Port migration

Hydrocarbon sensors (qv) placed directiy below the tank bottoms can be effective. However, old contamination or contamination from other tanks or piping can yield misleading results. In addition, the low permeabUity of some areas in the soil can prevent the migration of vapors to the sensing ports under the tank bottom. 

Angel, M.V., Vertical migration in the oceanic realm possible causes and probable effects, in Migration Mechanisms and Adaptive Significance, Rankin, M.A., Ed., Port Aransas, Marine Science Institute (Contributions in Marine Science Suppl. to vol. 27), 1986, 45. 

It would be interesting if in a solid metal both the electro-self-trans-port and the electro-isotope-transport could be measured. Lodding has tried to do this by subjecting In at 137°C. to a direct current of 5000 amps./cm. for about eight months. He preliminarily reported a self-transport and a transport of the light isotope towards the cathode (45) meanwhile in more elaborate measurements he found the reverse direction for the self-transport in solid indium (46). It remains a question in which direction the isotope migration in solid indium goes, because the isotope effect reported in Reference 45 was at the limit of measurability. 

Special proteins, called apoLipoproteins, are required for handling and traruv port of lipid droplets. These proteins are synthesized on the ER and enter the lumen of the ER, where they are assembled into large macromolecular structures. The relevant proteins include apolipoprotein A apo A) and apo lipoprotein B (apo B), Apo A and apo B combine with lipid droplets to form structures called chylomicrons, microscopic particles with large cores of lipid coated with a thin shell of protein. The chylomicrons are transferred to secretory vesicles, which migrate through the cytoplasm to the basal membrane of the cell. Here the vesicles fuse with the membrane, resulhng in the expulsion of chylomicrons from the cell. (If the vesicles fused with the apical membrane of the enterocyte, the effect would be a futile transfer of the dietary lipids back to the lumen of the small intestine.)... 

In the first case (Fig. 5.19a) the recycle pump is at a fixed position between two columns. Since all columns are moving upstream according to the SMB principle the recycle pump performs the same migration. This means that the flow rate of this pump has to be adjusted depending on the section it is located at present. This design results in a locally increased dead volume because of the recycle line and the pump itself. Such an unequal distribution of the dead volume can be compensated by asynchronous shifting of the external ports, as introduced by Flotier and Nicoud (1995). 

The classic thin-film CFE device depicted in Figure 1 consists of a thin, broad chamber through which a laminar curtain of buffered fluid flows axially. Feedstock is continuously injected into this flow near the chamber entrance and an electric field imposed across the curtain causes charged species to migrate laterally as they pass through the chamber. The solutes form discrete bands according to their electrophoretic mobilities and elute at the bottom of the chamber where the Individual bands are collected through a multiplicity of ports. 

In the RCFE effluent 1s continuously reinjected into the chamber via recycle streams as indicated in Figure 2. Each recycle stream reinjection port is offset from its corresponding elution port by a specified lateral distance, S, so that upon recycle the effluent is shifted back against the solute s electrophoretic migration. When the shift is small solute migrates in the positive z direction but if the shift is increased sufficiently... 

Figure 8. Schematic of RCFE with regenerators. The shift in the additional recycle sections is chosen to reverse the solute s direction of migration, constraining it to exit the chamber through the elution ports between the recycle section and the regenerators. Products are recovered at or near their feed concentration.

Shine 1. (2000). The use of confined aquatic disposal (CAD) ceUs to manage contaminated sediments in ports and harbors Chemical migration. Conference on Dredged Material Management Options and Environmental Considerations, December 3-6, MIT, Cambridge, MA, USA. 

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