| gray level also gray value | <microscopy> The brightness of pixels in a digitised video image, commonly expressed in integers ranging from 0 (black) to 255 (white) for an 8-bit digital signal. (05 Aug 1998) |
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| gross heating value | (GHV) The maximum potential energy in the fuel as received. It reflects the displacement of fibre by water present in the fuel. Expressed as: GHV = HHV (1 - MC / 100) (05 Dec 1998) |
| phenotypic value | In quantitative genetics, the metrical quantity of some trait associated with a particular phenotype. (05 Mar 2000) |
| Wilder's law of initial value | The direction of response of a body function to any agent depends to a large degree on the initial level of that function. Synonym: law of initial value. (05 Mar 2000) |
| CT value | <molecular biology> Concentration of DNA molecules (in moles) multiplied by time. The value is used to plot the renaturing (complementary single strands of DNA spontaneously forming into a double-stranded molecule) of DNA after it has been denatured (DNA molecule which has been broken into two individual single strands). (26 Mar 1998) |
| C value | <molecular biology> A measure of the amount of DNA in the haploid genome of an organism, which can be by mass or by molecular weight. (13 Nov 1997) |
| C value paradox | <molecular biology> Comparison of the amount of DNA present in the haploid genome of different organisms (the C value) reveals two problems: the value can differ widely between two closely related species and there seems to be far more DNA in higher organisms than could possibly be required to code for the modest increase in complexity. (21 May 1997) |
| half-value layer | <radiobiology> The thickness of a specified material (usually a specific absorber), which attenuates a beam of radiation so that the exposure rate or absorbed dose rate at a specified point is reduced by half. (20 Sep 2002) |
| predictive value | An expresion of the likelihood that a given test result correlates with the presence or absence of disease. A positive predictive value is the ratio of patients with the disease who test positive to the entire population of individuals with a positive test result; a negative predictive value is the ratio of patients without the disease who test negative to the entire population of individuals with a negative test. (05 Mar 2000) |
| predictive value of tests | In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test. (12 Dec 1998) |
| present value | The worth of future receipts or costs expressed in current value. To obtain present value, an interest rate is used to discount future receipts or costs. (05 Dec 1998) |
| heating value | The maximum amount of energy that is available from burning a substance. (05 Dec 1998) |
| Hehner value | The weight or percentage of the nonvolatile fatty acids yielded by 5 g of a saponified fat or oil. Synonym: Hehner value. (05 Mar 2000) |
| higher heating value | (HHV) The maximum potential energy in dry fuel. For wood, the range is 7,600 to 9,600 Btu/lb. (05 Dec 1998) |
| homing value | In a cybernetic system such as homeostasis, that value of a trait of interest that the restorative forces are directed towards maintaining. (05 Mar 2000) |