An improved approximation for the Rayleigh wave equation

We derive a simple expression, which gives an approximate value of the Rayleigh wave velocity in an isotropic solid. This approximation is five times better than that given by Viktorov. The velocity equation can be easily inverted in order to obtain an accurate determination of the elastic constants. This procedure can be worthwhile for elastic microanalysis of bulk materials by scanning acoustic microscopy.     

Orientation of Na(3p) states excited in Na-He collisions

The orientation of Na(3p) states created in 3–13 keV Na(3s)-He collisions has been studied by the polarised photon-scattered particle coincidence technique at scattering angles corresponding to the impact-parameter range 1–2 a.u. In the standard geometry, at large impact parameters the excitation process exhibits a very high degree of orientation with about 90% of the Na(3p) states havingm ₁=?1. Strong reduction in this propensity is observed at impact parameters smaller than about 1.3 a.u., where a molecular curve crossing causes simultaneous He(n=2) excitation. In this region, also ionisation becomes important.     

High diastereofacial selectivity in the 1,3-dipolar cycloaddition of chiral azomethine ylides

Excellent diastereofacial and endo/exo stereoselectivities have been obtained in cycloaddition of the chiral azomethine ylide generated from 4-phenyloxazolidine acetic acid (−)-8-phenylmenthyl ester 1e.     

Rotary birefringent and quarter-wave plates applied to photoelasticimetry

With the help of Poincare's geometric representation and associated matrices, the authors point out the different equivalent operators issued from the decomposition of the representative matrix of a rotating birefringent. They also show that it is possible to obtain achromatic quarter-wave plates within a second-order error by composition of birefringent and rotary-power plates. Original measure principles in ellipsometry and photoelasticimetry have been deduced by the use of both of these new operators. One obtains automatically and simultaneously angular parameters of a polarized light. The principle of the monochromatic and automatic photoelasticimeter described is consistent with the use of two wavelengths and it eliminates all the errors of the first order. In the field of three-dimensional photoelasticimetry with scattered light, the matrix elements representing an elliptic birefringent are directly obtained. One deduces properties of a linear birefringent added with this elliptic birefringent from the variation of this fast. The principles of this apparatus are very simple and enable one to obtain accurate and digital values of the photoelastic parameters and to allow a direct treatment of the results with a small calculator.     

Total Synthesis of Albicidin: A Lead Structure from Xanthomonas albilineans for Potent Antibacterial Gyrase Inhibitors

The peptide antibiotic albicidin, which is synthesized by the plant pathogenic bacterium Xanthomonas albilineans, displays remarkable antibacterial activity against various Gram‐positive and Gram‐negative microorganisms. The low amounts of albicidin obtainable from the producing organism or through heterologous expression are limiting factors in providing sufficient material for bioactivity profiling and structure–activity studies. Therefore, we developed a convergent total synthesis route toward albicidin. The unexpectedly difficult formation of amide bonds between the aromatic amino acids was achieved through a triphosgene‐mediated coupling strategy. The herein presented synthesis of albicidin confirms the previously determined chemical structure and underlines the extraordinary antibacterial activity of this compound. The synthetic protocol will provide multigram amounts of albicidin for further profiling of its drug properties.     

Non-accretive Schrödinger operators and exponential decay of their eigenfunctions

We consider non-self-adjoint electromagnetic Schrödinger operators on arbitrary open sets with complex scalar potentials whose real part is not necessarily bounded from below. Under a suitable sufficient condition on the electromagnetic potential, we introduce a Dirichlet realisation as a closed densely defined operator with non-empty resolvent set and show that the eigenfunctions corresponding to discrete eigenvalues satisfy an Agmon-type exponential decay.     

An APCI LC‐MS/MS method for routine determination of capecitabine and its metabolites in human plasma

The anticancer drug capecitabine and its metabolites [including the active metabolite 5‐fluorouracil (5‐FU)] display high pharmacokinetic inter‐patient variability. Such variability, which may lead to treatment failure or toxicity, could need drug concentration measurement to individualize dosing regimen. However, usual assay methods are often long and fastidious. A simultaneous and cost‐effective method was thus developed for the determination of the concentrations of these compounds in human plasma. Compounds were extracted via a classic liquid–liquid extraction. Chromatographic analysis was performed on a C18 reverse phase column with detection by atmosphere pressure chemical ionization LC‐MS/MS. Our method allows a good chromatographic separation of the compounds and was fully validated following Food and Drug Administration (FDA) recommendations (good selectivity, no carry‐over, linearity of the calibration curves without weighting, deviations from nominal concentrations of standard samples lower than 15%, intra‐ and inter‐assay precision and accuracy lower than 15%). Recovery and stability were also acceptable following the FDA guidelines. A matrix effect impairing the determination of 5‐FU was avoided by using a stable isotopic derivative of 5‐FU as internal standard. Interestingly, this method allows detection of TetraHydroUridine, an inhibitor of ex vivo degradation of metabolites, which is essential for the stability, the adequate conditioning of blood samples and for good laboratory practice, essential in routine determination. This method seems usable to routinely determine concentrations of capecitabine and its metabolites in blood and may be helpful in further studies aiming at performing therapeutic drug monitoring. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthèse d'analogues furanniques et nitro-2 furanniques du diméthyl-7,12 benzanthracène

A route to 1-formyl-2-hydroxy-9-methylanthracene and 1-formy 1-2-hydroxy-9,10-dimethylanthracene is desribed. These two aldehydes were further converted into mono- or dimethylanthra[2,1-b]furans, besides the corresponding acids and esters, by condensation with ethyl bromoacetate. The related mono- or dimethyl-2-nitroanthra[2,1-b]furans were also prepared by reaction between the above aldehydes and bromonitromethane, followaed by heating in toluene in the presence of p-toluene-sulfonic acid.