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The BIOPAN program started in the early nineties with an ESA contract for the a joint development by Kayser-Threde and Kayser Italia. It was based on the heritage of a low-tech Russian exposure container called KNA (Kontejner Nauchnoj Apparatury). The BIOPAN facilities are installed on the external surface of Foton descent capsules. It has a motor-driven hinged lid, which opens 180° in Earth orbit to expose the experiment samples to the harsh space environment. For re-entry, the closed facility is protected with an Ablative heat shield.
The BIOPAN facilities are equipped with thermometers, UV sensors, a radiometer, a pressure sensor and an active radiation dosimeter. Data acquired by the sensors is stored by BIOPAN throughout each mission and can be accessed after flight. The possibility of overheating during atmospheric re-entry was acknowledged early during the development, therefore, a quite massive heat shield was designed for it. While the total weight of BIOPAN is close to 27 kg, including the experiments, the heat shield is responsible for 12 kg of that figure.
The BIOPAN electronics consists of the following units: signal acquisition board, microcontroller board with its flight software, memory board and EGSE. | 1 | Applied and Interdisciplinary Chemistry |
Cys-loop receptors have structural elements that are well conserved, with a large extracellular domain (ECD) harboring an alpha-helix and 10 beta-strands. Following the ECD, four transmembrane segments (TMSs) are connected by intracellular and extracellular loop structures. Except the TMS 3-4 loop, their lengths are only 7-14 residues. The TMS 3-4 loop forms the largest part of the intracellular domain (ICD) and exhibits the most variable region between all of these homologous receptors. The ICD is defined by the TMS 3-4 loop together with the TMS 1-2 loop preceding the ion channel pore. Crystallization has revealed structures for some members of the family, but to allow crystallization, the intracellular loop was usually replaced by a short linker present in prokaryotic cys-loop receptors, so their structures as not known. Nevertheless, this intracellular loop appears to function in desensitization, modulation of channel physiology by pharmacological substances, and posttranslational modifications. Motifs important for trafficking are therein, and the ICD interacts with scaffold proteins enabling inhibitory synapse formation. | 1 | Applied and Interdisciplinary Chemistry |
Dielectrics are used in radio frequency (RF) transmission lines. In a coaxial cable, polyethylene can be used between the center conductor and outside shield. It can also be placed inside waveguides to form filters. Optical fibers are examples of dielectric waveguides. They consist of dielectric materials that are purposely doped with impurities so as to control the precise value of ε within the cross-section. This controls the refractive index of the material and therefore also the optical modes of transmission. However, in these cases it is technically the relative permittivity that matters, as they are not operated in the electrostatic limit. | 0 | Theoretical and Fundamental Chemistry |
Source: (1968–2002)
*2022 Cecília Rodrigues (University of Lisbon, Portugal)
*2019 Mathias Uhlen
*2018 Albert J.R. Heck
*2017 Carol V. Robinson
*2016 Kári Stefánsson
*2015 Jürgen Knoblich
*2014 Michael N. Hall
*2013 Richard J. Roberts
*2012 V. Ramakrishnan
*2011 Elena Conti
*2010 Harald Stenmark
*2009 Václav Hořejší
*2008 Tim Hunt
*2007 Tom Rapoport
*2006 Aaron Ciechanover
*2005 Thomas Jenuwein
*2004 Ryszard Gryglewski
*2003 No award?
*2002 Jacques Pouysségur
*2001 Sir Philip Cohen
*2000 Thomas Steitz
*1999 Stanley B. Prusiner
*1998 Bengt I. Samuelsson
*1997 David Baltimore
*1996 Josef Stefaan Schell
*1995 Kim Nasmyth
*1994 Jean-Pierre Changeux
*1993 Christiane Nüsslein-Volhard
*1992 Robert Huber
*1991 No Award
*1990 Pierre Chambon
*1989 Helmut Beinert
*1988 No award
*1987 Tom Blundell
*1986 Gottfried Schatz
*1985 Robert Joseph Paton Williams
*1984 Richard Henderson
*1983 Arthur Kornberg
*1982 François Jacob
*1981 Cesar Milstein
*1980 Sydney Brenner (No lecture due to illness)
*1979 Pierre Desnuelle
*1978 Peter D. Mitchell
*1977 Francis Crick
*1976 No award
*1975 Heinz-Gunter Wittmann
*1974 Charles Weissmann
*1973 Arthur B. Pardee
*1972 Ephraim Katchalski
*1971 David Chilton Phillips
*1970 No Award
*1969 Alexander Spirin
*1968 Max Perutz (inaugural award) | 1 | Applied and Interdisciplinary Chemistry |
* They are considered to be among the strongest of all types of chemical bonds. This often causes ionic compounds to be very stable.
* Ionic bonds have high bond energy. Bond energy is the mean amount of energy required to break the bond in the gaseous state.
* Most ionic compounds exist in the form of a crystal structure, in which the ions occupy the corners of the crystal. Such a structure is called a crystal lattice.
* Ionic compounds lose their crystal lattice structure and break up into ions when dissolved in water or any other polar solvent. This process is called solvation. The presence of these free ions makes aqueous ionic compound solutions good conductors of electricity. The same occurs when the compounds are heated above their melting point in a process known as melting. | 0 | Theoretical and Fundamental Chemistry |
In molecular biology, an arginine finger is an amino acid residue of some enzymes. Arginine fingers are often found in the protein superfamily of AAA+ ATPases, GTPases, and dUTPases, where they assist in the catalysis of the gamma phosphate or gamma and beta phosphates from ATP or GTP, which creates a release of energy which can be used to perform cellular work. They are also found in GTPase-activating proteins (GAP). Thus, they are essential for many forms of life, and are highly conserved. Arginine fingers function through non-covalent interactions. They may also assist in dimerization, and while they are found in a wide variety of enzymes, they are not ubiquitous. | 1 | Applied and Interdisciplinary Chemistry |
The hearths may be individually heated and the number, temperature, rotation rate, and size of each hearth determine the residence time and conditions for the calcining powder in order to achieve the desired final properties. | 1 | Applied and Interdisciplinary Chemistry |
Mesembrine is an alkaloid present in Sceletium tortuosum (kanna). It has been shown to act as a serotonin reuptake inhibitor (K = 1.4 nM), and more recently, has also been found to behave as a weak inhibitor of the enzyme phosphodiesterase 4 (PDE4) (K = 7,800 nM). In an in vitro study published in 2015, researchers concluded that "a high-mesembrine Sceletium extract" may exert anti-depressant effects by acting as a monoamine releasing agent." As such, mesembrine likely plays a dominant role in the antidepressant effects of kanna. The levorotatory isomer, (−)-mesembrine, is the natural form.
Rat studies have evaluated effects of kanna extract, finding analgesic and antidepressant potential. No adverse results were noted for a commercial extract up to 5000 mg/kg daily in rats.
Mesembrine has also been identified in Mesembryanthemum cordifolium, Delosperma echinatum and Oscularia deltoides. | 0 | Theoretical and Fundamental Chemistry |
Prostanoids were discovered through biological research studies conducted in the 1930s. The first discovery was seen through semen by a Swedish Physiologist Ulf von Euler, who assumed they originated from the prostate. After intensive study throughout the 1960-1970s Sune K. Bergström and Bengt Ingemar Samuelsson and British biochemist Sir John Robert Vane were able to understand the function and chemical formation of Prostanoids: receiving a Nobel Prize for their analysis of prostanoids. | 1 | Applied and Interdisciplinary Chemistry |
Type I, or IEC I, ferric or normal cassettes were historically the first, the most common and the least expensive; they dominated the prerecorded cassette market. The magnetic layer of a ferric tape consists of around 30% synthetic binder and 70% magnetic powder — acicular (oblong, needle-like) particles of gamma ferric oxide (γ-FeO), with a length of to . Each particle of such size contains a single magnetic domain. The powder was and still is manufactured in bulk by chemical companies specializing in mineral pigments for the paint industry. Ferric magnetic layers are brown in colour, whose shade and intensity depends mostly on the size of the particles.
Type I tapes must be recorded with normal (low) bias flux and replayed with a time constant. Over time, ferric oxide technology developed continuously, with new, superior generations emerging around every five years. Cassettes of various periods and price points can be sorted into three distinct groups: basic coarse-grained tapes; advanced fine-grained, or microferric, tapes; and highest-grade ferricobalt tapes, having ferric oxide particles encapsulated in a thin layer of cobalt-iron compound. Ferricobalt tapes are often called cobalt doped, however, this is historically incorrect. Cobalt doping in a strict sense involves uniform substitution of iron atoms with cobalt. This technology has been tried for audio and failed, losing to chromium dioxide. Later, the industry has chosen the far more reliable and repeatable process of cobalt adsorption — encapsulation of unmodified iron oxide particles in a thin layer of cobalt ferrite.
The remanence and squareness properties of the three groups substantially differ, while coercivity remains almost unchanged at around ( for the IEC reference tape approved in 1979). Quality Type I cassettes have higher midrange MOL than most Type II tapes, slow and gentle MOL roll-off at low frequencies, but less high-frequency headroom than Type II. In practice, that means that ferric tapes have lower fidelity compared to chrome tapes and metal tapes at high frequencies, but are often better at reproducing the low frequencies found in bass-heavy music. | 0 | Theoretical and Fundamental Chemistry |
The presence of atmospheric oxygen has led to the formation of ozone (O) and the ozone layer within the stratosphere:
:O + O :- O
The ozone layer is extremely important to modern life as it absorbs harmful ultraviolet radiation: | 0 | Theoretical and Fundamental Chemistry |
The conventional food contaminant test methods may be limited by complicated/tedious sample preparing procedure, long testing time, sumptuous instrument, and professional operator. However, some rapid, novel, sensitive, and easy to use and affordable methods were developed including:
* Cyanidin quantification by naphthalimide-based azo dye colorimetric probe.
* Lead quantification by modified immunoassay test strip based on a heterogeneously sized gold amplified probe.
* Microbial toxin by HPLC with UV-Vis or fluorescence detection and competitive immunoassays with ELISA configuration.
* Bacterial virulence genes detection reverse-transcription polymerase chain reaction (RT-PCR) and DNA colony hybridization.
* Pesticide detection and quantification by strip-based immunoassay, a test strip based on functionalized AuNPs, and test strip, surface-enhanced raman spectroscopy (SERS).
* Enrofloxacin (chickens antibiotic) quantification by a Ru(phen)3 2+- doped silica fluorescent nanoparticle (NP) based immunochromatographic test strip and a portable fluorescent strip reader.
* Nitrite quantification by The PRhB-based electrochemical sensors and Ion selective electrodes (ISEs). | 0 | Theoretical and Fundamental Chemistry |
Overall, research and development expenses relating to developing drugs amount to billions of dollars. A 2012 study found that research and development of a drug is riskier than product development in other industries because it is lengthy, costly, and highly uncertain, particularly due to unpredictable human physiological responses to drugs. As an example, in 2018, Roche spent $11 billion for research and developmental expenses, and had two failed Phase III trials for an Alzheimer's drug candidate. | 1 | Applied and Interdisciplinary Chemistry |
Sulfate uptake first occurs in roots that have a high affinity for sulfur. The maximal sulfate uptake rate is generally already reached at sulfate levels of 0.1 mM and lower. The uptake of sulfate by the roots and its transport to the shoot is strictly controlled and it appears to be one of the primary regulatory sites of sulfur assimilation.
Sulfate is actively taken up across the plasma membrane of the root cells, subsequently loaded into the xylem vessels and transported to the shoot by the transpiration stream. The uptake and transport of sulfate is energy dependent (driven by a proton gradient generated by ATPases) through a proton/sulfate co-transport. In the shoot the sulfate is unloaded and transported to the chloroplasts where it is reduced. The remaining sulfate in plant tissue is predominantly present in the vacuole, since the concentration of sulfate in the cytoplasm is kept rather constant.
Distinct sulfate transporter proteins mediate the uptake, transport and subcellular distribution of sulfate. The sulfate transporters gene family has been classified in up to 5 different groups according to their cellular and sub-cellular gene expression, and possible functioning. Each group of transporter proteins may be expressed exclusively in the roots or shoots of the plant, or both.
* Group 1 are high affinity sulfate transporters, which are involved in the uptake of sulfate by the roots.
* Group 2 are vascular transporters and are low affinity sulfate transporters.
* Group 3 is the so-called leaf group, however, still little is known about the characteristics of this group.
* Group 4 transporters are involved in the efflux of sulfate from the vacuoles, whereas the function of Group 5 sulfate transporters is not known yet, and likely function only as molybdate transporters.
Regulation and expression of the majority of sulfate transporters are controlled by the sulfur nutritional status of the plants. Upon sulfate deprivation, the rapid decrease in root sulfate is regularly accompanied by a strongly enhanced expression of most sulfate transporter genes (up to 100-fold), accompanied by a substantially enhanced sulfate uptake capacity. It is not yet fully understood whether sulfate and other metabolic products of sulfur assimilation (O-acetylserine, cysteine, glutathione) act as signals in the regulation of sulfate uptake and transport, or in the expression of the sulfate transporters involved. | 1 | Applied and Interdisciplinary Chemistry |
A single nucleotide change in a particular sequence, as seen in a double-stranded DNA, cannot be distinguished by gel electrophoresis techniques, which can be attributed to the fact that; the physical properties of the double strands are almost identical for both alleles. After denaturation, single-stranded DNA undergoes a characteristic 3-dimensional folding and may assume a unique conformational state based on its DNA sequence. The difference in shape between two single-stranded DNA strands with different sequences can cause them to migrate differently through an electrophoresis gel, even though the number of nucleotides is the same, which is, in fact, an application of SSCP. | 1 | Applied and Interdisciplinary Chemistry |
The molar concentration is defined as the amount of a constituent (in moles) divided by the volume of the mixture :
The SI unit is mol/m. However, more commonly the unit mol/L (= mol/dm) is used. | 0 | Theoretical and Fundamental Chemistry |
Continuous inkjet printers (as opposed to drop-on-demand inkjet printers) generate a cylindrical stream of ink that breaks up into droplets prior to staining printer paper. By adjusting the size of the droplets using tunable temperature or pressure perturbations and imparting electrical charge to the ink, inkjet printers then steer the stream of droplets using electrostatics to form specific patterns on printer paper | 1 | Applied and Interdisciplinary Chemistry |
Soil contaminated with heavy metals including radionuclides is mitigated primarily using chelating resins.
Chelating polymers (ion-exchange resins) were proposed for maintenance therapy of pathologies accompanied by iron accumulation, such as hereditary hemochromatosis (iron overload) or Wilson's disease (copper overload), by chelating the metal ions in GIT and thus limiting its biological availability. | 0 | Theoretical and Fundamental Chemistry |
Anthocyanins occur in the flowers of many plants, such as the blue poppies of some Meconopsis species and cultivars. Anthocyanins have also been found in various tulip flowers, such as Tulipa gesneriana, Tulipa fosteriana and Tulipa eichleri. | 0 | Theoretical and Fundamental Chemistry |
This receptor is found mediating slow EPSP at the ganglion in the postganglionic nerve, is common in exocrine glands and in the CNS.
It is predominantly found bound to G proteins of class G, which use upregulation of phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signaling pathway. A receptor so bound would not be susceptible to CTX or PTX. However, G (causing a downstream decrease in cAMP) and G (causing an increase in cAMP) have also been shown to be involved in interactions in certain tissues, and so would be susceptible to PTX and CTX, respectively. | 1 | Applied and Interdisciplinary Chemistry |
UV-A presents a potential hazard when eyes and skin are exposed, especially to high power sources. According to the World Health Organization, UV-A is responsible for the initial tanning of skin and it contributes to skin ageing and wrinkling. UV-A may also contribute to the progression of skin cancers. Additionally, UV-A can have negative effects on eyes in both the short-term and long-term. | 0 | Theoretical and Fundamental Chemistry |
The salt was prepared by Edmond Frémy by treating potassium carbonate or potassium hydroxide with hydrofluoric acid:
With one more equivalent of HF, (CAS#12178-06-2, m.p. 71.7 C) is produced:
Thermal decomposition of gives hydrogen fluoride: | 0 | Theoretical and Fundamental Chemistry |
Thermal radiation is one of the three principal mechanisms of heat transfer. It entails the emission of a spectrum of electromagnetic radiation due to an object's temperature. Other mechanisms are convection and conduction. | 0 | Theoretical and Fundamental Chemistry |
A first order reaction depends on the concentration of only one reactant (a unimolecular reaction). Other reactants can be present, but their concentration has no effect on the rate. The rate law for a first order reaction is
Although not affecting the above math, the majority of first order reactions proceed via intermolecular collisions. Such collisions, which contribute the energy to the reactant, are necessarily second order. The rate of these collisions is, however, masked by the fact that the rate determining step remains the unimolecular breakdown of the energized reactant.
The half-life is independent of the starting concentration and is given by . The mean lifetime is τ = 1/k.
Examples of such reactions are:
In organic chemistry, the class of S1 (nucleophilic substitution unimolecular) reactions consists of first-order reactions. For example, in the reaction of aryldiazonium ions with nucleophiles in aqueous solution, , the rate equation is where Ar indicates an aryl group. | 0 | Theoretical and Fundamental Chemistry |
While the radioactive silver isotopes that are produced quickly decay away leaving only stable silver, extracting it for use is not economical, unless as byproduct of platinum group metal extraction. | 0 | Theoretical and Fundamental Chemistry |
Surface plasmons have been used to enhance the surface sensitivity of several spectroscopic measurements including fluorescence, Raman scattering, and second-harmonic generation. In their simplest form, SPR reflectivity measurements can be used to detect molecular adsorption, such as polymers, DNA or proteins, etc. Technically, it is common to measure the angle of minimum reflection (angle of maximum absorption). This angle changes in the order of 0.1° during thin (about nm thickness) film adsorption. (See also the Examples.) In other cases the changes in the absorption wavelength is followed. The mechanism of detection is based on the adsorbing molecules causing changes in the local index of refraction, changing the resonance conditions of the surface plasmon waves. The same principle is exploited in the recently developed competitive platform based on loss-less dielectric multilayers (DBR), supporting surface electromagnetic waves with sharper resonances (Bloch surface waves).
If the surface is patterned with different biopolymers, using adequate optics and imaging sensors (i.e. a camera), the technique can be extended to surface plasmon resonance imaging (SPRI). This method provides a high contrast of the images based on the adsorbed amount of molecules, somewhat similar to Brewster angle microscopy (this latter is most commonly used together with a Langmuir–Blodgett trough).
For nanoparticles, localized surface plasmon oscillations can give rise to the intense colors of suspensions or sols containing the nanoparticles. Nanoparticles or nanowires of noble metals exhibit strong absorption bands in the ultraviolet–visible light regime that are not present in the bulk metal. This extraordinary absorption increase has been exploited to increase light absorption in photovoltaic cells by depositing metal nanoparticles on the cell surface. The energy (color) of this absorption differs when the light is polarized along or perpendicular to the nanowire. Shifts in this resonance due to changes in the local index of refraction upon adsorption to the nanoparticles can also be used to detect biopolymers such as DNA or proteins.
Related complementary techniques include plasmon waveguide resonance, QCM, extraordinary optical transmission, and dual-polarization interferometry. | 0 | Theoretical and Fundamental Chemistry |
RuCl(PPh) is the product of the reaction of ruthenium trichloride trihydrate with a methanolic solution of triphenylphosphine.
:2 RuCl(HO) + 7 PPh → 2 RuCl(PPh) + 2 HCl + 5 HO + OPPh
The coordination sphere of RuCl(PPh) can be viewed as either five-coordinate or octahedral. One coordination site is occupied by one of the hydrogen atoms of a phenyl group. This Ru---H agostic interaction is long (2.59 Å) and weak. The low symmetry of the compound is reflected by the differing lengths of the Ru-P bonds: 2.374, 2.412, and 2.230 Å. The Ru-Cl bond lengths are both 2.387 Å. | 0 | Theoretical and Fundamental Chemistry |
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century. It has been described as "the single most important operation used for the recovery and upgrading of sulfide ores". The development of froth flotation has improved the recovery of valuable minerals, such as copper- and lead-bearing minerals. Along with mechanized mining, it has allowed the economic recovery of valuable metals from much lower-grade ore than previously. | 1 | Applied and Interdisciplinary Chemistry |
The control equations can also be derived in a more rigorous fashion using the systems equation:
where is the stoichiometry matrix, is a vector of chemical species, and is a vector of parameters (or inputs) that can influence the system. In metabolic control analysis the key parameters are the enzyme concentrations. This approach was popularized by Heinrich, Rapoport, and Rapoport and Reder and Mazat. A detailed discussion of this approach can be found in Heinrich & Schuster and Hofmeyr. | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry, fermentation theory refers to the historical study of models of natural fermentation processes, especially alcoholic and lactic acid fermentation. Notable contributors to the theory include Justus Von Liebig and Louis Pasteur, the latter of whom developed a purely microbial basis for the fermentation process based on his experiments. Pasteurs work on fermentation later led to his development of the germ theory of disease, which put the concept of spontaneous generation to rest. Although the fermentation process had been used extensively throughout history prior to the origin of Pasteurs prevailing theories, the underlying biological and chemical processes were not fully understood. In the contemporary, fermentation is used in the production of various alcoholic beverages, foodstuffs, and medications. | 1 | Applied and Interdisciplinary Chemistry |
In subsequent phase II reactions, these activated xenobiotic metabolites are conjugated with charged species such as glutathione (GSH), sulfate, glycine, or glucuronic acid. Sites on drugs where conjugation reactions occur include carboxy (-COOH), hydroxy (-OH), amino (NH), and thiol (-SH) groups. Products of conjugation reactions have increased molecular weight and tend to be less active than their substrates, unlike Phase I reactions which often produce active metabolites. The addition of large anionic groups (such as GSH) detoxifies reactive electrophiles and produces more polar metabolites that cannot diffuse across membranes, and may, therefore, be actively transported.
These reactions are catalysed by a large group of broad-specificity transferases, which in combination can metabolise almost any hydrophobic compound that contains nucleophilic or electrophilic groups. One of the most important classes of this group is that of the glutathione S-transferases (GSTs). | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 3.945. | 0 | Theoretical and Fundamental Chemistry |
According to Agnes Arber's partial-shoot theory of the leaf, leaves are partial shoots, being derived from leaf primordia of the shoot apex. Early in development they are dorsiventrally flattened with both dorsal and ventral surfaces. Compound leaves are closer to shoots than simple leaves. Developmental studies have shown that compound leaves, like shoots, may branch in three dimensions. On the basis of molecular genetics, Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties." | 0 | Theoretical and Fundamental Chemistry |
The development of facile chemical glycosylation protocols is essential to synthesizing complex oligosaccharides. Among many diverse type of glycosidic linkages, the 1,2-cis-β-glycoside, which exists in many biologically relevant glycoconjugates and oligosaccharides, is arguably one of the most difficult to synthesize. The challenges in constructing β-mannose linkage have been well documented in several reviews. To date, a few laboratories have devised efficient methodologies to overcome these synthetic hurdles, and achieved varying degrees of success. Of those elegant approaches, a highly stereoselective β-mannosylation protocol developed by Crich and co-workers was realized as a breakthrough in β-mannoside synthesis. This strategy is based on the initial activation of α-mannosyl sulfoxides 1 with triflic anhydride (TfO) using DTBMP (2,6-di-tert-butyl-4-methylpyridine) as a base, followed by nucleophilic substitution of glycosyl acceptors (HOR) to provide the 1,2-cis-β-glycoside 2 in good yield and selectivity (Scheme 1). | 0 | Theoretical and Fundamental Chemistry |
The strength with which oxygen binds to hemoglobin is affected by several factors. These factors shift or reshape the oxyhemoglobin dissociation curve. A shift to right indicates that the hemoglobin under study has a decreased affinity for oxygen. This makes it more difficult for hemoglobin to bind to oxygen (requiring a higher partial pressure of oxygen to achieve the same oxygen saturation), but it makes it easier for the hemoglobin to release oxygen bound to it.
The effect of this shift of the curve increases the partial pressure of oxygen in the tissues when it is most needed, such as during exercise, or hemorrhagic shock.
In contrast, the curve is shifted to the left by the opposite of these conditions.
This shift indicates that the hemoglobin under study has an increased affinity for oxygen so that hemoglobin binds oxygen more easily, but unloads it more reluctantly.
Left shift of the curve is a sign of hemoglobin's increased affinity for oxygen (e.g. at the lungs).
Similarly, right shift shows decreased affinity, as would appear with an increase in either body temperature, hydrogen ions, 2,3-bisphosphoglycerate (2,3-BPG) concentration or carbon dioxide concentration.
Note:
* Left shift: higher O affinity
* Right shift: lower O affinity
* fetal hemoglobin has higher O affinity than adult hemoglobin; primarily due to much-reduced affinity to 2,3-bisphosphoglycerate .
The causes of shift to right can be remembered using the mnemonic, "CADET, face Right!" for CO, Acid, 2,3-DPG, Exercise and Temperature. Factors that move the oxygen dissociation curve to the right are those physiological states where tissues need more oxygen. For example, during exercise, muscles have a higher metabolic rate, and consequently need more oxygen, produce more carbon dioxide and lactic acid, and their temperature rises. | 1 | Applied and Interdisciplinary Chemistry |
As a result of the capacity of transposon mutagenesis to incorporate genes into most areas of target chromosomes, there are a number of functions associated with the process.
* Virulence genes in viruses and bacteria can be discovered by disrupting genes and observing for a change in phenotype. This has importance in antibiotic production and disease control.
* Non-essential genes can be discovered by inducing transposon mutagenesis in an organism. The transformed genes can then be identified by performing PCR on the organism's recovered genome using an ORF-specific primer and a transposon-specific primer. Since transposons can incorporate themselves into non-coding regions of DNA, the ORF-specific primer ensures that the transposon interrupted a gene. Because the organism survived after homologous integration, the interrupted gene was clearly non-essential.
* Cancer-causing genes can be identified by genome-wide mutagenesis and screening of mutants containing tumours. Based on the mechanism and results of the mutation, cancer-causing genes can be identified as oncogenes or tumour-suppressor genes. | 1 | Applied and Interdisciplinary Chemistry |
In enzymology, the committed step (also known as the first committed step) is an effectively irreversible enzymatic reaction that occurs at a branch point during the biosynthesis of some molecules.
As the name implies, after this step, the molecules are "committed" to the pathway and will ultimately end up in the pathway's final product. The first committed step should not be confused with the rate-limiting step, which is the step with the highest flux control coefficient. It is rare that the first committed step is in fact the rate-determining step. | 1 | Applied and Interdisciplinary Chemistry |
Humans express four epoxide hydrolase isozymes: mEH, sEH, EH3, and EH4. These isozymes are known (mEH and sEH) or presumed (EH3 and EH4) to share a common structure that includes containing an Alpha/beta hydrolase fold and a common reaction mechanism wherein they add water to epoxides to form vicinal cis (see (cis-trans isomerism); see (epoxide#Olefin (alkene) oxidation using organic peroxides and metal catalysts)) diol products. They differ, however, in subcellular location, substrate preferences, tissue expression, and/or function. | 1 | Applied and Interdisciplinary Chemistry |
The main application for air filters are combustion air to engines. The filter papers are transformed into filter cartridges, which then is fitted to a holder. The construction of the cartridges mostly requires that the paper is stiff enough to be self-supporting. A paper for air filters needs to be very porous and have a weight of 100–200 g/m. Normally particularly long fibrous pulp that is mercerised is used to get these properties. The paper is normally impregnated to improve the resistance to moisture. Some heavy duty qualities are made to be rinsed and thereby extend the life of the filter. | 0 | Theoretical and Fundamental Chemistry |
In the 1960s through the 1970s, Paul Boyer, a UCLA Professor, developed the binding change, or flip-flop, mechanism theory, which postulated that ATP synthesis is dependent on a conformational change in ATP synthase generated by rotation of the gamma subunit. The research group of John E. Walker, then at the MRC Laboratory of Molecular Biology in Cambridge, crystallized the F catalytic-domain of ATP synthase. The structure, at the time the largest asymmetric protein structure known, indicated that Boyer's rotary-catalysis model was, in essence, correct. For elucidating this, Boyer and Walker shared half of the 1997 Nobel Prize in Chemistry.
The crystal structure of the F showed alternating alpha and beta subunits (3 of each), arranged like segments of an orange around a rotating asymmetrical gamma subunit. According to the current model of ATP synthesis (known as the alternating catalytic model), the transmembrane potential created by (H+) proton cations supplied by the electron transport chain, drives the (H+) proton cations from the intermembrane space through the membrane via the F region of ATP synthase. A portion of the F (the ring of c-subunits) rotates as the protons pass through the membrane. The c-ring is tightly attached to the asymmetric central stalk (consisting primarily of the gamma subunit), causing it to rotate within the alphabeta of F causing the 3 catalytic nucleotide binding sites to go through a series of conformational changes that lead to ATP synthesis. The major F subunits are prevented from rotating in sympathy with the central stalk rotor by a peripheral stalk that joins the alphabeta to the non-rotating portion of F. The structure of the intact ATP synthase is currently known at low-resolution from electron cryo-microscopy (cryo-EM) studies of the complex. The cryo-EM model of ATP synthase suggests that the peripheral stalk is a flexible structure that wraps around the complex as it joins F to F. Under the right conditions, the enzyme reaction can also be carried out in reverse, with ATP hydrolysis driving proton pumping across the membrane.
The binding change mechanism involves the active site of a β subunit's cycling between three states. In the "loose" state, ADP and phosphate enter the active site; in the adjacent diagram, this is shown in pink. The enzyme then undergoes a change in shape and forces these molecules together, with the active site in the resulting "tight" state (shown in red) binding the newly produced ATP molecule with very high affinity. Finally, the active site cycles back to the open state (orange), releasing ATP and binding more ADP and phosphate, ready for the next cycle of ATP production. | 0 | Theoretical and Fundamental Chemistry |
Norşuntepe was occupied from the Chalcolithic to the Iron Age. The excavators have recognized 40 different occupation levels ranging in date from the fifth millennium BC to ca. 600 BC. Its occupation levels overlap to a large degree with those excavated at nearby Arslantepe. | 1 | Applied and Interdisciplinary Chemistry |
Arketamine appears to be more effective as a rapid-acting antidepressant than esketamine in preclinical research.
In rodent studies, esketamine produced hyperlocomotion, prepulse inhibition deficits, and rewarding effects, while arketamine did not, in accordance with its lower potency as an NMDA receptor antagonist and dopamine reuptake inhibitor. As such, arketamine may have a lower propensity for producing psychotomimetic effects and a lower abuse potential in addition to superior antidepressant efficacy.
A study conducted in mice found that ketamine's antidepressant activity is not caused by ketamine inhibiting NMDAR, but rather by sustained activation of a different glutamate receptor, the AMPA receptor, by a metabolite, (2R,6R)-hydroxynorketamine; as of 2017 it was unknown if this was happening in humans. Arketamine is an AMPA receptor agonist.
Paradoxically, arketamine shows greater and longer-lasting rapid antidepressant effects in animal models of depression relative to esketamine. It has been suggested that this may be due to the possibility of different activities of arketamine and esketamine and their respective metabolites at the α-nicotinic receptor, as norketamine and hydroxynorketamine are potent antagonists of this receptor and markers of potential rapid antidepressant effects (specifically, increased mammalian target of rapamycin function) correlate closely with their affinity for it. The picture is unclear however, and other mechanisms have also been implicated. | 0 | Theoretical and Fundamental Chemistry |
Photosynthate partitioning is the deferential distribution of photosynthates to plant tissues. A photosynthate is the resulting product of photosynthesis, these products are generally sugars. These sugars that are created from photosynthesis are broken down to create energy for use by the plant. Sugar and other compounds move via the phloem to tissues that have an energy demand. These areas of demand are called sinks. While areas with an excess of sugars and a low energy demand are called sources. Many times sinks are the actively growing tissues of the plant while the sources are where sugars are produced by photosynthesis—the leaves of plants. Sugars are actively loaded into the phloem and moved by a positive pressure flow created by solute concentrations and turgor pressure between xylem and phloem vessel elements (specialized plant cells). This movement of sugars is referred to as translocation. When sugars arrive at the sink they are unloaded for storage or broken down/metabolized.
The partitioning of these sugars depends on multiple factors such as the vascular connections that exist, the location of the sink to source, the developmental stage, and the strength of that sink. Vascular connections exist between sources and sinks and those that are the most direct have been shown to receive more photosynthates than those that must travel through extensive connections. This also goes for proximity: those closer to the source are easier to translocate sugars to. Developmental stage plays a large role in partitioning, organs that are young such as meristems and new leaves have a higher demand, as well as those that are entering reproductive maturity—creating fruits, flowers, and seeds. Many of these developing organs have a higher sink strength. Those with higher sink strengths receive more photosynthates than lower strength sinks. Sinks compete to receive these compounds and combination of factors playing in determining how much and how fast sinks receives photosynthates to grow and complete physiological activities. | 0 | Theoretical and Fundamental Chemistry |
The earlier Pantle & Buck method (1955) uses the same saprobic values s of each species, but not the weighting factor g. The Pantle-Buck saprobity index S, ranging from 0 to 4, is thus calculated:
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where the abundance A is expressed as one of nine subjective categories, ranging from "very rare" to "mass development". It does not require the organisms to be counted – which can save a lot of time – but raises the issues of intra- and inter-rater reliability. | 1 | Applied and Interdisciplinary Chemistry |
There have been many variations on the original composition which was Food and Drug Administration (FDA) approved and termed Bioglass. This composition is known as Bioglass 45S5. The compositions include:
* 45S5: 45 wt% SiO, 24.5 wt% CaO, 24.5 wt% NaO and 6.0 wt% PO. Bioglass
* S53P4: 53 wt% SiO, 23 wt% NaO, 20 wt% CaO and 4 wt% PO.
* 58S: 58 wt% SiO, 33 wt% CaO and 9 wt% PO.
* 70S30C: 70 wt% SiO, 30 wt% CaO.
* 13-93: 53 wt% SiO, 6 wt% NaO, 12 wt% KO, 5 wt% MgO, 20 wt% CaO, 4 wt% PO. | 0 | Theoretical and Fundamental Chemistry |
A metabolic network is the complete set of metabolic and physical processes that determine the physiological and biochemical properties of a cell. As such, these networks comprise the chemical reactions of metabolism, the metabolic pathways, as well as the regulatory interactions that guide these reactions.
With the sequencing of complete genomes, it is now possible to reconstruct the network of biochemical reactions in many organisms, from bacteria to human. Several of these networks are available online:
Kyoto Encyclopedia of Genes and Genomes (KEGG), EcoCyc, BioCyc and metaTIGER.
Metabolic networks are powerful tools for studying and modelling metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Clore is one of the most highly cited scientists in the fields of molecular biophysics, structural biology, biomolecular NMR and chemistry with over 550 published scientific articles and an h-index (number of papers cited h or more time) of 143. Clore is also one of only four NIH scientists to have been elected to both the United States National Academy of Sciences and The Royal Society, the other three being Julius Axelrod, Francis Collins and Harold Varmus. | 0 | Theoretical and Fundamental Chemistry |
A lysochrome is a soluble dye used for histochemical staining of lipids, which include triglycerides, fatty acids, and lipoproteins. Lysochromes such as Sudan IV dissolve in the lipid and show up as colored regions. The dye does not stick to any other substrates, so a quantification or qualification of lipid presence can be obtained.
The name was coined by John Baker (biologist) in his book "Principles of Biological Microtechnique", published in 1958, from the Greek words lysis (solution) and chroma (colour). | 1 | Applied and Interdisciplinary Chemistry |
After studying at the École nationale supérieure des industries chimiques de Nancy from 1958 to 1961, he obtained a doctorate under the supervision of Professor Serge David in 1966 and continued for two years at Harvard University in Massachusetts (United States) as a post-doctoral researcher with Professor Roger W. Jeanloz. He then entered the University of Orléans in 1969 as a professor, where he was Director of the Institute of Organic and Analytical Chemistry from 1978 to 1987. He then became Professor of Chemistry in 1986 at the Université Pierre-et-Marie-Curie, where he then headed the Laboratory of Selective Processes in Organic and Bioorganic Chemistry in the Department of Chemistry at the École normale supérieure. He then became Professor Emeritus at Sorbonne University in 2006 and joined the Paris Institute of Molecular Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Although the Pipeline and Hazardous Materials Safety Administration (PHMSA) has standard baseline incident frequencies to estimate the number of spills, TransCanada altered these assumptions based on improved pipeline design, operation, and safety. Whether these adjustments are justified is debatable as these assumptions resulted in a nearly 10-fold decrease in spill estimates. Given that the pipeline crosses 247 miles of the Ogallala Aquifer, or 14.5% of the entire pipeline length, and the 50-year life of the entire pipeline is expected to have between 11 – 91 spills, approximately 1.6 – 13.2 spills can be expected to occur over the aquifer. An estimate of 13.2 spills over the aquifer, each lasting 14 days, results in 184 days of potential exposure over the 50 year lifetime of the pipeline.
In the reduced-scope worst-case exposure scenario, the volume of a pinhole leak at 1.5% of max flow-rate for 14 days has been estimated at 189,000 barrels or 7.9 million gallons of oil. According to PHMSA's incident database, only 0.5% of all spills in the last 10 years were >10,000 barrels. | 1 | Applied and Interdisciplinary Chemistry |
Using a glia-conditioned medium to treat glia-free purified rat retinal ganglion microcultures has been shown to significantly increase the number of autapses per neuron compared to a control. This suggests that glia-derived soluble, proteinase K-sensitive factors induce autapse formation in rat retinal ganglion cells. | 1 | Applied and Interdisciplinary Chemistry |
Cross ventilation relies on many factors, such as the tightness of the establishment, wind direction and how much wind is available, its potential travel through chimneys, vents and other openings in the home. Casement windows can be installed to improve cross-breezes. Air quality may also affect cross ventilation.
Although cross ventilation is generally more direct at its job than stack ventilation, its cons include its effects being unproductive on hot, still days, when it is most necessary. Moreover, cross ventilation is generally only suitable for narrow buildings. The contrasting height of the openings (walls, sill, panels or furniture) ordered by the space also immediately influence the level and velocity of ventilation. | 1 | Applied and Interdisciplinary Chemistry |
The end of the first era of quantum mechanics was triggered by de Broglies publication of his hypothesis of matter waves, leading to Schrödingers discovery of wave mechanics for matter. Accurate predictions of the absorption spectrum of hydrogen ensured wide acceptance of the new quantum theory. | 1 | Applied and Interdisciplinary Chemistry |
In mathematics, a Meyer set or almost lattice is a relatively dense set X of points in the Euclidean plane or a higher-dimensional Euclidean space such that its Minkowski difference with itself is uniformly discrete. Meyer sets have several equivalent characterizations; they are named after Yves Meyer, who introduced and studied them in the context of diophantine approximation. Nowadays Meyer sets are best known as mathematical model for quasicrystals. However, Meyer's work precedes the discovery of quasicrystals by more than a decade and was entirely motivated by number theoretic questions. | 0 | Theoretical and Fundamental Chemistry |
Enantiomeric excess is defined as the absolute difference between the mole fraction of each enantiomer:
where
In practice, it is most often expressed as a percent enantiomeric excess.
The enantiomeric excess can be determined in another way if we know the amount of each enantiomer produced. If one knows the moles of each enantiomer produced then:
Enantiomeric excess is used as one of the indicators of the success of an asymmetric synthesis. For mixtures of diastereomers, there are analogous definitions and uses for diastereomeric excess and percent diastereomeric excess.
As an example, a sample with 70 % of isomer and 30 % of will have a percent enantiomeric excess of 40. This can also be thought of as a mixture of 40 % pure with 60 % of a racemic mixture (which contributes half 30 % and the other half 30 % to the overall composition).
If given the enantiomeric excess of a mixture, the fraction of the main isomer, say , can be determined using and the lesser isomer .
A non-racemic mixture of two enantiomers will have a net optical rotation. It is possible to determine the specific rotation of the mixture and, with knowledge of the specific rotation of the pure enantiomer, the optical purity can be determined.
: optical purity (%) = · 100
Ideally, the contribution of each component of the mixture to the total optical rotation is directly proportional to its mole fraction, and as a result the numerical value of the optical purity is identical to the enantiomeric excess. This has led to informal use the two terms as interchangeable, especially because optical purity was the traditional way of measuring enantiomeric excess. However, other methods such as chiral column chromatography and NMR spectroscopy can now be used for measuring the amount of each enantiomer individually.
The ideal equivalence between enantiomeric excess and optical purity does not always hold. For example,
* the specific rotation of (S)-2-ethyl-2-methyl succinic acid is found to be dependent on concentration
* in what is known as the Horeau effect the relationship between mole based ee and optical rotation based ee can be non-linear i.d. in the succinic acid example the optical activity at 50% ee is lower than expected.
* the specific rotation of enantiopure 1-phenylethanol can be enhanced by the addition of achiral acetophenone as an impurity.
The term enantiomeric excess was introduced in 1971 by Morrison and Mosher in their publication Asymmetric Organic Reactions. The use of enantiomeric excess has established itself because of its historic ties with optical rotation. It has been suggested that the concept of ee should be replaced by that of er which stands for enantiomeric ratio or er (S:R) or q (S/R) because determination of optical purity has been replaced by other techniques which directly measure R and S and because it simplifies mathematical treatments such as the calculation of equilibrium constants and relative reaction rates. The same arguments are valid for changing diastereomeric excess (de) to diastereomeric ratio (dr). | 0 | Theoretical and Fundamental Chemistry |
Another category of plant defenses are those features that indirectly protect the plant by enhancing the probability of attracting the natural enemies of herbivores. Such an arrangement is known as mutualism, in this case of the "enemy of my enemy" variety. One such feature are semiochemicals, given off by plants. Semiochemicals are a group of volatile organic compounds involved in interactions between organisms. One group of semiochemicals are allelochemicals; consisting of allomones, which play a defensive role in interspecies communication, and kairomones, which are used by members of higher trophic levels to locate food sources. When a plant is attacked it releases allelochemics containing an abnormal ratio of these s (HIPVs). Predators sense these volatiles as food cues, attracting them to the damaged plant, and to feeding herbivores. The subsequent reduction in the number of herbivores confers a fitness benefit to the plant and demonstrates the indirect defensive capabilities of semiochemicals. Induced volatiles also have drawbacks, however; some studies have suggested that these volatiles attract herbivores. Crop domestication has increased yield sometimes at the expense of HIPV production. Orre Gordon et al 2013 tests several methods of artificially restoring the plant-predator partnership, by combining companion planting and synthetic predator attractants. They describe several strategies which work and several which do not.
Plants sometimes provide housing and food items for natural enemies of herbivores, known as "biotic" defense mechanisms, as a means to maintain their presence. For example, trees from the genus Macaranga have adapted their thin stem walls to create ideal housing for an ant species (genus Crematogaster), which, in turn, protects the plant from herbivores. In addition to providing housing, the plant also provides the ant with its exclusive food source; from the food bodies produced by the plant. Similarly, several Acacia tree species have developed stipular spines (direct defenses) that are swollen at the base, forming a hollow structure that provides housing for protective ants. These Acacia trees also produce nectar in extrafloral nectaries on their leaves as food for the ants.
Plant use of endophytic fungi in defense is common. Most plants have endophytes, microbial organisms that live within them. While some cause disease, others protect plants from herbivores and pathogenic microbes. Endophytes can help the plant by producing toxins harmful to other organisms that would attack the plant, such as alkaloid producing fungi which are common in grasses such as tall fescue (Festuca arundinacea), which is infected by Neotyphodium coenophialum.
Trees of the same species form alliances with other tree species in order to improve their survival rate. They communicate and have dependent relationships through connections below the soil called underground mycorrhiza networks, which allows them to share water/nutrients and various signals for predatory attacks while also protecting its immune system. Within a forest of trees, the ones getting attacked send communication distress signals that alerts neighboring trees to alter their behavior (defense). The tree and fungi relationship is a symbiotic relationship. Fungi, intertwined with the trees roots, support communication between trees to locate nutrients. In return, the fungi receive some of the sugar that trees photosynthesize. Trees send out several forms of communication including chemical, hormonal, and slow pulsing electric signals. Farmers investigated the electrical signals between trees, using a voltage-based signal system, similar to an animals nervous system, where a tree faces distress and releases a warning signal to surrounding trees. | 1 | Applied and Interdisciplinary Chemistry |
The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily. The production of phosphine gas occurs in isolated and specific conditions. Therefore, the phosphorus cycle is primarily examined studying the movement of orthophosphate (PO), the form of phosphorus that is most commonly seen in the environment, through terrestrial and aquatic ecosystems.
Living organisms require phosphorus, a vital component of DNA, RNA, ATP, etc., for their proper functioning. Plants assimilate phosphorus as phosphate and incorporate it into organic compounds. In animals, phosphorus is a key component of bones, teeth, etc. On the land, phosphorus gradually becomes less available to plants over thousands of years, since it is slowly lost in runoff. Low concentration of phosphorus in soils reduces plant growth and slows soil microbial growth, as shown in studies of soil microbial biomass. Soil microorganisms act as both sinks and sources of available phosphorus in the biogeochemical cycle. Furthermore, phosphorus tends to be a limiting nutrient in aquatic ecosystems. However, as phosphorus enters aquatic ecosystems, it has the possibility to lead to over-production in the form of eutrophication, which can happen in both freshwater and saltwater environments. Short-term transformation of phosphorus is chemical, biological, or microbiological. In the long-term global cycle, however, the major transfer is driven by tectonic movement over geologic time.
Humans have caused major changes to the global phosphorus cycle primarily through the mining and subsequent shipping of phosphorus minerals for use in fertilizer and industrial products. Some phosphorus is also lost as effluent through the shipping process as well. | 0 | Theoretical and Fundamental Chemistry |
*1922-1941, 1945-1950 - Roentgen street, 3;
*1922-1941, 1945-1950 - Kamennoostrovsky Avenue, 23;
*1908-1941, 1945-1949 - Universitetskaya embankment, 7;
*1913-1941 - Bolshaya Zelenina street, 13;
*1945-1950 - Lesnoy Avenue, 61 (House of Specialists). | 0 | Theoretical and Fundamental Chemistry |
Secondary in contrast to primary metabolites are dispensable and not absolutely required for survival. Furthermore, secondary metabolites typically have a narrow species distribution.
Secondary metabolites have a broad range of functions. These include pheromones that act as social signaling molecules with other individuals of the same species, communication molecules that attract and activate symbiotic organisms, agents that solubilize and transport nutrients (siderophores etc.), and competitive weapons (repellants, venoms, toxins etc.) that are used against competitors, prey, and predators. For many other secondary metabolites, the function is unknown. One hypothesis is that they confer a competitive advantage to the organism that produces them. An alternative view is that, in analogy to the immune system, these secondary metabolites have no specific function, but having the machinery in place to produce these diverse chemical structures is important and a few secondary metabolites are therefore produced and selected for.
General structural classes of secondary metabolites include alkaloids, phenylpropanoids, polyketides, and terpenoids. | 1 | Applied and Interdisciplinary Chemistry |
Partially inelastic collisions are the most common form of collisions in the real world. In this type of collision, the objects involved in the collisions do not stick, but some kinetic energy is still lost. Friction, sound and heat are some ways the kinetic energy can be lost through partial inelastic collisions. | 0 | Theoretical and Fundamental Chemistry |
Sometimes a sewer has a tall vent pipe to release foul gases well up away from people. Common names are, stink pipe, stink pole, stench pipe and sewer ventilation pipe. | 1 | Applied and Interdisciplinary Chemistry |
In early "straight-through" urea plants, reactant recovery (the first step in "recycling") was done by letting down the system pressure to atmospheric to let the carbamate decompose back to ammonia and carbon dioxide. Originally, because it was not economic to recompress the ammonia and carbon dioxide for recycle, the ammonia at least would be used for the manufacture of other products such as ammonium nitrate or ammonium sulfate, and the carbon dioxide was usually wasted. Later process schemes made recycling unused ammonia and carbon dioxide practical. This was accomplished by the "total recycle process", developed in the 1940s to 1960s and now called the "conventional recycle process". It proceeds by depressurizing the reaction solution in stages (first to 18–25 bar and then to 2–5 bar) and passing it at each stage through a steam-heated carbamate decomposer, then recombining the resulting carbon dioxide and ammonia in a falling-film carbamate condenser and pumping the carbamate solution back into the urea reaction vessel. | 0 | Theoretical and Fundamental Chemistry |
Conjugated azomethine ylides are capable of [1,5]- and [1,7]-electrocyclizations. An example of a [1,7]-electrocyclization of a azomethine ylide is shown below. This conrotatory ring-closing is followed by a suprafacial [1,5]-hydride shift, which affords the rearomatized product. The sterics and geometry of the reacting phenyl ring play a major role in the success of the reaction.
The compounds resulting from this type of electrocyclization have been used as dienes in Diels–Alder reactions to attach compounds to fullerenes. | 0 | Theoretical and Fundamental Chemistry |
The difficulty of predicting stable crystal structures based on the knowledge of only the chemical composition has long been a stumbling block on the way to fully computational materials design. Now, with more powerful algorithms and high-performance computing, structures of medium complexity can be predicted using such approaches as evolutionary algorithms, random sampling, or metadynamics.
The crystal structures of simple ionic solids (e.g., NaCl or table salt) have long been rationalized in terms of Pauling's rules, first set out in 1929 by Linus Pauling, referred to by many since as the "father of the chemical bond". Pauling also considered the nature of the interatomic forces in metals, and concluded that about half of the five d-orbitals in the transition metals are involved in bonding, with the remaining nonbonding d-orbitals being responsible for the magnetic properties. Pauling was therefore able to correlate the number of d-orbitals in bond formation with the bond length, as well as with many of the physical properties of the substance. He subsequently introduced the metallic orbital, an extra orbital necessary to permit uninhibited resonance of valence bonds among various electronic structures.
In the resonating valence bond theory, the factors that determine the choice of one from among alternative crystal structures of a metal or intermetallic compound revolve around the energy of resonance of bonds among interatomic positions. It is clear that some modes of resonance would make larger contributions (be more mechanically stable than others), and that in particular a simple ratio of number of bonds to number of positions would be exceptional. The resulting principle is that a special stability is associated with the simplest ratios or "bond numbers": , , , , , etc. The choice of structure and the value of the axial ratio (which determines the relative bond lengths) are thus a result of the effort of an atom to use its valency in the formation of stable bonds with simple fractional bond numbers.
After postulating a direct correlation between electron concentration and crystal structure in beta-phase alloys, Hume-Rothery analyzed the trends in melting points, compressibilities and bond lengths as a function of group number in the periodic table in order to establish a system of valencies of the transition elements in the metallic state. This treatment thus emphasized the increasing bond strength as a function of group number. The operation of directional forces were emphasized in one article on the relation between bond hybrids and the metallic structures. The resulting correlation between electronic and crystalline structures is summarized by a single parameter, the weight of the d-electrons per hybridized metallic orbital. The "d-weight" calculates out to 0.5, 0.7 and 0.9 for the fcc, hcp and bcc structures respectively. The relationship between d-electrons and crystal structure thus becomes apparent.
In crystal structure predictions/simulations, the periodicity is usually applied, since the system is imagined as being unlimited in all directions. Starting from a triclinic structure with no further symmetry property assumed, the system may be driven to show some additional symmetry properties by applying Newton's Second Law on particles in the unit cell and a recently developed dynamical equation for the system period vectors
(lattice parameters including angles), even if the system is subject to external stress. | 0 | Theoretical and Fundamental Chemistry |
The mutation of Dally is a consequence of the P-element and the place where it is located. It is possible to differentiate between the mutants Dally-P1 and Dally-P2, depending on where the insertion of P-element is. It is known that Dally-P2 generates a bigger amount of defects. This mutated Dally disrupts the cell cycle progression, delaying the process during the G2-mitosis transition. As a matter of fact, mutations affecting Dally disrupt patterning of many tissues, for instance of the nervous system. Dally mutants display cell cycle progression defects in specific sets of dividing cells. Those mutations are pleiotropic and can affect viability and produce morphological defects in several adult tissues, such as the eye, antenna, wing and genitalia. | 1 | Applied and Interdisciplinary Chemistry |
FRI has tested various types of fractionation trays and packings (both generic and proprietary designs), with the objective of developing correlations for predicting tray efficiencies and pressure drops. This information is needed to design fractionators, absorbers and strippers. It has also tested performance of other column internals such as liquid distributors. It periodically reports its findings to the member companies.
The OSU library maintains an unrestricted collection of FRI progress reports, plant tests, topical reports, consultants’ reports and annual reports that were issued during the period 1954 – 1970.
FRI has also produced a number of unrestricted instructional films and videos, which are listed on its home page. These are available to non-members. | 1 | Applied and Interdisciplinary Chemistry |
Low-template DNA can happen when there is less than 0.1 ng() of DNA in a sample. This can lead to more stochastic effects (random events) such as allelic dropout or allelic drop-in which can alter the interpretation of a DNA profile. These stochastic effects can lead to the unequal amplification of the 2 alleles that come from a heterozygous individual. It is especially important to take low-template DNA into account when dealing with a mixture DNA sample. This is because for one (or more) of the contributors in the mixture, they are more likely to have less than the optimal amount of DNA for the PCR reaction to work properly. Therefore, stochastic thresholds are developed for DNA profile interpretation. The stochastic threshold is the minimum peak height (RFU value), seen in an electropherogram where dropout occurs. If the peak height value is above this threshold, then it is reasonable to assume that allelic dropout has not occurred. For example, if only 1 peak is seen for a particular locus in the electropherogram but its peak height is above the stochastic threshold, then we can reasonably assume that this individual is homozygous and is not missing its heterozygous partner allele that otherwise would have dropped out due to having low-template DNA. Allelic dropout can occur when there is low-template DNA because there is such little DNA to start with that at this locus the contributor to the DNA sample (or mixture) is a true heterozygote but the other allele is not amplified and so it would be lost. Allelic drop-in can also occur when there is low-template DNA because sometimes the stutter peak can be amplified. The stutter is an artifact of PCR. During the PCR reaction, DNA Polymerase will come in and add nucleotides off of the primer, but this whole process is very dynamic, meaning that the DNA Polymerase is constantly binding, popping off and then rebinding. Therefore, sometimes DNA Polymerase will rejoin at the short tandem repeat ahead of it, leading to a short tandem repeat that is 1 repeat less than the template. During PCR, if DNA Polymerase happens to bind to a locus in stutter and starts to amplify it to make lots of copies, then this stutter product will appear randomly in the electropherogram, leading to allelic drop-in. | 1 | Applied and Interdisciplinary Chemistry |
Hexafluoroethane is the perfluorocarbon counterpart to the hydrocarbon ethane. It is a non-flammable gas negligibly soluble in water and slightly soluble in methanol. It is an extremely potent and long-lived greenhouse gas. | 1 | Applied and Interdisciplinary Chemistry |
A polymeric material can be functionalized by the addition of small moieties, oligomers, and even other polymers (grafting copolymers) onto the surface or interface. | 0 | Theoretical and Fundamental Chemistry |
*King G.R., Mander L.N., Monck N.J.T., Morris J.C. and Zhang H. A New and Efficient Strategy for the Total Synthesis of Polycyclic Diterpenoids: The Preparation of Gibberellins (±)-GA103 and (±)-GA73. J. Am. Chem. Soc. 1997, 119, 3828–3829.
*Frey, B., Wells, A. P., Rogers, D. R. and Mander, L. N. Synthesis of the Unusual Diterpenoid Tropones, Hainanolidol and Harringtonolide. J. Am. Chem. Soc. 1998, 120, 1914–1915.
*Mander, L. N. Twenty years of gibberellin research. Natural Product Reports, 2003, 20, 49–69.
*Mander, L. N. and McLachlan, M. M. Total synthesis of the Galbulimima alkaloid GB 13. J. Am. Chem. Soc., 2003, 125, 2400–2401.
*Mander, L. N. and Thomson, R. J. Total synthesis of Sordaricin. Org. Lett., 2003, 5, 1321–1324. | 0 | Theoretical and Fundamental Chemistry |
In chemical kinetics, an intrinsic low-dimensional manifold is a technique to simplify the study of reaction mechanisms using dynamical systems, first proposed in 1992.
The ILDM approach fixes a low dimensional surface which describes well the slow dynamics and assumes that after a short time the fast dynamics are less important and the system can be described in the lower-dimensional space. | 0 | Theoretical and Fundamental Chemistry |
Unstable atomic nuclei with an excess of protons may undergo β decay, also called positron decay, where a proton is converted into a neutron, a positron, and an electron neutrino:
Beta-plus decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is greater than that of the parent nucleus, i.e., the daughter nucleus is a lower-energy state. | 0 | Theoretical and Fundamental Chemistry |
Since its discovery in 1967, serine protease DPP-4 has been a popular subject of research. Inhibitors of DPP-4 have long been sought as tools to elucidate the functional significance of the enzyme. The first inhibitors were characterized in the late 1980s and 1990s. Each inhibitor was important to establish an early structure activity relationship (SAR) for subsequent investigation. The inhibitors fall into two main classes, those that interact covalently with DPP-4 and those that do not. DPP-4 is a dipeptidase that selectively binds substrates that contain proline at the P1-position, thus many DPP-4 inhibitors have 5-membered heterocyclic rings that mimic proline, e.g. pyrrolidine, cyanopyrrolidine, thiazolidine and cyanothiazolidine. These compounds commonly form covalent bonds to the catalytic residue Ser630.
In 1994, researchers from Zeria Pharmaceuticals unveiled cyanopyrrolidines with a nitrile function group that was assumed to form an imidate with the catalytic serine. Concurrently other DPP-4 inhibitors without a nitrile group were published but they contained other serine-interacting motifs, e.g. boronic acids, phosphonates or diacyl hydroxylamines. These compounds were not as potent because of the similarity of DPP-4 and prolyl oligopeptidase (PEP) and also suffered from chemical instability. Ferring Pharmaceuticals filed for patent on two cyanopyrrolidine DPP-4 inhibitors, which they published in 1995. These compounds had excellent potency and improved chemical stability.
In 1995, Edwin B. Villhauer at Novartis started to explore N-substituted glycinyl-cyanopyrrolidines based on the fact that DPP-4 identifies N-methylglycine as an N-terminal amino acid. This group of new cyanopyrrolidines became extremely popular field of research in the following years. Some trials with dual inhibitors of DPP-4 and vasopeptidase have been represented, since vasopeptidase inhibition is believed to enhance the antidiabetic effect of DPP-4 inhibition by stimulating insulin secretion. Vasopeptidase-inhibiting motif is connected to the DPP-4 inhibitor at the N-substituent. | 1 | Applied and Interdisciplinary Chemistry |
Pathological changes associated with CYN poisoning were reported to be in four distinct stages: inhibition of protein synthesis, proliferation of membranes, lipid accumulation within cells, and finally cell death. Examination of mice livers removed at autopsy showed that on intraperitoneal injection of CYN, after 16 hours ribosomes from the rough endoplasmic reticulum (rER) had detached, and at 24 hours, marked proliferation of the membrane systems of the smooth ER and Golgi apparatus had occurred. At 48 hours, small lipid droplets had accumulated in the cell bodies, and at 100 hours, hepatocytes in the hepatic lobules were destroyed beyond function.
The process of protein synthesis inhibition has been shown to be irreversible, however is not conclusively the method of cytotoxicity of the compound. Froscio et al.. proposed that CYN has at least two separate modes of action: the previously reported protein synthesis inhibition, and an as-yet unclear method of causing cell death. It has been shown that cells can survive for long periods (up to 20 hours) with 90% inhibition of protein synthesis, and still maintain viability. Since CYN is cytotoxic within 16–18 hours it has been suggested that other mechanisms are the cause of cell death.
Cytochrome P450 has been implicated in the toxicity of CYN, as blocking the action of P450 reduces the toxicity of CYN. It has been proposed that an activated P450-derived metabolite (or metabolites) of CYN is the main cause of toxicity. Shaw et al.. demonstrated that the toxin could be metabolised in vivo, resulting in bound metabolites in the liver tissue, and that damage was more prevalent in rat hepatocytes than other cell types.
Due to the structure of CYN, which includes sulfate, guanidine and uracil groups, it has been suggested that CYN acts on DNA or RNA. Shaw et al.. reported covalent binding of CYN or its metabolites to DNA in mice, and DNA strand breakage has also been observed. Humpage et al. also supported this, and in addition postulated that CYN (or a metabolite) acts on either the spindle or centromeres during cell division, inducing loss of whole chromosomes.
The uracil group of CYN has been identified as a pharmacophore of the toxin. In two experiments, the vinylic hydrogen atom on the uracil ring was replaced with a chlorine atom to form 5-chlorocylindrospermopsin, and the uracil group was truncated to a carboxylic acid, to form cylindrospermic acid (Figure 6). Both products were assessed as being non-toxic, even at 50 times the LD of CYN. In the previous determination of the structure of deoxycylindrospermopsin, a toxicity assessment of the compound was carried out. Mice injected intraperitoneally with four times the 5-day median lethal dose of CYN showed no toxic effects. As this compound was shown to be relatively abundant, it was concluded that this analogue was comparatively non-toxic. Given that both CYN and epiCYN are toxic, the hydroxyl group on the uracil bridge can be considered necessary for toxicity. As yet, the relative toxicities of CYN and epiCYN have not been compared. | 0 | Theoretical and Fundamental Chemistry |
In 1910 British polar explorer Robert Scott hoped to be the first to reach the South Pole, but was beaten by Norwegian explorer Roald Amundsen. On foot, the expedition trudged through the frozen deserts of the Antarctic, marching for caches of food and kerosene deposited on the way. In early 1912, at the first cache, there was no kerosene; the cans – soldered with tin – were empty. The cause of the empty tins could have been related to tin pest. The tin cans were recovered and no tin pest was found when analyzed by the Tin Research Institute. Some observers blame poor quality soldering, as tin cans over 80 years old have been discovered in Antarctic buildings with the soldering in good condition. | 1 | Applied and Interdisciplinary Chemistry |
The Hopp–Woods hydrophilicity scale of amino acids is a method of ranking the amino acids in a protein according to their water solubility in order to search for surface locations on proteins, and especially those locations that tend to form strong interactions with other macromolecules such as proteins, DNA, and RNA.
Given the amino acid sequence of any protein, likely interaction sites can be identified by taking the moving average of six amino acid hydrophilicity values along the polypeptide chain, and looking for local peaks in the data plot.
In subsequent papers after their initial publication of the method, Hopp and Woods demonstrated that the data plots, or hydrophilicity profiles, contained much information about protein folding, and that the hydrophobic valleys of the profiles corresponded to internal structures of proteins such as beta-strands and alpha-helices. Furthermore, long hydrophobic valleys were shown to correspond quite closely to the membrane-spanning helices identified by the later-published Kyte and Doolittle hydropathic plotting method. | 1 | Applied and Interdisciplinary Chemistry |
If chloride ions have penetrated beyond the surface more rigorous treatment is required.
This typically involves soaking in acetone to displace any water in the specimen. Then soaking in a benzotriazole (BTA)–ethanol solution to chelate the copper and make it unreactive. Pits and holes may be filled with zinc powder, which is then painted over with shellac coloured to look like the specimen. | 1 | Applied and Interdisciplinary Chemistry |
SBO is currently made up of seven different vocabularies:
* systems description parameter (catalytic constant, thermodynamic temperature...)
* participant role (substrate, product, catalyst...)
* modelling framework (discrete, continuous...)
* mathematical expression (mass-action rate law, Hill-type rate law...)
* occurring entity representation (biochemical process, molecular or genetic interaction...)
* physical entity representation (transporter, physical compartment, observable...)
* metadata representation (annotation) | 1 | Applied and Interdisciplinary Chemistry |
The ability of palladium to absorb hydrogen was recognized as early as the nineteenth century by Thomas Graham. In the late 1920s, two Austrian-born scientists, Friedrich Paneth and Kurt Peters, originally reported the transformation of hydrogen into helium by nuclear catalysis when hydrogen was absorbed by finely divided palladium at room temperature. However, the authors later retracted that report, saying that the helium they measured was due to background from the air.
In 1927, Swedish scientist John Tandberg reported that he had fused hydrogen into helium in an electrolytic cell with palladium electrodes. On the basis of his work, he applied for a Swedish patent for "a method to produce helium and useful reaction energy". Due to Paneth and Peterss retraction and his inability to explain the physical process, his patent application was denied. After deuterium was discovered in 1932, Tandberg continued his experiments with heavy water. The final experiments made by Tandberg with heavy water were similar to the original experiment by Fleischmann and Pons. Fleischmann and Pons were not aware of Tandbergs work.
The term "cold fusion" was used as early as 1956 in an article in The New York Times about Luis Alvarez's work on muon-catalyzed fusion. Paul Palmer and then Steven Jones of Brigham Young University used the term "cold fusion" in 1986 in an investigation of "geo-fusion", the possible existence of fusion involving hydrogen isotopes in a planetary core. In his original paper on this subject with Clinton Van Siclen, submitted in 1985, Jones had coined the term "piezonuclear fusion". | 0 | Theoretical and Fundamental Chemistry |
The chemical properties of RNA make large RNA molecules inherently fragile, and they can easily be broken down into their constituent nucleotides through hydrolysis. These limitations do not make use of RNA as an information storage system impossible, simply energy intensive (to repair or replace damaged RNA molecules) and prone to mutation. While this makes it unsuitable for current DNA optimised life, it may have been acceptable for more primitive life. | 0 | Theoretical and Fundamental Chemistry |
Selegiline, also known as -deprenyl and sold under the brand names Eldepryl, Emsam, Selgin, among other names, is a medication which is used in the treatment of Parkinsons disease and major depressive disorder. It is provided in the form of a capsule or tablet taken by mouth or orally disintegrating tablets taken on the tongue for Parkinsons disease and as a patch applied to skin for depression.
Selegiline acts as a monoamine oxidase inhibitor, and increases levels of monoamine neurotransmitters in the brain. At typical clinical doses used for Parkinson's disease, selegiline is a selective and irreversible inhibitor of monoamine oxidase B (MAO-B), increasing levels of dopamine in the brain. In larger doses (more than 20 mg/day), it loses its specificity for MAO-B and also inhibits MAO-A, which increases serotonin and norepinephrine levels in the brain. | 0 | Theoretical and Fundamental Chemistry |
In the thermodynamic analysis, all states defined in the system are assumed to be in thermodynamic equilibrium; each state has mechanical, thermal, and phase equilibrium, and there is no macroscopic change with respect to time. For the analysis of the system, the first law and second law of thermodynamics can be applied.
In power plant analysis, a series of states can comprise a cycle. In this case, each state represents condition at the inlet/outlet of individual component. The example of components are pumpcompressor, turbine, reactor, and heat exchanger. By considering the constitutive equation for the given type of fluid, thermodynamic state of each point can be analyzed. As a result, the thermal efficiency of the cycle can be defined.
Examples of the cycle include the Carnot cycle, Brayton cycle, and Rankine cycle. Based on the simple cycle, modified or combined cycle also exists. | 0 | Theoretical and Fundamental Chemistry |
Stephen C. Harrison is professor of biological chemistry and molecular pharmacology, professor of pediatrics, and director of the Center for Molecular and Cellular Dynamics of Harvard Medical School, head of the Laboratory of Molecular Medicine at Boston Children's Hospital, and investigator of the Howard Hughes Medical Institute. | 1 | Applied and Interdisciplinary Chemistry |
A familiar radical reaction is combustion. The oxygen molecule is a stable diradical, best represented by O–O. Because spins of the electrons are parallel, this molecule is stable. While the ground state of oxygen is this unreactive spin-unpaired (triplet) diradical, an extremely reactive spin-paired (singlet) state is available. For combustion to occur, the energy barrier between these must be overcome. This barrier can be overcome by heat, requiring high temperatures. The triplet-singlet transition is also "forbidden". This presents an additional barrier to the reaction. It also means molecular oxygen is relatively unreactive at room temperature except in the presence of a catalytic heavy atom such as iron or copper.
Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed, termination reactions again dominate and the flame dies out. As indicated, promotion of propagation or termination reactions alters flammability. For example, because lead itself deactivates radicals in the gasoline-air mixture, tetraethyl lead was once commonly added to gasoline. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).
When a hydrocarbon is burned, a large number of different oxygen radicals are involved. Initially, hydroperoxyl radical (HOO) are formed. These then react further to give organic hydroperoxides that break up into hydroxyl radicals (HO). | 1 | Applied and Interdisciplinary Chemistry |
In a 2022 observational study aimed to identify preoperative serum metabolites that could predict postoperative opioid consumption, the role of imidazole-4-acetaldehyde was identified as one of the metabolites that showed different trends between gastric cancer patients with high postoperative opioid consumption and those with low opioid consumption group. The results suggest that imidazole-4-acetaldehyde, along with other metabolites, was significantly different between the two groups, so that that imidazole-4-acetaldehyde may serve as a potential biomarker for predicting postoperative opioid consumption in gastric cancer patients, still, the results of this study is inconclusive. | 1 | Applied and Interdisciplinary Chemistry |
DNA computing is an emerging branch of unconventional computing which uses DNA, biochemistry, and molecular biology hardware, instead of the traditional electronic computing. Research and development in this area concerns theory, experiments, and applications of DNA computing. Although the field originally started with the demonstration of a computing application by Len Adleman in 1994, it has now been expanded to several other avenues such as the development of storage technologies, nanoscale imaging modalities, synthetic controllers and reaction networks, etc. | 1 | Applied and Interdisciplinary Chemistry |
His research has involved study of molecular and interfacial forces. His work is applicable to a wide range of industrial and fundamental science problems. In particular, he has contributed significantly to the understanding of colloidal dispersions, biological systems, and polymer engineering applications. He has studied interfacial phenomena, the physics of thin films, and fundamental questions in rheology and tribology of surfaces.
Israelachvili has developed numerous techniques for the static and dynamic measurement of material and molecular properties of vapors, liquids, and surfaces. In particular, he pioneered a sensitive interfacial force-sensing technique known as the surface forces apparatus (SFA). This instrument involves carefully approaching two surfaces (usually immersed in a solvent, such as water), and measuring the force of attraction and repulsion between them. Using piezoelectric positional movement and optical interferometry for position sensing, this instrument can resolve distances to within 0.1 nanometer, and forces at the 10 N level. This technique is similar to measuring the force of interaction between an atomic force microscope (AFM) and a sample surface, except that the specialized SFA can measure much longer-range forces and is intended for surface-surface interaction measurements (as opposed to tip-surface or molecule-surface measurements). The results of SFA experiments can be used to characterize the nature of intermolecular potentials and other molecular properties.
Israelachvili is also well known as the author of the textbook "Intermolecular and Surface Forces," published by Academic Press. This authoritative book describes the fundamental concepts and equations applicable to all intermolecular and interfacial science disciplines.
Israelachvili was also founder of SurForce, LLC. The company specializes in researching surface force interactions and producing SFA systems.[https://www.surforcellc.com/about-us/] | 0 | Theoretical and Fundamental Chemistry |
EPIC-seq has been shown to be effective for inferal of epigenetic expression of classical Hodgkin Lymphomas (cHL) subtypes. Hodgkin and Reed/Sternberg cells and their corresponding T cells expression were inferred with EPIC-seq. Bulk single-cell RNA sequencing results shows significant correlation with EPIC-seq profilings of these cell types. | 1 | Applied and Interdisciplinary Chemistry |
Arformoterol is indicated for the maintenance treatment of bronchoconstriction in people with chronic obstructive pulmonary disease (COPD). | 0 | Theoretical and Fundamental Chemistry |
Metacresol purple or m-cresol purple, also called m-cresolsulfonphthalein, is a triarylmethane dye and a pH indicator. It is used as a capnographic indicator for detecting detect end-tidal carbon dioxide to ensure successful tracheal intubation in an emergency. It can be used to measure the pH in subzero temperatures of saline or hypersaline media.
In colorimetric capnography, the indicator is incorporated in an aqueous matrix that provides a pH just above the indicator's colour change. When exposed to carbon dioxide (CO), it undergoes a colour change from purple to yellow, because when CO dissolves in the matrix, it forms carbonic acid.
In chemistry, it has two useful indicator ranges:
* pH 1.2–2.8: red to yellow
* pH 7.4–9.0: yellow to purple | 1 | Applied and Interdisciplinary Chemistry |
In aerodynamics, the lift distribution over a finite wing may be approximated by assuming that each spanwise segment of the wing has a semi-infinite trailing vortex behind it. It is then possible to solve for the strength of the vortices using the criterion that there be no flow induced through the surface of the wing. This procedure is called the vortex panel method of computational fluid dynamics. The strengths of the vortices are then summed to find the total approximate circulation about the wing. According to the Kutta–Joukowski theorem, lift per unit of span is the product of circulation, airspeed, and air density. | 1 | Applied and Interdisciplinary Chemistry |
* Pharmaceutical and cosmetic creams, gels, and ointments, e.g. petroleum jelly, toothpaste, hand sanitizer
* Foods, e.g. pudding, guacamole, salsa, mayonnaise, whipping cream, peanut butter, jelly, jam | 0 | Theoretical and Fundamental Chemistry |
In a fluidic amplifier, a fluid supply, which may be air, water, or hydraulic fluid, enters at the bottom. Pressure applied to the control ports C or C deflects the stream, so that it exits via either port O or O. The stream entering the control ports may be much weaker than the stream being deflected, so the device has gain.
This basic device can be used to construct other fluidic logic elements, as well fluidic oscillators that can be used in analogous way as flip flops. Simple systems of digital logic can thus be built.
Fluidic amplifiers typically have bandwidths in the low kilohertz range, so systems built from them are quite slow compared to electronic devices. | 1 | Applied and Interdisciplinary Chemistry |
Denitrification generally proceeds through some combination of the following half reactions, with the enzyme catalyzing the reaction in parentheses:
* NO + 2 H + 2 e → + HO (Nitrate reductase)
* + 2 H + e → NO + HO (Nitrite reductase)
* 2 NO + 2 H + 2 e → + HO (Nitric-oxide reductase)
* + 2 H + 2 e → + HO (Nitrous-oxide reductase)
The complete process can be expressed as a net balanced redox reaction, where nitrate (NO) gets fully reduced to dinitrogen (N):
* 2 NO + 10 e + 12 H → N + 6 HO | 1 | Applied and Interdisciplinary Chemistry |
This section discusses bremsstrahlung emission and the inverse absorption process (called inverse bremsstrahlung) in a macroscopic medium. We start with the equation of radiative transfer, which applies to general processes and not just bremsstrahlung:
is the radiation spectral intensity, or power per (area × × photon frequency) summed over both polarizations. is the emissivity, analogous to defined above, and is the absorptivity. and are properties of the matter, not the radiation, and account for all the particles in the medium - not just a pair of one electron and one ion as in the prior section. If is uniform in space and time, then the left-hand side of the transfer equation is zero, and we find
If the matter and radiation are also in thermal equilibrium at some temperature, then must be the blackbody spectrum:
Since and are independent of , this means that must be the blackbody spectrum whenever the matter is in equilibrium at some temperature – regardless of the state of the radiation. This allows us to immediately know both and once one is known – for matter in equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Trimethyl orthoformate and triethylorthoacetate are reagents. Another example is the bicyclic OBO protecting group (4-methyl-2,6,7-trioxa-bicyclo[2.2.2]octan-1-yl) which is formed by the action of (3-methyloxetan-3-yl)methanol on activated carboxylic acids in the presence of Lewis acids. The group is base stable and can be cleaved in two steps under mild conditions, mildly acidic hydrolysis yields the ester of tris(hydroxymethyl)ethane which is then cleaved using e.g. an aqueous carbonate solution. | 0 | Theoretical and Fundamental Chemistry |
Exposure limits can be expressed as ceiling limits, a maximal value, short-term exposure limits (STEL), a 15-minute exposure limit or an 8-hour time-weighted average limit (TWA). Below is a sampling, not exhaustive, as less common isocyanates also have specific limits within the United States, and in some regions there are limits on total isocyanate, which recognizes some of the uncertainty regarding the safety of mixtures of chemicals as compared to pure chemical exposures. For example, while there is no OEL for HDI, NIOSH has a REL of 5 ppb for an 8-hour TWA and a ceiling limit of 20 ppb, consistent with the recommendations for MDI. | 0 | Theoretical and Fundamental Chemistry |
In plumbing and piping, a nipple is a fitting, consisting of a short piece of pipe, usually provided with a male pipe thread at each end, for connecting two other fittings.
The length of the nipple is usually specified by the overall length with thread. It may have a hexagonal section in the center for a wrench to grasp (sometimes referred to as a "hex nipple"), or it may simply be made from a short piece of pipe (sometimes referred to as a "barrel nipple" or "pipe nipple"). A "close nipple" has no unthreaded area; when screwed tightly between two female fittings, very little of the nipple remains exposed. A close nipple can only be unscrewed by gripping one threaded end with a pipe wrench which will damage the threads and necessitate replacing the nipple, or by using a specialty tool known as a nipple wrench (or known as an internal pipe wrench) which grips the inside of the pipe, leaving the threads undamaged. When the ends are of two different sizes it is called a reducer or unequal nipple.
Threads used on nipples are BSP, BSPT, NPT, NPSM and Metric. | 1 | Applied and Interdisciplinary Chemistry |
Formula: or
* Density: 0.180 kg/m at STP (0 °C, 101325 Pa).
* Atomic weight: 2.0141017926 Da.
* Mean abundance in ocean water (from VSMOW) 155.76 ± 0.1 atoms of deuterium per million atoms of all isotopes of hydrogen (about 1 atom of in 6420); that is, about 0.015% of all atoms of hydrogen (any isotope)
Data at approximately 18 K for H (triple point):
* Density:
** Liquid: 162.4 kg/m
** Gas: 0.452 kg/m
* Viscosity: 12.6 μPa·s at 300 K (gas phase)
* Specific heat capacity at constant pressure c:
** Solid: 2950 J/(kg·K)
** Gas: 5200 J/(kg·K) | 0 | Theoretical and Fundamental Chemistry |
While relatively unstable and requiring frequent standardization, sodium hypochlorite has been used in a very rapid thermometric titration method for the determination of ammonium ion. This is an alternative to the classical approach of ammonia distillation from basic solution and consequent acid–base titration. The thermometric titration is carried out in bicarbonate solution containing bromide ion (Brown et al., 1969). | 0 | Theoretical and Fundamental Chemistry |
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