| 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) |
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| 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) |
| soil value | The relative lightness or intensity of colour, approximately a function of the square root of the total amount of light, one of the three variables of colour. (09 Oct 1997) |
| net heating value | The potential energy available in the fuel as received, taking into account the energy loss in evapourating and superheating the water in the sample. Expressed as NVH = (HHV x (1- MC / 100)) - (LH(2)O x MC / 100) (05 Dec 1998) |
| net present value | The sum of the costs and benefits of a project or activity. Future benefits and costs are discounted to account for interest costs. (05 Dec 1998) |
| nutritive value | An indication of the contribution of a food to the nutrient content of the diet. This value depends on the quantity of a food which is digested and absorbed and the amounts of the essential nutrients (protein, fat, carbohydrate, minerals, vitamins) which it contains. This value can be affected by soil and growing conditions, handling and storage, and processing. (12 Dec 1998) |
| S value | Svedberg Unit. See: sedimentation coefficient. (18 Nov 1997) |
| iodine value | An indication of the quantity of unsaturated fatty acids present in a fat; it represents the number of grams of iodine absorbed by each 100 g of fat. See: hydrogen number. Synonym: iodine value. (05 Mar 2000) |