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Many of the NGS sequencing protocols rely on the production of a genomic library that contains thousands of fragments of the target nucleic acids that will then be sequenced by proper technologies. According to the sequencing methods to be used, libraries can be created differently (in the case of the Ion Torrent technology RNA fragments are directly attached to a magnetic bead through an adapter, while for Illumina sequencing, the RNA fragments are firstly ligated to the adapters and then attached to the surface of a plate): generally, universal adapters A and B (containing well known sequences comprehensive of Unique Molecular Identifiers that are used to quantify small RNAs in a sample and sample indexing that allows to discriminate between different RNA molecules deriving from different samples) are ligated to the 5 and 3 ends of the RNA fragments thanks to the activity of the T4 RNA ligase 2 truncated. After the adapters are ligated to both ends of the small RNAs, retrotranscription occurs producing complementary DNA molecules (cDNAs) which will be, eventually, amplified by different amplification techniques depending on the sequencing protocol that is being followed (Ion Torrent exploits the emulsion PCR, while Illumina requires a bridge PCR) in order to obtain up to billions of amplicons to be sequenced. Besides the regular PCR mix, masking oligonucleotides targeting 5.8s rRNA are added to increase sensitivity to small RNA targets and to improve the amplification results. Caution has to be used, as RNA samples are prone to degradation, and further improvement of this technique should be oriented towards the elimination of adapter dimers. Some specific RNA modifications (such as 5′ hydroxyl (5′-OH), 3′-phosphate (3′-P) and 2′,3′-cyclic phosphate (2′3′-cP)) can block the adapter ligation process, while some other RNA modifications ( such as m1A, m3C, m1G and m22G) can interfere with reverse transcription process. Small RNA bearing one or more of these modifications are often inefficiently and incompletely converted into cDNAs, leading to challenges with their detection and quantitation by deep sequencing, which can be overcome by enzyme (such as PNK and AlkB) pre-treatment. | 1 | Biochemistry |
Kocienski has made contributions to the design and development of new organometallic reagents in synthesis, and the applications of synthetic methods to complex natural products. Early work with Basil Lythgoe on the scope and stereochemistry of the Julia olefination with alpha-metallated sulphone reagents emphasised the value of this method in organic chemistry. His major contribution has been to research the synthesis and chemistry of novel metallated (lithium, copper and nickel) enol ethers, and to develop the uses of these intermediates in the synthesis of oxacyclic and geometrically defined alkene units in natural products of biological significance. Kocienski has synthesised the insecticide milbemycin beta 3, the potassium channel blocker talaromycin B, the hypotensive agent lacrimin, and the antihypertensive agent zoapatanol. His total synthesis of the insect toxin pederin, and his synthetic work toward the immunosuppressant FK 506, have made him regarded as one of the leading organic chemists in the field. | 0 | Organic Chemistry |
For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those trading in or using sugar syrups in bulk. | 4 | Stereochemistry |
Flap endonuclease (FEN) is an endonuclease that catalyzes structure-specific cleavage. This cleavage is highly sensitive to mismatches and can be used to interrogate SNPs with a high degree of specificity
In the basic Invader assay, a FEN called cleavase is combined with two specific oligonucleotide probes, that together with the target DNA, can form a tripartite structure recognized by cleavase. The first probe, called the Invader oligonucleotide is complementary to the 3’ end of the target DNA. The last base of the Invader oligonucleotide is a non-matching base that overlaps the SNP nucleotide in the target DNA. The second probe is an allele-specific probe which is complementary to the 5’ end of the target DNA, but also extends past the 3’ side of the SNP nucleotide. The allele-specific probe will contain a base complementary to the SNP nucleotide. If the target DNA contains the desired allele, the Invader and allele-specific probes will bind to the target DNA forming the tripartite structure. This structure is recognized by cleavase, which will cleave and release the 3’ end of the allele-specific probe. If the SNP nucleotide in the target DNA is not complementary to the allele-specific probe, the correct tripartite structure is not formed and no cleavage occurs. The Invader assay is usually coupled with fluorescence resonance energy transfer (FRET) system to detect the cleavage event. In this setup, a quencher molecule is attached to the 3’ end and a fluorophore is attached to the 5’ end of the allele-specific probe. If cleavage occurs, the fluorophore will be separated from the quencher molecule generating a detectable signal.
Only minimal cleavage occurs with mismatched probes making the Invader assay highly specific. However, in its original format, only one SNP allele could be interrogated per reaction sample and it required a large amount of target DNA to generate a detectable signal in a reasonable time frame. Several developments have extended the original Invader assay. By carrying out secondary FEN cleavage reactions, the Serial Invasive Signal Amplification Reaction (SISAR) allows both SNP alleles to be interrogated in a single reaction. SISAR Invader assay also requires less target DNA, improving the sensitivity of the original Invader assay. The assay has also been adapted in several ways for use in a high-throughput format. In one platform, the allele-specific probes are anchored to microspheres. When cleavage by FEN generates a detectable fluorescent signal, the signal is measured using flow-cytometry. The sensitivity of flow-cytometry, eliminates the need for PCR amplification of the target DNA (Rao et al. 2003). These high-throughput platforms have not progressed beyond the proof-of-principle stage and so far the Invader system has not been used in any large scale SNP genotyping projects. | 1 | Biochemistry |
Cellulose bioplastics are mainly the cellulose esters (including cellulose acetate and nitrocellulose) and their derivatives, including celluloid.
Cellulose can become thermoplastic when extensively modified. An example of this is cellulose acetate, which is expensive and therefore rarely used for packaging. However, cellulosic fibers added to starches can improve mechanical properties, permeability to gas, and water resistance due to being less hydrophilic than starch.
A group at Shanghai University was able to construct a novel green plastic based on cellulose through a method called hot pressing. | 7 | Physical Chemistry |
Magnetic-activated cell sorting (MACS) is a method for separation of various cell populations depending on their surface antigens (CD molecules) invented by Miltenyi Biotec. The name MACS is a registered trademark of the company.
The method was developed with Miltenyi Biotec's MACS system, which uses superparamagnetic nanoparticles and columns. The superparamagnetic nanoparticles are of the order of 100 nm. They are used to tag the targeted cells in order to capture them inside the column. The column is placed between permanent magnets so that when the magnetic particle-cell complex passes through it, the tagged cells can be captured. The column consists of steel wool which increases the magnetic field gradient to maximize separation efficiency when the column is placed between the permanent magnets.
Magnetic-activated cell sorting is a commonly used method in areas like immunology, cancer research, neuroscience, and stem cell research. Miltenyi sells microbeads which are magnetic nanoparticles conjugated to antibodies which can be used to target specific cells. | 1 | Biochemistry |
Certain AMGs encode proteins that directly interact with enzymes involved in metabolic reactions. This interaction can either enhance or inhibit enzyme activity, leading to changes in the rate of metabolic flux through specific pathways. | 1 | Biochemistry |
When the required steel had been formed, it was poured into ladles and then transferred into moulds while the lighter slag was left behind. The conversion process, called the "blow", was completed in approximately 20 minutes. During this period, the progress of the oxidation of the impurities was judged by the appearance of the flame issuing from the mouth of the converter. The modern use of photoelectric methods of recording the characteristics of the flame greatly aided the blower in controlling final product quality. After the blow, the liquid metal was recarburized to the desired point and other alloying materials were added, depending on the desired product.
A Bessemer converter could treat a "heat" (batch of hot metal) of 5 to 30 tons at a time. They were usually operated in pairs, one being blown while another was being filled or tapped. | 8 | Metallurgy |
Smoking or vaporizing hash oil is known colloquially as "dabbing", from the English verb to daub (Dutch dabben, French dauber), "to smear with something adhesive". Dabbing devices include special kinds of water pipes ("dab rigs"), vaporizers and vape pens similar in design to electronic cigarettes. Oil rigs include a glass water pipe and a quartz bucket which is often covered with a glass bubble or directional cap to direct the airflow and disperse the oil amongst the hot areas of the quartz "nail" (A nail is also referred to as a banger). The pipe is often heated with a butane blowtorch rather than a cigarette lighter.
The oil can also be sold in prefilled atomizer cartridges. The cartridge is used by connecting it to a battery and inhaling the vaporized oil from the cartridge's mouthpiece. | 7 | Physical Chemistry |
Random amplified polymorphic DNA (RAPD), pronounced "rapid", is a type of polymerase chain reaction (PCR), but the segments of DNA that are amplified are random. The scientist performing RAPD creates several arbitrary, short primers (10–12
nucleotides), then proceeds with the PCR using a large template of genomic DNA, hoping that fragments will amplify. By resolving the resulting patterns, a semi-unique profile can be gleaned from an RAPD reaction.
No knowledge of the DNA sequence of the targeted genome is required, as the primers will bind somewhere in the sequence, but it is not certain exactly where. This makes the method popular for comparing the DNA of biological systems that have not had the attention of the scientific community, or in a system in which relatively few DNA sequences are compared (it is not suitable for forming a cDNA databank). Because it relies on a large, intact DNA template sequence, it has some limitations in the use of degraded DNA samples. Its resolving power is much lower than targeted, species-specific DNA comparison methods, such as short tandem repeats. In recent years, RAPD has been used to characterize, and trace, the phylogeny of diverse plant and animal species. | 1 | Biochemistry |
Molecular fly-by collisions take little time, something like 10 s.
Optical transition of collisional complexes of molecules generate spectral
"lines" that are very broad - roughly five orders of magnitude broader
than the most familiar "ordinary" spectral lines (Heisenberg's uncertainty
relation). The resulting spectral "lines" usually strongly
overlap so that collision-induced spectral bands typically appear as continua
(as opposed to the bands of often discernible lines of ordinary molecules).
Collision-induced spectra appear at the frequencies of the rotovibrational and
electronic transition bands of the unperturbed molecules, and also at sums and
differences of such transition frequencies: simultaneous transitions in two (or
more) interacting molecules are well known to generate optical transitions of
molecular complexes. | 7 | Physical Chemistry |
Theoretical quantum-mechanical calculations become rather accurate to describe the energy structure of some simple electronic configurations. The results of theoretical developments were summarized by Condon and Shortley in 1935.
Edlén thoroughly analyzed spectra of MIA for many chemical elements and derived regularities in energy structures of MIA for many isoelectronic sequences (ions with the same number of electrons, but different nuclear charges). Spectra of rather high ionization stages (e.g. Cu XIX) were observed.
The most exciting event was in 1942, when Edlén proved the identification of some solar coronal lines on the basis of his precise analyses of spectra of MIA. This implied that the solar corona has a temperature of a million degrees, and strongly advanced understanding of solar and stellar physics.
After the WW II experiments on balloons and rockets were started to observe the VUV radiation of the Sun. (See X-ray astronomy). More intense research continued since 1960 including spectrometers on satellites.
In the same period the laboratory spectroscopy of MIA becomes relevant as a diagnostic tool for hot plasmas of thermonuclear devices (see Nuclear fusion) which begun with building Stellarator in 1951 by Spitzer, and continued with tokamaks, z-pinches and the laser produced plasmas. Progress in ion accelerators stimulated beam-foil spectroscopy as a means to measure lifetimes of exited states of MIA. Many various data on highly exited energy levels, autoionization and inner-core ionization states were obtained. | 7 | Physical Chemistry |
ANT has long been thought to function as a homodimer, but this concept was challenged by the projection structure of the yeast Aac3p solved by electron crystallography, which showed that the protein was three-fold symmetric and monomeric, with the translocation pathway for the substrate through the centre. The atomic structure of the bovine ANT confirmed this notion, and provided the first structural fold of a mitochondrial carrier. Further work has demonstrated that ANT is a monomer in detergents and functions as a monomer in mitochondrial membranes.
ADP/ATP translocase 1 is the major AAC in human cells and the archetypal protein of this family. It has a mass of approximately 30 kDa, consisting of 297 residues. It forms six transmembrane α-helices that form a barrel that results in a deep cone-shaped depression accessible from the outside where the substrate binds. The binding pocket, conserved throughout most isoforms, mostly consists of basic residues that allow for strong binding to ATP or ADP and has a maximal diameter of 20 Å and a depth of 30 Å. Indeed, arginine residues 96, 204, 252, 253, and 294, as well as lysine 38, have been shown to be essential for transporter activity. | 1 | Biochemistry |
Cupellation is a refining process in metallurgy in which ores or alloyed metals are treated under very high temperatures and subjected to controlled operations to separate noble metals, like gold and silver, from base metals, like lead, copper, zinc, arsenic, antimony, or bismuth, present in the ore. The process is based on the principle that precious metals typically oxidise or react chemically at much higher temperatures than base metals. When they are heated at high temperatures, the precious metals remain apart, and the others react, forming slags or other compounds.
Since the Early Bronze Age, the process was used to obtain silver from smelted lead ores. By the Middle Ages and the Renaissance, cupellation was one of the most common processes for refining precious metals. By then, fire assays were used for assaying minerals: testing fresh metals such as lead and recycled metals to determine their purity for jewellery and coin making. Cupellation is still in use today. | 8 | Metallurgy |
When a semiconductor comes into contact with a liquid (redox species), to maintain electrostatic equilibrium, there will be a charge transfer between the semiconductor and liquid phase if formal redox potential of redox species lies inside semiconductor band gap. At thermodynamic equilibrium, the Fermi level of semiconductor and the formal redox potential of redox species are aligned at the interface between semiconductor and redox species. This introduces an upward band bending in a n-type semiconductor for n-type semiconductor/liquid junction (Figure 1(a)) and a downward band bending in a p-type semiconductor for a p-type semiconductor/liquid junction (Figure 1(b)). This characteristic of semiconductor/liquid junctions is similar to a rectifying semiconductor/metal junction or Schottky junction. Ideally to get a good rectifying characteristics at the semiconductor/liquid interface, the formal redox potential must be close to the valence band of the semiconductor for a n-type semiconductor and close to the conduction band of the semiconductor for a p-type semiconductor. The semiconductor/liquid junction has one advantage over the rectifying semiconductor/metal junction in that the light is able to travel through to the semiconductor surface without much reflection; whereas most of the light is reflected back from the metal surface at a semiconductor/metal junction. Therefore, semiconductor/liquid junctions can also be used as photovoltaic devices similar to solid state p–n junction devices. Both n-type and p-type semiconductor/liquid junctions can be used as photovoltaic devices to convert solar energy into electrical energy and are called photoelectrochemical cells. In addition, a semiconductor/liquid junction could also be used to directly convert solar energy into chemical energy by virtue of photoelectrolysis at the semiconductor/liquid junction. | 5 | Photochemistry |
In order to study trace metal stable isotope biogeochemistry, it is necessary to compare the relative abundances of isotopes of trace metals in a given biological, geological, or chemical pool to a standard (discussed individually for each isotope system below) and monitor how those relative abundances change as a result of various biogeochemical processes. Conventional notations used to mathematically describe isotope abundances, as exemplified here for Fe, include the isotope ratio (R), fractional abundance (F) and delta notation (δFe). Furthermore, as different biogeochemical processes vary the relative abundances of the isotopes of a given trace metal, different reaction pools or substances will become enriched or depleted in specific isotopes. This partial separation of isotopes between different pools is termed isotope fractionation, and is mathematically described by fractionation factors α or ε (which express the difference in isotope ratio between two pools), or by "cap delta" (Δ; the difference between two δ values). For a more complete description of these notations, see the isotope notation section in Hydrogen isotope biogeochemistry. | 9 | Geochemistry |
Copper(I) thiophene-2-carboxylate or CuTC is a coordination complex derived from copper and thiophene-2-carboxylic acid. It is used as a reagent to promote the Ullmann reaction between aryl halides. | 0 | Organic Chemistry |
In organic chemistry, the vanillyl group (also known as vanilloyl) is a functional group. Compounds containing a vanillyl group are called vanilloids, and include vanillin, vanillic acid, capsaicin, vanillylmandelic acid, etc. | 0 | Organic Chemistry |
The introduction of a mechanical bond alters the chemistry of the sub components of rotaxanes and catenanes. Steric hindrance of reactive functionalities is increased and the strength of non-covalent interactions between the components are altered. | 6 | Supramolecular Chemistry |
Supramolecular polymers usually prepared in solution. However anomalous polymeric properties can be expected when these polymers are prepared without a conventional organic or aqueous medium. For instance, liquid crystal media may affect the elementary steps of supramolecular polymerization as demonstrated by Takashi Kato in 1998, in the supramolecular crosslinking polymerization of physical gelators, which form a liquid crystal physical gel. When monomers are designed to be highly affinitive toward the LC media, supramolecular polymerization causes an order-increasing phase transition, resulting in a core-shell columnar LC. Supramolecular polymers can also be prepared in the solid-state, for instance, a nucleobase-appended telechelic oligomer as a monomer, resulted in the formation of 1D fibers upon cooling from its hot melt. As a new class of materials, supramolecular polymers formed at electrode and at the interface also become available. | 6 | Supramolecular Chemistry |
The configuration index is a single digit which is defined as the priority number of the ligand on the stem of the "T". | 4 | Stereochemistry |
In 1908, it was reported that exposure of carvone to "Italian sunlight" for one year gives carvone-camphor. Subsequent investigations demonstrated the utility of the photochemical [2+2] cycloaddition of enones to alkenes, requiring only "sunlight in California for 6.5 months". | 5 | Photochemistry |
Primary energy (PE) is the energy found in nature that has not been subjected to any human engineered conversion process. It encompasses energy contained in raw fuels and other forms of energy, including waste, received as input to a system. Primary energy can be non-renewable or renewable.
Total primary energy supply (TPES) is the sum of production and imports, plus or minus stock changes, minus exports and international bunker storage.
The International Recommendations for Energy Statistics (IRES) prefers total energy supply (TES) to refer to this indicator. These expressions are often used to describe the total energy supply of a national territory.
Secondary energy is a carrier of energy, such as electricity. These are produced by conversion from a primary energy source.
Primary energy is used as a measure in energy statistics in the compilation of energy balances, as well as in the field of energetics. In energetics, a primary energy source (PES) refers to the energy forms required by the energy sector to generate the supply of energy carriers used by human society. Primary energy only counts raw energy and not usable energy and fails to account well for energy losses, particularly the large losses in thermal sources. It therefore generally grossly undercounts non thermal renewable energy sources . | 7 | Physical Chemistry |
Compounds or materials that are easily transformed (often by biological activity) are termed labile. For example, labile phosphate is that fraction of soil phosphate that is readily transformed into soluble or plant-available phosphate. Labile organic matter is the soil organic matter that is easily decomposed by microorganisms. | 1 | Biochemistry |
The definitions of VOCs used for control of precursors of photochemical smog used by the U.S. Environmental Protection Agency (EPA) and state agencies in the US with independent outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. Prominent is the VOC regulation issued by the South Coast Air Quality Management District in California and by the California Air Resources Board (CARB). However, this specific use of the term VOCs can be misleading, especially when applied to indoor air quality because many chemicals that are not regulated as outdoor air pollution can still be important for indoor air pollution.
Following a public hearing in September 1995, Californias ARB uses the term "reactive organic gases" (ROG) to measure organic gases. The CARB revised the definition of "Volatile Organic Compounds" used in their consumer products regulations, based on the committees findings.
In addition to drinking water, VOCs are regulated in pollutant discharges to surface waters (both directly and via sewage treatment plants) as hazardous waste, but not in non-industrial indoor air. The Occupational Safety and Health Administration (OSHA) regulates VOC exposure in the workplace. Volatile organic compounds that are classified as hazardous materials are regulated by the Pipeline and Hazardous Materials Safety Administration while being transported. | 0 | Organic Chemistry |
Benzeneselenol, also known as selenophenol, is the organoselenium compound with the chemical formula , often abbreviated PhSeH. It is the selenium analog of phenol. This colourless, malodorous compound is a reagent in organic synthesis. | 0 | Organic Chemistry |
Bearing heaters typically range from 1 kVA to 25 kVA and are used to heat parts from , dependent upon the application. The power required is a function of the weight, target temperature and cycle time to aid selection many manufacturers publish graphs and charts. | 8 | Metallurgy |
The mouth is the first part of the upper gastrointestinal tract and is equipped with several structures that begin the first processes of digestion. These include salivary glands, teeth and the tongue. The mouth consists of two regions; the vestibule and the oral cavity proper. The vestibule is the area between the teeth, lips and cheeks, and the rest is the oral cavity proper. Most of the oral cavity is lined with oral mucosa, a mucous membrane that produces a lubricating mucus, of which only a small amount is needed. Mucous membranes vary in structure in the different regions of the body but they all produce a lubricating mucus, which is either secreted by surface cells or more usually by underlying glands. The mucous membrane in the mouth continues as the thin mucosa which lines the bases of the teeth. The main component of mucus is a glycoprotein called mucin and the type secreted varies according to the region involved. Mucin is viscous, clear, and clinging. Underlying the mucous membrane in the mouth is a thin layer of smooth muscle tissue and the loose connection to the membrane gives it its great elasticity. It covers the cheeks, inner surfaces of the lips, and floor of the mouth, and the mucin produced is highly protective against tooth decay.
The roof of the mouth is termed the palate and it separates the oral cavity from the nasal cavity. The palate is hard at the front of the mouth since the overlying mucosa is covering a plate of bone; it is softer and more pliable at the back being made of muscle and connective tissue, and it can move to swallow food and liquids. The soft palate ends at the uvula. The surface of the hard palate allows for the pressure needed in eating food, to leave the nasal passage clear. The opening between the lips is termed the oral fissure, and the opening into the throat is called the fauces.
At either side of the soft palate are the palatoglossus muscles which also reach into regions of the tongue. These muscles raise the back of the tongue and also close both sides of the fauces to enable food to be swallowed. Mucus helps in the mastication of food in its ability to soften and collect the food in the formation of the bolus. | 1 | Biochemistry |
As typical for the CMGC kinase group, the catalytic site of MAP kinases has a very loose consensus sequence for substrates. Like all their relatives, they only require the target serine / threonine amino acids to be followed by a small amino acid, preferably proline ("proline-directed kinases"). But as SP/TP sites are extremely common in all proteins, additional substrate-recognition mechanisms have evolved to ensure signaling fidelity. Unlike their closest relatives, the cyclin-dependent kinases (CDKs), where substrates are recognized by the cyclin subunit, MAPKs associate with their substrates via auxiliary binding regions on their kinase domains. The most important such region consists of the hydrophobic docking groove and the negatively charged CD-region. Together they recognize the so-called MAPK docking or D-motifs (also called kinase interaction motif / KIM). D-motifs essentially consist of one or two positively charged amino acids, followed by alternating hydrophobic residues (mostly leucines), typically upstream of the phosphorylation site by 10–50 amino acids. Many of the known MAPK substrates contain such D-motifs that can not only bind to, but also provide specific recognition by certain MAPKs. D-motifs are not restricted to substrates: MAP2 kinases also contain such motifs on their N-termini that are absolutely required for MAP2K-MAPK interaction and MAPK activation. Similarly, both dual-specificity MAP kinase phosphatases and MAP-specific tyrosine phosphatases bind to MAP kinases through the same docking site. D-motifs can even be found in certain MAPK pathway regulators and scaffolds (e.g. in the mammalian JIP proteins).
Other, less well characterised substrate-binding sites also exist. One such site (the DEF site) is formed by the activation loop (when in the active conformation) and the MAP kinase-specific insert below it. This site can accommodate peptides with an FxFP consensus sequence, typically downstream of the phosphorylation site. Note that the latter site can only be found in proteins that need to selectively recognize the active MAP kinases, thus they are almost exclusively found in substrates. Different motifs may cooperate with each other, as in the Elk family of transcription factors, that possess both a D-motif and an FxFP motif. The presence of an FxFP motif in the KSR1 scaffold protein also serves to make it an ERK1/2 substrate, providing a negative feedback mechanism to set the correct strength of ERK1/2 activation. | 1 | Biochemistry |
It is a member of the small pentraxins family (also known as short pentraxins). The polypeptide encoded by this gene has 224 amino acids. The full-length polypeptide is not present in the body in significant quantities due to signal peptide, which is removed by signal peptidase before translation is completed. The complete protein, composed of five monomers, has a total mass of approximately 120,000 Da. In serum, it assembles into stable pentameric structure with a discoid shape. | 1 | Biochemistry |
Deacylations "play crucial roles in gene transcription and most likely in all eukaryotic biological processes that involve chromatin".
Acetylation is one type of post-translational modification of proteins. The acetylation of the ε-amino group of lysine, which is common, converts a charged side chain to a neutral one. Acetylation/deacetylation of histones also plays a role in gene expression and cancer. These modifications are effected by enzymes called histone acetyltransferases (HATs) and histone deacetylases (HDACs).
Two general mechanisms are known for deacetylation. One mechanism involves zinc binding to the acetyl oxygen. Another family of deacetylases require NAD, which transfers an ribosyl group to the acetyl oxygen. | 0 | Organic Chemistry |
The genes and receptor ligands are as follows:
(Hökfelt et al., 2001; Page, 2004; Pennefather et al., 2004; Maggi, 2000) | 1 | Biochemistry |
Staying dry and wearing proper clothing help to prevent hypothermia. Synthetic and wool fabrics are superior to cotton as they provide better insulation when wet and dry. Some synthetic fabrics, such as polypropylene and polyester, are used in clothing designed to wick perspiration away from the body, such as liner socks and moisture-wicking undergarments. Clothing should be loose fitting, as tight clothing reduces the circulation of warm blood. In planning outdoor activity, prepare appropriately for possible cold weather. Those who drink alcohol before or during outdoor activity should ensure at least one sober person is present responsible for safety.
Covering the head is effective, but no more effective than covering any other part of the body. While common folklore says that people lose most of their heat through their heads, heat loss from the head is no more significant than that from other uncovered parts of the body. However, heat loss from the head is significant in infants, whose head is larger relative to the rest of the body than in adults. Several studies have shown that for uncovered infants, lined hats significantly reduce heat loss and thermal stress. Children have a larger surface area per unit mass, and other things being equal should have one more layer of clothing than adults in similar conditions, and the time they spend in cold environments should be limited. However children are often more active than adults, and may generate more heat. In both adults and children, overexertion causes sweating and thus increases heat loss.
Building a shelter can aid survival where there is danger of death from exposure. Shelters can be constructed out of a variety of materials. Metal can conduct heat away from the occupants and is sometimes best avoided. The shelter should not be too big so body warmth stays near the occupants. Good ventilation is essential especially if a fire will be lit in the shelter. Fires should be put out before the occupants sleep to prevent carbon monoxide poisoning. People caught in very cold, snowy conditions can build an igloo or snow cave to shelter.
The United States Coast Guard promotes using life vests to protect against hypothermia through the 50/50/50 rule: If someone is in water for 50 minutes, they have a 50 percent better chance of survival if they are wearing a life jacket. A heat escape lessening position can be used to increase survival in cold water.
Babies should sleep at 16–20 °C (61–68 °F) and housebound people should be checked regularly to make sure the temperature of the home is at least 18 °C (64 °F). | 1 | Biochemistry |
In Complex IV (cytochrome c oxidase; ), sometimes called cytochrome AA3, four electrons are removed from four molecules of cytochrome c and transferred to molecular oxygen (O) and four protons, producing two molecules of water. The complex contains coordinated copper ions and several heme groups. At the same time, eight protons are removed from the mitochondrial matrix (although only four are translocated across the membrane), contributing to the proton gradient. The exact details of proton pumping in Complex IV are still under study. Cyanide is an inhibitor of Complex IV. | 1 | Biochemistry |
Knockout mice that completely lack the RIP140 molecule are lean and stay lean, even on a rich diet.
Knockout mice (females) are also infertile because they fail to ovulate. Failure of ovulation in these mice is caused by lack of cumulus expansion and altered expression of various genes, including amphiregulin, in ovarian follicles. | 1 | Biochemistry |
6-Methoxy-(8-p-toluenesulfonamido)quinoline (TSQ) is one of the most efficient fluorescent stains for zinc(II). It was introduced by Soviet biochemists Toroptsev and Eshchenko in the early 1970s. The popularity of TSQ as physiological stain rose after seminal works by Christopher Frederickson two decades later. TSQ forms a 2:1 (ligand-metal) complex with zinc and emits blue light upon excitation at 365 nanometers. TSQ has been extensively applied for determination of extracellular or intracellular levels of Zn in biological systems, also to study Zn in mossy fibers of the hippocampus. | 1 | Biochemistry |
The use of ractopamine in Russia is prohibited. On 6 June 2011, the Russian Ministry of Agriculture notified key meat import/exporters in Russia of a future prohibition of ractopamine in meat imported to Russia.
On 7 December 2012, the prohibition went into force, and pork and beef export to Russia required submission of compliance certificates confirming absence of ractopamine in exported meat. | 4 | Stereochemistry |
G stimulates the membrane-bound phospholipase C beta, which then cleaves PIP (a minor membrane phosphoinositol) into two second messengers, IP3 and diacylglycerol (DAG).
The Inositol Phospholipid Dependent Pathway is used as a signal transduction pathway for many hormones including:
* ADH (Vasopressin/AVP) – Induces the synthesis and release of glucocorticoids (Zona fasciculata of adrenal cortex); Induces vasoconstriction (V1 Cells of Posterior pituitary)
* TRH – Induces the synthesis and release of TSH (Anterior pituitary gland)
* TSH – Induces the synthesis and release of a small amount of T4 (Thyroid Gland)
* Angiotensin II – Induces Aldosterone synthesis and release (zona glomerulosa of adrenal cortex in kidney)
* GnRH – Induces the synthesis and release of FSH and LH (Anterior Pituitary) | 1 | Biochemistry |
Surface tension is visible in other common phenomena, especially when surfactants are used to decrease it:
* Soap bubbles have very large surface areas with very little mass. Bubbles in pure water are unstable. The addition of surfactants, however, can have a stabilizing effect on the bubbles (see Marangoni effect). Surfactants actually reduce the surface tension of water by a factor of three or more.
* Emulsions are a type of colloidal dispersion in which surface tension plays a role. Tiny droplets of oil dispersed in pure water will spontaneously coalesce and phase separate. The addition of surfactants reduces the interfacial tension and allow for the formation of oil droplets in the water medium (or vice versa). The stability of such formed oil droplets depends on many different chemical and environmental factors. | 6 | Supramolecular Chemistry |
Intracranial electrodes consist of conductive electrode arrays implanted on a polymer or silicon, or a wire electrode with an exposed tip and insulation everywhere that stimulation or recording is not desired. Biocompatibility is essential for the entire implant, but special attention is paid to the actual electrodes since they are the site producing the desired function. | 7 | Physical Chemistry |
Whether or not we say a transition between a state and a state is allowed often depends on how detailed the model is that we use for the atom-light interaction. From a particular model follow a set of selection rules that determine which transitions are allowed and which are not. Often these selection rules can be boiled down to conservation of angular momentum (the photon has angular momentum). In most cases we only consider an atom interacting with the electric dipole field of the photon. Then some transitions are not allowed at all, others are only allowed for photons of a certain polarization.
Consider for example the hydrogen atom. The transition from the state with m=-1/2 to the state with m=-1/2 is only allowed for light with polarization along the z axis (quantization axis) of the atom. The state with m=-1/2 therefore appears dark for light of other polarizations.
Transitions from the 2S level to the 1S level are not allowed at all. The 2S state can not decay to the ground state by emitting a single photon. It can only decay by collisions with other atoms or by emitting multiple photons. Since these events are rare, the atom can remain in this excited state for a very long time, such an excited state is called a metastable state. | 7 | Physical Chemistry |
Outdoor air may contain low levels of benzene from automobile service stations, wood smoke, tobacco smoke, the transfer of gasoline, exhaust from motor vehicles, and industrial emissions. About 50% of the entire nationwide (United States) exposure to benzene results from smoking tobacco or from exposure to tobacco smoke. After smoking 32 cigarettes per day, the smoker would take in about 1.8 milligrams (mg) of benzene. This amount is about 10 times the average daily intake of benzene by nonsmokers.
Inhaled benzene is primarily expelled unchanged through exhalation. In a human study 16.4 to 41.6% of retained benzene was eliminated through the lungs within five to seven hours after a two- to three-hour exposure to 47 to 110 ppm and only 0.07 to 0.2% of the remaining benzene was excreted unchanged in the urine. After exposure to 63 to 405 mg/m of benzene for 1 to 5 hours, 51 to 87% was excreted in the urine as phenol over a period of 23 to 50 hours. In another human study, 30% of absorbed dermally applied benzene, which is primarily metabolized in the liver, was excreted as phenol in the urine. | 2 | Environmental Chemistry |
The role of vitamin A in the visual cycle is specifically related to the retinal compound. Retinol is converted by the enzyme RPE65 within the retinal pigment epithelium into 11-cis-retinal. Within the eye, 11-cis-retinal is bound to the protein opsin to form rhodopsin in rod cells and iodopsin in cone cells. As light enters the eye, the 11-cis-retinal is isomerized to the all-trans form. The all-trans-retinal dissociates from the opsin in a series of steps called photo-bleaching. This isomerization induces a nervous signal along the optic nerve to the visual center of the brain. After separating from opsin, the all-trans-retinal is recycled and converted back to the 11-cis-retinal form by a series of enzymatic reactions, which then completes the cycle by binding to opsin to reform rhodopsin in the retina. In addition, some of the all-trans-retinal may be converted to all-trans-retinol form and then transported with an interphotoreceptor retinol-binding protein to the retinal pigmented epithelial cells. Further esterification into all-trans-retinyl esters allow for storage of all-trans-retinol within the pigment epithelial cells to be reused when needed. It is for this reason that a deficiency in vitamin A will inhibit the reformation of rhodopsin, and will lead to one of the first symptoms, night blindness. | 1 | Biochemistry |
Many alcohols are produced by hydroxylation, i.e., the installation of a hydroxy group using oxygen or a related oxidant. Hydroxylation is the means by which the body processes many poisons, converting lipophilic compounds into hydrophilic derivatives that are more readily excreted. Enzymes called hydroxylases and oxidases facilitate these conversions.
Many industrial alcohols, such as cyclohexanol for the production of nylon, are produced by hydroxylation. | 0 | Organic Chemistry |
A plasmonic antenna-reactor photocatalyst is a photocatalyst that combines a catalyst with attached antenna that increases the catalyst's ability to absorb light, thereby increasing its efficiency.
A Silicon dioxide| catalyst combined with an Au light absorber accelerated hydrogen sulfide-to-hydrogen reactions. The process is an alternative to the conventional Claus process that operates at .
A Fe catalyst combined with a Cu light absorber can produce hydrogen from ammonia () at ambient temperature using visible light. Conventional Cu-Ru production operates at . | 5 | Photochemistry |
In combustion, Zeldovich–Liñán model is a two-step reaction model for the combustion processes, named after Yakov Borisovich Zeldovich and Amable Liñán. The model includes a chain-branching and a chain-breaking (or radical recombination) reaction. The model was first introduced by Zel'dovich in 1948 and later analysed by Liñán using activation energy asymptotics in 1971. The mechanism reads as
where is the fuel, is an intermediate radical, is the third body and is the product. The first reaction is the chain-branching reaction, which is considered to be auto-catalytic (consumes no heat or releases no heat), with very large activation energy and the second reaction is the chain-breaking (or radical-recombination) reaction, where all of the heat in the combustion is released, with almost negligible activation energy. | 7 | Physical Chemistry |
The copper coulometer is a one application for the copper-copper(II) sulfate electrode. Such a coulometer consists of two identical copper electrodes immersed in slightly acidic pH-buffered solution of copper(II) sulfate. Passing of current through the element leads to the anodic dissolution of the metal on anode and simultaneous deposition of copper ions on the cathode. These reactions have 100% efficiency over a wide range of current density. | 7 | Physical Chemistry |
The petite is characterized by a deficiency in cytochromes (a, a3 + b) and a lack of respiratory enzymes which engage in respiration in mitochondria. Due to the error in the respiratory chain pathway, petite yeast is incapable of growing on media containing only non-fermentable carbon sources (such as glycerol or ethanol) and forming small colonies when grown in the presence of fermentable carbon sources (such as glucose). The absence of mitochondria can cause the petite phenotype, or by deletion mutations in mitochondrial DNA (termed "cytoplasmic Petites") which is a deletion mutation, or by mutations in nuclear-encoded genes involved in oxidative phosphorylation. | 1 | Biochemistry |
*X for any (pseudo)halogen atom (in the related MLXZ notation, X represents a one-electron donor ligand)
*L or L for a ligand or ligands (in the related MLXZ notation, L represents a two-electron donor ligand)
*M or Met for any metal atom ([M] is used to indicate a ligated metal, ML, when the identities of the ligands are unknown or irrelevant)
*E or El for any electrophile (in some contexts, E is also used to indicate any p-block element)
*Nu for any nucleophile
*Z for conjugating electron-withdrawing groups (in the related MLXZ notation, Z represents a zero-electron donor ligand; in unrelated usage, Z is also an abbreviation for the carboxybenzyl group.)
*D for deuterium (H)
*T for tritium (H) | 0 | Organic Chemistry |
The adverse effects of lithium include:
;Very Common (> 10% incidence) adverse effects
* Confusion
* Constipation (usually transient, but can persist in some)
* Decreased memory
* Diarrhea (usually transient, but can persist in some)
* Dry mouth
* EKG changes — usually benign changes in T waves
* Hand tremor (usually transient, but can persist in some) with an incidence of 27%. If severe, psychiatrist may lower lithium dosage, change lithium salt type or modify lithium preparation from long to short acting (despite lacking evidence for these procedures) or use pharmacological help
* Headache
* Hyperreflexia — overresponsive reflexes
* Leukocytosis — elevated white blood cell count
* Muscle weakness (usually transient, but can persist in some)
* Myoclonus — muscle twitching
* Nausea (usually transient)
* Polydipsia — increased thirst
* Polyuria — increased urination
* Renal (kidney) toxicity which may lead to chronic kidney failure
* Vomiting (usually transient, but can persist in some)
* Vertigo
* Weight gain
;Common (1–10%) adverse effects
* Acne
* Extrapyramidal side effects — movement-related problems such as muscle rigidity, parkinsonism, dystonia, etc.
* Euthyroid goitre — i.e. the formation of a goitre despite normal thyroid functioning
* Hypothyroidism — a deficiency of thyroid hormone.
* Hair loss/hair thinning
;Unknown incidence
* Sexual dysfunction
* Hypoglycemia
* Glycosuria
Lithium carbonate can induce a 1–2 kg of weight gain.
In addition to tremors, lithium treatment appears to be a risk factor for development of parkinsonism-like symptoms, although the causal mechanism remains unknown.
Most side effects of lithium are dose-dependent. The lowest effective dose is used to limit the risk of side effects. | 1 | Biochemistry |
This trend is also generally true of pentacoordinated main-group elements with one or more lone-pair-containing ligand, including the oxygen-pentacoordinated silicon examples shown below.
The Si-halogen bonds range from close to the expected van der Waals value in A (a weak bond) almost to the expected covalent single bond value in C (a strong bond). | 4 | Stereochemistry |
Medical organizations recommend that patients protect themselves from UV radiation by using sunscreen. Five sunscreen ingredients have been shown to protect mice against skin tumors. However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells. The amount of sunscreen that penetrates into the lower layers of the skin may be large enough to cause damage.
Sunscreen reduces the direct DNA damage that causes sunburn, by blocking UV‑B, and the usual SPF rating indicates how effectively this radiation is blocked. SPF is, therefore, also called UVB-PF, for "UV‑B protection factor". This rating, however, offers no data about important protection against UVA, which does not primarily cause sunburn but is still harmful, since it causes indirect DNA damage and is also considered carcinogenic. Several studies suggest that the absence of UV‑A filters may be the cause of the higher incidence of melanoma found in sunscreen users compared to non-users. Some sunscreen lotions contain titanium dioxide, zinc oxide, and avobenzone, which help protect against UV‑A rays.
The photochemical properties of melanin make it an excellent photoprotectant. However, sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin and therefore, if sunscreen ingredients penetrate into the lower layers of the skin, the amount of reactive oxygen species may be increased. The amount of sunscreen that penetrates through the stratum corneum may or may not be large enough to cause damage.
In an experiment by Hanson et al. that was published in 2006, the amount of harmful reactive oxygen species (ROS) was measured in untreated and in sunscreen treated skin. In the first 20 minutes, the film of sunscreen had a protective effect and the number of ROS species was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin. The study indicates that sunscreen must be reapplied within 2 hours in order to prevent UV light from penetrating to sunscreen-infused live skin cells. | 5 | Photochemistry |
In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response.
Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungi, and bacteria.
Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, antibodies are antigen-specific, meaning that an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react to bind more than one antigen. The reaction between an antigen and an antibody is called the antigen-antibody reaction.
Antigen can originate either from within the body ("self-protein" or "self antigens") or from the external environment ("non-self"). The immune system identifies and attacks "non-self" external antigens. Antibodies usually do not react with self-antigens due to negative selection of T cells in the thymus and B cells in the bone marrow. The diseases in which antibodies react with self antigens and damage the body's own cells are called autoimmune diseases.
Vaccines are examples of antigens in an immunogenic form, which are intentionally administered to a recipient to induce the memory function of the adaptive immune system towards antigens of the pathogen invading that recipient. The vaccine for seasonal influenza is a common example. | 1 | Biochemistry |
SBO is currently made up of seven different vocabularies:
* systems description parameter (catalytic constant, thermodynamic temperature...)
* participant role (substrate, product, catalyst...)
* modelling framework (discrete, continuous...)
* mathematical expression (mass-action rate law, Hill-type rate law...)
* occurring entity representation (biochemical process, molecular or genetic interaction...)
* physical entity representation (transporter, physical compartment, observable...)
* metadata representation (annotation) | 1 | Biochemistry |
Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink. It is also used as a hydration indicator for silica gel. Methyl violet 10B is also known as crystal violet (and many other names) and has medical uses. | 3 | Analytical Chemistry |
With surface chemistries that are weakly ionic, the choice of pH can affect the ionic nature of the column chemistry. Properly adjusted, the pH can be set to reduce the selectivity toward functional groups with the same charge as the column, or enhance it for oppositely charged functional groups. Similarly, the choice of pH affects the polarity of the solutes. However, for column surface chemistries that are strongly ionic, and thus resistant to pH values in the mid-range of the pH scale (pH 3.5–8.5), these separations will be reflective of the polarity of the analytes alone, and thus might be easier to understand when doing methods development. | 1 | Biochemistry |
Exemestane has been used in doping to raise luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels, which in turn increases the ratio of male over female sexual hormones and so improves performance. The drug also counteracts gynecomastia as well as fat and water retention following excessive aromatase production due to testosterone doping.
Along with other aromatase inhibitors, exemestane is on the World Anti-Doping Agency's list of prohibited substances. | 4 | Stereochemistry |
General purpose diagrams include:
*PV diagram
*T–s diagram
*h–s (Mollier) diagram
*Psychrometric chart
*Cooling curve
*Indicator diagram
*Saturation vapor curve
*Thermodynamic surface
Specific to weather services, there are mainly three different types of thermodynamic diagrams used:
* Skew-T log-P diagram
* Tephigram
* Emagram
All three diagrams are derived from the physical P–alpha diagram which combines pressure (P) and specific volume (alpha) as its basic coordinates. The P–alpha diagram shows a strong deformation of the grid for atmospheric conditions and is therefore not useful in atmospheric sciences. The three diagrams are constructed from the P–alpha diagram by using appropriate coordinate transformations.
Not a thermodynamic diagram in a strict sense, since it does not display the energy–area equivalence, is the
* Stüve diagram
But due to its simpler construction it is preferred in education.
Another widely-used diagram that does not display the energy–area equivalence is the θ-z diagram (Theta-height diagram), extensively used boundary layer meteorology. | 7 | Physical Chemistry |
Because one of the main purposes for biomedical engineering is to mimic body parts to sustain normal body functions, due to their biocompatible properties, biopolymers are used vastly for tissue engineering, medical devices and the pharmaceutical industry. Many biopolymers can be used for regenerative medicine, tissue engineering, drug delivery, and overall medical applications due to their mechanical properties. They provide characteristics like wound healing, and catalysis of bioactivity, and non-toxicity. Compared to synthetic polymers, which can present various disadvantages like immunogenic rejection and toxicity after degradation, many biopolymers are normally better with bodily integration as they also possess more complex structures, similar to the human body.
More specifically, polypeptides like collagen and silk, are biocompatible materials that are being used in ground-breaking research, as these are inexpensive and easily attainable materials. Gelatin polymer is often used on dressing wounds where it acts as an adhesive. Scaffolds and films with gelatin allow for the scaffolds to hold drugs and other nutrients that can be used to supply to a wound for healing.
As collagen is one of the more popular biopolymers used in biomedical science, here are some examples of their use:
Collagen based drug delivery systems: collagen films act like a barrier membrane and are used to treat tissue infections like infected corneal tissue or liver cancer. Collagen films have all been used for gene delivery carriers which can promote bone formation.
Collagen sponges: Collagen sponges are used as a dressing to treat burn victims and other serious wounds. Collagen based implants are used for cultured skin cells or drug carriers that are used for burn wounds and replacing skin.
Collagen as haemostat: When collagen interacts with platelets it causes a rapid coagulation of blood. This rapid coagulation produces a temporary framework so the fibrous stroma can be regenerated by host cells. Collagen based haemostat reduces blood loss in tissues and helps manage bleeding in organs such as the liver and spleen.
Chitosan is another popular biopolymer in biomedical research. Chitosan is derived from chitin, the main component in the exoskeleton of crustaceans and insects and the second most abundant biopolymer in the world. Chitosan has many excellent characteristics for biomedical science. Chitosan is biocompatible, it is highly bioactive, meaning it stimulates a beneficial response from the body, it can biodegrade which can eliminate a second surgery in implant applications, can form gels and films, and is selectively permeable. These properties allow for various biomedical applications of chitosan.
Chitosan as drug delivery: Chitosan is used mainly with drug targeting because it has potential to improve drug absorption and stability. In addition, chitosan conjugated with anticancer agents can also produce better anticancer effects by causing gradual release of free drug into cancerous tissue.
Chitosan as an anti-microbial agent: Chitosan is used to stop the growth of microorganisms. It performs antimicrobial functions in microorganisms like algae, fungi, bacteria, and gram-positive bacteria of different yeast species.
Chitosan composite for tissue engineering: Chitosan powder blended with alginate is used to form functional wound dressings. These dressings create a moist, biocompatible environment which aids in the healing process. This wound dressing is also biodegradable and has porous structures that allows cells to grow into the dressing. Furthermore, thiolated chitosans (see thiomers) are used for tissue engineering and wound healing, as these biopolymers are able to crosslink via disulfide bonds forming stable three-dimensional networks. | 1 | Biochemistry |
Although m6A sites could be profiled at high resolution using UV-based methods, the stoichiometry of m6A sites - the methylation status or the ratio m6A+ to m6A- for each individual site within a type of RNA - is still unknown. SCARLET (2013) and m6A-LAIC-seq (2016) allows for the quantitation of stoichiometry at a specific locus and transcriptome-wide, respectively.
Bioinformatics methods used to analyze m6A peaks do not make any prior assumptions about the sequence motifs within which m6A sites are usually found, and take into consideration all possible motifs. Therefore, it is less likely to miss sites. | 1 | Biochemistry |
Sulfuric acid is capable of causing very severe burns, especially when it is at high concentrations. In common with other corrosive acids and alkali, it readily decomposes proteins and lipids through amide and ester hydrolysis upon contact with living tissues, such as skin and flesh. In addition, it exhibits a strong dehydrating property on carbohydrates, liberating extra heat and causing secondary thermal burns. Accordingly, it rapidly attacks the cornea and can induce permanent blindness if splashed onto eyes. If ingested, it damages internal organs irreversibly and may even be fatal. Protective equipment should hence always be used when handling it. Moreover, its strong oxidizing property makes it highly corrosive to many metals and may extend its destruction on other materials. Because of such reasons, damage posed by sulfuric acid is potentially more severe than that by other comparable strong acids, such as hydrochloric acid and nitric acid.
Sulfuric acid must be stored carefully in containers made of nonreactive material (such as glass). Solutions equal to or stronger than 1.5 M are labeled "CORROSIVE", while solutions greater than 0.5 M but less than 1.5 M are labeled "IRRITANT". However, even the normal laboratory "dilute" grade (approximately 1 M, 10%) will char paper if left in contact for a sufficient time.
The standard first aid treatment for acid spills on the skin is, as for other corrosive agents, irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes to cool the tissue surrounding the acid burn and to prevent secondary damage. Contaminated clothing is removed immediately and the underlying skin washed thoroughly. | 7 | Physical Chemistry |
* Culliford, Bryan J., The Examination and Typing of Bloodstains in the Crime Laboratory, Washington, D.C.: U.S. Government Printing Office, 1971.
* Gaensslen, Robert E., Sourcebook in Forensic Serology, Immunology, and Biochemistry, Washington, D.C.: U.S. Government Printing Office, 1983.
* Kirk, Paul L., Crime Investigation, John Wiley and Son, 1974.
* Metropolitan Police Forensic Science Laboratory, Biology Methods Manual, 1978.
* Ponce, Ana Castelló; Pascual, Fernando A. Verdú, [http://projects.nfstc.org/workshops/resources/literature/Screening/10_Critical%20Revision%20of%20Presumptive%20Tests%20for%20Bloodstains.pdf "Critical Revision of Presumptive Tests for Bloodstains,"] Forensic Science Communications, vol. 1, No. 2, July 1999, pages 1–15.
* Saferstein, Richard, Forensic Science Handbook, Prentice Hall, Inc., 1982. | 3 | Analytical Chemistry |
Biohydrometallurgy is a technique in the world of metallurgy that utilizes biological agents (bacteria) to recover and treat metals such as copper. Modern biohydrometallurgy advances started with the bioleaching of copper more efficiently in the 1950's | 8 | Metallurgy |
CKLF like MARVEL transmembrane domain-containing 8 (i.e. CMTM8), previously termed chemokine-like factor superfamily 8 (i.e. CKLFSF8) has at least two isoforms, the CMTM8 and CMTM8-v2 proteins. Protein isoforms are variant products that are made by the alternative splicing of a single gene. The gene for these isoforms, CMTM8 (formerly termed CKLFSF8), is located in band 22 on the short (i.e. "p") arm of chromosome 3. The CMTM8 gene and its CMTM8 and CMTM8-v2 proteins belong to the CKLF-like MARVEL transmembrane domain-containing family of structurally and functionally related genes and proteins. The CMTM8 protein is the full-length and predominant product of the CMTM8 gene. This protein is expressed in a wide range of normal adult and fetal tissues while relatively little is known about the CMTM8-v2 protein. Studies suggest that the CMTM8 protein may be involved in the development of various cancers.
The levels of CMTM8 protein are lower in the tissues of non-small-cell lung carcinoma, colon cancer, rectal cancer, esophageal cancer, bladder cancer, stomach cancer, and glioblastoma brain tumors than in their respective adjacent normal organ tissues. The low levels of CMTM8 protein in bladder and stomach cancer tissues were associated with more aggressive diseases (e.g. presence of metastases) and poorer prognoses. These findings suggest that CMTM8 protein may inhibit the development and/or progression of the cited malignancies and therefore the CMTM8 gene functions as a tumor suppressor gene. However, further studies are required to support these conclusions and to determine if the levels of CMTM8 protein can be used as prognostic markers for these malignancies and/or as a targets for treating them. | 1 | Biochemistry |
It has been proposed that mutations in gatekeeper genes could, to an extent, offer a sort of selective advantage to the individual in which the change occurs. This is because cells with these mutations are able to replicate at a faster rate than nearby cells. This is known as "increased somatic fitness". Caretaker genes, on the other hand, confer selective disadvantage because the result is inherently decreased cellular success. However, increased somatic fitness could also arise from a mutation in a caretaker gene if mutations in tumor suppressor genes increase the net reproductive rate of the cell.
Although mutations in gatekeeper genes may lead to the same result as those of caretaker genes, namely cancer, the transcripts that gatekeeper genes encode are significantly different from those encoded by caretaker genes.
In many cases, gatekeeper genes encode a system of checks and balances that monitor cell division and death. In cases of tissue damage, for example, gatekeeper genes would ensure that balance of cell growth over cellular death remains in check. In the presence of competent gatekeeper genes, mutations of other genes would not lead to on-going growth imbalances.
Whether or not mutations in these genes confer beneficial or deleterious effects to the animal depends partially on the environmental context in which these changes occur, a context encoded by the landscaper genes. For example, tissues of the skin and colon reside in compartments of cells that rarely mix with one another. These tissues are replenished by stem cells. Mutations that occur within these cell lineages remain confined to the compartment in which they reside, increasing the future risk of cancer. This is also protective, however, because the cancer will remain confined to that specific area, rather than invading the rest of the body, a phenomenon known as metastasis.
In areas of the body compartmentalized into small subsets of cells, mutations that lead to cancer most often begin with caretaker genes. On the other hand, cancer progression in non-compartmentalized or large cell populations may be a result of initial mutations in gatekeepers.
These delineations offer a suggestion why different types of tissue within the body progress to cancer by differing mechanisms. | 1 | Biochemistry |
In the US, where the Midrex process was first developed, direct reduction was seen in the 1960s as a way of breathing new life into electric steelmaking. The techno-economic model of the mini-mill, based on flexibility and reduced plant size, was threatened by a shortage of scrap metal, and a consequent rise in its price. With the same shortage affecting metallurgical coke, a return to the blast furnace route did not seem an attractive solution.
Direct reduction is theoretically well-suited to the use of ores that are less compatible with blast furnaces (such as fine ores that clog furnaces), which are less expensive. It also requires less capital, making it a viable alternative to the two tried-and-tested methods of electric furnaces and blast furnaces.
The comparative table shows that the diversity of processes is also justified by the need for quality materials. The coking plant that feeds a battery of blast furnaces is just as expensive as the blast furnace and requires a specific quality of coal. Conversely, many direct-reduction processes are disadvantaged by the costly transformation of ore into pellets: these cost on average 70% more than raw ore. Finally, gas requirements can significantly increase investment costs: gas produced by a COREX is remarkably well-suited to feeding a Midrex unit, but the attraction of the low investment then fades. | 8 | Metallurgy |
The first discussion of obtaining an image of a surface using atoms was by King and Bigas, who showed that an image of a surface can be obtained by heating a sample and monitoring the atoms that evaporate from the surface. King and Bigas suggest that it could be possible to form an image by scattering atoms from the surface, though it was some time before this was demonstrated.
The idea of imaging with atoms instead of light was subsequently widely discussed in the literature.
The initial approach to producing a helium microscope assumed that a focussing element is required to produce a high intensity beam of atoms. An early approach was to develop an atomic mirror, which is appealing since the focussing is independent of the velocity distribution of the incoming atoms. However the material challenges to produce an appropriate surface that is macroscopically curved and defect free on an atomic length-scale has proved too challenging so far.
King and Bigas, showed that an image of a surface can be obtained by heating a sample and monitoring the atoms that evaporate from the surface. King and Bigas suggest it could be possible to form an image by scattering atoms from the surface, though it was some time before it was demonstrated.
Metastable atoms are atoms that have been excited out of the ground state, but remain in an excited state for a significant period of time. Microscopy using metastable atoms has been shown to be possible, where the metastable atoms release stored internal energy into the surface, releasing electrons that provide information on the electronic structure. The kinetic energy of the metastable atoms means that only the surface electronic structure is probed, but the large energy exchange when the metastable atom de-excites will still perturb delicate sample surfaces.
The first two-dimensional neutral helium images were obtained using a conventional Fresnel zone plate by Koch et al. in a transmission setup. Helium will not pass through a solid material, therefore a large change in the measured signal is obtained when a sample is placed between the source and the detector. By maximising the contrast and using transmission mode, it was much easier to verify the feasibility of the technique. However, the setup used by Koch et al. with a zone plate did not produce a high enough signal to observe the reflected signal from the surface at the time. Nevertheless, the focussing obtained with a zone plate offers the potential for improved resolution due to the small beam spot size in the future. Research into neutral helium microscopes that use a Fresnel zone plate is an active area in Holst’s group at the University of Bergen.
Since using a zone plate proved difficult due to the low focussing efficiency, alternative methods for forming a helium beam to produce images with atoms were explored.
Recent efforts have avoided focussing elements and instead are directly collimating a beam with a pinhole. The lack of atom optics means that the beam width will be significantly larger than in an electron microscope. The first published demonstration of a two-dimensional image formed by helium reflecting from the surface was by Witham and Sánchez, who used a pinhole to form the helium beam. A small pinhole is placed very close to a sample and the helium scattered into a large solid angle is fed to a detector. Images are collected by moving the sample around underneath the beam and monitoring how the scattered helium flux changes.
In parallel to the work by Witham and Sánchez, a proof of concept machine named the scanning helium microscope (SHeM) was being developed in Cambridge in collaboration with Dastoor's group from the University of Newcastle. The approach that was adopted was to simplify previous attempts that involved an atom mirror by using a pinhole, but to still use a conventional helium source to produce a high quality beam. Other differences from the Witham and Sánchez design include using a larger sample to pinhole distance, so that a larger variety of samples can be used and to use a smaller collection solid angle, so that it may be possible to observe more subtle contrast. These changes also reduced the total flux in the detector meaning that higher efficiency detectors are required (which in itself is an active area of research. | 7 | Physical Chemistry |
In early 1900, Max Trautz and William Lewis studied the rate of the reaction using collision theory, based on the kinetic theory of gases. Collision theory treats reacting molecules as hard spheres colliding with one another; this theory neglects entropy changes, since it assumes that the collision between molecules are completely elastic.
Lewis applied his treatment to the following reaction and obtained good agreement with experimental result.
2HI → H + I
However, later when the same treatment was applied to other reactions, there were large discrepancies between theoretical and experimental results. | 7 | Physical Chemistry |
Immunofluorescence (IF) on ethanol-fixed neutrophils is used to detect ANCA, although formalin-fixed neutrophils may be used to help differentiate ANCA patterns. ANCA can be divided into four patterns when visualised by IF; cytoplasmic ANCA (c-ANCA), C-ANCA (atypical), perinuclear ANCA (p-ANCA) and atypical ANCA (a-ANCA), also known as x-ANCA. c-ANCA shows cytoplasmic granular fluorescence with central interlobular accentuation. C-ANCA (atypical) shows cytoplasmic staining that is usually uniform and has no interlobular accentuation. p-ANCA has three subtypes, classical p-ANCA, p-ANCA without nuclear extension and granulocyte specific-antinuclear antibody (GS-ANA). Classical p-ANCA shows perinuclear staining with nuclear extension, p-ANCA without nuclear extension has perinuclear staining without nuclear extension and GS-ANA shows nuclear staining on granulocytes only. a-ANCA often shows combinations of both cytoplasmic and perinuclear staining. | 1 | Biochemistry |
The hydrolysis reaction for a hydrated metal ion in aqueous solution can be written as:
:p M + q HO ⇌ M(OH) + q H
and the corresponding formation constant as:
and associated equilibria can be written as:
:MO(OH)(s) + z H ⇌ M + (z–x) HO
:MO(OH)(s) + x HO ⇌ M + z OH
:p MO(OH)(s) + (pz–q) H ⇌ M(OH) + (pz–px–q) HO | 7 | Physical Chemistry |
MFGM may be capable of modulating immune function in the gut through distinct but potentially complementary mechanisms. Glycosylated proteins (MUC-1, MUC-15, butyrophilin, and lactadherin) and glycosylated sphingolipids from MFGM may promote the development of healthy gut microbiota by favoring beneficial Bifidobacterium species. Another key to the immunomodulatory function of MFGM may be that its structure is similar to that of the intestinal cell membrane, allowing human milk glycans (including those on glycoproteins and glycolipids) to competitively inhibit the binding of pathogens (bacteria, viruses, even toxins) to host cells.
A number of preclinical studies have demonstrated inhibitory effects of MFGM against several pathogens. Both whole bovine MFGM and its extracted lipid components were found to exhibit dose-dependent inhibition of rotavirus infectivity in vitro. Antibacterial effects of MFGM have included decreased gastric colonization and inflammation after H. pylori infection in mice; inhibition of shiga toxin gene expression by E. coli O157:H7; and decreased colonization and translocation of L. monocytogenes. Mice that were fed prophylactically with bovine whey glycoprotein fraction, including MFGM proteins, did not develop diarrhea after exposure to rotavirus. | 1 | Biochemistry |
no large clinical trials of CoQ in cancer treatment had been conducted. The US's National Cancer Institute identified issues with the few, small studies that had been carried out, stating, "the way the studies were done and the amount of information reported made it unclear if benefits were caused by the CoQ or by something else". The American Cancer Society concluded, "CoQ may reduce the effectiveness of chemo and radiation therapy, so most oncologists would recommend avoiding it during cancer treatment." | 1 | Biochemistry |
Gel electrophoresis is a method for separation and analysis of biomacromolecules (DNA, RNA, proteins, etc.) and their fragments, based on their size and charge. It is used in clinical chemistry to separate proteins by charge or size (IEF agarose, essentially size independent) and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge.
Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through a matrix of agarose or other substances. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving. Proteins are separated by the charge in agarose because the pores of the gel are too large to sieve proteins. Gel electrophoresis can also be used for the separation of nanoparticles.
Gel electrophoresis uses a gel as an anticonvective medium or sieving medium during electrophoresis, the movement of a charged particle in an electric current. Gels suppress the thermal convection caused by the application of the electric field, and can also act as a sieving medium, slowing the passage of molecules; gels can also simply serve to maintain the finished separation so that a post electrophoresis stain can be applied. DNA gel electrophoresis is usually performed for analytical purposes, often after amplification of DNA via polymerase chain reaction (PCR), but may be used as a preparative technique prior to use of other methods such as mass spectrometry, RFLP, PCR, cloning, DNA sequencing, or Southern blotting for further characterization. | 1 | Biochemistry |
eIF2B is a protein complex found in eukaryotes. It is the guanine nucleotide exchange factor for the eukaryotic initiation factor 2 and therefore converts the inactive eIF2-GDP to the active eIF2-GTP. This activation is hindered by phosphorylation of the alpha subunit of eIF2, which leads to a stable eIF2α-P-GDP-eIF2B complex and therefore inhibits translation initiation.
Human genes which encode eIF-2B proteins include:
* EIF2B1 – alpha subunit (26kDa)
* EIF2B2 – beta subunit (39kDa)
* EIF2B3 – gamma subunit (58kDa)
* EIF2B4 – delta subunit (67kDa)
* EIF2B5 – epsilon subunit (82kDa) | 1 | Biochemistry |
Global sensitivity measures such as the Hill coefficient do not characterise the local behaviours of the s-shaped curves. Instead, these features are well captured by the response coefficient measure defined as:
In systems biology, such responses are referred to as elasticities. | 1 | Biochemistry |
If water is left to stand in a tube for an extended period, the chemical characteristics of the water change as the mixed scale and corrosion products are deposited. In addition any loose scale that is not well adhered to the wall will not be flushed away and air dissolved in the water will form bubbles, producing air pockets. These processes can lead to a number of problems mainly on horizontal tube runs. Particles of scale that do not adhere to the walls and are not washed away tend to fall into the bottom of the tube producing a coarse porous deposit. Air pockets that develop in horizontal runs disrupt the formation of protective scales in two areas: the water lines at the sides, and the air space at the top of the tube.
In each of the areas that the scale has been disrupted there is the possibility of the initiation of Type 1 pitting. Once pitting has initiated, then even after the tube has been put back into service, the pit will continue to develop until the wall has perforated. This form of attack is often associated with the commissioning of a system. Once a system has been commissioned it should be either put immediately into service or drained down and dried by flushing with compressed air otherwise pitting may initiate. If either of these options is not possible then the system should be flushed through regularly until it is put into use. | 8 | Metallurgy |
In X-ray crystallography, crystallographic disorder describes the cocrystallization of more than one rotamer, conformer, or isomer where the center of mass of each form is identical or unresolvable. As a consequence of disorder, the crystallographic solution is the sum of the various forms. In many cases, the components of the disorder are equally abundant, and, in other cases, the weighting coefficients for each component differ. Disorder can entail a pair or several components, and usually arises when the forms are nearly equal in energy and the crystal lattice is sufficiently spacious to accommodate the various components. | 3 | Analytical Chemistry |
This section contains a discussion of the three most important properties of time reversal in quantum mechanics; chiefly,
# that it must be represented as an anti-unitary operator,
# that it protects non-degenerate quantum states from having an electric dipole moment,
# that it has two-dimensional representations with the property (for fermions).
The strangeness of this result is clear if one compares it with parity. If parity transforms a pair of quantum states into each other, then the sum and difference of these two basis states are states of good parity. Time reversal does not behave like this. It seems to violate the theorem that all abelian groups be represented by one-dimensional irreducible representations. The reason it does this is that it is represented by an anti-unitary operator. It thus opens the way to spinors in quantum mechanics.
On the other hand, the notion of quantum-mechanical time reversal turns out to be a useful tool for the development of physically motivated quantum computing and simulation settings, providing, at the same time, relatively simple tools to assess their complexity. For instance, quantum-mechanical time reversal was used to develop novel boson sampling schemes and to prove the duality between two fundamental optical operations, beam splitter and squeezing transformations. | 7 | Physical Chemistry |
Nitrene reactions include:
* Nitrene C–H insertion. A nitrene can easily insert into a carbon to hydrogen covalent bond yielding an amine or amide. A singlet nitrene reacts with retention of configuration. In one study a nitrene, formed by oxidation of a carbamate with potassium persulfate, gives an insertion reaction into the palladium to nitrogen bond of the reaction product of palladium(II) acetate with 2-phenylpyridine to methyl N-(2-pyridylphenyl)carbamate in a cascade reaction:
:A nitrene intermediate is suspected in this C–H insertion involving an oxime, acetic anhydride leading to an isoindole:
* Nitrene cycloaddition. With alkenes, nitrenes react to form aziridines, very often with nitrenoid precursors such as nosyl- or tosyl-substituted [N-(phenylsulfonyl)imino]phenyliodinane (PhI=NNs or PhI=NTs respectively)) but the reaction is known to work directly with the sulfonamide in presence of a transition metal based catalyst such as copper, palladium, or gold:
:In most cases, however, [N-(p-nitrophenylsulfonyl)imino]phenyliodinane (PhI=NNs) is prepared separately as follows:
:Nitrene transfer takes place next:
:In this particular reaction both the cis-stilbene illustrated and the trans form (not depicted) result in the same trans-aziridine product, suggesting a two-step reaction mechanism. The energy difference between triplet and singlet nitrenes can be very small in some cases, allowing interconversion at room temperature. Triplet nitrenes are thermodynamically more stable but react stepwise allowing free rotation and thus producing a mixture of stereochemistry.
* Arylnitrene ring-expansion and ring-contraction: Aryl nitrenes show ring expansion to 7-membered ring cumulenes, ring opening reactions and nitrile formations many times in complex reaction paths. For instance the azide 2 in the scheme below trapped in an argon matrix at 20 K on photolysis expels nitrogen to the triplet nitrene 4 (observed experimentally with ESR and ultraviolet-visible spectroscopy) which is in equilibrium with the ring-expansion product 6.
:The nitrene ultimately converts to the ring-opened nitrile 5 through the diradical intermediate 7. In a high-temperature reaction, FVT at 500–600 °C also yields the nitrile 5 in 65% yield. | 0 | Organic Chemistry |
In analytical chemistry, sub-sampling is a procedure by which a small, representative sample is taken from a larger sample. Good sub-sampling technique becomes important when the large sample is not homogeneous. | 3 | Analytical Chemistry |
Electrical properties include both electrical resistivity and conductivity, dielectric strength, electromagnetic permeability, and permittivity. Electrical conductors such as metals and alloys are contrasted with electrical insulators such as glasses and ceramics. Semiconductors behave somewhere in between. Whereas conductivity in metals is caused by electrons, both electrons and holes contribute to current in semiconductors. Alternatively, ions support electric current in ionic conductors.
Many materials also exhibit superconductivity at low temperatures; they include metallic elements such as tin and aluminium, various metallic alloys, some heavily doped semiconductors, and certain ceramics. The electrical resistivity of most electrical (metallic) conductors generally decreases gradually as the temperature is lowered, but remains finite. In a superconductor, however, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.
A dielectric, or electrical insulator, is a substance that is highly resistant to the flow of electric current. A dielectric, such as plastic, tends to concentrate an applied electric field within itself, which property is used in capacitors. A capacitor is an electrical device that can store energy in the electric field between a pair of closely spaced conductors (called plates). When voltage is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each plate. Capacitors are used in electrical circuits as energy-storage devices, as well as in electronic filters to differentiate between high-frequency and low-frequency signals. | 7 | Physical Chemistry |
The N-phenylimino derivative of CDI can be formed in a Wittig-like reaction with triphenylphosphine phenylimide.
:OCIm + PhP=NPh → PhN=CIm + PhPO
CDI can act as a carbonyl equivalent in the formation of tetronic acids or pulvinones from hydroxyketones and diketones in basic conditions.
An alcohol treated with at least 3 equivalents of an activated halide (such as allyl bromide or iodomethane) and CDI yields the corresponding halide with good yield. Bromination and iodination work best, though this reaction does not preserve the stereochemistry of the alcohol. In a similar context, CDI is often used in dehydration reactions.
As CDI is an equivalent of phosgene, it can be used in similar reaction, however, with increased selectivity: it allows the synthesis of asymmetric bis alkyl carbonates | 0 | Organic Chemistry |
Sodium dithiophosphate is the salt with the formula NaPSO. It is usually supplied as the hydrated solid or as an aqueous solution together with other thiophosphates such as sodium monothiophosphate and sodium trithiophosphate. It is a colorless compound, but commercial samples can appear dark owing to the presence of impurities. It is used to facilitate the isolation of molybdenum from its ores. | 8 | Metallurgy |
In an ideal conductor, where atoms are arranged in a perfect lattice structure, the electrons moving through it would experience no collisions and electromigration would not occur. In real conductors, defects in the lattice structure and the random thermal vibration of the atoms about their positions causes electrons to collide with the atoms and scatter, which is the source of electrical resistance (at least in metals; see electrical conduction). Normally, the amount of momentum imparted by the relatively low-mass electrons is not enough to permanently displace the atoms. However, in high-power situations (such as with the increasing current draw and decreasing wire sizes in modern VLSI microprocessors), if many electrons bombard the atoms with enough force to become significant, this will accelerate the process of electromigration by causing the atoms of the conductor to vibrate further from their ideal lattice positions, increasing the amount of electron scattering. High current density increases the number of electrons scattering against the atoms of the conductor, and hence the rate at which those atoms are displaced.
In integrated circuits, electromigration does not occur in semiconductors directly, but in the metal interconnects deposited onto them (see semiconductor device fabrication).
Electromigration is exacerbated by high current densities and the Joule heating of the conductor (see electrical resistance), and can lead to eventual failure of electrical components. Localized increase of current density is known as current crowding. | 7 | Physical Chemistry |
Glycogenin-1 is an enzyme that is involved in the biosynthesis of glycogen. It is capable of self-glucosylation, forming an oligosaccharide primer that serves as a substrate for glycogen synthase. This is done through an inter-subunit mechanism. It also plays a role in glycogen metabolism regulation. Recombinant human glycogenin-1 was expressed in E. coli and purified using conventional chromatography techniques. | 1 | Biochemistry |
Embryo transfer can be performed after various durations of embryo culture, conferring different stages in embryogenesis. The main stages at which embryo transfer is performed are cleavage stage (day 2 to 4 after co-incubation) or the blastocyst stage (day 5 or 6 after co-incubation).
Because in vivo, a cleavage stage embryo still resides in the fallopian tube and it is known that the nutritional environment of the uterus is different from that of the tube, it is postulated that this may cause stress on the embryo if transferred on day 3 resulting in reduced implantation potential. A blastocyst stage embryo does not have this problem as it is best suited for the uterine environment [https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD002118.pub5/full]
Embryos who reach the day 3 cell stage can be tested for chromosomal or specific genetic defects prior to possible transfer by preimplantation genetic diagnosis (PGD). Transferring at the blastocyst stage confers a significant increase in live birth rate per transfer, but also confers a decreased number of embryos available for transfer and embryo cryopreservation, so the cumulative clinical pregnancy rates are increased with cleavage stage transfer. It is uncertain whether there is any difference in live birth rate between transfer on day two or day three after fertilization.
Monozygotic twinning is not increased after blastocyst transfer compared with cleavage-stage embryo transfer.
There is a significantly higher odds of preterm birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) among births having reached the blastocyst stage compared with cleavage stage. Because of increased female embryo mortality due to epigenetic modifications induced by extended culture, blastocyst transfer leads to more male births (56.1% male) versus 2 or 3 day transfer (a normal sex ratio of 51.5% male). | 1 | Biochemistry |
For each uniform structure, there also exists a related but different structure, called a line-slip arrangement.
The differences between uniform and line-slip structures are marginal and difficult to spot from images of the sphere packings. However, by comparing their rolled-out contact networks, one can spot that certain lines (which represent contacts) are missing.
All spheres in a uniform structure have the same number of contacts, but the number of contacts for spheres in a line slip may differ from sphere to sphere. For the example line slip in the image on the right side, some spheres count five and others six contacts. Thus a line slip structure is characterised by these gaps or loss of contacts.
Such a structure is termed line slip because the losses of contacts occur along a line in the rolled-out contact network. It was first identified by Picket et al., but not termed line slip.
The direction, in which the loss of contacts occur can be denoted in the phyllotactic notation , since each number represents one of the lattice vectors in the hexagonal lattice. This is usually indicated by a bold number.
By shearing the row of spheres below the loss of contact against a row above the loss of contact, one can regenerate two uniform structures related to this line slip. Thus, each line slip is related to two adjacent uniform structures, one at a higher and one at a lower diameter ratio .
Winkelmann et al. were the first to experimentally realise such a structure using soap bubbles in a system of deformable spheres. | 3 | Analytical Chemistry |
Alaska had fewer than 4,000 gallons of dispersants available at the time of the Exxon Valdez oil spill, and no aircraft with which to dispense them. The dispersants introduced were relatively ineffective due to insufficient wave action to mix the oil and water, and their use was shortly abandoned.
A report by David Kirby for TakePart found that the main component of the Corexit 9527 formulation used during Exxon Valdez cleanup, 2-butoxyethanol, was identified as "one of the agents that caused liver, kidney, lung, nervous system, and blood disorders among cleanup crews in Alaska following the 1989 Exxon Valdez spill." | 2 | Environmental Chemistry |
The CBP of this type, also known as parG is composed of:
* N-terminal NTPase binding domain
* Ribon-Helix-Helix (RHH) domain
For this type, the parS site is called parC. | 1 | Biochemistry |
Siefert writes:
: proved a remarkable relation which allows to express the free energy difference between two equilibrium systems by a nonlinear average over the work required to drive the system in a non-equilibrium process from one state to the other. By comparing probability distributions for the work spent in the original process with the time-reversed one, Crooks found a “refinement” of the Jarzynski relation (JR), now called the Crooks fluctuation theorem. Both, this relation and another refinement of the JR, the Hummer-Szabo relation became particularly useful for determining free energy differences and landscapes of biomolecules. These relations are the most prominent ones within a class of exact results (some of which found even earlier and then rediscovered) valid for non-equilibrium systems driven by time-dependent forces. A close analogy to the JR, which relates different equilibrium states, is the Hatano-Sasa relation that applies to transitions between two different non-equilibrium steady states.
This is shown to be a special case of a more general relation. | 7 | Physical Chemistry |
The energetic requirements of a body are composed of the basal metabolic rate (BMR) and the physical activity level (ERAT, exercise-related activity thermogenesis). This caloric requirement can be met with protein, fat, carbohydrates, or a mixture of those. Glucose is the general metabolic fuel, and can be metabolized by any cell. Fructose and some other nutrients can be metabolized only in the liver, where their metabolites transform into either glucose stored as glycogen in the liver and in muscles, or into fatty acids stored in adipose tissue.
Because of the blood–brain barrier, getting nutrients to the human brain is especially dependent on molecules that can pass this barrier. The brain itself consumes about 18% of the basal metabolic rate: on a total daily intake of , this equates to , or about 80 g of glucose. About 25% of total body glucose consumption occurs in the brain.
Glucose can be obtained directly from dietary sugars and by the breakdown of other carbohydrates. In the absence of dietary sugars and carbohydrates, glucose is obtained from the breakdown of stored glycogen. Glycogen is a readily-accessible storage form of glucose, stored in notable quantities in the liver and skeletal muscle.
When the glycogen reserve is depleted, glucose can be obtained from the breakdown of fats from adipose tissue. Fats are broken down into glycerol and free fatty acids, with the glycerol being turned into glucose in the liver via the gluconeogenesis pathway.
When even the glucose made from glycerol reserves start declining, the liver starts producing ketone bodies. Ketone bodies are short-chain derivatives of the free fatty acids mentioned in the previous paragraph, and can cross the blood–brain barrier, meaning they can be used by the brain as an alternative metabolic fuel. Fatty acids can be used directly as an energy source by most tissues in the body, but are themselves too ionized to cross the blood–brain barrier. | 1 | Biochemistry |
Atmospheric nitrogen is inaccessible to most organisms, because its triple covalent bond is very strong. Most take up fixed nitrogen from various sources. For every 100 atoms of carbon, roughly 2 to 20 atoms of nitrogen are assimilated. The atomic ratio of carbon (C) : nitrogen (N) : phosphorus (P) observed on average in planktonic biomass was originally described by Alfred Redfield, who determined the stoichiometric relationship between C:N:P atoms, The Redfield Ratio, to be 106:16:1. | 1 | Biochemistry |
Amyloid-beta precursor protein (APP) is an integral membrane protein expressed in many tissues and concentrated in the synapses of neurons. It functions as a cell surface receptor and has been implicated as a regulator of synapse formation, neural plasticity, antimicrobial activity, and iron export. It is coded for by the gene APP and regulated by substrate presentation. APP is best known as the precursor molecule whose proteolysis generates amyloid beta (Aβ), a polypeptide containing 37 to 49 amino acid residues, whose amyloid fibrillar form is the primary component of amyloid plaques found in the brains of Alzheimer's disease patients. | 1 | Biochemistry |
Putrefaction is the fifth stage of death, following pallor mortis, livor mortis, algor mortis, and rigor mortis. This process references the breaking down of a body of an animal post-mortem. In broad terms, it can be viewed as the decomposition of proteins, and the eventual breakdown of the cohesiveness between tissues, and the liquefaction of most organs. This is caused by the decomposition of organic matter by bacterial or fungal digestion, which causes the release of gases that infiltrate the body's tissues, and leads to the deterioration of the tissues and organs.
The approximate time it takes putrefaction to occur is dependent on various factors. Internal factors that affect the rate of putrefaction include the age at which death has occurred, the overall structure and condition of the body, the cause of death, and external injuries arising before or after death. External factors include environmental temperature, moisture and air exposure, clothing, burial factors, and light exposure. Body farms are facilities that study the way various factors affect the putrefaction process.
The first signs of putrefaction are signified by a greenish discoloration on the outside of the skin on the abdominal wall corresponding to where the large intestine begins, as well as under the surface of the liver.
Certain substances, such as carbolic acid, arsenic, strychnine, and zinc chloride, can be used to delay the process of putrefaction in various ways based on their chemical make up. | 1 | Biochemistry |
Levofenfluramine (INN), or (−)-3-trifluoromethyl-N-ethylamphetamine, also known as (−)-fenfluramine or (R)-fenfluramine, is a drug of the amphetamine family that, itself (i.e., in enantiopure form), was never marketed. It is the levorotatory enantiomer of fenfluramine, the racemic form of the compound, whereas the dextrorotatory enantiomer is dexfenfluramine. Both fenfluramine and dexfenfluramine are anorectic agents that have been used clinically in the treatment of obesity (and hence, levofenfluramine has been as well since it is a component of fenfluramine). However, they have since been discontinued due to reports of causing cardiovascular conditions such as valvular heart disease and pulmonary hypertension, adverse effects that are likely to be caused by excessive stimulation of 5-HT receptors expressed on heart valves.
Dexfenfluramine is believed to be solely responsible for the appetite suppressant properties of fenfluramine, of which it has been demonstrated to mediate predominantly via activation of postsynaptic 5-HT and 5-HT receptors through a combination of indirect serotonin releasing agent and direct serotonin receptor agonist activities (the latter of which are mediated fully by its active metabolite dexnorfenfluramine). Contrarily, levofenfluramine is thought to contribute only to unwanted side effects. Paradoxically, however, it has been shown that levofenfluramine too acts as a relatively potent releaser of serotonin, though with approximately 1/3 of the efficacy of dexfenfluramine. As such, it would be expected to possess some degree of appetite suppressant properties as well, yet it does not. A potential explanation as to why levofenfluramine is not similarly an effective anorectic is that it has also been found to behave as a dopamine receptor antagonist, which, as dopamine antagonists like atypical antipsychotics are associated with causing increased appetite and weight gain—effects that their actions on dopamine receptors have been implicated in playing a role in the development of, is an action that could in theory cancel out the hypothetical serotonergically-mediated appetite suppressant effects of the compound. However, this is speculation and has not been proven.
Levonorfenfluramine, an active metabolite of levofenfluramine, is also a fairly potent serotonin releasing agent (with a potency of approximately 1/2 that of norfenfluramine and 1/6 that of dexfenfluramine) and, similarly to dexnorfenfluramine, is a 5-HT and 5-HT receptor agonist, as well as a somewhat less potent norepinephrine reuptake inhibitor (about 1/2 that of its efficacy as a serotonin releaser). As such, it likely contributes significantly to the biological activity—though not necessarily appetite suppressant effects—of not only levofenfluramine but of racemic fenfluramine as well. In contrast to levonorfenfluramine, levofenfluramine is virtually inactive as a reuptake inhibitor or releaser of norepinephrine, and neither compound has any effect on dopamine reuptake or release. | 4 | Stereochemistry |
The first potentiometric titration was carried out in 1893 by Robert Behrend at Ostwald's Institute in Leipzig. He titrated mercurous solution with potassium chloride, potassium bromide, and potassium iodide. He used a mercury electrode along with a mercury/mercurous nitrate reference electrode. He found that in a cell composed of mercurous nitrate and mercurous nitrate/mercury, the initial voltage is 0. If potassium chloride is added to mercurous nitrate on one side, mercury (I) chloride is precipitated. This decreased the osmotic pressure of mercury (I) ions on the side and creates a potential difference. This potential difference increases slowly as additional potassium chloride is added, but then increases more rapidly. He found the greatest potential difference is achieved once all of the mercurous nitrate has been precipitated. This was used to discern end points of titrations.
Wilhelm Böttger then developed the tool of potentiometric titration while working at Ostwald's Institute. He used potentiometric titration to observe the differences in titration between strong and weak acids, as well as the behavior of polybasic acids. He introduced the idea of using potentiometric titrations for acids and bases that could not be titrated in conjunction with a colorimetric indicator
Potentiometric titrations were first used for redox titrations by Crotogino. He titrated halide ions with potassium permanganate using a shiny platinum electrode and a calomel electrode. He said that if an oxidizing agent is added to a reducing solution then the equilibrium between the reducing substance and reaction product will shift towards the reaction product. This changes the potential very slowly until the amount of reducing substance becomes very small. A large change in potential will occur then once a small addition of the titrating solution is added, as the final amounts of reducing agent are removed and the potential corresponds solely to the oxidizing agent. This large increase in potential difference signifies the endpoint of the reaction. | 3 | Analytical Chemistry |
Progesterone binds extensively to plasma proteins, including albumin (50–54%) and transcortin (43–48%). It has similar affinity for albumin relative to the PR. | 0 | Organic Chemistry |
For ice, recrystallization refers to the growth of larger crystals at the expense of smaller ones. Some biological antifreeze proteins have been shown to inhibit this process, and the effect may be relevant in freezing-tolerant organisms. | 3 | Analytical Chemistry |
Leaves which have a petiole (leaf stalk) are said to be petiolate.
Sessile (epetiolate) leaves have no petiole and the blade attaches directly to the stem. Subpetiolate leaves are nearly petiolate or have an extremely short petiole and may appear to be sessile.
In clasping or decurrent leaves, the blade partially surrounds the stem.
When the leaf base completely surrounds the stem, the leaves are said to be perfoliate, such as in Eupatorium perfoliatum.
In peltate leaves, the petiole attaches to the blade inside the blade margin.
In some Acacia species, such as the koa tree (Acacia koa), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. There may or may not be normal pinnate leaves at the tip of the phyllode.
A stipule, present on the leaves of many dicotyledons, is an appendage on each side at the base of the petiole, resembling a small leaf. Stipules may be lasting and not be shed (a stipulate leaf, such as in roses and beans), or be shed as the leaf expands, leaving a stipule scar on the twig (an exstipulate leaf).
The situation, arrangement, and structure of the stipules is called the "stipulation".
;Free, lateral: As in Hibiscus.
;Adnate: Fused to the petiole base, as in Rosa.
;Ochreate: Provided with ochrea, or sheath-formed stipules, as in Polygonaceae; e.g., rhubarb.
;Encircling the petiole base: | 5 | Photochemistry |
Theodor W. Hänsch and John L. Hall shared half of the 2005 Nobel Prize in Physics for contributions to the development of laser-based precision spectroscopy, including the optical frequency-comb technique. The other half of the prize was awarded to Roy Glauber.
Also in 2005, the femtosecond comb technique was extended to the extreme ultraviolet range, enabling frequency metrology in that region of the spectrum. | 7 | Physical Chemistry |
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