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排序方式: 共有186条查询结果,搜索用时 31 毫秒
61.
Abdul Qadir Shah Tasneem Gul Kazi Muhammad Balal Arain Muhammad Khan Jamali Hassan Imran Afridi Nusrat Jalbani Jamil Ahmed Baig Ghulam Abbas Kandhro 《Food chemistry》2009
The aim of the study was to evaluate total arsenic (As) in five tissues (gills, mouthpiece, intestine, liver and muscles) of 10 fish species caught from As contaminated Manchar Lake (26°3′N: 67°6′E) Sindh Pakistan during 2006–2007. The total As concentration was determined by hydride generation atomic absorption spectrometry (HG-AAS), prior to microwave assisted acid digestion. The certified reference material DORM-2 (dogfish muscle) was used to check the quality control of the technique. The good agreement with the certified value at 95% confidence limit confirmed the validity of As determination method. The limit of detection (LOD) and limit of quantitation (LOQ) of As were 0.034 and 0.11 μg/g, respectively. 相似文献
62.
A real-coding jumping gene genetic algorithm (RJGGA) for multiobjective optimization 总被引:2,自引:0,他引:2
This paper presents a real jumping gene genetic algorithm (RJGGA) as an enhancement of the jumping gene genetic algorithm (JGGA) [T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, A jumping gene algorithm for multiobjective resource management in wideband CDMA systems, The Computer Journal 48 (6) (2005) 749-768; T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, Multiobjective optimization of radio-to-fiber repeater placement using a jumping gene algorithm, in: Proceedings of the IEEE International Conference on Industrial Technology (ICIT 2005), Hong Kong, 2005, pp. 291-296; K.F. Man, T.M. Chan, K.S. Tang, S. Kwong, Jumping-genes in evolutionary computing, in: Proceedings of the IEEE IECON’2004, Busan, 2004, pp. 1268-1272]. JGGA is a relatively new multiobjective evolutionary algorithm (MOEA) that imitates a jumping gene phenomenon discovered by Nobel Laureate McClintock during her work on the corn plants. The main feature of JGGA is that it only has a simple operation in which a transposition of gene(s) is induced within the same or another chromosome in the genetic algorithm (GA) framework. In its initial formulation, the search space solutions are binary-coded and it inherits the customary problems of conventional binary-coded GA (BCGA). This issue motivated us to remodel the JGGA into RJGGA. The performance of RJGGA has been compared to other MOEAs using some carefully chosen benchmark test functions. It has been observed that RJGGA is able to generate non-dominated solutions with a wider spread along the Pareto-optimal front and better address the issues regarding convergence and diversity in multiobjective optimization. 相似文献
63.
Mesoporous silica with regular geometries have been recently paid much attention owing to their scientific importance and great potentials in practical applications such as catalysis, adsorption, separation, sensing, medical usage, ecology, and nanotechnology. Especially, applications often require immobilization of the related functional groups in the mesopores. In order to achieve desire applications, modification of these mesoporous silica are indispensable. In this review, recent progresses of functionalization of mesoporous silica are comprehensively summarized. In the first parts, advances in three major methods, grafting (post-synthetic modification), co-condensation (direct synthesis), and techniques related with periodic mesoporous organosilicates, are explained. In the latter parts, new concepts for functionalization of mesoporous silica including functional template method and lizard template method are introduced. Most of the examples described here have been published in a new millennium. 相似文献
64.
Hydrophobically modified water-soluble block copolymers were prepared by aqueous micellar copolymerization of acrylamide and small amounts (2 and 3 mol %) of a hydrophobe (N-phenethylacrylamide) that is characterized by a long spacer that places the aromatic ring far away from the backbone, with the objective of investigating the copolymers' rheological behavior and surface and interfacial activities under various conditions such as polymer concentration, shear rate, temperature, and salinity. As expected, the block copolymers exhibit improved thickening properties attributed to intermolecular hydrophobic associations as the solution viscosity of the copolymers increases sharply with increasing polymer concentration. Additional evidence for intermolecular association is provided by the effect of NaCl, the presence of which substantially enhances the viscosity. An almost shear rate–independent viscosity (Newtonian plateau) is also exhibited at high shear rate and a typical non-Newtonian shear thinning behavior appears at low shear rates and high temperatures. Furthermore, the block copolymers exhibit high air–liquid surface and liquid–liquid interfacial activities as the surface and interfacial tensions decrease with increasing polymer concentration, indicating strong adsorption of the copolymer at the interface. The surface and interfacial tensions exhibited by the copolymers were found to be relatively insensitive to the concentration of salt (NaCl). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 467–476, 2001 相似文献
65.
Water Resources Management - The study attempts to investigate the significant spatiotemporal variations in the continental United States’ streamflow as a response to large-scale climate... 相似文献
66.
Molecular Determinants for Protein Stabilization by Insertional Fusion to a Thermophilic Host Protein 下载免费PDF全文
Brennal Pierre Jason W. Labonte Tina Xiong Edwin Aoraha Asher Williams Vandan Shah Edward Chau Kazi Yasin Helal Jeffrey J. Gray Prof. Jin Ryoun Kim 《Chembiochem : a European journal of chemical biology》2015,16(16):2392-2402
A universal method that improves protein stability and evolution has thus far eluded discovery. Recently, however, studies have shown that insertional fusion to a protein chaperone stabilized various target proteins with minimal negative effects. The improved stability was derived from insertion into a hyperthermophilic protein, Pyrococcus furiosus maltodextrin‐binding protein (PfMBP), rather than from changes to the target protein sequence. In this report, by evaluating the thermodynamic and kinetic stability of various inserted β‐lactamase (BLA) homologues, we were able to examine the molecular determinants of stability realized by insertional fusion to PfMBP. Results indicated that enhanced stability and suppressed aggregation of BLA stemmed from enthalpic and entropic mechanisms. This report also suggests that insertional fusion to a stable protein scaffold has the potential to be a useful method for improving protein stability, as well as functional protein evolution. 相似文献
67.
Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh
Radloff KA Cheng Z Rahman MW Ahmed KM Mailloux BJ Juhl AR Schlosser P Van Geen A 《Environmental science & technology》2007,41(10):3639-3645
Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout the study. Groundwater and gray sediment were collected as diluted slurries between 5 and 38 m in depth, a range over which ambient groundwater As concentrations increased from 20 to 100 microg L(-1). Arsenic was released to groundwater in slurries from 5 and 12 m in depth at a relatively constant rate of 21 +/- 4 (2 sigma) and 23 +/- 6 microg As kg(-1) yr(-1), respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 +/- 18 mirog kg(-1) yr(-1)). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation thatthe two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater. 相似文献
68.
Tanmay Chattopadhyay Kazi Sabnam Banu Soubhik Chattopadhyay Arpita Banerjee Sandip Mondal Eringathod Suresh Debasis Das 《Inorganic chemistry communications》2009,12(1):26-28
A new coordination chemistry of sodium has been developed by complexing it with a non-chelating neutral nitrogen donor ligand hexamethylenetetramine (urotropine) in presence of cadmium(II) iodide and the new coordination compound has been characterized by X-ray single crystal structural analysis. 相似文献
69.
The effect of weight loss with anorectic medications on sleep apnea, non-insulin-dependent diabetes, and steatohepatitis is illustrated in three cases from practice in a clinical nutrition setting. Prevention of obesity, a chronic disorder, is preferable, but when obesity becomes a major obstacle in the care of patients with respiratory, cardiovascular, and metabolic disorders and osteoarthritis, an intense course of weight reduction using anorectic medications under medical and dietetic guidance is essential for patients' survival and reduction of medical cost. 相似文献
70.
Data and a consistent physical and mathematical model for the kinetic and equilibrium sorptive behavior of cesium with a particulate, nuclear-grade graphite (H-451) is given. The most important conclusions are: (1) The kinetics of absorption and desorption of cesium by H-451 graphite in particulate form (size range 44–74μm) is such that, in general, several days are required to reach a near equilibrium state. Accordingly, the radiometric isopiestic method, although time consuming, appears to be the best method for obtaining equilibrium data in the cesium vapor pressure range of about 10 down to 10−4 Pa. (2) The kinetics data of the isopiestic experiment with graphite powder was found to be very well represented mathematically by an equation which is based on the site activation energy being approximately equal to the sorbate-sorbent site interaction energy, χ. In accordance with a theory for modified-exponential sorption which fits the equilibrium data well, the sites are taken to be non-uniformly distributed having a number which decreases exponentially with an interaction energy, χ, that has a finite upper limit χL. 相似文献