2,351 research outputs found
An H-theorem for the Brownian motion on the hyperbolic plane
We prove an theorem for the Brownian motion on the hyperbolic plane with
a drift, as studied by Comtet and Monthus; the entropy used here is not the
Boltzmann entropy but the R\'enyi entropy, the parameter of which being related
in a simple way to the value of the drift.Comment: Better versio
Viewing the Steklov eigenvalues of the Laplace operator as critical Neumann eigenvalues
We consider the Steklov eigenvalues of the Laplace operator as limiting
Neumann eigenvalues in a problem of boundary mass concentration. We discuss the
asymptotic behavior of the Neumann eigenvalues in a ball and we deduce that the
Steklov eigenvalues minimize the Neumann eigenvalues. Moreover, we study the
dependence of the eigenvalues of the Steklov problem upon perturbation of the
mass density and show that the Steklov eigenvalues violates a maximum principle
in spectral optimization problems.Comment: This is a preprint version of a paper that will appear in the
Proceedings of the 9th ISAAC Congress, Krak\'ow 201
Evidence of ion diffusion at room temperature in microcrystals of the Bi2Sr2CaCu2O8+delta superconductor
We have studied Bi-2212 microcrystals aged at ambient conditions for 40 days.
Combined x-ray absorption near edge structure and x-ray fluorescence
measurements with micrometer space resolution show both an increase of Cu
with respect to Cu and an enrichment in Cu vs Bi and Sr cation content
near the sample edges in the b-axis direction. A parallel study on an
electrically contacted sample has indirectly detected the O loss, observing
both a resistivity increase and an increase in sample thickness near the edges.
We conclude that the O out-diffusion along the b-axis is accompanied by Cu
cation migration in the same direction.Comment: RevTeX 4, 10 pages, 3 figure
Coordinatively unsaturated ruthenium complexes as efficient alkyne-azide cycloaddition catalysts
The performance of 16-electron ruthenium complexes with the general formula Cp*Ru(L)X (in which L = phosphine or N-heterocyclic carbene ligand; X = Cl or OCH2CF3) was explored in azideâalkyne cycloaddition reactions that afford the 1,2,3- triazole products. The scope of the Cp*Ru(PiPr3)Cl precatalyst was investigated for terminal alkynes leading to new 1,5-disubstituted 1,2,3-triazoles in high yields. Mechanistic studies were conducted and revealed a number of proposed intermediates. Cp*Ru- (PiPr3)(η2-HCCPh)Cl was observed and characterized by 1H, 13C, and 31P NMR at temperatures between 273 and 213 K. A rare example of N,N-Îș2-phosphazide complex, Cp*Ru(Îș2-iPr3PN3Bn)Cl, was fully characterized, and a single-crystal X-ray diffraction structure was obtained. DFT calculations describe a complete map of the catalytic reactivity with phenylacetylene and/or benzylazide.Publisher PDFPeer reviewe
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