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101.
Two uncoupled two-level atoms cannot be jointly excited by classical light under general circumstances, due to destructive interference of excitation pathways in two-photon absorption. However, with temporally entangled light, two-atom excitation is shown possible. Photons arising from three-level cascade decay are intrinsically ordered in time of emission. This field correlation induces a joint resonance in the two-atom excitation probability via suppression of one of the time-ordered excitation pathways. The relative gain in two-photon absorption increases with the time-frequency entanglement. 相似文献
102.
Vikram Sen Neeraj Panwar G.L. Bhalla 《Journal of Physics and Chemistry of Solids》2007,68(9):1685-1691
We report here the structural, magnetotransport and morphological studies of Sb-doped La2/3Ba1/3Mn1−xSbxO3 perovskite manganites. Pristine material La2/3Ba1/3MnO3 (LBMO) shows two insulator-metal (I-M) transitions in the electrical resistivity-temperature (ρ-T) behavior. While the higher temperature transition (TP1) at ∼340 K is reminiscent of the usual I-M transition in manganites, the lower temperature transition (TP2) at ∼250 K has been ascribed to the grain boundary (GB) effects arising out of the ionic size mismatch between the ions present at the rare-earth site (La3+ and Ba2+). With Sb-doping TP1 shifts to lower temperatures while TP2 remains invariant up to 3% and shifts to lower temperature for 5%. Room temperature electrical resistivity and the peak values also increase successively with Sb-doping. Scanning electron micrographs of the samples exhibit a gradual increase in their grain sizes with Sb indicating a gradual decrease in the GB density. Shift of TP1 with doping is explained on the basis of a competition between double-exchange and super-exchange mechanisms. The overall electrical resistivity increases and the shift in the electrical resistivity hump (TP2) with Sb-doping is found related to be gradually decreasing GB density and the ensuing lattice strain increase at the GBs. The intrinsic magnetoresistance (MR) gets suppressed and extrinsic MR gets enhanced with Sb-doping. At T>TP1, the electrical resistivity is found to follow the adiabatic polaron hopping model whereas the electron-magnon scattering is found to dominate in the metallic regime (T<TP1). 相似文献
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106.
N.S. Venkata Narayanan B.V. Ashok Raj S. Sampath 《Electrochemistry communications》2009,11(10):2027-2031
Room temperature, magnesium ion conducting binary molten electrolyte consisting of acetamide and magnesium perchlorate has been prepared and characterized. The molten liquid is very stable and shows high ionic conductivity, of the order of several mS cm−1 at 25 °C with other favourable physicochemical properties. Vibrational spectroscopic studies reveal that the free ion concentration is higher than that of ion pairs and aggregates in the melt. The electrochemical reversibility of magnesium deposition and dissolution is demonstrated using voltammetry and impedance studies. Preliminary studies on rechargeable batteries assembled using γ-MnO2 and Mg metal as the electrodes together with the molten electrolyte show high discharge capacity. 相似文献
107.
H. R. Khajuria S. K. Mehta Ashok K. Gupta 《Journal of Thermal Analysis and Calorimetry》1986,31(1):15-20
Clay from the Purmandal area of J&K State was separated into its different size fractions by the method of sedimentation and with Sharple's super centrifuge process. Dilatometric studies were performed on each clay fraction; the results obtained from the dilatation curves are discussed in detail. The results revealed that the finer fraction of clay is bentonitic in nature, whereas the other fractions are felsphatic and micaceous in nature. 相似文献
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109.
Subhash P. Chavan Mahesh Thakkar Ashok B. Pathak Mohan M. Bhadbhade 《Tetrahedron》2005,61(15):3873-3879
The first enantiospecific synthesis of (+)-β-herbertenol, from naturally occurring R-(+)-citronellal, employing Taber's diazo decomposition protocol as the key step, is described. 相似文献
110.
J. Barcelos-Neto Ashok Das J. Maharana 《Zeitschrift fur Physik C Particles and Fields》1986,30(3):401-405
We examine the algebra of the nonlocal charges in the supersymmetric nonlinear σ model and show that they satisfy a nonlinear algebra at the tree-level. We also discuss other interesting questions like the transformation of these charges under a supersymmetry transformation and speculate that this algebra possibly continues to hold in the full quantum theory. 相似文献