Mineral fibers growth

The composition range of mineral fibers is circumscribed by the natural associations of elements and compounds and fortuitous mechanisms of growth. The existence of so many different species is testimony to the relative ease... 

Among sheep with dietary insufficiencies, the minerals copper and zinc, when supplemented to the diet, have been shown to be important to wool fiber growth. Their effectiveness is attributed to the important roles these minerals play in sulfur amino acid metabolism copper serves to catalyze the oxidation of cysteine to cystine during fiber synthesis [109]. Zinc is required for cell division to occur, and it also appears to play a role in protein metabolism [110]. 

Mineral fibers, particularly asbestos, can activate protein kinase C and increase expression of ornithine decarboxylase, the proto-oncogenes, c-fos, and c-jun (18-20), and the nuclear transcription factor, NF-kB (21). All these events are associated with cell proliferation and, potentially, with neoplastic transformation. Recently, Zanella et al. (22) have shown that asbestos activates the mitosis-associated kinase (MAP) system, apparently through interaction with the epidermal growth factor receptor, probably implying that some of these events are mediated by signal transduction pathways that start on the cell surface, rather than by fiber uptake, although this point needs to be directly examined. 

In contrast to chrysotile fibers, the atomic crystal stmcture of amphiboles does not inherentiy lead to fiber formation. The formation of asbestiform amphiboles must result from multiple nucleation and specific growth conditions. Also, whereas the difference between asbestiform and massive amphibole minerals is obvious on the macroscopic scale, the crystalline stmctures of the two varieties do not exhibit substantial differences. Nonfibrous amphiboles also exhibit preferential cleavage directions, yielding fiber-shaped fragments. 

Besides water, the diet must provide metabolic fuels (mainly carbohydrates and lipids), protein (for growth and turnover of tissue proteins), fiber (for roughage), minerals (elements with specific metabolic functions), and vitamins and essential fatty acids (organic compounds needed in small amounts for essential metabolic and physiologic functions). The polysaccharides, tri-acylglycerols, and proteins that make up the bulk of the diet must be hydrolyzed to their constituent monosaccharides, fatty acids, and amino acids, respectively, before absorption and utilization. Minerals and vitamins must be released from the complex matrix of food before they can be absorbed and utifized. 

Besides watet, the diet must provide metaboEc fuels (carbohydrate and fat) fot bodily growth and activity protein fot synthesis of tissue proteins fiber for roughage minerals for specific metabolic functions cettain polyunsamtated fatty acids of the n-3 and n-6 famihes fot eicosanoid synthesis and other functions and vitamins, otganic compounds needed in small amounts for many varied essential functions. 

Growth of Minerals, Fibrous Minerals, and Synthetic Fibers... 

The pyroxene group of minerals, where cations substitute one for another at interchain sites, also have a tetrahedral Si site that may contain Al. Some of these substitutions, especially those at M2, can distort the ideal crystal structures, as is depicted in Fig. 2.10. The small distortions are detected as variations in bond lengths between adjacent atoms during crystal structure analyses. These data, combined with accurate composition analyses, could indicate some of the conditions present during growth of the crystal and contribute to our understanding of why some mineral species have formed as fibers. Unfortunately, few detailed crystal structural analyses have been performed on pyroxene minerals with fibrous habits. 

Seaweed [FOOD ADDITIVES] (Vol 11) agarose from [ELECTROSEPARATIONS - ELECTROPHORESIS] (Vol 9) gums from [GUMS] (Vol 12) mineral nutrients source [MINERAL NUTRIENTS] (Vol 16) plant growth regulators fiom [GROWTH REGULATIONS - PLANT] (Vol 12) source ofdietary fiber [DIETARY FIBER] (Vol 8)... 

The geological or commercial meaning of the word asbestos is broadly applied to fibrous forms of the silicaceous serpentine and amphibole minerals mentioned above. Asbestos minerals form under special physical conditions that promote the growth of fibers that are loosely bonded in a parallel array (fiber... 

The macroscopic level of consideration takes into account fiber length and differences in cell growth such as earlywood, latewood, reaction wood, sapwood, heartwood, mineral content, resin content, etc. Difierences in growth chemistry can cause significant differences in the strength of wood. 

---