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排序方式: 共有806条查询结果,搜索用时 203 毫秒
101.
R H Sarma C H Lee F E Evans N Yathindra M Sundaralingam 《Journal of the American Chemical Society》1974,96(23):7337-7348
102.
Zhang J Sarma KD Curran TT Belmont DT Davidson JG 《The Journal of organic chemistry》2005,70(15):5890-5895
Lewis acid catalyzed addition of active methylene compounds to mucochloric acid (1) and mucobromic acid (2) affording Knoevenagel aldol adducts, gamma-substituted gamma-butenolides, has been explored. Catalytic efficiencies of various Lewis acids have been compared. Indium acetate (0.25-5 mol %) was found to be the most efficient catalyst. 相似文献
103.
K S R Sarma K L Narasimham K Premchand S Bhuloka Reddy K Parthasaradhi V Lakshminarayana 《Pramana》1982,18(6):485-494
Total photon mass attenuation coefficients in C, Al, S, Ti, B2O3, LiF, ZnO, Y2O3 and H8O2C5 (perspex) are measured on a good geometry set-up using proportional counter, Si(Li) and Ge(Li) detecting systems in the energy
region from 6.47 to 52.014 keV employing x-rays and gamma rays from radioactive sources. The deduced photoelectric cross-sections
are found to agree with the theoretical values of Storm and Israel, Scofield and semiexperimental values of Veigele wherever
available within a few percent. The photo-electric cross-sections in elements, S, Ti and Y at their respectiveK-edges obtained by extrapolation technique agree with the theoretical values of Storm and Israel and Scofield at the respectiveK-edges except in S. In the case of S both the theoretical values atK-edges are found to be underestimations, more in the case of Scofield evaluations. 相似文献
104.
This paper deals with new results obtained in regard to the reconstruction properties of side-band Fresnel holograms (SBFH) of self-imaging type objects (for example, gratings) as compared with those of general objects. The major finding is that a distribution I2, which appears on the real-image plane along with the conventional real-image I1, remains a 2Z distribution (where 2Z is the axial distance between the object and its self-imaging plane) under a variety of situations, while its nature and focusing properties differ from one situation to another. It is demonstrated that the two distributions I1 and I2 can be used in the development of a novel technique for image subtraction. 相似文献
105.
106.
H. Karami J. Carr N.C. Debenham D.A. Garbutt W.G. Jones D.M. Binnie J. Keyne P. Moissidis H.N. Sarma I. Siotis 《Nuclear Physics B》1979,154(3):503-518
Measurements are reported of the differential cross section for the reaction π?+p→ω+n from threshold to a final-state c.m. momentum . The previously reported fall in total cross section below about 100 MeV/c is again seen. The differential cross section remains close to isotropic over the entire range. A paralle experiment on the variation in the elastic differential cross section across the threshold shows evidence of this threshold. The elastic data cover a range of incident moments from 1010 to 1180 MeV/c in steps of 5 MeV/c. 相似文献
107.
Novel hydrogenolysis of a CC bond linking a benzyl side chain in some octalones is described. 相似文献
108.
V. Pandu Ranga Rao V. V. Sarma A. S. R. Krishna Murty 《Proceedings Mathematical Sciences》1976,84(4):150-156
Extraction of vanadium (IV) in the presence of perchlorate, nitrate, halides, and thiocyanate and neutral oxygen donors liken-butanol, TBP and antipyrine into various solvents is studied. Composition of the extracting species and the stability constants are determined. The effectiveness of the three neutral oxygen donors studied in the extraction of vanadium (IV)-anion systems is found to follow the order: antipyrine > TBP >n-butanol. 相似文献
109.
Hwang BJ Chen CH Sarma LS Chen JM Wang GR Tang MT Liu DG Lee JF 《The journal of physical chemistry. B》2006,110(13):6475-6482
The understanding of the formation mechanism of nanoparticles is essential for the successful particle design and scaling-up process. This paper reports findings of an X-ray absorption spectroscopy (XAS) investigation, comprised of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions, to understand the mechanism of the carbon-supported Pt-Ru nanoparticles (NPs) formation process. We have utilized Watanabe's colloidal reduction method to synthesize Pt-Ru/C NPs. We slightly modified the Watanabe method by introducing a mixing and heat treatment step of Pt and Ru oxidic species at 100 degrees C for 8 h with a view to enhance the mixing efficiency of the precursor species, thereby one can achieve improved homogeneity and atomic distribution in the resultant Pt-Ru/C NPs. During the reduction process, in situ XAS measurements allowed us to follow the evolution of Pt and Ru environments and their chemical states. The Pt LIII-edge XAS indicates that when H2PtCl6 is treated with NaHSO3, the platinum compound is found to be reduced to a Pt(II) form corresponding to the anionic complex [Pt(SO3)4]6-. Further oxidation of this anionic complex with hydrogen peroxide forms dispersed [Pt(OH)6]2- species. Analysis of Ru K-edge XAS results confirms the reduction of RuIIICl3 to [RuII(OH)4]2- species upon addition of NaHSO3. Addition of hydrogen peroxide to [RuII(OH)4]2- causes dehydrogenation and forms RuOx species. Mixing of [Pt(OH)6]2- and RuOx species and heat treatment at 100 degrees C for 8 h produced a colloidal sol containing both Pt and Ru metallic as well as ionic contributions. The reduction of this colloidal mixture at 300 degrees C in hydrogen atmosphere for 2 h forms Pt-Ru nanoparticles as indicated by the presence of Pt and Ru atoms in the first coordination shell. Determination of the alloying extent or atomic distribution of Pt and Ru atoms in the resulting Pt-Ru/C NPs reveals that the alloying extent of Ru (JRu) is greater than that of the alloying extent of Pt (JPt). The XAS results support the Pt-rich core and Ru-rich shell structure with a considerable amount of segregation in the Pt region and with less segregation in the Ru region for the obtained Pt-Ru/C NPs. 相似文献
110.
We present an integrated Silicon-on-Insulator (SOI) based Mach-Zehnder interferometer (MZI) in order to perform ultrafast all-optical XOR logic gate operation with a bit rate of ∼ 0.33 Tb/s. A numerical simulation is carried out in order to study various parameters such as extinction ratio and eye-opening parameters, characterizing the performance of the XOR logic gate. The output XOR logic gate signal can have improved extinction and eye margin if the initial powers of primary signals and the probe continuous-wave (CW), and SOI waveguide length are judiciously adjusted. 相似文献