Fractal snowflake domain diffusion with boundary and interior drifts

We study a parabolic Ventsell problem for a second order differential operator in divergence form and with interior and boundary drift terms on the snowflake domain. We prove that under standard conditions a related Cauchy problem possesses a unique classical solution and explain in which sense it solves a rigorous formulation of the initial Ventsell problem. As a second result we prove that functions that are intrinsically Lipschitz on the snowflake boundary admit Euclidean Lipschitz extensions to the closure of the entire domain. Our methods combine the fractal membrane analysis, the vector analysis for local Dirichlet forms and PDE on fractals, coercive closed forms, and the analysis of Lipschitz functions.     

Amplification of ultra-short light pulses by ion collective modes in plasmas

The use of plasmas provides a way to overcome the damage threshold of classical solid-state based optical materials which is the main limitation encountered in producing extreme power laser pulses. In particular one can use plasmas to directly amplify ultra-short laser pulses to very high intensities. Multi-dimensional kinetic simulations and first proof-of-principle experiments show the feasibility of using plasma instabilities involving ion waves, such as stimulated Brillouin backscattering, in a controlled way to transfer energy from a long pump pulse to a short seed pulse and thereby increase the intensity of the latter. Plasma parametric amplification, and the use of plasma mirrors for focusing, is part of the newly developping domain of plasma optics, which eventually will pave the way to Exawatt lasers.     

Isochoric heating of solids by laser-accelerated protons: Experimental characterization and self-consistent hydrodynamic modeling

A study of isochoric heating of Al foil by laser-accelerated proton beam is presented, coupling self-consistent hydrodynamic simulations (including proton stopping) with experimental measurements. The proton source that induces the heating has been characterized experimentally and the induced heating has been inferred through critical density expansion velocity measurement. The low-energy part of the proton spectrum that plays the dominant part in the heating process has been studied in detail. The experimental results are compared with the results of 1-dimensional hydrodynamic simulations that use as input the measured proton source and good agreement between the two is found using the SESAME EOS.     

Ab initio analysis of lithium dimethylaminoborohydride

Ab initio calculations were used to determine the equilibrium geometries and energies of lithium dimethylaminoborohydride. Relative energies of the monomeric and dimeric species were calculated in the gas phase and for the dimethyl ether microsolvated molecules. The most stable structure was a dimer in which the lithium and boron atoms were bridged by two hydrogen atoms, similar to the three-center two-electron bonds in diborane. This hydrogen bridging was maintained in the lithium dimethylaminoborohydride bis(dimethyl ether) microsolvate.     

Energy forms on conformal C1‐diffeomorphic images of the Sierpinski gasket

The energy form on a conformal C¹‐diffeomorphic image G of the Sierpinski gasket K is constructed by integrating the Lagrangian LG on G, which is given in terms of the pullback of the Lagrangian LK on K and of the differential of the diffeomorphism. The extension of this approach to the class of nested fractals is outlined. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Incipient oxidation of Mg(0001) face studied by electronic energy loss spectroscopy and leed

The intensity change, upon O₂ exposure of Mg(0001), of the low energy (89 eV) electron loss peaks is interpreted by the nucleation and growth of islands of chemisorbed oxygen converting progressively to the MgO (111) structure while regions between the islands order differently.     

Surface reconstructions of the SnO2 (110) face

Various surface reconstructions of SnO₂ (110) faces have been observed : (1×1) before ion sputtering, (4×2) after annealing under 350°C, (4×1) up to 450°C, (1×1) at 500°C and (4×1) above 500°C. These structures are correlated with ELS spectra and with oxygen deficiencies as seen by AES.