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Several qualitative tests are used to detect the presence of reducing sugars. Two of them use solutions of copper(II) ions: Benedicts reagent (Cu in aqueous sodium citrate) and Fehlings solution (Cu in aqueous sodium tartrate). The reducing sugar reduces the copper(II) ions in these test solutions to copper(I), which then forms a brick red copper(I) oxide precipitate. Reducing sugars can also be detected with the addition of Tollens reagent, which consist of silver ions (Ag) in aqueous ammonia. When Tollens reagent is added to an aldehyde, it precipitates silver metal, often forming a silver mirror on clean glassware.
3,5-dinitrosalicylic acid is another test reagent, one that allows quantitative detection. It reacts with a reducing sugar to form 3-amino-5-nitrosalicylic acid, which can be measured by spectrophotometry to determine the amount of reducing sugar that was present.
Some sugars, such as sucrose, do not react with any of the reducing-sugar test solutions. However, a non-reducing sugar can be hydrolyzed using dilute hydrochloric acid. After hydrolysis and neutralization of the acid, the product may be a reducing sugar that gives normal reactions with the test solutions.
All carbohydrates are converted to aldehydes and respond positively in Molisch's test. But the test has a faster rate when it comes to monosaccharides. | 0 | Theoretical and Fundamental Chemistry |
The School is also home to a number of Emeritus Professors, pursuing their research interests after their formal retirement including:
* John Joule, Emeritus Professor
* William Byers Brown, Emeritus Professor and first Professor of Computational Chemistry in the department | 1 | Applied and Interdisciplinary Chemistry |
The model and its variants have a number of simplifying assumptions. Three of them are listing below.
#The organisms are modeled as gene regulatory networks. The models assume that gene expression is regulated exclusively at the transcriptional level;
#The product of a gene can regulate the expression of (be a regulator of) that source gene or other genes. The models assume that a gene can only produce one active transcriptional regulator;
#The effects of one regulator are independent of effects of other regulators on the same target gene. | 1 | Applied and Interdisciplinary Chemistry |
Hyper Rayleigh scattering optical activity (HRS OA) is arguably the most fundamental nonlinear chiral optical (chiroptical) effect; since other nonlinear chiroptical effects have additional requirements, which make them conceptually more involved, i.e. less fundamental. HRS OA is a scattering effect and therefore it does not require the frequency conversion process to be coherent, contrary to other nonlinear chiroptical effects, such as second harmonic generation circular dichroism or second harmonic generation optical rotation. Moreover, HRS OA is a parametric process: the initial and final quantum mechanical states of the excited electron are the same. Because the excitation proceeds via virtual states, there is no restriction on the frequency of incident light. By contrast, other nonlinear scattering effects, such as two-photon circular dichroism and hyper-Raman are non-parametric: they require real energy states that restrict the frequencies at which these effects can be observed. | 0 | Theoretical and Fundamental Chemistry |
Radiometric assays measure the incorporation of radioactivity into substrates or its release from substrates. The radioactive isotopes most frequently used in these assays are C, P, S and I. Since radioactive isotopes can allow the specific labelling of a single atom of a substrate, these assays are both extremely sensitive and specific. They are frequently used in biochemistry and are often the only way of measuring a specific reaction in crude extracts (the complex mixtures of enzymes produced when you lyse cells).
Radioactivity is usually measured in these procedures using a scintillation counter. | 1 | Applied and Interdisciplinary Chemistry |
A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then goes through a second polarizer where it is collected by a photomultiplier and the resulting image is projected onto a screen. This is known as a speckle pattern (Figure 1).
All of the molecules in the solution are being hit with the light and all of the molecules diffract the light in all directions. The diffracted light from all of the molecules can either interfere constructively (light regions) or destructively (dark regions). This process is repeated at short time intervals and the resulting set of speckle patterns is analyzed by an autocorrelator that compares the intensity of light at each spot over time.
The polarizers can be set up in two geometrical configurations. One is a vertical/vertical (VV) geometry, where the second polarizer allows light through that is in the same direction as the primary polarizer. In vertical/horizontal (VH) geometry the second polarizer allows light that is not in the same direction as the incident light. | 0 | Theoretical and Fundamental Chemistry |
Hemiaminal ethers have the following structure: R‴-C(NR')(OR")-R⁗. The glycosylamines are examples of cyclic hemiaminal ethers. | 0 | Theoretical and Fundamental Chemistry |
The pyroelectric coefficient may be described as the change in the spontaneous polarization vector with temperature:
where p (CmK) is the vector for the pyroelectric coefficient. | 0 | Theoretical and Fundamental Chemistry |
The concept of gene therapy is to fix a genetic problem at its source. If, for instance, a mutation in a certain gene causes the production of a dysfunctional protein resulting (usually recessively) in an inherited disease, gene therapy could be used to deliver a copy of this gene that does not contain the deleterious mutation and thereby produces a functional protein. This strategy is referred to as gene replacement therapy and could be employed to treat inherited retinal diseases.
While the concept of gene replacement therapy is mostly suitable for recessive diseases, novel strategies have been suggested that are capable of also treating conditions with a dominant pattern of inheritance.
* The introduction of CRISPR gene editing has opened new doors for its application and utilization in gene therapy, as instead of pure replacement of a gene, it enables correction of the particular genetic defect. Solutions to medical hurdles, such as the eradication of latent human immunodeficiency virus (HIV) reservoirs and correction of the mutation that causes sickle cell disease, may be available as a therapeutic option in the future.
* Prosthetic gene therapy aims to enable cells of the body to take over functions they physiologically do not carry out. One example is the so-called vision restoration gene therapy, that aims to restore vision in patients with end-stage retinal diseases. In end-stage retinal diseases, the photoreceptors, as the primary light sensitive cells of the retina are irreversibly lost. By the means of prosthetic gene therapy light sensitive proteins are delivered into the remaining cells of the retina, to render them light sensitive and thereby enable them to signal visual information towards the brain.
In vivo, gene editing systems using CRISPR have been used in studies with mice to treat cancer and have been effective at reducing tumors. In vitro, the CRISPR system has been used to treat HPV cancer tumors. Adeno-associated virus, Lentivirus based vectors have been to introduce the genome for the CRISPR system. | 1 | Applied and Interdisciplinary Chemistry |
Nucleogenesis (also known as nucleosynthesis) as a general phenomenon is a process usually associated with production of nuclides in the Big Bang or in stars, by nuclear reactions there. Some of these neutron reactions (such as the r-process and s-process) involve absorption by atomic nuclei of high-temperature (high energy) neutrons from the star. These processes produce most of the chemical elements in the universe heavier than zirconium (element 40), because nuclear fusion processes become increasingly inefficient and unlikely for elements heavier than this. By convention, such heavier elements produced in normal elemental abundance, are not referred to as "nucleogenic". Instead, this term is reserved for nuclides (isotopes) made on Earth from natural nuclear reactions.
Also, the term "nucleogenic" by convention excludes artificially produced radionuclides, for example tritium, many of which are produced in large amounts by a similar artificial processes, but using the copious neutron flux produced by conventional nuclear reactors. | 0 | Theoretical and Fundamental Chemistry |
The main benefit of electrodialysis is the high recovery, especially in the water recovery. Another advantage is the fact that not high pressure is applied which implies that the effect fouling is not significant and consequently no chemicals are required to fight against them. Moreover, the fouling layer is not compact which leads to a higher recovery and to a long membrane life. It is also important that the treatments are for concentrations higher than 70,000 ppm eliminating the concentration limit. Finally, the energy required to operate is low due to the non-phase change. In fact, it is lower in comparison with the needed in the multi effect distillation (MED) and mechanical vapour compression (MVC) processes.
The main drawback of electrodialysis is the current density limit, the process must be operated at a lower current density than the maximum allowed. The fact is that at certain voltage applied the diffusion of ions through the membrane are not linear leading to water dissociation, which would reduce the efficiency of the operation. Another aspect to take into account is that although low energy is required to operate, the higher the salt feed concentration is, the higher the energy needed will be. Finally, in the case of some products, it must be considered that electrodialysis does not remove microorganisms and organic contaminants, therefore a post-treatment is necessary. | 1 | Applied and Interdisciplinary Chemistry |
A more recent technique has been developed called high-frequency irreversible electroporation (H-FIRE). This technique uses electrodes to apply bipolar bursts of electricity at a high frequency, as opposed to unipolar bursts of electricity at a low frequency. This type of procedure has the same tumor ablation success as N-TIRE. However, it has one distinct advantage, H-FIRE does not cause muscle contraction in the patient and therefore there is no need for a paralytic agent. Furthermore, H-FIRE has been demonstrated to produce more predictable ablations due to the lesser difference in the electrical properties of tissues at higher frequencies. | 1 | Applied and Interdisciplinary Chemistry |
Sulfur has four stable isotopes, S, S, S, and S, of which S is the most abundant by a large margin due to the fact it is created by the very common C in supernovas. Sulfur isotope ratios are almost always expressed as ratios relative to S due to this major relative abundance (95.0%). Sulfur isotope fractionations are usually measured in terms of δS due to its higher abundance (4.25%) compared to the other stable isotopes of sulfur, though δS is also sometimes measured. Differences in sulfur isotope ratios are thought to exist primarily due to kinetic fractionation during reactions and transformations.
Sulfur isotopes are generally measured against standards; prior to 1993, the Canyon Diablo troilite standard (abbreviated to CDT), which has a S:S equal to 22.220, was used as both a reference material and the zero point for the isotopic scale. Since 1993, the Vienna-CDT standard has been used as a zero point, and there are several materials used as reference materials for sulfur isotope measurements. Sulfur fractionations by natural processes measured against these standards have been shown to exist between -72‰ and +147‰, as calculated by the following equation:
As a very redox-active element, sulfur can be useful for recording major chemistry-altering events throughout Earths history, such as marine evaporites which reflect the change in the atmospheres redox state brought about by the Oxygen Crisis. | 0 | Theoretical and Fundamental Chemistry |
In general, complex metal hydrides have the formula MMH, where M is an alkali metal cation or cation complex and M is a metal or metalloid. Well known examples feature group 13 elements, especially boron and aluminium including sodium aluminium hydride, NaAlH ), lithium aluminium hydride, LiAlH, and lithium borohydride, (LiBH). Complex metal hydrides are often soluble in etherial solvents. Other complex metal hydrides are numerous. Illustrative examples include the salts [MgBr(THF)]FeH and KReH. | 0 | Theoretical and Fundamental Chemistry |
When World War II ended with the use of atomic weapons which had been developed in secret by the Manhattan Project, Hecht was concerned that the American public was uninformed about the development of this new source of energy. He wrote a book Explaining the Atom (1947), to educate the public. He wrote,
:So long as one supposes this business is mysterious and secret, one cannot have a just evaluation of our possessions and security. Only by understanding the basis and development of atomic energy can one judge the legislation and foreign policy that concern it.
In a review in the New York Times (4/27/1947), Stephen Wheeler wrote that it was "by all odds the best book on atomic energy so far to be published for the ordinary reader." Similarly, James J. Jelinek wrote that it was an "invaluable contribution to the layman." He credits Hecht with "conveying to the layman the intellectual drama" of the development. Jelinek asserts that the book is "profoundly provocative in its political and sociological implications."
After Hecht died, a second edition was issued in 1959 by Eugene Rabinowitch. Both editions were recommended by George Gamow. | 0 | Theoretical and Fundamental Chemistry |
In bacteria, termination of RNA transcription can be rho-dependent or rho-independent. The former relies on the rho factor, which destabilizes the DNA-RNA heteroduplex and causes RNA release. The latter, also known as intrinsic termination, relies on a palindromic region of DNA. Transcribing the region causes the formation of a "hairpin" structure from the RNA transcription looping and binding upon itself. This hairpin structure is often rich in G-C base-pairs, making it more stable than the DNA-RNA hybrid itself. As a result, the 8 bp DNA-RNA hybrid in the transcription complex shifts to a 4 bp hybrid. These last 4 base pairs are weak A-U base pairs, and the entire RNA transcript will fall off the DNA.
Transcription termination in eukaryotes is less well understood than in bacteria, but involves cleavage of the new transcript followed by template-independent addition of adenines at its new 3′ end, in a process called polyadenylation. | 1 | Applied and Interdisciplinary Chemistry |
Beyond its immediate industrial applications, ledeburite holds a central position in metallurgical studies. The exploration of this unique microconstituent contributes to a deeper understanding of phase transformations, solidification processes, and the principles governing alloy behavior. Researchers and metallurgists leverage ledeburite as a model system to investigate the fundamental aspects of phase diagrams, eutectic reactions, and the kinetics of microstructural evolution during cooling and solidification.
Metallurgical studies involving ledeburite extend to the development of advanced materials with tailored properties. By comprehending the nuances of ledeburite formation and its impact on steel performance, scientists can design alloys with improved strength, hardness, and corrosion resistance. This knowledge is invaluable in pushing the boundaries of material science and engineering, paving the way for innovations in diverse fields. | 1 | Applied and Interdisciplinary Chemistry |
Grit consists of sand, gravel, rocks, and other heavy materials. Preliminary treatment may include a sand or grit removal channel or chamber, where the velocity of the incoming sewage is reduced to allow the settlement of grit. Grit removal is necessary to (1) reduce formation of deposits in primary sedimentation tanks, aeration tanks, anaerobic digesters, pipes, channels, etc. (2) reduce the frequency of tank cleaning caused by excessive accumulation of grit; and (3) protect moving mechanical equipment from abrasion and accompanying abnormal wear. The removal of grit is essential for equipment with closely machined metal surfaces such as comminutors, fine screens, centrifuges, heat exchangers, and high pressure diaphragm pumps.
Grit chambers come in three types: horizontal grit chambers, aerated grit chambers, and vortex grit chambers. Vortex grit chambers include mechanically induced vortex, hydraulically induced vortex, and multi-tray vortex separators. Given that traditionally, grit removal systems have been designed to remove clean inorganic particles that are greater than , most of the finer grit passes through the grit removal flows under normal conditions. During periods of high flow deposited grit is resuspended and the quantity of grit reaching the treatment plant increases substantially. | 1 | Applied and Interdisciplinary Chemistry |
Forskolin is commonly used as a tool in biochemistry to raise levels of cAMP in the study and research of cell physiology. | 1 | Applied and Interdisciplinary Chemistry |
A carbometallation is any reaction where a carbon-metal bond reacts with a carbon-carbon π-bond to produce a new carbon-carbon σ-bond and a carbon-metal σ-bond. The resulting carbon-metal bond can undergo further carbometallation reactions (oligomerization or polymerization see Ziegler-Natta polymerization) or it can be reacted with a variety of electrophiles including halogenating reagents, carbonyls, oxygen, and inorganic salts to produce different organometallic reagents. Carbometallations can be performed on alkynes and alkenes to form products with high geometric purity or enantioselectivity, respectively. Some metals prefer to give the anti-addition product with high selectivity and some yield the syn-addition product. The outcome of syn and anti- addition products is determined by the mechanism of the carbometallation. | 0 | Theoretical and Fundamental Chemistry |
Several pathways exist for the halogenation of organic compounds, including free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. The nature of the substrate determines the pathway. The facility of halogenation is influenced by the halogen. Fluorine and chlorine are more electrophilic and are more aggressive halogenating agents. Bromine is a weaker halogenating agent than both fluorine and chlorine, while iodine is the least reactive of them all. The facility of dehydrohalogenation follows the reverse trend: iodine is most easily removed from organic compounds, and organofluorine compounds are highly stable. | 0 | Theoretical and Fundamental Chemistry |
As widely accepted as this statement might be, it should not be considered synonymous with a lack of metal objects, as it points out native copper was relatively abundant, particularly in the Great Lakes region. The latest glacial period had resulted in the scouring of copper bearing rocks. Once the ice retreated, these were readily available for use in a variety of sizes. Copper was shaped via cold hammering into objects from very early dates (Archaic period in the Great Lakes region: 8000–1000 BCE). There is also evidence of actual mining of copper veins (Old Copper Complex), but disagreement exists as to the dates.
Extraction would have been extremely difficult. Hammerstones may have been used to break off pieces small enough to be worked. This labor-intensive process might have been eased by building a fire on top of the deposit, then quickly dousing the hot rock with water, creating small cracks. This process could be repeated to create more small cracks.
The copper could then be cold-hammered into shape, which would make it brittle, or hammered and heated in an annealing process to avoid this. The final object would then have to be ground and sharpened using local sandstone. Numerous bars have also been found, possibly indicative of trade for which their shaping into a bar would also serve as proof of quality.
Great Lake artifacts found in the Eastern Woodlands of North America seem to indicate there were widespread trading networks by 1000 BCE. Progressively the usage of copper for tools decreases with more jewelry and adornments being found. This is believed to be indicative of social changes to a more hierarchical society. Thousands of copper mining pits have been found along the lake shore of Lake Superior, and on Isle Royale. These pits may have been in use as far back as 8,000 years ago. This copper was mined and then made into objects such as heavy spear points and tools of all kinds. It was also made into mysterious crescent objects that some archaeologists believe were religious or ceremonial items. The crescents were too fragile for utilitarian use, and many have 28 or 29 notches along the inner edge, the approximate number of days in a lunar month.The Old Copper Culture mainly flourished in Ontario and Minnesota. However at least 50 Old Copper items, including spear points and ceremonial crescents have been discovered in Manitoba. A few more in Saskatchewan, and at least one, a crescent, has turned up in Alberta, 2,000 kilometres from its homeland in Ontario. It is most likely that these copper items arrived in the plains as trade goods rather than people of the Old Copper Culture moving into these new places. However from one excavated site in eastern Manitoba we can see that at least some people were moving northwest. At a site near Bissett archaeologists have found copper tools, weapons, and waste material of manufacture, along with a large nugget of raw copper. This site however was dated to around 4,000 years ago, a time of cooler climate when the boreal forest's treeline moved much further south. Though if these migrants moved with their metallurgy up the Winnipeg River at this time they may have continued onward, into Lake Winnipeg, and the Saskatchewan River system.
This Old Copper Culture never became particularity advanced, and never discovered the principle of creating alloys. This means that many, though they could make metal objects and weapons, continued to use their flint tools, which could maintain a sharper edge for much longer. The unalloyed copper could simply not compete, and in the later days of the Old Copper Culture the metal was almost exclusively used for ceremonial items.
However this Great Lake model as a unique source of copper and of copper technologies remaining somewhat static for over 6,000 years has recently come into some level of criticism, particularly since other deposits seem to have been available to ancient North Americans, even if much smaller. | 1 | Applied and Interdisciplinary Chemistry |
Recent studies have shown that decreased TFIIB levels do not affect transcription levels within cells, this is thought to be partially because over 90% of mammalian promoters do not contain a BRE or TATA box. However, it has been shown that TFIIB is vital to the in vitro transcription and regulation of the herpes simplex virus. This is thought to be due to similarity TFIIB has to cyclin A. In order to undergo replication, viruses often stop host cells progression through the cell cycle, using cyclins and other proteins. As TFIIB has a similar structure to cyclin A it has been suggested that depleted levels of TFIIB could have antiviral effects. | 1 | Applied and Interdisciplinary Chemistry |
Mine reclamation may involve soil amendment, replacement, or creation, particularly for areas that have been strip mined or suffered severe erosion or soil compaction. In some cases, the native soil may be removed before construction and replaced with fill for the duration of the work. After construction is completed, the fill is again removed and replaced with the reserved native soil for revegetation. | 1 | Applied and Interdisciplinary Chemistry |
Particle deposition occurs in numerous natural and industrial systems. Few examples are given below.
* Coatings and surface functionalization. Paints and adhesives often are concentrated suspensions of colloidal particles, and in order to adhere well to the surface the particles must deposit to the surface in question. Deposits of a monolayer of colloidal particles can be used to pattern the surface on a μm or nm scale, a process referred to as colloidal lithography.
* Filters and filtration membranes. When particle deposit to filters or filtration membranes, they lead to pore clogging a membrane fouling. When designing well functioning membranes, particle deposition must be avoided, and proper functionalization of the membranes is essential.
* Deposition of microorganisms. Microorganisms may deposit similarly to colloidal particles. This deposition is a desired phenomenon in subsurface waters, as the aquifer filters out eventually injected microorganisms during the recharge of aquifers. On the other hand, such deposition is highly undesired at the surface of human teeth as it represent the origin of dental plaques. Deposition of microorganisms is also relevant in the formation of biofilms. | 0 | Theoretical and Fundamental Chemistry |
* Given the ability of southwestern blotting towards studying the affinity of proteins towards binding to DNA, this information can further be used with regards to uncovering specific protein factors that bind to DNA as well. These protein factors may be involved in controlling gene expression.
* Unlike electrophoretic mobility shift and DNA foot printing, determination of molecular weight of unknown proteins that bind to DNA can occur.
* Bowen and colleagues not only experimented and demonstrated a procedure for detecting DNA-binding proteins but also procedures for RNA-binding proteins as well as histone-binding proteins.
* Results can be combined with mass spectrometry to assist in DNA-binding protein identification.
* Isoelectric point determination is possible through the use of 2D-SDS-PAGE instead of the standard one dimension. | 1 | Applied and Interdisciplinary Chemistry |
Zinc metal is inserted into the carbon-halogen bond of the α-haloester by oxidative addition 1. This compound dimerizes and rearranges to form two zinc enolates 2. The oxygen on an aldehyde or ketone coordinates to the zinc to form the six-member chair like transition state 3. A rearrangement occurs in which zinc switches to the aldehyde or ketone oxygen and a carbon-carbon bond is formed 4. Acid workup 5,6 removes zinc to yield zinc(II) salts and a β-hydroxy-ester 7. | 0 | Theoretical and Fundamental Chemistry |
Geopolymerization chemistry requires appropriate terminologies and notions that are evidently different from those in use by Portland cement experts.
Indeed, geopolymer cement is sometimes mixed up with alkali-activated cement and concrete, developed more than 50 years ago by V.D. Glukhovsky in Ukraine, during the period of the former Soviet Union. They were originally known under the names "soil silicate concretes" and "soil cements". Because Portland cement concretes can be affected by the deleterious alkali-aggregate reaction, coined AAR, also known as alkali–silica reaction, coined ASR (internal swelling of siliceous aggregates due to the reaction of amorphous silica with KOH and NaOH (dissolution of at high pH and swelling of the hygroscopic silica gel formed), for more details, see for example the RILEM Committee 219-ACS Aggregate Reaction in Concrete Structures), the wording alkali-activation sometimes has a negative impact on civil engineers. However, geopolymer cements do not in general show these deleterious reactions (see below in Properties), when an appropriate aggregate is selected. Terminology related to alkali-activated materials or alkali-activated geopolymers is also in wide (but debated) use. These cements, sometimes abbreviated AAM, encompass the specific fields of alkali-activated slags, alkali-activated coal fly ashes, and various blended cementing systems (see RILEM Technical committee 247-DTA). | 0 | Theoretical and Fundamental Chemistry |
In aquatic environments (rivers, lakes and ocean), dissolved Si is utilized by diatoms, dictyochales, radiolarians and sponges to produce solid bSiO structures. The biomineralized silica has an amorphous structure and therefore its properties may vary among the different organisms. Biomineralization by diatoms induces the largest Si flux within the ocean, and thus it has a crucial role in the global Si cycle. During Si uptake by diatoms, there is an isotopic discrimination against the heavy isotope, forming Si-depleted biogenic silica minerals. As a result, the remaining dissolved Si in the surrounding water is Si-enriched. Since diatoms rely on sunlight for photosynthesis, they inhabit in surface waters, and thus the surface water of the ocean are typically Si-enriched. Although there is less available data on the isotopic fractionation during biomineralization by radiolarians, it has been suggested that radiolarians also discriminate against the heavy isotope (Si), and that the magnitude of isotopic fractionation is of a similar range as biomineralization by diatoms. Sponges also show an isotopic preference for Si over Si, but the magnitude of their isotopic fractionation is often larger (For quantitative comparation, see Figure 2). | 0 | Theoretical and Fundamental Chemistry |
The Hall-Héroult electrolysis process is the major production route for primary aluminium. An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside the shell, cathode blocks are cemented together by ramming paste. The top lining is in contact with the molten metal and acts as the cathode. The molten electrolyte is maintained at high temperature inside the cell. The prebaked anode is also made of carbon in the form of large sintered blocks suspended in the electrolyte. A single Soderberg electrode or a number of prebaked carbon blocks are used as anode, while the principal formulation and the fundamental reactions occurring on their surface are the same.
An aluminium smelter consists of a large number of cells (pots) in which the electrolysis takes place. A typical smelter contains anywhere from 300 to 720 pots, each of which produces about a ton of aluminium a day, though the largest proposed smelters are up to five times that capacity. Smelting is run as a batch process, with the aluminium deposited at the bottom of the pots and periodically siphoned off. Particularly in Australia these smelters are used to control electrical network demand, and as a result power is supplied to the smelter at a very low price. However power must not be interrupted for more than 4–5 hours, since the pots have to be repaired at significant cost if the liquid metal solidifies. | 1 | Applied and Interdisciplinary Chemistry |
In 1980, Joan J. Taylor published the first comprehensive study of the available evidence, entitled Bronze Age Goldwork of the British Isles. In 1994, the archaeologist George Eogan published an academic monograph on the subject, entitled The Accomplished Art: Gold and Gold-Working in Britain and Ireland during the Bronze Age, which was brought out through the U.K.-based Oxbow Books. In it, Eogan noted that his study was "not a corpus or catalogue" of artefacts, instead being "an evaluation and interpretation of the material in social terms". | 1 | Applied and Interdisciplinary Chemistry |
Colloidal phase separation is an important organising principle for compartmentalisation of both the cytoplasm and nucleus of cells into biomolecular condensates—similar in importance to compartmentalisation via lipid bilayer membranes, a type of liquid crystal. The term biomolecular condensate has been used to refer to clusters of macromolecules that arise via liquid-liquid or liquid-solid phase separation within cells. Macromolecular crowding strongly enhances colloidal phase separation and formation of biomolecular condensates. | 0 | Theoretical and Fundamental Chemistry |
Commercially, homoserine can serve as precursor to the synthesis of isobutanol and 1,4-butanediol. Purified homoserine is used in enzyme structural studies. Also, homoserine has played important roles in studies to elucidate peptide synthesis and synthesis of proteoglycan glycopeptides. Bacterial cell lines can make copious amounts of this amino acid. | 1 | Applied and Interdisciplinary Chemistry |
A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope Tc of technetium from a decaying sample of molybdenum-99. Mo has a half-life of 66 hours and can be easily transported over long distances to hospitals where its decay product technetium-99m (with a half-life of only 6 hours, inconvenient for transport) is extracted and used for a variety of nuclear medicine diagnostic procedures, where its short half-life is very useful. | 0 | Theoretical and Fundamental Chemistry |
Cryochemistry is the study of chemical interactions at temperatures below . It is derived from the Greek word cryos, meaning cold. It overlaps with many other sciences, including chemistry, cryobiology, condensed matter physics, and even astrochemistry.
Cryochemistry has been a topic of interest since liquid nitrogen, which freezes at −210°C, became commonly available. Cryogenic-temperature chemical interactions are an important mechanism for studying the detailed pathways of chemical reactions by reducing the confusion introduced by thermal fluctuations. Cryochemistry forms the foundation for cryobiology, which uses slowed or stopped biological processes for medical and research purposes. | 0 | Theoretical and Fundamental Chemistry |
In the United Kingdom, the Food Standards Agency has published criteria for the use of several terms in food labeling. The guidance, in general, restricts the use of natural foods that have "ingredients produced by nature, not the work of man or interfered with by man." Natural flavorings are explicitly defined by separate laws.
There are different standards for various types of food, such as dairy products. It also gives standards for some food processing techniques, such as fermentation or pasteurization. The standard explicitly rules out "foods derived from novel processes, GM or cloning." | 1 | Applied and Interdisciplinary Chemistry |
Marine energy or marine power (also sometimes referred to as ocean energy or ocean power) refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences. The movement of water in the world's oceans creates a vast store of kinetic energy, or energy in motion. This energy can be harnessed to generate electricity to power homes, transport and industries.
The term marine energy encompasses both wave power—power from surface waves, and tidal power—obtained from the kinetic energy of large bodies of moving water. Offshore wind power is not a form of marine energy, as wind power is derived from the wind, even if the wind turbines are placed over water.
The oceans have a tremendous amount of energy and are close to many if not most concentrated populations. Ocean energy has the potential of providing a substantial amount of new renewable energy around the world. | 1 | Applied and Interdisciplinary Chemistry |
Blood feeding organisms digest hemoglobin and release high quantities of free toxic heme. To avoid destruction by this molecule, the parasite biocrystallizes heme to form hemozoin. To date, the only definitively characterized product of hematin disposal is the pigment hemozoin. Hemozoin is per definitionem not a mineral and therefore not formed by biomineralization. Heme biocrystallization has been found in blood feeding organisms of great medical importance including Plasmodium, Rhodnius and Schistosoma. Heme biocrystallization is inhibited by quinoline antimalarials such as chloroquine.
Targeting heme biocrystallization remains one of the most promising avenues for antimalarial drug development because the drug target is highly specific to the malarial parasite, and outside the genetic control of the parasite. | 1 | Applied and Interdisciplinary Chemistry |
As a form of energy, heat has the unit joule (J) in the International System of Units (SI). In addition, many applied branches of engineering use other, traditional units, such as the British thermal unit (BTU) and the calorie. The standard unit for the rate of heating is the watt (W), defined as one joule per second.
The symbol for heat was introduced by Rudolf Clausius and Macquorn Rankine in .
Heat released by a system into its surroundings is by convention a negative quantity (); when a system absorbs heat from its surroundings, it is positive (). Heat transfer rate, or heat flow per unit time, is denoted by , but it is not a time derivative of a function of state (which can also be written with the dot notation) since heat is not a function of state. Heat flux is defined as rate of heat transfer per unit cross-sectional area (watts per square metre). | 0 | Theoretical and Fundamental Chemistry |
T. Ohta suggested that the concept of energy quality may be more intuitive if one considers examples where the form of energy remains constant but the amount of energy flowing, or transferred is varied. For instance if we consider only the inertial form of energy, then the energy quality of a moving body is higher when it moves with a greater velocity. If we consider only the heat form of energy, then a higher temperature has higher quality. And if we consider only the light form of energy then light with higher frequency has greater quality (Ohta 1994, p. 90). All these differences in energy quality are therefore easily measured with the appropriate scientific instrument. | 0 | Theoretical and Fundamental Chemistry |
Methyl methanesulfonate (MMS), also known as methyl mesylate, is an alkylating agent and a carcinogen. It is also a suspected reproductive toxicant, and may also be a skin/sense organ toxicant. It is used in cancer treatment. | 0 | Theoretical and Fundamental Chemistry |
Mach number is a function of temperature and true airspeed.
Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature.
Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is found from Bernoulli's equation for (above):
The formula to compute Mach number in a supersonic compressible flow can be found from the Rayleigh supersonic pitot equation (above) using parameters for air:
where:
:q is the dynamic pressure measured behind a normal shock.
As can be seen, M appears on both sides of the equation, and for practical purposes a root-finding algorithm must be used for a numerical solution (the equation is a septic equation in M and, though some of these may be solved explicitly, the Abel–Ruffini theorem guarantees that there exists no general form for the roots of these polynomials). It is first determined whether M is indeed greater than 1.0 by calculating M from the subsonic equation. If M is greater than 1.0 at that point, then the value of M from the subsonic equation is used as the initial condition for fixed point iteration of the supersonic equation, which usually converges very rapidly. Alternatively, Newton's method can also be used. | 1 | Applied and Interdisciplinary Chemistry |
Stirred tank, also called agitation leaching, involves contacting material, which has usually undergone size reduction and classification, with leach solution in agitated tanks. The agitation can enhance reaction kinetics by enhancing mass transfer. Tanks are often configured as reactors in series. | 1 | Applied and Interdisciplinary Chemistry |
Microwave spectroscopy is the spectroscopy method that employs microwaves, i.e. electromagnetic radiation at GHz frequencies, for the study of matter. | 0 | Theoretical and Fundamental Chemistry |
The physical and mathematical basics of electron charge transfer absent chemical bonds leading to pseudocapacitance was developed by Rudolph A. Marcus. Marcus Theory explains the rates of electron transfer reactions—the rate at which an electron can move from one chemical species to another. It was originally formulated to address outer sphere electron transfer reactions, in which two chemical species change only in their charge, with an electron jumping. For redox reactions without making or breaking bonds, Marcus theory takes the place of Henry Eyring's transition state theory which was derived for reactions with structural changes. Marcus received the Nobel Prize in Chemistry in 1992 for this theory. | 0 | Theoretical and Fundamental Chemistry |
The Faraday-efficiency effect refers to the potential for misinterpretation of data from experiments in electrochemistry through failure to take into account a Faraday efficiency of less than 100 percent. | 0 | Theoretical and Fundamental Chemistry |
As a doctoral student at the University of Chicago, Herbert Brown studied the reactions of diborane, BH. Hermann Irving Schlesinger's laboratory at the University of Chicago was one of two laboratories that prepared diborane. It was a rare compound that was only prepared in small quantities. Schlesinger was researching the reactions of diborane to understand why the simplest hydrogen-boron compound is BH instead of BH.
When Brown started his own research, he observed the reactions of diborane with aldehydes, ketones, esters, and acid chlorides. He discovered that diborane reacts with aldehydes and ketones to produce dialkoxyboranes, which are hydrolyzed by water to produce alcohols. Until this point, organic chemists did not have an acceptable method of reducing carbonyls under mild conditions. Yet Brown's Ph.D. thesis published in 1939 received little interest. Diborane was too rare to be useful as a synthetic reagent.
In 1939, Brown became the research assistant in Schlesinger's laboratory. In 1940, they began to research volatile, low molecular weight uranium compounds for the National Defense Research Committee. Brown and Schlesinger successfully synthesized volatile uranium(IV) borohydride, which had a molecular weight of 298. The laboratory was asked to provide a large amount of the product for testing, but diborane was in short supply. They discovered that it could be formed by reacting lithium hydride with boron trifluoride in ethyl ether, allowing them to produce the chemical in larger quantities. This success was met with several new problems. Lithium hydride was also in short supply, so Brown and Schlesinger needed to find a procedure that would allow them to use sodium hydride instead. They discovered that sodium hydride and methyl borate reacted to produce sodium trimethoxyborohydride, which was viable as a substitute for the lithium hydride.
Soon they were informed that there was no longer a need for uranium borohydride, but it appeared that sodium borohydride could be useful in generating hydrogen. They began to look for a cheaper synthesis and discovered that adding methyl borate to sodium hydride at 250° produced sodium borohydride and sodium methoxide. When acetone was used in an attempt to separate the two products, it was discovered that sodium borohydride reduced the acetone.
Sodium borohydride is a mild reducing agent that works well in reducing aldehydes, ketones, and acid chlorides. Lithium aluminum hydride is a much more powerful reducing agent that can reduce almost any functional group. When Brown moved to Purdue University in 1947, he worked to find stronger borohydrides and milder aluminum hydrides that would provide a spectrum of reducing agents. The team of researchers at Purdue discovered that changing the metal ion of the borohydride to lithium, magnesium, or aluminum increases the reducing ability. They also found that introducing alkoxy substituents to the aluminum hydride decreases the reducing ability. They successfully developed a full spectrum of reducing agents.
While researching these reducing agents, Browns coworker, Dr. B. C. Subba Rao, discovered an unusual reaction between sodium borohydride and ethyl oleate. The borohydride added hydrogen and boron to the carbon-carbon double bond in the ethyl oleate. The organoborane product could then be oxidized to form an alcohol. This two-step reaction is now called hydroboration-oxidation and is a reaction that converts alkenes into anti-Markovnikov alcohols. Markovnikovs rule states that, in adding hydrogen and a halide or hydroxyl group to a carbon-carbon double bond, the hydrogen is added to the less-substituted carbon of the bond and the hydroxyl or halide group is added to the more-substituted carbon of the bond. In hydroboration-oxidation, the opposite addition occurs. | 0 | Theoretical and Fundamental Chemistry |
Food fermentation is the conversion of sugars and other carbohydrates into alcohol or preservative organic acids and carbon dioxide. All three products have found human uses. The production of alcohol is made use of when fruit juices are converted to wine, when grains are made into beer, and when foods rich in starch, such as potatoes, are fermented and then distilled to make spirits such as gin and vodka. The production of carbon dioxide is used to leaven bread. The production of organic acids is exploited to preserve and flavor vegetables and dairy products.
Food fermentation serves five main purposes: to enrich the diet through development of a diversity of flavors, aromas, and textures in food substrates; to preserve substantial amounts of food through lactic acid, alcohol, acetic acid, and alkaline fermentations; to enrich food substrates with protein, essential amino acids, and vitamins; to eliminate antinutrients; and to reduce cooking time and the associated use of fuel. | 1 | Applied and Interdisciplinary Chemistry |
Ashing is a test to deduce the amount of ash forming material present in a petroleum product so as to decide its use in certain applications. Ash-forming materials are considered to be undesirable impurities or contaminants.
In the ash analysis of petroleum products, ash content represents the incombustible component remaining after a sample of the furnace oil is completely burned. The ash content of petroleum products is generally low. It is defined as the inorganic residue that remains after combustion of the oil in air at specific high temperature. Ash typically ranges from 0.1 to 0.2% in oil. Some of the ash forming constituents occur naturally in crude oil; others are present as a result of refining or contamination during storage or distribution. Knowledge of the amount of ash-forming material present in a product can provide information as to whether or not the product is suitable application.
In the ash analysis of coal and other solid fuels, the amount of sulfur retained in the ash during the ashing process is not constant, but rather is dependent upon the conditions of ashing as well as the other inorganic constituents in the ash that may form sulfates during the ashing procedure. As such, different ashing procedures may yield different ash contents. | 0 | Theoretical and Fundamental Chemistry |
Thermal rearrangements of aromatic hydrocarbons have been shown to be important in areas of chemical research and industry including fullerene synthesis, materials applications, and the formation of soot in combustion. Thermal rearrangements of aceanthrylene and acephenanthrylene can yield fluoranthene, an important species in syntheses of corannulene and fullerenes that proceed through additional internal rearrangements.
Many of the polycyclic aromatic hydrocarbons known to be tumorigenic or mutagenic are found in atmospheric aerosols, which is connected to the thermal rearrangement of polycyclic aromatic hydrocarbons in fast soot formation during combustion. | 0 | Theoretical and Fundamental Chemistry |
Heating white cast iron (containing iron carbide, i.e. cementite, but no uncombined carbon) above causes the formation of austenite in crystals of primary cementite. This austenisation of white iron occurs in primary cementite at the interphase boundary with ferrite. When the grains of austenite form in cementite, they occur as lamellar clusters oriented along the cementite crystal layer surface. Austenite is formed by diffusion of carbon atoms from cementite into ferrite. | 1 | Applied and Interdisciplinary Chemistry |
Microsegregation is a non-uniform chemical separation and concentration of elements or impurities in alloys after they have solidified. | 0 | Theoretical and Fundamental Chemistry |
A boundary can be described by the orientation of the boundary to the two grains and the 3-D rotation required to bring the grains into coincidence. Thus a boundary has 5 macroscopic degrees of freedom. However, it is common to describe a boundary only as the orientation relationship of the neighbouring grains. Generally, the convenience of ignoring the boundary plane orientation, which is very difficult to determine, outweighs the reduced information.
The relative orientation of the two grains is described using the rotation matrix:
Using this system the rotation angle θ is:
while the direction [uvw] of the rotation axis is:
The nature of the crystallography involved limits the misorientation of the boundary. A completely random polycrystal, with no texture, thus has a characteristic distribution of boundary misorientations (see figure). However, such cases are rare and most materials will deviate from this ideal to a greater or lesser degree. | 1 | Applied and Interdisciplinary Chemistry |
During the early Eocene, the continental configuration was such that the Arctic sea was almost entirely cut off from the wider oceans. This meant that mixing — provided today by deep water currents such as the Gulf Stream — did not occur, leading to a stratified water column resembling today's Black Sea.
High temperatures and winds led to high evaporation, increasing the density of the ocean, and — through an increase in rainfall — high discharge from rivers which fed the basin. This low-density freshwater formed a nepheloid layer, floating on the surface of the dense sea.
Even a few centimetres of fresh water would be enough to allow colonization by Azolla; further, this river water would be rich in minerals such as phosphorus, which it would accumulate from mud and rocks it interacted with as it crossed the continents. To further aid the growth of the plant, concentrations of carbon (in the form of carbon dioxide) in the atmosphere are known to have been high at this time.
Blooms alone are not enough to have any geological impact; to permanently draw down CO and cause climate change, the carbon must be sequestered by the plants being buried and the remains rendered inaccessible to decomposing organisms. The anoxic bottom of the Arctic basin, a result of the stratified water column, permitted just this; the anoxic environment inhibits the activity of decomposing organisms and allows the plants to sit unrotted until they are buried by sediment. | 1 | Applied and Interdisciplinary Chemistry |
This transition is associated with the transition of a polymer chain from good solvent behavior through ideal or theta solvent behavior to poor solvent behavior. The canonical coil–globule transition is associated with the Upper critical solution temperature and the associated Flory theta point. In this case, collapse occurs with cooling and results from favorable attractive energy of the polymer to itself. A second type of coil–globule transition is instead associated with the lower critical solution temperature and its corresponding theta point. This collapse occurs with increasing temperature and is driven by an unfavorable entropy of mixing. An example of this type is embodied by the polymer PNIPAAM, mentioned above. Coil globule transitions may also be driven by charge effects, in the case of polyelectrolytes. In this case pH and ionic strength changes within the solution may trigger collapse, with increasing counterion concentration generally leading to collapse in a uniformly charged polyelectrolyte. In polyampholytes containing both positive and negative charges, the opposite may hold true. | 0 | Theoretical and Fundamental Chemistry |
Barium azide can be used to make azides of magnesium, sodium, potassium, lithium, rubidium and zinc with their respective sulfates.
It can also be used as a source for high purity nitrogen by heating:
This reaction liberates metallic barium, which is used as a getter in vacuum applications. | 0 | Theoretical and Fundamental Chemistry |
Lyngbyastatins 1 and 3 are encoded for by a 52 kb biosynthetic gene cluster (BGC) containing one polyketide synthase (PKS)/non-ribosomal peptide synthetase (NRPS) hybrid (LbnA), four NRPSs (LbnB-D, LbnF), and one PKS (LbnE).
Biosynthesis commences with PKS activity — thiolation of propanoic (Lyngbyastatin 1) or butyric (Lyngbyastatin 3) acid and subsequent loading onto the ketosynthase (KS) of LbnA. An acyl unit from malonyl CoA is then coupled onto the initial substrate via an acyltransferase (AT) and then methylated at the alpha carbon through a C-methyltransferase (CMT) before an aminotransferase (AmT) conducts a transamination of the initial substrate carbonyl. The latter half of LbnA follows traditional NRPS activity containing condensation (C), adenylation (A), and thiolation (T) domains to couple 2-hydroxy-3-methylvaleric acid, which is believed to be formed from the 2-oxo analog through PKS ketoreductase (KR) activity.
LbnB, a traditional NRPS, adds glycine into the growing thioester by its amino group. LbnC is another traditional NRPS that adds L-leucine and glycine, respectively, except the L-leucine domain possesses an active N-methyltransferase (NMT) domain that methylates the nitrogen of L-leucine.
NRPS LbnD then adds L-valine, L-tyrosine, and L or D-valine, respectively to the growing molecule. PKS LbnE couples an acyl unit from malonyl-CoA onto the C-terminus of the valine residue before a C-methyltransferase methylates the carbon alpha to the thioester twice to produce a quarternary alpha carbon.
NRPS LbnF completes the biosynthesis by coupling L-alanine before the thioesterase (TE) domain conducts a head-to-tail cyclization to produce the final depsipeptide products. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic nanochains are a class of new magnetoresponsive and superparamagnetic nanostructures with highly anisotropic shapes (chain-like) which can be manipulated using magnetic field and magnetic field gradient. The magnetic nanochains possess attractive properties which are significant added value for many potential uses including magneto-mechanical actuation-associated nanomedicines in low and super-low frequency alternating magnetic field and magnetic drug delivery.
Cell imaging
Nanoparticles have good biological labeling and sensing because of brightness and photostability; thus, certain self-assembled nanoparticles can be used as imaging contrast in various systems. Combined with polymer cross-linkers, the fluorescence intensity can also be enhanced. Surface modification with functional groups, can also lead to selective biological labeling. Self-assembled nanoparticles are also more biocompatible compared to standard drug delivery systems. | 0 | Theoretical and Fundamental Chemistry |
Virtually all ligands are known to bridge, with the exception of amines and ammonia. Common bridging ligands include most of the common anions.
Many simple organic ligands form strong bridges between metal centers. Many common examples include organic derivatives of the above inorganic ligands (R = alkyl, aryl): , , , (imido), (phosphido, note the ambiguity with the preceding entry), (phosphinidino), and many more. | 0 | Theoretical and Fundamental Chemistry |
Goldmans equation seeks to determine the voltage E across a membrane. A Cartesian coordinate system is used to describe the system, with the z direction being perpendicular to the membrane. Assuming that the system is symmetrical in the x and y directions (around and along the axon, respectively), only the z direction need be considered; thus, the voltage E is the integral of the z' component of the electric field across the membrane.
According to Goldmans model, only two factors influence the motion of ions across a permeable membrane: the average electric field and the difference in ionic concentration from one side of the membrane to the other. The electric field is assumed to be constant across the membrane, so that it can be set equal to E/L, where L is the thickness of the membrane. For a given ion denoted A with valence n, its flux j'—in other words, the number of ions crossing per time and per area of the membrane—is given by the formula
The first term corresponds to Ficks law of diffusion, which gives the flux due to diffusion down the concentration gradient, i.e., from high to low concentration. The constant D is the diffusion constant of the ion A. The second term reflects the flux due to the electric field, which increases linearly with the electric field; Formally, it is [A] multiplied by the drift velocity of the ions, with the drift velocity expressed using the Stokes–Einstein relation applied to electrophoretic mobility. The constants here are the charge valence n of the ion A (e.g., +1 for K, +2 for Ca and −1 for Cl), the temperature T (in kelvins), the molar gas constant R, and the faraday F', which is the total charge of a mole of electrons.
This is a first-order ODE of the form y = ay + b, with y = [A] and y = d[A]/dz; integrating both sides from z=0 to z=L with the boundary conditions [A](0) = [A] and [A](L) = [A], one gets the solution
where μ is a dimensionless number
and P is the ionic permeability, defined here as
The electric current density J equals the charge q of the ion multiplied by the flux j
Current density has units of (Amperes/m). Molar flux has units of (mol/(s m)). Thus, to get current density from molar flux one needs to multiply by Faraday's constant F (Coulombs/mol). F will then cancel from the equation below. Since the valence has already been accounted for above, the charge q of each ion in the equation above, therefore, should be interpreted as +1 or -1 depending on the polarity of the ion.
There is such a current associated with every type of ion that can cross the membrane; this is because each type of ion would require a distinct membrane potential to balance diffusion, but there can only be one membrane potential. By assumption, at the Goldman voltage E, the total current density is zero
(Although the current for each ion type considered here is nonzero, there are other pumps in the membrane, e.g. Na/K-ATPase, not considered here which serve to balance each individual ions current, so that the ion concentrations on either side of the membrane do not change over time in equilibrium.) If all the ions are monovalent—that is, if all the n' equal either +1 or -1—this equation can be written
whose solution is the Goldman equation
where
If divalent ions such as calcium are considered, terms such as e appear, which is the square of e; in this case, the formula for the Goldman equation can be solved using the quadratic formula. | 0 | Theoretical and Fundamental Chemistry |
While small generators may be cooled by air drawn through filters at the inlet, larger units generally require special cooling arrangements. Hydrogen gas cooling, in an oil-sealed casing, is used because it has the highest known heat transfer coefficient of any gas and for its low viscosity which reduces windage losses. This system requires special handling during start-up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in the air.
The hydrogen pressure inside the casing is maintained slightly higher than atmospheric pressure to avoid outside air ingress, and up to about two atmospheres pressure to improve heat transfer capacity. The hydrogen must be sealed against outward leakage where the shaft emerges from the casing. Mechanical seals around the shaft are installed with a very small annular gap to avoid rubbing between the shaft and the seals on smaller turbines, with labyrinth type seals on larger machines.. Seal oil is used to prevent the hydrogen gas leakage to atmosphere.
The generator also uses water cooling. Since the generator coils are at a potential of about 22 kV, an insulating barrier such as Teflon is used to interconnect the water line and the generator high-voltage windings. Demineralized water of low conductivity is used. | 1 | Applied and Interdisciplinary Chemistry |
Sonication is an efficient tool for the synthesis of polymers. The cavitational shear forces, which stretch out and break the chain in a non-random process, result in a lowering of the molecular weight and poly-dispersity. Furthermore, multi-phase systems are very efficient dispersed and emulsified, so that very fine mixtures are provided. This means that ultrasound increases the rate of polymerisation over conventional stirring and results in higher molecular weights with lower polydispersities. Ormosils (organically modified silicate) are obtained when silane is added to gel-derived silica during sol–gel process. The product is a molecular-scale composite with improved mechanical properties. Sono-Ormosils are characterized by a higher density than classic gels as well as an improved thermal stability. An explanation therefore might be the increased degree of polymerization. | 0 | Theoretical and Fundamental Chemistry |
Although the full electronic structure of an arene can only be computed using quantum mechanics, the directing effects of different substituents can often be guessed through analysis of resonance diagrams. Specifically, any formal negative or positive charges in minor resonance contributors (ones in accord with the natural polarization but not necessarily obeying the octet rule) reflect locations having a larger or smaller density of charge in the molecular orbital for a bond most likely to break. A carbon atom with a larger coefficient will be preferentially attacked, due to more favorable orbital overlap with the electrophile.
The perturbation of a conjugating electron-withdrawing or electron-donating group causes the π electron distribution on a benzene ring to resemble (very slightly!) an electron-deficient benzyl cation or electron-excessive benzyl anion, respectively. The latter species admit tractable quantum calculation using Hückel theory: the cation withdraws electron density at the ortho and para positions, favoring meta attack, whereas the anion releases electron density into the same positions, activating them for attack. This is precisely the result that the drawing of resonance structures would predict.
For example, aniline has resonance structures with negative charges around the ring system:
Attack occurs at ortho and para positions, because the (partial) formal negative charges at these positions indicate a local electron excess. On the other hand, the nitrobenzene resonance structures have positive charges around the ring system:
Attack occurs at the meta position, since the (partial) formal positive charges at the ortho and para positions indicate electron deficiency at these positions.
Another common argument, which makes identical predictions, considers the stabilization or destabilization by substituents of the Wheland intermediates resulting from electrophilic attack at the ortho/para or meta positions. The Hammond postulate then dictates that the relative transition state energies will reflect the differences in the ground state energies of the Wheland intermediates. | 0 | Theoretical and Fundamental Chemistry |
In materials science the flow stress, typically denoted as Y (or ), is defined as the instantaneous value of stress required to continue plastically deforming a material - to keep it flowing. It is most commonly, though not exclusively, used in reference to metals. On a stress-strain curve, the flow stress can be found anywhere within the plastic regime; more explicitly, a flow stress can be found for any value of strain between and including yield point () and excluding fracture (): .
The flow stress changes as deformation proceeds and usually increases as strain accumulates due to work hardening, although the flow stress could decrease due to any recovery process. In continuum mechanics, the flow stress for a given material will vary with changes in temperature, , strain, , and strain-rate, ; therefore it can be written as some function of those properties:
The exact equation to represent flow stress depends on the particular material and plasticity model being used. Hollomon's equation is commonly used to represent the behavior seen in a stress-strain plot during work hardening:
Where
is flow stress,
is a strength coefficient,
is the plastic strain, and
is the strain hardening exponent. Note that this is an empirical relation and does not model the relation at other temperatures or strain-rates (though the behavior may be similar).
Generally, raising the temperature of an alloy above 0.5 T results in the plastic deformation mechanisms being controlled by strain-rate sensitivity, whereas at room temperature metals are generally strain-dependent. Other models may also include the effects of strain gradients. Independent of test conditions, the flow stress is also affected by: chemical composition, purity, crystal structure, phase constitution, microstructure, grain size, and prior strain.
The flow stress is an important parameter in the fatigue failure of ductile materials. Fatigue failure is caused by crack propagation in materials under a varying load, typically a cyclically varying load. The rate of crack propagation is inversely proportional to the flow stress of the material. | 1 | Applied and Interdisciplinary Chemistry |
* Rosa Solis or Rosolio, probably originating in Renaissance Turin was derived from the carnivorous sundew plant. It was believed to not only invigorate the heart, but to be an aphrodisiac as well; according to the 17th century medical writer William Salmon, sundew "stirs up lust".
* Royal Usquebaugh was a spicy concoction containing flecks of gold leaf thought to capture the suns golden radiance. It was usually flavoured with aniseed, liquorice and saffron and sweetened with fruit sugar extracted from figs and raisins by maceration. The name derives from the Irish uisce beatha, which is literally the Gaelic translation of Latin aqua vitae, the water of life). The word whisky is also derived from the Irish uisce beatha', but this was not the same as the cordial consumed in 17th and 18th century England and France, and bore no resemblance to the spirit we now call whisky.
*Escubac dAngleterre', a more down-market relative of Royal Usquebaugh without the flecks of gold leaf, but was nevertheless a popular drink.
* Vespetrò, another popular liqueur of Italy (speciality of the town of Canzo), flavoured with anise, angelica and lemon. | 1 | Applied and Interdisciplinary Chemistry |
The washability analysis is widely known in bulk material analysis, where the specific density is the physical property describing the liberation and the separation results, which is then in the form of the partition curve. The partition curve is defined as the curve which gives as a function of a physical property or characteristic, the proportions in which different elemental classes of raw feed having the same property are split into separate products. It is thus per its definition not limited to, but predominantly applied in analysis of liberation and process efficiency of density separation processes. For sensor-based ore sorting, the partition (also called Tromp) curves for chromite, iron ore and coal are known and can thus be applied for process modelling. | 0 | Theoretical and Fundamental Chemistry |
For decades, the main cellular target for radiation induced damage was thought to be the DNA molecule. This view has been challenged by data indicating that in order to increase survival, the cells must protect their proteins, which in turn repair the damage in the DNA. An important part of protection of proteins (but not DNA) against the detrimental effects of reactive oxygen species (ROS), which are the main mechanism of radiation toxicity, is played by non-enzymatic complexes of manganese ions and small organic metabolites. These complexes were shown to protect the proteins from oxidation in vitro and also increased radiation survival in mice. An application of the synthetically reconstituted protective mixture with manganese was shown to preserve the immunogenicity of viral and bacterial epitopes at radiation doses far above those necessary to kill the microorganisms, thus opening a possibility for a quick whole-organism vaccine production. The intracellular manganese content and the nature of complexes it forms (both measurable by electron paramagnetic resonance) were shown to correlate with radiosensitivity in bacteria, archaea, fungi and human cells. An association was also found between total cellular manganese contents and their variation, and clinically inferred radioresponsiveness in different tumor cells, a finding that may be useful for more precise radiodosages and improved treatment of cancer patients. | 0 | Theoretical and Fundamental Chemistry |
Another beneficial cell modification is the adjustment of substrate and growth requirements of a cell. By changing cell needs, the raw material cost, equipment expenses, and skill required to grow and maintain cell cultures can be significantly reduced. For example, scientists have used foreign enzymes to engineer a common industrial yeast strain which allows the cells to grow on substrate cheaper than the traditional glucose. Because of the biological engineering focus on improving scale-up costs, research in this area is largely focused on the ability of various enzymes to metabolize low-cost substrates. | 1 | Applied and Interdisciplinary Chemistry |
The effective diffusion coefficient describes diffusion through the pore space of porous media. It is macroscopic in nature, because it is not individual pores but the entire pore space that needs to be considered. The effective diffusion coefficient for transport through the pores, D, is estimated as follows:
where
*D is the diffusion coefficient in gas or liquid filling the pores,
*ε is the porosity available for the transport (dimensionless),
*δ is the constrictivity (dimensionless),
*τ is the tortuosity (dimensionless).
The transport-available porosity equals the total porosity less the pores which, due to their size, are not accessible to the diffusing particles, and less dead-end and blind pores (i.e., pores without being connected to the rest of the pore system). The constrictivity describes the slowing down of diffusion by increasing the viscosity in narrow pores as a result of greater proximity to the average pore wall. It is a function of pore diameter and the size of the diffusing particles. | 1 | Applied and Interdisciplinary Chemistry |
The Guide to PHARMACOLOGY includes links to other relevant resources via target and ligand pages on both the concise and detailed view pages. Many of these resources maintain reciprocal links with the relevant Guide to PHARMACOLOGY pages.
*HUGO Gene Nomenclature Committee
*Mouse Genome Informatics
*Rat genome database
*Ensembl
*UniProt
*Entrez
*PubChem
*ChemSpider
*ChEMBL
*ChEBI
*KEGG
*Online Mendelian Inheritance in Man (OMIM)
*DrugBank
*Protein Data Bank | 1 | Applied and Interdisciplinary Chemistry |
All measurements are reported with their standard uncertainty. Measurements of particular combinations of oxygen and hydrogen isotopes are unnecessary because water molecules constantly exchange atoms with each other. | 0 | Theoretical and Fundamental Chemistry |
The biological pump transports 1–4 g C m y of POC below the thermocline annually. The export flux of POC in the temperate North Atlantic out of the surface waters was found to be 29 ± 10 g C m y. However, studies have shown that processes such as consumption and remineralization contribute to a significant amount of this POC being attenuated as it sinks below the thermocline (near overwintering depths of ~1000 m). Furthermore, the remaining quantity of carbon in the North Atlantic from the export of POC below the thermocline has been calculated (2–8 g C m y) to be comparable to the seasonal migration of C. finmarchicus in the North Atlantic (1–4 g C m y) through the lipid pump. Therefore, the lipid pump may contribute 50–100% of C sequestration to the biological pump as net transport that has not been included in its current estimates. | 0 | Theoretical and Fundamental Chemistry |
Medium-carbon steel has approximately 0.3–0.5% carbon content. It balances ductility and strength and has good wear resistance. It is used for large parts, forging and automotive components. | 1 | Applied and Interdisciplinary Chemistry |
Ocean acidification threatens coral reproduction throughout almost all aspects of the process. Gametogenesis may be indirectly affected by coral bleaching. Additionally, the stress that acidification puts on coral can potentially harm the viability of the sperm released. Larvae can also be affected by this process; metabolism and settlement cues could be altered, changing the size of the population or viability of reproduction. Other species of calcifying larvae have shown reduced growth rates under ocean acidification scenarios. Biofilm, a bioindicator for oceanic conditions, underwent a reduced growth rate and altered composition in acidification, possibly affecting larval settlement on the biofilm itself. | 0 | Theoretical and Fundamental Chemistry |
Barium iodate can be derived either as a product of a reaction of iodine and barium hydroxide or by combining barium chlorate with potassium iodate. | 0 | Theoretical and Fundamental Chemistry |
*Bark, L. S. and Bark, S. M.; (1969). Thermometric titrimetry. International Series of Monographs in Analytical Chemistry Vol 33 Pergamon Press (Oxford) Library of Congress Catalog Card No. 68-57883
*Barthel, J.; (1975) Thermometric titrations. John Wiley & Sons, New York. Library of Congress Catalog Card No. 75-17503
*Eatough, D. J.; Christensen, J. J. & Izatt R. M. ; (1974) Experiments in thermometric titrimetry and titration calorimetry. Brigham Young University Press, Provo, Utah. Library of Congress Catalog Card 74-13074
*Grime, J. K.; (1985) Analytical solution calorimetry. John Wiley & Sons, New York. Library of Congress Catalog Card No. 84-28424
*Vaughan, G.A.; (1973) Thermometric and enthalpimetric titrimetry. Van Nostrand Reinhold Company (London) Library of Congress Catalog Card No. 79-186764 | 0 | Theoretical and Fundamental Chemistry |
Flow cytometry is most frequently used to detect apoptotic DNA fragmentation. Analysis of DNA content by flow cytometry can identify apoptotic cells with fragmented DNA as the cells with fractional DNA content, often called the sub-G cells. The flow-cytometric assay utilizing the fluorochrome acridine orange shows that DNA fragmentation within individual cells is discontinuous likely reflecting different levels of restriction in accessibility of DNA to DNase, by the supranucleosomal and nucleosomal levels of chromatin structure. The presence of apoptotic "sub-Gcells" can also be detected in cells pre-fixed in ethanol but not after fixation in the crosslinking fixatives such as formaldehyde. The late-S and G apoptotic cells may not be detected with this approach because their fractional DNA content may overlap with that of the non-apoptotic G cells.
Treatment of cells with detergent, prior or concurrently with DNA fluorochrome, also reveals DNA fragmentation by virtue of the presence of the sub-G cells or cell fragments, as defined by Nicoletti et al.
Apoptotic DNA fragmentation can also be detected by the TUNEL assay. The fluorochrome-based TUNEL assay applicable for flow cytometry, correlates the detection of DNA strand breaks with the cellular DNA content and thus with cell cycle-phase position. The avidin-peroxidase labeling TUNEL assay is applicable for light absorption microscopy. Many TUNEL-related kits are commercially available.
Apoptotic DNA fragmentation is also analyzed using agarose gel electrophoresis to demonstrate a "ladder" pattern at ~180-BP intervals. Necrosis, on the other hand, is usually characterized by random DNA fragmentation which forms a "smear" on agarose gels. | 1 | Applied and Interdisciplinary Chemistry |
The critical structural element of all glycoproteins is having oligosaccharides bonded covalently to a protein. There are 10 common monosaccharides in mammalian glycans including: glucose (Glc), fucose (Fuc), xylose (Xyl), mannose (Man), galactose (Gal), N-acetylglucosamine (GlcNAc), glucuronic acid (GlcA), iduronic acid (IdoA), N-acetylgalactosamine (GalNAc), sialic acid, and 5-N-acetylneuraminic acid (Neu5Ac). These glycans link themselves to specific areas of the protein amino acid chain.
The two most common linkages in glycoproteins are N-linked and O-linked glycoproteins. An N-linked glycoprotein has glycan bonds to the nitrogen containing an asparagine amino acid within the protein sequence. An O-linked glycoprotein has the sugar is bonded to an oxygen atom of a serine or threonine amino acid in the protein.
Glycoprotein size and composition can vary largely, with carbohydrate composition ranges from 1% to 70% of the total mass of the glycoprotein. Within the cell, they appear in the blood, the extracellular matrix, or on the outer surface of the plasma membrane, and make up a large portion of the proteins secreted by eukaryotic cells. They are very broad in their applications and can function as a variety of chemicals from antibodies to hormones. | 0 | Theoretical and Fundamental Chemistry |
Search capacities of crystallographic databases differ widely. Basic functionality comprises search by keywords, physical properties, and chemical elements. Of particular importance is search by compound name and lattice parameters. Very useful are search options that allow the use of wildcard characters and logical connectives in search strings. If supported, the scope of the search can be constrained by the exclusion of certain chemical elements.
More sophisticated algorithms depend on the material type covered. Organic compounds might be searched for on the basis of certain molecular fragments. Inorganic compounds, on the other hand, might be of interest with regard to a certain type of coordination geometry. More advanced algorithms deal with conformation analysis (organics), supramolecular chemistry (organics), interpolyhedral connectivity (‘non-organics’) and higher-order molecular structures (biological macromolecules). Search algorithms used for a more complex analysis of physical properties, e.g. phase transitions or structure-property relationships, might apply group-theoretical concepts.
Modern versions of crystallographic databases are based on the relational database model. Communication with the database usually happens via a dialect of the Structured Query Language (SQL). Web-based databases typically process the search algorithm on the server interpreting supported scripting elements, while desktop-based databases run locally installed and usually precompiled search engines. | 0 | Theoretical and Fundamental Chemistry |
In the United States, Brownfield regulation and development is largely governed by state environmental agencies in cooperation with the Environmental Protection Agency (EPA). In 1995, the EPA launched the Brownfields Program, which was expanded in 2002 with the Brownfields Law.
The EPA, together with local and national government, can provide technical help and some funding for assessment and cleanup. From 2002 through 2013, the EPA awarded nearly 1,000 grants for clean up, for a total of almost $190 million. It can also provide tax incentives for cleanup that is not paid for outright; specifically, cleanup costs are fully tax-deductible in the year they are incurred. Many of the most important provisions on liability relief are contained in state codes that can differ significantly from state to state. | 1 | Applied and Interdisciplinary Chemistry |
The temperature-based phase behavior of ELPs can be utilized to produce stiff networks that may be compatible with cellular regeneration applications. At high concentrations (weight percent exceeding 15%), the ELP transition from a linear state to a spherical aggregate state above the transition temperature is arrested, leading to the formation of brittle gels. These otherwise brittle networks can then be modified chemically, via oxidative coupling, to yield hydrogels which can sustain high levels of mechanical stress and strain. Also, the modified gel networks contain pores, through which important cell-sustaining compounds can easily be delivered. Such strong hydrogels, when bathed in minimal cell media, have been found to promote the growth of human mesencyhmal stem cell populations. The ability of these arrested ELP networks to promote cell growth may prove indispensable in the production of tissue scaffolds that promote cartilage production, for example. Such an intervention may prove useful in the treatment of bone disease and rheumatoid arthritis. | 0 | Theoretical and Fundamental Chemistry |
There is a genetic variant, registered in the Single Nucleotide Polymorphism database (dbSNP) as rs11558538, found in 10% of the population worldwide, which means that the T allele presents at position 314 of HNMT instead of a usual C allele (c.314C>T). This variant causes the protein to be synthesized with threonine (Thr) replaced with isoleucine (Ile) at position 105 (p.Thr105Ile, T105I). This variant is described as loss-of-function allele reducing HNMT activity, and is associated with diseases such as asthma, allergic rhinitis, and atopic eczema (atopic dermatitis). For individuals with this variant, the intake of HNMT inhibitors, which hamper enzyme activity, and histamine liberators, which release histamine from the granules of mast cells and basophils, could potentially influence their histamine levels. Still, this genetic variant is associated with a reduced risk of Parkinson's disease.
Experiments involving Hnmt-knockout mice have shown that a deficiency in HNMT indeed leads to increased brain histamine concentrations, resulting in heightened aggressive behaviors and disrupted sleep-wake cycles in these mice. In humans, genetic variants that affect HNMT activity have been implicated in various brain disorders, such as Parkinsons disease and attention deficit disorder, but it remains unclear whether these alterations in HNMT are a primary cause or secondary effect of these conditions. Additionally, reduced histamine levels in cerebrospinal fluid have been consistently reported in patients with narcolepsy and other conditions characterized by excessive daytime sleepiness. The association between HNMT polymorphisms and gastrointestinal diseases is still uncertain. While mild polymorphisms can lead to diseases such as asthma and inflammatory bowel disease, they may also reduce the risk of brain disorders like Parkinsons disease. On the other hand, severe mutations in HNMT can result in intellectual disability. Despite these findings, the role of HNMT in human health is not fully understood and continues to be an active area of research. | 1 | Applied and Interdisciplinary Chemistry |
Meta-analyses of intervention and observational trials for various types of cancer report mixed results. Supplementation with β-carotene did not appear to decrease the risk of cancer overall, nor specific cancers including: pancreatic, colorectal, prostate, breast, melanoma, or skin cancer generally. High-dose β-carotene supplementation unexpectedly resulted in a higher incidence of lung cancer and of total mortality in people who were cigarette smokers.
For dietary retinol, no effects were observed for high dietary intake and breast cancer survival, risk of liver cancer, risk of bladder cancer or risk of colorectal cancer, although the last review did report lower risk for higher beta-carotene consumption. In contrast, an inverse association was reported between retinol intake and relative risk of esophageal cancer, gastric cancer, ovarian cancer, pancreatic cancer, lung cancer, melanoma, and cervical cancer. For lung cancer, an inverse association was also seen for beta-carotene intake, separate from the retinol results. When high dietary intake was compared to low dietary intake, the decreases in relative risk were in the range of 15 to 20%. For gastric cancer, a meta-analysis of prevention trials reported a 29% decrease in relative risk from retinol supplementation at 1500 μg/day. | 1 | Applied and Interdisciplinary Chemistry |
Carbonyl hydrido tris(triphenylphosphine)rhodium(I) [Carbonyl(hydrido)tris(triphenylphosphane)rhodium(I)] is an organorhodium compound with the formula [RhH(CO)(PPh)] (Ph = CH). It is a yellow, benzene-soluble solid, which is used industrially for hydroformylation. | 0 | Theoretical and Fundamental Chemistry |
Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions. absorbs moisture from air, converts to lanthanum hydroxide.
Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV. Its average room temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. has the lowest lattice energy of the rare earth oxides, with very high dielectric constant, ε = 27. | 0 | Theoretical and Fundamental Chemistry |
Particular chemoreceptors, called ASICs, detect the levels of carbon dioxide in the blood. To do this, they monitor the concentration of hydrogen ions in the blood, which decrease the pH of the blood. This can be a direct consequence of an increase in carbon dioxide concentration, because aqueous carbon dioxide in the presence of carbonic anhydrase reacts to form a proton and a bicarbonate ion.
The response is that the respiratory centre (in the medulla), sends nervous impulses to the external intercostal muscles and the diaphragm, via the intercostal nerve and the phrenic nerve, respectively, to increase breathing rate and the volume of the lungs during inhalation.
Chemoreceptors that regulate the depth and rhythm of breathing are broken down into two categories.
* central chemoreceptors are located on the ventrolateral surface of medulla oblongata and detect changes in pH of cerebrospinal fluid. They have also been shown experimentally to respond to hypercapnic hypoxia (elevated , decreased O2), and eventually desensitize, partly due to redistribution of bicarbonate out of the cerebrospinal fluid (CSF) and increased renal excretion of bicarbonate. These are sensitive to pH and .
* peripheral chemoreceptors: consists of aortic and carotid bodies. Aortic body detects changes in blood oxygen and carbon dioxide, but not pH, while carotid body detects all three. They do not desensitize. Their effect on breathing rate is less than that of the central chemoreceptors. | 0 | Theoretical and Fundamental Chemistry |
The starting materials for the Kröhnke synthesis are often trivial to prepare, lending to the convenience and broad scope of the method. Preparation of the α-pyridinium methyl ketone salts can be easily achieved by treatment of the corresponding bromomethyl ketone with pyridine. The α,β-unsaturated ketones are often available commercially or can be prepared using a number of known methods. Additionally, Mannich bases can also be utilized as the Michael acceptor for the scheme, further diversifying the scope of starting materials that can be incorporated into the Kröhnke scheme.
The reaction conditions for the Kröhnke synthesis are generally facile and the reactions often proceed in high yields with reaction temperatures generally not exceeding 140 °C. The Kröhnke synthesis is generally performed in either glacial acetic acid or methanol, but it can also be done under aqueous conditions, and more recently under solvent-free conditions.
1,3-dicarbonyl compounds have also been shown to be viable starting materials in place of the α-pyridinium methyl ketone salts. For example, treatment of 1,3-diketone 14 with base in ethanol followed by ammonium acetate, acetic acid, the corresponding enone and a Lewis acid yields 3-acyltriarylpyridines of the form 15. These acyl pyridine are attractive intermediates because they have an electrophilic handle that allows for additional functionality to be incorporated into the molecule. This allows for straightforward construction of complex polyaryl systems, an attractive method for library synthesis of drug targets containing functionalized pyridine moieties. | 0 | Theoretical and Fundamental Chemistry |
In the early history of the Solar System, radioactive isotopes having a half-life on the order of a few million years (such as aluminium-26 and iron-60) were sufficiently abundant to produce enough heat to cause internal melting of some moons and even some asteroids, such as Vesta noted above. After these radioactive isotopes had decayed to insignificant levels, the heat generated by longer-lived radioactive isotopes (such as potassium-40, thorium-232, and uranium-235 and uranium-238) was insufficient to keep these bodies molten unless they had an alternative source of internal heating, such as tidal heating. Thus, Earth's Moon, which has no alternative source of internal heating is now geologically dead, whereas a moon as small as Enceladus that has sufficient tidal heating (or at least had it recently) and some remaining radioactive heating, is able to maintain an active and directly detectable cryovolcanism. | 0 | Theoretical and Fundamental Chemistry |
Pipe incorporating a flexible metallic layer as the middle of three bonded layers. Barrier pipe is used, for example, to provide additional protection for the contents passing through the pipe (particularly drinking water) from aggressive chemicals or other pollution when laid in ground contaminated by previous use.
Most plastic pipe systems are made from thermoplastic materials. The production method involves melting the material, shaping and then cooling. Pipes are normally produced by extrusion. | 1 | Applied and Interdisciplinary Chemistry |
John Joseph Jolly Kyle FRSA (2 February 1838 – 23 February 1922) was a pioneering Argentine chemist. Born and educated in Scotland, he emigrated to Argentina in 1862, and on the outbreak of the Paraguayan War served as a pharmacist in the Argentine Army medical corps. He became an Argentine citizen in 1873. At the time Kyle was active specialisation was not an option in Latin American chemistry and it was necessary for a chemist to be a sort of polymath or jack-of-all-trades. Kyle was appointed professor of chemistry at the Colegio Nacional de Buenos Aires in 1871, and chief chemist to the Casa de Moneda de la República Argentina (the Argentine Mint) in 1881. He was appointed professor of organic chemistry at the University of Buenos Aires (1889); Chemist to the Inspectorate-General of Sanitary Works (1890); professor of industrial chemistry at the Colegio Nacional (1892); and professor of inorganic chemistry at Buenos Aires University (1896). He was director of the first chemistry doctoral thesis in Argentina (1901).
The , awarded quinquennially by the Argentine Chemical Association for the best contribution to any branch of chemistry, and its most prestigious prize, is named in his honour. | 0 | Theoretical and Fundamental Chemistry |
Traditionally, chemical sensing has been approached with a system that contains a covalently bound indicator to a receptor though a linker. Once the analyte binds, the indicator changes color or fluoresces. This technique is called the indicator-spacer-receptor approach (ISR). In contrast to ISR, indicator-displacement assay (IDA) utilizes a non-covalent interaction between a receptor (the host), indicator, and an analyte (the guest). Similar to ISR, IDA also utilizes colorimetric (C-IDA) and fluorescence (F-IDA) indicators. In an IDA assay, a receptor is incubated with the indicator. When the analyte is added to the mixture, the indicator is released to the environment. Once the indicator is released it either changes color (C-IDA) or fluoresces (F-IDA).
IDA offers several advantages versus the traditional ISR chemical sensing approach. First, it does not require the indicator to be covalently bound to the receptor. Secondly, since there is no covalent bond, various indicators can be used with the same receptor. Lastly, the media in which the assay may be used is diverse.
Chemical sensing techniques such as C-IDA have biological implications. For example, protamine is a coagulant that is routinely administered after cardiopulmonary surgery that counter acts the anti-coagulant activity of herapin. In order to quantify the protamine in plasma samples, a colorimetric displacement assay is used. Azure A dye is blue when it is unbound, but when it is bound to herapin, it shows a purple color. The binding between Azure A and heparin is weak and reversible. This allows protamine to displace Azure A. Once the dye is liberated it displays a purple color. The degree to which the dye is displaced is proportional to the amount of protamine in the plasma.
F-IDA has been used by Kwalczykowski and co-workers to monitor the activities of helicase in E.coli. In this study they used thiazole orange as the indicator. The helicase unwinds the dsDNA to make ssDNA. The fluorescence intensity of thiazole orange has a greater affinity for dsDNA than ssDNA and its fluorescence intensity increases when it is bound to dsDNA than when it is unbound. | 0 | Theoretical and Fundamental Chemistry |
Intrinsic termination is cued by signals directly encoded in the DNA and RNA. Signal appears in as a hairpin and is followed by 8 Uridines at the 3' end. This leads to a rapid dissociation of the elongation complex . Hairpin inactivates and destabilizes the TEC by weakening interactions in the RNA-DNA binding site and other sites that hold this complex together. The pausing induced by the stretch of uracils is important and provides time for hairpin formation. In absence of U-tract, hair pin formation does not result in efficient termination, indicating its importance in this process.
The elongation destabilization process occurs in four steps
# as RNA Polymerase transcribes the final nucleotides of the terminator U-tract, it pauses at end of U-tract, favoring the termination pathway in the kinetic competition between elongation and termination
# Terminator hairpin (Thp) Nucleation
# hairpin completion and elongation complex inactivation
# elongation complex dissociation A complete mechanism is likely to involve specific interactions of the polymerase, the RNA terminator hairpin, and dT-rich template sequences. | 1 | Applied and Interdisciplinary Chemistry |
* ?? – Jan Baptist van Helmont performed his famous tree plant experiment in which he shows that the substance of a plant derives from water, a forerunner of the discovery of photosynthesis.
* 1628 – William Harvey published An Anatomical Exercise on the Motion of the Heart and Blood in Animals
* 1651 – William Harvey concluded that all animals, including mammals, develop from eggs, and spontaneous generation of any animal from mud or excrement was an impossibility.
* 1665 – Robert Hooke saw cells in cork using a microscope.
* In 1661, 1664 and 1665, the blood cells were discerned by Marcello Malpighi. In 1678, the red blood corpuscles was described by Jan Swammerdam of Amsterdam, a Dutch naturalist and physician. The first complete account of the red cells was made by Anthony van Leeuwenhoek of Delft in the last quarter of the 17th century.
* 1668 – Francesco Redi disproved spontaneous generation by showing that fly maggots only appear on pieces of meat in jars if the jars are open to the air. Jars covered with cheesecloth contained no flies.
* 1672 – Marcello Malpighi published the first description of chick development, including the formation of muscle somites, circulation, and nervous system.
* 1676 – Anton van Leeuwenhoek observed protozoa and calls them animalcules.
* 1677 – Anton van Leeuwenhoek observed spermatozoa.
* 1683 – Anton van Leeuwenhoek observed bacteria. Leeuwenhoek's discoveries renew the question of spontaneous generation in microorganisms. | 1 | Applied and Interdisciplinary Chemistry |
In order to better understand the cause of the spray inefficiency, it is useful to reflect on the implications of the large range of droplet sizes produced by typical (hydraulic) spray nozzles. This has long been recognized to be one of the most important concepts in spray application (e.g. Himel, 1969), bringing about enormous variations in the properties of droplets.
Historically, dose-transfer to the biological target (i.e. the pest) has been shown to be inefficient. However, relating "ideal" deposits with biological effect is fraught with difficulty, but in spite of Hislop's misgivings about detail, there have been several demonstrations that massive amounts of pesticides are wasted by run-off from the crop and into the soil, in a process called endo-drift. This is a less familiar form of pesticide drift, with exo-drift causing much greater public concern. Pesticides are conventionally applied using [http://www.dropdata.org/DD/noz_data.htm#hydraulic hydraulic atomisers], either on hand-held sprayers or tractor booms, where formulations are mixed into high volumes of water.
Different droplet sizes have dramatically different dispersal characteristics, and are subject to complex macro- and micro-climatic interactions (Bache & Johnstone, 1992). Greatly simplifying these interactions in terms of droplet size and wind speed, Craymer & Boyle concluded that there are essentially three sets of conditions under which droplets move from the nozzle to the target. These are where:
* sedimentation dominates: typically larger (>100 µm) droplets applied at low wind-speeds; droplets above this size are appropriate for minimising drift contamination by herbicides.
* turbulent eddies dominate: typically small droplets (<50 µm) that are usually considered most appropriate for targeting flying insects, unless an electrostatic charge is also present that provides the necessary force to attract droplets to foliage. (NB: the latter effects only operate at very short distances, typically under 10 mm.)
* intermediate conditions where both sedimentation and drift effects are important. Most agricultural insecticide and fungicide spraying is optimised by using relatively small (say 50-150 µm) droplets in order to maximize “coverage” (droplets per unit area), but are also subject to drift. | 1 | Applied and Interdisciplinary Chemistry |
In the case of female patients who want to be treated with HCG Pubergen, Pregnyl:
a) Since infertile female patients who undergo medically assisted reproduction (especially those who need in vitro fertilization), are known to often be suffering from tubal abnormalities, after a treatment with this drug they might experience many more ectopic pregnancies. This is why early ultrasound confirmation at the beginning of a pregnancy (to see whether the pregnancy is intrauterine or not) is crucial. Pregnancies that have occurred after a treatment with this drug have a higher risk of multiple pregnancy. Female patients who have thrombosis, severe obesity, or thrombophilia should not be prescribed this medicine as they have a higher risk of arterial or venous thromboembolic events after or during a treatment with HCG Pubergen, Pregnyl. b)Female patients who have been treated with this medicine are usually more prone to pregnancy losses.
In the case of male patients: A prolonged treatment with HCG Pubergen, Pregnyl is known to regularly lead to increased production of androgen. Therefore: Patients who have overt or latent cardiac failure, hypertension, renal dysfunction, migraines, or epilepsy might not be allowed to start using this medicine or may require a lower dose of HCG Pubergen, Pregnyl. This drug should be used with extreme caution in the treatment of prepubescent teenagers in order to reduce the risk of precocious sexual development or premature epiphyseal closure. This type of patients' skeletal maturation should be closely and regularly monitored.
Both male and female patients who have the following medical conditions must not start a treatment with HCG Pubergen, Pregnyl: (1) Hypersensitivity to this drug or to any of its main ingredients. (2) Known or possible androgen-dependent tumors for example male breast carcinoma or prostatic carcinoma. | 1 | Applied and Interdisciplinary Chemistry |
Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be a complex mixture of different hydrocarbons. In contrast to ordinary emulsions, microemulsions form upon simple mixing of the components and do not require the high shear conditions generally used in the formation of ordinary emulsions. The three basic types of microemulsions are direct (oil dispersed in water, o/w), reversed (water dispersed in oil, w/o) and bicontinuous.
In ternary systems such as microemulsions, where two immiscible phases (water and ‘oil’) are present with a surfactant, the surfactant molecules may form a monolayer at the interface between the oil and water, with the hydrophobic tails of the surfactant molecules dissolved in the oil phase and the hydrophilic head groups in the aqueous phase. | 0 | Theoretical and Fundamental Chemistry |
# Leave out the Bravais type
# Convert all symmetry elements with translational components into their respective symmetry elements without translation symmetry (Glide planes are converted into simple mirror planes; Screw axes are converted into simple axes of rotation)
# Axes of rotation, rotoinversion axes and mirror planes remain unchanged. | 0 | Theoretical and Fundamental Chemistry |
For higher grade applications such as ferrous metals, coal and industrial minerals, sensor-based ore sorting can be applied to create a final product. Pre-condition is, that the liberation allows for the creation of a sellable product. Undersize material is usually bypassed as product, but can also be diverted to the waste fraction, if the composition does not meet the required specifications. This is case and application dependent. | 0 | Theoretical and Fundamental Chemistry |
Nuclear magnetic resonance observes small differences in molecular reactions to oscillating magnetic fields. It is able to characterize atoms with active nuclides that have a non-zero nuclear spin (e.g., C, H, O Cl, N, Cl), which makes it particularly useful for identifying certain isotopes. In typical proton or 13C NMR, the chemical shifts of protiums (1H) and carbon-13 atoms within a molecule are measured, respectively, as they are excited by a magnetic field and then relax with a diagnostic resonance frequency. With site specific natural isotope fractionation (SNIF) NMR, the relaxation resonances of the deuterium and 13C atoms. NMR does not have the sensitivity to detect isotopologues with multiple rare isotopes. The only peaks that appear in a SNIF-NMR spectra are those of the isotopologues with a single rare isotope. Since the instrument is only measuring the resonances of the rare isotopes, each isotopologue will have one peak. For example, a molecule with six chemically unique carbon atoms will have six peaks in a 13C SNIF NMR spectrum. The site of 13C substitution can be determined by the chemical shift of each of the peaks. As a result, NMR is able to identify site specific isotope enrichments within molecules. | 0 | Theoretical and Fundamental Chemistry |
Oxidative addition and reductive elimination are invoked in many catalytic processes in homogeneous catalysis, e.g., hydrogenations, hydroformylations, hydrosilylations, etc. Cross-coupling reactions like the Suzuki coupling, Negishi coupling, and the Sonogashira coupling also proceed by oxidative addition. | 0 | Theoretical and Fundamental Chemistry |
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