| field of view | <microscopy> The extent of the visible image field that can be seen. (05 Aug 1998) |
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| field planes | <microscopy> The set of planes in a microscope adjusted for Kohler illumination that are conjugate with the focused specimen. They include the plane of the specimen, the field diaphragm, the intermediate image plane, and the image on the retina, photographic emulsion, or the faceplate of the video pickup device. (05 Aug 1998) |
| field shaping coils | <radiobiology> Type of poloidal field coils (in a tokamak) which create magnetic fields which shape and control the plasma. Used to constrain horizontal and vertical displacements of the plasma, as well as (in some configurations) produce non-circular plasma cross-sections (poloidal cross-section) and/or create one or more divertor separatrices. (09 Oct 1997) |
| field survey | The planned collection of data among noninstitutionalised persons in the general population. (05 Mar 2000) |
| Field's rapid stain | <technique> A stain to permit rapid positive diagnosis of malaria in endemic areas by using thick films; it employs methylene blue and azure B in a phosphate buffer, with the preparation counterstained by eosin in a phosphate buffer. (05 Mar 2000) |
| field-emission microscope | <instrument, microscopy> Either one of two kinds of point-projection microscopes, both invented by E. W. Muller: (1) The older device (1936) is a specialised cathode-ray tube, employing field-emission of electrons from a negatively charged tip of a very sharp needle in a vacuum, by point-projection of the image onto a positively charged, fluorescent screen. (2) A later device (field-ion-mission microscope, 1950) emits absorbed helium ions from an anode. (05 Aug 1998) |
| field-reversed configuration | <radiobiology> A compact torus produced in a theta pinch and having (in principle) no toroidal field. The potential advantages for a fusion reactor include a simple (linear) machine geometry, an average plasma pressure close to the confining field pressure, and physical separation of formation and burn chambers. The are predicted to be violently unstable to tilting, but this is rarely observed. (09 Oct 1997) |
| field-vole | A species of field mouse (Microtus montebelloi), normal host of Leptospira hebdomadis, the cause of a type of leptospirosis resembling infectious mononucleosis. (05 Mar 2000) |
| fieldfare | <zoology> A small thrush (Turdus pilaris) which breeds in northern Europe and winters in Great Britain. The head, nape, and lower part of the back are ash-coloured; the upper part of the back and wing coverts, chestnut. Synonym: fellfare. Origin: OE. Feldfare, AS. Feldfare; field + faran to travel. Source: Websters Dictionary (01 Mar 1998) |
| Fielding's membrane | 1. <cell biology> Layer of reflective tissue just behind the pigmented retinal epithelium of many vertebrate eyes. May consist either of a layer of guanine crystals or a layer of connective tissue. In bovine eyes reflects a blue green iridescent colour. 2. <plant biology> Layer of cells in the sporangium of a vascular plant that nourishes the developing spores. (18 Nov 1997) |
| Fielding, George | <person> British anatomist, 1801-1871. See: Fielding's membrane. (05 Mar 2000) |
| fields of Forel | Three circumscript, myelin-rich regions of the subthalamus known as H fields (from Haubenfelder); 1) field H1, corresponding to the thalamic fasciculus, a horizontal fibre stratum at the junction of the subthalamus and the overlying thalamus, is composed of pallidothalamic and cerebellothalamic fibres (brachium conjunctivum) and is separated by the zona incerta from the more ventrally placed field H2; 2) field H2, formed by the lenticular fasciculus and arching over the dorsal border of the subthalamic nucleus, is composed largely of pallidothalamic fibres; 3) field H3 or prerubral field, is a large field of intermingling gray and white matter immediately rostral to the red nucleus, uniting fields H1 and H2 around the medial margin of the zona incerta; its gray matter forms the prerubral nucleus. See: lenticular loop. Synonym: campi foreli, tegmental fields of Forel. (05 Mar 2000) |
| microscopic field | The area within which objects are visible with microscope oculars and objectives of various magnifying powers. (05 Mar 2000) |
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| washed field technique | The cutting of cavity preparations in teeth utilizing a constant irrigant which is immediately removed from the mouth by means of a vacuum device. (05 Mar 2000) |
| Cohnheim's field | A polygonal mosaic-like figure formed by a group of myofibrils, as seen in the cross-section of a skeletal muscle fibre examined under the microscope; a shrinkage artifact of fixation. Synonym: Cohnheim's field. (05 Mar 2000) |
| Wernicke's field | The region of the cerebral cortex thought to be essential for understanding and formulating coherent, propositional speech; it encompasses a large region of the parietal and temporal lobes near the lateral sulcus of the left cerebral hemisphere; corresponding approximately to Brodmann's areas 40, 39, and 22. Synonym: sensory speech centre, Wernicke's area, Wernicke's field, Wernicke's region, Wernicke's zone. (05 Mar 2000) |
| wide field ocular | An ocular that gives a larger than usual field of view and a high eyepoint. (05 Mar 2000) |
| condenser, dark field | <microscopy> A condenser forming a hollow cone of light with its apex (or focal point) in the plane of the specimen. When used with an objective having a numerical aperture lower than the minimum numerical aperture of the hollow cone, only light deviated by the specimen enters the objective. Objects are seen as bright images against a dark background. The ordinary bright field condenser of low power, used with a central stop, makes a good dark field condenser. They all form a dark field while illuminating the specimen with a hollow cone of light. The lower limiting aperture of the condenser must be greater than the numerical aperture of the objective with which it is to be used. Thus, no direct light enters the objective, the specimen is seen by reflected or scattered light on a dark background. See: condensers See: special dark field condensers: paraboloid, cardioid and Cassegrainian. (05 Aug 1998) |
| constant field equation | An equation derived to predict membrane potentials in terms of the membrane's permeability to ions and their concentrations on either side. Synonym: constant field equation, Goldman-Hodgkin-Katz equation, GHK equation. (05 Mar 2000) |
| poloidal field | <physics> In toroidal devices, the magnetic field that encircles the plasma axis. (i.e., loops around the torus the short way.) (09 Oct 1997) |
| poloidal field coil | <radiobiology> In toroidal devices (e.g., tokamaks), the sets of windings which are (typically) aligned along the plasma axis and produce poloidal fields. These include ohmic heating, shaping, vertical, equilibrium, and divertor windings. (09 Oct 1997) |
| curvature of field | <microscopy> A property of lens that causes the image of a plane to be focused into a curved surface instead of a plane. The image plane formed by a single lens is naturally curved. While one part of the field will be in good focus, the rest will need refocusing to be sharp. While the eye may partially correct for this, a camera lens will not, and the final image as photographed will not be in perfect focus over the entire image plane. (05 Aug 1998) |
| prerubral field | See: fields of Forel. (05 Mar 2000) |
| pulsed-field gel electrophoresis | Gel electrophoresis in which, after electrophoretic migration has begun, the current is briefly stopped and reapplied in a different orientation; allows for the purification of long DNA molecules. Synonym: pulsed-field gel electrophoresis. (05 Mar 2000) |
| pulse field electrophoresis | <investigation> A method used for high resolution electrophoretic separation of very large (megabase) fragments of DNA. Electric fields 100 |
| pulse-field gel electrophoresis | Gel electrophoresis in which, after electrophoretic migration has begun, the current is briefly stopped and reapplied in a different orientation; allows for the purification of long DNA molecules. Synonym: pulsed-field gel electrophoresis. (05 Mar 2000) |
| nerve field | The regional distribution of nerve terminals. (05 Mar 2000) |