Pyrogenic Crystals

Ever since the discovery of analcime in tuffaceous rocks, most workers have assumed that the analcime formed directly from vitric material. The presence of vitroclastic texture and pyrogenic crystals in some anal-cimic tuffs seemed sufficient evidence however, these criteria do not necessarily prove that the glass altered directly to analcime. Hay (48) and Sheppard and Gude (123) concluded from a study of tuffs in saline-lake deposits that analcime commonly formed from alkalic, silicic zeolite precursors. Formation of analcime from clinoptilolite and phillipsite was documented in tuffs of the Miocene Barstow Formation. Relict fresh... 

M5. Malawista, S. E Duff, G. W., Atkin, E., Cheung, H. S and McCarty, D. J. Crystal-induced endogenous pyrogen production. A further look at gouty inflammation. Arthritis Rheum. 28, 1039-1046 (1985). 

Figure 1. The crystal structure (chain B) of the ISU-type protein from Streptococcus pyrogenes (Sp) (PDB ID ISUO) shown in steroview. Highlighted residues include Cys requiredfor Fe-S cluster formation (C40, C65, Cl 27) and highly conserved acidic residues (D16, D42, D77, E56, D57, andD28) Residue D42 is the homologous site for D37 found in human ISU.

The extraordinary photocatalytic performance of AEROXIDE TiOj P 25 in comparison to other nanoscaled titania particles has been published in several papers It is, for example, useful in the degradation of humic acid [71], of phenol and salicylic acid [72], of l,4dichlorobenzene [73], and in the photocatalytic reduction of Hg(II) [74]. It is also used in the oxidation of primary alcohols to aldehydes [75] or in the photopolymerization of methyl methacrylate [76]. Its use in cement can help reduce environmental pollution [77, 78]. A detailed study is reported by Bolte [79]. The results show that crystal size and filling ratio in mass are more important than the modification of the titania. Pyrogenic titania is not only useful in photocatalysis but also in other catalytic applications. 

FIGURE 1.20 Raman spectra of (1) nanosilica A-200 (200 mVg, 3.8 OH/nm ) and (2) precipitated silica P (175 mVg, 15 OH/nm ). (Adapted from J. Non-Crystal. Solids, 191, Hnmbert, H., Estimation of hydroxyl density at the surface of pyrogenic sRicas by complementary NMR and Raman experiments, 1995, 29-37. Copyright 1995, with permission from Elsevier.)... 

The treatment of magnesium silicate-containing rocks under pyrogenic conditions led to the crystallization of fluorosilicates in the form of fibrous-, thin-, and thick- prismatic crystals of the various length (Fig. 10). 

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