| secondary electron imaging | <microscopy> Production of secondary electrons is very topography related. Due to their low energy, 5eV, only secondaries that are very near the surface (less than 10nm) can exit the sample and be examined. Any changes in topography in the sample that are larger than this sampling depth will change the yield of secondaries due to collection efficiencies. Collection of these electrons is aided by using a collector in conjunction with the secondary electron detector. The collector is a grid or mesh with a +100V potential applied to it which is placed in front of the detector, attracting the negatively charged secondary electrons to it which then pass through the grid-holes and into the detector to be counted. When a Secondary Electrons collide with the solid-state saemiconductor detector an electron-hole pairs are created which are then counted. This quantity is translated into a pixel intensity and displayed on the CRT, forming the image. (05 Aug 1998) |
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| secondary encephalitis | Collective term for post-infectious, post-exanthem, and post-vaccinal encephalitides. (05 Mar 2000) |
| secondary failure | Failure of the function of an organ as a result of antecedent pathology elsewhere, decreasing responsiveness to a drug after an initial satisfactory response, usually occurring several months after initiation of treatment. (05 Mar 2000) |
| secondary fissure of cerebellum | A fissure that separates the uvula of the inferior vermis of the cerebellum from the pyramid. Synonym: fissura secunda cerebelli. (05 Mar 2000) |
| secondary follicle | A follicle in which the oocyte attains its full size and is surrounded by an extracellular glycoprotein layer (zona pellucida) that separates it from a peripheral layer of follicular cells permeated by one or more fluid-filled antra; the theca of the follicle develops into internal and external layers. Synonym: folliculus ovaricus vesiculosus, graafian follicle, secondary follicle. (05 Mar 2000) |
| secondary gain | Interpersonal or social advantages (e.g., assistance, attention, sympathy) gained indirectly from organic illness. Compare: primary gain. (05 Mar 2000) |
| secondary generalised epilepsy | A group of epilepsy syndromes of diverse aetiologies with diffuse or multifocal cerebral involvement. Patients typically have a variety of generalised seizure types, including tonic, atonic, myoclonic, atypical absence, and generalised tonic-clonic seizures. Partial seizures may also occur. One classic syndrome is the Lennox-Gastaut syndrome. Synonym: symptomatic epilepsy. (05 Mar 2000) |
| secondary glaucoma | Glaucoma occurring as a sequel of preexisting ocular disease or injury. (05 Mar 2000) |
| secondary haemorrhage | Haemorrhage at an interval after an injury or an operation. (05 Mar 2000) |
| secondary homonym | <zoology> Each of two or more identical species names, which, at the time of original publication, were proposed in combination with different generic names, but which, through subsequent transference, have come to bear the same combination of generic and specific names. See: homonym. (09 Jan 1998) |
| secondary host | <epidemiology> See vector. (05 Dec 1998) |
| secondary hydrocephalus | An accumulation of fluid in the cranial cavity, due to meningitis or obstruction to the venous flow. (05 Mar 2000) |
| secondary hyperparathyroidism | Hyperparathyroidism that arises as a result of disordered metabolism producing hypocalcaemia, as in chronic uraemia due to renal disease, malabsorption, rickets, or osteomalacia; associated with hyperplasia of the parathyroid glands. (05 Mar 2000) |
| secondary hypertension | Arterial hypertension produced by a known cause, e.g., hyperthyroidism, kidney disease, etc., in contrast to primary hypertension that is of unknown cause. (05 Mar 2000) |
| secondary hyperthyroidism | Hyperthyroidism due to stimulation of the thyroid gland by an excess of thyrotrophin secreted by the pituitary gland. (05 Mar 2000) |