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261.
Jacob LA Matos B Mostafa C Rodriguez J Tillotson JK 《Molecules (Basel, Switzerland)》2004,9(8):622-626
Benzyl selenocyanates can be made from the corresponding benzylic bromides or chlorides in 30-60 minutes using acetonitrile as a solvent. The products may be obtained pure in satisfactory yields without recourse to chromatography. 相似文献
262.
We experimentally demonstrate operation of a laterally deformable optical nanoelectromechanical system grating transducer. The device is fabricated in amorphous diamond with standard lithographic techniques. For small changes in the spacing of the subwavelength grating elements, lossy propagating resonant modes in the plane of the grating cause a large change in the optical reflection amplitude. An in-plane motion detection sensitivity of 160 fm/square root(Hz) was measured, exceeding that of any other optical microelectromechanical system transducer to our knowledge. Calculations predict that this sensitivity could be improved to better than 40 fm/square root(Hz) in future designs. In addition to having applications in the field of inertial sensors, this device could also be used as an optical modulator. 相似文献
263.
Total syntheses of (+)-bernumidine and its unnatural enantiomer were accomplished through chemoenzymatic dynamic kinetic resolution and ruthenium(II)-catalyzed enantioselective hydrogenation, which provided (R)-salsolidine propyl carbamate and N-acetyl (S)-salsolidine in high yields and enantiomeric excesses, respectively. Both enantiomers of salsolidine were accessed and converted into (+)- and (?)-bernumidine via simple and efficient transformations. 相似文献
264.
Highly direct asymmetric syntheses of phosphatidylinositol-3-phosphate (PI3P) in each enantiomerically pure form have been achieved. The key step involves catalytic asymmetric phosphorylation of meso-myo-inositol derivatives through desymmetrization. Protecting group schemes have been employed that allow for synthesis of PI3P with either saturated or arachidonate side chains, in analogy to the naturally occurring systems. Syntheses in each enantiomeric series are reported that rely on the choice of enantioselective peptide-based catalyst to define the enantiomeric series in which the syntheses are carried out. 相似文献
265.
In this work the effects of sludge disposal on pH values, buffer capacity and adsorption capacity of an acid soil were studied. A stabilized waste water sludge and a paper mill sludge were employed; the pH values of both sludges were higher than 8. The observed differences between soil-urban sludge and soil-paper mill sludge systems can be ascribed to the nature of the compounds present in the sludges and adsorbed on the soil. Both kinds of sludge are able to modify the natural pH of the soil, the buffer capacity and its capacity to retain metal. These modifications increase with increasing soil-sludge contact time and are higher for paper mill sludges. Temperature affects only the modifications due to urban sludge treatment. 相似文献
266.
Bianca Bitterlich Gopinathan Anilkumar Dr. Feyissa Gadissa Gelalcha Dr. Björn Spilker Dr. Anne Grotevendt Ralf Jackstell Dr. Man Kin Tse Dr. Matthias Beller Prof. Dr. 《化学:亚洲杂志》2007,2(4):521-529
The development of inexpensive and practical iron catalysts for the environmentally benign epoxidation of olefins with hydrogen peroxide as terminal oxidant is described. By systematic variation of ligands, metal sources, and reaction conditions, it was discovered that FeCl3?6H2O in combination with pyridine‐2,6‐dicarboxylic acid and different amines shows high reactivity and excellent selectivity towards the epoxidation of aromatic olefins and moderate reactivity towards that of aliphatic olefins. 相似文献
267.
Sylvia C.S. Teixeira Maria Margareth Moreira Aline P. Lima Luciene S. Santos Bianca M. da Rocha Edson S. de Lima Raphael A.A.F. da Costa Ana Lúcia N. da Silva Marisa C.G. Rocha Fernanda M.B. Coutinho 《Polymer Testing》2005,24(8):983-987
Calcium carbonate (CaCO3)/high density polyethylene (HDPE) composites were prepared in a HAAKE twin screw extruder. The influence of the CaCO3 particle size and content and the processing conditions were investigated by using a factorial experimental design. The dependent variables studied were tensile properties, such as Young's modulus, stress at break and toughness, and the rheological property, zero-shear viscosity, η0. Preliminary results have shown that the most significant processing variables were content and mineral filler type. Mathematical modeling has given us a more efficient evaluation of the results obtained and has become an important tool in the development of this work. 相似文献
268.
The isoxazol derivative leflunomide [N-(4'-trifluoromethylphenyl)-5-methylisoxazole-4-carboxamide] is an inhibitor of de novo pyrimidine synthesis used for the treatment of rheumatoid artrithis. In the present study, a liquid-liquid extraction-based reversed-phase HPLC method with UV detection was validated and applied for the analysis of leflunomide and its active metabolite, A77 1726, in human plasma. The analytes were separated using a mobile phase, consisting of acetonitrile, water and formic acid (40/59.8/0.2, v/v), at a flow rate of 0.5 mL/min, and UV detection at 261 nm. The retention times for A77 1726, leflunomide and warfarin (internal standard) were 8.2, 16.2 and 12.2 min, respectively. The validated quantification range of the method was 0.05-100 micro g/mL for leflunomide and 0.1-100 micro g/mL for A77 1726. The developed procedure was applied to assess steady-state plasma concentrations of A77 1726 in patients with rheumatoid arthritis treated with 10 or 20 mg leflunomide per day. 相似文献
269.
Non-covalent porphyrin and metalloporphyrin fibers of bimolecular thinness in bulk aqueous media are compared with the well-known H- and J-aggregates of cyanines. The J-aggregates of cyanines fluoresce and are useful as photographic sensitizers. The J-aggregates of porphyrins show light-induced charge separation and the corresponding metal complexes produce stable radical dimers. The distance between the metalloporphyrin centers is calculated from circular dichroism spectra to be 8 Å in the J-aggregates and about 4 Å in the H-aggregates. Multi-electron reactions of the fibers in the ground and excited states can therefore occur in the fibrous porphyrin assemblies. In amphiphilic tetraphenylporphyrins (“octopus porphyrin”), on the other hand, the porphyrin–porphyrin distance is much larger and the fiber dissolves electron-accepting compounds, e.g. quinones, which also allow for multiple charge separation within such a fiber. 相似文献
270.
21.0%‐efficient co‐diffused screen printed n‐type silicon solar cell with rear‐side boron emitter
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Nadine Wehmeier Bianca Lim Anja Nowack Jan Schmidt Thorsten Dullweber Rolf Brendel 《固体物理学:研究快报》2016,10(2):148-152
Plasma enhanced chemical vapor deposition (PECVD) is applied to deposit boron silicate glasses (BSG) acting as boron diffusion source during the fabrication of n‐type silicon solar cells. We characterize the resulting boron‐diffused emitter after boron drive‐in from PECVD BSG by measuring the sheet resistances Rsheet,B and saturation current densities J0,B. For process optimization, we vary the PECVD deposition parameters such as the gas flows of the precursor gases silane and diborane and the PECVD BSG layer thickness. We find an optimum gas flow ratio of SiH4/B2H6= 8% and layer thickness of 40 nm. After boron drive in from these PECVD BSG diffusion sources, a low J0,B values of 21 fA/cm2 is reached for Rsheet,B = 70 Ω/□. The optimized PECVD BSG layers together with a co‐diffusion process are implemented into the fabrication process of passivated emitter and rear totally diffused (PERT) back junction (BJ) cells on n‐type silicon. An independently confirmed energy conversion efficiency of 21.0% is achieved on 15.6 × 15.6 cm2 cell area with a simplified process flow. This is the highest efficiency reported for a co‐diffused n‐type PERT BJ cell using PECVD BSG as diffusion source. A loss analysis shows a small contribution of 0.13 mW/cm2 of the boron diffusion to the recombination loss proving the high quality of this diffusion source. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献