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Dosage quotient analysis is the usual method of interpreting MLPA data. If a and b are the signals from two amplicons in the patient sample, and A and B are the corresponding amplicons in the experimental control, then the dosage quotient DQ = (a/b) / (A/B). Although dosage quotients may be calculated for any pair of amplicons, it is usually the case that one of the pair is an internal reference probe. | 1 | Applied and Interdisciplinary Chemistry |
This annex contains a list of elements by atomic number, giving the names and standard symbols of the chemical elements from atomic number 1 (hydrogen, H) to 109 (unnilennium, Une).
The list given in ISO 31-8:1992 was quoted from the 1998 IUPAC "Green Book" Quantities, Units and Symbols in Physical Chemistry and adds in some cases in parentheses the Latin name for information, where the standard symbol has no relation to the English name of the element. Since the 1992 edition of the standard was published, some elements with atomic number above 103 have been discovered and renamed. | 0 | Theoretical and Fundamental Chemistry |
From 1985 to 1988, Bols did PhD with Professor Inge Lundt at the Technical University of Denmark. From 1988 to 1989, he did a post doc with professor Walter Szarek at Queens University before joining Leo Pharmaceuticals in 1989. From 1991 to 1995, he was Ass. Prof. at DTU only interrupted by a visit in the last 6 month of 1994 Gilbert Storks group at Columbia University. From 1995 to 2000, he was Assoc. Prof. (Lektor) at University of Aarhus during which period he became Dr. Scient. (1997). From 1998 to 2000 and from 2004 to 2006, he was Head of the chemistry department at university of Aarhus. From 2000 to 2005, he became Lundbeckfondsprofessor and subsequently (2005-2007) ordinary professor. In 2007, he became professor and Head of department of the Department of Chemistry at University of Copenhagen. | 0 | Theoretical and Fundamental Chemistry |
In molecular biology, restriction fragment length polymorphism (RFLP) is a technique that exploits variations in homologous DNA sequences, known as polymorphisms, populations, or species or to pinpoint the locations of genes within a sequence. The term may refer to a polymorphism itself, as detected through the differing locations of restriction enzyme sites, or to a related laboratory technique by which such differences can be illustrated. In RFLP analysis, a DNA sample is digested into fragments by one or more restriction enzymes, and the resulting restriction fragments are then separated by gel electrophoresis according to their size.
RFLP analysis is now largely obsolete due to the emergence of inexpensive DNA sequencing technologies, but it was the first DNA profiling technique inexpensive enough to see widespread application. RFLP analysis was an important early tool in genome mapping, localization of genes for genetic disorders, determination of risk for disease, and paternity testing. | 1 | Applied and Interdisciplinary Chemistry |
Realtime spectrum analyzers are able to produce much more information for users to examine the frequency spectrum in more detail. A normal swept spectrum analyzer would produce max peak, min peak displays for example but a realtime spectrum analyzer is able to plot all calculated FFT's over a given period of time with the added colour-coding which represents how often a signal appears. For example, this image shows the difference between how a spectrum is displayed in a normal swept spectrum view and using a "Persistence" view on a realtime spectrum analyzer. | 0 | Theoretical and Fundamental Chemistry |
Alkaliphiles are a class of extremophilic microbes capable of survival in alkaline (pH roughly 8.5–11) environments, growing optimally around a pH of 10. These bacteria can be further categorized as obligate alkaliphiles (those that require high pH to survive), facultative alkaliphiles (those able to survive in high pH, but also grow under normal conditions) and haloalkaliphiles (those that require high salt content to survive). | 1 | Applied and Interdisciplinary Chemistry |
Dilatancy in a colloid, or its ability to order in the presence of shear forces, is dependent on the ratio of interparticle forces. As long as interparticle forces such as Van der Waals forces dominate, the suspended particles remain in ordered layers. However, once shear forces dominate, particles enter a state of flocculation and are no longer held in suspension; they begin to behave like a solid. When the shear forces are removed, the particles spread apart and once again form a stable suspension.
Shear thickening behavior is highly dependent upon the volume fraction of solid particulate suspended within the liquid. The higher the volume fraction, the less shear required to initiate the shear thickening behavior. The shear rate at which the fluid transitions from a Newtonian flow to a shear thickening behavior is known as the critical shear rate. | 1 | Applied and Interdisciplinary Chemistry |
Polymer solutions are used in producing fibers, films, glues, lacquers, paints, and other items made of polymer materials. Thin layers of polymer solution can be used to produce light-emitting devices. Guar polymer solution gels can be used in hydraulic fracturing ("fracking"). | 0 | Theoretical and Fundamental Chemistry |
A piece of alloy metal containing a precious metal may also have the weight of its precious component referred to as its "fine weight". For example, 1 troy ounce of 18 karat gold (which is 75% gold) may be said to have a fine weight of 0.75 troy ounces.
Most modern government-issued bullion coins specify their fine weight. For example, the American Gold Eagle is embossed One Oz. Fine Gold and weighs 1.091 troy oz. | 1 | Applied and Interdisciplinary Chemistry |
Dyes and pigments are used in polymer materials to provide colour, however they can also effect the rate of photo-oxidation. Many absorb UV rays and in so doing protect the polymer, however absorption can cause the dyes to enter an excited state where they may attack the polymer or transfer energy to O to form damaging singlet oxygen. Cu-phthalocyanine is an example, it strongly absorbs UV light however the excited Cu-phthalocyanine may act as a photoinitiator by abstracting hydrogen atoms from the polymer. Its interactions may become even more complicated when other additives are present.
Fillers such as carbon black can screen out UV light, effectively stabilisers the polymer, whereas flame retardants tend to cause increased levels of photo-oxidation. | 0 | Theoretical and Fundamental Chemistry |
Flucloxacillin is insensitive to beta-lactamase (also known as penicillinase) enzymes secreted by many penicillin-resistant bacteria. The presence of the isoxazolyl group on the side chain of the penicillin nucleus facilitates the β-lactamase resistance, since they are relatively intolerant of side chain steric hindrance. Thus, it is able to bind to penicillin-binding proteins and inhibit peptidoglycan crosslinking, but is not bound by or inactivated by β-lactamases. | 0 | Theoretical and Fundamental Chemistry |
This similarity between the Chézy and Manning formulas shown above also means that the standardized Manning coefficients may be used to estimate open channel flow velocity with the Chézy formula, by using them to calculate the Chézy's coefficient as shown below. Manning derived the following relationship between Manning coefficient () to Chézy coefficient () based upon experiments:
where
* is the Chézy coefficient [length/time], a function of relative roughness and Reynolds number;
* is the hydraulic radius, which is the cross-sectional area of flow divided by the wetted perimeter (for a wide channel this is approximately equal to the water depth) [m];
* is Manning's coefficient [time/length]; and
* is a constant; k = 1 when using SI units and k = 1.49 when using BG units. | 1 | Applied and Interdisciplinary Chemistry |
The source of ADP-ribose for most enzymes that perform this modification is the redox cofactor NAD. In this transfer reaction, the N-glycosidic bond of NAD that bridges the ADP-ribose molecule and the nicotinamide group is cleaved, followed by nucleophilic attack by the target amino acid side chain. (ADP-ribosyl)transferases can perform two types of modifications: mono(ADP-ribosyl)ation and poly(ADP-ribosyl)ation. | 1 | Applied and Interdisciplinary Chemistry |
GaN crystals can be grown from a molten Na/Ga melt held under 100 atmospheres of pressure of N at 750 °C. As Ga will not react with N below 1000 °C, the powder must be made from something more reactive, usually in one of the following ways:
: 2 Ga + 2 NH → 2 GaN + 3 H
: GaO + 2 NH → 2 GaN + 3 HO
Gallium nitride can also be synthesized by injecting ammonia gas into molten gallium at at normal atmospheric pressure. | 0 | Theoretical and Fundamental Chemistry |
Karunadasa began her independent career at Stanford University in 2012. Her group synthesizes hybrid perovskite materials that combine small organic molecules with inorganic solids. Three-dimensional lead iodide perovskites are being investigated for solar cells, but they can be both unstable and toxic. For example, their sensitivity to water makes them difficult materials to use in the fabrication of large-scale devices. Karunadasa is interested in ways to mitigate these shortcomings, and any transient changes that may occur when these materials absorb light. In particular, Karunadasa has created two-dimensional perovskites, with thin inorganic sheets, that can be tuned to emit every colour of visible light. In these systems the organic small molecules are sandwiched between the sheets. In the case of thick inorganic sheets, the inorganic materials act as absorbers, and enhance the stability of the perovskite materials. The organo-metal-halide perovskites created by Karunadasa and her collaborator Michael D. McGehee can be processed in solution. She believes that through careful chemical design it is possible to determine the fate of photogenerated charge carriers. Karunadasa has investigated the lifetimes of acoustic phonons in lead iodide perovskites with Michael Toney and Aron Walsh. | 0 | Theoretical and Fundamental Chemistry |
Photochromic coordination complexes are relatively rare in comparison to the organic compounds listed above. There are two major classes of photochromic coordination compounds. Those based on sodium nitroprusside and the ruthenium sulfoxide compounds. The ruthenium sulfoxide complexes were created and developed by Rack and coworkers. The mode of action is an excited state isomerization of a sulfoxide ligand on a ruthenium polypyridine fragment from S to O or O to S. The difference in bonding from between Ru and S or O leads to the dramatic color change and change in Ru(III/II) reduction potential. The ground state is always S-bonded and the metastable state is always O-bonded. Typically, absorption maxima changes of nearly 100 nm are observed. The metastable states (O-bonded isomers) of this class often revert thermally to their respective ground states (S-bonded isomers), although a number of examples exhibit two-color reversible photochromism. Ultrafast spectroscopy of these compounds has revealed exceptionally fast isomerization lifetimes ranging from 1.5 nanoseconds to 48 picoseconds. | 0 | Theoretical and Fundamental Chemistry |
A periodic or cyclic boundary condition arises from a different type of symmetry in a problem. If a component has a repeated pattern in flow distribution more than twice, thus violating the mirror image requirements required for symmetric boundary condition. A good example would be swept vane pump (Fig.), where the marked area is repeated four times in r-theta coordinates. The cyclic-symmetric areas should have the same flow variables and distribution and should satisfy that in every Z-slice. | 1 | Applied and Interdisciplinary Chemistry |
Ski boots use flanges at the toe or heel to connect to the binding of the ski. The size and shape for flanges on alpine skiing boots is standardized in ISO 5355. Traditional telemark and cross country boots use the 75 mm Nordic Norm, but the toe flange is informally known as the "duckbill". New cross country bindings eliminate the flange entirely and use a steel bar embedded within the sole instead. | 1 | Applied and Interdisciplinary Chemistry |
A weld neck flange (also known as a high-hub flange and tapered hub flange) is a type of flange. There are two designs. The regular type is used with pipes. The long type is unsuitable for pipes and is used in process plant. A weld neck flange consists of a circular fitting with a protruding rim around the circumference. Generally machined from a forging, these flanges are typically butt welded to a pipe. The rim has a series of drilled holes that permit the flange to be affixed to another flange with bolts.
Such flanges are suitable for use in hostile environments that have extremes of temperature, pressure or other sources of stress. The resilience of this type of flange is achieved by sharing the environmental stress with the pipe with which it is welded. This type of flange has been used successfully at pressures up to 5,000 psi. | 1 | Applied and Interdisciplinary Chemistry |
In the presence of excess arsenic, GaAs boules grow with crystallographic defects; specifically, arsenic antisite defects (an arsenic atom at a gallium atom site within the crystal lattice). The electronic properties of these defects (interacting with others) cause the Fermi level to be pinned to near the center of the band gap, so that this GaAs crystal has very low concentration of electrons and holes. This low carrier concentration is similar to an intrinsic (perfectly undoped) crystal, but much easier to achieve in practice. These crystals are called "semi-insulating", reflecting their high resistivity of 10–10 Ω·cm (which is quite high for a semiconductor, but still much lower than a true insulator like glass). | 0 | Theoretical and Fundamental Chemistry |
Escitalopram increases intrasynaptic levels of the neurotransmitter serotonin by blocking the reuptake of the neurotransmitter into the presynaptic neuron. Over time, this leads to a downregulation of pre-synaptic 5-HT receptors, which is associated with an improvement in passive stress tolerance, and delayed downstream increase in expression of brain-derived neurotrophic factor, which may contribute to a reduction in negative affective biases.
Of the SSRIs currently available, escitalopram has the highest selectivity for the serotonin transporter (SERT) compared to the norepinephrine transporter (NET), making the side-effect profile relatively mild in comparison to less-selective SSRIs.
Escitalopram is a substrate of P-glycoprotein and hence P-glycoprotein inhibitors such as verapamil and quinidine may improve its blood brain barrier penetrability. In a preclinical study in rats combining escitalopram with a P-glycoprotein inhibitor, its antidepressant-like effects were enhanced. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration. The concentration can refer to any kind of chemical mixture, but most frequently refers to solutes and solvents in solutions. The molar (amount) concentration has variants, such as normal concentration and osmotic concentration. Dilution is reduction of concentration, e.g. by adding solvent to a solution. The verb to concentrate means to increase concentration, the opposite of dilute. | 0 | Theoretical and Fundamental Chemistry |
The first transfer of an embryo from one human to another resulting in pregnancy was reported in July 1983 and subsequently led to the announcement of the first human birth 3 February 1984. This procedure was performed at the Harbor UCLA Medical Center under the direction of Dr. John Buster and the University of California at Los Angeles School of Medicine.
In the procedure, an embryo that was just beginning to develop was transferred from one woman in whom it had been conceived by artificial insemination to another woman who gave birth to the infant 38 weeks later. The sperm used in the artificial insemination came from the husband of the woman who bore the baby.
This scientific breakthrough established standards and became an agent of change for women with infertility and for women who did not want to pass on genetic disorders to their children. Donor embryo transfer has given women a mechanism to become pregnant and give birth to a child that will contain their husband's genetic makeup. Although donor embryo transfer as practiced today has evolved from the original non-surgical method, it now accounts for approximately 5% of in vitro fertilization recorded births.
Prior to this, thousands of women who were infertile, had adoption as the only path to parenthood. This set the stage to allow open and candid discussion of embryo donation and transfer. This breakthrough has given way to the donation of human embryos as a common practice similar to other donations such as blood and major organ donations. At the time of this announcement the event was captured by major news carriers and fueled healthy debate and discussion on this practice which impacted the future of reproductive medicine by creating a platform for further advancements in woman's health.
This work established the technical foundation and legal-ethical framework surrounding the clinical use of human oocyte and embryo donation, a mainstream clinical practice, which has evolved over the past 25 years. | 1 | Applied and Interdisciplinary Chemistry |
The ability of enhancers to activate imprinted genes is dependent on the presence of an insulator on the unmethylated allele between the two genes. An example of this is the Igf2-H19 imprinted locus. In this locus the CTCF protein regulates imprinted expression by binding to the unmethylated maternal imprinted control region (ICR) but not on the paternal ICR. When bound to the unmethylated maternal sequence, CTCF effectively blocks downstream enhancer elements from interacting with the Igf2 gene promoter, leaving only the H19 gene to be expressed. | 1 | Applied and Interdisciplinary Chemistry |
Starting with the above given equations of motion for a medium at rest:
Let us now take to all be small quantities.
In the case that we keep terms to first order, for the continuity equation, we have the term going to 0. This similarly applies for the density perturbation times the time derivative of the velocity. Moreover, the spatial components of the material derivative go to 0. We thus have, upon rearranging the equilibrium density:
Next, given that our sound wave occurs in an ideal fluid, the motion is adiabatic, and then we can relate the small change in the pressure to the small change in the density by
Under this condition, we see that we now have
Defining the speed of sound of the system:
Everything becomes | 1 | Applied and Interdisciplinary Chemistry |
Levocetirizine, sold under the brand name Xyzal, among others, is a second-generation antihistamine used for the treatment of allergic rhinitis (hay fever) and long-term hives of unclear cause. It is less sedating than older antihistamines. It is taken by mouth.
Common side effects include sleepiness, dry mouth, cough, vomiting, and diarrhea. Use in pregnancy appears safe but has not been well studied and use when breastfeeding is of unclear safety. It is classified as a second-generation antihistamine and works by blocking histamine H-receptors.
Levocetirizine was approved for medical use in the United States in 2007. It is available as a generic medication. In 2021, it was the 190th most commonly prescribed medication in the United States, with more than 2million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
Aside from the practical application of this reaction in medicinal chemistry and natural product synthesis, recent work has also used the Tsuji–Trost reaction to detect palladium in various systems. This detection system is based on a non-fluorescent fluorescein-derived sensor (longer-wavelength sensors have also recently been developed for other applications) that becomes fluorescent only in the presence of palladium or platinum.
This palladium/platinum sensing ability is driven by the Tsuji–Trost reaction. The sensor contains an allyl group with the fluorescein functioning as the leaving group. The -allyl complex is formed and after a nucleophile attacks, the fluorescein is released, yielding a dramatic increase in fluorescence.
This simple, high-throughput method to detect palladium by monitoring fluorescence has been shown to be useful in monitoring palladium levels in metal ores, pharmaceutical products, and even in living cells. With the ever-increasing popularity of palladium catalysis, this type of quick detection should be very useful in reducing the contamination of pharmaceutical products and preventing the pollution of the environment with palladium and platinum. | 0 | Theoretical and Fundamental Chemistry |
* F. Hansgirg, "Thermal Reduction of Magnesium Compounds", Pt. 1, The Iron Age, Vol. 152, No. 21, pp.52–63, November 18, 1943.
*Fritz Hansgirg, "Koreas Industrial Development", originally appeared in Korea Economic Digest' (April 1945).
* Production of magnesium during carbothermal reduction of magnesium oxide by differential condensation of magnesium and alkali vapors | 0 | Theoretical and Fundamental Chemistry |
Paschen's law is an equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap length. It is named after Friedrich Paschen who discovered it empirically in 1889.
Paschen studied the breakdown voltage of various gases between parallel metal plates as the gas pressure and gap distance were varied:
* With a constant gap length, the voltage necessary to arc across the gap decreased as the pressure was reduced and then increased gradually, exceeding its original value.
* With a constant pressure, the voltage needed to cause an arc reduced as the gap size was reduced but only to a point. As the gap was reduced further, the voltage required to cause an arc began to rise and again exceeded its original value.
For a given gas, the voltage is a function only of the product of the pressure and gap length. The curve he found of voltage versus the pressure-gap length product (right) is called Paschens curve. He found an equation that fit these curves, which is now called Paschens law.
At higher pressures and gap lengths, the breakdown voltage is approximately proportional to the product of pressure and gap length, and the term Paschen's law is sometimes used to refer to this simpler relation. However, this is only roughly true, over a limited range of the curve. | 0 | Theoretical and Fundamental Chemistry |
Hydrometallurgy is a technique within the field of extractive metallurgy, the obtaining of metals from their ores. Hydrometallurgy involve the use of aqueous solutions for the recovery of metals from ores, concentrates, and recycled or residual materials. Processing techniques that complement hydrometallurgy are pyrometallurgy, vapour metallurgy, and molten salt electrometallurgy. Hydrometallurgy is typically divided into three general areas:
*Leaching
*Solution concentration and purification
*Metal or metal compound recovery | 1 | Applied and Interdisciplinary Chemistry |
In plants, ATP is synthesized in the thylakoid membrane of the chloroplast. The process is called photophosphorylation. The "machinery" is similar to that in mitochondria except that light energy is used to pump protons across a membrane to produce a proton-motive force. ATP synthase then ensues exactly as in oxidative phosphorylation. Some of the ATP produced in the chloroplasts is consumed in the Calvin cycle, which produces triose sugars. | 1 | Applied and Interdisciplinary Chemistry |
E74-like factor 1 (ets domain transcription factor) is a protein that in humans is encoded by the ELF1 gene. | 1 | Applied and Interdisciplinary Chemistry |
A receptor agonist is a chemical that binds to a receptor with the end result of directly inducing a conformational change in the bound receptor and activating a downstream effect. Some common examples are opium derivates, such as heroin and Toll-like receptor agonists. Heroin functions in this manner, along with other opioids, when bound to µ-opioid receptors. Opioids' manner of action are both concentration- and receptor-dependent, which provides a key difference between agonists and partial agonists. Another example is insulin, which activates cell receptors to instigate blood glucose uptake. | 1 | Applied and Interdisciplinary Chemistry |
PPIs can be divided into two groups based on their basic structure. Although all members have a substituted pyridine part, one group has linked to various benzimidazoles, whereas the other has linked to a substituted imidazopyridine. All marketed PPIs (omeprazole, lansoprazole, pantoprazole) are in the benzimidazole group.
Proton pump inhibitors are prodrugs and their actual inhibitory form is somewhat controversial. In acidic solution, the sulfenic acid is isolated before reaction with one or more cysteines accessible from the luminar surface of the enzyme, a tetracyclic sulfenamide. This is a planar molecule thus any enantiomer of a PPI loses stereospecifity upon activation.
The effectiveness of these drugs derives from two factors: their target, the H/K ATPase which is responsible for the last step in acid secretion; therefore, their action on acid secretion is independent of the stimulus to acid secretion, of histamine, acetylcholine, or other yet to be discovered stimulants. In addition, their mechanism of action involves covalent binding of the activated drug to the enzyme, resulting in a duration of action that exceeds their plasma half-life. | 1 | Applied and Interdisciplinary Chemistry |
The total potential energy, , is the sum of the elastic strain energy, , stored in the deformed body and the potential energy, , associated to the applied forces:
This energy is at a stationary position when an infinitesimal variation from such position involves no change in energy:
The principle of minimum total potential energy may be derived as a special case of the virtual work principle for elastic systems subject to conservative forces.
The equality between external and internal virtual work (due to virtual displacements) is:
where
* = vector of displacements
* = vector of distributed forces acting on the part of the surface
* = vector of body forces
In the special case of elastic bodies, the right-hand-side of () can be taken to be the change, , of elastic strain energy due to infinitesimal variations of real displacements.
In addition, when the external forces are conservative forces, the left-hand-side of () can be seen as the change in the potential energy function of the forces. The function is defined as:
where the minus sign implies a loss of potential energy as the force is displaced in its direction. With these two subsidiary conditions, becomes:
This leads to () as desired. The variational form of () is often used as the basis for developing the finite element method in structural mechanics. | 0 | Theoretical and Fundamental Chemistry |
Acknowledging the mindset of budding engineers to assimilate concepts in a practical way, Chemfluence'14 was a platform for several Workshops such as
* Programmable Logic Controllers
* Industrial Safety & Risk Analysis
* Statistical Tools for Researchers & Engineers
* Instrumental Methods of Analysis
* Computational Fluid Dynamics
* MATLAB | 1 | Applied and Interdisciplinary Chemistry |
TMAO is an organic osmolyte that has the useful biological function of protecting proteins against denaturing stresses such as high concentration of urea. Various bacteria grow anaerobically using TMAO as an alternative electron transport chain, allowing for growth on non-fermentable carbon sources such as glycerol. Bacteria capable of reducing TMAO to TMA are found throughout three different ecological niches. TMAO-reducing, to date, has been observed in marine bacteria, photosynthetic bacteria living in shallow ponds, and in enterobacteria.
TMAO reductases have been studied in several organisms, and a common conserved feature is the presence of a molybdenum cofactor in all the known terminal enzymes.
Based on their substrate specificity, these enzymes can be divided into two groups:
* TMAO reductases which have high substrate specificity
* DMSO/TMAO reductases which can reduce a broad range of N and S-oxide substrates.
The first group consists of species such as Escherichia coli, Shewanella putrefaciens, and Roseobacter denitrificans while the second group consists of species such as Proteus vulgaris, Rhodobacter capsulatus, and Rhodobacter sphaeroides.
The TMAO respiratory system has been mostly widely studied at the molecular level in E. coli and Rhodobacter species. | 1 | Applied and Interdisciplinary Chemistry |
AuAl has low electrical conductivity and relatively low melting point. AuAl's formation at the joint causes increase of electrical resistance, which can lead to electrical failure. AuAl typically forms at 95% of Au and 5% of Al by mass, its melting point is about 575 °C, which is the lowest among the major gold-aluminum intermetallic compounds. AuAl is a bright-purple compound and a brittle, its composition is about 78.5% Au and 21.5% Al by mass. AuAl is the most thermally stable specie of the Au–Al intermetallic compounds, it has a melting point of 1060 °C (see phase diagram), which is similar to the melting point of pure gold. AuAl can react with Au, therefore is often replaced by AuAl, a tan-colored substancewhich forms at composition of 93% of Au and 7% of Al by mass. It is also a poor conductor and can cause electrical failure of the joint, which further lead to mechanical failure. | 1 | Applied and Interdisciplinary Chemistry |
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recognize structurally conserved molecules derived from microbes. Once these microbes have reached physical barriers such as the skin or intestinal tract mucosa, they are recognized by TLRs, which activate immune cell responses. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12, and TLR13. Humans lack genes for TLR11, TLR12 and TLR13 and mice lack a functional gene for TLR10. The receptors TLR1, TLR2, TLR4, TLR5, TLR6, and TLR10 are located on the cell membrane, whereas TLR3, TLR7, TLR8, and TLR9 are located in intracellular vesicles (because they are sensors of nucleic acids).
TLRs received their name from their similarity to the protein coded by the toll gene. | 1 | Applied and Interdisciplinary Chemistry |
Rowley entered politics in 1981, where he unsuccessfully contested the Tobago West seat in the general election of that year. To date he has the distinction of being the only People's National Movement candidate to have contested a seat in a General Election in both Tobago and Trinidad. He first served in Parliament as an Opposition Senator from 1987 to 1990 (3rd Parliament). Subsequently, he was appointed as Minister of Agriculture, Land and Marine Resources (4th Parliament), Minister of Planning and Development and Minister of Housing (as cabinet reshuffled) (8th Parliament) and Minister of Trade and Industry (9th Parliament) until he was fired by then Prime Minister Patrick Manning. | 0 | Theoretical and Fundamental Chemistry |
Capillary electrochromatography (CEC) is an electrochromatography technique in which the liquid mobile phase is driven through a capillary containing the chromatographic stationary phase by electroosmosis. It is a combination of high-performance liquid chromatography and capillary electrophoresis. The capillaries is packed with HPLC stationary phase and a high voltage is applied to achieve separation is achieved by electrophoretic migration of the analyte and differential partitioning in the stationary phase. | 1 | Applied and Interdisciplinary Chemistry |
Although menopause is a natural barrier to further conception, IVF has allowed people to be pregnant in their fifties and sixties. People whose uteruses have been appropriately prepared receive embryos that originated from an egg donor. Therefore, although they do not have a genetic link with the child, they have a physical link through pregnancy and childbirth. Even after menopause, the uterus is fully capable of carrying out a pregnancy. | 1 | Applied and Interdisciplinary Chemistry |
While repeatedly reversed loading commonly leads to localisation of dislocation glide, creating linear extrusions and intrusions on a free surface, similar features can arise even if there is no load reversal. These arise from dislocations gliding on a particular slip plane, in a particular slip direction (within a single grain), under an external load. Steps can be created on the free surface as a consequence of the tendency for dislocations to follow one another along a glide path, of which there may be several in parallel with each other in the grain concerned. Prior passage of dislocations apparently makes glide easier for subsequent ones, and the effect may also be associated with dislocation sources, such as a Frank-Read source, acting in particular planes.
The appearance of such bands, which are sometimes termed “persistent slip lines”, is similar to that of those arising from cyclic loading, but the resultant steps are usually more localised and have lower heights. They also reveal the grain structure. They can often be seen on free surfaces that were polished before the deformation took place. For example, the figure shows micrographs (taken with different magnifications) of the region around an indent created in a copper sample with a spherical indenter. The parallel lines within individual grains are each the result of several hundred dislocations of the same type reaching the free surface, creating steps with a height of the order of a few microns. If a single slip system was operational within a grain, then there is just one set of lines, but it is common for more than one system to be activated within a grain (particularly when the strain is relatively high), leading to two or more sets of parallel lines. Other features indicative of the details of how the plastic deformation took place, such as a region of cooperative shear caused by deformation twinning, can also sometimes be seen on such surfaces. In the optical micrograph shown, there is also evidence of grain rotations – for example, at the “rim” of the indent and in the form of depressions at grain boundaries. Such images can thus be very informative. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin D is carried via the blood to the liver, where it is converted into the prohormone calcifediol. Circulating calcifediol may then be converted into calcitriol the biologically active form of vitamin D in the kidneys.
Whether synthesized in the skin or ingested, vitamin D is hydroxylated in the liver at position 25 (upper right of the molecule) to form 25-hydroxycholecalciferol (calcifediol or 25(OH)D). This reaction is catalyzed by the microsomal enzyme vitamin D 25-hydroxylase, the product of the CYP2R1 human gene, and expressed by hepatocytes. Once made, the product is released into the plasma, where it is bound to an α-globulin carrier protein named the vitamin D-binding protein.
Calcifediol is transported to the proximal tubules of the kidneys, where it is hydroxylated at the 1-α position (lower right of the molecule) to form calcitriol (1,25-dihydroxycholecalciferol, 1,25(OH)D). The conversion of calcifediol to calcitriol is catalyzed by the enzyme 25-hydroxyvitamin D 1-alpha-hydroxylase, which is the product of the CYP27B1 human gene. The activity of CYP27B1 is increased by parathyroid hormone, and also by low calcium or phosphate. Following the final converting step in the kidney, calcitriol is released into the circulation. By binding to vitamin D-binding protein, calcitriol is transported throughout the body, including to the intestine, kidneys, and bones. Calcitriol is the most potent natural ligand of the vitamin D receptor, which mediates most of the physiological actions of vitamin D. In addition to the kidneys, calcitriol is also synthesized by certain other cells, including monocyte-macrophages in the immune system. When synthesized by monocyte-macrophages, calcitriol acts locally as a cytokine, modulating body defenses against microbial invaders by stimulating the innate immune system. | 1 | Applied and Interdisciplinary Chemistry |
Sodium tris(carbonato)cobalt(III) is the inorganic compound with the formula NaCo(CO)•3HO. The salt contains an olive-green metastable cobalt(III) coordination complex. The salt, a homoleptic metal carbonato complex, is sometimes referred to as the “Field-Durrant precursor” and is prepared by the “Field-Durrant synthesis”. It is used in the synthesis of other cobalt(III) complexes. Otherwise cobalt(III) complexes are generated from cobalt(II) precursors, a process that requires an oxidant. | 0 | Theoretical and Fundamental Chemistry |
Anomers are diastereoisomers of glycosides, hemiacetals or related cyclic forms of sugars, or related molecules differing in configuration only at C-1. When the stereochemistry of the first carbon matches the stereochemistry of the last stereogenic center the sugar is the α-anomer when they are opposite the sugar is the β-anomer. | 0 | Theoretical and Fundamental Chemistry |
Ferritin is present in every cell type. It serves to store iron in a non-toxic form, to deposit it in a safe form, and to transport it to areas where it is required. The function and structure of the expressed ferritin protein varies in different cell types. This is controlled primarily by the amount and stability of messenger RNA (mRNA), but also by changes in how the mRNA is stored and how efficiently it is transcribed. One major trigger for the production of many ferritins is the mere presence of iron; an exception is the yolk ferritin of Lymnaea sp., which lacks an iron-responsive unit.
Free iron is toxic to cells as it acts as a catalyst in the formation of free radicals from reactive oxygen species via the Fenton reaction. Hence vertebrates have an elaborate set of protective mechanisms to bind iron in various tissue compartments. Within cells, iron is stored in a protein complex as ferritin or the related complex hemosiderin. Apoferritin binds to free ferrous iron and stores it in the ferric state. As ferritin accumulates within cells of the reticuloendothelial system, protein aggregates are formed as hemosiderin. Iron in ferritin or hemosiderin can be extracted for release by the RE cells, although hemosiderin is less readily available. Under steady-state conditions, the level of ferritin in the blood serum correlates with total body stores of iron; thus, the serum ferritin FR5Rl is the most convenient laboratory test to estimate iron stores.
Because iron is an important mineral in mineralization, ferritin is employed in the shells of organisms such as molluscs to control the concentration and distribution of iron, thus sculpting shell morphology and colouration. It also plays a role in the haemolymph of the polyplacophora, where it serves to rapidly transport iron to the mineralizing radula.
Iron is released from ferritin for use by ferritin degradation, which is performed mainly by lysosomes. | 1 | Applied and Interdisciplinary Chemistry |
PKM2 is a cytosolic enzyme that is associated with other glycolytic enzymes, i.e., hexokinase, glyceraldehyde 3-P dehydrogenase, phosphoglycerate kinase, phosphoglyceromutase, enolase, and lactate dehydrogenase within a so-called glycolytic enzyme complex.
However, PKM2 contains an inducible nuclear localization signal in its C-terminal domain. The role of PKM2 within the nucleus is complex, since pro-proliferative but also pro-apoptotic stimuli have been described. On the one hand, nuclear PKM2 was found to participate in the phosphorylation of histone 1 by direct phosphate transfer from PEP to histone 1. On the other hand, nuclear translocation of PKM2 induced by a somatostatin analogue, HO, or UV light has been linked with caspase-independent programmed cell death. | 1 | Applied and Interdisciplinary Chemistry |
Austrium is the name of a new chemical element proposed by Eduard Linnemann in 1886. As a chemist at the German University in Prague he experimented with the mineral orthite (from Arendal in Norway). In the course of his works over several years he detected spectral lines at 4165 and 4030 Angstrom, respectively, which he was not able to ascribe to any then known element. These findings were published only after his death after due consideration on May 6, 1886, by the Academy of Sciences of Prague.
Subsequently, the French chemist Paul Emile Lecoq de Boisbaudran pointed out that Linnemanns findings could also be attributed to gallium, an element which had been described by Lecoq himself in 1875. Finally, Richard Pribram from the University of Czernowitz set out to settle the question. He was able to conclude that Linnemanns austrium did not constitute a new element but was – as already presumed by Lecoq – nothing but gallium. At the same time Pribram himself surmised that he might have found unidentified spectral lines of yet another new element, for which he as a homage to Linnemann again proposed the name austrium. But also these claims could not be substantiated in further investigations. | 1 | Applied and Interdisciplinary Chemistry |
Brown spent 36 years in research before she switched over to education. From 1993 to 2002 she was a visiting professor at the New Jersey Institute of Technology, where she also helped recruit black students to enter STEM fields and worked on science education issues in the state. It was here that she also tutored middle school and high school chemistry teachers. She also won a grant from the Camille and Henry Dreyfus Foundation which she put towards tutoring chemistry teachers. Brown has also devoted significant professional effort to diversity and outreach projects; she served on the National Science Foundation Committee on Equal Opportunities for Women Minorities and Persons with Disabilities and was the historian of the American Chemical Society's Women Chemist Committee. To this day, Brown continues to mentor both middle and high school students through the Freddie and Ada Brown Award. She founded this award in 2010 in honor of her parents. | 1 | Applied and Interdisciplinary Chemistry |
Depending on whether the glycosidic bond lies "below" or "above" the plane of the cyclic sugar molecule, glycosides are classified as α-glycosides or β-glycosides. Some enzymes such as α-amylase can only hydrolyze α-linkages; others, such as emulsin, can only affect β-linkages.
There are four type of linkages present between glycone and aglycone:
* C-linkage/glycosidic bond, "nonhydrolysable by acids or enzymes"
* O-linkage/glycosidic bond
* N-linkage/glycosidic bond
* S-linkage/glycosidic bond | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Landau–Squire jet or Submerged Landau jet describes a round submerged jet issued from a point source of momentum into an infinite fluid medium of the same kind. This is an exact solution to the incompressible form of the Navier-Stokes equations, which was first discovered by Lev Landau in 1944 and later by Herbert Squire in 1951. The self-similar equation was in fact first derived by N. A. Slezkin in 1934, but never applied to the jet. Following Landau's work, V. I. Yatseyev obtained the general solution of the equation in 1950. | 1 | Applied and Interdisciplinary Chemistry |
Cells in tissues need to be able to sense and interpret changes in their environment. For example, cells must be able to detect when they are in physical contact with other cells in order to regulate their growth and avoid the generation of tumors (“carcinogenesis”). In order to do so, cells place receptor molecules on their surface, often with a section of the receptor exposed to the outside of the cell (extracellular environment), and a section inside the cell (intracellular environment). These molecules are exposed to the environment outside of the cell and, therefore, in position to sense it. They are called receptors because when these come into contact with particular molecules (termed ligands), then chemical changes are induced to the receptor. These changes typically involve alterations in the three-dimensional shape of the receptor. These 3D structure changes affect both the extracellular and intracellular parts (domains) of the receptor. As a result, interaction of a receptor with its specific ligand which is located outside of the cell causes changes to the receptor part which is inside the cell. A signal from the extracellular space, therefore, can affect the biochemical state inside the cell.
Following receptor activation by the ligand, several steps can sequentially ensue. For example, the 3D shape changes to the intracellular domain may render it recognizable to catalytic proteins (enzymes) that are located inside the cell and have physical access to it. These enzymes may then induce chemical changes to the intracellular domain of the activated receptor, including the addition of phosphate chemical groups to specific components of the receptor (phosphorylation), or the physical separation (cleavage) of the intracellular domain. Such modifications may enable the intracellular domain to act as an enzyme itself, meaning that it may now catalyze the modification of other proteins in the cell. Enzymes which catalyze phosphorylation modifications are termed kinases. These modified proteins may then also be activated and enabled to induce further modifications to other proteins, and so on. This sequence of catalytic modifications is termed a “signal transduction pathway” or “second messenger cascade”. It is a critical mechanism employed by cells to sense their environment and induce complex changes to their state. Such changes may include, as noted, chemical modifications to other molecules, as well as decisions concerning which genes are activated and which are not (transcriptional regulation).
There are many signal transduction pathways in a cell and each of these involves many different proteins. This provides many opportunities for different signal transduction pathways to intercept (cross-talk). As a result, a cell simultaneously processes and interprets many different signals, as would be expected since the extracellular environment contains many different ligands. Cross-talk also allows the cell to integrate these many signals as opposed to process them independently. For example, mutually opposing signals may be activated at the same time by different ligands, and the cell can interpret these signals as a whole.
Signal transduction pathways are widely studied in biology as they provide mechanistic understanding of how a cell operates and takes critical decisions (e.g. to multiply, move, die, activate genes etc.). These pathways also provide many drug targets and are of great relevance to drug discovery efforts. | 1 | Applied and Interdisciplinary Chemistry |
The separative work unit (SWU) is a measure of the amount of work done by the centrifuge and has units of mass (typically kilogram separative work unit). The work necessary to separate a mass of feed of assay into a mass of product assay , and tails of mass and assay is expressed in terms of the number of separative work units needed, given by the expression<br />
<br />
:where is the value function, defined as | 0 | Theoretical and Fundamental Chemistry |
There are two fundamental classifications of cells: prokaryotic and eukaryotic. Prokaryotic cells are distinguished from eukaryotic cells by the absence of a cell nucleus or other membrane-bound organelle. Prokaryotic cells are much smaller than eukaryotic cells, making them the smallest form of life. Prokaryotic cells include Bacteria and Archaea, and lack an enclosed cell nucleus. Eukaryotic cells are found in plants, animals, fungi, and protists. They range from 10 to 100 μm in diameter, and their DNA is contained within a membrane-bound nucleus. Eukaryotes are organisms containing eukaryotic cells. The four eukaryotic kingdoms are Animalia, Plantae, Fungi, and Protista.
They both reproduce through binary fission. Bacteria, the most prominent type, have several different shapes, although most are spherical or rod-shaped. Bacteria can be classed as either gram-positive or gram-negative depending on the cell wall composition. Gram-positive bacteria have a thicker peptidoglycan layer than gram-negative bacteria. Bacterial structural features include a flagellum that helps the cell to move, ribosomes for the translation of RNA to protein, and a nucleoid that holds all the genetic material in a circular structure. There are many processes that occur in prokaryotic cells that allow them to survive. In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase. The prokaryotic polymerase consists of a core enzyme of four protein subunits and a σ protein that assists only with initiation. For instance, in a process termed conjugation, the fertility factor allows the bacteria to possess a pilus which allows it to transmit DNA to another bacteria which lacks the F factor, permitting the transmittance of resistance allowing it to survive in certain environments. | 1 | Applied and Interdisciplinary Chemistry |
Consider the following acid–base reaction:
Acetic acid, , is an acid because it donates a proton to water () and becomes its conjugate base, the acetate ion (). is a base because it accepts a proton from and becomes its conjugate acid, the hydronium ion, ().
The reverse of an acid–base reaction is also an acid–base reaction, between the conjugate acid of the base in the first reaction and the conjugate base of the acid. In the above example, ethanoate is the base of the reverse reaction and hydronium ion is the acid.
One feature of the Brønsted–Lowry theory in contrast to Arrhenius theory is that it does not require an acid to dissociate. | 0 | Theoretical and Fundamental Chemistry |
:V09GA01 Technetium (Tc) sestamibi
:V09GA02 Technetium (Tc) tetrofosmin
:V09GA03 Technetium (Tc) teboroxime
:V09GA04 Technetium (Tc) human albumin
:V09GA05 Technetium (Tc) furifosmin
:V09GA06 Technetium (Tc) stannous agent labelled cells
:V09GA07 Technetium (Tc) apcitide | 1 | Applied and Interdisciplinary Chemistry |
The Pho regulon is controlled by a two-component regulatory system composed of a histidine kinase sensor protein (PhoR) within the inner membrane and a transcriptional response regulator (PhoB/PhoR) on the cytoplasmic side of the membrane. These proteins bind to upstream promoters in the pho regulon in order to induce a general change in gene transcription. This occurs when the cell senses low concentrations of phosphate within its internal environment causing the response regulator to be phosphorylated inducing an overall decrease in gene transcription. This mechanism is ubiquitous within gram-positive, gram-negative, cyanobacteria, yeasts, and archaea. | 1 | Applied and Interdisciplinary Chemistry |
Abouna showed that ammonia was released into the perfusate during 3 day kidney storage, and suggested that this might be toxic to the kidney cells unless removed by frequent replacement of the perfusate. Some support for the use of perfusate exchange during long perfusions was provided by Liu who used perfusate exchange in his successful 7 day storage experiments. Grundmann also found that 96-hour preservation quality was improved by the use of a double volume of perfusate or by perfusate exchange. However, Grundmann's conclusions were based on comparisons with a control group of only 3 dogs. Cohen was unable to demonstrate any production of ammonia during 8 days of perfusion and no benefit from perfusate exchange; the progressive alkalinity that occurred during perfusion was shown to be due to bicarbonate production. | 1 | Applied and Interdisciplinary Chemistry |
Due to their high reactivity, most metals were not discovered until the 19th century. A method for extracting aluminium from bauxite was proposed by Humphry Davy in 1807, using an electric arc. Although his attempts were unsuccessful, by 1855 the first sales of pure aluminium reached the market. However, as extractive metallurgy was still in its infancy, most aluminium extraction-processes produced unintended alloys contaminated with other elements found in the ore; the most abundant of which was copper. These aluminium-copper alloys (at the time termed "aluminum bronze") preceded pure aluminium, offering greater strength and hardness over the soft, pure metal, and to a slight degree were found to be heat treatable. However, due to their softness and limited hardenability these alloys found little practical use, and were more of a novelty, until the Wright brothers used an aluminium alloy to construct the first airplane engine in 1903. During the time between 1865 and 1910, processes for extracting many other metals were discovered, such as chromium, vanadium, tungsten, iridium, cobalt, and molybdenum, and various alloys were developed.
Prior to 1910, research mainly consisted of private individuals tinkering in their own laboratories. However, as the aircraft and automotive industries began growing, research into alloys became an industrial effort in the years following 1910, as new magnesium alloys were developed for pistons and wheels in cars, and pot metal for levers and knobs, and aluminium alloys developed for airframes and aircraft skins were put into use. | 1 | Applied and Interdisciplinary Chemistry |
There are two broad categories of screening techniques: ligand-based and structure-based. The remainder of this page will reflect Figure 1 Flow Chart of Virtual Screening. | 1 | Applied and Interdisciplinary Chemistry |
* Acid value
* Bromine number
* Epoxy value
* Hydroxyl value
* Iodine value
* Peroxide value
* Saponification value | 0 | Theoretical and Fundamental Chemistry |
There is very little known about the surface structures of transition metal oxides, but their bulk crystal structures are well researched. The approach to determine the surface structure is to assume the oxides are ideal crystal, where the bulk atomic arrangement is maintained up to and including the surface plane. The surfaces will be generated by cleavages along the planes of the bulk crystal structure. However, when a crystal is cleaved along a particular plane, the position of surface ions will differ from the bulk structure. Newly created surfaces will tend to minimize the surface Gibbs energy, through reconstruction, to obtain the most thermodynamically stable surface. The stability of these surface structures are evaluated by surface polarity, the degree of coordinative unsaturation and defect sites. | 0 | Theoretical and Fundamental Chemistry |
The 3rd group of anions consist of SO, PO and BO. They react neither with concentrated nor diluted HSO.
* Sulfates give a white precipitate of BaSO with BaCl which is insoluble in any acid or base.
* Phosphates give a yellow crystalline precipitate upon addition of HNO and ammonium molybdate and heating the solution.
* Borates give a green flame characteristic of ethyl borate when ignited with concentrated HSO and ethanol. | 0 | Theoretical and Fundamental Chemistry |
Villalobos was raised in Panama City. She received her BS in chemistry from the University of Panama, received her Ph.D. (1987) at the University of Kansas with Professor Lester A. Mitscher, and was a National Institutes of Health postdoctoral fellow at Yale University, working with Samuel J. Danishefsky. She joined Pfizer in 1989, working on a variety of Central nervous system (CNS) projects in medicinal chemistry, diagnostics, and Positron emission tomography imaging radiotracers against Alzheimer's disease. In 2001, Villalobos became Head of CNS Medicinal Chemistry, and in 2007 Head of Antibacterial and CNS Chemistry. By 2016, she was VP of Neuroscience and Pain medicinal chemistry, and published a video outreach campaign to describe her work. In 2017, Villalobos was recruited to be the Senior Vice President for Biotherapeutics & Medicinal Sciences at Biogen. | 1 | Applied and Interdisciplinary Chemistry |
In many cases, nuclides along the drip lines are not contiguous, but rather are separated by so-called one-particle and two-particle drip lines. This is a consequence of even and odd nucleon numbers affecting binding energy, as nuclides with even numbers of nucleons generally have a higher binding energy, and hence greater stability, than adjacent odd nuclei. These energy differences result in the one-particle drip line in an odd-Z or odd-N nuclide, for which prompt proton or neutron emission is energetically favorable in that nuclide and all other odd nuclides further outside the drip line. However, the next even nuclide outside the one-particle drip line may still be particle stable if its two-particle separation energy is non-negative. This is possible because the two-particle separation energy is always greater than the one-particle separation energy, and a transition to a less stable odd nuclide is energetically forbidden. The two-particle drip line is thus defined where the two-particle separation energy becomes negative, and denotes the outermost boundary for particle stability of a species.
The one- and two-neutron drip lines have been experimentally determined up to neon, though unbound odd-N isotopes are known or deduced through non-observance for every element up to magnesium. For example, the last bound odd-N fluorine isotope is F, though the last bound even-N isotope is F. | 0 | Theoretical and Fundamental Chemistry |
As soon as Columbus started his explorations of the Americas in the late 15th century, a European effort to find valuable medicinal plants among the flora of the New World to add to the medical canon got underway. Early New World medicines uncovered included guaiacum from the West Indies (for coughs, rheumatism and a wide variety of other uses), sassafras from Florida, copaiba from Brazil, Peru balsam and, most famously, cinchona bark from Peru, also called "Jesuit's bark" in honor of its discoverer, which became the first effective treatment for malaria. The active ingredient of this cinchona bark, quinine, was the primary treatment for malaria well into the 1940s. "About 170 drugs used by the Indians of British North America, and perhaps 50 used by the indigenous people of the Caribbean, Mexico, Central and South America" became important enough in the U.S. (as the practitioners of chemistry and pharmacy eventually catalogued, analyzed and understood them) to merit listing in the United States Pharmacopoeia (est. 1820) or the National Formulary.
In the early 1700s, James Oglethorpe, founder of the Georgia colony, with the financial backing of the Worshipful Society of Apothecaries of London and others, launched an effort to identify and transplant beneficial plant species from the tropical colonies to Savannah, Georgia. Unfortunately for Oglethorpe (and all the Southern colonists) the expedition that marked this first attempt by an organized group of Old World apothecaries to benefit from British North Americas potential as a medicine farm never bore fruit. The Caribbean expeditions lead investigator, botanist Robert Miller, was hampered by illness and uncooperative Spanish colonials, and all support from London ceased when Miller died without much success. | 1 | Applied and Interdisciplinary Chemistry |
The Euler equations written in terms of the Lamb vector is referred to as the Gromeka–Lamb equation, named after Ippolit S. Gromeka and Horace Lamb. This is given by | 1 | Applied and Interdisciplinary Chemistry |
Original ATM techniques involve rotating the sample at the focal point of a linearly polarized THz beam using a mechanically rotated sample mount. For this reason, the configuration is typically a far-field instrument in which a balanced detector (sensitive to infrared light) is placed a considerable distance from the sample. In the terahertz time-domain spectroscopy configuration, both the infrared and THz beams are transmitted through an electro-optic (EO) crystal like ZnTe or GaP. Here, the infrared beam detects the change in birefringence of the EO crystal due to the THz beam. When a sample is placed in the THz beam, the polarized THz beam is perturbed and the resulting degree of birefringence in the EO crystal is changed. The resulting perturbation of the infrared beam is sensed at the balanced detector.
Rotated sample ATM is very useful for large samples (0.1 to 1 cm). However, when measuring samples such as protein crystals that must be isolated inside a hydration chamber, for example, the sample cannot be easily rotated. Additionally, it is challenging to maintain the same location of a rotated sample at the precise focal point of a THz beam. | 0 | Theoretical and Fundamental Chemistry |
Conditionally essential nutrients are certain organic molecules that can normally be synthesized by an organism, but under certain conditions in insufficient quantities. In humans, such conditions include premature birth, limited nutrient intake, rapid growth, and certain disease states. Inositol, taurine, arginine, glutamine and nucleotides are classified as conditionally essential and are particularly important in neonatal diet and metabolism. | 0 | Theoretical and Fundamental Chemistry |
Assisted reproduction via MRT involves preimplantation genetic screening of the mother, preimplantation genetic diagnosis after the egg is fertilized, and in vitro fertilization. It has all the risks of those procedures.
In addition, both procedures used in MRT entail their own risks. On one level, the procedures physically disrupt two oocytes, removing nuclear genetic material from the recipient egg or fertilized egg and inserting the nuclear genetic material into the donor unfertilized or fertilized egg; the manipulations for both procedures may cause various forms of damage that were not well understood as of 2016.
Maternal mitochondria will be carried over to the donor egg; as of 2016 it was estimated that using techniques current in the UK, maternal mitochondria will comprise only around 2% or less of mitochondria in the resulting egg, a level that was considered safe by the HFEA and within the limits of mitochondrial variation that most people have.
Because MRT procedures involve actions at precise times during egg development and fertilization, and involves manipulating eggs, there is a risk that eggs may mature abnormally or that fertilization may happen abnormally; as of 2016 the HFEA judged that laboratory techniques in the UK had been well enough developed to manage these risks to proceed cautiously with making MRT available.
Because mitochondria in the final egg will come from a third party, different from the two parties whose DNA is in the nucleus, and because nuclear DNA encodes genes that make some of the proteins and mRNA used by mitochondria, there is a theoretical risk of adverse "mito–nuclear" interactions. While this theoretical risk could possibly be managed by attempting to match the haplotype of the donor and the recipient, as of 2016 there was no evidence that this is an actual risk.
Because MRT is a relatively new technology, there are concerns that it is not yet safe for public use as there have been limited studies that used MRT in large animal models.
Finally, there is a risk of epigenetic modification to DNA in the nucleus and mitochondria, caused by the procedure itself or by mito–nuclear interactions. As of 2016 these risks appeared to be minimal but were being monitored by long-term study of children born from the procedure. | 1 | Applied and Interdisciplinary Chemistry |
An ova bank, or cryobank, or egg cell bank is a facility that collects and stores human ova, mainly from ova donors, primarily for the purpose of achieving pregnancies of either the donor, at a later time (i.e. to overcome issues of infertility), or through third party reproduction, notably by artificial insemination. Ova donated in this way are known as donor ova. | 1 | Applied and Interdisciplinary Chemistry |
Cyanosulfidic chemistry has several limitations. While the products are all formed from the same starting materials, many of the reactions require the periodic delivery of new reagents which complicates the syntheses. The chemical synthesis is therefore not truly “one-pot” chemistry which would require all reactants to be provided at the beginning which no further alterations. Sutherland and colleagues argue that a “flow-chemistry” approach featuring the movement of compounds through a stream experiencing different geochemical conditions makes their proposed system plausible. | 0 | Theoretical and Fundamental Chemistry |
An aluminum‐based metal-organic framework made from 2‐aminoterephthalate can be modified by incorporating Ni cations into the pores through coordination with the amino groups.Molybdenum disulfide | 0 | Theoretical and Fundamental Chemistry |
Albert was deeply interested in astrology, as has been articulated by scholars such as Paola Zambelli and Scott Hendrix. Throughout the Middle Ages –and well into the early modern period– astrology was widely accepted by scientists and intellectuals who held the view that life on earth is effectively a microcosm within the macrocosm (the latter being the cosmos itself). It was believed that correspondence therefore exists between the two and thus the celestial bodies follow patterns and cycles analogous to those on earth. With this worldview, it seemed reasonable to assert that astrology could be used to predict the probable future of a human being. Albert argued that an understanding of the celestial influences affecting us could help us to live our lives more in accord with Christian precepts. The most comprehensive statement of his astrological beliefs is to be found in two separates works that he authored around 1260, known as the Speculum astronomiae and the De Fato. However, details of these beliefs can be found in almost everything he wrote, from his early De natura boni to his last work, the Summa theologiae. His speculum was critiqued by Gerard of Silteo. | 1 | Applied and Interdisciplinary Chemistry |
Previous work has shown that a worst-case exposure scenario can be limited to a specific set of conditions. Based on the advanced detection methods and pipeline shut-off SOP developed by TransCanada, the risk of a substantive or large release over a short period of time contaminating groundwater with benzene is unlikely. Detection, shutoff, and remediation procedures would limit the dissolution and transport of benzene. Therefore, the exposure of benzene would be limited to leaks that are below the limit of detection and go unnoticed for extended periods of time. Leak detection is monitored through a SCADA system that assesses pressure and volume flow every 5 seconds. A pinhole leak that releases small quantities that cannot be detected by the SCADA system (<1.5% flow) could accumulate into a substantive spill. Detection of pinhole leaks would come from a visual or olfactory inspection, aerial surveying, or mass-balance inconsistencies. It is assumed that pinhole leaks are discovered within the 14-day inspection interval, however snow cover and location (e.g. remote, deep) could delay detection. Benzene typically makes up 0.1 – 1.0% of oil and will have varying degrees of volatility and dissolution based on environmental factors.
Even with pipeline leak volumes within SCADA detection limits, sometimes pipeline leaks are misinterpreted by pipeline operators to be pump malfunctions, or other problems. The Enbridge Line 6B crude oil pipeline failure in Marshall, Michigan on July 25, 2010 was thought by operators in Edmonton to be from column separation of the dilbit in that pipeline. The leak in wetlands along the Kalamazoo River was only confirmed 17 hours after it happened by a local gas company employee. | 1 | Applied and Interdisciplinary Chemistry |
In its simplest form, an electrocoagulation reactor is made up of an electrolytic cell with one anode and one cathode. When connected to an external power source, the anode material will electrochemically corrode due to oxidation, while the cathode will be subjected to passivation.
An EC system essentially consists of pairs of conductive metal plates in parallel, which act as monopolar electrodes. It furthermore requires a direct current power source, a resistance box to regulate the current density and a multimeter to read the current values. The conductive metal plates are commonly known as "sacrificial electrodes." The sacrificial anode lowers the dissolution potential of the anode and minimizes the passivation of the cathode. The sacrificial anodes and cathodes can be of the same or of different materials.
The arrangement of monopolar electrodes with cells in series is electrically similar to a single cell with many electrodes and interconnections. In series cell arrangement, a higher potential difference is required for a given current to flow because the cells connected in series have higher resistance. The same current would, however, flow through all the electrodes. In contrast, in parallel or bipolar arrangement the electric current is divided between all the electrodes in relation to the resistance of the individual cells, and each face on the electrode has a different polarity.
During electrolysis, the positive side undergoes anodic reactions, while on the negative side, cathodic reactions are encountered. Consumable metal plates, such as iron or aluminum, are usually used as sacrificial electrodes to continuously produce ions in the water. The released ions neutralize the charges of the particles and thereby initiate coagulation. The released ions remove undesirable contaminants either by chemical reaction and precipitation, or by causing the colloidal materials to coalesce, which can then be removed by flotation. In addition, as water containing colloidal particulates, oils, or other contaminants move through the applied electric field, there may be ionization, electrolysis, hydrolysis, and free-radical formation which can alter the physical and chemical properties of water and contaminants. As a result, the reactive and excited state causes contaminants to be released from the water and destroyed or made less soluble.
It is important to note that electrocoagulation technology cannot remove infinitely soluble matter. Therefore, ions with molecular weights smaller than Ca or Mg cannot be dissociated from the aqueous medium. | 1 | Applied and Interdisciplinary Chemistry |
A thermogravitational cycle is a reversible thermodynamic cycle using the gravitational works of weight and buoyancy to respectively compress and expand a working fluid. | 0 | Theoretical and Fundamental Chemistry |
Georg Brandt (June 26, 1694 – April 29, 1768) was a Swedish chemist and mineralogist who discovered cobalt c. 1735. He was the first person to discover a metal unknown in ancient times. He is also known for exposing fraudulent alchemists operating during his lifetime. | 1 | Applied and Interdisciplinary Chemistry |
In case of gravity–capillary waves, where surface tension affects the waves, the dispersion relation becomes:
with σ the surface tension (in N/m).
For a water–air interface (with and ) the waves can be approximated as pure capillary waves – dominated by surface-tension effects – for wavelengths less than . For wavelengths above the waves are to good approximation pure surface gravity waves with very little surface-tension effects. | 1 | Applied and Interdisciplinary Chemistry |
In this field, whole genome sequencing represents a great set of improvements and challenges to be faced by the scientific community, as it makes it possible to analyze, quantify and characterize circulating tumor DNA (ctDNA) in the bloodstream. This serves as a basis for early cancer diagnosis, treatment selection and relapse monitoring, as well as for determining the mechanisms of resistance, metastasis and phylogenetic patterns in the evolution of cancer. It can also help in the selection of individualized treatments for patients suffering from this pathology and observe how existing drugs are working during the progression of treatment. Deep whole genome sequencing involves a subclonal reconstruction based on ctDNA in plasma that allows for complete epigenomic and genomic profiling, showing the expression of circulating tumor DNA in each case. | 1 | Applied and Interdisciplinary Chemistry |
Transition metal porphyrin complexes are a family of coordination complexes of the conjugate base of porphyrins. Iron porphyrin complexes occur widely in Nature, which has stimulated extensive studies on related synthetic complexes. The metal-porphyrin interaction is a strong one such that metalloporphyrins are thermally robust. They are catalysts and exhibit rich optical properties, although these complexes remain mainly of academic interest. | 1 | Applied and Interdisciplinary Chemistry |
In 1973, Sony introduced double-layer ferrichrome tapes having a five-micron ferric base coated with one micron of CrO pigment. The new cassettes were advertised as the best of both worlds — combining the good low-frequency MOL of microferric tapes with good high-frequency performance of chrome tapes. The novelty became part of the IEC standard, codenamed Type III; the Sony CS301 formulation became the IEC reference. However, the idea failed to attract followers. Apart from Sony, only BASF, Scotch and Agfa introduced their own ferrichrome cassette tapes.
These expensive ferrichrome tapes never gained substantial market share, and after the release of metal tapes they lost their perceived exclusivity. Their place in the market was taken over by superior and less expensive ferricobalt formulations. By 1983, tape deck manufacturers stopped providing an option for recording Type III tapes. Ferrichrome tape remained in the BASF and Sony lineups until 1984 and 1988, respectively.
The use of ferrichrome tapes was complicated by the conflicting rationale of the playback of these tapes. Officially, they were intended to be played back using equalisation. The information leaflet that Sony included in each box of ferrichrome cassette tapes recommended that, "If the selector has two positions, NORMAL and CrO, set it to the NORMAL position." (which applies equalisation). The leaflet notes that the high frequency range will be enhanced and that the tone control should be adjusted to compensate. The same leaflet recommends that if the playback machine offers a Fe-Cr selection, that this should be selected. On Sonys machines, this automatically selects equalisation. The service manual for the Sony TC-135SD, which was one of the few cassette decks offering a Fe-Cr' position, shows the tape type selector switch paralleling the ferrichrome equalisation selection with that of chrome dioxide (). Neither Sony nor BASF cassette tapes feature the notches on the back surface that automatically select equalisation on those machines that featured an automatic detection system. | 0 | Theoretical and Fundamental Chemistry |
There are two models describing of the distribution of the tracer compound between the two phases (the precipitate and the solution):
* Doerner-Hoskins law (logarithmic):
* Berthelot-Nernst law:
where:
: a and b are the initial concentrations of the tracer and carrier, respectively;
: a − x and b − y are the concentrations of tracer and carrier after separation;
: x and y are the amounts of the tracer and carrier on the precipitate;
: D and λ are the distribution coefficients.
For D and λ greater than 1, the precipitate is enriched in the tracer.
Depending on the co-precipitation system and conditions either λ or D may be constant.
The derivation of the Doerner-Hoskins law assumes that there in no mass exchange between the interior of the precipitating crystals and the solution. When this assumption is fulfilled, then the content of the tracer in the crystal is non-uniform (the crystals are said to be heterogeneous). When the Berthelot-Nernst law applies, then the concentration of the tracer in the interior of the crystal is uniform (and the crystals are said to be homogeneous). This is the case when diffusion in the interior is possible (like in the liquids) or when the initial small crystals are allowed to recrystallize. Kinetic effects (like speed of crystallization and presence of mixing) play a role. | 0 | Theoretical and Fundamental Chemistry |
Presumptive tests, in medical and forensic science, analyze a sample and establish one of the following:
#The sample is definitely not a certain substance.
#The sample probably is the substance.
For example, the Kastle–Meyer test will show either that a sample is not blood or that the sample is probably blood but may be a less common substance. Further chemical tests are needed to prove that the substance is blood.
Confirmatory tests are the tests required to confirm the analysis. Confirmatory tests cost more than simpler presumptive tests so presumptive tests are often done to see if confirmatory tests are necessary.
Similarly, in medicine, a presumptive diagnosis identifies the likely condition of a patient, and a confirmatory diagnosis is needed to confirm the condition. | 0 | Theoretical and Fundamental Chemistry |
A breakthrough has been brought about in the last decades by the development of large scale synchrotron radiation facilities. Here, bunches of relativistic electrons kept in orbit inside a storage ring are accelerated through bending magnets or insertion devices like wigglers and undulators to produce a high brilliance and high flux photon beam. The beam is orders of magnitude more intense and better collimated than typically produced by anode-based sources. Synchrotron radiation is also tunable over a wide wavelength range, and can be made polarized in several distinct ways. This way, photon can be selected yielding optimum photoionization cross-sections for probing a particular core level. The high photon flux, in addition, makes it possible to perform XPS experiments also from low density atomic species, such as molecular and atomic adsorbates.
One of the synchrotron facilities that allows XPS measurement is Max IV synchrotron in Lund, Sweden. The Hippie beam line of this facility also allows to perform in operando Ambient Pressure X-Ray Photoelectron Spectroscopy (AP-XPS9. This latter technique allows to measure samples in ambient conditions, rather than in vacuum. | 0 | Theoretical and Fundamental Chemistry |
The first discussion of obtaining an image of a surface using atoms was by King and Bigas, who showed that an image of a surface can be obtained by heating a sample and monitoring the atoms that evaporate from the surface. King and Bigas suggest that it could be possible to form an image by scattering atoms from the surface, though it was some time before this was demonstrated.
The idea of imaging with atoms instead of light was subsequently widely discussed in the literature.
The initial approach to producing a helium microscope assumed that a focussing element is required to produce a high intensity beam of atoms. An early approach was to develop an atomic mirror, which is appealing since the focussing is independent of the velocity distribution of the incoming atoms. However the material challenges to produce an appropriate surface that is macroscopically curved and defect free on an atomic length-scale has proved too challenging so far.
King and Bigas, showed that an image of a surface can be obtained by heating a sample and monitoring the atoms that evaporate from the surface. King and Bigas suggest it could be possible to form an image by scattering atoms from the surface, though it was some time before it was demonstrated.
Metastable atoms are atoms that have been excited out of the ground state, but remain in an excited state for a significant period of time. Microscopy using metastable atoms has been shown to be possible, where the metastable atoms release stored internal energy into the surface, releasing electrons that provide information on the electronic structure. The kinetic energy of the metastable atoms means that only the surface electronic structure is probed, but the large energy exchange when the metastable atom de-excites will still perturb delicate sample surfaces.
The first two-dimensional neutral helium images were obtained using a conventional Fresnel zone plate by Koch et al. in a transmission setup. Helium will not pass through a solid material, therefore a large change in the measured signal is obtained when a sample is placed between the source and the detector. By maximising the contrast and using transmission mode, it was much easier to verify the feasibility of the technique. However, the setup used by Koch et al. with a zone plate did not produce a high enough signal to observe the reflected signal from the surface at the time. Nevertheless, the focussing obtained with a zone plate offers the potential for improved resolution due to the small beam spot size in the future. Research into neutral helium microscopes that use a Fresnel zone plate is an active area in Holst’s group at the University of Bergen.
Since using a zone plate proved difficult due to the low focussing efficiency, alternative methods for forming a helium beam to produce images with atoms were explored.
Recent efforts have avoided focussing elements and instead are directly collimating a beam with a pinhole. The lack of atom optics means that the beam width will be significantly larger than in an electron microscope. The first published demonstration of a two-dimensional image formed by helium reflecting from the surface was by Witham and Sánchez, who used a pinhole to form the helium beam. A small pinhole is placed very close to a sample and the helium scattered into a large solid angle is fed to a detector. Images are collected by moving the sample around underneath the beam and monitoring how the scattered helium flux changes.
In parallel to the work by Witham and Sánchez, a proof of concept machine named the scanning helium microscope (SHeM) was being developed in Cambridge in collaboration with Dastoor's group from the University of Newcastle. The approach that was adopted was to simplify previous attempts that involved an atom mirror by using a pinhole, but to still use a conventional helium source to produce a high quality beam. Other differences from the Witham and Sánchez design include using a larger sample to pinhole distance, so that a larger variety of samples can be used and to use a smaller collection solid angle, so that it may be possible to observe more subtle contrast. These changes also reduced the total flux in the detector meaning that higher efficiency detectors are required (which in itself is an active area of research. | 0 | Theoretical and Fundamental Chemistry |
After graduating from the University of Cambridge, Dye worked for a short period as Junior Associate at Mitchell Madison Group from October 2000 until March 2001, before going back to the Department of Materials Science and Metallurgy, the University of Cambridge as a postdoctoral research associate also for a very short stint in 2001. He then joined the National Research Council (NRC) of Canada as Visiting fellow from late 2001 until 2003, working at the neutron spectroscopy facility at the AECL Chalk River Laboratories in Ontario, Canada. He then moved to the Department of Materials, Imperial College London as lecturer, and became a professor in 2015.
David Dye teaches metallurgy, and his research focuses primarily on the micromechanics, design, and fatigue processes of titanium and nickel/cobalt superalloys, with side interests in zirconium, twinning-induced plasticity steels, and superelastic NiTi-based alloys. Most of his work is done in collaboration with Rolls-Royce and other industries, including nuclear and aerospace.
Dye is an experimentalist. His work involves using Electron backscatter diffraction and traditional lab-based characterisation methods, transmission electron microscopy (TEM), neutron and X-rays synchrotron at facilities like ISIS Neutron and Muon Source, Diamond Light Source, European Synchrotron Radiation Facility, and in situ microbeam Laue synchrotron diffraction. | 1 | Applied and Interdisciplinary Chemistry |
Type R (87%Pt/13%Rh–Pt, by weight) thermocouples are used 0 to 1600 °C. Type R Thermocouples are quite stable and capable of long operating life when used in clean, favorable conditions. When used above 1100 °C ( 2000 °F), these thermocouples must be protected from exposure to metallic and non-metallic vapors. Type R is not suitable for direct insertion into metallic protecting tubes. Long term high temperature exposure causes grain growth which can lead to mechanical failure and a negative calibration drift caused by Rhodium diffusion to pure platinum leg as well as from Rhodium volatilization. This type has the same uses as type S, but is not interchangeable with it. | 1 | Applied and Interdisciplinary Chemistry |
Pseudoephedrine is a diastereomer of ephedrine and is readily reduced into methamphetamine or oxidized into methcathinone. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrates arise by condensation of monosaccharides such as glucose. The polymers can be classified into oligosaccharides (up to 10 residues) and polysaccharides (up to about 50,000 residues). The backbone chain is characterized by an ether bond between individual monosaccharides. This bond is called the glycosidic linkage. These backbone chains can be unbranched (containing one linear chain) or branched (containing multiple chains). The glycosidic linkages are designated as alpha or beta depending on the relative stereochemistry of the anomeric (or most oxidized) carbon. In a Fischer Projection, if the glycosidic linkage is on the same side or face as carbon 6 of a common biological saccharide, the carbohydrate is designated as beta and if the linkage is on the opposite side it is designated as alpha. In a traditional "chair structure" projection, if the linkage is on the same plane (equatorial or axial) as carbon 6 it is designated as beta and on the opposite plane it is designated as alpha. This is exemplified in sucrose (table sugar) which contains a linkage that is alpha to glucose and beta to fructose. Generally, carbohydrates which our bodies break down are alpha-linked (example: glycogen) and those which have structural function are beta-linked (example: cellulose). | 0 | Theoretical and Fundamental Chemistry |
Mars is fundamentally an igneous planet. Rocks on the surface and in the crust consist predominantly of minerals that crystallize from magma. Most of our current knowledge about the mineral composition of Mars comes from spectroscopic data from orbiting spacecraft, in situ analyses of rocks and soils from six landing sites, and study of the Martian meteorites. Spectrometers currently in orbit include THEMIS (Mars Odyssey), OMEGA (Mars Express), and CRISM (Mars Reconnaissance Orbiter). The two Mars exploration rovers each carry an Alpha Particle X-ray Spectrometer (APXS), a thermal emission spectrometer (Mini-TES), and Mössbauer spectrometer to identify minerals on the surface.
On October 17, 2012, the Curiosity rover on the planet Mars at "Rocknest" performed the first X-ray diffraction analysis of Martian soil. The results from the rover's CheMin analyzer revealed the presence of several minerals, including feldspar, pyroxenes and olivine, and suggested that the Martian soil in the sample was similar to the "weathered basaltic soils" of Hawaiian volcanoes. | 0 | Theoretical and Fundamental Chemistry |
Hecht was born in Glogau, then in the German Empire (now Głogów in Poland), the son of Mandel Hecht and Mirel Mresse. The family migrated to the USA in 1898, settling in New York City. His studies and talents led to Columbia University making him professor of biophysics in 1928.
In June 1917 Hecht received his Ph.D. and married Celia Huebschmann. Their daughter Maressa was born in 1924.
Hecht began his study into light sensitivity with clams (Mya arenaria) and insects. His specialty was photochemistry, the kinetics of the reactions initiated by light in the receptors. He made contributions to the knowledge of dark adaptation, visual acuity, brightness discrimination, color vision, and the mechanism of the visual threshold.
He spent time as a post-doctoral researcher with the group of Edward Charles Cyril Baly at the University of Liverpool, UK. Baly was a pioneer in the application of the technique of spectroscopy in chemistry, and Hecht took this further by applying it to biological molecules.
Hecht's responsibility in showing the protein character of rhodopsin was recounted by historians of protein science:
According to biographer Pirenne, Hecht was a "brilliant lecturer and expositor." Pirenne continues,
:The lack of synthesis discernible in present-day knowledge and teaching perturbed him, and he took an active interest in all the human implications of science. He dealt with persons and ideas on the basis of their intrinsic worth,... | 0 | Theoretical and Fundamental Chemistry |
The Sleeping Beauty transposon system (SBTS) is the first successful non-viral vector for incorporation of a gene cassette into a vertebrate genome. Up until the development of this system, the major problems with non-viral gene therapy have been the intracellular breakdown of the transgene due to it being recognized as Prokaryotes and the inefficient delivery of the transgene into organ systems. The SBTS revolutionized these issues by combining the advantages of viruses and naked DNA. It consists of a transposon containing the cassette of genes to be expressed, as well as its own transposase enzyme. By transposing the cassette directly into the genome of the organism from the plasmid, sustained expression of the transgene can be attained. This can be further refined by enhancing the transposon sequences and the transposase enzymes used. SB100X is a hyperactive mammalian transposase which is roughly 100x more efficient than the typical first-generation transposase. Incorporation of this enzyme into the cassette results in even more sustained transgene expression (over one year). Additionally, transgenesis frequencies can be as high as 45% when using pronuclear injection into mouse zygotes.
The mechanism of the SBTS is similar to the Tn5 transposon system, however the enzyme and gene sequences are eukaryotic in nature as opposed to prokaryotic. The systems tranposase can act in trans as well as in cis, allowing a diverse collection of transposon structures. The transposon itself is flanked by inverted repeat sequences, which are each repeated twice in a direct fashion, designated IR/DR sequences. The internal region consists of the gene or sequence to be transposed, and could also contain the transposase gene. Alternatively, the transposase can be encoded on a separate plasmid or injected in its protein form. Yet another approach is to incorporate both the transposon and the transposase genes into a viral vector, which can target a cell or tissue of choice. The transposase protein is extremely specific in the sequences that it binds, and is able to discern its IR/DR sequences from a similar sequence by three base pairs. Once the enzyme is bound to both ends of the transposon, the IR/DR sequences are brought together and held by the transposase in a Synaptic Complex Formation (SCF). The formation of the SCF is a checkpoint ensuring proper cleavage. HMGB1 is a non-histone protein from the host which is associated with eukaryotic chromatin. It enhances the preferential binding of the transposase to the IR/DR sequences and is likely essential for SCF complex formation/stability. Transposase cleaves the DNA at the target sites, generating 3 overhangs. The enzyme then targets TA dinucleotides in the host genome as target sites for integration. The same enzymatic catalytic site which cleaved the DNA is responsible for integrating the DNA into the genome, duplicating the region of the genome in the process. Although transposase is specific for TA dinucleotides, the high frequency of these pairs in the genome indicates that the transposon undergoes fairly random integration. | 1 | Applied and Interdisciplinary Chemistry |
Project name: Shadow Wood Preserve Green Roof Demonstration
* Location: Ft. Myers, FL, USA
* Size: 2400 sq.ft.
Project name: Charles R. Perry Construction Yard, University of Florida
* Location: Gainesville, FL, USA
* Size: 2600 sq.ft.
Project name: Student Union Expansion at the University of Central Florida (UCF)
* Location: Orlando, FL, USA
* Size: 1600 sq ft | 1 | Applied and Interdisciplinary Chemistry |
By flowing through the aspirator, water will suck out the air contained in the vacuum flask and the Büchner flask. There is therefore a difference in pressure between the exterior and the interior of the flasks : the contents of the Büchner funnel are sucked towards the vacuum flask. The filter, which is placed at the bottom of the Büchner funnel, separates the solids from the liquids.
The solid residue, which remains at the top of the Büchner funnel, is therefore recovered more efficiently: it is much drier than it would be with a simple filtration.
The rubber conical seal ensures the apparatus is hermetically closed, preventing the passage of air between the Büchner funnel and the vacuum flask. It maintains the vacuum in the apparatus and also avoids physical points of stress (glass against glass.) | 0 | Theoretical and Fundamental Chemistry |
While chemosensors were first defined in the 1980s, the first example of such a fluorescent chemosensor can be documented to be that of Friedrich Goppelsroder, who in 1867, developed a method for the determination/sensing of aluminium ion, using fluorescent ligand/chelate. This and subsequent work by others, gave birth to what is considered as modern analytical chemistry.
In the 1980s the development of chemosensing was achieved by Anthony W. Czarnik, A. Prasanna de Silva and Roger Tsien, who developed various types of luminescent probes for ions and molecules in solutions and within biological cells, for real-time applications. Tsien went on to study and developing this area of research further by developing and studding fluorescent proteins for applications in biology, such as green fluorescent proteins (GFP) for which he was awarded the Nobel Prize in Chemistry in 2008. The work of Lynn Sousa in the late 1970s, on the detection of alkali metal ions, possibly resulting in one of the first examples of the use of supramolecular chemistry in fluorescent sensing design, as well as that of J.-M. Lehn, H. Bouas-Laurent and co-workers at Université Bordeaux I, France. The development of PET sensing of transition metal ions was developed by L. Fabbrizzi, among others.
In chemosensing, the use of fluorophore connected to the receptor via a covalent spacer is now commonly referred to as fluorophores-spacer-receptor principle. In such systems, the sensing event is normally described as being due to changes in the photophysical properties of the chemosensor systems due to chelation induced enhanced fluorescence (CHEF), and photoinduced electron transfer (PET), mechanisms. In principle the two mechanisms are based on the same idea; the communication pathway is in the form of a through-space electron transfer from the electron rich receptors to the electron deficient fluorophores (through space). This results in fluorescence quenching (active electron transfer), and the emission from the chemosensor is switched off, for both mechanisms in the absence of the analytes. However, upon forming a host–guest complex between the analyte and receptor, the communication pathway is broken and the fluorescence emission from the fluorophores is enhanced, or switched on. In other words, the fluorescence intensity and quantum yield are enhanced upon analyte recognition.
The fluorophores-receptor can also be integrated within the chemosensor. This leads to changes in the emission wavelength, which often results in change in colour. When the sensing event results in the formation of a signal that is visible to the naked eye, such sensors are normally referred to as colorimetric. Many examples of colorimetric chemosensors for ions such as fluoride have been developed. A pH indicator can be consider as a colorimetric chemosensors for protons. Such sensors have been developed for other cations, as well as anions and larger organic and biological molecules, such as proteins and carbohydrates. | 0 | Theoretical and Fundamental Chemistry |
These elements are bound by specific uncharged tRNAs and modulate the expression of corresponding aminoacyl-tRNA synthetase operons. High levels of uncharged tRNA promote the anti-terminator sequence leading to increased concentrations of charged tRNA. These are considered by some to be a separate family of riboswitches but are significantly more complex than the previous class of attenuators. | 1 | Applied and Interdisciplinary Chemistry |
SDS is synthesized by treating lauryl alcohol with sulfur trioxide, oleum, or chlorosulfuric acid to produce hydrogen lauryl sulfate. Lauryl alcohol can be used in pure form or as a mixtures of fatty alcohols. When produced from these sources, "SDS" products are a mixture of various sodium alkyl sulfates with SDS being the main component. For instance, SDS is a component, along with other chain-length amphiphiles, when produced from coconut oil, and is known as sodium coco sulfate (SCS). SDS is available commercially in powder, pellet, and other forms (each differing in rates of dissolution), as well as in aqueous solutions of varying concentrations. | 1 | Applied and Interdisciplinary Chemistry |
The most confirmed function of plastid terminal oxidase in developed chloroplasts is its role in chlororespiration. In this process, NADPH dehydrogenase (NDH) reduces the quinone pool and the terminal oxidase oxidizes it, serving the same function as cytochrome c oxidase from mitochondrial electron transport. In Chlamydomonas, there are two copies of the gene for the oxidase. PTOX2 significantly contributes to the flux of electrons through chlororespiration in the dark. There is also evidence from experiments with tobacco that it functions in plant chlororespiration as well.
In fully developed chloroplasts, prolonged exposure to light increases the activity of the oxidase. Because the enzyme acts at the plastoquinone pool in between photosystem II and photosystem I, it may play a role in controlling electron flow through photosynthesis by acting as an alternative electron sink. Similar to its role in carotenoid synthesis, its oxidase activity may prevent the over-reduction of photosystem I electron acceptors and damage by photoinhibition. A recent analysis of electron flux through the photosynthetic pathway shows that even when activated, the electron flux plastid terminal oxidase diverts is two orders of magnitude less than the total flux through photosynthetic electron transport. This suggests that the protein may play less of a role than previously thought in relieving the oxidative stress in photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
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