Fiber concentration

First, in composites with high fiber concentrations, there is little matrix in the system that is not near a fiber surface. Inasmuch as polymerization processes are influenced by the diffusion of free radicals from initiators and from reactive sites, and because free radicals can be deactivated when they are intercepted at solid boundaries, the high interfacial area of a prepolymerized composite represents a radically different environment from a conventional bulk polymerization reactor, where solid boundaries are few and very distant from the regions in which most of the polymerization takes place. The polymer molecular weight distribution and cross-link density produced under such diffusion-controlled conditions will differ appreciably from those in bulk polymerizations. 

Determination of mechanical properties like tensile strength, tear strength, modulus, and elongation at break are the most common methods adopted to determine the cured properties of short fiber-mbber composites. Murty and De [133] discussed the technical properties of short fiber-mbber composites whereas Abrate [8] reviewed the mechanism of short fiber reinforcement of mbber. Fiber concentration in the matrix plays an important role in the optimization of the required... 

Mow e, G., B. Gylseth, F. Hartveit, and V. Skaug (1985). Fiber concentration in lung tissue of patients with malignant mesothelioma. A case-control study. Cancer 56 1089—1093. 

Wisker E, R. Nagel, T. K. Tanudjaja, and W. Feldheim. Calcium, magnesium, zinc, and iron balances in young women effects of a low-phytate barley-fiber concentrate. Am J Clin Nutr 1991 54(3) 553-559. 

Table 5 reports the chemical composition of five components from corn. The level of starch in grain was not as high as expected (50-60% is typical), perhaps because of the crop s late maturity. Fiber concentrations, either ADF or NDF, are good indicators to estimate the proportion of grain and stover in a whole-plant mix. 

X widefield or Huygenian eyepieces are used, one of which must be a focusing eye piece to hold the reticle. High eyepoint widefield eyepieces are more comfortable, especially if glasses are worn. The reticle defines the field to be counted. A Patterson Globe and Circle reticle defines a field which is twice the area defined by a Porton reticle. The larger field accumulates counts faster and is sometimes preferred for this reason since this may save time or improve statistics when the fiber concentration is low. 

Figure 4. Absorbance of ninhydrin solution obtained from fabric 605 (Lots 1 and 2) after heating at 150 °C as a function of fiber concentration. Key open symbols, Lot 1 filled symbols, Lot 2.

There is some evidence from animal studies that asbestos-induced lung cancer stems from regions in the lung with advanced fibrosis (asbestosis) however, lung cancer with chrysotile was also produced at fiber concentrations that did not lead to detectable fibrosis. 

Developmental Toxicity. Studies on potential developmental effects in humans exposed to asbestos are restricted to reports from one group of investigators reporting that asbestos fibers were detected in fetal and placental tissues from stillborn infants more frequently and at higher concentrations than in placental tissue from livebom infants (Haque et al. 1991, 1992, 1996, 1998). Understanding of the toxicological significance of these observations awaits confirmation and explanation from further research in other laboratories. It is presently unclear if the noted differences in fiber concentrations between stillborn and livebom tissue are due to differences in maternal exposures, differences in fetal or placental factors unrelated to asbestos exposure, or specimen contamination. 

---