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Yeast, and yeast nutrition, is mixed in the syrup. One gram pure yeast consumes approximately 0.2 grams sugar.
Yeasts will usually die out once the alcohol level reaches about 15% due to the toxicity of alcohol on the yeast cells physiology while the more alcohol tolerant Saccharomyces species take over. In addition to S. cerevisiae, Saccharomyces bayanus' is a species of yeast that can tolerate alcohol levels of 17–20%. | 1 | Biochemistry |
Automated mineralogy analytical solutions are characterised by integrating largely automated measurement techniques based on Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). Commercially available lab-based solutions include QEMSCAN and Mineral Liberation Analyzer (MLA) from FEI Company, Mineralogic from Zeiss, AZtecMineral from Oxford Instruments, the TIMA (Tescan integrated mineral analyzer) from TESCAN, AMICS from Bruker, and MaipSCAN from Rock Scientific. The first oil & gas wellsite solution was launched jointly by Zeiss and CGG Veritas in 2011 called RoqSCAN. This was followed approximately 6 months later by the release of QEMSCAN Wellsite by FEI Company. More recently in 2016, a ruggedized mine site solution for mining and mineral processing was launched by Zeiss called MinSCAN. | 7 | Physical Chemistry |
In geometry, the order-3 snub heptagonal tiling is a semiregular tiling of the hyperbolic plane. There are four triangles and one heptagon on each vertex. It has Schläfli symbol of sr{7,3}. The snub tetraheptagonal tiling is another related hyperbolic tiling with Schläfli symbol sr{7,4}. | 4 | Stereochemistry |
A solar cell or photovoltaic cell (PV cell) is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect. It is a form of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as "solar panels". The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.
Photovoltaic cells may operate under sunlight or artificial light. In addition to producing energy, they can be used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.
The operation of a PV cell requires three basic attributes:
* The absorption of light, generating excitons (bound electron-hole pairs), unbound electron-hole pairs (via excitons), or plasmons.
* The separation of charge carriers of opposite types.
* The separate extraction of those carriers to an external circuit.
In contrast, a solar thermal collector supplies heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation from heat. A "photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either to a type of photovoltaic cell (like that developed by Edmond Becquerel and modern dye-sensitized solar cells), or to a device that splits water directly into hydrogen and oxygen using only solar illumination.
Photovoltaic cells and solar collectors are the two means of producing solar power. | 7 | Physical Chemistry |
Brownfield is land that is abandoned or underutilized due to pollution from industrial use. The specific definition of brownfield land varies and is decided by policy makers and/or land developers within different countries. The main difference in definitions of whether a piece of land is considered a brownfield or not depends on the presence or absence of pollution. Overall, brownfield land is a site previously developed for industrial or commercial purposes and thus requires further development before reuse.
Examples of post industrial brownfield sites include abandoned factories, dry cleaning establishments, and gas stations. Typical contaminants include hydrocarbon spillages, solvents and pesticides, asbestos, and heavy metals like lead.
Many contaminated post-industrial brownfield sites sit unused because the cleaning costs may be more than the land is worth after redevelopment. Previously unknown underground wastes can increase the cost for study and clean-up. Depending on the contaminants and damage present adaptive re-use and disposal of a brownfield can require advanced and specialized appraisal analysis techniques. | 2 | Environmental Chemistry |
An anticarcinogen (also known as a carcinopreventive agent) is a substance that counteracts the effects of a carcinogen or inhibits the development of cancer. Anticarcinogens are different from anticarcinoma agents (also known as anticancer or anti-neoplastic agents) in that anticarcinoma agents are used to selectively destroy or inhibit cancer cells after cancer has developed. Interest in anticarcinogens is motivated primarily by the principle that it is preferable to prevent disease (preventive medicine) than to have to treat it (rescue medicine).
In theory, anticarcinogens may act via different mechanisms including enhancement of natural defences against cancer, deactivation of carcinogens, and blocking the mechanisms by which carcinogens act (such as free radical damage to DNA). Confirmation that a substance possesses anticarcinogenic activity requires extensive in vitro, in vivo, and clinical investigation. Health claims for anticarcinogens are regulated by various national and international organizations like the US Food and Drug Administration (FDA) and European Food Safety Authority (EFSA). | 1 | Biochemistry |
Rotaxane-based molecular machines have been of initial interest for their potential use in molecular electronics as logic molecular switching elements and as molecular shuttles. These molecular machines are usually based on the movement of the macrocycle on the dumbbell. The macrocycle can rotate around the axis of the dumbbell like a wheel and axle or it can slide along its axis from one site to another. Controlling the position of the macrocycle allows the rotaxane to function as a molecular switch, with each possible location of the macrocycle corresponding to a different state. These rotaxane machines can be manipulated both by chemical and photochemical inputs. Rotaxane based systems have also been shown to function as molecular muscles. In 2009, there was a report of a "domino effect" from one extremity to the other in a Glycorotaxane Molecular Machine. In this case, the C or C chair-like conformation of the mannopyranoside stopper can be controlled, depending on the localization of the macrocycle. In 2012, unique pseudo-macrocycles consisting of double-lasso molecular machines (also called rotamacrocycles) were reported in Chem. Sci. These structures can be tightened or loosened depending on pH. A controllable jump rope movement was also observed in these new molecular machines. | 6 | Supramolecular Chemistry |
Thiolactones can be prepared by dehydration of thiol-containing carboxylic acids. Thiolactones can be hydrolyzed back to the thiol acids under basic conditions. β-Thiolactones can be opened by reaction at the 4-position via S2 nucleophilic reactions. | 0 | Organic Chemistry |
In N,N-dialkylhydrazones the C=N bond can be hydrolysed, oxidised and reduced, the N–N bond can be reduced to the free amine. The carbon atom of the C=N bond can react with organometallic nucleophiles. The alpha-hydrogen atom is more acidic by 10 orders of magnitude compared to the ketone and therefore more nucleophilic. Deprotonation with for instance lithium diisopropylamide (LDA) gives an azaenolate which can be alkylated by alkyl halides. The hydrazines SAMP and RAMP function as chiral auxiliary. | 0 | Organic Chemistry |
The main advantages of this technique are the high pulling rates (60 times greater than the conventional Czochralski technique) and the possibility of growing materials with very high melting points. In addition, LHPG is a crucible-free technique, which allows single crystals to be grown with high purity and low stress.
The geometric shape of the crystals (the technique can produce small diameters), and the low production cost, make the single-crystal fibers (SCF) produced by LHPG suitable substitutes for bulk crystals in many devices, especially those that use high-melting-point materials. However, single-crystal fibers must have equal or superior optical and structural qualities compared to bulk crystals to substitute for them in technological devices. This can be achieved by carefully controlling the growth conditions. | 3 | Analytical Chemistry |
Polymorphism in binary metal oxides has attracted much attention because these materials are of significant economic value. One set of famous examples have the composition SiO, which form many polymorphs. Important ones include: α-quartz, β-quartz, tridymite, cristobalite, moganite, coesite, and stishovite. | 3 | Analytical Chemistry |
Dimitar Ivanov Popov () (October 13, 1894 – October 25, 1975) was a Bulgarian organic chemist and an academician of the Bulgarian Academy of Sciences.
Prof. D. Ivanov is known by his fathers name Ivanov rather than his familys name Popov.
He is the namesake of the Ivanov reaction in chemistry. | 0 | Organic Chemistry |
In 2004, separate civil suits alleging illegal marketing of citalopram and escitalopram for use by children and teenagers by Forest were initiated by two whistleblowers: a physician named Joseph Piacentile and a Forest salesman named Christopher Gobble. In February 2009, the suits were joined. Eleven states and the District of Columbia filed notices of intent to intervene as plaintiffs in the action.
The suits alleged that Forest illegally engaged in off-label promotion of Lexapro for use in children; hid the results of a study showing lack of effectiveness in children; paid kickbacks to physicians to induce them to prescribe Lexapro to children; and conducted so-called "seeding studies" that were, in reality, marketing efforts to promote the drug's use by doctors. Forest denied the allegations but ultimately agreed to settle with the plaintiffs for over $313 million. | 4 | Stereochemistry |
A fermionic condensate (or Fermi–Dirac condensate) is a superfluid phase formed by fermionic particles at low temperatures. It is closely related to the Bose–Einstein condensate, a superfluid phase formed by bosonic atoms under similar conditions. The earliest recognized fermionic condensate described the state of electrons in a superconductor; the physics of other examples including recent work with fermionic atoms is analogous. The first atomic fermionic condensate was created by a team led by Deborah S. Jin using potassium-40 atoms at the University of Colorado Boulder in 2003. | 7 | Physical Chemistry |
When two miscible liquids are brought into contact, and diffusion takes place, the macroscopic (or average) concentration evolves following Ficks law. On a mesoscopic scale, that is, between the macroscopic scale described by Ficks law and molecular scale, where molecular random walks take place, fluctuations cannot be neglected. Such situations can be successfully modeled with Landau-Lifshitz fluctuating hydrodynamics. In this theoretical framework, diffusion is due to fluctuations whose dimensions range from the molecular scale to the macroscopic scale.
In particular, fluctuating hydrodynamic equations include a Ficks flow term, with a given diffusion coefficient, along with hydrodynamics equations and stochastic terms describing fluctuations. When calculating the fluctuations with a perturbative approach, the zero order approximation is Ficks law. The first order gives the fluctuations, and it comes out that fluctuations contribute to diffusion. This represents somehow a tautology, since the phenomena described by a lower order approximation is the result of a higher approximation: this problem is solved only by renormalizing the fluctuating hydrodynamics equations. | 7 | Physical Chemistry |
Cohen was born in Boston, the son of a furrier from England, and was the first in his family with a college education. He graduated from Tufts University in 1951. He was guided towards science instead of medicine in a chance encounter with Isaac Asimov while working a summer job as a waiter, and completed his Ph.D. at the University of Southern California in 1955, helping to support his graduate studies by working as an extra in the movies of Katharine Hepburn and Spencer Tracy. His doctoral research, supervised by Jerome A. Berson, concerned the synthesis of alkaloids found in ipecac, and the chemical properties of pyridines.
After postdoctoral research as a Fulbright scholar at the University of Glasgow, working with Derek Barton, he joined the University of Pittsburgh chemistry faculty in 1956, and became one of the first professors at the university to bring in federal grant money for his research. He retired as a professor emeritus in 1999, but continued to do research in his laboratory, often working 80-hour weeks.
At the University of Pittsburgh, he was the doctoral advisor to over 40 students. | 0 | Organic Chemistry |
The release of a neurotransmitter is triggered by the arrival of a nerve impulse (or action potential) and occurs through an unusually rapid process of cellular secretion (exocytosis). Within the presynaptic nerve terminal, vesicles containing neurotransmitter are localized near the synaptic membrane. The arriving action potential produces an influx of calcium ions through voltage-dependent, calcium-selective ion channels at the down stroke of the action potential (tail current). Calcium ions then bind to synaptotagmin proteins found within the membranes of the synaptic vesicles, allowing the vesicles to fuse with the presynaptic membrane. The fusion of a vesicle is a stochastic process, leading to frequent failure of synaptic transmission at the very small synapses that are typical for the central nervous system. Large chemical synapses (e.g. the neuromuscular junction), on the other hand, have a synaptic release probability, in effect, of 1. Vesicle fusion is driven by the action of a set of proteins in the presynaptic terminal known as SNAREs. As a whole, the protein complex or structure that mediates the docking and fusion of presynaptic vesicles is called the active zone. The membrane added by the fusion process is later retrieved by endocytosis and recycled for the formation of fresh neurotransmitter-filled vesicles.
An exception to the general trend of neurotransmitter release by vesicular fusion is found in the type II receptor cells of mammalian taste buds. Here the neurotransmitter ATP is released directly from the cytoplasm into the synaptic cleft via voltage gated channels. | 1 | Biochemistry |
4-Nitrophenol can be used as a pH indicator. A solution of 4-nitrophenol appears colorless below pH 5.4 and yellow above pH 7.5. This color-changing property makes this compound useful as a pH indicator.
The yellow color of the 4-nitrophenolate form (or 4-nitrophenoxide) is due to a maximum of absorbance at 405 nm (ε = 18.3 to 18.4 mM cm in strong alkali). In contrast, 4-nitrophenol has a weak absorbance at 405 nm (ε = 0.2 mM cm).
The isosbestic point for 4-nitrophenol/4-nitrophenoxide is at 348 nm, with ε = 5.4 mM cm. | 3 | Analytical Chemistry |
Solar energy is required for converting carbon dioxide and water into organic matter, otherwise known as photosynthesis. As with temperature and nutrients, different algae have different rates of metabolic response to increasing light and also different optimal light conditions for growth, as some algae are more adapted for darker environments while others can outcompete in lighter conditions. Light can also interact with nutrients to affect species-specific algal productivity response to increasing light. These different responses at the organismal level propagate up to influence metabolism at the ecosystem level. Even in low-nutrient lakes where nutrients would be expected to be the limiting resource for primary productivity, light can still be the limiting resource, which has cascading negative effects on higher trophic levels such as fish productivity. Variability in light in different lake zones and within a lake through time creates patchiness in productivity both spatially and temporally.
In addition to controlling primary productivity, sunlight can also influence rates of respiration by partially oxidizing organic matter which can make it easier for bacteria to break down and convert into carbon dioxide. This partial photooxidation essentially increases the amount of organic matter that is available for mineralization. In some lakes, complete photooxidation or partial photooxidation can account for a majority of the conversion from organic to inorganic matter, however, the proportion to bacterial respiration varies greatly among lakes. | 1 | Biochemistry |
The BRENDA tissue ontology (BTO) represents a comprehensive structured encyclopedia. It provides terms, classifications, and definitions of tissues, organs, anatomical structures, plant parts, cell cultures, cell types, and cell lines of organisms from all taxonomic groups (animals, plants, fungi, protozoon) as enzyme sources. The information is connected to the functional data in the BRENDA ("BRaunschweig ENzyme DAtabase“) enzyme information system.
BTO is one of the first tissue-specific ontologies in life sciences, not restricted to a specific organism or a specific organism group providing a user-friendly access to the wide range of tissue and cell-type information. Databases, such as Ontology Lookup Service or ses, such as MIRIAM Registry or of the EBI-EMBL, the TissueDistributionDB, including the Tissue Synonym Library of the German Cancer Research Center (DKFZ) in Heidelberg or the Bioportal platform of the National Center for Biomedical Ontology in Stanford, USA rely on BTO and implement the encyclopedia as an essential repository of information into their respective platform.
BTO enables users from medical research and pharmaceutical sciences to search for the occurrence and histological detection of disease-related enzymes in tissues, which play an important role in diagnosis, therapies, and drug development. In biochemistry and biotechnology the organism-specific tissue terms linked to enzyme functional data are an important resource for the understanding of the metabolism and regulation in life sciences. Ontologies represent classification systems that provide controlled and structured vocabularies. They are important tools to illustrate and to link evolutionary correlations.
Development of BTO started in 2003, aimed to connect the biochemical and molecular biological enzyme data of BRENDA with a hierarchical and standardized collection of tissue-specific terms. The functional enzyme data and information in BRENDA have been manually annotated and structured by experts from biochemistry, biology, and chemistry. By October 2022, the BTO contained over 6,527 terms, linked to 6,065 synonyms and 5,474 definitions. The terms are classified under generic categories, rules, and formats of the Gene Ontology Consortium (GO,), organized as a directed acyclic graph (DAG) created using the open-source OBO-Edit. All terms from each level are directly connected the enzyme data in BRENDA. BTO is a suitable tool to distinguish between different enzymes which are expressed in a tissue-specific manner. | 1 | Biochemistry |
Neuromelanin is found in higher concentrations in humans than in other primates. Neuromelanin concentration increases with age, suggesting a role in neuroprotection (neuromelanin can chelate metals and xenobiotics) or senescence. | 1 | Biochemistry |
Although cells undergo multiple steps in order to ensure there are no mutations in the genetic sequence, sometimes specific deletions and other genetic changes during Okazaki fragment maturation go unnoticed. Because Okazaki fragments are the set of nucleotides for the lagging strand, any alteration including deletions, insertions, or duplications from the original strand can cause a mutation if it is not detected and fixed. Other causes of mutations include problems with the proteins that aid in DNA replication. For example, a mutation related to primase affects RNA primer removal and can make the DNA strand more fragile and susceptible to breaks. Another mutation concerns polymerase α, which impairs the editing of the Okazaki fragment sequence and incorporation of the protein into the genetic material. Both alterations can lead to chromosomal aberrations, unintentional genetic rearrangement, and a variety of cancers later in life.
In order to test the effects of the protein mutations on living organisms, researchers genetically altered lab mice to be homozygous for another mutation in protein related to DNA replication, flap endonuclease 1, or FEN1. The results varied based on the specific gene alterations. The homozygous knockout mutant mice experienced a "failure of cell proliferation" and "early embryonic lethality" (27). The mice with the mutation F343A and F344A (also known as FFAA) died directly after birth due to complications in birth including pancytopenia and pulmonary hypoplasia. This is because the FFAA mutation prevents the FEN1 from interacting with PCNA (proliferating cell nuclear antigen), consequently not allowing it to complete its purpose during Okazaki fragment maturation. The interaction with this protein is considered to be the key molecular function in the FEN1's biological function. The FFAA mutation causes defects in RNA primer removal and long-base pair repair, of which cause many breaks in the DNA. Under careful observation, cells homozygous for FFAA FEN1 mutations seem to display only partial defects in maturation, meaning mice heterozygous for the mutation would be able to survive into adulthood, despite sustaining multiple small nicks in their genomes. Inevitably however, these nicks prevent future DNA replication because the break causes the replication fork to collapse and causes double strand breaks in the actual DNA sequence. In time, these nicks also cause full chromosome breaks, which could lead to severe mutations and cancers. Other mutations have been implemented with altered versions of Polymerase α, leading to similar results. | 1 | Biochemistry |
The polymolybdates and polytungstates are derived, formally at least, from the dianionic [MO] precursors. The most common units for polymolybdates and polyoxotungstates are the octahedral {MO} centers, sometimes slightly distorted. Some polymolybdates contain pentagonal bipyramidal units. These building blocks are found in the molybdenum blues, which are mixed valence compounds. | 7 | Physical Chemistry |
Hydra polyps are small and transparent which makes it possible to trace single cells in vivo. In addition, transgenic Hydra provide a ready system for generating gain-of-function phenotypes. With the use of transgenes producing dominant-negative versions of proteins, one should be able to obtain loss-of-function phenotypes as well.
Current technology allows generation of reporter constructs using promoters of various Hydra genes fused to fluorescent proteins.
Since transgenic Hydra lines have become an important tool to dissect molecular mechanisms of development, a “Hydra Transgenic Facility” has been established at the Christian-Albrechts-University of Kiel (Germany). | 1 | Biochemistry |
Threonine proteases, such as the proteasome protease subunit and ornithine acyltransferases use the secondary hydroxyl of threonine in a manner analogous to the use of the serine primary hydroxyl. However, due to the steric interference of the extra methyl group of threonine, the base member of the triad is the N-terminal amide which polarises an ordered water which, in turn, deprotonates the catalytic hydroxyl to increase its reactivity. Similarly, there exist equivalent serine only and cysteine only configurations such as penicillin acylase G and penicillin acylase V which are evolutionarily related to the proteasome proteases. Again, these use their N-terminal amide as a base. | 1 | Biochemistry |
Polymers are chainlike molecules that are made of the same repetition unit. With a few exceptions such as proteins, a polymer consists of a mix of molecules with different chain lengths. Therefore, average values are given for the molecular weight like the number average, the weight average or the viscosity average molar mass. A measure for the width of the molecular weight distribution is the polydispersity index. The targeted manipulation of the molecular weight distribution of a polymer by removing short and/or long chain material is called polymer fractionation. | 7 | Physical Chemistry |
Dithionite () can also be used as a reductant. It is usually used in addition to iron reduce contaminants. A number of reactions take place and eventually the contaminant is removed. In the process, ditionite is consumed and the final product of all the reactions is 2 sulfur dioxide anions. The dithionite is not stable for a long period of time. | 2 | Environmental Chemistry |
When an atom or molecule interacts with an electromagnetic wave of frequency , it can undergo a transition from an initial to a final state of energy difference through the coupling of the electromagnetic field to the transition dipole moment. When this transition is from a lower energy state to a higher energy state, this results in the absorption of a photon. A transition from a higher energy state to a lower energy state results in the emission of a photon. If the charge, , is omitted from the electric dipole operator during this calculation, one obtains as used in oscillator strength. | 5 | Photochemistry |
The cellular response in signal transduction cascades involves alteration of the expression of effector genes or activation/inhibition of targeted proteins. Regulation of protein activity mainly involves phosphorylation/dephosphorylation events, leading to its activation or inhibition. It is the case for the vast majority of responses as a consequence of the binding of the primary messengers to membrane receptors. This response is quick, as it involves regulation of molecules that are already present in the cell. On the other hand, the induction or repression of the expression of genes requires the binding of transcriptional factors to the regulatory sequences of these genes. The transcriptional factors are activated by the primary messengers, in most cases, due to their function as nuclear receptors for these messengers. The secondary messengers like DAG or Ca could also induce or repress gene expression, via transcriptional factors. This response is slower than the first because it involves more steps, like transcription of genes and then the effect of newly formed proteins in a specific target. The target could be a protein or another gene. | 7 | Physical Chemistry |
The Zwikker reagent is used as a simple spot-test to presumptively identify barbiturates. It is composed of a mixture of two solutions. Part A is 0.5 g of copper (II) sulfate in 100 ml of distilled water. Part B consists of 5% pyridine (v/v) in chloroform. One drop of each is added to the substance to be tested and any change in colour is observed.
The test turns phenobarbital, pentobarbital and secobarbital light purple. Tea and tobacco turn yellow-green.
The test's lack of specificity and tendency to produce false positives means it is not widely used for presumptive drug testing, although it does still play a role as a thin layer chromatography stain.
It is named after the Dutch scientist Cornelis Zwikker. | 3 | Analytical Chemistry |
For all intents and purposes, each enantiomer in a pair has the same energy. However, theoretical physics predicts that due to parity violation of the weak nuclear force (the only force in nature that can "tell left from right"), there is actually a minute difference in energy between enantiomers (on the order of 10 eV or 10 kJ/mol or less) due to the weak neutral current mechanism. This difference in energy is far smaller than energy changes caused by even small changes in molecular conformation, and far too small to measure by current technology, and is therefore chemically inconsequential. In the sense used by particle physicists, the "true" enantiomer of a molecule, which has exactly the same mass-energy content as the original molecule, is a mirror-image that is also built from antimatter (antiprotons, antineutrons, and positrons). Throughout this article, "enantiomer" is used only in the chemical sense of compounds of ordinary matter that are not superposable on their mirror image. | 4 | Stereochemistry |
Ballast tanks on ships contain the fuels for corrosion. Water is one and air is usually present too and the water can become stagnant. Structural integrity is important for safety and to avoid marine pollution. Coatings have become the solution of choice to reduce the amount of corrosion in ballast tanks. Impressed current cathodic protection has also been used. Likewise sacrificial anode cathodic protection is also used. Since chlorides vastly accelerate corrosion, ballast tanks of marine vessels are particularly susceptible. | 8 | Metallurgy |
By changing specific amino acids by mutating the corresponding DNA base-pairs in the plasmids used, the importance of those amino acid residues in maintaining the interaction can be determined.
After using bacterial cell-based method to select DNA-binding proteins, it is necessary to check the specificity of these domains as there is a limit to the extent to which the bacterial cell genome can act as a sink for domains with an affinity for other sequences (or indeed, a general affinity for DNA). | 1 | Biochemistry |
FIA is an automated method of chemical analysis in which a sample is injected into a flowing carrier solution that mixes with reagents before reaching a detector. Over past 30 years, FIA techniques developed into a wide array of applications using spectrophotometry, fluorescence spectroscopy, atomic absorption spectroscopy, mass spectrometry, and other methods of instrumental analysis for detection.
Automated sample processing, high repeatability, adaptability to micro-miniaturization, containment of chemicals, waste reduction, and reagent economy in a system that operates at microliter levels are all valuable assets that contribute to the application of flow injection to real-world assays. The main assets of flow injection are the well defined concentration gradient that forms when an analyte is injected into the reagent stream (which offers an infinite number of well-reproduced analyte/reagent ratios) and the exact timing of fluidic manipulations (which provide exquisite control over the reaction conditions).
Based on computer control, FIA evolved into Sequential Injection and Bead Injection which are novel techniques based on flow programming. FIA literature comprises over 22,000 scientific papers and 22 monographs. | 3 | Analytical Chemistry |
In ancient history, Hippocrates discussed bile pigments in two of the four humours in the context of a relationship between yellow and black biles. Hippocrates visited Democritus in Abdera who was regarded as the expert in melancholy "black bile".
Relevant documentation emerged in 1827 when M. Louis Jacques Thénard examined the biliary tract of an elephant that had died at a Paris zoo. He observed dilated bile ducts were full of yellow magma, which he isolated and found to be insoluble in water. Treating the yellow pigment with hydrochloric acid produced a strong green color. Thenard suspected the green pigment was caused by impurities derived from mucus of bile.
Leopold Gmelin experimented with nitric acid in 1826 to establish the redox behavior in change from bilirubin to biliverdin, although the nomenclature did not exist at the time. The term biliverdin was coined by Jöns Jacob Berzelius in 1840, although he preferred "bilifulvin" (yellow/red) over "bilirubin" (red). The term "bilirubin" was thought to have become mainstream based on the works of Staedeler in 1864 who crystallized bilirubin from cattle gallstones.
Rudolf Virchow in 1847 recognized hematoidin to be identical to bilirubin. It is not always distinguished from hematoidin, which one modern dictionary defines as synonymous with it but another defines as "apparently chemically identical with bilirubin but with a different site of origin, formed locally in the tissues from hemoglobin, particularly under conditions of reduced oxygen tension." The synonymous identity of bilirubin and hematoidin was confirmed in 1923 by Fischer and Steinmetz using analytical crystallography.
In the 1930s, significant advances in bilirubin isolation and synthesis were described by Hans Fischer, Plieninger, and others, and pioneering work pertaining to endogenous formation of bilirubin from heme was likewise conducted in the same decade. The suffix IXα is partially based on a system developed Fischer, which means the bilin's parent compound was protoporphyrin IX cleaved at the alpha-methine bridge (see protoporphyrin IX nomenclature).
Origins pertaining to the physiological activity of bilirubin were described by Ernst Stadelmann in 1891, who may have observed the biotransformation of infused hemoglobin into bilirubin possibly inspired by Ivan Tarkhanov's 1874 works. Georg Barkan suggested the source of endogenous bilirubin to be from hemoglobin in 1932. Plieninger and Fischer demonstrated an enzymatic oxidative loss of the alpha-methine bridge of heme resulting in a bis-lactam structure in 1942. It is widely accepted that Irving London was the first to demonstrate endogenous formation of bilirubin from hemoglobin in 1950, and Sjostrand demonstrated hemoglobin catabolism produces carbon monoxide between 1949 and 1952. 14C labeled protoporphyrin biotransformation to bilirubin evidence emerged in 1966 by Cecil Watson. Rudi Schmid and Tenhunen discovered heme oxygenase, the enzyme responsible, in 1968. Earlier in 1963, Nakajima described a soluble "heme alpha-methnyl oxygeanse" which what later determined to be a non-enzymatic pathway, such as formation of a 1,2-Dioxetane intermediate at the methine bridge resulting in carbon monoxide release and biliverdin formation. | 1 | Biochemistry |
Secalin is a prolamin glycoprotein found in the grain rye, Secale cereale.
Secalin is one of the forms of gluten proteins that people with coeliac disease cannot tolerate, and thus rye should be avoided by people with this disease. It is generally recommended that such people follow a gluten free diet. | 1 | Biochemistry |
Alkyl substitution can be achieved when alkyl halides are used in conjunction with a Lewis acid; however, only activated (allylic, benzylic) or highly substituted (tert-butyl) halides are useful in this context. Nucleophilic catalysis of alkylation is rare, because protodesilylation tends to occur. Lewis acid activation is more commonly employed.
Allylsilane additions to carbonyl groups are common and synthetically useful. Vinylsilane additions are less common, as a variety of methods to access allylic alcohols are available (including epoxidation of allylsilanes; see below). If the γ position of the allylsilane is substituted, two diastereomeric products may result. In the presence of Lewis acids such as titanium tetrachloride, (E)-allylsilanes are highly selective for the syn diastereomer. (Z)-allylsilanes are much less selective (~60:40), but also favor the syn isomer.
Conjugate addition reactions of allylsilanes are possible, although unsaturated aldehydes undergo only 1,2 addition. The combination of an allylsilane with an α,β-unsaturated ketone in the presence of a Lewis acid is known as the Sakurai reaction. The enolate intermediate that results from addition can be functionalized with a separate electrophile or simply protonated. Intramolecular Sakurai reactions provide ene-6-ones
Acetals and ketals are excellent substrates for additions of allyl- and vinylsilanes. In some cases, these compounds react more cleanly than the corresponding carbonyl compounds.
Iminium ions generated in situ in the presence of protic acid react with allylsilanes to give homoallylic amines. | 0 | Organic Chemistry |
Flutamide was studied for the treatment of advanced breast cancer in two phase II clinical trials but was found to be ineffective. Out of a total of 47 patients, only three short-term responses occurred. However, the patients in the studies were selected irrespective of AR, , , or HER2 status, which were all unknown. | 4 | Stereochemistry |
Similarly to bond angles, the hybridisation of an atom can be related to the lengths of the bonds it forms. As bonding orbitals increase in s character, the σ bond length decreases.
By adding electronegative substituents and changing the hybridisation of the central atoms, bond lengths can be manipulated. If a molecule contains a structure X-A--Y, replacement of the substituent X by a more electronegative atom changes the hybridization of central atom A and shortens the adjacent A--Y bond.
Bonds between elements of disparate electronegativities will be polar and the electron density in such bonds will be shifted towards the more electronegative element. Applying this idea to the molecule fluoromethane illustrates the power of Bent's rule. Because carbon is more electronegative than hydrogen, the electron density in a C-H bond will be shortened and the C-F bond will be elongated.
The same trend also holds for the chlorinated analogs of methane, although the effect is less dramatic because chlorine is less electronegative than fluorine.
The above cases seem to demonstrate that the size of the chlorine is less important than its electronegativity. A prediction based on sterics alone would lead to the opposite trend, as the large chlorine substituents would be more favorable far apart. As the steric explanation contradicts the experimental result, Bent's rule is likely playing a primary role in structure determination. | 4 | Stereochemistry |
Note: These lists are illustrative, not exhaustive, and identification of noise effects is an active and expanding area of research.
* Gene expression levels: noise in gene expression causes differences in the fundamental properties of cells, limits their ability to biochemically control cellular dynamics, and directly or indirectly induce many of the specific effects below;
* Energy levels and transcription rate: noise in transcription rate, arising from sources including transcriptional bursting, is a significant source of noise in expression levels of genes. Extrinsic noise in mitochondrial content has been suggested to propagate to differences in the ATP concentrations and transcription rates (with functional relationships implied between these three quantities) in cells, affecting cells' energetic competence and ability to express genes;
* Phenotype selection: bacterial populations exploit extrinsic noise to choose a population subset to enter a quiescent state. In a bacterial infection, for example, this subset will not propagate quickly but will be more robust when the population is threatened by antibiotic treatment: the rapidly replicating, infectious bacteria will be killed more quickly than the quiescent subset, which may be capable of restarting the infection. This phenomenon is why courses of antibiotics should be finished even when symptoms seem to have disappeared;
* Development and stem cell differentiation: developmental noise in biochemical processes which need to be tightly controlled (for example, patterning of gene expression levels that develop into different body parts) during organismal development can have dramatic consequences, necessitating the evolution of robust cellular machinery. Stem cells differentiate into different cell types depending on the expression levels of various characteristic genes: noise in gene expression can clearly perturb and influence this process, and noise in transcription rate can affect the structure of the dynamic landscape that differentiation occurs on. There are review articles summarizing these effects from bacteria to mammalian cells;
* Drug resistance: Noise improves short-term survival and long-term evolution of drug resistance at high levels of drug treatment. Noise has the opposite effect at low levels of drug treatment;
* Cancer treatments: recent work has found extrinsic differences, linked to gene expression levels, in the response of cancer cells to anti-cancer treatments, potentially linking the phenomenon of fractional killing (whereby each treatment kills some but not all of a tumour) to noise in gene expression. Because individual cells could repeatedly and stochastically perform transitions between states associated with differences in responsiveness to a therapeutic modality (chemotherapy, targeted agent, radiation, etc.), therapy might need to be administered frequently (to ensure cells are treated soon after entering a therapy-responsive state, before they can rejoin the therapy-resistant subpopulation and proliferate) and over long times (to treat even those cells emerging late from the final residue of the therapy-resistant subpopulation).
* Evolution of genome: Genome are covered by chromatin that can be roughly classified into "open" (also known as euchromatin) or "closed" (also known as heterochromatin). Open chromatin leads to less noise in transcription compared to heterochromatin. Often "housekeeping" proteins (which are proteins that carry out tasks in the required for cellular survival) work large multiprotein complexes. If the noise in proteins of such complexes are to discoordinated, it can lead to reduced level of production of multiprotein complexes, with potentially deleterious effects. Reduction in noise may provide an evolutionary selection movement of essential genes into open chromatin.
* Information processing: as cellular regulation is performed with components that are themselves subject to noise, the ability of cells to process information and perform control is fundamentally limited by intrinsic noise | 1 | Biochemistry |
Erich Clar (23 August 1902 – 27 March 1987) was an Austrian organic chemist, born in Hřensko, who studied polycyclic aromatic hydrocarbon chemistry. He is considered as the father of that field. In 1941, he authored "Aromatische Kohlenwasserstoffe" (Springer-Verlag) and in 1964 the greatly expanded two-volume Polycyclic Hydrocarbons, which described the syntheses, properties, and UV-visible absorption spectra of hundreds of PAHs. He discovered the Clar reaction of the cyclic ketone perinaphthenone to form dibenzo[cd,lm]perylene in a 400 C melt of zinc dust, zinc (II) chloride, and sodium chloride. He created the Sextet Theory, now eponymously called Clars rule, to describe the behavior of polycyclic aromatic hydrocarbon isomers. This was described in his book The Aromatic Sextet'. He was awarded the August Kekulé Medal by the Chemical Society of the GDR in 1965, the highest award given by that society to foreign scientists, and the first Polycyclic Aromatic Hydrocarbon Research Award of the International Symposium on Polynuclear Aromatic Hydrocarbons in 1987. He died aged 84 in 1987 at Estepona. | 0 | Organic Chemistry |
One aspect of RNA silencing to consider is its possible off-target affects, toxicity, and delivery methods. If RNA silencing is to become a conventional drug, it must first pass the typical ethical issues of biomedicine. Using risk-benefit analysis, researchers can determine whether RNA silencing conforms to ethical ideologies such as nonmaleficence, beneficence, and autonomy.
There is a risk of creating infection-competent viruses that could infect non-consenting people. There is also a risk of affecting future generations based on these treatments. These two scenarios, in respect to autonomy, is possible unethical. At this moment, unsafe delivery methods and unintended aspects of vector viruses add to the argument against RNA silencing.
In terms of off-target effects, siRNA can induce innate interferon responses, inhibit endogenous miRNAs through saturation, and may have complementary sequences to other non-target mRNAs. These off-targets could also have target up-regulations such as oncogenes and antiapoptotic genes. The toxicity of RNA silencing is still under review as there are conflicting reports.
RNA silencing is quickly developing, because of that, the ethical issues need to be discussed further. With the knowledge of general ethical principles, we must continuously perform risk-benefit analysis. | 1 | Biochemistry |
*Melanopsin: in vertebrate retina, mediates pupillary reflex, involved in regulation of circadian rhythms
*Photopsin: reception of various colors of light in the cone cells of vertebrate retina
*Rhodopsin: green-blue light reception in the rod cells of vertebrate retina
*Protein Kinase C: mediates photoreceptor deactivation, and retinal degeneration
*OPN5: sensitive to UV-light | 1 | Biochemistry |
# Craddock P., 1995, Early Metal Mining and Production, Edinburgh University Press Ltd, Edinburgh
# Hauptmann A., T. Rehren & Schmitt-Strecker S., 2003, Early Bronze Age copper metallurgy at Shahr-i Sokhta (Iran), reconsidered, T. Stollner, G. Korlin, G. Steffens & J. Cierny, Eds., Man and mining, studies in honour of Gerd Weisgerber on occasion of his 65th birthday, Deutsches Bergbau Museum, Bochum
# Martinon-Torres M. & Rehren Th., 2009, Post Medieval crucible Production and Distribution: A Study of Materials and Materialities, Archaeometry Vol.51 No.1 pp49–74
# O. Faolain S., 2004, Bronze Artefact Production in Late Bronze Age Ireland: A Survey, British Archaeological Report, British Series 382, Archaeopress, Oxford
# Rehren, Th. and Papakhristu, O., 2000, Cutting Edge Technology – The Ferghana Process of Medieval crucible steel Smelting, Metalla, Bochum, 7(2) pp55–69
# Rehren T. & Thornton C. P, 2009, A truly refractory crucible from fourth millennium Tepe Hissar, Northeast Iran, Journal of Archaeological Science, Vol. 36, pp2700–2712
# Rehren Th., 1999, Small Size, Large Scale Roman brass Production in Germania Inferior, Journal of Archaeological Science, Vol. 26, pp 1083–1087
# Rehren Th., 2003, Crucibles as Reaction Vessels in Ancient Metallurgy, Ed in P. Craddock & J. Lang, Mining and Metal Production Through the Ages, British Museum Press, London pp207–215
# Roberts B. W., Thornton C. P. & Pigott V. C., 2009, Development of Metallurgy in Eurasia, Antiquity Vol. 83 pp 1012–1022
# Scheel B., 1989, Egyptian Metalworking and Tools, Shire Egyptology, Bucks
# Vavelidis M. & Andreou S., 2003, Gold and Gold working in Later Bronze Age Northern Greece, Naturwissenschaften, Vol. 95, pp 361–366
# Zwicker U., Greiner H., Hofmann K. & Reithinger M., 1985, Smelting, Refining and Alloying of copper and copper Alloys in Crucible Furnaces During Prehistoric up to Roman Times, P. Craddock & M. Hughes, Furnaces and Smelting Technology in Antiquity, British Museum, London | 3 | Analytical Chemistry |
Dioxane is produced by the acid-catalysed dehydration of diethylene glycol, which in turn is obtained from the hydrolysis of ethylene oxide.
In 1985, the global production capacity for dioxane was between 11,000 and 14,000 tons. In 1990, the total U.S. production volume of dioxane was between 5,250 and 9,150 tons. | 6 | Supramolecular Chemistry |
The use of microorganisms to degrade PCBs from contaminated sites, relying on multiple microorganisms co-metabolism, is known as bioremediation of polychlorinated biphenyl. Some micro-organisms degrade PCBs by reducing the C-Cl bonds. Microbial dechlorination tends to be rather slow-acting in comparison to other methods. Enzymes extracted from microbes can show PCB activity. In 2005, Shewanella oneidensis' biodegraded a high percentage of PCBs in soil samples. A low voltage current can stimulate the microbial degradation of PCBs. | 2 | Environmental Chemistry |
The first step in the investigation of archaeometallurgical slag is the identification and macro-analysis of slag in the field. Physical properties of slag such as shape, colour, porosity and even smell are used to make a primary classification to ensure representative samples from slag heaps are obtained for future micro-analysis.
For example, tap slag usually has a wrinkled upper face and a flat lower face due to contact with soil.
Furthermore, the macro-analysis of slag heaps can prove an estimated total weight which in turn can be used to determine the scale of production at a particular smelting location. | 8 | Metallurgy |
Tank and vat leaching involves placing ore, usually after size reduction and classification, into large tanks or vats at ambient operating conditions containing a leaching solution and allowing the valuable material to leach from the ore into solution.
In tank leaching the ground, classified solids are already mixed with water to form a slurry or pulp, and this is pumped into the tanks. Leaching reagents are added to the tanks to achieve the leaching reaction. In a continuous system the slurry will then either overflow from one tank to the next, or be pumped to the next tank. Ultimately the “pregnant” solution is separated from the slurry using some form of liquid/solid separation process, and the solution passes on to the next phase of recovery.
In vat leaching the solids are loaded into the vat, once full the vat is flooded with a leaching solution. The solution drains from the tank, and is either recycled back into the vat or is pumped to the next step of the recovery process.
. Vat leach units are rectangular containers (drums, barrels, tanks or vats), usually very big and made of wood or concrete, lined with material resistant to the leaching media. The treated ore is usually coarse.
The vats are usually run sequentially to maximize the contact time between the ore and the reagent. In such a series the leachate collected from one container is added to another vat with fresher ore
As mentioned previously tanks are equipped with agitators to keep the solids in suspension in the vats and improve the solid to liquid to gas contact. Agitation is further assisted by the use of tank baffles to increase the efficiency of agitation and prevent centrifuging of slurries in circular tanks... | 8 | Metallurgy |
A significant task, regularly carried out by CSMBLM since 1970, is the external assessment of the performance quality of all medical biochemistry laboratories in the Republic of Croatia. The external evaluation programs are updated and continually expanded according to the needs of the profession and in line with the European organizations for labor quality assessment (EQAL). Assessment results are the basis for the rating of medical laboratories carried out by the Croatian Chamber of Medical Biochemists.
In this way CSMBLM provides continuous professional and advisory help in harmonization and evaluation of laboratory results at national and international level for medical biochemistry laboratories and all other laboratories which work in a field of laboratory medicine. | 1 | Biochemistry |
* CCA1 – The CCA1 gene, also known as Circadian and Clock Associated Gene 1, is a gene that is especially important in maintaining the rhythmicity of plant cellular oscillations. Overexpression, results in the loss of rhythmic expression of clock controlled genes (CCGs), loss of photoperiod control, and loss of rhythmicity in LHY expression. See LHY gene below for more information.
* LHY – The LHY gene, also known as the Late Elongated Hypocotyl gene, is a gene found in plants that encodes components of mutually regulatory negative feedback loops with CCA1 in which overexpression of either results in dampening of both of their expression. This negative feedback loop affects the rhythmicity of multiple outputs creating a daytime protein complex.
* Toc1 gene – Toc1, also known as Timing of CAB Expression 1 gene, is an oscillating gene found in the plants that is known to control the expression of CAB. It has been shown to affect the period of circadian rhythms through its repression of transcription factors. This was found through mutations of toc1 in plants that had shortened period of CAB expression. | 1 | Biochemistry |
The cyanate ion is an anion with the chemical formula . It is a resonance of three forms: (61%) ↔ (30%) ↔ (4%).
Cyanate is the derived anion of isocyanic acid, H−N=C=O, and its lesser tautomer cyanic acid (a.k.a. cyanol), H−O−C≡N.
Any salt containing the ion, such as ammonium cyanate, is called a cyanate.
The cyanate ion is an isomer of the much-less-stable fulminate anion, or .
The cyanate ion is an ambidentate ligand, forming complexes with a metal ion in which either the nitrogen or oxygen atom may be the electron-pair donor. It can also act as a bridging ligand.
Compounds that contain the cyanate functional group, −O−C≡N, are known as cyanates or cyanate esters. The cyanate functional group is distinct from the isocyanate functional group, −N=C=O; the fulminate functional group, ; and the nitrile oxide functional group, or . | 0 | Organic Chemistry |
In 1968, the artist Robert Smithson made Mono Lake Non-Site (Cinders near Black Point) using pumice collected while visiting Mono on July 27, 1968, with his wife Nancy Holt and Michael Heizer (both prominent visual artists). In 2004, Nancy Holt made a short film entitled Mono Lake using Super 8 footage and photographs of this trip. An audio recording by Smithson and Heizer, two songs by Waylon Jennings, and Michel Legrands Le Jeu, the main theme of Jacques Demys film Bay of Angels (1963), were used for the soundtrack.
The Diver, a photo taken by Aubrey Powell of Hipgnosis for Pink Floyds album Wish You Were Here' (1975), features what appears to be a man diving into a lake, creating no ripples. The photo was taken at Mono Lake, and the tufa towers are a prominent part of the landscape. The effect was actually created when the diver performed a handstand underwater until the ripples dissipated. | 2 | Environmental Chemistry |
There are variations between human populations, so a SNP allele that is common in one geographical or ethnic group may be much rarer in another. However, this pattern of variation is relatively rare; in a global sample of 67.3 million SNPs, the Human Genome Diversity Project "found no such private variants that are fixed in a given continent or major region. The highest frequencies are reached by a few tens of variants present at >70% (and a few thousands at >50%) in Africa, the Americas, and Oceania. By contrast, the highest frequency variants private to Europe, East Asia, the Middle East, or Central and South Asia reach just 10 to 30%."
Within a population, SNPs can be assigned a minor allele frequency—the lowest allele frequency at a locus that is observed in a particular population. This is simply the lesser of the two allele frequencies for single-nucleotide polymorphisms.
With this knowledge scientists have developed new methods in analyzing population structures in less studied species. By using pooling techniques the cost of the analysis is significantly lowered. These techniques are based on sequencing a population in a pooled sample instead of sequencing every individual within the population by itself. With new bioinformatics tools there is a possibility of investigating population structure, gene flow and gene migration by observing the allele frequencies within the entire population. With these protocols there is a possibility in combining the advantages of SNPs with micro satellite markers. However, there are information lost in the process such as linkage disequilibrium and zygosity information. | 1 | Biochemistry |
In medicine, LDH is often used as a marker of tissue breakdown as LDH is abundant in red blood cells and can function as a marker for hemolysis. A blood sample that has been handled incorrectly can show false-positively high levels of LDH due to erythrocyte damage.
It can also be used as a marker of myocardial infarction. Following a myocardial infarction, levels of LDH peak at 3–4 days and remain elevated for up to 10 days. In this way, elevated levels of LDH (where the level of LDH1 is higher than that of LDH2, i.e. the LDH Flip, as normally, in serum, LDH2 is higher than LDH1) can be useful for determining whether a patient has had a myocardial infarction if they come to doctors several days after an episode of chest pain. | 1 | Biochemistry |
He married Ethel Marian Wood in 1901. She died in 1944. They had a daughter, who predeceased her father, and a son. He died at his son's home in Headley, Surrey. | 4 | Stereochemistry |
(AD 900–1500)
Utilitarian and ceremonial objects; objects of personal adornment
#Coatlán, Oaxaca
#Coixtlahuaca, Oaxaca
#Ejutla, Oaxaca
#Guiengola, Oaxaca
#Huajuapan, Oaxaca
#Huitzo, Oaxaca
#Juquila, Oaxaca
#Mitla, Oaxaca
#Monte Albán Oaxaca
#Sola de Vega, Oaxaca
#Tehuantepec, Oaxaca
#Teotitlán del Camino, Oaxaca
#Teotitlán del Valle, Oaxaca
#Tlacolula, Oaxaca
#Tlaxiaco, Oaxaca
#Tututepec, Oaxaca
#Xaaga, Oaxaca
#Yanhuitlán, Oaxaca
#Zachila, Oaxaca | 8 | Metallurgy |
"Hairs" on plants are properly called trichomes. Leaves can show several degrees of hairiness. The meaning of several of the following terms can overlap.
;Arachnoid, or arachnose: With many fine, entangled hairs giving a cobwebby appearance.
;Barbellate: With finely barbed hairs (barbellae).
;Bearded: With long, stiff hairs.
;Bristly: With stiff hair-like prickles.
;Canescent: Hoary with dense grayish-white pubescence.
;Ciliate: Marginally fringed with short hairs (cilia).
;Ciliolate: Minutely ciliate.
;Floccose: With flocks of soft, woolly hairs, which tend to rub off.
;Glabrescent: Losing hairs with age.
;Glabrous: No hairs of any kind present.
;Glandular: With a gland at the tip of the hair.
;Hirsute: With rather rough or stiff hairs.
;Hispid: With rigid, bristly hairs.
;Hispidulous: Minutely hispid.
;Hoary: With a fine, close grayish-white pubescence.
;Lanate, or lanose: With woolly hairs.
;Pilose: With soft, clearly separated hairs.
;Puberulent, or puberulous: With fine, minute hairs.
;Pubescent: With soft, short and erect hairs.
;Scabrous, or scabrid: Rough to the touch.
;Sericeous: Silky appearance through fine, straight and appressed (lying close and flat) hairs.
;Silky: With adpressed, soft and straight pubescence.
;Stellate, or stelliform: With star-shaped hairs.
;Strigose: With appressed, sharp, straight and stiff hairs.
;Tomentose: Densely pubescent with matted, soft white woolly hairs.
;Tomentulose: Minutely or only slightly tomentose.
;Villous: With long and soft hairs, usually curved.
;Woolly: With long, soft and tortuous or matted hairs. | 5 | Photochemistry |
DNA molecules are unique in that they are long, charged polymers which when in a separation medium, such as agarose gel, can exhibit highly non-linear velocity profiles in response to an electric field. As such, DNA is easily separated from other molecules that are not both charged and strongly non-linear, using SCODA | 1 | Biochemistry |
In surface science, a double layer (DL, also called an electrical double layer, EDL) is a structure that appears on the surface of an object when it is exposed to a fluid. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. The DL refers to two parallel layers of charge surrounding the object. The first layer, the surface charge (either positive or negative), consists of ions which are adsorbed onto the object due to chemical interactions. The second layer is composed of ions attracted to the surface charge via the Coulomb force, electrically screening the first layer. This second layer is loosely associated with the object. It is made of free ions that move in the fluid under the influence of electric attraction and thermal motion rather than being firmly anchored. It is thus called the "diffuse layer".
Interfacial DLs are most apparent in systems with a large surface-area-to-volume ratio, such as a colloid or porous bodies with particles or pores (respectively) on the scale of micrometres to nanometres. However, DLs are important to other phenomena, such as the electrochemical behaviour of electrodes.
DLs play a fundamental role in many everyday substances. For instance, homogenized milk exists only because fat droplets are covered with a DL that prevents their coagulation into butter. DLs exist in practically all heterogeneous fluid-based systems, such as blood, paint, ink and ceramic and cement slurry.
The DL is closely related to electrokinetic phenomena and electroacoustic phenomena. | 7 | Physical Chemistry |
In vinyl polymers the complete configuration can be further described by defining polymer head/tail configuration. In a regular macromolecule all monomer units are normally linked in a head to tail configuration so that all β-substituents are separated by three carbon atoms. In head to head configuration this separation is only by 2 carbon atoms and the separation with tail to tail configuration is by 4 atoms. Head/tail configurations are not part of polymer tacticity but should be taken into account when considering polymer defects. | 4 | Stereochemistry |
Martin's sulfurane is the organosulfur compound with the formula PhS[OC(CF)Ph] (Ph = CH). It is a white solid that easily undergoes sublimation. The compound is an example of a hypervalent sulfur compound called a sulfurane. As such, the sulfur adopts a see-saw structure, with a lone pair of electrons as the equatorial fifth coordinate of a trigonal bipyramid, like that of sulfur tetrafluoride (SF). The compound is a reagent in organic synthesis. One application is for the dehydration of a secondary alcohol to give an alkene:
:RCH(OH)CHR + PhS[OC(CF)Ph] → RCH=CHR + PhSO + 2 HOC(CF)Ph | 0 | Organic Chemistry |
Protofection is a developing technique and is continuously being improved. A specific protein transduction system has been created that is complexed with mtDNA, which enables the mtDNA to move across the targeted cell's membrane and specifically target mitochondria. The transduction system used consists of a protein transduction domain, mitochondrial localization sequences, and mitochondrial transcription factor A. Each of these play a specific role in protofection:
* A protein transduction domain is needed because they are small regions of proteins that can cross the cell membrane of cells, independently.
* A specific mitochondrial localization sequences is used for protofection because it permits mtDNA to enter the mitochondria.
* Mitochondrial transcription factor A is used because it unwinds the mtDNA that enters the mitochondria, which is critical for mtDNA replication.
This process can lead to an increase in the amount of mtDNA present in the mitochondria of the target cells.
The transduction system has been tweaked and modified, since the first use of protofection. To shorten the name of the complex, which was previously called PTD-MLS-TFAM complex, it is now named MTD-TFAM. MTD stands for mitochondrial transduction domain and it includes the protein transduction domain and the mitochondrial localization sequences. | 1 | Biochemistry |
Through supramolecular chemistry, pregel solution can solidify through reversible supramolecular interactions such as host-guest interactions. Such interaction can be manipulated through the mechanical force or the temperature. When energy exerted to the network is high enough, physical crosslinking point will break and the polymer will be at liquid state, after leaving the nozzle, the crosslinking can be rapidly formed to solidify the solution.
A case would be the Host–Guest Chemistry reported by Scherman et al. Where the formation of inclusion complex between [[Cucurbituril|Cucurbit[8]uril]] and [https://pubchem.ncbi.nlm.nih.gov/compound/1-Benzyl-3-methylimidazolium-bromide 1-benzyl-3-vinylimidazolium bromide] (BVIm) formed physical crosslinking point for the network. The formation of this physical crosslinking point is controlled by the temperature of the solution. By heating up the solution and cooling it down rapidly at extrusion nuzzle, the hydogel fiber is formed. Also, subsequent crosslinking is performed to form a perment network. | 7 | Physical Chemistry |
Resistance to herbicides can be based on one of the following biochemical mechanisms:
* Target-site resistance: In target-site resistance, the genetic change that causes the resistance directly alters the chemical mechanism the herbicide targets. The mutation may relate to an enzyme with a crucial function in a metabolic pathway, or to a component of an electron-transport system. For example, ALS-resistant weeds developed by genetic mutations leading to an altered enzyme. Such changes render the herbicide impotent. Target-site resistance may also be caused by an over-expression of the target enzyme (via gene amplification or changes in a gene promoter). A related mechanism is that an adaptable enzyme such as cytochrome P450 is redesigned to neutralize the pesticide itself.
* Non-target-site resistance: In non-target-site resistance, the genetic change giving resistance is not directly related to the target site, but causes the plant to be less susceptible by some other means. Some mechanisms include metabolic detoxification of the herbicide in the weed, reduced uptake and translocation, sequestration of the herbicide, or reduced penetration of the herbicide into the leaf surface. These mechanisms all cause less of the herbicide's active ingredient to reach the target site in the first place.
The following terms are also used to describe cases where plants are resistant to multiple herbicides at once:
* Cross-resistance: In this case, a single resistance mechanism causes resistance to several herbicides. The term target-site cross-resistance is used when the herbicides bind to the same target site, whereas non-target-site cross-resistance is due to a single non-target-site mechanism (e.g., enhanced metabolic detoxification) that entails resistance across herbicides with different sites of action.
* Multiple resistance: In this situation, two or more resistance mechanisms are present within individual plants, or within a plant population. | 2 | Environmental Chemistry |
Capillary electrophoresis (CE) is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro- and nanofluidic channels. Very often, CE refers to capillary zone electrophoresis (CZE), but other electrophoretic techniques including capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), capillary isotachophoresis and micellar electrokinetic chromatography (MEKC) belong also to this class of methods. In CE methods, analytes migrate through electrolyte solutions under the influence of an electric field. Analytes can be separated according to ionic mobility and/or partitioning into an alternate phase via non-covalent interactions. Additionally, analytes may be concentrated or "focused" by means of gradients in conductivity and pH. | 3 | Analytical Chemistry |
Fluorination with aminosulfuranes is a chemical reaction that transforms oxidized organic compounds into organofluorine compounds. Aminosulfuranes selectively exchange hydroxyl groups for fluorine, but are also capable of converting carbonyl groups, halides, silyl ethers, and other functionality into organofluorides. | 0 | Organic Chemistry |
The society awards some 25 awards every year at the annual conference. In addition, the member societies also disburse their own awards, including the Percy Nicholls Award, awarded by SME jointly with American Society of Mechanical Engineers. | 8 | Metallurgy |
There are many proposed applications for the boron-based carborane acids. For instance, they have been proposed as catalysts for hydrocarbon cracking and isomerization of n-alkanes to form branched isoalkanes ("isooctane", for example). Carborane acids may also be used as strong, selective Brønsted acids for fine chemical synthesis, where the low nucleophilicity of the counteranion may be advantageous. In mechanistic organic chemistry, they may be used in the study of reactive cationic intermediates. In inorganic synthesis, their unparalleled acidity may allow for the isolation of exotic species like salts of protonated xenon. | 7 | Physical Chemistry |
Alternative protein assays include:
* Ultraviolet–visible spectroscopy
* RGBradford
* Biuret protein assay
* Lowry protein assay
* BCA protein assay
* Amido black protein assay
* Colloidal gold protein assay | 3 | Analytical Chemistry |
Since [http://sourceforge.net/project/showfiles.php?group_id=71971&package_id=76633 Level 2 Version 2] SBML provides a mechanism to annotate model components with SBO terms, therefore increasing the semantics of the
model beyond the sole topology of interaction and mathematical expression. Modelling tools such as [https://github.com/draeger-lab/SBMLsqueezer SBMLsqueezer] interpret SBO terms to augment the mathematics in the SBML file. Simulation tools can check the consistency of a rate law, convert reaction from one modelling framework to another (e.g., continuous to discrete), or distinguish between identical mathematical expressions based on different assumptions (e.g., Michaelis–Menten vs. Briggs–Haldane). To add missing SBO terms to models, software such as [https://github.com/draeger-lab/SBOannotator SBOannotator] can be used. Other tools such as [http://www.semanticsbml.org/ semanticSBML] can use the SBO annotation to integrate individual models into a larger one. The use of SBO is not restricted to the development of models. Resources providing quantitative experimental information such as [https://web.archive.org/web/20061117195025/http://sabio.villa-bosch.de/SABIORK/ SABIO Reaction Kinetics] will be able to annotate the parameters (what do they mean exactly, how were they calculated) and determine relationships between them. | 1 | Biochemistry |
Energy intake is measured by the amount of calories consumed from food and fluids. Energy intake is modulated by hunger, which is primarily regulated by the hypothalamus, and choice, which is determined by the sets of brain structures that are responsible for stimulus control (i.e., operant conditioning and classical conditioning) and cognitive control of eating behavior. Hunger is regulated in part by the action of certain peptide hormones and neuropeptides (e.g., insulin, leptin, ghrelin, and neuropeptide Y, among others) in the hypothalamus. | 1 | Biochemistry |
Cram once admitted that his career wasnt without sacrifice. His first wife was Rollins classmate, Jean Turner, who also graduated in 1941, and went on to receive a masters degree in social work from Columbia University. His second wife, Jane, is a former chemistry professor at Mount Holyoke College. Cram chose not to have any children, "because I would either be a bad father or a bad scientist."
Cram died of cancer in 2001, at the age of 82. | 4 | Stereochemistry |
ASDs are complex; autism is a medical condition with several etiologies caused due to the interactions between environmental conditions and genetic vulnerability. The challenge in finding out the biomarkers related to ASDs is that they may reflect genetic or neurobiological changes that may be active only to a certain point. ASDs show heterogeneous clinical symptoms and genetic architecture, which have hindered the identification of common genetic susceptibility factors. Still, many researches are being done to find out the main reason behind the genetic incomparability. | 1 | Biochemistry |
Methylations are commonly performed using electrophilic methyl sources such as iodomethane, dimethyl sulfate, dimethyl carbonate, or tetramethylammonium chloride. Less common but more powerful (and more dangerous) methylating reagents include methyl triflate, diazomethane, and methyl fluorosulfonate (magic methyl). These reagents all react via S2 nucleophilic substitutions. For example, a carboxylate may be methylated on oxygen to give a methyl ester; an alkoxide salt may be likewise methylated to give an ether, ; or a ketone enolate may be methylated on carbon to produce a new ketone.
The Purdie methylation is a specific for the methylation at oxygen of carbohydrates using iodomethane and silver oxide. | 0 | Organic Chemistry |
Galvanism is a term invented by the late 18th-century physicist and chemist Alessandro Volta to refer to the generation of electric current by chemical action. The term also came to refer to the discoveries of its namesake, Luigi Galvani, specifically the generation of electric current within biological organisms and the contraction/convulsion of biological muscle tissue upon contact with electric current. While Volta theorized and later demonstrated the phenomenon of his "Galvanism" to be replicable with otherwise inert materials, Galvani thought his discovery to be a confirmation of the existence of "animal electricity," a vital force which gave life to organic matter. | 7 | Physical Chemistry |
An example of a photoacid which undergoes excited-state proton transfer without prior photolysis is the fluorescent dye pyranine (8-hydroxy-1,3,6-pyrenetrisulfonate or HPTS).
The Förster cycle was proposed by Theodor Förster and combines knowledge of the ground state acid dissociation constant (pK), absorption, and fluorescence spectra to predict the pK in the excited state of a photoacid.
The name photoacid can be abbreviated PAH, where the H does not stand for a word starting with H, but rather for a hydrogen atom which is lost when the molecule reacts as a Brønsted acid. This use of PAH should not be confused with other meanings of PAH in chemistry and in medicine. | 5 | Photochemistry |
Like related acyl chlorides, valeryl chloride hydrolyzes readily:
:CH(CH)C(O)Cl + HO → CH(CH)COH + HCl
Alcohols react to give esters:
:CH(CH)C(O)Cl + ROH → CH(CH)COR + HCl
Amines react to give amides:
:CH(CH)C(O)Cl + RNH → CH(CH)C(O)NR + HCl
Benzene reacts under conditions of the Friedel-Crafts reaction to give valerophenone:
:CH(CH)C(O)Cl + CH → CH(CH)C(O)CH + HCl | 0 | Organic Chemistry |
The Azolla event is a paleoclimatology scenario hypothesized to have occurred in the middle Eocene epoch, around , when blooms of the carbon-fixing freshwater fern Azolla are thought to have happened in the Arctic Ocean. As the fern died and sank to the stagnant sea floor, they were incorporated into the sediment over a period of about 800,000 years; the resulting draw-down of carbon dioxide has been speculated to have helped reverse the planet from the "greenhouse Earth" state of the Paleocene-Eocene Thermal Maximum, when the planet was hot enough for turtles and palm trees to prosper at the poles, to the current icehouse Earth known as the Late Cenozoic Ice Age. | 2 | Environmental Chemistry |
R-454B is not the only blend of R-32 and R-1234yf to be proposed as a refrigerant. Other blends include R-454A (35 percent R-32, 65 percent R-1234yf) and R-454C (21.5 percent R-32, 78.5 percent R1234yf). There are also several blends that include a third component. | 2 | Environmental Chemistry |
Primary alcohols () can be oxidized either to aldehydes () or to carboxylic acids (). The oxidation of secondary alcohols () normally terminates at the ketone () stage. Tertiary alcohols () are resistant to oxidation.
The direct oxidation of primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate () by reaction with water before it can be further oxidized to the carboxylic acid.
Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include Collins reagent and Dess-Martin periodinane. The direct oxidation of primary alcohols to carboxylic acids can be carried out using potassium permanganate or the Jones reagent. | 0 | Organic Chemistry |
One method that used to cool molecules to temperatures near absolute zero is laser cooling. In the Doppler cooling process, lasers are used to remove energy from electrons of a given molecule to slow or cool the molecule down. This method has applications in quantum mechanics and is related to particle traps and the Bose–Einstein condensate. All of these methods use a "trap" consisting of lasers pointed at opposite equatorial angles on a specific point in space. The wavelengths from the laser beams eventually hit the gaseous atoms and their outer spinning electrons. This clash of wavelengths decreases the kinetic energy state fraction by fraction to slow or cool the molecules down. Laser cooling has also been used to help improve atomic clocks and atom optics. Ultracold studies are not usually focused on chemical interactions, but rather on fundamental chemical properties.
Because of the extremely low temperatures, diagnosing the chemical status is a major issue when studying low temperature physics and chemistry. The primary techniques in use today are optical - many types of spectroscopy are available, but these require special apparatus with vacuum windows that provide room temperature access to cryogenic processes. | 7 | Physical Chemistry |
A field prototype of SOLID was first tested in 2005 in a simulated Mars drilling expedition called MARTE (Mars Analog Rio Tinto Experiment) where the researchers tested a drill in depth, sample-handling systems, and immunoassays relevant to the search for life in the Martian subsurface. MARTE was funded by the NASA Astrobiology Science and Technology for Exploring Planets (ASTEP) program. Using the sample cores, SOLID successfully detected several biological polymers in extreme environments in different parts of the world, including a deep South African mine, Antarctica's McMurdo Dry Valleys, Yellowstone, Iceland, Atacama Desert in Chile, and in the acid water of Rio Tinto.
Extracts obtained from Mars analogue sites on Earth were added to various perchlorate concentrations at −20 °C for 45 days and then the samples were analyzed with SOLID. The results showed no interference from acidity or from the presence of 50 mM perchlorate which is 20 times higher than that found at the Phoenix landing site. SOLID demonstrated that the chosen antibodies are unaffected by acidity, heat and oxidants such as perchlorates, and it has emerged as a viable choice for an astrobiology mission directly searching for biosignatures.
In 2018, another field test took place at the Atacama Desert with a rover called ARADS (Atacama Rover Astrobiology Drilling Studies) that carried a core drill, SOLID instrument, and another life detection system called Microfluidic Life Analyzer (MILA). MILA processes minuscule volumes of fluid samples to isolate amino acids, which are building blocks of proteins. The rover tested different strategies for searching for potential evidence of life in the soil, and established that roving, drilling and life detection can take place in concert. | 1 | Biochemistry |
PSII and PSI are connected by a transmembrane proton pump, cytochrome bf complex (plastoquinol—plastocyanin reductase; ). Electrons from PSII are carried by plastoquinol to cyt bf, where they are removed in a stepwise fashion (re-forming plastoquinone) and transferred to a water-soluble electron carrier called plastocyanin. This redox process is coupled to the pumping of four protons across the membrane. The resulting proton gradient (together with the proton gradient produced by the water-splitting complex in PSI) is used to make ATP via ATP synthase.
The structure and function of cytochrome bf (in chloroplasts) is very similar to cytochrome bc (Complex III in mitochondria). Both are transmembrane structures that remove electrons from a mobile, lipid-soluble electron carrier (plastoquinone in chloroplasts; ubiquinone in mitochondria) and transfer them to a mobile, water-soluble electron carrier (plastocyanin in chloroplasts; cytochrome c in mitochondria). Both are proton pumps that produce a transmembrane proton gradient. In fact, cytochrome b and subunit IV are homologous to mitochondrial cytochrome b and the Rieske iron-sulfur proteins of the two complexes are homologous. However, cytochrome f and cytochrome c are not homologous. | 5 | Photochemistry |
Ketosis can improve markers of metabolic syndrome through reduction in serum triglycerides, elevation in high-density lipoprotein (HDL) as well as increased size and volume of low-density lipoprotein (LDL) particles. These changes are consistent with an improved lipid profile despite potential increases in total cholesterol level. | 1 | Biochemistry |
Once a theory is formulated, its validity must be tested, that is, compare its predictions with the results of the experiments.
When the expression form of the rate constant is compared with the rate equation for an elementary bimolecular reaction, , it is noticed that
unit M⋅s (= dm⋅mol⋅s), with all dimension unit dm including k.
This expression is similar to the Arrhenius equation and gives the first theoretical explanation for the Arrhenius equation on a molecular basis. The weak temperature dependence of the preexponential factor is so small compared to the exponential factor that it cannot be measured experimentally, that is, "it is not feasible to establish, on the basis of temperature studies of the rate constant, whether the predicted T dependence of the preexponential factor is observed experimentally". | 7 | Physical Chemistry |
Some applications of the electrodialysis are explained below.
* The desalination of whey is the largest area of use for this type of dialysis in the food industry. It is necessary to remove crude cheese whey containing calcium, phosphorus and other inorganic salts to produce different foods such as cake, bread, ice cream and baby foods. The limit of whey demineralisation is almost 90%.
* De-acidification of fruit juice such as grape, orange, apple and lemon are processes in which electrodialysis is applied. An anion-exchange membrane is employed in this technique implying that citrate ions from the juice are extracted and replaced by hydroxide ions.
* Desalting of soy sauce can be done by electrodialysis. The conventional values of salt in brewed soy sauce are about 16-18 %, which is a quite high content. Electrodialysis is used to reduce the amount of salt present in the soy sauce. Nowadays diets of low salt content are very present in the society.
* Electrodialysis allows the separation of amino acids into acidic, basic and neutral groups. Specifically, cytoplasmic leaf proteins are extracted from alfalfa leaves applying electrodialysis. When proteins are denatured, the solutions can be desalted (of K ions) and acidified with H ions. | 1 | Biochemistry |
The widespread use of refrigeration allowed for a vast amount of new agricultural opportunities to open up in the United States. New markets emerged throughout the United States in areas that were previously uninhabited and far-removed from heavily populated areas. New agricultural opportunity presented itself in areas that were considered rural, such as states in the south and in the west. Shipments on a large scale from the south and California were both made around the same time, although natural ice was used from the Sierras in California rather than manufactured ice in the south. Refrigeration allowed for many areas to specialize in the growing of specific fruits. California specialized in several fruits, grapes, peaches, pears, plums, and apples, while Georgia became famous for specifically its peaches. In California, the acceptance of the refrigerated rail cars led to an increase of car loads from 4,500 carloads in 1895 to between 8,000 and 10,000 carloads in 1905. The Gulf States, Arkansas, Missouri and Tennessee entered into strawberry production on a large-scale while Mississippi became the center of the tomato industry. New Mexico, Colorado, Arizona, and Nevada grew cantaloupes. Without refrigeration, this would have not been possible. By 1917, well-established fruit and vegetable areas that were close to eastern markets felt the pressure of competition from these distant specialized centers. Refrigeration was not limited to meat, fruit and vegetables but it also encompassed dairy product and dairy farms. In the early twentieth century, large cities got their dairy supply from farms as far as . Dairy products were not as easily transported over great distances like fruits and vegetables due to greater perishability. Refrigeration made production possible in the west far from eastern markets, so much in fact that dairy farmers could pay transportation cost and still undersell their eastern competitors. Refrigeration and the refrigerated rail gave opportunity to areas with rich soil far from natural channel of transport such as a river, valley trail or harbors. | 7 | Physical Chemistry |
One can also plot the dihedral angles in polysaccharides (e.g. with [http://glycosciences.de/tools/carp/ CARP]). | 1 | Biochemistry |
The fossil record for lichens is poor. The extreme habitats that lichens dominate, such as tundra, mountains, and deserts, are not ordinarily conducive to producing fossils. There are fossilized lichens embedded in amber. The fossilized Anzia is found in pieces of amber in northern Europe and dates back approximately 40 million years. Lichen fragments are also found in fossil leaf beds, such as Lobaria from Trinity County in northern California, US, dating back to the early to middle Miocene.
The oldest fossil lichen in which both symbiotic partners have been recovered is Winfrenatia, an early zygomycetous (Glomeromycotan) lichen symbiosis that may have involved controlled parasitism, is permineralized in the Rhynie Chert of Scotland, dating from early Early Devonian, about 400 million years ago. The slightly older fossil Spongiophyton has also been interpreted as a lichen on morphological and isotopic grounds, although the isotopic basis is decidedly shaky. It has been demonstrated that Silurian-Devonian fossils Nematothallus and Prototaxites were lichenized. Thus lichenized Ascomycota and Basidiomycota were a component of Early Silurian-Devonian terrestrial ecosystems. Newer research suggests that lichen evolved after the evolution of land plants.
The ancestral ecological state of both Ascomycota and Basidiomycota was probably saprobism, and independent lichenization events may have occurred multiple times. In 1995, Gargas and colleagues proposed that there were at least five independent origins of lichenization; three in the basidiomycetes and at least two in the Ascomycetes. Lutzoni et al. (2001) suggest lichenization probably evolved earlier and was followed by multiple independent losses. Some non-lichen-forming fungi may have secondarily lost the ability to form a lichen association. As a result, lichenization has been viewed as a highly successful nutritional strategy.
Lichenized Glomeromycota may extend well back into the Precambrian. Lichen-like fossils consisting of coccoid cells (cyanobacteria?) and thin filaments (mucoromycotinan Glomeromycota?) are permineralized in marine phosphorite of the Doushantuo Formation in southern China. These fossils are thought to be 551 to 635 million years old or Ediacaran. Ediacaran acritarchs also have many similarities with Glomeromycotan vesicles and spores. It has also been claimed that Ediacaran fossils including Dickinsonia, were lichens, although this claim is controversial. Endosymbiotic Glomeromycota comparable with living Geosiphon may extend back into the Proterozoic in the form of 1500 million year old Horodyskia and 2200 million year old Diskagma. Discovery of these fossils suggest that fungi developed symbiotic partnerships with photoautotrophs long before the evolution of vascular plants, though the Ediacaran lichen hypothesis is largely rejected due to an inappropriate definition of lichens based on taphonomy and substrate ecology. However, a 2019 study by the same scientist who rejected the Ediacaran lichen hypothesis, Nelsen, used new time-calibrated phylogenies to conclude that there is no evidence of lichen before the existence of vascular plants.
Lecanoromycetes, one of the most common classes of lichen-forming fungi, diverged from its ancestor, which may have also been lichen forming, around 258 million years ago, during the late Paleozoic period. However, the closely related clade Euritiomycetes appears to have become lichen-forming only 52 million years ago, during the early Cenozoic period. | 2 | Environmental Chemistry |
The Centre for Gene Regulation and Expression, located within the School of Life Sciences, University of Dundee, is a research facility working in the field of gene expression and chromosome biology. Previously part of the Dundee Biocentre and receiving significant Wellcome Trust funding from 1995 onwards, it was awarded Wellcome Trust Centre status in 2008. Professor Tom Owen-Hughes is the centre's director.
The centre aims to enhance our understanding of how genes are regulated at both the single cell and whole organism level. Researchers use a wide range of advanced techniques, including live cell fluorescent imaging and mass spectrometry-based proteomics, to explore the functions of key proteins and molecular mechanisms in cell biology. | 1 | Biochemistry |
Space-based solar power (SBSP, SSP) is the concept of collecting solar power in outer space with solar power satellites (SPS) and distributing it to Earth. Its advantages include a higher collection of energy due to the lack of reflection and absorption by the atmosphere, the possibility of very little night, and a better ability to orient to face the Sun. Space-based solar power systems convert sunlight to some other form of energy (such as microwaves) which can be transmitted through the atmosphere to receivers on the Earth's surface.
Various SBSP proposals have been researched since the early 1970s, but none is economically viable with the space launch costs. Some technologists propose lowering launch costs with space manufacturing or with radical new space launch technologies other than rocketry.
Besides cost, SBSP also introduces several technological hurdles, including the problem of transmitting energy from orbit. Since wires extending from Earths surface to an orbiting satellite are not feasible with current technology, SBSP designs generally include the wireless power transmission with its associated conversion inefficiencies, as well as land use concerns for antenna stations to receive the energy at Earths surface. The collecting satellite would convert solar energy into electrical energy, power a microwave transmitter or laser emitter, and transmit this energy to a collector (or microwave rectenna) on Earths surface. Contrary to appearances in fiction, most designs propose beam energy densities that are not harmful if human beings were to be inadvertently exposed, such as if a transmitting satellites beam were to wander off-course. But the necessarily vast size of the receiving antennas would still require large blocks of land near the end users. The service life of space-based collectors in the face of long-term exposure to the space environment, including degradation from radiation and micrometeoroid damage, could also become a concern for SBSP.
As of 2020, SBSP is being actively pursued by Japan, China, Russia, India, the United Kingdom, and the US.
In 2008, Japan passed its Basic Space Law which established space solar power as a national goal. JAXA has a roadmap to commercial SBSP.
In 2015, the China Academy for Space Technology (CAST) showcased its roadmap at the International Space Development Conference. In February 2019, Science and Technology Daily (科技日报, Keji Ribao), the official newspaper of the Ministry of Science and Technology of the Peoples Republic of China, reported that construction of a testing base had started in Chongqings Bishan District. CAST vice-president Li Ming was quoted as saying China expects to be the first nation to build a working space solar power station with practical value. Chinese scientists were reported as planning to launch several small- and medium-sized space power stations between 2021 and 2025. In December 2019, Xinhua News Agency reported that China plans to launch a 200-tonne SBSP station capable of generating megawatts (MW) of electricity to Earth by 2035.
In May 2020, the US Naval Research Laboratory conducted its first test of solar power generation in a satellite. In August 2021, the California Institute of Technology (Caltech) announced that it planned to launch a SBSP test array by 2023, and at the same time revealed that Donald Bren and his wife Brigitte, both Caltech trustees, had been since 2013 funding the institute's Space-based Solar Power Project, donating over $100 million. A Caltech team successfully demonstrated beaming power to earth in 2023. | 7 | Physical Chemistry |
All volatile metabolites detectable by the human nose are termed an odour profile. The association of altered odour profiles with disease states has long been documented in both eastern and western medicine, and recent advances in robotic sample introduction have increased interest in the volatilome as a source for biomarkers that can be used for non-invasive screening for disease. Volatile profiles can be collected via active or passive sampling and analysis is predominantly undertaken using gas chromatography–mass spectrometry, with a variety of direct or indirect sample introduction techniques. | 1 | Biochemistry |
Knowledge of hydration is essential for calculating the masses for many compounds. The reactivity of many salt-like solids is sensitive to the presence of water.
The hydration and dehydration of salts is central to the use of phase-change materials for energy storage. | 3 | Analytical Chemistry |
The Claus reaction is an example of comproportionation reaction (the inverse of disproportionation) involving hydrogen sulfide () and sulfur dioxide () to produce elemental sulfur and water as follows:
The Claus reaction is one of the chemical reactions involved in the Claus process used for the desulfurization of gases in the oil refinery plants and leading to the formation of solid elemental sulfur, more easy to store, transport and dispose off. | 0 | Organic Chemistry |
Investment casting is a metallurgical processing technique in which a wax form is fabricated and used as a template for a ceramic mold. A ceramic mold is poured around the wax form and solidifies, the wax form is melted out of the ceramic mold, and molten metal is poured into the void left by the wax. This leads to a metal form in the same shape as the original wax form. Investment casting leads to a polycrystalline final product, as nucleation and growth of crystal grains occurs at numerous locations throughout the solid matrix. Generally, the polycrystalline product has no preferred grain orientation. | 8 | Metallurgy |
Lovastatin, sold under the brand name Mevacor among others, is a statin medication, to treat high blood cholesterol and reduce the risk of cardiovascular disease. Its use is recommended together with lifestyle changes. It is taken by mouth.
Common side effects include diarrhea, constipation, headache, muscles pains, rash, and trouble sleeping. Serious side effects may include liver problems, muscle breakdown, and kidney failure. Use during pregnancy may harm the baby and use during breastfeeding is not recommended. It works by decreasing the liver's ability to produce cholesterol by blocking the enzyme HMG-CoA reductase.
Lovastatin was patented in 1979 and approved for medical use in 1987. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2021, it was the 100th most commonly prescribed medication in the United States, with more than 6million prescriptions. | 0 | Organic Chemistry |
Several variants of pi coordinated phenyls have even been tested using transition metals for stacking η-phenyltropanes, using cyclopentadienyl and tricarbonyl in place of a benzene. Which in the case of the tricarbonyl doubled the compound's affinity for its intended ligand site (posited as due to resultant electrostatic influences being more conducive to the target). | 6 | Supramolecular Chemistry |
Pheromone programs are most effective when controlling low to moderate pest population densities. MD has also been identified as a pest control method in which the insect does not become resistant. The scientific community, together with governmental agencies throughout the world, understands the benefits of mating disruption using species-specific sex pheromones, and consider sex-pheromone-based insect control programs among the most environmentally friendly treatments to be used to manage and control insect pest populations. Insect pheromone has been successfully used as an effective tool to slow the spread and to eradicate pests from very large areas in the US; for example to control the spongy moth (Lymantria dispar), a devastating forestry pest, and to eradicate the boll weevil and pink bollworm, two of the most damaging pest of cotton. Conventional pesticide based control methods, kill insects directly, whereas mating disruption confuses male insects from accurately locating a mating partner, leading to the eventual collapse of the mating cycle. Mating disruption, due to the specificity of the sex pheromone of the insect species, has the benefit of only affecting the males of that species, while leaving other non target species unaffected. This allows for very targeted pest management, promoting the suppression of a single pest species, leaving the populations of beneficial insects (pollinators and natural enemies) intact. Mating disruption, like most pest management strategies, is a useful technique, but should not be considered a stand-alone treatment program for it targets only a single species in plant production systems that usually have several pests of concern. Mating disruption is a valuable tool that should be used in Integrated Pest Management(IPM) programs.
Pheromone programs have been used for several decades around the globe and to date (2009) there is no documented public health evidence to suggest that agricultural use of synthetic pheromones is harmful to humans or to any other non-target species. However, continuing research is being conducted. | 1 | Biochemistry |
Ortho-carborane is prepared by the addition of acetylenes to decaborane(14). Modern syntheses involve two stages, the first involving generation of an adduct of decaborane:
:BH + 2 SEt → BH(SEt) + H
In the second stage, the alkyne is installed as the source of two carbon vertices:
:BH(SEt) + CH → CBH + 2 SEt + H
Substituted acetylenes can be employed more conveniently than acetylene gas. For example bis(acetoxymethyl)acetylene adds to the decarborane readily.
:BH(SEt) + C(CHOCCH) → CBH(CHOCCH) + 2 SEt + H
The organic substituents are removed by ester hydrolysis followed by oxidation:
:3 CBH(CHOCH) + 10 KOH + + 8 KMnO → 3 CBH + 6 CHCOK + 8 MnO + 6 KCO + 8 HO | 7 | Physical Chemistry |
Lipidomics is the large-scale study of pathways and networks of cellular lipids in biological systems The word "lipidome" is used to describe the complete lipid profile within a cell, tissue, organism, or ecosystem and is a subset of the "metabolome" which also includes other major classes of biological molecules (such as amino acids, sugars, glycolysis & TCA intermediates, and nucleic acids). Lipidomics is a relatively recent research field that has been driven by rapid advances in technologies such as mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, fluorescence spectroscopy, dual polarisation interferometry and computational methods, coupled with the recognition of the role of lipids in many metabolic diseases such as obesity, atherosclerosis, stroke, hypertension and diabetes. This rapidly expanding field complements the huge progress made in genomics and proteomics, all of which constitute the family of systems biology.
Lipidomics research involves the identification and quantification of the thousands of cellular lipid molecular species and their interactions with other lipids, proteins, and other metabolites. Investigators in lipidomics examine the structures, functions, interactions, and dynamics of cellular lipids and the changes that occur during perturbation of the system.
Han and Gross first defined the field of lipidomics through integrating the specific chemical properties inherent in lipid molecular species with a comprehensive mass spectrometric approach. Although lipidomics is under the umbrella of the more general field of "metabolomics", lipidomics is itself a distinct discipline due to the uniqueness and functional specificity of lipids relative to other metabolites.
In lipidomic research, a vast amount of information quantitatively describing the spatial and temporal alterations in the content and composition of different lipid molecular species is accrued after perturbation of a cell through changes in its physiological or pathological state. Information obtained from these studies facilitates mechanistic insights into changes in cellular function. Therefore, lipidomic studies play an essential role in defining the biochemical mechanisms of lipid-related disease processes through identifying alterations in cellular lipid metabolism, trafficking and homeostasis. The growing attention on lipid research is also seen from the initiatives underway of the LIPID Metabolites And Pathways Strategy (LIPID MAPS Consortium). and The European Lipidomics Initiative (ELIfe). | 1 | Biochemistry |
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