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排序方式: 共有348条查询结果,搜索用时 15 毫秒
1.
Bonelli Giulio Grassi Alba Tanzini Alessandro 《Letters in Mathematical Physics》2019,109(9):1961-2001
Letters in Mathematical Physics - We propose that the grand canonical topological string partition functions satisfy finite-difference equations in the closed string moduli. In the case of genus... 相似文献
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David Ribera Marta Giamberini Angels Serra Ana Mantecn 《Journal of polymer science. Part A, Polymer chemistry》2006,44(21):6270-6286
We reacted various dimeric, liquid‐crystalline epoxy–imine monomers, differing in the length of the central aliphatic spacer or the dipolar moments, with heptanedioic acid. The resulting systems showed a liquid‐crystalline phase in some cases, depending on the dimer and on the reaction conditions. The systems were characterized with respect to their mesomorphic properties and then were submitted to dynamic mechanical thermal analysis in both fixed‐frequency and frequency‐sweep modes in the shear sandwich configuration. The arrangement in the liquid‐crystalline phase seemed to be mainly affected both by the polarization of the mesogen and by the reaction temperature, which favored the liquid‐crystalline arrangement when it was lying in the range of stability of the dimer mesophase. In agreement with other recent literature data, dynamic mechanical thermal analysis results suggested that the presence of the mesogen directly incorporated into the main chain increased the lifetimes of the elastic modes both in the isotropic phase and in the liquid‐crystalline phase with respect to side‐chain liquid‐crystalline elastomers and that the time–temperature superposition principle did not hold through the liquid‐crystalline‐to‐isotropic transition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:6270–6286, 2006 相似文献
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A. Alba M. A. Aramendia V. Borau C. Jimenez J. M. Marinas 《Reaction Kinetics and Catalysis Letters》1984,25(1-2):45-50
The reduction of ,-unsaturated (olefin) carbonyl compounds of the type using a 0.75 wt.% Pd catalyst supported on SiO2–AlPO4 (8020 w/w) in a Parr reactor at low hydrogen pressure is reported. Selectivity in the reduction of the C=C bond is 100% in every case, and the nature of the groups A and B affects reaction rate, thus suggesting a 1,4-hydrogen addition mechanism.
, - () , , 0,75 . % Pd, SiO2–AlPO4 (8020 /), . C=C 100% , A B , 1,4- .相似文献
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Le Faou JH Suomijärvi T Blumenfeld Y Piattelli P Agodi C Alamanos N Alba R Auger F Bellia G Chomaz P Coniglione R Del Zoppo A Finocchiaro P Frascaria N Gaardhoje JJ Garron JP Gillibert A Lamehi-Rachti M Liguori-Neto R Maiolino C Migneco E Russo G Roynette JC Santonocito D Sapienza P Scarpaci JA Smerzi A 《Physical review letters》1994,72(21):3321-3324
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Alba Díaz-Rodríguez 《Tetrahedron letters》2005,46(35):5835-5838
Regioselective syntheses of several O-crotonyl 2′-deoxynucleoside derivatives have been efficiently achieved using a biocatalytic methodology. While Candida antarctica lipase B (CAL-B) afforded the 5′-O-acylated compounds, immobilized lipase from Pseudomonas cepacia (PSL-C) provided the 3′-O-crotonylated analogs. Since classical chemical approaches did not work appropriately due to side isomerization reactions, a mixture of both lipases was used to achieve a useful synthetic route toward diacylated nucleosides. 相似文献
8.
P. Garrigues C. Raoux P. Lemaire A. Mathieu D. Ribera J. F. Narbonne 《International journal of environmental analytical chemistry》2013,93(3):379-387
Abstract Biochemical indices based on enzymatic activities have been determined in fish and mussels sampled in various different coastal locations in the Mediterranean Sea. Preliminary results show a good agreement between biochemical measurements in marine organisms and chemical analyses of polycyclic aromatic hydrocarbons present in sediments. The results obtained suggest the use of biochemical indices for application in chemical contaminant biomonitoring. 相似文献
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Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing 下载免费PDF全文
Judith Wollbrett‐Blitz Sébastien Joannès Rémi Bruant Christophe Le Clerc Marc Romero De La Osa Anthony Bunsell Alba Marcellan 《Journal of Polymer Science.Polymer Physics》2016,54(3):374-384
The transverse and longitudinal mechanical properties of aramid fibers like Kevlar? 29 (K29) fibers are strongly linked to their highly oriented structure. Mechanical characterization at the single fiber scale is challenging especially when the diameter is as small as 15 µm. Longitudinal tensile tests on single K29 fibers and single fiber transverse compression test (SFTCT) have been developed. Our approach consists of coupling morphological observations and mechanical experiments with SFTCT analysis by comparing analytical solutions and finite element modeling. New insights on the analysis of the transverse direction response are highlighted. Systematic loading/unloading compression tests enable to experimentally determine a transverse elastic limit. Taking account of the strong anisotropy of the fiber, the transverse mechanical response sheds light on a skin/core architecture. More importantly, results suggest that the skin of the fiber, typically representing a shell of one micrometer in thickness, has a transverse apparent modulus of 0.2 GPa. That is around more than fifteen times lower than the transverse modulus of 3.0 GPa in the core. By comparison, the measured longitudinal modulus is about 84 GPa. The stress distribution in the fiber is explored and the critical areas for damage initiation are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 374–384 相似文献
10.
In this work we present an optical lattice setup to realize a full Dirac Hamiltonian in 2+1 dimensions. We show how all possible external potentials coupled to the Dirac field can arise from perturbations of the existing couplings of the honeycomb lattice pattern. This greatly simplifies the proposed implementations, requiring only spatial modulations of the intensity of the laser beams to induce complex non-Abelian potentials. We finally suggest several experiments to observe the properties of the quantum field theory in the setup. 相似文献