Coordination compounds of 2-mercapto-1-methylimidazole with platinum(II), palladium(II), rhodium(III) and ruthenium(III)

Summary Complexes of 2-mercapto-1-methylimidazole (TMZ) with Pt^II, Pd^II, Rh^III and Ru^III of the general formulae Pt(TMZ)₂Cl₂, Pd(TMZ)₄Cl₂. Rh(TMZ)Cl₃ and Ru(TMZ)Cl₃ have been obtained. The thermal stabilities of the compounds were estimated by derivatographic measurements and the electron-donating atom of the measurements and the electron-donating atom of the ligand was identified from the i.r. absorbtion spectra. Lattice constants for the Pt^II and Pd^II complexes were estimated from their x-ray powder diffraction patterns.     

Lower bounds on the minimum average distance of binary codes

Let β(n,M) denote the minimum average Hamming distance of a binary code of length n and cardinality M. In this paper we consider lower bounds on β(n,M). All the known lower bounds on β(n,M) are useful when M is at least of size about 2ⁿ⁻¹/n. We derive new lower bounds which give good estimations when size of M is about n. These bounds are obtained using a linear programming approach. In particular, it is proved that lim_n→∞β(n,2n)=5/2. We also give a new recursive inequality for β(n,M).     

The influence of the size and position of the alkyl groups in alkylimidazole molecules on their acid‐base properties

Dissociation constants of HL⁺ acids, where L stands for 1‐alkylimidazole, 1‐alkyl‐2‐methylimidazole, 1‐alkyl‐2‐ethylimidazole, 1‐alkyl‐2‐propylimidazole, 1‐alkyl‐4‐methylimidazole and 1‐alkyl‐2‐ethyl‐4‐methylimidazole, were determined potentiometrically. For each of the homologous series of these bases, a relationship has been derived between the pK_a value and the number of carbon atoms in the hydrocarbon group for (CH₂)_n ≤ 13. The basicity of the alkylimidazoles has been found to increase linearly with increasing carbon chain length. The slopes of straight plots of pK_a = f(n_CH2) have been found to increase with increasing basicity of homologous series of the alkylimidazoles.     

On the Jacobian Newton polygon of plane curve singularities

We investigate the Jacobian Newton polygon of plane curve singularities. This invariant was introduced by Teissier in the more general context of hypersurfaces. The Jacobian Newton polygon determines the topological type of a branch (Merle’s result) but not of an arbitrary reduced curve (Eggers example). Our main result states that the Jacobian Newton Polygon determines the topological type of a non-degenerate unitangent singularity. The Milnor number, the Łojasiewicz exponent, the Hironaka exponent of maximal contact and the number of tangents are examples of invariants that can be calculated by means of the Jacobian Newton polygon. We show that the number of branches and the Newton number defined by Oka do not have this property. Dedicated to Professor Arkadiusz Płoski on his 60th birthday     

Hypercontractivity of Solutions to Hamilton-Jacobi Equations

We show that solutions to some Hamilton-Jacobi Equations associated to the problem of optimal control of stochastic semilinear equations enjoy the hypercontractivity property.     

PROTEIN GLOBULE SPEEDS UP THE HEME PHOTOREDUCTION

Abstract— To answer the question whether the external electron can be transferred through the protein globule, the rate of photoreduction of the free heme with dye radicals was compared with that of the heme in various protein environments, in cytochrome c, myoglobin and in heme-HSA complex. In all cases the globular part of proteins did not prevent the photoreduction of the heme; in fact, it speeded up the process. As determined by flash-photolysis, the rate constants(1–5) x 10⁸ M^-1 s^-1 are close to that of the diffusion controlled reactions between molecules of similar size. The experimental data confirm the hypothesis that the native protein globule can transfer external unpaired electrons rather effectively. We make the supposition that this ability is a general feature of proteins but not a function related to electron carriers only.     

Some properties of invariant measures of non symmetric dissipative stochastic systems

 We consider transition semigroups generated by stochastic partial differential equations with dissipative nonlinear terms. We prove an integration by part formula and a Logarithmic Sobolev inequality for the invariant measure. No symmetry or reversibility assumptions are made. Furthemore we prove some compactness results on the transition semigroup and on the embedding of the Sobolev spaces based on the invariant measure. We use these results to derive asymptotic properties for a stochastic reaction–diffusion equation. Received: 29 September 2000 / Revised version: 30 May 2001 / Published online: 14 June 2002     

OXIDATION OF WATER WITH PHOTOCATALYST—I. REDUCTION OF ELECTRON ACCEPTORS IN WATER SOLUTION WITHOUT ADDITIONAL ELECTRON DONORS

Photoreduction of electron acceptors—myoglobin, hemin and methyl viologen—sensitized by eosin or methylene blue in water solution was studied. The rate of photoreduction of acceptors grows with increasing pH. At pH 9.0 quantum yield of myoglobin reduction reached 1.5%, whereas the efficiency of the low molecular weight acceptors—hemin and methyl viologen—was much lower. Control experiments demonstrated that buffer molecules and the protein moiety were not the source of electrons for the reduction. All the data support the conclusion that in the process under the study hydroxide ions of water appear to be the linal electron donors.     

Body centered cubic magnesium niobium hydride with facile room temperature absorption and four weight percent reversible capacity

We have synthesized a new metastable metal hydride with promising hydrogen storage properties. Body centered cubic (bcc) magnesium niobium hydride (Mg(0.75)Nb(0.25))H(2) possesses 4.5 wt% hydrogen gravimetric density, with 4 wt% being reversible. Volumetric hydrogen absorption measurements yield an enthalpy of hydride formation of -53 kJ mol(-1) H(2), which indicates a significant thermodynamic destabilization relative to the baseline -77 kJ mol(-1) H(2) for rutile MgH(2). The hydrogenation cycling kinetics are remarkable. At room temperature and 1 bar hydrogen it takes 30 minutes to absorb a 1.5 μm thick film at sorption cycle 1, and 1 minute at cycle 5. Reversible desorption is achieved in about 60 minutes at 175 °C. Using ab initio calculations we have examined the thermodynamic stability of metallic alloys with hexagonal close packed (hcp) versus bcc crystal structure. Moreover we have analyzed the formation energies of the alloy hydrides that are bcc, rutile or fluorite.