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61.
2-Aminopyridinium maleate (2APM) is a recently discovered organic acid-base complex that crystallizes in a non-centrosymmetric space group Pc and hence has a nonzero second-order optical susceptibility. In 2APM the cation (aminopyridinium ion) is connected to the anion (maleate ion) through hydrogen bonds (N1-H10–O2 and N2-H12–O1), we have calculated the molecular properties of 2APM for varying strength of these hydrogen bonds. It is observed that the molecular hyperpolarizabilty varies for varying strength of these hydrogen bonds. These observations are interpreted in terms of the change in nature of the hydrogen bond interaction as its strength is varied. Macropscopic second-order optical susceptibility (d 0) of 2APM is obtained using the calculated value of molecular hyperpolarizability and the reported crystal structure of 2APM. In order to study the influence of molecular packing on the macroscopic non-linear optical property of the crystal, susceptibility calculations are repeated for 2-methyl-4nitroaniline (MNA) crystal, which is a very well known non-linear optical organic crystal with an exceptionally high value of second-order optical susceptibility. A comparison between the non-linear optical property of 2APM and MNA crystals is given. Comparing the values of d 0 of 2APM crystals with that of urea shows that the nonlinear optical response of 2APM crystals will be nearly 10 times that of a urea crystal. 相似文献
62.
G. Ranga Rao H. Ranjan Sahu Braja Gopal Mishra 《Colloids and surfaces. A, Physicochemical and engineering aspects》2003,220(1-3):261-269
Surface and catalytic properties of Cu–Ce–O composite materials prepared by solution combustion method have been investigated. The materials are characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and electron paramagnetic resonance spectroscopy (EPR). The results of EPR and TPR show finely dispersed Cu2+ species on ceria matrix with low copper content. The Cu2+ species exists in the form of dimers and clusters which are not evident in XRD. In addition CuO is also present as small clusters which grow to larger size at higher Cu content. There is no evidence of CuO forming a solid solution with fluorite CeO2 in combustion method. The Cu2+ species mostly appear on surface rather than in the bulk. Hydrogen peroxide decomposition kinetics has been carried out on Cu–Ce–O composite materials to investigate the effect of crystalline and well-dispersed copper oxide phases on CeO2. From kinetic results, the catalyst materials can be grouped into highly dispersed as well as crystalline CuO phases present on CeO2 matrix. Two parallel compensating lines for dispersed and crystalline CuO phases on CeO2 are observed in ln A versus Ea plot indicating the compensation effect in H2O2 decomposition. This observation is consistent with XRD and EPR results. 相似文献
63.
Dipak Ghosh Argha Deb Swarup Ranjan Sahoo Kanchan Kumar Patra Prabir Kumar Haldar Jayita Ghosh 《Czechoslovak Journal of Physics》2002,52(6):789-794
An analysis of data of target fragments of 28Si-AgBr (at 14.5 AGeV) reveals the existence of emission asymmetry in the azimuthal plane, which is found to depend on the number of target fragments. The comparison with the data of 32S-AgBr (at 200 AGeV) and 16O-AgBr (at 60 AGeV) interactions indicates that emission asymmetry depends on the projectile mass and energy. 相似文献
64.
Pulak Ranjan Giri 《International Journal of Theoretical Physics》2008,47(6):1776-1783
The existence of bound state of the polarizable neutral atom in the inverse square potential created by the electric field
of a single walled charged carbon nanotube (SWNT) is shown to be theoretically possible. The consideration of inequivalent
boundary conditions due to self-adjoint extensions lead to this nontrivial bound state solution. It is also shown that the
scaling anomaly is responsible for the existence of such bound state. Binding of the polarizable atoms in the coupling constant
interval η
2∈[0,1) may be responsible for the smearing of the edge of steps in quantized conductance, which has not been considered so
far in the literature. 相似文献
65.
We have first obtained that the equations of equilibrium governing the finite radial expansion (contraction) and longitudinal
shearing of a circular cylindrical shell become uncoupled for a class of harmonic materials (a class of isotropic homogeneous
compressible elastic materials). Next it has been assumed that the dilatation is uniform. Following this the exact solutions
of the uncoupled equations of equilibrium have been obtained for a simple harmonic material which is reduced to the Neo-Hookean
material for the incompressible case. The deformation is nonhomogeneous in nature. The stresses have been obtained.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
66.
Alan R. Katritzky Akornsri Chermprapai Susana Bravo Ranjan C. Patel 《Tetrahedron》1981,37(21):3603-3607
The corresponding “pseudobase” Δ2 -1,5-diketones (8) and (14) afford dihydrochromenylium (9b) and tetrahydro-xanthylium monofluorides (15). These convert aryl- and heteroarylamines into dihydroquinolinium (10) and tetrahydro-acridinium (16) monofluorides which at 130–250° give the deaminated arenes and heteroarenes (average overall yield 60%). 相似文献
67.
Sengupta J Mukhopadhyay R Bhattacharjya A Bhadbhade MM Bhosekar GV 《The Journal of organic chemistry》2005,70(21):8579-8582
3,5'-ether-linked pseudooligopentose derivatives were synthesized for the first time from readily available carbohydrate precursors. The 1,2-isopropylidene-protected ether-linked oligopentoses are potentially important as precursors of novel RNA analogues. Intramolecular cycloaddition of the nitrile oxides prepared from these derivatives led to the diastereoselective formation of chiral isoxazolines fused to 10-16-membered oxacycles. The stereochemistry of some of these isoxazolines was established by X-ray diffraction and NOESY analysis. 相似文献
68.
[reaction: see text] A divergent strategy for the synthesis of diverse azabicyclic ring systems has been developed in which a chiral N-allylpyrrolidine derivative, obtained from a carbohydrate precursor was converted to (-)-8-epi-swainsonine triacetate by RCM and to a pyrrolo[1,2-a]azepine derivative and a 3-hydroxymethyl-substituted indolizidine by N-allylcarbohydrate nitrone and nitrile oxide cycloadditions. 相似文献
69.
Hawking radiation from the black hole in Ho?ava–Lifshitz gravity is discussed by a reformulation of the tunneling method given in Banerjee and Majhi (2009) [17]. Using a density matrix technique the radiation spectrum is derived which is identical to that of a perfect black body. The temperature obtained here is proportional to the surface gravity of the black hole as occurs in usual Einstein gravity. The entropy is also derived by using the first law of black hole thermodynamics. Finally, the spectrum of entropy/area is obtained. The latter result is also discussed from the viewpoint of quasi-normal modes. Both methods lead to an equispaced entropy spectrum, although the value of the spacing is not the same. On the other hand, since the entropy is not proportional to the horizon area of the black hole, the area spectrum is not equidistant, a finding which also holds for the Einstein–Gauss–Bonnet theory. 相似文献
70.
Chen HT Yang H Singh R O'Hara JF Azad AK Trugman SA Jia QX Taylor AJ 《Physical review letters》2010,105(24):247402
In this Letter, we present resonance properties in terahertz metamaterials consisting of a split-ring resonator array made from high-temperature superconducting films. By varying the temperature, we observe efficient metamaterial resonance switching and frequency tuning. The results are well reproduced by numerical simulations of metamaterial resonance using the experimentally measured complex conductivity of the superconducting film. We develop a theoretical model that explains the tuning features, which takes into account the resistive resonance damping and additional split-ring inductance contributed from both the real and imaginary parts of the temperature-dependent complex conductivity. The theoretical model further predicts more efficient resonance tuning in metamaterials consisting of a thinner superconducting split-ring resonator array, which are also verified in subsequent experiments. 相似文献