Approximation of the lauricella hypergeometric functionsF D (N) by branched continued fractions

Applying recursion relations for the Lauricella hypergeometric functions F _D ^Nl , we construct an expansion of a ratio of these functions in branched continued fractions. We study the convergence of the resulting expansion in the case of real parameters. Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 39, No. 2, 1996, pp. 70–74.     

A new material for hydrogen storage; ScAl0.8Mg0.2

A novel aluminium rich alloy for hydrogen storage has been discovered, ScAl_0.8Mg_0.2, which has very promising properties regarding hydrogen storage capacity, kinetics and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. The absorption of hydrogen was found to be very fast, even without adding any catalyst, and reversible. The discovered alloy crystallizes in a CsCl-type structure, but decomposes to ScH₂ and Al(Mg) during hydrogen absorption. Detailed analysis of the hydrogen absorption in ScAl_0.8Mg_0.2 has been performed using in situ synchrotron radiation powder X-ray diffraction, neutron powder diffraction and quantum mechanical calculations. The results from theory and experiments are in good agreement with each other.     

Advances in methods and algorithms in a modern quantum chemistry program package

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.     

Structural and dynamical characterization of poly-gamma-glutamic acid-based cross-linked nanoparticles

This work describes the formation of water-soluble hydrophilic nanoparticles from biosynthetic poly-γ-glutamic acid (PGA). Nanoparticles were formed by cross-linking using 2,2′-(ethylenedioxy) diethylamine in the presence of water-soluble carbodiimide. The structure was determined by nuclear magnetic resonance spectroscopy and the particle size by transmission electron microscopy (TEM), size exclusion chromatography (SEC), and dynamic light-scattering (DLS) measurements. The results from TEM, SEC, and DLS reveal that the particle size depends on the ratio of cross-linking. Particle size values measured by TEM were between 20 and 90 nm. Formation of cross-linked nanoparticles results in a dramatic viscosity drop compared to the viscosity of the corresponding solution of the parent PGA. The viscosity and DLS experiments disclose an intriguing interplay between intrachain and interchain cross-linking of the polymer chains, depending on the cross-linker density and polymer concentration. The SEC measurements show that the retention time of the major portion of particles increase because of the higher cross-linking ratio. At moderate cross-linker concentration, intramolecular cross-linking is the dominant process, whereas at higher cross-linker densities, the interpolymer cross-linking plays an important role. As a result, large clusters are also formed.     

Probing the 3d spin momentum with X-ray emission spectroscopy: the case of molecular-spin transitions

We report X-ray emission spectra of Fe(III), Fe(II), and Co(II) spin-crossover compounds in their high-spin and low-spin forms. It is shown that all X-ray emission features are sensitive to the spin state. Variations of the Kbeta and the Kalpha emission line shapes, which are in agreement with theory, can be used as quantitative probes of the spin state; it is suggested that with appropriate reference experiments one can extract the spin momentum for a general case. Resonant X-ray emission spectra unveil details of the redistribution of electrons on the 3d levels associated with the spin-state change by revealing features at the X-ray absorption preedge not accessible through standard absorption measurements.     

Thermal degradation of wood during photodegradation

In this study, wood samples were exposed to light irradiations (direct sunlight, xenon lamp, mercury vapour lamp) and thermal treatments were carried out in dry- and in humid conditions at 90°C. One part of the samples was covered by an aluminium plate during light irradiation. The samples under the aluminium plate also suffered considerable chemical changes, monitored by infrared technique and colour measurement. The sunlight produced greater colour change under the aluminium plate than the artificial light sources. During light irradiation, the carbonyl band having two maximum at 1700 and 1,746 cm(-1) increased and the peak of the aromatic skeletal vibration arising from lignin (1,510 cm(-1)) decreased together with the guaiacyl vibrations at 1,275 cm(-1). There was absorption decrease at 1,174 cm(-1) because of the ether band splitting. Under the covered surface only the ether band at 1,174 cm(-1) decreased and one carbonyl band increased with a maximum at 1,715 cm(-1). Degradation of lignin was negligible for the covered surface. Colour change generated by thermal degradation was much greater in humid condition than in dry condition.