text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
A fire sprinkler system is an active fire protection method, consisting of a water supply system providing adequate pressure and flowrate to a water distribution piping system, to which fire sprinklers are connected. Although initially used only in factories and large commercial buildings, systems for homes and small buildings are now available at a cost-effective price.
Fire sprinkler systems are extensively used worldwide, with over 40 million sprinkler heads fitted each year. Fire sprinkler systems are generally designed as a life saving system, but are not necessarily designed to protect the building. Of buildings completely protected by fire sprinkler systems, if a fire did initiate, it was controlled by the fire sprinklers alone in 96% of these cases. | 1 | Applied and Interdisciplinary Chemistry |
The other possible case would be that the second step is slow and rate-determining, meaning that it is slower than the first step in the reverse direction: r ≪ r. In this hypothesis, r − r ≈ 0, so that the first step is (almost) at equilibrium. The overall rate is determined by the second step: r = r ≪ r, as very few molecules that react at the first step continue to the second step, which is much slower. Such a situation in which an intermediate (here ) forms an equilibrium with reactants prior to the rate-determining step is described as a pre-equilibrium For the reaction of and CO, this hypothesis can be rejected, since it implies a rate equation that disagrees with experiment.
# + → NO + (fast step)
# + CO → + (slow step, rate-determining)
If the first step were at equilibrium, then its equilibrium constant expression permits calculation of the concentration of the intermediate in terms of more stable (and more easily measured) reactant and product species:
The overall reaction rate would then be
which disagrees with the experimental rate law given above, and so disproves the hypothesis that the second step is rate-determining for this reaction. However, some other reactions are believed to involve rapid pre-equilibria prior to the rate-determining step, as shown below. | 0 | Theoretical and Fundamental Chemistry |
Water molecules stay close to each other (cohesion), due to the collective action of hydrogen bonds between water molecules. These hydrogen bonds are constantly breaking, with new bonds being formed with different water molecules; but at any given time in a sample of liquid water, a large portion of the molecules are held together by such bonds.
Water also has high adhesion properties because of its polar nature. On clean, smooth glass the water may form a thin film because the molecular forces between glass and water molecules (adhesive forces) are stronger than the cohesive forces. In biological cells and organelles, water is in contact with membrane and protein surfaces that are hydrophilic; that is, surfaces that have a strong attraction to water. Irving Langmuir observed a strong repulsive force between hydrophilic surfaces. To dehydrate hydrophilic surfaces—to remove the strongly held layers of water of hydration—requires doing substantial work against these forces, called hydration forces. These forces are very large but decrease rapidly over a nanometer or less. They are important in biology, particularly when cells are dehydrated by exposure to dry atmospheres or to extracellular freezing. | 1 | Applied and Interdisciplinary Chemistry |
* Davis, Frederick Rowe. "Pesticides and the perils of synecdoche in the history of science and environmental history." History of Science 57.4 (2019): 469–492.
* Davis, Frederick Rowe. Banned: a history of pesticides and the science of toxicology (Yale UP, 2014).
* Matthews, Graham A. A history of pesticides (CABI, 2018). | 1 | Applied and Interdisciplinary Chemistry |
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a nearly constant volume independent of pressure. It is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape.
The density of a liquid is usually close to that of a solid, and much higher than that of a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids.
A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Unlike a gas, a liquid maintains a fairly constant density and does not disperse to fill every space of a container.
Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is either gas (as interstellar clouds) or plasma (as stars). | 0 | Theoretical and Fundamental Chemistry |
When an acid catalyst is used, the initial step in the reaction mechanism involves acid-catalyzed tautomerization of the carbonyl compound to the enol. The acid also serves to activate the carbonyl group of another molecule by protonation, rendering it highly electrophilic. The enol is nucleophilic at the α-carbon, allowing it to attack the protonated carbonyl compound, leading to the aldol after deprotonation.
This under the right conditions can then dehydrate to give the unsaturated carbonyl compound, the aldol condensation product.
# Acid-catalyzed aldol addition
# Acid-catalyzed aldol dehydration | 0 | Theoretical and Fundamental Chemistry |
In multiphase flow in porous media, the relative permeability of a phase is a dimensionless measure of the effective permeability of that phase. It is the ratio of the effective permeability of that phase to the absolute permeability. It can be viewed as an adaptation of Darcy's law to multiphase flow.
For two-phase flow in porous media given steady-state conditions, we can write
where is the flux, is the pressure drop, is the viscosity. The subscript indicates that the parameters are for phase .
is here the phase permeability (i.e., the effective permeability of phase ), as observed through the equation above.
Relative permeability, , for phase is then defined from , as
where is the permeability of the porous medium in single-phase flow, i.e., the absolute permeability. Relative permeability must be between zero and one.
In applications, relative permeability is often represented as a function of water saturation; however, owing to capillary hysteresis one often resorts to a function or curve measured under drainage and another measured under imbibition.
Under this approach, the flow of each phase is inhibited by the presence of the other phases. Thus the sum of relative permeabilities over all phases is less than 1. However, apparent relative permeabilities larger than 1 have been obtained since the Darcean approach disregards the viscous coupling effects derived from momentum transfer between the phases (see assumptions below). This coupling could enhance the flow instead of inhibit it. This has been observed in heavy oil petroleum reservoirs when the gas phase flows as bubbles or patches (disconnected). | 1 | Applied and Interdisciplinary Chemistry |
Polymer brushes can be used in Area-selective deposition. Area-selective deposition is a promising technique for positional self-alignment of materials at a prepatterned surface. | 0 | Theoretical and Fundamental Chemistry |
Gaskets are the mechanical seals, or packings, used to prevent the leakage of a gas or fluids from valves. | 1 | Applied and Interdisciplinary Chemistry |
DNA spiking, also known as custom spiking, is the differing ratio of bases at a single degenerate position when synthesizing oligonucleotides. DNA spiking is a unequal proportions of bases at a given position (for example, 10% Adenine, 75% Guanine, 5% Cytosine & 10% Thymine). As an example, with the degenerate code R = A + G, 50% of the time that R position is adenine and the other 50% of the time it is guanine. However, with DNA Spiking, the R position could be adenine 70% of the time and guanine 30% of the time. The proportions do not need to be 70:30, the ratios can be anything else such as 12:82 and 64:36.
DNA spiking can also refer to a spike control in PCR, which is when DNA is added to a sample that will provide some signal (e.g. a plasmid or some synthetic DNA with a specific known sequence) to a reaction, and seeing if the reaction will amplify. This method is used to discover if the PCR method is working correctly, as in a PCR machine it may not amplify DNA properly, so by adding spiked DNA it can be observed how much DNA is produced. This is then compared to the amount of DNA that would be theoretically predicted if the machine was working properly so that any malfunctions can be discovered. | 1 | Applied and Interdisciplinary Chemistry |
In juvenile red deer (Cervus elaphus), the preorbital gland appears to play a role in the response to stress. The preorbital gland is closed in a relaxed calf, whereas it is opened in a stressed calf. One example of this is the signalling of hunger and satiety. Fawns open their preorbital glands as a signal that they are hungry, and close the gland after feeding, when they are no longer hungry.
The adult Indian muntjac (Muntiacus muntjac) is a solitary animal, other than during the rut (mating season) and for the first six months after giving birth. Adult males in particular are widely separated. Marking grass and bushes with secretions from their preorbital glands appears to be involved in the acquisition and maintenance of territory. | 1 | Applied and Interdisciplinary Chemistry |
Linolelaidic acid is an omega-6 trans fatty acid (TFA) and is a cis–trans isomer of linoleic acid. It is found in partially hydrogenated vegetable oils. It is a white (or colourless) viscous liquid.
TFAs are classified as conjugated and nonconjugated, corresponding usually to the structural elements and , respectively. Nonconjugated TFAs are represented by elaidic acid and linolelaidic acid. Their presence is linked heart diseases. The TFA vaccenic acid, which is of animal origin, poses less of a health risk. | 0 | Theoretical and Fundamental Chemistry |
Due to the inert pair effect of the heavy, organometallic compounds of Bi (III) show Lewis acid properties given the lower ability of the 6s electron pair to mix with molecular orbitals and form σ-bonds. The search for non-toxic equivalents of boronic acids in advancing the Suzuki-Miyaura carbon-carbon coupling reactions and expand the scope of carbon-nitrogen and carbon-oxygen coupling ones turned chemists' attention to organometallic bismuth chemistry. Two catalytic mechanisms were proposed in the C-C bond formation catalyzed by bismuth organometallic compounds. The major difference arises from the rate of the oxidative addition to Pd(0) into a C-Bi bond or C-O one, yielding cycles A and B, respectively (see image). | 0 | Theoretical and Fundamental Chemistry |
After a conflict with that university, Markovnikov was appointed professor at the University of Odesa in 1871 and, two years later, at the University of Moscow, where he stayed the rest of his career. He was elected as a member to the American Philosophical Society in 1901. | 0 | Theoretical and Fundamental Chemistry |
An ATM designed with a rotated sample is typically a far-field measurement configuration using a time-domain spectroscopy strategy.
A high power infrared laser is typically used. Its beam is split by a beamsplitter into two optical paths: a probe beam and a THz generation beam.
The THz generation beam typically receives the greater fraction of NIR power in order to maximize the power of the THz light commonly generated by a voltage-pulsed photoconductive antenna. The generated THz light is collected through a hyper-hemispherical silicon lens and passed to an off-axis parabolic mirror that collimates the THz beam for polarization by a THz polarizer that is often made of a simple wire-grid. The linearly polarized THz beam is then focused by a second off-axis parabolic mirror onto the sample. The THz beam transmitted through the sample is again collected by a third off-axis parabolic mirror, collimated onto a fourth parabolic mirror that then focuses the beam onto an electro-optic (EO) crystal whose birefringence is perturbed by the strength of the THz beam.
The NIR probe beam is passed through the EO crystal to probe the induced degree of birefringence caused by the THz beam and passed to a detection module that often consists of an NIR quarter wave plate, a Wollaston prism that spatially separates orthogonal polarization states of the probe beam into two optical paths that are individually detected at a balanced detector. The resulting signal reported by the balanced detector is a measure of the difference in magnitude of these two orthogonal components of the NIR probe beam and therefore a direct correlation of the degree of birefringence induced in the EO crystal by the THz beam passed through the sample. | 0 | Theoretical and Fundamental Chemistry |
Pyridine can be prepared by dealkylation of alkylated pyridines, which are obtained as byproducts in the syntheses of other pyridines. The oxidative dealkylation is carried out either using air over vanadium(V) oxide catalyst, by vapor-dealkylation on nickel-based catalyst, or hydrodealkylation with a silver- or platinum-based catalyst. Yields of pyridine up to be 93% can be achieved with the nickel-based catalyst. Pyridine can also be produced by the decarboxylation of nicotinic acid with copper chromite. | 0 | Theoretical and Fundamental Chemistry |
The oil and gas industry in general uses unsealed radioactive solids (powder and granular forms), liquids and gases to investigate or trace the movement of materials. The most common use of these radiotracers is at the well head for the measurement of flow rate for various purposes. A 1995 study found that radioactive tracers were used in over 15% of stimulated oil and gas wells.
Use of these radioactive tracers is strictly controlled. It is recommended that the radiotracer is chosen to have readily detectable radiation, appropriate chemical properties, and a half life and toxicity level that will minimize initial and residual contamination. Operators are to ensure that licensed material will be used, transported, stored, and disposed of in such a way that members of the public will not receive more than 1 mSv (100 mrem) in one year, and the dose in any unrestricted area will not exceed 0.02 mSv (2 mrem) in any one hour. They are required to secure stored licensed material from access, removal, or use by unauthorized personnel and control and maintain constant surveillance of licensed material when in use and not in storage. Federal and state nuclear regulatory agencies keep records of the radionuclides used.
As of 2003 the isotopes Antimony-124, argon-41, cobalt-60, iodine-131, iridium-192, lanthanum-140, manganese-56, scandium-46, sodium-24, silver-110m, technetium-99m, and xenon-133 were most commonly used by the oil and gas industry because they are easily identified and measured. Bromine-82, Carbon-14, hydrogen-3, iodine-125 are also used.
Examples of amounts used are:
In hydraulic fracturing, plastic pellets coated with Silver-110m or sand labelled with Iridium-192with may be added to a proppant when it is required to evaluate whether a fracturing process has penetrated rocks in the pay zone. Some radioactivity may by brought to the surface at the well head during testing to determine the injection profile and location of fractures. Typically this uses very small (50 kBq) Cobalt-60 sources and dilution factors are such that the activity concentrations will be very low in the topside plant and equipment. | 0 | Theoretical and Fundamental Chemistry |
It is possible to modify Tebbe's reagent through the use of different ligands. This can alter the reactivity of the complex, allowing for a broader range of reactions. For example, cyclopropanation can be achieved using a chlorinated analogue. | 0 | Theoretical and Fundamental Chemistry |
The intrinsic color of liquid water may be demonstrated by looking at a white light source through a long pipe that is filled with purified water and closed at both ends with a transparent window. The light cyan color is caused by weak absorption in the red part of the visible spectrum.
Absorptions in the visible spectrum are usually attributed to excitations of electronic energy states in matter. Water is a simple three-atom molecule, HO, and all its electronic absorptions occur in the ultraviolet region of the electromagnetic spectrum and are therefore not responsible for the color of water in the visible region of the spectrum. The water molecule has three fundamental modes of vibration. Two stretching vibrations of the O–H bonds in the gaseous state of water occur at = 3650 cm and = 3755 cm. Absorption due to these vibrations occurs in the infrared region of the spectrum. The absorption in the visible spectrum is due mainly to the harmonic = 14,318 cm, which is equivalent to a wavelength of 698 nm. In liquid state at 20°C these vibrations are red-shifted by hydrogen bonding, resulting in red absorption at 740 nm, other harmonics such as giving red absorption at 660 nm. The absorption curve for heavy water (DO) is of a similar shape, but is shifted further towards the infrared end of the spectrum, because the vibrational transitions have a lower energy. For this reason, heavy water does not absorb red light and thus large bodies of DO would lack the characteristic cyan color of the more commonly found light water (HO).
Absorption intensity decreases markedly with each successive overtone, resulting in very weak absorption for the third overtone. For this reason, the pipe needs to have a length of a meter or more and the water must be purified by microfiltration to remove any particles that could produce Mie scattering. | 0 | Theoretical and Fundamental Chemistry |
In ammonia production CO and CO are considered poisons to most commonly used catalysts. Methanation catalysts are added after several hydrogen producing steps to prevent carbon oxide buildup in the ammonia synthesis loop as methane does not have similar adverse effects on ammonia synthesis rates. | 0 | Theoretical and Fundamental Chemistry |
Extensive studies have been performed on the formation of enolates. It is possible to generate, in most cases, the desired enolate geometry:
For ketones, most enolization conditions give Z enolates. For esters, most enolization conditions give E enolates. The addition of HMPA is known to reverse the stereoselectivity of deprotonation.
The stereoselective formation of enolates has been rationalized with the Ireland model, although its validity is somewhat questionable. In most cases, it is not known which, if any, intermediates are monomeric or oligomeric in nature; nonetheless, the Ireland model remains a useful tool for understanding enolates.
In the Ireland model, the deprotonation is assumed to proceed by a six-membered or cyclic monomeric transition state. The larger of the two substituents on the electrophile (in the case above, methyl is larger than proton) adopts an equatorial disposition in the favored transition state, leading to a preference for E enolates. The model clearly fails in many cases; for example, if the solvent mixture is changed from THF to 23% HMPA-THF (as seen above), the enolate geometry is reversed, which is inconsistent with this model and its cyclic transition state. | 0 | Theoretical and Fundamental Chemistry |
The primitive unit cell for the body-centered cubic crystal structure contains several fractions taken from nine atoms (if the particles in the crystal are atoms): one on each corner of the cube and one atom in the center. Because the volume of each of the eight corner atoms is shared between eight adjacent cells, each BCC cell contains the equivalent volume of two atoms (one central and one on the corner).
Each corner atom touches the center atom. A line that is drawn from one corner of the cube through the center and to the other corner passes through 4r, where r is the radius of an atom. By geometry, the length of the diagonal is a. Therefore, the length of each side of the BCC structure can be related to the radius of the atom by
Knowing this and the formula for the volume of a sphere, it becomes possible to calculate the APF as follows: | 0 | Theoretical and Fundamental Chemistry |
To be effective on a given ore slurry, the collectors are chosen based upon their selective wetting of the types of particles to be separated. A good collector will adsorb, physically or chemically, with one of the types of particles. The wetting activity of a surfactant on a particle can in principle be quantified by measuring the contact angles of the liquid/bubble interface. Another important measure for attachment of bubbles to particles is induction time, the time required for the particle and bubble to rupture the thin film separating the particle and bubble. This rupturing is achieved by the surface forces between the particle and bubble.
The mechanisms for the bubble-particle attachment is complex but is viewed as consisting of three steps: collision, attachment, and detachment. The collision is achieved by particles being within the collision tube of a bubble and this is affected by the velocity of the bubble and radius of the bubble. The collision tube corresponds to the region in which a particle will collide with the bubble, with the perimeter of the collision tube corresponding to the grazing trajectory.
The attachment of the particle to the bubble is controlled by the induction time of the particle and bubble. The particle and bubble need to bind and this occurs if the time in which the particle and bubble are in contact with each other is larger than the required induction time. This induction time is affected by the fluid viscosity, particle and bubble size and the forces between the particle and bubbles.
The detachment of a particle and bubble occurs when the force exerted by the surface tension is exceeded by shear forces and gravitational forces. These forces are complex and vary within the cell. High shear will be experienced close to the impeller of a mechanical flotation cell and mostly gravitational force in the collection and cleaning zone of a flotation column.
Significant issues of entrainment of fine particles occurs as these particles experience low collision efficiencies as well as sliming and degradation of the particle surfaces. Coarse particles show a low recovery of the valuable mineral due to the low liberation and high detachment efficiencies. | 1 | Applied and Interdisciplinary Chemistry |
A nucleosome is the basic structural unit of DNA packaging in eukaryotes. The structure of a nucleosome consists of a segment of DNA wound around eight histone proteins and resembles thread wrapped around a spool. The nucleosome is the fundamental subunit of chromatin. Each nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones, which are known as a histone octamer. Each histone octamer is composed of two copies each of the histone proteins H2A, H2B, H3, and H4.
DNA must be compacted into nucleosomes to fit within the cell nucleus. In addition to nucleosome wrapping, eukaryotic chromatin is further compacted by being folded into a series of more complex structures, eventually forming a chromosome. Each human cell contains about 30 million nucleosomes.
Nucleosomes are thought to carry epigenetically inherited information in the form of covalent modifications of their core histones. Nucleosome positions in the genome are not random, and it is important to know where each nucleosome is located because this determines the accessibility of the DNA to regulatory proteins.
Nucleosomes were first observed as particles in the electron microscope by Don and Ada Olins in 1974, and their existence and structure (as histone octamers surrounded by approximately 200 base pairs of DNA) were proposed by Roger Kornberg. The role of the nucleosome as a regulator of transcription was demonstrated by Lorch et al. in vitro in 1987 and by Han and Grunstein and Clark-Adams et al. in vivo in 1988.
The nucleosome core particle consists of approximately 146 base pairs (bp) of DNA wrapped in 1.67 left-handed superhelical turns around a histone octamer, consisting of 2 copies each of the core histones H2A, H2B, H3, and H4. Core particles are connected by stretches of linker DNA, which can be up to about 80 bp long. Technically, a nucleosome is defined as the core particle plus one of these linker regions; however the word is often synonymous with the core particle. Genome-wide nucleosome positioning maps are now available for many model organisms and human cells.
Linker histones such as H1 and its isoforms are involved in chromatin compaction and sit at the base of the nucleosome near the DNA entry and exit binding to the linker region of the DNA. Non-condensed nucleosomes without the linker histone resemble "beads on a string of DNA" under an electron microscope.
In contrast to most eukaryotic cells, mature sperm cells largely use protamines to package their genomic DNA, most likely to achieve an even higher packaging ratio. Histone equivalents and a simplified chromatin structure have also been found in Archaea, suggesting that eukaryotes are not the only organisms that use nucleosomes. | 1 | Applied and Interdisciplinary Chemistry |
Joanna Sigfred Fowler (born August 9, 1942) is a scientist emeritus at the U.S. Department of Energys Brookhaven National Laboratory in New York. She served as professor of psychiatry at Mount Sinai School of Medicine and director of Brookhavens Radiotracer Chemistry, Instrumentation and Biological Imaging Program. Fowler studied the effect of disease, drugs, and aging on the human brain and radiotracers in brain chemistry. She has received many awards for her pioneering work, including the National Medal of Science. | 0 | Theoretical and Fundamental Chemistry |
Permeable paving surfaces have been demonstrated as effective in managing runoff from paved surfaces and recharging groundwater aquifers. Large volumes of urban runoff causes serious erosion and siltation in surface water bodies. Permeable pavers provide a solid ground surface, strong enough to take heavy loads, like large vehicles, while at the same time they allow water to filter through the surface and reach the underlying soils, mimicking natural ground absorption. They can reduce downstream flooding and stream bank erosion, and maintain base flows in rivers to keep ecosystems self-sustaining. Permeable pavers also combat erosion that occurs when grass is dry or dead, by replacing grassed areas in suburban and residential environments. The goal is to control stormwater at the source, reduce runoff and improve water quality by filtering pollutants in the subsurface layers. | 1 | Applied and Interdisciplinary Chemistry |
The dravya in Jainism are fundamental entities, called astikaya (literally, collection that exists). They are believed to be eternal, and the ontological building blocks that constitute and explain all existence, whether perceived or not. According to both Śvētāmbara and Digambara traditions of Jainism, there are six eternal substances in existence: Soul (jiva), Matter (pudgala), Space (akasha), motion (Dharma) and rest (Adharma) and "Time" (kala). In both traditions, the substance of space is conceptualized as "world space" (lokakasha) and "non-world space" (alokiakasha). Further, both soul and matter are considered as active ontological substances, while the rest are inactive. Another categorization found in Jain philosophy is jiva and ajiva, the latter being all dravya that is not jiva.
Out of the six dravyas, five except time have been described as astikayas, that is, extensions or conglomerates. Since like conglomerates, they have numerous space points, they are described as astikaya. There are innumerable space points in the sentient substance and in the media of motion and rest, and infinite ones in space; in matter they are threefold (i.e. numerable, innumerable and infinite). Time has only one; therefore it is not a conglomerate. Hence the corresponding conglomerates or extensions are called—jivastikaya (soul extension or conglomerate), pudgalastikaya (matter conglomerate), dharmastikaya (motion conglomerate), adharmastikaya (rest conglomerate) and akastikaya (space conglomerates). Together they are called pancastikaya or the five astikayas. | 1 | Applied and Interdisciplinary Chemistry |
DNA storage is an important aspect of DNA extraction projects as it ensures the integrity and stability of the extracted DNA for downstream applications.
One common method of DNA storage is ethanol precipitation, which involves adding ethanol and a salt, such as sodium chloride or potassium acetate, to the extracted DNA to precipitate it out of solution. The DNA is then pelleted by centrifugation and washed with 70% ethanol to remove any remaining contaminants. The DNA pellet is then air-dried and resuspended in a buffer, such as Tris-EDTA (TE) buffer, for storage.
Another method is freezing the DNA in a buffer such as TE buffer, or in a cryoprotectant such as glycerol or DMSO, at -20 or -80 degrees Celsius. This method preserves the integrity of the DNA and slows down the activity of any enzymes that may degrade it.
It's important to note that the choice of storage buffer and conditions will depend on the downstream application for which the DNA is intended. For example, if the DNA is to be used for PCR, it may be stored in TE buffer at 4 degrees Celsius, while if it is to be used for long-term storage or shipping, it may be stored in ethanol at -20 degrees Celsius. The extracted DNA should be regularly checked for its quality and integrity, such as by running a gel electrophoresis or spectrophotometry. The storage conditions should be also noted and controlled, such as the temperature and humidity.
It's also important to consider the long-term stability of the DNA and the potential for degradation over time. The extracted DNA should be stored for as short a time as possible, and the conditions for storage should be chosen to minimize the risk of degradation.
In general, the extracted DNA should be stored under the best possible conditions to ensure its stability and integrity for downstream applications. | 1 | Applied and Interdisciplinary Chemistry |
Electrochemical energy conversion is a field of energy technology concerned with electrochemical methods of energy conversion including fuel cells and photoelectrochemical. This field of technology also includes electrical storage devices like batteries and supercapacitors. It is increasingly important in context of automotive propulsion systems. There has been the creation of more powerful, longer running batteries allowing longer run times for electric vehicles. These systems would include the energy conversion fuel cells and photoelectrochemical mentioned above. | 0 | Theoretical and Fundamental Chemistry |
Faraday devised the laws of chemical electrodeposition of metals from solutions in 1857. He formulated the second law of electrolysis stating "the amounts of bodies which are equivalent to each other in their ordinary chemical action have equal quantities of electricity naturally associated with them." In other words, the quantities of different elements deposited by a given amount of electricity are in the ratio of their chemical equivalent weights.
An important aspect of the second law of electrolysis is electroplating, which together with the first law of electrolysis has a significant number of applications in industry, as when used to protectively coat metals to avoid corrosion. | 0 | Theoretical and Fundamental Chemistry |
From 1992 to 1993, Marrow was appointed as postdoctoral research associate in the Department of Materials, University of Oxford, and a junior research fellow at Linacre College, Oxford, but moved with an Engineering and Physical Sciences Research Council (EPSRC) postdoctoral research fellowship to the School of Metallurgy and Materials, University of Birmingham. In 2001, he joined the Manchester Materials Science Centre, University of Manchester, as senior lecturer in physical metallurgy, where he became assistant director of Materials Performance Centre in 2002 and the director in 2009.
Marrow moved to the University of Oxford to become Oxford Martin School co-director of the school programme in Nuclear and Energy Materials from 2010 to 2015, Professor in Energy Materials, Department of Materials, Oxford University, and Fellow of Mansfield College, Oxford. , Marrow is the Associate Head of Department of Materials (Teaching).
Marrow is a council member of the UK Forum for Engineering Structural Integrity (FESI), UK representative for the European Energy Research Alliance Joint Programme on Nuclear Materials, member (ex-chair) of the OECD-NEA Expert Group on Innovative Structural Materials, independent advisor to the UK Office of Nuclear Regulation on materials/structural integrity, and UK representative on Graphite for BEIS to the Generation IV International Forum. Marrow is the co-director of the Nuclear Research Centre (NRC), which is a joint venture between the University of Bristol and the University of Oxford to train new nuclear scientists and engineers. | 1 | Applied and Interdisciplinary Chemistry |
Extractable nuclear antigens (ENA) are a group of autoantigens that were originally identified as antibody targets in people with autoimmune disorders. They are termed ENA because they can be extracted from the cell nucleus with saline. The ENAs consist of ribonucleoproteins and non-histone proteins, named by either the name of the donor who provided the prototype serum (Sm, Ro, La, Jo), or the name of the disease setting in which the antibodies were found (SS-A, SS-B, Scl-70). | 1 | Applied and Interdisciplinary Chemistry |
The pzc is typically obtained by acid-base titrations of colloidal dispersions while monitoring the electrophoretic mobility of the particles and the pH of the suspension. Several titrations are required to distinguish pzc from iep, using different electrolytes (including varying the electrolyte ionic strength). Once satisfactory graphs are obtained (acid/base amount—pH, and pH—zeta potential), the pzc is established as the common intersection point (cip) of the lines. Therefore, pzc is also sometimes referred to as cip. | 0 | Theoretical and Fundamental Chemistry |
The Darcy-Weisbach's accuracy and universal applicability makes it the ideal formula for flow in pipes. The advantages of the equation are as follows:
* It is based on fundamentals.
* It is dimensionally consistent.
* It is useful for any fluid, including oil, gas, brine, and sludges.
* It can be derived analytically in the laminar flow region.
* It is useful in the transition region between laminar flow and fully developed turbulent flow.
* The friction factor variation is well documented. | 1 | Applied and Interdisciplinary Chemistry |
Conversely, a spinning superconductor generates a magnetic field, precisely aligned with the spin axis. The effect, the London moment, was put to good use in Gravity Probe B. This experiment measured the magnetic fields of four superconducting gyroscopes to determine their spin axes. This was critical to the experiment since it is one of the few ways to accurately determine the spin axis of an otherwise featureless sphere. | 0 | Theoretical and Fundamental Chemistry |
The microscopic structure of liquids is complex and historically has been the subject of intense research and debate. A few of the key ideas are explained below. | 0 | Theoretical and Fundamental Chemistry |
The Chemical Educator is a peer-reviewed journal in chemical education. It was published by Springer-Verlag from 1996 to 2002, and has been published online independently since 2003. The journal publishes six issues per volume and one volume per year, on current topics, experiments, and teaching methodology. | 1 | Applied and Interdisciplinary Chemistry |
Triethyloxonium tetrafluoroborate is prepared from boron trifluoride, diethyl ether and epichlorohydrin:
where the Et stands for ethyl. The trimethyloxonium salt is available from dimethyl ether via an analogous route. These salts do not have long shelf-lives at room temperature. They degrade by hydrolysis:
The propensity of trialkyloxonium salts for alkyl-exchange can be advantageous. For example, trimethyloxonium tetrafluoroborate, which reacts sluggishly due to its low solubility in most compatible solvents, may be converted in situ to higher alkyl/more soluble oxoniums, thereby accelerating alkylation reactions.
This reagent is useful for esterification of carboxylic acids under conditions where acid-catalyzed reactions are infeasible: | 0 | Theoretical and Fundamental Chemistry |
Seawater contains more dissolved ions than all types of freshwater. However, the ratios of solutes differ dramatically. For instance, although seawater contains about 2.8 times more bicarbonate than river water, the percentage of bicarbonate in seawater as a ratio of all dissolved ions is far lower than in river water. Bicarbonate ions constitute 48% of river water solutes but only 0.14% for seawater. Differences like these are due to the varying residence times of seawater solutes; sodium and chloride have very long residence times, while calcium (vital for carbonate formation) tends to precipitate much more quickly. The most abundant dissolved ions in seawater are sodium, chloride, magnesium, sulfate and calcium. Its osmolarity is about 1000 mOsm/L.
Small amounts of other substances are found, including amino acids at concentrations of up to 2 micrograms of nitrogen atoms per liter, which are thought to have played a key role in the origin of life. | 0 | Theoretical and Fundamental Chemistry |
Wolffram’s Red Salt is an inorganic compound with the double salt formula [Pt(CHNH)Cl] [Pt(CHNH)]Cl·4HO. This compound is an early example of a one-dimensional coordination polymer, serving as a representative structure for studies in solid-state physics. This species has been of interest due to the unusual mixed valence system of Pt(II) and Pt(IV) bridged by a chlorine atom. The deep red color of the double salt, where the components were colorless, piqued the interest of early inorganic chemists and ultimately inspired studies into the physical properties of the compound in search of potential applications. | 0 | Theoretical and Fundamental Chemistry |
Specific Fan Power (SFP) is a parameter that quantifies the energy-efficiency of fan air movement systems. It is a measure of the electric power that is needed to drive a fan (or collection of fans), relative to the amount of air that is circulated through the fan(s). It is not constant for a given fan, but changes with both air flow rate and fan pressure rise. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric corrosion generally refers to general corrosion in a non-specific environment. Prevention of atmospheric corrosion is typically handled by use of materials selection and coatings specifications. The use of zinc coatings also known as galvanization on steel structures is a form of cathodic protection where the zinc acts as a sacrificial anode and also a form of coating. Small scratches are expected to occur in the galvanized coating over time. The zinc being more active in the galvanic series corrodes in preference to the underlying steel and the corrosion products fil the scratch preventing further corrosion. As long as the scratches are fine, condensation moisture should not corrode the underlying steel as long as both the zinc and steel are in contact. As long as there is moisture, the zinc corrodes and eventually disappears. Impressed current cathodic protection is also used. | 1 | Applied and Interdisciplinary Chemistry |
Primary standards are compounds with known stoichiometry, high purity, and high stability. Standard solutions can be prepared using primary standards by accurately weighing a known quantity of the compound, followed by dilution to a precise volume. For example, a weighed sample of 0.15 g sodium chloride contains 2.6 x 10 moles of sodium chloride. The following dilution of this sample in a 50-mL volumetric flask will result in a concentration of 0.51 M. | 0 | Theoretical and Fundamental Chemistry |
The misorientation distribution (MD) is analogous to the ODF used in characterizing texture. The MD describes the probability of the misorientation between any two grains falling into a range around a given misorientation . While similar to a probability density, the MD is not mathematically the same due to the normalization. The intensity in an MD is given as "multiples of random density" (MRD) with respect to the distribution expected in a material with uniformly distributed misorientations. The MD can be calculated by either series expansion, typically using generalized spherical harmonics, or by a discrete binning scheme, where each data point is assigned to a bin and accumulated. | 0 | Theoretical and Fundamental Chemistry |
The major steps in the sulfo-SFT pathway are:
* isomerization of sulfoquinovose to sulfofructose (catalyzed by sulfoquinovose isomerase);
* transaldol reaction of sulfofructose to release sulfolactaldehyde (catalyzed by sulfofructose transaldolase), and transfer of the C3-(glycerone)-moiety to glyceraldehyde phosphate, yielding fructose-6-phosphate;
* sulfolactaldehyde may be reduced to (S)-2,3-dihydroxypropane-1-sulfonate (catalyzed by sulfolactaldehyde reductase and using NADH as a co-factor), or oxidized to sulfolactate (catalyzed by sulfolactaldehyde dehydrogenase using NAD+ as a co-factor).
The transaldolase can also catalyze transfer of the C3-(glycerone)-moiety to erythrose-4-phosphate, giving sedoheptulose-7-phosphate. | 1 | Applied and Interdisciplinary Chemistry |
In continuum mechanics, the Froude number (, after William Froude, ) is a dimensionless number defined as the ratio of the flow inertia to the external field (the latter in many applications simply due to gravity). The Froude number is based on the speed–length ratio which he defined as:
where is the local flow velocity, is the local external field, and is a characteristic length. The Froude number has some analogy with the Mach number. In theoretical fluid dynamics the Froude number is not frequently considered since usually the equations are considered in the high Froude limit of negligible external field, leading to homogeneous equations that preserve the mathematical aspects. For example, homogeneous Euler equations are conservation equations.
However, in naval architecture the Froude number is a significant figure used to determine the resistance of a partially submerged object moving through water. | 1 | Applied and Interdisciplinary Chemistry |
The etymology of the words valence (plural valences) and valency (plural valencies) traces back to 1425, meaning "extract, preparation", from Latin valentia "strength, capacity", from the earlier valor "worth, value", and the chemical meaning referring to the "combining power of an element" is recorded from 1884, from German Valenz.
The concept of valence was developed in the second half of the 19th century and helped successfully explain the molecular structure of inorganic and organic compounds.
The quest for the underlying causes of valence led to the modern theories of chemical bonding, including the cubical atom (1902), Lewis structures (1916), valence bond theory (1927), molecular orbitals (1928), valence shell electron pair repulsion theory (1958), and all of the advanced methods of quantum chemistry.
In 1789, William Higgins published views on what he called combinations of "ultimate" particles, which foreshadowed the concept of valency bonds. If, for example, according to Higgins, the force between the ultimate particle of oxygen and the ultimate particle of nitrogen were 6, then the strength of the force would be divided accordingly, and likewise for the other combinations of ultimate particles (see illustration).
The exact inception, however, of the theory of chemical valencies can be traced to an 1852 paper by Edward Frankland, in which he combined the older radical theory with thoughts on chemical affinity to show that certain elements have the tendency to combine with other elements to form compounds containing 3, i.e., in the 3-atom groups (e.g., , , , etc.) or 5, i.e., in the 5-atom groups (e.g., , , , etc.), equivalents of the attached elements. According to him, this is the manner in which their affinities are best satisfied, and by following these examples and postulates, he declares how obvious it is that
This "combining power" was afterwards called quantivalence or valency (and valence by American chemists). In 1857 August Kekulé proposed fixed valences for many elements, such as 4 for carbon, and used them to propose structural formulas for many organic molecules, which are still accepted today.
Lothar Meyer in his 1864 book, Die modernen Theorien der Chemie, contained an early version of the periodic table containing 28 elements, for the first time classified elements into six families by their valence. Works on organizing the elements by atomic weight, until then had been stymied by the widespread use of equivalent weights for the elements, rather than atomic weights.
Most 19th-century chemists defined the valence of an element as the number of its bonds without distinguishing different types of valence or of bond. However, in 1893 Alfred Werner described transition metal coordination complexes such as , in which he distinguished principal and subsidiary valences (German: Hauptvalenz and Nebenvalenz), corresponding to the modern concepts of oxidation state and coordination number respectively.
For main-group elements, in 1904 Richard Abegg considered positive and negative valences (maximal and minimal oxidation states), and proposed Abegg's rule to the effect that their difference is often 8.
An alternative definition of valence, developed in the 1920s and having modern proponents, differs in cases where an atoms formal charge is not zero. It defines the valence of a given atom in a covalent molecule as the number of electrons that an atom has used in bonding:
:valence = number of electrons in valence shell of free atom − number of non-bonding electrons on atom in molecule,
or equivalently:
:valence = number of bonds + formal charge.
In this convention, the nitrogen in an ammonium ion bonds to four hydrogen atoms, but it is considered to be pentavalent because all five of nitrogen's valence electrons participate in the bonding. | 0 | Theoretical and Fundamental Chemistry |
Double-walled pipe system may use plastic pressure pipe systems materials of high-density polyethylene (HDPE), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene (PP), polyvinylidene fluoride (PVDF), and ethylene chlorotrifluoroethylene copolymer (ECTFE). Dual-wall stainless steel tubing is most commonly used in semiconductor plants for the containment of highly toxic gases.
A leak detection system in the containment pipe indicates if the carrier pipe is leaking. Double wall pipes are usually hydrostatically tested, or tested to hold and maintain a target gas pressure before the first use.
A different special application of a double-walled pipe is a jacketed pipe, which is used to make high viscosity liquids flow at elevated temperature through the carrier pipe. The outer pipe circulates hot fluids that heat up the interior carrier pipe and its contents in turn. | 1 | Applied and Interdisciplinary Chemistry |
Stochastic thermodynamics can be applied to driven (i.e. open) quantum systems whenever the effects of quantum coherence can be ignored. The dynamics of an open quantum system is then equivalent to a classical stochastic one. However, this is sometimes at the cost of requiring unrealistic measurements at the beginning and end of a process.
Understanding non-equilibrium quantum thermodynamics more broadly is an important and active area of research. The efficiency of some computing and information theory tasks can be greatly enhanced when using quantum correlated states; quantum correlations can be used not only as a valuable resource in quantum computation, but also in the realm of quantum thermodynamics. New types of quantum devices in non-equilibrium states function very differently to their classical counterparts. For example, it has been theoretically shown that non-equilibrium quantum ratchet systems function far more efficiently then that predicted by classical thermodynamics. It has also been shown that quantum coherence can be used to enhance the efficiency of systems beyond the classical Carnot limit. This is because it could be possible to extract work, in the form of photons, from a single heat bath. Quantum coherence can be used in effect to play the role of Maxwell's demon though the broader information theory based interpretation of the second law of thermodynamics is not violated.
Quantum versions of stochastic thermodynamics have been studied for some time and the past few years have seen a surge of interest in this topic. Quantum mechanics involves profound issues around the interpretation of reality (e.g. the Copenhagen interpretation, many-worlds, de Broglie-Bohm theory etc are all competing interpretations that try to explain the unintuitive results of quantum theory) . It is hoped that by trying to specify the quantum-mechanical definition of work, dealing with open quantum systems, analyzing exactly solvable models, or proposing and performing experiments to test non-equilibrium predictions, important insights into the interpretation of quantum mechanics and the true nature of reality will be gained.
Applications of non-equilibrium work relations, like the Jarzynski equality, have recently been proposed for the purposes of detecting quantum entanglement and to improving optimization problems (minimize or maximize a function of multivariables called the cost function) via quantum annealing . | 0 | Theoretical and Fundamental Chemistry |
There are three classes of manufactured tubing: seamless, as-welded or electric resistant welded (ERW), and drawn-over-mandrel (DOM).
* Seamless tubing is produced via extrusion or rotary piercing.
* Drawn-over-mandrel tubing is made from cold-drawn electrical-resistance-welded tube that is drawn through a die and over a mandrel to create such characteristics as dependable weld integrity, dimensional accuracy, and an excellent surface finish. | 1 | Applied and Interdisciplinary Chemistry |
Athletes may adopt gene therapy technologies to improve their performance. Gene doping is not known to occur, but multiple gene therapies may have such effects. Kayser et al. argue that gene doping could level the playing field if all athletes receive equal access. Critics claim that any therapeutic intervention for non-therapeutic/enhancement purposes compromises the ethical foundations of medicine and sports. | 1 | Applied and Interdisciplinary Chemistry |
Many metal alkoxide compounds also feature oxo-ligands. Oxo-ligands typically arise via the hydrolysis, often accidentally, and via ether elimination: | 0 | Theoretical and Fundamental Chemistry |
In a small number of cases, plant genes are effective against an entire pathogen species, even though that species is pathogenic on other genotypes of that host species. Examples include barley MLO against powdery mildew, wheat Lr34 against leaf rust and wheat Yr36 against wheat stripe rust. An array of mechanisms for this type of resistance may exist depending on the particular gene and plant-pathogen combination. Other reasons for effective plant immunity can include a lack of coadaptation (the pathogen and/or plant lack multiple mechanisms needed for colonization and growth within that host species), or a particularly effective suite of pre-formed defenses. | 1 | Applied and Interdisciplinary Chemistry |
While gene knock-in technology has proven to be a powerful technique for the generation of models of human disease and insight into proteins in vivo, numerous limitations still exist. Many of these are shared with the limitations of knockout technology. First, combinations of knock-in genes lead to growing complexity in the interactions that inserted genes and their products have with other sections of the genome and can therefore lead to more side effects and difficult-to-explain phenotypes. Also, only a few loci, such as the ROSA26 locus have been characterized well enough where they can be used for conditional gene knock-ins; making combinations of reporter and transgenes in the same locus problematic. The biggest disadvantage of using gene knock-in for human disease model generation is that mouse physiology is not identical to that of humans and human orthologs of proteins expressed in mice will often not wholly reflect the role of a gene in human pathology. This can be seen in mice produced with the ΔF508 fibrosis mutation in the CFTR gene, which accounts for more than 70% of the mutations in this gene for the human population and leads to cystic fibrosis. While ΔF508 CF mice do exhibit the processing defects characteristic of the human mutation, they do not display the pulmonary pathophysiological changes seen in humans and carry virtually no lung phenotype. Such problems could be ameliorated by the use of a variety of animal models, and pig models (pig lungs share many biochemical and physiological similarities with human lungs) have been generated in an attempt to better explain the activity of the ΔF508 mutation. | 1 | Applied and Interdisciplinary Chemistry |
Supercritical fluid chromatography (SFC) is a form of normal phase chromatography that uses a supercritical fluid such as carbon dioxide as the mobile phase. It is used for the analysis and purification of low to moderate molecular weight, thermally labile molecules and can also be used for the separation of chiral compounds. Principles are similar to those of high performance liquid chromatography (HPLC); however, SFC typically utilizes carbon dioxide as the mobile phase. Therefore, the entire chromatographic flow path must be pressurized. Because the supercritical phase represents a state whereby bulk liquid and gas properties converge, supercritical fluid chromatography is sometimes called convergence chromatography. The idea of liquid and gas properties convergence was first envisioned by Giddings. | 0 | Theoretical and Fundamental Chemistry |
A superconductor is generally considered high-temperature if it reaches a superconducting state above a temperature of 30 K (−243.15 °C); as in the initial discovery by Georg Bednorz and K. Alex Müller. It may also reference materials that transition to superconductivity when cooled using liquid nitrogen – that is, at only T > 77 K, although this is generally used only to emphasize that liquid nitrogen coolant is sufficient. Low temperature superconductors refer to materials with a critical temperature below 30 K, and are cooled mainly by liquid helium (T > 4.2 K). One exception to this rule is the iron pnictide group of superconductors which display behaviour and properties typical of high-temperature superconductors, yet some of the group have critical temperatures below 30 K. | 0 | Theoretical and Fundamental Chemistry |
Fatty acid ethoxylates are a class of very versatile surfactants, which combine in a single molecule the characteristic of a weakly anionic, pH-responsive head group with the presence of stabilizing and temperature responsive ethyleneoxide units. | 0 | Theoretical and Fundamental Chemistry |
The cycling of and excretion of urea by the kidneys is a vital part of mammalian metabolism. Besides its role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephrons, that allows for reabsorption of water and critical ions from the excreted urine. Urea is reabsorbed in the inner medullary collecting ducts of the nephrons, thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henle, which makes the water reabsorb.
By action of the urea transporter 2, some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule, through the collecting ducts, and into the excreted urine. The body uses this mechanism, which is controlled by the antidiuretic hormone, to create hyperosmotic urine — i.e., urine with a higher concentration of dissolved substances than the blood plasma. This mechanism is important to prevent the loss of water, maintain blood pressure, and maintain a suitable concentration of sodium ions in the blood plasma.
The equivalent nitrogen content (in grams) of urea (in mmol) can be estimated by the conversion factor 0.028 g/mmol. Furthermore, 1 gram of nitrogen is roughly equivalent to 6.25 grams of protein, and 1 gram of protein is roughly equivalent to 5 grams of muscle tissue. In situations such as muscle wasting, 1 mmol of excessive urea in the urine (as measured by urine volume in litres multiplied by urea concentration in mmol/L) roughly corresponds to a muscle loss of 0.67 gram. | 0 | Theoretical and Fundamental Chemistry |
Product imaging of positive ions formed by REMPI detection is only one of the areas where charged particle imaging has become useful. Another area was in the detection of electrons. The first ideas along these lines seem to have an early history. Demkov et al. were perhaps the first to propose a "photoionization microscope". They realized that trajectories of an electron emitted from an atom in different directions may intersect again at a large distance from the atom and create an interference pattern. They proposed building an apparatus to observe the predicted rings. Blondel et al. eventually realized such a "microscope" and used it to study the photodetachment of Br. It was Helm and co-workers, however, who were the first to create an electron imaging apparatus. The instrument is an improvement on previous photoelectron spectrometers in that it provides information on all energies and all angles of the photoelectrons for each shot of the laser. Helm and his co-workers have now used this technique to investigate the ionization of Xe, Ne, H, and Ar. In more recent examples, Suzuki, Hayden, and Stolow have pioneered the use of femtosecond excitation and ionization to follow excited state dynamics in larger molecules. | 0 | Theoretical and Fundamental Chemistry |
HCFC-142b is used as a refrigerant, as a blowing agent for foam plastics production, and as feedstock to make polyvinylidene fluoride (PVDF). It was introduced to replace the chlorofluorocarbons (CFCs) that were initially undergoing a phase-out per the Montreal Protocol, but HCFCs still have a significant ozone-depletion ability. As of year 2020, HCFC's are replaced by non ozone depleting HFCs within many applications.
In the United States, the EPA stated that HCFCs could be used in "processes that result in the transformation or destruction of the HCFCs", such as using HCFC-142b as a feedstock to make PVDF. HCFCs could also be used in equipment that was manufactured before January 1, 2010. The point of these new regulations was to phase-out HCFCs in much the same way that CFCs were phased out. HCFC-142b production in non article 5 countries like the United States was banned on January 1, 2020, under the Montreal Protocol. | 1 | Applied and Interdisciplinary Chemistry |
For fission reactors, the fuel (typically based on uranium) is usually based on the metal oxide; the oxides are used rather than the metals themselves because the oxide melting point is much higher than that of the metal and because it cannot burn, being already in the oxidized state. | 0 | Theoretical and Fundamental Chemistry |
In 1957, Lagaly started his chemistry studies (as well as Physics, Mineralogy and Botany) at the Heidelberg University, receiving his degree as "Diplom-Chemiker" in 1962. He conducted his doctorate studies at the Institute for Inorganic Chemistry at the same institution under Armin Weiss, and was awarded his Doctor degree in 1967 with the work "Untersuchung von Quellungsvorgängen in n-Alkylammonium-Schichtsilicaten". From 1965 he worked as an Assistant at the Institute for Inorganic Chemistry of the Munich University where he concluded his Habilitation in 1971 and then was employed as lecturer ("Akademischer Rat/Oberrat"). In 1974 he was employed as Professor for Inorganic Chemistry at the University of Kiel, retiring in 2004.
His research lines concentrated on Clay chemistry, Colloid chemistry and Interface chemistry as well as chemistry from porous compounds, layered materials and intercalation chemistry.
Among his many contributions to the fields of clay and colloid chemistry, one of his most recognized developments was the Alkylammonium Method for the determination of layer charge in layered aluminosilicates.
He acted as treasurer of the German Colloid Society from 1979 to 2003. In 2004 the same institution awarded him with the Wolfgang Ostwald Prize. Lagaly was President of the German Clay Group (DTTG) from 1987 to 1992 and of the European Clay Groups Association (ECGA) from 1999 to 2003.
In addition, Lagaly acted for many years (1987-2004) as editor-in-chief for "Colloid and Polymer Science" and "Progress Colloid and Polymer Science" as well as editor for "Clay Minerals" (1982-1996) and "Applied Clay Science" (1985-1996). | 0 | Theoretical and Fundamental Chemistry |
Interference of atom matter waves was first observed by Esterman and Stern in 1930, when a Na beam was diffracted off a surface of NaCl. The short de Broglie wavelength of atoms prevented progress for many years until two technological breakthroughs revived interest: microlithography allowing precise small devices and laser cooling allowing atoms to be slowed, increasing their de Broglie wavelength.
Until 2006, the resolution of imaging systems based on atomic beams was not better than that of an optical microscope, mainly due to the poor performance of the focusing elements. Such elements use small numerical aperture; usually, atomic mirrors use grazing incidence, and the reflectivity drops drastically with increase of the grazing angle; for efficient normal reflection, atoms should be ultracold, and dealing with such atoms usually involves magnetic, magneto-optical or optical traps.
At the beginning of the 21st century scientific publications about "atom nano-optics", evanescent field lenses and ridged mirrors
showed significant improvement.
In particular, an atomic hologram can be realized. | 0 | Theoretical and Fundamental Chemistry |
Reuterin is an intermediate in the metabolism of glycerol to 1,3-propanediol catalysed by the coenzyme B12-dependent glycerol dehydratase.
Reuterin is a potent antimicrobial compound produced by Lactobacillus reuteri. It is an intermediate in the metabolism of glycerol to 1,3-propanediol catalysed by the coenzyme B12-dependent diol dehydrase. It inhibits the growth of some harmful Gram-negative and Gram-positive bacteria, along with yeasts, molds, and protozoa. L. reuteri can secrete sufficient amounts of reuterin to inhibit the growth of harmful gut organisms, without killing beneficial gut bacteria, allowing L. reuteri to remove gut invaders while keeping normal gut flora intact.
Reuterin is water-soluble, effective in a wide range of pH, resistant to proteolytic and lipolytic enzymes, and has been studied as a food preservative or auxiliary therapeutic agent.
Reuterin as an extracted compound has been shown capable of killing Escherichia coli O157:H7 and Listeria monocytogenes, with the addition of lactic acid increasing its efficacy. It has also been demonstrated to kill Escherichia coli O157:H7 when produced by L. reuteri. | 1 | Applied and Interdisciplinary Chemistry |
Broadly, aptamers are small molecules composed of either single-stranded DNA or RNA and are typically 20-100 nucleotides in length, or ~3-60 kDa. Because of their single-stranded nature, aptamers are capable of forming many secondary structures, including pseudoknots, stem loops, and bulges, through intra-strand base pairing interactions. The combinations of secondary structures present in an aptamer confer it a particular tertiary structure which in turn dictates the specific target the aptamer will selectively bind to. Because of the selective binding ability of aptamers, they are considering a promising biomolecule for use in pharmaceuticals. Additionally, aptamers exhibit tight binding to targets, with dissociation constants often in the pM to nM range. Besides their strong binding ability, aptamers are also valued because they can be used on targets that are not capable of being bound by small peptides generated by phage display or by antibodies, and they are able to differentiate between conformational isomers and amino acid substitutions. Also, because aptamers are nucleic-acid based, they can be directly synthesized, eliminating the need for cell-based expression and extraction as is the case in antibody production. RNA aptamers in particular are capable of producing a myriad of different structures, leading to speculations that they are more discriminating in their target affinity compared to DNA aptamers. | 1 | Applied and Interdisciplinary Chemistry |
Elastomers have to be used with more mechanically sensitive explosives like HMX. The elasticity of the matrix lowers sensitivity of the bulk material to shock and friction; their glass transition temperature is chosen to be below the lower boundary of the temperature working range (typically below -55 °C). Crosslinked rubber polymers are however sensitive to aging, mostly by action of free radicals and by hydrolysis of the bonds by traces of water vapor. Rubbers like Estane or hydroxyl-terminated polybutadiene (HTPB) are used for these applications extensively. Silicone rubbers and thermoplastic polyurethanes are also in use.
Fluoroelastomers, e.g. Viton, combine the advantages of both. | 0 | Theoretical and Fundamental Chemistry |
Samarium(II) iodide is a powerful reducing agent – for example it rapidly reduces water to hydrogen. It is available commercially as a dark blue 0.1 M solution in THF. Although used typically in superstoichiometric amounts, catalytic applications have been described. | 0 | Theoretical and Fundamental Chemistry |
Conjugated systems not only have low energy excitations in the visible spectral region but they also accept or donate electrons easily. Phthalocyanines, which, like Phthalocyanine Blue BN and Phthalocyanine Green G, often contain a transition metal ion, exchange an electron with the complexed transition metal ion that easily changes its oxidation state. Pigments and dyes like these are charge-transfer complexes. | 0 | Theoretical and Fundamental Chemistry |
The location of the ropB gene is directly and sequentially proximal to the subject of its transcriptional regulation (speB) which lies downstream of a 941 bp intergenic region between the two. Transcription of the ropB gene seems to necessitate a promoter within a series sequences between 238 and 480 bp and up to 800 bp upstream of the gene itself inside the highly repetitive intergenic region. | 1 | Applied and Interdisciplinary Chemistry |
Free hydride anions exist only under extreme conditions and are not invoked for homogeneous solution. Instead, many compounds have hydrogen centres with hydridic character.
Aside from electride, the hydride ion is the simplest possible anion, consisting of two electrons and a proton. Hydrogen has a relatively low electron affinity, 72.77 kJ/mol and reacts exothermically with protons as a powerful Lewis base.
The low electron affinity of hydrogen and the strength of the H–H bond () means that the hydride ion would also be a strong reducing agent | 0 | Theoretical and Fundamental Chemistry |
Transferrin has been shown to interact with insulin-like growth factor 2 and IGFBP3. Transcriptional regulation of transferrin is upregulated by retinoic acid. | 1 | Applied and Interdisciplinary Chemistry |
In circumstances where more than one laboratory is analysing samples and feeding data into a large programme of work such as the Harmonised monitoring scheme in the UK, AQC can also be applied to validate one laboratory against another. In such cases the work may be referred to as inter-laboratory calibration. | 1 | Applied and Interdisciplinary Chemistry |
Non-blunt ends are created by various overhangs. An overhang is a stretch of unpaired nucleotides in the end of a DNA molecule. These unpaired nucleotides can be in either strand, creating either 3 or 5 overhangs. These overhangs are in most cases palindromic.
The simplest case of an overhang is a single nucleotide. This is most often adenine and is created as a 3 overhang by some DNA polymerases. Most commonly this is used in cloning PCR products created by such an enzyme. The product is joined with a linear DNA molecule with a 3 thymine overhang. Since adenine and thymine form a base pair, this facilitates the joining of the two molecules by a ligase, yielding a circular molecule. Here is an example of an A-overhang:
Longer overhangs are called cohesive ends or sticky ends. They are most often created by restriction endonucleases when they cut DNA. Very often they cut the two DNA strands four base pairs from each other, creating a four-base 3 overhang in one molecule and a complementary 3 overhang in the other. These ends are called cohesive since they are easily joined back together by a ligase.
For example, these two "sticky" ends are compatible:
Also, since different restriction endonucleases usually create different overhangs, it is possible to create a plasmid by excising a piece of DNA (using a different enzyme for each end) and then joining it to another DNA molecule with ends trimmed by the same enzymes. Since the overhangs have to be complementary in order for the ligase to work, the two molecules can only join in one orientation. This is often highly desirable in molecular biology. | 1 | Applied and Interdisciplinary Chemistry |
For solid materials with a significant length, like rods or cables, an estimate of the amount of thermal expansion can be described by the material strain, given by and defined as:
where is the length before the change of temperature and is the length after the change of temperature.
For most solids, thermal expansion is proportional to the change in temperature:
Thus, the change in either the strain or temperature can be estimated by:
where
is the difference of the temperature between the two recorded strains, measured in degrees Fahrenheit, degrees Rankine, degrees Celsius, or kelvin, and is the linear coefficient of thermal expansion in "per degree Fahrenheit", "per degree Rankine", "per degree Celsius", or "per kelvin", denoted by , , , or , respectively. In the field of continuum mechanics, thermal expansion and its effects are treated as eigenstrain and eigenstress. | 0 | Theoretical and Fundamental Chemistry |
In many cases, denaturation is reversible (the proteins can regain their native state when the denaturing influence is removed). This process can be called renaturation. This understanding has led to the notion that all the information needed for proteins to assume their native state was encoded in the primary structure of the protein, and hence in the DNA that codes for the protein, the so-called "Anfinsen's thermodynamic hypothesis".
Denaturation can also be irreversible. This irreversibility is typically a kinetic, not thermodynamic irreversibility, as a folded protein generally has lower free energy than when it is unfolded. Through kinetic irreversibility, the fact that the protein is stuck in a local minimum can stop it from ever refolding after it has been irreversibly denatured. | 1 | Applied and Interdisciplinary Chemistry |
The initial melting of the material to be smelted is usually referred to as the smelting or matte smelting stage. It can be undertaken in a variety of furnaces, including the largely obsolete blast furnaces and reverberatory furnaces, as well as flash furnaces, Isasmelt furnaces, etc. The product of this smelting stage is a mixture of copper, iron and sulfur that is enriched in copper, which is called matte or copper matte. The term matte grade is normally used to refer to the copper content of the matte.
The purpose of the matte smelting stage is to eliminate as much of the unwanted iron, sulfur and gangue minerals (such as silica, magnesia, alumina and limestone) as possible, while minimizing the loss of copper. This is achieved by reacting iron sulfides with oxygen (in air or oxygen enriched air) to produce iron oxides (mainly as FeO, but with some magnetite (FeO)) and sulfur dioxide.
Copper sulfide and iron oxide can mix, but when sufficient silica is added, a separate slag layer is formed. Adding silica also reduces the melting point (or, more properly, the liquidus temperature) of the slag, meaning that the smelting process can be operated at a lower temperature.
The slag forming reaction is:
:FeO + SiO → FeO.SiO
Slag is less dense than matte, so it forms a layer that floats on top of the matte.
Copper can be lost from the matte in three ways: as cuprous oxide (CuO) dissolved in the slag, as sulfide copper dissolved in the slag or as tiny droplets (or prills) of matte suspended in the slag.
The amount of copper lost as oxide copper increases as the oxygen potential of the slag increases. The oxygen potential generally increases as the copper content of the matte is increased. Thus, the loss of copper as oxide increases as the copper content of the matte increases.
On the other hand, the solubility of sulfidic copper in slag decreases as the copper content of the matte increases beyond about 40%. Nagamori calculated that more than half the copper dissolved in slags from mattes containing less than 50% copper is sulfidic copper. Above this figure, oxidic copper begins to dominate.
The loss of copper as prills suspended in the slag depends on the size of the prills, the viscosity of the slag and the settling time available. Rosenqvist suggested that about half the copper losses to slag were due to suspended prills.
The mass of slag generated in the smelting stage depends on the iron content of the material fed into the smelting furnace and the target matte grade. The greater the iron content of the feed, the more iron that will need to be rejected to the slag for a given matte grade. Similarly, increasing the target matte grade requires the rejection of more iron and an increase in the slag volume.
Thus, the two factors that most affect the loss of copper to slag in the smelting stage are:
* matte grade
* mass of slag.
This means that there is a practical limit on how high the matte grade can be if the loss of copper to slag is to be minimized. Therefore, further stages of processing (converting and fire refining) are required.
The following subsections briefly describe some of the processes used in matte smelting. | 1 | Applied and Interdisciplinary Chemistry |
There are two main types of kineses, both resulting in aggregations. However, the stimulus does not act to attract or repel individuals.
Orthokinesis: in which the speed of movement of the individual is dependent upon the stimulus intensity. For example, the locomotion of the collembola, Orchesella cincta, in relation to water. With increased water saturation in the soil there is an increase in the direction of its movement towards the aimed place.
Klinokinesis: in which the frequency or rate of turning is proportional to stimulus intensity. For example, the behaviour of the flatworm (Dendrocoelum lacteum) which turns more frequently in response to increasing light thus ensuring that it spends more time in dark areas. | 1 | Applied and Interdisciplinary Chemistry |
Sulfur concrete has a low porosity and is a poorly permeable material. Its low hydraulic conductivity slows down water ingress in its low porosity matrix and so decreases the transport of harmful chemical species, such as chloride (pitting corrosion), towards the steel reinforcements (physical protection of steel as long as no microcracks develop in the sulfur concrete matrix). It is resistant to some compounds like acids which attack normal concrete.
Beside its impermeability, Loov et al. (1974) also consider amongst the beneficial characteristics of sulfur concrete its low thermal and electrical conductivities. Sulfur concrete does not cause adverse reaction with glass (no alkali–silica reaction), does not produce efflorescences, and also presents a smooth surface finish. They also mention amongst its main limitations, its high coefficient of thermal expansion, the possible formation of acid under the action of water and sunlight. It also reacts with copper and produces a smell when melted. | 1 | Applied and Interdisciplinary Chemistry |
Brown MX-5BR or Reactive Brown 10 has a formula of CHClCrNNaOS and a molecular weight of 1163.6 g/mol, containing two dichlorotriazine rings. Brown MX-5BR, for example, can be used to purify lysozyme, phosphinothricin acetyltransferase. It also shown that it can elute tryptophanyl-tRNA synthetase using Trp as eluant, however, tryptophanyl-tRNA and tyrosyl-tRNA synthetase are the only t-RNA that can be elute out using Brown MX-5BR. | 0 | Theoretical and Fundamental Chemistry |
Sr finds extensive use in medicine as a radioactive source for superficial radiotherapy of some cancers. Controlled amounts of Sr and Sr can be used in treatment of bone cancer, and to treat coronary restenosis via vascular brachytherapy. It is also used as a radioactive tracer in medicine and agriculture. | 0 | Theoretical and Fundamental Chemistry |
While the mechanical behavior of ceramics is often dominated by flaws, i.e. porosity, instead of grain size, grain-size strengthening is also observed in high-density ceramic specimens. Additionally, nanocrystalline ceramics have been shown to sinter more rapidly than bulk ceramics, leading to higher densities and improved mechanical properties, although extended exposure to the high pressures and elevated temperatures required to sinter the part to full density can result in coarsening of the nanostructure.
The large volume fraction of grain boundaries associated with nanocrystalline materials causes interesting behavior in ceramic systems, such as superplasticity in otherwise brittle ceramics. The large volume fraction of grain boundaries allows for a significant diffusional flow of atoms via Coble creep, analogous to the grain boundary sliding deformation mechanism in nanocrystalline metals. Because the diffusional creep rate scales as and linearly with the grain boundary diffusivity, refining the grain size from 10 μm to 10 nm can increase the diffusional creep rate by approximately 11 orders of magnitude. This superplasticity could prove invaluable for the processing of ceramic components, as the material may be converted back into a conventional, coarse-grained material via additional thermal treatment after forming. | 1 | Applied and Interdisciplinary Chemistry |
The White catalyst was originally developed for use in a branched allylic acetoxylation reaction. An enantioselective version of this reaction was subsequently reported, using chromium(III) salen fluoride as a chiral cocatalyst. A macrolactonization reaction based on the branched allylic esterification was developed for the preparation of 14- to 19-membered macrolides. This method was applied to the total synthesis of 6-deoxyerythronolide B. In addition to acetate, a wide variety of carboxylic acids may be employed as nucleophiles in the branch allylic esterification reaction. As the first step in an esterification/Heck sequence, aliphatic and aromatic carboxylates were demonstrated, including amino acids. | 0 | Theoretical and Fundamental Chemistry |
Hexamethylenetetramine, also known as methenamine, hexamine, or its trade name Urotropin, is a heterocyclic organic compound with the formula (CH)N. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like structure similar to adamantane. It is useful in the synthesis of other organic compounds, including plastics, pharmaceuticals, and rubber additives. It sublimes in vacuum at 280 °C. | 0 | Theoretical and Fundamental Chemistry |
The fission product mixture contains significant amounts of molybdenum. Molybdenum-99 is of enormous interest to nuclear medicine as the parent nuclide to but its short half life means it'll usually be decayed long before the spent fuel is reprocessed. can be produced both by fission followed by immediate reprocessing (usually only done in small scale research reactors) or in particle accelerators. As Molybdenum-100 only decays extremely slowly via double beta decay (half life longer than the age of the universe) the molybdenum content of spent fuel will be essentially stable after a few days have passed to allow the Molybdenum-99 to decay. | 0 | Theoretical and Fundamental Chemistry |
Suppose a single spin-1/2 is in the state , which is an eigenstate of the z-spin operator , that is . Similarly . Making use of the expansion of a Hermitian operator in terms of projections onto its eigenkets with eigenvalues as , the associated density operator is
where is the identity operator. Similarly, the density operator for the state is
Since the spin operators are all traceless and the expectation value of an operator for a system with density operator is , the terms proportional to the unit operator do not affect the expectations of the spin operators. Additionally those parts do not evolve in time, since they trivially commute with the Hamiltonian. Therefore those terms can be ignored, and the state corresponds to a density operator , while the state corresponds to a density operator . In exactly the same manner, polarisation along the positive x-axis, that is a state , corresponds to a density operator . This idea extends naturally to multiple spins, where the states and operators are direct products of single-spin states and operators. Hence operator terms in the density operator have a direct duality with states.
In the case of two spins , the terms in the density operator (ignoring the identity on its own) can be interpreted as representing
* - longitudinal magnetisation
* - in-phase transverse magnetisation, which is the observable quantity in NMR.
* - anti-phase longitudinal magnetisation
* - longitudinal two-spin order
* - other coherences, which are more difficult to interpret, but may evolve into other terms
where eg is a shorthand for the Kronecker product , where is the identity operator on the spin, and similarly is a shorthand for .
The factors of two in the true two-spin operators are to allow for convenient commutation relations in this specific spin-1/2 case - see below. Note also that we could instead choose to expand the density operator in the basis etc, where the transverse operators have been replaced with raising and lowering operators. With quadrature detection, the observable associated with an individual spin is effectively the non-Hermitian , so this is sometimes more convenient. | 0 | Theoretical and Fundamental Chemistry |
While the above techniques use a spatially extended, wide incident beam, section topography is based on a narrow beam on the order of some 10 micrometers (in one or, in the case of pinhole topography with a pencil beam, in both lateral dimensions). Section topographs therefore investigate only a restricted volume of the sample.
On its path through the crystal, the beam is diffracted at different depths, each one contributing to image formation on a different location on the detector (film). Section topography can therefore be used for depth-resolved defect analysis.
In section topography, even perfect crystals display fringes. The technique is very sensitive to crystalline defects and strain, as these distort the fringe pattern in the topograph. Quantitative analysis can be performed with the help of image simulation by computer algorithms, usually based on the Takagi-Taupin equations.
An enlarged synchrotron X-ray transmission section topograph on the right shows a diffraction image of the section of a sample having a gallium nitride (GaN) layer grown by metal-organic vapour phase epitaxy on sapphire wafer. Both the epitaxial GaN layer and the sapphire substrate show numerous defects. The GaN layer actually consists of about 20 micrometers wide small-angle grains connected to each other. Strain in the epitaxial layer and substrate is visible as elongated streaks parallel to the diffraction vector direction. The defects on the underside of the sapphire wafer section image are surface defects on the unpolished backside of the sapphire wafer. Between the sapphire and GaN the defects are interfacial defects. | 0 | Theoretical and Fundamental Chemistry |
The Mond gas could be produced very cheaply since it required only a low-quality coal, offering large savings for many processes. The production of Mond gas did not require much labor.
The Mond gas became popularized during the industrial power generation in the beginning of the 20th century, since industries were very interested in a source of low-cost energy. The Mond gas provided a boost to the gas engine industry in particular. For example, a large gas engine that used Mond gas was 5–6 times more efficient than a standard steam engine. This is primarily because Mond gas was produced from the lowest cost coal rather than steam coal, resulting in cheaper electricity at about 1/20 of the normal price. | 0 | Theoretical and Fundamental Chemistry |
*2-chloropropylene
*propenylbenzene (β-methylstyrene).
Many phenylpropanoids and their derivatives feature derivatives of propenylbenzene:
*Anethole
*Asarone
*Carpacin
*Coniferyl alcohol
*Isoeugenol
*Isosafrole
*Methyl isoeugenol
*Pseudoisoeugenol | 0 | Theoretical and Fundamental Chemistry |
In H-NMR spectroscopy, the coupling of two hydrogen atoms on adjacent carbon atoms is called vicinal coupling. The coupling constant J represents coupling of vicinal hydrogen atoms because they couple through three bonds. Depending on the other substituents, the vicinal coupling constant is typically a value between 0 and +20 Hz. The dependence of the vicinal coupling constant on the dihedral angle is described by the Karplus relation. | 0 | Theoretical and Fundamental Chemistry |
The commonly used radioisotopes have short half lives and so do not occur in nature in large amounts. They are produced by nuclear reactions. One of the most important processes is absorption of a neutron by an atomic nucleus, in which the mass number of the element concerned increases by 1 for each neutron absorbed. For example,
:C + n → C
In this case the atomic mass increases, but the element is unchanged. In other cases the product nucleus is unstable and decays, typically emitting protons, electrons (beta particle) or alpha particles. When a nucleus loses a proton the atomic number decreases by 1. For example,
:S + n → P + p
Neutron irradiation is performed in a nuclear reactor. The other main method used to synthesize radioisotopes is proton bombardment. The proton are accelerated to high energy either in a cyclotron or a linear accelerator. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, explosive boiling or phase explosion is a method whereby a superheated metastable liquid undergoes an explosive liquid-vapor phase transition into a stable two-phase state because of a massive homogeneous nucleation of vapor bubbles. This concept was pioneered by M. M. Martynyuk in 1976 and then later advanced by Fucke and Seydel. | 0 | Theoretical and Fundamental Chemistry |
Jaynes (1985, 2003, et passim) discussed the concept of probability. According to the MaxEnt viewpoint, the probabilities in statistical mechanics are determined jointly by two factors: by respectively specified particular models for the underlying state space (e.g. Liouvillian phase space); and by respectively specified particular partial descriptions of the system (the macroscopic description of the system used to constrain the MaxEnt probability assignment). The probabilities are objective in the sense that, given these inputs, a uniquely defined probability distribution will result, the same for every rational investigator, independent of the subjectivity or arbitrary opinion of particular persons. The probabilities are epistemic in the sense that they are defined in terms of specified data and derived from those data by definite and objective rules of inference, the same for every rational investigator. Here the word epistemic, which refers to objective and impersonal scientific knowledge, the same for every rational investigator, is used in the sense that contrasts it with opiniative, which refers to the subjective or arbitrary beliefs of particular persons; this contrast was used by Plato and Aristotle, and stands reliable today.
Jaynes also used the word subjective in this context because others have used it in this context. He accepted that in a sense, a state of knowledge has a subjective aspect, simply because it refers to thought, which is a mental process. But he emphasized that the principle of maximum entropy refers only to thought which is rational and objective, independent of the personality of the thinker. In general, from a philosophical viewpoint, the words subjective and objective are not contradictory; often an entity has both subjective and objective aspects. Jaynes explicitly rejected the criticism of some writers that, just because one can say that thought has a subjective aspect, thought is automatically non-objective. He explicitly rejected subjectivity as a basis for scientific reasoning, the epistemology of science; he required that scientific reasoning have a fully and strictly objective basis. Nevertheless, critics continue to attack Jaynes, alleging that his ideas are "subjective". One writer even goes so far as to label Jaynes' approach as "ultrasubjectivist", and to mention "the panic that the term subjectivism created amongst physicists".
The probabilities represent both the degree of knowledge and lack of information in the data and the model used in the analyst's macroscopic description of the system, and also what those data say about the nature of the underlying reality.
The fitness of the probabilities depends on whether the constraints of the specified macroscopic model are a sufficiently accurate and/or complete description of the system to capture all of the experimentally reproducible behavior. This cannot be guaranteed, a priori. For this reason MaxEnt proponents also call the method predictive statistical mechanics. The predictions can fail. But if they do, this is informative, because it signals the presence of new constraints needed to capture reproducible behavior in the system, which had not been taken into account. | 0 | Theoretical and Fundamental Chemistry |
There are five requirements for surfactants to successfully disperse oil:
*Dispersant must be on the oil's surface in the proper concentration
*Dispersant must penetrate (mix with) the oil
* Surfactant molecules must orient at the oil-water interface (hydrophobic in oil and hydrophilic in water)
* Oil-water interfacial tension must be lowered (so the oil can be broken up).
* Energy must be applied to the mix (for example, by waves) | 1 | Applied and Interdisciplinary Chemistry |
Pharmacogenetics focuses on identifying genetic variations including SNPs associated with differential responses to treatment. Many drug metabolizing enzymes, drug targets, or target pathways can be influenced by SNPs. The SNPs involved in drug metabolizing enzyme activities can change drug pharmacokinetics, while the SNPs involved in drug target or its pathway can change drug pharmacodynamics. Therefore, SNPs are potential genetic markers that can be used to predict drug exposure or effectiveness of the treatment. Genome-wide pharmacogenetic study is called pharmacogenomics. Pharmacogenetics and pharmacogenomics are important in the development of precision medicine, especially for life-threatening diseases such as cancers. | 1 | Applied and Interdisciplinary Chemistry |
RNA-Seq captures DNA variation, including single nucleotide variants, small insertions/deletions. and structural variation. Variant calling in RNA-Seq is similar to DNA variant calling and often employs the same tools (including SAMtools mpileup and GATK HaplotypeCaller) with adjustments to account for splicing. One unique dimension for RNA variants is allele-specific expression (ASE): the variants from only one haplotype might be preferentially expressed due to regulatory effects including imprinting and expression quantitative trait loci, and noncoding rare variants. Limitations of RNA variant identification include that it only reflects expressed regions (in humans, <5% of the genome), could be subject to biases introduced by data processing (e.g., de novo transcriptome assemblies underestimate heterozygosity), and has lower quality when compared to direct DNA sequencing. | 1 | Applied and Interdisciplinary Chemistry |
Four key assumptions in Scheil analysis enable determination of phases present in a cast part. These assumptions are:
# No diffusion occurs in solid phases once they are formed ()
# Infinitely fast diffusion occurs in the liquid at all temperatures by virtue of a high diffusion coefficient, thermal convection, Marangoni convection, etc. ()
# Equilibrium exists at the solid-liquid interface, and so compositions from the phase diagram are valid
# Solidus and liquidus are straight segments
The fourth condition (straight solidus/liquidus segments) may be relaxed when numerical techniques are used, such as those used in CALPHAD software packages, though these calculations rely on calculated equilibrium phase diagrams. Calculated diagrams may include odd artifacts (i.e. retrograde solubility) that influence Scheil calculations. | 1 | Applied and Interdisciplinary Chemistry |
Stark spectroscopy (sometimes known as electroabsorption/emission spectroscopy) is a form of spectroscopy based on the Stark effect. In brief, this technique makes use of the Stark effect (or electrochromism) either to reveal information about the physiochemical or physical properties of a sample using a well-characterized electric field or to reveal information about an electric field using a reference sample with a well-characterized Stark effect.
The use of the term "Stark effect" differs between the disciplines of chemistry and physics. Physicists tend to use the more classical definition of the term (see Stark effect), while chemists usually use the term to refer to what is technically electrochromism. In the former case, the applied electric field splits the atomic energy levels and is the electric field analog of the Zeeman effect. However, in the latter case, the applied electric field changes the molar absorption coefficient of the sample, which can be measured using traditional absorption or emission spectroscopic methods. This effect is known as electrochromism. | 0 | Theoretical and Fundamental Chemistry |
Empowering Women in Organic Chemistry (EWOC) is a scientific conference designed to bring the research and career interests of women in organic chemistry to the forefront and seeks to empower all marginalized individuals by promoting equity, justice, diversity, and inclusion across all chemistry fields. EWOC is the world's largest gathering of women in organic chemistry, and hosts an annual meeting of women (students, post-docs, faculty and professionals) who work or plan to work in the field of Organic Chemistry, broadly defined, from all types of institutions (academic, industry, biotech, non-profit and government).
The meeting goals are to
*Establish a peer group network for collaborating and recruiting diverse talent
* Afford a novel mechanism to provide advice and counsel for women organic chemists
* Share stories from different perspectives about career development and challenges faced – and overcome – along the way
* Establish an inclusive community, with an emphasis on Diversity, Inclusion and Belonging, to engage, network and support each other in the field of Organic Chemistry
* Provide support and guidance to graduate students and post-docs making career decisions
* Provide community support to enhance retention of women in chemistry. | 0 | Theoretical and Fundamental Chemistry |
Until 1986, physicists had believed that BCS theory forbade superconductivity at temperatures above about 30 K. In that year, Bednorz and Müller discovered superconductivity in lanthanum barium copper oxide (LBCO), a lanthanum-based cuprate perovskite material, which had a transition temperature of 35 K (Nobel Prize in Physics, 1987). It was soon found that replacing the lanthanum with yttrium (i.e., making YBCO) raised the critical temperature above 90 K.
This temperature jump is of particular engineering significance, since it allows liquid nitrogen as a refrigerant, replacing liquid helium. Liquid nitrogen can be produced relatively cheaply, even on-site. The higher temperatures additionally help to avoid some of the problems that arise at liquid helium temperatures, such as the formation of plugs of frozen air that can block cryogenic lines and cause unanticipated and potentially hazardous pressure buildup.
Many other cuprate superconductors have since been discovered, and the theory of superconductivity in these materials is one of the major outstanding challenges of theoretical condensed matter physics. There are currently two main hypotheses – the resonating-valence-bond theory, and spin fluctuation which has the most support in the research community. The second hypothesis proposed that electron pairing in high-temperature superconductors is mediated by short-range spin waves known as paramagnons.
In 2008, holographic superconductivity, which uses holographic duality or AdS/CFT correspondence theory, was proposed by Gubser, Hartnoll, Herzog, and Horowitz, as a possible explanation of high-temperature superconductivity in certain materials.
From about 1993, the highest-temperature superconductor known was a ceramic material consisting of mercury, barium, calcium, copper and oxygen (HgBaCaCuO) with T = 133–138 K.
In February 2008, an iron-based family of high-temperature superconductors was discovered. Hideo Hosono, of the Tokyo Institute of Technology, and colleagues found lanthanum oxygen fluorine iron arsenide (LaOFFeAs), an oxypnictide that superconducts below 26 K. Replacing the lanthanum in LaOFFeAs with samarium leads to superconductors that work at 55 K.
In 2014 and 2015, hydrogen sulfide () at extremely high pressures (around 150 gigapascals) was first predicted and then confirmed to be a high-temperature superconductor with a transition temperature of 80 K. Additionally, in 2019 it was discovered that lanthanum hydride () becomes a superconductor at 250 K under a pressure of 170 gigapascals.
In 2018, a research team from the Department of Physics, Massachusetts Institute of Technology, discovered superconductivity in bilayer graphene with one layer twisted at an angle of approximately 1.1 degrees with cooling and applying a small electric charge. Even if the experiments were not carried out in a high-temperature environment, the results are correlated less to classical but high temperature superconductors, given that no foreign atoms need to be introduced. The superconductivity effect came about as a result of electrons twisted into a vortex between the graphene layers, called "skyrmions". These act as a single particle and can pair up across the graphene's layers, leading to the basic conditions required for superconductivity.
In 2020, a room-temperature superconductor (critical temperature 288 K) made from hydrogen, carbon and sulfur under pressures of around 270 gigapascals was described in a paper in Nature. However, in 2022 the article was retracted by the editors because the validity of background subtraction procedures had been called into question. All nine authors maintain that the raw data strongly support the main claims of the paper.
On 31 December 2023 "Global Room-Temperature Superconductivity in Graphite" was published in the journal "Advanced Quantum Technologies" claiming to demonstrate superconductivity at room temperature and ambient pressure in Highly oriented pyrolytic graphite with dense arrays of nearly parallel line defects. | 0 | Theoretical and Fundamental Chemistry |
The kinetic isotope effect (KIE) of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) is the isotopic fractionation associated solely with the step in the Calvin-Benson cycle where a molecule of carbon dioxide () is attached to the 5-carbon sugar ribulose-1,5-bisphosphate (RuBP) to produce two 3-carbon sugars called 3-phosphoglycerate (3 PGA). This chemical reaction is catalyzed by the enzyme RuBisCO, and this enzyme-catalyzed reaction creates the primary kinetic isotope effect of photosynthesis. It is also largely responsible for the isotopic compositions of photosynthetic organisms and the heterotrophs that eat them. Understanding the intrinsic KIE of RuBisCO is of interest to earth scientists, botanists, and ecologists because this isotopic biosignature can be used to reconstruct the evolution of photosynthesis and the rise of oxygen in the geologic record, reconstruct past evolutionary relationships and environmental conditions, and infer plant relationships and productivity in modern environments. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.