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排序方式: 共有89条查询结果,搜索用时 15 毫秒
1.
Friedel-Crafts alkylation of indoles with epoxides to afford 3-alkyl indole derivatives at room temperature with moderate to good yields and high regioselectivity using nanocrystalline titanium(IV) oxide catalyst is described. 相似文献
2.
Dr. Papri Sutar Dr. Vasudeva Rao Bakuru Pooja Yadav Subhajit Laha Dr. Suresh Babu Kalidindi Prof. Dr. Tapas Kumar Maji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3268-3272
The composite hydrogel of a nanoscale metal–organic framework (NMOF) and nanoclay has emerged as a new soft-material with advanced properties and applications. Herein, we report a facile synthesis of a hydrogel nanocomposite by charge-assisted self-assembly of Pd@ZIF-8 nanoparticles with Laponite® nanoclay which coat the surface of Pd@ZIF-8 nanoparticles. Such surface coating significantly enhanced the thermal stability of the ZIF-8 compared to the pristine framework. Further, the Pd@ZIF-8+LP hydrogel nanocomposite shows better size-selective catalytic hydrogenation of olefins than Pd@ZIF-8 nanoparticles based on selective diffusion of the substrate. 相似文献
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5.
Laha S Gupta P Simien CE Gao H Castro J Pohl T Killian TC 《Physical review letters》2007,99(15):155001
We study the expansion of ultracold neutral plasmas in the regime in which inelastic collisions are negligible. The plasma expands due to the thermal pressure of the electrons, and for an initial spherically symmetric Gaussian density profile, the expansion is self-similar. Measurements of the plasma size and ion kinetic energy using fluorescence imaging and spectroscopy show that the expansion follows an analytic solution of the Vlasov equations for an adiabatically expanding plasma. 相似文献
6.
Although often used in molecular dynamics, in this work the Manning–Rosen potential is parameterized to compute the scattering phase shifts for the nucleon–nucleon and the alpha-nucleon systems by exploiting the standard phase function method. We obtain excellent agreement in phase shifts with the more sophisticated calculations up to partial waves ${\ell }=2.$ 相似文献
7.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
8.
Gupta P Laha S Simien CE Gao H Castro J Killian TC Pohl T 《Physical review letters》2007,99(7):075005
We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elastic-collision regime at low initial Gamma(e), which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma(e) in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and we experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas. 相似文献
9.
We have treated the Hulthén-modified separable potentials within the framework of the phase-function method and obtained a
closed form expression fors-wave scattering phase shift. Specializing to a rank one separable potential we have found out the limiting conditions in
which the Hulthén-modified phase shift goes over to its Coulomb counterpart. We demonstrate the usefulness of our approach
by means of a model calculation.
Based in part on a Ph.D. thesis to be submitted by one of the authors (AKJ) to Visva-Bharati University. 相似文献
10.
S. Laha Y. C. Chen P. Gupta C. E. Simien Y. N. Martinez P. G. Mickelson S. B. Nagel T. C. Killian 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):51-56
A study of ion equilibration in annular regions of ultracold strontium plasmas is reported. Plasmas are formed by photoionizing
laser-cooled atoms with a pulsed dye laser. The experimental probe is spatially-resolved absorption spectroscopy using the
2S1/2-2P1/2 transition of the Sr+ ion. The kinetic energy of the ions is calculated from the Doppler broadening of the spectrum, and it displays clear oscillations
during the first microsecond after plasma formation. The oscillations, which are a characteristic of strong coulomb coupling,
are fit with a simple phenomenological model incorporating damping and density variation in the plasma. 相似文献