| spin-spin 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 |
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| 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) |
| radiographic parallel line shadows | The images of bronchial walls, usually thickened; colloq., British. Synonym: radiographic parallel line shadows. (05 Mar 2000) |
| parallel | 1. Pertaining to straight lines or planes that do not intersect. 2. <physics> Pertaining to electric circuit components connected in parallel so that the current flow divides, each branch passing through one component and rejoins, applied by extension to any similar parallel circuit, for example the systemic circulation to the various organs. (18 Nov 1997) |
| parallel attachment | A frictional or mechanically retained unit used in fixed or removable prosthodontics, consisting of closely fitting male and female parts, an attachment that may be rigid in function or may incorporate a movable stress control unit to reduce the torque on the abutment. Synonym: frictional attachment, internal attachment, key attachment, keyway attachment, parallel attachment, slotted attachment. (05 Mar 2000) |
| Parallel Electron Energy Loss Spectroscopy | <technique> Electron energy loss spectroscopy analyses the inelastically scattered electrons present in the beam after it has been transmitted through the sample. An electron energy loss spectrum typically consists of a monatomic decreasing background on which are superimposed a number of peaks. Each peak is characteristic of the scattering process that has occurred in the sample. The peaks can be used to obtain information about the chemical composition and electronic structure of the sample. Electron energy loss spectra are acquired typically in a magnetic sector spectrometer located under the camera chamber of the transmission electron microscope. Spatial resolution is typically limited by the minimum probe diameter of the microscope. Electron energy loss spectroscopy tends to be complimentary to EDS in that it can be used to analyse very thin samples of low Z materials. Acronym: PEELS (05 Aug 1998) |