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Baopuzi () is a literary work written by Ge Hong (AD 283–343), (), a scholar during the turbulent Jin dynasty.
Baopuzi is divided into two main sections, the esoteric Neipian () and the section intended for the public to understand: Waipian (). The Taoist Inner Chapters discuss topics such as techniques to achieve "hsien" (), Chinese alchemy, elixirs, and demonology. The Confucian Outer Chapters discuss Chinese literature, Legalism, politics, and society. | 1 | Applied and Interdisciplinary Chemistry |
Sea salt aerosols can alter the Earth radiation budget through directly scattering solar radiation (direct effect), and indirectly changing the cloud albedo by serving as CCN (indirect effect). Different models give different predictions of annual mean radiative forcing induced by sea salt direct effect, but most of the previous studies give a number around 0.6-1.0 W m. Radiative forcing caused by indirect effects show even greater variations in model prediction because of the parameterization of aerosol indirect effect. However, model results present a stronger indirect effect on the Southern Hemisphere. | 0 | Theoretical and Fundamental Chemistry |
* The compound is prepared as a byproduct of trioxidane production.
* has also been synthesized by reaction among peroxy radicals at low temperature. | 0 | Theoretical and Fundamental Chemistry |
Pipelines conveying flammable or explosive material, such as natural gas or oil, pose special safety concerns. While corrosion, pressure, and equipment failure are common causes, excavation damage is also a leading accident type that can be avoided by calling 811 before digging near pipelines.
*1965 – A 32-inch gas transmission pipeline, north of Natchitoches, Louisiana, belonging to the Tennessee Gas Pipeline exploded and burned from stress corrosion cracking failure on March 4, killing 17 people. At least 9 others were injured, and 7 homes 450 feet from the rupture were destroyed. This accident, and others of the era, led then-President Lyndon B. Johnson to call for the formation of a national pipeline safety agency in 1967. The same pipeline had also had an explosion on May 9, 1955, just 930 feet (280 m) from the 1965 failure.
*June 16, 1976 – A gasoline pipeline was ruptured by a road construction crew in Los Angeles, California. Gasoline sprayed across the area, and soon ignited, killing 9, and injuring at least 14 others. Confusion over the depth of the pipeline in the construction area seemed to be a factor in the accident.
*June 4, 1989 – The Ufa train disaster: Sparks from two passing trains detonated gas leaking from a LPG pipeline near Ufa, Russia. At least 575 people were reported killed.
*October 17, 1998 – 1998 Jesse pipeline explosion: A petroleum pipeline exploded at Jesse on the Niger Delta in Nigeria, killing about 1,200 villagers, some of whom were scavenging gasoline.
*June 10, 1999 – A pipeline rupture in a Bellingham, Washington park led to the release of 277,200 gallons of gasoline. The gasoline was ignited, causing an explosion that killed two children and one adult. Misoperation of the pipeline and a previously damaged section of the pipe that was not detected before were identified as causing the failure.
*August 19, 2000 – A natural gas pipeline rupture and fire near Carlsbad, New Mexico; this explosion and fire killed 12 members of an extended family. The cause was due to severe internal corrosion of the pipeline.
*July 30, 2004 – A major natural gas pipeline exploded in Ghislenghien, Belgium near Ath (thirty kilometres southwest of Brussels), killing at least 24 people and leaving 132 wounded, some critically.
*May 12, 2006 – An oil pipeline ruptured outside Lagos, Nigeria. Up to 200 people may have been killed. See Nigeria oil blast.
*November 1, 2007 – A propane pipeline exploded near Carmichael, Mississippi, about south of Meridian, Mississippi. Two people were killed instantly and an additional four were injured. Several homes were destroyed and sixty families were displaced. The pipeline is owned by Enterprise Products Partners LP, and runs from Mont Belvieu, Texas, to Apex, North Carolina. Inability to find flaws in pre-1971 ERW seam welded pipe flaws was a contributing factor to the accident.
*September 9, 2010 – 2010 San Bruno pipeline explosion: A 30-inch diameter high pressure natural gas pipeline owned by the Pacific Gas and Electric Company exploded in the Crestmoor residential neighborhood 2 mi (3.2 km) west of San Francisco International Airport, killing 8, injuring 58, and destroying 38 homes. Poor quality control of the pipe used & of the construction were cited as factors in the accident.
*June 27, 2014 – An explosion occurred after a natural gas pipe line ruptured in Nagaram village, East Godavari district, Andhra Pradesh, India causing 16 deaths and destroying "scores of homes".
*July 31, 2014 – On the night of July 31, a series of explosions originating in underground gas pipelines occurred in the city of Kaohsiung, Taiwan. Leaking gas filled the sewers along several major thoroughfares and the resulting explosions turned several kilometers of road surface into deep trenches, sending vehicles and debris high into the air and igniting fires over a large area. At least 32 people were killed and 321 injured. | 1 | Applied and Interdisciplinary Chemistry |
Downregulation of glycine-N-methyltransferase has been linked to hepatocellular carcinoma and pancreatic cancer. Serving this as a reliable marker for oncogenesis. When compared to patients with deletions in GNMT, patients with no deletions early-stage pancreatic cancer had twice the median months overall survival. | 1 | Applied and Interdisciplinary Chemistry |
These are the solid reactants from which it is proposed to prepare a solid crystalline compound. The selection of reactant chemicals depends on the reaction conditions and expected nature of the product. The reactants are dried thoroughly prior to weighing. As increase in surface area enhances the reaction rate, fine grained materials should be used if possible. | 1 | Applied and Interdisciplinary Chemistry |
*SNP detection
*Real-time nucleic acid detection
*Real-time PCR quantification
*Allelic discrimination and identification
*Multiplex PCR assays
*Diagnostic clinical assays | 1 | Applied and Interdisciplinary Chemistry |
Fluorescence correlation spectroscopy (FCS) is a statistical analysis, via time correlation, of stationary fluctuations of the fluorescence intensity. Its theoretical underpinning originated from L. Onsager's regression hypothesis. The analysis provides kinetic parameters of the physical processes underlying the fluctuations. One of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent particles (molecules) in solution. In this application, the fluorescence emitted from a very tiny space in solution containing a small number of fluorescent particles (molecules) is observed. The fluorescence intensity is fluctuating due to Brownian motion of the particles. In other words, the number of the particles in the sub-space defined by the optical system is randomly changing around the average number. The analysis gives the average number of fluorescent particles and average diffusion time, when the particle is passing through the space. Eventually, both the concentration and size of the particle (molecule) are determined. Both parameters are important in biochemical research, biophysics, and chemistry.
FCS is such a sensitive analytical tool because it observes a small number of molecules (nanomolar to picomolar concentrations) in a small volume (~1 μm). In contrast to other methods (such as HPLC analysis) FCS has no physical separation process; instead, it achieves its spatial resolution through its optics. Furthermore, FCS enables observation of fluorescence-tagged molecules in the biochemical pathway in intact living cells. This opens a new area, "in situ or in vivo biochemistry": tracing the biochemical pathway in intact cells and organs.
Commonly, FCS is employed in the context of optical microscopy, in particular confocal microscopy or two-photon excitation microscopy. In these techniques light is focused on a sample and the measured fluorescence intensity fluctuations (due to diffusion, physical or chemical reactions, aggregation, etc.) are analyzed using the temporal autocorrelation. Because the measured property is essentially related to the magnitude and/or the amount of fluctuations, there is an optimum measurement regime at the level when individual species enter or exit the observation volume (or turn on and off in the volume). When too many entities are measured at the same time the overall fluctuations are small in comparison to the total signal and may not be resolvable – in the other direction, if the individual fluctuation-events are too sparse in time, one measurement may take prohibitively too long. FCS is in a way the fluorescent counterpart to dynamic light scattering, which uses coherent light scattering, instead of (incoherent) fluorescence.
When an appropriate model is known, FCS can be used to obtain quantitative information such as
* diffusion coefficients
* hydrodynamic radii
* average concentrations
* kinetic chemical reaction rates
* singlet-triplet dynamics
Because fluorescent markers come in a variety of colors and can be specifically bound to a particular molecule (e.g. proteins, polymers, metal-complexes, etc.), it is possible to study the behavior of individual molecules (in rapid succession in composite solutions). With the development of sensitive detectors such as avalanche photodiodes the detection of the fluorescence signal coming from individual molecules in highly dilute samples has become practical. With this emerged the possibility to conduct FCS experiments in a wide variety of specimens, ranging from materials science to biology. The advent of engineered cells with genetically tagged proteins (like green fluorescent protein) has made FCS a common tool for studying molecular dynamics in living cells. | 0 | Theoretical and Fundamental Chemistry |
In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). In the canonical Watson-Crick base pairing, adenine (A) forms a base pair with thymine (T) and guanine (G) forms one with cytosine (C) in DNA. In RNA, thymine is replaced by uracil (U). Alternate hydrogen bonding patterns, such as the wobble base pair and Hoogsteen base pair, also occur—particularly in RNA—giving rise to complex and functional tertiary structures. Importantly, pairing is the mechanism by which codons on messenger RNA molecules are recognized by anticodons on transfer RNA during protein translation. Some DNA- or RNA-binding enzymes can recognize specific base pairing patterns that identify particular regulatory regions of genes.
Hydrogen bonding is the chemical mechanism that underlies the base-pairing rules described above. Appropriate geometrical correspondence of hydrogen bond donors and acceptors allows only the "right" pairs to form stably. DNA with high GC-content is more stable than DNA with low GC-content, but contrary to popular belief, the hydrogen bonds do not stabilize the DNA significantly and stabilization is mainly due to stacking interactions.
The larger nucleobases, adenine and guanine, are members of a class of doubly ringed chemical structures called purines; the smaller nucleobases, cytosine and thymine (and uracil), are members of a class of singly ringed chemical structures called pyrimidines. Purines are only complementary with pyrimidines: pyrimidine-pyrimidine pairings are energetically unfavorable because the molecules are too far apart for hydrogen bonding to be established; purine-purine pairings are energetically unfavorable because the molecules are too close, leading to overlap repulsion. The only other possible pairings are GT and AC; these pairings are mismatches because the pattern of hydrogen donors and acceptors do not correspond. The GU wobble base pair, with two hydrogen bonds, does occur fairly often in RNA. | 0 | Theoretical and Fundamental Chemistry |
Uranium rhodium germanium (URhGe) is the first discovered metal that becomes superconducting in the presence of an extremely strong electromagnetic field. Very unlike other superconducting materials, whose superconducting properties can be lost due to strong magnetic fields, uranium rhodium germanium actually regains superconducting abilities at about 8 teslas. | 1 | Applied and Interdisciplinary Chemistry |
[[Diels–Alder reaction|[4+2] cycloadditions]] of a diene and an alkene have been used as DCvC reactions. These reactions are often reversible at high temperatures. In the case of furan–maleimide adducts, the retro-cycloaddition is accessible at temperatures as low as 40 °C. | 0 | Theoretical and Fundamental Chemistry |
Texture can be determined by various methods. Some methods allow a quantitative analysis of the texture, while others are only qualitative. Among the quantitative techniques, the most widely used is X-ray diffraction using texture goniometers, followed by the electron backscatter diffraction (EBSD) method in scanning electron microscopes. Qualitative analysis can be done by Laue photography, simple X-ray diffraction or with a polarized microscope. Neutron and synchrotron high-energy X-ray diffraction are suitable for determining textures of bulk materials and in situ analysis, whereas laboratory x-ray diffraction instruments are more appropriate for analyzing textures of thin films.
Texture is often represented using a pole figure, in which a specified crystallographic axis (or pole) from each of a representative number of crystallites is plotted in a stereographic projection, along with directions relevant to the materials processing history. These directions define the so-called sample reference frame and are, because the investigation of textures started from the cold working of metals, usually referred to as the rolling direction RD, the transverse direction TD and the normal direction ND'. For drawn metal wires the cylindrical fiber axis turned out as the sample direction around which preferred orientation is typically observed (see below). | 1 | Applied and Interdisciplinary Chemistry |
There's evidence of very early metallurgy at Aratashen, going back to the first half of the sixth millennium BCE. According to A. Courcier,
At Aratashen and Khatunakh/Aknashen, there are similarities to the contemporary sites of Kultepe I, and Alikemek-Tepesi. Another prehistoric site that is close to Aratashen is Masis Blur. | 1 | Applied and Interdisciplinary Chemistry |
Campbell shows the effect of different nozzle areas on the steady-state running line. Automatic control of the area was disabled for this investigation. In service the area is open at idle and progressively closes as the engine accelerates as shown by the area scheduling. An adjustable nozzle is not added for this particular purpose but if an afterburner is fitted then it can be used to reduce idle thrust and quicken acceleration times up to the thrust where the afterburner becomes operational. The ideal fan operating line on an augmented turbofan sets fan pressure ratio as high as possible to optimize fan performance and thrust while keeping adequate fan stall margin. The fan operating line is controlled by varying the nozzle area which acts like a throttling valve. The throttling is a combination of thermal from the burning fuel and geometric from the adjustable nozzle area. | 0 | Theoretical and Fundamental Chemistry |
For safety and convenience diazomethane is always prepared as needed as a solution in ether and used as such. It converts carboxylic acids to methyl esters and phenols into their methyl ethers. The reaction is thought to proceed via proton transfer from carboxylic acid to diazomethane to give methyldiazonium cation, which reacts with the carboxylate ion to give the methyl ester and nitrogen gas. Labeling studies indicate that the initial proton transfer is faster than the methyl transfer step. Since proton transfer is required for the reaction to proceed, this reaction is selective for the more acidic carboxylic acids (pK ~ 5) and phenols (pK ~ 10) over aliphatic alcohols (pK ~ 15).
In more specialized applications, diazomethane and homologues are used in Arndt-Eistert synthesis and the Büchner–Curtius–Schlotterbeck reaction for homologation.
Diazomethane reacts with alcohols or phenols in presence of boron trifluoride (BF) to give methyl ethers.
Diazomethane is also frequently used as a carbene source. It readily takes part in 1,3-dipolar cycloadditions. | 0 | Theoretical and Fundamental Chemistry |
Aerial respiration is the gulping of air at the surface of water to directly extract oxygen from the atmosphere. Aerial respiration evolved in fish that were exposed to more frequent hypoxia; also, species that engage in aerial respiration tend to be more hypoxia tolerant than those which do not air-breath during the hypoxia.
There are two main types of air breathing fish—facultative and non-facultative. Under normoxic conditions facultative fish can survive without having to breathe air from the surface of the water. However, non-facultative fish must respire at the surface even in normal dissolved oxygen levels because their gills cannot extract enough oxygen from the water.
Many air breathing freshwater teleosts use ABOs to effectively extract oxygen from air while maintaining functions of the gills. ABOs are modified gastrointestinal tracts, gas bladders, and labyrinth organs; they are highly vascularized and provide additional method of extracting oxygen from the air. Fish also use ABO for storing the retained oxygen. | 0 | Theoretical and Fundamental Chemistry |
Free evolution of nuclear spins is governed by a Hamiltonian (), which in the case of liquid-state nuclear magnetic resonance may be split into two major terms. The first term () corresponds to the Zeeman interaction between spins and the external magnetic field, which includes chemical shift (). The second term () corresponds to the indirect spin-spin, or J-coupling, interaction.
, where:
, and
Here the summation is taken over the whole system of coupled spins; denotes the reduced Planck constant; denotes the gyromagnetic ratio of spin a; denotes the isotropic part of the chemical shift for the a-th spin; denotes the spin operator of the a-th spin; is the external magnetic field experienced by all considered spins, and; is the J-coupling constant between spins a and b.
Importantly, the relative strength of and (and therefore the spin dynamics behavior of such a system) depends on the magnetic field. For example, in conventional NMR, is typically larger than 1 T, so the Larmor frequency of H exceeds tens of MHz. This is much larger than -coupling values which are typically Hz to hundreds of Hz. In this limit, is a perturbation to . In contrast, at nanotesla fields, Larmor frequencies can be much smaller than -couplings, and dominates. | 0 | Theoretical and Fundamental Chemistry |
Red blood cell transketolase activity is reduced in deficiency of thiamine (vitamin B), and may be used in the diagnosis of Wernicke encephalopathy and other B-deficiency syndromes if the diagnosis is in doubt. Apart from the baseline enzyme activity (which may be normal even in deficiency states), acceleration of enzyme activity after the addition of thiamine pyrophosphate may be diagnostic of thiamine deficiency (0-15% normal, 15-25% deficiency, >25% severe deficiency). | 0 | Theoretical and Fundamental Chemistry |
There are many theories on the kinetics of the bonding process but the most common theory divides the process into four main stages.
The stages are:
# dissolution of the interlayer
# homogenization of the liquid
# isothermal solidification
# homogenization of the bond region | 1 | Applied and Interdisciplinary Chemistry |
Müllers 1879 account was one of the earliest uses of a mathematical model in evolutionary ecology, and the first exact model of frequency-dependent selection. Mallet calls Müllers mathematical assumption behind the model "beguilingly simple". Müller presumed that the predators had to attack n unprofitable prey in a summer to experience and learn their warning coloration. Calling a and a the total numbers of two unprofitable prey species, Müller then argued that, if the species are completely unalike they each lose n individuals. However, if they resemble each other,
then species 1 loses
individuals,
and species 2 loses
individuals.
Species 1 therefore gains
and species 2 similarly gains
in absolute numbers of individuals not killed.
The proportional gain compared to the total population of species 1 is
and similarly for species 2
, giving the per head fitness gain of the mimicry when the predators have been fully educated.
Hence, Müller concluded, the proportion g1:g2 was
, which equals , and the rarer species gains far more than the commoner one.
The model is an approximation, and assumes the species are equally unprofitable. If one is more distasteful than the other, then the relative gains differ further, the less distasteful species benefiting more (as a square of the relative distastefulness) from the protection afforded by mimicry. This can be thought of as parasitic or quasi-Batesian, the mimic benefiting at the expense of the model. Later models are more complex and take factors such as rarity into account. The assumption of a fixed number n to be attacked is questionable. Müller also effectively assumed a step function, when a gradual change (a functional response) is more plausible. | 1 | Applied and Interdisciplinary Chemistry |
PCBs have entered the environment through both use and disposal. The environmental fate of PCBs is complex and global in scale. | 1 | Applied and Interdisciplinary Chemistry |
The database houses a wide range of information available for samples from all over the globe to be grouped into two categories: (a) observations and measurements (e.g. mineral data, images, chemical analyses), for which robust data models already exist, and (b) interpretative results (e.g. P-T conditions, crystallization ages, cooling rates, etc.), which are conclusions based on the observational data. Development of a robust data model for interpretative data is currently underway as of December 2010. The database system is beginning to incorporate a number of tools for data analysis and calculation that adds considerable power to the researcher.
MetPetDB differs from other Geochemistry relational databases (e.g. [https://web.archive.org/web/20070610152747/http://georoc.mpch-mainz.gwdg.de/georoc/ GEOROC], [http://www.navdat.org NAVDAT], PetDB) in that it incorporates unpublished data in addition to data published in peer-reviewed journals. The vast majority of data collected by metamorphic geologists is not presented in publication, and therefore a forum for sharing this data with the public is an objective of MetPetDB. Contributors to MetPetDB also have the ability to store private data and create projects, or collections of private, public, and published data for sharing and organization. A comprehensive list of the publications and their published samples are located at [http://metpetdb.rpi.edu/MetPetRest/parse_publications.html MetPetDB Published Samples] | 0 | Theoretical and Fundamental Chemistry |
In physics, a mass balance, also called a material balance, is an application of conservation of mass to the analysis of physical systems. By accounting for material entering and leaving a system, mass flows can be identified which might have been unknown, or difficult to measure without this technique. The exact conservation law used in the analysis of the system depends on the context of the problem, but all revolve around mass conservation, i.e., that matter cannot disappear or be created spontaneously.
Therefore, mass balances are used widely in engineering and environmental analyses. For example, mass balance theory is used to design chemical reactors, to analyse alternative processes to produce chemicals, as well as to model pollution dispersion and other processes of physical systems. Closely related and complementary analysis techniques include the population balance, energy balance and the somewhat more complex entropy balance. These techniques are required for thorough design and analysis of systems such as the refrigeration cycle.
In environmental monitoring, the term budget calculations is used to describe mass balance equations where they are used to evaluate the monitoring data (comparing input and output, etc.). In biology, the dynamic energy budget theory for metabolic organisation makes explicit use of mass and energy balance. | 1 | Applied and Interdisciplinary Chemistry |
ProMax is a chemical process simulator for process troubleshooting and design, developed and sold by Bryan Research and Engineering, Inc. Initially released in late 2005, ProMax is a continuance of two previous process simulators, PROSIM and TSWEET. ProMax is considered the industry standard for designing amine gas treating and glycol dehydration units. | 1 | Applied and Interdisciplinary Chemistry |
Alongside strontium, dietary calcium is deposited in bones teeth, however Ca is more readily deposited than Sr in humans and animals who consume primarily or exclusively plants. Therefore, the greater the Ca:Sr ratio in sample, the more herbivorous the animal was likely to be. | 0 | Theoretical and Fundamental Chemistry |
Siefert writes:
: proved a remarkable relation which allows to express the free energy difference between two equilibrium systems by a nonlinear average over the work required to drive the system in a non-equilibrium process from one state to the other. By comparing probability distributions for the work spent in the original process with the time-reversed one, Crooks found a “refinement” of the Jarzynski relation (JR), now called the Crooks fluctuation theorem. Both, this relation and another refinement of the JR, the Hummer-Szabo relation became particularly useful for determining free energy differences and landscapes of biomolecules. These relations are the most prominent ones within a class of exact results (some of which found even earlier and then rediscovered) valid for non-equilibrium systems driven by time-dependent forces. A close analogy to the JR, which relates different equilibrium states, is the Hatano-Sasa relation that applies to transitions between two different non-equilibrium steady states.
This is shown to be a special case of a more general relation. | 0 | Theoretical and Fundamental Chemistry |
Diffusional flow is a regime typically below dislocation creep and occurs at high temperatures due to the diffusion of point defects in the material. Diffusional flow can be further broken down into more specific mechanisms: Nabarro–Herring creep, Coble creep, and Harper–Dorn creep.
While most materials will exhibit Nabarro-Herring creep and Coble creep, Harper-Dorn creep is quite rare, having only been reported in a select few materials at low stresses including aluminium, lead, and tin.
The equation for Nabarro-Herring creep is dominated by vacancy diffusion within the lattice, whereas Coble creep is dominated by vacancy diffusion within the grain boundaries. The equation for these mechanisms is shown below where is the applied shear stress, Ω is the atomic volume, k is the Boltzmann constant ,d is the grain size, T is the temperature, and is the effective diffusion coefficient.
The effective diffusion coefficient, = (the volumetric diffusion constant) for Nabarro-Herring creep which dominates at high temperatures, and (where is the grain boundary width and is the diffusion coefficient in the boundary) for Coble creep which dominates at low-temperatures.
From these equations it becomes clear that the boundary between boundary diffusion and lattice diffusion is heavily dependent on grain size. For systems with larger grains, the Nabarro-Herring lattice diffusion region of the deformation mechanism map will be larger than in maps with very small grains. Additionally, the larger the grains, the less diffusional creep and thus the power-law creep region of the map will be larger for large grained materials. Grain boundary engineering is thus an effective strategy to manipulate creep rates. | 1 | Applied and Interdisciplinary Chemistry |
Pittcon Editors’ Awards honoured the best new products on show at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, or Pittcon, for 20 years from 1996 having been established by Dr Gordon Wilkinson, managing editor of Analytical Instrument Industry Report (later Instrumenta). On 8 March 2015, the event returned to the Morial Convention Center in New Orleans and this was the last occasion when the awards were presented.
The independent awards, which represented the results of an informal poll of leading editors, had become an important feature of the worlds largest trade show for the laboratory equipment industry. Pittcon organisers and media center supported the scheme and provided details and photographs on the exhibitions Press and Media Information page. In 2016 the group of editors and journalists that formed the core of the judging panel reluctantly decided to discontinue the awards program citing gradually dwindling support from ever-busier media representatives. | 0 | Theoretical and Fundamental Chemistry |
Since coenzyme A is, in chemical terms, a thiol, it can react with carboxylic acids to form thioesters, thus functioning as an acyl group carrier. It assists in transferring fatty acids from the cytoplasm to mitochondria. A molecule of coenzyme A carrying an acyl group is also referred to as acyl-CoA. When it is not attached to an acyl group, it is usually referred to as CoASH or HSCoA. This process facilitates the production of fatty acids in cells, which are essential in cell membrane structure.
Coenzyme A is also the source of the phosphopantetheine group that is added as a prosthetic group to proteins such as acyl carrier protein and formyltetrahydrofolate dehydrogenase. | 1 | Applied and Interdisciplinary Chemistry |
RNA ladders composed of RNA molecular-weight size markers were initially developed by using the synthetic circle method to produce different-sized markers. This technique was improved upon by inventor Eric T. Kool to use circular DNA vectors as a method for producing RNA molecular-weight size markers. As referred to as the rolling circle method, the improvements of this technique stems from its efficiency in synthesizing RNA oligonucleotides. From the circular DNA template, single-stranded RNA varying in length from 4-1500 bp can be produced without the need for primers and by recycling nucleotide triphosphate. DNA can also be synthesized from the circular template, adding to this technique's versatility. In comparison to runoff transcription, the synthetic circle method produces RNA oligonucleotides without the runoff. In comparison to PCR, the synthetic circle method produces RNA oligonucleotides without the need for polymerase nor a thermal cycler. This method is also cost-efficient in its ability to synthesize grand amounts of product at a lower error rate than machine synthesizers. | 1 | Applied and Interdisciplinary Chemistry |
In the Organic Rankine Cycle (ORC), zeotropic mixtures are more thermally efficient than pure fluids. Due to their higher boiling points, zeotropic working fluids have higher net outputs of energy at the low temperatures of the Rankine Cycle than pure substances. Zeotropic working fluids condense across a range of temperatures, allowing external heat exchangers to recover the heat of condensation as a heat source for the Rankine Cycle. The changing temperature of the zeotropic working fluid can be matched to that of the fluid being heated or cooled to save waste heat because the mixture's evaporation process occurs at a temperature glide (see Pinch Analysis).
R21/R245fa and R152a/R245fa are two examples of zeotropic working fluids that can absorb more heat than pure R245fa due to their increased boiling points. The power output increases with the proportion of R152a in R152a/R245fa. R21/R245fa uses less heat and energy than R245fa. Overall, zeotropic mixture R21/R245fa has better thermodynamic properties than pure R245fa and R152a/R245fa as a working fluid in the ORC. | 1 | Applied and Interdisciplinary Chemistry |
A mesophilic start in surface bodies of waters hypothesis has evolved from Darwins concept of a warm little pond' and the Oparin-Haldane hypothesis. Freshwater bodies under temperate climates can accumulate prebiotic materials while providing suitable environmental conditions conducive to simple life forms. The climate during the Archaean is still a highly debated topic, as there is uncertainty about what continents, oceans, and the atmosphere looked like then. Atmospheric reconstructions of the Archaean from geochemical proxies and models state that sufficient greenhouse gases were present to maintain surface temperatures between 0-40 °C. Under this assumption, there is a greater abundance of moderate temperature niches in which life could begin.
Strong lines of evidence for mesophily from biomolecular studies include Galtiers G+C nucleotide thermometer. G+C are more abundant in thermophiles due to the added stability of an additional hydrogen bond not present between A+T nucleotides. rRNA sequencing on a diverse range of modern lifeforms show that LUCAs reconstructed G+C content was likely representative of moderate temperatures.
Although most modern phylogenies are thermophilic or hyperthermophilic, it is possible that their widespread diversity today is a product of convergent evolution and horizontal gene transfer rather than an inherited trait from LUCA. The reverse gyrase topoisomerase is found exclusively in thermophiles and hyperthermophiles as it allows for coiling of DNA. The reverse gyrase enzyme requires ATP to function, both of which are complex biomolecules. If an origin of life is hypothesised to involve a simple organism that had not yet evolved a membrane, let alone ATP, this would make the existence of reverse gyrase improbable. Moreover, phylogenetic studies show that reverse gyrase had an archaeal origin, and that it was transferred to bacteria by horizontal gene transfer. This implies that reverse gyrase was not present in the LUCA. | 0 | Theoretical and Fundamental Chemistry |
The Geochemical Society presents the following annual awards:
*V. M. Goldschmidt Award – the society's highest honor, it is awarded for major achievements in geochemistry or cosmochemistry.
*F.W. Clarke Medal – named after Frank Wigglesworth Clarke (1847–1931), a chemist who determined the composition of the Earth's crust, it goes to an early-career scientist for an outstanding contribution to geochemistry or cosmochemistry.
*C.C. Patterson Medal – named after Clair Cameron Patterson (1922–1995), who developed uranium–lead dating, it recognizes an innovative breakthrough in environmental geochemistry, particularly one of value to society.
*Alfred Treibs Medal – Named after Alfred E. Treibs (1899–1983), whose papers on porphyrins were the beginning of the field of organic chemistry, it is awarded by the Organic Geochemistry Division (OGD) for major achievements in organic geochemistry. The OGD also presents an annual Best Paper Award for a publication in the previous year.
*Geochemical Fellows – Starting in 1996, the Geochemical Society and the European Association of Geochemistry (EAG) bestow this honor on outstanding scientists who have made a major contribution to the field of geochemistry. Holders of the Goldschmidt and Treibs medals, as well as the Urey Medal of the EAG, are automatically inducted.
The Distinguished Service Award, which recognizes outstanding service to the Society or the geochemical community, is not awarded every year.
The Geochemical Society sponsors a special lecture at the annual meeting of the Geological Society of America. Called the F. Earl Ingerson Lecture Series, it honors the first president of the Geochemical Society. At the Goldschmidt Conference, the Paul W. Gast Lecture is awarded to a mid-career scientist (under 45 years old) in honor of the first Goldschmidt medalist. | 0 | Theoretical and Fundamental Chemistry |
Christof Fattinger at Hoffmann-La-Roche in Basel already conceived the physical principles of focal molography in the 1990s when he investigated the bidiffractive grating-coupler. Yet it only emerged in a scientific collaboration between ETH Zürich and the Roche Innovation Center Basel in Switzerland from 2014 to 2020. | 1 | Applied and Interdisciplinary Chemistry |
The Orbitrap is a high-resolution Fourier transform mass spectrometer that has recently been adapted to allow for site-specific analyses. Molecules introduced into the Orbitrap are fragmented, accelerated, and analyzed. Because the Orbitrap characterizes molecular masses by measuring oscillations at radio frequencies, it is able to reach very high levels of precision, depending on measurement method (i.e., down to 0.1 per mille for long integration times). It is significantly faster than site-specific isotope measurements that can be performed using NMR, and can measure molecules with different rare isotopes but the same nominal mass at natural abundances (unlike GC and LCMS). It is also widely generalizable to molecules that can be introduced via gas or liquid solvent. Resolution of the Orbitrap is such that nominal isobars (e.g., H versus N versus C enrichments) can be distinguished from one another, and so molecules do not need to be converted into a homogeneous substrate to facilitate isotope analysis. Like other isotope measurements, measurements of site-specific enrichments on the Orbitrap should be compared to a standard of known composition. | 0 | Theoretical and Fundamental Chemistry |
The ozone molecule is represented by two contributing structures. In reality the two terminal oxygen atoms are equivalent and the hybrid structure is drawn on the right with a charge of − on both oxygen atoms and partial double bonds with a full and dashed line and bond order .
For hypervalent molecules, the rationalization described above can be applied to generate contributing structures to explain the bonding in such molecules. Shown below are the contributing structures of a 3c-4e bond in xenon difluoride. | 0 | Theoretical and Fundamental Chemistry |
Cavitation is usually an undesirable occurrence. In devices such as propellers and pumps, cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency. Noise caused by cavitation can be particularly undesirable in naval vessels where such noise may render them more easily detectable by passive sonar. Cavitation has also become a concern in the renewable energy sector as it may occur on the blade surface of tidal stream turbines.
When the cavitation bubbles collapse, they force energetic liquid into very small volumes, thereby creating spots of high temperature and emitting shock waves, the latter of which are a source of noise. The noise created by cavitation is a particular problem for military submarines, as it increases the chances of being detected by passive sonar.
Although the collapse of a small cavity is a relatively low-energy event, highly localized collapses can erode metals, such as steel, over time. The pitting caused by the collapse of cavities produces great wear on components and can dramatically shorten a propellers or pumps lifetime.
After a surface is initially affected by cavitation, it tends to erode at an accelerating pace. The cavitation pits increase the turbulence of the fluid flow and create crevices that act as nucleation sites for additional cavitation bubbles. The pits also increase the components' surface area and leave behind residual stresses. This makes the surface more prone to stress corrosion. | 1 | Applied and Interdisciplinary Chemistry |
A single water molecule can participate in a maximum of four hydrogen bonds because it can accept two bonds using the lone pairs on oxygen and donate two hydrogen atoms. Other molecules like hydrogen fluoride, ammonia, and methanol can also form hydrogen bonds. However, they do not show anomalous thermodynamic, kinetic, or structural properties like those observed in water because none of them can form four hydrogen bonds: either they cannot donate or accept hydrogen atoms, or there are steric effects in bulky residues. In water, intermolecular tetrahedral structures form due to the four hydrogen bonds, thereby forming an open structure and a three-dimensional bonding network, resulting in the anomalous decrease in density when cooled below 4 °C. This repeated, constantly reorganizing unit defines a three-dimensional network extending throughout the liquid. This view is based upon neutron scattering studies and computer simulations, and it makes sense in the light of the unambiguously tetrahedral arrangement of water molecules in ice structures.
However, there is an alternative theory for the structure of water. In 2004, a controversial paper from Stockholm University suggested that water molecules in the liquid state typically bind not to four but only two others; thus forming chains and rings. The term "string theory of water" (which is not to be confused with the string theory of physics) was coined. These observations were based upon X-ray absorption spectroscopy that probed the local environment of individual oxygen atoms. | 1 | Applied and Interdisciplinary Chemistry |
An important disadvantage of polycrystalline NiAl-based alloys are their room-temperature and high-temperature brittleness, which interferes with potential structural applications. This brittleness is generally attributed to the inability of dislocations to move in the highly ordered lattices. The introduction of small amount of boron can drastically increase the ductility by suppressing intergranular fracture.
Ni-based superalloys derive their strength from the formation of γ precipitates (NiAl) in the γ phase (Ni) which strengthen the alloys through precipitation hardening. In these alloys the volume fraction of the γ precipitates is as high as 80%. Because of this high volume fraction, the evolution of these γ precipitates during the alloys life cycles is important: a major concern is the coarsening of these γ precipitates at high temperature (800 to 1000 °C), which greatly reduces the alloys strength. This coarsening is due to the balance between interfacial and elastic energy in the γ + γ phase and is generally inevitable over long durations of time. This coarsening problem is addressed by introducing other elements such as Fe, Cr and Mo, which generate multiphase configurations that can significantly increase the creep resistance. This creep resistance is attributed to the formation of inhomogeneous precipitate CrMoNi, which pins dislocations and prevents further coarsening of the γ phase. The addition of Fe and Cr also drastically increases the weldability of the alloy. | 1 | Applied and Interdisciplinary Chemistry |
In addition to the oxidation routes, diaryl sulfoxides can be prepared by two Friedel–Crafts arylations of sulfur dioxide using an acid catalyst:
:2 ArH + SO → ArSO + HO
Both aryl sulfinyl chlorides and diaryl sulfoxides can be also prepared from arenes through reaction with thionyl chloride in the presence of Lewis acid catalysts such as BiCl, Bi(OTf), LiClO, or NaClO. | 0 | Theoretical and Fundamental Chemistry |
Full-field displacement, elastic strain, and the GND density provide quantifiable information about the material's elastic and plastic behaviour at the microscale. Measuring strain at the microscale requires careful consideration of other key details besides the change in length/shape (e.g., local texture, individual grain orientations). These micro-scale features can be measured using different techniques, e.g., hole drilling, monochromatic or polychromatic energy-dispersive X-ray diffraction or neutron diffraction (ND). EBSD has a high spatial resolution and is relatively sensitive and easy to use compared to other techniques. Strain measurements using EBSD can be performed at a high spatial resolution, allowing researchers to study the local variation in strain within a material. This information can be used to study the deformation and mechanical behaviour of materials, to develop models of material behaviour under different loading conditions, and to optimise the processing and performance of materials. Overall, strain measurement using EBSD is a powerful tool for studying the deformation and mechanical behaviour of materials, and is widely used in materials science and engineering research and development. | 0 | Theoretical and Fundamental Chemistry |
Given their high affinities to form inclusion complexes cucurbiturils have been employed as the macrocycles component of a rotaxane. After formation of the supramolecular assembly or threaded complex with a guest molecule such as hexamethylene diamine the two ends of the guest can be reacted with bulky groups that will then act as a stoppers preventing the two separate molecules from dissociating.
In another rotaxane system with a CB[7] wheel, the axle is a 4,4'-bipyridinium or viologen subunit with two carboxylic acid terminated aliphatic N-substituents at both ends. In water at concentration higher than 0.5 mM complexation is quantitative without need of stoppers. At pH = 2 the carboxylic end-groups are protonated and the wheel shuttles back and forth between them as evidenced by the presence of just two aromatic viologen protons in the proton NMR spectrum. At pH = 9 the wheel is locked around the viologen center. More recently, rotaxane with a CB[8] wheel was synthesized. This rotaxane can bind neutral guest molecules. | 0 | Theoretical and Fundamental Chemistry |
There are many applications in technology and lab work for this process to create desired morphologies of polymers. One of these applications is inscribing secondary nanostructures onto electrospun fibers. The use of poly(ε‐caprolactone) fibers, known as PCL, allows using solvents like acetone to move the amorphous chains of block polymers onto a pre-existing crystal, making the inscribed secondary structure. When the PCL is annealed with acetone, the amorphous chains can be mobilized to a given desired region, while the overall integrity of the fully crystallized regions stays intact. With a careful approach to the semi-crystalline polymer chosen and looking for appropriate solvent vapor, this simple process can be applied to many different systems and allows for the creation of many types of hierarchical polymer material.
Another application of SVA is its use in helping create and improve photovoltaic device efficiency through the annealing of perovskite materials. For the greater performance of these energy cells, the keys lie with higher quality perovskite materials and on the use of SVA to create these higher quality films that can retain energy more efficiently. Solvent engineering is the key to make the perovskite material and improving their quality through SVA in an anhydrous isopropanol environment, where the crystalline polymer has low solubility, which causes the performance to increase greatly. The use of SVA here leads to a more energy-efficient and promising path of using specific polymers to help move forward with the improvement of energy storage. | 0 | Theoretical and Fundamental Chemistry |
Non-B DNA can be classified into several types, including A-DNA, Z-DNA, H-DNA, G-quadruplexes, and Triplexes (Triple-stranded DNA).
A-DNA is a right-handed double helix structure for RNA-DNA duplexes and RNA-RNA duplexes that is less common than the more well-known B-DNA structure. A-DNA is a form of DNA that occurs when the DNA is in a dehydrated state or is bound to certain proteins, and it has a shorter and wider helix than B-DNA. The helix of A-DNA is also tilted and compressed compared to B-DNA. A-DNA is believed to play a role in certain biological processes, such as DNA replication and gene expression.
Z-DNA is a left-handed helix with a zigzag backbone, in contrast to the right-handed B-DNA helix. It is stabilized by the alternating purine-pyrimidine sequence and can form in regions of DNA with high GC-content, supercoiling, or negative superhelicity. Z-DNA has been implicated in gene regulation and immunity, but it can also induce DNA damage and inflammation.
H-DNA is a triple-stranded DNA structure that forms when two homologous DNA strands come together and one strand displaces the other. H-DNA is stabilized by Hoogsteen base pairing and can cause mutations, rearrangements, and genome instability. H-DNA is thought to be involved in DNA replication, recombination, and repair, but its precise biological functions remain unclear.
G-quadruplexes are four-stranded DNA structures formed by guanine-rich sequences. G-quadruplexes can form in telomeres, oncogene promoters, and other genomic regions and can affect gene expression, DNA replication, and telomere maintenance. G-quadruplexes are also potential targets for cancer therapy.
Triplexes are three-stranded DNA structures formed by the binding of a third strand to a DNA duplex. Triplexes can be formed by pyrimidine-rich or purine-rich third strands, and they can occur in genomic regions with inverted repeats, mirror repeats, or other special sequences. Triplexes can affect DNA replication, transcription, and recombination, but they can also cause DNA damage and mutagenesis. | 1 | Applied and Interdisciplinary Chemistry |
Despite the variable sources of a wastewater stream, a ZLD system is generally comprised by two steps:
# Pre-Concentration: Pre-concentrating a brine is usually achieved with membrane brine concentrators or electrodialysis. These technologies concentrate a stream to a high salinity and are able to recover up to 60–80% of the water.
# Evaporation/Crystallization: The next step, using thermal processes or evaporation, evaporates all the leftover water, collects it, and sends it to reuse. The waste that is left behind then goes to a crystallizer that boils all the water until all its impurities crystallize and can be filtered out as solids. | 1 | Applied and Interdisciplinary Chemistry |
1-Hydroxy-7-azabenzotriazole (HOAt) is a triazole used as a peptide coupling reagent. It suppresses racemization that can otherwise occur during the reaction.
HOAt has a melting point between 213 and 216 degrees Celsius. As a liquid, it is transparent and without any color. | 1 | Applied and Interdisciplinary Chemistry |
A cover meter is an instrument to locate rebars and measure the exact concrete cover. Rebar detectors are less sophisticated devices that can only locate metallic objects below the surface. Due to the cost-effective design, the pulse-induction method is one of the most commonly used solutions. | 1 | Applied and Interdisciplinary Chemistry |
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or by atomization of a larger mass of solid. Water vapor will condense into droplets depending on the temperature. The temperature at which droplets form is called the dew point. | 1 | Applied and Interdisciplinary Chemistry |
Iron smelting was unknown in pre-Columbian America.
Excavations at LAnse aux Meadows, Newfoundland, have found considerable evidence for the processing of bog iron and the production of iron in a bloomery by the Norse. The cluster of Viking Age (–1022 AD) at LAnse aux Meadows are situated on a raised marine terrace, between a sedge peat bog and the ocean. Estimates from the smaller amount of slag recovered archaeologically suggest 15 kg of slag was produced during what appears to have been a single smelting attempt. By comparing the iron content of the primary bog iron ore found in the purpose built furnace hut with the iron remaining in that slag, an estimated 3 kg iron bloom was produced. At a yield of at best 20% from what is a good iron rich ore, this suggests the workers processing the ore had not been particularly skilled. This supports the idea that iron processing knowledge was widespread and not restricted to major centers of trade and commerce. Archaeologists also found 98 nail, and importantly, ship rivet fragments, at the site as well as considerable evidence for woodworking – which points to boat or possibly ship repairs being undertaken at the site. (An important consideration remains that a potential 3 kg raw bloom most certainly does not make enough refined bar to manufacture the 3 kg of recovered nails and rivets.)
In the Spanish colonization of the Americas, bloomeries or "Catalan forges" were part of "self-sufficiency" at some of the missions, , and . As part of the Franciscan Spanish missions in Alta California, the "Catalan forges" at Mission San Juan Capistrano from the 1790s are the oldest existing facilities of their kind in the present day state of California. The bloomeries sign proclaims the site as being "part of Orange Countys first industrial complex".
The archaeology at Jamestown Virginia (circa 1610–1615) had recovered the remains of a simple short-shaft bloomery furnace, likely intended as yet another "resource test" like the one in Vinland much earlier. The English settlers of the Thirteen Colonies were prevented by law from manufacture; for a time, the British sought to situate most of the skilled artisanry at domestic locations. In fact, this was one of the problems that led to the revolution. The Falling Creek Ironworks was the first in the United States. The Neabsco Iron Works is an example of the early Virginian effort to form a workable American industry.
The earliest iron forge in colonial Pennsylvania was Thomas Rutter's bloomery near Pottstown, founded in 1716. In the Adirondacks, New York, new bloomeries using the hot blast technique were built in the 19th century. | 1 | Applied and Interdisciplinary Chemistry |
The titration process creates solutions with compositions ranging from pure acid to pure base. Identifying the pH associated with any stage in the titration process is relatively simple for monoprotic acids and bases. The presence of more than one acid or base group complicates these computations. Graphical methods, such as the equiligraph, have long been used to account for the interaction of coupled equilibria. | 0 | Theoretical and Fundamental Chemistry |
TNP-ATP is a fluorescent molecule that is able to determine whether a protein binds to ATP, and the constants associated with that binding. It is primarily used in fluorescence spectroscopy, but is also very useful as an acceptor molecule in FRET, and as a fluorescent probe in fluorescence microscopy and X-ray crystallography. | 0 | Theoretical and Fundamental Chemistry |
Protein degradation differs from protein catabolism. Proteins are produced and destroyed routinely as part of the normal operations of the cell. Transcription factors, proteins that help regulate protein synthesis, are targets of such degradations. Their degradation is not a significant contributor to the energy needs of the cell. The addition of ubiquitin (ubiquitylation) marks a protein for degradation via the proteasome. | 1 | Applied and Interdisciplinary Chemistry |
The common technique of cleaning silverware by immersion of the silver or sterling silver (or even just silver plated objects) and a piece of aluminium (foil is preferred because of its much greater surface area than that of ingots, although if the foil has a "non-stick" face, this must be removed with steel wool first) in a hot electrolytic bath (usually composed of water and sodium bicarbonate, i.e., household baking soda) is an example of galvanic corrosion. Silver darkens and corrodes in the presence of airborne sulfur molecules, and the copper in sterling silver corrodes under a variety of conditions. These layers of corrosion can be largely removed through the electrochemical reduction of silver sulfide molecules: the presence of aluminium (which is less noble than either silver or copper) in the bath of sodium bicarbonate strips the sulfur atoms off the silver sulfide and transfers them onto and thereby corrodes the piece of aluminium foil (a much more reactive metal), leaving elemental silver behind. No silver is lost in the process. | 1 | Applied and Interdisciplinary Chemistry |
There are a number of common stresses which are used to
* pH (acid/base)
Chemical processes are often catalysed by the presence of acids and bases. The exposure of materials to these can therefore accelerate degradation reactions.
* Temperature
In accordance to arrhenius kinetics, increasing temperature increases the rate of any degradation process. Temperature is often used in conjunction with other stresses to increase reaction rates.
* Oxidation
* Concentration
* Light | 1 | Applied and Interdisciplinary Chemistry |
Adding scalar quarks (squarks) and fermionic gluons (gluinos) to the theory makes it more tractable, but the thermodynamics of quark matter depends crucially on the fact that only fermions can carry quark number, and on the number of degrees of freedom in general. | 0 | Theoretical and Fundamental Chemistry |
Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. He trained and worked for much of his life as an apothecary, moving in later life to the university. His shop became the second-largest apothecary in Berlin, and the most productive artisanal chemical research center in Europe.
Klaproth was a major systematizer of analytical chemistry, and an independent inventor of gravimetric analysis. His attention to detail and refusal to ignore discrepancies in results led to improvements in the use of apparatus. He was a major figure in understanding the composition of minerals and characterizing the elements.
Klaproth discovered uranium (1789)
and zirconium (1789).
He was also involved in the discovery or co-discovery of
titanium (1795),
strontium (1793),
cerium (1803), and
chromium (1797) and confirmed the previous discoveries of
tellurium (1798) and
beryllium (1798).
Klaproth was a member and director of the Berlin Academy of Sciences.
He was recognized internationally as a member of the Royal Society in London, the Institut de France, and the Royal Swedish Academy of Sciences. | 1 | Applied and Interdisciplinary Chemistry |
Reaction with acids or fluorides such as tetra-n-butylammonium fluoride removes the silyl group when protection is no longer needed. Larger substituents increase resistance to hydrolysis, but also make introduction of the silyl group more difficult.
In acidic media, the relative resistance is:
:TMS (1) < TES (64) < TBS (20 000) < TIPS (700,000) < TBDPS (5,000,000)
In basic media, the relative resistance is:
:TMS (1) < TES (10-100) < TBS~TBDPS (20 000) < TIPS (100,000) | 0 | Theoretical and Fundamental Chemistry |
The most common application of the Hellmann–Feynman theorem is the calculation of intramolecular forces in molecules. This allows for the calculation of equilibrium geometries – the nuclear coordinates where the forces acting upon the nuclei, due to the electrons and other nuclei, vanish. The parameter corresponds to the coordinates of the nuclei. For a molecule with electrons with coordinates , and nuclei, each located at a specified point and with nuclear charge , the clamped nucleus Hamiltonian is
The -component of the force acting on a given nucleus is equal to the negative of the derivative of the total energy with respect to that coordinate. Employing the Hellmann–Feynman theorem this is equal to
Only two components of the Hamiltonian contribute to the required derivative – the electron-nucleus and nucleus-nucleus terms. Differentiating the Hamiltonian yields
Insertion of this in to the Hellmann–Feynman theorem returns the -component of the force on the given nucleus in terms of the electronic density and the atomic coordinates and nuclear charges: | 0 | Theoretical and Fundamental Chemistry |
A common application of block copolymers is to develop thermoplastic elastomers (TPEs). Early commercial TPEs were developed from polyurethranes (TPUs), consisting of alternating soft segments and hard segments, and are used in automotive bumpers and snowmobile treads. Styrenic TPEs entered the market later, and are used in footwear, bitumen modification, thermoplastic blending, adhesives, and cable insulation and gaskets. Modifying the linkages between the blocks resulted in newer TPEs based on polyesters (TPES) and polyamides (TPAs), used in hose tubing, sport goods, and automotive components.
Amphiphilic block copolymers have the ability to form micelles and nanoparticles. Due to this property, amphiphilic block copolymers have garnered much attention in research on vehicles for drug delivery. Similarly, amphiphilic block copolymers can be used for the removal of organic contaminants from water either through micelle formation or film preparation. | 0 | Theoretical and Fundamental Chemistry |
# Wash pipe area to be joined to create clean surfaces for joining
# Clean area where tapping tee will be placed with isopropyl alcohol
# Mark the pipes slightly beyond the edges of the tapping tee location
# Scrape pipe in marked areas to remove surface layer, allowing clean pipe material to contact the tapping tee
# Examine scraped area thoroughly, making sure that fresh pipe material is exposed throughout area
# Place tapping tee onto joint
# Secure tapping tee using clamp
# Connect fitting control box using electrical leads
# Apply fusion cycle
# Allow joint to be undisturbed for the entire prescribed cooling time
# Pressure test pipe
# Back fill pipe with appropriate contents
# Begin service | 0 | Theoretical and Fundamental Chemistry |
The injection loop is a segment of tubing of known volume which is filled with the sample solution before it is injected into the column. Loop volume can range from a few microliters to 50 ml or more. | 0 | Theoretical and Fundamental Chemistry |
*Rapid purification time: Products can be purified in short periods of time, relative to traditional techniques
*Product remains in solution: The product is not removed from solution, as in crystallization techniques.
*Reaction may be monitored: The purification process is controlled
*Traditional purity techniques may be employed
*Can be used in excess
*Removed by filtration
*Allow for the synthesis of complex compound libraries
*Can be customized: Different scavenger resins employed for different impurities.
*High solvent compatibility (can be used with many solvents) | 0 | Theoretical and Fundamental Chemistry |
Frame Lake is irregularly shaped, with a northern section and a southern section along a north-northeast to south-southwest axis approximately long, connected by a narrower central passage midway along its length where a wide peninsula extends from the western shore and an arm extends roughly to the east, curving northward. At their widest shorelines, both sections are roughly the same distance apart. Five small islands are located within the lake, three in the northern section and two in the southern section. Its total surface area is .
The lake lies at an elevation of . Surrounding terrain is gently undulating, with some of the small hills nearby cresting as high as and one of the islands rising to . Two unnamed streams drain into the lake south of the peninsula on the western side. The northerly of the two rises from drainage ditches surrounding the runways at Yellowknife Airport to the west, draining Robinson's Pond on the way to Frame Lake; the southerly has largely been channelized, draining Range Lake to the west, itself fed by a stream of similarly short length flowing into it from the west.
Surrounding terrain, as well as that of the islands, is primarily taiga forest, amid mostly bare outcrops of Canadian Shield bedrock typical of the Yellowknife area. Bare rock predominates on the shoreline, except for some shallow bays with weed beds. On the eastern shore, near the southern end of the lake, is an overgrown sandy area called McNiven Beach, after the city's first mayor.
The developed areas of Yellowknife form a "V" around the lake. On the eastern side, and the southern shore of the arm, is New Town, the citys modern downtown. Public buildings such as City Hall, the Royal Canadian Mounted Polices local headquarters, and the Canadian Forces Northern Area Headquarters Yellowknife are situated along the south side of the arm, their associated lawns coming almost to the edge of the lake.
South of City Hall along the lake shore is Somba Ke Park, open space with the only totally developed portion of shoreline. Beyond it, the taiga and bedrock buffer the lake from the city, except for the dead end of residential Matonabee Road. The Frame Lake Trail, a partially paved pathway in length, closely follows the shoreline past an extensive area of forest. Just south of McNiven Beach is a recreational facility with an arena and pool, again close to the waters edge.
At the south end, another residential neighborhood comes near the lake, after which a rocky area buffers Stanton Regional Hospital. Commercial strip development along Old Airport Road also comes close, and the road itself runs alongside part of the lakes southwestern shore for . After it curves away to the west, the northwestern side and northern end of the lake are all taiga and bedrock between Frame and nearby Robinsons Pond and Jackfish Lake, with just the trail alongside.
Amid a park-like setting on the northeastern corner of the lake, and the northern shore of the western arm, stand two other large public buildings: the Prince of Wales Northern Heritage Centre and Northwest Territories Legislative Assembly Building. The two are connected via paths and driveways through the intervening taiga and bedrock. A causeway carries the Frame Lake Trail across the tip of the arm, where the Northern Frontier Visitor Centre overlooks the lake. | 1 | Applied and Interdisciplinary Chemistry |
Baculovirus, a rod-shaped virus which infects insect cells, is used as the expression vector in this system. Insect cell lines derived from Lepidopterans (moths and butterflies), such as Spodoptera frugiperda, are used as host. A cell line derived from the cabbage looper is of particular interest, as it has been developed to grow fast and without the expensive serum normally needed to boost cell growth. The shuttle vector is called bacmid, and gene expression is under the control of a strong promoter pPolh. Baculovirus has also been used with mammalian cell lines in the BacMam system.
Baculovirus is normally used for production of glycoproteins, although the glycosylations may be different from those found in vertebrates. In general, it is safer to use than mammalian virus as it has a limited host range and does not infect vertebrates without modifications. | 1 | Applied and Interdisciplinary Chemistry |
In fluid mechanics, a splash is a sudden disturbance to the otherwise quiescent free surface of a liquid (usually water). The disturbance is typically caused by a solid object suddenly hitting the surface, although splashes can occur in which moving liquid supplies the energy. This use of the word is onomatopoeic; in the past, the term "plash" has also been used.
Splash also happens when a liquid droplet impacts on a liquid or a solid surface; in this case, a symmetric corona (resembling a coronet) is usually formed as shown in Harold Edgerton's famous milk splash photography, as milk is opaque. Historically, Worthington (1908) was the first one who systematically investigated the splash dynamics using photographs.
Splashes are characterized by transient ballistic flow, and are governed by the Reynolds number and the Weber number. In the image of a brick splashing into water, one can identify freely moving airborne water droplets, a phenomenon typical of high Reynolds number flows; the intricate non-spherical shapes of the droplets show that the Weber number is high. Also seen are entrained air bubbles in the body of the water, and an expanding ring of disturbance propagating away from the impact site.
Sand is said to splash if hit sufficiently hard (see dry quicksand) and sometimes the impact of a meteorite is referred to as splashing, if small bits of ejecta are formed.
Physicist Lei Xu and coworkers at the University of Chicago discovered that the splash due to the impact of a small drop of ethanol onto a dry solid surface could be suppressed by reducing the pressure below a specific threshold. For drops of diameter 3.4 mm falling through air, this pressure was about 20 kilopascals, or 0.2 atmosphere.
A plate made of a hard material on which a stream of liquid is designed to fall is called a "splash plate". It may serve to protect the ground from erosion by falling water, such as beneath an artificial waterfall or water outlet in soft ground. Splash plates are also part of spray nozzles, such as in irrigation sprinkler systems. | 1 | Applied and Interdisciplinary Chemistry |
Fahmi was born in Cairo on 14 August 1949. He has a twin brother, Hadi Fahmi. Sameh Fahmi holds a bachelor's degree in chemical engineering, which he received from Cairo University in June 1973. | 1 | Applied and Interdisciplinary Chemistry |
Investigators have hypothesized that the PHLPP isoforms may play roles in cancer, for several reasons. First, the genetic loci coding for PHLPP1 and 2 are commonly lost in cancer. The region including PHLPP1, 18q21.33, commonly undergoes loss of heterozygosity (LOH) in colon cancers, while 16q22.3, which includes the PHLPP2 gene, undergoes LOH in breast and ovarian cancers, Wilms tumors, prostate cancer and hepatocellular carcinoma. Second, experimental overexpression of PHLPP in cancer cell lines tends to decrease apoptosis and increase proliferation, and stable colon and glioblastoma cell lines overexpressing PHLPP1 show decreased tumor formation in xenograft models. Recent studies have also shown that Bcr-Abl, the fusion protein responsible for chronic myelogenous leukemia (CML), downregulates PHLPP1 and PHLPP2 levels, and that decreasing PHLPP levels interferes with the efficacy of Bcr-Abl inhibitors, including Gleevec, in CML cell lines.
Finally, both Akt and PKC are known to be tumor promoters, suggesting that their negative regulator PHLPP may act as a tumor suppressor. | 1 | Applied and Interdisciplinary Chemistry |
In the second step, the liquid mixtures of cells, matrix, and nutrients known as bioinks are placed in a printer cartridge and deposited using the patients' medical scans. When a bioprinted pre-tissue is transferred to an incubator, this cell-based pre-tissue matures into a tissue.
3D bioprinting for fabricating biological constructs typically involves dispensing cells onto a biocompatible scaffold using a successive layer-by-layer approach to generate tissue-like three-dimensional structures. Artificial organs such as livers and kidneys made by 3D bioprinting have been shown to lack crucial elements that affect the body such as working blood vessels, tubules for collecting urine, and the growth of billions of cells required for these organs. Without these components the body has no way to get the essential nutrients and oxygen deep within their interiors. Given that every tissue in the body is naturally composed of different cell types, many technologies for printing these cells vary in their ability to ensure stability and viability of the cells during the manufacturing process. Some of the methods that are used for 3D bioprinting of cells are photolithography, magnetic 3D bioprinting, stereolithography, and direct cell extrusion. | 1 | Applied and Interdisciplinary Chemistry |
Pinch analysis is a methodology for minimising energy consumption of chemical processes by calculating thermodynamically feasible energy targets (or minimum energy consumption) and achieving them by optimising heat recovery systems, energy supply methods and process operating conditions. It is also known as process integration, heat integration, energy integration or pinch technology.
The process data is represented as a set of energy flows, or streams, as a function of heat load (product of specific enthalpy and mass flow rate; SI unit W) against temperature (SI unit K). These data are combined for all the streams in the plant to give composite curves, one for all hot streams (releasing heat) and one for all cold streams (requiring heat). The point of closest approach between the hot and cold composite curves is the pinch point (or just pinch) with a hot stream pinch temperature and a cold stream pinch temperature. This is where the design is most constrained. Hence, by finding this point and starting the design there, the energy targets can be achieved using heat exchangers to recover heat between hot and cold streams in two separate systems, one for temperatures above pinch temperatures and one for temperatures below pinch temperatures. In practice, during the pinch analysis of an existing design, often cross-pinch exchanges of heat are found between a hot stream with its temperature above the pinch and a cold stream below the pinch. Removal of those exchangers by alternative matching makes the process reach its energy target. | 1 | Applied and Interdisciplinary Chemistry |
The first mesoionic carbenes based on pyrazole have been reported by Huynh in 2007. These carbenes are referred to as pyrazolin-3(or 4)-ylidenes. Pyrazolin-4-ylidenes are often tetrasubstituted with alkyl or aryl groups; however, the C3 and C5 positions could be substituted with nitrogen- or oxygen-based groups. The electronic properties of the groups in the C3 and C5 positions affect the overall electron properties of the ligand and influence catalytic activity. Free carbene have been produced as well as transition metal complexes. | 0 | Theoretical and Fundamental Chemistry |
Manchester has a long and distinguished history of Chemistry. John Dalton founded modern Chemistry in 1803 with his atomic theory. William Henry (1774 – 1836) was a Manchester chemist who developed what is known today as Henrys Law. James Joule pioneered the science of thermodynamics in the 1840s while working in Manchester. In the basement of the Royal Manchester Institution a laboratory was installed by Lyon Playfair who worked there briefly as Professor of Chemistry after he left Thomsons of Clitheroe. He was succeeded by Frederick Crace Calvert who made phenol which was used by Joseph Lister as an antiseptic.
Carl Schorlemmer, was appointed the first UK Professor of Organic Chemistry in 1874.
The teaching of chemistry in Owens College began in 1851 in a house in St John Street and was later transferred to the main college building in Quay Street. When the college removed to the present university site in 1873 the chemical laboratory was designed by Henry Roscoe. To this was added in 1895 the Schorlemmer laboratory for organic chemistry and in 1904 three more laboratories were added; these were the Dalton and Perkin laboratories and the Schunck laboratory which was brought from Kersal and rebuilt. The Morley laboratories (1909) provided further accommodation for organic chemistry. In October 1909 Rona Robinson and two other women were arrested for dressing in full academic regalia and interrupting a speech by the chancellor of the university at the celebration of the opening of the new chemical laboratories. They were demanding that the chancellor speak out against the force-feeding of imprisoned suffragette alumni of Manchester who were on hunger strike. The police were particularly rough with the women that day and the chancellor was sufficiently moved by the women's protest to pressure the university into not pressing charges, thus preventing Rona from going to prison again.
After the 2nd World War three more laboratories were built further down Burlington Street; these were the Dixon Laboratory (1946), the Robinson Laboratory (1950) and the Lapworth Laboratory (1950); all three were vacated in the 1960s when the present building in Brunswick Street was available. The architect for the present chemistry building was H. S. Fairhurst & Son. | 1 | Applied and Interdisciplinary Chemistry |
Reaction of carbon monoxide (CO), hydrogen sulfide (HS) and methanethiol CHSH in the presence of nickel sulfide and iron sulfide generates the methyl thioester of acetic acid [CH-CO-SCH] and presumably thioacetic acid (CH-CO-SH) as the simplest activated acetic acid analogues of acetyl-CoA. These activated acetic acid derivatives serve as starting materials for subsequent exergonic synthetic steps. They also serve for energy coupling with endergonic reactions, notably the formation of (phospho)anhydride compounds. However, Huber and Wächtershäuser reported low 0.5% acetate yields based on the input of CHSH (methanethiol) (8 mM) in the presence of 350 mM CO. This is about 500 times and 3700 times the highest CHSH and CO concentrations respectively measured to date in a natural hydrothermal vent fluid.
Reaction of nickel hydroxide with hydrogen cyanide (HCN) (in the presence or absence of ferrous hydroxide, hydrogen sulfide or methyl mercaptan) generates nickel cyanide, which reacts with carbon monoxide (CO) to generate pairs of α-hydroxy and α-amino acids: e.g. glycolate/glycine, lactate/alanine, glycerate/serine; as well as pyruvic acid in significant quantities. Pyruvic acid is also formed at high pressure and high temperature from CO, HO, FeS in the presence of nonyl mercaptan. Reaction of pyruvic acid or other α-keto acids with ammonia in the presence of ferrous hydroxide or in the presence of ferrous sulfide and hydrogen sulfide generates alanine or other α-amino acids. Reaction of α-amino acids in aqueous solution with COS or with CO and HS generates a peptide cycle wherein dipeptides, tripeptides etc. are formed and subsequently degraded via N-terminal hydantoin moieties and N-terminal urea moieties and subsequent cleavage of the N-terminal amino acid unit.
Proposed reaction mechanism for reduction of CO on FeS: Ying et al. (2007) have shown that direct transformation of mackinawite (FeS) to pyrite (FeS) on reaction with HS till 300 °C is not possible without the presence of critical amount of oxidant. In the absence of any oxidant, FeS reacts with HS up to 300 °C to give pyrrhotite. Farid et al. have experimentally shown that mackinawite (FeS) has ability to reduce CO to CO at temperature higher than 300 °C. They reported that the surface of FeS is oxidized, which on reaction with HS gives pyrite (FeS). It is expected that CO reacts with HO in the Drobner experiment to give H. | 1 | Applied and Interdisciplinary Chemistry |
As different proteins have different compositions of amino acids, different protein molecules precipitate at different concentrations of salt solution.
Unwanted proteins can be removed from a protein solution mixture by salting out as long as the solubility of the protein in various concentrations of salt solution is known.
After removing the precipitate by filtration or centrifugation, the desired protein can be precipitated by altering the salt concentration to the level at which the desired protein becomes insoluble.
One demerit of salting out in purification of proteins is that, in addition to precipitating a specific protein of interest, contaminants are also precipitated as well. Thus to obtain a purer protein of interest, additional purification methods such as ion exchange chromatography may be required. | 0 | Theoretical and Fundamental Chemistry |
The term "RuBisCO" was coined humorously in 1979, by David Eisenberg at a seminar honouring the retirement of the early, prominent RuBisCO researcher, Sam Wildman, and also alluded to the snack food trade name "Nabisco" in reference to Wildman's attempts to create an edible protein supplement from tobacco leaves.
The capitalization of the name has been long debated. It can be capitalized for each letter of the full name (Ribulose-1,5 bisphosphate carboxylase/oxygenase), but it has also been argued that is should all be in lower case (rubisco), similar to other terms like scuba or laser. | 0 | Theoretical and Fundamental Chemistry |
The presence of nitrogen activates the csiR gene located downstream of the gabP gene. The csiR gene encodes a protein that acts as a transcriptional repressor for csiD-ygaF-gab operon hence shutting off the GABA degradation pathway. | 1 | Applied and Interdisciplinary Chemistry |
* Norwegian University of Science and Technology (NTNU), Trondheim, Norway
* University of Southampton, Southampton, UK.
* MARINTEK : Marine Technology Centre, Trondheim, Norway
* MARIN : Maritime Research Institute Netherlands.
* MIT
* University of Michigan.
* Indian Institute of Technology Kharagpur, India.
* Saint Petersburg State University, Russia.
* National Maritime Research Institute, Japan.
* Research Institute of Applied Mechanics, Kyushu University, Japan.
* Computational Fluid Dynamics Laboratory, National Taiwan University of Science and Technology, Taiwan.
* Lee Dynamics, Houston, Texas, USA | 1 | Applied and Interdisciplinary Chemistry |
To create the first NanoPutian, dubbed the NanoKid, 1,4-dibromobenzene was iodinated in sulfuric acid. To this product, “arms”, or 3,3-Dimethylbutyne, were then added through Sonogashira coupling. Formylation of this structure was then achieved through using the organolithium reagent n-butyllithium followed by quenching with N,N-dimethylformamide (DMF) to create the aldehyde. 1,2-Ethanediol was added to this structure to protect the aldehyde using p-toluenesulfonic acid as a catalyst. Originally, Chanteau and Tour aimed to couple this structure with alkynes, but this resulted in very low yields of the desired products. To remedy this, the bromide was replaced with iodide through lithium-halogen exchange and quenching by using 1,2-diiodoethane. This created the final structure of the upper body for the NanoKid. | 1 | Applied and Interdisciplinary Chemistry |
Aptamers, single-stranded RNA and DNA sequences, bind to an analyte and change their conformation. They function as nucleic acids selectively binding molecules such as proteins, bacteria cells, metal ions, etc. Aptamers can be developed to have precise specificity to bind to a desired target. Aptamers change conformation upon binding, altering the electrochemical properties which can be measured. The Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process generates aptamers. Electrochemical aptamer-based (E-AB) biosensors is a device that takes advantage of the electrochemical and biological properties of aptamers to take real time, in vivo measurements.
An electrochemical aptamer-based (E-AB) biosensor to generates an electrochemical signal in response to specific target binding in vivo The signal is measured by a change in Faradaic current passed through an electrode. E-AB sensors are advantageous over previously reported aptamer-based sensors, such as fluorescence generating aptamers, due to their ability to detect target binding in vivo with real-time measurements. An E-AB sensor is composed of a three-electrode cell: an interrogating electrode, a reference electrode, and a counter electrode. A signal is generated within the electrochemical cell then measured and analyzed by a potentiostat. Several biochemical and electrochemical parameters optimize signal gain for E-AB biosensors. The density packing of DNA or RNA aptamers, the ACV frequency administered by the potentiostat, and the chemistry of the self assembling monolayer (SAM) are all factors that determine signal gain as well as the signal to noise ratio of target binding. E-AB biosensors provide a promising mechanism for in-situ sensing, feedback-controlled drug administration, and cancer biomarkers. | 0 | Theoretical and Fundamental Chemistry |
Since 1991, the city of Zürich has had a law stating all flat roofs (unless used as terraces) must be greened roofed surfaces. The main advantages as a result of this policy include increased biodiversity, rainwater storage and outflow delay, and micro-climatic compensation (temperature extremes, radiation balance, evaporation and filtration efficiency). Roof biotopes are stepping stones which, together with the earthbound green areas and the seeds distributed by wind and birds, make an important contribution to the urban green infrastructure. | 1 | Applied and Interdisciplinary Chemistry |
Chemoattractants and chemorepellents are inorganic or organic substances possessing chemotaxis-inducer effect in motile cells. These chemotactic ligands create chemical concentration gradients that organisms, prokaryotic and eukaryotic, move toward or away from, respectively.
Effects of chemoattractants are elicited via chemoreceptors such as methyl-accepting chemotaxis proteins (MCP). MCPs in E.coli include Tar, Tsr, Trg and Tap. Chemoattracttants to Trg include ribose and galactose with phenol as a chemorepellent. Tap and Tsr recognize dipeptides and serine as chemoattractants, respectively.
Chemoattractants or chemorepellents bind MCPs at its extracellular domain; an intracellular signaling domain relays the changes in concentration of these chemotactic ligands to downstream proteins like that of CheA which then relays this signal to flagellar motors via phosphorylated CheY (CheY-P). CheY-P can then control flagellar rotation influencing the direction of cell motility.
For E.coli, S. meliloti, and R. spheroides, the binding of chemoattractants to MCPs inhibit CheA and therefore CheY-P activity, resulting in smooth runs, but for B. substilis, CheA activity increases. Methylation events in E.coli cause MCPs to have lower affinity to chemoattractants which causes increased activity of CheA and CheY-P resulting in tumbles. In this way cells are able to adapt to the immediate chemoattractant concentration and detect further changes to modulate cell motility.
Chemoattractants in eukaryotes are well characterized for immune cells. Formyl peptides, such as fMLF, attract leukocytes such as neutrophils and macrophages, causing movement toward infection sites. Non-acylated methioninyl peptides do not act as chemoattractants to neutrophils and macrophages. Leukocytes also move toward chemoattractants C5a, a complement component, and pathogen-specific ligands on bacteria.
Mechanisms concerning chemorepellents are less known than chemoattractants. Although chemorepellents work to confer an avoidance response in organisms, Tetrahymena thermophila adapt to a chemorepellent, Netrin-1 peptide, within 10 minutes of exposure; however, exposure to chemorepellents such as GTP, PACAP-38, and nociceptin show no such adaptations. GTP and ATP are chemorepellents in micro-molar concentrations to both Tetrahymena and Paramecium. These organisms avoid these molecules by producing avoiding reactions to re-orient themselves away from the gradient. | 1 | Applied and Interdisciplinary Chemistry |
In 2013 a cell with 2 nanometers of nickel on a silicon electrode, paired with a stainless steel electrode, immersed in an aqueous electrolyte of potassium borate and lithium borate operated for 80 hours without noticeable corrosion, versus 8 hours for titanium dioxide. In the process, about 150 ml of hydrogen gas was generated, representing the storage of about 2 kilojoules of energy. | 0 | Theoretical and Fundamental Chemistry |
The product of the blast furnace is pig iron, which contains 4–5% carbon and usually some silicon. To produce a forgeable product a further process was needed, usually described as fining, rather than refining. From the 16th century, this was undertaken in a finery forge. At the end of the 18th century, this began to be replaced by puddling (in a puddling furnace), which was in turn gradually superseded by the production of mild steel by the Bessemer process. | 1 | Applied and Interdisciplinary Chemistry |
Since thienamycin decomposes in the presence of water, it is impractical for the clinical treatment of bacterial infections, so stable derivatives were created for medicinal consumption. One such derivative, imipenem, was formulated in 1985. Imipenem, an N-formimidoyl derivative of thienamycin, is rapidly metabolized by a renal dipeptidase enzyme found in the human body. To prevent its rapid degradation, imipenem is normally coadministered with cilastatin, an inhibitor of this enzyme. | 0 | Theoretical and Fundamental Chemistry |
In some situations where segregation is important, the segregant atoms do not have sufficient time to reach their equilibrium level as defined by the above adsorption theories. The kinetics of segregation become a limiting factor and must be analyzed as well. Most existing models of segregation kinetics follow the McLean approach. In the model for equilibrium monolayer segregation, the solute atoms are assumed to segregate to a grain boundary from two infinite half-crystals or to a surface from one infinite half-crystal. The diffusion in the crystals is described by Ficks laws. The ratio of the solute concentration in the grain boundary to that in the adjacent atomic layer of the bulk is given by an enrichment ratio, . Most models assume to be a constant, but in practice this is only true for dilute systems with low segregation levels. In this dilute limit, if is one monolayer, is given as .
The kinetics of segregation can be described by the following equation:
where for grain boundaries and 1 for the free surface, is the boundary content at time , is the solute bulk diffusivity, is related to the atomic sizes of the solute and the matrix, and , respectively, by . For short times, this equation is approximated by:
In practice, is not a constant but generally falls as segregation proceeds due to saturation. If starts high and falls rapidly as the segregation saturates, the above equation is valid until the point of saturation. | 0 | Theoretical and Fundamental Chemistry |
On-line Questions are uploaded again after the Winter School. The leftovers of the Winter School and other people who didn't join the Winter School have to take this test to join the Summer School 2. Second grade students in the high school take this test. In this test, almost half of these questions will be related to Organic Chemistry. 20 well-ranked students can join the Winter School 2. | 1 | Applied and Interdisciplinary Chemistry |
As in any technology that has long been conducted on the multi-million ton per year scale, flotation technologies have the potential to threaten the environment beyond the disruption caused by mining. Froth flotation employs a host of organic chemicals and relies upon elaborate machinery. Some of the chemicals (cyanide) are acutely toxic but hydrolyze to innocuous products. Naturally occurring fatty acids are widely used. Tailings and effluents are contained in lined ponds. Froth flotation is "poised for increased activity due to their potential usefulness in environmental site cleanup operations" including recycling of plastics and metals, not to mention water treatment. | 1 | Applied and Interdisciplinary Chemistry |
Astressin-B is a nonselective corticotropin releasing hormone antagonist that reduces the synthesis of adrenocorticotropic hormone and cortisol.
It reduces the synthesis of adrenocorticotropic hormone and improves the sexual drive of rats under stressing conditions.
Astressin-B is able to delay the emptying of solid food in mice. Astressin-B can prevent the release of adrenocorticotropic hormone in mice due to shock, alcohol and endotoxemia.
Treatment with astressin-B caused the sudden growth of hair in mice bred for a propensity for stress. | 1 | Applied and Interdisciplinary Chemistry |
Its water-solubility, together with its status as the only known photoactive protein containing a carotenoid, makes the OCP a valuable model for studying solution-state energetic and photophysical properties of carotenoids, which are a diverse class of molecules found across all domains of life. Moreover, carotenoids are widely investigated for their properties as anti-oxidants, and thus the protein may serve as a template for delivery of carotenoids for therapeutic purposes in human medicine.
Because of its high efficiency of fluorescence quenching, coupled to its low quantum yield of photoactivation by specific wavelengths of light, OCP has ideal properties as a photoswitch and has been proposed as a novel system for developing optogenetics technologies and may have other applications in optofluidics and biophotonics. | 0 | Theoretical and Fundamental Chemistry |
Various classification schemes can be applied. A commonly used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980:
C-C-C Diarylheptanoids are not included in this Harborne classification.
They can also be classified on the basis of their number of phenol groups. They can therefore be called simple phenols or monophenols, with only one phenolic group, or di- (bi-), tri- and oligophenols, with two, three or several phenolic groups respectively.
A diverse family natural phenols are the flavonoids, which include several thousand compounds, among them the flavonols, flavones, flavan-3ol (catechins), flavanones, anthocyanidins, and isoflavonoids.
The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid is a dimer of gallic acid and forms the class of ellagitannins, or a catechin and a gallocatechin can combine to form the red compound theaflavin, a process that also results in the large class of brown thearubigins in tea.
Two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignans.
Nomenclature of polymers: | 0 | Theoretical and Fundamental Chemistry |
The concept of theoretical plates and trays or equilibrium stages is used in the design of many different types of separation. | 1 | Applied and Interdisciplinary Chemistry |
The Hilsenhoff Biotic Index (HBI) is a quantitative method of evaluating the abundance of arthropod fauna in stream ecosystems as a measurement of estimating water quality based on the predetermined pollution tolerances of the observed taxa. This biotic index was created by William Hilsenhoff in 1977 to measure the effects of oxygen depletion in Wisconsin streams resulting from organic or nutrient pollution. | 0 | Theoretical and Fundamental Chemistry |
Sulfuranes are relatively specialized functional group that feature tetravalent sulfur, with the formula SR Likewise, persulfuranes feature hexavalent SR.
One of the few all-carbon persulfuranes has two methyl and two biphenylene ligands:
It is prepared from the corresponding sulfurane 1 with xenon difluoride / boron trifluoride in acetonitrile to the sulfuranyl dication 2 followed by reaction with methyllithium in tetrahydrofuran to (a stable) persulfurane 3 as the cis isomer. X-ray diffraction shows C−S bond lengths ranging between 189 and 193 pm (longer than the standard bond length) with the central sulfur atom in a distorted octahedral molecular geometry. | 0 | Theoretical and Fundamental Chemistry |
Hydrotropes have a low bioaccumulation potential, as the octanol-water partition coefficient is <1.0. Studies have found hydrotopes to be very slightly volatile, with vapor pressures <2.0x10-5 Pa. They are aerobically biodegradable. Removal via the secondary wastewater treatment process of activated sludge is >94%. Acute toxicity studies on fish show an LC50 >400 mg active ingredient (a.i.)/L. For Daphnia, the EC50 is >318 mg a.i./L. The most sensitive species is green algae with EC50 values in the range of 230–236 mg a.i./ L and No Observed Effect Concentrations (NOEC) in the range of 31–75 mg a.i./L. The aquatic Predicted No Effect Concentration (PNEC) was found to be 0.23 mg a.i./L. The Predicted Environmental Concentration (PEC)/PNEC ratio has been determined to be < 1 and, therefore, hydrotropes in household laundry and cleaning products have been determined to not be an environmental concern. | 0 | Theoretical and Fundamental Chemistry |
Plant disease resistance protects plants from pathogens in two ways: by pre-formed structures and chemicals, and by infection-induced responses of the immune system. Relative to a susceptible plant, disease resistance is the reduction of pathogen growth on or in the plant (and hence a reduction of disease), while the term disease tolerance describes plants that exhibit little disease damage despite substantial pathogen levels. Disease outcome is determined by the three-way interaction of the pathogen, the plant and the environmental conditions (an interaction known as the disease triangle).
Defense-activating compounds can move cell-to-cell and systematically through the plants vascular system. However, plants do not have circulating immune cells, so most cell types exhibit a broad suite of antimicrobial defenses. Although obvious qualitative differences in disease resistance can be observed when multiple specimens are compared (allowing classification as "resistant" or "susceptible" after infection by the same pathogen strain at similar inoculum levels in similar environments), a gradation of quantitative' differences in disease resistance is more typically observed between plant strains or genotypes. Plants consistently resist certain pathogens but succumb to others; resistance is usually specific to certain pathogen species or pathogen strains. | 1 | Applied and Interdisciplinary Chemistry |
In water solutions, the carbamate anion slowly equilibrates with the ammonium cation and the carbonate or bicarbonate anions:
Calcium carbamate is soluble in water, whereas calcium carbonate is not. Adding a calcium salt to an ammonium carbamate/carbonate solution will precipitate some calcium carbonate immediately, and then slowly precipitate more as the carbamate hydrolyzes. | 0 | Theoretical and Fundamental Chemistry |
When running simulations on a biological model, any simulation software evaluates a set of rules, starting from a specified set of initial conditions, and usually iterating through a series of time steps until a specified end time. One way to classify simulation algorithms is by looking at the level of analysis at which the rules are applied: they can be population-based, single-particle-based or hybrid. | 1 | Applied and Interdisciplinary Chemistry |
In the US, where the Midrex process was first developed, direct reduction was seen in the 1960s as a way of breathing new life into electric steelmaking. The techno-economic model of the mini-mill, based on flexibility and reduced plant size, was threatened by a shortage of scrap metal, and a consequent rise in its price. With the same shortage affecting metallurgical coke, a return to the blast furnace route did not seem an attractive solution.
Direct reduction is theoretically well-suited to the use of ores that are less compatible with blast furnaces (such as fine ores that clog furnaces), which are less expensive. It also requires less capital, making it a viable alternative to the two tried-and-tested methods of electric furnaces and blast furnaces.
The comparative table shows that the diversity of processes is also justified by the need for quality materials. The coking plant that feeds a battery of blast furnaces is just as expensive as the blast furnace and requires a specific quality of coal. Conversely, many direct-reduction processes are disadvantaged by the costly transformation of ore into pellets: these cost on average 70% more than raw ore. Finally, gas requirements can significantly increase investment costs: gas produced by a COREX is remarkably well-suited to feeding a Midrex unit, but the attraction of the low investment then fades. | 1 | Applied and Interdisciplinary Chemistry |
When a liquid drop is put onto a flat surface, two situations may result. If the contact angle is zero, the situation is referred to as complete wetting. If the contact angle is between 0 and 180°, the situation is called partial wetting. A wetting transition is a surface phase transition from partial wetting to complete wetting. | 0 | Theoretical and Fundamental Chemistry |
haemagglutination activity domain - haemolysin expression modulating protein family - hairpin - haploid - haploinsufficiency - HdeA family - helix-loop-helix - helminth protein - hematopoietic stem cell - hemophilia - heteroduplex DNA - heterozygous - highly conserved sequence - Hirschsprungs disease - histone - HLA-Y - hnRNA - holoprosencephaly - homologous recombination - homology - homozygous - host strain (bacterial) - HspQ protein domain - human artificial chromosome - Human Genome Project - human immunodeficiency virus - HumHot - Huntingtons disease - hybridization - hybridoma - hydrophilicity plot - hydroxydechloroatrazine ethylaminohydrolase - | 1 | Applied and Interdisciplinary Chemistry |
Alchemy has had a long-standing relationship with art, seen both in alchemical texts and in mainstream entertainment. Literary alchemy appears throughout the history of English literature from Shakespeare to J. K. Rowling, and also the popular Japanese manga Fullmetal Alchemist. Here, characters or plot structure follow an alchemical magnum opus. In the 14th century, Chaucer began a trend of alchemical satire that can still be seen in recent fantasy works like those of the late Sir Terry Pratchett.
Visual artists have had a similar relationship with alchemy. While some used it as a source of satire, others worked with the alchemists themselves or integrated alchemical thought or symbols in their work. Music was also present in the works of alchemists and continues to influence popular performers. In the last hundred years, alchemists have been portrayed in a magical and spagyric role in fantasy fiction, film, television, novels, comics and video games. | 1 | Applied and Interdisciplinary Chemistry |
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