Membrane-based microchannel device for continuous quantitative extraction of dissolved free sulfide from water and from oil

Underground fluids are important natural sources of drinking water, geothermal energy, and oil-based fuels. To facilitate the surveying of such underground fluids, a novel microchannel extraction device was investigated for in-line continuous analysis and flow injection analysis of sulfide levels in water and in oil. Of the four designs investigated, the honeycomb-patterned microchannel extraction (HMCE) device was found to offer the most effective liquid–liquid extraction. In the HMCE device, a thin silicone membrane was sandwiched between two polydimethylsiloxane plates in which honeycomb-patterned microchannels had been fabricated. The identical patterns on the two plates were accurately aligned. The extracted sulfide was detected by quenching monitoring of fluorescein mercuric acetate (FMA). The sulfide extraction efficiencies from water and oil samples of the HMCE device and of three other designs (two annular and one rectangular channel) were examined theoretically and experimentally. The best performance was obtained with the HMCE device because of its thin sample layer (small diffusion distance) and large interface area. Quantitative extraction from both water and oil could be obtained using the HMCE device. The estimated limit of detection for continuous monitoring was 0.05 μM, and sulfide concentrations in the range of 0.15–10 μM could be determined when the acceptor was 5 μM FMA alkaline solution. The method was applied to natural water analysis using flow injection mode, and the data agreed with those obtained using headspace gas chromatography-flame photometric detection. The analysis of hydrogen sulfide levels in prepared oil samples was also performed. The proposed device is expected to be used for real time survey of oil wells and groundwater wells.     

Deprotection of dithioacetals with 30% hydrogen peroxide catalyzed by tantalum(V) chloride–sodium iodide or niobium(V) chloride–sodium iodide

The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions.     

Crystal habit modifications of imatinib mesylate under various precipitation conditions

Abstract  

Crystals of the α-form of imatinib mesylate with various habits (e.g., polyhedral-like and plate-like) were prepared from various organic solvents (e.g., butyl lactate, 4-methyl-2-pentanone, 2-methyl-2-butanol, 2-isopropoxyethanol, propyl ether) by several precipitation methods. The methods provide imatinib mesylate in a non-needle-shaped crystalline α-form. The crystal modification was identified by hot-stage microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The analyses by DSC, IR, and XRPD indicate that imatinib mesylate crystals with various habits have the same crystal structure. The plate-like habit has been also observed in the system where the organic solvent acts as a precipitant.     

Pore size distribution of micelle-templated silicas studied by thermoporosimetry using water and n-heptane

Thermoporosimetry, i.e., DSC measurements of melting point depression of water and heptane confined in mesopores, has been used for determination the pore size distribution of several mesoporous silicas synthesized with the use of micelle templates. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of nonane. The pore size distributions obtained using the water thermoporosimetry were similar to those determined using the other methods, but the pore size values found for the narrow pore materials were underestimated by ca 1?nm. Too large pore sizes obtained for the wide pore silica from heptane thermoporosimetry were attributed to nonlinear dependence of the melting point depression on the reciprocal of the pore size.     

A Fractal Representation of the Complex Clifford Algebra Equivalent to the Fock Representation

We construct a representation of the infinite dimensional complex Clifford algebra on the Hilbert space of square-integrable complex-valued functions on the Cantor set, which we show to be equivalent to the classical Fock representation.     

Does Euclidean distance work well when the p-median model is applied in rural areas?

The p-median model is used to locate P centers to serve a geographically distributed population. A cornerstone of such a model is the measure of distance between a service center and demand points, i.e. the location of the population (customers, pupils, patients, and so on). Evidence supports the current practice of using Euclidean distance. However, we find that the location of multiple hospitals in a rural region of Sweden with a non-symmetrically distributed population is quite sensitive to distance measure, and somewhat sensitive to spatial aggregation of demand points.