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941.
Ramakrishnam Raju Addada Venkata Reddy Regalla Sivarami Reddy Gangireddy Venkata Venkata Naresh Vema Venkateswara Rao Anna 《Journal of heterocyclic chemistry》2019,56(3):815-817
A stereoselective total synthesis of parvistone C, an oxygenated natural styryllactone, has been accomplished in excellent overall yield by employing asymmetric aldol reaction, asymmetric epoxidation and regioselective epoxide ring opening as the key steps. Our synthetic strategy is very simple, concise and no use of protecting groups. 相似文献
942.
Catalyst deposition control is one of the overlooked areas of fuel cell fabrication and research that can affect the overall performance and cost of the fuel cell to manufacture for mass production. The effect of the different individual catalyst layer thicknesses and loadings of the cathode compartment of a direct methanol fuel cell (DMFC) was investigated. The drawdown method was performed at thicknesses varying from 1 mil to 8 mils with platinum loadings ranging from 0.25 mg cm?2 to 2.0 mg cm?2. The membrane electrode assemblies (MEAs) with thicker individual layers (8 mil and 4 mil) performed better overall compared to the ones prepared with thinner individual layers (1 mil). The power density maxima for the different loading levels followed an exponential decrease of platinum utilization at the higher loading levels. The painted MEAs tended to display the similar performance characteristics as the drawdown MEA layers closest to the thickness at the respective loadings. 相似文献
943.
944.
Török B Bucsi I Prakash GK Olah GA 《Chemical communications (Cambridge, England)》2002,(23):2882-2883
The newly developed stable DMEPHF (1/15) complex was found to be a highly effective reagent for the cleavage of peptides from Merrifield resins; ease of handling and its simple, complete removal from the reaction mixture make the reagent system a very useful HF equivalent for applications in solid-phase peptide synthesis. 相似文献
945.
946.
It has been shown that if all order corrections are taken into account in the momentum translation approximation there would not be any contribution to the multiphoton transition amplitude due to momentum translation factor exp (ie A·x). Thus the calculations performed using the momentum translation approximation method, without any consideration to higher order corrections, are incorrect. 相似文献
947.
948.
Structures of the complexes (1 and 8) of the guanidinium ion (H(2)N)(3)C(+) with super Lewis acidic BH(4)(+) and AlH(4)(+) were calculated using the DFT method at the B3LYP/6-311+G** level. (13)C NMR chemical shifts were also calculated by the GIAO-MP2 method. Each of the dicationic complexes contains a hypercoordinate boron or aluminum atom with a two-electron three-center (2e-3c) bond. Guanidinium ion was found to form a strong complex with BH(4)(+) but a relatively weak one with AlH(4)(+). On the other hand, complexations of guanidinium ion with neutral BH(3) and AlH(3) lead only to very weak complexes (5 and 9). The structures of mono- and dicationic complexes were compared with the structures of protonated and methylated guanidinium dications. 相似文献
949.
Ishimoto K Mitoma Y Nagashima S Tashiro H Prakash GK Olah GA Tashiro M 《Chemical communications (Cambridge, England)》2003,(4):514-515
The reduction of carbonyl compounds 1a-h using Ni-Al alloy in water under reflux proceeded to give the corresponding methylene compounds 2a-h within 2 h in 89.0-99.8% relative yields. 相似文献
950.
Effective atomic numbers (Zeff) for different materials of dosimetric interest have been calculated for total photon interaction in the energy region 1 keV–20 MeV. The calculations are made using the mass attenuation coefficients data from Tables of X-ray Mass Attenuation Coefficients and Mass Energy-absorption Coefficients 1 keV to 20 MeV for elements Z = 1 to 92 and 48 Additional Substances of Dosimetric Interest, J. H. Hubbell and S. M. Seltzer (Hubbell and Seltzer, 1995), NISTIR-5632. The variation of Zeff value with energy is discussed. 相似文献