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When beer at typical concentration is subjected to reverse osmosis, both water and alcohol pass across the membrane more readily than other components, leaving a "beer concentrate". The concentrate is then diluted with fresh water to restore the non-volatile components to their original intensity. | 3 | Analytical Chemistry |
Second generation proton sponges are known with even higher basicity. 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene or HMPN is prepared from 1,8-diaminonaphthalene by reaction with tris(dimethylamino)bromophosphonium bromide in the presence of triethylamine. HMPN has a pK of 29.9 in acetonitrile which is more than 11 orders of magnitude higher than Proton Sponge.
The aromatization of an additional ring in 4,12-Dihydrogen-4,8,12-triazatriangulene is utilized by Al-Yassiri and Puchta to get a representative for a new class of Δ-shaped proton sponges. This compound has a calculated proton affinity of 254 kcal/mol (B3LYP/6-311+G**) and is therefore between 1,8-Bis(dimethylamino)naphthalene and HMPN. | 0 | Organic Chemistry |
bonds adjacent to the carbonyl in ketones are more acidic pK ≈ 20) than the bonds in alkane (pK ≈ 50). This difference reflects resonance stabilization of the enolate ion that is formed upon deprotonation. The relative acidity of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl compounds. The acidity of the α-hydrogen also allows ketones and other carbonyl compounds to react as nucleophiles at that position, with either stoichiometric and catalytic base. Using very strong bases like lithium diisopropylamide (LDA, pK of conjugate acid ~36) under non-equilibrating conditions (–78 °C, 1.1 equiv LDA in THF, ketone added to base), the less-substituted kinetic enolate is generated selectively, while conditions that allow for equilibration (higher temperature, base added to ketone, using weak or insoluble bases, e.g., sodium ethoxide| in ethanol|, or NaH) provides the more-substituted thermodynamic enolate.
Ketones are also weak bases, undergoing protonation on the carbonyl oxygen in the presence of Brønsted acids. Ketonium ions (i.e., protonated ketones) are strong acids, with pK values estimated to be somewhere between –5 and –7. Although acids encountered in organic chemistry are seldom strong enough to fully protonate ketones, the formation of equilibrium concentrations of protonated ketones is nevertheless an important step in the mechanisms of many common organic reactions, like the formation of an acetal, for example. Acids as weak as pyridinium cation (as found in pyridinium tosylate) with a pK of 5.2 are able to serve as catalysts in this context, despite the highly unfavorable equilibrium constant for protonation (K ). | 0 | Organic Chemistry |
Similar to imprint nanolithography, capillary nanolithography employs a patterned elastomeric mold. However, instead of utilizing high pressure, when the temperature is raised above the Tg, capillary forces enable the polymer to fill the voids within the mold. Suh and Jon used molds made from (PUA). These were placed on spin coated, water-soluble polymer, polyethylene glycol (PEG), which was raised above PEG's Tg. This study found that the addition of nanotopography increased the contact angle, and this increase was dependent on the height of the nanotopography. Often, this technique produces a meniscus on the tip of the protruding nanostructures, characteristic of capillary action. The mold can later be dissolved away. Combinatorial lithography approaches are also used. One study used capillarity to fill PDMS molds with PUA, first partially curing the polymer resin with UV light. After microstructures were formed, pressure was applied to fabricate nanostructures, and UV curing was used again. This study is a good example of the use of hierarchical structures to increase surface hydrophobicity. | 7 | Physical Chemistry |
The protein AKT1 (also known as Protein Kinase B or PKB) in the PI3K/AKT/mTOR pathway is an important driver of the tumor glycolytic phenotype and stimulates ATP generation. AKT1 stimulates glycolysis by increasing the expression and membrane translocation of glucose transporters and by phosphorylating key glycolytic enzymes, such as hexokinase and phosphofructokinase 2. This leads to inhibition of forkhead box subfamily O transcription factors, leading to the increase of glycolytic capacity. Activated mTOR stimulates protein and lipid biosynthesis and cell growth in response to sufficient nutrient and energy conditions and is often constitutively activated during tumorigenesis. mTOR directly stimulates mRNA translation and ribosome biogenesis, and indirectly causes other metabolic changes by activating transcription factors such as hypoxia-inducible factor 1 (HIF1A). The subsequent HIF1-dependent metabolic changes are a major determinant of the glycolytic phenotype downstream of PI3K, AKT1 and mTOR. | 1 | Biochemistry |
Genome size varies among different organisms and the cloning vector must be selected accordingly. For a large genome, a vector with a large capacity should be chosen so that a relatively small number of clones are sufficient for coverage of the entire genome. However, it is often more difficult to characterize an insert contained in a higher capacity vector.
Below is a table of several kinds of vectors commonly used for genomic libraries and the insert size that each generally holds. | 1 | Biochemistry |
Developmental processes provide an example of how changes in synexpression control networks could significantly affect an organism's capacity to evolve and adapt effectively. In animals, it is often beneficial for appendages to co-evolve, and it has been observed that fore-and hind-limbs share expression of Hox genes early in metazoan development. Thus, changes in the regulatory patterns of these genes would affect the development of both the fore- and hind-limbs, facilitating co-evolution. | 1 | Biochemistry |
A dye-sensitized solar cell (DSSC, DSC, DYSC or Grätzel cell) is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a photoelectrochemical system. The modern version of a dye solar cell, also known as the Grätzel cell, was originally co-invented in 1988 by Brian O'Regan and Michael Grätzel at UC Berkeley and this work was later developed by the aforementioned scientists at the École Polytechnique Fédérale de Lausanne (EPFL) until the publication of the first high efficiency DSSC in 1991. Michael Grätzel has been awarded the 2010 Millennium Technology Prize for this invention.
The DSSC has a number of attractive features; it is simple to make using conventional roll-printing techniques, is semi-flexible and semi-transparent which offers a variety of uses not applicable to glass-based systems, and most of the materials used are low-cost. In practice it has proven difficult to eliminate a number of expensive materials, notably platinum and ruthenium, and the liquid electrolyte presents a serious challenge to making a cell suitable for use in all weather. Although its conversion efficiency is less than the best thin-film cells, in theory its price/performance ratio should be good enough to allow them to compete with fossil fuel electrical generation by achieving grid parity. Commercial applications, which were held up due to chemical stability problems, had been forecast in the European Union Photovoltaic Roadmap to significantly contribute to renewable electricity generation by 2020. | 5 | Photochemistry |
Albert Rakoto Ratsimamanga (28 December 1907 – 16 September 2001) was a Malagasy physician, biochemist and diplomat. Born into a disgraced royal family; Ratsimamanga trained as a doctor of exotic medicine in French Madagascar and France, where he pioneered modern nutraceuticals. Ratsimamanga returned to Madagascar and, with his wife, Suzanne Urverg-Ratsimamanga, in 1957, established the which specialised in herbal medicine.
While in France, Ratsimamanga was involved in Madagascars independence efforts, and after independence, he became the Malagasy Republics first ambassador to France and helped shape its foreign affairs. Ratsimamanga is considered one of Madagascars most renowned scholars and bestowed upon him the highest orders of merits nationally and internationally. He was also one of the founders of The World Academy of Sciences (1983) and the African Academy of Sciences (1985), and was selected Madagascars Man of the Century. | 1 | Biochemistry |
Anti-histone antibodies are found in the serum of up to 75–95% of people with drug-induced lupus and 75% of idiopathic SLE. Unlike anti-dsDNA antibodies in SLE, these antibodies do not fix complement. Although they are most commonly found in drug induced lupus, they are also found in some cases of SLE, scleroderma, rheumatoid arthritis and undifferentiated connective tissue disease. Many drugs are known to cause drug induced lupus and they produce various antigenic targets within the nucleosome that are often cross reactive with several histone proteins and DNA. Procainamide causes a form of drug-induced lupus that produces antibodies to the histone H2A and H2B complex. | 1 | Biochemistry |
By using the first law of thermodynamics, this internal energy can be expressed as a pressure, that is
where this expression remains valid for temperatures much smaller than the Fermi temperature. This pressure is known as the degeneracy pressure. In this sense, systems composed of fermions are also referred as degenerate matter.
Standard stars avoid collapse by balancing thermal pressure (plasma and radiation) against gravitational forces. At the end of the star lifetime, when thermal processes are weaker, some stars may become white dwarfs, which are only sustained against gravity by electron degeneracy pressure. Using the Fermi gas as a model, it is possible to calculate the Chandrasekhar limit, i.e. the maximum mass any star may acquire (without significant thermally generated pressure) before collapsing into a black hole or a neutron star. The latter, is a star mainly composed of neutrons, where the collapse is also avoided by neutron degeneracy pressure.
For the case of metals, the electron degeneracy pressure contributes to the compressibility or bulk modulus of the material. | 7 | Physical Chemistry |
In 1805, Thomas Young defined the contact angle θ by analyzing the forces acting on a fluid droplet resting on a solid surface surrounded by a gas.
where
: = Interfacial tension between the solid and gas
: = Interfacial tension between the solid and liquid
: = Interfacial tension between the liquid and gas
θ can be measured using a contact angle goniometer.
Wenzel determined that when the liquid is in intimate contact with a microstructured surface, θ will change to θ
where r is the ratio of the actual area to the projected area. Wenzel's equation shows that microstructuring a surface amplifies the natural tendency of the surface. A hydrophobic surface (one that has an original contact angle greater than 90°) becomes more hydrophobic when microstructured – its new contact angle becomes greater than the original. However, a hydrophilic surface (one that has an original contact angle less than 90°) becomes more hydrophilic when microstructured – its new contact angle becomes less than the original.
Cassie and Baxter found that if the liquid is suspended on the tops of microstructures, θ will change to θ:
where φ is the area fraction of the solid that touches the liquid. Liquid in the Cassie–Baxter state is more mobile than in the Wenzel state.
We can predict whether the Wenzel or Cassie–Baxter state should exist by calculating the new contact angle with both equations. By a minimization of free energy argument, the relation that predicted the smaller new contact angle is the state most likely to exist. Stated in mathematical terms, for the Cassie–Baxter state to exist, the following inequality must be true.
A recent alternative criterion for the Cassie–Baxter state asserts that the Cassie–Baxter state exists when the following 2 criteria are met:1) Contact line forces overcome body forces of unsupported droplet weight and 2) The microstructures are tall enough to prevent the liquid that bridges microstructures from touching the base of the microstructures.
A new criterion for the switch between Wenzel and Cassie-Baxter states has been developed recently based on surface roughness and surface energy. The criterion focuses on the air-trapping capability under liquid droplets on rough surfaces, which could tell whether Wenzels model or Cassie-Baxters model should be used for certain combination of surface roughness and energy.
Contact angle is a measure of static hydrophobicity, and contact angle hysteresis and slide angle are dynamic measures. Contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. When a pipette injects a liquid onto a solid, the liquid will form some contact angle. As the pipette injects more liquid, the droplet will increase in volume, the contact angle will increase, but its three-phase boundary will remain stationary until it suddenly advances outward. The contact angle the droplet had immediately before advancing outward is termed the advancing contact angle. The receding contact angle is now measured by pumping the liquid back out of the droplet. The droplet will decrease in volume, the contact angle will decrease, but its three-phase boundary will remain stationary until it suddenly recedes inward. The contact angle the droplet had immediately before receding inward is termed the receding contact angle. The difference between advancing and receding contact angles is termed contact angle hysteresis and can be used to characterize surface heterogeneity, roughness, and mobility. Surfaces that are not homogeneous will have domains that impede motion of the contact line. The slide angle is another dynamic measure of hydrophobicity and is measured by depositing a droplet on a surface and tilting the surface until the droplet begins to slide. In general, liquids in the Cassie–Baxter state exhibit lower slide angles and contact angle hysteresis than those in the Wenzel state. | 6 | Supramolecular Chemistry |
Since eIF2 is essential for most forms of translation initiation and therefore protein synthesis, defects in eIF2 are often lethal. The protein is highly conserved among evolutionary remote species - indicating a large impact of mutations on cell viability. Therefore, no diseases directly related to mutations in eIF2 can be observed. However, there are many illnesses caused by down-regulation of eIF2 through its upstream kinases. For example, increased concentrations of active PKR and inactive (phosphorylated) eIF2 were found in patients with neurodegenerative diseases such as Alzheimers, Parkinsons, and Huntingtons disease. There is also one proven example of a disease related to the GEF eIF2B. Mutations in all of the five subunits of eIF2B are associated with Vanishing White Matter (VWM) disease, a genetic leukodystrophy which causes the brains white matter to degenerate and disappear. It is still not fully understood why only brain cells seem to be affected by these defects. Potentially reduced levels of unstable regulatory proteins might play a role in the development of the diseases mentioned. | 1 | Biochemistry |
Several points of high symmetry are of special interest – these are called critical points.
Other lattices have different types of high-symmetry points. They can be found in the illustrations below. | 3 | Analytical Chemistry |
In polymers, such as plastics, thermal degradation refers to a type of polymer degradation where damaging chemical changes take place at elevated temperatures, without the simultaneous involvement of other compounds such as oxygen. Simply put, even in the absence of air, polymers will begin to degrade if heated high enough. It is distinct from thermal-oxidation, which can usually take place at less elevated temperatures.
The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature on this. Polymer devolatilization is similarly effected.
At high temperatures, the components of the long chain backbone of the polymer can break (chain scission) and react with one another (cross-link) to change the properties of the polymer. These reactions result in changes to the molecular weight (and molecular weight distribution) of the polymer and can affect its properties by causing reduced ductility and increased embrittlement, chalking, scorch, colour changes, cracking and general reduction in most other desirable physical properties. | 7 | Physical Chemistry |
There are several ways to retrieve the lost phases. The phase problem must be solved in x-ray crystallography, neutron crystallography, and electron crystallography.
Not all of the methods of phase retrieval work with every wavelength (x-ray, neutron, and electron) used in crystallography. | 3 | Analytical Chemistry |
The EBF was founded in the fall of 2006 at the initiative of twelve pharmaceutical companies, all of them having bioanalytical laboratory activities in Europe. The goal of bringing these companies together was to implement a platform for discussions of science and regulatory issues. Views and recommendations following from these discussions are either published in scientific journals, like for example on the controversial and much debated topic of incurred sample reproducibility or presented at international meetings. As of May 2010 the EBF consists of 28 member companies. | 3 | Analytical Chemistry |
Asp85 accepts a proton from the Schiff base N atom. In the M intermediate, neither the Schiff base nor Asp85 are charged. | 5 | Photochemistry |
Single-molecule fluorescence spectroscopy uses the fluorescence of a molecule for obtaining information on its environment, structure, and position. The technique affords the ability of obtaining information otherwise not available due to ensemble averaging (that is, a signal obtained when recording many molecules at the same time represents an average property of the molecules' dynamics). The results in many experiments of individual molecules are two-state trajectories. | 7 | Physical Chemistry |
Grazing-incidence small-angle scattering (GISAS) is a scattering technique used to study nanostructured surfaces and thin films. The scattered probe is either photons (grazing-incidence small-angle X-ray scattering, GISAXS) or neutrons (grazing-incidence small-angle neutron scattering, GISANS). GISAS combines the accessible length scales of small-angle scattering (SAS: SAXS or SANS) and the surface sensitivity of grazing incidence diffraction (GID). | 7 | Physical Chemistry |
Donor−acceptor (D−A) conjugated polymers have been investigated for the medicinal purposes. Nano-PCPDTBT CPs have two moieties: 2-ethylhexyl cyclopentadithiophene and 2,1,3-benzothiadiazole. When the PCPDTBT nanoparticle solution (0.115 mg/mL) was exposed to an 808 nm NIR laser (0.6 W/cm), the temperature could be increased by more than 30 °C. Wang et al. designed four NIR-absorbing D-A structured conjugated polymer dots (Pdots) containing diketopyrrolo-pyrrole (DPP) and thiophene units as effective photothermal materials with the PCE up to 65% for in vivo cancer therapy. Zhang et al. constructed PBIBDF-BT D-A CPs by using isoindigo derivative (BIBDF) and bithiophene (BT) as EA and ED respectively. PBIBDF-BT was further modified with poly(ethylene glycol)-block-poly(hexyl ethylene phosphate) (mPEG-b-PHEP) to obtain PBIBDF-BT@NP PPE with PCE of 46.7% and high stability in physiological environment. Yang’s group designed PBTPBF-BT CPs, in which the bis(5-oxothieno[3,2-b]pyrrole-6-ylidene)-benzodifurandione (BTPBF) and the 3,3′-didodecyl-2,2′-bithiophene (BT) units acting as EA and ED respectively. The D-A CPs have a maximum absorption peak at 1107 nm and a relative high photothermal conversion efficiency (66.4%). Pu et al. synthesized PC70BM-PCPDTBT D-A CPs via nanoprecipitation of EA (6,6)-phenyl-C71-butyric acid methyl ester (PC70BM) and ED PCPDTBT (SPs) for PA-guided PTT. Wang et al. developed D-A CPs TBDOPV-DT containing thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene) (TBDOPV) as EA unit and 2,2′-bithio-phene (DT) as ED unit. TBDOPV-DT CPs have a strong absorption at 1093 nm and achieve highly efficient NIR-II photothermal conversion. | 5 | Photochemistry |
In condensed matter physics and crystallography, the static structure factor (or structure factor for short) is a mathematical description of how a material scatters incident radiation. The structure factor is a critical tool in the interpretation of scattering patterns (interference patterns) obtained in X-ray, electron and neutron diffraction experiments.
Confusingly, there are two different mathematical expressions in use, both called structure factor. One is usually written ; it is more generally valid, and relates the observed diffracted intensity per atom to that produced by a single scattering unit. The other is usually written or and is only valid for systems with long-range positional order — crystals. This expression relates the amplitude and phase of the beam diffracted by the planes of the crystal ( are the Miller indices of the planes) to that produced by a single scattering unit at the vertices of the primitive unit cell. is not a special case of ; gives the scattering intensity, but gives the amplitude. It is the modulus squared that gives the scattering intensity. is defined for a perfect crystal, and is used in crystallography, while is most useful for disordered systems. For partially ordered systems such as crystalline polymers there is obviously overlap, and experts will switch from one expression to the other as needed.
The static structure factor is measured without resolving the energy of scattered photons/electrons/neutrons. Energy-resolved measurements yield the dynamic structure factor. | 3 | Analytical Chemistry |
Some children conceived by IVF using anonymous donors report being troubled over not knowing about their donor parent as well any genetic relatives they may have and their family history.
Alana Stewart, who was conceived using donor sperm, began an online forum for donor children called AnonymousUS in 2010. The forum welcomes the viewpoints of anyone involved in the IVF process. Olivia Pratten, a donor-conceived Canadian, sued the province of British Columbia for access to records on her donor fathers identity in 2008. "Im not a treatment, Im a person, and those records belong to me," Pratten said. In May 2012, a court ruled in Prattens favour, agreeing that the laws at the time discriminated against donor children and making anonymous sperm and egg donation in British Columbia illegal.
In the U.K., Sweden, Norway, Germany, Italy, New Zealand, and some Australian states, donors are not paid and cannot be anonymous.
In 2000, a website called Donor Sibling Registry was created to help biological children with a common donor connect with each other.
In 2012, a documentary called Anonymous Fathers Day' was released that focuses on donor-conceived children. | 1 | Biochemistry |
The Journal of Photochemistry and Photobiology is a series of peer-reviewed scientific journals covering the fields of photochemistry and photobiology, published by Elsevier. It was originally established in 1972, and split into Journal of Photochemistry and Photobiology A: Chemistry and Journal of Photochemistry and Photobiology B: Biology in 1987. A third title; Journal of Photochemistry and Photobiology C: Photochemistry Reviews, was established in 2000 and is the official journal of the Japanese Photochemistry Association. | 5 | Photochemistry |
In astrophysics and nuclear physics, nuclear pasta is a theoretical type of degenerate matter that is postulated to exist within the crusts of neutron stars. If it exists, nuclear pasta would be the strongest material in the universe. Between the surface of a neutron star and the quark–gluon plasma at the core, at matter densities of 10 g/cm, nuclear attraction and Coulomb repulsion forces are of comparable magnitude. The competition between the forces leads to the formation of a variety of complex structures assembled from neutrons and protons. Astrophysicists call these types of structures nuclear pasta because the geometry of the structures resembles various types of pasta. | 7 | Physical Chemistry |
A large part of the research involving PCO is now looking into utilising the anion as a synthetic building block to derive phosphorus containing analogues of small molecules.
The first major breakthrough in this area came from Goicoechea et al. in 2013; they published the reaction between the PCO anion and ammonium salts which yielded the phosphorus containing analogue of urea in which phosphorus replaces a nitrogen atom. The group predict that this heavier congener could have applications in new materials, anion sensing and coordination chemistry.
Goicoechea and co-workers were also able to isolate the heavily sought after phosphorus containing analogue of isocyanic acid, HPCO, in 2017. This molecule is thought to be a crucial intermediate in a lot of reactions involving PCO (including P-transfer to an imidazolium cation).
Moreover, the most recent addition to this class of small molecules is the phosphorus containing analogue of N,N-dimethylformamide. This work in which the phosphorus again replaces a nitrogen atom was published in 2018 by Stephan and co-workers. Generating acylphosphines in this manner is considered a much milder route than other current strategies that require multi-step syntheses involving toxic, volatile and pyrophoric reagents. | 7 | Physical Chemistry |
The oldest known example of applying the lost-wax technique to copper casting comes from a 6,000-year-old () copper, wheel-shaped amulet found at Mehrgarh, Pakistan.
Metal casting, by the Indus Valley civilization, produced some of the earliest known examples of lost-wax casting applied to the casting of copper alloys, a bronze figurine, found at Mohenjo-daro, and named the "dancing girl", is dated to 2300-1750 . Other examples include the buffalo, bull and dog found at Mohenjodaro and Harappa, two copper figures found at the Harappan site Lothal in the district of Ahmedabad of Gujarat, and likely a covered cart with wheels missing and a complete cart with a driver found at Chanhudaro.
During the post-Harappan period, hoards of copper and bronze implements made by the lost-wax process are known from Tamil Nadu, Uttar Pradesh, Bihar, Madhya Pradesh, Odisha, Andhra Pradesh and West Bengal. Gold and copper ornaments, apparently Hellenistic in style, made by cire perdue were found at the ruins at Sirkap. One example of this Indo-Greek art dates to the the juvenile figure of Harpocrates excavated at Taxila. Bronze icons were produced during the 3rd and 4th centuries, such as the Buddha image at Amaravati, and the images of Rama and Kartikeya in the Guntur district of Andhra Pradesh. A further two bronze images of Parsvanatha and a small hollow-cast bull came from Sahribahlol, Gandhara, and a standing Tirthankara () from Chausa in Bihar should be mentioned here as well. Other notable bronze figures and images have been found in Rupar, Mathura (in Uttar Pradesh) and Brahmapura, Maharashtra.
Gupta and post-Gupta period bronze figures have been recovered from the following sites: Saranath, Mirpur-Khas (in Pakistan), Sirpur (District of Raipur), Balaighat (near Mahasthan now in Bangladesh), Akota (near Vadodara, Gujarat), Vasantagadh, Chhatarhi, Barmer and Chambi (in Rajesthan). The bronze casting technique and making of bronze images of traditional icons reached a high stage of development in South India during the medieval period. Although bronze images were modelled and cast during the Pallava Period in the eighth and ninth centuries, some of the most beautiful and exquisite statues were produced during the Chola Period in Tamil Nadu from the tenth to the twelfth century. The technique and art of fashioning bronze images is still skillfully practised in South India, particularly in Kumbakonam. The distinguished patron during the tenth century was the widowed Chola queen, Sembiyan Maha Devi. Chola bronzes are the most soughtafter collectors’ items by art lovers all over the [https://ncert.nic.in/textbook/pdf/kefa107.pdf world]. The technique was used throughout India, as well as in the neighbouring countries Nepal, Tibet, Ceylon, Burma and Siam. | 8 | Metallurgy |
A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, however unlike an eye it is optimized to produce light, not absorb it. The bioluminescence can variously be produced from compounds during the digestion of prey, from specialized mitochondrial cells in the organism called photocytes ("light producing" cells), or, similarly, associated with symbiotic bacteria in the organism that are cultured.
The character of photophores is important in the identification of deep sea fishes. Photophores on fish are used for attracting food or for camouflage from predators by counter-illumination.
Photophores are found on some cephalopods including the firefly squid, which can create impressive light displays, as well as numerous other deep sea organisms such as the pocket shark Mollisquama mississippiensis and the strawberry squid. | 1 | Biochemistry |
Osmolarity and tonicity are related but distinct concepts. Thus, the terms ending in -osmotic (isosmotic, hyperosmotic, hyposmotic) are not synonymous with the terms ending in -tonic (isotonic, hypertonic, hypotonic). The terms are related in that they both compare the solute concentrations of two solutions separated by a membrane. The terms are different because osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of non-freely penetrating solutes only.
Penetrating solutes can diffuse through the cell membrane, causing momentary changes in cell volume as the solutes "pull" water molecules with them. Non-penetrating solutes cannot cross the cell membrane; therefore, the movement of water across the cell membrane (i.e., osmosis) must occur for the solutions to reach equilibrium.
A solution can be both hyperosmotic and isotonic. For example, the intracellular fluid and extracellular can be hyperosmotic, but isotonic – if the total concentration of solutes in one compartment is different from that of the other, but one of the ions can cross the membrane (in other words, a penetrating solute), drawing water with it, thus causing no net change in solution volume. | 3 | Analytical Chemistry |
Like almost all riffle beetles, spider water beetles are aquatic, feeding on algae and decaying wood tissue. However, they can not actively swim. They can be found crawling along or clinging with their claws on boulders or submerged wood in lotic riffles of streams and rivers.
The larvae are exclusively aquatic. They breathe by means of tracheal gills. Spider water beetle adults, like all members of the subfamily Elminae, can also remain indefinitely underwater by means of a plastron, a thin film of gas trapped by hydrophobic bristles (setae) on their body. As the insect breathes, the oxygen concentration in the gas film drops in comparison to the surrounding water, causing new oxygen to diffuse again into the plastron.
Because of their reliance on the plastron for breathing, spider water beetles are restricted to the highly oxygenated environments in moderate to fast-moving permanent running water. They are therefore extremely sensitive to water pollution and are potentially valuable bioindicators for measuring the health of river ecosystems.
Members of the Ancyronyx variegatus species group are mostly found in slightly to moderately polluted (mesosaprobic) rivers, almost always found on submerged wood (with the exception of Ancyronyx yunju which were collected from sand and grass roots). Members of the Ancyronyx patrolus species group, meanwhile, are only found in clean permanent streams, usually among rocks.
Ancyronyx malickyi have been caught using light traps, which might indicate phototaxis. | 2 | Environmental Chemistry |
The luteinizing hormone/choriogonadotropin receptor (LHCGR), also lutropin/choriogonadotropin receptor (LCGR) or luteinizing hormone receptor (LHR), is a transmembrane receptor found predominantly in the ovary and testis, but also many extragonadal organs such as the uterus and breasts. The receptor interacts with both luteinizing hormone (LH) and chorionic gonadotropins (such as hCG in humans) and represents a G protein-coupled receptor (GPCR). Its activation is necessary for the hormonal functioning during reproduction. | 1 | Biochemistry |
Both chemoenzymatic glycorandomization and neoglycorandomization use free reducing sugars and unprotected aglycons and are thereby a notable advance over classical glycosylation methods. A notable advantage of the enzymatic approach is the use of the corresponding genes encoding for the permissive kinases, nucleotidyltransferases and/or glycosyltransferases for in vivo synthetic biology applications to afford in vivo glycorandomization. However, it is important to note the enzymatic platform is dependent upon the permissivity of the enzymes employed. In contrast, the main hurdle to chemoselective neoglycorandomization is installation of the alkoxylamine handle. Unlike the enzymatic approach, the anomeric stereoselectivity of the chemoselective method depends upon the reducing sugar used and can, in some cases, lead to anomeric mixtures. | 0 | Organic Chemistry |
The Fast Fourier Transform (FFT) method was introduced in 1991 by Goodman, Draine, and Flatau for the discrete dipole approximation. They utilized a 3D FFT GPFA written by Clive Temperton. The interaction matrix was extended to twice its original size to incorporate negative lags by mirroring and reversing the interaction matrix. Several variants have been developed since then. Barrowes, Teixeira, and Kong in 2001 developed a code that uses block reordering, zero padding, and a reconstruction algorithm, claiming minimal memory usage. McDonald, Golden, and Jennings in 2009 used a 1D FFT code and extended the interaction matrix in the x, y, and z directions of the FFT calculations, suggesting memory savings due to this approach. This variant was also implemented in the MATLAB 2021 code by Shabaninezhad and Ramakrishna. Other techniques to accelerate convolutions have been suggested in a general context along with faster evaluations of Fast Fourier Transforms arising in DDA problem solvers. | 7 | Physical Chemistry |
The lipid pump sequesters carbon from the ocean's surface to deeper waters via lipids associated with overwintering vertically migratory zooplankton. Lipids are a class of hydrocarbon rich, nitrogen and phosphorus deficient compounds essential for cellular structures. This lipid carbon enters the deep ocean as carbon dioxide produced by respiration of lipid reserves and as organic matter from the mortality of zooplankton.
Compared to the more general biological pump, the lipid pump also results in a "lipid shunt", where other nutrients like nitrogen and phosphorus that are consumed in excess must be excreted back to the surface environment, and thus are not removed from the surface mixed layer of the ocean. This means that the carbon transported by the lipid pump does not limit the availability of essential nutrients in the ocean surface. Carbon sequestration via the lipid pump is therefore decoupled from nutrient removal, allowing carbon uptake by oceanic primary production to continue. In the Biological Pump, nutrient removal is always coupled to carbon sequestration; primary production is limited as carbon and nutrients are transported to depth together in the form of organic matter.
The contribution of the lipid pump to the sequestering of carbon in the deeper waters of the ocean can be substantial: the carbon transported below 1,000 metres (3,300 ft) by copepods of the genus Calanus in the Arctic Ocean almost equals that transported below the same depth annually by particulate organic carbon (POC) in this region. A significant fraction of this transported carbon would not return to the surface due to respiration and mortality. Research is ongoing to more precisely estimate the amount that remains at depth. The export rate of the lipid pump may vary from 1–9.3 g C m y across temperate and subpolar regions containing seasonally-migrating zooplankton. The role of zooplankton, and particularly copepods, in the food web is crucial to the survival of higher trophic level organisms whose primary source of nutrition is copepods. With warming oceans and increasing melting of ice caps due to climate change, the organisms associated with the lipid pump may be affected, thus influencing the survival of many commercially important fish and endangered marine mammals. As a new and previously unquantified component of oceanic carbon sequestration, further research on the lipid pump can improve the accuracy and overall understanding of carbon fluxes in global oceanic systems. | 9 | Geochemistry |
An allomone (from Ancient Greek "other" and pheromone) is a type of semiochemical produced and released by an individual of one species that affects the behaviour of a member of another species to the benefit of the originator but not the receiver. Production of allomones is a common form of defense against predators, particularly by plant species against insect herbivores. In addition to defense, allomones are also used by organisms to obtain their prey or to hinder any surrounding competitors.
Many insects have developed ways to defend against these plant defenses (in an evolutionary arms race). One method of adapting to allomones is to develop a positive reaction to them; the allomone then becomes a kairomone. Others alter the allomones to form pheromones or other hormones, and yet others adopt them into their own defensive strategies, for example by regurgitating them when attacked by an insectivorous insect.
A third class of allelochemical (chemical used in interspecific communication), synomones, benefit both the sender and receiver. | 1 | Biochemistry |
Metro and light rail sides of operation vary and might not match railways or roads in their country. Some systems where the metro matches the side of the national rail network but not the roads include those in Bilbao, Buenos Aires, Cairo, Catania, Jakarta, Lisbon, Lyon, Naples, and Rome. A small number of cities, including Madrid and Stockholm, originally ran on the same side as road traffic when the systems opened in 1919 and 1950 respectively, but had road traffic change in 1924 and 1967 respectively. Conversely, metros in France (except for the aforementioned Lyon) and mainland China run on the right just like roads, while mainline trains run on the left.
A small number of systems have situational reasons to differ from the norm. On the MTR in Hong Kong, the section originally known as the Ma On Shan line (now part of the Tuen Ma line) runs on the right to make interchanging with the East Rail line easier, while the rest of the system runs on the left. On the Seoul Metropolitan Subway, lines that integrate with Korail (except Line 3, which is disconnected from the rest of the network) run on the left, while the lines that are not run on the right. In Nizhny Novgorod, Line 2 runs on the left due to the track layout when it first opened as a branch of Line 1. In Lima, Line 1 runs entirely on the left, while Line 2 runs entirely on the right.
Metro Line M1 in Budapest is the only metro line to have switched sides. It originally ran on the left but switched to right hand-running during the line's reconstruction around 1973.
Because trams frequently operate on roads, they generally operate on the same side as other road traffic. | 4 | Stereochemistry |
Biological cell membranes and cell walls are polyanionic surfaces. This has important implications for the transport of ions, in particular because it has been shown that different membranes preferentially bind different ions. Both Mg and Ca regularly stabilize membranes by the cross-linking of carboxylated and phosphorylated head groups of lipids. However, the envelope membrane of E. coli has also been shown to bind Na, K, Mn and Fe. The transport of ions is dependent on both the concentration gradient of the ion and the electric potential (ΔΨ) across the membrane, which will be affected by the charge on the membrane surface. For example, the specific binding of Mg to the chloroplast envelope has been implicated in a loss of photosynthetic efficiency by the blockage of K uptake and the subsequent acidification of the chloroplast stroma. | 1 | Biochemistry |
Aluminium alloys are anodized to increase corrosion resistance and to allow dyeing (colouring), improved lubrication, or improved adhesion. However, anodizing does not increase the strength of the aluminium object. The anodic layer is insulative.
When exposed to air at room temperature, or any other gas containing oxygen, pure aluminium self-passivates by forming a surface layer of amorphous aluminium oxide 2 to 3 nm thick, which provides very effective protection against corrosion. Aluminium alloys typically form a thicker oxide layer, 5–15 nm thick, but tend to be more susceptible to corrosion. Aluminium alloy parts are anodized to greatly increase the thickness of this layer for corrosion resistance. The corrosion resistance of aluminium alloys is significantly decreased by certain alloying elements or impurities: copper, iron, and silicon, so 2000-, 4000-, 6000 and 7000-series Al alloys tend to be most susceptible.
Although anodizing produces a very regular and uniform coating, microscopic fissures in the coating can lead to corrosion. Further, the coating is susceptible to chemical dissolution in the presence of high- and low-pH chemistry, which results in stripping the coating and corrosion of the substrate. To combat this, various techniques have been developed either to reduce the number of fissures, to insert more chemically stable compounds into the oxide, or both. For instance, sulphuric-anodized articles are normally sealed, either through hydro-thermal sealing or precipitating sealing, to reduce porosity and interstitial pathways that allow corrosive ion exchange between the surface and the substrate. Precipitating seals enhance chemical stability but are less effective in eliminating ionic exchange pathways. Most recently, new techniques to partially convert the amorphous oxide coating into more stable micro-crystalline compounds have been developed that have shown significant improvement based on shorter bond lengths.
Some aluminium aircraft parts, architectural materials, and consumer products are anodized. Anodized aluminium can be found on MP3 players, smartphones, multi-tools, flashlights, cookware, cameras, sporting goods, firearms, window frames, roofs, in electrolytic capacitors, and on many other products both for corrosion resistance and the ability to retain dye. Although anodizing only has moderate wear resistance, the deeper pores can better retain a lubricating film than a smooth surface would.
Anodized coatings have a much lower thermal conductivity and coefficient of linear expansion than aluminium. As a result, the coating will crack from thermal stress if exposed to temperatures above 80 °C (353 K). The coating can crack, but it will not peel. The melting point of aluminium oxide is 2050°C (2323K), much higher than pure aluminium's 658°C (931K). This and the insulativity of aluminium oxide can make welding more difficult.
In typical commercial aluminium anodizing processes, the aluminium oxide is grown down into the surface and out from the surface by equal amounts. Therefore, anodizing will increase the part dimensions on each surface by half the oxide thickness. For example, a coating that is 2 μm thick will increase the part dimensions by 1 μm per surface. If the part is anodized on all sides, then all linear dimensions will increase by the oxide thickness. Anodized aluminium surfaces are harder than aluminium but have low to moderate wear resistance, although this can be improved with thickness and sealing. | 8 | Metallurgy |
The higher heating value (HHV; gross energy, upper heating value, gross calorific value GCV, or higher calorific value; HCV) indicates the upper limit of the available thermal energy produced by a complete combustion of fuel. It is measured as a unit of energy per unit mass or volume of substance. The HHV is determined by bringing all the products of combustion back to the original pre-combustion temperature, including condensing any vapor produced. Such measurements often use a standard temperature of . This is the same as the thermodynamic heat of combustion since the enthalpy change for the reaction assumes a common temperature of the compounds before and after combustion, in which case the water produced by combustion is condensed to a liquid. The higher heating value takes into account the latent heat of vaporization of water in the combustion products, and is useful in calculating heating values for fuels where condensation of the reaction products is practical (e.g., in a gas-fired boiler used for space heat). In other words, HHV assumes all the water component is in liquid state at the end of combustion (in product of combustion) and that heat delivered at temperatures below can be put to use. | 7 | Physical Chemistry |
Process requirements may change causing compressor conditions to vary. The compressor may be driven by a variable speed or constant speed machine. If driven by a constant speed electric motor it may be controlled with variable inlet guide vanes or suction and discharge throttling. Welch shows the effect of variable vane angle on the flow for a centrifugal compressor. | 7 | Physical Chemistry |
The calculation of K at a particular temperature from a known K at another given temperature can be approached as follows if standard thermodynamic properties are available. The effect of temperature on equilibrium constant is equivalent to the effect of temperature on Gibbs energy because:
where ΔG</sup> is the reaction standard Gibbs energy, which is the sum of the standard Gibbs energies of the reaction products minus the sum of standard Gibbs energies of reactants.
Here, the term "standard" denotes the ideal behaviour (i.e., an infinite dilution) and a hypothetical standard concentration (typically 1 mol/kg). It does not imply any particular temperature or pressure because, although contrary to IUPAC recommendation, it is more convenient when describing aqueous systems over wide temperature and pressure ranges.
The standard Gibbs energy (for each species or for the entire reaction) can be represented (from the basic definitions) as:
In the above equation, the effect of temperature on Gibbs energy (and thus on the equilibrium constant) is ascribed entirely to heat capacity. To evaluate the integrals in this equation, the form of the dependence of heat capacity on temperature needs to be known.
If the standard molar heat capacity C can be approximated by some analytic function of temperature (e.g. the Shomate equation), then the integrals involved in calculating other parameters may be solved to yield analytic expressions for them. For example, using approximations of the following forms:
*For pure substances (solids, gas, liquid):
*For ionic species at :
then the integrals can be evaluated and the following final form is obtained:
The constants A, B, C, a, b and the absolute entropy, S̆, required for evaluation of C(T), as well as the values of G and S for many species are tabulated in the literature. | 7 | Physical Chemistry |
In response to these market changes Eric Duckworth initiated changes of policy. Fulmer sought to extend its services to include the full range from R&D and testing to small scale manufacture, to extend its area of expertise to cover a wider range of materials and to develop new markets. It sought to collaborate with or to acquire organisations with complementary skills and facilities.
The aim was to be able to offer to industrial companies a comprehensive service in all aspects of materials technology.
Fulmer also changed its policy on intellectual property. Previously patents were applied for as part of sponsored projects so that all rights belonged to the sponsor.
Beginning in 1970, the policy also included the patenting of worthwhile ideas developed in-house before applying for sponsorship so that Fulmer could retain rights and benefit from subsequent exploitation.
Another new approach was to launch projects in which a number of clients jointly sponsored a development (multi-client projects).
There was also a change of management style. Early in his career Eric Duckworth had spent ten years at the Glacier Metal Company at the time when the Glacier Project - a pioneering new approach to management-staff relations - was being developed there by Wilfred (later Lord) Brown, the managing director, and Elliott Jaques of the Tavistock Institute of Human Relations.
When he joined Fulmer Eric Duckworth introduced a style of management heavily influenced by his experience of the Glacier Project. Over time this evolved into an open style with features such as a company council with
representatives from all staff, regular management briefing of staff and transparent grading and pay scales against which individual staff were appraised annually. The grading system enabled parity of career progression between managers and people who focussed on developing their technical expertise. | 8 | Metallurgy |
Expression systems using either S. cerevisiae or Pichia pastoris allow stable and lasting production of proteins that are processed similarly to mammalian cells, at high yield, in chemically defined media of proteins. | 1 | Biochemistry |
Halogen bonds occur when a halogen atom is electrostatically attracted to a partial negative charge. Necessarily, the atom must be covalently bonded in an antipodal σ-bond; the electron concentration associated with that bond leaves a positively charged "hole" on the other side. Although all halogens can theoretically participate in halogen bonds, the σ-hole shrinks if the electron cloud in question polarizes poorly or the halogen is so electronegative as to polarize the associated σ-bond. Consequently halogen-bond propensity follows the trend F < Cl < Br < I.
There is no clear distinction between halogen bonds and expanded octet partial bonds; what is superficially a halogen bond may well turn out to be a full bond in an unexpectedly relevant resonance structure. | 6 | Supramolecular Chemistry |
Almost any biological sample containing a full copy of the DNA—even a very small amount of DNA or ancient DNA—can provide the genetic material necessary for full genome sequencing. Such samples may include saliva, epithelial cells, bone marrow, hair (as long as the hair contains a hair follicle), seeds, plant leaves, or anything else that has DNA-containing cells.
The genome sequence of a single cell selected from a mixed population of cells can be determined using techniques of single cell genome sequencing. This has important advantages in environmental microbiology in cases where a single cell of a particular microorganism species can be isolated from a mixed population by microscopy on the basis of its morphological or other distinguishing characteristics. In such cases the normally necessary steps of isolation and growth of the organism in culture may be omitted, thus allowing the sequencing of a much greater spectrum of organism genomes.
Single cell genome sequencing is being tested as a method of preimplantation genetic diagnosis, wherein a cell from the embryo created by in vitro fertilization is taken and analyzed before embryo transfer into the uterus. After implantation, cell-free fetal DNA can be taken by simple venipuncture from the mother and used for whole genome sequencing of the fetus. | 1 | Biochemistry |
Amongst Rgg-like proteins, it has been observed that the pH sensitive histidine (particularly H144) and interacting amino acids (Y176, Y182, and E185) of ropB of Streptococcus pyogenes are conserved in S. porcinus, S. pseudoporcinus, S. salivarius , L. pentosus, Enterococcus sp., L. aviaries, E. faecalis, and L. reuteri. Thus, suggesting the usage of a pH sensitive histidine switch complex with gene regulating effector molecules in a slew of other bacteria [See Also: allosteric regulation]. | 1 | Biochemistry |
Square pyramidal geometry describes the shape of certain chemical compounds with the formula where L is a ligand. If the ligand atoms were connected, the resulting shape would be that of a pyramid with a square base. The point group symmetry involved is of type C. The geometry is common for certain main group compounds that have a stereochemically-active lone pair, as described by VSEPR theory. Certain compounds crystallize in both the trigonal bipyramidal and the square pyramidal structures, notably . | 4 | Stereochemistry |
Water is relatively transparent to visible light, near ultraviolet light, and far-red light, but it absorbs most ultraviolet light, infrared light, and microwaves. Most photoreceptors and photosynthetic pigments utilize the portion of the light spectrum that is transmitted well through water. Microwave ovens take advantage of waters opacity to microwave radiation to heat the water inside of foods. Waters light blue color is caused by weak absorption in the red part of the visible spectrum. | 2 | Environmental Chemistry |
Most analytical instruments produce a signal even when a blank (matrix without analyte) is analyzed. This signal is referred to as the noise level. The instrument detection limit (IDL) is the analyte concentration that is required to produce a signal greater than three times the standard deviation of the noise level. This may be practically measured by analyzing 8 or more standards at the estimated IDL then calculating the standard deviation from the measured concentrations of those standards.
The detection limit (according to IUPAC) is the smallest concentration, or the smallest absolute amount, of analyte that has a signal statistically significantly larger than the signal arising from the repeated measurements of a reagent blank.
Mathematically, the analyte's signal at the detection limit () is given by:
where, is the mean value of the signal for a reagent blank measured multiple times, and is the known standard deviation for the reagent blank's signal.
Other approaches for defining the detection limit have also been developed. In atomic absorption spectrometry usually the detection limit is determined for a certain element by analyzing a diluted solution of this element and recording the corresponding absorbance at a given wavelength. The measurement is repeated 10 times. The 3σ of the recorded absorbance signal can be considered as the detection limit for the specific element under the experimental conditions: selected wavelength, type of flame or graphite oven, chemical matrix, presence of interfering substances, instrument... . | 3 | Analytical Chemistry |
The use of coal-tar creosote on a commercial scale began in 1838, when a patent covering the use of creosote oil to treat timber was taken out by inventor John Bethell. The "Bethell process"—or as it later became known, the full-cell process—involves placing wood to be treated in a sealed chamber and applying a vacuum to remove air and moisture from wood "cells". The wood is then pressure-treated to imbue it with creosote or other preservative chemicals, after which vacuum is reapplied to separate the excess treatment chemicals from the timber. Alongside the zinc chloride-based "Burnett process", use of creosoted wood prepared by the Bethell process became a principal way of preserving railway timbers (most notably railway sleepers) to increase the lifespan of the timbers, and avoiding having to regularly replace them.
Besides treating wood, it was also used for lighting and fuel. In the beginning, it was only used for lighting needed in harbour and outdoor work, where the smoke that was produced from burning it was of little inconvenience. By 1879, lamps had been created that ensured a more complete combustion by using compressed air, removing the drawback of the smoke. Creosote was also processed into gas and used for lighting that way. As a fuel, it was used to power ships at sea and blast furnaces for different industrial needs, once it was discovered to be more efficient than unrefined coal or wood. It was also used industrially for the softening of hard pitch, and burned to produce lamp black. By 1890, the production of creosote in the United Kingdom totaled approximately 29,900,000 gallons per year.
In 1854, Alexander McDougall and Robert Angus Smith developed and patented a product called McDougalls Powder as a sewer deodorant; it mainly consisted of carbolic acid derived from creosote. McDougall, in 1864, experimented with his solution to remove entozoa parasites from cattle pasturing on a sewage farm. This later led to widespread use of creosote as a cattle wash and sheep dip. External parasites would be killed in a creosote diluted dip, and drenching tubes would be used to administer doses to the animals stomachs to kill internal parasites.
Creosoted wood blocks were a common road-paving material in the late 19th and early 20th centuries, but ultimately fell out of favor because they did not generally hold up well enough over time.
Two later methods for creosoting wood were introduced after the turn of the century, referred to as empty-cell processes, because they involve compressing the air inside the wood so that the preservative can only coat the inner cell walls rather than saturating the interior cell voids. This is a less effective, though usually satisfactory, method of treating the wood, but is used because it requires less of the creosoting material. The first method, the "Rüping process" was patented in 1902, and the second, the "Lowry process" was patented in 1906. Later in 1906, the "Allardyce process" and "Card process" were patented to treat wood with a combination of both creosote and zinc chloride. In 1912, it was estimated that a total of 150,000,000 gallons were produced in the US per year. | 7 | Physical Chemistry |
The quantum number J refers to the total angular momentum, as before. Since there are three independent moments of inertia, there are two other independent quantum numbers to consider, but the term values for an asymmetric rotor cannot be derived in closed form. They are obtained by individual matrix diagonalization for each J value. Formulae are available for molecules whose shape approximates to that of a symmetric top.
The water molecule is an important example of an asymmetric top. It has an intense pure rotation spectrum in the far infrared region, below about 200 cm. For this reason far infrared spectrometers have to be freed of atmospheric water vapour either by purging with a dry gas or by evacuation. The spectrum has been analyzed in detail. | 7 | Physical Chemistry |
Increased levels of methemoglobin are found in blood stains. Upon exiting the body, bloodstains transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO) to methemoglobin (met-Hb) and hemichrome (HC). | 1 | Biochemistry |
A 2016 compared AVECs ability to induce apoptosis and necrosis in HER2+ breast cancer compared to the commonly used drug Trastuzumab. It found that the cells was treated with AVEC had a statistically significant higher amount of both apoptosis and necrosis. The percentage of necrotic cells due to treatment with AVEC more than tripled compared to necrotic cells due to treatment with Trastuzumab. | 1 | Biochemistry |
Scribing is the removal of maskant on the areas to be etched. For decorative applications, this is often done by hand through the use of a scribing knife, etching needle or similar tool; modern industrial applications may involve an operator scribing with the aid of a template or use computer numerical control to automate the process. For parts involving multiple stages of etching, complex templates using colour codes and similar devices may be used. | 8 | Metallurgy |
Germann was born in Peru, Miami County, Indiana, eldest child of Mary Fredericke Mueller (1864–1942) and Gustave Adolph Germann (1860–1940). His only sibling was Frank Erhart Emmanuel Germann (1887–1974), who also became a physical chemist. Albert Germann graduated from Peru High School in 1904. Germann taught in Miami County rural schools while working his way through a chemistry major at Indiana University in Bloomington. He received the A.B. in chemistry in 1909 and the A.M. in chemistry in 1910, both from Indiana University, and the M.Sc. degree in chemistry from the University of Wisconsin in Madison, also in 1910. He received the Sc.D. degree (doctorat ès sciences physiques et chimiques) from the University of Geneva (Geneva, Switzerland) in 1914 under the guidance of Philippe-Auguste Guye (1862–1922). | 7 | Physical Chemistry |
Retinal is a chromophore that forms photosensitive Retinylidene proteins when covalently bound to proteins called opsins. Retinal can be photoisomerized by itself, but requires to be bound to an opsin protein to both trigger the phototransduction cascade and tune the spectral sensitivity to longer wavelengths, which enable color vision.
Retinal is a species of retinoid and the aldehyde form of Vitamin A. Retinal is interconvertible with retinol, the transport and storage form of vitamin A. During the visual cycle, retinal moves between several different isomers and is also converted to retinol and retinyl ester. Retinoids can be derived from the oxidation of carotenoids like beta carotene or can be consumed directly. To reach the retina, it is bound to Retinol Binding Protein (RBP) and Transthyretin, which prevents its filtration in the glomeruli.
As in transport via the RBP-Transthyretin pathway, retinoids must always be bound to Chaperone molecules, for several reasons. Retinoids are toxic, insoluble in aqueous solutions, and prone to oxidation, and as such they must be bound and protected when within the body. The body uses a variety of chaperones, particularly in the retina, to transport retinoids. | 1 | Biochemistry |
Simon's reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It reacts with secondary amines like MDMA and methamphetamine to give a blue solution. | 3 | Analytical Chemistry |
Polymer-bonded explosives have several potential advantages:
* If the polymer matrix is an elastomer (rubbery material), it tends to absorb shocks, making the PBX very insensitive to accidental detonation, and thus ideal for insensitive munitions.
* Hard polymers can produce PBX that is very rigid and maintains a precise engineering shape even under severe stress.
* PBX powders can be pressed into a desired shape at room temperature; casting normally requires hazardous melting of the explosive. High pressure pressing can achieve density for the material very close to the theoretical crystal density of the base explosive material.
* Many PBXes are safe to machine; turning solid blocks into complex three-dimensional shapes. For example, a billet of PBX can be precisely shaped on a lathe or CNC machine. This technique is used to machine explosive lenses necessary for modern nuclear weapons. | 7 | Physical Chemistry |
Ang has a prominent role in the pathology of cancer due to its functions in angiogenesis and cell survival. Since Ang possesses angiogenic activity, it makes Ang a possible candidate in therapeutic treatments of cancer. Studies of Ang and tumor relationships provide evidence for a connection between the two. The translocation of Ang to the nucleus causes an upregulation of transcriptional rRNA, while knockdown strains of Ang cause downregulation. The presence of Ang inhibitors that block translocation resulted in a decrease of tumor growth and overall angiogenesis. HeLa cells translocate Ang to the nucleus independent of cell density. In human umbilical vein endothelial cells (HUVECs), translocation of Ang to the nucleus stops after cells reach a specific density, while in HeLa cells translocation continued past that point. Inhibition of Ang affects the ability of HeLa cells to proliferate, which proposes an effective target for possible therapies. | 1 | Biochemistry |
emissions have also led to the stratosphere contracting by 400 meters since 1980, which could affect satellite operations, GPS systems and radio communications. | 2 | Environmental Chemistry |
In molecular biology and genetics, transcriptional regulation is the means by which a cell regulates the conversion of DNA to RNA (transcription), thereby orchestrating gene activity. A single gene can be regulated in a range of ways, from altering the number of copies of RNA that are transcribed, to the temporal control of when the gene is transcribed. This control allows the cell or organism to respond to a variety of intra- and extracellular signals and thus mount a response. Some examples of this include producing the mRNA that encode enzymes to adapt to a change in a food source, producing the gene products involved in cell cycle specific activities, and producing the gene products responsible for cellular differentiation in multicellular eukaryotes, as studied in evolutionary developmental biology.
The regulation of transcription is a vital process in all living organisms. It is orchestrated by transcription factors and other proteins working in concert to finely tune the amount of RNA being produced through a variety of mechanisms. Bacteria and eukaryotes have very different strategies of accomplishing control over transcription, but some important features remain conserved between the two. Most importantly is the idea of combinatorial control, which is that any given gene is likely controlled by a specific combination of factors to control transcription. In a hypothetical example, the factors A and B might regulate a distinct set of genes from the combination of factors A and C. This combinatorial nature extends to complexes of far more than two proteins, and allows a very small subset (less than 10%) of the genome to control the transcriptional program of the entire cell. | 1 | Biochemistry |
Methylation of rRNA upholds structural rigidity by blocking base pair stacking and surrounds the 2’-OH group to block hydrolysis. It occurs at specific parts of eukaryotic rRNA. The template for methylation consists of 10-21 nucleotides. 2-O-methylation of the ribose sugar is one of the most common rRNA modifications. Methylation is primarily introduced by small nucleolar RNAs, referred to as snoRNPs. There are two classes of snoRNPs that target methylation sites, and they are referred to box C/D and box H/ACA. One type of methylation, 2′-O-methylation, contributes to helical stabilization. | 1 | Biochemistry |
CcrM (or M.CcrMI) is an orphan DNA methyltransferase, that is involved in controlling gene expression in most Alphaproteobacteria. This enzyme modifies DNA by catalyzing the transference of a methyl group from the S-adenosyl-L methionine substrate to the N6 position of an adenine base in the sequence 5-GANTC-3 with high specificity. In some lineages such as SAR11, the homologous enzymes possess 5-GAWTC-3 specificity. In Caulobacter crescentus Ccrm is produced at the end of the replication cycle when Ccrm recognition sites are hemimethylated, rapidly methylating the DNA. CcrM is essential in other Alphaproteobacteria but its role is not yet determined. CcrM is a highly specific methyltransferase with a novel DNA recognition mechanism. | 1 | Biochemistry |
The wire-cut type of machine arose in the 1960s for making tools (dies) from hardened steel. The tool electrode in wire EDM is simply a wire. To avoid the erosion of the wire causing it to break, the wire is wound between two spools so that the active part of the wire is constantly changing. The earliest numerical controlled (NC) machines were conversions of punched-tape vertical milling machines. The first commercially available NC machine built as a wire-cut EDM machine was manufactured in the USSR in 1967. Machines that could optically follow lines on a master drawing were developed by David H. Dulebohn's group in the 1960s at Andrew Engineering Company for milling and grinding machines. Master drawings were later produced by computer numerical controlled (CNC) plotters for greater accuracy. A wire-cut EDM machine using the CNC drawing plotter and optical line follower techniques was produced in 1974. Dulebohn later used the same plotter CNC program to directly control the EDM machine, and the first CNC EDM machine was produced in 1976.
Commercial wire EDM capability and use has advanced substantially during recent decades. Feed rates have increased and surface finish can be finely controlled. | 8 | Metallurgy |
When bacterial cells run out of nutrients, they enter stationary phase and downregulate protein synthesis. Several processes mediate this transition. For instance, in E. coli, 70S ribosomes form 90S dimers upon binding with a small 6.5 kDa protein, ribosome modulation factor RMF. These intermediate ribosome dimers can subsequently bind a hibernation promotion factor (the 10.8 kDa protein, HPF) molecule to form a mature 100S ribosomal particle, in which the dimerization interface is made by the two 30S subunits of the two participating ribosomes. The ribosome dimers represent a hibernation state and are translationally inactive. A third protein that can bind to ribosomes when E. coli cells enter the stationary phase is YfiA (previously known as RaiA). HPF and YfiA are structurally similar, and both proteins can bind to the catalytic A- and P-sites of the ribosome. RMF blocks ribosome binding to mRNA by preventing interaction of the messenger with 16S rRNA. When bound to the ribosomes the C-terminal tail of E. coli YfiA interferes with the binding of RMF, thus preventing dimerization and resulting in the formation of translationally inactive monomeric 70S ribosomes.
In addition to ribosome dimerization, the joining of the two ribosomal subunits can be blocked by RsfS (formerly called RsfA or YbeB). RsfS binds to L14, a protein of the large ribosomal subunit, and thereby blocks joining of the small subunit to form a functional 70S ribosome, slowing down or blocking translation entirely. RsfS proteins are found in almost all eubacteria (but not archaea) and homologs are present in mitochondria and chloroplasts (where they are called C7orf30 and iojap, respectively). However, it is not known yet how the expression or activity of RsfS is regulated.
Another ribosome-dissociation factor in Escherichia coli is HflX, previously a GTPase of unknown function. Zhang et al. (2015) showed that HflX is a heat shock–induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes. The N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock and possibly other stress conditions. | 1 | Biochemistry |
Pattinson's process or pattinsonisation is a method for removing silver from lead, discovered by Hugh Lee Pattinson in 1829 and patented in 1833.
The process is dependent on the fact that lead which has least silver in it solidifies first on liquefaction, leaving the remaining liquid richer in silver.
In practice several crystallisations were required, so Pattinson's equipment consisted basically of nothing more complex than a row of up to 13 iron pots, which were heated from below. Some lead, naturally containing a small percentage of silver, was loaded into the central pot and melted. This was then allowed to cool. As the lead solidified it was removed using large perforated iron ladles and moved to the next pot in one direction, and the remaining metal which was now richer in silver was then transferred to the next pot in the opposite direction. The process was repeated from one pot to the next, the lead accumulating in the pot at one end and metal enriched in silver in the pot at the other.
The level of enrichment possible is limited by the lead-silver eutectic and typically the silver content of the silver-rich melt could not be raised above 2% (around 600 to 700 ounces per ton), so further separation is carried out by cupellation.
The process was economic for lead containing at least 250 grams of silver per ton. Being the first process applicable to low-grade lead, it supplemented earlier patio process and pan amalgamation.
It was replaced by the Parkes process in the mid-19th century. | 8 | Metallurgy |
"TGF" (Transforming Growth Factor) is a family of proteins that includes 33 members that encode dimeric, secreted polypeptides that regulate development. Many developmental processes are under its control including gastrulation, axis symmetry of the body, organ morphogenesis, and tissue homeostasis in adults. All TGF-β ligands bind to either Type I or Type II receptors, to create heterotetramic complexes. | 1 | Biochemistry |
Rotating-polarization coherent anti-Stokes Raman spectroscopy, (RP-CARS) is a particular implementation of the coherent anti-Stokes Raman spectroscopy (CARS). RP-CARS takes advantage of polarization-dependent selection rules in order to gain information about molecule orientation anisotropy and direction within the optical point spread function. | 3 | Analytical Chemistry |
Primary aromatic amines are used as a starting material for the manufacture of azo dyes. It reacts with nitrous acid to form diazonium salt, which can undergo coupling reaction to form an azo compound. As azo-compounds are highly coloured, they are widely used in dyeing industries, such as:
* Methyl orange
* Direct brown 138
* Sunset yellow FCF
* Ponceau | 0 | Organic Chemistry |
Cross-reactive carbohydrate determinants (CCDs) play a role in the context of allergy diagnosis. The terms CCD or CCDs describe protein-linked carbohydrate structures responsible for the phenomenon of cross-reactivity of sera from allergic patients towards a wide range of allergens from plants and insects. In serum-based allergy diagnosis, antibodies of the IgE class directed against CCDs therefore give the impression of polysensitization. Anti-CCD IgE, however, does not seem to elicit clinical symptoms. Diagnostic results caused by CCDs are therefore regarded as false positives. | 0 | Organic Chemistry |
Pločnik (archaeological site) is located in Pločnik, Prokuplje village in the Toplica District of Serbia. A 120 hectare settlement belonging to the Neolithic Vinča culture existed on the site from 5500 BCE until it was destroyed by fire in 4700 BCE.
The site was first discovered during railway construction in 1927, but was investigated only sporadically until excavations carried out by the Prokuplje Museum the National Museum of Serbia began in 1996.
The Vinča houses at Pločnik had stoves and special holes specifically for rubbish, and the dead were buried in cemeteries. People slept on woollen mats and fur and made clothes of wool, flax and leather. The figurines found not only represent deities but many show the daily life of the inhabitants while crude pottery finds appear to have been made by children. Women are depicted in short tops and skirt wearing jewellery. A thermal well found near the settlement might be evidence of Europe's oldest spa. | 8 | Metallurgy |
Many plants acquire sulfur through gaseous atmospheric compounds. Leaves of trees have δS values lying between those of air and soil, suggesting that there is uptake occurring from atmospheric and soil sources. The δS values of trees has also been demonstrated to be height dependent, with the foliage at the tops of conifers, bull rushes and deciduous trees having δS values more reflective of the atmosphere and lower foliage having δS values closer to that of soil. It has been proposed that this is due to upper foliage exerting a canopy action on the lower branches, taking up atmospheric sulfur before it can reach lower levels. This is further supported with the epiphytic lichens and mosses having δS values close to atmospheric S compounds. This occurs due to lichens and mosses having no access to soil and relying on the direct uptake of gaseous sulfur, dissolved sulfur through rainfall and dry fall accumulation, providing a cumulative record of atmospheric sulfur isotope composition.
Main forms of atmospheric sulfur come from the natural sulfur emissions formed biologically and emitted as HS or organic sulfur gases such as DMS (dimethyl sulfide), COS (carbonyl sulfide), and CS (carbon disulfide). These gases are predominantly formed over oceans, wetlands, salt marshes, and estuaries by algae and bacteria. Anthropogenic emissions have increased the concentration of sulfur in the atmosphere mainly through emissions of SO, from coal, oil, industrial processes, and biomass burning. In 2000, global anthropogenic emission of sulfur was estimated of 55.2–68 Tg S per year, which is much higher than the natural sulfur emissions estimated to be 34 Tg S per year. In the event of excess sulfur in plant tissue, it has been demonstrated that when exposed to high doses of sulfur dioxide, plants emit hydrogen sulfide (HS) and possibly other reduced sulfur compounds in response to high sulfur loading | 9 | Geochemistry |
Phytostabilisation is a form of phytoremediation that uses hyperaccumulator plants for long-term stabilisation and containment of tailings, by sequestering pollutants in soil near the roots. The plants presence can reduce wind erosion, or the plants roots can prevent water erosion, immobilise metals by adsorption or accumulation, and provide a zone around the roots where the metals can precipitate and stabilise. Pollutants become less bioavailable and livestock, wildlife, and human exposure is reduced. This approach can be especially useful in dry environments, which are subject to wind and water dispersion. | 8 | Metallurgy |
When food is cooked, some of its proteins become denatured. This is why boiled eggs become hard and cooked meat becomes firm.
A classic example of denaturing in proteins comes from egg whites, which are typically largely egg albumins in water. Fresh from the eggs, egg whites are transparent and liquid. Cooking the thermally unstable whites turns them opaque, forming an interconnected solid mass. The same transformation can be effected with a denaturing chemical. Pouring egg whites into a beaker of acetone will also turn egg whites translucent and solid. The skin that forms on curdled milk is another common example of denatured protein. The cold appetizer known as ceviche is prepared by chemically "cooking" raw fish and shellfish in an acidic citrus marinade, without heat. | 1 | Biochemistry |
Hemoglobin variants are a part of the normal embryonic and fetal development. They may also be pathologic mutant forms of hemoglobin in a population, caused by variations in genetics. Some well-known hemoglobin variants, such as sickle-cell anemia, are responsible for diseases and are considered hemoglobinopathies. Other variants cause no detectable pathology, and are thus considered non-pathological variants.
In embryos:
* Gower 1 (ζε).
* Gower 2 (αε) ().
* Hemoglobin Portland I (ζγ).
* Hemoglobin Portland II (ζβ).
In fetuses:
* Hemoglobin F (αγ) ().
In neonates (newborns inmmediately after birth):
* Hemoglobin A (adult hemoglobin) (αβ) () – The most common with a normal amount over 95%
* Hemoglobin A (αδ) – δ chain synthesis begins late in the third trimester and, in adults, it has a normal range of 1.5–3.5%
* Hemoglobin F (fetal hemoglobin) (αγ) – In adults Hemoglobin F is restricted to a limited population of red cells called F-cells. However, the level of Hb F can be elevated in persons with sickle-cell disease and beta-thalassemia.
Abnormal forms that occur in diseases:
* Hemoglobin D – (αβ) – A variant form of hemoglobin.
* Hemoglobin H (β) – A variant form of hemoglobin, formed by a tetramer of β chains, which may be present in variants of α thalassemia.
* Hemoglobin Barts (γ) – A variant form of hemoglobin, formed by a tetramer of γ chains, which may be present in variants of α thalassemia.
* Hemoglobin S (αβ) – A variant form of hemoglobin found in people with sickle cell disease. There is a variation in the β-chain gene, causing a change in the properties of hemoglobin, which results in sickling of red blood cells.
* Hemoglobin C (αβ) – Another variant due to a variation in the β-chain gene. This variant causes a mild chronic hemolytic anemia.
* Hemoglobin E (αβ) – Another variant due to a variation in the β-chain gene. This variant causes a mild chronic hemolytic anemia.
* Hemoglobin AS – A heterozygous form causing sickle cell trait with one adult gene and one sickle cell disease gene
* Hemoglobin SC disease – A compound heterozygous form with one sickle gene and another encoding Hemoglobin C.
* Hemoglobin Hopkins-2 – A variant form of hemoglobin that is sometimes viewed in combination with Hemoglobin S to produce sickle cell disease. | 7 | Physical Chemistry |
Despite having been integrated into genomes of vertebrates for millions of years, ERVs represent an intermediate stage between exogenous viruses and the host genome; it is suggested that immunological tolerance to HERV-derived proteins and peptides is imperfect due to the epigenetic silencing of HERV in the thymus and bone marrow, which prevents deletion of all HERV-specific T and B cells. As evidence of this, immunization of non-human primates with ERV-derived antigens mounted robust polyfunctional cytotoxic T cell response as well as high antibody titers. According to phylogenetic studies, among 30 HERV families existing in the human genome, HERV-K (HML-2) elements which integrated most recently are the most intact and biologically active forms. HERV-K env and HERV-H env, considered to be a new class of tumor-associated antigens, have been found to promote strong cytotoxic T-cell responses in patients with various types of cancers.
On a level of the innate immune sensing of nucleic acids, single-stranded RNA (ssRNA) and double-stranded RNA (dsRNA) derived from endogenous retroviruses are recognized by pattern recognition receptors (PRRs).
SsRNAs can be sensed by Toll-like receptors TLR-7 and TLR-8, resulting in secretion of IFN-α by stimulated dendritic cells (DCs) and macrophages, which was observed for ssRNAs derived from HIV-1.
DsRNAs might be one of the most immunogenic nucleic acid pathogen-associated molecular patterns (PAMPs), since they are not found in cells in a normal state. HERV-derived dsRNA can be recognized by TLR-3, RIG-I and MDA5; RIG-I and MDA5 are known to induce a type I IFN response.
When retrotranscribed into DNA, retroviruses can be sensed by cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, leading to the activation of nuclear factor-kappa B (NF-kB) and IFN regulatory factor 3 (IRF3), which in turn trigger a type I IFN response. DsDNA could also be sensed by DNA-dependent activator of IFN-regulatory factors (DAI); DNA:RNA hybrids could be recognized by TLR-9
The recognition of nucleic acids through PRRs provides a very efficient strategy to fight against viral infections, at the same time imposing the host to a risk due to the possibility of recognizing self-nucleic acids and promotion of autoimmunity. Not surprisingly, HERVs have been found to be associated with different autoimmune and inflammatory diseases, such as multiple sclerosis, amyotrophic lateral sclerosis (ALS), systemic lupus erythematosus (SLE), rheumathoid arthritis (RA), Sjögren syndrome (SS).
On a protein level, a direct interaction between TLRs and certain HERV proteins has been shown. For example, the surface unit of HERV-W Env (also known as Multiple sclerosis-associated retroviral element (MSRV) env) was found to bind to TLR4 and CD14, stimulating the production of pro-inflammatory cytokines including IL-1β, IL-6, and TNFα. HERV-W Env can trigger a maturation process in human dendritic cells, endowing them with the capacity to support a Th1-like type of Th cell differentiation.
Immunological studies have shown some evidence for T cell immune responses against HERVs in HIV-infected individuals. The hypothesis that HIV induces HERV expression in HIV-infected cells led to the proposal that a vaccine targeting HERV antigens could specifically eliminate HIV-infected cells. The potential advantage of this novel approach is that, by using HERV antigens as surrogate markers of HIV-infected cells, it could circumvent the difficulty inherent in directly targeting notoriously diverse and fast-mutating HIV antigens. | 1 | Biochemistry |
Articles relating to Tampa Bay, the body of water. For articles on the wider area, see :Category:Tampa Bay Area. | 2 | Environmental Chemistry |
An anodized oxide layer has a thickness in the range of to several micrometers. Standards for titanium anodizing are given by AMS 2487 and AMS 2488.
AMS 2488 Type III anodizing of titanium generates an array of different colours without dyes, for which it is sometimes used in art, costume jewellery, body piercing jewellery and wedding rings. The colour formed is dependent on the thickness of the oxide (which is determined by the anodizing voltage); it is caused by the interference of light reflecting off the oxide surface with light travelling through it and reflecting off the underlying metal surface. AMS 2488 Type II anodizing produces a thicker matte grey finish with higher wear resistance. | 8 | Metallurgy |
To overcome the problem of Doppler broadening without cooling down the sample to millikelvin temperatures, a classical pump–probe scheme is used. A laser with a relatively high intensity is sent through the atomic vapor, known as the pump beam. Another counter-propagating weak beam is also sent through the atoms at the same frequency, known as the probe beam. The absorption of the probe beam is recorded on a photodiode for various frequencies of the beams.
Although the two beams are at the same frequency, they address different atoms due to natural thermal motion. If the beams are red-detuned with respect to the atomic transition frequency, then the pump beam will be absorbed by atoms moving towards the beam source, while the probe beam will be absorbed by atoms moving away from that source at the same speed in the opposite direction. If the beams are blue-detuned, the opposite occurs.
If, however, the laser is approximately on resonance, these two beams address the same atoms, those with velocity vectors nearly perpendicular to the direction of laser propagation. In the two-state approximation of an atomic transition, the strong pump beam will cause many of the atoms to be in the excited state; when the number of atoms in the ground state and the excited state are approximately equal, the transition is said to be saturated. When a photon from the probe beam passes through the atoms, there is a good chance that, if it encounters an atom, the atom will be in the excited state and will thus undergo stimulated emission, with the photon passing through the sample. Thus, as the laser frequency is swept across the resonance, a small dip in the absorption feature will be observed at each atomic transition (generally hyperfine resonances). The stronger the pump beam, the wider and deeper the dips in the Gaussian Doppler-broadened absorption feature become. Under perfect conditions, the width of the dip can approach the natural linewidth of the transition.
A consequence of this method of counter-propagating beams on a system with more than two states is the presence of crossover lines. When two transitions are within a single Doppler-broadened feature and share a common ground state, a crossover peak at a frequency exactly between the two transitions can occur. This is the result of moving atoms seeing the pump and probe beams resonant with two separate transitions. The pump beam can cause the ground state to be depopulated, saturating one transition, while the probe beam finds much fewer atoms in the ground state because of this saturation, and its absorption falls. These crossover peaks can be quite strong, often stronger than the main saturated absorption peaks. | 7 | Physical Chemistry |
Host recognition of bacteriophages occur via bacteria-binding proteins that have strong binding affinities to specific protein or carbohydrate structures on the surface of the bacterial host. Bacteria-binding proteins derived from bacteriophage coating paramagnetic beads will bind to specific cell components present on the surface of host thus capturing the cells and facilitate the concentration of these bead-attached cells. The concentration process is created by a magnet placed on the side of the test tube bringing the beads to it. Due to the phage-ligand technology, AMS is superior to the antibody based immunomagnetic separation (IMS) on sorting bacterial cells. | 1 | Biochemistry |
Plant defense signaling is activated by the pathogen-detecting receptors that are described in an above section. The activated receptors frequently elicit reactive oxygen and nitric oxide production, calcium, potassium and proton ion fluxes, altered levels of salicylic acid and other hormones and activation of MAP kinases and other specific protein kinases. These events in turn typically lead to the modification of proteins that control gene transcription, and the activation of defense-associated gene expression. | 1 | Biochemistry |
There is an extreme constancy of the isotopic composition of igneous rocks. The mean value of δFe of terrestrial rocks is 0.00 ± 0.05‰. More precise isotopic measurements indicate that the small deviations from 0.00‰ may reflect a slight mass-dependent fractionation. This mass fractionation has been proposed to be F = 0.039 ± 0.008‰ per atomic mass unit relative to IRMM-014. There may also be slight isotopic variations in igneous rocks depending on their composition and process of formation. The average value of δFe for ultramafic igneous rocks is -0.06‰, whereas the average value of δFe for mid-ocean ridge basalts (MORB) is +0.03‰. Sedimentary rocks exhibit slightly larger variations in δFe, with values between -1.6‰ and +0.9‰ relative to IRMM-014. Banded iron formations δFe span the entire range observed on Earth, from -2.5‰ to +1‰. | 9 | Geochemistry |
There have been attempts to treat cancer using gene therapy. As of 2017, 65% of gene therapy trials were for cancer treatment.
Adenovirus vectors are useful for some cancer gene therapies because adenovirus can transiently insert genetic material into a cell without permanently altering the cell's nuclear genome. These vectors can be used to cause antigens to be added to cancers causing an immune response, or hinder angiogenesis by expressing certain proteins. An Adenovirus vector is used in the commercial products Gendicine and Oncorine. Another commercial product, Rexin G, uses a retrovirus-based vector and selectively binds to receptors that are more expressed in tumors.
One approach, suicide gene therapy, works by introducing genes encoding enzymes that will cause a cancer cell to die. Another approach is the use oncolytic viruses, such as Oncorine, which are viruses that selectively reproduce in cancerous cells leaving other cells unaffected.
mRNA has been suggested as a non-viral vector for cancer gene therapy that would temporarily change a cancerous cell's function to create antigens or kill the cancerous cells and there have been several trials. | 1 | Biochemistry |
Many natural building materials are hygroscopic, that is they can absorb (water condenses) and release water (water evaporates). The process is thus:
*Condensation (gas to liquid) ΔH<0; enthalpy decreases (exothermic process) gives off heat.
*Vaporization (liquid to gas) ΔH>0; enthalpy increases (endothermic process) absorbs heat (or cools).
While this process liberates a small quantity of energy, large surfaces area allows significant (1–2 °C) heating or cooling in buildings. The corresponding materials are wool insulation and earth/clay render finishes. | 7 | Physical Chemistry |
Complexometric titrations rely on the formation of a complex between the analyte and the titrant. In general, they require specialized complexometric indicators that form weak complexes with the analyte. The most common example is the use of starch indicator to increase the sensitivity of iodometric titration, the dark blue complex of starch with iodine and iodide being more visible than iodine alone. Other complexometric indicators are Eriochrome Black T for the titration of calcium and magnesium ions, and the chelating agent EDTA used to titrate metal ions in solution. | 3 | Analytical Chemistry |
This modification involves the addition of a methyl group (-CH3) group to the 6th nitrogen on the adenine base in an mRNA molecule. This was among the first mRNA modifications to be discovered in 1974. This modification is common in viral mRNA transcripts and is found in nearly 25% of them. The distribution of the modification not uniform with some transcripts containing more than 10. mA modifications are a dynamic process with many applications ranging from viral interactions with cellular machinery and structural adjustments to viral life cycle control. Studies have shown different regulatory patterns for different viruses depending on the context. For single stranded RNA viruses, the effects of the modifications appear to differ on the basis of the viral family. In the HIV-1 genome, the single stranded positive sense RNA contains mA modifications at multiple sites in both the untranslated and coding regions. The presence of this modifications in the viral transcript is enough to increase corresponding modifications in host cell mRNA through binding interactions between the HIV-1 gp 120 envelope protein, and the CD4 receptor in T lymphocytes without causing a corresponding increase in. For HIV-1 and other RNA viral families like chikungunya, enteroviruses and influenza, studies show both a positive and negative role for mA modifications on viral life replication and infection. For other families, the role effects are clearer. For the flaviridae family, the modification had a negative role and hindered viral replication. The modification in respiratory syncytial virus families showed a positive role and enhanced viral replication and infection. The causes of these apparently different roles from different responses within the same family of viruses and why the viral families like flaviridae conserve mA modifications when they negatively impact their cycles are currently unknown and under investigation.
Most of the RNA viruses carry out their cycles in the cytoplasm, away from the required machinery for writing and erasing mA modifications which are housed in the nucleus. For DNA viruses, that cycle in the nucleus with direct access to said machinery, no clear general positive or negative regulatory role can be attributed to mA modifications. In the simian virus and hepatitis B viruses, different mA reading complexes were shown to have different roles in regulation with some having a conserved positive role and others having a neutral or negative effect on replication. | 1 | Biochemistry |
Acidic solutions of fluoride (including hydrofluoric acid) can be determined by a simple thermometric titration with boric acid.
: B(OH) + 3F + 3H ↔ BF + 3HO
The titration plot illustrated in Figure 19 shows that the endpoint is quite rounded, suggesting that the reaction might not proceed to stoichiometric equilibrium. However, since the regions of the temperature curve immediately before and after the endpoint are quite linear, the second derivative of this curve (representing the intersection of tangents) will accurately locate the endpoint. Indeed, excellent precision can be obtained with this titration, with a CV of less than 0.1. | 3 | Analytical Chemistry |
SK potassium channels share the same basic architecture with Shaker-like voltage-gated potassium channels. Four subunits associate to form a tetramer. Each of the subunits has six transmembrane hydrophobic alpha helical domains (S1-S6). A loop between S5 and S6—called the P-loop—provides the pore-forming region that always faces the center of the channel. Each of the subunits has six hydrophobic alpha helical domains that insert into the cell membrane. A loop between the fifth and sixth transmembrane domains forms the potassium ion selectivity filter. SK channels may assemble as homotetrameric channels or as heterotetrameric channels, consisting of more than one SK channel subtype. In addition, SK potassium channels are tightly associated with the protein calmodulin, which accounts for the calcium sensitivity of these channels. Calmodulin participates as a subunit of the channel itself, bound to the cytoplasmic C-terminus region of the peptide called the calmodulin binding domain (CaMBD).
Additional association of the phosphorylating kinase CK2 and dephosphorylating phosphatase PP2A on the cytoplasmic face of the protein allow for enriched Ca-sensitivity—and thus—kinetics modulation. CK2 serves to phosphorylate the SKCa-bound CaM at the T80 residue, rather than the channel helices themselves, to reduce calcium sensitivity. This may only be accomplished when the channel pore is closed. PP2A dephosphorylates this residue upon CK2 inhibition. The selectivity filter of all SK channel subtypes—whether SK1, SK2, SK3, or SK4—is highly conserved and reflects the selectivity seen in any potassium channel, a GYGD amino acid residue sequence on the pore-forming loop. These channels are considered to be voltage-independent, as they possess only two of seven positively charged amino acid residues that are typically seen in a prototypical voltage-gated potassium channel. | 1 | Biochemistry |
The microprocessor complex consists minimally of two proteins: Drosha, a ribonuclease III enzyme; and DGCR8, a double-stranded RNA binding protein. (DGCR8 is the name used in mammalian genetics, abbreviated from "DiGeorge syndrome critical region 8"; the homologous protein in model organisms such as flies and worms is called Pasha, for Partner of Drosha.) The stoichiometry of the minimal complex was at one point experimentally difficult to determine, but it has been demonstrated to be a heterotrimer of two DGCR8 proteins and one Drosha.
In addition to the minimal catalytically active microprocessor components, other cofactors such as DEAD box RNA helicases and heterogeneous nuclear ribonucleoproteins may be present in the complex to mediate the activity of Drosha. Some miRNAs are processed by microprocessor only in the presence of specific cofactors. | 1 | Biochemistry |
The live birth rate is the percentage of all IVF cycles that lead to a live birth. This rate does not include miscarriage or stillbirth; multiple-order births, such as twins and triplets, are counted as one pregnancy. A 2019 summary compiled by the Society for Assisted Reproductive Technology (SART) which reports the average IVF success rates in the United States per age group using non-donor eggs compiled the following data:
In 2006, Canadian clinics reported a live birth rate of 27%. Birth rates in younger patients were slightly higher, with a success rate of 35.3% for those 21 and younger, the youngest group evaluated. Success rates for older patients were also lower and decrease with age, with 37-year-olds at 27.4% and no live births for those older than 48, the oldest group evaluated. Some clinics exceeded these rates, but it is impossible to determine if that is due to superior technique or patient selection, since it is possible to artificially increase success rates by refusing to accept the most difficult patients or by steering them into oocyte donation cycles (which are compiled separately). Further, pregnancy rates can be increased by the placement of several embryos at the risk of increasing the chance for multiples.
Because not each IVF cycle that is started will lead to oocyte retrieval or embryo transfer, reports of live birth rates need to specify the denominator, namely IVF cycles started, IVF retrievals, or embryo transfers. The SART summarised 2008–9 success rates for US clinics for fresh embryo cycles that did not involve donor eggs and gave live birth rates by the age of the prospective mother, with a peak at 41.3% per cycle started and 47.3% per embryo transfer for patients under 35 years of age.
IVF attempts in multiple cycles result in increased cumulative live birth rates. Depending on the demographic group, one study reported 45% to 53% for three attempts, and 51% to 71% to 80% for six attempts.
Effective from 15 February 2021 the majority of Australian IVF clinics publish their individual success rate online via YourIVFSuccess.com.au. This site also contains a predictor tool. | 1 | Biochemistry |
Intensities of spectra of individual atoms or molecules typically vary linearly
with the numerical gas density. However, if gas densities are sufficiently
increased, quite generally contributions may also be observed that vary as density
squared, cubed... These are the collision-induced spectra of two-body (and
quite possibly three-body,...) collisional complexes. The collision-induced spectra
have sometimes been separated from the continua of individual atoms and
molecules, based on the characteristic density dependences. In other words, a
virial expansion in terms of powers of the numerical gas density is often
observable, just as this is widely known for the virial expansion of the equation
of state of compressed gases. The first term of the expansion, which is linear
in density, represents the ideal gas (or "ordinary) spectra where these
exist. (This first term vanishes for the infrared inactive gases,) And
the quadratic, cubic,... terms of the virial expansions arise from optical
transitions of binary, ternary,... intermolecular complexes, which are
(often unjustifyably) neglected in the ideal gas approximation of spectroscopy. | 7 | Physical Chemistry |
The law of mass action also has implications in semiconductor physics. Regardless of doping, the product of electron and hole densities is a constant at equilibrium. This constant depends on the thermal energy of the system (i.e. the product of the Boltzmann constant, , and temperature, ), as well as the band gap (the energy separation between conduction and valence bands, ) and effective density of states in the valence and conduction bands. When the equilibrium electron and hole densities are equal, their density is called the intrinsic carrier density as this would be the value of and in a perfect crystal. Note that the final product is independent of the Fermi level : | 7 | Physical Chemistry |
In the 1970s–80s, it was realized that nanosized systems may affect ionic conductivity, opening a new field of nanoionics. In 1973, it was reported that ionic conductivity of lithium iodide (LiI) crystals could be increased 50 times by adding to it a fine powder of ‘’insulating’’ material (alumina). This effect was reproduced in the 1980s in Ag- and Tl-halides doped with alumina nanoparticles. Similarly, addition of insulating nanoparticles helped increase the conductivity of ionic polymers. These unexpected results were explained by charge separation at the matrix-nanoparticle interface that provided additional conductive channels to the matrix, and the small size of the filler particles was required to increase the area of this interface. Similar charge-separation effects were observed for grain boundaries in crystalline ionic conductors. | 7 | Physical Chemistry |
In pyrotechnics, it is used as fuel to make special mixtures, e.g. for production of smokes, in flash compositions, and in percussion caps. Specification for pyrotechnic calcium silicide is MIL-C-324C. In some mixtures it may be substituted with ferrosilicon. Silicon-based fuels are used in some time delay mixtures, e.g. for controlling of explosive bolts, hand grenades, and infrared decoys. Smoke compositions often contain hexachloroethane; during burning they produce silicon tetrachloride, which, like titanium tetrachloride used in smoke-screens, reacts with air moisture and produces dense white fog. Gum arabic is used in some mixtures to inhibit calcium silicide decomposition. | 8 | Metallurgy |
The boat conformation (C, below) is a transition state, allowing the interconversion between two different twist-boat conformations. While the boat conformation is not necessary for interconversion between the two chair conformations of cyclohexane, it is often included in the reaction coordinate diagram used to describe this interconversion because its energy is considerably lower than that of the half-chair, so any molecule with enough energy to go from twist-boat to chair also has enough energy to go from twist-boat to boat. Thus, there are multiple pathways by which a molecule of cyclohexane in the twist-boat conformation can achieve the chair conformation again. | 4 | Stereochemistry |
P2 receptor may refer to:
Nucleotides, if released into the extracellular environment, can lead to cell death or other harmful cellular consequences. To avoid cellular damage, nucleotides should be neutralized, which is accomplished by P2 receptors. Almost every cell type expresses P2 receptors. Purinergic signalling also has a pathophysiological role in several immune cells including calcium mobilization, actin polymerization, chemotaxis, the release of mediators, cell maturation, cytotoxicity, and cell death etc.
Depending on the nature of the receptor they are found to be of two types:
*P2Y receptors (metabotropic)
*P2X receptors (ionotropic)
P is for purinergic, P2 refers to ATP receptors, as opposed to P1 adenosine adenosine receptors. P2X receptors are ATP activated channels that allow the passage of ions across cell membranes. P2Y receptors are ATP activated G protein-coupled receptors (GPCRs) that initiate an intracellular chain of reactions.
Extracellular ATP and the related purine and pyrimidine nucleotides exert their functions via signalling through membrane-bound purinergic P2 receptors. These receptors are widely expressed throughout the body on various immune and nonimmune cells. P2X receptors are ionotropic receptors while P2Y are GPCR type receptors. P2X receptor family encompasses 7 genes. P2Y family has 8 receptors that can be divided into two sub-families depending upon the structural similarity. P2X receptors are activated with ATP while P2Y receptors are activated by diphosphates, triphosphates, purines, pyrimidines, etc. | 1 | Biochemistry |
Urea was first discovered in urine in 1727 by the Dutch scientist Herman Boerhaave, although this discovery is often attributed to the French chemist Hilaire Rouelle as well as William Cruickshank.
Boerhaave used the following steps to isolate urea:
# Boiled off water, resulting in a substance similar to fresh cream
# Used filter paper to squeeze out remaining liquid
# Waited a year for solid to form under an oily liquid
# Removed the oily liquid
# Dissolved the solid in water
# Used recrystallization to tease out the urea
In 1828, the German chemist Friedrich Wöhler obtained urea artificially by treating silver cyanate with ammonium chloride.
This was the first time an organic compound was artificially synthesized from inorganic starting materials, without the involvement of living organisms. The results of this experiment implicitly discredited vitalism, the theory that the chemicals of living organisms are fundamentally different from those of inanimate matter. This insight was important for the development of organic chemistry. His discovery prompted Wöhler to write triumphantly to Jöns Jakob Berzelius:
:"I must tell you that I can make urea without the use of kidneys, either man or dog. Ammonium cyanate is urea."
In fact, his second sentence was incorrect. Ammonium cyanate and urea are two different chemicals with the same empirical formula , which are in chemical equilibrium heavily favoring urea under standard conditions. Regardless, with his discovery, Wöhler secured a place among the pioneers of organic chemistry.
Uremic frost was first described in 1865 by Harald Hirschsprung, the first Danish pediatrician in 1870 who also described the disease that carries his name in 1886. Uremic frost has become rare since the advent of dialysis. It is the classical pre-dialysis era description of crystallized urea deposits over the skin of patients with prolonged kidney failure and severe uremia. | 0 | Organic Chemistry |
In some instances, an mRNA will be edited, changing the nucleotide composition of that mRNA. An example in humans is the apolipoprotein B mRNA, which is edited in some tissues, but not others. The editing creates an early stop codon, which, upon translation, produces a shorter protein. | 1 | Biochemistry |
Flutamide is the generic name of the drug and its , , , , and . Its names in Latin, German, and Spanish are flutamidum, flutamid, and flutamida, respectively. The medication has also been referred to by the name niftolide. | 4 | Stereochemistry |
The GDNF family receptor-α (GFRα) proteins are a group of co-receptors which form complexes with GDNF-family ligands (GFLs) to activate RET, the receptor of the GFLs. The GFRα co-receptors include the following:
* GFRα1 – preference for GDNF
* GFRα2 – preference for neurturin
* GFRα3 – preference for artemin
* GFRα4 – preference for persephin
* GFRAL - receptor for GDF15 | 1 | Biochemistry |
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