1.
Jmol
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Jmol is computer software for molecular modelling chemical structures in 3-dimensions. Jmol returns a 3D representation of a molecule that may be used as a teaching tool and it is written in the programming language Java, so it can run on the operating systems Windows, macOS, Linux, and Unix, if Java is installed. It is free and open-source software released under a GNU Lesser General Public License version 2.0, a standalone application and a software development kit exist that can be integrated into other Java applications, such as Bioclipse and Taverna. A popular feature is an applet that can be integrated into web pages to display molecules in a variety of ways, for example, molecules can be displayed as ball-and-stick models, space-filling models, ribbon diagrams, etc. Jmol supports a range of chemical file formats, including Protein Data Bank, Crystallographic Information File, MDL Molfile. There is also a JavaScript-only version, JSmol, that can be used on computers with no Java, the Jmol applet, among other abilities, offers an alternative to the Chime plug-in, which is no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS9. Jmol requires Java installation and operates on a variety of platforms. For example, Jmol is fully functional in Mozilla Firefox, Internet Explorer, Opera, Google Chrome, fast and Scriptable Molecular Graphics in Web Browsers without Java3D
2.
ChemSpider
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ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry, the database contains information on more than 50 million molecules from over 500 data sources including, Each chemical is given a unique identifier, which forms part of a corresponding URL. This is an approach to develop an online chemistry database. The search can be used to widen or restrict already found results, structure searching on mobile devices can be done using free apps for iOS and for the Android. The ChemSpider database has been used in combination with text mining as the basis of document markup. The result is a system between chemistry documents and information look-up via ChemSpider into over 150 data sources. ChemSpider was acquired by the Royal Society of Chemistry in May,2009, prior to the acquisition by RSC, ChemSpider was controlled by a private corporation, ChemZoo Inc. The system was first launched in March 2007 in a release form. ChemSpider has expanded the generic support of a database to include support of the Wikipedia chemical structure collection via their WiChempedia implementation. A number of services are available online. SyntheticPages is an interactive database of synthetic chemistry procedures operated by the Royal Society of Chemistry. Users submit synthetic procedures which they have conducted themselves for publication on the site and these procedures may be original works, but they are more often based on literature reactions. Citations to the published procedure are made where appropriate. They are checked by an editor before posting. The pages do not undergo formal peer-review like a journal article. The comments are moderated by scientific editors. The intention is to collect practical experience of how to conduct useful chemical synthesis in the lab, while experimental methods published in an ordinary academic journal are listed formally and concisely, the procedures in ChemSpider SyntheticPages are given with more practical detail. Comments by submitters are included as well, other publications with comparable amounts of detail include Organic Syntheses and Inorganic Syntheses
3.
European Chemicals Agency
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ECHA is the driving force among regulatory authorities in implementing the EUs chemicals legislation. ECHA helps companies to comply with the legislation, advances the safe use of chemicals, provides information on chemicals and it is located in Helsinki, Finland. The Agency, headed by Executive Director Geert Dancet, started working on 1 June 2007, the REACH Regulation requires companies to provide information on the hazards, risks and safe use of chemical substances that they manufacture or import. Companies register this information with ECHA and it is freely available on their website. So far, thousands of the most hazardous and the most commonly used substances have been registered, the information is technical but gives detail on the impact of each chemical on people and the environment. This also gives European consumers the right to ask whether the goods they buy contain dangerous substances. The Classification, Labelling and Packaging Regulation introduces a globally harmonised system for classifying and labelling chemicals into the EU. This worldwide system makes it easier for workers and consumers to know the effects of chemicals, companies need to notify ECHA of the classification and labelling of their chemicals. So far, ECHA has received over 5 million notifications for more than 100000 substances, the information is freely available on their website. Consumers can check chemicals in the products they use, Biocidal products include, for example, insect repellents and disinfectants used in hospitals. The Biocidal Products Regulation ensures that there is information about these products so that consumers can use them safely. ECHA is responsible for implementing the regulation, the law on Prior Informed Consent sets guidelines for the export and import of hazardous chemicals. Through this mechanism, countries due to hazardous chemicals are informed in advance and have the possibility of rejecting their import. Substances that may have effects on human health and the environment are identified as Substances of Very High Concern 1. These are mainly substances which cause cancer, mutation or are toxic to reproduction as well as substances which persist in the body or the environment, other substances considered as SVHCs include, for example, endocrine disrupting chemicals. Companies manufacturing or importing articles containing these substances in a concentration above 0 and they are required to inform users about the presence of the substance and therefore how to use it safely. Consumers have the right to ask the retailer whether these substances are present in the products they buy, once a substance has been officially identified in the EU as being of very high concern, it will be added to a list. This list is available on ECHA’s website and shows consumers and industry which chemicals are identified as SVHCs, Substances placed on the Candidate List can then move to another list
4.
PubChem
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PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information, a component of the National Library of Medicine, PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds, more than 80 database vendors contribute to the growing PubChem database. PubChem consists of three dynamically growing primary databases, as of 28 January 2016, Compounds,82.6 million entries, contains pure and characterized chemical compounds. Substances,198 million entries, contains also mixtures, extracts, complexes, bioAssay, bioactivity results from 1.1 million high-throughput screening programs with several million values. PubChem contains its own online molecule editor with SMILES/SMARTS and InChI support that allows the import and export of all common chemical file formats to search for structures and fragments. In the text search form the database fields can be searched by adding the name in square brackets to the search term. A numeric range is represented by two separated by a colon. The search terms and field names are case-insensitive, parentheses and the logical operators AND, OR, and NOT can be used. AND is assumed if no operator is used, example,0,5000,50,10 -5,5 PubChem was released in 2004. The American Chemical Society has raised concerns about the publicly supported PubChem database and they have a strong interest in the issue since the Chemical Abstracts Service generates a large percentage of the societys revenue. To advocate their position against the PubChem database, ACS has actively lobbied the US Congress, soon after PubChems creation, the American Chemical Society lobbied U. S. Congress to restrict the operation of PubChem, which they asserted competes with their Chemical Abstracts Service
5.
International Chemical Identifier
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Initially developed by IUPAC and NIST from 2000 to 2005, the format and algorithms are non-proprietary. The continuing development of the standard has supported since 2010 by the not-for-profit InChI Trust. The current version is 1.04 and was released in September 2011, prior to 1.04, the software was freely available under the open source LGPL license, but it now uses a custom license called IUPAC-InChI Trust License. Not all layers have to be provided, for instance, the layer can be omitted if that type of information is not relevant to the particular application. InChIs can thus be seen as akin to a general and extremely formalized version of IUPAC names and they can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications. Information about the 3-dimensional coordinates of atoms is not represented in InChI, the InChI algorithm converts input structural information into a unique InChI identifier in a three-step process, normalization, canonicalization, and serialization. The InChIKey, sometimes referred to as a hashed InChI, is a fixed length condensed digital representation of the InChI that is not human-understandable. The InChIKey specification was released in September 2007 in order to facilitate web searches for chemical compounds and it should be noted that, unlike the InChI, the InChIKey is not unique, though collisions can be calculated to be very rare, they happen. In January 2009 the final 1.02 version of the InChI software was released and this provided a means to generate so called standard InChI, which does not allow for user selectable options in dealing with the stereochemistry and tautomeric layers of the InChI string. The standard InChIKey is then the hashed version of the standard InChI string, the standard InChI will simplify comparison of InChI strings and keys generated by different groups, and subsequently accessed via diverse sources such as databases and web resources. Every InChI starts with the string InChI= followed by the version number and this is followed by the letter S for standard InChIs. The remaining information is structured as a sequence of layers and sub-layers, the layers and sub-layers are separated by the delimiter / and start with a characteristic prefix letter. The six layers with important sublayers are, Main layer Chemical formula and this is the only sublayer that must occur in every InChI. The atoms in the formula are numbered in sequence, this sublayer describes which atoms are connected by bonds to which other ones. Describes how many hydrogen atoms are connected to each of the other atoms, the condensed,27 character standard InChIKey is a hashed version of the full standard InChI, designed to allow for easy web searches of chemical compounds. Most chemical structures on the Web up to 2007 have been represented as GIF files, the full InChI turned out to be too lengthy for easy searching, and therefore the InChIKey was developed. With all databases currently having below 50 million structures, such duplication appears unlikely at present, a recent study more extensively studies the collision rate finding that the experimental collision rate is in agreement with the theoretical expectations. Example, Morphine has the structure shown on the right, as the InChI cannot be reconstructed from the InChIKey, an InChIKey always needs to be linked to the original InChI to get back to the original structure
6.
Simplified molecular-input line-entry system
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The simplified molecular-input line-entry system is a specification in form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the 1980s. It has since modified and extended. In 2007, a standard called OpenSMILES was developed in the open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. The Environmental Protection Agency funded the project to develop SMILES. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. In 2007, a standard called OpenSMILES was developed by the Blue Obelisk open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, in July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is generally considered to have the advantage of being slightly more human-readable than InChI, the term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings. However, the term SMILES is also used to refer to both a single SMILES string and a number of SMILES strings, the exact meaning is usually apparent from the context. The terms canonical and isomeric can lead to confusion when applied to SMILES. The terms describe different attributes of SMILES strings and are not mutually exclusive, typically, a number of equally valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol, algorithms have been developed to generate the same SMILES string for a given molecule, of the many possible strings, these algorithms choose only one of them. This SMILES is unique for each structure, although dependent on the algorithm used to generate it. These algorithms first convert the SMILES to a representation of the molecular structure. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, and these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES
7.
Chemical formula
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These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
8.
Enone
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An enone, also called an α, β-unsaturated carbonyl, is a type of organic compound consisting of an alkene conjugated to a ketone. The simplest enone is methyl vinyl ketone or CH2=CHCOCH3, an enal is the corresponding α, β-unsaturated aldehyde, an example being acrolein. Enones are typically produced using an Aldol condensation or Knoevenagel condensation, some commercially significant enones are produced by condensations of acetone, e. g. mesityl oxide and isophorone. In the Meyer–Schuster rearrangement the starting compound is a propargyl alcohol, cyclic enones can be prepared via the Pauson–Khand reaction. Enones undergo many kinds of reactions and they are electrophilic at both the carbonyl carbon as well as the β-carbon. Depending on conditions, either site is attacked by nucleophiles, addition to the alkene is called conjugate additions. Enones are often good dienophiles in Diels-Alder reactions and they are activated by Lewis acids, which bind to the carbonyl oxygen. They can undergo both reduction of the carbonyl and of the alkene, as well as both, enones undergo the Nazarov cyclization reaction and in the Rauhut–Currier reaction. Sterically unhindered enones such as methyl vinyl ketone are prone to polymerization, enones are good ligands for low-valent metal complexes, examples being Fe3 and trisdipalladium. Enone is not to be confused with ketene, an enamine is a cousin of an enone, with the carbonyl replaced by an amine group. Regiospecific formation is the controlled enolate formation by the specific deprotonation at one of the α-carbons of the starting molecule. This provides one of the best understood synthetic strategies to introduce chemical complexity in natural product, a prominent example of its use is in the total synthesis of progesterone illustrated in Figure Regiospecific enolate formation in the total synthesis of progesterone. When ketones are treated with base, enolates can be formed by deprotonation at either α-carbon, the selectivity is determined by both the steric and electronic effects on the α-carbons as well as the precise base used. Enolate formation will be thermodynamically favoured at the most acidic proton which depends on the stabilization of the resulting anion. However, the selectivity can be reversed by sterically hindering the thermodynamic product, traditional methods for regioselective enolate formation use either electronic activating groups or steric blocking groups. Enone can also serve as a precursor for regiospecific formation of enolate and this process is first described by Gilbert Stork who is best known for his contributions to the study of selective enolate formation methods in organic synthesis. The Stork method also uses enone as a “masked functionality” of enolate, reacting enone with lithium metal generates the enolate at the α-carbon of the enone. The enolate product can either be trapped or alkylated, by using “masked functionality”, it is possible to produce enolates that are not accessible by traditional methods
9.
Methyl vinyl ketone
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Methyl vinyl ketone is the organic compound with the formula CH3CCH=CH2. It is a reactive compound classified as an enone, in fact the simplest example thereof and it is a colorless, flammable, highly toxic liquid with a pungent odor. It is soluble in water and polar organic solvents and it is a useful intermediate in the synthesis of other compounds. MVK has been prepared industrially by the condensation of acetone and formaldehyde, the compound is typically stored with hydroquinone, which inhibits polymerization. As an electrophilic alkene, it forms an adduct with cyclopentadiene, the resulting norbornene derivative is an intermediate in the synthesis the pesticide biperiden. Via its cyanohydrin is also a precursor to vinclozolin and it is also a precursor to synthetic vitamin A. MVK is an intermediate in the synthesis of some pharmaceutical drugs including etorphine, buprenorphine, tolquinzole, butaclamol, and etretinate. MVK is extremely hazardous upon inhalation causing coughing, wheezing and shortness of breath even at low concentrations and it will also readily cause irritation of the skin, eyes, and mucous membranes
10.
1-Octene
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1-Octene is an organic compound with a formula CH2CHC6H13. 1-Octene is one of the important linear alpha olefins in industry, in industry, 1-octene is commonly manufactured by two main routes, oligomerization of ethylene and by Fischer-Tropsch synthesis followed by purification. Another route to 1-octene that has been used commercially on a scale is dehydration of alcohols. Prior to the 1970s, 1-octene was also manufactured by thermal cracking of waxes, there are five commercial processes that oligomerize ethylene to 1-octene. Four of these processes produce 1-octene as a part of a distribution of alpha-olefins. The only commercial process to isolate 1-octene from a mixture of C8 hydrocarbons is practiced by Sasol. Sasol is currently in the phase of a new 1-octene technology based on selective tetramerisation of ethylene. The main use of 1-octene is as a comonomer in production of polyethylene, high-density polyethylene and linear low-density polyethylene use approximately 2–4% and 8–10% of comonomers, respectively. Another significant use of 1-octene is for production of linear aldehyde via the oxo synthesis to give the C9 aldehyde, oxidation of this aldehyde gives the short-chain fatty acid nonanoic acid. Hydrogenation of the aldehyde gives the fatty alcohol 1-nonanol, which is used as a plasticizer
11.
Aroma compound
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An aroma-compound, also known as an odorant, aroma, fragrance, or flavor, is a chemical compound that has a smell or odor. A chemical-compound has a smell or odor when it is volatile to be transported to the olfactory system in the upper-part of the nose. Generally molecules meeting this specification have molecular weights of <300, flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be occurring, and fragrances tend to be synthetic. Aroma-compounds can be found in food, wine, spices, floral scent, perfumes, fragrance oils, for example, many form biochemically during the ripening of fruits and other crops. In wines, most form as byproducts of fermentation, an odorizer may add an odorant to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure. Note, Carvone, depending on its chirality, offers two different smells, furaneol 1-Hexanol cis-3-Hexen-1-ol Menthol High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas. Acetaldehyde Hexanal cis-3-Hexenal Furfural Hexyl cinnamaldehyde Isovaleraldehyde – nutty, fruity, cocoa-like Anisic aldehyde – floral, sweet and it is a crucial component of chocolate, vanilla, strawberry, raspberry, apricot, and others. Its smell is so potent it can be detected several hundred meters downwind mere seconds after a container is opened, butane-1-thiol, commonly called normal-butyl mercaptan is a chemical-intermediate. Olfactory-receptors are cell-membrane receptors on the surface of neurons in the olfactory system that detect air-borne. In mammals, olfactory-receptors are expressed on the surface of the epithelium in the nasal cavity. In 2005–06, fragrance-mix was the third-most-prevalent allergen in patch tests, Fragrance was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. The composition of fragrances is usually not disclosed in the label of products, hiding the actual chemicals of the formula, the EPA, however, does not conduct independent-safety testing but relies on data provided by the manufacturer. In 2010 the International Fragrance Association published a list of 3,059 chemicals used in 2011 based on a voluntary-survey of its members and it was estimated to represent about 90% of the worlds production-volume of fragrances
12.
Metal
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A metal is a material that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed. In bcc, each atom is positioned at the center of a cube of eight others, in fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium, platinum and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades. The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
13.
Blood
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Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma, plasma, which constitutes 55% of blood fluid, is mostly water, and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells themselves. Albumin is the protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are red blood cells, white blood cells. The most abundant cells in blood are red blood cells. These contain hemoglobin, a protein, which facilitates oxygen transport by reversibly binding to this respiratory gas. In contrast, carbon dioxide is mostly transported extracellularly as bicarbonate ion transported in plasma, vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this blood does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their system to suffice for supplying oxygen. Jawed vertebrates have an immune system, based largely on white blood cells. White blood cells help to resist infections and parasites, platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system, Blood is circulated around the body through blood vessels by the pumping action of the heart. Medical terms related to blood often begin with hemo- or hemato- from the Greek word αἷμα for blood. In terms of anatomy and histology, blood is considered a form of connective tissue, given its origin in the bones. The average adult has a volume of roughly 5 litres. These blood cells consist of erythrocytes, leukocytes, and thrombocytes, by volume, the red blood cells constitute about 45% of whole blood, the plasma about 54. 3%, and white cells about 0. 7%. Whole blood exhibits non-Newtonian fluid dynamics, if all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively. One microliter of blood contains,4.7 to 6.1 million,4.2 to 5.4 million erythrocytes, Red blood cells contain the bloods hemoglobin, mature red blood cells lack a nucleus and organelles in mammals
14.
Skin
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Skin is the soft outer tissue covering vertebrates. Other animal coverings, such as the arthropod exoskeleton have different developmental origin, structure, the adjective cutaneous means of the skin. In mammals, the skin is an organ of the system made up of multiple layers of ectodermal tissue. Skin of a different nature exists in amphibians, reptiles, all mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors, for example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented, the thickness of skin also varies from location to location on an organism. The skin on the palms and the soles of the feet is 4 mm thick, the speed and quality of wound healing in skin is promoted by the reception of estrogen. Primarily, fur augments the insulation the skin provides but can serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is hard and thick. Reptiles and fish have hard scales on their skin for protection. Amphibian skin is not a barrier, especially regarding the passage of chemicals via skin and is often subject to osmosis. For example, a sitting in an anesthetic solution would be sedated quickly. Amphibian skin plays key roles in everyday survival and their ability to exploit a range of habitats. Keratinocytes are the cells, constituting 95% of the epidermis, while Merkel cells, melanocytes. Keratinocytes from the stratum corneum are eventually shed from the surface, the epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The epidermis and dermis are separated by a sheet of fibers called the basement membrane. The dermis is the layer of skin beneath the epidermis consists of connective tissue and cushions the body from stress
15.
Decanal
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Decanal is an organic compound with the chemical formula C9H19CHO. It is the simplest ten-carbon aldehyde, decanal occurs naturally and is used in fragrances and flavoring. Decanal is an important component in citrus, along with octanal, citral, decanal is also an important component of buckwheat odour. Decanal is also the component of coriander herb essential oil. Decanal can be prepared by oxidation of the alcohol decanol. For safety information see the MSDS
16.
Nonanal
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Nonanal, also called nonanaldehyde, pelargonaldehyde or Aldehyde C-9, is an alkyl aldehyde. A colourless, oily liquid, nonanal is a component of perfumes, although it occurs in several natural oils, it is produced commercially by hydroformylation of 1-octene. Nonanal has been identified as a compound that attracts Culex mosquitoes, nonanal acts synergistically with carbon dioxide
17.
Redox
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Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions in which atoms have their oxidation state changed, in general, the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in terms, Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom. Reduction is the gain of electrons or a decrease in state by a molecule, atom. As an example, during the combustion of wood, oxygen from the air is reduced, the reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. Redox is a portmanteau of reduction and oxidation, the word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions, ultimately, the meaning was generalized to include all processes involving loss of electrons. The word reduction originally referred to the loss in weight upon heating a metallic ore such as an oxide to extract the metal. In other words, ore was reduced to metal, antoine Lavoisier showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the atom gains electrons in this process. The meaning of reduction then became generalized to all processes involving gain of electrons. Even though reduction seems counter-intuitive when speaking of the gain of electrons, it help to think of reduction as the loss of oxygen. Since electrons are charged, it is also helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes and these words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term hydrogenation could be used instead of reduction, since hydrogen is the agent in a large number of reactions. But, unlike oxidation, which has been generalized beyond its root element, the word redox was first used in 1928. The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction
18.
Chemical reaction
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A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Nuclear chemistry is a sub-discipline of chemistry that involves the reactions of unstable. The substance initially involved in a reaction are called reactants or reagents. Chemical reactions are characterized by a chemical change, and they yield one or more products. Reactions often consist of a sequence of individual sub-steps, the elementary reactions. Chemical reactions are described with chemical equations, which present the starting materials, end products. Chemical reactions happen at a characteristic reaction rate at a given temperature, typically, reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium, Reactions that proceed in the forward direction to approach equilibrium are often described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of energy to go forward. Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product, in biochemistry, a consecutive series of chemical reactions form metabolic pathways. These reactions are catalyzed by protein enzymes. Chemical reactions such as combustion in fire, fermentation and the reduction of ores to metals were known since antiquity, in the Middle Ages, chemical transformations were studied by Alchemists. They attempted, in particular, to lead into gold, for which purpose they used reactions of lead. The process involved heating of sulfate and nitrate minerals such as sulfate, alum. In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid, further optimization of sulfuric acid technology resulted in the contact process in the 1880s, and the Haber process was developed in 1909–1910 for ammonia synthesis. From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle, the phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of an element called phlogiston, which was contained within combustible bodies. This proved to be false in 1785 by Antoine Lavoisier who found the explanation of the combustion as reaction with oxygen from the air
19.
Lipid
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In biology, lipids comprise a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, phospholipids, and others. The main biological functions of lipids include storing energy, signaling, lipids have applications in the cosmetic and food industries as well as in nanotechnology. Biological lipids originate entirely or in part from two types of biochemical subunits or building-blocks, ketoacyl and isoprene groups. Although the term lipid is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides, lipids also encompass molecules such as fatty acids and their derivatives, as well as other sterol-containing metabolites such as cholesterol. Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids cannot be made this way, the word lipid stems etymologically from the Greek lipos. The fatty acid structure is one of the most fundamental categories of biological lipids, the carbon chain, typically between four and 24 carbons long, may be saturated or unsaturated, and may be attached to functional groups containing oxygen, halogens, nitrogen, and sulfur. If a fatty acid contains a double bond, there is the possibility of either a cis or trans geometric isomerism, cis-double bonds cause the fatty acid chain to bend, an effect that is compounded with more double bonds in the chain. This in turn plays an important role in the structure and function of cell membranes, most naturally occurring fatty acids are of the cis configuration, although the trans form does exist in some natural and partially hydrogenated fats and oils. Examples of biologically important fatty acids include the eicosanoids, derived primarily from arachidonic acid and eicosapentaenoic acid, that include prostaglandins, leukotrienes, docosahexaenoic acid is also important in biological systems, particularly with respect to sight. Other major lipid classes in the fatty acid category are the fatty esters, fatty esters include important biochemical intermediates such as wax esters, fatty acid thioester coenzyme A derivatives, fatty acid thioester ACP derivatives and fatty acid carnitines. The fatty amides include N-acyl ethanolamines, such as the cannabinoid neurotransmitter anandamide, glycerolipids are composed of mono-, di-, and tri-substituted glycerols, the best-known being the fatty acid triesters of glycerol, called triglycerides. The word triacylglycerol is sometimes used synonymously with triglyceride, in these compounds, the three hydroxyl groups of glycerol are each esterified, typically by different fatty acids. Because they function as a store, these lipids comprise the bulk of storage fat in animal tissues. The hydrolysis of the bonds of triglycerides and the release of glycerol. Additional subclasses of glycerolipids are represented by glycosylglycerols, which are characterized by the presence of one or more sugar residues attached to glycerol via a glycosidic linkage, examples of structures in this category are the digalactosyldiacylglycerols found in plant membranes and seminolipid from mammalian sperm cells. Glycerophospholipids, usually referred to as phospholipids, are ubiquitous in nature and are key components of the bilayer of cells, as well as being involved in metabolism. Neural tissue contains high amounts of glycerophospholipids, and alterations in their composition has been implicated in various neurological disorders. Examples of glycerophospholipids found in biological membranes are phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine, the major sphingoid base of mammals is commonly referred to as sphingosine
20.
Peroxide
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A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion, O2−2. The O−O group is called the group or peroxo group. In contrast to oxide ions, the atoms in the peroxide ion have an oxidation state of −1. The simplest stable peroxide is hydrogen peroxide, superoxides, dioxygenyls, ozones and ozonides are considered separately. Peroxide compounds can be classified into organic and inorganic. Whereas the inorganic peroxides have an ionic, salt-like character, the peroxides are dominated by the covalent bonds. The oxygen–oxygen chemical bond of peroxide is unstable and easily split into reactive radicals via homolytic cleavage, for this reason, peroxides are found in nature only in small quantities, in water, atmosphere, plants, and animals. Peroxides have an effect on organic substances and therefore are added to some detergents. Other large-scale applications include medicine and chemical industry, where peroxides are used in synthesis reactions or occur as intermediate products. With an annual production of over 2 million tonnes, hydrogen peroxide is the most economically important peroxide, many peroxides are unstable and hazardous substances, they cannot be stored and therefore are synthesized in situ and used immediately. Peroxides are usually very reactive and thus occur in only in a few forms. These include, in addition to hydrogen peroxide, a few products such as ascaridole. Hydrogen peroxide occurs in water, groundwater and in the atmosphere. It forms upon illumination or natural catalytic action by substances containing in water, sea water contains 0.5 to 14 μg/L of hydrogen peroxide, freshwater 1 to 30 μg/L and air 0.1 to 1 parts per billion. Hydrogen peroxide is formed in human and animal organisms as a product in biochemical processes and is toxic to cells. The toxicity is due to oxidation of proteins, membrane lipids, the class of biological enzymes called SOD is developed in nearly all living cells as an important antioxidant agent. They promote the disproportionation of superoxide into oxygen and hydrogen peroxide,2 O2 − +2 H + → SOD H2 O2 ⏞ hydrogen peroxide + O2 ⏞ oxygen Formation of hydrogen peroxide by superoxide dismutase Peroxisomes are organelles found in virtually all eukaryotic cells. This reaction is important in liver and kidney cells, where the peroxisomes neutralize various toxic substances that enter the blood, some of the ethanol humans drink is oxidized to acetaldehyde in this way
21.
Enzyme
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Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions, the molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology, enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules, enzymes specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy, some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5-phosphate decarboxylase, which allows a reaction that would take millions of years to occur in milliseconds. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules, inhibitors are molecules that decrease enzyme activity, many drugs and poisons are enzyme inhibitors. An enzymes activity decreases markedly outside its optimal temperature and pH, some enzymes are used commercially, for example, in the synthesis of antibiotics. French chemist Anselme Payen was the first to discover an enzyme, diastase and he wrote that alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, the word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. Eduard Buchner submitted his first paper on the study of yeast extracts in 1897, in a series of experiments at the University of Berlin, he found that sugar was fermented by yeast extracts even when there were no living yeast cells in the mixture. He named the enzyme that brought about the fermentation of sucrose zymase, in 1907, he received the Nobel Prize in Chemistry for his discovery of cell-free fermentation. Following Buchners example, enzymes are usually named according to the reaction they carry out, the biochemical identity of enzymes was still unknown in the early 1900s. Sumner showed that the enzyme urease was a protein and crystallized it. These three scientists were awarded the 1946 Nobel Prize in Chemistry, the discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This high-resolution structure of lysozyme marked the beginning of the field of structural biology, an enzymes name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase
22.
Lipoxygenase
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The typical lipoxygenase catalyzes the following reaction, The lipoxygenases are related to each other based upon their similar genetic structure and dioxygenation activity. g. Most lipoxygenases catalyze the formation of initially formed hydroperoxy products that have S chirality, exceptions to this rule include the 12R-lipoxygenases of hulmans and other mammals. Lipoxygenases depend on the availability of there polyunsaturated fatty acid substrates which, in mammals a number of lipoxygenases isozymes are involved in the metabolism of eicosanoids. Sequence data is available for the following lipoxygenases, Plants express a variety of cytosolic lipoxygenases as well as what seems to be a chloroplast isozyme, mammalian LOX genes contain 14 or 15 exons with exon/intron boundaries at highly conserved position. ALOX5 also metabolizes eicosapentaenoic acid to a set of metabolites that contain 5 double bounds as opposed to the 4 double bond-containing arachidonic acid metabolites and these resolvins are also classified as Specialized pro-resolving mediators. Arachidonate 12-lipoxygenase, also termed 12-lipoxygenase, platelet type platelet lipoxygenase 12-LOX and it metabolizes arachidonic acid to 12-hydroperoxyeiocsatetraeoic acid which is further metabolized to 12-hydroxyeicosatetraenoic acid or to various Hepoxilins. Arachidonate 15-lipoxygenase-1, also termed 15-lipoxygenase-1, erythrocyte type 15-lipoxygenase, reticulocyte type 15-lipoxygenase, 15-LO-1, ALOX15 actually prefers linoleic acid over arachidonic acid, metabolizing linoleic acid to 12-hydroperoxyoctadecaenoic acid which is further metabolized to 13-Hydroxyoctadecadienoic acid. ALOX15 can metabolize polyunsaturated fatty acids that are esterified to phospholipids and/or to the cholesterol, i. e. cholesterol esters, arachidonate 15-lipoxygenase type II, also termed 15-lipoxygenase-2, 15-LOX-2, and 15-LOX-2. It metabolizes arachidonic acid to 15-hydroperoxyeicosatetraenoic which is metabolized to 15-Hydroxyicosatetraenoic acid. ALOX15B has little or no ability to metabolize arachidonic acid to 12-hydroperoxeiocosatetraenoic acid (12-, arachidonate 12-lipoxygenase, 12R type, also termed 12R-lipoxygenase, 12R-LOX, and 12R-LO. In skin epidermal cells, ALOX12B metabolizes the linoleate in this esterified omega-hydroxyacyl-sphingosine to its 9R-hydroperoxy analog, inactivating mutations of ALOX12B are associated with the human skin disease, autosomal recessive Congenital ichthyosiform erythroderma. Epidermis-type lipoxygenase, also termed eLOX3 and lipoxygenase, epidermis type, unlike other lipoxygenases, ALOXE3 exhibits only a latent dioxygenase activity. Inactivating mutations in ALOX3 are also associated with the human disease Lamellar ichthyosis, two lipoxygenases may act in series to make di-hydroxy or tri-hydroxy products that have activities quite different than either lipoxyenases products. This serial metabolism may occur in different cell types that express one of the two lipoxygenases in a process termed transcellular metabolism. The mouse is a model to examine lipoxygenase function. However, there are key differences between the lipoxygenases between mice and men that make extrapolations from mice studies to humans difficult. In contrast to the 6 functional lipoxygenases in humans, mice have 7 functional lipoxygenases, alox5 appears to be similar in function to human ALOX5. e. Also, human ALOX15 prefers linoleic acid over arachidonic acid as a substrate, Alox15 can metabolize polyunsaturated fatty acids that are esterified to phospholipids and cholesterol
23.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
24.
Oxygen
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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
25.
Ketone
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In chemistry, a ketone /ˈkiːtoʊn/ is an organic compound with the structure RCR, where R and R can be a variety of carbon-containing substituents. Ketones and aldehydes are simple compounds that contain a carbonyl group and they are considered simple because they do not have reactive groups like −OH or −Cl attached directly to the carbon atom in the carbonyl group, as in carboxylic acids containing −COOH. Many ketones are known and many are of importance in industry. Examples include many sugars and the industrial solvent acetone, which is the smallest ketone, the word ketone is derived from Aketon, an old German word for acetone. According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone, the position of the carbonyl group is usually denoted by a number. For the most important ketones, however, traditional names are still generally used. The common names of ketones are obtained by writing separately the names of the two alkyl groups attached to the group, followed by ketone as a separate word. The names of the groups are written alphabetically. When the two groups are the same, the prefix di- is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being the adjacent to carbonyl group. If both alkyl groups in a ketone are the same then the ketone is said to be symmetrical, although used infrequently, oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used, for some common chemicals, keto or oxo refer to the ketone functional group. The term oxo is used widely through chemistry, for example, it also refers to an oxygen atom bonded to a transition metal. The ketone carbon is often described as sp2 hybridized, a description that includes both their electronic and molecular structure, ketones are trigonal planar around the ketonic carbon, with C−C−O and C−C−C bond angles of approximately 120°. Ketones differ from aldehydes in that the group is bonded to two carbons within a carbon skeleton. In aldehydes, the carbonyl is bonded to one carbon and one hydrogen and are located at the ends of carbon chains, ketones are also distinct from other carbonyl-containing functional groups, such as carboxylic acids, esters and amides. The carbonyl group is polar because the electronegativity of the oxygen is greater than that for carbon, thus, ketones are nucleophilic at oxygen and electrophilic at carbon. Because the carbonyl group interacts with water by bonding, ketones are typically more soluble in water than the related methylene compounds
26.
Alkene
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In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond. The words alkene, olefin, and olefine are used often interchangeably, acyclic alkenes, with only one double bond and no other functional groups, known as mono-enes, form a homologous series of hydrocarbons with the general formula CnH2n. Alkenes have two hydrogen atoms less than the corresponding alkane, the simplest alkene, ethylene, with the International Union of Pure and Applied Chemistry name ethene, is the organic compound produced on the largest scale industrially. Aromatic compounds are drawn as cyclic alkenes, but their structure and properties are different. This double bond is stronger than a single covalent bond and also shorter, each carbon of the double bond uses its three sp2 hybrid orbitals to form sigma bonds to three atoms. The unhybridized 2p atomic orbitals, which lie perpendicular to the created by the axes of the three sp² hybrid orbitals, combine to form the pi bond. This bond lies outside the main C–C axis, with half of the bond on one side of the molecule, rotation about the carbon–carbon double bond is restricted because it incurs an energetic cost to break the alignment of the p orbitals on the two carbon atoms. As a consequence, substituted alkenes may exist as one of two isomers, called cis or trans isomers, more complex alkenes may be named with the E–Z notation for molecules with three or four different substituents. For example, of the isomers of butene, the two groups of -but-2-ene appear on the same side of the double bond, and in -but-2-ene the methyl groups appear on opposite sides. These two isomers of butene are slightly different in their chemical and physical properties, a 90° twist of the C=C bond requires less energy than the strength of a pi bond, and the bond still holds. This contradicts a common assertion that the p orbitals would be unable sustain such a bond. In truth, the misalignment of the p orbitals is less than expected because pyramidalization takes place, trans-Cyclooctene is a stable strained alkene and the orbital misalignment is only 19° with a dihedral angle of 137° and a degree of pyramidalization of 18°. The trans isomer of cycloheptene is stable only at low temperatures, as predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions between groups attached to the carbons of the double bond. For example, the C–C–C bond angle in propylene is 123. 9°, for bridged alkenes, Bredts rule states that a double bond cannot occur at the bridgehead of a bridged ring system unless the rings are large enough. The physical properties of alkenes and alkanes are similar and they are colourless, nonpolar, combustable, and almost odorless. The physical state depends on mass, like the corresponding saturated hydrocarbons, the simplest alkenes, ethene, propene. Linear alkenes of approximately five to sixteen carbons are liquids, Alkenes are relatively stable compounds, but are more reactive than alkanes, either because of the reactivity of the carbon–carbon pi-bond or the presence of allylic CH centers
27.
Uncinula necator
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Uncinula necator is a fungus that causes powdery mildew of grape. It is a pathogen of Vitis species, including the wine grape. The fungus is believed to have originated in North America, european varieties of Vitis vinifera are more or less susceptible to this fungus. Uncinula necator infects all green tissue on the grapevine, including leaves and it can cause crop loss and poor wine quality if untreated. The sexual stage of this pathogen requires free moisture to release ascospores from its cleistothecia in the spring, however, free moisture is not needed for secondary spread via conidia, high atmospheric humidity is sufficient. Its anamorph is called Oidium tuckeri and it produces common odors such as 1-octen-3-one and -1, 5-octadien-3-one. This mildew can be treated with sulfur or fungicides, however resistance to several chemical classes such as Benomyl, the DMIs, while synthetic fungicides are often recommended as applications around bloom, it is common to include sulfur in a tank mix to help with resistance management. Powdery mildews are generally host-specific, and powdery mildew of grape is caused by a host-specific pathogen named Uncinula necator, Powdery mildew is a polycylic disease that thrives in warm, moist environments. Its symptoms are widely recognizable and include gray-white fungal growth on the surface of infected plants, a sulfur formulation, fungicides, and limiting the environmental factors that favor the growth of powdery mildews are all practices that can stall and/or halt its growth. Uncinula necator is the pathogen that causes powdery mildew on grape, the most susceptible hosts of this pathogen are members of the species Vitis. The signs of powdery mildews are widely recognizable and easily identifiable, the majority of them can be found on the upper sides of the leaves, however, it can also infect the bottom sides, buds, flowers, young fruit, and young stems. A gray-white, dusty, fungal growth consisting of mycelia, conidia, symptoms that occur as a result of the infection include necrosis, stunting, leaf curling, and a decrease in quality of the fruit produced. When the disease begins to develop, it looks like a white powdery substance, the primary inoculum process begins with an ascogonium and antheridium joining to produce an offspring. This offspring, a young clesitothecium, is used to infect the host immediately or overwinter on the host to infect when the timing is right, to infect, it produces a conidiophore that then bears conidia. These conidium move along to a surface to germinate. Once these spores or conidia germinate, they produce a structure called a haustoria, at this point, the fungi can infect leaves, buds and twigs that then reinfect other plants or further infect the current host. Germination of conidia occurs at temperatures between 7 and 31°C and is inhibited above 33°C, germination is greatest at 30-100% relative humidity. Powdery Mildew thrives in warm, moist environments and infects younger plant tissues like fruit, leaves, free water can disrupt conidia and only requires a humid microclimate for infection
28.
1-Octen-3-ol
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1-Octen-3-ol, octenol for short and also known as mushroom alcohol, is a chemical that attracts biting insects such as mosquitoes. It is contained in human breath and sweat, and it was believed that insect repellent DEET works by blocking the insects octenol odorant receptors. 1-Octen-3-ol is a secondary alcohol derived from 1-octene and it exists in the form of two enantiomers, --1-octen-3-ol and --1-octen-3-ol. Octenol is produced by plants and fungi, including edible mushrooms. Octenol is formed during oxidative breakdown of linoleic acid and it is also a wine fault, defined as a cork taint, occurring in wines made with bunch rot contaminated grape. Octenol is used, sometimes in combination with carbon dioxide, to insects in order to kill them with certain electronic devices. Its odor has been described as moldy or meaty, it is used in certain perfumes, octenol is approved by the U. S. Food and Drug Administration as a food additive. It is of moderate toxicity with an LD50 of 340 mg/kg, in an animal study, octenol has been found to disrupt dopamine homeostasis and may be an environmental agent involved in parkinsonism. Olfactory receptor Oct-1-en-3-one, the analog that gives blood on skin its typical metallic, mushroom-like smell 1-Octen-3-yl acetate
29.
PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
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