Global textures

The Orientation Density Function (ODF) is defined and the calculations for the general knowledge about texture analysis in poly crystalline materials. The difference between local and global textures allows to determine the ODF more precisely and to describe the grains orientation relationships. 

The trend in this field of texture analysis is now to combine information on global textures (obtained from statistical diffraction data) and local textures (obtained from individual orientation measurements in electron microscopy). This allows the determination of the ODFs as well as functions which describe the orientation relationships between the grains. Such studies will very likely improve the understanding of the behavior of polycrystalline materials and will therefore lead to the optimization of their properties. 

Perhaps the most well-known, unsolved problem in cosmochemistry is the question of the mechanism whereby dust grain aggregates were thermally processed to form chondrules and some rounded refractory inclusions. Chondrule compositions and textures require rapid heating and somewhat slower cooling for their explanation a globally hot nebula is inconsistent with these requirements... 

Dorr and Munnich (1990) described a technique for estimating gas fluxes from soils using parallel measurements of CO2 and Rn profiles in soils. This technique does not require chambers and has the advantage of using naturally produced Rn, which is conservative and is affected only by diffusion and radioactive decay. The technique was extended to measurements of CH4 consumption (Bom et al., 1990). Dorr et al. (1993) used soil texture parametrization to extend local measurements to the global scale, and arrived at an estimate of 28.7 Tg CH4 yr . Whalen et al. (1992) used the Rn technique in a boreal forest study comparing seven approaches to measuring soil CH4 oxidation. 

Bottled smoothies present a custom-made format for manufacturers to combine superfruits with nutrient fortification. The creamy, heavy texture of a smoothie often lends itself to reestablishing the dietary fiber content of a product. Although you will be greeted by a wide variety of products in this category, the global firm Nestle, two major American brands—Bolthouse Farms and Odwalla, and Arthurs Fresh Company, in Canada, provide examples among their numerous products that preserve the most nutrients from the fresh fruit. Here s a rundown ... 

After calcination at 450°C, hard blocks were obtained. The solid presents a 7-alumina structure and a type IV nitrogen isotherm (see Fig. 2-a), typical for mesoporous materials. The surface area was found equal to 400 50 mVg and the pore volume to 0.5 0.1 cm /g. The value of the pore diameters (centered on 5 nm) is in good agreement with SEM observations which indicate a textural mesoporosity. Many parameters of the reaction were studied. First, the composition of the initial mixture (dilution, global surfactants concentration and CTMABr/sodium palmitate ratio), secondly the procedure parameters (temperature, aging time, final pH and addition order of the chemicals) and third the nature of the chemicals (nature of the counterion of CTMA and nature of the acid) were varied. However, all the materials washed with water presented the same characteristics as described previously. 

TABLE 2 Boreal Zone Regional Soil Water Storage Capacities for 1° Latitude by 1° Longitude Grid Cells Based on the Global Soil Texture Database of Zobler (1986) with Hydraulic Parameter Values from Cosby etal. (1984)... 

Wetland areas with organic soils were excluded using the global database of Matthews (1989) as described by Matthews and Fung (1987) and in the text. Water storage capacities were derived from the difference between water contents determined in the laboratory on mineral soil cores subject to 10 and 100 or 10 and 1500 bPa of applied suction. From left to right, the mineral soil texture classes of Zobler (1986)/Cosby ctni (1984)(abbreviation, percentages of sand silt clay) are coarse/loamy sand (LS, 82 12 6), medium fme/sandy clay loam (SCL, 58 15 27), medium coarse/sandy loam (SL, 58 ,52 10), and medium/loam (L,43 39 18). 

Predictable variations in the SOC pool have been observed in either comparative. studies between soils from contrasting climates (Jenny, 1961 Trumbore, 1993) or contrasting soil textural types (Parton et ai, 1987), transects along climatic gradients (Townsend et ai, 1995), transects acro.ss soil chrono/topo sequences (Goh ct ai, 1976 ), and comparisons between disturbed and undisturbed areas (Townsend et ai, 1995 Desjardin et ai, 1993). In addition, some studies have attempted to look at SOC trends on the continental (e.g., Spain et ai, 1983 Moraes et ai, 1995) or global (e.g., Post et ai, 1982) scale using data compiled from literature sources and have been able to deduce major trends in SOC inventories with respect to climate and soil type, but generally with much scatter in the data. 

From this understanding of the behavior of the SOC pool, models such as Rothamsted (Jenkinson and Rayner, 1977) and Century (Parton et ai, 1993) have been developed that allow results from regional validation studies to be extrapolated to the global scale (Schimel et al, 1994). Such models divide the SOC pool up into three to five pools with turnover times ranging from years to thousands of years, and the sizes of the.se pools for a given. soil texture are determined by climate-driven interactions between plant carbon inputs, nutrients, microbial respiration, and leaching of DOC (Fig. 2). In some cases, the.se models have been tested... 

FIGURE 3 Potential mean soil carbon turnover rates extrapolated to the global scale using the temperature and soil texture relationships from the Century model (Schimel et al, 1994), See also color insert. 

Sandworld and clayworld, that is, observational estimates of SOC parameters from coarse- and fine-textured substrates distributed across the full spectrum of global climatic zones, are achievable technically and logistically. They represent a natural... 

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