| secondary constriction | A subsidiary narrowing of the chromosome associated in some cases with satellites. (05 Mar 2000) |
|---|---|
| secondary degeneration | <medicine> A form of degeneration occurring in nerve fibres as a result of their division; so called from Dr. Waller, who published an account of it in 1850. Source: Websters Dictionary (01 Mar 1998) |
| secondary dementia | Chronic dementia following and due to a psychosis or some other underlying disease process. Senile dementia, dementia of Alzheimer's disease developing after age 65. Toxic dementia, dementia caused by an exogenous agent. (05 Mar 2000) |
| secondary dentin | Dentin formed by normal pulp function after root end formation is complete. (05 Mar 2000) |
| secondary dentition | One of the 32 teeth belonging to the second or permanent dentition; eruption of the permanent teeth begins from the fifth to the seventh year, and is not completed until the seventeenth to the twenty-third year, when the last of the wisdom teeth appears. Synonym: dens permanens, dens succedaneus, second tooth, secondary dentition, succedaneous dentition, succedaneous tooth. (05 Mar 2000) |
| secondary deviation | Ocular deviation seen in paralysis of an ocular muscle when the paralysed eye is used for fixation. (05 Mar 2000) |
| secondary dextrocardia | Dextroposition of the heart by some disease of the lungs, pleura, or diaphragm. Synonym: type 4 dextrocardia. (05 Mar 2000) |
| secondary digestion | The change in the chyle effected by the action of the cells of the body, whereby the final products of digestion are assimilated in the process of metabolism. (05 Mar 2000) |
| secondary disease | A disease that follows and results from an earlier disease, injury, or event, a wasting disorder that follows successful transplantation of bone marrow into a lethally irradiated host; frequently severe and usually associated with fever, anorexia, diarrhoea, dermatitis, and desquamation. See: graft versus host disease. (05 Mar 2000) |
| secondary drives | Those drives not directly related to biological needs; a secondary drive can be learned as an offshoot of a primary drive, in which case it is often referred to as a motive. Synonym: acquired drives. (05 Mar 2000) |
| secondary drowning | Pulmonary oedema and resulting asphyxia, resulting from hypoxia and increased permeability of pulmonary capillaries occurring in a patient who has been immersed in and aspirated some water. (05 Mar 2000) |
| secondary dysmenorrhoea | Dysmenorrhoea due to inflammation, infection, tumour, or anatomical factors. (05 Mar 2000) |
| secondary egg membrane | See: egg membrane. (05 Mar 2000) |
| secondary electron | <microscopy> Produced by an incident electron passing near an atom in the specimen, near enough to impart some of its energy to a lower energy electron (usually in the K-shell). This causes a slight energy loss and path change in the incident electron and the ionisation of the electron in the specimen atom. This ionised electron then leaves the atom with a very small kinetic energy (5eV) and is then termed a secondary electron. Each incident electron can produce several secondary electrons. (05 Aug 1998) |
| 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) |