Plasma,gravitation, and force-free geometries

We show that it is possible, by a suitable choice of metrics and connections, to construct for a wide class of relativistic equations of motion a geometry wherein the interacting particles become free of nongravitational forces and move on autoparallels. Some examples prove the consistency of this extended geodesic principle.     

Determination of Sodium Diethyldithiocarbamate in Water by Anodic Voltammetry Using a Boron‐Doped Diamond Electrode

An electrochemical study was made of the anodic behavior of sodium diethyldithiocarbamate (DEDTC) using a boron‐doped diamond electrode (BDDE) in sodium sulfate supporting electrolyte. This paper presents a new alternative for the electroanalytical determination of DEDTC in protic media, using cyclic voltammetry or chronoamperometry. Linear plots of current vs. concentration correlated with anodic stepwise oxidation were obtained in delimited potential ranges with very good correlation coefficients.     

First observation of 55, 56Zn

In an experiment at the SISSI/LISE3 facility of GANIL, the most proton-rich zinc isotopes ^55,56Zn have been observed for the first time. The experiment was performed using a high-intensity ⁵⁸Ni beam at 74.5 MeV/nucleon impinging on a nickel target. The identification of ^55,56Zn opens the way to ⁵⁴Zn, a good candidate for two-proton radioactivity according to theoretical predictions. Received: 31 October 2000 / Accepted: 9 November 2000     

On the phenomena occurring at the interface between iron and iron–platinum thin films

FePt films were rf sputtered at room temperature and 550?C on MgO monocrystalline substrates. Room temperature films were post-annealed at 550?C. The high temperature growth induces a tetragonal distortion of the structure with the formation of L1₀-FePt phase. Soft iron layers, with different thickness, were e-beam deposited on these hard films. The phenomena occurring at the interface have been analysed and connected with the final magnetic behaviour of the system. It has been found that a strong exchange coupling between soft and hard layers has been established through the formation of an interfacial layer constituted by FePt small particles.     

Hypercoordinated diorganoantimony(III) compounds of types [2-(Me2NCH2)C6H4]2SbL and [PhCH2N(CH2C6H4)2]SbL (L = Cl,ONO2, OSO2CF3). Synthesis,structure and catalytic behaviour in the Henry reaction

The compounds [2-(Me₂NCH₂)C₆H₄]₂SbL (L = ONO₂ ( 2 ), OSO₂CF₃ ( 3 )) and [PhCH₂N(CH₂C₆H₄)₂]SbL (L = ONO₂ ( 5 ), OSO₂CF₃ ( 6 )) were prepared by reacting [2-(Me₂NCH₂)C₆H₄]₂SbCl ( 1 ) and [PhCH₂N(CH₂C₆H₄)₂]SbCl ( 4 ), respectively, with the appropriate silver(I) salt in a 1:1 molar ratio. The new species 2 – 6 were structurally characterized in solution using multinuclear NMR and in the solid state using infrared spectroscopy. The solid-state structures for compounds 2 , 4 and 6, as well as for the hydrolysis ionic product [{2-(Me₂N⁺HCH₂)C₆H₄}{2-(Me₂NCH₂)C₆H₄}SbOH][CF₃SO₃]⁻ ( 3h ) were determined using single-crystal X-ray diffraction. Medium to strong intramolecular N→ Sb interactions were observed in all these four compounds, thus resulting in hypercoordinated organoantimony(III) species 14-Sb-6 in 2 and 10-Sb-4 in the cation of 3h and in 4 and 6 . Compounds 1 – 6 and the starting amines PhCH₂NMe₂ and PhCH₂N(CH₂C₆H₄Br-2)₂ were investigated as catalysts in the Henry (nitroaldol) addition of nitromethane to benzaldehyde. The activity of compounds 1 – 6 resulted as an effect of the cooperation of the positively charged antimony with the negatively charged nitrogen.     

On interactive buckling in a sandwich structure

This work revisits an interactive buckling model for sandwich beams proposed relatively recently by Hunt and Wadee (Proc R Soc Lond A 454:1197–1216, 1998). Our asymptotic investigations reveal an interesting resonant behaviour which is shown to lie at the origin of the corresponding localised deformations reported in the literature. The very good agreement between the asymptotic results and various direct numerical simulations reinforces the validity of our theoretical arguments and provides an incentive for further research.     

Modification of the surface adsorption properties of alumina-supported Pd catalysts for the electrocatalytic hydrogenation of phenol

The electrocatalytic hydrogenation (ECH) of phenol has been studied using palladium supported on gamma-alumina (10% Pd-Al2O3) catalysts. The catalyst powders were suspended in aqueous supporting electrolyte solutions containing methanol and short-chain aliphatic acids (acetic acid, propionic acid, or butyric acid) and were dynamically circulated through a reticulated vitreous carbon cathode. The efficiency of the hydrogenation process was measured as a function of the total electrolytic charge and was compared for different types of supporting electrolyte and for various solvent compositions. Our results show that these experimental parameters strongly affect the overall ECH efficiency of phenol. The ECH efficiency and yields vary inversely with the quantity of methanol present in the electrolytic solutions, whereas the presence of aliphatic carboxylic acids increased the ECH efficiency in proportion to the chain length of the specific acids employed. In all cases, ECH efficiency was directly correlated with the adsorption properties of phenol onto the Pd-alumina catalyst in the studied electrolyte solution, as measured independently using dynamic adsorption isotherms. It is shown that the alumina surface binds the aliphatic acids via the carboxylate terminations and transforms the catalyst into an organically functionalized material. Temperature-programmed mass spectrometry analysis and diffuse-reflectance infrared spectroscopy measurements confirm that the organic acids are stably bound to the alumina surface below 200 degrees C, with coverages that are independent of the acid chain length. These reproducibly functionalized alumina surfaces control the adsorption/desorption equilibrium of the target phenol molecules and allow us to prepare new electrocatalytic materials to enhance the efficiency of the ECH process. The in situ grafting of specific aliphatic acids on general purpose Pd-alumina catalysts offers a new and flexible mechanism to control the ECH process to enhance the selectivity, efficiency, and yields according to the properties of the specific target molecule.     

Brownian and fractional Brownian stochastic currents via Malliavin calculus

By using Malliavin calculus and multiple Wiener-Itô integrals, we study the existence and the regularity of stochastic currents defined as Skorohod (divergence) integrals with respect to the Brownian motion and to the fractional Brownian motion. We consider also the multidimensional multiparameter case and we compare the regularity of the current as a distribution in negative Sobolev spaces with its regularity in the Watanabe spaces.