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There are over 150 natural products that are presumed to undergo a [4+2] Diels–Alder type cycloaddition, belonging to classes such as: polyketides, terpenoids, phenylpropanoids, and alkaloids. The Diels–Alder cycloaddition involves the overlap of the p-orbitals of two unsaturated systems: a 1,3-diene and dienophile. The conjugated diene reacts with the dienophile to form a cyclic product in a concerted fashion. This reaction is widely used in synthesis due to its facile nature and reio- and stereoselectivity under mild conditions. This reaction is very useful for forming carbon-carbon bonds, four-chiral centers, and quaternary stereogenic centers.[4,5] Natural products that are constructed biosynthetically via a Diels–Alder reaction occur both uncatalyzed and catalyzed by enzymes such as Diels–Alderase and RNA Diels-Alderase. In their report of the isolation and structural characterization of the natural product, Lee and co-worker proposed that the biosynthesis of torreyanic acid proceeded via an endo-selective [4+2] cycloaddition with a Diels–Alder dimerization of 2H-pyran monomers 2a and 2b. Key observations that indicate a natural product is biosynthesized via a Diels–Alder reaction include: (a) isolation of an adduct with its corresponding precursor, (b) presence of adducts and their regio- and diastereoisomers, (c) a non-enzymatic feasibility of a likely cycloaddition and (d) chirality of the adducts.
The proposed biosynthetic pathway is thought to involve: (a) an electrocyclic ring closure of 3, followed by (b) an enzymatic oxidation to furnish diastereomers 2a and 2b, and finally (c) a [4+2] cyclodimerization to generate torreyanic acid 1. The biosynthesis of torreyanic acid was studied extensively by Poroco et al. in their efforts to execute the first total synthesis of the natural product. Given that monomer ambuic acid was also isolated from the same endophytic fungus Pestalotiopsis microspora, it is further evidence that a Diels–Alder reaction is involved in the biosynthesis of torreyanic acid. The biomimetic synthesis of torreyanic acid involved the rapid conversion of aldehyde 3 to syn- and anti-pyrans 2a and 2b via an oxaelectrocyclization, with the pyrans existising as an equilibrium mixture. Next, a spontaneous Diels–Alder dimerization of 2a and 2b proceeded with complete and regio- and diastereoselectivity to furnish the endo-adduct, torreyanic acid 1. Further, a retro-Diels–Alder reaction carried out at 60 °C proved that torreyanic acid originated from 2a and 2b and ¹H-NMR spectra showed that no aldehyde 3 was observed. The stable transition state in the Diels–Alder reaction (shown with 2a and 2b) has an energy of 9.4kcal/mol, and coupled with the high reactivity of the diastereomers, it is indicated that the Diels–Alder reaction proceeds in a non-enzymatic manner. | 0 | Theoretical and Fundamental Chemistry |
After successful formation of a stable nucleus, a growth stage ensues in which free particles (atoms or molecules) adsorb onto the nucleus and propagate its crystalline structure outwards from the nucleating site. This process is significantly faster than nucleation. The reason for such rapid growth is that real crystals contain dislocations and other defects, which act as a catalyst for the addition of particles to the existing crystalline structure. By contrast, perfect crystals (lacking defects) would grow exceedingly slowly. On the other hand, impurities can act as crystal growth inhibitors and can also modify crystal habit. | 0 | Theoretical and Fundamental Chemistry |
Many supramolecular systems require their components to have suitable spacing and conformations relative to each other, and therefore easily employed structural units are required.
*Commonly used spacers and connecting groups include polyether chains, biphenyls and triphenyls, and simple alkyl chains. The chemistry for creating and connecting these units is very well understood.
*nanoparticles, nanorods, fullerenes and dendrimers offer nanometer-sized structure and encapsulation units.
*Surfaces can be used as scaffolds for the construction of complex systems and also for interfacing electrochemical systems with electrodes. Regular surfaces can be used for the construction of self-assembled monolayers and multilayers.
* The understanding of intermolecular interactions in solids has undergone a major renaissance via inputs from different experimental and computational methods in the last decade. This includes high-pressure studies in solids and "in situ" crystallization of compounds which are liquids at room temperature along with the use of electron density analysis, crystal structure prediction and DFT calculations in solid state to enable a quantitative understanding of the nature, energetics and topological properties associated with such interactions in crystals. | 0 | Theoretical and Fundamental Chemistry |
Protein methylation typically takes place on arginine or lysine amino acid residues in the protein sequence. Arginine can be methylated once (monomethylated arginine) or twice, with either both methyl groups on one terminal nitrogen (asymmetric dimethylarginine) or one on both nitrogens (symmetric dimethylarginine), by protein arginine methyltransferases (PRMTs). Lysine can be methylated once, twice, or three times by lysine methyltransferases. Protein methylation has been most studied in the histones. The transfer of methyl groups from S-adenosyl methionine to histones is catalyzed by enzymes known as histone methyltransferases. Histones that are methylated on certain residues can act epigenetically to repress or activate gene expression. Protein methylation is one type of post-translational modification. | 0 | Theoretical and Fundamental Chemistry |
A dipole-induced dipole interaction (Debye force) is due to the approach of a molecule with a permanent dipole to another non-polar molecule with no permanent dipole. This approach causes the electrons of the non-polar molecule to be polarized toward or away from the dipole (or "induce" a dipole) of the approaching molecule. Specifically, the dipole can cause electrostatic attraction or repulsion of the electrons from the non-polar molecule, depending on orientation of the incoming dipole. Atoms with larger atomic radii are considered more "polarizable" and therefore experience greater attractions as a result of the Debye force. | 0 | Theoretical and Fundamental Chemistry |
With the advance of digital technologies, real time processing and applications of PIV became possible. For instance, GPUs can be used to speed up substantially the direct of Fourier transform based correlations of single interrogation windows. Similarly multi-processing, parallel or multi-threading processes on several CPUs or multi-core CPUs are beneficial for the distributed processing of multiple interrogation windows or multiple images. Some of the applications use real time image processing methods, such as FPGA based on-the-fly image compression or image processing. More recently, the PIV real time measurement and processing capabilities are implemented for the future use in active flow control with the flow based feedback. | 1 | Applied and Interdisciplinary Chemistry |
In physics, terahertz time-domain spectroscopy (THz-TDS) is a spectroscopic technique in which the properties of matter are probed with short pulses of terahertz radiation. The generation and detection scheme is sensitive to the sample's effect on both the amplitude and the phase of the terahertz radiation. | 0 | Theoretical and Fundamental Chemistry |
Nagai was born in Myōdō District, Awa Province in what is now Tokushima Prefecture, as the son of a doctor and started studying rangaku medicine at the Dutch Medical School of Nagasaki (Igaku-Denshujo) in 1864. While in Nagasaki, he made the acquaintance of Ōkubo Toshimichi, Itō Hirobumi, and other future leaders of the Meiji government. | 0 | Theoretical and Fundamental Chemistry |
The consideration of energy quality was a fundamental driver of industrialization from the 18th through 20th centuries. Consider for example the industrialization of New England in the 18th century. This refers to the construction of textile mills containing power looms for weaving cloth. The simplest, most economical and straightforward source of energy was provided by water wheels, extracting energy from a millpond behind a dam on a local creek. If another nearby landowner also decided to build a mill on the same creek, the construction of their dam would lower the overall hydraulic head to power the existing waterwheel, thus hurting power generation and efficiency. This eventually became an issue endemic to the entire region, reducing the overall profitability of older mills as newer ones were built. The search for higher quality energy was a major impetus throughout the 19th and 20th centuries. For example, burning coal to make steam to generate mechanical energy would not have been imaginable in the 18th century; by the end of the 19th century, the use of water wheels was long outmoded. Similarly, the quality of energy from electricity offers immense advantages over steam, but did not become economic or practical until the 20th century.
The above example focused on the economic impacts of the exploitation of energy. A similar scenario plays out in nature and biology, where living organisms can extract energy of varying quality from nature, ultimately driven by solar energy as the primary driver of thermodynamic disequilibrium on Earth. The ecological balance of ecosystems is predicated on the energy flows through the system. For example, rainwater drives the erosion of rocks, which liberates chemicals that can be used as nutrients; these are taken up by plankton, using solar energy to grow and thrive; whales obtain energy by eating plankton, thus indirectly using solar energy as well, but this time in a much more concentrated and higher quality form.
Water wheels are also driven by rainwater, via the solar evaporation-condensation water cycle; thus ultimately, industrial cloth-making was driven by the day-night cycle of solar irradiation. This is a holistic view of energy sources as a system-in-the-large. Thus, discussions of energy quality can sometimes be found in the Humanities, such as dialectics, Marxism and postmodernism. This is effectively because disciplines such as economics failed to recognize the thermodynamic inputs into the economy (now recognized as thermoeconomics), while disciplines such as physics and engineering were unable to address either the economic impacts of human activity, or the impacts of thermodynamic flows in biological ecosystems. Thus, the broad-stroke, global system-in-the-large discussions were taken up by those best trained for the nebulous, non-specific reasoning that such complex systems require. The resulting mismatch of vocabulary and outlook across disciplines can lead to considerable contention. | 0 | Theoretical and Fundamental Chemistry |
Peroxide fusion is used to prepare samples for inductively coupled plasma (ICP), atomic absorption (AA) analysis and wet chemistry. Sodium peroxide (NaO) is used to oxidize the sample that becomes soluble in a diluted acid solution. This method allows complete dissolution of numerous refractory compounds like chromite, magnetite, ilmenite, rutile, and even silicon, carbides, alloys, noble metals and materials with high sulfide contents.
Peroxide fusion can be performed either manually or with automated systems. The latter have the advantage of increasing productivity, improving safety, maintaining repeatable preparation conditions, and avoiding spattering as well as cross-contamination. | 0 | Theoretical and Fundamental Chemistry |
If we attempt to build a densely packed collection of spheres, we will be tempted to always place the next sphere in a hollow between three packed spheres. If five spheres are assembled in this way, they will be consistent with one of the regularly packed arrangements described above. However, the sixth sphere placed in this way will render the structure inconsistent with any regular arrangement. This results in the possibility of a random close packing of spheres which is stable against compression. Vibration of a random loose packing can result in the arrangement of spherical particles into regular packings, a process known as granular crystallisation. Such processes depend on the geometry of the container holding the spherical grains.
When spheres are randomly added to a container and then compressed, they will generally form what is known as an "irregular" or "jammed" packing configuration when they can be compressed no more. This irregular packing will generally have a density of about 64%. Recent research predicts analytically that it cannot exceed a density limit of 63.4% This situation is unlike the case of one or two dimensions, where compressing a collection of 1-dimensional or 2-dimensional spheres (that is, line segments or circles) will yield a regular packing. | 0 | Theoretical and Fundamental Chemistry |
The working fluid's properties are essential for the full description of thermodynamic systems. Although working fluids have many physical properties which can be defined, the thermodynamic properties which are often required in engineering design and analysis are few. Pressure, temperature, enthalpy, entropy, specific volume, and internal energy are the most common.
If at least two thermodynamic properties are known, the state of the working fluid can be defined. This is usually done on a property diagram which is simply a plot of one property versus another.
When the working fluid passes through engineering components such as turbines and compressors, the point on a property diagram moves due to the possible changes of certain properties. In theory therefore it is possible to draw a line/curve which fully describes the thermodynamic properties of the fluid. In reality however this can only be done if the process is reversible. If not, the changes in property are represented as a dotted line on a property diagram. This issue does not really affect thermodynamic analysis since in most cases it is the end states of a process which are sought after. | 0 | Theoretical and Fundamental Chemistry |
The electric charge per mole of elementary charges is a constant called the Faraday constant, F, whose value had been essentially known since 1834 when Michael Faraday published his works on electrolysis. In 1910, Robert Millikan obtained the first measurement of the charge on an electron, −e. The quotient F/e provided an estimate of the Avogadro constant.
The classic experiment is that of Bower and Davis at NIST, and relies on dissolving silver metal away from the anode of an electrolysis cell, while passing a constant electric current I for a known time t. If m is the mass of silver lost from the anode and A the atomic weight of silver, then the Faraday constant is given by:
The NIST scientists devised a method to compensate for silver lost from the anode by mechanical causes, and conducted an isotope analysis of the silver used to determine its atomic weight. Their value for the conventional Faraday constant was F = , which corresponds to a value for the Avogadro constant of : both values have a relative standard uncertainty of . | 0 | Theoretical and Fundamental Chemistry |
In preparing a Walsh diagram, the geometry of a molecule must first be optimized for example using the Hartree–Fock (HF) method for approximating the ground-state wave function and ground-state energy of a quantum many-body system. Next, single-point energies are performed for a series of geometries displaced from the above-determined equilibrium geometry. Single-point energies (SPEs) are calculations of potential energy surfaces of a molecule for a specific arrangement of the atoms in that molecule. In conducting these calculations, bond lengths remain constant (at equilibrium values) and only the bond angle should be altered from its equilibrium value. The single-point computation for each geometry can then be plotted versus bond angle to produce the representative Walsh diagram. | 0 | Theoretical and Fundamental Chemistry |
Among all the lithological indicators, ice-rafted debris (IRD) is the most useful tool to reconstruct paleoclimate. High concentrations of IRD evidence the glacial intervals during which icebergs likely traveled far from Polar Regions。In the South Pacific, IRD has been used as proxy for glaciation in the Cenozoic and a glaciation history has been established for the Subantarctic region. The history is also supported by the foraminifera species diversity data.
In the western Arctic Ocean, investigation of ice-rafted debris has identified at least six glacial intervals in the last 1 million years.
Deep-sea cores with high rates of sedimentation allow high resolution analyses of IRD. In the North Pacific, records of IRD have delineated interstadials (short time thermal event during glacial interval), which could be correlated with the similar events in the North Atlantic. | 0 | Theoretical and Fundamental Chemistry |
The heads of the laboratory were the four consecutive Waynflete Professors of Chemistry:
# William Henry Perkin, Jr., from 1912 to 1929;
# Sir Robert Robinson, from 1930 to 1954. Nobel Prize winner, 1947;
# Sir Ewart Jones, from 1954 to 1978;
# Sir Jack Baldwin, from 1978 to 2003.
During its 87-year working life, the laboratory had an extremely distinguished career; it can claim a stake in shaping the scientific careers of two Nobel Laureates, namely Lord Todd (1957) and Sir John W. Cornforth (1975) who passed their formative years as young chemists in the laboratories. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide is marketed widely throughout the world, including in the United States, Canada, Europe, Australia, New Zealand, South Africa, Central and South America, East and Southeast Asia, India, and the Middle East. | 0 | Theoretical and Fundamental Chemistry |
The tritium breeding blanket (also known as a fusion blanket, lithium blanket or simply blanket), is a key part of many proposed fusion reactor designs. It serves several purposes; primarily it is to produce (or "breed") further tritium fuel for the nuclear fusion reaction, which owing to the scarcity of tritium would not be available in sufficient quantities, through the reaction of neutrons with lithium in the blanket. The blanket may also act as a cooling mechanism, absorbing the energy from the neutrons produced by the reaction between deuterium and tritium ("D-T"), and further serves as shielding, preventing the high-energy neutrons from escaping to the area outside the reactor and protecting the more radiation-susceptible portions, such as ohmic or superconducting magnets, from damage.
Of these three duties, it is only the breeding portion that cannot be replaced by other means. For instance, a large quantity of water makes an excellent cooling system and neutron shield, as in the case of a conventional nuclear reactor. However, tritium is not a naturally occurring resource, and thus is difficult to obtain in sufficient quantity to run a reactor through other means, so if commercial fusion using the D-T cycle is to be achieved, successful breeding of the tritium in commercial quantities is a requirement.
ITER runs a major effort in blanket design and will test a number of potential solutions. Concepts for the breeder blanket include helium-cooled lithium lead (HCLL), helium-cooled pebble bed (HCPB), and water-cooled lithium lead (WCLL) methods. Six different tritium breeding systems, known as Test Blanket Modules (TBM) wil be tested in ITER.
Some breeding blanket designs are based on lithium containing ceramics, with a focus on lithium titanate and lithium orthosilicate. These materials, mostly in a pebble form, are used to produce and extract tritium and helium; must withstand high mechanical and thermal loads; and should not become excessively radioactive upon completion of their useful service life.
To date no large-scale breeding system has been attempted, and it is an open question whether such a system is possible to create.
A fast breeder reactor uses a blanket of uranium or thorium. | 0 | Theoretical and Fundamental Chemistry |
The AMCA Certified Ratings Program (CRP) is a program which allows all manufacturers of air movement and air control devices to obtain an AMCA Seal when their equipment has been tested and rated in accordance with recognized test standards.
The goal of the AMCA CRP is to ensure that a manufacturers product lines have been tested and rated in conformance with an approved test standard and rating requirement. Only after the product has been tested and the manufacturers cataloged ratings have been submitted to and approved by AMCA Internationals staff, can performance seals be displayed in literature and on equipment. Additionally, each certified / licensed product line is subject to continuing check tests every three years in AMCA Internationals Laboratory or one of AMCA International's Independent Accredited laboratories. | 1 | Applied and Interdisciplinary Chemistry |
Liquid water and ice, for example, form a frigorific mixture at 0 °C or 32 °F. This mixture was once used to define 0 °C. That temperature is now defined as the triple point of Water with well-defined isotope ratios. A mixture of ammonium chloride, water, and ice form a frigorific mixture at about −17.8 °C or 0 °F. This mixture was once used to define 0 °F. | 0 | Theoretical and Fundamental Chemistry |
Many varieties of coordination cages exist.
In general, coordination cages are either homoleptic or heteroleptic. That is, they assembled either from a single type of ligand or multiple types. Generic coordination cages are often classified just as coordination complexes, with a MxLy formula. Heteroleptic complexes typically form more complex geometries, as illustrated with the following cages: [M(L)] and [M(μ-L)(μ-L)](BF). The former cage is assembled from a 2:3 ratio of metal (M) and ligand (L), where the metal can be copper, zinc, or cadmium. This cage is homoleptic and assembles into a hexadecanuclear framework. The second cage is assembled from a 4:1:4 ratio of MBF, the ligand L and the ligand L. This cage is heteroleptic and assembles into a dodecanuclear cuboctohedral framework. Four of the triangular faces of this shape are occupied by L, which acts as a triply bridging ligand. The twelve remaining edges are spanned with the edge ligands, L. Ligands are the building blocks of coordination cages, and the choice and ratio of ligands determine the final structure. Due to their highly symmetrical nature, coordination cages are also often referred to by their geometry. The geometry of high-symmetry cages is often that of Platonic or Archimedean solids; sometimes cages are casually referred to by their geometries.
Of the named categories of coordination cages, cavitand cages and metalloprisms are some of the more common. | 0 | Theoretical and Fundamental Chemistry |
Cells can metabolize DHA to products that possess an oxo (i.e. ketone) residue. These products include 13-oxo-DHA (termed EFOXD6) and 17-oxo-DHA (termed 18-EFOXD6). Both oxo metabolites possess anti-inflammatory activity as assesses in in vitro systems (see ). | 1 | Applied and Interdisciplinary Chemistry |
-CH-) has replaced a peptide bond in the peptide analogue sequence. To some extent the chemical structure of phosphinic peptides is similar to that of intermediates which are produced in hydrolysis of peptides by proteolytic enzymes. The hypothesis has been made that these pseudo-peptides mimic the structure of the enzyme substrates in their transition state and crystallography of zinc proteases in complex with phosphinic peptides supports that hypothesis. | 1 | Applied and Interdisciplinary Chemistry |
Testicular tissue-derived seipin is essential for male fertility by modulating testicular phospholipid homeostasis. The lack of seipin in germ cells results in complete male infertility and teratozoospermia. Spermatids devoid of seipin in germ cells are morphologically abnormal with large ectopic lipid droplets and aggregate in dysfunctional clusters. Elevated levels of phosphatidic acid accompanied with an altered ratio of polyunsaturated to monounsaturated and saturated fatty acids show impaired phospholipid homeostasis during spermiogenesis. | 1 | Applied and Interdisciplinary Chemistry |
Fas receptor has been shown to interact with:
* Caspase 8,
* Caspase 10,
* CFLAR,
* FADD,
* Fas ligand,
* PDCD6, and
* Small ubiquitin-related modifier 1. | 1 | Applied and Interdisciplinary Chemistry |
Sevoflurane is a potent vasodilator, as such it induces a dose dependent reduction in blood pressure and cardiac output. It is a bronchodilator, however, in patients with pre-existing lung pathology, it may precipitate coughing and laryngospasm. It reduces the ventilatory response to hypoxia and hypercapnia, and impedes hypoxic pulmonary vasoconstriction. Sevoflurane vasodilatory properties also cause it to increase intracranial pressure and cerebral blood flow. However, it reduces cerebral metabolic rate. | 1 | Applied and Interdisciplinary Chemistry |
Oxidation of RIS occurs rapidly under ambient conditions This is especially true for iron monosulfides, which have a higher surface area than iron disulfides.
Monosulfidic material will change from pitch black to light brown within minutes of being exposed to air (see images below). Consequently, acid sulfate soil samples should be immediately cooled to < 4°C to slow oxidation; and samples containing monosulfidic material should be immediately frozen (e.g., using a portable freezer or liquid nitrogen). The use of dry ice is recommended as the gaseous carbon dioxide should further hinder oxidation. Samples should be tested for ABA within 24 h of sampling. Otherwise, additional preservation techniques (e.g., freezing or drying at > 85°C) should be used. | 0 | Theoretical and Fundamental Chemistry |
Copurification procedures, such as co-immunoprecipitation, are commonly used to analyze interactions between proteins. Copurification is one method used to map the interactome of living organisms. | 0 | Theoretical and Fundamental Chemistry |
Yuan-Cheng "Bert" Fung (September 15, 1919 – December 15, 2019) was a Chinese-American bioengineer and writer. He is regarded as a founding figure of bioengineering, tissue engineering, and the "Founder of Modern Biomechanics". | 1 | Applied and Interdisciplinary Chemistry |
Phenylboronic acid is soluble in most polar organic solvents and is poorly soluble in hexanes and carbon tetrachloride. This planar compound has idealized C molecular symmetry. The boron atom is sp-hybridized and contains an empty p-orbital. The orthorhombic crystals use hydrogen bonding to form units made up of two molecules. These dimeric units are combined to give an extended hydrogen-bonded network. The molecule is planar with a minor bend around the C-B bond of 6.6° and 21.4° for the two PhB(OH) molecules. | 0 | Theoretical and Fundamental Chemistry |
Arsenic biochemistry refers to biochemical processes that can use arsenic or its compounds, such as arsenate. Arsenic is a moderately abundant element in Earth's crust, and although many arsenic compounds are often considered highly toxic to most life, a wide variety of organoarsenic compounds are produced biologically and various organic and inorganic arsenic compounds are metabolized by numerous organisms. This pattern is general for other related elements, including selenium, which can exhibit both beneficial and deleterious effects. Arsenic biochemistry has become topical since many toxic arsenic compounds are found in some aquifers, potentially affecting many millions of people via biochemical processes. | 1 | Applied and Interdisciplinary Chemistry |
The bonding between alkenes and transition metals is described by the Dewar–Chatt–Duncanson model, which involves donation of electrons in the pi-orbital on the alkene to empty orbitals on the metal. This interaction is reinforced by back bonding that entails sharing of electrons in other metal orbitals into the empty pi-antibonding level on the alkene. Early metals of low oxidation state (Ti(II), Zr(II), Nb(III) etc.) are strong pi donors, and their alkene complexes are often described as metallacyclopropanes. Treatment of such species with acids gives the alkanes. Late metals (Ir(I), Pt(II)), which are poorer pi-donors, tend to engage the alkene as a Lewis acid–Lewis base interaction. Similarly, CF is a stronger pi-acceptor than CH, as reflected in metal-carbon bond distances. | 0 | Theoretical and Fundamental Chemistry |
Cell–cell fusogens are glycoproteins that facilitate the fusion of cell to cell membranes. Cell–cell fusion is critical for the merging of gamete genomes and the development of organs in multicellular organisms. Cell-cell fusion occurs when both actin cytoskeleton and fusogenic proteins properly rearrange across the cell membrane. This process is led by actin-propelled membrane protrusions. | 1 | Applied and Interdisciplinary Chemistry |
Scandium(III) sulfide is a chemical compound of scandium and sulfur with the chemical formula ScS. It is a yellow solid. | 0 | Theoretical and Fundamental Chemistry |
The total synthesis of the complex biomolecule vitamin B was accomplished in two different approaches by the collaborating research groups of Robert Burns Woodward at Harvard and Albert Eschenmoser at ETH in 1972. The accomplishment required the effort of no less than 91 postdoctoral researchers (Harvard: 77, ETH: 14), and 12 Ph.D. students (at ETH) from 19 different nations over a period of almost 12 years. The synthesis project induced and involved a major change of paradigm in the field of natural product synthesis. | 0 | Theoretical and Fundamental Chemistry |
Since IEC and HIC conditions are the closest ones to physiological conditions which are fit for maintaining biological activity, the combinations of them are widely used in the separation of biological products. IEC/HIC MMC has improved separation power and selectivity on the grounds that it applies both electrostatic and hydrophobic interactions. One such example is [http://www.bio-rad.com/en-us/product/mixed-mode-media/nuvia-cprime-media Nuvia(tm) cPrime(tm)], from [http://www.bio-rad.com/ Bio-Rad Laboratories]. | 0 | Theoretical and Fundamental Chemistry |
The Voigt functions U, V, and H (sometimes called the line broadening function) are defined by
where
erfc is the complementary error function, and w(z) is the Faddeeva function. | 0 | Theoretical and Fundamental Chemistry |
Cell–cell fusogens are proteins that promote plasma membrane fusion among different cells. To be considered a fusogen, it must be required for fusion, fuse unfamiliar membranes, and be present on the fusing membrane when need be. These cells include but are not limited too: gametes, trophoblasts, epithelial, and other developmental cells. These fusogens mediate cell-cell fusion and can perform neuron repairs, auto-fusion, and sealing of the phagosomes. Although these proteins promote similar functions among cells, they have individual mechanisms. These are called unilateral (one fusing membrane needed to be present) and bilateral (same or different fusogens present at both membranes) mechanisms. Most fusogen mechanisms begin with hemifusion, but the mechanism for cell-cell fusogens consists of four separate steps. | 1 | Applied and Interdisciplinary Chemistry |
The fourth annual Empowering Women in Organic Chemistry Conference was a hybrid meeting on Thursday, June 23, and Friday, June 24, 2022. | 0 | Theoretical and Fundamental Chemistry |
Researchers in the 1960s investigating brown adipose tissue, found that in addition to producing more heat than typical of other tissues, brown adipose tissue seemed to short circuit, or uncouple, respiration coupling. Uncoupling protein 1 was discovered in 1976 by David G. Nicholls, Vibeke Bernson, and Gillian Heaton, and the discovery was published in 1978 and shown to be the protein responsible for this uncoupling effect. UCP1 was later purified for the first time in 1980 and was first cloned in 1988.
Uncoupling protein two (UCP2), a homolog of UCP1, was identified in 1997. UCP2 localizes to a wide variety of tissues, and is thought to be involved in regulating reactive oxygen species (ROS). In the past decade, three additional homologs of UCP1 have been identified, including UCP3, UCP4, and UCP5 (also known as BMCP1 or SLC25A14). | 1 | Applied and Interdisciplinary Chemistry |
Soluble adenylyl cyclase (sAC) is a regulatory cytosolic enzyme present in almost every cell. sAC is a source of cyclic adenosine 3’,5’ monophosphate (cAMP) – a second messenger that mediates cell growth and differentiation in organisms from bacteria to higher eukaryotes. sAC differentiates from the transmembrane adenylyl cyclase (tmACs) – an important source of cAMP; in that sAC is regulated by bicarbonate anions and it is dispersed throughout the cell cytoplasm. sAC has been found to have various functions in physiological systems different from that of the tmACs. | 1 | Applied and Interdisciplinary Chemistry |
The term surface enhanced Raman spectroscopy implies that it provides the same information that traditional Raman spectroscopy does, simply with a greatly enhanced signal. While the spectra of most SERS experiments are similar to the non-surface enhanced spectra, there are often differences in the number of modes present. Additional modes not found in the traditional Raman spectrum can be present in the SERS spectrum, while other modes can disappear. The modes observed in any spectroscopic experiment are dictated by the symmetry of the molecules and are usually summarized by Selection rules. When molecules are adsorbed to a surface, the symmetry of the system can change, slightly modifying the symmetry of the molecule, which can lead to differences in mode selection.
One common way in which selection rules are modified arises from the fact that many molecules that have a center of symmetry lose that feature when adsorbed to a surface. The loss of a center of symmetry eliminates the requirements of the mutual exclusion rule, which dictates that modes can only be either Raman or infrared active. Thus modes that would normally appear only in the infrared spectrum of the free molecule can appear in the SERS spectrum.
A molecule's symmetry can be changed in different ways depending on the orientation in which the molecule is attached to the surface. In some experiments, it is possible to determine the orientation of adsorption to the surface from the SERS spectrum, as different modes will be present depending on how the symmetry is modified. | 0 | Theoretical and Fundamental Chemistry |
Fluoropolymers are advantageous as binders due to their high density (yielding high detonation velocity) and inert chemical behavior (yielding long shelf stability and low aging). They are somewhat brittle, as their glass transition temperature is at room temperature or above. This limits their use to insensitive explosives (e.g. TATB) where the brittleness does not have detrimental effects on safety. They are also difficult to process. | 0 | Theoretical and Fundamental Chemistry |
The studies of metal-benzyne complexes were initiated with the preparation of zirconocene complex by reaction diphenylzirconocene with trimethylphosphine.
:CpZrPh + PMe → CpZr(CH)(PMe) + PhH
The preparation of Ta(η-CMe)(CH)Me proceeds similarly, requiring the phenyl complex Ta(η-CMe)(CH)Me. This complex is prepared by treatment of Ta(η-CMe)MeCl with phenyllithium. Upon heating, this complex eliminates methane, leaving the benzyne complex:
:Ta(η-CMe)(CH)Me → Ta(η-CMe)(CH)Me + CH
The second example of a benzyne complex is Ni(η-CH)(dcpe) (dcpe = CyPCHCHPCy). It is produced by dehalogenation of the bromophenyl complex NiCl(CHBr-2)(dcpe) with sodium amalgam. Its coordination geometry is close to trigonal planar. | 0 | Theoretical and Fundamental Chemistry |
Methyl isocyanate is usually manufactured by the reaction of monomethylamine and phosgene. For large-scale production it is advantageous to combine these reactants at higher temperature in the gas phase. A mixture of methyl isocyanate and two moles of hydrogen chloride is formed, but N-methylcarbamoyl chloride (MCC) forms as the mixture is condensed, leaving one mole of hydrogen chloride as a gas.
The methyl isocyanate is obtained by treating the MCC with a tertiary amine, such as N,N-dimethylaniline, or with pyridine, or by separating it by using distillation techniques.
Methyl isocyanate is also manufactured from N-methylformamide and air. In the latter process, it is immediately consumed in a closed-loop process to make methomyl. Other manufacturing methods have been reported. | 0 | Theoretical and Fundamental Chemistry |
Extending their work on MOS technology, Atalla and Kahng next did pioneering work on hot carrier devices, which used what would later be called a Schottky barrier. The Schottky diode, also known as the Schottky-barrier diode, was theorized for years, but was first practically realized as a result of the work of Atalla and Kahng during 19601961. They published their results in 1962 and called their device the "hot electron" triode structure with semiconductor-metal emitter. It was one of the first metal-base transistors. The Schottky diode went on to assume a prominent role in mixer applications. | 0 | Theoretical and Fundamental Chemistry |
Samples of proteorhodopsin expressing bacteria have been obtained from the Eastern Pacific Ocean, Central North Pacific Ocean and Southern Ocean, Antarctica. Subsequently, genes of proteorhodopsin variants have been identified in samples from the Mediterranean, Red Seas, the Sargasso Sea, and Sea of Japan, and the North Sea.
Proteorhodopsin variants are not spread randomly, but disperse along depth gradients based on the maximal absorption-tuning of the particular holoprotein sequence; this is mainly due to the electromagnetic absorption by water which creates wavelength gradients relative to depth. Oxyrrhis marina is a dinoflagellate protist with green-absorbing proteorhodopsin (a result of the L109 Group) that exists mostly in shallow tide pools and shores, where green light is still available. Karlodinium micrum, another dinolagelate, expresses a blue tuned proteorhodopsin (E109) which may be related to its deep water vertical migrations. O. marina was originally believed to be a heterotroph, however the proteorhodopsin may well partake in a functionally significant manner, as it was the most abundantly expressed nuclear gene and, furthermore, is dispersed unevenly in the organism, suggesting some organelle membrane function. Previously the only known eukaryotic solar energy transducing proteins were Photosystem I and Photosystem II. It has been hypothesized that lateral gene transfer is the method by which proteorhodopsin has made its way into numerous phyla. Bacteria, archaea and eukarya all colonize the photic zone where they come to light; Proteorhodopsin has been able to disseminate through this zone, but not to other portions of the water column. | 0 | Theoretical and Fundamental Chemistry |
Air pollutant concentrations, as measured or as calculated by air pollution dispersion modeling, must often be converted or corrected to be expressed as required by the regulations issued by various governmental agencies. Regulations that define and limit the concentration of pollutants in the ambient air or in gaseous emissions to the ambient air are issued by various national and state (or provincial) environmental protection and occupational health and safety agencies.
Such regulations involve a number of different expressions of concentration. Some express the concentrations as ppmv (parts per million by volume) and some express the concentrations as mg/m (milligrams per cubic meter), while others require adjusting or correcting the concentrations to reference conditions of moisture content, oxygen content or carbon dioxide content. This article presents methods for converting concentrations from ppmv to mg/m (and vice versa) and for correcting the concentrations to the required reference conditions.
All of the concentrations and concentration corrections in this article apply only to air and other gases. They are not applicable for liquids. | 1 | Applied and Interdisciplinary Chemistry |
The β-adrenergic receptor antagonists all have similar therapeutic and pharmacodynamic actions in patients with cardiovascular disorders. They vary greatly in their pharmacokinetic properties, as they demonstrate a high range of values in plasma protein binding, the percent of drug eliminated by metabolism or unchanged in the urine and hepatic extraction ratio. Each of the β-blockers possesses at least one chiral centre and a high degree of enantioselectivity when binding to the β-adrenergic receptor. For those β-blockers containing a single chiral centre, the (-) enantiomer has a much higher affinity in binding to the β-adrenergic receptor than the (+) enantiomer. All β-blockers used systemically are delivered as racemate, except for timolol. | 1 | Applied and Interdisciplinary Chemistry |
Improvements were gradual over the 1960s. This was also the reason that costs remained high, because space users were willing to pay for the best possible cells, leaving no reason to invest in lower-cost, less-efficient solutions. The price was determined largely by the semiconductor industry; their move to integrated circuits in the 1960s led to the availability of larger boules at lower relative prices. As their price fell, the price of the resulting cells did as well. These effects lowered 1971 cell costs to some $100 per watt.
In late 1969 Elliot Berman joined Exxon's task force which was looking for projects 30 years in the future and in April 1973 he founded Solar Power Corporation (SPC), a wholly owned subsidiary of Exxon at that time. The group had concluded that electrical power would be much more expensive by 2000, and felt that this increase in price would make alternative energy sources more attractive. He conducted a market study and concluded that a price per watt of about $20/watt would create significant demand. The team eliminated the steps of polishing the wafers and coating them with an anti-reflective layer, relying on the rough-sawn wafer surface. The team also replaced the expensive materials and hand wiring used in space applications with a printed circuit board on the back, acrylic plastic on the front, and silicone glue between the two, "potting" the cells. Solar cells could be made using cast-off material from the electronics market. By 1973 they announced a product, and SPC convinced Tideland Signal to use its panels to power navigational buoys, initially for the U.S. Coast Guard. | 0 | Theoretical and Fundamental Chemistry |
After the discovery of parity non-conservation (see History), it was found that, in beta decay, electrons are emitted mostly with negative helicity, i.e., they move, naively speaking, like left-handed screws driven into a material (they have negative longitudinal polarization). Conversely, positrons have mostly positive helicity, i.e., they move like right-handed screws. Neutrinos (emitted in positron decay) have negative helicity, while antineutrinos (emitted in electron decay) have positive helicity.
The higher the energy of the particles, the higher their polarization. | 0 | Theoretical and Fundamental Chemistry |
Himalayan Rivers Development envisages construction of storage reservoirs on the main Ganga and the Brahmaputra and their principal tributaries in India and Nepal along with inter-linking canal system to transfer surplus flows of the eastern tributaries of the Ganga to the West apart from linking of the main Brahmaputra with the Ganga. Apart from providing irrigation to an additional area of about 22 million hectares and generating about 30 million kilowatt of hydro-power, it will provide substantial flood control in the Ganga-Brahmaputra basin. The Scheme will benefit not only the States in the Ganga-Brahmaputra Basin, but also Nepal and Bangladesh, assuming river flow management treaties are successfully negotiated.
The Himalayan component would consist of a series of dams built along the Ganga and Brahmaputra rivers in India, Nepal and Bhutan for the purposes of storage. Canals would be built to transfer surplus water from the eastern tributaries of the Ganga to the west. This is expected to contribute to flood control measures in the Ganga and Brahmaputra river basins. It could also provide excess water for the Farakka Barrage to flush out the silt at the port of Kolkata.
By 2015, fourteen inter-links under consideration for Himalayan component are as follows, with feasibility study status identified: | 1 | Applied and Interdisciplinary Chemistry |
A variety of geologic and environmental settings have been proposed for an origin of life. These theories are often in competition with one another as there are many differing views of prebiotic compound availability, geophysical setting, and early life characteristics. The first organism on Earth likely looked different from LUCA. Between the first appearance of life and where all modern phylogenies began branching, an unknown amount of time passed. Within this time, unknown gene transfer, extinctions, and evolutions may have occurred, creating adaptations for a more diverse amount of environmental niches. One notable shifts is the one from an RNA-based to an RNA-DNA-protein world. There is more known about LUCA than the first organisms due to genomic reconstructions based on modern phylogenies.
The most popular hypotheses for settings in which an origin of life are possible are deep sea hydrothermal vents and surface bodies of water. Surface waters can be broken down into hot springs, moderate temperature lakes and ponds, and cold settings. | 0 | Theoretical and Fundamental Chemistry |
Applications in biotechnology were developed only most recently. This is due to the sensitivity of bioproducts such as proteins towards organic extractants.
One approach by C. van den Berg et al. focuses on the use of impregnated particles for in situ recovery of phenol from Pseudomonas putida fermentations using ionic liquids. Further development led to the use of high capacity polysulfone capsules. These capsules are basically hollow particles surrounded by a membrane. The interior is completely filled with extractant and thus increases the impregnation capacity as compared to classical SIRs.
A completely new approach of using SIRs for the separation or purification of biotechnological products such as proteins is based on the concept of impregnating porous particles with aqueous polymer solutions developed by B. Burghoff. These so-called Tunable Aqueous Polymer-Phase Impregnated Resins (TAPPIR) enhance aqueous two-phase extraction (ATPE) by applying the SIR technology. During classical aqueous two-phase extraction, biotechnological components such as proteins are extracted from aqueous solutions by using a second aqueous phase. This second aqueous phase contains e.g. polyethylene glycol (PEG). On the one hand, a low density difference and low interfacial tension between the two aqueous phases facilitate comparatively fast mass transfer between the phases. On the other hand, PEG appears to stabilize the protein molecules, which results in a comparatively low protein denaturation during the extraction. However, a significant drawback of ATPE is the persistent emulsification, which makes phase separation a challenge. The idea behind TAPPIR is to use the advantages posed by SIRs, namely low extractant loss due to immobilization in the pores and less emulsification than in liquid-liquid extraction. This way, the drawbacks of ATPE could be remedied. The setup would consist of a packed column or a fluidized bed rather than liquid-liquid extraction equipment with additional phase separation steps. Nonetheless, as yet only first feasibility studies are on the way to prove the concept. Adrawback of this method is the non-conitnous working mode. The packed column is run similar as a chromatographic column. | 0 | Theoretical and Fundamental Chemistry |
Copper has two naturally occurring stable isotopes: Cu and Cu, which exist in the following natural abundances:
The isotopic composition of Cu is conventionally reported in delta notation (in ‰) relative to a NIST SRM 976 standard: | 0 | Theoretical and Fundamental Chemistry |
In geophysical fluid dynamics, an approximation whereby the Coriolis parameter, f, is set to vary linearly in space is called a beta plane approximation.
On a rotating sphere such as the Earth, f varies with the sine of latitude; in the so-called f-plane approximation, this variation is ignored, and a value of f appropriate for a particular latitude is used throughout the domain. This approximation can be visualized as a tangent plane touching the surface of the sphere at this latitude.
A more accurate model is a linear Taylor series approximation to this variability about a given latitude :
, where is the Coriolis parameter at , is the Rossby parameter, is the meridional distance from , is the angular rotation rate of the Earth, and is the Earth's radius.
In analogy with the f-plane, this approximation is termed the beta plane, even though it no longer describes dynamics on a hypothetical tangent plane. The advantage of the beta plane approximation over more accurate formulations is that it does not contribute nonlinear terms to the dynamical equations; such terms make the equations harder to solve. The name beta plane derives from the convention to denote the linear coefficient of variation with the Greek letter β.
The beta plane approximation is useful for the theoretical analysis of many phenomena in geophysical fluid dynamics since it makes the equations much more tractable, yet retains the important information that the Coriolis parameter varies in space. In particular, Rossby waves, the most important type of waves if one considers large-scale atmospheric and oceanic dynamics, depend on the variation of f as a restoring force; they do not occur if the Coriolis parameter is approximated only as a constant. | 1 | Applied and Interdisciplinary Chemistry |
TMSCl is reactive toward nucleophiles, resulting in the replacement of the chloride. In a characteristic reaction of TMSCl, the nucleophile is water, resulting in hydrolysis to give the hexamethyldisiloxane:
The related reaction of trimethylsilyl chloride with alcohols can be exploited to produce anhydrous solutions of hydrochloric acid in alcohols, which find use in the mild synthesis of esters from carboxylic acids and nitriles as well as, acetals from ketones. Similarly, trimethylsilyl chloride is also used to silanize laboratory glassware, making the surfaces more lipophilic. | 0 | Theoretical and Fundamental Chemistry |
Before the mission of Lunar Prospector lunar satellite, it was commonly thought that these KREEP materials had been formed in a widespread layer beneath the crust. However, the measurements from the gamma-ray spectrometer on-board this satellite showed that the KREEP-containing rocks are primarily concentrated underneath the Oceanus Procellarum and the Mare Imbrium. This is a unique lunar geological province that is now known as the Procellarum KREEP Terrane.
Basins far from this province that dug deeply into the crust (and possibly the mantle), such as the Mare Crisium, the Mare Orientale, and the South Pole–Aitken basin, show only little or no enhancements of KREEP within their rims or ejecta. The enhancement of heat-producing radioactive elements within the crust (and/or the mantle) of the Procellarum KREEP Terrane is almost certainly responsible for the longevity and intensity of mare volcanism on the nearside of the Moon. | 0 | Theoretical and Fundamental Chemistry |
A cold fusion experiment usually includes:
* a metal, such as palladium or nickel, in bulk, thin films or powder; and
* deuterium, hydrogen, or both, in the form of water, gas or plasma.
Electrolysis cells can be either open cell or closed cell. In open cell systems, the electrolysis products, which are gaseous, are allowed to leave the cell. In closed cell experiments, the products are captured, for example by catalytically recombining the products in a separate part of the experimental system. These experiments generally strive for a steady state condition, with the electrolyte being replaced periodically. There are also "heat-after-death" experiments, where the evolution of heat is monitored after the electric current is turned off.
The most basic setup of a cold fusion cell consists of two electrodes submerged in a solution containing palladium and heavy water. The electrodes are then connected to a power source to transmit electricity from one electrode to the other through the solution. Even when anomalous heat is reported, it can take weeks for it to begin to appear—this is known as the "loading time," the time required to saturate the palladium electrode with hydrogen (see "Loading ratio" section).
The Fleischmann and Pons early findings regarding helium, neutron radiation and tritium were never replicated satisfactorily, and its levels were too low for the claimed heat production and inconsistent with each other. Neutron radiation has been reported in cold fusion experiments at very low levels using different kinds of detectors, but levels were too low, close to background, and found too infrequently to provide useful information about possible nuclear processes. | 0 | Theoretical and Fundamental Chemistry |
Mediator is involved in "looping" of chromatin, which brings distant regions of a chromosome into closer physical proximity. The ncRNA-a mentioned above is involved in such looping. Enhancer RNAs (eRNAs) can function similarly.
In addition to the looping of euchromatin, mediator appears to be involved in formation or maintenance of heterochromatin at centromeres and telomeres. | 1 | Applied and Interdisciplinary Chemistry |
Spectroscopists customarily refer to the spectrum arising from a given ionization state of a given element by the element's symbol followed by a Roman numeral. The numeral I is used for spectral lines associated with the neutral element, II for those from the first ionization state, III for those from the second ionization state, and so on. For example, "He I" denotes lines of neutral helium, and "C IV" denotes lines arising from the third ionization state, C, of carbon. This notation is used for example to retrieve data from the [http://physics.nist.gov/PhysRefData/ASD/levels_form.html NIST Atomic Spectrum Database]. | 0 | Theoretical and Fundamental Chemistry |
The Fast Fourier Transform (FFT) method was introduced in 1991 by Goodman, Draine, and Flatau for the discrete dipole approximation. They utilized a 3D FFT GPFA written by Clive Temperton. The interaction matrix was extended to twice its original size to incorporate negative lags by mirroring and reversing the interaction matrix. Several variants have been developed since then. Barrowes, Teixeira, and Kong in 2001 developed a code that uses block reordering, zero padding, and a reconstruction algorithm, claiming minimal memory usage. McDonald, Golden, and Jennings in 2009 used a 1D FFT code and extended the interaction matrix in the x, y, and z directions of the FFT calculations, suggesting memory savings due to this approach. This variant was also implemented in the MATLAB 2021 code by Shabaninezhad and Ramakrishna. Other techniques to accelerate convolutions have been suggested in a general context along with faster evaluations of Fast Fourier Transforms arising in DDA problem solvers. | 0 | Theoretical and Fundamental Chemistry |
A total synthesis of progesterone was reported in 1971 by W.S. Johnson. The synthesis begins with reacting the phosphonium salt with phenyl lithium to produce the phosphonium ylide . The ylide is reacted with an aldehyde to produce the alkene . The ketal protecting groups of are hydrolyzed to produce the diketone , which in turn is cyclized to form the cyclopentenone . The ketone of is reacted with methyl lithium to yield the tertiary alcohol , which in turn is treated with acid to produce the tertiary cation . The key step of the synthesis is the π-cation cyclization of in which the B-, C-, and D-rings of the steroid are simultaneously formed to produce . This step resembles the cationic cyclization reaction used in the biosynthesis of steroids and hence is referred to as biomimetic. In the next step the enol orthoester is hydrolyzed to produce the ketone . The cyclopentene A-ring is then opened by oxidizing with ozone to produce . Finally, the diketone undergoes an intramolecular aldol condensation by treating with aqueous potassium hydroxide to produce progesterone. | 0 | Theoretical and Fundamental Chemistry |
Rowley led the Peoples National Movement in the September 2015 general election, in which his party secured 23 out of 41 seats in the House of Representatives to form the government, defeating the previous Peoples Partnership coalition government. On 9 September 2015, Rowley was sworn in as Prime Minister of Trinidad and Tobago by President Anthony Carmona.
He becomes the seventh Prime Minister of Trinidad and Tobago and the second Tobago-born Prime Minister. Rowley again led the Peoples National Movement to victory in the 10 August 2020 general election for a second term in government under his premiership. He was sworn in as Prime Minister of Trinidad and Tobago on 19 August by President Paula-Mae Weekes at the Presidents House in St. Anns after the opposition party asked for recounts to be done in marginal constituencies.
During his tenure, on 5 February 2022, the Trinidad and Tobago coast guard fired upon a vessel with Venezuelan migrants while attempting to stop it, killing a nine-month-old baby and injuring his mother. The coast guard claimed that the shots were fired "in self-defense". Rowley deemed the action "legal and appropriate"; the Trinidadian police and coast guard opened an investigation of the event. | 0 | Theoretical and Fundamental Chemistry |
The central concept of thermodynamics is that of energy, the ability to do work. By the First Law, the total energy of a system and its surroundings is conserved. Energy may be transferred into a system by heating, compression, or addition of matter, and extracted from a system by cooling, expansion, or extraction of matter. In mechanics, for example, energy transfer equals the product of the force applied to a body and the resulting displacement.
Conjugate variables are pairs of thermodynamic concepts, with the first being akin to a "force" applied to some thermodynamic system, the second being akin to the resulting "displacement", and the product of the two equaling the amount of energy transferred. The common conjugate variables are:
* Pressure-volume (the mechanical parameters);
* Temperature-entropy (thermal parameters);
* Chemical potential-particle number (material parameters). | 0 | Theoretical and Fundamental Chemistry |
After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, an enzyme specific to chloroplast proteins phosphorylates, or adds a phosphate group to many (but not all) of them in their transit sequences.
Phosphorylation helps many proteins bind the polypeptide, keeping it from folding prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the cytosol. At the same time, they have to keep just enough shape so that they can be recognized by the chloroplast. These proteins also help the polypeptide get imported into the chloroplast.
From here, chloroplast proteins bound for the stroma must pass through two protein complexes—the TOC complex, or translocon on the outer chloroplast membrane, and the TIC translocon, or translocon on the inner chloroplast membrane translocon. Chloroplast polypeptide chains probably often travel through the two complexes at the same time, but the TIC complex can also retrieve preproteins lost in the intermembrane space. | 0 | Theoretical and Fundamental Chemistry |
In most hydrogen-fusing stars, including the Sun, a chemical cycle involved in stellar nucleosynthesis occurs which is known as a carbon-nitrogen-oxygen or (CNO cycle). In addition to this cycle, stars also have a helium cycle. Various cycles involving gas and dust have been found to occur in galaxies. | 0 | Theoretical and Fundamental Chemistry |
Manual analysis of an AA′BB′ or AA′XX′ system is possible, if a sufficient number of peaks are detected. The A/A′ and B/B′ chemical shifts and the several coupling constants between each spin can be accurately obtained by quantum-mechanical simulation of the spin transition probabilities, given a set of guessed chemical shift and coupling constant values, and subsequent refinement of those values by iterative spectral fitting. Several software packages are available for this purpose, a sampling of which is (in no particular order):
* SPINEVOLUTION. Website: http://spinevolution.org
* NMR Simulator (free online use). Website: http://www.nmrdb.org/simulator
* WINDNMR-Pro (shareware download). Website: http://www.chem.wisc.edu/areas/reich/plt/windnmr.htm
* SpinWorks (freeware download). Websites: http://nmrwiki.org/wiki/index.php?title=SpinWorks and http://home.cc.umanitoba.ca/~wolowiec/spinworks/index.html
* PERCH NMR Software, Website: http://www.perchsolutions.com | 0 | Theoretical and Fundamental Chemistry |
Otherwise called a knock-on electron, the term "delta ray" is also used in high energy physics to describe single electrons in particle accelerators that are exhibiting characteristic deceleration. In a bubble chamber, electrons will lose their energy more quickly than other particles through Bremsstrahlung and will create a spiral track due to their small mass and the magnetic field. The Bremsstrahlung rate is proportional to the square of the acceleration of the electron. | 0 | Theoretical and Fundamental Chemistry |
Phytovolatilization involves the capture and subsequent transpiration of radionuclides into the atmosphere. It does not remove contaminants but releases them in volatile form (less harmful). Despite not having too many applications for radioactive waste, it is very useful for the treatment of tritium, because it exploits plants' ability to transpire enormous amounts of water.
The treatment applied to tritium (shielded by air produces almost no external radiation exposure, but its incorporation in water presents a health hazard when absorbed into the body) uses polluted effluents to irrigate phreatophytes. It becomes a system with a low operation cost and low maintenance, with savings of about 30% in comparison to conventional methods of pumping and covering with asphalt. | 1 | Applied and Interdisciplinary Chemistry |
In aluminium alloys containing magnesium, magnesium oxides (MgO), cuboids (MgAlO-cuboid) and metallurgical spinel (MgAlO-spinel) can form. They result from the reaction between magnesium and oxygen in the melt. More of them will form with time and temperature.
Spinel can be highly detrimental because of its big size and high hardness. | 1 | Applied and Interdisciplinary Chemistry |
Less studied than above-ground interactions, but proving to be increasingly important, are the below-ground interactions that influence plant defense. There is a complex network of signal transduction pathways involved in plant responses to stimuli, and soil microbes can influence these responses. Certain soil microbes aid plant growth, producing increased tolerance to various environmental stressors, and can protect their host plants from many different pathogens by inducing systemic resistance. Organisms in above- and below-ground environments can interact indirectly through plants. Many studies have shown both the positive and negative effects that one organism in one environment can have on other organisms in the same or opposite environment, with the plant acting as the intermediary.
The colonization of plant roots with mycorhizae typically results in a mutualistic relationship between the plant and the fungus, inducing a number of changes in the plant. Such colonization has a mixed impact on herbivores; insects with different feeding methods are affected differently, some positively and others negatively. The mycorhizal species involved also matters. One common species, Rhizophagus irregularis, has been observed to have a negative effect on the feeding success of chewing herbivores, whereas other species studied have positive effects.
The roots of some maize plants produce a defense chemical when roots are damaged by leaf beetle larvae; this chemical attracts the entomopathogenic nematode species Heterorhabditis megidis. Only certain maize varieties produce this chemical; plants that release the chemical see up to five times as much parasitization of leaf beetle larvae as those that do not. Incorporating these varieties or their genes into commercial maize production could increase the efficacy of nematode treatments.
Further studies suggest that the plant-emitted chemicals act as the primary source of attractant to the nematodes. Herbivores are believed to have evolved to evade detection on the part of the nematodes, whereas the plants have evolved to release highly attractive chemical signals. A high degree of specificity is involved; species that make up these tritrophic interactions have evolved with one another over a long period of time and as a result have close interrelationships.
Microorganisms can also influence tritrophic interactions. The bacterium Klebsiella aerogenes produces the volatile 2,3-butanediol, which modulates interactions between plants, pathogens, and insects. When maize plants are grown in a soil culture containing the bacterium or the plants are inoculated with the bacterium, the maize is more resistant to the fungus Setosphaeria turcica. The bacterium does not deter insect herbivory; it actually increases weight gain and leaf consumption in the caterpillar Spodoptera littoralis. However, the parasitic wasp Cotesia marginiventris is attracted more readily to maize plants grown in soil cultures containing either the volatile-producing bacterium or pure 2,3-butanediol. | 1 | Applied and Interdisciplinary Chemistry |
One major issue engineers come across working with pneumatic cylinders has to do with the compressibility of a gas. Many studies have been completed on how the precision of a pneumatic cylinder can be affected as the load acting on the cylinder tries to further compress the gas used. Under a vertical load, a case where the cylinder takes on the full load, the precision of the cylinder is affected the most. A study at the National Cheng Kung University in Taiwan, concluded that the accuracy is about ± 30 nm, which is still within a satisfactory range but shows that the compressibility of air has an effect on the system. | 1 | Applied and Interdisciplinary Chemistry |
Current trends in climate change lead to higher ocean temperatures and acidity, thus modifying marine ecosystems. Also, acid rain and polluted runoff from agriculture and industry change the oceans chemical composition. Such changes can have dramatic effects on highly sensitive ecosystems such as coral reefs, thus limiting the oceans ability to absorb carbon from the atmosphere on a regional scale and reducing oceanic biodiversity globally.
The exchanges of carbon between the atmosphere and other components of the Earth system, collectively known as the carbon cycle, currently constitute important negative (dampening) feedbacks on the effect of anthropogenic carbon emissions on climate change. Carbon sinks in the land and the ocean each currently take up about one-quarter of anthropogenic carbon emissions each year.
These feedbacks are expected to weaken in the future, amplifying the effect of anthropogenic carbon emissions on climate change. The degree to which they will weaken, however, is highly uncertain, with Earth system models predicting a wide range of land and ocean carbon uptakes even under identical atmospheric concentration or emission scenarios. Arctic methane emissions indirectly caused by anthropogenic global warming also affect the carbon cycle and contribute to further warming. | 0 | Theoretical and Fundamental Chemistry |
Bioisosteres of some patented compounds can be discovered automatically and used to circumvent Markush structure patent claims. It has been proposed that key force field features, that is the pharmacophore, be patented instead. | 1 | Applied and Interdisciplinary Chemistry |
Point groups can be classified into chiral (or purely rotational) groups and achiral groups.
The chiral groups are subgroups of the special orthogonal group SO(d): they contain only orientation-preserving orthogonal transformations, i.e., those of determinant +1. The achiral groups contain also transformations of determinant −1. In an achiral group, the orientation-preserving transformations form a (chiral) subgroup of index 2.
Finite Coxeter groups or reflection groups are those point groups that are generated purely by a set of reflectional mirrors passing through the same point. A rank n Coxeter group has n mirrors and is represented by a Coxeter–Dynkin diagram. Coxeter notation offers a bracketed notation equivalent to the Coxeter diagram, with markup symbols for rotational and other subsymmetry point groups. Reflection groups are necessarily achiral (except for the trivial group containing only the identity element). | 0 | Theoretical and Fundamental Chemistry |
IEC Type II tapes are intended for recording using high (150% of normal) bias and replay with the 70μs time constant. All generations of Type II reference tapes, including the 1971 DIN reference that pre-dated the IEC standard, were manufactured by BASF. Type II has been historically known as chromium dioxide tape or simply chrome tape, but in reality most Type II cassette tapes do not contain chromium. The "pseudochromes" (including almost all Type IIs made by the Big Three Japanese makers — Maxell, Sony and TDK) are actually ferricobalt formulations optimized for Type II recording and playback settings. A true chrome tape may have a distinctive old crayon smell, more specifically, any oil or wax chalks that have chrome dioxide pigments in them like chrome yellow, which is missing in "pseudochromes". Both kinds of Type II tapes have, on average, lower high-frequency MOL and SOL, and higher signal-to-noise ratio than quality Type I tapes. This is caused by the midrange and treble pre-emphasis applied during recording to match the 70μs equalization at playback. | 0 | Theoretical and Fundamental Chemistry |
This aspect of agricultural chemistry deals with the role of molecular chemistry in agriculture as well as the negative consequences. | 1 | Applied and Interdisciplinary Chemistry |
Translation promotes transcription elongation and regulates transcription termination. Functional coupling between transcription and translation is caused by direct physical interactions between the ribosome and RNA polymerase ("expressome complex"), ribosome-dependent changes to nascent mRNA secondary structure which affect RNA polymerase activity (e.g. "attenuation"), and ribosome-dependent changes to nascent mRNA availability to transcription termination factor Rho ("polarity"). | 1 | Applied and Interdisciplinary Chemistry |
Due to its similar structure and properties, pentavalent arsenic metabolites are capable of replacing the phosphate group of many metabolic pathways. The replacement of phosphate by arsenate is initiated when arsenate reacts with glucose and gluconate in vitro. This reaction generates glucose-6-arsenate and 6-arsenogluconate, which act as analogs for glucose-6-phosphate and 6-phosphogluconate. At the substrate level, during glycolysis, glucose-6-arsenate binds as a substrate to glucose-6-phosphate dehydrogenase, and also inhibits hexokinase through negative feedback. Unlike the importance of phosphate in glycolysis, the presence of arsenate restricts the generation of ATP by forming an unstable anhydride product, through the reaction with D-glyceraldehyde-3-phosphate. The anhydride 1-arsenato-3-phospho-D-glycerate generated readily hydrolyzes due to the longer bond length of As-O compared to P-O. At the mitochondrial level, arsenate uncouples the synthesis of ATP by binding to ADP in the presence of succinate, thus forming an unstable compound that ultimately results in a decrease of ATP net gain. Arsenite (III) metabolites, on the other hand, have limited effect on ATP production in red blood cells. | 1 | Applied and Interdisciplinary Chemistry |
*ANXA6
*ANXA7
*ARPC1A Actin-related peptide
*ARPC2
*ARPC5L
*CAPZA2
*CAPZB
*RHOA also implicated in regulation of cell cycle
*RHOB
*RHOT1 mitochondrial trafficking
*RHOT2
*TUBB Tubulin, beta polypeptide
*WDR1 actin disassembly? | 1 | Applied and Interdisciplinary Chemistry |
Season cracking is a form of stress-corrosion cracking of brass cartridge cases originally reported from British forces in India. During the monsoon season, military activity was temporarily reduced, and ammunition was stored in stables until the dry weather returned. Many brass cartridges were subsequently found to be cracked, especially where the case was crimped to the bullet. It was not until 1921 that the phenomenon was explained by Moor, Beckinsale and Mallinson: ammonia from horse urine, combined with the residual stress in the cold-drawn metal of the cartridges, was responsible for the cracking.
Season cracking is characterised by deep brittle cracks which penetrate into affected components. If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results. However, if the concentration of ammonia is very high, then attack is much more severe, and attack over all exposed surfaces occurs. The problem was solved by annealing the brass cases after forming so as to relieve the residual stresses. | 1 | Applied and Interdisciplinary Chemistry |
Willauer et al. (2012) estimated that jet fuel could be synthesized from seawater in quantities up to per day, at a cost of three to six U.S. dollars per gallon. Willauer et al. (2014) showed that the Fischer-Tropsch catalyst could be modified to synthesize various fuels such as methanol and natural gas, as well as the olefins that can be used as the building blocks for jet fuel.
Willauer et al. calculated that about of seawater must be driven through the process to obtain the quantities of hydrogen and CO necessary to synthesize one gallon of jet fuel.
Seawater was chosen because it contains 140 times more CO by volume than the atmosphere, and conventional water electrolysis also yields H. The equipment for processing seawater is much smaller than that for processing air. Willauer considered that seawater was the "best option" for a source of synthetic jet fuel. By April 2014, the Willauer's team had not yet made fuel to the quality standard required for military jets, but they were able in September 2013 to use the fuel to fly a radio-controlled model airplane powered by a common two-stroke internal combustion engine.
Because the process requires a considerable input of electrical energy (~ 250 MW electricity mainly for the H production by water electrolysis and also to a lesser extent for the CO recovery from seawater), it cannot be performed on a large ship, even on a nuclear aircraft-carrier. The installations processing seawater to obtain H and CO (in fact CO), the two essential ingredients necessary for the Fischer–Tropsch process, must be constructed on-shore, close to the sea, on islands in strategic remote locations (e.g., Hawai, Guam, Diego-Garcia) and powered by a nuclear reactor, or by ocean thermal energy conversion (OTEC). | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the term 2-norbornyl cation (or 2-bicyclo[2.2.1]heptyl cation) describes one of the three carbocations formed from derivatives of norbornane. Though 1-norbornyl and 7-norbornyl cations have been studied, the most extensive studies and vigorous debates have been centered on the exact structure of the 2-norbornyl cation.
The 2-norbornyl cation has been formed from a variety of norbornane derivatives and reagents. First reports of its formation and reactivity published by Saul Winstein sparked controversy over the nature of its bonding, as he invoked a three-center two-electron bond to explain the stereochemical outcome of the reaction. Herbert C. Brown challenged this assertion on the grounds that classical resonance structures could explain these observations without needing to adapt a new perspective of bonding. Both researchers' views had its supporters, and dozens of scientists contributed ingeniously designed experiments to provide evidence for one viewpoint or the other. Over time, the dispute became increasingly bitter and acrimonious, and the debate took on a personal or ad hominem character.
Evidence of the non-classical nature of the 2-norbornyl cation grew over the course of several decades, mainly through spectroscopic data gathered using methods such as nuclear magnetic resonance (NMR). Crystallographic confirmation of its non-classical nature did not come until 2013. Although most chemists now agree that 2-norbornyl cation itself is non-classical, it is also widely recognized that the energetic landscape for carbocations tends to be "flat", with many potential structures differing only minutely in energy. Certainly, not all bicyclic carbocations are non-classical; the energy difference between classical and non-classical structures is often delicately balanced. Thus, certain alkyl-substituted 2-bicyclo[2.2.1]heptyl cations are now known to adopt classical structures.
The nature of bonding in the 2-norbornyl cation incorporated many new ideas into the field’s understanding of chemical bonds. Similarities can be seen between this cation and others, such as boranes. | 0 | Theoretical and Fundamental Chemistry |
He joined the Baltimore Copper Smelting & Rolling Company in 1890, becoming vice president in 1895, and later, president of the company. Under his management, the company became one of the major copper producer of the United States. In 1928, the company merged with five other copper companies, to create the Revere Copper Company. Described as "one of the foremost metallurgists of his time", Peirce became the vice president, director and a member of the Executive Committee of Revere from its incorporation in 1928 until his resignation in 1933. | 1 | Applied and Interdisciplinary Chemistry |
Corrosion fatigue is fatigue in a corrosive environment. It is the mechanical degradation of a material under the joint action of corrosion and cyclic loading. Nearly all engineering structures experience some form of alternating stress, and are exposed to harmful environments during their service life. The environment plays a significant role in the fatigue of high-strength structural materials like steel, aluminum alloys and titanium alloys. Materials with high specific strength are being developed to meet the requirements of advancing technology. However, their usefulness depends to a large extent on the degree to which they resist corrosion fatigue.
The effects of corrosive environments on the fatigue behavior of metals were studied as early as 1930.
The phenomenon should not be confused with stress corrosion cracking, where corrosion (such as pitting) leads to the development of brittle cracks, growth and failure. The only requirement for corrosion fatigue is that the sample be under tensile stress. | 1 | Applied and Interdisciplinary Chemistry |
Rutledge received his BSc in chemistry and biochemistry from the University of Auckland in 1993. He received his MSc from the same institution with first class honours in chemistry in 1995. He left New Zealand in 1995 and obtained his DPhil at Magdalen College, Oxford working with Jack Edward Baldwin in 1999. He was a postdoctoral research fellow at the same institution until 2003. | 0 | Theoretical and Fundamental Chemistry |
When the DNA hairpin is unzipped into single-strand, oligonucleotides complementary to the hairpin sequence are allowed to hybridize. During the time course of the rezipping process, the bound oligonucleotides cause transient blockages. The time course measurement of hairpin length allows for the determination of the exact position of the hybridization, as well as the presence of mismatches between the oligonucleotide and the hairpin. | 1 | Applied and Interdisciplinary Chemistry |
Once mRNA is purified, an oligo-dT primer (a short sequence of deoxy-thymidine nucleotides) is bound to the poly-A tail of the RNA. The primer is required to initiate DNA synthesis by the enzyme reverse transcriptase. This results in the creation of RNA-DNA hybrids where a single strand of complementary DNA is bound to a strand of mRNA. To remove the mRNA, the RNAse H enzyme is used to cleave the backbone of the mRNA and generate free 3-OH groups, which is important for the replacement of mRNA with DNA. DNA polymerase I is then added, the cleaved RNA acts as a primer the DNA polymerase I can identify and initiate replacement of RNA nucleotides with those of DNA. This is provided by the sscDNA itself by coiling on itself at the 3 end, generating a hairpin loop. The polymerase extends the 3-OH end, and later the loop at 3 end is opened by the scissoring action of S nuclease. Restriction endonucleases and DNA ligase are then used to clone the sequences into bacterial plasmids.
The cloned bacteria are then selected, commonly through the use of antibiotic selection. Once selected, stocks of the bacteria are created which can later be grown and sequenced to compile the cDNA library. | 1 | Applied and Interdisciplinary Chemistry |
The SUPERFAMILY database has numerous research applications and has been used by many research groups for various studies. It can serve either as a database for proteins that the user wishes to examine with other methods, or to assign a function and structure to a novel or uncharacterized protein. One study found SUPERFAMILY to be very adept at correctly assigning an appropriate function and structure to a large number of domains of unknown function by comparing them to the databases hidden Markov models. Another study used SUPERFAMILY to generate a data set of 1,733 Fold superfamily domains (FSF) in use of a comparison of proteomes and functionomes for to identify the origin of cellular diversification. | 1 | Applied and Interdisciplinary Chemistry |
HER2 is overexpressed in 20-30% of breast cancers and is commonly associated with poor prognosis. It is therefore an oncogene whose differently spliced variants have been shown to have different functions. Knocking down hnRNP H1 was shown to increase the amount of an oncogenic variant Δ16HER2. HER2 is an upstream regulator of cyclin D1 and p27, and its overexpression leads to the deregulation of the G1/S checkpoint. | 1 | Applied and Interdisciplinary Chemistry |
In developing countries, connection to sewer systems is often costly for poor households, despite typically low monthly sewer tariffs. This apparent paradox is explained by the high costs of in-plot and in-house sanitary installations that have to be paid entirely by the user, by sometimes high sewer connection fees levied by utilities, and by a lack of community consultation. As a result, in many cities in developing countries conventional sewers are laid at high costs under a street, while many users on that street do not connect to them. In Brazil, in some cities connection rates in the early 1990s were less than 40% of the intended beneficiary population. | 1 | Applied and Interdisciplinary Chemistry |
Iterons are directly repeated DNA sequences which play an important role in regulation of plasmid copy number in bacterial cells. It is one among the three negative regulatory elements found in plasmids which control its copy number. The others include antisense RNAs and ctRNAs. Iterons complex with cognate replication (Rep) initiator proteins to achieve the required regulatory effect. | 1 | Applied and Interdisciplinary Chemistry |
Toluene hydrodealkylation converts toluene to benzene. In this hydrogen-intensive process, toluene is mixed with hydrogen, then passed over a chromium, molybdenum, or platinum oxide catalyst at 500–650 °C and 20–60 atm pressure. Sometimes, higher temperatures are used instead of a catalyst (at the similar reaction condition). Under these conditions, toluene undergoes dealkylation to benzene and methane:
This irreversible reaction is accompanied by an equilibrium side reaction that produces
biphenyl (aka diphenyl) at higher temperature:
If the raw material stream contains much non-aromatic components (paraffins or naphthenes), those are likely decomposed to lower hydrocarbons such as methane, which increases the consumption of hydrogen.
A typical reaction yield exceeds 95%. Sometimes, xylenes and heavier aromatics are used in place of toluene, with similar efficiency.
This is often called "on-purpose" methodology to produce benzene, compared to conventional BTX (benzene-toluene-xylene) extraction processes. | 1 | Applied and Interdisciplinary Chemistry |
The α-amylases () (CAS 9014-71-5) (alternative names: 1,4-α--glucan glucanohydrolase; glycogenase) are calcium metalloenzymes. By acting at random locations along the starch chain, α-amylase breaks down long-chain saccharides, ultimately yielding either maltotriose and maltose from amylose, or maltose, glucose and "limit dextrin" from amylopectin. They belong to glycoside hydrolase family 13 (https://www.cazypedia.org/index.php/Glycoside_Hydrolase_Family_13).
Because it can act anywhere on the substrate, α-amylase tends to be faster-acting than β-amylase. In animals, it is a major digestive enzyme, and its optimum pH is 6.7–7.0.
In human physiology, both the salivary and pancreatic amylases are α-amylases.
The α-amylase form is also found in plants, fungi (ascomycetes and basidiomycetes) and bacteria (Bacillus). | 1 | Applied and Interdisciplinary Chemistry |
Thomsen–Friedenreich antigen (Galβ1-3GalNAcα1-Ser/Thr) is a disaccharide that serves as a core 1 structure in O-linked glycosylation. First described by Thomsen as a red blood cell's antigen, later research have determined it to be an oncofetal antigen. it is present in the body as a part of membrane transport proteins where it is normally masked from the immune system. It is commonly demasked in cancer cells, with it being expressed in up to 90% of carcinomas, making it a potential target for immunotherapy. | 1 | Applied and Interdisciplinary Chemistry |
This coordination compound is prepared by the reaction of tungsten hexacarbonyl with 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (Hhpp) in o-dichlorobenzene at 200 °C:
The reaction gives W(hpp)Cl. Dichlorobenzene provides the chlorine atoms and is itself reductively coupled to 2,2′-dichlorobiphenyl. The bond order between the tungsten centers in W(hpp)Cl is three.
This dichloride is further reduced by potassium metal to W(hpp). This species has a quadruple bond between the two tungsten centers. Related quadruply bonded complexes include [WCl] and [[Potassium octachlorodimolybdate|[MoCl]]]. Because of its low ionization energy, W(hpp) is easily oxidized back to the dichloride by dichloromethane. It is readily oxidized to the corresponding cation with the oxidants fullerene and with tetracyanoquinodimethane. (hpp) was proposed to be a potentially useful powerful reducing agent akin to CpCo and CpCr, so far this reagent has not become part of the synthetic chemist's armament. grand total of 7 refs in 5 years--> | 0 | Theoretical and Fundamental Chemistry |
SuperSAGE is a derivative of SAGE that uses the type III-endonuclease EcoP15I of phage P1, to cut 26 bp long sequence tags from each transcript's cDNA, expanding the tag-size by at least 6 bp as compared to the predecessor techniques SAGE and LongSAGE. The longer tag-size allows for a more precise allocation of the tag to the corresponding transcript, because each additional base increases the precision of the annotation considerably.
Like in the original SAGE protocol, so-called ditags are formed, using blunt-ended tags. However, SuperSAGE avoids the bias observed during the less random LongSAGE 20 bp ditag-ligation. By direct sequencing with high-throughput sequencing techniques (next-generation sequencing, i.e. pyrosequencing), hundred thousands or millions of tags can be analyzed simultaneously, producing very precise and quantitative gene expression profiles. Therefore, tag-based gene expression profiling also called "digital gene expression profiling" (DGE) can today provide most accurate transcription profiles that overcome the limitations of microarrays. | 1 | Applied and Interdisciplinary Chemistry |
The vast majority of refined bitumen is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use, bitumen is produced to specification. This is achieved either by refining or blending. It is estimated that the current world use of bitumen is approximately 102 million tonnes per year. Approximately 85% of all the bitumen produced is used as the binder in asphalt concrete for roads. It is also used in other paved areas such as airport runways, car parks and footways. Typically, the production of asphalt concrete involves mixing fine and coarse aggregates such as sand, gravel and crushed rock with asphalt, which acts as the binding agent. Other materials, such as recycled polymers (e.g., rubber tyres), may be added to the bitumen to modify its properties according to the application for which the bitumen is ultimately intended.
A further 10% of global bitumen production is used in roofing applications, where its waterproofing qualities are invaluable.
The remaining 5% of bitumen is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet tile backing and paint. Bitumen is applied in the construction and maintenance of many structures, systems, and components, such as:
* Highways
* Airport runways
* Footways and pedestrian ways
* Car parks
* Racetracks
* Tennis courts
* Roofing
* Damp proofing
* Dams
* Reservoir and pool linings
* Soundproofing
* Pipe coatings
* Cable coatings
* Paints
* Building water proofing
* Tile underlying waterproofing
* Newspaper ink production | 0 | Theoretical and Fundamental Chemistry |
The yeast S. cerevisiae was the model organism used during the two-hybrid technique's inception. It is commonly known as the Y2H system. It has several characteristics that make it a robust organism to host the interaction, including the ability to form tertiary protein structures, neutral internal pH, enhanced ability to form disulfide bonds and reduced-state glutathione among other cytosolic buffer factors, to maintain a hospitable internal environment. The yeast model can be manipulated through non-molecular techniques and its complete genome sequence is known. Yeast systems are tolerant of diverse culture conditions and harsh chemicals that could not be applied to mammalian tissue cultures.
A number of yeast strains have been created specifically for Y2H screens, e.g. Y187 and AH109, both produced by Clontech. Yeast strains R2HMet and BK100 have also been used. | 1 | Applied and Interdisciplinary Chemistry |
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