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123.
Rolando Gonzlez-Pea Rosa María Cibrin-Ortiz de Anda Angel J Pino-Velazquez Jos Soler-de la Cruz Yhoama Gonzlez-Jorge 《Optics and Lasers in Engineering》2000,34(2)
Speckle metrology and holographic interferometry (HI) have been used in several civil engineering applications. We present the results obtained by applying speckle photography (SP) to the study of two quadratic shearwalls with different boundary conditions, and the potential of the technique in the study of this kind of structures is described. The analysis of Young's fringes obtained with this technique at certain points on each shearwall provides the whole field of displacement measurements. HI has been used to measure the three components of absolute displacement, verifying that the bulging phenomenon does not affect the in-plane components when the applied load remains on the same plane as the shearwall. A qualitative analysis is carried out following an electronic speckle pattern interferometry (ESPI) technique. The results obtained by optical techniques are compared to the numerical results obtained by the finite element method (FEM), finding good correlation between them in all the cases. 相似文献
124.
Juan M. Antelo Florencio Arce Juan Crugeiras Julia Franco Pilar Rodriguez Angel Varela 《国际化学动力学杂志》1990,22(12):1271-1282
This article reports the kinetics of the decomposition of N-bromoserine formed rapidly by bromation of serine by BrO?. The main decomposition products are glycolaldehyde, ammonia, carbon dioxide, and bromide ions at pH < 11.5, and β-hydroxypyruvic acid, ammonia, and bromide ions at pH > 11.5. The reaction is of order one with respect to N-bromoserine, and is independent of ionic strength and excess serine. The rate constant increases with increasing pH at pH > 11 and with decreasing pH at pH < 8, and over the range pH 8–11 has the constant value 1.67 × 10?3 s?1 at 298 K. 相似文献
125.
126.
José Angel Brito Helena Teruel Stéphane Massou Montserrat Gómez 《Magnetic resonance in chemistry : MRC》2009,47(7):573-577
Oxomolybdenum(VI) complexes containing diverse ligands from an electronic and topological point of view have been analysed by means of 95Mo NMR in solution with the purpose of using this technique as a tool to study their coordination chemistry and reactivity. The relationship between the electronic density on the metal tuned by the electron‐donor ability of the coordinated ligands and the 95Mo chemical shift has been proved for mono‐ and bimetallic complexes showing a hexa‐ or hepta‐coordination around the metal centre. The different origins of the signal broadening (associated either to the symmetry of the metallic polyhedron or to the presence of isomers or to the ligand de‐coordination) have been also considered to rationalise the obtained data. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
127.
Jacqueline Jiménez Mildred López Vladimir Carranza Angel Mendoza Jenaro Varela Estibaliz Sansinenea Aurelio Ortiz 《Tetrahedron letters》2017,58(3):235-239
An alternative methodology for the synthesis of chiral 3-(p-tolyl) butanoic acids is presented. This was accomplished through the diastereoselective hydrogenation reaction of different chiral N-3-(p-tolyl) but-2-enamides, using Pd/C in EtOH, to produce the corresponding chiral N-3-(p-tolyl) butanamides with high chemical yields and moderate diastereomeric ratios. Removal of the chiral auxiliary from N-3-(p-tolyl) butanamides gave the respective enantiomerically pure acids. 相似文献
128.
Zhanghua Zeng Dr. Angel A. J. Torriero Dr. Alan M. Bond Prof. Leone Spiccia Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9154-9163
The [Fc? bis{ZnII(TACN)(Py)}] complex, comprising two ZnII(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7‐triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene‐bearing ZnII(TACN) units are arranged in a trans‐like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di‐ and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by 31P NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(ZnII(TACN)) moiety of [Fc? bis{ZnII(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(ZnII(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fc? bis{ZnII(TACN)(Py)}] among the anions tested based on a six‐fold fluorescence enhancement and 0.1 V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475 nm in CH3CN/Tris‐HCl (1:9) buffer solution (10.0 mM , pH 7.4). These measurements confirmed that pyrophosphate binds more strongly (Kb=(4.45±0.41)×106 M ?1) than the other nucleotide di‐ and triphosphates (Kb=1–50×105 M ?1) tested. 相似文献
129.
Angel Marcos-Fernández Alberto Tena José G. de la Campa Laura Palacio Antonio Hernández 《European Polymer Journal》2010,46(12):2352-2364
Polyimides having long poly(ethylene oxide), PEO, moieties in the main chain have been synthesized by a classical two-steps polycondensation method with good yield and high molecular weight. In contrast with previous works on this topic, essentially full conversion of the polyamic acid to polyimide was attained by heating at relatively low temperatures (around 160 °C).These copolyimides undergo an increase of phase separation between the PEO part and the polyimide one after a thermal annealing. This phase separation increases gas separation properties of membranes made up of these copolymers. An exhaustive study of polymer properties as a function of the thermal treatment has been carried out in order to figure out the origin of this behavior. The analysis performed included TGA, DSC, SAXS and mechanical testing.The polymers studied in this paper have medium thermal stability. In fact, degradation of the polyether chain under nitrogen takes place at temperatures above 300 °C. However, their thermal stabilities were much lower under oxidant atmosphere. 相似文献
130.
Joaquim Messeguer Marisol Montolio Eduardo Soriano Angel Messeguer 《Tetrahedron》2010,66(13):2444-5027
A study on the preparation of N-alkylglycines (peptoids) that contain tertiary amino residues on the N-alkyl side chains is reported. The appropriate combination of the submonomer strategy with N-alkylglycine monomer couplings depending upon the structure of the N-alkyl side chain that must be incorporated into the peptoid is determinant for the efficiency of the synthetic pathway. The application of this strategy to the preparation of SICHI, an N-alkyglycine trimer containing tertiary amino residues in the three N-alkyl branches, and that has been identified as a potent Semaphorin 3A inhibitor, is presented. 相似文献