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81.
Sirsch P Clark NL Onuţ L Burchell RP Decken A McGrady GS Daoud-Aladine A Gutmann MJ 《Inorganic chemistry》2010,49(24):11395-11402
The neutron and X-ray structures of [Na(15-crown-5)][BH(4)] and [Na(15-crown-5)][AlH(4)], respectively, are reported, along with a topological analysis of their DFT-computed charge densities that explores the bonding between the anionic complex hydride [EH(4)](-) (E = B, Al) and the counterion [Na(15-crown-5)](+). In each case, the interaction is weak and mainly electrostatic in nature; however, notable differences are observed in the manner in which [BH(4)](-) and [AlH(4)](-) bind to the metal, which explains their different coordination modes. A range of unconventional E-H···H-C contacts is revealed to play an important role in the overall bonding and crystal packing of both complexes. These interactions can be classified as weak dihydrogen bonds based on the atoms in molecules approach. 相似文献
82.
83.
Aziz Elkechai Abdou Boucekkine Lotfi Belkhiri Didier Hauchard Caroline Clappe Michel Ephritikhine 《Comptes Rendus Chimie》2010,13(6-7):860-869
Electron affinities (EAs) of a series of biscyclopentadienyl and phospholyl uranium(IV) complexes L2U(BH4)2 [L2 = Cp2, (tmp)2, (tBuCp)2, (Cp*)(tmp) and Cp*2] related to the U(III)/U(IV) redox system were calculated using relativistic Density Functional Theory (DFT) based methods coupled with the Conductor-like Screening Model for Real Solvents (COSMO-RS) approach. Electrochemical measurements of half-wave potentials in solution (tetrahydrofuran THF) were carried out for all these compounds under the same rigorous conditions. A good correlation (r2 = 0.99) is obtained between the calculated EA values, at the ZORA/BP86/TZ2P level, and the half-wave reduction potentials measured by electrochemistry. The investigations bring to light the importance of spin-orbit coupling and solvent effect and the use of a large basis set in order to achieve such a good agreement between theory and experiment. The study confirms the instability of the Cp2U(BH4)2 complex during the reduction process. The influence of the substituted aromatic ligand L2, namely their electron donating ability, on EA was studied. The role of involved orbitals (singled occupied molecular orbital –SOMO– of anionic species or lowest unoccupied molecular orbital –LUMO– of neutral species) in the redox process was revealed. 相似文献
84.
A. Aziz S. Jan F. Waqar B. Mohammad M. Hakim W. Yawar 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):117-121
An ion exchange method has been developed for the separation of uranium from trace level metallic impurities prior to their
determination by inductively coupled plasma optical emission spectrometry (ICP-OES) in uranium materials. Selective separation
of uranium from trace level metallic impurities consisting Cr, Co, Cu, Fe, Mn, Cd, Gd, Dy, Ni, and Ca was achieved on anion
exchange resin Dowex 1 × 8 in sulphate medium. The resin (100–200 mesh, in chloride form) was packed in a small Teflon column
(7.8 cm × 0.8 cm I.D.) and brought into sulphate form by passing 0.2 N ammonium sulphate solution. Optimum experimental conditions
including pH and concentration of sulphate in the liquid phase were investigated for the effective uptake of uranium by the
column. Uranium was selectively retained on the column as anionic complex with sulphate, while impurities were passed through
the column. Post column solution was collected and analyzed by ICP-OES for the determination of metallic impurities. Up to
2,500 μg/mL of uranium was retained with >99% efficiency after passing 25 mL sample through the column at pH 3. Percentage
recoveries obtained for most of the metallic impurities were >95% with relative standard deviations <5%. The method established
was applied for the determination of gadolinium in urania–gadolinia (UO2–Gd2O3) ceramic nuclear fuel and excellent results were achieved. Solvent extraction method using tributylphosphate (TBP) as extractant
was also applied for the separation of uranium in urania–gadolinia nuclear fuel samples prior to the determination of gadolinium
by ICP-OES. The results obtained with the present method were found very comparable with those of the solvent extraction method. 相似文献
85.
Aziz A. Fallah S. Siavash Saei-Dehkordi Mohammad Rahnama 《Radiation Physics and Chemistry》2010,79(10):1073-1078
Ready-to-cook Iranian barbecued chicken consists of cubed chicken breast, lemon juice, salt, red pepper, onion, saffron and vegetable oil with an overall pH value of about 5.5. This product is sometimes consumed under-cooked, hence it may pose health hazards to consumers when contaminated with food-borne pathogens. In this study, the effect of gamma irradiation (0, 1.5, 3 and 4.5 kGy) on the microbial quality of ready-to-cook (RTC) barbecued chicken samples stored at 4 °C for 15 days was investigated. Moreover, the effectiveness of irradiation for inactivating Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella typhimurium inoculated into the samples was also studied. Irradiation of the samples resulted in dose dependent reduction in counts of aerobic mesophilic bacteria, yeasts and molds, Enterobacteriaceae and lactic acid bacteria. Among the microbial flora, yeasts and molds and Enterobacteriaceae were more sensitive to irradiation and got completely eliminated at dose of 3 kGy. D10 values of L. monocytogenes, E. coli O157:H7 and S. typhimurium inoculated into the samples were 0.680, 0.397 and 0.601 kGy, respectively. An irradiation dose of 3 kGy reduced the counts of E. coli O157:H7 to an undetectable level in RTC barbecued chicken but was ineffective on elimination of L. monocytogenes and S. typhimurium. However, none of the food-borne pathogens were detected in the samples irradiated at 4.5 kGy. This study showed that irradiation had no undesirable effects on the initial sensory attributes of barbecued chicken. At the end of the storage period, irradiated samples were more acceptable compared to non-irradiated ones. 相似文献
86.
Anti-reflection coatings of solar cells have been fabricated using different techniques. The techniques used include SiO2 thermal oxidation, ZnO/TiO2 sputtering deposition and porous silicon prepared by electrochemical etching. Surface morphology and structural properties of solar cells were investigated by using scanning electron microscopy and atomic forces microscopy. Optical reflectance was obtained by using optical reflectometer. I-V characterizations were studied under 80 mW/cm2 illumination conditions. Porous silicon was found to be an excellent anti-reflection coating against incident light when it is compared with another anti-reflection coating and exhibited good light-trapping of a wide wavelength spectrum which produced high efficiency solar cells. 相似文献
87.
The influence of Ga and Al atoms interdiffusion on the band structure and absorption coefficient of coupled double quantum wells are investigated on the basis of a potential composed of four modified Wood–Saxon potentials. Wave functions of the real potential are expressed as a superposition of the stationary state wave functions of the “basal” potential. It is shown that interdiffusion leads to the smearing of the rectangular profile of the potential and to the disappearance of the barrier between the wells, as a result of which, the degradation of doublet character of the electron energetic spectrum is observed. It is also shown that interdiffusion leads to the significant change in oscillator strength and in the enhancement of the thermal stability of the absorption spectrum of the considered heterostructure. 相似文献
88.
A. S. Abd‐El‐Aziz E. K. Todd G. Z. Ma 《Journal of polymer science. Part A, Polymer chemistry》2001,39(8):1216-1231
Soluble organoiron polyethers, thioethers, and amines were synthesized via nucleophilic aromatic substitution reactions. The synthesis of these classes of organometallic polymers involved either the reaction of cyclopentadienyliron complexes of dichloroarenes with various oxygen and sulfur dinucleophiles or the reaction of ether‐ or amine‐containing diiron complexes with dithiols. Polymerization reactions with the diiron complexes gave rise to organoiron polymers with alternating ether/thioether or amine/thioether bridges. Removal of the iron moieties from the backbone of these polymers allowed for the production of the corresponding organic materials. Furthermore, the organometallic polymers had much higher solubilities than their organic analogues. Thermogravimetric analysis of the organoiron polymers indicated that the polymers lost their metallic moieties at approximately 200 °C, whereas degradation of the polymer backbones occurred around 500 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1216–1231, 2001 相似文献
89.
Biosensors based on cholinesterase inhibition for insecticides, nerve agents and aflatoxin B1 detection (review) 总被引:1,自引:0,他引:1
Fabiana Arduini Aziz Amine Danila Moscone Giuseppe Palleschi 《Mikrochimica acta》2010,170(3-4):193-214
The present review reports the research carried out during last 9 years on biosensors based on cholinesterase inhibition for nerve agents, organophosphorus and carbammic insecticides, and aflatoxin B1 detection. Relative applications in environmental and food areas are also reported. Special attention is paid to the optimization of parameters such as enzyme immobilization, substrate concentration, and incubation time in the case of reversible inhibition by aflatoxin B1 or irreversible inhibition by organophosphorus and carbamic insecticides, and nerve agents in order to optimize and improve the analytical performances of the biosensor. Evaluation of selectivity of the system is also discussed. 相似文献
90.
Hermann Bouly Duc-Cuong Dang Aziz Moukrim 《4OR: A Quarterly Journal of Operations Research》2010,8(1):49-70
The team orienteering problem (TOP) is a generalization of the orienteering problem. A limited number of vehicles is available
to visit customers from a potential set. Each vehicle has a predefined running-time limit, and each customer has a fixed associated
profit. The aim of the TOP is to maximize the total collected profit. In this paper we propose a simple hybrid genetic algorithm
using new algorithms dedicated to the specific scope of the TOP: an Optimal Split procedure for chromosome evaluation and
local search techniques for mutation. We have called this hybrid method a memetic algorithm for the TOP. Computational experiments
conducted on standard benchmark instances clearly show our method to be highly competitive with existing ones, yielding new
improved solutions in at least 5 instances. 相似文献