An interactive computer code for calculation of gas-phase chemical equilibrium (EQLBRM)

A user friendly, menu driven, interactive computer program known as EQLBRM which calculates the adiabatic equilibrium temperature and product composition resulting from the combustion of hydrocarbon fuels with air, at specified constant pressure and enthalpy is discussed. The program is developed primarily as an instructional tool to be run on small computers to allow the user to economically and efficiency explore the effects of varying fuel type, air/fuel ratio, inlet air and/or fuel temperature, and operating pressure on the performance of continuous combustion devices such as gas turbine combustors, Stirling engine burners, and power generation furnaces

Quasi-Chemical Theory and Implicit Solvent Models for Simulations

A statistical thermodynamic development is given of a new implicit solvent model that avoids the traditional system size limitations of computer simulation of macromolecular solutions with periodic boundary conditions. This implicit solvent model is based upon the quasi-chemical approach, distinct from the common integral equation trunk of the theory of liquid solutions. The physical content of this theory is the hypothesis that a small set of solvent molecules are decisive for these solvation problems. A detailed derivation of the quasi-chemical theory escorts the development of this proposal. The numerical application of the quasi-chemical treatment to Li$^+$ ion hydration in liquid water is used to motivate and exemplify the quasi-chemical theory. Those results underscore the fact that the quasi-chemical approach refines the path for utilization of ion-water cluster results for the statistical thermodynamics of solutions.Comment: 30 pages, contribution to Santa Fe Workshop on Treatment of Electrostatic Interactions in Computer Simulation of Condensed Medi

Lifetimes and Sizes from Two-Particle Correlation Functions

We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the two-particle correlation function for azimuthally symmetric expanding sources. We derive model-independent expressions for the YKP fit parameters and discuss their physical interpretation. We use them to evaluate the YKP fit parameters and their momentum dependence for a simple model for the emission function and propose new strategies for extracting the source lifetime. Longitudinal expansion of the source can be seen directly in the rapidity dependence of the Yano-Koonin velocity.Comment: 15 pages REVTEX, 2 figures included, submitted to Phys. Lett. B, Expanded discussion of disadvantages of standard HBT fit and of Fig.

Hydration of Kr(aq) in dilute and concentrated solutions

Molecular dynamics simulations of water with both multi-Kr and single Kr atomic solutes are carried out to implement quasi-chemical theory evaluation of the hydration free energy of Kr(aq). This approach obtains free energy differences reflecting Kr-Kr interactions at higher concentrations. Those differences are negative changes in hydration free energies with increasing concentrations at constant pressure. The changes are due to a slight reduction of packing contributions in the higher concentration case. The observed Kr-Kr distributions, analyzed with the extrapolation procedure of Kr\"{u}ger, \emph{et al.}, yield a modestly attractive osmotic second virial coefficient, $B_2\approx -60~\mathrm{cm}^3$/mol. The thermodynamic analysis interconnecting these two approaches shows that they are closely consistent with each other, providing support for both.Comment: 6 pages, 7 figures. Revision follows the extrapolation procedure of Refs. 33 and 34 which works nicely. The thermodynamic results are now clearly consistent. The $k \rightarrow 0$ extrapolation of the Fourier transform was not was satisfactor

Analyzing Correlation Functions with Tesseral and Cartesian Spherical Harmonics

The dependence of inter-particle correlations on the orientation of particle relative-momentum can yield unique information on the space-time features of emission in reactions with multiparticle final states. In the present paper, the benefits of a representation and analysis of the three-dimensional correlation information in terms of surface spherical harmonics is presented. The harmonics include the standard complex tesseral harmonics and the real cartesian harmonics. Mathematical properties of the lesser-known cartesian harmonics are illuminated. The physical content of different angular harmonic components in a correlation is described. The resolving power of different final-state effects with regarding to determining angular features of emission regions is investigated. The considered final-state effects include identity interference and strong and Coulomb interactions. The correlation analysis in terms of spherical harmonics is illustrated with the cases of gaussian and blast-wave sources for proton-charged meson and baryon-baryon pairs.Comment: 32 pages 10 figure

An XMM-Newton observation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission

In the optical and ultraviolet regions of the electromagnetic spectrum, UX Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec XMM-Newton observation to further constrain the origin of the X-rays. The combination of spectral and timing information allows us to identify two components in the X-ray emission of the system. The soft component, dominant below photon energies of 2 keV, can be fitted with a multi-temperature plasma model and is uneclipsed. The hard component, dominant above 3 keV, can be fitted with a kT ~ 5 keV plasma model and appears to be deeply eclipsed. We suggest that the most likely source of the hard X-ray emission in UX UMa, and other systems in high mass transfer states, is the boundary layer.Comment: To appear in MNRAS Letter