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Industrial brownfield sites can be valuable ecosystems, supporting rare species of plants, animals and invertebrates. Increasingly in demand for redevelopment, these habitats are under threat. "Brown roofs", also known as "biodiverse roofs", can partly mitigate this loss of habitat by covering the flat roofs of new developments with a layer of locally sourced material. Construction techniques for brown roofs are typically similar to those used to create flat green roofs, the main difference being the choice of growing medium (usually locally sourced rubble, gravel, soil, etc...) to meet a specific biodiversity objective. In Switzerland, it is common to use alluvial gravels from the foundations; in London, a mix of brick rubble and some concrete has been used.
The original idea was to allow the roofs to self-colonise with plants, but they are sometimes seeded to increase their biodiversity potential in the short term. Such practices are derided by purists. The roofs are colonised by spiders and insects (many of which are becoming extremely rare in the UK as such sites are developed) and provide a feeding site for insectivorous birds. Laban, a centre for contemporary dance in London, has a brown roof specifically designed to encourage the nationally rare black redstart. A green roof, above ground level, and claimed to be the highest in the UK and Europe "and probably in the world" to act as nature reserve, is on the Barclays Bank HQ in Canary Wharf. Designed combining the principles of green and brown roofs, it is already home to a range of rare invertebrates. | 1 | Applied and Interdisciplinary Chemistry |
Enolates can be oxidized by sulfonyloxaziridines. The enolate reacts by nucleophilic displacement at the electron deficient oxygen of the oxaziridine ring.
This reaction type is extended to asymmetric synthesis by the use of chiral oxaziridines derived from camphor (camphorsulfonyl oxaziridine). Each isomer gives exclusive access to one of the two possible enantiomers. This modification is applied in the Holton taxol total synthesis.
In the enolate oxidation of the cyclopentaenone below with either camphor enantiomer, the trans isomer is obtained because access for the hydroxyl group in the cis position is limited. The use of the standard oxaziridine did not result in an acyloin. | 0 | Theoretical and Fundamental Chemistry |
PV work is path-dependent and is, therefore, a thermodynamic process function. In general, the term is not an exact differential. The statement that a process is quasi-static gives important information about the process but does not determine the P–V path uniquely, because the path can include several slow goings backwards and forward in volume, slowly enough to exclude friction within the system occasioned by departure from the quasi-static requirement. An adiabatic wall is one that does not permit passage of energy by conduction or radiation.
The first law of thermodynamics states that .
For a quasi-static adiabatic process, so that
Also so that
It follows that so that
Internal energy is a state function so its change depends only on the initial and final states of a process. For a quasi-static adiabatic process, the change in internal energy is equal to minus the integral amount of work done by the system, so the work also depends only on the initial and final states of the process and is one and the same for every intermediate path. As a result, the work done by the system also depends on the initial and final states.
If the process path is other than quasi-static and adiabatic, there are indefinitely many different paths, with significantly different work amounts, between the initial and final states. (Again the internal energy change depends only on the initial and final states as it is a state function).
In the current mathematical notation, the differential is an inexact differential.
In another notation, is written (with a horizontal line through the d). This notation indicates that is not an exact one-form. The line-through is merely a flag to warn us there is actually no function (0-form) which is the potential of . If there were, indeed, this function , we should be able to just use Stokes Theorem to evaluate this putative function, the potential of , at the boundary of the path, that is, the initial and final points, and therefore the work would be a state function. This impossibility is consistent with the fact that it does not make sense to refer to the work on a point in the PV diagram; work presupposes a path. | 0 | Theoretical and Fundamental Chemistry |
Some trans-spliced snRNAs have been observed to have a N,N,7-trimethylguanosine cap. This particular modification to the guanosine cap is rare in snRNAs. Trans-splicing is a phenomenon in which exons from two different primary RNA transcripts are ligated together. These rare variants have been seen during development in C.elegans and are associated with polysomes. How this modification is regulated in certain cell types and the exact function of this modification remains largely unknown, although it has been speculated that this modification may help define a special subset of trimethylguanosine-regulated RNAs. | 1 | Applied and Interdisciplinary Chemistry |
The CD V-700 is a Geiger counter employing a probe equipped with a Geiger–Müller tube manufactured by several companies under contract to US federal civil defense agencies in the 1950s and 1960s. This unit is quite sensitive and can be used to measure low levels of gamma radiation and detect beta radiation. In cases of high-radiation fields, the Geiger tube can saturate, causing the meter to read a very low level of radiation (close to 0 R/h) hence the necessity of the companion ion-chamber survey meters. | 0 | Theoretical and Fundamental Chemistry |
The two-dimensional stream function is based on the following assumptions:
* The space domain is three-dimensional.
* The flow field can be described as two-dimensional plane flow, with velocity vector
* The velocity satisfies the continuity equation for incompressible flow:
Although in principle the stream function doesn't require the use of a particular coordinate system, for convenience the description presented here uses a right-handed Cartesian coordinate system with coordinates . | 1 | Applied and Interdisciplinary Chemistry |
Signaling pathways are often inactivated by enzymes that reverse the activation state and/or induce the degradation of signaling components. Scaffolds have been proposed to protect activated signaling molecules from inactivation and/or degradation. Mathematical modeling has shown that kinases in a cascade without scaffolds have a higher probability of being dephosphorylated by phosphatases before they are even able to phosphorylate downstream targets. Furthermore, scaffolds have been shown to insulate kinases from substrate- and ATP-competitive inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
Drop-based bioprinting makes cellular developments utilizing droplets of an assigned material, which has oftentimes been combined with a cell line. Cells themselves can also be deposited in this manner with or without polymer. When printing polymer scaffolds using these methods, each drop starts to polymerize upon contact with the substrate surface and merge into a larger structure as droplets start to coalesce. Polymerization can happen through a variety of methods depending on the polymer used. For instance, alginate polymerization is started by calcium ions in the substrate, which diffuse into the liquified bioink and permit for the arrangement of a strong gel. Drop-based bioprinting is commonly utilized due to its productive speed. However, this may make it less appropriate for more complicated organ structures. | 1 | Applied and Interdisciplinary Chemistry |
The ribbon synapse is a special type of synapse found in sensory neurons such as photoreceptor cells, retinal bipolar cells, and hair cells. Ribbon synapses contain a dense protein structure that tethers an array of vesicles perpendicular to the presynaptic membrane. In an electron micrograph it appears as a ribbon like structure perpendicular to the membrane. Unlike the traditional synapse, ribbon synapses can maintain a graded release of vesicles. In other words, the more depolarized a neuron the higher the rate of vesicle fusion. The Ribbon synapse active zone is separated into two regions, the archiform density and the ribbon. The archiform density is the site of vesicle fusion and the ribbon stores the releasable pool of vesicles. The ribbon structure is composed primarily of the protein RIBEYE, about 64–69% of the ribbon volume, and is tethered to the archiform density by scaffolding proteins such as Bassoon. | 1 | Applied and Interdisciplinary Chemistry |
The second pair of cephalic appendages in free-living copepods is usually the main time-averaged source of propulsion, beating like oars to pull the animal through the water. However, different groups have different modes of feeding and locomotion, ranging from almost immotile for several minutes (e.g. some harpacticoid copepods) to intermittent motion (e.g., some cyclopoid copepods) and continuous displacements with some escape reactions (e.g. most calanoid copepods).
Some copepods have extremely fast escape responses when a predator is sensed, and can jump with high speed over a few millimetres. Many species have neurons surrounded by myelin (for increased conduction speed), which is very rare among invertebrates (other examples are some annelids and malacostracan crustaceans like palaemonid shrimp and penaeids). Even rarer, the myelin is highly organized, resembling the well-organized wrapping found in vertebrates (Gnathostomata). Despite their fast escape response, copepods are successfully hunted by slow-swimming seahorses, which approach their prey so gradually, it senses no turbulence, then suck the copepod into their snout too suddenly for the copepod to escape.
Several species are bioluminescent and able to produce light. It is assumed this is an antipredatory defense mechanism.
Finding a mate in the three-dimensional space of open water is challenging. Some copepod females solve the problem by emitting pheromones, which leave a trail in the water that the male can follow. Copepods experience a low Reynolds number and therefore a high relative viscosity. One foraging strategy involves chemical detection of sinking marine snow aggregates and taking advantage of nearby low-pressure gradients to swim quickly towards food sources. | 1 | Applied and Interdisciplinary Chemistry |
The ores are treated by a sulfatizing roast in a fluidized bed furnace to convert copper and cobalt sulfides into soluble sulfates and iron into insoluble hematite. The calcine is subsequently leached with sulfuric acid from the spent copper recovery electrolyte. Oxide concentrates are introduced at this leaching step to maintain the acid balance in the circuit. Iron and aluminum are removed from the leach solution by the addition of lime, and copper is electrowon on copper cathodes. A part of the spent electrolyte enters the cobalt recovery circuit and is purified by the removal of iron, copper, nickel, and zinc prior to the precipitation of cobalt as its hydroxide. This is accomplished by the addition of more lime to raise the pH until the remaining copper precipitates. This copper is sent back to the copper circuit. As more lime is then added, a copper-cobaltite precipitates and is fed back to the leaching process. Sodium hydrosulfide (NaHS) is added (along with some metallic cobalt as a catalyst) to precipitate nickel sulfide (NiS). Hydrogen sulfide (HS) and sodium carbonate (NaCO) are then added to precipitate zinc sulfide (ZnS).). In the final stages, this cobalt hydroxide is redissolved and the metal is refined by electrolysis. The resulting cobalt cathodes are crushed and vacuum degassed to obtain a pure cobalt metal. | 1 | Applied and Interdisciplinary Chemistry |
The G-less cassette technique is used to determine promoter strength beyond basal levels of transcription (i.e. in the presence of transcription activators or transcription factors). For example, to measure the effects of a TATA box consensus sequence modification in Saccharomyces cerevisiae in the presence of TFIID, G-less cassettes were implemented to measure the relative strength of each promoter. | 1 | Applied and Interdisciplinary Chemistry |
Accurate and consistent measurement of gases and deposition at every monitoring site is of the utmost importance to the NADP. This is accomplished, in part, by ensuring that all sites adhere to specific standard operating procedures. This provides consistent methodology at all sites within the networks. The SOPs can be viewed here:
* http://nadp.slh.wisc.edu/siteops/ | 1 | Applied and Interdisciplinary Chemistry |
This molecular logic gate illustrated demonstrates the advancement from redox-fluorescent switches to multi-input logic gates with an electrochemical switch. This two-input AND logic gate incorporates a tertiary amine proton receptor and a tetrathiafulvalene redox donor. These groups, when attached to anthracene, can simultaneously process information concerning acid concentration and oxidizing ability of the solution. | 0 | Theoretical and Fundamental Chemistry |
The radical-pair mechanism emerged as an explanation to CIDNP and CIDEP and was proposed in 1969 by Closs; Kaptein and Oosterhoff. | 0 | Theoretical and Fundamental Chemistry |
The methodologies outlined in the methods section facilitate the determination of flood occurrences, magnitude, and ages. Through these techniques, paleoflood data can be extended back over thousands of years, enriching the precision of flood-frequency curves. This extended historical perspective is invaluable in contemporary flood-frequency analysis, significantly amplifying the effective length of the record. The incorporation of historical flood data enhances the analysis, offering a more comprehensive understanding of the dynamics and patterns involved in flooding events.
Paleohydrological data serves as a valuable tool in unraveling the climatic variability of the past. Evidence of climatic changes is seen in lake and ocean sediment, as well as in the mass balance of glaciers. Over the last 10,000 years, the climate has undergone significant fluctuations, impacting floods, droughts, and hydrologic patterns. Understanding this historical climatic variability is crucial for predicting future climate changes. Take, for instance, the Colorado River, a vital freshwater source for the southwestern United States. By analyzing data from past droughts, it becomes evident that recent climatic variability could potentially reduce streamflow by 35 percent. This knowledge is indispensable for informed future planning, ensuring water availability for the populations that depend on it.
Hydrological fluctuations are linked to the factors causing them, and paleohydrological data can be used to validate climate models. On the orbital time scale, paleohydrological data reflects variations in the Earth's orbit and the cycle of glacial periods and interglacials. For example, variations in the water level of Lake Lisan correlates with data showing temperature fluctuations collected from polar ice core samples. On a shorter time scale, minuscule climatic variations can have large hydrological effects as when excess rainwater entering the North Atlantic was linked with a serious drought in the eastern Mediterranean. The Little Ice Age in northern Europe was linked with drought in East Africa, heavy rains in the African lakes, and persistent El Niño–Southern Oscillation conditions in the Pacific.
Another application is in the quantification of erosion caused by rivers under differing climatological conditions. Increased erosion rates following deforestation, and pollution resulting from lead-mining activities by the Romans show up in lake sediments. | 1 | Applied and Interdisciplinary Chemistry |
Deprotonation of methylcyclopentadiene gives the aromatic methylcyclopentadienyl anion. This ion is useful as a ligand for organometallic complexes. Relative to the corresponding cyclopentadienyl (Cp) complexes, complexes of Cp′ exhibit enhanced solubility in organic solvents.
Cp′ can be used to probe the structure of organometallic complexes. For example, Cp′Fe(PPh)(CO)I has four different signals in the H NMR spectrum for the ring hydrogens and five different signals in the C NMR spectrum for the ring carbons. There is therefore no symmetry within the ring even accounting for rotation around the ring–metal axis, but instead there is a diastereotopic relationship as a result of being part of a chiral complex. The achiral precursor complex Cp′Fe(CO)I has only two signals for those hydrogens and three for those carbons, indicating a symmetric structure. | 0 | Theoretical and Fundamental Chemistry |
Barium azide may be prepared by reacting sodium azide with a soluble barium salt. Care should be taken to prevent large crystals from forming in the solution as barium azide crystals will explode if subjected to friction/shock or if fully dried. The product should be stored submerged in ethanol. | 0 | Theoretical and Fundamental Chemistry |
Prime editors may be used in gene drives. A prime editor may be incorporated into the Cleaver half of a Cleave and Rescue/ClvR system. In this case it is not meant to perform a precise alteration but instead to merely disrupt.
PE is among recently introduced technologies which allow the transfer of single-nucleotide polymorphisms (SNPs) from one individual crop plant to another. PE is precise enough to be used to recreate an arbitrary SNP in an arbitrary target, including deletions, insertions, and all 12 point mutations without also needing to perform a double-stranded break or carry a donating template. | 1 | Applied and Interdisciplinary Chemistry |
Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body.
For example:
* Fluorodeoxyglucose ([F]FDG or FDG) is commonly used to detect cancer;
* [[Sodium fluoride#Medical imaging|[F]Sodium fluoride]] (NaF) is widely used for detecting bone formation;
* Oxygen-15 (O) is sometimes used to measure blood flow.
PET is a common imaging technique, a medical scintillography technique used in nuclear medicine. A radiopharmaceutical – a radioisotope attached to a drug – is injected into the body as a tracer. When the radiopharmaceutical undergoes beta plus decay, a positron is emitted, and when the positron interacts with an ordinary electron, the two particles annihilate and two gamma rays are emitted in opposite directions. These gamma rays are detected by two gamma cameras to form a three-dimensional image.
PET scanners can incorporate a computed tomography scanner (CT) and are known as PET-CT scanners. PET scan images can be reconstructed using a CT scan performed using one scanner during the same session.
One of the disadvantages of a PET scanner is its high initial cost and ongoing operating costs. | 1 | Applied and Interdisciplinary Chemistry |
Most processes begin with phosphorous acid (aka phosphonic acid, HPO), exploiting its reactive P−H bond.
Phosphonic acid can be alkylated via the Kabachnik–Fields reaction or Pudovik reaction to give aminophosphonate, which are useful as chelating agents. One example is the industrial preparation of nitrilotris(methylenephosphonic acid):
:NH + 3 HPO + 3 CHO → N(CHPOH) + 3 HO
Phosphonic acid also can be alkylated with acrylic acid derivatives to afford carboxyl functionalized phosphonic acids. This reaction is a variant of the Michael addition:
:CH=CHCOR + 3 HPO → (HO)P(O)CHCHCOR
In the Hirao coupling dialkyl phosphites (which can also be viewed as di-esters of phosphonic acid: (O=PH(OR)) undergo a palladium-catalyzed coupling reaction with an aryl halide to form a phosphonate. | 0 | Theoretical and Fundamental Chemistry |
Cereblon E3 ligase modulators, also known as immunomodulatory imide drugs (IMiDs), are a class of immunomodulatory drugs (drugs that adjust immune responses) containing an imide group. The IMiD class includes thalidomide and its analogues (lenalidomide, pomalidomide, mezigdomide
and iberdomide). These drugs may also be referred to as Cereblon modulators. Cereblon (CRBN) is the protein targeted by this class of drugs.
The name "IMiD" alludes to both "IMD" for "immunomodulatory drug" and the forms imide, imido-, imid-, and imid.
The development of analogs of thalidomide was precipitated by the discovery of the anti-angiogenic and anti-inflammatory properties of the drug yielding a new way of fighting cancer as well as some inflammatory diseases after it had been banned in 1961. The problems with thalidomide included teratogenic side effects, high incidence of other adverse reactions, poor solubility in water and poor absorption from the intestines.
In 1998 thalidomide was approved by the U.S. Food and Drug Administration (FDA) for use in newly diagnosed multiple myeloma (MM) under strict regulations. This has led to the development of a number of analogs with fewer side effects and increased potency which include lenalidomide and pomalidomide, which are currently marketed and manufactured by Celgene. | 1 | Applied and Interdisciplinary Chemistry |
Secondary metabolites are compounds made in the stationary phase; penicillin, for instance, prevents the growth of bacteria which could compete with Penicillium molds for resources. Some bacteria, such as Lactobacillus species, are able to produce bacteriocins which prevent the growth of bacterial competitors as well. These compounds are of obvious value to humans wishing to prevent the growth of bacteria, either as antibiotics or as antiseptics (such as gramicidin S). Fungicides, such as griseofulvin are also produced as secondary metabolites. Typically secondary metabolites are not produced in the presence of glucose or other carbon sources which would encourage growth, and like primary metabolites are released into the surrounding medium without rupture of the cell membrane.
In the early days of the biotechnology industry, most biopharmaceutical products were made in E. coli; by 2004 more biopharmaceuticals were manufactured in eukaryotic cells, such as CHO cells, than in microbes, but used similar bioreactor systems. Insect cell culture systems came into use in the 2000s as well. | 1 | Applied and Interdisciplinary Chemistry |
Of the seven metals known in antiquity, only gold regularly occurs in nature as a native metal. The others – copper, lead, silver, tin, iron, and mercury – occur primarily as minerals, although native copper is occasionally found in commercially significant quantities. These minerals are primarily carbonates, sulfides, or oxides of the metal, mixed with other components such as silica and alumina. Roasting the carbonate and sulfide minerals in the air converts them to oxides. The oxides, in turn, are smelted into the metal. Carbon monoxide was (and is) the reducing agent of choice for smelting. It is easily produced during the heating process, and as a gas comes into intimate contact with the ore.
In the Old World, humans learned to smelt metals in prehistoric times, more than 8000 years ago. The discovery and use of the "useful" metals – copper and bronze at first, then iron a few millennia later – had an enormous impact on human society. The impact was so pervasive that scholars traditionally divide ancient history into Stone Age, Bronze Age, and Iron Age.
In the Americas, pre-Inca civilizations of the central Andes in Peru had mastered the smelting of copper and silver at least six centuries before the first Europeans arrived in the 16th century, while never mastering the smelting of metals such as iron for use with weapon craft. | 1 | Applied and Interdisciplinary Chemistry |
Microwave-assisted peptide synthesis has been used to complete long peptide sequences with high degrees of yield and low degrees of racemization. | 1 | Applied and Interdisciplinary Chemistry |
The test chamber has a set volume of 300L. The construction of the inner housing of the chamber and the devices for arranging the samples must be made of inert and corrosion-resistant materials so that there is no reaction between the sample to be tested and the material of the chamber. The SO injection can be performed manually or automatically depending on the chamber. | 1 | Applied and Interdisciplinary Chemistry |
Richard Chenevix (ca. 1774 – 5 April 1830) was an Irish chemist, mineralogist and playwright who also wrote on a range of other topics. He was known for his sharp cynicism and for engaging in combative criticism. | 1 | Applied and Interdisciplinary Chemistry |
An atom or a molecule can absorb light and undergo a transition from
one quantum state to another.
The oscillator strength of a transition from a lower state
to an upper state may be defined by
where is the mass of an electron and is
the reduced Planck constant. The quantum states 1,2, are assumed to have several
degenerate sub-states, which are labeled by . "Degenerate" means
that they all have the same energy .
The operator is the sum of the x-coordinates
of all electrons in the system, i.e.
The oscillator strength is the same for each sub-state .
The definition can be recast by inserting the Rydberg energy and Bohr radius
In case the matrix elements of are the same, we can get rid of the sum and of the 1/3 factor | 0 | Theoretical and Fundamental Chemistry |
Fluorenylidene reacts with olefins as predicted by the Skell-Woodworth rules. The stereochemistry of cycloaddition products depends on the relative rates of cyclopropanation (or other reactions) and intersystem crossing. Stabilization of specific spin states, and, by extension, increased stereospecificity can be achieved by using solvents of different polarities . | 0 | Theoretical and Fundamental Chemistry |
The absolute bioavailability of a drug, when administered by an extravascular route, is usually less than one (i.e., F< 100%). Various physiological factors reduce the availability of drugs prior to their entry into the systemic circulation. Whether a drug is taken with or without food will also affect absorption, other drugs taken concurrently may alter absorption and first-pass metabolism, intestinal motility alters the dissolution of the drug and may affect the degree of chemical degradation of the drug by intestinal microflora. Disease states affecting liver metabolism or gastrointestinal function will also have an effect.
Other factors may include, but are not limited to:
* Physical properties of the drug (hydrophobicity, pKa, solubility)
* The drug formulation (immediate release, excipients used, manufacturing methods, modified release – delayed release, extended release, sustained release, etc.)
* Whether the formulation is administered in a fed or fasted state
* Gastric emptying rate
* Circadian differences
* Interactions with other drugs/foods:
** Interactions with other drugs (e.g., antacids, alcohol, nicotine)
** Interactions with other foods (e.g., grapefruit juice, pomello, cranberry juice, brassica vegetables)
* Transporters: Substrate of efflux transporters (e.g. P-glycoprotein)
* Health of the gastrointestinal tract
* Enzyme induction/inhibition by other drugs/foods:
** Enzyme induction (increased rate of metabolism), e.g., Phenytoin induces CYP1A2, CYP2C9, CYP2C19, and CYP3A4
** Enzyme inhibition (decreased rate of metabolism), e.g., grapefruit juice inhibits CYP3A → higher nifedipine concentrations
* Individual variation in metabolic differences
** Age: In general, drugs are metabolized more slowly in fetal, neonatal, and geriatric populations
** Phenotypic differences, enterohepatic circulation, diet, gender
* Disease state
** E.g., hepatic insufficiency, poor renal function
Each of these factors may vary from patient to patient (inter-individual variation), and indeed in the same patient over time (intra-individual variation). In clinical trials, inter-individual variation is a critical measurement used to assess the bioavailability differences from patient to patient in order to ensure predictable dosing. | 1 | Applied and Interdisciplinary Chemistry |
Of the material sold during the 1936 Sothebys auction, several documents indicate an interest by Newton in the procurement or development of the philosophers stone. Most notably are documents entitled Artephius his secret Book, followed by The Epistle of Iohn Pontanus, wherein he beareth witness of ye book of Artephius; these are themselves a collection of excerpts from another work entitled Nicholas Flammel, His Exposition of the Hieroglyphicall Figures which he caused to be painted upon an Arch in St Innocents Church-yard in Paris. Together with The secret Booke of Artephius, And the Epistle of Iohn Pontanus: Containing both the Theoricke and the Practicke of the Philosophers Stone. This work may also have been referenced by Newton in its Latin version found within Lazarus Zetzners Theatrum Chemicum, a volume often associated with the Turba Philosophorum and other early European alchemical manuscripts. Nicolas Flamel, one subject of the aforementioned work, was a notable, though mysterious figure, often associated with the discovery of the philosophers stone, hieroglyphical figures, early forms of tarot, and occultism. Artephius, and his "secret book", were also subjects of interest to 17th-century alchemists.
Also in the 1936 auction of Newtons collection was The Epitome of the treasure of health written by Edwardus Generosus Anglicus innominatus who lived Anno Domini 1562. This is a twenty-eight-page treatise on the philosophers stone, the Animal or Angelicall Stone, the Prospective stone or magical stone of Moses, and the vegetable or the growing stone. The treatise concludes with an alchemical poem. | 1 | Applied and Interdisciplinary Chemistry |
Conservation and restoration of glass objects is one aspect of conservation and restoration of cultural heritage. The nature and varying composition of the material, and the variety of types of object made from it, demand certain specialized techniques. The conservator needs to be aware of "agents of deterioration" presenting particular risk to glass objects, and how to prevent or counteract their effects. Relevant education and training is available in certain countries through museums, conservation institutes and universities. | 0 | Theoretical and Fundamental Chemistry |
As well as enabling data exchange, CCPN aims to develop software for processing, analysis and interpretation of macromolecular NMR data. To this end CCPN has created CcpNmr Analysis; a graphical program for spectrum visualisation, assignment and NMR data analysis. Here, the requirement was for a program that used a modern graphical user interface and could run on many types of computer. It would be supported and maintained by CCPN and would allow modification and extension, including for new NMR techniques. The first version of Analysis was released in 2005 and is now at version 2.1. Analysis is built directly on the CCPN data model and its design is partly inspired by the older ANSIG. and SPARKY programs, but it has continued to develop from the suggestions, requirements and computational contributions of its user community. Analysis is freely available to academic and non-profit institutions. Commercial users are required to subscribe to CCPN for a moderate fee. CCPN software, including Analysis, is available for download at the CCPN web site and is supported by an active JISC email discussion group. | 0 | Theoretical and Fundamental Chemistry |
The Two-dimensional (2-D) polymers formed by topochemical polymerization are popular topics in material chemistry. By synthesizing and polymerizing monomers with functionality greater than 2, the 2-D networks instead of linear polymers can be obtained. [4+4] and [4+2] involving anthracene units are popular choices for 2D-polymer synthesis. 2-D covalent networks with high crystallinity can be produced in this way in high conversion. Recently, schluter et al. synthesized a 2D polymer via 2+2 topochemical cycloaddition reaction.[https://pubs.acs.org/doi/10.1021/jacs.6b11857] | 0 | Theoretical and Fundamental Chemistry |
Arsenic may be measured in blood or urine to monitor excessive environmental or occupational exposure, confirm a diagnosis of poisoning in hospitalized victims or to assist in the forensic investigation in a case of fatal over dosage. Some analytical techniques are capable of distinguishing organic from inorganic forms of the element. Organic arsenic compounds tend to be eliminated in the urine in unchanged form, while inorganic forms are largely converted to organic arsenic compounds in the body prior to urinary excretion. The current biological exposure index for U.S. workers of 35 µg/L total urinary arsenic may easily be exceeded by a healthy person eating a seafood meal.
Tests are available to diagnose poisoning by measuring arsenic in blood, urine, hair, and fingernails. The urine test is the most reliable test for arsenic exposure within the last few days. Urine testing needs to be done within 24–48 hours for an accurate analysis of an acute exposure. Tests on hair and fingernails can measure exposure to high levels of arsenic over the past 6–12 months. These tests can determine if one has been exposed to above-average levels of arsenic. They cannot predict, however, whether the arsenic levels in the body will affect health. Chronic arsenic exposure can remain in the body systems for a longer period of time than a shorter term or more isolated exposure and can be detected in a longer time frame after the introduction of the arsenic, important in trying to determine the source of the exposure.
Hair is a potential bioindicator for arsenic exposure due to its ability to store trace elements from blood. Incorporated elements maintain their position during growth of hair. Thus for a temporal estimation of exposure, an assay of hair composition needs to be carried out with a single hair which is not possible with older techniques requiring homogenization and dissolution of several strands of hair. This type of biomonitoring has been achieved with newer microanalytical techniques like synchrotron radiation based X-ray fluorescence spectroscopy and microparticle induced X-ray emission. The highly focused and intense beams study small spots on biological samples allowing analysis to micro level along with the chemical speciation. In a study, this method has been used to follow arsenic level before, during and after treatment with arsenious oxide in patients with acute promyelocytic leukemia. | 1 | Applied and Interdisciplinary Chemistry |
The pulse-induction method is based on electromagnetic pulse induction technology to detect rebars. Coils in the probe are periodically charged by current pulses and thus generate a magnetic field. On the surface of any electrically conductive material which is in the magnetic field eddy currents are produced. They induce a magnetic field in opposite directions. The resulting change in voltage can be utilized for the measurement. Rebars that are closer to the probe or of larger size produce a stronger magnetic field.
Modern rebar detectors use different coil arrangements to generate several magnetic fields. Advanced signal processing supports not only the localization of rebars but also the determination of the cover and the estimation of the bar diameter. This method is unaffected by all non conductive materials such as concrete, wood, plastics, bricks, etc. However any kind of conductive materials within the magnetic field will have an influence on the measurement.
Advantages of the pulse induction method:
* high accuracy
* not influenced by moisture and heterogeneities of the concrete
* unaffected by environmental influences
* low costs
Disadvantage of the pulse induction method:
* Limited detection range
* Minimum bar spacing depends on cover depths | 1 | Applied and Interdisciplinary Chemistry |
Berlin has undertaken research on a broad range of areas in both physical and theoretical chemistry, involving stochastic dynamics of complex systems, chemical kinetics and transport of active species in condensed phase and in biological molecules, physical chemistry of liquids and solids, theoretical biophysics and physical aspects of prebiotic evolution, physical methods for the initiation of chemical reactions, in particular cryochemistry, radiation chemistry, photo, and high pressure chemistry. His research covers a vast range of fields, such as the theory of excess electrons in non-polar liquids and liquid noble gases, charge transfer under extreme conditions, chemical processes coupled to structural rearrangements of molecular environment, dispersive kinetics, the effects of correlated fluctuations in chemical and biological properties, the role of static and dynamic disorder in the mechanism of chemical processes in condensed media. Later works are focused on mechanism and kinetics of charge transfer and transport in DNA, culminated in a series of studies of various DNA constructs as building blocks of molecular circuitry. Berlin has published over 170 papers in scientific journals. | 0 | Theoretical and Fundamental Chemistry |
Household ammonia can be used. A couple of drops are placed on the flesh. For example, Boletus spadiceus gives a fleeting blue to blue-green reaction. | 0 | Theoretical and Fundamental Chemistry |
A polymeric foam is a special foam, in liquid or solidified form, formed from polymers.
Examples include:
* Ethylene-vinyl acetate (EVA) foam, the copolymers of ethylene and vinyl acetate; also referred to as polyethylene-vinyl acetate (PEVA)
* Low-density polyethylene (LDPE) foam, first grade of polyethylene (PE)
* Nitrile rubber (NBR) foam, the copolymers of acrylonitrile (ACN) and butadiene
* Polychloroprene foam or Neoprene
* Polyimide foam
* Polypropylene (PP) foam, including expanded polypropylene (EPP) and polypropylene paper (PPP)
* Polystyrene (PS) foam, including expanded polystyrene (EPS), extruded polystyrene foam (XPS) and sometimes polystyrene paper (PSP)
** Styrofoam, including extruded polystyrene foam (XPS) and sometimes expanded polystyrene (EPS)
* Polyurethane (PU) foam
** LRPu low-resilience polyurethane
** Memory foam
** Sorbothane
*Polyurea foam
*Polyethylene foam, as used in PEF rod
* Polyvinyl chloride (PVC) foam
** Closed-cell PVC foamboard
* Silicone foam
* Microcellular foam | 0 | Theoretical and Fundamental Chemistry |
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (FeO·nHO) and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)), and is typically associated with the corrosion of refined iron.
Given sufficient time, any iron mass, in the presence of water and oxygen, could eventually convert entirely to rust. Surface rust is commonly flaky and friable, and provides no passivational protection to the underlying iron, unlike the formation of patina on copper surfaces. Rusting is the common term for corrosion of elemental iron and its alloys such as steel. Many other metals undergo similar corrosion, but the resulting oxides are not commonly called "rust".
Several forms of rust are distinguishable both visually and by spectroscopy, and form under different circumstances. Other forms of rust include the result of reactions between iron and chloride in an environment deprived of oxygen. Rebar used in underwater concrete pillars, which generates green rust, is an example. Although rusting is generally a negative aspect of iron, a particular form of rusting, known as stable rust, causes the object to have a thin coating of rust over the top. If kept in low relative humidity, it makes the "stable" layer protective to the iron below, but not to the extent of other oxides such as aluminium oxide on aluminium. | 1 | Applied and Interdisciplinary Chemistry |
An ideal solution would follow Raoult's law, but most solutions deviate from ideality. Interactions between gas molecules are typically quite small, especially if the vapor pressures are low. However, the interactions in a liquid are very strong. For a solution to be ideal, the interactions between unlike molecules must be of the same magnitude as those between like molecules. This approximation is only true when the different species are almost chemically identical. One can see that from considering the Gibbs free energy change of mixing:
This is always negative, so mixing is spontaneous. However, the expression is, apart from a factor , equal to the entropy of mixing. This leaves no room at all for an enthalpy effect and implies that must be equal to zero, and this can only be true if the interactions between the molecules are indifferent.
It can be shown using the Gibbs–Duhem equation that if Raoult's law holds over the entire concentration range in a binary solution then, for the second component, the same must also hold.
If deviations from the ideal are not too large, Raoults law is still valid in a narrow concentration range when approaching for the majority phase (the solvent). The solute also shows a linear limiting law, but with a different coefficient. This relationship is known as Henrys law.
The presence of these limited linear regimes has been experimentally verified in a great number of cases, though large deviations occur in a variety of cases. Consequently, both its pedagogical value and utility have been questioned at the introductory college level. In a perfectly ideal system, where ideal liquid and ideal vapor are assumed, a very useful equation emerges if Raoults law is combined with Daltons Law:
where is the mole fraction of component in the solution, and is its mole fraction in the gas phase. This equation shows that, for an ideal solution where each pure component has a different vapor pressure, the gas phase is enriched in the component with the higher vapor pressure when pure, and the solution is enriched in the component with the lower pure vapor pressure. This phenomenon is the basis for distillation. | 0 | Theoretical and Fundamental Chemistry |
An increasing offset between the optical phase and the maximum of the wave envelope of an optical pulse can be seen on the right.
Each line is displaced from a harmonic of the repetition rate by the carrier–envelope offset frequency. The carrier–envelope offset frequency is the rate at which the peak of the carrier frequency slips from the peak of the pulse envelope on a pulse-to-pulse basis.
Measurement of the carrier–envelope offset frequency is usually done with a self-referencing technique, in which the phase of one part of the spectrum is compared to its harmonic. Different possible approaches for carrier–envelope offset phase control were proposed in 1999. The two simplest approaches, which require only one nonlinear optical process, are described in the following.
In the "f − 2f" technique, light at the lower-energy side of the broadened spectrum is doubled using second-harmonic generation (SHG) in a nonlinear crystal, and a heterodyne beat is generated between that and light at the same wavelength on the upper-energy side of the spectrum. This beat signal, detectable with a photodiode, includes a difference-frequency component, which is the carrier–envelope offset frequency.
Alternatively, difference-frequency generation (DFG) can be used. From light of opposite ends of the broadened spectrum the difference frequency is generated in a nonlinear crystal, and a heterodyne beat between this mixing product and light at the same wavelength of the original spectrum is measured. This beat frequency, detectable with a photodiode, is the carrier–envelope offset frequency.
Because the phase is measured directly, and not the frequency, it is possible to set the frequency to zero and additionally lock the phase, but because the intensity of the laser and this detector is not very stable, and because the whole spectrum beats in phase,
one has to lock the phase on a fraction of the repetition rate. | 0 | Theoretical and Fundamental Chemistry |
The Platinum Metal Review journal was established in 1957 and was published by Johnson Mattley and Co. From April 1998, it was published as open access and from the July 2004 issue in electronic format only. In 2014 the name of the journal was changed to Johnson Matthey Technology Review. | 1 | Applied and Interdisciplinary Chemistry |
The gene for the FSHR is found on chromosome 2 p21 in humans. The gene sequence of the FSHR consists of about 2,080 nucleotides. | 1 | Applied and Interdisciplinary Chemistry |
The Szilard–Chalmers effect is the breaking of a chemical bond as a result of a kinetic energy imparted from radioactive decay. It operates by the absorption of neutrons by an atom and subsequent emission of gamma rays, often with significant amounts of kinetic energy. This kinetic energy, by Newton's third law, pushes back on the decaying atom, which causes it to move with enough speed to break a chemical bond. This effect can be used to separate isotopes by chemical means.
The Szilard–Chalmers effect was discovered in 1934 by Leó Szilárd and Thomas A. Chalmers. They observed that after bombardment by neutrons, the breaking of a bond in liquid ethyl iodide allowed radioactive iodine to be removed. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the electromeric effect is a molecular polarization occurring by an intramolecular electron displacement characterized by the substitution of one electron pair for another within the same atomic octet of electrons. It is sometimes called the conjugative mechanism, and previously, the tautomeric mechanism). The electromeric effect is often considered along with the inductive effect as types of electron displacement. Although some people refer it as an effect produced by the presence of a reagent like an electrophile or a nucleophile, IUPAC does not define it as such. The term electromeric effect is no longer used in standard texts and is considered as obsolete. The concepts implied by the terms electromeric effect and mesomeric effect are absorbed in the term resonance effect. This effect can be represented using curved arrows which symbolize the electron shift, as in the diagram below: | 0 | Theoretical and Fundamental Chemistry |
Frequency modulated Doppler-broadened signals can be modeled basically as ordinary fm-signals, although an extended description has to be used if the transition is optically saturated. Wavelength modulated Doppler broadened can be modeled by applying the conventional theory for wavelength modulation on the fm-signals.
Since the electrical field in NICE-OHMS consists of three modes, a carrier and two sidebands, which propagate in positive and negative directions in the cavity, up to nine sub-Doppler signals can appear; four appearing at the absorption and five at the dispersion phase. Each of these signals can, in turn, originate from interactions between several groups of molecules with various pairs of modes (e.g. carrier-carrier, sideband-carrier, sideband-sideband in various combinations). In addition, since sub-Doppler signals necessarily involve optical saturation, each of these interactions has to be modeled by a more extensive description. This implies that the situation can be complex. In fact, there are still some types of sub-Doppler signals for which there so far are no adequate theoretical description. | 0 | Theoretical and Fundamental Chemistry |
There are several models used to predict liquidus and solidus curves for various systems.
Detailed measurements of solidus and liquidus can be made using techniques such as differential scanning calorimetry and differential thermal analysis. | 0 | Theoretical and Fundamental Chemistry |
PEX genes encode the protein machinery (peroxins) required for proper peroxisome assembly. Peroxisomal membrane proteins are imported through at least two routes, one of which depends on interaction between peroxin 19 and peroxin 3, while the other is required for import of peroxin 3, either of which may occur without the import of matrix (lumen) enzymes, which possess the peroxisomal targeting signal PTS1 or PTS2 as previously discussed. Elongation of the peroxisome membrane and the final fission of the organelle are regulated by Pex11p.
Genes that encode peroxin proteins include: PEX1, PEX2 (PXMP3), PEX3, PEX5, PEX6, PEX7, PEX9, PEX10, PEX11A, PEX11B, PEX11G, PEX12, PEX13, PEX14, PEX16, PEX19, PEX26, PEX28, PEX30, and PEX31. Between organisms, PEX numbering and function can differ. | 1 | Applied and Interdisciplinary Chemistry |
The Oddy test is a procedure created at the British Museum by conservation scientist William Andrew Oddy in 1973, in order to test materials for safety in and around art objects.
Often, materials for construction and museum contexts (including artefact conservation) are evaluated for safety. However, though materials may be safe for building purposes, they may emit trace amounts of chemicals that can harm art objects over time. Acids, formaldehyde, and other pollutants can damage and even destroy delicate artifacts if placed too close. | 1 | Applied and Interdisciplinary Chemistry |
A biological oxidizer is a device that uses micro-organisms to treat wastewater and the volatile organic compounds produced by commercial and industrial operations. Biological oxidation devices convert biodegradable organic compounds into carbon dioxide and water. This is a natural occurring process which differs from traditional chemical and thermal oxidizing agents and methods. Some of the more commonly used micro-organisms are heterotrophic bacteria, which play an important role in biological degradation processes. Generally, these micro-organisms are rod shaped and facultative. Biological oxidizers provide a stable environment which allows bacteria to naturally oxidize and stabilize a large number of organics in a more efficient manner. Some of the emissions that may be treated biologically include:
* heterocyclic compounds (such as quinoline or pyridine);
* polyaromatic hydrocarbons (PAHs);
* pharmaceutical substances;
* polychlorinated biphenyls;
* hydrocarbons (oil);
* benzene, toluene, ethylbenzene, and xylene (BETEX);
* methyl ethyl ketone (MEK);
* some metals.
The prompt removal of a wide range of wastes and pollutants from the environment is the foremost requisite leading to minimal negative environmental impact and sustainability. Microorganisms offer excellent anabolic and catabolic adaptability to degrade and produce stabilized organic matters from contaminants. Microbiology is providing significant views of regulatory metabolic pathways as well as effectiveness to adaption and biological degradation in our changing environment. | 1 | Applied and Interdisciplinary Chemistry |
Conformational strain and structural rigidity can effectively prevent the inversion of amine groups. Trögers base analogs (including the Hünlichs base) are examples of compounds whose nitrogen atoms are chirally stable stereocenters and therefore have significant optical activity. | 0 | Theoretical and Fundamental Chemistry |
It has been used to produce smoke screens since it produces a heavy, white smoke that has little tendency to rise. "Tickle" was the standard means of producing on-set smoke effects for motion pictures, before being phased out in the 1980s due to concerns about hydrated HCl's effects on the respiratory system. | 0 | Theoretical and Fundamental Chemistry |
The National Association of Women Pharmacists was founded in London on 15 June 1905, following discussions between Margaret Elizabeth Buchanan and Isabella Skinner Clarke. Early meetings were held at Clarke's home. Membership was restricted to those who had passed the major or minor examination and 50 women joined immediately. By 1912 Buchanan claimed that practically all women practicing pharmacy were members. | 1 | Applied and Interdisciplinary Chemistry |
The most common NMR techniques used when discriminating chiral compounds are H-NMR, F-NMR and C-NMR. H-NMR is the primary technique used to assign absolute configuration. F-NMR is almost exclusive applied to optical purity studies, and C-NMR is primarily used to characterize substrates that do not have protons that are directly bonded to an asymmetrical carbon atom. | 0 | Theoretical and Fundamental Chemistry |
A convenient synthesis of chloromethyl methyl ether in situ involves the reaction of dimethoxymethane and acetyl chloride in the presence of a Lewis acid catalyst This route affords a methyl acetate solution of chloromethyl methyl ether of high purity. A similar method, using a high-boiling acyl chloride, can be used to prepare pure, dimethoxymethane being the only contaminant. In contrast, the classical procedure reported in Organic Syntheses employing formaldehyde, methanol, and hydrogen chloride yields material significantly contaminated with the dangerous bis(chloromethyl) ether and requires fractional distillation. | 0 | Theoretical and Fundamental Chemistry |
* Bannock Basin in Levantine Sea, eastern Mediterranean Sea;
* Black Sea Basin, off eastern Europe, below 50 metres (150 feet);
* Caspian Sea Basin, below 100 metres (300 feet);
* Cariaco Basin, off north central Venezuela;
* Gotland Deep, in the Baltic off Sweden;
* L'Atalante basin, eastern Mediterranean Sea
* Mariager Fjord, off Denmark;
* Orca Basin, northeast Gulf of Mexico;
* Saanich Inlet, off Vancouver Island, Canada; | 0 | Theoretical and Fundamental Chemistry |
On some other instances in biology (not necessarily about cell signaling), the term "Scaffold protein" is used in a broader sense, where a protein holds several things together for any purpose.
;In chromosome folding: Chromosome scaffold has important role to hold the chromatin into compact chromosome. Chromosome scaffold is made of proteins including condensin, topoisomerase IIα and kinesin family member 4 (KIF4) Chromosome scaffold constituent proteins are also called scaffold protein.
;In enzymatic reaction: Large multifunctional enzymes that performs a series or chain of reaction in a common pathway, sometimes called scaffold proteins. such as Pyruvate dehydrogenase.
;In molecule shape formation: An enzyme or structural protein that holds several molecules together to hold them in proper spatial arrangement, such as Iron sulphur cluster scaffold proteins.
;Structural scaffold: In cytoskeleton and ECM, the molecules provide mechanical scaffold. Such as type 4 collagen | 1 | Applied and Interdisciplinary Chemistry |
The combination medicine dextromethorphan/bupropion is approved for major depressive disorder under the brand name Auvelity. | 0 | Theoretical and Fundamental Chemistry |
When two metals touch each other and water is present, electrolysis occurs. One well known example is the reaction between zinc (Zn) and iron (Fe). Zinc atoms will lose electrons in preference to the iron as they are more electropositive and therefore zinc is oxidized and corrodes.
Zn(s)→(aq) +2e (oxidation) | 0 | Theoretical and Fundamental Chemistry |
In addition to the variety of verified DNA structures, there have been a range of proposed DNA models that have either been disproven, or lack evidence.
Some of these structures were proposed during the 1950s before the structure of the double helix was solved, most famously by Linus Pauling. Non-helical or "side-by-side" models of DNA were proposed in the 1970s to address what appeared at the time to be problems with the topology of circular DNA chromosomes during replication (subsequently resolved via the discovery of enzymes that modify DNA topology). These were also rejected due to accumulating experimental evidence from X-ray crystallography, solution NMR, and atomic force microscopy (of both DNA alone, and bound to DNA-binding proteins). Although localised or transient non-duplex helical structures exist, non-helical models are not currently accepted by the mainstream scientific community. Finally, there exists a persistent set of contemporary fringe theories proposing a range of unsupported models. | 1 | Applied and Interdisciplinary Chemistry |
When all of the isoprene units in a network chain have been forced to reside in just a few extended rotational conformations, the chain becomes taut. It may be regarded as sensibly straight, except for the zigzag path that the C-C bonds make along the chain contour. However, further extension is still possible by bond distortions, e.g., bond angle increases, bond stretches and dihedral angle rotations. These forces are spring-like and are not associated with entropy changes. A taut chain can be extended by only about 40%. At this point the force along the chain is sufficient to mechanically rupture the C-C covalent bond. This tensile force limit has been calculated via quantum chemistry simulations and it is approximately 7 nN, about a factor of a thousand greater than the entropic chain forces at low strain. The angles between adjacent backbone C-C bonds in an isoprene unit vary between about 115–120 degrees and the forces associated with maintaining these angles are quite large, so within each unit, the chain backbone always follows a zigzag path, even at bond rupture. This mechanism accounts for the steep upturn in the elastic stress, observed at high strains (Fig. 1). | 0 | Theoretical and Fundamental Chemistry |
Reverse [2+2] photocycloaddition, decomposition of 1,2-dioxetanedione, is stated as the mechanism that produces light in glow sticks. | 0 | Theoretical and Fundamental Chemistry |
Photocathodes operate in a vacuum, so their design parallels vacuum tube technology. Since
most cathodes are sensitive to air the construction of photocathodes typically occurs after the enclosure has been evacuated. In operation the photocathode requires an electric field with a nearby positive anode to assure electron emission. Molecular beam epitaxy is broadly applied in todays manufacturing of photocathode. By using a substrate with matched lattice parameters, crystalline photocathodes can be made and electron beams can come out from the same position in lattices Brillouin zone to get high brightness electron beams.
Photocathodes divide into two broad groups; transmission and reflective. A transmission type is typically a coating upon a glass window in which the light strikes one surface and electrons exit from the opposite surface. A reflective type is typically formed on an opaque metal electrode base, where the light enters and the electrons exit from the same side. A variation is the double reflection type, where the metal base is mirror-like, causing light that passed through the photocathode without causing emission to be bounced back for a second try. This mimics the retina on many mammals.
The effectiveness of a photocathode is commonly expressed as quantum efficiency, that being the ratio of emitted electrons vs. impinging quanta (of light). The efficiency varies with construction as well, as it can be improved with a stronger electric field. | 0 | Theoretical and Fundamental Chemistry |
Solar cells were first used in a prominent application when they were proposed and flown on the Vanguard satellite in 1958, as an alternative power source to the primary battery power source. By adding cells to the outside of the body, the mission time could be extended with no major changes to the spacecraft or its power systems. In 1959 the United States launched Explorer 6, featuring large wing-shaped solar arrays, which became a common feature in satellites. These arrays consisted of 9600 Hoffman solar cells.
By the 1960s, solar cells were (and still are) the main power source for most Earth orbiting satellites and a number of probes into the solar system, since they offered the best power-to-weight ratio. However, this success was possible because in the space application, power system costs could be high, because space users had few other power options, and were willing to pay for the best possible cells. The space power market drove the development of higher efficiencies in solar cells up until the National Science Foundation "Research Applied to National Needs" program began to push development of solar cells for terrestrial applications.
In the early 1990s the technology used for space solar cells diverged from the silicon technology used for terrestrial panels, with the spacecraft application shifting to gallium arsenide-based III-V semiconductor materials, which then evolved into the modern III-V multijunction photovoltaic cell used on spacecraft.
In recent years, research has moved towards designing and manufacturing lightweight, flexible, and highly efficient solar cells. Terrestrial solar cell technology generally uses photovoltaic cells that are laminated with a layer of glass for strength and protection. Space applications for solar cells require that the cells and arrays are both highly efficient and extremely lightweight. Some newer technology implemented on satellites are multi-junction photovoltaic cells, which are composed of different PN junctions with varying bandgaps in order to utilize a wider spectrum of the sun's energy. Additionally, large satellites require the use of large solar arrays to produce electricity. These solar arrays need to be broken down to fit in the geometric constraints of the launch vehicle the satellite travels on before being injected into orbit. Historically, solar cells on satellites consisted of several small terrestrial panels folded together. These small panels would be unfolded into a large panel after the satellite is deployed in its orbit. Newer satellites aim to use flexible rollable solar arrays that are very lightweight and can be packed into a very small volume. The smaller size and weight of these flexible arrays drastically decreases the overall cost of launching a satellite due to the direct relationship between payload weight and launch cost of a launch vehicle.
In 2020, the US Naval Research Laboratory conducted its first test of solar power generation in a satellite, the Photovoltaic Radio-frequency Antenna Module (PRAM) experiment aboard the Boeing X-37. | 0 | Theoretical and Fundamental Chemistry |
Persephin is a neurotrophic factor in the glial cell line-derived neurotrophic factor (GDNF) family. Persephin shares around a 40% similarity in amino acid sequence compared to GDNF and neurturin, two members of the GDNF family. | 1 | Applied and Interdisciplinary Chemistry |
Armando Bukele Kattán was born in San Salvador, on December 16, 1944, the son of Humberto Bukele Salman and Victoria Kattán de Bukele. His parents were Palestinian Christians from Bethlehem in Ottoman Palestine and had emigrated to El Salvador at the beginning of the 20th century as part of an emigration wave. He completed his high school studies at the Liceo Salvadoreño. | 1 | Applied and Interdisciplinary Chemistry |
There are two types of continuous cooling diagrams drawn for practical purposes.
* Type 1: This is the plot beginning with the transformation start point, cooling with a specific transformation fraction and ending with a transformation finish temperature for all products against transformation time for each cooling curve.
* Type 2: This is the plot beginning with the transformation start point, cooling with specific transformation fraction and ending with a transformation finish temperature for all products against cooling rate or bar diameter of the specimen for each type of cooling medium.. | 1 | Applied and Interdisciplinary Chemistry |
The Stern–Volmer relationship, named after Otto Stern and Max Volmer, allows the kinetics of a photophysical intermolecular deactivation process to be explored.
Processes such as fluorescence and phosphorescence are examples of intramolecular deactivation processes. An intermolecular deactivation is where the presence of another chemical species can accelerate the decay rate of a chemical in its excited state. In general, this process can be represented by a simple equation:
or
where A is one chemical species, Q is another (known as a quencher) and * designates an excited state.
The kinetics of this process follows the Stern–Volmer relationship:
Where is the intensity, or rate of fluorescence, without a quencher, is the intensity, or rate of fluorescence, with a quencher, is the quencher rate coefficient, is the lifetime of the emissive excited state of A without a quencher present, and is the concentration of the quencher.
For diffusion-limited quenching (i.e., quenching in which the time for quencher particles to diffuse toward and collide with excited particles is the limiting factor, and almost all such collisions are effective), the quenching rate coefficient is given by , where is the ideal gas constant, is temperature in kelvins is the viscosity of the solution. This formula is derived from the Stokes–Einstein relation and is only useful in this form in the case of two spherical particles of identical radius that react every time they approach a distance R, which is equal to the sum of their two radii. The more general expression for the diffusion limited rate constant is
Where and are the radii of the two molecules and is an approach distance at which unity reaction efficiency is expected (this is an approximation).
In reality, only a fraction of the collisions with the quencher are effective at quenching, so the true quenching rate coefficient must be determined experimentally. | 0 | Theoretical and Fundamental Chemistry |
The advantages of LFV are
* LFV is a non-contact techniques of flow rate measurement.
* LFV can be successfully applied for aggressive and high-temperature fluids like liquid metals.
* Mean flow rate or mean velocity of fluid can be obtained without depending on flow's inhomogeneities and zones of turbulence.
The limitations of the LFV are
* Necessity of temperature control of measurement system because of strong dependence of magnet's magnetic field on temperature. High temperature could cause irretrievable loss of the magnetic properties of permanent magnet (Curie temperature).
* Restriction of measurement zone by permanent magnet's dimensions.
* Necessity of liquid level's control in case of work with open channel.
* Rapid decay of the magnetic fields give rise to tiny forces on the magnet system. | 1 | Applied and Interdisciplinary Chemistry |
For flows in porous media with Reynolds numbers greater than about 1 to 10, inertial effects can also become significant. Sometimes an inertial term is added to the Darcy's equation, known as Forchheimer term. This term is able to account for the non-linear behavior of the pressure difference vs flow data.
where the additional term is known as inertial permeability, in units of length .
The flow in the middle of a sandstone reservoir is so slow that Forchheimers equation is usually not needed, but the gas flow into a gas production well may be high enough to justify use of Forchheimers equation. In this case, the inflow performance calculations for the well, not the grid cell of the 3D model, is based on the Forchheimer equation. The effect of this is that an additional rate-dependent skin appears in the inflow performance formula.
Some carbonate reservoirs have many fractures, and Darcys equation for multiphase flow is generalized in order to govern both flow in fractures and flow in the matrix (i.e. the traditional porous rock). The irregular surface of the fracture walls and high flow rate in the fractures may justify the use of Forchheimers equation. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the hydrogenation of carbon–nitrogen double bonds is the addition of the elements of dihydrogen (H) across a carbon–nitrogen double bond, forming amines or amine derivatives. Although a variety of general methods have been developed for the enantioselective hydrogenation of ketones, methods for the hydrogenation of carbon–nitrogen double bonds are less general. Hydrogenation of imines is complicated by both syn/anti isomerization and tautomerization to enamines, which may be hydrogenated with low enantioselectivity in the presence of a chiral catalyst. Additionally, the substituent attached to nitrogen affects both the reactivity and spatial properties of the imine, complicating the development of a general catalyst system for imine hydrogenation. Despite these challenges, methods have been developed that address particular substrate classes, such as N-aryl, N-alkyl, and endocyclic imines.
If the complex is chiral and non-racemic and the substrate is prochiral, an excess of a single enantiomer of a chiral product can result. | 0 | Theoretical and Fundamental Chemistry |
Lipidomics is the complete profile of all lipids in a biological system at a given time. This is used to identify and quantify the lipids that can be detected. Since lipids have a variety of functions in the body, being able to understand which specific types are present in the body and at what levels is crucial to understand the diseases that result due to lipids. Methods of lipidomic analysis include mass spectrometry and chromatography. Monitoring lipid concentration can reveal much about an organism's health. | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acid metabolism is a collective term that refers to the variety of chemical reactions by which nucleic acids (DNA and/or RNA) are either synthesized or degraded. Nucleic acids are polymers (so-called "biopolymers") made up of a variety of monomers called nucleotides. Nucleotide synthesis is an anabolic mechanism generally involving the chemical reaction of phosphate, pentose sugar, and a nitrogenous base. Degradation of nucleic acids is a catabolic reaction and the resulting parts of the nucleotides or nucleobases can be salvaged to recreate new nucleotides. Both synthesis and degradation reactions require multiple enzymes to facilitate the event. Defects or deficiencies in these enzymes can lead to a variety of diseases. | 1 | Applied and Interdisciplinary Chemistry |
The crystal structure of APR resembles that of scheelite, with atomic cation is replaced by ammonium. The pertechnetate (NHTcO), periodate (NHIO), tetrachlorothallate (NHTlCl), and tetrachloroindate (NHInCl) follow this motif. It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell, resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient. APR does not give hydrates. | 0 | Theoretical and Fundamental Chemistry |
Addition of CO to a solution in contact with a solid can (over time) affect the alkalinity, especially for carbonate minerals in contact with groundwater or seawater. The dissolution (or precipitation) of carbonate rock has a strong influence on the alkalinity. This is because carbonate rock is composed of CaCO and its dissociation will add Ca and into solution. Ca will not influence alkalinity, but will increase alkalinity by 2 units. Increased dissolution of carbonate rock by acidification from acid rain and mining has contributed to increased alkalinity concentrations in some major rivers throughout the eastern U.S. The following reaction shows how acid rain, containing sulfuric acid, can have the effect of increasing river alkalinity by increasing the amount of bicarbonate ion:
:2 CaCO + HSO → 2 Ca + 2 +
Another way of writing this is:
:CaCO + H ⇌ Ca +
The lower the pH, the higher the concentration of bicarbonate will be. This shows how a lower pH can lead to higher alkalinity if the amount of bicarbonate produced is greater than the amount of H remaining after the reaction. This is the case since the amount of acid in the rainwater is low. If this alkaline groundwater later comes into contact with the atmosphere, it can lose CO, precipitate carbonate, and thereby become less alkaline again. When carbonate minerals, water, and the atmosphere are all in equilibrium, the reversible reaction
:CaCO + 2 H ⇌ Ca + CO + HO
shows that pH will be related to calcium ion concentration, with lower pH going with higher calcium ion concentration. In this case, the higher the pH, the more bicarbonate and carbonate ion there will be, in contrast to the paradoxical situation described above, where one does not have equilibrium with the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
;Gatorade
Erioglaucine, a food colorant and a redox dye, was found to be an effective substitute for methylene blue in the blue bottle experiment. Since some candies and drinks such as Gatorade contain the dye and a reducing sugar, only sodium hydroxide need be added to turn these food products into a blue bottle solution.
;Purple flask
Thionine can be used in the green version of the experiment in combination with copper/iron catalyst to create the purple flask. | 1 | Applied and Interdisciplinary Chemistry |
The linear noise approximation has become a popular technique for estimating the size of intrinsic noise in terms of coefficients of variation and Fano factors for molecular species in intracellular pathways. The second moment obtained from the linear noise approximation (on which the noise measures are based) are exact only if the pathway is composed of first-order reactions. However bimolecular reactions such as enzyme-substrate, protein-protein and protein-DNA interactions are ubiquitous elements of all known pathways; for such cases, the linear noise approximation can give estimates which are accurate in the limit of large reaction volumes. Since this limit is taken at constant concentrations, it follows that the linear noise approximation gives accurate results in the limit of large molecule numbers and becomes less reliable for pathways characterized by many species with low copy numbers of molecules.
A number of studies have elucidated cases of the insufficiency of the linear noise approximation in biological contexts by comparison of its predictions with those of stochastic simulations. This has led to the investigation of higher order terms of the system size expansion that go beyond the linear approximation. These terms have been used to obtain more accurate moment estimates for the mean concentrations and for the variances of the concentration fluctuations in intracellular pathways. In particular, the leading order corrections to the linear noise approximation yield corrections of the conventional rate equations. Terms of higher order have also been used to obtain corrections to the variances and covariances estimates of the linear noise approximation. The linear noise approximation and corrections to it can be computed using the open source software intrinsic Noise Analyzer. The corrections have been shown to be particularly considerable for allosteric and non-allosteric enzyme-mediated reactions in intracellular compartments. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is dominated by their prevalence in DNA and RNA, but phosphodiesters occur in other biomolecules, e.g. acyl carrier proteins, phospholipids and the cyclic forms of GMP and AMP (cGMP and cAMP). | 1 | Applied and Interdisciplinary Chemistry |
Biophotons may be detected with photomultipliers or by means of an ultra low noise CCD camera to produce an image, using an exposure time of typically 15 minutes for plant materials. Photomultiplier tubes have been used to measure biophoton emissions from fish eggs, and some applications have measured biophotons from animals and humans. Electron Multiplying CCD (EM-CCD) optimized for the detection of ultraweak light have also been used to detect the bioluminescence produced by yeast cells at the onset of their growth.
The typical observed radiant emittance of biological tissues in the visible and ultraviolet frequencies ranges from 10 to 10 W/cm with a photon count from a few to nearly 1000 photons per cm in the range of 200 nm to 800 nm. | 1 | Applied and Interdisciplinary Chemistry |
* Frederick Gowland Hopkins (1914-1943)
* Albert Chibnall (1943-1949)
* Frank George Young (1949-1975)
* Hans Kornberg (1975-1995)
* Tom Blundell (1995-2009)
* Gerard Evan (2009-2022)
* Laura Machesky (2022- ) | 1 | Applied and Interdisciplinary Chemistry |
The SK channel gating mechanism is controlled by intracellular calcium levels. Calcium enters the cell via voltage activated calcium channels as well as through NMDA receptors. Calcium does not directly bind to the SK channel. Even in the absence of calcium, the SK channel binds to the C-lobe of the protein calmodulin (CaM). When the N-lobe binds calcium, it traps the S4-S5 linker on the intracellular subunit of the SK channel. When each of the four S4-S5 linkers are bound to the N-lobe of calmodulin, the SK channel changes conformation. Calmodulin pushes the S4-S5 linker to allow the expansion of the S6 bundle crossing, leading to opening of the pore. The idea that this transitions the channel from a tetramer of monomers to a folded dimer of dimers, which results in rotation of the CaM-binding domains is now abandoned, and the most recent observations are not compatible with the proposal that this rotation causes the mechanical opening of the channel gate. The time constant of SK channel activation is approximately 5 ms. When calcium levels are depleted, the time constant for channel deactivation ranges from 15–60 ms. | 1 | Applied and Interdisciplinary Chemistry |
The LEXO uses bio-based phase-change and advanced heat transfer materials to absorb the initial heat of the beverage and cool it to a more drinkable temperature. When the temperature begins to drop, the LEXO slowly releases the stored heat back into the drink. The LEXO can also insulate cold liquids.
The LEXO has three layers of 18/8 stainless-steel and BPA-free plastic lids. | 0 | Theoretical and Fundamental Chemistry |
The first practical MHD power research was funded in 1938 in the U.S. by Westinghouse in its Pittsburgh, Pennsylvania laboratories, headed by Hungarian Bela Karlovitz. The initial patent on MHD is by B. Karlovitz, U.S. Patent No. 2,210,918, "Process for the Conversion of Energy", August 13, 1940.
World War II interrupted development. In 1962, the First International Conference on MHD Power was held in Newcastle upon Tyne, UK by Dr. Brian C. Lindley of the International Research and Development Company Ltd. The group set up a steering committee to set up further conferences and disseminate ideas. In 1964, the group set up a second conference in Paris, France, in consultation with the European Nuclear Energy Agency.
Since membership in the ENEA was limited, the group persuaded the International Atomic Energy Agency to sponsor a third conference, in Salzburg, Austria, July 1966. Negotiations at this meeting converted the steering committee into a periodic reporting group, the ILG-MHD (international liaison group, MHD), under the ENEA, and later in 1967, also under the International Atomic Energy Agency. Further research in the 1960s by R. Rosa established the practicality of MHD for fossil-fueled systems.
In the 1960s, AVCO Everett Aeronautical Research began a series of experiments, ending with the Mk. V generator of 1965. This generated 35MW, but used about 8 MW to drive its magnet. In 1966, the ILG-MHD had its first formal meeting in Paris, France. It began issuing a periodic status report in 1967. This pattern persisted, in this institutional form, up until 1976. Toward the end of the 1960s, interest in MHD declined because nuclear power was becoming more widely available.
In the late 1970s, as interest in nuclear power declined, interest in MHD increased. In 1975, UNESCO became persuaded the MHD might be the most efficient way to utilise world coal reserves, and in 1976, sponsored the ILG-MHD. In 1976, it became clear that no nuclear reactor in the next 25 years would use MHD, so the International Atomic Energy Agency and ENEA (both nuclear agencies) withdrew support from the ILG-MHD, leaving UNESCO as the primary sponsor of the ILG-MHD. | 1 | Applied and Interdisciplinary Chemistry |
Reactions of linear topology are the most common, and consist of all transformations whose transition states are acyclic, including addition, elimination, substitution, and (some types of) fragmentation reactions. By contrast, in pericyclic reactions, the atoms under chemical change form a single closed cycle, and include reactions like the Diels–Alder reaction and Cope rearrangement, among many others.
In contrast to these types of reactions, a coarctate reaction is characterized by a doubly cyclic transition state, in which at least one atom undergoes the simultaneous making and breaking of two bonds. Thus, the topology of the transition state of a coarctate reaction is a constricted cycle that meets with itself (resembling a figure eight) while the topology of pericyclic and linear reactions are a circle (or Möbius strip) and line segment, respectively. The concept was first proposed by Rainer Herges. | 0 | Theoretical and Fundamental Chemistry |
AMCA International publishes over 64 publications and standards, including testing methods, a Certified Ratings Program (CRP), application guides, educational texts, and safety guides. AMCA is an accredited ANSI developer, and all AMCA standards are proposed as American National Standards. | 1 | Applied and Interdisciplinary Chemistry |
The Grove cell voltage is about 1.9 volts and arises from the following reaction:
: Zn + HSO + 2 HNO ZnSO + 2 HO + 2 NO↑ | 0 | Theoretical and Fundamental Chemistry |
ASF/SF2 has the ability to be phosphorylated at the serines in its RS domain by the SR specific protein kinase, SRPK1. SRPK1 and ASF/SF2 form an unusually stable complex of apparent K of 50nM. SRPK1 selectively phosphorylates up to twelve serines in the RS domain of ASF/SF2 through a directional and processive mechanism, moving from the C terminus to the N terminus. This multi-phosphorylation directs ASF/SF2 to the nucleus, influencing a number of protein-protein interactions associated with splicing. ASF/SF2's function in export of mature mRNA from the nucleus is dependent on its phosphorylation state; dephosphorylation of ASF/SF2 facilitates binding to TAP, while phosphorylation directs ASF/SF2 to nuclear speckles. Both phosphorylation and dephosphorylation of ASF/SF2 are important and necessary for proper splicing to occur, as sequential phosphorylation and dephosphorylation marks the transitions between stages in the splicing process. In addition, hypophosphorylation and hyperphosphorylation of ASF/SF2 by Clk/Sty can lead to inhibition of splicing. | 1 | Applied and Interdisciplinary Chemistry |
The Lippmann–Schwinger equation is useful in a very large number of situations involving two-body scattering. For three or more colliding bodies it does not work well because of mathematical limitations; Faddeev equations may be used instead. However, there are approximations that can reduce a many-body problem to a set of two-body problems in a variety of cases. For example, in a collision between electrons and molecules, there may be tens or hundreds of particles involved. But the phenomenon may be reduced to a two-body problem by describing all the molecule constituent particle potentials together with a pseudopotential. In these cases, the Lippmann–Schwinger equations may be used. Of course, the main motivations of these approaches are also the possibility of doing the calculations with much lower computational efforts. | 0 | Theoretical and Fundamental Chemistry |
Liquids are sometimes used in measuring devices. A thermometer often uses the thermal expansion of liquids, such as mercury, combined with their ability to flow to indicate temperature. A manometer uses the weight of the liquid to indicate air pressure.
The free surface of a rotating liquid forms a circular paraboloid and can therefore be used as a telescope. These are known as liquid-mirror telescopes. They are significantly cheaper than conventional telescopes, but can only point straight upward (zenith telescope). A common choice for the liquid is mercury. | 0 | Theoretical and Fundamental Chemistry |
Is the linkage of chemical reactions in a way that the product of one reaction becomes the substrate of another reaction.
* This allows organisms to utilize energy and resources efficiently. For example, in cellular respiration, energy released by the breakdown of glucose is coupled in the synthesis of ATP. | 1 | Applied and Interdisciplinary Chemistry |
Actaplanin is a complex of broad-spectrum antibiotics made by Actinoplanes bacteria. Research carried out by a group in Eli Lilly and Co. in 1984 identified several actaplanins using high-performance liquid chromatography. Actaplanins A, B, B, B, C and G were shown to be composed of the same peptide core, an amino sugar, and varying amounts of glucose, mannose, and rhamnose. | 0 | Theoretical and Fundamental Chemistry |
It can be shown that there are four types of Euclidean plane isometries. (Note: the notations for the types of isometries listed below are not completely standardised.) | 0 | Theoretical and Fundamental Chemistry |
Chlororespiration is a respiratory process that takes place within plants. Inside plant cells there is an organelle called the chloroplast which is surrounded by the thylakoid membrane. This membrane contains an enzyme called NAD(P)H dehydrogenase which transfers electrons in a linear chain to oxygen molecules. This electron transport chain (ETC) within the chloroplast also interacts with those in the mitochondria where respiration takes place. Photosynthesis is also a process that Chlororespiration interacts with. If photosynthesis is inhibited by environmental stressors like water deficit, increased heat, and/or increased/decreased light exposure, or even chilling stress then chlororespiration is one of the crucial ways that plants use to compensate for chemical energy synthesis. | 1 | Applied and Interdisciplinary Chemistry |
In this case a material is stretched in the direction X and compresses in the directions Y and Z, so to keep volume constant.
The gradients of velocity are:
Thus, | 1 | Applied and Interdisciplinary Chemistry |
Stemming from the National Pollutant Discharge Elimination System (NPDES) EPA permitting guidelines, point and nonpoint discharges may adversely affect sediment quality. As per state regulatory criteria, information on point and nonpoint source contamination, and its effects on sediment quality may be required for assessment of compliance. For example, Washington State Sediment Management Standards, Part IV, mandates sediment control standards which allow for establishment of discharge sediment monitoring requirements, and criteria for creation and maintenance of sediment impact zones (WADOE 2013). In this instance, the SQT could be particularly useful encompassing multiple relevant analyses simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
A 2024 article used a substrate with a web of thin cracks under a heat flow, similar to the environment of deep-ocean vents, as a mechanism to separate and concentrate prebiotically relevant building blocks from a dilute mixture, purifying their concentration by up to three orders of magnitude. The authors propose this as a plausible model for the origin of complex biopolymers. | 0 | Theoretical and Fundamental Chemistry |
The diverse genome-wide repeats are derived from transposable elements, which are now understood to "jump" about different genomic locations, without transferring their original copies. Subsequent shuttling of the same sequences over numerous generations ensures their multiplicity throughout the genome. The limited recombination of the sequences between two distinct sequence elements known as conservative site-specific recombination (CSSR) results in inversions of the DNA segment, based on the arrangement of the recombination recognition sequences on the donor DNA and recipient DNA. Again, the orientation of two of the recombining sites within the donor DNA molecule relative to the asymmetry of the intervening DNA cleavage sequences, known as the crossover region, is pivotal to the formation of either inverted repeats or direct repeats. Thus, recombination occurring at a pair of inverted sites will invert the DNA sequence between the two sites. Very stable chromosomes have been observed with comparatively fewer numbers of inverted repeats than direct repeats, suggesting a relationship between chromosome stability and the number of repeats. | 1 | Applied and Interdisciplinary Chemistry |
The classic view of pRb's role as a tumor suppressor and cell cycle regulator developed through research investigating mechanisms of interactions with E2F family member proteins. Yet, more data generated from biochemical experiments and clinical trials reveal other functions of pRb within the cell unrelated (or indirectly related) to tumor suppression. | 1 | Applied and Interdisciplinary Chemistry |
In metazoans, small interfering RNAs (siRNAs) processed by Dicer are incorporated into a complex known as the RNA-induced silencing complex or RISC. This complex contains an endonuclease that cleaves perfectly complementary messages to which the siRNA binds. The resulting mRNA fragments are then destroyed by exonucleases. siRNA is commonly used in laboratories to block the function of genes in cell culture. It is thought to be part of the innate immune system as a defense against double-stranded RNA viruses. | 1 | Applied and Interdisciplinary Chemistry |
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