The strengthened C.B.S. inequality constant for second order elliptic partial differential operator and for hierarchical bilinear finite element functions

We estimate the constant in the strengthened Cauchy-Bunyakowski-Schwarz inequality for hierarchical bilinear finite element spaces and elliptic partial differential equations with coefficients corresponding to anisotropy (orthotropy). It is shown that there is a nontrivial universal estimate, which does not depend on anisotropy. Moreover, this estimate is sharp and the same as for hierarchical linear finite element spaces.This research was supported by the Grant Agency of Czech Republic under the contract No. 201/02/0595.     

Spironolactone and its Complexes with β-cyclodextrin: Modern NMR Characterization and Structural DFTB-SCC Calculations

In the present work, inclusion complexes of spironolactone (SP) with β-cyclodextrin (β-CD) in solid phase and aqueous solution were studied by solubility methods, NMR spectroscopy and thermal analysis. The results showed different kinds of complexations when freeze-drying and kneading methods were used. The freeze-drying product (1:1, SP:β-CD) showed lower degree of complexation and stability than the (1:2, SP:β-CD) compound obtained by kneading method. The spironolactone molecule was also studied by NMR spectroscopy at 400 MHz. The chemical shifts of all spironolactone atoms and their inclusion compounds were assigned. Extensive use of 1D and 2D NMR techniques, including ROESY experiment, allowed verifying the position of the spironolactone molecule inside the cyclodextrin cavity in both situations. In addition, DFTB-SCC quantum mechanical calculations of the inclusion compounds were performed. The predicted structural properties are in good agreement with ROESY NMR results.     

Crystallographic report: The crystal structure of bis(η5‐cyclopentadienyl)‐ diazido‐vanadium(IV)

The crystal structure of the cyclopentadienyl vanadocene complex (η⁵‐C₅H₅)₂V(N₃)₂ was determined. The molecule has a typical bent metallocene structure in which two η⁵‐bonded cyclopentadienyl rings and two nitrogen atoms of azide ligands occupy the pseudotetrahedral coordination sites around the vanadium(IV) center. Copyright © 2005 John Wiley & Sons, Ltd.     

Generalization of the stabilization method for green functions and quantum resonances

The stabilization method provides an efficient approach to many problems in atomic and molecular dynamics. Real avoided crossings and smoothing techniques provide the relevant information to compute real density of states. The aim of this letter is to present an extension of the stabilization method that allows for a direct determination of full Green functions and resonance energies. The method is based on the use of optical potentials and perturbation theory. Real avoided crossings of the original stabilization method become complex and resonance energies appear to stabilize in the complex-energy plane. A numerical illustration is presented for a simple model of shape resonance. Accurate results are obtained with a small number of real square-integrable functions as in the original stabilization method. The computational efficiency of the approach and its generality are emphasized.     

Crystallographic report: Bis(η5‐methyl‐cyclopentadienyl)‐bis(cyanato)‐vanadium(IV)

The crystal structure of the first cyclopentadienyl vanadium(IV) pseudohalide complex, (η⁵‐C₅H₄CH₃)₂V(NCO)₂, was determined. The molecule has a typical bent metallocene structure in which two η⁵‐bonded methyl‐cyclopentadienyl rings and two nitrogen atoms of cyanato ligands occupy the pseudotetrahedral coordination sites around the vanadium(IV) center. Copyright © 2005 John Wiley & Sons, Ltd.     

History dependent structural properties of alumina-supported nickel oxide

The formation of nickel oxide from Ni–Al takovite-like compounds has been investigated. Information about the stoichiometry of the NiO phase obtained by Diffuse Reflectance (DR) spectroscopy is discussed in connection with TPR and solubility data.     

Nanoporous Network Channels from Self‐Assembled Triblock Copolymer Supramolecules

Supramolecular complexes of a poly(tert‐butoxystyrene)‐block‐polystyrene‐block‐poly(4‐vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self‐assemble into a core–shell gyroid morphology with the core channels formed by the hydrogen‐bonded P4VP(PDP)complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well‐ordered nanoporous films that were used as templates for nickel plating.

     

Solution phase synthesis of a library of tetrasubstituted pyrrole amides

An efficient strategy for the solution-phase parallel synthesis of a library of pyrrole-amides is described. Key reactions include functional homologation of beta-ketoesters with a set of aldehydes followed by oxidation to produce a series of differently substituted 1,4-dicarbonyl compounds. Rapid cyclization using a microwave-assisted Paal-Knorr reaction provided a set of 24 pyrrole esters that were further functionalized through a trimethylaluminum-mediated aminolysis to obtain a larger library of 288 diverse pyrrole-3-amides. The tetrasubstitution allows a good exploration of the chemical space around the central pyrrole core. The last step was entirely automated with a Bohdan Myriad personal synthesizer.     

Electrochemical behavior of phytochelatins and related peptides at the hanging mercury drop electrode in the presence of cobalt(II) ions

Direct current voltammetry and differential pulse voltammetry have been used to investigate the electrochemical behaviour of two phytochelatins: heptapeptide (gamma-Glu-Cys)3-Gly and pentapeptide (gamma-Glu-Cys)2-Gly, tripeptide glutathione gamma-Glu-Cys-Gly and its fragments: dipeptides Cys-Gly and gamma-Glu-Cys at the hanging mercury drop electrode in the presence of cobalt(II) ions. Most interesting results were obtained with direct current voltammetry in the potential region of -0.80 V up to -1.80 V. Differential pulse voltammetry of the same solutions of Co(II) with peptides gives more complicated voltammograms with overlapping peaks, probably in connection with the influence of adsorption at slow scan rates necessarily used in this method. However, in using Brdicka catalytic currents for analytical purposes, differential pulse voltammograms seem to be more helpful. Presented investigations have shown that particularly the prewave of cobalt(II) allows distinguishing among phytochelatins, glutathione, and its fragments.     

Methanol-water mixtures: a microsolvation study using the effective fragment potential method

The formation process of methanol-water mixtures, (MeOH/H2O)n, n = 2, 3,..., 8 is studied at the molecular level using the general effective fragment potential (EFP2) method and second-order perturbation theory (MP2). Extensive Monte Carlo/simulated annealing global optimizations were used to locate global minimum structures for each n, for both homo and hetero clusters. Mixing at the microscopic level was investigated, and some general conclusions about the microsolvation behavior of these mixtures are presented. For all of these clusters, incomplete mixing is observed at the molecular level. Low-energy (MeOH/H2O)n clusters retain much of their initial structure in the global minima of the mixed clusters.