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Aerobic granules have been successfully used in real wastewater treatment and are relatively new technology. It was started in the 1990s with a mixture of microbial communities generated into wastewater using an aerobic sequencing batch reactor. Aerobic granules are different from AGS due to their microbial flocs. Aerobic granules can still be effective even without the flocculating agents. Thus, the reduction of biomass makes the granules cost effective and more advantageous. Instead of having two tanks, the aeration tank and the settling tank, aerobic granules can use the same reactor for both treatments. By using one reactor we can save space and less time constructing a second tank, which takes lots of time and money. Making the switch from an AGR to aerobic granules saves 75% land capacity to create a wastewater treatment plant. | 1 | Applied and Interdisciplinary Chemistry |
The word alchemy comes from old French alquemie, alkimie, used in Medieval Latin as . This name was itself adopted from the Arabic word (). The Arabic in turn was a borrowing of the Late Greek term khēmeía (), also spelled khumeia () and khēmía (), with al- being the Arabic definite article the. Together this association can be interpreted as the process of transmutation by which to fuse or reunite with the divine or original form. Several etymologies have been proposed for the Greek term. The first was proposed by Zosimos of Panopolis (3rd–4th centuries), who derived it from the name of a book, the Khemeu. Hermann Diels argued in 1914 that it rather derived from χύμα, used to describe metallic objects formed by casting.
Others trace its roots to the Egyptian name (hieroglyphic 𓆎𓅓𓏏𓊖 ), meaning black earth, which refers to the fertile and auriferous soil of the Nile valley, as opposed to red desert sand. According to the Egyptologist Wallis Budge, the Arabic word ʾ actually means "the Egyptian [science]", borrowing from the Coptic word for "Egypt", (or its equivalent in the Mediaeval Bohairic dialect of Coptic, ). This Coptic word derives from Demotic , itself from ancient Egyptian . The ancient Egyptian word referred to both the country and the colour "black" (Egypt was the "black Land", by contrast with the "red Land", the surrounding desert). | 1 | Applied and Interdisciplinary Chemistry |
Alexander C. Filippou (born 19 August 1958, Thessaloniki, Greece) has been a Professor of Inorganic Chemistry at the Rheinische-Friedrich-Wilhelms-University Bonn since 2005. | 0 | Theoretical and Fundamental Chemistry |
Britain led the worlds Industrial Revolution with its early commitment to coal mining, steam power, textile mills, machinery, railways, and shipbuilding. Britains demand for iron and steel, combined with ample capital and energetic entrepreneurs, made it the world leader in the first half of the 19th century. Steel has a vital role during the industrial revolution.
In 1875, Britain accounted for 47% of world production of pig iron, a third of which came from the Middlesbrough area and almost 40% of steel. 40% of British output was exported to the U.S., which was rapidly building its rail and industrial infrastructure. Two decades later in 1896, however, the British share of world production had plunged to 29% for pig iron and 22.5% for steel, and little was sent to the U.S. The U.S. was now the world leader and Germany was catching up to Britain. Britain had lost its American market, and was losing its role elsewhere; indeed American products were now underselling British steel in Britain.
The growth of pig iron output was dramatic. Britain went from 1.3 million tons in 1840 to 6.7 million in 1870 and 10.4 in 1913. The US started from a lower base, but grew faster; from 0.3 million tons in 1840, to 1.7 million in 1870, and 31.5 million in 1913. Germany went from 0.2 million tons in 1859 to 1.6 in 1871 and 19.3 in 1913. France, Belgium, Austria-Hungary, and Russia, combined, went from 2.2 million tons in 1870 to 14.1 million tons in 1913, on the eve of the First World War. During the war the demand for artillery shells and other supplies caused a spurt in output and a diversion to military uses. | 1 | Applied and Interdisciplinary Chemistry |
The term "redox" stands for reduction-oxidation. It refers to electrochemical processes involving electron transfer to or from a molecule or ion, changing its oxidation state. This reaction can occur through the application of an external voltage or through the release of chemical energy. Oxidation and reduction describe the change of oxidation state that takes place in the atoms, ions or molecules involved in an electrochemical reaction. Formally, oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. An atom or ion that gives up an electron to another atom or ion has its oxidation state increase, and the recipient of the negatively charged electron has its oxidation state decrease.
For example, when atomic sodium reacts with atomic chlorine, sodium donates one electron and attains an oxidation state of +1. Chlorine accepts the electron and its oxidation state is reduced to −1. The sign of the oxidation state (positive/negative) actually corresponds to the value of each ion's electronic charge. The attraction of the differently charged sodium and chlorine ions is the reason they then form an ionic bond.
The loss of electrons from an atom or molecule is called oxidation, and the gain of electrons is reduction. This can be easily remembered through the use of mnemonic devices. Two of the most popular are "OIL RIG" (Oxidation Is Loss, Reduction Is Gain) and "LEO" the lion says "GER" (Lose Electrons: Oxidation, Gain Electrons: Reduction). Oxidation and reduction always occur in a paired fashion such that one species is oxidized when another is reduced. For cases where electrons are shared (covalent bonds) between atoms with large differences in electronegativity, the electron is assigned to the atom with the largest electronegativity in determining the oxidation state.
The atom or molecule which loses electrons is known as the reducing agent, or reductant, and the substance which accepts the electrons is called the oxidizing agent, or oxidant. Thus, the oxidizing agent is always being reduced in a reaction; the reducing agent is always being oxidized. Oxygen is a common oxidizing agent, but not the only one. Despite the name, an oxidation reaction does not necessarily need to involve oxygen. In fact, a fire can be fed by an oxidant other than oxygen; fluorine fires are often unquenchable, as fluorine is an even stronger oxidant (it has a weaker bond and higher electronegativity, and thus accepts electrons even better) than oxygen.
For reactions involving oxygen, the gain of oxygen implies the oxidation of the atom or molecule to which the oxygen is added (and the oxygen is reduced). In organic compounds, such as butane or ethanol, the loss of hydrogen implies oxidation of the molecule from which it is lost (and the hydrogen is reduced). This follows because the hydrogen donates its electron in covalent bonds with non-metals but it takes the electron along when it is lost. Conversely, loss of oxygen or gain of hydrogen implies reduction. | 0 | Theoretical and Fundamental Chemistry |
The consequence of an electron transfer is the rearrangement of charges, and this greatly influences the solvent environment. For the dipolar solvent molecules rearrange in the direction of the field of the charges (this is called orientation polarisation), and also the atoms and electrons in the solvent molecules are slightly displaced (atomic and electron polarization, respectively). It is this solvent polarization which determines the free energy of activation and thus the reaction rate.
Substitution, elimination and isomerization reactions differ from the outer sphere redox reaction not only in the structural changes outlined above, but also in the fact that the movements of the nuclei and the shift of charges (charge transfer, CT) on the reactions path take place in a continuous and concerted way: nuclear configurations and charge distribution are always "in equilibrium". This is illustrated by the S2 substitution of the saponification of an alkyl halide where the rear side attack of the OH ion pushes out a halide ion and where a transition state with a five-coordinated carbon atom must be visualized. The system of the reactants becomes coupled so tightly during the reaction that they form the activated complex as an integral entity. The solvent here has a minor effect.
By contrast, in outer sphere redox reactions the displacement of nuclei in the reactants are small, here the solvent has the dominant role. Donor-acceptor coupling is weak, both keep their identity during the reaction. Therefore, the electron, being an elementary particle, can only "jump" as a whole (electron transfer, ET). If the electron jumps, the transfer is much faster than the movement of the large solvent molecules, with the consequence that the nuclear positions of the reaction partners and the solvent molecules are the same before and after the electron jump (Franck–Condon principle). The jump of the electron is governed by quantum mechanical rules, it is only possible if also the energy of the ET system does not change "during" the jump.
The arrangement of solvent molecules depends on the charge distribution on the reactants. If the solvent configuration must be the same before and after the jump and the energy may not change, then the solvent cannot be in the solvation state of the precursor nor in that of the successor complex as they are different, it has to be somewhere in between. For the self-exchange reaction for symmetry reasons an arrangement of the solvent molecules exactly in the middle of those of precursor and successor complex would meet the conditions. This means that the solvent arrangement with half of the electron on both donor and acceptor would be the correct environment for jumping. Also, in this state the energy of precursor and successor in their solvent environment would be the same.
However, the electron as an elementary particle cannot be divided, it resides either on the donor or the acceptor and arranges the solvent molecules accordingly in an equilibrium. The "transition state", on the other hand, requires a solvent configuration which would result from the transfer of half an electron, which is impossible. This means that real charge distribution and required solvent polarization are not in an "equilibrium". Yet it is possible that the solvent takes a configuration corresponding to the "transition state", even if the electron sits on the donor or acceptor. This, however, requires energy. This energy may be provided by the thermal energy of the solvent and thermal fluctuations can produce the correct polarization state. Once this has been reached the electron can jump. The creation of the correct solvent arrangement and the electron jump are decoupled and do not happen in a synchronous process. Thus the energy of the transition state is mostly polarization energy of the solvent. | 0 | Theoretical and Fundamental Chemistry |
It is not necessary that the embryo transfer be performed on the female who provided the eggs. Thus another female whose uterus is appropriately prepared can receive the embryo and become pregnant.
Embryo transfer may be used where a woman who has eggs but no uterus and wants to have a biological baby; she would require the help of a gestational carrier or surrogate to carry the pregnancy. Also, a woman who has no eggs but a uterus may utilize egg donor IVF, in which case another woman would provide eggs for fertilization and the resulting embryos are placed into the uterus of the patient. Fertilization may be performed using the womans partners sperm or by using donor sperm. Spare embryos which are created for another couple undergoing IVF treatment but which are then surplus to that couples needs may also be transferred (called embryo donation). Embryos may be specifically created by using eggs and sperm from donors and these can then be transferred into the uterus of another woman. A surrogate may carry a baby produced by embryo transfer for another couple, even though neither she nor the commissioning' couple is biologically related to the child. Third party reproduction is controversial and regulated in many countries. Persons entering gestational surrogacy arrangements must make sense of an entirely new type of relationship that does not fit any of the traditional scripts we use to categorize relations as kinship, friendship, romantic partnership or market relations. Surrogates have the experience of carrying a baby that they conceptualize as not of their own kin, while intended mothers have the experience of waiting through nine months of pregnancy and transitioning to motherhood from outside of the pregnant body. This can lead to new conceptualizations of body and self. | 1 | Applied and Interdisciplinary Chemistry |
Two hydrated bilayers experience strong repulsion as they approach each other. These forces have been measured using the Surface forces apparatus (S.F.A), an instrument used for measuring forces between surfaces. This repulsion was first proposed by Langmuir and was thought to arise due to water molecules that hydrate the bilayers. Hydration repulsion can thus be defined as the work required in removing the water molecules around hydrophilic molecules (like lipid head groups) in the bilayer system. As water molecules have an affinity towards hydrophilic head groups, they try to arrange themselves around the head groups of the lipid molecules and it becomes very hard to separate this favorable combination.
Experiments performed through SFA have confirmed that the nature of this force is an exponential decline. The potential V is given by
where C (>0) is a measure of the hydration interaction energy for hydrophilic molecules of the given system, λ is a characteristic length scale of hydration repulsion and z is the distance of separation. In other words, it is on distances up to this length that molecules/surfaces fully experience this repulsion. | 0 | Theoretical and Fundamental Chemistry |
Halons are usually defined as hydrocarbons where the hydrogen atoms have been replaced by bromine, along with other halogens. They are referred to by a system of code numbers similar to (but simpler than) the system used for freons. The first digit specifies the number of carbon atoms in the molecule, the second is the number of fluorine atoms, the third is the chlorine atoms, and the fourth is the number of bromine atoms. If the number includes a fifth digit, the fifth number indicates the number of iodine atoms (though iodine in halon is rare). Any bonds not taken up by halogen atoms are then allocated to hydrogen atoms.
For example, consider Halon 1211. This halon has number 1211 in its name, which tells it has 1 carbon atom, 2 fluorine atoms, 1 chlorine atom, and 1 bromine atom. A single carbon only has four bonds, all of which are taken by the halogen atoms, so there is no hydrogen. Thus its formula is , hence its IUPAC name is bromochlorodifluoromethane. | 1 | Applied and Interdisciplinary Chemistry |
* the first wife - Raisa (died in 1906) - their marriage lasted 25 years.
* the second wife - Evgenia Kuzmina-Karavaeva, pianist - their marriage lasted 25 years.
**daughter Raisa Zelinskaya-Plate (1910-2001).
*the third wife - Nina Evgenievna Zhukovskaya-Bok, an artist - their marriage lasted 20 years.
**son Andrei (1933).
**son Nikolai (1940) | 0 | Theoretical and Fundamental Chemistry |
*"The Kalpa Sûtra" translated in English by Hermann Jacobi is published by Motilal Banarsidass Publishers in Delhi in " The Sacred Books of the East" (Vol 22) (1989) | 1 | Applied and Interdisciplinary Chemistry |
The role of the activators is primarily disruption and removal of the oxide layer on the metal surface (and also the molten solder), to facilitate direct contact between the molten solder and metal. The reaction product is usually soluble or at least dispersible in the molten vehicle. The activators are usually either acids, or compounds that release acids at elevated temperature.
The general reaction of oxide removal is:
:Metal oxide + Acid → Salt + Water
Salts are ionic in nature and can cause problems from metallic leaching or dendrite growth, with possible product failure. In some cases, particularly in high-reliability applications, flux residues must be removed.
The activity of the activator generally increases with temperature, up to a certain value where activity ceases, either due to thermal decomposition or excessive volatilization. However the oxidation rate of the metals also increases with temperature.
At high temperatures, copper oxide reacts with hydrogen chloride to water-soluble and mechanically weak copper chloride, and with rosin to salts of copper and abietic acid which is soluble in molten rosin.
Some activators may also contain metal ions, capable of exchange reaction with the underlying metal; such fluxes aid soldering by chemically depositing a thin layer of easier solderable metal on the exposed base metal. An example is the group of fluxes containing zinc, tin or cadmium compounds, usually chlorides, sometimes fluorides or fluoroborates. | 1 | Applied and Interdisciplinary Chemistry |
All polymers (amorphous or semi-crystalline) go through glass transitions. The glass-transition temperature (T) is a crucial physical parameter for polymer manufacturing, processing, and use. Below T, molecular motions are frozen and polymers are brittle and glassy. Above T, molecular motions are activated and polymers are rubbery and viscous. The glass-transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of plasticizers.
Whereas crystallization and melting are first-order phase transitions, the glass transition is not. The glass transition shares features of second-order phase transitions (such as discontinuity in the heat capacity, as shown in the figure), but it is generally not considered a thermodynamic transition between equilibrium states. | 0 | Theoretical and Fundamental Chemistry |
A muffle furnace or muffle oven (sometimes retort furnace in historical usage) is a furnace in which the subject material is isolated from the fuel and all of the products of combustion, including gases and flying ash. After the development of high-temperature heating elements and widespread electrification in developed countries, new muffle furnaces quickly moved to electric designs. | 1 | Applied and Interdisciplinary Chemistry |
The Medicines Discovery Catapult (MDC) is the United Kingdom's catapult centre for medicine research and innovation, headquartered at Alderley Park in Cheshire. | 1 | Applied and Interdisciplinary Chemistry |
The lithium metasilicate in the exposed regions of the glass can be etched by hydrofluoric acid (HF). This forms glass microstructures with a roughness in the range of 5 μm, resulting in a three-dimensional image of the mask to be produced. to 0.7 μm. | 0 | Theoretical and Fundamental Chemistry |
Aggregation-induced emission (AIE) is a phenomenon that is observed with certain organic luminophores (fluorescent dyes).
The photoemission efficiencies of most organic compounds is higher in solution than in the solid state. Photoemission from some organic compounds follows the reverse pattern, being greater in the solid than in solution. The effect is attributed to the decreased flexibility in the solid. | 0 | Theoretical and Fundamental Chemistry |
This assay was patented in 2006 by Randall Nelson, Peter Williams and Jennifer Reeve Krone. The idea first came about with the development of ELISA and RIA. An earlier patent method suggested tagging antigens or antibodies with stable isotopes or long-lived radioactive elements. But limitations to both methods called for a better detection methods of a protein or proteins. The invention combines antigen-antibody binding with a mass spectrometer which aids in identifying qualitatively and quantifying analytes respectively.
An early MSIA experiment was done on a venom laced human blood sample for the Antigen myotoxin. The experiment was successful in that the mass spectrum resulting from the analysis showed a distinct response for myotoxin at the molecular weight corresponding to 4,822 Da (a). The m/z ratio at 5,242 Da (b) is the molecular weight of the modified variant H-myotoxina, used as an internal reference species. The figure of the mass spectrum is shown below. | 1 | Applied and Interdisciplinary Chemistry |
Optimized configuration of pyroelectric sensors in optoelectronic technology. It has been shown that in the case of constant laser power, the response of the pyroelectric sensor would not depend on the spatial distribution of the intensity of the laser beam. Therefore, depending on the voltage model, the signal amplitude will be inversely proportional to the effective range of the sensor. In addition, the thermoelectric signal may increase once the effective area decreases and the total area of the sensor remains constant. Based on this, by optimizing the metal electrode structure of the sensor, a method is proposed to improve the PPE signal measured in voltage mode. The experiment shows that this improved method can increase the signal amplitude by 10 times without increasing the electrical noise. | 0 | Theoretical and Fundamental Chemistry |
Alkoxyaluminium hydrides are typically prepared by treatment of lithium aluminium hydride with the corresponding alcohol. Hydrogen evolution indicates the formation of alkoxyaluminium hydride products. Hindered hydrides such as lithium tri-(tert-butoxy)aluminium hydride (LTBA) are stable for long periods of time under inert atmosphere, but lithium trimethoxyaluminium hydride (LTMA) undergoes disproportionation and should be used immediately after preparation. Pure, solid Red-Al is stable for several hours under inert atmosphere and is available commercially as a 70%-solution in toluene under the trade name Vitride or Synhydrid. | 0 | Theoretical and Fundamental Chemistry |
Various techniques are available for strengthening concrete structures, to increase the load-carrying capacity or else to improve the in-service performance. These include increasing the concrete cross-section and adding material such as steel plate or fiber composites to enhance the tensile capacity or increase the confinement of the concrete for improved compression capacity. | 1 | Applied and Interdisciplinary Chemistry |
Hydrocyanation is an industrial method for producing nitriles from hydrogen cyanide and alkenes. The process requires homogeneous catalysts. An example of hydrocyanation is the production of adiponitrile, a precursor to nylon-6,6 from 1,3-butadiene: | 0 | Theoretical and Fundamental Chemistry |
Since the Civil War, North Alabama became one of the countrys leading iron and steel manufacturers. The Birmingham District was particularly well positioned to be an iron-and-steel production centre in the southern United States. The development of Alabamas iron and steel industry was primarily stimulated by the abundance of raw materials; coal, iron ore, limestone, and dolomite. The most powerful and profitable companies in North Alabama were those which had direct control over mines, as well as other facilities necessary for extracting and assembling raw materials, such as blast furnaces. Being dependent on raw materials and relevant infrastructural facilities, iron and steel makers expanded the furnaces in Alabama. Those manufacturers also attempted to incorporate new charging machines to increase the overall production of iron. Since iron and steel production was a resource-intensive industry this required powerful iron and steel manufacturing enterprises to hold a control over the regional railroads in Alabama. A typical example was the Woodward Iron Company whose holdings were mostly linked by a company-owned railroad. This railroad originally measured 12 miles in length but the company extended it outward from its blast furnaces, to its quarries of limestone and dolomite, and further to its coal mines and ore mines. | 1 | Applied and Interdisciplinary Chemistry |
As shown in Scheme 1, the first steps in the synthesis created the bicyclo[5.3.1]undecane AB ring system of Taxol. Reaction of epoxide 1 with tert-butyllithium removed the acidic α-epoxide proton, leading to an elimination reaction and simultaneous ring-opening of the epoxide to give allylic alcohol 2. The allylic alcohol was epoxidized to epoxyalcohol 3 using tert-butyl hydroperoxide and titanium(IV)tetraisopropoxide. In the subsequent reaction, the Lewis acid boron trifluoride catalyzed the ring opening of the epoxide followed by skeletal rearrangement and an elimination reaction to give unsaturated diol 4. The newly created hydroxyl group was protected as the triethylsilyl ether (5). A tandem epoxidation with meta-chloroperbenzoic acid and Lewis acid-catalyzed Grob fragmentation gave ketone 6, which was then protected as the tert-butyldimethylsilyl ether 7 in 94% yield over three steps. | 0 | Theoretical and Fundamental Chemistry |
The Rankine body, discovered by Scottish physicist and engineer Macquorn Rankine, is a feature of naval architecture involving the flow of liquid around a body/surface.
In fluid mechanics, a fluid flow pattern formed by combining a uniform stream with a source and a sink of equal strengths, with the line joining the source and sink along the stream direction, conforms to the shape of a Rankine body. | 1 | Applied and Interdisciplinary Chemistry |
Modern chemical and petrochemical processing plants are complex systems containing many steps (often called unit operations) involved in producing one or more products from various raw materials. In order to control the many processes, for both improved product quality and operational safety, many measurements are made at the different stages of processing. These measurements, either from simple sensors (such as temperature, pressure, flow, etc.) or from sophisticated chemical analyzers (providing composition of one or more components in the chemical stream), are typically used as inputs to process control algorithms to give a "snapshot" of the process operation and to control the process to ensure it is operating efficiently and safely.
Traditionally, most of the measurements (with the exception of temperature, pressure and flow) were performed "off-line" by taking a sample from the process and analyzing it in the laboratory. Beginning in the latter of part of the 1930s, a trend aimed at moving the analysis from the laboratory to the process plant began. With the advent of more sophisticated analyzers, this concept known as Process Analytics become much more prevalent in the 1980s and a new discipline called Process Analytical Chemistry (PAC) emerged which combined chemical engineering and analytical chemistry.
One of the main driving forces for PAC (See also: PAT) is to remove the bottleneck and time lag associated with sending the samples to the lab and waiting for the analysis results. By moving the analysis to the process, results can be obtained closer to real-time which effectively improves the ability for the control action to correct for process changes (i.e., feedback and feed forward control).
By far, the most common implementation of PAC (especially for more complex analyzers) utilizes what is known as extractive sampling. This typically involves the continuous (or sometimes periodic) removal of a small portion of sample from a much larger piping system or process vessel. This sample is then conditioned (filtered, pressure regulated, flow controlled, etc.) and introduced to the analyzer where the chemical composition or the intrinsic physical properties of process fluids (vapours and liquids) are measured. In industrial plants, the majority of sample systems and their related analyzers are installed in analyzer houses.
The hardware (traditionally metal tubing, compression fittings, valves, regulators, rotameters and filters) associated with extractive sampling is collectively referred to as the sampling system. Sample systems are used to condition or adjust the sample conditions (pressure, amount of particulate allowed, temperature and flow) to a level suitable for use with an analytical device (analyzer) such as a gas chromatograph, an oxygen analyzer or an infra red spectrometer. Despite the simple explanation just given, modern sampling systems can be quite large, complex, and expensive. The design features of analytical sample systems have changed little, when the discipline of Process Analytics began in Germany, right through until the present day. An example of an early analyzer and sample system used at the Buna Chemical Works (Schkopau, Germany), is shown in the following photograph. Process analytics remains exceptional in the fact that it is the last outpost of low level automation (retains manual adjustments and visible checks) within the process industries. | 1 | Applied and Interdisciplinary Chemistry |
Dry water or empty water, a form of "powdered liquid", is an air–water emulsion in which water droplets are surrounded by a silica coating. Dry water consists of 95% liquid water, but the silica coating prevents the water droplets from combining and turning back into a bulk liquid. The result is a white powder. | 0 | Theoretical and Fundamental Chemistry |
; Water–rock–bacteria nanoscience
: Although by no means developed, nearly all aspects (both geo- and bioprocesses) of weathering, soil, and water–rock interaction science are inexorably linked to nanoscience. Within the Earth's near-surface, materials that are broken down, as well as materials that are produced, are often in the nanoscale regime. Further, as organic molecules, simple and complex, as well as bacteria and all flora and fauna in soils and rocks interact with the mineral components present, nanodimensions and nanoscale processes are the order of the day.
; Metal transport nanoscience
: On land, researchers study how nanosized minerals capture toxins such as arsenic, copper, and lead from the soil. Facilitating this process, called soil remediation, is a tricky business.
Nanogeoscience is in a relatively early stage of development. The future directions of nanoscience in the geosciences will include a determination of the identity, distribution, and unusual chemical properties of nanosized particles and/or films in the oceans, on the continents, and in the atmosphere, and how they drive Earth processes in unexpected ways. Further, nanotechnology will be the key to developing the next generation of Earth and environmental sensing systems. | 0 | Theoretical and Fundamental Chemistry |
Oxide dispersion strengthening is based on incoherency of the oxide particles within the lattice of the material. Coherent particles have a continuous lattice plane from the matrix to the particles whereas incoherent particles do not have this continuity and therefore both lattice planes end at the interface. This mismatch in interfaces results in a high interfacial energy, which impedes dislocation. The oxide particles instead are stable in the matrix, which helps prevent creep. Particle stability implies little dimensional change, embrittlement, effects on properties, stable particle spacing, and general resistance to change at high temperatures.
Since the oxide particles are incoherent, dislocations can only overcome the particles by climb. If instead the particles are semi-coherent or coherent with the lattice, dislocations can simply cut the particles by a more favourable process that requires less energy called dislocation glide or by Orowan bowing between particles, both of which are athermal mechanisms. Dislocation climb is a diffusional process, which is less energetically favourable, and mostly occurs at higher temperatures that provide enough energy to advance via the addition and removal of atoms. Because the particles are incoherent, glide mechanisms alone are not enough and the more energetically exhausting climb process is dominant, meaning that dislocations are stopped more effectively. Climb can occur either at the particle-dislocation interface (local climb) or by overcoming multiple particles at once (general climb). In local climb, the part of the dislocation that is between two particles stays in the glide plane while the rest of the dislocation is climbing along the surface of the particle. For general climb, the dislocations all come out the glide plane. General climb requires less energy because the mechanism decreases the dislocation line length which reduces the elastic strain energy and therefore is the common climb mechanism. For γ’ volume fractions of 0.4 to 0.6 in nickel-based alloys, the threshold stress for local climb is only about 1.25 to 1.40 times higher than general climb.
Dislocations are not limited to either all local or all general climb as the path that requires less energy is taken. Cooperative climb is an example of a more nuanced mechanism where a dislocation travels around a group of particles rather than climbing past each particle individually. McLean stated that the dislocation is most relaxed when climbing over multiple particles because of the skipping of some of the abrupt interfaces between segments in the glide plane to segments that travel along the particle surface.
The presence of incoherent particles introduces a threshold stress (σ), since an additional stress will have to be applied for the dislocations to move past the oxides by climb. After overcoming a particle by climb, dislocations can remain pinned at the particle-matrix interface with an attractive phenomenon called interfacial pinning, which requires additional threshold stress to free a dislocation out of this pinning, which must be overcome for plastic deformation to occur. This detachment phenomenon is a result of the interaction between the particle and the dislocation where total elastic strain energy is reduced. Schroder and Arzt explain that the additional stress required is due to the relaxation caused by the reduction in the stress field as the dislocation climbs and accommodates the shear traction. The following equations represent the strain rate and stress as a result of oxide introduction.
Strain Rate:
Threshold Shear Stress: | 1 | Applied and Interdisciplinary Chemistry |
Flutamide has been researched and used extensively in the treatment of androgen-dependent skin and hair conditions in women including acne, seborrhea, hirsutism, and scalp hair loss, as well as in hyperandrogenism (e.g., in polycystic ovary syndrome or congenital adrenal hyperplasia), and is effective in improving the symptoms of these conditions. The dosages used are lower than those used in the treatment of prostate cancer. Although flutamide continues to be used for these indications, its use in recent years has been limited due to the risk of potentially fatal hepatotoxicity, and it is no longer recommended as a first- or second-line therapy. The related NSAA bicalutamide has also been found to be effective in the treatment of hirsutism in women and appears to have comparable effectiveness to that of flutamide, but has a far lower and only small risk of hepatotoxicity in comparison.
Aside from its risk of liver toxicity and besides other nonsteroidal antiandrogens, it has been said that flutamide is likely the best typically used antiandrogen medication for the treatment of androgen-dependent symptoms in women. This is related to its high effectiveness and minimal side effects. | 0 | Theoretical and Fundamental Chemistry |
For the bulk of carbonaceous adsorbents regeneration efficiency decreases over subsequent cycles as a result of pore blockages and damage to adsorption sites by the applied current. Decreases in regeneration efficiency are typically a further 2% per cycle. Current leading edge research focuses on developing adsorbents able to regenerate 100% of their adsorptive capacity through electrochemical regeneration. | 0 | Theoretical and Fundamental Chemistry |
For steady generalized Beltrami flow, we have and since it is also planar we have . Introduce the stream function
Integration of gives . So, complete solution is possible if it satisfies all the following three equations
A special case is considered when the flow field has uniform vorticity . Wang (1991) gave the generalized solution as
assuming a linear function for . Substituting this into the vorticity equation and introducing the separation of variables with the separating constant results in
The solution obtained for different choices of can be interpreted differently, for example, represents a flow downstream a uniform grid, represents a flow created by a stretching plate, represents a flow into a corner, represents an Asymptotic suction profile etc. | 1 | Applied and Interdisciplinary Chemistry |
Elizabeth Kujawinski is an American oceanographer who is Senior Scientist at the Woods Hole Oceanographic Institution, where she works as Program Director of the Center for Chemical Currencies of a Microbial Planet. Her research considers analytical chemistry, chemical oceanography, microbiology and microbial ecology. She is interested in what controls the composition of organic materials in aquatic systems. | 0 | Theoretical and Fundamental Chemistry |
Hyper-IL-6 has been used to test which cells depend on Interleukin-6 trans-signaling in their response to the cytokine Interleukin-6. To this end, cells were treated with Interleukin-6 and alternatively with Hyper-IL-6. Cells, which respond to Interleukin-6 alone do express an Interleukin-6 receptor whereas cells, which only respond to Hyper-IL-6 but not to Interleukin-6 alone depend in their response to the cytokine on Interleukin-6 trans-signaling. It turned out that hematopoietic stem cells, neural cells, smooth muscle cells and endothelial cells are typical target cells of Interleukin-6 trans-signaling. | 1 | Applied and Interdisciplinary Chemistry |
In September 2020, Morgan Boardman, an Industrial Fellow and Strategic Advisory Consultant with the Aspire Diamond Group at the South West Nuclear Hub of the University of Bristol, was appointed CEO of a new company called Arkenlight, which was created explicitly to commercialize their diamond battery technology and possibly other nuclear radiation devices under research or development at Bristol University. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, stereospecificity is the property of a reaction mechanism that leads to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one (or a subset) of the stereoisomers.
In contrast, stereoselectivity is the property of a reactant mixture where a non-stereospecific mechanism allows for the formation of multiple products, but where one (or a subset) of the products is favored by factors, such as steric access, that are independent of the mechanism.
A stereospecific mechanism specifies the stereochemical outcome of a given reactant, whereas a stereoselective reaction selects products from those made available by the same, non-specific mechanism acting on a given reactant. Given a single, stereoisomerically pure starting material, a stereospecific mechanism will give 100% of a particular stereoisomer (or no reaction), although loss of stereochemical integrity can easily occur through competing mechanisms with different stereochemical outcomes. A stereoselective process will normally give multiple products even if only one mechanism is operating on an isomerically pure starting material.
The term stereospecific reaction is ambiguous, since the term reaction itself can mean a single-mechanism transformation (such as the Diels–Alder reaction), which could be stereospecific, or the outcome of a reactant mixture that may proceed through multiple competing mechanisms, specific and non-specific. In the latter sense, the term stereospecific reaction is commonly misused to mean highly stereoselective reaction.
Chiral synthesis is built on a combination of stereospecific transformations (for the interconversion of existing stereocenters) and stereoselective ones (for the creation of new stereocenters), where also the optical activity of a chemical compound is preserved.
The quality of stereospecificity is focused on the reactants and their stereochemistry; it is concerned with the products too, but only as they provide evidence of a difference in behavior between reactants. Of stereoisomeric reactants, each behaves in its own specific way. Stereospecificity towards enantiomers is called enantiospecificity. | 0 | Theoretical and Fundamental Chemistry |
RO removes both harmful contaminants and desirable minerals. Some studies report some relation between long-term health effects and consumption of water low on calcium and magnesium, although these studies are of low quality. | 0 | Theoretical and Fundamental Chemistry |
Decreased TOR activity has been found to increase life span in S. cerevisiae, C. elegans, and D. melanogaster. The mTOR inhibitor rapamycin has been confirmed to increase lifespan in mice.
It is hypothesized that some dietary regimes, like caloric restriction and methionine restriction, cause lifespan extension by decreasing mTOR activity. Some studies have suggested that mTOR signaling may increase during aging, at least in specific tissues like adipose tissue, and rapamycin may act in part by blocking this increase. An alternative theory is mTOR signaling is an example of antagonistic pleiotropy, and while high mTOR signaling is good during early life, it is maintained at an inappropriately high level in old age. Calorie restriction and methionine restriction may act in part by limiting levels of essential amino acids including leucine and methionine, which are potent activators of mTOR. The administration of leucine into the rat brain has been shown to decrease food intake and body weight via activation of the mTOR pathway in the hypothalamus.
According to the free radical theory of aging, reactive oxygen species cause damage to mitochondrial proteins and decrease ATP production. Subsequently, via ATP sensitive AMPK, the mTOR pathway is inhibited and ATP-consuming protein synthesis is downregulated, since mTORC1 initiates a phosphorylation cascade activating the ribosome. Hence, the proportion of damaged proteins is enhanced. Moreover, disruption of mTORC1 directly inhibits mitochondrial respiration. These positive feedbacks on the aging process are counteracted by protective mechanisms: Decreased mTOR activity (among other factors) upregulates removal of dysfunctional cellular components via autophagy.
mTOR is a key initiator of the senescence-associated secretory phenotype (SASP). Interleukin 1 alpha (IL1A) is found on the surface of senescent cells where it contributes to the production of SASP factors due to a positive feedback loop with NF-κB. Translation of mRNA for IL1A is highly dependent upon mTOR activity. mTOR activity increases levels of IL1A, mediated by MAPKAPK2. mTOR inhibition of ZFP36L1 prevents this protein from degrading transcripts of numerous components of SASP factors. | 1 | Applied and Interdisciplinary Chemistry |
Single nucleotide polymorphism annotation (SNP annotation) is the process of predicting the effect or function of an individual SNP using SNP annotation tools. In SNP annotation the biological information is extracted, collected and displayed in a clear form amenable to query. SNP functional annotation is typically performed based on the available information on nucleic acid and protein sequences. | 1 | Applied and Interdisciplinary Chemistry |
The Association for Clinical Biochemistry and Laboratory Medicine is a United Kingdom-based learned society dedicated to the practice and promotion of clinical biochemistry. It was founded in 1953 and its official journal is the Annals of Clinical Biochemistry. The association is a full, national society member of the International Federation of Clinical Chemistry and Laboratory Medicine IFCC as well as a full member of the regional European Federation of Clinical Chemistry and Laboratory Medicine. | 1 | Applied and Interdisciplinary Chemistry |
Solar cell efficiency may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of these individual metrics.
The power conversion efficiency of a solar cell is a parameter which is defined by the fraction of incident power converted into electricity.
A solar cell has a voltage dependent efficiency curve, temperature coefficients, and allowable shadow angles.
Due to the difficulty in measuring these parameters directly, other parameters are substituted: thermodynamic efficiency, quantum efficiency, integrated quantum efficiency, V ratio, and fill factor. Reflectance losses are a portion of quantum efficiency under "external quantum efficiency". Recombination losses make up another portion of quantum efficiency, V ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of quantum efficiency, V ratio.
The fill factor is the ratio of the actual maximum obtainable power to the product of the open-circuit voltage and short-circuit current. This is a key parameter in evaluating performance. In 2009, typical commercial solar cells had a fill factor > 0.70. Grade B cells were usually between 0.4 and 0.7. Cells with a high fill factor have a low equivalent series resistance and a high equivalent shunt resistance, so less of the current produced by the cell is dissipated in internal losses.
Single p–n junction crystalline silicon devices are now approaching the theoretical limiting power efficiency of 33.16%, noted as the Shockley–Queisser limit in 1961. In the extreme, with an infinite number of layers, the corresponding limit is 86% using concentrated sunlight.
In 2014, three companies broke the record of 25.6% for a silicon solar cell. Panasonics was the most efficient. The company moved the front contacts to the rear of the panel, eliminating shaded areas. In addition they applied thin silicon films to the (high quality silicon) wafers front and back to eliminate defects at or near the wafer surface.
In 2015, a 4-junction GaInP/GaAs//GaInAsP/GaInAs solar cell achieved a new laboratory record efficiency of 46.1% (concentration ratio of sunlight = 312) in a French-German collaboration between the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), CEA-LETI and SOITEC.
In September 2015, Fraunhofer ISE announced the achievement of an efficiency above 20% for epitaxial wafer cells. The work on optimizing the atmospheric-pressure chemical vapor deposition (APCVD) in-line production chain was done in collaboration with NexWafe GmbH, a company spun off from Fraunhofer ISE to commercialize production.
For triple-junction thin-film solar cells, the world record is 13.6%, set in June 2015.
In 2016, researchers at Fraunhofer ISE announced a GaInP/GaAs/Si triple-junction solar cell with two terminals reaching 30.2% efficiency without concentration.
In 2017, a team of researchers at National Renewable Energy Laboratory (NREL), EPFL and CSEM (Switzerland) reported record one-sun efficiencies of 32.8% for dual-junction GaInP/GaAs solar cell devices. In addition, the dual-junction device was mechanically stacked with a Si solar cell, to achieve a record one-sun efficiency of 35.9% for triple-junction solar cells. | 0 | Theoretical and Fundamental Chemistry |
According to the FDA approved prescribing information, levofloxacin is pregnancy category C. This designation indicates that animal reproduction studies have shown adverse effects on the fetus and there are no adequate and well-controlled studies in humans, but the potential benefit to the mother may in some cases outweigh the risk to the fetus. Available data point to a low risk for the unborn child. Exposure to quinolones, including levofloxacin, during the first-trimester is not associated with an increased risk of stillbirths, premature births, birth defects, or low birth weight.
Levofloxacin does penetrate into breastmilk, though the concentration of levofloxacin in the breastfeeding infant is expected to be low. Due to potential risks to the baby, the manufacturer does not recommend that nursing mothers take levofloxacin. However, the risk appears to be very low, and levofloxacin can be used in breastfeeding mothers with proper monitoring of the infant, combined with delaying breastfeeding for 4–6 hours after taking levofloxacin. | 0 | Theoretical and Fundamental Chemistry |
In implicit scheme, the temperature is dependent at the new time level . After using implicit scheme, it was found that all coefficients are positive. It makes the implicit scheme unconditionally stable for any size of time step. This scheme is preferred for general purpose transient calculations because of its robustness and unconditional stability. The disadvantage of this method is that more procedures are involved and due to larger , truncation error is also larger. | 1 | Applied and Interdisciplinary Chemistry |
From Bjerrum plots, it is found that a decrease in the salinity of an aqueous fluid will act to increase the value of the carbon dioxide-carbonate system equilibrium constants, (pK*). This means that the relative proportion of carbonate with respect to carbon dioxide is higher in more saline fluids, e.g. seawater, than in fresher waters. Of crucial importance for paleoclimatology is the observation that an increase in salinity will thus reduce the solubility of carbon dioxide in the oceans. Since there is thought to have been a 120 m depression in sea level at the last glacial maximum due to the extensive formation of ice sheets (which are solely freshwater), this represents a significant fractionation towards saltier seas during glacial periods. Correspondingly, this will cause a net outgassing of carbon dioxide into the atmosphere because of its reduced solubility, acting to increase atmospheric carbon dioxide by 6.5‰. This is thought to partly offset the net decrease of 80-100‰ observed during glacial periods. | 0 | Theoretical and Fundamental Chemistry |
Humans have a deeply rooted history of not only being aware of toxicity, but also taking advantage of it as a tool. Archaeologists studying bone arrows from caves of Southern Africa have noted the likelihood that some aging 72,000 to 80,000 years old were dipped in specially prepared poisons to increase their lethality. Although scientific instrumentation limitations make it difficult to prove concretely, archaeologists hypothesize the practice of making poison arrows was widespread in cultures as early as the paleolithic era. The San people of Southern Africa have managed to preserved this practice into the modern era, with the knowledge base to form complex mixtures from poisonous beetles and plant derived extracts, yielding an arrow-tip product with a shelf life beyond several months to a year. | 1 | Applied and Interdisciplinary Chemistry |
Phosphoryl transfer only occurs on closing of the open lid. This causes an exclusion of water molecules that brings the substrates in proximity to each other, lowering the energy barrier for the nucleophilic attack by the α-phosphoryl of AMP on the γ-phosphoryl group of ATP resulting in formation of ADP by transfer of the γ-phosphoryl group to AMP. In the crystal structure of the ADK enzyme from E. coli with inhibitor Ap5A, the Arg88 residue binds the Ap5A at the α-phosphate group. It has been shown that the mutation R88G results in 99% loss of catalytic activity of this enzyme, suggesting that this residue is intimately involved in the phosphoryl transfer. Another highly conserved residue is Arg119, which lies in the adenosine binding region of the ADK, and acts to sandwich the adenine in the active site. It has been suggested that the promiscuity of these enzymes in accepting other NTPs is due to this relatively inconsequential interactions of the base in the ATP binding pocket. A network of positive, conserved residues (Lys13, Arg123, Arg156, and Arg167 in ADK from E. coli') stabilize the buildup of negative charge on phosphoryl group during the transfer. Two distal aspartate residues bind to the arginine network, causing the enzyme to fold and reduces its flexibility. A magnesium cofactor is also required, essential for increasing the electrophilicity of the phosphate on AMP, though this magnesium ion is only held in the active pocket by electrostatic interactions and dissociates easily. | 1 | Applied and Interdisciplinary Chemistry |
Maharram Əli oğlu Mammadyarov (; 17 October 1924 – 2 January 2022) was an Azerbaijani scientist, doctor of chemistry, real member of Azerbaijan National Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
Various methods are used to prevent and protect against corrosion, such as cathodic protection, selection and injection of chemicals such as corrosion inhibitors or other ways to prevent corrosion. However, in order to see the results of these methods and how effective these measures are, corrosion monitoring should be done and, if necessary, corrosion protection methods should be modified or optimized based on the results obtained from corrosion monitoring. In many industries, preventive measures are used to protect against corrosion, but obviously without knowing the results of these measures, protection is a chance, that is, either full protection will not be done or in case of excessive protection, it will waste capital and resources. | 1 | Applied and Interdisciplinary Chemistry |
There are several types of flowmeter that rely on Bernoulli's principle. The pressure is measured either by using laminar plates, an orifice, a nozzle, or a Venturi tube to create an artificial constriction and then measure the pressure loss of fluids as they pass that constriction, or by measuring static and stagnation pressures to derive the dynamic pressure. | 1 | Applied and Interdisciplinary Chemistry |
Consider the axisymmetric flow in cylindrical coordinate system with velocity components and vorticity components . Since in axisymmetric flows, the vorticity components are
Continuity equation allows to define a stream function such that
(Note that the vorticity components and are related to in exactly the same way that and are related to ). Therefore the azimuthal component of vorticity becomes
The inviscid momentum equations , where is the Bernoulli constant, is the fluid pressure and is the fluid density, when written for the axisymmetric flow field, becomes
in which the second equation may also be written as , where is the material derivative. This implies that the circulation round a material curve in the form of a circle centered on -axis is constant.
If the fluid motion is steady, the fluid particle moves along a streamline, in other words, it moves on the surface given by constant. It follows then that and , where . Therefore the radial and the azimuthal component of vorticity are
The components of and are locally parallel. The above expressions can be substituted into either the radial or axial momentum equations (after removing the time derivative term) to solve for . For instance, substituting the above expression for into the axial momentum equation leads to
But can be expressed in terms of as shown at the beginning of this derivation. When is expressed in terms of , we get
This completes the required derivation. | 1 | Applied and Interdisciplinary Chemistry |
Ultraviolet light can be generated by some light-emitting diodes, but wavelengths shorter than 380 nm are uncommon, and the emission peaks are broad, so only the very lowest energy UV photons are emitted, within predominant not visible light. | 0 | Theoretical and Fundamental Chemistry |
* River Dee, Wales and England
* River Mersey. The second highest tidal bore after the Severn bore, up to high. The bore tends to form around the Manchester Ship Canal.
* The Severn bore on the River Severn, Wales and England, up to high
* The Trent Aegir on the River Trent, England, up to high. Also other tributaries of the Humber Estuary.
* River Parrett
* River Welland
* The Arnside Bore on the River Kent
* River Great Ouse
* River Ouse, Yorkshire. Like the Trent bore, this is also known as "the Aegir".
* River Eden
* River Esk
* River Nene. This was also known as the Eagre.
* River Nith
* River Lune, Lancashire
* River Ribble, Lancashire
* River Yealm, Devon
* River Leven, Cumbria | 1 | Applied and Interdisciplinary Chemistry |
*Jan Anderson (Ph.D. 1959 Chemistry) - investigation of photosynthesis
*Frances Arnold (Ph.D. 1985 Chemical Engineering) - Nobel laureate (2018)
*Thomas Cech (Ph.D. 1975 Chemistry) - Nobel laureate (1989)
*Robert F. Curl, Jr. (Ph.D. 1957 Chemistry) - Nobel laureate (1996)
*Henry Eyring - (Ph.D. 1927 Chemistry) - National Medal of Science (1966)
*Andrew Grove (Ph.D. 1963 Chemical Engineering) - cofounder of Intel
*Richard A. Houghten (Ph.D. 1975 Chemistry) - Florida Inventors Hall of Fame (2018)
*Willis Lamb (B.S. 1934 Chemistry) - Nobel laureate in Physics (1955)
*Gordon Moore (B.S. 1950 Chemistry) - cofounder of Intel
*Mario Molina (Ph.D. 1972 Chemistry) - Nobel laureate (1995)
*Kary Mullis (Ph.D. 1972 Biochemistry) - Nobel laureate (1993)
*Geraldine Richmond (Ph.D. 1980 Chemistry) - Priestley Medal (2018)
*Susan Solomon (Ph.D. 1981 Atmospheric Chemistry) - Nobel Peace Prize (2007), National Medal of Science (1999)
*Henry Taube (Ph.D. 1940 Chemistry) - Nobel laureate (1983)
*Harold C. Urey (Ph.D. 1923 Chemistry) - Nobel laureate (1934)
*A.R. Frank Wazzan (B.S. 1959 Chemical Engineering) - Dean, UCLA School of Engineering and Applied Sciences 1986 - 2001.
*Ahmed Zewail (Postdoc. 1974 Chemistry) - Nobel laureate (1999) | 1 | Applied and Interdisciplinary Chemistry |
Various combinations of the driving force and moving phase determine various electrokinetic effects. According to J.Lyklema, the complete family of electrokinetic phenomena includes:
* electrophoresis, as motion of charged particles under influence of electric field;
* electro-osmosis, as motion of liquid in porous body under influence of electric field;
* diffusiophoresis, as motion of particles under influence of a chemical potential gradient;
* capillary osmosis, as motion of liquid in porous body under influence of the chemical potential gradient;
* sedimentation potential, as electric field generated by sedimenting colloid particles;
* streaming potential/current, as either electric potential or current generated by fluid moving through porous body, or relative to flat surface;
* colloid vibration current, as electric current generated by particles moving in fluid under influence of ultrasound;
* electric sonic amplitude, as ultrasound generated by colloidal particles in oscillating electric field. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, molecular Borromean rings are an example of a mechanically-interlocked molecular architecture in which three macrocycles are interlocked in such a way that breaking any macrocycle allows the others to dissociate. They are the smallest examples of Borromean rings. The synthesis of molecular Borromean rings was reported in 2004 by the group of J. Fraser Stoddart. The so-called Borromeate is made up of three interpenetrated macrocycles formed through templated self assembly as complexes of zinc.
The synthesis of the macrocyclic systems involves self-assembles of two organic building blocks: 2,6-diformylpyridine (an aromatic compound with two aldehyde groups positioned ortho to the nitrogen atom of the pyridine ring) and a symmetric diamine containing a meta-substituted 2,2'-bipyridine group. Zinc acetate is added as the template for the reaction, resulting in one zinc cation in each of the six pentacoordinate complexation sites. Trifluoroacetic acid (TFA) is added to catalyse the imine bond-forming reactions. The preparation of the tri-ring Borromeate involves a total of 18 precursor molecules and is only possible because the building blocks self-assemble through 12 aromatic pi-pi interactions and 30 zinc to nitrogen dative bonds. Because of these interactions, the Borromeate is thermodynamically the most stable reaction product out of potentially many others. As a consequence of all the reactions taking place being equilibria, the Borromeate is the predominant reaction product.
Reduction with sodium borohydride in ethanol affords the neutral Borromeand. With the zinc removed, the three macrocycles are no longer chemically bonded but remain "mechanically entangled in such a way that that if only one of the rings is removed the other two can part company." The Borromeand is thus a true Borromean system as cleavage of just one imine bond (to an amine and an acetal) in this structure breaks the mechanical bond between the three constituent macrocycles, releasing the other two individual rings. A borromeand differs from a [[catenane|[3]catenane]] in that none of its three macrocycles is concatenated with another other; if one bond in a [3]catenane is broken and a cycle removed, a [2]catenane can remain.
Organic synthesis of this seemingly complex compound is in reality fairly simple; for this reason, the Stoddart group has suggested it as a gram-scale laboratory activity for undergraduate organic chemistry courses. | 0 | Theoretical and Fundamental Chemistry |
Solvents can be broadly classified into two categories: polar and non-polar. A special case is elemental mercury, whose solutions are known as amalgams; also, other metal solutions exist which are liquid at room temperature.
Generally, the dielectric constant of the solvent provides a rough measure of a solvent's polarity. The strong polarity of water is indicated by its high dielectric constant of 88 (at 0 °C). Solvents with a dielectric constant of less than 15 are generally considered to be nonpolar.
The dielectric constant measures the solvents tendency to partly cancel the field strength of the electric field of a charged particle immersed in it. This reduction is then compared to the field strength of the charged particle in a vacuum. Heuristically, the dielectric constant of a solvent can be thought of as its ability to reduce the solutes effective internal charge. Generally, the dielectric constant of a solvent is an acceptable predictor of the solvent's ability to dissolve common ionic compounds, such as salts. | 1 | Applied and Interdisciplinary Chemistry |
Many azo pigments are non-toxic, although some, such as dinitroaniline orange, ortho-nitroaniline orange, or pigment orange 1, 2, and 5 have been found to be mutagenic. Likewise, several case studies have linked azo pigments with basal cell carcinoma. | 0 | Theoretical and Fundamental Chemistry |
In Cartesian coordinates the 3 basis vectors are represented by a cell tensor :
The volume of the unit cell, , is given by the determinant of the cell tensor:
For the special case of a cubic, tetragonal, or orthorhombic cell, the matrix is diagonal, and we have that: | 0 | Theoretical and Fundamental Chemistry |
The equilibrium reaction involving diamond is
Examining the oxygen fugacity of the upper mantle and transition enables us to compare it with the conditions (equilibrium reaction shown above) required for diamond formation. The results show that the is usually 2 units lower than the carbonate-carbon reaction which means favoring the formation of diamond at transition zone conditions.
It has also been reported that pH decrease would also facilitate the formation of diamond in Mantle conditions.
where the subscript aq means aqueous, implying H is dissolved in the solution.
Deep diamonds have become important windows to look into the mineralogy of the Earth's interior. Minerals not stable at the surface could possibly be found within inclusions of superdeep diamonds-- implying they were stable where these diamond crystallized. Because of the hardness of diamonds, the high pressure environment is retained even after transporting to the surface. So far, these superdeep minerals brought by diamonds include ringwoodite, ice-VII, cubic δ-N and Ca-perovskite. | 0 | Theoretical and Fundamental Chemistry |
Ligands can be decomplexed by displacement with another ligand, e.g., a highly basic ligand or the use of high pressures of carbon monoxide. Arenes are liberated from (arene)Cr(CO) with pyridine:
:(arene)Cr(CO) + 3 CHN → Cr(CO)(NCH) + arene
In this case Cr(CO)(pyridine) can be recycled. Illustrative of this approach is the synthesis of (–)-steganone via a chromium haloarene complex. The synthesis is completed by decomplexation, liberating the natural product.
1,4,7-Trithiacyclononane can be prepared within the coordination sphere of a metal, and then isolated by decomplexation. | 0 | Theoretical and Fundamental Chemistry |
He has published over 222 papers (200 indexed publications) coedited four books, 9 book chapters and 3 patents. H impact factor= 41 (Web of Science), H= 42 Scopus and H= 48 (Google Scholar) with more 7460 citations in Google. He has created three patents with the Chilean Navy on electrode materials for energy conversion. He has presented more than 300 papers in national and international meetings, including some plenary and invited lectures and keynotes worldwide. He has been a guest editor for the Journal of Applied Electrochemistry, The International Journal of Electrochemistry and recently in Current Opinion in Electrochemistry | 0 | Theoretical and Fundamental Chemistry |
Pyrite (FeS) is a mineral formed by the reaction of hydrogen sulfide (HS) and bioreactive iron (Fe). In oxic bottom waters pyrite can only form in sediments where HS is present. However, in iron-rich euxinic environments, pyrite formation can occur at higher rates in both the water column and in sediments due to higher concentrations of HS. Therefore the presence of euxinic conditions can be inferred by the ratio of pyrite-bound iron to the total iron in sediments. High ratios of pyrite-bound iron can be used as an indicator of past euxinic conditions. Similarly, if >45% of the bioreactive iron in sediments is pyrite-bound, then anoxic or euxinic conditions can be inferred. While useful, these methods do not provide definitive proof of euxinia because not all euxinic waters have the same concentrations of bioreactive iron available. These relationships have been found to be present in the modern euxinic Black Sea. | 0 | Theoretical and Fundamental Chemistry |
A magic pipe is a surreptitious change to a ship's oily water separator (OWS), or other waste-handing equipment, which allows waste liquids to be discharged in contravention of maritime pollution regulations. Such equipment alterations may allow hundreds of thousands of gallons of contaminated water to be discharged untreated, causing extensive pollution of marine waters. | 1 | Applied and Interdisciplinary Chemistry |
Observations of an extracellularly secreted glucosyltransferase (gtfG) sequentially proximal to and activated by an rgg gene with inverted repeats in the intergenic region of Streptococcus gordonii served as a basis for studying its homology between Streptococcus pyogenes. It was discovered that S. pyogenes also shared an rgg/ropB gene located directly next to the subject of its transcriptional regulation, in this case speB protease, with intergenic inverted repeats. Confirmation of linkage between rgg/ropB and speB secretion activation was achieved by means of ropB insertional disruption which resulted in decreased speB production. | 1 | Applied and Interdisciplinary Chemistry |
Prp24 has a molecular weight of 50 kDa and has been shown to contain four RNA recognition motifs (RRMs) and a conserved 12-amino acid sequence at the C-terminus. RRMs 1 and 2 have been shown to be important for high-affinity binding of U6, while RRMs 3 and 4 bind at lower affinity sites on U6. The first three RRMs interact extensively with each other and contain canonical folds that contain a four-stranded beta-sheet and two alpha-helices. The electropositive surface of RRMs 1 and 2 is a RNA annealing domain while the cleft between RRMs 1 and 2 including the beta-sheet face of RRM2 is a sequence-specific RNA binding site. The C-terminal motif is required for association with LSm proteins and contributes to substrate (U6) binding and not the catalytic rate of splicing. | 1 | Applied and Interdisciplinary Chemistry |
Although the energy difference between coplanar anisole and its isomer is quite large, the rotation between the O–CH bond becomes favorable when the electronic properties of methoxy group on aromatic rings need to be altered to stabilize an unusual intermediate or a transition state. In the following reaction, the regioselectivity could be rationalized as the out-of-plane rotation of the O–C bond which changes the methoxy group from an in-plane donor group to an out-of-plane acceptor group.
The intermediate of the above reaction is the di-anion and the stereoelectronic effect that stabilizes this intermediate over the other one is the fact that the anionic charge at the para position could delocalize to the oxygen atom via orbital interaction: π(benzene) → σ*(O–CH). | 0 | Theoretical and Fundamental Chemistry |
In quantum mechanical processes, the total number of particles may not be preserved. The concept is therefore generalized to the particle number operator, that is, the observable that counts the number of constituent particles. In quantum field theory, the particle number operator (see Fock state) is conjugate to the phase of the classical wave (see coherent state). | 0 | Theoretical and Fundamental Chemistry |
Intermolecular forces govern the particle interaction in self-assembled systems. The forces tend to be intermolecular in type rather than ionic or covalent because ionic or covalent bonds will “lock” the assembly into non-equilibrium structures. The types intermolecular forces seen in self-assembly processes are van der Waals, hydrogen bonds, and weak polar forces, just to name a few. In self-assembly, regular structural arrangements are frequently observed, therefore there must be a balance of attractive and repulsive between molecules otherwise an equilibrium distance will not exist between the particles. The repulsive forces can be electron cloud-electron cloud overlap or electrostatic repulsion. | 0 | Theoretical and Fundamental Chemistry |
Monosaccharides which contain an aldehyde group are known as aldoses, and those with a ketone group are known as ketoses. The aldehyde can be oxidized via a redox reaction in which another compound is reduced. Thus, aldoses are reducing sugars. Sugars with ketone groups in their open chain form are capable of isomerizing via a series of tautomeric shifts to produce an aldehyde group in solution. Therefore, ketones like fructose are considered reducing sugars but it is the isomer containing an aldehyde group which is reducing since ketones cannot be oxidized without decomposition of the sugar. This type of isomerization is catalyzed by the base present in solutions which test for the presence of reducing sugars. | 0 | Theoretical and Fundamental Chemistry |
The class IA phospholipid kinase, PI-3 kinase, is activated by the majority of RTKs. Similarly to other SH2 domain-containing proteins, PI-3 kinase forms a complex with PY sites on activated receptors. The main function of PI3K activation is the generation of PIP3, which functions as a second messenger to activate downstream tyrosine kinases Btk and Itk, the Ser/Thr kinases PDK1 and Akt (PKB). The major biological functions of Akt activation can be classified into three categories – survival, proliferation and cell growth. Akt is also known to be implicated in several cancers, particularly breast. PLCγ is immediately recruited by an activated RTK through the binding of its SH2 domains to phosphotyrosine sites of the receptor. After activation, PLCγ hydrolyses its substrate PtdIns(4,5)P2 and forms two second messengers, diacylglycerol and Ins(1,4,5)P3. Ins(1,4,5)P3 stimulates the release of Ca 2+ from intracellular supplies. Ca 2+ then binds to calmodulin, which subsequently activates a family of calmodulindependent protein kinases (CamKs). In addition, both diacylglycerol and Ca 2+ activate members of the PKC family. The second messengers generated by PtdIns(4,5)P2 hydrolysis stimulate a variety of intracellular processes such as proliferation, angiogenesis, cell motility. | 1 | Applied and Interdisciplinary Chemistry |
* 1593 – Galileo Galilei invents one of the first thermoscopes, also known as Galileo thermometer
* 1650 – Otto von Guericke builds the first vacuum pump
* 1660 – Robert Boyle experimentally discovers Boyle's Law, relating the pressure and volume of a gas (published 1662)
* 1665 – Robert Hooke published his book Micrographia, which contained the statement: "Heat being nothing else but a very brisk and vehement agitation of the parts of a body."
* 1667 – J. J. Becher puts forward a theory of combustion involving combustible earth in his book Physica subterranea (see Phlogiston theory).
* 1676–1689 – Gottfried Leibniz develops the concept of vis viva, a limited version of the conservation of energy
* 1679 – Denis Papin designed a steam digester which inspired the development of the piston-and-cylinder steam engine.
* 1694–1734 – Georg Ernst Stahl names Becher's combustible earth as phlogiston and develops the theory
* 1698 – Thomas Savery patents an early steam engine
* 1702 – Guillaume Amontons introduces the concept of absolute zero, based on observations of gases
* 1738 – Daniel Bernoulli publishes Hydrodynamica, initiating the kinetic theory
* 1749 – Émilie du Châtelet, in her French translation and commentary on Newtons Philosophiae Naturalis Principia Mathematica', derives the conservation of energy from the first principles of Newtonian mechanics.
* 1761 – Joseph Black discovers that ice absorbs heat without changing its temperature when melting
* 1772 – Blacks student Daniel Rutherford discovers nitrogen, which he calls phlogisticated air', and together they explain the results in terms of the phlogiston theory
* 1776 – John Smeaton publishes a paper on experiments related to power, work, momentum, and kinetic energy, supporting the conservation of energy
* 1777 – Carl Wilhelm Scheele distinguishes heat transfer by thermal radiation from that by convection and conduction
* 1783 – Antoine Lavoisier discovers oxygen and develops an explanation for combustion; in his paper "Réflexions sur le phlogistique", he deprecates the phlogiston theory and proposes a caloric theory
* 1784 – Jan Ingenhousz describes Brownian motion of charcoal particles on water
* 1791 – Pierre Prévost shows that all bodies radiate heat, no matter how hot or cold they are
* 1798 – Count Rumford (Benjamin Thompson) publishes his paper An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction detailing measurements of the frictional heat generated in boring cannons and develops the idea that heat is a form of kinetic energy; his measurements are inconsistent with caloric theory, but are also sufficiently imprecise as to leave room for doubt. | 0 | Theoretical and Fundamental Chemistry |
Concerns over the resistance to the freeze-thaw cycle have limited the use of pervious concrete in cold weather environments. The rate of freezing in most applications is dictated by the local climate. Entrained air may help protect the paste as it does in regular concrete. The addition of a small amount of fine aggregate to the mixture increases the durability of the pervious concrete. Avoiding saturation during the freeze cycle is the key to the longevity of the concrete. Related, having a well prepared 8 to 24 inch (200 to 600 mm) sub-base and a good drainage preventing water stagnation will reduce the possibility of freeze-thaw damage.
Using permeable concrete for pavements can make them safer for pedestrians in the winter because water won't settle on the surface and freeze leading to dangerously icy conditions. Roads can also be made safer for cars by the use of permeable concrete as the reduction in the formation of standing water will reduce the possibility of aquaplaning, and porous roads will also reduce tire noise. | 1 | Applied and Interdisciplinary Chemistry |
Norethisterone acetate (NETA), also known as norethindrone acetate and sold under the brand name Primolut-Nor among others, is a progestin medication which is used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders. The medication available in low-dose and high-dose formulations and is used alone or in combination with an estrogen. It is ingested orally.
Side effects of NETA include menstrual irregularities, headaches, nausea, breast tenderness, mood changes, acne, increased hair growth, and others. NETA is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It has weak androgenic and estrogenic activity and no other important hormonal activity. The medication is a prodrug of norethisterone in the body.
NETA was patented in 1957 and was introduced for medical use in 1964. It is sometimes referred to as a "first-generation" progestin. NETA is marketed widely throughout the world. It is available as a generic medication. | 1 | Applied and Interdisciplinary Chemistry |
The relative entropy was introduced by Solomon Kullback and Richard Leibler in as "the mean information for discrimination between and per observation from ", where one is comparing two probability measures , and are the hypotheses that one is selecting from measure (respectively). They denoted this by , and defined the "divergence between and " as the symmetrized quantity , which had already been defined and used by Harold Jeffreys in 1948. In , the symmetrized form is again referred to as the "divergence", and the relative entropies in each direction are referred to as a "directed divergences" between two distributions; Kullback preferred the term discrimination information. The term "divergence" is in contrast to a distance (metric), since the symmetrized divergence does not satisfy the triangle inequality. Numerous references to earlier uses of the symmetrized divergence and to other statistical distances are given in . The asymmetric "directed divergence" has come to be known as the Kullback–Leibler divergence, while the symmetrized "divergence" is now referred to as the Jeffreys divergence. | 0 | Theoretical and Fundamental Chemistry |
* ISO 15519-1:2010(en): Specification for diagrams for process industry — Part 1: General rules
* ISO 15519-2:2015(en): Specifications for diagrams for process industry — Part 2: Measurement and control
* ISO 10628-1:2014(en): Diagrams for the chemical and petrochemical industry — Part 1: Specification of diagrams
* ISO 10628-2:2012(en): Diagrams for the chemical and petrochemical industry — Part 2: Graphical symbols
* ANSI Y32.11: Graphical Symbols For Process Flow Diagrams (withdrawn 2003)
* SAA AS 1109: Graphical Symbols For Process Flow Diagrams For The Food Industry | 1 | Applied and Interdisciplinary Chemistry |
Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball bearing). Spalling and spallation both describe the process of surface failure in which spall is shed.
The terms spall, spalling, and spallation have been adopted by particle physicists; in neutron scattering instruments, neutrons are generated by bombarding a uranium (or other) target with a stream of atoms. The neutrons that are ejected from the target are known as "spall". | 1 | Applied and Interdisciplinary Chemistry |
Most diseases are heterogeneous in cause, meaning that one "disease" is often many different diseases at the molecular level, though symptoms exhibited and response to treatment may be identical. How diseases of different molecular origin respond to treatments is partially addressed in the discipline of pharmacogenomics.
Not listed here are the many kinds of cancers involving aberrant transcriptional regulation owing to creation of chimeric genes through pathological chromosomal translocation. Importantly, intervention in the number or structure of promoter-bound proteins is one key to treating a disease without affecting expression of unrelated genes sharing elements with the target gene. Some genes whose change is not desirable are capable of influencing the potential of a cell to become cancerous. | 1 | Applied and Interdisciplinary Chemistry |
Disulfide bonds play an important protective role for bacteria as a reversible switch that turns a protein on or off when bacterial cells are exposed to oxidation reactions. Hydrogen peroxide (HO) in particular could severely damage DNA and kill the bacterium at low concentrations if not for the protective action of the SS-bond. Archaea typically have fewer disulfides than higher organisms. | 0 | Theoretical and Fundamental Chemistry |
Visiting professor: University of British Columbia, Vancouver, Canada 1972; Energy Research Center, Hebrew University of Jerusalem, Israel, 1979; University of Strasbourg, France, 1990; University of Leuven, Belgium, 1991; University of Bordeaux, France, 1994. Chairman: Gruppo Italiano di Fotochimica (1982–1986), European Photochemistry Association (1988–92); XII IUPAC Symposium on Photochemistry (1988); International Symposium on "Photochemistry and Photophysics of Coordination Compounds (since 1989, now Honorary Chairman); PhD course in Chemistry Sciences (2002–2007) e Laurea specialistica in Photochemistry and Chemistry of Materials (2004–2007), University of Bologna.
Director: Institute of Photochemistry and High Energy Radiations (FRAE), National Research Council (Italy), Bologna (1977–1988) and Center for the Photochemical Conversion of Solar Energy, University of Bologna (1981–1998). Member of the Scientific Committee of several international scientific journals. Member of the Scientific Committee of the Urban Plan for Sustainable Mobility (PUMS), of the Bologna metropolitan area (2008–).
Political activity: In 2009 he started the Science and Society interdisciplinary course at the University of Bologna with the aim of bridging the gap between University and City; it has long been hoping for the strengthening of similar initiatives for the cultural growth of the Metropolitan City. In 2014 he founded the Energia per l'Italia group,[2] formed by 22 professors and researchers of the University and of the most important research centers of Bologna, with the aim of offering the Government and local politicians guidelines to tackle the energy problem according to a broad perspective that includes scientific, social, environmental and cultural aspects.
Coordinator and editor: Supramolecular Photochemistry, NATO ASI Series n. 214, Reidel, Dordrecht (1987); Supramolecular Chemistry, NATO ASI Series n. 371, Reidel, Dordrecht (1992) (with L. De Cola); Guest Editor, Supramolecular Photochemistry, New J. Chem., N.7–8, vol. 20 (1996); Editor in chief of the Handbook on Electron Transfer in Chemistry, in five volumes, Wiley-VCH, Weinheim (2001); Topics in Current Chemistry, volumes 280 and 281 on Photochemistry and Photophysics of Coordination Compounds (2007). | 0 | Theoretical and Fundamental Chemistry |
British physician George Oliver and physiologist Edward Albert Schäfer, professor at University College London, collaborated on the physiological effects of adrenal extracts. They first published their findings in two reports in 1894, a full publication followed in 1895. Though frequently falsely attributed to secretin, found in 1902 by Bayliss and Starling, Oliver and Schäfer's adrenal extract containing adrenaline, the substance causing the physiological changes, was the first hormone to be discovered. The term hormone would later be coined by Starling. | 1 | Applied and Interdisciplinary Chemistry |
Because the Edman degradation proceeds from the N-terminus of the protein, it will not work if the N-terminus has been chemically modified (e.g. by acetylation or formation of pyroglutamic acid). Sequencing will stop if a non-α-amino acid is encountered (e.g. isoaspartic acid), since the favored five-membered ring intermediate is unable to be formed. Edman degradation is generally not useful to determine the positions of disulfide bridges. It also requires peptide amounts of 1 picomole or above for discernible results. | 0 | Theoretical and Fundamental Chemistry |
Lersivirine belongs to the pyrazole family and is another next generation NNRTI in clinical trials developed by the pharmaceutical company ViiV Healthcare. The resistance profile is similar to that of other next generation NNRTIs. In the end of 2009 lersivirine was in phase IIb. In February 2013, ViiV Healthcare announced a stop of the development program investigating lersivirine. | 1 | Applied and Interdisciplinary Chemistry |
There are three types of glycosylation disorders sorted by the type of alterations that are made to the glycosylation process: congenital alterations, acquired alterations and non-enzymatic acquired alterations.
* Congenital alterations: Over 40 congenital disorders of glycosylation (CGDs) have been reported in humans. These can be divided into four groups: disorders of protein N-glycosylation, disorders of protein O-glycosylation, disorders of lipid glycosylation and disorders of other glycosylation pathways and of multiple glycosylation pathways. No effective treatment is known for any of these disorders. 80% of these affect the nervous system.
* Acquired alterations: In this second group the main disorders are infectious diseases, autoimmune illnesses or cancer. In these cases, the changes in glycosylation are the cause of certain biological events. For example, in Rheumatoid Arthritis (RA), the body of the patient produces antibodies against the enzyme lymphocytes galactosyltransferase which inhibits the glycosylation of IgG. Therefore, the changes in the N-glycosylation produce the immunodeficiency involved in this illness. In this second group we can also find disorders caused by mutations on the enzymes that control the glycosylation of Notch proteins, such as Alagille syndrome.
* Non-enzymatic acquired alterations: Non-enzymatic disorders, are also acquired, but they are due to the lack of enzymes that attach oligosaccharides to the protein. In this group the illnesses that stand out are Alzheimer's disease and diabetes.
All these diseases are difficult to diagnose because they do not only affect one organ, they affect many of them and in different ways. As a consequence, they are also hard to treat. However, thanks to the many advances that have been made in next-generation sequencing, scientists can now understand better these disorders and have discovered new CDGs. | 0 | Theoretical and Fundamental Chemistry |
Single-layer blue phosphorus was first produced in 2016 by the method of molecular beam epitaxy from black phosphorus as precursor. | 0 | Theoretical and Fundamental Chemistry |
Sucrose of fatty acid esters (E 473) is used for surface treatment of some climacteric fruits such as peaches, pears, cherries, apples, bananas, etc. E473 is allowed for application on fruit surfaces in the EU at whatever level is needed to achieve a technical effect (‘quantum satis’) and has limited allowance in the US as a component of protective coatings for fruits (CFR §172.859, limited categories inc. avocados, apples, limes [but not other citrus], peaches, pars, plums, pineapples).The coating preserves the fruits by blocking respiratory gases. | 0 | Theoretical and Fundamental Chemistry |
Axungia is a kind of soft animal fat, usually from around the kidneys of geese or pigs, used in pre-modern western medicine. It differs from lard, which is firm, and suet or adeps, which is dry.
The ancient Romans distinguished fat into pinguedo or axungia, and adeps or sebum; but writers often interchange the terms.
In pre-modern medicine, physicians made use of the axungia of the goose, the dog, the viper, and some others, especially that of humans, considered of "extraordinary service in the drawing and ripening of tumors, etc." (see attrahent) | 1 | Applied and Interdisciplinary Chemistry |
The thicknesses of SAMs can be measured using ellipsometry and X-ray photoelectron spectroscopy (XPS), which also give information on interfacial properties. The order in the SAM and orientation of molecules can be probed by Near Edge Xray Absorption Fine Structure (NEXAFS) and Fourier Transform Infrared Spectroscopy in Reflection Absorption Infrared Spectroscopy (RAIRS) studies. Numerous other spectroscopic techniques are used such as Second-harmonic generation (SHG), Sum-frequency generation (SFG), Surface-enhanced Raman scattering (SERS), as well as High-resolution electron energy loss spectroscopy (HREELS). The structures of SAMs are commonly determined using scanning probe microscopy techniques such as atomic force microscopy (AFM) and scanning tunneling microscopy (STM). STM has been able to help understand the mechanisms of SAM formation as well as determine the important structural features that lend SAMs their integrity as surface-stable entities. In particular STM can image the shape, spatial distribution, terminal groups and their packing structure. AFM offers an equally powerful tool without the requirement of the SAM being conducting or semi-conducting. AFM has been used to determine chemical functionality, conductance, magnetic properties, surface charge, and frictional forces of SAMs. The scanning vibrating electrode technique (SVET) is a further scanning probe microscopy which has been used to characterize SAMs, with defect free SAMs showing homogeneous activity in SVET. More recently, however, diffractive methods have also been used. The structure can be used to characterize the kinetics and defects found on the monolayer surface. These techniques have also shown physical differences between SAMs with planar substrates and nanoparticle substrates.
An alternative characterisation instrument for measuring the self-assembly in real time is dual polarisation interferometry where the refractive index, thickness, mass and birefringence of the self assembled layer are quantified at high resolution. Another method that can be used to measure the self-assembly in real-time is Quartz Crystal Microbalance with Dissipation monitoring technology where the mass and viscoelastic properties of the adlayer are quantified. Contact angle measurements can be used to determine the surface free-energy which reflects the average composition of the surface of the SAM and can be used to probe the kinetics and thermodynamics of the formation of SAMs. The kinetics of adsorption and temperature induced desorption as well as information on structure can also be obtained in real time by ion scattering techniques such as low energy ion scattering (LEIS) and time of flight direct recoil spectroscopy (TOFDRS). | 0 | Theoretical and Fundamental Chemistry |
Electron current is inherent to microbial metabolism. Microorganisms transfer electrons from an electron donor (lower potential species) to an electron acceptor (higher potential species). If the electron acceptor is an external ion or molecule, the process is called respiration. If the process is internal, electron transfer is called fermentation. The microorganism attempts to maximize their energy gain by selecting the electron acceptor with the highest potential available. In nature, mainly minerals containing iron or manganese oxides are reduced. Often soluble electron acceptors are depleted in the microbial environment. The microorganism can also maximize their energy by selecting a good electron donor that can be easily metabolized. These processes are done by extracellular electron transfer (EET). The theoretical free energy change (ΔG) for microorganisms relates directly to the potential difference between the electron acceptor and the donor. However, inefficiencies like internal resistance will decrease this free energy change. The advantage of these devices is their high selectivity in high speed processes limited by kinetic factors.
The most commonly studied species are Shewanella oneidensis and Geobacter sulfurreducens. However, more species have been studied in recent years.
On March 25, 2013, scientists at the University of East Anglia were able to transfer electrical charge by allowing bacteria to touch a metal or mineral surface. The research shows that it is possible to tether bacteria directly to electrodes. | 1 | Applied and Interdisciplinary Chemistry |
Protein adsorption is a process that has a fundamental role in the field of biomaterials. Indeed, biomaterial surfaces in contact with biological media, such as blood or serum, are immediately coated by proteins. Therefore, living cells do not interact directly with the biomaterial surface, but with the adsorbed proteins layer. This protein layer mediates the interaction between biomaterials and cells, translating biomaterial physical and chemical properties into a "biological language". In fact, cell membrane receptors bind to protein layer bioactive sites and these receptor-protein binding events are transduced, through the cell membrane, in a manner that stimulates specific intracellular processes that then determine cell adhesion, shape, growth and differentiation. Protein adsorption is influenced by many surface properties such as surface wettability, surface chemical composition and surface nanometre-scale morphology.
Surfactant adsorption is a similar phenomenon, but utilising surfactant molecules in the place of proteins. | 0 | Theoretical and Fundamental Chemistry |
In supramolecular chemistry, host–guest chemistry describes complexes that are composed of two or more molecules or ions that are held together in unique structural relationships by forces other than those of full covalent bonds. Host–guest chemistry encompasses the idea of molecular recognition and interactions through non-covalent bonding. Non-covalent bonding is critical in maintaining the 3D structure of large molecules, such as proteins and is involved in many biological processes in which large molecules bind specifically but transiently to one another.
Although non-covalent interactions could be roughly divided into those with more electrostatic or dispersive contributions, there are few commonly mentioned types of non-covalent interactions: ionic bonding, hydrogen bonding, van der Waals forces and hydrophobic interactions.
Host-guest interaction has raised dramatical attention since it was discovered. It is an important field, because many biological processes require the host-guest interaction, and it can be useful in some material designs. There are several typical host molecules, such as, cyclodextrin, crown ether, et al. | 0 | Theoretical and Fundamental Chemistry |
The stagnation point flow corresponds to a linear dependence on the coordinates, that can be described in the Cartesian coordinates with velocity components as follows
where are constants referred as the strain rates; these constants are not completely arbitrary since the continuity equation requires , that is to say, only two of the three constants are independent. We shall assume so that flow is towards the stagnation point in the direction and away from the stagnation point in the direction. Without loss of generality, one can assume that . The flow field can be categorized into different types based on a single parameter | 1 | Applied and Interdisciplinary Chemistry |
* when the electronegativity difference between two bonded atoms is very small (as in HPO). Two almost equivalent pairs of oxidation states, arbitrarily chosen, are obtained for these atoms.
* when an electronegative p-block atom forms solely homonuclear bonds, the number of which differs from the number of two-electron bonds suggested by rules. Examples are homonuclear finite chains like azide| (the central nitrogen connects two atoms with four two-electron bonds while only three two-electron bonds are required by 8 − N rule) or triiodide| (the central iodine connects two atoms with two two-electron bonds while only one two-electron bond fulfills the 8 − N rule). A sensible approach is to distribute the ionic charge over the two outer atoms. Such a placement of charges in a polysulfide (where all inner sulfurs form two bonds, fulfilling the 8 − N rule) follows already from its Lewis structure.
* when the isolated tandem of a heteronuclear and a homonuclear bond leads to a bonding compromise in between two Lewis structures of limiting bond orders. An example is NO:
:The typical oxidation state of nitrogen in NO is +1, which also obtains for both nitrogens by a molecular orbital approach. The formal charges on the right comply with electronegativities, which implies an added ionic bonding contribution. Indeed, the estimated N−N and N−O bond orders are 2.76 and 1.9, respectively, approaching the formula of integer bond orders that would include the ionic contribution explicitly as a bond (in green):
:Conversely, formal charges against electronegativities in a Lewis structure decrease the bond order of the corresponding bond. An example is carbon monoxide with a bond-order estimate of 2.6. | 0 | Theoretical and Fundamental Chemistry |
One can determine indirectly (via its relation with the structure factor ) using neutron scattering or x-ray scattering data. The technique can be used at very short length scales (down to the atomic level) but involves significant space and time averaging (over the sample size and the acquisition time, respectively). In this way, the radial distribution function has been determined for a wide variety of systems, ranging from liquid metals to charged colloids. Going from the experimental to is not straightforward and the analysis can be quite involved.
It is also possible to calculate directly by extracting particle positions from traditional or confocal microscopy. This technique is limited to particles large enough for optical detection (in the micrometer range), but it has the advantage of being time-resolved so that, aside from the statical information, it also gives access to dynamical parameters (e.g. diffusion constants) and also space-resolved (to the level of the individual particle), allowing it to reveal the morphology and dynamics of local structures in colloidal crystals, glasses, gels, and hydrodynamic interactions.
Direct visualization of a full (distance-dependent and angle-dependent) pair correlation function was achieved by a scanning tunneling microscopy in the case of 2D molecular gases. | 0 | Theoretical and Fundamental Chemistry |
A compound containing the epoxide functional group can be called an epoxy, epoxide, oxirane, and ethoxyline. Simple epoxides are often referred to as oxides. Thus, the epoxide of ethylene (CH) is ethylene oxide (CHO). Many compounds have trivial names; for instance, ethylene oxide is called "oxirane". Some names emphasize the presence of the epoxide functional group, as in the compound 1,2-epoxyheptane, which can also be called 1,2-heptene oxide.
A polymer formed from epoxide precursors is called an epoxy, but such materials do not contain epoxide groups (or contain only a few residual epoxy groups that remain unreacted in the formation of the resin). | 0 | Theoretical and Fundamental Chemistry |
Widespread interest and funding for research on regenerative medicine has prompted institutions in the United States and around the world to establish departments and research institutes that specialize in regenerative medicine including: The Department of Rehabilitation and Regenerative Medicine at Columbia University, the Institute for Stem Cell Biology and Regenerative Medicine at Stanford University, the Center for Regenerative and Nanomedicine at Northwestern University, the Wake Forest Institute for Regenerative Medicine, and the British Heart Foundation Centers of Regenerative Medicine at the University of Oxford. In China, institutes dedicated to regenerative medicine are run by the Chinese Academy of Sciences, Tsinghua University, and the Chinese University of Hong Kong, among others. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 4.569. | 0 | Theoretical and Fundamental Chemistry |
Neurturin signaling is mediated by the activation of a multi-component receptor system including the ret tyrosine kinase (RET), a cell-surface bound GDNF family receptor-α (GFRα) protein, and a glycosyl phosphatidylinositol (GPI)-linked protein. Neurturin preferentially binds to the GFRα2 co-receptor. Upon assembly of the complex, specific tyrosine residues are phosphorylated within two molecules of RET that are brought together to initiate signal transduction and the MAP kinase signaling pathway. | 1 | Applied and Interdisciplinary Chemistry |
Although there are many types of water masses, they all share characteristics. Water Masses are formed from regions of water having different temperatures. When ice is being formed in a cold climate like Antarctica, the cold temperatures separate the molecular bonds of the water causing it to become less dense. However, because water increases its volume by about 9% when frozen, this makes the ice less dense than the water which is why glaciers float. This also in turn causes the salinity of the water to decrease. The salinity of the water makes water freeze at lower temperatures than freshwater. Freshwater freezes at the standard 0 °C (32 °F), while saltwater freezes at an average of -2 °C (28.4 °F). | 0 | Theoretical and Fundamental Chemistry |
A simple substance (like water) may exist in equilibrium with its thermal decomposition products, effectively halting the decomposition. The equilibrium fraction of decomposed molecules increases with the temperature.
Since thermal decomposition is a kinetic process, the observed temperature of its beginning in most instances will be a function of the experimental conditions and sensitivity of the experimental setup. For a rigorous depiction of the process, the use of thermokinetic modeling is recommended.
main definition: Thermal decomposition is the breakdown of a compound into two or more different substances using heat, and it is an endothermic reaction | 0 | Theoretical and Fundamental Chemistry |
The conformation of any polymer is affected by a number of factors, notably the polymer architecture and the solvent affinity. In the case of polyelectrolytes, charge also has an effect. Whereas an uncharged linear polymer chain is usually found in a random conformation in solution (closely approximating a self-avoiding three-dimensional random walk), the charges on a linear polyelectrolyte chain will repel each other via double layer forces, which causes the chain to adopt a more expanded, rigid-rod-like conformation. The charges will be screened if the solution contains a great deal of added salt. Consequently, the polyelectrolyte chain will collapse to a more conventional conformation (essentially identical to a neutral chain in good solvent).
Polymer conformation affects many bulk properties (such as viscosity, turbidity, etc.). Although the statistical conformation of polyelectrolytes can be captured using variants of conventional polymer theory, it is, in general, quite computationally intensive to properly model polyelectrolyte chains, owing to the long-range nature of the electrostatic interaction.
Techniques such as static light scattering can be used to study polyelectrolyte conformation and conformational changes. | 0 | Theoretical and Fundamental Chemistry |
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