The effect of molecular dynamics on basic parameters of cw-epr spectrum of pyridinium tetrafluoroborate single crystal

This paper presents an investigation of the phase transitions and molecular dynamics of radicals in pyridinium tetrafluoroborate single crystals by CW-EPR combined with the Computer Resolution Enhancement Method. We present the advantages following from the computer method for enhancement of resolution by the example of applying it in the analysis of complex CW-EPR spectra of organic radicals. The method enabled determination of basic parameters such as spectroscopic splitting factor, hyperfine coupling constants and widths of individual spectral lines in CW-EPR spectra of pyridinium tetrafluoroborate recorded in a wide range of temperatures. Phase transitions and changes in molecular dynamics of radicals may imply changes in their electronic structure, which may affect the above-mentioned parameters of CW-EPR spectra.     

State of hydrogen in idealized carbon slitlike nanopores at 77 K

The purpose of this letter is to clarify recent findings and answer to the question: "What is the state of hydrogen in carbon slitlike pores at 77 K?" For this purpose, we determined the volumetric density of hydrogen in idealized carbon pores of molecular dimension at 77 K and pressure up to 1 MPa. We used quantum corrected grand canonical Monte Carlo simulation. We recognized the highest volumetric density of confined hydrogen (around 71% of hydrogen liquid at boiling point) for effective pore width 5.6 angstroms (H* = 3.04) in the considered pressure range. Our computational results are in agreement with the calculations performed by Wang and Johnson and Rzepka et al. In contrast, we did not observe the high volumetric density of hydrogen in slitlike carbon pores exceeding the density of hydrogen liquid at the boiling point as was reported by Jagiello and Thommes. Moreover, we obtained qualitative agreement between the simulation results and some experimental findings reported by Nijkamp.     

Equilibrium properties of dense hydrogen isotope gases based on the theory of simple fluids

We present a new method for the prediction of the equilibrium properties of dense gases containing hydrogen isotopes. The proposed approach combines the Feynman-Hibbs effective potential method and a deconvolution scheme introduced by Weeks et al. The resulting equations of state and the chemical potentials as functions of pressure for each of the hydrogen isotope gases depend on a single set of Lennard-Jones parameters. In addition to its simplicity, the proposed method with optimized Lennard-Jones potential parameters accurately describes the equilibrium properties of hydrogen isotope fluids in the regime of moderate temperatures and pressures. The present approach should find applications in the nonlocal density functional theory of inhomogeneous quantum fluids and should also be of particular relevance to hydrogen (clean energy) storage and to the separation of quantum isotopes by novel nanomaterials.     

128Cs as the best example revealing chiral symmetry breaking

The results of the Doppler-shift attenuation method lifetime measurements in partner bands of 128Cs and 132La are presented. Experimental reduced transition probabilities in 128Cs are compared with theoretical calculations done in the frame of the core-quasiparticle coupling model. The electromagnetic properties, energy and spin of levels belonging to the partner bands show that 128Cs is the best known example revealing the chiral symmetry breaking phenomenon.     

Numerical simulation of shear and normal forces in standard and shear flow sequencing batch reactor (SF-SBR)

The purpose of this contribution is to compare the shear and the normal stresses in two different types of bioreactors. In the first one (SBR), the granules are generated by liquid and bubbles flow, whereas in the second one (SF-SBR), the shear rate is achieved by installing a rotating cylinder inside the reactor. Such shear flow can be applied for anaerobic process in the wastewater treatment. The results demonstrate the effective role of the process parameters and the reactor geometry on the shear and normal stresses and consequently on the granulation process. Hereby, the different tendencies of the velocity fields, the particle sedimentation as well as Taylor vortices in (SF-SBR), are observed. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Schur complement preconditioners for anisotropic problems

We present two new variants of Schur complement domain decompositionpreconditioners suitable for 2D anisotropic problems. Thesevariants are based on adaptations of the probing idea, describedby Chan et al (1992 Fifth Int. Symp. on Domain DecompositionMethods for Partial Differential Equations, Philadelphia: SIAM,pp 236-249), used in conjunction with a coarse grid approximationas introduced by Bramble et al (1986 Math. Comput. 47, 103-134).The new methods are specifically designed for situations wherethe coupling between neighbouring interfaces is stronger thanthe coupling within an interface. Taking into account this strongcoupling, one variant uses a multicolour probing technique toavoid distortion in the probe approximations that appear whenusing the method proposed by Chan et al. The second techniqueuses additional probe matrices to approximate not only the couplingwithin the interfaces but also the coupling between interfacepoints across the subdomains. This latter procedure looks somewhatlike an alternating line relaxation method for anisotropic problems,see Brandt (1977 Math. Comput.. 31, 333-390). To assess therelevance of the new preconditioners, we compare their numericalbehaviour with well known robust preconditioners such as thebalanced Neumann-Neumann method proposed by Mandel (1993 Commun.Numer. Methods Eng.. 9, 233-241).     

A Class of Pattern-Forming Models

Summary. A general class of nonlinear evolution equations is described, which support stable spatially oscillatory steady solutions. These equations are composed of an indefinite self-adjoint linear operator acting on the solution plus a nonlinear function, a typical example of the latter being a double-well potential. Thus a Lyapunov functional exists. The linear operator contains a parameter ρ which could be interpreted as a measure of the pattern-forming tendency for the equation. Examples in this class of equations are an integrodifferential equation studied by Goldstein, Muraki, and Petrich and others in an activator-inhibitor context, and a class of fourth-order parabolic PDE's appearing in the literature in various physical connections and investigated rigorously by Coleman, Leizarowitz, Marcus, Mizel, Peletier, Troy, Zaslavskii, and others. The former example reduces to the real Ginzburg-Landau equation when ρ = 0 . The most complete results, including threshold results for the appearance of globally minimizing patterns and many other properties of the patterns themselves, are given for complex-valued solutions in one space variable. A complete linear stability analysis for all such sinusoidal solutions is also given; it extends the set of stable solutions considerably beyond the global minimizers. Other results, including threshold results and the existence of large amplitude patterns as well as of bifurcating solutions, are provided for real-valued solutions; these results are relatively independent of the number of space variables. Finally, a slightly different class of evolution equations is given for which no patterned global minimizer exists, but a sequence of patterned solutions exist whose instabilities (if they are unstable) become ever weaker and the fineness of the oscillation becomes ever more pronounced. Received March 2, 1998; revised January 5, 1999; accepted March 16, 1999     

Interactions of molecules with nucleic acids. VII. Evaluation and presentation of steric contours and molecules in bonding sites

A technique to generate steric contours is developed and applied to the presentation of molecules that interact with DNA. The contours are generated by a Taylor's expansion in an extrapolation procedure designed to avoid infinite derivatives and correct for reversal in the direction of the drawing of the curve. A solution to the hidden line problem in computer graphics is presented for the case of steric contours ordered in parallel planes. The techniques developed in this article are demonstrated with stereographic orthographic projections for B-DNA, for intercalation complexes of lucanthone and actinomycin-D with DNA, and for the binding of benzo[a]pyrene diol epoxides (BPDEs) to guanine. The latter example illustrates the value of steric contours in demonstrating the lack of fit of BPDEs to B-DNA and by the need to unwind DNA to accommodate this molecule. Electrostatic contours in planes may be generated by this same procedure.     

Focusing of a shock wave in a rarefied gas A numerical study

The process of focusing of a shock wave in a rarefied noble gas is investigated by a numerical solution of the corresponding two dimensional initial–boundary value problem for the Boltzmann equation. The numerical method is based on the splitting algorithm in which the collision integral is computed by a Monte Carlo quadrature, and the free flow equation is solved by a finite volume method. We analyse the development of the shock wave which reflects from a suitably shaped reflector, and we study influence of various factors, involved in the mathematical model of the problem, on the process of focusing. In particular, we investigate the pressure amplification factor and its dependence on the strength of the shock and on the accommodation coefficient appearing in the Maxwell boundary condition modelling the gas-surface interaction. Moreover, we study the dependence of the shock focusing phenomenon on the shape of the reflector, and on the Mach number of the incoming shock. Received 25 May 1998 / Accepted 4 January 2000