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Currently, receptor modulators are categorized in the Agonist, Partial Agonist, Selective Tissue Modulators, Antagonist, and Inverse Agonist categories in terms of the effect they cause. They are further divided into Orthosteric or Allosteric Modulators according to how they effect said result. Typically, a chemical acts in an agonist fashion whenever it instigates or else facilitates a particular reaction by binding to a particular receptor. In contract, a chemical acts as an antagonist whenever binding to a particular receptor blocks or inhibits a particular response. Between these endpoints exists a gradient defined by a number of variables. One example is Selective Tissue Modulators, which mean a given ligand can behave differently according to the tissue type it is in. As for orthosteric and allosteric modulation, this describes the manner in which the ligand binds to the receptor in question: if it binds directly to the prescribed binding site of a receptor, the ligand is orthosteric in this instance; if the ligand alters the receptor by interacting with it at any place other than a binding site, allosteric interaction occurred. Note that a drug's categorization does not dictate how another drug of the same family could be categorized or whether the same drug may also function in another category. An example is found in medications used to treat opioid addiction, with methadone, buprenorphine, naloxone, and naltrexone all in separate categories or in more than one simultaneously. In addition, depending on the cell type, the specific effect, whether agonist, antagonist, inverse agonist, etc., could have a unique specific effect. An example is seen in insulin, under "Receptor Agonists," as it interacts with multiple different cell types as an agonist, but incites multiple and different responses in both. | 1 | Applied and Interdisciplinary Chemistry |
Phosphonates are also used as concrete retarder. They delay the cement setting time, allowing a longer time to place the concrete or to spread the cement hydration heat on a longer period of time to avoid too high temperature and resulting cracks. They also have favourable dispersing properties and so are investigated as a possible new class of superplasticizers. However, presently, phosphonates are not commercially available as superplasticizers. Superplasticizers are concrete admixtures designed to increase the concrete fluidity and workability of concrete or to decrease its water-to-cement (w/c) ratio. By reducing the water content in concrete, it decreases its porosity, improving so the mechanical properties (compressive and tensile strength) and the durability of concrete (lower water, gas and solutes transport properties). | 0 | Theoretical and Fundamental Chemistry |
While the superposition approximation is actually exact at larger distances, it is no longer accurate at smaller separations. Solutions of the DH or PB equations in between the plates provide a more accurate picture at these conditions. Let us only discuss the symmetric situation within the DH model here. This discussion will introduce the notion of charge regulation, which suggests that the surface charge (and the surface potential) may vary (or regulate) upon approach.
The DH equation can be solved exactly for two plates. The boundary conditions play an important role, and the surface potential and surface charge density
and become functions of the surface separation h and they may differ from the corresponding quantities ψ and σ for the isolated surface. When the surface charge remains constant upon approach, one refers to the constant charge (CC) boundary conditions. In this case, the diffuse layer potential will increase upon approach. On the other hand, when the surface potential is kept constant, one refers to constant potential (CP) boundary condition. In this case, the surface charge density decreases upon approach. Such decrease of charge can be caused by adsorption of desorption of charged ions from the surface. Such variation of adsorbed species upon approach has also been referred to as proximal adsorption. The ability of the surface to regulate its charge can be quantified by the regulation parameter
where C = ε ε κ is the diffuse layer capacitance and C the inner (or regulation) capacitance. The CC conditions are found when p = 1 while the CP conditions for p = 0. The realistic case will be typically situated in between. By solving the DH equation one can show that diffuse layer potential varies upon approach as
while the surface charged density obey a similar relation
The swelling pressure can be found by inserting the exact solution of the DH equation into the expressions above and one finds
Repulsion is strongest for the CC conditions (p = 1) while it is weaker for the CP conditions (p = 0). The result of the superposition approximation is always recovered at larger distances but also for p = 1/2 at all distances. The latter fact explains why the superposition approximation can be very accurate even at small separations. Surfaces regulate their charge and not infrequently the actual regulation parameter is not far away from 1/2.
The situation is exemplified in the figure below. From stability considerations one can show that p < 1 and that this parameter may also becomes negative. These results can be extended to asymmetric case in a straightforward way.
When surface potentials are replaced by effective potentials, this simple DH picture is applicable for more highly charged surfaces at sufficiently larger distances. At shorter distances, however, one may enter the PB regime and the regulation parameter may not remain constant. In this case, one must solve the PB equation together with an appropriate model of the surface charging process. It was demonstrated experimentally that charge regulation effects can become very important in asymmetric systems. | 0 | Theoretical and Fundamental Chemistry |
A selenenic acid is an organoselenium compound and an oxoacid with the general formula RSeOH, where R ≠ H. It is the first member of the family of organoselenium oxoacids, which also include seleninic acids and selenonic acids, which are RSeOH and RSeOH, respectively. Selenenic acids derived from selenoenzymes are thought to be responsible for the antioxidant activity of these enzymes. This functional group is sometimes called SeO-selenoperoxol. | 0 | Theoretical and Fundamental Chemistry |
PAC is one of the artificial chromosome vectors. Some other artificial chromosomes include: bacterial artificial chromosome, yeast artificial chromosome and the human artificial chromosome. Compared to other artificial chromosomes, it can carry relatively large DNA fragments, however less so than the yeast artificial chromosome(YAC). Some advantages of PACs compared to YACs includes easier manipulation of bacteria system, easier separation from DNA hosts, higher transformation rate, more stable inserts, and they are non-chimeric which means they do not rearrange and ligate to form new DNA strand, allowing for a user friendly vector choice. | 1 | Applied and Interdisciplinary Chemistry |
Fluid particle is the smallest unit (atoms or molecules) in the fluid phase (gas, liquid or plasma) without breaking any chemical bond. Energy of fluid particle is divided into potential, electronic, translational, vibrational, and rotational energies. The heat (thermal) energy storage in fluid particle is through the temperature-dependent particle motion (translational, vibrational, and rotational energies). The electronic energy is included only if temperature is high enough to ionize or dissociate the fluid particles or to include other electronic transitions. These quantum energy states of the fluid particles are found using their respective quantum Hamiltonian. These are H = −(ħ/2m)∇, H = −(ħ/2m)∇ + Γx/2 and H = −(ħ/2I)∇ for translational, vibrational and rotational modes. (Γ: spring constant, I: the moment of inertia for the molecule). From the Hamiltonian, the quantized fluid particle energy state E and partition functions Z [with the Maxwell–Boltzmann (MB) occupancy distribution] are found as
* translational
* vibrational
* rotational
* total
Here, g is the degeneracy, n, l, and j are the transitional, vibrational and rotational quantum numbers, T is the characteristic temperature for vibration (= ħω/k, : vibration frequency), and T is the rotational temperature [= ħ/(2Ik)]. The average specific internal energy is related to the partition function through Z,
With the energy states and the partition function, the fluid particle specific heat capacity c is the summation of contribution from various kinetic energies (for non-ideal gas the potential energy is also added). Because the total degrees of freedom in molecules is determined by the atomic configuration, c has different formulas depending on the configuration,
* monatomic ideal gas
* diatomic ideal gas
* nonlinear, polyatomic ideal gas
where R is the gas constant (= Nk, N: the Avogadro constant) and M is the molecular mass (kg/kmol). (For the polyatomic ideal gas, N is the number of atoms in a molecule.) In gas, constant-pressure specific heat capacity c has a larger value and the difference depends on the temperature T, volumetric thermal expansion coefficient β and the isothermal compressibility κ [c – c = Tβ/(ρκ), ρ : the fluid density]. For dense fluids that the interactions between the particles (the van der Waals interaction) should be included, and c and c would change accordingly.
The net motion of particles (under gravity or external pressure) gives rise to the convection heat flux q = ρcuT. Conduction heat flux q for ideal gas is derived with the gas kinetic theory or the Boltzmann transport equations, and the thermal conductivity is
where ⟨u⟩ is the RMS (root mean square) thermal velocity (3kT/m from the MB distribution function, m: atomic mass) and τ is the relaxation time (or intercollision time period) [(2π dn ⟨u⟩) from the gas kinetic theory, ⟨u⟩: average thermal speed (8kT/πm), d: the collision diameter of fluid particle (atom or molecule), n: fluid number density].
k is also calculated using molecular dynamics (MD), which simulates physical movements of the fluid particles with the Newton equations of motion (classical) and force field (from ab initio or empirical properties). For calculation of k, the equilibrium MD with Green–Kubo relations, which express the transport coefficients in terms of integrals of time correlation functions (considering fluctuation), or nonequilibrium MD (prescribing heat flux or temperature difference in simulated system) are generally employed.
Fluid particles can interact with other principal particles. Vibrational or rotational modes, which have relatively high energy, are excited or decay through the interaction with photons. Gas lasers employ the interaction kinetics between fluid particles and photons, and laser cooling has been also considered in CO gas laser. Also, fluid particles can be adsorbed on solid surfaces (physisorption and chemisorption), and the frustrated vibrational modes in adsorbates (fluid particles) is decayed by creating e-h pairs or phonons. These interaction rates are also calculated through ab initio calculation on fluid particle and the Fermi golden rule. | 0 | Theoretical and Fundamental Chemistry |
In 1999 the laboratory of Prof. Dr. Ben L. Feringa at the University of Groningen, The Netherlands, reported the creation of a unidirectional molecular rotor. Their 360° molecular motor system consists of a bis-helicene connected by an alkene double bond displaying axial chirality and having two stereocenters.
One cycle of unidirectional rotation takes 4 reaction steps. The first step is a low temperature endothermic photoisomerization of the trans (P,P) isomer 1 to the cis (M,M) 2 where P stands for the right-handed helix and M for the left-handed helix. In this process, the two axial methyl groups are converted into two less sterically favorable equatorial methyl groups.
By increasing the temperature to 20 °C these methyl groups convert back exothermally to the (P,P) cis axial groups (3) in a helix inversion. Because the axial isomer is more stable than the equatorial isomer, reverse rotation is blocked. A second photoisomerization converts (P,P) cis 3 into (M,M) trans 4, again with accompanying formation of sterically unfavorable equatorial methyl groups. A thermal isomerization process at 60 °C closes the 360° cycle back to the axial positions.
A major hurdle to overcome is the long reaction time for complete rotation in these systems, which does not compare to rotation speeds displayed by motor proteins in biological systems. In the fastest system to date, with a fluorene lower half, the half-life of the thermal helix inversion is 0.005 seconds. This compound is synthesized using the Barton-Kellogg reaction. In this molecule the slowest step in its rotation, the thermally induced helix-inversion, is believed to proceed much more quickly because the larger tert-butyl group makes the unstable isomer even less stable than when the methyl group is used. This is because the unstable isomer is more destabilized than the transition state that leads to helix-inversion. The different behaviour of the two molecules is illustrated by the fact that the half-life time for the compound with a methyl group instead of a tert-butyl group is 3.2 minutes.
The Feringa principle has been incorporated into a prototype nanocar. The car synthesized has a helicene-derived engine with an oligo (phenylene ethynylene) chassis and four carborane wheels and is expected to be able to move on a solid surface with scanning tunneling microscopy monitoring, although so far this has not been observed. The motor does not perform with fullerene wheels because they quench the photochemistry of the motor moiety. Feringa motors have also been shown to remain operable when chemically attached to solid surfaces. The ability of certain Feringa systems to act as an asymmetric catalyst has also been demonstrated.
In 2016, Feringa was awarded a Nobel prize for his work on molecular motors. | 0 | Theoretical and Fundamental Chemistry |
Anammox stands for anaerobic ammonia oxidation and the organisms responsible were relatively recently discovered, in the late 1990s. This form of metabolism occurs in members of the Planctomycetota (e.g. "Candidatus Brocadia anammoxidans") and involves the coupling of ammonia oxidation to nitrite reduction. As oxygen is not required for this process, these organisms are strict anaerobes. Amazingly, hydrazine ( – rocket fuel) is produced as an intermediate during anammox metabolism. To deal with the high toxicity of hydrazine, anammox bacteria contain a hydrazine-containing intracellular organelle called the anammoxasome, surrounded by highly compact (and unusual) ladderane lipid membrane. These lipids are unique in nature, as is the use of hydrazine as a metabolic intermediate. Anammox organisms are autotrophs although the mechanism for carbon dioxide fixation is unclear. Because of this property, these organisms could be used to remove nitrogen in industrial wastewater treatment processes. Anammox has also been shown to have widespread occurrence in anaerobic aquatic systems and has been speculated to account for approximately 50% of nitrogen gas production in the ocean. | 1 | Applied and Interdisciplinary Chemistry |
B. Jill Venton is a professor of chemistry at University of Virginia, where she serves as the department chair since 2019. Venton's research focuses on developing analytical chemistry methods to enable detection of molecules in the brain. | 0 | Theoretical and Fundamental Chemistry |
Measuring the composition of a cow's rumen can also indicate the quality of its feed, a process called a forage analysis.
Once the cannula is surgically placed, the cow is then allowed to graze for a certain period of time—for example, 30 to 45 minutes, in a 1960 study at the University of Nevada, Reno. Researchers will then remove some or all of the ruminated material through the cannula. Analyzing rumen this way can indicate whether particular grasses on which cows are grazing are nutritionally adequate. | 1 | Applied and Interdisciplinary Chemistry |
The dynamic behavior of compressible flows is governed by the dimensionless thermodynamic quantity , which is known as the fundamental derivative of gasdynamics and is defined as
where
* is the speed of sound [m/s];
* is the specific entropy per unit mass [J/(kg K)].
From a mathematical point of view, the fundamental derivative is a non-dimensional measure of the curvature of isentropes in the pressure-volume thermodynamic plane. From a physical point of view, the definition of tells that the speed of sound increases with pressure in isentropic transformations for values of , while, by contrast, it decreases with pressure for .
Based on the value of , three gasdynamic regimes can be defined:
* ideal gasdynamic regime for ;
* non-ideal classical gasdynamic regime for ;
* non-classical gasdynamic regime for . | 0 | Theoretical and Fundamental Chemistry |
In the thermodynamic stream of thinking, the specified mechanisms of heat transfer are conduction and radiation. These mechanisms presuppose recognition of temperature; empirical temperature is enough for this purpose, though absolute temperature can also serve. In this stream of thinking, quantity of heat is defined primarily through calorimetry.
Though its definition of them differs from that of the mechanical stream of thinking, the empirical stream of thinking nevertheless presupposes the existence of adiabatic enclosures. It defines them through the concepts of heat and temperature. These two concepts are coordinately coherent in the sense that they arise jointly in the description of experiments of transfer of energy as heat. | 0 | Theoretical and Fundamental Chemistry |
Another potential solid-state refrigeration technique and a relatively new area of study comes from a special property of super elastic materials. These materials undergo a temperature change when experiencing an applied mechanical stress (called the elastocaloric effect). Since super elastic materials deform reversibly at high strains, the material experiences a flattened elastic region in its stress-strain curve caused by a resulting phase transformation from an austenitic to a martensitic crystal phase.
When a super elastic material experiences a stress in the austenitic phase, it undergoes an exothermic phase transformation to the martensitic phase, which causes the material to heat up. Removing the stress reverses the process, restores the material to its austenitic phase, and absorbs heat from the surroundings cooling down the material.
The most appealing part of this research is how potentially energy efficient and environmentally friendly this cooling technology is. The different materials used, commonly shape-memory alloys, provide a non-toxic source of emission free refrigeration. The most commonly studied materials studied are shape-memory alloys, like nitinol and Cu-Zn-Al. Nitinol is of the more promising alloys with output heat at about 66 J/cm and a temperature change of about 16–20 K. Due to the difficulty in manufacturing some of the shape memory alloys, alternative materials like natural rubber have been studied. Even though rubber may not give off as much heat per volume (12 J/cm ) as the shape memory alloys, it still generates a comparable temperature change of about 12 K and operates at a suitable temperature range, low stresses, and low cost.
The main challenge however comes from potential energy losses in the form of hysteresis, often associated with this process. Since most of these losses comes from incompatibilities between the two phases, proper alloy tuning is necessary to reduce losses and increase reversibility and efficiency. Balancing the transformation strain of the material with the energy losses enables a large elastocaloric effect to occur and potentially a new alternative for refrigeration. | 0 | Theoretical and Fundamental Chemistry |
Julius Tafel discovered that hydroxylamine hydrochloride or sulfate salts can be produced by electrolytic reduction of nitric acid with HCl or Sulfuric acid| respectively:
Hydroxylamine can also be produced by the reduction of nitrous acid or potassium nitrite with bisulfite:
: (100 °C, 1 h)
Hydrochloric acid disproportionates nitromethane to hydroxylamine hydrochloride and carbon monoxide via the hydroxamic acid.
A direct production of hydroxylamine from molecular nitrogen is also possible in water plasma. | 0 | Theoretical and Fundamental Chemistry |
Nuclear fusion is normally understood to occur at temperatures in the tens of millions of degrees. This is called "thermonuclear fusion". Since the 1920s, there has been speculation that nuclear fusion might be possible at much lower temperatures by catalytically fusing hydrogen absorbed in a metal catalyst. In 1989, a claim by Stanley Pons and Martin Fleischmann (then one of the world's leading electrochemists) that such cold fusion had been observed caused a brief media sensation before the majority of scientists criticized their claim as incorrect after many found they could not replicate the excess heat. Since the initial announcement, cold fusion research has continued by a small community of researchers who believe that such reactions happen and hope to gain wider recognition for their experimental evidence. | 0 | Theoretical and Fundamental Chemistry |
Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its thermal conductivity, and is denoted .
Heat spontaneously flows along a temperature gradient (i.e. from a hotter body to a colder body). For example, heat is conducted from the hotplate of an electric stove to the bottom of a saucepan in contact with it. In the absence of an opposing external driving energy source, within a body or between bodies, temperature differences decay over time, and thermal equilibrium is approached, temperature becoming more uniform.
In conduction, the heat flow is within and through the body itself. In contrast, in heat transfer by thermal radiation, the transfer is often between bodies, which may be separated spatially. Heat can also be transferred by a combination of conduction and radiation. In solids, conduction is mediated by the combination of vibrations and collisions of molecules, propagation and collisions of phonons, and diffusion and collisions of free electrons. In gases and liquids, conduction is due to the collisions and diffusion of molecules during their random motion. Photons in this context do not collide with one another, and so heat transport by electromagnetic radiation is conceptually distinct from heat conduction by microscopic diffusion and collisions of material particles and phonons. But the distinction is often not easily observed unless the material is semi-transparent.
In the engineering sciences, heat transfer includes the processes of thermal radiation, convection, and sometimes mass transfer. Usually, more than one of these processes occurs in a given situation. | 1 | Applied and Interdisciplinary Chemistry |
Silyl enol ethers are neutral, mild nucleophiles (milder than enamines) that react with good electrophiles such as aldehydes (with Lewis acid catalysis) and carbocations. Silyl enol ethers are stable enough to be isolated, but are usually used immediately after synthesis. | 0 | Theoretical and Fundamental Chemistry |
The idea behind transition engineering originated from many different roots, both technical and non-technical. The concept of sustainable development has been around since 1987 and the problem of sustainability was a driving force in the development of transition engineering. The Transition Town movement provided further inspiration as it showed that there were many groups of people around the world motivated to prepare for peak oil and climate change. Transition towns and ecovillages demonstrate the need for engineers to build systems that manage un-sustainable risks and provide people with sustainable options. Engineers are ethically required to "hold paramount the safety, health and welfare of the public" and answer society's need for sustainable development
The origins of safety engineering provided much of the inspiration for transition engineering. At the beginning of the 1900s, business owners viewed workplace safety as a wasted investment and politicians were slow to change. After the Triangle Shirtwaist Factory fire in New York City killed 156 trapped workers, 62 engineers came together to investigate how to make the workplace a safer place to be. This eventually lead to the formation of the American Society of Safety Engineers.
As safety engineering manages the risks of unsafe conditions, transition engineering manages the risks of unsustainable conditions. To give engineers a better grasp of sustainability, transition engineering defines the problem as UN-sustainability. This is similar to the problem of un-safe conditions that is the purpose of safety engineering. We do not necessarily know what a perfectly safe system looks like, but we do know what unsafe systems look like and how to improve them; the same applies to unsustainability of systems. By reducing unsustainability issues we take steps in the right direction | 1 | Applied and Interdisciplinary Chemistry |
There are several laboratory experiments that demonstrate how a small amount of one enantiomer at the start of a reaction can lead to a large excess of a single enantiomer as the product. For example, the Soai reaction is autocatalytic. If the reaction is started with some of one of the product enantiomers already present, the product acts as an enantioselective catalyst for production of more of that same enantiomer. The initial presence of just 0.2 equivalent one enantiomer can lead to up to 93% enantiomeric excess of the product.
Another study concerns the proline catalyzed aminoxylation of propionaldehyde by nitrosobenzene. In this system, a small enantiomeric excess of catalyst leads to a large enantiomeric excess of product.
Serine octamer clusters are also contenders. These clusters of 8 serine molecules appear in mass spectrometry with an unusual homochiral preference, however there is no evidence that such clusters exist under non-ionizing conditions and amino acid phase behavior is far more prebiotically relevant. The recent observation that partial sublimation of a 10% enantioenriched sample of leucine results in up to 82% enrichment in the sublimate shows that enantioenrichment of amino acids could occur in space. Partial sublimation processes can take place on the surface of meteors where large variations in temperature exist. This finding may have consequences for the development of the Mars Organic Detector scheduled for launch in 2013 which aims to recover trace amounts of amino acids from the Mars surface exactly by a sublimation technique.
A high asymmetric amplification of the enantiomeric excess of sugars are also present in the amino acid catalyzed asymmetric formation of carbohydrates
One classic study involves an experiment that takes place in the laboratory. When sodium chlorate is allowed to crystallize from water and the collected crystals examined in a polarimeter, each crystal turns out to be chiral and either the form or the form. In an ordinary experiment the amount of crystals collected equals the amount of crystals (corrected for statistical effects). However, when the sodium chlorate solution is stirred during the crystallization process the crystals are either exclusively or exclusively . In 32 consecutive crystallization experiments 14 experiments deliver -crystals and 18 others -crystals. The explanation for this symmetry breaking is unclear but is related to autocatalysis taking place in the nucleation process.
In a related experiment, a crystal suspension of a racemic amino acid derivative continuously stirred, results in a 100% crystal phase of one of the enantiomers because the enantiomeric pair is able to equilibrate in solution (compare with dynamic kinetic resolution). | 0 | Theoretical and Fundamental Chemistry |
There exist several variants of the stable carbenes above where one of the nitrogen atoms adjacent to the carbene center (the α nitrogens) has been replaced by an alternative heteroatom, such as oxygen, sulfur, or phosphorus.
In particular, the formal substitution of sulfur for one of the nitrogens in imidazole would yield the aromatic heterocyclic compound thiazole. A thiazole based carbene (analogous to the carbene postulated by Breslow) has been prepared and characterised by X-ray crystallography. Other non-aromatic aminocarbenes with O, S and P atoms adjacent (i.e. alpha) to the carbene centre have been prepared, for example, thio- and oxyiminium based carbenes have been characterised by X-ray crystallography.
Since oxygen and sulfur are divalent, steric protection of the carbenic centre is limited especially when the N–C–X unit is part of a ring. These acyclic carbenes have diagnostic C NMR chemical shift values between 250 and 300 ppm for the carbenic carbon, further downfield than any other types of stable carbene. X-ray structures have shown N–C–X bond angles of around 104° and 109° respectively.
Carbenes that formally derive from imidazole-2-ylidenes by substitution of sulfur, oxygen, or other chalcogens for both α-nitrogens are expected to be unstable, as they have the potential to dissociate into an alkyne (RC≡CR) and a carbon dichalcogenide (X=C=X). | 0 | Theoretical and Fundamental Chemistry |
The concept of plotting the free energies of reaction of various elements with a given gas-phase reactant may be extended beyond oxidation reactions. The original paper by Ellingham explicitly to the reduction of both oxygen and sulfur by metallurgical processes, and anticipated the use of such diagrams for other compounds, including chlorides, carbides, and sulfates. The concept is generally useful for studying the comparative stability of compounds across a range of partial pressures and temperatures. The construction of an Ellingham diagram is especially useful when studying the stability of compounds in the presence of a reductant. Ellingham diagrams are now available for bromides, chlorides, fluorides, hydrides, iodides, nitrides, oxides, sulfides, selenides, and tellurides. | 1 | Applied and Interdisciplinary Chemistry |
Huntingtin protein co-localizes with ATM repair protein at sites of DNA damage. Huntingtin is a scaffolding protein in the ATM oxidative DNA damage response complex. Huntingtons disease patients with aberrant huntingtin protein are deficient in repair of oxidative DNA damage. Oxidative DNA damage appears to underlie Huntingtons disease pathogenesis. Huntington's disease is likely caused by the dysfunction of mutant huntingtin scaffold protein in DNA repair leading to increased oxidative DNA damage in metabolically active cells. | 1 | Applied and Interdisciplinary Chemistry |
The first step in Gateway cloning is the preparation of a Gateway Entry clone. There are a few different ways to make entry clone.
# Gateway attB1 and attB2 sequences are added to the 5 and 3 end of a gene fragment, respectively, using gene-specific PCR primers and PCR amplification. The PCR amplification products are then mixed with a proprietary mixture of plasmids called Gateway "Donor vectors" (Invitrogen terminology) and proprietary "BP Clonase" enzymes. The enzyme mix catalyzes the recombination and insertion of the PCR product containing the attB sequence into the attP recombination sites in the Gateway Donor vector. When the cassette is part of the target plasmid, it is referred to as an "Entry clone" in Gateway nomenclature and the recombination sequences are referred to as Gateway "attL" type.
# A short end containing attL is added using the TOPO method, a technique in which DNA fragments are cloned into specific vectors without the need for DNA ligases.
# The desired DNA sequence can be cloned into a multicloning site containing attL using restriction enzyme.
The second step in Gateway cloning is the preparation of a Gateway Destination vector. It is important to choose the target vector that best suits your target when preparing the expression clone. The gene cassette in the Gateway Entry clone can then be simply and efficiently transferred into any Gateway Destination vector (Invitrogen nomenclature for any Gateway plasmid that contains Gateway “attR” recombination sequences and elements such as promoters and epitope tags, but not ORFs) using the proprietary enzyme mix, “LR Clonase”. Thousands of Gateway Destination plasmids have been made and are freely shared amongst researchers across the world. Gateway Destination vectors are similar to classical expression vectors containing multiple cloning sites, before the insertion of a gene of interest, using restriction enzyme digestion and ligation. Gateway Destination vectors are commercially available from Invitrogen, EMD (Novagen) and Covalys.
The third step in Gateway cloning is the preparation of express your gene of interest. Make sure to use sequencing or a restriction digest to check the integrity of your expression clone. Once your construct is working, you can transform or transfect the cells you intend to employ in your investigations.
Since Gateway cloning uses patented recombination sequences, and proprietary enzyme mixes available only from Invitrogen, the technology does not allow researchers to switch vendors and contributes to the lock-in effect of all such patented procedures.
To summarize the different steps involved in Gateway cloning:
* Gateway BP reaction: PCR-product with flanking att B sites (this step can also use other methods of DNA isolation, such as restriction-digestion) + Donor vector containing attP sites + BP clonase => Gateway Entry clone, containing att L sites, flanking gene of interest
* Gateway LR reaction: Entry clone containing att L sites + Destination vector containing att R sites, and promoters and tags + LR clonase => Expression clone containing attB sites, flanking gene of interest, ready for gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Chinese Chemistry Olympiad () is an annual academic competition held by Chinese Chemical Society. CAS changed its official Chinese name in February 2014, though its English translation remains the same.
The first CChO was held in 1984, 16 years after IChO. The event has been held every year since then. China has selected excellent high school students to take part in IChO through the competition since 1987. | 1 | Applied and Interdisciplinary Chemistry |
If we place two detectors at the same angle from the target, one on the right and one on the left, they will generally measure a different number of electrons and . Consequently it is possible to define the asymmetry , as
The Sherman function is a measure of the probability of a spin-up electron to be scattered, at a specific angle , to the right or to the left of the target, due to spin-orbit coupling. It can assume values ranging from -1 (spin-up electron is scattered with 100% probability to the left of the target) to +1 (spin-up electron is scattered with 100% probability to the right of the target). The value of the Sherman function depends on the energy of the incoming electron, evaluated via the parameter . When , spin-up electrons will be scattered with the same probability to the right and to the left of the target.
Then it is possible to write
Plugging these formulas inside the definition of asymmetry, it is possible to obtain a simple expression for the evaluation of the asymmetry at a specific angle , i.e.:
Theoretical calculations are available for different atomic targets and for a specific target, as a function of the angle. | 0 | Theoretical and Fundamental Chemistry |
Photothermal therapy (PTT) refers to efforts to use electromagnetic radiation (most often in infrared wavelengths) for the treatment of various medical conditions, including cancer. This approach is an extension of photodynamic therapy, in which a photosensitizer is excited with specific band light. This activation brings the sensitizer to an excited state where it then releases vibrational energy (heat), which is what kills the targeted cells.
Unlike photodynamic therapy, photothermal therapy does not require oxygen to interact with the target cells or tissues. Current studies also show that photothermal therapy is able to use longer wavelength light, which is less energetic and therefore less harmful to other cells and tissues. | 0 | Theoretical and Fundamental Chemistry |
Alpha particle, beta particle, and gamma ray radioactive emissions are industrially useful. Most sources of these are synthetic radioisotopes. Areas of use include the petroleum industry, industrial radiography, homeland security, process control, food irradiation and underground detection. | 0 | Theoretical and Fundamental Chemistry |
Chemically, phosphatidylethanols are phospholipids carrying two fatty acid chains, which are variable in structure, and one phosphate ethyl ester. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a Zintl phase is a product of a reaction between a group 1 (alkali metal) or group 2 (alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ionic bonding. Zintl phases are a subgroup of brittle, high-melting intermetallic compounds that are diamagnetic or exhibit temperature-independent paramagnetism and are poor conductors or semiconductors.
This type of solid is named after German chemist Eduard Zintl who investigated them in the 1930s. The term "Zintl Phases" was first used by Laves in 1941. In his early studies, Zintl noted that there was an atomic volume contraction upon the formation of these products and realized that this could indicate cation formation. He suggested that the structures of these phases were ionic, with complete electron transfer from the more electropositive metal to the more electronegative main group element. The structure of the anion within the phase is then considered on the basis of the resulting electronic state. These ideas are further developed in the Zintl-Klemm-Busmann concept, where the polyanion structure should be similar to that of the isovalent element. Further, the anionic sublattice can be isolated as polyanions (Zintl ions) in solution and are the basis of a rich subfield of main group inorganic chemistry. | 0 | Theoretical and Fundamental Chemistry |
* 2011 National Science Foundation CAREER Award
* 2016 American Chemical Society Early-Career Award in Experimental Physical Chemistry
* 2019 Rice Institute of Biosciences and Bioengineering Hamill Innovation Award
* 2019 National Academy of Sciences Kavli Fellow
* 2020 National Science Foundation Award for Special Creativity | 0 | Theoretical and Fundamental Chemistry |
For example, a commonly used reaction to profile hydrogen with an energetic N ion beam is
:N + H → C + α + γ (4.43 MeV)
with a sharp resonance in the reaction cross section at 6.385 MeV of only 1.8 keV. Since the incident N ion loses energy along its trajectory in the material it must have an energy higher than the resonance energy to induce the nuclear reaction with hydrogen nuclei deeper in the target.
This reaction is usually written H(N,αγ)C. It is inelastic because the Q-value is not zero (in this case it is 4.965 MeV). Rutherford backscattering (RBS) reactions are elastic (Q = 0), and the interaction (scattering) cross-section σ given by the famous formula derived by Lord Rutherford in 1911. But non-Rutherford cross-sections (so-called EBS, elastic backscattering spectrometry) can also be resonant: for example, the O(α,α)O reaction has a strong and very useful resonance at 3038.1 ± 1.3 keV.
In the H(N,αγ)C reaction (or indeed the N(p,αγ)C inverse reaction), the energetic emitted γ ray is characteristic of the reaction and the number that are detected at any incident energy is proportional to the hydrogen concentration at the respective depth in the sample. Due to the narrow peak in the reaction cross section primarily ions of the resonance energy undergo a nuclear reaction. Thus, information on the hydrogen distribution can be straight forward obtained by varying the N incident beam energy.
Hydrogen is an element inaccessible to Rutherford backscattering spectrometry since nothing can backscatter from H (since all atoms are heavier than hydrogen!). But it is often analysed by elastic recoil detection. | 0 | Theoretical and Fundamental Chemistry |
The Rayleigh flow model has many analytical uses, most notably involving aircraft engines. For instance, the combustion chambers inside turbojet engines usually have a constant area and the fuel mass addition is negligible. These properties make the Rayleigh flow model applicable for heat addition to the flow through combustion, assuming the heat addition does not result in dissociation of the air-fuel mixture. Producing a shock wave inside the combustion chamber of an engine due to thermal choking is very undesirable due to the decrease in mass flow rate and thrust. Therefore, the Rayleigh flow model is critical for an initial design of the duct geometry and combustion temperature for an engine.
The Rayleigh flow model is also used extensively with the Fanno flow model. These two models intersect at points on the enthalpy-entropy and Mach number-entropy diagrams, which is meaningful for many applications. However, the entropy values for each model are not equal at the sonic state. The change in entropy is 0 at M = 1 for each model, but the previous statement means the change in entropy from the same arbitrary point to the sonic point is different for the Fanno and Rayleigh flow models. If initial values of s and M are defined, a new equation for dimensionless entropy versus Mach number can be defined for each model. These equations are shown below for Fanno and Rayleigh flow, respectively.
Figure 3 shows the Rayleigh and Fanno lines intersecting with each other for initial conditions of s = 0 and M = 3.0 The intersection points are calculated by equating the new dimensionless entropy equations with each other, resulting in the relation below.
The intersection points occur at the given initial Mach number and its post-normal shock value. For Figure 3, these values are M = 3.0 and 0.4752, which can be found the normal shock tables listed in most compressible flow textbooks. A given flow with a constant duct area can switch between the Rayleigh and Fanno models at these points. | 1 | Applied and Interdisciplinary Chemistry |
The origins of colloidal crystals go back to the mechanical properties of bentonite sols, and the optical properties of Schiller layers in iron oxide sols. The properties are supposed to be due to the ordering of monodisperse inorganic particles. Monodisperse colloids, capable of forming long-range ordered arrays, existing in nature. The discovery by W.M. Stanley of the crystalline forms of the tobacco and tomato viruses provided examples of this. Using X-ray diffraction methods, it was subsequently determined that when concentrated by centrifuging from dilute water suspensions, these virus particles often organized themselves into highly ordered arrays.
Rod-shaped particles in the tobacco mosaic virus could form a two-dimensional triangular lattice, while a body-centered cubic structure was formed from the almost spherical particles in the tomato Bushy Stunt Virus. In 1957, a letter describing the discovery of "A Crystallizable Insect Virus" was published in the journal Nature. Known as the Tipula Iridescent Virus, from both square and triangular arrays occurring on crystal faces, the authors deduced the face-centered cubic close-packing of virus particles. This type of ordered array has also been observed in cell suspensions, where the symmetry is well adapted to the mode of reproduction of the organism. The limited content of genetic material places a restriction on the size of the protein to be coded by it. The use of a large number of the same proteins to build a protective shell is consistent with the limited length of RNA or DNA content.
It has been known for many years that, due to repulsive Coulombic interactions, electrically charged macromolecules in an aqueous environment can exhibit long-range crystal-like correlations with interparticle separation distances often being considerably greater than the individual particle diameter. In all of the cases in nature, the same iridescence is caused by the diffraction and constructive interference of visible lightwaves which falls under Bragg’s law.
Because of the rarity and pathological properties, neither opal nor any of the organic viruses have been very popular in scientific laboratories. The number of experiments exploring the physics and chemistry of these “colloidal crystals” has emerged as a result of the simple methods which have evolved in 20 years for preparing synthetic monodisperse colloids, both polymer and mineral, and, through various mechanisms, implementing and preserving their long-range order formation. | 0 | Theoretical and Fundamental Chemistry |
Charles Hatchett FRS FRSE (2 January 1765 – 10 March 1847) was an English mineralogist and analytical chemist who discovered the element niobium, for which he proposed the name "columbium".
Hatchett was elected a Fellow of the Linnaean Society in 1795,
and of the Royal Society in 1797. Hatchett was elected to the Literary Club in London in 1809 and became its treasurer in 1829. | 1 | Applied and Interdisciplinary Chemistry |
The word metabolome appears to be a blending of the words "metabolite" and "chromosome". It was constructed to imply that metabolites are indirectly encoded by genes or act on genes and gene products. The term "metabolome" was first used in 1998 and was likely coined to match with existing biological terms referring to the complete set of genes (the genome), the complete set of proteins (the proteome) and the complete set of transcripts (the transcriptome). The first book on metabolomics was published in 2003. The first journal dedicated to metabolomics (titled simply "Metabolomics") was launched in 2005 and is currently edited by Prof. Roy Goodacre. Some of the more significant early papers on metabolome analysis are listed in the references below. | 1 | Applied and Interdisciplinary Chemistry |
Particles crossing a nanopore are detected one at a time as a transient change in the ionic current flow, which is denoted as a blockade event with its amplitude denoted as the blockade magnitude. As blockade magnitude is proportional to particle size, accurate particle sizing can be achieved after calibration with a known standard. This standard is composed of particles of a known size and concentration. For TRPS, carboxylated polystyrene particles are often used.
Nanopore-based detection allows particle-by-particle assessment of complex mixtures. By selecting an appropriately sized nanopore and adjusting its stretch, the nanopore size can be optimized for particle size and improve measurement accuracy.
Adjustments to nanopore stretch, in combination with a fine-control of pressure and voltage allow TRPS to determine sample concentration and to accurately derive individual particle zeta potential in addition to particle size information. | 0 | Theoretical and Fundamental Chemistry |
In multichannel scaling (MCS) mode, the MCA records a pulse count-rate over time. Unlike PHA, MCS does not differentiate pulses of different amplitudes. Instead, the MCA records all measured counts in one channel for a set time interval (called the "dwell time"), then switches to the next channel to record the subsequent time interval, and so on.
The internal control voltage signal used to switch channels when the dwell time elapses is often available to the experimenter and can be used to trigger changes in the experimental setup. In this arrangement, the MCA acts as an X–Y recorder, observing changes in the count rate as a function of the controlled experimental parameter. For example, a Geiger counter connected to an MCA in MCS mode could be used to record the amount of ionizing radiation emitted by a neutron generator at different voltages. | 0 | Theoretical and Fundamental Chemistry |
TGGE and DGGE are broadly useful in biomedical and ecological research; selected applications are described below. | 1 | Applied and Interdisciplinary Chemistry |
The role of glutathione(GSH) is to remove accumulated reactive oxygen species which may damage cells. During this process, its thiol side chain is oxidised and two glutathione molecules are connected by a disulphide bond to form a dimer(GSSG). In order to regenerate glutathione the disulphide bond has to be broken, In human cells, this is done by glutathione reductase(GR).
Glutathione reductase is a dimer that contains two identical subunits. It requires one NADP and one FAD as the cofactors. The active site is located in the linkage between two subunits. The NADPH is involved in the generation of FADH-. In the active site, there are two cysteine residues besides the FAD cofactor and are used to break the disulphide bond during the catalytic reaction. NADPH is bound by three positively charged residues: Arg-218, His-219 and Arg-224.
The catalytic process starts when the FAD is reduced by NADPH to accept one electron and from FADH. It then attacks the disulphide bond formed between 2 cysteine residues, forming one SH bond and a single S group. This S group will act as a nucleophile to attack the disulphide bond in the oxidised glutathione(GSSG), breaking it and forming a cysteine-SG complex. The first SG anion is released and then receives one proton from adjacent SH group and from the first glutathione monomer. Next the adjacent S group attack disulphide bond in cysteine-SG complex and release the second SG anion. It receives one proton in solution and forms the second glutathione monomer. | 1 | Applied and Interdisciplinary Chemistry |
Manganese deficiency in humans, which is rare, results in a number of medical problems. Many common vitamin and mineral supplement products fail to include manganese in their compositions. Relatively high dietary intake of other minerals such as iron, magnesium, and calcium may inhibit the proper intake of manganese. A deficiency of manganese causes skeletal deformation in animals and inhibits the production of collagen in wound healing. | 1 | Applied and Interdisciplinary Chemistry |
Archaerhodopsins are active transporters, using the energy from sunlight to pump H ions out of the cell to generate a proton motive force that is used for ATP synthesis. Removal of the retinal cofactor (e.g. by treatment with hydroxylamine) abolishes the transporter function and dramatically alters the absorption spectra of the proteins. The proton pumping ability of AR3 has been demonstrated in recombinant E. coli cells and of AR4 in liposomes.
In the resting or ground state of archaerhodopsin, the bound retinal is in the all-trans form, but on absorption of a photon of light, it isomerizes to 13-cis. The protein surrounding the chromophore reacts to the change of shape and undergoes an ordered sequence of conformational changes, which are collectively known as the photocycle. These changes alter the polarity of the local environment surrounding titratable amino acid side chains inside the protein, enabling H to be pumped from the cytoplasm to the extracellular side of the membrane. The intermediate states of the photocycle may be identified by their absorption maxima. | 0 | Theoretical and Fundamental Chemistry |
Similarly to Rosetta@home, Foldit is a means to discover native protein structures faster through distributed computing. However, Foldit has a greater emphasis on community collaboration through its forums, where users can collaborate on certain folds. Furthermore, Foldits crowdsourced approach places a greater emphasis on the user. Foldits virtual interaction and gamification create a unique and innovative environment with the potential to greatly advance protein folding research. | 1 | Applied and Interdisciplinary Chemistry |
Due to macromolecular crowding, enzyme assays and biophysical measurements performed in dilute solution may fail to reflect the actual process and its kinetics taking place in the cytosol. One approach to produce more accurate measurements would be to use highly concentrated extracts of cells, to try to maintain the cell contents in a more natural state. However, such extracts contain many kinds of biologically active molecules, which can interfere with the phenomena being studied. Consequently, crowding effects are mimicked in vitro by adding high concentrations of relatively inert molecules such as polyethylene glycol, ficoll, dextran, or serum albumin to experimental media. However, using such artificial crowding agents can be complicated, as these crowding molecules can sometimes interact in other ways with the process being examined, such as by binding weakly to one of the components. | 0 | Theoretical and Fundamental Chemistry |
The correct name of the method is guanidinium thiocyanate-phenol-chloroform extraction. The use of TRIzol can result in DNA yields comparable to other extraction methods, and it leads to >50% bigger RNA yield. An alternative method for RNA extraction is phenol extraction and TCA/acetone precipitation. Chloroform should be exchanged with 1-bromo-3-chloropropane when using the new generation TRI Reagent.
DNA and RNA from TRIzol and TRI reagent can also be extracted using the Direct-zol Miniprep kit by Zymo Research. This method eliminates the use of Chloroform and 1-bromo-3-chloropropane completely, bypassing phase-separation and precipitation steps.
TRIzol is light-sensitive and is often stored in a dark-colored, glass container covered in foil. It is stored at room temperature.
When used, it resembles cough syrup, bright pink. The smell of the phenol is extremely strong. TRIzol works by maintaining RNA integrity during tissue homogenization, while at the same time disrupting and breaking down cells and cell components. | 1 | Applied and Interdisciplinary Chemistry |
Born in Baltimore, Maryland, he was the only son of Jacob Hackerman and Anna Raffel, immigrants from the Baltic regions of the Russian Empire that later became Estonia and Latvia, respectively.
Hackerman earned his bachelors degree in 1932 and his doctors degree in chemistry in 1935 from Johns Hopkins University. He taught at Johns Hopkins, Loyola College in Baltimore and the Virginia Polytechnic Institute and State University in Blacksburg, Virginia, before working on the Manhattan Project in World War II.
He joined the University of Texas in 1945 as an assistant professor of chemistry, became an associate professor in 1946, a full professor in 1950, a department chair in 1952, dean of research in 1960, vice president and provost in 1961, and vice chancellor for academic affairs for the University of Texas System in 1963. Hackerman left the University of Texas in 1970 for Rice, where he retired 15 years later. He was named professor emeritus of chemistry at the University of Texas in 1985 and taught classes until the end of his life.
He was a member of the National Academy of Sciences, the American Philosophical Society, and the American Academy of Arts and Sciences. Among his many honors are the Olin Palladium Award of the Electrochemical Society, the Gold Medal of the American Institute of Chemists (1978), the Charles Lathrop Parsons Award, the Vannevar Bush Award and the National Medal of Science. He was awarded the Acheson Award by the Electrochemical Society in 1984.
Hackerman served on advisory committees and boards of several technical societies and government agencies, including the National Science Board, the Texas Governors Task Force on Higher Education and the Scientific Advisory Board of the Welch Foundation. He also served as editor of the Journal of the Electrochemical Society' and as president of the Electrochemical Society. | 0 | Theoretical and Fundamental Chemistry |
The quinhydrone electrode may be used to measure the hydrogen ion concentration (pH) of a solution containing an acidic substance. | 0 | Theoretical and Fundamental Chemistry |
Often it is the colour of freshwater or how clear or hazy the water is that is the most obvious visual characteristic. Unfortunately neither colour nor turbidity are strong indicators of the overall chemical composition of water. However both colour and turbidity reduce the amount of light penetrating the water and can have significant impact on algae and macrophytes. Some algae in particular are highly dependent on water with low colour and turbidity.
Many rivers draining high moor-lands overlain by peat have a very deep yellow brown colour caused by dissolved humic acids. | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acid thermodynamics is the study of how temperature affects the nucleic acid structure of double-stranded DNA (dsDNA). The melting temperature (T) is defined as the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state. T depends on the length of the DNA molecule and its specific nucleotide sequence. DNA, when in a state where its two strands are dissociated (i.e., the dsDNA molecule exists as two independent strands), is referred to as having been denatured by the high temperature. | 1 | Applied and Interdisciplinary Chemistry |
* [http://www.thebiogrid.org/ BioGRID] database
* [http://mentha.uniroma2.it mentha] the interactome browser
* [http://www.ebi.ac.uk/intact IntAct: The Molecular Interaction Database]
* [http://interactome.org Interactome.org] — a dedicated interactome web site. | 1 | Applied and Interdisciplinary Chemistry |
The majority of proteins in a cell are the product of messenger RNA transcribed from nuclear genes, including most of the proteins of the organelles, which are produced in the cytoplasm like all nuclear gene products and then transported to the organelle. Genes in the nucleus are arranged in a linear fashion upon chromosomes, which serve as the scaffold for replication and the regulation of gene expression. As such, they are usually under strict copy-number control, and replicate a single time per cell cycle. Nuclear cells such as platelets do not possess nuclear DNA and therefore must have alternative sources for the RNA that they need to generate proteins. With the nuclear genome's 3.3 billion DNA base pairs in humans, one good example of a nuclear gene is MDH1 or the malate dehydrogenase 1 gene. In various metabolic pathways, including the citric acid cycle, MDH1 is a protein-coding gene that encodes an enzyme that catalyzes the NAD/NADH-dependent, reversible oxidation of malate to oxaloacetate. This gene codes for the cytosolic isozyme, which is involved in the malate-aspartate shuttle, which allows malate to cross past the mitochondrial membrane and be converted to oxaloacetate to perform further cellular functions. This gene among many exhibits its huge purposeful role in the entirety of an organism’s physiologic function. Although non-nuclear genes may exist in its functional nature, the role of nuclear genes in response and in coordination with non-nuclear genes is fundamental. | 1 | Applied and Interdisciplinary Chemistry |
Many traditional solids exhibit different properties when they shrink to nanometer sizes. For example, nanoparticles of usually yellow gold and gray silicon are red in color; gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C); and metallic nanowires are much stronger than the corresponding bulk metals. The high surface area of nanoparticles makes them extremely attractive for certain applications in the field of energy. For example, platinum metals may provide improvements as automotive fuel catalysts, as well as proton exchange membrane (PEM) fuel cells. Also, ceramic oxides (or cermets) of lanthanum, cerium, manganese and nickel are now being developed as solid oxide fuel cells (SOFC). Lithium, lithium-titanate and tantalum nanoparticles are being applied in lithium ion batteries. Silicon nanoparticles have been shown to dramatically expand the storage capacity of lithium ion batteries during the expansion/contraction cycle. Silicon nanowires cycle without significant degradation and present the potential for use in batteries with greatly expanded storage times. Silicon nanoparticles are also being used in new forms of solar energy cells. Thin film deposition of silicon quantum dots on the polycrystalline silicon substrate of a photovoltaic (solar) cell increases voltage output as much as 60% by fluorescing the incoming light prior to capture. Here again, surface area of the nanoparticles (and thin films) plays a critical role in maximizing the amount of absorbed radiation. | 0 | Theoretical and Fundamental Chemistry |
Both alkyl and aryl sulfonic acids are known, most large-scale applications are associated with the aromatic derivatives. | 0 | Theoretical and Fundamental Chemistry |
For vinylic fluorine substituents, the following formula allows for estimation of F chemical shfits:where Z is the statistical substituent chemical shift (SSCS) for the substituent in the listed position, and S is the interaction factor. Some representative values for use in this equation are provided in the table below: | 0 | Theoretical and Fundamental Chemistry |
Alkynes are named using the same system, with the suffix "-yne" indicating a triple bond: ethyne (acetylene), propyne (methylacetylene). | 0 | Theoretical and Fundamental Chemistry |
The protein encoded by this gene is a transcriptional regulatory protein. It contains paired amphipathic helix (PAH) domains, which are important for protein-protein interactions and may mediate repression by the Mad-Max complex. | 1 | Applied and Interdisciplinary Chemistry |
In theoretical thermodynamics, respected authors vary in their approaches to the definition of quantity of heat transferred. There are two main streams of thinking. One is from a primarily empirical viewpoint (which will here be referred to as the thermodynamic stream), to define heat transfer as occurring only by specified macroscopic mechanisms; loosely speaking, this approach is historically older. The other (which will here be referred to as the mechanical stream) is from a primarily theoretical viewpoint, to define it as a residual quantity calculated after transfers of energy as macroscopic work, between two bodies or closed systems, have been determined for a process, so as to conform with the principle of conservation of energy or the first law of thermodynamics for closed systems; this approach grew in the twentieth century, though was partly manifest in the nineteenth. | 0 | Theoretical and Fundamental Chemistry |
Community participation in the planning of any sewer system is a fundamental requirement to achieve higher household connection rates and to increase the likelihood of proper maintenance of in-block sewers. In addition, it can motivate users to assume parts of the costs of the sewer system that they are able to assume, such as contribution of labor for construction and/or maintenance.
Typically, in the planning process for a simplified sewerage system, meetings are carried out at the housing block (condominio) level for information, discussions and clarifications required for a joint group decision on network design, community contributions during construction and maintenance responsibilities. Users might finance and implement in-house sanitary installations and household connections and would agree on a suitable type of condominial branch. They are asked to comply with agreements established for construction and operation of the condominial branch, as well as payment of tariffs. In turn, the service provider agrees to fulfill his responsibilities as established in the “Terms of Connection ” between the parties.
The community participation process also provides a good opportunity for complementary actions like hygiene promotion, which can have a significant impact on public health at a relatively limited cost. | 1 | Applied and Interdisciplinary Chemistry |
The Exxon process, also Kuhlmann- or PCUK – oxo process, is used for the hydroformylation of C6–C12 olefins. The process relies on cobalt catalysts. In order to recover the catalyst, an aqueous sodium hydroxide solution or sodium carbonate is added to the organic phase. By extraction with olefin and neutralization by addition of sulfuric acid solution under carbon monoxide pressure the metal carbonyl hydride can recovered. This is stripped out with syngas, absorbed by the olefin, and returned to the reactor. Similar to the BASF process, the Exxon process is carried out at a pressure of about 30 MPa and at a temperature of about 160 to 180 °C. | 0 | Theoretical and Fundamental Chemistry |
Glass coloring and color marking may be obtained in several ways.
# by the addition of coloring ions,
# by precipitation of nanometer-sized colloids (so-called striking glasses such as "gold ruby" or red "selenium ruby"),
#by colored inclusions (as in milk glass and smoked glass)
#by light scattering (as in phase separated glass)
#by dichroic coatings (see dichroic glass), or
#by colored coatings | 0 | Theoretical and Fundamental Chemistry |
The early studies indicating anomalous increases in nanofluid thermal properties over those of the base fluid, particularly the heat transfer coefficient, have been largely discredited. One of the main conclusions taken from a study involving over thirty labs throughout the world was that "no anomalous enhancement of thermal conductivity was observed in the limited set of nanofluids tested in this exercise". The COST funded research programme, Nanouptake (COST Action CA15119)[http://www.nanouptake.eu/] was founded with the intention "to develop and foster the use of nanofluids as advanced heat transfer/thermal storage materials to increase the efficiency of heat exchange and storage systems". One of the final outcomes, involving an experimental study in five different labs, concluded that "there are no anomalous or unexplainable effects".
Despite these apparently conclusive experimental investigations theoretical papers continue to follow the claim of anomalous enhancement, see, particularly via Brownian and thermophoretic mechanisms, as suggested by Buongiorno. Brownian diffusion is due to the random drifting of suspended nanoparticles in the base fluid which originates from collisions between the nanoparticles and liquid molecules. Thermophoresis induces nanoparticle migration from warmer to colder regions, again due to collisions with liquid molecules. The mismatch between experimental and theoretical results is explained in Myers et al. In particular it is shown that Brownian motion and thermophoresis effects are too small to have any significant effect: their role is often amplified in theoretical studies due to the use of incorrect parameter values. Experimental validation of the assertions of are provided in Alkasmoul et al. Brownian diffusion as a cause for enhanced heat transfer is dismissed in the discussion of the use of nanofluids in solar collectors. | 0 | Theoretical and Fundamental Chemistry |
There are biocompatible microalgae hybrid microrobots for active drug-delivery in the lungs and the gastrointestinal tract. The microrobots proved effective in tests with mice. In the two studies, "Fluorescent dye or cell membrane–coated nanoparticle functionalized algae motors were further embedded inside a pH-sensitive capsule" and "antibiotic-loaded neutrophil membrane-coated polymeric nanoparticles [were attached] to natural microalgae". | 1 | Applied and Interdisciplinary Chemistry |
A point symmetry operation is a symmetry operation f for which at least one point p has the property p = f(p).
Table 1. Point symmetry operations in three dimensions.
a R stands for a number ≥ 1.
b The Schoenflies system uses rotoreflections (given the symbol S) instead of rotoinversions. For each rotoinversion operation, there is an equivalent rotoreflection; examples of how these operations match up are : –3 = S ; –4 = S ; –6 = S . | 0 | Theoretical and Fundamental Chemistry |
In the Eulerian specification of a field, the field is represented as a function of position x and time t. For example, the flow velocity is represented by a function
On the other hand, in the Lagrangian specification, individual fluid parcels are followed through time. The fluid parcels are labelled by some (time-independent) vector field x. (Often, x is chosen to be the position of the center of mass of the parcels at some initial time t. It is chosen in this particular manner to account for the possible changes of the shape over time. Therefore the center of mass is a good parameterization of the flow velocity u of the parcel.) In the Lagrangian description, the flow is described by a function
giving the position of the particle labeled x at time t.
The two specifications are related as follows:
because both sides describe the velocity of the particle labeled x at time t.
Within a chosen coordinate system, x and x are referred to as the Lagrangian coordinates and Eulerian coordinates of the flow respectively. | 1 | Applied and Interdisciplinary Chemistry |
Chronic pain and neuropathic pain are indications for which there is high unmet need in the clinic. PEA has been tested in a variety of animal models for chronic and neuropathic pain, because cannabinoids, such as THC, have been proven to be effective in neuropathic pain states. The analgesic and antihyperalgesic effects of PEA in two models of acute and persistent pain seemed to be explained at least partly via the de novo neurosteroid synthesis. In chronic granulomatous pain and inflammation model, PEA could prevent nerve formation and sprouting, mechanical allodynia, and PEA inhibited dorsal root ganglia activation, which is a hallmark for winding up in neuropathic pain. The mechanism of action of PEA as an analgesic and anti-inflammatory molecule is probably based on different aspects. PEA inhibits the release of both preformed and newly synthesised mast cell mediators, such as histamine and TNF-alpha. PEA, as well as its analogue adelmidrol (di-amide derivative of azelaic acid), can both down-regulate mast cells. PEA reduces the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) and prevents IkB-alpha degradation and p65 NF-kappaB nuclear translocation, the latter related to PEA as an endogenous PPAR-alpha agonist.
In 2012 it became clear that PEA can also reduce reperfusion injury and the negative impact of shock on various outcome parameters, such as renal dysfunction, ischemic injury and inflammation, most probably via the PPAR-alpha pathway. Studies have shown that PEA activates PPAR-alpha and TRPV1 receptors that control inflammation and the sensation of pain. Among the reperfusion and inflammation markers measured PEA could reduce the increase in creatinine, γGT, AST, nuclear translocation of NF-κBp65; kidney MPO activity and MDA levels, nitrotyrosine, PAR and adhesion molecules expression, the infiltration and activation of mast cells and apoptosis.
The biological responses to PEA dosing in animal models and in humans are being investigated vis-à-vis its involvement in a repair mechanism relevant to patient conditions of chronic inflammation and chronic pain. In a model of visceral pain (inflammation of the urinary bladder) PEA was able to attenuate the viscero-visceral hyper-reflexia induced by inflammation of the urinary bladder, one of the reasons why PEA is currently explored in the painful bladder syndrome. In a different model for bladder pain, the turpentine-induced urinary bladder inflammation in the rat, PEA also attenuated a referred hyperalgesia in a dose-dependent way. Chronic pelvic pain in patients seem to respond favourably to a treatment with PEA. | 1 | Applied and Interdisciplinary Chemistry |
Karl Ernst Claus, also known as Karl Klaus or Carl Claus (; 22 January 1796 – 24 March 1864), was a Russian chemist and naturalist of Baltic German origin. Claus was a professor at Kazan State University and a member of the Russian Academy of Sciences. He was primarily known as a chemist and discoverer of the chemical element ruthenium, which he named after his homeland of Russia, but also as one of the first scientists who applied quantitative methods in botany. | 1 | Applied and Interdisciplinary Chemistry |
Prof Paul Sabatier FRS(For) HFRSE (; 5 November 1854 – 14 August 1941) was a French chemist, born in Carcassonne. In 1912, Sabatier was awarded the Nobel Prize in Chemistry along with Victor Grignard. Sabatier was honoured for his work improving the hydrogenation of organic species in the presence of metals. | 0 | Theoretical and Fundamental Chemistry |
Birth control pills containing ethinylestradiol and a progestin are associated with an increased risk of venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE). The incidence is about 4-fold higher on average than in women not taking a birth control pill. The absolute risk of VTE with ethinylestradiol-containing birth control pills is small, in the area of 3 to 10 out of 10,000 women per year, relative to 1 to 5 out of 10,000 women per year not taking a birth control pill. The risk of VTE during pregnancy is 5 to 20 in 10,000 women per year and during the postpartum period is 40 to 65 per 10,000 women per year. The higher risk of VTE with combined birth control pills is thought to be due to the ethinylestradiol component, as ethinylestradiol has estrogenic effects on liver synthesis of coagulation factors which result in a procoagulatory state. In contrast to ethinylestradiol-containing birth control pills, neither progestogen-only birth control nor the combination of transdermal estradiol and an oral progestin in menopausal hormone therapy is associated with an increased risk of VTE.
Different progestins in ethinylestradiol-containing birth control pills have been associated with different risks of VTE. Birth control pills containing progestins such as desogestrel, gestodene, drospirenone, and cyproterone acetate have been found to have 2- to 3-fold the risk of VTE of birth control pills containing levonorgestrel in retrospective cohort and nested case–control observational studies. However, this area of research is controversial, and confounding factors may have been present in these studies. Other observational studies, specifically prospective cohort and case control studies, have found no differences in risk between different progestins, including between birth control pills containing drospirenone and birth control pills containing levonorgestrel. These kinds of observational studies have certain advantages over the aforementioned types of studies, like better ability to control for confounding factors. Systematic reviews and meta-analyses of all of the data in the mid-to-late 2010s found that birth control pills containing cyproterone acetate, desogestrel, drospirenone, or gestodene overall were associated with a risk of VTE of about 1.3- to 2.0-fold compared to that of levonorgestrel-containing birth control pills.
Androgenic progestins have been found to antagonize to some degree the effects of ethinylestradiol on coagulation. As a result, more androgenic progestins, like levonorgestrel and norethisterone, may oppose the procoagulatory effects of ethinylestradiol and result in a lower increase in risk of VTE. Conversely, this would be the case less or not at all with progestins that are less androgenic, like desogestrel and gestodene, as well as with progestins that are antiandrogenic, like drospirenone and cyproterone acetate.
In the early 2010s, the FDA updated the label for birth control pills containing drospirenone and other progestins to include warnings for stopping use prior to and after surgery, and to warn that such birth control pills may have a higher risk of blood clots. | 0 | Theoretical and Fundamental Chemistry |
* In emulsions a phase inversion is when the dispersed phase becomes the dispersion medium and the dispersion medium becomes the dispersed phase, for example when cream becomes butter. | 0 | Theoretical and Fundamental Chemistry |
Many hydroperoxides are derived from fatty acids, steroids, and terpenes. The biosynthesis of these species is affected extensively by enzymes. | 0 | Theoretical and Fundamental Chemistry |
Testing and/or inspection are typically included in component manufacturing lines to verify the product meets some set of standards to ensure the desired performance in the field. Improper testing or inspection would circumvent these quality checks and could allow a part with a defect that would normally disqualify the component from field use to be sold to a customer, potentially leading to a failure. | 1 | Applied and Interdisciplinary Chemistry |
The number average molar mass is a way of determining the molecular mass of a polymer. Polymer molecules, even ones of the same type, come in different sizes (chain lengths, for linear polymers), so the average molecular mass will depend on the method of averaging. The number average molecular mass is the ordinary arithmetic mean or average of the molecular masses of the individual macromolecules. It is determined by measuring the molecular mass of polymer molecules, summing the masses, and dividing by .
The number average molecular mass of a polymer can be determined by gel permeation chromatography, viscometry via the (Mark–Houwink equation), colligative methods such as vapor pressure osmometry, end-group determination or proton NMR.
High number-average molecular mass polymers may be obtained only with a high fractional monomer conversion in the case of step-growth polymerization, as per the Carothers' equation. | 0 | Theoretical and Fundamental Chemistry |
Degradation depends on the sensitivity of the material to the wavelength of X-rays used, the total dose of the X-rays, the temperature of the surface and the level of the vacuum. Metals, alloys, ceramics and most glasses are not measurably degraded by either non-monochromatic or monochromatic X-rays. Some, but not all, polymers, catalysts, certain highly oxygenated compounds, various inorganic compounds and fine organics are. Non-monochromatic X-ray sources produce a significant amount of high energy Bremsstrahlung X-rays (1–15 keV of energy) which directly degrade the surface chemistry of various materials. Non-monochromatic X-ray sources also produce a significant amount of heat (100 to 200 °C) on the surface of the sample because the anode that produces the X-rays is typically only 1 to away from the sample. This level of heat, when combined with the Bremsstrahlung X-rays, acts to increase the amount and rate of degradation for certain materials. Monochromatised X-ray sources, because they are farther away (50–100 cm) from the sample, do not produce noticeable heat effects. In those, a quartz monochromator system diffracts the Bremsstrahlung X-rays out of the X-ray beam, which means the sample is only exposed to one narrow band of X-ray energy. For example, if aluminum K-alpha X-rays are used, the intrinsic energy band has a FWHM of 0.43 eV, centered on 1,486.7 eV (E/ΔE = 3,457). If magnesium K-alpha X-rays are used, the intrinsic energy band has a FWHM of 0.36 eV, centered on 1,253.7 eV (E/ΔE = 3,483). These are the intrinsic X-ray line widths; the range of energies to which the sample is exposed depends on the quality and optimization of the X-ray monochromator. Because the vacuum removes various gases (e.g., O, CO) and liquids (e.g., water, alcohol, solvents, etc.) that were initially trapped within or on the surface of the sample, the chemistry and morphology of the surface will continue to change until the surface achieves a steady state. This type of degradation is sometimes difficult to detect. | 0 | Theoretical and Fundamental Chemistry |
Cyclophosphazenes such as hexachlorophosphazene are distinguished by notable stability and equal P–N bond lengths which, in many such cyclic molecules, would imply delocalization or even aromaticity. To account for these features, early bonding models starting from the mid-1950s invoked a delocalised π system arising from the overlap of N 2p and P 3d orbitals. | 0 | Theoretical and Fundamental Chemistry |
A beamsplitter is used to divide a single ultrashort optical pulse into two separate beams. A 50/50 beamsplitter is often used, supplying equal optical power to the terahertz generator and detector, though it is common to provide the terahertz generation path with more power given the inefficiency of the terahertz generation process compared to the detection efficiency of infrared (typically 800 nm wavelength) light. | 0 | Theoretical and Fundamental Chemistry |
In 1934 Frédéric and Irène Joliot-Curie bombarded aluminium with alpha particles (emitted by polonium) to effect the nuclear reaction + → + , and observed that the product isotope emits a positron identical to those found in cosmic rays by Carl David Anderson in 1932. This was the first example of decay (positron emission). The Curies termed the phenomenon "artificial radioactivity", because is a short-lived nuclide which does not exist in nature. The discovery of artificial radioactivity would be cited when the husband-and-wife team won the Nobel Prize. | 0 | Theoretical and Fundamental Chemistry |
Formiminoglutamic acid (FIGLU; conjugate base, formiminoglutamate) is an intermediate in the catabolism of L-histidine to L-glutamic acid. It thus is also a biomarker for intracellular levels of folate. The FIGLU test is used to identify vitamin B₁₂ deficiency, folate deficiency, and liver failure or liver disease. It is elevated with folate trapping, where it is accompanied by decreased methylmalonic acid, increased folate and a decrease in homocysteine. | 1 | Applied and Interdisciplinary Chemistry |
A myc tag is a polypeptide protein tag derived from the c-myc gene product that can be added to a protein using recombinant DNA technology. It can be used for affinity chromatography, then used to separate recombinant, overexpressed protein from wild type protein expressed by the host organism. It can also be used in the isolation of protein complexes with multiple subunits.
A myc tag can be used in many different assays that require recognition by an antibody and was originally identified in 1985. If there is no antibody against the studied protein, adding a myc-tag allows one to follow the protein with an antibody against the Myc epitope. Examples are cellular localization studies by immunofluorescence or detection by Western blotting.
The peptide sequence of the myc-tag is (in 1- and 3-letter codes, respectively): EQKLISEEDL and Glu-Gln-Lys-Leu-Ile-Ser-Glu-Glu-Asp-Leu. The tag is approximately 1202 daltons in atomic mass and has 10 amino acids.
It can be fused to the C-terminus and the N-terminus of a protein. It is advisable not to fuse the myc-tag directly behind the signal peptide of a secretory protein, since it can interfere with translocation into the secretory pathway.
A monoclonal antibody against the myc epitope, named 9E10, is available from the non-commercial Developmental Studies Hybridoma Bank. | 1 | Applied and Interdisciplinary Chemistry |
While humans are highly dependent upon visual cues, when in close proximity smells also play a role in sociosexual behaviors. An inherent difficulty in studying human pheromones is the need for cleanliness and odorlessness in human participants. Though various researchers have investigated the possibility of their existence, no pheromonal substance has ever been demonstrated to directly influence human behavior in a peer reviewed study. Experiments have focused on three classes of possible human pheromones: axillary steroids, vaginal aliphatic acids, and stimulators of the vomeronasal organ, including [https://academic.oup.com/scan/article/14/7/719/5532402 this 2018 study] claiming pheromones affect men's sexual cognition. | 1 | Applied and Interdisciplinary Chemistry |
The first decade of the 20th century brought the basics of quantum theory (Planck, Einstein) and interpretation of spectral series of hydrogen by Lyman in VUV and by Paschen in infrared. Ritz formulated the combination principle.
John William Nicholson had created an atomic model in 1912, a year before Niels Bohr, that was both nuclear and quantum in which he showed that electron oscillations in his atom matched the solar and nebular spectral lines. Bohr had been working on his atom during this period, but Bohr's model had only a single ground state and no spectra until he incorporated the Nicholson model and referenced the Nicholson papers in his model of the atom.
In 1913, Bohr formulated his quantum mechanical model of atom. This stimulated empirical term analysis. Bohr published a theory of the hydrogen-like atoms that could explain the observed wavelengths of spectral lines due to electrons transitioning from different energy states. In 1937 "E. Lehrer created the first fully-automated spectrometer" to help more accurately measure spectral lines. With the development of more advanced instruments such as photo-detectors scientists were then able to more accurately measure specific wavelength absorption of substances. | 0 | Theoretical and Fundamental Chemistry |
This information can then be used to measure velocity or path length, or as a way to learn about the particle or medium's properties (such as composition or flow rate). The traveling object may be detected directly (direct time of flight, dToF, e.g., via an ion detector in mass spectrometry) or indirectly (indirect time of flight, iToF, e.g., by light scattered from an object in laser doppler velocimetry). Time of flight technology has found valuable applications in the monitoring and characterization of material and biomaterials, hydrogels included. | 0 | Theoretical and Fundamental Chemistry |
The region of space enclosed by open system boundaries is usually called a control volume. It may or may not correspond to physical walls. It is convenient to define the shape of the control volume so that all flow of matter, in or out, occurs perpendicular to its surface. One may consider a process in which the matter flowing into and out of the system is chemically homogeneous. Then the inflowing matter performs work as if it were driving a piston of fluid into the system. Also, the system performs work as if it were driving out a piston of fluid. Through the system walls that do not pass matter, heat () and work () transfers may be defined, including shaft work.
Classical thermodynamics considers processes for a system that is initially and finally in its own internal state of thermodynamic equilibrium, with no flow. This is feasible also under some restrictions, if the system is a mass of fluid flowing at a uniform rate. Then for many purposes a process, called a flow process, may be considered in accord with classical thermodynamics as if the classical rule of no flow were effective. For the present introductory account, it is supposed that the kinetic energy of flow, and the potential energy of elevation in the gravity field, do not change, and that the walls, other than the matter inlet and outlet, are rigid and motionless.
Under these conditions, the first law of thermodynamics for a flow process states: the increase in the internal energy of a system is equal to the amount of energy added to the system by matter flowing in and by heating, minus the amount lost by matter flowing out and in the form of work done by the system. Under these conditions, the first law for a flow process is written:
where and respectively denote the average internal energy entering and leaving the system with the flowing matter.
There are then two types of work performed: flow work described above, which is performed on the fluid in the control volume (this is also often called work), and shaft work, which may be performed by the fluid in the control volume on some mechanical device with a shaft. These two types of work are expressed in the equation:
Substitution into the equation above for the control volume cv yields:
The definition of enthalpy, , permits us to use this thermodynamic potential to account jointly for internal energy and work in fluids for a flow process:
During steady-state operation of a device (see turbine, pump, and engine), any system property within the control volume is independent of time. Therefore, the internal energy of the system enclosed by the control volume remains constant, which implies that in the expression above may be set equal to zero. This yields a useful expression for the power generation or requirement for these devices with chemical homogeneity in the absence of chemical reactions:
This expression is described by the diagram above. | 0 | Theoretical and Fundamental Chemistry |
Heat denaturation of DNA, also called melting, causes the double helix structure to unwind to form single stranded DNA. When DNA in solution is heated above its melting temperature (usually more than 80 °C), the double-stranded DNA unwinds to form single-stranded DNA. The bases become unstacked and can thus absorb more light. In their native state, the bases of DNA absorb light in the 260-nm wavelength region. When the bases become unstacked, the wavelength of maximum absorbance does not change, but the amount absorbed increases by 37%. A double stranded DNA strand dissociating to two single strands produces a sharp cooperative transition.
Hyperchromicity can be used to track the condition of DNA as temperature changes. The transition/melting temperature (T) is the temperature where the absorbance of UV light is 50% between the maximum and minimum, i.e. where 50% of the DNA is denatured. A ten fold increase of monovalent cation concentration increases the temperature by 16.6 °C.
The hyperchromic effect is the striking increase in absorbance of DNA upon denaturation. The two strands of DNA are bound together mainly by the stacking interactions, hydrogen bonds and hydrophobic effect between the complementary bases. The hydrogen bond limits the resonance of the aromatic ring so the absorbance of the sample is limited as well. When the DNA double helix is treated with denatured agents, the interaction force holding the double helical structure is disrupted. The double helix then separates into two single strands which are in the random coiled conformation. At this time, the base-base interaction will be reduced, increasing the UV absorbance of DNA solution because many bases are in free form and do not form hydrogen bonds with complementary bases. As a result, the absorbance for single-stranded DNA will be 37% higher than that for double stranded DNA at the same concentration. | 0 | Theoretical and Fundamental Chemistry |
* Albert Brahms (1692–1758)
* Antoine de Chézy (1718–1798)
* Claude-Louis Navier (1785–1836)
* Adhémar Jean Claude Barré de Saint-Venant (1797–1886)
* Gotthilf Heinrich Ludwig Hagen (1797–1884)
* Jean Léonard Marie Poiseuille (1797–1869)
* Henri P. G. Darcy (1803–1858)
* Julius Ludwig Weisbach (1806–1871)
* Charles Storrow (1809–1904)
* Robert Manning (1816–1897)
* Wilhelm Rudolf Kutter (1818–1888)
* Emile Oscar Ganguillet (1818–1894)
* Sir George Stokes (1819–1903)
* Philippe Gaspard Gauckler (1826–1905)
* Henri-Émile Bazin (1829–1917)
* Alphonse Fteley (1837–1903)
* Frederic Stearns (1851–1919)
* Ludwig Prandtl (1875–1953)
* Paul Richard Heinrich Blasius (1883–1970)
* Albert Strickler (1887–1963)
* Cyril Frank Colebrook (1910–1997) | 1 | Applied and Interdisciplinary Chemistry |
Columnar structures appear in various research fields on a broad range of length scales from metres down to the nanoscale. On the largest scale, such structures can be found in botany where seeds of a plant assemble around the stem. On a smaller scale bubbles of equal size crystallise to columnar foam structures when confined in a glass tube. In nanoscience such structures can be found in man-made objects which are on length scales from a micron to the nanoscale. | 0 | Theoretical and Fundamental Chemistry |
The chemical inverse of a proton sponge would be a hydride sponge. This property is exhibited by CH(BMe), which reacts with potassium hydride to afford K[CH(BMe)H]. | 0 | Theoretical and Fundamental Chemistry |
Photoconductive atomic force microscopy (PC-AFM) is a variant of atomic force microscopy that measures photoconductivity in addition to surface forces. | 0 | Theoretical and Fundamental Chemistry |
The thylakoid membrane is the site of the light-dependent reactions of photosynthesis with the photosynthetic pigments embedded directly in the membrane. It is an alternating pattern of dark and light bands measuring each 1 nanometre. The thylakoid lipid bilayer shares characteristic features with prokaryotic membranes and the inner chloroplast membrane. For example, acidic lipids can be found in thylakoid membranes, cyanobacteria and other photosynthetic bacteria and are involved in the functional integrity of the photosystems. The thylakoid membranes of higher plants are composed primarily of phospholipids and galactolipids that are asymmetrically arranged along and across the membranes. Thylakoid membranes are richer in galactolipids rather than phospholipids; also they predominantly consist of hexagonal phase II forming monogalacotosyl diglyceride lipid. Despite this unique composition, plant thylakoid membranes have been shown to assume largely lipid-bilayer dynamic organization. Lipids forming the thylakoid membranes, richest in high-fluidity linolenic acid are synthesized in a complex pathway involving exchange of lipid precursors between the endoplasmic reticulum and inner membrane of the plastid envelope and transported from the inner membrane to the thylakoids via vesicles. | 0 | Theoretical and Fundamental Chemistry |
Janus-type material is used as a surfactant-like heterogeneous catalyst for the synthesis of adipic acid. | 0 | Theoretical and Fundamental Chemistry |
John Krige () is a historian of science and technology and the Kranzberg Professor at the School of History, Technology and Society, Georgia Institute of Technology, Atlanta. | 0 | Theoretical and Fundamental Chemistry |
The term is used to describe a transient chemical species. As a general example, if a molecule exists in a particular conformation for a short lifetime, before adopting a lower energy conformation (structural arrangement), the former molecular structure is said to have high lability (such as C, a 25-carbon fullerene spheroid). The term is sometimes also used in reference to reactivity – for example, a complex that quickly reaches equilibrium in solution is said to be labile (with respect to that solution). Another common example is the cis effect in organometallic chemistry, which is the labilization of CO ligands in the cis position of octahedral transition metal complexes. | 1 | Applied and Interdisciplinary Chemistry |
During high-energy milling the powder particles are repeatedly flattened, cold welded, fractured and rewelded. Whenever two steel balls collide, some powder is trapped between them. Typically, around 1000 particles with an aggregate weight of about 0.2 mg are trapped during each collision. The force of the impact plastically deforms the powder particles, leading to work hardening and fracture. The new surfaces thus created enable the particles to weld together; this leads to an increase in particle size. Since in the early stages of milling, the particles are soft (if using either ductile-ductile or ductile-brittle material combination), their tendency to weld together and form large particles is high. A broad range of particle sizes develops, with some as large as three times larger than the starting particles. The composite particles at this stage have a characteristic layered structure consisting of various combinations of the starting constituents. With continued deformation particles become work hardened, and fracture by a fatigue failure mechanism and/or by the fragmentation of fragile flakes. | 1 | Applied and Interdisciplinary Chemistry |
Demulsifiers, or emulsion breakers, are a class of specialty chemicals used to separate emulsions, for example, water in oil. They are commonly used in the processing of crude oil, which is typically produced along with significant quantities of saline water. This water (and salt) must be removed from the crude oil prior to refining. If the majority of the water and salt are not removed, significant corrosion problems can occur in the refining process.
Demulsifiers are typically based on the following chemistry:
* Acid catalysed phenol-formaldehyde resins
* Base catalysed phenol-formaldehyde resins
* Epoxy resins
* Polyethyleneimines
* Polyamines
* Di-epoxides
* Polyols
* dendrimer
The above are usually ethoxylated (and/or propoxylated) to provide the desired degree of water/oil solubility.
The addition of ethylene oxide increases water solubility, propylene oxide decreases it.
Commercially available demulsifier formulations are typically a mixture of two to four different chemistries, in carrier solvent(s) such as xylene, heavy aromatic naphtha (HAN), Isopropanol, methanol, 2-Ethylhexanol or diesel.
Demulsifiers are manufactured by chemical manufacturers including:
* Arkema
* Baker Hughes
* BASF
* ChampionX
* Clariant
* Dow Chemical Company
* Lubrizol
* Nouryon
* [https://purechemservices.com/ PureChem Services] ([https://www.cesenergysolutions.com/ CES])
* SI Group
* Chembiotec Additives
* Solvay
* Stepan
* Starborn Chemical
* Dorf Ketal Chemicals | 0 | Theoretical and Fundamental Chemistry |
Nanoparticles can be made from different materials such as metals, ceramics and polymers. The stability of the nanoparticles can be an issue as nanoparticles have a tendency to lower their very high surface energy, which originates from their high surface-to-bulk ratio. Bare nanoparticles tend to stabilize themselves either by sorption of molecules from the surroundings or by lowering the surface area through coagulation and agglomeration. Usually the formation of these aggregates is unwanted. The tendency of a nanoparticle to coagulate can be controlled by modifying the surface layer. In a liquid medium, suitable ligand molecules are commonly attached to the nanoparticle surface, as they provide solubility in suitable solvents and prevent coagulation. | 0 | Theoretical and Fundamental Chemistry |
Reductions with diimide are a chemical reactions that convert unsaturated organic compounds to reduced alkane products. In the process, diimide () is oxidized to dinitrogen. | 0 | Theoretical and Fundamental Chemistry |
Protons, neutrons, and many nuclei carry nuclear spin, which gives rise to a gyromagnetic ratio as above. The ratio is conventionally written in terms of the proton mass and charge, even for neutrons and for other nuclei, for the sake of simplicity and consistency. The formula is:
where is the nuclear magneton, and is the -factor of the nucleon or nucleus in question. The ratio equal to , is 7.622593285(47) MHz/T.
The gyromagnetic ratio of a nucleus plays a role in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). These procedures rely on the fact that bulk magnetization due to nuclear spins precess in a magnetic field at a rate called the Larmor frequency, which is simply the product of the gyromagnetic ratio with the magnetic field strength. With this phenomenon, the sign of determines the sense (clockwise vs counterclockwise) of precession.
Most common nuclei such as H and C have positive gyromagnetic ratios. Approximate values for some common nuclei are given in the table below. | 0 | Theoretical and Fundamental Chemistry |
The snRNAs (U1, U2, U4, U5, and the less abundant U11, U12 and U4atac) quickly interact with the SMN (survival of motor neuron protein); encoded by SMN1 gene) and Gemins 2-8 (Gem-associated proteins: GEMIN2, GEMIN3, GEMIN4, GEMIN5, GEMIN6, GEMIN7, GEMIN8) forming the SMN complex. It is here that the snRNA binds to the SmD1-SmD2-SmF-SmE-SmG pentamer, followed by addition of the SmD3-SmB dimer to complete the Sm ring around the so-called Sm site of the snRNA. This Sm site is a conserved sequence of nucleotides in these snRNAs, typically AUUUGUGG (where A, U and G represent the nucleosides adenosine, uridine and guanosine, respectively). After assembly of the Sm ring around the snRNA, the 5 terminal nucleoside (already modified to a 7-methylguanosine cap) is hyper-methylated to 2,2,7-trimethylguanosine and the other (3) end of the snRNA is trimmed. This modification, and the presence of a complete Sm ring, is recognized by the snurportin 1 protein. | 1 | Applied and Interdisciplinary Chemistry |
Ultraviolet helps detect organic material deposits that remain on surfaces where periodic cleaning and sanitizing may have failed. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are inspected.
Perennial news features for many television news organizations involve an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such. | 0 | Theoretical and Fundamental Chemistry |
The ionotropic glutamate receptors bind the neurotransmitter glutamate. They form tetramers, with each subunit consisting of an extracellular amino terminal domain (ATD, which is involved tetramer assembly), an extracellular ligand binding domain (LBD, which binds glutamate), and a transmembrane domain (TMD, which forms the ion channel). The transmembrane domain of each subunit contains three transmembrane helices as well as a half membrane helix with a reentrant loop. The structure of the protein starts with the ATD at the N terminus followed by the first half of the LBD which is interrupted by helices 1,2 and 3 of the TMD before continuing with the final half of the LBD and then finishing with helix 4 of the TMD at the C terminus. This means there are three links between the TMD and the extracellular domains. Each subunit of the tetramer has a binding site for glutamate formed by the two LBD sections forming a clamshell like shape. Only two of these sites in the tetramer need to be occupied to open the ion channel. The pore is mainly formed by the half helix 2 in a way which resembles an inverted potassium channel. | 1 | Applied and Interdisciplinary Chemistry |
The europium anomaly is the phenomenon whereby the europium (Eu) concentration in a mineral is either enriched or depleted relative to some standard, commonly a chondrite or mid-ocean ridge basalt (MORB). In geochemistry a europium anomaly is said to be "positive" if the Eu concentration in the mineral is enriched relative to the other rare-earth elements (REEs), and is said to be "negative" if Eu is depleted relative to the other REEs.
While all lanthanides form relatively large trivalent (3+) ions, Eu and cerium (Ce) have additional valences, europium forms 2+ ions, and Ce forms 4+ ions, leading to chemical reaction differences in how these ions can partition versus the 3+ REEs. In the case of Eu, its reduced divalent (2+) cations are similar in size and carry the same charge as Ca, an ion found in plagioclase and other minerals. While Eu is an incompatible element in its trivalent form (Eu) in an oxidizing magma, it is preferentially incorporated into plagioclase in its divalent form (Eu) in a reducing magma, where it substitutes for calcium (Ca).
Enrichment or depletion is generally attributed to europiums tendency to be incorporated into plagioclase preferentially over other minerals. If a magma crystallizes stable plagioclase, most of the Eu will be incorporated into this mineral, causing a higher than expected concentration of Eu in the mineral versus other REE in that mineral (a positive anomaly). The rest of the magma will then be relatively depleted in Eu with a concentration of Eu lower than expected versus the concentrations of other REEs in that magma. If the Eu-depleted magma is then separated from its plagioclase crystals and subsequently solidifies, its chemical composition will display a negative Eu anomaly (because the Eu is locked up in the plagioclase left in the magma chamber). Conversely, if a magma accumulates' plagioclase crystals before solidification, its rock composition will display a relatively positive Eu anomaly.
A well-known example of the Eu anomaly is seen on the Moon. REE analyses of the Moons light-colored lunar highlands show a large positive Eu anomaly due to the plagioclase-rich anorthosite comprising the highlands. The darker lunar mare, consisting mainly of basalt, shows a large negative Eu anomaly. This has led geologists to speculate as to the genetic relationship between the lunar highlands and mare. It is possible that much of the Moons Eu was incorporated into the earlier, plagioclase-rich highlands, leaving the later basaltic mare strongly depleted in Eu. | 0 | Theoretical and Fundamental Chemistry |
A dipole can align to stabilize or destabilize the formation or loss of a charge, thereby decreasing (if stabilized) or increasing (if destabilized) the activation barrier to a chemical event. Field effects can therefore tune the acidity or basicity of bonds within their fields by donating or withdrawing charge density. With respect to acidity, a common trend to note is that, inductively, an electron-withdrawing substituent in the vicinity of an acidic proton will lower the pKa (i.e. increase the acidity) and, correspondingly, an electron-donating substituent will raise the pKa. The reorganization of charge due to field effects will have the same result. An electric dipole field propagated through the space around, or in the middle of, a molecule in the direction of an acidic proton will decrease the acidity, while a dipole pointed away will increase the acidity and concomitantly elongate the X-H bond. These effects can therefore help to tune the acidity/basicity of a molecule to protonate/deprotonate a specific compound, or enhance hydrogen bond-donor ability for molecular recognition or anion sensing applications. Field effects have also been shown in substituted arenes to dominate the electrostatic potential maps, which are maps of electron density used to explain intermolecular interactions. | 0 | Theoretical and Fundamental Chemistry |
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