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101.
102.
Samuel Margueron Solène Ropers Alban Maertens Ouarda Legrani Frédéric Genty Ausrine Bartasyte Thierry Belmonte 《Materials Chemistry and Physics》2014
Photoluminescence of (0001) epitaxial ZnO films with thicknesses of 10, 30 and 100 nm on C-sapphire substrates have been studied at room temperature and after exposure to Ar, Ar–O2, Ar–N2 and Ar–H by remote microwave and radiofrequency plasmas. The photoluminescence are not modified by remote plasma treatments where only neutral species were involved. On the contrary, the photoluminescence signal is enhanced or quenched after radiofrequency plasma treatments when energetic ion species are involved in the surface treatment processes. Little changes of electric properties are observed, however, the optical transmission indicates that the absorption edge and probably also the index of refraction are affected. Photoluminescence peak shifts, widths and intensities changes show very strong similarities with polarized emission of ZnO single crystal where it exists a strong dichroism. The photoluminescence emission properties may then result from this optical modification. However, the plasma treatments on the different samples show very low stability in time, except, for the treatment in argon plasma alone. In this later case, in-situ monitoring of photoluminescence as a function of temperature revealed a partial recovery of the photoluminescence properties after a heat treatment at 400 °C for few minutes. These results indicate that photoluminescence of (0001) ZnO thin film, related to σ-emission polarized emission from c-axis polar surfaces, is highly affected by surface and implanted charged species. 相似文献
103.
J. P. Franck I. Isaac G. Zhang J. E. Gordon C. Marcenat R. Lortz C. Meingast F. Bouquet R. A. Fisher N.E. Phillips 《Journal of Superconductivity and Novel Magnetism》2002,15(6):571-577
We present a study of the paramagnetic to ferromagnetic transition in the CMR compound La0.65Ca0.35MnO3 and its dependence on magnetic field and oxygen mass. The transition is characterized by two temperatures, the thermodynamic transition temperature at T c, obtained from specific heat and thermal expansion data, and the resistive transition obtained from the resistivity maximum. The resistive transition occurs well within the paramagnetic range. The magnetic susceptibility in the paramagnetic range is isotope dependent up to 400 K. The magnitude of the Curie-Weiss constant indicates the presence of small clusters of about 4–5 unit cells. The resistive transition occurs when the percolation limit for these clusters is reached. 相似文献
104.
Given a linear functional system (e.g., an ordinary/partial differential system, a differential time-delay system, a difference system), Serre’s reduction aims at finding an equivalent linear functional system which contains fewer equations and fewer unknowns. The purpose of this paper is to study Serre’s reduction of underdetermined linear systems of partial differential equations with either polynomial, formal power series or locally convergent power series coefficients, and with holonomic adjoints in the sense of algebraic analysis. We prove that these linear partial differential systems can be defined by means of only one linear partial differential equation. In the case of polynomial coefficients, we give an algorithm to compute the corresponding equation. 相似文献
105.
Logical foundations of multilevel databases 总被引:2,自引:0,他引:2
In this paper, we propose a formal model for multilevel databases. This model aims at being a generic model, that is it can be interpreted for any kind of database (relational, object-oriented …). Our model has three layers. The first layer corresponds to a model for a non-protected database. The second layer corresponds to a model for a multilevel database. In this second layer, we propose a list of theorems that must be respected in order to build a secure multilevel database. We also propose a new solution to manage cover stories without using the ambiguous technique of polyinstantiation. The third layer corresponds to a model for a MultiView database, that is, a database that provides at each security level a consistent view of the multilevel database. Finally, as an illustration, we interpret our 3-layer model in the case of an object-oriented database. 相似文献
106.
R.M. Calderón-Olvera E.A. Albanés-Ojeda M. García-Hipólito J.M. Hernández-Alcántara M.A. Álvarez-Perez C. Falcony O. Álvarez-Fregoso 《Ceramics International》2018,44(7):7917-7925
SrAl2O4, SrAl2O4:Tb3+ and SrAl2O4:Eu3+:Eu2+ films were synthesized by means of the ultrasonic spray pyrolysis technique. These samples, characterized by X-Ray Diffraction, showed the monoclinic phase of the strontium aluminate. Images of the surface morphology of these films were obtained by SEM and the chemical composition was measured by EDS and XPS. The photoluminescence and cathodoluminescence characteristics of the films were studied as a function of the terbium and europium concentrations. The optimal PL emission intensities were reached at 8?at% for terbium doped films and 6?at% for europium doped samples. The CL emission spectra for europium doped films showed the typical bands of Eu3+ ions and also a broadband centered at 525?nm which is attributed to Eu2+ ions. XPS measurements confirm the presence of Eu3+ and Eu2+ in europium doped SrAl2O4 films, without having been subjected to a reducing atmosphere. Chromatic diagrams exhibited green color for SrAl2O4:Tb3+ films, red and yellow colors for SrAl2O4:Eu3+:Eu2+ films. The PL decay curves were also obtained: the averaged decay time was 2.7?ms for SrAl2O4:Tb3+ films and 1.9?ms for SrAl2O4:Eu3+ films. Similar results were obtained by the stretched exponential model. 相似文献
107.
Victoria N. Jordan Dr. Alban Ordureau Dr. Heeseon An 《Chembiochem : a European journal of chemical biology》2023,24(16):e202300108
Controlled protein degradation by the ubiquitin-proteasome pathway is critical for almost all cellular processes. E3 ubiquitin ligases are responsible for targeting proteins for ubiquitylation and subsequent proteasomal degradation with spatial and temporal precision. While studies have revealed various E3-substrate pairs involved in distinct biological processes, the complete substrate profiles of individual E3 ligases are largely unknown. Here we report a new approach to identify substrates of an E3 ligase for proteasomal degradation using unnatural amino acid incorporation pulse-chase proteomics (degradomics). Applying this approach, we determine the steady-state substrates of the C -t erminal to L isH (CTLH) E3 ligase, a multi-component complex with poorly defined substrates. By comparing the proteome degradation profiles of active and inactive CTLH-expressing cells, we successfully identify previously known and new potential substrates of CTLH ligase. Altogether, degradomics can comprehensively identify degradation substrates of an E3 ligase, which can be adapted for other E3 ligases in various cellular contexts. 相似文献