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.     

First-principles study of the electro-optic effect in ferroelectric oxides

We first present a method to compute the electro-optic tensor from first principles, explicitly taking into account the electronic, ionic and piezoelectric contributions. We then study the nonlinear optic behavior of three paradigmatic ferroelectric oxides. Our calculations reveal the dominant contribution of the soft mode to the electro-optic coefficients in LiNbO3 and BaTiO3 and its minor role in PbTiO3. We identify the coupling between the electric field and the polar atomic displacements along the B-O chains as the origin of the large electro-optic response in perovskite ABO3 compounds.     

Easy access to diastereomerically pure platinacycles

The synthesis of the first examples of diastereomerically pure platinacycles having simultaneously a chiral carbon and a sigma[Pt-C(sp(2), ferrocene)] bond is described.