Finite volume evolution Galerkin method for hyperbolic conservation laws with spatially varying flux functions

We present a generalization of the finite volume evolution Galerkin scheme [M. Lukacova-Medvid'ova,J. Saibertov'a, G. Warnecke, Finite volume evolution Galerkin methods for nonlinear hyperbolic systems, J. Comp. Phys. (2002) 183 533-562; M. Luacova-Medvid'ova, K.W. Morton, G. Warnecke, Finite volume evolution Galerkin (FVEG) methods for hyperbolic problems, SIAM J. Sci. Comput. (2004) 26 1-30] for hyperbolic systems with spatially varying flux functions. Our goal is to develop a genuinely multi-dimensional numerical scheme for wave propagation problems in a heterogeneous media. We illustrate our methodology for acoustic waves in a heterogeneous medium but the results can be generalized to more complex systems. The finite volume evolution Galerkin (FVEG) method is a predictor-corrector method combining the finite volume corrector step with the evolutionary predictor step. In order to evolve fluxes along the cell interfaces we use multi-dimensional approximate evolution operator. The latter is constructed using the theory of bicharacteristics under the assumption of spatially dependent wave speeds. To approximate heterogeneous medium a staggered grid approach is used. Several numerical experiments for wave propagation with continuous as well as discontinuous wave speeds confirm the robustness and reliability of the new FVEG scheme.

Tyrosine kinases and calcium dependent activation of endothelial cell phospholipase D by diperoxovanadate

Reactive oxygen species (ROS) mediated modulation of signal transduction pathways represent an important mechanism of cell injury and barrier dysfunction leading to the development of vascular disorders. Towards understanding the role of ROS in vascular dysfunction, we investigated the effect of diperoxovanadate (DPV), derived from mixing hydrogen peroxide and vanadate, on the activation of phospholipase D (PLD) in bovine pulmonary artery endothelial cells (BPAECs). Addition of DPV to BPAECs in the presence of .05% butanol resulted in an accumulation of [P-32] phosphatidylbutanol (PBt) in a dose- and time-dependent manner. DPV also caused an increase in tyrosine phosphorylation of several protein bands (Mr 20-200 kD), as determined by Western blot analysis with antiphosphotyrosine antibodies. The DPV-induced [P-32] PBt-accumulation was inhibited by putative tyrosine kinase inhibitors such as genistein, herbimycin, tyrphostin and by chelation of Ca2+ with either EGTA or BAPTA, however, pretreatment of BPAECs with the inhibitor PKC bisindolylmaleimide showed minimal inhibition. Also down-regulation of PKC alpha and epsilon, the major isotypes of PKC in BPAECs, by TPA (100 nM, 18 h) did not attenuate the DPV-induced PLD activation. The effects of putative tyrosine kinase and PKC inhibitors were specific as determined by comparing [P-32] PBt formation between DPV and TPA. In addition to tyrosine kinase inhibitors, antioxidants such as N-acetylcysteine and pyrrolidine dithiocarbamate also attenuated DPV-induced protein tyrosine phosphorylation and PLD stimulation. These results suggest that oxidation, prevented by reduction with thiol compounds, is involved in DPV-dependent protein tyrosine phosphorylation and PLD activation.

Hydrogen and fluorine in crystal engineering: systematics from crystallographic studies of hydrogen bonded tartrate-amine complexes and fluoro-substituted coumarins, styrylcoumarins and butadienes

Three aspects of crystal engineering in molecular crystals are presented to emphasize the role of intermolecular interactions and factors influencing crystal packing. Hydrogen bonded tartrate-amine complexes have been analyzed with the propensity for formation of multidirectional hydrogen bonding as a key design element in the generation of materials for second harmonic generation (SHG). The invariance of the framework in DBT and its possible implications on SHG is outlined. The role of Fluorine in orienting molecules of coumarins, styrylcoumarins and butadienes for photodimerization is described with particular emphasis on its steering capability. Usage of coumarin as an design element for the generation of polymorphs of substituted styrylcoumarins is examined with specific examples.

Structure of tri-1-naphthylborane-benzene (1/1) complex, c30h21b.c6h6

M r= 470.46, rhombohedral, R3, a =8.710(4)A, a=91.10(3) o, V= 660.4 (9) A 3, Z= 1,D m= 1.170 (flotation in KI solution), D x=1.183 Mg m -a, Mo Kct, 2 = 0.7107/~,, /t =0.033 mm -1, F(000) - 248.0, T= 293 K, R -- 4.6%(481 unique reflections). The molecule has C a symmetry and is propeller shaped, the angle of twist about the B-C bond being 41.5 (7) °. The space group being chiral, this is yet another example of spontaneous resolution. The results of a thermal-motion analysis are discussed.

Fluidity, Permeability And Antioxidant Behavior Of Model Membranes Incorporated With Alpha-Tocopherol And Vitamin-E Acetate

Magnetic resonance studies reveal a marked difference between the binding of α-tocopherol and that of the corresponding acetate (vitamin E acetate) with dipalmitoylphosphatidylcholine (DPPC) vesicles. This is reflected in differences in the phase-transition curves of the DPPC vesicles incorporated with the two compounds, as well as in the 13C relaxation times and line widths. A model for the incorporation of these molecules in lipid bilayers has been suggested. α-Tocopherol binds strongly with the lipids, possibly through a hydrogen bond formation between the hydroxyl group of the former and one of the oxygen atoms of the latter. The possibility of such a hydrogen bond formation is excluded in vitamin E acetate, which binds loosely through the normal hydrophobic interaction. The model for lipid-vitamin interaction explains the in vitro decomposition of H2O2 by α-tocopherol. α-Tocopherol in conjuction with H2O2 can also act as a free-radical scavenger in the lipid phase. The incorporation of α-tocopherol and vitamin E acetate in DPPC vesicles enhances the permeability of lipid bilayers for small molecules such as sodium ascorbate.

Isolation and characterization of binding proteins for retinol from the cytosol, nucleosol and chromatin of the oviduct magnum of laying hens

Protein fractions that bind retinol were isolated from the cytosol, nucleosol and chromatin of the oviduct magnum of laying hens. The proteins isolated from the three sources showed similar elution profiles on chromatography through Sephadex G-75 and G-50 columns, and comparable mobility during electrophoresis on sodium dodecyl sulphate/polyacrylamide gels. Their molecular weights were calculated to be around 14500. When oviducts from vitamin A-depleted and vitamin A-repleted immature chicks given oestrogen injections for 6 consecutive days were incubated with [3H]retinyl acetate, uptake of the radioactivity in the nuclei of the vitamin A-depleted tissue was severalfold higher than that in the nuclei from the vitamin A-repleted tissue.

Sequence-dependent conformation of an A-DNA double helix: The crystal structure of the octamer d(G-G-T-A-T-A-C-C)

The crystal structures of the synthetic self-complementary octamer d(G-G-T-A-T-A-C-C) and its 5-bromouracil-containing analogue have been refined to R values of 20% and 14% at resolutions of 1·8 and 2·25 Å, respectively. The molecules adopt an A-DNA type double-helical conformation, which is minimally affected by crystal forces. A detailed analysis of the structure shows a considerable influence of the nucleotide sequence on the base-pair stacking patterns. In particular, the electrostatic stacking interactions between adjacent guanine and thymine bases produce symmetric bending of the double helix and a major-groove widening. The sugar-phosphate backbone appears to be only slightly affected by the base sequence. The local variations in the base-pair orientation are brought about by correlated adjustments in the backbone torsion angles and the glycosidic orientation. Sequence-dependent conformational variations of the type observed here may contribute to the specificity of certain protein-DNA interactions.

Resolution of racemic gossypol and interaction of individual enantiomers with serum albumins and model peptides

Racemic gossypol has been resolved by HPLC separation of diastereomeric (−) norepinephrine adducts on a reverse-phase column. The binding constants for the interaction of the three gossypol forms (+, − and −) with human and bovine serum albumins have been determined by fluoresence quenching studies. The KD values demonstrate that all three forms bind equally effectively to the two proteins, suggesting an absence of chiral discrimination in albumin-gossypol interactions. Circular dichroism studies of (+)-gossypol binding to the model dibasic peptides, Boc-Lys-Pro-Aib-Lys-NHMe and gramicidin S, suggesting that distortions of binaphthyl geometry may occur only for specific orientations of interacting residues at the receptor site.

Supersymmetric Solution Of Gauge Hierarchy Problem

Some recent developments with respect to the resolution of the gauge hierarchy problem in grand unified theories by supersymmetry are presented. A general argument is developed to show how global supersymmetry maintains the stability of the different mass-scales under perturbative effects.

Switching transients in ferroelectric dicalcium strontium propionate (DSP) and azoxybenzene

The switching transients in dicalcium strontium propionate and azoxybenzene were studied by the use of the Merz method. It was observed that the switching time depends linearly on the applied electric field. Under similar electric fields, the switching processes in DSP and azoxybenzene are slower than in triglycine sulphate (TGS) at 27°C.

Indole oxygenase from the leaves of Tecoma stans

A new indole oxygenase from the leaves of Tecoma stans was isolated and purified to near homogeneity. The purified enzyme system catalyses the conversion of indole to anthranilic acid. It is optimally active at pH 5.2 and at 30°C. Oxygen (2 mol) is consumed and anthranilic acid (1 mol) is formed for every mole of indole oxidized. Neither sulfhydryl reagents nor sulfhydryl compounds inhibited the enzyme activity. The oxygenase also attacks, apart from indole, 5-hydroxyindole, 5-bromoindole and 5-methylindole. It is not inhibited by copper specific chelators or non-heme iron specific chelators. Atebrin did not inhibit the enzyme activity suggesting that it is not a flavoprotein, unlike other indole oxygenases and indole oxidases. Dialysis resulted in complete loss of enzyme activity. The inactive enzyme could not be reactivated by addition of various cofactors.

Molecular analysis of inorganic nitrogen assimilation in yeasts

Assimilation of nitrate and various other inorganic nitrogen compounds by different yeasts was investigated. Nitrate, nitrite, hydroxylamine, hydrazine, ammonium sulphate, urea and L-asparagine were tested as sole sources of nitrogen for the growth of Candida albicans, C. pelliculosa, Debaryomyces hansenii, Saccharomyces cerevisiae, C. tropicalis, and C. utilis. Ammonium sulphate and L-asparagine supported the growth of all the yeasts tested except D. hansenii while hydroxylamine and hydrazine failed to support the growth of any. Nitrate and nitrite were assimilated only by C. utilis. Nitrate utilization by C. utilis was also accompanied by the enzymatic activities of NAD(P)H: nitrate oxidoreductase (EC 1.6.6.2) and NAD(P)H: nitrite oxidoreductase (EC 1.6.6.4), but not reduced methyl viologen-or FAD-nitrate oxidoreductases (EC 1.7.99.4). It is demonstrated here that nitrate and nitrite reductase activities are responsible for the ability of C. utilis to assimilate primary nitrogen.

Ultrasonic velocities and thermal expansion coefficients of amorphous Se80Te20 and Se90Te10 alloys near glass transitions

Precise measurements of the ultrasonic velocities and thermal expansivities of amorphous Se80Te20 and Se90Te10 alloys are reported near the glass transition. The samples are produced by liquid quenching. The longitudinal and transverse velocities are measured at 10 MHz frequency using the McSkimin pulse superposition technique. The thermal expansivities,agr, are measured using a three-terminal capacitance bridge. Theagr-values show a sharp maximum near the glass transition temperature,T g. The ultrasonic velocities also show a large temperature derivative, dV/dT nearT g. The data are discussed in terms of existing theories of the glass transition. The continuous change inagr shows that the glass transition is not a first-order transition, as suggested by some theories. The samples are found to be deformed by small loads nearT g. The ultrasonic velocities and dV/dT have contributions arising from this deformation.

Multiaction learning automata possessing ergodicity of the mean

Multiaction learning automata which update their action probabilities on the basis of the responses they get from an environment are considered in this paper. The automata update the probabilities according to whether the environment responds with a reward or a penalty. Learning automata are said to possess ergodicity of the mean if the mean action probability is the state probability (or unconditional probability) of an ergodic Markov chain. In an earlier paper [11] we considered the problem of a two-action learning automaton being ergodic in the mean (EM). The family of such automata was characterized completely by proving the necessary and sufficient conditions for automata to be EM. In this paper, we generalize the results of [11] and obtain necessary and sufficient conditions for the multiaction learning automaton to be EM. These conditions involve two families of probability updating functions. It is shown that for the automaton to be EM the two families must be linearly dependent. The vector defining the linear dependence is the only vector parameter which controls the rate of convergence of the automaton. Further, the technique for reducing the variance of the limiting distribution is discussed. Just as in the two-action case, it is shown that the set of absolutely expedient schemes and the set of schemes which possess ergodicity of the mean are mutually disjoint.

The Crystal Structure of Pivaloyl- D- prolyl-L- prolyl- L-alanyl-N- methylamide

Pivaloyl-D-prolyl-L-prolyl-L-analyl-N-methylam~de (I), C1UH32N40c4r,y stallizes in the orthorhombic space group P21212,w ith four molecules in a unit cell of dimensions a = 9.982 (l),b = 10.183 (3), c = 20.746 (2)A . The structure has been refined to R 0.048 for 1 745 observed reflections. All the peptide bonds in the molecule are trans and both the prolyl residues are in the CY-exo-conformation. The molecule assumes a highly folded conformation in which a Type II' DL bend is followed by a Type I LL bend, both stabilised by intramolecular 4 + 1 hydrogen bonds. This conformation, which has been observed for the first time, is of interest in relation to the structure of gramicidin S.