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In addition to simple oxidation of aromatic rings to form carbonyl compounds (see ), trifluoroperacetic acid can fully cleave the carbon–carbon bonds within the ring. Unlike other oxidations of alkylaromatic structures, which yield benzoic acids and related compounds by cleavage of the alkyl chain at the reactive benzylic position, trifluoroperacetic acid causes an "inverse oxidation", cleaving the aromatic ring itself while leaving the alkyl group intact.
This selectivity for certain types of bonds allows it to be used to decompose complex mixtures of hydrocarbons, such as coal, in order to determine structural details.
Aromatic systems containing heteroatoms are resistant to this ring-opening as heteroatom oxidation occurs preferentially and deactivates the ring towards electrophilic attack by the peroxy acid. For example, purines, pyridines, and quinolines instead form N-oxides, while sulfur systems like octafluorodibenzothiophene are converted to sulfones.
Aromatic systems with ring-activating substituents can be oxidised to form phenols instead of undergoing a ring-opening reaction. Mesitylene, for example, reacts with trifluoroperacetic acid to form mesitol (2,4,6-trimethylphenol). Researchers attempting to form a lactone by Baeyer–Villiger oxidation of 7-oxodeacetamidocolchicine were unable to prepare the desired product, but did achieve oxidation of the aromatic ring to produce a phenol-derivative in high yield: | 0 | Theoretical and Fundamental Chemistry |
Ethylene receptors are functionally similar to bacterial two-component system which has two activation sites named response regulator and histidine kinase. The cytoplasmic carboxy-terminal part of ethylene receptor is similar in amino acid sequence to these response regulator and histidine kinase in bacteria; although the N-terminal region is altogether different. Such genetic and protein relationships indicate that receptors and bacterial two-component receptors as well as phytochromes and cytokinin receptors in plants evolved from and were acquired by plants from a cyanobacterium that gave rise to plastids, the power organelles in plants and protists.
Phylogenetic analysis also shows the common origin of the ethylene receptor in plants and ethylene-binding domain in cyanobacteria. In 2016, Randy F. Lacey and Brad M. Binder at the University of Tennessee discovered that a cyanobacterium, Synechocystis sp. PCC 6803 response to ethylene signal and has a functional ethylene receptor, which they named Synechocystis Ethylene Response1 (SynEtr1). They further showed that SynEtr1 acts similar to plant ethylene receptor in binding ethylene, indicating the origin of ethylene receptor from Synechocystis-related cyanobacterium. The functional difference however is that kinase activity is not compulsory for ethylene binding in plants, but is the key role of SynEtr1. | 1 | Applied and Interdisciplinary Chemistry |
A conjugate vaccine is a type of vaccine which combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen. | 1 | Applied and Interdisciplinary Chemistry |
The Gaia hypothesis posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. The hypothesis contends that this system as a whole, called Gaia, seeks a physical and chemical environment optimal for contemporary life.
Gaia evolves through a cybernetic feedback system operated by the biota, leading to broad stabilization of the conditions of habitability in a full homeostasis. Many processes in the Earths surface, essential for the conditions of life, depend on the interaction of living forms, especially microorganisms, with inorganic elements. These processes establish a global control system that regulates Earths surface temperature, atmosphere composition and ocean salinity, powered by the global thermodynamic disequilibrium state of the Earth system.
The existence of a planetary homeostasis influenced by living forms had been observed previously in the field of biogeochemistry, and it is being investigated also in other fields like Earth system science. The originality of the Gaia hypothesis relies on the assessment that such homeostatic balance is actively pursued with the goal of keeping the optimal conditions for life, even when terrestrial or external events menace them. | 0 | Theoretical and Fundamental Chemistry |
The thin sidewall Geiger-Mueller (GM) tube enclosed within the brass probe body detects beta radiation and gamma radiation with the detecting probe's beta shield open, or gamma only when the shield is closed. The brass body of the probe has an energy-compensation effect on the readings taken from the probe, reducing the over-reporting of events from low-energy gamma radiation as can be encountered with non-compensated GM probes.
In the case of the common Victoreen 6A model, the tube employed in the probe is an EON 62l0, of metal construction and halogen-quenched. It is sensitive to both gamma and hard beta radiation. The tube is approximately 90 mm long, has a diameter of 8.5 mm and operates at a relatively high voltage of 900 volts. The choice of this tube is intended to strike a balance between sensitivity and ruggedness and detects gamma radiation at energy levels of between 20 and 1000 Kev. The analogue dial is calibrated in both milliroentgens per hour and Counts Per Minute (CPM). When new and in calibration, these units can be expected to deliver accuracy to within +/− 10%. There are 3 possible scales of reading:
* x1 (0–0.5 mR/h or 0–300 C/m)
* x10 (0–5 mR/h or 0–3000 C/m)
* x100 (0–50 mR/h or 0–30000 C/m)
A drop-in replacement for the EON 6210 or the 6993 tube is the LND 720, manufactured by LND, Inc. of New York, USA.
A small number of CD V-700s were modified by the addition of a much larger end-window probe to detect alpha radiation in addition to betas and gammas and which operated at considerably lower voltages, resulting to changes in the high voltage electronics. These units were redesignated as the CD V-700M and were issued on the basis of six units per state emergency management agency. Their primarily intended use was for detecting and cleaning up low-level radioactive contamination in state RADEF calibration laboratories, though they could be used to detect alpha radiation in the field, if needed. | 0 | Theoretical and Fundamental Chemistry |
The root ar- is used in organic chemistry to form classification names for classes of organic compounds which contain a carbon skeleton and one or multiple aromatic rings. It was extracted from the word aromatic. See e.g. aryl. | 0 | Theoretical and Fundamental Chemistry |
Creaming, in the laboratory sense, is the migration of the dispersed phase of an emulsion under the influence of buoyancy. The particles float upwards or sink depending on how large they are and density compared to the continuous phase as well as how viscous or how thixotropic the continuous phase might be. For as long as the particles remain separated, the process is called creaming.
Where it is important that either the form or the concentration of the emulsion should be stable, it is desirable that the continuous and the dispersed phases should have similar densities and it also is desirable that the continuous phase should be viscous or thixotropic. Thixotropy is particularly valuable in paints, sauces, and similar products, partly because it counteracts tendencies towards creaming. It also is important that the particles be as small as practicable because that reduces their tendency to migrate under the influence of buoyant forces due to Brownian motion, which keeps the particles in suspension. The electric charges on their surfaces should preferably tend to be uniform, so that the particles repel rather than attract each other.
Creaming is usually seen as undesirable because it causes difficulties in storage and handling and can be dangerous in health care settings by causing a fat embolism (fat in the blood stream) or occluding capillaries (blockage of capillaries) if an emulsion that has undergone creaming is administered intravenously. It can be useful in special cases especially where it is desirable to concentrate an emulsion. A particular example is in the separation of dairy cream, either to achieve a desired concentration of butterfat, or to make butter.
Depending on whether the dispersed particles are less dense or more dense than the continuous phase, they may move either to the top or bottom of a sample. In this it differs from flocculation (where particles clump) or emulsion breaking (where particles coalesce). Unlike flocculation and breaking, creaming of an emulsion is a relatively simple process to reverse. | 0 | Theoretical and Fundamental Chemistry |
Isomerization is the process by which one molecule is transformed into another molecule that has exactly the same atoms, but the atoms are rearranged. In some molecules and under some conditions, isomerization occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerization occurs intramolecularly, it is considered a rearrangement reaction.
An example of an organometallic isomerization is the production of decaphenylferrocene, [(η-CPh)Fe] from its linkage isomer.
;Synthesis of fumaric acid
Industrial synthesis of fumaric acid proceeds via the cis-trans isomerization of maleic acid:
Topoisomerases are enzymes that can cut and reform circular DNA and thus change its topology. | 0 | Theoretical and Fundamental Chemistry |
Dealkalization is a process of surface modification applicable to glasses containing alkali ions, wherein a thin surface layer is created that has a lower concentration of alkali ions than is present in the underlying, bulk glass. This change in surface composition commonly alters the observed properties of the surface, most notably enhancing corrosion resistance.
Many commercial glass products such as containers are made of soda-lime glass, and therefore have a substantial percentage of sodium ions in their internal structure. Since sodium is an alkali element, its selective removal from the surface results in a dealkalized surface. A classic example of dealkalization is the treatment of glass containers, where a special process is used to create a dealkalized inside surface that is more resistant to interactions with liquid products put inside the container. However, the term dealkalization may also be generally applied to any process where a glass surface forms a thin surface layer that is depleted of alkali ions relative to the bulk. A common example is the initial stages of glass corrosion or weathering, where alkali ions are leached from the surface region by interactions with water, forming a dealkalized surface layer.
A dealkalized surface may have either no alkali remaining or may just have less than the bulk. In silicate glasses, dealkalized surfaces are also often considered "silica-rich" since the selective removal of alkali ions can be thought to leave behind a surface composed primarily of silica (SiO). To be precise, dealkalization does not generally involve the outright removal of alkali from the glass, but rather its replacement with protons (H) or hydronium ions (HO) in the structure through the process of ion-exchange. | 0 | Theoretical and Fundamental Chemistry |
DAVID (the database for annotation, visualization and integrated discovery) is a free online bioinformatics resource developed by the Laboratory of Human Retrovirology and Immunoinformatics ([https://david.ncifcrf.gov/content.jsp?file=about_us.html LHRI]). All tools in the DAVID Bioinformatics Resources aim to provide functional interpretation of large lists of genes derived from genomic studies, e.g. microarray and proteomics studies. DAVID can be found at https://david.ncifcrf.gov/
The DAVID Bioinformatics Resources consists of the DAVID Knowledgebase and five integrated, web-based functional annotation tool suites: the DAVID Gene Functional Classification Tool, the DAVID Functional Annotation Tool, the DAVID Gene ID Conversion Tool, the DAVID Gene Name Viewer and the DAVID NIAID Pathogen Genome Browser. The expanded DAVID Knowledgebase now integrates almost all major and well-known public bioinformatics resources centralized by the DAVID Gene Concept, a single-linkage method to agglomerate tens of millions of diverse gene/protein identifiers and annotation terms from a variety of public bioinformatics databases. For any uploaded gene list, the DAVID Resources now provides not only the typical gene-term enrichment analysis, but also new tools and functions that allow users to condense large gene lists into gene functional groups, convert between gene/protein identifiers, visualize many-genes-to-many-terms relationships, cluster redundant and heterogeneous terms into groups, search for interesting and related genes or terms, dynamically view genes from their lists on bio-pathways and more.
DAVID 2021 update was released in December 2021. The knowledgebase has been scheduled to update quarterly. | 1 | Applied and Interdisciplinary Chemistry |
The silencing of genes created by abnormal DNA methylation is a major contributor to the formation of cancerous tumors. Variations in DNA methylation of normal cells compared to malignant cells shows a prominent mechanism in how cancerous cells proliferate. Those variations are particularly prevalent in cell cycle regulation, DNA repair, and natural tumor suppression mechanisms. A leading therapeutic strategy in treating solid tumors stems from the use of demethylating agents to suppress DNA methylation in cancerous growths. Azacitidine and decitabine are both frequently used demethylating agents while decitabine is significantly more potent in its demethylating abilities. Both of these drugs are inhibitors of DNA Methyltransferases (DNMT) which are enzymes that are responsible for methylating DNA. In the 1970’s, these drugs have shown promising results in hematological cancers in organisms such as mice. The FDA initially rejected the use of azacitidine clinically due to negative side effects caused by elevated toxicity levels. However, in later clinical trials performed on patients with MDS, myelodysplastic syndromes, azacitidine provided effective and exhibited consistent results which led to FDA approval in 2004. The commercial name of azacitidine became Vidaza. Decitabine, with the commercial name Dacogen, followed with FDA approval in 2006. As more research is completed in the field of genetic mutations, specifically involving DNA Methylation, these drugs can be utilized to their maximum efficiency to clinically treat cancerous tumors. As of 2017, there were no approved demethylating agents for the treatment of solid tumors which can be a focus of research in the future. Treatment utilizing demethylating agents can have further clinical use by targeting cancer stem cells and triggering apoptosis. Demethylating agents and their relevance in clinical studies as therapy to treat lymphocytic leukemia can be seen in. Procaine can also be used as therapeutic development to inhibit the growth of cancer cells in humans. There is a new world of possibilities of using demethylating agents to treat different diseases such as leukemia and cancer as therapeutic treatment.
Procaine (PCA) is a demethylating agent considered to be effective in inhibiting the growth of human cancer cells. Several studies have explored and elucidated the effects of procaine on human liver cancer cells and breast cancer cells. Studies have shown that procaine, as an inhibitor of DNA methylation in breast cancer cells, can effectively cause hypomethylation and demethylation of the entire group of breast cancer cell DNA genomes by reducing 5-methylcytosine DNA content. In addition, procaine can effectively restore the gene expression of tumor suppressor genes by demethylating densely hypermethylated CpG-enriched DNA. For human liver cancer cells, procaine is capable of reducing tumor volume by suppressing the cell viability of HLE, HuH7, and HuH6 cells, and it has shown effective inhibition of S/G2/M transition in HLE cells. | 1 | Applied and Interdisciplinary Chemistry |
For residential buildings, which mostly rely on infiltration for meeting their ventilation needs, a common ventilation rate measure is the air change rate (or air changes per hour): the hourly ventilation rate divided by the volume of the space (I or ACH; units of 1/h). During the winter, ACH may range from 0.50 to 0.41 in a tightly air-sealed house to 1.11 to 1.47 in a loosely air-sealed house.
ASHRAE now recommends ventilation rates dependent upon floor area, as a revision to the 62-2001 standard, in which the minimum ACH was 0.35, but no less than 15 CFM/person (7.1 L/s/person). As of 2003, the standard has been changed to 3 CFM/100 sq. ft. (15 L/s/100 sq. m.) plus 7.5 CFM/person (3.5 L/s/person). | 1 | Applied and Interdisciplinary Chemistry |
In general, the hydroxyl group makes alcohols polar. Those groups can form hydrogen bonds to one another and to most other compounds. Owing to the presence of the polar OH alcohols are more water-soluble than simple hydrocarbons. Methanol, ethanol, and propanol are miscible in water. Butanol, with a four-carbon chain, is moderately soluble.
Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ethers. The boiling point of the alcohol ethanol is 78.29 °C, compared to 69 °C for the hydrocarbon hexane, and 34.6 °C for diethyl ether. | 0 | Theoretical and Fundamental Chemistry |
For the C. finmarchicus species specifically, the start of reproduction is linked to the start of the spring bloom. Thus, changes in the timing of the spring bloom would directly influence the reproductive capabilities of C. finmarchicus and alter the food chain from the bottom-up. However, the food chain could also be altered from the top-down through habitat disturbance and the removal of marine mammals and fish. Large-scale commercial fisheries exert top-down effects by lowering the abundance of larger species and increasing the amount of lipid-rich copepods and even paving way for other species to consume them. Under warming ocean conditions, prey switching is to be expected. Egg production and hatching success may also be affected with increasing sea surface temperatures and ocean acidification. | 0 | Theoretical and Fundamental Chemistry |
Another fundamental property becomes visible if a superfluid is placed in a rotating container. Instead of rotating uniformly with the container, the rotating state consists of quantized vortices. That is, when the container is rotated at speeds below the first critical angular velocity, the liquid remains perfectly stationary. Once the first critical angular velocity is reached, the superfluid will form a vortex. The vortex strength is quantized, that is, a superfluid can only spin at certain "allowed" values. Rotation in a normal fluid, like water, is not quantized. If the rotation speed is increased more and more quantized vortices will be formed which arrange in nice patterns similar to the Abrikosov lattice in a superconductor. | 1 | Applied and Interdisciplinary Chemistry |
These baroclinic instabilities may be initiated by the process of sloping convection or slanted thermal convection. To understand this, consider a fluid in steady state and under the thermal-wind balance. Initially, a fluid parcel is at location A. The fluid parcel is slightly perturbed to location B, while still retaining its original density. Therefore, the fluid parcel is now in a location with a lower density than itself and the parcel will just sink down to its original position; the fluid parcel is now stable. However, when a parcel displaced to location C, it is surrounded by fluid with a higher density than the parcel itself. Due to its relatively low density with respect to its surroundings, the parcel will float up even further. Now a small perturbation grows into a larger one, which implies a baroclinic instability.
A criterion for an instability to occur can be defined. As stated before, in a baroclinic fluid, the thermal-wind balance holds, which implies the following two relations:
and ,
where is the density and , and are the spatial coordinates in the horizontal (latitudinal and longitudinal) and vertical direction, respectively. and represent the horizontal (zonal and meridional) components of the velocity vector in the - and -direction, respectively. Now thus and are the two horizontal density gradients. is the gravitational acceleration at the surface of the Earth and the Coriolis parameter.
Therefore a horizontal density gradient in the -direction leads to a gradient in horizontal flow velocity over depth .
The slope of the displacement is defined as
where and are the horizontal and vertical velocities of the perturbation, respectively.
An instability now occurs when the slope of the displacement is smaller than the slope of the isopycnals. The isopycnals can be mathematically described as . Now this results in an instability when:
From now on, only a two layer system with and the slopes of the top and bottom layer, respectively, is considered to simplify the problem. This is now similar to the classic Philips model. From the thermal-wind balance it now follows that
where is the reduced gravity and the Coriolis-parameter at the equator according to the beta-plane approximation.
Performing a scale analysis on the slope of the perturbation allows to assign physical quantities to this mathematical problem. This now results in
where is the scale height, the horizontal length scale, and is the Rossby-parameter.
From this it can be stated that an instability occurs when
or ,
where is the reduced gravity and is the velocity difference between the lower and upper layer. This criterion can be used to identify whether a small perturbation will grow into a larger one and thus whether an instability is expected to occur. From this it follows that you need some kind of shear to obtain an instability, it is easier to get an instability for long waves (perturbations) with large , and the and therefore the beta-effect is stabilizing.
Furthermore, for the baroclinic Rossby radius of deformation it holds that . Now the instability criteria simplify to
or .
From this analysis it also follows that baroclinic instabilities are important for small Rossby numbers, where . | 1 | Applied and Interdisciplinary Chemistry |
Silica (the chemical compound SiO) has a number of distinct crystalline forms in addition to the quartz structure. Nearly all of the crystalline forms involve tetrahedral SiO units linked together by shared vertices in different arrangements (stishovite, composed of linked SiO octahedra, is the main exception). Si-O bond lengths vary between the different crystal forms. For example, in α-quartz the bond length is , whereas in α-tridymite it ranges from . The Si-O-Si bond angle also varies from 140° in α-tridymite to 144° in α-quartz to 180° in β-tridymite. Any deviations from these standard parameters constitute microstructural differences or variations that represent an approach to an amorphous, vitreous or glassy solid.
The transition temperature T in silicates is related to the energy required to break and re-form covalent bonds in an amorphous (or random network) lattice of covalent bonds. The T is clearly influenced by the chemistry of the glass. For example, addition of elements such as B, Na, K or Ca to a silica glass, which have a valency less than 4, helps in breaking up the network structure, thus reducing the T. Alternatively, P, which has a valency of 5, helps to reinforce an ordered lattice, and thus increases the T.
T is directly proportional to bond strength, e.g. it depends on quasi-equilibrium thermodynamic parameters of the bonds e.g. on the enthalpy H and entropy S of configurons – broken bonds: T = H / [S + R ln[(1 − f)/ f] where R is the gas constant and f is the percolation threshold. For strong melts such as SiO the percolation threshold in the above equation is the universal Scher–Zallen critical density in the 3-D space e.g. f = 0.15, however for fragile materials the percolation thresholds are material-dependent and f ≪ 1. The enthalpy H and the entropy S of configurons – broken bonds can be found from available experimental data on viscosity. | 0 | Theoretical and Fundamental Chemistry |
Plutonium in the δ phase (delta phase) normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded in weapons applications. The δ phase has more typical metallic character, and is roughly as strong and malleable as aluminium. In fission weapons, the explosive shock waves used to compress a plutonium core will also cause a transition from the usual δ phase plutonium to the denser α phase, significantly helping to achieve supercriticality. The plutonium-gallium alloy is the most common δ-stabilized alloy.
Gallium, aluminium, americium, scandium and cerium can stabilize the δ phase of plutonium for room temperature. Silicon, indium, zinc and zirconium allow formation of a metastable δ state when rapidly cooled. High amount of hafnium, holmium and thallium also allows retaining some of the δ phase at room temperature. Neptunium is the only element that can stabilize the α phase at higher temperatures. Titanium, hafnium and zirconium stabilize the β phase at room temperature when rapidly cooled. | 0 | Theoretical and Fundamental Chemistry |
On the basis of his reasoning R.A. Marcus developed a classical theory with the aim of calculating the polarization energy of the said non-equilibrium state. From thermodynamics it is well known that the energy of such a state can be determined if a reversible path to that state is found. Marcus was successful in finding such a path via two reversible charging steps for the preparation of the "transition state" from the precursor complex.
Four elements are essential for the model on which the theory is based:
# Marcus employs a classical, purely electrostatic model. The charge (many elementary charges) may be transferred in any portion from one body to another.
# Marcus separates the fast electron polarisation P and the slow atom and orientation polarisation P of the solvent on grounds of their time constants differing several orders of magnitude.
# Marcus separates the inner sphere (reactant + tightly bound solvent molecules, in complexes + ligands) and the outer sphere (free solvent )
# In this model Marcus confines himself to calculating the outer sphere energy of the non-equilibrium polarization of the "transition state". The outer sphere energy is often much larger than the inner sphere contribution because of the far reaching electrostatic forces (compare the Debye–Hückel theory of electrochemistry).
Marcus' tool is the theory of dielectric polarization in solvents. He solved the problem in a general way for a transfer of charge between two bodies of arbitrary shape with arbitrary surface and volume charge. For the self-exchange reaction, the redox pair (e.g. Fe(HO) / Fe(HO)) is substituted by two macroscopic conducting spheres at a defined distance carrying specified charges. Between these spheres a certain amount of charge is reversibly exchanged.
In the first step the energy W of the transfer of a specific amount of charge is calculated, e.g. for the system in a state when both spheres carry half of the amount of charge which is to be transferred. This state of the system can be reached by transferring the respective charge from the donor sphere to the vacuum and then back to the acceptor sphere. Then the spheres in this state of charge give rise to a defined electric field in the solvent which creates the total solvent polarization P + P. By the same token this polarization of the solvent interacts with the charges.
In a second step the energy W of the reversible (back) transfer of the charge to the first sphere, again via the vacuum, is calculated. However, the atom and orientation polarization P is kept fixed, only the electron polarization P may adjust to the field of the new charge distribution and the fixed P. After this second step the system is in the desired state with an electron polarization corresponding to the starting point of the redox reaction and an atom and orientation polarization corresponding to the "transition state". The energy W + W of this state is, thermodynamically speaking, a Gibbs free energy G.
Of course, in this classical model the transfer of any arbitrary amount of charge Δe is possible. So the energy of the non-equilibrium state, and consequently of the polarization energy of the solvent, can be probed as a function of Δe. Thus Marcus has lumped together, in a very elegant way, the coordinates of all solvent molecules into a single coordinate of solvent polarization Δp which is determined by the amount of transferred charge Δe. So he reached a simplification of the energy representation to only two dimensions: G = f(Δe). The result for two conducting spheres in a solvent is the formula of Marcus
Where r and r are the radii of the spheres and R is their separation, ε and ε are the static and high frequency (optical) dielectric constants of the solvent, Δe the amount of charge transferred. The graph of G vs. Δe is a parabola (Fig. 1). In Marcus theory the energy belonging to the transfer of a unit charge (Δe = 1) is called the (outer sphere) reorganization energy λ, i.e. the energy of a state where the polarization would correspond to the transfer of a unit amount of charge, but the real charge distribution is that before the transfer. In terms of exchange direction the system is symmetric. | 0 | Theoretical and Fundamental Chemistry |
Z2 spin liquid obtained using slave-particle approach may be the first theoretical example of string-net liquid. | 0 | Theoretical and Fundamental Chemistry |
In earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments to minimize the amount of construction labor. | 1 | Applied and Interdisciplinary Chemistry |
Mineral sands are the predominant type of titanium, zirconium, and thorium deposit. They are formed by accumulation of such heavy minerals within beach systems, and are a type of placer deposits. The minerals which contain titanium are ilmenite, rutile, and leucoxene, zirconium is contained within zircon, and thorium is generally contained within monazite. These minerals are sourced from primarily granite bedrock by erosion and transported to the sea by rivers where they accumulate within beach sands. Rarely, but importantly, gold, tin, and platinum deposits can form in beach placer deposits. | 0 | Theoretical and Fundamental Chemistry |
Chemical cycling describes systems of repeated circulation of chemicals between other compounds, states and materials, and back to their original state, that occurs in space, and on many objects in space including the Earth. Active chemical cycling is known to occur in stars, many planets and natural satellites.
Chemical cycling plays a large role in sustaining planetary atmospheres, liquids and biological processes and can greatly influence weather and climate. Some chemical cycles release renewable energy, others may give rise to complex chemical reactions, organic compounds and prebiotic chemistry. On terrestrial bodies such as the Earth, chemical cycles involving the lithosphere are known as geochemical cycles. Ongoing geochemical cycles are one of the main attributes of geologically active worlds. A chemical cycle involving a biosphere is known as a biogeochemical cycle. | 0 | Theoretical and Fundamental Chemistry |
In the first step, sulfur is burned to produce sulfur dioxide.
The sulfur dioxide is oxidized to sulfur trioxide by oxygen in the presence of a vanadium(V) oxide catalyst. This reaction is reversible and the formation of the sulfur trioxide is exothermic.
The sulfur trioxide is absorbed into 97–98% to form oleum (), also known as fuming sulfuric acid or pyrosulphuric acid. The oleum is then diluted with water to form concentrated sulfuric acid.
Directly dissolving in water, called the "wet sulfuric acid process", is rarely practiced because the reaction is extremely exothermic, resulting in a hot aerosol of sulfuric acid that requires condensation and separation. | 0 | Theoretical and Fundamental Chemistry |
The simplest phenotypic screens employ cell lines and monitor a single parameter such as cellular death or the production of a particular protein. High-content screening where changes in the expression of several proteins can be simultaneously monitored is also often used. High-content imaging of dye-labeled cellular components can also reveal effects of compounds on cell cultures in vitro, distinguishing the phenotypic effects of a broad variety of drugs. | 1 | Applied and Interdisciplinary Chemistry |
Conjugated Schiff bases absorb strongly in the UV-visible region of the electromagnetic spectrum. This absorption is the basis of the anisidine value, which is a measure of oxidative spoilage for fats and oils. | 0 | Theoretical and Fundamental Chemistry |
If Albert Einstein's photoelectric law is applied to a free molecule, the kinetic energy () of an emitted photoelectron is given by
where h is Plancks constant, ν is the frequency of the ionizing light, and I is an ionization energy for the formation of a singly charged ion in either the ground state or an excited state. According to Koopmans theorem, each such ionization energy may be identified with the energy of an occupied molecular orbital. The ground-state ion is formed by removal of an electron from the highest occupied molecular orbital, while excited ions are formed by removal of an electron from a lower occupied orbital. | 0 | Theoretical and Fundamental Chemistry |
The adiabatic (no heat exchanged) expansion of a gas may be carried out in a number of ways. The change in temperature experienced by the gas during expansion depends not only on the initial and final pressure, but also on the manner in which the expansion is carried out.
*If the expansion process is reversible, meaning that the gas is in thermodynamic equilibrium at all times, it is called an isentropic expansion. In this scenario, the gas does positive work during the expansion, and its temperature decreases.
*In a free expansion, on the other hand, the gas does no work and absorbs no heat, so the internal energy is conserved. Expanded in this manner, the temperature of an ideal gas would remain constant, but the temperature of a real gas decreases, except at very high temperature.
*The method of expansion discussed in this article, in which a gas or liquid at pressure P flows into a region of lower pressure P without significant change in kinetic energy, is called the Joule–Thomson expansion. The expansion is inherently irreversible. During this expansion, enthalpy remains unchanged (see proof below). Unlike a free expansion, work is done, causing a change in internal energy. Whether the internal energy increases or decreases is determined by whether work is done on or by the fluid; that is determined by the initial and final states of the expansion and the properties of the fluid.
The temperature change produced during a Joule–Thomson expansion is quantified by the Joule–Thomson coefficient, . This coefficient may be either positive (corresponding to cooling) or negative (heating); the regions where each occurs for molecular nitrogen, N, are shown in the figure. Note that most conditions in the figure correspond to N being a supercritical fluid, where it has some properties of a gas and some of a liquid, but can not be really described as being either. The coefficient is negative at both very high and very low temperatures; at very high pressure it is negative at all temperatures. The maximum inversion temperature (621 K for N) occurs as zero pressure is approached. For N gas at low pressures, is negative at high temperatures and positive at low temperatures. At temperatures below the gas-liquid coexistence curve, N condenses to form a liquid and the coefficient again becomes negative. Thus, for N gas below 621 K, a Joule–Thomson expansion can be used to cool the gas until liquid N forms. | 0 | Theoretical and Fundamental Chemistry |
1,1-Dichloro-1-fluoroethane can be a non-flammable, colourless liquid under room-temperature atmospheric conditions. The compound is very volatile with a boiling point of 32°C. Its critical temperature is near 204°C. Its smell has been described as "usually ethereal" (like ether). | 1 | Applied and Interdisciplinary Chemistry |
In a study of imidazole-4-acetaldehyde presence in the reaction mixture during the coupling reaction of fungal amine oxidase and bacterial aldehyde oxidase for histamine elimination, imidazole 4-acetaldehyde was not detected, which suggests that imidazole 4-acetaldehyde was not produced as a result of the coupling reaction between fungal amine oxidase and aldehyde oxidase, as such, its absence in the reaction mixture implies that the fungal amine oxidase-aldehyde oxidase coupling reaction likely proceeded directly from histamine to [https://pubchem.ncbi.nlm.nih.gov/compound/Imidazoleacetic-acid imidazole-4-acetic acid] with an apparent yield of 100%, without the intermediate formation of imidazole 4-acetaldehyde. | 1 | Applied and Interdisciplinary Chemistry |
The Weibull distribution, now named for Waloddi Weibull was first identified by and first applied by to describe particle size distributions. It is still widely used in mineral processing to describe particle size distributions in comminution processes.
where
:: Particle size
:: 80th percentile of the particle size distribution
:: Parameter describing the spread of the distribution
The inverse distribution is given by:
where
:: Mass fraction | 0 | Theoretical and Fundamental Chemistry |
Compounds containing both a primary or secondary amine and carbonyl functional group are often labile. This guideline applies to amino aldehydes, amino-ketones, and amino-esters; indeed a molecule cannot carry simultaneously (unprotected) aldehyde and amine groups. Aminoacetone, the simplest amino ketone, cannot be isolated as a liquid or solid, and 2-aminobenzaldehyde oligomerizes in solution or in the melt. An α-formyl aziridine, reduced with DIBAL from the ester, reversibly dimerizes to an oxazolidine: | 0 | Theoretical and Fundamental Chemistry |
The Wellman–Lord process is a regenerable process to remove sulfur dioxide from flue gas (flue-gas desulfurization) without creating a throwaway sludge product.
In this process, sulfur dioxide from flue gas is absorbed in a sodium sulfite solution in water forming sodium bisulfite; other components of flue gas are not absorbed. After lowering the temperature the bisulfite is converted to the sodium pyrosulfite which precipitates.
Upon heating, the two previously described chemical reactions are reversed, and sodium pyrosulfite is converted to a concentrated stream of sulfur dioxide and sodium sulfite. The sulfur dioxide can be used for further reactions (e.g. the production of sulfuric acid), and the sulfite is reintroduced into the process.
:NaSO + SO + HO → 2NaHSO
:2NaHSO → NaSO↓ + HO
:NaSO + HO → 2NaHSO
:2NaHSO → NaSO + SO + HO
In its initial version (Crane Station, Maryland, 1968) the process was based on potassium sulfite, but the economic prognosis was poor. Interest in the process occurred because of the worldwide shortage of sulfur in 1967 and resulting high prices; power-plant flue gas was viewed as an additional source of sulfur to relieve the shortage. the later version used sodium sulfite and was installed (as a demonstration system funded by USEPA) at Mitchell Station, Indiana in 1974. It was coupled with the Allied reduction (by natural gas) process to make elemental sulfur which can be shipped anywhere, for example to a sulfuric acid plant. Additional installations of W-L were made in New Mexico. The process has been offered commercially by Davy Powergas in Lakeland, Florida. Because of side reactions forming thiosulfate (nonregenerable), there is a small makeup requirement in the form of trona (sodium carbonate). | 1 | Applied and Interdisciplinary Chemistry |
In compressible fluid dynamics, impact pressure (dynamic pressure) is the difference between total pressure (also known as pitot pressure or stagnation pressure) and static pressure. In aerodynamics notation, this quantity is denoted as or .
When input to an airspeed indicator, impact pressure is used to provide a calibrated airspeed reading. An air data computer with inputs of pitot and static pressures is able to provide a Mach number and, if static temperature is known, true airspeed.
Some authors in the field of compressible flows use the term dynamic pressure or compressible dynamic pressure instead of impact pressure. | 1 | Applied and Interdisciplinary Chemistry |
Laboratory scale flow reactors are ideal systems for using gases, particularly those that are toxic or associated with other hazards. The gas reactions that have been most successfully adapted to flow are hydrogenation and carbonylation, although work has also been performed using other gases, e.g. ethylene and ozone.
Reasons for the suitability of flow systems for hazardous gas handling are:
*Systems allow the use of a fixed bed catalyst. Combined with low solution concentrations, this allows all compounds to be adsorbed to the catalyst in the presence of gas
*Comparatively small amounts of gas are continually exhausted by the system, eliminating the need for many of the special precautions normally required for handling toxic and/or flammable gases
*The addition of pressure means that a far greater proportion of the gas will be in solution during the reaction than is the case conventionally
*The greatly enhanced mixing of the solid, liquid, and gaseous phases allows the researcher to exploit the kinetic benefits of elevated temperatures without being concerned about the gas being displaced from the solution | 1 | Applied and Interdisciplinary Chemistry |
Every nitrate ion reduced to ammonia produces one OH ion. To maintain a pH balance, the plant must either excrete it into the surrounding medium or neutralize it with organic acids. This results in the medium around the plants roots becoming alkaline when they take up nitrate.
To maintain ionic balance, every NO taken into the root must be accompanied by either the uptake of a cation or the excretion of an anion. Plants like tomatoes take up metal ions like K, Na, Ca and Mg to exactly match every nitrate taken up and store these as the salts of organic acids like malate and oxalate. Other plants like the soybean balance most of their NO intake with the excretion of OH or HCO.
Plants that reduce nitrates in the shoots and excrete alkali from their roots need to transport the alkali in an inert form from the shoots to the roots. To achieve this they synthesize malic acid in the leaves from neutral precursors like carbohydrates. The potassium ions brought to the leaves along with the nitrate in the xylem are then sent along with the malate to the roots via the phloem. In the roots, the malate is consumed. When malate is converted back to malic acid prior to use, an OH is released and excreted. (RCOO + HO -> RCOOH +OH) The potassium ions are then recirculated up the xylem with fresh nitrate. Thus the plants avoid having to absorb and store excess salts and also transport the OH.
Plants like castor reduce a lot of nitrate in the root itself, and excrete the resulting base. Some of the base produced in the shoots is transported to the roots as salts of organic acids while a small amount of the carboxylates are just stored in the shoot itself. | 1 | Applied and Interdisciplinary Chemistry |
When herbivores trigger an inducible chemical defense pathway, the resulting HIPVs may be emitted either from the site of feeding damage (local induction) or from undamaged tissues belonging to a damaged plant (systemic induction). For example, when an herbivore feeds on a single corn seedling leaf, the plant will emit volatiles from all its leaves, whether or not they too have been damaged. Locally induced defenses aid parasitoids in targeting their foraging behaviors to the exact location of the herbivore on the plant. Systemic defenses are less spatially specific and may serve to confuse the enemy once the source plant is located. A plant might employ both local and systemic responses simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
The synthetically most useful reaction of the nitrile ylides is the 1,3-dipolar cycloaddition to dipolarophiles: with electron-deficient alkenes, good yields of pyrrolines are obtained. Alkynes, carbonyl compounds, imines and azirines can also act as dipolarophile.
Nitrile ylides react with weak acids like methanol by protonation finally leading to a methoxyimine. | 0 | Theoretical and Fundamental Chemistry |
The compound has been prepared in a multistep process starting with the base hydrolysis of phosphorus pentasulfide:
:PS + 6 NaOH → 2 NaPOS + HS + 2 HO
The salt is isolated as the hydrate NaPOS(HO). It is prone to hydrolysis, especially when it is heated as an aqueous solutions:
:NaPOS + 2 HO → NaPOS + HS
Its structure has been examined by X-ray crystallography. | 1 | Applied and Interdisciplinary Chemistry |
Ken A. Dill and Hue Sun Chan (1997) illustrated a folding pathway design based on Levinthals Paradox, named the "golf-course" landscape, where a random searching for the native states would prove impossible, due to the hypothetically "flat playing field" since the protein "ball" would take a really long time to find a fall into the native "hole". However, a rugged pathway deviated from the initial smooth golf-course creates a directed tunnel where the denatured protein goes through to reach its native structure, and there can exist valleys (intermediate states) or hills (transition states) long the pathway to a proteins native state. Yet, this proposed pathway yields a contrast between pathway dependence versus pathway independence, or the Levinthal dichotomy and emphasizes the one-dimensional route of conformation.
Another approach to protein folding eliminates the term "pathway" and replaces with "funnels" where it is concerned with parallel processes, ensembles and multiple dimensions instead of a sequence of structures a protein has to go through. Thus, an ideal funnel consists of a smooth multi-dimensional energy landscape where increasing interchain contacts correlate with decreasing degree of freedom and ultimately achievement of native state.
Unlike an idealized smooth funnel, a rugged funnel demonstrates kinetic traps, energy barriers, and some narrow throughway paths to native state. This also explains an accumulation of misfolded intermediates where kinetic traps prevent protein intermediates from achieving their final conformation. For those that are stuck in this trap, they would have to break away favorable contacts that do not lead to their native state before reaching their original starting point and find another different search downhill. A Moat landscape, on the other hand, illustrates the idea of a variation of routes including an obligatory kinetic trap route that protein chains take to reach their native state. This energy landscape stems from a study by Christopher Dobson and his colleagues about hen egg white lysozyme, in which half of its population undergo normal fast folding, while the other half first forms α-helices domain quickly then β-sheet one slowly. It is different from the rugged landscape since there are no accidental kinetic traps but purposeful ones required for portions of protein to go through before reaching the final state. Both the rugged landscape and the Moat landscape nonetheless present the same concept in which protein configurations might come across kinetic traps during their folding process. On the other hand, the Champagne Glass landscape involves free energy barriers due to conformational entropy that partly resembles the random golf-course pathway in which a protein chain configuration is lost and has to spend time searching for the path downhill. This situation can be applied to a conformational search of polar residues that will eventually connect two hydrophobic clusters. | 1 | Applied and Interdisciplinary Chemistry |
Born in Paris on 15 May 1859, Pierre Curie was the son of Eugène Curie (1827–1910), a doctor of French Huguenot Protestant origin from Alsace, and Sophie-Claire Curie (née Depouilly; 1832–1897). He was educated by his father and in his early teens showed a strong aptitude for mathematics and geometry. When he was 16, he earned his Bachelor of Science in mathematics. By the age of 18, he earned his license, the equivalent of a U.S. master's degree, in physical sciences from the Faculty of Sciences at the Sorbonne, also known as the University of Paris. He did not proceed immediately to a doctorate due to lack of money. Instead, he worked as a laboratory instructor. When Pierre Curie was preparing for his Bachelor of Science degree, he worked in the laboratory of Jean-Gustave Bourbouze in the Faculty of Science. In 1895, he went on to receive his doctorate at the University of Paris. The submission material for his doctorate consisted of his research over magnetism. After obtaining his doctorate, he became professor of physics and in 1900, he became professor in the faculty of sciences.
In 1880, Pierre and his older brother Paul-Jacques (1856–1941) demonstrated that an electric potential was generated when crystals were compressed, i.e., piezoelectricity. To aid this work they invented the piezoelectric quartz electrometer. The following year they demonstrated the reverse effect: that crystals could be made to deform when subject to an electric field. Almost all digital electronic circuits now rely on this in the form of crystal oscillators. In subsequent work on magnetism Pierre Curie defined the Curie scale. This work also involved delicate equipment – balances, electrometers, etc.
Pierre Curie was introduced to Maria Skłodowska by their friend, physicist Józef Wierusz-Kowalski. Curie took her into his laboratory as his student. His admiration for her grew when he realized that she would not inhibit his research. He began to regard Skłodowska as his muse. She refused his initial proposal, but finally agreed to marry him on 26 July 1895.
The Curies had a happy, affectionate marriage, and they were known for their devotion to each other. | 1 | Applied and Interdisciplinary Chemistry |
Nitrogen is removed through the biological oxidation of nitrogen from ammonia to nitrate (nitrification), followed by denitrification, the reduction of nitrate to nitrogen gas. Nitrogen gas is released to the atmosphere and thus removed from the water.
Nitrification itself is a two-step aerobic process, each step facilitated by a different type of bacteria. The oxidation of ammonia (NH) to nitrite (NO) is most often facilitated by bacteria such as Nitrosomonas spp. (nitroso refers to the formation of a nitroso functional group). Nitrite oxidation to nitrate (NO), though traditionally believed to be facilitated by Nitrobacter spp. (nitro referring the formation of a nitro functional group), is now known to be facilitated in the environment predominantly by Nitrospira spp.
Denitrification requires anoxic conditions to encourage the appropriate biological communities to form. Anoxic conditions refers to a situation where oxygen is absent but nitrate is present. Denitrification is facilitated by a wide diversity of bacteria. The activated sludge process, sand filters, waste stabilization ponds, constructed wetlands and other processes can all be used to reduce nitrogen. Since denitrification is the reduction of nitrate to dinitrogen (molecular nitrogen) gas, an electron donor is needed. This can be, depending on the wastewater, organic matter (from the sewage itself), sulfide, or an added donor like methanol. The sludge in the anoxic tanks (denitrification tanks) must be mixed well (mixture of recirculated mixed liquor, return activated sludge, and raw influent) e.g. by using submersible mixers in order to achieve the desired denitrification.
Over time, different treatment configurations for activated sludge processes have evolved to achieve high levels of nitrogen removal. An initial scheme was called the Ludzack–Ettinger Process. It could not achieve a high level of denitrification. The Modified Ludzak–Ettinger Process (MLE) came later and was an improvement on the original concept. It recycles mixed liquor from the discharge end of the aeration tank to the head of the anoxic tank. This provides nitrate for the facultative bacteria.
There are other process configurations, such as variations of the Bardenpho process. They might differ in the placement of anoxic tanks, e.g. before and after the aeration tanks. | 1 | Applied and Interdisciplinary Chemistry |
Advances in massively parallel sequencing has led to the development of RNA-Seq technology, that enables a whole transcriptome shotgun approach to characterize and quantify gene expression. Unlike microarrays, which need a reference genome and transcriptome to be available before the microarray itself can be designed, RNA-Seq can also be used for new model organisms whose genome has not been sequenced yet. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, thioacyl chloride is a functional group of the type RC(S)Cl, where R is an organic substituent. Thioacyl chlorides are analogous to acid chlorides, but much rarer and less robust. The best studied is thiobenzoyl chloride, a purple oil first prepared by chlorination of dithiobenzoic acid with a combination of chlorine and thionyl chloride.
A more modern preparation employs phosgene as the chlorinating agent, this also generates carbonyl sulfide as a by-product.
PhCSH + COCl → PhC(S)Cl + HCl + COS
The most common thioacyl chloride is thiophosgene. | 0 | Theoretical and Fundamental Chemistry |
Current data suggest that by quantifying pathway reporter gene expression, molecular phenotyping is able to cluster compounds based on pathway profiles and dissect associations between pathway activities and disease phenotypes simultaneously. Furthermore, molecular phenotyping can be applicable to compounds with a range of binding specificities and is able to triage false positives derived from high-content screening assays. Furthermore, molecular phenotyping allows integration of data derived from in vitro and in vivo models as well as patient data into the drug discovery process. | 1 | Applied and Interdisciplinary Chemistry |
Esomeprazole is combined with the antibiotics clarithromycin and amoxicillin (or metronidazole instead of amoxicillin in penicillin-hypersensitive patients) in a 10-day eradication triple therapy for Helicobacter pylori. Infection by H. pylori is a causative factor in the majority of peptic and duodenal ulcers. | 0 | Theoretical and Fundamental Chemistry |
The inhabitants of Ban Na Di were casting bronze from to 200 AD, using the lost-wax technique to manufacture bangles. Bangles made by the lost-wax process are characteristic of northeast Thailand. Some of the bangles from Ban Na Di revealed a dark grey substance between the central clay core and the metal, which on analysis was identified as an unrefined form of insect wax. It is likely that decorative items, like bracelets and rings, were made by cire perdue at Non Nok Tha and Ban Chiang. There are technological and material parallels between northeast Thailand and Vietnam concerning the lost-wax technique. The sites exhibiting artifacts made by the lost-mould process in Vietnam, such as the Dong Son drums, come from the Dong Son, and Phung Nguyen cultures, such as one sickle and the figure of a seated individual from Go Mun (near Phung Nguyen, the Bac Bo Region), dating to the Go Mun phase (end of the General B period, up until the 7th century BC). | 1 | Applied and Interdisciplinary Chemistry |
Of sulfur nucleophiles, hydrogen sulfide and its salts, thiols (RSH), thiolate anions (RS), anions of thiolcarboxylic acids (RC(O)-S), and anions of dithiocarbonates (RO-C(S)-S) and dithiocarbamates (RN-C(S)-S) are used most often.
In general, sulfur is very nucleophilic because of its large size, which makes it readily polarizable, and its lone pairs of electrons are readily accessible. | 0 | Theoretical and Fundamental Chemistry |
J. J. Thomson observed while experimenting with positive rays. He believed that it was an ionised form of H from about 1911. He believed that H was a stable molecule and wrote and lectured about it. He stated that the easiest way to make it was to target potassium hydroxide with cathode rays. In 1913 Johannes Stark proposed that three hydrogen nuclei and electrons could form a stable ring shape. In 1919 Niels Bohr proposed a structure with three nuclei in a straight line, with three electrons orbiting in a circle around the central nucleus. He believed that would be unstable, but that reacting with H could yield neutral H. Stanley Allen's structure was in the shape of a hexagon with alternating electrons and nuclei.
In 1916 Arthur Dempster showed that H gas was unstable, but at the same time also confirmed that the cation existed. In 1917 Gerald Wendt and William Duane discovered that hydrogen gas subjected to alpha particles shrank in volume and thought that diatomic hydrogen was converted to triatomic. After this researchers thought that active hydrogen could be the triatomic form. Joseph Lévine went so far as to postulate that low pressure systems on the Earth happened due to triatomic hydrogen high in the atmosphere.
In 1920 Wendt and Landauer named the substance "Hyzone" in analogy to ozone and its extra reactivity over normal hydrogen. Earlier Gottfried Wilhelm Osann believed he had discovered a form of hydrogen analogous to ozone which he called "Ozonwasserstoff". It was made by electrolysis of dilute sulfuric acid. In those days no one knew that ozone was triatomic so he did not announce triatomic hydrogen. This was later shown to be a mixture with sulfur dioxide, and not a new form of hydrogen.
In the 1930s active hydrogen was found to be hydrogen with hydrogen sulfide contamination, and scientists stopped believing in triatomic hydrogen. Quantum mechanical calculations showed that neutral H was unstable but that ionised could exist. When the concept of isotopes came along, people such as Bohr then thought there may be an eka-hydrogen with atomic weight 3. This idea was later proven with the existence of tritium, but that was not the explanation of why molecular weight 3 was observed in mass spectrometers. J. J. Thomson later believed that the molecular weight 3 molecule he observed was Hydrogen deuteride. In the Orion nebula lines were observed that were attributed to nebulium which could have been the new element eka-hydrogen, especially when its atomic weight was calculated as near 3. Later this was shown to be ionised nitrogen and oxygen.
Gerhard Herzberg was the first to actually observe the spectrum of neutral H, and this triatomic molecule was the first to have a Rydberg spectrum measured where its own ground state was unstable. | 0 | Theoretical and Fundamental Chemistry |
A chafery is a variety of hearth used in ironmaking for reheating a bloom of iron, in the course of its being drawn out into a bar of wrought iron.
The equivalent term for a bloomery was string hearth, except in 17th century Cumbria, where the terminology was that of the finery forge.
A finery forge for the Walloon process would typically have one chafery to work two fineries (but sometimes one or three fineries).
Chaferies were also used in the potting and stamping forges of the industrial revolution. | 1 | Applied and Interdisciplinary Chemistry |
Bioluminescence in bacteria can be regulated through a phenomenon known as autoinduction or quorum sensing. Quorum sensing is a form of cell-to-cell communication that alters gene expression in response to cell density. Autoinducer is a diffusible pheromone produced constitutively by bioluminescent bacteria and serves as an extracellular signalling molecule. When the concentration of autoinducer secreted by bioluminescent cells in the environment reaches a threshold (above 10 cells per mL), it induces the expression of luciferase and other enzymes involved in bioluminescence. Bacteria are able to estimate their density by sensing the level of autoinducer in the environment and regulate their bioluminescence such that it is expressed only when there is a sufficiently high cell population. A sufficiently high cell population ensures that the bioluminescence produced by the cells will be visible in the environment.
A well known example of quorum sensing is that which occurs between Aliivibrio fischeri and its host. This process is regulated by LuxI and LuxR, encoded by luxI and luxR respectively. LuxI is autoinducer synthase that produces autoinducer (AI) while LuxR functions as both a receptor and transcription factor for the lux operon. When LuxR binds AI, LuxR-AI complex activates transcription of the lux operon and induces the expression of luciferase. Using this system, A. fischeri has shown that bioluminescence is expressed only when the bacteria are host-associated and have reached sufficient cell densities.
Another example of quorum sensing by bioluminescent bacteria is by Vibrio harveyi, which are known to be free-living. Unlike Aliivibrio fischeri, V. harveyi do not possess the luxI/luxR regulatory genes and therefore have a different mechanism of quorum sensing regulation. Instead, they use the system known as three-channel quorum sensing system. Vibrio use small non-coding RNAs called Qrr RNAs to regulate quorum sensing, using them to control translation of energy-costly molecules. | 1 | Applied and Interdisciplinary Chemistry |
In eye care, collyrium is an antique term for a lotion or liquid wash used as a cleanser for the eyes, particularly in diseases of the eye. The word collyrium comes from the Greek , eye-salve. The same name was also given to unguents used for the same purpose, such as unguent of tutty (Sanskrit tuttha meaning variously zinc oxide or blue vitriol). Lastly, the name was given, though improperly, to some liquid medicines used against venereal diseases.
Pre-modern medicine distinguished two kinds of collyriums: the one liquid, the other dry. Liquid collyriums were composed of ophthalmic powders, or waters, such as rose-water, plantain-water, that of fennel, eyebright, etc., in which was dissolved tutty, white vitriol, or some other proper powder. Dry collyriums were pastilles of Rhasis, sugar-candy, iris, tutty prepared and blown into the eye with a little pipe.
The 2nd century Mishnah mentions [https://www.sefaria.org/Mishnah_Shabbat.8?lang=bi collyrium]. The Sunan Abu Dawood reports, "Prophet Muhammad said: Among the best types of collyrium is antimony (ithmid) for it clears the vision and makes the hair sprout." Maimonides (12th century Egypt) mentions the use of this eye salve. | 1 | Applied and Interdisciplinary Chemistry |
PSII is a transmembrane structure found in all chloroplasts. It splits water into electrons, protons and molecular oxygen. The electrons are transferred to plastoquinol, which carries them to a proton pump. The oxygen is released into the atmosphere.
The emergence of such an incredibly complex structure, a macromolecule that converts the energy of sunlight into chemical energy and thus potentially useful work with efficiencies that are impossible in ordinary experience, seems almost magical at first glance. Thus, it is of considerable interest that, in essence, the same structure is found in purple bacteria. | 0 | Theoretical and Fundamental Chemistry |
The first implementation of a/LCI used a Michelson interferometer, the same model used in the famous Michelson–Morley experiment. The Michelson interferometer splits one beam of light into two paths, one reference path and one sampling path, and recombines them again to produce a waveform resulting from interference. The difference between the reference beam and the sampling beam thus reveal the properties of the sample in the way it scatters light.
The early a/LCI device used a movable mirror and lens in the reference arm so that researchers could replicate different angles and depths in the reference beam as they occurred in the collected backscattered light. This allowed isolation of the backscattered light at varying depths of reflection in the sample.
In order to transform the data into measurements of cell structure, angular scattering distributions are then compared to the predictions of Mie theory—which calculates the size of spheres relative to their light scattering patterns.
The a/LCI technique was first validated in studies of polystyrene microspheres, the sizes of which were known and relatively homogeneous. A later study expanded the signal processing method to compensate for the nonspherical and inhomogeneous nature of cell nuclei.
This early system required up to 40 minutes to acquire the data for a 1 mm² point in a sample, but proved the feasibility of the idea. | 0 | Theoretical and Fundamental Chemistry |
Drug-drug interactions can occur when certain drugs are administered at the same time. Effects of this can be additive (outcome is greater than those of one individual drug), less than additive (therapeutic effects are less than those of one individual drug), or functional alterations (one drug changes how another is absorbed, distributed, and metabolized). Drug-drug interactions can be of serious concern for patients who are undergoing multi-drug therapies. Coadministration of chloroquine, an anti-malaria drug, and statins for treatment of cardiovascular diseases has been shown to cause inhibition of organic anion-transporting polypeptides (OATPs) and lead to systemic statin exposure. | 1 | Applied and Interdisciplinary Chemistry |
In psychiatry research, the accepted criteria which a biomarker must fulfill to be called an endophenotype include:
# An endophenotype must segregate with illness in the population.
# An endophenotype must be heritable.
# An endophenotype must not be state-dependent (i.e., manifests whether illness is active or in remission).
# An endophenotype must co-segregate with illness within families.
# An endophenotype must be present at a higher rate within affected families than in the population.
# An endophenotype must be amenable to reliable measurement, and be specific to the illness of interest. | 1 | Applied and Interdisciplinary Chemistry |
The term neuston describes the organisms in the SML and was first suggested by Naumann in 1917. As in other marine ecosystems, bacterioneuston communities have important roles in SML functioning. Bacterioneuston community composition of the SML has been analysed and compared to the underlying water in different habitats with varying results, and has primarily focused on coastal waters and shelf seas, with limited study of the open ocean . In the North Sea, a distinct bacterial community was found in the SML with Vibrio spp. and Pseudoalteromonas spp. dominating the bacterioneuston. During an artificially induced phytoplankton bloom in a fjord mesocosm experiment, the most dominant denaturing gradient gel electrophoresis (DGGE) bands of the bacterioneuston consisted of two bacterial families: Flavobacteriaceae and Alteromonadaceae. Other studies have however, found little or no differences in the bacterial community composition of the SML and the ULW. Difficulties in direct comparisons between studies can arise because of the different methods used to sample the SML, which result in varied sampling depths.
Even less is known about the community control mechanisms in the SML and how the bacterial community assembles at the air-sea interface. The bacterioneuston community could be altered by differing wind conditions and radiation levels, with high wind speeds inhibiting the formation of a distinct bacterioneuston community. Wind speed and radiation levels refer to external controls, however, bacterioneuston community composition might also be influenced by internal factors such as nutrient availability and organic matter (OM) produced either in the SML or in the ULW.
One of the principal OM components consistently enriched in the SML are transparent exopolymer particles (TEP), which are rich in carbohydrates and form by the aggregation of dissolved precursors excreted by phytoplankton in the euphotic zone. Higher TEP formation rates in the SML, facilitated through wind shear and dilation of the surface water, have been proposed as one explanation for the observed enrichment in TEP. Also, due to their natural positive buoyancy, when not ballasted by other particles sticking to them, TEP ascend through the water column and ultimately end up at the SML . A second possible pathway of TEP from the water column to the SML is by bubble scavenging.
Next to rising bubbles, another potential transport mechanism for bacteria from the ULW to the SML could be ascending particles or more specifically TEP. Bacteria readily attach to TEP in the water column. TEP can serve as microbial hotspots and can be used directly as a substrate for bacterial degradation, and as grazing protection for attached bacteria, e.g., by acting as an alternate food source for zooplankton. TEP have also been suggested to serve as light protection for microorganisms in environments with high irradiation. | 0 | Theoretical and Fundamental Chemistry |
In materials science, the sessile drop technique is a method used for the characterization of solid surface energies, and in some cases, aspects of liquid surface energies. The main premise of the method is that by placing a droplet of liquid with a known surface energy and contact angle, the surface energy of the solid substrate can be calculated. The liquid used for such experiments is referred to as the probe liquid, and the use of several different probe liquids is required. | 0 | Theoretical and Fundamental Chemistry |
During his early years at Allahabad University, Basu received the E. G. Hill Memorial Prize of the university in 1949 for the best research work by a member of the science faculty. The Indian National Science Academy elected Basu as a fellow in 1964 and the University of London honored him with the degree of Doctor of Science in 1965. The ensuing years would see him receive several honoris causa doctorates from Indian universities viz. Meerut University (1976), Kanpur University (1996), Jhansi University (2000) and Banares Hindu University (2000). The Council of Scientific and Industrial Research awarded him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards, in 1965. The Federation of Indian Chambers of Commerce & Industry awarded him the FICCI Award for Science and Technology in 1975 and he received the Professor T. R. Seshadri Seventieth Birthday Commemoration Medal of the Indian National Science Academy in 1976 and the P. C. Ray Award of the Indian Chemical Society in 1977. He was awarded the National Fellowship by the University Grants Commission in 1980 and the Golden Jubilee Medal by the Institute of Science, Mumbai in 1984.
The J. C. Ghosh Medal of the Indian Chemical Society reached Mehrotra in 1986, followed by the Academic Achievements Award of the Sōka University in 1987. The Indian Science Congress Association honored him with four awards; starting with the Platinum Jubilee Distinguished Service Award in 1988; followed by G. P. Chatterjee Award in 1991, Acharya Narendra Dev Award in 1992 and Ashutosh Mukherjee Award in 1993. In between, he received the inaugural Atmaram Award of the Central Institute of Hindi. The Chemical Research Society of India awarded him Lifetime Achievement Award in 1999 and the Indian Chemical Society awarded him the Platinum Jubilee Award in 2000. He was an elected fellow of the Indian Academy of Sciences, Indian National Science Academy and National Academy of Sciences, India and a fellow of the Chemical Society of London, Royal Institute of Chemistry and the Indian Chemical Society. He also delivered several award orations and featured lectures; Special lecture at the XVII International Conference on Coordination Chemistry (1977), Plenary lecture at the XIX International Conference on Coordination Chemistry (1978), Plenary lecture at the IV International Conference on Solute-Solvent Interaction (1978), Clarence Karcher Memorial Lecture of University of Oklahoma (1982), the inaugural Foundation Lecture of the Federation of Asian Chemical Societies (1987) and N. R. Dhar Memorial Award Lecture of the National Academy of Science, India (1991) are some of the notable ones. | 0 | Theoretical and Fundamental Chemistry |
The basic metabolic rate varies between individuals. One study of 150 adults representative of the population in Scotland reported basal metabolic rates from as low as per day to as high as ; with a mean BMR of per day. Statistically, the researchers calculated that 62% of this variation was explained by differences in fat free mass. Other factors explaining the variation included fat mass (7%), age (2%), and experimental error including within-subject difference (2%). The rest of the variation (27%) was unexplained. This remaining difference was not explained by sex nor by differing tissue size of highly energetic organs such as the brain.
A cross-sectional study of more than 1400 subjects in Europe and the US showed that once adjusted for differences in body composition (lean and fat mass) and age, BMR has fallen over the past 35 years. The decline was also observed in a meta-analysis of more than 150 studies dating back to the early 1920s, translating into a decline in total energy expenditure of about 6%. | 1 | Applied and Interdisciplinary Chemistry |
An equilibrium constant is related to the standard Gibbs energy change for the reaction, so for an acid dissociation constant
R is the gas constant and T is the absolute temperature. Note that and . At 25 °C, ΔG in kJ·mol ≈ 5.708 pK (1 kJ·mol = 1000 joules per mole). Free energy is made up of an enthalpy term and an entropy term.
The standard enthalpy change can be determined by calorimetry or by using the van t Hoff equation, though the calorimetric method is preferable. When both the standard enthalpy change and acid dissociation constant have been determined, the standard entropy change is easily calculated from the equation above. In the following table, the entropy terms are calculated from the experimental values of pK and ΔH'. The data were critically selected and refer to 25 °C and zero ionic strength, in water.
The first point to note is that, when pK is positive, the standard free energy change for the dissociation reaction is also positive. Second, some reactions are exothermic and some are endothermic, but, when ΔH is negative TΔS is the dominant factor, which determines that ΔG is positive. Last, the entropy contribution is always unfavourable () in these reactions. Ions in aqueous solution tend to orient the surrounding water molecules, which orders the solution and decreases the entropy. The contribution of an ion to the entropy is the partial molar entropy which is often negative, especially for small or highly charged ions. The ionization of a neutral acid involves formation of two ions so that the entropy decreases (). On the second ionization of the same acid, there are now three ions and the anion has a charge, so the entropy again decreases.
Note that the standard free energy change for the reaction is for the changes from the reactants in their standard states to the products in their standard states. The free energy change at equilibrium is zero since the chemical potentials of reactants and products are equal at equilibrium. | 0 | Theoretical and Fundamental Chemistry |
A 2009 statement from the ASRM found no persuasive evidence that children are harmed or disadvantaged solely by being raised by single parents, unmarried parents, or homosexual parents. It did not support restricting access to assisted reproductive technologies on the basis of a prospective parents marital status or sexual orientation. A 2018 study found that childrens psychological well-being did not differ when raised by either same-sex parents or heterosexual parents, even finding that psychological well-being was better amongst children raised by same-sex parents.
Ethical concerns include reproductive rights, the welfare of offspring, nondiscrimination against unmarried individuals, homosexual, and professional autonomy.
A controversy in California focused on the question of whether physicians opposed to same-sex relationships should be required to perform IVF for a lesbian couple. Guadalupe T. Benitez, a lesbian medical assistant from San Diego, sued doctors Christine Brody and Douglas Fenton of the North Coast Womans Care Medical Group after Brody told her that she had "religious-based objections to treating her and homosexuals in general to help them conceive children by artificial insemination," and Fenton refused to authorise a refill of her prescription for the fertility drug Clomid on the same grounds. The California Medical Association had initially sided with Brody and Fenton, but the case, North Coast Womens Care Medical Group v. Superior Court, was decided unanimously by the California State Supreme Court in favour of Benitez on 19 August 2008.
Nadya Suleman came to international attention after having twelve embryos implanted, eight of which survived, resulting in eight newborns being added to her existing six-child family. The Medical Board of California sought to have fertility doctor Michael Kamrava, who treated Suleman, stripped of his licence. State officials allege that performing Sulemans procedure is evidence of unreasonable judgment, substandard care, and a lack of concern for the eight children she would conceive and the six she was already struggling to raise. On 1 June 2011 the Medical Board issued a ruling that Kamravas medical licence be revoked effective 1 July 2011. | 1 | Applied and Interdisciplinary Chemistry |
For many chains of reasoning in thermodynamics, it is convenient to think of the combination of two systems into one. It is imagined that the two systems, separated from their surroundings, are juxtaposed and (by a shift of viewpoint) regarded as constituting a new, composite system. The composite system is imagined amid its new overall surroundings. This sets up the possibility of interaction between the two subsystems and between the composite system and its overall surroundings, for example by allowing contact through a wall with a particular kind of permeability. This conceptual device was introduced into thermodynamics mainly in the work of Carathéodory, and has been widely used since then. | 0 | Theoretical and Fundamental Chemistry |
S. pyogenes causes diseases ranging from pharyngitis to life-threatening impetigo including necrotizing fasciitis. An MLST scheme for S. pyogenes has been developed. At present, the database ([http://www.mlst.net mlst.net]) contains the allelic profiles of isolates that represent the worldwide diversity of the organism and isolates from serious invasive disease. | 1 | Applied and Interdisciplinary Chemistry |
*The Keeling Curve, a record of atmospheric carbon dioxide levels initiated in 1958 by Charles David Keeling of the Scripps Institution of Oceanography at the University of California, San Diego, with samples taken at the National Oceanic and Atmospheric Administration's Mauna Loa Observatory in Hilo, Hawaii.
*William Kelly's pneumatic iron refining process, patented in 1857, at the Lyon County Public Library in Eddyville, Kentucky, and at Murray State University in Murray, Kentucky.
*Edwin H. Lands invention of instant photography (also known by the companys name, Polaroid), at the former Polaroid Corporation Laboratory (now owned by the Massachusetts Institute of Technology) in Cambridge, Massachusetts.
*The discovery and isolation of phytochrome, a photoreceptive pigment in plants that controls their germination, growth, and flowering. Phytochrome was isolated in 1959 at the U.S. Department of Agriculture's Beltsville Area Research Center in Beltsville, Maryland. | 1 | Applied and Interdisciplinary Chemistry |
A typical vapor phase osmometer consists of: (1) two thermistors, one with a polymer-solvent solution droplet adhered to it and another with a pure solvent droplet adhered to it; (2) a thermostatted chamber with an interior saturated with solvent vapor; (3) a liquid solvent vessel in the chamber; and (4) an electric circuit to measure the bridge output imbalance difference between the two thermistors. The voltage difference is an accurate way of measuring the temperature difference between the two thermistors, which is a consequence of solvent vapor condensing on the solution droplet (the solution droplet has a lower vapor pressure than the solvent). | 0 | Theoretical and Fundamental Chemistry |
In eukaryotes, N-linked glycans are derived from a core 14-sugar unit assembled in the cytoplasm and endoplasmic reticulum. First, two N-acetylglucosamine residues are attached to dolichol monophosphate, a lipid, on the external side of the endoplasmic reticulum membrane. Five mannose residues are then added to this structure. At this point, the partially finished core glycan is flipped across the endoplasmic reticulum membrane, so that it is now located within the reticular lumen. Assembly then continues within the endoplasmic reticulum, with the addition of four more mannose residues. Finally, three glucose residues are added to this structure. Following full assembly, the glycan is transferred en bloc by the glycosyltransferase oligosaccharyltransferase to a nascent peptide chain, within the reticular lumen. This core structure of N-linked glycans, thus, consists of 14 residues (3 glucose, 9 mannose, and 2 N-acetylglucosamine).
Image: https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=glyco.figgrp.469
Dark squares are N-acetylglucosamine; light circles are mannose; dark triangles are glucose. | 0 | Theoretical and Fundamental Chemistry |
On March 27, 1791, Galvani published a book about his work on animal electricity. It contained comprehensive details of his 11 years of research and experimentation on the topic.
The 1797 edition of Gren’s Grundriss der Naturlehre provides the first explicit definition of galvanism as clearly reflecting Volta’s opinion in the following terms: | 0 | Theoretical and Fundamental Chemistry |
The area thermal expansion coefficient relates the change in a material's area dimensions to a change in temperature. It is the fractional change in area per degree of temperature change. Ignoring pressure, one may write:
where is some area of interest on the object, and is the rate of change of that area per unit change in temperature.
The change in the area can be estimated as:
This equation works well as long as the area expansion coefficient does not change much over the change in temperature , and the fractional change in area is small . If either of these conditions does not hold, the equation must be integrated. | 0 | Theoretical and Fundamental Chemistry |
PumpLinx is a 3-D computational fluid dynamics (CFD) software developed for the analysis of fluid pumps, motors, compressors, valves, propellers, hydraulic systems, and other fluid devices with rotating or sliding components. | 1 | Applied and Interdisciplinary Chemistry |
The EPA has published a standards handbook for the interpretation of water quality in Ireland in which definitions of water hardness are given.
In this section, reference to original EU documentation is given, which sets out no limit for hardness. The handbook also gives no "Recommended or Mandatory Limit Values" for hardness. The handbook does indicate that above the midpoint of the ranges defined as "Moderately Hard", effects are seen increasingly: "The chief disadvantages of hard waters are that they neutralise the lathering power of soap[...] and, more important, that they can cause blockage of pipes and severely reduced boiler efficiency because of scale formation. These effects will increase as the hardness rises to and beyond 200 mg/L ." | 0 | Theoretical and Fundamental Chemistry |
Scottish chemist Thomas Graham (1805–1869) found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles. In other words, the ratio of the rates of effusion of two gases at the same temperature and pressure is given by the inverse ratio of the square roots of the masses of the gas particles.
where and represent the molar masses of the gases.
This equation is known as Graham's law of effusion.
The effusion rate for a gas depends directly on the average velocity of its particles. Thus, the faster the gas particles are moving, the more likely they are to pass through the effusion orifice. | 0 | Theoretical and Fundamental Chemistry |
Few homoleptic carbonato complexes have been characterized. One is [Zr(CO)], featuring 8-ccordinate Zr(IV). Tris(carbonato)cobalt(III) ([Co(CO)]) is another example. | 0 | Theoretical and Fundamental Chemistry |
In thermal convection problems, Richardson number represents the importance of natural convection relative to the forced convection. The Richardson number in this context is defined as
where g is the gravitational acceleration, is the thermal expansion coefficient, T is the hot wall temperature, T is the reference temperature, L is the characteristic length, and V is the characteristic velocity.
The Richardson number can also be expressed by using a combination of the Grashof number and Reynolds number,
Typically, the natural convection is negligible when Ri < 0.1, forced convection is negligible when Ri > 10, and neither is negligible when 0.1 < Ri < 10. It may be noted that usually the forced convection is large relative to natural convection except in the case of extremely low forced flow velocities. However, buoyancy often plays a significant role in defining the laminar–turbulent transition of a mixed convection flow. In the design of water filled thermal energy storage tanks, the Richardson number can be useful. | 1 | Applied and Interdisciplinary Chemistry |
Cloning a cell means to derive a population of cells from a single cell. In the case of unicellular organisms such as bacteria and yeast, this process is remarkably simple and essentially only requires the inoculation of the appropriate medium. However, in the case of cell cultures from multi-cellular organisms, cell cloning is an arduous task as these cells will not readily grow in standard media.
A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings (cylinders). In this technique a single-cell suspension of cells that have been exposed to a mutagenic agent or drug used to drive selection is plated at high dilution to create isolated colonies, each arising from a single and potentially clonal distinct cell. At an early growth stage when colonies consist of only a few cells, sterile polystyrene rings (cloning rings), which have been dipped in grease, are placed over an individual colony and a small amount of trypsin is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth. | 1 | Applied and Interdisciplinary Chemistry |
There have been a variety of long-overlap-based assembly methods developed in recent years. One of the most commonly used methods, the Gibson assembly method, was developed in 2009, and provides a one-pot DNA assembly method that does not require the use of restriction enzymes or integrases. Other similar overlap-based assembly methods include Circular Polymerase Extension Cloning (CPEC), Sequence and Ligase Independent Cloning (SLIC) and Seamless Ligation Cloning Extract (SLiCE). Despite the presence of many overlap assembly methods, the Gibson assembly method is still the most popular. Besides the methods listed above, other researchers have built on the concepts used in Gibson assembly and other assembly methods to develop new assembly strategies like the Modular Overlap-Directed Assembly with Linkers (MODAL) strategy, or the Biopart Assembly Standard for Idempotent Cloning (BASIC) method. | 1 | Applied and Interdisciplinary Chemistry |
Of historical interest but not often of practical value, the first isocyanide, allyl isocyanide, was prepared by the reaction of allyl iodide and silver cyanide.
:RI + AgCN → RNC + AgI | 0 | Theoretical and Fundamental Chemistry |
Generally speaking, there are two distinct mechanistic pathways that lead to C-C bond activation: (a) the β-carbon elimination of metal complexes. In this mechanism, a M–C intermediate and a double bond are formed at the same time; and (b) the direct oxidative addition of C–C bonds into low-valent metal adducts to form a bis(organyl)metal complex. | 0 | Theoretical and Fundamental Chemistry |
The biosynthetic pathway of phycocyanobilin begins with 5-Aminolevulinic acid (5-ALA). Two molecules of 5-ALA undergo a condensation reaction catalyzed by Porphobilinogen (PBG) Synthase to yield a molecule of Porphobilinogen (PBG) (not shown). Four molecules of PBG are polymerized into a linear tetrapyrrole by Porphobilinogen deaminase. This reaction releases four ammonia molecules in the process. Completion of the tetrapyrrole is performed by Uroporphyrinogen III synthase which results in the macrocyclic Uroporphyrinogen III. Uroporphyrinogen III is then converted to a Heme by a Uroporphyrinogen III decarboxylase. The heme molecule is converted to Biliverdin IX α. Biliverdin is then finally reduced to Phycocyanobilin (PCB) by the Phycocyanin Ferredoxin Oxidoreductase PcyA. Literature circa 1989 includes phytochromobilin as an intermediate in this final conversion. | 1 | Applied and Interdisciplinary Chemistry |
In DVD drives, the signal produced from the disc is a reflection of the addressing laser beam, and is therefore very intense. For 3D optical storage however, the signal must be generated within the tiny volume that is addressed, and therefore it is much weaker than the laser light. In addition, fluorescence is radiated in all directions from the addressed point, so special light collection optics must be used to maximize the signal. | 0 | Theoretical and Fundamental Chemistry |
MAPK pathways of fungi are also well studied. In yeast, the Fus3 MAPK is responsible for cell cycle arrest and mating in response to pheromone stimulation. The pheromone alpha-factor is sensed by a seven transmembrane receptor. The recruitment and activation of Fus3 pathway components are strictly dependent on heterotrimeric G-protein activation. The mating MAPK pathway consist of three tiers (Ste11-Ste7-Fus3), but the MAP2 and MAP3 kinases are shared with another pathway, the Kss1 or filamentous growth pathway. While Fus3 and Kss1 are closely related ERK-type kinases, yeast cells can still activate them separately, with the help of a scaffold protein Ste5 that is selectively recruited by the G-proteins of the mating pathway. The trick is that Ste5 can associate with and "unlock" Fus3 for Ste7 as a substrate in a tertiary complex, while it does not do the same for Kss1, leaving the filamentous growth pathway to be activated only in the absence of Ste5 recruitment.
Fungi also have a pathway reminiscent of mammalian JNK/p38 signaling. This is the Hog1 pathway: activated by high osmolarity (in Saccharomyces cerevisiae) or a number of other abiotic stresses (in Schizosaccharomyces pombe). The MAP2 kinase of this pathway is called Pbs2 (related to mammalian MKK3/4/6/7), the dedicated MAP3 kinases involved in activation are Ssk2 and SSk22. The system in S. cerevisiae is activated by a sophisticated osmosensing module consisting of the Sho1 and Sln1 proteins, but it is yet unclear how other stimuli can elicit activation of Hog1. Yeast also displays a number of other MAPK pathways without close homologs in animals, such as the cell wall integrity pathway (Mpk1/Slt2) or the sporulation pathway (Smk1). | 1 | Applied and Interdisciplinary Chemistry |
In eukaryotes, O-linked glycans are assembled one sugar at a time on a serine or threonine residue of a peptide chain in the Golgi apparatus. Unlike N-linked glycans, there is no known consensus sequence yet. However, the placement of a proline residue at either -1 or +3 relative to the serine or threonine is favourable for O-linked glycosylation. | 0 | Theoretical and Fundamental Chemistry |
Bioreactor design is a relatively complex engineering task, which is studied in the discipline of biochemical/bioprocess engineering. Under optimum conditions, the microorganisms or cells are able to perform their desired function with limited production of impurities. The environmental conditions inside the bioreactor, such as temperature, nutrient concentrations, pH, and dissolved gases (especially oxygen for aerobic fermentations) affect the growth and productivity of the organisms. The temperature of the fermentation medium is maintained by a cooling jacket, coils, or both. Particularly exothermic fermentations may require the use of external heat exchangers. Nutrients may be continuously added to the fermenter, as in a fed-batch system, or may be charged into the reactor at the beginning of fermentation. The pH of the medium is measured and adjusted with small amounts of acid or base, depending upon the fermentation. For aerobic (and some anaerobic) fermentations, reactant gases (especially oxygen) must be added to the fermentation. Since oxygen is relatively insoluble in water (the basis of nearly all fermentation media), air (or purified oxygen) must be added continuously. The action of the rising bubbles helps mix the fermentation medium and also "strips" out waste gases, such as carbon dioxide. In practice, bioreactors are often pressurized; this increases the solubility of oxygen in water. In an aerobic process, optimal oxygen transfer is sometimes the rate limiting step. Oxygen is poorly soluble in water—even less in warm fermentation broths—and is relatively scarce in air (20.95%). Oxygen transfer is usually helped by agitation, which is also needed to mix nutrients and to keep the fermentation homogeneous. Gas dispersing agitators are used to break up air bubbles and circulate them throughout the vessel.
Fouling can harm the overall efficiency of the bioreactor, especially the heat exchangers. To avoid it, the bioreactor must be easily cleaned. Interior surfaces are typically made of stainless steel for easy cleaning and sanitation. Typically bioreactors are cleaned between batches, or are designed to reduce fouling as much as possible when operated continuously. Heat transfer is an important part of bioreactor design; small vessels can be cooled with a cooling jacket, but larger vessels may require coils or an external heat exchanger. | 1 | Applied and Interdisciplinary Chemistry |
A chemical system is said to be in equilibrium when the quantities of the chemical entities involved do not and cannot change in time without the application of an external influence. In this sense a system in chemical equilibrium is in a stable state. The system at chemical equilibrium will be at a constant temperature, pressure or volume and a composition. It will be insulated from exchange of heat with the surroundings, that is, it is a closed system. A change of temperature, pressure (or volume) constitutes an external influence and the equilibrium quantities will change as a result of such a change. If there is a possibility that the composition might change, but the rate of change is negligibly slow, the system is said to be in a metastable state. The equation of chemical equilibrium can be expressed symbolically as
:reactant(s) product(s)
The sign means "are in equilibrium with". This definition refers to macroscopic properties. Changes do occur at the microscopic level of atoms and molecules, but to such a minute extent that they are not measurable and in a balanced way so that the macroscopic quantities do not change. Chemical equilibrium is a dynamic state in which forward and backward reactions proceed at such rates that the macroscopic composition of the mixture is constant. Thus, equilibrium sign symbolizes the fact that reactions occur in both forward and backward directions.
A steady state, on the other hand, is not necessarily an equilibrium state in the chemical sense. For example, in a radioactive decay chain the concentrations of intermediate isotopes are constant because the rate of production is equal to the rate of decay. It is not a chemical equilibrium because the decay process occurs in one direction only.
Thermodynamic equilibrium is characterized by the free energy for the whole (closed) system being a minimum. For systems at constant volume the Helmholtz free energy is minimum and for systems at constant pressure the Gibbs free energy is minimum. Thus a metastable state is one for which the free energy change between reactants and products is not minimal even though the composition does not change in time.
The existence of this minimum is due to the free energy of mixing of reactants and products being always negative. For ideal solutions the enthalpy of mixing is zero, so the minimum exists because the entropy of mixing is always positive. The slope of the reaction free energy, δG with respect to the reaction coordinate, ξ, is zero when the free energy is at its minimum value. | 0 | Theoretical and Fundamental Chemistry |
The genetic instructions of every replicating cell in a living organism are contained within its DNA. Throughout the cell's lifetime, this information is transcribed and replicated by cellular mechanisms to produce proteins or to provide instructions for daughter cells during cell division, and the possibility exists that the DNA may be altered during these processes. This is known as a mutation. At the molecular level, there are regulatory systems that correct most — but not all — of these changes to the DNA before it is replicated.
The functionality of a protein is highly dependent on its structure. Changing a single amino acid in a protein may reduce its ability to carry out this function, or the mutation may even change the function that the protein carries out. Changes like these may severely impact a crucial function in a cell, potentially causing the cell — and in extreme cases, the organism — to die. Conversely, the change may allow the cell to continue functioning albeit differently, and the mutation can be passed on to the organism's offspring. If this change does not result in any significant physical disadvantage to the offspring, the possibility exists that this mutation will persist within the population. The possibility also exists that the change in function becomes advantageous.
The 20 amino acids translated by the genetic code vary greatly by the physical and chemical properties of their side chains. However, these amino acids can be categorised into groups with similar physicochemical properties. Substituting an amino acid with another from the same category is more likely to have a smaller impact on the structure and function of a protein than replacement with an amino acid from a different category.
Sequence alignment is a fundamental research method for modern biology. The most common sequence alignment for protein is to look for similarity between different sequences in order to infer function or establish evolutionary relationships. This helps researchers better understand the origin and function of genes through the nature of homology and conservation. Substitution matrices are utilized in algorithms to calculate the similarity of different sequences of proteins; however, the utility of Dayhoff PAM Matrix has decreased over time due to the requirement of sequences with a similarity more than 85%. In order to fill in this gap, Henikoff and Henikoff introduced BLOSUM (BLOcks SUbstitution Matrix) matrix which led to marked improvements in alignments and in searches using queries from each of the groups of related proteins. | 1 | Applied and Interdisciplinary Chemistry |
Anion exchange sorbents are derivatized with positively charged functional groups that interact and retain negatively charged anions, such as acids. Strong anion exchange sorbents contain quaternary ammonium groups that have a permanent positive charge in aqueous solutions, and weak anion exchange sorbents use amine groups which are charged when the pH is below about 9. Strong anion exchange sorbents are useful because any strongly acidic impurities in the sample will bind to the sorbent and usually will not be eluted with the analyte of interest; to recover a strong acid a weak anion exchange cartridge should be used. To elute the analyte from either the strong or weak sorbent, the stationary phase is washed with a solvent that neutralizes the charge of either the analyte, the stationary phase, or both. Once the charge is neutralized, the electrostatic interaction between the analyte and the stationary phase no longer exists and the analyte will elute from the cartridge. | 0 | Theoretical and Fundamental Chemistry |
Random sequential adsorption (RSA) refers to a process where particles are randomly introduced in a system, and if they do not overlap any previously adsorbed particle, they adsorb and remain fixed for the rest of the process. RSA can be carried out in computer simulation, in a mathematical analysis, or in experiments. It was first studied by one-dimensional models: the attachment of pendant groups in a polymer chain by Paul Flory, and the car-parking problem by Alfréd Rényi. Other early works include those of Benjamin Widom. In two and higher dimensions many systems have been studied by computer simulation, including in 2d, disks, randomly oriented squares and rectangles, aligned squares and rectangles, various other shapes, etc.
An important result is the maximum surface coverage, called the saturation coverage or the packing fraction. On this page we list that coverage for many systems.
The blocking process has been studied in detail in terms of the random sequential adsorption (RSA) model. The simplest RSA model related to deposition of spherical particles considers irreversible adsorption of circular disks. One disk after another is placed randomly at a surface. Once a disk is placed, it sticks at the same spot, and cannot be removed. When an attempt to deposit a disk would result in an overlap with an already deposited disk, this attempt is rejected. Within this model, the surface is initially filled rapidly, but the more one approaches saturation the slower the surface is being filled. Within the RSA model, saturation is sometimes referred to as jamming. For circular disks, saturation occurs at a coverage of 0.547. When the depositing particles are polydisperse, much higher surface coverage can be reached, since the small particles will be able to deposit into the holes in between the larger deposited particles. On the other hand, rod like particles may lead to much smaller coverage, since a few misaligned rods may block a large portion of the surface.
For the one-dimensional parking-car problem, Renyi has shown that the maximum coverage is equal to
the so-called Renyi car-parking constant.
Then followed the conjecture of Ilona Palásti, who proposed that the coverage of d-dimensional aligned squares, cubes and hypercubes is equal to θ. This conjecture led to a great deal of work arguing in favor of it, against it, and finally computer simulations in two and three dimensions showing that it was a good approximation but not exact. The accuracy of this conjecture in higher dimensions is not known.
For -mers on a one-dimensional lattice, we have for the fraction of vertices covered,
When goes to infinity, this gives the Renyi result above. For k = 2, this gives the Flory result .
For percolation thresholds related to random sequentially adsorbed particles, see Percolation threshold. | 0 | Theoretical and Fundamental Chemistry |
The Britton–Robinson buffer (aka BRB aka PEM) is a "universal" pH buffer used for the pH range from 2 to 12. It has been used historically as an alternative to the McIlvaine buffer, which has a smaller pH range of effectiveness (from 2 to 8).
Universal buffers consist of mixtures of acids of diminishing strength (increasing pK), so that the change in pH is approximately proportional to the amount of alkali added. It consists of a mixture of 0.04 M boric acid, 0.04 M phosphoric acid and 0.04 M acetic acid that has been titrated to the desired pH with 0.2 M sodium hydroxide. Britton and Robinson also proposed a second formulation that gave an essentially linear pH response to added alkali from pH 2.5 to pH 9.2 (and buffers to pH 12). This mixture consists of 0.0286 M citric acid, 0.0286 M monopotassium phosphate, 0.0286 M boric acid, 0.0286 M veronal and 0.0286 M hydrochloric acid titrated with 0.2 M sodium hydroxide.
The buffer was invented in 1931 by the English chemist Hubert Thomas Stanley "Kevin" Britton (1892–1960) and the New Zealand chemist Robert Anthony Robinson (1904–1979). | 0 | Theoretical and Fundamental Chemistry |
Heterogeneous metal catalyzed cross-coupling is a subset of metal catalyzed cross-coupling in which a heterogeneous metal catalyst is employed. Generally heterogeneous cross-coupling catalysts consist of a metal dispersed on an inorganic surface or bound to a polymeric support with ligands. Heterogeneous catalysts provide potential benefits over homogeneous catalysts in chemical processes in which cross-coupling is commonly employed—particularly in the fine chemical industry—including recyclability and lower metal contamination of reaction products. However, for cross-coupling reactions, heterogeneous metal catalysts can suffer from pitfalls such as poor turnover and poor substrate scope, which have limited their utility in cross-coupling reactions to date relative to homogeneous catalysts. Heterogeneous metal catalyzed cross-couplings, as with homogeneous metal catalyzed ones, most commonly use Pd as the cross-coupling metal. | 0 | Theoretical and Fundamental Chemistry |
Nuclear stability is limited to those combinations of protons and neutrons described by the chart of the nuclides, also called the valley of stability. The boundaries of this valley are the neutron drip line on the neutron-rich side, and the proton drip line on the proton-rich side. These limits exist because of particle decay, whereby an exothermic nuclear transition can occur by the emission of one or more nucleons (not to be confused with particle decay in particle physics). As such, the drip line may be defined as the boundary beyond which proton or neutron separation energy becomes negative, favoring the emission of a particle from a newly formed unbound system. | 0 | Theoretical and Fundamental Chemistry |
Shanon Shah was also the former full-time Columns and Comments Editor at The Nut Graph, a bilingual, independent, Malaysian online news site aiming "to provide space for columnists and reader comments from as broad a political spectrum, and from as many sectors of interest, as possible". He contributed several English-language features, commentaries and interviews on the politics of Islam in Malaysia. His fortnightly Malay-language column, Secubit Garam, often took a light-hearted approach to serious political concerns through the fictional agony aunt Kak Nora.
Shanon has also been published in other print anthologies. His 5,000-word essay "The Khutbah Diaries" was published in New Malaysian Essays 2 in 2009. In the same year his essay, "Muslim 2 Muslim", was published in Body 2 Body, an English-language anthology of fiction and non-fiction on sexual diversity in Malaysia. Body 2 Body was published by writer-director Amir Muhammad's publishing company, Matahari Books.
In June 2012, Shanons essay "Lots Legacy" was published in the third issue of Critical Muslim (Fear and Loathing), a British "quarterly magazine of ideas and issues showcasing ground-breaking thinking on Islam and what it means to be a Muslim in a rapidly changing, interconnected world". The magazine is co-edited by London-based Muslim scholar and critic Ziauddin Sardar. | 1 | Applied and Interdisciplinary Chemistry |
For any substance, the number density can be expressed in terms of its amount concentration c (in mol/m) as
where is the Avogadro constant. This is still true if the spatial dimension unit, metre, in both n and c is consistently replaced by any other spatial dimension unit, e.g. if n is in cm and c is in mol/cm, or if n is in L and c is in mol/L, etc. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen embrittlement can be prevented through several methods, all of which are centered on minimizing contact between the metal and hydrogen, particularly during fabrication and the electrolysis of water. Embrittling procedures such as acid pickling should be avoided, as should increased contact with elements such as sulfur and phosphate.
If the metal has not yet started to crack, hydrogen embrittlement can be reversed by removing the hydrogen source and causing the hydrogen within the metal to diffuse out through heat treatment. This de-embrittlement process, known as low hydrogen annealing or "baking", is used to overcome the weaknesses of methods such as electroplating which introduce hydrogen to the metal, but is not always entirely effective because a sufficient time and temperature must be reached. Tests such as ASTM F1624 can be used to rapidly identify the minimum baking time (by testing using design of experiments, a relatively low number of samples can be used to pinpoint this value). Then the same test can be used as a quality control check to evaluate if baking was sufficient on a per-batch basis.
In the case of welding, often pre-heating and post-heating the metal is applied to allow the hydrogen to diffuse out before it can cause any damage. This is specifically done with high-strength steels and low alloy steels such as the chromium/molybdenum/vanadium alloys. Due to the time needed to re-combine hydrogen atoms into the hydrogen molecules, hydrogen cracking due to welding can occur over 24 hours after the welding operation is completed.
Another way of preventing this problem is through materials selection. This will build an inherent resistance to this process and reduce the need of post processing or constant monitoring for failure. Certain metals or alloys are highly susceptible to this issue, so choosing a material that is minimally affected while retaining the desired properties would also provide an optimal solution. Much research has been done to catalog the compatibility of certain metals with hydrogen.
Tests such as ASTM F1624 can also be used to rank alloys and coatings during materials selection to ensure (for instance) that the threshold of cracking is below the threshold for hydrogen-assisted stress corrosion cracking. Similar tests can also be used during quality control to more effectively qualify materials being produced in a rapid and comparable manner. | 0 | Theoretical and Fundamental Chemistry |
The principle of thermal conductivity of gases can also be used to measure the concentration of a gas in a binary mixture of gases.
Working: if the same gas is present around all the Wheatstone bridge filaments, then the same temperature is maintained in all the filaments and hence same resistances are also maintained; resulting in a balanced Wheatstone bridge. However, If the dissimilar gas sample (or gas mixture) is passed over one set of two filaments and the reference gas on the other set of two filaments, then the Wheatstone bridge becomes unbalanced. And the resulting net voltage output of the circuit will be correlated with the database to identify the constituents of the sample gas.
Using this technique many unknown gas samples can be identified by comparing their thermal conductivity with other reference gas of known thermal conductivity. The most commonly used reference gas is nitrogen; as the thermal conductivity of most common gases (except hydrogen and helium) are similar to that of nitrogen. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, treadmilling is a phenomenon observed within protein filaments of the cytoskeletons of many cells, especially in actin filaments and microtubules. It occurs when one end of a filament grows in length while the other end shrinks, resulting in a section of filament seemingly "moving" across a stratum or the cytosol. This is due to the constant removal of the protein subunits from these filaments at one end of the filament, while protein subunits are constantly added at the other end. Treadmilling was discovered by Wegner, who defined the thermodynamic and kinetic constraints. Wegner recognized that: “The equilibrium constant (K) for association of a monomer with a polymer is the same at both ends, since the addition of a monomer to each end leads to the same polymer.”; a simple reversible polymer can’t treadmill; ATP hydrolysis is required. GTP is hydrolyzed for microtubule treadmilling. | 1 | Applied and Interdisciplinary Chemistry |
Mutations in the collagen gene can lead to the disease Osteogenesis Imperfecta, which is characterized by brittle bones. In the illustration, a stem-loop formed from an imperfect inverted repeat is mutated with a thymine (T) nucleotide insertion as a result of an inter- or intrastrand switch. The addition of the T creates a base-pairing "match up" with the adenine (A) that was previously a "bump" on the left side of the stem. While this addition makes the stem stronger and perfects the inverted repeat, it also creates a frameshift mutation in the nucleotide sequence which alters the reading frame and will result in an incorrect expression of the gene. | 1 | Applied and Interdisciplinary Chemistry |
Selegiline is considered by some to be a nootropic, both at clinical and sub-clinical dosages, and has been used off-label to improve cognitive performance. It has been shown to have protective activity against a range of neurotoxins and to increase the production of several brain growth factors, such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor. It has been demonstrated in numerous animal models to improve learning ability and preserve it during both ischemia and aging. | 0 | Theoretical and Fundamental Chemistry |
Doping fullerenes with electropositive metals takes place in an arc reactor or via laser evaporation. The metals can be transition metals like scandium, yttrium as well as lanthanides like lanthanum and cerium. Also possible are endohedral complexes with elements of the alkaline earth metals like barium and strontium, alkali metals like potassium and tetravalent metals like uranium, zirconium and hafnium. The synthesis in the arc reactor is however unspecific. Besides unfilled fullerenes, endohedral metallofullerenes develop with different cage sizes like La@C or La@C and as different isomer cages. Aside from the dominant presence of mono-metal cages, numerous di-metal endohedral complexes and the tri-metal carbide fullerenes like ScC@C were also isolated.
In 1999 a discovery drew large attention. With the synthesis of the ScN@C by Harry Dorn and coworkers, the inclusion of a molecule fragment in a fullerene cage had succeeded for the first time. This compound can be prepared by arc-vaporization at temperatures up to 1100 °C of graphite rods packed with scandium(III) oxide iron nitride and graphite powder in a K-H generator in a nitrogen atmosphere at 300 Torr.
Endohedral metallofullerenes are characterised by the fact that electrons will transfer from the metal atom to the fullerene cage and that the metal atom takes a position off-center in the cage. The size of the charge transfer is not always simple to determine. In most cases it is between 2 and 3 charge units, in the case of the La@C however it can be even about 6 electrons such as in ScN@C which is better described as [ScN]@[C]. These anionic fullerene cages are very stable molecules and do not have the reactivity associated with ordinary empty fullerenes. They are stable in air up to very high temperatures (600 to 850 °C).
The lack of reactivity in Diels-Alder reactions is utilised in a method to purify [C] compounds from a complex mixture of empty and partly filled fullerenes of different cage size. In this method Merrifield resin is modified as a cyclopentadienyl resin and used as a solid phase against a mobile phase containing the complex mixture in a column chromatography operation. Only very stable fullerenes such as [ScN]@[C] pass through the column unreacted.
In Ce@C the two metal atoms exhibit a non-bonded interaction. Since all the six-membered rings in C-I are equal the two encapsulated Ce atoms exhibit a three-dimensional random motion. This is evidenced by the presence of only two signals in the C-NMR spectrum. It is possible to force the metal atoms to a standstill at the equator as shown by x-ray crystallography when the fullerene is exahedrally functionalized by an electron donation silyl group in a reaction of Ce@C with 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disilirane.
Gd@C(OH), an endohedral metallofluorenol, can competitively inhibit the WW domain in the oncogene YAP1 from activating. It was originally developed as an MRI contrast agent. | 0 | Theoretical and Fundamental Chemistry |
The "diarylethenes" were first introduced by Irie and have since gained widespread interest, largely on account of their high thermodynamic stability. They operate by means of a 6-pi electrocyclic reaction, the thermal analog of which is impossible due to steric hindrance. Pure photochromic dyes usually have the appearance of a crystalline powder, and in order to achieve the color change, they usually have to be dissolved in a solvent or dispersed in a suitable matrix. However, some diarylethenes have so little shape change upon isomerization that they can be converted while remaining in crystalline form. | 0 | Theoretical and Fundamental Chemistry |
Source:
*1946 – David E. Green
*1947 – Van R. Potter
*1948 – Albert L. Lehninger
*1949 – Henry A. Lardy
*1950 – Britton Chance
*1951 – Arthur Kornberg
*1952 – Bernard L. Horecker
*1953 – Earl R. Stadtman
*1954 – Alton Meister
*1955 – Paul D. Boyer
*1956 – Merton F. Utter
*1957 – G. Robert Greenberg
*1958 – Eugene P. Kennedy
*1959 – Minor J. Coon
*1960 – Arthur Pardee
*1961 – Frank M. Huennekens
*1962 – Jack L. Strominger
*1963 – Charles Gilvarg
*1964 – Marshall Nirenberg
*1965 – Frederic M. Richards
*1966 – Samuel B. Weiss
*1967 – P. Roy Vagelos & Salih J. Wakil
*1968 – William J. Rutter
*1969 – Robert T. Schimke
*1970 – Herbert Weissbach
*1971 – Jack Preiss
*1972 – Ekkehard K. F. Bautz
*1973 – Howard M. Temin
*1974 – Michael J. Chamberlin
*1975 – Malcolm L. Gefter
*1976 – Michael S. Brown & Joseph L. Goldstein
*1977 – Stephen J. Benkovic
*1978 – Paul Schimmel
*1979 – Frederik C. Hartman
*1980 – Thomas A. Steitz
*1981 – Daniel V. Santi
*1982 – Richard R. Burgess
*1983 – Paul L. Modrich
*1984 – Robert T.N. Tjian
*1985 – Thomas R. Cech
*1986 – JoAnne Stubbe
*1987 – Gregory Petsko
*1988 – John W. Kozarich
*1989 – Kenneth A. Johnson
*1990 – James A. Wells
*1991 – Ronald Vale
*1992 – Carl O. Pabo
*1993 – Michael H. Gelb
*1994 – Donald Hilvert
*1995 – Gerald F. Joyce
*1996 – P. Andrew Karplus
*1997 – Daniel Herschlag
*1998 – Ronald T. Raines
*1999 – David W. Christianson
*2000 – Eric T. Kool
*2001 – Ruma Banerjee
*2002 – Karin Musier-Forsyth
*2003 – Dorothee Kern
*2004 – Wilfred A. van der Donk
*2005 – Nicole S. Sampson
*2006 – James Berger
*2007 – Neil L. Kelleher
*2008 – Carsten Krebs
*2009 – Virginia Cornish
*2010 – Vahe Bandarian
*2011 – Sarah O’Connor
*2012 – Jin Zhang
*2013 – Kate Carroll
*2014 – Hening Lin
*2015 – Douglas Mitchell
*2016 – Michelle C. Chang
*2017 – Emily Balskus
*2018 – Mohammad Seyedsayamdost
*2019 – Kenichi Yokoyama
*2020 – Rahul Kohli
*2021 – Amie K. Boal | 1 | Applied and Interdisciplinary Chemistry |
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