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The onset of Görtler vortices can be predicted using the dimensionless number called Görtler number (G). It is the ratio of centrifugal effects to the viscous effects in the boundary layer and is defined as
where
: = external velocity
: = momentum thickness
: = kinematic viscosity
: = radius of curvature of the wall
Görtler instability occurs when G exceeds about 0.3. | 1 | Applied and Interdisciplinary Chemistry |
Banded iron formations (BIFs) are particularly important when considering the surface environments of the early Earth, which were significantly different from the surface environments observed today. This is manifested in the mineralogy of these formations, which are indicative of different redox conditions. Additionally, BIFs are interesting in that they were deposited while major changes were occurring in the atmosphere and in the biosphere 2.8 to 1.8 billion years ago. Iron isotopic studies can reveal the details of the formation of BIFs, which allows for the reconstruction of redox and climatic conditions at the time of deposition.
BIFs formed as a result of the oxidation of iron by oxygen, which was likely generated by the evolution of cyanobacteria. This was followed by the subsequent precipitation of iron particles in the ocean. Observed variations in the iron isotopic composition of BIFs span the entire range observed on Earth, with δFe values between -2.5 and +1‰. The cause of these variations are hypothesized to occur for three reasons. The first relates to the varying mineralogy of the BIFs. Within the BIFs, minerals such as hematite, magnetite, siderite, and pyrite are observed. These minerals each having varying isotopic fractionation, likely as a result of their structures and the kinetics of their growth. The isotopic composition of the BIFs is indicative of the fluids from which they precipitated, which has applications when reconstructing environmental conditions of the ancient Earth. It has also been suggested that BIFs may be biologic in origin. The range of their δFe values fall within the range of those observed to occur as a result of biologic processes relating to bacterial metabolic processes, such as those of anoxygenic phototrophic iron-oxidizing bacteria. Ultimately, the improved understanding of BIFs using iron isotope fractionations would allow for the reconstruction of past environments and the constraint of processes occurring on the ancient Earth. However, given that the values observed as a result of biogenic and abiogenic fractionation are relatively similar, the exact processes of BIFs are still unclear. Thus, the continued study and improved understanding of biologic and abiologic fractionation effects would be beneficial in providing better details regarding BIF formation. | 0 | Theoretical and Fundamental Chemistry |
Steel casing pipe protects one or many of various types of utilities such as water mains, gas pipes, electrical power cables, fiber-optic cables, etc. The utility lines that are run through the steel casing pipe are most commonly mounted and spaced within the steel casing pipe by using "casing spacers" that are made of various materials, including stainless steel or carbon steel and the more economical plastic versions. The ends of a steel casing pipe "run" are normally sealed with "casing end seals", which can be of the "pull-on" or "wrap-around" rubber varieties. Steel casing pipe is also used in the construction of deep foundations. | 1 | Applied and Interdisciplinary Chemistry |
An azeotrope () or a constant heating point mixture is a mixture of two or more components in fluidic states whose proportions cannot be altered or changed by simple distillation. This happens because when an azeotrope is boiled, the vapour has the same proportions of constituents as the unboiled mixture. Azeotropic mixture behavior is important for fluid separation processes.
Each azeotrope has a characteristic boiling point. The boiling point of an azeotrope is either less than the boiling point temperatures of any of its constituents (a positive azeotrope), or greater than the boiling point of any of its constituents (a negative azeotrope). For both positive and negative azeotropes, it is not possible to separate the components by fractional distillation and azeotropic distillation is usually used instead.
For technical applications, the pressure-temperature-composition behavior of a mixture is the most important, but other important thermophysical properties are also strongly influenced by azeotropy, including the surface tension and transport properties.
Some azeotropic mixtures of pairs of compounds are known, and many azeotropes of three or more compounds are also known. | 1 | Applied and Interdisciplinary Chemistry |
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology. | 1 | Applied and Interdisciplinary Chemistry |
Stop codons were historically given many different names, as they each corresponded to a distinct class of mutants that all behaved in a similar manner. These mutants were first isolated within bacteriophages (T4 and lambda), viruses that infect the bacteria Escherichia coli. Mutations in viral genes weakened their infectious ability, sometimes creating viruses that were able to infect and grow within only certain varieties of E. coli. | 1 | Applied and Interdisciplinary Chemistry |
In organometallic chemistry, a dicarbollide is an anion of the formula [CBH]. Various isomers exist, but most common is 1,2-dicarbollide derived from ortho-carborane. These dianions function as ligands, related to the cyclopentadienyl anion. Substituted dicarbollides are also known such as [CBH(pyridine)] (pyridine bonded to B) and [CRBH] (R groups bonded to carbon). | 0 | Theoretical and Fundamental Chemistry |
Pattinson's process or pattinsonisation is a method for removing silver from lead, discovered by Hugh Lee Pattinson in 1829 and patented in 1833.
The process is dependent on the fact that lead which has least silver in it solidifies first on liquefaction, leaving the remaining liquid richer in silver.
In practice several crystallisations were required, so Pattinson's equipment consisted basically of nothing more complex than a row of up to 13 iron pots, which were heated from below. Some lead, naturally containing a small percentage of silver, was loaded into the central pot and melted. This was then allowed to cool. As the lead solidified it was removed using large perforated iron ladles and moved to the next pot in one direction, and the remaining metal which was now richer in silver was then transferred to the next pot in the opposite direction. The process was repeated from one pot to the next, the lead accumulating in the pot at one end and metal enriched in silver in the pot at the other.
The level of enrichment possible is limited by the lead-silver eutectic and typically the silver content of the silver-rich melt could not be raised above 2% (around 600 to 700 ounces per ton), so further separation is carried out by cupellation.
The process was economic for lead containing at least 250 grams of silver per ton. Being the first process applicable to low-grade lead, it supplemented earlier patio process and pan amalgamation.
It was replaced by the Parkes process in the mid-19th century. | 1 | Applied and Interdisciplinary Chemistry |
DNA methylation involves the addition of a methyl group to the carbon-5 position of the cytosine ring in the CpG dinucleotide and converting it to methylcytosine. This process is catalyzed by DNA methyltransferase. In numerous cancers, the CpG islands of selected genes are aberrantly methylated (hypermethylated) which results in transcriptional repression. This may be an alternate mechanism of gene inactivation.
Multiple genes have been discovered to be frequently methylated in cancers and leukemias. More specifically, the deregulation of the Wnt signaling pathway has been implicated in a wide array of cancers that is mainly seen as a result of loss-of-function mutations of APC and axin or as a gain-of-function mutation of CTNNB1 (B-catenin). The GC content of the SFRP1 promoter in humans is 56.3%.
It has been found that the overexpression of B-catenin may lead to enhanced proliferation in myeloma plasma cells; thus, soluble Wnt inhibitors are potential tumor suppressor genes and, if inactivated, may contribute to myeloma pathogenesis. This led Chim et al. to investigate the role of aberrant gene methylation of a panel of soluble Wnt antagonists, including SFRP1. Complete methylation led to silencing of respective genes (no transcripts), whereas absence of gene methylation was associated with constitutive gene expression. Methylation of soluble Wnt antagonists would be important in the pathogenesis of multiple myeloma if Wnt signaling was regulated by an autocrine loop by Wnt and Fz. If an autocrine loops exists, then both the ligand (Wz) and receptor (Fzd) should be simultaneously expressed in myeloma cells and growth of tumour cells should be inhibited upon addition of SFRP1. Chim et al. demonstrated simultaneous expression of Wz and Fzd in myeloma plasma cells. Moreover, treatment with recombinant SFRP1 inhibited the growth of myeloma cells in a dose-dependent manner. These findings implicate soluble Wnt inhibitors as tumor suppressors that could be inactivated by methylation.
Veeck and colleagues found all of their eight breast cancer cell lines had complete methylation in the SFRP1 promoter region, while no methylation was detectable in non-malignant cell lines. After treatment with 5-Aza-2’-deoxycytidine (DAC), an inhibitor of DNA methyltransferase, SFRP1 expression was restored in all four treated breast cancer cell lines, supporting the hypothesis of methylation-mediated SFRP1 gene silencing in breast cancer.
Furthermore, the transcriptional silencing mechanism underlying DNA methylation which is brought about through the hypermethylation of CpG-rich islands present in the promoter region of genes, can cooperate with histone deacetylation to change chromatin structure to a repressed form. Lo and colleagues looked at the effects of DAC and trichostatin A (TSA, selectively inhibits the mammalian histone deacetylase family of enzymes) on cancer cells. In 4 breast cancer cell lines, SFRP1 expression was significantly restored after treatment with DAC alone. TSA, only in combination with DAC, had a slightly enhanced effect on SFRP1 expression in these cell lines. A different breast cancer cell line (SKBR3, showed loss of SFRP1 expression without significant methylation of the SFRP1 promoter. Lo et al. hypothesized that this may be due to silencing via histone deacetylation. After SKBR3 cells were treated with TSA, SFRP1 expression was restored in a dose- and time-dependent manner. Yet another breast cancer cell line (T47D) required both DAC and TSA to upregulate SFRP1 expression. This indicates that T47D cells are tightly regulated by two layers of epigenetic control (DNA methylation and histion deacetylation) and relieving inhibition by both mechanisms is necessary for reactivation of SFRP1. This study shows that both the epigenetic mechanisms, DNA methylation and histone deacetylation, are involved in silencing of SFRP1. | 1 | Applied and Interdisciplinary Chemistry |
Sequencing batch reactors (SBR) or sequential batch reactors are a type of activated sludge process for the treatment of wastewater. SBRs treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. Oxygen is bubbled through the mixture of wastewater and activated sludge to reduce the organic matter (measured as biochemical oxygen demand (BOD) and chemical oxygen demand (COD)). The treated effluent may be suitable for discharge to surface waters or possibly for use on land. | 1 | Applied and Interdisciplinary Chemistry |
A native of California, Fahy holds a Bachelor of Science degree in Biology from the University of California, Irvine and a PhD in pharmacology and cryobiology from the Medical College of Georgia in Augusta.
He currently serves on the board of directors of two organizations and as a referee for numerous scientific journals and funding agencies, and holds 35 patents on cryopreservation methods, aging interventions, transplantation, and other topics. | 1 | Applied and Interdisciplinary Chemistry |
Mouza Sulaiman Mohamed Al-Wardi (Arabic: موزة سليمان محمد الوردي) is a curator and historian from Oman, who is Director of the Collections Department at the National Museum. She specialises in the history of silverworking in the Oman region. | 1 | Applied and Interdisciplinary Chemistry |
Irène was born in Paris, France, on 12 September 1897 and was the first of Marie and Pierres two daughters. Her sister was Ėve. They lost their father early on in 1906 due to a horse-drawn wagon incident and Marie was left to raise them. Education was important to Marie and Irènes education began at a school near the Paris Observatory. This school was chosen because it had a more challenging curriculum than the school nearby the Curie's home. In 1906, it was obvious Irène was talented in mathematics and her mother chose to focus on that instead of public school. Marie joined forces with a number of eminent French scholars, including the prominent French physicist Paul Langevin, to form "The Cooperative", which included a private gathering of nine students that were children of the most distinguished academics in France. Each contributed to educating these children in their respective homes. The curriculum of The Cooperative was varied and included not only the principles of science and scientific research but such diverse subjects as Chinese and sculpture and with great emphasis placed on self-expression and play. Irène studied in this environment for about two years.
Irène and her sister Ève were sent to Poland to spend the summer with their Aunt Bronia (Maries sister) when Irène was thirteen. Irènes education was so rigorous that she still had a German and trigonometry lesson every day of that break. Irène re-entered a more orthodox learning environment by going back to high school at the Collège Sévigné in central Paris until 1914. She then went onto the Faculty of Science at the Sorbonne to complete her baccalaureate, until 1916 when her studies were interrupted by World War I. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion , called hydroxide, and the neutral radical , known as the hydroxyl radical, consist of an unbonded hydroxy group.
According to IUPAC definitions, the term hydroxyl refers to the hydroxyl radical () only, while the functional group is called a hydroxy group. | 0 | Theoretical and Fundamental Chemistry |
Zeotropic mixtures have different characteristics in convective boiling than pure substances or azeotropic mixtures. Overall, zeotropic mixtures transfer heat more efficiently at the bottom of the fluid, whereas pure and azeotropic substances transfer heat better at the top. During convective flow boiling, the thickness of the liquid film is less at the top of the film than at the bottom because of gravity. In the case of pure liquids and azeotropic mixtures, this decrease in thickness causes a decrease in the resistance to heat transfer. Thus, more heat is transferred and the heat transfer coefficient is higher at the top of the film. The opposite occurs for zeotropic mixtures. The decrease in film thickness near the top causes the component in the mixture with the higher boiling point to decrease in mass fraction. Thus, the resistance to mass transfer increases near the top of the liquid. Less heat is transferred, and the heat transfer coefficient is lower than at the bottom of the liquid film. Because the bottom of the liquid transfers heat better, it requires a lower wall temperature near the bottom than at the top to boil the zeotropic mixture. | 1 | Applied and Interdisciplinary Chemistry |
Kopin Liu (; born 25 January 1949) is a Taiwanese physical chemist.
Liu is a 1971 graduate of National Tsing Hua University. He moved to the United States to pursue a doctorate at Ohio State University. Liu began his research career at the Georgia Institute of Technology. After one year, he moved to Argonne National Laboratory, where he remained until 1993. Since his return to Taiwan, Liu has held several posts at Academia Sinica. He said in 2000 that working at Academia Sinica meant a large pay cut, but that he returned to teach Taiwan's future scientists while working on research. Liu received two five-year grants as a fellow of the Foundation for the Advancement of Outstanding Scholarship, an organization founded by Yuan T. Lee in 1994. In 1998, Liu was granted fellowship by the American Physical Society. Equivalent honors were bestowed by The World Academy of Sciences in 2005, and the Royal Society of Chemistry in 2013. He became a member of the Academia Sinica in 2004 and the European Academy of Sciences in 2018. Liu has served as distinguished research chair professor within the department of physics at National Taiwan University since 2010. From 2010 to 2012, Liu was honorary chair professor at National Tsing Hua University. He is a 2011 recipient of the Humboldt Research Award. | 0 | Theoretical and Fundamental Chemistry |
In coordination chemistry, the ligand cone angle (θ) is a measure of the steric bulk of a ligand in a transition metal coordination complex. It is defined as the solid angle formed with the metal at the vertex of a cone and the outermost edge of the van der Waals spheres of the ligand atoms at the perimeter of the base of the cone. Tertiary phosphine ligands are commonly classified using this parameter, but the method can be applied to any ligand. The term cone angle was first introduced by Chadwick A. Tolman, a research chemist at DuPont. Tolman originally developed the method for phosphine ligands in nickel complexes, determining them from measurements of accurate physical models. | 0 | Theoretical and Fundamental Chemistry |
In fractional order reactions, the order is a non-integer, which often indicates a chemical chain reaction or other complex reaction mechanism. For example, the pyrolysis of acetaldehyde () into methane and carbon monoxide proceeds with an order of 1.5 with respect to acetaldehyde: The decomposition of phosgene () to carbon monoxide and chlorine has order 1 with respect to phosgene itself and order 0.5 with respect to chlorine:
The order of a chain reaction can be rationalized using the steady state approximation for the concentration of reactive intermediates such as free radicals. For the pyrolysis of acetaldehyde, the Rice-Herzfeld mechanism is
;Initiation :
;Propagation :
;Termination :
where • denotes a free radical. To simplify the theory, the reactions of the to form a second are ignored.
In the steady state, the rates of formation and destruction of methyl radicals are equal, so that
so that the concentration of methyl radical satisfies
The reaction rate equals the rate of the propagation steps which form the main reaction products and CO:
in agreement with the experimental order of 3/2. | 0 | Theoretical and Fundamental Chemistry |
Many years ago radium-226 and radon-222 were used as gamma-ray sources for industrial radiography: for instance, a radon-222 source was used to examine the mechanisms inside an unexploded V-1 flying bomb, while some of the early Bathyspheres could be examined using radium-226 to check for cracks. Because both radium and radon are very radiotoxic and very expensive due to their natural rarity, these natural radioisotopes have fallen out of use over the last half-century, replaced by artificially created radioisotopes. Radon therapy sits on the edge of radioactive quackery and genuine radiotherapy in part due to the lack of reliable data on the stated health benefits. | 0 | Theoretical and Fundamental Chemistry |
* Measurement of the emissivities of gases at temperatures up to 1000 °C. Emissivity values were required for gaseous aluminium chlorides as part of the development of the sub-halide distillation process mentioned above. A flowing column of the gas to be measured, heated in a refractory tube, was maintained at a fixed length by gas barriers at each end, formed by balanced opposing streams of argon. The radiation emitted by the gas was measured by a thermopile. A diaphragm was set up to shield this sensor from radiation emitted by the furnace and other hot parts of the equipment. The whole apparatus was mounted on a water-cooled optical bench.
* X-ray diffraction determination of the structures of liquid metals. There was a need for structural studies of liquid sodium and sodium-potassium alloys because these were used as coolants in fast-breeder reactors. Fulmer developed a high temperature x-ray diffractometer for investigating the structures of liquid metals and alloys. In addition to its studies of liquid alkali metals, Fulmer discovered that certain eutectics, such as those in the gold-silicon and gold-germanium systems, have a structure in the liquid phase that has to be disrupted on crystallization. This gives rise to considerable supercooling which results in multiple nucleation, and hence a very fine grain size in the resulting polycrystalline alloy.
* Production of high purity austenitic stainless steel. High purity austenitic stainless steel was of interest as a potential cladding material for nuclear fuel elements. Fulmer produced high purity chromium by electro-deposition from a fluoride bath. Zone refining using induction heating was used to produce high-purity iron and nickel and to remove oxygen from chromium. Impurity levels of 1-40 parts per million were achieved.
* Chromium with improved ductility. Uses of chromium as a high temperature material are limited by its brittleness. Starting with electro-deposited flakes of high purity chromium, investigators at Fulmer used argon-arc melting to form electrodes for ingot production in a consumable electrode furnace. Ingots were then heated in an inert or hydrogen atmosphere and extruded to give a fine grained structure. Critical warm working, below the recrystallization temperature, then gave improved room-temperature ductility.
* Statistical studies of the strength of ceramics. The strength of brittle materials such as ceramics is inherently variable. Fulmer undertook numerous strength tests on sets of nominally identical specimens of engineering ceramics such as silicon nitride and silicon carbide. They devised graphical techniques for finding the probability distribution of test results and contributed to criteria for engineering design with these materials. | 1 | Applied and Interdisciplinary Chemistry |
Sumner is the author of a widely used anti-harassment statement that she made public so that other universities and institutes could use it as a model. A leader in helping institutions develop anti-harassment plans, Sumner presented to a workshop at the 2016 American Geophysical Union on “Addressing harassment and improving workplace climate.” She was also an invited presenter for Association of Polar Early Career Scientists webinar on sexual harassment during fieldwork. Sumner is presently chair of advisory board for The Feminist Research Institute at the UC, Davis In June 2020 she became the leader of the Anti-Racism Action Committee in her department (Earth and Planetary Science) at UC Davis. Sumner also wrote four letters concerning racism and its effects on the science community between late May and early June 2020 | 0 | Theoretical and Fundamental Chemistry |
Type E (chromel–constantan) has a high output (68 μV/°C), which makes it well suited to cryogenic use. Additionally, it is non-magnetic.
Wide range is −270 °C to +740 °C
and narrow range is −110 °C to +140 °C. | 1 | Applied and Interdisciplinary Chemistry |
A Rydberg molecule is an electronically excited chemical species. Electronically excited molecular states are generally quite different in character from electronically excited atomic states. However, particularly for highly electronically excited molecular systems, the ionic core interaction with an excited electron can take on the general aspects of the interaction between the proton and the electron in the hydrogen atom. The spectroscopic assignment of these states follows the Rydberg formula, named after the Swedish physicist Johannes Rydberg, and they are called Rydberg states of molecules. Rydberg series are associated with partially removing an electron from the ionic core.
Each Rydberg series of energies converges on an ionization energy threshold associated with a particular ionic core configuration. These quantized Rydberg energy levels can be associated with the quasiclassical Bohr atomic picture. The closer you get to the ionization threshold energy, the higher the principal quantum number, and the smaller the energy difference between near threshold Rydberg states. As the electron is promoted to higher energy levels in a Rydberg series, the spatial excursion of the electron from the ionic core increases and the system is more like the Bohr quasiclassical picture.
The Rydberg states of molecules with low principal quantum numbers can interact with the other excited electronic states of the molecule. This can cause shifts in energy. The assignment of molecular Rydberg states often involves following a Rydberg series from intermediate to high principal quantum numbers. The energy of Rydberg states can be refined by including a correction called the quantum defect in the Rydberg formula. The quantum defect correction can be associated with the presence of a distributed ionic core.
The experimental study of molecular Rydberg states has been conducted with traditional methods for generations. However, the development of laser-based techniques such as Resonance Ionization Spectroscopy has allowed relatively easy access to these Rydberg molecules as intermediates. This is particularly true for Resonance Enhanced Multiphoton Ionization (REMPI) spectroscopy, since multiphoton processes involve different selection rules from single photon processes. The study of high principal quantum number Rydberg states has spawned a number of spectroscopic techniques. These "near threshold Rydberg states" can have long lifetimes, particularly for the higher orbital angular momentum states that do not interact strongly with the ionic core.
Rydberg molecules can condense to form clusters of Rydberg matter which has an extended lifetime against de-excitation.
Dihelium (He) was the first known Rydberg molecule. | 0 | Theoretical and Fundamental Chemistry |
Like related acyl chlorides, valeryl chloride hydrolyzes readily:
:CH(CH)C(O)Cl + HO → CH(CH)COH + HCl
Alcohols react to give esters:
:CH(CH)C(O)Cl + ROH → CH(CH)COR + HCl
Amines react to give amides:
:CH(CH)C(O)Cl + RNH → CH(CH)C(O)NR + HCl
Benzene reacts under conditions of the Friedel-Crafts reaction to give valerophenone:
:CH(CH)C(O)Cl + CH → CH(CH)C(O)CH + HCl | 0 | Theoretical and Fundamental Chemistry |
Some amidrazones have been employed as insecticides. They were known in 1993 by an agent of Dow Chemical for their low undesirable toxicity, low production cost, and effectiveness against insects resistant to known insecticides. Compounds of amidrazones were employed as early as 1993 for controlling plant-destructive insects in crops of cultivated plants, ornamentals, and forestry. | 0 | Theoretical and Fundamental Chemistry |
*[https://web.archive.org/web/20051104014927/http://www.nuc.berkeley.edu/thyd/ne161/ncabreza/samphtml.html Physical description of LWR fuel]
*[http://www.nucleartourist.com/areas/bwr-in1.htm Links to BWR photos from the nuclear tourist webpage] | 0 | Theoretical and Fundamental Chemistry |
Although organic radicals are generally stable intrinsically (in isolation), practically speaking their existence is only transient because they tend to dimerize. Some are quite long-lived. Generally organic radicals are stabilized by any or all of these factors: presence of electronegativity, delocalization, and steric hindrance. The compound 2,2,6,6-tetramethylpiperidinyloxyl illustrates the combination of all three factors. It is a commercially available solid that, aside from being magnetic, behaves like a normal organic compound. | 1 | Applied and Interdisciplinary Chemistry |
By early 2000, several research groups realized that protein chemical shifts could be more efficiently and accurately calculated by combining different methods together as shown in Figure 1. This led to the development of several programs and web servers that rapidly calculate protein chemical shifts when provided with protein coordinate data. These “hybrid” programs, along with some of their features and URLs, are listed below in Table 1. | 0 | Theoretical and Fundamental Chemistry |
Hydroxylamine or its salts (salts containing hydroxylammonium cations ) can be produced via several routes but only two are commercially viable. It is also produced naturally as discussed in a section on biochemistry. | 0 | Theoretical and Fundamental Chemistry |
* Rh-catalyzed Trp and Cys alkylation
Using in situ generated Rh-carbenoid by activation of vinyl-substituted diazo compounds with Rh(OAc), tryptophans and cysteines were shown to be selectively alkylated in aqueous media.
However, this method is limited to surface tryptophans and cysteines possibly because of steric constraints.
* Ir-catalyzed Lys and N-terminus (reductive) alkylation
Imines formed from the condensation of aldehydes with lysines or the N-terminus can be reduced efficient by an water-stable [Cp*Ir(bipy)(HO)]SO complex in the presence of formate ions (serving as the hydride source). The reaction happens readily under physiologically relevant conditions and results in high conversion for various aromatic aldehydes.
* Pd-catalyzed Tyr O-alkylation
By using a pre-formed electrophilic π-allylpalladium(II) reagent derived from allylic acetate or carbamate precursors, selective allylic alkylation of tyrosines can be achieved in aqueous solution at room temperature and in the presence of cysteines.
* Au-catalyzed Cys alkylation
Cysteine-containing peptides have been shown to undergo 1,2-addition to allenes in the presence of gold(I) and/or silver(I) salts, producing hydroxyl substituted vinyl thioethers. The reaction with peptides proceeds with high yields and is selective for cysteines over other nucleophilic residues.
However, the reactivity towards proteins is much decreased, potentially due to the coordination of gold to the protein backbone. | 1 | Applied and Interdisciplinary Chemistry |
Lithium-associated hyperparathyroidism is the leading cause of hypercalcemia in lithium-treated patients. Lithium may lead to exacerbation of pre-existing primary hyperparathyroidism or cause an increased set-point of calcium for parathyroid hormone suppression, leading to parathyroid hyperplasia. | 1 | Applied and Interdisciplinary Chemistry |
* tert-Butyl nitrite has been shown to be an effective reagent for the selective nitration of phenols and aryl sulfonamides
* n-Butyl nitrite and ammonia convert phenylhydroxylamine to its nitrosamine derivative cupferron. Likewise pyrrolidine is a substrate for ethyl nitrite.
* Alkyl nitrites are also used in the formation of oximes with the stronger carbon acids and acid or base catalysis for example in the reaction of 2-butanone, ethyl nitrite and hydrochloric acid forming the oxime, the similar reaction with phenacyl chloride, or the reaction of phenylacetonitrile with methyl nitrite and sodium hydroxide.
An isolated but classic example of the use of alkyl nitrites can be found in Woodward and Doering's quinine total synthesis:
for which they proposed this reaction mechanism: | 0 | Theoretical and Fundamental Chemistry |
An endogenous retrovirus is a retrovirus without virus pathogenic effects that has been integrated into the host genome by inserting their inheritable genetic information into cells that can be passed onto the next generation like a retrotransposon. Because of this, they share features with retroviruses and retrotransposons. When the retroviral DNA is integrated into the host genome they evolve into endogenous retroviruses that influence eukaryotic genomes. So many endogenous retroviruses have inserted themselves into eukaryotic genomes that they allow insight into biology between viral-host interactions and the role of retrotransposons in evolution and disease.
Many retrotransposons share features with endogenous retroviruses, the property of recognising and fusing with the host genome. However, there is a key difference between retroviruses and retrotransposons, which is indicated by the env gene. Although similar to the gene carrying out the same function in retroviruses, the env gene is used to determine whether the gene is retroviral or retrotransposon. If the gene is retroviral it can evolve from a retrotransposon into a retrovirus. They differ by the order of sequences in pol genes. Env genes are found in LTR retrotransposon types Ty1-copia (Pseudoviridae), Ty3-gypsy (Metaviridae) and BEL/Pao. They encode glycoproteins on the retrovirus envelope needed for entry into the host cell. Retroviruses can move between cells whereas LTR retrotransposons can only move themselves into the genome of the same cell. Many vertebrate genes were formed from retroviruses and LTR retrotransposons. One endogenous retrovirus or LTR retrotransposon has the same function and genomic locations in different species, suggesting their role in evolution. | 1 | Applied and Interdisciplinary Chemistry |
Though characterization of 2-norbornyl cation crystals may have significantly precluded further debates about its electronic structure, it does not crystallize under any standard conditions. Recently, the crystal structure has been obtained and reported through a creative means: addition of aluminium tribromide to 2-norbornyl bromide in dibromomethane at low temperatures afforded crystals of [][]·. By examining the resulting crystal structure, researchers were able to confirm that the crystalline geometry best supports the case for delocalized bonding in the stable 2-norbornyl cation. Bond lengths between the "bridging" carbon 6 and each of carbons 1 and 2 were found to be slightly longer than typical alkane bonds. According to the nonclassical picture, one would expect a bond order between 0 and 1 for these bonds, signifying that this explains the crystal structure well. The bond length between carbons 1 and 2 was reported as being between typical single and double carbon-carbon bond lengths, which agrees with nonclassical predictions of a bond order slightly above 1. Investigators who crystallized the 2-norbornyl cation commented that the cation proved impossible to crystallize unless provided a chemical environment that locked it into one definite orientation. | 0 | Theoretical and Fundamental Chemistry |
The exact temperatures at which iron will transition from one crystal structure to another depends on how much and what type of other elements are dissolved in the iron. The phase boundary between the different solid phases is drawn on a binary phase diagram, usually plotted as temperature versus percent iron. Adding some elements, such as Chromium, narrows the temperature range for the gamma phase, while others increase the temperature range of the gamma phase. In elements that reduce the gamma phase range, the alpha-gamma phase boundary connects with the gamma-delta phase boundary, forming what is usually called the Gamma loop. Adding Gamma loop additives keeps the iron in a body-centered cubic structure and prevents the steel from suffering phase transition to other solid states. | 1 | Applied and Interdisciplinary Chemistry |
If an atom, A, is double-bonded to another atom, then atom A should be treated as though it is "connected to the same atom twice". An atom that is double-bonded has a higher priority than an atom that is single bonded. When dealing with double bonded priority groups, one is allowed to visit the same atom twice as one creates an arc.
When B is replaced with a list of attached atoms, A itself, but not its "phantom", is excluded in accordance with the general principle of not doubling back along a bond that has just been followed. A triple bond is handled the same way except that A and B are each connected to two phantom atoms of the other. | 0 | Theoretical and Fundamental Chemistry |
The city of Los Angeles diverted water from the Owens River into the Los Angeles Aqueduct in 1913. In 1941, the Los Angeles Department of Water and Power extended the Los Angeles Aqueduct system farther northward into the Mono Basin with the completion of the Mono Craters Tunnel between the Grant Lake Reservoir on Rush Creek and the Upper Owens River. So much water was diverted that evaporation soon exceeded inflow and the surface level of Mono Lake fell rapidly. By 1982 the lake was reduced to , 69 percent of its 1941 surface area. By 1990, the lake had dropped 45 vertical feet and had lost half its volume relative to the 1941 pre-diversion water level. As a result, alkaline sands and formerly submerged tufa towers became exposed, the water salinity doubled, and Negit Island became a peninsula, exposing the nests of California gulls to predators (such as coyotes), and forcing the gull colony to abandon this site.
In 1974, ecologist David Gaines and his student David Winkler studied the Mono Lake ecosystem and became instrumental in alerting the public of the effects of the lower water level with Winkler's 1976 ecological inventory of the Mono Basin. The National Science Foundation funded the first comprehensive ecological study of Mono Lake, conducted by Gaines and undergraduate students. In June 1977, the Davis Institute of Ecology of the University of California published a report, "An Ecological Study of Mono Lake, California," which alerted California to the ecological dangers posed by the redirection of water away from the lake for municipal uses.
Gaines formed the Mono Lake Committee in 1978. He and Sally Judy, a UC Davis student, led the committee and pursued an informational tour of California. They joined with the Audubon Society to fight a now famous court battle, the National Audubon Society v. Superior Court, to protect Mono Lake through state public trust laws. While these efforts have resulted in positive change, the surface level is still below historical levels, and exposed shorelines are a source of significant alkaline dust during periods of high winds.
Owens Lake, the once-navigable terminus of the Owens River which had sustained a healthy ecosystem, is now a dry lake bed during dry years due to water diversion beginning in the 1920s. Mono Lake was spared this fate when the California State Water Resources Control Board (after over a decade of litigation) issued an order (SWRCB Decision 1631) to protect Mono Lake and its tributary streams on September 28, 1994. SWRCB Board Vice-chair Marc Del Piero was the sole Hearing Officer (see D-1631). In 1941 the surface level was at above sea level. As of October 2022, Mono Lake was at above sea level. The lake level of above sea level is the goal, designed to ensure that the lake would be able to reach and sustain a minimum surface level that is generally agreed to be the minimum for keeping the ecosystem healthy. It has been more difficult during years of drought in the American West. | 1 | Applied and Interdisciplinary Chemistry |
Whether carbon capture and storage technology is adopted worldwide will "...depend less on science than on economics. Cleaning coal is very expensive." | 1 | Applied and Interdisciplinary Chemistry |
MicroPIXE is a useful technique for the non-destructive analysis of paintings and antiques. Although it provides only an elemental analysis, it can be used to distinguish and measure layers within the thickness of an artifact. The technique is comparable with destructive techniques such as the ICP family of analyses. | 0 | Theoretical and Fundamental Chemistry |
Dispensing of microspheres can be a difficult task. When utilizing microspheres as a filler for standard mixing and dispensing machines, a breakage rate of up to 80% can occur, depending upon factors such as pump choice, material viscosity, material agitation, and temperature. Customized dispensers for microsphere-filled materials may reduce the microsphere breakage rate to a minimal amount. A progressive cavity pump is the pump of choice for dispensing materials with microspheres, which can reduce microsphere breakage as much as 80%. | 0 | Theoretical and Fundamental Chemistry |
The instrumentation needed in order to conduct the data acquisition include a multimode optical fiber, single-mode or few-mode fibers, photon-counting avalanche photodiodes (APDs), multi-tau correlator board, and a computer.
The first step of data acquisition is probing the tissue with multimode optical fibers that deliver a long coherence length laser light to the tissue. The second step of data acquisition is collecting photons emitted from the tissue surface with single-mode or few-mode fibers. The third step of data acquisition is the APDs detect the photons from the single-mode or few-mode fibers. The APDs act like detectors. The APDs will have a transistor-transistor logic output or binary outputs with the use of transistors. These outputs will be fed into the multi-tau correlator board which will calculate the temporal intensity auto-correlation functions of the detected signal. Then, the function outputs onto the computer where the functions are fitted to the diffusion equation in the previous section in order to determine optical properties about the tissue as well as properties of the scatters or red blood cells such as blood flow index and many more. | 0 | Theoretical and Fundamental Chemistry |
Michael Franz Lappert (31 December 1928 – 28 March 2014) was a Czech-born British inorganic chemist. Mainly located at the University of Sussex, he was recognized for contributions to organometallic complexes. | 0 | Theoretical and Fundamental Chemistry |
Tight junctions are multi-protein complexes that hold cells of a same tissue together and prevent movement of water and water-soluble molecules between cells. In epithelial cells, they function also to separate the extracellular fluid surrounding their apical and basolateral membranes. These junctions exist as a continuous band located just below the apical surface between the membranes of neighboring epithelial cells. The tight junctions on adjacent cells line up so as to produce a seal between different tissues and body cavities. For example, the apical surface of gastrointestinal epithelial cells serve as a selective permeable barrier that separates the external environment from the body. The permeability of these junctions is dependent on a variety of factors including protein makeup of that junction, tissue type and signaling from the cells.
Tight junctions are made up of many different proteins. The four main transmembrane proteins are occludin, claudin, junctional adhesion molecules (JAMs) and tricellulins. The extracellular domains of these proteins form the tight junction barrier by making homophilic (between proteins of the same kind) and heterophilic interactions (between different types of proteins) with the protein domains on adjacent cells. Their cytoplasmic domains interact with the cell cytoskeleton to anchor them. | 1 | Applied and Interdisciplinary Chemistry |
In the context of a clinical trial, quality typically refers to the absence of errors which can impact decision making, both during the conduct of the trial and in use of the trial results. | 1 | Applied and Interdisciplinary Chemistry |
The first intelectin was discovered in Xenopus laevis oocyte and is named XL35 or XCGL-1. X. laevis oocyte also contains a closely related XCGL-2. In addition, X. laevis embryos secrete Xenopus embryonic epidermal lectin into the environmental water, presumably to bind microbes. XSL-1 and XSL-2 are also expressed in X. laevis serum when stimulated with lipopolysaccharide. Two additional intestinal intelectins are discovered in X. laevis
Human has two intelectins: hIntL-1 (omentin) and hIntL-2. Mouse also has two intelectins: mIntL-1 and mIntL-2. | 1 | Applied and Interdisciplinary Chemistry |
The electrodes are typically separated by a thin porous foil (with a thickness between 0.050 to 0.5 mm), commonly referred to as diaphragm or separator. The diaphragm is non-conductive to electrons, thus avoiding electrical shorts between the electrodes while allowing small distances between the electrodes. The ionic conductivity is supplied by the aqueous alkaline solution, which penetrates in the pores of the diaphragm. The state-of-the-art diaphragm is Zirfon, a composite material of zirconia and Polysulfone. The diaphragm further avoids the mixing of the produced hydrogen and oxygen at the cathode and anode, respectively.
Typically, Nickel based metals are used as the electrodes for alkaline water electrolysis. Considering pure metals, Ni is the least active non-noble metal. The high price of good noble metal electrocatalysts such as platinum group metals and their dissolution during the oxygen evolution is a drawback. Ni is considered as more stable during the oxygen evolution, but stainless steel has shown good stability and better catalytic activity than Ni at high temperatures during the Oxygen Evolution Reaction (OER).
High surface area Ni catalysts can be achieved by dealloying of Nickel-Zinc or Nickel-Aluminium alloys in alkaline solution, commonly referred to as Raney nickel. In cell tests the best performing electrodes thus far reported consisted of plasma vacuum sprayed Ni alloys on Ni meshes
and hot dip galvanized Ni meshes. The latter approach might be interesting for large scale industrial manufacturing as it is cheap and easily scalable, but unfortunately, all the strategies show some degradation. | 0 | Theoretical and Fundamental Chemistry |
An anion exchange membrane (AEM) is a semipermeable membrane generally made from ionomers and designed to conduct anions but reject gases such as oxygen or hydrogen. | 0 | Theoretical and Fundamental Chemistry |
During his time at NCAR he served as president of the International Commission on Atmospheric Chemistry and Radioactivity within the International Association of Meteorology and Atmospheric Sciences. He was also a of the American Association for the Advancement of Science and a member of numerous other scientific societies.
He served as an expert witness during hearings before the U.S. Congress and United Nations on radioactive fallout. He also spearheaded the cleanup of plutonium contamination in the soil surrounding the Rocky Flats nuclear weapons manufacturing facility located outside of Boulder, after measuring levels of radioactivity surrounding the site. He also supported the Southern Poverty Law Center which represented the victims of government-sponsored radiation testing on low-income black citizens. | 0 | Theoretical and Fundamental Chemistry |
Metal–π interactions play a major role in organometallics. Linear and cyclic π systems bond to metals allowing organic complexes to bond to metals. | 0 | Theoretical and Fundamental Chemistry |
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from one neuron to another, playing a key role in enabling rapid and direct communication by creating circuits. In addition, a synapse serves as a junction where both the transmission and processing of information occur, making it a vital means of communication between neurons. Neurons are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon and the postsynaptic part is located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission. Synapses (at least chemical synapses) are stabilized in position by synaptic adhesion molecules (SAMs) projecting from both the pre- and post-synaptic neuron and sticking together where they overlap; SAMs may also assist in the generation and functioning of synapses. Moreover, SAMs coordinate the formation of synapses, with various types working together to achieve the remarkable specificity of synapses. In essence, SAMs function in both excitatory and inhibitory synapses, likely serving as devices for signal transmission. | 1 | Applied and Interdisciplinary Chemistry |
Anodizing can also be performed in borate or tartrate baths in which aluminium oxide is insoluble. In these processes, the coating growth stops when the part is fully covered, and the thickness is linearly related to the voltage applied. These coatings are free of pores, relative to the sulfuric and chromic acid processes. This type of coating is widely used to make electrolytic capacitors because the thin aluminium films (typically less than 0.5 μm) would risk being pierced by acidic processes. | 1 | Applied and Interdisciplinary Chemistry |
Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymator (tear gas) product containing the compound capsaicin as the active ingredient that irritates the eyes to cause burning and pain sensations, as well as temporary blindness. Its inflammatory effects cause the eyes to close, temporarily taking away vision. This temporary blindness allows officers to more easily restrain subjects and permits people in danger to use pepper spray in self-defense for an opportunity to escape. It also causes temporary discomfort and burning of the lungs which causes shortness of breath. Pepper spray is used as a less lethal weapon in policing, riot control, crowd control, and self-defense, including defense against dogs and bears.
Pepper spray was engineered originally for defense against bears, mountain lions, wolves and other dangerous predators, and is often referred to colloquially as bear spray.
Kamran Loghman, the person who developed it for use in riot control, wrote the guide for police departments on how it should be used. It was successfully adapted, except for improper usages such as when police sprayed peaceful protestors at University of California, Davis in 2011. Loghman commented, "I have never seen such an inappropriate and improper use of chemical agents", prompting court rulings completely barring its use on docile persons. | 1 | Applied and Interdisciplinary Chemistry |
At the high temperatures for Earth, no volatiles would be in the solid state, and the dust would be made up of silicate and metal.
The continental crust and lower mantle have average K/U values of about 12,000. mid-ocean ridge basalt (MORB) or upper mantle have more volatiles and have a K/U ratio of about 19,000.
Volatile depletion explains why Earth's sodium (volatile) content is about 10% of its calcium (refractory) content, despite the similar abundance in chondrites. | 0 | Theoretical and Fundamental Chemistry |
Zur Folge nach der Entstehung des 2,3 Tage-Isotops des Elements 93 aus Uran G-151 (27 February 1942) by Otto Hahn and Fritz Straßmann was published in Kernphysikalische Forschungsberichte (Research Reports in Nuclear Physics), an internal publication of the German Uranverein. Reports in this publication were classified as "Top Secret". The reports therefore had very limited distribution, and the authors were not allowed to keep copies. The reports were confiscated under the Allied Operation Alsos and sent to the United States Atomic Energy Commission for evaluation. In 1971, the reports were declassified and returned to Germany. The reports are available at the Karlsruhe Nuclear Research Center and the American Institute of Physics. | 0 | Theoretical and Fundamental Chemistry |
Calorimetry in real time is a calorimetry technique based on heat flux sensors that are located on the wall of the reactor vessels. The sensors measure heat across the reactor wall directly and thus, the measurement is independent of temperature, the properties or the behavior of the reaction mass. Heat flow as well as heat transfer information are obtained immediately without any calibrations during the experiment. | 1 | Applied and Interdisciplinary Chemistry |
RNA aptamers can be designed to act as antagonists, agonists, or so-called ”RNA decoy aptamers." In the case of antagonists, the RNA aptamer is used either to prevent binding of a certain protein to its cell membrane receptor or to prevent the protein from performing its activity by binding to the proteins target. Currently, the only RNA aptamer-based therapies that have advanced to clinical trials act as antagonists. When RNA aptamers are designed to act as agonists, they promote immune cell activation as a co-stimulatory molecule, thus aiding in the mobilization of the bodys own defense system. For RNA decoy aptamers, the synthetic RNA aptamer resembles a native RNA molecule. As such, proteins(s) which bind to the native RNA target instead bind to the RNA aptamer, possibly interfering with the biomolecular pathway of a particular disease. In addition to their utility as direct therapeutic agents, RNA aptamers are also being considered for other therapeutic roles. For instance, by conjugating the RNA aptamer to a drug compound, the RNA aptamer can act as a targeted delivery system for that drug. Such RNA aptamers are known as ApDCs. Additionally, through conjugation to radioisotope or a fluorescent dye molecule, RNA aptamers may be useful in diagnostic imaging.
Because of the SELEX process utilized to select RNA aptamers, RNA aptamers can be generated for many potential targets. By directly introducing the RNA aptamers to the target during SELEX, a very selective, high-affinity, homogeneous pool of RNA aptamers can be produced. As such, RNA aptamers can be made to target small peptides and proteins, as well as cell fragments, whole cells, and even specific tissues. Examples of RNA aptamer molecular targets and potential targets include vascular endothelial growth factor, osteoblasts, and C-X-C Chemokine Ligand 12 (CXCL2).
An example of an RNA aptamer therapy includes Pegaptanib (aka Macugen ® ), the only FDA-approved RNA aptamer treatment. Originally approved in 2004 to treat age-related macular degeneration, Pegaptanib is a 28 nucleotide RNA aptamer that acts as a VEGF antagonist. However, it is not as effective as antibody-based treatments such as bevacizumab and ranibizumab. Another example of an RNA aptamer therapeutic is NOX-A12, a 45 nucleotide RNA aptamer that is in clinical trials for chronic lymphocytic leukemia, pancreatic cancer, as well as other cancers. NOX-A12 acts as antagonist for CXCL12/SDF-1, a chemokine involved in tumor growth. | 1 | Applied and Interdisciplinary Chemistry |
A computer simulation of a typical bathroom found that none of the above theories pan out in their analysis, but instead found that the spray from the shower-head drives a horizontal vortex. This vortex has a low-pressure zone in the centre, which sucks the curtain.
David Schmidt of the University of Massachusetts was awarded the 2001 Ig Nobel Prize in Physics for his partial solution to the question of why shower curtains billow inwards. He used a computational fluid dynamics code to achieve the results. Professor Schmidt is adamant that this was done "for fun" in his own free time without the use of grants. | 1 | Applied and Interdisciplinary Chemistry |
In nature, carbon exists as three isotopes: two stable, nonradioactive (carbon-12 (), and carbon-13 (), and one radioactive carbon-14 (), also known as "radiocarbon"). The half-life of (the time it takes for half of a given amount of to decay) is about 5,730 years, so its concentration in the atmosphere might be expected to decrease over thousands of years, but is constantly being produced in the lower stratosphere and upper troposphere, primarily by galactic cosmic rays, and to a lesser degree by solar cosmic rays. These cosmic rays generate neutrons as they travel through the atmosphere which can strike nitrogen-14 () atoms and turn them into . The following nuclear reaction is the main pathway by which is created:
n + → + p
where n represents a neutron and p represents a proton.
Once produced, the quickly combines with the oxygen () in the atmosphere to form first carbon monoxide (), and ultimately carbon dioxide ().
Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is taken up by plants via photosynthesis. Animals eat the plants, and ultimately the radiocarbon is distributed throughout the biosphere. The ratio of to is approximately 1.25 parts of to 10 parts of . In addition, about 1% of the carbon atoms are of the stable isotope .
The equation for the radioactive decay of is:
By emitting a beta particle (an electron, e) and an electron antineutrino (), one of the neutrons in the nucleus changes to a proton and the nucleus reverts to the stable (non-radioactive) isotope . | 0 | Theoretical and Fundamental Chemistry |
BREEAM (Building Research Establishment Environmental Assessment Method), first published by the Building Research Establishment (BRE) in 1990, is the worlds longest established method of assessing, rating, and certifying the sustainability of buildings. More than 550,000 buildings have been BREEAM-certified' and over two million are registered for certification in more than 50 countries worldwide. BREEAM also has a tool which focuses on neighbourhood development. | 1 | Applied and Interdisciplinary Chemistry |
Salmon calcitonin () is the type of calcitonin hormone found in salmon.
Similar to humans, salmon calcitonin is a peptide hormone produced in the ultimobranchial region by parafollicular cells in response to hypercalcemia and lowers blood calcium and phosphate by promoting renal excretion. | 1 | Applied and Interdisciplinary Chemistry |
The case of a vertical line emitting at a fixed rate a constant quantity of fluid Q per unit length is a line source. The problem has a cylindrical symmetry and can be treated in two dimension on the orthogonal plane.
Line sources and line sinks (below) are important elementary flows because they play the role of monopole(s) for incompressible fluids (which can also be considered examples of solenoidal fields i.e. divergence free fields). Generic flow patterns can be also de-composed in terms of multipole expansions, in the same manner as for electric and magnetic fields where the monopole is essentially the first non-trivial (e.g. constant) term of the expansion.
This flow pattern is also both irrotational and incompressible.
This is characterized by a cylindrical symmetry:
Where the total outgoing flux is constant
Therefore,
This is derived from a stream function
or from a potential function | 1 | Applied and Interdisciplinary Chemistry |
The Frozen Zoo at the San Diego Zoo's Institute for Conservation Research currently stores a collection of 8,400 samples from over 800 species and subspecies. Frozen Zoo at San Diego Zoo Conservation Research has acted as a forebear to similar projects at other zoos in the United States and Europe. However, there are still less than a dozen frozen zoos worldwide.
At the United Arab Emirates Breeding Centre for Endangered Arabian Wildlife (BCEAW) in Sharjah, the embryos stored include the extremely endangered Gordons wildcat (Felis silvestris gordoni) and the Arabian leopard (Panthera pardus nimr) (of which there are only 50 in the wild).
The Audubon Center for Research of Endangered Species, affiliated with the University of New Orleans, is maintaining a frozen zoo. In 2000 the Center implanted a frozen-thawed embryo from the highly endangered African wildcat into the uterus of a domestic house cat, resulting in a healthy male wildcat.
The Frozen Ark is a frozen zoo established in 2004 and jointly managed by the Zoological Society of London, the London Natural History Museum, and the University of Nottingham. This organization operates as a charity with many different departments including the DNA laboratory, consortium, taxon expert groups, and the database. In the DNA laboratory, samples are contained after collection from scientists, and different research projects are conducted there. The consortium acts as a bridge to bring together different, but important, groups from zoos, aquariums, museums, and universities. The taxon expert groups monitor the major phyla and lists like the IUCN Red List. The database is the essential piece as it holds all reports and records needed to perform all of the other functions for the charity. The hope for the future is for zoos and aquariums to be able to collect samples from their threatened and/or endangered species in house to help with conservation efforts. The collection and freezing of these samples allows for the distribution of gametes among populations. Samples can be collected from living hosts and from deceased hosts as well.
The University of Georgia's Regenerative Bioscience Center is building a frozen zoo. RBC Director Steven Stice and animal and dairy science assistant professor Franklin West created the facility with the thought of saving endangered cat species. The scientists have already extracted cells from a Sumatran tiger, which could be used for artificial insemination. Artificial insemination provides a remedy for animals who, due to anatomical or physiological reasons, are unable to reproduce in the natural way. Reproduction of stored genetic material also allows for the fostering of genetic improvements, and the prevention of inbreeding. Modern technology allows for genetic manipulation in animals without keeping them in captivity. However, the success of their restoration into the wild would require the application of new science and a sufficient amount of previously collected material. | 1 | Applied and Interdisciplinary Chemistry |
Iodometry in its many variations is extremely useful in volumetric analysis. Examples include the determination of copper(II), chlorate, hydrogen peroxide, and dissolved oxygen:
Available chlorine refers to chlorine liberated by the action of dilute acids on hypochlorite. Iodometry is commonly employed to determine the active amount of hypochlorite in bleach responsible for the bleaching action. In this method, excess but known amount of iodide is added to known volume of sample, in which only the active (electrophilic) can oxidize iodide to iodine. The iodine content and thus the active chlorine content can be determined with iodometry.
The determination of arsenic(V) compounds is the reverse of the standardization of iodine solution with sodium arsenite, where a known and excess amount of iodide is added to the sample:
For analysis of antimony(V) compounds, some tartaric acid is added to solubilize the antimony(III) product. | 0 | Theoretical and Fundamental Chemistry |
Differential static light scatter (DSLS) is a term coined to represent the change in total light scatter of a system over time or temperature in a static environment.
Static light scattering or SLS and its many types are well outlined in literature and is the base principal for DSLS but varies specifically in that the difference (before and after) is the focus of this measurement. Typically the system will commence measurement at T and over the course of time measure the change in light scatter. One of the more practical applications of DSLS is in the area of proteomic research and protein based chemistry. Solution conditions can be varied across samples of a specific protein in a screening scenario and the system can be kept at either a static temperature or be ramped up, or in some cases down. The change will be observed over time and the focus of the calculation is on the amount of change in signal from T to T . This method of analysis provides researchers with data that helps them predict a protein or compound's stability in various conditions and further, in the case of proteomic structural work, can help identify the best protein candidates, and their optimal conditions to crystallize and thereby undergo x-ray crystallography for structural analysis.
There are other technologies or techniques using similar concepts such as DLS (dynamic light scattering) to obtain this information with the help of fluorophores and the use of lasers for excitation however the primary focus in this arena is on particle sizing. Also DLS has a greater focus in flow-based instrumentation. Many proteins are discovered on an annual basis and in the field of drug discovery it is very important characterize the structure of a novel peptides as well as the best conditions to keep them in solution. Because of this staggering number of potential therapeutics churning out of this research sector today there is a strong need for instrumentation to best capture this data and to date there are a few solutions that are DSLS focused. One such oriented instrument designed for high throughput scenarios utilizing standard HTS (high-throughput screening) SBS standard type plates (or automation friendly) is the StarGazer2.
There are other solutions also available that have either wider focus to include particular sizing and Zeta potential but are limited but are limited by how many samples can be run at once, thus, non-HTS. As DSLS in principal measures particles as they either aggregate (or grow larger) or, in theory, breakdown and grow smaller, this technology and method of measurement will pull in a number of great applications in the future in the food and beverage, or environmental sector as the technology is stretched into new applications beyond proteomics. | 0 | Theoretical and Fundamental Chemistry |
Chapter traditions of service to their chemical engineering departments commonly prevail rather than broader, national traditions. | 1 | Applied and Interdisciplinary Chemistry |
After a BSc and a MSc in organic chemistry he worked for the Department of Scientific and Industrial Research, before earning a scholarship to go to the University of Liverpool for a PhD under Thomas Percy Hilditch, studying fish liver oils and fats from farm animals.
After his retirement in 1969, he held several honorary posts at Victoria University of Wellington. He died on 8 June 1999 and was cremated at Karori Crematorium. | 0 | Theoretical and Fundamental Chemistry |
α-Alkyltryptamines are a group of substituted tryptamines which possess an alkyl group, such as a methyl or ethyl group, attached at the alpha carbon, and in most cases no substitution on the amine nitrogen. α-Alkylation of tryptamine makes it much more metabolically stable and resistant to degradation by monoamine oxidase, resulting in increased potency and greatly lengthened half-life. This is analogous to α-methylation of phenethylamine into amphetamine.
Many α-alkyltryptamines are drugs, acting as monoamine releasing agents, non-selective serotonin receptor agonists, and/or monoamine oxidase inhibitors, and produce psychostimulant, entactogen, and/or psychedelic effects. The most well-known of these agents are α-methyltryptamine (αMT) and α-ethyltryptamine (αET), both of which were used clinically as antidepressants for a brief period of time in the past and are abused as recreational drugs. In accordance with its action as a dual releasing agent of serotonin and dopamine, αET has been found to produce serotonergic neurotoxicity similarly to amphetamines like MDMA and PCA, and the same is also likely to hold true for other serotonin and dopamine-releasing α-alkyltryptamines such as αMT, 5-MeO-αMT, and various others. | 0 | Theoretical and Fundamental Chemistry |
John Robert Huizenga was born on a farm near Fulton, Illinois, the son of Henry and Josie (Brands) Huizenga. He attended Erie High School and Morrison High School, graduating from the latter in 1940. He continued his education at Calvin College in Michigan, from which he received a bachelors degree in 1944. He would maintain his ties to Calvin later in life, for example collaborating on fundamental nuclear research with his Calvin friend Roger Griffioen, who had gone on to become a professor there. Calvin would name him one of the colleges Distinguished Alumni in 1975.
Along with other Calvin students, he was recruited after graduation to work for the Manhattan Project, at the Project's site in Oak Ridge, Tennessee, that was dedicated to the production of highly enriched uranium. Following his time in Oak Ridge, he continued his education at the University of Illinois, receiving a Doctor of Philosophy degree in physical chemistry in 1949. On completing his studies he held joint appointments at the University of Chicago and Argonne National Laboratory. | 0 | Theoretical and Fundamental Chemistry |
Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
Carbon isotopes are analysed in archaeology to determine the source of carbon at the base of the foodchain. Examining the C/C isotope ratio, it is possible to determine whether animals and humans ate predominantly C3 or C4 plants. Potential C3 food sources include wheat, rice, tubers, fruits, nuts and many vegetables, while C4 food sources include millet and sugar cane. Carbon isotope ratios can also be used to distinguish between marine, freshwater, and terrestrial food sources.
Carbon isotope ratios can be measured in bone collagen or bone mineral (hydroxylapatite), and each of these fractions of bone can be analysed to shed light on different components of diet. The carbon in bone collagen is predominantly sourced from dietary protein, while the carbon found in bone mineral is sourced from all consumed dietary carbon, included carbohydrates, lipids, and protein.
Nitrogen isotopes can be used to infer soil conditions, with enriched δ15N used to infer the addition of manure. A complication is that enrichment also occurs as a result of environmental factors, such as wetland denitrification, salinity, aridity, microbes, and clearance.
To obtain an accurate picture of palaeodiets, it is important to understand processes of diagenesis that may affect the original isotopic signal. It is also important for the researcher to know the variations of isotopes within individuals, between individuals, and over time. | 0 | Theoretical and Fundamental Chemistry |
The growth rate hypothesis, also known as the resource availability hypothesis, states that defense strategies are determined by the inherent growth rate of the plant, which is in turn determined by the resources available to the plant. A major assumption is that available resources are the limiting factor in determining the maximum growth rate of a plant species. This model predicts that the level of defense investment will increase as the potential of growth decreases. Additionally, plants in resource-poor areas, with inherently slow-growth rates, tend to have long-lived leaves and twigs, and the loss of plant appendages may result in a loss of scarce and valuable nutrients.
One test of this model involved a reciprocal transplants of seedlings of 20 species of trees between clay soils (nutrient rich) and white sand (nutrient poor) to determine whether trade-offs between growth rate and defenses restrict species to one habitat. When planted in white sand and protected from herbivores, seedlings originating from clay outgrew those originating from the nutrient-poor sand, but in the presence of herbivores the seedlings originating from white sand performed better, likely due to their higher levels of constitutive carbon-based defenses. These finding suggest that defensive strategies limit the habitats of some plants. | 1 | Applied and Interdisciplinary Chemistry |
Before the 1860s and 1870s—when Pasteur published his work on this theory—it was believed that microorganisms and even some small animals such as frogs would spontaneously generate. Spontaneous generation was historically explained in a variety of ways. Aristotle, an ancient Greek philosopher, theorized that creatures appeared out of certain concoctions of earthly elements, such as clay or mud mixing with water and sunlight. Later on, Felix Pouchet argued for the existence of plastic forces within plant and animal debris capable of spontaneously generating eggs, and new organisms were born from these eggs. On top of this, a common piece of evidence that seemed to corroborate the theory was the appearance of maggots on raw meat after it was left exposed to open air.
In the 1860s and 1870s, Pasteurs interest in spontaneous generation led him to criticize Pouchets theories and conduct experiments of his own. In his first experiment, he took boiled sugared yeast-water and sealed it in an airtight contraption. Feeding hot, sterile air into the mixture left it unaltered, while introducing atmospheric dust resulted in microbes and mold appearing within the mixture. This result was also strengthened by the fact that Pasteur used asbestos, a form of totally inorganic matter, to carry the atmospheric dust. In a second experiment, Pasteur used the same flasks and sugar-yeast mixture, but left it idle in swan-neck flasks instead of introducing any extraneous matter. Some flasks were kept open to the common air as the control group, and these exhibited mold and microbial growths within a day or two. When the swan-neck flasks failed to show these same microbial growths, Pasteur concluded that the structure of the necks blocked the passage of atmospheric dust into the solution. From the two experiments, Pasteur concluded that the atmospheric dust carried germs responsible for the spontaneous generation in his broths. Thus, Pasteur's work provided proof that the emergent growth of bacteria in nutrient broths is caused by biogenesis rather than some form of spontaneous generation. | 1 | Applied and Interdisciplinary Chemistry |
Martin Albrecht completed his undergraduate education at the University of Bern from 1991 to 1996. His early research career started in 1996 during his PhD studies under the supervision of Prof. Dr. Gerard van Koten at Utrecht University, in The Netherlands. He studied the formation and properties of novel inorganic materials using the privileged pincer ligand platform which led, for example, to discoveries such as organoplatinium complexes that appeared applicable as very sensitive SO sensors. In 2001, Martin Albrecht was awarded the Backer price from the Royal Dutch Chemical Society (KNCV) in recognition of his PhD thesis work. | 0 | Theoretical and Fundamental Chemistry |
In astrophysics, photodissociation is one of the major processes through which molecules are broken down (but new molecules are being formed). Because of the vacuum of the interstellar medium, molecules and free radicals can exist for a long time. Photodissociation is the main path by which molecules are broken down. Photodissociation rates are important in the study of the composition of interstellar clouds in which stars are formed.
Examples of photodissociation in the interstellar medium are ( is the energy of a single photon of frequency ): | 0 | Theoretical and Fundamental Chemistry |
The parent of this family of ligands is the amino acid glycine, HNCHCOOH, in which the amino group, NH, is separated from the carboxyl group, COOH by a single methylene group, CH. When the carboxyl group is deprotonated the glycinate ion can function as a bidentate ligand, binding the metal centre through the nitrogen and one of two carboxylate oxygen atoms, to form chelate complexes of metal ions.
Replacement of a hydrogen atom on the nitrogen of glycine by another acetate residue, –CHCOOH gives iminodiacetic acid, IDA, which is a tridentate ligand. Further substitution gives nitrilotriacetic acid, NTA, which is a tetradentate ligand. These compounds can be described as aminopolycarboxylates. Related ligands can be derived from other amino acids other than glycine, notably aspartic acid.
Higher density is achieved by linking two or more glycinate or IDA units together. EDTA contains two IDA units with the nitrogen atoms linked by two methylene groups and is hexadentate. DTPA has two CHCH bridges linking three nitrogen atoms and is octadentate. TTHA has ten potential donor atoms. | 0 | Theoretical and Fundamental Chemistry |
Lithium toxicity, also known as lithium overdose, is the condition of having too much lithium. Symptoms may include a tremor, increased reflexes, trouble walking, kidney problems, and an altered level of consciousness. Some symptoms may last for a year after levels return to normal. Complications may include serotonin syndrome.
Lithium toxicity can occur due to excessive intake or decreased excretion. Excessive intake may be either a suicide attempt or accidental. Decreased excretion may occur as a result of dehydration such as from vomiting or diarrhea, a low sodium diet, or from kidney problems. The diagnosis is generally based on symptoms and supported by a lithium level in blood serum of greater than 1.2 mEq/L.
Gastric lavage and whole bowel irrigation may be useful if done early. Activated charcoal is not effective. For severe toxicity hemodialysis is recommended. The risk of death is generally low. Acute toxicity generally has better outcomes than chronic toxicity. In the United States about 5,000 cases are reported to poison control centers a year. Lithium toxicity was first described in 1898. | 1 | Applied and Interdisciplinary Chemistry |
The model assumes that the oxidation reaction occurs at the interface between the oxide layer and the substrate material, rather than between the oxide and the ambient gas. Thus, it considers three phenomena that the oxidizing species undergoes, in this order:
# It diffuses from the bulk of the ambient gas to the surface.
# It diffuses through the existing oxide layer to the oxide-substrate interface.
# It reacts with the substrate.
The model assumes that each of these stages proceeds at a rate proportional to the oxidants concentration. In the first step, this means Henrys law; in the second, Fick's law of diffusion; in the third, a first-order reaction with respect to the oxidant. It also assumes steady state conditions, i.e. that transient effects do not appear. | 1 | Applied and Interdisciplinary Chemistry |
Directed-, chelation-assisted-, or "guided" C-H activation involves directing groups that influence regio- and stereochemistry. This is the most useful style of C-H activation in organic synthesis. N,N-dimethylbenzylamine undergoes cyclometalation readily by many transition metals. A semi-practical implementations involve weakly coordinating directing groups, as illustrated by the Murai reaction.
The mechanism for the Pd-catalyzed C-H activation reactions of 2-phenylpyridine involves a metallacycle intermediate. The intermediate is oxidized to form a Pd species, followed by reductive elimination to form the C-O bond and release the product. | 0 | Theoretical and Fundamental Chemistry |
Phenoxymethylpenicillin, also known as penicillin V (PcV) and penicillin VK, is an antibiotic useful for the treatment of a number of bacterial infections. Specifically it is used for the treatment of strep throat, otitis media, and cellulitis. It is also used to prevent rheumatic fever and to prevent infections following removal of the spleen. It is given by mouth.
Side effects include diarrhea, nausea, and allergic reactions including anaphylaxis. It is not recommended in those with a history of penicillin allergy. It is relatively safe for use during pregnancy. It is in the penicillin and beta lactam family of medications. It usually results in bacterial death.
Phenoxymethylpenicillin was first made in 1948 by Eli Lilly. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2021, it was the 256th most commonly prescribed medication in the United States, with more than 1million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
Petroleum, in one form or another, has been used since ancient times. More than 4300 years ago, bitumen was mentioned when the Sumerians used it to make boats. A tablet of the legend of the birth of Sargon of Akkad mentions a basket which was closed by straw and bitumen. More than 4000 years ago, according to Herodotus and Diodorus Siculus, asphalt was used in the construction of the walls and towers of Babylon; there were oil pits near Ardericca and Babylon, and a pitch spring on Zakynthos. Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society.
The use of petroleum in ancient China dates back to more than 2000 years ago. The I Ching, one of the earliest Chinese writings, cites that oil in its raw state, without refining, was first discovered, extracted, and used in China in the first century BCE. In addition, the Chinese were the first to record the use of petroleum as fuel as early as the fourth century BCE. By 347 CE, oil was produced from bamboo-drilled wells in China.
In the 7th century, petroleum was among the essential ingredients for Greek fire, an incendiary projectile weapon that was used by Byzantine Greeks against Arab ships, which were then attacking Constantinople. Crude oil was also distilled by Persian chemists, with clear descriptions given in Arabic handbooks such as those of Abu Bakr al-Razi (Rhazes). The streets of Baghdad were paved with tar, derived from petroleum that became accessible from natural fields in the region.
In the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan. These fields were described by the Arab geographer Abu Bakr al-Razi in the 10th century, and by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. Arab and Persian chemists also distilled crude oil to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century. It has also been present in Romania since the 13th century, being recorded as păcură.
Sophisticated oil pits, deep, were dug by the Seneca people and other Iroquois in Western Pennsylvania as early as 1415–1450. The French General Louis-Joseph de Montcalm encountered Seneca using petroleum for ceremonial fires and as a healing lotion during a visit to Fort Duquesne in 1750.
Early British explorers to Myanmar documented a flourishing oil extraction industry based in Yenangyaung that, in 1795, had hundreds of hand-dug wells under production.
Merkwiller-Pechelbronn is said to be the first European site where petroleum has been explored and used. The still active Erdpechquelle, a spring where petroleum appears mixed with water has been used since 1498, notably for medical purposes. | 0 | Theoretical and Fundamental Chemistry |
Pyocyanase was the first antibiotic drug to be used in hospitals. It is no longer used today.
Rudolph Emmerich and Oscar Löw, two German physicians who were the first to make an effective medication from microbes, conducted experiments in the 1890s, roughly 30 years after Louis Pasteur showed that many diseases were caused by bacteria and nearly 40 years before the effective prescription of penicillin. They proved that the germs that caused one disease may be the cure for another.
Emmerich and Löw isolated germs from infected bandages that caused green infections in open wounds. The germ was a bacterium then called Bacillus pyocyaneus (now called Pseudomonas aeruginosa, it produces pyocyanin, a characteristic green-blue phenazine pigment). They then mixed the isolate with other bacteria and showed that B. pyocyaneus and extracts from its cultures were able to destroy other strains of bacteria. Among the bacteria that it killed were those that caused cholera, typhoid, diphtheria, and anthrax.
From these experiments Emmerich and Löw created a medication based on extracts of B. pyocyaneus that they called pyocyanase. It was the first antibiotic to be used in hospitals. Unfortunately, its effectiveness was sporadic, did not work equally on all patients, and the presence of large amounts of phenazines such as pyocyanin made it quite toxic to humans. As a result, the drug was eventually abandoned. | 1 | Applied and Interdisciplinary Chemistry |
Crystallization requires an initiation step. This can be spontaneous or can be done by adding a small amount of the pure compound (a seed crystal) to the saturated solution, or can be done by simply scratching the glass surface to create a seeding surface for crystal growth. It is thought that even dust particles can act as simple seeds. | 0 | Theoretical and Fundamental Chemistry |
Single-cell genomics is heavily dependent on increasing the copies of DNA found in the cell so there is enough to be sequenced. This has led to the development of strategies for whole genome amplification (WGA). Currently WGA strategies can be grouped into three categories:
* Controlled priming and PCR Amplification: Adapter-Linker PCR WGA
* Random priming and PCR Amplification: DOP-PCR, MALBAC
* Random priming and isothermal amplification: MDA
The Adapter Linker PCR WGA is reported in many comparative studies to be best performing for diploid single cell mutation analysis, thanks to its very low Allelic Dropout effect, and for copy number variation profiling due to its low noise, both with aCGH and with NGS low Pass Sequencing. This method is only applicable to human cells, both fixed and unfixed.
One widely adopted WGA techniques is called degenerate oligonucleotide–primed polymerase chain reaction (DOP-PCR). This method uses the well established DNA amplification method PCR to try and amplify the entire genome using a large set of primers. Although simple, this method has been shown to have very low genome coverage. An improvement on DOP-PCR is Multiple displacement amplification (MDA), which uses random primers and a high fidelity enzyme, usually Φ29 DNA polymerase, to accomplish the amplification of larger fragments and greater genome coverage than DOP-PCR. Despite these improvement MDA still has a sequence dependent bias (certain parts of the genome are amplified more than others because of their sequence). The method shown to largely avoid the bias seen in DOP-PCR and MDA is Multiple Annealing and Looping–Based Amplification Cycles (MALBAC). Bias in this system is reduced by only copying off the original DNA strand instead of making copies of copies. The main draw backs to using MALBA, is it has reduced accuracy compared to DOP-PCR and MDA due to the enzyme used to copy the DNA. Once amplified using any of the above techniques, the DNA can be sequenced using Sanger or next-generation sequencing (NGS). | 1 | Applied and Interdisciplinary Chemistry |
After production in the upper atmosphere, the carbon-14 atoms react rapidly to form mostly (about 93%) (carbon monoxide), which subsequently oxidizes at a slower rate to form , radioactive carbon dioxide. The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale in the order of weeks). Carbon dioxide also dissolves in water and thus permeates the oceans, but at a slower rate. The atmospheric half-life for removal of has been estimated to be roughly 12 to 16 years in the northern hemisphere. The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate.
In 2009 the activity of was 238 Bq per kg carbon of fresh terrestrial biomatter, close to the values before atmospheric nuclear testing (226 Bq/kg C; 1950). | 0 | Theoretical and Fundamental Chemistry |
A variety of organisms including bacteria, fungi, and plants, produce small molecule secondary metabolites also known as natural products, which play a role in cell signaling, pigmentation and in defense against predation. Secondary metabolites are a rich source of biologically active compounds and hence are often used as research tools and leads for drug discovery. Examples of secondary metabolites include:
* Alkaloids
* Glycosides
* Lipids
* Nonribosomal peptides, such as actinomycin-D
* Phenazines
* Natural phenols (including flavonoids)
* Polyketide
* Terpenes and terpenoids, including steroids
* Tetrapyrroles. | 1 | Applied and Interdisciplinary Chemistry |
Oligosaccharides and polysaccharides are an important class of polymeric carbohydrates found in virtually all living entities. Their structural features make their nomenclature challenging and their roles in living systems make their nomenclature important. | 0 | Theoretical and Fundamental Chemistry |
The C sulfonates DHPS and SL are metabolized for their carbon content, as well as to mineralize their sulfur content. Metabolism of DHPS typically involves conversion to SL. Metabolism of SL can occur in several ways including:
* elimination of sulfite to afford pyruvate;
* oxidation to sulfopyruvate, transamination to cysteate, and elimination of sulfite to afford pyruvate and ammonia;
* oxidation to sulfopyruvate, decarboxylation to sulfoacetaldehyde, and phosphorylation to afford acetylphosphate and sulfite. | 1 | Applied and Interdisciplinary Chemistry |
For the analysis of volatile compounds, a purge and trap (P&T) concentrator system may be used to introduce samples. The target analytes are extracted by mixing the sample with water and purge with inert gas (e.g. Nitrogen gas) into an airtight chamber, this is known as purging or sparging. The volatile compounds move into the headspace above the water and are drawn along a pressure gradient (caused by the introduction of the purge gas) out of the chamber. The volatile compounds are drawn along a heated line onto a trap. The trap is a column of adsorbent material at ambient temperature that holds the compounds by returning them to the liquid phase. The trap is then heated and the sample compounds are introduced to the GC–MS column via a volatiles interface, which is a split inlet system. P&T GC–MS is particularly suited to volatile organic compounds (VOCs) and BTEX compounds (aromatic compounds associated with petroleum).
A faster alternative is the "purge-closed loop" system. In this system the inert gas is bubbled through the water until the concentrations of organic compounds in the vapor phase are at equilibrium with concentrations in the aqueous phase. The gas phase is then analysed directly. | 0 | Theoretical and Fundamental Chemistry |
PHLPP1 and 2 also dephosphorylate the hydrophobic motifs of two classes of the protein kinase C (PKC) family: the conventional PKCs and the novel PKCs. (The third class of PKCs, known as the atypicals, have a phospho-mimetic at the hydrophobic motif, rendering them insensitive to PHLPP.)
The PKC family of kinases consists of 10 isoforms, whose sensitivity to various second messengers is dictated by their domain structure. The conventional PKCs can be activated by calcium and diacylglycerol, two important mediators of G protein-coupled receptor signaling. The novel PKCs are activated by diacylglycerol but not calcium, while the atypical PKCs are activated by neither.
The PKC family, like Akt, plays roles in cell survival and motility. Most PKC isoforms are anti-apoptotic, although PKCδ (a novel PKC isoform) is pro-apoptotic in some systems.
Although PKC possesses the same phosphorylation sites as Akt, its regulation is quite different. PKC is constitutively phosphorylated, and its acute activity is regulated by binding of the enzyme to membranes. Dephosphorylation of PKC at the hydrophobic motif by PHLPP allows PKC to be dephosphorylated at two other sites (the activation loop and the turn motif). This in turn renders PKC sensitive to degradation. Thus, prolonged increases in PHLPP expression or activity inhibit PKC phosphorylation and stability, decreasing the total levels of PKC over time. | 1 | Applied and Interdisciplinary Chemistry |
The anion is abbreviated PP, standing for inorganic pyrophosphate. It is formed by the hydrolysis of ATP into AMP in cells.
:ATP → AMP + PP
For example, when a nucleotide is incorporated into a growing DNA or RNA strand by a polymerase, pyrophosphate (PP) is released. Pyrophosphorolysis is the reverse of the polymerization reaction in which pyrophosphate reacts with the 3′-nucleosidemonophosphate (NMP or dNMP), which is removed from the oligonucleotide to release the corresponding triphosphate (dNTP from DNA, or NTP from RNA).
The pyrophosphate anion has the structure , and is an acid anhydride of phosphate. It is unstable in aqueous solution and hydrolyzes into inorganic phosphate:
or in biologists' shorthand notation:
In the absence of enzymic catalysis, hydrolysis reactions of simple polyphosphates such as pyrophosphate, linear triphosphate, ADP, and ATP normally proceed extremely slowly in all but highly acidic media.
(The reverse of this reaction is a method of preparing pyrophosphates by heating phosphates.)
This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PP irreversible, and biochemical reactions coupled to this hydrolysis are irreversible as well.
PP occurs in synovial fluid, blood plasma, and urine at levels sufficient to block calcification and may be a natural inhibitor of hydroxyapatite formation in extracellular fluid (ECF). Cells may channel intracellular PP into ECF. ANK is a nonenzymatic plasma-membrane PP channel that supports extracellular PP levels. Defective function of the membrane PP channel ANK is associated with low extracellular PP and elevated intracellular PP. Ectonucleotide pyrophosphatase/phosphodiesterase (ENPP) may function to raise extracellular PP.
From the standpoint of high energy phosphate accounting, the hydrolysis of ATP to AMP and PP requires two high-energy phosphates, as to reconstitute AMP into ATP requires two phosphorylation reactions.
:AMP + ATP → 2 ADP
:2 ADP + 2 P → 2 ATP
The plasma concentration of inorganic pyrophosphate has a reference range of 0.58–3.78 µM (95% prediction interval). | 1 | Applied and Interdisciplinary Chemistry |
* 2000 Outstanding Graduate Research Award from the Wirt and Mary Cornell Prize
* 2003 American Chemical Society (PMSE Division), Arthur K. Doolittle Award
* 2007 YWCA Rising Star
* 2007 OH Bioscience Thirty in Their 30s Award
* 2012 American Society of Gene and Cell Therapy Outstanding New Investigator Award
* 2012 American Chemical Society, Polymer Materials: Science and Engineering Division Macro 2012 Lecture Award
* 2016 American Institute for Medical and Biological Engineering Fellow
* 2016 University of Minnesota Sara Evans Faculty Woman Scholar/Leader Award
* 2016 University of Minnesota George W. Taylor Award for Distinguished Research
* 2017 American Chemical Society Polymer Chemistry Division Carl S. Marvel Creative Polymer Chemistry Award
* 2018 Danisco Foundation DuPont Nutrition and Health Science Excellence Medal
* 2018 American Chemical Society POLY Fellow Award
* 2018 Big 10 Alliance Academic Leadership Program Fellow | 1 | Applied and Interdisciplinary Chemistry |
When a swimmer enters a pool, they add up to one billion organisms to the water. Chlorination kills all organisms harmful to swimmers such as those that cause ear infections and athlete's foot. The advantages of electrochlorination in this process are as follows:
*Not irritating to skin or soft tissue.
*Active in small concentrations.
*Longer lifespan of chemical and therefore less replacement necessary.
*Easily measurable. | 0 | Theoretical and Fundamental Chemistry |
A number of organisms, instead of using inorganic compounds as terminal electron acceptors, are able to use organic compounds to accept electrons from respiration. Examples include:
* Fumarate reduction to succinate
* Trimethylamine N-oxide (TMAO) reduction to trimethylamine (TMA)
* Dimethyl sulfoxide (DMSO) reduction to Dimethyl sulfide (DMS)
* Reductive dechlorination
TMAO is a chemical commonly produced by fish, and when reduced to TMA produces a strong odor. DMSO is a common marine and freshwater chemical which is also odiferous when reduced to DMS. Reductive dechlorination is the process by which chlorinated organic compounds are reduced to form their non-chlorinated endproducts. As chlorinated organic compounds are often important (and difficult to degrade) environmental pollutants, reductive dechlorination is an important process in bioremediation. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, SNP array is a type of DNA microarray which is used to detect polymorphisms within a population. A single nucleotide polymorphism (SNP), a variation at a single site in DNA, is the most frequent type of variation in the genome. Around 335 million SNPs have been identified in the human genome, 15 million of which are present at frequencies of 1% or higher across different populations worldwide. | 1 | Applied and Interdisciplinary Chemistry |
Like other iron oxalates, ferrous oxalates feature octahedral Fe centers. The dihydrate FeCO(HO) is a coordination polymer, consisting of chains of oxalate-bridged ferrous centers, each with two aquo ligands.<br />
When heated to 120 °C, the dihydrate dehydrates, and the anhydrous ferrous oxalate decomposes near 190 °C. The products of thermal decomposition is a mixture of iron oxides and pyrophoric iron metal, as well as released carbon dioxide, carbon monoxide, and water.
Ferrous oxalates are precursors to iron phosphates, which are of value in batteries. | 0 | Theoretical and Fundamental Chemistry |
The separation of uranium requires the material in a gaseous form; uranium hexafluoride (UF) is used for uranium enrichment. Upon entering the centrifuge cylinder, the UF gas is rotated at a high speed. The rotation creates a strong centrifugal force that draws more of the heavier gas molecules (containing the U-238) toward the wall of the cylinder, while the lighter gas molecules (containing the U-235) tend to collect closer to the center. The stream that is slightly enriched in U-235 is withdrawn and fed into the next higher stage, while the slightly depleted stream is recycled back into the next lower stage. | 0 | Theoretical and Fundamental Chemistry |
The pattern of fluoride release from glass ionomer cement is characterised by an initial rapid release of appreciable amounts of fluoride, followed by a taper in the release rate over time. An initial fluoride “burst” effect is desirable to reduce the viability of remaining bacteria in the inner carious dentin, hence, inducing enamel or dentin remineralization. The constant fluoride release during the following days are attributed to the fluoride ability to diffuse through cement pores and fractures. Thus, continuous small amounts of fluoride surrounding the teeth reduces demineralization of the tooth tissues. A study by Chau et al. shows a negative correlation between acidogenicity of the biofilm and the fluoride release by GIC, suggestive that enough fluoride release may decrease the virulence of cariogenic biofilms. In addition, Ngo et al. (2006) studied the interaction between demineralised dentine and Fuji IX GP which includes a strontium – containing glass as opposed to the more conventional calcium-based glass in other GICs. A substantial amount of both strontium and fluoride ions was found to cross the interface into the partially demineralised dentine affected by caries. This promoted mineral depositions in these areas where calcium ion levels were low. Hence, this study supports the idea of glass ionomers contributing directly to remineralisation of carious dentine, provided that good seal is achieved with intimate contact between the GIC and partly demineralised dentine. This, then raises a question, “Is glass ionomer cement a suitable material for permanent restorations?” due to the desirable effects of fluoride release by glass ionomer cement. | 0 | Theoretical and Fundamental Chemistry |
The National Institutes of Health announced on 27 February 2015 the commencement of a randomized controlled trial of ZMapp to be conducted in Liberia and the United States. From March 2015 through November 2015, 72 individuals infected with the Ebola virus were enrolled in the trial; investigators stopped enrolling new subjects in January 2016, having failed to reach its enrollment goal of 200 due to the waning of the Ebola outbreak. As a result, although a 40% lower risk of death was calculated for those who received ZMapp, the difference was not statistically significant and ultimately it could not be determined whether the use of ZMapp was superior to the optimized standard of care alone. However, ZMapp was found to be safe and well tolerated. | 1 | Applied and Interdisciplinary Chemistry |
The Human Tissue (Scotland) Act 2006 (asp 4) is an Act of the Scottish Parliament to consolidate and overhaul previous legislation regarding the handling of human tissue.
It deals with three distinct uses of human tissue: its donation primarily for the purpose of transplantation, but also for research, education or training and audit; its removal, retention and use following a post-mortem examination; and for the purposes of the Anatomy Act 1984 as amended for Scotland by the 2006 Act.
Its counterpart in the rest of the United Kingdom is the Human Tissue Act 2004. | 1 | Applied and Interdisciplinary Chemistry |
RDRP – sometimes misleadingly called free radical polymerization – is one of the most widely used polymerization processes since it can be applied
*to a great variety of monomers
*it can be carried out in the presence of certain functional groups
*the technique is rather simple and easy to control
*the reaction conditions can vary from bulk over solution, emulsion, miniemulsion to suspension
*it is relatively inexpensive compared with competitive techniques
The steady-state concentration of the growing polymer chains is 10 M by order of magnitude, and the average life time of an individual polymer radical before termination is about 5–10 s. A drawback of the conventional radical polymerization is the limited control of chain architecture, molecular weight distribution, and composition. In the late 20th century it was observed that when certain components were added to systems polymerizing by a chain mechanism they are able to react reversibly with the (radical) chain carriers, putting them temporarily into a dormant state.
This had the effect of prolonging the lifetime of the growing polymer chains (see above) to values comparable with the duration of the experiment. At any instant most of the radicals are in the inactive (dormant) state, however, they are not irreversibly terminated (‘dead’). Only a small fraction of them are active (growing), yet with a fast rate of interconversion of active and dormant forms, faster than the growth rate, the same probability of growth is ensured for all chains, i.e., on average, all chains are growing at the same rate. Consequently, rather than a most probable distribution, the molecular masses (degrees of polymerization) assume a much narrower Poisson distribution, and a lower dispersity prevails.
IUPAC also recognizes the alternative name, ‘controlled reversible-deactivation radical polymerization’ as acceptable, "provided the controlled context is specified, which in this instance comprises molecular mass and molecular mass distribution." These types of radical polymerizations are not necessarily ‘living’ polymerizations, since chain termination reactions are not precluded".
The adjective ‘controlled’ indicates that a certain kinetic feature of a polymerization or structural aspect of the polymer molecules formed is controlled (or both). The expression ‘controlled polymerization’ is sometimes used to describe a radical or ionic polymerization in which reversible-deactivation of the chain carriers is an essential component of the mechanism and interrupts the propagation that secures control of one or more kinetic features of the polymerization or one or more structural aspects of the macromolecules formed, or both. The expression ‘controlled radical polymerization’ is sometimes used to describe a radical polymerization that is conducted in the presence of agents that lead to e.g. atom-transfer radical polymerization (ATRP), nitroxide-(aminoxyl) mediated polymerization (NMP), or reversible-addition-fragmentation chain transfer (RAFT) polymerization. All these and further controlled polymerizations are included in the class of reversible-deactivation radical polymerizations. Whenever the adjective ‘controlled’ is used in this context the particular kinetic or the structural features that are controlled have to be specified. | 0 | Theoretical and Fundamental Chemistry |
Unit conversion is a notorious source of errors. Many people apply individual rules, e.g. "to obtain length in centimeters multiply the length in inches by 2.54", but combining several such conversions is laborious and prone to mistakes. A better way is to use the factor-label method, which is closely related to dimensional analysis, and quantity calculus explained in sections 1.1 and 7.1 of this compilation. | 0 | Theoretical and Fundamental Chemistry |
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