. Biophysique élémentaires : les thèmes choisis. La biophysique. INTRODUCTION 69. o-S • - a - rt £ £.5. 50  % de l'efficacité, fig. 31. Une représentation de la puissance produite en fonction de l'effi- cacité de l'aide de la force appliquée. L'efficacité de la production d'électricité est égal à 50  % lorsque la puissance fournie est à sa valeur maximale. (À partir de Odum et Pinkerton, American Scientist, 43, 331, 1955 ; avec la permission de l'auteur et le scientifique américain, Princeton, N. J.) résistance. Vous verrez que sa main est rapidement déplacée, mais que vous exercent très peu de force. Deuxièmement, demandez-lui de vous proposer ses re- sist maximale

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. Elementary biophysics: selected topics. Biophysics. INTRODUCTION 69 o.-S • - a — £ rt £.5. 50 Efficiency, % Fig. 31. A representation of the power produced as a function of the effi- ciency of using the force being applied. The efficiency of power production is equal to 50% when the power delivered is at its maximum value. (From Odum and Pinkerton, American Scientist, 43, 331, 1955; courtesy the authors and American Scientist, Princeton, N. J.) resistance. You will see that his hand is rapidly displaced, but that you are exerting very little force. Second, have him offer his maximal re- sistance. You will see that his hand is displaced at a minimal rate, but that you are now exerting your own maximum force. One interesting point seems worth an appreciable digression here. This concerns the design of biological structure from the point of view of energy expenditure. Are biological systems designed to give maximum efficiency (least energy loss) or maximum power deliverable? Clearly, we could conceive that some systems producing energy could be designed for one purpose and some for the other, and perhaps some for other purposes, too. What differences are involved in making this decision? In an interesting paper on this topic, Odum and Pinkerton point out that the work done depends on the forces and rates. When the rates of displacement are very small, there is maximum force exerted. The power delivered is the product of these two factors so that, since v is very small, the power delivered is small. On the other hand, when the force is very small, the value of v is large, but the product is again small. It is then plausible, and they actually prove, that at intermediate forces and displacement rates, the power delivered is greater than at the two extreme values we have mentioned. This is sketched in Fig. 31. In the cases they discuss, Odum and Pinkerton were able to deduce the exact form of the curve. There is an optimal force to be expected for maximum power de

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