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There are several challenges to the application of thorium as a nuclear fuel, particularly for solid fuel reactors:
In contrast to uranium, naturally occurring thorium is effectively mononuclidic and contains no fissile isotopes; fissile material, generally , or plutonium, must be added to achieve criticality. This, along with the high sintering temperature necessary to make thorium-dioxide fuel, complicates fuel fabrication. Oak Ridge National Laboratory experimented with thorium tetrafluoride as fuel in a molten salt reactor from 1964 to 1969, which was expected to be easier to process and separate from contaminants that slow or stop the chain reaction.
In an open fuel cycle (i.e. utilizing in situ), higher burnup is necessary to achieve a favorable neutron economy. Although thorium dioxide performed well at burnups of 170,000 MWd/t and 150,000 MWd/t at Fort St. Vrain Generating Station and AVR respectively, challenges complicate achieving this in light water reactors (LWR), which compose the vast majority of existing power reactors.
In a once-through thorium fuel cycle, thorium-based fuels produce far less long-lived transuranics than uranium-based fuels,
some long-lived actinide products constitute a long-term radiological impact, especially and . On a closed cycle, and can be reprocessed. is also considered an excellent burnable poison absorber in light water reactors.
Another challenge associated with the thorium fuel cycle is the comparatively long interval over which breeds to . The half-life of is about 27 days, which is an order of magnitude longer than the half-life of . As a result, substantial develops in thorium-based fuels. is a significant neutron absorber and, although it eventually breeds into fissile , this requires two more neutron absorptions, which degrades neutron economy and increases the likelihood of transuranic production.
Alternatively, if solid thorium is used in a closed fuel cycle in which is recycled, remote handling is necessary for fuel fabrication because of the high radiation levels resulting from the decay products of . This is also true of recycled thorium because of the presence of , which is part of the decay sequence. Further, unlike proven uranium fuel recycling technology (e.g. PUREX), recycling technology for thorium (e.g. THOREX) is only under development.
Although the presence of complicates matters, there are public documents showing that has been used once in a nuclear weapon test. The United States tested a composite -plutonium bomb core in the MET (Military Effects Test) blast during Operation Teapot in 1955, though with much lower yield than expected.
Advocates for liquid core and molten salt reactors such as LFTRs claim that these technologies negate thorium's disadvantages present in solid fuelled reactors. As only two liquid-core fluoride salt reactors have been built (the ORNL ARE and MSRE) and neither have used thorium, it is hard to validate the exact benefits. | 0 | Theoretical and Fundamental Chemistry |
In electrochemistry, a thermoneutral voltage is a voltage drop across an electrochemical cell which is sufficient not only to drive the cell reaction, but to also provide the heat necessary to maintain a constant temperature. For a reaction of the form
The thermoneutral voltage is given by
where is the change in enthalpy and F is the Faraday constant. | 0 | Theoretical and Fundamental Chemistry |
The thanatotranscriptome denotes all RNA transcripts produced from the portions of the genome still active or awakened in the internal organs of a body following its death. It is relevant to the study of the biochemistry, microbiology, and biophysics of thanatology, in particular within forensic science. Some genes may continue to be expressed in cells for up to 48 hours after death, producing new mRNA. Certain genes that are generally inhibited since the end of fetal development may be expressed again at this time. | 1 | Applied and Interdisciplinary Chemistry |
*Stefan Lovgren, [https://web.archive.org/web/20050319053238/http://news.nationalgeographic.com/news/2005/03/0318_050318_cryonics.html "Corpses Frozen for Future Rebirth by Arizona Company"], March 2005, National Geographic | 1 | Applied and Interdisciplinary Chemistry |
With the advent of practical steam power, ceiling fans could finally be used for ventilation. Reid installed four steam-powered fans in the ceiling of St Georges Hospital in Liverpool, so that the pressure produced by the fans would force the incoming air upward and through vents in the ceiling. Reids pioneering work provides the basis for ventilation systems to this day. He was remembered as "Dr. Reid the ventilator" in the twenty-first century in discussions of energy efficiency, by Lord Wade of Chorlton. | 1 | Applied and Interdisciplinary Chemistry |
Graham Charles Wood FRS (6 February 1934—4 November 2016) was an English corrosion scientist.
Born in Farnborough, he went on to study metallurgy at Cambridge. Following postdoctoral work at Cambridge, he moved to Manchester, where his career in corrosion science would be based, starting at the Manchester College of Science and Technology (now the University of Manchester) where he joined the Department of Chemical Engineering as a lecturer in corrosion science. In 1972 he established and led the Corrosion and Protection Centre at UMIST (University of Manchester Institute of Science and Technology) as professor of corrosion science. In 1973 he helped to establish a consulting organisation, Corrosion and Protection Centre Industrial Service (CAPCIS – now part of Intertek).
Graham served terms as President of the Corrosion and Protection Association and the Institution of Corrosion Science and Technology ([https://www.icorr.org/ Institute of Corrosion]), and chaired the National Council for Corrosion Societies. He also served as a UK representative on the International Corrosion Council for 15 years, for which he also served as vice-chair and chair.
At UMIST, he held several administerial roles, including vice-principal for academic development, dean, and pro-vice chancellor.
He was elected Fellow of the Royal Academy of Engineering in 1990, and Fellow of the Royal Society in 1997. | 1 | Applied and Interdisciplinary Chemistry |
Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca, and the binding of Ca is required for the activation of calmodulin. Once bound to Ca, calmodulin acts as part of a calcium signal transduction pathway by modifying its interactions with various target proteins such as kinases or phosphatases. | 1 | Applied and Interdisciplinary Chemistry |
Trimethylsilyl iodide may be prepared by the oxidative cleavage of hexamethyldisilane by iodine or by the cleavage of hexamethyldisiloxane with aluminium triiodide.
: TMS-TMS + I → 2 TMSI (TMS = (CH)Si)
: 3 TMS-O-TMS + 2 AlI → 6 TMSI + AlO | 0 | Theoretical and Fundamental Chemistry |
Acid catalysis is mainly used for organic chemical reactions. Many acids can function as sources for the protons. Acid used for acid catalysis include hydrofluoric acid (in the alkylation process), phosphoric acid, toluenesulfonic acid, polystyrene sulfonate, heteropoly acids, zeolites.
Strong acids catalyze the hydrolysis and transesterification of esters, e.g. for processing fats into biodiesel. In terms of mechanism, the carbonyl oxygen is susceptible to protonation, which enhances the electrophilicity at the carbonyl carbon. | 0 | Theoretical and Fundamental Chemistry |
Translational regulation of MITF is still an unexplored area with only two peer-reviewed papers (as of 2019) highlighting the importance. During glutamine starvation of melanoma cells ATF4 transcripts increases as well as the translation of the mRNA due to eIF2α phosphorylation. This chain of molecular events leads to two levels of MITF suppression: first, ATF4 protein binds and suppresses MITF transcription and second, eIF2α blocks MITF translation possibly through the inhibition of eIF2B by eIF2α.
MITF can also be directly translationally modified by the RNA helicase DDX3X. The 5 UTR of MITF contains important regulatory elements (IRES) that is recognized, bound and activated by DDX3X. Although, the 5 UTR of MITF only consists of a nucleotide stretch of 123-nt, this region is predicted to fold into energetically favorable RNA secondary structures including multibranched loops and asymmetric bulges that is characteristics of IRES elements. Activation of this cis-regulatory sequences by DDX3X promotes MITF expression in melanoma cells. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic dipole–dipole interaction, also called dipolar coupling, refers to the direct interaction between two magnetic dipoles. Roughly speaking, the magnetic field of a dipole goes as the inverse cube of the distance, and the force of its magnetic field on another dipole goes as the first derivative of the magnetic field. It follows that the dipole-dipole interaction goes as the inverse fourth power of the distance.
Suppose and are two magnetic dipole moments that are far enough apart that they can be treated as point dipoles in calculating their interaction energy. The potential energy of the interaction is then given by:
where is the magnetic constant, is a unit vector parallel to the line joining the centers of the two dipoles, and || is the distance between the centers of and . Last term with -function vanishes everywhere but the origin, and is necessary to ensure that vanishes everywhere. Alternatively, suppose and are gyromagnetic ratios of two particles with spin quanta and . (Each such quantum is some integral multiple of .) Then:
where is a unit vector in the direction of the line joining the two spins, and || is the distance between them.
Finally, the interaction energy can be expressed as the dot product of the moment of either dipole into the field from the other dipole:
where is the field that dipole 2 produces at dipole 1, and is the field that dipole 1 produces at dipole 2. It is not the sum of these terms.
The force arising from the interaction between and is given by:
The Fourier transform of can be calculated from the fact that
and is given by | 0 | Theoretical and Fundamental Chemistry |
Wiggins realised that water can exist in two different states, and that the existence of these states explains the way that living cells work, and has implications for DNA and protein structure. | 0 | Theoretical and Fundamental Chemistry |
After the last solute has been eluted, it is necessary to strip the displacer from the column. Since the displacer was chosen for high affinity, this can pose a challenge. On reverse-phase materials, a wash with a high percentage of organic solvent may suffice. Large pH shifts are also often employed. One effective strategy is to remove the displacer by chemical reaction; for instance if hydrogen ion was used as displacer it can be removed by reaction with hydroxide, or a polyvalent metal ion can be removed by reaction with a chelating agent. For some matrices, reactive groups on the stationary phase can be titrated to temporarily eliminate the binding sites, for instance weak-acid ion exchangers or chelating resins can be converted to the protonated form. For gel-type ion exchangers, selectivity reversal at very high ionic strength can also provide a solution. Sometimes the displacer is specifically designed with a titratable functional group to shift its affinity. After the displacer is washed out, the column is washed as needed to restore it to its initial state for the next run. | 0 | Theoretical and Fundamental Chemistry |
The extent of reaction is a useful quantity in computations with equilibrium reactions. Consider the reaction
:2 A ⇌ B + 3 C
where the initial amounts are , and the equilibrium amount of A is 0.5 mol. We can calculate the extent of reaction in equilibrium from its definition
In the above, we note that the stoichiometric number of a reactant is negative. Now when we know the extent, we can rearrange the equation and calculate the equilibrium amounts of B and C. | 0 | Theoretical and Fundamental Chemistry |
There is an international standard on presenting various characteristic particle sizes, the ISO 9276 (Representation of results of particle size analysis). This set of various average sizes includes median size, geometric mean size, average size. In the selection of specific small-size particles is common the use of ISO 565 and ISO 3310-1 to the choice of mesh size. | 0 | Theoretical and Fundamental Chemistry |
A sensor device embedded on microprocessors used to monitor the temperature of the processor's die is also known as a "thermal diode".
This application of thermal diode is based on the property of electrical diodes to change voltage across it linearly according to temperature. As the temperature increases, diodes forward voltage decreases. Microprocessors having high clock rate encounter high thermal loads. To monitor the temperature limits thermal diodes are used. They are usually placed in that part of the processor core where highest temperature is encountered. Voltage developed across it varies with the temperature of the diode. All modern AMD and Intel CPUs, as well as AMD and Nvidia GPUs have on-chip thermal diodes. As the sensor is located directly on the processor die, it provides most local and relevant CPU and GPU temperature readings. The silicon diodes have temperature dependency of -2mV per degree Celsius. Thus the junction temperature can be determined by passing a set current through the diode and then measuring voltage developed across it. In addition to processors, the same technology is widely used in dedicated temperature sensor ICs. | 0 | Theoretical and Fundamental Chemistry |
is a trigonal pyramidal molecule with C molecular symmetry. The length of the P−H bond is 1.42 Å, the H−P−H bond angles are 93.5°. The dipole moment is 0.58 D, which increases with substitution of methyl groups in the series: , 1.10 D; , 1.23 D; , 1.19 D. In contrast, the dipole moments of amines decrease with substitution, starting with ammonia, which has a dipole moment of 1.47 D. The low dipole moment and almost orthogonal bond angles lead to the conclusion that in the P−H bonds are almost entirely and phosphorus 3s orbital contributes little to the P-H bonding. For this reason, the lone pair on phosphorus is predominantly formed by the 3s orbital of phosphorus. The upfield chemical shift of it P NMR signal accords with the conclusion that the lone pair electrons occupy the 3s orbital (Fluck, 1973). This electronic structure leads to a lack of nucleophilicity in general and lack of basicity in particular (pK = –14), as well as an ability to form only weak hydrogen bonds.
The aqueous solubility of is slight: 0.22 cm of gas dissolves in 1 cm of water. Phosphine dissolves more readily in non-polar solvents than in water because of the non-polar P−H bonds. It is technically amphoteric in water, but acid and base activity is poor. Proton exchange proceeds via a phosphonium () ion in acidic solutions and via phosphanide () at high pH, with equilibrium constants K = and K = . Phosphine reacts with water only at high pressure and temperature, producing phosphoric acid and hydrogen:
Burning phosphine in the air produces phosphoric acid): | 0 | Theoretical and Fundamental Chemistry |
He was appointed a lecturer at the TU in 1955 and, in 1957, professor and then, in 1959, C4 professor. In 1964 he took the Chair of Inorganic Chemistry at the TU.
In 1964, he was elected a member of the Mathematics/Natural Science section of the Bavarian Academy of Sciences. In 1969 he was appointed a member of the German Academy of Natural Scientists, Leopoldina and in 1972 was given an honorary doctorate by the Faculty of Chemistry and Pharmacy of the University of Munich.
He lectured across the world on metal complexes of cyclopentadienyl, indenyl, arenes, olefins, and metal carbonyls. In the 1960s his group discovered a metal alkylidene and alkylidyne complexes, since referred to as Fischer carbenes and Fischer-carbynes. Overall he published about 450 journal articles and he trained many PhD and postdoctoral students, many of whom went on to noteworthy careers. Among his many foreign lectureships, he was Firestone Lecturer at the University of Wisconsin–Madison (1969), visiting professor at the University of Florida (1971), and Arthur D. Little visiting professor at the Massachusetts Institute of Technology (1973).
He has received many awards including, in 1973 with Geoffrey Wilkinson, the Nobel Prize in Chemistry for his work on organometallic compounds. | 0 | Theoretical and Fundamental Chemistry |
In plumbing, a trap is a U-shaped portion of pipe designed to trap liquid or gas to prevent unwanted flow; most notably sewer gases from entering buildings while allowing waste materials to pass through. In oil refineries, traps are used to prevent hydrocarbons and other dangerous gases and chemical fumes from escaping through drains. In heating systems, the same feature is used to prevent thermo-siphoning which would allow heat to escape to locations where it is not wanted. Similarly, some pressure gauges are connected to systems using U bends to maintain a local gas while the system uses liquid. For decorative effect, they can be disguised as complete loops of pipe, creating more than one U for added efficacy. | 1 | Applied and Interdisciplinary Chemistry |
Filtration is a unit operation that is commonly used both in laboratory and production conditions. This apparatus, adapted for laboratory work, is often used to isolate the product of synthesis of a reaction when the product is a solid in suspension. The product of synthesis is then recovered faster, and the solid is drier than in the case of a simple filtration. Other than isolating a solid, filtration is also a stage of purification: the soluble impurities in the solvent are eliminated in the filtrate (liquid).
This apparatus is often used to purify a liquid. When a synthesised product is filtered, the insolubles (catalysers, impurities, sub-products of the reaction, salts, ...) remain in the filter. In this case, vacuum filtration is also more efficient that a simple filtration: there is more liquid recovered, and the yield is therefore better. | 0 | Theoretical and Fundamental Chemistry |
LD is very similar to Circular Dichroism (CD), but with two important differences. (i) CD spectroscopy uses circularly polarized light whereas LD uses linearly polarized light. (ii) In CD experiments molecules are usually free in solution so they are randomly oriented. The observed spectrum is then a function only of the chiral or asymmetric nature of the molecules in the solution. With biomacromolecules CD is particularly useful for determining the secondary structure. By way of contrast, in LD experiments the molecules need to have a preferential orientation otherwise the LD=0. With biomacromolecules flow orientation is often used, other methods include stretched films, magnetic fields, and squeezed gels. Thus LD gives information such as alignment on a surface or the binding of a small molecule to a flow-oriented macromolecule, endowing it with different functionality from other spectroscopic techniques. The differences between LD and CD are complementary and can be a potent means for elucidating the structure of biological molecules when used in conjunction with one another, the combination of techniques revealing far more information than a single technique in isolation. For example, CD tells us when a membrane peptide or protein folds whereas LD tells when it inserts into a membrane. | 0 | Theoretical and Fundamental Chemistry |
Efficiency, temperature resistance and cost are the three major factors for choosing a TPV emitter. Efficiency is determined by energy absorbed relative to incoming radiation. High temperature operation is crucial because efficiency increases with operating temperature. As emitter temperature increases, black-body radiation shifts to shorter wavelengths, allowing for more efficient absorption by photovoltaic cells. | 0 | Theoretical and Fundamental Chemistry |
The resolution of the questions concerning the motion of fluids was effected by means of Leonhard Eulers partial differential coefficients. This calculus was first applied to the motion of water by dAlembert, and enabled both him and Euler to represent the theory of fluids in formulae restricted by no particular hypothesis. | 1 | Applied and Interdisciplinary Chemistry |
Single crystal growth starts with a seed crystal that is used to template growth of a larger crystal. The overall process is lengthy, and machining is necessary after the single crystal is grown. | 1 | Applied and Interdisciplinary Chemistry |
Pseudokinases are catalytically-deficient pseudoenzyme variants of protein kinases that are represented in all kinomes across the kingdoms of life. Pseudokinases have both physiological (signal transduction) and pathophysiological functions. | 1 | Applied and Interdisciplinary Chemistry |
The thermocouples/unicouples attached to the outer shell consist of a SiGe alloy n-leg doped with boron and a SiGe p-leg doped with phosphorus to provide thermoelectric polarity to the couple. The electrical and thermal currents of the system are separated by bonding the SiGe alloy thermocouple to a multifoil cold stack assembly of molybdenum, tungsten, stainless steel, copper, and alumina components. Several layers of [https://web.archive.org/web/20150219015544/http://jpsglass.com/aerospace.html Astroquartz] silica fiber yarn electrically insulate the legs of the SiGe thermocouples. In between the inner insulation system and the outer shell, copper connectors form the electrical circuit, which uses a two-string, series-parallel wiring design to connect the unicouples. The circuit loop arrangement minimizes the net magnetic field of the generator. | 0 | Theoretical and Fundamental Chemistry |
The hydrosphere is 33% oxygen by volume present mainly as a component of water molecules, with dissolved molecules including free oxygen and carbolic acids (HCO). | 0 | Theoretical and Fundamental Chemistry |
A cause is defined as an unconditional and invariable antecedent of an effect and an effect as an unconditional and invariable consequent of a cause. The same cause produces the same effect; and the same effect is produced by the same cause. The cause is not present in any hidden form whatsoever in its effect.
The following conditions should be met:
# The cause must be antecedent [Purvavrtti]
# Invariability [Niyatapurvavrtti]
# Unconditionality [Ananyathasiddha]
Nyaya recognizes five kinds of accidental antecedents [Anyathasiddha]
# Mere accidental antecedent. E.g., The colour of the potter's cloth.
# Remote cause is not a cause because it is not unconditional. E.g., The father of the potter.
# The co-effects of a cause are not causally related.
# Eternal substances, or eternal conditions are not unconditional antecedents, e.g. space.
# Unnecessary things, e.g. the donkey of the potter.
Nyaya recognizes three kinds of cause:
# Samavayi, material cause, e.g. thread of a cloth.
# Asamavayi, colour of the thread which gives the colour of the cloth.
# Nimitta, efficient cause, e.g. the weaver of the cloth. | 1 | Applied and Interdisciplinary Chemistry |
Any free system with a constant gyromagnetic ratio, such as a rigid system of charges, a nucleus, or an electron, when placed in an external magnetic field (measured in teslas) that is not aligned with its magnetic moment, will precess at a frequency (measured in hertz), that is proportional to the external field:
For this reason, values of , in units of hertz per tesla (Hz/T), are often quoted instead of . | 0 | Theoretical and Fundamental Chemistry |
The word gas was first used by the early 17th-century Flemish chemist Jan Baptist van Helmont. He identified carbon dioxide, the first known gas other than air. Van Helmonts word appears to have been simply a phonetic transcription of the Ancient Greek word – the g in Dutch being pronounced like ch in "loch" (voiceless velar fricative, ) – in which case Van Helmont simply was following the established alchemical usage first attested in the works of Paracelsus. According to Paracelsuss terminology, chaos meant something like .
An alternative story is that Van Helmonts term was derived from "gahst (or geist), which signifies a ghost or spirit". That story is given no credence by the editors of the Oxford English Dictionary'. In contrast, the French-American historian Jacques Barzun speculated that Van Helmont had borrowed the word from the German , meaning the froth resulting from fermentation. | 0 | Theoretical and Fundamental Chemistry |
The crystallographic restriction theorem in its basic form was based on the observation that the rotational symmetries of a crystal are usually limited to 2-fold, 3-fold, 4-fold, and 6-fold. However, quasicrystals can occur with other diffraction pattern symmetries, such as 5-fold; these were not discovered until 1982 by Dan Shechtman.
Crystals are modeled as discrete lattices, generated by a list of independent finite translations . Because discreteness requires that the spacings between lattice points have a lower bound, the group of rotational symmetries of the lattice at any point must be a finite group (alternatively, the point is the only system allowing for infinite rotational symmetry). The strength of the theorem is that not all finite groups are compatible with a discrete lattice; in any dimension, we will have only a finite number of compatible groups. | 0 | Theoretical and Fundamental Chemistry |
Oregon, a ship in the Oregon Files series of books by author Clive Cussler, has a magnetohydrodynamic drive. This allows the ship to turn very sharply and brake instantly, instead of gliding for a few miles. In Valhalla Rising, Clive Cussler writes the same drive into the powering of Captain Nemos Nautilus.'
The film adaptation of The Hunt for Red October popularized the magnetohydrodynamic drive as a "caterpillar drive" for submarines, a nearly undetectable "silent drive" intended to achieve stealth in submarine warfare. In reality, the current traveling through the water would create gases and noise, and the magnetic fields would induce a detectable magnetic signature. In the film, it was suggested that this sound could be confused with geological activity. In the novel from which the film was adapted, the caterpillar that Red October used was actually a pump-jet of the so-called "tunnel drive" type (the tunnels provided acoustic camouflage for the cavitation from the propellers).
In the Ben Bova novel The Precipice, the ship where some of the action took place, Starpower 1, built to prove that exploration and mining of the Asteroid Belt was feasible and potentially profitable, had a magnetohydrodynamic drive mated to a fusion power plant. | 1 | Applied and Interdisciplinary Chemistry |
One might believe that sodium or potassium hydride would be the ideal base for deprotonating these precursor salts. The hydride should react irreversibly with the loss of hydrogen to give the desired carbene, with the inorganic by-products and excess hydride being removed by filtration. In practice this reaction is often too slow, requiring the addition of DMSO or t-BuOH. These reagents generate soluble catalysts, which increase the rate of reaction of this heterogeneous system, via the generation of tert-butoxide or dimsyl anion. However, these catalysts have proved ineffective for the preparation of non-imidazolium adducts as they tend to act as nucleophiles towards the precursor salts and in so doing are destroyed. The presence of hydroxide ions as an impurity in the metal hydride could also destroy non-aromatic salts.
Deprotonation with sodium or potassium hydride in a mixture of liquid ammonia/THF at −40 °C has been reported for imidazole-based carbenes. Arduengo and coworkers managed to prepare a dihydroimidazol-2-ylidene using NaH. However, this method has not been applied to the preparation of diaminocarbenes. In some cases, potassium tert-butoxide can be employed without the addition of a metal hydride. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, the Rayleigh–Plesset equation or Besant–Rayleigh–Plesset equation is a nonlinear ordinary differential equation which governs the dynamics of a spherical bubble in an infinite body of incompressible fluid. Its general form is usually written aswhere
: is the density of the surrounding liquid, assumed to be constant
: is the radius of the bubble
: is the kinematic viscosity of the surrounding liquid, assumed to be constant
: is the surface tension of the bubble-liquid interface
:, in which, is the pressure within the bubble, assumed to be uniform and is the external pressure infinitely far from the bubble
Provided that is known and is given, the Rayleigh–Plesset equation can be used to solve for the time-varying bubble radius .
The Rayleigh–Plesset equation is derived from the Navier–Stokes equations under the assumption of spherical symmetry. | 1 | Applied and Interdisciplinary Chemistry |
Similar to other d transition metals, Nb(III) produce adducts with alkynes. These derivatives are sometimes called Nb(V) alkenediyls metallacyclopropenes.
These alkendiyl complexes function as latent dianion equivalents. They react with electrophiles to give alkene derivatives. | 0 | Theoretical and Fundamental Chemistry |
Söllner married Herta (Helen) Rosenberg on July 23, 1934. Their daughter Barbara Sollner-Webb embarked on a scientific career. | 0 | Theoretical and Fundamental Chemistry |
For a general time-dependent wavefunction satisfying the time-dependent Schrödinger equation, the Hellmann–Feynman theorem is not valid.
However, the following identity holds:
For | 0 | Theoretical and Fundamental Chemistry |
Chemical laws are those laws of nature relevant to chemistry. The most fundamental concept in chemistry is the law of conservation of mass, which states that there is no detectable change in the quantity of matter during an ordinary chemical reaction. Modern physics shows that it is actually energy that is conserved, and that energy and mass are related; a concept which becomes important in nuclear chemistry. Conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics.
The laws of stoichiometry, that is, the gravimetric proportions by which chemical elements participate in chemical reactions, elaborate on the law of conservation of mass. Joseph Proust's law of definite composition says that pure chemicals are composed of elements in a definite formulation.
Dalton's law of multiple proportions says that these chemicals will present themselves in proportions that are small whole numbers (i.e. 1:2 O:H in water); although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. Such compounds are known as non-stoichiometric compounds.
The third stoichiometric law is the law of reciprocal proportions, which provides the basis for establishing equivalent weights for each chemical element. Elemental equivalent weights can then be used to derive atomic weights for each element.
More modern laws of chemistry define the relationship between energy and transformations.
* In equilibrium, molecules exist in mixture defined by the transformations possible on the timescale of the equilibrium, and are in a ratio defined by the intrinsic energy of the molecules—the lower the intrinsic energy, the more abundant the molecule.
* Transforming one structure to another requires the input of energy to cross an energy barrier; this can come from the intrinsic energy of the molecules themselves, or from an external source which will generally accelerate transformations. The higher the energy barrier, the slower the transformation occurs.
* There is a transition state (TS), that corresponds to the structure at the top of the energy barrier. The Hammond-Leffler Postulate states that this state looks most similar to the product or starting material which has intrinsic energy closest to that of the energy barrier. Stabilizing this transition state through chemical interaction is one way to achieve catalysis.
* All chemical processes are reversible (law of microscopic reversibility) although some processes have such an energy bias, they are essentially irreversible. | 1 | Applied and Interdisciplinary Chemistry |
The proopiomelanocortin gene (POMC) is expressed in the hypothalamus, in the pituitary gland. It yields a range of biologically active peptides and hormones and undergoes tissue-specific posttranslational processing to yield a range of biologically active peptides producing adrenocorticotropic hormone (ACTH), b-endorphin, and a-, b- and c-melanocyte-stimulating hormone (MSH). These peptides then interact with different melanocortin receptors (MCRs) and are involved in a wide range of processes including the regulation of body weight (MC3R and MC4R), adrenal steroidogenesis (MC2R) and hair pigmentation (MC1R). Published in the British Associations of Dermatologists in 2012, Lack of red hair phenotype in a North-African obese child homozygous for a novel POMC null mutation showed nonsense-mediated decay RNA evaluation in a hair pigment chemical analysis. They found that inactivating the POMC gene mutation results in obesity, adrenal insufficiency, and red hair. This has been seen in both in humans and mice. In this experiment they described a 3-year-old boy from Rome, Italy. He was a source of focus because he had Addison's disease and early onset obesity. They collected his DNA and amplified it using PCR. Sequencing analysis revealed a homozygous single substitution determining a stop codon. This caused an aberrant protein and the corresponding amino acid sequence indicated the exact position of the homozygous nucleotide. The substitution was localized in exon 3 and nonsense mutation at codon 68. The results from this experiment strongly suggest that the absence of red hair in non-European patients with early onset obesity and hormone deficiency does not exclude the occurrence of POMC mutations. By sequencing the patients DNA they found that this novel mutation has a collection of symptoms because of a malfunctioning nonsense-mediated mRNA decay surveillance pathway. | 1 | Applied and Interdisciplinary Chemistry |
Radical disproportionation encompasses a group of reactions in organic chemistry in which two radicals react to form two different non-radical products. Radicals in chemistry are defined as reactive atoms or molecules that contain an unpaired electron or electrons in an open shell. The unpaired electrons can cause radicals to be unstable and reactive. Reactions in radical chemistry can generate both radical and non-radical products. Radical disproportionation reactions can occur with many radicals in solution and in the gas phase. Due to the reactive nature of radical molecules, disproportionation proceeds rapidly and requires little to no activation energy. The most thoroughly studied radical disproportionation reactions have been conducted with alkyl radicals, but there are many organic molecules that can exhibit more complex, multi-step disproportionation reactions. | 0 | Theoretical and Fundamental Chemistry |
To start with, the raw material must be obtained. Copper can be found in over 160 different minerals, but mining activities are entailed to obtain them in large quantities if a reasonable amount of copper is wanted. Some of the most commonly exploited minerals are cuprite, malachite, azurite, chalcopyrite, chrysocolla and tennantite; e.g. malachite was extracted in Rudna Glava (Serbia), Cabrierés (France) or Chinflón (Riotinto, Spain). In fact, one of the possible explanations about what Ötzi the Iceman, the ancient mummy found in the Alps who lived around 3300 years BCE, was doing at of altitude is that he could have been prospecting for new ores of minerals.
Secondly, the mineral is separated from the gangue. This is only possible by smelting or beneficiation. To do so, it is necessary to use a furnace that is able to reach at least .
Lastly, a wide range of specific tools and resources have to be available, such as furnaces, moulds, crucibles, mauls, etc.
*Stage A: Although native copper nowadays is frequently displayed in museum showcases of mineral collections, it once occurred copiously during prehistoric times. In Cyprus or Crete, collecting the mineral was once as easy as simply picking it up from the ground. In fact, native copper is no longer as easy to find in that state these days. The treatment of this native mineral was also uncomplicated through cold-hammering. This only permitted the production of a limited range of artifacts like awls, pins, or beads. In larger objects, the metal cracks when it is cold-hammered.
*Stage B: Annealing the metal on an open fire ( is hot enough) reduces its hardness considerably and gives in malleability. This permits the manufacture of slightly more sophisticated objects, like bracelets, but is still a rather limited technique.
*Stage C: In the first two steps, the material used was native copper that does not actually need specialized technology. Probably, due to the situation that native copper was increasingly difficult to find, copper ore is used in this third step. This is a very significant development. In fact, this is truly the beginning of the metallurgy, as the mineral has to be smelted to separate the copper from the gangue, requiring technology. | 1 | Applied and Interdisciplinary Chemistry |
Uniporters play an essential role in carrying out various cellular functions. Each uniporter is specialized to facilitate the transport of a specific molecule or ion across the cell membrane. Examples of a few of the physiological roles uniporters aid in include:
# Nutrient Uptake: Uniporters facilitate the transport of essential nutrients into the cell. Glucose transporters (GLUTs) are uniporters that uptake glucose for energy production.
# Ion homeostasis: Uniporters facilitate in maintaining the balance of ions (i.e., Na+, K+, Ca2+, Cl-) within cells
# Metabolism: Uniporters are involved in the transport of essential ions, amino acids and molecules required for the metabolic pathway, protein synthesis and energy production
# Cell signaling: Calcium uniporters help regulate intercellular calcium levels essential for signal transduction
# Waste removal: Uniporters aid in removing metabolic waste products and toxins from cells
# pH regulation: Transport of ions by uniporters also helps to maintain the overall acid-base balance within cells | 1 | Applied and Interdisciplinary Chemistry |
NETA metabolizes into ethinylestradiol at a rate of 0.20 to 0.33% across a dose range of 10 to 40 mg. Peak levels of ethinylestradiol with a 10, 20, or 40 mg dose of NETA were 58, 178, and 231 pg/mL, respectively. For comparison, a 30 to 40 μg dose of oral ethinylestradiol typically results in a peak ethinylestradiol level of 100 to 135 pg/mL. As such, in terms of ethinylestradiol exposure, 10 to 20 mg NETA may be equivalent to 20 to 30 μg ethinylestradiol and 40 mg NETA may be similar to 50 μg ethinylestradiol. In another study however, 5 mg NETA produced an equivalent of 28 μg ethinylestradiol (0.7% conversion rate) and 10 mg NETA produced an equivalent of 62 μg ethinylestradiol (1.0% conversion rate). Due to its estrogenic activity via ethinylestradiol, high doses of NETA have been proposed for add-back in the treatment of endometriosis without estrogen supplementation. Generation of ethinylestradiol with high doses of NETA may increase the risk of venous thromboembolism but may also decrease menstrual bleeding relative to progestogen exposure alone. | 1 | Applied and Interdisciplinary Chemistry |
Expression systems using either S. cerevisiae or Pichia pastoris allow stable and lasting production of proteins that are processed similarly to mammalian cells, at high yield, in chemically defined media of proteins. | 1 | Applied and Interdisciplinary Chemistry |
The following publications provide specifications and guidelines for participants in the Certified Ratings Program.
*AMCA Publication 11 - Certified Ratings Program Operating Manual contains requirements common to all AMCA International's Certified Ratings Programs. Specific requirements that only pertain to a category of product will be found in a Product Rating Manual for that category. Publication 11 is effective on the same date as a Product Rating Manual that references it.
*AMCA Publication 111 - Laboratory Accreditation Program outlines procedure for obtaining AMCA International recognition of a laboratory as qualified to perform tests in accordance with AMCA International test methods. Registration qualifications may be applied to individual test results. The latest revision adds AMCA 260-07, Laboratory Methods of Testing Induced Flow Fans for Rating, to the list of standard test methods in which a laboratory can be accredited to perform.
*AMCA Publication 211 - Certified Ratings Program - Product Rating Manual for Fan Air Performance describes in detail the certification and check test procedures used in implementing the program under which the AMCA International Certified Ratings Seal for air performance is granted.
*AMCA Publication 212 - Certified Ratings Program - Product Rating Manual for Smoke Management Fan Performance describes in detail the certification and check test procedures used in implementing the program under which the AMCA International Certified Ratings Seal for Smoke Management Fans is granted.
*AMCA Publication 311 - Certified Ratings Program - Product Rating Manual for Fan Sound Performance explains in detail the certification procedures for both ducted and non-ducted fans under which the use of the AMCA International Certified Ratings Program Seal for sound performance is granted.
*AMCA Publication 511 - Certified Ratings Program - Product Rating Manual for Air Control Devices describes the certification procedures under which the AMCA International Certified Ratings Seal is granted for sound, air performance, air leakage, water penetration and wind driven rain for air control products.
*AMCA Publication 611 - Certified Ratings Program - Product Rating Manual for Airflow Measurement Devices describes in detail the certification procedure for airflow measurement stations under which the use of the AMCA International Certified Ratings Seal for Airflow Measurement Performance is granted.
*AMCA Publication 1011 - Certified Ratings Program - Product Rating Manual for Acoustical Duct Silencers provides a detailed description of the procedure under which the AMCA International Certified Ratings Seal is granted for acoustical duct silencers. | 1 | Applied and Interdisciplinary Chemistry |
The choice of culture medium might affect the physiological relevance of findings from cell culture experiments due to the differences in the nutrient composition and concentrations. A systematic bias in generated datasets was recently shown for CRISPR and RNAi gene silencing screens (especially for metabolic genes), and for metabolic profiling of cancer cell lines. For example, a stronger dependence on ASNS (asparagine synthetase) was found in cell lines cultured in DMEM, which lacks asparagine, compared to cell lines cultured in RPMI or F12 (containing asparagine). Avoiding such bias might be achieved by using a uniform media for all screened cell lines, and ideally, using a growth medium that better represents the physiological levels of nutrients. Recently, such media types, as Plasmax and Human Plasma Like Medium (HPLM), were developed. | 1 | Applied and Interdisciplinary Chemistry |
Hypertension is reported to complicate one out of ten pregnancies, which makes it the most common medical disorder in pregnancy. It is important to have a correct diagnosis of hypertension during pregnancy, with the emphasis on differentiating pre-existing hypertension from pregnancy induced hypertension (gestational and the syndrome of pre-eclampsia). During pregnancy, the challenge is to determine when to use antihypertensive medications and which level of blood pressure to target. A balance has to be found between the potential risk to the health of the baby related to drug-exposure and the risk to the mother and baby due to an untreated medical condition (severe hypertension).
Antihypertensive drug use during pregnancy is relatively common and increasing. Only a small proportion of available antihypertensive drugs have been tested in pregnant women, and many are contraindicated. It is important to make the exposure of medications to the baby as small as possible. It is not clear if treating women who have mild or moderate hypertension during pregnancy with anti-hypertensive medication is beneficial.
The most common first trimester antihypertensive are β-blockers. The consequences of treatment with β-blocker during pregnancy are disputable. Some studies report a connection between β-blocker treatment and small for-gestational-age (SGA) of newborns and pre-term birth, while others do not. Based on meta-analyses, first trimester oral β-blocker use showed no increase in odds of major congenital anomalies. However, analyses examining organ-specific malformations observed increased odds of cardiovascular defects, cleft lip and neural tube defects. The U.S. Food and Drug Administration (FDA) categorises β-blockers into different pregnancy categories depending on the safety of the drugs and they range from category B to D, that is, no β-blockers is completely safe for using during pregnancy | 1 | Applied and Interdisciplinary Chemistry |
Charlestown (also known as Charlestown-on-Forth) is a village in Fife, Scotland. It lies on the north shore of the Firth of Forth, around west of Limekilns and south-west of Dunfermline. The village is known for its historic 18th century lime kilns and its Georgian planned housing. | 1 | Applied and Interdisciplinary Chemistry |
Consider two-dimensional plane flow with two infinitesimally close points and lying in the same horizontal plane. From calculus, the corresponding infinitesimal difference between the values of the stream function at the two points is
Suppose takes the same value, say , at the two points and . Then this gives
implying that the vector is normal to the surface . Because everywhere (e.g., see In terms of vector rotation), each streamline corresponds to the intersection of a particular stream surface and a particular horizontal plane. Consequently, in three dimensions, unambiguous identification of any particular streamline requires that one specify corresponding values of both the stream function and the elevation ( coordinate).
The development here assumes the space domain is three-dimensional. The concept of stream function can also be developed in the context of a two-dimensional space domain. In that case level sets of the stream function are curves rather than surfaces, and streamlines are level curves of the stream function. Consequently, in two dimensions, unambiguous identification of any particular streamline requires that one specify the corresponding value of the stream function only. | 1 | Applied and Interdisciplinary Chemistry |
Inertial cavitation was first observed in the late 19th century, considering the collapse of a spherical void within a liquid. When a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is coined cavitation inception and may occur behind the blade of a rapidly rotating propeller or on any surface vibrating in the liquid with sufficient amplitude and acceleration. A fast-flowing river can cause cavitation on rock surfaces, particularly when there is a drop-off, such as on a waterfall.
Vapor gases evaporate into the cavity from the surrounding medium; thus, the cavity is not a vacuum at all, but rather a low-pressure vapor (gas) bubble. Once the conditions which caused the bubble to form are no longer present, such as when the bubble moves downstream, the surrounding liquid begins to implode due its higher pressure, building up momentum as it moves inward. As the bubble finally collapses, the inward momentum of the surrounding liquid causes a sharp increase of pressure and temperature of the vapor within. The bubble eventually collapses to a minute fraction of its original size, at which point the gas within dissipates into the surrounding liquid via a rather violent mechanism which releases a significant amount of energy in the form of an acoustic shock wave and as visible light. At the point of total collapse, the temperature of the vapor within the bubble may be several thousand Kelvin, and the pressure several hundred atmospheres.
The physical process of cavitation inception is similar to boiling. The major difference between the two is the thermodynamic paths that precede the formation of the vapor. Boiling occurs when the local temperature of the liquid reaches the saturation temperature, and further heat is supplied to allow the liquid to sufficiently phase change into a gas. Cavitation inception occurs when the local pressure falls sufficiently far below the saturated vapor pressure, a value given by the tensile strength of the liquid at a certain temperature.
In order for cavitation inception to occur, the cavitation "bubbles" generally need a surface on which they can nucleate. This surface can be provided by the sides of a container, by impurities in the liquid, or by small undissolved microbubbles within the liquid. It is generally accepted that hydrophobic surfaces stabilize small bubbles. These pre-existing bubbles start to grow unbounded when they are exposed to a pressure below the threshold pressure, termed Blake's threshold. The presence of an incompressible core inside a cavitation nucleus substantially lowers the cavitation threshold below the Blake threshold.
The vapor pressure here differs from the meteorological definition of vapor pressure, which describes the partial pressure of water in the atmosphere at some value less than 100% saturation. Vapor pressure as relating to cavitation refers to the vapor pressure in equilibrium conditions and can therefore be more accurately defined as the equilibrium (or saturated) vapor pressure.
Non-inertial cavitation is the process in which small bubbles in a liquid are forced to oscillate in the presence of an acoustic field, when the intensity of the acoustic field is insufficient to cause total bubble collapse. This form of cavitation causes significantly less erosion than inertial cavitation, and is often used for the cleaning of delicate materials, such as silicon wafers.
Other ways of generating cavitation voids involve the local deposition of energy, such as an intense focused laser pulse (optic cavitation) or with an electrical discharge through a spark. These techniques have been used to study the evolution of the bubble that is actually created by locally boiling the liquid with a local increment of temperature. | 1 | Applied and Interdisciplinary Chemistry |
Bulk gold exhibits a face-centered cubic (fcc) structure. As gold particle size decreases the fcc structure of gold transforms into a centered-icosahedral structure illustrated by . It can be shown that the fcc structure can be extended by a half unit cell in order to make it look like a cuboctahedral structure. The cuboctahedral structure maintains the cubic-closed pack and symmetry of fcc. This can be thought of as redefining the unit cell into a more complicated cell. Each edge of the cuboctahedron represents a peripheral Au–Au bond. The cuboctahedron has 24 edges while the icosahedron has 30 edges; the transition from cuboctahedron to icosahedron is favored since the increase in bonds contributes to the overall stability of the icosahedron structure.
The centered icosahedral cluster is the basis of constructing large gold nanoclusters. is the endpoint of atom-by-atom growth. In other words, starting with one gold atom up to , each successful cluster is created by adding one additional atom. The icosahedral motif is found in many gold clusters through vertex sharing ( and ), face-fusion ( and ), and interpenetrating biicosahedrons (, , , and ). Large gold nanoclusters can essentially be reduced to a series of icosahedrons connecting, overlapping, and/or surrounding each other. The crystallization process of gold nanoclusters involves the formation of surface segments that grow towards the center of the cluster. The cluster assumes an icosahedral structure because of the associated surface energy reduction. | 0 | Theoretical and Fundamental Chemistry |
The method developed by Bjerrum is still the main method in use today, though the precision of the measurements has greatly increased. Most commonly, a solution containing the metal ion and the ligand in a medium of high ionic strength is first acidified to the point where the ligand is fully protonated. This solution is then titrated, often by means of a computer-controlled auto-titrator, with a solution of CO-free base. The concentration, or activity, of the hydrogen ion is monitored by means of a glass electrode. The data set used for the calculation has three components: a statement defining the nature of the chemical species that will be present, called the model of the system, details concerning the concentrations of the reagents used in the titration, and finally the experimental measurements in the form of titre and pH (or emf) pairs.
Other ion-selective electrodes (ISE) may be used. For example, a fluoride electrode may be used with the determination of stability complexes of fluoro-complexes of a metal ion.
It is not always possible to use an ISE. If that is the case, the titration can be monitored by other types of measurement. Ultraviolet–visible spectroscopy, fluorescence spectroscopy and NMR spectroscopy are the most commonly used alternatives. Current practice is to take absorbance or fluorescence measurements at a range of wavelengths and to fit these data simultaneously. Various NMR chemical shifts can also be fitted together.
The chemical model will include values of the protonation constants of the ligand, which will have been determined in separate experiments, a value for log K and estimates of the unknown stability constants of the complexes formed. These estimates are necessary because the calculation uses a non-linear least-squares algorithm. The estimates are usually obtained by reference to a chemically similar system. The stability constant databases can be very useful in finding published stability constant values for related complexes.
In some simple cases the calculations can be done in a spreadsheet. Otherwise, the calculations are performed with the aid of a general-purpose computer programs. The most frequently used programs are:
* Potentiometric and/or spectrophotometric data: PSEQUAD
*Potentiometric data: [http://www.hyperquad.co.uk/HQ2013.htm HYPERQUAD], BEST, [http://jplusconsulting.com/products/reactlab-equilibria/ ReactLab pH PRO]
* Spectrophotometric data: [http://www.hyperquad.co.uk/HypSpec.htm HypSpec], SQUAD, SPECFIT, [http://jplusconsulting.com/products/reactlab-equilibria/ ReactLab EQUILIBRIA].
* NMR data [http://www.hyperquad.co.uk/hypnmr.htm HypNMR], [http://www.nuigalway.ie/chem/Mike/wineqnmr.htm WINEQNMR2]
In biochemistry, formation constants of adducts may be obtained from Isothermal titration calorimetry (ITC) measurements. This technique yields both the stability constant and the standard enthalpy change for the equilibrium. It is mostly limited, by availability of software, to complexes of 1:1 stoichiometry. | 0 | Theoretical and Fundamental Chemistry |
Retroviruses are established pathogens of veterinary importance. They are generally a cause of cancer or immune deficiency. | 1 | Applied and Interdisciplinary Chemistry |
When fasting, the activation of lipolysis provides fatty acids as the preferred fuel source for respiration. In the liver β-oxidation of fatty acids fulfills the local energy needs and may lead to ketogenesis (creating ketone bodies out of fatty acids.) The ketone bodies are then used to meet the demands of tissues other than the liver. This inhibition of glucose oxidation at the level of pyruvate dehydrogenase preserves pyruvate and lactate, both of which are gluconeogenic precursors. | 1 | Applied and Interdisciplinary Chemistry |
Ferrophosphorus is a ferroalloy, an alloy of iron and phosphorus. It contains high proportion of iron phosphides, FeP and FeP. Its CAS number is 8049-19-2. The usual grades contain either 18 or 25% of phosphorus. It is a gray solid material with melting point between 1050-1100 °C. It may liberate phosphine in contact with water. Very fine powder can be combustible.
Ferrophosphorus is used in metallurgy as a source of phosphorus for alloying, for deoxidizing the melt and for removal of unwanted compounds into slag.
Ferrophosphorus is a byproduct of phosphorus production in submerged-arc furnaces from apatites, by their reduction with carbon. It is formed from the iron oxide impurities.
Addition of ferrophosphorus is used to produce powder metallurgy (P/M) steels with favorable magnetic properties, e.g. high saturation induction. Iron phosphide acts here as a solid solution hardener and a sintering aid. Usually about 0.45 w/o of phosphorus is added to iron; higher amount can improve magnetic properties but at above about 0.8 w/o the process parameters have to be too tightly controlled to prevent phosphorus segregation on grain boundaries and resulting excessive brittleness.
Ferrophosphorus can be added to cast iron, where the phosphorus improves fluidity and therefore quality of the castings, can increase wear resistance and cutability. In steels its addition to some alloys can improve corrosion resistance.
Ferrophosphorus can be used as a construction aggregate for production of high-density concrete for radiation shielding, as an alternative to usually used steel punchings and shot. It can be used with both Portland cement and magnesia cement.
Ferrophosphorus, reacted with sulfur or pyrite, is used for production of phosphorus pentasulfide.
Ferrophosphorus can be used for production of lithium iron phosphate, necessary as electrode material for LiFePO4 batteries.
Ferrophosphorus can be used instead of zinc powder in some paints and coatings. It has good adhesion, anticorrosive properties, electrical and thermal conductivity, and wear resistance.
Ferrophosphorus can be used as a reducing agent to produce sodium or potassium from sodium carbonate or potassium carbonate. | 1 | Applied and Interdisciplinary Chemistry |
The emulsion test is a simple method used educational settings to determine the presence of lipids using wet chemistry. The procedure is for the sample to be suspended in ethanol, allowing lipids present to dissolve (lipids are soluble in alcohols). The liquid (alcohol with dissolved fat) is then decanted into water. Since lipids do not dissolve in water while ethanol does, when the ethanol is diluted, it falls out of the solution to give a cloudy white emulsion. This method is not typically used in research or industry.
<br /> | 0 | Theoretical and Fundamental Chemistry |
First developed in 1836 by Danish archaeologist Christian Jürgensen Thomsen as a part of his "Three-age system", the term "Bronze Age" is used by archaeologists to refer to those societies which have developed bronze technology but not yet learned how to work the more complicated process involved in making iron objects. The European Bronze Age lasted from , when the Aegean civilizations of Greece first developed bronze technology, right through to , when the Nordic Bronze Age came to an end with the development of iron among Scandinavian communities.
The period known by archaeologists as Bronze Age Britain lasted from through to , and was defined by the adoption of copper and bronze technologies on the island. Bronze Age Ireland followed a similar, yet distinct course.
The Early Bronze Age in the British Isles was marked by the adoption of what archaeologists call the "Beaker culture", which had arrived from continental Europe. Eogan noted that the "evidence from archaeology is that Beaker-using communities were the earliest metallurgists in Britain and Ireland", with their produce including "copper artefacts such as tanged daggers but also gold objects as well as the use of gold for embellishment." | 1 | Applied and Interdisciplinary Chemistry |
Low-emissivity windows in houses are a more complicated technology, since they must have low emissivity at thermal wavelengths while remaining transparent to visible light. To reduce the heat transfer from a surface, such as a glass window, a clear reflective film with a low emissivity coating can be placed on the interior of the surface. "Low-emittance (low-E) coatings are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow". By adding this coating we are limiting the amount of radiation that leaves the window thus increasing the amount of heat that is retained inside the window. | 0 | Theoretical and Fundamental Chemistry |
The bond length in a heavy Rydberg system is 10,000 times larger than in a typical diatomic molecule. As well as producing the characteristic hydrogen-like behaviour, this also makes them extremely sensitive to perturbation by external electric and magnetic fields.
Heavy Rydberg systems have a relatively large reduced mass, given by:
This leads to a very slow time evolution, which makes them easy to manipulate both spatially and energetically, while their low binding energy makes them relatively simple to detect through field dissociation and detection of the resulting ions, in a process known as threshold ion-pair production spectroscopy.
Kepler's third law states that the period of an orbit is proportional to the cube of the semi-major axis; this can be applied to the Coulomb force:
where is the time-period, is the reduced mass, is the semi-major axis and .
Classically we can say that a system with a large reduced mass has a long orbital period. Quantum mechanically, a large reduced mass in a system leads to narrow spacing of the energy levels and the rate of time-evolution of the wavefunction depends on this energy spacing. This slow time-evolution makes heavy Rydberg systems ideal for experimentally probing the dynamics of quantum systems. | 0 | Theoretical and Fundamental Chemistry |
Liden applied the HBV model to estimate the riverine transport of three different substances, nitrogen, phosphorus and suspended sediment in four different countries: Sweden, Estonia, Bolivia and Zimbabwe. The relation between internal hydrological model variables and nutrient transport was assessed. A model for nitrogen sources was developed and analysed in comparison with a statistical method. A model for suspended sediment transport in tropical and semi-arid regions was developed and tested. It was shown that riverine total nitrogen could be well simulated in the Nordic climate and riverine suspended sediment load could be estimated fairly well in tropical and semi-arid climates. The HBV model for material transport generally estimated material transport loads well. The main conclusion of the study was that the HBV model can be used to predict material transport on the scale of the drainage basin during stationary conditions, but cannot be easily generalised to areas not specifically calibrated. In a different work, Castanedo et al. applied an evolutionary algorithm to automated watershed model calibration.
The United States EPA developed the DSSAM Model to analyze water quality impacts from land use and wastewater management decisions in the Truckee River basin, an area which include the cities of Reno and Sparks, Nevada as well as the Lake Tahoe basin. The model satisfactorily predicted nutrient, sediment and dissolved oxygen parameters in the river. It is based on a pollutant loading metric called "Total Maximum Daily Load" (TMDL). The success of this model contributed to the EPAs commitment to the use of the underlying TMDL protocol in EPAs national policy for management of many river systems in the United States.
The DSSAM Model is constructed to allow dynamic decay of most pollutants; for example, total nitrogen and phosphorus are allowed to be consumed by benthic algae in each time step, and the algal communities are given a separate population dynamic in each river reach (e.g. based upon river temperature). Regarding stormwater runoff in Washoe County, the specific elements within a new xeriscape ordinance were analyzed for efficacy using the model. For the varied agricultural uses in the watershed, the model was run to understand the principal sources of impact, and management practices were developed to reduce in-river pollution. Use of the model has specifically been conducted to analyze survival of two endangered species found in the Truckee River and Pyramid Lake: the Cui-ui sucker fish (endangered 1967) and the Lahontan cutthroat trout (threatened 1970). | 1 | Applied and Interdisciplinary Chemistry |
Epothilone B is a 16-membered polyketide macrolactone with a methylthiazole group connected to the macrocycle by an olefinic bond. The polyketide backbone was synthesized by type I polyketide synthase (PKS) and the thiazole ring was derived from a cysteine incorporated by a nonribosomal peptide synthetase (NRPS). In this biosynthesis, both PKS and NRPS use carrier proteins, which have been post-translationally modified by phosphopantetheine groups, to join the growing chain. PKS uses coenzyme-A thioester to catalyze the reaction and modify the substrates by selectively reducing the β carbonyl to the hydroxyl (Ketoreductase, KR), the alkene (Dehydratase, DH), and the alkane (Enoyl Reductase, ER). PKS-I can also methylate the α carbon of the substrate. NRPS, on the other hand, uses amino acids activated on the enzyme as aminoacyl adenylates. Unlike PKS, epimerization, N-methylation, and heterocycle formation occurs in the NRPS enzyme.
Epothilone B starts with a 2-methyl-4-carboxythiazole starter unit, which was formed through the translational coupling between PKS, EPOS A (epoA) module, and NRPS, EPOS P(epoP) module. The EPOS A contains a modified β-ketoacyl-synthase (malonyl-ACP decarboxylase, KSQ), an acyltransferase (AT), an enoyl reductase (ER), and an acyl carrier protein domain (ACP). The EPOS P however, contains a heterocylization, an adenylation, an oxidase, and a thiolation domain. These domains are important because they are involved in the formation of the five-membered heterocyclic ring of thiazole. As seen in Figure 4, the EPOS P activates the cysteine and binds the activated cysteine as an aminoacyl-S-PCP. Once the cysteine has been bound, EPOS A loads an acetate unit onto the EPOS P complex, thus initiating the formation of the thiazoline ring by intramolecular cyclodehydration.
Once the 2-methylthiazole ring has been made, it is then transferred to the PKS EPOS B (epoB), EPOS C (epoC), EPOS D (epoD), EPOS E (epoE), and EPOS F (epoF) for subsequent elongation and modification to generate the olefinic bond, the 16-membered ring, and the epoxide, as seen in Figure 5. One important thing to note is the synthesis of the gem-dimethyl unit in module 7. These two dimethyls were not synthesized by two successive C-methylations. Instead, one of the methyl groups was derived from the propionate extender unit, while the second methyl group was integrated by a C-methyl-transferase domain. | 0 | Theoretical and Fundamental Chemistry |
The separated DNA bands are often used for further procedures, and a DNA band may be cut out of the gel as a slice, dissolved and purified. Contaminants however may affect some downstream procedures such as PCR, and low melting point agarose may be preferred in some cases as it contains fewer of the sulphates that can affect some enzymatic reactions. The gels may also be used for blotting techniques. | 1 | Applied and Interdisciplinary Chemistry |
In 1906, James accepted a position at the National Refining Company in West Chester, New York. Once in the United States, he was offered an assistant professorship in chemistry by Charles Parsons, at New Hampshire College of Agriculture and the Mechanic Arts in Durham, New Hampshire. Founded in 1866 by chemist Ezekiel Dimond, the school's main focus was chemistry. Parsons was a founder of the national American Chemical Society, and Parsons and James were founding members of a national chemistry fraternity: Alpha Chi Sigma.
In 1911, Parsons moved to the U.S. Bureau of Mines. James became a full professor and succeeded Parsons as head of the chemistry department at New Hampshire College. | 1 | Applied and Interdisciplinary Chemistry |
It is synthesized as a by-product in the autoxidation of cumene, which mainly affords cumene hydroperoxide. Alternatively, it can be produced by the addition of hydrogen peroxide to α-methylstyrene.
Of the ca. 60,000 ton/y production of dialkyl peroxides, dicumyl peroxide is dominant. | 0 | Theoretical and Fundamental Chemistry |
Although globe valves in the past had the spherical bodies which gave them their name, many modern globe valves do not have much of a spherical shape. However, the term globe valve is still often used for valves that have such an internal mechanism. In plumbing, valves with such a mechanism are also often called stop valves since they dont have the spherical housing, but the term stop valve' may refer to valves which are used to stop flow even when they have other mechanisms or designs. | 1 | Applied and Interdisciplinary Chemistry |
In 1960, Haines married painter Adrienne Rappaport, who used the name Adrian Rappin professionally. They had one daughter, Avril Haines, an attorney who is serving as the current Director of National Intelligence in the Biden administration. Rappaport died in 1985 after developing chronic obstructive pulmonary disease and later contracting avian tuberculosis.
In 1986, Haines married his current wife, economist [http://www.mcleveland.org/ Mary "Polly" Cleveland].
In 1964, Haines and Rappaport purchased two small run-down rent-controlled apartment buildings on New York's Upper West Side for $140,000, $10,000 down and for a time employed Al Pacino as the building superintendent.
When Haines and Cleveland sold the buildings for many millions of dollars in 2009, they put half the net proceeds into a foundation for the benefit of scientific and economic education. | 1 | Applied and Interdisciplinary Chemistry |
An evaporation pan is used to hold water during observations for the determination of the quantity of evaporation at a given location. Such pans are of varying sizes and shapes, the most commonly used being circular or square. The best known of the pans are the "Class A" evaporation pan and the "Sunken Colorado Pan". In Europe, India and South Africa, a Symons Pan (or sometimes Symons Tank) is used. Often the evaporation pans are automated with water level sensors and a small weather station is located nearby. | 1 | Applied and Interdisciplinary Chemistry |
When used for detection of genetic and genomic changes, jumping clones require validation by Sanger sequencing. | 1 | Applied and Interdisciplinary Chemistry |
In a review of Behes paper Design vs. Randomness in Evolution: Where Do the Data Point?, Denis Lamoureux criticized Darwins Black Box as having become central to fundamentalist and evangelical anti-evolution critiques against biological evolution. Behe supports the historically incorrect misrepresentation that Darwins views on the origin of life were atheistic, when On the Origin of Species repeatedly refers to a Creator in a positive and supportive context as impressing laws on matter. Though Behe has avoided committing himself to the view that God intervenes directly in nature to create purportedly irreducibly complex structures, Darwins Black Box briefly speculates that divine intervention might have caused the direct creation of a cell from which all of life evolved, supporting creationist views of miraculous acts of creation, but ironically echoing Darwins stated: "view of life, with its several powers, having been originally breathed into a few forms or into one." Behes claim that the creation of an original first cell represents a "gap" in the laws of nature needing divine intervention appears to be the problematic God of the gaps position which is subject to the gaps being filled by scientific discoveries. Behe's thesis that irreducible structures are created in "one fell swoop" is opposed by other biochemists, including many who are devout Christians, and has no support from the fossil record. | 1 | Applied and Interdisciplinary Chemistry |
The speed of sound in a liquid is given by where is the bulk modulus of the liquid and the density. As an example, water has a bulk modulus of about 2.2 GPa and a density of 1000 kg/m, which gives c = 1.5 km/s. | 0 | Theoretical and Fundamental Chemistry |
Following the flood of 4November 1966 when Venice, Chioggia and the other built-up areas in the lagoon were submerged by a tide of , the first Special Law for Venice declared the problem of safeguarding the city to be of "priority national interest". This marked the beginning of a long legislative and technical process to guarantee Venice and the lagoon an effective sea defence system.
To this end, in 1975 the State Ministry of Public Works issued a competitive tender, but the process ended without a project being chosen from those presented as no hypothesis for action satisfied all the mandated requirements. The Ministry subsequently acquired documents presented during the call for tender and passed them to a group of experts commissioned to draw up a project to preserve the hydraulic balance of the lagoon and protect Venice from floods (the "Progettone" of 1981).
A few years later, a further Special Law (Law no. 798/1984) emphasised the need for a unified approach to safeguarding measures, set up a committee for policy, coordination and control of these activities (the "Comitatone", chaired by the President of the Council of Ministers and consisting of representatives of the competent national and local authorities and institutions) and entrusted design and implementation to a single body, the Consorzio Venezia Nuova, recognising its ability to manage the safeguarding activities as a whole.
The Venice Water Authority – Consorzio Venezia Nuova presented a complex system of interventions to safeguard Venice (the REA "Riequilibrio E Ambiente", "Rebalancing and the Environment" Project), which included mobile barriers at the inlets to regulate tides in the lagoon. In this context, between 1988 and 1992, experiments were carried out on a prototype gate (MOdulo Sperimentale Elettromeccanico, hence the name MOSE) and in 1989, a conceptual design for the mobile barriers was drawn up. This was completed in 1992 and subsequently approved by the Higher Council of Public Works then subjected to an Environmental Impact Assessment procedure and further developed as requested by the Comitatone. In 2002 the final design was presented and on 3April 2003, the Comitatone gave the go-ahead for its implementation. The same year, construction sites opened at the three lagoon inlets of Lido, Malamocco and Chioggia. | 1 | Applied and Interdisciplinary Chemistry |
As with DNA electrophoresis, conditions such as buffers, charge/voltage, and concentration should be taken into account when selecting a protein marker. | 1 | Applied and Interdisciplinary Chemistry |
Reduction is the final, high-temperature step in smelting, in which the oxide becomes the elemental metal. A reducing environment (often provided by carbon monoxide, made by incomplete combustion in an air-starved furnace) pulls the final oxygen atoms from the raw metal. The carbon source acts as a chemical reactant to remove oxygen from the ore, yielding the purified metal element as a product. The carbon source is oxidized in two stages. First, carbon (C) combusts with oxygen (O) in the air to produce carbon monoxide (CO). Second, the carbon monoxide reacts with the ore (e.g. FeO) and removes one of its oxygen atoms, releasing carbon dioxide (). After successive interactions with carbon monoxide, all of the oxygen in the ore will be removed, leaving the raw metal element (e.g. Fe). As most ores are impure, it is often necessary to use flux, such as limestone (or dolomite), to remove the accompanying rock gangue as slag. This calcination reaction emits carbon dioxide.
The required temperature varies both in absolute terms and in terms of the melting point of the base metal. Examples:
* Iron oxide becomes metallic iron at roughly 1250 °C (2282 °F or 1523 K), almost 300 degrees below iron's melting point of 1538 °C (2800 °F or 1811 K).
* Mercuric oxide becomes vaporous mercury near 550 °C (1022 °F or 823 K), almost 600 degrees above mercurys melting point of -38 °C (-36.4 °F or 235 K), and also above mercurys boiling point. | 1 | Applied and Interdisciplinary Chemistry |
Reef Ball Foundation, Inc. is a 501(c)(3) non-profit organization that functions as an international environmental non-governmental organization. The foundation uses reef ball artificial reef technology, combined with coral propagation, transplant technology, public education, and community training to build, restore and protect coral reefs. The foundation has established "reef ball reefs" in 59 countries. Over 550,000 reef balls have been deployed in more than 4,000 projects. | 1 | Applied and Interdisciplinary Chemistry |
The GFP organizes numerous national and regional conferences and workshops. Its flagship event is the Colloque national du GFP, held each November in a different French city, with a typical attendance of 180-250 participants. In addition, the JEPO is an annual conference aimed at students and early career researchers, while the RNJP targets newly established researchers in permanent positions. Finally the GFP organizes regular workshops and training sessions on more specialized subjects. | 1 | Applied and Interdisciplinary Chemistry |
The molality of a solution is defined as the amount of a constituent (in moles) divided by the mass of the solvent (not the mass of the solution):
The SI unit for molality is mol/kg. | 0 | Theoretical and Fundamental Chemistry |
A laser beam passes through the electrophoresis cell, irradiates the particles dispersed in it, and is scattered by the particles. The scattered light is detected by a photo-multiplier after passing through two pinholes. There are two types of optical systems: heterodyne and fringe.
Ware and Flygare developed a heterodyne-type ELS instrument, that was the first instrument of this type. In a fringe optics ELS instrument, a laser beam is divided into two beams. Those cross inside the electrophresis cell at a fixed angle to produce a fringe pattern. The scattered light from the particles, which migrates inside the fringe, is intensity-modulated. The frequency shifts from both types of optics obey the same equations. The observed spectra resemble each other.
Oka et al. developed an ELS instrument of heterodyne-type optics that is now available commercially. Its optics is shown in Fig. 3.
If the frequencies of the intersecting laser beams are the same then it is not possible to resolve the direction of the motion of the migrating particles. Instead, only the magnitude of the velocity (i.e., the speed) can be determined. Hence, the sign of the zeta potential cannot be ascertained. This limitation can be overcome by shifting the frequency of one of the beams relative to the other. Such shifting may be referred to as frequency modulation or, more colloquially, just modulation. Modulators used in ELS may include piezo-actuated mirrors or acousto-optic modulators. This modulation scheme is employed by the heterodyne light scattering method, too.
Phase-analysis light scattering (PALS) is a method for evaluating zeta potential, in which the rate of phase change of the interference between light scattered by the sample and the modulated reference beam is analyzed. This rate is compared with a mathematically generated sine wave predetermined by the modulator frequency. The application of large fields, which can lead to sample heating and breakdown of the colloids is no longer required. But any non-linearity of the modulator or any change in the characteristics of the modulator with time will mean that the generated sine wave will no longer reflect the real conditions, and the resulting zeta-potential measurements become less reliable.
A further development of the PALS technique is the so-called "continuously monitored PALS" (cmPALS) technique, which addresses the non-linearity of the modulators. An extra modulator detects the interference between the modulated and unmodulated laser light. Thus, its beat frequency is solely the modulation frequency and is therefore independent of the electrophoretic motion of the particles. This results in faster measurements, higher reproducibility even at low applied electric fields as well as higher sensitivity of the measurement. | 0 | Theoretical and Fundamental Chemistry |
In medieval times patients could buy mummy juice (powder made of oversea mummies mixed with liquid), burnt hedgehogs powder, burnt bees, bat powder, snakeskin potion and unicorn horn powder for treatments.
Also, available were earthworms, swallow's nests and various herbs and spirits, distilled at the spot.
Food was also sold such as candies, cookies, preserves and marzipan and jellied peel. Spicy cookies called "morsells" were a specialty.
One could even find a glass of Klaret (a locally sugared and spiced Rhine-wine wine). Later, the pharmacy acquired the privilege to import around 400 liters of French cognac tax-free on an annual basis.
The pharmacy also sold paper, ink, sealing-wax, dyes, gunpowder, pellets, spices, candles and torches. When tobacco was brought to Europe and eventually to Estonia, the pharmacy was the first to sell it. | 1 | Applied and Interdisciplinary Chemistry |
Vitrification in cryopreservation is used to preserve, for example, human egg cells (oocytes) (in oocyte cryopreservation) and embryos (in embryo cryopreservation). It prevents ice crystal formation and is a very fast process: -23,000°C/min.
Currently, vitrification techniques have only been applied to brains (neurovitrification) by Alcor and to the upper body by the Cryonics Institute, but research is in progress by both organizations to apply vitrification to the whole body.
Many woody plants living in polar regions naturally vitrify their cells to survive the cold. Some can survive immersion in liquid nitrogen and liquid helium. Vitrification can also be used to preserve endangered plant species and their seeds. For example, recalcitrant seeds are considered hard to preserve. Plant vitrification solution (PVS), one of application of vitrification, has successfully preserved Nymphaea caerulea seeds.
Additives used in cryobiology or produced naturally by organisms living in polar regions are called cryoprotectants. | 1 | Applied and Interdisciplinary Chemistry |
Although siphons can exceed the barometric height of the liquid in special circumstances, e.g. when the liquid is degassed and the tube is clean and smooth, in general the practical maximum height can be found as follows.
Setting equations 1 and 3 equal to each other gives:
Maximum height of the intermediate high point occurs when it is so high that the pressure at the intermediate high point is zero; in typical scenarios this will cause the liquid to form bubbles and if the bubbles enlarge to fill the pipe then the siphon will "break". Setting P = 0:
Solving for h:
:General height of siphon:
This means that the height of the intermediate high point is limited by pressure along the streamline being always greater than zero.
:Maximum height of siphon:
This is the maximum height that a siphon will work. Substituting values will give approximately for water and, by definition of standard pressure, for mercury. The ratio of heights (about 13.6) equals the ratio of densities of water and mercury (at a given temperature). As long as this condition is satisfied (pressure greater than zero), the flow at the output of the siphon is still only governed by the height difference between the source surface and the outlet. Volume of fluid in the apparatus is not relevant as long as the pressure head remains above zero in every section. Because pressure drops when velocity is increased, a static siphon (or manometer) can have a slightly higher height than a flowing siphon. | 1 | Applied and Interdisciplinary Chemistry |
To curate and maintain SBO, a dedicated resource has been developed and the public interface of the SBO browser can be accessed at [http://www.ebi.ac.uk/sbo http://www.ebi.ac.uk/sbo].
A relational database management system (MySQL) at the back-end is
accessed through a web interface based on Java Server Pages (JSP) and JavaBeans. Its
content is encoded in UTF-8, therefore supporting a large set of
characters in the definitions of terms. Distributed curation is made possible
by using a custom-tailored locking system allowing concurrent access.
This system allows a continuous update of the ontology with immediate
availability and suppress merging problems.
Several exports formats ([http://www.godatabase.org/dev/doc/obo_format_spec.html OBO] flat file, [http://www.ebi.ac.uk/sbo/docs/sboxml_schema.xsd SBO-XML] and [http://www.w3.org/TR/owl-features/ OWL]) are generated daily or on request and can be downloaded from the web interface.
To allow programmatic access to the resource, Web Services have been implemented based on [http://ws.apache.org/axis/ Apache Axis] for the communication layer and [http://www.castor.org/ Castor] for the validation. The libraries, full documentation, samples and tutorial are available [http://www.ebi.ac.uk/sbo/SBOWSLib/ws.html online].
The SourceForge project can be accessed at [http://sourceforge.net/projects/sbo/ http://sourceforge.net/projects/sbo/]. | 1 | Applied and Interdisciplinary Chemistry |
The earliest rationale for the effects of hypothermia as a neuroprotectant focused on the slowing of cellular metabolism resulting from a drop in body temperature. For every one degree Celsius drop in body temperature, cellular metabolism slows by 5–7%. Accordingly, most early hypotheses suggested that hypothermia reduces the harmful effects of ischemia by decreasing the body's need for oxygen. The initial emphasis on cellular metabolism explains why the early studies almost exclusively focused on the application of deep hypothermia, as these researchers believed that the therapeutic effects of hypothermia correlated directly with the extent of temperature decline.
In the special case of infants with perinatal asphyxia, it appears that apoptosis is a prominent cause of cell death and that hypothermia therapy for neonatal encephalopathy interrupts the apoptotic pathway. In general, cell death is not directly caused by oxygen deprivation, but occurs indirectly as a result of the cascade of subsequent events. Cells need oxygen to create ATP, a molecule used by cells to store energy, and cells need ATP to regulate intracellular ion levels. ATP is used to fuel both the importation of ions necessary for cellular function and the removal of ions that are harmful to cellular function. Without oxygen, cells cannot manufacture the necessary ATP to regulate ion levels and thus cannot prevent the intracellular environment from approaching the ion concentration of the outside environment. It is not oxygen deprivation itself that precipitates cell death, but rather without oxygen the cell can not make the ATP it needs to regulate ion concentrations and maintain homeostasis.
Notably, even a small drop in temperature encourages cell membrane stability during periods of oxygen deprivation. For this reason, a drop in body temperature helps prevent an influx of unwanted ions during an ischemic insult. By making the cell membrane more impermeable, hypothermia helps prevent the cascade of reactions set off by oxygen deprivation. Even moderate dips in temperature strengthen the cellular membrane, helping to minimize any disruption to the cellular environment. It is by moderating the disruption of homeostasis caused by a blockage of blood flow that many now postulate, results in hypothermia's ability to minimize the trauma resultant from ischemic injuries.
Targeted temperature management may also help to reduce reperfusion injury, damage caused by oxidative stress when the blood supply is restored to a tissue after a period of ischemia. Various inflammatory immune responses occur during reperfusion. These inflammatory responses cause increased intracranial pressure, which leads to cell injury and in some situations, cell death. Hypothermia has been shown to help moderate intracranial pressure and therefore to minimize the harmful effects of a patients inflammatory immune responses during reperfusion. The oxidation that occurs during reperfusion also increases free radical production. Since hypothermia reduces both intracranial pressure and free radical production, this might be yet another mechanism of action for hypothermias therapeutic effect. Overt activation of N-methyl-D-aspartate (NMDA) receptors following brain injuries can lead to calcium entry which triggers neuronal death via the mechanisms of excitotoxicity. | 1 | Applied and Interdisciplinary Chemistry |
The bx1 gene encodes a protein, BX1, that forms indol from indol-3-glycerol phosphate in the plastid. It is the first step in the pathway and determines much of the natural variation in levels of DIMBOA in maize. The next steps in the pathway occur in the endoplasmic reticulum, also referred to as the microsomes in cell fractionation experiments, and are carried by proteins encoded by genes bx2, bx3, bx4, and bx5. | 1 | Applied and Interdisciplinary Chemistry |
The growing knowledge behind the mechanism of autocrine signaling in cancer progression has revealed new approaches for therapeutic treatment. For example, autocrine Wnt signaling could provide a novel target for therapeutic intervention by means of Wnt antagonists or other molecules that interfere with ligand-receptor interactions of the Wnt pathway. In addition, VEGF-A production and VEGFR-2 activation on the surface of breast cancer cells indicates the presence of a distinct autocrine signaling loop that enables breast cancer cells to promote their own growth and survival by phosphorylation and activation of VEGFR-2. This autocrine loop is another example of an attractive therapeutic target.
In HER2 overexpressing breast cancers, the HER2–IL-6–STAT3 signaling relationship could be targeted to develop new therapeutic strategies. HER2 kinase inhibitors, such as lapatinib, have also demonstrated clinical efficacy in HER2 overexpressing breast cancers by disrupting a neuregulin-1 (NRG1)-mediated autocrine loop.
In the case of PDGFR signalling, overexpression of a dominant-negative PDGFR or application of the cancer drug STI571 are both approaches being explored to therapeutically interference with metastasis in mice.
In addition, drugs may be developed that activate autocrine signaling in cancer cells that would not otherwise occur. For example, a small-molecule mimetic of Smac/Diablo that counteracts the inhibition of apoptosis has been shown to enhance apoptosis caused by chemotherapeutic drugs through autocrine-secreted tumor necrosis factor alpha (TNFα). In response to autocrine TNFα signaling, the Smac mimetic promotes formation of a RIPK1-dependent caspase-8-activating complex, leading to apoptosis. | 1 | Applied and Interdisciplinary Chemistry |
Dispersions do not display any structure; i.e., the particles (or in case of emulsions: droplets) dispersed in the liquid or solid matrix (the "dispersion medium") are assumed to be statistically distributed. Therefore, for dispersions, usually percolation theory is assumed to appropriately describe their properties.
However, percolation theory can be applied only if the system it should describe is in or close to thermodynamic equilibrium. There are only very few studies about the structure of dispersions (emulsions), although they are plentiful in type and in use all over the world in innumerable applications (see below).
In the following, only such dispersions with a dispersed phase diameter of less than 1 µm will be discussed. To understand the formation and properties of such dispersions (incl emulsions), it must be considered that the dispersed phase exhibits a "surface", which is covered ("wet") by a different "surface" that, hence, are forming an interface (chemistry). Both surfaces have to be created (which requires a huge amount of energy), and the interfacial tension (difference of surface tension) is not compensating the energy input, if at all.
Experimental evidence suggests dispersions have a structure very much different from any kind of statistical distribution (which would be characteristics for a system in thermodynamic equilibrium), but in contrast display structures similar to self-organisation, which can be described by non-equilibrium thermodynamics. This is the reason why some liquid dispersions turn to become gels or even solid at a concentration of a dispersed phase above a critical concentration (which is dependent on particle size and interfacial tension). Also, the sudden appearance of conductivity in a system of a dispersed conductive phase in an insulating matrix has been explained. | 0 | Theoretical and Fundamental Chemistry |
Neutron backscattering was proposed by Heinz Maier-Leibnitz in 1966, and realized by some of his students in a test setup at the research reactor FRM I in Garching bei München, Germany. Following this successful demonstration of principle, permanent spectrometers were built at Forschungszentrum Jülich and at the Institut Laue-Langevin (ILL). Later instruments brought an extension of the accessible momentum transfer range (IN13 at ILL), the introduction of focussing optics (IN16 at ILL), and a further increase of intensity by a compact design with a phase-space transform chopper (HFBS at NIST, SPHERES at FRM II, IN16B at the Institut Laue-Langevin). | 0 | Theoretical and Fundamental Chemistry |
The Roman philosopher-poet Lucretius' scientific poem "On the Nature of Things" () has a remarkable description of the motion of dust particles in verses 113–140 from Book II. He uses this as a proof of the existence of atoms:
Although the mingling, tumbling motion of dust particles is caused largely by air currents, the glittering, jiggling motion of small dust particles is caused chiefly by true Brownian dynamics; Lucretius "perfectly describes and explains the Brownian movement by a wrong example".
While Jan Ingenhousz described the irregular motion of coal dust particles on the surface of alcohol in 1785, the discovery of this phenomenon is often credited to the botanist Robert Brown in 1827. Brown was studying pollen grains of the plant Clarkia pulchella suspended in water under a microscope when he observed minute particles, ejected by the pollen grains, executing a jittery motion. By repeating the experiment with particles of inorganic matter he was able to rule out that the motion was life-related, although its origin was yet to be explained.
The first person to describe the mathematics behind Brownian motion was Thorvald N. Thiele in a paper on the method of least squares published in 1880. This was followed independently by Louis Bachelier in 1900 in his PhD thesis "The theory of speculation", in which he presented a stochastic analysis of the stock and option markets. The Brownian motion model of the stock market is often cited, but Benoit Mandelbrot rejected its applicability to stock price movements in part because these are discontinuous.
Albert Einstein (in one of his 1905 papers) and Marian Smoluchowski (1906) brought the solution of the problem to the attention of physicists, and presented it as a way to indirectly confirm the existence of atoms and molecules. Their equations describing Brownian motion were subsequently verified by the experimental work of Jean Baptiste Perrin in 1908. | 0 | Theoretical and Fundamental Chemistry |
Below are useful results from the Maxwell–Boltzmann distribution for an ideal gas, and the implications of the Entropy quantity. The distribution is valid for atoms or molecules constituting ideal gases.
Corollaries of the non-relativistic Maxwell–Boltzmann distribution are below. | 0 | Theoretical and Fundamental Chemistry |
Capillary condensation bridges two surfaces together, with the formation of a meniscus, as is stated above. In the case of atomic-force microscopy (AFM) a capillary bridge of water can form between the tip and the surface, especially in cases of a hydrophilic surface in a humid environment when the AFM is operated in contact mode. While studies have been done on the formation of the meniscus between the tip and the sample, no specific conclusion can be drawn as to the optimum height away from the sample the tip can be without meniscus formation. Scientific studies have been done on the relationship between relative humidity and the geometry of the meniscus created by capillary condensation. One particular study, done by Weeks, illustrated that with the increase in relative humidity, there is a large increase in the size of the meniscus. This study also states that no meniscus formation is observed when the relative humidity is less than 70%, although there is uncertainty in this conclusion due to limits of resolution.
The formation of the meniscus is the basis of the Dip-Pen Nanolithography technique. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of methyl fluoroacetate consists of a two-step process:
# Potassium fluoride (KF) and the catalyst are added into the solvent within the reactor; this is then stirred and heated up. The catalyst mentioned in this step is a phase-transfer catalyst and can be the chemicals dodecyl(trimethyl)ammonium chloride , tetrabutylammonium chloride , tetrabutylammonium bromide , or tetramethylammonium chloride . The mass ratio of the potassium fluoride and the catalyst in this step is 0.5~1 : 0.02~0.03. With the solvent mentioned in this step being a mixture of dimethylformamide () and acetamide () with a mass ratio of 1.4~1.6: 1. The mass ratio of the solvent and potassium fluoride is 1.1~2.0 : 0.5~1.
# When the reaction temperature of 100~160 °C is reached, methyl chloroacetate is continuously added in the reactor at a speed of 5~10 kg/min with the mass ratio of methyl chloroacetate and potassium fluoride being 1:0.5～1. The reaction between these chemicals produces a gas mixture, with the gases within this mixture then being split between two condensers according to their condensation temperature. Methyl chloroacetate is condensed within the condenser set at 100~105 °C, it is then returned to the reactor to continue participating in the chemical reaction. Methyl fluoroacetate in the other condenser then enters a two-stage nitration condensation at a temperature of 20~25 °C which then ensures that the methyl fluoroacetate is condensed into a liquid with it being the product of this reaction. | 1 | Applied and Interdisciplinary Chemistry |
Hierlemann's research initially was mostly in the area of chemical sensors and microsensors. In particular, he worked on the detection of organic volatiles and the discrimination of enantiomers in the gas phase. He then adopted microtechnology and, specifically, CMOS-based microelectronics to devise complex microsensor systems. The current interdisciplinary research is rooted in engineering and physics and targeted at questions in biology and medicine. It includes the development of CMOS-based integrated chemical and biomicrosystems, as well as bioelectronics and high-density microelectrode arrays. The high-density microelectrode arrays are used for fundamental research in information processing and signaling characteristics of neurons or brain cells. Moreover, the research group is engaged in the development of microfluidics for investigating the characteristics of single cells and microtissues.
Applications of Hierlemanns and his groups technologies are in the fields of systems biology, drug testing, personalized medicine, and neuroscience. | 0 | Theoretical and Fundamental Chemistry |
A fluid inclusion is a bubble of liquid and/or gas that is trapped within a crystal. As minerals often form from a liquid or aqueous medium, tiny bubbles of that liquid can become trapped within the crystal, or along healed crystal fractures. These inclusions usually range in size from 0.01 mm to 1 mm and are only visible in detail by microscopic study, however specimens of fenster or skeletal quartz may include thin sheet-like inclusions that are many millimetres in length and breadth within their lamellar voids.
These inclusions occur in a wide variety of environments. For example, they are found within cementing minerals of sedimentary rocks, in gangue minerals such as quartz or calcite in hydrothermal circulation deposits, in fossil amber, and in deep ice cores from the Greenland and Antarctic ice caps. The inclusions can provide information about the conditions existing during the formation of the enclosing mineral. Fourier transform infrared spectroscopy and Raman spectroscopy can be used to determine the composition of fluid inclusions. | 0 | Theoretical and Fundamental Chemistry |
Pharmacotoxicology entails the study of the consequences of toxic exposure to pharmaceutical drugs and agents in the health care field. The field of pharmacotoxicology also involves the treatment and prevention of pharmaceutically induced side effects. Pharmacotoxicology can be separated into two different categories: pharmacodynamics (the effects of a drug on an organism), and pharmacokinetics (the effects of the organism on the drug). | 1 | Applied and Interdisciplinary Chemistry |
Urban forests are forests located in cities. They are an important component of urban green infrastructure systems. Urban forests use appropriate tree and vegetation species, instead of noxious and invasive kinds, which reduce the need of maintenance and irrigation. In addition, native species also provide aesthetic value while reducing cost. Diversity of plant species should also be considered in design of urban forests to avoid monocultures; this makes the urban forests more durable and resilient to pests and other harms.
;Benefits
* Energy use: According to a study conducted by the Lawrence Berkeley National Laboratory and Sacramento Municipal Utility District, it was found that strategically located shade trees planted around houses can provide up to 47% energy savings for heating and cooling.
* Urban heat island mitigation: Maximum air temperature for tree groves were found to be lower than that of open areas without trees. This is contributed to by the principal processes of evaporative cooling from transpiration, radiation interception from the shading effect of canopies, and increasing urban surface roughness to enhance its convective cooling efficiency.
* Water management: Urban forests helps with city water management on diverting storm water from water channels. Trees intercept a large amount of rainfall that hit them.
* Air pollution: Trees hold carbon, which improves air quality in cities.
* Property values: In response to fluctuating demand from residents wanting increased amounts of urban greenery, increasing vegetation like tree cover within urban areas can result in the surrounding areas of real estate to increase in value.
* Public health: Urban greenery can also improve mental health and well-being. Creating urban forests affects public health in many ways. Urban heat islands are created by the condensation of heat due to the materials and infrastructure used in metropolitan areas, which can negatively impact human health. Urban forests provide natural shading structures at a fraction of the cost of artificial shading structures and it counters the negative health impacts of increasing global temperatures. Beyond countering the negative impacts of man-made infrastructure, green infrastructure has the potential to enhance existing ecosystems and make them more stable, which has been historically done in traditional Japanese agriculture. Green infrastructure in an urbanized area can help restore and enhance the resiliency of an ecosystem to natural disturbances and disasters that disrupt the lives of residents. Building new urban forests in an existing metropolitan area creates new labor jobs that do not require a high level of education, which can decrease unemployment in the working class which benefits society. Furthermore, green infrastructure helps states to implement the principles of the 1992 Rio Declaration on Environment and Development that was designed to alleviate the social and economic consequences of environmental degradation. | 1 | Applied and Interdisciplinary Chemistry |
Magnet-assisted transfection is a relatively new and time-saving method to introduce nucleic acids into a target cell with increased efficiency. In particular, adherent mammalian cell lines and primary cell cultures show very high transfection rates. Suspension cells and cells from other organisms can also be successfully transfected. A major advantage of the method is the mild treatment of the cells in comparison to liposome-based transfection reagents (lipofection) and electroporation, which may result in the death of 20-50% of cells. In addition, the transfection efficiency is increased in numerous cases by the directed transport in a magnetic field, especially for low amounts of nucleic acids. In contrast, methods like lipofection offer only statistical hits between cargo and cells, because of the three-dimensional motion of cells and transfection aggregates in a liquid suspension. Magnet-assisted transfection can also be performed in the presence of serum, which is a further benefit. Currently, there are over 150 cells known to be successfully transfected. Additionally, synergistic effects in transfection efficiency can arise from the possible combination of lipofection and magnet-assisted transfection.
In future, this technology might be also an alternative strategy to the currently used viral and non-viral vectors in gene-therapy and gene transfer. | 1 | Applied and Interdisciplinary Chemistry |
A typical application of GISAS is the characterisation of self-assembly and self-organization on the nanoscale in thin films. Systems studied by GISAS include quantum dot arrays,
growth instabilities formed during in-situ growth,
self-organized nanostructures in thin films of block copolymers,
silica mesophases,
and nanoparticles.
GISAXS was introduced by Levine and Cohen to study the dewetting of gold deposited on a glass surface. The technique was further developed by Naudon and coworkers to study metal agglomerates on surfaces and in buried interfaces. With the advent of nanoscience other applications evolved quickly, first in hard matter such as the characterization of quantum dots on semiconductor surfaces and the in-situ characterization of metal deposits on oxide surfaces. This was soon to be followed by soft matter systems such as ultrathin polymer films, polymer blends, block copolymer films and other self-organized nanostructured thin films that have become indispensable for nanoscience and technology. Future challenges of GISAS may lie in biological applications, such as proteins, peptides, or viruses attached to surfaces or in lipid layers. | 0 | Theoretical and Fundamental Chemistry |
In molecular genetics, a regulon is a group of genes that are regulated as a unit, generally controlled by the same regulatory gene that expresses a protein acting as a repressor or activator. This terminology is generally, although not exclusively, used in reference to prokaryotes, whose genomes are often organized into operons; the genes contained within a regulon are usually organized into more than one operon at disparate locations on the chromosome. Applied to eukaryotes, the term refers to any group of non-contiguous genes controlled by the same regulatory gene.
A modulon is a set of regulons or operons that are collectively regulated in response to changes in overall conditions or stresses, but may be under the control of different or overlapping regulatory molecules. The term stimulon is sometimes used to refer to the set of genes whose expression responds to specific environmental stimuli. | 1 | Applied and Interdisciplinary Chemistry |
GBE is encoded by the GBE1 gene.
Through Southern blot analysis of DNA derived from human/rodent somatic cell hybrids, GBE1 has been identified as an autosomal gene located on the short arm of chromosome 3 at position 12.3. The human GBE gene was also isolated by a function complementation of the Saccharomyces cerevisiae GBE deficiency. From the isolated cDNA, the length of the gene was found to be approximately 3 kb. Additionally, the coding sequence was found to comprise 2,106 base pairs and encode a 702-amino acid long GBE. The molecular mass of human GBE was calculated to be 80,438 Da. | 1 | Applied and Interdisciplinary Chemistry |
As magmatic gas travelling upward encounters meteoric water in an aquifer, steam is produced. Latent magmatic heat can also cause meteoric waters to ascend as a vapour phase. Extended fluid-rock interaction of this hot mixture can leach constituents out of the cooling magmatic rock and also the country rock, causing volume changes and phase transitions, reactions and thus an increase in ionic strength of the upward percolating fluid. This process also decreases the fluid's pH. Cooling can cause phase separation and mineral deposition, accompanied by a shift toward more reducing conditions. At the surface expression of such hydrothermal systems, low-temperature volcanic gases (<400 °C) are either emanating as steam-gas mixtures or in dissolved form in hot springs. At the ocean floor, such hot supersaturated hydrothermal fluids form gigantic chimney structures called black smokers, at the point of emission into the cold seawater.
Over geological time, this process of hydrothermal leaching, alteration, and/or redeposition of minerals in the country rock is an effective process of concentration that generates certain types of economically valuable ore deposits. | 1 | Applied and Interdisciplinary Chemistry |
During lagging strand synthesis, DNA ligase I connects the Okazaki fragments, following replacement of the RNA primers with DNA nucleotides by DNA polymerase δ. Okazaki fragments that are not ligated could cause double-strand-breaks, which cleaves the DNA. Since only a small number of double-strand breaks are tolerated, and only a small number can be repaired, enough ligation failures could be lethal to the cell.
Further research implicates the supplementary role of proliferating cell nuclear antigen (PCNA) to DNA ligase Is function of joining Okazaki fragments. When the PCNA binding site on DNA ligase I is inactive, DNA ligase Is ability to connect Okazaki fragments is severely impaired. Thus, a proposed mechanism follows: after a PCNA-DNA polymerase δ complex synthesizes Okazaki fragments, the DNA polymerase δ is released. Then, DNA ligase I binds to the PCNA, which is clamped to the nicks of the lagging strand, and catalyzes the formation of phosphodiester bonds. | 1 | Applied and Interdisciplinary Chemistry |
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