The finite sample properties of sparse M-estimators with pseudo-observations

Annals of the Institute of Statistical Mathematics - We provide finite sample properties of general regularized statistical criteria in the presence of pseudo-observations. Under the restricted...     

Chiral separation of atropine by high-performance liquid chromatography

The separation and quantitation of the enantiomers and also the determination of the enantiomeric purity are now current and indispensable tasks for the pharmaceutical analysis. Among the various techniques, liquid chromatography remains the best modality owing to several advantages. High speed, sensitivity, and reproducible results make LC the method of choice in almost all laboratories. Phases that contain alpha1-acid glycoprotein as chiral selector are suitable for separation of charged and uncharged enantiomers with widely different structure. Atropine is widely used as parasympatolytic, anticholinergic and antiemetic drugs. It is one of the preferred antidote for immediate management of toxicity associated with nerve agents. Stereoselective separation was achieved with a prepacked alpha1-acid glycoprotein column without any derivatization procedure. The liquid chromatography system is coupled to mass spectrometry with an atmospheric pressure chemical ionization interface in the positive-ion mode. The chromatographed analytes are detected in selective ion monitoring after optimisation using factorial experimental design. Small amount of enantiomeric composition can be evaluated either by MS or by UV spectrometry (less than 5%).     

Analysis of heavy organic pollutants of confined atmospheres

Summary An improved procedure for the determination of the less volatile air pollutants of recycled closed atmospheres by activated carbon-Soxhlet extraction is proposed. After total treatment of desorbate, PAH determination is then accomplished by RP-HPLC using both adsorptiometric and fluorimetric UV detection; phenolic compounds are determined by GC-MS.This technique is suitable for very low levels of PAH and phenolic compounds.     

Convergence of zeta functions of graphs

The -zeta function of an infinite graph (defined previously in a ball around zero) has an analytic extension. For a tower of finite graphs covered by , the normalized zeta functions of the finite graphs converge to the -zeta function of .

     

Asymptotics for steady‐state voltage potentials in a bidimensional highly contrasted medium with thin layer

We study the behaviour of steady‐state voltage potentials in two kinds of bidimensional media composed of material of complex permittivity equal to 1 (respectively, α) surrounded by a thin membrane of thickness h and of complex permittivity α (respectively, 1). We provide in both cases a rigorous derivation of the asymptotic expansion of steady‐state voltage potentials at any order as h tends to zero, when Neumann boundary condition is imposed on the exterior boundary of the thin layer. Our complex parameter α is bounded but may be very small compared to 1, hence our results describe the asymptotics of steady‐state voltage potentials in all heterogeneous and highly heterogeneous media with thin layer. The asymptotic terms of the potential in the membrane are given explicitly in local coordinates in terms of the boundary data and of the curvature of the domain, while these of the inner potential are the solutions to the so‐called dielectric formulation with appropriate boundary conditions. The error estimates are given explicitly in terms of h and α with appropriate Sobolev norm of the boundary data. We show that the two situations described above lead to completely different asymptotic behaviours of the potentials. Copyright © 2007 John Wiley & Sons, Ltd.     

Metabolic probes for imaging endosymbiotic bacteria within toxic dinoflagellates

Fluorescence microscopy offers an important tool for the study of complex biological phenomena such as symbiosis. Here we identify a strategy that adapts the unique differences between the secondary metabolism in host and guest symbiotic species to selectively image endosymbiotic organisms. The method is demonstrated by application to the complex symbiotic relationships in toxic marine dinoflagellates.     

Solid-State 13C-NMR spectral evidence for charge transfer complex formation in aromatic diimides and dianhydrides

Solution and solid-state proton decoupled ¹³C-NMR spectra were determined on two diimides derived from 4, 4′-oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′-isophthaloyldiphthalic anhydride (IDPA) and 4, 4′-terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid-state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides.     

Growth of Betti numbers

We discuss growth rates of Betti numbers in a family of coverings of a compact cell complex X, when the corresponding L² Betti number of X is zero. We show that the Betti numbers are bounded by a function, sub-linear in the order of the covering. If the appropriate Novikov-Shubin invariant of X is positive, the rate bounds are improved. For well behaved families (such as congruence covers of symmetric spaces), if the L² spectrum of X? has a gap at zero then the growth rate is bounded by the order of the covering raised to a power less than one.