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991.
Wang X Ischebeck R Muggli P Katsouleas T Joshi C Mori WB Hogan MJ 《Physical review letters》2008,101(12):124801
A novel approach for generating and accelerating positron bunches in a plasma wake is proposed and modeled. The system consists of a plasma with an embedded thin foil into which two electron beams are shot. The first beam creates a region for accelerating and focusing positrons and the second beam provides positrons to be accelerated. Monte Carlo and 3D PIC simulations show a large number of positrons (10(7) approximately 10(8)) are trapped and accelerated to approximately 5 GeV over 1 m with relatively narrow energy spread and low emittance. 相似文献
992.
Six new polyfluorinated monothio-l,3-diketones have been synthesized from the corresponding fluorinated aceto- phenones and appropriate 0-alkyl thioesters in the presence of sodamide. All these monothio-1,3-diketones are characterized by I.R. and 1H N.M.R. spectral studies. 相似文献
993.
994.
Kalpesh H. Jani K. B. Modi H. H. Joshi P. D. Babu S. K. Paranjpe 《Journal of magnetism and magnetic materials》2004,280(2-3):334-345
The spinel oxide system ZnzTizFe2−x−zCrx−zCoO4; z=x2; x=0.60, 0.65, 0.70 and 0.80, was studied using neutron diffraction technique, low field DC magnetization measurements (ZFC–FC measurements), magnetic hysterisis, Mössbauer spectroscopy and low field AC susceptibility measurements. All the compositions show significantly less B-site magnetic moments at 10 K temperature derived from neutron diffraction data than the free ions site moments deduced assuming collinear arrangement of spins. This combined with some other features seen in the low temperature neutron diffraction patterns suggest localized canting of spins (LCS) type of magnetic ordering in the present system where a long range order of longitudinal component of moments co-exists along with totally disordered transverse component of moments. The conclusion is also supported by the features seen in the other measurements. The magnetic moments derived from 10 K neutron diffraction data are explained using the LCS approach for different exchange integrals ratios. 相似文献
995.
U. S. Taralkar P. S. Niphadkar P. N. Joshi 《Journal of Sol-Gel Science and Technology》2009,51(2):244-250
Steam assisted dry gel conversion method was employed for the synthesis of Si-MCM-41 from ternary SiO2:CTAOH:H2O systems wherein fumed silica was used as a source of silica. The influence of synthesis time, molar ratios of CTAOH/SiO2 in dry gel and the water content at the bottom of autoclave on the quality and formation of mesophases has been investigated.
Powder XRD, N2 adsorption–desorption, TEM and hydrothermal stability test were the techniques used for sample characterization. Keeping
molar ratio of CTAOH/SiO2 constant, shorter synthesis time, lower unit cell parameter and d spacing were observed when steam assisted dry gel conversion method was employed in place of conventional hydrothermal method.
There exists an optimum lower limit for water content at the bottom of autoclave for reducing the synthesis period. Keeping
synthesis temperature and CTAOH/SiO2 molar ratio fixed, Si-MCM-41 with improved hydrothermal stability was obtained by steam assisted dry gel conversion route. 相似文献
996.
Ashavani Kumar Hrushikesh M. Joshi Anandrao B. Mandale Rajendra Srivastava Suguna D. Adyanthaya Renu Pasricha Murali Sastry 《Journal of Chemical Sciences》2004,116(5):293-300
In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from
an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum
nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture,
the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA
molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in
the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that
is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic
activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The
nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission
electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) 相似文献
997.
Anti-reflection (AR) sol–gel coatings are deposited on wedge glass optics for high-power lasers using spin coating technique. Characterization of these coatings on BK-7 glass substrates is carried out in terms of thickness profile across the surface, thickness variation w.r.t. wedge angle, and its effect on AR coating reflectivity, at different wedge angles from 1° to 7°. Results of the study are used to deposit AR coatings on inclined end faces of Nd:phosphate glass laser rods. 相似文献
998.
Absolute measurement for He-α resonance (1s2 1S0?1s2p1 P 1, at 40.2 Å) line emission from a laser-produced carbon plasma has been studied as a function of laser intensity. The optimum laser intensity is found to be ≈1.3×1012 W/cm2 for the maximum emission of 3.2 × 1013 photons sr?1 pulse?1. Since this line lies in the water window spectral region, it has potential application in x-ray microscopic imaging of biological sample in wet condition. Theoretical calculation using corona model for the emission of this line is also carried out with appropriate ionization and radiative recombination rate coefficients 相似文献
999.
G.P. Joshi T.P. Sharma S.C.K. Mishra 《Journal of Physics and Chemistry of Solids》2003,64(12):2391-2396
Simultaneous measurements of effective thermal conductivity (λe) and effective thermal diffusivity (χe) of four samples S1 (polyaniline mixed with 100% Ni), S2 (polyaniline mixed with 90% Ni and 10% Al), S3 (polyaniline mixed with 80% Ni and 20% Al) and S4 (polyaniline mixed with 70% Ni and 30% Al) of polyaniline mix with metal Ni and Al in different percentage have been made using transient plane source technique. In the temperature range from room temperature to 170 °C. Both λe and χe increase with increase in temperature. Addition of aluminium concentration at the cost of nickel in the composite increases the value of λe and χe over the entire range of temperature under investigation. It has been found that the values of λe and χe are maximum when 70% of Ni and 30% of Al are mixed in polyaniline matrix. This behaviour is also predicted by an empirical relation, which is obtained from polynomial fit of the experimental data and is explained on the basis of bond formation between metal (Ni and Al) and nitrogen of polyaniline matrix. 相似文献
1000.
Kirti Joshi 《Comptes Rendus Mathematique》2004,338(11):869-872
We show that the locally free sheaf of locally exact differentials on a smooth projective curve of genus g?2 over an algebraically closed field k of characteristic p is a stable bundle. This answers a question of Raynaud. To cite this article: K. Joshi, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献