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Remaining Discrepancy (remaining + discrepancy)
Selected AbstractsEquation of state for the viscosity of Lennard-Jones fluids,AICHE JOURNAL, Issue 2 2006Leslie V. Woodcock Abstract A one-parameter model constitutive transport equation for the viscosity of the Lennard-Jones (L-J) fluid that is accurate for all equilibrium states of liquid and gas is proposed: The form of this equation is based upon the soft-sphere scaling laws for the residual density-dependent viscosity discovered originally by Ashurst and Hoover and uses their empirical coefficient (CAH). Enskog's density-independent limit theoretical term (,0) is included to reproduce the viscosity in the limit of zero density accurately. Remaining discrepancies at low temperatures, for both gas and liquid densities, are largely removed when the linear-density Rainwater-Friend coefficient is added. The equation is comparable in accuracy to the 24-parameter empirical equation of state proposed by Rowley and Painter. Comparison with this correlation and previous MD results reveals a discrepancy near the triple point. To test the equation, new MD data for three fluid states are reported. Here, the viscosity is computed from time correlation functions resolved into the single-particle auto- and cross-correlation terms. It is found that, at high density (,* > 0.8), the cross,correlations extend beyond 7, (molecule diameters) and oscillate in sign. This explains the wide scatter of previous MD viscosities for small L-J systems. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Toward the Complete Prediction of the 1H and 13C NMR Spectra of Complex Organic Molecules by DFT Methods: Application to Natural SubstancesCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2006Alessandro Bagno Prof. Abstract The NMR parameters (1H and 13C chemical shifts and coupling constants) for a series of naturally occurring molecules have been calculated mostly with DFT methods, and their spectra compared with available experimental ones. The comparison includes strychnine as a test case, as well as some examples of recently isolated natural products (corianlactone, daphnipaxinin, boletunone B) featuring unusual and/or crowded structures and, in the case of boletunone B, being the subject of a recent revision. Whenever experimental spectra were obtained in polar solvents, the calculation of NMR parameters was also carried out with the Integral Equation-Formalism Polarizable Continuum Model (IEF-PCM) continuum method. The computed results generally show a good agreement with experiment, as judged not only by statistical parameters but also by visual comparison of line spectra. The origin of the remaining discrepancies is attributed to the incomplete modeling of conformational and specific solvent effects. [source] Primary carbonate/CO2 inclusions in sapphirine-bearing granulites from central Sri LankaJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2000Bolder-Schrijver High-density CO2 -rich fluid inclusions from a sapphirine-bearing granulite (Hakurutale, Sri Lanka) have been studied by microthermometry, Raman spectrometry and SEM analysis. Based on textural evidence, two groups of inclusions can be identified: primary, negative crystal shaped inclusions (group I) and pseudo-secondary inclusions, which experienced a local, limited post-trapping modification (group II). Both groups contain magnesite as a daughter mineral, occurring in a relatively constant fluid/solid inclusion volume ratio (volsolid =0.15 total volume). CO2 densities for group I and II differ only slightly. Both groups contain a fluid, which was initially trapped at peak metamorphic conditions as a homogeneous (CO2+MgCO3) mixture. Thermodynamic calculations suggest that such a fluid (CO2+15 vol% MgCO3) is stable under granulite facies conditions. After trapping, magnesite separated upon cooling, while the remaining CO2 density suffered minor re-adjustments. A model isochore based on the integration of the magnesite molar volume in the CO2 fluid passes about 1.5,2 kbar below peak metamorphic conditions. This remaining discrepancy can be explained by the possible role of a small quantity of additional water. [source] The mass assembly of fossil groups of galaxies in the Millennium simulationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007Ali Dariush ABSTRACT The evolution of present-day fossil galaxy groups is studied in the Millennium simulation. Using the corresponding Millennium gas simulation and semi-analytic galaxy catalogues, we select fossil groups at redshift zero according to the conventional observational criteria, and trace the haloes corresponding to these groups backwards in time, extracting the associated dark matter, gas and galaxy properties. The space density of the fossils from this study is remarkably close to the observed estimates and various possibilities for the remaining discrepancy are discussed. The fraction of X-ray bright systems which are fossils appears to be in reasonable agreement with observations, and the simulations predict that fossil systems will be found in significant numbers (3,4 per cent of the population) even in quite rich clusters. We find that fossils assemble a higher fraction of their mass at high redshifts, compared to non-fossil groups, with the ratio of the currently assembled halo mass to final mass, at any epoch, being about 10,20 per cent higher for fossils. This supports the paradigm whereby fossils represent undisturbed, early-forming systems in which large galaxies have merged to form a single dominant elliptical. [source] | ||||||||||