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Thermodynamic potentials are different quantitative measures of the stored energy in a system. Potentials are used to measure the energy changes in systems as they evolve from an initial state to a final state. The potential used depends on the constraints of the system, such as constant temperature or pressure. For example, the Helmholtz and Gibbs energies are the energies available in a system to do useful work when the temperature and volume or the pressure and temperature are fixed, respectively.
The five most well known potentials are:
where is the temperature, the entropy, the pressure, the volume, the chemical potential, the number of particles in the system, and is the count of particles types in the system.
Thermodynamic potentials can be derived from the energy balance equation applied to a thermodynamic system. Other thermodynamic potentials can also be obtained through Legendre transformation. | 0 | Theoretical and Fundamental Chemistry |
Microbial growth in alkaline conditions presents several complications to normal biochemical activity and reproduction, as high pH is detrimental to normal cellular processes. For example, alkalinity can lead to denaturation of DNA, instability of the plasma membrane and inactivation of cytosolic enzymes, as well as other unfavorable physiological changes. Thus, to adequately circumvent these obstacles, alkaliphiles must either possess specific cellular machinery that works best in the alkaline range, or they must have methods of acidifying the cytosol in relation to the extracellular environment. To determine which of the above possibilities an alkaliphile uses, experimentation has demonstrated that alkaliphilic enzymes possess relatively normal pH optimums. The determination that these enzymes function most efficiently near physiologically neutral pH ranges (about 7.5–8.5) was one of the primary steps in elucidating how alkaliphiles survive intensely basic environments. Since the cytosolic pH must remain nearly neutral, alkaliphiles must have one or more mechanisms of acidifying the cytosol when in the presence of a highly alkaline environment. | 1 | Applied and Interdisciplinary Chemistry |
Evelyn Brower Man (October 7, 1904 – September 3, 1992) was an American biochemist. She was a leading woman in developing the first test to detect hormone levels in the thyroid gland. | 1 | Applied and Interdisciplinary Chemistry |
The dynamic viscosity of water is about 0.89 mPa·s at room temperature (25 °C). As a function of temperature in kelvins, the viscosity can be estimated using the semi-empirical Vogel-Fulcher-Tammann equation:
where A = 0.02939 mPa·s, B = 507.88 K, and C = 149.3 K. Experimentally determined values of the viscosity are also given in the table below. The values at 20 °C are a useful reference: there, the dynamic viscosity is about 1 cP and the kinematic viscosity is about 1 cSt. | 1 | Applied and Interdisciplinary Chemistry |
Another important class of condensation polymers are polyesters. They arise from the reaction of a carboxylic acid and an alcohol. An example is polyethyleneterephthalate, the common plastic PETE (recycling #1 in the USA):
:n HO-X-OH + n HOC-Y-COH → [O-X-OC-Y-C(O)] + (2n-1) HO | 0 | Theoretical and Fundamental Chemistry |
Rotavirus mRNAs are capped but not polyadenylated, and viral proteins are translated by the cellular translation machinery. This is accomplished through the action of the viral Nonstructural Protein NSP3 which specifically binds the 3' consensus sequence of viral mRNAs and interacts with the eukaryotic translation initiation factor eIF4G I.
RoXaN (rotavirus X protein associated with NSP3) is 110-kDa cellular protein that contains a minimum of three regions predicted to be involved in protein–protein or nucleic acid–protein interactions. A tetratricopeptide repeat region, a protein–protein interaction domain most often found in multiprotein complexes, is present in the amino-terminal region. In the carboxy terminus, at least five zinc finger motifs are observed, further suggesting the capacity of RoXaN to bind other proteins or nucleic acids. Between these two regions exists a paxillin leucine-aspartate repeat (LD) motif which is involved in protein–protein interactions. | 1 | Applied and Interdisciplinary Chemistry |
Cells are least sensitive when in the S phase, then the G phase, then the G phase, and most sensitive in the M phase of the cell cycle. This is described by the law of Bergonié and Tribondeau, formulated in 1906: X-rays are more effective on cells which have a greater reproductive activity.
From their observations, they concluded that quickly dividing tumor cells are generally more sensitive than the majority of body cells. This is not always true. Tumor cells can be hypoxic and therefore less sensitive to X-rays because most of their effects are mediated by the free radicals produced by ionizing oxygen.
It has meanwhile been shown that the most sensitive cells are those that are undifferentiated, well nourished, dividing quickly and highly active metabolically. Amongst the body cells, the most sensitive are spermatogonia and erythroblasts, epidermal stem cells, gastrointestinal stem cells. The least sensitive are nerve cells and muscle fibers.
Very sensitive cells are also oocytes and lymphocytes, although they are resting cells and do not meet the criteria described above. The reasons for their sensitivity are not clear.
There also appears to be a genetic basis for the varied vulnerability of cells to ionizing radiation. This has been demonstrated across several cancer types and in normal tissues. | 0 | Theoretical and Fundamental Chemistry |
Within molecular and cell biology, Qa-1b is a MHC class I molecule and is the functional homolog of HLA-E in humans. Qa-1b is characterised by its limited polymorphisms and small peptide repertoire. Qa-1b binds to peptides derived from signal peptides of MHC class Ia molecule and interact with the CD94/NKG2 receptors on natural killer cells. The Qa-1b-peptide complex signals natural killer cells not to engage in cell lysis. Despite its homology with HLA-E, it seems that Qa-1b evolved a similar function to HLA-E coincidentally. | 1 | Applied and Interdisciplinary Chemistry |
The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
It is named after the Czech physicist and philosopher Ernst Mach.
where:
: is the local Mach number,
: is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and
: is the speed of sound in the medium, which in air varies with the square root of the thermodynamic temperature.
By definition, at Mach1, the local flow velocity is equal to the speed of sound. At Mach0.65, is 65% of the speed of sound (subsonic), and, at Mach1.35, is 35% faster than the speed of sound (supersonic). Pilots of high-altitude aerospace vehicles use flight Mach number to express a vehicle's true airspeed, but the flow field around a vehicle varies in three dimensions, with corresponding variations in local Mach number.
The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas. The Mach number is primarily used to determine the approximation with which a flow can be treated as an incompressible flow. The medium can be a gas or a liquid. The boundary can be travelling in the medium, or it can be stationary while the medium flows along it, or they can both be moving, with different velocities: what matters is their relative velocity with respect to each other. The boundary can be the boundary of an object immersed in the medium, or of a channel such as a nozzle, diffuser or wind tunnel channelling the medium. As the Mach number is defined as the ratio of two speeds, it is a dimensionless quantity. If < 0.2–0.3 and the flow is quasi-steady and isothermal, compressibility effects will be small and simplified incompressible flow equations can be used. | 1 | Applied and Interdisciplinary Chemistry |
In geometry, the order-3 snub heptagonal tiling is a semiregular tiling of the hyperbolic plane. There are four triangles and one heptagon on each vertex. It has Schläfli symbol of sr{7,3}. The snub tetraheptagonal tiling is another related hyperbolic tiling with Schläfli symbol sr{7,4}. | 0 | Theoretical and Fundamental Chemistry |
Cation-exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained. Barium (Ba) and ammonium (NH) are frequently used as exchanger cations, although many other methods are available.
CEC measurements depend on pH, and therefore are often made with a buffer solution at a particular pH value. If this pH differs from the natural pH of the soil, the measurement will not reflect the true CEC under normal conditions. Such CEC measurements are called "potential CEC". Alternatively, measurement at the native soil pH is termed "effective CEC", which more closely reflects the real value, but can make direct comparison between soils more difficult. | 0 | Theoretical and Fundamental Chemistry |
A rotaxane () is a mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (see graphical representation). The two components of a rotaxane are kinetically trapped since the ends of the dumbbell (often called stoppers) are larger than the internal diameter of the ring and prevent dissociation (unthreading) of the components since this would require significant distortion of the covalent bonds.
Much of the research concerning rotaxanes and other mechanically interlocked molecular architectures, such as catenanes, has been focused on their efficient synthesis or their utilization as artificial molecular machines. However, examples of rotaxane substructure have been found in naturally occurring peptides, including: cystine knot peptides, cyclotides or lasso-peptides such as microcin J25. | 0 | Theoretical and Fundamental Chemistry |
Treat the number of colors N, which is actually 3, as a large number, and expand in powers of 1/N. It turns out that at high density the higher-order corrections are large, and the expansion gives misleading results. | 0 | Theoretical and Fundamental Chemistry |
The cell determines whether the amphibolic pathway will function as an anabolic or catabolic pathway by enzyme–mediated regulation at a transcriptional and post-transcriptional level. As many reactions in amphibolic pathways are freely reversible or can be bypassed, irreversible steps that facilitate their dual function are necessary. The pathway uses a different enzyme for each direction for the irreversible step in the pathway, allowing independent regulation of catabolism and anabolism. Due their inherent duality, amphibolic pathways represent the regulation modes of both anabolic by its negative feedback end product and catabolic by feedback by energy indicator sequences. | 1 | Applied and Interdisciplinary Chemistry |
Alogliptin (Figure 9) is a novel DPP-4 inhibitor developed by the Takeda Pharmaceutical Company. Researchers hypothesized that a quinazolinone based structure (Figure 9) would have the necessary groups to interact with the active site on the DPP-4 complex. Quinazolinone based compounds interacted effectively with the DPP-4 complex, but suffered from low metabolic half-life. It was found that when replacing the quinazolinone with a pyrimidinedione, the metabolic stability was increased and the result was a potent, selective, bioavailable DPP-4 inhibitor named alogliptin. The quinazoline based compounds showed potent inhibition and excellent selectivity over related protease, DPP-8. However, short metabolic half-life due to oxidation of the A-ring phenyl group was problematic. At first, the researchers tried to make a fluorinated derivative. The derivative showed improved metabolic stability and excellent inhibition of the DPP-4 enzyme. However, it was also found to inhibit CYP 450 3A4 and block the hERG channel. The solution to this problem was to replace the quinazolinone with other heterocycles, but the quinazolinone could be replaced without any loss of DPP-4 inhibition. Alogliptin was discovered when quinazolinone was replaced with a pyrimidinedione. Alogliptin has shown excellent inhibition of DPP-4 and extraordinary selectivity, greater than 10.000 fold over the closely related serine proteases DPP-8 and DPP-9. Also, it does not inhibit the CYP 450 enzymes nor block the hERG channel at concentration up to 30 µM. Based on this data, alogliptin was chosen for preclinical evaluation. In January 2007 alogliptin was undergoing the phase III clinical trial and in October 2008 it was being reviewed by the U.S. Food and Drug Administration. | 1 | Applied and Interdisciplinary Chemistry |
Mutations in K2.3 are suspected to be a possible underlying cause for several neurological disorders, including schizophrenia, bipolar disorder, Alzheimer's disease, anorexia nervosa and ataxia as well as myotonic muscular dystrophy. | 1 | Applied and Interdisciplinary Chemistry |
If water is left to stand in a tube for an extended period, the chemical characteristics of the water change as the mixed scale and corrosion products are deposited. In addition any loose scale that is not well adhered to the wall will not be flushed away and air dissolved in the water will form bubbles, producing air pockets. These processes can lead to a number of problems mainly on horizontal tube runs. Particles of scale that do not adhere to the walls and are not washed away tend to fall into the bottom of the tube producing a coarse porous deposit. Air pockets that develop in horizontal runs disrupt the formation of protective scales in two areas: the water lines at the sides, and the air space at the top of the tube.
In each of the areas that the scale has been disrupted there is the possibility of the initiation of Type 1 pitting. Once pitting has initiated, then even after the tube has been put back into service, the pit will continue to develop until the wall has perforated. This form of attack is often associated with the commissioning of a system. Once a system has been commissioned it should be either put immediately into service or drained down and dried by flushing with compressed air otherwise pitting may initiate. If either of these options is not possible then the system should be flushed through regularly until it is put into use. | 1 | Applied and Interdisciplinary Chemistry |
Piano stool complexes of the type (η-CH)M(CO) are typically synthesized by heating the appropriate metal carbonyl compound with benzene. Alternately, the same compounds can be obtained by carbonylation of the bis(arene) sandwich compounds, such as (η-CH)M compound with the metal carbonyl compound. This second approach may be more appropriate for arene ligands containing thermally fragile substituents. | 0 | Theoretical and Fundamental Chemistry |
One of the most outspoken critics of some concepts of "molecular assemblers" was Professor Richard Smalley (1943–2005) who won the Nobel prize for his contributions to the field of nanotechnology. Smalley believed that such assemblers were not physically possible and introduced scientific objections to them. His two principal technical objections were termed the "fat fingers problem" and the "sticky fingers problem". He believed these would exclude the possibility of "molecular assemblers" that worked by precision picking and placing of individual atoms. Drexler and coworkers responded to these two issues in a 2001 publication.
Smalley also believed that Drexlers speculations about apocalyptic dangers of self-replicating machines that have been equated with "molecular assemblers" would threaten the public support for development of nanotechnology. To address the debate between Drexler and Smalley regarding molecular assemblers Chemical & Engineering News' published a point-counterpoint consisting of an exchange of letters that addressed the issues. | 0 | Theoretical and Fundamental Chemistry |
Samples of water from the natural environment are routinely taken and analysed as part of a pre-determined monitoring programme by regulatory authorities to ensure that waters remain unpolluted, or if polluted, that the levels of pollution are not increasing or are falling in line with an agreed remediation plan. An example of such a scheme is the harmonised monitoring scheme operated on all the major river systems in the UK. The parameters analysed will be highly dependent on nature of the local environment and/or the polluting sources in the area. In many cases the parameters will reflect the national and local water quality standards determined by law or other regulations. Typical parameters for ensuring that unpolluted surface waters remain within acceptable chemical standards include pH, major cations and anions including ammonia, nitrate, nitrite, phosphate, conductivity, phenol, chemical oxygen demand (COD) and biochemical oxygen demand (BOD). | 0 | Theoretical and Fundamental Chemistry |
*Aerosol compound
**Cone pattern dispersion - wide pattern, don't have to aim precisely. It can be blown back by wind and if used inside a building, will eventually make room temporarily uninhabitable.
**Fog pattern dispersion (fogger)
**Stream pattern dispersion
**Grenade
*Gel compound: has greater accuracy and a reduced risk of blowback and area cross-contamination as the carrying gel does not disperse over a large area. The gel compound also adheres to the target making it more difficult to remove.
*Foam compound | 1 | Applied and Interdisciplinary Chemistry |
Supramolecular polymers usually prepared in solution. However anomalous polymeric properties can be expected when these polymers are prepared without a conventional organic or aqueous medium. For instance, liquid crystal media may affect the elementary steps of supramolecular polymerization as demonstrated by Takashi Kato in 1998, in the supramolecular crosslinking polymerization of physical gelators, which form a liquid crystal physical gel. When monomers are designed to be highly affinitive toward the LC media, supramolecular polymerization causes an order-increasing phase transition, resulting in a core-shell columnar LC. Supramolecular polymers can also be prepared in the solid-state, for instance, a nucleobase-appended telechelic oligomer as a monomer, resulted in the formation of 1D fibers upon cooling from its hot melt. As a new class of materials, supramolecular polymers formed at electrode and at the interface also become available. | 0 | Theoretical and Fundamental Chemistry |
A USB sound card can serve as a cheap, consumer off-the-shelf ADC, a technique pioneered by Marek Dolleiser. The data is sent to the computer as normal sound and stored in a WAV file. Specialized software processes the "sound" to perform pulse-height analysis and multichannel scaling, forming a complete MCA.
Sound cards have high-speed but low-resolution (up to 192 kHz) ADC chips, allowing for reasonable gamma spectroscopy performance for a low-to-medium count rate. The "sound card spectrometer" has been further refined in amateur and professional circles. | 0 | Theoretical and Fundamental Chemistry |
As an approximation, the roughness length is approximately one-tenth of the height of the surface roughness elements. For example, short grass of height 0.01 meters has a roughness length of approximately 0.001 meters. Surfaces are rougher if they have more protrusions. Forests have much larger roughness lengths than tundra, for example. Roughness length is an important concept in urban meteorology as the building of tall structures, such as skyscrapers, has an effect on roughness length and wind patterns.
For urban areas, the roughness length changes with the wind direction | 1 | Applied and Interdisciplinary Chemistry |
The boiling point of an element (or its compounds) is able to control the percentage of that element that a power reactor accident releases. The ability of an element to form a solid controls the rate it is deposited on the ground after having been injected into the atmosphere by a nuclear detonation or accident. | 0 | Theoretical and Fundamental Chemistry |
* 1669 - In his book De solido intra solidum naturaliter contento Nicolas Steno asserted that, although the number and size of crystal faces may vary from one crystal to another, the angles between corresponding faces are always the same. This was the original statement of the first law of crystallography (Steno's law). | 1 | Applied and Interdisciplinary Chemistry |
These case studies represent some potential applications for position specific isotope analysis, but certainly not all. The opportunities for samples to measure and processes to characterize are virtually unlimited, and new methodological developments will help make these measurements possible going forward. | 0 | Theoretical and Fundamental Chemistry |
A number of researchers have pointed out that the harm caused by communicating with patients about potential treatment adverse events raises an ethical issue. In order to respect autonomy, one is required to inform a patient about what harms a treatment is likely to cause. Yet the way in which potential harms are communicated could cause additional harm, which may violate the ethical principle of non-maleficence. It may be possible that nocebo effects can be reduced while respecting autonomy using different models of informed consent, including the use of a framing effect and the authorized concealment. | 1 | Applied and Interdisciplinary Chemistry |
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S or a compound containing one or more S ions. Solutions of sulfide salts are corrosive. Sulfide also refers to large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (HS) and bisulfide (SH) are the conjugate acids of sulfide. | 0 | Theoretical and Fundamental Chemistry |
Numerous gold artifacts recovered in the Philippines are believed to have ceremonial purposes. Some of these figures indicate the Hindu and Buddhist influence which came to the Philippines through regional trade in maritime southeast asia, while others reflect nature-based religious beliefs.
A notable artifact reflecting indigenous beliefs depicts what has been described as "the large, triangular face of a woman drawn in sharp lines with little shoulders and arms raised in a gesture of worship."
Visayan indigenous healing beliefs are likewise reflected in a particular variant of kamagi necklaces known as "tunga," which were snake-like in shape and made of “half gold and half tumbaga” gears strung together. These were believed to protect the wearer from the "folk illness" known as pasma.
Other notable ceremonial artifacts include: the Agusan Image which depicts a female Hindu or Buddhist deity whose identity is disputed, and the gold kinnari, which shows a mythical half-human half-bird figure common in hindu and buddhist parts of Maritime Southeast Asia. | 1 | Applied and Interdisciplinary Chemistry |
NeSSI (for New Sampling/Sensor Initiative) is a global and open initiative sponsored by the Center for Process Analysis and Control (CPAC) at the University of Washington, in Seattle.
The NeSSI initiative was begun to simplify the tasks and reduce the overall costs associated with engineering, installing, and maintaining chemical process analytical systems. Process analytical systems are commonly used by the chemical, oil refining and petrochemical industries to measure and control both chemical composition as well as certain intrinsic physical properties (such as viscosity). The specific objectives of NeSSI are:
# Increasing the reliability of these systems through the use of increased automation,
# Shrinking their physical size and energy use by means of miniaturization,
# Promoting the creation and use of industry standards for process analytical systems,
# Helping create the infrastructure needed to support the use of the emerging class of robust and selective microAnalytical sensors.
To date, NeSSI has served as a forum for the adoption and improvement of an industrial standard which specifies the use of miniature and modular Lego-like flow components. NeSSI has also issued a specification which has been instrumental in spurring the development and commercialization of a plug and play low power communication bus (NeSSI-bus) specifically designed for use with process analytical sample systems in electrically hazardous environments. As part of its development road map, NeSSI has defined the electrical and mechanical interfaces, as well as compiled a list of automated (smart) software features, which are now beginning to be used by microanalytical manufacturers for industrial applications. | 1 | Applied and Interdisciplinary Chemistry |
The Stokes-Einstein equation describes a frictional force on a sphere of diameter as where is the viscosity of the solution. Inserting this into 9 gives an estimate for as , where R is the gas constant, and is given in centipoise. For the following molecules, an estimate for is given: | 0 | Theoretical and Fundamental Chemistry |
Hattori has made contributions to the field of earth sciences, utilizing trace element geochemistry and stable and radiogenic isotopes to understand the earth processes. During the early stages of her career, she focused on studying active volcanoes and associated hydrothermal activity. However, a tragic accident atop a Colombian volcano, resulting in the loss of several colleagues, prompted her to shift her research focus to ancient volcanic terranes in Canada. Over the past 14 years, she has conducted research in various regions of subduction zones worldwide, where oceanic crust subducts and forms arc volcanoes and mountain belts. Her investigations involve examining rocks and collecting samples to analyze the intricate processes of subduction and the subsequent return of materials to the surface through volcanoes. Her research areas have included the Himalayas (Northern Pakistan, Northern India), Italian and French Alps, Turkey, China, Japan, Philippines, Peru, and the Dominican Republic.
Hattoris contributions to the earth sciences primarily center on utilizing the abundance of redox-sensitive elements and their isotopic compositions to interpret processes from the surface to the mantle. Her discoveries include the timing of the abrupt rise in atmospheric oxygen content at around 2.2 billion years ago during Earths evolution, the definition of osmium isotope evolution in the mantle, the identification of serpentine as the reservoir of water and fluid-mobile elements in the mantle, and the provision of evidence that oxidized mafic magmas bring base metals and sulfur from the mantle to form giant copper deposits that supply many critical metals for society. In addition, her work has contributed to the discovery of such critical metal deposits through the mobility of metals in surface waters. | 0 | Theoretical and Fundamental Chemistry |
Iron isotopes have been applied for a number of purposes on planetary bodies. Their variations have been measured to more precisely determine the processes that occurred during planetary accretion. In the future, the comparison of observed biological fractionation of iron on Earth to fractionation on other planetary bodies may have astrobiological implications. | 0 | Theoretical and Fundamental Chemistry |
One of Lavoisiers main influences was Étienne Bonnet, abbé de Condillac. Condillacs approach to scientific research, which was the basis of Lavoisiers approach in Traité, was to demonstrate that human beings could create a mental representation of the world using gathered evidence. In Lavoisiers preface to Traité, he statesLavoisier clearly ties his ideas in with those of Condillac, seeking to reform the field of chemistry. His goal in Traité was to associate the field with direct experience and observation, rather than assumption. His work defined a new foundation for the basis of chemical ideas and set a direction for the future course of chemistry. | 1 | Applied and Interdisciplinary Chemistry |
After rearranging the expression defining K, and putting , one obtains
This is the Henderson–Hasselbalch equation, from which the following conclusions can be drawn.
* At half-neutralization the ratio ; since , the pH at half-neutralization is numerically equal to pK. Conversely, when , the concentration of HA is equal to the concentration of A.
* The buffer region extends over the approximate range pK ± 2. Buffering is weak outside the range pK ± 1. At pH ≤ pK − 2 the substance is said to be fully protonated and at pH ≥ pK + 2 it is fully dissociated (deprotonated).
* If the pH is known, the ratio may be calculated. This ratio is independent of the analytical concentration of the acid.
In water, measurable pK values range from about −2 for a strong acid to about 12 for a very weak acid (or strong base).
A buffer solution of a desired pH can be prepared as a mixture of a weak acid and its conjugate base. In practice, the mixture can be created by dissolving the acid in water, and adding the requisite amount of strong acid or base. When the pK and analytical concentration of the acid are known, the extent of dissociation and pH of a solution of a monoprotic acid can be easily calculated using an ICE table. | 0 | Theoretical and Fundamental Chemistry |
Water's Lewis base character makes it a common ligand in transition metal complexes, examples of which include metal aquo complexes such as to perrhenic acid, which contains two water molecules coordinated to a rhenium center. In solid hydrates, water can be either a ligand or simply lodged in the framework, or both. Thus, consists of [Fe(HO)] centers and one "lattice water". Water is typically a monodentate ligand, i.e., it forms only one bond with the central atom. | 1 | Applied and Interdisciplinary Chemistry |
Hydroxylamine reacts with electrophiles, such as alkylating agents, which can attach to either the oxygen or the nitrogen atoms:
The reaction of with an aldehyde or ketone produces an oxime.
: (in NaOH solution)
This reaction is useful in the purification of ketones and aldehydes: if hydroxylamine is added to an aldehyde or ketone in solution, an oxime forms, which generally precipitates from solution; heating the precipitate with an inorganic acid then restores the original aldehyde or ketone.
Oximes such as dimethylglyoxime are also employed as ligands.
reacts with chlorosulfonic acid to give hydroxylamine-O-sulfonic acid:
When heated, hydroxylamine explodes. A detonator can easily explode aqueous solutions concentrated above 80% by weight, and even 50% solution might prove detonable if tested in bulk. In air, the combustion is rapid and complete:
Absent air, pure hydroxylamine requires stronger heating and the detonation does not complete combustion:
Partial isomerisation to the amine oxide contributes to the high reactivity. | 0 | Theoretical and Fundamental Chemistry |
In the late 1800s, with the large investments financed by northern bankers and southern investors, as well as the technological expertise provided by northern and mid-western engineers, the iron and steel industry began to flourish in Birmingham, Alabama. In addition, the growth of Alabamas iron and steel industry was further facilitated by the influx of a large labour force at that time. During the last decades of the nineteenth century, Alabamas agricultural sector was mainly dominated by the economic models of sharecropping and tenant farming. This tenancy system encompassed over 60 percent of the farming population in Alabama; however, under its influence, landless farmers had to suffer from a legacy of illiteracy and poverty. Driven by poverty, many labourers, including unemployed and impoverished freedmen and white people, began to search for jobs in the iron-and-steel manufacturing industry, which was considered to be a more attractive alternative to sharecropping and tenant farming. Moreover, the introduction of convict-lease system also provided Alabamas iron and steel manufacturers with abundant cheap labour. The convict-lease system functioned in the state and counties of Alabama between 1875 and 1928, through which iron manufacturers paid to the local governments in exchange for prison labour. As regulated by the system, prisoners had to work for the companies that leased them from the governments. Until its abolition in 1928, the convict-lease system had provided iron manufacturers, owners of coal mines, and other enterprises in Alabama with a substantial number of prisoners as cheap labourers. At the end of the nineteenth century, due to the regions abundant geographical resources coupled with its low raw-material assembly costs, Alabama experienced a period of rocket development. | 1 | Applied and Interdisciplinary Chemistry |
The Toda oscillator is a dynamical system of any origin, which can be described with dependent coordinate and independent coordinate , characterized in that the evolution along independent coordinate can be approximated with equation
where
, and prime denotes the derivative. | 0 | Theoretical and Fundamental Chemistry |
Lee (1977) designed a seepage meter, which consists of a chamber which is connected to a sampling port and a plastic bag. The chamber is inserted into the sediment and water discharging through the sediments is caught within the plastic bag. The change in volume of water which is caught in the plastic bag over time represents the freshwater flux. | 0 | Theoretical and Fundamental Chemistry |
Nitridoiron and imidoiron compounds are closely related to iron-dinitrogen chemistry. The biological significance of nitridoiron(V) porphyrins has been reviewed. A widely applicable method to generate high-valent nitridoiron species is the thermal or photochemical oxidative elimination of molecular nitrogen from an azide complex. | 0 | Theoretical and Fundamental Chemistry |
Consider an overdamped Brownian particle under external force :where the term is negligible (the meaning of "overdamped"). Thus, it is just . The Fokker–Planck equation for this particle is the Smoluchowski diffusion equation:
Where is the diffusion constant and . The importance of this equation is it allows for both the inclusion of the effect of temperature on the system of particles and a spatially dependent diffusion constant.
Starting with the Langevin Equation of a Brownian particle in external field , where is the friction term, is a fluctuating force on the particle, and is the amplitude of the fluctuation.
At equilibrium the frictional force is much greater than the inertial force, . Therefore, the Langevin equation becomes,
Which generates the following Fokker–Planck equation,
Rearranging the Fokker–Planck equation,
Where . Note, the diffusion coefficient may not necessarily be spatially independent if or are spatially dependent.
Next, the total number of particles in any particular volume is given by,
Therefore, the flux of particles can be determined by taking the time derivative of the number of particles in a given volume, plugging in the Fokker–Planck equation, and then applying Gauss's Theorem.
In equilibrium, it is assumed that the flux goes to zero. Therefore, Boltzmann statistics can be applied for the probability of a particles location at equilibrium, where is a conservative force and the probability of a particle being in a state is given as .
This relation is a realization of the fluctuation–dissipation theorem. Now applying to and using the Fluctuation-dissipation theorem,
Rearranging,
Therefore, the Fokker–Planck equation becomes the Smoluchowski equation,
for an arbitrary force . | 1 | Applied and Interdisciplinary Chemistry |
Proteinase K has two disulfide bonds, but it exhibits higher proteolytic activity in the presence of reducing agents (e.g. 5 mM DTT), suggesting that the presumed reduction of its own disulfide bonds does not lead to its irreversible inactivation. Proteinase K is inhibited by serine protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF), diisopropylfluorophosphate (DFP), or 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). Proteinase K activity is unaffected by the sulfhydryl modifying reagents: para-chloromercuribenzoic acid (PCMB), N-alpha-tosyl-L-lysyl-chloromethyl-ketone (TLCK), or N-alpha-Tosyl-l-phenylalanine Chloromethyl Ketone (TPCK), although presumably if these reagents were included alongside disulfide reducing reagents which exposed the typically-unavailable Proteinase K thiols, it may then become inhibited. | 1 | Applied and Interdisciplinary Chemistry |
Honey bees (Apis mellifera) also use quorum sensing to make decisions about new nest sites. Large colonies reproduce through a process called swarming, in which the queen leaves the hive with a portion of the workers to form a new nest elsewhere. After leaving the nest, the workers form a swarm that hangs from a branch or overhanging structure. This swarm persists during the decision-making phase until a new nest site is chosen.
The quorum sensing process in honey bees is similar to the method used by Temnothorax ants in several ways. A small portion of the workers leave the swarm to search out new nest sites, and each worker assesses the quality of the cavity it finds. The worker then returns to the swarm and recruits other workers to her cavity using the honey bee waggle dance. However, instead of using a time delay, the number of dance repetitions the worker performs is dependent on the quality of the site. Workers that found poor nests stop dancing sooner, and can, therefore, be recruited to the better sites. Once the visitors to a new site sense that a quorum number (usually 10–20 bees) has been reached, they return to the swarm and begin using a new recruitment method called piping. This vibration signal causes the swarm to take off and fly to the new nest location. In an experimental test, this decision-making process enabled honey bee swarms to choose the best nest site in four out of five trials. | 1 | Applied and Interdisciplinary Chemistry |
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Fluorine forms diatomic molecules () that are gaseous at room temperature with a density about 1.3 times that of air. Though sometimes cited as yellow-green, pure fluorine gas is actually a very pale yellow. The color can only be observed in concentrated fluorine gas when looking down the axis of long tubes, as it appears transparent when observed from the side in normal tubes or if allowed to escape into the atmosphere. The element has a "pungent" characteristic odor that is noticeable in concentrations as low as 20 ppb.
Fluorine condenses to a bright yellow liquid at −188 °C (−307 °F), which is near the condensation temperatures of oxygen and nitrogen.
The solid state of fluorine relies on Van der Waals forces to hold molecules together, which, because of the small size of the fluorine molecules, are relatively weak. Consequently, the solid state of fluorine is more similar to that of oxygen or the noble gases than to those of the heavier halogens.
Fluorine solidifies at −220 °C (−363 °F) into a cubic structure, called beta-fluorine. This phase is transparent and soft, with significant disorder of the molecules; its density is 1.70 g/cm. At −228 °C (−378 °F) fluorine undergoes a solid–solid phase transition into a monoclinic structure called alpha-fluorine.
This phase is opaque and hard, with close-packed layers of molecules, and is denser at 1.97 g/cm. The solid state phase change requires more energy than the melting point transition and can be violent, shattering samples and blowing out sample holder windows. | 0 | Theoretical and Fundamental Chemistry |
*Food dehydration technology developed at the USDA-Agricultural Research Service-Eastern Regional Research Center in the 1950s-1970s
*Chemical Abstracts Service, established by the American Chemical Society in 1907
*Scotch Tape, developed by Richard Gurley Drew at 3M in 1930
*Chemistry at Jamestown, Virginia, the earliest evidence of European chemical technologies in the United States, circa 1607 | 1 | Applied and Interdisciplinary Chemistry |
The hydrogen cycle consists of hydrogen exchanges between biotic (living) and abiotic (non-living) sources and sinks of hydrogen-containing compounds.
Hydrogen (H) is the most abundant element in the universe. On Earth, common H-containing inorganic molecules include water (HO), hydrogen gas (H), hydrogen sulfide (HS), and ammonia (NH). Many organic compounds also contain H atoms, such as hydrocarbons and organic matter. Given the ubiquity of hydrogen atoms in inorganic and organic chemical compounds, the hydrogen cycle is focused on molecular hydrogen, H.
As a consequence of microbial metabolisms or naturally occurring rock-water interactions, hydrogen gas can be created. Other bacteria may then consume free H2, which may also be oxidised photochemically in the atmosphere or lost to space. Hydrogen is also thought to be an important reactant in pre-biotic chemistry and the early evolution of life on Earth, and potentially elsewhere in the Solar System. | 1 | Applied and Interdisciplinary Chemistry |
The number of Unleashed Registrants has increased 10 fold since the integration of BIND. As of December 2006 registration fell just short of 10,000. Subscribers to the commercial versions of BOND fall into six general categories; agriculture and food, biotechnology, pharmaceuticals, informatics, materials and other. The biotechnology sector is the largest of these groups, holding 28% of subscriptions. Pharmaceuticals and informatics follow with 22% and 18% respectively. The United States holds the bulk of these subscriptions, 69%. Other countries with access to the commercial versions of BOND include Canada, the United Kingdom, Japan, China, Korea, Germany, France, India and Australia. All of these countries fall below 6% in user share. | 1 | Applied and Interdisciplinary Chemistry |
Water vapor and dry air density calculations at 0 °C:
* The molar mass of water is , as calculated from the sum of the atomic masses of its constituent atoms.
* The average molar mass of air (approx. 78% nitrogen, N; 21% oxygen, O; 1% other gases) is at standard temperature and pressure (STP).
* Obeying Avogadro's Law and the ideal gas law, moist air will have a lower density than dry air. At max. saturation (i. e. rel. humidity = 100% at 0 °C) the density will go down to 28.51 g/mol.
* STP conditions imply a temperature of 0 °C, at which the ability of water to become vapor is very restricted. Its concentration in air is very low at 0 °C. The red line on the chart to the right is the maximum concentration of water vapor expected for a given temperature. The water vapor concentration increases significantly as the temperature rises, approaching 100% (steam, pure water vapor) at 100 °C. However the difference in densities between air and water vapor would still exist (0.598 vs. 1.27 g/L). | 1 | Applied and Interdisciplinary Chemistry |
Rapid amplification of cDNA ends (RACE) is a technique used in molecular biology to obtain the full length sequence of an RNA transcript found within a cell. RACE results in the production of a cDNA copy of the RNA sequence of interest, produced through reverse transcription, followed by PCR amplification of the cDNA copies (see RT-PCR). The amplified cDNA copies are then sequenced and, if long enough, should map to a unique genomic region. RACE is commonly followed up by cloning before sequencing of what was originally individual RNA molecules. A more high-throughput alternative which is useful for identification of novel transcript structures, is to sequence the RACE-products by next generation sequencing technologies. | 1 | Applied and Interdisciplinary Chemistry |
The spallation process at SNS begins with negatively charged hydrogen ions that are produced by an ion source. Each ion consists of a proton orbited by two electrons. The ions are injected into a linear particle accelerator, or linac, which accelerates them to an energy of about one GeV (or to about 90% the speed of light). The ions pass through a foil, which strips off each ion's two electrons, converting it to a proton. The protons pass into a ring-shaped structure, a proton accumulator ring, where they spin around at very high speeds and accumulate in "bunches." Each bunch of protons is released from the ring as a pulse, at a rate of 60 times per second (60 hertz). The high-energy proton pulses strike a target of liquid mercury, where spallation occurs. The spalled neutrons are then slowed in a moderator and guided through beam lines to areas containing special instruments where they are used in a wide variety of experiments. | 0 | Theoretical and Fundamental Chemistry |
Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from the presence of nanomolar concentrations of oxygen (e.g. Bacteroides fragilis). Like other anaerobes, these organisms do not require oxygen for growth. This growth benefit requires the expression of an oxygen respiratory chain that is typically associated with microaerophilic respiration. Recent studies suggest that respiration in low concentrations of oxygen is an ancient process which predates the emergence of oxygenic photosynthesis. | 1 | Applied and Interdisciplinary Chemistry |
In recent years, benzene is generally depicted as a hexagon with alternating single and double bonds, much like the structure Kekulé originally proposed in 1872. As mentioned above, the alternating single and double bonds of "1,3,5-cyclohexatriene" are understood to be a drawing of one of the two equivalent canonical forms of benzene (the one explicitly shown and the one with the opposite pattern of formal single and double bonds), in which all carbon–carbon bonds are of equivalent length and have a bond order of exactly 1.5. For aryl rings in general, the two analogous canonical forms are almost always the primary contributors to the structure, but they are nonequivalent, so one structure may make a slightly greater contribution than the other, and bond orders may differ somewhat from 1.5.
An alternate representation that emphasizes this delocalization uses a circle, drawn inside the hexagon of single bonds, to represent the delocalized pi orbital. This style, based on one proposed by Johannes Thiele, used to be very common in introductory organic chemistry textbooks and is still frequently used in informal settings. However, because this depiction does not keep track of electron pairs and is unable to show the precise movement of electrons, it has largely been superseded by the Kekuléan depiction in pedagogical and formal academic contexts. | 0 | Theoretical and Fundamental Chemistry |
Bartlett's main specialty was the chemistry of fluorine and of compounds containing fluorine. In 1962, Bartlett prepared the first noble gas compound, xenon hexafluoroplatinate, Xe[PtF]. This contradicted established models of the nature of valency, as it was believed that all noble gases were entirely inert to chemical combination. His discovery incited other chemists to discover several other fluorides of xenon: XeF, XeF, and XeF. | 0 | Theoretical and Fundamental Chemistry |
Zone axis, a term sometimes used to refer to "high-symmetry" orientations in a crystal, most generally refers to any direction referenced to the direct lattice (as distinct from the reciprocal lattice) of a crystal in three dimensions. It is therefore indexed with direct lattice indices, instead of with Miller indices.
High-symmetry zone axes through a crystal lattice, in particular, often lie in the direction of tunnels through the crystal between planes of atoms. This is because, as we see below, such zone axis directions generally lie within more than one plane of atoms in the crystal. | 0 | Theoretical and Fundamental Chemistry |
The closing of atoms into rings may lock particular atoms with distinct substitution by functional groups such that the result is stereochemistry and chirality of the compound, including some manifestations that are unique to rings (e.g., configurational isomers). | 0 | Theoretical and Fundamental Chemistry |
Permutation re-sampling requires a computationally demanding number of permutations to get reliable estimates of the p-values for the most differentially expressed genes, if n is large. Eisinga, Breitling and Heskes (2013) provide the exact probability mass distribution of the rank product statistic. Calculation of the exact p-values offers a substantial improvement over permutation approximation, most significantly for that part of the distribution rank product analysis is most interested in, i.e., the thin right tail. However, exact statistical significance of large rank products may take unacceptable long amounts of time to compute. Heskes, Eisinga and Breitling (2014) provide a method to determine accurate approximate p-values of the rank product statistic in a computationally fast manner. | 1 | Applied and Interdisciplinary Chemistry |
Thermochemistry rests on two generalizations. Stated in modern terms, they are as follows:
#Lavoisier and Laplace's law (1780): The energy change accompanying any transformation is equal and opposite to energy change accompanying the reverse process.
#Hess' law of constant heat summation (1840): The energy change accompanying any transformation is the same whether the process occurs in one step or many.
These statements preceded the first law of thermodynamics (1845) and helped in its formulation.
Thermochemistry also involves the measurement of the latent heat of phase transitions. Joseph Black had already introduced the concept of latent heat in 1761, based on the observation that heating ice at its melting point did not raise the temperature but instead caused some ice to melt.
Gustav Kirchhoff showed in 1858 that the variation of the heat of reaction is given by the difference in heat capacity between products and reactants: dΔH / dT = ΔC. Integration of this equation permits the evaluation of the heat of reaction at one temperature from measurements at another temperature. | 0 | Theoretical and Fundamental Chemistry |
Alkaline earth metal complexes have been synthesized by RTLE, employing the same methodology used in synthesizing lanthanide complexes. The use of diphenylmercury in alkaline-earth metal reactions leads to the production of elemental mercury. The handling and disposal of elemental mercury is challenging due to its toxicity to humans and the environment. This led to the desire for an alternative RTLE reagent that would be less toxic and still very effective. Triphenylbismuth, BiPh, was discovered to be a suitable alternative. Mercury and bismuth have similar electronegativity values and behave similarly in RTLE reactions. BiPh has been used to synthesize alkaline-earth metal amides and alkaline-earth metal cyclopentadienides. The difference between HgPh and BiPh in these syntheses was that the reaction time was longer when using BiPh. | 0 | Theoretical and Fundamental Chemistry |
The in vivo bioreactor is a tissue engineering paradigm that uses bioreactor methodology to grow neotissue in vivo that augments or replaces malfunctioning native tissue. Tissue engineering principles are used to construct a confined, artificial bioreactor space in vivo that hosts a tissue scaffold and key biomolecules necessary for neotissue growth. Said space often requires inoculation with pluripotent or specific stem cells to encourage initial growth, and access to a blood source. A blood source allows for recruitment of stem cells from the body alongside nutrient delivery for continual growth. This delivery of cells and nutrients to the bioreactor eventually results in the formation of a neotissue product. | 1 | Applied and Interdisciplinary Chemistry |
Numerous synthetic chlorins with different functional groups and/or ring modifications have been examined.
Contracted chlorins can be synthesised by reduction of B(III)subporphyrin or by oxidation of corresponding B(III)subbacteriochlorin. The B(III)subchlorins were directly synthesized as meso-ester B(III)subchlorin from meso-diester tripyrromethane, these class of compound showed very good fluorescence quantum yield and singlet oxygen producing efficiency | 1 | Applied and Interdisciplinary Chemistry |
In construction, a sleeve is used both by the electrical and mechanical trades to create a penetration in a solid wall, ceilling or floor. | 1 | Applied and Interdisciplinary Chemistry |
Although the unsteady mechanism of idealized 2D experiments has already been studied comprehensively, the dynamic stall on a rotor presents strong three-dimensional character differences. According to a well-collected in-flight data by Bousman, the generation location of the DSV is "tightly grouped", where lift overshoots and large nose-down pitching moments are featured and can be classified into three groups. | 1 | Applied and Interdisciplinary Chemistry |
* Head of Department: Prof. David Procter
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* International Studies: Dr. Lu Shin Wong | 1 | Applied and Interdisciplinary Chemistry |
Other molecules besides ATP undergo dephosphorylation as part of other biological systems. Different compounds produce different free energy changes as a result of dephosphorylation.
Psilocybin also relies on dephosphorylation to be metabolized into psilocin and further eliminated. No information on psilocybin's effect on the change in free energy is currently available. | 1 | Applied and Interdisciplinary Chemistry |
In Wolf–Rayet stars, the triple-alpha reaction is accommodated by the low-energy of resonance. However, in neutron stars the temperature in the core is so low that the triple-alpha reactions can occur via the pycnonuclear pathway. | 0 | Theoretical and Fundamental Chemistry |
When the electric potentials or charge densities are not too high, the PB equation can be simplified to the Debye-Hückel (DH) equation. By expanding the exponential function in the PB equation into a Taylor series, one obtains
: where
The parameter κ is referred to as the Debye length, and some representative values for a monovalent salt in water at 25°C with ε ≃ 80 are given in the table on the right. In non-aqueous solutions, Debye length can be substantially larger than the ones given in the table due to smaller dielectric constants. The DH model represents a good approximation, when the surface potentials are sufficiently low with respect to the limiting values
The numerical value refers to a monovalent salt and 25°C. In practice, the DH approximation remains rather accurate up to surface potentials that are comparable to the limiting values given above. The disjoining pressure can be obtained from the PB equation given above, which can also be simplified to the DH case by expanding into Taylor series. The resulting expression is
The substantial advantage of the DH model over the PB model is that the forces can be obtained analytically. Some of the relevant cases will be discussed below. | 0 | Theoretical and Fundamental Chemistry |
The collection sample should contain 100+ arthropods. A tolerance value of 0 to 10 is assigned to each arthropod species (or genera) based on its known prevalence in stream habitats with varying states of detritus contamination. A highly tolerant species would receive a value of 10, while a species collected only in unaltered streams with high water quality would receive a value of 0. The sum products of the number of individuals in each species (or genera) multiplied by the tolerance of the species is divided by the total number of specimens in the sample to determine the HBI value.
where n = number of specimens in taxa; a = tolerance value of taxa; N = total number of specimens in the sample.
Precautions should be taken to account for confounding variables, such as the effects of dominant species over-abundance, seasonal temperature stress, and water currents. Limiting the collection of individuals from each species to a maximum of 10 (10-Max BI) has been shown to minimize the effects of these phenomena on the True BI.
The biotic index is then ranked for water quality and degree of organic pollution, as follows: | 0 | Theoretical and Fundamental Chemistry |
The Meselson-Stahl experiment was a landmark experiment in molecular biology that provided evidence for the semiconservative replication of DNA. Conducted in 1958 by Matthew Meselson and Franklin Stahl, the experiment involved growing E. coli bacteria in a medium containing heavy isotope of nitrogen (N) for several generations. This caused all the newly synthesized bacterial DNA to be incorporated with the heavy isotope.
After allowing the bacteria to replicate in a medium containing normal nitrogen (N), samples were taken at various time points. These samples were then subjected to centrifugation in a density gradient, which separated the DNA molecules based on their density.
The results showed that after one generation of replication in the N medium, the DNA formed a band of intermediate density between that of pure N DNA and pure N DNA. This supported the semiconservative DNA replication proposed by Watson and Crick, where each strand of the parental DNA molecule serves as a template for the synthesis of a new complementary strand, resulting in two daughter DNA molecules, each consisting of one parental and one newly synthesized strand.
The Meselson-Stahl experiment provided compelling evidence for the semiconservative replication of DNA, which is fundamental to the understanding of genetics and molecular biology. | 1 | Applied and Interdisciplinary Chemistry |
The symbol used to represent temperature in equations is T with SI units of kelvins.
The speed of a gas particle is proportional to its absolute temperature. The volume of the balloon in the video shrinks when the trapped gas particles slow down with the addition of extremely cold nitrogen. The temperature of any physical system is related to the motions of the particles (molecules and atoms) which make up the [gas] system. In statistical mechanics, temperature is the measure of the average kinetic energy stored in a molecule (also known as the thermal energy). The methods of storing this energy are dictated by the degrees of freedom of the molecule itself (energy modes). Thermal (kinetic) energy added to a gas or liquid (an endothermic process) produces translational, rotational, and vibrational motion. In contrast, a solid can only increase its internal energy by exciting additional vibrational modes, as the crystal lattice structure prevents both translational and rotational motion. These heated gas molecules have a greater speed range (wider distribution of speeds) with a higher average or mean speed. The variance of this distribution is due to the speeds of individual particles constantly varying, due to repeated collisions with other particles. The speed range can be described by the Maxwell–Boltzmann distribution. Use of this distribution implies ideal gases near thermodynamic equilibrium for the system of particles being considered. | 0 | Theoretical and Fundamental Chemistry |
The history of the Haber process begins with the invention of the Haber process at the dawn of the twentieth century. The process allows the economical fixation of atmospheric dinitrogen in the form of ammonia, which in turn allows for the industrial synthesis of various explosives and nitrogen fertilizers, and is probably the most important industrial process developed during the twentieth century.
Well before the start of the industrial revolution, farmers would fertilize the land in various ways, mainly using feces and urine, well aware of the benefits of an intake of essential nutrients for plant growth. Although it was frowned upon, farmers took it upon themselves to fertilize their fields using natural means and remedies that had been passed down from generation to generation. The 1840s works of Justus von Liebig identified nitrogen as one of these important nutrients. The same chemical compound could already be converted to nitric acid, the precursor of gunpowder and powerful explosives like TNT and nitroglycerine. Scientists also already knew that nitrogen formed the dominant portion of the atmosphere, but manmade chemistry had yet to establish a means to fix it.
Then, in 1909, German chemist Fritz Haber successfully fixed atmospheric nitrogen in a laboratory. This success had extremely attractive military, industrial and agricultural applications. In 1913, barely five years later, a research team from BASF, led by Carl Bosch, developed the first industrial-scale application of the Haber process, sometimes called the Haber–Bosch process.
The industrial production of nitrogen prolonged World War I by providing Germany with the gunpowder and explosives necessary for the war effort even though it no longer had access to guano. During the interwar period, the lower cost of ammonia extraction from the virtually inexhaustible atmospheric reservoir contributed to the development of intensive agriculture and provided support for worldwide population growth. During World War II, the efforts to industrialize the Haber process benefited greatly from the Bergius process, allowing Nazi Germany access to the synthesized fuel produced by IG Farben, thereby decreasing oil imports.
In the early twenty-first century, the effectiveness of the Haber process (and its analogues) is such that these processes satisfy more than 99% of global demand for synthetic ammonia, a demand which exceeds 100 million tons annually. Nitrogen fertilizers and synthetic products, such as urea and ammonium nitrate, are mainstays of industrial agriculture, and are essential to the nourishment of at least two billion people. Industrial facilities using the Haber process and its analogues have a significant ecological impact. Half of the nitrogen in the great quantities of synthetic fertilizers employed today is not assimilated by plants but finds its way into rivers and the atmosphere as volatile chemical compounds. | 1 | Applied and Interdisciplinary Chemistry |
A fecal coliform (British: faecal coliform) is a facultatively anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Coliform bacteria generally originate in the intestines of warm-blooded animals. Fecal coliforms are capable of growth in the presence of bile salts or similar surface agents, are oxidase negative, and produce acid and gas from lactose within 48 hours at 44 ± 0.5°C. The term thermotolerant coliform is more correct and is gaining acceptance over "fecal coliform".
Coliform bacteria include genera that originate in feces (e.g. Escherichia) as well as genera not of fecal origin (e.g. Enterobacter, Klebsiella, Citrobacter). The assay is intended to be an indicator of fecal contamination; more specifically of E. coli which is an indicator microorganism for other pathogens that may be present in feces. Presence of fecal coliforms in water may not be directly harmful, and does not necessarily indicate the presence of feces. | 0 | Theoretical and Fundamental Chemistry |
1,3-Bisphosphoglycerate is the conjugate base of 1,3-bisphosphoglyceric acid. It is phosphorylated at the number 1 and 3 carbons. The result of this phosphorylation gives 1,3BPG important biological properties such as the ability to phosphorylate ADP to form the energy storage molecule ATP. | 0 | Theoretical and Fundamental Chemistry |
Some chemicals contain another anion in addition to borate. These include borate chlorides, borate carbonates, borate nitrates, borate sulfates, borate phosphates. | 0 | Theoretical and Fundamental Chemistry |
An alternative approach used to measure the relative abundance of radiogenic isotopes when working with a solid surface is secondary-ion mass spectrometry (SIMS). This type of ion-microprobe analysis normally works by focusing a primary (oxygen) ion beam on a sample in order to generate a series of secondary positive ions that can be focused and measured based on their mass/charge ratios.
SIMS is a common method used in U-Pb analysis, as the primary ion beam is used to bombard the surface of a single zircon grain in order to yield a secondary beam of Pb ions. The Pb ions are analyzed using a double focusing mass spectrometer that comprises both an electrostatic and magnetic analyzer. This assembly allows the secondary ions to be focused based on their kinetic energy and mass-charge ratio in order to be accurately collected using a series of Faraday cups.
A major issue that arises in SIMS analysis is the generation of isobaric interference between sputtered molecular ions and the ions of interest. This issue occurs with U–Pb dating as Pb ions have essentially the same mass as HfO. In order to overcome this problem, a sensitive high-resolution ion microprobe (SHRIMP) can be used. A SHRIMP is a double-focusing mass spectrometer that allows for a large spatial separation between different ion masses based on its relatively large size. For U-Pb analysis, the SHRIMP allows for the separation of Pb from other interfering molecular ions, such as HfO. | 0 | Theoretical and Fundamental Chemistry |
Structured-wall pipes and fittings are products which have an optimized design with regard to material usage to achieve the physical, mechanical and performance requirements. Structured Wall Pipes are tailor made solutions of piping systems, for a variety of applications and in most cases developed in cooperation with users. | 1 | Applied and Interdisciplinary Chemistry |
Spectrophotometers designed for the infrared region are quite different because of the technical requirements of measurement in that region. One major factor is the type of photosensors that are available for different spectral regions, but infrared measurement is also challenging because virtually everything emits IR as thermal radiation, especially at wavelengths beyond about 5 μm.
Another complication is that quite a few materials such as glass and plastic absorb infrared, making it incompatible as an optical medium. Ideal optical materials are salts, which do not absorb strongly. Samples for IR spectrophotometry may be smeared between two discs of potassium bromide or ground with potassium bromide and pressed into a pellet. Where aqueous solutions are to be measured, insoluble silver chloride is used to construct the cell. | 0 | Theoretical and Fundamental Chemistry |
Dimethyl malonate is a diester derivative of malonic acid. It is a common reagent for organic synthesis used, for example, as a precursor for barbituric acid. It is also used in the malonic ester synthesis. It can be synthesized from dimethoxymethane and carbon monoxide.
Dimethyl malonate is used extensively in the fragrance industry as a raw material in the synthesis of jasmonates. For example, methyl dihydrojasmonate is synthesized from cyclopentanone, pentanal and dimethyl malonate. Hedione is used in almost all fine fragrances and is found in Christian Diors Eau Sauvage and "Diorella", Hermes "Voyage dHermes Parfum", Calvin Kleins "CKOne", Chanels "Chanel No. 19", and Mark Jacobs "Blush", among others. As of 2009, Hedione was Firmenich's top selling compound by volume.
Hebei Chengxin is the world's largest producer of dimethyl malonate by volume and uses a chloroacetic acid/sodium cyanide process developed in the 1940s. | 0 | Theoretical and Fundamental Chemistry |
Alizarine Yellow R is a yellow colored azo dye made by the diazo coupling reaction. It is usually commercially available as a sodium salt. In its pure form, it is a rust-colored solid. It is mainly used as a pH indicator. | 0 | Theoretical and Fundamental Chemistry |
Electrowinning and electrorefining respectively involve the recovery and purification of metals using electrodeposition of metals at the cathode, and either metal dissolution or a competing oxidation reaction at the anode. | 1 | Applied and Interdisciplinary Chemistry |
π systems are important building blocks in supramolecular assembly because of their versatile noncovalent interactions with various functional groups.
A notable example of applying π–π interactions in supramolecular assembly is the synthesis of catenane. The major challenge for the synthesis of catenane is to interlock molecules in a controlled fashion. Stoddart and co-workers developed a series of systems utilizing the strong π–π interactions between electron-rich benzene derivatives and electron-poor pyridinium rings. [2]Catanene was synthesized by reacting bis(pyridinium) (A), bisparaphenylene-34-crown-10 (B), and 1, 4-bis(bromomethyl)benzene (C) (Fig. 2). The π–π interaction between A and B directed the formation of an interlocked template intermediate that was further cyclized by substitution reaction with compound C to generate the [2]catenane product. | 0 | Theoretical and Fundamental Chemistry |
The word electrolyte derives from Ancient Greek ήλεκτρο- (ēlectro-), prefix related to electricity, and λυτός (lytos), meaning "able to be untied or loosened". | 0 | Theoretical and Fundamental Chemistry |
Art in bronze and brass dates from remote antiquity. These important metals are alloys, bronze composed of copper and tin and brass of copper and zinc.
Proportions of each alloy vary slightly. Bronze may be normally considered as nine parts of copper to one of tin. Other ingredients which are occasionally found are more or less accidental. The result is a metal of a rich golden brown colour, capable of being worked by casting — a process little applicable to its component parts, but peculiarly successful with bronze, the density and hardness of the metal allowing it to take any impression of a mould, however delicate. It is thus possible to create ornamental work of various kinds. | 1 | Applied and Interdisciplinary Chemistry |
LDA is commonly formed by treating a cooled (0 to −78 °C) mixture of tetrahydrofuran and diisopropylamine with n-butyllithium.
When dissociated, the diisopropylamide anion can become protonated to form diisopropylamine. Diisopropylamine has a pK value of 36. Therefore, its conjugate base is suitable for the deprotonation of compounds with greater acidity, importantly, such weakly acidic compounds (carbon acids) of the type , where Z = C(O)R, C(O)OR or CN. Conventional protic functional groups such as alcohols and carboxylic acids are readily deprotonated.
Like most organolithium reagents, LDA is not a salt, but is highly polar. It forms aggregates in solution, with the extent of aggregation depending on the nature of the solvent. In THF its structure is primarily that of a solvated dimer. In nonpolar solvents such as toluene, it forms a temperature-dependent oligomer equilibrium. At room temperature trimers and tetramers are the most likely structures. With decreasing temperature the aggregation extends to pentameric and higher oligomeric structures.
Solid LDA is pyrophoric, but its solutions are generally not. As such it is commercially available as a solution in polar aprotic solvents such as THF and ether; however, for small scale use (less than 50 mmol), it is common and more cost effective to prepare LDA in situ. | 0 | Theoretical and Fundamental Chemistry |
*For biodiesel fuel: waste vegetable oil (WVO) must be neutralized before a batch may be processed. A portion of WVO is titrated with a base to determine acidity, so the rest of the batch may be neutralized properly. This removes free fatty acids from the WVO that would normally react to make soap instead of biodiesel fuel.
*Kjeldahl method: a measure of nitrogen content in a sample. Organic nitrogen is digested into ammonia with sulfuric acid and potassium sulfate. Finally, ammonia is back titrated with boric acid and then sodium carbonate.
*Acid value: the mass in milligrams of potassium hydroxide (KOH) required to titrate fully an acid in one gram of sample. An example is the determination of free fatty acid content.
*Saponification value: the mass in milligrams of KOH required to saponify a fatty acid in one gram of sample. Saponification is used to determine average chain length of fatty acids in fat.
*Ester value (or ester index): a calculated index. Ester value = Saponification value – Acid value.
*Amine value: the mass in milligrams of KOH equal to the amine content in one gram of sample.
*Hydroxyl value: the mass in milligrams of KOH corresponding to hydroxyl groups in one gram of sample. The analyte is acetylated using acetic anhydride then titrated with KOH. | 0 | Theoretical and Fundamental Chemistry |
The Carter–Goddard–Malrieu–Trinquier model (better known as CGMT model) is a model in inorganic chemistry, used for the description and prediction of distortions in multiple bonding systems of main group elements. | 0 | Theoretical and Fundamental Chemistry |
Consider a steady potential flow that is characterized by the velocity potential Then satisfies
where , the sound speed is expressed as a function of the velocity magnitude For a polytropic gas, we can write
where is the specific heat ratio, is the stagnation sound speed (i.e., the sound speed in a gas at rest) and is the stagnation enthalpy. Let be the characteristic velocity scale and is the characteristic value of the sound speed, then the function is of the form
where is the relevant Mach number.
For small Mach numbers, we can introduce the series
Substituting this governing equation and collecting terms of different orders of leads to a set of equations. These are
and so on. Note that is independent of with which the latter quantity appears in the problem for . | 1 | Applied and Interdisciplinary Chemistry |
A membraneless battery relies on laminar flow in which two liquids are pumped through a channel, where they undergo electrochemical reactions to store or release energy. The solutions stream through in parallel, with little mixing. The flow naturally separates the liquids, eliminating the need for a membrane.
Membranes are often the most costly and least reliable components of batteries, as they can be corroded by repeated exposure to certain reactants. The absence of a membrane enables the use of a liquid bromine solution and hydrogen: this combination is problematic when membranes are used, because they form hydrobromic acid that can destroy the membrane. Both materials are available at low cost. The design uses a small channel between two electrodes. Liquid bromine flows through the channel over a graphite cathode and hydrobromic acid flows under a porous anode. At the same time, hydrogen gas flows across the anode. The chemical reaction can be reversed to recharge the battery – a first for any membraneless design.
One such membraneless flow battery published in August 2013 produced a maximum power density of 0.795 mW/cm, three times as much power as other membraneless systems— and an order of magnitude higher than lithium-ion batteries.
In 2018, a macroscale membraneless redox flow battery capable of recharging and recirculation of the same electrolyte streams for multiple cycles has been demonstrated. The battery is based on immiscible organic catholyte and aqueous anolyte liquids, which exhibits high capacity retention and Coulombic efficiency during cycling. | 0 | Theoretical and Fundamental Chemistry |
M receptors are found in the CNS.
M receptors work via G receptors to decrease cAMP in the cell and, thus, produce generally inhibitory effects. Possible bronchospasm may result if stimulated by muscarinic agonists | 1 | Applied and Interdisciplinary Chemistry |
Both the lower pH and higher aluminium concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals. At pH lower than 5 most fish eggs will not hatch and lower pH can kill adult fish. As lakes and rivers become more acidic biodiversity is reduced. Acid rain has eliminated insect life and some fish species, including the brook trout in some lakes, streams, and creeks in geographically sensitive areas, such as the Adirondack Mountains of the United States.
However, the extent to which acid rain contributes directly or indirectly via runoff from the catchment to lake and river acidity (i.e., depending on characteristics of the surrounding watershed) is variable. The United States Environmental Protection Agency's (EPA) website states: "Of the lakes and streams surveyed, acid rain caused acidity in 75% of the acidic lakes and about 50% of the acidic streams". Lakes hosted by silicate basement rocks are more acidic than lakes within limestone or other basement rocks with a carbonate composition (i.e. marble) due to buffering effects by carbonate minerals, even with the same amount of acid rain.
Sulfur dioxide and nitrous oxide concentration has many implication on aquatic ecosystems, including acidity change, increased nitrogen and aluminum content, and altering biogeochemical processes. Typically, sulfur dioxide and nitrous oxide do not have direct physiological effects upon exposure; most effects are developed by accumulation and prolonged exposure of these gases in the environment, modifying soil and water chemistry. | 1 | Applied and Interdisciplinary Chemistry |
Endogenous steroid sulfates include:
* Cholesterol sulfate (formed from cholesterol by SULT2B1b)
* Pregnenolone sulfate (formed from pregnenolone by SULT2A1 and SULT2B1a)
* sulfate (formed from by SULT2A1 and SULT1E1)
* Androstenediol sulfate (formed from androstenediol)
* Androsterone sulfate (formed from androsterone by SULT2A1)
* Estrone sulfate (formed from estrone by SULT1E1)
* Estradiol sulfate (formed from estradiol by SULT1A1 and SULT1E1)
* Testosterone sulfate (formed from testosterone) | 1 | Applied and Interdisciplinary Chemistry |
Plants have an array of volatile compounds they can release to signal other plants. By unleashing these cues, plants learn more about their environment and sufficiently respond. However, there are still many factors about plant scents scientists are still trying to understand. Scientists have studied how many of the volatile compounds released by plants are from a floral source. A study concluded that floral cues are as important as other volatile compounds and are pertinent for plant-to-plant communication. Further research found that plants who receive the floral volatiles have higher fitness than other volatile cues because floral cues are the only compounds released by plants that indicate their kind of mating environment. Plants are able to respond to these mating cues and change adjustable floral phenotypes that can affect plant pollination and mating. Floral volatiles can ward off or attract pollinators/mates all at once. Depending on the number of floral signals released by a plant can control the level of attracting/repelling the plant wants. The composition of floral compounds and the rate of their release are the potential factors that control attraction/repellence. These two elements can be in response to ecological cues like high plant density and temperature. For instance, in sexually deceptive orchids, floral scents emitted after pollination reduce the flower's attractiveness to pollinators. This mechanism acts as a signal to pollinators to visit unpollinated flowers.
Environmental conditions can affect plant communication and signaling. Signal factors include temperature and plant density. Environmentally high temperatures increase the rate of releasing floral compounds, which can increase the amount of signal released and thus its ability to reach more plants. When plant density increases, plant communication increases as well, since plants would be near each other and have signals reach many neighboring plants. This can also increase the signal's reliability and lowering the chance the signal will degrade before it can reach other plants. | 1 | Applied and Interdisciplinary Chemistry |
A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings (but not stormwater) to a sewage treatment plant or disposal.
Sanitary sewers are a type of gravity sewer and are part of an overall system called a "sewage system" or sewerage. Sanitary sewers serving industrial areas may also carry industrial wastewater. In municipalities served by sanitary sewers, separate storm drains may convey surface runoff directly to surface waters. An advantage of sanitary sewer systems is that they avoid combined sewer overflows. Sanitary sewers are typically much smaller in diameter than combined sewers which also transport urban runoff. Backups of raw sewage can occur if excessive stormwater inflow or groundwater infiltration occurs due to leaking joints, defective pipes etc. in aging infrastructure. | 1 | Applied and Interdisciplinary Chemistry |
Vukić Mićović (Serbian: Вукић Мићовић; Bare Kraljske, near Andrijevica, Montenegro, 1 January 1896 – Belgrade, Serbia, Yugoslavia, 19 January 1981) was a Serbian chemist, professor and dean of the Faculty of Natural Sciences and Mathematics in Belgrade, rector of the University of Belgrade and academician of SANU. | 0 | Theoretical and Fundamental Chemistry |
In two dimensions, any lattice can be specified by the length of its two primitive translation vectors and the angle between them. There are an infinite number of possible lattices one can describe in this way. Some way to categorize different types of lattices is desired. One way to do so is to recognize that some lattices have inherent symmetry. One can impose conditions on the length of the primitive translation vectors and on the angle between them to produce various symmetric lattices. These symmetries themselves are categorized into different types, such as point groups (which includes mirror symmetries, inversion symmetries and rotation symmetries) and translational symmetries. Thus, lattices can be categorized based on what point group or translational symmetry applies to them.
In two dimensions, the most basic point group corresponds to rotational invariance under 2π and π, or 1- and 2-fold rotational symmetry. This actually applies automatically to all 2D lattices, and is the most general point group. Lattices contained in this group (technically all lattices, but conventionally all lattices that don't fall into any of the other point groups) are called oblique lattices. From there, there are 4 further combinations of point groups with translational elements (or equivalently, 4 types of restriction on the lengths/angles of the primitive translation vectors) that correspond to the 4 remaining lattice categories: square, hexagonal, rectangular, and centered rectangular. Thus altogether there are 5 Bravais lattices in 2 dimensions.
Likewise, in 3 dimensions, there are 14 Bravais lattices: 1 general "wastebasket" category (triclinic) and 13 more categories. These 14 lattice types are classified by their point groups into 7 lattice systems (triclinic, monoclinic, orthorhombic, tetragonal, cubic, rhombohedral, and hexagonal). | 0 | Theoretical and Fundamental Chemistry |
Early theories of the origin of life included spontaneous generation from non-living matter and panspermia, the arrival of life on earth from other bodies in space. The question of how life originated became urgent when Charles Darwins 1859 On the Origin of Species' became widely accepted by biologists. The evolution of new species by splitting off from older ones implied that all life forms were derived from a few such forms, perhaps only one, as Darwin had suggested at the end of his book. Darwin suggested that life could have originated in some "warm little pond" containing a suitable mixture of chemical compounds. The question has continued to be debated into the 21st century.
Nick Lane is a biochemist at University College London; he researches "evolutionary biochemistry and bioenergetics, focusing on the origin of life and the evolution of complex cells." He has become known as a science writer, having written four books about evolutionary biochemistry. | 1 | Applied and Interdisciplinary Chemistry |
Ampicillin can be administered by mouth, an intramuscular injection (shot) or by intravenous infusion. The oral form, available as capsules or oral suspensions, is not given as an initial treatment for severe infections, but rather as a follow-up to an IM or IV injection. For IV and IM injections, ampicillin is kept as a powder that must be reconstituted.
IV injections must be given slowly, as rapid IV injections can lead to convulsive seizures. | 0 | Theoretical and Fundamental Chemistry |
Work, i.e. "weight lifted through a height", was originally defined in 1824 by Sadi Carnot in his famous paper Reflections on the Motive Power of Fire, where he used the term motive power for work. Specifically, according to Carnot: | 0 | Theoretical and Fundamental Chemistry |
Nuclei with a spin quantum number >1/2 have a non-spherical charge distribution and an associated electric quadrupole moment tensor. The nuclear electric quadrupole moment couples with surrounding electric field gradients. The nuclear quadrupole coupling is one of the largest interactions in NMR spectroscopy, often comparable in size to the Zeeman coupling. When the nuclear quadrupole coupling is not negligible relative to the Zeeman coupling, higher order corrections are needed to describe the NMR spectrum correctly. In such cases, the first-order correction to the NMR transition frequency leads to a strong anisotropic line broadening of the NMR spectrum. However, all symmetric transitions, between and levels are unaffected by the first-order frequency contribution. The second-order frequency contribution depends on the P Legendre polynomial, which has zero points at 30.6° and 70.1°. These anisotropic broadenings can be removed using DOR (DOuble angle Rotation) where you spin at two angles at the same time, or DAS (Double Angle Spinning) where you switch quickly between the two angles. Both techniques were developed in the late 1980s, and require specialized hardware (probe). Multiple quantum magic angle spinning (MQMAS) NMR was developed in 1995 and has become a routine method for obtaining high resolution solid-state NMR spectra of quadrupolar nuclei. A similar method to MQMAS is satellite transition magic angle spinning (STMAS) NMR developed in 2000. | 0 | Theoretical and Fundamental Chemistry |
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