Fibers with polar functional

Polyethylene fibers can be functionalized by chromium trioxide and ozone oxidation to generate carboxylic acid groups [148]. Surface properties may be modified by derivatization with a polar carbohydrate or PEG spacer for direct biomolecular solid-phase assays (see Fig. 10). 

PO fibers with a paraffinic hydrocarbon structure contain no reactive or polar functional groups, which would anchor the dyestuff within the polymer to achieve good fastness to light and good resistance to rubbing, laundering, or dry-cleaning. 

Eor semivolatile analytes, polarity with respect to fiber type was critical. The more polar analytes were best extracted by polar fibers such as polyacrylate and CW-DVB. The less polar analytes were extracted by both polar and nonpolar fibers and, in some cases, were extracted better with the polyacrylate fiber. The functional group that increases polarity was also important. Amines were extracted well with the PDMS-DVB fiber, whereas CW-DVB and polyacrylate were better for other polar functional groups. 

Adsorption and Surface Chemical Grafting. As with siHca and many other siHcate minerals, the surface of asbestos fibers exhibit a significant chemical reactivity. In particular, the highly polar surface of chrysotile fibers promotes adsorption (physi- or chemisorption) of various types of organic or inorganic substances (22). Moreover, specific chemical reactions can be performed with the surface functional groups (OH groups from bmcite or exposed siHca). 

The distance of each reflection from the center of the pattern is a function of the fiber-to-film distance, as well as the unit-cell dimensions. Therefore, by measuring the positions of the reflections, it is possible to determine the unit-cell dimensions and, subsequently, index (or assign Miller indices to) all the reflections. Their intensities are measured with a microdensitometer or digitized with a scanner and then processed.8-10 After applying appropriate geometrical corrections for Lorentz and polarization effects, the observed structure amplitudes are computed. This experimental X-ray data set is crucial for the determination and refinement of molecular and packing models, and also for the adjudication of alternatives. 

Equations (20-66) and (20-67) present single-pass formulas relating retentate solute concentration, retentate crossflow, permeate flow, and membrane area. For relevant low-feed-concentration applications, polarization is minimal and the flux is mainly a function of pressure. Spiral or hollow fiber modules with low feed channel and permeate pressure drops are preferred. 

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