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β-blockers can be selective for either β, β adrenergic receptor, or to be non-selective. By blocking β receptor it is possible to reduce heart rate, conduction of velocity and contractility. The blocking of β receptor promotes vascular smooth muscle contraction, which results in increase of peripheral resistance. Blockade of the β receptor effectively reduces the sympathetic activity, which results in reduce of the associated platelet-and coagulation activation. This is why a non-selective β-blocker treatment may result in a lower risk of both arterial and venous embolic events. | 1 | Applied and Interdisciplinary Chemistry |
The committee established an acceptable daily intake of 0.02 mg/kg/day in a meeting on pesticide residues. | 0 | Theoretical and Fundamental Chemistry |
In an electrolyte or a colloidal suspension, the Debye length for a monovalent electrolyte is usually denoted with symbol κ
where
* I is the ionic strength of the electrolyte in number/m units,
* ε is the permittivity of free space,
* ε is the dielectric constant,
* k is the Boltzmann constant,
* T is the absolute temperature in kelvins,
* is the elementary charge,
or, for a symmetric monovalent electrolyte,
where
* R is the gas constant,
* F is the Faraday constant,
* C is the electrolyte concentration in molar units (M or mol/L).
Alternatively,
where is the Bjerrum length of the medium in nm,
and the factor derives from transforming unit volume from cubic dm to cubic nm.
For deionized water at room temperature, at pH=7, λ ≈ 1μm.
At room temperature (), one can consider in water the relation:
where
* κ is expressed in nanometres (nm)
* I is the ionic strength expressed in molar (M or mol/L)
There is a method of estimating an approximate value of the Debye length in liquids using conductivity, which is described in ISO Standard, and the book. | 0 | Theoretical and Fundamental Chemistry |
Retention distance, or R, is a concept in thin layer chromatography, designed for quantitative measurement of equal-spreading of the spots on the chromatographic plate and one of the Chromatographic response functions. It is calculated from the following formula:
where n is the number of compounds separated, R are the Retention factor of the compounds sorted in non-descending order, R = 0 and R = 1. | 0 | Theoretical and Fundamental Chemistry |
Different definitions have been put forward for secondary flow in turbomachinery, such as "Secondary flow in broad terms means flow at right angles to intended primary flow".
Secondary flows occur in the main, or primary, flowpath in turbomachinery compressors and turbines (see also unrelated use of term for flow in the secondary air system of a gas turbine engine). They are always present when a wall boundary layer is turned through an angle by a curved surface. They are a source of total pressure loss and limit the efficiency that can be achieved for the compressor or turbine. Modelling the flow enables blade, vane and end-wall surfaces to be shaped to reduce the losses.
Secondary flows occur throughout the impeller in a centrifugal compressor but are less marked in axial compressors due to shorter passage lengths. Flow turning is low in axial compressors but boundary layers are thick on the annulus walls which gives significant secondary flows. Flow turning in turbine blading and vanes is high and generates strong secondary flow.
Secondary flows also occur in pumps for liquids and include inlet prerotation, or intake vorticity, tip clearance flow (tip leakage), flow separation when operating away from the design condition, and secondary vorticity.
The following, from Dixon, shows the secondary flow generated by flow turning in an axial compressor blade or stator passage. Consider flow with an approach velocity c1. The velocity profile will be non-uniform due to friction between the annulus wall and the fluid. The vorticity of this boundary layer is normal to the approach velocity and of magnitude
where z is the distance to the wall.
As the vorticity of each blade onto each other will be of opposite directions, a secondary vorticity will be generated. If the deflection angle, e, between the guide vanes is small, the magnitude of the secondary vorticity is represented as
This secondary flow will be the integrated effect of the distribution of secondary vorticity along the blade length. | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, the limit of local stability with respect to small fluctuations is clearly defined by the condition that the second derivative of Gibbs free energy is zero.
The locus of these points (the inflection point within a G-x or G-c curve, Gibbs free energy as a function of composition) is known as the spinodal curve. For compositions within this curve, infinitesimally small fluctuations in composition and density will lead to phase separation via spinodal decomposition. Outside of the curve, the solution will be at least metastable with respect to fluctuations. In other words, outside the spinodal curve some careful process may obtain a single phase system. Inside it, only processes far from thermodynamic equilibrium, such as physical vapor deposition, will enable one to prepare single phase compositions. The local points of coexisting compositions, defined by the common tangent construction, are known as a binodal coexistence curve, which denotes the minimum-energy equilibrium state of the system. Increasing temperature results in a decreasing difference between mixing entropy and mixing enthalpy, and thus the coexisting compositions come closer. The binodal curve forms the basis for the miscibility gap in a phase diagram. The free energy of mixing changes with temperature and concentration, and the binodal and spinodal meet at the critical or consolute temperature and composition. | 0 | Theoretical and Fundamental Chemistry |
Carbon Nanofoams have been shown to have great application as solar steam generators. They possess excellent light absorption, good thermal stability, low density, and low thermal conductivity, all factors important to solar generators. In experiments done, carbon nanofoams showed superior solar photo-thermal performance with an evaporation rate of 1.68 kg m−2 h−1 achieved under 1 sun irradiation.
Additionally, carbon nanofoams have also been used to create extremely efficient aerosol filters. Using cellulose nanofibers collected from recycled milk jugs, researchers were able to develop a carbon nanofoam that achieved a very high filtration efficacy (>99.5%) in tests run with 0.7 wt% nanofoam sample for particles smaller than 360 nm. This efficiency value even meets the standard requirements of the N95 respirator face masks. The structure of the nanofoam filter gives it an advantage in performance over normal filters when dealing with high particle bearing | 0 | Theoretical and Fundamental Chemistry |
Burks-Houck was dedicated to the establishment of the NOBCChE on the West Coast and its national endeavours. She was invited to Dakar, Senegal to represent NOBCChE as an environmental chemist and deliver a presentation titled: "Environmental Applications and Regulatory Reporting". She served as the first chair of the San Francisco Bay Area Chapter from 1984 – 1990 organizing educational and professional development events for the community. Burks-Houck was elected in 1991 as the national vice-president of NOBCChE, a position she held until elected as the first female president of the organization in 1993. Burks-Houck held this role for an unprecedented four consecutive terms before stepping down in 2001. Her involvement was credited with more than 100% increase in the number of student and professional chapters, instituting new scholarships through public and private entities, updating telephone and computer systems at the National Office, and establishing the Science Quiz Bowl and the Science Fair at the National level. Burks-Houck was also credited with building partnerships with other organizations such as the American Association for the Advancement of Science (AAAS), American Chemical Society (ACS), American Indian Science and Engineering Alliance, National Aeronautics and Space Administration (NASA), and the Society for the Advancement of Chicanos and Native Americans in Science (SACNAS).
Burks-Houck's legacy with the NOBCChE was expanded upon in 2010, after her death, through the creation of the Winifred Burks-Houck Professional Leadership Awards and Symposium to honour the contributions of African American women in science and technology. There are four categories of awards: Distinguished Lecturer, Professional Awardee, Graduate Student Awardee, and Undergraduate Awardee to recognize scientific achievements, creativity, leadership, and community service. | 0 | Theoretical and Fundamental Chemistry |
Many early scientists who studied the IR spectra of compounds had to develop and build their own instruments to be able to record their measurements making it very difficult to get accurate measurements. During World War II, the U.S. government contracted different companies to develop a method for the polymerization of butadiene to create rubber, but this could only be done through analysis of C4 hydrocarbon isomers. These contracted companies started developing optical instruments and eventually created the first infrared spectrometers. With the development of these commercial spectrometers, Infrared Spectroscopy became a more popular method to determine the "fingerprint" for any molecule. Raman spectroscopy was first observed in 1928 by Sir Chandrasekhara Venkata Raman in liquid substances and also by "Grigory Landsberg and Leonid Mandelstam in crystals". Raman spectroscopy is based on the observation of the raman effect which is defined as "The intensity of the scattered light is dependent on the amount of the polarization potential change". The raman spectrum records light intensity vs. light frequency (wavenumber) and the wavenumber shift is characteristic to each individual compound. | 0 | Theoretical and Fundamental Chemistry |
Isozymes were first described by R. L. Hunter and Clement Markert (1957) who defined them as different variants of the same enzyme having identical functions and present in the same individual. This definition encompasses (1) enzyme variants that are the product of different genes and thus represent different loci (described as isozymes) and (2) enzymes that are the product of different alleles of the same gene (described as allozymes).
Isozymes are usually the result of gene duplication, but can also arise from polyploidisation or nucleic acid hybridization. Over evolutionary time, if the function of the new variant remains identical to the original, then it is likely that one or the other will be lost as mutations accumulate, resulting in a pseudogene. However, if the mutations do not immediately prevent the enzyme from functioning, but instead modify either its function, or its pattern of expression, then the two variants may both be favoured by natural selection and become specialised to different functions. For example, they may be expressed at different stages of development or in different tissues.
Allozymes may result from point mutations or from insertion-deletion (indel) events that affect the coding sequence of the gene. As with any other new mutations, there are three things that may happen to a new allozyme:
* It is most likely that the new allele will be non-functional—in which case it will probably result in low fitness and be removed from the population by natural selection.
* Alternatively, if the amino acid residue that is changed is in a relatively unimportant part of the enzyme (e.g., a long way from the active site), then the mutation may be selectively neutral and subject to genetic drift.
* In rare cases, the mutation may result in an enzyme that is more efficient, or one that can catalyse a slightly different chemical reaction, in which case the mutation may cause an increase in fitness, and be favoured by natural selection. | 1 | Applied and Interdisciplinary Chemistry |
Light microscopes are designed for placement of the specimen's polished surface on the specimen stage either upright or inverted. Each type has advantages and disadvantages. Most LOM work is done at magnifications between 50 and 1000X. However, with a good microscope, it is possible to perform examination at higher magnifications, e.g., 2000X, and even higher, as long as diffraction fringes are not present to distort the image. However, the resolution limit of the LOM will not be better than about 0.2 to 0.3 micrometers. Special methods are used at magnifications below 50X, which can be very helpful when examining the microstructure of cast specimens where greater spatial coverage in the field of view may be required to observe features such as dendrites.
Besides considering the resolution of the optics, one must also maximize visibility by maximizing image contrast. A microscope with excellent resolution may not be able to image a structure, that is there is no visibility, if image contrast is poor. Image contrast depends upon the quality of the optics, coatings on the lenses, and reduction of flare and glare; but, it also requires proper specimen preparation and good etching techniques. So, obtaining good images requires maximum resolution and image contrast. | 1 | Applied and Interdisciplinary Chemistry |
To calculate the elastic response of a rubber sample, the three chain force models (regimes Ia, Ib and II) and the network morphology must be combined in a micro-mechanical network model. Using the joint probability distribution in equation () and the force extension models, it is possible to devise numerical algorithms to both construct a faithful representative volume element of a network and to simulate the resulting mechanical stress as it is subjected to strain. An iterative relaxation algorithm is used to maintain approximate force equilibrium at each network node as strain is imposed. When the force constant obtained for kinks having 2 or 3 isoprene units (approximately one Kuhn length) is used in numerical simulations, the predicted stress is found to be consistent with experiments. The results of such a calculation are shown in Fig. 1 (dashed red line) for sulfur cross-linked natural rubber and compared with experimental data (solid blue line). These simulations also predict a steep upturn in the stress as network chains become taut and, ultimately, material failure due to bond rupture. In the case of sulfur cross-linked natural rubber, the S-S bonds in the cross-link are much weaker than the C-C bonds on the chain backbone and are the network failure points. The plateau in the simulated stress, starting at a strain of about 7, is the limiting value for the network. Stresses greater than about 7 MPa cannot be supported and the network fails. Near this stress limit, the simulations predict that less than 10% of the chains are taut, i.e. in the high chain extension regime and less than 0.1% of the chains have ruptured. While the very low rupture fraction may seem surprising, it is not inconsistent with our experience of stretching a rubber band until it breaks. The elastic response of the rubber after breaking is not noticeably different from the original. | 0 | Theoretical and Fundamental Chemistry |
* Thionyl chloride can engage in a range of different electrophilic addition reactions. It adds to alkenes in the presence of to form an aluminium complex which can be hydrolysed to form a sulfinic acid. Both aryl sulfinyl chlorides and diaryl sulfoxides can be prepared from arenes through reaction with thionyl chloride in triflic acid or the presence of catalysts such as , , or .
* In the laboratory, a reaction between thionyl chloride and an excess of anhydrous alcohol can be used to produce anhydrous alcoholic solutions of HCl.
* Thionyl chloride undergoes halogen exchange reactions to give other thionyl species.
:Reactions with fluorinating agents such as antimony trifluoride give thionyl fluoride:
: A reaction with hydrogen bromide gives thionyl bromide:
:Thionyl iodide can likewise be prepared by a reaction with potassium iodide, but is reported to be highly unstable. | 0 | Theoretical and Fundamental Chemistry |
In Greece, Hippocrates (born 460 BC) was a philosopher later known as the Father of Medicine. He founded a school of medicine that focused on treating the causes of disease rather than its symptoms. Disease was dictated by natural laws and therefore could be treated through close observation of symptoms. His treatises, Aphorisms and Prognostics, discuss 265 drugs, the importance of diet and external treatments for diseases. | 1 | Applied and Interdisciplinary Chemistry |
The Payne rearrangement occurs with inversion of stereochemistry at C-2. Substrates containing multiple adjacent hydroxyl groups may undergo "cascade" epoxide migrations with inversion at each site of nucleophilic attack. In one example, inversion of three contiguous stereocenters results after two epoxide migrations, opening of the epoxide by carboxylate, and hydrolysis of the resulting lactone. | 0 | Theoretical and Fundamental Chemistry |
Atmospheric concentrations are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound or absorption by bodies of water). | 1 | Applied and Interdisciplinary Chemistry |
William Zismans contribution of what is called today as the Zisman Plot revolutionized the world of adhesive bonding and surface chemistry by giving a fast, effective, and quantitative way to measure the wettability or critical surface tension of a solid. This spawned the work of many others over the past few decades. This spans from Danns work in the late 1960s to David and Neumann's work in 2014. The Zisman Plot is still used today, and it has many variations since the y-axis is unitless and can be found more easily and accurately using modern regression software packages. | 0 | Theoretical and Fundamental Chemistry |
Biohydrometallurgy represents the overlap of the world of microorganisms to the process of hydrometallurgy. The usage of microorganisms can be used for recovery and extraction of metals. | 1 | Applied and Interdisciplinary Chemistry |
In Nahuatl, the language of the Aztecs, the word for calcium hydroxide is nextli. In a process called nixtamalization, maize is cooked with nextli to become , also known as hominy. Nixtamalization significantly increases the bioavailability of niacin (vitamin B3), and is also considered tastier and easier to digest. Nixtamal is often ground into a flour, known as masa, which is used to make tortillas and tamales.
In chewing coca leaves, calcium hydroxide is usually chewed alongside to keep the alkaloid stimulants chemically available for absorption by the body. Similarly, Native Americans traditionally chewed tobacco leaves with calcium hydroxide derived from burnt mollusc shells to enhance the effects. It has also been used by some indigenous American tribes as an ingredient in yopo, a psychedelic snuff prepared from the beans of some Anadenanthera species. | 0 | Theoretical and Fundamental Chemistry |
Source: [https://www.biochemistry.org/grants-and-awards/awards/the-portland-press-excellence-in-science-award/ Biochemical Society]
; Novartis Medal and Prize
* 2021: Bart Vanhaesebroeck
* 2019: Caroline Dean
* 2018: Laurence Pearl
* 2017: Doreen Cantrell
* 2014: Jeff Errington
* 2013: Tony Kouzarides
* 2010: D. Grahame Hardie
* 2009: Louise Johnson
* 2008: Stephen C. West
* 2007: Adrian Bird
* 2006: James Barber
* 2005: Alan Hall
* 2004: Jean D. Beggs
* 2003: Iain D. Campbell
* 2002: Michael S. Neuberger
* 2000: Kiyoshi Nagai
* 1999: Christopher J. Marshall
* 1998: Richard N. Perham
* 1997: Ronald Laskey
* 1996: John E. Walker
* 1995: Christopher F. Higgins
* 1993: T. Rabbitts
* 1992: Philip Cohen
* 1991: Paul Nurse
* 1987: Thomas L. Blundell
* 1985: E. A. Barnard
* 1984: Philip J. Randle
* 1983: George K. Radda
* 1981: I. Helen Muir
* 1980: Sydney Brenner
* 1979: J. B. Gurdon
* 1978: J. Rodney Quayle
* 1977: César Milstein
* 1976: Samuel V. Perry
* 1973: Peter D. Mitchell
* 1972: R. T. Williams
* 1971: D. H. Northcote
* 1970: D. C. Phillips
* 1968: William J. Whelan
* 1967: D. M. Blow
* 1966: R. R. Porter
* 1965: J. W. Cornforth and
Source: | 1 | Applied and Interdisciplinary Chemistry |
The half-life of delta bilirubin is equivalent to that of albumin since the former is bound to the latter, yields 2–3 weeks.
A free-of-bound bilirubin has a half-life of 2 to 4 hours. | 1 | Applied and Interdisciplinary Chemistry |
The method combines the reactions of copper ions with the peptide bonds under alkaline conditions (the Biuret test) with the oxidation of aromatic protein residues. The Lowry method is based on the reaction of Cu, produced by the oxidation of peptide bonds, with Folin–Ciocalteu reagent (a mixture of phosphotungstic acid and phosphomolybdic acid in the Folin–Ciocalteu reaction). The reaction mechanism is not well understood, but involves reduction of the Folin–Ciocalteu reagent and oxidation of aromatic residues (mainly tryptophan, also tyrosine). Experiments have shown that cysteine is also reactive to the reagent. Therefore, cysteine residues in protein probably also contribute to the absorbance seen in the Lowry assay. The result of this reaction is an intense blue molecule known as heteropolymolybdenum Blue. The concentration of the reduced Folin reagent (heteropolymolybdenum Blue) is measured by absorbance at 660 nm. As a result, the total concentration of protein in the sample can be deduced from the concentration of tryptophan and tyrosine residues that reduce the Folin–Ciocalteu reagent.
The method was first proposed by Lowry in 1951. The bicinchoninic acid assay and the Hartree–Lowry assay are subsequent modifications of the original Lowry procedure. | 1 | Applied and Interdisciplinary Chemistry |
Yves Jeannin is a French chemist born on 11 April 1931 in Boulogne sur Seine. He is the son of Raymond Jeannin, architect, and Suzanne Armynot du Chatelet. He married Suzanne Bellé in 1956 and has two children, Philippe and Sylvie, born in 1961 and 1969.
He is a corresponding member of the French Academy of sciences and Professor Emeritus at the Pierre and Marie Curie University. | 0 | Theoretical and Fundamental Chemistry |
LHASA (Logic and Heuristics Applied to Synthetic Analysis) is a computer program developed in 1971 by the research group of Elias James Corey at the Harvard University Department of Chemistry. The program uses artificial intelligence techniques to discover sequences of reactions which may be used to synthesize a molecule. This program was one of the first to use a graphical interface to input and display chemical structures. | 0 | Theoretical and Fundamental Chemistry |
In the 1990s, paroxysmal depolarizing shift-type interictal epileptiform discharges has been suggested to be primarily dependent on autaptic activity for solitary excitatory hippocampal rat neurons grown in microculture.
More recently, in human neocortical tissues of patients with intractable epilepsy, the GABAergic output autapses of fast-spiking (FS) neurons have been shown to have stronger asynchronous release (AR) compared to both non-epileptic tissue and other types of synapses involving FS neurons. The study found similar results using a rat model as well. An increase in residual Ca2+ concentration in addition to the action potential amplitude in FS neurons was suggested to cause this increase in AR of epileptic tissue. Anti-epileptic drugs could potentially target this AR of GABA that seems to rampantly occur at FS neuron autapses. | 1 | Applied and Interdisciplinary Chemistry |
Keepers are substances (typically solvents, but sometimes adsorbent solids) added in relatively small quantities during an evaporative procedure in analytical chemistry, such as concentration of an analyte-solvent mixture by rotary evaporation. The purpose of a keeper is to reduce losses of a target analyte during the procedure. Keepers typically have reduced volatility and are added to a more volatile solvent.
In the case of volatile target analytes, it is difficult to totally avoid loss of the analyte in an evaporative procedure, but the presence of a keeper solvent or solid is intended to preferentially solvate or adsorb the analyte, so that the volatility of the analyte is reduced as the evaporative procedure continues. In the case of non-volatile target analytes, the presence of the keeper solvent or solid is intended to prevent all the solvent from being evaporated off, thereby preventing the loss of analytes which might irreversibly adsorb to the container walls when completely dried, or if it is totally dried (in the case of a solid keeper), provide a surface where the analyte can be reversibly rather than irreversibly adsorbed. A solid keeper of sodium sulfate has been shown to be effective for reducing losses of polycyclic aromatic hydrocarbons (PAHs) in evaporative procedures. | 0 | Theoretical and Fundamental Chemistry |
Monitoring the biological pump is critical to understanding how the Earth's carbon cycle is changing. A variety of techniques are used to monitor the biological pump, which can be deployed from various platforms such as ships, autonomous vehicles, and satellites. At present, satellite remote sensing is the only tool available for viewing the entire surface ocean at high temporal and spatial scales. | 0 | Theoretical and Fundamental Chemistry |
If the p-i stimulation resulted in T cell expansion and activation (MPE, DRESS), some of the p-i-activated T cells might continue to react in the absence of drug: their TCR may be cross-reactive with unmodified, self HLA presenting exogenous peptides (mainly of herpes virus origin) or some self-peptides: this kind of cross-reactivity with exogenous or self peptides and self-HLA explain two late complications after severe DHR, mostly DRESS: one is viral reactivation: herpes viruses are permanently harboured in various cell types after infection (fibroblasts, endothelial cells, hematopoietic cells, brain cells, etc.) and are controlled by T cells. When these herpes-virus specific T cells are activated by p-i, they react with the herpes virus peptide expressing cells and damage them by their cytotoxic potential: a consequence is the release virus particles into the circulation and symptoms of viral reactivation (high virus load, possibly increase of liver enzymes and of activated lymphocytes) appear.
A second wave of peptide reactivity may end up in autoimmunity: the abnormal stimulation by p-i includes T cells from the naïve and memory T cell pool. It may include self-peptide reactive T cells, which, if the corresponding self-peptides are presented and are encountered, release cytokines and exert cytotoxicity - autoimmunity may arise. As such self-peptide reactive T cells are present in relatively low amounts, they need >6–8 weeks to expand and appear after the virus-reactivations. Autoimmunity occurs in a minority of patients (<20%), and may is often manifested as autoimmune poly-endocrine syndrome.
Multiple drug hypersensitivity (MDH): a further consequence of p-i stimulations like DRESS or severe MPE is MDH; such patients develop an additional DHR to a structurally different drug, with the same or different clinical manifestations. MDH occurs in ca. 20% of patients with DRESS, and can occur any time, from the start of DRESS (often to a combination therapy), during the initial activation, and can even appear years after the first DHR | 1 | Applied and Interdisciplinary Chemistry |
The largest and one of the fastest growing human impacts on the carbon cycle and biosphere is the extraction and burning of fossil fuels, which directly transfer carbon from the geosphere into the atmosphere. Carbon dioxide is also produced and released during the calcination of limestone for clinker production. Clinker is an industrial precursor of cement.
, about 450 gigatons of fossil carbon have been extracted in total; an amount approaching the carbon contained in all of Earth's living terrestrial biomass. Recent rates of global emissions directly into the atmosphere have exceeded the uptake by vegetation and the oceans. These sinks have been expected and observed to remove about half of the added atmospheric carbon within about a century. Nevertheless, sinks like the ocean have evolving saturation properties, and a substantial fraction (20–35%, based on coupled models) of the added carbon is projected remain in the atmosphere for centuries to millennia. | 0 | Theoretical and Fundamental Chemistry |
Because of the link between chlorophyll content and nitrogen content in leaves, chlorophyll fluorometers can be used to detect nitrogen deficiency in plants, by several methods.
Based on several years of research and experimentation, polyphenols can be the indicators of nitrogen status of a plant. For instance, when a plant is under optimal conditions, it favours its primary metabolism and synthesises the proteins (nitrogen molecules) containing chlorophyll, and few flavonols (carbon-based secondary compounds). On the other hand, in case of lack of nitrogen, we will observe an increased production of flavonols by the plant.
The NBI (Nitrogen Balance Index) by Force-A, allows the assessment of nitrogen conditions of a culture by calculating the ratio between Chlorophyll and Flavonols (related to Nitrogen/Carbon allocation) . | 0 | Theoretical and Fundamental Chemistry |
In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior.
According to Hutton's law of inclusions, fragments included in a host rock are older than the host rock itself. | 1 | Applied and Interdisciplinary Chemistry |
The heat deflection temperature or heat distortion temperature (HDT, HDTUL, or DTUL) is the temperature at which a polymer or plastic sample deforms under a specified load. This property of a given plastic material is applied in many aspects of product design, engineering and manufacture of products using thermoplastic components. | 0 | Theoretical and Fundamental Chemistry |
There are several differences in the regulation of metabolic control in eukaryotes and in prokaryotes. Prokaryotes vary the numbers of specific enzymes made in their cells in order to regulate gene expression, which is slow metabolic control, and also regulate enzymatic pathways through mechanisms such as feedback inhibition and allosteric regulation, which is rapid metabolic control. The genes of prokaryotes are grouped together based on similar functions into units called operons which consist of a promoter and an operator. The operator is the binding site for the repressor and thus has a function equivalent to the silencer region in Eukaryotic DNA. When a repressor protein is bound to the operator, RNA polymerase cannot bind to the promoter to initiate the transcription of the operon. | 1 | Applied and Interdisciplinary Chemistry |
The behavior of pipe flow is governed mainly by the effects of viscosity and gravity relative to the inertial forces of the flow. Depending on the effect of viscosity relative to inertia, as represented by the Reynolds number, the flow can be either laminar or turbulent. For circular pipes of different surface roughness, at a Reynolds number below the critical value of approximately 2000 pipe flow will ultimately be laminar, whereas above the critical value turbulent flow can persist, as shown in Moody chart. For non-circular pipes, such as rectangular ducts, the critical Reynolds number is shifted, but still depending on the aspect ratio. Earlier transition to turbulence, happening at Reynolds number one order of magnitude smaller, i.e. , can happen in channels with special geometrical shapes, such as the Tesla valve.
Flow through pipes can roughly be divided into two:
*Laminar flow - see Hagen-Poiseuille flow
*Turbulent flow - see Moody diagram | 1 | Applied and Interdisciplinary Chemistry |
At least for vitiligo, narrowband ultraviolet B (UVB) nanometer phototherapy is now used more commonly than PUVA since it does not require the use of the psoralen. As with PUVA, treatment is carried out 2 to 3 times a week in a clinic or every day at home, and there is no need to use psoralen.
Narrowband UVB therapy is less effective for the legs and hands, compared to the face and neck. To the hands and legs PUVA may be more effective. The reason can be because UVA penetrates deeper in the skin, and the melanocytes in the skin of the hands and legs are positioned deeper in the skin. Narrowband UVB 311 nanometer is blocked by the topmost skin layer, and UVA 365 nanometer reaches the melanocytes that are in the bottom skin layer.
Melanin is a dark pigment of the skin and the melanocytes produce it. The melanocytes produce melanin when their receptors detect UV light. The purpose of the melanin is to block UV light so that it will not cause damage to the body cells under the skin. | 0 | Theoretical and Fundamental Chemistry |
Stereochemical control within [4+4] reactions is not common, however it does exist. Enol-exo stereoselectivity is possible using certain cross-linking techniques and has been met with moderate success.
Control over the configuration at newly established bridgehead centers by use of preexisting stereocenters has been largely unsuccessful, apart from one specialized example. | 0 | Theoretical and Fundamental Chemistry |
Atomic, molecular, and optical physics (AMO) is the study of matter–matter and light–matter interactions, at the scale of one or a few atoms and energy scales around several electron volts. The three areas are closely interrelated. AMO theory includes classical, semi-classical and quantum treatments. Typically, the theory and applications of emission, absorption, scattering of electromagnetic radiation (light) from excited atoms and molecules, analysis of spectroscopy, generation of lasers and masers, and the optical properties of matter in general, fall into these categories. | 0 | Theoretical and Fundamental Chemistry |
Scholarly information about the use of gold in early Philippine history comes mostly from artifacts that have been discovered in various sites in the Philippines, and from historical accounts from the early Spanish colonial period. Archeological excavation sites include ones in Batangas, Mindoro, Luzon, Samar, Butuan and Surigao. | 1 | Applied and Interdisciplinary Chemistry |
* Jayko, A.S., et al. (2013). [https://purl.fdlp.gov/GPO/gpo45331 Methods and Spatial Extent of Geophysical Investigations, Mono Lake, California, 2009 to 2011.] Reston, Va.: U.S. Department of the Interior, U.S. Geological Survey. | 1 | Applied and Interdisciplinary Chemistry |
Researchers at Utah State University compared measurements for PPF and YPF using different types of equipment. They measured the PPF and YPF of seven common radiation sources with a spectroradiometer, then compared with measurements from six quantum sensors designed to measure PPF, and three quantum sensors designed to measure YPF.
They found that the PPF and YPF sensors were the least accurate for narrow-band sources (narrow spectrum of light) and most accurate for broad-band sources (fuller spectra of light). They found that PPF sensors were significantly more accurate under metal halide, low-pressure sodium and high-pressure sodium lamps than YPF sensors (>9% difference). Both YPF and PPF sensors were very inaccurate (>18% error) when used to measure light from red-light-emitting diodes. | 0 | Theoretical and Fundamental Chemistry |
Boiler water treatment is used to control alkalinity, prevent scaling, correct pH, and to control conductivity. The boiler water needs to be alkaline and not acidic, so that it does not ruin the tubes. There can be too much conductivity in the feed water when there are too many dissolved solids. These correct treatments can be controlled by efficient operator and use of treatment chemicals. The main objectives to treat and condition boiler water is to exchange heat without scaling, protect against scaling, and produce high quality steam. The treatment of boiler water can be put into two parts. These are internal treatment and external treatment. (Sendelbach, p. 131) The internal treatment is for boiler feed water and external treatment is for make-up feed water and the condensate part of the system. Internal treatment protects against feed water hardness by preventing precipitating of scale on the boiler tubes. This treatment also protects against concentrations of dissolved and suspended solids in the feed water without priming or foaming. These treatment chemicals also help with the alkalinity of the feed water making it more of a base to help protect against boiler corrosion. The correct alkalinity is protected by adding phosphates. These phosphates precipitate the solids to the bottom of the boiler drum. At the bottom of the boiler drum there is a bottom blow to remove these solids. These chemicals also include anti-scaling agents, oxygen scavengers, and anti-foaming agents. Sludge can also be treated by two approaches. These are by coagulation and dispersion. When there is a high amount of sludge content it is better to coagulate the sludge to form large particles in order to just use the bottom blow to remove them from the feed water. When there is a low amount of sludge content it is better to use dispersants because it disperses the sludge throughout the feed water so sludge does not form. | 1 | Applied and Interdisciplinary Chemistry |
His academic career began in 1948 with a teaching position at Iowa State College; he served as Assistant Professor of Chemistry. In his capacity there he published his eponymous postulate which is now widely known as the most important publication in the field of organic photochemistry. He moved to the University of Oxford and University of Basel as a Guggenheim Fellow and National Science Foundation Fellow, respectively. In 1958, he moved to the California Institute of Technology as a Professor of Organic Chemistry. Later he was appointed the Arthur Amos Noyes Professor of Chemistry and subsequently went on to lead the Departments of Chemistry and Chemical Engineering. After 14 years teaching and serving as an academic administrator at Caltech he moved in 1972 to the University of California Santa Cruz. At University of California Santa Cruz he served as both a professor and the Chancellor of the natural sciences. | 0 | Theoretical and Fundamental Chemistry |
Modeling eddy development, as it relates to turbulence and fate transport phenomena, is vital in grasping an understanding of environmental systems. By understanding the transport of both particulate and dissolved solids in environmental flows, scientists and engineers will be able to efficiently formulate remediation strategies for pollution events. Eddy formations play a vital role in the fate and transport of solutes and particles in environmental flows such as in rivers, lakes, oceans, and the atmosphere. Upwelling in stratified coastal estuaries warrant the formation of dynamic eddies which distribute nutrients out from beneath the boundary layer to form plumes. Shallow waters, such as those along the coast, play a complex role in the transport of nutrients and pollutants due to the proximity of the upper-boundary driven by the wind and the lower-boundary near the bottom of the water body. | 1 | Applied and Interdisciplinary Chemistry |
The in the atmosphere transfers to the ocean by dissolving in the surface water as carbonate and bicarbonate ions; at the same time the carbonate ions in the water are returning to the air as . This exchange process brings from the atmosphere into the surface waters of the ocean, but the thus introduced takes a long time to percolate through the entire volume of the ocean. The deepest parts of the ocean mix very slowly with the surface waters, and the mixing is uneven. The main mechanism that brings deep water to the surface is upwelling, which is more common in regions closer to the equator. Upwelling is also influenced by factors such as the topography of the local ocean bottom and coastlines, the climate, and wind patterns. Overall, the mixing of deep and surface waters takes far longer than the mixing of atmospheric with the surface waters, and as a result water from some deep ocean areas has an apparent radiocarbon age of several thousand years. Upwelling mixes this "old" water with the surface water, giving the surface water an apparent age of about several hundred years (after correcting for fractionation). This effect is not uniform – the average effect is about 400 years, but there are local deviations of several hundred years for areas that are geographically close to each other. These deviations can be accounted for in calibration, and users of software such as CALIB can provide as an input the appropriate correction for the location of their samples. The effect also applies to marine organisms such as shells, and marine mammals such as whales and seals, which have radiocarbon ages that appear to be hundreds of years old. | 0 | Theoretical and Fundamental Chemistry |
Hydrosilylation, also called catalytic hydrosilation, describes the addition of Si-H bonds across unsaturated bonds. Ordinarily the reaction is conducted catalytically and usually the substrates are unsaturated organic compounds. Alkenes and alkynes give alkyl and vinyl silanes; aldehydes and ketones give silyl ethers. Hydrosilylation has been called the "most important application of platinum in homogeneous catalysis." | 0 | Theoretical and Fundamental Chemistry |
PPA is a metastable polymer known for its ease of synthesis and rapid depolymerization. In addition, its properties can be easily influenced and manipulated upon either functionalizing the phthalaldehyde monomer with different groups, most efficiently, electron withdrawing groups, or employing different functional groups as end caps. | 0 | Theoretical and Fundamental Chemistry |
As sea ice freezes, it rejects increasingly salty water, which drains through narrow brine channels that thread through the ice. The brine flowing through the brine channels and out of the bottom of the ice is very cold and salty, so it sinks in the warmer, fresher seawater under the ice, forming a plume. The plume is colder than the freezing point of sea water under the ice, so the seawater can freeze where it touches the plume. Ice freezing around the edges of the plume gradually builds a hollow icicle-like tube, called a brinicle. These frozen stalactite-like forms are fragile during early stages, but if brine drainage ceases, they may freeze solid. In calm waters, brinicles can reach the sea floor, freezing it fairly abruptly. | 0 | Theoretical and Fundamental Chemistry |
Surface roughness and texture has an undeniable influence on protein adsorption on all materials, but with the ubiquity of metal machining processes, it is useful to address how these impact protein behavior. The initial adsorption is important, as well as maintained adhesion and integrity. Research has shown that surface roughness can encourage the adhesion of scaffold proteins and osteoblasts, and results in an increase in surface mineralization. Surfaces with more topographical features and roughness will have more exposed surface area for proteins to interact with. In terms of biomedical engineering applications, micromachining techniques are often used to increase protein adhesion to implants in the hopes of shortening recovery time. The technique of laserpatterning introduces grooves and surface roughness that will influence adhesion, migration and alignment. Grit-blasting, a method analogous to sand blasting, and chemical etching have proven to be successful surface roughening techniques that promote the long-term stability of titanium implants. The increase in stability is a direct result of the observed increase in extracellular matrix and collagen attachment, which results in increased osteoblast attachment and mineralization when compared to non-roughened surfaces. Adsorption is not always desirable, however. Machinery can be negatively affected by adsorption, particularly with Protein adsorption in the food industry. | 1 | Applied and Interdisciplinary Chemistry |
The levonorgestrel intrauterine system (LNG-IUS) is a type of long-term birth control that releases the progestin into the uterine cavity. Levonorgestrel is released at a constant, gradual rate of 0.02 mg per day by the polydimethylsiloxane membrane of the device, which renders it effective for up to five years. Because it is inserted directly into the uterus, levonorgestrel is present in the endometrium in much higher concentrations that would result from a LNG-containing oral pill; the LNG-IUS delivers 391 ng of levonorgestrel to the inner uterine region while a comparable oral contraceptive delivers only 1.35 ng. This high level of levonorgestrel impedes the function of the endometrium, making it hostile for sperm transport, fertilization, and implantation of an ovum. | 0 | Theoretical and Fundamental Chemistry |
The amount of transcription factories found per nucleus appears to be determined by cell type, species and the type of measurement. Cultured mouse embryonic fibroblasts have been found to have roughly 1500 factories through immunofluorescence detection of RNAP II however cells taken from different tissues of the same mouse group had between 100 and 300 factories. Measurements of the number of transcription factories in HeLa cells give a varied result. For example, using the traditional fluorescence microscopy approach 300 – 500 factories were found but using both confocal and electron microscopy roughly 2100 were detected. | 1 | Applied and Interdisciplinary Chemistry |
*Microarray-Based Study by Metal Nanoparticle Probes
Recently, studies by using metal nanoparticle probes to detect the carbohydrate–protein interactions were reported. Use of gold and silver nanoparticle probes in resonant light scattering (RLS) gives particular high sensitivity. Zhenxin Wang and coworker the same principle applied this method to detect the interaction between carbohydrate and protein.
*Carbohydrate biosensor
As Lectin can strongly bind to specific carbohydrate, scientists develop several lectin-based carbohydrate biosensors. Designed lectin contains specific groups can be detected by analytical method.
*Isothermal Titration Calorimetry | 0 | Theoretical and Fundamental Chemistry |
The thermal expansion of liquids is usually higher than in solids because the intermolecular forces present in liquids are relatively weak and its constituent molecules are more mobile. Unlike solids, liquids have no definite shape and they take the shape of the container. Consequently, liquids have no definite length and area, so linear and areal expansions of liquids only have significance in that they may be applied to topics such as thermometry and estimates of sea level rising due to global climate change. Sometimes, α is still calculated from the experimental value of α.
In general, liquids expand on heating, except cold water; below 4 °C it contracts, leading to a negative thermal expansion coefficient. At higher temperatures it shows more typical behavior, with a positive thermal expansion coefficient. | 0 | Theoretical and Fundamental Chemistry |
Mitogen-activated protein kinase kinase kinase kinase (MAP4K) is a family of proteins involved in cellular signal transduction.
* MAP4K1 (aka HPK1)
* MAP4K2 (aka GCK)
* MAP4K3 (aka GLK)
* MAP4K4 (aka HGK)
* MAP4K5 (aka KHS)
* MAP4K6 (aka MINK) | 1 | Applied and Interdisciplinary Chemistry |
The Étang de Berre (, "Lagoon of Berre"; in Provençal Occitan: estanh de Bèrra / mar de Bèrra according to classical orthography, estang de Berro / mar de Berro according to Mistralian orthography) is a brackish water lagoon on the Mediterranean coast of France, about north-west of Marseille. | 1 | Applied and Interdisciplinary Chemistry |
Longer stretches of DNA are entropically elastic under tension. When DNA is in solution, it undergoes continuous structural variations due to the energy available in the thermal bath of the solvent. This is due to the thermal vibration of the molecule combined with continual collisions with water molecules. For entropic reasons, more compact relaxed states are thermally accessible than stretched out states, and so DNA molecules are almost universally found in a tangled relaxed layouts. For this reason, one molecule of DNA will stretch under a force, straightening it out. Using optical tweezers, the entropic stretching behavior of DNA has been studied and analyzed from a polymer physics perspective, and it has been found that DNA behaves largely like the Kratky-Porod worm-like chain model under physiologically accessible energy scales. | 0 | Theoretical and Fundamental Chemistry |
Metal carbon dioxide complexes are coordination complexes that contain carbon dioxide ligands. Aside from the fundamental interest in the coordination chemistry of simple molecules, studies in this field are motivated by the possibility that transition metals might catalyze useful transformations of CO. This research is relevant both to organic synthesis and to the production of "solar fuels" that would avoid the use of petroleum-based fuels. | 0 | Theoretical and Fundamental Chemistry |
A figure is achiral with an orthogonal matrix and a vector . The determinant of is either 1 or −1 then. If it is −1 the isometry is orientation-reversing, otherwise it is orientation-preserving.
A general definition of chirality based on group theory exists. It does not refer to any orientation concept: an isometry is direct if and only if it is a product of squares of isometries, and if not, it is an indirect isometry. The resulting chirality definition works in spacetime. | 0 | Theoretical and Fundamental Chemistry |
Androstanedione, also known as 5α-androstanedione or as 5α-androstane-3,17-dione, is a naturally occurring androstane (5α-androstane) steroid and an endogenous metabolite of androgens like testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), and androstenedione. It is the C5 epimer of etiocholanedione (5β-androstanedione). Androstanedione is formed from androstenedione by 5α-reductase and from DHT by 17β-hydroxysteroid dehydrogenase. It has some androgenic activity.
In female genital skin, the conversion of androstenedione into DHT through 5α-androstanedione appears to be more important than the direct conversion of testosterone into DHT. | 1 | Applied and Interdisciplinary Chemistry |
A drain field may be designed to offer several separate disposal areas for effluent from a single septic tank. One area may be "rested" while effluent is routed to a different area. The nematode community in the resting drain field continues feeding on the accumulated biofilm and fats when the anaerobic septic tank effluent is no longer available. This natural cleansing process may reduce bioclogging to improve the hydraulic capacity of the field by increasing the available interstitial area of the soil as the accumulated organic material is oxidized. The percolation rate after resting may approach, but is unlikely to match, the original clean water percolation rate of the site. | 1 | Applied and Interdisciplinary Chemistry |
Boric acid can be used as an antiseptic for minor burns or cuts and is sometimes used in salves and dressings, such as boracic lint. Boric acid is applied in a very dilute solution as an eye wash. Boric acid vaginal suppositories can be used for recurrent candidiasis due to non-albicans candida as a second line treatment when conventional treatment has failed. It is less effective than conventional treatment overall. Boric acid largely spares lactobacilli within the vagina. As TOL-463, it is under development as an intravaginal medication for the treatment for vulvovaginal candidiasis.
As an antibacterial compound, boric acid can also be used as an acne treatment. It is also used as prevention of athlete's foot, by inserting powder in the socks or stockings. Various preparations can be used to treat some kinds of (ear infection) in both humans and animals. The preservative in urine sample bottles in the UK is boric acid.
Boric acid solutions used as an eye wash or on abraded skin are known to be toxic, particularly to infants, especially after repeated use; this is because of its slow elimination rate.
Boric acid is one of the most commonly used substances that can counteract the harmful effects of reactive hydrofluoric acid (HF) after an accidental contact with the skin. It works by forcing the free anions into the inert tetrafluoroborate anion. This process defeats the extreme toxicity of hydrofluoric acid, particularly its ability to sequester ionic calcium from blood serum which can lead to cardiac arrest and bone decomposition; such an event can occur from just minor skin contact with HF. | 0 | Theoretical and Fundamental Chemistry |
Glycosides are also classified according to the chemical nature of the aglycone. For purposes of biochemistry and pharmacology, this is the most useful classification. | 0 | Theoretical and Fundamental Chemistry |
Since these drugs may cause paralysis of the diaphragm, mechanical ventilation should be at hand to provide respiration.
In addition, these drugs may exhibit cardiovascular effects, since they are not fully selective for the nicotinic receptor and hence may have effects on muscarinic receptors. If nicotinic receptors of the autonomic ganglia or adrenal medulla are blocked, these drugs may cause autonomic symptoms. Also, neuromuscular blockers may facilitate histamine release, which causes hypotension, flushing, and tachycardia.
Succinylcholine may also trigger malignant hyperthermia in rare cases in patients who may be susceptible.
In depolarizing the musculature, suxamethonium may trigger a transient release of large amounts of potassium from muscle fibers. This puts the patient at risk for life-threatening complications, such as hyperkalemia and cardiac arrhythmias. Other effects include myalgia, increased intragastric pressure, increased intraocular pressure, increased intracranial pressure, cardiac dysrhythmias (bradycardia is the most common type) and allergic reactions. As a result, it is contraindicated for patients with susceptibility to malignant hyperthermia, denervating conditions, major burns after 48 hours, and severe hyperkalemia.
For nondepolarizing NMBAs except vecuronium, pipecuronium, doxacurium, cisatracurium, rocuronium and rapacuronium, they produce certain extent of cardiovascular effect. Moreover, Tubocurarine can produce hypotension effect while Pancuronium can lead to moderate increase in heart rate and small increase in cardiac output with little or no increase in systemic vascular resistance, which is unique in nondeploarizing NMBAs.
Certain drugs such as aminoglycoside antibiotics and polymyxin and some fluoroquinolones also have neuromuscular blocking action as their side-effect. | 1 | Applied and Interdisciplinary Chemistry |
ATP-dependent chromatin-remodeling complexes regulate gene expression by either moving, ejecting or restructuring nucleosomes. These protein complexes have a common ATPase domain and energy from the hydrolysis of ATP allows these remodeling complexes to reposition nucleosomes (often referred to as "nucleosome sliding") along the DNA, eject or assemble histones on/off of DNA or facilitate exchange of histone variants, and thus creating nucleosome-free regions of DNA for gene activation. Also, several remodelers have DNA-translocation activity to carry out specific remodeling tasks.
All ATP-dependent chromatin-remodeling complexes possess a sub unit of ATPase that belongs to the SNF2 superfamily of proteins. In association to the sub unit's identity, two main groups have been classified for these proteins. These are known as the SWI2/SNF2 group and the imitation SWI (ISWI) group. The third class of ATP-dependent complexes that has been recently described contains a Snf2-like ATPase and also demonstrates deacetylase activity. | 1 | Applied and Interdisciplinary Chemistry |
With rapid developments in the field of biomarker research, many infections and disorders that have not been possible to diagnose via in vitro testing, are becoming increasingly possible. SOFIA is predicted to be of broader use in diagnostic assay development for infections and disorders beyond the scope of prion diseases. A major potential application is for other protein misfolding diseases, in particular Alzheimer's. | 1 | Applied and Interdisciplinary Chemistry |
A lateral flow test (LFT), is an assay also known as a lateral flow device (LFD), lateral flow immunochromatographic assay, or rapid test. It is a simple device intended to detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment. LFTs are widely used in medical diagnostics in the home, at the point of care, and in the laboratory. For instance, the home pregnancy test is an LFT that detects a specific hormone. These tests are simple and economical and generally show results in around five to thirty minutes. Many lab-based applications increase the sensitivity of simple LFTs by employing additional dedicated equipment. Because the target substance is often a biological antigen, many lateral flow tests are rapid antigen tests (RAT or ART).
LFTs operate on the same principles of affinity chromatography as the enzyme-linked immunosorbent assays (ELISA). In essence, these tests run the liquid sample along the surface of a pad with reactive molecules that show a visual positive or negative result. The pads are based on a series of capillary beds, such as pieces of porous paper, microstructured polymer, or sintered polymer. Each of these pads has the capacity to transport fluid (e.g., urine, blood, saliva) spontaneously.
The sample pad acts as a sponge and holds an excess of sample fluid. Once soaked, the fluid flows to the second conjugate pad in which the manufacturer has stored freeze dried bio-active particles called conjugates (see below) in a salt–sugar matrix. The conjugate pad contains all the reagents required for an optimized chemical reaction between the target molecule (e.g., an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle's surface. This marks target particles as they pass through the pad and continue across to the test and control lines. The test line shows a signal, often a color as in pregnancy tests. The control line contains affinity ligands which show whether the sample has flowed through and the bio-molecules in the conjugate pad are active. After passing these reaction zones, the fluid enters the final porous material, the wick, that simply acts as a waste container.
LFTs can operate as either competitive or sandwich assays. | 1 | Applied and Interdisciplinary Chemistry |
Typically, two catalysts are needed for this reaction: a zerovalent palladium complex and a copper(I) halide salt. Common examples of palladium catalysts include those containing phosphine ligands such as Tetrakis(triphenylphosphine)palladium(0)|. Another commonly used palladium source is [, but complexes containing bidentate phosphine ligands, such as , , and (1,1'-Bis(diphenylphosphino)ferrocene)palladium(II) dichloride| have also been used. The drawback to such catalysts is the need for high loadings of palladium (up to 5 mol %), along with a larger amount of a copper co-catalyst.
Pd complexes are in fact pre-catalysts since they must be reduced to Pd before catalysis can begin. Pd complexes generally exhibit greater stability than Pd complexes and can be stored under normal laboratory conditions for months. Pd catalysts are reduced to Pd in the reaction mixture by an amine, a phosphine ligand, or another reactant in the mixture allowing the reaction to proceed. For instance, oxidation of triphenylphosphine to triphenylphosphine oxide can lead to the formation of Pd in situ when is used.
Copper(I) salts, such as CuI, react with the terminal alkyne and produce a copper(I) acetylide, which acts as an activated species for the coupling reactions. Cu(I) is a co-catalyst in the reaction, and is used to increase the rate of the reaction. | 0 | Theoretical and Fundamental Chemistry |
Production of CPs for industrial use started in the 1930s, with global production in 2000 being about 2 million tonnes. Currently, over 200 CP formulations are in use for a wide range of industrial applications, such as flame retardants and plasticisers, as additives in metal working fluids, in sealants, paints, adhesives, textiles, leather fat and coatings. | 1 | Applied and Interdisciplinary Chemistry |
When a drug is used therapeutically, it is important to understand the margin of safety that exists between the dose needed for the desired effect and the dose that produces unwanted and possibly dangerous side-effects (measured by the TD, the dose that produces toxicity in 50% of individuals). This relationship, termed the therapeutic index, is defined as the ratio TD:ED. In general, the narrower this margin, the more likely it is that the drug will produce unwanted effects. The therapeutic index emphasizes the importance of the margin of safety, as distinct from the potency, in determining the usefulness of a drug. | 1 | Applied and Interdisciplinary Chemistry |
A recent area of work has been the destruction of toxic organic compounds by irradiation; after irradiation, "dioxins" (polychlorodibenzo-p-dioxins) are dechlorinated in the same way as PCBs can be converted to biphenyl and inorganic chloride. This is because the solvated electrons react with the organic compound to form a radical anion, which decomposes by the loss of a chloride anion. If a deoxygenated mixture of PCBs in isopropanol or mineral oil is irradiated with gamma rays, then the PCBs will be dechlorinated to form inorganic chloride and biphenyl. The reaction works best in isopropanol if potassium hydroxide (caustic potash) is added. The base deprotonates the hydroxydimethylmethyl radical to be converted into acetone and a solvated electron, as the result the G value (yield for a given energy due to radiation deposited in the system) of chloride can be increased because the radiation now starts a chain reaction, each solvated electron formed by the action of the gamma rays can now convert more than one PCB molecule. If oxygen, acetone, nitrous oxide, sulfur hexafluoride or nitrobenzene is present in the mixture, then the reaction rate is reduced. This work has been done recently in the US, often with used nuclear fuel as the radiation source.
In addition to the work on the destruction of aryl chlorides, it has been shown that aliphatic chlorine and bromine compounds such as perchloroethylene, Freon (1,1,2-trichloro-1,2,2-trifluoroethane) and halon-2402 (1,2-dibromo-1,1,2,2-tetrafluoroethane) can be dehalogenated by the action of radiation on alkaline isopropanol solutions. Again a chain reaction has been reported.
In addition to the work on the reduction of organic compounds by irradiation, some work on the radiation induced oxidation of organic compounds has been reported. For instance, the use of radiogenic hydrogen peroxide (formed by irradiation) to remove sulfur from coal has been reported. In this study it was found that the addition of manganese dioxide to the coal increased the rate of sulfur removal. The degradation of nitrobenzene under both reducing and oxidizing conditions in water has been reported. | 0 | Theoretical and Fundamental Chemistry |
Fluorine-18 is usually produced by irradiation of O-enriched water (HO) with high-energy (about 18 MeV) protons prepared in a cyclotron or a linear accelerator, yielding an aqueous solution of F fluoride. This solution is then used for rapid synthesis of a labeled molecule, often with the fluorine atom replacing a hydroxyl group. The labeled molecules or radiopharmaceuticals have to be synthesized after the radiofluorine is prepared, as the high energy proton radiation would destroy the molecules.
Large amounts of oxygen-18 enriched water are used in positron emission tomography centers, for on-site production of F-labeled fludeoxyglucose (FDG).
An example of the production cycle is a 90-minute irradiation of 2 milliliters of O-enriched water in a titanium cell, through a 25 μm thick window made of Havar (a cobalt alloy) foil, with a proton beam having an energy of 17.5 MeV and a beam current of 30 microamperes.
The irradiated water has to be purified before another irradiation, to remove organic contaminants, traces of tritium produced by a O(p,t)O reaction, and ions leached from the target cell and sputtered from the Havar foil. | 0 | Theoretical and Fundamental Chemistry |
Typical COC material has a higher modulus than HDPE and PP, similar to PET or PC. COC also has a high moisture barrier for a clear polymer along with a low moisture absorption rate. In medical and analytical applications, COC is noted to be a high purity product with low extractables. COC is also a halogen-free and BPA-free product. Some grades of COC have shown a lack of estrogenic activity.
The optical properties of COC are exceptional, and in many ways very similar to glass. COC materials offer exceptional transparency, low birefringence, high Abbe number and high heat resistance. The moisture insensitivity of COC is often an advantage over competing materials such as polycarbonate and acrylics. The high flow of COC enables higher aspect ratio (squatter and shallower) optical component fabrication than other optical polymers. High ultraviolet transmission is a hallmark of COC materials, with optimized grades the leading polymer alternatives to quartz glass in analytical and diagnostic applications.
Some properties vary due to monomer content. These include glass transition temperature, viscosity, and stiffness. The glass transition temperature of these polymers can exceed 200°C. COC resins are commonly supplied in pellet form and are suited to standard polymer processing techniques such as single and twin screw extrusion, injection molding, injection blow molding and stretch blow molding (ISBM), compression molding, extrusion coating, biaxial orientation, thermoforming and many others. COC is noted for high dimensional stability with little change seen after processing.
COC and COP are generally attacked by non-polar solvents, such as toluene. COC shows good chemical resistance and barrier to other solvents, such as alcohols, and is very resistant to attack from acids and bases.
Electronic properties of COC are in some respects similar to fluoropolymers, most notably a similarly low dissipation factor or tan delta, and low permittivity. It is a very good insulator. | 0 | Theoretical and Fundamental Chemistry |
Alkalinity measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate, defined as pH 4.5 for many oceanographic/limnological studies. The alkalinity is equal to the stoichiometric sum of the bases in solution. In most Earth surface waters carbonate alkalinity tends to make up most of the total alkalinity due to the common occurrence and dissolution of carbonate rocks and other geological weathering processes that produce carbonate anions. Other common natural components that can contribute to alkalinity include borate, hydroxide, phosphate, silicate, dissolved ammonia, and the conjugate bases of organic acids (e.g., acetate). Solutions produced in a laboratory may contain a virtually limitless number of species that contribute to alkalinity. Alkalinity is frequently given as molar equivalents per liter of solution or per kilogram of solvent. In commercial (e.g. the swimming pool industry) and regulatory contexts, alkalinity might also be given in parts per million of equivalent calcium carbonate (ppm CaCO). Alkalinity is sometimes incorrectly used interchangeably with basicity. For example, the addition of CO lowers the pH of a solution, thus reducing basicity while alkalinity remains unchanged (see example below).
A variety of titrants, endpoints, and indicators are specified for various alkalinity measurement methods. Hydrochloric and sulfuric acids are common acid titrants, while phenolpthalein, methyl red, and bromocresol green are common indicators. | 0 | Theoretical and Fundamental Chemistry |
In EPR spectroscopy, g-strain refers to broadening of g-values owing to small sample inhomogeneity owing to slight variations in the orientation of the paramagnetic centers. The phenomenon is indicated by broadening of the g-values that depends on the frequency of the spectrometer, such as X- or Q-band. If the line width were determined only by hyperfine coupling (which are field-independent), then the line widths would also be field independent, but they often are not. In iron-sulfur proteins, some other metalloproteins, as well as some solids, g-strain can be substantial. | 0 | Theoretical and Fundamental Chemistry |
Simple alkylcerium reagents are well known. One example is .
Although they are described as RCeCl, their structures are far more complex.. Furthermore, the solvent seems to alter the solution structure of the complex, with differences noted between reagents prepared in diethyl ether and tetrahydrofuran. There is evidence that the parent chloride forms a polymeric species in THF solution, of the form [Ce(μ-Cl)(HO)(THF)], but whether this type of polymer exists once the organometallic reagent is formed is unknown. | 0 | Theoretical and Fundamental Chemistry |
Broadband viscoelastic spectroscopy (BVS) is a technique for studying viscoelastic solids in both bending and torsion. It provides the ability to measure viscoelastic behavior over eleven decades (orders of magnitude) of time and frequency: from 10 to 10 Hz. BVS is typically either used to investigate viscoelastic properties isothermally over a large frequency range or as a function of temperature at a single frequency. It is capable of measuring mechanical properties directly over these frequency and temperature ranges; as such, it does not require time-temperature superposition or the assumption that material properties obey an Arrhenius-type temperature dependence. As a result, it can be used for heterogeneous and anisotropic specimens for which these assumptions do not apply. BVS is often used for the determination of attenuation coefficients, dynamic moduli, and especially damping ratios.
BVS was developed primarily to overcome shortcomings in the functional ranges of other viscoelastic characterization techniques. For example, resonant ultrasound spectroscopy (RUS), another popular technique for studying viscoelastic solids, experiences difficulty in determining a material's parameters below its resonant frequency. Furthermore, BVS is less sensitive to sample preparation than RUS. | 0 | Theoretical and Fundamental Chemistry |
Ex situ conservation, while helpful in humankinds efforts to sustain and protect our environment, is rarely enough to save a species from extinction. It is to be used as a last resort, or as a supplement to in situ conservation because it cannot recreate the habitat as a whole: the entire genetic variation of a species, its symbiotic counterparts, or those elements which, over time, might help a species adapt to its changing surroundings. Instead, ex situ conservation removes the species from its natural ecological contexts, preserving it under semi-isolated conditions whereby natural evolution and adaptation processes are either temporarily halted or altered by introducing the specimen to an unnatural habitat. In the case of cryogenic storage methods, the preserved specimens adaptation processes are (quite literally) frozen altogether. The downside to this is that, when re-released, the species may lack the genetic adaptations and mutations which would allow it to thrive in its ever-changing natural habitat.
Furthermore, ex situ conservation techniques are often costly, with cryogenic storage being economically infeasible in most cases since species stored in this manner cannot provide a profit but instead slowly drain the financial resources of the government or organization determined to operate them. Seedbanks are ineffective for certain plant genera with recalcitrant seeds that do not remain fertile for long periods of time. Diseases and pests foreign to the species, to which the species has no natural defense, may also cripple crops of protected plants in ex situ plantations and in animals living in ex situ breeding grounds. These factors, combined with the specific environmental needs of many species, some of which are nearly impossible to recreate by man, make ex situ conservation impossible for a great number of the world's endangered flora and fauna. | 1 | Applied and Interdisciplinary Chemistry |
Stokes's law is actually an asymptotic approximation for low frequencies of a more general formula involving relaxation time :
The relaxation time for water is about per radian, corresponding to an angular frequency of radians (500 gigaradians) per second and therefore a frequency of about . | 1 | Applied and Interdisciplinary Chemistry |
Anthocyanins may have a protective role in plants against extreme temperatures. Tomato plants protect against cold stress with anthocyanins countering reactive oxygen species, leading to a lower rate of cell death in leaves. | 0 | Theoretical and Fundamental Chemistry |
Donnan potential is the difference in the Galvani potentials which appears as a result of Donnan equilibrium, named after Frederick G. Donnan, which refers to the distribution of ion species between two ionic solutions separated by a semipermeable membrane or boundary. The boundary layer maintains an unequal distribution of ionic solute concentration by acting as a selective barrier to ionic diffusion. Some species of ions may pass through the barrier while others may not. The solutions may be gels or colloids as well as ionic liquids, and as such the phase boundary between gels or a gel and a liquid can also act as a selective barrier. Electric potential arises between two solutions is called Donnan potential.
Donnan equilibrium is prominent in the triphasic model for articular cartilage proposed by Mow and Ratcliffe, as well as in electrochemical fuel cells and dialysis.
The Donnan effect is extra osmotic pressure attributable to cations (Na and K) attached to dissolved plasma proteins. | 0 | Theoretical and Fundamental Chemistry |
Many woody plants regrow around injuries, such as those caused by pruning. In time, such regrowth often completely covers the damaged area as the cambium growth layer produces new tissues. Well-pruned trees with undamaged branch collars often recover well, where poorly-pruned trees rot below the wound. | 1 | Applied and Interdisciplinary Chemistry |
The reversible work is the maximal useful work which can be obtained, , and can only be fully utilized in an ideal reversible process. An irreversible process produces some work , which is less than . The lost work is then ; in other words, is the work which was lost or not exploited during the process due to irreversibilities. In terms of lost work, the theorem generally stateswhere is the rate at which work is lost, and is the rate at which entropy is generated. Time derivatives are denoted by dots. The theorem, as stated above, holds only for the entire thermodynamic universe - the system along with its surroundings, together:where the index "tot" denotes the total quantities produced within or by the entire universe.
Note that is a relative quantity, in that it is measured in relation to a specific thermal reservoir. In the above equations, is defined in reference to the environment reservoir, at . When comparing the actual process to an ideal, reversible process between the same endpoints (in order to evaluate , so as to find the value of ), only the heat interaction with the reference reservoir is allowed to vary. The heat interactions between the system and other reservoirs are kept the same. So, if a different reference reservoir is chosen, the theorem would read , where this time is in relation to , and in the corresponding reversible process, only the heat interaction with is different.
By integrating over the lifetime of the process, the theorem can also be expressed in terms of final quantities, rather than rates: . | 0 | Theoretical and Fundamental Chemistry |
Strong bases attack aluminium. Sodium hydroxide reacts with aluminium and water to release hydrogen gas. The aluminium takes an oxygen atom from sodium hydroxide, which in turn takes an oxygen atom from water, and releases two hydrogen atoms. The reaction thus produces hydrogen gas and sodium aluminate. In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in.
Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as , , , or . Formation of sodium tetrahydroxoaluminate(III) or hydrated sodium aluminate is given by:
This reaction can be useful in etching, removing anodizing, or converting a polished surface to a satin-like finish, but without further passivation such as anodizing or alodining the surface may become degraded, either under normal use or in severe atmospheric conditions.
In the Bayer process, sodium hydroxide is used in the refining of alumina containing ores (bauxite) to produce alumina (aluminium oxide) which is the raw material used to produce aluminium via the electrolytic Hall-Héroult process. Since the alumina is amphoteric, it dissolves in the sodium hydroxide, leaving impurities less soluble at high pH such as iron oxides behind in the form of a highly alkaline red mud.
Other amphoteric metals are zinc and lead which dissolve in concentrated sodium hydroxide solutions to give sodium zincate and sodium plumbate respectively. | 0 | Theoretical and Fundamental Chemistry |
In physics, the reciprocal lattice emerges from the Fourier transform of another lattice. The direct lattice or real lattice is a periodic function in physical space, such as a crystal system (usually a Bravais lattice). The reciprocal lattice exists in the mathematical space of spatial frequencies, known as reciprocal space or k space, where refers to the wavevector.
In quantum physics, reciprocal space is closely related to momentum space according to the proportionality , where is the momentum vector and is the reduced Planck constant. The reciprocal lattice of a reciprocal lattice is equivalent to the original direct lattice, because the defining equations are symmetrical with respect to the vectors in real and reciprocal space. Mathematically, direct and reciprocal lattice vectors represent covariant and contravariant vectors, respectively.
The reciprocal lattice is the set of all vectors , that are wavevectors of plane waves in the Fourier series of a spatial function whose periodicity is the same as that of a direct lattice . Each plane wave in this Fourier series has the same phase or phases that are differed by multiples of at each direct lattice point (so essentially same phase at all the direct lattice points).
The reciprocal lattice plays a fundamental role in most analytic studies of periodic structures, particularly in the theory of diffraction. In neutron, helium and X-ray diffraction, due to the Laue conditions, the momentum difference between incoming and diffracted X-rays of a crystal is a reciprocal lattice vector. The diffraction pattern of a crystal can be used to determine the reciprocal vectors of the lattice. Using this process, one can infer the atomic arrangement of a crystal.
The Brillouin zone is a Wigner–Seitz cell of the reciprocal lattice. | 0 | Theoretical and Fundamental Chemistry |
Part Two aired 24 April 2006 and is set a year later, dealing with more long-term repercussions such as the social and economic climate. The main characters are revisited and interviewed. | 0 | Theoretical and Fundamental Chemistry |
In the acetalisation reaction, under acidic or basic conditions, an alcohol adds to the carbonyl group and a proton is transferred to form a hemiacetal. Under acidic conditions, the hemiacetal and the alcohol can further react to form an acetal and water. Simple hemiacetals are usually unstable, although cyclic ones such as glucose can be stable. Acetals are stable, but revert to the aldehyde in the presence of acid. Aldehydes can react with water to form hydrates, . These diols are stable when strong electron withdrawing groups are present, as in chloral hydrate. The mechanism of formation is identical to hemiacetal formation. | 0 | Theoretical and Fundamental Chemistry |
β-W has a cubic A15 structure with space group , which belongs to the Frank–Kasper phases family. Each unit cell contains eight tungsten atoms. The structure can be seen as a cubic lattice with one atom at each corner, one atom in the center, and two atoms on each face. There are two inequivalent tungsten sites corresponding to Wyckoff positions and , respectively. On the first site, Wyckoff position , each tungsten atom is bonded to twelve equivalent W atoms to form a mixture of edge- and face-sharing WW cuboctahedratungsten. On the second site, with Wyckoff position , each tungsten atom is bonded to fourteen neighboring tungsten atoms, and there is a spread of W–W bond lengths ranging from 2.54 to 3.12 Å. The experimentally measured lattice parameter of β-W is 5.036 Å, while the DFT calculated value is 5.09 Å. | 0 | Theoretical and Fundamental Chemistry |
In 1935, H. Staudinger and co-workers found that the reaction of butadiene and SO at room temperature gives a second product in addition to 3-sulfolene. This second product is an amorphous solid polymer. By free-radical polymerization of 3-sulfolene in peroxide-containing diethyl ether, up to 50% insoluble high-molecular-weight poly-sulfolene was obtained. The polymer resists degradation by sulfuric and nitric acids.
In subsequent investigations, polymerization of 3-sulfolene was initiated above 100 °C with the radical initiator azobis(isobutyronitrile) (AIBN). 3-sulfolene does not copolymerize with vinyl compounds, however. On the other hand, 2-sulfolene does not homopolymerize, but forms copolymers with vinyl compounds, e.g. acrylonitrile and vinyl acetate. | 0 | Theoretical and Fundamental Chemistry |
The OR gate is based on the activation of molecule A, and thus pass electron / photon to molecule Cs excited state orbitals (C*). The electron from molecule A inter system crosses to C* via the excited state orbitals of B, eventually utilised as a signal in the C* emission. The OR gate uses two inputs of light (photons) to molecule A in two separate electron transfer chains, both of which are capable of transferring to C* and thus producing the output of an OR gate. Therefore, if either electron transfer chain is activated, molecule Cs excitation produces a valid/ output emission. | 0 | Theoretical and Fundamental Chemistry |
Since EosFP can be used in fusion constructs while maintaining functionality of the protein of interest, it is a popular choice for multi-colour labelling studies. In a dual-colour labelling experiment to map the stages of mitosis, HEK293 cells were first stably transfected with tubulin-binding protein cDNA fused to EGFP for visualization of the spindle apparatus. Then, transient transfection of recombination signal-binding protein (RBP) fused to d2EosFP was used to visualize the beginning of mitosis. Photoconversion was completed by fluorescent microscopy and highlighted the separation between two sets of chromosomes during anaphase, telophase and cytokinesis. | 1 | Applied and Interdisciplinary Chemistry |
In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is known as a magma series. | 0 | Theoretical and Fundamental Chemistry |
In the general case of two convex bodies, the effective radius can be expressed as follows
where R and R" are the principal radii of curvature for the surfaces i' = 1 and 2, evaluated at points of closest approach distance, and φ is the angle between the planes spanned by the circles with smaller curvature radii. When the bodies are non-spherical around the position of closest approach, a torque between the two bodies develops and is given by
where
The above expressions for two spheres are recovered by setting R = R" = R. The torque vanishes in this case.
The expression for two perpendicularly crossing cylinders is obtained from R = R and R"' → ∞. In this case, torque will tend to orient the cylinders perpendicularly for repulsive forces.
For attractive forces, the torque will tend to align them.
These general formulas have been used to evaluate approximate interaction forces between ellipsoids. | 0 | Theoretical and Fundamental Chemistry |
Fluid that is less dense than its surroundings tends to rise until it has the same density as its surroundings. If there is not much energy input to the system, it will tend to become stratified. On a large scale, Earth's atmosphere is divided into a series of layers. Going upwards from the ground, these are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The density of air is mainly determined by temperature and water vapor content, the density of sea water by temperature and salinity, and the density of lake water by temperature. Where stratification occurs, there may be thin layers in which temperature or some other property changes more rapidly with height or depth than the surrounding fluid. Depending on the main sources of buoyancy, this layer may be called a pycnocline (density), thermocline (temperature), halocline (salinity), or chemocline (chemistry, including oxygenation).
The same buoyancy that gives rise to stratification also drives gravity waves. If the gravity waves occur within the fluid, they are called internal waves.
In modeling buoyancy-driven flows, the Navier-Stokes equations are modified using the Boussinesq approximation. This ignores variations in density except where they are multiplied by the gravitational acceleration .
If the pressure depends only on density and vice versa, the fluid dynamics are called barotropic. In the atmosphere, this corresponds to a lack of fronts, as in the tropics. If there are fronts, the flow is baroclinic, and instabilities such as cyclones can occur. | 1 | Applied and Interdisciplinary Chemistry |
Some hydrogen sulfide gas diffuses into the headspace environment above the wastewater. Moisture evaporated from warm sewage may condense on unsubmerged walls of sewers, and is likely to hang in partially formed droplets from the horizontal crown of the sewer. As a portion of the hydrogen sulfide gas and oxygen gas from the air above the sewage dissolves into these stationary droplets, they become a habitat for sulfur oxidizing bacteria (SOB), of the genus Acidithiobacillus. Colonies of these aerobic bacteria metabolize the hydrogen sulfide gas to sulfuric acid. | 1 | Applied and Interdisciplinary Chemistry |
A methylene blue active substances assay, or MBAS assay, is a colorimetric analysis test method that uses methylene blue to detect the presence of anionic surfactants (such as a detergent or foaming agent) in a sample of water. An anionic surfactant detected by the color reaction is called a methylene blue active substance (MBAS).
After first acidifying a water sample (with boric acid, for example), one adds to it chloroform and a solution of methylene blue et al. Methylene blue is a cationic dye. The biphasic solution is then agitated to distribute these reagents throughout the aqueous and organic phases. If an anionic surfactant is present, then the cationic methylene blue and the anionic surfactant forms an ion pair, which is extracted into the organic phase. The color saturation of the chloroform increases with the concentration of anionic surfactants.
MBAS assay is an ASTM International standard technique for detecting anionic surfactants. These include carboxylates, phosphates, sulfates, and sulfonates. An MBAS assay alone does not, however, identify specific surfactants. ASTM withdrew the standard (ASTM D2330-02) in 2011 pending a review and update of the method, which was last approved in 2003.
The publication Standard Methods for the Examination of Water and Wastewater lists the following methods used by certified laboratories testing wastewater in the United States.
* Method 5540B describes surfactant separation by sublation.
* Method 5540C discusses anionic surfactants as methylene blue active substances (MBAS).
* Method 5540D discusses nonionic surfactants as cobalt thiocyanate active substances (CTAS). | 0 | Theoretical and Fundamental Chemistry |
Biolistic transformation involves the integration of a functional fragment of DNA—known as a DNA construct—into target cells. A gene construct is a DNA cassette containing all required regulatory elements for proper expression within the target organism. While gene constructs may vary in their design depending on the desired outcome of the transformation procedure, all constructs typically contain a combination a promoter sequence, a terminator sequence, the gene of interest, and a reporter gene.
;Promoter:Promoters control the location and magnitude of gene expression and function as “the steering wheel and gas pedal” of a gene. Promoters precede the gene of interest in the DNA construct and can be changed through laboratory design to fine-tune transgene expression. The 35S promoter from Cauliflower mosaic virus is an example of a commonly used promoter that results in robust constitutive gene expression within plants.
;Terminator:Terminator sequences are required for proper gene expression and are placed after the coding region of the gene of interest within the DNA construct. A common terminator for biolistic transformation is the NOS terminator derived from Agrobacterium tumefaciens. Due to the high frequency of use of this terminator in genetically engineered plants, strategies have been developed to detect its presence within the food supply to monitor for unauthorized GE crops.
;Reporter gene: A gene encoding a selectable marker is a common element within DNA constructs and is used to select for properly transformed cells. The selectable marker chosen will depend on the species being transformed, but it will typically be a gene granting cells a detoxification capacity for certain herbicides or antibiotics such as kanamycin, hygromycin B, or glyphosate.
;Additional elements: Optional components of a DNA construct include elements such as cre-lox sequences that allow for controlled removal of the construct from the target genome. Such elements are chosen by the construct developer to perform specialized functions alongside the main gene of interest. | 1 | Applied and Interdisciplinary Chemistry |
The arrangement of atoms and ions within a material is one of the most important structural properties of a biomaterial. The atomic structure of a material can be viewed at different levels, the sub atomic level, atomic or molecular level, as well as the ultra-structure created by the atoms and molecules. Intermolecular forces between the atoms and molecules that compose the material will determine its material and chemical properties.
The sub atomic level observes the electrical structure of an individual atom to define its interactions with other atoms and molecules. The molecular structure observes the arrangement of atoms within the material. Finally the ultra-structure observes the 3-D structure created from the atomic and molecular structures of the material. The solid-state of a material is characterized by the intramolecular bonds between the atoms and molecules that comprise the material. Types of intramolecular bonds include: ionic bonds, covalent bonds, and metallic bonds. These bonds will dictate the physical and chemical properties of the material, as well as determine the type of material (ceramic, metal, or polymer). | 1 | Applied and Interdisciplinary Chemistry |
After initial sporadic work, archaeometallurgy was more widely institutionalised in the 1960s and 70s, with research groups in Britain (The British Museum, the UCL Institute of Archaeology, the Institute for Archeo-Metallurgical Studies (iams)), Germany (Deutsches Bergbau Museum) and the US (MIT and Harvard).
Specialisations within metallurgical focus on metallography of finished objects, mineralogy of waste products such as slag and manufacturing studies. | 1 | Applied and Interdisciplinary Chemistry |
A perfectly inelastic collision occurs when the maximum amount of kinetic energy
of a system is lost. In a perfectly inelastic collision, i.e., a zero coefficient of restitution, the colliding particles stick together. In such a collision, kinetic energy is lost by bonding the two bodies together. This bonding energy usually results in a maximum kinetic energy loss of the system. It is necessary to consider conservation of momentum: (Note: In the sliding block example above, momentum of the two body system is only conserved if the surface has zero friction. With friction, momentum of the two bodies is transferred to the surface that the two bodies are sliding upon. Similarly, if there is air resistance, the momentum of the bodies can be transferred to the air.) The equation below holds true for the two-body (Body A, Body B) system collision in the example above. In this example, momentum of the system is conserved because there is no friction between the sliding bodies and the surface.
where v is the final velocity, which is hence given by
The reduction of total kinetic energy is equal to the total kinetic energy before the collision in a center of momentum frame with respect to the system of two particles, because in such a frame the kinetic energy after the collision is zero. In this frame most of the kinetic energy before the collision is that of the particle with the smaller mass. In another frame, in addition to the reduction of kinetic energy there may be a transfer of kinetic energy from one particle to the other; the fact that this depends on the frame shows how relative this is. The change in kinetic energy is hence:
where μ is the reduced mass and u is the relative velocity of the bodies before collision. With time reversed we have the situation of two objects pushed away from each other, e.g. shooting a projectile, or a rocket applying thrust (compare the derivation of the Tsiolkovsky rocket equation). | 0 | Theoretical and Fundamental Chemistry |
In the decades after the discovery of the Conia-ene reaction, several improvements allowed for milder reaction conditions and greater control of product stereo- and regiochemistry. For example, the carbonyl component, formerly a ketone or aldehyde, became a substituted β-ketoester or malonate ester. Such carbonyls enolize much more readily, yielding better access to the desired enol tautomer. Additionally, the alkene component was replaced with an alkyne, which not only gave better cyclization in accordance with Baldwin’s rules, but also furnished a product containing an alkene that served as a useful handle for further transformations. Finally, recent efforts have featured metal-mediated and metal-catalyzed Conia-ene reactions that can be rendered asymmetric using chiral ligands. | 0 | Theoretical and Fundamental Chemistry |
Plasma electrolytic oxidation is a similar process, but where higher voltages are applied. This causes sparks to occur and results in more crystalline/ceramic type coatings. | 1 | Applied and Interdisciplinary Chemistry |
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