Recycling asymmetric hydrogenation catalysts by their immobilisation onto ion-exchange resins

New systems based on cationic chiral phosphine-rhodium complexes anchored to a commercial cation-exchange gel-type resin showed high efficiency and easy recycling in the asymmetric hydrogenation of prochiral olefins.     

Self-similar solutions of the porous medium equation in a half-space with a nonlinear boundary condition: existence and symmetry

We find existence of a nonnegative compactly supported solution of the problem Δu=u^α in , ∂u/∂ν=u on . Moreover, we prove that every nonnegative solution with finite energy is compactly supported and radially symmetric in the tangential variables.     

Numerical blow‐up for the porous medium equation with a source

We study numerical approximations of positive solutions of the porous medium equation with a nonlinear source, where m > 1, p > 0 and L > 0 are parameters. We describe in terms of p, m, and L when solutions of a semidiscretization in space exist globally in time and when they blow up in a finite time. We also find the blow‐up rates and the blow‐up sets, proving that there is no regional blow‐up for the numerical scheme. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004     

Delayed crossing in the \pi h_{9/2} 1/2-[541] band of 173 Lu

High-spin states in the odd-proton nucleus ¹⁷³Lu have been populated in a ¹⁷⁰Er(⁷Li,4n) reaction and the emitted -radiation was detected with the GASP array. The favoured and unfavoured sequences of the band have been considerably extended. The favoured sequence does not show any indication of a band crossing up to a rotational frequency of 0.45 MeV. This is the largest crossing frequency ever observed for 1/2^- [541] bands of odd-proton nuclei with and . Previous Cranked Shell Model (CSM) calculations underestimate the crossing frequency by 100 keV.Received: 19 May 2003, Published online: 11 November 2003PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.70. + q      

Temperature-dependent fermi gap opening in the c(6x4)-C60/Ag(100) two-dimensional superstructure

High-resolution angle-integrated photoemission of one monolayer of C (60) chemisorbed on Ag(100) shows the reversible opening of a gap at the Fermi level at temperatures 25< or =T< or =300 K. The gap reaches a maximum value of approximately 10 meV at T< or =70 K. This finding is the first evidence of an electronic phase transition in C60 monolayers and has implications on the ongoing debate about surface superconductivity in C60-based bulk materials.     

Nature of charge transport in quantum-cascade lasers

The first global quantum simulation of semiconductor-based quantum-cascade lasers is presented. Our three-dimensional approach allows us to study in a purely microscopic way the current-voltage characteristics of state-of-the-art unipolar nanostructures, and therefore to answer the long-standing controversial question: Is charge transport in quantum-cascade lasers mainly coherent or incoherent? Our analysis shows that (i) quantum corrections to the semiclassical scenario are minor and (ii) inclusion of carrier-phonon and carrier-carrier scattering gives excellent agreement with experimental results.     

Abelian fourfold of Mumford-type and Kuga-Satake varieties

Let X be a complex abelian fourfold of Mumford-type and let V = H¹(X, ). The complex Mumford-Tate group of X is isogenous to SL(2)³. We recover information about the Hodge structure of X using representations of the Lie algebras (2)³ and (8) acting on V . Using these techniques we show that there is a Kuga-Satake variety A associated to X in such a way that A is isogenous to X³².     

Cohen-Macaulay Local Rings of Embedding Dimension e + d - 3

In this paper we determine the possible Hilbert functions ofa Cohen–Macaulay local ring of dimension d and multiplicitye, in the case where the embedding dimension v satisfies v =e + d – 3 and the Cohen–Macaulay type is less thanor equal to e – 3. 1991 Mathematics Subject Classification:primary 13D40; secondary 13P99.     

Universality class of absorbing phase transitions with a conserved field

We investigate the critical behavior of systems exhibiting a continuous absorbing phase transition in the presence of a conserved field coupled to the order parameter. The results obtained point out the existence of a new universality class of nonequilibrium phase transitions that characterizes a vast set of systems including conserved threshold transfer processes and stochastic sandpile models.