. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 1. Schematic drawings illustrating the mechanical (physical) basis for the generation of gravity- dependent orientation torque. Gravity (FG), buoyancy (FB), and hvdrodynamic force (FH) are balanced in sinking microorganisms; these forces act at the center of mass (G), the centroid (B). and the reaction center of hydrodynamic stress (//), respectively, (a) Three forces act at the same point in the body of prolate spheroid with uniform density, (b) The center of mass is deviated to the rear end of the body of prolate sp
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 1. Schematic drawings illustrating the mechanical (physical) basis for the generation of gravity- dependent orientation torque. Gravity (FG), buoyancy (FB), and hvdrodynamic force (FH) are balanced in sinking microorganisms; these forces act at the center of mass (G), the centroid (B). and the reaction center of hydrodynamic stress (//), respectively, (a) Three forces act at the same point in the body of prolate spheroid with uniform density, (b) The center of mass is deviated to the rear end of the body of prolate spheroid, which generates the torque in proportion to Fa and the sine of the orientation angle to the gravity vector (W). (c) The reaction center of hydrodynamic stress is deviated to the front end of the body with fore-aft asymmetry but with uniform density, which generates the torque in proportion to the vector sum of FCl and FH and the sine of the orientation angle. the first power of rotational velocity (dQIdt). In such cases equations of rotational motion are given by -flTj~ = TvorTK, (7) where R is the coefficient of resistance for rotational motion and T) is the viscosity of the external fluid. From these equations the rotational velocity of each model is given as a common form of dO -=3sin0. (8) where the proportional factor is the instantaneous rate at 0 = 90 degrees, and given by (9) (10) Rj] V(p,-p)gLH Rr, for the gravity-buoyancy and drag-gravity models, respec- tively. Equations 9 and 10 indicate that /3r is insensitive to changes in the density of the external medium (p), whereas f3K reverses the sign as p exceeds the density of organisms (p,-). This means that the two models can be distinguished by increasing p greater than p,. When im- mobilized organisms are immersed in the hyper-density medium (p > p,), they would orient upwards during floating upwards if they obeyed the gravity-buoyancy model, whereas they would orient downwards if they obeyed the drag-gravi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
