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A polytropic process is a thermodynamic process that obeys the relation: = where p is the pressure , V is volume , n is the polytropic index , and C is a constant. The polytropic process equation describes expansion and compression processes which include heat transfer.
It is the equation which is behind the 2005 Dietary Guidelines for Americans and the new food pyramid, MyPyramid. The Institute of Medicine equation uses a different approach to most others. The equation doesn't measure basal metabolic rate, but uses experiments based on doubly labelled water.
Neutron stars are well modeled by polytropes with index between n = 0.5 and n = 1. A polytrope with index n = 1.5 is a good model for fully convective star cores [5] [6] (like those of red giants), brown dwarfs, giant gaseous planets (like Jupiter). With this index, the polytropic exponent is 5/3, which is the heat capacity ratio (γ) for ...
A food pyramid's tip is the smallest part, so the fats and sweets in the top of the Food Pyramid should comprise the smallest percentage of the diet. The foods at the top of the food pyramid should be eaten sparingly because they provide calories, but not much in the way of nutrition.
A food pyramid and a corresponding food web, demonstrating some of the simpler patterns in a food web A graphic representation of energy transfer between trophic layers in an ecosystem Energy flow is the flow of energy through living things within an ecosystem . [ 1 ]
Pages for logged out editors learn more. Contributions; Talk; Polytropic index
KF developed a food pyramid because it could depict basic foods as its base, and introduced the guide to the public in 1974 in their magazine, Vi. At the base were bread, cereals, potatoes, milk, cheese and margarine; above it was a large section of supplemental vegetables and fruit ; and at the top was an apex of supplemental meat, fish and eggs.
The particular choice of a polytropic gas as given above makes the mathematical statement of the problem particularly succinct and leads to the Lane–Emden equation. The equation is a useful approximation for self-gravitating spheres of plasma such as stars, but typically it is a rather limiting assumption.