Amberly surfaces

Iron is associated with silica sand, usually as a light surface stain on the grains. Amber glass develops ionic color centers or complexes of Fe-S-C added to the batch as iron sulfide and powdered anthracite. Although the Fe content be four or five times that shown in the example in Table I, it appears to be bound in the complex so that no greater extraction occurs with the S and C. Titanium is associated with sand as... 

This chapter reviewed some of our group s contributions to the development and application of QM/MM methods specifically as applied to enzymatic reactions, including the use of sequential MD/QM methods, the use of effective fragment potentials for reaction mechanisms, the development of the new QM/MM interface in Amber, as well as the implementation and optimization of the SCC-DFTB method in the Amber program. This last implementation allows the application of advanced MD and sampling techniques available in Amber to QM/MM problems, as exemplified by the potential and free energy surface surfaces for the reaction catalyzed by the Tripanosoma cruzi enzyme /ram-sialidasc shown here. 

Some of the above mentioned studies also use two-layer ONIOM QM MM approaches to include the full protein in an MM description. Other examples of QM MM calculations of metal enzymes include heme oxygenase [89], nitrate reductase [90] and peptide deformylase [91]. Finally, we note that the ONIOM (I IF Amber) potential energy surface has been directly used in a molecular dynamics study (ONIOM/MD) of cytidine deaminase [92],... 

PPII helix-forming propensities have been measured by Kelly et al. (2001) and A. L. Rucker, M. N. Campbell, and T. P. Creamer (unpublished results). In the simulations the peptide backbone was constrained to be in the PPII conformation, defined as (0,VO = ( — 75 25°, +145 25°), using constraint potentials described previously (Yun and Hermans, 1991 Creamer and Rose, 1994). The AMBER/ OPLS potential (Jorgensen and Tirado-Rives, 1988 Jorgensen and Severance, 1990) was employed at a temperature of 298° K, with solvent treated as a dielectric continuum of s = 78. After an initial equilibration period of 1 x 104 cycles, simulations were run for 2 x 106 cycles. Each cycle consisted of a number of attempted rotations about dihedrals equal to the total number of rotatable bonds in the peptide. Conformations were saved for analysis every 100 cycles. Solvent-accessible surface areas were calculated using the method of Richmond (1984) and a probe of 1.40 A radius. 

The fulvene route was also successfully employed in the preparation of a compound, which can be regarded as one of the most advanced molecular models for a catalytically active titanium center on a silica surface. When Cp Ti(C5Me4CH2) was reacted with the monosilylated silsesquioxane precursor 12 in refluxing toluene a color change from deep purple to amber was observed. Crystallization afforded a bright-yellow material, which was subsequently shown to be the novel mo o(pentamethyleyclopentadienyl) titanium(IV) silsesquioxane complex 126 (69% yield). Its formation is illustrated schematically in Scheme 42. 

F. Wibel described a wooden casket in die Museum of Useful Arts at Hamburg, made in 1557. Over a chalk background attached with wax or glue, it has a metallic surface about one millimeter thick, overlaid witii gold or amber lacquer. Investigation of this surface proved it to be bismuth. In the latter part of the eighteenth century, bismutii painting was superseded by a cheaper process in which perfected lacquers were applied directly to the wood (47). 

Since electric charges may be transferred by rubbing surfaces of nonconductors against each other, the ancients were able to develop a crude triboelectric series based on amber, glass, and other available nonconductors. 

A typical feed composition was 1000 g capsul, 2334 g deionized water and 200 g orange oil. The finished powders were stored in amber bottles at -25prior to accelerated storage study and relevant analyses. Particle Size Analysis. To ascertain the effect of atomizer voltage on the particle size, the particle size distributions of three powders were first determined. The Microtrac laser light particle size analyzer (Medallion Laboratories, Minneapolis, MN) was used in this study. The volume percent data over particle diameter ranging 2.8 p. to 176 jii was recorded. Mean value of the volume percent distribution and calculated surface area were also obtained. 

Successfully applying the method used by Fenton to prepare his concentrates depends upon two factors. First, there must be adequate density differences between the macerals in the sample, and second, there must be an initially high concentration of the required maceral. In attempting to separate either resinite or cutinite from sporinite of the same coal, neither of these conditions can be fulfilled, at least when the coal is of bituminous rank or higher. If, however, samples on a semi microscale are acceptable, it is possible to prepare concentrates of resinites of satisfactory purity from bituminous coals by simple mechanical means. The method has been described by Murchison and Jones (17) and mainly involves picking with fine probes on differently prepared surfaces of coal under a stereoscopic microscope. Resinites from lignites pose less of a problem because their occurrence in fairly substantial lumps is quite common these and fossil resins such as kauri gum and amber usually can be prepared to a purity of almost 100% with ease. 

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