| van der Waals attraction | <chemistry> Electrodynamic forces arise between atoms, molecules and assemblies of molecules due to their vibrations giving rise to electromagnetic interactions, these are attractive when the vibrational frequencies and absorptions are identical or similar, repulsive when nonidentical. Other interactions originally proposed by van der Waals were included in this name, but these are usually separated into the Coulomb's force, the Keesom force and the London force. Only the last is of electrodynamic nature. Probably important in holding lipid membranes into that structure and possibly in other interactions, for example cell adhesion. Electrodynamic forces between large scale assemblies can be of relatively long range nature. (18 Nov 1997) |
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| van der Waals' forces | First postulated by van der Waals in 1873 to explain deviations from ideal gas behaviour seen in real gases; the attractive force's between atoms or molecules other than electrostatic (ionic), covalent (sharing of electrons), or hydrogen bonding (sharing a proton); generally ascribed to dipolar and dispersion effects, π-electrons, etc.; these relatively nondescript force's contribute to the mutual attraction of organic molecules. Synonym: London forces. (05 Mar 2000) |
| van der Waals, Johannes | <person> Dutch physicist and Nobel laureate, 1837-1923. See: van der Waals' forces. (05 Mar 2000) |
| van der Hoeve's syndrome | <syndrome> A subtype of osteogenesis imperfecta in which progressive conductive hearing loss begins in childhood because of stapedial fixation. (05 Mar 2000) |
| van der Kolk, Jacobus | <person> Dutch physician, 1797-1862. See: van der Kolk's law. (05 Mar 2000) |
| van der Kolk's law | In a mixed nerve, the sensory fibres are distributed to the parts moved by the muscles controlled by the motor fibres. (05 Mar 2000) |
| van der Velden, Reinhardt | <person> German physician, 1851-1903. See: van der Velden's test. (05 Mar 2000) |
| van der Velden's test | A test for free hydrochloric acid, the presence of which turns an added solution of methylene blue from violet to green. (05 Mar 2000) |
| acylmercaptan bond | A high energy bond formed by the condensation of a carboxyl group (-COOH) and a mercaptan (or thiol) group (-SH); widely formed in the course of intermediary metabolism, notably in the oxidation of fats, where the -SH is part of coenzyme A and the -COOH is part of the fatty acid being oxidised. (05 Mar 2000) |
| apolar bond | <chemistry> The attractive force between molecules due to the close positioning of non-hydrophilic portions of the two molecules. (09 Oct 1997) |
| bond | 1. That which binds, ties, fastens,or confines, or by which anything is fastened or bound, as a cord, chain, etc.; a band; a ligament; a shackle or a manacle. "Gnawing with my teeth my bonds in sunder, I gained my freedom." (Shak) 2. The state of being bound; imprisonment; captivity, restraint. "This man doeth nothing worthy of death or of bonds." 3. A binding force or influence; a cause of union; a uniting tie; as, the bonds of fellowship. "A people with whom I have no tie but the common bond of mankind." (Burke) 4. Moral or political duty or obligation. "I love your majesty According to my bond, nor more nor less." (Shak) 5. A writing under seal, by which a person binds himself, his heirs, executors, and administrators, to pay a certain sum on or before a future day appointed. This is a single bond. But usually a condition is added, that, if the obligor shall do a certain act, appear at a certain place, conform to certain rules, faithfully perform certain duties, or pay a certain sum of money, on or before a time specified, the obligation shall be void; otherwise it shall remain in full force. If the condition is not performed, the bond becomes forfeited, and the obligor and his heirs are liable to the payment of the whole sum. 6. An instrument (of the nature of the ordinary legal bond) made by a government or a corporation for purpose of borrowing money; as, a government, city, or railway bond. 7. The state of goods placed in a bonded warehouse till the duties are paid; as, merchandise in bond. 8. The union or tie of the several stones or bricks forming a wall. The bricks may be arranged for this purpose in several different ways, as in English or block bond (Fig. 1), where one course consists of bricks with their ends toward the face of the wall, called headers, and the next course of bricks with their lengths parallel to the face of the wall, called stretchers; Flemish bond (Fig.2), where each course consists of headers and stretchers alternately, so laid as always to break joints; Cross bond, which differs from the English by the change of the second stretcher line so that its joints come in the middle of the first, and the same position of stretchers comes back every fifth line; Combined cross and English bond, where the inner part of the wall is laid in the one method, the outer in the other. 9. <chemistry> A unit of chemical attraction; as, oxygen has two bonds of affinity. It is often represented in graphic formulae by a short line or dash. See Diagram of Benzene nucleus, and Valence. Arbitration bond. See Arbitration. Bond crediter, a debt contracted under the obligation of a bond. Bond (or lap) of a slate, the distance between the top of one slate and the bottom or drip of the second slate above, i. E, the space which is covered with three thicknesses; also, the distance between the nail of the under slate and the lower edge of the upper slate. Bond timber, timber worked into a wall to tie or strengthen it longitudinally. Synonym: Chains, fetters, captivity, imprisonment. Origin: The same word as band. Cf. Band, Bend. Source: Websters Dictionary (01 Mar 1998) |
| bond angle | This refers to the angle formed between two nuclei which are linked together. (09 Oct 1997) |
| bond dissociation energy | This is the energy needed to break the bonds between two linked atoms. (09 Oct 1997) |
| bond energy | The energy needed to break a molecular bond. (09 Oct 1997) |
| bond length | This is the distance between the nuclei of two atoms which have formed bonds with each other. (09 Oct 1997) |