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CSPD ([3-(1-chloro-3-methoxyspiro[adamantane-4,4-dioxetane]-3'-yl)phenyl] dihydrogen phosphate) is a chemical substance with formula CHClOP. It is a component of enhanced chemiluminescence enzyme-linked immunosorbent assay (ELISA) kits, used for the detection of minute amounts of various substances such as proteins. | 1 | Applied and Interdisciplinary Chemistry |
Several species of fungi can be used for bioleaching. Fungi can be grown on many different substrates, such as electronic scrap, catalytic converters, and fly ash from municipal waste incineration. Experiments have shown that two fungal strains (Aspergillus niger, Penicillium simplicissimum) were able to mobilize Cu and Sn by 65%, and Al, Ni, Pb, and Zn by more than 95%. Aspergillus niger can produce some organic acids such as citric acid. This form of leaching does not rely on microbial oxidation of metal but rather uses microbial metabolism as source of acids that directly dissolve the metal. | 1 | Applied and Interdisciplinary Chemistry |
There is a hypoxic zone covers the coasts of Oregon and Washington that reached peak size in 2006 at an area of over 1,158 square miles. Strong surface winds between April and September cause frequent upwelling that results in an increase of algae blooms, rendering the hypoxia a seasonal occurrence. The upwelling has contributed to lower temperatures within the zone. The dead zone has resulted in sea organisms such as crabs and fish relocating and an interference of commercial fishing. Organisms that cannot relocate have been found to suffocate, leaving them unable to be used by fishermen. In 2009, one scientist described "thousands and thousands" of suffocated, crabs, worms, and sea stars along the seafloor of the hypoxic zone. In 2021, 1.9 million dollars were put into monitoring and continuing to study the hypoxic conditions in the area that the dead zone occurs in. | 0 | Theoretical and Fundamental Chemistry |
Graft copolymers are generated by attaching chains of one monomer to the main chain of another polymer; a branched block copolymer is formed. Furthermore, end groups play an important role in the process of initiation, propagation and termination of graft polymers. Graft polymers can be achieved by either "grafting from" or "grafting to"; these different methods are able to produce a vast array of different polymer structures, which can be tailored to the application in question. The "grafting from" approach involves, for example, generation of radicals along a polymer chain, which can then be reacted with monomers to grow a new polymer from the backbone of another. In "grafting from," the initiation sites on the backbone of the first polymer can be part of the backbone structure originally or generated in situ. The "grafting to" approach involves the reaction of functionalized monomers to a polymer backbone. In graft polymers, end groups play an important role, for example, in the "grafting to" technique the generation of the reactive functionalized monomers occurs at the end group, which is then tethered to the polymer chain. There are various methods to synthesize graft polymers some of the more common include redox reaction to produce free radicals, by free radical polymerization techniques avoiding chain termination (ATRP, RAFT, nitroxide mediated, for example) and step-growth polymerization. A schematic of "grafting from" and "grafting to" is illustrated in the figure below.
The "grafting from" technique involves the generation of radicals along the polymer backbone from an abstraction of a halogen, from either the backbone or a functional group along the backbone. Monomers are reacted with the radicals along the backbone and subsequently generate polymers which are grafted from the backbone of the first polymer. The schematic for "grafting to" shows an example using anionic polymerizations, the polymer containing the carbonyl functionalities gets attacked by the activated polymer chain and generates a polymer attached to the associated carbon along with an alcohol group, in this example. These examples show us the potential of fine tuning end groups of polymer chains to target certain copolymer structures. | 0 | Theoretical and Fundamental Chemistry |
The primary molecular mechanism behind an oscillating gene is best described as a transcription/translation feedback loop. This loop contains both positive regulators, which increase gene expression, and negative regulators, which decrease gene expression. The fundamental elements of these loops are found across different phyla. In the mammalian circadian clock, for example, transcription factors CLOCK and BMAL1 are the positive regulators. CLOCK and BMAL1 bind to the E-box of oscillating genes, such as Per1, Per2, and Per3 and Cry1 and Cry2, and upregulate their transcription. When the PERs and CRYs form a heterocomplex in the cytoplasm and enter the nucleus again, they inhibit their own transcription. This means that over time the mRNA and protein levels of PERs and CRYs, or any other oscillating gene under this mechanism, will oscillate.
There also exists a secondary feedback loop, or stabilizing loop, which regulates the cyclic expression of Bmal1. This is caused by two nuclear receptors, REV-ERB and ROR, which suppresses and activates Bmal1 transcription, respectively.
In addition to these feedback loops, post-translational modifications also play a role in changing the characteristics of the circadian clock, such as its period. Without any type of feedback repression, the molecular clock would have a period of just a few hours. Casein kinase members CK1ε and CK1δ were both found to be mammalian protein kinases involved in circadian regulation. Mutations in these kinases are associated with familial advanced sleep phase syndrome (FASPS). In general, phosphorylation is necessary for the degradation of PERs via ubiquitin ligases. In contrast, phosphorylation of BMAL1 via CK2 is important for accumulation of BMAL1. | 1 | Applied and Interdisciplinary Chemistry |
These structural mimetics include molecules that are highly modified when compared to their parent peptide sequence. Usually, a small-molecular scaffold is appyled to project groups in analogy to the bioactive conformation of a peptide. | 0 | Theoretical and Fundamental Chemistry |
Pewter () is a malleable metal alloy consisting of tin (85–99%), antimony (approximately 5–10%), copper (2%), bismuth, and sometimes silver. In the past it was an alloy of tin and lead, but most modern pewter, in order to prevent lead poisoning, is not made with lead. Pewter has a low melting point, around , depending on the exact mixture of metals. The word pewter is probably a variation of "spelter", a term for zinc alloys (originally a colloquial name for zinc). | 1 | Applied and Interdisciplinary Chemistry |
The types of toxicities where substances may cause lethality to the entire body, lethality to specific organs, major/minor damage, or cause cancer. These are globally accepted definitions of what toxicity is. Anything falling outside of the definition cannot be classified as that type of toxicant. | 1 | Applied and Interdisciplinary Chemistry |
There are fourteen naturally occurring enediynes. The other existing classes of enediynes have been synthesized in the lab.
Enediynes have been split into two sub-families: those with nine members in the core enediyne ring and those with ten-membered rings. | 0 | Theoretical and Fundamental Chemistry |
The number density (symbol: n or ρ) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density. Population density is an example of areal number density. The term number concentration (symbol: lowercase n, or C, to avoid confusion with amount of substance indicated by uppercase N) is sometimes used in chemistry for the same quantity, particularly when comparing with other concentrations. | 0 | Theoretical and Fundamental Chemistry |
An important group of SNPs are those that corresponds to missense mutations causing amino acid change on protein level. Point mutation of particular residue can have different effect on protein function (from no effect to complete disruption its function). Usually, change in amino acids with similar size and physico-chemical properties (e.g. substitution from leucine to valine) has mild effect, and opposite. Similarly, if SNP disrupts secondary structure elements (e.g. substitution to proline in alpha helix region) such mutation usually may affect whole protein structure and function. Using those simple and many other machine learning derived rules a group of programs for the prediction of SNP effect was developed:
* [http://sift-dna.org SIFT] This program provides insight into how a laboratory induced missense or nonsynonymous mutation will affect protein function based on physical properties of the amino acid and sequence homology.
* [https://gsponerlab.msl.ubc.ca/software/list/ LIST] (Local Identity and Shared Taxa) estimates the potential deleteriousness of mutations resulted from altering their protein functions. It is based on the assumption that variations observed in closely related species are more significant when assessing conservation compared to those in distantly related species.
* [https://rostlab.org/services/snap SNAP2]
* [http://www.sbg.bio.ic.ac.uk/suspect/index.html SuSPect]
* [http://genetics.bwh.harvard.edu/pph2/ PolyPhen-2]
* [http://loschmidt.chemi.muni.cz/predictsnp/ PredictSNP]
* MutationTaster: [http://www.mutationtaster.org/ official website]
* [http://www.ensembl.org/info/docs/tools/vep/index.html Variant Effect Predictor] from the Ensembl project
* [https://genomicscomputbiol.org/ojs3/GCB/article/view/48/182 SNPViz] This program provides a 3D representation of the protein affected, highlighting the amino acid change so doctors can determine pathogenicity of the mutant protein.
* [http://provean.jcvi.org/index.php PROVEAN]
* [http://phyrerisk.bc.ic.ac.uk PhyreRisk] is a database which maps variants to experimental and predicted protein structures.
* [http://www.sbg.bio.ic.ac.uk/~missense3d/ Missense3D] is a tool which provides a stereochemical report on the effect of missense variants on protein structure. | 1 | Applied and Interdisciplinary Chemistry |
In 1968, he received an honorary degree from the Technical University of Berlin. In 1970 he received the Marie Curie Medal from the Curie Institute, and officially retired from his chair at Newcastle. In 1972 the Association for Radiation Research established the Weiss Medal, named after him. | 0 | Theoretical and Fundamental Chemistry |
A colloidal crystal is a highly ordered array of particles which can be formed over a long range (to about a centimeter). Arrays such as this appear to be analogous to their atomic or molecular counterparts with proper scaling considerations. A good natural example of this phenomenon can be found in precious opal, where brilliant regions of pure spectral color result from close-packed domains of colloidal spheres of amorphous silicon dioxide, SiO (see above illustration). The spherical particles precipitate in highly siliceous pools and form highly ordered arrays after years of sedimentation and compression under hydrostatic and gravitational forces. The periodic arrays of spherical particles make similar arrays of interstitial voids, which act as a natural diffraction grating for light waves in photonic crystals, especially when the interstitial spacing is of the same order of magnitude as the incident lightwave. | 0 | Theoretical and Fundamental Chemistry |
Work from the Widom laboratory has shown that nucleosomal DNA is in equilibrium between a wrapped and unwrapped state. Measurements of these rates using time-resolved FRET revealed that DNA within the nucleosome remains fully wrapped for only 250 ms before it is unwrapped for 10-50 ms and then rapidly rewrapped. This implies that DNA does not need to be actively dissociated from the nucleosome but that there is a significant fraction of time during which it is fully accessible. Indeed, this can be extended to the observation that introducing a DNA-binding sequence within the nucleosome increases the accessibility of adjacent regions of DNA when bound. This propensity for DNA within the nucleosome to "breathe" has important functional consequences for all DNA-binding proteins that operate in a chromatin environment. In particular, the dynamic breathing of nucleosomes plays an important role in restricting the advancement of RNA polymerase II during transcription elongation. | 1 | Applied and Interdisciplinary Chemistry |
The presence of surface active elements such as oxygen and sulfur will have a large impact on the measurements obtained with this technique. Surface active elements will exist in larger concentrations at the surface than in the bulk of the liquid, meaning that the total levels of these elements must be carefully controlled to a very low level. For example, the presence of only 50 ppm sulphur in liquid iron will reduce the surface tension by approximately 20%. | 0 | Theoretical and Fundamental Chemistry |
A Biomolecular Analysis Mass Spectrometry (BAMS) facility was officially opened in 2003, headed by Professor Newton and Dr Dudley. It was a collaborative entity between the Department of Biological Sciences and the Medical School. It focused on the study of nucleosides, nucleotides and cyclic nucleotides. | 0 | Theoretical and Fundamental Chemistry |
A biosignature must be detectable with the current technology to be relevant in scientific investigation. This seems to be an obvious statement, however, there are many scenarios in which life may be present on a planet yet remain undetectable because of human-caused limitations. | 1 | Applied and Interdisciplinary Chemistry |
Quasi-solid, Falsely-solid, or semisolid is the physical term for something whose state lies between a solid and a liquid. While similar to solids in some respects, such as having the ability to support their own weight and hold their shapes, a quasi-solid also shares some properties of liquids, such as conforming in shape to something applying pressure to it and the ability to flow under pressure. The words quasi-solid, semisolid, and semiliquid may be used interchangeably.
Quasi-solids and semisolids are sometimes described as amorphous because at the microscopic scale they have a disordered structure unlike crystalline solids. They should not be confused with amorphous solids as they are not solids and exhibit properties such as flow which bulk solids do not. | 0 | Theoretical and Fundamental Chemistry |
PECO has also shown promise as a means of air purification. For people with severe allergies, air purifiers are important to protect them from allergens within their own homes. However, some allergens are too small to be removed by normal purification methods. Air purifiers using PECO filters are able to remove particles as small as 0.1 nm.
These filters work as photons excite a photocatalyst, creating hydroxyl free radicals, which are extremely reactive and oxidize organic material and microorganisms that cause allergy symptoms, forming harmless products like carbon dioxide and water. Researchers testing this technology with patients suffering from allergies drew promising conclusions from their studies, observing significant reductions in total symptom scores (TSS) for both nasal (TNSS) and ocular (TOSS) allergies after just 4 weeks of using the PECO filter. This research demonstrates strong potential for impactful health improvements who suffer from severe allergies and asthma. | 0 | Theoretical and Fundamental Chemistry |
In cancers, loss of expression of genes occurs about 10 times more frequently by transcription silencing (caused by promoter hypermethylation of CpG islands) than by mutations. As Vogelstein et al. point out, in a colorectal cancer there are usually about 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. In contrast, in colon tumors compared to adjacent normal-appearing colonic mucosa, there are about 600 to 800 heavily methylated CpG islands in promoters of genes in the tumors while these CpG islands are not methylated in the adjacent mucosa.
Using gene set enrichment analysis, 569 out of 938 gene sets were hypermethylated and 369 were hypomethylated in cancers. Hypomethylation of CpG islands in promoters results in increased transcription of the genes or gene sets affected.
One study listed 147 specific genes with colon cancer-associated hypermethylated promoters and 27 with hypomethylated promoters, along with the frequency with which these hyper/hypo-methylations were found in colon cancers. At least 10 of those genes had hypermethylated promoters in nearly 100% of colon cancers. They also indicated 11 microRNAs whose promoters were hypermethylated in colon cancers at frequencies between 50% and 100% of cancers. MicroRNAs (miRNAs) are small endogenous RNAs that pair with sequences in messenger RNAs to direct post-transcriptional repression. On average, each microRNA represses or inhibits transcriptional expression of several hundred target genes. Thus microRNAs with hypermethylated promoters may be allowing enhanced transcription of hundreds to thousands of genes in a cancer. | 1 | Applied and Interdisciplinary Chemistry |
Otto Perutz (27 July 1847, Teplice, Bohemia – 18 January 1922, Munich Germany) was an Austrian-German chemist.
From 1872 to 1876, Perutz was director of Bayerische Aktiengesellschaft für chemische und landwirtschaftlich-chemische Fabrikate (Bavarian Corporation for Chemical and Agrochemical Products Inc., later Süd-Chemie AG) in Munich-Heufeld.
In 1880, he founded his own firm Otto Perutz Trockenplattenfabrik in Munich. He developed a method for the industrial production of Eosin-Silver-Plates which had been invented by Hermann Wilhelm Vogel and Johann Baptist Obernetter. This was crucial to develop colour photography. In 1896, Perutz-Plates were used for radiography for the first time.
Perutz sold his firm in 1897. He was member of the supervisory board of Bayerische Aktiengesellschaft für chemische und landwirtschaftlich-chemische Fabrikate from 1902 until his death in 1922. The Perutz-Photowerke became part of Agfa in 1964. | 0 | Theoretical and Fundamental Chemistry |
Technically, Hammonds postulate only describes the geometric structure of a chemical reaction. However, Hammonds postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell–Evans–Polanyi principle, which describes the experimental observation that the enthalpy and rate of a similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a S1 reaction. Although two transition states occur during a S1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step.
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally S1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation product when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation product, then it will be higher in energy. | 0 | Theoretical and Fundamental Chemistry |
The Danheiser benzannulation is a regiocontrolled phenol annulation. This annulation provides an efficient route to form an aromatic ring in one step. It is a thermal combination of a substituted cyclobutenones with heterosubstituted acetylenes to produce highly substituted aromatic compounds, specifically phenols or resorcinols (Scheme 1). This benzannulation reaction creates previously unaccessed aromatic substitution patterns. A variety of substituted aromatic rings can be prepared using this method including: phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles.
The modified Danheiser benzannulation allows the synthesis of polycyclic aromatic and heteroaromatic systems. This also includes napthalenes, benzofurans and indoles. This second generation aromatic annulation is achieved by irradiation of a solution of acetylene and a vinyl or aryl α-diazo ketone in dichloroethane. This reaction utilizes the photochemical Wolff rearrangement of a diazoketone to generate an aryl or vinylketene. These ketene intermediates cannot be isolated due to their high reactivity to form diketenes. These rearrangements are performed in the presence of unsaturated compounds which undergo [2+2] cycloadditions with the in situ generated ketenes. When ketenes are formed in the presence of alkynes they proceed through pericyclic reactions to generate a substituted aromatic ring (Scheme 2). Avoiding the use of the high energy cyclobutenone starting materials provides access to a wider variety of substituted aromatic compounds.
This reaction is quite complementary to the Wulff–Dötz reaction. This is a [2+1] cycloaddition of a carbene to an alkyne or alkene (more specifically in the Dӧtz reaction a carbene coordinated to a metal carbonyl group) to produce substituted aromatic phenols. | 0 | Theoretical and Fundamental Chemistry |
The case to be heard at the High Court in 2009 represented 18 young people who alleged that toxic waste dumped by Corby Borough Council between 1984 and 1999 was the cause of their deformities. All had serious disabilities, including missing or underdeveloped fingers and deformities of their feet. They alleged that their mothers ingested or inhaled the toxic substances that affected the development of their limbs while they were still in the womb. All of their mothers either lived in or regularly visited Corby between 1984 and 1999 when the work was carried out across the town.
The case had taken ten years to reach this point largely because of the difficulties encountered in obtaining disclosure of information from Corby Borough Council. | 1 | Applied and Interdisciplinary Chemistry |
Two parts of a molecule that are connected by just one single bond can rotate about that bond. While the bond itself is indifferent to that rotation, attractions and repulsions between the atoms in the two parts normally cause the energy of the whole molecule to vary (and possibly also the two parts to deform) depending on the relative angle of rotation φ between the two parts. Then there will be one or more special values of φ for which the energy is at a local minimum. The corresponding conformations of the molecule are called rotational isomers or rotamers.
Thus, for example, in an ethane molecule , all the bond angles and length are narrowly constrained, except that the two methyl groups can independently rotate about the axis. Thus, even if those angles and distances are assumed fixed, there are infinitely many conformations for the ethane molecule, that differ by the relative angle φ of rotation between the two groups. The feeble repulsion between the hydrogen atoms in the two methyl groups causes the energy to minimized for three specific values of φ, 120° apart. In those configurations, the six planes or are 60° apart. Discounting rotations of the whole molecule, that configuration is a single isomer – the so-called staggered conformation.
Rotation between the two halves of the molecule 1,2-dichloroethane ( also has three local energy minima, but they have different energies due to differences between the , , and interactions. There are therefore three rotamers: a trans isomer where the two chlorines are on the same plane as the two carbons, but with oppositely directed bonds; and two gauche isomers, mirror images of each other, where the two groups are rotated about 109° from that position. The computed energy difference between trans and gauche is ~1.5 kcal/mol, the barrier for the ~109° rotation from trans to gauche is ~5 kcal/mol, and that of the ~142° rotation from one gauche to its enantiomer is ~8 kcal/mol. The situation for butane is similar, but with sightly lower gauche energies and barriers.
If the two parts of the molecule connected by a single bond are bulky or charged, the energy barriers may be much higher. For example, in the compound biphenyl – two phenyl groups connected by a single bond – the repulsion between hydrogen atoms closest to the central single bond gives the fully planar conformation, with the two rings on the same plane, a higher energy than conformations where the two rings are skewed. In the gas phase, the molecule has therefore at least two rotamers, with the ring planes twisted by ±47°, which are mirror images of each other. The barrier between them is rather low (~8 kJ/mol). This steric hindrance effect is more pronounced when those four hydrogens are replaced by larger atoms or groups, like chlorines or carboxyls. If the barrier is high enough for the two rotamers to be separated as stable compounds at room temperature, they are called atropisomers. | 0 | Theoretical and Fundamental Chemistry |
Some catastrophins affect catastrophe by binding to the ends of microtubules and promoting the dissociation of tubulin dimers.
Different mathematical models of microtubule development are being developed to take into account in vitro and in vivo observations. Meanwhile, there are new in vitro models of microtubule polymerization dynamics, of which catastrophins take a part in, being tested to emulate in vivo behaviors of microtubules. | 1 | Applied and Interdisciplinary Chemistry |
Source: [http://www.aps.org/programs/honors/prizes/langmuir.cfm American Physical Society] and [https://www.acs.org/content/acs/en/funding-and-awards/awards/national/bytopic/irving-langmuir-award-in-chemical-physics.html American Chemical Society] | 0 | Theoretical and Fundamental Chemistry |
Bioconjugation of TGF-β to iron oxide nanoparticles and its activation through magnetic hyperthermia in-vitro has been reported. This was done by using 1-(3-dimethylaminopropyl)ethylcarbodiimide combined with N-Hydroxysuccinimide to form primary amide bonds with the free primary amines on the growth factor. Carbon nanotubes have been successfully used in conjunction with bioconjugation to link TGF-β followed by an activation with near-infrared light. Typically, these reactions have involved the use of a crosslinker, but some of these add molecular space between the compound of interest and base material and in turn causes higher degrees of non-specific binding and unwanted reactivity. | 1 | Applied and Interdisciplinary Chemistry |
SELDI is often criticized for its reproducibility due to differences in the mass spectra obtained when using different batches of chip surfaces. While the method has been successful with analyzing low molecular weight proteins, consistent results have not been obtained when analyzing high molecular weight proteins. There also exists a potential for sample bias, as nonspecific absorption matrices favor the binding of analytes with higher abundances in the sample at the expense of less abundant analytes. While SELDI-TOF-MS has detection limits in the femtomolar range, the baseline signal in the spectra varies and noise due to the matrix is maximal below 2000 Da, with Ciphergen Biosystems suggesting to ignore spectral peaks below 2000 Da. | 1 | Applied and Interdisciplinary Chemistry |
There are many variations to the general phycobilisome structure. Their shape can be hemidiscoidal (in cyanobacteria) or hemiellipsoidal (in red algae). Species lacking phycoerythrin have at least two disks of phycocyanin per rod, which is sufficient for maximum photosynthesis.
The phycobiliproteins themselves show little sequence evolution due to their highly constrained function (absorption and transfer of specific wavelengths).
In some species of cyanobacteria, when both phycocyanin and phycoerythrin is present, the phycobilisome can undergo significant restructuring as response to light color. In green light the distal portions of the rods are made of red colored phycoerythrin, which absorbs green light better. In red light, this is replaced by blue colored phycocyanin, which absorbs red light better. This reversible process is known as complementary chromatic adaptation. It is the component of photosynthetic system of cyanobacteria, as a particle with which various structures are linked (i.e. thylakoid membrane, etc). | 0 | Theoretical and Fundamental Chemistry |
Spin chemistry is a sub-field of chemistry positioned at the intersection of chemical kinetics, photochemistry, magnetic resonance and free radical chemistry, that deals with magnetic and spin effects in chemical reactions. Spin chemistry concerns phenomena such as chemically induced dynamic nuclear polarization (CIDNP), chemically induced electron polarization (CIDEP), magnetic isotope effects in chemical reactions, and it is hypothesized to be key in the underlying mechanism for avian magnetoreception and consciousness. | 0 | Theoretical and Fundamental Chemistry |
In order to determine significance of the Strouhal number at varying scales, one may perform scale analysis–a simplification method to analyze the impact of factors as they change with respect to some scale. When considered in the context of microrobotics and nanorobotics, size is the factor of interest when performing scale analysis.
Scale analysis of the Strouhal number allows for analysis of the relationship between mass and inertial forces as both change with respect to size. Taking its original underived form, , we can then relate each term to size and see how the ratio changes as size changes.
Given where m is mass, V is volume, and is density, we can see mass is directly related to size as volume scales with length (L). Taking the volume to be , we can directly relate mass and size as
Characteristic speed (U) is in terms of , and relative distance scales with size, therefore
The net external forces (F) scales in relation to mass and acceleration, given by . Acceleration is in terms of , therefore . The mass-size relationship was established to be , so considering all three relationships, we get
Length (L) already denotes size and remains L.
Taking all of this together, we get
With the Strouhal number relating the mass to inertial forces, this can be expected as these two factors will scale proportionately with size and neither will increase nor decrease in significance with respect to their contribution to the body’s behavior in the cyclic motion of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
* Wide range of genomic applications and scientific questions, including de novo genome assembly, haplotype phasing, structural variant analysis, and transcriptome and epigenetic analysis.
* Accuracy and scalability.
* Method requires small quantities of input DNA, which can be beneficial for small samples or single cell studies.
* More cost effective per sample in comparison with long-read technologies such as Oxford Nanopore sequencing.
* Libraries produced by linked-read can be processed using Illumina short read sequencing, increasing accessibility. | 1 | Applied and Interdisciplinary Chemistry |
NSAIDs, anticholinergics, haemostatic drugs, antifibrinolytics, Hormone Replacement Therapy (HRT), bone regulators, beta-receptor agonists, follicle stimulating hormone, luteinising hormone, LHRH, gamolenic acid, gonadotropin release inhibitor, progestogen, dopamine agonists, oestrogen, prostaglandins, gonadorelin, clomiphene, tamoxifen, diethylstilbestrol. | 1 | Applied and Interdisciplinary Chemistry |
Differently than low-temperature electrochemical technologies, rSOCs can process also carbon containing species with reduced risk of catalyst poisoning. Methane can be internally reformed on the Ni particles to produce hydrogen, similarly to what happens in steam reforming reactors. Subsequently, the produced hydrogen can undergo the electro-oxidation. Moreover, when working in SOEC modality, water and carbon dioxide can be co-electrolyzed to generate hydrogen and carbon monoxide to form syngas mixtures with various composition.
The reactions taking place on the oxygen electrode are the same considered for the hydrogen/steam case. Even if characterized by much slower kinetics with respect to the one involving hydrogen and steam, the direct electro-oxidation of carbon monoxide (forward reaction) or the direct electro-reduction of carbon dioxide (backward reaction) can be considered as well:
The thermoneutral voltage of the electrolysis is equal to 1.48 V.
One useful way to depict the cycling between SOFC and SOEC mode of the rSOC operation with carbonaceous reactants is the C-H-O ternary diagram. Each point in the diagram represents a gas mixture with a different number of carbon, hydrogen or oxygen atoms. When dealing with the operation on reversible solid oxide cells, three distinct regions can be distinguished in the graph. For different operating conditions (i.e., different temperature and pressure), distinct boundary lines between these regions can be drawn. The three regions are:
* the carbon deposition region: gas mixtures lying in this region are characterized by compositions that are prone to carbon deposition on the fuel electrode;
* the fully oxidized region: this region is characterized by gas mixtures that are fully oxidized, hence they cannot be used as fuels in the rSOC;
* the operating region: this region is characterized by gas mixtures that are suitable for the rSOC operation.
In the operating region, the fuel mixture and the exhaust mixture can be depicted. These two points are connected by a line which runs through points characterized by a constant H/C ratio. In fact, during the rSOC operation in both modalities, the gases on the fuel electrode exchange with the oxygen electrode only oxygen atoms, while hydrogen and carbon are confined inside the fuel electrode. During the SOFC operation, the composition of the gas in the fuel electrode moves towards the boundary line of the fully oxidized region, increasing its oxygen content. During SOEC operation, on the other hand, the gas mixture evolves away from the fully oxidized region towards the carbon deposition region, while reducing its oxygen content. | 0 | Theoretical and Fundamental Chemistry |
The dimensionless magnetic Reynolds number, , is also used in cases where there is no physical fluid involved.
: × (characteristic length) × (characteristic velocity)
::where
:: is the magnetic permeability
:: is the electrical conductivity.
For the skin effect is negligible and the eddy current braking torque follows the theoretical curve of an induction motor.
For the skin effect dominates and the braking torque decreases much slower with increasing speed than predicted by the induction motor model. | 1 | Applied and Interdisciplinary Chemistry |
Conformational study on neuromuscular blocking drugs is relatively new and developing. Traditional SAR studies do not specify environmental factors on molecules. Computer-based conformational searches assume that the molecules are in vacuo, which is not the case in vivo. Solvation models take into account the effect of a solvent on the conformation of the molecule. However, no system of solvation can mimic the effect of the complex fluid composition of the body.
The division of muscle relaxants to rigid and non-rigid is at most qualitative. The energy required for conformational changes may give a more precise and quantitative picture. Energy required for reducing onium head distance in the longer muscle relaxant chains may quantify their ability to bend and fit its receptive sites. Using computers it is possible to calculate the lowest energy state conformer and thus most populated and best representing the molecule. This state is referred to as the global minimum. The global minimum for some simple molecules can be discovered quite easily with certainty. Such as for decamethonium the straight line conformer is clearly the lowest energy state. Some molecules, on the other hand, have many rotatable bonds and their global minimum can only be approximated. | 1 | Applied and Interdisciplinary Chemistry |
Brunauer, Emmett and Teller (BET) derived the first isotherm for multilayer adsorption. It assumes a random distribution of sites that are empty or that are covered with by one monolayer, two layers and so on, as illustrated alongside. The main equation of this model is
where
and [A] is the total concentration of molecules on the surface, given by
where
in which [A] is the number of bare sites, and [A] is the number of surface sites covered by i molecules. | 0 | Theoretical and Fundamental Chemistry |
The compounds are pale-yellow viscous liquids. They are hydrophobic, with low water solubilities: 0.0027–0.42 ng/L for Aroclors brand, but they have high solubilities in most organic solvents, oils, and fats. They have low vapor pressures at room temperature. They have dielectric constants of 2.5–2.7, very high thermal conductivity, and high flash points (from 170 to 380 °C).
The density varies from 1.182 to 1.566 g/cm. Other physical and chemical properties vary widely across the class. As the degree of chlorination increases, melting point and lipophilicity increase, and vapour pressure and water solubility decrease.
PCBs do not easily break down or degrade, which made them attractive for industries. PCB mixtures are resistant to acids, bases, oxidation, hydrolysis, and temperature change. They can generate extremely toxic dibenzodioxins and dibenzofurans through partial oxidation. Intentional degradation as a treatment of unwanted PCBs generally requires high heat or catalysis (see Methods of destruction below).
PCBs readily penetrate skin, PVC (polyvinyl chloride), and latex (natural rubber). PCB-resistant materials include Viton, polyethylene, polyvinyl acetate (PVA), polytetrafluoroethylene (PTFE), butyl rubber, nitrile rubber, and Neoprene. | 1 | Applied and Interdisciplinary Chemistry |
Iron–sulfur clusters are molecular ensembles of iron and sulfide. They are most often discussed in the context of the biological role for iron–sulfur proteins, which are pervasive. Many Fe–S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters (see Figure). It is believed that the last universal common ancestor had many iron-sulfur clusters. | 0 | Theoretical and Fundamental Chemistry |
In the field of quantum sciences, microcoils play an increasing role for fast spin control in nanoscale devices as multi-qubit spin registers and quantum memories or for the actuation of single nuclear spins e.g. around a Nitrogen-vacancy center. In contrast to traditional NMR, microcoils are used here as an actuator only. The nuclear spin signal is detected via the optical readout of a single electron spin. | 0 | Theoretical and Fundamental Chemistry |
The [FeS] ferredoxins may be further subdivided into low-potential (bacterial-type) and high-potential (HiPIP) ferredoxins.
Low- and high-potential ferredoxins are related by the following redox scheme:
The formal oxidation numbers of the iron ions can be [2Fe, 2Fe] or [1Fe, 3Fe] in low-potential ferredoxins. The oxidation numbers of the iron ions in high-potential ferredoxins can be [3Fe, 1Fe] or [2Fe, 2Fe]. | 0 | Theoretical and Fundamental Chemistry |
Pneumatic systems are often found in settings where even rare and brief system failure is unacceptable. In such situations, locks can sometimes serve as a safety mechanism in case of loss of air supply (or its pressure falling) and, thus remedy or abate any damage arising in such a situation.
Leakage of air from the input or output reduces the output pressure. | 1 | Applied and Interdisciplinary Chemistry |
Ring-opening polymerization is defined as a polymerization in which a cyclic monomer yields a monomeric unit which is acyclic or contains fewer cycles than the monomer. Generally, the ring-opening polymerization is carried out under mild conditions, and the by-product is less than in the polycondensation reaction. A high molecular weight polymer is easily obtained.
Common ring-opening polymerization products includes polypropylene oxide, polytetrahydrofuran, , polyoxymethylene, polycaprolactam and polysiloxane. | 0 | Theoretical and Fundamental Chemistry |
The ensemble is initialized to be the thermal equilibrium state (see quantum statistical mechanics). In mathematical parlance, this state is given by the density matrix:
where H is the hamiltonian matrix of an individual molecule and
where is the Boltzmann constant and the temperature. That the initial state in NMR quantum computing is in thermal equilibrium is one of the main differences compared to other quantum computing techniques, where they are initialized in a pure state. Nevertheless, suitable mixed states are capable of reflecting quantum dynamics which lead to Gershenfeld and Chuang to term them "pseudo-pure states."
Operations are performed on the ensemble through radio frequency (RF) pulses applied perpendicular to a strong, static magnetic field, created by a very large magnet. See nuclear magnetic resonance.
Consider applying a magnetic field along the z axis, fixing this as the principal quantization axis, on a liquid sample. The Hamiltonian for a single spin would be given by the Zeeman or chemical shift term:
where is the operator for the z component of the nuclear angular momentum, and is the resonance frequency of the spin, which is proportional to the applied magnetic field.
Considering the molecules in the liquid sample to contain two spin ½ nuclei, the system Hamiltonian will have two chemical shift terms and a dipole coupling term:
Control of a spin system can be realized by means of selective RF pulses applied perpendicular to the quantization axis. In the case of a two spin system as described above, we can distinguish two types of pulses: “soft” or spin-selective pulses, whose frequency range encompasses one of the resonant frequencies only, and therefore affects only that spin; and “hard” or nonselective pulses whose frequency range is broad enough to contain both resonant frequencies and therefore these pulses couple to both spins. For detailed examples of the effects of pulses on such a spin system, the reader is referred to Section 2 of work by Cory et al. | 0 | Theoretical and Fundamental Chemistry |
Coal-tar creosote, despite its toxicity, was used as a stimulant and escharotic, as a caustic agent used to treat ulcers and malignancies, cauterize wounds, and prevent infection and decay. It was particularly used in dentistry to destroy tissues and arrest necrosis. | 0 | Theoretical and Fundamental Chemistry |
In 1924 Louis de Broglie published a breakthrough hypothesis: matter has wave properties. Building on Einsteins proposal that the photoelectric effect can be described using quantized energy transfers and by Einsteins separate proposal, from special relativity, that mass at rest is equivalent to energy via , de Broglie proposed that matter in motion appears to have an associated wave with wavelength where is the matter momentum from the motion. Requiring his wavelength to encircle an atom, he explained quantization of Bohr's orbits. Simultaneously this showed that the wave behavior of light was essentially a quantum effect.
De Broglie expanded the Bohr model of the atom by showing that an electron in orbit around a nucleus could be thought of as having wave-like properties. In particular, an electron is observed only in situations that permit a standing wave around a nucleus. An example of a standing wave is a violin string, which is fixed at both ends and can be made to vibrate. The waves created by a stringed instrument appear to oscillate in place, moving from crest to trough in an up-and-down motion. The wavelength of a standing wave is related to the length of the vibrating object and the boundary conditions. For example, because the violin string is fixed at both ends, it can carry standing waves of wavelengths , where l is the length and n is a positive integer. De Broglie suggested that the allowed electron orbits were those for which the circumference of the orbit would be an integer number of wavelengths. The electrons wavelength, therefore, determines that only Bohr orbits of certain distances from the nucleus are possible. In turn, at any distance from the nucleus smaller than a certain value, it would be impossible to establish an orbit. The minimum possible distance from the nucleus is called the Bohr radius. De Broglies treatment of the Bohr atom was ultimately unsuccessful, but his hypothesis served as a starting point for Schrödinger's wave equation.
Matter behaving as a wave was first demonstrated experimentally for electrons: a beam of electrons can exhibit diffraction, just like a beam of light or a water wave. Three years after de Broglie published his hypothesis two different groups demonstrated electron diffraction. At the University of Aberdeen, George Paget Thomson and Alexander Reid passed a beam of electrons through a thin celluloid film, then later metal films, and observed the predicted interference patterns. (Alexander Reid, who was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned.) At Bell Labs, Clinton Joseph Davisson and Lester Halbert Germer reflected an electron beam from a nickel sample in their experiment, observing well-defined beams predicted by wave models returning form the crystal. De Broglie was awarded the Nobel Prize in Physics in 1929 for his hypothesis; Thomson and Davisson shared the Nobel Prize for Physics in 1937 for their experimental work.
Building on de Broglies approach, modern quantum mechanics was born in 1925, when the German physicists Werner Heisenberg, Max Born, and Pascual Jordan developed matrix mechanics and the Austrian physicist Erwin Schrödinger invented wave mechanics and the non-relativistic Schrödinger equation as an approximation of the generalised case of de Broglies theory. Schrödinger subsequently showed that the two approaches were equivalent. The first applications of quantum mechanics to physical systems were the algebraic determination of the hydrogen spectrum by Wolfgang Pauli and the treatment of diatomic molecules by Lucy Mensing. | 1 | Applied and Interdisciplinary Chemistry |
In 1957, Davies suggested a method based on calculating a value based on the chemical groups of the molecule. The advantage of this method is that it takes into account the effect of stronger and weaker hydrophilic groups. The method works as follows:
where:
- Number of hydrophilic groups in the molecule
- Value of the hydrophilic groups (see tables)
- Number of lipophilic groups in the molecule | 0 | Theoretical and Fundamental Chemistry |
The decomposition process starts after death and can proceed in the water column as the gelatinous organisms are sinking. Decay happens faster in the tropics than in temperate and subpolar waters as a result of warmer temperatures. In the tropics, a jelly-fall may take less than 2 days to decay in warmer, surface water, but as many as 25 days when it is lower than 1000 m deep. However, lone gelatinous organisms may spend less time on the sea floor as one study found that jellies could be decomposed by scavengers in the Norwegian deep sea in under two and a half hours.
Decomposition of jelly-falls is largely aided by these kinds of scavengers. In general, echinoderms, such as sea stars, have emerged as the primary consumer of jelly-falls, followed by crustaceans and fish. However, which scavengers find their way to jelly-falls is highly reliant on each ecosystem. For example, in an experiment in the Norwegian deep sea, hagfish were the first scavengers to find the traps of decaying jellies, followed by squat lobsters, and finally decapod shrimp. Photographs taken off the coast of Norway on natural jelly-falls also revealed caridean shrimp feeding on jelly carcasses.
With increased populations and blooms becoming more common, with favorable conditions and a lack of other filter feeders in the area to consume plankton, environments with jellies present will have carbon pumps be more primarily supplied with jelly-falls. This could lead to issues of habitats with established biological pumps succumbing to nonequilibrium as the presence of jellies would change the food web as well as changes to the amount of carbon deposited into the sediment.
Finally, decomposition is aided by the microbial community. In a case study on the Black Sea, the number of bacteria increased in the presence of jelly-falls, and the bacteria were shown to preferentially use nitrogen released from decaying jelly carcasses while mostly leaving carbon. In a study conducted by Andrew Sweetman in 2016, it was discovered using core samples of the sediment in Norwegian fjords, the presence of jelly-falls significantly impacted the biochemical process of these benthic communities. Bacteria consume jelly carcasses rapidly, removing opportunities of acquiring sustenance for bottoming feeding macrofauna, which has impacts traveling up the trophic levels. In addition, with the exclusion of scavengers, jelly-falls develop a white layer of bacteria over the decaying carcasses and emit a black residue over the surrounding area, which is from sulfide. This high level of microbial activity requires a lot of oxygen, which can lead zones around jelly-falls to become hypoxic and inhospitable to larger scavengers. | 0 | Theoretical and Fundamental Chemistry |
Van der Waals forces are a subset of electrostatic interactions involving permanent or induced dipoles (or multipoles). These include the following:
* permanent dipole–dipole interactions, alternatively called the Keesom force
* dipole-induced dipole interactions, or the Debye force
* induced dipole-induced dipole interactions, commonly referred to as London dispersion forces
Hydrogen bonding and halogen bonding are typically not classified as Van der Waals forces. | 0 | Theoretical and Fundamental Chemistry |
The high solubility and stability of PPA in organic solvents have allowed its investigation as a base material in first generation amplified photoresist for lithography in the early 80s by three scientists, Grant Willson, Jean Fréchet, and Hiroshi Ito who were working at IBM at the time. The story of how this successful achievement started and progressed can be found in the review paper written by Hiroshi Ito. Because PPA by itself does not undergo complete depolymerization upon its subjection to light, it is usually end-capped or used along photoacid generators (PAGs) for enhanced sensitivity. In this case, depolymerization is triggered upon irradiation either by end-cap removal and self-immolation or by the generated acid. Ober et al. stated that the use of PPA as photoresist under extreme ultraviolet (EUV) irradiation is yet to be successful due to the instability of PPA and the volatility of its monomers. However, they were able to report one of the first PPA derivatives without the use of PAGs with enhanced photoresist properties upon EUV exposure. | 0 | Theoretical and Fundamental Chemistry |
Palliser and Parry have examined about 100 scales and found that they can use them for locating B-strands on the surface of proteins. Hydrophobicity scales were also used to predict the preservation of the genetic code. Trinquier observed a new order of the bases that better reflect the conserved character of the genetic code. They believed new ordering of the bases was uracil-guanine-cystosine-adenine (UGCA) better reflected the conserved character of the genetic code compared to the commonly seen ordering UCAG. | 0 | Theoretical and Fundamental Chemistry |
SU-8 is composed of Bisphenol A Novolac epoxy that is dissolved in an organic solvent (gamma-butyrolactone GBL or cyclopentanone, depending on the formulation) and up to 10 wt% of mixed Triarylsulfonium/hexafluoroantimonate salt as the photoacid generator.
SU-8 absorbs light in the UV region, allowing fabrication of relatively thick (hundreds of micrometers) structures with nearly vertical side walls. The fact that a single photon can trigger multiple polymerizations makes the SU-8 a chemically amplified resist which is polymerized by photoacid generation. The light irradiated on the resist interacts with the salt in the solution, creating hexafluoroantimonic acid that then protonates the epoxides groups in the resin monomers. The monomer are thus activated but the polymerization will not proceed significantly until the temperature is raised as part of the post-expose bake. It is at this stage that the epoxy groups in the resin cross-link to form the cured structure. When fully cured, the high crosslinking degree gives to the resist its excellent mechanical properties.
The processing of SU-8 is similar to other negative resists with particular attention on the control of the temperature in the baking steps. The baking times depend on the SU-8 layer thickness; the thicker the layer, the longer the baking time. The temperature is controlled during the baking in order to reduce stress formation in the thick layer (leading to cracks) as the solvent evaporates.
The soft bake is the most important of the bake steps for stress formation. It is performed after spin coating. Its function is to remove the solvent from the resist and make the layer solid. Typically at least 5% of the solvent remains in the layer after the soft bake, however the thicker the coating, the harder it becomes to remove the solvent, as evaporating solvent through thick layers becomes increasingly difficult with coating thickness. The bake is performed on a programmable hot plate to reduce the skinning effect of solvent depletion at the surface creating a dense layer which makes the remainder of the solvent more difficult to remove. In order to reduce stress, the bake procedure is generally a two-step process made up of holding at 65 °C before ramping to 95 °C and holding again for a time dependent on the layer thickness. The temperature is then lowered slowly to room temperature.
When dry films are used, the photoresist is laminated rather than spin-coated. As this formulation is essentially solventless (less than 1% solvent remaining), it does not require a soft bake step and does not suffer stress or skinning. For enhanced adhesion, a post lamination bake can be added. This step is carried out in a similar way to the solution based resist - i.e. holding at 65 °C then 95 °C, the time dependent on film thickness.
After this stage the SU-8 layer can now be exposed. Typically this is through a photomask with an inverse pattern, as the resist is negative. The exposure time is a function of exposure dose and film thickness. After exposure the SU-8 needs to be baked again to complete the polymerization. This baking step is not as critical as the prebake but the rising of the temperature (again to 95 °C) needs to be slow and controlled. At this point the resist is ready to be developed.
The main developer for SU-8 is 1-methoxy-2-propanol acetate. Development time is primarily a function of SU-8 thickness.
After exposing and developing, its highly cross-linked structure gives it high stability to chemicals and radiation damage - hence the name "resist". Cured cross-linked SU-8 shows very low levels of outgassing in a vacuum.
However it is very difficult to remove, and tends to outgas in an unexposed state. | 0 | Theoretical and Fundamental Chemistry |
A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise occurs in the liquid surface. The rapidly flowing liquid is abruptly slowed and increases in height, converting some of the flow's initial kinetic energy into an increase in potential energy, with some energy irreversibly lost through turbulence to heat. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself similar to how a shockwave forms.
It was first observed and documented by Leonardo da Vinci in the 1500s. The mathematics were first described by Giorgio Bidone of Turin University when he published a paper in 1820 called Experiences sur le remou et sur la propagation des ondes.
The phenomenon is dependent upon the initial fluid speed. If the initial speed of the fluid is below the critical speed, then no jump is possible. For initial flow speeds which are not significantly above the critical speed, the transition appears as an undulating wave. As the initial flow speed increases further, the transition becomes more abrupt, until at high enough speeds, the transition front will break and curl back upon itself. When this happens, the jump can be accompanied by violent turbulence, eddying, air entrainment, and surface undulations, or waves.
There are two main manifestations of hydraulic jumps and historically different terminology has been used for each. However, the mechanisms behind them are similar because they are simply variations of each other seen from different frames of reference, and so the physics and analysis techniques can be used for both types.
The different manifestations are:
* The stationary hydraulic jump – rapidly flowing water transitions in a stationary jump to slowly moving water as shown in Figures 1 and 2.
* The tidal bore – a wall or undulating wave of water moves upstream against water flowing downstream as shown in Figures 3 and 4. If one considers a frame of reference which moves along with the wave front, then the wave front is stationary relative to the frame and has the same essential behavior as the stationary jump.
A related case is a cascade – a wall or undulating wave of water moves downstream overtaking a shallower downstream flow of water as shown in Figure 5. If considered from a frame of reference which moves with the wave front, this is amenable to the same analysis as a stationary jump.
These phenomena are addressed in an extensive literature from a number of technical viewpoints.
Hydraulic Jump is used sometimes in mixing chemicals. | 1 | Applied and Interdisciplinary Chemistry |
Bharat has been awarded many prizes and fellowships. These include a 2018 Vallee Research Scholarship, the 2019 EMBL John Kendrew Award the 2020 Philip Leverhulme Prize for Biological Sciences, the 2021 Eppendorf Award for Young European Investigators, and the 2021 Lister Prize, the 2022 Colworth Medal from the Biochemical Society and the 2023 Fleming Prize from the Microbiology Society. | 1 | Applied and Interdisciplinary Chemistry |
Molecular beacons are synthetic oligonucleotides whose preparation is well documented. In addition to the conventional set of nucleoside phosphoramidites, the synthesis also requires a solid support derivatized with a quencher and a phosphoramidite building block designed for the attachment of a protected fluorescent dye.
The first use of the term molecular beacons, synthesis and demonstration of function was in 1996. | 1 | Applied and Interdisciplinary Chemistry |
Consider a classical measurement where a single particle is scattered off a single stationary target particle. Conventionally, a spherical coordinate system is used, with the target placed at the origin and the axis of this coordinate system aligned with the incident beam. The angle is the scattering angle, measured between the incident beam and the scattered beam, and the is the azimuthal angle.
The impact parameter is the perpendicular offset of the trajectory of the incoming particle, and the outgoing particle emerges at an angle . For a given interaction (Coulombic, magnetic, gravitational, contact, etc.), the impact parameter and the scattering angle have a definite one-to-one functional dependence on each other. Generally the impact parameter can neither be controlled nor measured from event to event and is assumed to take all possible values when averaging over many scattering events. The differential size of the cross section is the area element in the plane of the impact parameter, i.e. . The differential angular range of the scattered particle at angle is the solid angle element . The differential cross section is the quotient of these quantities, .
It is a function of the scattering angle (and therefore also the impact parameter), plus other observables such as the momentum of the incoming particle. The differential cross section is always taken to be positive, even though larger impact parameters generally produce less deflection. In cylindrically symmetric situations (about the beam axis), the azimuthal angle is not changed by the scattering process, and the differential cross section can be written as
In situations where the scattering process is not azimuthally symmetric, such as when the beam or target particles possess magnetic moments oriented perpendicular to the beam axis, the differential cross section must also be expressed as a function of the azimuthal angle.
For scattering of particles of incident flux off a stationary target consisting of many particles, the differential cross section at an angle is related to the flux of scattered particle detection in particles per unit time by
Here is the finite angular size of the detector (SI unit: sr), is the number density of the target particles (SI units: m), and is the thickness of the stationary target (SI units: m). This formula assumes that the target is thin enough that each beam particle will interact with at most one target particle.
The total cross section may be recovered by integrating the differential cross section over the full solid angle ( steradians):
It is common to omit the “differential” qualifier when the type of cross section can be inferred from context. In this case, may be referred to as the integral cross section or total cross section. The latter term may be confusing in contexts where multiple events are involved, since “total” can also refer to the sum of cross sections over all events.
The differential cross section is extremely useful quantity in many fields of physics, as measuring it can reveal a great amount of information about the internal structure of the target particles. For example, the differential cross section of Rutherford scattering provided strong evidence for the existence of the atomic nucleus.
Instead of the solid angle, the momentum transfer may be used as the independent variable of differential cross sections.
Differential cross sections in inelastic scattering contain resonance peaks that indicate the creation of metastable states and contain information about their energy and lifetime. | 0 | Theoretical and Fundamental Chemistry |
Take samples from the chamber and let them dry in the room air. An initial assessment is made before any corrosion products are removed. When the tested parts are cleaned, the evaluation criteria must be taken into account.
Possible characteristics for evaluation: appearance after the test, appearance after removal of the corrosion products, number and size of imperfections, time to first corrosion, loss of mass.
The results are described in a test report. | 1 | Applied and Interdisciplinary Chemistry |
John Gofman graduated from Oberlin College with a bachelor's in chemistry in 1939, and received a doctorate in nuclear and physical chemistry from Berkeley in 1943, where he worked as a graduate student under Glenn T. Seaborg, the discoverer of plutonium and later a chairman of the US Atomic Energy Commission. In his PhD dissertation, Gofman described the discovery of radioisotopes protactinium-232, uranium-232, protactinium-233, as well as uranium-233 and the characterization of its fissionability. Seaborg had a very high opinion of Gofman : he called Gofman one of his "most brilliant students" when, in 1963, he appointed him to head the Biomedical Research Division at the Lawrence Livermore Laboratory; he wrote that his PhD dissertation was "very brilliant".
Gofman shared three patents with collaborators on their discoveries :
* n° 3,123,535 (Glenn T. Seaborg, John W. Gofman, Raymond W. Stoughton): The slow and fast neutron fissionability of uranium-233, with its application to production of nuclear power or nuclear weapons.
* n° 2,671,251 (John W. Gofman, Robert E. Connick, Arthur C. Wahl): The sodium uranyl acetate process for the separation of plutonium in irradiated fuel from uranium and fission products.
* n° 2,912,302 (Robert E. Connick, John W. Gofman, George C. Pimentel): The columbium oxide process for the separation of plutonium in irradiated fuel from uranium and fission products.
Gofman later became the group co-leader of the Plutonium Project, an offshoot of the Manhattan Project. | 0 | Theoretical and Fundamental Chemistry |
Plants are a major source of complex and highly structurally diverse chemical compounds (phytochemicals), this structural diversity attributed in part to the natural selection of organisms producing potent compounds to deter herbivory (feeding deterrents). Major classes of phytochemical include phenols, polyphenols, tannins, terpenes, and alkaloids. Though the number of plants that have been extensively studied is relatively small, many pharmacologically active natural products have already been identified. Clinically useful examples include the anticancer agents paclitaxel and omacetaxine mepesuccinate (from Taxus brevifolia and Cephalotaxus harringtonii, respectively), the antimalarial agent artemisinin (from Artemisia annua), and the acetylcholinesterase inhibitor galantamine (from Galanthus spp.), used to treat Alzheimer's disease. Other plant-derived drugs, used medicinally and/or recreationally include morphine, cocaine, quinine, tubocurarine, muscarine, and nicotine. | 1 | Applied and Interdisciplinary Chemistry |
The Arc system connects the electron transport chain to regulation of certain genes, allowing aerobic respiration to occur in the presence of oxygen and fermentation to take place when no oxygen is present. This is done through the connection of ArcB with quinones from the electron transport chain. Oxidized quionones, from the electron transport chain, act to inhibit autophosphorylation of ArcB during aerobic respiration. This in turn prevents the phosphorylation of ArcA, turning off the activated operons.
It has been determined that the Arc system regulates as many as 30 genes, with repression of the following examples: cytochrome o oxidase, cytochrome d oxidase, and various gluconeogenic enzymes, such as for the glyoxylate cycle, and fatty acid oxidation. It also induces the expression of Pyruvate formate lyase.
One of the major genes controlled is the sdh-lacZ operon. This, in part, codes for the synthesis of succinate dehydrogenase, a key element in the TCA cycle. ArcA turns expression of the sdh-lacZ operon off in the presence of oxygen, stopping procession of the TCA cycle. It also activates lctD and pyruvate formate lyase. These genes are critical in the lactic acid fermentation process. They are activated in anoxic conditions to allow the cell to continue producing ATP and growing even in less favorable conditions. ArcA represses many of the other enzymes involved in the TCA cycle as well including flavoprotein dehydrogenases, and ubiquinones oxidases. It also represses enzymes involved in synthesizing glyoxylate, some dehydrognases used in aerobic growth, and enzymes involved in fatty acid oxidation. Activated operons include genes for the pyruvate formate-lyase pathway and enzymes involved in synthesizing cobalamin.
Another of the genes effected codes for the production of certain cytochromes. ArcA respresses cytochrome bo oxidase and activates cytochrome bd oxidase. Cytochromes are classified based on the hemes they possess, in this case cytochrome bo possesses a heme c while cytochorme bd oxidase psoseses a heme d. Cytochormes bo oxidase is one of the main electron transporters during the elctron transport chain of aerobic respiration. It has the ability to reduce most organic compounds found in cellular metabolism. Cytochrome bd oxidase is activated in anaerobic conditions. It has a higher affinity for oxygen than cytochrome bo oxidase which may be useful to cells in anoxic conditions. | 1 | Applied and Interdisciplinary Chemistry |
Fumaric acid is an organic compound with the formula HOCCH=CHCOH. A white solid, fumaric acid occurs widely in nature. It has a fruit-like taste and has been used as a food additive. Its E number is E297. The salts and esters are known as fumarates. Fumarate can also refer to the ion (in solution). Fumaric acid is the trans isomer of butenedioic acid, while maleic acid is the cis isomer. | 1 | Applied and Interdisciplinary Chemistry |
Depending on the nature of the signal amplification system assays may be of numerous types, to name a few:
#Enzyme assay: Enzymes may be tested by their highly repeating activity on a large number of substrates when loss of a substrate or the making of a product may have a measurable attribute like color or absorbance at a particular wavelength or light or Electrochemiluminescence or electrical/redox activity.
#Light detection systems that may use amplification e.g. by a photodiode or a photomultiplier tube or a cooled charge coupled device.
#Radioisotope labeled substrates as used in radioimmunoassays and equilibrium dialysis assays and can be detected by the amplification in Gamma counters or X-ray plates, or phosphorimager
#Polymerase Chain Reaction Assays that amplify a DNA (or RNA) target rather than the signal
#Combination Methods Assays may utilize a combination of the above and other amplification methods to improve sensitivity. e.g. Enzyme-linked immunoassay or EIA, enzyme linked immunosorbent assay. | 1 | Applied and Interdisciplinary Chemistry |
This hypothesis originated in a 1964 paper by Paul Ehrlich and Peter Raven, "Butterflies and plants: a study in coevolution". While this paper outlined the concept, the actual term "escape and radiate" was not actually coined until 1989 by John N. Thompson. The theory has been highly influential in chemical ecology and plant evolutionary ecology, but remains controversial due to the difficulty of collecting decisive evidence as well as uncertainty about the mechanisms linking ecological escape with evolutionary diversification. | 1 | Applied and Interdisciplinary Chemistry |
In molecular orbital theory, the main alternative to valence bond theory, the molecular orbitals (MOs) are approximated as sums of all the atomic orbitals (AOs) on all the atoms; there are as many MOs as AOs. Each AO has a weighting coefficient c that indicates the AOs contribution to a particular MO. For example, in benzene, the MO model gives us 6 π MOs which are combinations of the 2p AOs on each of the 6 C atoms. Thus, each π MO is delocalized over the whole benzene molecule and any electron occupying' an MO will be delocalized over the whole molecule. This MO interpretation has inspired the picture of the benzene ring as a hexagon with a circle inside. When describing benzene, the VB concept of localized σ bonds and the MO concept of delocalized π orbitals are frequently combined in elementary chemistry courses.
The contributing structures in the VB model are particularly useful in predicting the effect of substituents on π systems such as benzene. They lead to the models of contributing structures for an electron-withdrawing group and electron-releasing group on benzene. The utility of MO theory is that a quantitative indication of the charge from the π system on an atom can be obtained from the squares of the weighting coefficient c on atom C. Charge q ≈ c. The reason for squaring the coefficient is that if an electron is described by an AO, then the square of the AO gives the electron density. The AOs are adjusted (normalized) so that AO = 1, and q ≈ (cAO) ≈ c. In benzene, q = 1 on each C atom. With an electron-withdrawing group q > 1 for an electron-releasing group. | 0 | Theoretical and Fundamental Chemistry |
The terms "relative fluorescence units" (RFU) and "RFU peak" refer to measurements in electrophoresis methods, such as for DNA analysis. A "relative fluorescence unit" is a unit of measurement used in analysis which employs fluorescence detection. Fluorescence is detected using a charged coupled device (CCD) array, when the labeled fragments, which are separated within a capillary by using electrophoresis, are energized by laser light and travel across the detection window. A computer program measures the results, determining the quantity or size of the fragments, at each data point, from the level of fluorescence intensity. Samples which contain higher quantities of amplified DNA will have higher corresponding RFU values.
An "RFU peak" is a relative maximum point along a graph of the analyzed data. The data can be normalized to DNA input or additional normalizing genes. The RFU heights can range from 0 to several thousands. | 1 | Applied and Interdisciplinary Chemistry |
The first scientific publication in which knockout moss was used to identify the function of a hitherto-unknown gene appeared in 1998, and was authored by Ralf Reski and coworkers. They deleted the ftsZ-gene and thus functionally identified the first gene pivotal for the division of an organelle in any eukaryote. | 1 | Applied and Interdisciplinary Chemistry |
Thermal ellipsoids, more formally termed atomic displacement parameters or anisotropic displacement parameters, are ellipsoids used in crystallography to indicate the magnitudes and directions of the thermal vibration of atoms in crystal structures. Since the vibrations are usually anisotropic (different magnitudes in different directions in space), an ellipsoid is a convenient way of visualising the vibration and therefore the symmetry and time averaged position of an atom in a crystal. Their theoretical framework was introduced by D. W. J. Cruickshank in 1956 and the concept was popularized through the program ORTEP (Oak Ridge Thermal-Ellipsoid Plot Program), first released in 1965.
Thermal ellipsoids can be defined by a tensor, a mathematical object which allows the definition of magnitude and orientation of vibration with respect to three mutually perpendicular axes. The three principal axes of the thermal vibration of an atom are denoted , , and , and the corresponding thermal ellipsoid is based on these axes. The size of the ellipsoid is scaled so that it occupies the space in which there is a particular probability of finding the electron density of the atom. The particular probability is usually 50%. | 0 | Theoretical and Fundamental Chemistry |
Stability constant values are exploited in a wide variety of applications. Chelation therapy is used in the treatment of various metal-related illnesses, such as iron overload in β-thalassemia sufferers who have been given blood transfusions. The ideal ligand binds to the target metal ion and not to others, but this degree of selectivity is very hard to achieve. The synthetic drug deferiprone achieves selectivity by having two oxygen donor atoms so that it binds to Fe in preference to any of the other divalent ions that are present in the human body, such as Mg, Ca and Zn. Treatment of poisoning by ions such as Pb and Cd is much more difficult since these are both divalent ions and selectivity is harder to accomplish. Excess copper in Wilson's disease can be removed by penicillamine or Triethylene tetramine (TETA). DTPA has been approved by the U.S. Food and Drug Administration for treatment of plutonium poisoning.
DTPA is also used as a complexing agent for gadolinium in MRI contrast enhancement. The requirement in this case is that the complex be very strong, as Gd is very toxic. The large stability constant of the octadentate ligand ensures that the concentration of free Gd is almost negligible, certainly well below toxicity threshold. In addition the ligand occupies only 8 of the 9 coordination sites on the gadolinium ion. The ninth site is occupied by a water molecule which exchanges rapidly with the fluid surrounding it and it is this mechanism that makes the paramagnetic complex into a contrast reagent.
EDTA forms such strong complexes with most divalent cations that it finds many uses. For example, it is often present in washing powder to act as a water softener by sequestering calcium and magnesium ions.
The selectivity of macrocyclic ligands can be used as a basis for the construction of an ion selective electrode. For example, potassium selective electrodes are available that make use of the naturally occurring macrocyclic antibiotic valinomycin.
An ion-exchange resin such as chelex 100, which contains chelating ligands bound to a polymer, can be used in water softeners and in chromatographic separation techniques. In solvent extraction the formation of electrically neutral complexes allows cations to be extracted into organic solvents. For example, in nuclear fuel reprocessing uranium(VI) and plutonium(VI) are extracted into kerosene as the complexes [MO(TBP)(NO)] (TBP = tri-n-butyl phosphate). In phase-transfer catalysis, a substance which is insoluble in an organic solvent can be made soluble by addition of a suitable ligand. For example, potassium permanganate oxidations can be achieved by adding a catalytic quantity of a crown ether and a small amount of organic solvent to the aqueous reaction mixture, so that the oxidation reaction occurs in the organic phase.
In all these examples, the ligand is chosen on the basis of the stability constants of the complexes formed. For example, TBP is used in nuclear fuel reprocessing because (among other reasons) it forms a complex strong enough for solvent extraction to take place, but weak enough that the complex can be destroyed by nitric acid to recover the uranyl cation as nitrato complexes, such as [UO(NO)] back in the aqueous phase. | 0 | Theoretical and Fundamental Chemistry |
Puddling is the process of converting pig iron to bar (wrought) iron in a coal fired reverberatory furnace. It was developed in England during the 1780s. The molten pig iron was stirred in a reverberatory furnace, in an oxidizing environment to burn the carbon, resulting in wrought iron. It was one of the most important processes for making the first appreciable volumes of valuable and useful bar iron (malleable wrought iron) without the use of charcoal. Eventually, the furnace would be used to make small quantities of specialty steels.
Though it was not the first process to produce bar iron without charcoal, puddling was by far the most successful, and replaced the earlier potting and stamping processes, as well as the much older charcoal finery and bloomery processes. This enabled a great expansion of iron production to take place in Great Britain, and shortly afterwards, in North America. That expansion constitutes the beginnings of the Industrial Revolution so far as the iron industry is concerned. Most 19th century applications of wrought iron, including the Eiffel Tower, bridges, and the original framework of the Statue of Liberty, used puddled iron. | 1 | Applied and Interdisciplinary Chemistry |
There are several methods that can be used as an alternative to FAIRE-seq. DNase-seq uses the ability of the DNase I enzyme to cleave free/open/accessible DNA to identify and sequence open chromatin. The subsequently developed ATAC-seq employs the Tn5 transposase, which inserts specified fragments or transposons into accessible regions of the genome to identify and sequence open chromatin. | 1 | Applied and Interdisciplinary Chemistry |
The organizational structure of the NADP follows the State Agricultural Experiment Station Guidelines for Multi-State Research Activities (SAESD, 2006). This framework allows any individual or institution to participate in any segment of NADP, whether it be the monitoring or the research aspect of atmospheric deposition. NADP is managed by two groups. The first being Program Management, which is largely a volunteer group made up of site sponsors and supervisors, policy experts from several agencies (at the federal, state, and local levels), scientists and research specialists, and anyone with an interest in atmospheric deposition. Program management is organized through an Executive Committee, Technical Subcommittees, several advisory subcommittees, science subcommittees, and ad hoc groups. The second group is Program Operations, which is managed by a professional staff housed at the Wisconsin State Laboratory of Hygiene at the University of Wisconsin-Madison. The Program Office oversees day to day tasks, including coordinating with the Executive Committee, the individual monitoring networks, the analytical laboratories, the External Quality Assurance Program, and the Network Equipment Depot. | 1 | Applied and Interdisciplinary Chemistry |
Isotherms are used to quantify the amount of adsorbed protein on a surface at a constant temperature, depending on the concentration of protein above the surface. Researchers have used a Langmuir-type isotherm model to describe experimental values for protein adsorption.
In this equation
* is the amount of adsorbed protein
* is the surface area per molecule
* is the partial molar volume of protein
* is the negative of the Gibbs Free Energy of adsorption per unit area and
* is the equilibrium protein concentration.
This equation has been applied to a laboratory setting of protein adsorption at temperatures higher than 50 °C from a model solution of protein and water. It is especially useful for modeling protein fouling in milk processing. | 1 | Applied and Interdisciplinary Chemistry |
* The bicinchoninic acid assay tests for proteins
* The Biuret test tests for proteins and polypeptides
* Bradford protein assay measures protein quantitatively
* The Phadebas amylase test determines alpha-amylase activity | 0 | Theoretical and Fundamental Chemistry |
-Photo-leucine is a synthetic derivative of the -leucine amino acid that is used as its natural analog and is characterized for having photo-reactivity, which makes it suitable for observing and characterizing protein-protein interactions (PPI). When a protein containing this amino acid (A) is exposed to
ultraviolet light while interacting with another protein (B), the complex formed from these two proteins (AB) remains attached and can be isolated for study.
Photo-leucine, as well as another photo-reactive amino acid derived from methionine, photo-methionine, were first synthesized in 2005 by Monika Suchanek, Anna Radzikoska and Christoph Thiele from the Max Planck Institute of Molecular Cell Biology and Genetics with the objective of identifying protein to protein interaction throughout a simple western blot test that would provide high specificity.
The resemblance of the photo-reactive amino acids to the natural ones allows the former ones to avoid the extensive control mechanisms that take place during the protein synthesis within the cell. | 0 | Theoretical and Fundamental Chemistry |
A hydrant is an outlet from a fluid main often consisting of an upright pipe with a valve attached, from which fluid (e.g. water or fuel) can be tapped.
Depending on the fluid involved, the term may refer to:
* Fire hydrant for firefighting water supply
* Flushing hydrant for cleaning water mains
* Hydrant network systems used to transport aviation fuel from an oil depot to an airport, to fuel aircraft
* Snowmaking hydrants, which use water and air
* Standpipe (street), a type of domestic or neighbourhood hydrant for dispensing water when supply is interrupted or absent | 1 | Applied and Interdisciplinary Chemistry |
The Rydberg states of an atom or molecule are electronically excited states with energies that follow the Rydberg formula as they converge on an ionic state with an ionization energy. Although the Rydberg formula was developed to describe atomic energy levels, it has been used to describe many other systems that have electronic structure roughly similar to atomic hydrogen. In general, at sufficiently high principal quantum numbers, an excited electron-ionic core system will have the general character of a hydrogenic system and the energy levels will follow the Rydberg formula. Rydberg states have energies converging on the energy of the ion. The ionization energy threshold is the energy required to completely liberate an electron from the ionic core of an atom or molecule. In practice, a Rydberg wave packet is created by a laser pulse on a hydrogenic atom and thus populates a superposition of Rydberg states. Modern investigations using pump-probe experiments show molecular pathways – e.g. dissociation of (NO) – via these special states. | 0 | Theoretical and Fundamental Chemistry |
The Thyroid Feedback Quantile-based Index (TFQI) is another parameter for thyrotropic pituitary function. It was defined to be more robust to distorted data than JTI and TTSI. It is calculated with
from quantiles of FT4 and TSH concentration (as determined based on cumulative distribution functions). Per definition the TFQI has a mean of 0 and a standard deviation of 0.37 in a reference population. Higher values of TFQI are associated with obesity, metabolic syndrome, impaired renal function, diabetes, and diabetes-related mortality. TFQI results are also elevated in takotsubo syndrome, potentially reflecting type 2 allostatic load in the situation of psychosocial stress. Reductions have been observed in subjects with schizophrenia after initiation of therapy with oxcarbazepine, potentially reflecting declining allostatic load. | 1 | Applied and Interdisciplinary Chemistry |
It is important to note that although some cycles have a typical combustion location (internal or external), they often can be implemented with the other. For example, John Ericsson developed an external heated engine running on a cycle very much like the earlier Diesel cycle. In addition, externally heated engines can often be implemented in open or closed cycles. In a closed cycle the working fluid is retained within the engine at the completion of the cycle whereas is an open cycle the working fluid is either exchanged with the environment together with the products of combustion in the case of the internal combustion engine or simply vented to the environment in the case of external combustion engines like steam engines and turbines. | 0 | Theoretical and Fundamental Chemistry |
One of the primary challenges in the study of planetary accretion is the fact that many tracers of the processes occurring in the early Solar System have been eliminated as a result of subsequent geologic events. Because transition metals do not show large stable isotope fractionations as a result of these events and because iron is one of the most abundant elements in the terrestrial planets, its isotopic variability has been used as a tracer of early Solar System processes.
Variations in δFe between samples from Vesta, Mars, the Moon, and Earth have been observed, and these variations cannot be explained by any known petrological, geochemical, or planetary processes, thus, it has been inferred that the observed fractionations are a result of planetary accretion. It is interesting to note that the isotopic compositions of the Earth and the Moon are much heavier than that of Vesta and Mars. This provides strong support for the giant-impact hypothesis as an impact of this energy would generate large amounts of energy, which would melt and vaporize iron, leading to the preferential escape of the lighter iron isotopes to space. More of the heavier isotopes would remain, resulting in the heavier iron isotopic compositions observed for the Earth and the Moon. The samples from Vesta and Mars exhibit minimal fractionation, consistent with the theory of runaway growth for their formations, as this process would not yield significant fractionations. Further study of the stable isotope of iron in other planetary bodies and samples could provide further evidence and more precise constraints for planetary accretion and other processes that occurred in the early Solar System. | 0 | Theoretical and Fundamental Chemistry |
During the first half of 1808, Davy conducted a series of further electrolysis experiments on alkaline earths including lime, magnesia, strontites and barytes. At the beginning of June, Davy received a letter from the Swedish chemist Berzelius claiming that he, in conjunction with Dr. Pontin, had successfully obtained amalgams of calcium and barium by electrolysing lime and barytes using a mercury cathode. Davy managed to successfully repeat these experiments almost immediately and expanded Berzelius' method to strontites and magnesia. He noted that while these amalgams oxidised in only a few minutes when exposed to air they could be preserved for lengthy periods of time when submerged in naphtha before becoming covered with a white crust.
On 30 June 1808 Davy reported to the Royal Society that he had successfully isolated four new metals which he named barium, calcium, strontium and magnium (later changed to magnesium) which were subsequently published in the Philosophical Transactions. Although Davy conceded magnium was an "undoubtedly objectionable" name he argued the more appropriate name magnesium was already being applied to metallic manganese and wished to avoid creating an equivocal term.
The observations gathered from these experiments also led to Davy isolating boron in 1809. Berzelius called Davys 1806 Bakerian Lecture On Some Chemical Agencies of Electricity' "one of the best memoirs which has ever enriched the theory of chemistry." | 1 | Applied and Interdisciplinary Chemistry |
The osmotic-controlled release oral delivery system (OROS) is an advanced controlled release oral drug delivery system in the form of a rigid tablet with a semi-permeable outer membrane and one or more small laser drilled holes in it. As the tablet passes through the body, water is absorbed through the semipermeable membrane via osmosis, and the resulting osmotic pressure is used to push the active drug through the laser drilled opening(s) in the tablet and into the gastrointestinal tract. OROS is a trademarked name owned by ALZA Corporation, which pioneered the use of osmotic pumps for oral drug delivery. | 1 | Applied and Interdisciplinary Chemistry |
;Novartis-Drew Award
*2003: Elaine Fuchs; Philip A. Sharp; David Botstein
*2002: Frank McCormick; Brian J. Druker; Harold Varmus
*2001: Sidney Brenner; Eric Lander; Craig Venter
*2000: Susan L. Lindquist
*1999: Elizabeth Helen Blackburn; Joan Steitz
*1998: Tom Maniatis; Alexander Varshavsky
*1997: Edward Alan Berger
;Ciba-Drew Award
*1996: H. Robert Horvitz; Stanley J. Korsmeyer
*1995: Joseph Schlessinger; Günter Blobel ; Arnold J. Levine
*1994: Thomas R. Cech; Albert Eschenmoser; Manfred Eigen
*1993: Leroy Hood; Francis S. Collins
*1992: Stuart L. Schreiber ; Peter G. Schultz ; Richard Lerner
*1991: Sir Michael Berridge
*1990: Roger David Kornberg; Nicholas R. Cozzarelli
*1989: Robert William Mahley
*1988: Samuel Broder; Robert C. Gallo ; Luc Montagnier
*1987: Thomas A. Waldmann
*1986: Michael H. Wigler
*1985: Jean-Pierre Changeux; Solomon Halbert Snyder
*1984: Albrecht Fleckenstein; Harald Reuter
*1983: Ronald Levy;
*1981: C. Ronald Kahn; Donald F. Steiner ; Sydney Brenner
*1980: Bengt I. Samuelsson; John Robert Vane
*1979: Paul Greengard
*1977: Robert C. Gallo; Fred Rapp | 1 | Applied and Interdisciplinary Chemistry |
Used for the first time in 1951 to localize leaks in a drinking water supply system of Munich, Germany, iodine-131 became one of the most commonly used gamma-emitting industrial radioactive tracers, with applications in isotope hydrology and leak detection.
Since the late 1940s, radioactive tracers have been used by the oil industry. Tagged at the surface, water is then tracked downhole, using the appropriated gamma detector, to determine flows and detect underground leaks. I-131 has been the most widely used tagging isotope in an aqueous solution of sodium iodide. It is used to characterize the hydraulic fracturing fluid to help determine the injection profile and location of fractures created by hydraulic fracturing. | 0 | Theoretical and Fundamental Chemistry |
Light scattering spectroscopy (LSS) is a spectroscopic technique typically used to evaluate morphological changes in epithelial cells in order to study mucosal tissue and detect early cancer and precancer.
Light scattering spectroscopy relies upon elastic scattering of photons reflected from the epithelium. Most of the signal is generated by light scattering from small intracellular structures, but larger intracellular structures, such as nuclei, also scatter light, with their relative contribution increasing in the backscatter direction. As changes in the morphology of epithelial cells are hallmarks of pre-cancer and early cancer, LSS can be used for early cancer diagnosis.
In addition to photons backscattering from epithelial cells, a major portion of photons penetrates the epithelium, reaching optically turbid connective tissue where they are scattered multiple times and partially absorbed by hemoglobin. As a result, it is not possible to measure single backscattering events directly in human tissue, with polarization gating and spatial gating well-suited for endoscopy applications. | 0 | Theoretical and Fundamental Chemistry |
Thylakoids contain many integral and peripheral membrane proteins, as well as lumenal proteins. Recent proteomics studies of thylakoid fractions have provided further details on the protein composition of the thylakoids. These data have been summarized in several plastid protein databases that are available online.
According to these studies, the thylakoid proteome consists of at least 335 different proteins. Out of these, 89 are in the lumen, 116 are integral membrane proteins, 62 are peripheral proteins on the stroma side, and 68 peripheral proteins on the lumenal side. Additional low-abundance lumenal proteins can be predicted through computational methods. Of the thylakoid proteins with known functions, 42% are involved in photosynthesis. The next largest functional groups include proteins involved in protein targeting, processing and folding with 11%, oxidative stress response (9%) and translation (8%). | 0 | Theoretical and Fundamental Chemistry |
Hydroinformatics is a branch of informatics which concentrates on the application of information and communications technologies (ICTs) in addressing the increasingly serious problems of the equitable and efficient use of water for many different purposes. Growing out of the earlier discipline of computational hydraulics, the numerical simulation of water flows and related processes remains a mainstay of hydroinformatics, which encourages a focus not only on the technology but on its application in a social context.
On the technical side, in addition to computational hydraulics, hydroinformatics has a strong interest in the use of techniques originating in the so-called artificial intelligence community, such as artificial neural networks or recently support vector machines and genetic programming. These might be used with large collections of observed data for the purpose of data mining for knowledge discovery, or with data generated from an existing, physically based model in order to generate a computationally efficient emulator of that model for some purpose.
Hydroinformatics recognises the inherently social nature of the problems of water management and of decision-making processes, and strives to understand the social processes by which technologies are brought into use. Since the problems of water management are most severe in the majority world, while the resources to obtain and develop technological solutions are concentrated in the hands of the minority, the need to examine these social processes are particularly acute.
Hydroinformatics draws on and integrates hydraulics, hydrology, environmental engineering and many other disciplines. It sees application at all points in the water cycle from atmosphere to ocean, and in artificial interventions in that cycle such as urban drainage and water supply systems. It provides support for decision making at all levels from governance and policy through management to operations.
Hydroinformatics has a growing world-wide community of researchers and practitioners, and postgraduate programmes in Hydroinformatics are offered by many leading institutions. The Journal of Hydroinformatics provides a specific outlet for Hydroinformatics research, and the community gathers to exchange ideas at the biennial conferences. These activities are coordinated by the joint IAHR, IWA, IAHS [http://www.iwahq.org/Home/Networks/Specialist_groups/List_of_groups/Hydroinformatics/ Hydroinformatics Section].
[https://shop.elsevier.com/books/handbook-of-hydroinformatics/eslamian/978-0-12-821285-1 Classic Soft-Computing Techniques] is the first volume of the three, in the Handbook of HydroInformatics series (Elsevier) by Saeid Eslamian.
Handbook of HydroInformatics, Volume II: [https://shop.elsevier.com/books/handbook-of-hydroinformatics/eslamian/978-0-12-821961-4 Advanced Machine Learning Techniques] presents both the art of designing good learning algorithms, as well as the science of analyzing an algorithm's computational and statistical properties and performance guarantees
Handbook of HydroInformatics Volume III: [https://shop.elsevier.com/books/handbook-of-hydroinformatics/eslamian/978-0-12-821962-1 Water Data Management Best Practices] presents the latest and most updated data processing techniques that are fundamental to Water Science and Engineering disciplines. | 1 | Applied and Interdisciplinary Chemistry |
This book describes separating silver from copper or iron. This is achieved by adding large amounts of lead at a temperature just above the melting point of lead. The lead will liquate out with the silver. This process will need to be repeated several times. The lead and silver can be separated by cupellation. | 1 | Applied and Interdisciplinary Chemistry |
Most commonly, amino acids coordinate to metal ions as N,O bidentate ligands, utilizing the amino group and the carboxylate. They are "L-X" ligands. A five-membered chelate ring is formed. The chelate ring is only slightly ruffled at the sp-hybridized carbon and nitrogen centers.
For those amino acids containing coordinating substituents, the resulting complexes are more structurally diverse since these substituents can coordinate. Histidine, aspartic acid, methionine, and cysteine sometimes form tridentate N,N,O, N,O,O, S,N,O, and S,N,O complexes, respectively.
Using kinetically inert metal ions, complexes containing monodentate amino acids have been characterized. These complexes exist in either the N or the O linkage isomers. It can be assumed that such monodentate complexes exist transiently for many kinetically labile metal ions (e.g. Zn). | 0 | Theoretical and Fundamental Chemistry |
Linear chain compounds exhibiting CDW transport have CDW wavelengths λ = π/k incommensurate with (i.e., not an integer multiple of) the lattice constant. In such materials, pinning is due to impurities that break the translational symmetry of the CDW with respect to φ. The simplest model treats the pinning as a sine-Gordon potential of the form u(φ) = u[1 – cosφ], while the electric field tilts the periodic pinning potential until the phase can slide over the barrier above the classical depinning field. Known as the overdamped oscillator model, since it also models the damped CDW response to oscillatory (AC) electric fields, this picture accounts for the scaling of the narrow-band noise with CDW current above threshold.
However, since impurities are randomly distributed throughout the crystal, a more realistic picture must allow for variations in optimum CDW phase φ with position – essentially a modified sine-Gordon picture with a disordered washboard potential. This is done in the Fukuyama-Lee-Rice (FLR) model, in which the CDW minimizes its total energy by optimizing both the elastic strain energy due to spatial gradients in φ and the pinning energy. Two limits that emerge from FLR include weak pinning, typically from isoelectronic impurities, where the optimum phase is spread over many impurities and the depinning field scales as n (n being the impurity concentration) and strong pinning, where each impurity is strong enough to pin the CDW phase and the depinning field scales linearly with n. Variations of this theme include numerical simulations that incorporate random distributions of impurities (random pinning model). | 0 | Theoretical and Fundamental Chemistry |
Organohalide respiration (OHR) (previously named halorespiration or dehalorespiration) is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration.
Organohalide respiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics (PCE, TCE, chloroform) and chlorinated phenols. Organohalide-respiring bacteria are highly diverse. This trait is found in some Campylobacterota, Thermodesulfobacteriota, Chloroflexota (green nonsulfur bacteria), low G+C gram positive Clostridia, and ultramicrobacteria. | 0 | Theoretical and Fundamental Chemistry |
Excitation A→A* by photon, whereby the promoted electron is passed down to the C* molecular orbital. A second photon applied to the system () causes the excitation of the electron in the C* molecular orbital to the C** molecular orbital -analogous pump probe spectroscopy.
Above, the energy level diagram illustrating the principle of pump probe spectroscopy –the excitation of an excited state.
The AND gate is produced by the necessity of both A→A* and the C**→C excitations occurring at the same time -input and , are simultaneously required.
To prevent erroneous emissions of light from a single input to the AND gate, it would be necessary to have an electron transfer series with ability accept any electrons (energy) from C* energy level. The electron transfer series would terminate with a low (non-radiative decay) of the energy
The alternatives for producing an AND gate, using molecular photphysics, are two.
(1) The emission produced by the electron drop from C*→C () is not a valid output frequency. The emission from the C** ( + , ) molecular orbital is a valid output signal;. to be used in subsequent logic gates -arranged to respond to the emission.
The second input of photon(s) to trigger the rapid conversion of a molecule used to complete the electron transfer chain. A very complex molecule like a protein can be engineered to possess high strain energies, so that in the absence of the second light frequency molecule B is inactive (B). The second photon input triggers B→B' where the forward rate constant is much smaller than the reverse. If such a molecule is used as molecule B, the transfer chain can be switched on and off. | 0 | Theoretical and Fundamental Chemistry |
Initiatives to spur adoption by clinicians include the [https://upgx.eu/ Ubiquitous Pharmacogenomics (U-PGx)] program in Europe and the Clinical Pharmacogenetics Implementation Consortium (CPIC) in the United States. In a 2017 survey of European clinicians, in the prior year two-thirds had not ordered a pharmacogenetic test.
In 2010, Vanderbilt University Medical Center launched Pharmacogenomic Resource for Enhanced Decisions in Care and Treatment (PREDICT); in 2015 survey, two-thirds of the clinicians had ordered a pharmacogenetic test.
In 2019, the largest private health insurer, UnitedHealthcare, announced that it would pay for genetic testing to predict response to psychiatric drugs.
In 2020, Canada's 4th largest health and dental insurer, Green Shield Canada, announced that it would pay for pharmacogenetic testing and its associated clinical decision support software to optimize and personalize mental health prescriptions. | 1 | Applied and Interdisciplinary Chemistry |
The development of an analytical instrument that utilizes the reduction-oxidation (redox) chemistry of oxygen in the presence of dissimilar metal electrodes was introduced during the 1950s. This redox electrode utilized an oxygen-permeable membrane to allow the diffusion of the gas into an electrochemical cell and its concentration determined by polarographic or galvanic electrodes. This analytical method is sensitive and accurate down to levels of ± 0.1 mg/L dissolved oxygen. Calibration of the redox electrode of this membrane electrode still requires the use of the Henry's law table or the Winkler test for dissolved oxygen. | 0 | Theoretical and Fundamental Chemistry |
A laser SBSP could also power a base or vehicles on the surface of the Moon or Mars, saving on mass costs to land the power source. A spacecraft or another satellite could also be powered by the same means. In a 2012 report presented to NASA on space solar power, the author mentions another potential use for the technology behind space solar power could be for solar electric propulsion systems that could be used for interplanetary human exploration missions. | 0 | Theoretical and Fundamental Chemistry |
The use of metal hydrides (tin, silicon and mercury hydrides) is common in radical cyclization reactions; the primary limitation of this method is the possibility of reduction of the initially formed radical by H-M. Fragmentation methods avoid this problem by incorporating the chain-transfer reagent into the substrate itself—the active chain-carrying radical is not released until after cyclization has taken place. The products of fragmentation methods retain a double bond as a result, and extra synthetic steps are usually required to incorporate the chain-carrying group.
Atom-transfer methods rely on the movement of an atom from the acyclic starting material to the cyclic radical to generate the product. These methods use catalytic amounts of weak reagents, preventing problems associated with the presence of strong reducing agents (such as tin hydride). Hydrogen- and halogen-transfer processes are known; the latter tend to be more synthetically useful.
Oxidative and reductive cyclization methods also exist. These procedures require fairly electrophilic and nucleophilic radicals, respectively, to proceed effectively. Cyclic radicals are either oxidized or reduced and quenched with either external or internal nucleophiles or electrophiles, respectively. | 0 | Theoretical and Fundamental Chemistry |
Azaborane usually refers a borane cluster where BH vertices are replaced by N or NR (R stands typically for H or organic substituent). Like many of the related boranes, these clusters are polyhedra and can be classified as closo-, nido-, arachno-, etc..
Within the context of Wades rules, NR is a 4-electron vertex, and N is a 3-electron vertex. Prominent examples are the charge-neutral nido- (i.e. ) and closo'- (i.e. ).
Azaboranes can also refer to simpler compounds including iminoboranes (RB=NR, where R and R stand typically for H or organic substituent) and borazines. | 0 | Theoretical and Fundamental Chemistry |
Many properties of nanoparticles, notably stability, solubility, and chemical or biological activity, can be radically altered by coating them with various substances — a process called functionalization. Functionalized nanomaterial-based catalysts can be used for catalysis of many known organic reactions.
For example, suspensions of graphene particles can be stabilized by functionalization with gallic acid groups.
For biological applications, the surface coating should be polar to give high aqueous solubility and prevent nanoparticle aggregation. In serum or on the cell surface, highly charged coatings promote non-specific binding, whereas polyethylene glycol linked to terminal hydroxyl or methoxy groups repel non-specific interactions. By the immobilization of thiol groups on the surface of nanoparticles or by coating them with thiomers high (muco)adhesive and cellular uptake enhancing properties can be introduced.
Nanoparticles can be linked to biological molecules that can act as address tags, directing them to specific sites within the body specific organelles within the cell, or causing them to follow specifically the movement of individual protein or RNA molecules in living cells. Common address tags are monoclonal antibodies, aptamers, streptavidin, or peptides. These targeting agents should ideally be covalently linked to the nanoparticle and should be present in a controlled number per nanoparticle. Multivalent nanoparticles, bearing multiple targeting groups, can cluster receptors, which can activate cellular signaling pathways, and give stronger anchoring. Monovalent nanoparticles, bearing a single binding site, avoid clustering and so are preferable for tracking the behavior of individual proteins.
It has been shown that catalytic activity and sintering rates of a functionalized nanoparticle catalyst is correlated to nanoparticles' number density
Coatings that mimic those of red blood cells can help nanoparticles evade the immune system. | 0 | Theoretical and Fundamental Chemistry |
Surface diffusion is a critically important concept in heterogeneous catalysis, as reaction rates are often dictated by the ability of reactants to "find" each other at a catalyst surface. With increased temperature adsorbed molecules, molecular fragments, atoms, and clusters tend to have much greater mobility (see equation 1). However, with increased temperature the lifetime of adsorption decreases as the factor kT becomes large enough for the adsorbed species to overcome the barrier to desorption, Q (see figure 2). Reaction thermodynamics aside because of the interplay between increased rates of diffusion and decreased lifetime of adsorption, increased temperature may in some cases decrease the overall rate of the reaction. | 0 | Theoretical and Fundamental Chemistry |
Within the Fallout videogame universe many Nuka-Cola flavors are created using less than ethical ways. In particular the flavor, Nuka Cola Quantum, has a distinctive bright blue glow that comes from the added Strontium-90. This was also the last flavor to be created by Nuka Cola before the Great War. | 0 | Theoretical and Fundamental Chemistry |
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