Transient turbidity

Transient turbidity is an optical technique for measuring the size of magnetic particles [63,64], It does this by aligning particles in an electric field, removing the field, and following their return to random orientation induced by Brownian motion. Their relaxation is measured by turbidity and this can be related to particle size distribution if assumptions are made 

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The simplest technique used to grow protein crystals is the batch method in which the protein is mixed with salts or other precipitants to achieve supersaturation (Fig. 2), and the vessel is sealed and set aside until crystals appear. Frequently, the supersaturation point required to induce nucleation is empirically determined by observing the onset of transient turbidity as powdered salt is progressively added to the solution. Crystals of hen egg white lysozyme used for most systematic studies of protein crystallization are grown by batch methods (Blundell and Johnson, 1976). Mouse pancreatic ribonuclease (Perry and Palmer, 1988) and the biotin operon repressor (Brennan et al., 1989) represent recent examples of use of the batch method. 

To avoid undesirable appearance of a transient turbidity in the micellar solution, the acidic solution was not injected directly into the neutral or basic reverse micellar solution. 

Applications of optical methods to study dilute colloidal dispersions subject to flow were pioneered by Mason and coworkers. These authors used simple turbidity measurements to follow the orientation dynamics of ellipsoidal particles during transient shear flow experiments [175,176], In addition, the superposition of shear and electric fields were studied. The goal of this work was to verify the predictions of theories predicting the orientation distributions of prolate and oblate particles, such as that discussed in section 7.2.I.2. This simple technique clearly demonstrated the phenomena of particle rotations within Jeffery orbits, as well as the effects of Brownian motion and particle size distributions. The method employed a parallel plate flow cell with the light sent down the velocity gradient axis. 

Abril, G., Riou, S.A., Etcheber, H., Frankigoulle, M., deWitt, R., and Middelburg, J.J. (2000) Transient, tidal time-scale, nitrogen transformations in an estuarine turbidity maximum-fluid mud system (The Gironde, south-west France). Estuar. Coastal Shelf Sci. 50, 703-715. 

Transient approach to charge equilibrium, 207-208 Transmittance, 265 Tribo electrification, 183-184 Tube deposition, 152-160 Turbidity coefficient, 267-269, 275 Turbulence ... 

For the lowest [OH ]o values, the gel reaches a collapsed stationary state with a turbid core and a thin transparent shell. Snapshots taken during the transient propagation of the collapsed state into the swollen state are shown in Figure 5. The length of the gel cylinder in the collapsed state is typically 40% of the maximal length in the swollen state. When the gel is collapsed, a bubble structure is observed as in Figure 5 (bottom). 

What we have attempted to do here is to present rheological tests for identifying the development and relaxation of orientation and structure in liquid crystalline polymers. Because these fluids are typically quite turbid, it is difficult to use rheo-optical techniques. The interpretation of the rheological tests must then come partly from studies on quenched solid specimens. In summary, it is believed that a detailed set of rheological tests based on the transient response of LCP can be used to evaluate various liquid crystalline polymers and identify processing conditions which will lead to the optimum physical properties. 

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