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Precious metals such as gold and platinum, but also many other rare and noble metals, largely originated within neutron star collisions - collisions between exceedingly heavy massive and dense remnants of supernovas. In the final moments of the collision, the physical conditions are so extreme that these heavy rare elements can be formed, and are sprayed into space. Interstellar dust and gas clouds contain some of these elements, as did the dust cloud from which our solar system formed.
Those heavy metals fell to the centre of the molten core of earth, and are no longer accessible. However about 200 million years after Earth formed, a late heavy bombardment of meteors impacted earth. As Earth had already begun to cool and solidify, the material (including heavy metals) in that bombardment became part of earth's crust, rather than falling deep into the core. They became processed and exposed by geological processes over billions of years. It is believed that this represents the origin of many elements, and all heavy metals, that are found on earth today. | 0 | Theoretical and Fundamental Chemistry |
Patients who suffer from obstructive sleep apnea can experience impaired cardiac repolarization, increasing the morbidity and mortality of the condition greatly. Especially at higher altitudes, patients are much more susceptible to repolarization disturbances. This can be somewhat mitigated through the use of medications such as acetazolamide, but the drugs do not provide sufficient protection. Acetazolamide and similar drugs are known to be able to improve the oxygenation and sleep apnea for patients in higher altitudes, but the benefits of the drug have been observed only when traveling at altitudes temporarily, not for people who remain at a higher altitude for a longer time. | 0 | Theoretical and Fundamental Chemistry |
In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon as dissolved inorganic carbon (DIC) from the ocean's surface to its interior. | 0 | Theoretical and Fundamental Chemistry |
The applicability domain (AD) (for both chemistry and machine learning) of a QSAR model is the physico-chemical, structural or biological space, knowledge or information on which the training set of the model has been developed, and for which it is applicable to make predictions for new compounds.
The purpose of AD is to state whether the model's assumptions are met, and for which chemicals the model can be reliably applicable. In general, this is the case for interpolation rather than for extrapolation. Up to now there is no single generally accepted algorithm for determining the AD: a comprehensive survey can be found in a Report and Recommendations of ECVAM Workshop 52. There exists a rather systematic approach for defining interpolation regions. The process involves the removal of outliers and a probability density distribution method using kernel-weighted sampling.
Another widely used approach for the structural AD of the regression QSAR models is based on the leverage calculated from the diagonal values of the hat matrix of the modeling molecular descriptors.
A recent rigorous benchmarking study of several AD algorithms identified standard-deviation of model predictions as the most reliable approach.
To investigate the AD of a training set of chemicals one can directly analyse properties of the multivariate descriptor space of the training compounds or more indirectly via distance (or similarity) metrics. When using distance metrics care should be taken to use an orthogonal and significant vector space. This can be achieved by different means of feature selection and successive principal components analysis. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a C–H···O interaction is occasionally described as a special type of weak hydrogen bond. These interactions frequently occur in the structures of important biomolecules like amino acids, proteins, sugars, DNA and RNA. | 0 | Theoretical and Fundamental Chemistry |
Heteroepitaxial growth is classified into three primary growth modes-- Volmer–Weber (VW), Frank–van der Merwe (FM) and Stranski–Krastanov (SK).
In the VW growth regime, the epitaxial film grows out of 3D nuclei on the growth surface. In this mode, the adsorbate-adsorbate interactions are stronger than adsorbate-surface interactions, leading to island formation by local nucleation and the epitaxial layer is formed when the islands join.
In the FM growth mode, adsorbate-surface and adsorbate-adsorbate interactions are balanced, which promotes 2D layer-by-layer or step-flow epitaxial growth.
The SK mode is a combination of VW and FM modes. In this mechanism, the growth initiates in the FM mode, forming 2D layers, but after reaching a critical thickness, enters a VW-like 3D island growth regime.
Practical epitaxial growth, however, takes place in a high supersaturation regime, away from thermodynamic equilibrium. In that case, the epitaxial growth is governed by adatom kinetics rather than thermodynamics, and 2D step-flow growth becomes dominant. | 0 | Theoretical and Fundamental Chemistry |
Plastic deformation happens when stresses flatten, bend, or twist a material until it cannot return to its original shape. This can create cracks in the material and decrease its lifetime. | 1 | Applied and Interdisciplinary Chemistry |
G protein-coupled receptors (GPCRs) are a large family of integral membrane proteins that respond to a variety of extracellular stimuli. Each GPCR binds to and is activated by a specific ligand stimulus that ranges in size from small molecule catecholamines, lipids, or neurotransmitters to large protein hormones. When a GPCR is activated by its extracellular ligand, a conformational change is induced in the receptor that is transmitted to an attached intracellular heterotrimeric G protein complex. The G alpha subunit of the stimulated G protein complex exchanges GDP for GTP and is released from the complex.
In a cAMP-dependent pathway, the activated G alpha subunit binds to and activates an enzyme called adenylyl cyclase, which, in turn, catalyzes the conversion of ATP into cyclic adenosine monophosphate (cAMP).
Increases in concentration of the second messenger cAMP may lead to the activation of
* cyclic nucleotide-gated ion channels
* exchange proteins activated by cAMP (EPAC) such as RAPGEF3
* popeye domain containing proteins (Popdc)
* an enzyme called protein kinase A (PKA).
The PKA enzyme is also known as cAMP-dependent enzyme because it gets activated only if cAMP is present. Once PKA is activated, it phosphorylates a number of other proteins including:
* enzymes that convert glycogen into glucose
* enzymes that promote muscle contraction in the heart leading to an increase in heart rate
* transcription factors, which regulate gene expression
* also phosphorylate AMPA receptors
Specificity of signaling between a GPCR and its ultimate molecular target through a cAMP-dependent pathway may be achieved through formation of a multiprotein complex that includes the GPCR, adenylyl cyclase, and the effector protein. | 1 | Applied and Interdisciplinary Chemistry |
The age of the Earth is 4.54 Gya as found by radiometric dating of calcium-aluminium-rich inclusions in carbonaceous chrondrite meteorites, the oldest material in the Solar System. The Hadean Earth (from its formation until 4 Gya) was at first inhospitable to any living organisms. During its formation, the Earth lost a significant part of its initial mass, and consequentially lacked the gravity to hold molecular hydrogen and the bulk of the original inert gases. Soon after initial accretion of Earth at 4.48 Ga, its collision with Theia, a hypothesised impactor, is thought to have created the ejected debris that would eventually form the Moon. This impact would have removed the Earth's primary atmosphere, leaving behind clouds of viscous silicates and carbon dioxide. This unstable atmosphere was short-lived and condensed shortly after to form the bulk silicate Earth, leaving behind an atmosphere largely consisting of water vapor, nitrogen, and carbon dioxide, with smaller amounts of carbon monoxide, hydrogen, and sulfur compounds. The solution of carbon dioxide in water is thought to have made the seas slightly acidic, with a pH of about 5.5.
Condensation to form liquid oceans is theorised to have occurred as early as the Moon-forming impact. This scenario has found support from the dating of 4.404 Gya zircon crystals with high δO values from metamorphosed quartzite of Mount Narryer in Western Australia. The Hadean atmosphere has been characterized as a "gigantic, productive outdoor chemical laboratory," similar to volcanic gases today which still support some abiotic chemistry. Despite the likely increased volcanism from early plate tectonics, the Earth may have been a predominantly water world between 4.4 and 4.3 Gya. It is debated whether or not crust was exposed above this ocean due to uncertainties of what early plate tectonics looked like. For early life to have developed, it is generally thought that a land setting is required, so this question is essential to determining when in Earth's history life evolved. The post-Moon-forming impact Earth likely existed with little if any continental crust, a turbulent atmosphere, and a hydrosphere subject to intense ultraviolet light from a T Tauri stage Sun, from cosmic radiation, and from continued asteroid and comet impacts. Despite all this, niche environments likely existed conducive to life on Earth in the Late-Hadean to Early-Archaean.
The Late Heavy Bombardment hypothesis posits that a period of intense impact occurred at ~3.9 Gya during the Hadean. A cataclysmic impact event would have had the potential to sterilise all life on Earth by volatilising liquid oceans and blocking the Sun needed for photosynthesising primary producers, pushing back the earliest possible emergence of life to after Late Heavy Bombardment. Recent research questions both the intensity of the Late Heavy Bombardment as well as its potential for sterilisation. Uncertainties as to whether Late Heavy Bombardment was one giant impact or a period of greater impact rates greatly changed the implication of its destructive power. The 3.9 Ga date arises from dating of Apollo return mission samples collected mostly near the Imbrium Basin, biasing the age of recorded impacts. Impact modelling of the lunar surface reveals that rather than a cataclysmic event at 3.9 Ga, multiple small-scale, short-lived periods of bombardment likely occurred. Terrestrial data backs this idea by showing multiple periods of ejecta in the rock record both before and after the 3.9 Ga marker, suggesting that the early Earth was subject to continuous impacts that would not have had as great an impact on extinction as previously thought. If the Late Heavy Bombardment did not take place, this allows for the emergence of life to have taken place far before 3.9 Ga.
If life evolved in the ocean at depths of more than ten meters, it would have been shielded both from late impacts and the then high levels of ultraviolet radiation from the sun. Geothermically heated oceanic crust could have yielded far more organic compounds through deep hydrothermal vents than the Miller–Urey experiments indicated. The available energy is maximized at 100–150 °C, the temperatures at which hyperthermophilic bacteria and thermoacidophilic archaea live. | 0 | Theoretical and Fundamental Chemistry |
Cellulose is synthesized by cellulose synthase or Rosette terminal complexes which reside on a cells membrane. As cellulose fibrils are synthesized and grow extracellularly they push up against neighboring cells. Since the neighboring cell can not move easily the Rosette complex is instead pushed around the cell through the fluid phospholipid membrane. Eventually this results in the cell becoming wrapped in a microfibril layer. This layer becomes the cell wall. The organization of microfibrils forming the primary cell wall is rather disorganized. However, another mechanism is used in secondary cell walls leading to its organization. Essentially, lanes on the secondary cell wall are built with microtubules. These lanes force microfibrils to remain in a certain area while they wrap. During this process microtubules can spontaneously depolymerize and repolymerize in a different orientation. This leads to a different direction in which the cell continues getting wrapped.
Fibrillin microfibrils are found in connective tissues, which mainly makes up fibrillin-1 and provides elasticity. During the assembly, mirofibrils exhibit a repeating stringed-beads arrangement produced by the cross-linking of molecules forming a striated pattern with a given periodicity when viewed stained under an electron microscope. In the formation of elastic fiber, fibrillin microfibrils guides the deposit of tropoelastin and remains in the outer layer of mature elastin fibers. The microfibril is also associated in cell communication. Formation of fibrillin microfibrils in the pericellular region affects the activity of a growth factor called TGFβ. | 1 | Applied and Interdisciplinary Chemistry |
Dicloxacillin is used to treat mild-to-moderate staphylococcal infections. To decrease the development of resistance, dicloxacillin is recommended to treat infections that are suspected or proven to be caused by beta-lactamase-producing bacteria.
Dicloxacillin is similar in pharmacokinetics, antibacterial activity, and indications to flucloxacillin, and the two agents are considered interchangeable. It is believed to have lower incidence of severe hepatic adverse effects than flucloxacillin, but a higher incidence of renal adverse effects.
Dicloxacillin is used for the treatment of infections caused by susceptible bacteria. Specific approved indications include:
*Staphylococcal skin infections and cellulitis – including impetigo, otitis externa, folliculitis, boils, carbuncles, and mastitis
*Pneumonia (adjunct)
*Osteomyelitis, septic arthritis, throat infections, streptococcus
*Septicaemia
*Empirical treatment for endocarditis
*Surgical prophylaxis | 0 | Theoretical and Fundamental Chemistry |
SCI organises over 100 [https://www.soci.org/events conferences and events] per year which are focused on cutting edge scientific and special interest subjects. These are primarily organised through SCI member-led technical, international and regional interest groups.
SCI runs free Public Evening Lectures, both at its headquarters as well as online, through its [https://www.soci.org/news/general-news/sci-launches-new-series-of-public-talks SCITalks!] programme.
The society has an extensive awards programmes designed to raise awareness of the benefits of the practical application of chemistry and related sciences across scientific disciplines and industrial sectors. The SCI also confers scholarships and travel bursaries to student members, and celebrates accomplished scientists, educators and business people through a number of international awards, medals, and lectureships. | 1 | Applied and Interdisciplinary Chemistry |
Experimental Exchangeability was devised by Yampolsky and Stoltzfus. It is the measure of the mean effect of exchanging one amino acid into a different amino acid.
It is based on analysis of experimental studies where 9671 amino acids replacements from different proteins, were compared for effect on protein activity. | 1 | Applied and Interdisciplinary Chemistry |
Various radionuclides emit beta particles, high-speed electrons or positrons, through radioactive decay of their atomic nucleus. These can be used in a range of different industrial, scientific, and medical applications. This article lists some common beta-emitting radionuclides of technological importance, and their properties. | 0 | Theoretical and Fundamental Chemistry |
It has been rigorously experimentally established that: <br>
a) When a true (thermodynamic) equilibrium is reached between a crystalline solid phase (electrolyte) and a solution, the microcomponent present in the solution and isomorphic with the solid phase is distributed between the two immiscible solvents according to the Berthelot-Nernst law and at that in all known cases in its simple form: Ск/Ср=К or
</div>
where x is the amount of microcomponent transferred into crystals, a is the total amount of microcomponent, y and b are the corresponding values for macrocomponent.<br>
b) The mechanism responsible for achieving true equilibrium between the crystalline phase and the solution is reduced to the process of multiple recrystallization of the solid phase, that replaces in the considered case practically absent under ordinary conditions the diffusion process in the solid state. Recrystallization at submicroscopic sizes of crystals proceeds extremely fast, thus in crystallization from supersaturated solutions recrystallization and establishment of equilibrium are finished at the stage when crystallites are small enough.
c) In the case of slow crystallization not from supersaturated solutions, but from saturated ones, in particular, due to slow evaporation, the true equilibrium between crystals and solution is not observed, and the distribution of the microcomponent between the solid phase and solution proceeds in this case according to the logarithmic law of Goskins and Derner, developed on the basis of the idea of continuous ion exchange between the faces of the growing crystal and the solution </div>
Here, as above: a is the total amount of microcomponent, x is the amount of microcomponent transferred to the solid phase, b is the total amount of macrocomponent, y is the amount of macrocomponent transferred to the solid phase. <br>
d) An abrupt change in the value of D with a change in temparature or in the composition of the liquid phase is an indicator of the occurrence of a new chemical equilibrium in solution or in the solid phase.
The case of distribution of the microcomponent between the crystalline solid phase and the solution (according to the Berthelot-Nernst or Goskins and Derner law) can serve as evidence for the formation between the microcomponent and the anion or cation of the solid phase of compounds crystallizing isomorphically with the solid phase. | 0 | Theoretical and Fundamental Chemistry |
Casein kinase 2 ()(CK2/CSNK2) is a serine/threonine-selective protein kinase that has been implicated in cell cycle control, DNA repair, regulation of the circadian rhythm, and other cellular processes. De-regulation of CK2 has been linked to tumorigenesis as a potential protection mechanism for mutated cells. Proper CK2 function is necessary for survival of cells as no knockout models have been successfully generated. | 1 | Applied and Interdisciplinary Chemistry |
Both the trimer and tetramer in hydrocarbon solutions photochemically react forming clear liquids identified as alkyl-substituted derivatives , where n = 3, 4. Such reactions proceed under prolonged UVC (mercury arc) illumination without affecting the rings. Solid films of the trimer and tetramer will not undergo any chemical change under such irradiation conditions. | 0 | Theoretical and Fundamental Chemistry |
Eukaryote expression vectors require sequences that encode for:
*Polyadenylation tail: Creates a polyadenylation tail at the end of the transcribed pre-mRNA that protects the mRNA from exonucleases and ensures transcriptional and translational termination: stabilizes mRNA production.
*Minimal UTR length: UTRs contain specific characteristics that may impede transcription or translation, and thus the shortest UTRs or none at all are encoded for in optimal expression vectors.
*Kozak sequence: Vectors should encode for a Kozak sequence in the mRNA, which assembles the ribosome for translation of the mRNA. | 1 | Applied and Interdisciplinary Chemistry |
In the process of transcription (by any polymerase), there are three main stages:
#Initiation: the construction of the RNA polymerase complex on the gene's promoter with the help of transcription factors
#Elongation: the actual transcription of the majority of the gene into a corresponding RNA sequence
#Termination: the cessation of RNA transcription and the disassembly of the RNA polymerase complex. | 1 | Applied and Interdisciplinary Chemistry |
Nitrazine or phenaphthazine is a pH indicator dye often used in medicine. More sensitive than litmus, nitrazine indicates pH in the range of 4.5 to 7.5. Nitrazine is usually used as the disodium salt. | 0 | Theoretical and Fundamental Chemistry |
A concentric reducer is used to join pipe sections or tube sections on the same axis. The concentric reducer is cone-shaped, and is used when there is a shift in diameter between pipes. For example, when a 1" pipe transitions into a 3/4" pipe and the top or bottom of the pipe doesn't need to remain level. This pipe reducer may be used when there is a single diameter change or multiple diameter changes.
Unlike eccentric reducers, concentric reducers have a common center line. Concentric reducers are useful when cavitation is present.
Eccentricity occurs when the centerline is offset. | 1 | Applied and Interdisciplinary Chemistry |
Pyruvate is an important chemical compound in biochemistry. It is the output of the metabolism of glucose known as glycolysis. One molecule of glucose breaks down into two molecules of pyruvate, which are then used to provide further energy, in one of two ways. Pyruvate is converted into acetyl-coenzyme A, which is the main input for a series of reactions known as the Krebs cycle (also known as the citric acid cycle or tricarboxylic acid cycle). Pyruvate is also converted to oxaloacetate by an anaplerotic reaction, which replenishes Krebs cycle intermediates; also, the oxaloacetate is used for gluconeogenesis.
These reactions are named after Hans Adolf Krebs, the biochemist awarded the 1953 Nobel Prize for physiology, jointly with Fritz Lipmann, for research into metabolic processes. The cycle is also known as the citric acid cycle or tricarboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions.
If insufficient oxygen is available, the acid is broken down anaerobically, creating lactate in animals and ethanol in plants and microorganisms (and carp). Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation, or to acetaldehyde (with the enzyme pyruvate decarboxylase) and then to ethanol in alcoholic fermentation.
Pyruvate is a key intersection in the network of metabolic pathways. Pyruvate can be converted into carbohydrates via gluconeogenesis, to fatty acids or energy through acetyl-CoA, to the amino acid alanine, and to ethanol. Therefore, it unites several key metabolic processes. | 1 | Applied and Interdisciplinary Chemistry |
An organism is considered viable if it reaches a stable gene expression pattern. An organism with oscillated expression pattern is discarded and cannot enter the next generation. | 1 | Applied and Interdisciplinary Chemistry |
On an industrial scale, the reaction of acetic anhydride with hydrogen chloride produces a mixture of acetyl chloride and acetic acid:
Common syntheses of acyl chlorides also entail the reaction of carboxylic acids with phosgene, thionyl chloride, and phosphorus trichloride Phosphorus pentabromide is used for acyl bromides, which are rarely of value. | 0 | Theoretical and Fundamental Chemistry |
Emulsions contain both a dispersed and a continuous phase, with the boundary between the phases called the "interface". Emulsions tend to have a cloudy appearance because the many phase interfaces scatter light as it passes through the emulsion. Emulsions appear white when all light is scattered equally. If the emulsion is dilute enough, higher-frequency (shorter-wavelength) light will be scattered more, and the emulsion will appear bluer – this is called the "Tyndall effect". If the emulsion is concentrated enough, the color will be distorted toward comparatively longer wavelengths, and will appear more yellow. This phenomenon is easily observable when comparing skimmed milk, which contains little fat, to cream, which contains a much higher concentration of milk fat. One example would be a mixture of water and oil.
Two special classes of emulsions – microemulsions and nanoemulsions, with droplet sizes below 100 nm – appear translucent. This property is due to the fact that light waves are scattered by the droplets only if their sizes exceed about one-quarter of the wavelength of the incident light. Since the visible spectrum of light is composed of wavelengths between 390 and 750 nanometers (nm), if the droplet sizes in the emulsion are below about 100 nm, the light can penetrate through the emulsion without being scattered. Due to their similarity in appearance, translucent nanoemulsions and microemulsions are frequently confused. Unlike translucent nanoemulsions, which require specialized equipment to be produced, microemulsions are spontaneously formed by "solubilizing" oil molecules with a mixture of surfactants, co-surfactants, and co-solvents. The required surfactant concentration in a microemulsion is, however, several times higher than that in a translucent nanoemulsion, and significantly exceeds the concentration of the dispersed phase. Because of many undesirable side-effects caused by surfactants, their presence is disadvantageous or prohibitive in many applications. In addition, the stability of a microemulsion is often easily compromised by dilution, by heating, or by changing pH levels.
Common emulsions are inherently unstable and, thus, do not tend to form spontaneously. Energy input – through shaking, stirring, homogenizing, or exposure to power ultrasound – is needed to form an emulsion. Over time, emulsions tend to revert to the stable state of the phases comprising the emulsion. An example of this is seen in the separation of the oil and vinegar components of vinaigrette, an unstable emulsion that will quickly separate unless shaken almost continuously. There are important exceptions to this rule – microemulsions are thermodynamically stable, while translucent nanoemulsions are kinetically stable.
Whether an emulsion of oil and water turns into a "water-in-oil" emulsion or an "oil-in-water" emulsion depends on the volume fraction of both phases and the type of emulsifier (surfactant) (see Emulsifier, below) present. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen-bond catalysts can also accelerate reactions by assisting in the formation of electrophilic species through abstracting and/or coordinating an anion such as a halide. Urea and thiourea catalysts are the most common donors in anion-binding catalysis, and their ability to bind halides and other anions has been well established in the literature. The use of chiral anion-binding catalysts can create an asymmetric ion pair and induce remarkable stereoselectivity.
One of the first reactions proposed to proceed through anion-binding catalysis is the Pictet-Spengler-type cyclization of hydroxylactams with TMSCl under thiourea catalysis. In the proposed mechanism, after initial substitution of the hydroxyl group with chloride, the key ion pair is formed. The activated iminium ion is closely associated with the chiral thiourea-bound chloride, and intramolecular cyclization proceeds with high stereoselectivity.
Asymmetric ion pairs can also be attacked in intermolecular reactions. In an interesting example, asymmetric addition of enol silane nucleophiles to oxocarbenium ions can be effected by catalytically forming the oxocarbenium through anion binding. Starting from an acetal, the chloroether is generated with boron trichloride and reacted with the enol silane and catalyst. The mechanism of formation of the oxocarbenium-thiourea-chloride complex is not fully resolved. It is thought that under the reaction conditions, the chloroether can epimerize and thiourea can stereoselectively bind chloride to form a closely associated ion pair. This asymmetric ion pair is then attacked by the silane to generate alkylated product.
A notable example of the anion-binding mechanism is the hydrocyanation of imines catalyzed by Jacobsen's amido-thiourea catalyst depicted in the below diagram. This reaction is also one of the most extensively studied through computational, spectroscopic, labeling and kinetic experiments. While direct addition of cyanide to a catalyst-bound imine was considered, an alternative mechanism involving formation of an iminium-cyanide ion pair controlled by catalyst was calculated to have a barrier that is lower by 20 kcal/mol. The proposed most likely mechanism begins with binding of the catalyst to HNC, which exists in equilibrium with HCN. This complex then protonates a molecule of imine, forming an iminium-cyanide ion pair with the catalyst binding and stabilizing the cyanide anion. The iminium is thought to also interact with the amide carbonyl on the catalyst molecule (see bifunctional catalysis below). The bound cyanide anion then rotates, and attacks the iminium through carbon. The investigators conclude that though imine-urea binding was observed through spectroscopy and was supported by early kinetic experiments, imine binding is off-cycle and all evidence points toward this mechanism involving thiourea-bound cyanide. | 0 | Theoretical and Fundamental Chemistry |
* ASTM F67 Unalloyed (Commercially Pure) Titanium
* ASTM F136 Ti-6Al-4V-ELI
* ASTM F1295 Ti-6Al-7Nb
* ASTM F1472 Ti-6Al-4V | 1 | Applied and Interdisciplinary Chemistry |
In most solids, ions rigidly occupy fixed positions, strongly embraced by neighboring atoms or ions. In some solids, selected ions are highly mobile allowing ionic conduction. The mobility increases with temperature. Materials exhibiting this property are used in batteries. A well-known ion conductive solid is β-alumina ("BASE"), a form of aluminium oxide that has channels through which sodium cations can hop. When this ceramic is complexed with a mobile ion, such as Na, it behaves as so-called fast ion conductor. BASE is used as a membrane in several types of molten salt electrochemical cell. | 0 | Theoretical and Fundamental Chemistry |
In solution, reducing monosaccharides exist in equilibrium between their acyclic and cyclic forms with less than 1% in the acyclic form. The open chain form can close to give the pyranose and furanose with both the α- and β-anomers present for each. The equilibrium population of conformers depends on their relative energies which can be determined to a rough approximation using steric and stereoelectronic arguments. It has been shown that cations in solution can shift the equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Cupellation was also being used in parts of Europe to extract gold, silver, zinc, and tin by the late ninth to tenth century AD. Here, one of the earliest examples of an integrated unit process for extracting more than one precious metal was first introduced by Theophilus around the twelfth century. First, the gold-silver ore is melted down in the crucible, but with an excess amount of lead. The intense heat then oxidizes the lead which reacts quickly and binds with the impurities in the gold-silver ore. Since both gold and silver have low reactivity with the impurities, they remain behind once the slag is removed. The last stage involves parting, in which the silver is separated from the gold. First the gold-silver alloy is hammered into thin sheets and placed into a vessel. The sheets were then covered in urine, which contains sodium chloride (NaCl). The vessel is then capped and heated for several hours until the chlorides bind with the silver, creating silver chloride (AgCl). Finally, the silver chloride powder is then removed and smelted to recover the silver, while the pure gold remains intact. | 1 | Applied and Interdisciplinary Chemistry |
Veige joined the faculty of the University of Florida as an assistant professor of chemistry (inorganic chemistry) in 2004. In 2010, Veige received the Alfred P. Sloan fellowship award, the only researcher to be so honored in Florida in 2010. He was promoted to an associate professor in 2011. He is currently the director of the Center for Catalysis in the Department of Chemistry at the University of Florida.
His research focuses on the design, synthesis, isolation, and characterization of novel inorganic molecules for application in the production of fertilizers, polymers, and pharmaceuticals. His research has included the preparation of chiral catalysts, synthesis of nitriles via N-atom transfer to acid chlorides, chromium catalyzed aerobic oxidation, an alkene isomerization catalyst, a highly active alkene polymerization catalyst, and a highly active alkyne polymerization catalyst. | 0 | Theoretical and Fundamental Chemistry |
Pockels spent much of her life caring for her sick parents, which she noted to be "very challenging". Her father died in 1906 and her mother died in 1914. By that time, Pockels was herself in ill health, necessitating a stay for a time in a sanatorium. She traveled in Europe for enjoyment. During Pockels' later years, she was known for her role as an aunt, "Auntie Agnes."
Pockels died in 1935 in Brunswick, Germany, in the town where she had lived for the duration of her career. | 0 | Theoretical and Fundamental Chemistry |
Freeze-dried samples of Caldora penicillata had EtOAc−MeOH and HO−EtOH applied to them in order to extract Caldoramide. The extracts were partitioned with n-BuOH and HO and then fractions were taken based on solubility in either EtOAc or BuOH. Caldoramide was extracted from the BuOH soluble fraction. | 1 | Applied and Interdisciplinary Chemistry |
From the general mole balance on some species , where for a CSTR steady state and perfect mixing are assumed,
Assuming a constant volumetric flow rate , which is the case for a liquid reactor or a gas phase reaction with no net generation of moles,
where the space-time is defined to be the ratio of the reactor volume to volumetric flow rate. It is the time required for a slug of fluid to pass through the reactor. For a decomposition reaction, the rate of reaction is proportional to some power of the concentration of . In addition, for a single reaction a conversion may be defined in terms of the limiting reactant, for the simple decomposition that is species
As can be seen, as the Damköhler number increases, the other term must decrease. The ensuing polynomial can be solved and the conversion for the rule of thumb Damköhler numbers found. Alternatively, one can graph the expressions and see where they intersect with the line given by the inverse Damköhler number to see the solution for conversion. In the plot below, the y-axis is the inverse Damköhler number and the x-axis the conversion. The rule-of-thumb Damköhler numbers have been placed as dashed horizontal lines. | 1 | Applied and Interdisciplinary Chemistry |
The origin is the word lixiviate, meaning to leach or to dissolve out, deriving from the Latin lixivium. A lixiviant assists in rapid and complete leaching, for example during in situ leaching. The metal can be recovered from it in a concentrated form after leaching. | 1 | Applied and Interdisciplinary Chemistry |
Stearoylethanolamide (SEA) is an endocannabinoid neurotransmitter.
Stearoylethanolamide (CHNO; 18:0), also called N-(octadecanoyl)ethanolamine, is an N-acylethanolamine and the ethanolamide of octadecanoic acid (CHO; 18:0) and ethanolamine (MEA: CHNO), and functionally related to an octadecanoic acid.
Levels of SEA correlate with changes in pain intensity, indicating this SEA change, reflect the pain reduction effects of IPRP. | 1 | Applied and Interdisciplinary Chemistry |
* Cyanogen - ()
* Isocyanogen - ()
* Diisocyanogen - ()
* Paracyanogen - a cyanogen polymer,
* Paraisocyanogen - a cyanogen polymer, | 0 | Theoretical and Fundamental Chemistry |
* KEGG Pathway database is a popular pathway search database highly used by biologists.
* WikiPathways is a community curated pathway database using the "wiki" concept. All pathways have an open license and can be freely used.
* Reactome is a free and manually curated online database of biological pathways.
* NCI-Nature Pathway Interaction Database is a free biomedical database of human cellular signaling pathways (new official name: NCI Nature Pathway Interaction Database: Pathway, synonym: PID).
* PhosphoSitePlus is a database of observed post-translational modifications in human and mouse proteins; an online systems biology resource providing comprehensive information and tools for the study of protein post-translational modifications (PTMs) including phosphorylation, ubiquitination, acetylation and methylation.
* BioCyc database collection is an assortment of organism specific Pathway/Genome Databases.
* Human Protein Reference Database is a centralized platform to visually depict and integrate information pertaining to domain architecture, post-translational modifications, interaction networks and disease association for each protein in the human proteome (the last release was #9 in 2010).
* PANTHER (Protein ANalysis THrough Evolutionary Relationships) is a large curated biological database of gene/protein families and their functionally related subfamilies that can be used to classify and identify the function of gene products.
* TRANSFAC (TRANScription FACtor database) is a manually curated database of eukaryotic transcription factors, their genomic binding sites and DNA binding profiles (provided by geneXplain GmbH).
* MiRTarBase is a curated database of MicroRNA-Target Interactions.
* DrugBank is a comprehensive, high-quality, freely accessible, online database containing information on drugs and drug targets.
* esyN is a network viewer and builder that allows to import pathways from the biomodels database or from biogrid, flybase pombase and see what drugs interact with the proteins in your network.
* Comparative Toxicogenomics Database (CTD) is a public website and research tool that curates scientific data describing relationships between chemicals/drugs, genes/proteins, diseases, taxa, phenotypes, GO annotations, pathways, and interaction modules; CTD illuminates how environmental chemicals affect human health.
* Pathway commons is a project and database that uses BioPAX language to convert, integrate and query other biological pathway and interaction databases. | 1 | Applied and Interdisciplinary Chemistry |
* National Museum of Australia
* Australian Museum
* National Museum of Natural History, Smithsonian Institution
* Art Gallery of New South Wales
* South Australian Museum
* State Herbarium of South Australia
* Art Gallery of South Australia
* State Library of South Australia (literary collections)
* Tasmanian Museum and Art Gallery
* Art Gallery of Western Australia
* Queensland Art Gallery
* National Gallery of Victoria | 1 | Applied and Interdisciplinary Chemistry |
Here we have . Integration of gives and the three equations are
The first equation is the Hicks equation. Marris and Aswani (1977) showed that the only possible solution is and the remaining equations reduce to
A simple set of solutions to the above equation is
represents a flow due to two opposing rotational stream on a parabolic surface, represents rotational flow on a plane wall, represents a flow ellipsoidal vortex (special case – Hill's spherical vortex), represents a type of toroidal vortex etc.
The homogeneous solution for as shown by Berker
where are the Bessel function of the first kind and Bessel function of the second kind respectively. A special case of the above solution is Poiseuille flow for cylindrical geometry with transpiration velocities on the walls. Chia-Shun Yih found a solution in 1958 for Poiseuille flow into a sink when . | 1 | Applied and Interdisciplinary Chemistry |
In 1986, a meeting at the Institute Of Medicine defined gene therapy as the addition or replacement of a gene in a targeted cell type. In the same year, the FDA announced that it had jurisdiction over approving "gene therapy" without defining the term. The FDA added a very broad definition in 1993 of any treatment that would ‘modify or manipulate the expression of genetic material or to alter the biological properties of living cells’. In 2018 this was narrowed to ‘products that mediate their effects by transcription or translation of transferred genetic material or by specifically altering host (human) genetic sequences’.
Writing in 2018, in the Journal of Law and the Biosciences, Sherkow et al. argued for a narrower definition of gene therapy than the FDAs in light of new technology that would consist of any treatment that intentionally and permanently modified a cells genome, with the definition of genome including episomes outside the nucleus but excluding changes due to episomes that are lost over time. This definition would also exclude introducing cells that did not derive from a patient themselves, but include ex vivo approaches, and would not depend on the vector used.
During the COVID-19 pandemic, some academics insisted that the mRNA vaccines for COVID were not gene therapy to prevent the spread of incorrect information that the vaccine could alter DNA, other academics maintained that the vaccines were a gene therapy because they introduced genetic material into a cell. Fact-checkers, such as Full Fact, Reuters, PolitiFact, and FactCheck.org said that calling the vaccines a gene therapy was incorrect. Podcast host Joe Rogan was criticized for calling mRNA vaccines gene therapy as was British politician Andrew Bridgen, with fact checker Full Fact calling for Bridgen to be removed from the conservative party for this and other statements. | 1 | Applied and Interdisciplinary Chemistry |
One, two or three IVF treatments are government subsidised for people who are younger than 40 and have no children. The rules for how many treatments are subsidised, and the upper age limit for the people, vary between different county councils. Single people are treated, and embryo adoption is allowed. There are also private clinics that offer the treatment for a fee. | 1 | Applied and Interdisciplinary Chemistry |
A non-Kekulé molecule is a conjugated hydrocarbon that cannot be assigned a classical Kekulé structure.
Since non-Kekulé molecules have two or more formal charges or
radical centers, their spin-spin interactions can cause electrical conductivity or ferromagnetism (molecule-based magnets), and applications to functional materials are expected. However, as these molecules are quite reactive and most of them are easily decomposed or polymerized at room temperature, strategies for stabilization are needed for their practical use. Synthesis and observation of these reactive molecules are generally accomplished by matrix-isolation methods. | 0 | Theoretical and Fundamental Chemistry |
While most genes of E. coli can be recognized by an RNAP with one and only one type of sigma factor (e.g. sigma 70), a few genes (~ 5%) have what is called a “dual sigma factor preference”, that is, they can respond to two different sigma factors, as reported in RegulonDB. The most common ones are those promoters that can respond to both sigma 70 and to sigma 38 (iIlustrated in the figure) . Studies of the dynamics of these genes showed that when the cells enter stationary growth they are almost as induced as those genes that have preference for σ38 alone. This induction level was shown to be predictable from their promoter sequence. A model of their dynamics is shown in the figure. In the future, these promoters may become useful tools in synthetic genetic constructs in E. coli. | 1 | Applied and Interdisciplinary Chemistry |
Sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. The process allows for castings small enough fit in the palm of one's hand to those large enough for a train car bed (one casting can create the entire bed for one rail car). Sand casting also allows most metals to be cast depending on the type of sand used for the molds.
Sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates (1–20 pieces/hr-mold) and is unsurpassed for large-part production. Green (moist) sand, which is black in color, has almost no part weight limit, whereas dry sand has a practical part mass limit of . Minimum part weight ranges from . The sand is bonded using clays, chemical binders, or polymerized oils (such as motor oil). Sand can be recycled many times in most operations and requires little maintenance. | 1 | Applied and Interdisciplinary Chemistry |
Plastid differentiation is not permanent, in fact many interconversions are possible. Chloroplasts may be converted to chromoplasts, which are pigment-filled plastids responsible for the bright colors seen in flowers and ripe fruit. Starch storing amyloplasts can also be converted to chromoplasts, and it is possible for proplastids to develop straight into chromoplasts. Chromoplasts and amyloplasts can also become chloroplasts, like what happens when a carrot or a potato is illuminated. If a plant is injured, or something else causes a plant cell to revert to a meristematic state, chloroplasts and other plastids can turn back into proplastids. Chloroplast, amyloplast, chromoplast, proplastid are not absolute; state—intermediate forms are common. | 0 | Theoretical and Fundamental Chemistry |
Membranes, composed of either regenerated cellulose or cellulose esters, are manufactured through distinct processes of modifying and cross-linking cellulose fibers (derived from wood pulp or cotton fibers) to form films with differing properties and pore sizes. Variations in the manufacturing process significantly change the properties and pore sizes of the films; depending on the cross-linkages introduced in cellulose, the size of pores can be modulated. While similar in composition, most of the cellulose-based membranes currently manufactured are not necessarily useful for dialysis. Cellulose-based membranes are also widely used for applications ranging from food wrapping, film stock, or “plastic” wrap.
For dialysis applications, regenerated cellulose-based membranes are extruded as tubing or sheets and then dried. Glycerol is frequently added as a humectant to prevent cracking during drying and to help maintain the desired pore structure. Regenerated cellulose membranes are very hydrophilic and hydrate rapidly when introduced to water. Due to their additional crosslinking, regenerated cellulose membranes have better chemical compatibility and heat stability than membranes made from cellulose esters. Regenerated cellulose membranes are more resistant to organic solvents and to the weak or dilute acids and bases that are commonly used in protein and molecular biology applications. Membranes based on cellulose esters are typically supplied wet and come in a greater range of MWCOs. Pore sizes are typically more consistent across cellulose acetate membranes. | 1 | Applied and Interdisciplinary Chemistry |
C. Gardner Swain and Elmer C. Lupton Jr. from the Massachusetts Institute of Technology redefined the substituent parameter, σ, based on the idea that no more than two variables (resonance effects and field effects) are necessary to describe the effects of any given substituent. Field effects, F, are defined to include all effects (inductive and pure field). Likewise, effects due to resonance, R, are due to the average of electron-donating ability and electron-accepting ability. These two effects are assumed to be independent of each other and therefore can be written as a linear combination:
These two parameters are treated as independent terms because of the assumption that Swain and Lupton made; the substituent is kept distant by three or more saturated centers or if the substituent is (CH)N. All other terms are then negligible and leads to the Swain–Lupton equation (). | 0 | Theoretical and Fundamental Chemistry |
The Rüchardt experiment, invented by Eduard Rüchardt, is a famous experiment in thermodynamics, which determines the ratio of the molar heat capacities of a gas, i.e. the ratio of (heat capacity at constant pressure) and (heat capacity at constant volume) and is denoted by (gamma, for ideal gas) or (kappa, isentropic exponent, for real gas). It arises because the temperature of a gas changes as pressure changes.
The experiment directly yields the heat capacity ratio or adiabatic index of the gas, which is the ratio of the heat capacity at constant pressure to heat capacity at constant volume. The results are sometimes also known as the isentropic expansion factor. | 0 | Theoretical and Fundamental Chemistry |
Passive daytime radiative cooling (PDRC) is a zero-energy building cooling method proposed as a solution to reduce air conditioning, lower urban heat island effect, cool human body temperatures in extreme heat, move toward carbon neutrality and control global warming by enhancing terrestrial heat flow to outer space through the installation of thermally-emissive surfaces on Earth that require zero energy consumption or pollution. In contrast to compression-based cooling systems that are prevalently used (e.g., air conditioners), consume substantial amounts of energy, have a net heating effect, require ready access to electricity and often require coolants that are ozone-depleting or have a strong greenhouse effect, application of PDRCs may also increase the efficiency of systems benefiting from a better cooling, such like photovoltaic systems, dew collection techniques, and thermoelectric generators.
PDRC surfaces are designed to be high in solar reflectance (to minimize heat gain) and strong in longwave infrared (LWIR) thermal radiation heat transfer through the atmosphere's infrared window (8–13 µm) to cool temperatures even during the daytime. It is also referred to as passive radiative cooling, daytime passive radiative cooling, radiative sky cooling, photonic radiative cooling, and terrestrial radiative cooling. PDRC differs from solar radiation management because it increases radiative heat emission rather than merely reflecting the absorption of solar radiation.
Some estimates propose that if 1–2% of the Earth's surface area were dedicated to PDRC that warming would cease and temperature increases would be rebalanced to survivable levels. Regional variations provide different cooling potentials with desert and temperate climates benefiting more from application than tropical climates, attributed to the effects of humidity and cloud cover on reducing the effectiveness of PDRCs. Low-cost scalable PDRC materials feasible for mass production have been developed, such as coatings, thin films, metafabrics, aerogels, and biodegradable surfaces.
PDRCs can be included in self-adaptive systems, switching from passive cooling to heating to mitigate any potential "overcooling" effects in urban environments. They have also been developed in colors other than white, although there is generally a tradeoff in cooling potential, since darker color surfaces are less reflective. Research, development, and interest in PDRCs has grown rapidly since the 2010s, which has been attributed to a scientific breakthrough in the use of photonic metamaterials to achieve daytime cooling in 2014, along with growing concerns over energy use and global warming. | 0 | Theoretical and Fundamental Chemistry |
Atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES) is a spectroanalytical procedure for the quantitative determination of chemical elements by free atoms in the gaseous state. Atomic absorption spectroscopy is based on absorption of light by free metallic ions.
In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electrothermal vaporization, and is used in pharmacology, biophysics,
archaeology and toxicology research.
Atomic emission spectroscopy (AAS) was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.
The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.
Atomic absorption spectrometry has many uses in different areas of chemistry such as clinical analysis of metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, hair, muscle tissue. Atomic absorption spectrometry can be used in qualitative and quantitative analysis. | 0 | Theoretical and Fundamental Chemistry |
There is clearly a demand for sustainable biofuel production, but whether a particular biofuel will be used ultimately depends not on sustainability but cost efficiency. Therefore, research is focusing on cutting the cost of algal biofuel production to the point where it can compete with conventional petroleum. The production of several products from algae has been mentioned as the most important factor for making algae production economically viable. Other factors are the improving of the solar energy to biomass conversion efficiency (currently 3%, but 5 to 7% is theoretically attainable)and making the oil extraction from the algae easier.
In a 2007 report a formula was derived estimating the cost of algal oil in order for it to be a viable substitute to petroleum diesel:
::C = 25.9 × 10 C
where: C is the price of microalgal oil in dollars per gallon and C is the price of crude oil in dollars per barrel. This equation assumes that algal oil has roughly 80% of the caloric energy value of crude petroleum.
The IEA estimates that algal biomass can be produced for a little as $0.54/kg in open pond in a warm climate to $10.20/kg in photobioreactors in cooler climates. Assuming that the biomass contains 30% oil by weight, the cost of biomass for providing a liter of oil would be approximately $1.40 ($5.30/gal) and $1.81 ($6.85/gal) for photobioreactors and raceways, respectively. Oil recovered from the lower cost biomass produced in photobioreactors is estimated to cost $2.80/L, assuming the recovery process contributes 50% to the cost of the final recovered oil. If existing algae projects can achieve biodiesel production price targets of less than $1 per gallon, the United States may realize its goal of replacing up to 20% of transport fuels by 2020 by using environmentally and economically sustainable fuels from algae production.
Whereas technical problems, such as harvesting, are being addressed successfully by the industry, the high up-front investment of algae-to-biofuels facilities is seen by many as a major obstacle to the success of this technology. Only few studies on the economic viability are publicly available, and must often rely on the little data (often only engineering estimates) available in the public domain. Dmitrov examined the GreenFuel's photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel. A study by Alabi et al. examined raceways, photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels. Raceways might be cost-effective in warm climates with very low labor costs, and fermenters may become cost-effective subsequent to significant process improvements. The group found that capital cost, labor cost and operational costs (fertilizer, electricity, etc.) by themselves are too high for algae biofuels to be cost-competitive with conventional fuels. Similar results were found by others, suggesting that unless new, cheaper ways of harnessing algae for biofuels production are found, their great technical potential may never become economically accessible. In 2012, Rodrigo E. Teixeira demonstrated a new reaction and proposed a process for harvesting and extracting raw materials for biofuel and chemical production that requires a fraction of the energy of current methods, while extracting all cell constituents. | 1 | Applied and Interdisciplinary Chemistry |
Angus Lamond, a Wellcome Principal Research Fellow, studies the composition and function of organelles and multiprotein complexes found within the nucleus. This work is helping to explain how a cell's nucleus is organised, an area that has particular importance to human diseases such as inherited genetic conditions which can have modified or disrupted organelles.
Jason Swedlow is a Wellcome Trust Senior Research Fellow and investigates how chromosomes are separated during cell division. The driving force behind this process are strands known as microtubules, which pull the chromosomes apart. His work looks at specialised structures known as kinetochores and the mechanisms which monitor the correct attachment of microtubules to the chromosomes.
Tomo Tanaka studies the processes by which eukaryotic cells maintain their genetic integrity. His group use budding yeast to study chromosome duplication and segregation. By understanding the processes that occur during cell division, it is hoped that a better knowledge will be gained of human diseases such as cancer which are often characterised by chromosome instability. | 1 | Applied and Interdisciplinary Chemistry |
Strong electrolytes are hypothesized to dissociate completely in solution. The conductivity of a solution of a strong electrolyte at low concentration follows Kohlrausch's Law
where is known as the limiting molar conductivity, is an empirical constant and is the electrolyte concentration. (Limiting here means "at the limit of the infinite dilution".) In effect, the observed conductivity of a strong electrolyte becomes directly proportional to concentration, at sufficiently low concentrations i.e. when
As the concentration is increased however, the conductivity no longer rises in proportion.
Moreover, Kohlrausch also found that the limiting conductivity of an electrolyte;
: and are the limiting molar conductivities of the individual ions.
The following table gives values for the limiting molar conductivities for some selected ions.
An interpretation of these results was based on the theory of Debye and Hückel, yielding the Debye–Hückel–Onsager theory:
where and are constants that depend only on known quantities such as temperature, the charges on the ions and the dielectric constant and viscosity of the solvent. As the name suggests, this is an extension of the Debye–Hückel theory, due to Onsager. It is very successful for solutions at low concentration. | 0 | Theoretical and Fundamental Chemistry |
Cytokines are somnogenic and are likely key mediators of sleep responses to infection and food. Some proinflammatory cytokines correlate with daytime sleepiness. | 1 | Applied and Interdisciplinary Chemistry |
Silicon carbide is used as a raw ingredient in some glazes applied to ceramics. At high temperatures it can reduce metal oxides forming silica and carbon dioxide. This can be used to make the glaze foam and crater due to the evolved carbon dioxide gas, or to reduce the colorant oxides and achieve colors such as copper reds otherwise only possible in a fuel powered reduction firing in an electric kiln. | 1 | Applied and Interdisciplinary Chemistry |
Some researchers also identify a third class of transposable elements, which has been described as "a grab-bag consisting of transposons that dont clearly fit into the other two categories". Examples of such TEs are the Foldback (FB) elements of Drosophila melanogaster, the TU elements of Strongylocentrotus purpuratus', and Miniature Inverted-repeat Transposable Elements. | 1 | Applied and Interdisciplinary Chemistry |
Bromothymol blue may be used for observing photosynthetic activities, or as a respiratory indicator (turns yellow as CO is added). A common demonstration of BTB's pH indicator properties involves exhaling through a tube into a neutral solution of BTB. As CO is absorbed from the breath into the solution, forming carbonic acid, the solution changes color from green to yellow. Thus, BTB is commonly used in science classes to demonstrate that the more that muscles are used, the greater the CO output.
Bromothymol blue has been used in conjunction with phenol red to monitor the fungal asparaginase enzyme activity with phenol red turning pink and bromothymol blue turning blue indicating an increase in pH and therefore enzyme activity. However, a recent study suggests that methyl red is more useful in determining activity due to the bright yellow ring formed in the zone of enzyme activity.
It may also be used in the laboratory as a biological slide stain. At this point, the bromothymol is already blue, and a few drops of BTB are used on a water slide. The specimen is mixed with blue BTB solution and fixed to a slide by a cover slip. It is sometimes used to define cell walls or nuclei under the microscope.
Bromothymol is used in obstetrics for detecting premature rupture of membranes. Amniotic fluid typically has a pH > 7.2, bromothymol will therefore turn blue when brought in contact with fluid leaking from the amnion. As vaginal pH normally is acidic, the blue color indicates the presence of amniotic fluid. The test may be false-positive in the presence of other alkaline substances such as blood or semen, or in the presence of bacterial vaginosis. | 0 | Theoretical and Fundamental Chemistry |
Sala began publishing extensively in the disciplines of chemistry and medicines in about 1608-9, including a book of medications in 1624. He subscribed to corpuscular theory, asserting, for instance, that fermentation was a regrouping of elementary particles that resulted in the formation of new substances, an idea that was supported by Sala's experiments which provided evidence that the same substance persisted through a series of chemical changes, so that it could be assumed that minute atoms were the unchangeable parts that persisted through all the steps.
Sala would not let himself be misled by the illusions of the alchemists, as he asserts in many places in his works. In his treatise on the seven metals he reveals the gross artifice by which tin can be shown converting into silver: "Beware of the Crysopoeans who pledge to transform tin into silver. For [...] this crystal [silver nitrate] can be so cleverly conjoined with purified soda, unless the weight of the fallacy is detected," and also issues warning in "a brief demonstration of what vitriol is, or of what substances it is composed, and how much they deceive those who think that vitriol and water of vitriol can in fact transform iron into brass" Sala decomposed copper (blue) vitriol into copper ash, acid spirit (spirit of sulphur), and water, proving its decomposition through recombining the materials into the original vitriol. Likewise he synthesised sal ammoniac from the spirit of salt (hydrochloric acid) and the volatile salt of urine (ammonium carbonate). In Ternarius bezoardicorum he explicitly declares that he does not want to have anything in common with those of his colleagues "ensnared in vain hope" who still dream of the possibility of being able to obtain the philosopher's stone. | 1 | Applied and Interdisciplinary Chemistry |
The Flippin–Lodge (FL) angle, is the latter-derived of two angles that fully define the geometry of "attack" (approach via collision) of a nucleophile on a trigonal unsaturated center of an electrophilic molecule (the second being the Bürgi–Dunitz angle, , see below). Theory and application of these angles falls into the area of synthetic, and of physical organic chemistry (in the specializations of chemical structure and reaction mechanism), in the latter, within a sub-specialty called structure correlation. Studies of and can be theoretical, based on calculations, or experimental (either quantitative, based on X-ray crystallography, or inferred and semiquantitative, rationalizing results of particular chemical reactions), or a combination of these.
Nucleophiles in this addition reaction may range from single atoms (hydride, chloride), to polar organic functional groups (amines, alcohols), to complex systems (nucleophilic enolates with chiral catalysts, amino acid side chains in enzyme active sites; see below). Planar electrophiles include aldehydes and ketones, carboxylic acid-derivatives such as esters, and amides, and the carbon-carbon double bonds of particular alkenes (olefins). In the example of nucleophilic attack at a carbonyl, is a measure of the "offset" of the nucleophiles approach to the electrophile, toward one or the other of the two substituents attached to the carbonyl carbon. The relative values of angles for pairs of reactions can be inferred and semiquantitative, based on rationalizations of the products of the reactions; alternatively, as noted in the figure, values may be formally derived from crystallographic coordinates by geometric calculations, or graphically, e.g., after projection of Nu onto the carbonyl plane and measuring the angle supplementary to LNu-C-O (where Nu is the projected atom). This often overlooked angle of the nucleophiles trajectory was named the Flippin-Lodge angle by Clayton H. Heathcock after his contributing collaborators Lee A. Flippin and Eric P. Lodge. The second angle defining the geometry, the more well known Bürgi–Dunitz angle, , describes the Nu-C-O bond angle and was named after crystallographers Hans-Beat Bürgi and Jack D. Dunitz, its first senior investigators (see that related article).
The Flippin–Lodge angle has been abbreviated variously by the symbols φ, ψ, θ, and or ; the latter pair to closely associate the Flippin–Lodge angle with its sister angle, the Bürgi–Dunitz, which was originally abbreviated as by its discoverers/formulators (e.g., see Bürgi et al., 1974.). The symbols and are used here, respectively, to refer to the Flippin-Lodge and Bürgi-Dunitz concepts and measured values. | 0 | Theoretical and Fundamental Chemistry |
Fellgetts advantage or the multiplex advantage is an improvement in signal-to-noise ratio (SNR) that is gained when taking multiplexed measurements rather than direct measurements. The name is derived from P. B. Fellgett, who first made the observation as part of his PhD. When measuring a signal whose noise is dominated by detector noise, a multiplexed measurement such as the signal generated by a Fourier transform spectrometer can produce a relative improvement in SNR, compared to an equivalent scanning monochromator, of the order of the square root of m, where m' is the number of sample points comprising the spectrum. | 0 | Theoretical and Fundamental Chemistry |
In a variation, the Ruff–Fenton degradation (Otto Ruff 1898, H.J.H. Fenton 1893) converts the aldose first to the alpha-hydroxy-carboxylic acid with bromine and calcium hydroxide and then to the shortened aldose by reaction with Iron(III) sulfate and hydrogen peroxide. | 0 | Theoretical and Fundamental Chemistry |
The carbon atom at which the initial deprotonation takes place is a stereocenter. If, for example, D-glucose (an Aldose) rearranges to D-fructose, the ketose, the stereochemical configuration is lost in the enol form. In the chemical reaction the enol can be protonated from two faces, resulting in the backformation of glucose or the formation of the epimer D-mannose. The final product is a mix of D-glucose, D-fructose and D-mannose. | 0 | Theoretical and Fundamental Chemistry |
Unlike the above assumption of a fundamental split between prokaryotes and eukaryotes, the most important difference between biota may be the division between bacteria and the rest (archaea and eukaryota). For instance, DNA replication differs fundamentally between bacteria and archaea (including that in eukaryotic nuclei), and it may not be homologous between these two groups. Moreover, ATP synthase, though common (homologous) in all organisms, differs greatly between bacteria (including eukaryotic organelles such as mitochondria and chloroplasts) and the archaea/eukaryote nucleus group. The last common antecessor of all life (called LUCA, last universal common ancestor) should have possessed an early version of this protein complex. As ATP synthase is obligate membrane bound, this supports the assumption that LUCA was a cellular organism. The RNA world hypothesis might clarify this scenario, as LUCA might have been a ribocyte (also called ribocell) lacking DNA, but with an RNA genome built by ribosomes as primordial self-replicating entities. A Peptide-RNA world (also called RNP world) hypothesis has been proposed based on the idea that oligopeptides may have been built together with primordial nucleic acids at the same time, which also supports the concept of a ribocyte as LUCA. The feature of DNA as the material base of the genome might have then been adopted separately in bacteria and in archaea (and later eukaryote nuclei), presumably by help of some viruses (possibly retroviruses as they could reverse transcribe RNA to DNA). As a result, prokaryota comprising bacteria and archaea may also be polyphyletic. | 1 | Applied and Interdisciplinary Chemistry |
Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator. Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution and a base solution. Dipping red litmus paper in the red solution will turn it blue, while dipping blue litmus paper in the blue solution will turn it red. This property gives Congo red a metachromatic property as a dye, both in strongly acidic solutions and with strongly acidophilic tissue.
Congo red has a propensity to aggregate in aqueous and organic solutions. The proposed mechanisms suggest hydrophobic interactions between the aromatic rings of the dye molecules, leading to a π–π stacking phenomenon. Although these aggregates are present under various sizes and shapes, the "ribbon-like micelles" of a few molecules seem to be the predominant form (even if the "micelle" term is not an entirely appropriate name for it). This aggregation phenomenon is more prevalent in high Congo red concentrations, at high salinity and/or low pH. | 0 | Theoretical and Fundamental Chemistry |
Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K (The divalent state is unstable in water, producing hydrogen whilst being oxidised to a higher valency state (Baes and Mesmer, 1976). The reliability of the data is in doubt.): | 0 | Theoretical and Fundamental Chemistry |
Kenneth Storey studied biochemistry at the University of Calgary (B.Sc. 71) and zoology at the University of British Columbia (Ph.D. 74). Storey is a Professor of Biochemistry, cross-appointed in the Departments of Biology, Chemistry and Neuroscience and holds the Canada Research Chair in Molecular Physiology at Carleton University in Ottawa, Canada.
Storey is an elected fellow of the Royal Society of Canada, of the Society for Cryobiology and of the American Association for the Advancement of Science. He has won fellowships and awards for research excellence including the Fry medal from the Canadian Society of Zoologists (2011), the Flavelle medal from the Royal Society of Canada (2010), Ottawa Life Sciences Council Basic Research Award (1998), a [https://killamprogram.canadacouncil.ca/ Killam Senior Research Fellowship] (1993–1995), the Ayerst Award from the [https://csmb-scbm.ca/ Canadian Society for Molecular Biosciences] (1989), an E.W.R. Steacie Memorial Fellowship from the Natural Sciences and Engineering Research Council of Canada (1984–1986), and four Carleton University Research Achievement Awards. Storey is the author of over 1200 research articles, the editor of seven books, has given over 500 talks at conferences and institutes worldwide, and organized numerous international symposia. | 1 | Applied and Interdisciplinary Chemistry |
Personalized cancer treatment is a tuned method based on the patient's diagnosis and background. Microfluidic technology offers sensitive detection with higher throughput, as well as reduced time and costs. For personalized cancer treatment, tumor composition and drug sensitivities are very important.
A patient's drug response can be predicted based on the status of biomarkers, or the severity and progression of the disease can be predicted based on the atypical presence of specific cells. Drop-qPCR is a droplet microfluidic technology in which droplets are transported in a reusable capillary and alternately flow through two areas maintained at different constant temperatures and fluorescence detection. It can be efficient with a low contamination risk to detect Her2. A digital droplet‐based PCR method can be used to detect the KRAS mutations with TaqMan probes, to enhance detection of the mutative gene ratio. In addition, accurate prediction of postoperative disease progression in breast or prostate cancer patients is essential for determining post-surgery treatment. A simple microfluidic chamber, coated with a carefully formulated extracellular matrix mixture is used for cells obtained from tumor biopsy after 72 hours of growth and a thorough evaluation of cells by imaging.
Microfluidics is also suitable for circulating tumor cells (CTCs) and non-CTCs liquid biopsy analysis. Beads conjugate to anti‐epithelial cell adhesion molecule (EpCAM) antibodies for positive selection in the CTCs isolation chip (iCHIP). CTCs can also be detected by using the acidification of the tumor microenvironment and the difference in membrane capacitance. CTCs are isolated from blood by a microfluidic device, and are cultured on-chip, which can be a method to capture more biological information in a single analysis. For example, it can be used to test the cell survival rate of 40 different drugs or drug combinations. Tumor‐derived extracellular vesicles can be isolated from urine and detected by an integrated double‐filtration microfluidic device; they also can be isolated from blood and detected by electrochemical sensing method with a two‐level amplification enzymatic assay.
Tumor materials can directly be used for detection through microfluidic devices. To screen primary cells for drugs, it is often necessary to distinguish cancerous cells from non-cancerous cells. A microfluidic chip based on the capacity of cells to pass small constrictions can sort the cell types, metastases. Droplet‐based microfluidic devices have the potential to screen different drugs or combinations of drugs, directly on the primary tumor sample with high accuracy. To improve this strategy, the microfluidic program with a sequential manner of drug cocktails, coupled with fluorescent barcodes, is more efficient. Another advanced strategy is detecting growth rates of single-cell by using suspended microchannel resonators, which can predict drug sensitivities of rare CTCs.
Microfluidics devices also can simulate the tumor microenvironment, to help to test anticancer drugs. Microfluidic devices with 2D or 3D cell cultures can be used to analyze spheroids for different cancer systems (such as lung cancer and ovarian cancer), and are essential for multiple anti-cancer drugs and toxicity tests. This strategy can be improved by increasing the throughput and production of spheroids. For example, one droplet-based microfluidic device for 3D cell culture produces 500 spheroids per chip. These spheroids can be cultured longer in different surroundings to analyze and monitor. The other advanced technology is organs‐on‐a‐chip, and it can be used to simulate several organs to determine the drug metabolism and activity based on vessels mimicking, as well as mimic pH, oxygen... to analyze the relationship between drugs and human organ surroundings.
A recent strategy is single-cell chromatin immunoprecipitation (ChiP)‐Sequencing in droplets, which operates by combining droplet‐based single cell RNA sequencing with DNA‐barcoded antibodies, possibly to explore the tumor heterogeneity by the genotype and phenotype to select the personalized anti-cancer drugs and prevent the cancer relapse. | 1 | Applied and Interdisciplinary Chemistry |
The primary commercial use of dimethyl methylphosphonate is as a flame retardant. Other commercial uses are a preignition additive for gasoline, anti-foaming agent, plasticizer, stabilizer, textile conditioner, antistatic agent, and an additive for solvents and low-temperature hydraulic fluids. It can be used as a catalyst and a reagent in organic synthesis, as it can generate a highly reactive ylide. The yearly production in the United States varies between .
About 190 liters of dimethyl methylphosphonate, together with other chemicals, were released during the crash of El Al Flight 1862 at Bijlmer in Amsterdam in 1992. | 1 | Applied and Interdisciplinary Chemistry |
Bionic leaves have been considered as an alternative to vertical greenery systems (VGS), also known as green facades. Like VGS, bionic facades can be implemented in buildings to reduce energy consumption from cooling, absorb solar radiation, and reduce CO emissions. Unlike their natural counterpart, bionic facades require less costly maintenance (irrigation, fertilization, pest-control) and can be potentially adjusted to external conditions like the changing of seasons. The general structure of the bionic leaves used for these experiments can be characterized as a photovoltaic (PV) cell or plate resistive heater backed with a ceramic evaporative matrix. An experiment comparing the performance of a PV panel alone versus the bionic leaf panel showed increased electricity production of up to 6.6% due to the evaporative cooling from the matrix. The bionic facade also had a comparable effect on lowering the ambient temperature at the building-to-air interface as a green facade planted with ivy. The cooling effect paired with the electricity output of the bionic facade showed a CO emissions reduction that was 25 times greater than the daily average CO consumption of the ivy wall. | 0 | Theoretical and Fundamental Chemistry |
Due to the existence of stoppers on the ends of the rotaxanes units, polyrotaxanes are more thermodynamically stable than polypseudorotaxanes (similar structure to polyrotaxane but without stoppers at two ends). Also, if the interactions between guest and host molecules are attractive, such as hydrogen bonding or charge transfer, they have better stabilities than those without attractive interactions. However, specific salts, changes of pH condition or temperature that can disturb or interrupt the interactions between ring-ring, ring-backbone, or backbone-backbone will destroy the structural integrity of polyrotaxanes. For example, dimethylformamide or dimethyl sulfoxide is able to interrupt the hydrogen bonding between cyclodextrins in the cyclodextrin-based polyrotaxanes. Also, change of pH or high temperature can also destroy the crystalline domains. Some chemical bonds between stoppers and chains are not stable in acidic or basic solution. As the stoppers cut from the chain, the rings will dethread from the axles, which leads to the dissociation of the polyrotaxanes.
For example, a "molecular necklace" assembled by α-cyclodextrins and polyethylene glycol is insoluble in water and dimethylfomamide, although their parents' components α-cyclodextrin and polyethylene glycol can be dissolved and this synthesis can happen in water. The product is soluble in dimethyl sulfoxide or 0.1 M sodium hydroxide solution. This is because the hydrogen bonding between the cyclodextrins. As the hydrogen bonding is destroyed by dimethyl sulfoxide or base solution, it can be dissolved, but the water does not deform the hydrogen interaction between cyclodextrins. In addition, the complexation process is exothermic in thermodynamic tests, which is also corresponding with the existence of hydrogen bonding. | 0 | Theoretical and Fundamental Chemistry |
Supplemental potassium decreases the risk of experiencing a life-threatening heart rhythm problem from arsenic trioxide. | 1 | Applied and Interdisciplinary Chemistry |
A phosphorane (IUPAC name: λ-phosphane) is a functional group in organophosphorus chemistry with pentavalent phosphorus. Phosphoranes have the general formula PR.
Phosphoranes of the type PX adopt a trigonal bipyramidal molecular geometry with the two apical bonds longer than the three equatorial bonds. Hypervalent bonding is described by inclusion of non-bonding MOs, as also invoked for the closely related molecule phosphorus pentafluoride. | 0 | Theoretical and Fundamental Chemistry |
To measure cosmogenic isotopes produced within solid earth materials, such as rock, samples are generally first put through a process of mechanical separation. The sample is crushed and desirable material, such as a particular mineral (quartz in the case of Be-10), is separated from non-desirable material by using a density separation in a heavy liquid medium such as lithium sodium tungstate (LST). The sample is then dissolved, a common isotope carrier added (Be-9 carrier in the case of Be-10), and the aqueous solution is purified down to an oxide or other pure solid.
Finally, the ratio of the rare cosmogenic isotope to the common isotope is measured using accelerator mass spectrometry. The original concentration of cosmogenic isotope in the sample is then calculated using the measured isotopic ratio, the mass of the sample, and the mass of carrier added to the sample. | 0 | Theoretical and Fundamental Chemistry |
Arthur Eichengrün was born in Aachen as the son of a Jewish cloth merchant and manufacturer. In 1885, he took up studies in chemistry at the University of Aachen, later moved to Berlin, and finally to Erlangen, where he received a doctoral degree in 1890.
In 1896, he joined Bayer, working in the pharmaceutical laboratory. In 1908, he quit Bayer and founded his own pharmaceutical factory, the Cellon-Werke in Berlin. His company was "Aryanized" by the Nazis in 1938.
In 1943, he was arrested and sentenced to four months in prison for having failed to include the word "Israel" in his name in a letter to a Reich official (Nazi law required Jewish men to be identified as such, as they required Jewish women to identify as "Sarah".). In May 1944, he was arrested again on the same charge and deported to the concentration camp Theresienstadt, where he spent 14 months until the end of World War II in Europe, escaping death.
After the liberation, he returned to Berlin, but moved to Bad Wiessee in Bavaria in 1948, where he died the following year at the age of 82. | 0 | Theoretical and Fundamental 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. | 0 | Theoretical and Fundamental Chemistry |
Roasting is a process of heating a sulfide ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is often a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component(s). Often before roasting, the ore has already been partially purified, e.g. by froth flotation. The concentrate is mixed with other materials to facilitate the process. The technology is useful in making certain ores usable but it can also be a serious source of air pollution.
Roasting consists of thermal gas–solid reactions, which can include oxidation, reduction, chlorination, sulfation, and pyrohydrolysis. In roasting, the ore or ore concentrate is treated with very hot air. This process is generally applied to sulfide minerals. During roasting, the sulfide is converted to an oxide, and sulfur is released as sulfur dioxide, a gas. For the ores CuS (chalcocite) and ZnS (sphalerite), balanced equations for the roasting are:
:2 CuS + 3 O → 2 CuO + 2 SO
:2 ZnS + 3 O → 2 ZnO + 2 SO
The gaseous product of sulfide roasting, sulfur dioxide (SO) is often used to produce sulfuric acid. Many sulfide minerals contain other components such as arsenic that are released into the environment.
Up until the early 20th century, roasting was started by burning wood on top of ore. This would raise the temperature of the ore to the point where its sulfur content would become its source of fuel, and the roasting process could continue without external fuel sources. Early sulfide roasting was practiced in this manner in "open hearth" roasters, which were manually stirred (a practice called "rabbling") using rake-like tools to expose unroasted ore to oxygen as the reaction proceeded.
This process released large amounts of acidic, metallic, and other toxic compounds. Results of this include areas that even after 60–80 years are still largely lifeless, often exactly corresponding to the area of the roast bed, some of which are hundreds of metres wide by kilometres long. Roasting is an exothermic process. | 1 | Applied and Interdisciplinary Chemistry |
A well studied pioneer factor family is the Groucho-related (Gro/TLE/Grg) transcription factors that often have a negative effect on transcription. These chromatin binding domains can span up to 3-4 nucleosomes. These large domains are scaffolds for further protein interactions and also modify the chromatin for other pioneer factors such as FoxA1 which has been shown to bind to Grg3. Transcription factors with zinc finger DNA binding domains, such as the GATA family and glucocorticoid receptor. The zinc finger domains do not appear to bind nucleosomes well and can be displaced by FOX factors.
In the skin epidermis, SOX family transcription factor, SOX9, also behaves as a pioneer factor that governs hair follicle cell fate and can reprogram epidermal stem cells to a hair follicle fate. | 1 | Applied and Interdisciplinary Chemistry |
The high surface area of a material in nanoparticle form allows heat, molecules, and ions to diffuse into or out of the particles at very large rates. The small particle diameter, on the other hand, allows the whole material to reach homogeneous equilibrium with respect to diffusion in a very short time. Thus many processes that depend on diffusion, such as sintering can take place at lower temperatures and over shorter time scales inducing catalysis. | 0 | Theoretical and Fundamental Chemistry |
There are three main components to the hybrid fusion fuel cycle: deuterium, tritium, and fissionable elements. Deuterium can be derived by the separation of hydrogen isotopes in seawater (see heavy water production). Tritium may be generated in the hybrid process itself by absorption of neutrons in lithium bearing compounds. This would entail an additional lithium-bearing blanket and a means of collection. Small amounts of tritium are also produced by neutron activation in nuclear fission reactors, particularly when heavy water is used as a neutron moderator or coolant. The third component is externally derived fissionable materials from demilitarized supplies of fissionables, or commercial nuclear fuel and waste streams. Fusion driven fission also offers the possibility of using thorium as a fuel, which would greatly increase the potential amount of fissionables available. The extremely energetic nature of the fast neutrons emitted during the fusion events (up to 0.17 the speed of light) can allow normally non-fissioning U to undergo fission directly (without conversion first to Pu), enabling refined natural Uranium to be used with very low enrichment, while still maintaining a deeply subcritical regime. | 0 | Theoretical and Fundamental Chemistry |
Ozone in the troposhere is determined by photochemical production and destruction, dry deposition and cross-tropopause transport of ozone from the stratosphere. In the Arctic troposphere, transport and photochemical reactions involving nitrogen oxides and volatile organic compounds (VOCs) as a result of human emissions also produce ozone resulting in a background mixing ratio of 30 to 50 nmol mol−1 (ppb). Nitrogen oxides play a key role in recycling active free radicals (such as reactive halogens) in the atmosphere and indirectly affect ozone depletion. Ozone depletion events (ODEs) are phenomena associated with the sea ice zone. They are routinely observed at coastal locations when incoming winds have traversed sea ice covered areas. | 1 | Applied and Interdisciplinary Chemistry |
Latex paints (emulsion paints British English, not to be confused with latex rubber) are an emulsion of polymer particles dispersed in water. Macroemulsions in latex paint are inherently unstable and phase separate, so surfactants are added to lower interfacial tension and stabilize polymer particles to prevent demulsification.
Anionic surfactants such as sodium dodecyl sulfate are most commonly used for stabilizing emulsions because of their affinity for hydrogen bonding with the aqueous medium. Nonionic surfactants are rarely used alone due to their inferior efficiency in creating stable emulsions in comparison to anionic surfactants. Because of this, non-ionic surfactants are usually used in tandem with anionic surfactants and impart a second method of colloidal stabilization through steric interference of the van der Waals forces amid polymer and pigment particles. Latexes that require stability over large pH ranges use larger nonionic to anionic surfactant ratios. Cationic surfactants are least commonly used because of their high cost, inefficient emulsifying capability, and undesirable effects on initiator decomposition. High speed application, low temperature storage, shear stresses from pumping, and other extreme storage or application conditions can cause the failure of a surfactant to adequately stabilize a paint dispersion.
The thermodynamic explanation for demulsification is the gain in Gibbs Free Energy resulting from lowering the total area of high energy surface interactions.
The energy gained from demulsification is dependent on the total area of interface and the surface tension of that interface. Surfactants lower the surface tension (γ) and thus gibbs energy is gained from demulsification. This slows the process of demulsification and stabilizes the latex paint.
The size of the droplets of dispersed polymer in a latex paint can be modeled with the following equation:
The radius of a droplet in the emulsion is dependent on surfactant length, L, volume fraction of dispersed phase, φ, and volume fraction of surfactant, φ. | 0 | Theoretical and Fundamental Chemistry |
The eluviation of chelate compounds is the downward movement of soil chelates. The eluviation of chelate compounds can be affected by:
* Acidity. Organic acids produced under acidic conditions can increase the solubility of metal elements such as iron and aluminum, thereby enhancing soil eluviation. Iron and aluminum are easily leached at low pH. As the pH increases, ferric hydroxide and aluminum hydroxide compounds precipitate.
* Redox conditions. Under reducing conditions, more organic acids are produced and metal ions are reduced to soluble metal complexes that migrate into the soil. Under oxidative conditions, metal ions are easily precipitated, and the chelate is easily polymerized, thereby separating the chelate from the metal ions.
* Soil texture. Clay has a certain adsorption capacity for chelates, which weakens the leaching of complexes. On the other hand, soils with a coarse texture and water-saturated soils will likely enhance the leaching effect of chelates. | 0 | Theoretical and Fundamental Chemistry |
Due to its very low power density, conversion efficiency and high cost, a C betavoltaic device is very similar to other existing betavoltaic devices which are suited to niche applications needing very little power (microwatts) for several years in situations where conventional batteries cannot be replaced or recharged using conventional energy harvesting techniques. Due to its longer half-life, C betavoltaics may have an advantage in service life when compared to other betavoltaics using tritium or nickel. However, this will likely come at the cost of further reduced power density. | 0 | Theoretical and Fundamental Chemistry |
The SH2 domain of Grb2 binds to phosphorylated tyrosine-containing peptides on receptors or scaffold proteins with a preference for pY-X-N-X, where X is generally a hydrophobic residue such as valine (see [http://sh2domain.org]).
The N-terminal SH3 domain binds to proline-rich peptides and can bind to the Ras-guanine exchange factor SOS.
The C-terminal SH3 domain binds to peptides conforming to a P-X-I/L/V/-D/N-R-X-X-K-P motif that allows it to specifically bind to proteins such as Gab-1. | 1 | Applied and Interdisciplinary Chemistry |
Methionine sulfoximine (MSO, also known as MetSox) is an irreversible glutamine synthetase inhibitor. It is the sulfoximine derivative of methionine with convulsant effects.
Methionine sulfoximine is composed of two different diastereomers, which are L-S-Methionine sulfoximine and L-R-Methionine sulfoximine. These affect the longevity of the model mouse for Lou Gehrig's disease. Overproduction of glutamate results to excitotoxicity, which kills the cell. Since methionine sulfoximine inhibits glutamate production in the brain, it prevents excitotoxicity. Thus, increasing the longevity of the mice. | 1 | Applied and Interdisciplinary Chemistry |
The plasmid is often transformed into a bacterium like E. coli. Ideally when the bacterium divides the plasmid should also be replicated. In the best case scenario, each bacterial cell should have several copies of the plasmid. After a good number of bacterial colonies have grown, they can be miniprepped to harvest the plasmid DNA. | 1 | Applied and Interdisciplinary Chemistry |
Electroosmotic flow is caused by the Coulomb force induced by an electric field on net mobile electric charge in a solution. Because the chemical equilibrium between a solid surface and an electrolyte solution typically leads to the interface acquiring a net fixed electrical charge, a layer of mobile ions, known as an electrical double layer or Debye layer, forms in the region near the interface. When an electric field is applied to the fluid (usually via electrodes placed at inlets and outlets), the net charge in the electrical double layer is induced to move by the resulting Coulomb force. The resulting flow is termed electroosmotic flow. | 0 | Theoretical and Fundamental Chemistry |
Gas-diffusion electrocrystallization is a process electrochemically driven at porous gas-diffusion electrodes, in which a triple phase boundary is established between a liquid solution, an oxidizing gas, and an electrically conducting electrode. The liquid solution containing dissolved metal ions (e.g., CuCl, ZnCl) flows through an electrochemical cell equipped with a gas diffusion electrode, making contact with its electrically conducting part (typially a porous layer). The oxidizing gas (e.g., pure O, O in air, CO, etc.) percolates through a hydrophobic layer on the gas diffusion electrode, acting as a cathode. After the gas diffuses to the electrically conducting layer acting as an electrocatalyst (e.g., hydrophilic activated carbon), the gas is electrochemically reduced. For instance, by imposing specific cathodic polarization conditions (e.g., −0.145 VSHE O is reduced, to HO in a 2 electron (2 e) transfer process and HO in a 4 electron (4 e) transfer process. OH are also produced in the process. As this happens, abrupt local pH and local electrolyte redox potential changes arise within the cathode porosity. As the hydroxyl ions spread to the bulk electrolyte, systematic pH increases become consistently manifest in the electrolyte bulk. In due course, low amounts of HO are generated. In steady state, a reaction front is fully developed throughout the hydrodynamic boundary layer. This creates local saturation conditions at the electrochemical interface, where metal ions precipitate in metastable or stable phases depending on the operational variables. When oxygen is the oxidizing gas, the mechanism for gas-diffusion electrocrystallization has been explained as an oxidation-assisted alkaline precipitation using gas-diffusion electrodes. | 0 | Theoretical and Fundamental Chemistry |
As one of the primary segments of the guidelines, there are several essential parts on the checklist for the qPCR process itself. This includes the full set of conditions used for the reaction, the volume of both the reaction and the cDNA, the concentrations for the probes, magnesium ions, and dNTPs, what kind of polymerase was used and its concentration, what kit was used and its manufacturer, what additives to the reaction were used, who manufactured the qPCR machine, and what parameters were set for the thermocycling process. The only additional desired pieces of information are the chemical composition of the buffer used, who manufactured the plates and tubes used and what their catalog number is, and whether the reaction was set up manually or by a machine. | 1 | Applied and Interdisciplinary Chemistry |
Although early medical experimentation was performed often, the use of a control group to provide an accurate comparison for the demonstration of the intervention's efficacy was generally lacking. For instance, Lady Mary Wortley Montagu, who campaigned for the introduction of inoculation (then called variolation) to prevent smallpox, arranged for seven prisoners who had been sentenced to death to undergo variolation in exchange for their life. Although they survived and did not contract smallpox, there was no control group to assess whether this result was due to the inoculation or some other factor. Similar experiments performed by Edward Jenner over his smallpox vaccine were equally conceptually flawed.
The first proper clinical trial was conducted by the Scottish physician James Lind. The disease scurvy, now known to be caused by a Vitamin C deficiency, would often have terrible effects on the welfare of the crew of long-distance ocean voyages. In 1740, the catastrophic result of Anson's circumnavigation attracted much attention in Europe; out of 1900 men, 1400 had died, most of them allegedly from having contracted scurvy. John Woodall, an English military surgeon of the British East India Company, had recommended the consumption of citrus fruit (it has an antiscorbutic effect) from the 17th century, but their use did not become widespread.
Lind conducted the first systematic clinical trial in 1747. He included a dietary supplement of an acidic quality in the experiment after two months at sea, when the ship was already afflicted with scurvy. He divided twelve scorbutic sailors into six groups of two. They all received the same diet but, in addition, group one was given a quart of cider daily, group two twenty-five drops of elixir of vitriol (sulfuric acid), group three six spoonfuls of vinegar, group four half a pint of seawater, group five received two oranges and one lemon, and the last group a spicy paste plus a drink of barley water. The treatment of group five stopped after six days when they ran out of fruit, but by then one sailor was fit for duty while the other had almost recovered. Apart from that, only group one also showed some effect of its treatment. Each year, May 20 is celebrated as Clinical Trials Day in honor of Lind's research.
After 1750 the discipline began to take its modern shape. The English doctor John Haygarth demonstrated the importance of a control group for the correct identification of the placebo effect in his celebrated study of the ineffective remedy called Perkins tractors'. Further work in that direction was carried out by the eminent physician Sir William Gull, 1st Baronet in the 1860s.
Frederick Akbar Mahomed (d. 1884), who worked at Guy's Hospital in London, made substantial contributions to the process of clinical trials, where "he separated chronic nephritis with secondary hypertension from what we now term essential hypertension. He also founded the Collective Investigation Record for the British Medical Association; this organization collected data from physicians practicing outside the hospital setting and was the precursor of modern collaborative clinical trials." | 1 | Applied and Interdisciplinary Chemistry |
Coordination complexes and organometallic compounds are also photoreactive. These reactions can entail cis-trans isomerization. More commonly, photoreactions result in dissociation of ligands, since the photon excites an electron on the metal to an orbital that is antibonding with respect to the ligands. Thus, metal carbonyls that resist thermal substitution undergo decarbonylation upon irradiation with UV light. UV-irradiation of a THF solution of molybdenum hexacarbonyl gives the THF complex, which is synthetically useful:
:Mo(CO) + THF → Mo(CO)(THF) + CO
In a related reaction, photolysis of iron pentacarbonyl affords diiron nonacarbonyl (see figure):
:2 Fe(CO) → Fe(CO) + CO
Select photoreactive coordination complexes can undergo oxidation-reduction processes via single electron transfer. This electron transfer can occur within the inner or outer coordination sphere of the metal. | 0 | Theoretical and Fundamental Chemistry |
Several methods have been developed that make use of the estimated (via 1H or 13C shifts) or predicted (via sequence) secondary structure content of the protein being analyzed. These programs include PSSI, CheckShift, LACS, and PANAV. Both PANAV <[https://web.archive.org/web/20140413150003/http://www.wishartlab.com/web_servers/panav]> and CheckShift are also available as web servers.
The PSSI and PANAV programs use the secondary structure determined by 1H shifts (which are almost never mis-referenced) to adjust the target protein’s 13C and 15N shifts to match the 1H-derived secondary structure. LACS uses the difference between secondary 13Cα and 13Cβ shifts plotted against secondary 13Cα shifts or secondary 13Cβ shifts to determine reference offsets. A more recent version of LACS has been adapted to identify 15N chemical shift mis-referencing. This new version of LACS exploits the well-known relationship between secondary 15N shifts and the secondary 13Cα and 13Cβ shifts of the preceding residue. In contrast to LACS and PANAV/PSSI, CheckShift uses secondary structure predicted from high-performance secondary structure prediction programs such as PSIPRED to iteratively adjust 13C and 15N chemical shifts so that their secondary shifts match the predicted secondary structure. These programs have all been shown to accurately identify mis-referenced and properly re-reference protein chemical shifts deposited in the BMRB,. Note that both LACS and CheckShift are programmed to always predict the same offset for 13Cα and 13Cβ shifts, whereas PSSI and PANAV do not make this assumption. As a general rule, PANAV and PSSI typically exhibit a smaller spread (or standard deviation) in calculated reference offsets, indicating that these programs are slightly more precise than either LACS or CheckShift. Neither LACS nor CheckShift are able to handle proteins that have the extremely large (above 40 ppm) reference offsets, whereas PANAV and PSSI seem to be able to deal with these kinds of anomalous proteins.
In a recent study, a chemical shift re-referencing program (PANAV) was run on a total of 2421 BMRB entries that had a sufficient proportion of (>80%) of assigned chemical shifts to perform a robust chemical shift reference correction. A total of 243 entries were found with 13Cα shifts offset by more than 1.0 ppm, 238 entries with 13Cβ shifts offset of more than 1.0 ppm, 200 entries with 13C’ shifts offset of more than 1.0 ppm and 137 entries with 15N shifts offset by more than 1.5 ppm. From this study, 19.7% of the entries in the BMRB appear to be mis-referenced. Evidently, chemical shift referencing continues to be a significant, and as yet unresolved problem for the biomolecular NMR community. | 0 | Theoretical and Fundamental Chemistry |
The Unruh effect would also cause the decay rate of accelerating particles to differ from inertial particles. Stable particles like the electron could have nonzero transition rates to higher mass states when accelerating at a high enough rate. | 0 | Theoretical and Fundamental Chemistry |
Previously called "ideal ATM" and "polarization-varying ATM," stationary sample ATM (SSATM) involves rotation of the linearly polarized state of the THz beam in a time-domain spectroscopy (TDS) configuration parallel to the interrogated material sample. In a SSATM configuration, the THz beam polarization is rotated through 360° in a plane perpendicular to the propagation direction of the beam. Measurements of the sample's anisotropy is measured at several THz polarization angles.
At least two methods to achieve THz polarization rotation for SSATM have been demonstrated: 1) by using a THz quarter waveplate (THz-QWP) together with an infrared polarizer and 2) by rotating the photoconductive antenna.
In the case of employing a THz-QWP and an infrared polarizer, the magnitude of the measured signal, , where is a time delay between THz generation and the detected pulses in a THz-TDS system is dependent on the relative polarization angle of the THz light, and the polarization angle of the ultrafast near-infrared (NIR) probe beam, , at the sample by the relationship
The objective is to maintain equal magnitude of the THz electric field at the sample for all measurement angles, . This requires adjustment of for every . | 0 | Theoretical and Fundamental Chemistry |
* 2002 and 2005 Grossman Award, ASM International
* 2005 Grunfeld Medal, Institute of Materials, Minerals and Mining (IOM3)
* 2010 Harvey Flower Titanium prize, Institute of Materials, Minerals and Mining
* 2014 Defence Aerospace award, Rolls-Royce
* 2017 Cook/Ablett Medal, Institute of Materials, Minerals and Mining
* 2018 EPD Division Science awards, The Minerals, Metals & Materials Society (TMS)
* 2022 Silver Medal, Acta Materialia | 1 | Applied and Interdisciplinary Chemistry |
Lipinski received his PhD from the University of California, Berkeley in 1968 in physical organic chemistry. The Advanced Drug Delivery Reviews article reporting his "rule of five" is one of the most cited publications in the journals history. In 2006, he received an honorary law degree from the University of Dundee and he has won various awards, including being the Society for Biomolecular Sciences winner of the 2006 SBS Achievement Award for Innovation in HTS. | 1 | Applied and Interdisciplinary Chemistry |
Orcein, also archil, orchil, lacmus and C.I. Natural Red 28, are names for dyes extracted from several species of lichen, commonly known as "orchella weeds", found in various parts of the world. A major source is the archil lichen, Roccella tinctoria. Orcinol is extracted from such lichens. It is then converted to orcein by ammonia and air. In traditional dye-making methods, urine was used as the ammonia source. If the conversion is carried out in the presence of potassium carbonate, calcium hydroxide, and calcium sulfate (in the form of potash, lime, and gypsum in traditional dye-making methods), the result is litmus, a more complex molecule. The manufacture was described by Cocq in 1812 and in the UK in 1874. Edmund Roberts noted orchilla as a principal export of the Cape Verde islands, superior to the same kind of "moss" found in Italy or the Canary Islands, that in 1832 was yielding an annual revenue of $200,000. Commercial archil is either a powder (called cudbear) or a paste. It is red in acidic pH and blue in alkaline pH. | 0 | Theoretical and Fundamental Chemistry |
The carrier gas is sent through the central channel and into the very hot plasma. The sample is then exposed to radio frequency which converts the gas into a plasma. The high temperature of the plasma is sufficient to cause a very large portion of the sample to form ions. This fraction of ionization can approach 100% for some elements (e.g. sodium), but this is dependent on the ionization potential. A fraction of the formed ions passes through a ~1 mm hole (sampler cone) and then a ~0.4 mm hole (skimmer cone). The purpose of which is to allow a vacuum that is required by the mass spectrometer.
The vacuum is created and maintained by a series of pumps. The first stage is usually based on a roughing pump, most commonly a standard rotary vane pump. This removes most of the gas and typically reaches a pressure of around 133 Pa. Later stages have their vacuum generated by more powerful vacuum systems, most often turbomolecular pumps. Older instruments may have used oil diffusion pumps for high vacuum regions. | 0 | Theoretical and Fundamental Chemistry |
Translation is one of the key energy consumers in cells, hence it is strictly regulated. Numerous mechanisms have evolved that control and regulate translation in eukaryotes as well as prokaryotes. Regulation of translation can impact the global rate of protein synthesis which is closely coupled to the metabolic and proliferative state of a cell. To delve deeper into this intricate process, scientists typically use a technique known as ribosome profiling. This method enables researchers to take a snapshot of the translatome, showing which parts of the mRNA are being translated into proteins by ribosomes at a given time. Ribosome profiling provides valuable insights into translation dynamics, revealing the complex interplay between gene sequence, mRNA structure, and translation regulation. Expanding on this concept, a more recent development is single-cell ribosome profiling, a technique that allows us to study the translation process at the resolution of individual cells. Single-cell ribosome profiling has the potential to shed light on the heterogeneous nature of cells, leading to a more nuanced understanding of how translation regulation can impact cell behavior, metabolic state, and responsiveness to various stimuli or conditions. | 1 | Applied and Interdisciplinary Chemistry |
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