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Numerous attempts have been made to quantify aromaticity with respect to the observed ring current. One method is called diamagnetic susceptibility exaltation Λ defined as the difference between the measured magnetic susceptibility of a compound and a calculated value based on group additivity tables. Large negative values are aromatic, for example, benzene (Λ = −13.4). Values close to zero are non-aromatic, for example, borazine (Λ = −1.7) and cyclohexane (Λ = 1.1). Large positive values are antiaromatic, for example, cyclobutadiene (Λ = +18).
Another measurable quantity is the chemical shift of lithium ions Li in complexes of lithium with aromatic structures because lithium tends to bond as a π-coordinate complex to the face of the aromatic rings. Thus the lithium atom in cyclopentadienyl lithium (CpLi) has a chemical shift of −8.6 ppm (aromatic) and its CpLi complex a shift of −13.1.
Both methods suffer from the disadvantage that values depend on ring size. | 0 | Theoretical and Fundamental Chemistry |
Adenosine is very relevant in bone metabolism, as it plays a role in formation and activation of both osteoclasts and osteoblasts. Adenosine acts by binding to purinergic receptors and influencing adenylyl cyclase activity and the formation of cAMP and PKA 54. Adenosine may have opposite effects on bone metabolism, because while certain purinergic receptors stimulate adenylyl cyclase activity, others have the opposite effect. Under certain circumstances adenosine stimulates bone destruction and in other situations it promotes bone formation, depending on the purinergic receptor that is being activated. | 0 | Theoretical and Fundamental Chemistry |
Point mutations in multiple tumor suppressor proteins cause cancer. For instance, point mutations in Adenomatous Polyposis Coli promote tumorigenesis. A novel assay, Fast parallel proteolysis (FASTpp), might help swift screening of specific stability defects in individual cancer patients. | 1 | Applied and Interdisciplinary Chemistry |
A disadvantage to MIKES is that observations are made later in the ion flight path when compared to other methods. Also, a smaller number of ions will typically decompose. This will in turn cause the sensitivity to be lower than other kinetic energy spectroscopy methods. | 0 | Theoretical and Fundamental Chemistry |
Ted Ellis has over his career created art in a number of styles and has incorporated several primary influences.
African American history and African American culture play central roles in Ellis art, which regularly feature themes like Buffalo Soldiers, cotton fields, and Jazz music; his Jazz works especially lean towards the impressionistic. Other common themes range from fisherman to religious scenes as in Thee Baptism, My Fathers Baptism, and Deacons Door, to African ethnic scenes like Afrimage and Ashanti'.
The Church-related themes in his art he attributes to formative experiences with his mother at their local house of worship, "Beulah Land Church".
While he is best known for his ethnic art, many of Ellis' pieces are landscapes, seascapes, and portraits.
Ted Ellis is a self-taught artist. He has describes his style at times as "conventional realism", as a bold blend of realism and impressionism, and as impressionist and naturalist, an old masters' style that is sometimes figurative and sometimes folk art. "I try to capture the essence in one stroke" he said.
Ellis has also coined the term "Tedism" to describe his style. "Tedism" blends impressionism, soul, and folk stories to create representational pieces.
Ted Ellis considers himself to be a social, political and spiritual artist as well as educator and "creative historian". "I paint subjects that are representative of the many facets of American life as I know it" says Ellis. "I like to think of myself as a creative historian. I was put here to record history...all aspects of American culture and heritage. My sole purpose has always been to educate through my art". He draws inspiration from peoples memories of family or from history, and says that hes "a history buff at heart. I read a lot, and I have more books than paint."
As an artist who focuses on African American history, Ellis intentionally does not approach its difficult chapters from a position of pain: "I have to be careful what I do [...] theres a power to art. I dont want to be from an angry position. Thats out there, and maybe they do that to shake you up and make you think. I want to be one step ahead. When youre talking about healing, you're in the right zone." As such, his images of slavery and historical Southern life focus on positive values such as family, character, and church.
Ellis attributes a love for and influence in his art to New Orleans and its rich culture of creativity. He compared the city to an incubator for young talent. The city offered Ted art clubs and opportunities to design murals for school and create signs for special events. New Orleans gave him access to art classes, summer art programs, and the vibrant Jackson Square, somewhere he could talk with and get to know many artists.
Ellis favorite artists include Henry Ossawa Tanner, Edward Bannister, Jacob Lawrence, Samella Lewis, and John T. Scott, while among his work the favorite painting is Sunday Worship'. | 0 | Theoretical and Fundamental Chemistry |
CREB-regulated transcription coactivator 3 is a protein that in humans is encoded by the CRTC3 gene.
This gene has been shown to be linked to weight gain. | 1 | Applied and Interdisciplinary Chemistry |
The insulator element that is found in the gypsy retrotransposon of Drosophila is one of several sequences that have been studied in detail. The gypsy insulator can be found in the 5 untranslated region (UTR) of the retrotransposon element. Gypsy' affects the expression of adjacent genes pending insertion into a new genomic location, causing mutant phenotypes that are both tissue specific and present at certain developmental stages. The insulator likely has an inhibitory effect on enhancers that control the spatial and temporal expression of the affected gene. | 1 | Applied and Interdisciplinary Chemistry |
Chlorination is one of the oldest known substitution reactions in chemistry. The French chemist Jean-Baptiste Dumas investigated the substitution of hydrogen for chlorine by acetic acid in candle wax as early as 1830. He showed that for each mole of chlorine introduced into a hydrocarbon, one mole of hydrogen chloride is also formed and noted the light-sensitivity of this reaction.
The idea that these reactions might be chain reactions is attributed to Max Bodenstein (1913). He assumed that in the reaction of two molecules not only the end product of the reaction can be formed, but also unstable, reactive intermediates which can continue the chain reaction.
Photochlorination garnered commercial attention with the availability of cheap chlorine from chloralkali electrolysis.
Chlorinated alkanes found an initial application in pharyngeal sprays. These contained chlorinated alkanes in relatively large quantities as solvents for chloramine T from 1914 to 1918. The Sharpless Solvents Corporation commissioned the first industrial photochloration plant for the chlorination of pentane in 1929. The commercial production of chlorinated paraffins for use as high-pressure additives in lubricants began around 1930. Around 1935 the process was technically stable and commercially successful. However, it was only in the years after World War II that a greater build-up of photochloration capacity began. In 1950, the United States produced more than 800,000 tons of chlorinated paraffin hydrocarbons. The major products were ethyl chloride, tetrachlorocarbon and dichloromethane. Because of concerns about health and environmentally relevant problems such as the ozone depletion behavior of light volatile chlorine compounds, the chemical industry developed alternative procedures that did not require chlorinated compounds. As a result of the following replacement of chlorinated by non-chlorinated products, worldwide production volumes have declined considerably over the years. | 0 | Theoretical and Fundamental Chemistry |
Water molecules dissociate into equal amounts of HO and OH, so their concentrations are almost exactly at 25 °C and 0.1 MPa. A solution in which the HO and OH concentrations equal each other is considered a neutral solution. In general, the pH of the neutral point is numerically equal to pK.
Pure water is neutral, but most water samples contain impurities. If an impurity is an acid or base, this will affect the concentrations of hydronium ion and hydroxide ion. Water samples that are exposed to air will absorb some carbon dioxide to form carbonic acid (HCO) and the concentration of HO will increase due to the reaction HCO + HO = HCO + HO. The concentration of OH will decrease in such a way that the product [HO][OH] remains constant for fixed temperature and pressure. Thus these water samples will be slightly acidic. If a pH of exactly 7.0 is required, it must be maintained with an appropriate buffer solution. | 0 | Theoretical and Fundamental Chemistry |
A potentially significant problem following bisulfite treatment is incomplete desulfonation of pyrimidine residues due to inadequate alkalization of the solution. This may inhibit some DNA polymerases, rendering subsequent PCR difficult. However, this situation can be avoided by monitoring the pH of the solution to ensure that desulfonation will be complete.
A final concern is that bisulfite treatment greatly reduces the level of complexity in the sample, which can be problematic if multiple PCR reactions are to be performed (2006). Primer design is more difficult, and inappropriate cross-hybridization is more frequent. | 1 | Applied and Interdisciplinary Chemistry |
For example, the common restriction enzyme EcoRI recognizes the palindromic sequence GAATTC and cuts between the G and the A on both the top and bottom strands. This leaves an overhang (an end-portion of a DNA strand with no attached complement) known as a sticky end on each end of AATT. The overhang can then be used to ligate in (see DNA ligase) a piece of DNA with a complementary overhang (another EcoRI-cut piece, for example).
Some restriction enzymes cut DNA at a restriction site in a manner which leaves no overhang, called a blunt end. Blunt ends are much less likely to be ligated by a DNA ligase because the blunt end doesnt have the overhanging base pair that the enzyme can recognize and match with a complementary pair. Sticky ends of DNA however are more likely to successfully bind with the help of a DNA ligase because of the exposed and unpaired nucleotides. For example, a sticky end trailing with AATTG is more likely to bind with a ligase than a blunt end where both the 5 and 3' DNA strands are paired. In the case of the example the AATTG would have a complementary pair of TTAAC which would reduce the functionality of the DNA ligase enzyme. | 1 | Applied and Interdisciplinary Chemistry |
India currently stores only 30 days of rainfall, while developed nations strategically store 900 days worth of water demand in arid areas river basins, and reservoirs. Indias dam reservoirs store only 200 cubic meters per person. India also relies excessively on groundwater, which accounts for over 50 percent of the irrigated area with 20 million tube wells installed. About 15 percent of Indias food is being produced using rapidly depleting groundwater. The end of the era of massive expansion in groundwater use is going to demand greater reliance on surface water supply systems. Proponents of the project suggest India's water situation is already critical, and it needs sustainable development and management of surface water and groundwater usage. Some proponents feel that India is not running out of water but water is running out of India. | 1 | Applied and Interdisciplinary Chemistry |
Based on molecular orbital theory, He should not exist, and a chemical bond cannot form between the atoms. However, the van der Waals force exists between helium atoms as shown by the existence of liquid helium, and at a certain range of distances between atoms the attraction exceeds the repulsion. So a molecule composed of two helium atoms bound by the van der Waals force can exist. The existence of this molecule was proposed as early as 1930.
He is the largest known molecule of two atoms when in its ground state, due to its extremely long bond length. The He molecule has a large separation distance between the atoms of about 5200 pm (= 52 ångström). This is the largest for a diatomic molecule without ro-vibronic excitation. The binding energy is only about 1.3 mK, 10eV or 1.1×10 kcal/mol. According to high-level theoretical calculations, the bond is 5000 times weaker than the covalent bond in the hydrogen molecule.
Both helium atoms in the dimer can be ionized by a single photon with energy 63.86 eV. The proposed mechanism for this double ionization is that the photon ejects an electron from one atom, and then that electron hits the other helium atom and ionizes that as well. The dimer then explodes as two helium cations ions repel each other with the same speed but opposite directions.
A dihelium molecule bound by Van der Waals forces was first proposed by John Clarke Slater in 1928. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, thioketenes are organosulfur compounds analogous to ketenes with the general formula , where R is alkyl or aryl. The parent thioketene (ethenthione) has the formula . It is the simplest thioketene. Thioketene is stable as a gas, but like most thioketenes, it polymerizes upon condensation.
Some thioketenes are produced as transient species upon pyrolysis of 1,2,3-thiadiazoles. It has been suggested that thioketene could be involved in cell damage processes. | 0 | Theoretical and Fundamental Chemistry |
The circulation around a closed material contour is defined by:
where u is the velocity vector, and ds is an element along the closed contour.
The governing equation for an inviscid fluid with a conservative body force is
where D/Dt is the convective derivative, ρ is the fluid density, p is the pressure and Φ is the potential for the body force. These are the Euler equations with a body force.
The condition of barotropicity implies that the density is a function only of the pressure, i.e. .
Taking the convective derivative of circulation gives
For the first term, we substitute from the governing equation, and then apply Stokes' theorem, thus:
The final equality arises since owing to barotropicity. We have also made use of the fact that the curl of any gradient is necessarily 0, or for any function .
For the second term, we note that evolution of the material line element is given by
Hence
The last equality is obtained by applying gradient theorem.
Since both terms are zero, we obtain the result | 1 | Applied and Interdisciplinary Chemistry |
For an endothermic reaction, heat is absorbed, making the net enthalpy change positive. Thus, according to the definition of the slope:
When the reaction is endothermic, (and the gas constant ), so
Thus, for an endothermic reaction, the Van 't Hoff plot should always have a negative slope. | 0 | Theoretical and Fundamental Chemistry |
After harvesting the algae, the biomass is typically processed in a series of steps, which can differ based on the species and desired product; this is an active area of research and also is the bottleneck of this technology: the cost of extraction is higher than those obtained. One of the solutions is to use filter feeders to "eat" them. Improved animals can provide both foods and fuels. An alternative method to extract the algae is to grow the algae with specific types of fungi. This causes bio-flocculation of the algae which allows for easier extraction. | 1 | Applied and Interdisciplinary Chemistry |
Bicycloaromaticity in chemistry is an extension of the concept of homoaromaticity with two aromatic ring currents situated in a non-planar molecule and sharing the same electrons. The concept originates with Melvin Goldstein who first reported about it in 1967. It is of some importance in academic research. Using MO theory the bicyclo[3.2.2]nonatrienyl cation was predicted to be destabilised and the corresponding anion predicted to be stabilised by bicycloaromaticity.
Bicycloaromaticity has been studied by others in relation to the bicyclo[3.2.2]nonatrienyl cation and in relation to specific carbanions. In 2017 experimental evidence was reported for bicycloaromaticity (dual aromaticity) to exist in a bicyclic porphyrinoid. This system has been described as aromatic with two ring systems of 26 (n=6) and 34 (n=8) electrons. By oxidation, another system was described as a triplet-state biradical, again considered aromatic by application of Baird's rule. | 0 | Theoretical and Fundamental Chemistry |
The first headquarters of the newly fledged Society of Chemical Industry was established in 1881 at Palace Chambers, Bridge Street, Westminster, London. After a series of changes of address, the society finally moved to its fifth and present location at 14/15 – and initially 16 – Belgrave Square in 1955. Owned by the Duke of Westminster, along with the rest of Belgravia, the building was and still is part of the Grosvenor Estate and had recently been commandeered by the Ministry of Defence during World War II. The former Nazi commander Rudolf Hess is believed to have been interrogated in the building after he flew to Britain late in the war. | 1 | Applied and Interdisciplinary Chemistry |
Research agrochemicals are created and evaluated to select effective substances for commercial off-the-shelf end-user products. Many research agrochemicals are never publicly marketed. Agricultural research chemicals often use sequential code names. | 1 | Applied and Interdisciplinary Chemistry |
Already now large quantities of water undersaturated in aragonite are upwelling close to the Pacific continental shelf area of North America, from Vancouver to Northern California. These continental shelves play an important role in marine ecosystems, since most marine organisms live or are spawned there. Other shelf areas may be experiencing similar effects.
At depths of 1000s of meters in the ocean, calcium carbonate shells begin to dissolve as increasing pressure and decreasing temperature shift the chemical equilibria controlling calcium carbonate precipitation. The depth at which this occurs is known as the carbonate compensation depth. Ocean acidification will increase such dissolution and shallow the carbonate compensation depth on timescales of tens to hundreds of years. Zones of downwelling are being affected first.
In the North Pacific and North Atlantic, saturation states are also decreasing (the depth of saturation is getting more shallow). Ocean acidification is progressing in the open ocean as the CO travels to deeper depth as a result of ocean mixing. In the open ocean, this causes carbonate compensation depths to become more shallow, meaning that dissolution of calcium carbonate will occur below those depths. In the North Pacific these carbonate saturations depths are shallowing at a rate of 1–2 m per year.
It is expected that ocean acidification in the future will lead to a significant decrease in the burial of carbonate sediments for several centuries, and even the dissolution of existing carbonate sediments. | 0 | Theoretical and Fundamental Chemistry |
Sustainable Remediation is a term adopted internationally and encompasses sustainable approaches, as described by the Brundtland Report, to the investigation, assessment and management (including institutional controls) of potentially contaminated land and groundwater.
The process of identifying sustainable remediation is defined by The UK Sustainable remediation Forum as “the practice of demonstrating, in terms of environmental, economic and social indicators, that the benefit of undertaking remediation is greater than its impact, and that the optimum remediation solution is selected through the use of a balanced decision-making process.”
Sustainable remediation is the practice of considering the effects of implementing an environmental cleanup and incorporating options to minimize the footprint of the cleanup actions. Opportunities for green and sustainable practices exist throughout the site remediation process of remedial investigation, design, construction, operation, and monitoring. Five core elements are evaluated as part of the environmental footprint analysis including 1) energy, 2) air and atmosphere, 3) materials and waste, 4) land and ecosystem, and 5) water. The cleanup remedy is evaluated for each core element to 1) minimize total energy use and maximize renewable energy use, 2) minimize air pollutants and greenhouse gas emissions, 3) minimize water use and impacts to water resources, 4) reduce, reuse, and recycle materials and waste, and 5) minimize land use and protect ecosystems. | 1 | Applied and Interdisciplinary Chemistry |
The , developed in 1908 with Elias Anton Cappelen Smith, significantly improved the converting of copper matte.
Before this invention, the converter was a cylindrical barrel, lined with an acid refractory lining, made of sand and clay. It was developed by two French engineers, Pierre Manhès and from 1880 to 1884. Their copper-converting process, named the Manhès–David process, was directly derived from the Bessemer process. In this horizontal chemical reactor, where air was injected into copper matte, a molten sulfide material containing iron, sulphur and copper, to become molten blister, an alloy containing 99% copper. But the basic slag produced during the blowing combined with the acid silica refractory lining, thereby causing a very short lifetime of the lining.
By developing a basic refractory material adapted to the matte refining process (in magnesia bricks), Peirce and his engineer Smith found a way to drastically increase the lifetime of the lining. It has been stated that, in some cases, the process allowing an increase from 10 to 2500 tons of copper produced without relining the converters. A reduction of the cost of copper converting from 15–20 USD to 4–5 USD has been stated.
The Peirce-Smith converter quickly replaced the Manhès–David converter: by March 1912, the Peirce-Smith Converting Co claimed that "over 80% of the copper produced in [the U.S.] is being converted either in P-S type converters or on basic lining, under license, in the old acid shells".
It is still in use today, although the process has been significantly improved since then. In 2010, with 250 converters working in the world, the Peirce-Smith converters refine 90% of the copper matte. | 1 | Applied and Interdisciplinary Chemistry |
Responsibility for the safety of the subjects in a clinical trial is shared between the sponsor, the local site investigators (if different from the sponsor), the various IRBs that supervise the study, and (in some cases, if the study involves a marketable drug or device), the regulatory agency for the country where the drug or device will be sold.
A systematic concurrent safety review is frequently employed to assure research participant safety. The conduct and on-going review is designed to be proportional to the risk of the trial. Typically this role is filled by a Data and Safety Committee, an externally appointed Medical Safety Monitor, an Independent Safety Officer, or for small or low-risk studies the principal investigator.
For safety reasons, many clinical trials of drugs are designed to exclude women of childbearing age, pregnant women, or women who become pregnant during the study. In some cases, the male partners of these women are also excluded or required to take birth control measures. | 1 | Applied and Interdisciplinary Chemistry |
The development of protein-directed DCC has not been straightforward because the reversible reactions employed must occur in aqueous solution at biological pH and temperature, and the components of the DCL must be compatible with proteins.
Several reversible reactions have been proposed and/or applied in protein-directed DCC. These included boronate ester formation, diselenides-disulfides exchange, disulphide formation, hemithiolacetal formation, hydrazone formation, imine formation and thiol-enone exchange. | 1 | Applied and Interdisciplinary Chemistry |
After many decades since its inception, supramolecular chemistry's application in practical catalysis remains elusive. Supramolecular catalysis has not yet made significant contribution in the area of industrial chemistry or synthetic methodology. Here are few problems associated with this field. | 0 | Theoretical and Fundamental Chemistry |
Lisinopril is the lysine-analog of enalapril. Unlike other ACE inhibitors, it is not a prodrug, is not metabolized by the liver, and is excreted unchanged in the urine. | 0 | Theoretical and Fundamental Chemistry |
In cancerous cells, initiation factors assist in cellular transformation and development of tumors. The survival and growth of cancer is directly related to the modification of initiation factors and is used as a target for pharmaceuticals. Cells need increased energy when cancerous and derive this energy from proteins. Over-expression of initiation factors correlates with cancers, as they increase protein synthesis for proteins needed in cancers. Some initiation factors, such as eIF4E, are important in synthesizing specific proteins needed for the proliferation and survival of cancer. The careful selection of proteins ensures that proteins that are usually limited in translation and only proteins needed for cancer cell growth will be synthesized. This includes proteins involved in growth, malignancy, and angiogenesis. The eIF4E factor, along with eIF4A and eIF4G, also play a role in transitioning benign cancer cells to metastatic.
The largest initiation factor, eIF3, is another significant initiation factor in human cancers. Due to its role in creating the 43S pre-initiation complex, it helps to bind the ribosomal subunit to the mRNA. The initiation factor has been linked to cancers through over-expression. For example, one of the thirteen eIF3 proteins, eIF3c, interacts with and represses proteins used in tumor suppression. Limited expression of certain eIF3 proteins, such as eIF3a an eIF3d, has been proven to decrease the vigorous growth of cancer cells. The over-expression of eIF3a has been linked to breast, lung, cervix, esophagus, stomach, and colon cancers. It is prevalent during early stages of oncogenesis and likely selectively translates proteins needed for cell proliferation. When eIF3a is suppressed, it has shown to decrease the malignancy of breast and lung cancer, most likely due to its role in tumor growth. | 1 | Applied and Interdisciplinary Chemistry |
Luciferases can be produced in the lab through genetic engineering for a number of purposes. Luciferase genes can be synthesized and inserted into organisms or transfected into cells. As of 2002, mice, silkworms, and potatoes are just a few of the organisms that have already been engineered to produce the protein.
In the luciferase reaction, light is emitted when luciferase acts on the appropriate luciferin substrate. Photon emission can be detected by light sensitive apparatus such as a luminometer or an optical microscope with a CCD camera. This allows observation of biological processes. Since light excitation is not needed for luciferase bioluminescence, there is minimal autofluorescence and therefore the bioluminescent signal is virtually background-free. Therefore, as little as 0.02 pg can still be accurately measured using a standard scintillation counter.
In biological research, luciferase is commonly used as a reporter to assess the transcriptional activity in cells that are transfected with a genetic construct containing the luciferase gene under the control of a promoter of interest. Additionally, proluminescent molecules that are converted to luciferin upon activity of a particular enzyme can be used to detect enzyme activity in coupled or two-step luciferase assays. Such substrates have been used to detect caspase activity and cytochrome P450 activity, among others.
Luciferase can also be used to detect the level of cellular ATP in cell viability assays or for kinase activity assays. Luciferase can act as an ATP sensor protein through biotinylation. Biotinylation will immobilize luciferase on the cell-surface by binding to a streptavidin-biotin complex. This allows luciferase to detect the efflux of ATP from the cell and will effectively display the real-time release of ATP through bioluminescence. Luciferase can additionally be made more sensitive for ATP detection by increasing the luminescence intensity by changing certain amino acid residues in the sequence of the protein.
Whole organism imaging (referred to as in vivo when intact or, otherwise called ex vivo imaging for example of living but explanted tissue) is a powerful technique for studying cell populations in live plants or animals, such as mice. Different types of cells (e.g. bone marrow stem cells, T-cells) can be engineered to express a luciferase allowing their non-invasive visualization inside a live animal using a sensitive charge-couple device camera (CCD camera).This technique has been used to follow tumorigenesis and response of tumors to treatment in animal models. However, environmental factors and therapeutic interferences may cause some discrepancies between tumor burden and bioluminescence intensity in relation to changes in proliferative activity. The intensity of the signal measured by in vivo imaging may depend on various factors, such as -luciferin absorption through the peritoneum, blood flow, cell membrane permeability, availability of co-factors, intracellular pH and transparency of overlying tissue, in addition to the amount of luciferase.
Luciferase is a heat-sensitive protein that is used in studies on protein denaturation, testing the protective capacities of heat shock proteins. The opportunities for using luciferase continue to expand. | 1 | Applied and Interdisciplinary Chemistry |
Intrinsically disordered proteins (IDPs) have very limited innate structure in solution but gain shape specifically when interacting with partner molecules such as proteins or RNA; however, their resultant structure is often dictated by this interaction. In addition, some proteins have sections of sequence without structure, termed intrinsically disordered regions (IDRs), that also gain structure on interaction. Having different shapes with different partners means they are functionally, as well as structurally flexible, making them centrally important to signalling pathways and as regulation/control factors for example. IDPs (and IDRs if capable of being isolated from the rest of the protein) have a distinct SRCD spectral appearance in solution which means that changes in their spectra that arise through interactions offer an ideal opportunity to gain insight into what is happening both structurally and functionally. In addition, SRCD studies have demonstrated that when the solvating water is removed from these proteins, generating a film, there is a gain in structure and more CD transition bands can be measured into the lower VUV wavelength region because the water absorption band is not present
Myelin is the insulating sheath that is formed in the central (CNS) and peripheral nervous systems (PNS) to surround nerve cell axons thereby increasing and maintaining the electrical impulse, the action potential, sent along them. Formed mostly of lipids, there are specific proteins within the myelin components whose roles are to structure the myelin into linked layers. Two of these proteins are myelin basic protein (MBP), an IDP primarily in the CNS, and myelin protein zero (P0) which contains an IDR section (P0ct) and is key within the PNS. MBP and P0ct were employed in a study which used SRCD data as a key factor to establish if there was any significance to the predictions of their IDP and IDR protein structures generated by Alphafold2, an artificial intelligence program developed by DeepMind. PDB2CD, a package that generates SRCD spectra from protein atomic coordinates, was used to calculate spectra from the Alphafold2 structures, and these spectra were then compared against SRCD experimental spectra collected from the MBP and P0ct proteins in various ambient conditions; solution, detergent and lipid-bound states. The study reported that from the SRCD comparisons, the structures predicted by Alphafold2 for MBP and P0ct bore a strong resemblance to those when they were bound to the lipid membrane. | 0 | Theoretical and Fundamental Chemistry |
The existence of discrete inheritable units was first suggested by Gregor Mendel (1822–1884). From 1857 to 1864, in Brno, Austrian Empire (todays Czech Republic), he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. He described these mathematically as 2 combinations where n is the number of differing characteristics in the original peas. Although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured Wilhelm Johannsens distinction between genotype (the genetic material of an organism) and phenotype (the observable traits of that organism). Mendel was also the first to demonstrate independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the phenomenon of discontinuous inheritance.
Prior to Mendels work, the dominant theory of heredity was one of blending inheritance, which suggested that each parent contributed fluids to the fertilization process and that the traits of the parents blended and mixed to produce the offspring. Charles Darwin developed a theory of inheritance he termed pangenesis, from Greek pan ("all, whole") and genesis ("birth") / genos ("origin"). Darwin used the term gemmule' to describe hypothetical particles that would mix during reproduction.
Mendels work went largely unnoticed after its first publication in 1866, but was rediscovered in the late 19th century by Hugo de Vries, Carl Correns, and Erich von Tschermak, who (claimed to have) reached similar conclusions in their own research. Specifically, in 1889, Hugo de Vries published his book Intracellular Pangenesis, in which he postulated that different characters have individual hereditary carriers and that inheritance of specific traits in organisms comes in particles. De Vries called these units "pangenes" (Pangens in German), after Darwins 1868 pangenesis theory.
Twenty years later, in 1909, Wilhelm Johannsen introduced the term gene and in 1906, William Bateson, that of genetics while Eduard Strasburger, amongst others, still used the term pangene for the fundamental physical and functional unit of heredity. | 1 | Applied and Interdisciplinary Chemistry |
The coenzyme NAD is also consumed in ADP-ribose transfer reactions. For example, enzymes called ADP-ribosyltransferases add the ADP-ribose moiety of this molecule to proteins, in a posttranslational modification called ADP-ribosylation. ADP-ribosylation involves either the addition of a single ADP-ribose moiety, in mono-ADP-ribosylation, or the transferral of ADP-ribose to proteins in long branched chains, which is called poly(ADP-ribosyl)ation. Mono-ADP-ribosylation was first identified as the mechanism of a group of bacterial toxins, notably cholera toxin, but it is also involved in normal cell signaling. Poly(ADP-ribosyl)ation is carried out by the poly(ADP-ribose) polymerases. The poly(ADP-ribose) structure is involved in the regulation of several cellular events and is most important in the cell nucleus, in processes such as DNA repair and telomere maintenance. In addition to these functions within the cell, a group of extracellular ADP-ribosyltransferases has recently been discovered, but their functions remain obscure.
NAD may also be added onto cellular RNA as a 5'-terminal modification.
Another function of this coenzyme in cell signaling is as a precursor of cyclic ADP-ribose, which is produced from NAD by ADP-ribosyl cyclases, as part of a second messenger system. This molecule acts in calcium signaling by releasing calcium from intracellular stores. It does this by binding to and opening a class of calcium channels called ryanodine receptors, which are located in the membranes of organelles, such as the endoplasmic reticulum, and inducing the activation of the transcription factor NAFC3
NAD is also consumed by different NAD+-consuming enzymes, such as CD38, CD157, PARPs and the NAD-dependent deacetylases (sirtuins,such as Sir2.). These enzymes act by transferring an acetyl group from their substrate protein to the ADP-ribose moiety of NAD; this cleaves the coenzyme and releases nicotinamide and O-acetyl-ADP-ribose. The sirtuins mainly seem to be involved in regulating transcription through deacetylating histones and altering nucleosome structure. However, non-histone proteins can be deacetylated by sirtuins as well. These activities of sirtuins are particularly interesting because of their importance in the regulation of aging.
Other NAD-dependent enzymes include bacterial DNA ligases, which join two DNA ends by using NAD as a substrate to donate an adenosine monophosphate (AMP) moiety to the 5 phosphate of one DNA end. This intermediate is then attacked by the 3 hydroxyl group of the other DNA end, forming a new phosphodiester bond. This contrasts with eukaryotic DNA ligases, which use ATP to form the DNA-AMP intermediate.
Li et al. have found that NAD directly regulates protein-protein interactions. They also show that one of the causes of age-related decline in DNA repair may be increased binding of the protein DBC1 (Deleted in Breast Cancer 1) to PARP1 (poly[ADP–ribose] polymerase 1) as NAD levels decline during aging. The decline in cellular concentrations of NAD during aging likely contributes to the aging process and to the pathogenesis of the chronic diseases of aging. Thus, the modulation of NAD may protect against cancer, radiation, and aging. | 0 | Theoretical and Fundamental Chemistry |
Numerous experiments have searched for neutrinoless double beta decay. The best-performing experiments have a high mass of the decaying isotope and low backgrounds, with some experiments able to perform particle discrimination and electron tracking. In order to remove backgrounds from cosmic rays, most experiments are located in underground laboratories around the world.
Recent and proposed experiments include:
* Completed experiments:
** Gotthard TPC
** Heidelberg-Moscow, Ge detectors (1997–2001)
** IGEX, Ge detectors (1999–2002)
** NEMO, various isotopes using tracking calorimeters (2003–2011)
** Cuoricino, Te in ultracold TeO crystals (2003–2008)
* Experiments taking data as of November 2017:
** COBRA, Cd in room temperature CdZnTe crystals
** CUORE, Te in ultracold TeO crystals
** EXO, a Xe and Xe search
** GERDA, a Ge detector
** KamLAND-Zen, a Xe search. Data collection from 2011.
** , using high purity Ge p-type point-contact detectors.
** XMASS using liquid Xe
* Proposed/future experiments:
** CUPID, neutrinoless double-beta decay of Mo
** CANDLES, Ca in CaF at Kamioka Observatory
** MOON, developing Mo detectors
** AMoRE, Mo enriched CaMoO crystals at YangYang underground laboratory
** nEXO, using liquid Xe in a time projection chamber
** LEGEND, Neutrinoless Double-beta Decay of Ge.
** LUMINEU, exploring Mo enriched ZnMoO crystals at LSM, France.
** NEXT, a Xenon TPC. NEXT-DEMO ran and NEXT-100 will run in 2016.
** SNO+, a liquid scintillator, will study Te
** SuperNEMO, a NEMO upgrade, will study Se
** TIN.TIN, a Sn detector at INO
** PandaX-III, an experiment with 200 kg to 1000 kg of 90% enriched Xe
** DUNE, a TPC filled with liquid Argon doped with Xe. | 0 | Theoretical and Fundamental Chemistry |
Using a glass pipette, the photolysed cell is isolated by aspiration. Cells are lysed and affinity purification is performed using streptavidin-coated beads that bind, immobilize and purify the biotinylated TIVA tag. | 1 | Applied and Interdisciplinary Chemistry |
The Crich β-mannosylation in organic chemistry is a synthetic strategy which is used in carbohydrate synthesis to generate a 1,2-cis-glycosidic bond. This type of linkate is generally very difficult to make, and specific methods like the Crich β-mannosylation are used to overcome these issues. The technique takes its name from its developer, Professor David Crich. | 0 | Theoretical and Fundamental Chemistry |
By convention, naming rights for newly discovered chemical elements go to their discoverers. For elements 104, 105, and 106, there was a controversy between Soviet researchers at the Joint Institute for Nuclear Research and American researchers at Lawrence Berkeley National Laboratory regarding which group had discovered them first. Both parties suggested their own names for elements 104 and 105, not recognizing the other's name.
The American name of seaborgium for element 106 was also objectionable to some, because it referred to American chemist Glenn T. Seaborg who was still alive at the time this name was proposed. (Einsteinium and fermium had also been proposed as names of new elements while Albert Einstein and Enrico Fermi were still living, but only made public after their deaths, due to Cold War secrecy.) | 1 | Applied and Interdisciplinary Chemistry |
A broad range of enzymes including DNA ligase, DNA polymerase and nucleases have been employed to generate high-fidelity SNP genotyping methods. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a nitrate ester is an organic functional group with the formula , where R stands for any organyl group. They are the esters of nitric acid and alcohols. A well-known example is nitroglycerin, which is not a nitro compound, despite its name. | 0 | Theoretical and Fundamental Chemistry |
One of the main advantages of hydrogen-bond catalysis is the ability to construct catalysts that engage in multiple non-covalent interactions to promote the reaction. In addition to using hydrogen-bond donors to activate or stabilize a reactive center during the reaction, it is possible to introduce other functional groups, such as Lewis bases, arenes, or addition hydrogen-bonding sites to lend additional stabilization or to influence the other reactive partner.
For instance, the natural enzyme chorismate mutase, which catalyzes the Claisen rearrangement of chorismate, features many other interactions in addition to the hydrogen bonds involved in stabilizing the enolate-like fragment, which is an example of the anionic fragment stabilization strategy discussed above. A key interaction is the stabilization of the other cationic allyl fragment through a cation-pi interaction in the transition state. The use of many additional hydrogen bonds has several putative purposes. The stabilization of multiple hydrogen bonds to the enzyme helps overcome the entropic cost of binding. Additionally, the interactions help hold the substrate in a reactive conformation, and the enzyme-catalyzed reaction has near-zero entropy of activation, while typical Claisen rearrangements in solution have very negative entropies of activation.
The use of cation-pi interactions has also been successfully implemented in reactions with synthetic catalysts. A combination of anion-binding and cation-pi strategies can be used to effect enantioselective cationic polycyclizations. In the transition state, it is proposed that the thiourea group binds chloride, while the aromatic system stabilizes the associated polyene cation. In support of this, increasing the size of the aromatic ring leads to improvements both in yield and stereoselectivity. The enantioselectivity correlates well with both the polarizability and the quadrupole moment of the aryl group.
Since such a large number of catalysts and reactions involve binding to electrophiles to stabilize the transition state, many bifunctional catalysts also present a Lewis-basic, hydrogen-bond acceptor site. As a representative example, Deng and coworkers have developed a thiourea-amine catalyst capable of promoting stereoselective Michael reactions. In the proposed transition state, one of the thiourea N–H donors is coordinated to the Michael acceptor and will stabilize the negative charge buildup. The basic nitrogen lone pair acts as a hydrogen-bond acceptor to coordinate the nucleophile, but in the transition state acts as a general base to promote the nucleophilic enolate addition.
This motif of engaging both the nucleophilic and electrophilic partners in a reaction and stabilizing them in the transition state is very common in bifunctional catalysis and many more examples can be found in the article on thiourea organocatalysis.
A relatively new strategy of using synthetic oligopeptides to perform catalysis has yielded many successful examples of catalytic methods. Peptides feature multiple potential sites for hydrogen bonding and it is generally not understood how these engage substrate or how they promote reaction. Peptides have the advantage of being extremely modular and often these catalysts are screened in large arrays. Highly enantioselective reactions have been discovered in this manner such as the aldol reaction depicted below.
Other transformations successfully catalyzed by synthetic peptides include hydrocyanation, acylation, conjugate additions, aldehyde-imine couplings, aldol reaction and bromination. Although the nature of the transition states is unclear, in many examples small changes in the catalyst structure have dramatic effects on reactivity. It is hypothesized that a large number of hydrogen bonds both within the peptide and between catalyst and substrate must cooperate to meet the geometrical requirements for successful catalysis. Beyond this, understanding of catalyst design and mechanism has not yet progressed beyond requiring the testing of libraries of peptides. | 0 | Theoretical and Fundamental Chemistry |
In plants, production of 5-ALA is the step on which the speed of synthesis of chlorophyll is regulated. Plants that are fed by external 5-ALA accumulate toxic amounts of chlorophyll precursor, protochlorophyllide, indicating that the synthesis of this intermediate is not suppressed anywhere downwards in the chain of reaction. Protochlorophyllide is a strong photosensitizer in plants. Controlled spraying of 5-ALA at lower doses (up to 150 mg/L) can however help protect plants from stress and encourage growth. | 1 | Applied and Interdisciplinary Chemistry |
Oxidative additions of nonpolar substrates such as hydrogen and hydrocarbons appear to proceed via concerted pathways. Such substrates lack π-bonds, consequently a three-centered σ complex is invoked, followed by intramolecular ligand bond cleavage of the ligand (probably by donation of electron pair into the sigma* orbital of the inter ligand bond) to form the oxidized complex. The resulting ligands will be mutually cis, although subsequent isomerization may occur.
This mechanism applies to the addition of homonuclear diatomic molecules such as H. Many C–H activation reactions also follow a concerted mechanism through the formation of an M–(C–H) agostic complex.
A representative example is the reaction of hydrogen with Vaskas complex, trans'-IrCl(CO)[P(CH)]. In this transformation, iridium changes its formal oxidation state from +1 to +3. The product is formally bound to three anions: one chloride and two hydride ligands. As shown below, the initial metal complex has 16 valence electrons and a coordination number of four whereas the product is a six-coordinate 18 electron complex.
Formation of a trigonal bipyramidal dihydrogen intermediate is followed by cleavage of the H–H bond, due to electron back donation into the H–H σ*-orbital, i.e. a sigma complex. This system is also in chemical equilibrium, with the reverse reaction proceeding by the elimination of hydrogen gas with simultaneous reduction of the metal center.
The electron back donation into the H–H σ*-orbital to cleave the H–H bond causes electron-rich metals to favor this reaction. The concerted mechanism produces a cis dihydride, while the stereochemistry of the other oxidative addition pathways do not usually produce cis adducts. | 0 | Theoretical and Fundamental Chemistry |
The term blue carbon was coined in 2009. At the time, the term was coined to highlight that coastal vegetated ecosystems have a disproportionately large contribution to global carbon sequestration. Others use the term to describe the carbon captured by the entire ocean, not just the coastal ecosystems. The role of blue carbon in climate change mitigation and adaptation has now reached international prominence.
The vegetated coastal ecosystems of tidal marshes, mangroves and seagrasses (which are grouped as "blue carbon") have high carbon burial rates. This is because they accumulate carbon in their soils and sediments.
Such ecosystems can contribute to climate change mitigation and also to ecosystem-based adaptation. However, when coastal blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere.
Mangroves, salt marshes and seagrasses can store carbon and are highly efficient carbon sinks. They capture from the atmosphere by sequestering the carbon in their underlying sediments, in underground and below-ground biomass, and in dead biomass.
Although vegetated coastal ecosystems cover less area and have less aboveground biomass than terrestrial plants they have the potential to impact long term C sequestration, particularly in sediment sinks.
One of the main concerns with blue carbon is that the rate of loss of these important marine ecosystems is much higher than any other ecosystem on the planet, even compared to rainforests. Current estimates suggest a loss of 2-7% per year, which is not only lost carbon sequestration, but also lost habitat that is important for managing climate, coastal protection, and health.
As habitats that sequester carbon are altered and decreased, that stored amount of C is being released into the atmosphere, continuing the current accelerated rate of climate change. Impacts on these habitats globally will directly and indirectly release the previously stored carbon, which had been sequestered in the sediments of these habitats. Declines in vegetated coastal habitats are seen worldwide.
Quantifying rates of decrease are difficult to calculate, however measurements have been estimated by researchers indicating that if blue carbon ecosystems continue to decline, for any number of reasons, 30-40% of tidal marshes and seagrasses and approximately 100% of mangroves could be gone in the next century.
Reasons for the decline of mangroves, seagrass, and marshes include land use changes, climate and drought related effects, dams built in the watershed, convergence to aquaculture and agriculture, land development and sea-level rise due to climate change. Increases in these activities can lead to significant decreases in habitat availability and thus increases in released C from sediments.
As anthropogenic effects and climate change are heightened, the effectiveness of blue carbon sinks will diminish and CO emissions will be further increased. Data on the rates at which CO is being released into the atmosphere is not robust currently; however, research is being conducted to gather better information to analyze trends. Loss of underground biomass (roots and rhizomes) will allow for CO to be emitted changing these habitats into sources rather than carbon sinks. | 0 | Theoretical and Fundamental Chemistry |
In contrast to beta decay, the fundamental interactions responsible for alpha decay are a balance between the electromagnetic force and nuclear force. Alpha decay results from the Coulomb repulsion between the alpha particle and the rest of the nucleus, which both have a positive electric charge, but which is kept in check by the nuclear force. In classical physics, alpha particles do not have enough energy to escape the potential well from the strong force inside the nucleus (this well involves escaping the strong force to go up one side of the well, which is followed by the electromagnetic force causing a repulsive push-off down the other side).
However, the quantum tunnelling effect allows alphas to escape even though they do not have enough energy to overcome the nuclear force. This is allowed by the wave nature of matter, which allows the alpha particle to spend some of its time in a region so far from the nucleus that the potential from the repulsive electromagnetic force has fully compensated for the attraction of the nuclear force. From this point, alpha particles can escape. | 0 | Theoretical and Fundamental Chemistry |
In both marine and freshwater environments, algae – particularly green algae and diatoms – make up the dominant component of surface growth communities. Small crustaceans, rotifers, and protozoans are also commonly found in fresh water and the sea, but insect larvae, oligochaetes and tardigrades are peculiar to freshwater aufwuchs faunas. | 1 | Applied and Interdisciplinary Chemistry |
Electrochromatography is a chemical separation technique in analytical chemistry, biochemistry and molecular biology used to resolve and separate mostly large biomolecules such as proteins. It is a combination of size exclusion chromatography (gel filtration chromatography) and gel electrophoresis. These separation mechanisms operate essentially in superposition along the length of a gel filtration column to which an axial electric field gradient has been added. The molecules are separated by size due to the gel filtration mechanism and by electrophoretic mobility due to the gel electrophoresis mechanism. Additionally there are secondary chromatographic solute retention mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
In rare cases, a mutation in the genes controlling the production of lactate dehydrogenase will lead to a medical condition known as lactate dehydrogenase deficiency. Depending on which gene carries the mutation, one of two types will occur: either lactate dehydrogenase-A deficiency (also known as glycogen storage disease XI) or lactate dehydrogenase-B deficiency. Both of these conditions affect how the body breaks down sugars, primarily in certain muscle cells. Lactate dehydrogenase-A deficiency is caused by a mutation to the LDHA gene, while lactate dehydrogenase-B deficiency is caused by a mutation to the LDHB gene.
This condition is inherited in an autosomal recessive pattern, meaning that both parents must contribute a mutated gene in order for this condition to be expressed.
A complete lactate dehydrogenase enzyme consists of four protein subunits. Since the two most common subunits found in lactate dehydrogenase are encoded by the LDHA and LDHB genes, either variation of this disease causes abnormalities in many of the lactate dehydrogenase enzymes found in the body. In the case of lactate dehydrogenase-A deficiency, mutations to the LDHA gene result in the production of an abnormal lactate dehydrogenase-A subunit that cannot bind to the other subunits to form the complete enzyme. This lack of a functional subunit reduces the amount of enzyme formed, leading to an overall decrease in activity. During the anaerobic phase of glycolysis (the Cori cycle), the mutated enzyme is unable to convert pyruvate into lactate to produce the extra energy the cells need. Since this subunit has the highest concentration in the LDH enzymes found in the skeletal muscles (which are the primary muscles responsible for movement), high-intensity physical activity will lead to an insufficient amount of energy being produced during this anaerobic phase. This in turn will cause the muscle tissue to weaken and eventually break down, a condition known as rhabdomyolysis. The process of rhabdomyolysis also releases myoglobin into the blood, which will eventually end up in the urine and cause it to become red or brown: another condition known as myoglobinuria. Some other common symptoms are exercise intolerance, which consists of fatigue, muscle pain, and cramps during exercise, and skin rashes. In severe cases, myoglobinuria can damage the kidneys and lead to life-threatening kidney failure. In order to obtain a definitive diagnosis, a muscle biopsy may be performed to confirm low or absent LDH activity. There is currently no specific treatment for this condition.
In the case of lactate dehydrogenase-B deficiency, mutations to the LDHB gene result in the production of an abnormal lactate dehydrogenase-B subunit that cannot bind to the other subunits to form the complete enzyme. As with lactate dehydrogenase-A deficiency, this mutation reduces the overall effectiveness in the enzyme. However, there are some major differences between these two cases. The first is the location where the condition manifests itself. With lactate dehydrogenase-B deficiency, the highest concentration of B subunits can be found within the cardiac muscle, or the heart. Within the heart, lactate dehydrogenase plays the role of converting lactate back into pyruvate so that the pyruvate can be used again to create more energy. With the mutated enzyme, the overall rate of this conversion is decreased. However, unlike lactate dehydrogenase-A deficiency, this mutation does not appear to cause any symptoms or health problems linked to this condition. At the present moment, it is unclear why this is the case. Affected individuals are usually discovered only when routine blood tests indicate low LDH levels present within the blood. | 1 | Applied and Interdisciplinary Chemistry |
Like inorganic carbon, there are two main forms of organic carbon found in the ocean (dissolved and particulate). Dissolved organic carbon (DOC) is defined operationally as any organic molecule that can pass through a 0.2 µm filter. DOC can be converted into particulate organic carbon through heterotrophy and it can also be converted back to dissolved inorganic carbon (DIC) through respiration.
Those organic carbon molecules being captured on a filter are defined as particulate organic carbon (POC). POC is composed of organisms (dead or alive), their fecal matter, and detritus. POC can be converted to DOC through disaggregation of molecules and by exudation by phytoplankton, for example. POC is generally converted to DIC through heterotrophy and respiration. | 0 | Theoretical and Fundamental Chemistry |
Because the reference of the first flush is not always clear, the terms "concentration-based first flush" (CBFF) and "mass-based first flush" (MBFF) have been introduced.
Apart from this definition, there are a number of rating parameters in literature to determine the occurrence of a first flush. | 1 | Applied and Interdisciplinary Chemistry |
After a neurotransmitter molecule binds to a receptor molecule, it must be removed to allow for the postsynaptic membrane to continue to relay subsequent EPSPs and/or IPSPs. This removal can happen through one or more processes:
*The neurotransmitter may diffuse away due to thermally-induced oscillations of both it and the receptor, making it available to be broken down metabolically outside the neuron or to be reabsorbed.
*Enzymes within the subsynaptic membrane may inactivate/metabolize the neurotransmitter.
*Reuptake pumps may actively pump the neurotransmitter back into the presynaptic axon terminal for reprocessing and re-release following a later action potential. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a resorcinarene (also resorcarene or calix[4]resorcinarene) is a macrocycle, or a cyclic oligomer, based on the condensation of resorcinol (1,3-dihydroxybenzene) and an aldehyde. Resorcinarenes are a type of calixarene. Other types of resorcinarenes include the related pyrogallolarenes and octahydroxypyridines, derived from pyrogallol and 2,6-dihydroxypyridine, respectively.
Resorcinarenes interact with other molecules forming a host–guest complex. Resorcinarenes and pyrogallolarenes self-assemble into larger supramolecular structures. Both in the crystalline state and in organic solvents, six resorcinarene molecules are known to form hexamers with an internal volume of around one cubic nanometer (nanocapsules) and shapes similar to the Archimedean solids. Hydrogen bonds appear to hold the assembly together. A number of solvent or other molecules reside inside. The resorcinarene is also the basic structural unit for other molecular recognition scaffolds, typically formed by bridging the phenolic oxygens with alkyl or aromatic spacers. A number of molecular structures are based on this macrocycle, namely cavitands and carcerands. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the Perkin rearrangement (coumarin–benzofuran ring contraction) is a rearrangement reaction in which a 2-halocoumarin in the presence of hydroxide undergoes a ring contraction to form a benzofuran. The name reaction recognizes William Henry Perkin, who first reported it in 1870. Several proposals have been made for the reaction mechanism, all of which involve initial opening of the lactone to give a carboxylate and phenolate. | 0 | Theoretical and Fundamental Chemistry |
Palytoxin, PTX or PLTX is an intense vasoconstrictor, and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice.
Palytoxin is a polyhydroxylated and partially unsaturated compound (8 double bonds) with a long carbon chain. It has water-soluble and fat-soluble parts, 40 hydroxy groups and 64 chiral centers. Due to chirality and possible double bond cis-trans isomerism, it has over 10 alternative stereoisomers. It is thermostable, and treatment with boiling water does not remove its toxicity. It remains stable in aqueous solutions for prolonged periods but rapidly decomposes and loses its toxicity in acidic or alkaline solutions. It has multiple analogues with a similar structure like ostreocin-D, mascarenotoxin-A and -B.
Palytoxin occurs at least in tropics and subtropics where it is made by Palythoa corals and Ostreopsis dinoflagellates, or possibly by bacteria occurring in these organisms. It can be found in many more species like fish and crabs due to the process of biomagnification. It can also be found in organisms living close to palytoxin producing organisms like sponges, mussels, starfish and cnidaria.
People are rarely exposed to palytoxin. Exposures have happened in people who have eaten sea animals like fish and crabs, but also in aquarium hobbyists who have handled Palythoa corals incorrectly and in those who have been exposed to certain algal blooms.
Palytoxin targets the sodium-potassium pump protein by locking it into a position where it allows passive transport of both sodium and potassium ions, thereby destroying the ion gradient that is essential for life. Because palytoxin can affect every type of cell in the body, the symptoms can be very different for the various routes of exposure.
Palytoxin's planar chemical structure was solved in 1981 by two research groups independently from each other. Stereochemistry was solved in 1982. Palytoxin carboxylic acid was synthesized by Yoshito Kishi and colleagues in 1989 and actual palytoxin in 1994 by Kishi and Suh. | 0 | Theoretical and Fundamental Chemistry |
In the early 1990s, technical personnel from the then Union Miniére worked with MIM Holdings personnel to develop an ISASMELT-based process to treat scrap materials and residues containing copper and lead. Union Miniére operated a smelter at Hoboken, near Antwerpen in Belgium, that specialised in recycling scrap non-ferrous materials. The test work program was undertaken using an ISASMELT test rig at MIM Holdings’ lead refinery, Britannia Refined Metals, at Northfleet in the United Kingdom.
A demonstration plant was designed by MIM Holdings personnel and operated for several months at the Hoboken smelter site. The new smelter was commissioned in the final quarter of 1997 and in 2007 was treating up to 300,000 t/y of secondary materials. The installation of the ISASMELT furnace replaced a roasting plant, a sinter plant, 1 of two sulfuric acid plants, a copper blast furnace and four Hoboken converters. It substantially reduced operating costs at the Hoboken smelter.
Umicore's Hoboken plant uses a two-step process in a single furnace. The first step involves the oxidation of the feed to form a copper matte and a lead-rich slag. The slag is then tapped and the remaining copper matte is then converted to blister copper. The lead-rich slag is subsequently reduced in a blast furnace to produce lead metal, while the copper is refined and the contained precious metals recovered. | 1 | Applied and Interdisciplinary Chemistry |
The challenge in sealing larger gaps with caissons lies in the diminishing flow area as more caissons are placed, resulting in significantly increased flow speeds (exceeding the aforementioned 2.5 m/s), complicating the final caisson's proper placement. This issue is addressed through the use of sluice caissons, essentially a box equipped with gates on one side. During installation, these gates are shut to maintain buoyancy, and the opposite side is sealed with wooden boards.
Once each caisson is positioned, the boards are removed, and the gates opened, allowing the tidal current to pass with minimal impedance. This approach ensures that the flow area doesn't drastically reduce, and flow velocities remain manageable, facilitating the placement of subsequent caissons. After all caissons are set, the gates are closed at slack water, completing the closure. Subsequently, sand is sprayed in front of the dam, and the gates along with other movable mechanisms are removed, available for reuse in future closures.
Sluice caissons were first employed in closing the Veerse Gat, and subsequently utilized at the Brouwersdam and the Volkerak. They were also deployed in the closure of the Lauwerszee. | 1 | Applied and Interdisciplinary Chemistry |
Shodex is the brand name of HPLC columns and is best known for polymer-based columns. The product range covers aqueous and organic Size Exclusion Chromatography columns for large (bio-)molecules, columns for the routine analysis of sugars and organic acids, and a variety of Reversed Phase and HILIC columns. Additionally they offer Ion Chromatography (IC) and Ion Exchange columns.
Shodex HPLC Columns are manufactured in Japan by Resonac (formerly known as Showa Denko), one of the largest Japanese chemical companies and listed in the Nikkei 225 index. They produce around 260 different columns, most packed with polymer-based particles, and have been doing so since 1974.
The portfolio includes standard analytical columns, semi-micro columns, and preparative columns. Also size exclusion chromatography calibration standards are available (Pullulan, Polystyrene, Polymethylmethacrylate)
Shodex is distributed worldwide by the different sales offices and by a range of local distributors. | 0 | Theoretical and Fundamental Chemistry |
At this point in the synthesis of Taxol, the material was a racemic mixture. To obtain the desired enantiomer, allylic alcohol 4.9 was acylated with (1S)-(−)-camphanic chloride and dimethylaminopyridine, giving two diastereomers. These were then separated using standard column chromatography. The desired enantiomer was then isolated when one of the separated disatereomers was treated with potassium bicarbonate in methanol. | 0 | Theoretical and Fundamental Chemistry |
Initially, the presence of chlororespiration as a legitimate respiratory process in plants was heavily doubted. However, experimentation on Chlamydomonas reinhardtii, discovered Plastoquinone (PQ) to be a redox carrier. The role of this redox carrier is to transport electrons from the NAD(P)H enzyme to oxygen molecules on the thylakoid membrane. Using this cyclic electron chain around photosystem one (PS I), chlororespiration compensates for the lack of light. This cyclic pathway also allows electrons to re-enter the PQ pool through NAD(P)H enzyme activity and production, which is then used to supply ATP molecules (energy) to plant cells.
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In the year 2002, the discovery of the molecules; plastid terminal oxidase (PTOX) and NDH complexes have revolutionised the concept of chlororespiration. Using evidence from experimentation on the plant species Rosa Meillandina, this latest model observes the role of PTOX to be an enzyme that prevents the PQ pool from over-reducing, by stimulating its reoxidation. Whereas, the NDH complexes are responsible for providing a gateway for electrons to form an ETC. The presence of such molecules are apparent in the non-appressed thylakoid membranes of higher order plants like Rosa Meillandina. | 1 | Applied and Interdisciplinary Chemistry |
A related class of octahedral clusters are of the type MXL where M is a metal usually of group 6 or group 7, X is a ligand and more specifically an inner ligand of the chalcohalide group such as chloride or sulfide and L is an "outer ligand." The metal atoms define the vertices of an octahedron. The overall point group symmetry is O. Each face of the octahedron is capped with a chalcohalide and eight such atoms are at the corners of a cube. For this reason this geometry is called a face capped octahedral cluster. Examples of this type of clusters are the ReSCl anion. | 0 | Theoretical and Fundamental Chemistry |
hnRNP serves a variety of processes in the cell, some of which include:
# Preventing the folding of pre-mRNA into secondary structures that may inhibit its interactions with other proteins.
# Possible association with the splicing apparatus.
# Transport of mRNA out of the nucleus.
The association of a pre-mRNA molecule with a hnRNP particle prevents formation of short secondary structures dependent on base pairing of complementary regions, thereby making the pre-mRNA accessible for interactions with other proteins. | 1 | Applied and Interdisciplinary Chemistry |
The macadamia (genus Macadamia) nut was discovered by the European settlers, and subsequently the tree was named after him by his friend and colleague, Ferdinand von Mueller (1825-1896), Director of the Royal Botanic Gardens, Melbourne. The tree gave his name to macadamia nuts. The genus Macadamia was first described scientifically in 1857 by Dr. Mueller and he named the new genus in honour of his friend Dr John Macadam. Mueller had done a great deal of taxonomy of the flora, naming innumerable genera but chose this "...a beautiful genus dedicated to John Macadam, M.D. the talented and deserving secretary of our institute." | 0 | Theoretical and Fundamental Chemistry |
As nickel can be harmful to skin, its use in daily products must be regulated. A safety directive has been in place in Europe since 2004. Denmark in 1980, and then shortly after the European Union (EU), enacted legislation that limited the amount of free nickel in consumer products that come in contact with the skin. This resulted in significantly decreased rates of sensitization among Danish children 0 to 18 years of age from 24.8% to 9.2% between 1985 and 1998, with similar reductions in sensitization throughout the EU.
No such directive exists in the United States, but efforts are under way to mandate safe use guidelines for nickel. In August 2015, the American Academy of Dermatology (AAD) adopted a nickel safety position paper. The exact prevalence of Ni-ACD in the general population in the US is largely unknown. However, current estimates gauge that roughly 2.5 million US adults and 250,000 children have a nickel allergy, which costs an estimated $5.7 billion per year for treatment of symptoms. Loma Linda University, Nickel Allergy Alliance, and Dermatitis Academy created the first open access self-reported patient registry to record nickel allergy prevalence data in the US.[ref 23] | 1 | Applied and Interdisciplinary Chemistry |
When resistance is first suspected or confirmed, the efficacy of alternatives is likely to be the first consideration. If there is resistance to a single group of herbicides, then the use of herbicides from other groups may provide a simple and effective solution, at least in the short term. For example, many triazine-resistant weeds have been readily controlled by the use of alternative herbicides such as dicamba or glyphosate. | 1 | Applied and Interdisciplinary Chemistry |
We shall consider pure water electrolysis as an example to explain the concept of the Virtual breakdown mechanism. | 0 | Theoretical and Fundamental Chemistry |
The structure of eukaryotic genes includes features not found in prokaryotes. Most of these relate to post-transcriptional modification of pre-mRNAs to produce mature mRNA ready for translation into protein. Eukaryotic genes typically have more regulatory elements to control gene expression compared to prokaryotes. This is particularly true in multicellular eukaryotes, humans for example, where gene expression varies widely among different tissues.
A key feature of the structure of eukaryotic genes is that their transcripts are typically subdivided into exon and intron regions. Exon regions are retained in the final mature mRNA molecule, while intron regions are spliced out (excised) during post-transcriptional processing. Indeed, the intron regions of a gene can be considerably longer than the exon regions. Once spliced together, the exons form a single continuous protein-coding regions, and the splice boundaries are not detectable. Eukaryotic post-transcriptional processing also adds a 5' cap to the start of the mRNA and a poly-adenosine tail to the end of the mRNA. These additions stabilise the mRNA and direct its transport from the nucleus to the cytoplasm, although neither of these features are directly encoded in the structure of a gene. | 1 | Applied and Interdisciplinary Chemistry |
LAGP belongs to phosphate-based solid electrolytes and, in spite of showing a moderate ionic conductivity compared to other families of solid ionic conductors, it possesses some intrinsic advantages with respect to sulfides and oxides:
* Extremely high chemical stability in humid air;
* Wide electrochemical stability window;
* Low to negligible electronic conductivity.
One of the main advantages of LAGP is its chemical stability in the presence of oxygen, water vapour, and carbon dioxide, which simplifies the manufacture process preventing the use of a glovebox or protected environments. Unlike sulfide-based solid electrolytes, which react with water releasing poisonous gaseous hydrogen sulfide, and garnet-type lithium lanthanum zirconium oxide (LLZO), which react with water and CO to form passivating layers of LiOH and LiCO, LAGP is practically inert in humid air.
Another important advantage of LAGP is its wide electrochemical stability window, up to 6 V, which allows the use of such electrolyte in contact with high-voltage cathodes, thus enabling high energy densities. However, the stability at very low voltages and against lithium metal is controversial: even if LAGP is more stable than LATP because of the absence of titanium, some literature works report on the reduction of Ge by lithium as well, with formation of Ge and metallic germanium at the electrode-electrolyte interface and dramatic increase of interfacial resistance.
The possible decomposition mechanism of LAGP in contact with metallic lithium is reported in the equation below: | 0 | Theoretical and Fundamental Chemistry |
Contrary to a neutral solute, the partition coefficient of an ion depends on the Galvani potential difference between the two phases: | 0 | Theoretical and Fundamental Chemistry |
It is based on the principle that the intensity of light received by the observer depends upon the distance of the observer from the source and the temperature of the distant source. A modern pyrometer has an optical system and a detector. The optical system focuses the thermal radiation onto the detector. The output signal of the detector (temperature T) is related to the thermal radiation or irradiance of the target object through the Stefan–Boltzmann law, the constant of proportionality σ, called the Stefan–Boltzmann constant and the emissivity ε of the object:
This output is used to infer the object's temperature from a distance, with no need for the pyrometer to be in thermal contact with the object; most other thermometers (e.g. thermocouples and resistance temperature detectors (RTDs)) are placed in thermal contact with the object and allowed to reach thermal equilibrium.
Pyrometry of gases presents difficulties. These are most commonly overcome by using thin-filament pyrometry or soot pyrometry. Both techniques involve small solids in contact with hot gases. | 1 | Applied and Interdisciplinary Chemistry |
Bartlett and Beaudry discovered that IBX is a valuable reagent for the transformation of β-hydroxyketones to β-diketones. IBX provides yields superior to both the Swern and Dess–Martin oxidation protocols. | 0 | Theoretical and Fundamental Chemistry |
In parallel to the advances in highthroughput biology, machine learning applications to biomedical data analysis are flourishing. The integration of multi-omics data analysis and machine learning has led to the discovery of new biomarkers. For example, one of the methods of the [http://mixomics.org/ mixOmics] project implements a method based on sparse Partial Least Squares regression for selection of features (putative biomarkers). A unified and flexible statistical framewok for heterogeneous data integration called "Regularized Generalized Canonical Correlation Analysis" (RGCCA ) enables identifying such putative biomarkers. This framework is implemented and made freely avalaible within the [https://cran.r-project.org/web/packages/RGCCA/ RGCCA R package] . | 1 | Applied and Interdisciplinary Chemistry |
Metal casting processes uses the following terminology:
*Pattern: An approximate duplicate of the final casting used to form the mold cavity.
*Molding material: The material that is packed around the pattern and then the pattern is removed to leave the cavity where the casting material will be poured.
*Flask: The rigid wood or metal frame that holds the molding material.
**Cope: The top half of the pattern, flask, mold, or core.
**Drag: The bottom half of the pattern, flask, mold, or core.
*Core: An insert in the mold that produces internal features in the casting, such as holes.
**Core print: The region added to the pattern, core, or mold used to locate and support the core.
*Mold cavity: The combined open area of the molding material and core, where the metal is poured to produce the casting.
*Riser: An extra void in the mold that fills with molten material to compensate for shrinkage during solidification.
*Gating system: The network of connected channels that deliver the molten material to the mold cavities.
**Pouring cup or pouring basin: The part of the gating system that receives the molten material from the pouring vessel.
**Sprue: The pouring cup attaches to the sprue, which is the vertical part of the gating system. The other end of the sprue attaches to the runners.
**Runners: The horizontal portion of the gating system that connects the sprues to the gates.
**Gates: The controlled entrances from the runners into the mold cavities.
*Vents: Additional channels that provide an escape for gases generated during the pour.
*Parting line or parting surface: The interface between the cope and drag halves of the mold, flask, or pattern.
*Draft: The taper on the casting or pattern that allow it to be withdrawn from the mold
*Core box: The mold or die used to produce the cores.
*Chaplet: Long vertical holding rod for core that after casting it become the integral part of casting, provide the support to the core.
Some specialized processes, such as die casting, use additional terminology. | 1 | Applied and Interdisciplinary Chemistry |
Rosenthals reagent is a metallocene bis(trimethylsilyl)acetylene complex with zirconium (CpZr) or titanium (CpTi) used as central atom of the metallocene fragment CpM. Additional ligands such as pyridine or THF are commonly used as well. With zirconium as central atom and pyridine as ligand, a dark purple to black solid with a melting point of 125–126 °C is obtained. Synthesizing Rosenthals reagent of a titanocene source yields golden-yellow crystals of the titanocene bis(trimethylsilyl)acetylene complex with a melting point of 81–82 °C. This reagent enables the generation of the themselves unstable titanocene and zirconocene under mild conditions.
The reagent is named after the German chemist (born 1950) and was first synthesized by him and his co-workers in 1995. | 0 | Theoretical and Fundamental Chemistry |
Proteins are biomolecules that are composed of amino acid subunits. Each amino acid has a side chain that gains or loses charge depending on the pH of the surrounding environment, as well as its own individual polar/nonpolar qualities. Charged regions can greatly contribute to how that protein interacts with other molecules and surfaces, as well as its own tertiary structure (protein folding). As a result of their hydrophilicity, charged amino acids tend to be located on the outside of proteins, where they are able to interact with surfaces. It is the unique combination of amino acids that gives a protein its properties. In terms of surface chemistry, protein adsorption is a critical phenomenon that describes the aggregation of these molecules on the exterior of a material. The tendency for proteins to remain attached to a surface depends largely on the material properties such as surface energy, texture, and relative charge distribution. Larger proteins are more likely to adsorb and remain attached to a surface due to the higher number of contact sites between amino acids and the surface (Figure 1). | 1 | Applied and Interdisciplinary Chemistry |
Ernest Basil Verney (1894–1967) succeeded Clark. He held the Chair of Pharmacology from 1926 to 1934.
While at UCL Verney discovered the antidiuretic hormone and also the mechanism by which structures in the brain sense minute changes in blood osmotic pressure. Both findings were of profound importance for the understanding of water and electrolyte balance. Verney was also instrumental in arranging for Otto Krayer to come to the department, albeit for only a short period, following Krayer's exclusion from all academic positions in German universities because of his objection to the expulsion of Jewish scientists from their posts. Krayer was later to head the Department of Pharmacology at Harvard with the greatest distinction.
In 1934 Verney moved to an academic post at the University of Cambridge where he later became the first Sheild Professor of Pharmacology | 1 | Applied and Interdisciplinary Chemistry |
The simplest equation for the rate of an enzyme-catalysed reaction as a function of the substrate concentration is the Michaelis-Menten equation, which can be written as follows:
in which is the rate at substrate saturation (when approaches infinity, or limiting rate, and is the value of at half-saturation, i.e. for , known as the Michaelis constant. Eadie and Hofstee independently transformed this into straight-line relationships, as follows: Taking reciprocals of both sides of the equation gives the equation underlying the Lineweaver–Burk plot:
: ·
This can be rearranged to express a different straight-line relationship:
: ·
which shows that a plot of against is a straight line with intercept on the ordinate, and slope (Hofstee plot). In the Eadie plot the axes are reversed, but the principle is the same. These plots are kinetic versions of the Scatchard plot used in ligand-binding experiments. | 1 | Applied and Interdisciplinary Chemistry |
Central to the MaxEnt thesis is the principle of maximum entropy. It demands as given some partly specified model and some specified data related to the model. It selects a preferred probability distribution to represent the model. The given data state "testable information" about the probability distribution, for example particular expectation values, but are not in themselves sufficient to uniquely determine it. The principle states that one should prefer the distribution which maximizes the Shannon information entropy,
This is known as the Gibbs algorithm, having been introduced by J. Willard Gibbs in 1878, to set up statistical ensembles to predict the properties of thermodynamic systems at equilibrium. It is the cornerstone of the statistical mechanical analysis of the thermodynamic properties of equilibrium systems (see partition function).
A direct connection is thus made between the equilibrium thermodynamic entropy S, a state function of pressure, volume, temperature, etc., and the information entropy for the predicted distribution with maximum uncertainty conditioned only on the expectation values of those variables:
k, the Boltzmann constant, has no fundamental physical significance here, but is necessary to retain consistency with the previous historical definition of entropy by Clausius (1865) (see Boltzmann constant).
However, the MaxEnt school argue that the MaxEnt approach is a general technique of statistical inference, with applications far beyond this. It can therefore also be used to predict a distribution for "trajectories" Γ "over a period of time" by maximising:
This "information entropy" does not necessarily have a simple correspondence with thermodynamic entropy. But it can be used to predict features of nonequilibrium thermodynamic systems as they evolve over time.
For non-equilibrium scenarios, in an approximation that assumes local thermodynamic equilibrium, with the maximum entropy approach, the Onsager reciprocal relations and the Green–Kubo relations fall out directly. The approach also creates a theoretical framework for the study of some very special cases of far-from-equilibrium scenarios, making the derivation of the entropy production fluctuation theorem straightforward. For non-equilibrium processes, as is so for macroscopic descriptions, a general definition of entropy for microscopic statistical mechanical accounts is also lacking.
Technical note: For the reasons discussed in the article differential entropy, the simple definition of Shannon entropy ceases to be directly applicable for random variables with continuous probability distribution functions. Instead the appropriate quantity to maximize is the "relative information entropy",
H is the negative of the Kullback–Leibler divergence, or discrimination information, of m(x) from p(x), where m(x) is a prior invariant measure for the variable(s). The relative entropy H is always less than zero, and can be thought of as (the negative of) the number of bits of uncertainty lost by fixing on p(x) rather than m(x). Unlike the Shannon entropy, the relative entropy H has the advantage of remaining finite and well-defined for continuous x, and invariant under 1-to-1 coordinate transformations. The two expressions coincide for discrete probability distributions, if one can make the assumption that m(x) is uniform – i.e. the principle of equal a-priori probability, which underlies statistical thermodynamics. | 0 | Theoretical and Fundamental Chemistry |
Macrophages and related cells employ a different mechanism to recognize the pathogen. Their receptors recognize certain motifs present on the invading pathogen that are very unlikely to be present on a host cell. Such repeating motifs are recognized by pattern recognition receptors (PRRs) like the toll-like receptors (TLRs) expressed by the macrophages. Since the same receptor could bind to a given motif present on surfaces of widely disparate microorganisms, this mode of recognition is relatively nonspecific, and constitutes an innate immune response. | 1 | Applied and Interdisciplinary Chemistry |
When an area element is radiating as a result of being illuminated by an external source, the irradiance (energy or photons /time/area) landing on that area element will be proportional to the cosine of the angle between the illuminating source and the normal. A Lambertian scatterer will then scatter this light according to the same cosine law as a Lambertian emitter. This means that although the radiance of the surface depends on the angle from the normal to the illuminating source, it will not depend on the angle from the normal to the observer. For example, if the moon were a Lambertian scatterer, one would expect to see its scattered brightness appreciably diminish towards the terminator due to the increased angle at which sunlight hit the surface. The fact that it does not diminish illustrates that the moon is not a Lambertian scatterer, and in fact tends to scatter more light into the oblique angles than a Lambertian scatterer.
The emission of a Lambertian radiator does not depend on the amount of incident radiation, but rather from radiation originating in the emitting body itself. For example, if the sun were a Lambertian radiator, one would expect to see a constant brightness across the entire solar disc. The fact that the sun exhibits limb darkening in the visible region illustrates that it is not a Lambertian radiator. A black body is an example of a Lambertian radiator. | 0 | Theoretical and Fundamental Chemistry |
Scintillons are not identical in different species. Scintillons isolated from dinoflagellates belonging to the genus Pyrocystis such as P. lunula (previously Dissodinium lunula) or P. noctiluca are less dense than those of L. polyedra and do not contain LBP. Little is known about the structure or composition of scintillons in species other than L. polyedra. | 1 | Applied and Interdisciplinary Chemistry |
Arabinoxylans are found in both the primary and secondary cell walls of plants and are the copolymers of two sugars: arabinose and xylose. They may also have beneficial effects on human health. | 0 | Theoretical and Fundamental Chemistry |
Ocean acidity due to carbon dioxide has already increased by 25% since the industrial revolution. As carbon dioxide emissions continually increase and accumulate, this will negatively affect the lives of many marine ecosystems. The calcium carbonate used to form many marine organisms' exoskeletons will begin to break down, leaving these animals vulnerable and unable to live in their habitats. This ultimately has a flow on effect to predators, further affecting the function of many food webs globally. | 1 | Applied and Interdisciplinary Chemistry |
NeurogesX has successfully completed three Phase III clinical studies of Qutenza (NGX-4010) that met studies primary endpoints. Qutenza is a synthetic trans-capsaicin and drug delivery is by a rapid-delivery patch application system NeurogesX plans to launch Qutenza in the United States in the first half of November 2010.
Anesiva, another biotechnology company, has completed two Phase III trials of Adlea (ALGRX 4975), an injectable capsaicin. Adlea is promising as a pain reliever and both trials showed that Adlea's safety profile of adverse events, wound healing, and wound sensory function were similar to placebo over the study duration. | 1 | Applied and Interdisciplinary Chemistry |
Blocking antibodies have been used in clinical trials of cancer treatments. The blocking antibody ipilimumab has been effectively used in the clinical treatment of melanoma, RCC, and NSCLC with some degree of success. This is accomplished through the blocking of the coinhibitory molecule CTLA-4. The blocking antibody does not directly target tumor cells, but rather blocks the regulatory functions of CTLA-4, resulting in enhanced T-cell function.
Some new treatments hypothesize the blocking of PD-1, a programmed cell-death protein, which will result in longer-lived T-cells. The blocking antibody BMS-936559 has been shown to bind to PD-L1 and prevent its binding to PD-1.
These new treatments are not without side-effects and immune-related adverse events have been observed in a variety of patients. The tolerance that immune cells normally have to host tissues can be lost, resulting in permanent damage to host cells. | 1 | Applied and Interdisciplinary Chemistry |
Mesembrine was first isolated and characterized by Bodendorf, et al. in 1957. It is a tricyclic molecule and has two bridgehead chiral carbons between the five-membered ring and the six-membered ring (highlighted in green in the figure below). Because of its structure and bioactivity, mesembrine has been a target for total synthesis over the past 40 years. Over 40 total syntheses have been reported for mesembrine, most of which focused on different approaches and strategies for the construction of the bicyclic ring system and the quaternary carbon.
The first total synthesis of mesembrine was reported by Shamma, et al. in 1965. This route has 21 steps, which was among the longest synthetic routes for mesembrine. Key steps involve the construction of the six-membered ketone ring by Diels-Alder reaction, α-allylation for synthesis of the quaternary carbon, and conjugate addition reaction for the final five-membered ring closure. The final product from this route is a racemic mixture of (+)- and (-)-mesembrine.
In 1971, Yamada, et al. reported the first asymmetric total synthesis of (+)-mesembrine. The quaternary carbon was introduced by asymmetric Robinson annulation reaction mediated by an -proline derivative. | 0 | Theoretical and Fundamental Chemistry |
In a liquid mixture, the fugacity of each component is equal to that of a vapor component in equilibrium with the liquid. In an ideal solution, the fugacities obey the Lewis-Randall rule:
where is the mole fraction in the liquid and is the fugacity of the pure liquid phase. This is a good approximation when the component molecules have similar size, shape and polarity.
In a dilute solution with two components, the component with the larger molar fraction (the solvent) may still obey Raoults law even if the other component (the solute) has different properties. That is because its molecules experience essentially the same environment that they do in the absence of the solute. By contrast, each solute molecule is surrounded by solvent molecules, so it obeys a different law known as Henrys law. By Henrys law, the fugacity of the solute is proportional to its concentration. The constant of proportionality (a measured Henrys constant) depends on whether the concentration is represented by the mole fraction, molality or molarity. | 0 | Theoretical and Fundamental Chemistry |
N-Methylmorpholine N-oxide (more correctly 4-methylmorpholine 4-oxide), NMO or NMMO is an organic compound. This heterocyclic amine oxide and morpholine derivative is used in organic chemistry as a co-oxidant and sacrificial catalyst in oxidation reactions for instance in osmium tetroxide oxidations and the Sharpless asymmetric dihydroxylation or oxidations with TPAP. NMO is commercially supplied both as a monohydrate CHNO·HO and as the anhydrous compound. The monohydrate is used as a solvent for cellulose in the lyocell process to produce cellulose fibers. | 0 | Theoretical and Fundamental Chemistry |
Embalming is the process of preserving human remains by delaying decomposition. This is acquired through the use of embalming fluid, which is a mixture of formaldehyde, methanol, and various other solvents. The most common reasons to preserve the body are for viewing purposes at a funeral, for above-ground interment or distant transportation of the deceased, and for medical or religious practices. | 1 | Applied and Interdisciplinary Chemistry |
Companies may use seawater for this process due to its low cost. The water used is usually brackish water or brine (i.e. a solution with >0.5% salinity). In these cases, additional contaminant chemicals may be present in the water feed. The low voltage DC current still performs electrochlorination. The excess chemicals are left untouched and can be easily discarded. | 0 | Theoretical and Fundamental Chemistry |
A siphon drainage method is being implemented in several expressways as of 2022. Recent studies found that it can reduce groundwater level behind expressway retaining walls, and there was no indication of clogging. This new drainage system is being pioneered as a long-term method to limit leakage hazard in the retaining wall. Siphon drainage is also used in draining unstable slopes, and siphon roof-water drainage systems have been in use since the 1960s. | 1 | Applied and Interdisciplinary Chemistry |
A systematic review by Schuman 2023 finds that most studies on plant volatiles relate to herbivore interactions. Schuman also finds that laboratory studies are overrepresented despite the wide differences in herbivore behaviour between natural and artificial settings. | 1 | Applied and Interdisciplinary Chemistry |
Lysosome-targeting chimeras (LYTACs) have been developed, combining target-binding compounds or antibodies and glycopeptide ligands to stimulate the lysosomal degradation pathway. Unlike the proteasome pathway, this enables the targeted degradation of extracellular and membrane-bound proteins in addition to cytoplasmic ones. Autophagy-targeting chimeras (AUTACs) can be employed to degrade proteins as well as protein aggregates and organelles. AUTAC degradation tags are typically derived from guanine though the particular mechanism of action is still unclear. Autophagosome-tethering compounds (ATTECs) mimic this strategy, directly appending a target protein to the autophagosome membrane for degradation absent the use of a linker. Phosphorylation-inducing chimeric small molecules (PHICS) employ the warhead-linker-recruiter structure to direct phosphorylation of a given target by proximity to a desired kinase. This technique does not necessarily involve protein degradation and may instead be used to modulate protein function to direct or inhibit certain pathways. Further work in the Crews Lab has used chimeric oligonucleotides, the dCas9 protein, and chimeric small molecules to create the TRAFTAC system for generalizable transcription factor degradation. | 1 | Applied and Interdisciplinary Chemistry |
Many PDRC thin films have been developed which have demonstrated very high solar reflectance and heat emittance. However, films with precise patterns or structures are not scalable "due to the cost and technical difficulties inherent in large-scale precise lithography," as per Khan et al., or "due to complex nanoscale lithography/synthesis and rigidity," as per Zhou et al.
The polyacrylate hydrogel film from the later study has broader applications, including potential uses in building construction and large-scale thermal management systems. This research focuses on a polyacrylate film developed for hybrid passive cooling. The film uses sodium polyacrylate, a low-cost industrial material, to achieve high solar reflectance and high mid-infrared emittance. A significant aspect of this material is its ability to absorb atmospheric moisture, enabling it to provide both radiative and evaporative cooling. This dual mechanism allows for efficient cooling even under varying atmospheric conditions, including high humidity or limited access to clear skies.
Some researchers have attempted to overcome this with various methods:
* Zhang et al. (2020), facile microstamping method film on low-cost polymer PDMS, solar reflectance 95%, heat emittance 96%, daytime temperature reduction up to 5.1 °C, "promising for scale-up production."
* Zhang et al. (2021), low-cost film developed with a phase inversion process using cellulose acetate and calcium silicate, solar reflectance 97.3%, heat emittance 97.2%, daytime temperature reduction up to 7.3 °C below ambient (average net cooling power of 90.7 W m), "a low-cost, scalable composite film with novel dendritic cell like structures," tested in Qingdao.
* Fan et al. (2022), eco-friendly preparation of superhydrophobic porous polydimethylsiloxane (PDMS) radiative cooling film, daytime temperature reduction up to 11.52 °C below ambient, "the film is promising to be widely used for long-term cooling for outdoor applications."
* Nie et al. (2022), composite film made of fluorine-free reagents and particles, solar reflectance 85%, heat emittance 95%, daytime temperature reduction average 12.2 °C, manufactured with "a simple preparation process, which has characteristics of low-cost environmental friendliness and excellent machinal durability," tested in Hubei.
* Zhong et al. (2023), hierarchical flexible fibrous cellulose (wood pulp) film, solar reflectance 93.8%, heat emittance 98.3%, daytime temperature reduction up to 11.3 °C below ambient, study is "the first time to realize high crystallinity and hierarchical microstructures in regenerated cellulose materials by the self-assembly of cellulose macromolecules at the molecular level," which "will provide new perspectives for the development of flexible cellulose materials." | 0 | Theoretical and Fundamental Chemistry |
When inhaled, trichloroethylene produces central nervous system depression resulting in general anesthesia. These effects may be mediated by trichloroethylene acting as a positive allosteric modulator of inhibitory GABA and glycine receptors. Its high blood solubility results in a less desirable slower induction of anesthesia. At low concentrations, it is relatively non-irritating to the respiratory tract. Higher concentrations result in tachypnea. Many types of cardiac arrhythmias can occur and are exacerbated by epinephrine (adrenaline). It was noted in the 1940s that TCE reacted with carbon dioxide (CO) absorbing systems (soda lime) to produce dichloroacetylene by dehydrochlorination and phosgene. Cranial nerve dysfunction (especially the fifth cranial nerve) was common when TCE anesthesia was given using CO absorbing systems. ] Muscle relaxation with TCE anesthesia sufficient for surgery was poor. For these reasons as well as problems with hepatotoxicity, TCE lost popularity in North America and Europe to more potent anesthetics such as halothane by the 1960s.
The symptoms of acute non-medical exposure are similar to those of alcohol intoxication, beginning with headache, dizziness, and confusion and progressing with increasing exposure to unconsciousness. Much of what is known about the chronic human health effects of trichloroethylene is based on occupational exposures. Besides the effects to the central nervous system, workplace exposure to trichloroethylene has been associated with toxic effects in the liver and kidney. A history of long-term exposure to high concentrations of trichloroethylene is a suspected environmental risk of Parkinson's disease. | 1 | Applied and Interdisciplinary Chemistry |
In inorganic chemistry, a homoleptic chemical compound is a metal compound with all ligands identical. The term uses the "homo-" prefix to indicate that something is the same for all. Any metal species which has more than one type of ligand is heteroleptic.
Some compounds with names that suggest that they are homoleptic are in fact heteroleptic, because they have ligands in them which are not featured in the name. For instance dialkyl magnesium complexes, which are found in the equilibrium which exists in a solution of a Grignard reagent in an ether, have two ether ligands attached to each magnesium centre. Another example is a solution of trimethyl aluminium in an ether solvent (such as THF); similar chemistry should be expected for a triaryl or trialkyl borane.
It is possible for some ligands such as DMSO to bind with two or more different coordination modes. It would still be reasonable to consider a complex which has only one type of ligand but with different coordination modes to be homoleptic. For example, the complex dichlorotetrakis(dimethyl sulfoxide)ruthenium(II) features DMSO coordinating via both sulfur and oxygen atoms (though this is not homoleptic since there are also chloride ligands). | 0 | Theoretical and Fundamental Chemistry |
The above groundwater flow equations are valid for three dimensional flow. In unconfined aquifers, the solution to the 3D form of the equation is complicated by the presence of a free surface water table boundary condition: in addition to solving for the spatial distribution of heads, the location of this surface is also an unknown. This is a non-linear problem, even though the governing equation is linear.
An alternative formulation of the groundwater flow equation may be obtained by invoking the Dupuit–Forchheimer assumption, where it is assumed that heads do not vary in the vertical direction (i.e., ). A horizontal water balance is applied to a long vertical column with area extending from the aquifer base to the unsaturated surface. This distance is referred to as the saturated thickness, b. In a confined aquifer, the saturated thickness is determined by the height of the aquifer, H, and the pressure head is non-zero everywhere. In an unconfined aquifer, the saturated thickness is defined as the vertical distance between the water table surface and the aquifer base. If , and the aquifer base is at the zero datum, then the unconfined saturated thickness is equal to the head, i.e., b=h.
Assuming both the hydraulic conductivity and the horizontal components of flow are uniform along the entire saturated thickness of the aquifer (i.e., and ), we can express Darcys law in terms of integrated groundwater discharges, Q and Q':
Inserting these into our mass balance expression, we obtain the general 2D governing equation for incompressible saturated groundwater flow:
Where n is the aquifer porosity. The source term, N (length per time), represents the addition of water in the vertical direction (e.g., recharge). By incorporating the correct definitions for saturated thickness, specific storage, and specific yield, we can transform this into two unique governing equations for confined and unconfined conditions:
(confined), where S=Sb is the aquifer storativity and
(unconfined), where S is the specific yield of the aquifer.
Note that the partial differential equation in the unconfined case is non-linear, whereas it is linear in the confined case. For unconfined steady-state flow, this non-linearity may be removed by expressing the PDE in terms of the head squared:
Or, for homogeneous aquifers,
This formulation allows us to apply standard methods for solving linear PDEs in the case of unconfined flow. For heterogeneous aquifers with no recharge, Potential flow methods may be applied for mixed confined/unconfined cases. | 1 | Applied and Interdisciplinary Chemistry |
Lipases in the gastrointestinal tract play a critical role in fat digestion. More than 95% of fat in food consists of triglycerides, which are categorized based on the length of fatty acids connected to glyceride backbone. The length of long-chain triglycerides prevent their absorption through the intestinal mucosa. For that reason lipases in the gastrointestinal tract must hydrolyse it to smaller molecules, free fatty acids and monoglyceride, before absorption can occur. | 1 | Applied and Interdisciplinary Chemistry |
The light compensation point (I) is the light intensity on the light curve where the rate of photosynthesis exactly matches the rate of cellular respiration. At this point, the uptake of CO through photosynthetic pathways is equal to the respiratory release of carbon dioxide, and the uptake of O by respiration is equal to the photosynthetic release of oxygen. The concept of compensation points in general may be applied to other photosynthetic variables, the most important being that of CO concentration – CO compensation point (Γ).Interval of time in day time when light intensity is low due to which net gaseous exchange is zero is called as compensation point.
In assimilation terms, at the compensation point, the net carbon dioxide assimilation is zero. Leaves release CO by photorespiration and cellular respiration, but CO is also converted into carbohydrate by photosynthesis. Assimilation is therefore the difference in the rate of these processes. At a given partial pressure of CO (0.343 hPa in 1980 atmosphere), there is an irradiation at which the net assimilation of CO is zero. For instance, in the early morning and late evenings, the light compensation point I may be reached as photosynthetic activity decreases and respiration increases. The concentration of CO also affects the rates of photosynthesis and photorespiration. Higher CO concentrations favour photosynthesis whereas low CO concentrations favor photorespiration, producing a CO compensation point Γ for a given irradiation. | 0 | Theoretical and Fundamental Chemistry |
According to the Agency for Toxic Substances and Disease Registry (ATSDR) (2007), benzene is both a synthetically made and naturally occurring chemical from processes that include: volcanic eruptions, wild fires, synthesis of chemicals such as phenol, production of synthetic fibers, and fabrication of rubbers, lubricants, pesticides, medications, and dyes. The major sources of benzene exposure are tobacco smoke, automobile service stations, exhaust from motor vehicles, and industrial emissions; however, ingestion and dermal absorption of benzene can also occur through contact with contaminated water. Benzene is hepatically metabolized and excreted in the urine. Measurement of air and water levels of benzene is accomplished through collection via activated charcoal tubes, which are then analyzed with a gas chromatograph. The measurement of benzene in humans can be accomplished via urine, blood, and breath tests; however, all of these have their limitations because benzene is rapidly metabolized in the human body.
Exposure to benzene may lead progressively to aplastic anemia, leukaemia, and multiple myeloma.
OSHA regulates levels of benzene in the workplace. The maximum allowable amount of benzene in workroom air during an 8-hour workday, 40-hour workweek is 1 ppm. As benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the recommended (8-hour) exposure limit of 0.1 ppm. | 1 | Applied and Interdisciplinary Chemistry |
A liquid rheostat or water rheostat or salt water rheostat is a type of variable resistor.
This may be used as a dummy load or as a starting resistor for large slip ring motors.
In the simplest form it consists of a tank containing brine or other electrolyte solution, in which electrodes are submerged to create an electrical load. The electrodes may be raised or lowered into the liquid to respectively increase or decrease the electrical resistance of the load. To stabilize the load, the mixture must not be allowed to boil.
Modern designs use stainless steel electrodes, and sodium carbonate, or other salts, and do not use the container as one electrode. In some designs the electrodes are fixed and the liquid is raised and lowered by an external cylinder or pump. Motor start systems used for frequent and rapid starts and re-starts, thus a high heat load to the rheostats, may include water circulation to external heat exchangers. In such cases anti-freeze and anti-corrosion additives must be carefully chosen to not change the resistance or support the growth of algae or bacteria.
The salt water rheostat operates at unity power factor and presents a resistance with negligible series inductance compared to a wire wound equivalent, and was widely used by generator assemblers, until 20 years ago, as a matter of course. They are still sometimes constructed on-site for the commissioning of large diesel generators in remote places, where discarded oil drums and scaffold tubes may form an improvised tank and electrodes. | 0 | Theoretical and Fundamental Chemistry |
Khimera is a software product from Kintech Lab intended for calculation of the kinetic parameters of microscopic processes, thermodynamic and transport properties of substances and their mixtures in gases, plasmas and also of heterogeneous processes.
The development of a kinetic mechanism is a key stage of present-day technologies for the creation of hi-tech devices and processes in a wide range of fields, such as microelectronics, chemical industry, and the design and optimization of combustion engines and power stations.
Khimera with Chemical WorkBench, another software product from Kintech Lab, allows both the development of complex physical and chemical mechanisms and their validation. Essential feature of Khimera is its user-friendly interface for importing and utilizing the results of quantum-chemical calculations for estimating rate constants of elementary processes and thermodynamic and transport properties. | 0 | Theoretical and Fundamental Chemistry |
Two widely employed applications of migratory insertion of carbonyl groups are hydroformylation and the production of acetic acid by carbonylation of methanol. The former converts alkenes, hydrogen, and carbon monoxide into aldehydes. The production of acetic acid by carbonylation proceeds via two similar industrial processes. More traditional is the Monsanto acetic acid process, which relies on a rhodium-iodine catalyst to transform methanol into acetic acid. This process has been superseded by the Cativa process which uses a related iridium catalyst, [Ir(CO)I] (1). By 2002, worldwide annual production of acetic acid stood at 6 million tons, of which approximately 60% is produced by the Cativa process.
The Cativa process catalytic cycle, shown above, includes both insertion and de-insertion steps. The oxidative addition reaction of methyl iodide with (1) involves the formal insertion of the iridium(I) centre into the carbon-iodine bond, whilst step (3) to (4) is an example of migratory insertion of carbon monoxide into the iridium-carbon bond. The active catalyst species is regenerated by the reductive elimination of acetyl iodide from (4), a de-insertion reaction. | 0 | Theoretical and Fundamental Chemistry |
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