Gravitational flow through system

Figure 2.6. A top view of a gravitational flow-through system used in the study of how chemical cues from predators affect larval behavior. Tanks 3 and 4 hold either a predator (treatment) or are empty (control). In panel A, tank 5 is the experimental arena and larvae are given a simultaneous choice between predator-scented and control water. In panel B, Tanks 5 and 6 are separate experimental arenas for treatment and control stimuli (a nochoice test). The figure was redrawn and modified from one in Petranka et al. (1987).

Figure 6.3. Gravitational flow-through system used to test responses of larval amphibians to chemical stimuli. Water contained in the upper-most tubs flows through plastic tubing to the lowermost tubs. In system A, water from tubs 3 and 4 flows along either side of the solid partition of tub 5. By placing a predator in either tub 3 or 4, a chemical gradient is established in the experimental chamber of tub 5. In this system, the behavioral responses typically quantified include avoidance of the area where the chemical stimuli enters the test chamber and overall activity level of the test animals. In system B, a chemical gradient is not established in the test tub. Instead, the behavioral responses typically quantified include shelter use and overall activity levels. Redrawn from Petranka et al. (1987).

Gravitational forces may have a profound influence on blood flow through the circulatory system. As a result, VR and CO may be affected. Imagine that the circulatory system is a column of blood that extends from the heart to the feet. As in any column of fluid, the pressure at the surface is equal to zero. Due to the weight of the fluid, the pressure increases incrementally below the surface. This pressure is referred to as the hydrostatic pressure. 

A centrifugal pump is used to pump a liquid in steady turbulent flow through a smooth pipe from one tank to another. Develop an expression for the system total head A/t in terms of the static heads on the discharge and suction sides zd and zs respectively, the gas pressures above the tanks on the discharge and suction sides Pd and Ps respectively, the liquid density p, the liquid dynamic viscosity p, the gravitational acceleration g, the total equivalent lengths on... 

The classification into different size fractions can be realised by gravitation (sedimentation FFF), by centrifugal fields (centrifugation FFF), by thermophoresis in temperature gradients (thermal FFF), by electric fields (electrical FFF), or by hydrodynamic fields, i.e. crossflow through the wall(s) (flow FFF). Even though the main fields of application are coUoidal systems, one can also employ FFF for the classification of micrometre particles (x > 1 pm). In that case, diffusion can be usually neglected, yet hydrodynamic lift forces and steric effects counteract the external field and cause a reversal of the size dependency. 

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