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991.
The biosorption of uranium by the seaweed Sargassum filipendula was investigated under dynamic conditions at various bed heights. Our results indicate that a bed height of 40.0 cm (111.9 g biomass) was the most efficient for long-term operation of the continuous system. Our results also indicate that the effluent solutions produced are in accordance with Brazilian legislation for safe discharge of uranium in aqueous streams. The efficiency of the process increased with an increase in bed height from 5.0 to 40.0 cm due to changes in the transfer zone. In treatment of a real effluent contaminated with uranium, stable heavy metals and essential metals, 64% of the uranium was biosorbed, as well as the stable heavy metals chromium, lead and barium. The essential metals calcium, magnesium, iron and manganese were not biosorbed by the seaweed, in fact, their concentrations in the solution increased due to ion-exchange mechanisms with the constituent polysaccharides of the biomass. Another important result was the 85–87% reduction of mass obtained after drying and calcination of the biomass. This is a relevant indication that long-term storage of biomass loaded with radionuclides and heavy metals is possible after concentration of the contaminants. In the present work, the reduction in total mass of the loaded biomass was considerable, thus facilitating storage of the contaminated seaweed.  相似文献   
992.
The development of micro-flow devices by direct-milling on poly(methyl methacrylate) (PMMA) substrates and incorporating the optic detector into the same structure is presented, evaluated and applied to the determination of chlorhexidine. Hydrodynamic characteristics of the developed devices were compared against those obtained from flow systems based on classic Teflon reactors. The optical detector integrated in the PMMA substrate is composed of a light emitting diode (λ?=?627 nm) and light dependence resistance as light source and light detector, respectively. The performance of the optical detector was evaluated and optimized. The applicability of the fluidic device was assessed in the determination of chlorhexidine through its colorimetric reaction with bromocresol green. Micro-pumps were used as propulsion units. Results obtained in real sample analysis were in good agreement with those obtained by the reference procedure.  相似文献   
993.
A sensitive and expeditious CE-ESI-MS analytical method for the separation, identification and determination of seven selected antioxidants (cinnamic and benzoic acids), including three isomers of coumaric acid (ortho-, meta- and para-) has been developed. In order to obtain the analytical separation, capillary electrophoresis and CE-MS interface parameters (e.g., buffer pH and composition, sheath liquid and gas flow rates, sheath liquid composition, electrospray voltage, etc.) were carefully optimized.The polar fraction containing the selected phenolic acids was obtained using a previously optimized SPE pretreatment. An MS detector in order to extract structural information about the target compounds and facilitate their qualitative analysis was used in the negative ion mode. The proposed off-line SPE CE-ESI-MS method was validated by assessing its precision, LODs and LOQs, linearity range and accuracy.The optimized and validated method was used in order to quantify the selected antioxidants in various samples of virgin olive oil and extra-virgin olive oil obtained from the main olive varieties cropped in Castilla-La Mancha, Spain. Salicylic acid was used as internal standard throughout in order to ensure reproducibility in the quantitative analysis of the oil samples.The results confirmed the presence of hydroxyphenyl acetic, p-coumaric, ferulic and vanillic acids in substantial amounts (μg g−1 level) in all samples.  相似文献   
994.
A fast access to novel 5-carboxamide-substituted tetrahydrochromeno[7,8-d]imidazoles 4 was developed using the readily available preclinical candidate BYK 405879 (1) as starting material. The 5-amino function was installed by the Curtius rearrangement of carboxylic acid 2 or by the Hofmann rearrangement of carboxamide 8 furnishing benzimidazole 3 as key intermediate. In the Ghosh Schild rat, some of the target compounds 10-14 showed noteworthy activity as potassium-competitive acid blockers.  相似文献   
995.
A variety of α,β-unsaturated aryl esters were prepared by the direct reaction of unsymmetrical aryltellurides and ethyl acrylate, catalyzed by PdCl2 via a Heck cross-coupling reaction.  相似文献   
996.
Partition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na2SO4 and Li2SO4). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li2SO4 ? Na2SO4. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li2SO4 and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li2SO4 and low pH values within the ranges studied.  相似文献   
997.
We report on the first proficiency test in the context of honey bee disease testing on a broad international scale. Honey samples were distributed to 12 participating laboratories for isolation and identification of spores of the etiological agent of American foulbrood, Paenibacillus larvae. Of the 11 laboratories responding to this proficiency testing event, only 6 (54%) provided data that were in full agreement with the previously determined status of the honey samples; eight (72%) laboratories fell within the threshold for qualification as defined a priori in this proficiency test (=level of agreement of at least 90%). Some lessons can now be drawn from the organizational point of view and will certainly improve new initiatives to be taken.  相似文献   
998.
We consider a proper, umbilic-free immersion of an n-dimensional manifold M in the sphere S n+1. We show that M is a Moebius isoparametric hypersurface if, and only if, it is a cyclide of Dupin or a Dupin hypersurface with constant Moebius curvature.  相似文献   
999.
The Trichilia genus (Meliaceae) consists of about 230 species distributed throughout tropical America and its phytochemical profile is rich in terpenic metabolites. Droplet counter-current chromatography (DCCC) was used for the isolation and purification of secondary metabolites obtained from a dichloromethane fraction (2.9 g) of Trichilia quadrijuga stems. A hexane–ethyl acetate–methanol–water (1:2:1.75:1, v/v/v/v) solvent system was chosen to isolate 2β,3β,4β-trihydroxypregnan-16-one (1, 24.5 mg, 0.8%), kudtdiol (2, 45.0 mg, 1.6%) and 3-O-β-d-glucopyranosylsitosterol (3, 6.0 mg, 0.2%). The results showed that DCCC was a very effective tool for the isolation of terpenes from T. quadrijuga.  相似文献   
1000.
The aim of this study was to investigate antimicrobial activity of textiles doped with silver in different forms. Three types of textiles were prepared and examined: textiles doped with commercially available Ag nanoparticles, textiles doped with commercial colloidal silver and textiles doped with silver silica SiO2/Ag spheres. The specimens of silica submicron spheres were synthesized by the sol–gel method as a matrix for biological active silver. The results of microbiological tests revealed that among three kinds of Ag doped textiles only these doped with SiO2/Ag spheres are bacteriostatically active. During the experiments minimal inhibiting bacteria growth concentration of active SiO2/Ag spheres added to textiles was determined.  相似文献   
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