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alkB is an iron-dependent oxidoreductase, and it is associated with DNA repair because this gene is able to repair lesions in phage DNA prior to infection. It has been also demonstrated that alkB is required for reactivation of MMS-treated (methylating agent methyl methanesulfonate) single-stranded phage and since there are no lesions to be removed, it has been suggested that alkBB is involved in replication of damaged template DNA. Also, the fact that alkB can confer resistance to a methylating agent it suggests that it functions by itself.

Biochemistry

Yeast artificial chromosomes (YACs) are genetically engineered chromosomes derived from the DNA of the yeast, Saccharomyces cerevisiae [https://www.genome.gov/genetics-glossary/Yeast-Artificial-Chromosome], which is then ligated into a bacterial plasmid. By inserting large fragments of DNA, from 100–1000 kb, the inserted sequences can be cloned and physically mapped using a process called chromosome walking. This is the process that was initially used for the Human Genome Project, however due to stability issues, YACs were abandoned for the use of bacterial artificial chromosome [https://www.genome.gov/genetics-glossary/Bacterial-Artificial-Chromosome] The bakers yeast S. cerevisiae' is one of the most important experimental organisms for studying eukaryotic molecular genetics. Beginning with the initial research of the Rankin et al., Strul et al., and Hsaio et al., the inherently fragile chromosome was stabilized by discovering the necessary autonomously replicating sequence (ARS); a refined YAC utilizing this data was described in 1983 by Murray et al. The primary components of a YAC are the ARS, centromere [https://www.nature.com/articles/nrm.2015.5], and telomeres [https://www.nature.com/articles/350569a0] from S. cerevisiae. Additionally, selectable marker genes, such as antibiotic resistance and a visible marker, are utilized to select transformed yeast cells. Without these sequences, the chromosome will not be stable during extracellular replication, and would not be distinguishable from colonies without the vector.

Biochemistry

4-nitro phenol is a slightly yellow, crystalline material, moderately toxic. It shows two polymorphs in the crystalline state. The alpha-form is colorless pillars, unstable at room temperature, and stable toward sunlight. The beta-form is yellow pillars, stable at room temperature, and gradually turns red upon irradiation of sunlight. Usually 4-nitrophenol exists as a mixture of these two forms. In solution, 4-nitrophenol has a dissociation constant (pK) of 7.15 at 25 °C.

Analytical Chemistry

In addition to hydrogenation reactions, other bonds have been formed using DKR and are highly successful. The aldol reaction has been extensively researched primarily because of the inherent challenge of forming a carbon-carbon bond. Ward and colleagues have been able to use the proline-catalyzed aldol reaction in tandem with dynamic kinetic resolution to obtain a high enantioselective reaction. In this reaction proline catalyzes the reaction through creation of an enamine intermediate that is highly nucleophilic. The acid group on the catalyst helps facilitate the carbon-carbon bond formation by coordinating with the aldehyde oxygen. This greatly improves stereoselectivity and yield. Ward and his associates also found that by adding trace amounts of water to the DMSO solvent, it greatly increase the yield of the reaction, most likely by aiding proton transfer from proline to the newly forming alcohol. The selectivity for this product can best be explained by the Felkin model. The cyclic (E)-enamine is able to undergo a favorable transition state where the aldehyde adopts an anti relationship relative to the incoming nucleophile, as well as a 1,2 syn relationship between the aldehyde and its adjacent ring system. The transition state is shown above.

Stereochemistry

Oxamic acid is an organic compound with the formula . It is a white, water-soluble solid. It is the monoamide of oxalic acid. Oxamic acid inhibits lactate dehydrogenase A. The active site of lactate dehydrogenase (LDH) is closed off once oxamic acid attaches to the LDH-NADH complex, effectively inhibiting it. Oxamic acid also has applications in polymer chemistry. It increases the water solubility of certain polymers, including polyester, epoxide, and acrylic upon binding with them.

Biochemistry

The Toda chain equations of motion, in the continuous limit in which the distance between neighbors goes to zero, become the Korteweg–de Vries equation (KdV) equation. Here the index labeling the particle in the chain becomes the new spatial coordinate. In contrast, the Toda field theory is achieved by introducing a new spatial coordinate which is independent of the chain index label. This is done in a relativistically invariant way, so that time and space are treated on equal grounds. This means that the Toda field theory is not a continuous limit of the Toda chain.

Physical Chemistry

Zwolinski and Wilhoit defined, in 1972, "gross" and "net" values for heats of combustion. In the gross definition the products are the most stable compounds, e.g. (l), (l), (s) and (l). In the net definition the products are the gases produced when the compound is burned in an open flame, e.g. (g), (g), (g) and (g). In both definitions the products for C, F, Cl and N are (g), (g), (g) and (g), respectively. The heating value of a fuel can be calculated with the results of ultimate analysis of fuel. From analysis, percentages of the combustibles in the fuel (carbon, hydrogen, sulfur) are known. Since the heat of combustion of these elements is known, the heating value can be calculated using Dulong's Formula: HHV [kJ/g]= 33.87m + 122.3(m - m ÷ 8) + 9.4m where m, m, m, m, and m are the contents of carbon, hydrogen, oxygen, nitrogen, and sulfur on any (wet, dry or ash free) basis, respectively.

Physical Chemistry

In heat transfer and thermodynamics, a thermodynamic system is said to be in thermal contact with another system if it can exchange energy through the process of heat. Perfect thermal isolation is an idealization as real systems are always in thermal contact with their environment to some extent. When two solid bodies are in contact, a resistance to heat transfer exists between the bodies. The study of heat conduction between such bodies is called thermal contact conductance (or thermal contact resistance).

Physical Chemistry

Over time, many parts of the chloroplast genome were transferred to the nuclear genome of the host, a process called endosymbiotic gene transfer. As a result, the chloroplast genome is heavily reduced compared to that of free-living cyanobacteria. Chloroplasts may contain 60–100 genes whereas cyanobacteria often have more than 1500 genes in their genome. Contrarily, there are only a few known instances where genes have been transferred to the chloroplast from various donors, including bacteria. Endosymbiotic gene transfer is how we know about the lost chloroplasts in many chromalveolate lineages. Even if a chloroplast is eventually lost, the genes it donated to the former hosts nucleus persist, providing evidence for the lost chloroplasts existence. For example, while diatoms (a heterokontophyte) now have a red algal derived chloroplast, the presence of many green algal genes in the diatom nucleus provide evidence that the diatom ancestor (probably the ancestor of all chromalveolates too) had a green algal derived chloroplast at some point, which was subsequently replaced by the red chloroplast. In land plants, some 11–14% of the DNA in their nuclei can be traced back to the chloroplast, up to 18% in Arabidopsis, corresponding to about 4,500 protein-coding genes. There have been a few recent transfers of genes from the chloroplast DNA to the nuclear genome in land plants.

Photochemistry

Metabolism is also dependent on the species of organism; different organisms have slightly different P450 enzymes that metabolize certain PCBs better than others. Looking at the PCB metabolism in the liver of four sea turtle species (green, olive ridley, loggerhead and hawksbill), green and hawksbill sea turtles have noticeably higher hydroxylation rates of PCB 52 than olive ridley or loggerhead sea turtles. This is because the green and hawksbill sea turtles have higher P450 2-like protein expression. This protein adds three hydroxyl groups to PCB 52, making it more polar and water-soluble. P450 3-like protein expression that is thought to be linked to PCB 77 metabolism, something that was not measured in this study.

Environmental Chemistry

CellCognition is a free open-source computational framework for quantitative analysis of high-throughput fluorescence microscopy (time-lapse) images in the field of bioimage informatics and systems microscopy. The CellCognition framework uses image processing, computer vision and machine learning techniques for single-cell tracking and classification of cell morphologies. This enables measurements of temporal progression of cell phases, modeling of cellular dynamics and generation of phenotype map.

Biochemistry

The Department of Systems and Synthetic Microbiology, headed by Victor Sourjik, aims to elucidate general principles of evolutionary optimization of cellular networks and implement these principles in the design of novel networks in microorganisms. Having a single research group, microbial networks is also led by Sourjik.

Geochemistry

In an effort to explain the surprising stereoselectivities in the systems above, alternative explanations to the Cieplak effect have been proposed. In substituted cyclohexanones, the tendency of small reducing agents to add hydride axially is proposed to be caused by torsional strain instead of hyperconjugation. In an equatorial attack, the nucleophile approaches by eclipsing a neighboring hydrogen atom and subsequently pushes the carbonyl substituents into eclipsing positions as it pyramidalizes the carbonyl carbon. In an axial approach, the nucleophile approaches gauche to neighboring hydrogen atoms and so does not cause eclipsing interactions while pyramidalizing the carbonyl carbon. It is this torsional strain—the energy cost of rotating the bonds out of an eclipsed position—that favors axial over equatorial approach. In the case of substituted norbornones, stereoselectivity may be explained by electrostatic interactions between substituents and nucleophiles. Electron-withdrawing groups create a partial positive charge on the alpha carbon, which interacts favorably with the partial negative charge on the incoming nucleophile. This interaction may guide attack syn to the electron-withdrawing substituent, and anti to electron-donating substituents. This conclusion is supported by computations, where modeling the partial charges predicts product distribution without including orbital interactions. The same explanation has been made to justify similar results in the case of substituted adamantones. Similarly, in Houk's trans-decalone system, the nucleophile with its partial negative charge prefers to attack away from the partial negative charge of the acyl ester. When this substituent is axial, the equatorial pathway brings the nucleophile into closer proximity and is therefore disfavored. This is less pronounced for equatorially substituted ester because the group is now positioned further away from the carbonyl.

Organic Chemistry

Hypophosphorous acid (HPA), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent with molecular formula HPO. It is a colorless low-melting compound, which is soluble in water, dioxane and alcohols. The formula for this acid is generally written HPO, but a more descriptive presentation is HOP(O)H, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites. HOP(O)H exists in equilibrium with the minor tautomer HP(OH). Sometimes the minor tautomer is called hypophosphorous acid and the major tautomer is called phosphinic acid.

Organic Chemistry

Railways commonly used salt water load banks in the 1950s to test the output power of diesel-electric locomotives. They were subsequently replaced by specially designed resistive load banks. Some early three-phase AC electric locomotives also used liquid rheostats for starting up the motors and balancing load between multiple locomotives. Liquid rheostats were sometimes used in large (thousands of kilowatts/horsepower) wound rotor motor drives, to control the rotor circuit resistance and so the speed of the motor. Electrode position could be adjusted with a small electrically operated winch or a pneumatic cylinder. A cooling pump and heat exchanger were provided to allow slip energy to be dissipated into process water or other water system. Massive rheostats were once used for dimming theatrical lighting, but solid-state components have taken their place in most high-wattage applications.

Physical Chemistry

The Kröhnke method is featured in a solvent-free synthesis of triarylpyridines that proceeds via a homo-coupling of two diaryl substituted α, β-unsaturated carbonyl compounds. This strategy offers a facile means for preparation of pyridnyl aryl systems that are important fragments of many useful drug scaffolds. In 1992, Robinson and co-workers developed a similar pyridine synthesis using enamino nitriles as one of the three-carbon fragments in place of an α-pyridinium methyl ketone. This improvement increases the reactivity of the system and allows for formation of fully substituted pyridines whereas use of an α-pyridinium methyl ketone requires that the 3- or 5- position on the resulting pyridine be unsubstituted. Kröhnke condensation of enamino nitrile 20 with enone 21 yielded fused pyridine 22. The mechanism of this Kröhnke-type reaction likely proceeds via a vinylogous cyanamide 23 which undergoes elimination of hydrocyanic acid, deprotonation to form enamine 24 and cyclization to form intermediate 25, which is then dehydrated to form the desired pyridine product. A clean one-pot Kröhnke method in aqueous media generates 4’-aryl-2,2’:6’, 2’’-terpyridines. Reaction of aryl aldehyde 26 with two equivalents of 2-acetylpyridine (27) yielded terpyridines of the form 28. In addition to variations on the original method, a number of combinatorial studies using the Kröhnke synthesis and its variations have been employed to synthesize vast libraries of highly functionalized pyridines. Janda and co-workers utilized the general Kröhnke reaction scheme to generate a 220 compound library. Various methyl ketones 29 and aldehydes 30 were coupled via aldol condensation to give enones of the form 31. These compounds were then reacted with various α-pyridinium methyl ketones 32 to give the desired tri-substituted pyridine 33. In 2009, Tu and coworkers developed a 3 fragment, one-pot combinatorial strategy for developing 3-cyanoterpyridines 34and 1-amino-2-acylterpyridines 35. These combinatorial variations of the Kröhnke reaction provide an efficient synthetic strategy to poly arylpyridine scaffolds. This methodology would also be advantageous for biological assays and screening experiments.

Organic Chemistry

Unlike other aerial photographic and satellite image interpretation work, these multispectral images do not make it easy to identify directly the feature type by visual inspection. Hence the remote sensing data has to be classified first, followed by processing by various data enhancement techniques so as to help the user to understand the features that are present in the image. Such classification is a complex task which involves rigorous validation of the training samples depending on the classification algorithm used. The techniques can be grouped mainly into two types. * Supervised classification techniques * Unsupervised classification techniques Supervised classification makes use of training samples. Training samples are areas on the ground for which there is ground truth, that is, what is there is known. The spectral signatures of the training areas are used to search for similar signatures in the remaining pixels of the image, and we will classify accordingly. This use of training samples for classification is called supervised classification. Expert knowledge is very important in this method since the selection of the training samples and a biased selection can badly affect the accuracy of classification. Popular techniques include the maximum likelihood principle and convolutional neural network. The Maximum likelihood principle calculates the probability of a pixel belonging to a class (i.e. feature) and allots the pixel to its most probable class. Newer convolutional neural network based methods account for both spatial proximity and entire spectra to determine the most likely class. In case of unsupervised classification no prior knowledge is required for classifying the features of the image. The natural clustering or grouping of the pixel values, i.e. the gray levels of the pixels, are observed. Then a threshold is defined for adopting the number of classes in the image. The finer the threshold value, the more classes there will be. However, beyond a certain limit the same class will be represented in different classes in the sense that variation in the class is represented. After forming the clusters, ground truth validation is done to identify the class the image pixel belongs to. Thus in this unsupervised classification apriori information about the classes is not required. One of the popular methods in unsupervised classification is k-means clustering.

Physical Chemistry

Arformoterol is indicated for the maintenance treatment of bronchoconstriction in people with chronic obstructive pulmonary disease (COPD).

Stereochemistry

As the deep waters sink into the ocean basins, they displace the older deep-water masses, which gradually become less dense due to continued ocean mixing. Thus, some water is rising, in what is known as upwelling. Its speeds are very slow even compared to the movement of the bottom water masses. It is therefore difficult to measure where upwelling occurs using current speeds, given all the other wind-driven processes going on in the surface ocean. Deep waters have their own chemical signature, formed from the breakdown of particulate matter falling into them over the course of their long journey at depth. A number of scientists have tried to use these tracers to infer where the upwelling occurs. Wallace Broecker, using box models, has asserted that the bulk of deep upwelling occurs in the North Pacific, using as evidence the high values of silicon found in these waters. Other investigators have not found such clear evidence. Computer models of ocean circulation increasingly place most of the deep upwelling in the Southern Ocean, associated with the strong winds in the open latitudes between South America and Antarctica. Direct estimates of the strength of the thermohaline circulation have also been madeat 26.5°N in the North Atlantic, by the UK-US RAPID programme. It combines direct estimates of ocean transport using current meters and subsea cable measurements with estimates of the geostrophic current from temperature and salinity measurements to provide continuous, full-depth, basin-wide estimates of the meridional overturning circulation. However, it has only been operating since 2004, which is too short when the timescale of the circulation is measured in centuries.

Geochemistry

Facultative anaerobes are able to grow in both the presence and absence of oxygen due to the expression of both aerobic and anaerobic respiratory chains using either oxygen or an alternative electron acceptor. For example, in the absence of oxygen, E. coli can use fumarate, nitrate, nitrite, dimethyl sulfoxide, or trimethylamine oxide as an electron acceptor. This flexibility allows facultative anaerobes to survive in a number of environments, and in environments with frequently changing conditions. Several species of protists use a facultative anaerobic metabolism to enhance their ATP production, and some can produce dihydrogen through this process.

Biochemistry

Superhydrophobic coatings can be made from many different materials. The following are known possible bases for the coating: * Manganese oxide polystyrene (MnO/PS) nano-composite * Zinc oxide polystyrene (ZnO/PS) nano-composite * Precipitated calcium carbonate * Carbon nano-tube structures * Silica nano-coating * Fluorinated silanes and Fluoropolymer coatings. The silica-based coatings are perhaps the most cost effective to use. They are gel-based and can be easily applied either by dipping the object into the gel or via aerosol spray. In contrast, the oxide polystyrene composites are more durable than the gel-based coatings, however the process of applying the coating is much more involved and costly. Carbon nano-tubes are also expensive and difficult to produce with current technology. Thus, the silica-based gels remain the most economically viable option at present.

Physical Chemistry

Unlike DNA, which is a highly stable molecule, proteins are a heterogeneous class of molecules with different stability and physiochemical properties. Maintaining the proteins’ folding and function in an immobilized state over long periods of storage is a major challenge for protein microarrays. Cell-free methods provide the option to quickly obtaining protein microarrays on demand, thus eliminating any problems associated with long-term storage.

Biochemistry

The Rigveda refers to ayas, and also states that the Dasyus had ayas (RV 2.20.8). In RV 4.2.17, "the gods [are] smelting like copper/metal ore the human generations". The references to ayas in the Rig Veda probably refer to bronze or copper rather than to iron. Scholars like Bhargava maintain that Rigveda was written in the Vedic state of Brahmavarta and Khetri Copper mines formed an important location in Brahmavarta. Vedic people had used Copper extensively in agriculture, Water purification, tools, utensils etc., D. K. Chakrabarti (1992) argued: "It should be clear that any controversy regarding the meaning of ayas in the Rgveda or the problem of the Rgvedic familiarity or unfamiliarity with iron is pointless. There is no positive evidence either way. It can mean both copper-bronze and iron and, strictly on the basis of the contexts, there is no reason to choose between the two."

Metallurgy

When measuring water treated with water softeners, high levels of total dissolved solids do not correlate to hard water, as water softeners do not reduce TDS; rather, they replace magnesium and calcium ions, which cause hard water, with an equal charge of sodium or potassium ions, e.g. Ca ⇌ 2 Na, leaving overall TDS unchanged or even increased. Hard water can cause scale buildup in pipes, valves, and filters, reducing performance and adding to system maintenance costs. These effects can be seen in aquariums, spas, swimming pools, and reverse osmosis water treatment systems. Typically, in these applications, total dissolved solids are tested frequently, and filtration membranes are checked in order to prevent adverse effects. In the case of hydroponics and aquaculture, TDS is often monitored in order to create a water quality environment favorable for organism productivity. For freshwater oysters, trouts, and other high value seafood, highest productivity and economic returns are achieved by mimicking the TDS and pH levels of each species' native environment. For hydroponic uses, total dissolved solids is considered one of the best indices of nutrient availability for the aquatic plants being grown. Because the threshold of acceptable aesthetic criteria for human drinking water is 500 mg/L, there is no general concern for odor, taste, and color at a level much lower than is required for harm. A number of studies have been conducted and indicate various species' reactions range from intolerance to outright toxicity due to elevated TDS. The numerical results must be interpreted cautiously, as true toxicity outcomes will relate to specific chemical constituents. Nevertheless, some numerical information is a useful guide to the nature of risks in exposing aquatic organisms or terrestrial animals to high TDS levels. Most aquatic ecosystems involving mixed fish fauna can tolerate TDS levels of 1000 mg/L. The fathead minnow (Pimephales promelas), for example, realizes an concentration of 5600 ppm based upon a 96-hour exposure. LD50 is the concentration required to produce a lethal effect on 50 percent of the exposed population. Daphnia magna, a good example of a primary member of the food chain, is a small planktonic crustacean, about 0.5 mm in length, having an LD50 of about 10,000 ppm TDS for a 96-hour exposure. Spawning fishes and juveniles appear to be more sensitive to high TDS levels. For example, it was found that concentrations of 350 mg/L TDS reduced spawning of Striped bass (Morone saxatilis) in the San Francisco Bay-Delta region, and that concentrations below 200 mg/L promoted even healthier spawning conditions. In the Truckee River, EPA found that juvenile Lahontan cutthroat trout were subject to higher mortality when exposed to thermal pollution stress combined with high total dissolved solids concentrations. For terrestrial animals, poultry typically possess a safe upper limit of TDS exposure of approximately 2900 mg/L, whereas dairy cattle are measured to have a safe upper limit of about 7100 mg/L. Research has shown that exposure to TDS is compounded in toxicity when other stressors are present, such as abnormal pH, high turbidity, or reduced dissolved oxygen with the latter stressor acting only in the case of Animalia. In countries with often-unsafe/unclean tap water supplies, the TDS of drinking water is often checked by technicians to gauge how effectively their RO/Water Filtration devices are working. While TDS readings will not give an answer as to the amount of microorganisms present in a sample of water, they can get a good idea as to the efficiency of the filter by how much TDS is present.

Environmental Chemistry

A/LCI combines low-coherence interferometry with angle-resolved scattering to solve the inverse problem of determining scatterer geometry based on far field diffraction patterns. Similar to optical coherence domain reflectometry (OCDR) and optical coherence tomography (OCT), a/LCI uses a broadband light source in an interferometry scheme in order to achieve optical sectioning with a depth resolution set by the coherence length of the source. Angle-resolved scattering measurements capture light as a function of the scattering angle, and invert the angles to deduce the average size of the scattering objects via a computational light scattering model such as Mie theory, which predicts angles based on the size of the scattering sphere. Combining these techniques allows construction of a system that can measure average scatter size at various depths within a tissue sample. At present the most significant medical application of the technology is determining the state of tissue health based on measurements of average cell nuclei size. It has been found that as tissue changes from normal to cancerous, the average cell nuclei size increases. Several recent studies have shown that via cell nuclei measurements, a/LCI can detect the presence of low- and high-grade dysplasia with 91% sensitivity and distinguish between normal and dysplastic with 97% specificity.

Physical Chemistry

The 43S is an important intermediate complex during cap-dependent translation initiation. In the canonical model of translation initiation, the 43S PIC is pre-formed as a stable complex and recruited to the 5 cap of eukaryotic messenger RNAs (mRNAs) by the eIF4F complex. The 43S PIC then "scans" in the 5 --> 3' direction along the mRNA in an ATP-dependent fashion (via eIF4A and/or other RNA helicases such as Ded1/DDX3 and DHX29) to locate the start codon. Start codon recognition occurs through base-pairing between the Met-tRNA and AUG in the ribosomal P-site and a number of associated changes, and is followed by joining of the large 60S ribosomal subunit to form the 80S ribosome.

Biochemistry

This kind of equilibrium constant measures how a substance distributes or partitions itself between two immiscible solvents. It is called the partition coefficient or distribution coefficient.

Physical Chemistry

Under basic, protic conditions, 2,3-epoxy alcohols undergo a rearrangement in which the alcohol oxygen opens the epoxide with inversion of configuration, forming an isomeric 1,2-epoxy alcohol. Overall, the Payne rearrangement represents a migration of the epoxide. Although the migration itself is fully reversible, nucleophilic opening under Curtin–Hammett conditions provides good yields of functionalized diols derived from a single epoxy alcohol isomer. Intramolecular electrophilic trapping of the new alkoxide generated upon rearrangement may also be used to drive the reaction to completion. In some cases, the thermodynamic difference between epoxide isomers is large enough to obtain a single isomer in synthetically useful yield without relying on kinetic differences associated with trapping. Strongly basic conditions are required to induce equilibration, which limits the synthetic utility of the transformation to substrates lacking base-labile functionality. Many epoxy alcohol equilibria are very finely balanced; however, taking advantage of the trapping strategies described above may lead to high yields of single isomers.

Organic Chemistry

The sigma-2 receptor (σR) is a sigma receptor subtype that has attracted attention due to its involvement in diseases such as neurological diseases, neurodegenerative, neuro-ophthalmic and cancer. It is currently under investigation for its potential diagnostic and therapeutic uses. Although the sigma-2 receptor was identified as a separate pharmacological entity from the sigma-1 receptor in 1990, the gene that codes for the receptor was identified as TMEM97 only in 2017. TMEM97 was shown to regulate the cholesterol transporter NPC1 and to be involved in cholesterol homeostasis. The sigma-2 receptor is a four-pass transmembrane protein located in the endoplasmic reticulum. It has been found to play a role in both hormone signaling and calcium signaling, in neuronal signaling, in cell proliferation and death, and in binding of antipsychotics.

Biochemistry

One of the major issues that hinders the ncRNA therapy is the stability of the single stranded RNA molecule. RNA is typically single stranded therefore slightly unstable as compared to dsDNA molecules. This however can be overcome by fabricating the single stranded RNA to double stranded RNA(dsRNA). This is quite effective as the dsRNA is more stable at room temperature and has a longer shelf life. Second major issue is the cell/tissue/organ specific targeting of the RNA molecules. Generally, this is overcome by containing the dsRNA in a lipid nanoparticle and using that as a ligand to bind to a receptor on the surface of the target cell. The lipid particles are taken into the liver cells through their specific receptors and this mechanism seems to be effective at targeting the liver cells/cancer. Another organ with a relatively easy delivery mechanism is the eye. This requires an invasive technique of directly injecting the ncRNA of interest directly into the eye. These techniques are not only invasive but also don’t ensure if all the cells in the target organ are being targeted by the ncRNA of interest. Additional issues arise once the RNA molecule enters the cell. One of the issues being the immune system. Our immune system can recognize RNA using the intracellular pathogen associated molecular pattern (PAMP) receptors and extracellular toll-like receptors (TLR). Activation of the receptors leads to a cytokine (IFNy-Interferon gamma) mediated immune response. Common applications to overcome the immune response include second generation chemical modifications. This process includes the introduction of small one at a time chemical modifications to avoid the immune response. However, there are some reports of adverse immune responses in clinical trials employing such modified reagents. There’s no fixed answer to issues with immunogenicity and ncRNA therapy. Modified adenovirus vectors have been used extensively in many clinical trials as a ncRNA delivery mechanism. In particular, adenovirus vector is considered an efficient delivery system due to its stability within live cells and non-pathogenicity. Even though viral transfections have achieved significant results in basic research, one of the issues is the non-specificity leading to off target transfections. Further research needs to be done to improve the accuracy of viral transfections for future tests and clinical trials.

Biochemistry

PSDs can be measured microscopically by sizing against a graticule and counting, but for a statistically valid analysis, millions of particles must be measured. This is impossibly arduous when done manually, but automated analysis of electron micrographs is now commercially available. It is used to determine the particle size within the range of 0.2 to 100 micrometers.

Physical Chemistry

The terms isoelectric point (IEP) and point of zero charge (PZC) are often used interchangeably, although under certain circumstances, it may be productive to make the distinction. In systems in which H/OH are the interface potential-determining ions, the point of zero charge is given in terms of pH. The pH at which the surface exhibits a neutral net electrical charge is the point of zero charge at the surface. Electrokinetic phenomena generally measure zeta potential, and a zero zeta potential is interpreted as the point of zero net charge at the shear plane. This is termed the isoelectric point. Thus, the isoelectric point is the value of pH at which the colloidal particle remains stationary in an electrical field. The isoelectric point is expected to be somewhat different from the point of zero charge at the particle surface, but this difference is often ignored in practice for so-called pristine surfaces, i.e., surfaces with no specifically adsorbed positive or negative charges. In this context, specific adsorption is understood as adsorption occurring in a Stern layer or chemisorption. Thus, point of zero charge at the surface is taken as equal to isoelectric point in the absence of specific adsorption on that surface. According to Jolivet, in the absence of positive or negative charges, the surface is best described by the point of zero charge. If positive and negative charges are both present in equal amounts, then this is the isoelectric point. Thus, the PZC refers to the absence of any type of surface charge, while the IEP refers to a state of neutral net surface charge. The difference between the two, therefore, is the quantity of charged sites at the point of net zero charge. Jolivet uses the intrinsic surface equilibrium constants, pK and pK to define the two conditions in terms of the relative number of charged sites: For large ΔpK (>4 according to Jolivet), the predominant species is MOH while there are relatively few charged species – so the PZC is relevant. For small values of ΔpK, there are many charged species in approximately equal numbers, so one speaks of the IEP.

Physical Chemistry

Guggenheim had proposed an extension of the Debye-Hückel equation which is the basis of SIT theory. The equation can be written, in its simplest form for a 1:1 electrolyte, MX, as is the mean molal activity coefficient. The first term on the right-hand side is the Debye–Hückel term, with a constant, A, and the ionic strength I. β is an interaction coefficient and b the molality of the electrolyte. As the concentration decreases so the second term becomes less important until, at very low concentrations, the Debye-Hückel equation gives a satisfactory account of the activity coefficient. Leroy A. Bromley observed that experimental values of were often approximately proportional to ionic strength. Accordingly, he developed the equation, for a salt of general formula At 25 °C A is equal to 0.511 and ρ is equal to one. Bromley tabulated values of the interaction coefficient B. He noted that the equation gave satisfactory agreement with experimental data up to ionic strength of 6 molal, though with decreasing precision when extrapolating to very high ionic strength. As with other equations, it is not satisfactory when there is ion association as, for example, with divalent metal sulfates. Bromley also found that B could be expressed in terms of single-ion quantities as where the + subscript refers to a cation and the minus subscript refers to an anion. Bromley's equation can easily be transformed for the calculation of osmotic coefficients, and Bromley also proposed extensions to multicomponent solutions and for the effect of temperature change. A modified version of the Bromley equation has been used extensively by Madariaga and co-workers. In a comparison of Bromley, SIT and Pitzer models, little difference was found in the quality of fit. The Bromley equation is essentially an empirical equation. The B parameters are relatively easy to determine. However, SIT theory, as extended by Scatchard. and Ciavatta is much more widely used. By contrast the Pitzer equation is based on rigorous thermodynamics. The determination Pitzer parameters is more laborious. Whilst the Bromley and SIT approaches are based on pair-wise interactions between oppositely charged ions, the Pitzer approach also allows for interactions between three ions. These equations are important for the understanding of the behaviour of ions in natural waters such as rivers, lakes and sea-water. For some complex electrolytes, Ge et al. obtained the new set of Bromley parameters using up-to-date measured or critically reviewed osmotic coefficient or activity coefficient data.

Physical Chemistry

Magnetic sequencing is a single-molecule sequencing method in development. A DNA hairpin, containing the sequence of interest, is bound between a magnetic bead and a glass surface. A magnetic field is applied to stretch the hairpin open into single strands, and the hairpin refolds after decreasing of the magnetic field. The hairpin length can be determined by direct imaging of the diffraction rings of the magnetic beads using a simple microscope. The DNA sequences are determined by measuring the changes in the hairpin length following successful hybridization of complementary nucleotides.

Biochemistry

An ion beam is a type of charged particle beam consisting of ions. Ion beams have many uses in electronics manufacturing (principally ion implantation) and other industries. A variety of ion beam sources exists, some derived from the mercury vapor thrusters developed by NASA in the 1960s. The most common ion beams are of singly-charged ions.

Physical Chemistry

Signal peptides function to prompt a cell to translocate the protein, usually to the cellular membrane. In prokaryotes, signal peptides direct the newly synthesized protein to the SecYEG protein-conducting channel, which is present in the plasma membrane. A homologous system exists in eukaryotes, where the signal peptide directs the newly synthesized protein to the Sec61 channel, which shares structural and sequence homology with SecYEG, but is present in the endoplasmic reticulum. Both the SecYEG and Sec61 channels are commonly referred to as the translocon, and transit through this channel is known as translocation. While secreted proteins are threaded through the channel, transmembrane domains may diffuse across a lateral gate in the translocon to partition into the surrounding membrane.

Biochemistry

The concept for an airborne LIFT instrument was developed by Zbigniew Kolber at Rutgers University in 1998. The first field test was conducted at Biosphere 2 in Arizona in 2002 using a stationary large LIFT setup equipped with a laser operating at a distance of up to 50 meters. The prototype instrument was later refined and improved at the Carnegie Institute, Stanford, and the Agricultural Research Center in Arizona, where the first attempt to operate it on a tractor frame was made. In 2010 several instruments were transferred from Carnegie to the Forschungszentrum Jülich where they are used for laboratory and field research in robotic positioning systems for non-invasive, high-throughput data acquisition.

Photochemistry

Tarenflurbil, Flurizan or R-flurbiprofen, is a single enantiomer of the racemate NSAID flurbiprofen. For several years, research and trials for the drug were conducted by Myriad Genetics, to investigate its potential as a treatment for Alzheimer's disease; that investigation concluded in June 2008 when the company announced it would discontinue development of the compound.

Stereochemistry

Initially, this particular lactoperoxidase-catalyzed compound was originally discovered while viewing the specific environment of cystic fibrosis patients' weakened respiratory immune system against bacterial infection. Symptoms of cystic fibrosis include an inability to secrete sufficient quantities of SCN which results in a shortage of necessary hypothiocyanite, resulting in increasing mucous viscosity, inflammation and bacterial infection in the respiratory tract. Lactoferrin with hypothiocyanite has been granted orphan drug status by the EMEA and the FDA. Naturally, the discovery correlated with studies exploring different methods seeking to further gain alternative antibiotics, understanding that most older antibiotics are decreasing in effectiveness against bacteria with antibiotic resistance. OSCN, which is not an antibiotic, has proved efficacy on superbugs including MRSA reference strains, BCC, Mucoid PA Schema of LPO/SCN/HO in human lung:

Biochemistry

MimoDB is a database of peptides that have been selected from random peptide libraries based on their ability to bind small compounds, nucleic acids, proteins, cells, and tissues through phage display.

Biochemistry

Phenethylamine is produced by a wide range of species throughout the plant and animal kingdoms, including humans; it is also produced by certain fungi and bacteria (genera: Lactobacillus, Clostridium, Pseudomonas and the family Enterobacteriaceae) and acts as a potent antimicrobial against certain pathogenic strains of Escherichia coli (e.g., the O157:H7 strain) at sufficient concentrations.

Biochemistry

Prior to World War II, the center of organic chemistry research and industrial production was Germany. Students interested in pursuing a career in organic chemistry needed to learn German to read articles and textbooks, and often went to graduate school in Germany. When the war broke out, an effort to jumpstart a native US organic chemical industry and academic network was initiated. As part of this effort, the journal was launched. The first volume was published in 1942, with Roger Adams as editor-in-chief. In the early years a volume would come out every two years or so, but the pace of publishing has accelerated, with volume 100 issued in 2019.

Organic Chemistry

Despite its increased efficacy, the edit inserted by PE2 might still be removed due to DNA mismatch repair of the edited strand. To avoid this problem during DNA heteroduplex resolution, an additional single guide RNA (sgRNA) is introduced. This sgRNA is designed to match the edited sequence introduced by the pegRNA, but not the original allele. It directs the Cas9 nickase portion of the fusion protein to nick the unedited strand at a nearby site, opposite to the original nick. Nicking the non-edited strand causes the cell's natural repair system to copy the information in the edited strand to the complementary strand, permanently installing the edit. However, there are drawbacks to this system as nicking the unaltered strand can lead to additional undesired indels.

Biochemistry

A Phred quality score is a measure of the quality of the identification of the nucleobases generated by automated DNA sequencing. It was originally developed for the computer program Phred to help in the automation of DNA sequencing in the Human Genome Project. Phred quality scores are assigned to each nucleotide base call in automated sequencer traces. The FASTQ format encodes phred scores as ASCII characters alongside the read sequences. Phred quality scores have become widely accepted to characterize the quality of DNA sequences, and can be used to compare the efficacy of different sequencing methods. Perhaps the most important use of Phred quality scores is the automatic determination of accurate, quality-based consensus sequences.

Biochemistry

Many coactivators also function as corepressors under certain circumstances. Cofactors such as TAF1 and BTAF1 can initiate transcription in the presence of an activator (act as a coactivator) and repress basal transcription in the absence of an activator (act as a corepressor).

Biochemistry

Kopin Liu (; born 25 January 1949) is a Taiwanese physical chemist. Liu is a 1971 graduate of National Tsing Hua University. He moved to the United States to pursue a doctorate at Ohio State University. Liu began his research career at the Georgia Institute of Technology. After one year, he moved to Argonne National Laboratory, where he remained until 1993. Since his return to Taiwan, Liu has held several posts at Academia Sinica. He said in 2000 that working at Academia Sinica meant a large pay cut, but that he returned to teach Taiwan's future scientists while working on research. Liu received two five-year grants as a fellow of the Foundation for the Advancement of Outstanding Scholarship, an organization founded by Yuan T. Lee in 1994. In 1998, Liu was granted fellowship by the American Physical Society. Equivalent honors were bestowed by The World Academy of Sciences in 2005, and the Royal Society of Chemistry in 2013. He became a member of the Academia Sinica in 2004 and the European Academy of Sciences in 2018. Liu has served as distinguished research chair professor within the department of physics at National Taiwan University since 2010. From 2010 to 2012, Liu was honorary chair professor at National Tsing Hua University. He is a 2011 recipient of the Humboldt Research Award.

Physical Chemistry

The cleaved amplified polymorphic sequence (CAPS) method is a technique in molecular biology for the analysis of genetic markers. It is an extension to the restriction fragment length polymorphism (RFLP) method, using polymerase chain reaction (PCR) to more quickly analyse the results. Like RFLP, CAPS works on the principle that genetic differences between individuals can create or abolish restriction endonuclease restriction sites, and that these differences can be detected in the resulting DNA fragment length after digestion. In the CAPS method, PCR amplification is directed across the altered restriction site, and the products digested with the restriction enzyme. When fractionated by agarose or polyacrylamide gel electrophoresis, the digested PCR products will give readily distinguishable patterns of bands. Alternatively, the amplified segment can be analyzed by allele-specific oligonucleotide (ASO) probes, a process that can often be done by a simple dot blot.

Biochemistry

High-angle grain boundaries, which have large misorientations between adjacent grains, tend to have higher interfacial energy and are more effective in impeding dislocation motion. In contrast, low-angle grain boundaries with small misorientations and lower interfacial energy may allow for easier dislocation transmission and exhibit weaker grain boundary strengthening effects.

Metallurgy

The von Braun reaction is an organic reaction in which a tertiary amine reacts with cyanogen bromide to an organocyanamide. An example is the reaction of N,N-dimethyl-1-naphthylamine: These days, most chemist have replaced cyanogen bromide reagent with chloroethyl chloroformate reagent instead. It appears as though Olofson et al. was the first chemist to have reported this.

Organic Chemistry

The use of NHC-Pd-PEPPSI complexes in Negishi cross-coupling has resulted in high turnover numbers and turnover frequencies. Additionally, NHC-Pd complexes can be used to couple sp3 centers to sp3 centers in higher yield than their non-NHC Pd analogs. However, studies of Pd-NHC complexes and their utility in Negishi coupling are currently lacking despite these promising results.

Organic Chemistry

Several definitions describe a "molecular machine" as a class of molecules typically described as an assembly of a discrete number of molecular components intended to produce mechanical movements in response to specific stimuli. The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level. A few prime requirements for a molecule to be considered a "molecular machine" are: the presence of moving parts, the ability to consume energy, and the ability to perform a task. Molecular machines differ from other stimuli-responsive compounds that can produce motion (such as cis-trans isomers) in their relatively larger amplitude of movement (potentially due to chemical reactions) and the presence of a clear external stimulus to regulate the movements (as compared to random thermal motion). Piezoelectric, magnetostrictive, and other materials that produce a movement due to external stimuli on a macro-scale are generally not included, since despite the molecular origin of the motion the effects are not useable on the molecular scale. This definition generally applies to synthetic molecular machines, which have historically gained inspiration from the naturally occurring biological molecular machines (also referred to as "nanomachines"). Biological machines are considered to be nanoscale devices (such as molecular proteins) in a living system that convert various forms of energy to mechanical work in order to drive crucial biological processes such as intracellular transport, muscle contractions, ATP generation and cell division.

Supramolecular Chemistry

In the glycolytic pathway, 1,3-bisphosphoglycerate is dephosphorylated to form 3-phosphoglyceric acid in a coupled reaction producing two ATP via substrate-level phosphorylation. The single phosphate group left on the 3-PGA molecule then moves from an end carbon to a central carbon, producing 2-phosphoglycerate. This phosphate group relocation is catalyzed by phosphoglycerate mutase, an enzyme that also catalyzes the reverse reaction.

Photochemistry

Recently, it has been proposed that autapses could possibly form as a result of neuronal signal transmission blockage, such as in cases of axonal injury induced by poisoning or impeding ion channels. Dendrites from the soma in addition to an auxiliary axon may develop to form an autapse to help remediate the neuron's signal transmission.

Biochemistry

α,β-Unsaturated thioesters are intermediates in several enzymatic processes. Two prominent examples are coumaroyl-coenzyme A and crotonyl-coenzyme A. They arise by the action of acyl-CoA dehydrogenases. Flavin adenine dinucleotide (FAD) is a required co-factor.

Organic Chemistry

Since EosFP can be used in fusion constructs while maintaining functionality of the protein of interest, it is a popular choice for multi-colour labelling studies. In a dual-colour labelling experiment to map the stages of mitosis, HEK293 cells were first stably transfected with tubulin-binding protein cDNA fused to EGFP for visualization of the spindle apparatus. Then, transient transfection of recombination signal-binding protein (RBP) fused to d2EosFP was used to visualize the beginning of mitosis. Photoconversion was completed by fluorescent microscopy and highlighted the separation between two sets of chromosomes during anaphase, telophase and cytokinesis.

Biochemistry

Acetogenesis is a process through which acetate is produced by prokaryote microorganisms either by the reduction of CO or by the reduction of organic acids, rather than by the oxidative breakdown of carbohydrates or ethanol, as with acetic acid bacteria. The different bacterial species capable of acetogenesis are collectively termed acetogens. Reduction of CO to acetate by anaerobic bacteria occurs via the Wood–Ljungdahl pathway and requires an electron source (e.g., H, CO, formate, etc.). Some acetogens can synthesize acetate autotrophically from carbon dioxide and hydrogen gas. Reduction of organic acids to acetate by anaerobic bacteria occurs via fermentation.

Biochemistry

Thyroid hormone binding ratio (THBR) is a thyroid function test that measures the "uptake" of T3 or T4 tracer by thyroid-binding globulin (TBG) in a given serum sample. This provides an indirect and reciprocal estimate of the available binding sites on TBG within the sample. The results are then reported as a ratio to normal serum.

Biochemistry

The enhancers determining early segmentation in Drosophila melanogaster embryos are among the best characterized developmental enhancers. In the early fly embryo, the gap gene transcription factors are responsible for activating and repressing a number of segmentation genes, such as the pair rule genes. The gap genes are expressed in blocks along the anterior-posterior axis of the fly along with other maternal effect transcription factors, thus creating zones within which different combinations of transcription factors are expressed. The pair-rule genes are separated from one another by non-expressing cells. Moreover, the stripes of expression for different pair-rule genes are offset by a few cell diameters from one another. Thus, unique combinations of pair-rule gene expression create spatial domains along the anterior-posterior axis to set up each of the 14 individual segments. The 480 bp enhancer responsible for driving the sharp stripe two of the pair-rule gene even-skipped (eve) has been well-characterized. The enhancer contains 12 different binding sites for maternal and gap gene transcription factors. Activating and repressing sites overlap in sequence. Eve is only expressed in a narrow stripe of cells that contain high concentrations of the activators and low concentration of the repressors for this enhancer sequence. Other enhancer regions drive eve expression in 6 other stripes in the embryo.

Biochemistry

Schymanski graduated with a B.Sc. in Chemistry and a B.E. in Environmental Engineering from the University of Western Australia in 2003. While at the University of Western Australia, Schymanski combined chemistry and environmental engineering to study contaminated sites that required assessment and remediation. As an undergraduate, she participated in the 2002 Nobel Laureate conference which brings Nobel laureates and young scientists together; Schymanski and Pia Sappl were the first students from the University of Western Australia to receive this invitation and possibly the first Australians. After college, Schymanski spent three years at Golder Associates in Perth as an environmental engineer and then joined the Helmholtz Centre for Environmental Research in Leipzig Germany where she finished her Ph.D. in 2011. Schymanski's subsequent postdoctoral position was at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) including a Marie Curie Intra-European Postdoctoral Fellowship. Schymanski is currently an Associate Professor at the University of Luxembourg where she is the head of the Environmental Cheminformatics Group. In 2021, Schymanski was interviewed by the Metabolomics Society article in MetaboNews and during the interview she describes her introduction to the field of metabolomics, the current strengths of the field, and potential future applications of metabolomics research.

Organic Chemistry

Source: [https://scheringstiftung.de/en/programm/lebenswissenschaften/ernst-schering-preis/ Schering Foundation] *1992 , (Center for Molecular Biology, University of Heidelberg, Germany) *1993 Christiane Nüsslein-Volhard, (Max Planck Institute for Developmental Biology in Tübingen, Germany) *1994 Bert Vogelstein, (Oncology Center, Johns Hopkins University, Baltimore, Maryland, US) *1995 Yasutomi Nishizuka, (Kobe University, Japan) *1996 Judah Folkman, (Harvard Medical School, Harvard University, Boston, US) *1997 Johann Mulzer, (Institute for Organic Chemistry, University of Vienna, Austria) *1998 Ilme Schlichting, (Max Planck Institute for Molecular Physiology in Dortmund, Germany) *1999 Michael Berridge, (Babraham Institute in Cambridge, UK) *2000 , (University of Tokyo, Japan) *2001 Kyriacos Nicolaou, (University of California, San Diego, California, and The Scripps Research Institute, La Jolla, California, US) *2002 Ian Wilmut, (The Roslin Institute in Edinburgh, UK) *2003 Svante Pääbo, (Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany) *2004 , (National Institute of Neurological Disorders and Stroke (NINDS), Bethesda, Maryland, US) *2005 Thomas Tuschl, (Laboratory of RNA Molecular Biology, Rockefeller University, New York) *2006 Wolfgang Baumeister, (Max Planck Institute of Biochemistry in Martinsried, Germany) *2007 Carolyn Bertozzi, (University of California, Berkeley, US) *2008 Klaus Rajewsky, (Harvard Medical School, Boston, US) *2009 Rudolf Jaenisch, (Whitehead Institute, Cambridge, Massachusetts, US) *2010 Marc Feldmann and Sir Ravinder Maini, (Kennedy Institute of Rheumatology at Imperial College London, UK) *2011 Bert W. O'Malley, (Tom Thompson Distinguished Service Professor and Chair of Molecular and Cellular Biology at Baylor College of Medicine in Houston, Texas) *2012 Matthias Mann, (Max Planck Institute of Biochemistry in Martinsried, Germany) *2013 , (Institute of Molecular Virology at the Ulm University Medical Center in Ulm, Germany) *2014 Magdalena Götz, (Director of the Institute of Stem Cell Research at the Helmholtz Zentrum München and chair of Physiological Genomics at the University of Munich (LMU) in Munich, Germany) *2015 David MacMillan, (Professor of Chemistry at Princeton University, US). *2016 Franz-Ulrich Hartl, (Max Planck Institute of Biochemistry in Martinsried, Germany). *2017 Elly Tanaka, (Senior Scientist at Research Institute of Molecular Pathology in Vienna, Austria) *2018 Bonnie L. Bassler, (Princeton University, New Jersey) *2019 Patrick Cramer, (Director at the Max Planck Institute for Biophysical Chemistry in Göttingen) *2020 , (Director at the ( in Cologne) *2021 Aviv Regev, (Head of Genentech Research and Early Development in South San Francisco, US) *2022 (Professor of Computer-Assisted Drug Design at the Institute of Pharmaceutical Sciences at ETH Zurich and director of the Singapore-ETH Center) *2023 Matthias Tschöp (CEO and scientific director at Helmholtz Zentrum München, Germany. Alexander von Humboldt Professor at the Technical University of Munich (TUM), and Helmholtz Vice President of Health Research

Biochemistry

An experimental device working according to thermogravitational cycle principle was developed in a laboratory of the University of Bordeaux and patented in France. Such thermogravitational electric generator is based on inflation and deflation cycles of an elastic bag made of nitrile elastomer cut from a glove finger. The bag is filled with a volatile working fluid that has low chemical affinity for the elastomer such as perfluorohexane (CF). It is attached to a strong NdFeB spherical magnet that acts both as a weight and for transducing the mechanical energy into voltage. The glass cylinder is filled with water acting as transporting fluid. It is heated at the bottom by a hot circulating water-jacket, and cooled down at the top by a cold water bath. Due to its low boiling point temperature (56 °C), the perfluorohexane drop contained in the bag vaporizes and inflates the balloon. Once its density is lower than the water density, the balloon raises according to Archimedes’ principle. Cooled down at the column top, the balloon deflates partially until its gets effectively denser than water and starts to fall down. As seen from the videos, the cyclic motion has a period of several seconds. These oscillations can last for several hours and their duration is limited only by leaks of the working fluid through the rubbery membrane. Each time the magnet goes through the coil produces a variation in the magnetic flux. An electromotive force is created and detected through an oscilloscope. It has been estimated that the average power of this machine is 7 μW and its efficiency is 4.8 x 10. Although these values are very small, this experiment brings a proof of principle of renewable energy device for harvesting electricity from a weak waste heat source without need of other external energy supply, e.g. for a compressor in a regular heat engine. The experiment was successfully reproduced by undergraduate students in preparatory classes of the Lycée Hoche in Versailles. Several other applications based on the thermogravitational cycles could be found in the literature. For example: * In solar balloons, heat from the sun is absorbed which causes a balloon filled with air to rise and convert its movement in an electric signal. * In a gravity driven organic Rankine cycle, gravity is used instead of a pump to pressurize a working fluid. In literature, different authors have studied the working fluid characteristics best suited to optimize their efficiency for gravity-driven ORC devices. * In a version of a magnetic fluid generator, a refrigerant fluid is vaporized at the bottom of a column by an external heat source, and its bubbles move across a magnetized ferrofluid, thereby producing electric voltage via a linear generator. * In a conceptual hybrid of several patents, solar or geothermal energy is harnessed by means of a modified organic Rankine cycle with high columns of water below ground

Physical Chemistry

The continuum definition of surface free energy is the amount of reversible work performed to create new area of surface, expressed as: In this definition the number of atoms at the surface is proportional to the area. Gibbs was the first to define another surface quantity, different from the surface free energy , that is associated with the reversible work per unit area needed to elastically stretch a pre-existing surface. In a continuum approach one can define a surface stress tensor that relates the work associated with the variation in , the total excess free energy of the surface due to a strain tensor In general there is no change in area for shear, which means that for the second term on the right and , using the Kronecker delta. Cancelling the area then gives called the Shuttleworth equation. An alternative approach is an atomistic one, which defines all quantities in terms of the number of atoms, not continuum measures such as areas. This is related to the ideal of using Gibb's equimolar quantities rather than continuum numbers such as area, that is keeping the number of surface atoms constant. In this case the surface stress is defined as the derivative of the surface energy with strain, that is (deliberately using a different symbol) This second definition is more convenient in many cases. A conventional liquid cannot sustain strains, so in the continuum definition the surface stress and surface energies are the same, whereas in the atomistic approach the surface stress is zero for a liquid. So long as care is taken the choice of the two does not matter, although this has been a little contentious in the literature.

Physical Chemistry

The identity of the inverting atom has a dominating influence on the barrier. Inversion of ammonia is rapid at room temperature, inverting 30 billion times per second. Three factors contribute to the rapidity of the inversion: a low energy barrier (24.2 kJ/mol; 5.8 kcal/mol), a narrow barrier width (distance between geometries), and the low mass of hydrogen atoms, which combine to give a further 80-fold rate enhancement due to quantum tunnelling. In contrast, phosphine (PH) inverts very slowly at room temperature (energy barrier: 132 kJ/mol). Consequently, amines of the type RR′R"N usually are not optically stable (enantiomers racemize rapidly at room temperature), but P-chiral phosphines are. Appropriately substituted sulfonium salts, sulfoxides, arsines, etc. are also optically stable near room temperature. Steric effects can also influence the barrier.

Stereochemistry

The water molecule may either gain or lose a proton. It is said to be amphiprotic. The ionization equilibrium can be written where in aqueous solution denotes a solvated proton. Often this is written as the hydronium ion , but this formula is not exact because in fact there is solvation by more than one water molecule and species such as , , and are also present. The equilibrium constant is given by With solutions in which the solute concentrations are not very high, the concentration can be assumed to be constant, regardless of solute(s); this expression may then be replaced by The self-ionization constant of water, K, is thus just a special case of an acid dissociation constant. A logarithmic form analogous to pK may also be defined These data can be modelled by a parabola with From this equation, pK = 14 at 24.87 °C. At that temperature both hydrogen and hydroxide ions have a concentration of 10 M.

Physical Chemistry

Many structures have been characterized by single-crystal X-ray crystallography. Metallacrowns typically contain fused chelate rings in their structure, which imparts them with substantial stability. Metallacrowns have been synthesized with substantial variety. Mixed ligand and mixed ring-metal, and mixed-oxidation state metallacrowns are known. Inverse metallacrowns have been reported that contain metal ions oriented towards the center of the ring. Metallacryptates, metallahelicates, and fused metallacrowns are known. Among the interesting features of metallacrowns are the similarities between certain structures and the corresponding crown ether. For example, in the 12-C-4, the cavity size is 2.79 Å and the bite distance is 0.6 Å. In the 12-MC-4, the cavity size is 2.67 Å and the bite distance is 0.5 Å.

Supramolecular Chemistry

The Born equation can be used for estimating the electrostatic component of Gibbs free energy of solvation of an ion. It is an electrostatic model that treats the solvent as a continuous dielectric medium (it is thus one member of a class of methods known as continuum solvation methods). It was derived by Max Born. where: *N = Avogadro constant *z = charge of ion *e = elementary charge, 1.6022 C *ε = permittivity of free space *r = effective radius of ion *ε = dielectric constant of the solvent

Physical Chemistry

ScBSi has a tetragonal crystal structure with space group P422 (No. 92) or P422 and lattice constants of a, b = 1.03081(2) and c = 1.42589(3) nm; it is isotypic to the α-AlB structure type. There are 28 atomic sites in the unit cell, which are assigned to 3 scandium atoms, 24 boron atoms and one silicon atom. Atomic coordinates, site occupancies and isotropic displacement factors are listed in table VI. The boron framework of ScBSi is based on one B icosahedron and one B unit. This unit can be observed in β-tetragonal boron and is a modification of the B unit of α-AlB (or B unit in early reports). The B unit is a twinned icosahedron made from B13 to B22 sites with two vacant sites and one B atom (B23) bridging both sides of the unit. The twinned icosahedron is shown in figure 18a. B23 was treated as an isolated atom in the early reports; it is bonded to each twinned icosahedra through B18 and to another icosahedron through B5 site. If the twinned icosahedra were independent without twinning then B23 would be a bridge site linking three icosahedra. However, because of twinning, B23 shifts closer to the twinned icosahedra than another icosahedron; thus B23 is currently treated as a member of the twinned icosahedra. In ScBSi, the two B24 sites which correspond to the vacant sites in the B unit are partially occupied; thus, the unit should be referred to as a B cluster which is occupied by about 20.6 boron atoms. Scandium atoms occupy 3 of 5 Al sites of α-AlB, that is Sc1, Sc2 and Sc3 correspond to Al4, Al1 and Al2 sites of α-AlB, respectively. The Al3 and Al5 sites are empty for ScBSi, and the Si site links two B units. This phase also exists without silicon. Figure 19a shows the network of boron icosahedra in the boron framework of ScBSi. In this network, 4 icosahedra form a supertetrahedron (figure 18b); its one edge is parallel to the a-axis, and the icosahedra on this edge make up a chain along the a-axis. The opposite edge of the supertetrahedron is parallel to the b-axis and the icosahedra on this edge form a chain along the b-axis. As shown in figure 19, there are wide tunnels surrounded by the icosahedron arrangement along the a- and b-axes. The tunnels are filled by the B units which strongly bond to the surrounding icosahedra; the connection of the B units is helical and it runs along the c-axis as shown in figure 19b. Scandium atoms occupy the voids in the boron network as shown in figure 19c, and the Si atoms bridge the B units.

Analytical Chemistry

Criteria for EBSP selection can be one or a mixture of: * Selecting from points with low GND density or low Kernel average misorientation (KAM) based on the Hough measured local grain misorientations; * Selecting from points with high image quality (IQ), which may have a low defect density within its electron interaction volume, is therefore assumed to be a low-strained region of a polycrystalline material. However, IQ does not carry a clear physical meaning, and the magnitudes of the measured relative lattice distortion are insensitive to the IQ of EBSP; * EBSP can also be manually selected to be far from potential stress concentrations such as grain boundaries, inclusions, or cracks using subjective criteria; * Selecting an EBSP after examining the empirical relationship between the cross-correlation parameter and angular error, used in an iterative algorithm to identify the optimal reference pattern that maximises the precision of HR-EBSD. These criteria assume these parameters can indicate the strain conditions at the reference point, which can produce an accurate measurements of up to 3.2×10 elastic strain. However, experimental measurements point to the inaccuracy of HR-EBSD in determining the out-of-plane shear strain components distribution and magnitude.

Physical Chemistry

In a gridded ion source, DC or RF discharge are used to generate ions, which are then accelerated and decimated using grids and apertures. Here, the DC discharge current or the RF discharge power are used to control the beam current. The ion current density that can be accelerated using a gridded ion source is limited by the space charge effect, which is described by Child's law: where is the voltage between the grids, is the distance between the grids, and is the ion mass. The grids are placed as closely as possible to increase the current density, typically . The ions used have a significant impact on the maximum ion beam current, since . Everything else being equal, the maximum ion beam current with krypton is only 69% the maximum ion current of an argon beam, and with xenon the ratio drops to 55%.

Physical Chemistry

Theoretically, the ATP yield for each oxidation cycle where two carbons are broken down at a time is 17, as each NADH produces 3 ATP, FADH produces 2 ATP and a full rotation of Acetyl-CoA in citric acid cycle produces 12 ATP. In practice, it is closer to 14 ATP for a full oxidation cycle as 2.5 ATP per NADH molecule is produced, 1.5 ATP per each FADH molecule is produced and Acetyl-CoA produces 10 ATP per rotation of the citric acid cycle (according to the P/O ratio). This breakdown is as follows: For an even-numbered saturated fat (C), 0.5 * n - 1 oxidations are necessary, and the final process yields an additional acetyl CoA. In addition, two equivalents of ATP are lost during the activation of the fatty acid. Therefore, the total ATP yield can be stated as: or For instance, the ATP yield of palmitate (C, n = 16) is: Represented in table form:

Biochemistry

Heme A (or haem A) is a heme, a coordination complex consisting of a macrocyclic ligand called a porphyrin, chelating an iron atom. Heme A is a biomolecule and is produced naturally by many organisms. Heme A, often appears a dichroic green/red when in solution, is a structural relative of heme B, a component of hemoglobin, the red pigment in blood.

Biochemistry

A fire requires heat, fuel, and an oxidizing agent. The energy required to overcome the activation energy barrier for combustion is transferred as heat into the system, resulting in changes to the systems internal energy. In a process, the energy input to start a fire may comprise both work and heat, such as when one rubs tinder (work) and experiences friction (heat) to start a fire. The ensuing combustion is highly exothermic, which releases heat. The overall change in internal energy does not reveal the mode of energy transfer and quantifies only the net work and heat. The difference between initial and final states of the systems internal energy does not account for the extent of the energy interactions transpired. Therefore, internal energy is a state function (i.e. exact differential), while heat and work are path functions (i.e. inexact differentials) because integration must account for the path taken.

Physical Chemistry

The synthesis and degradation of (p)ppGpp have been most extensively characterized in the bacterial model organism Escherichia coli.

Biochemistry

A nitrocellulose slide (or nitrocellulose film slide) is a glass microscope slide that is coated with nitrocellulose that is used to bind biological material, often protein, for colorimetric and fluorescence detection assays. For this purpose, a nitrocellulose slide is generally considered to be superior to glass, because it binds a great deal more protein, and protects the tertiary structure of the protein (and other biological material, i.e.: cells). Typically, nitrocellulose slides have a thin, opaque film of nitrocellulose on a standard 25mm × 75 mm glass microscope slide. The film is extremely sensitive to contact, and to foreign material; contact causes deformation and deposition of material, especially liquids. A nitrocellulose slide is different from a nitrocellulose membrane, which usually filters protein from solution (i.e.: physician's office pregnancy tests), but that it serves a similar goal: to detect the presence and/or concentration level of certain biological material.

Biochemistry

The Earths night sky is illuminated by diffuse light, called airglow, that is produced by radiative transitions of atoms and molecules. Among the most intense such features observed in the Earths night sky is a group of infrared transitions at wavelengths between 700 nanometers and 900 nanometers. In 1950, Aden Meinel showed that these were transitions of the hydroxyl molecule, OH.

Organic Chemistry

Systematic pairwise deletion of genes or inhibition of gene expression can be used to identify genes with related function, even if they do not interact physically. Epistasis refers to the fact that effects for two different gene knockouts may not be additive; that is, the phenotype that results when two genes are inhibited may be different from the sum of the effects of single knockouts.

Biochemistry

Cell signaling involves many different processes and proteins. One of the most studied cell signaling phenomena involving proline is the interactions with p53 and prolyl isomerases, specifically Pin1. The protein p53, along with p63 and p73, are responsible for ensuring that alterations to the genome are corrected and for preventing the formation and growth of tumors. proline residues are found throughout the p53 proteins and without the phosphorylation and isomerization of specific Serine/Threonine-Proline motifs within p53, they cannot exhibit control over their target genes. The main signalling processes that are affected by p53 are apoptosis and cell cycle arrest, both of which are controlled by specific isomerization of the prolines in p53.

Stereochemistry

The hydrolysis of nitriles is conducted on an industrial scale to produce fatty amides. Laboratory procedures are also available.

Organic Chemistry

In organic chemistry, vinylogy is the transmission of electronic effects through a conjugated organic bonding system. The concept was introduced in 1926 by Ludwig Claisen to explain the acidic properties of formylacetone and related ketoaldehydes. Formylacetone, technically , only exists in the ionized form or . Its adjectival form, vinylogous, is used to describe functional groups in which the standard moieties of the group are separated by a carbon–carbon double bond. For example, a carboxylic acid is defined as a carbonyl group () directly attached to a hydroxyl group (): O=C–OH. A vinylogous carboxylic acid has a vinyl unit (, vinylene) between the two groups that define the acid: O=C–C=C–OH. The usual resonance of a carboxylate can propagate through the alkene of a vinylogous carboxylate. Likewise, 3-dimethylaminoacrolein is the vinylogous-amide analog of dimethylformamide. Due to the transmission of electronic information through conjugation, vinylogous functional groups often possess "analogous" reactivity or chemical properties compared to the parent functional group. Hence, vinylogy is a useful heuristic for the prediction of the behavior of systems that are structurally similar but contain intervening C=C bonds that are conjugated to the attached functional groups. For example, a key property of carboxylic acids is their Brønsted acidity. The simplest carboxylic acid, formic acid (), is a moderately strong organic acid with a pK of 3.7. We would expect vinylogous carboxylic acids to have similar acidity. Indeed, the vinylog of formic acid, 2-formyl-1-ethen-1-ol, has a substantial Brønsted acidity, with an estimated pK ~ 5–6. In particular, vinylogous carboxylic acids are substantially stronger acids than typical enols (pK ~ 12). Vitamin C (ascorbic acid, see below) is a biologically important example of a vinylogous carboxylic acid. The insertion of a o- or p-phenylene (i.e., a benzene ring in the 1,2- or 1,4-orientation) also results in some similarities in reactivity (called "phenylogy"), although the effect is generally weaker, as conjugation through the aryl ring requires consideration of resonance forms or intermediates in which aromaticity is disrupted. Vinylogous reactions are believed to occur when orbitals of the double bonds of the vinyl group and of an attached electron-withdrawing group (EWG; the π orbitals) are aligned and so can overlap and mix (i.e., are conjugated). Electron delocalization enables the EWG to receive electron density through participation of the conjugated system.

Physical Chemistry

The equatorial plane of a cell-like structure can be imaged using phase contrast microscopy to obtain a video showing the fluctuations of the membrane. On the video, the contours can be found using image analysis algorithms, which can then be used to determine the power spectrum of the fluctuation modes in real space amplitude. This can be used, following the steps above, to obtain relevant parameters such as the bending modulus, which is useful for a number of applications in membrane structure research.

Physical Chemistry

Snapping involves two separate parts of the thread, both containing a bulky group. one part of the thread is then threaded to the macrocycle, forming a semi rotaxane, and end is closed of by the other part of the thread forming the rotaxane.

Supramolecular Chemistry

Cyclisation of 27 took place by alkylation (LiN(TMS), dioxane, microwave irradiation) to tricycle 28. Subsequent steps were cyanohydrin hydrolysis (camphorsulfonic acid), TMS deprotection (KOH) and allylic oxidation (SeO, tBuOH, salicylic acid) to ketone 29, then Upjohn dihydroxylation to triol 30, then acylation (AcCl, DMAP) and mesitylation (MsCl, DMAP) to 31, then benzyl group and benzyloxy group removal (hydrogenation / Palladium on carbon) followed by carbonate protection (triphosgene, pyridine) to 32, then secondary alcohol protection (TESCl, pyridine) and primary alcohol deprotection (potassium carbonate) to diol 33, then oxetane formation (DIPEA, HMPA) to 34, then acylation (AcO, DMAP), then benzoylation (phenyllithium) to 35, then oxidation (tBuOK, (PhSeO)O, THF) to the acyloin 36, then isomerisation (tBuOK) and acylation (AcO, DMAP, pyr) to 37, then oxidation at the allylic position (PCC, celite, NaOAc, benzene), ketone group oxidation (NaBH) and TES protecting group removal (HF·pyr) to baccatin III (38).

Organic Chemistry

, along with many substituted derivatives like the alkoxy-methyl derivative , can be deposited as a thin film with intrinsic semiconductor properties; said properties arise due to its radical nature and its low reduction potential compared to other metal phthalocyanines. This initially green film exhibits electrochromism; the oxidized form is red, whereas the reduced form is blue and the next two reduced forms are dark blue and violet, respectively. The green/red oxidation cycle can be repeated over 10,000 times in aqueous solution with dissolved alkali metal halides, before it is degraded by hydroxide ions; the green/blue redox degrades faster in water.

Analytical Chemistry

Similar to the dissection procedure, animals are injected with a low dose of a radiolabelled compound. At the chosen time points after injection, PET or SPECT images are acquired, typically also a CT or MR image for anatomical reference. The radioactivity concentration is measured from the PET or SPECT images for the various organs of interest. This may include measuring the volume of these organs e.g. from the CT image (rather than weighing the organs as in the dissection procedure) or assessing the radioactivity concentration in a representative part of the organ. Normalizing the tissue radioactivity concentrations to the injected dose gives values in units of percent of the injected dose per milliliter of organ or biological tissue. A benefit of imaging is that the animals can be anaesthetized for imaging for several or all the required time points, that is few animals are required for this procedure and all of them are kept alive. This is considered a non-invasive procedure. In addition, the procedure is in essence the same as for medical diagnostic imaging in the clinic with two main differences: (1) novel compounds under development may be injected into animals subject to scrutiny and approval of the detailed experimental plan while clinicians can only inject radiolabelled compounds that had been tested rigorously and approved for use in humans; (2) animals usually need to be anaesthetized for the duration of the scan (on the order of minutes) while humans are awake and simply need to stay still during the scan.

Biochemistry

Photocatalysts must conform to several key principles in order to be considered effective at water splitting. A key principle is that and evolution should occur in a stoichiometric 2:1 ratio; significant deviation could be due to a flaw in the experimental setup and/or a side reaction, neither of which indicate a reliable photocatalyst for water splitting. The prime measure of photocatalyst effectiveness is quantum yield (QY), which is: : QY (%) = (Photochemical reaction rate) / (Photon absorption rate) × 100% To assist in comparison, the rate of gas evolution can also be used. A photocatalyst that has a high quantum yield and gives a high rate of gas evolution is a better catalyst. The other important factor for a photocatalyst is the range of light that is effective for operation. For example, a photocatalyst is more desirable to use visible photons than UV photons.

Photochemistry

Types of deficiency The so-called optical component surface defects mainly refer to surface rickets and surface contaminants. Surface rickets refer to various processing defects such as pitting, scratches, open bubbles, broken edges, and broken spots on the surface of polished optical components. The main reason is processing or subsequent processing. Scratches are the scratches on the surface of an optical component. Due to the length of the scratch, it can be divided into long scratches and short scratches, with a limit of 2 mm. If the scratch length is greater than 2 mm, it is a long scratch, and if it is less than 2 mm, it is a short scratch . For short scratches, the evaluation criterion is to detect their cumulative length. Relatively speaking, scratches are easier to detect than defects such as pitting. Pitting refers to pits and defects on the surface of an optical component. The surface roughness in the pit is large, the width and depth are approximately the same, and the edges are irregular. Typically, defects with an aspect ratio greater than 4:1 are scratches, while defects less than 4:1 are pitting. The bubbles are formed by gases that are not removed in time during the manufacture or processing of the optical component. Since the pressure of the gas in each direction is evenly distributed, the shape of the bubble is usually spherical. Broken edges are a criticism of the edge of optical components. Although it is outside the effective area of the light source, it is also a source of light scattering, which also has an effect on optical performance. Negative impact caused by the deficiency Surface rickets, as a microscopic local defect caused by man-made process, have a certain influence on the surface properties of optical components, which may lead to serious consequences such as optical instrument operation errors. In short, the surface defects of optical components can be detrimental to the performance of optical systems, and the root cause is the scattering characteristics of light. The damage of optical component surface defects to itself and the entire optical system is manifested in the following aspects: (1) The quality of the beam is degraded. The surface scattering defect of the component produces a scattering effect of light, so that the energy of the beam is greatly consumed after passing through the defect, thereby reducing the quality of the beam. (2) The thermal effect of defects. Since the area where the surface defects are located absorbs more energy than other areas, the thermal effect phenomenon may cause local particial deformation of the component, damage the film layer, etc., and thus damage the entire optical system. (3) Damage to other optical components in the system. In a laser system, under the illumination of a high-energy laser beam, the scattered light generated by the surface of the component is absorbed by other optical components in the system, resulting in uneven light received by the component. When the damage threshold of the optical component material is reached. The quality of the transmitted light is affected, and the optical components are damaged, which is more likely to cause serious damage to the optical system. (4) Rickets can affect the cleanliness of the field of view. When there are too many rickets on the optical components, it will affect the microscopic aesthetics. In addition, the cockroaches will leave tiny dust, microorganisms, polishing powder and other impurities, which will cause the components to be corroded, moldy, and foggy. Will significantly affect the basic performance of the component.

Physical Chemistry

Monoamine precursors are precursors of monoamines and monoamine neurotransmitters in the body. The amino acids -tryptophan and -5-hydroxytryptophan (5-HTP; oxitriptan) are precursors of serotonin and melatonin, while the amino acids -phenylalanine, -tyrosine, and -DOPA (levodopa) are precursors of dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline). Administration of monoamine precursors can increase the levels of monoamine neurotransmitters in the body and brain. Monoamine precursors may be used in combination with peripherally selective aromatic -amino acid decarboxylase inhibitors (AAAD inhibitors; also known as DOPA decarboxylase (DDC) inhibitors) such as carbidopa and benserazide. Carbidopa/levodopa is used to increase brain dopamine levels in the treatment of Parkinson's disease while carbidopa/oxitriptan (EVX-101) is under development as an antidepressant for possible use in the treatment of depression.

Biochemistry

DNA Fragmentation plays an important part in forensics, especially that of DNA profiling. * Restriction Fragment Length Polymorphism (RFLP) is a technique for analyzing the variable lengths of DNA fragments that result from digesting a DNA sample with a restriction endonuclease. The restriction endonuclease cuts DNA at a specific sequence pattern known as a restriction endonuclease recognition site. The presence or absence of certain recognition sites in a DNA sample generates variable lengths of DNA fragments, which are separated using gel electrophoresis. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. * In polymerase chain reaction (PCR) analysis, millions of exact copies of DNA from a biological sample are made. It used to amplify a specific region of a DNA strand (the DNA target). Most PCR methods typically amplify DNA fragments of between 0.1 and 10 kilo base pairs (kb), although some techniques allow amplification of fragments up to 40 kb in size. PCR also uses heat to separate the DNA strands. * DNA fragmented during apoptosis, of a size from 1 to 20 nucleosomes, can be selectively isolated from the cells fixed in the denaturing fixative ethanol

Biochemistry

Using simple algebraic manipulation, it can be stated that increases or decreases monotonically within all range, if or with , respectively. When and , the activity coefficient curve of component 1 shows a maximum and compound 2 minimum at: Same expression can be used when and , but in this situation the activity coefficient curve of component 1 shows a minimum and compound 2 a maximum. It is easily seen that when A=0 and A>0 that a maximum in the activity coefficient of compound 1 exists at x=1/3. Obvious, the activity coefficient of compound 2 goes at this concentration through a minimum as a result of the Gibbs-Duhem rule. The binary system Chloroform(1)-Methanol(2) is an example of a system that shows a maximum in the activity coefficient of Chloroform. The parameters for a description at 20 °C are A=0.6298 and A=1.9522. This gives a minimum in the activity of Chloroform at x=0.17. In general, for the case A=A=A, the larger parameter A, the more the binary systems deviates from Raoult's law; i.e. ideal solubility. When A>2 the system starts to demix in two liquids at 50/50 composition; i.e. plait point is at 50 mol%. Since: For asymmetric binary systems, A≠A, the liquid-liquid separation always occurs for Or equivalently: The plait point is not located at 50 mol%. It depends on the ratio of the limiting activity coefficients.

Physical Chemistry

Antiaromatic compounds, often being very unstable, can be highly reactive in order to relieve the antiaromatic destabilization. Cyclobutadiene, for example, rapidly dimerizes with no potential energy barrier via a 2 + 2 cycloaddition reaction to form tricyclooctadiene. While the antiaromatic character of cyclobutadiene is the subject of debate, the relief of antiaromaticity is usually invoked as the driving force of this reaction. Antiaromaticity can also have a significant effect on pK. The linear compound propene has a pK of 44, which is relatively acidic for an sp carbon center because the resultant allyl anion can be resonance stabilized. The analogous cyclic system appears to have even more resonance stabilized, as the negative charge can be delocalized across three carbons instead of two. However, the cyclopropenyl anion has 4 π electrons in a cyclic system and in fact has a substantially higher pK than 1-propene because it is antiaromatic and thus destabilized. Because antiaromatic compounds are often short-lived and difficult to work with experimentally, antiaromatic destabilization energy is often modeled by simulation rather than by experimentation. Some antiaromatic compounds are stable, especially larger cyclic systems (in which the antiaromatic destabilization is not as substantial). For example, the aromatic species 1 can be reduced to 2 with a relatively small penalty for forming an antiaromatic system. The antiaromatic 2 does revert to the aromatic species 1 over time by reacting with oxygen in the air because the aromaticity is preferred. The loss of antiaromaticity can sometimes be the driving force of a reaction. In the following keto-enol tautomerization, the product enol is more stable than the original ketone even though the ketone contains an aromatic benzene moiety (blue). However, there is also an antiaromatic lactone moiety (green). The relief of antiaromatic destabilization provides a driving force that outweighs even the loss of an aromatic benzene.

Physical Chemistry

Birch won a scholarship to attend the University of Sydney graduating with a BSc in 1937 and a MSc in 1938. He travelled to the University of Oxford to undertake his D.Phil., graduating in 1940.

Organic Chemistry

Reuterin (3-hydroxypropionaldehyde) is the organic compound with the formula HOCHCHCHO. It is a bifunctional molecule, containing both a hydroxy and aldehyde functional groups. The name reuterin is derived from Lactobacillus reuteri, which produces the compound biosynthetically from glycerol as a broad-spectrum antibiotic (bacteriocin). L. reuteri itself is named after the microbiologist Gerhard Reuter, who did early work in distinguishing it as a distinct species.

Biochemistry

The detection of eRNAs is fairly recent (2010) and has been made possible through the use of genome-wide investigation techniques such as RNA sequencing (RNA-seq) and chromatin immunoprecipitation-sequencing (ChIP-seq). RNA-seq permits the direct identification of eRNAs by matching the detected transcript to the corresponding enhancer sequence through bioinformatic analyses. ChIP-seq represents a less direct way to assess enhancer transcription but can also provide crucial information as specific chromatin marks are associated with active enhancers. Although some data remain controversial, the consensus in the literature is that the best combination of histone post-translational modifications at active enhancers is made of H2AZ, H3K27ac, and a high ratio of H3K4me1 over H3K4me3. ChIP experiments can also be conducted with antibodies that recognize RNA Pol II, which can be found at sites of active transcription. The experimental detection of eRNAs is complicated by their low endogenous stability conferred by exosome degradation and nonsense-mediated decay. A comparative study showed that assays enriching for capped and nascent RNAs (with strategies like nuclei run-on and size selection) could capture more eRNAs compared to canonical RNA-seq. These assays include Global/Precision Run-on with cap-selection (GRO/PRO-cap), capped-small RNA-seq (csRNA-seq), Native Elongating Transcript-Cap Analysis of Gene Expression (NET-CAGE), and Precision Run-On sequencing (PRO-seq). Nonetheless, the fact that eRNAs tend to be expressed from active enhancers might make their detection a useful tool to distinguish between active and inactive enhancers.

Biochemistry

The ideal gas law can also be derived from first principles using the kinetic theory of gases, in which several simplifying assumptions are made, chief among which are that the molecules, or atoms, of the gas are point masses, possessing mass but no significant volume, and undergo only elastic collisions with each other and the sides of the container in which both linear momentum and kinetic energy are conserved. First we show that the fundamental assumptions of the kinetic theory of gases imply that Consider a container in the Cartesian coordinate system. For simplicity, we assume that a third of the molecules moves parallel to the -axis, a third moves parallel to the -axis and a third moves parallel to the -axis. Next we temporarily assume that all molecules with the same velocity . We choose an area on a wall of the container, perpendicular to the -axis. When time elapses, all molecules in the volume moving in the positive direction of the -axis will hit the area. There are molecules in a part of volume of the container, but only one sixth (i.e. a half of a third) of them moves in the positive direction of the -axis. Therefore, the number of molecules that will hit the area when the time elapses is . When a molecule bounces off the wall of the container, it changes its momentum to . Hence the magnitude of change of the momentum of one molecule is . The magnitude of the change of momentum of all molecules that bounce off the area when time elapses is then . From and we get We supposed that all molecules move with the same velocity , but in fact they move with different velocities, so we replace in the equation by the arithmetic mean of all squares of all velocities of the molecules, i.e. by Therefore which gives the desired formula. Using the Maxwell–Boltzmann distribution, the fraction of molecules that have a speed in the range to is , where and denotes the Boltzmann constant. The root-mean-square speed can be calculated by Using the integration formula it follows that from which we get the ideal gas law:

Physical Chemistry

Odum et al. viewed the maximum power theorem as a principle of power-efficiency reciprocity selection with wider application than just electronics. For example, Odum saw it in open systems operating on solar energy, like both photovoltaics and photosynthesis (1963, p. 438). Like the maximum power theorem, Odums statement of the maximum power principle relies on the notion of matching, such that high-quality energy maximizes power by matching and amplifying energy (1994, pp. 262, 541): "in surviving designs a matching of high-quality energy with larger amounts of low-quality energy is likely to occur" (1994, p. 260). As with electronic circuits, the resultant rate of energy transformation will be at a maximum at an intermediate power efficiency. In 2006, T.T. Cai, C.L. Montague and J.S. Davis said that, "The maximum power principle is a potential guide to understanding the patterns and processes of ecosystem development and sustainability. The principle predicts the selective persistence of ecosystem designs that capture a previously untapped energy source." (2006, p. 317). In several texts H.T. Odum gave the Atwood machine as a practical example of the principle' of maximum power.

Physical Chemistry

Second group of TI antigens consists mainly of highly repetitive surface structures (epitopes) of encapsulated bacteria. They do not have an intrinsic B-cell activating activity. The activation of B lymphocytes is caused by cross-linking of a critical number of B cell receptors, which leads to accumulation of BCRs and cross activation of these receptors. It results in proliferation and differentiation of B lymphocytes and production of antibodies. TI-2 antigens can activate only mature B lymphocytes. Immature B cells are anergized, so they do not elicit any immune response. That may explain why children up to 5 years are not capable of producing effective antibodies against polysaccharide antigens, as the majority of their B cell population is immature. Even though the response on TI antigens is not dependent on T lymphocytes, there are some cytokines, produced mainly by T lymphocytes and natural killer (NK) cells, necessary for eliciting reaction against these antigens. The most necessary are interleukin 2 (IL-2), interleukin 3 (IL-3) and interferon γ (IFN-γ). Moreover, additional stimulation by dendritic cells (DC) and macrophages is required.

Biochemistry

Typical nitrones sources are hydroxylamine oxidation or condensation with carbonyl compounds. Secondary hydroxylamines oxidize to nitrones in air over a timescale of several weeks, a process cupric salts accelerate. The most general reagent used for the oxidation of hydroxylamines is aqueous mercury(II) oxide: However, a hydroxylamine with two α hydrogens may unsaturate on either side. Carbonyl condensation avoids this ambiguity... ...but is inhibited if both ketone substituents are bulky. In principle, N-alkylation could produce nitrones from oximes, but in practice electrophiles typically perform a mixture of N- and O-attack.

Organic Chemistry

The Museum Weavers are housed in a barn, featuring more than 50 working looms for weaving. Members of this club meet weekly to learn and practice weaving, rug-making and rope-making.

Metallurgy

The very nature of hyrax middens implies that they comprise a mixture of materials, which include animal metabolic products, undigested food, and any allochtonous material blown into the middens or deposited via feet or fur. In terms of organic matter, the existence of such potentially distinct sources (i.e. extraneous organic matter and animal metabolites) implies that a range of information concerning inter alia: animal diet, animal behaviour, metabolic responses to environmental stress, changing behaviour, as well the wider palaeoecological setting of the site may all be preserved within hyraceum.

Geochemistry

Due to the polar nature of the water molecule itself, other polar molecules are generally able to dissolve in water. Most nonpolar molecules are water-insoluble (hydrophobic) at room temperature. Many nonpolar organic solvents, such as turpentine, are able to dissolve nonpolar substances.

Physical Chemistry