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Quality of measurements made in chemistry and other areas is an important issue in today's world as measurements influence quality of life, cross-border trade and commerce. In this respect, EN ISO 17025 is the main standard used by testing and calibration laboratories as to appropriately tackle quality management related issues. While chapter four of the standard deals with management requirements, chapter five describes requirements for technical competence. Management related issues can be found in other standards as well e.g. ISO 9000, however the technical requirements are specific for calibration and testing laboratories. | 0 | Theoretical and Fundamental Chemistry |
Gas phase species absorb and display unique spectra between 120 – 240 nm where high energy σ→σ*, n→σ*, π→π*, n → π* electronic transitions can be excited and probed. VUV spectra reflect the absorbance cross section of compounds and are specific to their electronic structure and functional group arrangement. The ability of VUV detectors to produce spectra for most compounds results in universal and highly selective compound identification. VUV spectroscopy data is highly characteristic while also providing quantitative information. Many commonly used GC detectors such as the electron capture detector (ECD), flame ionization detector (FID), and thermal conductivity detector (TCD) produce quantitative but not qualitative detail. Gas chromatography–mass spectrometry (GC-MS) generates qualitative and quantitative data but has difficulty characterizing labile and low mass compounds, as well as differentiating between isomers. GC-VUV complements MS by overcoming its limitations and providing a secondary method of confirmation. It also offers a single instrument alternative to the use of multiple detectors for qualitative and quantitative analysis.
Naphthols, xylenes, and cis- and trans- fatty acids are compounds that are prohibitively difficult to distinguish according to their electron ionization mass spectral profiles. Xylenes present the additional challenge of natural co-elution that makes separating their isoforms problematic. Figure 2 shows the distinct VUV spectra of m-, p-, and o-xylene. These compounds can be differentiated despite their only difference being the position of two methyl groups around a benzene ring. The spectral differences of these isomers enable their co-elution to be resolved through spectral deconvolution.
Fatty acid screening and profiling is an application that commonly requires the use of multiple detectors to achieve quantitative and qualitative results. FID is a quantitative detector that is suitable for routine screening when guided by retention index information. GC-MS has traditionally been used for qualitative compound profiling, but falls short where isobaric analytes are prevalent. It especially struggles with differentiating cis and trans fatty acid isomers. Electron impact ionization can also cause double bond migration and lead to ambiguous fatty acid structural data.
Determining cis and trans fatty acid distribution in oils and fats is important in assessing their potential health impacts. VUV spectra of trans-containing fatty acid methyl ester (FAME) isomers typically found in butter and vegetable oils are shown in Figure 3. These trans-containing isomers separate chromatographically from cis-containing isomers and have the tendency to co-elute with each other and, in some cases, with select C20:1 isomers. GC-VUV is not only able to differentiate the C18:3 FAME variants, but is also capable of telling cis isomers apart from trans isomers. Degrees of unsaturation such as C20:1 vs. C18:3 can additionally be distinguished. Previous work has demonstrated how distinct VUV spectra enable straightforward deconvolution and accurate quantitation of cis and trans FAME isomers. | 0 | Theoretical and Fundamental Chemistry |
The nine-membered enediynes are also referred to as chromoproteins because they have an attached protein as a variable group. This protein is necessary for transport and stabilization of the enediyne group. | 0 | Theoretical and Fundamental Chemistry |
The mechanism of thiol–disulfide exchange between oxidoreductases is understood to begin with the nucleophilic attack on the sulfur atoms of a disulfide bond in the oxidised partner, by a thiolate anion derived from a reactive cysteine in a reduced partner. This generates mixed disulfide intermediates, and is followed by a second, this time intramolecular, nucleophilic attack by the remaining thiolate anion in the formerly reduced partner, to liberate both oxidoreductases. The balance of evidence discussed thus far supports a model in which oxidising equivalents are sequentially transferred from Ero1 via a thiol–disulfide exchange reaction to PDI, with PDI then undergoing a thiol–disulfide exchange with the nascent polypeptide, thereby enabling the formation of disulfide bonds within the nascent polypeptide. | 1 | Applied and Interdisciplinary Chemistry |
In lipidomics, the process of shotgun lipidomics (named by analogy with shotgun sequencing) uses analytical chemistry to investigate the biological function, significance, and sequelae of alterations in lipids and protein constituents mediating lipid metabolism, trafficking, or biological function in cells.
Lipidomics has been greatly facilitated by recent advances in, and novel applications of, electrospray ionization mass spectrometry (ESI/MS).
Lipidomics is a research field that studies the pathways and networks of cellular lipids in biological systems (i.e., lipidomes) on a large scale. It involves the identification and quantification of the thousands of cellular lipid molecular species and their interactions with other lipids, proteins, and other moieties in vivo. Investigators in lipidomics examine the structures, functions, interactions, and dynamics of cellular lipids and the dynamic changes that occur during pathophysiologic perturbations. Lipidomic studies play an essential role in defining the biochemical mechanisms of lipid-related disease processes through identifying alterations in cellular lipid metabolism, trafficking and homeostasis. The two major platforms currently used for lipidomic analyses are HPLC-MS and shotgun lipidomics. | 1 | Applied and Interdisciplinary Chemistry |
Function Maize gene for first step in biosynthesis of benzoxazin, which aids in resistance to insect pests, pathogenic fungi and bacteria.
First report Hamilton 1964, as a mutant sensitive to the herbicide atrazine, and lacking benzoxazinoids (less than 1% of non-mutant plants).
Molecular characterization reveals that the BX1 protein is a homologue to the alpha-subunit of tryptophan synthase. The reference mutant allele has a deletion of about 900 bp, located at the 5-terminus and comprising sequence upstream of the transcription start site and the first exon. Additional alleles are given by a Mu transposon insertion in the fourth exon (Frey et al. 1997 ) and a Ds' transposon insertion in the maize inbred line W22 genetic background (Betsiashvili et al. 2014). Gene sequence diversity analysis has been performed for 281 inbred lines of maize, and the results suggest that bx1 is responsible for much of the natural variation in DIMBOA (a benzoxazinoid compound) synthesis (Butron et al. 2010). Genetic variation in benzoxazinoid content influences maize resistance to several insect pests (Meihls et al. 2013; McMullen et al. 2009). | 1 | Applied and Interdisciplinary Chemistry |
Non-metallic inclusions are chemical compounds and nonmetals that are present in steel and other alloys. They are the product of chemical reactions, physical effects, and contamination that occurs during the melting and pouring process. These inclusions are categorized by origin as either endogenous or exogenous. Endogenous inclusions, also known as indigenous, occur within the metal and are the result of chemical reactions. These products precipitate during cooling and are typically very small. Exogenous inclusions are caused by the entrapment of nonmetals. Their size varies greatly and their source can include slag, dross, flux residues, and pieces of the mold. | 1 | Applied and Interdisciplinary Chemistry |
Q-FISH combines FISH with PNAs and computer software to quantify fluorescence intensity. This technique is used routinely in telomere length research. | 1 | Applied and Interdisciplinary Chemistry |
Relaxivities, nuclear relaxation rates, line shape and other parameters were reported useful in structural studies of carbohydrates. | 0 | Theoretical and Fundamental Chemistry |
To enhance the performance of surfactant properties of natural sophorolipids, chemical modification methods have been actively pursued. Recently, researchers demonstrated the possibility of applying sophorolipids as building blocks via ring-opening metathesis polymerization for a new type of polymers, known as polysophorolipids which show promising potentials in biomaterials applications. | 0 | Theoretical and Fundamental Chemistry |
IR Spectrum Table by Frequency
IR Spectra Table by Compound Class
To use an IR spectrum table, first need to find the frequency or compound in the first column, depending on which type of chart that is being used. Then find the corresponding values for absorption, appearance and other attributes. The value for absorption is usually in cm. | 0 | Theoretical and Fundamental Chemistry |
In plants, ATP synthase is also present in chloroplasts (CFF-ATP synthase). The enzyme is integrated into thylakoid membrane; the CF-part sticks into stroma, where dark reactions of photosynthesis (also called the light-independent reactions or the Calvin cycle) and ATP synthesis take place. The overall structure and the catalytic mechanism of the chloroplast ATP synthase are almost the same as those of the bacterial enzyme. However, in chloroplasts, the proton motive force is generated not by respiratory electron transport chain but by primary photosynthetic proteins. The synthase has a 40-aa insert in the gamma-subunit to inhibit wasteful activity when dark. | 0 | Theoretical and Fundamental Chemistry |
Tarnish is a product of a chemical reaction between a metal and a nonmetal compound, especially oxygen and sulfur dioxide. It is usually a metal oxide, the product of oxidation; sometimes it is a metal sulfide. The metal oxide sometimes reacts with water to make the hydroxide, or with carbon dioxide to make the carbonate. It is a chemical change. There are various methods to prevent metals from tarnishing. | 1 | Applied and Interdisciplinary Chemistry |
Superalloys were originally iron-based and cold wrought prior to the 1940s when investment casting of cobalt base alloys significantly raised operating temperatures. The 1950s development of vacuum melting allowed for fine control of the chemical composition of superalloys and reduction in contamination and in turn led to a revolution in processing techniques such as directional solidification of alloys and single crystal superalloys.
Processing methods vary widely depending on the required properties of each item. | 1 | Applied and Interdisciplinary Chemistry |
In order for two flows to be similar, they must have the same geometry and equal Reynolds and Euler numbers. When comparing fluid behavior at corresponding points in a model and a full-scale flow, the following holds:
where is the Reynolds number for the model, and is full-scale Reynolds number, and similarly for the Euler numbers.
The model numbers and design numbers should be in the same proportion, hence
This allows engineers to perform experiments with reduced scale models in water channels or wind tunnels and correlate the data to the actual flows, saving on costs during experimentation and on lab time. Note that true dynamic similitude may require matching other dimensionless numbers as well, such as the Mach number used in compressible flows, or the Froude number that governs open-channel flows. Some flows involve more dimensionless parameters than can be practically satisfied with the available apparatus and fluids, so one is forced to decide which parameters are most important. For experimental flow modeling to be useful, it requires a fair amount of experience and judgment of the engineer.
An example where the mere Reynolds number is not sufficient for the similarity of flows (or even the flow regime – laminar or turbulent) are bounded flows, i.e. flows that are restricted by walls or other boundaries. A classical example of this is the Taylor–Couette flow, where the dimensionless ratio of radii of bounding cylinders is also important, and many technical applications where these distinctions play an important role. Principles of these restrictions were developed by Maurice Marie Alfred Couette and Geoffrey Ingram Taylor and developed further by Floris Takens and David Ruelle.
;Typical values of Reynolds number
* Dictyostelium amoebae: ~ 1 × 10
* Bacterium ~ 1 × 10
* Ciliate ~ 1 × 10
* Smallest fish ~ 1
* Blood flow in brain ~ 1 × 10
* Blood flow in aorta ~ 1 × 10
* Onset of turbulent flow ~ 2.3 × 10 to 5.0 × 10 for pipe flow to 10 for boundary layers
* Typical pitch in Major League Baseball ~ 2 × 10
* Person swimming ~ 4 × 10
* Fastest fish ~ 1 × 10
* Blue whale ~ 4 × 10
* A large ship (Queen Elizabeth 2) ~ 5 × 10
* Atmospheric tropical cyclone ~ 1 x 10 | 1 | Applied and Interdisciplinary Chemistry |
The chemical model consists of a set of chemical species present in solution, both the reactants added to the reaction mixture and the complex species formed from them. Denoting the reactants by A, B..., each complex species is specified by the stoichiometric coefficients that relate the particular combination of reactants forming them.
When using general-purpose computer programs, it is usual to use cumulative association constants, as shown above. Electrical charges are not shown in general expressions such as this and are often omitted from specific expressions, for simplicity of notation. In fact, electrical charges have no bearing on the equilibrium processes other that there being a requirement for overall electrical neutrality in all systems.
With aqueous solutions the concentrations of proton (hydronium ion) and hydroxide ion are constrained by the self-dissociation of water.
With dilute solutions the concentration of water is assumed constant, so the equilibrium expression is written in the form of the ionic product of water.
When both H and OH must be considered as reactants, one of them is eliminated from the model by specifying that its concentration be derived from the concentration of the other. Usually the concentration of the hydroxide ion is given by
In this case the equilibrium constant for the formation of hydroxide has the stoichiometric coefficients −1 in regard to the proton and zero for the other reactants. This has important implications for all protonation equilibria in aqueous solution and for hydrolysis constants in particular.
It is quite usual to omit from the model those species whose concentrations are considered negligible. For example, it is usually assumed then there is no interaction between the reactants and/or complexes and the electrolyte used to maintain constant ionic strength or the buffer used to maintain constant pH. These assumptions may or may not be justified. Also, it is implicitly assumed that there are no other complex species present. When complexes are wrongly ignored a systematic error is introduced into the calculations.
Equilibrium constant values are usually estimated initially by reference to data sources. | 0 | Theoretical and Fundamental Chemistry |
The development of the winnowing barn allowed rice plantations in South Carolina to increase their yields dramatically. | 0 | Theoretical and Fundamental Chemistry |
Main methods to study protein–ligand interactions are principal hydrodynamic and calorimetric techniques, and principal spectroscopic and structural methods such as
*Fourier transform spectroscopy
*Raman spectroscopy
*Fluorescence spectroscopy
*Circular dichroism
*Nuclear magnetic resonance
*Mass spectrometry
*Atomic force microscope
*Paramagnetic probes
*Dual polarisation interferometry
*Multi-parametric surface plasmon resonance
*Ligand binding assay and radioligand binding assay
Other techniques include:
fluorescence intensity,
bimolecular fluorescence complementation,
FRET (fluorescent resonance energy transfer) / FRET quenching
surface plasmon resonance,
bio-layer interferometry,
Coimmunopreciptation
indirect ELISA,
equilibrium dialysis,
gel electrophoresis,
far western blot,
fluorescence polarization anisotropy,
electron paramagnetic resonance,
microscale thermophoresis,
switchSENSE.
The dramatically increased computing power of supercomputers and personal computers has made it possible to study protein–ligand interactions also by means of computational chemistry. For example, a worldwide grid of well over a million ordinary PCs was harnessed for cancer research in the project grid.org, which ended in April 2007. Grid.org has been succeeded by similar projects such as World Community Grid, Human Proteome Folding Project, Compute Against Cancer and Folding@Home. | 1 | Applied and Interdisciplinary Chemistry |
DNA is an information storage macromolecule that encodes the complete set of instructions (the genome) that are required to assemble, maintain, and reproduce every living organism.
DNA and RNA are both capable of encoding genetic information, because there are biochemical mechanisms which read the information coded within a DNA or RNA sequence and use it to generate a specified protein. On the other hand, the sequence information of a protein molecule is not used by cells to functionally encode genetic information.
DNA has three primary attributes that allow it to be far better than RNA at encoding genetic information. First, it is normally double-stranded, so that there are a minimum of two copies of the information encoding each gene in every cell. Second, DNA has a much greater stability against breakdown than does RNA, an attribute primarily associated with the absence of the 2'-hydroxyl group within every nucleotide of DNA. Third, highly sophisticated DNA surveillance and repair systems are present which monitor damage to the DNA and repair the sequence when necessary. Analogous systems have not evolved for repairing damaged RNA molecules. Consequently, chromosomes can contain many billions of atoms, arranged in a specific chemical structure. | 0 | Theoretical and Fundamental Chemistry |
The company was founded in 1975 by Robert Gielow and James Paul, two Professional Engineers with backgrounds in the aerospace industry. They quickly realized that the analysis techniques they applied to projects such as the Apollo program Moon rockets and commercial aircraft design could be used to advance a wide variety of other industries. Early years of the company were focused on aerodynamic optimization of vehicles such as cars, tractor trailers, and rail cars to minimize drag and fuel consumption. This work involved both wind tunnel testing and numerical simulation.
In the 1970s and 1980s, ASC developed a range of simulation software for potential flow and viscous flow analysis, writing its own CFD solver (VISCOUS). The capabilities of this cartesian-based CFD software eventually included advanced physics such as combustion, particulate transport and drying simulations, time-dependence, and convection/conduction/radiation heat transfer. In the 1990s and early 2000s, ASC personnel developed a new CFD software package, AzoreCFD, featuring a modern, polyhedral based solver in order to analyze highly complex geometries and physics. Azore development continues with new features and simulations capabilities incorporated to allow more unique flow problems to be analyzed.
In addition to simulation of flow and heat transfer, ASC has advanced its field testing capabilities on a regular basis over the years. Many of the tests ASC is requested to perform are new or unique, requiring development and fabrication of custom flow measurement equipment. Today's testing capabilities include velocity, temperature, pressure, particulate sampling, gas species and emissions, and more. | 1 | Applied and Interdisciplinary Chemistry |
The French physician Martin Mathee published in 1553 the French translation of De Materia Medica, printed by Balthazar Arnoullet, in Lyons. This granted much more access for the students of medicine to the teachings.
The Greek version was reprinted in 1518, 1523 and 1529, and reprinted in 1518, 1523 and 1529. Between 1555 and 1752 there were at least 12 Spanish editions; and as many in Italian from 1542. French editions appeared from 1553; and German editions from 1546. | 1 | Applied and Interdisciplinary Chemistry |
The frit fast atom bombardment (FAB) and continuous flow-FAB (CF-FAB) interfaces were developed in 1985 and 1986 respectively. Both interfaces were similar, but they differed in that the first used a porous frit probe as connecting channel, while CF-FAB used a probe tip. From these, the CF-FAB was more successful as a LC–MS interface and was useful to analyze non-volatile and thermally labile compounds. In these interfaces, the LC effluent passed through the frit or CF-FAB channels to form a uniform liquid film at the tip. There, the liquid was bombarded with ion beams or high energy atoms (fast atoms). For stable operation, the FAB based interfaces were able to handle liquid flow rates of only 1–15 μl and were also restricted to microbore and capillary columns. In order to be used in FAB MS ionization sources, the analytes of interest had to be mixed with a matrix (e.g., glycerol) that could be added before or after the separation in the LC column. FAB based interfaces were extensively used to characterize peptides, but lost applicability with the advent of electrospray based interfaces in 1988. | 0 | Theoretical and Fundamental Chemistry |
A collection of data from the United States found that about half the water stations tested had hardness over 120 mg per litre of calcium carbonate equivalent, placing them in the categories "hard" or "very hard". The other half were classified as soft or moderately hard. More than 85% of American homes have hard water. The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the regions throughout the country. The hardest waters (greater than 1,000 ppm) are in streams in Texas, New Mexico, Kansas, Arizona, Utah, parts of Colorado, southern Nevada, and southern California. | 0 | Theoretical and Fundamental Chemistry |
*Paul Alivisatos (Ph.D. 1986) - Professor Emeritus, National Medal of Science (2015); Priestley Medal (2020)
*Neil Bartlett - Professor (1969)
*Carolyn Bertozzi (Ph.D. 1993) - Professor (1996-2015), Nobel Prize (2022)
*Melvin Calvin (B.S. 1931, Ph.D. 1935) - Professor, Nobel laureate (1961)
*Robert E. Connick (Ph.D. 1942) - Professor Emeritus of Chemistry, Dean
*Jennifer Doudna - Professor, Wolf Award (2020), Nobel laureate (2020)
*William F. Giauque (B.S. 1920, Ph.D. 1922) - Professor, Nobel laureate (1949)
*John F. Hartwig - Professor, Wolf Award (2019)
*Martin Head-Gordon (B.S. 1983, Ph.D. 1989) - Professor (1992), Medal of the International Academy of Quantum Molecular Sciences (1998)
*Dudley R. Herschbach - Assistant Professor, Nobel laureate (1986)
*Joel Henry Hildebrand (Ph.D. 1906) - Dean (1949–1951), Chairman of the Dept. of Chemistry (1941–1943), Professor
*Darleane Hoffman - Professor, National Medal of Science (1997)
*Judith Klinman - Professor, National Medal of Science (2012)
*Yuan T. Lee (Ph.D. 1965) - Professor, Nobel laureate (1986)
*Gilbert Newton Lewis - Dean (1912–1941), Professor
*Willard F. Libby (B.S. 1931, Ph.D. 1933) - Professor (1933-1941), Nobel laureate (1960)
*Jeffrey R. Long - Professor, National Science Foundation Special Creativity Award
*David MacMillan - Professor (1998-2000), Nobel Prize (2021)
*George C. Pimentel (Ph.D. 1949) - Professor (1949-1989), National Medal of Science (1985)
*Kenneth Pitzer (Ph.D. 1937) - Dean (1951–60), Professor, President of Rice University and Stanford University
*John Prausnitz - Professor, National Medal of Science (2003)
*Glenn T. Seaborg (Ph.D. 1937) - Professor, Nobel laureate (1951)
*Gabor Somorjai - Professor, National Medal of Science (2002)
*Andrew Streitwieser - Professor, National Academy of Science
*Peidong Yang - Professor, MacArthur Genius Award (2015)
*Omar Yaghi - Professor, Wolf Award (2018) | 1 | Applied and Interdisciplinary Chemistry |
As PACs consist of a light sensor and an enzyme in a single protein, they can be expressed in other species and cell types to manipulate cAMP levels with light. When bPAC is expressed in mouse sperm, blue light illumination speeds up the swimming of transgenic sperm cells and aids fertilization. When expressed in neurons, illumination changes the branching pattern of growing axons. PAC has been used in mice to clarify the function of neurons in the hypothalamus, which use cAMP signaling to control mating behavior. Expression of PAC together with K-specific cyclic-nucleotide-gated ion channels (CNGs) has been used to hyperpolarize neurons at very low light levels, which prevents them from firing action potentials. | 1 | Applied and Interdisciplinary Chemistry |
The Mori synthesis ((-) chiral, 2003) was the first one containing an asymmetric reaction step. It also features a large number of Pd catalyzed reactions. In it N-tosyl amine 1 reacted with allyl carbonate 2 in an allylic asymmetric substitution using Pd(dba) and asymmetric ligand (S-BINAPO) to chiral secondary amine 3. Desilylation of the TBDMS group next took place by HCl to the hydroxide and then to the nitrile 4 (NaCN) through the bromide (PBr). Heck reaction (Pd(OAc) / MePPh) and debromination (AgCO) afforded tricycle 5. LiALH Nitrile reduction to the amine and its BocO protection to boc amine 6 was then followed by a second allylic oxidation (Pd(OAc) / AcOH / benzoquinone / MnO) to tetracycle 7. Hydroboration-oxidation (9-BBN / HO) gave alcohol 8 and subsequent Swern oxidation ketone 9. Reaction with LDA / PhNTf gave enol triflate 10 and the triflate group was removed in alkene 11 by reaction with Pd(OAc) and PPh.
Detosylation of 11 (sodium naphthalenide) and amidation with acid chloride 3-bromoacryloyl chloride gave amide 12 and another Heck reaction gave pentacycle 13. double bond isomerization (sodium / iPrOH), Boc group deprotection (triflic acid) and amine alkylation with (Z)-BrCHCICH=CHOTBDMS (see Rawal) gave compound 14 (identical to one of the Vollhardt intermediates). A final heck reaction (15) and TBDMS deprotection formed (−)-isostrychnine 16. | 0 | Theoretical and Fundamental Chemistry |
Experimentally, the concentration of the molecule complex [AB] is obtained indirectly from the measurement of the concentration of a free molecules, either [A] or [B].
In principle, the total amounts of molecule [A] and [B] added to the reaction are known.
They separate into free and bound components according to the mass conservation principle:
To track the concentration of the complex [AB], one substitutes the concentration of the free molecules ([A] or [B]), of the respective conservation equations, by the definition of the dissociation constant,
This yields the concentration of the complex related to the concentration of either one of the free molecules | 0 | Theoretical and Fundamental Chemistry |
Metamerism, in chemistry, is used to define the isomeric relationship between compounds with the same polyvalent functional group with heteroatom but differ in the main carbon chain or any of the side chains. It has rather been an obsolete term for isomerism, which has not been recognised by IUPAC in its publications. When Jöns Jacob Berzelius used the term mesomerism in 1831, he did so to describe those substances which possess the same percentage composition but had different properties. What Berzelius implied to be called metamerism is now considered as isomerism. | 0 | Theoretical and Fundamental Chemistry |
Pipefitters install, assemble, fabricate, maintain, repair, and troubleshoot pipe carrying fuel, chemicals, water, steam, and air in heating, cooling, lubricating, and various other process piping systems. Pipefitters are employed in the maintenance departments of power stations, refineries, offshore installations, factories, and similar establishments, by pipefitting contractors. | 1 | Applied and Interdisciplinary Chemistry |
smFRET is a group of methods using various microscopic techniques to measure a pair of donor and acceptor fluorophores that are excited and detected at the single molecule level. In contrast to "ensemble FRET" or "bulk FRET" which provides the FRET signal of a high number of molecules, single-molecule FRET is able to resolve the FRET signal of each individual molecule. The variation of the smFRET signal is useful to reveal kinetic information that an ensemble measurement cannot provide, especially when the system is under equilibrium. Heterogeneity among different molecules can also be observed. This method has been applied in many measurements of biomolecular dynamics such as DNA/RNA/protein folding/unfolding and other conformational changes, and intermolecular dynamics such as reaction, binding, adsorption, and desorption that are particularly useful in chemical sensing, bioassays, and biosensing. | 1 | Applied and Interdisciplinary Chemistry |
Because of its antimicrobial activity, it is used to treat ich in fish. However, it usually is illegal to use in fish intended for human consumption. | 0 | Theoretical and Fundamental Chemistry |
Dopamine is one of neurotransmitters in the body which helps cells send impulses. Polydopamine (PDA) is obtained through the self-aggregation of dopamine to form a melanin-like substance under mild alkaline conditions. PDA has strong NIR absorption, good photothermal stability, excellent biocompatibility and biodegradability, and high photothermal conversion efficiency. Furthermore, with π conjugated structure and different active groups, PDA can be easily combined with various materials to achieve multifunction, such as fluorescence imaging, MRI, CT, PA, targeted therapy etc. In view of this, PDA and its composite nanomaterials have a broad application prospect in the biomedical field.
Dopamine-melanin colloidal nanospheres is an efficient near-infrared photothermal therapeutic agent for in vivo cancer therapy. PDA can also be modified on the surface of other PTAs, such as gold nanorods, carbon-based materials, to enhance the photothermal stability and efficiency in vivo. For example, PDA-modified spiky gold nanoparticles (SGNP@PDAs) have been investigated for chemo-photothermal therapy. | 0 | Theoretical and Fundamental Chemistry |
Acicular ferrite is a microstructure of ferrite in steel that is characterised by needle-shaped crystallites or grains when viewed in two dimensions. The grains, actually three-dimensional in shape, have a thin lenticular shape. This microstructure is advantageous over other microstructures for steel because of its chaotic ordering, which increases toughness.
Acicular ferrite is formed in the interior of the original austenitic grains by direct nucleation on the inclusions, resulting in randomly oriented short ferrite needles with a basket weave appearance. Acicular ferrite is also characterised by high angle boundaries between the ferrite grains. This further reduces the chance of cleavage, because these boundaries impede crack propagation.
In C-Mn steel weld metals, it is reported that nucleation of various ferrite morphologies is aided by non-metallic inclusion; in particular oxygen-rich inclusions of a certain type and size are associated with the intragranular nucleation of acicular ferrite, as observed, for example, by,. Acicular ferrite is a fine Widmanstätten constituent, which is nucleated by an optimum intragranular dispersion of oxide/sulfide/silicate particles. The interlocking nature of acicular ferrite, together with its fine grain size (0.5 to 5 μm with aspect ratio from 3:1 to 10:1), provides maximum resistance to crack propagation by cleavage.
Composition control of weld metal is often performed to maximise the volume fraction of acicular ferrite due to the toughness it imparts. During continuous cooling, higher alloy contents or faster cooling generally delay transformation, which will then take place at lower temperatures, below the bainite start temperature, and lead to higher hardness. The efficacy of inclusions as nucleation sites in modern low alloy steel weld metals is such that fine-scale intragranular bainite can nucleate on them, both by continuous cooling and by isothermal transformation below the bainite start temperature. Some confusion has arisen in the literature, as this fine-scale intragranular bainite, which can resemble acicular ferrite in appearance in the optical microscope, has been called acicular ferrite by some researchers. See, for example. | 1 | Applied and Interdisciplinary Chemistry |
α-Glucans (alpha-glucans) are polysaccharides of D-glucose monomers
linked with glycosidic bonds of the alpha form. α-Glucans use cofactors in a cofactor site in order to activate a glucan phosphorylase enzyme. This enzyme causes a reaction that transfers a glucosyl portion between orthophosphate and α-I,4-glucan. The position of the cofactors to the active sites on the enzyme are critical to the overall reaction rate thus, any alteration to the cofactor site leads to the disruption of the glucan binding site.
Alpha-glucan is also commonly found in bacteria, yeasts, plants, and insects. Whereas the main pathway of α-glucan synthesis is via glycosidic bonds of glucose monomers, α-glucan can be comparably synthesized via the maltosyl transferase GlgE and branching enzyme GlgB. This alternative pathway is common in many bacteria, which use GlgB and GlgE or the GlgE pathway exclusively for the biosynthesis of α-glucan. The GlgE pathway is especially prominent in actinomycetes, such as mycobacteria and streptomycetes. However, α-glucans in mycobacteria have a slight variation in the length of linear chains, which point to the fact that the branching enzyme in mycobacteria makes shorter branches compared to glycogen synthesis. For organisms that can utilize both classic glycogen synthesis and the GlgE pathway, only GlgB enzyme is present, which indicates that the GlgB enzyme is shared between both pathways.
Other uses for α-glucan have been developed based on its availability in bacteria. The accumulation of glycogen Neisseria polysacchera and other bacteria are able to use in α-glucan to catalyze glucose units to form α-1,4-glucan and liberating fructose in the process. To regulate carbohydrate metabolism, more resistant starch was necessary. An α-glucan coated starch molecule produced from Neisseria polysacchera was able to improve some of the physiochemical properties in comparison to raw normal starch, especially in loading efficiency of bioactive molecules. Alpha-glucan was used in conjunction with modified starch molecules that contained porous starch granules via hydrolysis with amylotic enzymes such as α-amylase, β-amylase, and glucoamylase. An α-glucan coating boasts protection from digestive environments, such as the small intestine, efficient encapsulation, and preservation rates. This design promotes the growth of the development of α-glucan-based bio-materials and many implications for its usage in food and pharmaceutical industries. | 1 | Applied and Interdisciplinary Chemistry |
Secondary production is the generation of biomass of heterotrophic (consumer) organisms in a system. This is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food. Secondary production is sometimes defined to only include consumption of primary producers by herbivorous consumers (with tertiary production referring to carnivorous consumers), but is more commonly defined to include all biomass generation by heterotrophs.
Organisms responsible for secondary production include animals, protists, fungi and many bacteria.
Secondary production can be estimated through a number of different methods including increment summation, removal summation, the instantaneous growth method and the Allen curve method. The choice between these methods will depend on the assumptions of each and the ecosystem under study. For instance, whether cohorts should be distinguished, whether linear mortality can be assumed and whether population growth is exponential.
Net ecosystem production is defined as the difference between gross primary production (GPP) and ecosystem respiration. The formula to calculate net ecosystem production is NEP = GPP - respiration (by autotrophs) - respiration (by heterotrophs). The key difference between NPP and NEP is that NPP focuses primarily on autotrophic production, whereas NEP incorporates the contributions of other aspects of the ecosystem to the total carbon budget. | 0 | Theoretical and Fundamental Chemistry |
Labile cells refer to cells that constantly divide by entering and remaining in the cell cycle. These are contrasted with "stable cells" and "permanent cells".
An important example of this is in the epithelium of the cornea, where cells divide at the basal level and move upwards, and the topmost cells die and fall off. | 1 | Applied and Interdisciplinary Chemistry |
The coxibs are widely distributed throughout the body. All of the coxibs achieve sufficient brain concentrations to have a central analgesic effect, and all reduce prostaglandin formation in inflamed joints. All are well absorbed, but peak concentration may differ between the coxibs. The coxibs are highly protein-bound, and the published estimate of half-lives is variable between the coxibs. | 1 | Applied and Interdisciplinary Chemistry |
Energetic helium nuclei (helium ions) may be produced by cyclotrons, synchrotrons, and other particle accelerators. Convention is that they are not normally referred to as "alpha particles." | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, a quantity that is well defined so as to describe the path of a process through the equilibrium state space of a thermodynamic system is termed a process function, or, alternatively, a process quantity, or a path function. As an example, mechanical work and heat are process functions because they describe quantitatively the transition between equilibrium states of a thermodynamic system.
Path functions depend on the path taken to reach one state from another. Different routes give different quantities. Examples of path functions include work, heat and arc length. In contrast to path functions, state functions are independent of the path taken. Thermodynamic state variables are point functions, differing from path functions. For a given state, considered as a point, there is a definite value for each state variable and state function.
Infinitesimal changes in a process function are often indicated by to distinguish them from infinitesimal changes in a state function which is written . The quantity is an exact differential, while is not, it is an inexact differential. Infinitesimal changes in a process function may be integrated, but the integral between two states depends on the particular path taken between the two states, whereas the integral of a state function is simply the difference of the state functions at the two points, independent of the path taken.
In general, a process function may be either holonomic or non-holonomic. For a holonomic process function, an auxiliary state function (or integrating factor) may be defined such that is a state function. For a non-holonomic process function, no such function may be defined. In other words, for a holonomic process function, may be defined such that is an exact differential. For example, thermodynamic work is a holonomic process function since the integrating factor (where is pressure) will yield exact differential of the volume state function . The second law of thermodynamics as stated by Carathéodory essentially amounts to the statement that heat is a holonomic process function since the integrating factor (where is temperature) will yield the exact differential of an entropy state function . | 0 | Theoretical and Fundamental Chemistry |
In vitro, thiomers were shown to have antimicrobial activity towards Gram-positive bacteria. In particular, N-acyl thiolated chitosans show great potential as highly efficient, biocompatible and cost-effective antimicrobial compounds. Metabolism and mechanistic studies are under way to optimize these thiomers for clinical applications. Because of their antimicrobial activity, thiolated polymers are also used as coatings that avoid bacterial adhesion. | 0 | Theoretical and Fundamental Chemistry |
The nitrate esters isosorbide dinitrate (Isordil) and isosorbide mononitrate (Imdur, Ismo, Monoket, Mononitron) are converted in the body to nitric oxide, a potent natural vasodilator. In medicine, these esters are used as a medicine for angina pectoris (ischemic heart disease). | 0 | Theoretical and Fundamental Chemistry |
Gill remodelling happens in only a few species of fish, and it involves the buildup or removal of an inter-lamellar cell mass (ILCM). As a response to hypoxia, some fish are able to remodel their gills to increase respiratory surface area, with some species such as goldfish doubling their lamellar surface areas in as little as 8 hours. The increased respiratory surface area comes as a trade-off with increased metabolic costs because the gills are a very important site for many important processes including respiratory gas exchange, acid-base regulation, nitrogen excretion, osmoregulation, hormone regulation, metabolism, and environmental sensing.
The crucian carp is one species able to remodel its gill filaments in response to hypoxia. Their inter-lamellar cells have high rates of mitotic activity which are influenced by both hypoxia and temperature. In cold (15 °C) water the crucian carp has more ILCM, but when the temperature is increased to 25 °C the ILCM is removed, just as it would be in hypoxic conditions. This same transition in gill morphology occurs in the goldfish when the temperature was raised from 7.5 °C to 15 °C. This difference may be due to the temperature regimes that these fish are typically found in, or there could be an underlying protective mechanism to prevent a loss of ion balance in stressful temperatures. Temperature also affects the speed at which the gills can be remodelled: for example, at 20 °C in hypoxia, the crucian carp can completely remove its ILCM in 6 hours, whereas at 8 °C, the same process takes 3–7 days. The ILCM is likely removed by apoptosis, but it is possible that when the fish is faced with the double stress of hypoxia at high temperature, the lamellae may be lost by physical degradation. Covering the gill lamellae may protect species like the crucian carp from parasites and environmental toxins during normoxia by limiting their surface area for inward diffusion while still maintaining oxygen transport due to an extremely high hemoglobin oxygen binding affinity.
The naked carp, a closely related species native to the high-altitude Lake Qinghai, is also able to remodel their gills in response to hypoxic conditions. In response to oxygen levels 95% lower than normoxic conditions, apoptosis of ILCM increases lamellar surface area by up to 60% after just 24 hours. However, this comes at a significant osmoregulatory cost, reducing sodium and chloride levels in the cytoplasm by over 10%. The morphological response to hypoxia by scaleless carp is the fastest respiratory surface remodelling reported in vertebrates thus far. | 0 | Theoretical and Fundamental Chemistry |
Wöhlers discoveries had a significant influence on the theoretical basis of chemistry. The journals of every year from 1820 to 1881 contain his original scientific contributions. The Scientific American' supplement for 1882 stated that "for two or three of his researches he deserves the highest honor a scientific man can obtain, but the sum of his work is overwhelming. Had he never lived, the aspect of chemistry would be very different from that it is now".
Wöhler's notable research students included chemists Georg Ludwig Carius, Heinrich Limpricht, Rudolph Fittig, Adolph Wilhelm Hermann Kolbe, Albert Niemann, Vojtěch Šafařík, Wilhelm Kühne, and Augustus Voelcker.
Wöhler was elected a Fellow of the Royal Society of London in 1854. He was an Honorary Fellow of the Royal Society of Edinburgh. In 1862, Wöhler was elected a member of the American Philosophical Society.
The Life and Work of Friedrich Wöhler (1800–1882) (2005) by Robin Keen is considered to be "the first detailed scientific biography" of Wöhler.
On the 100th anniversary of Wöhler's death, the West German government issued a stamp depicting the structure of urea with its synthesis formula listed directly below. | 1 | Applied and Interdisciplinary Chemistry |
FCCS is an extension of the fluorescence correlation spectroscopy (FCS) method that uses two fluorescent molecules instead of one that emits different colours. The technique measures coincident green and red intensity fluctuations of distinct molecules that correlate if green and red labelled particles move together through a predefined confocal volume. FCCS utilizes two species that are independently labeled with two different fluorescent probes of different colours. These fluorescent probes are excited and detected by two different laser light sources and detectors typically labeled as "green" and "red". By combining FCCS with a confocal microscope, the technique's capabilities are highlighted, as it becomes possible to detect fluorescence molecules in femtoliter volumes within the nanomolar range, with a high signal-to-noise ratio, and at a microsecond time scale.
The normalized cross-correlation function is defined for two fluorescent species, G and R, which are independent green and red channels, respectively:
where differential fluorescent signals at a specific time, and at a delay time, later is correlated with each other. In the absence of spectral bleed-through – when the fluorescence signal from an adjacent channel is visible in the channel being observed – the cross-correlation function is zero for non-interacting particles. In contrast to FCS, the cross-correlation function increases with increasing numbers of interacting particles.
FCCS is mainly used to study bio-molecular interactions both in living cells and in vitro. It allows for measuring simple molecular stoichiometries and binding constants. It is one of the few techniques that can provide information about protein–protein interactions at a specific time and location within a living cell. Unlike fluorescence resonance energy transfer, FCCS does not have a distance limit for interactions making it suitable for probing large complexes. However, FCCS requires active diffusion of the complexes through the microscope focus on a relatively short time scale, typically seconds. | 0 | Theoretical and Fundamental Chemistry |
A lactim is a cyclic imidic acid compound characterized by an endocyclic carbon-nitrogen double bond. They are formed when lactams undergo tautomerization. | 0 | Theoretical and Fundamental Chemistry |
Mesoionic carbenes (MICs) are similar to N-heterocyclic carbenes (NHCs) except that canonical resonance structures with the carbene depicted cannot be drawn without adding additional charges. Mesoionic carbenes are also referred to as abnormal N-heterocyclic carbenes (aNHC) or remote N-heterocyclic carbenes (rNHC). A variety of free carbenes can be isolated and are stable at room temperature. Other free carbenes are not stable and are susceptible to intermolecular decomposition pathways. | 0 | Theoretical and Fundamental Chemistry |
Ler positively regulates the LEE genes by competition with its homolog, H-NS. H-NS silences LEE genes via rigid filament structures bound to the DNA that Ler disrupts and replaces through unknown mechanisms. Though little is known of the mechanism of Ler regulation, Ler interacts with DNA in specific ways. Ler binds DNA non-cooperatively, bends DNA in low concentrations, stiffens it in high concentration, and forms toroidal nucleoprotein complexes along DNA in vivo. | 1 | Applied and Interdisciplinary Chemistry |
Parecoxib sodium is a water-soluble inactive ester amide prodrug of valdecoxib, a novel second-generation COX-2-specific inhibitor and the first such agent to be developed for injectable use. It is rapidly converted by hepatic enzymatic hydrolysis to the active form valdecoxib. The compound then undergoes another conversion, which involves both cytochrome P450-mediated pathway (CYP2C9, CYP3A4) and non-cytochrome P450-mediated pathway, to hydroxylated metabolite and glucuronide metabolite. The hydroxylated metabolite, that also has weak COX-2-specific inhibitory properties, is then further metabolized by non-cytochrome P450 pathway to a glucuronide metabolite. These metabolites are excreted in the urine.
After intra-muscular administration of Parecoxib sodium peak plasma concentration is reached within 15 minutes. The plasma concentration decreases rapidly after administration because of a rather short serum half-life, which is about 15–52 minutes. This can be explained by the rapid formation of Valdecoxib. In contrast to the rapid clearance of Parecoxib, plasma concentration of Valdecoxib declines slowly because of a longer half-life. On the other hand, when Valdecoxib is taken orally it is absorbed rapidly (1–2 hours), but presence of food can delay peak serum concentration. It then undergoes the same metabolism that is described above. It is extensively protein-bound (98%), and the plasma half-life is about 7–8 hours. Note that the half-life can be significantly prolonged in the elderly or those with hepatic impairment, and can lead to drug accumulation.
The hydroxyl metabolite reaches its highest mean plasma concentration within 3 to 4 hours from administration, but it is considerably lower than of Valdecoxib or about 1/10 of the plasma levels of Valdecoxib. | 1 | Applied and Interdisciplinary Chemistry |
Fluid feed rate and operating pressure range are the key parameters of an injector, and vacuum pressure and evacuation rate are the key parameters for an ejector.
Compression ratio and the entrainment ratio may also be defined:
The compression ratio of the injector, , is defined as ratio of the injector's outlet pressure to the inlet pressure of the suction fluid .
The entrainment ratio of the injector, , is defined as the amount (in kg/h) of suction fluid that can be entrained and compressed by a given amount (in kg/h) of motive fluid. | 1 | Applied and Interdisciplinary Chemistry |
Yulia Sister (, ; born September 12, 1936, in Chișinău, Bessarabia, Romania) is a Soviet Moldavian and Israeli analytical chemist engaged in chemical research with the use of polarography and chromatography, a science historian, and a researcher of Russian Jewry in Israel, France, and other countries. She holds the position of Director General of the Research Centre for Russian Jews abroad and in Israel. | 0 | Theoretical and Fundamental Chemistry |
A Jacobi ellipsoid is a triaxial (i.e. scalene) ellipsoid under hydrostatic equilibrium which arises when a self-gravitating, fluid body of uniform density rotates with a constant angular velocity. It is named after the German mathematician Carl Gustav Jacob Jacobi. | 1 | Applied and Interdisciplinary Chemistry |
The ocean is an extensive network of particle transport. Thorium isotopes can help researchers decipher the vertical and horizontal movement of matter. Th has a constant, well-defined production rate in the ocean and a half-life of 24 days. This naturally occurring isotope has been shown to vary linearly with depth. Therefore, any changes in this linear pattern can be attributed to the transport of Th on particles. For example, low isotopic ratios in surface water with very high values a few meters down would indicate a vertical flux in the downward direction. Furthermore, the thorium isotope may be traced within a specific depth to decipher the lateral transport of particles. | 0 | Theoretical and Fundamental Chemistry |
Archaea have variants of the Entner-Doudoroff Pathway. These variants are called the semiphosphorylative ED (spED) and the nonphosphorylative ED (npED):
* spED is found in halophilic euryachaea and Clostridium species.
* In spED, the difference is where phosphorylation occurs. In the standard ED, phosphorylation occurs at the first step from glucose to G-6-P. In spED, the glucose is first oxidized to gluconate via a glucose dehydrogenase. Next, gluconate dehydratase converts gluconate into 2-keto-3-deoxy-gluconate (KDG). The next step is where phosphorylation occurs as KDG kinase converts KDG into KDPG. KDPG is then cleaved into glyceraldehyde 3-phosphate (GAP) and pyruvate via KDPG aldolase and follows the same EMP pathway as the standard ED. This pathway produces the same amount of ATP as the standard ED.
* npED is found in thermoacidophilic Sulfolobus, Euryarchaeota Tp. acidophilum, and Picrophilus species.
* In npED, there is no phosphorylation at all. The pathway is the same as spED but instead of phosphorylation occurring at KDG, KDG is instead cleaved GA and pyruvate via KDG aldolase. From here, GA is oxidized via GA dehydrogenase into glycerate. The glycerate is phosphorylated by glycerate kinase into 2PG. 2PG then follows the same pathway as ED and is converted into pyruvate via ENO and PK. In this pathway though, there is no ATP produced.
Some archaea such as Crenacraeota Sul. solfacaricus and Tpt. tenax have what is called branched ED. In branched ED, the organism have both spED and npED that are both operative and work in parallel. | 1 | Applied and Interdisciplinary Chemistry |
In agriculture, windrow composting is the production of compost by piling organic matter or biodegradable waste, such as animal manure and crop residues, in long rows – windrow.
As the process is aerobic, it is also known as Open Windrow Composting (OWC) or Open Air Windrow Composting (OAWC).
This method is suited to producing large volumes of compost. These rows are generally turned to improve porosity and oxygen content, mix in or remove moisture, and redistribute cooler and hotter portions of the pile. Windrow composting is a commonly used farm scale composting method. Composting process control parameters include the initial ratios of carbon and nitrogen rich materials, the amount of bulking agent added to assure air porosity, the pile size, moisture content, and turning frequency. The temperature of the windrows must be measured and logged constantly to determine the optimum time to turn them for quicker compost production. | 1 | Applied and Interdisciplinary Chemistry |
MCEF or Major Cdk9-interacting elongation factor is a transcription factor related to Af4. It is the fourth member of the Af4 family (AFF) of transcription factors, involved in numerous pathologies, including Acute Lymphoblastic Leukemia (ALL), abnormal CNS development, breast cancer and azoospermia.
Because it apparently interacts with the species-specific human co-factor (P-TEFb) for HIV-1 transcription, and because it can repress HIV-1 replication, MCEF (also known as AFF4 or AF5q31) may have future therapeutic uses.
MCEF was originally cloned and named by Mario Clemente Estable of Ryerson University, while he was a post-doctoral fellow in the laboratory of Robert G. Roeder, at the Rockefeller University. | 1 | Applied and Interdisciplinary Chemistry |
The benzene dimer is the prototypical system for the study of pi stacking, and is experimentally bound by 8–12 kJ/mol (2–3 kcal/mol) in the gas phase with a separation of 4.96 Å between the centers of mass for the T-shaped dimer. The small binding energy makes the benzene dimer difficult to study experimentally, and the dimer itself is only stable at low temperatures and is prone to cluster.
Other evidence against pi stacking comes from X-ray crystal structure determination. Perpendicular and offset parallel configurations can be observed in the crystal structures of many simple aromatic compounds. Similar offset parallel or perpendicular geometries were observed in a survey of high-resolution x-ray protein crystal structures in the Protein Data Bank. Analysis of the aromatic amino acids phenylalanine, tyrosine, histidine, and tryptophan indicates that dimers of these side chains have many possible stabilizing interactions at distances larger than the average van der Waals radii. | 0 | Theoretical and Fundamental Chemistry |
NMR spectroscopy is used in industrially relevant systems to study the sequence distribution of copolymers or the occurrence of transesterification in polyester blends. A change in sequence distribution can effect the crystallinity, and transesterification can affect the compatibility of two otherwise incompatible polyesters. Depending on their degree of randomness, copolyesters can show different thermal transitions and behaviours. | 0 | Theoretical and Fundamental Chemistry |
Ørsted was a published poet, as well as scientist. His poetry series ("The Airship") was inspired by the balloon flights of fellow physicist and stage magician Étienne-Gaspard Robert.
In 1850, shortly before his death, he submitted for publication a two-volume collection of philosophical articles in German under the title ("The Soul in Nature"). It was translated into English and published in one volume in 1852, the year after his death.
Other works:
**, containing correspondence with Jöns Jacob Berzelius, Christopher Hansteen, and Christian Samuel Weiss.
**, containing correspondence with Johann Wilhelm Ritter and numerous others, including Michael Faraday and Carl Friedrich Gauss.
A significant number of Ørsted's papers were made available in English for the first time in a compilation published in 1998: | 1 | Applied and Interdisciplinary Chemistry |
Perey was born in 1909 in Villemomble, France, just outside Paris where the Curie's Radium Institute was located. Although she hoped to study medicine, the death of her father left the family in financial difficulties.
Perey earned a chemistry diploma from Paris Technical School of Womens Education in 1929; while not a "degree", it did qualify her to work as a chemistry technician. In 1929 at the age of 19, Perey interviewed for a role as a personal assistant (technician) to Marie Curie at Curie's Radium Institute in Paris, France, and was hired. Marie Curie took on a mentoring role to Perey, taking her on as her personal assistant. | 1 | Applied and Interdisciplinary Chemistry |
John Dalton was an English chemist who developed the idea of atomic theory of chemical elements. Daltons atomic theory of chemical elements assumed that each element had unique atoms associated with and specific to that atom. This was in opposition to Lavoisiers definition of elements which was that elements are substances that chemists could not break down further into simpler parts. Daltons idea also differed from the idea of corpuscular theory of matter, which believed that all atoms were the same, and had been a supported theory since the 17th century. To help support his idea, Dalton worked on defining the relative weights of atoms in chemicals in his work New System of Chemical Philosophy, published in 1808. His text showed calculations to determine the relative atomic weights of Lavoisiers different elements based on experimental data pertaining to the relative amounts of different elements in chemical combinations. Dalton argued that elements would combine in the simplest form possible. Water was known to be a combination of hydrogen and oxygen, thus Dalton believed water to be a binary compound containing one hydrogen and one oxygen.
Dalton was able to accurately compute the relative quantity of gases in atmospheric air. He used the specific gravity of azotic (nitrogen), oxygenous, carbonic acid (carbon dioxide), and hydrogenous gases as well as aqueous vapor determined by Lavoisier and Davy to determine the proportional weights of each as a percent of a whole volume of atmospheric air. Dalton determined that atmospheric air contains 75.55% azotic gas, 23.32% oxygenous gas, 1.03% aqueous vapor, and 0.10% carbonic acid gas. | 1 | Applied and Interdisciplinary Chemistry |
Ion interaction chromatography (ion-pair chromatography) is a laboratory technique for separating ions with chromatography. In this technique ions are mixed with ion pairing reagents (IPR). The analyte combines with its reciprocal ion in the IPR, this corresponds to retention time. Often organic salts are selected to pair with solute(s). The formation of this pair affects the interaction of the pair with the mobile phase and the stationary phase. | 0 | Theoretical and Fundamental Chemistry |
Condensation polymerization is an important class of step-growth polymerization, which is formed simply by the reaction of two monomers and results in the release of a water molecule. Since these polymers are typically made up of two or more monomers, the resulting end groups are from the monomer functionality. Examples of condensation polymers can be seen with polyamides, polyacetals and polyesters. An example of polyester is polyethylene terephthalate (PET), which is made from the monomers terephthalic acid and ethylene glycol. If one of the components in the polymerization is in excess, then that polymers functionality will be at the ends of the polymers (a carboxylic acid or alcohol group respectively). | 0 | Theoretical and Fundamental Chemistry |
Amine alkylation (amino-dehalogenation) is a type of organic reaction between an alkyl halide and ammonia or an amine. The reaction is called nucleophilic aliphatic substitution (of the halide), and the reaction product is a higher substituted amine. The method is widely used in the laboratory, but less so industrially, where alcohols are often preferred alkylating agents.
When the amine is a tertiary amine the reaction product is a quaternary ammonium salt in the Menshutkin reaction:
Amines and ammonia are generally sufficiently nucleophilic to undergo direct alkylation, often under mild conditions. The reactions are complicated by the tendency of the product (a primary amine or a secondary amine) to react with the alkylating agent. For example, reaction of 1-bromooctane with ammonia yields almost equal amounts of the primary amine and the secondary amine. Therefore, for laboratory purposes, N-alkylation is often limited to the synthesis of tertiary amines. An exception is the amination of alpha-halo carboxylic acids that do permit synthesis of primary amines with ammonia. Intramolecular reactions of haloamines X-(CH)-NH give cyclic aziridines, azetidines and pyrrolidines.
N-alkylation is a general and useful route to quaternary ammonium salts from tertiary amines, because overalkylation is not possible.
Examples of N-alkylation with alkyl halides are the syntheses of benzylaniline, 1-benzylindole, and azetidine. Another example is found in the derivatization of cyclen. Industrially, ethylenediamine is produced by alkylation of ammonia with 1,2-dichloroethane. | 0 | Theoretical and Fundamental Chemistry |
Paul Kazuo Kuroda (1 April 1917 – 16 April 2001) was a Japanese-American chemist and nuclear scientist.
He held the esteemed title of honorary professor at the University of Arkansas and is widely recognized as the pioneering scientist who achieved the distinction of becoming the first individual from Japan to naturalize in the United States.
He employed Enrico Fermi's recently unveiled reactor theory to propose the possibility of the formation of natural atomic reactors under suitable conditions in ancient uranium deposits where the ratio of uranium-235 to uranium-238 was higher than its present value.
Furthermore, he demonstrated the presence of plutonium-244 in the early solar system by analyzing the xenon content released from meteorites, which is believed to have been emitted during nuclear fission of Pu-244. He supervised 64 Ph.D. students and authored or co-authored around 400 publications. | 0 | Theoretical and Fundamental Chemistry |
Mathematically, lubrication theory can be seen as exploiting the disparity between two length scales. The first is the characteristic film thickness, , and the second is a characteristic substrate length scale . The key requirement for lubrication theory is that the ratio is small, that is, .
The Navier–Stokes equations (or Stokes equations, when fluid inertia may be neglected) are expanded in this small parameter, and the leading-order equations are then
where and are coordinates in the direction of the substrate and perpendicular to it respectively. Here is the fluid pressure, and is the fluid velocity component parallel to the substrate; is the fluid viscosity. The equations show, for example, that pressure variations across the gap are small, and that those along the gap are proportional to the fluid viscosity. A more general formulation of the lubrication approximation would include a third dimension, and the resulting differential equation is known as the Reynolds equation.
Further details can be found in the literature or in the textbooks given in the bibliography. | 1 | Applied and Interdisciplinary Chemistry |
Whereas Gram-negative bacteria primarily use acylated homoserine lactones, Gram-positive bacteria generally use oligopeptides as autoinducers for quorum sensing. These molecules are often synthesized as larger polypeptides that are cleaved post-translationally to produce “processed” peptides. Unlike AHLs that can freely diffuse across cell membranes, peptide autoinducers usually require specialized transport mechanisms (often ABC transporters). Additionally, they do not freely diffuse back into cells, so bacteria that use them must have mechanisms to detect them in their extracellular environments. Most Gram-positive bacteria use a two-component signaling mechanism in quorum sensing. Secreted peptide autoinducers accumulate as a function of cell density. Once a quorum level of autoinducer is achieved, its interaction with a sensor kinase at the cell membrane initiates a series of phosphorylation events that culminate in the phosphorylation of a regulator protein intracellularly. This regulator protein subsequently functions as a transcription factor and alters gene expression. Similar to Gram-negative bacteria, the autoinduction and quorum sensing system in Gram-positive bacteria is conserved, but again, individual species have tailored specific aspects for surviving and communicating in unique niche environments. | 1 | Applied and Interdisciplinary Chemistry |
The conditional entropy,
is the number of bits which would have to be transmitted to identify from equally likely possibilities, less the relative entropy of the product distribution from the true joint distribution — i.e. less the expected number of bits saved which would have had to be sent if the value of were coded according to the uniform distribution rather than the conditional distribution of given . | 0 | Theoretical and Fundamental Chemistry |
The process of photosynthesis provides the main input of free energy into the biosphere, and is one of four main ways in which radiation is important for plant life.
The radiation climate within plant communities is extremely variable, in both time and space.
In the early 20th century, Frederick Blackman and Gabrielle Matthaei investigated the effects of light intensity (irradiance) and temperature on the rate of carbon assimilation.
* At constant temperature, the rate of carbon assimilation varies with irradiance, increasing as the irradiance increases, but reaching a plateau at higher irradiance.
* At low irradiance, increasing the temperature has little influence on the rate of carbon assimilation. At constant high irradiance, the rate of carbon assimilation increases as the temperature is increased.
These two experiments illustrate several important points: First, it is known that, in general, photochemical reactions are not affected by temperature. However, these experiments clearly show that temperature affects the rate of carbon assimilation, so there must be two sets of reactions in the full process of carbon assimilation. These are the light-dependent photochemical temperature-independent stage, and the light-independent, temperature-dependent stage. Second, Blackman's experiments illustrate the concept of limiting factors. Another limiting factor is the wavelength of light. Cyanobacteria, which reside several meters underwater, cannot receive the correct wavelengths required to cause photoinduced charge separation in conventional photosynthetic pigments. To combat this problem, Cyanobacteria have a light-harvesting complex called Phycobilisome. This complex is made up of a series of proteins with different pigments which surround the reaction center. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally obtained by replacing one or more of the hydrogen atoms by other organic functional groups; as well as salts with the carbamate anion (e.g. ammonium carbamate).
Polymers whose repeat units are joined by carbamate like groups are an important family of plastics, the polyurethanes. See Etymology for clarification. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an organic catalyst. This "organocatalyst" consists of carbon, hydrogen, sulfur and other nonmetal elements found in organic compounds. Because of their similarity in composition and description, they are often mistaken as a misnomer for enzymes due to their comparable effects on reaction rates and forms of catalysis involved.
Organocatalysts which display secondary amine functionality can be described as performing either enamine catalysis (by forming catalytic quantities of an active enamine nucleophile) or iminium catalysis (by forming catalytic quantities of an activated iminium electrophile). This mechanism is typical for covalent organocatalysis. Covalent binding of substrate normally requires high catalyst loading (for proline-catalysis typically 20–30 mol%).
Noncovalent interactions such as hydrogen-bonding facilitates low catalyst loadings (down to 0.001 mol%).
Organocatalysis offers several advantages. There is no need for metal-based catalysis thus making a contribution to green chemistry. In this context, simple organic acids have been used as catalyst for the modification of cellulose in water on multi-ton scale. When the organocatalyst is chiral an avenue is opened to asymmetric catalysis; for example, the use of proline in aldol reactions is an example of chirality and green chemistry. Organic chemists David MacMillan and Benjamin List were both awarded the 2021 Nobel Prize in chemistry for their work on asymmetric organocatalysis. | 0 | Theoretical and Fundamental Chemistry |
Chester (Chet) Sutula obtained his Bachelor of Science degree in chemistry from Holy Cross College, Worcester, Massachusetts in 1954 and his Ph.D. degree in physical chemistry from Iowa State University, Ames, Iowa in 1959. He worked for eight years for Marathon Oil Company, Littleton, Colorado, performing research on the influence of capillarity and surface chemical forces in secondary oil production, and, the structural properties of microemulsions using small angle x-ray scattering. In 1967, he joined Ames Company, a division of Miles Laboratories, Inc. in Elkhart, Indiana, and became its research director in 1970. His team at Ames performed fundamental and applied research on the properties of solid, porous analytical devices, such as, Lateral flow device (strip test) for urinalysis, blood chemistry, microbiology and quantitative, simple measurement of blood glucose for daily use by diabetics. In 1976, he joined Ortho Diagnostics Systems, a division of Johnson & Johnson, Inc., as vice president of R&D and worked on new systems for blood typing, high volume immunoassays, and tests to detect hepatitis, pregnancy and blood coagulation disorders.
In 1981, with his wife, Jane, and a technology partner in Europe, Dr. Sutula founded Agdia, Inc., Elkhart, Indiana, to develop and provide reliable and practical diagnostics for the detection of plant pathogens.
Dr. Sutula has served on American Phytopathological Society (APS) committees for Industry, for Virology, and for Diagnostics and has been a reviewer for Plant Disease. He has authored several articles and many posters and presentations dealing with the detection of plant pathogens. | 0 | Theoretical and Fundamental Chemistry |
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression. Structural gene products include enzymes and structural proteins. Also encoded by structural genes are non-coding RNAs, such as rRNAs and tRNAs (but excluding any regulatory miRNAs and siRNAs). | 1 | Applied and Interdisciplinary Chemistry |
A SILAC approach involving incorporation of tyrosine labeled with nine carbon-13 atoms (C) instead of the normal carbon-12 (C) has been utilized to study tyrosine kinase substrates in signaling pathways. SILAC has emerged as a very powerful method to study cell signaling, post translation modifications such as phosphorylation, protein–protein interaction and regulation of gene expression. In addition, SILAC has become an important method in secretomics, the global study of secreted proteins and secretory pathways. It can be used to distinguish between proteins secreted by cells in culture and serum contaminants. Standardized protocols of SILAC for various applications have also been published. | 1 | Applied and Interdisciplinary Chemistry |
In condensed matter physics, an ultracold atom is an atom with a temperature near absolute zero. At such temperatures, an atom's quantum-mechanical properties become important.
To reach such low temperatures, a combination of several techniques typically has to be used. First, atoms are trapped and pre-cooled via laser cooling in a magneto-optical trap. To reach the lowest possible temperature, further cooling is performed using evaporative cooling in a magnetic or optical trap. Several Nobel prizes in physics are related to the development of the techniques to manipulate quantum properties of individual atoms (e.g. 1989, 1996, 1997, 2001, 2005, 2012, 2018).
Experiments with ultracold atoms study a variety of phenomena, including quantum phase transitions, Bose–Einstein condensation (BEC), bosonic superfluidity, quantum magnetism, many-body spin dynamics, Efimov states, Bardeen–Cooper–Schrieffer (BCS) superfluidity and the BEC–BCS crossover. Some of these research directions utilize ultracold atom systems as quantum simulators to study the physics of other systems, including the unitary Fermi gas and the Ising and Hubbard models. Ultracold atoms could also be used for realization of quantum computers. | 0 | Theoretical and Fundamental Chemistry |
Flowability, also known as powder flow is a property that defines an ability of a powdered material to flow, related to cohesion.
Powder flowability depends on many traits:
* the shape and size of the powder particles due to intermolecular force,
* porosity
* electrostatic activity
* hygroscopy
* bulk density
* angle of repose
* presence of glidants
* oxidation rate (of a metallic powder)
* humidity
ISO 4490:2018 norm (and its precedent, ISO 4490:2014) standardizes a method for determining the flow rate of metallic powders. It uses a normalized/calibrated funnel, named Hall flowmeter. | 0 | Theoretical and Fundamental Chemistry |
Because of their resistant to cold water dissolution, which severely destroys the calcareous planktonic fossils at depth worldwide, Radiolarians has become one of the most commonly studied siliceous planktonic fossils for paleotemperature reconstruction.
Study of Radiolarians in the North Pacific deep sea cores has revealed that increases in both species diversity and abundance correspond to major glaciation events of the last 16 million years. Changes in Radiolarian compositions are also evident to reflect in general sea surface temperature.
By applying statistical analyses (Q-mode factor analysis), many quantitative studies of Radiolarian assemblages from surface sediments have established a transfer function which enables the estimation of paleo-sea surface temperature. For example, Pisias et al. (1997) were able to identify assemblages representative to the present Pacific biogeography and used these assemblages to predict sea surface temperature of the last glacier maximum. | 0 | Theoretical and Fundamental Chemistry |
Paracrine signaling of growth factors between nearby cells has been shown to exacerbate carcinogenesis. In fact, mutant forms of a single RTK may play a causal role in very different types of cancer. The Kit proto-oncogene encodes a tyrosine kinase receptor whose ligand is a paracrine protein called stem cell factor (SCF), which is important in hematopoiesis (formation of cells in blood). The Kit receptor and related tyrosine kinase receptors actually are inhibitory and effectively suppresses receptor firing. Mutant forms of the Kit receptor, which fire constitutively in a ligand-independent fashion, are found in a diverse array of cancerous malignancies. | 1 | Applied and Interdisciplinary Chemistry |
Thalidomides teratogenicity has been a subject of much debate and over the years numerous hypotheses have been proposed. Two of the best-known have been the anti-angiogenesis hypothesis and oxidative stress model hypothesis, with considerable experimental evidence supporting these two hypotheses regarding thalidomides teratogenicity.
Recently, new findings have emerged that suggest a novel mechanism of teratogenicity. Cereblon is a 51 kDa protein localized in the cytoplasm, nucleus and peripheral membrane of cells in numerous parts of the body. It acts as a component of the E3 ubiquitin ligase, regulating various developmental processes, including embryogenesis, carcinogenesis and cell cycle regulation, through degradation (ubiquitination) of unknown substrates. Thalidomide has been shown to bind to cereblon, inhibiting the activity of the E3 ubiquitin ligase, resulting in accumulation of the ligase substrates and downregulation of fibroblast growth factor 8 (FGF8) and FGF10. This disrupts the positive feedback loop between the two growth factors, possibly causing both multiple birth defects and anti-myeloma effects.
Findings also support the hypothesis that an increase in the expression of cereblon is an essential element of the anti-myeloma effect of both lenalidomide and pomalidomide. Cereblon expression was three times higher in responding patients compared to non-responders and higher cereblon expression was also associated with partial or full response while lower expression was associated with stable or progressive disease. | 1 | Applied and Interdisciplinary Chemistry |
Several different structural and compositional motifs can be prepared using the Stöber process by the addition of chemical compounds to the reaction mixture. These additives can interact with the silica through chemical and/or physical means either during or after the reaction, leading to substantial changes in morphology of the silica particles. | 0 | Theoretical and Fundamental Chemistry |
An unusual triad is found in sedolisin proteases. The low pK of the glutamate carboxylate group means that it only acts as a base in the triad at very low pH. The triad is hypothesised to be an adaptation to specific environments like acidic hot springs (e.g. kumamolysin) or cell lysosome (e.g. tripeptidyl peptidase). | 1 | Applied and Interdisciplinary Chemistry |
*Memorial plaque on the building of the Radium Institute
*A memorial plaque was installed on the building at 3 Roentgen Street in 1952 (architect Z. M. Vilensky).
*A memorial plaque was installed on the building at 23 Kamennoostrovsky Prospekt in 1990 (sculptor E. N. Rotanov, architect S. L. Mikhailov).
*In 1996, a memorial plaque was installed on the building at 7 Universitetskaya embankment with erroneous dates in the text: “In this building, from 1908 to 1949, the outstanding scientist, organizer of the nuclear industry, founder of the Department of Radiochemistry V. G. Khlopin studied and worked.” (In 1941-1945 he was evacuated to Kazan.)
In the 1950s, a memorial plaque was installed on the house at 61 Lesnoy Avenue with the text: “The outstanding Russian chemist Vitaly Grigorievich Khlopin lived in this house from 1945 to 1950.” | 0 | Theoretical and Fundamental Chemistry |
Recombinant adeno-associated virus (rAAV) based genome engineering is a genome editing platform centered on the use of recombinant AAV vectors that enables insertion, deletion or substitution of DNA sequences into the genomes of live mammalian cells. The technique builds on Mario Capecchi and Oliver Smithies' Nobel Prize–winning discovery that homologous recombination (HR), a natural hi-fidelity DNA repair mechanism, can be harnessed to perform precise genome alterations in mice. rAAV mediated genome-editing improves the efficiency of this technique to permit genome engineering in any pre-established and differentiated human cell line, which, in contrast to mouse ES cells, have low rates of HR.
The technique has been widely adopted for use in engineering human cell lines to generate isogenic human disease models. It has also been used to optimize bioproducer cell lines for the biomanufacturing of protein vaccines and therapeutics. In addition, due to the non-pathogenic nature of rAAV, it has emerged as a desirable vector for performing gene therapy in live patients. | 1 | Applied and Interdisciplinary Chemistry |
The Cys-loop ligand-gated ion channel superfamily is composed of nicotinic acetylcholine, GABA, GABA-ρ, glycine, 5-HT, and zinc-activated (ZAC) receptors. These receptors are composed of five protein subunits which form a pentameric arrangement around a central pore. There are usually 2 alpha subunits and 3 other beta, gamma, or delta subunits (some consist of 5 alpha subunits).
The name of the family refers to a characteristic loop formed by 13 highly conserved amino acids between two cysteine (Cys) residues, which form a disulfide bond near the N-terminal extracellular domain.
Cys-loop receptors are known only in eukaryotes, but are part of a larger family of pentameric ligand-gated ion channels. Only the Cys-loop clade includes the pair of bridging cysteine residues. The larger superfamily includes bacterial (e.g. GLIC) as well as non-Cys-loop eukaryotic receptors, and is referred to as "pentameric ligand-gated ion channels", or "Pro-loop receptors".
All subunits consist of a large conserved extracellular N-terminal domain, three highly conserved transmembrane domains, a cytoplasmic loop of variable size and amino acid sequence, and a fourth transmembrane region with a relatively short and variable extracellular C-terminal domain.
Neurotransmitters bind at the interface between subunits in the extracellular domain.
Each subunit contains four membrane-spanning alpha helices (M1, M2, M3, M4). The pore is formed primarily by the M2 helices. The M3-M4 linker is the intracellular domain that binds the cytoskeleton. | 1 | Applied and Interdisciplinary Chemistry |
Neuraminidase inhibitors inhibit enzymatic activity of the enzyme neuraminidase (sialidase). These type of inhibitors have been introduced as anti-influenza drugs as they prevent the virus from exiting infected cells and thus stop further spreading of the virus. Neuraminidase inhibitors for human neuraminidase (hNEU) have the potential to be useful drugs as the enzyme plays a role in several signaling pathways in cells and is implicated in diseases such as diabetes and cancer. | 1 | Applied and Interdisciplinary Chemistry |
Of course, the composition of the material that is used as the counter electrode is extremely important to creating a working photovoltaic, as the valence and conduction energy bands must overlap with those of the redox electrolyte species to allow for efficient electron exchange.
In 2018, Jin et al. prepared ternary nickel cobalt selenide (NiCoSe) films at various stoichiometric ratios of nickel and cobalt to understand its impact on the resulting cell performance. Nickel and cobalt bimetallic alloys were known to have outstanding electron conduction and stability, so optimizing its stoichiometry would ideally produce a more efficient and stable cell performance than its singly metallic counterparts. Such is the result that Jin et al. found, as NiCoSe achieved superior power conversion efficiency (8.61%), lower charge transfer impedance, and higher electrocatalytic ability than both its platinum and binary selenide counterparts. | 0 | Theoretical and Fundamental Chemistry |
The descendants of European settlers began coming to the area of the lake in the early 20th century, first using it as a staging area for bush pilots flying to mining camps and settlements further north. In the mid-1930s, abundant gold deposits in the area triggered the establishment of Yellowknife as a permanent settlement. While at the time development was concentrated on the peninsula extending into Great Slave Lakes Yellowknife Bay, an area known today as Old Town, later analysis of lake sediments lends some support to accounts from that time of Frame Lake being used for the disposal of tailings and sewage from outlying mines. The lake took its name from Bill Frame, an early miner who owned part of the citys bus and taxi franchise.
Yellowknifes growth was briefly interrupted by World War II, but when it resumed afterwards, the higher ground closer to the lake was chosen for expansion. The area just east of the lake became New Town, today the citys downtown. McNiven Beach, named after the city's first mayor, was developed with facilities for swimming; sometimes floatplanes landed nearby as well. Residents also went boating on the lake.
At the same time, runoff from storms carried increasingly nutrient-rich waters into the lake. In colder months when the lake surface was not frozen over, the city dumped plowed snow into the lake, adding even more nutrients. Sewage dumped into nearby Niven Lake, heavily used for that purpose for almost 35 years of Yellowknife's postwar growth, may also have flowed into Frame, offering more nutrients.
By the early 1970s the lakes decline had been noted. A later study by the earth science department at Carleton University concluded that the 1970 construction of the causeway across the end of the lakes eastern arm was the "tipping point" for Frame Lake. It cut off the stream between it and Niven Lake to the north, the only outlet the lake had had during human habitation of the area. With the lack of water throughput, nutrient levels in the water column rose, nurturing aquatic plants during the summertime. In the winter, however, when the lake froze over and snow cover blocked much of the limited sunlight available, those same plants died off for lack of ability to photosynthesize. The decomposed plant matter began accumulating on the lake floor, steadily deoxygenating its waters.
In a 1973 limnological study of seven lakes in the Yellowknife area, including Frame, for a possible experimental fishery, scientists from the Fisheries Research Board noted that Frame was the only one in which they were unable to catch any fish for study. Over the preceding winter, they also observed that the lake had "become rapidly anoxic".
As the lake declined, development came closer. Yellowknife built its current city hall by the lake edge in 1975, and the Prince of Wales Northern Heritage Centre, the territorial museum, followed nearby four years later. Sometime later that decade, the number of swimmers at McNiven Beach declined sufficiently for the city to remove the facilities there, as the beach itself began to grow over with grass.
Residents were still swimming and boating in the lake in the early 1980s, but in smaller numbers. Some were scared off by reports of leeches that had in one instance supposedly covered an entire child. A local journalist recalled in 2015 how he had had to watch his step to avoid deep, malodorous deposits while catching tadpoles in the shallow waters near his home at that time. Later the Frame Lake South area was developed for residential and commercial use as the city grew. Storm sewers installed for these projects diverted the runoff that had once fed the lake, increasing the concentration of nutrients in the water. | 1 | Applied and Interdisciplinary Chemistry |
"Polarity" is a gene expression mechanism in which transcription terminates prematurely due to a loss of coupling between transcription and translation. Transcription outpaces translation when the ribosome pauses or encounters a premature stop codon. This allows the transcription termination factor Rho to bind the mRNA and terminate mRNA synthesis. Consequently, genes that are downstream in the operon are not transcribed, and therefore not expressed. Polarity serves as mRNA quality control, allowing unused transcripts to be terminated prematurely, rather than synthesized and degraded.
The term "polarity" was introduced to describe the observation that the order of genes within an operon is important: a nonsense mutation within an upstream gene effects the transcription of downstream genes. Furthermore, the position of the nonsense mutation within the upstream gene modulates the "degree of polarity", with nonsense mutations at the start of the upstream genes exerting stronger polarity (more reduced transcription) on downstream genes.
Unlike the mechanism of attenuation, which involves intrinsic termination of transcription at well-defined programmed sites, polarity is Rho-dependent and termination occurs at variable position. | 1 | Applied and Interdisciplinary Chemistry |
In comparison to many other Taoist texts, the origins of the Baopuzi are well documented. Ge completed the book during the era of Jianwu (), 317–318, when Emperor Yuan of Jin founded the Eastern Jin dynasty. Ge Hongu subsequently revised revised Baopuzi during the era of Xianhe (), 326–334.
Ge Hongs autobiography (Outer Chapter 50) records writing the Baopuzi'.
Compare the more literal translation of Davis and Ch'en, "I left off writing for ten and odd years, for I was constantly on the road, until the era Chien-wu (317-318 A.D.) when I got it ready."
Ges autobiography mentions his military service fighting rebels against the Jin dynasty, and successfully defending his hometown of Jurong (), in modern Zhenjiang, Jiangsu. In 330 Emperor Cheng of Jin granted Ge the fief of "Marquis of Guanzhong" with income from 200 Jurong households. Scholars believe Ge revised the Baopuzi' during this period, sometime around 330 or 332.
The Baopuzi consists of 70 pian () "chapters; books" divided between the 20 "Inner Chapters" and 50 "Outer Chapters" (which can be compared with the Zhuangzi textual division). Nathan Sivin described it as "not one book but two, considerably different in theme". The Neipian and Waipian "led entirely separate physical existences; they were not combined under a single title until a millennium after Ko's time".
The (1444–1445) Ming dynasty Daozang "Taoist canon" first printed the two Baopuzi parts together. This Zhengtong Daozang (), or "Taoist Canon of the Zhengtong Era (1436-1450)", bibliographically categorized the Baopuzi under the Taiqing "Supreme Clarity" section for alchemical texts. Daozang editions encompass six juan ( "scrolls; fascicles; volumes"), three each for the Inner and Outer Chapters. Most received versions of Baopuzi descend from this Ming Daozang text. | 1 | Applied and Interdisciplinary Chemistry |
In a treatise entitled as Risala fi l-Illa al-Failali l-Madd wa l-Fazr (Treatise on the Efficient Cause of the Flow and Ebb), al-Kindi presents a theory on tides which "depends on the changes which take place in bodies owing to the rise and fall of temperature." In order to support his argument, he gave a description of a scientific experiment as follows:
In explaining the natural cause of the wind, and the difference for its directions based on time and location, he wrote: | 1 | Applied and Interdisciplinary Chemistry |
There are different possible glucuronides that can be used as substrates for the β-glucuronidase, depending on the type of detection needed (histochemical, spectrophotometrical, fluorimetrical). The most common substrate for GUS histochemical staining is 5-bromo-4-chloro-3-indolyl glucuronide (X-Gluc). X-Gluc is hydrolyzed by GUS into the product 5,5-dibromo-4,4-dichloro-indigo (diX-indigo). DiX-indigo will appear blue, and can be seen using light microscopy. This process is analogous to hydrolysis of X-gal by Beta-galactosidase to produce blue cells as is commonly practiced in bacterial reporter gene assays.
For other types of detection, common substrates are [https://pubchem.ncbi.nlm.nih.gov/compound/p-nitrophenyl-beta-D-glucuronide p-nitrophenyl β-D-glucuronide] for the spectrophotometric assay and [https://pubchem.ncbi.nlm.nih.gov/compound/4-Methylumbelliferyl-glucuronide 4-methylumbelliferyl-beta-D-glucuronide] (MUG) for the fluorimetric assay. | 1 | Applied and Interdisciplinary Chemistry |
The six-factor formula is used in nuclear engineering to determine the multiplication of a nuclear chain reaction in a non-infinite medium.
The symbols are defined as:
*, and are the average number of neutrons produced per fission in the medium (2.43 for uranium-235).
* and are the microscopic fission and absorption cross sections for fuel, respectively.
* and are the macroscopic absorption cross sections in fuel and in total, respectively.
* is the number density of atoms of a specific nuclide.
* is the resonance integral for absorption of a specific nuclide.
* is the average lethargy gain per scattering event.
**Lethargy is defined as decrease in neutron energy.
* (fast utilization) is the probability that a fast neutron is absorbed in fuel.
* is the probability that a fast neutron absorption in fuel causes fission.
* is the probability that a thermal neutron absorption in fuel causes fission.
* is the geometric buckling.
* is the diffusion length of thermal neutrons.
* is the age to thermal.
** is the evaluation of where is the energy of the neutron at birth. | 0 | Theoretical and Fundamental Chemistry |
Tripotassium phosphate can be used in foods as a buffering agent, emulsifying agent, and for nutrient fortification. It can serve as a sodium-free substitute for trisodium phosphate. The ingredient is most common in dry cereals but is also found in meat, sauces, and cheeses. | 0 | Theoretical and Fundamental Chemistry |
In plants the glyoxylate cycle occurs in special peroxisomes which are called glyoxysomes. This cycle allows seeds to use lipids as a source of energy to form the shoot during germination. The seed cannot produce biomass using photosynthesis because of lack of an organ to perform this function. The lipid stores of germinating seeds are used for the formation of the carbohydrates that fuel the growth and development of the organism.
The glyoxylate cycle can also provide plants with another aspect of metabolic diversity. This cycle allows plants to take in acetate both as a carbon source and as a source of energy. Acetate is converted to acetyl CoA (similar to the TCA cycle). This acetyl CoA can proceed through the glyoxylate cycle, and some succinate is released during the cycle. The four carbon succinate molecule can be transformed into a variety of carbohydrates through combinations of other metabolic processes; the plant can synthesize molecules using acetate as a source for carbon. The acetyl CoA can also react with glyoxylate to produce some NADPH from NADP+, which is used to drive energy synthesis in the form of ATP later in the electron transport chain. | 1 | Applied and Interdisciplinary Chemistry |
Unfortunately, the Tsuji–Wilkinson decarbonylation is stoichiometric. The product bis(triphenylphosphine)rhodium carbonyl chloride is not readily converted back to a CO-free reagent. Above 200 °C, carbon monoxide RhCl(CO)(PPh) does decarbonylate, however these high temperatures are often prohibitive. The ideal Tsuji–Wilkinson decarbonylation would be by catalytic near ambient temperatures.
The reaction has been carried out in flow conditions at low temperatures in which a biphasic liquid-gas flow decarbonylation was developed employing N as a gas carrier. However, the temperature required for this reaction is 200 °C.
Significant improvements of the Tsuji–Wilkinson decarbonylation have been made by using cationic rhodium complexes with chelating bisphosphines. | 0 | Theoretical and Fundamental Chemistry |
Vat level and drum speed are the two basic operating parameters for any rotary vacuum drum filter. These parameters are adjusted dependently to each other to optimize the filtration performance.
Valve level determines the proportion filter cycle in the filter. The filter cycle consist of the filter drum rotation, release of cake formation from slurry and the drying period for the cake formation shown in figure 1. By default, operate the vat at its maximum level to maximise the rate of filtration. Reduce vat level if discharged solid is in the form of thin and slimy cake or if the discharged solid is very thick.
Decrease in the vat level eventually leads to a decrease in the portion of the drum being submerge under the slurry, more surface exposure for the cake dying surface hence, larger cake formation to dry time ratio. This result in less moisture content of formed solid and lessen the thickness of the form solid. In addition to operating at lower vat level, the flow rate per drum revolution decreases and ultimately thinner cake formation occurs. In the case of pre coat discharge the filter aid efficiency increases.
Drum speed is the driving factor for the filter output and its units is in the form of minutes per drum revolution. At steady operating conditions, adjusting the drum speed gives a proportional relationship with the filter throughput as shown as in figure 2. | 0 | Theoretical and Fundamental Chemistry |
Since the work of Gerold Schwarzenbach in 1949, phosphonic acids are known as effective chelating agents. The introduction of an amine group into the molecule to obtain −NH−C−PO(OH) increases the metal binding abilities of the phosphonate. Examples for such compounds are NTMP, EDTMP and DTPMP. These phosphonates are the structural analogues to the well-known aminopolycarboxylate such as EDTA. The stability of the metal complexes increases with increasing number of phosphonic acid groups. Phosphonates are highly water-soluble while the phosphonic acids are only sparingly so.
Phosphonates are effective chelating agents. That is, they bind tightly to di- and trivalent metal ions, which is useful in water softening. In this way, they prevent formation of insoluble precipitates (scale). The binding of these ligands also suppresses the catalytic properties of metal ions. They are stable under harsh conditions. For these reasons, an important industrial use of phosphonates is in cooling waters, desalination systems, and in oil fields to inhibit scale formation. Phosphonates are also regularly used in reverse osmosis systems as antiscalants. Phosphonates in cooling water systems also serve to control corrosion of iron and steel. In pulp and paper manufacturing and in textile industry they serve as "peroxide bleach stabilizers", by chelating metals that could inactivate the peroxide. In detergents they are used as a combination of chelating agent, scale inhibitor, and bleach stabilizer. Phosphonates are also increasingly used in medicine to treat disorders associated with bone formation and calcium metabolism. Furthermore, they serve as carriers for radionuclides in bone cancer treatments (see samarium-153-ethylene diamine tetramethylene phosphonate). | 0 | Theoretical and Fundamental Chemistry |
Minerals of copper were known from ancient times. In Crete, little fragments of malachite and azurite were powdered and used as make up or to decorate ceramic as early as 6000 BCE.
Therefore, the minerals were not collected because people were looking for copper but for virtues like those mentioned or simply because of its brightness and colour, but this knowledge of the minerals is critical since they already knew how to recognize them and where to collect them when, later, they started the systematic search for ores.
Numerous examples of mines are known all over Europe, from the east: Rudna Glava (Serbia), Ai Bunar (Bulgaria); to the west: Mount Gabriel (Ireland), Great Orme, Alderley Edge (United Kingdom); crossing Central Europe: Mitterberg (Salzach, Austria), Neuchâtel (Switzerland), Cabrierés (France); to the south: Riotinto, Mola Alta de Serelles (Spain); and the Mediterranean: Corsica, Cyprus, and the Cyclades islands. It is remarkable that, usually, it is not a single mine but a complex, with a variable, large number of mineshafts, as in Rudna Glava (30) or Mount Gabriel (31). | 1 | Applied and Interdisciplinary Chemistry |
Regarding their applications, amorphous metallic layers played an important role in the discovery of superconductivity in amorphous metals made by Buckel and Hilsch. The superconductivity of amorphous metals, including amorphous metallic thin films, is now understood to be due to phonon-mediated Cooper pairing. The role of structural disorder can be rationalized based on the strong-coupling Eliashberg theory of superconductivity. | 0 | Theoretical and Fundamental Chemistry |
Kenneth D. Karlin was born on October 30, 1948, in Pasadena, California, a professor of chemistry at Johns Hopkins University in Baltimore, Maryland. Research in his group focuses on coordination chemistry relevant to biological and environmental processes, involving copper or heme complexes. Of particular interest are reactivities of such complexes with nitrogen oxides, O, and the oxidation of substrates by the resultant compounds. He is also the Editor-in-Chief of the book series Progress in Inorganic Chemistry. | 0 | Theoretical and Fundamental Chemistry |
In a solid, only those particles that are at the surface can be involved in a reaction. Crushing a solid into smaller parts means that more particles are present at the surface, and the frequency of collisions between these and reactant particles increases, and so reaction occurs more rapidly. For example, Sherbet (powder) is a mixture of very fine powder of malic acid (a weak organic acid) and sodium hydrogen carbonate. On contact with the saliva in the mouth, these chemicals quickly dissolve and react, releasing carbon dioxide and providing for the fizzy sensation. Also, fireworks manufacturers modify the surface area of solid reactants to control the rate at which the fuels in fireworks are oxidised, using this to create diverse effects. For example, finely divided aluminium confined in a shell explodes violently. If larger pieces of aluminium are used, the reaction is slower and sparks are seen as pieces of burning metal are ejected. | 0 | Theoretical and Fundamental Chemistry |
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