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排序方式: 共有75条查询结果,搜索用时 15 毫秒
1.
Summary Epitaxial films of YBa2Cu3O7−x
were depositedin situ on LaAlO3 substrates using single-target 90° off-axis sputtering. The films were characterized by magnetization measurements (M vs. T, H), applying the field parallel toc-axis. The observed differences in theT
c andJ
c values are attributed to the different oxygen content in the superconducting films.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
2.
Marie-Noelle Avettand-Fènoël N. David G. Reumont J. -M. Fiorani M. Vilasi P. Perrot 《Journal of Thermal Analysis and Calorimetry》2007,90(2):329-332
The Fe-Sn-Zn system is of interest because Sn is one element added to the Zn galvanizing bath to overcome the drawbacks due
to the presence of Si in semi-killed steels. This work has been undertaken with the aim to understand the tin effect on the
microstructure and the layers growth in batch galvanized coatings on low alloyed steels.
Various experimental techniques such as metallography, scanning electron microscopy (SEM) coupled with X-ray energy dispersive
spectroscopy (EDX) are used in order to characterize the microstructure and the properties of such coatings elaborated in
a zinc bath enriched with tin.
Solidification phenomena and layers growth mechanisms during galvanization are explained by means of the ternary phase diagram
Fe-Sn-Zn at 450°C. The Calphad method allows to obtain this phase diagram from the three optimized binary phase diagrams Fe-Sn,
Fe-Zn and Sn-Zn and some experimental data inside the ternary Fe-Sn-Zn system. 相似文献
3.
E. Tronc P. Prene J. P. Jolivet F. d'Orazio F. Lucari D. Fiorani M. Godinho R. Cherkaoui M. Nogues J. L. Dormann 《Hyperfine Interactions》1995,95(1):129-148
-Fe2O3 nanoparticles with varying state of dispersion in a polymer have been investigated by Mössbauer spectroscopy, static magnetic measurements at low applied field, and alternative susceptibility measurements over a large range of frequencies (2×10–2–104 Hz). The dynamical behaviour was characterized through the variation of the blocking temperature with the characteristic time of the measurement. The Mössbauer blocking temperature was determined according to a procedure described. For quasi-isolated particles an Arrhenius law is demonstrated. Effects of interparticle interactions in concentrated and aggregated systems are satisfactorily explained by the previous model. Dependence of the superparamagnetic susceptibility on the experimental conditions interpreted using the Lorentz or Onsager fields is mentioned. 相似文献
4.
Molecular Size and Electronic Structure Combined Effects on the Electrogenerated Chemiluminescence of Sulfurated Pyrene‐Cored Dendrimers
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Dr. Giovanni Valenti Dr. Andrea Fiorani Dr. Simone Di Motta Dr. Giacomo Bergamini Prof. Marc Gingras Prof. Paola Ceroni Prof. Fabrizia Negri Prof. Francesco Paolucci Prof. Massimo Marcaccio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2936-2947
The electrochemistry, photophysics, and electrochemically generated chemiluminescence (ECL) of a family of polysulfurated dendrimers with a pyrene core have been thoroughly investigated and complemented by theoretical calculations. The redox and luminescence properties of dendrimers are dependent on the generation number. From low to higher generation it is both easier to reduce and oxidize them and the emission efficiency increases along the family, with respect to the polysulfurated pyrene core. The analysis of such data evidences that the formation of the singlet excited state by cation–anion annihilation is an energy‐deficient process and, thus, the ECL has been justified through the triplet–triplet annihilation pathway. The study of the dynamics of the ECL emission was achieved both experimentally and theoretically by molecular mechanics and quantum chemical calculations. It has allowed rationalization of a possible mechanism and the experimental dependence of the transient ECL on the dendrimer generation. The theoretically calculated Marcus electron‐transfer rate constant compares very well with that obtained by the finite element simulation of the whole ECL mechanism. This highlights the role played by the thioether dendrons in modulating the redox and photophysical properties, responsible for the occurrence and dynamics of the electron transfer involved in the ECL. Thus, the combination of experimental and computational results allows understanding of the dendrimer size dependence of the ECL transient signal as a result of factors affecting the annihilation electron transfer. 相似文献
5.
6.
Carbon Dioxide as a Protecting Group: Highly Efficient and Selective Catalytic Access to Cyclic cis‐Diol Scaffolds
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Victor Laserna Dr. Giulia Fiorani Dr. Christopher J. Whiteoak Dr. Eddy Martin Eduardo Escudero‐Adán Prof. Dr. Arjan W. Kleij 《Angewandte Chemie (International ed. in English)》2014,53(39):10416-10419
The efficient and highly selective formation of a wide range of (hetero)cyclic cis‐diol scaffolds using aminotriphenolate‐based metal catalysts is reported. The key intermediates are cyclic carbonates, which are obtained in high yield and with high levels of diastereo‐ and chemoselectivity from the parent oxirane precursors and carbon dioxide. Deprotection of the carbonate structures affords synthetically useful cis‐diol scaffolds with different ring sizes that incorporate various functional groups. This atom‐efficient method allows the simple construction of diol synthons using inexpensive and accessible precursors and green metal catalysts and showcases the use of CO2 as a temporary protecting group. 相似文献
7.
High resolution gas chromatography (HRGC) coupled to a “purge and trap” extraction-injection technique is described as a method of determining 1,2,4-trichlorobenzene in water at levels as low as parts-per-trillion (ppt). In order to investigate the interference from other volatile organic compounds (VOCs) several detection systems were compared: flame ionization, electron capture, and mass spectrometry-multiple ion detection. Concentrations ranging from 15 to 600 ng/L were analyzed in 20 ml standard aqueous solutions. The mean accuracy of the method varied from 89 to 103%, and its mean precision varied from ± 0.85 to ± 7.5 % for all detectors. The detection limits were 20 ng/L for FID, 2 ng/L for ECD and 0.5 ng/L for MID-MS detectors. The procedure was successfully applied to the analysis of industrial waste waters. The necessity of an appropriate internal standard to improve the quantitative determination and to determine possible losses or degradation of 1,2,4-trichlorobenzene during handling or storage is discussed. 相似文献
8.
Magnetic measurements have been performed on polycrystalline solid solutions CoxZn1?xRh2O4 with a spinel structure. The samples with 0.50? x ? 1.00 are antiferromagnets. The samples with x?0.40 do not show a magnetic order, and their magnetic behavior can be explained taking into account the presence of finite clusters of Co2+ ions and paramagnetic isolated ions. 相似文献
9.
10.
I. Diop N. David J.M. Fiorani R. Podor M. Vilasi 《The Journal of chemical thermodynamics》2009,41(3):420-432
In the present work, the experimental characterization of the pseudo-binary PbO–Bi2O3 cut has been performed by differential thermal analysis (DTA), isothermal annealing, powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). A thermodynamic assessment according to the Calphad method was also performed based on the present results as well as previous experimental data using the ThermoCalc software. 相似文献