Subject sedimentation coefficient

On the other hand, while the MW dependence of , diffusion, and sedimentation coefficients of these bottlebrushes were quantitatively described by the wormlike chain model, a significant disagreement between that of [q] and the theory was also reported [65-67]. This is an unsolved subject to be studied further. 

A particle will move through a liquid medium when subjected to a centrifugal force. A convenient means of quantifying the rate of movement is to calculate the sedimentation coefficient, s, of a particle by using the following equation ... 

Experimentally, sedimentation or permeation allow the effective frictional coefficient per monomer to be measured. In a sedimentation experiment measuring the drift velocity of monomers subjected to a centrifugal acceleration y, the sedimentation coefficient, defined as sq = Um/y, is determined. Each monomer experiences a forced = m y, where m is the apparent mass of the monomer immersed in the solution using Eq. (D-1), we have... 

Fisher NS, Fowler SW, Boisson F, et al. 1999. Radionuclide bioconcentration factors and sediment partition coefficients in Arctic seas subject to contamination from dumped nuclear wastes. Environ Sci Technol33 1979-1982. 

Diffusion coefficients can also be obtained from sedimentation velocity experiments, but the precision is quite low and subject to some ques-don. Quasi-elastic light scattering is a much more useful technique to obtain diffusion coefficients (see below). 

Transport and Transformation of Chemicals A Perspective. - Transport Processes in Air. - Solubility, Partition Coefficients, Volatility, and Evaporation Rates. - Adsorption Processes in Soil. - Sedimentation Processes in the Sea. - Chemical and Photo Oxidatioa - Atmospheric Photochemistry. -Photochemistry at Surfaces and Interphases. -Microbial Metabolism. - Plant Uptake, Transport and Metabolism. - Metabolism and Distribution by Aquatic Animals. - Laboratory Microecosystems. - Reaction Types in the Environment. -Subject Index. 

In order to apply Eqs. (6.3) or (6.4) to the sediment zone subject to bioturbation or physical disturbance, a number of researchers have suggested that the effects of biogenic or physical reworking on pore-water distributions be lumped into an effective or apparent transport coefficient (Hammond eta/., 1975 Vanderborght eta/., 1977 Goldhaber eta/., 1977). D is arbitrarily adjusted until the observed pore-water profile is fit to the appropriate solution, say, to Eq. (6.4). This approach has been found to work reasonably well in sediments where biogenic or physical disturbance is limited to the upper few centimeters (Vanderborght et al., 1977 Aller,... 

In the case of significant accidental exposures, it will often be necessary to use parameter values in the calculation of tissue or organ equivalent doses and effective dose that ate specific to the conditions of exposure and to the individual. Similarly, in routine situations it may be necessary to take account of the particular circumstances of exposure rather than using default parameters. The new model for the respiratory tract [34] adopts an AMAD of 5 pm as a default particle size when no specific information is available. Regional deposition of airborne particles is subject to the mechanisms of sedimentation, impaction and diffusion. Deposition throughout the respiratory system and hence inhalation dose coefficients depend upon aerosol parameters, such as the AMAD. Similarly, ingestion dose coefficients depend upon the choice of an appropriate/j value. 

A brief review of the limited number of in situ measurements is then presented. This is followed by a review of the available correlations proposed for estimating these kinds of MTCs in Section 12.4. Section 12.5 is concerned with the subject of classical molecular diffusion in porous media at steady state. The presentation includes a brief description of the upper sediment layers, measurement techniques, laboratory measurement data of effective diffusion coefficients, and models for prediction and extrapolation. A guide appears in Section 12.6 to steer users to suggested procedures for estimating these two types of MTCs. The chapter ends with some example problems and their solutions in Section 12.7. 

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