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排序方式: 共有131条查询结果,搜索用时 15 毫秒
1.
A. A. Sonzogni A. S. M. A. Romo M. J. Ozafran S. J. Nassiff 《Journal of Radioanalytical and Nuclear Chemistry》1992,165(5):295-303
Stacks of natural erbium were bombared with -particles with energie of 85 MeV. Cumulative cross sections for the productions of different nuclei were measured using -ray spectroscopy. The data are compared with the theoretical predictions provided by the equilibrium and preequilibrium reaction model. 相似文献
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A. A. Sonzogni A. S. M. A. Romo H. O. Mosca S. J. Nassiff 《Journal of Radioanalytical and Nuclear Chemistry》1993,170(1):143-156
The stacked foil technique was used in combination with γ-ray spectroscopy to obtain excitation functions for the production of different nuclei using natural vanadium as target and 85 MeV α-particles and 46.5 MeV deuterons as projectiles. The data are compared with theoretical predictions provided by an equilibrium and pre-equilibrium reaction model. In most cases the theoretical predictions seriously under-estimated the measured cross sections. 相似文献
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[reaction: see text] Monoenolates of C(2)-symmetric, proline-derived piperazine-2,5-diones were generated and trapped with a variety of electrophiles to produce, in a highly diastereoselective fashion, functionalized diketopiperazines (DKPs). These reactions provide the basis for an asymmetric, desymmetrization strategy toward the marine alkaloids phakellstatin and phakellin. The relative stereochemistry of the functionalized DKPs was confirmed by single-crystal X-ray analysis and/or NOE experiments. Bis-functionalization of the DKPs was also found to proceed with high levels of diastereoselectivity. 相似文献
4.
Hydroxyl Radical Generation and DNA Nuclease Activity: A Mechanistic Study Based on a Surface‐Immobilized Copper Thioether Clip‐Phen Derivative
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Adolfo I. B. Romo Dieric S. Abreu Dr. Tércio de F. Paulo Dr. Marta S. P. Carepo Prof. Eduardo H. S. Sousa Prof. Luis Lemus Prof. Carolina Aliaga Prof. Alzir A. Batista Prof. Otaciro R. Nascimento Prof. Héctor D. Abruña Prof. Izaura C. N. Diógenes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10081-10089
Coordination compounds of copper have been invoked as major actors in processes involving the reduction of molecular oxygen, mostly with the generation of radical species the assignment for which has, so far, not been fully addressed. In the present work, we have carried out studies in solution and on surfaces to gain insights into the nature of the radical oxygen species (ROS) generated by a copper(II) coordination compound containing a thioether clip‐phen derivative, 1,3‐bis(1,10‐phenanthrolin‐2‐yloxy)‐N‐(4‐(methylthio)benzylidene)propan‐2‐amine (2CP‐Bz‐SMe), enabling its adsorption/immobilization to gold surfaces. Whereas surface plasmon resonance (SPR) and electrochemistry of the adsorbed complex indicated the formation of a dimeric CuI intermediate containing molecular oxygen as a bridging ligand, scanning electrochemical microscopy (SECM) and nuclease assays pointed to the generation of a ROS species. Electron paramagnetic resonance (EPR) data reinforced such conclusions, indicating that radical production was dependent on the amount of oxygen and H2O2, thus pointing to a mechanism involving a Fenton‐like reaction that results in the production of OH.. 相似文献
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Adriana Reyes‐Mayer Bonifacio Alvarado‐Tenorio Angel Romo‐Uribe Michael Jaffe 《先进技术聚合物》2013,24(12):1029-1039
The influence of heat treatment on the texture, microstructure and tensile mechanical properties of extruded thin films of a series of high‐performance thermotropic liquid crystal polymers (LCPs) was investigated. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were kindly supplied by the former Hoechst Celanese Corp as 50 µm thick extruded tapes. The LCPs, denoted B‐N, COTBP and RD1000, have B and N as common comonomers and vary the other comonomers. Thus, this study also enables the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid‐to‐nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B‐N and RD1000), or increased significantly Ts→n (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young's modulus, E, along the extrusion axis, increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as‐extruded film. The results also showed that the optimum treatment time for improving the Young modulus, under dry air atmosphere, was between 3 and 4 h. Wide‐angle X‐ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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In this paper we study a family of stochastic orders of random variables defined via the comparison of their percentile residual life functions. Some interpretations of these stochastic orders are given, and various properties of them are derived. The relationships to other stochastic orders are also studied. Finally, some applications in reliability theory and finance are described. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
9.
[reaction: see text] Beta-lactones are useful synthetic intermediates allowing access to a number of functional arrays. In this report, enantiomerically pure 4-trichloromethyl-2-oxetanone is shown to be a versatile amino acid synthon leading to a variety of gamma-substituted alpha-amino acid precursors. The utility of this methodology was demonstrated by the concise synthesis of a protected homoserine equivalent, alpha-azidobutyro lactone, and a naturally occurring alpha-amino acid from the seeds of Blighia unijugata. 相似文献
10.
[reaction: see text] The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels-Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence. 相似文献