Diffusion of small light particles in a solvent of large massive molecules

We study diffusion of small light particles in a solvent which consists of large heavy particles. The intermolecular interactions are chosen to approximately mimic a water-sucrose (or water-polysaccharide) mixture. Both computer simulation and mode coupling theoretical (MCT) calculations have been performed for a solvent-to-solute size ratio five and for a large variation of the mass ratio, keeping the mass of the solute fixed. Even in the limit of large mass ratio the solute motion is found to remain surprisingly coupled to the solvent dynamics. Interestingly, at intermediate values of the mass ratio, the self-intermediate scattering function of the solute, F_{s}(k,t) (where k is the wavenumber and t the time), develops a stretching at long time which could be fitted to a stretched exponential function with a k-dependent exponent, \beta. For very large mass ratio, we find the existence of two stretched exponentials separated by a power law type plateau. The analysis of the trajectory shows the coexistence of both hopping and continuous motions for both the solute and the solvent particles. It is found that for mass ratio five, the MCT calculations of the self-diffusion underestimates the simulated value by about 20 %, which appears to be reasonable because the conventional form of MCT does not include the hopping mode. However, for larger mass ratio, MCT appears to breakdown more severely. The breakdown of the MCT for large mass ratio can be connected to a similar breakdown near the glass transition.Comment: RevTex4, 9 pages, 10 figure

Characterization of Limestone Sample from Northeast India and its Implication on Beneficiation

Two limestone samples, from the same source (Assam, north-east India) have been petromineralogically characterized. In hand specimens, both samples are quite similar and are highly fossiliferous. Under optical microscope the fossils that are indentified belong mostly to two different Phy-llum, viz., Protozoa and Mollusca. The Protozoans are mainly Foraminifera and the Molluscans are Lamellibran-chia. Both categories have been petrified to calcium carbonate only and the fossils are embedded in a lime matrix. Due to the dominance of Nummulite fossils, the samples can be named as 'Nummulitic limestones'.The fossil records indicate that the limestones may be of Eocene age (< 65 million years)

Effect of Fibonacci Modulation On Superconductivity

We have studied finite-sized single band models with short range pairing interactions between electrons in presence of diagonal Fibonacci modulation in one dimension. Two models, namely the attractive Hubbard model and the Penson-Kolb model, have been investigated at half-filling at zero temperature by solving the Bogoliubov-de Gennes equations in real space within a mean field approximation. The competition between ``disorder'' and the pairing interaction leads to a suppression of superconductivity (of usual pairs with zero centre-of-mass momenta) in the strong-coupling limit while an enhancement of the pairing correlation is observed in the weak-coupling regime for both the models. However, the dissimilarity of the pairing mechanisms in these two models brings about notable difference in the results. The extent to which the bond ordered wave and the $\eta$-paired (of pairs with centre-of-mass momenta = $\pi$) phases of the Penson-Kolb model are affected by the disorder has also been studied in the present calculation. Some finite size effects are also identified.Comment: 14 pages, 13 figure

Separation response of iron ores during gravity concentration

Two types of iron ores namely soft laminated ore and goethitic-lateritic ore is studied in details from Jilling-Langalota deposit, Singhbhum-N, Orissa Craton, Eastern India. The soft laminated iron ore contained relatively high hematite as compared to Goethitic-lateric ore which contained goethite in large quantity. Beneficiation of iron ores by gravity separation method is studied. The ore samples are beneficiated with a view to produce sinter quality concentrate. The soft laminated ore contained 61.29% total iron, 5.04% silica and 4.29% alumina while the Goethitic-lateritic ore contained 53.34% total iron, 7.4% silica and 5.49% alumina. Liberation analysis of different size fraction suggested that grain size reduction lower than 150 mm size would be necessary to achieve sufficient liberation of iron ore minerals from the associated gangue (kaolinite and gibbsite). However, the percentage of interlocking is higher in case of Goethitic-lateritic ore compared to soft laminated ore. Considering the characterisation data, the soft laminated ore is ground separately to three size fractions namely 300 mm, 250 mm and 150 mm sizes, while the goethitic ore is ground to 150 mm size and subjected to flowing film concentration in Wilfley Table. The grade of the soft laminated ore is improved from 61% Fe to 66% Fe while for the Goethitic-lateritic ore the Fe content is enriched from 53% to 64% in simple one-stage concentration operation. The nature of the ore mineral plays important role in the separation process. Due to enrichment of goethite and friable nature of Goethitic-lateritic ore significant amount of Fe is lost during the process as compared to soft laminated ore

Steric Effect in Ni(II) & Co(II) Complexes of Methyl Substituted N-Benzoyl-N-phenylhydroxylamines (N-phenylbenzohydroxamic Acids)

354-35

Adducts of Some Methyl substituted N-phenylbenzo-hydroxamates of Cobalt(II) with Different Nitrogen Bases

747-74