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* 2008 Spanish Royal Society of Chemistry Young Investigator Award
* 2011 Thieme Chemistry Journals Award
* 2011 Chemical Society Review Emerging Investigator Award
* 2013 Swiss Chemical Society Werner Prize
* 2019 Royal Society of Chemistry Organometallic Chemistry
*2021 Margaret Faul Women in Chemistry Award | 0 | Organic Chemistry |
For quasi-static and reversible processes, the first law of thermodynamics is:
where δQ is the heat supplied to the system and δW is the work done by the system. | 7 | Physical Chemistry |
In previous stages acetyl-CoA is transferred from the mitochondria to the cytoplasm where fatty acid synthase resides. The acetyl-CoA is transported as a citrate, which has been previously formed in the mitochondrial matrix from acetyl-coA and oxaloacetate. This reaction usually initiates the citric acid cycle, but when there is no need of energy it is transported to the cytoplasm where it is broken down to cytoplasmic acetyl-CoA and oxaloacetate.
Another part of the cycle requires NADPH for the synthesis of fatty acids. Part of this reducing power is generated when the cytosolic oxaloacetate is returned to the mitochondria as long as the internal mitochondrial layer is non-permeable for oxaloacetate. Firstly the oxaloacetate is reduced to malate using NADH. Then the malate is decarboxylated to pyruvate. Now this pyruvate can easily enter the mitochondria, where it is carboxylated again to oxaloacetate by pyruvate carboxylase. In this way, the transfer of acetyl-CoA that is from the mitochondria into the cytoplasm produces a molecule of NADH. The overall reaction, which is spontaneous, may be summarized as:
:HCO + ATP + acetyl-CoA → ADP + P + malonyl-CoA | 1 | Biochemistry |
In isolated systems it is consistently observed that as time goes on internal rearrangements diminish and stable conditions are approached. Pressures and temperatures tend to equalize, and matter arranges itself into one or a few relatively homogeneous phases. A system in which all processes of change have gone practically to completion is considered in a state of thermodynamic equilibrium. The thermodynamic properties of a system in equilibrium are unchanging in time. Equilibrium system states are much easier to describe in a deterministic manner than non-equilibrium states. In some cases, when analyzing a thermodynamic process, one can assume that each intermediate state in the process is at equilibrium. Such a process is called quasistatic.
For a process to be reversible, each step in the process must be reversible. For a step in a process to be reversible, the system must be in equilibrium throughout the step. That ideal cannot be accomplished in practice because no step can be taken without perturbing the system from equilibrium, but the ideal can be approached by making changes slowly.
The very existence of thermodynamic equilibrium, defining states of thermodynamic systems, is the essential, characteristic, and most fundamental postulate of thermodynamics, though it is only rarely cited as a numbered law. According to Bailyn, the commonly rehearsed statement of the zeroth law of thermodynamics is a consequence of this fundamental postulate. In reality, practically nothing in nature is in strict thermodynamic equilibrium, but the postulate of thermodynamic equilibrium often provides very useful idealizations or approximations, both theoretically and experimentally; experiments can provide scenarios of practical thermodynamic equilibrium.
In equilibrium thermodynamics the state variables do not include fluxes because in a state of thermodynamic equilibrium all fluxes have zero values by definition. Equilibrium thermodynamic processes may involve fluxes but these must have ceased by the time a thermodynamic process or operation is complete bringing a system to its eventual thermodynamic state. Non-equilibrium thermodynamics allows its state variables to include non-zero fluxes, which describe transfers of mass or energy or entropy between a system and its surroundings. | 7 | Physical Chemistry |
Wittig's contributions also include the preparation of phenyllithium and the discovery of the 1,2-Wittig rearrangement and the 2,3-Wittig rearrangement.
Wittig was well known in the chemistry community for being a consummate experimenter and observer of chemical transformations, while caring very little for the theoretical and mechanistic underpinnings of the work he produced.
Georg also has his name on a literature work titled on a compound labelled Colopidalol. | 4 | Stereochemistry |
Current research regarding Botrytis-induced kinase1 aims to determine how BIK1 interacts with MAPK pathway proteins as well as with the OXI1 kinase. Also, studies are being conducted to determine the relationship between BIK1 and the phosphorylizing homolog kinases PEPR1 and PEPR2. Though it is believed that PEPR1 and PEPR2 act as enzymes toward BIK1 and phosphorylate the kinase, research is still being done to examine the effects of the interaction on a broader scale. Previously published research suggests that PEPR1 and PEPR2 work with the ET signal pathway and Botrytis-induced kinase1 in order to amplify the defense mechanism in immune response. Additionally, future research may explore the mechanism that allows BIK1 and BAK1 to cooperate with the FLS2 receptor to initiate defense response. While it is known that the three work together and each is required for the process to occur efficiently, but the exact relationship between the three remains unknown and the specific binding residues for each component have yet to be determined in vivo. | 1 | Biochemistry |
Cegelski's work has earned her several awards:
* Presidential Early Career Award for Scientists and Engineers (PECASE)
*Burroughs Wellcome Career Award at the Scientific Interface, for "Mapping the structural and functional landscape of the microbial extracellular matrix."
* 2010 NIH Director's New Innovator Award, for "Structure, Function, and Disruption of Microbial Amyloid Assembly and Biofilm Formation."
* National Science Foundation CAREER Award, for "Form and Function of Bacterial Amyloid Fibers." | 7 | Physical Chemistry |
In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction
known as dissociation in the context of acid–base reactions. The chemical species HA is an acid that dissociates into , the conjugate base of the acid and a hydrogen ion, . The system is said to be in equilibrium when the concentrations of its components will not change over time, because both forward and backward reactions are occurring at the same rate.
The dissociation constant is defined by
: or
where quantities in square brackets represent the concentrations of the species at equilibrium. As a simple example for a weak acid with K = 10, log K is the exponent which is -5, so that pK = 5. And for acetic acid with K = 1.8 x 10, pK is close to 5. A higher K corresponds to a stronger acid which is more dissociated at equilibrium. For the more convenient logarithmic scale, a lower pK means a stronger acid. | 7 | Physical Chemistry |
In 1998 the consumption of phosphonates was 56,000 tons worldwide – 40,000 tons in the US, 15,000 tons in Europe and less than 800 tons in Japan. The demand of phosphonates grows steadily at 3% annually. | 0 | Organic Chemistry |
The first transcriptome studies were based on microarray techniques (also known as DNA chips). Microarrays consist of thin glass layers with spots on which oligonucleotides, known as "probes" are arrayed; each spot contains a known DNA sequence.
When performing microarray analyses, mRNA is collected from a control and an experimental sample, the latter usually representative of a disease. The RNA of interest is converted to cDNA to increase its stability and marked with fluorophores of two colors, usually green and red, for the two groups. The cDNA is spread onto the surface of the microarray where it hybridizes with oligonucleotides on the chip and a laser is used to scan. The fluorescence intensity on each spot of the microarray corresponds to the level of gene expression and based on the color of the fluorophores selected, it can be determined which of the samples exhibits higher levels of the mRNA of interest.
One microarray usually contains enough oligonucleotides to represent all known genes; however, data obtained using microarrays does not provide information about unknown genes. During the 2010s, microarrays were almost completely replaced by next-generation techniques that are based on DNA sequencing. | 1 | Biochemistry |
The Swedish assay office, the SP Technical Research Institute of Sweden, is in Borås. The assay office is privatized and the concession, given to the Inspecta Corporation, is an independent, international qualification requirements fulfilling inspection, testing, measurement and certification services provider. Inspecta is accredited by SWEDAC. | 3 | Analytical Chemistry |
When the incoming field is very intense , the interaction of the electron with the electromagnetic field is completely equivalent to the interaction of the electron with multiple photons, with no need of explicitly quantize the electromagnetic field of the incoming low-energy radiation. While the interaction with the radiation field, i.e. the emitted photon, is treated with perturbation theory: the probability of photon emission is evaluated considering the transition between the states of the electron in presence of the electromagnetic field. This problem has been solved primarily in the case in which electric and magnetic fields are orthogonal and equal in magnitude (crossed field); in particular, the case of a plane electromagnetic wave has been considered. Crossed fields represent in good approximation many existing fields so the found solution can be considered quite general. The spectrum of non-linear inverse Compton scattering, obtained with this approach and valid for and , is:
where the parameter , is now defined as:A related quantity is the rate of photon emission:<math display="block">
\dfrac{dN}{dt}=\dfrac{\sqrt{3}}{2\pi}\dfrac{q^2 m c}{\hbar^2 }\dfrac{\chi}{\gamma} \int_0^{\chi}\dfrac{F(\chi,\eta)}{\eta}d\eta
no photons can be produced. This rate of photon emission depends explicitly on electron quantum parameter and on the Lorentz factor for the electron. | 7 | Physical Chemistry |
EPIC-seq enables the subclassification of NSCLC into histological subtypes such as lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). EPIC-seq can also aid with the classification of cell-of-origin (COO) subtypes in DLBCL. By analyzing epigenetic and transcriptional signatures, EPIC-seq-derived classifiers provide valuable insights into tumor heterogeneity and molecular subtyping , providing valuable insights for tailored treatment strategies. | 1 | Biochemistry |
*Pacey, A.J. & Fisher, S.J. (1967) "Daniel Bernoulli and the vis viva of compressed air", The British Journal for the History of Science 3 (4), pp. 388–392,
*British Transport Commission (1957) Handbook for Railway Steam Locomotive Enginemen, London : B.T.C., p. 81, (facsimile copy publ. Ian Allan (1977), ) | 7 | Physical Chemistry |
Infrared photodissociation spectroscopy maintains a powerful capability to study bond energies of coordination complexes. IRPD can measure varying bond energies of compounds, including dative bonds and coordination energies of molecular clusters. Structural information about analytes can acquired by using mass selectivity and interpreting fragmentation. The spectroscopic information usually resembles that of linear infrared spectra and can be used to obtain detailed structural information of gas-phase species, in case of metal complexes, insights into ligand coordination, bond activations and successive reactions can be obtained. | 7 | Physical Chemistry |
When a swimmer enters a pool, they add up to one billion organisms to the water. Chlorination kills all organisms harmful to swimmers such as those that cause ear infections and athlete's foot. The advantages of electrochlorination in this process are as follows:
*Not irritating to skin or soft tissue.
*Active in small concentrations.
*Longer lifespan of chemical and therefore less replacement necessary.
*Easily measurable. | 7 | Physical Chemistry |
Hart graduated from MIT with a bachelors degree in geology in 1956 and a masters degree in geochemistry in 1957 from Caltech. In 1960 he received his doctorate in geochemistry from MIT with thesis Mineral ages and metamorphism under the supervision of Patrick M. Hurley. After a year as a Carnegie Fellow, Hart was from 1961 to 1975 at the Carnegie Institution in Washington, D.C. in the Department of Terrestrial Magnetism. From 1975 to 1989 he was a professor of Earth, Atmospheric and Planetary Sciences at MIT and from 1989 to 1992 a visiting professor there. From 1989 to 2007 he was a Senior Scientist in geology and geophysics at Woods Hole Oceanographic Institution. He retired from Woods Hole in 2007 as Scientist Emeritus.
Hart is a leading pioneer in the introduction of geochemistry into the Earth sciences. He developed comparative geochronology, which accounts for geological perturbations in various geochronometers. At the Carnegie Institution of Washington, he worked with George Wetherill, George Tilton, L. T. Aldrich, and G. L. Davis on mapping Precambrian rocks in the USA using comparative geochronology. There Hart became the leader of a group including Thomas Krogh, Albrecht Hofmann, Christopher Brooks, and others.
According to Claude Allègre:
Hart focused on the application of isotopic chemistry to age determination in geology, the geochemical evolution of mantle and oceanic lithosphere, and the geochemistry of strontium, neodymium, and lead isotopes in volcanic rocks. He also studied the long-term behavior of the chemical composition of the oceans due to their interaction with the oceanic crust and the experimental determination of fundamental geochemical properties such as mineral-melt partition coefficients in silicates and solid-state diffusion rates. In 1968, together with John S. Steinhart, he published the Steinhart-Hart equation, which provides a mathematical model of how the temperature and the electrical resistance of a thermistor vary, based upon 3 so-called Steinhart-Hart coefficients.
He was a co-editor from 1970 to 1972 of the Reviews of Geophysics, from 1970 to 1976 of the Geochimica et Cosmochimica Acta, and from 1975 to 1992 of Physics of the Earth and Planetary Interiors. In 1975/76 he chaired the US National Committee for Geochemistry. His doctoral students include Erik Hauri.
Hart has three children, one daughter from his first marriage, which ended in divorce in 1978, and a son and a daughter from his second marriage which began in 1980. | 9 | Geochemistry |
Chromatographic assays measure product formation by separating the reaction mixture into its components by chromatography. This is usually done by high-performance liquid chromatography (HPLC), but can also use the simpler technique of thin layer chromatography. Although this approach can need a lot of material, its sensitivity can be increased by labelling the substrates/products with a radioactive or fluorescent tag. Assay sensitivity has also been increased by switching protocols to improved chromatographic instruments (e.g. ultra-high pressure liquid chromatography) that operate at pump pressure a few-fold higher than HPLC instruments (see High-performance liquid chromatography#Pump pressure). | 1 | Biochemistry |
The amount of electric charge (quantity of electricity) passed through the cell can easily be determined by measuring the change in mass of either electrode and calculating:
where:
* is the quantity of electricity (coulombs)
* is the mass transported (gm)
* is the charge of the copper ions, equal to +2
* is the Faraday constant (96485.3383 coulombs per mole)
* is the atomic weight of copper, equal to 63.546 grams per mole.
Although this apparatus is interesting from a theoretical and historical point of view, present-day electronic measurement of time and electric current provide in their multiplication the amount of passed coulombs much easier, with greater precision, and in a shorter period of time than is possible by weighing the electrodes. | 7 | Physical Chemistry |
Immunoturbidimetry is an important tool in the broad diagnostic field of clinical chemistry. It is used to determine serum proteins not detectable with classical clinical chemistry methods. Immunoturbidimetry uses the classical antigen-antibody reaction. The antigen-antibody complexes aggregate to form particles that can be optically detected by a photometer. | 7 | Physical Chemistry |
It has been discovered that this protein has a catalytic activity, in other words, it has the ability to increase the speed of chemical reactions which would not occur so fast. It is known to catalysis the following reaction (which requires the following cofactor: Mg(2+)):
ATP + RNA(n) ⇄ diphosphate + RNA(n+1)
Depending on the surroundings the optimal pH varies from 8 in the cytoplasm to 8.3 in the nucleus. | 1 | Biochemistry |
Kanu was the first member of his family to attend university. He attended University of Sierra Leone, where he studied chemistry in Fourah Bay College. He was involved with track and field as an undergraduate student. Kanu was awarded a Commonwealth Scholarship, and moved from Sierra Leone to Manchester for his graduate studies. When he arrived at the University of Manchester Kanu started to work on gas chromatography–mass spectrometry. For his doctoral degree he developed miniaturised systems for environmental monitoring. His doctoral research formed the basis of two patents focussing on membrane sampling, which reduced sampling time by 60%. | 3 | Analytical Chemistry |
Escitalopram is sold under many brand names worldwide such as Cipralex, Lexapro, Lexam, Mozarin, Aciprex, Depralin, Ecytara, Elicea, Gatosil, Nexpram, Nexito, Nescital, Szetalo, Stalopam, Pramatis, Betesda, Scippa and Rexipra. | 4 | Stereochemistry |
In order to isolate clones that contain regions of interest from a library, the library must first be screened. One method of screening is hybridization. Each transformed host cell of a library will contain only one vector with one insert of DNA. The whole library can be plated onto a filter over media. The filter and colonies are prepared for hybridization and then labeled with a probe. The target DNA- insert of interest- can be identified by detection such as autoradiography because of the hybridization with the probe as seen below.
Another method of screening is with polymerase chain reaction (PCR). Some libraries are stored as pools of clones and screening by PCR is an efficient way to identify pools containing specific clones. | 1 | Biochemistry |
In organosulfur chemistry, a Bunte salt is an archaic name for salts with the formula RSSONa. They are also called S-alkylthiosulfates or S-arylthiosulfates. These compounds are typically derived from alkylation on the pendant sulfur of sodium thiosulfate:
:RX + NaSO → Na[OSR] + NaX
They have been used as intermediates in the synthesis of thiols. They are also used to generate unsymmetrical disulfides:
:Na[OSR] + NaSR → RSSR + NaSO
According to X-ray crystallography, they adopt the expected structure with tetrahedral sulfur(VI) atom, a sulfur-sulfur single bond, and three equivalent sulfur-oxygen bonds. | 0 | Organic Chemistry |
On September 5, 2019, the United States Food and Drug Administration (US FDA) announced that 10 out of 18, or 56% of the samples of vape liquids sent in by states, linked to recent vaping related lung disease outbreak in the United States, tested positive for vitamin E acetate which had been used as a thickening agent by illicit THC vape cartridge manufacturers. On November 8, 2019, the Centers for Disease Control and Prevention (CDC) identified vitamin E acetate as a very strong culprit of concern in the vaping-related illnesses, but has not ruled out other chemicals or toxicants as possible causes. The CDC's findings were based on fluid samples from the lungs of 29 patients with vaping-associated pulmonary injury, which provided direct evidence of vitamin E acetate at the primary site of injury in all the 29 lung fluid samples tested. Research suggests when vitamin E acetate is inhaled, it may interfere with normal lung functioning. "Vitamin E oil might be in 60-70% of street carts, insiders say." | 7 | Physical Chemistry |
PRR3, PRR5, PRR7 and PRR9 participate in the repressilator of a negative autoregulatory feedback loop that synchronizes to environmental inputs. The repressilator has a morning, evening, and night loop that are regulated in part by the pseudo-response regulator proteins' interactions with CCA1 and LHY. CCA1 and LHY exhibit peak binding to PRR9, PRR7, and PRR5 in the morning, evening, and night, respectively. | 1 | Biochemistry |
Fluorescent X-rays are scattered by atoms in a sample and provide the object wave, which is referenced to non-scattered X-rays. A holographic pattern is recorded by scanning a detector around the sample, which allows researchers to investigate the local 3D structure around a specific element in a sample. | 7 | Physical Chemistry |
Alkoxy radicals which contain unpaired electrons on an oxygen atom display a higher k/k compared to alkyl radicals. The oxygen has a partial negative charge which removes electron density from the donor carbon atom thereby facilitating hydrogen abstraction. The rate of disproportionation is also aided by the more electronegative oxygen on the acceptor molecule. | 0 | Organic Chemistry |
The first frozen zoo was established at the San Diego Zoo by pathologist Kurt Benirschke in 1972. At the time there was no technology available to make use of the collection, but Benirschke believed such technology would be developed in the future. The frozen zoo idea was later supported in Gregory Benford's 1992 paper proposing a Library of Life. Zoos such as the San Diego Zoo and research programs such as the Audubon Center for Research of Endangered Species cryopreserve genetic material in order to protect the diversity of the gene pool of endangered species, or to provide for a prospective reintroduction of such extinct species as the Tasmanian tiger and the mammoth.
Gathering material for a frozen zoo is rendered simple by the abundance of sperm in males. Sperm can be taken from an animal following death. The production of eggs, which in females is usually low, can be increased through hormone treatment to obtain 10–20 oocytes, dependent on the species. Some frozen zoos prefer to fertilize eggs and freeze the resulting embryo, as embryos are more resilient under the cryopreservation process. Some centers also collect skin cell samples of endangered animals or extinct species. The Scripps Research Institute has successfully made skin cells into cultures of special cells called induced pluripotent stem cells (IPS cells). It is theoretically possible to make sperm and egg cells from these IPS cells.
Several animals whose cells were preserved in frozen zoos have been cloned to increase the genetic diversity of endangered species, . One attempt to clone an extinct species was made in 2003; the newborn Pyrenean ibex died of a development disorder which may have been linked to the cloning, and there are not enough genetic samples in frozen zoos to re-create a breeding Pyrenean ibex population. | 1 | Biochemistry |
Site-directed mutagenesis is used to mutate specific bases (and thus amino acids). This is critical to investigate the function of specific amino acids in a protein, e.g. in the active site of an enzyme. | 1 | Biochemistry |
When applied to existing constructions, the lifetime can be extended considerably. If no macroscopically visible cracks are present, HiFIT is a very suitable remediation tool.
With timely remediation of existing structures there is practically no difference to the life of new treated welds. This gives the potential to use existing constructions far beyond the planned lifetime. The HiFIT-method is used very efficient e.g. at highway bridges in steel hollow box-section design on the fly. Costs for reconstruction are low compared to conventional methods. In the commercial vehicle industry and other industries highly stressed welds on existing and new structures are treated with HiFIT to extend lifetime successfully. | 8 | Metallurgy |
The process involves an electron (hole) incident on the interface from the normal state material at energies less than the superconducting energy gap. The incident electron (hole) forms a Cooper pair in the superconductor with the retroreflection of a hole (electron) of opposite spin and velocity but equal momentum to the incident electron (hole), as seen in the figure. The barrier transparency is assumed to be high, with no oxide or tunnel layer which reduces instances of normal electron-electron or hole-hole scattering at the interface. Since the pair consists of an up and down spin electron, a second electron (hole) of opposite spin to the incident electron (hole) from the normal state forms the pair in the superconductor, and hence the retroreflected hole (electron). Through time-reversal symmetry, the process with an incident electron will also work with an incident hole (and retroreflected electron).
The process is highly spin-dependent – if only one spin band is occupied by the conduction electrons in the normal-state material (i.e. it is fully spin-polarized), Andreev reflection will be inhibited due to inability to form a pair in the superconductor and impossibility of single-particle transmission. In a ferromagnet or material where spin-polarization exists or may be induced by a magnetic field, the strength of the Andreev reflection (and hence conductance of the junction) is a function of the spin-polarization in the normal state.
The spin-dependence of AR gives rise to the Point Contact Andreev Reflection (or PCAR) technique, whereby a narrow superconducting tip (often niobium, antimony or lead) is placed into contact with a normal material at temperatures below the critical temperature of the tip. By applying a voltage to the tip, and measuring differential conductance between it and the sample, the spin polarization of the normal metal at that point (and magnetic field) may be determined. This is of use in such tasks as measurement of spin-polarized currents or characterizing spin polarization of material layers or bulk samples, and the effects of magnetic fields on such properties.
In an AR process, the phase difference between the electron and hole is −π/2 plus the phase of the superconducting order parameter. | 7 | Physical Chemistry |
Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, nucleic acids, and proteins) into smaller units (such as monosaccharides, fatty acids, nucleotides, and amino acids, respectively). Catabolism is the breaking-down aspect of metabolism, whereas anabolism is the building-up aspect.
Cells use the monomers released from breaking down polymers to either construct new polymer molecules or degrade the monomers further to simple waste products, releasing energy. Cellular wastes include lactic acid, acetic acid, carbon dioxide, ammonia, and urea. The formation of these wastes is usually an oxidation process involving a release of chemical free energy, some of which is lost as heat, but the rest of which is used to drive the synthesis of adenosine triphosphate (ATP). This molecule acts as a way for the cell to transfer the energy released by catabolism to the energy-requiring reactions that make up anabolism.
Catabolism is a destructive metabolism and anabolism is a constructive metabolism. Catabolism, therefore, provides the chemical energy necessary for the maintenance and growth of cells. Examples of catabolic processes include glycolysis, the citric acid cycle, the breakdown of muscle protein in order to use amino acids as substrates for gluconeogenesis, the breakdown of fat in adipose tissue to fatty acids, and oxidative deamination of neurotransmitters by monoamine oxidase. | 1 | Biochemistry |
Conjugating TNP to ATP renders this nucleotide triphosphate fluorescent and colored whilst allowing it to retain its biological activity. TNP-ATP is thus a fluorescent analog of ATP. This conjugation is very useful in providing information about interactions between ATP and an ATP-binding protein because TNP-ATP interacts with proteins and enzymes as a substitute for its parent nucleotide, and has a strong binding affinity for most systems that require ATP.
TNP is excited at a wavelength of 408 and 470 nm, and fluoresces in the 530–560 nm range. This is a very useful range of excitation because it is far from where proteins or nucleotides absorb. When TNP-ATP is in water or other aqueous solutions, this emission is very weak. However, once TNP-ATP binds to a protein, there is a dramatic increase in fluorescent intensity. This property enables researchers to study various proteins’ binding interaction with ATP. Thus, with enhanced fluorescence, it can be seen whether a protein binds to ATP.
When TNP-ATP in water is excited at 410 nm, TNP-ATP shows a single fluorescence maximum at 561 nm. This maximum shifts as the fluid's viscosity changes. For example, in N,N-dimethylformamide, instead of having its maxima at 561 nm as in water, the maxima is instead at 533 nm.
Binding to a protein will also change the wavelength of maximal emission, as well as a change in fluorescent intensity. For example, binding to the chemotaxis protein CheA indicates a severalfold enhancement of fluorescence intensity and a blue-shift in wavelength of the maximal emission.
Using this TNP nucleotide analog has been shown in many instances to be superior to traditional radionucleotide-labelling based techniques. The health concerns and the cost associated with the use of radioactive isotopes makes TNP-ATP an attractive alternative.
The first fluorescent ribose-modified ATP is 2’,3’-O-(2,4,7-trinitrocyclohexadienylidene) adenosine 5’triphosphate (TNP-ATP), and was introduced in 1973 by Hiratsuka and Uchida. TNP-ATP was originally synthesized to investigate the ATP binding site of myosin ATPase. Reports of TNP-ATP’s success in the investigation of this motor protein extended TNP-ATP’s use to other proteins and enzymes. TNP-ATP has now been used as a spectroscopic probe for numerous proteins suspected to have ATP interactions. These include several protein kinases, ATPases, myosin, and other nucleotide binding proteins. Over the past twenty years, there have been hundreds of papers describing TNP-ATP’s use and applications. Many applications involving this fluorescently labeled nucleotide have helped to clarify structure-function relationships of many ATP-requiring proteins and enzymes. There have also been a growing number of papers that display TNP-ATP use as a means of assessing the ATP-binding capacity of various mutant proteins. | 7 | Physical Chemistry |
Euglenophytes are a group of common flagellated protists that contain chloroplasts derived from a green alga. Euglenophyte chloroplasts have three membranes—it is thought that the membrane of the primary endosymbiont was lost, leaving the cyanobacterial membranes, and the secondary host's phagosomal membrane. Euglenophyte chloroplasts have a pyrenoid and thylakoids stacked in groups of three. Photosynthetic product is stored in the form of paramylon, which is contained in membrane-bound granules in the cytoplasm of the euglenophyte. | 5 | Photochemistry |
The Le Bail method extracts intensities (I) from powder diffraction data. This is done in order to find intensities that are suitable to determine the atomic structure of a crystalline material and to refine the unit cell and has the added advantage of checking phase-purity. Generally, the intensities of powder diffraction data are complicated by overlapping diffraction peaks with similar d-spacings. For the Le Bail method, the unit cell and the approximate space group of the sample must be predetermined because they are included as a part of the fitting technique. The algorithm involves refining the unit cell, the profile parameters, and the peak intensities to match the measured powder diffraction pattern. It is not necessary to know the structural factor and associated structural parameters, since they are not considered in this type of analysis. Le Bail can be used to find phase transitions in high pressure and temperature experiments. It generally provides a quick method to refine the unit cell, which allows better experimental planning. Le Bail analysis provides a more reliable estimate for the intensities of allowed reflections for different crystal symmetries.
Crystallographic structural determination can be accomplished in multiple ways. Le Bail technique is relevant for diffraction studies that involve using a radiation source, which may be neutron or synchrotron, to collect a high resolution, high quality powder diffraction profile. Initially, peak positions are found in the data. Next, the pattern is indexed in order to determine the unit cell or lattice parameters. Then, space group determination follows based on symmetry and the presence or absence of certain reflections. Then, either Le Bail or Pawley technique may be used to extract intensities and refine the unit cell. | 3 | Analytical Chemistry |
The creatine phosphate shuttle is an intracellular energy shuttle which facilitates transport of high energy phosphate from muscle cell mitochondria to myofibrils. This is part of phosphocreatine metabolism. In mitochondria, Adenosine triphosphate (ATP) levels are very high as a result of glycolysis, TCA cycle, oxidative phosphorylation processes, whereas creatine phosphate levels are low. This makes conversion of creatine to phosphocreatine a highly favored reaction. Phosphocreatine is a very-high-energy compound. It then diffuses from mitochondria to myofibrils.
In myofibrils, during exercise (contraction) ADP levels are very high, which favors resynthesis of ATP. Thus, phosphocreatine breaks down to creatine, giving its inorganic phosphate for ATP formation. This is done by the enzyme creatine phosphokinase which transduces energy from the transport molecule of phosphocreatine to the useful molecule for contraction demands, ATP, an action performed by ATPase in the myofibril. The resulting creatine product acts as a signal molecule indicating myofibril contraction and diffuses in the opposite direction of phosphocreatine, back towards the mitochondrial intermembrane space where it can be rephosphorylated by creatine phosphokinase.
At the onset of exercise phosphocreatine is broken down to provide ATP for muscle contraction. ATP hydrolysis results in products of ADP and inorganic phosphate. The inorganic phosphate will be transported into the mitochondrial matrix, while the free creatine passes through the outer membrane where it will be resynthesised into PCr. The antiporter transports the ADP into the matrix, while transporting ATP out. Due to the high concentration of ATP around the mitochondrial creatine kinase, it will convert ATP into PCr which will then move back out into the cells cytoplasm to be converted into ATP (by cytoplasmic creatine kinase) to be used as energy for muscle contraction.
In some vertebrates, arginine phosphate plays a similar role. | 1 | Biochemistry |
SAC solders have outperformed high-Pb solders C4 joints in ceramic ball grid array (CBGA) systems, which are ball-grid arrays with a ceramic substrate. The CBGA showed consistently better results in thermal cycling for Pb-free alloys. The findings also show that SAC alloys are proportionately better in thermal fatigue as the thermal cycling range decreases. SAC performs better than Sn-Pb at the less extreme cycling conditions. Another advantage of SAC is that it appears to be more resistant to gold embrittlement than Sn-Pb. In test results, the strength of the joints is substantially higher for the SAC alloys than the Sn-Pb alloy. Also, the failure mode is changed from a partially brittle joint separation to a ductile tearing with the SAC. | 8 | Metallurgy |
* In Chesapeake Shores, the O'Brien family lives in a small town in the Bay, not far from Baltimore.
* In MeatEater by Steven Rinella, Season 8, Episode 3-4 "Ghosts of the Chesapeake" features the Chesapeake Bay eastern shore. | 2 | Environmental Chemistry |
Donnan dialysis is a separation process which is used to exchange ions between two aqueous solutions which are separated by a CEM or an AEM membrane. In the case of a cation exchange membrane separating two solutions with different acidity, protons (H) go through the membrane to the less acidic side. This induces an electrical potential that will instigate a flux of the cations present in the less acidic side to the more acidic side. The process will finish when the variation of concentration of H is the same order of magnitude as the difference of concentration of the separated cation. | 1 | Biochemistry |
Cryopreservation can be performed as oocyte cryopreservation before fertilisation, or as embryo cryopreservation after fertilisation.
The Rand Consulting Group has estimated there to be 400,000 frozen embryos in the United States in 2006. The advantage is that patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy. Spare oocytes or embryos resulting from fertility treatments may be used for oocyte donation or embryo donation to another aspiring parent, and embryos may be created, frozen and stored specifically for transfer and donation by using donor eggs and sperm. Also, oocyte cryopreservation can be used for those who are likely to lose their ovarian reserve due to undergoing chemotherapy.
By 2017, many centres have adopted embryo cryopreservation as their primary IVF therapy, and perform few or no fresh embryo transfers. The two main reasons for this have been better endometrial receptivity when embryos are transferred in cycles without exposure to ovarian stimulation and also the ability to store the embryos while awaiting the results of preimplantation genetic testing.
The outcome from using cryopreserved embryos has uniformly been positive with no increase in birth defects or development abnormalities. | 1 | Biochemistry |
As shown in Scheme 7, Ojima lactam 7.1 reacted with alcohol 7.2 with sodium bis(trimethylsilyl)amide as a base. This alcohol is the triethylsilyl ether of the naturally occurring compound baccatin III. The related compound, 10-deacetylbaccatin III, is found in Taxus baccata, also known as the European Yew, in concentrations of 1 gram per kilogram leaves. Removal of the triethylsilyl protecting group gave Taxol. | 0 | Organic Chemistry |
A thermal oscillator is a system where conduction along thermal gradients overshoots thermal equilibrium, resulting in thermal oscillations where parts of the system oscillate between being colder and hotter than average. | 7 | Physical Chemistry |
Through a variety of physical and chemical processes, chemical elements change in concentration and move around in what are called geochemical cycles. An understanding of these changes requires both detailed observation and theoretical models. Each chemical compound, element or isotope has a concentration that is a function of position and time, but it is impractical to model the full variability. Instead, in an approach borrowed from chemical engineering, geochemists average the concentration over regions of the Earth called geochemical reservoirs. The choice of reservoir depends on the problem; for example, the ocean may be a single reservoir or be split into multiple reservoirs. In a type of model called a box model, a reservoir is represented by a box with inputs and outputs.
Geochemical models generally involve feedback. In the simplest case of a linear cycle, either the input or the output from a reservoir is proportional to the concentration. For example, salt is removed from the ocean by formation of evaporites, and given a constant rate of evaporation in evaporite basins, the rate of removal of salt should be proportional to its concentration. For a given component , if the input to a reservoir is a constant and the output is for some constant , then the mass balance equation is
This expresses the fact that any change in mass must be balanced by changes in the input or output. On a time scale of , the system approaches a steady state in which . The residence time is defined as
where and are the input and output rates. In the above example, the steady-state input and output rates are both equal to , so .
If the input and output rates are nonlinear functions of , they may still be closely balanced over time scales much greater than the residence time; otherwise, there will be large fluctuations in . In that case, the system is always close to a steady-state and the lowest order expansion of the mass balance equation will lead to a linear equation like Equation (). In most systems, one or both of the input and output depend on , resulting in feedback that tends to maintain the steady-state. If an external forcing perturbs the system, it will return to the steady-state on a time scale of . | 9 | Geochemistry |
Nitrobenzene can be obtained by treating benzenediazonium fluoroborate with sodium nitrite in presence of copper. Alternatively, the diazotisation of the aniline can be conducted in presence of cuprous oxide, which generates cuprous nitrite in situ: | 0 | Organic Chemistry |
Independent of the developments for electrons in vacuum, at about the same time the components of quantum mechanics were being assembled. In 1924 Louis de Broglie in his PhD thesis Recherches sur la théorie des quanta introduced his theory of electron waves. He suggested that an electron around a nucleus could be thought of as standing waves, and that electrons and all matter could be considered as waves. He merged the idea of thinking about them as particles (or corpuscles), and of thinking of them as waves. He proposed that particles are bundles of waves (wave packets) that move with a group velocity and have an effective mass, see for instance Figure 4. Both of these depend upon the energy, which in turn connects to the wavevector and the relativistic formulation of Albert Einstein a few years before.
This rapidly became part of what was called by Erwin Schrödinger undulatory mechanics, now called the Schrödinger equation or wave mechanics. As stated by Louis de Broglie on September 8, 1927, in the preface to the German translation of his theses (in turn translated into English):
The Schrödinger equation combines the kinetic energy of waves and the potential energy due to, for electrons, the Coulomb potential. He was able to explain earlier work such as the quantization of the energy of electrons around atoms in the Bohr model, as well as many other phenomena. Electron waves as hypothesized by de Broglie were automatically part of the solutions to his equation, see also introduction to quantum mechanics and matter waves.
Both the wave nature and the undulatory mechanics approach were experimentally confirmed for electron beams by experiments from two groups performed independently, the first the Davisson–Germer experiment, the other by George Paget Thomson and Alexander Reid; see note for more discussion. Alexander Reid, who was Thomsons graduate student, performed the first experiments, but he died soon after in a motorcycle accident and is rarely mentioned. These experiments were rapidly followed by the first non-relativistic diffraction model for electrons by Hans Bethe based upon the Schrödinger equation, which is very close to how electron diffraction is now described. Significantly, Clinton Davisson and Lester Germer noticed that their results could not be interpreted using a Braggs law approach as the positions were systematically different; the approach of Hans Bethe which includes the refraction due to the average potential yielded more accurate results. These advances in understanding of electron wave mechanics were important for many developments of electron-based analytical techniques such as Seishi Kikuchi's observations of lines due to combined elastic and inelastic scattering, gas electron diffraction developed by Herman Mark and Raymond Weil, diffraction in liquids by Louis Maxwell, and the first electron microscopes developed by Max Knoll and Ernst Ruska. | 7 | Physical Chemistry |
The table below essentially simplifies the ideal gas equation for a particular processes, thus making this equation easier to solve using numerical methods.
A thermodynamic process is defined as a system that moves from state 1 to state 2, where the state number is denoted by subscript. As shown in the first column of the table, basic thermodynamic processes are defined such that one of the gas properties (P, V, T, S, or H) is constant throughout the process.
For a given thermodynamics process, in order to specify the extent of a particular process, one of the properties ratios (which are listed under the column labeled "known ratio") must be specified (either directly or indirectly). Also, the property for which the ratio is known must be distinct from the property held constant in the previous column (otherwise the ratio would be unity, and not enough information would be available to simplify the gas law equation).
In the final three columns, the properties (p, V, or T) at state 2 can be calculated from the properties at state 1 using the equations listed.
a. In an isentropic process, system entropy (S) is constant. Under these conditions, pV = pV, where γ is defined as the heat capacity ratio, which is constant for a calorifically perfect gas. The value used for γ is typically 1.4 for diatomic gases like nitrogen (N) and oxygen (O), (and air, which is 99% diatomic). Also γ is typically 1.6 for mono atomic gases like the noble gases helium (He), and argon (Ar). In internal combustion engines γ varies between 1.35 and 1.15, depending on constitution gases and temperature.
b. In an isenthalpic process, system enthalpy (H) is constant. In the case of free expansion for an ideal gas, there are no molecular interactions, and the temperature remains constant. For real gasses, the molecules do interact via attraction or repulsion depending on temperature and pressure, and heating or cooling does occur. This is known as the Joule–Thomson effect. For reference, the Joule–Thomson coefficient μ for air at room temperature and sea level is 0.22 °C/bar. | 7 | Physical Chemistry |
Androstanedione, also known as 5α-androstanedione or as 5α-androstane-3,17-dione, is a naturally occurring androstane (5α-androstane) steroid and an endogenous metabolite of androgens like testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), and androstenedione. It is the C5 epimer of etiocholanedione (5β-androstanedione). Androstanedione is formed from androstenedione by 5α-reductase and from DHT by 17β-hydroxysteroid dehydrogenase. It has some androgenic activity.
In female genital skin, the conversion of androstenedione into DHT through 5α-androstanedione appears to be more important than the direct conversion of testosterone into DHT. | 1 | Biochemistry |
Aminoallyl nucleotide is a nucleotide with a modified base containing an allylamine. They are used in post-labeling of nucleic acids by fluorescence detection in microarray. They are reactive with N-Hydroxysuccinimide ester group which helps attach a fluorescent dye to the primary amino group on the nucleotide. These nucleotides are known as 5-(3-aminoallyl)-nucleotides since the aminoallyl group is usually attached to carbon 5 of the pyrimidine ring of uracil or cytosine. The primary amine group in the aminoallyl moiety is aliphatic and thus more reactive compared to the amine groups that are directly attached to the rings (aromatic) of the bases. Common names of aminoallyl nucleosides are initially abbreviated with aa- or AA- to indicate aminoallyl. The 5-carbon sugar is indicated with or without the lowercase "d" indicating deoxyribose if included or ribose if not. Finally the nitrogenous base and number of phosphates are indicated (i.e. aa-UTP = aminoallyl uridine triphosphate). | 1 | Biochemistry |
For each equilibrium involving a host, H, and a guest G
the equilibrium constant, , is defined as
The values of the free concentrations, and are obtained by solving the equations of mass balance with known or estimated values for the stability constants.
Then, the concentrations of each complex species may also be calculated as . The relationship between a species' concentration and the measured quantity is specific for the measurement technique, as indicated in each section above. Using this relationship, the set of parameters, the stability constant values and values of properties such as molar absorptivity or specified chemical shifts, may be refined by a non-linear least-squares refinement process. For a more detailed exposition of the theory see Determination of equilibrium constants.
Some dedicated computer programs are listed at Implementations. | 6 | Supramolecular Chemistry |
THF is deprotonated by butyllithium, especially in the presence of TMEDA, by loss of one of four protons adjacent to oxygen. This process, which consumes butyllithium to generate butane, induces a ring opening to give enolate of acetaldehyde and ethylene. Therefore, reactions of BuLi in THF are typically conducted at low temperatures, such as –78 °C, as is conveniently produced by a freezing bath of dry ice and acetone. Higher temperatures (−25 °C or even −15 °C) are also used. | 0 | Organic Chemistry |
Photogeochemistry merges photochemistry and geochemistry into the study of light-induced chemical reactions that occur or may occur among natural components of Earth's surface. The first comprehensive review on the subject was published in 2017 by the chemist and soil scientist Timothy A Doane, but the term photogeochemistry appeared a few years earlier as a keyword in studies that described the role of light-induced mineral transformations in shaping the biogeochemistry of Earth; this indeed describes the core of photogeochemical study, although other facets may be admitted into the definition. | 5 | Photochemistry |
Early quantum models included a soliton pair creation model by Maki and a proposal by John Bardeen that condensed CDW electrons tunnel coherently through a tiny pinning gap, fixed at ±k unlike the Peierls gap. Makis theory lacked a sharp threshold field and Bardeen only gave a phenomenological interpretation of the threshold field. However, a 1985 paper by Krive and Rozhavsky pointed out that nucleated solitons and antisolitons of charge ±q generate an internal electric field E* proportional to q/ε. The electrostatic energy (1/2)ε[E ± E*] prevents soliton tunneling for applied fields E less than a threshold E = E*/2 without violating energy conservation. Although this Coulomb blockade threshold can be much smaller than the classical depinning field, it shows the same scaling with impurity concentration since the CDWs polarizability and dielectric response ε vary inversely with pinning strength.
Building on this picture, as well as a 2000 article on time-correlated soliton tunneling, a more recent quantum model proposes Josephson-like coupling (see Josephson effect) between complex order parameters associated with nucleated droplets of charged soliton dislocations on many parallel chains. Following Richard Feynman in The Feynman Lectures on Physics, Vol. III, Ch. 21, their time-evolution is described using the Schrödinger equation as an emergent classical equation. The narrow-band noise and related phenomena result from the periodic buildup of electrostatic charging energy and thus do not depend on the detailed shape of the washboard pinning potential. Both a soliton pair-creation threshold and a higher classical depinning field emerge from the model, which views the CDW as a sticky quantum fluid or deformable quantum solid with dislocations, a concept discussed by Philip Warren Anderson. | 7 | Physical Chemistry |
The melting point of ice is at standard pressure; however, pure liquid water can be supercooled well below that temperature without freezing if the liquid is not mechanically disturbed. It can remain in a fluid state down to its homogeneous nucleation point of about . The melting point of ordinary hexagonal ice falls slightly under moderately high pressures, by /atm or about /70 atm as the stabilization energy of hydrogen bonding is exceeded by intermolecular repulsion, but as ice transforms into its polymorphs (see crystalline states of ice) above , the melting point increases markedly with pressure, i.e., reaching at (triple point of Ice VII). | 2 | Environmental Chemistry |
The major appeal of biodegradation is that, in theory, the polymer will be completely consumed in the environment without needing complex waste management and that the products of this will be non-toxic.
Most common plastics biodegrade very slowly, sometimes to the extent that they are considered non-biodegradable. As polymers are ordinarily too large to be absorbed by microbes, biodegradation initially relies on secreted extracellular enzymes to reduce the polymers to manageable chain-lengths. This requires the polymers bare functional groups the enzymes can recognise, such as ester or amide groups. Long-chain polymers with all-carbon backbones like polyolefins, polystyrene and PVC will not degrade by biological action alone and must first be oxidised to create chemical groups which the enzymes can attack.
Oxidation can be caused by melt-processing or weathering in the environment. Oxidation may be intentionally accelerated by the addition of biodegradable additives. These are added to the polymer during compounding to improve the biodegradation of otherwise very resistant plastics. Similarly, biodegradable plastics have been designed which are intrinsically biodegradable, provided they are treated like compost and not just left in a landfill site where degradation is very difficult because of the lack of oxygen and moisture. | 7 | Physical Chemistry |
In diazo transfer certain carbon acids react with tosyl azide in the presence of a weak base like triethylamine or DBU. The byproduct is the corresponding tosylamide (p-toluenesulfonamide). This reaction is also called the Regitz diazo transfer. Examples are the synthesis of tert-butyl diazoacetate and diazomalonate. Methyl phenyldiazoacetate is generated in this way by treating methyl phenylacetate with p-acetamidobenzenesulfonyl azide in the presence of base.
The mechanism involves attack of the enolate at the terminal nitrogen, proton transfer, and expulsion of the anion of the sulfonamide. Use of the β-carbonyl aldehyde leads to a deformylative variant of the Regitz transfer, which is useful for the preparation of diazo compounds stabilized by only one carbonyl group. | 0 | Organic Chemistry |
Cheon Jinwoo is the H.G. Underwood Professor at Yonsei University and the Director of the Center for Nanomedicine, Institute for Basic Science (IBS). As a leading chemist in inorganic materials chemistry and nanomedicine Cheon and his group research chemical principles for the preparation of complex inorganic materials. He has been a Clarivate Analytics Highly Cited Researcher both in the field of chemistry in 2014, 2015, 2016 and cross-field in 2018. He is a fellow of the American Chemical Society, Royal Society of Chemistry, and Korean Academy of Science and Technology, a senior editor of Accounts of Chemical Research and an editorial advisory board member of Journal of Materials Chemistry, Nano Letters and Materials Horizons. | 0 | Organic Chemistry |
Sometimes, stereoelectronic effects can win over extreme steric clash. In a similar cyclobutene ring-opening reaction, the trimethylsilyl group, which is very bulky, still favors the inward rotation. The stereoelectronic effect, which is the interaction shown above when the acceptor orbital is the σ*(Si–CH), appears to be a more predominant factor in determining the reaction selectivity against the steric hindrance and even wins over the penalty of the disrupted conjugation system of the product due to steric clash.
Furthermore, the acceptor orbitals are not limited to the antibonding orbitals of carbon-heteroatom bonds or the empty orbitals; in the following case, the acceptor orbital is the σ*(B–O) orbital. In the six-membered ring transition state, the stereoelectronic interaction is σ(C–X) → σ*(B–O). | 4 | Stereochemistry |
A genetically modified organism (GMO) is any organism whose genetic material has been altered using genetic engineering techniques. The exact definition of a genetically modified organism and what constitutes genetic engineering varies, with the most common being an organism altered in a way that "does not occur naturally by mating and/or natural recombination". A wide variety of organisms have been genetically modified (GM), including animals, plants, and microorganisms.
Genetic modification can include the introduction of new genes or enhancing, altering, or knocking out endogenous genes. In some genetic modifications, genes are transferred within the same species, across species (creating transgenic organisms), and even across kingdoms. Creating a genetically modified organism is a multi-step process. Genetic engineers must isolate the gene they wish to insert into the host organism and combine it with other genetic elements, including a promoter and terminator region and often a selectable marker. A number of techniques are available for inserting the isolated gene into the host genome. Recent advancements using genome editing techniques, notably CRISPR, have made the production of GMOs much simpler. Herbert Boyer and Stanley Cohen made the first genetically modified organism in 1973, a bacterium resistant to the antibiotic kanamycin. The first genetically modified animal, a mouse, was created in 1974 by Rudolf Jaenisch, and the first plant was produced in 1983. In 1994, the Flavr Savr tomato was released, the first commercialized genetically modified food. The first genetically modified animal to be commercialized was the GloFish (2003) and the first genetically modified animal to be approved for food use was the AquAdvantage salmon in 2015.
Bacteria are the easiest organisms to engineer and have been used for research, food production, industrial protein purification (including drugs), agriculture, and art. There is potential to use them for environmental purposes or as medicine. Fungi have been engineered with much the same goals. Viruses play an important role as vectors for inserting genetic information into other organisms. This use is especially relevant to human gene therapy. There are proposals to remove the virulent genes from viruses to create vaccines. Plants have been engineered for scientific research, to create new colors in plants, deliver vaccines, and to create enhanced crops. Genetically modified crops are publicly the most controversial GMOs, in spite of having the most human health and environmental benefits. Animals are generally much harder to transform and the vast majority are still at the research stage. Mammals are the best model organisms for humans. Livestock is modified with the intention of improving economically important traits such as growth rate, quality of meat, milk composition, disease resistance, and survival. Genetically modified fish are used for scientific research, as pets, and as a food source. Genetic engineering has been proposed as a way to control mosquitos, a vector for many deadly diseases. Although human gene therapy is still relatively new, it has been used to treat genetic disorders such as severe combined immunodeficiency and Leber's congenital amaurosis.
Many objections have been raised over the development of GMOs, particularly their commercialization. Many of these involve GM crops and whether food produced from them is safe and what impact growing them will have on the environment. Other concerns are the objectivity and rigor of regulatory authorities, contamination of non-genetically modified food, control of the food supply, patenting of life, and the use of intellectual property rights. Although there is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, GM food safety is a leading issue with critics. Gene flow, impact on non-target organisms, and escape are the major environmental concerns. Countries have adopted regulatory measures to deal with these concerns. There are differences in the regulation for the release of GMOs between countries, with some of the most marked differences occurring between the US and Europe. Key issues concerning regulators include whether GM food should be labeled and the status of gene-edited organisms. | 1 | Biochemistry |
Humic substances (HS) are coloured recalcitrant organic compounds naturally formed during long-term decomposition and transformation of biomass residues. The colour of humic substances varies from yellow to brown to black. Humic substances represent the major part of organic matter in soil, peat, coal and sediments and are important components of dissolved natural organic matter (NOM) in lakes (especially, dystrophic lakes), rivers and sea water.
"Humic substances" is an umbrella term covering humic acid, fulvic acid, humin and hymatomelanic acid which differ in solubility. By definition, humic acid is soluble in water at neutral and alkaline pH, but insoluble at acidic pH < 2. Fulvic acid is soluble in water at any pH. Humin is not soluble in water at any pH. Hymatomelanic acid is part of humic acid that is soluble in ethanol.
This definition of humic substances is largely operational. It is rooted in the history of soil science and, more precisely, in the tradition of alkaline extraction, which dates back to 1786, when Franz Karl Achard treated peat with a solution of potassium hydroxide and, after subsequent addition of an acid, obtained an amorphous dark precipitate (i.e., humic acid). Aquatic humic substances were isolated for the first time later, in 1806, from spring water by Jöns Jakob Berzelius.
In terms of chemistry, fulvic acid, humic acid and humin share more similarities than differences and represent a continuum of humic molecules. All of them are constructed from similar aromatic, polyaromatic, aliphatic and carbohydrate units and contain the same functional groups (mainly, carboxylic, phenolic and ester) albeit in varying proportions.
Water solubility of humic substances is primarily governed by interplay of two factors: the amount of ionizable functional groups (mainly, carboxylic) and the molecular weight. In general, fulvic acid has higher amount of carboxylic groups and lower average molecular weight than humic acid. However, molecular weight distributions of humic and fulvic acids significantly overlap.
Age and origin of the source material determine the chemical structure of humic substances. In general, humic substances derived from soil and peat (which takes hundreds to thousands of years to form) have higher molecular weight, higher amount of functional groups, more carbohydrate units and less polyaromatic units than humic substances derived from leonardite (which takes millions of years to form).
Humic matter in isolation is the result of a chemical extraction from the soil organic matter or the dissolved organic matter and represent the humic molecules distributed in the soil or water. A new understanding views humic substances not as high-molecular-weight macropolymers but as heterogeneous and relatively small molecular components of the soil organic matter auto-assembled in supramolecular associations and composed of a variety of compounds of biological origin and synthesized by abiotic and biotic reactions in soil. It is the large molecular complexity of the soil humeome that confers to humic matter its bioactivity in soil and its role as plant growth promoter.
The academic definition of humic substances is under debate as "humification" becomes unsupported as a special case, leading to some radical definitions expanding HS to encompass all difficult-to-characterize soil organic matter, at the cost of clarity. There is also a call to forgo the traditional alkali extract method and directly analyze the soil, but its complexity prevents widespread adoption in agriculture. In practice, this means some sources may apply a traditional acid-base analysis to compost, then state the results in term of "humic substances". | 9 | Geochemistry |
Derived structure parameters that describe constant properties of the overall feedback control system may add useful information for special purposes, e.g. in diagnosis of nonthyroidal illness syndrome or central hypothyroidism. | 1 | Biochemistry |
After initial encapsulation the remaining molecules form connections between the individual micelles to form a network within the aqueous media called a hydrogel, creating a diffuse and relatively constant concentration of the encapsulated particle within the gel. The formation of hydrogels is a phenomenon observed in superabsorbent polymers, or "slush powders," in which the polymer, often in the form of a powder, absorbs water, becoming up to 99% liquid and 30-60 times larger in size. | 7 | Physical Chemistry |
In the quantum theory of the electromagnetic field, classical wave amplitudes and are replaced by operators and that satisfy:
The classical quantity appearing in the classical expression for the energy of a field mode is replaced in quantum theory by the photon number operator . The fact that:
implies that quantum theory does not allow states of the radiation field for which the photon number and a field amplitude can be precisely defined, i.e., we cannot have simultaneous eigenstates for and . The reconciliation of wave and particle attributes of the field is accomplished via the association of a probability amplitude with a classical mode pattern. The calculation of field modes is entirely classical problem, while the quantum properties of the field are carried by the mode "amplitudes" and associated with these classical modes.
The zero-point energy of the field arises formally from the non-commutativity of and . This is true for any harmonic oscillator: the zero-point energy appears when we write the Hamiltonian:
It is often argued that the entire universe is completely bathed in the zero-point electromagnetic field, and as such it can add only some constant amount to expectation values. Physical measurements will therefore reveal only deviations from the vacuum state. Thus the zero-point energy can be dropped from the Hamiltonian by redefining the zero of energy, or by arguing that it is a constant and therefore has no effect on Heisenberg equations of motion. Thus we can choose to declare by fiat that the ground state has zero energy and a field Hamiltonian, for example, can be replaced by:
without affecting any physical predictions of the theory. The new Hamiltonian is said to be normally ordered (or Wick ordered) and is denoted by a double-dot symbol. The normally ordered Hamiltonian is denoted , i.e.:
In other words, within the normal ordering symbol we can commute and . Since zero-point energy is intimately connected to the non-commutativity of and , the normal ordering procedure eliminates any contribution from the zero-point field. This is especially reasonable in the case of the field Hamiltonian, since the zero-point term merely adds a constant energy which can be eliminated by a simple redefinition for the zero of energy. Moreover, this constant energy in the Hamiltonian obviously commutes with and and so cannot have any effect on the quantum dynamics described by the Heisenberg equations of motion.
However, things are not quite that simple. The zero-point energy cannot be eliminated by dropping its energy from the Hamiltonian: When we do this and solve the Heisenberg equation for a field operator, we must include the vacuum field, which is the homogeneous part of the solution for the field operator. In fact we can show that the vacuum field is essential for the preservation of the commutators and the formal consistency of QED. When we calculate the field energy we obtain not only a contribution from particles and forces that may be present but also a contribution from the vacuum field itself i.e. the zero-point field energy. In other words, the zero-point energy reappears even though we may have deleted it from the Hamiltonian. | 7 | Physical Chemistry |
RNA editing is the insertion, deletion, and substitution of nucleotides in a mRNA transcript prior to translation to protein. The highly oxidative environment inside chloroplasts increases the rate of mutation so post-transcription repairs are needed to conserve functional sequences. The chloroplast editosome substitutes C -> U and U -> C at very specific locations on the transcript. This can change the codon for an amino acid or restore a non-functional pseudogene by adding an AUG start codon or removing a premature UAA stop codon.
The editosome recognizes and binds to cis sequence upstream of the editing site. The distance between the binding site and editing site varies by gene and proteins involved in the editosome. Hundreds of different PPR proteins from the nuclear genome are involved in the RNA editing process. These proteins consist of 35-mer repeated amino acids, the sequence of which determines the cis binding site for the edited transcript.
Basal land plants such as liverworts, mosses and ferns have hundreds of different editing sites while flowering plants typically have between thirty and forty. Parasitic plants such as Epifagus virginiana show a loss of RNA editing resulting in a loss of function for photosynthesis genes. | 5 | Photochemistry |
Prostaglandin E is a family of naturally occurring prostaglandins that are used as medications.
Types include:
* Prostaglandin E also known as alprostadil
* Prostaglandin E also known as dinoprostone
Both types are on the World Health Organization's List of Essential Medicines.
Prostaglandin E play an important role in thermoregulation of the human brain. Decreased formation of prostaglandin E through inhibition of cyclooxygenase is the basis for the antipyretic of nonsteroidal anti-inflammatory drugs (NSAIDs). | 1 | Biochemistry |
Photosynthesis is the natural process that converts CO using light to produce hydrocarbon compounds such as sugar. The depletion of fossil fuels encourages scientists to find alternatives to produce hydrocarbon compounds. Artificial photosynthesis is a promising method mimicking the natural photosynthesis to produce such compounds. The photoelectrochemical reduction of is much studied because of its worldwide impact. Many researchers aim to find new semiconductors to develop stable and efficient photo-anodes and photo-cathodes. | 5 | Photochemistry |
From the late 1950s through 1977, Westinghouse Electric used PCBs in the manufacture of capacitors in its Bloomington, Indiana, plant. Reject capacitors were hauled and dumped in area salvage yards and landfills, including Bennetts Dump, Neals Landfill and Lemon Lane Landfill. Workers also dumped PCB oil down factory drains, which contaminated the city sewage treatment plant. The City of Bloomington gave away the sludge to area farmers and gardeners, creating anywhere from 200 to 2,000 sites, which remain unaddressed.
Over 2 million pounds of PCBs were estimated to have been dumped in Monroe and Owen counties. Although federal and state authorities have been working on the sites' environmental remediation, many areas remain contaminated. Concerns have been raised regarding the removal of PCBs from the karst limestone topography, and regarding the possible disposal options. To date, the Westinghouse Bloomington PCB Superfund site case does not have a Remedial Investigation/Feasibility Study (RI/FS) and Record of Decision (ROD), although Westinghouse signed a US Department of Justice Consent Decree in 1985. The 1985 consent decree required Westinghouse to construct an incinerator that would incinerate PCB-contaminated materials. Because of public opposition to the incinerator, however, the State of Indiana passed a number of laws that delayed and blocked its construction. The parties to the consent decree began to explore alternative remedies in 1994 for six of the main PCB contaminated sites in the consent decree. Hundreds of sites remain unaddressed as of 2014. Monroe County will never be PCB-free, as noted in a 2014 Indiana University program about the local contamination.
On February 15, 2008, Monroe County approved a plan to clean up the three remaining contaminated sites in the City of Bloomington, at a cost of $9.6 million to CBS Corp., the successor of Westinghouse. In 1999, Viacom bought CBS, so they are current responsible party for the PCB sites. | 2 | Environmental Chemistry |
The French iron industry lagged behind Britain and Belgium in the early 19th century. After 1850 it also lagged behind Germany and Luxembourg. Its industry comprised too many small, inefficient firms. 20th century growth was not robust, due more to traditional social and economic attitudes than to inherent geographic, population, or resource factors. Despite a high national income level, the French steel industry remained laggard. The industry was based on large supplies of coal and iron ore, and was dispersed across the country. The greatest output came in 1929, at 10.4 million metric tons. The industry suffered sharply during the Great Depression and World War II. Prosperity returned by mid-1950s, but profits came largely from strong domestic demand rather than competitive capacity. Late modernization delayed the development of powerful unions and collective bargaining. | 8 | Metallurgy |
NHCs are widely used as ancillary ligand in organometallic chemistry. One practical application is the ruthenium-based Grubbs' catalyst and NHC-Palladium Complexes for cross-coupling reactions. NHC-metal complexes, specifically Ag(I)-NHC complexes have been widely tested for their biological applications. | 0 | Organic Chemistry |
Fans generate noise from the rapid flow of air around blades and obstacles causing vortexes, and from the motor. Fan noise is roughly proportional to the fifth power of fan speed; halving speed reduces noise by about 15 dB.
The perceived loudness of fan noise also depends on the frequency distribution of the noise. This in turn depends on the shape and distribution of moving parts, especially of the blades, and of stationary parts, struts in particular. Like with tire treads, and similar to the principle of acoustic diffusors, an irregular shape and distribution can flatten the noise spectrum, making the noise sound less disturbing.
The inlet shape of the fan can also influence the noise levels generated by the fan. | 7 | Physical Chemistry |
LINE elements propagate by a so-called target primed reverse transcription mechanism (TPRT), which was first described for the R2 element from the silkworm Bombyx mori.
ORF2 (and ORF1 when present) proteins primarily associate in cis with their encoding mRNA, forming a ribonucleoprotein (RNP) complex, likely composed of two ORF2s and an unknown number of ORF1 trimers. The complex is transported back into the nucleus, where the ORF2 endonuclease domain opens the DNA (at TTAAAA hexanucleotide motifs in mammals). Thus, a 3'OH group is freed for the reverse transcriptase to prime reverse transcription of the LINE RNA transcript. Following the reverse transcription the target strand is cleaved and the newly created cDNA is integrated
New insertions create short target site duplications (TSDs), and the majority of new inserts are severely 5’-truncated (average insert size of 900bp in humans) and often inverted (Szak et al., 2002). Because they lack their 5’UTR, most of new inserts are non functional. | 1 | Biochemistry |
LaAlO doped with neodymium gave laser emission at 1080 nm. Mixed methylammonium lead halide () cells fashioned into optically pumped vertical-cavity surface-emitting lasers (VCSELs) convert visible pump light to near-IR laser light with a 70% efficiency. | 3 | Analytical Chemistry |
It is also used in molecular biology as an oxidising agent, for example to oxidise free thiols to form disulfide bonds in proteins. | 0 | Organic Chemistry |
The G subunit will eventually hydrolyze the attached GTP to GDP by its inherent enzymatic activity, allowing it to re-associate with G and starting a new cycle. A group of proteins called Regulator of G protein signalling (RGSs), act as GTPase-activating proteins (GAPs), are specific for G subunits. These proteins accelerate the hydrolysis of GTP to GDP, thus terminating the transduced signal. In some cases, the effector itself may possess intrinsic GAP activity, which then can help deactivate the pathway. This is true in the case of phospholipase C-beta, which possesses GAP activity within its C-terminal region. This is an alternate form of regulation for the G subunit. Such G GAPs do not have catalytic residues (specific amino acid sequences) to activate the G protein. They work instead by lowering the required activation energy for the reaction to take place. | 1 | Biochemistry |
Silicon carbide, dissolved in a basic oxygen furnace used for making steel, acts as a fuel. The additional energy liberated allows the furnace to process more scrap with the same charge of hot metal. It can also be used to raise tap temperatures and adjust the carbon and silicon content. Silicon carbide is cheaper than a combination of ferrosilicon and carbon, produces cleaner steel and lower emissions due to low levels of trace elements, has a low gas content, and does not lower the temperature of steel. | 8 | Metallurgy |
* In 2021 Kubista's organization, TATAA was on Sweden Technology Fast 50 list
* In 2019, Global Health & Pharma recognized and awarded TATAA as the "Best Nucleic Acid Analysis Service Provider – Europe."
* In 2013 TATAA Biocenter was honored with the Frost & Sullivan Award for Customer Value Leadership for their outstanding services in analyzing genetic material
* In 2012, Pioneer of the year in western Sweden
* In 1996, won Innovation Cup in western Sweden for the LightUp probes | 1 | Biochemistry |
Ye became interested in science fiction as a child. She was particularly interested in a story by Ye Yonglie that included a castle made from diamond. Ye learned that photocatalysis could split water into hydrogen and oxygen. She then became inspired by Jules Vernes The Mysterious Island', She studied chemistry at the Zhejiang University. After completing her undergraduate degree, she moved to Japan, where she joined the University of Tokyo. After earning her doctorate in 1990, she joined Osaka University as a research associate. | 5 | Photochemistry |
Typical aminophosphines undergo oxidation to the oxide. Alkylation, e.g. by methyl iodide, gives the phosphonium cation. | 0 | Organic Chemistry |
In biological systems, a double layer is the surface where two different phases of matter are in contact. Biological double layers are much like their interfacial counterparts, but with several notable distinctions.
The surface of biological cells carry many different types of chemical groups, each with a different dissociation constant, causing them to have varying electric charges at a physiological pH. This indicates that biosurfaces are chemically heterogeneous. This biospecific feature is typical for all biosurfaces, including proteins, macromolecules and biological cells.
In certain organisms, cells are covered with the glycocalyx layer, which can be modeled as a polyelectrolyte layer with a volume spread electric charge. This means that the notion of a surface charge is located on certain flat surfaces. This does not apply; instead, the cell surface is a finite thickness polyelectrolyte layer with a volume charge. At equilibrium, the relationship between these polyelectrolyte layers and a fluid bulk is called the Donnan equilibrium. The polyelectrolyte volume charge creates an equilibrated electric potential known as the Donnan potential. Part of the Donnan potential is located inside of the polyelectrolyte layer, while the other part is associated with the external double layer located in the dispersion medium.
In another feature, the cells are not in an equilibrium with the fluid bulk. There is a constant ion exchange between living cells and a fluid. Consequently, there is a difference in electric potentials between the cell interior and a fluid bulk, known as the transmembrane potential. This non-equilibrium potential affects the structure of the double layer. | 7 | Physical Chemistry |
Gene gating is a phenomenon by which transcriptionally active genes are brought next to nuclear pore complexes (NPCs) so that nascent transcripts can quickly form mature mRNA associated with export factors. Gene gating was first hypothesised by Günter Blobel in 1985. It has been shown to occur in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster as well as mammalian model systems.
The proteins that constitute the NPCs, known as nucleoporins, have been shown to play a role in DNA binding and mRNA transport, making gene gating possible. In addition, gene gating is orchestrated by two protein complexes, Spt-Ada-Gcn5-acetyltransferase (SAGA) and transcription–export complex 2 (TREX-2 complex). SAGA is a chromatin remodeling complex responsible for activating the transcription of certain inducible genes. The SAGA complex binds to gene promoters and also interacts with the TREX-2 complex. In turn, the TREX-2 complex interacts with the NPC, thus favouring the relocation of actively transcribed genes to the periphery of the cell nucleus. In contrast, the rest of the periphery, i.e. those parts not associated with NPCs, is transcriptionally silent heterochromatin. | 1 | Biochemistry |
Perilipin is part of a gene family with six currently-known members. In vertebrates, closely related genes include adipophilin (also known as adipose differentiation-related protein or Perilipin 2), TIP47 (Perilipin 3), Perilipin 4 and Perilipin 5 (also called MLDP, LSDP5, or OXPAT). Insects express related proteins, LSD1 and LSD2, in fat bodies. The yeast Saccharomyces cerevisiae expresses PLN1 (formerly PET10), that stabilizes lipid droplets and aids in their assembly. | 1 | Biochemistry |
A biomolecular complex, also called a biomacromolecular complex, is any biological complex made of more than one biopolymer (protein, RNA, DNA,
carbohydrate) or large non-polymeric biomolecules (lipid). The interactions between these biomolecules are non-covalent.
Examples:
* Protein complexes, some of which are multienzyme complexes: proteasome, DNA polymerase III holoenzyme, RNA polymerase II holoenzyme, symmetric viral capsids, chaperonin complex GroEL-GroES, photosystem I, ATP synthase, ferritin.
* RNA-protein complexes: ribosome, spliceosome, vault, SnRNP. Such complexes in cell nucleus are called ribonucleoproteins (RNPs).
* DNA-protein complexes: nucleosome.
* Protein-lipid complexes: lipoprotein.
The biomacromolecular complexes are studied structurally by X-ray crystallography, NMR spectroscopy of proteins, cryo-electron microscopy and successive single particle analysis, and electron tomography.
The atomic structure models obtained by X-ray crystallography and biomolecular NMR spectroscopy can be docked into the much larger structures of biomolecular complexes obtained by lower resolution techniques like electron microscopy, electron tomography, and small-angle X-ray scattering.
Complexes of macromolecules occur ubiquitously in nature, where they are involved in the construction of viruses and all living cells. In addition, they play fundamental roles in all basic life processes (protein translation, cell division, vesicle trafficking, intra- and inter-cellular exchange of material between compartments, etc.). In each of these roles, complex mixtures of become organized in specific structural and spatial ways. While the individual macromolecules are held together by a combination of covalent bonds and intramolecular non-covalent forces (i.e., associations between parts within each molecule, via charge-charge interactions, van der Waals forces, and dipole–dipole interactions such as hydrogen bonds), by definition MAs themselves are held together solely via the noncovalent forces, except now exerted between molecules (i.e., intermolecular interactions). | 1 | Biochemistry |
In this regulatory scheme, every current polluting facility is given or may purchase on an open market an emissions allowance for each unit of a designated pollutant it emits. Operators can then install pollution control equipment, and sell portions of their emissions allowances they no longer need for their own operations, thereby recovering some of the capital cost of their investment in such equipment. The intention is to give operators economic incentives to install pollution controls.
The first emissions trading market was established in the United States by enactment of the Clean Air Act Amendments of 1990. The overall goal of the Acid Rain Program established by the Act is to achieve significant environmental and public health benefits through reductions in emissions of sulfur dioxide (SO) and nitrogen oxides (NO), the primary causes of acid rain. To achieve this goal at the lowest cost to society, the program employs both regulatory and market based approaches for controlling air pollution. | 2 | Environmental Chemistry |
Anomerism is an identity for single bonded ring structures where "cis" or "Z" and "trans" or "E" (geometric isomerism) needs to name the substitutions on a carbon atom that also displays the identity of chirality; so anomers have carbon atoms that have geometric isomerism and optical isomerism (enantiomerism) on one or more of the carbons of the ring. Anomers are named "alpha" or "axial" and "beta" or "equatorial" when substituting a cyclic ring structure that has single bonds between the carbon atoms of the ring for example, a hydroxyl group, a methyl hydroxyl group, a methoxy group or another pyranose or furanose group which are typical single bond substitutions but not limited to these. Axial geometric isomerism will be perpendicular (90 degrees) to a reference plane and equatorial will be 120 degrees away from the axial bond or deviate 30 degrees from the reference plane. | 4 | Stereochemistry |
Macro-scale biological processes, such as the spread of virus infections, can be followed using GFP labeling. In the past, mutagenic ultra violet light (UV) has been used to illuminate living organisms (e.g., see) to detect and photograph the GFP expression. Recently, a technique using non-mutagenic LED lights have been developed for macro-photography. The technique uses an epifluorescence camera attachment based on the same principle used in the construction of epifluorescence microscopes. | 1 | Biochemistry |
G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine. These structures are normally located at the telomeres (the ends of the chromosomes). The G-quadruplex can either be parallel or antiparallel depending on the loop configuration, which is a component of the structure. If all the DNA strands run in the same direction, it is termed to be a parallel quadruplex, and is known as a strand-reversal/propeller, connecting adjacent parallel strands. If one or more of the DNA strands run in opposite direction, it is termed as an anti-parallel quadruplex, and can either be in a form of a lateral/edgewise, connecting adjacent anti-parallel strands, or a diagonal, joining two diagonally opposite strands. The structure of these G-quadruplexes can be determined by a cation. | 1 | Biochemistry |
In environmental chemistry, air sparging is an in situ remediation technique that removes volatile pollutants from contaminated groundwater and soil. | 8 | Metallurgy |
Stripping is mainly conducted in trayed towers (plate columns) and packed columns, and less often in spray towers, bubble columns, and centrifugal contactors.
Trayed towers consist of a vertical column with liquid flowing in the top and out the bottom. The vapor phase enters in the bottom of the column and exits out of the top. Inside of the column are trays or plates. These trays force the liquid to flow back and forth horizontally while the vapor bubbles up through holes in the trays. The purpose of these trays is to increase the amount of contact area between the liquid and vapor phases.
Packed columns are similar to trayed columns in that the liquid and vapor flows enter and exit in the same manner. The difference is that in packed towers there are no trays. Instead, packing is used to increase the contact area between the liquid and vapor phases. There are many different types of packing used and each one has advantages and disadvantages. | 3 | Analytical Chemistry |
In organic chemistry, kinetic resolution is a means of differentiating two enantiomers in a racemic mixture. In kinetic resolution, two enantiomers react with different reaction rates in a chemical reaction with a chiral catalyst or reagent, resulting in an enantioenriched sample of the less reactive enantiomer. As opposed to chiral resolution, kinetic resolution does not rely on different physical properties of diastereomeric products, but rather on the different chemical properties of the racemic starting materials. The enantiomeric excess (ee) of the unreacted starting material continually rises as more product is formed, reaching 100% just before full completion of the reaction. Kinetic resolution relies upon differences in reactivity between enantiomers or enantiomeric complexes.
Kinetic resolution can be used for the preparation of chiral molecules in organic synthesis. Kinetic resolution reactions utilizing purely synthetic reagents and catalysts are much less common than the use of enzymatic kinetic resolution in application towards organic synthesis, although a number of useful synthetic techniques have been developed in the past 30 years. | 4 | Stereochemistry |
Ecology
Calanus spp. are abundantly distributed copepods, particularly in the polar and temperate North Atlantic. Studies attempting to quantify the lipid pump have primarily focused on the cousin species of C. finmarchicus, Calanus glacialis and Calanus helgolandicus, C. hyperboreus. C. hyperboreous, the largest of these species, uses an overwintering diapause (hibernation) strategy, and its life-history will be described in more detail as a representative Calanus spp. With a life cycle of two to six years on average, each C. hyperboreous individual can go through multiple overwintering periods. Positively buoyant eggs are spawned by females at depth and rise to the surface. Larvae (nauplii) first develop from these eggs, and complete their maturation into an early juvenile (copepodite) within one season, after which they undergo their first overwintering. Copepodite have three stages before maturing to the adult stages. While female Calanus spp. are generally expected to experience mortality after spawning, some may return to the surface to build up lipid stores before entering another overwintering and reproductive cycle.
Lipid accumulation and metabolism
Lipids are stored by all copepodite and adult Calanus spp. in an oil sac, which can account for up to 60% of an individuals dry weight. Calanus spp. accumulate these lipids while feeding closer to the ocean surface during the spring and summer months, aligning with phytoplankton blooms. Early in the growing season, Calanus spp. biogenergetics are allocated to reproduction, feeding and growth, but eventually shift to the production of lipids to provide energy during diapause. These lipids take the form of wax esters, energy-rich compounds like omega-3 fatty acids, and long-chain carbon molecules. At the end of the feeding/growing season, Calanus spp. migrate downward, with to depths varying from 600 to 3000m, but with the requirement that Calanus spp.' settle below the thermocline to prevent premature return to the surface waters. Stored lipids are metabolized at these depths, accounting for approximately 25% of the basal metabolic rate. A 6–8 month-long overwintering period can drain a substantial fraction (44–93%) of the stored lipids despite the decreased metabolism.
Physical characteristics
The physical characteristics of Calanus spp. (i.e., dry weight, prosome length, lipid content, and carbon content) are always changing, varying between different regions, temporally, and across life stages. Based on isomorphism, or the similarity in form or structure of organisms, Calanus spp. may deviate in size but their basic physical structure remains constant across different overwintering stages and between different copepod species. The only significant taxonomic difference is the number of segments on the tail across developmental stage CIII and older (CIV, CV). With an outcome of isomorphism, dry weight (d [mg]) and prosome length (p [mm]) can be scaled as they are related as d = cp, where c is a coefficient. Observations identify the relationship between dry weight and prosome length with a coefficient between 3.3 and 3.5 for C. hyperboreus. Although this relationship is not supported extensively by empirical evidence, it has been used for model frameworks to observe Calanus spp. carbon content.
Relationships between NAO and Calanus spp. populations
In the North Atlantic and Nordic Seas, a primary long-term forcing that affects Calanus spp. and its habitat is the North Atlantic Oscillation (NAO) index, defined as the normalized difference in sea surface pressure between the Azores High and the Icelandic Low. While high NAO index values indicate a net flow of Atlantic water to the northeast and into the Norwegian Sea, low NAO index values indicate a reduced Atlantic water inflow into the Nordic Seas. In the Northwestern Atlantic, positive trends in the abundances of Calanus spp. correspond with higher sea surface temperatures and positive NAO forcing with a lag of one or two years. However, the influence of the NAO in explaining Calanus spp. abundance was substantially diminished when temporal autocorrelation and detrending analyses were involved. | 9 | Geochemistry |
Blood plasma is the liquid component of blood, which contains dissolved proteins, nutrients, ions, and other soluble components. In whole blood, red blood cells, white blood cells, and platelets are suspended within the plasma. The goal of plasma purification and processing is to extract specific materials that are present in blood, and use them for restoration and repair. There are several components that make up blood plasma, one of which is the protein albumin. Albumin is a highly water-soluble protein with considerable structural stability. It serves as a transportation device for materials such as hormones, enzymes, fatty acids, metal ions, and medicinal products. It is also used for therapeutic purposes, being essential in restoration and maintenance of circulating blood volume in imperative situations such as severe trauma or surgery. With little room for error, extremely pure samples that are lacking impurities needs to be at hand in good amount. Human blood plasma is important for the body so the nutrients etc. can be stored. | 3 | Analytical Chemistry |
* U.S. Commissioner of Corporations. Report on the Steel Industry (1913).
* Warne, Colston E. ed. The Steel Strike of 1919 (1963), primary and secondary documents | 8 | Metallurgy |
Prime editing is a search-and-replace genome editing technology in molecular biology by which the genome of living organisms may be modified. The technology directly writes new genetic information into a targeted DNA site. It uses a fusion protein, consisting of a catalytically impaired Cas9 endonuclease fused to an engineered reverse transcriptase enzyme, and a prime editing guide RNA (pegRNA), capable of identifying the target site and providing the new genetic information to replace the target DNA nucleotides. It mediates targeted insertions, deletions, and base-to-base conversions without the need for double strand breaks (DSBs) or donor DNA templates.
The technology has received mainstream press attention due to its potential uses in medical genetics. It utilizes methodologies similar to precursor genome editing technologies, including CRISPR/Cas9 and base editors. Prime editing has been used on some animal models of genetic disease and plants. | 1 | Biochemistry |
Phred quality scores are logarithmically related to the base-calling error probabilities and defined as
This relation can also be written as
For example, if Phred assigns a quality score of 30 to a base, the chances that this base is called incorrectly are 1 in 1000.
The phred quality score is the negative ratio of the error probability to the reference level of expressed in Decibel (dB). | 1 | Biochemistry |
The alpha effect is also dependent on solvent but not in a predictable way: it can increase or decrease with solvent mix composition or even go through a maximum. At least in some cases, the alpha effect has been observed to vanish if the reaction is conducted in the gas phase, leading some to conclude that it is primarily a solvation effect. However, this explanation has limitations since similar alpha effects could be found in different solvent systems and also because the solvation affects both the basicity and the nucleophilicity of the nucleophile. | 7 | Physical Chemistry |
A skeletal isomer of a compound is a structural isomer that differs from it in the atoms and bonds that are considered to comprise the "skeleton" of the molecule. For organic compounds, such as alkanes, that usually means the carbon atoms and the bonds between them.
For example, there are three skeletal isomers of pentane: n-pentane (often called simply "pentane"), isopentane (2-methylbutane) and neopentane (dimethylpropane).
If the skeleton is acyclic, as in the above example, one may use the term chain isomerism. | 4 | Stereochemistry |
Pyrometers are suited especially to the measurement of moving objects or any surfaces that cannot be reached or cannot be touched. Contemporary multispectral pyrometers are suitable for measuring high temperatures inside combustion chambers of gas turbine engines with high accuracy.
Temperature is a fundamental parameter in metallurgical furnace operations. Reliable and continuous measurement of the metal temperature is essential for effective control of the operation. Smelting rates can be maximized, slag can be produced at the optimal temperature, fuel consumption is minimized and refractory life may also be lengthened. Thermocouples were the traditional devices used for this purpose, but they are unsuitable for continuous measurement because they melt and degrade.
Salt bath furnaces operate at temperatures up to 1300 °C and are used for heat treatment. At very high working temperatures with intense heat transfer between the molten salt and the steel being treated, precision is maintained by measuring the temperature of the molten salt. Most errors are caused by slag on the surface, which is cooler than the salt bath.
The tuyère pyrometer is an optical instrument for temperature measurement through the tuyeres, which are normally used for feeding air or reactants into the bath of the furnace.
A steam boiler may be fitted with a pyrometer to measure the steam temperature in the superheater.
A hot air balloon is equipped with a pyrometer for measuring the temperature at the top of the envelope in order to prevent overheating of the fabric.
Pyrometers may be fitted to experimental gas turbine engines to measure the surface temperature of turbine blades. Such pyrometers can be paired with a tachometer to tie the pyrometer output with the position of an individual turbine blade. Timing combined with a radial position encoder allows engineers to determine the temperature at exact points on blades moving past the probe. | 8 | Metallurgy |
NpPS is a compound related to Lawessons reagent formed by the reaction of 1-bromonaphthalene with PS, this is a 1,3,2,4-dithiadiphosphetane 2,4-disulfide which has a naphth-1,8-diyl group holding the two phosphorus atoms together. The mechanism by which the NpPS forms is not yet elucidated, but it is thought to occur by a process involving free radicals, and naphthalene has been detected as a side product in its synthesis. In general, NpPS has been found to be less reactive than Lawessons reagent, in agreement with the hypothesis that the dithiophosphine ylides are responsible for the majority of the chemical reactions of the 1,3,2,4-dithiadiphosphetane 2,4-disulfides.
NpPS has been found to react with many hydroxyl compounds, such as methanol, ethylene glycol and a catechol to form species with oxygen atoms bonded to the phosphorus atoms.
NpPS when refluxed in methanol reacts to form a heterocycle CHOPS with one O-methyl and one S-methyl bonded to the two phosphorus atoms. | 0 | Organic Chemistry |
Usually called RTD – Riverine Tailings Disposal. In most environments, not a particularly environmentally sound practice, it has seen significant utilisation in the past, leading to such spectacular environmental damage as done by the Mount Lyell Mining and Railway Company in Tasmania to the King River, or the poisoning from the Panguna mine on Bougainville Island, which led to large-scale civil unrest on the island, and the eventual permanent closing of the mine.
As of 2005, only three mines operated by international companies continued to use river disposal: The Ok Tedi mine, the Grasberg mine and the Porgera mine, all on New Guinea. This method is used in these cases due to seismic activity and landslide dangers which make other disposal methods impractical and dangerous. | 8 | Metallurgy |
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