text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
Several applications exist that capitalize on the properties of the various isotopes of a given element. Isotope separation is a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighter elements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compounds such as CO and NO. The separation of hydrogen and deuterium is unusual because it is based on chemical rather than physical properties, for example in the Girdler sulfide process. Uranium isotopes have been separated in bulk by gas diffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project) by a type of production mass spectrometry. | 0 | Theoretical and Fundamental Chemistry |
A simple example is a semi-infinite domain bounded by a rigid wall and filled with viscous fluid. At time the wall is made to move with constant speed in a fixed direction (for definiteness, say the direction and consider only the plane), one can see that there is no distinguished length scale given in the problem. This is known as the Rayleigh problem. The boundary conditions of no-slip is
Also, the condition that the plate has no effect on the fluid at infinity is enforced as
Now, from the Navier-Stokes equations
one can observe that this flow will be rectilinear, with gradients in the direction and flow in the direction, and that the pressure term will have no tangential component so that
. The component of the Navier-Stokes equations then becomes
and the scaling arguments can be applied to show that
which gives the scaling of the co-ordinate as
This allows one to pose a self-similar ansatz such that, with and dimensionless,
The above contains all the relevant physics and the next step is to solve the equations, which for many cases will include numerical methods. This equation is
with solution satisfying the boundary conditions that
which is a self-similar solution of the first kind. | 1 | Applied and Interdisciplinary Chemistry |
An important physical property characterizing the flow of liquids is viscosity. Intuitively, viscosity describes the resistance of a liquid to flow.
More technically, viscosity measures the resistance of a liquid to deformation at a given rate, such as when it is being sheared at finite velocity. A specific example is a liquid flowing through a
pipe: in this case the liquid undergoes shear deformation since it flows more slowly near the walls of the pipe
than near the center. As a result, it exhibits viscous resistance to flow. In order to maintain flow, an external force must be applied, such as a pressure difference between the ends of the pipe.
The viscosity of liquids decreases with increasing temperature.
Precise control of viscosity is important in many applications, particularly the lubrication industry. One way to achieve such control is by blending two or more liquids of differing viscosities in precise ratios.
In addition, various additives exist which can modulate the temperature-dependence of the
viscosity of lubricating oils. This capability is important since machinery often operate over a range of
temperatures (see also viscosity index).
The viscous behavior of a liquid can be either Newtonian or non-Newtonian. A Newtonian liquid exhibits a linear strain/stress curve, meaning its viscosity is independent of time, shear rate, or shear-rate history. Examples of Newtonian liquids include water, glycerin, motor oil, honey, or mercury. A non-Newtonian liquid is one where the viscosity is not independent of these factors and either thickens (increases in viscosity) or thins (decreases in viscosity) under shear. Examples of non-Newtonian liquids include ketchup, custard, or starch solutions. | 0 | Theoretical and Fundamental Chemistry |
Before Werner, chemists defined the valence of an element as the number of its bonds without distinguishing different types of bonds. However, in complexes such as [Co(NH)]Cl for example, Werner considered that the Co-Cl bonds correspond to a "primary" valence of 3 at long distance, while the Co-NH bonds which correspond to a "secondary" or weaker valence of 6 at shorter length. This secondary valence of 6 he referred to as the coordination number which he defined as the number of molecules (here of NH) directly linked to the central metal atom. In other complexes, he found coordination numbers of 4 or 8.
On these views, and other similar views, in 1904 Richard Abegg formulated what is now known as Abegg's rule which states that the difference between the maximum positive and negative valence of an element is frequently eight. This rule was used later in 1916 when Gilbert N. Lewis formulated the "octet rule" in his cubical atom theory.
In modern terminology, Werner's primary valence corresponds to the oxidation state, and his secondary valence is called coordination number. The Co-Cl bonds (in the above example) are now classed as ionic, and each Co-N bond is a coordinate covalent bond between the Lewis acid Co and the Lewis base NH. | 0 | Theoretical and Fundamental Chemistry |
As illustrated by the diagram on the right, additional carbon dioxide () is absorbed by the ocean and reacts with water, carbonic acid () is formed and broken down into both bicarbonate () and hydrogen () ions (gray arrow), which reduces bioavailable carbonate () and decreases ocean pH (black arrow). This is likely to enhance nitrogen fixation by diazotrophs (gray arrow), which utilize ions to convert nitrogen into bioavailable forms such as ammonia () and ammonium ions (). However, as pH decreases, and more ammonia is converted to ammonium ions (gray arrow), there is less oxidation of ammonia to nitrite (NO), resulting in an overall decrease in nitrification and denitrification (black arrows). This in turn would lead to a further build-up of fixed nitrogen in the ocean, with the potential consequence of eutrophication. Gray arrows represent an increase while black arrows represent a decrease in the associated process. | 1 | Applied and Interdisciplinary Chemistry |
Zinc–carbon batteries were the first commercially available battery type and are still somewhat frequently used, although they have largely been replaced by the similarly composed alkaline battery. Like the alkaline battery, the zinc–carbon battery contains manganese dioxide and zinc electrodes. Unlike the alkaline battery, the zinc–carbon battery uses ammonium chloride as the electrolyte (zinc chloride in the case of "heavy-duty" zinc–carbon batteries), which is acidic.
Either when it has been completely consumed or after three to five years from its manufacture (its shelf life), a zinc–carbon battery is prone to leaking. The byproducts of the leakage may include manganese hydroxide, zinc ammonium chloride, ammonia, zinc chloride, zinc oxide, water and starch. This combination of materials is corrosive to metals, such as those of the battery contacts and surrounding circuitry.
Anecdotal evidence suggests that zinc–carbon battery leakage can be effectively cleaned with sodium bicarbonate (baking soda). | 1 | Applied and Interdisciplinary Chemistry |
In scientific visualization, line integral convolution (LIC) is a method to visualize a vector field, such as fluid motion. | 1 | Applied and Interdisciplinary Chemistry |
PhSnH, as it is more commonly abbreviated, is prepared by treatment of triphenyltin chloride with lithium aluminium hydride. Although PhSnH is treated as a source of "H·", in fact it does not release free hydrogen atoms, which are extremely reactive species. Instead, PhSnH transfers H to substrates usually via a radical chain mechanism. This reactivity exploits the relatively good stability of "PhSn·" | 0 | Theoretical and Fundamental Chemistry |
In radial stagnation flows, instead of a stagnation point, we have a stagnation circle and the stagnation plane is replaced by a stagnation cylinder. The radial stagnation flow is described using the cylindrical coordinate system with velocity components as follows
where is the location of the stagnation cylinder. | 1 | Applied and Interdisciplinary Chemistry |
Attempts to save a metal from becoming anodic are of two general types. Anodic regions dissolve and destroy the structural integrity of the metal.
While it is almost impossible to prevent anode/cathode formation, if a non-conducting material covers the metal, contact with the electrolyte is not possible and corrosion will not occur. | 0 | Theoretical and Fundamental Chemistry |
A prokaryote (, also spelled procaryote) is a single-cell organism whose cell lacks a nucleus and other membrane-bound organelles. The word prokaryote comes from the Ancient Greek πρό () before and κάρυον () nut, kernel. In the two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. But in the three-domain system, based upon molecular analysis, prokaryotes are divided into two domains: Bacteria (formerly Eubacteria) and Archaea (formerly Archaebacteria). Organisms with nuclei are placed in a third domain, Eukaryota.
Prokaryotes evolved before eukaryotes, and lack nuclei, mitochondria or most of the other distinct organelles that characterize the eukaryotic cell. It was once thought that prokaryotic cellular components were unenclosed within the cytoplasm except for an outer cell membrane, but bacterial microcompartments, which are thought to be quasi-organelles enclosed in protein shells (such as the encapsulin protein cages), have been discovered, along with other prokaryotic organelles. While being unicellular, some prokaryotes, such as cyanobacteria, may form colonies held together by biofilms, and large colonies can create multilayered microbial mats. Others, such as myxobacteria, have multicellular stages in their life cycles. Prokaryotes are asexual, reproducing via binary fission without any fusion of gametes, although horizontal gene transfer may take place.
Molecular studies have provided insight into the evolution and interrelationships of the three domains of life. The division between prokaryotes and eukaryotes reflects the existence of two very different levels of cellular organization; only eukaryotic cells have an enveloped nucleus that contains its chromosomal DNA, and other characteristic membrane-bound organelles including mitochondria. Distinctive types of prokaryotes include extremophiles and methanogens; these are common in some extreme environments. | 1 | Applied and Interdisciplinary Chemistry |
A correct reaction mechanism is an important part of accurate predictive modeling. For many combustion and plasma systems, detailed mechanisms are not available or require development.
Even when information is available, identifying and assembling the relevant data from a variety of sources, reconciling discrepant values and extrapolating to different conditions can be a difficult process without expert help. Rate constants or thermochemical data are often not available in the literature, so computational chemistry techniques or group additivity methods must be used to obtain the required parameters.
Computational chemistry methods can also be used to calculate potential energy surfaces for reactions and determine probable mechanisms. | 0 | Theoretical and Fundamental Chemistry |
Milton Kerker (September 25, 1920 — May 2, 2016) was an American physical chemist and former professor at department of chemistry at Clarkson University. He is best known for his work on aerosol, interface and colloid science, as well as for pioneering surface-enhanced Raman spectroscopy. Kerker effect in optics is named after him. | 0 | Theoretical and Fundamental Chemistry |
Using the heat-mass transfer analogy, a mass transfer St equivalent can be found using the Sherwood number and Schmidt number in place of the Nusselt number and Prandtl number, respectively.
where
* is the mass Stanton number;
* is the Sherwood number based on length;
* is the Reynolds number based on length;
* is the Schmidt number;
* is defined based on a concentration difference (kg s m);
* is the velocity of the fluid | 1 | Applied and Interdisciplinary Chemistry |
7-nt primer library, 5′-NNNNNNrX-3′, are used in the ligation of a short degenerate oligonucleotide fragmentin, in which N represents any of the four deoxyribonucleotides and Nr represents any of the four ribonucleotides, X is the tested base(A,G,C,T). The ligation to a primer strand of each of the four tested bases in hairpin opening and closing cycles are tested. | 1 | Applied and Interdisciplinary Chemistry |
The degree of compressibility of a fluid has strong implications for its dynamics. Most notably, the propagation of sound is dependent on the compressibility of the medium. | 1 | Applied and Interdisciplinary Chemistry |
To function in active transport, a membrane protein must meet certain requirements. The first of these is that the interior of the protein must contain a cavity that is able to contain its corresponding molecule or ion. Next, the protein must be able to assume at least two different conformations, one with its cavity open to the extracellular space and the other with its cavity open to the cytosol. This is crucial for the movement of molecules from one side of the membrane to the other. Finally, the cavity of the protein must contain binding sites for its ligands, and these binding sites must have a different affinity for the ligand in each of the protein's conformations. Without this, the ligand will not be able to bind to the transporter on one side of the plasma membrane and be released from it on the other side. As transporters, antiporters have all of these features.
Because antiporters are highly diverse, their structure can vary widely depending upon the type of molecules being transported and their location in the cell. However, there are some common features that all antiporters share. One of these is multiple transmembrane regions that span the lipid bilayer of the plasma membrane and form a channel through which hydrophilic molecules can pass. These transmembrane regions are typically structured from alpha helices and are connected by loops in both the extracellular space and cytosol. These loops are what contain the binding sites for the molecules associated with the antiporter.
These features of antiporters allow them to carry out their function in maintaining cellular homeostasis. They provide a space where a hydrophilic molecule can pass through the hydrophobic lipid bilayer, allowing them them to bypass the hydrophobic interactions of the plasma membrane. This enables the efficient movement of molecules needed for the environment of the cell, such as in the acidification of organelles. The varying affinity of the antiporter for each ion or molecule on either side of the plasma membrane allows it to bind to and release its ligands on the appropriate side of the membrane according to the electrochemical gradient of the ion being harnessed for its energetically favorable concentration. | 1 | Applied and Interdisciplinary Chemistry |
BOGS was formed in 1987. The founding members were Prof G.A. Wolff (University of Liverpool),
Dr G.D. Abbott (Newcastle University), Dr J. McEvoy (then at University of Bangor) and Prof S.J. Rowland (University of Plymouth). | 0 | Theoretical and Fundamental Chemistry |
Bombs in the arctic area of Novaja Zemlja and bombs detonated in or near the stratosphere released cesium-137 that landed in upper Lapland, Finland. Measurements of cesium-137 in 1960's was reportedly 45,000 becquerels. Figures from 2011 have a mid range of about 1,100 becquerels, but strangely, cancer cases are no more common there than elsewhere. | 0 | Theoretical and Fundamental Chemistry |
The unexpected fall in 2011 of a heavy light fixture from the ceiling of the Big Dig vehicular tunnel in Boston revealed that corrosion had weakened its support. Improper use of aluminium in contact with stainless steel had caused rapid corrosion in the presence of salt water. The electrochemical potential difference between stainless steel and aluminium is in the range of 0.5 to 1.0V, depending on the exact alloys involved, and can cause considerable corrosion within months under unfavorable conditions. Thousands of failing lights would have to be replaced, at an estimated cost of $54 million. | 1 | Applied and Interdisciplinary Chemistry |
Examples include a series of isoretical catecholate-based MOFs employing hexahudroxytriphenylene (HHTP) as thee organic linker and Ni/Cu/Co as metal nodes. For the hydrothermal synthesis of these MOFs, both organic linker (hexahydroxytriphenylene) and metal ion is dissolved in HO, aqueous ammonia is added and mixture is heated. Cu(HHTP) also known as (Cu-CAT-1) showed a conductivity up to 2.1 × 10−1 S cm. Another MOF based on hexaaminotriphenylene (HATP) organic linker and Ni metal ion showed an electronic conductivity of 40 S cm when measured by using Van der Pauw method . | 0 | Theoretical and Fundamental Chemistry |
There are four main limiting factors leading to no initiation of replication in iterons:
*Transcriptional autorepression
*Initiator dimerization
*Initiator titration
*Handcuffing
Transcriptional auto-repression is thought to reduce initiator synthesis by repressing the formation of the Rep proteins. Since these proteins work to promote binding of replication machinery, replication can be halted in this form. Another factor used to stop replication is known as dimerization. It works to dimerize these Rep proteins and as a result monomers of these proteins are no longer in a high enough concentration to initiate replication. Another limiting factor, titration, occurs after replication and works to prevent saturation by distributing monomers to daughter origins so that no are fully saturated. Finally, handcuffing refers to pairing origins leading to inactivation. This is mediated by monomers and inactivation is due to steric hindrance between the origins.
Another less prevalent limitation thought to be present in these iterons is the presence of extra repeats. If a plasmid contains an extra supply of iterons outside of the saturation site it has been shown this can decrease plasmid copy number. In contrast, removing these extra iterons will increase copy number. | 1 | Applied and Interdisciplinary Chemistry |
A countercurrent multiplication loop is a system where fluid flows in a loop so that the entrance and exit are at similar low concentration of a dissolved substance but at the far end of the loop there is a high concentration of that substance. A buffer liquid between the incoming and outgoing tubes receives the concentrated substance. The incoming and outgoing tubes do not touch each other.
The system allows the buildup of a high concentration gradually, by allowing a natural buildup of concentration towards the tip inside the in-going tube, (for example using osmosis of water out of the input pipe and into the buffer fluid), and the use of many active transport pumps each pumping only against a very small gradient, during the exit from the loop, returning the concentration inside the output pipe to its original concentration.
The incoming flow starting at a low concentration has a semipermeable membrane with water passing to the buffer liquid via osmosis at a small gradient. There is a gradual buildup of concentration inside the loop until the loop tip where it reaches its maximum.
Theoretically a similar system could exist or be constructed for heat exchange.
In the example shown in the image, water enters at 299 mg/L (NaCl / HO). Water passes because of a small osmotic pressure to the buffer liquid in this example at 300 mg/L (NaCl / HO). Further up the loop there is a continued flow of water out of the tube and into the buffer, gradually raising the concentration of NaCl in the tube until it reaches 1199 mg/L at the tip. The buffer liquid between the two tubes is at a gradually rising concentration, always a bit over the incoming fluid, in this example reaching 1200 mg/L. This is regulated by the pumping action on the returning tube as will be explained immediately.
The tip of the loop has the highest concentration of salt (NaCl) in the incoming tube—in the example 1199 mg/L, and in the buffer 1200 mg/L. The returning tube has active transport pumps, pumping salt out to the buffer liquid at a low difference of concentrations of up to 200 mg/L more than in the tube. Thus when opposite the 1000 mg/L in the buffer liquid, the concentration in the tube is 800 and only 200 mg/L are needed to be pumped out. But the same is true anywhere along the line, so that at exit of the loop also only 200 mg/L need to be pumped.
In effect, this can be seen as a gradually multiplying effect—hence the name of the phenomena: a countercurrent multiplier or the mechanism: Countercurrent multiplication, but in current engineering terms, countercurrent multiplication is any process where only slight pumping is needed, due to the constant small difference of concentration or heat along the process, gradually raising to its maximum. There is no need for a buffer liquid, if the desired effect is receiving a high concentration at the output pipe. | 1 | Applied and Interdisciplinary Chemistry |
A partially coherent interphase boundary is an intermediate type of IPB that lies between the completely coherent and non-coherent IPBs. In this type of boundary, there is a partial match between the atomic arrangements of the particle and the matrix, but not a perfect match. As a result, coherency strains are partially relieved, but not completely eliminated. The periodic introduction of dislocations along the boundary plays a key role in partially relieving the coherency strains. These dislocations act as periodic defects that accommodate the lattice mismatch between the particle and the matrix. The dislocations can be introduced during the precipitation process or during subsequent annealing treatments. | 1 | Applied and Interdisciplinary Chemistry |
Radiochemistry, radiation chemistry and nuclear chemical engineering play a very important role for uranium and thorium fuel precursors synthesis, starting from ores of these elements, fuel fabrication, coolant chemistry, fuel reprocessing, radioactive waste treatment and storage, monitoring of radioactive elements release during reactor operation and radioactive geological storage, etc. | 0 | Theoretical and Fundamental Chemistry |
Starting with the sulfate and using ammonium hydroxide as the base, depending on the conditions, one obtains the 9-hydrate, the 6-hydrate, or the 4-hydrate of hexol sulfate. These salts form dark brownish-violet or black tabular crystals, with low solubility in water. When treated with concentrated hydrochloric acid, hexol sulfate converts to cis-diaquotetramminecobalt(III) sulfate. In boiling dilute sulfuric acid, hexol sulfate further degrades with evolution of oxygen and nitrogen. | 0 | Theoretical and Fundamental Chemistry |
The naming of monomeric oxyanions follows the following rules.
Here the halogen group (group 7A, 17) is referred to as group VII and the noble gases group (group 8A) is referred to as group VIII.
; If central atom is not in Group VII or VIII
; If central atom is in Group VII or VIII | 0 | Theoretical and Fundamental Chemistry |
Salt compounds dissociate in aqueous solutions. This property is exploited in the process of salting out. When the salt concentration is increased, some of the water molecules are attracted by the salt ions, which decreases the number of water molecules available to interact with the charged part of the protein.
There are hydrophobic amino acids and hydrophilic amino acids in protein molecules.
After protein folding in aqueous solution, hydrophobic amino acids usually form protected hydrophobic areas while hydrophilic amino acids interact with the molecules of solvation and allow proteins to form hydrogen bonds with the surrounding water molecules. If enough of the protein surface is hydrophilic, the protein can be dissolved in water.
When salt is added to the solution, there is more frequent interaction between solvent molecules and salt ions. As a result, the protein and salt ions compete to interact with the solvent molecules with the result that there are fewer solvent molecules available for interaction with the protein molecules than before. The protein–protein interactions thus become stronger than the solvent–solute interactions and the protein molecules associate by forming hydrophobic interactions with each other. After dissociation in a given solvent, the negatively charged atoms from a chosen salt begin to compete for interactions with positively charged molecules present in the solution. Similarly, the positively charged cations compete for interactions with the negatively charged molecules of the solvent. This process is known as salting out.
Soaps are easily precipitated by concentrated salt solution, the metal ion in the salt reacts with the fatty acids forming back the soap and glycerin (glycerol). To separate glycerin from the soap, the pasty boiling mass is treated with brine (NaCl solution). Contents of the kettle salt out (separate) into an upper layer that is a curdy mass of impure soap and a lower layer that consists of an aqueous salt solution with the glycerin dissolved in it. The slightly alkaline salt solution, termed spent lye, is extracted from the bottom of the pan or kettle and may be subsequently treated for glycerin recovery. | 0 | Theoretical and Fundamental Chemistry |
The Chemical Heritage Foundations collections include such pioneering and landmark instruments as a 1934 Beckman Model G pH Meter, a DuPont 900 Differential Thermal Analyzer, an early custom Electro-spray Ionization Mass Spectrometer used by John B. Fenn, a 1947 Mettler B5 Single-Pan Balance, a 1963 Perkin-Elmer Model 125 Infrared Grating Spectrophotometer, and a s Automated Peptide Synthesizer created by Bruce Merrifield.
The foundation expanded its instrument collections slowly, mostly through donations of single instruments or small groups of instruments. In 2000, the CIMG was transformed into the Heritage Council Instruments and Artifacts Committee (HCIAC), which included staff and supporters and began meeting under founding chair W. Richard Howe. In 2002, the institution was given hundreds of instruments by Stephen P. DeFalco, president of PerkinElmer, after the company closed a plant in Überlingen, Germany. An interim exhibition of Revolutionary Tools was curated at the Chemical Heritage Foundation by David Brock, showing fifteen 20th-century instruments, including Arnold Beckman's pH meter.
In 2004, a list of "50 Instruments That Changed the World" was identified as a basis for further expansion. In 2008, the institution released a list of its ten most wanted instruments. | 1 | Applied and Interdisciplinary Chemistry |
The simulation on the right was completed using a Brownian dynamics simulation. Starting with a Langevin equation for the system,
where is the friction term, is a fluctuating force on the particle, and is the amplitude of the fluctuation. At equilibrium the frictional force is much greater than the inertial force, . Therefore, the Langevin equation becomes,
For the Brownian dynamic simulation the fluctuation force is assumed to be Gaussian with the amplitude being dependent of the temperature of the system . Rewriting the Langevin equation,
where is the Einstein relation. The integration of this equation was done using the Euler–Maruyama method to numerically approximate the path of this Brownian particle. | 1 | Applied and Interdisciplinary Chemistry |
The AIRMoN sites were primarily used to assess the impacts of emission changes such as potential effects from new sources, federal Clean Air Act controls, and source-receptor relationships in atmospheric models. The network measured the same contaminants as the NTN, but sampling occurred daily during precipitation to provide greater temporal resolution. This consistent, high-resolution sampling improved the researchers’ ability to evaluate the data and, therefore, provide reliable results. The network was discontinued in September 2019. | 1 | Applied and Interdisciplinary Chemistry |
The hydroformylation of alkenes to give aldehydes is an important industrial process. Almost 6 million tons of aldehydes are produced by this method annually.
Rhodium complexes containing diphosphine ligands are active hydroformylation catalysts.
The ratio of linear to branched aldehyde product depends on the structure of the catalyst.
One intermediate, [Rh(H)(alkene)(CO)L], exists in two different isomers, depending on the position of phosphine ligands (Figure 4).
Diphosphine ligands such as dppe, which has a bite angle of about 90°, span the equatorial and apical positions (AE isomer). Diphosphines with larger bite angles (above 120°) preferentially occupy a pair of equatorial positions (EE isomer). It is believed that the EE isomer favors formation of linear aldehydes, the desired product. In an effort to create rhodium complexes in which the phosphine ligands preferentially occupy the equatorial positions, the use of diphosphine ligands with wide bite angles such as BISBI (Figure 5) has been investigated.
With a bite angle of approximately 113°, BISBI spans sites on equatorial plane of the trigonal bipyramidal intermediate complex (Figure 6).
The structure of the intermediate [Rh(H)(diphosphine)(CO)] does not however determine the regioselectivity of the hydroformylation. Instead, the formation of the linear vs. branched aldehydes is determined upon formation of [Rh(H)(diphosphine)CO(alkene)] and the subsequent hydride migration step. The bite angle affect the steric crowding at the Rh atom that results from the interactions of the bulky backbone of the ligand with substrate. The wide bite angle that results from the backbone allows the five-coordinate [Rh(H)(diphosphine)CO(alkene)] intermediate to adopt a structure that relieves steric hindrance. Thus, BISBI occupies the equatorial positions, where it has the most space. This preference of a transition state that relieves steric hindrance favors the formation of the linear aldehyde. The regioselectivity is also controlled by the hydride migration, which is usually irreversible in the formation of linear aldehydes.
Furthermore, studies using Xantphos ligands (ligands with bulky backbones) in hydroformylation have indicated an increase in the rate of catalysis in metal complexes that contain diphosphine ligands with larger bite angles. The electronic effect of this increase in reaction rate is uncertain since it mainly depends on the bonding between the alkene and rhodium. Large bite angles promote alkene to rhodium electron donation, which results in an accumulation of electron density on the rhodium atom. This increased electron density would be available for π-donation into the anti-bonding orbitals of other ligands, which could weaken other M-L bonds within the catalyst, leading to higher rates.
The application of diphosphine ligands to catalysts is not limited to the process of hydroformylation. Hydrocyanation and hydrogenation reactions also implement phosphine-mediated catalysts. | 0 | Theoretical and Fundamental Chemistry |
Side reactions of the alkenes are the isomerization and hydrogenation of the double bond. While the alkanes resulting from hydrogenation of the double bond do not participate further in the reaction, the isomerization of the double bond with subsequent formation of the n-alkyl complexes is a desired reaction. The hydrogenation is usually of minor importance; However, cobalt-phosphine-modified catalysts can have an increased hydrogenation activity, where up to 15% of the alkene is hydrogenated. | 0 | Theoretical and Fundamental Chemistry |
In the field of "nano" spray drying a new heating system is used to provide the drying gas to produce the particles. The gas flow in the system is laminar and not turbulent as in common spray drying. The advantage of a laminar flow is that the particles fall straight down from the spray head and do not stick to the glass wall.
The laminar flow is produced by pressing the air through a porous metal foam. | 0 | Theoretical and Fundamental Chemistry |
Transition metal carbyne complexes are most common for the early transition metals, especially niobium, tantalum, molybdenum, tungsten, and rhenium. They can also have low-valence metals as well as high-valence metals.
The first Fischer carbyne complex was reported in 1973. Two years later in 1975, the first "Schrock carbyne" was reported.
Many high-valent carbyne complexes have since been prepared, often by dehydrohalogenation of carbene complexes. Alternatively, amino-substituted carbyne ligands sometimes form upon protonation of electron-rich isonitrile complexes. Similarly, O-protonation of μ-CO ligands in clusters gives hydroxycarbyne complexes. Vinyl ligands have been shown to rearrange into carbyne ligands. Addition of electrophiles to vinylidene ligands also affords carbyne complexes. | 0 | Theoretical and Fundamental Chemistry |
A goniometer is used to document initial and subsequent range of motion, at the visits for occupational injuries, and by disability evaluators to determine a permanent disability. This is to evaluate progress, and also for medico-legal purposes. It is a tool to evaluate Waddell's signs (findings that may indicate symptom magnification.) | 0 | Theoretical and Fundamental Chemistry |
The fundamental aminophosphines have the formulae PH(NH) (n = 1, 2, 3). These species cannot be isolated in a practical quantities, although they have been examined theoretically. HNPH is predicted to be more stable than the P(V) tautomer HN=PH.
With secondary amines, the chemistry is more straightforward. Trisaminophosphines are prepared by treatment of phosphorus trichloride with secondary amines:
:PCl + 6 HNMe → (MeN)P + 3 [HNMe]Cl | 0 | Theoretical and Fundamental Chemistry |
Surface stress was first defined by Josiah Willard Gibbs (1839–1903) as the amount of the reversible work per unit area needed to elastically stretch a pre-existing surface. Depending upon the convention used, the area is either the original, unstretched one which represents a constant number of atoms, or sometimes is the final area; these are atomistic versus continuum definitions. Some care is needed to ensure that the definition used is also consistent with the elastic strain energy, and misinterpretations and disagreements have occurred in the literature.
A similar term called "surface free energy", the excess free energy per unit area needed to create a new surface, is sometimes confused with "surface stress". Although surface stress and surface free energy of liquid–gas or liquid–liquid interface are the same, they are very different in solid–gas or solid–solid interface. Both terms represent an energy per unit area, equivalent to a force per unit length, so are sometimes referred to as "surface tension", which contributes further to the confusion in the literature. | 0 | Theoretical and Fundamental Chemistry |
C/N ratios in the range 4-10:1 are usually from marine sources, whereas higher ratios are likely to come from a terrestrial source. Vascular plants from terrestrial sources tend to have C/N ratios greater than 20. The lack of cellulose, which has a chemical formula of (CHO), and greater amount of proteins in algae versus vascular plants causes this significant difference in the C/N ratio. | 0 | Theoretical and Fundamental Chemistry |
A recently described method by Ehrich et al. further takes advantage of bisulfite-conversions by adding a base-specific cleavage step to enhance the information gained from the nucleotide changes. By first using in vitro transcription of the region of interest into RNA (by adding an RNA polymerase promoter site to the PCR primer in the initial amplification), RNase A can be used to cleave the RNA transcript at base-specific sites. As RNase A cleaves RNA specifically at cytosine and uracil ribonucleotides, base-specificity is achieved by adding incorporating cleavage-resistant dTTP when cytosine-specific (C-specific) cleavage is desired, and incorporating dCTP when uracil-specific (U-specific) cleavage is desired. The cleaved fragments can then be analyzed by MALDI-TOF. Bisulfite treatment results in either introduction/removal of cleavage sites by C-to-U conversions or shift in fragment mass by G-to-A conversions in the amplified reverse strand. C-specific cleavage will cut specifically at all methylated CpG sites. By analyzing the sizes of the resulting fragments, it is possible to determine the specific pattern of DNA methylation of CpG sites within the region, rather than determining the extent of methylation of the region as a whole. This method demonstrated efficacy for high-throughput screening, allowing for interrogation of numerous CpG sites in multiple tissues in a cost-efficient manner. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked with the double dagger (‡) symbol.
As an example, the transition state shown below occurs during the S2 reaction of bromoethane with a hydroxide anion:
The activated complex of a reaction can refer to either the transition state or to other states along the reaction coordinate between reactants and products, especially those close to the transition state.
According to the transition state theory, once the reactants have passed through the transition state configuration, they always continue to form products. | 0 | Theoretical and Fundamental Chemistry |
4-Toluenesulfonyl chloride (p-toluenesulfonyl chloride, toluene-p-sulfonyl chloride) is an organic compound with the formula CHCHSOCl. This white, malodorous solid is a reagent widely used in organic synthesis. Abbreviated TsCl or TosCl, it is a derivative of toluene and contains a sulfonyl chloride (−SOCl) functional group. | 0 | Theoretical and Fundamental Chemistry |
Many template reactions are only stoichiometric, and the decomplexation of the "templating ion" can be difficult. The alkali metal-templated syntheses of crown ether syntheses are notable exceptions. Metal Phthalocyanines are generated by metal-templated condensations of phthalonitriles, but the liberation of metal-free phthalocyanine is difficult.
Some so-called template reactions proceed similarly in the absence of the templating ion. One example being the condensation of acetone and ethylenediamine, which yields isomeric 14-membered tetraaza rings. Similarly, porphyrins, which feature 16-membered central rings, form in the absence of metal templates. | 0 | Theoretical and Fundamental Chemistry |
The enhancers determining early segmentation in Drosophila melanogaster embryos are among the best characterized developmental enhancers. In the early fly embryo, the gap gene transcription factors are responsible for activating and repressing a number of segmentation genes, such as the pair rule genes. The gap genes are expressed in blocks along the anterior-posterior axis of the fly along with other maternal effect transcription factors, thus creating zones within which different combinations of transcription factors are expressed. The pair-rule genes are separated from one another by non-expressing cells. Moreover, the stripes of expression for different pair-rule genes are offset by a few cell diameters from one another. Thus, unique combinations of pair-rule gene expression create spatial domains along the anterior-posterior axis to set up each of the 14 individual segments. The 480 bp enhancer responsible for driving the sharp stripe two of the pair-rule gene even-skipped (eve) has been well-characterized. The enhancer contains 12 different binding sites for maternal and gap gene transcription factors. Activating and repressing sites overlap in sequence. Eve is only expressed in a narrow stripe of cells that contain high concentrations of the activators and low concentration of the repressors for this enhancer sequence. Other enhancer regions drive eve expression in 6 other stripes in the embryo. | 1 | Applied and Interdisciplinary Chemistry |
The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain. These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Various polymer structures can be produced depending on the monomers and reaction conditions: A polymer may consist of linear macromolecules containing each only one unbranched chain. In the case of unbranched polyethylene, this chain is a long-chain n-alkane. There are also branched macromolecules with a main chain and side chains, in the case of polyethylene the side chains would be alkyl groups. In particular unbranched macromolecules can be in the solid state semi-crystalline, crystalline chain sections highlighted red in the figure below.
While branched and unbranched polymers are usually thermoplastics, many elastomers have a wide-meshed cross-linking between the "main chains". Close-meshed crosslinking, on the other hand, leads to thermosets. Cross-links and branches are shown as red dots in the figures. Highly branched polymers are amorphous and the molecules in the solid interact randomly. | 0 | Theoretical and Fundamental Chemistry |
The noise emitted by a jet engine has many sources. These include, in the case of gas turbine engines, the fan, compressor, combustor, turbine and propelling jet/s.
The propelling jet produces jet noise which is caused by the violent mixing action of the high speed jet with the surrounding air. In the subsonic case the noise is produced by eddies and in the supersonic case by Mach waves. The sound power radiated from a jet varies with the jet velocity raised to the eighth power for velocities up to 2,000 ft/sec and varies with the velocity cubed above 2,000 ft/sec. Thus, the lower speed exhaust jets emitted from engines such as high bypass turbofans are the quietest, whereas the fastest jets, such as rockets, turbojets, and ramjets, are the loudest. For commercial jet aircraft the jet noise has reduced from the turbojet through bypass engines to turbofans as a result of a progressive reduction in propelling jet velocities. For example, the JT8D, a bypass engine, has a jet velocity of 1450 ft/sec whereas the JT9D, a turbofan, has jet velocities of 885 ft/sec (cold) and 1190 ft/sec (hot).
The advent of the turbofan replaced the very distinctive jet noise with another sound known as "buzz saw" noise. The origin is the shockwaves originating at the supersonic fan blades at takeoff thrust. | 1 | Applied and Interdisciplinary Chemistry |
Several types of atmospheric aerosol have a significant effect on Earth's climate: volcanic, desert dust, sea-salt, that originating from biogenic sources and human-made. Volcanic aerosol forms in the stratosphere after an eruption as droplets of sulfuric acid that can prevail for up to two years, and reflect sunlight, lowering temperature. Desert dust, mineral particles blown to high altitudes, absorb heat and may be responsible for inhibiting storm cloud formation. Human-made sulfate aerosols, primarily from burning oil and coal, affect the behavior of clouds.
Although all hydrometeors, solid and liquid, can be described as aerosols, a distinction is commonly made between such dispersions (i.e. clouds) containing activated drops and crystals, and aerosol particles. The atmosphere of Earth contains aerosols of various types and concentrations, including quantities of:
* natural inorganic materials: fine dust, sea salt, or water droplets
* natural organic materials: smoke, pollen, spores, or bacteria
* anthropogenic products of combustion such as: smoke, ashes or dusts
Aerosols can be found in urban ecosystems in various forms, for example:
* Dust
* Cigarette smoke
* Mist from aerosol spray cans
* Soot or fumes in car exhaust
The presence of aerosols in the Earth's atmosphere can influence its climate, as well as human health. | 0 | Theoretical and Fundamental Chemistry |
Revegetation is often used to join up patches of natural habitat that have been lost and can be a very important tool in places where much of the natural vegetation has been cleared. It is therefore particularly important in urban environments, and research in Brisbane has shown that revegetation projects can significantly improve urban bird populations. The Brisbane study showed that connecting a revegetation patch with existing habitat improved bird species richness, while simply concentrating on making large patches of habitat was the best way to increase bird abundance. Revegetation plans, therefore, need to consider how the revegetated sites are connected with existing habitat patches. Revegetation in agricultural areas can support breeding bird populations, but often it supports more common species, rather than those that are in decline. | 1 | Applied and Interdisciplinary Chemistry |
There are at least five hormones that aid and regulate the digestive system in mammals. There are variations across the vertebrates, as for instance in birds. Arrangements are complex and additional details are regularly discovered. Connections to metabolic control (largely the glucose-insulin system) have been uncovered.
* Gastrin – is in the stomach and stimulates the gastric glands to secrete pepsinogen (an inactive form of the enzyme pepsin) and hydrochloric acid. Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low pH.
* Secretin – is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver. This hormone responds to the acidity of the chyme.
* Cholecystokinin (CCK) – is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder. This hormone is secreted in response to fat in chyme.
* Gastric inhibitory peptide (GIP) – is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach. Another function is to induce insulin secretion.
* Motilin – is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin. | 1 | Applied and Interdisciplinary Chemistry |
Although selenium is an essential trace element, it is toxic if taken in excess. Exceeding the Tolerable Upper Intake Level of 400 micrograms per day can lead to selenosis. This 400 microgram (µg) Tolerable Upper Intake Level is based primarily on a 1986 study of five Chinese patients who exhibited overt signs of selenosis and a follow-up study on the same five people in 1992. The 1992 study actually found the maximum safe dietary Se intake to be approximately 800 micrograms per day (15 micrograms per kilogram body weight), but suggested 400 micrograms per day to not only avoid toxicity, but also to avoid creating an imbalance of nutrients in the diet and to account for data from other countries. In China, people who ingested corn grown in extremely selenium-rich stony coal (carbonaceous shale) have suffered from selenium toxicity. This coal was shown to have selenium content as high as 9.1%, the highest concentration in coal ever recorded in literature.
Symptoms of selenosis include a garlic odor on the breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage. Extreme cases of selenosis can result in cirrhosis of the liver, pulmonary edema, and death. Elemental selenium and most metallic selenides have relatively low toxicities because of their low bioavailability. By contrast, selenates and selenites are very toxic, having an oxidant mode of action similar to that of arsenic trioxide. The chronic toxic dose of selenite for humans is about 2400 to 3000 micrograms of selenium per day for a long time. Hydrogen selenide is an extremely toxic, corrosive gas. Selenium also occurs in organic compounds, such as dimethyl selenide, selenomethionine, selenocysteine and methylselenocysteine, all of which have high bioavailability and are toxic in large doses.
Selenium poisoning of water systems may result whenever new agricultural runoff courses through normally dry, undeveloped lands. This process leaches natural soluble selenium compounds (such as selenates) into the water, which may then be concentrated in new "wetlands" as the water evaporates. High selenium levels produced in this fashion have been found to have caused certain congenital disorders in wetland birds.
In fish and other wildlife, low levels of selenium cause deficiency while high levels cause toxicity. For example, in salmon, the optimal concentration of selenium in the fish tissue (whole body) is about 1 microgram selenium per gram of tissue (dry weight). At levels much below that concentration, young salmon die from selenium deficiency; much above that level they die from toxic excess. | 1 | Applied and Interdisciplinary Chemistry |
The long-term water management plan for the Mount Polley mine site has been approved by an independent statutory-decision maker from the Ministry of Environment and is expected to be fully in place by fall 2017 and will replace the short-term water management plan that has been in place since 30 November 2015.
Mount Polley Mining Corporation submitted its formal permit amendment application, which included the long-term water management plan and supporting Technical Assessment Report, in October 2016. The documents were subject to extensive public consultation, including First Nations and local communities. The application also underwent a full technical review from the Cariboo Mine Development Review Committee (CMDRC), which includes representatives from provincial and federal agencies, First Nations, local governments (City of Williams Lake and Cariboo Regional District), and the community of Likely.
The Mount Polley Mining Corporation (MPMC) treats mine site water with water treatment plant technology by Veolia prior to release into Quesnel lake. The water is monitored for turbidity at 15 second intervals and water quality is assessed at Quesnel lake as part of MPMCs Comprehensive Environmental Monitoring Plan. About 15,000 cubic meters of site water is discharged into Quesnel lake per day. This is below the 29,000 cubic meters threshold allowed under the mining corporations permit. The water at Quesnel lake, Quesnel river, Polley lake, and Hazeltine creek are regularly monitored by the Ministry of Environment. | 1 | Applied and Interdisciplinary Chemistry |
Safety pharmacology is a branch of pharmacology specialising in detecting and investigating potential undesirable pharmacodynamic effects of new chemical entities (NCEs) on physiological functions in relation to exposure in the therapeutic range and above.
Primary organ systems (so-called core battery systems) are:
* Central Nervous System
* Cardiovascular System
* Respiratory System
Secondary organ systems of interest are:
* Gastrointestinal System
* Renal System
Safety pharmacology studies are required to be completed prior to human exposure (i.e., Phase I clinical trials), and regulatory guidance is provided in ICH S7A and other documents. | 1 | Applied and Interdisciplinary Chemistry |
This is an example of a system with several phases, which at ordinary temperatures are two solids and a gas. There are three chemical species (CaCO, CaO and CO) and one reaction:
: CaCO CaO + CO.
The number of components is then 3 - 1 = 2. | 0 | Theoretical and Fundamental Chemistry |
Anodized aluminium surfaces that are not regularly cleaned are susceptible to panel edge staining, a unique type of surface staining that can affect the structural integrity of the metal. | 1 | Applied and Interdisciplinary Chemistry |
The microcystin-producing Microcystis is a genus of freshwater cyanobacteria and thrives in warm water conditions, especially in stagnant waters. The EPA predicted in 2013 that climate change and changing environmental conditions may lead to harmful algae growth and may negatively impact human health. Algal growth is also encouraged through the process of eutrophication (oversupply of nutrients). In particular, dissolved reactive phosphorus promotes algal growth.
Microcystins may have evolved as a way to deal with low iron supply in cyanobacteria: the molecule binds iron, and non-producing strains are significantly worse at coping with low iron levels. Low iron supply up-regulates McyD, one of the microcystin synthetic operons. Sufficient iron supply, however, can still boost microcystin production by making the bacterium better at photosynthesis, therefore producing sufficient ATP for MC biosynthesis.
Microcystin production is also positively correlated with temperature. Bright light and red light increases transcription of McyD, but blue light reduces it. A wide range of other factors such as pH may also affect MC production, but comparison is complicated due to a lack of standard testing conditions. | 1 | Applied and Interdisciplinary Chemistry |
Aluminium is sometimes used due to its low cost, resistance to corrosion and solvents, and its ductility. Aluminium tube is more desirable than steel for the conveyance of flammable solvents, since it cannot create sparks when manipulated. Aluminium tubing can be connected by flare or compression fittings, or it can be welded by the TIG or heliarc processes. | 1 | Applied and Interdisciplinary Chemistry |
The concentration of calcium in the cell nucleus can increase in response to signals from the environment. Nuclear calcium is an evolutionary conserved potent regulator of gene expression that allows cells to undergo long-lasting adaptive responses. The 'Nuclear Calcium Hypothesis’ by Hilmar Bading describes nuclear calcium in neurons as an important signaling end-point in synapse-to-nucleus communication that activates gene expression programs needed for persistent adaptations. In the nervous system, nuclear calcium is required for long-term memory formation, acquired neuroprotection, and the development of chronic inflammatory pain. In the heart, nuclear calcium is important for the development of cardiac hypertrophy. In the immune system, nuclear calcium is required for human T cell activation. Plants use nuclear calcium to control symbiosis signaling. | 1 | Applied and Interdisciplinary Chemistry |
STAT5 has been found to be constitutively phosphorylated in cancer cells, implying that the protein is always present in its active form. This constant activation is brought about either by mutations or by aberrant expressions of cell signalling, resulting in poor regulation, or complete lack of control, of the activation of transcription for genes influenced by STAT5. This leads to constant and increased expression of these genes. For example, mutations may lead to increased expression of anti-apoptotic genes, the products of which actively prevent cell death. The constant presence of these products preserves the cell in spite of it having become cancerous, causing the cell to eventually become malignant. | 1 | Applied and Interdisciplinary Chemistry |
Early in his career, Kai Simons pursued research in the field of medical biochemistry. Both his master's thesis and postgraduate research focused on vitamin B12 absorption. After returning from his post-doc scholarship he continued research on vitamin B12 as well as on blood plasma proteins, but soon started investigating Semliki Forest virus, focusing on its membrane and its lipid composition and their role in the virus budding and its transport, as the model for lipid and protein secretion. During this period, Simons also investigated the application of detergents in biochemistry with a special attention to their role in biological membrane research.
The virus lifecycle and how it uses components of vesicular pathways while shuttling to the cell surface, turned Simons' attention toward vesicular transport pathways and cell polarization. Applying epithelial model cells – MDCK (Madin-Darby canine kidney), he investigated lipid transport, protein sorting and their role in polarizing cells.
In these studies, he described the role of the trans-Golgi network (TGN) in protein and lipid sorting according to their destination. In his works from 1988, together with Gerit van Meer, Simons proposed the existence of lipid microdomains in cell membranes for the first time. Such microdomains differ in their composition from the surrounding membrane and have special functions. Simons coined the term lipid rafts to describe these microdomains. This concept was developed over the years to be presented more fully in 1997 in Nature journal by Simons and Ikonen. This paper became one of the most frequently cited works in the field of membrane research. Other Simons' paper, on role of lipid rafts in the signal transduction is second highest cited work and Simons is fourth highest cited scientist in the field of signal transduction. Kai Simons was also recognized by ISI Web of Knowledge, as one of the most cited scientist ever.
In subsequent years, Simons continued to work on the role of lipid rafts, and more generally lipids, in cell polarization and protein sorting. He was interested also in the role of lipids and protein sorting in neurodegenerative diseases, especially in Alzheimer's disease.
His scientific record includes more than 350 scientific articles, mostly in the field of biochemistry, molecular organization of the cell, and biochemistry and physiology of a cell membrane.
Considering his work from years 1996–2007 tracked until May 2009, Simons was 12. in the list of the most frequently cited scientists in the field cell biology with 90 articles and 16,299 citations. | 1 | Applied and Interdisciplinary Chemistry |
The basic method is that the valence V of an atom is the sum of the individual bond valences v surrounding the atom:
The individual bond valences in turn are calculated from the observed bond lengths.
R is the observed bond length, R is a tabulated parameter expressing the (ideal) bond length when the element i has exactly valence 1, and b is an empirical constant, typically 0.37 Å.
Another formula for has also been used: | 0 | Theoretical and Fundamental Chemistry |
The term "biological target" is frequently used in pharmaceutical research to describe the native protein in the body whose activity is modified by a drug resulting in a specific effect, which may be a desirable therapeutic effect or an unwanted adverse effect. In this context, the biological target is often referred to as a drug target. The most common drug targets of currently marketed drugs include:
* proteins
** G protein-coupled receptors (target of 50% of drugs)
** enzymes (especially protein kinases, proteases, esterases, and phosphatases)
** ion channels
*** ligand-gated ion channels
*** voltage-gated ion channels
** nuclear hormone receptors
** structural proteins such as tubulin
** membrane transport proteins
* nucleic acids | 1 | Applied and Interdisciplinary Chemistry |
SAMs are an inexpensive and versatile surface coating for applications including control of wetting and adhesion, chemical resistance, bio compatibility, sensitization, and molecular recognition for sensors and nano fabrication. Areas of application for SAMs include biology, electrochemistry and electronics, nanoelectromechanical systems (NEMS) and microelectromechanical systems (MEMS), and everyday household goods. SAMs can serve as models for studying membrane properties of cells and organelles and cell attachment on surfaces. SAMs can also be used to modify the surface properties of electrodes for electrochemistry, general electronics, and various NEMS and MEMS. For example, the properties of SAMs can be used to control electron transfer in electrochemistry. They can serve to protect metals from harsh chemicals and etchants. SAMs can also reduce sticking of NEMS and MEMS components in humid environments. In the same way, SAMs can alter the properties of glass. A common household product, Rain-X, utilizes SAMs to create a hydrophobic monolayer on car windshields to keep them clear of rain. Another application is an anti-adhesion coating on nanoimprint lithography (NIL) tools and stamps. One can also coat injection molding tools for polymer replication with a Perfluordecyltrichlorosilane SAM.
Thin film SAMs can also be placed on nanostructures. In this way they functionalize the nanostructure. This is advantageous because the nanostructure can now selectively attach itself to other molecules or SAMs. This technique is useful in biosensors or other MEMS devices that need to separate one type of molecule from its environment. One example is the use of magnetic nanoparticles to remove a fungus from a blood stream. The nanoparticle is coated with a SAM that binds to the fungus. As the contaminated blood is filtered through a MEMS device the magnetic nanoparticles are inserted into the blood where they bind to the fungus and are then magnetically driven out of the blood stream into a nearby laminar waste stream. | 0 | Theoretical and Fundamental Chemistry |
Due to the difficulty of C-C activation, a driving force is required to facilitate the reaction. One common strategy is to form stable metal complexes. One example is reported by Milstein and coworkers, in which the C(sp)–C(sp) bond of bisphosphine ligands was selectively cleaved by a number of metals to afford stable pincer complexes under mild conditions.
Aromatization is another driving force that is utilized for C–C bond activation. For example, Chaudret group reported that the C–C bond of steroid compounds can be cleaved through the Ru-promoted aromatization of the B ring. At the same time, a methane molecule is released, which is possibly another driving force for this reaction.
In addition, the metalloradical has also been proven to have the ability to cleave the C–C single bond. Chan group reported the C–C bond scission of cyclooctane via 1,2-addition with Rh(III) porphyrin hydride, which involved [Rh(ttp)]· radical as the key intermediate. | 0 | Theoretical and Fundamental Chemistry |
Mechanical screening, often just called screening, is the practice of taking granulated or crushed ore material and separating it into multiple grades by particle size.
This practice occurs in a variety of industries such as mining and mineral processing, agriculture, pharmaceutical, food, plastics, and recycling.
A method of separating solid particles according to size alone is called screening. | 1 | Applied and Interdisciplinary Chemistry |
Growing algae as a source of biofuel has also been shown to have numerous environmental benefits, and has presented itself as a much more environmentally friendly alternative to current biofuels. For one, it is able to utilize run-off, water contaminated with fertilizers and other nutrients that are a by-product of farming, as its primary source of water and nutrients. Because of this, it prevents this contaminated water from mixing with the lakes and rivers that currently supply our drinking water. In addition to this, the ammonia, nitrates, and phosphates that would normally render the water unsafe actually serve as excellent nutrients for the algae, meaning that fewer resources are needed to grow the algae. Many algae species used in biodiesel production are excellent bio-fixers, meaning they are able to remove carbon dioxide from the atmosphere to use as a form of energy for themselves. Because of this, they have found use in industry as a way to treat flue gases and reduce GHG emissions. | 1 | Applied and Interdisciplinary Chemistry |
Several cities in Poland have implemented policies and incentives to encourage the installation of green roofs, including Warsaw, Krakow, and Wroclaw. These policies have helped to increase the adoption of green roofs in the country, particularly in urban areas, where they are seen as an important tool for mitigating the environmental impacts of urbanization and improving the quality of life for city residents. The University of Warsaw green roof is one of the most impressive and well-known examples of green roofs in Poland. It covers an area of approximately 10,000 square meters and includes over 30,000 plants from more than 70 different species. | 1 | Applied and Interdisciplinary Chemistry |
In outer sphere redox reactions no bonds are formed or broken; only an electron transfer (ET) takes place. A quite simple example is the Fe/Fe redox reaction, the self exchange reaction which is known to be always occurring in an aqueous solution containing the aquo complexes [Fe(HO)] and [Fe(HO)6]. Redox occurs with Gibbs free reaction energy .
From the reaction rates temperature dependence an activation energy is determined, and this activation energy is interpreted as the energy of the transition state in a reaction diagram. The latter is drawn, according to Arrhenius and Eyring, as an energy diagram with the reaction coordinate as the abscissa. The reaction coordinate describes the minimum energy path from the reactants to the products, and the points of this coordinate are combinations of distances and angles between and in the reactants in the course of the formation and/or cleavage of bonds. The maximum of the energy diagram, the transition state, is characterized by a specific configuration of the atoms. Moreover, in Eyrings TST a quite specific change of the nuclear coordinates is responsible for crossing the maximum point, a vibration in this direction is consequently treated as a translation.
For outer sphere redox reactions there cannot be such a reaction path, but nevertheless one does observe an activation energy. The rate equation for activation-controlled reactions has the same exponential form as the Eyring equation,
is the Gibbs free energy of the formation of the transition state, the exponential term represents the probability of its formation, A contains the probability of crossing from precursor to successor complex. | 0 | Theoretical and Fundamental Chemistry |
* The 1967 novel Landslide by Desmond Bagley, tells the story of a quick-clay landslide in Canada. The book was also adapted into a 1992 television film by the same name, directed by Jean-Claude Lord, and starring Anthony Edwards. | 0 | Theoretical and Fundamental Chemistry |
Reductions with hydrosilanes are methods used for hydrogenation and hydrogenolysis of organic compounds. The approach is a subset of ionic hydrogenation. In this particular method, the substrate is treated with a hydrosilane and auxiliary reagent, often a strong acid, resulting in formal transfer of hydride from silicon to carbon. This style of reduction with hydrosilanes enjoys diverse if specialized applications. | 0 | Theoretical and Fundamental Chemistry |
α-Keggin anions have been used as catalyst in the following reactions: hydration, polymerization and oxidation reaction as catalysts. Japanese chemical companies have commercialized the use of the compounds in hydration of propene, oxidation of methacrolein, hydration of isobutene and n-butene, and polymerization of THF. | 0 | Theoretical and Fundamental Chemistry |
A heterogeneous electrocatalyst is one that is present in a different phase of matter from the reactants, for example, a solid surface catalyzing a reaction in solution. Different types of heterogeneous electrocatalyst materials are shown above in green. Since heterogeneous electrocatalytic reactions need an electron transfer between the solid catalyst (typically a metal) and the electrolyte, which can be a liquid solution but also a polymer or a ceramic capable of ionic conduction, the reaction kinetics depend on both the catalyst and the electrolyte as well as on the interface between them. The nature of the electrocatalyst surface determines some properties of the reaction including rate and selectivity. | 0 | Theoretical and Fundamental Chemistry |
Hollow cathode lamps (HCL) are the most common radiation source in LS AAS. Inside the sealed lamp, filled with argon or neon gas at low pressure, is a cylindrical metal cathode containing the element of interest and an anode. A high voltage is applied across the anode and cathode, resulting in an ionization of the fill gas. The gas ions are accelerated towards the cathode and, upon impact on the cathode, sputter cathode material that is excited in the glow discharge to emit the radiation of the sputtered material, i.e., the element of interest. In the majority of cases single element lamps are used, where the cathode is pressed out of predominantly compounds of the target element. Multi-element lamps are available with combinations of compounds of the target elements pressed in the cathode. Multi element lamps produce slightly less sensitivity than single element lamps and the combinations of elements have to be selected carefully to avoid spectral interferences. Most multi-element lamps combine a handful of elements, e.g.: 2 - 8. Atomic Absorption Spectrometers can feature as few as 1-2 hollow cathode lamp positions or in automated multi-element spectrometers, a 8-12 lamp positions may be typically available. | 0 | Theoretical and Fundamental Chemistry |
The specific activity of an enzyme is another common unit. This is the activity of an enzyme per milligram of total protein (expressed in μmol min mg). Specific activity gives a measurement of enzyme purity in the mixture. It is the micro moles of product formed by an enzyme in a given amount of time (minutes) under given conditions per milligram of total proteins. Specific activity is equal to the rate of reaction multiplied by the volume of reaction divided by the mass of total protein. The SI unit is katal/kg, but a more practical unit is μmol/mgmin.
Specific activity is a measure of enzyme processivity (the capability of enzyme to be processed), at a specific (usually saturating) substrate concentration, and is usually constant for a pure enzyme.
An active site titration process can be done for the elimination of errors arising from differences in cultivation batches and/or misfolded enzyme and similar issues. This is a measure of the amount of active enzyme, calculated by e.g. titrating the amount of active sites present by employing an irreversible inhibitor. The specific activity should then be expressed as μmol min mg active enzyme. If the molecular weight of the enzyme is known, the turnover number, or μmol product per second per μmol of active enzyme, can be calculated from the specific activity. The turnover number can be visualized as the number of times each enzyme molecule carries out its catalytic cycle per second. | 1 | Applied and Interdisciplinary Chemistry |
Between the three variants of the AnMBR, there are many factors that weigh into their industrial use.
Cost: The submerged AnMBR variant is the most cost-effective due to the low negative pressure requirements. In addition, the liquid does not need to be pumped into an external chamber to go through the filtration process. Due to both of these characteristics of the submerged AnMBR, it has a lower energy requirement, therefore costing less to operate than the external AnMBR variants.
Operability: The external AnMBR/ external submerged AnMBR variants are the most advantageous in terms of operability. In these variants, less membrane fouling occurs, and therefore these variants are functional for long periods of time. Additionally, due to the two units being separated, they are much simpler to clean when compared with the submerged AnMBR.
Size: While one of the main overall advantages of the AnMBR is its relatively compact size, the submerged AnMBR variant is the most compact of the three, keeping all of its operations within a single unit.
Despite the disadvantages that the submerged AnMBR harbors in terms of operability, its cost and size are both desirable traits to companies, subsequently making it the frequented variant in the industry. | 1 | Applied and Interdisciplinary Chemistry |
Plastocyanin is an electron carrier that transfers the electron from cytochrome b6f to the P700 cofactor of PSI in its ionized state P700. | 0 | Theoretical and Fundamental Chemistry |
Ferritin concentrations increase drastically in the presence of an infection or cancer. Endotoxins are an up-regulator of the gene coding for ferritin, thus causing the concentration of ferritin to rise. By contrast, organisms such as Pseudomonas, although possessing endotoxin, cause plasma ferritin levels to drop significantly within the first 48 hours of infection. Thus, the iron stores of the infected body are denied to the infective agent, impeding its metabolism. | 1 | Applied and Interdisciplinary Chemistry |
BEI is very hazardous since it attacks nucleic acids and proteins as described above. It can be neutralised by sodium thiosulfate; the thiosulfate is a nucleophile which opens the three-membered ring.
The presence of BEI can be tested for using silver nitrate solution. | 0 | Theoretical and Fundamental Chemistry |
The Permian–Triassic extinction event, triggered by runaway from the Siberian Traps, was marked by ocean deoxygenation.
The boundary between the Ordovician and Silurian periods is marked by repetitive periods of anoxia, interspersed with normal, oxic conditions. In addition, anoxic periods are found during the Silurian. These anoxic periods occurred at a time of low global temperatures (although levels were high), in the midst of a glaciation.
Jeppsson (1990) proposes a mechanism whereby the temperature of polar waters determines the site of formation of downwelling water. If the high latitude waters are below , they will be dense enough to sink; as they are cool, oxygen is highly soluble in their waters, and the deep ocean will be oxygenated. If high latitude waters are warmer than , their density is too low for them to sink below the cooler deep waters. Therefore, thermohaline circulation can only be driven by salt-increased density, which tends to form in warm waters where evaporation is high. This warm water can dissolve less oxygen, and is produced in smaller quantities, producing a sluggish circulation with little deep water oxygen. The effect of this warm water propagates through the ocean, and reduces the amount of that the oceans can hold in solution, which makes the oceans release large quantities of into the atmosphere in a geologically short time (tens or thousands of years). The warm waters also initiate the release of clathrates, which further increases atmospheric temperature and basin anoxia. Similar positive feedbacks operate during cold-pole episodes, amplifying their cooling effects.
The periods with cold poles are termed "P-episodes" (short for primo), and are characterised by bioturbated deep oceans, a humid equator and higher weathering rates, and terminated by extinction events—for example, the Ireviken and Lau events. The inverse is true for the warmer, oxic "S-episodes" (secundo), where deep ocean sediments are typically graptolitic black shales.
A typical cycle of secundo-primo episodes and ensuing event typically lasts around 3 Ma.
The duration of events is so long compared to their onset because the positive feedbacks must be overwhelmed. Carbon content in the ocean-atmosphere system is affected by changes in weathering rates, which in turn is dominantly controlled by rainfall. Because this is inversely related to temperature in Silurian times, carbon is gradually drawn down during warm (high ) S-episodes, while the reverse is true during P-episodes. On top of this gradual trend is overprinted the signal of Milankovic cycles, which ultimately trigger the switch between P- and S- episodes.
These events become longer during the Devonian; the enlarging land plant biota probably acted as a large buffer to carbon dioxide concentrations.
The end-Ordovician Hirnantian event may alternatively be a result of algal blooms, caused by sudden supply of nutrients through wind-driven upwelling or an influx of nutrient-rich meltwater from melting glaciers, which by virtue of its fresh nature would also slow down oceanic circulation. | 0 | Theoretical and Fundamental Chemistry |
The Protein Information Resource (PIR), located at Georgetown University Medical Center, is an integrated public bioinformatics resource to support genomic and proteomic research, and scientific studies. It contains protein sequences databases | 1 | Applied and Interdisciplinary Chemistry |
m + n + o + p − q = 2 + 20 + 0 + 0 + 0 = 22 SEPs are required; 16 BH units provide 16 pairs; four shared boron atoms provide 6 pairs, which describes why is stable as a neutral species. | 0 | Theoretical and Fundamental Chemistry |
The biogeography of Southern Ocean phytoplankton controls the local biogeochemistry and the export of macronutrients to lower latitudes and depth. Of particular relevance is the competitive interaction between coccolithophores and diatoms, with the former being prevalent along the Great Calcite Belt (40–60°S), while diatoms tend to dominate the regions south of 60°S, as illustrated in the diagram on the right.
The ocean is changing at an unprecedented rate as a consequence of increasing anthropogenic CO emissions and related climate change. Changes in density stratification and nutrient supply, as well as ocean acidification, lead to changes in phytoplankton community composition and consequently ecosystem structure and function. Some of these changes are already observable today and may have cascading effects on global biogeochemical cycles and oceanic carbon uptake. Changes in Southern Ocean (SO) biogeography are especially critical due to the importance of the Southern Ocean in fuelling primary production at lower latitudes through the lateral export of nutrients and in taking up anthropogenic CO. For the carbon cycle, the ratio of calcifying and noncalcifying phytoplankton is crucial due to the counteracting effects of calcification and photosynthesis on seawater pCO, which ultimately controls CO exchange with the atmosphere, and the differing ballasting effect of calcite and silicic acid shells for organic carbon export.
Calcifying coccolithophores and silicifying diatoms are globally ubiquitous phytoplankton functional groups. Diatoms are a major contributor to global phytoplankton biomass and annual net primary production. In comparison, coccolithophores contribute less to biomass and to global NPP.
However, coccolithophores are the major phytoplanktonic calcifier. thereby significantly impacting the global carbon cycle. Diatoms dominate the phytoplankton community in the Southern Ocean, but coccolithophores have received increasing attention in recent years. Satellite imagery of particulate inorganic carbon (PIC, a proxy for coccolithophore abundance) revealed the "Great Calcite Belt", an annually reoccurring circumpolar band of elevated PIC concentrations between 40 and 60°S. In situ observations confirmed coccolithophore abundances of up to 2.4×10 cells mL in the Atlantic sector (blooms on the Patagonian Shelf), up to 3.8×10 cells mL in the Indian sector, and up to 5.4×10 cells mL in the Pacific sector of the Southern Ocean with Emiliania huxleyi being the dominant species. However, the contribution of coccolithophores to total Southern Ocean phytoplankton biomass and NPP has not yet been assessed. Locally, elevated coccolithophore abundance in the GCB has been found to turn surface waters into a source of CO for the atmosphere, emphasising the necessity to understand the controls on their abundance in the Southern Ocean in the context of the carbon cycle and climate change. While coccolithophores have been observed to have moved polewards in recent decades, their response to the combined effects of future warming and ocean acidification is still subject to debate. As their response will also crucially depend on future phytoplankton community composition and predator–prey interactions, it is essential to assess the controls on their abundance in today's climate. | 0 | Theoretical and Fundamental Chemistry |
The Belgian Society of Biochemistry and Molecular Biology (BMB) is a Belgian non-profit organization, concerned with biochemistry and molecular biology.
The BMB was created, based on an initiative of Marcel Florkin, so a Belgian society could join the new International Union of Biochemistry. The first charter of the society was drafted by Edouard J. Bigwood, Jean Brachet, Christian de Duve, Marcel Florkin, Lucien Massart, Paul Putzeys, Laurent Vandendriessche and Claude Lièbecq. The first general assembly was held on 12 January 1952, and the first President of the society was Marcel Florkin, with Claude Lièbecq as secretary and treasurer. | 1 | Applied and Interdisciplinary Chemistry |
Magnesium oxalate can by synthesized by combining a magnesium salt or ion with an oxalate.
: Mg + CO → MgCO
A specific example of a synthesis would be mixing Mg(NO) and KOH and then adding that solution to dimethyl oxalate, (COOCH).
When heated, magnesium oxalate will decompose. First, the dihydrate will decompose at 150 °C into the anhydrous form.
: MgCO•2HO → MgCO + 2 HO
With additional heating the anhydrous form will decompose further into magnesium oxide and carbon oxides between 420 °C and 620 °C. First, carbon monoxide and magnesium carbonate form. The carbon monoxide then oxidizes to carbon dioxide, and the magnesium carbonate decomposes further to magnesium oxide and carbon dioxide.
: MgCO → MgCO + CO
: CO + 1/2 O → CO
: MgCO → MgO + CO
Magnesium oxalate dihydrate has also been used in the synthesis of nano sized particles of magnesium oxide, which have larger surface are to volume ratio than conventionally synthesized particles and are optimal for various applications, such as in catalysis. By using a sol-gel synthesis, which involves combining a magnesium salt, in this case magnesium oxalate, with a gelating agent, nano sized particles of magnesium oxide can be produced. | 0 | Theoretical and Fundamental Chemistry |
The general location of the proton drip line is well established. For all elements occurring naturally on earth and having an odd number of protons, at least one species with a proton separation energy less than zero has been experimentally observed. Up to germanium, the location of the drip line for many elements with an even number of protons is known, but none past that point are listed in the evaluated nuclear data. There are a few exceptional cases where, due to nuclear pairing, there are some particle-bound species outside the drip line, such as B and Au. One may also note that nearing the magic numbers, the drip line is less understood. A compilation of the first unbound nuclei known to lie beyond the proton drip line is given below, with the number of protons, Z and the corresponding isotopes, taken from the National Nuclear Data Center. | 0 | Theoretical and Fundamental Chemistry |
* 2021 Royal Society Elected fellow
* 2018 Gesellschaft Deutscher Chemiker Otto Roelen Medal
* 2017 UK Catalysis Hub Sir John Meurig Thomas Catalysis Medal
* 2016 Royal Society of Chemistry Corday-Morgan Prize
* 2015 WISE Campaign Research Award
* 2011 Bio-Environmental Polymer Society Outstanding Young Scientist Award
* 2009 Royal Society of Chemistry Energy, Environment and Sustainability Early Career Award
* 2005 Royal Society of Chemistry Meldola Medal and Prize
* 2001 Royal Society of Chemistry Laurie Verangno Award
Williams was appointed Officer of the Order of the British Empire (OBE) in the 2020 Birthday Honours for services to chemistry. | 0 | Theoretical and Fundamental Chemistry |
Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells. LDH catalyzes the conversion of pyruvate to lactate and back, as it converts NAD to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one molecule to another.
LDH exists in four distinct enzyme classes. This article is specifically about the NAD(P)-dependent -lactate dehydrogenase. Other LDHs act on -lactate and/or are dependent on cytochrome c: D-lactate dehydrogenase (cytochrome) and L-lactate dehydrogenase (cytochrome).
LDH is expressed extensively in body tissues, such as blood cells and heart muscle. Because it is released during tissue damage, it is a marker of common injuries and disease such as heart failure. | 1 | Applied and Interdisciplinary Chemistry |
A high concentration of biomass allows for microbes such as nitrifiers, denitrifiers, phosphorus accumulating organisms, and denitrifying phosphorus accumulating organisms to effectively treat domestic wastewater. Carbon source is of vital importance to biological phosphorus removal due to the availability of volatile fatty acids, which ultimately shape the compositions of phosphorus accumulating organisms. Recent studies revealed that adding glucose as a carbon source can reduce diversity in the microbial community. Glucose was more favorable for accumulation of nitrite oxidizing bacteria than Ammonia Oxidizing bacteria in contrast with sodium acetate. This study suggested that mixed carbon source by sodium acetate and glucose might act as a strategy to adjust the microbial community compositions within the simultaneous nitrification, denitrification and phosphorus removal system. | 1 | Applied and Interdisciplinary Chemistry |
The discreteness condition means that there is some positive real number ε, such that for every translation T in the group, the vector v has length at least ε (except of course in the case that v is the zero vector, but the independent translations condition prevents this, since any set that contains the zero vector is linearly dependent by definition and thus disallowed).
The purpose of this condition is to ensure that the group has a compact fundamental domain, or in other words, a "cell" of nonzero, finite area, which is repeated through the plane. Without this condition, one might have for example a group containing the translation T for every rational number x, which would not correspond to any reasonable wallpaper pattern.
One important and nontrivial consequence of the discreteness condition in combination with the independent translations condition is that the group can only contain rotations of order 2, 3, 4, or 6; that is, every rotation in the group must be a rotation by 180°, 120°, 90°, or 60°. This fact is known as the crystallographic restriction theorem, and can be generalised to higher-dimensional cases. | 0 | Theoretical and Fundamental Chemistry |
*Antibiotics
Disrupt growth and development and reduce longevity of adults e.g. toxins or digestibility reducing factors.
*Antixenotics
Disrupt normal host selection behaviour e.g. Repellents, suppressants, locomotory excitants. | 1 | Applied and Interdisciplinary Chemistry |
The molecular formula HNO (molar mass: 62.03 g/mol) may refer to:
* Hyponitrite ion
* Hyponitrous acid
* Nitramide | 0 | Theoretical and Fundamental Chemistry |
Selegiline is metabolized by cytochrome P450 to -desmethylselegiline and levomethamphetamine. Desmethylselegiline has some activity against MAO-B, but much less than that of selegiline. It is thought to be further metabolized by CYP2C19. Levomethamphetamine (the less potent of the two enantiomers of methamphetamine) is converted to levoamphetamine (the less potent of the two enantiomers of amphetamine, with regards to psychological effects).
Due to the presence of these metabolites, people taking selegiline may test positive for "amphetamine" or "methamphetamine" on drug screening tests. While the amphetamine metabolites may contribute to selegiline's ability to inhibit reuptake of the neurotransmitters dopamine and norepinephrine, they have also been associated with orthostatic hypotension and hallucinations. The recovery of selegiline from urine is high at 87%, which has caused some researchers to question the clinical relevance of its amphetamine metabolites. The amphetamine metabolites are hydroxylated and, in phase II, conjugated by glucuronyltransferase.
A newer anti-Parkinson MAO-B inhibitor, rasagiline, metabolizes into 1(R)-aminoindan, which has no amphetamine-like characteristics. | 0 | Theoretical and Fundamental Chemistry |
These second generation mTOR inhibitors bind to ATP-binding site in mTOR kinase domain required for the functions of both mTORC1 and mTORC2, and result in downregulation of mTOR signaling pathway. Due to PI3K and mTORC2 ability to regulate AKT phosphorylation, these two compounds play a key role in minimizing the feedback activation of AKT. | 1 | Applied and Interdisciplinary Chemistry |
Substantial intensity of ultrasound and high ultrasonic vibration amplitudes are required for many processing applications, such as nano-crystallization, nano-emulsification, deagglomeration, extraction, cell disruption, as well as many others. Commonly, a process is first tested on a laboratory scale to prove feasibility and establish some of the required ultrasonic exposure parameters. After this phase is complete, the process is transferred to a pilot (bench) scale for flow-through pre-production optimization and then to an industrial scale for continuous production. During these scale-up steps, it is essential to make sure that all local exposure conditions (ultrasonic amplitude, cavitation intensity, time spent in the active cavitation zone, etc.) stay the same. If this condition is met, the quality of the final product remains at the optimized level, while the productivity is increased by a predictable "scale-up factor". The productivity increase results from the fact that laboratory, bench and industrial-scale ultrasonic processor systems incorporate progressively larger ultrasonic horns, able to generate progressively larger high-intensity cavitation zones and, therefore, to process more material per unit of time. This is called "direct scalability". It is important to point out that increasing the power capacity of the ultrasonic processor alone does not result in direct scalability, since it may be (and frequently is) accompanied by a reduction in the ultrasonic amplitude and cavitation intensity. During direct scale-up, all processing conditions must be maintained, while the power rating of the equipment is increased in order to enable the operation of a larger ultrasonic horn.
Finding the optimum operation condition for this equipment is a challenge for process engineers and needs deep knowledge about side effects of ultrasonic processors. | 1 | Applied and Interdisciplinary Chemistry |
Also more complex azeotropes exist, which comprise both a minimum-boiling and a maximum-boiling point. Such a system is called a double azeotrope, and will have two azeotropic compositions and boiling points. An example is water and N-methylethylenediamine as well as benzene and hexafluorobenzene. | 1 | Applied and Interdisciplinary Chemistry |
Cells metabolize DHA to 17S-hydroperoxy-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid (17-HpDHA) and then rapidly reduce this hydroperoxide to 17S-hydroxy-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid (17-HDHA) and similarly metabolize DHA to 13S-hydroperoxy-4Z,7Z,10Z,14Z,16Z,19Z-docosahexaenoic acid (13-HpDHA) and then to 13S-hydroxy-4Z,7Z,10Z,14Z,16Z,19Z-docosahexaenoic acid (13-HDHA). 17-HDHA exhibits potent in vitro as well as in vivo (animal model) anti-inflammatory activity while 17-HpDHA and to a lesser extent 17-HDHA inhibit the growth of cultured human breast cancer cells. Other SPM docosanoids, e.g. RvD1 and RvD2, have anti-growth effects against cancer cells in animal models. | 1 | Applied and Interdisciplinary Chemistry |
The molecule displays P(═O)H to P–OH tautomerism similar to that of phosphorous acid; the P(═O) form is strongly favoured.
HPA is usually supplied as a 50% aqueous solution and heating at low temperatures (up to about 90°C) prompts it to react with water to form phosphorous acid and hydrogen gas.
: HPO + HO → HPO + H
Heating above 110°C causes hypophosphorous acid to undergo disproportionation to give phosphorous acid and phosphine.
: 3 HPO → 2 HPO + PH | 0 | Theoretical and Fundamental Chemistry |
Moving bed biofilm reactors have shown promising results to remove micropollutations (MPs) from wastewater. MPs fall into several groups of chemicals such as pharmaceuticals, organophosphorus pesticides (OPs), care products and endocrine disruptors. A 2012 article reported described the use of MBBR technology to remove pharmaceuticals such as beta-blockers, analgesics, anti-depressants, and antibiotics from hospital wastewater. Moreover, application of MBBR as a biological technique combined with chemical treatment has attracted a great deal of attention for removal of organophosphorous pesticide from wastewater. The advantage of MBBRs can be associated with its high solid retention time, which allows the proliferation of slow-growing microbial communities with multiple functions in biofilms. The dynamics of such microbial communities greatly depends on organic loading in MBBR systems.
Moving bed biofilm reactors can efficiently treat hospital wastewater and remove pharmaceutical micropollutants. A 2023 study has shown that a strictly anaerobic MBBR, combined with an aerobic biofilm reactor can achieve high removal rates of pharmaceuticals, such as metronidazole, trimethoprim, sulfamethoxazole, and valsartan. | 1 | Applied and Interdisciplinary Chemistry |
Methylations are commonly performed using electrophilic methyl sources such as iodomethane, dimethyl sulfate, dimethyl carbonate, or tetramethylammonium chloride. Less common but more powerful (and more dangerous) methylating reagents include methyl triflate, diazomethane, and methyl fluorosulfonate (magic methyl). These reagents all react via S2 nucleophilic substitutions. For example, a carboxylate may be methylated on oxygen to give a methyl ester; an alkoxide salt may be likewise methylated to give an ether, ; or a ketone enolate may be methylated on carbon to produce a new ketone.
The Purdie methylation is a specific for the methylation at oxygen of carbohydrates using iodomethane and silver oxide. | 0 | Theoretical and Fundamental Chemistry |
The human hNanog protein coded by the NANOG gene, consists of 305 amino acids and possesses 3 functional domains: the N-terminal domain, the C- terminal domain, and the conserved homeodomain motif. The homeodomain region facilitates DNA binding. The NANOG is located on chromosome 12, and the mRNA contains a 915 bp open reading frame (ORF) with 4 exons and 3 introns.
The N-terminal region of hNanog is rich in serine, threonine and proline residues, and the C-terminus contains a tryptophan-rich domain. The homeodomain in hNANOG ranges from residues 95 to 155. There are also additional NANOG genes (NANOG2, NANOG p8) which potentially affect ESCs differentiation. Scientists have shown that NANOG' is fundamental for self-renewal and pluripotency, and NANOG p8 is highly expressed in cancer cells. | 1 | Applied and Interdisciplinary Chemistry |
Impregnation is, in essence, the converse of extraction. A substance is dissolved in the supercritical fluid, the solution flowed past a solid substrate, and is deposited on or dissolves in the substrate. Dyeing, which is readily carried out on polymer fibres such as polyester using disperse (non-ionic) dyes, is a special case of this. Carbon dioxide also dissolves in many polymers, considerably swelling and plasticising them and further accelerating the diffusion process. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.