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A medium that experiences no transmission () is opaque, in which case absorptivity and reflectivity sum to unity: | 0 | Theoretical and Fundamental Chemistry |
RNA Polymerase II exists in two forms unphosphorylated and phosphorylated, IIA and IIO respectively. The transition between the two forms facilitates different functions for transcription. The phosphorylation of CTD is catalyzed by one of the six general transcription factors, TFIIH. TFIIH serves two purposes: one is to unwind the DNA at the transcription start site and the other is to phosphorylate. The form polymerase IIA joins the preinitiation complex, this is suggested because IIA binds with higher affinity to the TBP (TATA-box binding protein), the subunit of the general transcription factor TFIID, than polymerase IIO form. The form polymerase IIO facilitates the elongation of the RNA chain. The method for the elongation initiation is done by the phosphorylation of Serine at position 5 (Ser5), via TFIIH. The newly phosphorylated Ser5 recruits enzymes to cap the 5 end of the newly synthesized RNA and the "3 processing factors to poly(A) sites". Once the second Serine is phosphorylated, Ser2, elongation is activated. In order to terminate elongation dephosphorylation must occur. Once the domain is completely dephosphorylated the RNAP II enzyme is "recycled" and catalyzes the same process with another initiation site. | 1 | Applied and Interdisciplinary Chemistry |
Electrodiffusiophoresis is a motion of particles dispersed in liquid induced by external homogeneous electric field, which makes it similar to electrophoresis. | 0 | Theoretical and Fundamental Chemistry |
Glycogen is a multi-branched polysaccharide. It is primary means of glucose storage in animal cells. In the human body, the two main tissues which store glycogen are liver and skeletal muscle. Glycogen is typically more concentrated in the liver, but because humans have much more muscle mass, our muscles store about three quarters of the total glycogen in our body. | 1 | Applied and Interdisciplinary Chemistry |
While multiple classification standards for tissue clearing exist, the most common classifications use the chemical principle and mechanism of clearing to group tissue clearing methods. These include hydrophobic clearing methods, which may also be known as organic, solvent-based, organic solvent-based, or dehydration clearing methods; hydrophilic clearing methods, which may also be known as aqueous-based or water-based methods, and may be further sub-categorized into simple immersion and hyperhydration (also called delipidation/ hydration); and hydrogel-based clearing methods, which may also be known as detergent or hydrogel embedding methods. Tissue-expansion clearing methods use hydrogel, and may be included under hydrogel-based clearing or as their own category. | 1 | Applied and Interdisciplinary Chemistry |
The vast majority of plants are C3, meaning they photorespire when necessary.Certain species of plants or algae have mechanisms to lower uptake of molecular oxygen by RuBisCO. These are commonly referred to as Carbon Concentrating Mechanisms (CCMs), as they increase the concentration of so that RuBisCO is less likely to produce glycolate through reaction with . | 0 | Theoretical and Fundamental Chemistry |
A single material may have several distinct solid states capable of forming separate phases. Water is a well-known example of such a material. For example, water ice is ordinarily found in the hexagonal form ice I, but can also exist as the cubic ice I, the rhombohedral ice II, and many other forms. Polymorphism is the ability of a solid to exist in more than one crystal form. For pure chemical elements, polymorphism is known as allotropy. For example, diamond, graphite, and fullerenes are different allotropes of carbon. | 0 | Theoretical and Fundamental Chemistry |
The thylakoids are the site of the light-dependent reactions of photosynthesis. These include light-driven water oxidation and oxygen evolution, the pumping of protons across the thylakoid membranes coupled with the electron transport chain of the photosystems and cytochrome complex, and ATP synthesis by the ATP synthase utilizing the generated proton gradient. | 0 | Theoretical and Fundamental Chemistry |
Non-synonymous is the variant in exons that change the amino acid sequence encoded by the gene, including single base changes and non frameshift indels. It has been extremely investigated the function of non-synonymous variants on protein and many algorithms have been developed to predict the deleteriousness and pathogenesis of single nucleotide variants (SNVs). Classical bioinformatics tools, such as SIFT, Polyphen and MutationTaster, successfully predict the functional consequence of non-synonymous substitution. PopViz webserver provides a gene-centric approach to visualize the mutation damage prediction scores (CADD, SIFT, PolyPhen-2) or the population genetics (minor allele frequency) versus the amino acid positions of all coding variants of a certain human gene. PopViz is also cross-linked with UniProt database, where the protein domain information can be found, and to then identify the predicted deleterious variants fall into these protein domains on the PopViz plot. | 1 | Applied and Interdisciplinary Chemistry |
In August 2012, Ferrier celebrated his 80th birthday and retired a second time. Later that year, the Ferrier Trust was set up in his honour, to bring a scientist to New Zealand each year, to engage with chemistry students and lecture. Peppi Prasit, a Ferrier PhD graduate and founder of Amira Pharmaceuticals and Inception Sciences in the US, was the trust's foundation donor. He was able to attend the inaugural Ferrier Lecture in March 2013. | 0 | Theoretical and Fundamental Chemistry |
Pool boiling is boiling at a stagnant fluid. Its behavior is well characterized by Nukiyama boiling curve, which shows the relation between the amount of surface superheat and applied heat flux on the surface. With the varying degrees of the superheat, the curve is composed of natural convection, onset of nucleate boiling, nucleate boiling, critical heat flux, transition boiling, and film boiling. Each regime has a different mechanism of heat transfer and has different correlation for heat transfer coefficient. | 0 | Theoretical and Fundamental Chemistry |
Elevated blood ketone levels are most often caused by accelerated ketone production but may also be caused by consumption of exogenous ketones or precursors.
When glycogen and blood glucose reserves are low, a metabolic shift occurs in order to save glucose for the brain which is unable to use fatty acids for energy. This shift involves increasing fatty acid oxidation and production of ketones in the liver as an alternate energy source for the brain as well as the skeletal muscles, heart, and kidney. Low levels of ketones are always present in the blood and increase under circumstances of low glucose availability. For example, after an overnight fast, 2–6% of energy comes from ketones and this increases to 30–40% after a 3-day fast.
The amount of carbohydrate restriction required to induce a state of ketosis is variable and depends on activity level, insulin sensitivity, genetics, age and other factors, but ketosis will usually occur when consuming less than 50 grams of carbohydrates per day for at least three days.
Neonates, pregnant women and lactating women are populations that develop physiological ketosis especially rapidly in response to energetic challenges such as fasting or illness. This can progress to ketoacidosis in the setting of illness, although it occurs rarely. Propensity for ketone production in neonates is caused by their high-fat breast milk diet, disproportionately large central nervous system and limited liver glycogen. | 1 | Applied and Interdisciplinary Chemistry |
Although a number of algaecides have been effective in killing algae, they have been used mostly in small bodies of water. For large algal blooms, however, adding algaecides such as silver nitrate or copper sulfate can have worse effects, such as killing fish outright and harming other wildlife. Cyanobacteria can also develop resistance to copper-containing algaecides, requiring a larger quantity of the chemical to be effective for HAB management, but introducing a greater risk to other species in the region. The negative effects can therefore be worse than letting the algae die off naturally.
In 2019, Chippewa Lake in Northeast Ohio became the first lake in the U.S. to successfully test a new chemical treatment. The chemical formula killed all of the toxic algae in the lake within a single day. The formula has already been used in China, South Africa and Israel.
In February 2020, Roodeplaat Dam in Gauteng Province, South Africa was treated with a new algicide formulation against a severe bloom of Microcystis sp. This formulation allows the granular product to float and slow-release its active ingredient, sodium percarbonate, that releases hydrogen peroxide (HO), on the water surface. Consequently, the effective concentrations are limited, vertically, to the surface of the water; and spatially to areas where cyanobacteria are abundant. This provide the aquatic organisms a "safe haven" in untreated areas and avoids the adverse effects associated with the use of standard algicides.
Bioactive compounds isolated from terrestrial and aquatic plants, particularly seaweeds, have seen results as a more environmentally friendly control for HABs. Molecules found in seaweeds such as Corallina, Sargassum, and Saccharina japonica have shown to inhibit some bloom-forming microalgae. In addition to their anti-microalgal effects, the bioactive molecules found in these seaweeds also have antibacterial, antifungal, and antioxidant properties. | 0 | Theoretical and Fundamental Chemistry |
Since 2009, two editions of the ABC (Active, Beautiful, Clean) Waters Design Guidelines have been published by the Public Utilities Board, Singapore. The latest version (2011) contains planning and design considerations for the holistic integration of drains, canals and reservoirs with the surrounding environment. The Public Utilities Board encourages the various stakeholders — landowners, private developers to incorporate ABC Waters design features into their developments, and the community to embrace these infrastructures for recreational & educational purposes.
The main benefits outlined in the ABC Waters Concept include:
* Treating stormwater runoff closer to the source naturally, without the use of chemicals through the use of plants and soil media, so that cleaner water is discharged into waterways and eventually our reservoirs.
* Enhancing biodiversity and site aesthetics.
* Bringing people closer to water, and creating new recreational and community spaces for people to enjoy. | 1 | Applied and Interdisciplinary Chemistry |
I decays with a half-life of 8.02 days with beta minus and gamma emissions. This isotope of iodine has 78 neutrons in its nucleus, while the only stable nuclide, I, has 74. On decaying, I most often (89% of the time) expends its 971 keV of decay energy by transforming into stable xenon-131 in two steps, with gamma decay following rapidly after beta decay:
The primary emissions of I decay are thus electrons with a maximal energy of 606 keV (89% abundance, others 248–807 keV) and 364 keV gamma rays (81% abundance, others 723 keV). Beta decay also produces an antineutrino, which carries off variable amounts of the beta decay energy. The electrons, due to their high mean energy (190 keV, with typical beta-decay spectra present) have a tissue penetration of . | 0 | Theoretical and Fundamental Chemistry |
Hemoglycin (previously termed hemolithin) is a space polymer that is the first polymer of amino acids found in meteorites. | 0 | Theoretical and Fundamental Chemistry |
Transition engineering is the professional-engineering discipline that deals with the application of the principles of science to the design, innovation and adaptation of engineered systems that meet the needs of today without compromising the ecological, societal and economic systems on which future generations will depend to meet their own needs. Today safety is an expected consideration in design, operation and end use. Transition Engineering aims for a similar consideration of sustainability. Transition engineering is a trans-disciplinary field that addresses wicked problems while creating opportunities to increase resilience and adaptation through change projects. | 1 | Applied and Interdisciplinary Chemistry |
It is an old joke in chemistry to draw a polycyclic hexagonal chemical structure and call this fictional compound chickenwire. By adding one or two simple chemical groups to this skeleton, the compound can then be named following the official chemical naming convention. An example is:
* 1,2-Dimethyl-chickenwire in a [https://web.archive.org/web/20070927205644/http://www.nearingzero.net/screen_res/nz079.jpg cartoon] by Nick D. Kim | 0 | Theoretical and Fundamental Chemistry |
Nickel allergy results in a skin response after the skin comes in contact with an item that releases a large amount of nickel from its surface. It is commonly associated with nickel-containing belt buckles coming into prolonged contact with the skin. The skin reaction can occur at the site of contact, or sometimes spread beyond to the rest of the body. Free (released) nickel that is able to penetrate the skin is taken up by scavenger (dendritic) cells and then presented to the immune system T-Cells. With each subsequent exposure to nickel these T cells become stimulated and duplicate themselves. With enough exposure to nickel, the amassing clones of T-cells reach "threshold" and the skin develops a rash. The rash can appear as acute, subacute, or chronic eczema-like skin patches, primarily at the site of contact with the nickel (e.g., earlobe from nickel earrings). From the time of exposure, the rash usually appears within 12–120 hours and can last for 3–4 weeks or for the continued duration of nickel contact/exposure.
Three simultaneous conditions must occur to trigger Ni-ACD:
#Direct skin contact with nickel-releasing item
#Prolonged skin contact with nickel-releasing item
#A sufficient amount of nickel is released and absorbed into the skin to cause a reaction
The pathophysiology is divided into induction elicitation phases. Induction is the critical phase (immunological event) when skin contact to nickel results in antigen presentation to the T cells, and T cell duplication (cloning) occurs. The metal cation Ni is a low molecular weight hapten that easily penetrates the stratum corneum (top layer of skin). Nickel then binds to skin protein carriers creating an antigenic epitope. The determining factor in sensitization is exposure of significant amounts of "free nickel". This is important because different metal alloys release different amounts of free nickel. The antigenic epitope is collected by dermal dendritic cells and Langerhans cells, the antigen-presenting cells (APC) of the skin, and undergo maturation and migration to regional lymph nodes. The complex is predominantly expressed on major histocompatibility complex (MHC) II, which activates and clonally expands naive CD4+ T cells. Upon re-exposure these now primed T cells will be activated and massively recruited to the skin, resulting in the elicitation phase and the clinical presentation of Ni-ACD.
Although ACD has been considered a Th1 predominate process, recent studies highlight a more complex picture. In Ni-ACD other cells are involved including: Th17, Th22, Th1/IFN and the innate immune responses consistent with toll-like receptor 4. | 1 | Applied and Interdisciplinary Chemistry |
Moving-boundary electrophoresis (MBE also free-boundary electrophoresis) is a technique for separation of chemical compounds by electrophoresis in a free solution. | 0 | Theoretical and Fundamental Chemistry |
Bertram Oliver "Bert" Fraser-Reid (23 February 1934 – 25 May 2020) was a Jamaican synthetic organic chemist who has been widely recognised for his work using carbohydrates as starting materials for chiral materials and on the role of oligosaccharides in immune response. | 0 | Theoretical and Fundamental Chemistry |
The burning velocity of the stretched flame can be derived by subtracting suitable terms from the unstretched flame speed, for small curvature and small strain, as given by
where
* is the burning velocity of unstretched flame
* is the term corresponding to the imposed strain rate on the flame due to the flow field
* is the Markstein length, proportional to the laminar flame thickness , the constant of proportionality is Markstein number
* is the flame curvature, which is positive if the flame front is convex with respect to the unburnt mixture and vice versa. | 1 | Applied and Interdisciplinary Chemistry |
Given the ability to knock down, in essence, any gene of interest, RNAi via siRNAs has generated a great deal of interest in both basic and applied biology.
One of the biggest challenges to siRNA and RNAi based therapeutics is intracellular delivery. siRNA also has weak stability and pharmacokinetic behavior. Delivery of siRNA via nanoparticles has shown promise. siRNA oligos in vivo are vulnerable to degradation by plasma and tissue endonucleases and exonucleases and have shown only mild effectiveness in localized delivery sites, such as the human eye. Delivering pure DNA to target organisms is challenging because its large size and structure prevents it from diffusing readily across membranes. siRNA oligos circumvent this problem due to their small size of 21-23 oligos. This allows delivery via nano-scale delivery vehicles called nanovectors.
A good nanovector for siRNA delivery should protect siRNA from degradation, enrich siRNA in the target organ and facilitate the cellular uptake of siRNA. The three main groups of siRNA nanovectors are: lipid based, non-lipid organic-based, and inorganic. Lipid based nanovectors are excellent for delivering siRNA to solid tumors, but other cancers may require different non-lipid based organic nanovectors such as cyclodextrin based nanoparticles.
siRNAs delivered via lipid based nanoparticles have been shown to have therapeutic potential for central nervous system (CNS) disorders. Central nervous disorders are not uncommon, but the blood brain barrier (BBB) often blocks access of potential therapeutics to the brain. siRNAs that target and silence efflux proteins on the BBB surface have been shown to create an increase in BBB permeability. siRNA delivered via lipid based nanoparticles is able to cross the BBB completely.
A huge difficulty in siRNA delivery is the problem of off-targeting. Since genes are read in both directions, there exists a possibility that even if the intended antisense siRNA strand is read and knocks out the target mRNA, the sense siRNA strand may target another protein involved in another function.
Phase I results of the first two therapeutic RNAi trials (indicated for age-related macular degeneration, aka AMD) reported at the end of 2005 that siRNAs are well tolerated and have suitable pharmacokinetic properties.
In a phase 1 clinical trial, 41 patients with advanced cancer metastasised to liver were administered RNAi delivered through lipid nanoparticles. The RNAi targeted two genes encoding key proteins in the growth of the cancer cells, vascular endothelial growth factor, (VEGF), and kinesin spindle protein (KSP). The results showed clinical benefits, with the cancer either stabilized after six months, or regression of metastasis in some of the patients. Pharmacodynamic analysis of biopsy samples from the patients revealed the presence of the RNAi constructs in the samples, proving that the molecules reached the intended target.
Proof of concept trials have indicated that Ebola-targeted siRNAs may be effective as post-exposure prophylaxis in humans, with 100% of non-human primates surviving a lethal dose of Zaire Ebolavirus, the most lethal strain. | 1 | Applied and Interdisciplinary Chemistry |
Advantages include minimal overlap in metal signals meaning the instrument is theoretically capable of detecting 100 parameters per cell, entire cell signaling networks can be inferred organically without reliance on prior knowledge, and one well-constructed experiment produces large amounts of data.
Disadvantages, in the case of CyTOF, include the practical flow rate is around 500 cells per second versus several thousand in flow cytometry and current reagents available limit cytometer use to around 50 parameters per cell. Additionally, mass cytometry is a destructive method and cells cannot be sorted for further analysis. In the case of IMC, the resolution of the data is relatively low (1μm2/pixel), the technique is as well destructive, acquiring of the data is also very slow, and it requires specialized expensive equipment and expertise. | 0 | Theoretical and Fundamental Chemistry |
Such as trace minerals, micronutrients, human-induced cycles for synthetic compounds such as polychlorinated biphenyl (PCB). | 0 | Theoretical and Fundamental Chemistry |
There is evidence for high concentrations of over 6,000 ppm between 600 and 400 million years ago, and of over 3,000 ppm between 200 and 150 million years ago.
Indeed, higher CO concentrations are thought to have prevailed throughout most of the Phanerozoic Eon, with concentrations four to six times current concentrations during the Mesozoic era, and ten to fifteen times current concentrations during the early Palaeozoic era until the middle of the Devonian period, about 400 million years ago. The spread of land plants is thought to have reduced CO concentrations during the late Devonian, and plant activities as both sources and sinks of CO have since been important in providing stabilizing feedbacks.
Earlier still, a 200-million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 Ma, by a colossal volcanic outgassing that raised the concentration of the atmosphere abruptly to 12%, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day. This episode marked the close of the Precambrian Eon, and was succeeded by the generally warmer conditions of the Phanerozoic, during which multicellular animal and plant life evolved. No volcanic CO emission of comparable scale has occurred since. In the modern era, emissions to the atmosphere from volcanoes are approximately 0.645 billion tons of per year, whereas humans contribute 29 billion tons of each year. | 1 | Applied and Interdisciplinary Chemistry |
Founded in 1929, by eight Lake Charles area businessmen, with land purchased from Jim Gardiner. The company was formed with 2250 common shares of stock with share-holders including, W. P. Weber, H. G. Chalkley, C. O. Noble, Henry Pomeroy, George M. King and Frank Roberts, M. J. Muller, and purchased 21,000 acres that included farm machinery, implements, stock, and cattle bought for $380,000.00, that included what was the Lowery and Illinois plantations, that became known as "The Illinois Plant", and "The Lowery Plant".
The Lacassane company continued with the previous form of tenant farming, increasing the original cattle herd, establishing trapping, hunting, oil and gas leases, and then the wetlands mitigation project. The Lacassine National Wildlife Refuge was established in 1937, when the company sold south of the Illinois Plant to the United States Government for $51,774.00. | 1 | Applied and Interdisciplinary Chemistry |
In nucleophilic trifluoromethylation the active species is the CF anion. It was, however, widely believed that the trifluoromethyl anion is a transient species and thus cannot be isolated or observed in the condensed phase. Contrary to the popular belief, the CF anion, with [K(18-crown-6)] as a countercation, was produced and characterized by Prakash and coworkers. The challenges associated with observation of CF anion are alluded to its strong basic nature and its tendency to form pentacoordinated silicon species, such as [MeSi(CF)] or [MeSi(F)(CF)].
The reactivity of fluoroform in combination with a strong base such as t-BuOK with carbonyl compounds in DMF is an example. Here CF and DMF form an hemiaminolate adduct ([MeNCH(O)CF]K). | 0 | Theoretical and Fundamental Chemistry |
The reversible Michaelis–Menten law, as with many enzymatic rate laws, can be decomposed into a capacity term, a thermodynamic term, and an enzyme saturation level. This is more easily seen when we write the reversible rate law as:
where is the capacity term, the thermodynamic term and
the saturation term. The separation can be even better appreciated if we look at the elasticity coefficient . According to elasticity algebra, the elasticity of a product is the sum of the sub-term elasticities, that is:
Hence the elasticity of the reversible Michaelis–Menten rate law can easily be shown to be:
Since the capacity term is a constant, the first elasticity is zero. The thermodynamic term can be easily shown to be:
where is the disequilibrium ratio and equals and the mass–action ratio
The saturation term becomes: | 0 | Theoretical and Fundamental Chemistry |
A 50% (v/v) alcohol solution is composed of 50% alcohol and 50% water in which water acts as a solvent. By igniting a paper banknote completely soaked with 50% alcohol solution, the alcohol (which is the fuel in the fire triangle) is combusted into carbon dioxide and water vapour. On the other hand, water is heated up with some being evaporated as it absorbs energy from the combustion of alcohol. The evaporation of water helps cool down the system, so not all water is evaporated and the paper banknote is not burnt. The water to alcohol ratio should be 50% or higher; a lower ratio leads to the banknote being slightly burnt because there is not enough water to absorb the combustion energy and cool down the system.
CHOH + (3n/2) O → n CO + (n+1) HO
Common alcohol fuels for this experiment can be methanol (n=1), ethanol (n=2) and both isomers of propanol (n=3). The fire lit in this scenario is categorized as a class B fire (fire from flammable liquids), while the fire from burning paper (banknote) is categorized as class A. The alcohol-water mixture flame can be hard to detect, so sodium chloride can be added to give the flames an orange-yellow color. For safety purpose, a water tray should be prepared for emergency use in case a paper banknote caught a fire, and flammable and combustible materials should not be kept or put near the flame. | 1 | Applied and Interdisciplinary Chemistry |
He began his professional career in 1954 as a professor of Applied Physics at Waseda University in Tokyo. He held this position until 1960 when he came to the United States on an exchange program with Duke University. At Duke, he taught polymer rheology. In the early 1960s Tokita joined the U. S. Rubber Company in New Jersey, later Uniroyal, working there for 30 years on elastomer processing. He later joined Uniroyal Goodrich Tire Company in Akron in a research role. He joined Cabot Corporation in Billerica in 1990. During his career he produced 9 U.S. Patents. His most cited scientific article treated the subject of morphology formation in elastomer blends. | 0 | Theoretical and Fundamental Chemistry |
Monoalkyl boranes are relatively rare. When the alkyl group is small, such as methyl, the monoalkylboranes tend to redistribute to give mixtures of diborane and di- and trialkylboranes. Monoalkylboranes typically exist as dimers of the form [RBH]. One example is thexylborane (ThxBH), produced by the hydroboration of tetramethylethylene:
:BH + 2 MeC=CMe → [MeCHCMeBH]
A chiral example is monoisopinocampheylborane. Although often written as IpcBH, it is a dimer [IpcBH]. It is obtained by hydroboration of (−)‐α‐pinene with borane dimethyl sulfide.
Species of the form RBH are available for R = alkyl and halide. Monobromo- and monochloro-borane can be prepared from BMS and the corresponding boron trihalides. The stable complex of monochloroborane and 1,4-dioxane effects hydroboration of terminal alkenes. | 0 | Theoretical and Fundamental Chemistry |
Genetic variants in the CYP21A2 gene cause a disturbance in the development of the enzyme, leading to congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. Gene conversion events involving the functional gene and the pseudogene account for many cases of steroid 21-hydroxylase deficiency. CAH is an autosomal recessive disorder. There are multiple forms of CAH, defined as classical and nonclassical forms based on the amount of enzyme function still present in the patient.
The classical forms occur in approximately 1 in to 1 in births globally, and includes both the salt-wasting (excessive excretion of sodium via the urine causing hyponatremia and dehydration) and simple-virilizing forms. Complete loss of enzymatic activity causes the salt-wasting form. Variations in the structure of steroid 21-hydroxylase are related to the clinical severity of congenital adrenal hyperplasia. Cortisol and aldosterone deficits are associated with life-threatening sodium loss, as the steroids play roles in regulating sodium homeostasis. Simple-virilizing CAH patients (~1-2% enzyme function) maintain adequate sodium homeostasis, but exhibit other symptoms shared by the salt-wasting form, including accelerated growth in childhood and ambiguous genitalia in female neonates.
The nonclassical form is the mildest condition, retaining about 20% to 50% of enzyme function. This form is associated with mild and clinically silent cortisol impairment, but an excess of androgens post-puberty. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two organyl groups (e.g., alkyl or aryl). They have the general formula , where R and R′ represent organyl groups (e.g., alkyl or aryl). Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether" (). Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin. | 0 | Theoretical and Fundamental Chemistry |
The Doppler cooling limit for electric dipole transitions is typically in the hundreds of microkelvins. In the 1980s this limit was seen as the lowest achievable temperature. It was a surprise then when sodium atoms were cooled to 43 microkelvin when their Doppler cooling limit is 240 microkelvin, the new low was explained by the addition of more atomic states in combination to laser polarization. Previous conceptions of laser cooling were decided to have been too simplistic. The major laser cooling breakthroughs in the 70s and 80s led to several improvements to preexisting technology and new discoveries with temperatures just above absolute zero. The cooling processes were utilized to make atomic clocks more accurate and to improve spectroscopic measurements, and led to the observation of a new state of matter at ultracold temperatures. The new state of matter, the Bose–Einstein condensate, was observed in 1995 by Eric Cornell, Carl Wieman, and Wolfgang Ketterle.
Laser cooling was primarily used to create ultracold atoms. For example, the experiments in quantum physics need to perform near absolute zero where unique quantum effects such as Bose–Einstein condensation can be observed. Laser cooling is also a primary tool in optical clock experiments. | 0 | Theoretical and Fundamental Chemistry |
After Planck identified that Wien's law can be extended to all frequencies, even very low ones, by interpolating with the classical equipartition law for radiation, physicists wanted to understand the quantum behavior of other systems.
The Planck radiation law quantized the motion of the field oscillators in units of energy proportional to the frequency:
The quantum can only depend on the energy/frequency by adiabatic invariance, and since the energy must be additive when putting boxes end-to-end, the levels must be equally spaced.
Einstein, followed by Debye, extended the domain of quantum mechanics by considering the sound modes in a solid as quantized oscillators. This model explained why the specific heat of solids approached zero at low temperatures, instead of staying fixed at as predicted by classical equipartition.
At the Solvay conference, the question of quantizing other motions was raised, and Lorentz pointed out a problem, known as Rayleigh–Lorentz pendulum. If you consider a quantum pendulum whose string is shortened very slowly, the quantum number of the pendulum cannot change because at no point is there a high enough frequency to cause a transition between the states. But the frequency of the pendulum changes when the string is shorter, so the quantum states change energy.
Einstein responded that for slow pulling, the frequency and energy of the pendulum both change, but the ratio stays fixed. This is analogous to Wien's observation that under slow motion of the wall the energy to frequency ratio of reflected waves is constant. The conclusion was that the quantities to quantize must be adiabatic invariants.
This line of argument was extended by Sommerfeld into a general theory: the quantum number of an arbitrary mechanical system is given by the adiabatic action variable. Since the action variable in the harmonic oscillator is an integer, the general condition is
This condition was the foundation of the old quantum theory, which was able to predict the qualitative behavior of atomic systems. The theory is inexact for small quantum numbers, since it mixes classical and quantum concepts. But it was a useful half-way step to the new quantum theory. | 0 | Theoretical and Fundamental Chemistry |
* Jean Baptiste Carnoy
* Peter Agre
* Günter Blobel
* Robert Brown
* Geoffrey M. Cooper
* Christian de Duve
* Henri Dutrochet
* Robert Hooke
* H. Robert Horvitz
* Marc Kirschner
* Anton van Leeuwenhoek
* Ira Mellman
* Marta Miączyńska
* Peter D. Mitchell
* Rudolf Virchow
* Paul Nurse
* George Emil Palade
* Keith R. Porter
* Ray Rappaport
* Michael Swann
* Roger Tsien
* Edmund Beecher Wilson
* Kenneth R. Miller
* Matthias Jakob Schleiden
* Theodor Schwann
* Yoshinori Ohsumi
* Jan Evangelista Purkyně | 1 | Applied and Interdisciplinary Chemistry |
Chlorosulfuric acid (IUPAC name: sulfurochloridic acid) is the inorganic compound with the formula HSOCl. It is also known as chlorosulfonic acid, being the sulfonic acid of chlorine. It is a distillable, colorless liquid which is hygroscopic and a powerful lachrymator. Commercial samples usually are pale brown or straw colored.
Salts and esters of chlorosulfuric acid are known as chlorosulfates. | 0 | Theoretical and Fundamental Chemistry |
Some key factors that determine overall rate include protein half-life, pH, and temperature.
Protein half-life helps determine the overall rate as this designates the first step in protein catabolism. Depending on whether this step is short or long will influence the rest of the metabolic process. One key component in determining the protein half-life is based on the N-end rule. This states that the amino acid present at the N-terminus of a protein helps determine the protein's half-life. | 1 | Applied and Interdisciplinary Chemistry |
The total volumetric flux through the test surface is
where is an arc-length parameter defined on the curve , with at the point and at the point .
Here is the unit vector perpendicular to the test surface, i.e.,
where is the rotation matrix corresponding to a anticlockwise rotation about the positive axis:
The integrand in the expression for is independent of , so the outer integral can be evaluated to yield | 1 | Applied and Interdisciplinary Chemistry |
Single nucleotide polymorphisms (SNPs) in TCF7L2 gene have shown an increase in susceptibility to schizophrenia in Arab, European and Chinese Han populations. In the Chinese Han population, SNP rs12573128 in TCF7L2 is the variant that was associated with an increase in schizophrenia risk. This marker is used as a pre-diagnostic marker for schizophrenia. TCF7L2 has also been reported as a risk gene in autism spectrum disorder and has been linked to it in recent large-scale genetic studies.
The mechanism behind TCF7L2s involvement in the emergence of neurodevelopmental disorders is not fully understood, as there have been few studies characterizing its role in brain development in detail. It was shown that during embryogenesis TCF7L2 is involved in the development of fish-specific habenula asymmetry in Danio rerio, and that the dominant negative TCF7L2 isoform influences cephalic separation in the embryo by inhibiting the posteriorizing effect of the Wnt pathway. It was also shown that in Tcf7l2' knockout mice the number of proliferating cells in cortical neural progenitor cells is reduced. In contrast, no such effect was found in the midbrain.
More recently it was shown that TCF7L2 plays a crucial role in both the embryonic development and postnatal maturation of the thalamus through direct and indirect regulation of many genes previously reported to be important for both processes. In late gestation TCF7L2 regulates the expression of many thalamus-enriched transcription factors (e.g. Foxp2, Rora, Mef2a, Lef1, Prox1), axon guidance molecules (e.g. Epha1, Epha4, Ntng1, Epha8) and cell adhesion molecules (e.g. Cdh6, Cdh8, Cdhr1). Accordingly, a total knockout of Tcf7l2 in mice leads to improper growth of thalamocortical axons, changed anatomy and improper sorting of the cells in the thalamo-habenular region. In the early postnaral period TCF7L2 starts to regulate the expression of many genes necessary for the acquisition of characteristic excitability patterns in the thalamus, mainly ion channels, neurotransmitters and their receptors and synaptic vescicle proteins (e.g. Cacna1g, Kcnc2, Slc17a7, Grin2b), and an early postnatal knockout of Tcf7l2 in mouse thalamus leads to significant reduction in the number and frequency of action potentials generated by the thalamocortical neurons. The mechanism that leads to the change in TCF7L2 target genes between gestation and early postnatal period is unknown. It is likely that a perinatal change in the proportion of TCF7L2 isoforms expressed in the thalamus is partially responsible. Abnormalities in the anatomy of the thalamus and the activity of its connections to the cerebral cortex are frequently detected in patients with schizophrenia and autism. Such abnormalities could arise from developmental aberrations in patients with unfavorable mutations of TCF7L2, further strengthening the link between TCF7L2 and neurodevelopmental disorders. | 1 | Applied and Interdisciplinary Chemistry |
Oil-in-water emulsions are common in food products:
* Mayonnaise and Hollandaise sauces – these are oil-in-water emulsions stabilized with egg yolk lecithin, or with other types of food additives, such as sodium stearoyl lactylate
* Homogenized milk – an emulsion of milk fat in water, with milk proteins as the emulsifier
* Vinaigrette – an emulsion of vegetable oil in vinegar, if this is prepared using only oil and vinegar (i.e., without an emulsifier), an unstable emulsion results
Water-in-oil emulsions are less common in food, but still exist:
* Butter – an emulsion of water in butterfat
* Margarine
Other foods can be turned into products similar to emulsions, for example meat emulsion is a suspension of meat in liquid that is similar to true emulsions. | 0 | Theoretical and Fundamental Chemistry |
A protein skimmer or foam fractionator is a device used to remove organic compounds such as food and waste particles from water. It is most commonly used in commercial applications like municipal water treatment facilities, public aquariums, and aquaculture facilities. Smaller protein skimmers are also used for filtration of home saltwater aquariums and even freshwater aquariums and ponds. | 0 | Theoretical and Fundamental Chemistry |
Mice treated with tetrahydrocannabinol (THC) show suppression of long-term potentiation in the hippocampus, a process that is essential for the formation and storage of long-term memory. These results may concur with anecdotal evidence suggesting that smoking cannabis impairs short-term memory. Consistent with this finding, mice without the CB receptor show enhanced memory and long-term potentiation indicating that the endocannabinoid system may play a pivotal role in the extinction of old memories. One study found that the high-dose treatment of rats with the synthetic cannabinoid HU-210 over several weeks resulted in stimulation of neural growth in the rats' hippocampus region, a part of the limbic system playing a part in the formation of declarative and spatial memories, but did not investigate the effects on short-term or long-term memory. Taken together, these findings suggest that the effects of endocannabinoids on the various brain networks involved in learning and memory may vary. | 1 | Applied and Interdisciplinary Chemistry |
Anammox, an abbreviation for "anaerobic ammonium oxidation", is a globally important microbial process of the nitrogen cycle that takes place in many natural environments. The bacteria mediating this process were identified in 1999, and were a great surprise for the scientific community. In the anammox reaction, nitrite and ammonium ions are converted directly into diatomic nitrogen and water.
The bacteria that perform the anammox process are genera that belong to the bacterial phylum Planctomycetota. The anammox bacteria all possess one anammoxosome, a lipid bilayer membrane-bound compartment inside the cytoplasm in which the anammox process takes place. The anammoxosome membranes are rich in ladderane lipids; the presence of these lipids is so far unique in biology.
"Anammox" is also the trademarked name for an anammox-based ammonium removal technology developed by the Delft University of Technology. | 1 | Applied and Interdisciplinary Chemistry |
The iron-tin intermetallic forms at around and naturally assumes a kagome structure. Quenching in an ice bath then cools the material to room temperature without disrupting the atomic structure. | 1 | Applied and Interdisciplinary Chemistry |
Uricotelism is the excretion of excess nitrogen in the form of uric acid. Uricotelic animals include insects, birds and most reptiles. Though requiring more metabolic energy to make than urea, uric acid's low toxicity and low solubility in water allow it to be concentrated into a small volume of pasty white suspension in feces, compared to the liquid urine of mammals. Notably however, great apes and humans, while ureotelic, are also uricotelic to a small extent, with uric acid potentially causing problems such as kidney stones and gout, but also functioning as a blood antioxidant. | 1 | Applied and Interdisciplinary Chemistry |
Biomonitoring involves the use of organisms to assess environmental contamination, such as of surrounding air or water. It can be done qualitatively by observing and noting changes in organisms, or quantitatively by measuring accumulation of chemicals in organism tissues. By observing or measuring the effects the environment has on its resident organisms, pollution may be suspected or inferred.
Historically, public health regulations have been based on theoretical risk calculations according to known levels of chemical substances in air, water, soil, food, other consumer products and other sources of potential exposure. Human biomonitoring offers the opportunity to analyze the actual internal levels of bodily substances from all potential routes of exposure at one time, which may contribute to improving risk assessments.
Scientific advancements have made it possible to detect a greater number of chemical substances in smaller concentrations in the body, with some chemicals detectable at levels as low as parts per trillion. A single biomonitoring measurement is only one snapshot in time and may not accurately reflect the level of exposure over longer periods.
The presence of an environmental chemical in the body does not necessarily indicate harm. The analytical chemistry of detecting chemicals has advanced more rapidly than the ability to interpret the potential health consequences. Health risks are usually established from toxicity studies in laboratory animals and epidemiological evidence in humans. Lead is a well studied chemical with a CDC action level of concern, currently at 10 µg/dL, or 100 parts per billion, in blood; however, neurobehavioral impairment has been noted below this level. Because this approach requires establishment of cause and effect in epidemiological studies and a thorough understanding of human dose response, data to support these types of action levels exist for only a few environmental chemicals. The concept of Biomonitoring Equivalents (BEs) has been developed as an alternative approach to aid in interpreting and communicating biomonitoring results in the context of potential risks to health.
There are different types of biomarkers that indicate exposure, effect, or susceptibility. | 1 | Applied and Interdisciplinary Chemistry |
Several techniques are currently employed to assess average telomere length in eukaryotic cells. One method is the Terminal Restriction Fragment (TRF) southern blot. There is a Web-based Analyser of the Length of Telomeres ([https://www.ceitec.eu/chromatin-molecular-complexes/rg51/tab?tabId=125 WALTER]), software processing the TRF pictures. A Real-Time PCR assay for telomere length involves determining the Telomere-to-Single Copy Gene (T/S) ratio, which is demonstrated to be proportional to the average telomere length in a cell.
Tools have also been developed to estimate the length of telomere from whole genome sequencing (WGS) experiments. Amongst these are TelSeq, Telomerecat and telomereHunter. Length estimation from WGS typically works by differentiating telomere sequencing reads and then inferring the length of telomere that produced that number of reads. These methods have been shown to correlate with preexisting methods of estimation such as PCR and TRF. Flow-FISH is used to quantify the length of telomeres in human white blood cells. A semi-automated method for measuring the average length of telomeres with Flow FISH was published in Nature Protocols in 2006.
While multiple companies offer telomere length measurement services, the utility of these measurements for widespread clinical or personal use has been questioned. Nobel Prize winner Elizabeth Blackburn, who was co-founder of one company, promoted the clinical utility of telomere length measures. | 1 | Applied and Interdisciplinary Chemistry |
Glucagon-like peptide-2 (GLP-2) is a 33 amino acid peptide with the sequence HADGSFSDEMNTILDNLAARDFINWLIQTKITD (see Proteinogenic amino acid) in humans. GLP-2 is created by specific post-translational proteolytic cleavage of proglucagon in a process that also liberates the related glucagon-like peptide-1 (GLP-1). GLP-2 is produced by the intestinal endocrine L cell and by various neurons in the central nervous system. Intestinal GLP-2 is co-secreted along with GLP-1 upon nutrient ingestion.
When externally administered, GLP-2 produces a number of effects in humans and rodents, including intestinal growth, enhancement of intestinal function, reduction in bone breakdown and neuroprotection. GLP-2 may act in an endocrine fashion to link intestinal growth and metabolism with nutrient intake. GLP-2 and related analogs may be treatments for short bowel syndrome, Crohn's disease, osteoporosis and as adjuvant therapy during cancer chemotherapy.
GLP-2 has an antidepressant effect in a mouse model of depression when delivered via intracerebroventricular injection. However, a GLP-2 derivative (PAS-CPP-GLP-2) was shown to be efficiently delivered to the brain intranasally, with similar efficacy. | 1 | Applied and Interdisciplinary Chemistry |
Amination is the process by which an amine group is introduced into an organic molecule. This type of reaction is important because organonitrogen compounds are pervasive. | 0 | Theoretical and Fundamental Chemistry |
Aliphatic metal alkoxides decompose in water as summarized in this idealized equation:
In the transesterification process, metal alkoxides react with esters to bring about an exchange of alkyl groups between metal alkoxide and ester. With the metal alkoxide complex in focus, the result is the same as for alcoholysis, namely the replacement of alkoxide ligands, but at the same time the alkyl groups of the ester are changed, which can also be the primary goal of the reaction. Sodium methoxide in solution, for example, is commonly used for this purpose, a reaction that is used in the production of biodiesel. | 0 | Theoretical and Fundamental Chemistry |
First, a DNA fragment can be converted into a new sequence in which each original nucleotide is encoded by a specific 8-nt sequence (A8, T8, G8 and C8) and then ligated to a hairpin. | 1 | Applied and Interdisciplinary Chemistry |
During the more than 80 years of technical development of sensor-based ore sorting equipment, various types of machines have been developed. This includes the channel-type, bucket-wheel type and cone type sorters. The main machine types being installed in the mining industry today are belt-type and chute-type machines. Harbeck made a good comparison of both disadvantages and advantages of the systems for different sorting applications. The selection of a machine-type for an application depends various case-dependent factors, including the detection system applied, particle size, moisture, yield amongst others. | 0 | Theoretical and Fundamental Chemistry |
Darken's second equation relates the chemical diffusion coefficient, , of a binary system to the atomic fractions of the two components. Similar to the first equation, this equation is applicable when the system does not undergo a volume change. This equation also only applies to multicomponent systems, including binary systems, that obey the equations of state and the Gibbs–Duhem equations. | 0 | Theoretical and Fundamental Chemistry |
The term calcareous can be applied to a sediment, sedimentary rock, or soil type which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite. | 0 | Theoretical and Fundamental Chemistry |
The speed of sound is defined in classical mechanics as:
It follows, by replacing partial derivatives, that the isentropic compressibility can be expressed as: | 1 | Applied and Interdisciplinary Chemistry |
Devolatilization can be carried out when a polymer is in the solid or liquid phase, with the volatile components going into a liquid or gas phase. Examples are:
* Solid polymer, liquid phase: Extraction of caprolactam from Polyamides with water.
* Solid polymer, gas phase: Removal of ethylene from Polyethylene via air or nitrogen in silos.
* Liquid polymer, gas phase: Removal of Styrene from Polystyrene via vacuum.
It is usual for different types of devolatilization steps to be combined to overcome limitations in the individual steps. | 1 | Applied and Interdisciplinary Chemistry |
* Fellow, King's College, Cambridge University (1969–1973, 2007– for Life)
* Professor at H.E.J. Research Institute of Chemistry at Karachi University
* Professor Emeritus at H.E.J. Research Institute of Chemistry at Karachi University (2012)
* Coordinator General of COMSTECH(1996–2012)
* Federal Minister of Science & Technology (2000–2002)
* Federal Minister of Education (2002)
* Federal Minister/Chairman, Higher Education Commission, Pakistan (resigned due to govt issues)(2002–2008)
* Advisor to the Prime Minister of Pakistan on Science and Technology(2002–2008) | 0 | Theoretical and Fundamental Chemistry |
The main role of NAD in metabolism is the transfer of electrons from one molecule to another. Reactions of this type are catalyzed by a large group of enzymes called oxidoreductases. The correct names for these enzymes contain the names of both their substrates: for example NADH-ubiquinone oxidoreductase catalyzes the oxidation of NADH by coenzyme Q. However, these enzymes are also referred to as dehydrogenases or reductases, with NADH-ubiquinone oxidoreductase commonly being called NADH dehydrogenase or sometimes coenzyme Q reductase.
There are many different superfamilies of enzymes that bind NAD / NADH. One of the most common superfamilies includes a structural motif known as the Rossmann fold. The motif is named after Michael Rossmann, who was the first scientist to notice how common this structure is within nucleotide-binding proteins.
An example of a NAD-binding bacterial enzyme involved in amino acid metabolism that does not have the Rossmann fold is found in Pseudomonas syringae pv. tomato (; ).
When bound in the active site of an oxidoreductase, the nicotinamide ring of the coenzyme is positioned so that it can accept a hydride from the other substrate. Depending on the enzyme, the hydride donor is positioned either "above" or "below" the plane of the planar C4 carbon, as defined in the figure. Class A oxidoreductases transfer the atom from above; class B enzymes transfer it from below. Since the C4 carbon that accepts the hydrogen is prochiral, this can be exploited in enzyme kinetics to give information about the enzyme's mechanism. This is done by mixing an enzyme with a substrate that has deuterium atoms substituted for the hydrogens, so the enzyme will reduce NAD by transferring deuterium rather than hydrogen. In this case, an enzyme can produce one of two stereoisomers of NADH.
Despite the similarity in how proteins bind the two coenzymes, enzymes almost always show a high level of specificity for either NAD or NADP. This specificity reflects the distinct metabolic roles of the respective coenzymes, and is the result of distinct sets of amino acid residues in the two types of coenzyme-binding pocket. For instance, in the active site of NADP-dependent enzymes, an ionic bond is formed between a basic amino acid side-chain and the acidic phosphate group of NADP. On the converse, in NAD-dependent enzymes the charge in this pocket is reversed, preventing NADP from binding. However, there are a few exceptions to this general rule, and enzymes such as aldose reductase, glucose-6-phosphate dehydrogenase, and methylenetetrahydrofolate reductase can use both coenzymes in some species. | 0 | Theoretical and Fundamental Chemistry |
Mating disruption (MD) is a pest management technique designed to control certain insect pests by introducing artificial stimuli that confuse the individuals and disrupt mate localization and/or courtship, thus preventing mating and blocking the reproductive cycle. It usually involves the use of synthetic sex pheromones, although other approaches, such as interfering with vibrational communication, are also being developed. | 1 | Applied and Interdisciplinary Chemistry |
The gene gun was originally a Crosman air pistol modified to fire dense tungsten particles. It was invented by John C Sanford, Ed Wolf, and Nelson Allen at Cornell University along with Ted Klein of DuPont between 1983 and 1986. The original target was onions (chosen for their large cell size), and the device was used to deliver particles coated with a marker gene which would relay a signal if proper insertion of the DNA transcript occurred. Genetic transformation was demonstrated upon observed expression of the marker gene within onion cells.
The earliest custom manufactured gene guns (fabricated by Nelson Allen) used a 22 caliber nail gun cartridge to propel a polyethylene cylinder (bullet) down a 22 caliber Douglas barrel. A droplet of the tungsten powder coated with genetic material was placed onto the bullet and shot down into a Petri dish below. The bullet welded to the disk below the Petri plate, and the genetic material blasted into the sample with a doughnut effect involving devastation in the middle of the sample with a ring of good transformation around the periphery. The gun was connected to a vacuum pump and was placed under a vacuum while firing. The early design was put into limited production by a Rumsey-Loomis (a local machine shop then at Mecklenburg Road in Ithaca, NY, USA).
Biolistics, Inc sold Dupont the rights to manufacture and distribute an updated device with improvements including the use of helium as a non-explosive propellant and a multi-disk collision delivery mechanism to minimize damage to sample tissues. Other heavy metals such as gold and silver are also used to deliver genetic material with gold being favored due to lower cytotoxicity in comparison to tungsten projectile carriers. | 1 | Applied and Interdisciplinary Chemistry |
The Joliot-Curies had become increasingly aware of the growth of the fascist movement. They opposed its ideals and joined the Socialist Party in 1934, the Comité de vigilance des intellectuels antifascistes a year later, and in 1936 they actively supported the Republican faction in the Spanish Civil War. In the same year, Joliot-Curie was appointed Undersecretary of State for Scientific Research by the French government, in which capacity she helped in founding the Centre National de la Recherche Scientifique.
Frédéric and Irène visited Moscow for the two hundred and twentieth anniversary of the Russian Academy of Science and returned sympathizing with Russian colleagues. Frédérics close connection with the Communist Party caused Irène to later be detained on Ellis Island during her third trip to the US, coming to speak in support of Spanish refugees, at the Joint Antifascist Refugee Committees invitation.
The Joliot-Curies had continued Pierre and Marie's policy of publishing all of their work for the benefit of the global scientific community, but afraid of the danger that might result should it be developed for military use, they stopped: on 30 October 1939, they placed all of their documentation on nuclear fission in the vaults of the French Academy of Sciences, where it remained until 1949.
Joliot-Curies political career continued after the war and she became a commissioner in the Commissariat à lénergie atomique. However, she still found time for scientific work and in 1946 became director of her mothers Institut Curie'.
Joliot-Curie became actively involved in promoting womens education, serving on the National Committee of the Union of French Women (Comité National de lUnion des Femmes Françaises) and the World Peace Council. The Joliot-Curies were given memberships to the French Légion dhonneur'; Irène as an officer and Frédéric as a commander, recognising his earlier work for the resistance. | 0 | Theoretical and Fundamental Chemistry |
The valence isomers are not restricted to isomers of benzene. Valence isomers are also seen in the series (CH). Due to the larger number of units, the number of possible valence isomers is also greater and at least 21: | 0 | Theoretical and Fundamental Chemistry |
For fusion to take place, it has to overcome huge repulsive forces due to the strong hydration repulsion between hydrophilic lipid head groups. However, it has been hard to exactly determine the connection between adhesion, fusion and interbilayer forces. The forces that promote cell adhesion are not the same as the ones that promote membrane fusion. Studies show that by creating a stress on the interacting bilayers, fusion can be achieved without disrupting the interbilayer interactions. It has also been suggested that membrane fusion takes place through a sequence of structural rearrangements that help to overcome the barrier that prevents fusion. Thus, interbilayer fusion takes place through
* local approach of membrane
* structural rearrangements causing hydration repulsion forces to be overcome
* complete merging to form a single entity | 0 | Theoretical and Fundamental Chemistry |
Prostaglandin E is a family of naturally occurring prostaglandins that are used as medications.
Types include:
* Prostaglandin E also known as alprostadil
* Prostaglandin E also known as dinoprostone
Both types are on the World Health Organization's List of Essential Medicines.
Prostaglandin E play an important role in thermoregulation of the human brain. Decreased formation of prostaglandin E through inhibition of cyclooxygenase is the basis for the antipyretic of nonsteroidal anti-inflammatory drugs (NSAIDs). | 1 | Applied and Interdisciplinary Chemistry |
The relation between partial molar properties and the apparent ones can be derived from the definition of the apparent quantities and of the molality.
The relation holds also for multicomponent mixtures, just that in this case subscript i is required. | 0 | Theoretical and Fundamental Chemistry |
Oncosis and apoptosis are distinct processes of cellular death. Oncosis is characterized by cellular swelling caused by a failure in ion transporter function. Apoptosis, or programmed cell death involves a series of cell shrinking processes, beginning with cell size reduction and pyknosis, followed by cell budding and karyorrhexis, and phagocytosis by macrophages or neighboring cells due to size decrease. The phagocytic disposal of apoptotic cells prevents the release of cellular debris that could induce an inflammatory response in neighboring cells. In opposition, the leakage of cellular content associated with membrane disruption in oncosis often incites an inflammatory response in neighboring tissue, causing further cellular injury. Additionally, apoptosis and the degradation of intracellular organelles is mediated by caspase activation, particularly caspase-3. Oligonuclosomal DNA fragmentation is initiated by caspase-activated deoxyribonuclease following caspase-3 mediated cleavage of the enzyme’s inhibitor, ICAD. In contrast, the oncotic pathway has been shown to be caspase-3 independent.
The primary determinant of cell death occurring via the oncotic or apoptotic pathway is cellular ATP levels. Apoptosis is contingent upon ATP levels to form the energy dependent apoptosome. A distinct biochemical event only seen in oncosis is the rapid depletion of intracellular ATP. The lack of intracellular ATP results in a deactivation of sodium and potassium ATPase within the compromised cell membrane. The lack of ion transport at the cell membrane leads to an accumulation of sodium and chloride ions within the cell with a concurrent water influx, contributing to the hallmark cellular swelling of oncosis. As with apoptosis, oncosis has been shown to be genetically programmed and dependent on expression levels of uncoupling protein-2 (UCP-2) in HeLa cells. An increase in UCP-2 levels leads to a rapid decrease in mitochondrial membrane potential, reducing mitochondrial NADH and intracellular ATP levels, initiating the oncotic pathway. The anti-apoptotic gene product Bcl-2 is not an active inhibitor of UCP-2 initiated cell death, further distinguishing oncosis and apoptosis as distinct cellular death mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Nuclei which have neutron numbers and proton (atomic) numbers both equal to one of the magic numbers are called "doubly magic", and are generally very stable against decay. The known doubly magic isotopes are helium-4, helium-10, oxygen-16, calcium-40, calcium-48, nickel-48, nickel-56, nickel-78, tin-100, tin-132, and lead-208. While only helium-4, oxygen-16, calcium-40, and lead-208 are completely stable, calcium-48 is extremely long-lived and therefore found naturally, disintegrating only by a very inefficient double beta minus decay process. Double beta decay in general is so rare that several nuclides exist which are predicted to decay by this mechanism but in which no such decay has yet been observed. Even in nuclides whose double beta decay has been confirmed through observations, half lives usually exceed the age of the universe by orders of magnitude, and emitted beta or gamma radiation is for virtually all practical purposes irrelevant. On the other hand, helium-10 is extremely unstable, and has a half-life of just ().
Doubly magic effects may allow the existence of stable isotopes which otherwise would not have been expected. An example is calcium-40, with 20 neutrons and 20 protons, which is the heaviest stable isotope made of the same number of protons and neutrons. Both calcium-48 and nickel-48 are doubly magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons. Calcium-48 is very neutron-rich for such a relatively light element, but like calcium-40, it is stabilized by being doubly magic. As an exception, although oxygen-28 has 8 protons and 20 neutrons, it is unbound with respect to four-neutron decay and appears to lack closed neutron shells, so it is not regarded as doubly magic.
Magic number shell effects are seen in ordinary abundances of elements: helium-4 is among the most abundant (and stable) nuclei in the universe and lead-208 is the heaviest stable nuclide (at least by known experimental observations). Alpha decay (the emission of a He nucleus – also known as an alpha particle – by a heavy element undergoing radioactive decay) is common in part due to the extraordinary stability of helium-4, which makes this type of decay energetically favored in most heavy nuclei over neutron emission, proton emission or any other type of cluster decay. The stability of He also leads to the absence of stable isobars of mass number 5 and 8; indeed, all nuclides of those mass numbers decay within fractions of a second to produce alpha particles.
Magic effects can keep unstable nuclides from decaying as rapidly as would otherwise be expected. For example, the nuclides tin-100 and tin-132 are examples of doubly magic isotopes of tin that are unstable, and represent endpoints beyond which stability drops off rapidly. Nickel-48, discovered in 1999, is the most proton-rich doubly magic nuclide known. At the other extreme, nickel-78 is also doubly magic, with 28 protons and 50 neutrons, a ratio observed only in much heavier elements, apart from tritium with one proton and two neutrons (Ni: 28/50 = 0.56; U: 92/146 = 0.63).
In December 2006, hassium-270, with 108 protons and 162 neutrons, was discovered by an international team of scientists led by the Technical University of Munich, having a half-life of 9 seconds. Hassium-270 evidently forms part of an island of stability, and may even be doubly magic due to the deformed (American football- or rugby ball-like) shape of this nucleus.
Although Z = 92 and N = 164 are not magic numbers, the undiscovered neutron-rich nucleus uranium-256 may be doubly magic and spherical due to the difference in size between low- and high-angular momentum orbitals, which alters the shape of the nuclear potential. | 0 | Theoretical and Fundamental Chemistry |
Coagulation itself results in the formation of floc but flocculation is required to help the floc further aggregate and settle. The coagulation-flocculation process itself removes only about 60%-70% of Natural Organic Matter (NOM) and thus, other processes like oxidation, filtration and sedimentation are necessary for complete raw water or wastewater treatment. Coagulant aids (polymers that bridge the colloids together) are also often used to increase the efficiency of the process. | 1 | Applied and Interdisciplinary Chemistry |
The pre-mRNA processing at the 3 end of the RNA molecule involves cleavage of its 3 end and then the addition of about 250 adenine residues to form a poly(A) tail. The cleavage and adenylation reactions occur primarily if a polyadenylation signal sequence (5- AAUAAA-3) is located near the 3 end of the pre-mRNA molecule, which is followed by another sequence, which is usually (5-CA-3') and is the site of cleavage. A GU-rich sequence is also usually present further downstream on the pre-mRNA molecule. More recently, it has been demonstrated that alternate signal sequences such as UGUA upstream off the cleavage site can also direct cleavage and polyadenylation in the absence of the AAUAAA signal.
It is important to understand that these two signals are not mutually independent and often coexist. After the synthesis of the sequence elements, several multi-subunit proteins are transferred to the RNA molecule. The transfer of these sequence specific binding proteins cleavage and polyadenylation specificity factor (CPSF), Cleavage Factor I (CF I) and cleavage stimulation factor (CStF) occurs from RNA Polymerase II. The three factors bind to the sequence elements. The AAUAAA signal is directly bound by CPSF. For UGUA dependent processing sites, binding of the multi protein complex is done by Cleavage Factor I (CF I). The resultant protein complex formed contains additional cleavage factors and the enzyme Polyadenylate Polymerase (PAP). This complex cleaves the RNA between the polyadenylation sequence and the GU-rich sequence at the cleavage site marked by the (5-CA-3) sequences. Poly(A) polymerase then adds about 200 adenine units to the new 3 end of the RNA molecule using ATP as a precursor. As the poly(A) tail is synthesized, it binds multiple copies of poly(A)-binding protein, which protects the 3end from ribonuclease digestion by enzymes including the CCR4-Not complex. | 1 | Applied and Interdisciplinary Chemistry |
GFP has a beta barrel structure consisting of eleven β-strands with a pleated sheet arrangement, with an alpha helix containing the covalently bonded chromophore 4-(p-hydroxybenzylidene)imidazolidin-5-one (HBI) running through the center. Five shorter alpha helices form caps on the ends of the structure. The beta barrel structure is a nearly perfect cylinder, 42Å long and 24Å in diameter (some studies have reported a diameter of 30Å), creating what is referred to as a "β-can" formation, which is unique to the GFP-like family. HBI, the spontaneously modified form of the tripeptide Ser65–Tyr66–Gly67, is nonfluorescent in the absence of the properly folded GFP scaffold and exists mainly in the un-ionized phenol form in wtGFP. Inward-facing sidechains of the barrel induce specific cyclization reactions in Ser65–Tyr66–Gly67 that induce ionization of HBI to the phenolate form and chromophore formation. This process of post-translational modification is referred to as maturation. The hydrogen-bonding network and electron-stacking interactions with these sidechains influence the color, intensity and photostability of GFP and its numerous derivatives. The tightly packed nature of the barrel excludes solvent molecules, protecting the chromophore fluorescence from quenching by water. In addition to the auto-cyclization of the Ser65-Tyr66-Gly67, a 1,2-dehydrogenation reaction occurs at the Tyr66 residue. Besides the three residues that form the chromophore, residues such as Gln94, Arg96, His148, Thr203, and Glu222 all act as stabilizers. The residues of Gln94, Arg96, and His148 are able to stabilize by delocalizing the chromophore charge. Arg96 is the most important stabilizing residue due to the fact that it prompts the necessary structural realignments that are necessary from the HBI ring to occur. Any mutation to the Arg96 residue would result in a decrease in the development rate of the chromophore because proper electrostatic and steric interactions would be lost. Tyr66 is the recipient of hydrogen bonds and does not ionize in order to produce favorable electrostatics. | 1 | Applied and Interdisciplinary Chemistry |
Bax works in the field of biomolecular NMR spectroscopy, and has been involved in the development of many of the standard methods in the field. He collaborated extensively with fellow NIH scientists Marius Clore, Angela Gronenborn and Dennis Torchia in the development of multidimensional protein NMR. Bax is a pioneer in the development of triple resonance experiments and technology for resonance assignment of isotopically enriched proteins. He was also heavily involved in the development of using residual dipolar couplings and chemical shifts for determining RNA and protein structures.
Much of his recent work focuses on the roles of proteins in membranes.
He was the world's most cited chemist over two decades (1981-1997). | 0 | Theoretical and Fundamental Chemistry |
In humans, ERVs have been proposed to be involved in multiple sclerosis (MS). A specific association between MS and the ERVWE1, or "syncytin", gene, which is derived from an ERV insertion, has been reported, along with the presence of an "MS-associated retrovirus" (MSRV), in patients with the disease. Human ERVs (HERVs) have also been implicated in ALS and addiction.
In 2004 it was reported that antibodies to HERVs were found in greater frequency in the sera of people with schizophrenia. Additionally, the cerebrospinal fluid of people with recent onset schizophrenia contained levels of a retroviral marker, reverse transcriptase, four times higher than control subjects. Researchers continue to look at a possible link between HERVs and schizophrenia, with the additional possibility of a triggering infection inducing schizophrenia. | 1 | Applied and Interdisciplinary Chemistry |
Selenols are easily oxidized to diselenides, compounds containing an bond. For example, treatment of benzeneselenol with bromine gives diphenyl diselenide.
In the presence of base, selenols are readily alkylated to give selenides. This relationship is illustrated by the methylation of methaneselenol to give dimethylselenide. | 0 | Theoretical and Fundamental Chemistry |
Sigma hole interactions have applications in a variety of fields. The ability to induce stabilizing and strongly directional intermolecular interactions which can be easily tuned via minor structural substitutions makes leveraging these interactions particularly value in fields in which control over supramolecular organization is desired. As such, sigma hole interactions have been used in the field of crystal engineering to design molecular building blocks for self-assembly, to improve the properties of liquid crystals, and to design magnetic materials. | 0 | Theoretical and Fundamental Chemistry |
pH is defined operationally as follows. For a solution X, first measure the electromotive force E of the galvanic cell
:reference electrode | concentrated solution of KCl | solution X | H | Pt
and then also measure the electromotive force E of a galvanic cell that differs from the above one only by the replacement of the solution X of unknown pH, pH(X), by a solution S of a known standard pH, pH(S). Then obtain the pH of X as
:pH(X) = pH(S) + (E − E) F / (RT ln 10)
where
:F is the Faraday constant;
:R is the molar gas constant;
:T is the thermodynamic temperature.
Defined this way, pH is a quantity of dimension 1, that is it has no unit. Values pH(S) for a range of standard solutions S are listed in [http://www.iupac.org/publications/pac/1985/pdf/5703x0531.pdf Definitions of pH scales, standard reference values, measurement of pH, and related terminology]. Pure Appl. Chem. (1985), 57, pp 531–542, where further details can be found.
pH has no fundamental meaning; its official definition is a practical one. However, in the restricted range of dilute aqueous solutions having amount-of-substance concentrations less than 0.1 mol/L, and being neither strongly alkaline nor strongly acidic (2 < pH < 12), the definition is such that
:pH = −log[c(H) y / (1 mol/L)] ± 0.02
where c(H) denotes the amount-of-substance concentration of hydrogen ion H and y denotes the activity coefficient of a typical uni-univalent electrolyte in the solution. | 0 | Theoretical and Fundamental Chemistry |
The operation of the Kitchen rudder is performed with the propeller engaged, even when the boat is stationary. The rudder is controlled by a small wheel on the tiller. | 1 | Applied and Interdisciplinary Chemistry |
PSCs-derived cells from patients are used in vitro to recreate specific pathologies. The specific cell type affected in the pathology is at the base of the model. For example, motoneurons are used to study spinal muscular atrophy (SMA) and cardiomyocytes are used to study arrythmia. This can allow for a better understanding of the pathogenesis and the development of new treatments through drug discovery. Immature PSC-derived cell types can be matured in vitro by various strategies, such as in vitro ageing, to modelize age-related disease in vitro.
Major diseases being modelized with PSCs-derived cells are amyotrophic lateral sclerosis (ALS), Alzheimers (AD), Parkinsons (PD), fragile X syndrome (FXS), Huntington disease (HD), Down syndrome, Spinal muscular atrophy (SMA), muscular dystrophies, cystic fibrosis, Long QT syndrome, and Type I diabetes. | 1 | Applied and Interdisciplinary Chemistry |
There is tenuous evidence that a virus common to peppers, the Pepper Mild Mottle Virus (PMMoV) may have moved on to infect humans. This is a rare and unlikely event as, to enter a cell and replicate, a virus must "bind to a receptor on its surface, and a plant virus would be highly unlikely to recognize a receptor on a human cell. One possibility is that the virus does not infect human cells directly. Instead, the naked viral RNA may alter the function of the cells through a mechanism similar to RNA interference, in which the presence of certain RNA sequences can turn genes on and off," according to Virologist Robert Garry. | 1 | Applied and Interdisciplinary Chemistry |
In imaging spectroscopy (also hyperspectral imaging or spectral imaging) each pixel of an image acquires many bands of light intensity data from the spectrum, instead of just the three bands of the RGB color model. More precisely, it is the simultaneous acquisition of spatially coregistered images in many spectrally contiguous bands.
Some spectral images contain only a few image planes of a spectral data cube, while others are better thought of as full spectra at every location in the image. For example, solar physicists use the spectroheliograph to make images of the Sun built up by scanning the slit of a spectrograph, to study the behavior of surface features on the Sun; such a spectroheliogram may have a spectral resolution of over 100,000 () and be used to measure local motion (via the Doppler shift) and even the magnetic field (via the Zeeman splitting or Hanle effect) at each location in the image plane. The multispectral images collected by the Opportunity rover, in contrast, have only four wavelength bands and hence are only a little more than 3-color images.
One application is spectral geophysical imaging, which allows quantitative and qualitative characterization of the surface and of the atmosphere, using radiometric measurements. These measurements can then be used for unambiguous direct and indirect identification of surface materials and atmospheric trace gases, the measurement of their relative concentrations, subsequently the assignment of the proportional contribution of mixed pixel signals (e.g., the spectral unmixing problem), the derivation of their spatial distribution (mapping problem), and finally their study over time (multi-temporal analysis). The Moon Mineralogy Mapper on Chandrayaan-1 was a geophysical imaging spectrometer. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2012 impact factor of 2.125. | 1 | Applied and Interdisciplinary Chemistry |
Pure sodium hydroxide is a colorless crystalline solid that melts at without decomposition and boils at . It is highly soluble in water, with a lower solubility in polar solvents such as ethanol and methanol. Sodium hydroxide is insoluble in ether and other non-polar solvents.
Similar to the hydration of sulfuric acid, dissolution of solid sodium hydroxide in water is a highly exothermic reaction where a large amount of heat is liberated, posing a threat to safety through the possibility of splashing. The resulting solution is usually colorless and odorless. As with other alkaline solutions, it feels slippery with skin contact due to the process of saponification that occurs between and natural skin oils. | 0 | Theoretical and Fundamental Chemistry |
Several indices to measure bioavailability have been suggested: Respiration Index, Oxygen Supply Index, and the Metabolic Index. The Respiration Index describes oxygen availability based on the free energy available in the reactants and products of the stoichiometric equation for respiration. However, organisms have ways of altering their oxygen intake and carbon dioxide release, so the strict stoichiometric equation is not necessarily accurate. The Oxygen Supply Index accounts for oxygen solubility and partial pressure, along with the Q of the organism, but does not account for behavioral or physiological changes in organisms to compensate for reduced oxygen availability. The Metabolic Index accounts for the supply of oxygen in terms of solubility, partial pressure, and diffusivity of oxygen in water, and the organism's metabolic rate. The metabolic index is generally viewed as a closer approximation of oxygen bioavailability than the other indices.
There are two thresholds of oxygen required by organisms:
* P (critical partial pressure)- the oxygen level below which an organism cannot support a normal respiration rate
* P (lethal partial pressure)- the oxygen level below which an organism cannot support the minimum respiration rate necessary for survival.
Since bioavailability is specific to each organism and temperature, calculation of these thresholds is done experimentally by measuring activity and respiration rates under different temperature and oxygen conditions, or by collecting data from separate studies. | 0 | Theoretical and Fundamental Chemistry |
Gofman retired as a teaching professor in 1973 and became a professor emeritus of molecular and cell biology.
Gofman testified on the behalf of Samuel Lovejoy at Lovejoys 1974 trial. Lovejoy was charged with malicious destruction of property for toppling a weather tower in Montague, Massachusetts, owned by Northeast Utilities. Lovejoys actions were an act of protest against a proposed nuclear power plant, Montague Nuclear Power Plant, to be built on Montague Plains. Lovejoy was inspired by Gofmans book, Poisoned Power'.
Gofman used his low-level radiation health model to predict 333 excess cancer or leukemia deaths from the 1979 Three Mile Island accident. Studies of the health effects of the Three Mile Island accident have so far (by 2013) not observed any excess mortality. A retrospective study of Pennsylvania Cancer Registry found an increased incidence of thyroid cancer in counties south of TMI and in high-risk age groups. The Talbott lab at the University of Pittsburgh reported finding only a few, small, mostly statistically non-significant, increased cancer risks within the TMI population. However, excess leukemia among males was observed. The ongoing TMI epidemiological research has been accompanied by a discussion of epidemiological methodology, such as problems in dose and illness classifications.
Three months after the Chernobyl disaster, Gofman predicted that Chernobyl would cause "475,000 fatal cancers plus about
an equal number of additional non-fatal cases, occurring over time both inside and outside the ex-Soviet Union". In contrast, even some 19 years later in September 2005, an official UN IAEA report claimed 4,000 deaths as the final estimated toll from Chernobyl. In their 2006 book Alexey V. Yablokov and other Russian and East European researchers estimated that Chernobyl caused a million deaths through 2004, nearly 170,000 of them in North America. The books English translation Chernobyl: Consequences of the Catastrophe for People and the Environment was published by the New York Academy of Sciences in 2009. The book cites "5,000 mainly Slavic-language scientific papers the IAEA overlooked", notwithstanding the fact that 13 of the authors of the Chernobyl Forum were from Ukraine, Russia or Belarus. M. I. Balonov criticized the methodology of the book. M. I. Balonov criticized the methodology of the books estimation of Chernobyl's excess deaths and radiation-induced health effects and claimed the numbers were exaggerations which "could lead quite unnecessarily to a panic reaction". Rosalie Bertell has asserted the above estimates of Gofman (1986) and Yablokov (2006) are too conservative.
After a speech Gofman gave on nuclear waste at a national conference of activists in the summer of 1990, Charles Butler approached him for help. Butler was a retired physicist living in the Mojave Desert town of Needles, California, and was looking for help to stop the proposed low-level nuclear waste facility at Ward Valley. Gofman referred him to the Abalone Alliance Clearinghouse in San Francisco. With less than two weeks before the closure of the Environmental Impact Statement, the Alliance was able to mount a letter writing campaign that helped delay the EIS for an additional 90 days. This initial delay gave activists the time to form Don't Waste California and build a grassroots campaign that eventually stopped Ward Valley from opening.
Gofman also did work on the Diablo Canyon Power Plant. | 0 | Theoretical and Fundamental Chemistry |
ASF/SF2 is an integral part of numerous components of the splicing process. ASF/SF2 is required for 5’ splice site cleavage and selection, and is capable of discriminating between cryptic and authentic splice sites. Subsequent lariat formation during the first chemical step of pre-mRNA splicing also requires ASF/SF2. ASF/SF2 promotes recruitment of the U1 snRNP to the 5’ splice site, and bridges the 5’ and 3’ splice sites to facilitate splicing reactions. ASF/SF2 also associates with the U2 snRNP. During the reaction, ASF/SF2 promotes the use of intron proximal sites and hinders the use of intron distal sites, affecting alternative splicing. Alternative splicing is affected by ASF/SF2 in a concentration-dependent manner; differing concentrations of ASF/SF2 is a mechanism for alternative splicing regulation, and will result in differing amounts of product isoforms. ASF/SF2 accomplishes this regulation through direct or indirect binding to exonic splicing enhancer (ESE) sequences. | 1 | Applied and Interdisciplinary Chemistry |
The classical macroscopic photoelectrochemical system consists of a semiconductor in electric contact with a counter-electrode. For N-type semiconductor particles of sufficiently small dimension, the particles polarize into anodic and cathodic regions, effectively forming microscopic photoelectrochemical cells. The illuminated surface of a particle catalyzes a photooxidation reaction, while the “dark” side of the particle facilitates a concomitant reduction.
Photoelectrochemical oxidation may be thought of as a special case of photochemical oxidation (PCO). Photochemical oxidation entails the generation of radical species that enable oxidation reactions, with or without the electrochemical interactions involved in semiconductor-catalyzed systems, which occur in photoelectrochemical oxidation. | 0 | Theoretical and Fundamental Chemistry |
IBX is also available as silica gel or polystyrene bound IBX. In many applications, IBX is replaced by Dess–Martin periodinane which is more soluble in common organic solvents. A sample reaction is an IBX oxidation used in the total synthesis of eicosanoid: More and Finney and Van Arman have demonstrated that common organic solvents are suitable for many IBX oxidations, despite its low solubility, and in fact may simplify product purification.
In 2001, K. C. Nicolaou and co-workers published a series of papers in the Journal of the American Chemical Society demonstrating, among other transformations, the use of IBX to oxidize primary and secondary benzylic carbons to aromatic aldehydes and ketones, respectively. | 0 | Theoretical and Fundamental Chemistry |
The diagram above depicts a reaction between m-cresol and methanol where a c-alkylation product is produced. The c-alkylation reaction means that instead of replacing the hydrogen atom on the -OH group, the methyl group (from the methanol) replaces the hydrogen on a carbon in the benzene ring. The products of this c-alkylation can be in either a para- or ortho- orientation on the molecule, as seen in the diagram, and water, which is not shown. Isomers of the dimethylphenol (DMP) compound are the products of the para- and ortho-c-alkylation. Dimethylphenol (DMP) compound is listed as an aquatic hazard by characteristic, and is toxic with long lasting effects. | 0 | Theoretical and Fundamental Chemistry |
M is the molar mass and G are the group contributions (different for all three properties) for functional groups of a molecule. | 0 | Theoretical and Fundamental Chemistry |
Levich is one of the pioneers in induced-charge electrokinetic field. He calculated the perturbed slip profile around a conducting particle in contact with electrolyte. He also theoretically predicted that vortices induced around this particle once the electric filed is applied. | 0 | Theoretical and Fundamental Chemistry |
Drug-based contraception has been available since the development of the contraceptive pill. As well as their contraceptive effects, contraceptive drugs can also have adverse sexual and reproductive side-effects. Prior to the availability of effective contraceptives, some substances were also used as abortifacients to terminate pregnancy; medical abortion exists as a modern medical practice. | 1 | Applied and Interdisciplinary Chemistry |
Inhomogeneous broadening is a general term for broadening because some emitting particles are in a different local environment from others, and therefore emit at a different frequency. This term is used especially for solids, where surfaces, grain boundaries, and stoichiometry variations can create a variety of local environments for a given atom to occupy. In liquids, the effects of inhomogeneous broadening is sometimes reduced by a process called motional narrowing. | 0 | Theoretical and Fundamental Chemistry |
From Maxwell's equations, the electromagnetic energy of a "free" field i.e. one with no sources, is described by:
We introduce the "mode function" that satisfies the Helmholtz equation:
where and assume it is normalized such that:
We wish to "quantize" the electromagnetic energy of free space for a multimode field. The field intensity of free space should be independent of position such that should be independent of for each mode of the field. The mode function satisfying these conditions is:
where in order to have the transversality condition satisfied for the Coulomb gauge in which we are working.
To achieve the desired normalization we pretend space is divided into cubes of volume and impose on the field the periodic boundary condition:
or equivalently
where can assume any integer value. This allows us to consider the field in any one of the imaginary cubes and to define the mode function:
which satisfies the Helmholtz equation, transversality, and the "box normalization":
where is chosen to be a unit vector which specifies the polarization of the field mode. The condition means that there are two independent choices of , which we call and where and . Thus we define the mode functions:
in terms of which the vector potential becomes:
or:
where and , are photon annihilation and creation operators for the mode with wave vector and polarization . This gives the vector potential for a plane wave mode of the field. The condition for shows that there are infinitely many such modes. The linearity of Maxwell's equations allows us to write:
for the total vector potential in free space. Using the fact that:
we find the field Hamiltonian is:
This is the Hamiltonian for an infinite number of uncoupled harmonic oscillators. Thus different modes of the field are independent and satisfy the commutation relations:
Clearly the least eigenvalue for is:
This state describes the zero-point energy of the vacuum. It appears that this sum is divergent – in fact highly divergent, as putting in the density factor
shows. The summation becomes approximately the integral:
for high values of . It diverges proportional to for large .
There are two separate questions to consider. First, is the divergence a real one such that the zero-point energy really is infinite? If we consider the volume is contained by perfectly conducting walls, very high frequencies can only be contained by taking more and more perfect conduction. No actual method of containing the high frequencies is possible. Such modes will not be stationary in our box and thus not countable in the stationary energy content. So from this physical point of view the above sum should only extend to those frequencies which are countable; a cut-off energy is thus eminently reasonable. However, on the scale of a "universe" questions of general relativity must be included. Suppose even the boxes could be reproduced, fit together and closed nicely by curving spacetime. Then exact conditions for running waves may be possible. However the very high frequency quanta will still not be contained. As per John Wheeler's "geons" these will leak out of the system. So again a cut-off is permissible, almost necessary. The question here becomes one of consistency since the very high energy quanta will act as a mass source and start curving the geometry.
This leads to the second question. Divergent or not, finite or infinite, is the zero-point energy of any physical significance? The ignoring of the whole zero-point energy is often encouraged for all practical calculations. The reason for this is that energies are not typically defined by an arbitrary data point, but rather changes in data points, so adding or subtracting a constant (even if infinite) should be allowed. However this is not the whole story, in reality energy is not so arbitrarily defined: in general relativity the seat of the curvature of spacetime is the energy content and there the absolute amount of energy has real physical meaning. There is no such thing as an arbitrary additive constant with density of field energy. Energy density curves space, and an increase in energy density produces an increase of curvature. Furthermore, the zero-point energy density has other physical consequences e.g. the Casimir effect, contribution to the Lamb shift, or anomalous magnetic moment of the electron, it is clear it is not just a mathematical constant or artifact that can be cancelled out. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Hicks equation, sometimes also referred as Bragg–Hawthorne equation or Squire–Long equation, is a partial differential equation that describes the distribution of stream function for axisymmetric inviscid fluid, named after William Mitchinson Hicks, who derived it first in 1898. The equation was also re-derived by Stephen Bragg and William Hawthorne in 1950 and by Robert R. Long in 1953 and by Herbert Squire in 1956. The Hicks equation without swirl was first introduced by George Gabriel Stokes in 1842. The Grad–Shafranov equation appearing in plasma physics also takes the same form as the Hicks equation.
Representing as coordinates in the sense of cylindrical coordinate system with corresponding flow velocity components denoted by , the stream function that defines the meridional motion can be defined as
that satisfies the continuity equation for axisymmetric flows automatically. The Hicks equation is then given by
where
where is the total head, c.f. Bernoulli's Principle. and is the circulation, both of them being conserved along streamlines. Here, is the pressure and is the fluid density. The functions and are known functions, usually prescribed at one of the boundary; see the example below. If there are closed streamlines in the interior of the fluid domain, say, a recirculation region, then the functions and are typically unknown and therefore in those regions, Hicks equation is not useful; Prandtl–Batchelor theorem provides details about the closed streamline regions. | 1 | Applied and Interdisciplinary Chemistry |
Site-directed spin labeling (SDSL) is a technique for investigating the structure and local dynamics of proteins using electron spin resonance. The theory of SDSL is based on the specific reaction of spin labels with amino acids. A spin label's built-in protein structure can be detected by EPR spectroscopy. SDSL is also a useful tool in examinations of the protein folding process. | 0 | Theoretical and Fundamental Chemistry |
* RdRps can be used as drug targets for viral pathogens as their function is not necessary for eukaryotic survival. By inhibiting RNA-dependent RNA polymerase function, new RNAs cannot be replicated from an RNA template strand, however, DNA-dependent RNA polymerase will remain functional.
* There are currently antiviral drugs against Hepatitis C and COVID-19 that specifically target RdRp. These include Sofosbuvir and Ribavirin against Hepatitis C and Remdesivir, the only FDA approved drug against COVID-19.
* GS-441524 triphosphate, is a substrate for RdRp, but not mammalian polymerases. It results in premature chain termination and inhibition of viral replication. GS-441524 triphosphate is the biologically active form of the phosphate pro-drug, Remdesivir. Remdesivir is classified as a nucleotide analog in which it works to inhibit the function of RdRp by covalently binding to and interrupting termination of the nascent RNA through early or delayed termination or preventing further elongation of the RNA polynucleotide. This early termination leads to nonfunctional RNA that will be degraded through normal cellular processes. | 1 | Applied and Interdisciplinary Chemistry |
Proteorhodopsin functions throughout the Earth's oceans as a light-driven H+ pump, by a mechanism similar to that of bacteriorhodopsin. As in bacteriorhodopsin, the retinal chromophore of proteorhodopsin is covalently bound to the apoprotein via a protonated Schiff base at Lys231. The configuration of the retinal chromophore in unphotolyzed proteorhodopsin is predominantly all-trans
, and isomerizes to 13-cis upon illumination with light. Several models of the complete proteorhodopsin photocycle have been proposed, based on FTIR and UV–visible spectroscopy; they resemble established photocycle models for bacteriorhodopsin. Complete proteorhodopsin based photosystems have been discovered and expressed in E. coli, giving them additional light mediated energy gradient capability for ATP generation without external need for retinal or precursors; with the PR, gene five other proteins code for the photopigment biosynthetic pathway. | 0 | Theoretical and Fundamental Chemistry |
The photoreceptor cells involved in vertebrate vision are the rods, the cones, and the photosensitive ganglion cells (ipRGCs). These cells contain a chromophore (11-cis-retinal, the aldehyde of vitamin A1 and light-absorbing portion) that is bound to a cell membrane protein, opsin. Rods are responsible for vision under low light intensity and contrast detections. Because they all have the same response across frequencies, no color information can be deduced from the rods only, as in low light conditions for example. Cones, on the other hand, are of different kinds with different frequency response, such that color can be perceived through comparison of the outputs of different kinds of cones. Each cone type responds best to certain wavelengths, or colors, of light because each type has a slightly different opsin. The three types of cones are L-cones, M-cones and S-cones that respond optimally to long wavelengths (reddish color), medium wavelengths (greenish color), and short wavelengths (bluish color) respectively. Humans have trichromatic photopic vision consisting of three opponent process channels that enable color vision.
Rod photoreceptors are the most common cell type in the retina and develop quite late. Most cells become postmitotic before birth, but differentiation occurs after birth. In the first week after birth, cells mature and the eye becomes fully functional at the time of opening. The visual pigment rhodopsin (rho) is the first known sign of differentiation in rods. | 1 | Applied and Interdisciplinary Chemistry |
The Romans made full use of the brown- and ochre-coloured stone in the Weald, and many of their roads there are the means of transport for the ore, and were extensively metalled with slag from iron smelting. The sites of about 113 bloomeries have been identified as Roman, mainly in East Sussex. The Weald was in this period one of the most important iron-producing regions in Roman Britain. Excavations at a few sites have produced tiles of the Classis Britannica, suggesting that they were actually run by, or were supplying iron to this Roman fleet. Total iron production has been estimated at 750 tons per year, but under 200 tons per year after 250 AD. | 1 | Applied and Interdisciplinary Chemistry |
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