Topological properties of regular generalized function algebras

We investigate density of various subalgebras of regular generalized functions in the special Colombeau algebra of generalized functions.Comment: 6 page

Dihydroxyacetone conversion into lactic acid in an aqueous medium in the presence of metal salts: influence of the ionic thermodynamic equilibrium on the reaction performance

International audienceThe catalytic conversion of dihydroxyacetone (DHA) to lactic acid (LA) via pyruvaldehyde (PA) in aqueous media was studied using different homogeneous metal salts. A kinetic model was developed and the parameters corresponding to each reaction steps were estimated. Agreement between experiments and simulated results was excellent and the performance of the different catalysts was consistent with previous studies described in the literature. Aluminium salts, which show the best performance, were tested in a whole range of concentrations and at different pH, in order to identify the catalytically active ionic species. It was confirmed that the DHA to pyruvaldehyde (PA) dehydration step is catalyzed by both Brønsted and Lewis acids whereas the consecutive reaction of PA to LA is solely catalyzed by Lewis acids. Moreover, comparing thermodynamic analysis of the reaction media and kinetic parameters demonstrated that cationic hydroxyl-aluminium complexes [Al(OH)h] (3-h)+ formed in situ by the hydrolysis of the aluminium aqua complexes like [Al(OH2)6] 3+ are the most active Lewis acids

Generalized Fourier Integral Operators on spaces of Colombeau type

Generalized Fourier integral operators (FIOs) acting on Colombeau algebras are defined. This is based on a theory of generalized oscillatory integrals (OIs) whose phase functions as well as amplitudes may be generalized functions of Colombeau type. The mapping properties of these FIOs are studied as the composition with a generalized pseudodifferential operator. Finally, the microlocal Colombeau regularity for OIs and the influence of the FIO action on generalized wave front sets are investigated. This theory of generalized FIOs is motivated by the need of a general framework for partial differential operators with non-smooth coefficients and distributional data

Volcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano, Italia

We made a stratigraphic, structural and morphologic study of Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist all around the margin of the volcano. These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of the edifice of Amiata onto its weak substratum, formed by the late Triassic evaporites (Anidriti of Burano) and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes (Ligurian Complex). Regional doming created a slope in the basement forcing the outward flow and spreading of the ductile layers below the volcano. We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a solution. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time. Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for the formation of trains of adjacent diapirs. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays’ exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks (which host an extensive fresh-water aquifer) and the rocks of the geothermal field, constitute ideal pathways for water recharge during vapour extraction for geothermal energy production. We think that volcanic spreading could maintain faults in a critically stressed state, facilitating the occurrence of triggered seismicity

A ^(119)Sn Mössbauer Spectrometry Study of Li-SnO Anode Materials for Li-Ion Cells

Anodes of SnO were charged reversibly with Li to capacities greater than 600 mAh/g, The anode materials were characterized by 119Sn Mössbauer spectrometry at 11 and 300 K, and by X-ray diffractometry at 300 K. Trends in the valence of Sn were as expected when the Sn oxides are reduced in the presence of Li. At low Li capacities the SnO is reduced to small particles of β-Sn, and with increasing Li capacity an alloy of Li_(22)Sn_5 is formed. Although the Li_(22)Sn_5 develops over a range of Li concentrations in the anode material, the Li_(22)Sn_5 that forms at low Li insertions is not typical of bulk Li_(22)Sn_5 in either its structural or electrochemical properties. The recoil-free fraction of the Sn oxide (and perhaps the metallic Sn) in the anode materials showed an anomalously large temperature dependence. This is indicative of nanoparticles or a severely defective structure. We monitored the changes in the Li-SnO and Li-Sn materials during atmospheric exposure over times up to 2 months. This oxidation process of Sn was very much the reverse of the Sn reduction during the Li insertion, although it occurred over a much longer time scale. We also report the temperature dependencies of recoil-free fractions for standard samples of β-Sn, SnO_2, and the alloy Li_(22)Sn_5