CovalentBond Classification is also referred to as the L X Notation. It was developed by M. H. Green ref http www.sciencedirect.com science article pii 0022328X9500508N M.L.H. Green J. Organomet. Chem., 1995, 500, 127 nowiki nowiki ref in the mid 1990s as a solution for the need to describe organometallic complexes in a way that isn t as prone to limitations, like those that arise from the very definition of oxidation state . ref Crabtree, Mingos. Comprehensive Organometallic Chemistry III Vol.1. Elsevier Oxford, 2007 pg. 22 29. ref Instead this method looks at the nature of the ligand s as opposed to the transition metal center of the complex. ref http www.columbia.edu chemistry groups parkin cbc.htm ref By focusing on the ligands, it can acknowledge the fact that many situations regardless of the ligand, that the 18 electron rule is being obeyed. sup 1 sup According to this method there are three basic types of interactions that allow for binding between the metal center and the ligands to occur. These three interactions can then be labeled, and therefore distinguished, as X, L and Z. These are differentiated by differences in how they bond with the metal center. Types of Ligands X type ligands are those that donate one electron to the metal and accept one electron from the metal when using the neutral ligand method of electron counting , or donate two electrons to the metal ... neutral or anionic, these ligands yield normal covalent bonds . sup 3 sup A few examples .... sup 4 sup The bonds formed between these ligands and the metal are dative covalent bonds , which are also known as coordinate bonds. Examples of this type of ligand include CO, PR sub 3 sub , NH sub ..., these ligands also form dative covalent bonds like the L type. sup 3 sup This type of ligand ... number and the ligand bond number sup 3 sup can be calculated. Electron Count N x 2l Q Where N is the group ... dn N OS N x Q Valence Number VN x 2z Ligand Bond Number LBN l x z Other Uses This template of writing ... more details
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 ... 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 R AB are measured ... 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. R H&ndash ... BondCovalent Radii for Elements 1 118 journal Chemistry A European Journal volume 15 year 2009 pages ... title Molecular Double BondCovalent Radii for Elements Li E112 journal Chemistry A European Journal ... Triple BondCovalent Radii journal Chemistry A European Journal volume 11 year 2005 pages 3511 3520 ... bond ref name Calc3 covalent radii in pm , determined using typically br 400 experimental or calculated ... 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 elements ... 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 lengths ... title Table of Bond Lengths Determined by X Ray and Neutron Diffraction journal J. Chem. Soc., Perkin ... David G. last6 Taylor first6 Robin title Supplement. Tables of bond lengths determined by X ray ... 10.1039 DT98900000S1 issue 12 ref has rendered covalent radii obsolete in many situations. Table of covalent ... experimental bond lengths from the Cambridge Structural Database. ref name CSD cite journal author ... more details
Unreferenced 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 et Reaktsioonikoordinaat es Coordenada de reacci n fr Coordonn e de r action it Coordinata di reazione hu Reak ... 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
of a covalent radius to predict the length of such a bond is inadequate and the bond lengths calculated ... journal last1 Gillespie first1 Ronald J. last2 Robinson first2 Edward A. title Bond lengths in covalent ... value of 60 pm for the covalentbond length of fluorine. ref cite journal last1 Robinson ...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 ... Stevenson proposed an empirical equation to determine the bond length of an atom based on the differences ... where d sub AB sub is the predicted bond length or distance between two atoms, r sub A sub and r sub B sub are the covalent radii in picometers of the two atoms, and xA xB is the absolute difference in the electronegativities ... pm. ref name REJTG This equation predicts a bond length which closer to the experimental value. Its major weakness is the use of the covalent radius of fluorine that is known as being too large ... atomic orbital in the atom it is bonded to, giving the bonds a certain amount of sigma bond ... back from the central atom giving rise to double bond character through p p or p d back bonding ... 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 delocalized 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, which is also contrary to most forms of metallic bonds. Graphite is an allotrope of carbon. In this allotrope, each atom of carbon forms three covalent bonds, leaving one electron in each outer orbital delocalized, 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 Silicon carbide moissanite, SiC Graphite carbon Category Chemical bonding chemistry stub de Atomgitter et Aatomv re hu Atomr cs nl Covalent netwerk ... more details
. In geometry , a coordinate system is a system which uses one or more number s, or coordinates , to uniquely ... such as Euclidean space . ref Woods p. 1 ref ref MathWorld title Coordinate System urlname CoordinateSystem ... in an ordered tuple and sometimes by a letter, as in the x coordinate . In elementary mathematics ... abstract system such as a commutative ring . The use of a coordinate system allows problems in geometry ... of assigning longitude and latitude to geographical locations. In physics , a coordinate system ... and unreferenced, try to put in another section if refs found Although a specific coordinate system ... 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 ... 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 geometry ... 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 this point is taken ... point. The pole is represented by 0, for any value of . Cylindrical and spherical 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 and polar coordinates ... r , z to polar coordinates , giving a triple , , Homogeneous coordinate ... more details
Wiktionary 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
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 ... efficient see random coordinate descent method for more details about them . Description Coordinate ... , one fixes descent direction at the outset. For instances, one chooses search directions from the coordinate ... function along one coordinate direction a time, iterating through the list of search directions cyclically. It follows that, if math mathbf x k math is given, the math i math th coordinate of math ... as steepest descent. No improvement after one cycle of line search along coordinate directions implies a stationary point is reached. This process is illustrated below. File coordinate descent.jpg Examples Coordinate descent has problems with non smooth functions. The following picture shows that coordinate ... are not smooth. File nonsmooth.jpg Extensions Adaptive coordinate descent Recently proposed adaptive coordinate descent approach gradually builds a transformation of the coordinate system such that the new ... coordinate descent was shown to be competitive to the state of the art evolutionary algorithms ... M. Schoenauer and M. Sebag title Adaptive Coordinate Descent booktitle Genetic and Evolutionary Computation ... Component Analysis a is used to extend Coordinate Descent method c to the optimization of non separable problems d . File ACD.png center x400px The adaptation of an appropriate coordinate system allows Adaptive Coordinate Descent to outperform Coordinate Descent on non separable functions. The following ... Coordinate Descent reaches the target value after only 325 function evaluations about 70 times faster than Coordinate Descent , that is comparable to Gradient descent gradient based methods . See also ... first Zhiquan last2 Tseng first2 P. year 1992 title On the convergence of the coordinate descent method ... 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
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 Three dimensional space spatial coordinates. The time specified by the time coordinate is referred to as coordinate time ... , by convention the coordinate time at an event is the same as the proper time measured by a clock ... inertial observers, and in general relativity , coordinate systems can be chosen more freely. For a clock ... and coordinate time math t math , i.e. the rate of time dilation , is given by math frac d tau dt ... proper and coordinate time in terms of more easily recognizable quantities in dynamics math frac d ... 1981 , Transformation from proper time on Earth to coordinate time in solar system barycentric space ... in three orthogonal space like coordinates x, y, z and in the coordinate time t sub c sub of the clock ... equation for the relation between proper time and coordinate time, i.e. for time dilation. A derivation ... together . Coordinate time, proper time, and clock synchronization Fuller explanation of the concept of coordinate time comes from its relationships with proper time and with clock synchronization ... if the chosen coordinate time has the same value for both of them ref S A Klioner 2008 , http www.aanda.org ... , vol.478 2008 , pp.951 958, at section 5 On the concept of coordinate time scales , esp. p.955. ref ... from the standpoint of another reference frame. ref name klnr1992 But the coordinate time is not a time ... frame, e.g. a clock located 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 ... on which the proper time of the clock would coincide with coordinate time such an observer and clock ... 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
when they are row vectors . Standard basis The coordinate space F sup n sup comes with a standard ... vector spaces instead of F sup n sup is that it is often preferable to work in a coordinate ... to view a coordinate space duality mathematics dually as the set of F valued functions on a finite ... 1,2....n and codomain F . The function sends an element i of 1,2....n to the value of the i 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
A dipolar bond , ref GoldBookRef file D01752 title dipolar bond ref also known as dative covalentbond ref GoldBookRef file D01523 title dative bond ref or coordinatebond ref GoldBookRef file C01329 title coordinatebond ref is a kind of 2 centre, 2 electron covalentbond in which the two electrons derive from the same atom. Typically, a dipolar bond is formed when a Lewis base donates a pair of electrons to a Lewis acid . This description of bonding is a characteristic of valence bond theory . It has no place in molecular orbital theory or ligand field theory of coordination complexes. Examples File NH3 BF3 adduct bond lengthening 2D.png thumb Adduct of ammonia and boron trifluoride The term dipolar bond is used in organic chemistry for compounds such as amine oxide s for which the electronic structure can be described in terms of the basic amine donating two electrons to an oxygen atom. R sub 3 sub N&rarr O The arrow indicates that both electrons in the bond originate from the amine moiety. In a standard covalentbond each atom contributes one electron. Therefore, an alternative description is that the amine gives away one electron to the oxygen atom, which is then used, with the remaining unpaired electron on the nitrogen atom, to form a standard covalentbond. The process of transferring ... formed are described as coordinate bonds. In all cases the bond is a covalentbond. The prefix dipolar, dative or coordinate merely serves to indicate the origin of the electrons used in creating the bond. References reflist Chemical bonds DEFAULTSORT Dipolar Bond Category Chemical bonding Category ... III chloride This electronic structure has an electric dipole , hence the name dipolar bond. In reality the atoms carry fractional charge s the more electronegative atom of the two involved in the bond will carry a fractional negative charge. An example of a dative covalentbond is provided by the interaction ... covalent coordinat de Koordinative Bindung es Enlace de coordinaci n fa fr Liaison covalente ... 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 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 Loan 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 Albert Austin as Friend Charlie Chaplin Charles Chaplin as Charlie Sydney Chaplin as The Kaiser Edna Purviance as Charlie s Wife External links Commons category The Bond imdb title id 0008907 title The Bond Internet Archive film CC 1918 09 29 TheBond The Bond Charlie Chaplin DEFAULTSORT Bond, The Category 1918 films Category Black and white films Category Films directed by Charlie Chaplin Category ... Category Articles containing video clips war film stub de Die Anleihe es The Bond fr The Bond it The Bond ja pl Po yczka wolno ci 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
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
A triple bond in chemistry is a chemical bond between two chemical elements involving six bonding electron s instead of the usual two in a covalentbondcovalent single bond . The most common triple bond, that between two carbon atoms, can be found in alkynes . Other functional group s containing a triple bond are cyanide s and isocyanide s. Some diatomic molecules, such as dinitrogen and carbon monoxide are also triple bonded. In skeletal formula the triple bond is drawn as three parallel lines may be encoded on WP as &equiv between the two connected atoms in typography, this is accomplished with the Triple bar identity operator . ref JerryMarch ref ref Organic Chemistry 2nd Ed. John McMurry ref Triple bonds are stronger than covalentbond single bonds or double bond s and they are also shorter. The bond order is three. align center class wikitable center File Acetylene CRC IR dimensions 2D.png 150px center center File Cyanogen 2D dimensions.png 180px center center File Carbon monoxide 2D.svg 100px center acetylene , H&minus C&equiv C&minus H cyanogen , N&equiv C&minus C&equiv N carbon monoxide , C&equiv O Colspan 100 Chemical compounds with triple bonds Bonding The type of bonding can be explained in terms of orbital hybridization . In the case of acetylene each carbon atom has two sp orbital s and two p orbital s. The two sp orbitals are linear with 180 angles and occupy the x axis cartesian coordinate system . The p orbitals are perpendicular on the y axis and the z axis. When the carbon atoms approach each other the sp orbitals overlap to form a sp sp sigma bond . At the same time the p sub z sub orbitals approach and together they form a p sub z sub p sub z sub pi bond . Likewise, the other pair of p sub y sub orbitals form a p sub y sub p sub y sub pi bond. The result is formation of one sigma bond and two pi bonds. In bent bond bent bond theory the triple bond can also formed by the overlapping of three sp sup 3 sup lobes without the need to invoke a pi bond ... more details
The mechanical bond is a type of chemical bond found in mechanically interlocked molecular architectures such as catenane s and rotaxane s. Unlike classical molecular structures, interlocked molecules consist of two or more separate components which are not connected by chemical i.e. covalent bonds. These structures are true molecules and not a supramolecular species, as each component is intrinsically linked to the other resulting in a mechanical bond which prevents dissociation without cleavage of one or more covalent bonds. Mechanical bond is a relatively new term and at this point has limited usage in chemical literature relative to more well established bonds, such as covalent, hydrogen, or ionic bonds. External links The Nature of the Mechanical Bond James Fraser Stoddart http www.snic.org.sg events author 20info.html Article Chemical bonds Category Chemical bonding Category Supramolecular chemistry es Enlace mec nico ... more details
File 3D model hydrogen bonds in water.svg right thumb 225px Model of polar bonds between molecules of water. In chemistry , a polar bond is a type of covalent bond between two atoms or more in which electrons are shared unequally. Because of this, one end of the molecule has a slight, relative negative charge and the other a slight, relative positive charge. An example of atoms bonded by a polar bond is the water molecule , which is made up of two hydrogen atoms and one oxygen atom. See Also Chemical properties Covalent bond Bond dipole moment Partial charge Dipoles Molecular dipoles Molecular dipole Electronegativity Category Chemical bonding simple Polar bond uk ... more details
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