INDEX migration

The blends, irrespective of the concentration of fluororubber, show surface energy lower than neat rubbers. This is attributed to the migration of silicone mbber to the surface. The presence of silicone rubber on the surface of the blends also contributes to their lower limited oxygen index compared to that of fluoroelastomers. 

A hydrophobidty scale based on the migration index from emulsion electrokinetic chromatography of anionic solutes. Anal. Chem. 1996, 68, 1028-1032. 

For compacted, low-permeability soil liners, the U.S. EPA draft guidance recommends natural soil materials, such as clays and silts. However, soils amended or blended with different additives (e.g., lime, cement, bentonite clays, and borrow clays) may also meet the current selection criteria of low hydraulic conductivity, or permeability, and sufficient thickness to prevent hazardous constituent migration out of the landfill unit. Therefore, U.S. EPA does not exclude compacted soil liners that contain these amendments. Additional factors affecting the design and construction of CCLs include plasticity index (PI), Atterburg limits, grain sizes, clay mineralogy, and attenuation properties. 

Fig. 5. Relationship between fasting intestinal motility [x-axis migrating motor complex (MMC) index] and bacterial colonization of small bowel in 41 patients with late radiation enteropathy (LRE) is shown by two plots. Relationship to Gram-negative bacilli (a) and to total bacterial count (b) in the duodenum is shown. Note that no significant Gram-negative colonization was found in patients with normal MMC (index = 3). The vertical dotted lines show the normal limit for MMC index. Increased bacterial counts due to URT flora were found in some patients with normal MMC (b). Tied observations are indicated as follows n = 1 n = 2 1 n = 3 1 n = 4 + n = 6 For n > 6...

Moving-boundary electrophoretic techniques, originally demonstrated by Tiselius in 1937, employ a U-tube with the sample occupying the lower part of the U and the two limbs being carefully filled with a buffered electrolyte so as to maintain sharp boundaries with the sample. Electrodes are immersed in the electrolyte and direct current passed between them. The rate of migration of the sample in the electric field is measured by observing the movement of the boundary as a function of time. For colourless samples, differences in refractive index may be used to detect the boundary. Such moving-boundary techniques are used mainly in either studies of the physical characteristics of molecules or bulk preparative processes. 

When a combination of CE and HPLC systems would be considered, the most dissimilar from the global set could be selected according to the above approach. For the CE methods, a response should be selected and applied with values in the same order of magnitude as the retention factors of the CSs, e.g., the migration times. Another possibility would be to use the so-called normalized migration indexes (see further Section III.C) for both the CE and the HPLC measurements. ... 

Vassort et al. introduced a normalized migration index (NMI) to allow the direct comparison of HPEC and CE-based methods. For HPLC, this index was calculated with the following equation ... 

For MEEKC, the migration index (MI) scale is quite effective in improving the reproducibility. This was introduced by Muijselaar et al. in MEKC (44) and then modified to extend the range of the migration window of the reference compounds as follows (47) ... 

Figure 3.38. Principle of the photorefractive effect By photoexcitation, charges are generated that have different mobilities, (a) The holographic irradiation intensity proHle. Due to the different diffusion and migration velocity of negative and positive charge carriers, a space-charge modulation is formed, (b) The charge density proHle. The space-charge modulation creates an electric Held that is phase shifted by 7t/2. (c) The electric field profile. The refractive index modulation follows the electric field by electrooptic response, (d) The refractive index profile.

The most useful of the known photorefractives are LiNbC>3 and BaTiC>3. Both are ferroelectric materials. Light absorption, presumably by impurities, creates electron/hole pairs within the material which migrate anisotropically in the internal field of the polar crystal, to be trapped eventually with the creation of new, internal space charge fields which alter the local index of refraction of the material via the Pockels effect. If this mechanism is correct (and it appears established for the materials known to date), then only polar, photoconductive materials will be effective photorefractives. However, if more effective materials are to be discovered, a new mechanism will probably have to be discovered in order to increase the speed, now limited by the mobility of carriers in the materials, and sensitivity of the process. 

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