The definition of a mobilized system and its efficiency are introduced. The existence of an optimal (maximally efficient) system is proved by an application of Young measures and compensated compactness.

The effect of age and body size on the total mechanical work done during walking is studied in children of 3-12 years of age and in adults. The total mechanical work per stride (W tot) is measured as the sum of the external work, W ext (i.e. the work required to move the centre of mass of the body relative to the surroundings), and the internal work, W int (i.e. the work required to move the li...

Molecular motors operate in an environment dominated by viscous friction and thermal fluctuations. The chemical reaction in a motor may produce an active force at the reaction site to directly move the motor forward. Alternatively a molecular motor may generate a unidirectional motion by rectifying thermal fluctuations using free energy barriers established in the chemical reaction. The reactio...

Thirty-eight adults with valvular and/or myocardial disease had heart catheterization with coronary blood flow and myocardial O2 consumption (MVO2) per 100 g measured by the nitrous oxide washout technique. Quantitative biplane angiocardiography was performed to assess left ventricular volume, mass, ejection fraction and work. Left ventricular efficiency was calculated from work, MVO2/100 g and...