Conformal blocks and generalized theta functions

LetSU _X r be the moduli space of rankr vector bundles with trivial determinant on a Riemann surfaceX. This space carries a natural line bundle, the determinant line bundleL. We describe a canonical isomorphism of the space of global sections ofL ^k with the space of conformal blocks defined in terms of representations of the Lie algebrasl _r (C((z))). It follows in particular that the dimension ofH ⁰(SU _X r,L ^k ) is given by the Verlinde formula.Both authors were partially supported by the European Science Project Geometry of Algebraic Varieties, Contract no. SCI-0398-C(A)     

Chemical modification of a polyacrylamide: Enhanced decontamination of soils and surfaces after a nuclear accident

This contribution concerns the decontamination of soils and surfaces polluted by cesium and strontium after a nuclear accident. The decontamination rate by means of an industrial polyacrylamide previously selected for its mechanical covering properties is studied. The characteristics of the polymer and its cation-exchange capacity (CEC) are specified. The chemical modification of the polymer, involving a crosslinking path and functional grafting, affords an improvement of its decontaminating properties.     

Absolute Continuity of the Invariant Measures for Some Stochastic PDEs

We consider a free system and an interacting systems having invariant measures μ and ν respectively. Under suitable assumptions we prove an explicit formula relating ν with μ and implying the absolute continuity of ν with respect to μ. We apply our result to a reaction-diffusion equation and to the Burgers equation.     

Complexing properties of an N,N′-methylated diaza-crown-ether

The nature and stability of some transition and heavy metal cation complexes of an N,N′-methylated diaza-crown-ether have been determined in 0.1 M Et₄NClO₄ aqueous solution by means of pH metric measurements. The results are compared to previous ones concerning the homologous unmethylated ligand.     

PHOTODYNAMIC KILLING OF Dictyostelium discoideum AMOEBAE MEDIATED BY 4',5'-DIIODOFLUORESCEIN ISOTHIOCYANATE DEXTRAN. A STRATEGY FOR THE ISOLATION OF THERMOCONDITIONAL ENDOCYTOSIS MUTANTS

4′, 5′-Diiodofluorescein dextran has been synthesized by iodination of fluorescein dextran and it was used as a sensitizer in photodynamic killing of amoebae of the cellular slime mold Dictyostelium discoideum. Amoebae from axenic strain AX2 incubated in the presence of 4′,5′-diiodofluorescein dextran efficiently internalized the molecule by fluid-phase pinocytosis. Subsequently, illumination of cells showed dose- and time-dependent loss of viability. The tertiary amine, 2,4- diaza[2,2,2]bicyclooctane, significantly decreased phototoxicity, whereas the presence of D₂O increased phototoxicity. These effects were fully consistent with a role for excited-state singlet oxygen generated inside the endosomal compartments in the mechanism of photoinjury. A strategy was developed to enrich for temperature-sensitive Dictyostelium endocytosis mutants in a nitrosoguanidine mutagenized population. Incubation with 4′,5′-diiodofluorescein dextran at 27°C to load endosomal compartments was followed by light treatment to kill parent-type cells selectively. In contrast, mutants unable to internalize the fluid-phase marker would survive the treatment. Six temperature-sensitive clones were selected that grew normally at 21°C but did not grow at 27°C. They all showed markedly decreased fluid-phase pinocytosis capacity at nonpermissive temperature as compared to their activity at 21 °C. These mutant strains should be useful in studies designed to characterize endocytosis mechanisms in Dictyostelium.     

Relationship between vitamin D status and skin phototype in general adult population

A link between bone mineral density and skin color has been reported recently, and pigmentation has been shown to affect cutaneous vitamin D production. In the present study, we investigated the relationship between phototype, global self-assessed sun exposure, geographical location and vitamin D serum levels in 1191 French adults. When the factors were analyzed separately, individuals with lower phototypes as well as those with lower sun exposure showed significantly lower levels of vitamin D than those with darker phototypes or those with higher sun exposure. However, when factors were analyzed as a whole, the vitamin D status was no longer linked with the phototype, but with sun exposure and geographical location. Since phototypes and global self-assessments of sun exposure were positively linked, our data suggest that lower vitamin D levels in fair-skinned individuals are due to their sun exposure behavior.     

ELECTRON SPIN RESONANCE OF MELANIN FROM HAIR. EFFECTS OF TEMPERATURE, pH AND LIGHT IRRADIATION

Abstract— The variation with temperature, pH and light of the ESR signal of hydrated melanin powders from Japanese black hair has been studied. An explanation of the results is proposed on the basis of quinhydrone type complexes and of acid-base equilibria of melanin and its semiquinone radicals. During exposure to light of wavelengths 254–600 nm, both stable and unstable radicals have been observed. The action spectrum for the formation of stable melanin radicals has been determined.     

Etude comparative des composés TiX2 (X = S,Se, Te). Structures de TiTe2 et TiSeTe

The evolution of crystal-structure and chemical-bond characteristics is studied for the series of isotypical compounds TiX₂, with X = S, Se, Te. The structure determination of TiTe₂ and TiSeTe confirms the existence of an increasing trigonal C_3v distortion of metal sites when the chalcogen electronegativity decreases. The ESCA study shows that this distortion is associated with augmentation of the covalent or metallic character of the bonds. The structural and spectroscopic differences appearing from TiS₂ to TiSe₂ can be interpreted by an orbital delocalization in TiSe₂ and TiTe₂, which would explain the semimetallic behavior of these compounds.     

Purification and characterization of an intracellular β-glucosidase from a Candida sake strain isolated from fruit juices

A yeast strain isolated in the laboratory from fruit juices was studied and classified as Candida sake. The strain produces an intracellular beta-glucosidase when grown with cellobiose as the carbon source. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular beta-glucosidase, estimated by gel filtration, was 240 kDa. The tetrameric structure of the beta-glucosidase was determined following treatment of the purified enzyme with sodium dodecyl sulfate. The enzyme exhibited optimum activity at 52 degrees C and pH 4.25 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with the (1-->4)-beta configuration, and from Lineweaver Burk plots, a Km value of 6.9 mmol/L was found for p-nitrophenyl-beta-D-glucopyranoside. The beta-glucosidase was found to be tolerant to glucose inhibition with a Ki value of 0.2 mol/L.