An investigation of the reliability of the Galerkin-Petrov method

It is shown that the Galerkin-Petrov method if applied in a controlled way yields reliable results for excited states of the same symmetry classifications as the ground state. Computations are performed for the 2¹ S and 3¹ S states of He. The problem of optimizing nonlinear parameters of the basis functions by means of the GP method is discussed. A special optimization scheme is suggested and numerically illustrated for someS states of He.     

Relativistic perturbation theory of molecular structure

Summary The recently developed relativistic double perturbation theory is extended to handle relativistic changes of molecular structure more easily. This is achieved by simple coordinate scalings. Accurate higher order mixed perturbation energies for H ₂ ⁺ are calculated. The relativistic changes of bond energy,DE, of bond length,R _e , and especially of force constant,k, and of anharmonicity,a, are large, up to 100%·(Z/c)². The dominant contributions tok anda are due to the indirect change of the nonrelativistick anda connected with the relativistic change of bond length. Accordingly the relativistic changes obey Badger's and Gordy's rules (–RDEk).Dedicated to Prof. Klaus Ruedenberg in appreciation of his fundamental contributions to both formal theory and physical explanations in quantum chemistry     

A Rapidly Reversible Chemical Dimerizer System to Study Lipid Signaling in Living Cells

Chemical dimerizers are powerful tools for non‐invasive manipulation of enzyme activities in intact cells. Here we introduce the first rapidly reversible small‐molecule‐based dimerization system and demonstrate a sufficiently fast switch‐off to determine kinetics of lipid metabolizing enzymes in living cells. We applied this new method to induce and stop phosphatidylinositol 3‐kinase (PI3K) activity, allowing us to quantitatively measure the turnover of phosphatidylinositol 3,4,5‐trisphosphate (PIP₃) and its downstream effectors by confocal fluorescence microscopy as well as standard biochemical methods.     

Hexagonal nanorods of tungsten trioxide: Synthesis, structure, electrochemical properties and activity as supporting material in electrocatalysis

Tungsten trioxide, unhydrated with hexagonal structure (h-WO₃), has been prepared by hydrothermal method at a temperature of 180 °C in acidified sodium tungstate solution. Thus prepared h-WO₃ has been characterized by X-ray diffraction (XRD) method and using electrochemical techniques. The morphology has been examined by scanning and transmission electron microscopies (SEM and TEM) and it is consistent with existence of nanorods of 50-70 nm diameter and up to 5 μm length. Cyclic voltammetric characterization of thin films of h-WO₃ nanorods has revealed reversible redox behaviour with charge-discharge cycling corresponding to the reversible lithium intercalation/deintercalation into the crystal lattice of the h-WO₃ nanorods. In propylene carbonate containing LiClO₄, two successive redox processes of hexagonal WO₃ nanorods are observed at the scan rate of 50 mV/s. Such behaviour shall be attributed to the presence of at least two W atoms of different surroundings in the lattice structure of h-WO₃ nanorods. On the other hand, in aqueous LiClO₄ solution, only one redox process is observed at the scan rate of 10 mV/s. The above observations can be explained in terms of differences in the diffusion of ions inside two types of channel cavities existing in the structure of the h-WO₃ nanorods. Moreover, the material can be applied as active support for the catalytic bi-metallic Pt-Ru nanoparticles during electrooxidation of ethanol in acid medium (0.5 mol dm⁻³ H₂SO₄).     

Rotating ring-disk voltammetry: Diagnosis of catalytic activity of metallic copper catalysts toward CO<Subscript>2</Subscript> electroreduction

Using the rotating ring (platinum)—disk (glassy carbon) electrode methodology, electrocatalytic activity of the microstructured copper centers (imbedded within the polyvinylpyrrolidone polymer matrix and deposited onto the glassy carbon disk electrode) has been monitored during electroreduction of carbon dioxide both in acid (HClO₄) and neutral (KHCO₃) media as well as diagnosed (at Pt ring) with respect to formation of the electroactive products. Combination of the stripping-type and rotating ring-disk voltammetric approaches has led to the observation that, regardless the overlapping reduction phenomena, the reduction of carbon dioxide at copper catalyst is, indeed, operative and coexists with hydrogen evolution reaction. Using the fundamental concepts of surface electrochemistry and analytical voltammetry, the reaction products (thrown onto the platinum ring electrode) could be considered and identified as adsorbates (on Pt) under conditions of the stripping-type oxidation experiment. Judging from the potentials at which the stripping voltammetric peaks appear in neutral CO₂-saturated KHCO₃ (pH 6.8), formic acid or carbon monoxide seem to be the most likely reaction products or intermediates. The proposed methodology also permits correlation between the CO₂ electroreduction products and the potentials applied to the disk electrode. By performing the comparative stripping-type voltammetric experiments in acid medium (HClO₄ at pH 1) with the adsorbates of formic acid, ethanol and acetaldehyde (on Pt ring), it can be rationalized that, although C₂H₅OH or CH₃CHO are very likely CO₂-reduction electroactive products, formation of some HCOOH, CH₃OH or even CO cannot be excluded.     

Accuracy of first-order wavefunctions for ten-electron atomic systems

It is demonstrated that for Ne-like systems, the zeroth-plus-first-order wavefunctions, obtained within Rayleigh—Schrödinger perturbation theory based on H₀ = H_HF, are of the same accuracy as variational wavefunctions obtained in CI calculations using very extensive sets of singly and doubly excited configurations. Variational correlation energies for Na⁺, Mg²⁺ and Ar⁸⁺ are reported for the first time.     

Correction to: Foreword to the memorial issue for Professor Roberto Marassi

Journal of Solid State Electrochemistry -     

The influence of chemical structure on thermal properties and surface morphology of polyurethane materials

The surface morphology and thermal properties of polyurethanes can be correlated to their chemical composition. The hydrophilicity, surface morphology, and thermal properties of polyurethanes (differed in soft segments and in linear/cross-linked structure) were investigated. The influence of poly([R,S]-3-hydroxybutyrate) presence in soft segments and blending of polyurethane with polylactide on surface topography were also estimated. The linear polyurethanes (partially crystalline) had the granular surface, whereas the surface of cross-linked polyurethanes (almost amorphous) was smooth. Round aggregates of polylactide un-uniformly distributed in matrix of polyurethane were clearly visible. It was concluded that some modification of soft segment (by mixing of poly([R,S]-3-hydroxybutyrate) with different polydiols and polytriol) and blending of polyurethanes with small amount of polylactide influence on crystallinity and surface topography of obtained polyurethanes.