Eigenvalues in Non-Linear Potential Theory

In this work, we study the existence of eigenvalues for a type of non-linear equations and we give some conditions to get positive eigenfunctions. Particularly, we show that under some appropriate conditions, the set of eigenvalues is an interval.     

Gly311 residue triggers the enantioselectivity of Staphylococcus xylosus lipase: a monolayer study

Using emulsified triacylglycerols, we have shown recently [Mosbah et al., 2007, submitted for publication] that amino acid residue G311 of Staphylococcus xylosus lipase (SXL) is critically involved in substrate selectivity, pH and temperature dependency. Using the monomolecular film technique, we show in the present study that the four single mutants of this residue (G311L, G311W, G311D, and G311K), interact efficiently with egg-phosphatidyl choline (egg-PC) monomolecular films, comparably to the wild-type (G311). A critical surface pressure (pi(c)) of about 25 mN/m was obtained with the SXL wild-type (SXL-WT) and its mutants. These results support our conclusion that the G311 residue is not involved in the interfacial adsorption step of SXL. A kinetic study on the surface pressure dependency, stereoselectivity, and regioselectivity of SXL-WT and its G311 mutants was also performed using optically pure enantiomers of diacylglycerols (1,2-sn-dicaprin and 2,3-sn-dicaprin) and a prochiral isomer (1,3-sn-dicaprin) spread as monomolecular films at the air-water interface. Our results indicated that the mutation of one single residue at position 311 affects critically the catalytic activity, the stereo- and the regioselectivity of SXL. As previously observed with emulsified substrates [Mosbah et al., 2007, submitted for publication] we observed that an increase in the size of the 311 amino acid side chain residue was accompanied by a decrease of lipase activity measured on dicaprin monolayer. We also noticed that the substitution of G311 by a basic or acidic residue (G311K and G311D), induces a significant shift of the pH optimum from 8 to 9.5 or from 8 to 6.5, respectively.     

Structure dependence of near-infrared stimulated blue emission in polycrystalline Ln2(WO4)3 (Ln=Gd and Lu) doped with Tm and Yb

Tm- and Yb-doped gadolinium tungstate, (Gd_xTm_yYb_1−x−y)₂(WO₄)₃ (x=0.7-0.9; y=0.001-0.01), have been prepared by the polymerized complex method to achieve a homogeneous dispersion of dopants and to stabilize the host structure. Decomposition (900 °C 5 h) of the precursors with x=0.8-0.9 yielded a pure monoclinic phase, while that of x=0.7 resulted in formation of an orthorhombic impurity. The monoclinic phase exhibits bright up-converted blue emission due to the ¹G₄→³H₆ transition of Tm³⁺ (472 nm) upon excitation into the Yb³⁺:²F_7/2→²F_5/2 absorption band as a result of energy transfer from Yb to Tm. The orthorhombic impurity acts as a strong quencher of emission, and the quenching mechanism has been discussed on the basis of structural and spectroscopic properties of orthorhombic Lu₂(WO₄)₃:Tm,Yb prepared by the same method.     

The nuclear microprobe: A complementary tool to NAA characterization

The nuclear microprobe enables the localization and the quantitative determination of all elements from hydrogen to uranium using atomic and/or nuclear methods: PIXE, PIGE, RBS, ERDA, NRA, STIM, etc. These methods and the apparatus required are shortly described. Three examples show that complementary information is obtained by nuclear microprobe analysis and NAA. The first example is the study of the abnormal behavior of metallic impurities during the purification of metallurgical grade silicon by directional solidification. This behavior is due to the presence of silicon carbide micro-precipitates at the bottom of the ingots. The second example concerns the determination of trace element (Ni, Mn, Rb, Sr) partition coefficients between a solid phase (mineral) and a liquid phase (lava-glass inclusions). These determinations enable the specification and modelling of the processes which govern the magma evolution in volcanological contexts. The third example deals with the study of trace elements in archeological bones. Using PIXE, PIGE, NRA and NAA, it is possible to correlate the concentrations of some elements, such as C, N, F, and Zn in the femoral diaphyse with both the age, the pathology and diagenetic mechanism of the human being at the moment of death.     

Some remarks on the ring

Some properties like factoriality, seminormality and being a Krull domain, … are studied on power series rings , and over a commutative ring A. If \(\mathbb{X}\) is an uncountable set, there is an other sub-ring of that stands strictly between and , we denote it by . In this paper, we study properties mentioned before on the ring .     

Influence of annealing temperature on the properties of ZnO thin films deposited by thermal evaporation

ZnO thin films were deposited by thermal evaporation of a ZnO powder. The as-deposited films are dark brown, rich zinc and present a low transmittance. Then, these films were annealed in air atmosphere at different temperatures between 100 and 400 °C. Their microstructure and composition were studied using XRD and RBS measurements respectively. By increasing the temperature, it was found that film oxidation starts at 250 °C. XRD peaks related to ZnO appear and peaks related to Zn decrease. At 300 °C, zinc was totally oxidised and the films became totally transparent. The electrical conductivity measurement that were carried out in function of the annealing temperature showed the transition from highly conductive Zn thin film to a lower conductive ZnO thin film. The optical gap (E_g) was deduced from the UV-vis transmittance, and its variation was linked to the formation of ZnO.     

Reactivite Des N 1 -Tosylamidrazones Vis-À-Vis du Chlorure de Thionyle et du Reactif de Lawesson: Obtention Des Thiatriazoles et Des Triazaphospholines

Thionyl chloride 2 and Lawesson Reagent (L.R.) 4 react with N 1 -tosylamidrazones 1 to give respectively 1-oxyde-1,2,3,5-thiatriazole 3 and triazaphospholines 5 derivatives. The structure of products 3 and 5 is confirmed by IR and NMR spectroscopy.     

REACTIVITE DES N 1-TOSYLAMIDRAZONES VIS-À-VIS DU TRICHLORURE DE THIOPHOSPHORYLE ET DU DISULFURE DE CARBONE: OBTENTION DES TRIAZAPHOSPHOLINES ET DES TRIAZOLETHIONES

The condensation of N ¹ -tosylamidrazones with thiophosphorus trichloride and carbone disulfide forms a new synthetic method for access to new phosphorus or sulfur heterocycles such as triazaphospholines and triazolethiones.     

Problème de Dirichlet relatif à une perturbation non lineaire des espaces harmoniques

In this paper, we prove for a more general semi-linear perturbation of linear harmonic spaces, the existence and the unicity of the solution of the Dirichlet problem and we apply our results for the non-linear stationary Schrödinger equation.     

Effect of doping by low content of yttrium at Ca and Sr sites of Bi(Pb)-2212 superconducting ceramics

In this work, a comparative study of the effect of doping by low content of Y³⁺ between (Ca site) and out of (Sr site) the CuO₂ planes of Bi(Pb)-2212 phase is presented. Ceramics of Bi_1.6Pb_0.4Sr₂Ca_1−xY_xCu₂O_8+d (called CY series) and Bi_1.6Pb_0.4Sr_2−xY_xCaCu₂O_8+d (called SY series) with x=0, 0.025, 0.05, 0.075 and 0.1 are elaborated in air by conventional solid state reaction. They are characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy (SEM), density, Vickers microhardness and resistivity measurements. The refinement of cell parameters is done by considering the structural modulation. In comparison with the undoped sample (x=0), the cell parameters a, b and c are reduced by the doping for both series while the b component of the modulation vector increases. A good correlation between the variations of the bulk density and the Vickers microhardness with x is obtained. For both series, the SEM analysis shows that the doped samples exhibit a reduced grain size than that of the undoped one. The variation of resistivity with temperature shows that all samples exhibit a metallic-like character in the normal state. For all doping levels, the CY series presents higher onset critical transition temperature than that of the undoped sample, which is equal to 85.43 K. The opposite is obtained for SY series. The highest value of this temperature is obtained for x=0.075 in the doped samples and is about 92.15 and 79.96 K for CY and SY series, respectively. These values may correspond to a near optimally doped state since the slope (dρ/dT) of resistivity shows a maximum at the same value of x=0.075. For both series, when Y³⁺ is introduced into the samples, the residual resistivity decreases first for x=0.025 and increases gradually after this value until x=0.1.