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The oocyte is the female cell involved in reproduction. There is a close relationship between the oocyte and the surrounding follicular cells which is crucial to the development of both. GDF9 and BMP15 produced by the oocyte bind to BMPR2 receptors on follicular cells activating SMADs 2/3, ensuring follicular development. Concomitantly, oocyte growth is initiated by binding of KITL to its receptor KIT in the oocyte, leading to the activation of PI3K/Akt pathway, allowing oocyte survival and development. During embryogenesis, oocytes initiate meiosis and stop in prophase I. This arrest is maintained by elevated levels of cAMP within the oocyte. It was recently suggested that cGMP cooperates with cAMP to maintain the cell cycle arrest. During meiotic maturation, the LH peak that precedes ovulation activates MAPK pathway leading to gap junction disruption and breakdown of communication between the oocyte and the follicular cells. PDE3A is activated and degrades cAMP, leading to cell cycle progression and oocyte maturation. The LH surge also leads to the production of progesterone and prostaglandins that induce the expression of ADAMTS1 and other proteases, as well as their inhibitors. This will lead to degradation of the follicular wall, but limiting the damage and ensuring that the rupture occurs in the appropriate location, releasing the oocyte into the fallopian tubes. Oocyte activation depends on fertilization by sperm. It is initiated with sperms attraction induced by prostaglandins produced by the oocyte, which will create a gradient that will influence the sperms direction and velocity. After fusion with the oocyte, PLC ζ of the spermatozoa is released into the oocyte leading to an increase in Ca2+ levels that will activate CaMKII which will degrade MPF, leading to the resumption of meiosis. The increased Ca levels will induce the exocytosis of cortical granules that degrade ZP receptors, used by sperm to penetrate the oocyte, blocking polyspermy. Deregulation of these pathways will lead to several diseases like, oocyte maturation failure syndrome which results in infertility. Increasing our molecular knowledge of oocyte development mechanisms could improve the outcome of assisted reproduction procedures, facilitating conception. | 0 | Theoretical and Fundamental Chemistry |
Fusing angular rings around a benzene moiety leads to an increase in stability. The Clar structure of anthracene, for instance, has only one π-sextet, but moving one ring into the angular position phenanthrene is obtained, the Clar structure of which carries two circles instead of one – notice that this molecule can be thought of as a benzene moiety with two fused rings; a third ring can be fused to obtain triphenylene, with three aromatic π-sextets in its Clar structure. The chemical stability of these molecules is greatly influenced by the degree of aromaticity of their Clar structures. As a result, while anthracene reacts with maleic acid, phenanthrene does not, and triphenylene is the most stable species of these three. | 0 | Theoretical and Fundamental Chemistry |
C-myc mRNA is a type of mRNA that serves as a template for the MYC protein which is implicated in the rapid growth of cancer cells. This mRNA is a topic of ongoing research to investigate the viability of preventing cancer growth by cleaving or degrading the c-myc mRNA. | 1 | Applied and Interdisciplinary Chemistry |
Reflectometric interference spectroscopy (RIfS) is a physical method based on the interference of white light at thin films, which is used to investigate molecular interaction. | 0 | Theoretical and Fundamental Chemistry |
In sub-Saharan West Africa, there were only two known source of copper that were commercially viable: Dkra near Nioro, Mali and Takedda in Azelik, Niger. Akjoujt was a significant source of copper, but due to the lack of timber it lost its significance in early historic times. The sources for West Africa's copper came from southern Morocco, northwestern Mauritania, the Byzantine Empire and Central Europe.
In West Africa, there is a great deal of documentation about copper in trade, but the travelers who wrote these documents only visited the major centers of West African polities and there is no information on the people who lived out the polities or from the savanna and forest zones to the south, in terms of their use of copper. Arab and European trader documented that the principal goods that were in demand in West African markets were salt and copper. There has been a lack of research done in the savannah and forest regions of West Africa so the evidence of the diffusion copper there is spotty at best. Despite West Africa's rich gold resources, high status people were most often buried with copper grave goods. The only sites prior to 1500 AD to have gold were Djenné, Tedaoust, and several tumuli in Senegal. | 1 | Applied and Interdisciplinary Chemistry |
The Hill equation is used extensively in pharmacology to quantify the functional parameters of a drug and are also used in other areas of biochemistry.
The Hill equation can be used to describe dose-response relationships, for example ion channel open-probability (P-open) vs. ligand concentration. | 1 | Applied and Interdisciplinary Chemistry |
Aegyptiacum, or ægyptiacum, was used in pharmacy as a kind of detersive, or cleansing unguent. It is so called from its dusky hue or color, which resembles the swarthy complexion of the Egyptian people.
It is composed of verdigris, vinegar, and honey, boiled to a consistency.
The prescription is Masawaiyh's. It is chiefly used for eating off rotten flesh and cleaning foul ulcers, particularly venereal ones in the throat, and mouth ulcers.
One of the ingredients in a wound-cleansing plaster made by Henry VIII of Englands Surgeon Thomas Gale in his handbook, Certaine Workes of Chirurgerie.'
"A mundicative
Aegyptiacum Unguent 2 ounces
Alum 1 ounce
Frankincense 1/2 ounce
Myrrh 1 dram
Red Wine 2 pounds
Boil" | 1 | Applied and Interdisciplinary Chemistry |
The American-Australian Scientific Expedition to Arnhem Land (also known as the Arnhem Land Expedition) remains one of the most significant, most ambitious and least understood expeditions. Commenced in February 1948, it was one of the largest scientific expeditions to have taken place in Australia and was conducted by a team of Australian and American researchers and support staff. | 1 | Applied and Interdisciplinary Chemistry |
Z-HIT, also denoted as ZHIT, Z-HIT relationship , is a bidirectional mathematical tranformation, connecting the two parts of a complex function, - i.e. its modulus and its phase. Z-HIT relations are somewhat similar to the Kramers–Kronig relations, where the real part can be computed from the imaginary part (or vice versa). In contrast to the Kramers–Kronig relations, in the Z-HIT the impedance modulus is computed from the course of the phase angle (or vice versa). The main practical advantage of Z-HIT relationships over Kramers–Kronig relationships is, that the Z-HIT integration limits do not require any extrapolation: instead, an intergration over the experimentally available frequency range provides accurate data.
More specifically, the angular frequency (ω) boundaries for computing one component of the complex function from the other one using the Kramers-Kronig relations, are ω=0 and ω=∞; these boundaries require extrapolation procedures of the measured impedance spectra. Concerning the ZHIT however, the computing of the course of the impedance modulus from the course of the phase shift can be performed within the measured frequency range, without the need of extrapolation. This avoids complications which may arise from the fact that impedance spectra can only be measured in a limited frequency range. Therefore, the Z-HIT-algorithm allows for verification of the stationarity of the measured test object as well as calculating the impedance values using the phase data. The latter property becomes important when drift effects are present in the impedance spectra which had to be detected or even removed when analysing and/or interpreting the spectra.
Z-HIT relations find use in Dielectric spectroscopy and in Electrochemical Impedance Spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
Specifically, in the basal state Perilipin A allows a low level of basal lipolysis by reducing the access of cytosolic lipases to stored triacylglycerol in LDs. It is found at their surface in a complex with CGI-58, the co-activator of ATGL. ATGL might also be in this complex but it is quiescent.
Under lipolytically stimulated conditions, PKA is activated and phosphorylates up to 6 Serine residues on Perilipin A (Ser81, 222, 276, 433, 492, and 517) and 2 on HSL (Ser659, and 660). Although PKA also phosphorylates HSL, which can increase its activity, the more than 50-fold increase in fat mobilization (triggered by epinephrine) is primarily due to Perilipin phosphorylation.
Then, Phosphorylated HSL translocates to the LD surface and associates with Perilipin A and Adipocyte fatty acid-binding protein (AFABP). Consequently, HSL gains access to triacylglycerol (TAG) and diacylglycerol (DAG), substrates in LDs. Also, CGI-58 separates from the LD outer layer which leads to a redistribution of ATGL. In particular, ATGL interacts with Perilipin A through phosphorylated Ser517.
As a result, PKA phosphorylation implies an enriched colocation of HLS and ATGL which facilitates maximal lipolysis by the two lipases. | 1 | Applied and Interdisciplinary Chemistry |
"Water spray" systems are operationally identical to a deluge system, but the piping and discharge nozzle spray patterns are designed to protect a uniquely configured hazard, usually being three-dimensional components or equipment (i.e. as opposed to a deluge system, which is designed to cover the horizontal floor area of a room). The nozzles used may not be listed fire sprinklers, and are usually selected for a specific spray pattern to conform to the three-dimensional nature of the hazard (e.g. typical spray patterns being oval, fan, full circle, narrow jet). Examples of hazards protected by water spray systems are electrical transformers containing oil for cooling or turbo-generator bearings. Water spray systems can also be used externally on the surfaces of tanks containing flammable liquids or gases (such as hydrogen). Here the water spray is intended to cool the tank and its contents to prevent tank rupture/explosion (BLEVE) and fire spread. | 1 | Applied and Interdisciplinary Chemistry |
This technique is an extension of "chromosome walking" that allows larger "steps" along the chromosome.
If steps of length N kb are desired, very high molecular weight DNA is necessary. Once isolated, it is partially digested with a frequent-cutting restriction enzyme (such as MboI or BamHI). Next, obtained fragments are selected for size which should be around N kb in length. DNA must then be ligated at low concentration to favour ligation into circles rather than formation of multimers. A DNA marker (such as the amber suppressor tRNA gene supF) can be included at this time point within the covalently linked circle to allow for selection of junction fragments. Circles are subsequently fully digested with a second restriction enzyme (such as EcoRI) to generate a large number of fragments. Such fragments are ligated into vectors (such as a λ vector) which should be selected for using the DNA marker introduced earlier. The remaining fragments thus represent the library of junction fragments, or "jumping library".
The next step is to screen this library with a probe that represents a "starting point" of the desired "chromosome hop", i.e. determining the location of the genome that is being interrogated. Clones obtained from this final selection step will consist of DNA that is homologous to our probe, separated by our DNA marker from another DNA sequence that was originally located N kb away (thus being called "jumping").
By generating several libraries of different N values, eventually the entire genome can be mapped, allowing movement from one location to another, while controlling direction, by any value of N desired. | 1 | Applied and Interdisciplinary Chemistry |
Stereolithography, digital imaging, and 3D inkjet printing are just a few 3D printing technologies that make use of photopolymerization pathways. 3D printing usually utilizes CAD-CAM software, which creates a 3D computer model to be translated into a 3D plastic object. The image is cut in slices; each slice is then reconstructed through radiation curing of the liquid polymer, converting the image into a solid object. Photopolymers used in 3D imaging processes require sufficient cross-linking and should ideally be designed to have minimal volume shrinkage upon polymerization in order to avoid distortion of the solid object. Common monomers utilized for 3D imaging include multifunctional acrylates and methacrylates, often combined with a non-polymeric component in order to reduce volume shrinkage. A competing composite mixture of epoxide resins with cationic photoinitiators is becoming increasingly used since their volume shrinkage upon ring-opening polymerization is significantly below those of acrylates and methacrylates. Free-radical and cationic polymerizations composed of both epoxide and acrylate monomers have also been employed, gaining the high rate of polymerization from the acrylic monomer, and better mechanical properties from the epoxy matrix. | 0 | Theoretical and Fundamental Chemistry |
There are numerous reasons that each of the four processes can occur (detailed in each article). Generally speaking, sources of acid gain include:
# Retention of carbon dioxide
# Production of nonvolatile acids from the metabolism of proteins and other organic molecules
# Loss of bicarbonate in feces or urine
# Intake of acids or acid precursors
Sources of acid loss include:
# Use of hydrogen ions in the metabolism of various organic anions
# Loss of acid in the vomitus or urine
# Gastric aspiration in hospital
# Severe diarrhea
# Carbon dioxide loss through hyperventilation | 0 | Theoretical and Fundamental Chemistry |
The reaction is usually initiated by copper(II) chloride (CuCl), which is the most common catalyst in the production of 1,2-dichloroethane. In some cases, CuCl is supported on silica in presence of KCl, LaCl, or AlCl as cocatalysts. Aside from silica, a variety of supports have also been used including various types of alumina, diatomaceous earth, or pumice. Because this reaction is highly exothermic (238 kJ/mol), the temperature is monitored, to guard against thermal degradation of the catalyst. The reaction is as follows:
:CH=CH + 2 CuCl → 2 CuCl + ClHC-CHCl
The copper(II) chloride is regenerated by sequential reactions of the cuprous chloride with oxygen and then hydrogen chloride:
:½ O + 2 CuCl → CuOCuCl
:2 HCl + CuOCuCl → 2 CuCl + HO | 0 | Theoretical and Fundamental Chemistry |
This method is based on magnetic resonance imaging of the distribution of ions comprising NMR-active nuclei (usually 1H, 19F, 7Li) in an electrochemical cells upon application of electric current | 0 | Theoretical and Fundamental Chemistry |
Bosons are quantum mechanical particles that follow Bose–Einstein statistics, or equivalently, that possess integer spin. These particles can be classified as elementary: these are the Higgs boson, the photon, the gluon, the W/Z and the hypothetical graviton; or composite like the atom of hydrogen, the atom of O, the nucleus of deuterium, mesons etc. Additionally, some quasiparticles in more complex systems can also be considered bosons like the plasmons (quanta of charge density waves).
The first model that treated a gas with several bosons, was the photon gas, a gas of photons, developed by Bose. This model leads to a better understanding of Plancks law and the black-body radiation. The photon gas can be easily expanded to any kind of ensemble of massless non-interacting bosons. The phonon gas', also known as Debye model, is an example where the normal modes of vibration of the crystal lattice of a metal, can be treated as effective massless bosons. Peter Debye used the phonon gas model to explain the behaviour of heat capacity of metals at low temperature.
An interesting example of a Bose gas is an ensemble of helium-4 atoms. When a system of He atoms is cooled down to temperature near absolute zero, many quantum mechanical effects are present. Below 2.17 kelvins, the ensemble starts to behave as a superfluid, a fluid with almost zero viscosity. The Bose gas is the most simple quantitative model that explains this phase transition. Mainly when a gas of bosons is cooled down, it forms a Bose–Einstein condensate, a state where a large number of bosons occupy the lowest energy, the ground state, and quantum effects are macroscopically visible like wave interference.
The theory of Bose-Einstein condensates and Bose gases can also explain some features of superconductivity where charge carriers couple in pairs (Cooper pairs) and behave like bosons. As a result, superconductors behave like having no electrical resistivity at low temperatures.
The equivalent model for half-integer particles (like electrons or helium-3 atoms), that follow Fermi–Dirac statistics, is called the Fermi gas (an ensemble of non-interacting fermions). At low enough particle number density and high temperature, both the Fermi gas and the Bose gas behave like a classical ideal gas. | 0 | Theoretical and Fundamental Chemistry |
According to the Web of Science, the journal's two most cited papers () are:
* (cited 766 times)
* (cited 722 times) | 0 | Theoretical and Fundamental Chemistry |
Sphere packing on the corners of a hypercube (with the spheres defined by Hamming distance) corresponds to designing error-correcting codes: if the spheres have radius t, then their centers are codewords of a (2t + 1)-error-correcting code. Lattice packings correspond to linear codes. There are other, subtler relationships between Euclidean sphere packing and error-correcting codes. For example, the binary Golay code is closely related to the 24-dimensional Leech lattice.
For further details on these connections, see the book Sphere Packings, Lattices and Groups by Conway and Sloane. | 0 | Theoretical and Fundamental Chemistry |
Activation refers to the opening of ion channels, i.e. the conformational change that allows ions to pass. | 0 | Theoretical and Fundamental Chemistry |
The pressure head is dependent on the density of water, which can vary depending on both the temperature and chemical composition (salinity, in particular). This means that the hydraulic head calculation is dependent on the density of the water within the piezometer. If one or more hydraulic head measurements are to be compared, they need to be standardized, usually to their fresh water head, which can be calculated as:
where
* is the fresh water head (Length, measured in m or ft), and
* is the density of fresh water (Mass per unit volume, typically in kg·m) | 1 | Applied and Interdisciplinary Chemistry |
Joan Berkowitz<br>
Paul Crutzen (Nobel Prize in Chemistry, 1995)<br>
Philip Gschwend<br>
Alice Hamilton<br>
John M. Hayes<br>
Charles David Keeling<br>
Ralph Keeling<br>
Mario Molina (Nobel Prize in Chemistry, 1995)<br>
James J. Morgan<br>
Clair Patterson<br>
Roger Revelle<br>
Sherry Roland (Nobel Prize in Chemistry, 1995)<br>
Robert Angus Smith<br>
Susan Solomon<br>
Werner Stumm<br>
Ellen Swallow Richards<br>
Hans Suess<br>
John Tyndall | 1 | Applied and Interdisciplinary Chemistry |
The potential exposure of humans and animals on the ground to the high power microwave beams is a significant concern with these systems. At the Earth's surface, a suggested SPSP microwave beam would have a maximum intensity at its center, of 23 mW/cm. While this is less than 1/4 the solar irradiation constant, microwaves penetrate much deeper into tissue than sunlight, and at this level would exceed the current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves at 10 mW/cm At 23 mW/cm, studies show humans experience significant deficits in spatial learning and memory. If the diameter of the proposed SPSP array is increased by 2.5x, the energy density increases to 1 W/cm. At this level, the median lethal dose for mice is 30-60 seconds of microwave exposure. While designing an array with 2.5x larger diameter should be avoided, the dual-use military potential of such a system is readily apparent.
With good array sidelobe design, outside the receiver may be less than the OSHA long-term levels as over 95% of the beam energy will fall on the rectenna. However, any accidental or intentional mis-pointing of the satellite could be deadly to life on Earth within the beam.
Exposure to the beam can be minimized in various ways. On the ground, assuming the beam is pointed correctly, physical access must be controllable (e.g., via fencing). Typical aircraft flying through the beam provide passengers with a protective metal shell (i.e., a Faraday Cage), which will intercept the microwaves. Other aircraft (balloons, ultralight, etc.) can avoid exposure by using controlled airspace, as is currently done for military and other controlled airspace. In addition, a design constraint is that the microwave beam must not be so intense as to injure wildlife, particularly birds. Suggestions have been made to locate rectennas offshore, but this presents serious problems, including corrosion, mechanical stresses, and biological contamination.
A commonly proposed approach to ensuring fail-safe beam targeting is to use a retrodirective phased array antenna/rectenna. A "pilot" microwave beam emitted from the center of the rectenna on the ground establishes a phase front at the transmitting antenna. There, circuits in each of the antennas subarrays compare the pilot beams phase front with an internal clock phase to control the phase of the outgoing signal. This forces the transmitted beam to be centered precisely on the rectenna and to have a high degree of phase uniformity; if the pilot beam is lost for any reason (if the transmitting antenna is turned away from the rectenna, for example) the phase control value fails and the microwave power beam is automatically defocused. Such a system would not focus its power beam very effectively anywhere that did not have a pilot beam transmitter. The long-term effects of beaming power through the ionosphere in the form of microwaves has yet to be studied. | 0 | Theoretical and Fundamental Chemistry |
Metabolic regulation of nitrogen-containing molecules, such as amino acids, is also kept at steady state. The amino acid pool, which describes the level of amino acids in the body, is maintained at a relatively constant concentration by balancing the rate of input (i.e. from dietary protein ingestion, production of metabolic intermediates) and rate of depletion (i.e. from formation of body proteins, conversion to energy-storage molecules). Amino acid concentration in lymph node cells, for example, is kept at steady state with active transport as the primary source of entry, and diffusion as the source of efflux. | 0 | Theoretical and Fundamental Chemistry |
D-glyceraldehyde 3-phosphate is formed from the following three compounds in reversible reactions:
*Fructose-1,6-bisphosphate (F1,6BP), catalyzed by aldolase.
The numbering of the carbon atoms indicates the fate of the carbons according to their position in fructose 6-phosphate.
*Dihydroxyacetone phosphate (DHAP), catalyzed by triose phosphate isomerase.
*1,3-bisphosphoglycerate (1,3BPG), catalyzed by glyceraldehyde 3-phosphate dehydrogenase. | 0 | Theoretical and Fundamental Chemistry |
Contig can also refer to the overlapping clones that form a physical map of a chromosome when the top-down or hierarchical sequencing strategy is used. In this sequencing method, a low-resolution map is made prior to sequencing in order to provide a framework to guide the later assembly of the sequence reads of the genome. This map identifies the relative positions and overlap of the clones used for sequencing. Sets of overlapping clones that form a contiguous stretch of DNA are called contigs; the minimum number of clones that form a contig that covers the entire chromosome comprise the tiling path that is used for sequencing. Once a tiling path has been selected, its component BACs are sheared into smaller fragments and sequenced. Contigs therefore provide the framework for hierarchical sequencing.
The assembly of a contig map involves several steps. First, DNA is sheared into larger (50–200kb) pieces, which are cloned into BACs or PACs to form a BAC library. Since these clones should cover the entire genome/chromosome, it is theoretically possible to assemble a contig of BACs that covers the entire chromosome. Reality, however, is not always ideal. Gaps often remain, and a scaffold—consisting of contigs and gaps—that covers the map region is often the first result. The gaps between contigs can be closed by various methods outlined below. | 1 | Applied and Interdisciplinary Chemistry |
Biliproteins are pigment protein compounds that are located in photosynthesising organisms such as algae, and sometimes also in certain insects. They refer to any protein that contains a bilin chromophore. In plants and algae, the main function of biliproteins is to make the process of light accumulation required for photosynthesis more efficient; while in insects they play a role in growth and development. Some of their properties: including light-receptivity, light-harvesting and fluorescence have made them suitable for applications in bioimaging and as indicators; while other properties such as anti-oxidation, anti-aging and anti-inflammation in phycobiliproteins have given them potential for use in medicine, cosmetics and food technology. While research on biliproteins dates back as far as 1950, it was hindered due to issues regarding biliprotein structure, lack of methods available for isolating individual biliprotein components, as well as limited information on lyase reactions (which are needed to join proteins with their chromophores). Research on biliproteins has also been primarily focused on phycobiliproteins; but advances in technology and methodology, along with the discovery of different types of lyases, has renewed interest in biliprotein research, allowing new opportunities for investigating biliprotein processes such as assembly/disassembly and protein folding. | 1 | Applied and Interdisciplinary Chemistry |
Combinatorial chemistry comprises chemical synthetic methods that make it possible to prepare a large number (tens to thousands or even millions) of compounds in a single process. These compound libraries can be made as mixtures, sets of individual compounds or chemical structures generated by computer software. Combinatorial chemistry can be used for the synthesis of small molecules and for peptides.
Strategies that allow identification of useful components of the libraries are also part of combinatorial chemistry. The methods used in combinatorial chemistry are applied outside chemistry, too. | 1 | Applied and Interdisciplinary Chemistry |
Sumner has presented lectures to public and school groups, and she has participated in videos and films on exploring Mars. These have included presentations at Sierra College, a Northern California Rotary Club, and Sacramento State University's Science in the River City. She appeared in several videos on Mars exploration, including ones hosted by UC Davis and in the Finnish documentary film “The Other Side of Mars”.
Dawn Sumner's research has been covered in local and national media outlets, including Popular Science, Wired Magazine, KPCC public radio, the television series Take Part, and the BBC. | 0 | Theoretical and Fundamental Chemistry |
Aside from physical or chemical analyses to determine the handling and pollutant profile of a coal, the energy output of a coal is determined using a bomb calorimeter which measures the specific energy output of a coal during complete combustion. This is required particularly for coals used in steam generation. | 0 | Theoretical and Fundamental Chemistry |
RNA silencing-based resistance is a powerful tool for engineering resistant crops. The advantage of RNAi as a novel gene therapy against fungal, viral and bacterial infection in plants lies in the fact that it regulates gene expression via messenger RNA degradation, translation repression and chromatin remodelling through small non-coding RNAs. Mechanistically, the silencing processes are guided by processing products of the double-stranded RNA (dsRNA) trigger, which are known as small interfering RNAs and microRNAs. | 1 | Applied and Interdisciplinary Chemistry |
Dispersive mass transfer, in fluid dynamics, is the spreading of mass from highly concentrated areas to less concentrated areas. It is one form of mass transfer.
Dispersive mass flux is analogous to diffusion, and it can also be described using Fick's first law:
where c is mass concentration of the species being dispersed, E is the dispersion coefficient, and x is the position in the direction of the concentration gradient. Dispersion can be differentiated from diffusion in that it is caused by non-ideal flow patterns (i.e. deviations from plug flow) and is a macroscopic phenomenon, whereas diffusion is caused by random molecular motions (i.e. Brownian motion) and is a microscopic phenomenon. Dispersion is often more significant than diffusion in convection-diffusion problems. The dispersion coefficient is frequently modeled as the product of the fluid velocity, U, and some characteristic length scale, α: | 1 | Applied and Interdisciplinary Chemistry |
Transcriptomics has been characterised by the development of new techniques which have redefined what is possible every decade or so and rendered previous technologies obsolete. The first attempt at capturing a partial human transcriptome was published in 1991 and reported 609 mRNA sequences from the human brain. In 2008, two human transcriptomes, composed of millions of transcript-derived sequences covering 16,000 genes, were published, and by 2015 transcriptomes had been published for hundreds of individuals. Transcriptomes of different disease states, tissues, or even single cells are now routinely generated. This explosion in transcriptomics has been driven by the rapid development of new technologies with improved sensitivity and economy. | 1 | Applied and Interdisciplinary Chemistry |
Cumulative dose is the total dose resulting from repeated exposures of ionizing radiation to an occupationally exposed worker to the same portion of the body, or to the whole body, over a period of time.
In medicine, the total amount of a drug or radiation given to a patient over time; for example, the total dose of radiation given in a series of radiation treatments or imaging exams. Recent studies have drawn attention to high cumulative doses (>100 mSv) to millions of patients undergoing recurrent CT scans during a 1- to 5-year period. This has resulted in a debate on whether CT is really a low-dose imaging modality. | 0 | Theoretical and Fundamental Chemistry |
Another calculation performed describes the molecules of the exclusion zone using Quantum Mechanics and Quantum Electrodynamics. In this model the liquid bulk water is in a gaseous state. Then, above a certain density threshold and below a specific critical temperature, those molecules go to another quantum state, with lower energy.
In this lower energy, coherent state, the cloud of electrons oscillate between two quantum states: a ground state, and an excited state where one electron per molecule is almost
free (the binding energy is about 0.5 eV). In this coherent state the quantum superposition has a component with coefficient 0.9 of the ground state, and a component with 0.1 of the excited state. The electrons in this quantum state oscillate between the ground state and the excited state with a certain frequency, and this oscillation creates an electromagnetic field, which is confined within the super-molecular structure, so that no radiation is observed. The molecules of the structure, together with the confined electromagnetic field, constitute in this model the exclusion zone. | 1 | Applied and Interdisciplinary Chemistry |
ARBs have a large therapeutic index and therefore their (mostly low) oral bioavailability does not appear to be of clinical significance.
As can be seen in table 1, these drugs are highly plasma protein-bound and therefore oral administration once a day should provide sufficient antihypertensive effects.
Around 14% of orally ingested losartan is metabolized to its 5-carboxylic acid metabolite EXP 3174. As mentioned before, candesartan cilexetil and olmesartan medoxomil are inactive ester prodrugs that are completely hydrolyzed to their active forms by esterases during absorption from the gastrointestinal tract. These three metabolites are more potent AT receptor antagonists than their prodrugs. The other ARBs do not have active metabolites.
All of the ARBs, except for valsartan and olmesartan, are metabolized in some way by the cytochrome P450 (CYP) enzyme 2C9, that is found in the human liver. CYP2C9 is for example responsible for the metabolizing of losartan to EXP 3174 and the slow metabolizing of valsartan and candesartan to their inactive metabolites. Telmisartan is, on the other hand, in part metabolized by glucuronidation and olmesartan is excreted as the unchanged drug.
Telmisartan is the only ARB that can cross the blood–brain barrier and can therefore inhibit centrally mediated effects of Ang II, contributing to even better blood pressure control.
All of the ARBs have the same mechanism of action and differences in their potency can be related to their different pharmacokinetic profiles. A few clinical head-to-head comparisons have been made and candesartan, irbesartan and telmisartan appear to be slightly more effective than losartan in lowering blood pressure. This difference may be related to different strengths of activity at the receptor level, such as duration and strength of receptor binding. | 1 | Applied and Interdisciplinary Chemistry |
One-compartment kinetics for a chemical compound specifies that the uptake in the compartment is proportional to the concentration outside the compartment, and the elimination is proportional to the concentration inside the compartment. Both the compartment and the environment outside the compartment are considered to be homogeneous (well mixed).The compartment typically represents some organism (e.g. a fish or a daphnid).
This model is used in the simplest versions of the DEBtox method for the quantification of effects of toxicants. | 1 | Applied and Interdisciplinary Chemistry |
AREs are recognized by RNA binding proteins such as tristetraprolin (TTP), AUF1, and Hu Antigen R (HuR). Although the exact mechanism is not very well understood, recent publications have attempted to propose the action of some of these proteins. AUF1, also known as hnRNP D, binds AREs through RNA recognition motifs (RRMs). AUF1 is also known to interact with the translation initiation factor eIF4G and with poly(A)-binding protein, indicating that AUF1 senses the translational status of mRNA and decays accordingly through the excision of the poly(A) tail.
TTP's expression is rapidly induced by insulin. Immunoprecipitation experiments have shown that TTP co-precipitates with an exosome, suggesting that it helps recruit exosomes to the mRNA containing AREs. Alternatively, HuR proteins have a stabilizing effect—their binding to AREs increases the half-life of mRNAs. Similar to other RNA-binding proteins, this class of proteins contain three RRMs, two of which are specific to ARE elements. A likely mechanism for HuR action relies on the idea that these proteins compete with other proteins that normally have a destabilizing effect on mRNAs. HuRs are involved in genotoxic response—they accumulate in the cytoplasm in response to UV exposure and stabilize mRNAs that encode proteins involved in DNA repair. | 1 | Applied and Interdisciplinary Chemistry |
From early studies an initial model of PDE, active site topography was derived. This early model can be summarized into the following steps concerning cAMP active site topography:
# cAMP substrate with its adenine and ribose moieties in an "anti" relationship
# The phosphate atom in cAMP binds to PDE active site, using an arginine residue and a water molecule, which was initially associated with Mg. A second arginine residue and the Mg may also play roles during binding and/or play roles in the next step
# S2 attack of phosphorus by HO with formation of a trigonal bipyramid transition state
# 5´-AMP is formed as an "inverted" product. Electronic charges conserve the net charge overall and across the transition state | 1 | Applied and Interdisciplinary Chemistry |
The carbon–fluorine bond stretching appears in the infrared spectrum between 1000 and 1360 cm. The wide range is due to the sensitivity of the stretching frequency to other substituents in the molecule. Monofluorinated compounds have a strong band between 1000 and 1110 cm; with more than one fluorine atoms, the band splits into two bands, one for the symmetric mode and one for the asymmetric. The carbon–fluorine bands are so strong that they may obscure any carbon–hydrogen bands that might be present.
Organofluorine compounds can also be characterized using NMR spectroscopy, using carbon-13, fluorine-19 (the only natural fluorine isotope), or hydrogen-1 (if present). The chemical shifts in F NMR appear over a very wide range, depending on the degree of substitution and functional group. The table below shows the ranges for some of the major classes. | 0 | Theoretical and Fundamental Chemistry |
New chloroplasts may contain up to 100 copies of their DNA, though the number of chloroplast DNA copies decreases to about 15–20 as the chloroplasts age. They are usually packed into nucleoids, which can contain several identical chloroplast DNA rings. Many nucleoids can be found in each chloroplast.
In primitive red algae, the chloroplast DNA nucleoids are clustered in the center of the chloroplast, while in green plants and green algae, the nucleoids are dispersed throughout the stroma.
Though chloroplast DNA is not associated with true histones, in red algae, similar proteins that tightly pack each chloroplast DNA ring into a nucleoid have been found. | 0 | Theoretical and Fundamental Chemistry |
Thermal hydraulics (also called thermohydraulics) is the study of hydraulic flow in thermal fluids. The area can be mainly divided into three parts: thermodynamics, fluid mechanics, and heat transfer, but they are often closely linked to each other. A common example is steam generation in power plants and the associated energy transfer to mechanical motion and the change of states of the water while undergoing this process. Thermal-hydraulic analysis can determine important parameters for reactor design such as plant efficiency and coolability of the system.
The common adjectives are "thermohydraulic", "thermal-hydraulic" and "thermalhydraulic". | 0 | Theoretical and Fundamental Chemistry |
Other possible deposition methods include methods utilizing particle self-assembly by solvent evaporation, doctor blade, chemical vapor deposition and transfer printing. Some of these methods like solvent evaporation are extremely simple but produce low-quality films. Other methods such as the chemical vapor deposition are effective for certain types of particles and substrates but are limited in particle types that can be used and require heavier instrumentation investments. Also hybrid methods such as combining self-assembly to Langmuir-Blodgett have been used. | 0 | Theoretical and Fundamental Chemistry |
Starting with a zerovalent palladium species and a substrate containing a leaving group in the allylic position, the Tsuji–Trost reaction proceeds through the catalytic cycle outlined below.
First, the palladium coordinates to the alkene, forming a η -allyl-Pd Π complex. The next step is oxidative addition in which the leaving group is expelled with inversion of configuration and a η -allyl-Pd is created (also called ionization). The nucleophile then adds to the allyl group regenerating the η -allyl-Pd complex. At the completion of the reaction, the palladium detaches from the alkene and can start again in the catalytic cycle. | 0 | Theoretical and Fundamental Chemistry |
The main components of an XPS system are the source of X-rays, an ultra-high vacuum (UHV) chamber with mu-metal magnetic shielding, an electron collection lens, an electron energy analyzer, an electron detector system, a sample introduction chamber, sample mounts, a sample stage with the ability to heat or cool the sample, and a set of stage manipulators.
The most prevalent electron spectrometer for XPS is the hemispherical electron analyzer. They have high energy resolution and spatial selection of the emitted electrons. Sometimes, however, much simpler electron energy filters - the cylindrical mirror analyzers are used, most often for checking the elemental composition of the surface. They represent a trade-off between the need for high count rates and high angular/energy resolution. This type consists of two co-axial cylinders placed in front of the sample, the inner one being held at a positive potential, while the outer cylinder is held at a negative potential. Only the electrons with the right energy can pass through this setup and are detected at the end. The count rates are high but the resolution (both in energy and angle) is poor.
Electrons are detected using electron multipliers: a single channeltron for single energy detection, or arrays of channeltrons and microchannel plates for parallel acquisition. These devices consists of a glass channel with a resistive coating on the inside. A high voltage is applied between the front and the end. An incoming electron is accelerated to the wall, where it removes more electrons, in such a way that an electron avalanche is created, until a measurable current pulse is obtained. | 0 | Theoretical and Fundamental Chemistry |
Atomistic philosophies are found very early in Islamic philosophy and were influenced originally by earlier Greek and, to some extent, Indian philosophy. Islamic speculative theology in general approached issues in physics from an atomistic framework. | 1 | Applied and Interdisciplinary Chemistry |
The AFLP technology has the capability to detect various polymorphisms in different genomic regions simultaneously. It is also highly sensitive and reproducible. As a result, AFLP has become widely used for the identification of genetic variation in strains or closely related species of plants, fungi, animals, and bacteria. The AFLP technology has been used in criminal and paternity tests, also to determine slight differences within populations, and in linkage studies to generate maps for quantitative trait locus (QTL) analysis.
There are many advantages to AFLP when compared to other marker technologies including randomly amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP), and microsatellites. AFLP not only has higher reproducibility, resolution, and sensitivity at the whole genome level compared to other techniques, but it also has the capability to amplify between 50 and 100 fragments at one time. In addition, no prior sequence information is needed for amplification (Meudt & Clarke 2007). As a result, AFLP has become extremely beneficial in the study of taxa including bacteria, fungi, and plants, where much is still unknown about the genomic makeup of various organisms.
The AFLP technology is covered by patents and patent applications of Keygene N.V. AFLP is a registered trademark of Keygene N.V. | 1 | Applied and Interdisciplinary Chemistry |
For purposes of theoretical calculations about a thermodynamic system, one can imagine fictive idealized thermodynamic "processes" that occur so slowly that they do not incur friction within or on the surface of system; they can then be regarded as virtually reversible. These fictive processes proceed along paths on geometrical surfaces that are described exactly by a characteristic equation of the thermodynamic system. Those geometrical surfaces are the loci of possible states of thermodynamic equilibrium for the system. Really possible thermodynamic processes, occurring at practical rates, even when they occur only by work assessed in the surroundings as adiabatic, without heat transfer, always incur friction within the system, and so are always irreversible. The paths of such really possible processes always depart from those geometrical characteristic surfaces. Even when they occur only by work assessed in the surroundings as adiabatic, without heat transfer, such departures always entail entropy production. | 0 | Theoretical and Fundamental Chemistry |
Whole genome sequencing studies enable the assessment of associations between complex traits and both coding and noncoding rare variants (minor allele frequency (MAF) < 1%) across the genome. Single-variant analyses typically have low power to identify associations with rare variants, and variant set tests have been proposed to jointly test the effects of given sets of multiple rare variants. SNP annotations help to prioritize rare functional variants, and incorporating these annotations can effectively boost the power of genetic association of rare variants analysis of whole genome sequencing studies. Some tools have been specifically developed to provide all-in-one rare variant association analysis for whole-genome sequencing data, including integration of genotype data and their functional annotations, association analysis, result summary and visualization.
Meta-analysis of whole genome sequencing studies provides an attractive solution to the problem of collecting large sample sizes for discovering rare variants associated with complex phenotypes. Some methods have been developed to enable functionally informed rare variant association analysis in biobank-scale cohorts using efficient approaches for summary statistic storage. | 1 | Applied and Interdisciplinary Chemistry |
Isotopic ratio relative to each component in the system, each with its isotopic expression, with respect to the concentration of its most abundant isotopologue | 0 | Theoretical and Fundamental Chemistry |
Neutral detergent fiber (NDF) is the most common measure of fiber used for animal feed analysis, but it does not represent a unique class of chemical compounds. NDF measures most of the structural components in plant cells (i.e. lignin, hemicellulose and cellulose), but not pectin. Further analysis can be done to the sample to determine individual components such as acid detergent fiber (ADF) analysis.
The process of determining NDF content involves a neutral detergent that dissolves plant pectins, proteins, sugars and lipids. This leaves behind the fibrous parts such as cellulose, lignin and hemicellulose.
Recent nutritional requirement tables for ruminants report limits for NDF intake.
The level of NDF in the animal ration influences the animal's intake of dry matter and the time of rumination. The concentration of NDF in feeds is negatively correlated with energy concentration. | 0 | Theoretical and Fundamental Chemistry |
The Curiosity rover encountered rocks of special interest on the surface of Aeolis Palus near Aeolis Mons ("Mount Sharp") in Gale Crater. In the autumn of 2012, rocks studied, on the way from Bradbury Landing to Glenelg Intrigue, included "Coronation" rock (August 19, 2012), "Jake Matijevic" rock (September 19, 2012), "Bathurst Inlet" rock (September 30, 2012). | 0 | Theoretical and Fundamental Chemistry |
A related family of reactions are the transmetalations, wherein two organometallic compounds exchange their metals. Many examples of such reactions involve lithium exchange with tin:
:CHLi + MeSnAr → CHSnMe + LiAr (where Ar is aryl and Me is methyl)
The tin–lithium exchange reactions have one major advantage over the halogen–lithium exchanges for the preparation of organolithium reagents, in that the product tin compounds (CHSnMe in the example above) are much less reactive towards lithium reagents than are the halide products of the corresponding halogen–lithium exchanges (CHBr or CHCl). Other metals and metalloids which undergo such exchange reactions are organic compounds of mercury, selenium, and tellurium. | 0 | Theoretical and Fundamental Chemistry |
polySia is involved in many natural human functions. The major examples include membranes, neuron signaling, the immune system, neutrophil extracellular trap formation, and macrophage and microglia function. First, polySia makes membrane modifications due to interactions with a variety of factors. These could include repulsive forces between the polyanionic polySia and the mostly negatively charged glycocalyx. Because of these interactions the membrane is edited in its ability to interact with other cells, its surface charge distribution, inter-membrane interaction, pH, and membrane potential. Hydration and charge were noted before and after removing polySia from a membrane and a 25% decrease in the distance between cells was observed. This is due to the anti-adhesive properties of polySia. polySia does not only have repulsive interactions, as there are positive charge molecules located in lipid rafts, such as NCAM. The interaction between polySia and NCAM greatly affects NCAM's signaling ability as its composition is altered when they meet. Other forms of neuron signaling polySia is involved in include brain-derived neurotrophic factor (BDNF) and fibroblast growth factor 2 (FGF2). With nearly the same mechanism, the act of polysialylation causes BDNF or FGF2 complexes through electrostatic interactions. This allows for the binding of polySia and these complexes causing polySia to be a reservoir. polySia then regulates the concentration of neurotrophins. Because they are not allowed to diffuse, signaling is more efficient. polySia is also found on immune cell surfaces. Some of the proteins are known, but many are not and the mechanisms are still being studied. However, it is known that polySia is in regulatory functions in the immune system leading to protection from invaders and response to damaged tissue. polySia is involved in NETosis which is a reactionary function of the body in the presence of foreign invaders. It is the intentional death of neutrophils. polySia ensures that this targeted cell death does not kill cells that are healthy and unaffected, as well as containing antimicrobial attributes. This is done by polySia by binding to lactoferrin, another antimicrobial molecule, surrounding neutrophils. polySia binding causes a tighter shell of lactoferrin around the cell membrane. polySia binds with Siglec-11 allowing for the regulation of microglia through exosomes. This shows that polySia binding with Siglec-11 causes a delay in neurodegeneration and control of neuroinflammation. polySia also limits inflammation in macrophages. polySia was found to have limited the expression of tumour necrosis factor (TNF). | 1 | Applied and Interdisciplinary Chemistry |
In gases, the scintillation process is due to the de-excitation of single atoms excited by the passage of an incoming particle (a very rapid process: ≈1 ns). | 0 | Theoretical and Fundamental Chemistry |
Titer has the same origin as the word "title", from the French word titre, meaning "title" but referring to the documented purity of a substance, often gold or silver. This comes from the Latin word titulus, also meaning "title". | 1 | Applied and Interdisciplinary Chemistry |
Positive and negative controls should be run after preparation of each lot of medium.
Positive control: Escherichia coli
Negative control: Klebsiella | 0 | Theoretical and Fundamental Chemistry |
Oxoferryl species are commonly proposed as intermediates in catalytic cycles, especially biological systems in which O activation is required. Diatomic oxygen has a high reduction potential (E = 1.23 V), but the first step required to harness this potential is a thermodynamically unfavorable one electron reduction E = -0.16 V. This reduction occurs in nature by the formation of a superoxide complex in which a reduced metal is oxidized by O. The product of this reaction is a peroxide radical that is more readily reactive. A widely applicable method for the generation of high-valent oxoferryl species is the oxidation with iodosobenzene: | 0 | Theoretical and Fundamental Chemistry |
HACNS1 (also known as CENTG2 and located in the Human Accelerated Region 2) is a gene enhancer "that may have contributed to the evolution of the uniquely opposable human thumb, and possibly also modifications in the ankle or foot that allow humans to walk on two legs". Evidence to date shows that of the 110,000 gene enhancer sequences identified in the human genome, HACNS1 has undergone the most change during the evolution of humans following the split with the ancestors of chimpanzees. | 1 | Applied and Interdisciplinary Chemistry |
Primary Infrastructure
The primary infrastructure of RSN consists of seven primary nodes which were installed in 2012 by [http://www.l-3mps.com/maripro/index.aspx L-3 Maripro]. They are terminal points which help distribute power and bandwidth to the networks of deployed sensors.
Approximately 900 kilometers of cable (referred to as backbone cable) have been used to connect the primary nodes together. These cables make landfall at the shore station in Pacific, City, Oregon.
In 2005, over 175 scientists across the United States responded to a Request for Assistance from the National Science Foundation to develop a cabled observatory on the Juan de Fuca Plate. Nodes are located at pre-selected experimental sites throughout the Juan de Fuca plate. Axial Seamount, Hydrate Ridge on the Cascadia Margin and shallow water sites west of Newport, Oregon (the Endurance Array) all have primary nodes installed. The primary nodes are all located in environmentally benign areas.
Nodes also convert the 10kVdc voltage levels from the backbone cable to 375Vdc which is then directed to the secondary infrastructure. The 375V switching systems and Node telemetry systems were designed and manufactured by Texcel Technology Plc based in England. The software to manage the ports and telemetry protection systems was also supplied by Texcel as an element manager sitting under a Network Management System (NMS).
The primary nodes have a number of extra ports which offer the potential for large-scale future expansion (>100 kilometers).
Secondary Infrastructure
The converted 375Vdc voltage from the primary nodes is then directed at low-and medium-power nodes and junction boxes. The nodes and junction boxes (similar to power strips) offer direct power and communications to the instruments at the experimental sites. In concert, these parts make up the RSN secondary infrastructure.
Extension cables are used to link the primary nodes to the secondary infrastructure, providing power and communications.
Equipment is linked using wet-mate connectors. Different types of cable were installed depending on load requirements. Bandwidth from these cables ranges from 10 Gbit/s to 1 Gbit/s.
During the VISIONS ’13 expedition to continue construction of RSN, over 22,000 meters of extension cables were installed on the ocean floor. The cables all successfully went online.
Upon completion in 2014, over 100 cabled seafloor and water column instruments will be operational. These instruments will allow monitoring of biological, chemical, geological, and geophysical processes in the ocean. The secondary infrastructure will also include six mooring systems for water-column profilers.
Cables are frequently deployed all across the world in ocean basins and margins. They have considerably long lifetimes. The backbone cable was installed in the summer of 2011. The commercial cable-laying ship, [http://www.subcom.com/process/install-and-test/fleet.aspx TE SubCom Dependable], carried out this phase of the project.
Special environmental requirements were also taken into account. Certain cables are substantially well-armored, especially those deployed in volcanic areas, such as Axial Seamount. | 0 | Theoretical and Fundamental Chemistry |
where S is a singlet and T a triplet whose subscripts denote states (0 is the ground state, and 1 the excited state). Transitions can also occur to higher energy levels, but the first excited state is denoted for simplicity. | 0 | Theoretical and Fundamental Chemistry |
* The analyst wishes to simplify the conduct of a variety of titrations by using one sensor for all. For example, a laboratory might conduct routinely acid/base, redox, complexometric, sulfate and chloride titrations. A single thermometric sensor in conjunction with an autosampler will enable all titrations to be performed in the same carousel load without having to change titration sensors. After preparation of the samples and placing in the carousel, the analyst assigns the appropriate thermometric method to the beaker position in the carousel.
* The titration environment is considered unsuitable for conventional titration sensors. For example, glass membrane pH electrodes must be kept adequately hydrated for proper operation. The use of such electrodes in substantially non-aqueous media as in the determination of trace acids in lipids and lubricating oils can lead to loss of performance as the membrane fouls and dehydrates, and/or if the reference junction is partly or completely blocked. It is often necessary to keep a number of electrodes cycling through a rejuvenation program in order to keep up with an analytical workload. Thermometric sensors have no electrochemical interaction with the titrating solution, and therefore can be used on a continuous basis with essentially no maintenance. Similarly, the potentiometric titration of sulfate with barium chloride in various industrial samples can lead to rapid degradation of the indicating barium ion selective electrode.
* A thermometric titration methodology which cannot be emulated using other types of titration sensors will deliver superior or results otherwise unobtainable by other techniques. Examples are the determination of fluoride by titration with boric acid, the analysis of orthophosphate by titration with magnesium ions, and the direct titration of aluminium with fluoride ions. | 0 | Theoretical and Fundamental Chemistry |
With respect to acute toxicity, simple alcohols have low acute toxicities. Doses of several milliliters are tolerated. For pentanols, hexanols, octanols, and longer alcohols, LD50 range from 2–5 g/kg (rats, oral). Ethanol is less acutely toxic. All alcohols are mild skin irritants.
The metabolism of methanol (and ethylene glycol) is affected by the presence of ethanol, which has a higher affinity for liver alcohol dehydrogenase. In this way, methanol will be excreted intact in urine. | 0 | Theoretical and Fundamental Chemistry |
A knot is called achiral if it can be continuously deformed into its mirror image, otherwise it is called a chiral knot. For example, the unknot and the figure-eight knot are achiral, whereas the trefoil knot is chiral. | 0 | Theoretical and Fundamental Chemistry |
"The Talking Stone" is a science fiction mystery short story by American writer Isaac Asimov, which first appeared in the October 1955 issue of The Magazine of Fantasy and Science Fiction and was reprinted in the 1968 collection Asimovs Mysteries. "The Talking Stone" was the second of Asimovs Wendell Urth stories. | 1 | Applied and Interdisciplinary Chemistry |
It is an intermediate in the catabolism of aromatic amino acids such as phenylalanine and tyrosine.
4-Hydroxyphenylpyruvate (produced by transamination of tyrosine) is acted upon by the enzyme 4-hydroxyphenylpyruvate dioxygenase to yield homogentisate. If active and present, the enzyme homogentisate 1,2-dioxygenase further degrades homogentisic acid to yield 4-maleylacetoacetic acid. | 1 | Applied and Interdisciplinary Chemistry |
As the figure suggests, the effect of Reynolds numbers seems to be minor, with a low value of reduced frequency k=0.004, stall overshoot is minimal and most of the hysteresis loop is attributable to a delay in reattachment, rather than vortex shedding. | 1 | Applied and Interdisciplinary Chemistry |
Some stochastic models have been proposed to account for the effects of positive supercoiling buildup (PSB) in gene expression dynamics (e.g. in bacterial gene expression), differing in, e.g., the level of detail. In general, the detail increases when adding processes affected by and affecting supercoiling. As this addition occurs, the complexity of the model increases.
For example, in two models of different complexity are proposed. In the most detailed one, events were modeled at the nucleotide level, while in the other the events were modeled at the promoter region alone, and thus required much less events to be accounted for.
Examples of stochastic models that focus on the effects of PSB on a promoter's activity can be found in:. In general, such models include a promoter, Pro, which is the region of DNA controlling transcription and, thus, whose activity/locking is affected by PSB. Also included are RNA molecules (the product of transcription), RNA polymerases (RNAP) which control transcription, and Gyrases (G) which regulate PSB. Finally, there needs to be a means to quantify PSB on the DNA (i.e. the promoter) at any given moment. This can be done by having some component in the system that is produced over time (e.g., during transcription events) to represent positive supercoils, and that is removed by the action of Gyrases. The amount of this component can then be set to affect the rate of transcription. | 1 | Applied and Interdisciplinary Chemistry |
A uniform structure is identified by each sphere having the same number of contacting neighbours. This gives each sphere an identical neighbourhood. In the example image on the side each sphere has six neighbouring contacts.
The number of contacts is best visualised in the rolled-out contact network. It is created by rolling out the contact network into a plane of height and azimuthal angle of each sphere. For a uniform structure such as the one in the example image, this leads to a regular hexagonal lattice. Each dot in this pattern represents a sphere of the packing and each line a contact between adjacent spheres.
For all uniform structures above a diameter ratio of , the regular hexagonal lattice is its characterising feature since this lattice type has the maximum number of contacts. For different uniform structures the rolled-out contact pattern only varies by a rotation in the plane. Each uniform structure is thus distinguished by its periodicity vector , which is defined by the phyllotactic triplet . | 0 | Theoretical and Fundamental Chemistry |
Grafting, in the context of polymer chemistry, refers to the addition of polymer chains onto a surface. In the so-called grafting onto mechanism, a polymer chain adsorbs onto a surface out of solution. In the more extensive grafting from mechanism, a polymer chain is initiated and propagated at the surface. Because pre-polymerized chains used in the grafting onto method have a thermodynamically favored conformation in solution (an equilibrium hydrodynamic volume), their adsorption density is self-limiting. The radius of gyration of the polymer therefore is the limiting factor in the number of polymer chains that can reach the surface and adhere. The grafting from technique circumvents this phenomenon and allows for greater grafting densities.
The processes of grafting "onto", "from", and "through" are all different ways to alter the chemical reactivity of the surface they attach with. Grafting onto allows a preformed polymer, generally in a "mushroom regime", to adhere to the surface of either a droplet or bead in solution. Due to the larger volume of the coiled polymer and the steric hindrance this causes, the grafting density is lower for onto in comparison to grafting from. The surface of the bead is wetted by the polymer and the interaction in the solution caused the polymer to become more flexible. The extended conformation of the polymer grafted, or polymerized, from the surface of the bead means that the monomer must be in the solution and there for lyophilic. This results with a polymer that has favorable interactions with the solution, allowing the polymer to form more linearly. Grafting from therefore has a higher grafting density since there are more access to chain ends.
Peptide synthesis can provide one example of a grafting from synthetic process. In this process, an amino acid chain is grown by a series of condensation reaction from a polymer bead surface. This grafting technique allows for excellent control over the peptide composition as the bonded chain can be washed without desorption from the polymer.
Polymeric coatings are another area of applied grafting techniques. In the formulation of water-borne paint, latex particles are often surface modified to control particle dispersion and thus coating characteristics such as viscosity, film formation, and environmental stability (UV exposure and temperature variations). | 0 | Theoretical and Fundamental Chemistry |
Polymeric nanoparticles are synthetic polymers with a size ranging from 10 to 100 nm. Common synthetic polymeric nanoparticles include polyacrylamide, polyacrylate, and chitosan. Drug molecules can be incorporated either during or after polymerization. Depending on the polymerization chemistry, the drug can be covalently bonded, encapsulated in a hydrophobic core, or conjugated electrostatically. Common synthetic strategies for polymeric nanoparticles include microfluidic approaches, electrodropping, high pressure homogenization, and emulsion-based interfacial polymerization.
Polymer biodegradability is an important aspect to consider when choosing the appropriate nanoparticle chemistry. Nanocarriers composed of biodegradable polymers undergo hydrolysis in the body, producing biocompatible small molecules such as lactic acid and glycolic acid.
Polymeric nanoparticles can be created via self assembly or other methods such as particle replication in nonwetting templates (PRINT) which allows customization of composition, size, and shape of the nanoparticle using tiny molds. | 0 | Theoretical and Fundamental Chemistry |
In 1920, Nikola Tesla patented a valvular conduit or Tesla valve that works as a fluidic diode. It's a leaky diode, i.e. the reverse flow is non-zero for any applied pressure difference. Tesla valve also has non-linear response, as its diodicity has frequency dependence. It could be used in fluid circuits, such as a full-wave rectifier, to convert AC to DC.
In 1957, Billy M. Horton of the Harry Diamond Laboratories (which later became a part of the Army Research Laboratory) first came up with the idea for the fluidic amplifier when he realized that he could redirect the direction of flue gases using a small bellows. He proposed a theory on stream interaction, stating that one can achieve amplification by deflecting a stream of fluid with a different stream of fluid. In 1959, Horton and his associates, Dr. R. E. Bowles and Ray Warren, constructed a family of working vortex amplifiers out of soap, linoleum, and wood. Their published result caught the attention of several major industries and created a surge of interest in applying fluidics (then called fluid amplification) to sophisticated control systems, which lasted throughout the 1960s. Horton is credited for developing the first fluid amplifier control device and launching the field of fluidics. In 1961, Horton, Warren, and Bowles were among the 27 recipients to receive the first Army Research and Development Achievement Award for developing the fluid amplifier control device. | 1 | Applied and Interdisciplinary Chemistry |
Canonical bases may have either a carbonyl or an amine group on the carbons surrounding the nitrogen atom furthest away from the glycosidic bond, which allows them to base pair (Watson-Crick base pairing) via hydrogen bonds (amine with ketone, purine with pyrimidine). Adenine and 2-aminoadenine have one/two amine group(s), whereas thymine has two carbonyl groups, and cytosine and guanine are mixed amine and carbonyl (inverted in respect to each other).
The precise reason why there are only four nucleotides is debated, but there are several unused possibilities.
Furthermore, adenine is not the most stable choice for base pairing: in Cyanophage S-2L, diaminopurine (DAP) is used instead of adenine. Diaminopurine basepairs perfectly with thymine as it is identical to adenine but has an amine group at position 2 forming 3 intramolecular hydrogen bonds, eliminating the major difference between the two types of basepairs (weak A-T vs strong C-G). This improved stability affects protein-binding interactions that rely on those differences.
Other combination include:
* Isoguanine and isocytosine, which have their amine and ketone inverted compared to standard guanine and cytosine. They are not used probably as tautomers are problematic for base pairing, but isoC and isoG can be amplified correctly with PCR even in the presence of the 4 canonical bases.
* Diaminopyrimidine and xanthine, which bind like 2-aminoadenine and thymine but with inverted structures. This pair is not used as xanthine is a deamination product.
However, correct DNA structure can form even when the bases are not paired via hydrogen bonding; that is, the bases pair thanks to hydrophobicity, as studies have shown with DNA isosteres (analogues with same number of atoms) such as the thymine analogue 2,4-difluorotoluene (F) or the adenine analogue 4-methylbenzimidazole (Z). An alternative hydrophobic pair could be isoquinoline and pyrrolo[2,3-b]pyridine
Other noteworthy basepairs:
* Several fluorescent bases have also been made, such as the 2-amino-6-(2-thienyl)purine and pyrrole-2-carbaldehyde base pair.
* Metal-coordinated bases, such as pairing between a pyridine-2,6-dicarboxylate (tridentate ligand) and a pyridine (monodentate ligand) through square planar coordination to a central copper ion.
* Universal bases may pair indiscriminately with any other base, but, in general, lower the melting temperature of the sequence considerably; examples include 2'-deoxyinosine (hypoxanthine deoxynucleotide) derivatives, nitroazole analogues, and hydrophobic aromatic non-hydrogen-bonding bases (strong stacking effects). These are used as proof of concept and, in general, are not utilized in degenerate primers (which are a mixture of primers).
* The numbers of possible base pairs is doubled when xDNA is considered. xDNA contains expanded bases, in which a benzene ring has been added, which may pair with canonical bases, resulting in four additional possible base-pairs (xA-T, xT-A, xC-G, xG-C) with eight bases (or 16 bases if the unused arrangements are used). Another form of benzene added bases is yDNA, in which the base is widened by the benzene. | 1 | Applied and Interdisciplinary Chemistry |
At molecular weights between 6 and 10 kilodaltons the R-PEG hydrogel acts as a Maxwell material, which means the fluid has both viscosity and elasticity. This is determined by measuring the plateau modulus, the elastic modulus for a viscoelastic polymer is constant or "relaxed" when deformed, at a range of frequencies via oscillatory rheology. Plotting the first- vs second-order integrals of the modulus values, a Cole-Cole plot is obtained, which, when fitted to a Maxwell model, provides the following relationship:
Where
* is the plateau modulus
* is the oscillation frequency in radians per second | 0 | Theoretical and Fundamental Chemistry |
Non-mononuclidic elements are marked with an asterisk, and the long-lived primordial radioisotope given. In two cases (indium and rhenium), the most abundant naturally occurring isotope is the mildly radioactive one, and in the case of europium, nearly half of it is.
# Beryllium-9
# Fluorine-19
# Sodium-23
# Aluminium-27
# Phosphorus-31
# Scandium-45
# Vanadium-51* naturally occurs with 0.25% of radioactive vanadium-50
# Manganese-55
# Cobalt-59
# Arsenic-75
# Rubidium-85* naturally occurs with 27.835% of radioactive rubidium-87
# Yttrium-89
# Niobium-93
# Rhodium-103
# Indium-113* naturally occurs with majority (95.7%) radioactive isotope indium-115
# Iodine-127
# Caesium-133
# Lanthanum-139* naturally occurs with 0.09% radioactive lanthanum-138
# Praseodymium-141
# Europium-153* naturally occurs with 47.8% radioactive europium-151
# Terbium-159
# Holmium-165
# Thulium-169
# Lutetium-175* naturally occurs with 2.59% radioactive lutetium-176
# Rhenium-185* naturally occurs with majority (62.6%) radioactive isotope rhenium-187
# Gold-197 | 0 | Theoretical and Fundamental Chemistry |
Until 1969 there was no obvious relationship except that the two methods lead to the same predictions. As noted earlier, the Woodward–Hoffmann method requires symmetry. But in 1969 and 1970 a general formulation was published, namely, A ground-state pericyclic change is symmetry-allowed when the total number of (4q + 2) and (4r) components is odd. The 1969–1970 Woodward–Hoffmann general formulation is seen to be equivalent to the Zimmerman Möbius–Hückel concept. Thus each (4r) component provides one plus-minus overlap in the cyclic array (i.e. an odd number) for 4n electrons. The (4q + 2) component just makes certain that the number of electrons in symmetric bonds is 4n + 2.
The equivalency of the more recent formulation of the Woodward–Hoffmann rules has been discussed. | 0 | Theoretical and Fundamental Chemistry |
Tumor necrosis factor receptor 2 (TNFR2), also known as tumor necrosis factor receptor superfamily member 1B (TNFRSF1B) and CD120b, is one of two membrane receptors that binds tumor necrosis factor-alpha (TNFα). Like its counterpart, tumor necrosis factor receptor 1 (TNFR1), the extracellular region of TNFR2 consists of four cysteine-rich domains which allow for binding to TNFα. TNFR1 and TNFR2 possess different functions when bound to TNFα due to differences in their intracellular structures, such as TNFR2 lacking a death domain (DD). | 1 | Applied and Interdisciplinary Chemistry |
In addition, extremely high energy helium nuclei sometimes referred to as alpha particles make up about 10 to 12% of cosmic rays. The mechanisms of cosmic ray production continue to be debated. | 0 | Theoretical and Fundamental Chemistry |
For equilibria in a gas phase, fugacity, f, is used in place of activity. However, fugacity has the dimension of pressure, so it must be divided by a standard pressure, usually 1 bar, in order to produce a dimensionless quantity, . An equilibrium constant is expressed in terms of the dimensionless quantity. For example, for the equilibrium 2NO NO,
Fugacity is related to partial pressure, , by a dimensionless fugacity coefficient ϕ: . Thus, for the example,
Usually the standard pressure is omitted from such expressions. Expressions for equilibrium constants in the gas phase then resemble the expression for solution equilibria with fugacity coefficient in place of activity coefficient and partial pressure in place of concentration. | 0 | Theoretical and Fundamental Chemistry |
Before analyzing target genome structural aberration and copy number variation (CNV) with ESP, the target genome is usually amplified and conserved with artificial chromosome construction. The classic strategy to construct an artificial chromosome is bacterial artificial chromosome (BAC). Basically, the target chromosome is randomly digested and inserted into plasmids which are transformed and cloned in bacteria. The size of fragments inserted is 150–350 kb. Another commonly used artificial chromosome is fosmid. The difference between BAC and fosmids is the size of the DNA inserted. Fosmids can only hold 40 kb DNA fragments, which allows a more accurate breakpoint determination. | 1 | Applied and Interdisciplinary Chemistry |
Southern Research's Drug Discovery division conducts research focused on oncology, infectious disease, and neuroscience. Their current service areas include: High Throughput Screening (HTS), Chemistry, Oncology, Infectious Disease, Neuroscience, and the Center for Neuromolecular Research.
Southern Research is a founding member of the Alabama Drug Discovery Alliance (ADDA) along with the University of Alabama at Birmingham School of Medicine (SOM). The UAB Center for Clinical and Translational Science (CCTS), and the UAB Comprehensive Cancer Center (CCC) are also crucial contributors to the ADDA.
Mark J. Suto is vice president of Drug Discovery at Southern Research. He has been named a Fellow of the National Academy of Inventors (NAI) in recognition of his wide-ranging contributions to pharmaceutical research and drug discovery efforts. | 1 | Applied and Interdisciplinary Chemistry |
His last name is often seen hyphenated ("Folch-Pi"). In the Spanish tradition of providing two identifiers, he often signed with both his paternal and his maternal last names. When he moved to America and married, he decided to hyphenate his paternal and maternal last names, so that his children would bear his full family heritage: "Folch-Pi". His last names are often mispronounced "Foltsch Pie" or "Folk Pie" but the correct Catalan pronunciation is "Folk Pea". | 1 | Applied and Interdisciplinary Chemistry |
Targeted drug delivery can be used to treat many diseases, such as the cardiovascular diseases and diabetes. However, the most important application of targeted drug delivery is to treat cancerous tumors. In doing so, the passive method of targeting tumors takes advantage of the enhanced permeability and retention (EPR) effect. This is a situation specific to tumors that results from rapidly forming blood vessels and poor lymphatic drainage. When the blood vessels form so rapidly, large fenestrae result that are 100 to 600 nanometers in size, which allows enhanced nanoparticle entry. Further, the poor lymphatic drainage means that the large influx of nanoparticles are rarely leaving, thus, the tumor retains more nanoparticles for successful treatment to take place.
The American Heart Association rates cardiovascular disease as the number one cause of death in the United States. Each year 1.5 million myocardial infarctions (MI), also known as heart attacks, occur in the United States, with 500,000 leading to deaths. The costs related to heart attacks exceed $60 billion per year. Therefore, there is a need to come up with an optimum recovery system. The key to solving this problem lies in the effective use of pharmaceutical drugs that can be targeted directly to the diseased tissue. This technique can help develop many more regenerative techniques to cure various diseases. The development of a number of regenerative strategies in recent years for curing heart disease represents a paradigm shift away from conventional approaches that aim to manage heart disease.
Stem cell therapy can be used to help regenerate myocardium tissue and return the contractile function of the heart by creating/supporting a microenvironment before the MI. Developments in targeted drug delivery to tumors have provided the groundwork for the burgeoning field of targeted drug delivery to cardiac tissue. Recent developments have shown that there are different endothelial surfaces in tumors, which has led to the concept of endothelial cell adhesion molecule-mediated targeted drug delivery to tumors.
Liposomes can be used as drug delivery for the treatment of tuberculosis. The traditional treatment for TB is skin to chemotherapy which is not overly effective, which may be due to the failure of chemotherapy to make a high enough concentration at the infection site. The liposome delivery system allows for better microphage penetration and better builds a concentration at the infection site. The delivery of the drugs works intravenously and by inhalation. Oral intake is not advised because the liposomes break down in the Gastrointestinal System.
3D printing is also used by doctors to investigate how to target cancerous tumors in a more efficient way. By printing a plastic 3D shape of the tumor and filling it with the drugs used in the treatment the flow of the liquid can be observed allowing the modification of the doses and targeting location of the drugs. | 1 | Applied and Interdisciplinary Chemistry |
The most frequent quantitative definition of noise is the coefficient of variation:
where is the noise in a quantity , is the mean value of and is the standard deviation of . This measure is dimensionless, allowing a relative comparison of the importance of noise, without necessitating knowledge of the absolute mean.
Other quantities often used for mathematical convenience are the Fano factor:
and the normalized variance: | 1 | Applied and Interdisciplinary Chemistry |
The reaction is irreproducible in each run due to the initial inhomogeneity of the mixture which result from variation in stirring rate, overall volume as well as geometry of the reactors. Repeating the reaction in the statistically meaningful manners leads to the reproducible cumulative probability distribution curve. The example for this clock is iodate/arsenous acid reaction.
One reaction may fall into more than one classification above depending on the circumstance. For example, iodate−arsenous acid reaction can be substrate-depletive clock reaction, autocatalysis-driven clock reaction and crazy clock reaction. | 0 | Theoretical and Fundamental Chemistry |
In the practice of medicine it had been long understood that, as Ambroise Paré (1510–1590) had expressed it, the physician's duty was to "cure occasionally, relieve often, console always" ("Guérir quelquefois, soulager souvent, consoler toujours"). Accordingly, placebos were widespread in medicine until the 20th century, and were often endorsed as necessary deceptions.
According to Nicholas Jewson, eighteenth century English medicine was gradually moving away from a model in which the patient had considerable interaction with the physician – and, through this consultative relationship, had an equal influence on the physician's therapeutic approach. It was moving towards a paradigm in which the patient became the recipient of a more standardized form of intervention that was determined by the prevailing opinions of the medical profession of the day.
Jewson characterized this as parallel to the changes that were taking place in the manner in which medical knowledge was being produced; namely, a transition from "bedside medicine", through to "hospital medicine", and finally to "laboratory medicine".
The last vestiges of the "consoling" approach to treatment were the prescription of morale-boosting and pleasing remedies, such as the "sugar pill", electuary or pharmaceutical syrup; all of which had no known pharmacodynamic action, even at the time. Those doctors who provided their patients with these sorts of morale-boosting therapies (which, while having no pharmacologically active ingredients, provided reassurance and comfort) did so either to reassure their patients while the Vis medicatrix naturae (i.e., "the healing power of nature") performed its normalizing task of restoring them to health, or to gratify their patients' need for an active treatment.
In 1811, Hoopers Quincys Lexicon–Medicum defined placebo as "an epithet given to any medicine adapted more to please than benefit the patient".
Early implementations of placebo controls date back to 16th-century Europe with Catholic efforts to discredit exorcisms. Individuals who claimed to be possessed by demonic forces were given false holy objects. If the person reacted with violent contortions, it was concluded that the possession was purely imagination.
Use of the placebo effect as a medical treatment has been controversial throughout history, and was common until the mid twentieth century. In 1903 Richard Cabot concluded that it should be avoided because it is deceptive. Newman points out the "placebo paradox" – it may be unethical to use a placebo, but also unethical "not to use something that heals". He suggests to solve this dilemma by appropriating the meaning response in medicine, that is make use of the placebo effect, as long as the "one administering... is honest, open, and believes in its potential healing power".
John Haygarth was the first to investigate the efficacy of the placebo effect in the 18th century. He tested a popular medical treatment of his time, called "Perkins tractors", and concluded that the remedy was ineffectual by demonstrating that the results from a dummy remedy were just as useful as from the alleged "active" remedy.
Émile Coué, a French pharmacist, working as an apothecary at Troyes between 1882 and 1910, also advocated the effectiveness of the "Placebo Effect". He became known for reassuring his clients by praising each remedys efficiency and leaving a small positive notice with each given medication. His book Self-Mastery Through Conscious Autosuggestion' was published in England (1920) and in the United States (1922).
Placebos remained widespread in medicine until the 20th century, and they were sometimes endorsed as necessary deceptions. In 1903, Richard Cabot said that he was brought up to use placebos, but he ultimately concluded by saying that "I have not yet found any case in which a lie does not do more harm than good".
T. C. Graves first defined the "placebo effect" in a published paper in The Lancet in 1920. He spoke of "the placebo effects of drugs" being manifested in those cases where "a real psychotherapeutic effect appears to have been produced". | 1 | Applied and Interdisciplinary Chemistry |
In an isolated system, thermodynamic equilibrium by definition persists over an indefinitely long time. In classical physics it is often convenient to ignore the effects of measurement and this is assumed in the present account.
To consider the notion of fluctuations in an isolated thermodynamic system, a convenient example is a system specified by its extensive state variables, internal energy, volume, and mass composition. By definition they are time-invariant. By definition, they combine with time-invariant nominal values of their conjugate intensive functions of state, inverse temperature, pressure divided by temperature, and the chemical potentials divided by temperature, so as to exactly obey the laws of thermodynamics. But the laws of thermodynamics, combined with the values of the specifying extensive variables of state, are not sufficient to provide knowledge of those nominal values. Further information is needed, namely, of the constitutive properties of the system.
It may be admitted that on repeated measurement of those conjugate intensive functions of state, they are found to have slightly different values from time to time. Such variability is regarded as due to internal fluctuations. The different measured values average to their nominal values.
If the system is truly macroscopic as postulated by classical thermodynamics, then the fluctuations are too small to detect macroscopically. This is called the thermodynamic limit. In effect, the molecular nature of matter and the quantal nature of momentum transfer have vanished from sight, too small to see. According to Buchdahl: "... there is no place within the strictly phenomenological theory for the idea of fluctuations about equilibrium (see, however, Section 76)."
If the system is repeatedly subdivided, eventually a system is produced that is small enough to exhibit obvious fluctuations. This is a mesoscopic level of investigation. The fluctuations are then directly dependent on the natures of the various walls of the system. The precise choice of independent state variables is then important. At this stage, statistical features of the laws of thermodynamics become apparent.
If the mesoscopic system is further repeatedly divided, eventually a microscopic system is produced. Then the molecular character of matter and the quantal nature of momentum transfer become important in the processes of fluctuation. One has left the realm of classical or macroscopic thermodynamics, and one needs quantum statistical mechanics. The fluctuations can become relatively dominant, and questions of measurement become important.
The statement that the system is its own internal thermodynamic equilibrium may be taken to mean that indefinitely many such measurements have been taken from time to time, with no trend in time in the various measured values. Thus the statement, that a system is in its own internal thermodynamic equilibrium, with stated nominal values of its functions of state conjugate to its specifying state variables, is far far more informative than a statement that a set of single simultaneous measurements of those functions of state have those same values. This is because the single measurements might have been made during a slight fluctuation, away from another set of nominal values of those conjugate intensive functions of state, that is due to unknown and different constitutive properties. A single measurement cannot tell whether that might be so, unless there is also knowledge of the nominal values that belong to the equilibrium state. | 0 | Theoretical and Fundamental Chemistry |
Non-specific binding of the repressor to DNA plays a crucial role in the repression and induction of the Lac-operon. The specific binding site for the Lac-repressor protein is the operator. The non-specific interaction is mediated mainly by charge-charge interactions while binding to the operator is reinforced by hydrophobic interactions. Additionally, there is an abundance of non-specific DNA sequences to which the repressor can bind. Essentially, any sequence that is not the operator, is considered non-specific. Studies have shown, that without the presence of non-specific binding, induction (or unrepression) of the Lac-operon could not occur even with saturated levels of inducer. It had been demonstrated that, without non-specific binding, the basal level of induction is ten thousand times smaller than observed normally. This is because the non-specific DNA acts as sort of a "sink" for the repressor proteins, distracting them from the operator. The non-specific sequences decrease the amount of available repressor in the cell. This in turn reduces the amount of inducer required to unrepress the system. | 1 | Applied and Interdisciplinary Chemistry |
Specifically it is used as mefloquine hydrochloride.
Mefloquine is a chiral molecule with two asymmetric carbon centres, which means it has four different stereoisomers. The drug is currently manufactured and sold as a racemate of the (R,S)- and (S,R)-enantiomers by Hoffmann-La Roche, a Swiss pharmaceutical company. Essentially, it is two drugs in one. Plasma concentrations of the (–)-enantiomer are significantly higher than those for the (+)-enantiomer, and the pharmacokinetics between the two enantiomers are significantly different. The (+)-enantiomer has a shorter half-life than the (–)-enantiomer. | 0 | Theoretical and Fundamental Chemistry |
Depending on the nature of the substance, an elementary entity may be an atom, a molecule, an ion, an ion pair, or a subatomic particle such as a proton. For example, 10 moles of water (a chemical compound) and 10 moles of mercury (a chemical element) contain equal numbers of substance, with one atom of mercury for each molecule of water, despite the two quantities having different volumes and different masses.
The mole corresponds to a given count of entities. Usually the entities counted are chemically identical and individually distinct. For example, a solution may contain a certain number of dissolved molecules that are more or less independent of each other. However, in a solid the constituent entities are fixed and bound in a lattice arrangement, yet they may be separable without losing their chemical identity. Thus the solid is composed of a certain number of moles of such entities. In yet other cases, such as diamond, where the entire crystal is essentially a single molecule, the mole is still used to express the number of atoms bound together, rather than a count of molecules. Thus, common chemical conventions apply to the definition of the constituent entities of a substance, in other cases exact definitions may be specified.
The mass of a substance is equal to its relative atomic (or molecular) mass multiplied by the molar mass constant, which is almost exactly 1 g/mol. | 0 | Theoretical and Fundamental Chemistry |
Chemical defense is a strategy employed by many organisms to avoid consumption by producing toxic or repellent metabolites or chemical warnings which incite defensive behavioral changes. The production of defensive chemicals occurs in plants, fungi, and bacteria, as well as invertebrate and vertebrate animals. The class of chemicals produced by organisms that are considered defensive may be considered in a strict sense to only apply to those aiding an organism in escaping herbivory or predation. However, the distinction between types of chemical interaction is subjective and defensive chemicals may also be considered to protect against reduced fitness by pests, parasites, and competitors. Repellent rather than toxic metabolites are allomones, a sub category signaling metabolites known as semiochemicals. Many chemicals used for defensive purposes are secondary metabolites derived from primary metabolites which serve a physiological purpose in the organism. Secondary metabolites produced by plants are consumed and sequestered by a variety of arthropods and, in turn, toxins found in some amphibians, snakes, and even birds can be traced back to arthropod prey. There are a variety of special cases for considering mammalian antipredatory adaptations as chemical defenses as well. | 1 | Applied and Interdisciplinary Chemistry |
REST/NRSF in conjunction with RE1/NRSE also acts outside the nervous system as regulators and repressors. Current research has linked RE1/NRSE activity with the regulation of the expression of the atrial natriuretic peptide (ANP) gene. An NRSE regulatory region is present in the 3’ untranslated region of the ANP gene and acts as a mediator for its appropriate expression. The protein encoded by the ANP gene is important during embryonic development for the maturation and development of cardiac myocytes. However, during early childhood and throughout adulthood, ANP expression is suppressed or kept to a minimum in the ventricle. Thus, an abnormal induction of the ANP gene can lead to ventricular hypertrophy and severe cardiac consequences. In order to maintain the repression of the gene, NRSF (neuron-restrictive silencer factor) or REST binds to the NRSE region in the 3’untranslated region of the ANP gene. Furthermore, the NRSF-NRSE complex recruits a transcriptional corepressor known as mSin3. This leads to the activity of histone deacetylase in the region and the repression of the gene. Therefore, studies have revealed the correlation between REST/NRSF and RE1/NRSE in regulating the ANP gene expression in ventricular myocytes. A mutation in either the NRSF or NRSE can lead to an undesirable development of ventricular myocytes, due to lack of repression, which can then cause ventricular hypertrophy. Left ventricular hypertrophy, for example, increases an individuals chance of sudden death due to a ventricular arrhythmia resulting from the increased ventricular mass. In addition to the influence on the ANP' gene, the NRSE sequence regulates other cardiac embryonic genes, such as brain natriuretic peptide BNP, skeletal α-actin, and Na, K – ATPase α3 subunit. Hence, the regulatory activity of both NRSE and NRSF in mammals prevents not only neural dysfunctions but also physiological and phenotypical abnormalities in other non-neuronal regions of the body. | 1 | Applied and Interdisciplinary Chemistry |
The underground property has changed hands over the years. The property sold in 1990 for $1.3 million after Henderson passed away, and again in 2005 for $2 million. The current owners bought it in 2014 for $1,150,000. In 2019 it was again on the market for $18 million, then in 2024 reduced to $5.9 million. The purchasers, under the name "Society for the Preservation of Near Extinct Species," made the decision to maintain their anonymity while acquiring the property, which is now recognized as the Stasis Foundation. | 0 | Theoretical and Fundamental Chemistry |
In a medical laboratory, flocculation is the core principle used in various diagnostic tests, for example the rapid plasma reagin test. | 1 | Applied and Interdisciplinary Chemistry |
Total selenium in selenium yeast can be reliably determined using open acid digestion to extract selenium from the yeast matrix followed by flame atomic absorption spectrometry. Determination of the selenium species selenomethionine can be achieved via proteolytic digestion of selenium yeast followed by high-performance liquid chromatography with inductively coupled plasma mass spectrometry. | 1 | Applied and Interdisciplinary Chemistry |
The method is based on the set of the nodal equations which are simply mathematical representation of Kirchhoff's first law which states that the inlet and outlet flow at each node should be equal. Initial approximation is made to the nodal pressures. The approximation is then successively corrected until the final solution is reached. | 1 | Applied and Interdisciplinary Chemistry |
The Zener ratio is a dimensionless number that is used to quantify the anisotropy for cubic crystals. It is sometimes referred as anisotropy ratio and is named after Clarence Zener. Conceptually, it quantifies how far a material is from being isotropic (where the value of 1 means an isotropic material).
Its mathematical definition is
where refers to Elastic constants in Voigt notation. | 0 | Theoretical and Fundamental Chemistry |
The deep ocean basins are stably stratified, so mixing of surface waters with the deep ocean waters occurs only very slowly. The dissolved CO of the surface waters of the ocean is roughly in equilibrium with the partial pressure of CO in the atmosphere. As atmospheric CO levels are rising, the oceans are absorbing some CO from the atmosphere. When surface waters sink, they carry considerable amounts of CO into the deep oceans, away from the atmosphere. Because these waters are able to contain a large amount of CO, they have helped slow the rise in atmospheric CO concentrations, thus slowing some aspects of climate change.
Climate change could have different effects on ice melt and brine rejection. Previous studies have suggested that as ice cover thins, it will become a weaker insulator, resulting in larger ice production during the autumn and winter. The consequent increase in winter brine rejection will drive ocean ventilation and strengthen the inflow of warm Atlantic waters. Studies of the last glacial maximum have indicated that a drastic reduction in the production of sea ice, and thus reduction of brine rejection, would result in the weakening of the stratification in the global deep oceans and in CO release into the shallow oceans and the atmosphere, triggering global deglaciation. | 0 | Theoretical and Fundamental Chemistry |
The Sonogashira reaction is typically run under mild conditions. The cross-coupling is carried out at room temperature with a base, typically an amine, such as diethylamine, that also acts as the solvent. The reaction medium must be basic to neutralize the hydrogen halide produced as the byproduct of this coupling reaction, so alkylamine compounds such as triethylamine and diethylamine are sometimes used as solvents, but also DMF or ether can be used as solvent. Other bases such as potassium carbonate or cesium carbonate are occasionally used. In addition, deaerated conditions are formally needed for Sonogashira coupling reactions because the palladium(0) complexes are unstable in the air, and oxygen promotes the formation of homocoupled acetylenes. Recently, development of air-stable organopalladium catalysts enable this reaction to be conducted in the ambient atmosphere. In addition, R.M Al-Zoubi and co-workers successfully developed a method with high regioselectivity for 1,2,3-trihaloarene derivatives in good to high yields under ambient conditions. | 0 | Theoretical and Fundamental Chemistry |
Bonds between hydrogen and the other elements range from highly to somewhat covalent. Some hydrides, e.g. boron hydrides, do not conform to classical electron counting rules and the bonding is described in terms of multi-centered bonds, whereas the interstitial hydrides often involve metallic bonding. Hydrides can be discrete molecules, oligomers or polymers, ionic solids, chemisorbed monolayers, bulk metals (interstitial), or other materials. While hydrides traditionally react as Lewis bases or reducing agents, some metal hydrides behave as hydrogen-atom donors and act as acids. | 0 | Theoretical and Fundamental Chemistry |
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