Grain nature

Atoms Humbug Rarely does a major new eoneept receive unanimous acceptance. Despite the atomie theory s impact, several major seientists denied the existence of atoms for another eentury. In 1877, Adolf Kolbe, an eminent organic chemisf said [Dalton s atoms are]. .. no more than stupid hallucinations. .. mere table-tapping and supernatural explanations. The influential physicist Ernst Mach believed that scientists should look at facts, not hypothetical entities such as atoms. It was not until 1908 that the famous chemist and outspoken opponent of atomism Wilhelm Ostwald wrote, I am now convinced [by recent] experimental evidence of the discrete or grained nature of matter, which the atomic hypothesis sought in vain for hundreds and thousands of years. (p.45)... 

It is the purpose of this section to review ways in which processes involving electrons are either explicitly accounted for in calculations on polymeric systems or in which a more or less rigorous abstraction from the electronic degrees of freedom into effective models of a coarser-grained nature is performed. The next level up from electrons is obviously atoms. Hence, this section deals mainly with the connection between quantum chemistry and atomistic (force field) simulations. Calculations which exclusively use quantum chemistry are not covered. This excludes, for example, all of the recent work on metallocene catalysis. 

Russell WA, Papanastassiou DA, Tombrello TA (1978b) Ca isotope fractionation on the Earth and other solar system materials. Geochim Cosmochim Acta 42 1075-1090 Scharer U, Allegre CJ (1982) Uranium-lead system in fragments of a single zircon grain. Nature 295 585-587... 

Sulphide minerals were recovered only In the 0.25-0.5 mm fraction because of their fine-grained nature in the bedrock. A preliminary set of indicator minerals Include ... 

The growth rate minima cannot be explained by the secondary nucleation theory in its present form. The two major simplifications that the LH theory makes are (a) neglect of the segmental ( fine-grain ) nature of stem... 

Moore, C. J., and Turner, J. F. 1969. ADP-glucose pyrophosphorylase in wheat grains. Nature London) 223, 303-304. 

Further, the coarse grained nature of the algorithm will allow the extension of modeling of proton transport in bulk water to PFSA membranes because hydrated protons form similar Zundel-ion-like stractme and Eigen-ion-like structure with the oxygen of the sulfonate groups, which can be easily integrated into the RMD formalism. 

Gallino R., Busso M., Picchio G., and Raiteri C. M. (1990) On the astrophysical interpretation of isotope anomalies in meteoritic SiC grains. Nature 348, 298-302. 

Wider R., Kehm K., Meshik A. P., and Hohenberg C. M. (1996) Secular changes in the xenon and krypton abundances in the solar wind recorded in single lunar grains. Nature 384, 46-49. 

A boromuscovite structure determination is complicated by the fine-grained nature... 

Fine grained natural material, plastic with appropriate water content, hardens when dried/fired... 

The primitive chain shares some of the statistical properties with the parent test chain. Both are ideal. Their end-to-end distance is the same. The conformation of the primitive chain is a coarse-grained version of the conformation of the test chain. When we apply the random-walk model to the primitive chain, its step length is equal to the tube diameter ft, (Fig. 4.32). Because the tube eucases the test chain, bf > b. We can appreciate the coarse-grained nature of the primitive chain in this inequality. The contour length L of the primitive chain is shorter than that of the test chain. We can estimate L as follows. For the primitive chain to have a contour length of L, the random walk must have L/, steps. We equate the meau square end-to-end distance of the test chain and that of the primitive chain b (L/b = b N. Then,... 

Identification by all techniques is usually complicated by the fine-grained nature of most minerals and by the likelihood that two or more species are intergrown intimately. Fortunately, all the techniques, XR PD, EM, IR and optics, can utilize small amounts of material. Careful preparation can require separation of material under a microscope. It is usually imperative to utilize single-phase samples to facilitate the interpretation of the experimental data. Many questionable identifications can be traced to poor sample preparation. 

Generally, coarse-grained, naturally occurring minerals are the raw materials for mechanical methods. The particle size is brought down by different equipments to get the final size. When economy is needed and purity is not the primary concern, these methods are used. Traditional ceramic products are generally made from the powders obtained from these methods. 

Discussion Whereas the coarse-grained nature of the molecular model employed does not allow one to expect quantitative agreement with parameters obtained for atomistic models, we do note that the values obtained show qualitative agreement. For the strength parameters, for example, we obtain = 6605kA, ... 

Thompson, R.D., 2000. Turning fields into grains. Nature 408,39-41. 

The model therefore displays the correct thermodynamic behavior and interfadal fluctuations. It can also be extended to model amphiphilic mixtures by introducing dimers consisting of tethered A and B particles. If the A and B components of the dimers participate in the same collisions as the solvent, they behave like amphiphilic molecules in binary oil-water mixtures. The resulting model displays a rich phase behavior as a function of pF and the number of dimers, Ad. Both the formation of droplets and micelles, as shown in Fig. 5 (left panel), and a bicontinuous phase, as illustrated in Fig. 5 (right panel), have been observed [45]. The coarse-grained nature... 

Brindley and his colleagues (Brindley [1949, 1951,] Brindley and Youell [1953,] and Youell [1955]) have made most structural studies of this mineral. Because of its fine-grained nature and the presence of much structural disorder, no detailed structural analysis is yet available. A monoclinic one-layer form of the mineral occurs with a = 5.39, b = 9.33, c = 7.04, and j8 = 104.5°. The monoclinic angle corresponds to displacements of successive layers by —al3, as is common with the dioctahedral kaolin minerals. An orthorhombic or orthohexagonal one-layer form also occurs with similar cell dimensions, but with P = 90°. Presumably in this form, the layers occur directly one upon the other. 

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