Effects of finite temperatures,valence bands and energy gaps on the indirect exchange interaction in intrinsic semiconductors

The indirect exchange interaction between localized magnetic moments via virtual excitations from the valence band in intrinsic semiconductors is calculated taking into account the temperature, energy gaps, finite valence bands and effective masses. The inclusion of finite temperature effects changes significantly the phase and magnitude of the oscillations. For small gap semiconductors the oscillatory character and the possibility of ferro-magnetic as well as anti-ferromagnetic coupling are obtained. The exchange interaction oscillates with temperature suggesting interesting applications of this model.     

Strongly regular graphs

In this paper we have tried to summarize the known results on strongly regular graphs. Both groupal and combinatorial aspects of the theory have been included. We give the list of all known strongly regular graphs and a large bibliography of this subject.     

Delayed fracture in porous media

The fracture of porous media subjected to a constant load is studied. Contrary to homogeneous solids in which fracture usually happens instantaneously at a well-defined breaking strength, the fracture of a porous medium can occur with a delay, allowing us to quantify the average lifetime of the unbroken material. We show that the average fracture probability, a key property for risk analysis in civil engineering, is given by the probability of crack nucleation. The nucleation process can be understood qualitatively by calculating the activation energy for crack nucleation, taking into account the porosity of the medium.     

Synthesis of ring-oxidized retinoids as substrates of mouse class I alcohol dehydrogenase (ADH1)

Ring-oxidized retinoids have been synthesized stereoselectively using the Stille cross-coupling reaction. Kinetic constants of mouse class I alcohol dehydrogenase (ADH1) with these retinoids were determined.     

Tensor Gauge Fields in Arbitrary Representations of GL(D, ℝ). Duality and Poincaré Lemma

Using a mathematical framework which provides a generalization of the de Rham complex (well-designed for p-form gauge fields), we have studied the gauge structure and duality properties of theories for free gauge fields transforming in arbitrary irreducible representations of GL(D, ). We have proven a generalization of the Poincaré lemma which enables us to solve the above-mentioned problems in a systematic and unified way.     

An efficient, stereoselective approach to syn-1,2-diols protected as cyclic carbonates

Enantioenriched 4-hydroxyalk-2-ynyl carbonates (or benzoates) have been prepared by stereoselective zinc-mediated addition of alkyl 2-propynyl carbonates (or their benzoate analogues) to aldehydes. Their partial reduction to Z-olefins followed by cyclization under mild Pd-catalyzed conditions allowed a straightforward access to enantioenriched syn-1,2-diols protected as cyclic carbonates.     

Amino-aryl-carbenes: alternative ligands for transition metals?

Despite the presence of a single amino substituent, an amino-anthryl-carbene was found to behave as a strong sigma-donor weak pi-acceptor ligand toward rhodium(I) fragments.     

Interferences in clinical capillary zone electrophoresis of serum proteins

Capillary zone electrophoresis (CZE) of serum proteins has become a well-accepted method for the separation of serum proteins and for the detection of monoclonal proteins in clinical laboratories. As CZE uses ultraviolet detection for direct protein quantification, exogenous ultraviolet-absorbing substances are a novel challenge, not present in conventional gel-based methods in which protein is quantified by dye binding. This minireview gives a survey of interfering substances, including iodinated contrast agents and antibiotics.