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排序方式: 共有1418条查询结果,搜索用时 62 毫秒
101.
Dr. Nina Erini Vera Beermann Martin Gocyla Manuel Gliech Dr. Marc Heggen Dr. Rafal E. Dunin-Borkowski Prof. Peter Strasser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6633-6638
Direct ethanol fuel cells are attractive power sources based on a biorenewable, high energy-density fuel. Their efficiency is limited by the lack of active anode materials which catalyze the breaking of the C−C bond coupled to the 12-electron oxidation to CO2. We report shape-controlled PtNiRh octahedral ethanol oxidation electrocatalysts with excellent activity and previously unachieved low onset potentials as low as 0.1 V vs. RHE, while being highly selective to complete oxidation to CO2. Our comprehensive characterization and in situ electrochemical ATR studies suggest that the formation of a ternary surface site ensemble around the octahedral Pt3Ni1Rhx nanoparticles plays a crucial mechanistic role for this behavior. 相似文献
102.
Noe Oña Antonio Romero Carmen Assiego Claudia Bello Pierre Vogel M. Soledad Pino-González 《Tetrahedron: Asymmetry》2010,21(17):2092-2099
An approach to the synthesis of polyhydroxyazepane derivatives from sugar-based epoxyamides or epoxyalcohols, in which the total regioselective epoxide opening by nitrogen nucleophiles is the key step, is described. Thus, novel polyhydroxyazepane carboxamides and aminomethyl polyhydroxyazepanes, with potential pharmacological interest, are synthesized from diacetone d-mannose. Configurational assignments of the obtained products were determined. 相似文献
103.
Maria J. Alves Vera C.M. Duarte Hélio Faustino António Gil Fortes 《Tetrahedron: Asymmetry》2010,21(15):1817-1820
Erythrose benzylidene-acetal 1,3-butadienes are studied as partners in Diels–Alder cycloadditions. A high diastereofacial improvement is found in cases where both the alcohol function is protected and a π–π interaction between the diene and dienophile is possible. Several competing factors have been studied independently in order to explain its influence on the selectivity of the cycloadditions. 相似文献
104.
The mixed aggregate (MA) method was evaluated for the routine determination of total ethoxylated nonionic surfactants in municipal raw and treated sewage. Nonionics in wastewater samples were enriched with a C8 solid-phase extraction cartridge, eluted with ethyl acetate-methanol, and separated from interferences with stacked strong anionic (quaternary ammonium form) and cationic (benzenesulfonic acid form) exchange columns. Sample extracts were evaporated to dryness and redissolved in distilled water. The total amount of ethoxylates, on a weight basis, was determined by measuring the critical micelle concentration of a mixed micelle made up of ethoxylates and the anionic surfactant sodium dodecyl sulfate, used as the reagent. The dye Coomassie Brilliant Blue G was used as a photometric probe. The minimum amount of ethoxylate required for a single determination was 1 microg. For raw sewage samples, mean recoveries and standard deviations were 98 +/- 6 and 98 +/- 4% at fortification levels of 0.3 and 0.6 microg/mL, respectively. For treated sewage samples, mean recoveries and standard deviations were 95 +/- 2 and 100 +/- 2% at fortification levels of 0.03 and 0.06 microg/mL, respectively. The MA method and the classical bismuth active substances and cobalt thiocyanate active substances procedures were compared. The former offers some significant advantages over the classical procedures in terms of sensitivity, selectivity, precision, simplicity, and rapidity; the type of response is independent of both the molecular weight and the chain length of the surfactant. 相似文献
105.
Alpha-galactosyl ceramide has been identified to be a potent stimulatory agent for a novel immunological process, mediated by CD1 molecules. This paper describes a short and efficient synthesis of alpha-galactosyl ceramide. Starting from commercially available 2-deoxy galactose, a suitable sphingosine derivative was obtained in nine steps and 36% overall yield, which was subsequently glycosylated to give the target molecule. This flexible route will provide various glycolipids for further exploration of this interesting biological process. 相似文献
106.
Experiments are presented elucidating how the evolution of foam microstructure by gas diffusion from high to low pressure bubbles can significantly speed up the rate of gravitational drainage, and vice versa. This includes detailed data on the liquid-fraction dependence of the coarsening rate, and on the liquid-fraction and the bubble-size profiles across a sample. These results can be described by a "coarsening equation" for the increase of bubble growth rate for drier foams. Spatial variation of the average bubble size and liquid fraction can also affect the growth and drainage rates. 相似文献
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J. Stach U. Abram R. Kirmse W. Dietzsch Vera K. Belyaeva I.N. Marov 《Polyhedron》1983,2(11):1205-1207
During the reaction of [Cu(mnt)2]2? with CuX2 (X = Cl, Br) [Cu(mnt)X2]2? species are formed and characterized EPR spectroscopically supporting a dissociative mechanism for ligand exchange reactions between [Cu(mnt)2]2? and other Cu(II), Ni(II) and Pd(II) complexes which contain unsaturated dichalcogeno ligands. 相似文献