wiktionarypar covalentCovalent may refer to Covalentbond , a type of chemical bondCovalent radius , half the distance between two covalently bonded atoms Covalent modulation , the alteration of protein structure by covalent bonding disambig tr Kovalent anlam ayr m ... more details
Atomic radius The covalent radius , r sub cov sub , is a measure of the size of an atom that forms part of one covalentbond . It is usually measured either in picometre s pm or angstrom s , with 1 100 pm. In principle, the sum of the two covalent radii should equal the covalentbond ... the polar covalentbond s are shorter than would be expected on the basis of the sum of covalent radii. Tabulated values of covalent radii are either average or idealized values, which nevertheless show a certain transferability between different situations, that makes them useful. The bond lengths ... spectroscopy can also give extremely accurate values of bond lengths. For homonuclear A A bonds, Linus Pauling took the covalent radius to be half the single bond length in the element, e.g. ... Single BondCovalent Radii for Elements 1 118 journal Chemistry A European Journal volume 15 year ..., M. Atsumi title Molecular Double BondCovalent Radii for Elements Li E112 journal Chemistry A European ... title Triple BondCovalent Radii journal Chemistry A European Journal volume 11 year 2005 pages ... 0 auto Single, ref name Calc1 double, ref name Calc2 and triple bond ref name Calc3 covalent radii ..., it is usual to obtain an average value from a variety of covalent compounds, although the difference is usually small. Sanderson has published a recent set of non polar covalent radii for the main group ... and Bond Energy journal Journal of the American Chemical Society volume 105 pages 2259 2261 issue 8 unused data author Sanderson, R. T. ref but the availability of large collections of bond .... year 1987 title Table of Bond Lengths Determined by X Ray and Neutron Diffraction journal J. Chem ... Watson first5 David G. last6 Taylor first6 Robin title Supplement. Tables of bond lengths determined ... 1989 doi 10.1039 DT98900000S1 issue 12 ref has rendered covalent radii obsolete in many situations. Table of covalent radii The values in the table below are based on a statistical analysis of more than ... more details
Unreferenced stub auto yes date December 2009 Orphan date February 2009 Covalent modulation is the alteration of a protein s shape and function by covalent bonding of chemical groups to it. Covalent modulation is the alteration of a protein s shape and function by covalent bonding of chemical groups to it. Enzymes that control metabolic pathwas can be subject to reversible regulation by phosphorylation of specific sites. This reversible phosphorylation affects the activity of the enzyme. Enzymes that control metabolic pathwas can be subject to reversible regulation by phosphorylation of specific sites. This reversible phosphorylation affects the activity of the enzyme. Types Phosphorylation Glycosylation DEFAULTSORT Covalent Modulation Category Proteins Protein stub ... more details
Covalent semiconductor s are such solids as diamond , silicon , germanium , silicon carbide and silicon germanium where atoms are linked by covalentbond s. Most of those materials, at least in their bulk form, are well studied and rarely hit the front pages of the top scientific journals in the last decade. However, http scitation.aip.org dbt dbt.jsp?KEY PRLTAO&Volume 93&Issue 23 issue 23 of volume 93 2004 of a major physics journal Physical Review Letters contained as many as 4 papers on diamond. ref L. Boeri, J. Kortus and O. K. Andersen http www.nims.go.jp NFM paper1 SuperconductingDiamond 04PhysRevLett 93 237002.pdf Three Dimensional MgB2 Type Superconductivity in Hole Doped Diamond , K. W. Lee and W. E. Pickett http www.nims.go.jp NFM paper1 SuperconductingDiamond 04PhysRevLett 93 237003.pdf Superconductivity in Boron Doped Diamond , X. Blase, Ch. Adessi and D. Connetable http www.nims.go.jp NFM paper1 SuperconductingDiamond 04PhysRevLett 93 237004.pdf Role of the Dopant in the Superconductivity of Diamond , E. Bustarret et al. http www.nims.go.jp NFM paper1 SuperconductingDiamond 04PhysRevLett 93 237005.pdf Dependence of the Superconducting Transition Temperature on the Doping Level in Single Crystalline Diamond Films free download ref Those papers were a reaction to a breakthrough discovery of superconductivity in synthetic diamond grown by high pressure high temperature HPHT method. ref name nature cite journal author E. Ekimov et al. title Superconductivity in diamond journal Nature volume 428 year 2004 page 542 url http www.nims.go.jp NFM paper1 SuperconductingDiamond 01nature02449.pdf doi 10.1038 nature02449 pmid 15057827 arxiv cond mat 0404156 bibcode 2004Natur.428 ... has not been considered seriously in covalent semiconductors. Diamond Superconductivity ... earlier . The same could be said about superconductivity in covalent semiconductors. Superconductivity ... SuperconductingDiamond.html Some papers on superconducting diamond DEFAULTSORT Covalent Superconductor ... more details
Image Activation2 updated.svg thumb 300px Diagram of a catalytic reaction, showing the energy niveau depending on the reaction coordinate. For a catalysed reaction, the activation energy is lower. In chemistry , a reaction coordinate ref GoldBookRef file R05168 title reaction coordinate ref is an abstract one dimensional coordinate which represents progress along a reaction pathway . It is usually a geometric parameter that changes during the conversion of one or more molecular entity molecular entities . These coordinates can sometimes represent a real coordinate system such as bond length , bond angle ... , although, for more complex reactions especially, this can be difficult and non geometric parameters are used, e.g., bond order . Reaction coordinates are often plotted against Thermodynamic free energy free energy to demonstrate in some schematic form the potential energy profile an intersection of a potential energy surface associated to the reaction. In the formalism of transition state theory the reaction coordinate is that coordinate in set of curvilinear coordinates obtained from the conventional ones for the reactants which, for each reaction step, leads smoothly from the configuration of the reactants through that of the transition state to the configuration of the product chemistry products . The reaction coordinate is typically chosen to follow the path along the gradient path of shallowest ascent deepest descent of potential energy from reactants to products. For example, in the homolytic dissociation of molecular hydrogen , an apt coordinate system to choose would be the coordinate corresponding to the bond length . Notes and references reflist atomic physics stub chem stub Category Physical chemistry Category Quantum chemistry Category Theoretical chemistry Category Computational chemistry Category Molecular physics ca Coordenada de reacci es Coordenada de reacci n fr Coordonn e de r action it Coordinata di reazione hu Reakci koordin ta sv Reaktion ... more details
A coordinate free , or component free , treatment of a scientific theory or mathematical topic develops its ideas without reference to any particular coordinate system . Coordinate free treatments generally allow for simpler systems of equations, allowing greater mathematical elegance at the cost of some abstraction from the detailed formulae needed to evaluate these equations within a particular system of coordinates. Coordinate free treatments were the only possible approach to geometry before the development of analytic geometry by Descartes . After several centuries of generally coordinate based exposition, the modern tendency is now generally to introduce students to coordinate free treatments early on, and then to derive the coordinate based treatments from the coordinate free treatment, rather than vice versa . Fields which are now often introduced with coordinate free treatments include vector calculus , tensor s, and differential geometry . In physics, the existence of coordinate free treatments of physical theories is a corollary of the principle of general covariance . See also Change of basis Differential geometry Coordinate conditions Component free treatment of tensors Category Coordinate systems physics stub math stub ... more details
. In geometry , a coordinate system is a system which uses one or more number s, or coordinates , to uniquely .... 1 ref ref MathWorld title Coordinate System urlname CoordinateSystem ref The order of the coordinates ... by a letter, as in the x coordinate . In elementary mathematics the coordinates are taken to be real ... of a more abstract system such as a commutative ring . The use of a coordinate system allows ... use is the system of assigning longitude and latitude to geographical locations. In physics , a coordinate ... coordinate system is useful for numerical calculations in a given space, the space itself is considered ... example of a coordinate system is the identification of points on a line with real numbers using the number line . In this system, an arbitrary point O the origin is chosen on a given line. The coordinate ... is given a unique coordinate and each real number is the coordinate of a unique point. ref Woods p. 8 ref File Number line.gif center The number line Cartesian coordinate system main Cartesian coordinate system Image Cartesian coordinate system.svg right thumb 250px The Cartesian coordinate system in the plane. The prototypical example of a coordinate system is the Cartesian coordinate system. In the Plane ... in n dimensional Euclidean space . Polar coordinate system main Polar coordinate system Image CircularCoordinates.svg thumb 250px The Polar coordinate system in the plane. Another common coordinate system for the plane is the Polar coordinate system . A point is chosen as the pole and a ray from ... coordinate systems main Cylindrical coordinate system Spherical coordinate system There are two common methods for extending the polar coordinate system to three dimensions. In the cylindrical coordinate system , a z coordinate with the same meaning as in Cartesian coordinates is added to the r ... Homogeneous coordinate system main Homogeneous coordinates A point in the plane may be represented ... of the point. This introduces an extra coordinate since only two are needed to specify a point ... more details
form. In other words, the real world does not care about our coordinate systems. However, it is often useful to fix upon a particular coordinate system, in order to solve actual problems or make actual predictions. A coordinate condition selects such coordinate system s . Indeterminacy in general ... by gauge fixing . Thus, coordinate conditions are a type of gauge condition. ref Salam, Abdus ... conditions 22 Selected Papers of Abdus Salam, page 391 World Scientific 1994 . ref No coordinate condition is generally covariant, but many coordinate conditions are Lorentz covariant or Rotational invariance rotationally covariant . Naively, one might think that coordinate conditions would take ... coordinate condition they can be put in that form. However, it is more usual for them to appear ... to the coordinate system. It might seem that they would since there are ten equations to determine ... products . Harmonic coordinates main Harmonic coordinate condition A particularly useful coordinate ... . Although the harmonic coordinate condition is not generally covariant, it is Lorentz covariant. This coordinate condition resolves the ambiguity of the metric tensor math g mu nu math by providing ... coordinates main Synchronous coordinates Another particularly useful coordinate condition is the synchronous ... aUZNx j2musC&pg PA20&dq synchronous and coordinate conditions&num 100 General Relativity, page 20 ... 7&ndash 25 year 1995 doi 10.1086 176550 bibcode 1995ApJ...455....7M ref The synchronous coordinate condition is neither generally covariant nor Lorentz covariant. This coordinate condition resolves ... tensor must satisfy. Other coordinates Many other coordinate conditions have been employed by physicists, though none as pervasively as those described above. Almost all coordinate conditions used by physicists, including the harmonic and synchronous coordinate conditions, would be satisfied ... the harmonic and synchronous coordinate conditions, some commonly used coordinate conditions may ... more details
Coordinate descent is a Non derivative Mathematical optimization optimization algorithm . To find a local minimum of a function, one does line search along one Coordinate system coordinate direction at the current point in each iteration. One uses different coordinate directions cyclically throughout the procedure. Iterations of a cycle of line search in all directions is equivalent to one gradient descent iteration. Description Coordinate descent is based on the idea that one can minimize a multivariable function math F mathbf x math by minimizing it along one direction at a time. Instead of varying descent direction according to gradient , one fixes descent direction at the outset. For instances, one chooses search directions from the coordinate directions math mathbf e 1, mathbf e 2, dots, mathbf e n math . One minimizes the objective function along one coordinate direction a time, iterating ..., the math i math th coordinate of math mathbf x k 1 math is given by math mathbf x k 1 i arg ... search along coordinate directions implies a stationary point is reached. This process is illustrated in the picture below. File coordinate descent.jpg Examples Coordinate descent has problems with non smooth functions. The following picture shows that coordinate descent iteration may get stuck ... Adaptive Coordinate Descent Recently proposed Adaptive Coordinate Descent approach gradually builds a transformation of the coordinate system such that the new coordinates are as decorrelated as possible with respect to the objective function. The Adaptive Coordinate Descent was shown to be competitive ... Coordinate Descent booktitle Genetic and Evolutionary Computation Conference GECCO pages 885 892 publisher ... of the coordinate descent method for convex differentiable minimization periodical Journal of Optimization ... Coordinate descent algorithms for Lasso penalized regression periodical The Annals of Applied Statistics ... variable version of coordinate descent periodical Journal of Optimization theory and applications ... more details
In the theory of relativity , it is convenient to express results in terms of a spacetime coordinate system relative to an implied Observer special relativity observer . In many but not all coordinate systems, an event relativity event is specified by one time coordinate and three spatial coordinates. The time specified by the time coordinate is referred to as coordinate time to distinguish it from proper time . In the special case of an inertial observer in special relativity , by convention the coordinate ... relativity , coordinate systems can be chosen more freely. For a clock whose spatial coordinates are constant, the relationship between proper time math tau math tau and coordinate time math ..., correct to the order of terms in 1 c sup 2 sup , gives the relation between proper and coordinate ... from proper time on Earth to coordinate time in solar system barycentric space time frame of reference ... space like coordinates x, y, z and in the coordinate time t sub c sub of the clock s position in the chosen ... between proper time and coordinate time, i.e. for time dilation. A derivation, starting from ... due to gravitation and motion together Time dilation due to gravitation and motion together . Coordinate time, proper time, and clock synchronization Fuller explanation of the concept of coordinate time ... Two events are called simultaneous in a chosen reference frame if and only if the chosen coordinate ... 958, at section 5 On the concept of coordinate time scales , esp. p.955. ref and this condition allows ... of another reference frame. ref name klnr1992 But the coordinate time is not a time that could be measured ... at the solar system barycenter would not measure the coordinate time of the barycentric reference frame, and a clock located at the geocenter would not measure the coordinate time of a geocentric reference frame. ref S A Klioner 2008 , cited above, at page 954. ref The coordinate times cannot ... time of the clock would coincide with coordinate time such an observer and clock have to be conceived ... more details
when they are row vectors . Standard basis The coordinate space F sup n sup comes with a standard ... with abstract vector spaces instead of F sup n sup is that it is often preferable to work in a coordinate ... desirable to view a coordinate space duality mathematics dually as the set of F valued functions ... th coordinate of the point , so F sup n sup is, dually, a set of functions. See also real coordinate space , R sup n sup complex coordinate space , C sup n sup examples of vector spaces DEFAULTSORT Coordinate ... more details
expert mathematics date October 2011 unreferenced date February 2009 In linear algebra , a coordinate vector is an explicit representation of a Euclidean vector in an Real coordinate space Intuitive overview abstract vector space as an ordered list of numbers or, equivalently, as an element of the coordinate space F sup n sup . Coordinate vectors allow calculations with abstract objects to be transformed into calculations with blocks of numbers matrix mathematics matrices , column vector s and row vector s . The idea of a coordinate vector can also be used for infinite dimensional vector spaces, as addressed below. Definition Let V be a vector space of dimension vector space dimension n over a field mathematics field F and let math B b 1, b 2, ldots, b n math be an ordered basis for V . Then for every math v in V math there is a unique linear combination of the basis vectors that equals v math v alpha 1 b 1 alpha 2 b 2 cdots alpha n b n math The linear independence of vectors in the basis ensures that the s are determined uniquely by v and B . Now, we define the coordinate vector of v relative to B to be the following sequence of coordinates math v B alpha 1, alpha 2, cdots, alpha ... the order in which the coefficients are listed in the coordinate vector. Coordinate vectors ... by a square matrix math M C B math see Coordinate vector Basis transformation matrix below , resulting ... with respect to B , that takes every vector to its coordinate representation math phi B v v B math . Then math ... coordinate vector to the polynomial math p left x right a 0 a 1 x a 2 x 2 a 3 x 3 math is math ... give rise to unique coordinate representations exactly as described before. The only change is that the indexing ... combination of basis elements, the only nonzero entries of the coordinate vector for v will be the nonzero coefficients of the linear combination representing v . Thus the coordinate vector for v is zero ... it Coordinate di un vettore he ... more details
Wiktionarypar bondBond , bonds , bonded , and bonding may refer to Peace bonding , something which makes a weapon unusable as a weapon TOC right Fiduciary Bond finance , in finance, a type of debt security Government bond , a bond issued by a national government War bond s, a type of government bond used to raise funding for a war effort Municipal bond , a bond issued by a city or local government Corporate bond , a bond issued by a corporation Mortgage bond , in South Africa a bond or mortgage bond is the usual term for property mortgage. Insurance bond or investment bond , a life assurance based single premium investment Surety bond , a three party contract, where the surety promises to pay the obligee for non performance or dishonesty by the principal Performance bond , a surety bond for completion of work under a contract Bail bond agent, or bail bondsman , a person or corporation providing a surety bond for return of a person to a court Tenancy bond or damage deposit , a deposit taken by a landlord in relation to rental of a property Catastrophe bond or cat bond , a form of reinsurance ... Bond of association , a basic building block of credit unions and co operative banks Bond vigilante , a form of political protest by selling bonds Judiciary Peace bond , a protection order from a Canadian court Bond of manrent , a Scottish clan treaty Bond of Association , a British legal document from the 16th century Bond v. United States 2000 Bond v. United States 2000 , a U.S. Supreme Court case regarding the fourth amendment Bond v The Queen , a 2000 High Court of Australia case Physical sciences Bond number , in fluid mechanics, a dimensionless number expressing the ratio of gravitational forces to surface tension forces Chemical bond , the physical phenomenon of chemical substances being held together by attraction of atoms Covalentbond , between nonmetals Ionic bond , between metal and nonmetals Metallic bond , between metals Bond albedo , a measure of the electromagnetic radiation ... more details
of a covalent radius to predict the length of such a bond is inadequate and the bond lengths calculated ... bond length or distance between two atoms, r sub A sub and r sub B sub are the covalent radii in picometers ... predicts a bond length which closer to the experimental value. Its major weakness is the use of the covalent .... last2 Robinson first2 Edward A. title Bond lengths in covalent fluorides. A new value for the covalent ... atom, the longer the bond length of fluorine. Finally, the most accurate value for the covalent radius ...The covalent radius of fluorine is a measure of the size of a fluorine atom it is approximated at about 60 picometre s. Since fluorine is a relatively small atom with a large electronegativity , its covalent radius is difficult to evaluate. The covalent radius is defined as half the bond lengths between two neutral atoms of the same kind connected with a single bond . By this definition, the covalent radius of F is 71 pm. However, the F F bond in F sub 2 sub is abnormally weak and long. Besides ..., the bond length of F is influenced by its ionic radius , the size of ion s in an ionic crystal ... covalent radius. When F becomes F sup sup , it gains one electron but has the same number of protons ... The first attempt at trying to find the covalent radius of fluorine was in 1938, by Brockway. ref ... , it was determined that the bond length between the two fluorine atoms was about 145 pm. ref name Brockway He therefore assumed that the covalent radius of fluorine was half this value ... equation to determine the bond length of an atom based on the differences in electronegativities of the two ... to, giving the bonds a certain amount of sigma bond character. In addition, the fluorine atom ... bond character through p p or p d back bonding . Thus, this model suggests that the observed shortening of the lengths of bonds is due to these double bond characteristics. ref name REJTG ref Pauling, L. The Nature ofthe Chemical Bond, 3rd ed. Cornell University Press Ithaca, NY, 1960 p. 224 ... more details
A network solid or covalent network solid is a chemical compound in which the atoms are bonded by covalentbond s in a continuous network. In a network solid there are no individual molecule s and the entire crystal may be considered a macromolecule . Formulas for network solids as those for ionic compound s are simple ratios of the component atoms represented by a formula unit . Examples of network solids include diamond with a continuous network of carbon atoms and silicon dioxide or quartz with a continuous three dimensional network of SiO sub 2 sub units. Graphite and the mica group of silicate mineral s structurally consist of continuous two dimensional layers covalently bonded within the layer with other bond types holding the layers together. Properties Electrical conductivity Poor, as there are no free electrons. When molten, unlike ionic compounds, the substance is still unable to conduct electricity as the macromolecule consists of uncharged atoms, not ions as seen in previously mentioned ionic compounds. Contrary to this rule is graphite . Graphite is an allotrope of Carbon. In this allotrope, each atom of Carbon forms three covalent bonds, leaving one electron in each outer orbital de localised, creating multiple free electrons within each plane of Carbon. This grants graphite electrical conductivity. Melting point High, due to the large amount of energy required to rearrange the covalent bonds. Hardness Hard, due to the strong covalentbond throughout the lattice however, the layers of carbon atoms in graphite can be easily displaced, allowing the substance to be malleable . Solubility Generally insoluble in any solvent due to the difficulty of solvating a very large molecule. Examples Quartz SiO sub 2 sub Diamond Carbon Graphite Carbon References Zumdahl, Steven S., and Susan A. Zumdahl, Chemistry, Houghton Mifflin, 5th ed., 2000, pp. 470 476 ISBN 0 618 03591 5 Category Chemical bonding chemistry stub de Atomgitter hu Atomr cs et Aatomv re ... more details
In Bond may refer to Bottled in bond When American made whiskeys are made to certain quality. Wines in bond Under UK law, wines in bond are wines that must be stored in a bonded warehouse approved by HM Customs & Excise. disambig ... more details
solids can be used to describe materials such as Zeolite , Metal organic framework s MOFs , and Covalent ... class of porous polymeric materials, consisting of porous, crystalline, covalent bonds that usually ... name JACS Han 2008 Han, S. Hurukawa, H. Yaghi, O. M. Goddard, W. A. Covalent Organic Frameworks as Exceptional .... A Belt Shaped, Blue Luminescent, and Semiconducting Covalent Organic Framework. Angew. Chem. Int. Ed .... M. Designed Synthesis of 3D Covalent Organic Frameworks. Science . 2007 , 316 , pp 268 272. doi 10.1126 ... example of this chemistry. ref name Angew Kuhn 2008 Kuhn, P. Antonietti, M. Thomas, A. Porous, Covalent ... with benzaldehyde that results in imine bond formation with elimination of water. COF 300 is a good .... Klck, C. O Keeffe, M. Yaghi, O. M. A Crystalline Imine Linked 3 D Porous Covalent Organic Framework ... more details
Infobox Film name The Bond image image size caption director Charlie Chaplin producer writer Charlie Chaplin narrator starring Edna Purviance br Albert Austin br Sydney Chaplin music cinematography editing distributor First National First National Pictures Inc. released 1918 in film 1918 runtime 11 minutes country USA language Silent film br English language English intertitles budget The Bond is a propaganda film created by Charlie Chaplin at his own expense for the Liberty Load Committee for theatrical release to help sell U.S. War bond Liberty Bonds during World War I . Made in 1918 with Edna Purviance , Albert Austin and Sydney Chaplin , the film has a distinctive visual motif set in a simple plain black set with starkly lit simple props and arrangements. The story is a series of sketches humorously illustrating various bonds like the bond of friendship and of marriage and, most important, the Liberty Bond, to knockout K.O. the Kaiser which Charlie does literally. There was also a United Kingdom British version with Uncle Sam replaced by John Bull and promotes War Bonds. Media gallery widths 250px Image Charlie Chaplin, bond of friendship, 1918.ogg A video clip from the silent film, The Bond 1918 Image Charlie Chaplin, the Marriage Bond.ogg A video clip from the silent film, The Bond 1918 Image Charlie Chaplin, The Bond, 1918.ogg A video clip from the silent film, The Bond 1918 gallery Cast Charles Chaplin Charlie Edna Purviance Charlie s Wife Albert Austin Friend Sydney Chaplin The Kaiser External links Commonscat The Bond imdb title id 0008907 title The Bond http www.archive.org details CC 1918 09 29 TheBond Complete film at Archive.org Charlie Chaplin DEFAULTSORT Bond, The Category 1918 films Category Black and white films Category Films directed by Charlie Chaplin ... films Category Articles containing video clips war film stub de Die Anleihe es The Bond fr The Bond it The Bond ja pt The Bond ru , 1918 ... more details
About the BOND database software Bond disambiguation Bond orphan date June 2010 BOND Building Object Network Databases started development in late 2000 as a rapid application development tool for the GNOME Desktop by Treshna Enterprises . Its aim was to fill a gap that traditional Microsoft Windows applications like Borland Delphi , Microsoft Access and Visual Basic filled on the Windows desktop, but targeted for the Linux environment. Its goal was to allow developers to quickly build database forms in Extensible Markup Language XML for backend SQL databases. It has been employed extensively by Treshna Enterprises to develop applications such as PayMaster an opensource payroll application and GymMaster a commercial gym management application . Description It uses PostgreSQL as its backend database and GTK as its front end. Windows and HTML driven front ends are also available. While it initially worked closely with Glade Interface Designer Glade and the Gnome Desktop, newer versions have focused on more web oriented with Ajax programming AJAX driven Widget computing widgets . The Glade Extensible Markup Language XML format was abandoned a number of years ago and a new XML schema was developed to be more flexible with the range of data required for storing database information. BOND makes use of BONDDB which serves as a layer between the BOND API and the PostgreSQL backend. In the future, BOND aims to be a free open source solution that allows users to quickly create their own databases from scratch without being a skilled programmer or DBA. External links http www.treshna.com bondBOND development website Category GNOME database software stub ... more details
Summary Information Description picture of covalent bonding Source I created this work entirely by myself. Date 01 20, 15 April 2009 UTC Author User Jayron32 Jayron32 . User talk Jayron32 small talk small . Special Contributions Jayron32 small contribs small other versions Licensing self cc by sa 3.0 GFDL Copy to Wikimedia Commons bot Fbot ... more details
In supramolecular chemistry , dynamic covalent chemistry is a strategy that aims at organic synthesis synthesizing large complex molecule s. In it a reversible reaction is under thermodynamic reaction control and a specific reaction product out of many is captured. ref cite journal author1 Rowan SJ author2 Cantrill SJ author3 Cousins GR author4 Sanders JK authorlink4 Jeremy Sanders author5 Stoddart JF authorlink5 James Fraser Stoddart author separator , title Dynamic covalent chemistry journal Angew. Chem. Int. Ed. Engl. volume 41 issue 6 pages 898 952 year 2002 month March pmid 12491278 doi 10.1002 1521 3773 20020315 41 6 898 AID ANIE898 3.0.CO 2 E ref Because all the components in the reaction mixture are able to equilibrate quickly, according to its advocates some degree of error checking and proof reading is enabled. The concept of dynamic covalent chemistry was demonstrated in the development of specific molecular Borromean rings . The underlying idea is that rapid equilibration allows the coexistence of a huge variety of different species among which one can select molecules with desired chemical , pharmaceutical and biological properties. For instance, the addition of a proper template will shift the equilibrium toward the component that forms the complex of higher stability thermodynamic template effect . After the new chemical equilibrium equilibrium is established, the researcher modifies the reaction conditions so as to stop equilibration. The optimal binder for the template is then extracted from the reactional mixture by the usual laboratory procedures. The concept is demonstrated in a minor but illustrative example involving Polyoxymethylene polyacetal macrocycle s. ref cite journal author Cacciapaglia R, Di Stefano S, Mandolini L title Metathesis reaction of formaldehyde acetals an easy entry into the dynamic covalent chemistry of cyclophane formation journal J. Am. Chem. Soc. volume 127 issue 39 pages 13666 71 year 2005 month October pmid 16190732 doi ... more details
Unreferenced date December 2006 Astronomical coordinate systems are coordinate system s used in astronomy to describe the location of objects in the sky and in the universe. The most commonly occurring such systems are coordinate systems on the celestial sphere , but extragalactic coordinates systems are also important for describing more distant objects. Coordinate systems on the celestial sphere See Celestial coordinate system . Horizontal coordinate system Equatorial coordinate system based on Earth rotation Meridional coordinate system Ecliptic coordinate system based on Solar System rotation Galactic coordinate system based on Milky Way rotation Extragalactic coordinate systems See Extragalactic astronomy . supergalactic coordinate system based on plane of local supercluster of galaxy galaxies comoving coordinates valid to particle horizon DEFAULTSORT Astronomical Coordinate Systems Category Coordinate systems Category Celestial coordinate system Category Extragalactic astronomy Astronomy stub ... more details
Expert subject Chemistry date November 2008 ICM stands for Internal Coordinate Mechanics and was first designed and built to predict low energy conformations of biomolecules. ICM also is a programming environment for various tasks in computational chemistry and computational structural biology, sequence analysis and rational drug design. The original goal was to develop algorithms for energy optimization of several biopolymers with respect to an arbitrary subset of internal coordinates such as bond lengths, bond angles torsion angles and phase angles. The efficient and general global optimization method which evolved from the original ICM method is still the central piece of the program. It is this basic algorithm which is used for peptide prediction, homology modeling and loop simulations, flexible macromolecular docking and energy refinement. However the complexity of problems related to structure prediction and analysis, as well as the desire for perfection, compactness and consistency, led to the program s expansion into neighboring areas such as graphics, chemistry, sequence analysis and database searches, mathematics, statistics and plotting. The original meaning became too narrow, but the name was kept. The current integrated ICM shell contains hundreds of variables, functions, commands, database and web tools, novel algorithms for structure prediction and analysis into a powerful, yet compact program which is still called ICM. The seven principal areas are centered around a general core of shell language and data analysis and visualization. See also ICM Browser References reflist Abagyan, R.A. and Totrov, M.M. Biased Probability Monte Carlo Conformational Searches and Electrostatic Calculations For Peptides and Proteins J. Mol. Biol., 235 , 983 1002, 1994 . PMID 8289329 Abagyan, R.A., Totrov, M.M., and Kuznetsov, D.A. ICM A New Method For Protein Modeling and Design ... Parallelization of The Energy, Surface and Derivative Calculations For internal Coordinate Mechanics ... more details
Refimprove date January 2010 Orphan date November 2009 In mathematics , a coordinate induced basis is a basis for the tangent space or cotangent space of a manifold that is induced by a certain coordinate system. Given the coordinate system math x a math , the coordinate induced basis math e a math of the tangent space is given by math e a frac partial partial x a math and the dual basis math omega a math of the cotangent space is math omega a dx a. , math References D.J. Hurley, M.A. Vandyck Topics in Differential Geometry a New Approach Using D Differentiation 2002 Springer p. 5 DEFAULTSORT Coordinate Induced Basis Category Differential geometry differential geometry stub ... more details
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