was found to interact with ribosomal proteins and later shown to be involved in bacterial and eukaryotic (but not archaeal) translation. Although such predictions may be based on single interactions, usually several interactions are found. Thus, the whole network of interactions can be used to predict protein functions, given that certain functions are usually enriched among the interactors. The term hypothome has been used to denote an interactome wherein at least one of the genes or proteins is a hypothetical protein. | 1 | Applied and Interdisciplinary Chemistry |
A tosylhydrazone in organic chemistry is a functional group with the general structure RR'C=N-NH-Ts where Ts is a tosyl group. Organic compounds having this functional group can be accessed by reaction of an aldehyde or ketone with tosylhydrazine. | 0 | Theoretical and Fundamental Chemistry |
The use of the term explosion is somewhat loose in this context, and can be confusing. This confusion is exacerbated by the tendency for airburst energies to be expressed in terms of nuclear weapon yields, as when the Tunguska airburst is given a rating in megatons of TNT. Large meteoroids do not explode in the sense of chemical or nuclear explosives. Rather, at a critical moment in its atmospheric entry the enormous ram pressure experienced by the leading face of the meteoroid converts the body's immense momentum into a force blowing it apart over a nearly instantaneous span of time.
In essence, the meteoroid is ripped apart by its own speed. This occurs when fine tendrils of superheated air force their way into cracks and faults in the leading faces surface. Once this high pressure plasma gains entry to the meteoroids interior it exerts tremendous force on the bodys internal structure. This occurs because the superheated air now exerts its force over a much larger surface area, as when the wind suddenly fills a sail. This sudden rise in the force exerted on the meteoroid overwhelms the bodys structural integrity and it begins to break up. The breakup of the meteoroid yields an even larger total surface area for the superheated air to act upon and a cycle of amplification rapidly occurs. This is the explosion, and it causes the meteoroid to disintegrate with hypersonic velocity, a speed comparable to that of explosive detonation. | 1 | Applied and Interdisciplinary Chemistry |
Because prokaryotic mRNA does not need to be processed or transported, translation by the ribosome can begin immediately after the end of transcription. Therefore, it can be said that prokaryotic translation is coupled to transcription and occurs co-transcriptionally.
Eukaryotic mRNA that has been processed and transported to the cytoplasm (i.e., mature mRNA) can then be translated by the ribosome. Translation may occur at ribosomes free-floating in the cytoplasm, or directed to the endoplasmic reticulum by the signal recognition particle. Therefore, unlike in prokaryotes, eukaryotic translation is not directly coupled to transcription. It is even possible in some contexts that reduced mRNA levels are accompanied by increased protein levels, as has been observed for mRNA/protein levels of EEF1A1 in breast cancer. | 1 | Applied and Interdisciplinary Chemistry |
Until Yukito Tanabe and Satoru Sugano published their paper "On the absorption spectra of complex ions", in 1954, little was known about the excited electronic states of complex metal ions. They used Hans Bethes crystal field theory and Giulio Racahs linear combinations of Slater integrals, now called Racah parameters, to explain the absorption spectra of octahedral complex ions in a more quantitative way than had been achieved previously. Many spectroscopic experiments later, they estimated the values for two of Racah's parameters, B and C, for each d-electron configuration based on the trends in the absorption spectra of isoelectronic first-row transition metals. The plots of the energies calculated for the electronic states of each electron configuration are now known as Tanabe–Sugano diagrams.
Number must be fit for each octahedral coordination complex because the C/B can deviate strongly from the theoretical value of 4.0. This ratio changes the relative energies of the levels in the Tanabe–Sugano diagrams, and thus the diagrams may vary slightly between sources depending on what C/B ratio was selected when plotting. | 0 | Theoretical and Fundamental Chemistry |
These are solutions containing FSL Kode constructs where the construct will exist as a clear micellular dispersion. FSL-GB3 as a solution/gel has been used to inhibit HIV infection and to neutralise Shiga toxin. FSL blood group A as a solution has been used to neutralise circulating antibodies in a mouse model and allow incompatible blood group A (murine kodecytes) transfusion. This model experiment was used to demonstrate the potential of FSLs to neutralise circulating antibody and allow for incompatible blood transfusion or organ transplantation. | 1 | Applied and Interdisciplinary Chemistry |
Based on the statistics presented in earlier discussions, there is controversy with regard to a perceived lack of diversity within the donor sperm pool of many sperm banks. This includes, but is not limited to, height requirements implemented by some sperm banks. As a result, it is alleged that potential sperm recipients often encounter very limited sperm donor pool options. Lack of diversity results in very limited choices especially among ethnic minorities within the United States. Whenever an individual chooses to specify their preferred donor background, the number of available options (sperm donors that meet the particular individuals criteria) can dwindle down to the low single digits. Scott Brown from California Cryobank admitted: "We dont get as many minority applicants as we [would] like." Even after numerous attempts to reach out to numerous ethnic communities, the response can be nearly nonexistent.
At the California Cryoback, Brown mentions that one out of 100 would be able to become final sperm donor while Ottey from the Fairfax Cryobank mentions one out of 200 would be able to become ultimate sperm donors. In addition, locations of the California Cryobank are in Los Angeles, Los Altos, California; mid-Manhattan, and Cambridge Massachusetts. These locations are known to have a population with higher socioeconomic latitude and being more likely to afford the services. Moreover, one of the requirements includes the potential sperm donor to be able to live nearby the sperm bank in order to provide samples once to twice a month for at least a term of six months. This could create potential barriers for populations who are at socioeconomic disadvantage and do not have their own forms of transportation; often having to rely on multiple forms of public transportation to reach certain places. This factor could cause a significant decrease in the sperm donor pool and less diverse availability for sperm recipients.
Some controversy stems from the fact that donors father children for others, in the majority of cases, for single people or same-sex couples, but usually take no part in the upbringing of such children. The issue of sperm banks providing fertility services to single women and coupled lesbians so that they can have their own biological children by a donor is itself, often controversial in some jurisdictions but in many countries where sperm banks operate, this group form the main body of recipients. Donors usually do not have a say in who may be a recipient of their sperm.
Another controversy centers around the use of sperm posthumously, or after the death of the sperm donor, as pioneered by California Cryobank. Within the United States, there were differences when it came to a child conceived after the fathers death and the eligibility for survivors benefits. Under California law, there was one court case (Vernoff vs. Astrue) in which the mothers child (conceived after the fathers death) was not eligible for the survivors benefits. However, Arizona courts had a different approach when it came to children who were born after fathers death that the children are eligible for the survivors benefits. There were numerous other stories of similar situations across different states in the United States and even the United Kingdom. Canada, France, Germany, and Sweden do not permit the retrieval use of sperm posthumously. | 1 | Applied and Interdisciplinary Chemistry |
Blood glucose levels are maintained at a steady state concentration by balancing the rate of entry of glucose into the blood stream (i.e. by ingestion or released from cells) and the rate of glucose uptake by body tissues. Changes in the rate of input will be met with a change in consumption, and vice versa, so that blood glucose concentration is held at about 5 mM in humans. A change in blood glucose levels triggers the release of insulin or glucagon, which stimulates the liver to release glucose into the bloodstream or take up glucose from the bloodstream in order to return glucose levels to steady state. Pancreatic beta cells, for example, increase oxidative metabolism as a result of a rise in blood glucose concentration, triggering secretion of insulin. Glucose levels in the brain are also maintained at steady state, and glucose delivery to the brain relies on the balance between the flux of the blood brain barrier and uptake by brain cells. In teleosts, a drop of blood glucose levels below that of steady state decreases the intracellular-extracellular gradient in the bloodstream, limiting glucose metabolism in red blood cells. | 0 | Theoretical and Fundamental Chemistry |
The arrangement of the ligands is fixed for a given complex, but in some cases it is mutable by a reaction that forms another stable isomer.
There exist many kinds of isomerism in coordination complexes, just as in many other compounds. | 0 | Theoretical and Fundamental Chemistry |
The oily bilge waste comes from a ship's engines and fuel systems. The waste is required to be offloaded when a ship is in port and either burned in an incinerator or taken to a waste management facility. In rare occasions, bilge water can be discharged into the ocean but only after almost all oil is separated out. | 1 | Applied and Interdisciplinary Chemistry |
BMS has been employed for the reduction of many functional groups. Reductions of aldehydes, ketones, epoxides, esters, and carboxylic acids give the corresponding alcohols. Lactones are reduced to diols, and nitriles are reduced to amines. Acid chlorides and nitro groups are not reduced by BMS.
Borane dimethylsulfide is one of the most common bulk reducing agents used in the Corey–Itsuno reduction. The dimethylsulfide ligand attenuates the reactivity of the borane. Activation by the nitrogen of the chiral oxazaborolidine catalyst of the stoichiometric reducing agent allows for asymmetric control of the reagent. In general BMS does not lead to significantly greater enantiomeric selectivities than borane-THF, however its increased stability in the presence of moisture and oxygen makes it the reagent of choice for the reduction. | 0 | Theoretical and Fundamental Chemistry |
The M-N-O unit in nitrosyl complexes is usually linear, or no more than 15° from linear. In some complexes, however, especially when back-bonding is less important, the M-N-O angle can strongly deviate from 180°. Linear and bent NO ligands can be distinguished using infrared spectroscopy. Linear M-N-O groups absorb in the range 1650–1900 cm, whereas bent nitrosyls absorb in the range 1525–1690 cm. The differing vibrational frequencies reflect the differing N-O bond orders for linear (triple bond) and bent NO (double bond).
The bent NO ligand is sometimes described as the anion, NO. Prototypes for such compounds are the organic nitroso compounds, such as nitrosobenzene. A complex with a bent NO ligand is trans-[Co(en)(NO)Cl]. The NO is also common for alkali-metal or alkaline-earth metal-NO molecules. For example. LiNO and BeNO bear LiNO and BeNO ionic form.
The adoption of linear vs bent bonding can be analyzed with the Enemark-Feltham notation. In their framework, the factor that determines the bent vs linear NO ligands is the sum of electrons of pi-symmetry. Complexes with "pi-electrons" in excess of 6 tend to have bent NO ligands. Thus, [Co(en)(NO)Cl], with eight electrons of pi-symmetry (six in t orbitals and two on NO, {CoNO}), adopts a bent NO ligand, whereas [Fe(CN)(NO)], with six electrons of pi-symmetry, {FeNO}), adopts a linear nitrosyl. In a further illustration, the {MNO} d-electron count of the [Cr(CN)NO] anion is shown. In this example, the cyanide ligands are "innocent", i.e., they have a charge of −1 each, −5 total. To balance the fragments overall charge, the charge on {CrNO} is thus +2 (−3 = −5 + 2). Using the neutral electron counting scheme, Cr has 6 d electrons and NO· has one electron for a total of 7. Two electrons are subtracted to take into account that fragments overall charge of +2, to give 5. Written in the Enemark-Feltham notation, the d electron count is {CrNO}. The results are the same if the nitrosyl ligand were considered NO or NO. | 0 | Theoretical and Fundamental Chemistry |
The Centre for Industry Education Collaboration (CIEC) is a British education resource for information about the chemical industry in the UK. | 1 | Applied and Interdisciplinary Chemistry |
Electrochemical engineering combines the study of heterogeneous charge transfer at electrode/electrolyte interphases with the development of practical materials and processes. Fundamental considerations include electrode materials and the kinetics of redox species. The development of the technology involves the study of the electrochemical reactors, their potential and current distribution, mass transport conditions, hydrodynamics, geometry and components as well as the quantification of its overall performance in terms of reaction yield, conversion efficiency, and energy efficiency. Industrial developments require further reactor and process design, fabrication methods, testing, and product development.
Electrochemical engineering considers current distribution, fluid flow, mass transfer, and the kinetics of the electro reactions to design efficient electrochemical reactors.
Most electrochemical operations are performed in filter-press reactors with parallel plate electrodes or, less often, in stirred tanks with rotating cylinder electrodes. Fuel cell and flow battery stacks are types of filter-press reactors. Most of them are continuous operations. | 0 | Theoretical and Fundamental Chemistry |
Mefloquine is contraindicated in those with a previous history of seizures or a recent history of psychiatric disorders. | 0 | Theoretical and Fundamental Chemistry |
Some antibacterial drugs such as penicillin interfere with the production of peptidoglycan by binding to bacterial enzymes known as penicillin-binding proteins or DD-transpeptidases. Penicillin-binding proteins form the bonds between oligopeptide crosslinks in peptidoglycan. For a bacterial cell to reproduce through binary fission, more than a million peptidoglycan subunits (NAM-NAG+oligopeptide) must be attached to existing subunits. Mutations in genes coding for transpeptidases that lead to reduced interactions with an antibiotic are a significant source of emerging antibiotic resistance. Since peptidoglycan is also lacking in L-form bacteria and in mycoplasmas, both are resistant against penicillin.
Other steps of peptidoglycan synthesis can also be targeted. The topical antibiotic bacitracin targets the utilization of C55-isoprenyl pyrophosphate. Lantibiotics, which includes the food preservative nisin, attack lipid II.
Lysozyme, which is found in tears and constitutes part of the body's innate immune system exerts its antibacterial effect by breaking the β-(1,4)-glycosidic bonds in peptidoglycan (see above). Lysozyme is more effective in acting against Gram-positive bacteria, in which the peptidoglycan cell wall is exposed, than against Gram-negative bacteria, which have an outer layer of LPS covering the peptidoglycan layer. Several bacterial peptidoglycan modifications can result in resistance to degradation by lysozyme. Susceptibility of bacteria to degradation is also considerably affected by exposure to antibiotics. Exposed bacteria synthesize peptidoglycan that contains shorter sugar chains that are poorly crosslinked and this peptidoglycan is then more easily degraded by lysozyme. | 1 | Applied and Interdisciplinary Chemistry |
Macro-creatine kinase (macro-CK) is a macroenzyme, an enzyme of high molecular weight and prolonged half-life found in human serum. It is one of the most common macroenzymes. Macro-CK type 1 is a complex formed by one of the creatine kinase isoenzyme types, typically CK-BB, and antibodies; typically IgG, sometimes IgA, rarely IgM. Macro-CK type 2 is formed from mitochondrial CK polymer.
Macro-CK type 1 has been associated with autoimmune and other chronic conditions. Macro-CK type 2 has been associated with malignancy.
Macro-CK has been implicated as a source of interference in interpretation of medical labs. | 1 | Applied and Interdisciplinary Chemistry |
Phycoerythrocyanin is a kind of phycobiliprotein, magenta chromoprotein involved in photosynthesis of some Cyanobacteria. This chromoprotein consists of alpha- and beta-subunits, generally aggregated as hexamer. Alpha-phycoerythrocyanin contains a phycoviolobilin, a violet bilin, that covalently attached at Cys-84, and beta-phycoerythrocyanin contains two phycocyanobilins, a blue bilin, that covalently attached at Cys-84 and -155, respectively. Phycoerythrocyanin is similar to phycocyanin, an important component of the light-harvesting complex (phycobilisome) of cyanobacteria and red algae.
While only phycocyanobilin is covalently bound to phycocyanin, leading to an absorption maximum around 620 nm, phycoerythrocyanin containing both phycoviolobilin and phycocyanobilin leads to an absorption maximum around 575 nm. As both phycoerythrocyanin and phycocyanin have phycocyanobilin acting as the terminal acceptor of energy transfer, they fluoresce around 635 nm, which is absorbed by allophycocyanins that have maximal absorption around 650 nm and maximal fluorescence around 670 nm. Finally, the light energy absorbed by phycoerythrocyanin is transferred to photosynthetic reaction center. | 1 | Applied and Interdisciplinary Chemistry |
The translational energy of the molecule is given by the kinetic energy expression:
where is the mass of the molecule and is its velocity. | 0 | Theoretical and Fundamental Chemistry |
The Rayleigh–Kuo criterion (sometimes called the Kuo criterion) is a stability condition for a fluid. This criterion determines whether or not a barotropic instability can occur, leading to the presence of vortices (like eddies and storms). The Kuo criterion states that for barotropic instability to occur, the gradient of the absolute vorticity must change its sign at some point within the boundaries of the current. Note that this criterion is a necessary condition, so if it does not hold it is not possible for a barotropic instability to form. But it is not a sufficient condition, meaning that if the criterion is met, this does not automatically mean that the fluid is unstable. If the criterion is not met, it is certain that the flow is stable.
This criterion was formulated by Hsiao-Lan Kuo and is based on Rayleigh's equation named after the Lord Rayleigh who first introduced this equation in fluid dynamics. | 1 | Applied and Interdisciplinary Chemistry |
*Airy wave theory
*Benjamin–Bona–Mahony equation
*Boussinesq approximation (water waves)
*Cnoidal wave
*Camassa–Holm equation
*Davey–Stewartson equation
*Kadomtsev–Petviashvili equation (also known as KP equation)
*Korteweg–de Vries equation (also known as KdV equation)
*Luke's variational principle
*Nonlinear Schrödinger equation
*Shallow water equations
*Stokes' wave theory
*Trochoidal wave
*Wave turbulence
*Whitham equation | 1 | Applied and Interdisciplinary Chemistry |
Heavily doped semiconductors, such as silicon-germanium (SiGe) thermoelectric couples (also called thermocouples or unicouples), are used in space exploration.
SiGe alloys present good thermoelectric properties. Their performance in thermoelectric power production is characterized by high dimensionless figures-of-merit (ZT) under high temperatures, which has been shown to be near 2 in some nanostructured-SiGe models.
SiGe alloy devices are mechanically rugged and can withstand severe shock and vibration due to its high tensile strength (i.e. >7000 psi) and low dislocation density. SiGe material is malleable with standard metallurgical equipment and bonds easily to construct components. SiGe alloy devices can operate under high temperatures (i.e. >1300 ˚C) without degradation due to their electronic stability, low thermal expansion coefficient and high oxidation resistance.
Near the Sun, solar cell performance deteriorates from high incident particle flux and high temperatures from heat flux. However, thermoelectric energy conversion systems that use thermoelectric materials (e.g. SiGe alloys) as a supplemental source of power for missions near the Sun can operate unprotected in vacuum and air environments under high temperatures due to their low sensitivity to radiation damage. Such properties have made SiGe thermoelectrics convenient for power generation in space.
The multifoil cold stack assembly, composed of molybdenum, tungsten, stainless steel, copper, and alumina materials, provides the insulation between the electrical and thermal currents of the system. The SiGe n-leg doped with boron and SiGe p-leg doped with phosphorus act as the intermediary between the heat source and electrical assembly. | 0 | Theoretical and Fundamental Chemistry |
The 1904 petition to the Chemical Society was a petition written by 19 female chemists setting out the reasons why they should be afforded the status of Fellow of the Chemical Society. The petition is of importance as it eventually led to the admission of women as Fellows of the Society (one of the Societies that amalgamated to become the Royal Society of Chemistry), as well as identifying prominent female chemists working in Britain at this time. | 1 | Applied and Interdisciplinary Chemistry |
Conformations can be described by dihedral angles, which are used to determine the placements of atoms and their distance from one another and can be visualized by Newman projections. A dihedral angle can indicate staggered and eclipsed orientation, but is specifically used to determine the angle between two specific atoms on opposing carbons. Different conformations have unequal energies, creating an energy barrier to bond rotation which is known as torsional strain. In particular, eclipsed conformations tend to have raised energies due to the repulsion of the electron clouds of the eclipsed substituents. The relative energies of different conformations can be visualized using graphs. In the example of ethane, such a graph shows that rotation around the carbon-carbon bond is not entirely free but that an energy barrier exists. The ethane molecule in the eclipsed conformation is said to suffer from torsional strain, and by a rotation around the carbon carbon bond to the staggered conformation around 12.5 kJ/mol of torsional energy is released. In the case of butane and its four-carbon chain, three carbon-carbon bonds are available to rotate. The example below is looking down the C2 and C3 bond. Below is the sawhorse and Newman representation of butane in an eclipsed conformation with the two CH groups (C1 and C4) at a 0 degree angle from one another (left).
If the front is rotated 60° clockwise, the butane molecule is now in a staggered conformation (right). This conformation is more specifically referred to as the gauche conformation of butane. This is due to the fact that the methyl groups are staggered, but only 60° from one another. This conformation is more energetically favored than the eclipsed conformation, but it is not the most energetically favorable conformation. Another 60° rotation gives us a second eclipsed conformation where both methyl groups are aligned with hydrogen atoms. One more 60 rotation produces another staggered conformation referred to as the anti conformation. This occurs when the methyl groups are positioned opposite (180°) of one another. This is the most energetically favorable conformation.
The minima can be seen on the graph at 60, 180 and 300 degrees while the maxima can bee see at 0, 120, 240, and 360 degrees. The maxima represent the eclipsed conformations due to the dihedral angle of zero degrees. | 0 | Theoretical and Fundamental Chemistry |
Bloch equations are used to calculate the nuclear magnetization M = (M, M, M) as a function of time when relaxation times T and T are present. Bloch equations are phenomenological equations that were introduced by Felix Bloch in 1946.
Where is the cross-product, γ is the gyromagnetic ratio and B(t) = (B(t), B(t), B + B(t)) is the magnetic flux density experienced by the nuclei.
The z component of the magnetic flux density B is typically composed of two terms: one, B, is constant in time, the other one, B(t), is time dependent. It is present in magnetic resonance imaging and helps with the spatial decoding of the NMR signal.
The equation listed above in the section on T and T relaxation are those in the Bloch equations. | 0 | Theoretical and Fundamental Chemistry |
A riffle box is a box containing a number (between 3 and 12) of "chutes" - slotted paths through which particles of the sample may slide. The sample is dropped into the top, and the box produces two equally divided subsamples. Riffle boxes are commonly used in mining to reduce the size of crushed rock samples prior to assaying. | 0 | Theoretical and Fundamental Chemistry |
Anodizing is one of the more environmentally friendly metal finishing processes. Except for organic (aka integral colour) anodizing, the by-products contain only small amounts of heavy metals, halogens, or volatile organic compounds. Integral color anodizing produces no VOCs, heavy metals, or halogens as all of the byproducts found in the effluent streams of other processes come from their dyes or plating materials. The most common anodizing effluents, aluminium hydroxide and aluminium sulfate, are recycled for the manufacturing of alum, baking powder, cosmetics, newsprint and fertilizer or used by industrial wastewater treatment systems. | 1 | Applied and Interdisciplinary Chemistry |
* 1912: Nobel Prize in Chemistry for his discovery of the Grignard reagent (shared the award with fellow Frenchman Paul Sabatier).
* 1912: Lavoisier Medal, Société Chimique de France
* 1933: Légion d'Honneur, Commander | 0 | Theoretical and Fundamental Chemistry |
Common roll-to-roll coating processes include:
* Air knife coating
* Anilox coater
* Flexo coater
* Gap Coating
** Knife-over-roll coating
* Gravure coating
* Hot melt coating- when the necessary coating viscosity is achieved by temperature rather than solution of the polymers etc. This method commonly implies slot-die coating above room temperature, but it also is possible to have hot-melt roller coating; hot-melt metering-rod coating, etc.
* Immersion dip coating
* Kiss coating
* Metering rod (Meyer bar) coating
* Roller coating
** Forward roller coating
** Reverse roll coating
* Silk Screen coater
** Rotary screen
*Slot Die coating - Slot die coating was originally developed in the 1950s. Slot die coating has a low operational cost and is an easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. Slot die coating technology is used to deposit a variety of liquid chemistries onto substrates of various materials such as glass, metal, and polymers by precisely metering the process fluid and dispensing it at a controlled rate while the coating die is precisely moved relative to the substrate. The complex inner geometry of conventional slot dies require machining or can be accomplished with 3-D printing.
*Extrusion coating - generally high pressure, often high temperature, and with the web travelling much faster than the speed of the extruded polymer
**Curtain coating- low viscosity, with the slot vertically above the web and a gap between slot-die and web.
** Slide coating- bead coating with an angled slide between the slot-die and the bead. Commonly used for multilayer coating in the photographic industry.
** Slot die bead coating- typically with the web backed by a roller and a very small gap between slot-die and web.
** Tensioned-web slot-die coating- with no backing for the web.
* Inkjet printing
* Lithography
* Flexography | 1 | Applied and Interdisciplinary Chemistry |
Some elements like potassium, uranium, and thorium are naturally radioactive and give off gamma rays as they decay. Electromagnetic radiation from these isotopes can be detected by a Gamma-Ray Spectrometer (GRS) dropped toward the planetary surface or observed from orbit. An orbiting instrument can map the surface distribution of many elements for an entire planet.
Uncrewed spacecraft programs such as Venera and the Vega program have flown to Venus and sent back data allowing estimates of the K/U ratio of the surface rocks.
The Lunar Prospector mission used a GRS to map the Earth's Moon.
To determine the elemental makeup of the Martian surface, the Mars Odyssey used a GRS and two neutron detectors.
These GRS readings can be compared to direct elemental measurements of chondrites meteorites, Earth, and Moon samples brought back from Apollo program missions, as well as to meteorites that are believed to have come from Mars. | 0 | Theoretical and Fundamental Chemistry |
Whilst calculation of thermal transmittance can readily be carried out with the help of software which is compliant with ISO 6946, a thermal transmittance calculation does not fully take workmanship into account and it does not allow for adventitious circulation of air between, through and around sections of insulation. To take the effects of workmanship-related factors fully into account it is necessary to carry out a thermal transmittance measurement.
ISO 9869 describes how to measure the thermal transmittance of a roof or a wall by using heat flux sensor. These heat flux meters usually consist of thermopiles which provide an electrical signal which is in direct proportion to the heat flux. Typically they might be about in diameter and perhaps about thick and they need to be fixed firmly to the roof or wall which is under test in order to ensure good thermal contact. When the heat flux is monitored over a sufficiently long time, the thermal transmittance can be calculated by dividing the average heat flux by the average difference in temperature between the inside and outside of the building. For most wall and roof constructions the heat flux meter needs to monitor heat flows (and internal and external temperatures) continuously for a period of 72 hours to be conform the ISO 9869 standards.
Generally, thermal transmittance measurements are most accurate when:
*The difference in temperature between the inside and outside of the building is at least .
*The weather is cloudy rather than sunny (this makes accurate measurement of temperature easier).
*There is good thermal contact between the heat flux meter and the wall or roof being tested.
*The monitoring of heat flow and temperatures is carried out over at least 72 hours.
*Different spots on a building element are measured or a thermographic camera is used to secure the homogeneity of the building element.
When convection currents play a part in transmitting heat across a building component, then thermal transmittance increases as the temperature difference increases. For example, for an internal temperature of and an external temperature of , the optimum gap between panes in a double glazed window will be smaller than the optimum gap for an external temperature of .
The inherent thermal transmittance of materials can also vary with temperaturethe mechanisms involved are complex, and the transmittance may increase or decrease as the temperature increases. | 0 | Theoretical and Fundamental Chemistry |
After the processed antigen (peptide) is complexed to the MHC molecule, they both migrate together to the cell membrane, where they are exhibited (elaborated) as a complex that can be recognized by the CD 4+ (T helper cell) – a type of white blood cell. This is known as antigen presentation. However, the epitopes (conformational epitopes) that are recognized by the B cell prior to their digestion may not be the same as that presented to the T helper cell. Additionally, a B cell may present different peptides complexed to different MHC-II molecules. | 1 | Applied and Interdisciplinary Chemistry |
Chemical milling is normally performed in a series of five steps: cleaning, masking, scribing, etching, and demasking. [https://www.youtube.com/watch?v=YtnUZanxtLs Video of chemical milling process] [https://www.fotofab.com/photo-etching-process/ Learn more about the video] | 1 | Applied and Interdisciplinary Chemistry |
Several configurations of the refrigeration cycle incorporate an economizer, and benefit from this idea. The design of these systems requires expertise and extra components. Pressure drop, electronic valve control, and oil drag, must all be considered. | 0 | Theoretical and Fundamental Chemistry |
In the immersed Membrane Bioreactor (iMBR) configuration, the filtration element is installed in either the main bioreactor vessel or in a separate tank. The modules are positioned above the aeration system, fulfilling two functions, the supply of oxygen and the cleaning of the membranes. The membranes can be a flat sheet or tubular or a combination of both and can incorporate an online backwash system which reduces membrane surface fouling by pumping membrane permeate back through the membrane. In systems where the membranes are in a separate tank from the bioreactor, individual trains of membranes can be isolated to undertake cleaning regimes incorporating membrane soaks, however, the biomass must be continuously pumped back to the main reactor to limit mixed liquor suspended solids concentration increases. Additional aeration is also required to provide air scouring to reduce fouling. Where the membranes are installed in the main reactor, membrane modules are removed from the vessel and transferred to an offline cleaning tank. Usually, the internal/submerged configuration is used for larger-scale lower strength applications. To optimize the reactor volume and minimize the production of sludge, submerged membrane bioreactor systems typically operate with mixed liquor suspended solids concentrations comprised between 12000 mg/L and 20000 mg/L, hence they offer good flexibility in the selection of the design Sludge retention time. It is mandatory to take into account that an excessively high content of mixed liquor suspended solids may render the aeration system less effective; the classical solution to this optimization problem is to ensure a concentration of mixed liquor suspended solids which approaches 10.000 mg/L to guarantee a good mass transfer of oxygen with a good permeation flux. This type of solution is widely accepted in larger-scale units, where the internal/submerged configuration is typically used, because of the higher relative cost of the membrane compared to the additional tank volume required.
Immersed MBR has been the preferred configuration due to its low energy consumption level, high biodegradation efficiency, and low fouling rate compared to side stream membrane bioreactors. In addition, iMBR systems can handle higher suspended solids concentrations, while traditional systems work only with suspended solids concentrations between 2.5-3.5, iMBR can handle concentrations between 4-12 g/L, an increase in range of 300%. This type of configuration is adopted in industrial sectors including textile, food & beverage, oil & gas, mining, power generation, pulp & paper. | 1 | Applied and Interdisciplinary Chemistry |
The oxidation state in compound naming for transition metals and lanthanides and actinides is placed either as a right superscript to the element symbol in a chemical formula, such as Fe or in parentheses after the name of the element in chemical names, such as iron(III). For example, is named iron(III) sulfate and its formula can be shown as Fe. This is because a sulfate ion has a charge of −2, so each iron atom takes a charge of +3. | 0 | Theoretical and Fundamental Chemistry |
Casting in bronze reached high perfection in England, where a number of monuments yet remain. William Torel, goldsmith and citizen of London, made a bronze effigy of Henry III, and later that of Queen Eleanor for their tombs in Westminster Abbey; the effigy of Edward III was probably the work of one of his pupils. No bronze fonts are found in English churches, but a number of processional crucifixes have survived from the 15th century, all following the same design and of crude execution. Sanctuary rings or knockers exist at Norwich, Gloucester and elsewhere; the most remarkable is that on the north door of the nave of Durham Cathedral which has sufficient character of its own to differentiate it from its Continental brothers and to suggest a Northern origin.
The Gloucester Candlestick in the Victoria and Albert Museum in South Kensington, displays the power and imagination of the designer as well as an extraordinary manipulative skill on the part of the founder. According to an inscription on the object, this candlestick, which stands some high and is made of an alloy allied to bronze, was made for Abbot Peter who ruled from 1109 to 1112. While the outline is carefully preserved, the ornament consists of a mass of figures of monsters, birds and men, mixed and intertwined to the verge of confusion. As a piece of casting it is a triumph of technical ability. For secular use the mortar was one of the commonest of objects in England as on the Continent; early examples of Gothic design are of great beauty. In later examples a mixture of styles is found in the bands of Gothic and Renaissance ornament, which are freely used in combination. Bronze ewers must have been common; of the more ornate kind two may be seen, one at South Kensington and a second at the British Museum. These are large vessels of about in height, with shields of arms and inscriptions in bell-founders' lettering. Many objects for domestic use, such as mortars, skillets, etc., were produced in later centuries. | 1 | Applied and Interdisciplinary Chemistry |
Therapeutic monoclonal antibodies act through multiple mechanisms, such as blocking of targeted molecule functions, inducing apoptosis in cells which express the target, or by modulating signalling pathways. | 1 | Applied and Interdisciplinary Chemistry |
Streptococcus pyogenes has evolved an interwoven complex of gene regulatory mechanisms in the SIP signaling pathway by implanting a pH sensitive histidine switch onto the quorum-sensing ropB protein. During the neutral to basic pH conditions whether synthetically induced or naturally caused by low population density of S. pyogenes, the interaction between the unprotonated functionally involved histidine (H144) with relevant sidechains (Y176, Y182, E185) in the SIP binding pocket domain is impaired and speB protease expression is inhibited. On the other hand, as extracellular pH decreases to be more acidic in cases of high population density, S. pyogenes has no elaborate pH homeostatic capabilities relative to non-lactic bacteria, therefore intracellular cytosolic pH levels will more easily resemble extracellular levels. Cytosolic acidification mobilizes the SIP pathway to allow for the SIP-ropB protein complex to form and increasing SIP production. Furthermore, increased cytosolic acidity enhances the maturation of speB zymogen (speBz) into mature speB protease (speBm) to dramatically increase its proteolytic activity and virulence. | 1 | Applied and Interdisciplinary Chemistry |
Nitroalkenes are useful intermediates for various chemical functionalities.
* A nitroalkene behaving as a Michael acceptor in the synthesis of Lycoricidine:
* Nitroalkene acting as an activated dienophile toward butadiene in a Diels-Alder cycloaddition:
* The synthesis of pyrrole derivatives via the Barton–Zard reaction:
* Pericyclic reaction of a nitroalkene yielding an indole:
* Partial hydrogenation to an alkene baring a hydroxylamine functional group:
* Reduction to primary amines:
* Asymmetric Stetter reaction: | 0 | Theoretical and Fundamental Chemistry |
In general, TST has provided researchers with a conceptual foundation for understanding how chemical reactions take place. Even though the theory is widely applicable, it does have limitations. For example, when applied to each elementary step of a multi-step reaction, the theory assumes that each intermediate is long-lived enough to reach a Boltzmann distribution of energies before continuing to the next step. When the intermediates are very short-lived, TST fails. In such cases, the momentum of the reaction trajectory from the reactants to the intermediate can carry forward to affect product selectivity. An example of such a reaction is the ring closure of cyclopentane biradicals generated from the gas-phase thermal decomposition of 2,3-diazabicyclo[2.2.1]hept-2-ene.
Transition state theory is also based on the assumption that atomic nuclei behave according to classical mechanics. It is assumed that unless atoms or molecules collide with enough energy to form the transition structure, then the reaction does not occur. However, according to quantum mechanics, for any barrier with a finite amount of energy, there is a possibility that particles can still tunnel across the barrier. With respect to chemical reactions this means that there is a chance that molecules will react, even if they do not collide with enough energy to overcome the energy barrier. While this effect is negligible for reactions with large activation energies, it becomes an important phenomenon for reactions with relatively low energy barriers, since the tunneling probability increases with decreasing barrier height.
Transition state theory fails for some reactions at high temperature. The theory assumes the reaction system will pass over the lowest energy saddle point on the potential energy surface. While this description is consistent for reactions occurring at relatively low temperatures, at high temperatures, molecules populate higher energy vibrational modes; their motion becomes more complex and collisions may lead to transition states far away from the lowest energy saddle point. This deviation from transition state theory is observed even in the simple exchange reaction between diatomic hydrogen and a hydrogen radical.
Given these limitations, several alternatives to transition state theory have been proposed. A brief discussion of these theories follows. | 0 | Theoretical and Fundamental Chemistry |
Nowadays descriptions of gene regulation are based on the approximations of equilibrium binding in dilute solutions, although it is clear that these assumptions are in fact violated in chromatin. The dilute-solution approximation is violated for two reasons. First, the chromatin content is far from being dilute, and second, the numbers of the participating molecules are sometimes so small, that it does not make sense to talk about the bulk concentrations. Further differences from dilute solutions arise due to the different binding affinities of proteins to condensed and uncondensed DNA. Thus in condensed DNA both the reaction rates can be changed and their dependence on the concentrations of reactants may become nonlinear. | 1 | Applied and Interdisciplinary Chemistry |
*[https://www.aivc.org/resources/airbase Publications] from the Air Infiltration & Ventilation Centre (AIVC) | 1 | Applied and Interdisciplinary Chemistry |
In electrochemistry differential capacitance is a parameter introduced for characterizing electrical double layers:
where σ is surface charge and ψ is electric surface potential.
Capacitance is usually defined as the stored charge between two conducting surfaces separated by a dielectric divided by the voltage between the surfaces. Another definition is the rate of change of the stored charge or surface charge (σ) divided by the rate of change of the voltage between the surfaces or the electric surface potential (ψ). The latter is called the "differential capacitance," but usually the stored charge is directly proportional to the voltage, making the capacitances given by the two definitions equal.
This type of differential capacitance may be called "parallel plate capacitance," after the usual form of the capacitor. However, the term is meaningful when applied to any two conducting bodies such as spheres, and not necessarily ones of the same size, for example, the elevated terminals of a Tesla wireless system and the earth. These are widely spaced insulated conducting bodies positioned over a spherically conducting ground plane.
Another form of differential capacitance refers to single isolated conducting bodies. It is usually discussed in books under the topic of "electrostatics." This capacitance is best defined as the rate of change of charge stored in the body divided by the rate of change of the potential of the body. The definition of the absolute potential of the body depends on what is selected as a reference. This is sometimes referred to as the "self-capacitance" of a body. If the body is a conducting sphere, the self-capacitance is proportional to its radius, and is roughly 1pF per centimetre of radius. | 0 | Theoretical and Fundamental Chemistry |
Haloalkanes are reactive towards nucleophiles. They are polar molecules: the carbon to which the halogen is attached is slightly electropositive where the halogen is slightly electronegative. This results in an electron deficient (electrophilic) carbon which, inevitably, attracts nucleophiles. | 0 | Theoretical and Fundamental Chemistry |
Otto Hahn was born in Frankfurt am Main on 8 March 1879, the youngest son of Heinrich Hahn (1845–1922), a prosperous glazier (and founder of the Glasbau Hahn company), and Charlotte Hahn née Giese (1845–1905). He had an older half-brother Karl, his mothers son from her previous marriage, and two older brothers, Heiner and Julius. The family lived above his fathers workshop. The younger three boys were educated at Klinger Oberrealschule in Frankfurt. At the age of 15, he began to take a special interest in chemistry, and carried out simple experiments in the laundry room of the family home. His father wanted Otto to study architecture, as he had built or acquired several residential and business properties, but Otto persuaded him that his ambition was to become an industrial chemist.
In 1897, after passing his Abitur, Hahn began to study chemistry at the University of Marburg. His subsidiary subjects were mathematics, physics, mineralogy and philosophy. Hahn joined the Students Association of Natural Sciences and Medicine, a student fraternity and a forerunner of todays Landsmannschaft Nibelungi (Coburger Convent der akademischen Landsmannschaften und Turnerschaften). He spent his third and fourth semesters at the University of Munich, studying organic chemistry under Adolf von Baeyer, physical chemistry under Friedrich Wilhelm Muthmann, and inorganic chemistry under Karl Andreas Hofmann. In 1901, Hahn received his doctorate in Marburg for a dissertation entitled "On Bromine Derivates of Isoeugenol", a topic in classical organic chemistry. He completed his one-year military service (instead of the usual two because he had a doctorate) in the 81st Infantry Regiment, but unlike his brothers, did not apply for a commission. He then returned to the University of Marburg, where he worked for two years as assistant to his doctoral supervisor, Geheimrat professor Theodor Zincke. | 0 | Theoretical and Fundamental Chemistry |
In some molecules, torsional strain can contribute to ring strain in addition to angle strain. One example of such a molecule is cyclopropane. Cyclopropanes carbon-carbon bonds form angles of 60°, far from the preferred angle of 109.5° angle in alkanes, so angle strain contributes most to cyclopropanes ring strain. However, as shown in the Newman projection of the molecule, the hydrogen atoms are eclipsed, causing some torsional strain as well. | 0 | Theoretical and Fundamental Chemistry |
Most metal ores contain metals of interest (e.g. gold, copper, nickel) in some oxidized states and thus the goal of most metallurgical operations is to chemically reduce them to their pure metallic form. The question is how to convert highly impure metal ores into purified bulk metals. A vast array of operations have been developed to accomplish those tasks, one of which is electrowinning. In an ideal case, ore is extracted into a solution which is then subjected to electrolysis. The metal is deposited on the cathode. In a practical sense, this idealized process is complicated by some or all of the following considerations: the metal content is low (a few percent is typical), other metals deposit competitively with the desired one, the ore is not easily or efficiently dissolved. For these reasons, electrowinning is usually only used on purified solutions of a desired metal, e.g. cyanide-extracts of gold ores.
Because metal deposition rates are related to available surface area, maintaining properly working cathodes is important. Two cathode types exist, flat-plate and reticulated cathodes, each with its own advantages and disadvantages. Flat-plate cathodes can be cleaned and reused, and plated metals recovered by either mechanically scraping the cathode (or, the electrolyzed metal has a lower melting point than the cathode, heating the cathode to the electrolyzed metals melting point causing the electrolyzed metal to liquify and separate from the cathode, which remains solid). Reticulated cathodes have a much higher deposition rate compared to flat-plate cathodes due to their greater surface area. However, reticulated cathodes are not reusable and must' be sent off for recycling. Alternatively, starter cathodes of pre-refined metals can be used, which become an integral part of the finished metal ready for rolling or further processing. | 1 | Applied and Interdisciplinary Chemistry |
The Ecophysiology Department, headed by Lotte Søgaard-Andersen, focuses on understanding how intracellular signalling networks are wired to allow bacteria to adapt and differentiate in response to changes in the environment or in response to self-generated signals. Specifically, the department has two aims. Firstly, they aim to understand how bacteria process information to generate appropriate output responses (e.g. changes in gene expression, changes in motility behavior). Secondly, they aim to understand how molecular machines involved in motility and secretion function and how their activity is regulated. Ecophysiology currently has three research groups led by the following in parentheses:
* Bacterial secretion systems (Andreas Diepold)
* The intracellular organization and differentiation of bacteria (Simon Ringgaard)
* Bacterial development & differentiation (Lotte Søgaard-Andersen) | 0 | Theoretical and Fundamental Chemistry |
Certain azo dyes can break down under reductive conditions to release any of a group of defined aromatic amines. Consumer goods which contain listed aromatic amines originating from azo dyes were prohibited from manufacture and sale in European Union countries in September 2003. As only a small number of dyes contained an equally small number of amines, relatively few products were affected. | 0 | Theoretical and Fundamental Chemistry |
Unhindered settling is a process that removes the discrete particles in a very low concentration without interference from nearby particles. In general, if the concentration of the solutions is lower than 500 mg/L total suspended solids, sedimentation will be considered discrete. Concentrations of raceway effluent total suspended solids (TSS) in the west are usually less than 5 mg/L net. TSS concentrations of off-line settling basin effluent are less than 100 mg/L net. The particles keep their size and shape during discrete settling, with an independent velocity. With such low concentrations of suspended particles, the probability of particle collisions is very low and consequently the rate of flocculation is small enough to be neglected for most calculations. Thus the surface area of the settling basin becomes the main factor of sedimentation rate. All continuous flow settling basins are divided into four parts: inlet zone, settling zone, sludge zone and outlet zone (Figure 2).
In the inlet zone, flow is established in a same forward direction. Sedimentation occurs in the settling zone as the water flow towards to outlet zone. The clarified liquid is then flow out from outlet zone.
Sludge zone: settled will be collected here and usually we assume that it is removed from water flow once the particles arrives the sludge zone.
In an ideal rectangular sedimentation tank, in the settling zone, the critical particle enters at the top of the settling zone, and the settle velocity would be the smallest value to reach the sludge zone, and at the end of outlet zone, the velocity component of this critical particle are the settling velocity in vertical direction (v) and in horizontal direction (v).
From Figure 1, the time needed for the particle to settle;
:t =H/v=L/v (3)
Since the surface area of the tank is WL, and v = Q/WL, v = Q/WH, where Q is the flow rate and W, L, H is the width, length, depth of the tank.
According to Eq. 1, this also is a basic factor that can control the sedimentation tank performance which called overflow rate.
Eq. 2 also shows that the depth of sedimentation tank is independent to the sedimentation efficiency, only if the forward velocity is low enough to make sure the settled mass would not suspended again from the tank floor. | 0 | Theoretical and Fundamental Chemistry |
In epigenetics, proline isomerization is the effect that cis-trans isomerization of the amino acid proline has on the regulation of gene expression. Similar to aspartic acid, the amino acid proline has the rare property of being able to occupy both cis and trans isomers of its prolyl peptide bonds with ease. Peptidyl-prolyl isomerase, or PPIase, is an enzyme very commonly associated with proline isomerization due to their ability to catalyze the isomerization of prolines. PPIases are present in three types: cyclophilins, FK507-binding proteins, and the parvulins. PPIase enzymes catalyze the transition of proline between cis and trans isomers and are essential to the numerous biological functions controlled and affected by prolyl isomerization (i.e. cell signalling, protein folding, and epigenetic modifications) Without PPIases, prolyl peptide bonds will slowly switch between cis and trans isomers, a process that can lock proteins in a nonnative structure that can affect render the protein temporarily ineffective. Although this switch can occur on its own, PPIases are responsible for most isomerization of prolyl peptide bonds. The specific amino acid that precedes the prolyl peptide bond also can have an effect on which conformation the bond assumes. For instance, when an aromatic amino acid is bonded to a proline the bond is more favorable to the cis conformation. Cyclophilin A uses an "electrostatic handle" to pull proline into cis and trans formations. Most of these biological functions are affected by the isomerization of proline when one isomer interacts differently than the other, commonly causing an activation/deactivation relationship. As an amino acid, proline is present in many proteins. This aids in the multitude of effects that isomerization of proline can have in different biological mechanisms and functions. | 0 | Theoretical and Fundamental Chemistry |
* Journal of Agricultural and Food Chemistry
* Journal of the American Oil Chemists Society'
* [http://www.elsevier.com/wps/find/journaldescription.cws_home/522499/description#description Biophysical Chemistry journal]
* Magnetic Resonance in Chemistry
* Starke/ Starch Journal
* [http://journalofdairyscience.org/ Journal of Dairy Science (JDS)]
* Chemical Physics Letters
* Zeitschrift für Physikalische Chemie (1887)
* Biopolymers
* Journal of Food Science (IFT, USA)
* [http://www.wiley.com/bw/journal.asp?ref=0950-5423 International Journal of Food Science & Technology]
* Macromolecular Chemistry and Physics (1947)
* [http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0010 Journal of the Science of Food and Agriculture]
* [http://www.polyacs.org/11.html Polymer Preprints] (ACS)
* [http://pubs.rsc.org/en/journals/journalissues/ib Integrative Biology] Journal of the Royal Society of Chemistry
* [http://pubs.rsc.org/en/journals/journalissues/ob Organic & Biomolecular Chemistry] (An RSC Journal)
* Nature
** Nature Precedings
* Journal of Biological Chemistry
* Proceedings of the National Academy of Sciences of the United States of America | 0 | Theoretical and Fundamental Chemistry |
Stress corrosion cracking mainly affects metals and metallic alloys. A comparable effect also known as environmental stress cracking also affects other materials such as polymers, ceramics and glass. | 1 | Applied and Interdisciplinary Chemistry |
Self-cleaning surfaces are a class of materials with the inherent ability to remove any debris or bacteria from their surfaces in a variety of ways. The self-cleaning functionality of these surfaces are commonly inspired by natural phenomena observed in lotus leaves, gecko feet, and water striders to name a few. The majority of self-cleaning surfaces can be placed into three categories:<br>
# superhydrophobic<br>
# superhydrophilic<br>
# photocatalytic. | 0 | Theoretical and Fundamental Chemistry |
Using correlation diagrams one can derive selection rules for the following generalized classes of pericyclic reactions. Each of these particular classes is further generalized in the generalized Woodward–Hoffmann rules. The more inclusive bond topology descriptors antarafacial and suprafacial subsume the terms conrotatory and disrotatory, respectively. Antarafacial refers to bond making or breaking through the opposite face of a π system, p orbital, or σ bond, while suprafacial refers to the process occurring through the same face. A suprafacial transformation at a chiral center preserves stereochemistry, whereas an antarafacial transformation reverses stereochemistry. | 0 | Theoretical and Fundamental Chemistry |
In-Methylcyclophanes are organic compounds and members of a larger family of cyclophanes. These compounds are used to study how chemical bonds in molecules adapt to strain. In-methylcyclophanes in particular have a methyl group in proximity to a benzene ring. This is only possible when both methyl group and ring are attached to the same rigid scaffold. In one In-methylcyclophane molecule this is accomplished with a triptycene frame.
This particular compound is synthesed starting from anthracene with a methyl group added to each arene ring (1,8,9-trimethylanthracene). A triptycene compound is formed from a reaction of this anthracene compound with an aryne in a Diels-Alder reaction in isoamyl nitrite. In this synthesis the precursor to the reactive aryne is 2-amino-6-methylbenzoic acid. Next the methyl substituents are functionalized with bromine groups by the photochemical reaction with N-bromosuccinimide or NBS. The final cyclophane is put together by reaction with 1,3,5-tris(mercaptomethyl)benzene with nucleophilic sulfhydryl groups and electrophilic alkyl bromides in a nucleophilic aliphatic Substitution.
X-ray crystallography of the tri-sulfone derivative of this cyclophane shows that the methyl group located 289.6 picometers from the center of the benzene ring. The carbon-to-carbon bond linking the methyl group to the triptycene frame is actually shortened and measures 147.5 to 149.5 pm. The similar bond in the triptycene precursor is 154 pm. Proton NMR analysis shows a chemical shift of 2.52 ppm for the methyl protons compared to that of 3.16 to 3.85 in the anthracene compound. The reason for this anomaly is that the methyl protons are in line with the aromatic ring current of the benzene ring and are therefore severely shielded, an effect similar to the nucleus-independent chemical shift method of analyzing aromaticity. | 0 | Theoretical and Fundamental Chemistry |
A settling basin, settling pond or decant pond is an earthen or concrete structure using sedimentation to remove settleable matter and turbidity from wastewater. The basins are used to control water pollution in diverse industries such as agriculture, aquaculture, and mining. Turbidity is an optical property of water caused by scattering of light by material suspended in that water. Although turbidity often varies directly with weight or volumetric measurements of settleable matter, correlation is complicated by variations in size, shape, refractive index, and specific gravity of suspended matter. Settling ponds may be ineffective at reducing turbidity caused by small particles with specific gravity low enough to be suspended by Brownian motion. | 1 | Applied and Interdisciplinary Chemistry |
Electroless deposition (ED) or electroless plating is defined as the autocatalytic process through which metals and metal alloys are deposited onto nonconductive surfaces.These nonconductive surfaces include plastics, ceramics, and glass etc., which can then become decorative, anti-corrosive, and conductive depending on their final functions. Electroless deposition is a chemical processes that create metal coatings on various materials by autocatalytic chemical reduction of metal cations in a liquid bath. | 1 | Applied and Interdisciplinary Chemistry |
hMeRIP-seq is an immunoprecipitation method, in which RNA–protein complexes are crosslinked for stability, and antibodies specific to hm5C are added. Using this method, over 3,000 hm5C peaks have been called in Drosophila melanogaster S2 cells. | 1 | Applied and Interdisciplinary Chemistry |
Polyamorphism has also been observed in organic compounds, such as liquid triphenyl phosphite at temperatures between 210 K and 226 K and n-butanol at temperatures between 120 K and 140 K.
Polyamorphism is also an important area in pharmaceutical science. The amorphous form of a drug typically has much better aqueous solubility (compared to the analogous crystalline form) but the actual local structure in an amorphous pharmaceutical can be different, depending on the method used to form the amorphous phase.
Mannitol is the first pharmaceutical substance featuring polyamorphism. In addition to the regular amorphous phase, a second amorphous phase can be prepared at room temperature and pressure. This new phase has substantially lower energy, lower density and higher glass transition temperature. Since mannitol is widely used in pharmaceutical tablet formulations, mannitol polyamorphism offers a powerful tool to engineer the property and behavior of tablets. | 0 | Theoretical and Fundamental Chemistry |
A biomaterial should perform its intended function within the living body without negatively affecting other bodily tissues and organs. In order to prevent unwanted organ and tissue interactions, biomaterials should be non-toxic. The toxicity of a biomaterial refers to the substances that are emitted from the biomaterial while in vivo. A biomaterial should not give off anything to its environment unless it is intended to do so. Nontoxicity means that biomaterial is: noncarcinogenic, nonpyrogenic, nonallergenic, blood compatible, and noninflammatory. However, a biomaterial can be designed to include toxicity for an intended purpose. For example, application of toxic biomaterial is studied during in vivo and in vitro cancer immunotherapy testing. Toxic biomaterials offer an opportunity to manipulate and control cancer cells. One recent study states: "Advanced nanobiomaterials, including liposomes, polymers, and silica, play a vital role in the codelivery of drugs and immunomodulators. These nanobiomaterial-based delivery systems could effectively promote antitumor immune responses and simultaneously reduce toxic adverse effects." This is a prime example of how the biocompatibility of a biomaterial can be altered to produce any desired function. | 1 | Applied and Interdisciplinary Chemistry |
A simple method for finding the particular integral for in two dimensions was devised by Isao Imai and Ernst Lamla. In two dimensions, the problem can be handled using complex analysis by introducing the complex potential formally regarded as the function of and its conjugate ; here is the stream function, defined such that
where is some reference value for the density. The perturbation series of is given by
where is an analytic function since and , being solutions of the Laplace equation, are harmonic functions. The integral for the first-order problem leads to the Imai–Lamla formula
where is the homogeneous solution (an analytic function), that can be used to satisfy necessary boundary conditions. The series for the complex velocity potential is given by
where and | 1 | Applied and Interdisciplinary Chemistry |
An enzyme inhibitor is characterised by its dissociation constant K, the concentration at which the inhibitor half occupies the enzyme. In non-competitive inhibition the inhibitor can also bind to the enzyme-substrate complex, and the presence of bound substrate can change the affinity of the inhibitor for the enzyme, resulting in a second dissociation constant K. Hence K and K are the dissociation constants of the inhibitor for the enzyme and to the enzyme-substrate complex, respectively. The enzyme-inhibitor constant K can be measured directly by various methods; one especially accurate method is isothermal titration calorimetry, in which the inhibitor is titrated into a solution of enzyme and the heat released or absorbed is measured. However, the other dissociation constant K is difficult to measure directly, since the enzyme-substrate complex is short-lived and undergoing a chemical reaction to form the product. Hence, K is usually measured indirectly, by observing the enzyme activity under various substrate and inhibitor concentrations, and fitting the data via nonlinear regression to a modified Michaelis–Menten equation.
where the modifying factors α and α' are defined by the inhibitor concentration and its two dissociation constants
Thus, in the presence of the inhibitor, the enzymes effective K and V become (α/α)K and (1/α)V, respectively. However, the modified Michaelis-Menten equation assumes that binding of the inhibitor to the enzyme has reached equilibrium, which may be a very slow process for inhibitors with sub-nanomolar dissociation constants. In these cases the inhibition becomes effectively irreversible, hence it is more practical to treat such tight-binding inhibitors as irreversible (see below). kinetically if K is measured independently.|date=July 2022}}-->
The effects of different types of reversible enzyme inhibitors on enzymatic activity can be visualised using graphical representations of the Michaelis–Menten equation, such as Lineweaver–Burk, Eadie-Hofstee or Hanes-Woolf plots. An illustration is provided by the three Lineweaver–Burk plots depicted in the Lineweaver–Burk diagrams figure. In the top diagram the competitive inhibition lines intersect on the y-axis, illustrating that such inhibitors do not affect V. In the bottom diagram the non-competitive inhibition lines intersect on the x-axis, showing these inhibitors do not affect K. However, since it can be difficult to estimate K and K' accurately from such plots, it is advisable to estimate these constants using more reliable nonlinear regression methods. | 1 | Applied and Interdisciplinary Chemistry |
Oxidative stress is suspected to be important in neurodegenerative diseases including Lou Gehrigs disease (aka MND or ALS), Parkinsons disease, Alzheimers disease, Huntingtons disease, depression, and multiple sclerosis. It is also indicated in Neurodevelopmental conditions such as Autism Spectrum Disorder. Indirect evidence via monitoring biomarkers such as reactive oxygen species, and reactive nitrogen species production indicates oxidative damage may be involved in the pathogenesis of these diseases, while cumulative oxidative stress with disrupted mitochondrial respiration and mitochondrial damage are related to Alzheimers disease, Parkinsons disease, and other neurodegenerative diseases.
Oxidative stress is thought to be linked to certain cardiovascular disease, since oxidation of LDL in the vascular endothelium is a precursor to plaque formation. Oxidative stress also plays a role in the ischemic cascade due to oxygen reperfusion injury following hypoxia. This cascade includes both strokes and heart attacks. Oxidative stress has also been implicated in chronic fatigue syndrome (ME/CFS). Oxidative stress also contributes to tissue injury following irradiation and hyperoxia, as well as in diabetes. In hematological cancers, such as leukemia, the impact of oxidative stress can be bilateral. Reactive oxygen species can disrupt the function of immune cells, promoting immune evasion of leukemic cells. On the other hand, high levels of oxidative stress can also be selectively toxic to cancer cells.
Oxidative stress is likely to be involved in age-related development of cancer. The reactive species produced in oxidative stress can cause direct damage to the DNA and are therefore mutagenic, and it may also suppress apoptosis and promote proliferation, invasiveness and metastasis. Infection by Helicobacter pylori which increases the production of reactive oxygen and nitrogen species in human stomach is also thought to be important in the development of gastric cancer.
Oxidative stress can cause DNA damage in neurons. In neuronal progenitor cells, DNA damage is associated with increased secretion of amyloid beta proteins Aβ40 and Aβ42. This association supports the existence of a causal relationship between oxidative DNA damage and Aβ accumulation and suggests that oxidative DNA damage may contribute to Alzheimer's disease (AD) pathology. AD is associated with an accumulation of DNA damage (double-strand breaks) in vulnerable neuronal and glial cell populations from early stages onward, and DNA double-strand breaks are increased in the hippocampus of AD brains compared to non-AD control brains. | 1 | Applied and Interdisciplinary Chemistry |
In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography, where the phase problem has to be solved for the determination of a structure from diffraction data. The phase problem is also met in the fields of imaging and signal processing. Various approaches of phase retrieval have been developed over the years. | 0 | Theoretical and Fundamental Chemistry |
Thure Cerling and James Ehleringer, a biology professor at the University of Utah, founded Isoforensics in 2003, a company with the aim of interpreting the stable isotope composition of various biological and synthetic materials. This was the first step for the discovery they made which was first published on February 25, 2008, by the "Proceedings of the National Academy of Sciences" with the title "Hydrogen and oxygen isotope ratios in human hair are related to geography".
To know where people have been and where they lived for a while are information that became available by analyzing the stable isotope composition of their scalp hair. Cerling discovered that a strand of hair could provide valuable clues about a person's travels by studying the variation of hydrogen-2 (δ2H) and oxygen-18 (δ18O) isotopes and comparing them to the ones in the drinking water. The extent of the information that can be deduced depends on the length of the hair: the longer is the hair, the greater is the extraction of information. The variation with geography of isotope concentrations is linked with precipitations, cloud temperatures and with the amount of water that evaporates from soil and plants. When clouds move off the ocean towards inland the ratios of oxygen-18 to oxygen-16 and hydrogen-2 to hydrogen-1 tend to decrease because of the rain water with oxygen-18 and hydrogen-2, being heavier, tends to fall first.
Samples of tap water were collected from more than 600 cities across the United States as well as hair samples from the barbershops in 65 cities in 20 states. The comparison showed that both hair and drinking water samples had the same isotopic variations. In order to display these information, the scientists produced color-coded maps based on the correlation of the isotopes in hair to those in drinking water. This maps show how ratios of hydrogen and oxygen isotopes in scalp hair vary in different areas of the United States. It was so proved that the water drank by a human being leaves in the hair an evidence which contain oxygen and hydrogen isotopes equal to the ones in the tap water.
This technique would have been a new tool for policemen, anthropologists, archaeologists and doctors. | 0 | Theoretical and Fundamental Chemistry |
Nucleotides are initially made with ribose as the sugar component, which is a feature of RNA. DNA, however, requires deoxyribose, which is missing the 2'-hydroxyl (-OH group) on the ribose. The reaction to remove this -OH is catalyzed by ribonucleotide reductase. This enzyme converts NDPs (ucleoside-ihosphate) to dNDPs (eoxyucleoside-ihosphate). The nucleotides must be in the diphosphate form for the reaction to occur.
In order to synthesize thymidine, a component of DNA which only exists in the deoxy form, uridine is converted to deoxyuridine (by ribonucleotide reductase), and then is methylated by thymidylate synthase to create thymidine. | 1 | Applied and Interdisciplinary Chemistry |
Sterlite Industries ("Sterlite"), a subsidiary of Vedanta Resources, built a copper smelter in Tuticorin using an ISASMELT furnace and Peirce-Smith converters. The smelter was commissioned in 1996 and was designed to produce 60,000 t/y of copper (450,000 t/y of copper concentrate), but by increasing the oxygen content of the lance air and making modifications to other equipment, the ISASMELT furnace feed rate was increased to the point where the smelter was producing 180,000 t/y of copper.
Sterlite commissioned a new ISASMELT furnace in May 2005 that was designed to treat 1.3 million t/y of copper concentrate, and the smelters production capacity was expanded to 300,000 t/y of copper. The new plant reached its design capacity, measured over a three-month period, six months after it started treating its first feed. Vedantas website states that the new ISASMELT furnace was successfully ramped up "in a record period of 45 days".
Since then Sterlite decided to further expand its copper production by installing a third ISASMELT smelter and new refinery using IsaKidd technology. The new smelter has a design capacity of 1.36 million t/y of copper concentrate (containing 400,000 t/y of copper), processed through a single ISASMELT furnace. | 1 | Applied and Interdisciplinary Chemistry |
The Woodward–Hoffmann rules can also explain bimolecular cycloaddition reactions through correlation diagrams. A [p + q] cycloaddition brings together two components, one with p π-electrons, and the other with q π-electrons. Cycloaddition reactions are further characterized as suprafacial (s) or antarafacial (a) with respect to each of the π components. (See below "General formulation" for a detailed description of the generalization of WH notation to all pericyclic processes.) | 0 | Theoretical and Fundamental Chemistry |
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