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排序方式: 共有155条查询结果,搜索用时 24 毫秒
71.
Lincoln Brum de Leite Gusm?o Pinheiro Alcione Roberto Jurelo Francisco Carlos Serbena Pedro Rodrigues Carlos Eugênio Foerster Adilson Luiz Chinelatto 《Physica C: Superconductivity and its Applications》2010,470(11-12):465-469
The effect of Er substitution on the mechanical properties of ab- and a(b)c-planes of melt-textured YBa2Cu3O7?δ is reported in the present work. The non-oxygenated samples were characterized by scanning electron microscopy, X-ray diffraction and mechanical properties by instrumented indentation and conventional Vickers indentation whereas the superconducting properties were determined by resistivity measurements on oxygenated samples. The X-ray pattern and EDS analysis revealed the presence of Y-123, Y-211 and BaCeO3 phases. Er substitution up to 5 wt.% did not affect the superconducting properties. No difference in hardness was observed for the ab- and a(b)c-planes. Elastic modulus of the a(b)c-plane was 10% higher than of the ab-plane. Differences in indentation fracture toughness obtained by conventional Vickers indentation of the ab- and a(b)c-planes was observed. The addition of 5 wt.% of Er did not affect significantly the mechanical properties of melt-textured samples when compared with pure melt-textured YBa2Cu3O7?δ. 相似文献
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Ohne Zusammenfassung 相似文献
76.
Menaa F Braghini CA Vasconcellos JP Menaa B Costa VP Figueiredo ES Melo MB 《Molecules (Basel, Switzerland)》2011,16(7):5402-5421
MYOC encodes a secretary glycoprotein of 504 amino acids named myocilin. MYOC is the first gene to be linked to juvenile open-angle glaucoma (JOAG) and some forms of adult-onset primary open-angle glaucoma (POAG). The gene was identified as an up-regulated molecule in cultured trabecular meshwork (TM) cells after treatment with dexamethasone and was originally referred to as trabecular meshwork-inducible glucocorticoid response (TIGR). Elevated intraocular pressure (IOP), due to decreased aqueous outflow, is the strongest known risk factor for POAG. Increasing evidence showed that the modulation of the wild-type (wt) myocilin protein expression is not causative of glaucoma while some misfolded and self-assembly aggregates of mutated myocilin may be associated with POAG in related or unrelated populations. The etiology of the disease remains unclear. Consequently, a better understanding of the molecular mechanisms underlying POAG is required to obtain early diagnosis, avoid potential disease progression, and develop new therapeutic strategies. In the present study, we review and discuss the most relevant studies regarding structural characterizations, expressions, molecular interactions, putative functions of MYOC gene and/or its corresponding protein in POAG etiology. 相似文献
77.
Garrido NM Jorge M Queimada AJ Macedo EA Economou IG 《Physical chemistry chemical physics : PCCP》2011,13(20):9155-9164
A methodology is proposed for the prediction of the Gibbs energy of solvation (Δ(Solv)G) based on MD simulations. The methodology is then used to predict Δ(Solv)G of four solutes (namely propane, benzene, ethanol and acetone) in several solvents of different polarities (including n-hexane, n-hexadecane, ethylbenzene, 1-octanol, acetone and water) while testing the validity of the TraPPE force field parameters. Excellent agreement with experimental data is obtained, with average deviations of 0.2, 1.1, 0.8 and 1.2 kJ mol(-1), for the four solutes respectively. Subsequently, partition coefficients (log P) for forty different solute/solvent systems are predicted. The a priori knowledge of partition coefficient values is of high importance in chemical and pharmaceutical separation process design or as a measure of the increasingly important environmental fate. Here again, the agreement between experimental data and simulation predictions is excellent, with an absolute average deviation of 0.28 log P units. However, this deviation can be decreased down to 0.14 log P units, just by optimizing partial atomic charges of acetone in the water phase. Consequently, molecular simulation is proven to be a tool with strong physical basis able to predict log P with competitive accuracy when compared to the popular statistical methods with weak physical basis. 相似文献
78.
In this article, we present an alternative expansion scheme called Floquet-Magnus expansion (FME) used to solve a time-dependent linear differential equation which is a central problem in quantum physics in general and solid-state nuclear magnetic resonance (NMR) in particular. The commonly used methods to treat theoretical problems in solid-state NMR are the average Hamiltonian theory (AHT) and the Floquet theory (FT), which have been successful for designing sophisticated pulse sequences and understanding of different experiments. To the best of our knowledge, this is the first report of the FME scheme in the context of solid state NMR and we compare this approach with other series expansions. We present a modified FME scheme highlighting the importance of the (time-periodic) boundary conditions. This modified scheme greatly simplifies the calculation of higher order terms and shown to be equivalent to the Floquet theory (single or multimode time-dependence) but allows one to derive the effective Hamiltonian in the Hilbert space. Basic applications of the FME scheme are described and compared to previous treatments based on AHT, FT, and static perturbation theory. We discuss also the convergence aspects of the three schemes (AHT, FT, and FME) and present the relevant references. 相似文献
79.
Teodorico C. Ramalho Luiz C. A. Oliveira Kele T. G. Carvalho Eugênio F. Souza Elaine F. F. da Cunha Marcelo Nazzaro 《Molecular physics》2013,111(2):171-179
This paper describes the preparation and use of a new class of materials based on synthetic niobia as catalysts in the oxidation of organic compounds in aqueous medium. The chemical reactions were carried out in the presence of hydrogen peroxide (H2O2). The material was characterized with X-ray diffraction, XPS and H2-TPR (temperature-programmed reduction) measurements. The organic molecule methylene-blue was used in the decomposition study as a probe contaminant. The analysis using the ESI-MS technique showed complete oxidation observed through different intermediates. This suggests the use of niobia species as an efficient Fenton-like catalyst in degradation reactions. Theoretical quantum DFT calculations were carried out in order to understand the degradation mechanism. 相似文献
80.
Lincoln Brum Leite Gusmão Pinheiro Francisco Carlos Serbena Carlos Eugênio Foerster Pedro Rodrigues Júnior Alcione Roberto Jurelo Adilson Luiz Chinelatto Jorge Luiz Pimentel Júnior 《Physica C: Superconductivity and its Applications》2011,471(5-6):179-184
The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr2GdCu2O8 superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m1/2. 相似文献