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51.
A new enantioselective synthesis of the anti-influenza agent (-)-oseltamivir free base (7.1% overall yield; 98% ee) and (-)-methyl 3-epi-shikimate (16% overall yield; 98% ee) has been described from readily available raw materials. Sharpless asymmetric epoxidation and diastereoselective Barbier allylation of an aldehyde are the key reactions employed in the incorporation of chirality, while the cyclohexene carboxylic ester core was constructed through a ring closing metathesis reaction. 相似文献
52.
In this paper, the effect of bismuth doping on the structural, morphological, optical and electrical properties of Cu2ZnSnS4 (CZTS) films has been investigated. The undoped and bismuth doped CZTS films (0, 0.5, 1, 1.5 and 2 mol%) were deposited on glass substrates by solution based method. The XRD result shows a significant improvement in the crystallinity of the films with increase in bismuth concentration. The Raman spectra of the films show the dominant peak at 334 cm–1 corresponding to A1 vibrational mode of CZTS kesterite phase. The FESEM micrographs of the films show an enhancement in the grain size and densification with the addition of bismuth ion concentration. The optical bandgap of the films was found to vary (1.59–1.40 eV) with the doping of bismuth ions. The I –V characteristics indicate twofold increment in the photoconductivity for the bismuth doped CZTS films under 100 mW/cm2 illumination suggesting their potential application in photovoltaic devices. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
53.
S. KaramatR.S. Rawat T.L. TanP. Lee S.V. SpringhamE. Ghareshabani R. ChenH.D. Sun 《Applied Surface Science》2011,257(6):1979-1985
Pulsed laser deposition synthesized ZnO thin films, grown at 400 °C substrate temperature in different oxygen gas pressures, were irradiated with 6 shots of pulsed nitrogen ions obtained from 2.94 kJ dense plasma focus to achieve the nitrogen doping in ZnO. Structural, compositional and optical properties of as-deposited and nitrogen ion irradiated ZnO thin films were investigated to confirm the successful doping of nitrogen in irradiated samples. Spectral changes have been seen in the nitrogen irradiated ZnO thin film samples from the low temperature PL measurements. Free electron to acceptor emissions can be observed from the irradiated samples, which hints towards the successful nitrogen doping in films. Compositional analysis by X-ray photoelectron spectroscopy and corresponding shifts in binding energy core peaks of oxygen and nitrogen confirmed the successful use of plasma focus device as a novel source for nitrogen ion doping in ZnO thin films. 相似文献
54.
Pramana - This work concerns the modelling of the dynamics of polarisation of a centrosymmetric material subjected to an amplitude-modulated excitation (AME). The dynamic equation obtained for the... 相似文献
55.
G. Chourasiya R. K. Duggal C. P. Singh A. S. Rawat S. K. Aggarwal H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1985,89(1):89-95
A direct evaporation method is described for the preparation of sources using stainless steel as the backing material and tetraethylene glycol (TEG) as a spreading agent in the presence of large amounts of uranium. It is shown that FWHM and tail contribution at the low energy peak due to energy degradation of the high energy peak can be optimized by heating the source under controlled conditions in a furnace at 500–600°C for about 15 min. An accuracy of 0.5–1% is demonstrated for the determination of238Pu/(239Pu+240Pu) alpha activity ratio in the U/Pu range of 10 to 1500 generally encountered in dissolver solution of irradiated fuel. 相似文献
56.
V.B. Tiwari S. Singh S.R. Mishra H.S. Rawat S.C. Mehendale 《Optics Communications》2006,263(2):249-255
57.
A. Rawat P. J. Jojo A. Kumar R. Prasad 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(5):365-372
The trace uranium concentrations have been determined in tobacco obtained from different brands of commercially available cigarette, beedi, chewing tobacco and also in pan masala, using fission track registration technique. Consumption of tobacco orally or by smoking may result in the intake of radioactive elements into the human body causing hazardous effects. External detector method was employed for the determination of uranium using Makrofol-KG as the fission track detector. The range of uranium was found to vary between 0.066–0.106 ppm, 0.042–0.079 ppm and 0.043–0.092 ppm, in tobacco from samples of cigarette, beedi and chewing tobacco, respectively, and between 0.073–0.203 ppm in pan masala samples. 相似文献
58.
The first examples of reactions of Fischer carbene complexes with triynes are reported. The regioselectivity of the reaction of the two different alkyne functions in the symmetrical triyne depends on the nature of the substituent of the triyne. Bis-silyl-substituted triynes react at the central alkyne unit, whereas bis-aryl- and bis-alkyl-substituted triynes react at the end alkyne unit. The reaction of a Fischer carbene complex with a phenyl substituent also reacts with a bis-silyl-substituted triyne at the central alkyne unit but gives a furan product rather than the normal phenol product. It was also demonstrated that all three of the alkyne units in conjugated triynes could react in turn with a Fischer carbene complex to give access to trisquinones. 相似文献
59.
Kamlakar Avasthi Diwan S. Rawat Sanjay Sarkhel Prakas R. Maulik 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):o325-o327
The title compound, 6‐methylsulfanyl‐1‐(3‐phenylpropyl)‐4,5‐dihydro‐1H‐pyrazolo[3,4‐d]pyrimidin‐4‐one, C15H16N4OS, crystallizes in space group Pbca, with two molecules of similar structure in the asymmetric unit. The molecular structure shows the absence of intramolecular stacking in the crystalline state, as indicated by earlier 1H NMR analysis in solution. In addition, the crystal packing reveals the formation of a layered structure, due mainly to intermolecular N—H?O=C hydrogen bonding and arene–arene interactions. 相似文献
60.
S. Kumar N. Rawat A. S. Kanekar B. S. Tomar V. K. Manchanda M. S. Sonavane N. L. Sonar K. Raj 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(2):225-228
Diffusion of sodium in Mn and Ti bearing sodium borosilicate glass used for the immobilization of the high level waste at
the Waste Immobilization Plant, Tarapur has been studied by heterogeneous isotopic exchange using 24Na as the radiotracer for sodium. The temperature dependence of the self-diffusion coefficient of sodium in the glass was
found to follow Arrhenius equation below the glass transition temperature. 相似文献