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The total quantity of ATP in the human body is about 0.1 mol/L. The majority of ATP is recycled from ADP by the aforementioned processes. Thus, at any given time, the total amount of ATP + ADP remains fairly constant.
The energy used by human cells in an adult requires the hydrolysis of 100 to 150 mol/L of ATP daily, which means a human will typically use their body weight worth of ATP over the course of the day. Each equivalent of ATP is recycled 1000–1500 times during a single day (), at approximately 9×10 molecules/s. | 1 | Applied and Interdisciplinary Chemistry |
Orgel diagrams are correlation diagrams which show the relative energies of electronic terms in transition metal complexes, much like Tanabe–Sugano diagrams. They are named after their creator, Leslie Orgel. Orgel diagrams are restricted to only show weak field (i.e. high spin) cases, and offer no information about strong field (low spin) cases. Because Orgel diagrams are qualitative, no energy calculations can be performed from these diagrams; also, Orgel diagrams only show the symmetry states of the highest spin multiplicity instead of all possible terms, unlike a Tanabe–Sugano diagram. Orgel diagrams will, however, show the number of spin allowed transitions, along with their respective symmetry designations. In an Orgel diagram, the parent term (P, D, or F) in the presence of no ligand field is located in the center of the diagram, with the terms due to that electronic configuration in a ligand field at each side. There are two Orgel diagrams, one for d, d, d, and d configurations and the other with d, d, d, and d configurations.
In an Orgel diagram, lines with the same Russell–Saunders terms will diverge due to the non-crossing rule, but all other lines will be linear. Also, for the D Orgel diagram, the left side contains d and d tetrahedral and d and d octahedral complexes. The right side contains d and d tetrahedral and d and d octahedral complexes. For the F Orgel diagram, the left side contains d and d tetrahedral and d and d octahedral complexes. The right side contains d and d tetrahedral and d and high spin d octahedral complexes. | 0 | Theoretical and Fundamental Chemistry |
Strychnine is a neurotoxin that causes death by affecting nerves that control muscular contraction and cause respiration difficulty. The impulse is transmitted between the synapse through a neurotransmitter called acetylcholine. It is released into the synapse between nerve cells and binds to receptors in the postsynaptic cell. Then an action potential is generated and transmitted through the postsynaptic cell to start a new cycle.
Glycine can inhibit the activity of neurotransmitter receptors, thus a larger amount of acetylcholinesterase is required to trigger an action potential. This makes sure that the generation of nerve impulses is tightly controlled. However, this control is broken down when strychnine is added. It inhibits glycine receptors(a chloride channel) and a much lower level of neurotransmitter concentration can trigger an action potential. Nerves now constantly transmit signals and cause excessive muscular contraction, leading to asphyxiation and death. | 1 | Applied and Interdisciplinary Chemistry |
Iron was not the only metal to be used in Africa; copper and brass were widely utilised too. However the steady spread of iron meant it must have had more favourable properties for many different uses. Its durability over copper meant that it was used to make many tools from farming pieces to weaponry. Iron was used for personal adornment in jewelry, impressive pieces of artwork and even instruments. It was used for coins and currencies of varying forms. For example, kisi pennies; a traditional form of iron currency used for trading in West Africa. They are twisted iron rods ranging from <30 cm to >2m in length. Suggestions for their uses vary from marital transactions, or simply that they were a convenient shape for transportation, melting down and reshaping into a desired object. There are many different forms of iron currency, often regionally differing in shape and value. Iron did not replace other materials, such as stone and wooden tools, but the quantity of production and variety of uses met were significantly high by comparison. | 1 | Applied and Interdisciplinary Chemistry |
The original commercial AFM-IR instruments required most samples to be thicker than 50 nm to achieve sufficient sensitivity. Sensitivity improvements were achieved using specialized cantilever probes with an internal resonator and by wavelet based signal processing techniques. Sensitivity was further improved by Lu et al. by using quantum cascade laser (QCL) sources. The high repetition rate of the QCL allows absorbed infrared light to continuously excite the AFM tip at a "contact resonance" of the AFM cantilever. This resonance-enhanced AFM-IR, in combination with electric field enhancement from metallic tips and substrates led to the demonstration of AFM-IR spectroscopy and compositional imaging of films as thin as single self-assembled monolayers. AFM-IR has also been integrated with other sources including a picosecond OPO offering a tuning range 1.55 μm to 16 μm (from 6450 cm to 625 cm).
In its initial development, with samples deposited on transparent prisms and using OPO laser sources, the sensitivity of AFM-IR was limited to a minimal thickness of the sample of circa 50-100 nm as mentioned above. The advent of quantum cascade lasers (QCL) and the use of the electromagnetic field enhancement between metallic probes and substrates have improved the sensitivity and spatial resolution of AFM-IR down to the measurement of large (>0.3 μm) and flat (~2–10 nm) self-assembled monolayers, where still hundreds of molecules are present. Ruggeri et al. have recently developed off-resonance, low power and short pulse AFM-IR (ORS-nanoIR) to prove the acquisition of infrared absorption spectra and chemical maps at the single molecule level, in the case of macromolecular assemblies and large protein molecules with a spatial resolution of ca. 10 nm. | 0 | Theoretical and Fundamental Chemistry |
Isocyanides exhibit a strong absorption in their IR spectra in the range of 2165–2110 cm.
The electronic symmetry about the isocyanide N nucleus results in a slow quadrupolar relaxation so that C-N nuclear spin coupling can be observed, with coupling constants of ca. 5 Hz for the isocyanide C nucleus and 5–14 Hz for the C nucleus which the isocyanide group is attached to. | 0 | Theoretical and Fundamental Chemistry |
Many cells produce specific carbohydrate-binding proteins known as lectins, which mediate cell adhesion with oligosaccharides. Selectins, a family of lectins, mediate certain cell–cell adhesion processes, including those of leukocytes to endothelial cells. In an immune response, endothelial cells can express certain selectins transiently in response to damage or injury to the cells. In response, a reciprocal selectin–oligosaccharide interaction will occur between the two molecules which allows the white blood cell to help eliminate the infection or damage. Protein-Carbohydrate bonding is often mediated by hydrogen bonding and van der Waals forces. | 0 | Theoretical and Fundamental Chemistry |
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures, such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted to smaller molecules in the process of releasing energy, such as for carbohydrates, lipids, proteins, and fermentation products (ethanol or vinegar), leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.
Different types of organisms have different essential nutrients. Ascorbic acid (vitamin C) is essential to humans and some animal species, but most other animals and many plants are able to synthesize it. Nutrients may be organic or inorganic: organic compounds include most compounds containing carbon, while all other chemicals are inorganic. Inorganic nutrients include nutrients such as iron, selenium, and zinc, while organic nutrients include, protein, fats, sugars, and vitamins.
A classification used primarily to describe nutrient needs of animals divides nutrients into macronutrients and micronutrients. Consumed in relatively large amounts (grams or ounces), macronutrients (carbohydrates, fats, proteins, water) are primarily used to generate energy or to incorporate into tissues for growth and repair. Micronutrients are needed in smaller amounts (milligrams or micrograms); they have subtle biochemical and physiological roles in cellular processes, like vascular functions or nerve conduction. Inadequate amounts of essential nutrients, or diseases that interfere with absorption, result in a deficiency state that compromises growth, survival and reproduction. Consumer advisories for dietary nutrient intakes, such as the United States Dietary Reference Intake, are based on the amount required to prevent deficiency, and provide macronutrient and micronutrient guides for both lower and upper limits of intake. In many countries, regulations require that food product labels display information about the amount of any macronutrients and micronutrients present in the food in significant quantities. Nutrients in larger quantities than the body needs may have harmful effects. Edible plants also contain thousands of compounds generally called phytochemicals which have unknown effects on disease or health, including a diverse class with non-nutrient status called polyphenols, which remain poorly understood as of 2017. | 0 | Theoretical and Fundamental Chemistry |
Let be the velocity field of an incompressible irrotational fluid and be that of any other incompressible fluid motion with same normal component velocity at the boundary of the domain, where is the unit vector of the bounding surface (and, if the domain extends to infinity, there). Then the difference between the kinetic energy is given by
can be rearranged to give
Since is irrotational and the domain is simply-connected, a single-valued velocity potential exists, i.e., . Using this, the second integral in the above equation can be written as
The second integral is identically zero for steady incompressible fluid, i.e., . Applying the Gauss theorem for the first integral we find
where the surface integral is zero since normal component of velocities are equal there. Thus, one concludes
or in other words, , where the equality holds only if , thereby proving the theorem. | 1 | Applied and Interdisciplinary Chemistry |
To analyze the transport of ions in the channel, behaviors of system in electrochemistry as well as fluid mechanics need to be considered. The Poisson–Nernst–Planck (PNP) equations are utilized to describe ionic current flowing through a channel, and the Navier–Stokes (NS) equations are used to represent the fluid dynamics in the channel.
The PNP equations consist of the Poisson equation:
and the Nernst–Planck equations, which gives the particle flux of ion species due to a concentration gradient and electric potential gradient:
where is the electrostatic potential, is the unit charge of electron, is the permittivity in vacuum, and is the dielectric constant of solution; , and are the diffusivity, the number density of ions, and the valence of ion species .
The solution in steady-state satisfies the continuity equation. To describe fluid velocity field in the channel, using Navier–Stokes equations:
where , , , and are pressure, velocity vector, viscosity, and density of fluid, respectively. The equations above are usually solved with numerical algorithm to determine the velocity, pressure, electric potential, and ionic concentration in the fluid, as well as the electric current flow through the channel. | 0 | Theoretical and Fundamental Chemistry |
By normalizing the above equation by the extent of a system, such as the total number of moles, the Gibbs–Duhem equation provides a relationship between the intensive variables of the system. For a simple system with different components, there will be independent parameters or "degrees of freedom". For example, if we know a gas cylinder filled with pure nitrogen is at room temperature (298 K) and 25 MPa, we can determine the fluid density (258 kg/m), enthalpy (272 kJ/kg), entropy (5.07 kJ/kg⋅K) or any other intensive thermodynamic variable. If instead the cylinder contains a nitrogen/oxygen mixture, we require an additional piece of information, usually the ratio of oxygen-to-nitrogen.
If multiple phases of matter are present, the chemical potentials across a phase boundary are equal. Combining expressions for the Gibbs–Duhem equation in each phase and assuming systematic equilibrium (i.e. that the temperature and pressure is constant throughout the system), we recover the Gibbs' phase rule.
One particularly useful expression arises when considering binary solutions. At constant P (isobaric) and T (isothermal) it becomes:
or, normalizing by total number of moles in the system substituting in the definition of activity coefficient and using the identity :
This equation is instrumental in the calculation of thermodynamically consistent and thus more accurate expressions for the vapor pressure of a fluid mixture from limited experimental data. | 0 | Theoretical and Fundamental Chemistry |
The IscR stability element is a conserved secondary structure found in the intergenic regions of iscRSUA polycistronic mRNA. This secondary structure prevents the degradation of the iscR mRNA.
The iscRSUA operon encodes for the proteins required in iron–sulfur cluster biosynthesis where the expression of this operon is regulated by RyhB and iscR, a transcription repressor. Under sufficient iron conditions RyhB binds to iscRSUA mRNA and promotes the degradation of the mRNA located downstream of iscR. Scanning the intergenic regions of this polycistronic mRNA and using Mfold software a secondary structure was predicted within the intergenic region between iscR and iscS and later confirmed by lead acetate probing. Mutations that disrupt this secondary structure resulted in the degradation of iscR mRNA after RyhB binding. 3′ RACE analysis of the iscR mRNA fragment identified the intergenic RNA at the 3′ end. These results suggest that this intergenic RNA element acts as an iscR mRNA stability element by protecting iscR from exonuclease degradation. | 1 | Applied and Interdisciplinary Chemistry |
The uses that have been derived from Vectorette PCR are many and have been useful to the science of biology. For example, it gives rise to methods that can help during the outbreaks of diseases by making it easier to subtype pathogens that are similar or closely related. It can also be used to help diagnose certain diseases. Earlier in this page it was noted that Vectorette PCR can give rise to multiple functions that can be performed on novel DNA sequences located near a sequence that is already known. These functions like isolating DNA, amplifying it, and analyzing it are behind the uses for Vectorette PCR. These uses are things like genome walking, DNA sequencing for the termini of Yeast Artificial Chromosomes (YAC) and cosmid inserts, being able to map introns and promoters in genomic DNA and regions with mutations, facilitating the sequencing of clones of a large size, and filling in the gaps that arise during the mapping of genomes.
An intron is a DNA sequence that is flanked by exons and therefore located in between them. It is the region that gets cut out while exons are expressed, and so introns do not affect the code of amino acids. Gene expression can be affected by only a number of intronic sequences. Vectorette PCR has been found to be beneficial when it comes to the characterization of these intronic sequences when they are found to be next to known sequences.
cDNA or complementary DNA is a DNA sequence which is complementary to the RNA that is the template when synthesizing DNA during the reverse transcriptase process. Vectorette PCR that utilizes the primers that originate from cDNA gives rise to a method that is capable of acquiring intron sequences which are located adjacent to exons and aiding in the development of the structure of genes. It is able to achieve this when initializing the process with a sequence of cDNA and a clone of a genome.
Vectorette PCR also gives the user an advantage than if he/she were using other existing technologies. The user will be able to carry out tasks like gene manipulation that is cell-free, Vectorette PCR with minimal material to start with, and performing Vectorette PCR with DNA that needs not be of high purity. These advantages allow the user to save time and resources while increasing the range of DNA that can be targeted. | 1 | Applied and Interdisciplinary Chemistry |
The three types of coatings are: diffusion coatings, overlay coatings, and thermal barrier coatings. Diffusion coatings, mainly constituted with aluminide or platinum-aluminide, is the most common. MCrAlX-based overlay coatings (M=Ni or Co, X=Y, Hf, Si) enhance resistance to corrosion and oxidation. Compared to diffusion coatings, overlay coatings are more expensive, but less dependent on substrate composition, since they must be carried out by air or vacuum plasma spraying (APS/VPS) or electron beam physical vapour deposition (EB-PVD). Thermal barrier coatings provide by far the best enhancement in working temperature and coating life. It is estimated that modern TBC of thickness 300 μm, if used in conjunction with a hollow component and cooling air, has the potential to lower metal surface temperatures by a few hundred degrees. | 1 | Applied and Interdisciplinary Chemistry |
Sephadex is a cross-linked dextran gel used for gel filtration. It was launched by Pharmacia in 1959, after development work by Jerker Porath and Per Flodin. The name is derived from separation Pharmacia dextran. It is normally manufactured in a bead form and most commonly used for gel filtration columns. By varying the degree of cross-linking, the fractionation properties of the gel can be altered.
These highly specialized gel filtration and chromatographic media are composed of macroscopic beads synthetically derived from the polysaccharide dextran. The organic chains are cross-linked to give a three-dimensional network having functional ionic groups attached by ether linkages to glucose units of the polysaccharide chains.
Available forms include anion and cation exchangers, as well as gel filtration resins, with varying degrees of porosity; bead sizes fall in discrete ranges between 20 and 300 µm.
Sephadex is also used for ion-exchange chromatography.
Sephadex is crosslinked with epichlorohydrin. | 1 | Applied and Interdisciplinary Chemistry |
Chloromethane has been detected in the low-mass Class 0 protostellar binary, IRAS 16293–2422, using the Atacama Large Millimeter Array (ALMA). It was also detected in the comet 67P/Churyumov–Gerasimenko (67P/C-G) using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument on the Rosetta spacecraft. The detections reveal that chloromethane can be formed in star-forming regions before planets or life is formed. | 1 | Applied and Interdisciplinary Chemistry |
A particularly vexing question in the study of the chemical origins of life is the selection of ribose, which forms the backbone of the nucleic acids found in modern biological systems. Eschenmoser's work on a variant of the formose reaction that produces phosphorylated ribose in relatively significant concentrations has provided significant insight. Eschenmoser and colleagues demonstrated that phosphorylated glycolaldehyde when condensed with glyceraldehyde (a product of successive formaldehyde condensations) produces phosphorylated ribose differentially, providing a plausible explanation for the origin of both the sugar ribose, and the phosphate group required to polymerize monomeric nucleotides, in modern biochemistry. | 0 | Theoretical and Fundamental Chemistry |
Because an organism's metabolome is largely defined by its genome, different species will have different metabolomes. Indeed, the fact that the metabolome of a tomato is different from the metabolome of an apple is the reason why these two fruits taste so different. Furthermore, different tissues, different organs and biofluids associated with those organs and tissues can also have distinctly different metabolomes. The fact that different organisms and different tissues/biofluids have such different metabolomes has led to the development of a number of organism-specific and biofluid-specific metabolome databases. Some of the better known metabolome databases include the Human Metabolome Database or HMDB, the Yeast Metabolome Database or YMDB, the E. coli Metabolome Database or ECMDB, the Arabidopsis metabolome database or AraCyc as well as the Urine Metabolome Database, the Cerebrospinal Fluid (CSF) Metabolome Database and the Serum Metabolome Database. The latter three databases are specific to human biofluids. A number of very popular general metabolite databases also exist including KEGG, MetaboLights, the Golm Metabolome Database, MetaCyc, LipidMaps and Metlin. Metabolome databases can be distinguished from metabolite databases in that metabolite databases contain lightly annotated or synoptic metabolite data from multiple organisms while metabolome databases contain richly detailed and heavily referenced chemical, pathway, spectral and metabolite concentration data for specific organisms. | 1 | Applied and Interdisciplinary Chemistry |
*4.A.1 The PTS Glucose-Glucoside (Glc) Family
*4.A.2 The PTS Fructose-Mannitol (Fru) Family
*4.A.3 The PTS Lactose-N,N'-Diacetylchitobiose-β-glucoside (Lac) Family
*4.A.4 The PTS Glucitol (Gut) Family
*4.A.5 The PTS Galactitol (Gat) Family
*4.A.6 The PTS Mannose-Fructose-Sorbose (Man) Family
*4.A.7 The PTS L-Ascorbate (L-Asc) Family | 1 | Applied and Interdisciplinary Chemistry |
Alternatively, it can be made as a carbonated soft drink by two methods.
When served before the fermentation process is complete. Kilju made this way is high in sugar and carbon dioxide (CO) content, and has little to no alcohol, being similar to a sweet lemon soda. It is a family tradition to many. The simple production process also makes it accessible to underage drinkers. Cf. sima, commonly seasoned with lemon and unpurified cane sugar, leading to a small beer or a light mead.
To make homemade alcopop (typically to 3–7%) water is added to kilju after the fermentation process is complete to dilute the ABV accordingly. The solution is then carbonated with a soda machine, and soft drink syrup (which will lower the ABV approximately 10%) is added. Alternatively, it can be made as a carbonated soft drink when served before the fermentation process is complete. Fermented water made this way is high in sugar and carbon dioxide (CO) content, and do not need to be diluted with water because it has little to no alcohol depending on how many days it has been fermented, being similar to a sweet lemon soda. | 1 | Applied and Interdisciplinary Chemistry |
Absorption coefficients for 200 nm and 900 nm are almost equal at 6.9 m (attenuation length of 14.5 cm). Very weak light absorption, in the visible region, by liquid water has been measured using an integrating cavity absorption meter (ICAM). The absorption was attributed to a sequence of overtone and combination bands whose intensity decreases at each step, giving rise to an absolute minimum at 418 nm, at which wavelength the attenuation coefficient is about 0.0044 m, which is an attenuation length of about 227 meters. These values correspond to pure absorption without scattering effects. The attenuation of, e.g., a laser beam would be slightly stronger. | 0 | Theoretical and Fundamental Chemistry |
Discontinuous recrystallization is heterogeneous; there are distinct nucleation and growth stages. It is common in materials with low stacking-fault energy. Nucleation then occurs, generating new strain-free grains which absorb the pre-existing strained grains. It occurs more easily at grain boundaries, decreasing the grain size and thereby increasing the amount of nucleation sites. This further increases the rate of discontinuous dynamic recrystallization.
Discontinuous Dynamic Recrystallization has 5 main characteristics:
* Recrystallization does not occur until the threshold strain has been reached
* The stress-strain curve may have several peaks – there is not a universal equation
* Nucleation generally occurs along pre-existing grain boundaries
* Recrystallization rates increase as the initial grain size decreases
* There is a steady grain size which is approached as recrystallization proceeds
Discontinuous dynamic recrystallization is caused by the interplay of work hardening and recovery. If the annihilation of dislocations is slow relative to the rate at which they are generated, dislocations accumulate. Once critical dislocation density is achieved, nucleation occurs on grain boundaries. Grain boundary migration, or the atoms transfer from a large pre-existing grain to a smaller nucleus, allows the growth of the new nuclei at the expense of the pre-existing grains. The nucleation can occur through the bulging of existing grain boundaries. A bulge forms if the subgrains abutting a grain boundary are of different sizes, causing a disparity in energy from the two subgrains. If the bulge achieves a critical radius, it will successfully transition to a stable nucleus and continue its growth. This can be modeled using Cahn’s theories pertaining to nucleation and growth.
Discontinuous dynamic recrystallization commonly produces a ‘necklace’ microstructure. Since new grain growth is energetically favorable along grain boundaries, new grain formation and bulging preferentially occurs along pre-existing grain boundaries. This generates layers of new, very fine grains along the grain boundary initially leaving the interior of the pre-existing grain unaffected. As the dynamic recrystallization continues, it consumes the unrecrystallized region. As deformation continues, the recrystallization does not maintain coherency between layers of new nuclei, producing a random texture. | 1 | Applied and Interdisciplinary Chemistry |
# Selection of ingredients: The first step in creating a nanoemulsion is to select the ingredients, which include the oil, water, and emulsifying agent. The type and proportions of these ingredients will affect the stability and properties of the final emulsion.
# Preparation of oil and aqueous phases: The oil and water phases are separately prepared, with any desired ingredients, such as surfactants or flavoring agents, added at this step.
# Mixing oil and emulsifier with stirrer: Next, the oil and water phases are mixed in the presence of an emulsifying agent, typically using a high-shear mixing device such as a homogenizer or a high-pressure homogenizer.
# Aging and stabilization: The emulsion is typically aged at room temperature to allow the droplets to stabilize, after which it can be cooled or heated as required.
# Optimizing and characterization: The droplet size and stability are then optimized by adjusting the ingredients and process parameters, such as temperature, pH, and mixing conditions. The nanoemulsion is also sterilized by filtration with 0.22μm. Several methods, such as DLS, TEM, and SEM, can characterize the final nanoemulsion's properties.
# Analyzing the quality of the particle sizer | 0 | Theoretical and Fundamental Chemistry |
François Diederich (9 July 1952, in Ettelbruck – 23 September 2020) was a Luxembourgian chemist specializing in organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
In vivo, when alacepril undergoes deacetylation, it loses a molecule similar to the amino acid phenylalanine which transforms it into captopril. Captopril then provides its blood pressure lowering effect through two way. First, it inhibits the conversion of angiotensin 1, a precursor molecule, to angiotensin II, a vasoconstrictor that narrows blood vessels. Secondly, captopril prevents the breakdown of bradykinin, a vasodilator peptide that naturally relaxes blood vessels. | 0 | Theoretical and Fundamental Chemistry |
Magnetic fields are vector quantities characterized by both strength and direction. The strength of a magnetic field is measured in units of tesla in the SI units, and in gauss in the cgs system of units. 10,000 gauss are equal to one tesla. Measurements of the Earths magnetic field are often quoted in units of nanotesla (nT), also called a gamma. The Earths magnetic field can vary from 20,000 to 80,000 nT depending on location, fluctuations in the Earths magnetic field are on the order of 100 nT, and magnetic field variations due to magnetic anomalies can be in the picotesla (pT) range. Gaussmeters and teslameters' are magnetometers that measure in units of gauss or tesla, respectively. In some contexts, magnetometer is the term used for an instrument that measures fields of less than 1 millitesla (mT) and gaussmeter is used for those measuring greater than 1 mT. | 0 | Theoretical and Fundamental Chemistry |
In a two-dimensional isotropic material the grain boundary tension would be the same for the grains. This would give angle of 120° at GB junction where three grains meet. This would give the structure a hexagonal pattern which is the metastable state (or mechanical equilibrium) of the 2D specimen. A consequence of this is that, to keep trying to be as close to the equilibrium as possible, grains with fewer sides than six will bend the GB to try keep the 120° angle between each other. This results in a curved boundary with its curvature towards itself. A grain with six sides will, as mentioned, have straight boundaries, while a grain with more than six sides will have curved boundaries with its curvature away from itself. A grain with six boundaries (i.e. hexagonal structure) is in a metastable state (i.e. local equilibrium) within the 2D structure. In three dimensions structural details are similar but much more complex and the metastable structure for a grain is a non-regular 14-sided polyhedra with doubly curved faces. In practice all arrays of grains are always unstable and thus always grow until prevented by a counterforce.
Grains strive to minimize their energy, and a curved boundary has a higher energy than a straight boundary. This means that the grain boundary will migrate towards the curvature. The consequence of this is that grains with less than 6 sides will decrease in size while grains with more than 6 sides will increase in size.
Grain growth occurs due to motion of atoms across a grain boundary. Convex surfaces have a higher chemical potential than concave surfaces, therefore grain boundaries will move toward their center of curvature. As smaller particles tend to have a higher radius of curvature and this results in smaller grains losing atoms to larger grains and shrinking. This is a process called Ostwald ripening. Large grains grow at the expense of small grains.
Grain growth in a simple model is found to follow:
Here G is final average grain size, G is the initial average grain size, t is time, m is a factor between 2 and 4, and K is a factor given by:
Here Q is the molar activation energy, R is the ideal gas constant, T is absolute temperature, and K is a material dependent factor. In most materials the sintered grain size is proportional to the inverse square root of the fractional porosity, implying that pores are the most effective retardant for grain growth during sintering. | 1 | Applied and Interdisciplinary Chemistry |
All microbial metabolisms can be arranged according to three principles:
1. How the organism obtains carbon for synthesizing cell mass:
* autotrophic – carbon is obtained from carbon dioxide ()
* heterotrophic – carbon is obtained from organic compounds
* mixotrophic – carbon is obtained from both organic compounds and by fixing carbon dioxide
2. How the organism obtains reducing equivalents (hydrogen atoms or electrons) used either in energy conservation or in biosynthetic reactions:
* lithotrophic – reducing equivalents are obtained from inorganic compounds
* organotrophic – reducing equivalents are obtained from organic compounds
3. How the organism obtains energy for living and growing:
* phototrophic – energy is obtained from light
* chemotrophic – energy is obtained from external chemical compounds
In practice, these terms are almost freely combined. Typical examples are as follows:
* chemolithoautotrophs obtain energy from the oxidation of inorganic compounds and carbon from the fixation of carbon dioxide. Examples: Nitrifying bacteria, sulfur-oxidizing bacteria, iron-oxidizing bacteria, Knallgas-bacteria
* photolithoautotrophs obtain energy from light and carbon from the fixation of carbon dioxide, using reducing equivalents from inorganic compounds. Examples: Cyanobacteria (water () as reducing equivalent = hydrogen donor), Chlorobiaceae, Chromatiaceae (hydrogen sulfide () as hydrogen donor), Chloroflexus (hydrogen () as reducing equivalent donor)
* chemolithoheterotrophs obtain energy from the oxidation of inorganic compounds, but cannot fix carbon dioxide (). Examples: some Thiobacilus, some Beggiatoa, some Nitrobacter spp., Wolinella (with as reducing equivalent donor), some Knallgas-bacteria, some sulfate-reducing bacteria
* chemoorganoheterotrophs obtain energy, carbon, and hydrogen for biosynthetic reactions from organic compounds. Examples: most bacteria, e. g. Escherichia coli, Bacillus spp., Actinomycetota
* photoorganoheterotrophs obtain energy from light, carbon and reducing equivalents for biosynthetic reactions from organic compounds. Some species are strictly heterotrophic, many others can also fix carbon dioxide and are mixotrophic. Examples: Rhodobacter, Rhodopseudomonas, Rhodospirillum, Rhodomicrobium, Rhodocyclus, Heliobacterium, Chloroflexus (alternatively to photolithoautotrophy with hydrogen) | 1 | Applied and Interdisciplinary Chemistry |
In Cartesian coordinates the basis vectors are represented by a cell tensor :
The hypervolume of the unit cell, , is given by the determinant of the cell tensor: | 0 | Theoretical and Fundamental Chemistry |
Plants lack specialized immune cells—all plant cells participate in the plant immune response. Chloroplasts, along with the nucleus, cell membrane, and endoplasmic reticulum, are key players in pathogen defense. Due to its role in a plant cell's immune response, pathogens frequently target the chloroplast.
Plants have two main immune responses—the hypersensitive response, in which infected cells seal themselves off and undergo programmed cell death, and systemic acquired resistance, where infected cells release signals warning the rest of the plant of a pathogen's presence.
Chloroplasts stimulate both responses by purposely damaging their photosynthetic system, producing reactive oxygen species. High levels of reactive oxygen species will cause the hypersensitive response. The reactive oxygen species also directly kill any pathogens within the cell. Lower levels of reactive oxygen species initiate systemic acquired resistance, triggering defense-molecule production in the rest of the plant.
In some plants, chloroplasts are known to move closer to the infection site and the nucleus during an infection.
Chloroplasts can serve as cellular sensors. After detecting stress in a cell, which might be due to a pathogen, chloroplasts begin producing molecules like salicylic acid, jasmonic acid, nitric oxide and reactive oxygen species which can serve as defense-signals. As cellular signals, reactive oxygen species are unstable molecules, so they probably don't leave the chloroplast, but instead pass on their signal to an unknown second messenger molecule. All these molecules initiate retrograde signaling—signals from the chloroplast that regulate gene expression in the nucleus.
In addition to defense signaling, chloroplasts, with the help of the peroxisomes, help synthesize an important defense molecule, jasmonate. Chloroplasts synthesize all the fatty acids in a plant cell—linoleic acid, a fatty acid, is a precursor to jasmonate. | 0 | Theoretical and Fundamental Chemistry |
The Electrochemical Society Interface is a publication for those in the field of solid-state and electrochemical science and technology. Published quarterly, this four-color magazine contains technical articles about the latest developments in the field and presents news and information about and for Society members. | 0 | Theoretical and Fundamental Chemistry |
Oxidative DNA damage may block RNA polymerase II transcription and cause strand breaks. An RNA templated transcription-associated recombination process has been described that can protect against DNA damage. During the G1/G0 stages of the cell cycle, cells exhibit assembly of homologous recombination factors at double-strand breaks within actively transcribed regions. It appears that transcription is coupled to repair of DNA double-strand breaks by RNA templated homologous recombination. This repair process efficiently and accurately rejoins double-strand breaks in genes being actively transcribed by RNA polymerase II. | 1 | Applied and Interdisciplinary Chemistry |
Biomass Controls PBC is a U.S. Delaware public benefit corporation that delivered the first biogenic refinery (OP) prototype to New Delhi, India, in 2014 in partnership with the Climate Foundation. This system was designed to process non-sewered sanitation for populations between 100 and 10,000 people. The prototype was funded by the Bill and Melinda Gates Foundation. In 2016 a biogenic refinery was delivered to Kivalina, Alaska, for the processing of urine-diverting dry toilets (UDDTs) as part of the Alaska Water & Sewer Challenge. In 2017, three systems were shipped to India and installed in the cities of Wai, Warangal and Narsapur in partnership with Tide Technocrats. In 2018 a prototype was shown that can generate electricity (mCHP) from the thermal energy from the processing of fecal sludge, at the Bill and Melinda Gates Foundation reinvented toilet event in Beijing, China. In 2019, a system was set up at a dairy farm to process the separated solids from cow manure. This system demonstrated a significant reduction in greenhouse gas emissions while reducing solids volume by over 90% and producing biochar. | 1 | Applied and Interdisciplinary Chemistry |
The Kröhnke synthesis for making pyridines possesses a number of succinct advantages over other methods. Unlike the Hantzsch synthesis, the Kröhnke method does not require oxidation to generate the desired product since the α-pyridinium methyl ketone already possesses the correct oxidation state.
Another advantage of the Kröhnke synthesis is its high atom economy. For example, the Chichibabin synthesis requires 2 equivalents of unsaturated starting material. Additionally, the byproducts of the Kröhnke synthesis is water and pyridine, which allow for easy workup and purification protocols. Unlike comparable methods for pyridine synthesis, the Kröhkne synthesis benefits from being a high-yielding one pot synthesis, which ultimately allows for abbreviation of synthetic pathways and further simplifies combinatorial library cataloging. | 0 | Theoretical and Fundamental Chemistry |
One characteristic of adhesion GPCRs is their extended extracellular region. This region is modular in nature, often possessing a variety of structurally defined protein domains and a membrane proximal GAIN domain. In the aptly named Very Large G protein-coupled Receptor 1 VLGR1 the extracellular region extends up to almost 6000 amino acids. Human adhesion GPCRs possess domains including EGF-like (), Cadherin (), thrombospondin (), Immunoglobulin (), Pentraxin (), Calx-beta () and Leucine-rich repeats (). In non-vertebrate species multiple other structural motifs including Kringle, Somatomedin B (), SRCR () may be contained with the extracellular region. Since many of these domains have been demonstrated to mediate protein-protein interactions within other proteins, they are believed to play the same role in adhesion GPCRs. Indeed, many ligands have been discovered for adhesion GPCRs (see ligands section). Many of the adhesion GPCR possess long stretches of amino acids with little homology to known protein domains suggesting the possibility of new structural domains being elucidated within their extracellular regions. | 1 | Applied and Interdisciplinary Chemistry |
Lanthanum hydroxide does not react much with alkaline substances, however is slightly soluble in acidic solution. In temperatures above 330 °C it decomposes into lanthanum oxide hydroxide (LaOOH), which upon further heating decomposes into lanthanum oxide ():
: LaOOH
:2 LaOOH
Lanthanum hydroxide crystallizes in the hexagonal crystal system. Each lanthanum ion in the crystal structure is surrounded by nine hydroxide ions in a tricapped trigonal prism. | 0 | Theoretical and Fundamental Chemistry |
These forces arise due to dipole–dipole interactions (induced/permanent) between molecules of bilayers. As molecules come closer, this attractive force arises due to the ordering of these dipoles; like in the case of magnets that align and attract each other as they approach. This also implies that any surface would experience a van der waals attraction. In bilayers, the form taken by van der Waals interaction potential V is given by
where H is the Hamaker constant and D and z are the bilayers thickness and the distance of separation respectively. | 0 | Theoretical and Fundamental Chemistry |
Zinc was extracted in India as early as in the 4th to 3rd century BCE. Zinc production may have begun in India, and ancient northwestern India is the earliest known civilization that produced zinc on an industrial scale. The distillation technique was developed around 1200 CE at Zawar in Rajasthan.
In the 17th century, China exported Zinc to Europe under the name of totamu or tutenag. The term tutenag may derive from the South Indian term Tutthanagaa (zinc). In 1597, Libavius, a metallurgist in England received some quantity of Zinc metal and named it as Indian/Malabar lead. In 1738, William Champion is credited with patenting in Britain a process to extract zinc from calamine in a smelter, a technology that bore a strong resemblance to and was probably inspired by the process used in the Zawar zinc mines in Rajasthan. His first patent was rejected by the patent court on grounds of plagiarising the technology common in India. However, he was granted the patent on his second submission of patent approval. Postlewayts Universal Dictionary of 1751 still wasnt aware of how Zinc was produced.
The Arthashastra describes the production of zinc. The Rasaratnakara by Nagarjuna describes the production of brass and zinc. There are references of medicinal uses of zinc in the Charaka Samhita (300 BCE). The Rasaratna Samuchaya (800 CE) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. It also describes two methods of zinc distillation. | 1 | Applied and Interdisciplinary Chemistry |
In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer. | 0 | Theoretical and Fundamental Chemistry |
Known as a major facet in the study of quantum hydrodynamics and macroscopic quantum phenomena, the superfluidity effect was discovered by Pyotr Kapitsa and John F. Allen, and Don Misener in 1937. Onnes possibly observed the superfluid phase transition on August 2, 1911, the same day that he observed superconductivity in mercury. It has since been described through phenomenological and microscopic theories.
In the 1950s, Hall and Vinen performed experiments establishing the existence of quantized vortex lines in superfluid helium. In the 1960s, Rayfield and Reif established the existence of quantized vortex rings. Packard has observed the intersection of vortex lines with the free surface of the fluid,
and Avenel and Varoquaux have studied the Josephson effect in superfluid helium-4. In 2006, a group at the University of Maryland visualized quantized vortices by using small tracer particles of solid hydrogen.
In the early 2000s, physicists created a Fermionic condensate from pairs of ultra-cold fermionic atoms. Under certain conditions, fermion pairs form diatomic molecules and undergo Bose–Einstein condensation. At the other limit, the fermions (most notably superconducting electrons) form Cooper pairs which also exhibit superfluidity. This work with ultra-cold atomic gases has allowed scientists to study the region in between these two extremes, known as the BEC-BCS crossover.
Supersolids may also have been discovered in 2004 by physicists at Penn State University. When helium-4 is cooled below about 200 mK under high pressures, a fraction (≈1%) of the solid appears to become superfluid. By quench cooling or lengthening the annealing time, thus increasing or decreasing the defect density respectively, it was shown, via torsional oscillator experiment, that the supersolid fraction could be made to range from 20% to completely non-existent. This suggested that the supersolid nature of helium-4 is not intrinsic to helium-4 but a property of helium-4 and disorder. Some emerging theories posit that the supersolid signal observed in helium-4 was actually an observation of either a superglass state or intrinsically superfluid grain boundaries in the helium-4 crystal. | 1 | Applied and Interdisciplinary Chemistry |
Modification of the R side chain on bisphosphonates is very minor today, single hydroxyl group at that position seems to give the best results in terms of activity. The hydroxyl group plays a role in forming a water-induced bond with glutamine (Gln240) on the target enzyme. Drugs that have no hydroxyl group initially cause better inhibition than parent compounds, without hydroxyl group the drug seems to fit more easily into the open active site. The absence of hydroxyl group however reduces the ability to hold the target enzyme complex in isomerized state. Biological activity of bisphosphonates with hydroxyl group, therefore, appears over longer time. | 1 | Applied and Interdisciplinary Chemistry |
Keto–enol tautomerism is important in several areas of biochemistry.
The high phosphate-transfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is "trapped" in the less thermodynamically favorable enol form, whereas after dephosphorylation it can assume the keto form.
The enzyme enolase catalyzes the dehydration of 2-phosphoglyceric acid to the enol phosphate ester. Metabolism of PEP to pyruvic acid by pyruvate kinase (PK) generates adenosine triphosphate (ATP) via substrate-level phosphorylation. | 0 | Theoretical and Fundamental Chemistry |
It is crucial to note that although most of the gene deserts explored here are essential, it could be that the majority of the contents in gene deserts are still likely to be inessential and disposable. Naturally, this is not to say that the roles that gene deserts play are inessential or unimportant, rather than their functions may include buffering effects. An example of essential gene deserts with inessential DNA content are the telomeres that protect the ends of genomes. Telomeres can be categorized as true gene deserts, given that they solely contain repeats of TTAGGG (in humans) and do not have apparent protein-coding functions. Without these telomeres, human genomes would be severely mutated within a fixed number of cell cycles. On the other hand, since telomeres do not code for proteins, their loss ensures that there is no effect in important processes. Therefore, the term “junk” DNA should no longer be applied to any region of the genome; every portion of the genome should play a role in protecting, regulating, or repairing the protein coding regions that determine the functions of life. Although there is still much to learn about the nooks and crannies of the immense (yet limited) human genome, with the aid of various new technologies and the synthesis of the full human genome, we may perhaps unravel a great collection of secrets in the approaching years about the marvels of our genetic code. | 1 | Applied and Interdisciplinary Chemistry |
Given that a virtually uncountable variety of octahedral complexes exist, it is not surprising that a wide variety of reactions have been described. These reactions can be classified as follows:
* Ligand substitution reactions (via a variety of mechanisms)
* Ligand addition reactions, including among many, protonation
* Redox reactions (where electrons are gained or lost)
* Rearrangements where the relative stereochemistry of the ligand changes within the coordination sphere.
Many reactions of octahedral transition metal complexes occur in water. When an anionic ligand replaces a coordinated water molecule the reaction is called an anation. The reverse reaction, water replacing an anionic ligand, is called aquation. For example, the slowly yields in water, especially in the presence of acid or base. Addition of concentrated HCl converts the aquo complex back to the chloride, via an anation process. | 0 | Theoretical and Fundamental Chemistry |
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low concentration across a concentration gradient. In one (spatial) dimension, the law can be written in various forms, where the most common form (see) is in a molar basis:
where
* is the diffusion flux, of which the dimension is the amount of substance per unit area per unit time. measures the amount of substance that will flow through a unit area during a unit time interval.
* is the diffusion coefficient or diffusivity. Its dimension is area per unit time.
* is the concentration gradient
* (for ideal mixtures) is the concentration, with a dimension of amount of substance per unit volume.
* is position, the dimension of which is length.
is proportional to the squared velocity of the diffusing particles, which depends on the temperature, viscosity of the fluid and the size of the particles according to the Stokes–Einstein relation. In dilute aqueous solutions the diffusion coefficients of most ions are similar and have values that at room temperature are in the range of . For biological molecules the diffusion coefficients normally range from 10 to 10 m/s.
In two or more dimensions we must use , the del or gradient operator, which generalises the first derivative, obtaining
where denotes the diffusion flux vector.
The driving force for the one-dimensional diffusion is the quantity , which for ideal mixtures is the concentration gradient. | 0 | Theoretical and Fundamental Chemistry |
The very large incentives given to pharmaceutical companies to produce orphan drugs have led to the impression that the financial support afforded to make these drugs possible is akin to abuse. Because drugs can be used to treat multiple conditions, companies can take drugs that were filed with their government agency as orphan drugs to receive financial assistance, and then market it to a wide population to increase their profit margin. For example AstraZeneca's cholesterol drug Crestor was filed as a treatment for the rare disease pediatric familial hypercholesterolemia. After the drug was approved for orphan drug designation, and AstraZeneca had received tax breaks and other advantages, AstraZeneca later applied and received FDA approval for the drug to be used to treat cholesterol in all diabetics. | 1 | Applied and Interdisciplinary Chemistry |
Many systems are in place to repair DNA and RNA lesions but it is possible for lesions to escape these measures. This may lead to mutations or large genome abnormalities, which can threaten the cell or organism's ability to live. Several cancers are a result of DNA lesions. Even repair mechanisms to heal the damage may end up causing more damage. Mismatch repair defects, for example, cause instability that predisposes to colorectal and endometrial carcinomas.
DNA lesions in neurons may lead to neurodegenerative disorders such as Alzheimers, Huntingtons, and Parkinsons diseases. These come as a result of neurons generally being associated with high mitochondrial respiration and redox species production, which can damage nuclear DNA. Since these cells often cannot be replaced after being damaged, the damage done to them leads to dire consequences. Other disorders stemming from DNA lesions and their association with neurons include but are not limited to Fragile X syndrome, Friedreichs ataxia, and Spinocerebellar ataxias.
During replication, usually DNA polymerases are unable to go past the lesioned area, however, some cells are equipped with special polymerases which allow for translesion synthesis (TLS). TLS polymerases allow for the replication of DNA past lesions and risk generating mutations at a high frequency. Common mutations that occur after undergoing this process are point mutations and frameshift mutations. Several diseases come as a result of this process including several cancers and Xeroderma pigmentosum.
The effect of oxidatively damaged RNA has resulted in a number of human diseases and is especially associated with chronic degeneration. This type of damage has been observed in many neurodegenerative diseases such as Amyotrophic lateral sclerosis, Alzheimers, Parkinsons, dementia with Lewy bodies, and several prion diseases. It is important to note that this list is rapidly growing and data suggests that RNA oxidation occurs early in the development of these diseases, rather than as an effect of cellular decay. RNA and DNA lesions are both associated with the development of diabetes mellitus type 2. | 1 | Applied and Interdisciplinary Chemistry |
Dextroamphetamine is also used recreationally as a euphoriant and aphrodisiac, and like other amphetamines is used as a club drug for its energetic and euphoric high. Dextroamphetamine is considered to have a high potential for misuse in a recreational manner since individuals typically report feeling euphoric, more alert, and more energetic after taking the drug. Dextroamphetamine's dopaminergic (rewarding) properties affect the mesocorticolimbic circuit; a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), positive reinforcement and positively-valenced emotions, particularly ones involving pleasure. Large recreational doses of dextroamphetamine may produce symptoms of dextroamphetamine overdose. Recreational users sometimes open dexedrine capsules and crush the contents in order to insufflate (snort) it or subsequently dissolve it in water and inject it. Immediate-release formulations have higher potential for abuse via insufflation (snorting) or intravenous injection due to a more favorable pharmacokinetic profile and easy crushability (especially tablets).
The reason for using crushed spansules for insufflation and injection methods is evidently due to the "instant-release" forms of the drug seen in tablet preparations often containing a sizable amount of inactive binders and fillers alongside the active d-amphetamine, such as dextrose. Injection into the bloodstream can be dangerous because insoluble fillers within the tablets can block small blood vessels. Chronic overuse of dextroamphetamine can lead to severe drug dependence, resulting in withdrawal symptoms when drug use stops. | 0 | Theoretical and Fundamental Chemistry |
In the first half of the 20th century, Turner and Winks discovered that borosilicate glasses can be leached by acids. Their investigations showed that not only the chemical stability can be influenced by thermal treatment but also density, refractive index, thermal expansion and viscosity. In 1934, Nordberg and Hood discovered that alkali borosilicate glasses separate in soluble (sodium borate rich) and insoluble (silica rich) phases if the glass is thermally treated. By extraction using mineral acids the soluble phase can be removed and a porous silica network remains. During a sintering process after extraction, a silica glass is generated, which has properties approaching those of quartz glass. The manufacturing of such high-silica glasses has been published as the VYCOR-process. | 0 | Theoretical and Fundamental Chemistry |
Beyond its canonical role in the SIR complex, SIR2 also plays a role in rDNA repression. As part of the cells regulation mechanism, rDNA repeats are excised from the chromosome so they cannot be expressed. SIR2 forms a complex with NET1 (a nuclear protein) and CDC14 (a phosphatase) to form the regulator of nucleolar silencing and telophase (RENT) complex. The RENT complex sequesters excised rDNA in extrachromosomal circles, preventing recombination. Accumulation of these circles has been linked to premature aging. Sirtuin 2 (SIRT2), SIR2s human analog, has also been linked to age-related disease. | 1 | Applied and Interdisciplinary Chemistry |
Calmodulin belongs to one of the two main groups of calcium-binding proteins, called EF hand proteins. The other group, called annexins, bind calcium and phospholipids such as lipocortin. Many other proteins bind calcium, although binding calcium may not be considered their principal function in the cell. | 1 | Applied and Interdisciplinary Chemistry |
Seeding implants with growth factors, such as neural progenitor cells (NPCs), improves the brain-implant interface. NPCs are progenitor cells that have the ability to differentiate into neurons or cells found in the brain. By coating the implant with NPCs, it can reduce the foreign body reaction and improve biocompatibility. To attach the NPCs, prior surface modification of the implant is required; these modifications can be done via the immobilization of laminin (an extracellular matrix derived protein) on an implant, such as silicon. To verify the success of surface immobilization, Fourier transform infrared spectroscopy (FTIR) and an analysis of hydrophobicity can be used. The Fourier transform infrared spectroscopy can be used to characterize the chemical composition of the surface or a contact angle goniometer can be used to determine the contact angle of water to determine the hydrophobicity. A higher contact angle indicates higher hydrophobicity, showing successful modification of the surface via the laminin protein. The laminin immobilized surface promotes the attachment and growth of the NPCs and also allows for their differentiation, thereby reducing the glial response and foreign body response to the implant. | 0 | Theoretical and Fundamental Chemistry |
*When a reaction is reversed, the magnitude of ΔH stays the same, but the sign changes.
*When the balanced equation for a reaction is multiplied by an integer, the corresponding value of ΔH must be multiplied by that integer as well.
*The change in enthalpy for a reaction can be calculated from the enthalpies of formation of the reactants and the products
*Elements in their standard states make no contribution to the enthalpy calculations for the reaction, since the enthalpy of an element in its standard state is zero. Allotropes of an element other than the standard state generally have non-zero standard enthalpies of formation. | 0 | Theoretical and Fundamental Chemistry |
Biohydrometallurgy is used to perform processes involving metals, for example, microbial mining, oil recovery, bioleaching, water-treatment and others. Biohydrometallurgy is mainly used to recover certain metals from sulfide ores. It is usually utilized when conventional mining procedures are too expensive or ineffective in recovering a metal such as copper, cobalt, gold, lead, nickel, uranium and zinc. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, metal-catalysed hydroboration is a reaction used in organic synthesis. It is one of several examples of homogeneous catalysis. | 0 | Theoretical and Fundamental Chemistry |
The Favorskii reaction is an alternative set of reaction conditions, which involves prereaction of the acetylene with an alkali metal hydroxide such as KOH. The reaction proceeds through equilibria, making the reaction reversible:
To overcome this reversibility, the reaction often uses an excess of base to trap the water as hydrates. | 0 | Theoretical and Fundamental Chemistry |
Strategies for improving platinum-based anticancer drugs usually involve changes in the neutral spectator ligands, changes in the nature of the anions (halides vs various carboxylates), or changes in the oxidation state of the metal (Pt(II) vs Pt(IV)). Nanotechnology has been explored to deliver platinum more efficiently in the case of lipoplatin, which is introduced into the tumor sites thereby reducing the chance of toxicity.
Cisplatin was the first to be developed. Cisplatin is particularly effective against testicular cancer; the cure rate was improved from 10% to 85%. Similarly, the addition of cisplatin to adjuvant chemotherapy led to a marked increase in disease-free survival rates for patients with medulloblastoma - again, up to around 85%. This application of cisplatin was developed by pediatric oncologist Roger Packer in the early 1980s. | 1 | Applied and Interdisciplinary Chemistry |
The simulation of false brinelling is possible with the help of the finite element method. For the simulation, the relative displacements (slip) between rolling element and raceway as well as the pressure in the rolling contact are determined. For comparison between simulation and experiments, the friction work density is used, which is the product of friction coefficient, slip and local pressure. The simulation results can be used to determine critical application parameters or to explain the damage mechanisms.
Physical simulation of the false brinelling mechanism has been standardized since the 1980's in the Fafnir Bearing test instrument, where two sets of thrust ball bearings are compressed with a fixed load, and the bearings are oscillated by an excentric arm under standardised conditions. This culminated in the ASTM D4170 standard. Although an old method, this is still the leading quality control method for greases that need to avoid the false brinelling damage. | 1 | Applied and Interdisciplinary Chemistry |
Ocean turbidity is a measure of the amount of cloudiness or haziness in sea water caused by individual particles that are too small to be seen without magnification. Highly turbid ocean waters are those with many scattering particulates in them. In both highly absorbing and highly scattering waters, visibility into the water is reduced. Highly scattering (turbid) water still reflects much light, while highly absorbing water, such as a blackwater river or lake, is very dark. The scattering particles that cause the water to be turbid can be composed of many things, including sediments and phytoplankton. | 0 | Theoretical and Fundamental Chemistry |
Dilithium, Li, is a strongly electrophilic, diatomic molecule comprising two lithium atoms covalently bonded together. Li is known in the gas phase.
It has a bond order of 1, an internuclear separation of 267.3 pm and a bond energy of 102 kJ/mol or 1.06 eV in each bond.
The electron configuration of Li may be written as σ.
It has been observed that 1% (by mass) of lithium in the vapor phase is in the form of dilithium.
Being the lightest stable neutral homonuclear diatomic molecule after H, and the helium dimer, dilithium is an extremely important model system for studying fundamentals of physics, chemistry, and electronic structure theory.
It is the most thoroughly characterized compound in terms of the accuracy and completeness of the empirical potential energy curves of its electronic states. Analytic empirical potential energy curves have been constructed for the X-state, a-state, A-state, c-state, B-state, 2d-state, l-state, E-state, and the F-state . The most reliable of these potential energy curves are of the Morse/Long-range variety (see entries in the table below).
Li potentials are often used to extract atomic properties. For example, the C value for atomic lithium extracted from the A-state potential of Li by Le Roy et al. in is more precise than any previously measured atomic oscillator strength.
This lithium oscillator strength is related to the radiative lifetime of atomic lithium and is used as a benchmark for atomic clocks and measurements of fundamental constants. | 0 | Theoretical and Fundamental Chemistry |
Radiation Portal Monitor (RPM) was designed to detect traces of radiation emitted from an object passing through a RPM. Gamma radiation is detected, and in some cases complemented by neutron detection when sensitivity for nuclear material is desired. | 0 | Theoretical and Fundamental Chemistry |
Sloshing or shifting cargo, water ballast, or other liquid (e.g., from leaks or fire fighting) can cause disastrous capsizing in ships due to free surface effect; this can also affect trucks and aircraft.
The effect of slosh is used to limit the bounce of a roller hockey ball. Water slosh can significantly reduce the rebound height of a ball but some amounts of liquid seem to lead to a resonance effect. Many of the balls for roller hockey commonly available contain water to reduce the bounce height. | 1 | Applied and Interdisciplinary Chemistry |
If the neutrino is a Majorana particle (i.e., the antineutrino and the neutrino are actually the same particle), and at least one type of neutrino has non-zero mass (which has been established by the neutrino oscillation experiments), then it is possible for neutrinoless double beta decay to occur. Neutrinoless double beta decay is a lepton number violating process. In the simplest theoretical treatment, known as light neutrino exchange, a nucleon absorbs the neutrino emitted by another nucleon. The exchanged neutrinos are virtual particles.
With only two electrons in the final state, the electrons' total kinetic energy would be approximately the binding energy difference of the initial and final nuclei, with the nuclear recoil accounting for the rest. Because of momentum conservation, electrons are generally emitted back-to-back. The decay rate for this process is given by
where G is the two-body phase-space factor, M is the nuclear matrix element, and m is the effective Majorana mass of the electron neutrino. In the context of light Majorana neutrino exchange, m is given by
where m are the neutrino masses and the U are elements of the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix. Therefore, observing neutrinoless double beta decay, in addition to confirming the Majorana neutrino nature, can give information on the absolute neutrino mass scale and Majorana phases in the PMNS matrix, subject to interpretation through theoretical models of the nucleus, which determine the nuclear matrix elements, and models of the decay.
The observation of neutrinoless double beta decay would require that at least one neutrino is a Majorana particle, irrespective of whether the process is engendered by neutrino exchange. | 0 | Theoretical and Fundamental Chemistry |
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect;
* the specified minimum for copper does not exceed 0.40%;
* or the specified maximum for any of the following elements does not exceed the percentages noted: manganese 1.65%; silicon 0.60%; copper 0.60%.
The term carbon steel may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels. High carbon steel has many different uses such as milling machines, cutting tools (such as chisels) and high strength wires. These applications require a much finer microstructure, which improves the toughness.
As the carbon content percentage rises, steel has the ability to become harder and stronger through heat treating; however, it becomes less ductile. Regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the higher carbon content lowers the melting point. | 1 | Applied and Interdisciplinary Chemistry |
In the first paper on AFM-based infrared by Hammiche et al., the relevant well-established theoretical considerations were outlined that predict that high spatial resolution can be achieved using rapid modulation frequencies because of the consequent reduction in the thermal diffusion length. They estimated that spatial resolutions in the range of 20 nm-30 nm should be achievable. The most readily available sources that can achieve high modulation frequencies are pulsed lasers: even when the rapidity of the pulses is not high, the square wave form of a pulse contains very high modulation frequencies in Fourier space. In 2001, Hammiche et al. used a type of bench-top tuneable, pulsed infrared laser known as an optical parametric oscillator or OPO and obtained the first probe-based infrared spectrum with a pulsed laser, however, they did not report any images.
Nanoscale spatial resolution AFM-IR imaging using a pulsed laser was first demonstrated by Dazzi et al at the University of Paris-Sud, France. Dazzi and his colleagues used a wavelength-tuneable, free electron laser at the CLIO facility in Orsay, France to provide an infrared source with short pulses. Like earlier workers, they used a conventional AFM probe to measure thermal expansion but introduced a novel optical configuration: the sample was mounted on an IR-transparent prism so that it could be excited by an evanescent wave. Absorption of short infrared laser pulses by the sample caused rapid thermal expansion that created a force impulse at the tip of the AFM cantilever. The thermal expansion pulse induced transient resonant oscillations of the AFM cantilever probe. This has led to the technique being dubbed Photo-Thermal Induced Resonance (PTIR), by some workers in the field. Some prefer the terms PTIR or PTMS to AFM-IR as the technique is not necessarily restricted to infrared wavelengths. The amplitude of the cantilever oscillation is directly related to the amount of infrared radiation absorbed by the sample. By measuring the cantilever oscillation amplitude as a function of wavenumber, Dazzi's group was able to obtain absorption spectra from nanoscale regions of the sample. Compared to earlier work, this approach improved spatial resolution because the use of short laser pulses reduced the duration of the thermal expansion pulse to the point that the thermal diffusion lengths can be on the scale of nanometres rather than microns.
A key advantage of the use of a tuneable laser source, with a narrow wavelength range, is the ability to rapidly map the locations of specific chemical components on the sample surface. To achieve this, Dazzis group tuned their free electron laser source to a wavelength corresponding to the molecular vibration of the chemical of interest, then mapped the cantilever oscillation amplitude as function of position across the sample. They demonstrated the ability to map chemical composition in E. coli bacteria. They could also visualize polyhydroxybutyrate (PHB) vesicles inside Rhodobacter capsulatus' cells and monitor the efficiency of PHB production by the cells.
At the University of East Anglia in the UK, as part of an EPSRC-funded project led by M. Reading and S. Meech, Hill and his co-workers followed the earlier work of Reading et al. and Hammiche et al. and measured thermal expansion using an optical configuration that illuminated the sample from above in contrast to Dazzi et al. who excited the sample with an evanescent wave from below. Hill also made use of an optical parametric oscillator as the infrared source in the manner of Hammiche et al. This novel combination of topside illumination, OPO source and measuring thermal expansion proved capable of nanoscale spatial resolution for infrared imaging and spectroscopy (the figures show a schematic of the UEA apparatus and results obtained with it). The use by Hill and co-workers of illumination from above allowed a substantially wider range of samples to be studied than was possible using Dazzi's technique. By introducing the use of a bench top IR source and topdown illumination, the work of Hammiche, Hill and their coworkers made possible the first commercially viable SPM-based infrared instrument (see Commercialization). | 0 | Theoretical and Fundamental Chemistry |
In general, the Gouy-Stodola theorem is used to quantify irreversibilities in a system and to perform exergy analysis. That is, it allows one to take a thermodynamic system and better understand how inefficient it is (energy-wise), how much work is lost, how much room there is for improvement and where. The second law of thermodynamics states, in essence, that the entropy of a system only increases. Over time, thermodynamic systems tend to gain entropy and lose energy (in approaching equilibrium): thus, the entropy is "somehow" related to how much exergy or potential for useful work a system has. The Gouy-Stodola theorem provides a concrete link. For the most part, this is how the theorem is used - to find and quantify inefficiencies in a system. | 0 | Theoretical and Fundamental Chemistry |
Time crystals do not violate the laws of thermodynamics: energy in the overall system is conserved, such a crystal does not spontaneously convert thermal energy into mechanical work, and it cannot serve as a perpetual store of work. But it may change perpetually in a fixed pattern in time for as long as the system can be maintained. They possess "motion without energy"—their apparent motion does not represent conventional kinetic energy. Recent experimental advances in probing discrete time crystals in their periodically driven nonequilibrium states have led to the beginning exploration of novel phases of nonequilibrium matter.
Time crystals do not evade the Second Law of Thermodynamics, although they spontaneously break "time-translation symmetry", the usual rule that a stable object will remain the same throughout time. In thermodynamics, a time crystal's entropy, understood as a measure of disorder in the system, remains stationary over time, marginally satisfying the second law of thermodynamics by not decreasing. | 0 | Theoretical and Fundamental Chemistry |
A FMN-binding fluorescent protein (FbFP), also known as a LOV-based fluorescent protein, is a small, oxygen-independent fluorescent protein that binds flavin mononucleotide (FMN) as a chromophore.
They were developed from blue-light receptors (so called LOV-domains) found in plants and various bacteria. They complement the GFP-derivatives and –homologues and are particularly characterized by their independence of molecular oxygen and their small size. FbFPs absorb blue light and emit light in the cyan-green spectral range. | 1 | Applied and Interdisciplinary Chemistry |
Eddies are common in the ocean, and range in diameter from centimeters to hundreds of kilometers. The smallest scale eddies may last for a matter of seconds, while the larger features may persist for months to years.
Eddies that are between about 10 and 500 km (6 and 300 miles) in diameter and persist for periods of days to months are known in oceanography as mesoscale eddies.
Mesoscale eddies can be split into two categories: static eddies, caused by flow around an obstacle (see animation), and transient eddies, caused by baroclinic instability.
When the ocean contains a sea surface height gradient this creates a jet or current, such as the Antarctic Circumpolar Current. This current as part of a baroclinically unstable system meanders and creates eddies (in much the same way as a meandering river forms an oxbow lake). These types of mesoscale eddies have been observed in many major ocean currents, including the Gulf Stream, the Agulhas Current, the Kuroshio Current, and the Antarctic Circumpolar Current, amongst others.
Mesoscale ocean eddies are characterized by currents that flow in a roughly circular motion around the center of the eddy. The sense of rotation of these currents may either be cyclonic or anticyclonic (such as Haida Eddies). Oceanic eddies are also usually made of water masses that are different from those outside the eddy. That is, the water within an eddy usually has different temperature and salinity characteristics to the water outside the eddy. There is a direct link between the water mass properties of an eddy and its rotation. Warm eddies rotate anti-cyclonically, while cold eddies rotate cyclonically.
Because eddies may have a vigorous circulation associated with them, they are of concern to naval and commercial operations at sea. Further, because eddies transport anomalously warm or cold water as they move, they have an important influence on heat transport in certain parts of the ocean. | 1 | Applied and Interdisciplinary Chemistry |
Trace metals are the metals subset of trace elements; that is, metals normally present in small but measurable amounts in animal and plant cells and tissues. Some of these trace metals are a necessary part of nutrition and physiology. Some biometals are trace metals. Ingestion of, or exposure to, excessive quantities can be toxic. However, insufficient plasma or tissue levels of certain trace metals can cause pathology, as is the case with iron.
Trace metals within the human body include iron, lithium, zinc, copper, chromium, nickel, cobalt, vanadium, molybdenum, manganese and others.
Some of the trace metals are needed by living organisms to function properly and are depleted through the expenditure of energy by various metabolic processes of living organisms. They are replenished in animals through diet as well as environmental exposure, and in plants through the uptake of nutrients from the soil in which the plant grows. Human vitamin pills and plant fertilizers can be a source of trace metals.
Trace metals are sometimes referred to as trace elements, although the latter includes minerals and is a broader category. See also Dietary mineral. Trace elements are required by the body for specific functions. Things such as vitamins, sports drinks, fresh fruits and vegetables are sources. Taken in excessive amounts, trace elements can cause problems. For example, fluorine is required for the formation of bones and enamel on teeth. However, when taken in an excessive amount can cause a disease called "Fluorosis', in which bone deformations and yellowing of teeth are seen. Fluorine can occur naturally in some areas in ground water. | 0 | Theoretical and Fundamental Chemistry |
A localized surface plasmon (LSP) is the result of the confinement of a surface plasmon in a nanoparticle of size comparable to or smaller than the wavelength of light used to excite the plasmon. When a small spherical metallic nanoparticle is irradiated by light, the oscillating electric field causes the conduction electrons to oscillate coherently. When the electron cloud is displaced relative to its original position, a restoring force arises from Coulombic attraction between electrons and nuclei. This force causes the electron cloud to oscillate. The oscillation frequency is determined by the density of electrons, the effective electron mass, and the size and shape of the charge distribution. The LSP has two important effects: electric fields near the particles surface are greatly enhanced and the particles optical absorption has a maximum at the plasmon resonant frequency. Surface plasmon resonance can also be tuned based on the shape of the nanoparticle. The plasmon frequency can be related to the metal dielectric constant. The enhancement falls off quickly with distance from the surface and, for noble metal nanoparticles, the resonance occurs at visible wavelengths. Localized surface plasmon resonance creates brilliant colors in metal colloidal solutions.
For metals like silver and gold, the oscillation frequency is also affected by the electrons in d-orbitals. Silver is a popular choice in plasmonics, which studies the effect of coupling light to charges, because it can support a surface plasmon over a wide range of wavelengths (300-1200 nm), and its peak absorption wavelength is easily changed. For instance, the peak absorption wavelength of triangular silver nanoparticles was altered by changing the corner sharpness of the triangles. It underwent a blue-shift as corner sharpness of the triangles decreased. Additionally, peak absorption wavelength underwent a red-shift as a larger amount of HAuCl was added and porosity of the particles increased. For semiconductor nanoparticles, the maximum optical absorption is often in the near-infrared and mid-infrared region. | 0 | Theoretical and Fundamental Chemistry |
Pulsed-field extraction magnetometry is another method making use of pickup coils to measure magnetization. Unlike VSMs where the sample is physically vibrated, in pulsed-field extraction magnetometry, the sample is secured and the external magnetic field is changed rapidly, for example in a capacitor-driven magnet. One of multiple techniques must then be used to cancel out the external field from the field produced by the sample. These include counterwound coils that cancel the external uniform field and background measurements with the sample removed from the coil. | 0 | Theoretical and Fundamental Chemistry |
There is a collection of alternative splicing databases. These databases are useful for finding genes having pre-mRNAs undergoing alternative splicing and alternative splicing events or to study the functional impact of alternative splicing.
* AspicDB database
* Intronerator database
* ProSAS database | 1 | Applied and Interdisciplinary Chemistry |
Solar cells started in 1876 with William Grylls Adams along with an undergraduate student of his. A French scientist, by the name of Edmond Becquerel, first discovered the photovoltaic effect in the summer of 1839. He theorized that certain elements on the periodic table, such as silicon, reacted to the exposure of sunlight in very unusual ways. Solar power is created when solar radiation is converted to heat or electricity. English electrical engineer Willoughby Smith, between 1873 and 1876, discovered that when selenium is exposed to light, it produced a high amount of electricity. The use of selenium was highly inefficient, but it proved Becquerel's theory that light could be converted into electricity through the use of various semi-metals on the periodic table, that were later labelled as photo-conductive material. By 1953, Calvin Fuller, Gerald Pearson, and Daryl Chapin discovered the use of silicon to produce solar cells was extremely efficient and produced a net charge that far exceeded that of selenium. Today solar power has many uses, from heating, electrical production, thermal processes, water treatment and storage of power that is highly prevalent in the world of renewable energy. | 0 | Theoretical and Fundamental Chemistry |
A famous example is the detection of cyclobutadiene released upon oxidation of cyclobutadieneiron tricarbonyl. When this degradation is conducted in the presence of an alkyne, the cyclobutadiene is trapped as a bicyclohexadiene. The requirement for this trapping experiment is that the oxidant (ceric ammonium nitrate) and the trapping agent be mutually compatible. | 0 | Theoretical and Fundamental Chemistry |
A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the striking voltage, the gas ionization becomes self-sustaining, and the tube glows with a colored light. The color depends on the gas used.
Glow discharges are used as a source of light in devices such as neon lights, cold cathode fluorescent lamps and plasma-screen televisions. Analyzing the light produced with spectroscopy can reveal information about the atomic interactions in the gas, so glow discharges are used in plasma physics and analytical chemistry. They are also used in the surface treatment technique called sputtering. | 0 | Theoretical and Fundamental Chemistry |
The hydrodynamic resistance force is evaluated following the Stokes’ law.
The electrophoretic force is evaluated following the Coulomb’s law.
In these equations r presents the hydrodynamic radius of the colloids, – the speed of electrophoretic migration, – the dynamic viscosity of the solutions, – dielectric constant in vacuum, is water’s relative dielectric constant at 298 K, is the zeta potential, E is the electric field. The hydrodynamic radius is the sum of particles’ radiuses and the stationary solvent interface.
By steady state electrophoretic migration of charged colloids the electrophoretic force and the hydrodynamic resistance force are in equilibrium, described by:
:F + F = 0
Those effects influence the electrofiltration of biopolymers, which could be also charged, not only by the hydrodynamic resistance force but also by the electric field force. Focusing on the cathode side reveals that the negatively charged particles are affected by the electric field force, which is opposite to the hydrodynamic resistance force. In this manner the formation of filter cake on this side is impeded or in ideal situation filter cake is not formed at all. In this case the electric field is referred as critical electric field E. As a result of the equilibrium of those forces, liquids subjected to the influence of electric force become charged. In addition to the applied hydraulic pressure ∆pH the process is influenced also by the electro-osmotic pressure P.
Modifying the Darcy’s basic equation, describing filter cake formation, with electro-kinetic effects by integration under assumption of using the constants of electro-osmotic pressure P, the critical electric field E and the electric field E results:
Previous scientific works conducted in the [http://www.bio-ag.de/ Dept. of Bioprocess Engineering, Institute of Engineering in Life Sciences, University of Karlsruhe] demonstrated that electrofiltration is effective for the concentration of charged biopolymers. Very promising results concerning purification of the charged polysaccharide xanthan are already obtained. Figure 2 represents xanthan filter cake. | 0 | Theoretical and Fundamental Chemistry |
The dependence of the water ionization on temperature and pressure has been investigated thoroughly. The value of pK decreases as temperature increases from the melting point of ice to a minimum at c. 250 °C, after which it increases up to the critical point of water c. 374 °C. It decreases with increasing pressure.
With electrolyte solutions, the value of pK is dependent on ionic strength of the electrolyte. Values for sodium chloride are typical for a 1:1 electrolyte. With 1:2 electrolytes, MX, pK decreases with increasing ionic strength.
The value of K is usually of interest in the liquid phase. Example values for superheated steam (gas) and supercritical water fluid are given in the table.
:Notes to the table. The values are for supercritical fluid except those marked: at saturation pressure corresponding to 350 °C. superheated steam. compressed or subcooled liquid. | 0 | Theoretical and Fundamental Chemistry |
The water in and around at least 126 U.S. military bases has been contaminated by high levels of PFASs because of their use of firefighting foams since the 1970s, according to a study by the U.S. Department of Defense. Of these, 90 bases reported PFAS contamination that had spread to drinking water or groundwater off the base. A 2022 Pentagon report acknowledged that approximately 175,000 U.S. military personnel at two dozen American military facilities drank water contaminated by PFAS that exceeded the U.S. EPA limit. However, according to an analysis of the Pentagon report by the non-partisan Environmental Working Group, the Pentagon report downplayed the number of people exposed to PFAS, which was much higher, probably in excess of 640,000 at 116 military facilities, than the number advanced by the Pentagon report. The EWG found that the Pentagon also omitted from its report some types of diseases that are likely to be caused by PFAS exposure, such as testicular cancer, kidney disease, and fetal abnormalities. | 0 | Theoretical and Fundamental Chemistry |
Peatlands hold approximately 30% of the carbon in our ecosystem. When they are drained for agricultural land and urbanization, because peatlands are so vast, large quantities of carbon decompose and emit into the atmosphere. The loss of one peatland could potentially produce more carbon than 175–500 years of methane emissions.
Peat bogs act as a sink for carbon because they accumulate partially decayed biomass that would otherwise continue to decay completely. There is a variance on how much the peatlands act as a carbon sink or carbon source that can be linked to varying climates in different areas of the world and different times of the year. By creating new bogs, or enhancing existing ones, the amount of carbon that is sequestered by bogs would increase. | 0 | Theoretical and Fundamental Chemistry |
One advantage to hypolimnetic withdrawal is that it is relatively inexpensive to install an Olszewski tube or any similar device. Along with low initial cost, it also has a relatively low annual maintenance cost. The following are four systems installed in the United States (2002), their area in hectares, the rate of flow in cube-meters per minute, and their initial installation costs in US dollars:
* Lake Ballinger
41 ha<br />
3.4 m/min<br />
* Lake Waramaug
287 ha<br />
6.3 m/min<br />
* Devil's Lake
151 ha<br />
9.1 m/min<br />
* Pine Lake
412 ha<br />
5.3 m/min<br /> | 1 | Applied and Interdisciplinary Chemistry |
Transcription factor 4 (TCF-4) also known as immunoglobulin transcription factor 2 (ITF-2) is a protein that in humans is encoded by the TCF4 gene located on chromosome 18q21.2. | 1 | Applied and Interdisciplinary Chemistry |
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica. Gene transcription occurs in both eukaryotic and prokaryotic cells. Unlike prokaryotic RNA polymerase that initiates the transcription of all different types of RNA, RNA polymerase in eukaryotes (including humans) comes in three variations, each translating a different type of gene. A eukaryotic cell has a nucleus that separates the processes of transcription and translation. Eukaryotic transcription occurs within the nucleus where DNA is packaged into nucleosomes and higher order chromatin structures. The complexity of the eukaryotic genome necessitates a great variety and complexity of gene expression control.
Eukaryotic transcription proceeds in three sequential stages: initiation, elongation, and termination.
The RNAs transcribed serve diverse functions. For example, structural components of the ribosome are transcribed by RNA polymerase I. Protein coding genes are transcribed by RNA polymerase II into messenger RNAs (mRNAs) that carry the information from DNA to the site of protein synthesis. More abundantly made are the so-called non-coding RNAs account for the large majority of the transcriptional output of a cell. These non-coding RNAs perform a variety of important cellular functions. | 1 | Applied and Interdisciplinary Chemistry |
The document compiles thirty-four recipes of elixirs that potentially could cause harm. Of these, three recipes mention saltpeter as an ingredient. A warning is given regarding a particularly dangerous combination of materials:
The ingredients would have produced a weak form of gunpowder—a mixture of sulphur, saltpeter, and carbon—with honey acting as the source of carbon. | 1 | Applied and Interdisciplinary Chemistry |
Project Sherwood was the codename for a United States program in controlled nuclear fusion during the period it was classified. After 1958, when fusion research was declassified around the world, the project was reorganized as a separate division within the United States Atomic Energy Commission (AEC) and lost its codename.
Sherwood developed out of a number of ad hoc efforts dating back to about 1951. Primary among these was the stellarator program at Princeton University, itself code-named Project Matterhorn. Since then the weapons labs had clamored to join the club, Los Alamos with its z-pinch efforts, Livermores magnetic mirror program, and later, Oak Ridges fuel injector efforts. By 1953 the combined budgets were increasing into the million dollar range, demanding some sort of oversight at the AEC level.
The name "Sherwood" was suggested by Paul McDaniel, Deputy Director of the AEC. He noted that funding for the wartime Hood Building was being dropped and moved to the new program, so they were "robbing Hood to pay Friar Tuck", a reference to the British physicist and fusion researcher James L. Tuck. The connection to Robin Hood and Friar Tuck gave the project its name.
Lewis Strauss strongly supported keeping the program secret until pressure from the United Kingdom led to a declassification effort at the 2nd Atoms for Peace meeting in the fall of 1958. After this time a number of purely civilian organizations also formed to organize meetings on the topic, with the American Physical Society organizing meetings under their Division of Plasma Physics. These meetings have been carried on to this day and were renamed International Sherwood Fusion Theory Conference. The original Project Sherwood became simply the Controlled Thermonuclear Research program within the AEC and its follow-on organizations. | 0 | Theoretical and Fundamental Chemistry |
The first theoretical study of the water dimer was an ab initio calculation published in 1968 by Morokuma and Pedersen. Since then, the water dimer has been the focus of sustained interest by theoretical chemists concerned with hydrogen bonding—a search of the CAS database up to 2006 returns over 1100 related references (73 of them in 2005). In addition to serving as a model for hydrogen bonding, (HO) is thought to play a significant role in many atmospheric processes, including chemical reactions, condensation, and solar energy absorption by the atmosphere. In addition, a complete understanding of the water dimer is thought to play a key role in a more thorough understanding of hydrogen bonding in liquid and solid forms of water. | 0 | Theoretical and Fundamental Chemistry |
When two streams either of two-dimensional or axisymmetric nature impinge on each other, a stagnation plane is created, where the incoming streams are diverted tangentially outwards; thus on the stagnation plane, the velocity component normal to that plane is zero, whereas the tangential component is non-zero. In the neighborhood of the stagnation point, a local description for the velocity field can be described. | 1 | Applied and Interdisciplinary Chemistry |
In crystallography, a crystallographic point group is a three dimensional point group whose symmetry operations are compatible with a three dimensional crystallographic lattice. According to the crystallographic restriction it may only contain one-, two-, three-, four- and sixfold rotations or rotoinversions. This reduces the number of crystallographic point groups to 32 (from an infinity of general point groups). These 32 groups are one-and-the-same as the 32 types of morphological (external) crystalline symmetries derived in 1830 by Johann Friedrich Christian Hessel from a consideration of observed crystal forms.
In the classification of crystals, to each space group is associated a crystallographic point group by "forgetting" the translational components of the symmetry operations. That is, by turning screw rotations into rotations, glide reflections into reflections and moving all symmetry elements into the origin. Each crystallographic point group defines the (geometric) crystal class of the crystal.
The point group of a crystal determines, among other things, the directional variation of physical properties that arise from its structure, including optical properties such as birefringency, or electro-optical features such as the Pockels effect. | 0 | Theoretical and Fundamental Chemistry |
There are a wide variety of adhesives used for optical bonding processes. Three of the most commonly used are silicone, epoxy, and polyurethane. Below are overviews of the pros/cons of each adhesive type.
* Silicone: The most commonly found adhesive in optical bonding processes that dates back to the 1970s as a solution. Silicone's core properties of low conductivity and chemical reactivity, thermal stability, and ability to repel water and form watertight seals make it a common solution for optical bonding. Also, because it is a soft material, it is very feasible to rework for bonds that become damaged over time. However, debris often forms around the edges of the bonds if they are rubbed during handling. To reduce this, edges of optically bonded displays should be covered or configured so that edges are not exposed.
* Epoxy: When used as a structural glue, epoxy resin creates a more rigid bond than silicone, thus eliminating the formation of particulate debris, which is common with silicone bonding processes. However, epoxy bonding is not reworkable.
* Polyurethane: Polyurethane adhesives are commonly utilized in bonding applications for displays in avionic technology and polar technology. However, this bonding adhesive yellows over time when exposed to light, so by today's standards it is considered an obsolete adhesive. | 0 | Theoretical and Fundamental Chemistry |
Geopolymers are inorganic, typically ceramic, materials that form long-range, covalently bonded, non-crystalline (amorphous) networks. Geopolymers are a sub-class of alkali-activated cements. They are mainly produced by a chemical reaction between a chemically reactive aluminosilicate powder (e.g. metakaolin or other clay-derived powders, natural pozzolan, or suitable glasses), and an aqueous solution (alkaline or acidic) that causes this powder to react and form into a solid monolith. The most common pathway to produce geopolymers is by the reaction of metakaolin with sodium silicate, which is an alkaline solution, but other processes are also possible.
Commercially produced geopolymers may be used for fire- and heat-resistant coatings and adhesives, medicinal applications, high-temperature ceramics, new binders for fire-resistant fiber composites, toxic and radioactive waste encapsulation, and as cementing components in making concrete. The properties and uses of geopolymers are being explored in many scientific and industrial disciplines: modern inorganic chemistry, physical chemistry, colloid chemistry, mineralogy, geology, and in other types of engineering process technologies.
The original raw materials used in the synthesis of geopolymers were mainly rock-forming minerals of geological origin, hence the name: geopolymer was coined by Joseph Davidovits in 1978 These materials and associated terminology were then popularized over the following decades via his work with the Institut Géopolymère (Geopolymer Institute).
One can distinguish between two synthesis routes, respectively:
* in alkaline medium (Na, K, Li, Cs, Ca…), and;
* in acidic medium (phosphoric acid: ).
The alkaline route is the most important in terms of R&D and commercial applications and will be described below. Details on the acidic route have been published by Wagh in 2004, by Perera et al. in 2008, and by Cao et al. in 2005. | 0 | Theoretical and Fundamental Chemistry |
Thanks to Holtz and Blaschko it was clear that animals synthesized noradrenaline. What was needed to attribute a transmitter role to it was proof of its presence in tissues at effective concentrations and not only as a short-lived intermediate. On April 16, 1945, Ulf von Euler of Karolinska Institute in Stockholm, who had already discovered or co-discovered substance P and prostaglandins, submitted to Nature the first of a series of papers that gave this proof. After many bioassays and chemical assays on organ extracts he concluded that mammalian sympathetically innervated tissues as well as, in small amounts, the brain, but not the nerve-free placenta, contained noradrenaline and that noradrenaline was the sympathy of Cannon and Rosenblueth, the ″physiological transmitter of adrenergic nerve action in mammals″. Overflow of noradrenaline into the venous blood of the cat's spleen upon sympathetic nerve stimulation two years later bore out the conclusion. In amphibian hearts, on the other hand, the transmitter role of adrenaline was confirmed.
The war prevented Peter Holtz and his group in Rostock from being recognized side by side with von Euler as discoverers of the second catecholamine transmitter noradrenaline. Their approach was different. They sought for catecholamines in human urine and found a blood pressure-increasing material Urosympathin that they identified as a mixture of dopamine, noradrenaline and adrenaline. “As to the origin of Urosympathin we would like to suggest the following. Dopamine in urine is the fraction that was not consumed for the synthesis of sympathin E and I. … Sympathin E and I, i.e. noradrenaline and adrenaline, are liberated in the region of the sympathetic nerve endings when these are excited.” The manuscript was received by Springer-Verlag in Leipzig on October 8, 1944. On October 15, the printing office in Braunschweig was destroyed by an airstrike. Publication was delayed to volume 204, 1947, of Naunyn-Schmiedebergs Archiv für Pharmakologie und Experimentelle Pathologie. Peter Holtz later used to cite the paper as ″Holtz et al. 1944/47″ or ″Holtz, Credner and Kroneberg 1944/47″.
Remembering his and Barger's structure-activity analysis of 1910, Dale wrote in 1953: “Doubtless I ought to have seen that nor-adrenaline might be the main transmitter – that Elliott’s theory might be right in principle and faulty only in this detail. … It is easy, of course, to be wise in the light of facts recently discovered; lacking them I failed to jump to the truth, and I can hardly claim credit for having crawled so near and then stopped short of it.”
The next step led to the central nervous system. It was taken by Marthe Vogt, a refugee from Germany who at that time worked with John Henry Gaddum in the Institute of Pharmacology of the University of Edinburgh. ″The presence of noradrenaline and adrenaline in the brain has been demonstrated by von Euler (1946) and Holtz (1950). These substances were supposed, undoubtedly correctly, to occur in the cerebral vasomotor nerves. The present work is concerned with the question whether these sympathomimetic amines, besides their role as transmitters at vasomotor endings, play a part in the function of the central nervous tissue itself. In this paper, these amines will be referred to as sympathin, since they were found invariably to occur together, with noradrenaline representing the major component, as is characteristic for the transmitter of the peripheral sympathetic system.″ Vogt created a detailed map of noradrenaline in the dog brain. Its uneven distribution, not reflecting the distribution of vasomotor nerves, and its persistence after removal of the superior cervical ganglia made it ″tempting to assign to the cerebral sympathin a transmitter role like that which we assign to the sympathin found in the sympathetic ganglia and their postganglionic fibers.″ Her assignment was confirmed, the finishing touch being the visualization of the noradrenaline as well as adrenaline and dopamine pathways in the central nervous system by Annica Dahlström and with the formaldehyde fluorescence method developed by Nils-Åke Hillarp (1916–1965) and Bengt Falck (born 1927) in Sweden and by immunochemistry techniques. | 1 | Applied and Interdisciplinary Chemistry |
Consider a freely jointed chain of N bonds of length subject to a constant elongational force f applied to its ends along the z axis and an environment temperature . An example could be a chain with two opposite charges +q and -q at its ends in a constant electric field applied along the axis as sketched in the figure on the right. If the direct Coulomb interaction between the charges is ignored, then there is a constant force at the two ends.
Different chain conformations are not equally likely, because they correspond to different energy of the chain in the external electric field.
Thus, different chain conformation have different statistical Boltzmann factors .
The partition function is:
Every monomer connection in the chain is characterized by a vector of length and angles in the spherical coordinate system. The end-to-end vector can be represented as: . Therefore:
The Gibbs free energy G can be directly calculated from the partition function:
The Gibbs free energy is used here because the ensemble of chains corresponds to constant temperature and constant force (analogous to the isothermal-isobaric ensemble, which has constant temperature and pressure).
The average end-to-end distance corresponding to a given force can be obtained as the derivative of the free energy:
This expression is the Langevin function , also mentioned in previous paragraphs:
where, .
For small relative elongations () the dependence is approximately linear,
and follows Hooke's law as shown in previous paragraphs: | 0 | Theoretical and Fundamental Chemistry |
Due to the hydrophilic property of sucrose and the lipophilic property of fatty acids, the overall hydrophilicity of sucrose esters can be tuned by the number of hydroxyl groups that are reacted with fatty acids and the identity of the fatty acids. The fewer free hydroxyl groups and the more lipophilic fatty acids, the less hydrophilic the resulting sucrose ester becomes. Sucrose esters' HLB values can range from 1-16. Low HLB (3.5-6.0) sucrose esters act as a water-in-oil emulsifier while high HLB (8-18) sucrose esters act as an oil-in-water emulsifier. | 0 | Theoretical and Fundamental Chemistry |
Copepods are known to be the primary consumers of diatoms in the water column and initiate the production of PUA upon grazing. The consumption of PUA-producing diatoms by copepods has been shown to diminish their reproductive success. Specifically, female copepods that consume diatoms spawn eggs with low viabilities and offspring with high teratogenesis rates. The compounds mainly act by preventing cell division and promoting apoptosis in copepod embryos, though the mechanism behind this is still poorly understood. | 1 | Applied and Interdisciplinary Chemistry |
To distinguish whether the geometry of the coordination center is trigonal bipyramidal or square pyramidal, the (originally just ) parameter was proposed by Addison et al.:
where: are the two greatest valence angles of the coordination center.
When is close to 0 the geometry is similar to square pyramidal, while if is close to 1 the geometry is similar to trigonal bipyramidal: | 0 | Theoretical and Fundamental Chemistry |
Anti-histone antibodies are found in the serum of up to 75–95% of people with drug-induced lupus and 75% of idiopathic SLE. Unlike anti-dsDNA antibodies in SLE, these antibodies do not fix complement. Although they are most commonly found in drug induced lupus, they are also found in some cases of SLE, scleroderma, rheumatoid arthritis and undifferentiated connective tissue disease. Many drugs are known to cause drug induced lupus and they produce various antigenic targets within the nucleosome that are often cross reactive with several histone proteins and DNA. Procainamide causes a form of drug-induced lupus that produces antibodies to the histone H2A and H2B complex. | 1 | Applied and Interdisciplinary Chemistry |
Transformations are often seen to follow a characteristic s-shaped, or sigmoidal, profile where the transformation rates are low at the beginning and the end of the transformation but rapid in between.
The initial slow rate can be attributed to the time required for a significant number of nuclei of the new phase to form and begin growing. During the intermediate period the transformation is rapid as the nuclei grow into particles and consume the old phase while nuclei continue to form in the remaining parent phase.
Once the transformation approaches completion, there remains little untransformed material for further nucleation, and the production of new particles begins to slow. Additionally, the previously formed particles begin to touch one another, forming a boundary where growth stops. | 0 | Theoretical and Fundamental Chemistry |
Note: Where a given letter is used in both capital and lower case form (, and , ) the capital letter refers to the macroscopic observable and the lower case letter to the corresponding variable for an individual particle or layer of the material. Greek symbols are used for properties of a single particle.
: – absorption fraction of a single layer
: – remission fraction of a single layer
: – transmission fraction of a single layer
: , , – the absorption, remission, and transmission fractions for a sample composed of layers
: – absorption fraction of a particle
: – back-scattering from a particle
: – isotropic scattering from a particle
: – absorption coefficient defined as the fraction of incident light absorbed by a very thin layer divided by the thickness of that layer
: – scattering coefficient defined as the fraction of incident light scattered by a very thin layer divided by the thickness of that layer | 0 | Theoretical and Fundamental Chemistry |
The reverse Krebs cycle (also known as the reverse tricarboxylic acid cycle, the reverse TCA cycle, or the reverse citric acid cycle, or the reductive tricarboxylic acid cycle, or the reductive TCA cycle)
is a sequence of chemical reactions that are used by some bacteria to produce carbon compounds from carbon dioxide and water by the use of energy-rich reducing agents as electron donors.
The reaction is the citric acid cycle run in reverse. Where the Krebs cycle takes carbohydrates and oxidizes them to CO and water, the reverse cycle takes CO and HO to make carbon compounds.
This process is used by some bacteria (such as Aquificota) to synthesize carbon compounds, sometimes using hydrogen, sulfide, or thiosulfate as electron donors. This process can be seen as an alternative to the fixation of inorganic carbon in the reductive pentose phosphate cycle which occurs in a wide variety of microbes and higher organisms. | 1 | Applied and Interdisciplinary Chemistry |
Starting from the 1950s, Schwab was allowed to return to West Germany, with his first post being guest professor at the Technical University of Darmstadt (1949) before he was appointed to the illustrious Professorship of Physical Chemistry at the University of Munich in 1950. While holding the corresponding seat in Athens, Schwab continued visiting Greece to offer lectures on his course.
Meanwhile, he engaged in notable novel research regarding surface catalytic interactions. In the 1955–1956 academic year he was Dean of the Faculty of Natural Sciences of the University of Munich. He retired in 1967 with the title of Emeritus Professor of Physical Chemistry, which he held until his death in 1984. | 0 | Theoretical and Fundamental Chemistry |
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