Gravitational stability

The general conditions necessary to ensure gravitational stability at all times during the free diffusion process and at all positions in the diffusing boundary have... 

A protoplanetary nebula containing enough mass to rapidly form a lOM giant-planet core would have been quite close to the limit of gravitational stability beyond 5 AU (Boss,... 

Conditions Synthesis period, h Viscosity, Pa s Solid residual, % Average size of polymer particle, pm Gravitational stability of dispersion, 24 h(T = 45 °C) Monomer odour (acryl- nitrile)... 

The apparatus which Hittorf employed consisted essentially of a glass cylinder with a cathode near the top and an anode near the bottom. The anode was chosen to be of the same metal as in the salt used (e.g.. copper in work with copper sulphate solutions) in order to maintain the chemical nature of the electrolyte. The cathode was of platinum, gold or silver on which the metal ions plated out. The upper catholyte solution therefore became more dilute during electrolysis and the lower anolyte more concentrated, so ensuring gravitational stability. After the passage of a known quantity of electricity (measured with a silver coulometer) the upper half of the cell was slid sideways by means of a glass plate and the catholyte solution was analysed. In the next paper (2.) Hittorf analysed the anolyte solution also and introduced middle sections but unfortunately separated the compartments by means of intestinal membranes. He did make it plain, however, that the results should be calculated with respect to the mass of water in the final solution. 

Met with great skepticism for more than twenty years, Perrin s experiments are no longer in doubt but the subject of gravitational stability of colloids is often treated as a curiosity or an afterthought in today s textbooks. Although the number of publications on gravity effects on sols is small compared to the whole of colloid literature, such studies shine the light on intrinsic properties of these solutions and allow quantitative measurements of fundamental interactions between particles. 

The distance above the catalyst bed in which the flue gas velocity has stabilized is refened to as the transport disengaging height (TDH). At this distance, there is no further gravitation of catalyst. The center-line of the first-stage cyclone inlets should be at TDH or higher otherwise, excessive catalyst entrainment will cause extreme catalyst losses. 

Aerosols are solid or liquid particles, suspended in the liquid state, that have stability to gravitational separation over a period of observation. Slow coagulation by Brownian motion is implied. 

Recently, the size and shape of a liquid droplet at the molten tip of an arc electrode have been studied,12151 and an iterative method for the shape of static drops has been proposed. 216 Shapes, stabilities and oscillations of pendant droplets in an electric field have also been addressed in some investigations. 217 218 The pendant drop process has found applications in determining surface tensions of molten substances. 152 However, the liquid dripping process is not an effective means for those practical applications that necessitate high liquid flow rates and fine droplets (typically 1-300 pm). For such fine droplets, gravitational forces become negligible in the droplet formation mechanism. 

Position C does not correspond to the lowest minimum of the energy following a small displacement, the block will return to the initial position whereas large displacements will move the block to the more stable position A. In A there is an (absolutely) stable equilibrium and in C a metastable equilibrium. For this mechanical system the stability conditions and the trends of spontaneous (natural) processes are related to minima (relative or absolute) of the gravitational potential energy. 

Electrophoretic separations in the purely liquid phase, as used by Tiselius, were complicated by the need to keep stable boundary conditions. Problems arose from convectional and gravitational mixing. In the 1950s various attempts were made to increase the stability and thus the reproducibility of the procedure by using filter paper, or more effec-... 

Note 1 Owing to their size, the partieles of the dispersed phase have a eomparatively small settling velocity and hence exhibit some degree of stability in the earth s gravitational field. 

Figure 4-16 Role of kinetics in determining which of the two stable products to form, compared with stability of a ball on uneven ground, (a) Because the activation energy for forming product 1 is smaller, product 1 will form even though it is less stable than product 2. (b) Stability of a ball on uneven ground. The ball is initially in hole R. It would be gravitationally more stable if it goes to either hole PI or P2. The most stable position would be hole P2. However, if the ball was given an initial push (similar to thermal motion of molecules), it is much more likely that it would end up in hole PI.

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