Temperature, H2 loading and ultra violet irradiation effects in germanosilicate optical fibers: laser spectroscopy measurements

The effects of heat-treatment and ultraviolet (UV) light at 325 nm on virgin and hydrogen loaded germanosilicate optical fibers have been investigated by using laser spectroscopy technique. The luminescence band around 650 nm is sensitive to heat treatment. The hydrogen reloading of the hydrogen loaded fibers subsequent to heat treatment showed a new emission band around 570 nm. The irradiated fibers have an emission band around 383 nm which was not detected in hydrogen loaded fibers.     

A flow pattern map for gas—liquid flow in horizontal pipes

Various flow pattern maps for two-phase gas—liquid flow in horizontal pipes are tested against the 5935 flow pattern observations presently contained in the UC Multiphase Pipe Flow Data Bank.A new flow regime correlation representing an extension of the work done by Govier and Aziz [3] is presented and is shown to be in better agreement with the data than the other correlations tested. A computer program for this correlation is included.It is also shown that there is no significant improvement obtained by including the effects of the physical properties of the fluids using any of the physical property parameters which have been proposed so far.     

Insights into metal borohydride and aluminohydride bonding: X-ray and neutron diffraction structures and a DFT and charge density study of [Na(15-crown-5)][EH(4)] (E = B, Al)

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.     

Electron affinities of biscyclopentadienyl and phospholyl uranium(IV) borohydride complexes: Experimental and DFT studies

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.     

Selective ion exchange separation of uranium from concomitant impurities in uranium materials and subsequent determination of the impurities by ICP-OES

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.     

Enhancement of microbial quality and inactivation of pathogenic bacteria by gamma irradiation of ready-to-cook Iranian barbecued chicken

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.     

HPLC-MS-MS法测定水体中残留的氨基甲酸酯类农药

应用高效液相色谱-串联质谱(HPLC-MS-MS)联用技术,建立了检测水体中氨基甲酸酯类农药残留的方法。水样经氨基柱固相萃取,二氯甲烷洗脱,梯度流动相洗脱,电喷雾正离子(ESI+)模式采集、选择反应性监测模式(SRM)对定性、定量离子进行MS/MS测定。5种氨基甲酸酯类农药在5～200ng/L范围内线性关系良好,回收率为80%～92%,相对标准偏差均小于10%,方法检出限分别为:异丙威和仲丁威为1.4ng/L,克百威和甲萘威为1.5ng/L,恶虫威为1.6ng/L。该方法适用于水体中氨基甲酸酯类农药残留的检测。     

The effect of anti-reflection coating of porous silicon on solar cells efficiency

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.