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During the last 5–10 years, a new kind of DSSC has been developed – the solid state dye-sensitized solar cell. In this case the liquid electrolyte is replaced by one of several solid hole conducting materials. From 2009 to 2013 the efficiency of Solid State DSSCs has dramatically increased from 4% to 15%. Michael Grätzel announced the fabrication of Solid State DSSCs with 15.0% efficiency, reached by the means of a hybrid perovskite CHNHPbI dye, subsequently deposited from the separated solutions of CHNHI and PbI.
The first architectural integration was demonstrated at EPFL's SwissTech Convention Center in partnership with Romande Energie. The total surface is 300 m, in 1400 modules of 50 cm x 35 cm. Designed by artists Daniel Schlaepfer and Catherine Bolle. | 0 | Theoretical and Fundamental Chemistry |
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins produce messenger RNA (mRNA). Other segments of DNA are transcribed into RNA molecules called non-coding RNAs (ncRNAs).
Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript.
In virology, the term transcription may also be used when referring to mRNA synthesis from an RNA molecule (i.e., equivalent to RNA replication). For instance, the genome of a negative-sense single-stranded RNA (ssRNA -) virus may be a template for a positive-sense single-stranded RNA (ssRNA +). This is because the positive-sense strand contains the sequence information needed to translate the viral proteins needed for viral replication. This process is catalyzed by a viral RNA replicase. | 1 | Applied and Interdisciplinary Chemistry |
The members of genus Orbivirus within the Reoviridae family are arthropod borne viruses and are responsible for high morbidity and mortality in ruminants. Bluetongue virus (BTV) which causes disease in livestock (sheep, goat, cattle) has been in the forefront of molecular studies for the last three decades and now represents the best understood orbivirus at the molecular and structural levels. BTV, like other members of the family, is a complex non-enveloped virus with seven structural proteins and a RNA genome consisting of 10 variously sized dsRNA segments. | 1 | Applied and Interdisciplinary Chemistry |
Hitherto, recent publications that broke the wall of putative chemical understanding and presented detection/isolation of novel compounds with intriguing bonding characters can still be provocative at times. The stir in such discoveries arose partly from the lack of a universally accepted bond descriptor. While bond dissociation energies (BDE) and rigid force constants have been generally regarded as primary tools for such interpretation, they are prone to flawed definition of chemical bonds in certain scenarios whether simple or controversial.
Such reasons prompted the necessity to seek an alternative approach to describe covalent and non-covalent interactions more rigorously. , a German chemist at the TU Braunschweig and his Ph.D. student at the time, Kai Brandhorst, developed a program COMPLIANCE (freely available to the public), which harnesses compliance constants for tackling the aforementioned tasks. The authors use an inverted matrix of force constants, i.e., inverted Hessian matrix, originally introduced by W. T. Taylor and K. S. Pitzer. The insight in choosing the inverted matrix is from the realization that not all elements in the Hessian matrix are necessary—and thus redundant—for describing covalent and non-covalent interactions. Such redundancy is common for many molecules, and more importantly, it ushers in the dependence of the elements of the Hessian matrix on the choice of coordinate system. Therefore, the author claimed that force constants albeit more widely used are not an appropriate bond descriptor whereas non-redundant and coordinate system-independent compliance constants are. | 0 | Theoretical and Fundamental Chemistry |
Until now, ten anammox species have been described, including seven that are available in laboratory enrichment cultures. All have the taxonomical status of Candidatus, as none were obtained as classical pure cultures. Known species are divided over five genera:
# Kuenenia, one species: Kuenenia stuttgartiensis.
# Brocadia, three species: B. anammoxidans, B. fulgida, and B. sinica.
# Anammoxoglobus, one species: A. propionicus.
# Jettenia, one species: J. asiatica.
# Scalindua, four species: S. brodae, S. sorokinii, S. wagneri, and S. profunda.
Representatives of the first four genera were enriched from sludge from wastewater treatment plants; K. stuttgartiensis, B. anammoxidans, B. fulgida, and A. propionicus were even obtained from the same inoculum. Scalindua dominates the marine environment, but is also found in some freshwater ecosystems and wastewater treatment plants.
Together, these 10 species likely only represent a minute fraction of anammox biodiversity. For instance, there are currently over 2000 16S rRNA gene sequences affiliated with anammox bacteria that have been deposited to the Genbank (https://www.ncbi.nlm.nih.gov/genbank/), representing an overlooked continuum of species, subspecies, and strains, each apparently having found its specific niche in the wide variety of habitats where anammox bacteria are encountered. Species microdiversity is particularly impressive for the marine representative Scalindua. A question that remains to be investigated is which environmental factors determine species differentiation among anammox bacteria.
The sequence identities of the anammox 16S rRNA genes range from 87 to 99%, and phylogenetic analysis places them all within the phylum Planctomycetota, which form the PVC superphylum together with Verrucomicrobia and Chlamydiae. Within the Planctomycetota, anammox bacteria deeply branch as a monophyletic clade. Their phylogenetic position together with a broad range of specific physiological, cellular, and molecular traits give anammox bacteria their own order Brocadiales. | 1 | Applied and Interdisciplinary Chemistry |
The Society for Applied Spectroscopy (SAS) is an organization promoting research and education in the fields of spectroscopy, optics, and analytical chemistry. Founded in 1958, it is currently headquartered in Frederick, MD. In 2006 it had about 2,000 members worldwide.
SAS is perhaps best known for its technical conference with the Federation of Analytical Chemistry and Spectroscopy Societies and short courses on various aspects of spectroscopy and data analysis. The society publishes the scientific journal Applied Spectroscopy.
SAS is affiliated with American Institute of Physics (AIP), Coblentz, Council for Near Infrared Spectroscopy (CNIRS), Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), The Instrumentation, Systems, and Automation Society (ISA), and Optical Society of America (OSA).
SAS provides a number of awards with honorariums to encourage and recognize outstanding achievements. | 0 | Theoretical and Fundamental Chemistry |
The formation of electrical double layer (EDL) has been traditionally assumed to be entirely dominated by ion adsorption and redistribution. With considering the fact that the contact electrification between solid-solid is dominated by electron transfer, it is suggested by Wang that the EDL is formed by a two-step process. In the first step, when the molecules in the solution first approach a virgin surface that has no pre-existing surface charges, it may be possible that the atoms/molecules in the solution directly interact with the atoms on the solid surface to form strong overlap of electron clouds. Electron transfer occurs first to make the “neutral” atoms on solid surface become charged, i.e., the formation of ions. In the second step, if there are ions existing in the liquid, such as H+ and OH-, the loosely distributed negative ions in the solution would be attracted to migrate toward the surface bonded ions due to electrostatic interactions, forming an EDL. Both electron transfer and ion transfer co-exist at liquid-solid interface. | 0 | Theoretical and Fundamental Chemistry |
The dynamic pressure, along with the static pressure and the pressure due to elevation, is used in Bernoulli's principle as an energy balance on a closed system. The three terms are used to define the state of a closed system of an incompressible, constant-density fluid.
When the dynamic pressure is divided by the product of fluid density and acceleration due to gravity, g, the result is called velocity head, which is used in head equations like the one used for pressure head and hydraulic head. In a venturi flow meter, the differential pressure head can be used to calculate the differential velocity head, which are equivalent in the adjacent picture. An alternative to velocity head is dynamic head. | 1 | Applied and Interdisciplinary Chemistry |
It is believed that a major driving force in the origin of aerobic fermentation was its simultaneous origin with modern fruit (~125 mya). These fruits provided an abundance of simple sugar food source for microbial communities, including both yeast and bacteria. Bacteria, at that time, were able to produce biomass at a faster rate than the yeast. Producing a toxic compound, like ethanol, can slow the growth of bacteria, allowing the yeast to be more competitive. However, the yeast still had to use a portion of the sugar it consumes to produce ethanol. Crabtree-positive yeasts also have increased glycolytic flow, or increased uptake of glucose and conversion to pyruvate, which compensates for using a portion of the glucose to produce ethanol rather than biomass. Therefore, it is believed that the original driving force was to kill competitors. This is supported by research that determined the kinetic behavior of the ancestral ADH protein, which was found to be optimized to make ethanol, rather than consume it.
Further evolutionary events in the development of aerobic fermentation likely increased the efficiency of this lifestyle, including increased tolerance to ethanol and the repression of the respiratory pathway. In high sugar environments, S. cerevisiae outcompetes and dominants all other yeast species, except its closest relative Saccharomyces paradoxus. The ability of S. cerevisiae to dominate in high sugar environments evolved more recently than aerobic fermentation and is dependent on the type of high-sugar environment. Other yeasts' growth is dependent on the pH and nutrients of the high-sugar environment. | 1 | Applied and Interdisciplinary Chemistry |
Many high strength or electrically conductive polymers contain imide subunits, i.e., the polyimides. One example is Kapton where the repeat unit consists of two imide groups derived from aromatic tetracarboxylic acids. Another example of polyimides is the polyglutarimide typically made from polymethylmethacrylate (PMMA) and ammonia or a primary amine by aminolysis and cyclization of the PMMA at high temperature and pressure, typically in an extruder. This technique is called reactive extrusion. A commercial polyglutarimide product based on the methylamine derivative of PMMA, called Kamax, was produced by the Rohm and Haas company. The toughness of these materials reflects the rigidity of the imide functional group.
Interest in the bioactivity of imide-containing compounds was sparked by the early discovery of the high bioactivity of the Cycloheximide as an inhibitor of protein biosynthesis in certain organisms. Thalidomide, famous for its adverse effects, is one result of this research. A number of fungicides and herbicides contain the imide functionality. Examples include Captan, which is considered carcinogenic under some conditions, and Procymidone.
In the 21st century new interest arose in thalidomide's immunomodulatory effects, leading to the class of immunomodulators known as immunomodulatory imide drugs (IMiDs). | 0 | Theoretical and Fundamental Chemistry |
Assay sensitivity is a property of a clinical trial defined as the ability of a trial to distinguish an effective treatment from a less effective or ineffective intervention. Without assay sensitivity, a trial is not internally valid and is not capable of comparing the efficacy of two interventions. | 1 | Applied and Interdisciplinary Chemistry |
Assume that the phase space of the underlying dynamical system is the material configuration space of a continuum, such as a fluid or a deformable body. For instance, for a dynamical system generated by an unsteady velocity field
the open set of possible particle positions is a material configuration space. In this space, LCSs are material surfaces, formed by trajectories. Whether or not a material trajectory is contained in an LCS is a property that is independent of the choice of coordinates, and hence cannot depend of the observer. As a consequence, LCSs are subject to the basic objectivity (material frame-indifference) requirement of continuum mechanics. The objectivity of LCSs requires them to be invariant with respect to all possible observer changes, i.e., linear coordinate changes of the form
where is the vector of the transformed coordinates; is an arbitrary proper orthogonal matrix representing time-dependent rotations; and is an arbitrary -dimensional vector representing time-dependent translations. As a consequence, any self-consistent LCS definition or criterion should be expressible in terms of quantities that are frame-invariant. For instance, the strain rate and the spin tensor defined as
transform under Euclidean changes of frame into the quantities
A Euclidean frame change is, therefore, equivalent to a similarity transform for , and hence an LCS approach depending only on the eigenvalues and eigenvectors of is automatically frame-invariant. In contrast, an LCS approach depending on the eigenvalues of is generally not frame-invariant.
A number of frame-dependent quantities, such as , , , as well as the averages or eigenvalues of these quantities, are routinely used in heuristic LCS detection. While such quantities may effectively mark features of the instantaneous velocity field , the ability of these quantities to capture material mixing, transport, and coherence is limited and a priori unknown in any given frame. As an example, consider the linear unsteady fluid particle motion
which is an exact solution of the two-dimensional Navier–Stokes equations. The (frame-dependent) Okubo-Weiss criterion classifies the whole domain in this flow as elliptic (vortical) because holds, with referring to the Euclidean matrix norm. As seen in Fig. 3, however, trajectories grow exponentially along a rotating line and shrink exponentially along another rotating line. In material terms, therefore, the flow is hyperbolic (saddle-type) in any frame.
Since Newton’s equation for particle motion and the Navier–Stokes equations for fluid motion are well known to be frame-dependent, it might first seem counterintuitive to require frame-invariance for LCSs, which are composed of solutions of these frame-dependent equations. Recall, however, that the Newton and Navier–Stokes equations represent objective physical principles for material particle trajectories. As long as correctly transformed from one frame to the other, these equations generate physically the same material trajectories in the new frame. In fact, we decide how to transform the equations of motion from an -frame to a -frame through a coordinate change precisely by upholding that trajectories are mapped into trajectories, i.e., by requiring to hold for all times. Temporal differentiation of this identity and substitution into the original equation in the -frame then yields the transformed equation in the -frame. While this process adds new terms (inertial forces) to the equations of motion, these inertial terms arise precisely to ensure the invariance of material trajectories. Fully composed of material trajectories, LCSs remain invariant in the transformed equation of motion defined in the -frame of reference. Consequently, any self-consistent LCS definition or detection method must also be frame-invariant. | 1 | Applied and Interdisciplinary Chemistry |
Pitzer equations are important for the understanding of the behaviour of ions dissolved in natural waters such as rivers, lakes and sea-water. They were first described by physical chemist Kenneth Pitzer. The parameters of the Pitzer equations are linear combinations of parameters, of a virial expansion of the excess Gibbs free energy, which characterise interactions amongst ions and solvent. The derivation is thermodynamically rigorous at a given level of expansion. The parameters may be derived from various experimental data such as the osmotic coefficient, mixed ion activity coefficients, and salt solubility. They can be used to calculate mixed ion activity coefficients and water activities in solutions of high ionic strength for which the Debye–Hückel theory is no longer adequate. They are more rigorous than the equations of specific ion interaction theory (SIT theory), but Pitzer parameters are more difficult to determine experimentally than SIT parameters. | 0 | Theoretical and Fundamental Chemistry |
Mg(I) dimers have the potential to be reducing agents that can be utilized in organic and organometallic synthesis. The thermal stability, moderate air and water sensitivity, and wide range of solubility in organic solvents may make the dimer attractive to chemists. An example of this can be shown through low oxidation state germanium (Ge) chemistry. Using Mg(I) dimers led to a Ge double bond. It can also be noted that the product had low yield. Additionally, the ligand, Nacnac has poor solubility in the reaction solvent of ether. This allows for easy separation too.
Additionally, hydrogen storage has been gained significant research attention as an alternative to fossil fuels.
Ammonia borane, NHBH, has a high H-content, at 19.6%, concerning hydrogen storage material. However, there are issues regarding the safety, kinetics, and practical characteristics of the compound. Alternatively, more s-block amidoboranes have been researched as an alternative, with some interest lying in magnesium amidoborane. Some studies have shown that using reductive dehydrogenation of ammonia borane can be achieved using Mg(I) dimers. | 0 | Theoretical and Fundamental Chemistry |
An Epsilon ray or Epsilon radiation is a type of tertiary radiation. Epsilon rays are a form of particle radiation and are composed of electrons. The term was coined by J. J. Thomson, but is very rarely used as of 2019. | 0 | Theoretical and Fundamental Chemistry |
Bacterial transcription is the process in which a segment of bacterial DNA is copied into a newly synthesized strand of messenger RNA (mRNA) with use of the enzyme RNA polymerase.
The process occurs in three main steps: initiation, elongation, and termination; and the end result is a strand of mRNA that is complementary to a single strand of DNA. Generally, the transcribed region accounts for more than one gene. In fact, many prokaryotic genes occur in operons, which are a series of genes that work together to code for the same protein or gene product and are controlled by a single promoter. Bacterial RNA polymerase is made up of four subunits and when a fifth subunit attaches, called the sigma factor (σ-factor), the polymerase can recognize specific binding sequences in the DNA, called promoters. The binding of the σ-factor to the promoter is the first step in initiation. Once the σ-factor releases from the polymerase, elongation proceeds. The polymerase continues down the double stranded DNA, unwinding it and synthesizing the new mRNA strand until it reaches a termination site. There are two termination mechanisms that are discussed in further detail below. Termination is required at specific sites for proper gene expression to occur. Gene expression determines how much gene product, such as protein, is made by the gene. Transcription is carried out by RNA polymerase but its specificity is controlled by sequence-specific DNA binding proteins called transcription factors. Transcription factors work to recognize specific DNA sequences and based on the cells needs, promote or inhibit additional transcription. Similar to other taxa, bacteria experience bursts of transcription. The work of the Jones team in Jones et al 2014 explains some of the underlying causes of bursts and other variability, including stability of the resulting mRNA, the strength of promotion encoded in the relevant promoter and the duration of transcription due to strength of the TF binding site. They also found that bacterial TFs linger too briefly for TFs binding characteristics to explain the sustained transcription of bursts.
Bacterial transcription differs from eukaryotic transcription in several ways. In bacteria, transcription and translation can occur simultaneously in the cytoplasm of the cell, whereas in eukaryotes transcription occurs in the nucleus and translation occurs in the cytoplasm. There is only one type of bacterial RNA polymerase whereas eukaryotes have 3 types. Bacteria have a σ-factor that detects and binds to promoter sites but eukaryotes do not need a σ-factor. Instead, eukaryotes have transcription factors that allow the recognition and binding of promoter sites.
Overall, transcription within bacteria is a highly regulated process that is controlled by the integration of many signals at a given time. Bacteria heavily rely on transcription and translation to generate proteins that help them respond specifically to their environment. | 1 | Applied and Interdisciplinary Chemistry |
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number greatly affects nuclear properties, but its effect on chemical properties is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly). The term isotopes (originally also isotopic elements, now sometimes isotopic nuclides) is intended to imply comparison (like synonyms or isomers). For example, the nuclides , , are isotopes (nuclides with the same atomic number but different mass numbers), but , , are isobars (nuclides with the same mass number). However, isotope is the older term and so is better known than nuclide and is still sometimes used in contexts in which nuclide might be more appropriate, such as nuclear technology and nuclear medicine. | 0 | Theoretical and Fundamental Chemistry |
ELPs modified with certain functional groups have the capacity to be conjugated with drugs, including chemotherapeutic agents. Together, the ELP-drug complex can be taken up by tumor cells to a greater extent, promoting the cytotoxic activity of the drug. The reason that the complexes preferentially target the tumor cells is that these cells tend to be associated with more permeable blood vessels and also possess a weaker lymphatic presence. This essentially means that the drugs can cross over from the vessels to the tumor cells more frequently and can remain in the vessels for a longer period of time, without being filtered out. The phase transition associated with ELPs can also be used to promote tumor cell uptake of the drug. By locally heating tumor cell regions, the ELP-drug complex will aggregate into spherical clumps. If this ELP-drug complex is engineered to expose functional domains in the spherical clump shape that are recognized by tumor cell surfaces, then this cell surface interaction would promote uptake of the drug as the tumor cell would mistake the ELP-drug complex as being a harmless substance. | 0 | Theoretical and Fundamental Chemistry |
In physics, maximum entropy thermodynamics (colloquially, MaxEnt thermodynamics) views equilibrium thermodynamics and statistical mechanics as inference processes. More specifically, MaxEnt applies inference techniques rooted in Shannon information theory, Bayesian probability, and the principle of maximum entropy. These techniques are relevant to any situation requiring prediction from incomplete or insufficient data (e.g., image reconstruction, signal processing, spectral analysis, and inverse problems). MaxEnt thermodynamics began with two papers by Edwin T. Jaynes published in the 1957 Physical Review. | 0 | Theoretical and Fundamental Chemistry |
In the presence of base or cyanide, 3-sulfolene isomerizes to a mixture of 2-sulfolene and 3-sulfolene.
At 50 °C an equilibrium mixture is obtained containing 42% 3-sulfolene and 58% 2-sulfolene. The thermodynamically more stable 2-sulfolene can be isolated from the mixture of isomers as pure substance in the form of white plates (m.p. 48-49 °C) by heating for several days at 100 °C, because of the thermal decomposition of the 3-sulfolene at temperatures above 80 °C. | 0 | Theoretical and Fundamental Chemistry |
Once a nickel allergy is detected, the best treatment is avoidance of nickel-releasing items. The top 13 categories that contain nickel include beauty accessories, eyeglasses, money, cigarettes, clothes, kitchen and household, electronics and office equipment, metal utensils, aliment, jewelry, batteries, orthodontic and dental appliances, and medical equipment. Other than strict avoidance of items that release free nickel, there are other treatment options for reduction of exposure. The first step is to limit friction between skin and metallic items. Susceptible people may try to limit sweating while wearing nickel items, to reduce nickel release and thus decrease chances for developing sensitization or allergy. Another option is to shield electronics, metal devices, and tools with fabric, plastic, or acrylic coverings.
There are dimethylglyoxime test kits that can be very helpful to check for nickel release from items prior to purchasing. The American Contact Dermatitis Society find a provider resource can help identify clinicians with training in providing guidance lists of safe items. In addition to avoidance, healthcare providers may prescribe additional creams or medications to help relieve the skin reaction. | 1 | Applied and Interdisciplinary Chemistry |
L-amino-acid alpha-ligase - L-ornithine N5 monooxygenase - lambda - Lamprin - Laser capture microdissection - latarcin - leucine zipper - leukemia - leukotriene-B4 20-monooxygenase - library - licodione synthase - ligase - linear epitope - linkage - linker protein - linoleate diol synthase - lipofectin - lipopolysaccharide kinase (Kdo/WaaP) family - lipopolysaccharide-transporting ATPase - lithocholate 6beta-hydroxylase - locus - LOD score - Long intergenic non-protein coding rna 1157 - lymphocyte - lysine—tRNA(Pyl) ligase - | 1 | Applied and Interdisciplinary Chemistry |
The Dawson structure is a well-known structural motif for heteropoly acids. The Dawson structure can be viewed as the fusion of two defect Keggin structure, fragments with three missing octahedra. As in Keggin structures, the Dawson structure has an oxyanion at its core. Unlike Keggin structures, there are two such anions, one at each side of the ellipsoidal anion. An example is , which can also be described as .
Commonly, Dawson structures feature phosphate as the central oxyanions. When the Keggin anion is allowed to stand in aqueous solution, it converts to . | 0 | Theoretical and Fundamental Chemistry |
Catenin beta-1, also known as β-catenin (beta-catenin), is a protein that in humans is encoded by the CTNNB1 gene.
β-Catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcription. In humans, the CTNNB1 protein is encoded by the CTNNB1 gene. In Drosophila, the homologous protein is called armadillo. β-catenin is a subunit of the cadherin protein complex and acts as an intracellular signal transducer in the Wnt signaling pathway. It is a member of the catenin protein family and homologous to γ-catenin, also known as plakoglobin. β-Catenin is widely expressed in many tissues. In cardiac muscle, β-catenin localizes to adherens junctions in intercalated disc structures, which are critical for electrical and mechanical coupling between adjacent cardiomyocytes.
Mutations and overexpression of β-catenin are associated with many cancers, including hepatocellular carcinoma, colorectal carcinoma, lung cancer, malignant breast tumors, ovarian and endometrial cancer. Alterations in the localization and expression levels of β-catenin have been associated with various forms of heart disease, including dilated cardiomyopathy. β-Catenin is regulated and destroyed by the beta-catenin destruction complex, and in particular by the adenomatous polyposis coli (APC) protein, encoded by the tumour-suppressing APC gene. Therefore, genetic mutation of the APC gene is also strongly linked to cancers, and in particular colorectal cancer resulting from familial adenomatous polyposis (FAP). | 1 | Applied and Interdisciplinary Chemistry |
See Fullmers work for a full list of Davys articles.
Humphry Davy's books are as follows:
* (on Davy's safety lamp)
Davy also contributed articles on chemistry to Reess Cyclopædia', but the topics are not known.
His collected works were published in 1839–1840: | 1 | Applied and Interdisciplinary Chemistry |
Esters react with nucleophiles at the carbonyl carbon. The carbonyl is weakly electrophilic but is attacked by strong nucleophiles (amines, alkoxides, hydride sources, organolithium compounds, etc.). The C–H bonds adjacent to the carbonyl are weakly acidic but undergo deprotonation with strong bases. This process is the one that usually initiates condensation reactions. The carbonyl oxygen in esters is weakly basic, less so than the carbonyl oxygen in amides due to resonance donation of an electron pair from nitrogen in amides, but forms adducts. | 0 | Theoretical and Fundamental Chemistry |
Pseudoenzymes are variants of enzymes (usually proteins) that are catalytically-deficient (usually inactive), meaning that they perform little or no enzyme catalysis. They are believed to be represented in all major enzyme families in the kingdoms of life, where they have important signaling and metabolic functions, many of which are only now coming to light. Pseudoenzymes are becoming increasingly important to analyse, especially as the bioinformatic analysis of genomes reveals their ubiquity. Their important regulatory and sometimes disease-associated functions in metabolic and signalling pathways are also shedding new light on the non-catalytic functions of active enzymes, of moonlighting proteins, the re-purposing of proteins in distinct cellular roles (Protein moonlighting). They are also suggesting new ways to target and interpret cellular signalling mechanisms using small molecules and drugs. The most intensively analyzed, and certainly the best understood pseudoenzymes in terms of cellular signalling functions are probably the pseudokinases, the pseudoproteases and the pseudophosphatases. Recently, the pseudo-deubiquitylases have also begun to gain prominence. | 1 | Applied and Interdisciplinary Chemistry |
TopFIND is the Termini oriented protein Function Inferred Database (TopFIND) is an integrated knowledgebase focused on protein termini, their formation by proteases and functional implications. It contains information about the processing and the processing state of proteins and functional implications thereof derived from research literature, contributions by the scientific community and biological databases. | 1 | Applied and Interdisciplinary Chemistry |
Much of what is known about uranium carbide is in the form of pin-type fuel elements for liquid metal fast reactors during their intense study during the 1960s and 1970s. However, recently there has been a revived interest in uranium carbide in the form of plate fuel and most notably, micro fuel particles (such as TRISO particles).
The high thermal conductivity and high melting point makes uranium carbide an attractive fuel. In addition, because of the absence of oxygen in this fuel (during the course of irradiation, excess gas pressure can build from the formation of O or other gases) as well as the ability to complement a ceramic coating (a ceramic-ceramic interface has structural and chemical advantages), uranium carbide could be the ideal fuel candidate for certain Generation IV reactors such as the gas-cooled fast reactor. While the neutron cross section of carbon is low, during years of burnup, the predominantly will undergo neutron capture to produce stable as well as radioactive . Unlike the produced by using Uranium nitrate, the will make up only a small isotopic impurity in the overall carbon content and thus make the entirety of the carbon content unsuitable for non-nuclear uses but the concentration will be too low for use in nuclear batteries without enrichment. Nuclear graphite discharged from reactors where it was used as a moderator presents the same issue. | 0 | Theoretical and Fundamental Chemistry |
The IUPAC name of alcohols can derive from the following rules:
# Identify the longest carbon chain, and number each carbon. Name the base alkane according to the organic nomenclature rules.
# Identify the hydroxyl group and which carbon it is on. To be alcohol, the -OH must be bonded to a carbon.
# Use the suffix -ol to denote which carbon the alcohol group is on. A three-carbon chain with the -OH on the second carbon would be propan-2-ol. Note that in some instances, common names are better.
# If the -OH is on the end of the chain, or the carbon chain is only 1 or 2, use no number.
# Use standard Greek prefixes to name molecules with two or more -OH groups (di- for 2, and so on). | 0 | Theoretical and Fundamental Chemistry |
Products using amphetamine base are now marketed. Dyanavel XR, a liquid suspension form became available in 2015, and contains about 24% levoamphetamine. Adzenys XR, an orally dissolving tablet came to market in 2016 and contains 25% levoamphetamine. | 0 | Theoretical and Fundamental Chemistry |
The related sulfinamides (R(S=O)NHR) are amides of sulfinic acids (R(S=O)OH) (see sulfinyl). Chiral sulfinamides such as tert-butanesulfinamide, p-toluenesulfinamide and 2,4,6-trimethylbenzenesulfinamide are relevant to asymmetric synthesis. | 0 | Theoretical and Fundamental Chemistry |
A sinusoidal wave, of small surface-elevation amplitude and with a constant wavelength, propagates with the phase velocity, also called celerity or phase speed. While the phase velocity is a vector and has an associated direction, celerity or phase speed refer only to the magnitude of the phase velocity. According to linear theory for waves forced by gravity, the phase speed depends on the wavelength and the water depth. For a fixed water depth, long waves (with large wavelength) propagate faster than shorter waves.
In the left figure, it can be seen that shallow water waves, with wavelengths λ much larger than the water depth h, travel with the phase velocity
with g the acceleration by gravity and c the phase speed. Since this shallow-water phase speed is independent of the wavelength, shallow water waves do not have frequency dispersion.
Using another normalization for the same frequency dispersion relation, the figure on the right shows that for a fixed wavelength λ the phase speed c increases with increasing water depth. Until, in deep water with water depth h larger than half the wavelength λ (so for h/λ > 0.5), the phase velocity c is independent of the water depth:
with T the wave period (the reciprocal of the frequency f, T=1/f ). So in deep water the phase speed increases with the wavelength, and with the period.
Since the phase speed satisfies c = λ/T = λf, wavelength and period (or frequency) are related. For instance in deep water:
The dispersion characteristics for intermediate depth are given below. | 1 | Applied and Interdisciplinary Chemistry |
Sir Frederick Charles Frank, OBE, FRS (6 March 1911 – 5 April 1998) was a British theoretical physicist. He is best known for his work on crystal dislocations, including (with Thornton Read) the idea of the Frank–Read source of dislocations. He also proposed the cyclol reaction in the mid-1930s, and made many other contributions to solid-state physics, geophysics, and the theory of liquid crystals. | 0 | Theoretical and Fundamental Chemistry |
Perfluorocarbon emulsions are emulsions containing either bubbles or droplets which have perfluorocarbons inside them. Some of them are commonly used in medicine as ultrasound contrast agents, and others have been studied for use as oxygen therapeutics. | 0 | Theoretical and Fundamental Chemistry |
For efficient TTA upconversion, the sensitizer should absorb strongly in the desired excitation range and have high conversion efficiency from the singlet excited state to the triplet excited state. The emitter should have a singlet energy level just below twice the energy of the first triplet excited state. Both the emitter and sensitizer should have long triplet-state lifetimes so that the TTA mechanism has enough time to occur. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R groups must be organic fragments not hydrogen. The two R groups can be equivalent to each other (a "symmetric acetal") or not (a "mixed acetal"). Acetals are formed from and convertible to aldehydes or ketones and have the same oxidation state at the central carbon, but have substantially different chemical stability and reactivity as compared to the analogous carbonyl compounds. The central carbon atom has four bonds to it, and is therefore saturated and has tetrahedral geometry.
The term ketal is sometimes used to identify structures associated with ketones (both R groups organic fragments rather than hydrogen) rather than aldehydes and, historically, the term acetal was used specifically for the aldehyde-related cases (having at least one hydrogen in place of an R on the central carbon). The IUPAC originally deprecated the usage of the word ketal altogether, but has since reversed its decision. However, in contrast to historical usage, ketals are now a subset of acetals, a term that now encompasses both aldehyde- and ketone-derived structures.
If one of the R groups has an oxygen as the first atom (that is, there are more than two oxygens single-bonded to the central carbon), the functional group is instead an orthoester. In contrast to variations of R, both R groups are organic fragments. If one R is a hydrogen, the functional group is instead a hemiacetal, while if both are H, the functional group is a ketone hydrate or aldehyde hydrate.
Formation of an acetal occurs when the hydroxyl group of a hemiacetal becomes protonated and is lost as water. The carbocation that is produced is then rapidly attacked by a molecule of alcohol. Loss of the proton from the attached alcohol gives the acetal.
Acetals are stable compared to hemiacetals but their formation is a reversible equilibrium as with esters. As a reaction to create an acetal proceeds, water must be removed from the reaction mixture, for example, with a Dean–Stark apparatus, lest it hydrolyse the product back to the hemiacetal. The formation of acetals reduces the total number of molecules present (carbonyl + 2 alcohol → acetal + water) and therefore is generally not favourable with regards to entropy. One situation where it is not entropically unfavourable is when a single diol molecule is used rather than two separate alcohol molecules (carbonyl + diol → acetal + water). Another way to avoid the entropic cost is to perform the synthesis by acetal exchange, using a pre-existing acetal-type reagent as the OR'-group donor rather than simple addition of alcohols themselves. One type of reagent used for this method is an orthoester. In this case, water produced along with the acetal product is destroyed when it hydrolyses residual orthoester molecules, and this side reaction also produces more alcohol to be used in the main reaction.
Acetals are used as protecting groups for carbonyl groups in organic synthesis because they are stable with respect to hydrolysis by bases and with respect to many oxidizing and reducing agents. They can either protect the carbonyl in a molecule (by temporarily reacting it with an alcohol) or a diol (by temporarily reacting it with a carbonyl). That is, either the carbonyl, or the alcohols, or both could be part of the molecule whose reactivity is to be controlled.
Various specific carbonyl compounds have special names for their acetal forms. For example, an acetal formed from formaldehyde (two hydrogens attached to the central carbon) is sometimes called a formal or the methylenedioxy group. The acetal formed from acetone is sometimes called an acetonide.
Used in a more general sense, the term X,Y-acetal also refers to any functional group that consists of a carbon bearing two heteroatoms X and Y. For example, N,O-acetal refers to compounds of type RRC(OR)(NR) (R,R ≠ H) also known as a hemiaminal ether) and S,S-acetal refers to compounds of type RRC(SR)(SR) (R,R ≠ H, also known as a thioacetal).
Besides protecting against nucleophilic addition or oxidation, acetals also find application as chiral auxiliaries. Indeed acetals of chiral glycols like, e.g. derivatives of tartaric acid can be asymmetrically opened with high selectivity. This enables the construction of new chiral centers. | 0 | Theoretical and Fundamental Chemistry |
Vibrational spectroscopy provides the most widely used means for characterizing ion associates. Both infrared spectroscopy and Raman spectroscopy have been used. Anions containing a CN group, such as cyanide, cyanate and thiocyanide have a vibration frequency a little above 2000 cm, which can be easily observed, as the spectra of most solvents (other than nitriles) are weak in this region. The anion vibration frequency is "shifted" on formation of ion pairs and other associates, and the extent of the shift gives information about the nature of the species. Other monovalent anions that have been studied include nitrate, nitrite and azide. Ion pairs of monatomic anions, such as halide ions, cannot be studied by this technique. Standard NMR spectroscopy is not very useful, as association/dissociation reactions tend to be fast on the NMR time scale, giving time-averaged signals of the cation and/or anion. However, diffusion ordered spectroscopy (DOSY), with which the sample tube is not spinning, can be used as ion pairs diffuse more slowly than do single ions due to their greater size.
Nearly the same shift of vibration frequency is observed for solvent-shared ion pairs of LiCN, Be(CN) and Al(CN) in liquid ammonia. The extent of this type of ion pairing decreases as the size of the cation increases. Thus, solvent-shared ion pairs are characterized by a rather small shift of vibration frequency with respect to the "free" solvated anion, and the value of the shift is not strongly dependent on the nature of the cation. The shift for contact ion pairs is, by contrast, strongly dependent on the nature of the cation and decreases linearly with the ratio of the cations charge to the squared radius:
:Cs > Rb > K > Na > Li;
:Ba > Sr > Ca.
The extent of contact ion pairing can be estimated from the relative intensities of the bands due to the ion pair and free ion. It is greater with the larger cations. This is counter to the trend expected if coulombic energy were the determining factor. Instead, the formation of a contact ion pair is seen to depend more on the energy needed to displace a solvent molecule from the primary solvation sphere of the cation. This energy decreases with the size of the cation, making ion pairing occur to a greater extent with the larger cations. The trend may be different in other solvents.
Higher ion aggregates, sometimes triples MXM, sometimes dimers of ion pairs (MX), or even larger species can be identified in the Raman spectra of some liquid-ammonia solutions of Na salts by the presence of bands that cannot be attributed to either contact- or solvent-shared ion pairs.
Evidence for the existence of fully solvated ion pairs in solution is mostly indirect, as the spectroscopic properties of such ion pairs are indistinguishable from those of the individual ions. Much of the evidence is based on the interpretation of conductivity measurements. | 0 | Theoretical and Fundamental Chemistry |
Pitch, a traditional naval store, was traditionally used to help caulk the seams of wooden sailing vessels (see shipbuilding). Other important historic uses included coating earthenware vessels for the preservation of wine, waterproofing wooden containers, and making torches. Petroleum-derived pitch is black in colour, hence the adjectival phrase, "pitch-black".
The viscoelastic properties of pitch make it well suited for the polishing of high-quality optical lenses and mirrors. In use, the pitch is formed into a lap or polishing surface, which is charged with iron oxide (Jewelers' rouge) or cerium oxide. The surface to be polished is pressed into the pitch, then rubbed against the surface so formed. The ability of pitch to flow, albeit slowly, keeps it in constant uniform contact with the optical surface.
Chasers pitch is a combination of pitch and other substances, used in jewelry making. | 0 | Theoretical and Fundamental Chemistry |
The table below describes properties of several different thermocouple types. Within the tolerance columns, T represents the temperature of the hot junction, in degrees Celsius. For example, a thermocouple with a tolerance of ±0.0025×T would have a tolerance of ±2.5 °C at 1000 °C.
Each cell in the Color Code columns depicts the end of a thermocouple cable, showing the jacket color and the color of the individual leads. The background color represents the color of the connector body. | 1 | Applied and Interdisciplinary Chemistry |
Xylose, fucose, mannose, and GlcNAc phosphoserine glycans have been reported in the literature. Fucose and GlcNAc have been found only in Dictyostelium discoideum, mannose in Leishmania mexicana, and xylose in Trypanosoma cruzi. Mannose has recently been reported in a vertebrate, the mouse, Mus musculus, on the cell-surface laminin receptor alpha dystroglycan. It has been suggested this rare finding may be linked to the fact that alpha dystroglycan is highly conserved from lower vertebrates to mammals. | 0 | Theoretical and Fundamental Chemistry |
To derive the Rayleigh equation for a barotropic fluid, the barotropic vorticity equation is used. This equation assumes that the absolute vorticity is conserved: here, is the material derivative. The absolute vorticity is the relative vorticity plus the planetary vorticity: Here, and are the zonal and meridional components of the flow and is the relative vorticity induced by the perturbations on the flow ( and ). is the mean zonal flow and is derivative of the planetary vorticity with respect to . | 1 | Applied and Interdisciplinary Chemistry |
The first substrate-level phosphorylation occurs after the conversion of 3-phosphoglyceraldehyde and Pi and NAD+ to 1,3-bisphosphoglycerate via glyceraldehyde 3-phosphate dehydrogenase. 1,3-bisphosphoglycerate is then dephosphorylated via phosphoglycerate kinase, producing 3-phosphoglycerate and ATP through a substrate-level phosphorylation.
The second substrate-level phosphorylation occurs by dephosphorylating phosphoenolpyruvate, catalyzed by pyruvate kinase, producing pyruvate and ATP.
During the preparatory phase, each 6-carbon glucose molecule is broken into two 3-carbon molecules. Thus, in glycolysis dephosphorylation results in the production of 4 ATP. However, the prior preparatory phase consumes 2 ATP, so the net yield in glycolysis is 2 ATP. 2 molecules of NADH are also produced and can be used in oxidative phosphorylation to generate more ATP. | 1 | Applied and Interdisciplinary Chemistry |
The aforementioned hydrodynamic and hydrostatic instruments may be employed in a variety of ways, or modes of operation, in order to address the particular separation needs of the scientist. Many modes of operation have been devised to take advantage of the strengths and potentialities of the countercurrent chromatography technique. Generally, the following modes may be performed with commercially available instruments. | 0 | Theoretical and Fundamental Chemistry |
A planet is in thermal equilibrium when the incident energy reaching it (typically the solar irradiance from its parent star) is equal to the infrared energy radiated away to space. | 0 | Theoretical and Fundamental Chemistry |
Improvements in viticulture and warmer vintages have led to increasing levels of sugar in wine grapes, which have translated to higher levels of alcohol - which can reach over 15% ABV in Zinfandels from California. Some producers feel that this unbalances their wine, and use spinning cones to reduce the alcohol by 1-2 percentage points. In this case the wine is passed through the column once to distill out the most volatile aroma compounds which are then put to one side while the wine goes through the column a second time at higher temperature to extract alcohol. The aroma compounds are then mixed back into the wine. Some producers such as Joel Peterson of Ravenswood argue that technological "fixes" such as spinning cones remove a sense of terroir from the wine; if the wine has the tannins and other components to balance 15% alcohol, Peterson argues that it should be accepted on its own terms.
The use of spinning cones, and other technologies such as reverse osmosis, was banned in the EU until recently, although for many years they could freely be used in wines imported into the EU from certain New World wine producing countries such as Australia and the USA. In November 2007, the Wine Standards Branch (WSB) of the UK's Food Standards Agency banned the sale of a wine called Sovio, made from Spanish grapes that would normally produce wines of 14% ABV. Sovio runs 40-50% of the wine over spinning cones to reduce the alcohol content to 8%, which means that under EU law it could not be sold as wine as it was below 8.5%; above that, under the rules prevailing at the time, it would be banned because spinning cones could not be used in EU winemaking.
Subsequently, the EU legalized dealcoholization with a 2% adjustment limit in its Code of Winemaking Practices, publishing that in its Commission Regulation (EC) No 606/2009 and stipulating that the dealcoholization must be accomplished by physical separation techniques which would embrace the spinning cone method.
More recently, in International Organisation of Vine and Wine Resolutions OIV-OENO 394A-2012 and OIV-OENO 394B-2012 of June 22, 2012 EU recommended winemaking procedures were modified to permit use of the spinning cone column and membrane techniques such as reverse osmosis on wine, subject to a limitation on the adjustment. That limitation is currently under review following the proposal by some EU members that it be eliminated altogether. The limitation is applicable only to products formally labeled as "wine". | 0 | Theoretical and Fundamental Chemistry |
Vitamin A is found in many foods. Vitamin A in food exists either as preformed retinol an active form of vitamin A found in animal liver, dairy and egg products, and some fortified foods, or as provitamin A carotenoids, which are plant pigments digested into vitamin A after consuming carotenoid-rich plant foods, typically in red, orange, or yellow colors. Carotenoid pigments may be masked by chlorophylls in dark green leaf vegetables, such as spinach. The relatively low bioavailability of plant-food carotenoids results partly from binding to proteins chopping, homogenizing or cooking disrupts the plant proteins, increasing provitamin A carotenoid bioavailability.
Vegetarian and vegan diets can provide sufficient vitamin A in the form of provitamin A carotenoids if the diet contains carrots, carrot juice, sweet potatoes, green leafy vegetables such as spinach and kale, and other carotenoid-rich foods. In the U.S., the average daily intake of β-carotene is in the range 2–7 mg.
Some manufactured foods and dietary supplements are sources of vitamin A or beta-carotene.
Despite the US setting an adult upper limit of 3,000 μg/day, some companies sell vitamin A (as retinal palmitate) as a dietary supplement with amounts of 7,500 μg/day. Two examples are WonderLabs and Pure Prescriptions. | 1 | Applied and Interdisciplinary Chemistry |
Solid foams, both open-cell and closed-cell, are considered as a sub-class of cellular structures. They often have lower nodal connectivity as compared to other cellular structures like honeycombs and truss lattices, and thus, their failure mechanism is dominated by bending of members. Low nodal connectivity and the resulting failure mechanism ultimately lead to their lower mechanical strength and stiffness compared to honeycombs and truss lattices.
The strength of foams can be impacted by the density, the material used, and the arrangement of the cellular structure (open vs closed and pore isotropy). To characterize the mechanical properties of foams, compressive stress-strain curves are used to measure their strength and ability to absorb energy since this is an important factor in foam based technologies. | 0 | Theoretical and Fundamental Chemistry |
The MG-RAST pipeline incorporates a series of steps for quality control and artifacts removal, ensuring robust processing of metagenomic and metatranscriptome datasets. The initial stage involves trimming low-quality regions using SolexaQA and eliminating reads with inappropriate lengths. In the case of metagenome and metatranscriptome datasets, a dereplication step is introduced to enhance data processing efficiency.
The subsequent step employs DRISEE (Duplicate Read Inferred Sequencing Error Estimation) to evaluate sample sequencing errors by measuring Artificial Duplicate Reads (ADRs). This assessment contributes to enhancing the accuracy of downstream analyses.
Finally, the pipeline offers the option to screen reads using the Bowtie aligner. It identifies and removes reads that exhibit matches close to the genomes of model organisms, including fly, mouse, cow, and human. This step aids in refining the dataset by filtering out reads associated with potential contaminants or unintended sequences. | 1 | Applied and Interdisciplinary Chemistry |
Fluid models describe plasmas in terms of smoothed quantities, like density and averaged velocity around each position (see Plasma parameters). One simple fluid model, magnetohydrodynamics, treats the plasma as a single fluid governed by a combination of Maxwell's equations and the Navier–Stokes equations. A more general description is the two-fluid plasma, where the ions and electrons are described separately. Fluid models are often accurate when collisionality is sufficiently high to keep the plasma velocity distribution close to a Maxwell–Boltzmann distribution. Because fluid models usually describe the plasma in terms of a single flow at a certain temperature at each spatial location, they can neither capture velocity space structures like beams or double layers, nor resolve wave-particle effects. | 0 | Theoretical and Fundamental Chemistry |
Production of QGP in the laboratory is achieved by colliding heavy atomic nuclei (called heavy ions as in an accelerator atoms are ionized) at relativistic energy in which matter is heated well above the Hagedorn temperature T = 150 MeV per particle, which amounts to a temperature exceeding 1.66×10 K. This can be accomplished by colliding two large nuclei at high energy (note that is not the energy of the colliding beam). Lead and gold nuclei have been used for such collisions at CERN SPS and BNL RHIC, respectively. The nuclei are accelerated to ultrarelativistic speeds (contracting their length) and directed towards each other, creating a "fireball", in the rare event of a collision. Hydrodynamic simulation predicts this fireball will expand under its own pressure, and cool while expanding. By carefully studying the spherical and elliptic flow, experimentalists put the theory to test. | 0 | Theoretical and Fundamental Chemistry |
A slip bond is a type of chemical noncovalent bond whose dissociation lifetime decreases with tensile force applied to the bond. This is the expected behaviour for chemical bonds, but exceptions, like catch bonds exist. | 1 | Applied and Interdisciplinary Chemistry |
SEC can be used as a measure of both the size and the polydispersity of a synthesized polymer, that is, the ability to find the distribution of the sizes of polymer molecules. If standards of a known size are run previously, then a calibration curve can be created to determine the sizes of polymer molecules of interest in the solvent chosen for analysis (often THF). In alternative fashion, techniques such as light scattering and/or viscometry can be used online with SEC to yield absolute molecular weights that do not rely on calibration with standards of known molecular weight. Due to the difference in size of two polymers with identical molecular weights, the absolute determination methods are, in general, more desirable. A typical SEC system can quickly (in about half an hour) give polymer chemists information on the size and polydispersity of the sample. The preparative SEC can be used for polymer fractionation on an analytical scale. | 1 | Applied and Interdisciplinary Chemistry |
Extensive research has been carried out on the metallurgical material from Tell Hammeh. Both excavation and archaeometric analyses were carried out by Dr H.A. Veldhuijzen, first at Leiden University, then since 2001 at the UCL Institute of Archaeology, as a part of the joint excavations conducted by Yarmouk University and Leiden University and co-directed by Prof. Dr. Zeidan Kafafi and Dr. Gerrit Van der Kooij. | 1 | Applied and Interdisciplinary Chemistry |
Two functional groups contribute significantly to aminosteroidal neuromuscular blocking potency, it is presumed to enable them to bind the receptor at two points. A bis-quaternary two point arrangement on A and D-ring (binding inter-site) or a D-ring acetylcholine moiety (binding at two points intra-site) are most likely to succeed. A third group can have variable effects. The quaternary and acetyl groups on the A and D ring of pipecuronium prevent it from binding intra-site (binding to two points at the same site). Instead, it must bind as bis-quaternary (inter-site). These structures are very dissimilar from acetylcholine and free pipecuronium from nicotinic or muscarinic side-effects linked to acetylcholine moiety. Also, they protect the molecule from hydrolysis by cholinesterases, which explain its nature of kidney excretion. The four methyl-groups on the quaternary N atoms make it less lipophilic than most aminosteroids. This also affects pipecuroniums metabolism by resisting hepatic uptake, metabolism, and biliary excretion. The length of the molecule (2.1 nm, close to ideal) and its rigidness make pipecuronium the most potent and clean one-bulk bis-quaternary. Even though the N-N distance (1.6 nm) is far away from what is considered ideal, its onium heads are well-exposed, and the quaternary groups help to bring together the onium heads to the anionic centers of the receptors without chirality issues.
Adding more than two onium heads in general does not add to potency. Though the third onium head in gallamine seems to help position the two outside heads near the optimum molecular length, it can interfere unfavorably and gallamine turns out to be a weak muscle relaxant, like all multi-quaternary compounds.
Considering acetylcholine a quaternizing group larger than methyl and an acyl group larger than acetyl would reduce the molecule's potency. The charged N and the carbonyl O atoms are distanced from structures they bind to on receptive sites and, thus, decrease potency. The carbonyl O in vecuronium for example is thrust outward to appose the H-bond donor of the receptive site. This also helps explain why gallamine, rocuronium, and rapacuronium are of relatively low potency.
In general, methyl quaternization is optimal for potency but, opposing this rule, the trimethyl derivatives of gallamine are of lower potency than gallamine. The reason for this is that gallamine has a suboptimal N-N distance. Substituting the ethyl groups with methyl groups would make the molecular length also shorter than optimal. Methoxylation of tetrahydroisoquinolinium agents seems to improve their potency. How methoxylation improves potency is still unclear.
Histamine release is a common attribute of benzylisoquinolinium muscle relaxants. This problem generally decreases with increased potency and smaller doses. The need for larger doses increases the degree of this side-effect. Conformational or structural explanations for histamine release are not clear. | 1 | Applied and Interdisciplinary Chemistry |
The convention for a polypeptide is to list its constituent amino acid residues as they occur from the amino terminus to the carboxylic acid terminus. The amino acid residues are always joined by peptide bonds. Protein, though used colloquially to refer to any polypeptide, refers to larger or fully functional forms and can consist of several polypeptide chains as well as single chains. Proteins can also be modified to include non-peptide components, such as saccharide chains and lipids. | 1 | Applied and Interdisciplinary Chemistry |
Cadet's fuming liquid was a red-brown oily liquid prepared in 1760 by the French chemist Louis Claude Cadet de Gassicourt (1731-1799) by the reaction of potassium acetate with arsenic trioxide. It consisted mostly of dicacodyl (((CH)As)) and cacodyl oxide (((CH)As)O).
The global reaction (mass balance) corresponding to the oxide formation is the following:
These were the first organometallic substances prepared; as such, Cadet has been regarded as the father of organometallic chemistry.
This liquid develops white fumes when exposed to air, resulting in a pale flame producing carbon dioxide, water, and arsenic trioxide. It has a nauseating and very disagreeable garlic-like odor.
Around 1840, Robert Bunsen did much work on characterizing the compounds in the liquid and its derivatives. His research was important in the development of radical theory. | 0 | Theoretical and Fundamental Chemistry |
Physical Chemistry Chemical Physics is a weekly peer-reviewed scientific journal publishing research and review articles on any aspect of physical chemistry, chemical physics, and biophysical chemistry. It is published by the Royal Society of Chemistry on behalf of eighteen participating societies. The editor-in-chief is Anouk Rijs, (Vrije Universiteit Amsterdam).
The journal was established in 1999 as the results of a merger between Faraday Transactions and a number of other physical chemistry journals published by different societies. | 0 | Theoretical and Fundamental Chemistry |
Woodward and Eschenmoser embarked on the project of a chemical synthesis of vitamin B independently from each other. The ETH group started with a model study on how to synthesize a corrin ligand system in December 1959. In August 1961, the Harvard group began attacking the buildup of the B structure directly by aiming at the most complex part of the B molecule, the "western half" that contains the direct junction between rings A and D (the A-D-component). Already in October 1960, the ETH group had commenced the synthesis of a ring-B precursor of vitamin B.
At the beginning, progress at Harvard was rapid, until an unexpected stereochemical course of a central ring formation step interrupted the project. Woodward's recognition of the stereochemical enigma that came to light by the irritating behavior of one of his carefully planned synthetic steps became, according to his own writings, part of the developments that led to the orbital symmetry rules.
After 1965, the Harvard group continued work towards an A-D-component along a modified plan, using (−)-camphor as the source of ring D. | 0 | Theoretical and Fundamental Chemistry |
Anthraquinone glycosides are found in senna, rhubarb, and Aloe.
The cardiac glycosides are phytochemicals from plants including foxglove and lily of the valley. They include digoxin and digitoxin which act as diuretics. | 1 | Applied and Interdisciplinary Chemistry |
These sterically constrained phosphorus compounds show remarkable reactivity towards protic reagents such as primary amines and alcohols, which results in intermolecular oxidative addition of these O−H and N−H bonds. This reaction tolerates a variety of different substrates, including ammonia and water. Two mechanisms have been suggested for the understanding of the unusual insertion of phosphorus atoms into polar X−H bonds by oxidative addition.
Nontrigonal phosphorus compounds can also react with ammonia–borane to form a formal dihydrogen oxidative addition product. This compound proved to facilitate the catalytic reduction of azobenzene. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the law of mass action is the proposition that the rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants. It explains and predicts behaviors of solutions in dynamic equilibrium. Specifically, it implies that for a chemical reaction mixture that is in equilibrium, the ratio between the concentration of reactants and products is constant.
Two aspects are involved in the initial formulation of the law: 1) the equilibrium aspect, concerning the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementary reactions. Both aspects stem from the research performed by Cato M. Guldberg and Peter Waage between 1864 and 1879 in which equilibrium constants were derived by using kinetic data and the rate equation which they had proposed. Guldberg and Waage also recognized that chemical equilibrium is a dynamic process in which rates of reaction for the forward and backward reactions must be equal at chemical equilibrium. In order to derive the expression of the equilibrium constant appealing to kinetics, the expression of the rate equation must be used. The expression of the rate equations was rediscovered independently by Jacobus Henricus van 't Hoff.
The law is a statement about equilibrium and gives an expression for the equilibrium constant, a quantity characterizing chemical equilibrium. In modern chemistry this is derived using equilibrium thermodynamics. It can also be derived with the concept of chemical potential. | 0 | Theoretical and Fundamental Chemistry |
Cornforth was the focus of a skit on an episode of Comedy Inc., whereby a fictional Who Wants to Be A Millionaire? contestant (played by Genevieve Morris) is asked "Which Australian scientist won the Nobel Prize for Chemistry in 1975?" for the million-dollar question. As it happens, the contest gleefully claims they are second cousins with Conforth (despite being nearly 50 years his junior) and knows Cornforth is the answer, confidently rattling off a bunch of highly specific and esoteric facts about Cornforths life and achievements, all the while the host (a satirical portrayal of Eddie McGuire) stubbornly and continuously stalls her for dramatic effect, asking her for several minutes if shed like to think about it more to an absurd degree.
On September 7, 2017, Google celebrated his 100th birthday with a Google Doodle. | 0 | Theoretical and Fundamental Chemistry |
A biological half-life or elimination half-life is the time it takes for a substance (drug, radioactive nuclide, or other) to lose one-half of its pharmacologic, physiologic, or radiological activity. In a medical context, the half-life may also describe the time that it takes for the concentration of a substance in blood plasma to reach one-half of its steady-state value (the "plasma half-life").
The relationship between the biological and plasma half-lives of a substance can be complex, due to factors including accumulation in tissues, active metabolites, and receptor interactions.
While a radioactive isotope decays almost perfectly according to so-called "first order kinetics" where the rate constant is a fixed number, the elimination of a substance from a living organism usually follows more complex chemical kinetics.
For example, the biological half-life of water in a human being is about 9 to 10 days, though this can be altered by behavior and other conditions. The biological half-life of caesium in human beings is between one and four months.
The concept of a half-life has also been utilized for pesticides in plants, and certain authors maintain that pesticide risk and impact assessment models rely on and are sensitive to information describing dissipation from plants.
In epidemiology, the concept of half-life can refer to the length of time for the number of incident cases in a disease outbreak to drop by half, particularly if the dynamics of the outbreak can be modeled exponentially. | 0 | Theoretical and Fundamental Chemistry |
An avalanche breakdown process can happen in semiconductors, which in some ways conduct electricity analogously to a mildly ionized gas. Semiconductors rely on free electrons knocked out of the crystal by thermal vibration for conduction. Thus, unlike metals, semiconductors become better conductors the higher the temperature. This sets up conditions for the same type of positive feedback—heat from current flow causes temperature to rise, which increases charge carriers, lowering resistance, and causing more current to flow. This can continue to the point of complete breakdown of normal resistance at a semiconductor junction, and failure of the device (this may be temporary or permanent depending on whether there is physical damage to the crystal). Certain devices, such as avalanche diodes, deliberately make use of the effect. | 0 | Theoretical and Fundamental Chemistry |
In systematics, an ideotype is a specimen identified as belonging to a specific taxon by the author of that taxon, but collected from somewhere other than the type locality.
The concept of ideotype in plant breeding was introduced by Donald in 1968 to describe the idealized appearance of a plant variety. It literally means a form denoting an idea. According to Donald, an ideotype is a biological model which is expected to perform or behave in a particular manner within a defined environment: "a crop ideotype is a plant model, which is expected to yield a greater quantity or quality of grain, oil or other useful product when developed as a cultivar." Donald and Hamblin (1976) proposed the concepts of isolation, competition and crop ideotypes. Market ideotype, climatic ideotype, edaphic ideotype, stress ideotype and disease/pest ideotypes are its other concepts. The term ideotype has the following synonyms: model plant type, ideal model plant type and ideal plan type.
The term is also used in cognitive science and cognitive psychology, where Ronaldo Vigo (2011, 2013, 2014) introduced it to refer to a type of concept metarepresentation that is a compound memory trace consisting of the structural information detected by humans in categorical stimuli. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of metal carbonyls is a widely studied subject of organometallic research. Since the work of Mond and then Hieber, many procedures have been developed for the preparation of mononuclear metal carbonyls as well as homo- and heterometallic carbonyl clusters. | 0 | Theoretical and Fundamental Chemistry |
FRET is often used to detect and track interactions between proteins. Additionally, FRET can be used to measure distances between domains in a single protein by tagging different regions of the protein with fluorophores and measuring emission to determine distance. This provides information about protein conformation, including secondary structures and protein folding. This extends to tracking functional changes in protein structure, such as conformational changes associated with myosin activity. Applied in vivo, FRET has been used to detect the location and interactions of cellular structures including integrins and membrane proteins. | 1 | Applied and Interdisciplinary Chemistry |
The bacteriophage P1 was first isolated by Dr. Giuseppe Bertani. In his study, he noticed that the lysogen produced abnormal non-continuous phages, and later found phage P1 was produced from the Lisbonne lysogen strain, in addition to bacteriophages P2 and P3. P1 has the ability to copy a bacteria's host genome and integrate that DNA information into other bacteria hosts, also known as generalized transduction. Later on, P1 was developed as a cloning vector by Nat Sternberg and colleagues in the 1990s. It is capable of Cre-Lox recombination. The P1 vector system was first developed to carry relatively large DNA fragments in plasmids (95-100kb). | 1 | Applied and Interdisciplinary Chemistry |
The thermocouple's behaviour is captured by a characteristic function , which needs only to be consulted at two arguments:
In terms of the Seebeck coefficients, the characteristic function is defined by
The constant of integration in this indefinite integral has no significance, but is conventionally chosen such that .
Thermocouple manufacturers and metrology standards organizations such as NIST provide tables of the function that have been measured and interpolated over a range of temperatures, for particular thermocouple types (see External links section for access to these tables). | 1 | Applied and Interdisciplinary Chemistry |
Octahedral clusters are inorganic or organometallic cluster compounds composed of six metals in an octahedral array. Many types of compounds are known, but all are synthetic. | 0 | Theoretical and Fundamental Chemistry |
The following classification method is based on the American AISI/SAE standard. Other international standards including DIN (Germany), GB (China), BS/EN (UK), AFNOR (France), UNI (Italy), SS (Sweden) , UNE (Spain), JIS (Japan), ASTM standards, and others.
Carbon steel is broken down into four classes based on carbon content: | 1 | Applied and Interdisciplinary Chemistry |
The Wealden iron industry was located in the Weald of south-eastern England. It was formerly an important industry, producing a large proportion of the bar iron made in England in the 16th century and most British cannon until about 1770. Ironmaking in the Weald used ironstone from various clay beds, and was fuelled by charcoal made from trees in the heavily wooded landscape. The industry in the Weald declined when ironmaking began to be fuelled by coke made from coal, which does not occur accessibly in the area. | 1 | Applied and Interdisciplinary Chemistry |
Michel Strickmann, a scholar of Daoist and Buddhist studies, analyzed the well-documented Shangqing Schools alchemy in the Maoshan revelations and in the life of Tao Hongjing, and concluded that scholars need to reexamine the Western stereotype of "accidental elixir poisoning" that supposedly applied to "misguided alchemists and their unwitting imperial patrons". Since Six Dynasties and Tang period Daoist literature thoroughly, "even rapturously", described the deadly toxic qualities of many elixirs, Strickmann proposed that some of the recorded alchemical deaths were intentional ritual suicide. Two reviewers disagreed about Strickmanns conclusions. The first questions why he defends the logic of alchemical suicide rather than simply accepting the idea of accidental elixir poisoning, and says Tao Hongjing never experimented with alchemy seriously enough to achieve suicide himself—but fails to mention Strickmanns prime example: Taos disciple Zhou Ziliang whom Shangqing deities reportedly instructed to prepare a poisonous elixir and commit suicide in order to achieve immortality. The second describes Strickmanns chapter as "one of the most thorough and useful" in the volume, and says he proves that it is "almost ludicrous to assume that a Taoist (commoner or emperor) could have died from accidental' elixir poisoning". | 1 | Applied and Interdisciplinary Chemistry |
Tic100 is a nuclear encoded protein thats 871 amino acids long. The 871 amino acids collectively weigh slightly less than 100 thousand daltons, and since the mature protein probably doesnt lose any amino acids when itself imported into the chloroplast (it has no cleavable transit peptide), it was named Tic100. Tic100 is found at the edges of the 1 million dalton complex on the side that faces the chloroplast intermembrane space. | 0 | Theoretical and Fundamental Chemistry |
The United States became interested in gas turbine development around 1905. From 1910-1915, austenitic ( γ phase) stainless steels were developed to survive high temperatures in gas turbines. By 1929, 80Ni-20Cr alloy was the norm, with small additions of Ti and Al. Although early metallurgists did not know it yet, they were forming small γ' precipitates in Ni-based superalloys. These alloys quickly surpassed Fe- and Co-based superalloys, which were strengthened by carbides and solid solution strengthening.
Although Cr was great for protecting the alloys from oxidation and corrosion up to 700 °C, metallurgists began decreasing Cr in favor of Al, which had oxidation resistance at much higher temperatures. The lack of Cr caused issues with hot corrosion, so coatings needed to be developed.
Around 1950, vacuum melting became commercialized, which allowed metallurgists to create higher purity alloys with more precise composition.
In the 60s and 70s, metallurgists changed focus from alloy chemistry to alloy processing. Directional solidification was developed to allow columnar or even single-crystal turbine blades. Oxide dispersion strengthening could obtain very fine grains and superplasticity. | 1 | Applied and Interdisciplinary Chemistry |
Acetylcholine (ACh) is a neurotransmitter found in the brain, neuromuscular junctions and the autonomic ganglia.
Muscarinic receptors are used in the following roles: | 1 | Applied and Interdisciplinary Chemistry |
Many synthetic ionophores are based on crown ethers, cryptands, and calixarenes. Pyrazole-pyridine and bis-pyrazole derivatives have also been synthesized. These synthetic species are often macrocyclic. Some synthetic agents are not macrocyclic, e.g. carbonyl cyanide-p-trifluoromethoxyphenylhydrazone. Even simple organic compounds, such as phenols, exhibit ionophoric properties. The majority of synthetic receptors used in the carrier-based anion-selective electrodes employ transition elements or metalloids as anion carriers, although simple organic urea- and thiourea-based receptors are known. | 0 | Theoretical and Fundamental Chemistry |
Specific mutations in different splice sites in various genes that cause inherited disorders, including, for example, Type 1 diabetes (e.g., PTPN22, TCF1 (HCF-1A)), hypertension (e.g., LDL, LDLR, LPL), Marfan syndrome (e.g., FBN1, TGFBR2, FBN2), cardiac diseases (e.g., COL1A2, MYBPC3, ACTC1), eye disorders (e.g., EVC, VSX1) have been uncovered. A few example mutations in the donor and acceptor splice sites in different genes causing a variety of inherited disorders identified using S&S are shown in Table 2. | 1 | Applied and Interdisciplinary Chemistry |
Photosynthetic pigments convert light into biochemical energy. Examples for photosynthetic pigments are chlorophyll, carotenoids and phycobilins. These pigments enter a high-energy state upon absorbing a photon which they can release in the form of chemical energy. This can occur via light-driven pumping of ions across a biological membrane (e.g. in the case of the proton pump bacteriorhodopsin) or via excitation and transfer of electrons released by photolysis (e.g. in the photosystems of the thylakoid membranes of plant chloroplasts). In chloroplasts, the light-driven electron transfer chain in turn drives the pumping of protons across the membrane. | 1 | Applied and Interdisciplinary Chemistry |
DNA computing is a form of parallel computing in that it takes advantage of the many different molecules of DNA to try many different possibilities at once. For certain specialized problems, DNA computers are faster and smaller than any other computer built so far. Furthermore, particular mathematical computations have been demonstrated to work on a DNA computer.
DNA computing does not provide any new capabilities from the standpoint of computability theory, the study of which problems are computationally solvable using different models of computation.
For example,
if the space required for the solution of a problem grows exponentially with the size of the problem (EXPSPACE problems) on von Neumann machines, it still grows exponentially with the size of the problem on DNA machines.
For very large EXPSPACE problems, the amount of DNA required is too large to be practical. | 1 | Applied and Interdisciplinary Chemistry |
The forerunners of the chemistry set were 17th century books on "natural magick", "which all excellent wise men do admit and embrace, and worship with great applause; neither is there any thing more highly esteemed, or better thought of, by men of learning." Authors, such as Giambattista della Porta, included chemical magic tricks and scientific puzzles along with more serious topics.
The earliest chemistry sets were developed in the 18th century in England and Germany to teach chemistry to adults. In 1791, Description of a portable chest of chemistry : or, Complete collection of chemical tests for the use of chemists, physicians, mineralogists, metallurgists, scientific artists, manufacturers, farmers, and the cultivators of natural philosophy by Johann Friedrich August Göttling, translated from German, was published in English. Friedrich Accum of London, England also sold portable chemistry sets and materials to refill them. Primarily used for training druggists and medical students, they could also be carried and used in the field.
Scientific kits also attracted well-educated members of the upper class who enjoyed experimenting and demonstrating their results. James Woodhouse of Philadelphia presented a Young Chemists Pocket Companion (1797) with an accompanying portable laboratory, specifically targeted ladies and gentlemen. Jane Marcets books on chemistry helped to popularize chemistry as a well-to-do pastime for both men and women.
Beginning in the late 1850s John J. Griffin & Sons sold a line of "chemical cabinets", eventually offering 11 categories. These were marketed primarily to adults including elementary school teachers as well as students at the Royal Naval College, the Royal Agricultural Society, and the universities of Oxford and Cambridge.
In the mid to late 1800s England, magic and illusion toys enabled children to make their own fireworks, create disappearing inks and cause changes in color, tricks which were mostly chemically based. The Columbian Cyclopedia of 1897 defines "CHEMISTRY TOYS" as "mostly pyrotechnic; recommended as illustrating to the young the rudiments of chemistry, but probably more dangerous than efficient for such use", listing a variety of hazardous examples. | 1 | Applied and Interdisciplinary Chemistry |
Binding of a ligand to a binding site on protein often triggers a change in conformation in the protein and results in altered cellular function. Hence binding site on protein are critical parts of signal transduction pathways. Types of ligands include neurotransmitters, toxins, neuropeptides, and steroid hormones. Binding sites incur functional changes in a number of contexts, including enzyme catalysis, molecular pathway signaling, homeostatic regulation, and physiological function. Electric charge, steric shape and geometry of the site selectively allow for highly specific ligands to bind, activating a particular cascade of cellular interactions the protein is responsible for. | 1 | Applied and Interdisciplinary Chemistry |
RNA-Seq experiments generate a large volume of raw sequence reads which have to be processed to yield useful information. Data analysis usually requires a combination of bioinformatics software tools (see also List of RNA-Seq bioinformatics tools) that vary according to the experimental design and goals. The process can be broken down into four stages: quality control, alignment, quantification, and differential expression. Most popular RNA-Seq programs are run from a command-line interface, either in a Unix environment or within the R/Bioconductor statistical environment. | 1 | Applied and Interdisciplinary Chemistry |
Inhibitors disrupt the interaction between enzyme and substrate, slowing down the rate of a reaction. There are different types of inhibitor, including both reversible and irreversible forms.
Competitive inhibitors are inhibitors that only target free enzyme molecules. They compete with substrates for free enzyme acceptor and can be overcome by increasing the substrate concentration. They have two mechanisms. Competitive inhibitors usually have structural similarities to the substrates and or ES complex. As a result, they can fit into the active site and trigger favourable interactions to fill in the space and block substrates from entry. They can also induce transient conformational changes in the active site so substrates cannot fit perfectly with it. After a short period of time, competitive inhibitors will drop off and leave the enzyme intact.
Inhibitors are classified as non-competitive inhibitors when they bind both free enzyme and ES complex. Since they do not compete with substrates for the active site, they cannot be overcome by simply increasing the substrate concentration. They usually bind to a different site on the enzyme and alter the 3-dimensional structure of the active site to block substrates from entry or leaving the enzyme.
Irreversible inhibitors are similar to competitive inhibitors as they both bind to the active site. However, irreversible inhibitors form irreversible covalent bonds with the amino acid residues in the active site and never leave. Therefore, the active site is occupied and the substrate cannot enter. Occasionally the inhibitor will leave but the catalytic site is permanently altered in shape. These inhibitors usually contain electrophilic groups like halogen substitutes and epoxides. As time goes by more and more enzymes are bound by irreversible inhibitors and cannot function anymore. | 1 | Applied and Interdisciplinary Chemistry |
Natural isotopes are either stable isotopes or radioactive isotopes that have a sufficiently long half-life to allow them to exist in substantial concentrations in the Earth (such as bismuth-209, with a half-life of 1.9 years, potassium-40 with a half-life of 1.251(3) years), daughter products of those isotopes (such as Th, with a half-life of 24 days) or cosmogenic elements. The heaviest stable isotope is lead-208, but the heaviest natural isotope is U-238.
Many elements have both natural and artificial isotopes. For example, hydrogen has three natural isotopes and another four known artificial isotopes. A further distinction among stable natural isotopes is division into primordial (existed when the Solar System formed) and cosmogenic (created by cosmic ray bombardment or other similar processes). | 0 | Theoretical and Fundamental Chemistry |
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as inorganic chemistry.
Inorganic compounds comprise most of the Earth's crust, although the compositions of the deep mantle remain active areas of investigation.
All allotropes (structurally different pure forms of an element) and some simple carbon compounds are often considered inorganic. Examples include the allotropes of carbon (graphite, diamond, buckminsterfullerene, graphene, etc.), carbon monoxide , carbon dioxide , carbides, and salts of inorganic anions such as carbonates, cyanides, cyanates, thiocyanates, isothiocyanates, phosphates, sulphates, chlorates, etc. Many of these are normal parts of mostly organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it cannot occur within living things. | 0 | Theoretical and Fundamental Chemistry |
When an electronic conductor is brought in contact with a solid or liquid ionic conductor (electrolyte), a common boundary (interface) among the two phases appears. Hermann von Helmholtz was the first to realize that charged electrodes immersed in electrolyte solutions repel the co-ions of the charge while attracting counterions to their surfaces. Two layers of opposite polarity form at the interface between electrode and electrolyte. In 1853 he showed that an electrical double layer (DL) is essentially a molecular dielectric and stores charge electrostatically. Below the electrolyte's decomposition voltage, the stored charge is linearly dependent on the voltage applied.
This early model predicted a constant differential capacitance independent from the charge density depending on the dielectric constant of the electrolyte solvent and the thickness of the double-layer.
This model, with a good foundation for the description of the interface, does not consider important factors including diffusion/mixing of ions in solution, the possibility of adsorption onto the surface, and the interaction between solvent dipole moments and the electrode. | 0 | Theoretical and Fundamental Chemistry |
CH has been measured directly in the environment since the 1970s. The Earth's atmospheric methane concentration has increased 160% since preindustrial levels in the mid-18th century.
Long term atmospheric measurements of methane by NOAA show that the build up of methane nearly tripled since pre-industrial times since 1750. In 1991 and 1998 there was a sudden growth rate of methane representing a doubling of growth rates in previous years. The June 15, 1991 eruption of Mount Pinatubo, measuring VEI-6was the second-largest terrestrial eruption of the 20th century. In 2007 it was reported that unprecedented warm temperatures in 1998the warmest year since surface records were recordedcould have induced elevated methane emissions, along with an increase in wetland and rice field emissions and the amount of biomass burning.
Data from 2007 suggested methane concentrations were beginning to rise again. This was confirmed in 2010 when a study showed methane levels were on the rise for the 3 years 2007 to 2009. After a decade of near-zero growth in methane levels, "globally averaged atmospheric methane increased by [approximately] 7 nmol/mol per year during 2007 and 2008. During the first half of 2009, globally averaged atmospheric CH was [approximately] 7 nmol/mol greater than it was in 2008, suggesting that the increase will continue in 2009." From 2015 to 2019 sharp rises in levels of atmospheric methane have been recorded.
In 2010, methane levels in the Arctic were measured at 1850 nmol/mol which is over twice as high as at any time in the last 400,000 years. According to the IPCC AR5, since 2011 concentrations continued to increase. After 2014, the increase accelerated and by 2017, it reached 1,850 (parts per billion) ppb. The annual average for methane (CH) was 1866 ppb in 2019 and scientists reported with "very high confidence" that concentrations of CH were higher than at any time in at least 800,000 years. The largest annual increase occurred in 2021 with current concentrations reaching a record 260% of pre-industrialwith the overwhelming percentage caused by human activity.
In 2013, IPCC scientists said with "very high confidence", that concentrations of atmospheric methane CH "exceeded the pre-industrial levels by about 150% which represented "levels unprecedented in at least the last 800,000 years." The globally averaged concentration of methane in Earth's atmosphere increased by about 150% from 722 ± 25 ppb in 1750 to 1803.1 ± 0.6 ppb in 2011. As of 2016, methane contributed radiative forcing of 0.62 ± 14% Wm, or about 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. The atmospheric methane concentration has continued to increase since 2011 to an average global concentration of 1911.8 ± 0.6 ppb as of 2022. The May 2021 peak was 1891.6 ppb, while the April 2022 peak was 1909.4 ppb, a 0.9% increase. The Global Carbon Project consortium produces the Global Methane Budget. Working with over fifty international research institutions and 100 stations globally, it updates the methane budget every few years.
In 2013, the balance between sources and sinks of methane was not yet fully understood. Scientists were unable to explain why the atmospheric concentration of methane had temporarily ceased to increase.
The focus on the role of methane in anthropogenic climate change has become more relevant since the mid-2010s. | 1 | Applied and Interdisciplinary Chemistry |
*2021: Murray Goodman Memorial Prize
*2021: Honorary Doctorate of Science (DSc) from University College London
*2021: Royal Society of Chemistry Khorana Prize
*2020: Elected Fellow of the Royal Society
*2020: Biophysical Society Innovation Award
*2015: Elected Foreign Member of the Academia Europaea.
*2014: Elected Member of the United States National Academy of Sciences (Biophysics and Computational Biology section)
*2012: Biochemical Society 2013 Centenary Award (previously known as the Jubilee Medal) and Sir Frederick Gowland Hopkins Memorial Lecture (U.K.)
*2011: Royal Society of Chemistry Centenary Prize
*2011: Elected Fellow of the International Society of Magnetic Resonance
*2010: Elected Fellow of the American Academy of Arts and Sciences
*2010: Hillebrand Award of the Washington Chemical Society
*2009: Elected Fellow of the Biophysical Society
*2003: Elected Member of the Lister Institute of Preventive Medicine (U.K.)
*2001: Original member, Institute for Scientific Information (ISI) Highly Cited Researchers Database (in Biology & Biochemistry and Chemistry sections).
*1999: Elected Fellow of the American Association for the Advancement of Science.
*1993: Dupont-Merck Young Investigator Award of the Protein Society
*1990: Elected Fellow of the Royal Society of Chemistry (FRSC) (U.K). | 0 | Theoretical and Fundamental Chemistry |
Phenol red, sometimes labelled with a different name, such as "Guardex Solution #2", is used as a pH indicator in home swimming pool test kits.
Chlorine can result in the bleaching of the dye in the absence of thiosulfate to inhibit the oxidizing chlorine. High levels of bromine can convert phenol red to bromophenol red (dibromophenolsulfonephthalein, whose lowered pK results in an indicator with a range shifted in the acidic direction – water at pH 6.8 will appear to test at 7.5). Even higher levels of bromine (>20 ppm) can result in the secondary conversion of bromophenol red to bromophenol blue with an even lower pK, erroneously giving the impression that the water has an extremely high pH despite being dangerously low. | 0 | Theoretical and Fundamental Chemistry |
Mechanical alloying (MA) is a solid-state and powder processing technique involving repeated cold welding, fracturing, and re-welding of blended powder particles in a high-energy ball mill to produce a homogeneous material. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or pre-alloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. | 1 | Applied and Interdisciplinary Chemistry |
Similar to other N-linked glycan types, the biosynthesis of paucimannosidic proteins across most species has been documented to be facilitated by the actions of a limited set of glyco-enzymes including beta-N-acetylhexosaminidases (Hex) and alpha-mannosidases, through GnT-I-dependent and -independent truncation pathways. | 1 | Applied and Interdisciplinary Chemistry |
It is anecdotally said that hot peppers help people in the tropics “cool off.” This theory is consistent with the peripheral vasodilatory effect of capsaicin that has been shown to lower skin temperature in humans exposed to a hot environment. Capsaicin feels hot in the mouth because it activates sensory receptors on the tongue otherwise used to detect thermal heat. This receptor is called Transient Receptor Potential Vanilloid 1 (TRPV1). TRPV1 receptors are also located in the gut and in other organs. Stimulation of TRPV1 receptors is known to bring about activation of the sympathetic nervous system (SNS). Capsaicin has been shown to increase fat burning in humans and animals through stimulation of the SNS.
Like capsaicin, capsinoids activate TRPV1 receptors, although they are not hot in the mouth. Capsinoids cannot reach the TRPV1 oral cavity receptors, located slightly below the surface in the mouth, because of structural differences from capsaicin. On the other hand, both capsaicin and capsinoids activate TRPV1 receptors in the same manner. Research has indicated that the TRPV1 receptors in the gut are important for the metabolic effects of capsaicin and capsinoids.
Both energy metabolism and body temperature increases are observed in humans following extracted capsinoids or CH-19 Sweet administration. Animal studies also demonstrate these increases, as well as suppressed in body fat accumulation following capsinoids intake. The exact mechanisms and the relative importance of each remain under investigation, as are the effects of capsinoids on appetite and satiation. | 1 | Applied and Interdisciplinary Chemistry |
The following excerpt from Takashi Fujii (1960) summarises well the limits of the Vegard’s law in the context of mineralogy and also makes the link with the Gladstone–Dale equation: | 1 | Applied and Interdisciplinary Chemistry |
Reactive transport models couple a large number chemical reactions with mass transport. Certain applications, such as geothermal energy production and ore deposit modeling, require the additional calculation of heat transfer. In modeling carbon sequestration and hydraulic fracturing, moreover, it may be necessary to describe rock deformation resulting from mineral growth or abnormally high fluid pressure. Description of transport through the unsaturated zone and multiphase flow modeling, as applied to transport of petroleum and natural gas; non-aqueous phase liquids (DNAPL or LNAPL); and supercritical carbon dioxide requires increasingly complex models which are prone to considerable uncertainty.
In many cases the processes simulated in reactive transport models are highly related. Mineral dissolution and precipitation, for example, can affect the porosity and permeability of the domain, which in turn affect the flow field and groundwater velocity. Heat transport greatly affects the viscosity of water and its ability to flow. Below are many of the physical and chemical processes which can be simulated with reactive transport models.
Geochemical reactions:
*Acid-base reactions
*Aqueous complexation
*Mineral dissolution and precipitation
*Reduction and oxidation (redox) reactions, including those catalyzed by enzymes, surfaces, and microorganisms
*Sorption, ion exchange, and surface complexation
*Gas dissolution and exsolution
*Stable isotope fractionation
*Radioactive decay
Mass Transport:
*Advection
*Molecular scale diffusion
*Hydrodynamic dispersion
*Colloid-facilitated transport
Heat transport:
*Advection
*Conduction
*Convection
Medium deformation:
*Compression or expansion of the domain
*Fracture formation | 0 | Theoretical and Fundamental Chemistry |
Understanding of genetic regulatory circuits are key in the field of synthetic biology, where disparate genetic elements are combined to produce novel biological functions. These biological gene circuits can be used synthetically to act as physical models for studying regulatory function.
By engineering genetic regulatory circuits, cells can be modified to take information from their environment, such as nutrient availability and developmental signals, and react in accordance to changes in their surroundings . In plant synthetic biology, genetic regulatory circuits can be used to program traits to increase crop plant efficiency by increasing their robustness to environmental stressors. Additionally, they are used to produce biopharmaceuticals for medical intervention. | 1 | Applied and Interdisciplinary Chemistry |
NMR chemical shifts are often called the mileposts of nuclear magnetic resonance spectroscopy. Chemists have used chemical shifts for more than 50 years as highly reproducible, easily measured parameters to map out the covalent structure of small organic molecules. Indeed, the sensitivity of NMR chemical shifts to the type and character of neighbouring atoms, combined with their reasonably predictable tendencies has made them invaluable for both deciphering and describing the structure of thousands of newly synthesized or newly isolated compounds
The same sensitivity to a variety of important protein structural features has made protein chemical shifts equally valuable to protein chemists and biomolecular NMR spectroscopists. In particular, protein chemical shifts are sensitive not only to substituent or covalent atom effects (such as electronegativity, redox states or ring currents) but they are also sensitive to backbone torsion angles (i.e. secondary structure), hydrogen bonding, local atomic motions and solvent accessibility. | 0 | Theoretical and Fundamental Chemistry |
Linear resistance meters, also called laminar flowmeters, measure very low flows at which the measured differential pressure is linearly proportional to the flow and to the fluid viscosity. Such flow is called viscous drag flow or laminar flow, as opposed to the turbulent flow measured by orifice plates, Venturis and other meters mentioned in this section, and is characterized by Reynolds numbers below 2000. The primary flow element may consist of a single long capillary tube, a bundle of such tubes, or a long porous plug; such low flows create small pressure differentials but longer flow elements create higher, more easily measured differentials. These flowmeters are particularly sensitive to temperature changes affecting the fluid viscosity and the diameter of the flow element, as can be seen in the governing Hagen–Poiseuille equation. | 1 | Applied and Interdisciplinary Chemistry |
Upregulation of PDE5 gene expression has been observed in animal models of pulmonary hypertension, and is thought to contribute to vasoconstriction in the lung. Several randomised controlled trials investigating PDE5 inhibitors use in pulmonary arterial hypertension, a subtype of pulmonary hypertension, have demonstrated their potent effects in reducing pulmonary hypertension and vascular remodelling and improving symptoms and mortality in patients with the condition. Long-term treatment with a PDE5 inhibitor has been shown to enhance natriuretic peptide-cGMP pathway, downregulate Ca signaling pathway and alter vascular tone in pulmonary arteries in rat models. | 1 | Applied and Interdisciplinary Chemistry |
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