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iv: intravenous, sc: subcutaneous, HIT: heparin-induced thrombocytopenia, VTE: Venous thromboembolism, DVT: Deep vein thrombosis, PTCA: Percutaneous transluminal coronary angioplasty, PCI: percutaneous coronary intervention, FDA: Food and Drug Administration, AF: Atrial fibrillation, TI: Therapeutic index | 1 | Applied and Interdisciplinary Chemistry |
Reaction progress data may often most simply be presented as plot of substrate concentration ([A]) vs. time (t) or fraction conversion (F) vs. time (t). The latter requires minor algebraic manipulation to convert concentration/absorbance values to fractional conversion (F), by:
:F =
where [A] is the amount, absorbance, or concentration of substrate initially present and [A] is the amount, absorbance, or concentration of that reagent at time, t. Normalizing data to fractional conversion may be particularly helpful as it allows multiple reactions run with different absolute amounts or concentrations to be compared on the same plot.
Data may also commonly be presented as a plot of reaction rate (v) vs. time (t). Again, simple algebraic manipulation is required; for example, calorimetric experiments give:
:v =
where q is the instantaneous heat transfer, ΔH is the known enthalpy change of the reaction, and V is the reaction volume.
Data from reaction progress kinetics experiments are also often presented via a rate (v) vs. substrate concentration ([S]) plot. This requires obtaining and combining both the [S] vs. t and the v vs. t plots described above (note that one may be obtained from the other by simple differentiation or integration.) The combination leads to a standard set of curves in which reaction progress is read from right to left along the x-axis and reaction rate is read from bottom to top along the y-axis. While these plots often provide a visually compelling demonstration of basic kinetic trends, differential methods are generally superior for extracting numerical rate constants. (see below) | 0 | Theoretical and Fundamental Chemistry |
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA at first non-coding RNA molecules, typically 20–24 (normally 21) base pairs in length, similar to miRNA, and operating within the RNA interference (RNAi) pathway. It interferes with the expression of specific genes with complementary nucleotide sequences by degrading mRNA after transcription, preventing translation.
It was discovered in 1998, by Andrew Fire at Carnegie Institution for Science in Washington DC and Craig Mello at University of Massachusetts in Worcester. | 1 | Applied and Interdisciplinary Chemistry |
Fans generate noise from the rapid flow of air around blades and obstacles causing vortexes, and from the motor. Fan noise is roughly proportional to the fifth power of fan speed; halving speed reduces noise by about 15 dB.
The perceived loudness of fan noise also depends on the frequency distribution of the noise. This in turn depends on the shape and distribution of moving parts, especially of the blades, and of stationary parts, struts in particular. Like with tire treads, and similar to the principle of acoustic diffusors, an irregular shape and distribution can flatten the noise spectrum, making the noise sound less disturbing.
The inlet shape of the fan can also influence the noise levels generated by the fan. | 0 | Theoretical and Fundamental Chemistry |
Diffusive–thermal instability or thermo–diffusive instability is an intrinsic flame instability that occurs both in premixed flames and in diffusion flames and arises because of the difference in the diffusion coefficient values for the fuel and heat transport, characterized by non-unity values of Lewis numbers. The instability mechanism that arises here is the same as in Turing instability explaining chemical morphogenesis, although the mechanism was first discovered in the context of combustion by Yakov Zeldovich in 1944 to explain the cellular structures appearing in lean hydrogen flames. Quantitative stability theory for premixed flames were developed by Gregory Sivashinsky (1977), Guy Joulin and Paul Clavin (1979) and for diffusion flames by Jong S. Kim and Forman A. Williams (1996,1997). | 1 | Applied and Interdisciplinary Chemistry |
Installation of couplers and tapping tee fittings require slightly different procedures. Common installation steps for each are given below. | 0 | Theoretical and Fundamental Chemistry |
Because RIP is so efficient at detecting and mutating repeats, fungal biologists often use it as a tool for mutagenesis. A second copy of a single-copy gene is first transformed into the genome. The fungus must then mate and go through its sexual cycle to activate the RIP machinery. Many different mutations within the duplicated gene are obtained from even a single fertilization event so that inactivated alleles, usually due to nonsense mutations, as well as alleles containing missense mutations can be obtained. | 1 | Applied and Interdisciplinary Chemistry |
Following oral administration of lisinopril, peak serum concentrations of lisinopril occur within about seven hours, although there was a trend to a small delay in time taken to reach peak serum concentrations in acute myocardial infarction patients. The peak effect of lisinopril is about 6 hours after administration for most people. Declining serum concentrations exhibit a prolonged terminal phase, which does not contribute to drug accumulation. This terminal phase probably represents saturable binding to ACE and is not proportional to dose. Lisinopril does not undergo metabolism and absorbed drug is excreted unchanged entirely in the urine. Based on urinary recovery, the mean extent of absorption of lisinopril is approximately 25% (reduced to 16% in people with New York Heart Association Functional Classification (NYHA) Class II–IV heart failure), with large interpatient variability (6 to 60%) at all doses tested (5 to 80 mg). Lisinopril absorption is not affected by the presence of food in the gastrointestinal tract.
Studies in rats indicate that lisinopril crosses the blood-brain barrier poorly. Multiple doses of lisinopril in rats result in little or no accumulation in brain tissue. | 0 | Theoretical and Fundamental Chemistry |
Binary liquid is a type of chemical combination, which creates a special reaction or feature as a result of mixing two liquid chemicals, that are normally inert or have no function by themselves. A number of chemical products are produced as a result of mixing two chemicals as a binary liquid, such as plastic foams and some explosives. | 1 | Applied and Interdisciplinary Chemistry |
Some other confinement principles have been investigated.
* Antimatter-initialized fusion uses small amounts of antimatter to trigger a tiny fusion explosion. This has been studied primarily in the context of making nuclear pulse propulsion, and pure fusion bombs feasible. This is not near becoming a practical power source, due to the cost of manufacturing antimatter alone.
* Pyroelectric fusion was reported in April 2005 by a team at UCLA. The scientists used a pyroelectric crystal heated from −34 to 7 °C (−29 to 45 °F), combined with a tungsten needle to produce an electric field of about 25 gigavolts per meter to ionize and accelerate deuterium nuclei into an erbium deuteride target. At the estimated energy levels, the D–D fusion reaction may occur, producing helium-3 and a 2.45 MeV neutron. Although it makes a useful neutron generator, the apparatus is not intended for power generation since it requires far more energy than it produces. D–T fusion reactions have been observed with a tritiated erbium target.
* Nuclear fusion–fission hybrid (hybrid nuclear power) is a proposed means of generating power by use of a combination of nuclear fusion and fission processes. The concept dates to the 1950s, and was briefly advocated by Hans Bethe during the 1970s, but largely remained unexplored until a revival of interest in 2009, due to the delays in the realization of pure fusion.
* Project PACER, carried out at Los Alamos National Laboratory (LANL) in the mid-1970s, explored the possibility of a fusion power system that would involve exploding small hydrogen bombs (fusion bombs) inside an underground cavity. As an energy source, the system is the only fusion power system that could be demonstrated to work using existing technology. However it would also require a large, continuous supply of nuclear bombs, making the economics of such a system rather questionable.
* Bubble fusion also called sonofusion was a proposed mechanism for achieving fusion via sonic cavitation which rose to prominence in the early 2000s. Subsequent attempts at replication failed and the principal investigator, Rusi Taleyarkhan, was judged guilty of research misconduct in 2008. | 0 | Theoretical and Fundamental Chemistry |
Graham's research on the diffusion of gases was triggered by his reading about the observations of German chemist Johann Döbereiner that hydrogen gas diffused out of a small crack in a glass bottle faster than the surrounding air diffused in to replace it. Graham measured the rate of diffusion of gases through plaster plugs, through very fine tubes, and through small orifices. In this way he slowed down the process so that it could be studied quantitatively. He first stated in 1831 that the rate of effusion of a gas is inversely proportional to the square root of its density, and later in 1848 showed that this rate is inversely proportional to the square root of the molar mass. Graham went on to study the diffusion of substances in solution and in the process made the discovery that some apparent solutions actually are suspensions of particles too large to pass through a parchment filter. He termed these materials colloids, a term that has come to denote an important class of finely divided materials.
Around the time Graham did his work, the concept of molecular weight was being established largely through the measurements of gases. Daniel Bernoulli suggested in 1738 in his book Hydrodynamica that heat increases in proportion to the velocity, and thus kinetic energy, of gas particles. Italian physicist Amedeo Avogadro also suggested in 1811 that equal volumes of different gases contain equal numbers of molecules. Thus, the relative molecular weights of two gases are equal to the ratio of weights of equal volumes of the gases. Avogadro's insight together with other studies of gas behaviour provided a basis for later theoretical work by Scottish physicist James Clerk Maxwell to explain the properties of gases as collections of small particles moving through largely empty space.
Perhaps the greatest success of the kinetic theory of gases, as it came to be called, was the discovery that for gases, the temperature as measured on the Kelvin (absolute) temperature scale is directly proportional to the average kinetic energy of the gas molecules. Graham's law for diffusion could thus be understood as a consequence of the molecular kinetic energies being equal at the same temperature.
The rationale of the above can be summed up as follows:
Kinetic energy of each type of particle (in this example, Hydrogen and Oxygen, as above) within the system is equal, as defined by thermodynamic temperature:
Which can be simplified and rearranged to:
or:
Ergo, when constraining the system to the passage of particles through an area, Graham's Law appears as written at the start of this article. | 0 | Theoretical and Fundamental Chemistry |
AutoAnalyzers were used mainly for routine repetitive medical laboratory analyses, but they had been replaced during the last years more and more by discrete working systems which allow lower reagent consumption. These instruments typically determine levels of albumin, alkaline phosphatase, aspartate transaminase (AST), blood urea nitrogen, bilirubin, calcium, cholesterol, creatinine, glucose, inorganic phosphorus, proteins, and uric acid in blood serum or other bodily samples. AutoAnalyzers automate repetitive sample analysis steps which would otherwise be done manually by a technician, for such medical tests as the ones mentioned previously. This way, an AutoAnalyzer can analyze hundreds of samples every day with one operating technician. Early AutoAnalyzer instruments each tested multiple samples sequentially for individual analytes. Later model AutoAnalyzers such as the SMAC tested for multiple analytes simultaneously in the samples.
In 1959 a competitive system of analysis was introduced by Hans Baruch of Research Specialties Company. That system became known as Discrete Sample Analysis and was represented by an instrument known as the "Robot Chemist." Over the years the Discrete Sample Analysis method slowly replaced the Continuous Flow system in the clinical laboratory. | 0 | Theoretical and Fundamental Chemistry |
Sensor-based sorting has been introduced by Wotruba and Harbeck as an umbrella term for all applications where particles are singularly detected by a sensor technique and then rejected by an amplified mechanical, hydraulic or pneumatic process. | 0 | Theoretical and Fundamental Chemistry |
Deuterium-depleted water (DDW) is water which has a lower concentration of deuterium than occurs naturally at sea level on Earth.
DDW is sometimes known as light water or protium water, although "light water" has long referred to ordinary water, specifically in nuclear reactors. | 0 | Theoretical and Fundamental Chemistry |
TIVA tags are created initially via solid-phase synthesis with the cell-penetrating peptide conjugated afterwards. The functional components of the tag can be summarized as following:
* Biotin: binds to streptavidin beads for tag isolation.
* Cy3 fluorophore: used to validated cleavage of photocleavable linker. If cleaved, cell will appear green upon exposure to 514 nm light.
* Cy5 fluorophore: used to validate uptake into cells. If uptake is successful, and if Cy5 is not yet cleaved from the TIVA tag, energy from a 514 nm light will be absorbed via FRET from Cy3 to Cy5, where cells that have taken up the TIVA will appear red.
* PolyU 18-mer oligonucleotide: used to bind mRNA via complementary base pairing of their polyadenylated tails. Before cleavage of photocleavable linkers, it is caged by complementary base pairing to two polyA 7-mer oligonucleotides.
* PolyA 7-mer oligonucleotides: before the cleavage of photocleavable linkers, 2 polyA 7-mer molecules conjugate to polyU oligonucleotides to cage the TIVA tag, and thus prevent it from binding mRNA molecules. After photocleavable linkers are cleaved, the melting temperature decreases from 59 °C to less than 25 °C, leading to the disassociation of the PolyA 7-mer oligonucleotides from the TIVA tag.
* Photocleavable linker: links and stabilizes Cy5 fluorophore and PolyA 7-mer oligonucleotides to the TIVA tag. It is cleaved upon photoactivation.
* Cell-penetrating peptide CPP: guides the TIVA tag through cell membranes into tissues. It is linked to the TIVA tag by a disulphide bond that is cleaved once exposed to extracellular environment. | 1 | Applied and Interdisciplinary Chemistry |
Literature distinguishes two major mechanisms of solubilization process of oil by surfactant micelles, affecting the kinetics of solubilization: surface reaction, i.e., by transient adsorption of micelles at the water-oil interface, and bulk reaction, whereby the surfactant micelles capture dissolved oil molecules. | 0 | Theoretical and Fundamental Chemistry |
Researchers have been looking for a material that can mimic tissue properties to make the tissue engineering process more effective and less invasive to the human body. The porous, interconnecting network of nanocomposite hydrogels, created through cross-link, enable wastes and nutrients to easily enter and exit the structure, and their elastomeric properties let them acquire the desired anatomical shape without needing prior molding. The porous structure of this material would also make the process of drug delivery easier where the pharmaceutical compounds present in the hydrogel can easily escape and be absorbed by the body. Aside from that, researchers are also looking into incorporating nanocomposite hydrogels with silver nanoparticles for antibacterial applications and microorganism elimination in medical and food packing and water treatment. Hydrogels infused with nanoparticles have a number of biological applications, including: tissue engineering, chemical and biological sensing and drug and gene delivery. | 0 | Theoretical and Fundamental Chemistry |
Typically, ellipsometry is done only in the reflection setup. The exact nature of the polarization change is determined by the sample's properties (thickness, complex refractive index or dielectric function tensor). Although optical techniques are inherently diffraction-limited, ellipsometry exploits phase information (polarization state), and can achieve sub-nanometer resolution. In its simplest form, the technique is applicable to thin films with thickness of less than a nanometer to several micrometers. Most models assume the sample is composed of a small number of discrete, well-defined layers that are optically homogeneous and isotropic. Violation of these assumptions requires more advanced variants of the technique (see below).
Methods of immersion or multiangular ellipsometry are applied to find the optical constants of the material with rough sample surface or presence of inhomogeneous media. New methodological approaches allow the use of reflection ellipsometry to measure physical and technical characteristics of gradient elements in case the surface layer of the optical detail is inhomogeneous. | 0 | Theoretical and Fundamental Chemistry |
The compound with empirical formula FeSn is the first known kagome magnet. It is an intermetallic compound composed of iron (Fe) and tin (Sn), with alternating planes of FeSn and Sn. | 1 | Applied and Interdisciplinary Chemistry |
The scientific work of Leonidas Zervas had a global resonance and his contribution was recognised by multiple awards throughout his life. In 1960 he received an honorary doctorate from the University of Basel on the occasion of the university's 500th anniversary, upon recommendation of Hans Erlenmeyer and Nobel laureate Tadeusz Reichstein. In 1969 he was bestowed honorary membership of the American Society of Biological Chemists. In 1976 he was conferred the (1st class) by the Socialist Republic of Romania. In the same year Zervas was made Foreign Member of the USSR Academy of Sciences, an indication of the great respect for his work in the Eastern Block, too. The Max-Bergmann-Kreis company of German peptide chemists planned to present Zervas with the first Max Bergmann golden medal for peptide chemistry in 1980, but his sudden death necessitated a posthumous award ceremony.
In honour of Zervas, a commemorative bust has been unveiled in his birthtown Megalopolis in 1991 and the main conference hall of the National Hellenic Research Foundation is called the "Leonidas Zervas amphitheatre".
The European Peptide Society has established the Leonidas Zervas Award "in commemoration of his outstanding contributions to peptide science", awarded biennially since 1988. The award is given to the "scientist who has made the most outstanding contributions to the chemistry, biochemistry and/or biology of peptides in the five years preceding the date of selection". | 0 | Theoretical and Fundamental Chemistry |
Before joining the faculty of the University of Oregon in 1962, Mazo was a postdoctoral fellow at Institute voor Theoretische Physica, University of Amsterdam and a research associate at the University of Chicago (sponsored by the National Science Foundation). He also held an assistant professorship at the California Institute of Technology.
Mazo's research interests were "Exclusively theoretical", and have included "Brownian motion processes, Markov processes, Probabilities, Statistical mechanics, and Transport theory."
During Mazo's 33 year career at the University of Oregon, he served at various times as chair of the chemistry department, director of the Institute Theoretical Science, and as associate dean of the graduate school. He was also a program director of the National Science Foundation. | 0 | Theoretical and Fundamental Chemistry |
On the other hand, softer, more polarisable centres prefer to coordinate in a more covalent manner through the phosphorus atom. Examples of this include complexes accommodating a neutral or sparsely charged transition metal centre. The first example of this nature of PCO binding was published by Grutzmacher and co-workers in 2012. The groups studies used a Re(I) complex and the analysis of its bonding parameters and electronic structure showed that the phosphaethynolate anion coordinated in a bent fashion. This suggested the Re(I) – P bond possessed a highly covalent character thus the complex would be best described as a metallaphosphaketene. It wasnt until four years later that a second example of this coordination nature of PCO was identified. This time it came in the form of a W(0) pentacarbonyl complex produced by the Goicoechea group. | 0 | Theoretical and Fundamental Chemistry |
The microstructure of a material refers to the structure of an object, organism, or material as viewed at magnifications exceeding 25 times. It is composed of the different phases of form, size, and distribution of grains, pores, precipitates, etc. The majority of solid microstructures are crystalline, however some materials such as certain polymers will not crystallize when in the solid state. | 1 | Applied and Interdisciplinary Chemistry |
In order for paracrine factors to successfully induce a response in the receiving cell, that cell must have the appropriate receptors available on the cell membrane to receive the signals, also known as being competent. Additionally, the responding cell must also have the ability to be mechanistically induced. | 1 | Applied and Interdisciplinary Chemistry |
The structural trans effect can be measured experimentally using X-ray crystallography, and is observed as a stretching of the bonds between the metal and the ligand trans to a trans-influencing ligand. Stretching by as much as 0.2 Å occurs with strong trans-influencing ligands such as hydride. A cis influence can also be observed, but is smaller than the trans influence. The relative importance of the cis and trans influences depends on the formal electron configuration of the metal center, and explanations have been proposed based on the involvement of the atomic orbitals. | 0 | Theoretical and Fundamental Chemistry |
There are also other types of interactions that generalize the idea of interacting p orbitals in a conjugated system. The concept of hyperconjugation holds that certain σ bonds can also delocalize into a low-lying unoccupied orbital of a π system or an unoccupied p orbital. Hyperconjugation is commonly invoked to explain the stability of alkyl substituted radicals and carbocations. Hyperconjugation is less important for species in which all atoms satisfy the octet rule, but a recent computational study supports hyperconjugation as the origin of the increased stability of alkenes with a higher degree of substitution (Zaitsev's rule).
Homoconjugation is an overlap of two π-systems separated by a non-conjugating group, such as CH. Unambiguous examples are comparatively rare in neutral systems, due to a comparatively minor energetic benefit that is easily overridden by a variety of other factors; however, they are common in cationic systems in which a large energetic benefit can be derived from delocalization of positive charge (see the article on homoaromaticity for details.). Neutral systems generally require constrained geometries favoring interaction to produce significant degrees of homoconjugation. In the example below, the carbonyl stretching frequencies of the IR spectra of the respective compounds demonstrate homoconjugation, or lack thereof, in the neutral ground state molecules.
Due to the partial π character of formally σ bonds in a cyclopropane ring, evidence for transmission of "conjugation" through cyclopropanes has also been obtained.
Two appropriately aligned π systems whose ends meet at right angles can engage in spiroconjugation.
Vinylogy is the extension of a functional group through a conjugated organic bonding system, which transmits electronic effects. | 0 | Theoretical and Fundamental Chemistry |
Inositol trisphosphate or inositol 1,4,5-trisphosphate abbreviated InsP or Ins3P or IP is an inositol phosphate signaling molecule. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP), a phospholipid that is located in the plasma membrane, by phospholipase C (PLC).
Together with diacylglycerol (DAG), IP is a second messenger molecule used in signal transduction in biological cells. While DAG stays inside the membrane, IP is soluble and diffuses through the cell, where it binds to its receptor, which is a calcium channel located in the endoplasmic reticulum. When IP binds its receptor, calcium is released into the cytosol, thereby activating various calcium regulated intracellular signals. | 1 | Applied and Interdisciplinary Chemistry |
Heteroatom-promoted lateral lithiation is the site-selective replacement of a benzylic hydrogen atom for lithium for the purpose of further functionalization. Heteroatom-containing substituents may direct metalation to the benzylic site closest to the heteroatom or increase the acidity of the ring carbons via an inductive effect. | 0 | Theoretical and Fundamental Chemistry |
Sonoporation is performed with a dedicated sonoporator. Sonoporation may also be performed with custom-built piezoelectric transducers connected to bench-top function generators and acoustic amplifiers. Standard ultrasound medical devices may also be used in some applications.
Measurement of the acoustics used in sonoporation is listed in terms of mechanical index, which quantifies the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a non-thermal action based on pressure. | 1 | Applied and Interdisciplinary Chemistry |
Vacuum fusion is an analytical chemistry technique, used for determining the oxygen, hydrogen, and sometimes nitrogen content of metals. While ineffective when used on alkali or earth metals, vacuum fusion remains a viable means when applied to almost all other metals. | 0 | Theoretical and Fundamental Chemistry |
CFCs were phased out via the Montreal Protocol due to their part in ozone depletion.
The atmospheric impacts of CFCs are not limited to their role as ozone-depleting chemicals. Infrared absorption bands prevent heat at that wavelength from escaping Earth's atmosphere. CFCs have their strongest absorption bands from C-F and C-Cl bonds in the spectral region of 7.8–15.3 µm—referred to as the "atmospheric window" due to the relative transparency of the atmosphere within this region.
The strength of CFC absorption bands and the unique susceptibility of the atmosphere at wavelengths where CFCs (indeed all covalent fluorine compounds) absorb radiation creates a "super" greenhouse effect from CFCs and other unreactive fluorine-containing gases such as perfluorocarbons, HFCs, HCFCs, bromofluorocarbons, SF, and NF. This "atmospheric window" absorption is intensified by the low concentration of each individual CFC. Because CO is close to saturation with high concentrations and few infrared absorption bands, the radiation budget and hence the greenhouse effect has low sensitivity to changes in CO concentration; the increase in temperature is roughly logarithmic. Conversely, the low concentration of CFCs allow their effects to increase linearly with mass, so that chlorofluorocarbons are greenhouse gases with a much higher potential to enhance the greenhouse effect than CO.
Groups are actively disposing of legacy CFCs to reduce their impact on the atmosphere.
According to NASA in 2018, the hole in the ozone layer has begun to recover as a result of CFC bans. However, research released in 2019 reports an alarming increase in CFCs, pointing to unregulated use in China. | 1 | Applied and Interdisciplinary Chemistry |
For materials that are difficult to sinter, a process called liquid phase sintering is commonly used. Materials for which liquid phase sintering is common are SiN, WC, SiC, and more. Liquid phase sintering is the process of adding an additive to the powder which will melt before the matrix phase. The process of liquid phase sintering has three stages:
*rearrangement – As the liquid melts capillary action will pull the liquid into pores and also cause grains to rearrange into a more favorable packing arrangement.
*solution-precipitation – In areas where capillary pressures are high (particles are close together) atoms will preferentially go into solution and then precipitate in areas of lower chemical potential where particles are not close or in contact. This is called contact flattening. This densifies the system in a way similar to grain boundary diffusion in solid state sintering. Ostwald ripening will also occur where smaller particles will go into solution preferentially and precipitate on larger particles leading to densification.
*final densification – densification of solid skeletal network, liquid movement from efficiently packed regions into pores.
For liquid phase sintering to be practical the major phase should be at least slightly soluble in the liquid phase and the additive should melt before any major sintering of the solid particulate network occurs, otherwise rearrangement of grains will not occur. Liquid phase sintering was successfully applied to improve grain growth of thin semiconductor layers from nanoparticle precursor films. | 1 | Applied and Interdisciplinary Chemistry |
The compound is unaffected by acids. It can even be recrystallized from conc. HNO.
The protons in the 2- and 5-positions rapidly exchange with deuterium oxide under alkaline conditions. Sodium cyanide catalyzes this reaction. | 0 | Theoretical and Fundamental Chemistry |
In the developed world, the estimated daily intake of CoQ has been determined at 3–6 mg per day, derived primarily from meat.
South Koreans have an estimated average daily CoQ (Q + Q) intake of 11.6 mg/d, derived primarily from kimchi. | 1 | Applied and Interdisciplinary Chemistry |
The P element is a class II transposon, and moves by a DNA-based "cut and paste" mechanism. The recognition sequence comprises four exons separated by three introns. Complete splicing of the introns produces the transposase enzyme, while alternative partial splicing of introns 1 and 2, leaving only intron 3 in the mRNA transcript, encodes the P element repressor. The complete, autonomous P element encodes a transposase enzyme, which recognizes the 31-bp terminal inverted repeats at either end of the P element and catalyzes P element excision and re-insertion. The complete element is 2,907 bp in length; non-autonomous P elements contain an internal deletion of varying length which abolishes transposase production, but such elements can still be mobilized if a functional transposase is encoded elsewhere in the genome. P element insertion and subsequent excision necessarily leaves behind 8-bp direct repeats at the excision site; thus the presence of such repeats is indicative of previous P element activity.
All P elements have a canonical structure containing 31-bp terminal inverted repeats and 11-bp internal inverted repeats located at the THAP domain of the transposase. The shortest and longest P elements are non-autonomous elements. The longest P elements encode transposase needed for transposition. The same sequence that encodes the transposase also encodes a suppressor of transposition, which accumulates in the cytoplasm during the development of cells. Thus, in a cross of a P or M male with a P female, the female cytoplasm contains the suppressor, which binds to any P elements and prevents their transposition. | 1 | Applied and Interdisciplinary Chemistry |
Ribozymes, antisense oligonucleotides, and more recently RNAi have been used to target mRNA molecules involved in asthma. These experiments have suggested that siRNA may be used to combat other respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis. COPD is characterized by goblet cell hyperplasia and mucus hypersecretion. Mucus secretion was found to be reduced when the transforming growth factor (TGF)-α was targeted by siRNA in NCI-H292 human airway epithelial cells. In addition to mucus hypersecretion, chronic inflammation and damaged lung tissue are characteristic of COPD and asthma. The transforming growth factor TGF-β is thought to play a role in these manifestations. As a result, when interferon (IFN)-γ was used to knock down TGF-β, fibrosis of the lungs, caused by damage and scarring to lung tissue, was improved. | 1 | Applied and Interdisciplinary Chemistry |
For ionic compounds, the standard enthalpy of formation is equivalent to the sum of several terms included in the Born–Haber cycle. For example, the formation of lithium fluoride,
may be considered as the sum of several steps, each with its own enthalpy (or energy, approximately):
# , the standard enthalpy of atomization (or sublimation) of solid lithium.
# , the first ionization energy of gaseous lithium.
# , the standard enthalpy of atomization (or bond energy) of fluorine gas.
# , the electron affinity of a fluorine atom.
# , the lattice energy of lithium fluoride.
The sum of these enthalpies give the standard enthalpy of formation () of lithium fluoride:
In practice, the enthalpy of formation of lithium fluoride can be determined experimentally, but the lattice energy cannot be measured directly. The equation is therefore rearranged to evaluate the lattice energy: | 0 | Theoretical and Fundamental Chemistry |
Since NMR spectroscopy has been available to chemists, there have been numerous studies on the applications of this technique. One of these noted the difference in the chemical shift (i.e. the distance between the peaks) of two diastereomers. Conversely, two compounds that are enantiomers have the same NMR spectral properties. It was reasoned that if a mix of enantiomers could be converted into a mix of diastereomers by bonding them to another chemical that was itself chiral, it would be possible to distinguish this new mixture using NMR, and therefore learn about the original enantiomeric mixture. The first popular example of this technique was published in 1969 by Harry S. Mosher. The chiral agent used was a single enantiomer of MTPA (α-methoxy-α-(trifluoromethyl)phenylacetic acid), also known as Moshers acid. The corresponding acid chloride is also known as Moshers acid chloride, and the resultant diastereomeric esters are known as Moshers esters. Another system is Pirkles Alcohol developed in 1977. | 0 | Theoretical and Fundamental Chemistry |
Demarçay's interests moved from organic chemistry to organometallics and then to inorganic chemistry. He applied for a professorial position at the Academie des sciences in 1878, but was not accepted.
He became particularly interested in studying nitrogen sulfides, publishing three papers in 1880–1881. These compounds appear stable at room temperature, but are sensitive to heat, friction, and shock, and are likely to explode when heated. During an experiment with nitrogen and sulfur, a cast-iron vessel exploded and destroyed the sight in one of his eyes.
He established his own private laboratory at 2 Boulevard Berthier, Paris. In 1881–1882, he developed a vacuum system to control temperature during experiments. 1.5 metres high, it consisted of 3 concentric vessels and a compressor driven by a six horsepower gas engine. Temperature in the center vessel could be reduced to −85 °C. Demarçay used this to study the volatility of substances such as zinc, cadmium, and gold at low temperatures.
Demarçay became a specialist in reading the line patterns of spectroscopy. He developed new techniques for the identification of spectra from rare earth metals. He developed an instrument for obtaining spectra, using an induction coil with pure platinum electrodes to produce a high spark temperature that eliminated impurities that could cause foreign spectral lines. By eliminating sources of error, he made it possible to separate out purer samples of various rare earths than had previously been available.
In 1896, he suspected that samples of the recently discovered element samarium were contaminated with another unknown element, predicting that it would be located between samarium and gadolinium. To obtain pure enough samples, he developed a new separation technique involving crystallization of double magnesium nitrate salts. By 1901, he had isolated samples of sufficient purity to confirm the isolation of europium.
In 1898, using his skills of spectroscopy, he help Marie and Pierre Curie confirm the isolation of a new element, radium. After extracting polonium from pitchblende they observed that the remaining sample was still radioactive. They consulted Demarçay, who reported a line in the spectrograph indicative of a new element. | 1 | Applied and Interdisciplinary Chemistry |
As shown in the figure, a protein is firstly conjugated with the initiator and the polymer chain then grows from the protein core in a controlled manner via living polymerization. Likewise, to the earlier discussed methods, grafting from approach can be designed for site-specific or random attachment. | 1 | Applied and Interdisciplinary Chemistry |
The GLIC receptor is a bacterial (loeobacter) igand-gated on hannel, homolog to the nicotinic acetylcholine receptors. It is a proton-gated (the channel opens when it binds a proton, ion), cation-selective channel (it selectively lets the positive ions through). Like the nicotinic acetylcholine receptors is a functional pentameric oligomer (the channel normally works as an assembly of five subunits). However while its eukaryotic homologues are hetero-oligomeric (assembled from different subunits), all until now known bacteria known to express LICs encode a single monomeric unit, indicating the GLIC to be functionally homo-oligomeric (assembled from identical subunits).
The similarity of amino-acid sequence to the eukaryotic LGICs is not localized to any single or particular tertiary domain, indicating the similar function of the GLIC to its eukaryotic equivalents. Regardless, the purpose of regulating the threshold for action potential excitation in the nerve signal transmission of multicellular organisms cannot translate to single-cell organisms, thereby not making the purpose of bacterial LGICs immediately obvious. | 1 | Applied and Interdisciplinary Chemistry |
In cycloalkanes, each carbon is bonded nonpolar covalently to two carbons and two hydrogen. The carbons have sp hybridization and should have ideal bond angles of 109.5°. Due to the limitations of cyclic structure, however, the ideal angle is only achieved in a six carbon ring — cyclohexane in chair conformation. For other cycloalkanes, the bond angles deviate from ideal.
Molecules with a high amount of ring strain consist of three, four, and some five-membered rings, including: cyclopropanes, cyclopropenes, cyclobutanes, cyclobutenes, [1,1,1]propellanes, [2,2,2]propellanes, epoxides, aziridines, cyclopentenes, and norbornenes. These molecules have bond angles between ring atoms which are more acute than the optimal tetrahedral (109.5°) and trigonal planar (120°) bond angles required by their respective sp and sp bonds. Because of the smaller bond angles, the bonds have higher energy and adopt more p-character to reduce the energy of the bonds. In addition, the ring structures of cyclopropanes/enes and cyclclobutanes/enes offer very little conformational flexibility. Thus, the substituents of ring atoms exist in an eclipsed conformation in cyclopropanes and between gauche and eclipsed in cyclobutanes, contributing to higher ring strain energy in the form of van der Waals repulsion.
monocycles
*cyclopropane (29 kcal/mol), CH — the C-C-C bond angles are 60° whereas tetrahedral 109.5° bond angles are expected. The intense angle strain leads to nonlinear orbital overlap of its sp orbitals. Because of the bond's instability, cyclopropane is more reactive than other alkanes. Since any three points make a plane and cyclopropane has only three carbons, cyclopropane is planar. The H-C-H bond angle is 115° whereas 106° is expected as in the CH groups of propane.
*cyclobutane (26.3 kcal/mol), CH — if cyclobutane were completely square planar, its bond angles would be 90° whereas tetrahedral 109.5° bond angles are expected. However, the actual C-C-C bond angle is 88° because it has a slightly folded form to relieve some torsional strain at the expense of slightly more angle strain. The high strain energy of cyclobutane is primarily from angle strain.
*cyclopentane (7.4 kcal/mol), CH — if it was a completely regular planar pentagon its bond angles would be 108°, but tetrahedral 109.5° bond angles are expected. However, it has an unfixed puckered shape that undulates up and down.
*cyclohexane (1.3 kcal/mol), CH — Although the chair conformation is able to achieve ideal angles, the unstable half-chair conformation has angle strain in the C-C-C angles which range from 109.86° to 119.07°.
Bicyclics
*[[Bicyclobutane|bicyclo[1.1.0]butane]] (66.3 kcal/mol),
*[[housane|bicyclo[1.2.0]pentane]] (54.7 kcal/mol),
*[[bicyclo[1.3.0]hexane]] (26 kcal/mol),
*norbornane (16.6 kcal/mol),
Ring strain can be considerably higher in bicyclic systems. For example, bicyclobutane, CH, is noted for being one of the most strained compounds that is isolatable on a large scale; its strain energy is estimated at 63.9 kcal mol (267 kJ mol).
Cyclopropane has a lesser amount of ring strain since it has the least amount of unsaturation; as a result, increasing the amount of unsaturation leads to greater ring strain. For example, cyclopropene has a greater amount of ring strain than cyclopropane because it has more unsaturation. | 0 | Theoretical and Fundamental Chemistry |
Feringa was born as the son of farmer Geert Feringa (1918–1993) and his wife Lies Feringa née Hake (1924–2013). Feringa was the second of ten siblings in a Catholic family. He spent his youth on the family's farm, which is directly on the border with Germany, in Barger-Compascuum in the Bourtange moor. He is of Dutch and German descent. Among his ancestors is the settler Johann Gerhard Bekel. Together with his wife Betty Feringa, he has three daughters. He lives in Paterswolde near Groningen. | 0 | Theoretical and Fundamental Chemistry |
From 1985 to 1991, Hierlemann studied chemistry at the University of Tübingen, Germany. He received a PhD from the University of Tübingen in 1996 for his work on Mass-sensitive detection of organic volatiles using modified polysiloxanes. 1997–98 he held postdoctoral positions at Texas A&M University in College Station, Texas, USA, and at Sandia National Laboratories in Albuquerque, New Mexico, USA. From 1999 to 2004 he was research team leader at the Physical Electronics Laboratory in the Department of Physics of ETH Zürich, Switzerland, becoming associate professor for microsensors in 2004. In 2008 he was named full professor of Biosystems Engineering, Department of Biosystems Science and Engineering of ETH Zurich in Basel, Switzerland. | 0 | Theoretical and Fundamental Chemistry |
The Biogeography of Deep-Water Chemosynthetic Ecosystems is a field project of the Census of Marine Life programme (CoML). The main aim of ChEss is to determine the biogeography of deep-water chemosynthetic ecosystems at a global scale and to understand the processes driving these ecosystems. ChEss addresses the main questions of CoML on diversity, abundance and distribution of marine species, focusing on deep-water reducing environments such as hydrothermal vents, cold seeps, whale falls, sunken wood and areas of low oxygen that intersect with continental margins and seamounts. | 0 | Theoretical and Fundamental Chemistry |
Borate esters are organic compounds, which are conveniently prepared by the stoichiometric condensation reaction of boric acid with alcohols (or their chalcogen analogs). | 0 | Theoretical and Fundamental Chemistry |
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian mimics is that predators only need one unpleasant encounter with one member of a set of Müllerian mimics, and thereafter avoid all similar coloration, whether or not it belongs to the same species as the initial encounter. It is named after the German naturalist Fritz Müller, who first proposed the concept in 1878, supporting his theory with the first mathematical model of frequency-dependent selection, one of the first such models anywhere in biology.
Müllerian mimicry was first identified in tropical butterflies that shared colourful wing patterns, but it is found in many groups of insects such as bumblebees, and other animals such as poison frogs and coral snakes. The mimicry need not be visual; for example, many snakes share auditory warning signals. Similarly, the defences involved are not limited to toxicity; anything that tends to deter predators, such as foul taste, sharp spines, or defensive behaviour can make a species unprofitable enough to predators to allow Müllerian mimicry to develop.
Once a pair of Müllerian mimics has formed, other mimics may join them by advergent evolution (one species changing to conform to the appearance of the pair, rather than mutual convergence), forming mimicry rings. Large rings are found for example in velvet ants. Since the frequency of mimics is positively correlated with survivability, rarer mimics are likely to adapt to resemble commoner models, favouring both advergence and larger Müllerian mimicry rings. Where mimics are not strongly protected by venom or other defences, honest Müllerian mimicry becomes, by degrees, the better-known bluffing of Batesian mimicry. | 1 | Applied and Interdisciplinary Chemistry |
For a system undergoing a reversible reaction described by the general chemical equation
a thermodynamic equilibrium constant, denoted by , is defined to be the value of the reaction quotient Q when forward and reverse reactions occur at the same rate. At chemical equilibrium, the chemical composition of the mixture does not change with time, and the Gibbs free energy change for the reaction is zero. If the composition of a mixture at equilibrium is changed by addition of some reagent, a new equilibrium position will be reached, given enough time. An equilibrium constant is related to the composition of the mixture at equilibrium by
where {X} denotes the thermodynamic activity of reagent X at equilibrium, [X] the numerical value of the corresponding concentration in moles per liter, and γ the corresponding activity coefficient. If X is a gas, instead of [X] the numerical value of the partial pressure in bar is used. If it can be assumed that the quotient of activity coefficients, , is constant over a range of experimental conditions, such as pH, then an equilibrium constant can be derived as a quotient of concentrations.
An equilibrium constant is related to the standard Gibbs free energy change of reaction by
where R is the universal gas constant, T is the absolute temperature (in kelvins must be a pure number and cannot have a dimension, since logarithms can only be taken of pure numbers. must also be a pure number. On the other hand, the reaction quotient at equilibrium
does have the dimension of concentration raised to some power (see , below). Such reaction quotients are often referred to, in the biochemical literature, as equilibrium constants.
For an equilibrium mixture of gases, an equilibrium constant can be defined in terms of partial pressure or fugacity.
An equilibrium constant is related to the forward and backward rate constants, k and k of the reactions involved in reaching equilibrium: | 0 | Theoretical and Fundamental Chemistry |
Dr. Keith Fagnou was born on June 27, 1971, in Saskatoon, Saskatchewan. Fagnou, a former naval reserve officer, pursued studies at the University of Saskatchewan and received a Bachelor of Education (B.Ed.) in 1995. After teaching at the high school level for a short period, he continued his studies in chemistry at the University of Toronto in 1998 under the supervision of Mark Lautens. In 2000 he received his M.Sc. degree, and in 2002 his Ph.D. Professor Lautens said that Keith "was exceptionally bright and exceptionally down-to-earth and was the most productive person, in the history of his research group." After his PhD, he joined the faculty at the University of Ottawa as an assistant professor and in 2007 was promoted to associate professor with tenure and awarded a University of Ottawa Research Chair in the Development of Novel Catalytic Transformations.
While at the University of Ottawa, he established a research program primarily devoted to the development of novel "direct arylation" reactions which allow for the rapid synthesis of important building blocks in medicinal chemistry. Of note, the development of direct arylation of benzene and pyridine N-oxide. Members of his research group are sometimes referred to as "The Fagnou Factory". His contributions in the field were rewarded with numerous awards and have been included in reviews published on the subject.
Dr. Keith Fagnou died of complications resulting from a H1N1 influenza infection on November 11, 2009, at the age of 38.
The University of Ottawa established the "Keith Fagnou Scholarship in Science" in his memory. The members of his research group also organized a symposium (KFOS) in his honour which was held May 5–7, 2010. The Pacifichem chemistry conference also held a memorial symposium titled "C-H Functionalization, Memorial Symposium for Professor Keith Fagnou". In 2011, Keith was recognized as the #77 chemist in the world over the period 2000-2010 on the basis of citations per paper, according to Thomson-Reuters' Sciencewatch.com. | 0 | Theoretical and Fundamental Chemistry |
Hardenability is the depth to which a steel is hardened after putting it through a heat treatment process. It should not be confused with hardness, which is a measure of a sample's resistance to indentation or scratching. It is an important property for welding, since it is inversely proportional to weldability, that is, the ease of welding a material. | 1 | Applied and Interdisciplinary Chemistry |
N-philes are group of radical molecules which are specifically attracted to the C=N bonds, defying often the selectivity rules of electrophilic attack. N-philes can often masquerade as electrophiles, where acyl radicals are excellent examples which interact with pi electrons of aryl groups. | 0 | Theoretical and Fundamental Chemistry |
Like other enzymes, the activity of FF ATP synthase is reversible. Large-enough quantities of ATP cause it to create a transmembrane proton gradient, this is used by fermenting bacteria that do not have an electron transport chain, but rather hydrolyze ATP to make a proton gradient, which they use to drive flagella and the transport of nutrients into the cell.
In respiring bacteria under physiological conditions, ATP synthase, in general, runs in the opposite direction, creating ATP while using the proton motive force created by the electron transport chain as a source of energy. The overall process of creating energy in this fashion is termed oxidative phosphorylation.
The same process takes place in the mitochondria, where ATP synthase is located in the inner mitochondrial membrane and the F-part projects into the mitochondrial matrix. By pumping proton cations into the matrix, the ATP-synthase converts ADP into ATP. | 0 | Theoretical and Fundamental Chemistry |
Many natural phenols are chiral. An example of such molecules is catechin. Cavicularin is an unusual macrocycle because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality and axial chirality. | 0 | Theoretical and Fundamental Chemistry |
Many problems in molecular reaction dynamics demand the simultaneous measurement of a particle's speed and angular direction; the most demanding require the measurement of this velocity in coincidence with internal energy. Studies of molecular reactions, energy transfer processes and photodissociation can only be understood completely if the internal energies and velocities of all products can be specified.
Product imaging approaches this goal by determining the three-dimensional velocity distribution of one state-selected product of the reaction. For a reaction producing two products, because the speed of the unobserved sibling product is related to that of the measured product through conservation of momentum and energy, the internal state of the sibling can often be inferred. | 0 | Theoretical and Fundamental Chemistry |
A key concept in the dynamics of vortices is the vorticity, a vector that describes the local rotary motion at a point in the fluid, as would be perceived by an observer that moves along with it. Conceptually, the vorticity could be observed by placing a tiny rough ball at the point in question, free to move with the fluid, and observing how it rotates about its center. The direction of the vorticity vector is defined to be the direction of the axis of rotation of this imaginary ball (according to the right-hand rule) while its length is twice the ball's angular velocity. Mathematically, the vorticity is defined as the curl (or rotational) of the velocity field of the fluid, usually denoted by and expressed by the vector analysis formula , where is the nabla operator and is the local flow velocity.
The local rotation measured by the vorticity must not be confused with the angular velocity vector of that portion of the fluid with respect to the external environment or to any fixed axis. In a vortex, in particular, may be opposite to the mean angular velocity vector of the fluid relative to the vortex's axis. | 1 | Applied and Interdisciplinary Chemistry |
The second law of thermodynamics is a statistical law. Hence, occasionally, single molecules may not obey the law. All molecules are subject to the molecular storm, i.e. the random movement of molecules in the cytoplasm and the extracellular fluid. Molecular demons or molecular machines either biological or artificially constructed are continuously pushed around by the random thermal motion in a direction that sometimes violates the law. When this happens and the gliding back of the macromolecule from the movement it had made or the conformational change it underwent to its original state can be prevented, as is the case with molecular demons, the molecule works as a ratchet; it is possible to observe for example the creation of a gradient of ions or other molecules across the cell membrane, the movement of motor proteins along filament proteins or also the accumulation of products deriving from an enzymatic reaction. Even some artificial molecular machines and experiments are capable of forming a ratchet apparently defying the second law of thermodynamics. All these molecular demons have to be reset to their original state consuming external energy that is subsequently dissipated as heat. This final step in which entropy increases is therefore irreversible. If the demons were reversible, no work would be done. | 0 | Theoretical and Fundamental Chemistry |
The ASTM D6866 method has been developed to certify the biologically derived content of bioplastics. Cosmic rays colliding with the atmosphere mean that some of the carbon is the radioactive isotope carbon-14. CO from the atmosphere is used by plants in photosynthesis, so new plant material will contain both carbon-14 and carbon-12. Under the right conditions, and over geological timescales, the remains of living organisms can be transformed into fossil fuels. After ~100,000 years all the carbon-14 present in the original organic material will have undergone radioactive decay leaving only carbon-12. A product made from biomass will have a relatively high level of carbon-14, while a product made from petrochemicals will have no carbon-14. The percentage of renewable carbon in a material (solid or liquid) can be measured with an accelerator mass spectrometer.
There is an important difference between biodegradability and biobased content. A bioplastic such as high-density polyethylene (HDPE) can be 100% biobased (i.e. contain 100% renewable carbon), yet be non-biodegradable. These bioplastics such as HDPE nonetheless play an important role in greenhouse gas abatement, particularly when they are combusted for energy production. The biobased component of these bioplastics is considered carbon-neutral since their origin is from biomass. | 0 | Theoretical and Fundamental Chemistry |
Reis was born and has always lived in Porto, being one of three children of a chemical engineering professor and a domestic. Reis spent a small part of his childhood in Metangula, Mozambique, a small town near Lake Niassa, while his father was engaged in military service during the Portuguese Colonial War. He is married with Olga Paiva and has one son, Bernardo Reis (born in 2001). He is a strong supporter of FC Porto.
Reis graduated in Metallurgical Engineering, University of Porto, Portugal, in 1990. He then completed a master's degree at the University of Porto, Portugal, in 1994. Reis did his PhD on Polymer Engineering – Biomaterials, Regenerative Medicine & Tissue Engineering, in the University of Minho, Portugal and Brunel University London, in 1999. He also completed a Doctor of Science (D.Sc.) degree on Biomedical Engineering - Biomaterials & Tissue Engineering, by University of Minho, Portugal, in 2007.
Reis has also received two Honoris Causa degrees: A first in Medicine from University of Granada, Spain, in 2010 and a second in Engineering from University Polytechnica of Bucharest, Romania, in 2018. | 1 | Applied and Interdisciplinary Chemistry |
The radiation of heat is generally denoted by the word emission. It is frequently described that surfaces "emit" radiation, however this is purely a simplification. According to the conservation of energy, emission always takes place at the expense of other forms of energy (electrical, chemical, etc.). Hence only material particles can emit heat, not geometrical volumes or surfaces. In reality, the radiation comes from the particles within a body and passes through its surfaces. | 0 | Theoretical and Fundamental Chemistry |
In May, a new method using an altered version of HIV as a lentivirus vector was reported in the treatment of 50 children with ADA-SCID obtaining positive results in 48 of them, this method is expected to be safer than retroviruses vectors commonly used in previous studies of SCID where the development of leukemia was usually observed and had already been used in 2019, but in a smaller group with X-SCID.
In June a clinical trial on six patients affected with transthyretin amyloidosis reported a reduction the concentration of missfolded transthretin (TTR) protein in serum through CRISPR-based inactivation of the TTR gene in liver cells observing mean reductions of 52% and 87% among the lower and higher dose groups.This was done in vivo without taking cells out of the patient to edit them and reinfuse them later.
In July results of a small gene therapy phase I study was published reporting observation of dopamine restoration on seven patients between 4 and 9 years old affected by aromatic L-amino acid decarboxylase deficiency (AADC deficiency). | 1 | Applied and Interdisciplinary Chemistry |
The major source of sound when a droplet hits a liquid surface is the resonance of excited bubbles trapped underwater. These oscillating bubbles are responsible for most liquid sounds, such as running water or splashes, as they actually consist of many drop-liquid collisions. | 1 | Applied and Interdisciplinary Chemistry |
DNA banking is used to conserve genetic material, especially that of organisms that face extinction. This is a more prominent issue today due to deforestation and climate change, which serve as a threat to biodiversity. The genetic information can be stored within lambda phage and plasma vectors. The National Institute of Agrobiological Sciences (NIAS) DNA Bank, for example, collects the DNA of agricultural organisms, such as rice and fish, for scientific research. Most DNA provided by DNA banks is used for studies to attempt to develop more productive or more environmentally friendly agricultural species. Some DNA banks also store the DNA of rare or endangered species to ensure their survival.
The DNA bank can be used to compare and analyze DNA samples. Comparison of DNA samples allowed scientists to work on the Human Genome Project, which maps out many of the genes on human DNA. It has also led to the development of preventive genetics. Samples from the DNA bank have been used to identify patterns and determine which genes lead to specific disorders. Once people know which genes lead to disorders, people can take steps to lessen the effects of that disorder. This can occur through adjustments in lifestyle, as demonstrated in preventive healthcare, or even through gene therapy. DNA can be banked at any time during a person's life.
DNA banks were introduced to the criminal justice system in the 1980s. This system makes it possible to rule out or confirm the verdict of a suspect based on their personal genetic code. Once an individual’s DNA is stored, it remains in the system permanently; allowing law enforcement to identify and track criminals more easily. There is some controversy about this topic as some individuals believe the storage of citizen's DNA is an invasion of privacy.
DNA banking capsules are also starting to be used for retaining the DNA of the deceased, a service offered by some funeral homes. | 1 | Applied and Interdisciplinary Chemistry |
Langmuir is a peer-reviewed scientific journal that was established in 1985 and is published by the American Chemical Society. It is the leading journal focusing on the science and application of systems and materials in which the interface dominates structure and function. Research areas covered include surface and colloid chemistry.
Langmuir publishes original research articles, invited feature articles, perspectives, and editorials.
The title honors Irving Langmuir, winner of the 1932 Nobel Prize for Chemistry. The founding editor-in-chief was Arthur W. Adamson. | 0 | Theoretical and Fundamental Chemistry |
During his chemical revolution, Lavoisier created a new instrument for precisely measuring out gases. He called this instrument the gazomètre. He had two different versions; the one he used in demonstrations to the Académie and to the public, which was a large expensive version meant to make people believe that it had a large precision, and the smaller, more lab practical, version with a similar precision. This more practical version was cheaper to construct, allowing more chemists to use Lavoisier's instrument. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to solid electrolyte systems under high temperatures (usually higher than 200 °C), EPOC has rarely been reported in low-temperature aqueous systems (particularly at room temperature). Only a few examples have been demonstrated for the EPOC in an aqueous electrolyte solution at ambient temperature: H oxidation at Pt catalyst surface in alkaline solutions, hydrocarbon isomerization reaction occurring at the nanoparticulate Pt catalyst, hydrazine oxidation operating at the Ni alloy catalyst in alkaline media, and reduction at the Pd-based gas diffusion electrode. Even though the perturbation of the local work function and tuning of surface binding strengths of intermediate species were suggested as the origin for the EPOC effects in the liquid electrolyte systems as similar to the EPOC examples of high-temperature solid electrolyte systems, thorough theoretical studies supported by clear experimental evidence have not been addressed. Very recently, it was additionally hypothesized for the cases of the hydrazine oxidation and the CO reduction that the mechanistic origin of the EPOC phenomena observed in these cases can be contributed to structurally non-disparate transition states and/or surface bound intermediate species for the corresponding bifurcated faradaic and non-faradaic reactions. | 0 | Theoretical and Fundamental Chemistry |
The equation is also usable as a PVT equation for compressible fluids (e.g. polymers). In this case specific volume changes are small and it can be written in a simplified form:
where p is the pressure, V is specific volume, T is the temperature and A, B, C are parameters. | 0 | Theoretical and Fundamental Chemistry |
Amino acids contain both amino and carboxylic acid functional groups. (In biochemistry, the term amino acid is used when referring to those amino acids in which the amino and carboxylate functionalities are attached to the same carbon, plus proline which is not actually an amino acid).
Modified amino acids are sometimes observed in proteins; this is usually the result of enzymatic modification after translation (protein synthesis). For example, phosphorylation of serine by kinases and dephosphorylation by phosphatases is an important control mechanism in the cell cycle. Only two amino acids other than the standard twenty are known to be incorporated into proteins during translation, in certain organisms:
* Selenocysteine is incorporated into some proteins at a UGA codon, which is normally a stop codon.
* Pyrrolysine is incorporated into some proteins at a UAG codon. For instance, in some methanogens in enzymes that are used to produce methane.
Besides those used in protein synthesis, other biologically important amino acids include carnitine (used in lipid transport within a cell), ornithine, GABA and taurine. | 0 | Theoretical and Fundamental Chemistry |
In genetics and molecular biology, a corepressor is a molecule that represses the expression of genes. In prokaryotes, corepressors are small molecules whereas in eukaryotes, corepressors are proteins. A corepressor does not directly bind to DNA, but instead indirectly regulates gene expression by binding to repressors.
A corepressor downregulates (or represses) the expression of genes by binding to and activating a repressor transcription factor. The repressor in turn binds to a gene's operator sequence (segment of DNA to which a transcription factor binds to regulate gene expression), thereby blocking transcription of that gene. | 1 | Applied and Interdisciplinary Chemistry |
* Менделеев Д. И. [http://runivers.ru/bookreader/book144952/#page/3/mode/1up Периодический закон (DjVu)]. Т. 1. // Собрание сочинений в 3 томах — М.: Издательство Академии наук СССР — via Runivers
* Менделеев Д. И. [http://runivers.ru/bookreader/book144957/#page/3/mode/1up Растворы (DjVu)]. Т. 2. (DjVu)]. Т. 2. // Собрание сочинений в 3 томах — М.: Издательство Академии наук СССР — via Runivers
* Менделеев Д. И. [http://runivers.ru/bookreader/book144965/#page/3/mode/1up Периодический закон. Дополнительные материалы (DjVu)]. Т. 3. // Собрание сочинений в 3 томах — М.: Издательство Академии наук СССР — via Runivers
* Менделеев Д. И. [http://nn.mi.ras.ru/?bi=125 Ещё о расширении жидкостей (Ответ профессору Авенариусу)]. — СПб.: Тип. В. Демакова, 1884. — 18 с.
* Менделеев Д. И. [http://nn.mi.ras.ru/?bi=127 Об опытах над упругостью газов]. Сообщение Д. И. Менделеева в Императорском Русском техническом обществе — 21 янв. 1881 г. — СПб., 1881. — 22 с.
* Менделеев Д. И. [http://nn.mi.ras.ru/?bi=146 Дополнения к познанию России]. Посмертное издание. СПб.: А. С. Суворин, 1907. — 109 с. + I л. портрет.
* Менделеев Д. И. [http://nn.mi.ras.ru/?bi=446 Изоморфизм в связи с другими отношениями кристаллической формы к составу]. Диссертация, представленная при окончании курса в Главном педагогическом институте студентом Д. Менделеевым. — СПб., 1856. — 234 с.
* Менделеев Д. И. [http://e-heritage.ru/ras/view/publication/general.html?id=42069948 О сопротивлении жидкостей и о воздухоплавании]: Вып. 1. — СПб.: Тип. В. Демакова, 1880. — 80 с.: табл.
* Менделеев Д. И. Заветные мысли (1905)
* Менделеев Д. И. Попытка химического понимания мирового эфира (1902)
* 54 articles for the Brockhaus and Efron Encyclopedic Dictionary | 0 | Theoretical and Fundamental Chemistry |
* Single molecule DNA sequencing requires a high level of precision to match the confidence from the redundant read coverage provided by current next-generation sequencing technologies.
* Nicks on both strands at similar positions resulting in low template during sequence-by-synthesis.
* Fluorochrome-labeled nucleotides are not removed after incorporation and because of these bulky labels, multiple incorporation might be difficult. | 1 | Applied and Interdisciplinary Chemistry |
Ernst Homburg was born in Venlo, the Netherlands, on 2 August 1952.
From 1964 to 1969 he was educated at the Protestant Lyceum (nowadays Huygens Lyceum), Eindhoven. From 1969 to 1978 Homburg studied chemistry at the Free University Amsterdam and at the University of Amsterdam. At the Free University he followed a course in the History of Science by Professor Reijer Hooykaas, one of the Dutch pioneers in this field. Homburg wrote a thesis on the Disproportionation of Propene.
In 1978 and 1979 he worked at the Department of Pharmacy of the University of Groningen and from 1979 to 1983 he was research fellow in the History of Science in the Chemistry Department of the University of Nijmegen. Here he worked on a study of the development of the dye industry, supervised by Willem J. Hornix. From 1984 to 1993 he was assistant professor for Chemistry and Society at the same department. In the period from 1989 to 1993 he was also a part-time assistant professor for History of Technology in the Department of Philosophy and Social Sciences of the Technical University Eindhoven.
In 1993 he received his Doctorate in History at the University of Nijmegen with a dissertation entitled Van beroep "Chemiker": De opkomst van de industriële chemicus en het polytechnische onderwijs in Duitsland, 1790-1850 ("Chemiker" by occupation : the rise of the industrial chemist and polytechnic education in Germany, 1790-1850). His supervisor was dr. P.M.M. (Paul) Klep (Professor of Economic and Social History).
From 1993 to 2001 Homburg became assistant professor History of Technology in the Department of History of the Faculty of Arts and Sciences of Maastricht University. This period was followed by a full professorate at the same institute on a chair endowed by the Dutch Stichting Historie der Techniek (SHT) (Foundation for the History of Technology).
In August 2018 he retired. | 1 | Applied and Interdisciplinary Chemistry |
For the 3D uniform Fermi gas, with fermions of spin-½, the number of particles as a function of the energy is obtained by substituting the Fermi energy by a variable energy :
from which the density of states (number of energy states per energy per volume) can be obtained. It can be calculated by differentiating the number of particles with respect to the energy:
This result provides an alternative way to calculate the total energy of a Fermi sphere of fermions (which occupy all energy states within the Fermi sphere): | 0 | Theoretical and Fundamental Chemistry |
Cast iron DWV pipe and fittings are still used in premium construction because they muffle the sound of wastewater rushing through them, but today they are rarely joined with traditional lead joints. Instead, pipe and fittings with plain (non-belled) connections are butted against each other, and clamped with special rubber sleeve (or "no-hub") fittings. The rubber sleeves are typically secured with stainless steel worm drive clamping bands, which compress the rubber to make a tight seal around the pipes and fittings. These pipe clamps are similar to hose clamps, but are heavier-duty and ideally are made completely of stainless steel (including the screw) to provide maximum service life. Optionally, the entire rubber sleeve may be jacketed with thin sheet metal, to provide extra stiffness, durability, and resistance to accidental penetration by a misplaced nail or screw. Although the fittings are not cheap, they are reasonably durable (the rubber is typically neoprene or flexible PVC).
An alternative design also allows the selective use of belled fittings made entirely of flexible rubber, including more-complex shapes such as wyes or tee-wyes. They are secured to cast iron pipe segments by use of stainless steel worm drive clamps. Because these fittings are not as stiff as traditional cast-iron fittings, the heavy pipe segments may need better anchoring and support to prevent unwanted movement. The lighter rubber fittings may not muffle sound as well as the heavy cast-iron fittings.
An advantage of flexible rubber fittings is that they can accommodate small misalignments and can be flexed slightly for installation in tight locations. A flexible fitting may be preferred to connect a shower or heavy tub to the drainage system without transmitting slight movements or stresses, which could eventually cause cracking. Flexible fittings may also be used to reduce the transmission of vibration into the DWV system.
If necessary, clamped joints can be disassembled later, and the fittings and pipe may be reconfigured. However, it is often not customary to re-use the clamps and rubber sleeves, which their previous installation may deform and may not seal well after rearranging. Clamped fittings may occasionally need to be disassembled to provide access for "snaking" or "rodding-out" with a unique tool to clear blockage or clogs. This is also an indication that a clean-out fitting could be installed to provide easier future access. | 1 | Applied and Interdisciplinary Chemistry |
In proteins and amino acids, the α-carbon is the backbone carbon before the carbonyl carbon atom in the molecule. Therefore, reading along the backbone of a typical protein would give a sequence of –[N—Cα—carbonyl C]– etc. (when reading in the N to C direction). The α-carbon is where the different substituents attach to each different amino acid. That is, the groups hanging off the chain at the α-carbon are what give amino acids their diversity. These groups give the α-carbon its stereogenic properties for every amino acid except for glycine. Therefore, the α-carbon is a stereocenter for every amino acid except glycine. Glycine also does not have a β-carbon, while every other amino acid does.
The α-carbon of an amino acid is significant in protein folding. When describing a protein, which is a chain of amino acids, one often approximates the location of each amino acid as the location of its α-carbon. In general, α-carbons of adjacent amino acids in a protein are about 3.8 ångströms (380 picometers) apart. | 0 | Theoretical and Fundamental Chemistry |
Calcium carbide is produced industrially in an electric arc furnace from a mixture of lime and coke at approximately . This is an endothermic reaction requiring per mole and high temperatures to drive off the carbon monoxide. This method has not changed since its invention in 1892:
:CaO + 3 C → CaC + CO
The high temperature required for this reaction is not practically achievable by traditional combustion, so the reaction is performed in an electric arc furnace with graphite electrodes. The carbide product produced generally contains around 80% calcium carbide by weight. The carbide is crushed to produce small lumps that can range from a few mm up to 50 mm. The impurities are concentrated in the finer fractions. The CaC content of the product is assayed by measuring the amount of acetylene produced on hydrolysis. As an example, the British and German standards for the content of the coarser fractions are 295 L/kg and 300 L/kg respectively (at 101 kPa pressure and temperature). Impurities present in the carbide include calcium phosphide, which produces phosphine when hydrolysed.
This reaction was an important part of the industrial revolution in chemistry, and was made possible in the United States as a result of massive amounts of inexpensive hydroelectric power produced at Niagara Falls before the turn of the 20th century.
The electric arc furnace method was discovered in 1892 by T. L. Willson, and independently in the same year by H. Moissan. In Jajce, Bosnia and Herzegovina, the Austrian industrialist Josef Kranz and his "Bosnische-Elektrizitäts AG" company, whose successor later became "Elektro-Bosna", opened the largest chemical factory for the production of calcium carbide at the time in Europe in 1899. A hydroelectric power station on the Pliva river with an installed capacity of 8 MW was constructed to supply electricity for the factory, the first power station of its kind in Southeast Europe, and became operational on 24 March 1899. | 1 | Applied and Interdisciplinary Chemistry |
The stopped-flow method depends on the existence of spectroscopic properties that can be used for following the reaction. When that is not the case quenched flow provides an alternative that uses conventional chemical methods for analysis. Instead of a mechanical stopping system the reaction is stopped by quenching, the products being delivered to a recipient that stops the reaction immediately, either by instantaneous freezing or by denaturing the enzyme with a chemical denaturant or exposing the sample to a denaturing light source. As in the continuous-flow method, the time between mixing and quenching can be varied by varying the length of the tube.
The pulsed quenched flow method introduced by Alan Fersht and Ross Jakes overcomes the need for a long tube. The reaction is initiated exactly as in a stopped-flow experiment, but there is a third syringe that brings about quenching a definite and preset time after the initiation.
Quenched flow has both advantages and disadvantages with respect to stopped flow. On the one hand, chemical analysis makes it clear what process is being measured, whereas it may not always be obvious what process a spectroscopic signal represents. On the other hand, quenched flow is much more laborious, as each point along the time course must be determined separately. The image at left for catalysis by nitrogenase from Klebsiella pneumoniae illustrates both of these points: the agreement in half times indicates that the absorbance at 420 nm measured the release of P, but the quenched-flow experiment required 11 data points. | 0 | Theoretical and Fundamental Chemistry |
In continuum mechanics the flow velocity in fluid dynamics, also macroscopic velocity in statistical mechanics, or drift velocity in electromagnetism, is a vector field used to mathematically describe the motion of a continuum. The length of the flow velocity vector is scalar, the flow speed.
It is also called velocity field; when evaluated along a line, it is called a velocity profile (as in, e.g., law of the wall). | 1 | Applied and Interdisciplinary Chemistry |
HTS experiments have the ability to screen tens of thousands (or even millions) of compounds rapidly. Hence, it is a challenge to glean chemical/biochemical significance from mounds of data in the process of hit selection. To address this challenge, appropriate analytic methods have been adopted for hit selection. There are two main strategies of selecting hits with large effects. One is to use certain metric(s) to rank and/or classify the compounds by their effects and then to select the largest number of potent compounds that is practical for validation assays. The other strategy is to test whether a compound has effects strong enough to reach a pre-set level. In this strategy, false-negative rates (FNRs) and/or false-positive rates (FPRs) must be controlled.
There are two major types of HTS experiments, one without replicates (usually in primary screens) and one with replicates (usually in confirmatory screens). The analytic methods for hit selection differ in those two types of HTS experiments. For example, the z-score method is suitable for screens without replicates whereas the t-statistic is suitable for screens with replicate. The calculation of SSMD for screens without replicates also differs from that for screens with replicates. | 1 | Applied and Interdisciplinary Chemistry |
Velocimetry can be traced back to the days of Leonardo da Vinci, who would float grass seeds on a flow and sketch the resulting trajectories of the seeds that he observed (a Lagrangian measurement). Eventually da Vinci's flow visualizations were used in his cardio vascular studies, attempting to learn more about blood flow throughout the human body.
Methods similar to da Vinci's were carried out for close to four hundred years due to technological limitations. One other notable study comes from Felix Savart in 1833. Using a stroboscopic instrument, he sketched water jet impacts.
In the late 19th century a huge breakthrough was made in these technologies when it became possible to take photographs of flow patterns. One notable instance of this is Ludwig Mach using particles unresolvable by the naked eye to visualize streamlines. Another notable contribution occurred in the 20th century by Étienne-Jules Marey who used photographic techniques to introduce the concept of the smoke box. This model allowed both for the directions of the flow to be tracked but also the speed, as streamlines closer together indicated faster flow.
More recently, high speed cameras and digital technology has revolutionized the field. allowing for the possibility of many more techniques and rendering of flow fields in three dimensions. | 1 | Applied and Interdisciplinary Chemistry |
Because of the decreased basicity compared to pyridine, electrophilic substitution of pyrimidine is less facile. Protonation or alkylation typically takes place at only one of the ring nitrogen atoms. Mono-N-oxidation occurs by reaction with peracids.
Electrophilic C-substitution of pyrimidine occurs at the 5-position, the least electron-deficient. Nitration, nitrosation, azo coupling, halogenation, sulfonation, formylation, hydroxymethylation, and aminomethylation have been observed with substituted pyrimidines.
Nucleophilic C-substitution should be facilitated at the 2-, 4-, and 6-positions but there are only a few examples. Amination and hydroxylation have been observed for substituted pyrimidines. Reactions with Grignard or alkyllithium reagents yield 4-alkyl- or 4-aryl pyrimidine after aromatization.
Free radical attack has been observed for pyrimidine and photochemical reactions have been observed for substituted pyrimidines. Pyrimidine can be hydrogenated to give tetrahydropyrimidine. | 1 | Applied and Interdisciplinary Chemistry |
The specific characteristics of MSGE as compared with MSNE is that the emitted neutral particles are limited to gas molecules. MSGE is opposite to Mechanically Stimulated Gas Absorption that usually occurs under fretting corrosion of metals, exposure to gases at high pressures, etc.
There are three main sources of MSGE:
: I. Gas molecules adsorbed on the surface of a solid
: IIa. Gases dissolved in the material bulk
: IIb. Gases occluded or trapped in micro- and nanovoids, discontinuities and on defects in the material bulk
: III. Gases generated as a result of mechanical activation of chemical reactions.
Generally, for producing MSGE, the mechanical action on the solid can be of any type including tension, compression, torsion, shearing, rubbing, fretting, rolling, indentation, etc. In previous studies carried out by various groups it was found that MSGE is associated mainly with plastic deformation, fracture, wear and other irreversible modifications of a solid. Under elastic deformation MSGE is almost negligible and only was observed just below elastic limit due to possible microplastic deformation.
In accordance to the main sources, the emitted gases usually contain hydrogen (source type IIa), argon (for coatings obtained using PVD in Ar plasma - source type IIb), methane (source type III), water (source type I and/or III), carbon mono- and dioxide (source type I/III).
The knowledge on the mechanisms of MSGE is still vague. On the basis of the experimental findings it was speculated that the following processes can be related with MSGE:
# Transport of gas atoms by moving dislocations
# Gas diffusion in the bulk driven by gradient of mechanical stress
# Phase transformation induced by deformation
# Removal of oxide and other surface layers, which prevent exit of dissolved atoms on the surface
# Extension of free surface
Thermal effect seems to be irrelevant to the gas emission under light load conditions. | 0 | Theoretical and Fundamental Chemistry |
A different, albeit physically closely related challenge is the detection of deeply lying flaws and inhomogeneities in electrically conducting solid materials.
In the traditional version of eddy current testing an alternating (AC) magnetic field is used to induce eddy currents inside the material to be investigated. If the material contains a crack or flaw which make the spatial distribution of the electrical conductivity nonuniform, the path of the eddy currents is perturbed and the impedance of the coil which generates the AC magnetic field is modified. By measuring the impedance of this coil, a crack can hence be detected. Since the eddy currents are generated by an AC magnetic field, their penetration into the subsurface region of the material is limited by the skin effect. The applicability of the traditional version of eddy current testing is therefore limited to the analysis of the immediate vicinity of the surface of a material, usually of the order of one millimeter. Attempts to overcome this fundamental limitation using low frequency coils and superconducting magnetic field sensors have not led to widespread applications.
A recent technique, referred to as Lorentz force eddy current testing (LET), exploits the advantages of applying DC magnetic fields and relative motion providing deep and relatively fast testing of electrically conducting materials. In principle, LET represents a modification of the traditional eddy current testing from which it differs in two aspects, namely (i) how eddy currents are induced and (ii) how their perturbation is detected. In LET eddy currents are generated by providing the relative motion between the conductor under test and a permanent magnet (see figure 10). If the magnet is passing by a defect, the Lorentz force acting on it shows a distortion whose detection is the key for the LET working principle. If the object is free of defects, the resulting Lorentz force remains constant. | 1 | Applied and Interdisciplinary Chemistry |
As a precursor of a photosensitizer, 5ALA is also used as an add-on agent for photodynamic therapy. In contrast to larger photosensitizer molecules, it is predicted by computer simulations to be able to penetrate tumor cell membranes. | 1 | Applied and Interdisciplinary Chemistry |
The adsorption of methylene blue serves as an indicator defining the adsorptive capacity of granular activated carbon in water filters. Adsorption of methylene blue is very similar to adsorption of pesticides from water, this quality makes methylene blue serve as a good predictor for filtration qualities of carbon. It is as well a quick method of comparing different batches of activated carbon of the same quality.
A color reaction in an acidified, aqueous methylene blue solution containing chloroform can detect anionic surfactants in a water sample. Such a test is known as an MBAS assay (methylene blue active substances assay).
The MBAS assay cannot distinguish between specific surfactants, however. Some examples of anionic surfactants are carboxylates, phosphates, sulfates, and sulfonates. | 0 | Theoretical and Fundamental Chemistry |
In 1916, Irving Langmuir presented his model for the adsorption of species onto simple surfaces. Langmuir was awarded the Nobel Prize in 1932 for his work concerning surface chemistry. He hypothesized that a given surface has a certain number of equivalent sites to which a species can “stick”, either by physisorption or chemisorption. His theory began when he postulated that gaseous molecules do not rebound elastically from a surface, but are held by it in a similar way to groups of molecules in solid bodies.
Langmuir published two papers that confirmed the assumption that adsorbed films do not exceed one molecule in thickness. The first experiment involved observing electron emission from heated filaments in gases. The second, a more direct evidence, examined and measured the films of liquid onto an adsorbent surface layer. He also noted that generally the attractive strength between the surface and the first layer of adsorbed substance is much greater than the strength between the first and second layer. However, there are instances where the subsequent layers may condense given the right combination of temperature and pressure. | 0 | Theoretical and Fundamental Chemistry |
Atomic hydrogen diffusing through metals may collect at internal defects like inclusions and laminations and form molecular hydrogen. High pressures may be built up at such locations due to continued absorption of hydrogen leading to blister formation, growth and eventual bursting of the blister. Such hydrogen induced blister cracking has been observed in steels, aluminium alloys, titanium alloys and nuclear structural materials. Metals with low hydrogen solubility (such as tungsten) are more susceptible to blister formation. While in metals with high hydrogen solubility like vanadium, hydrogen prefers to induce stable metal-hydrides instead of bubbles or blisters. | 1 | Applied and Interdisciplinary Chemistry |
If the pressure difference is zero, as in a soap film without gravity, the interface will assume the shape of a minimal surface. | 1 | Applied and Interdisciplinary Chemistry |
The degree of stomatal resistance can be determined by measuring leaf gas exchange of a leaf. The transpiration rate is dependent on the diffusion resistance provided by the stomatal pores and also on the humidity gradient between the leafs internal air spaces and the outside air. Stomatal resistance (or its inverse, stomatal conductance) can therefore be calculated from the transpiration rate and humidity gradient. This allows scientists to investigate how stomata respond to changes in environmental conditions, such as light intensity and concentrations of gases such as water vapor, carbon dioxide, and ozone. Evaporation (E') can be calculated as
where e and e are the partial pressures of water in the leaf and in the ambient air respectively, P is atmospheric pressure, and r is stomatal resistance.
The inverse of r is conductance to water vapor (g), so the equation can be rearranged to
and solved for g:
Photosynthetic CO assimilation (A) can be calculated from
where C and C are the atmospheric and sub-stomatal partial pressures of CO respectively. The rate of evaporation from a leaf can be determined using a photosynthesis system. These scientific instruments measure the amount of water vapour leaving the leaf and the vapor pressure of the ambient air. Photosynthetic systems may calculate water use efficiency (A/E), g, intrinsic water use efficiency (A/g), and C. These scientific instruments are commonly used by plant physiologists to measure CO uptake and thus measure photosynthetic rate. | 0 | Theoretical and Fundamental Chemistry |
Using Kickstarter, the project's founders raised $484,000 on June 8, 2013. This was significantly more than the initial target of $65,000.
Seeds were initially scheduled to be delivered in April 2014, and subsequently scheduled for the fall of 2014. In March 2016, delivery of seeds was forecast for 2016 on the Glowing Plant website. The company encountered difficulty in producing plants that emit significant amounts of light, resulting in a transition to producing moss that emits a patchouli scent. They later announced via email December 2017 that the company was permanently ceasing operations. | 1 | Applied and Interdisciplinary Chemistry |
Temperature is another interesting parameter to discuss since protein solubility is a function of temperature. In protein crystallization, manipulation of temperature to yield successful crystals is one common strategy. Unlike pH, temperature of different components of the crystallography experiments could impact the final results such as temperature of buffer preparation, temperature of the actual crystallization experiment, etc. | 0 | Theoretical and Fundamental Chemistry |
The Calvin cycle starts by using the enzyme RuBisCO to fix CO into five-carbon Ribulose bisphosphate (RuBP) molecules. The result is unstable six-carbon molecules that immediately break down into three-carbon molecules called 3-phosphoglyceric acid, or 3-PGA.
The ATP and NADPH made in the light reactions is used to convert the 3-PGA into glyceraldehyde-3-phosphate, or G3P sugar molecules. Most of the G3P molecules are recycled back into RuBP using energy from more ATP, but one out of every six produced leaves the cycle—the end product of the dark reactions. | 0 | Theoretical and Fundamental Chemistry |
L-isoaspartyl methyltransferase repairs isoaspartate and D-aspartate residues by sticking a methyl group onto the side chain carboxyl group in the residue, creating an ester. The ester rapidly and spontaneously turns into the succinimide (red), and randomly turns back into normal aspartic acid (black) or isoaspartate again (green) for another attempt. | 1 | Applied and Interdisciplinary Chemistry |
Since the model assumes homogeneous mixture, the theory is well applicable to study the explosive behavior of solid fuels (spontaneous ignition of bio fuels, organic materials, garbage, etc.,). This is also used to design explosives and fire crackers. The theory predicted critical values accurately for low conductivity fluids/solids with high conductivity thin walled containers. | 1 | Applied and Interdisciplinary Chemistry |
There is usually a high-pressure turbine at one end, followed by an intermediate-pressure turbine, and finally one, two, or three low-pressure turbines, and the shaft that connects to the generator. As steam moves through the system and loses pressure and thermal energy, it expands in volume, requiring increasing diameter and longer blades at each succeeding stage to extract the remaining energy. The entire rotating mass may be over 200 metric tons and long. It is so heavy that it must be kept turning slowly even when shut down (at 3 rpm) so that the shaft will not bow even slightly and become unbalanced. This is so important that it is one of only six functions of blackout emergency power batteries on site. (The other five being emergency lighting, communication, station alarms, generator hydrogen seal system, and turbogenerator lube oil.)
For a typical late 20th-century power station, superheated steam from the boiler is delivered through diameter piping at and to the high-pressure turbine, where it falls in pressure to and to in temperature through the stage. It exits via diameter cold reheat lines and passes back into the boiler, where the steam is reheated in special reheat pendant tubes back to . The hot reheat steam is conducted to the intermediate pressure turbine, where it falls in both temperature and pressure and exits directly to the long-bladed low-pressure turbines and finally exits to the condenser. | 1 | Applied and Interdisciplinary Chemistry |
Reverse transfection is a technique for the transfer of genetic material into cells. As DNA is printed on a glass slide for the transfection process (the deliberate introduction of nucleic acids into cells) to occur before the addition of adherent cells, the order of addition of DNA and adherent cells is reverse that of conventional transfection. Hence, the word “reverse” is used. | 1 | Applied and Interdisciplinary Chemistry |
In electrochemistry, there are two types of ideal electrode, the ideal polarizable electrode and the ideal non-polarizable electrode. Simply put, the ideal polarizable electrode is characterized by charge separation at the electrode-electrolyte boundary and is electrically equivalent to a capacitor, while the ideal non-polarizable electrode is characterized by no charge separation and is electrically equivalent to a short. | 0 | Theoretical and Fundamental Chemistry |
N-substituted derivatives are somewhat stable. They are invoked but rarely observed as intermediates in the Mannich reaction. These N,N,N-trisubstituted hexahydro-1,3,5-triazines arise from the condensation of the amine and formaldehyde as illustrated by the route to 1,3,5-trimethyl-1,3,5-triazacyclohexane:
Although adducts generated from primary amines or ammonia are usually unstable, the hemiaminals have been trapped in a cavity. | 0 | Theoretical and Fundamental Chemistry |
The Galileo spacecraft launched on October 18, 1989, the Ulysses on October 6, 1990, the Cassini on October 15, 1997, and the New Horizons on January 19, 2006. All of these spacecraft contain the general purpose heat source (GPHS) RTG commissioned by the U.S. Department of Energy. The GPHS-RTG employs identical heat-to-electrical conversion technology used in the MHW-RTGs from the Voyager missions, using SiGe thermocouples/unicouples and the Pu-238–fueled GPHS. New Horizons made its historic flyby past Pluto and its moons on July 14, 2015 ([http://pluto.jhuapl.edu/ see JHU Applied Physics website]). The spacecrafts next destination will be a small Kuiper Belt object (KBO) known as 486958 Arrokoth that orbits nearly a billion miles beyond Pluto. Based on performance, data and modeling for the SiGe alloy RTGs, the GPHS-RTGs on Ulysses, Cassini and New Horizons' are expected to meet or exceed the remaining power performance requirements for their deep-space missions. | 0 | Theoretical and Fundamental Chemistry |
The pheromone is synthesized in the same region as venom, or other primary hormonal departments within the organism. Often, trail pheromone synthesis occurs in the ventral venom gland, poison gland, Dufour's gland, sternal gland, or hindgut. When secreted, the pheromone is dropped in a blotch-like fashion from the foraging organism onto the surface leading to the food source. As the organism proceeds to the food source, the trail pheromone creates a narrow and precise pathway between the food source and the nesting location, which another organism of the same species, and often the same nest, follows precisely. Commonly, an organism, when initially laying down the trail may renew the trail a number of times to demonstrate the value of the food source while running in tandem. Once the trail is laid, other members of the species will recognize the chemical signal and follow the trail, and each individually renew the trail on the way back to the home source. While this pheromone is constantly deposited by its members, the chemicals diffuse up into the environment propagating its message. Once the food source runs out the organisms will simply skip the task of renewing the trail on the way back, thus resulting in the diffusion and weakening of the pheromone. Studies have shown that with quality of food, distance from nest, and amounts of food, the strength of the trail pheromone may vary. Often the foraging individual may synthesize the trail pheromone as a mixture of chemicals produced by different glands which allows such specificity. While members of the same species who discovered the food constantly renew this trail pathway, as the chemical is secreted into the environment as a signal for food in their umwelt, the very same chemical can often be interpreted as a territorial mark for outside species. | 1 | Applied and Interdisciplinary Chemistry |
Most enzymes are sensitive to pH and have specific ranges of activity. All have an optimum pH. The pH can stop enzyme activity by denaturating (altering) the three-dimensional shape of the enzyme by breaking ionic, and hydrogen bonds. Most enzymes function between a pH of 6 and 8; however pepsin in the stomach works best at a pH of 2 and trypsin at a pH of 8. | 1 | Applied and Interdisciplinary Chemistry |
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