| electromagnetic coupling | <physics> A means of extracting energy from a magnetically confined plasma, where the plasma expands and pushes on the confining magnetic field, causing electrical energy to be generated in the external field-generating circuits. (09 Oct 1997) |
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| energy coupling | <chemistry> The tranfer of energy produced in one reaction to another. (09 Oct 1997) |
| excitation contraction coupling | <physiology> Name given to the chain of processes coupling excitation of a muscle by the arrival of a nervous impulse at the motor end plate to the contraction of the filaments of the sarcomere. The crucial link is the release of calcium from the sarcoplasmic reticulum and the analogy is often drawn between this and stimulus secretion coupling, that also involves calcium release into the cytoplasm. (18 Nov 1997) |
| fixed coupling | Where several premature beats are seen, the interval between each of them and the preceding normal beat is constant. Synonym: constant coupling. Variable coupling, where several extrasystoles are seen, the interval between each of them and the preceding sinus beat varies. (05 Mar 2000) |
| spin | 1. To practice spinning; to work at drawing and twisting threads; to make yarn or thread from fibre; as, the woman knows how to spin; a machine or jenny spins with great exactness. "They neither know to spin, nor care to toll." (Prior) 2. To move round rapidly; to whirl; to revolve, as a top or a spindle, about its axis. "Round about him spun the landscape, Sky and forest reeled together." (Longfellow) "With a whirligig of jubilant mosquitoes spinning about each head." (G. W. Cable) 3. To stream or issue in a thread or a small current or jet; as, blood spinsfrom a vein. 4. To move swifty; as, to spin along the road in a carriage, on a bicycle, etc. 1. To draw out, and twist into threads, either by the hand or machinery; as, to spin wool, cotton, or flax; to spin goat's hair; to produce by drawing out and twisting a fibrous material. "All the yarn she [Penelope] spun in Ulysses' absence did but fill Ithaca full of moths." (Shak) 2. To draw out tediously; to form by a slow process, or by degrees; to extend to a great length; with out; as, to spin out large volumes on a subject. "Do you mean that story is tediously spun out?" (Sheridan) 3. To protract; to spend by delays; as, to spin out the day in idleness. "By one delay after another they spin out their whole lives." (L'Estrange) 4. To cause to turn round rapidly; to whirl; to twirl; as, to spin a top. 5. To form (a web, a cocoon, silk, or the like) from threads produced by the extrusion of a viscid, transparent liquid, which hardens on coming into contact with the air; said of the spider, the silkworm, etc. 6. <mechanics> To shape, as malleable sheet metal, into a hollow form, by bending or buckling it by pressing against it with a smooth hand tool or roller while the metal revolves, as in a lathe. To spin a yarn, to twist it into ropes for convenient carriage on an expedition. To spin street yarn, to gad about gossiping. Origin: AS. Spinnan; akin to D. & G. Spinnen, Icel. & Sw. Spinna, Dan. Spinde, Goth. Spinnan, and probably to E. Span. Cf. Span, Spider. 1. The act of spinning; as, the spin of a top; a spin a bicycle. 2. <physics> Velocity of rotation about some specified axis. Source: Websters Dictionary (01 Mar 1998) |
| spin density | The number of nuclear dipoles per unit volume. (05 Mar 2000) |
| spin echo | A commonly used technique to recover T2 relaxation signals in magnetic resonance imaging, by using a 180 |
| spin labelling | <chemistry, technique> The technique of introducing a grouping with an unpaired electron to act as an electron spin resonance (ESR) reporter species. This is almost invariably a nitroxide compound (N O) in which the nitrogen forms part of a sterically hindered ring. (18 Nov 1997) |
| spin labels | Molecules which contain an atom or a group of atoms exhibiting an unpaired electron spin that can be detected by electron spin resonance spectroscopy and can be bonded to another molecule. (12 Dec 1998) |
| spin-lattice relaxation | In nuclear magnetic resonance, the return of the magnetic dipoles of the hydrogen nuclei (magnetization vector) to equilibrium parallel to the magnetic field, after they have been flipped 90 |
| spin-polarized fusion | <radiobiology> A method to enhance nuclear fusion reaction rates in some fusion fuels by polarizing the nuclear spins. (09 Oct 1997) |
| spin trapping | A technique for detecting short-lived reactive free radicals in biological systems by providing a nitrone or nitrose compound for an addition reaction to occur which produces an electron spin resonance spectroscopy-detectable aminoxyl radical. In spin trapping, the compound trapping the radical is called the spin trap and the addition product of the radical is identified as the spin adduct. (free rad res comm 1990;9(3-6):163) (12 Dec 1998) |
| electron spin resonance | <physics> A spectrometric method, based on measurement of electron spins and magnetic moments, for detecting and estimating free radicals in reactions and in biological systems. Synonym: electron paramagnetic resonance. (05 Mar 2000) |
| electron spin resonance spectroscopy | <radiology> A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. electron nuclear double resonance (endor) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications. (12 Dec 1998) |
| acid dissociation constant | <chemistry> This is the equilibrium constant for the breaking apart of a weak acid into its hydrogen and conjugate base in a water solution. (09 Oct 1997) |