Compositional diversity

Spinels. There are limited experimental data on uranium and thorium partitioning between magnetite and melt (Nielsen et al. 1994 Blundy and Brooker 2003). Both studies find U and Th to be moderately incompatible. Blundy and Brooker s results for a hydrous dacitic melt at 1 GPa and 1025°C give Du and D h. of approximately 0.004. The accuracy of these values is compromised by the very low concentrations in the crystals and the lack of suitable SIMS secondary standards for these elements in oxide minerals. Nonetheless, these values are within the range of Djh of magnetites at atmospheric pressure 0.003-0.025 (Nielsen et al. 1994). It is difficult to place these values within the context of the lattice strain model, firstly because there are so few systematic experimental studies of trace element partitioning into oxides and secondly because of the compositional diversity of the spinels and their complex intersite cation ordering. 

The silicoaluminophosphate (SAPO) family [30] includes over 16 microporous structures, eight of which were never before observed in zeolites. The SAPO family includes a silicon analog of the 18-ring VPI-5, Si-VPI-5 [31], a number of large-pore 12-ring structures including the important SAPO-37 (FAU), medium-pore structures with pore sizes of 0.6-0.65 nm and small-pore structures with pore sizes of 0.4-0.43 nm, including SAPO-34 (CHA). The SAPOs exhibit both structural and compositional diversity. 

The third mineral group included in the category of biopyriboles is the micas. The micas are indicated by bio, which comes from biotite, one of a large number of compositionally diverse species that make up the micas, a commonly encountered group of minerals. 

Two categories of mesoporous solids are of special interest M41S type materials and pillared or delaminated derivatives of layered zeolite precursors (pillared zeolites in short). The M41S family, first reported in early 1990 s [1], has been extensively studied [2,3]. These materials exhibit broad structural and compositional diversity coupled with relative ease of preparation, which provides new opportunities for applications as catalysts, sorption and support media. The second class owes its existence to the discovery that some zeolite crystallizations can produce a lamellar intermediate phase, structurally resembling zeolites but lacking complete 3-dimensional connectivity in the as-synthesized form [4]. The complete zeolite framework is obtained from such layered zeolite precursor as the layers become fused, e.g. upon calcination. The layers posses zeolitic characteristics such as strong acidity and microporosity. Consequently, mesoporous solids derived from layered zeolite precursors have potentially attractive characteristics different from M41S and the zeolite species... 

Petrological and geochemical variations along the arc are considered to result from variable relative amounts of slab-released fluids and melts added to the mantle wedge, as well as from higher amounts of subducted sediments added to the mantle beneath eastern islands. Variation of pre-metasomatic mantle composition, from MORB-type in the central arc to OIB-type in the external islands, is also considered as an important factor for compositional diversity along the arc. 

Taking into account the limitations of methods for determining the species composition of viruses and bacteria, we may suggest that the total number of species should be somewhat greater. In terms of the species composition diversity, the pelagic zone is poorer than the bottom fauna and flora. The multicellular fauna includes about 2000 species, which agrees with previous estimates [45]. 

Ginger oil displays considerable compositional diversity but is typically characterized by a high content of sesquiterpene hydrocarbons, including zingiberene, ar-curcumene, (3-bisabolene and (S-sesquiphellandrene. 

The two-dimensional structures are extended networks formed by the linking of the metal-oxygen polyhedra and the phosphate tetrahedra. These are sheet structures and often resemble those of naturally occurring clay minerals. The sheets are usually anionic and the protonated (cationic) amine molecules, located between the two sheets, render the framework neutral. The two-dimensional structures are intermediates between the one-dimensional chains and the three-dimensional structures, and the literature on phosphate networks contains descriptions of several layered materials, owing to the wide compositional diversity exhibited by them [22-24]. The layered materials are of interest because they act as precursors for the three-dimensional structures. 

Compositional variability can have a significant impact on biomass conversion process economics. The large effect (i.e., at least 0.30/gal ethanol) of observed compositional diversity on process economics is shown in Fig. 33.19 and is primarily due to the fact that the maximum theoretical product yield is proportional to feedstock carbohydrate content (Fig. 33.20).131 Yield is the major economic driver for the technoeconomic model used to assess the economic impact of composition on minimum product selling price,130 as can be seen from the data in Fig. 33.21. 

The various subclassifications for mare basalt we describe below may seem arbitrary but, as will be discussed in the next section, mare basalt compositional diversity is in general not systematic, but haphazard. On Earth, volcanic diversity is largely a function of systematic global tectonics, such as upwelling at mid-ocean ridges to generate MORE. But plate tectonics probably never occurred on the Moon and it surely never occurred during the comparatively late era of mare volcanism. 

Leeman W. P., Smith D. R., Hildreth W., Palacz Z., and Rogers N. W. (1990) Compositional diversity in Late Cenozoic basalts in a transect across the southern Washington Cascades. J. Geophys. Res. 95, 19561-19582. 

The compositions of the planets in the solar system and those of chondritic meteorites provide a guide to the bulk Earth composition (see Chapter 2.01). However, the rich compositional diversity of these bodies presents a problem insofar as there is no single meteorite composition that can be used to characterize the Earth. The solar system is compositionally zoned planets with lesser concentrations of volatile elements are closer to the Sun. Thus, as compared to Mercury and Jupiter, the Earth has an intermediate uncompressed density (roughly a proportional measure of metal to rock) and volatile element inventory, and is more depleted in volatile elements than CI-chondrites, the most primitive of all of the meteorites. 

Nakada S., Bacon C. R., and Gartner A. E. (1994) Origin of phenocrysts and compositional diversity in pre-Mazama rhyodacite lavas. Crater Lake, Oregon. J. Petrol. 35, 127-162. 

CH2)6N/iH3 H20 i 1041 built up from the strict alternation of A10 /A106 and PO4 units, aluminophosphate APO-HDA with intersecting 12-ring and 18-ring channels, and numerous other 3-D anionic framework and 2-D layer structures. The Al/P ratios of these compounds include 1/1, 1/2, 2/3, 3/4, 4/5, 5/6, 11/12, 12/13, 13/18, etc. This greatly enriches the open-framework aluminophosphate family, showing their structural and compositional diversity.1641... 

Many of the non-silica compositions showed problems with the stability and quality of the structure. Efforts to address these issues have been on going and quite successful in some cases such as all-alumina compositions (see below). Silica-based materials remain dominant as the most versatile and best quality molecular sieves (structure and stability) available by a facile synthesis. These attributes, especially the convenient synthesis made mesoporous silicate attractive for post-synthesis functionalization with other elements as well as organic moieties with active groups/ccnters. Recently the compositional diversity has been extended further to include both silica and organic moieties within the framework. The new class is referred to as periodic mesoporous organosilicas (PMOs). The synthesis involves surfactant-assisted assembly by hydrolysis of organo-silicon compounds. Additional discussion of the PMOs is presented below. 

Aluminophosphate based molecular sieves are known to exist in a wide range of structural and compositional diversity . Substitution of silicon in the framework of aluminophosphate molecular sieves (SAPO) imparts acidity to the material and thus makes it active for acid catalyzed reactions. Through controlled substitution of the amount of Si in aluminophosphate, the catalytic activities due to its acidic properties can be altered. The extent of Si substitution in the aluminophosphates is however limited and is determined by the topology of the structure. 

Combinatorial methods only make sense when very large numbers of different materials are made and screened quickly. Compositional diversity across a library is obtained by varying the... 

The extensive and detailed analytical results given in Table 1 of Forster (1998a) illustrate the extreme compositional diversity exhibited by natural monazites. In fact, Forster has even reported the existence of a monazite-group mineral that is intermediate between monazite and huttonite. Forster s analysis indicated that complete miscibility exists between common monazite-(Ce) and the phosphate mineral brabanite [Ca,Th,U(P04)2]- The monazite/xenotime compositional systematics have also been examined by Fleinrich et al. (1997). Additional data related to the compositional diversity of monazites can be found in the work of Bea (1996), Bea et al. (1994), and Hinton and Patterson (1994). 

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