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His parents emigrated from Switzerland to the United States, where Nef studied chemistry at Harvard University until 1884. Upon graduation, he joined Adolf von Baeyer at the University of Munich, where he received his Ph.D. in 1887.
He was a professor at Purdue University from 1887 till 1889 and at Clark University from 1889 till 1892. In 1892 Nef joined the newly formed University of Chicago as professor of chemistry, where he spent the rest of his academic career.
His son John Ulric Nef (1899–1988) became a professor of economic history and published several books. | 0 | Organic Chemistry |
The second variant of the method construct the approximations to the Green's operator
now with vectors
The chain fraction for T-matrix now also holds, with little bit different definition of coefficients . | 7 | Physical Chemistry |
Cathleen M. Crudden is a Canadian chemist. She is a Canada Research Chair in Metal Organic Chemistry at Queen's University at Kingston. In February 2021, she took up the role of Editor-in-chief at ACS Catalysis. | 0 | Organic Chemistry |
Molecular imprinting is a technique to create template-shaped cavities in polymer matrices with predetermined selectivity and high affinity. This technique is based on the system used by enzymes for substrate recognition, which is called the "lock and key" model. The active binding site of an enzyme has a shape specific to a substrate. Substrates with a complementary shape to the binding site selectively bind to the enzyme; alternative shapes that do not fit the binding site are not recognized.
Molecularly imprinted materials are prepared using a template molecule and functional monomers that assemble around the template and subsequently get cross-linked to each other. The monomers, which are self-assembled around the template molecule by interaction between functional groups on both the template and monomers, are polymerized to form an imprinted matrix (commonly known in the scientific community as a molecular imprinted polymer (MIP)). The template is subsequently removed in part or entirely, leaving behind a cavity complementary in size and shape to the template. The obtained cavity can work as a selective binding site for the templated molecule.
In recent decades, the molecular imprinting technique has been developed for use in drug delivery, separations, biological and chemical sensing, and more. Taking advantage of the shape selectivity of the cavity, use in catalysis for certain reactions has also been facilitated. | 6 | Supramolecular Chemistry |
A world effort was triggered in the 1960s to study magnetohydrodynamic converters in order to bring MHD power conversion to market with commercial power plants of a new kind, converting the kinetic energy of a high velocity plasma into electricity with no moving parts at a high efficiency. Research was also conducted in the field of supersonic and hypersonic aerodynamics to study plasma interaction with magnetic fields to eventually achieve passive and even active flow control around vehicles or projectiles, in order to soften and mitigate shock waves, lower thermal transfer and reduce drag.
Such ionized gases used in "plasma technology" ("technological" or "engineered" plasmas) are usually weakly ionized gases in the sense that only a tiny fraction of the gas molecules are ionized. These kinds of weakly ionized gases are also nonthermal "cold" plasmas. In the presence of magnetics fields, the study of such magnetized nonthermal weakly ionized gases involves resistive magnetohydrodynamics with low magnetic Reynolds number, a challenging field of plasma physics where calculations require dyadic tensors in a 7-dimensional phase space. When used in combination with a high Hall parameter, a critical value triggers the problematic electrothermal instability which limited these technological developments. | 7 | Physical Chemistry |
Triazabicyclodecene (1,5,7-triazabicyclo[4.4.0]dec-5-ene or TBD) is an organic compound consisting of a bicyclic guanidine. For a charge-neutral compound, it is a relatively strong base that is effective for a variety of organic transformations. TBD is colorless solid that is soluble in a variety of solvents. | 0 | Organic Chemistry |
The Dimetcote patent was approved in 1948 by the U.S. Patent Office. The owner of the patent is PPG Industries. Dimetcote, which was created to protect the surface of metal, could be coloured by being mixed with other paints. | 8 | Metallurgy |
Galvanization or galvanizing (also spelled galvanisation or galvanising) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are coated by submerging them in a bath of hot, molten zinc. | 8 | Metallurgy |
The information on this page is partially translated from the equivalent page in French :fr:Alain Berton (Chimiste) licensed under the Creative Commons/Attribution Sharealike [https://creativecommons.org/licenses/by-sa/3.0/]. History of contributions can be checked here:[https://fr.wikipedia.org/w/index.php?title=Alain_Berton_%28chimiste%29&action=history] | 3 | Analytical Chemistry |
XPS is widely used to generate an empirical formula because it readily yields excellent quantitative accuracy from homogeneous solid-state materials. Absolute quantification requires the use of certified (or independently verified) standard samples, and is generally more challenging, and less common. Relative quantification involves comparisons between several samples in a set for which one or more analytes are varied while all other components (the sample matrix) are held constant. Quantitative accuracy depends on several parameters such as: signal-to-noise ratio, peak intensity, accuracy of relative sensitivity factors, correction for electron transmission function, surface volume homogeneity, correction for energy dependence of electron mean free path, and degree of sample degradation due to analysis. Under optimal conditions, the quantitative accuracy of the atomic percent (at%) values calculated from the major XPS peaks is 90-95% for each peak. The quantitative accuracy for the weaker XPS signals, that have peak intensities 10-20% of the strongest signal, are 60-80% of the true value, and depend upon the amount of effort used to improve the signal-to-noise ratio (for example by signal averaging). Quantitative precision (the ability to repeat a measurement and obtain the same result) is an essential consideration for proper reporting of quantitative results. | 7 | Physical Chemistry |
The Romans were already familiar with the ability of a prism to generate a rainbow of colors. Newton is traditionally regarded as the founder of spectroscopy, but he was not the first scientist who studied and reported on the solar spectrum. The works of Athanasius Kircher (1646), Jan Marek Marci (1648), Robert Boyle (1664), and Francesco Maria Grimaldi (1665), predate Newtons optics experiments (1666–1672). Newton published his experiments and theoretical explanations of dispersion of light in his Opticks. His experiments demonstrated that white light could be split up into component colors by means of a prism and that these components could be recombined to generate white light. He demonstrated that the prism is not imparting or creating the colors but rather separating constituent parts of the white light. Newtons corpuscular theory of light was gradually succeeded by the wave theory. It was not until the 19th century that the quantitative measurement of dispersed light was recognized and standardized. As with many subsequent spectroscopy experiments, Newton's sources of white light included flames and stars, including the Sun. Subsequent studies of the nature of light include those of Hooke, Huygens, Young. Subsequent experiments with prisms provided the first indications that spectra were associated uniquely with chemical constituents. Scientists observed the emission of distinct patterns of colour when salts were added to alcohol flames. | 7 | Physical Chemistry |
Glycans can be found attached to proteins as in glycoproteins and proteoglycans. In general, they are found on the exterior surface of cells. O- and N-linked glycans are very common in eukaryotes but may also be found, although less commonly, in prokaryotes. | 0 | Organic Chemistry |
Chayen earned her first degree in pharmacy at the Hebrew University of Jerusalem. During her undergraduate studies, she visited the Kennedy Institute of Rheumatology to learn histochemistry. She subsequently pursued MSc and PhD research at the Kennedy Institute. In 1983, Chayen submitted her thesis on stimulus-response coupling in smooth muscle cells and received a PhD from Brunel University London.
Chayen began her first postdoctoral fellowship at Imperial College London, where she studied the biophysics of muscle proteins. When her grant was not renewed, she joined the lab of David Mervyn Blow to develop novel protein crystallization techniques. There, she began her influential work of utilizing phase diagrams to optimize conditions for crystal growth.
Currently, Chayen is a professor of Biomedical Sciences and head of the Crystallization Group in Computational and Systems Medicine at Imperial College London. | 1 | Biochemistry |
Oligomer Restriction (abbreviated OR) is a procedure to detect an altered DNA sequence in a genome. A labeled oligonucleotide probe is hybridized to a target DNA, and then treated with a restriction enzyme. If the probe exactly matches the target, the restriction enzyme will cleave the probe, changing its size. If, however, the target DNA does not exactly match the probe, the restriction enzyme will have no effect on the length of the probe. The OR technique, now rarely performed, was closely associated with the development of the popular polymerase chain reaction (PCR) method. | 1 | Biochemistry |
systems are important building blocks in supramolecular assembly because of their versatile noncovalent interactions with various functional groups. Particularly, , and interactions are widely used in supramolecular assembly and recognition.
concerns the direct interactions between two -systems; and interaction arises from the electrostatic interaction of a cation with the face of the -system. Unlike these two interactions, the interaction arises mainly from charge transfer between the C–H orbital and the -system. | 6 | Supramolecular Chemistry |
The lacUV5 promoter is a mutated promoter from the Escherichia coli lac operon which is used in molecular biology to drive gene expression on a plasmid. lacUV5 is very similar to the classical lac promoter, containing just 2 base pair mutations in the -10 hexamer region, compared to the lac promoter. LacUV5 is among the most commonly used promoters in molecular biology because it requires no additional activators and it drives high levels of gene expression.
The lacUV5 promoter sequence conforms more closely to the consensus sequence recognized by bacterial sigma factors than the traditional lac promoter does. Due to this, lacUV5 recruits RNA Polymerase more effectively, thus leading to higher transcription of target genes. Additionally, unlike the lac promoter, lacUV5 works independently of activator proteins or other cis regulatory elements (apart from the -10 and -35 promoter regions). While no activators are required, lacUV5 promoter expression can be regulated by the LacI repressor and can be induced with IPTG, which is an effective inducer of protein expression when used in the concentration range of 100 μM to 1.5 mM. Due to this control, the lacUV5 promoter is commonly found on expression plasmids and is used when controllable but high levels of a product are desired.
The lacUV5 mutation was first identified in 1970 in a study of lac promoter mutants that produce higher yields. Some of them, including UV5, has lost catabolite repression at the CAP site. Development into cloning vectors is known since 1982, when a UV5-carrying phage known as "λ h80 lacUV5 cI857" has its genome spliced with the HaeIII restriction enzyme to make plasmids carrying the fragment with UV5. | 1 | Biochemistry |
Colonies of lichens may be spectacular in appearance, dominating the surface of the visual landscape as part of the aesthetic appeal to visitors of Yosemite National Park, Sequoia National Park, and the Bay of Fires. Orange and yellow lichens add to the ambience of desert trees, tundras, and rocky seashores. Intricate webs of lichens hanging from tree branches add a mysterious aspect to forests. Fruticose lichens are used in model railroading and other modeling hobbies as a material for making miniature trees and shrubs. | 2 | Environmental Chemistry |
While such diagrams can be drawn for any chemical system, it is important to note that the addition of a metal binding agent (ligand) will often modify the diagram. For instance, carbonate () has a great effect upon the diagram for uranium. (See diagrams at right). The presence of trace amounts of certain species such as chloride ions can also greatly affect the stability of certain species by destroying passivating layers. | 7 | Physical Chemistry |
An action potential occurs when the membrane potential of a specific cell rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells.
In neurons, action potentials play a central role in cell–cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin. Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials generated by a neuron is called its "spike train". A neuron that emits an action potential, or nerve impulse, is often said to "fire".
Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane. These channels are shut when the membrane potential is near the (negative) resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold voltage, depolarising the transmembrane potential. When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential towards zero. This then causes more channels to open, producing a greater electric current across the cell membrane and so on. The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential. The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, and the ion channels then rapidly inactivate. As the sodium channels close, sodium ions can no longer enter the neuron, and they are then actively transported back out of the plasma membrane. Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization.
In animal cells, there are two primary types of action potentials. One type is generated by voltage-gated sodium channels, the other by voltage-gated calcium channels. Sodium-based action potentials usually last for under one millisecond, but calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which then produces muscle contraction. | 7 | Physical Chemistry |
Some humans produce flatus that contains methane. In one study of the feces of nine adults, five of the samples contained archaea capable of producing methane. Similar results are found in samples of gas obtained from within the rectum.
Even among humans whose flatus does contain methane, the amount is in the range of 10% or less of the total amount of gas. | 1 | Biochemistry |
Anti-nuclear ribonucleoprotein (anti-nRNP) antibodies, also known as anti-U1-RNP antibodies, are found in 30–40% of SLE. They are often found with anti-Sm antibodies, but they may be associated with different clinical associations. In addition to SLE, these antibodies are highly associated with mixed connective tissue disease. Anti-nRNP antibodies recognise the A and C core units of the snRNPs and because of this they primarily bind to the U1-snRNP. The immune response to RNP may be caused by the presentation of the nuclear components on the cell membrane in apoptotic blebs. Molecular mimicry has also been suggested as a possible mechanism for the production of antibodies to these proteins because of similarity between U1-RNP polypeptides and Epstein-Barr virus polypeptides. | 1 | Biochemistry |
1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC, EDAC or EDCI) is a water-soluble carbodiimide usually handled as the hydrochloride.
It is typically employed in the 4.0-6.0 pH range. It is generally used as a carboxyl activating agent for the coupling of primary amines to yield amide bonds. While other carbodiimides like dicyclohexylcarbodiimide (DCC) or diisopropylcarbodiimide (DIC) are also employed for this purpose, EDC has the advantage that the urea byproduct formed (often challenging to remove in the case of DCC or DIC) can be washed away from the amide product using dilute acid. Additionally, EDC can also be used to activate phosphate groups in order to form phosphomonoesters and phosphodiesters. Common uses for this carbodiimide include peptide synthesis, protein crosslinking to nucleic acids, but also in the preparation of immunoconjugates. EDC is often used in combination with N-hydroxysuccinimide (NHS) for the immobilisation of large biomolecules. Recent work has also used EDC to assess the structure state of uracil nucleobases in RNA. | 1 | Biochemistry |
Walter Hieber prepared the first metal carbonyl hydride in 1931 by the so-called Hieber base reaction of metal carbonyls. In this reaction a hydroxide ion reacts with the carbon monoxide ligand of a metal carbonyl such as iron pentacarbonyl in a nucleophilic attack to form a metallacarboxylic acid. This intermedia releases of carbon dioxide in a second step, giving the iron tetracarbonyl hydride anion. The synthesis of cobalt tetracarbonyl hydride (HCo(CO)) proceeds in the same way.
:Fe(CO) + NaOH → Na[Fe(CO)COH]
:Na[Fe(CO)COH] → Na[HFe(CO)] + CO
A further synthetic route is the reaction of the metal carbonyl with hydrogen. The protonation of metal carbonyl anions, e.g. [Co(CO)], leads also to the formation of metal carbonyl hydrides. | 0 | Organic Chemistry |
Ethyl 3-bromopropionate is the organobromine compound with the formula BrCHCHCOCH. It is a colorless liquid and an alkylating agent. It is prepared by the esterification of 3-bromopropionic acid. Alternatively, it can be prepared by hydrobromination of ethyl acrylate, a reaction that proceeds in an anti-Markovnikov sense. | 0 | Organic Chemistry |
Proteorhodopsin (PR or pRhodopsin) was first discovered in 2000 within a bacterial artificial chromosome from previously uncultivated marine Gammaproteobacteria, still only referred to by their ribotype metagenomic data, SAR86. More species of Gammaproteobacteria, both Gram-positive and Gram-negative, were found to express the protein. | 5 | Photochemistry |
In 1991, Yamamoto disclosed the first catalytic enantioselective method for carbonyl allylation, which employed a chiral boron Lewis acid-catalyst in combination with allyltrimethylsilane. Numerous other catalytic enantioselective methods for carbonyl allylation followed. Catalytic variants of the Nozaki-Hiyama-Kishi reaction represent an alternative method for asymmetric carbonyl allylation, but stoichiometric metallic reductants are required.
Whereas the aforementioned asymmetric carbonyl allylations rely on preformed allylmetal reagents, the Krische allylation exploits allyl acetate for enantioselective carbonyl allylation. Selected methods for asymmetric carbonyl allylation are summarized below. | 0 | Organic Chemistry |
In 2020, the FDA granted orphan drug designation deulinoleate ethyl for the treatment of patients with progressive supranuclear palsy (PSP). PSP is a disease involving modification and dysfunction of tau protein; mechanism of action of deulinoleate ethyl both lowers lipid peroxidation and prevents mitochondrial cell death of neurons which is associated with disease onset and progression. | 1 | Biochemistry |
*President-Royal Australian Chemical Institute (Queensland Division)
*Chair, International Relations Committee of RACI
*Member, National Committee for Chemistry
*Executive Secretary, World Chemistry Congress/IUPAC General Assembly (2001)
*Chair, Board of Australian Science Innovations
*Organiser, Chemistry-Biotechnology Symposium at World Chemistry Congress (Torino, 2007); 27th International Symposium on the Chemistry of Natural Products (Brisbane, 2011)
*Organiser, Women sharing a Chemical Moment in Time, International Year of Chemistry (2011)
*Leadership roles in Division III (organic and biomolecular) of International Union of Pure and Applied Chemistry (IUPAC) as Titular Member (2006-2007), Secretary (2008-2011), President-elect (2012–2013), Division President and Bureau Member (2014–2015), then as Past-President (2016-2017)
*Elected to Membership of the Bureau of the International Union of Pure and Applied Chemistry (2018-2021)
*Co-chair IUPAC100 (centennial) Management Committee (2016-2019)
*Co-convenor of Women's Global Breakfast networking event held in over 100 countries since 2019; the theme for the 2024 breakfast event on February 27 is "Catalyzing Change in Chemistry"
*Incoming Vice-President/President-elect, and Chair of the Science Board, of the International Union of Pure and Applied Chemistry for 2024-2025 | 0 | Organic Chemistry |
Electron spectroscopy refers to a group formed by techniques based on the analysis of the energies of emitted electrons such as photoelectrons and Auger electrons. This group includes X-ray photoelectron spectroscopy (XPS), which also known as Electron Spectroscopy for Chemical Analysis (ESCA), Electron energy loss spectroscopy (EELS), Ultraviolet photoelectron spectroscopy (UPS), and Auger electron spectroscopy (AES). These analytical techniques are used to identify and determine the elements and their electronic structures from the surface of a test sample. Samples can be solids, gases or liquids.
Chemical information is obtained only from the uppermost atomic layers of the sample (depth 10 nm or less) because the energies of Auger electrons and photoelectrons are quite low, typically 20 - 2000 eV. For this reason, electron spectroscopy techniques are used to analyze surface chemicals. | 7 | Physical Chemistry |
Minerals of copper were known from ancient times. In Crete, little fragments of malachite and azurite were powdered and used as make up or to decorate ceramic as early as 6000 BCE.
Therefore, the minerals were not collected because people were looking for copper but for virtues like those mentioned or simply because of its brightness and colour, but this knowledge of the minerals is critical since they already knew how to recognize them and where to collect them when, later, they started the systematic search for ores.
Numerous examples of mines are known all over Europe, from the east: Rudna Glava (Serbia), Ai Bunar (Bulgaria); to the west: Mount Gabriel (Ireland), Great Orme, Alderley Edge (United Kingdom); crossing Central Europe: Mitterberg (Salzach, Austria), Neuchâtel (Switzerland), Cabrierés (France); to the south: Riotinto, Mola Alta de Serelles (Spain); and the Mediterranean: Corsica, Cyprus, and the Cyclades islands. It is remarkable that, usually, it is not a single mine but a complex, with a variable, large number of mineshafts, as in Rudna Glava (30) or Mount Gabriel (31). | 8 | Metallurgy |
In the context of machine learning, is often called the information gain achieved if would be used instead of which is currently used. By analogy with information theory, it is called the relative entropy of with respect to .
Expressed in the language of Bayesian inference, is a measure of the information gained by revising one's beliefs from the prior probability distribution to the posterior probability distribution . In other words, it is the amount of information lost when is used to approximate . | 7 | Physical Chemistry |
Chemical metallurgy is the science of obtaining metals from their concentrates, semi products, recycled bodies and solutions, and of considering reactions of metals with an approach of disciplines belonging to chemistry. As such, it involves reactivity of metals and it is especially concerned with the reduction and oxidation, and the chemical performance of metals.
Subjects of study in chemical metallurgy include the extraction of metals, thermodynamics, electrochemistry, and chemical degradation (corrosion). | 8 | Metallurgy |
Concrete cancer may refer to:
* Rebar corrosion and spalling of the concrete cover above rebar caused by the rust expansion and accelerated by chloride attack and pitting corrosion of the steel reinforcements.
* Alkali–silica reaction (ASR), also known as alkali-aggregate reaction (AAR), when reactive amorphous silica aggregates exposed to alkaline conditions (high pH) swell inside the concrete matrix leading to the development of a network of cracks.
It may also refer to:
* Sulfate attacks, an hat appellation covering different concrete degradation mechanisms:
** Delayed ettringite formation (DEF), also known as internal sulfate attack (ISA) when the temperature of fresh concrete exceeds 65 °C during its setting and hardening;
** External sulfate attack (ESA), and;
** Thaumasite form of sulfate attack (TSA). | 8 | Metallurgy |
DMSO is a widely used solvent.
The sulfoxide functional group occurs in several drugs. Notable is esomeprazole, the optically pure form of the proton-pump inhibitor omeprazole. Another commercially important sulfoxides include armodafinil.
Methionine sulfoxide forms from the amino acid methionine and its accumulation is associated with aging. The enzyme DMSO reductase catalyzes the interconversion of DMSO and dimethylsulfide.
Naturally-occurring chiral sulfoxides include alliin and ajoene. | 0 | Organic Chemistry |
The winnowing-fan (λίκνον [líknon], also meaning a "cradle") featured in the rites accorded Dionysus and in the Eleusinian Mysteries: "it was a simple agricultural implement taken over and mysticized by the religion of Dionysus," Jane Ellen Harrison remarked. Dionysus Liknites ("Dionysus of the winnowing fan") was wakened by the Dionysian women, in this instance called Thyiades, in a cave on Parnassus high above Delphi; the winnowing-fan links the god connected with the mystery religions to the agricultural cycle, but mortal Greek babies too were laid in a winnowing-fan. In Callimachus Hymn to Zeus, Adrasteia lays the infant Zeus in a golden líknon, her goat suckles him and he is given honey. In the Odyssey, the dead oracle Teiresias tells Odysseus to walk away from Ithaca with an oar until a wayfarer tells him it is a winnowing fan (i.e., until Odysseus has come so far from the sea that people dont recognize oars), and there to build a shrine to Poseidon. | 3 | Analytical Chemistry |
Meteorites come in a variety of compositions, but chemical analysis can determine whether they were once in planetesimals that melted or differentiated. Chondrites are undifferentiated and have round mineral inclusions called chondrules. With the ages of 4.56 billion years, they date to the early solar system. A particular kind, the CI chondrite, has a composition that closely matches that of the Sun's photosphere, except for depletion of some volatiles (H, He, C, N, O) and a group of elements (Li, B, Be) that are destroyed by nucleosynthesis in the Sun. Because of the latter group, CI chondrites are considered a better match for the composition of the early Solar System. Moreover, the chemical analysis of CI chondrites is more accurate than for the photosphere, so it is generally used as the source for chemical abundance, despite their rareness (only five have been recovered on Earth). | 9 | Geochemistry |
#Rutile (TiO) frequently exhibits a prismatic or acicular growth habit. In the presence of alkali dopants or a solid-state ZrSiO dopant, rutile has been observed to crystallise from an anatase parent-phase in the form of abnormally large grains existing in a matrix of finer, equiaxed anatase or rutile grains.
# Alumina, AlO with silica and/or yttria dopants/impurities has been reported to exhibit undesirable AGG.
#BaTiO barium titanate with an excess of TiO is known to exhibit abnormal grain growth with profound consequences on piezoelectric performance.
#Tungsten carbide has been reported to exhibit AGG of faceted grains in the presence of a liquid cobalt-containing phase at grain boundaries
#Silicon nitride (SiN) may exhibit AGG depending on the size distribution of β-phase material in an α-SiN precursor. This type of grain growth is of importance in the toughening of silicon nitride materials
#Silicon carbide has been shown to exhibit improved fracture toughness as the result of AGG processes yielding elongated crack-tip/wake-bridging grains, with consequences for applications in ballistic armor. This enhancement of fracture toughness in ceramic materials via crack-bridging resulting from AGG is consistent with reported morphological effects on crack propagation in ceramics
#Strontium barium niobate, used for electro-optics and dielectric applications, is known to exhibit AGG with significant consequences on the electronic performance of the material
#Calcium titanate (CaTiO, perovskite) systems doped with BaO have been observed to exhibit AGG without the formation of liquid as the result of polytype interfaces between solid phases | 3 | Analytical Chemistry |
Insert size of up to 350 kb can be cloned in bacterial artificial chromosome (BAC). BACs are maintained in E. coli with a copy number of only 1 per cell. BACs are based on F plasmid, another artificial chromosome called the PAC is based on the P1 phage. | 1 | Biochemistry |
Halohydrins are usually prepared by treatment of an alkene with a halogen, in the presence of water. The reaction is a form of electrophilic addition, with the halogen acting as electrophile. In that regard, it resembles the halogen addition reaction and proceeds with anti addition, leaving the newly added X and OH groups in a trans configuration. The chemical equation for the conversion of ethylene to ethylene chlorohydrin is:
:HC=CH + Cl + HO → H(OH)C-CHCl + HCl
When bromination is desired, N-bromosuccinimide (NBS) can be preferable to bromine because fewer side-products are produced. | 0 | Organic Chemistry |
In biochemistry, a Ramachandran plot (also known as a Rama plot, a Ramachandran diagram or a [φ,ψ] plot), originally developed in 1963 by G. N. Ramachandran, C. Ramakrishnan, and V. Sasisekharan, is a way to visualize energetically allowed regions for backbone dihedral angles ψ against φ of amino acid residues in protein structure. The figure on the left illustrates the definition of the φ and ψ backbone dihedral angles (called φ and φ' by Ramachandran). The ω angle at the peptide bond is normally 180°, since the partial-double-bond character keeps the peptide bond planar. The figure in the top right shows the allowed φ,ψ backbone conformational regions from the Ramachandran et al. 1963 and 1968 hard-sphere calculations: full radius in solid outline, reduced radius in dashed, and relaxed tau (N-Cα-C) angle in dotted lines. Because dihedral angle values are circular and 0° is the same as 360°, the edges of the Ramachandran plot "wrap" right-to-left and bottom-to-top. For instance, the small strip of allowed values along the lower-left edge of the plot are a continuation of the large, extended-chain region at upper left. | 1 | Biochemistry |
Messenger RNA (mRNA) is a single-stranded RNA molecule that is complementary to one of the DNA strands of a gene. An mRNA molecule transfers a portion of the DNA code to other parts of the cell for making proteins. DNA therapeutics needs access to the nucleus to be transcribed into RNA, and its functionality depends on nuclear envelope breakdown during cell division. However, mRNA therapeutics do not need to enter into the nucleus to be functional since it will be translated immediately once it has reached to the cytoplasm. Moreover, unlike plasmids and viral vectors, mRNAs do not integrate into the genome and therefore do not have the risk of insertional mutagenesis, making them suitable for use in cancer vaccines, tumor immunotherapy and infectious disease prevention. | 1 | Biochemistry |
Jones married Vera Haines, a dispensing chemist in Gympie in 1923. They had two children. He died on 11 August 1970 in Brisbane. | 0 | Organic Chemistry |
Heat conduction in a Newtonian context is modelled by the Fourier equation, namely a parabolic partial differential equation of the kind:
where θ is temperature, t is time, α = k/(ρ c) is thermal diffusivity, k is thermal conductivity, ρ is density, and c is specific heat capacity. The Laplace operator, , is defined in Cartesian coordinates as
This Fourier equation can be derived by substituting Fourier’s linear approximation of the heat flux vector, q, as a function of temperature gradient,
into the first law of thermodynamics
where the del operator, ∇, is defined in 3D as
It can be shown that this definition of the heat flux vector also satisfies the second law of thermodynamics,
where s is specific entropy and σ is entropy production. This mathematical model is inconsistent with special relativity: the Green function associated to the heat equation (also known as heat kernel) has support that extends outside the light-cone, leading to faster-than-light propagation of information. For example, consider a pulse of heat at the origin; then according to Fourier equation, it is felt (i.e. temperature changes) at any distant point, instantaneously. The speed of propagation of heat is faster than the speed of light in vacuum, which is inadmissible within the framework of relativity. | 7 | Physical Chemistry |
Heavy chain contains similar gene segments such as VH, JH and CH, but also has another gene segment called D (diversity). Unlike the light chain multigene family, VDJ gene segments code for the variable region of the heavy chain. The rearrangement and reorganization of gene segments in this multigene family is more complex . The rearranging and joining of segments produced different end products because these are carried out by different RNA processes. The same reason is why the IgM and IgG are generates at the time. | 1 | Biochemistry |
Pool boiling is boiling at a stagnant fluid. Its behavior is well characterized by Nukiyama boiling curve, which shows the relation between the amount of surface superheat and applied heat flux on the surface. With the varying degrees of the superheat, the curve is composed of natural convection, onset of nucleate boiling, nucleate boiling, critical heat flux, transition boiling, and film boiling. Each regime has a different mechanism of heat transfer and has different correlation for heat transfer coefficient. | 7 | Physical Chemistry |
A wide range of organosulfur compounds are known which contain one or more halogen atom ("X" in the chemical formulas that follow) bonded to a single sulfur atom, e.g.: sulfenyl halides, RSX; sulfinyl halides, RS(O)X; sulfonyl halides, RSOX; alkyl and arylsulfur trichlorides, RSCl and trifluorides, RSF; and alkyl and arylsulfur pentafluorides, RSF. Less well known are dialkylsulfur tetrahalides, mainly represented by the tetrafluorides, e.g., RSF. | 9 | Geochemistry |
SAMs are an inexpensive and versatile surface coating for applications including control of wetting and adhesion, chemical resistance, bio compatibility, sensitization, and molecular recognition for sensors and nano fabrication. Areas of application for SAMs include biology, electrochemistry and electronics, nanoelectromechanical systems (NEMS) and microelectromechanical systems (MEMS), and everyday household goods. SAMs can serve as models for studying membrane properties of cells and organelles and cell attachment on surfaces. SAMs can also be used to modify the surface properties of electrodes for electrochemistry, general electronics, and various NEMS and MEMS. For example, the properties of SAMs can be used to control electron transfer in electrochemistry. They can serve to protect metals from harsh chemicals and etchants. SAMs can also reduce sticking of NEMS and MEMS components in humid environments. In the same way, SAMs can alter the properties of glass. A common household product, Rain-X, utilizes SAMs to create a hydrophobic monolayer on car windshields to keep them clear of rain. Another application is an anti-adhesion coating on nanoimprint lithography (NIL) tools and stamps. One can also coat injection molding tools for polymer replication with a Perfluordecyltrichlorosilane SAM.
Thin film SAMs can also be placed on nanostructures. In this way they functionalize the nanostructure. This is advantageous because the nanostructure can now selectively attach itself to other molecules or SAMs. This technique is useful in biosensors or other MEMS devices that need to separate one type of molecule from its environment. One example is the use of magnetic nanoparticles to remove a fungus from a blood stream. The nanoparticle is coated with a SAM that binds to the fungus. As the contaminated blood is filtered through a MEMS device the magnetic nanoparticles are inserted into the blood where they bind to the fungus and are then magnetically driven out of the blood stream into a nearby laminar waste stream. | 6 | Supramolecular Chemistry |
Scale of temperature is a methodology of calibrating the physical quantity temperature in metrology. Empirical scales measure temperature in relation to convenient and stable parameters or reference points, such as the freezing and boiling point of water. Absolute temperature is based on thermodynamic principles: using the lowest possible temperature as the zero point, and selecting a convenient incremental unit.
Celsius, Kelvin, and Fahrenheit are common temperature scales. Other scales used throughout history include Rankine, Rømer, Newton, Delisle, Réaumur, Gas mark, Leiden and Wedgwood. | 7 | Physical Chemistry |
A "lasagna cell" is accidentally produced when salty moist food such as lasagna is stored in a steel baking pan and is covered with aluminium foil. After a few hours the foil develops small holes where it touches the lasagna, and the food surface becomes covered with small spots composed of corroded aluminium. In this example, the salty food (lasagna) is the electrolyte, the aluminium foil is the anode, and the steel pan is the cathode. If the aluminium foil touches the electrolyte only in small areas, the galvanic corrosion is concentrated, and corrosion can occur fairly rapidly. If the aluminium foil was not used with a dissimilar metal container, the reaction was probably a chemical one. It is possible for heavy concentrations of salt, vinegar or some other acidic compounds to cause the foil to disintegrate. The product of either of these reactions is an aluminium salt. It does not harm the food, but any deposit may impart an undesired flavor and color. | 8 | Metallurgy |
In chemistry, a racemic mixture or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. | 4 | Stereochemistry |
Hydrocracking is a catalytic cracking process assisted by the presence of added hydrogen gas. Unlike a hydrotreater, hydrocracking uses hydrogen to break C-C bonds (hydrotreatment is conducted prior to hydrocracking to protect the catalysts in a hydrocracking process). In 2010, 265 million tons of petroleum was processed with this technology. The main feedstock is vacuum gas oil, a heavy fraction of petroleum.
The products of this process are saturated hydrocarbons; depending on the reaction conditions (temperature, pressure, catalyst activity) these products range from ethane, LPG to heavier hydrocarbons consisting mostly of isoparaffins. Hydrocracking is normally facilitated by a bifunctional catalyst that is capable of rearranging and breaking hydrocarbon chains as well as adding hydrogen to aromatics and olefins to produce naphthenes and alkanes.
The major products from hydrocracking are jet fuel and diesel, but low sulphur naphtha fractions and LPG are also produced. All these products have a very low content of sulfur and other contaminants. It is very common in Europe and Asia because those regions have high demand for diesel and kerosene. In the US, fluid catalytic cracking is more common because the demand for gasoline is higher.
The hydrocracking process depends on the nature of the feedstock and the relative rates of the two competing reactions, hydrogenation and cracking. Heavy aromatic feedstock is converted into lighter products under a wide range of very high pressures (1,000-2,000 psi) and fairly high temperatures (750°-1,500 °F, 400-800 °C), in the presence of hydrogen and special catalysts. | 0 | Organic Chemistry |
The matrix consists of crystallized molecules, of which the three most commonly used are sinapinic acid, α-cyano-4-hydroxycinnamic acid (α-CHCA, alpha-cyano or alpha-matrix) and 2,5-dihydroxybenzoic acid (DHB). A solution of one of these molecules is made, often in a mixture of highly purified water and an organic solvent such as acetonitrile (ACN) or ethanol. A counter ion source such as trifluoroacetic acid (TFA) is usually added to generate the [M+H] ions. A good example of a matrix-solution would be 20 mg/mL sinapinic acid in ACN:water:TFA (50:50:0.1).
The identification of suitable matrix compounds is determined to some extent by trial and error, but they are based on some specific molecular design considerations. They are of a fairly low molecular weight (to allow easy vaporization), but are large enough (with a low enough vapor pressure) not to evaporate during sample preparation or while standing in the mass spectrometer. They are often acidic, therefore act as a proton source to encourage ionization of the analyte. Basic matrices have also been reported. They have a strong optical absorption in either the UV or IR range, so that they rapidly and efficiently absorb the laser irradiation. This efficiency is commonly associated with chemical structures incorporating several conjugated double bonds, as seen in the structure of cinnamic acid. They are functionalized with polar groups, allowing their use in aqueous solutions. They typically contain a chromophore.
The matrix solution is mixed with the analyte (e.g. protein-sample). A mixture of water and organic solvent allows both hydrophobic and water-soluble (hydrophilic) molecules to dissolve into the solution. This solution is spotted onto a MALDI plate (usually a metal plate designed for this purpose). The solvents vaporize, leaving only the recrystallized matrix, but now with analyte molecules embedded into MALDI crystals. The matrix and the analyte are said to be co-crystallized. Co-crystallization is a key issue in selecting a proper matrix to obtain a good quality mass spectrum of the analyte of interest.
In analysis of biological systems, inorganic salts, which are also part of protein extracts, interfere with the ionization process. The salts can be removed by solid phase extraction or by washing the dried-droplet MALDI spots with cold water. Both methods can also remove other substances from the sample. The matrix-protein mixture is not homogeneous because the polarity difference leads to a separation of the two substances during co-crystallization. The spot diameter of the target is much larger than that of the laser, which makes it necessary to make many laser shots at different places of the target, to get the statistical average of the substance concentration within the target spot.
The matrix can be used to tune the instrument to ionize the sample in different ways. As mentioned above, acid-base like reactions are often utilized to ionize the sample, however, molecules with conjugated pi systems, such as naphthalene like compounds, can also serve as an electron acceptor and thus a matrix for MALDI/TOF. This is particularly useful in studying molecules that also possess conjugated pi systems. The most widely used application for these matrices is studying porphyrin-like compounds such as chlorophyll. These matrices have been shown to have better ionization patterns that do not result in odd fragmentation patterns or complete loss of side chains. It has also been suggested that conjugated porphyrin like molecules can serve as a matrix and cleave themselves eliminating the need for a separate matrix compound. | 1 | Biochemistry |
Sedimentation potential is measured by attaching electrodes to a glass column filled with the dispersion of interest. A voltmeter is attached to measure the potential generated from the suspension. To account for different geometries of the electrode, the column is typically rotated 180 degrees while measuring the potential. This difference in potential through rotation by 180 degrees is twice the sedimentation potential. The zeta potential can be determined through measurement by sedimentation potential, as the concentration, conductivity of the suspension, density of the particle, and potential difference are known. By rotating the column 180 degrees, drift and geometry differences of the column can be ignored.
When dealing with the case of concentrated systems, the zeta potential can be determined through measurement of the sedimentation potential , from the potential difference relative to the distance between the electrodes. The other parameters represent the following: the viscosity of the medium; the bulk conductivity; the relative permittivity of the medium; the permittivity of free space; the density of the particle; the density of the medium; is the acceleration due to gravity; and σ is the electrical conductivity of the bulk electrolyte solution.
An improved design cell was developed to determine sedimentation potential, specific conductivity, volume fraction of the solids as well as pH. Two pairs of electrodes are used in this set up, one to measure potential difference and the other for resistance. A flip switch is utilized to avoid polarization of the resistance electrodes and buildup of charge by alternating the current. The pH of the system could be monitored and the electrolyte was drawn into the tube using a vacuum pump. | 7 | Physical Chemistry |
There is compelling evidence that components within some UCMs are toxic to marine organisms. The clearance rate (also known as feeding feed) of mussels was reduced by 40% following exposure to a monoaromatic UCM derived from a Norwegian crude oil. The toxicity of monoaromatic UCM components was further evidenced by an elegant set of experiments using transplantations of clean and polluted mussels. Recent analysis by GC×GC-ToF-MS of UCMs extracted from the mussel tissues, has shown that they contain a vast array of both known and unknown compounds. The comparative analysis of UCMs extracted from mussels known to possess high, moderate and low Scope for Growth (SfG), a measure of the capacity for growth and reproduction, revealed that branched alkylbenzenes represented the largest structural class within the UCM of mussels with low SfG; also, branched isomers of alkyltetralins, alkylindanes and alkylindenes were prominent in the stressed mussels. Laboratory toxicity tests using both commercially available and specially synthesised compounds revealed that such branched alkylated structures were capable of producing the observed poor health of the mussels. The reversible effects observed in mussels following exposure to the UCM hydrocarbons identified to date are consistent with non-specific narcosis (also known as baseline) mode of action of toxicity. There is no evidence that toxic UCM components can biomagnify through the food chain. Crabs (Carcinus maenas) that were fed a diet of mussels contaminated with environmentally realistic concentrations of branched alkylbenzenes, suffered behavioural disruption but only a small concentration of the compounds were retained in the midgut of the crabs. Within marsh sediments still contaminated with high concentrations of UCM hydrocarbons from the Florida barge oil spill in 1969 (see above,) the behaviour and feeding of fiddler crabs (Uca pugnax) was reported to be affected. | 3 | Analytical Chemistry |
By detecting the associated mRNA, UCP2, UCP4, and UCP5 were shown to reside in neurons throughout the human central nervous system. These proteins play key roles in neuronal function. While many study findings remain controversial, several findings are widely accepted.
For example, UCPs alter the free calcium concentrations in the neuron. Mitochondria are a major site of calcium storage in neurons, and the storage capacity increases with potential across mitochondrial membranes. Therefore, when the uncoupling proteins reduce potential across these membranes, calcium ions are released to the surrounding environment in the neuron. Due to the high concentrations of mitochondria near axon terminals, this implies UCPs play a role in regulating calcium concentrations in this region. Considering calcium ions play a large role in neurotransmission, scientists predict that these UCPs directly affect neurotransmission.
As discussed above, neurons in the hippocampus experience increased concentrations of ATP in the presence of these uncoupling proteins. This leads scientists to hypothesize that UCPs improve synaptic plasticity and transmission. | 1 | Biochemistry |
NMR spectroscopy is used in industrially relevant systems to study the sequence distribution of copolymers or the occurrence of transesterification in polyester blends. A change in sequence distribution can effect the crystallinity, and transesterification can affect the compatibility of two otherwise incompatible polyesters. Depending on their degree of randomness, copolyesters can show different thermal transitions and behaviours. | 7 | Physical Chemistry |
The pharmacology of dextrorphan is similar to that of dextromethorphan (DXM). However, dextrorphan is much more potent as an NMDA receptor antagonist as well much less active as a serotonin reuptake inhibitor, but retains DXM's activity as a norepinephrine reuptake inhibitor.
It also has more affinity for the opioid receptors than dextromethorphan, significantly so at high doses. | 4 | Stereochemistry |
Larry Verdansky, a repair technician assigned alone on Station Five, is interested in "siliconies", the silicon-based life forms found on some asteroids. The creatures typically grow to a maximum size of by absorbing gamma rays from radioactive ores. Some are telepathic.
When the space freighter Robert Q appears at the station with a giant of a "silicony" in diameter, Verdansky deduces that the crew has found an incredibly rich source of uranium. Verdansky contacts the authorities, but before a patrol ship can reach her, the Robert Q is hit by a meteor, killing the three human crew members. The silicony itself is fatally injured from the explosive decompression.
When questioned, the dying silicony states that the coordinates of its home are written on "the asteroid". Dr. Wendell Urth deduces that the silicony meant that the numbers were actually engraved on the hull of the Robert Q, disguised as serial and registration numbers, since the ship fit the definition of an asteroid (a small body orbiting the Sun) the ship's crew had read to it from an ancient astronomy book. | 1 | Biochemistry |
Two bands may overlap with the head of one on top of another band or close to each other. This may make a stepped appearance. The two band heads close to each other are called a double head. | 7 | Physical Chemistry |
Biochemical research in Australia began in the 1920s in the Australian national science agency Council for Scientific and Industrial Research (now the CSIRO). The first university biochemistry department then started at the University of Adelaide under Thorburn Brailsford Robertson. There was initially a joint biochemistry and physiology section within the Australian and New Zealand Association for the Advancement of Science.
The society began in 1955 as the Australian Biochemical Society, with Rudi Lemberg as its founding president. It was based on Lembergs experience with the British Biochemical Society and Hugh Ennors meetings with the International Union of Biochemistry and relevant university department heads in Australia. Additional key initial members included Frederick Collins as treasurer and Victor Trikojus in a recruitment role. | 1 | Biochemistry |
The methylglyoxal pathway is an offshoot of glycolysis found in some prokaryotes, which converts glucose into methylglyoxal and then into pyruvate. However unlike glycolysis the methylglyoxal pathway does not produce adenosine triphosphate, ATP. The pathway is named after the substrate methylglyoxal which has three carbons and two carbonyl groups located on the 1st carbon and one on the 2nd carbon. Methylglyoxal is, however, a reactive aldehyde that is very toxic to cells, it can inhibit growth in E. coli at milimolar concentrations. The excessive intake of glucose by a cell is the most important process for the activation of the methylglyoxal pathway. | 1 | Biochemistry |
Gunnar Aksnes (8 August 1926 in Kvam, Hardanger – 31 January 2010 in Bergen, Hordaland) was a Norwegian chemist and poet, the brother of the astronomer Kaare Aksnes, married to Milly Aksnes (b. 1928) | 0 | Organic Chemistry |
Quantum versions of most of the common thermodynamic cycles have been studied, for example the Carnot cycle, Stirling cycle and Otto cycle.
The Otto cycle can serve as a template for other reciprocating cycles.
It is composed of the following four segments:
*Segment isomagnetic or isochoric process, partial equilibration with the cold bath under constant Hamiltonian. The dynamics of the working medium is characterized by the propagator .
*Segment magnetization or adiabatic compression, the external field changes expanding the gap between energy levels of the Hamiltonian. The dynamics is characterized by the propagator .
*Segment isomagnetic, or isochoric process partial equilibration with the hot bath described by the propagator .
*Segment demagnetization or adiabatic expansion reducing the energy gaps in the Hamiltonian, characterized by the propagator .
The propagator of the four stroke cycle
becomes , which is the ordered product of the segment propagators:
The propagators are linear operators defined on a vector space which completely determines the state of the working medium.
Common to all thermodynamic cycles the consecutive segment propagators do not commute .
Commuting propagators will lead to zero power.
In a reciprocating quantum heat engine the working medium is a quantum system such as spin systems or an harmonic oscillator. For maximum power the cycle time should be optimized.
There are two basic timescales in the reciprocating refrigerator the cycle time and the internal
timescale . In general when the
engine operates in quasi-adiabatic conditions. The only quantum effect can be found at low temperatures
where the unit of energy of the device becomes instead of .
The efficiency at this limit is , always smaller than the Carnot efficiency . At high temperature and for the harmonic working medium the efficiency at maximum power becomes which is the endoreversible thermodynamics result.
For shorter cycle times the working medium cannot follow adiabatically the change in the external parameter.
This leads to friction-like phenomena. Extra power is required to drive the system faster.
The signature of such dynamics is the development of coherence causing extra dissipation.
Surprisingly the dynamics leading to friction is quantized meaning that frictionless solutions to the adiabatic expansion/compression
can be found in finite time.
As a result, optimization has to be carried out only with respect to the time allocated
to heat transport. In this regime the quantum feature of coherence degrades the performance.
Optimal frictionless performance is obtained when the coherence can be cancelled.
The shortest cycle times , sometimes termed sudden cycles, have universal features. In this case coherence contributes to the cycles power.
A two-stroke engine quantum cycle equivalent to the Otto cycle based on two qubits has been proposed.
The first qubit has frequency and the second . The cycle is composed
of a first stroke of partial equilibration of the two qubits with the hot and cold bath in parallel.
The second power stroke is composed of a partial or full swap between the qubits.
The swap operation is generated by a unitary transformation which preserves the entropy
as a result it is a pure power stroke.
The quantum Otto cycle refrigerators shares the same cycle with magnetic refrigeration. | 7 | Physical Chemistry |
It is a moderate-spectrum, bacteriolytic, β-lactam antibiotic in the aminopenicillin family used to treat susceptible Gram-positive and Gram-negative bacteria. It is usually the drug of choice within the class because it is better-absorbed, following oral administration, than other β-lactam antibiotics.
In general, Streptococcus, Bacillus subtilis, Enterococcus, Haemophilus, Helicobacter, and Moraxella are susceptible to amoxicillin, whereas Citrobacter, Klebsiella and Pseudomonas aeruginosa are resistant to it. Some E. coli and most clinical strains of Staphylococcus aureus have developed resistance to amoxicillin to varying degrees. | 4 | Stereochemistry |
::</big>
and
::</big>
where:
* C is concentration
* D is the diffusion coefficient
* V is the velocity of flow
* x is the distance down the channel
* γ is the wall shear rate
* b is the height of the channel
This equation is especially applicable to analyzing protein adsorption to biomedical devices in arteries, e.g. stents. | 1 | Biochemistry |
In the case of low material loss, the Nicolson–Ross–Weir method is known to be unstable for sample thicknesses at integer multiples of one half wavelength due to resonance phenomenon. Improvements over the standard algorithm have been presented in engineering literature to alleviate this effect. Furthermore, complete filling of a waveguide with sample material may pose a particular challenge: presence of gaps during the filling of the waveguide section would excite higher-order modes, which may yield errors in scattering parameter results. In such cases, more advanced methods based on the rigorous modal analysis of partially-filled waveguides or optimization methods can be used. A modification of the method for single-port measurements was also reported.
In addition to homogenous materials, the extension of the method was developed to obtain constitutive parameters of isotropic and bianisotropic metamaterials. | 7 | Physical Chemistry |
It ranges from Ontario west to Alaska, and south to Missouri, north-central Nebraska, the northern half of Wyoming, and central Washington south through Idaho into north-central Utah. A disjunct subset of its range occurs from central Colorado to northwestern New Mexico. An isolated population was formerly found in Chihuahua, Mexico, but has since been extirpated. The United States portion of the Souris River is alternately known as the Mouse River because of the large numbers of field mice that lived along its banks. | 2 | Environmental Chemistry |
A quark–gluon plasma (QGP) or quark soup is a state of matter in quantum chromodynamics (QCD) which exists at extremely high temperature and/or density. This state is thought to consist of asymptotically free strong-interacting quarks and gluons, which are ordinarily confined by color confinement inside atomic nuclei or other hadrons. This is in analogy with the conventional plasma where nuclei and electrons, confined inside atoms by electrostatic forces at ambient conditions, can move freely. Experiments to create artificial quark matter started at CERN in 1986/87, resulting in first claims that were published in 1991. It took several years before the idea became accepted in the community of particle and nuclear physicists. Formation of a new state of matter in Pb–Pb collisions was officially announced at CERN in view of the convincing experimental results presented by the CERN SPS WA97 experiment in 1999, and later elaborated by Brookhaven National Laboratory's Relativistic Heavy Ion Collider. Quark matter can only be produced in minute quantities and is unstable and impossible to contain, and will radioactively decay within a fraction of a second into stable particles through hadronization; the produced hadrons or their decay products and gamma rays can then be detected. In the quark matter phase diagram, QGP is placed in the high-temperature, high-density regime, whereas ordinary matter is a cold and rarefied mixture of nuclei and vacuum, and the hypothetical quark stars would consist of relatively cold, but dense quark matter. It is believed that up to a few microseconds (10 to 10 seconds) after the Big Bang, known as the quark epoch, the Universe was in a quark–gluon plasma state.
The strength of the color force means that unlike the gas-like plasma, quark–gluon plasma behaves as a near-ideal Fermi liquid, although research on flow characteristics is ongoing. Liquid or even near-perfect liquid flow with almost no frictional resistance or viscosity was claimed by research teams at RHIC and LHC's Compact Muon Solenoid detector. QGP differs from a "free" collision event by several features; for example, its particle content is indicative of a temporary chemical equilibrium producing an excess of middle-energy strange quarks vs. a nonequilibrium distribution mixing light and heavy quarks ("strangeness production"), and it does not allow particle jets to pass through ("jet quenching").
Experiments at CERNs Super Proton Synchrotron (SPS) begun experiments to create QGP in the 1980s and 1990s: the results led CERN to announce evidence for a "new state of matter" in 2000. Scientists at Brookhaven National Laboratorys Relativistic Heavy Ion Collider announced they had created quark–gluon plasma by colliding gold ions at nearly the speed of light, reaching temperatures of 4 trillion degrees Celsius. Current experiments (2017) at the Brookhaven National Laboratorys Relativistic Heavy Ion Collider (RHIC) on Long Island (New York, USA) and at CERNs recent Large Hadron Collider near Geneva (Switzerland) are continuing this effort, by colliding relativistically accelerated gold and other ion species (at RHIC) or lead (at LHC) with each other or with protons. Three experiments running on CERN's Large Hadron Collider (LHC), on the spectrometers ALICE, ATLAS and CMS, have continued studying the properties of QGP. CERN temporarily ceased colliding protons, and began colliding lead ions for the ALICE experiment in 2011, in order to create a QGP. A new record breaking temperature was set by ALICE: A Large Ion Collider Experiment at CERN in August 2012 in the ranges of 5.5 trillion () kelvin as claimed in their Nature PR.
The formation of a quark–gluon plasma occurs as a result of a strong interaction between the partons (quarks, gluons) that make up the nucleons of the colliding heavy nuclei called heavy ions. Therefore, experiments are referred to as relativistic heavy ion collision experiments. Theoretical and experimental works show that the formation of a quark–gluon plasma occurs at the temperature of T ≈ 150–160 MeV, the Hagedorn temperature, and an energy density of ≈ 0.4–1 GeV / fm. While at first a phase transition was expected, present day theoretical interpretations propose a phase transformation similar to the process of ionisation of normal matter into ionic and electron plasma. | 7 | Physical Chemistry |
The extracellular type II and type I kinase receptors binding to the TGF-β ligands. Transforming growth factor-β (TGF-β) is a superfamily of cytokines that play a significant upstream role in regulating of morphogenesis, homeostasis, cell proliferation, and differentiation. The significance of TGF-β is apparent with the human diseases that occur when TGF-β processes are disrupted, such as cancer, and skeletal, intestinal and cardiovascular diseases. TGF-β is pleiotropic and multifunctional, meaning they are able to act on a wide variety of cell types. | 1 | Biochemistry |
A helical wheel is a type of plot or visual representation used to illustrate the properties of alpha helices in proteins.
The sequence of amino acids that make up a helical region of the protein's secondary structure are plotted in a rotating manner where the angle of rotation between consecutive amino acids is 100°, so that the final representation looks down the helical axis. | 1 | Biochemistry |
As PACs consist of a light sensor and an enzyme in a single protein, they can be expressed in other species and cell types to manipulate cAMP levels with light. When bPAC is expressed in mouse sperm, blue light illumination speeds up the swimming of transgenic sperm cells and aids fertilization. When expressed in neurons, illumination changes the branching pattern of growing axons. PAC has been used in mice to clarify the function of neurons in the hypothalamus, which use cAMP signaling to control mating behavior. Expression of PAC together with K-specific cyclic-nucleotide-gated ion channels (CNGs) has been used to hyperpolarize neurons at very low light levels, which prevents them from firing action potentials. | 1 | Biochemistry |
Prolonged exposure to pyridine may result in liver, heart and kidney damage. Evaluations as a possible carcinogenic agent showed that there is inadequate evidence in humans for the carcinogenicity of pyridine, although there is sufficient evidence in experimental animals. Therefore, IARC considers pyridine as possibly carcinogenic to humans (Group 2B). | 0 | Organic Chemistry |
The hepatocyte is a complex and multifunctional differentiated cell whose cell response will be influenced by the zone in hepatic lobule, because concentrations of oxygen and toxic substances present in the hepatic sinusoids change from periportal zone to centrilobular zone10. The hepatocytes of the intermediate zone have the appropriate morphological and functional features since they have the environment with average concentrations of oxygen and other substances.
This specialized cell is capable of:
* Regulate glucose metabolism
# Via cAMP/PKA/TORC (transducers of regulated CREB)/CRE, PIP3 /PKB and PLC /IP3
# Expression of enzymes for synthesis, storage and distribution of glucose
* Synthesis of acute phase proteins
# Via JAK /STAT /APRE (acute phase response element)
# Expression of C-reactive protein, globulin protease inhibitors, complement, coagulation and fibrinolytic systems and iron homeostasis
* Regulate iron homeostasis (acute phase independent)
# Via Smads /HAMP
# Hepcidin expression
* Regulate lipid metabolism
# Via LXR /LXRE (LXR response element)
# Expression of ApoE CETP, FAS and LPL
* Exocrine production of bile salts and other compounds
# Via LXR /LXRE
# Expression of CYP7A1 and ABC transporters
* Degradate of toxic substances
# Via LXR /LXRE
# Expression of ABC transporters
* Endocrine production
# Via JAK/STAT /GHRE (growth hormone response element)
:IGF-1 and IGFBP-3 expression
# Via THR/THRE (thyroid hormone response element)
:Angiotensinogen expression
* Regenerate itself by hepatocyte mitosis
# Via STAT and Gab1: RAS/MAPK, PLC/IP3 and PI3K/FAK
# Cell growth, proliferation, survival, invasion and motility
The hepatocyte also regulates other functions for constitutive synthesis of proteins (albumin, ALT and AST) that influences the synthesis or activation of other molecules (synthesis of urea and essential amino acids), activate vitamin D, utilization of vitamin K, transporter expression of vitamin A and conversion of thyroxine. | 7 | Physical Chemistry |
Most modern MCP detectors consist of two microchannel plates with angled channels, rotated 180° from each other - producing a shallow chevron (v-like) shape. In a chevron MCP, the electrons that exit the first plate start the cascade in the next plate. The angle between the channels reduces ion feedback in the device, as well as producing significantly more gain at a given voltage, compared to a straight channel MCP. The two MCPs can either be pressed together to preserve spatial resolution, or have a small gap between them to spread the charge across multiple channels, which further increases the gain. | 7 | Physical Chemistry |
Sodium–potassium alloy, colloquially called NaK (commonly pronounced ), is an alloy of the alkali metals sodium (Na, atomic number 11) and potassium (K, atomic number 19) that is normally liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water (like its constituent elements) and may catch fire when exposed to air, so must be handled with special precautions. | 8 | Metallurgy |
Lithiasis (formation of stones) is a global human health problem. Stones can form in both urinary and gastrointestinal tracts. Related to the formation of stones is the formation of crystals; this can occur in joints (e.g. gout) and in the viscera. | 1 | Biochemistry |
Atomic physics is the subfield of AMO that studies atoms as an isolated system of electrons and an atomic nucleus, while molecular physics is the study of the physical properties of molecules. The term atomic physics is often associated with nuclear power and nuclear bombs, due to the synonymous use of atomic and nuclear in standard English. However, physicists distinguish between atomic physics — which deals with the atom as a system consisting of a nucleus and electrons — and nuclear physics, which considers atomic nuclei alone. The important experimental techniques are the various types of spectroscopy. Molecular physics, while closely related to atomic physics, also overlaps greatly with theoretical chemistry, physical chemistry and chemical physics.
Both subfields are primarily concerned with electronic structure and the dynamical processes by which these arrangements change. Generally this work involves using quantum mechanics. For molecular physics, this approach is known as quantum chemistry. One important aspect of molecular physics is that the essential atomic orbital theory in the field of atomic physics expands to the molecular orbital theory. Molecular physics is concerned with atomic processes in molecules, but it is additionally concerned with effects due to the molecular structure. Additionally to the electronic excitation states which are known from atoms, molecules are able to rotate and to vibrate. These rotations and vibrations are quantized; there are discrete energy levels. The smallest energy differences exist between different rotational states, therefore pure rotational spectra are in the far infrared region (about 30 - 150 µm wavelength) of the electromagnetic spectrum. Vibrational spectra are in the near infrared (about 1 - 5 µm) and spectra resulting from electronic transitions are mostly in the visible and ultraviolet regions. From measuring rotational and vibrational spectra properties of molecules like the distance between the nuclei can be calculated.
As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular, and optical physics. Physics research groups are usually so classified. | 7 | Physical Chemistry |
Arylsulfonic acids are susceptible to hydrolysis, the reverse of the sulfonation reaction. Whereas benzenesulfonic acid hydrolyzes above 200 °C, most related derivatives are easier to hydrolyze. Thus, heating aryl sulfonic acids in aqueous acid produces the parent arene. This reaction is employed in several scenarios. In some cases the sulfonic acid serves as a water-solubilizing protecting group, as illustrated by the purification of para-xylene via its sulfonic acid derivative. In the synthesis of 2,6-dichlorophenol, phenol is converted to its 4-sulfonic acid derivative, which then selectively chlorinates at the positions flanking the phenol. Hydrolysis releases the sulfonic acid group. | 0 | Organic Chemistry |
Mikhail Tsvet was born on 14 May 1872 in Asti, Italy. His mother was Italian, and his father was a Russian official. His mother died soon after his birth, and he was raised in Geneva, Switzerland. He received his BS degree from the Department of Physics and Mathematics at the University of Geneva in 1893. However, he decided to dedicate himself to botany and received his PhD degree in 1896 for his work on cell physiology. He moved to Saint Petersburg, Russia, in 1896 because his father was recalled from the foreign service. There he started to work at the Biological Laboratory of the Russian Academy of Sciences. His Geneva degrees were not recognized in Russia, and he had to earn Russian degrees. In 1897 he became a teacher of botany courses for women. In 1902 he became a laboratory assistant at the Institute of Plant Physiology of the Warsaw University (now in Poland). In 1903 he became an assistant professor and taught also at other Warsaw universities. After the beginning of World War I, the Warsaw University of Technology was evacuated to Moscow, Russia, and in 1916 again to Gorki near Moscow. In 1917 he became a Professor of Botany and the director of the botanical gardens at the University of Tartu (Yuryev) (now in Estonia). In 1918 when German troops occupied the city, the university was evacuated to Voronezh, a large city in the south of Central Russia. Tsvet died of a chronic inflammation of the throat on 26 June 1919 at the age of 47. | 3 | Analytical Chemistry |
There are three major epidermal cell types which all ultimately derive from the outermost (L1) tissue layer of the shoot apical meristem, called protodermal cells: trichomes, pavement cells and guard cells, all of which are arranged in a non-random fashion.
An asymmetrical cell division occurs in protodermal cells resulting in one large cell that is fated to become a pavement cell and a smaller cell called a meristemoid that will eventually differentiate into the guard cells that surround a stoma. This meristemoid then divides asymmetrically one to three times before differentiating into a guard mother cell. The guard mother cell then makes one symmetrical division, which forms a pair of guard cells. Cell division is inhibited in some cells so there is always at least one cell between stomata.
Stomatal patterning is controlled by the interaction of many signal transduction components such as EPF (Epidermal Patterning Factor), ERL (ERecta Like) and YODA (a putative MAP kinase kinase kinase). Mutations in any one of the genes which encode these factors may alter the development of stomata in the epidermis. For example, a mutation in one gene causes more stomata that are clustered together, hence is called Too Many Mouths (TMM). Whereas, disruption of the SPCH (SPeecCHless) gene prevents stomatal development all together. Inhibition of stomatal production can occur by the activation of EPF1, which activates TMM/ERL, which together activate YODA. YODA inhibits SPCH, causing SPCH activity to decrease, preventing asymmetrical cell division that initiates stomata formation. Stomatal development is also coordinated by the cellular peptide signal called stomagen, which signals the activation of the SPCH, resulting in increased number of stomata.
Environmental and hormonal factors can affect stomatal development. Light increases stomatal development in plants; while, plants grown in the dark have a lower amount of stomata. Auxin represses stomatal development by affecting their development at the receptor level like the ERL and TMM receptors. However, a low concentration of auxin allows for equal division of a guard mother cell and increases the chance of producing guard cells.
Most angiosperm trees have stomata only on their lower leaf surface. Poplars and willows have them on both surfaces. When leaves develop stomata on both leaf surfaces, the stomata on the lower surface tend to be larger and more numerous, but there can be a great degree of variation in size and frequency about species and genotypes. White ash and white birch leaves had fewer stomata but larger in size. On the other hand sugar maple and silver maple had small stomata that were more numerous. | 5 | Photochemistry |
The basic requirements for the formation of euxinic conditions are the absence of oxygen (O), and the presence of sulfate ions (SO), organic matter (CHO), and bacteria capable of reducing sulfate to hydrogen sulfide (HS). The bacteria utilize the redox potential of sulfate as an oxidant and organic matter as a reductant to generate chemical energy through cellular respiration. The chemical species of interest can be represented via the reaction:
2CHO + SO → HS + 2HCO
In the reaction above, the sulfur has been reduced to form the byproduct hydrogen sulfide, the characteristic compound present in water under euxinic conditions. Although sulfate reduction occurs in waters throughout the world, most modern-day aquatic habitats are oxygenated due to photosynthetic production of oxygen and gas exchange between the atmosphere and surface water. Sulfate reduction in these environments is often limited to occurring in seabed sediments that have a strong redox gradient and become anoxic at some depth below the sediment-water interface. In the ocean the rate of these reactions is not [https://online.science.psu.edu/biol011_active002/node/4343 limited] by sulfate, which has been present in large quantities throughout the oceans for the past 2.1 billion years. The Great Oxygenation Event increased atmospheric oxygen concentrations such that oxidative weathering of sulfides became a major source of sulfate to the ocean. Despite plentiful sulfate ions being present in solution, they are not preferentially used by most bacteria. The reduction of sulfate does not give as much energy to an organism as reduction of oxygen or nitrate, so the concentrations of these other elements must be nearly zero for sulfate-reducing bacteria to out-compete aerobic and denitrifying bacteria. In most modern settings these conditions only occur in a small portion of sediments, resulting in insufficient concentrations of hydrogen sulfide to form euxinic waters.
Conditions required for the formation of persistent euxinia include anoxic waters, high nutrient levels, and a stratified water column. These conditions are not all-inclusive and are based largely on modern observations of euxinia. Conditions leading up to and triggering large-scale euxinic events, such as the Canfield ocean, are likely the result of multiple interlinking factors, many of which have been inferred through studies of the geologic record at relevant locations. The formation of stratified anoxic waters with high nutrient levels is influenced by a variety of global and local-scale phenomena such as the presence of nutrient traps and a warming climate. | 9 | Geochemistry |
A molecular-weight size marker, also referred to as a protein ladder, DNA ladder, or RNA ladder, is a set of standards that are used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to migration rate through a gel matrix. Therefore, when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known).
Protein, DNA, and RNA markers with pre-determined fragment sizes and concentrations are commercially available. These can be run in either agarose or polyacrylamide gels. The markers are loaded in lanes adjacent to sample lanes before the commencement of the run. | 1 | Biochemistry |
Any charged particle, such as an ion, feels a force from an electric or magnetic field. Ion traps work by using this force to confine ions in a small, isolated volume of space so that they can be studied or manipulated. Although any static (constant in time) electromagnetic field produces a force on an ion, it is not possible to confine an ion using only a static electric field. This is a consequence of Earnshaw's theorem. However, physicists have various ways of working around this theorem by using combinations of static magnetic and electric fields (as in a Penning trap) or by an oscillating electric field and a static electric field(Paul trap). Ion motion and confinement in the trap is generally divided into axial and radial components, which are typically addressed separately by different fields. In both Paul and Penning traps, axial ion motion is confined by a static electric field. Paul traps use an oscillating electric field to confine the ion radially and Penning traps generate radial confinement with a static magnetic field. | 7 | Physical Chemistry |
An important early contribution was made by Pierre Prevost in 1791. Prevost considered that what is nowadays called the photon gas or electromagnetic radiation was a fluid that he called "free heat". Prevost proposed that free radiant heat is a very rare fluid, rays of which, like light rays, pass through each other without detectable disturbance of their passage. Prevost's theory of exchanges stated that each body radiates to, and receives radiation from, other bodies. The radiation from each body is emitted regardless of the presence or absence of other bodies.
Prevost in 1791 offered the following definitions (translated):
Prevost went on to comment that "The heat of several portions of space at the same temperature, and next to one another, is at the same time in the two species of equilibrium." | 7 | Physical Chemistry |
*Children
*Pregnancy
*Lactation
*Situations where a patient has a history of hypersensitivity
*Kidney failure | 4 | Stereochemistry |
Episomes in prokaryotes are special sequences which can divide either separate from or integrated into the prokaryotic chromosome. | 1 | Biochemistry |
A concentration cell is an electrochemical cell where the two electrodes are the same material, the electrolytes on the two half-cells involve the same ions, but the electrolyte concentration differs between the two half-cells.
An example is an electrochemical cell, where two copper electrodes are submerged in two copper(II) sulfate solutions, whose concentrations are 0.05 M and 2.0 M, connected through a salt bridge. This type of cell will generate a potential that can be predicted by the Nernst equation. Both can undergo the same chemistry (although the reaction proceeds in reverse at the anode)
:Cu + 2 e → Cu
Le Chateliers principle indicates that the reaction is more favorable to reduction as the concentration of Cu ions increases. Reduction will take place in the cells compartment where the concentration is higher and oxidation will occur on the more dilute side.
The following cell diagram describes the concentration cell mentioned above:
:Cu | Cu (0.05 M) || Cu (2.0 M) | Cu
where the half cell reactions for oxidation and reduction are:
:Oxidation: Cu → Cu (0.05 M) + 2 e
:Reduction: Cu (2.0 M) + 2 e → Cu
:Overall reaction: Cu (2.0 M) → Cu (0.05 M)
The cell's emf is calculated through the Nernst equation as follows:
The value of E° in this kind of cell is zero, as electrodes and ions are the same in both half-cells.
After replacing values from the case mentioned, it is possible to calculate cell's potential:
or by:
However, this value is only approximate, as reaction quotient is defined in terms of ion activities which can be approximated with the concentrations as calculated here.
The Nernst equation plays an important role in understanding electrical effects in cells and organelles. Such effects include nerve synapses and cardiac beat as well as the resting potential of a somatic cell. | 7 | Physical Chemistry |
In their reactions with metal complexes, diazonium cations behave similarly to . For example, low-valent metal complexes add with diazonium salts. Illustrative complexes are and the chiral-at-metal complex . | 0 | Organic Chemistry |
Cyanobacteria use the energy of sunlight to drive photosynthesis, a process where the energy of light is used to synthesize organic compounds from carbon dioxide. Because they are aquatic organisms, they typically employ several strategies which are collectively known as a " concentrating mechanism" to aid in the acquisition of inorganic carbon ( or bicarbonate). Among the more specific strategies is the widespread prevalence of the bacterial microcompartments known as carboxysomes, which co-operate with active transporters of CO and bicarbonate, in order to accumulate bicarbonate into the cytoplasm of the cell. Carboxysomes are icosahedral structures composed of hexameric shell proteins that assemble into cage-like structures that can be several hundreds of nanometres in diameter. It is believed that these structures tether the -fixing enzyme, RuBisCO, to the interior of the shell, as well as the enzyme carbonic anhydrase, using metabolic channeling to enhance the local concentrations and thus increase the efficiency of the RuBisCO enzyme. | 5 | Photochemistry |
Aminosulfuranes are highly selective for the replacement of hydroxyl groups with fluoride, but in the absence of alcohol functionality, they have the ability to transform a wide array of substrates into the corresponding fluorides or acyl fluorides. For example, ketones are converted to geminal difluorides. However, unlike sulfur tetrafluoride, aminosulfuranes do not convert carboxylic acids into trifluoromethyl groups; the reaction halts at the acyl fluoride stage. Silyl ethers are converted to organofluorides in the presence of DAST.
Aldehydes and ketones react with DAST to form the corresponding geminal difluorides. Fluorination of enolizable ketones gives a mixture of the difluoroalkane and vinyl fluoride. In glyme with fuming sulfuric acid, the vinyl fluoride product predominates. Electron-rich carbonyl compounds, such as esters and amides, do not react with DAST or other aminosulfuranes.
Epoxides may yield a variety of products depending on their structure. Generally, the products that form in highest yield are vicinal difluorides and bis(α-fluoroalkyl)ethers. However, this reaction results in low yields and is not synthetically useful.
The polar mechanism of fluorination by DAST implies that certain substrates may suffer Wagner-Meerwein rearrangements. This process has been observed in the fluorination of pivalaldehyde, which affords a mixture of 1,2-difluoro-1,2-dimethylpropane, 1,1-difluoro-2,2-dimethylpropane, and 1-fluoro-2,2-dimethylethylene.
Diols can undergo pinacol rearrangement under fluorination conditions.
When sulfoxides are treated with DAST, an interesting Pummerer-type rearrangement occurs to afford α-fluoro sulfides. | 0 | Organic Chemistry |
Falipamil is a bradycardic drug focused on decreasing the heart rate of animals. The drug focuses on treating sinuses in some animals, with the most common experiments being conducted in dogs. Falipamil is commonly administered to reduce sinus, and different dosage administrations have proven to bear different results When given in small doses, the drug is effective in reducing sinus rate, but when given in high doses, the drug increases the sinus rate as the drug increases the atrial pumping rate, thus increasing the amount of body fluid pumped through the body to the face. When falipamil is administered, the drug decreases the ventricular rate of the heart, which in turn helps reduce the sinus rate in an organism.
Falipamil has different effects on the electrophysiological structure of the heart, where different dosages result in different heart activity rates with diverse vagolytic actions. Recent studies have been carried out on dogs to determine the effectiveness of the drug in treating sinuses. When administered to a conscious dog, the sinus heart rate of the dog increases, whereas when administered to a stale dog, the animal experiences a lessened heart rate. The electrophysiological result of administering falipamil shows that the drug decreases the maximal atrial driving frequency when administered to a conscious dog, which is an effective measure in reducing sinus in a living organism. Falipamil administration also shows that the administration of the drug increases the bodys action potential exerting less bradycardic effects that are effective in reducing sinuses. Fallipamil does have different recovery times when administered to dogs involved in different activities. Intact dogs are likely to have short sinus recovery time-conscious dogs. Falipamil has a positive effect on the hearts refractory period, where the drug prolongs the atrial refractory period. | 1 | Biochemistry |
This jumping library uses adaptors containing markers for fragment selection in combination with barcodes for multiplexing. The protocol was developed by Talkowski et al. and based on mate-pair library preparation for SOLiD sequencing. The selected DNA fragment size is 3.5 – 4.5 kb. Two adaptors were involved: one containing an EcoP15I recognition site and an AC overhang; the other containing a GT overhang, a biotinylated thymine, and an oligo barcode. The circularized DNA was digested and the fragments with biotynylated adaptors were selected for (see Figure 3). The EcoP15I recognition site and barcode help to distinguish junction fragments from nonjump fragments. These targeted fragments should contain 25 to 27bp of genomic DNA, the EcoP15I recognition site, the overhang, and the barcode. | 1 | Biochemistry |
Pioneer factors can exhibit their greatest range of effects on transcription through the modulation of epigenetic factors by recruiting activating or repressing histone modification enzymes and controlling CpG methylation by protecting specific cysteine residues. This has effects on controlling the timing of transcription during cell differentiation processes. | 1 | Biochemistry |
Luciferins have been shown to be largely conserved among different species while luciferases show a greater degree of diversity. Eighty percent of the species that exhibit bioluminescence exist in aquatic habitats. | 1 | Biochemistry |
Quantitative filter paper, also called ash-free filter paper, is used for quantitative and gravimetric analysis. During the manufacturing, producers use acid to make the paper ash-less and achieve high purity. | 3 | Analytical Chemistry |
The process of converting pig iron into wrought iron (also known as bar iron) was at that time carried out in a finery forge, which was fuelled by charcoal. Charcoal was a limited resource, but coal, more widely available, could not be used because the sulphur in coal would adversely affect the quality of the wrought iron.
George Cranege worked in Coalbrookdale in Shropshire, at the ironworks established by Abraham Darby I, and his brother Thomas worked at a forge in Bridgnorth in Shropshire. They suggested to Richard Reynolds, manager of the works at Coalbrookdale, that the conversion process could be done in a reverbatory furnace, where the iron did not mix with the coal. Reynolds was sceptical, but authorized the brothers to try out the idea.
Richard Reynolds, in a letter dated 25 April 1766 to his colleague Thomas Goldney III, described his conversation with the Craneges and the experiment:
A patent for the process, dated 17 June 1766, in the name of the brothers Cranege, was secured. It apparently made little difference to the lives of the brothers. The process was improved soon afterwards, by Peter Onions who received a patent in 1783, and by Henry Cort who received patents in 1783 and 1784 for his improvements. | 8 | Metallurgy |
The largest steps towards the modern treatment was the formulation of quantum mechanics with the matrix mechanics approach by Werner Heisenberg and the discovery of the Schrödinger equation by Erwin Schrödinger.
There are a variety of semi-classical treatments within AMO. Which aspects of the problem are treated quantum mechanically and which are treated classically is dependent on the specific problem at hand. The semi-classical approach is ubiquitous in computational work within AMO, largely due to the large decrease in computational cost and complexity associated with it.
For matter under the action of a laser, a fully quantum mechanical treatment of the atomic or molecular system is combined with the system being under the action of a classical electromagnetic field. Since the field is treated classically it can not deal with spontaneous emission. This semi-classical treatment is valid for most systems, particular those under the action of high intensity laser fields. The distinction between optical physics and quantum optics is the use of semi-classical and fully quantum treatments respectively.
Within collision dynamics and using the semi-classical treatment, the internal degrees of freedom may be treated quantum mechanically, whilst the relative motion of the quantum systems under consideration are treated classically. When considering medium to high speed collisions, the nuclei can be treated classically while the electron is treated quantum mechanically. In low speed collisions the approximation fails.
Classical Monte-Carlo methods for the dynamics of electrons can be described as semi-classical in that the initial conditions are calculated using a fully quantum treatment, but all further treatment is classical. | 7 | Physical Chemistry |
In biochemistry, a rate-limiting step is a step that controls the rate of a series of biochemical reactions. The statement is, however, a misunderstanding of how a sequence of enzyme catalyzed reaction steps operate. Rather than a single step controlling the rate, it has been discovered that multiple steps control the rate. Moreover, each controlling step controls the rate to varying degrees.
Blackman (1905) stated as an axiom: "when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest factor." This implies that it should be possible, by studying the behavior of a complicated system such as a metabolic pathway, to characterize a single factor or reaction (namely the slowest), which plays the role of a master or rate-limiting step. In other words, the study of flux control can be simplified to the study of a single enzyme since, by definition, there can only be one rate-limiting step. Since its conception, the rate-limiting step has played a significant role in suggesting how metabolic pathways are controlled. Unfortunately, the notion of a rate-limiting step is erroneous, at least under steady-state conditions. Modern biochemistry textbooks have begun to play down the concept. For example, the seventh edition of Lehninger Principles of Biochemistry explicitly states: "It has now become clear that, in most pathways, the control of flux is distributed among several enzymes, and the extent to which each contributes to the control varies with metabolic circumstances". However, the concept is still incorrectly used in research articles. | 1 | Biochemistry |
Roofing shingles and roll roofing account for most of the remaining bitumen consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Bitumen is used to make Japan black, a lacquer known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker. Bitumen is also used to seal some alkaline batteries during the manufacturing process. | 7 | Physical Chemistry |
During the night, a plant employing CAM has its stomata open, allowing to enter and be fixed as organic acids by a PEP reaction similar to the pathway. The resulting organic acids are stored in vacuoles for later use, as the Calvin cycle cannot operate without ATP and NADPH, products of light-dependent reactions that do not take place at night. | 5 | Photochemistry |
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