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71.
Na Z Cho JY Lee HJ Chung JH Park KD Lee YJ Shin SC Rim YS Park KH Moon JH 《Magnetic resonance in chemistry : MRC》2007,45(3):275-278
Four sesquiterpene glucosides were isolated from Ixeris sonchifolia Hance. The structure of a new compound (1) was assigned as 9beta-monohydroxy-2,12-dioxo-guaia-3,11(13)-dien-1alpha,5alpha,6beta,7alpha,9beta,10alphaH-12,6-olide-9-O-beta-D- glucopyranoside (ixerinoside). In addition, unambiguous and complete assignments of (1)H NMR chemical shifts for crepidiaside A (2), ixerin Z (3), and 11,13alpha-dihydroixerin Z (4) are presented. The assignments were achieved by two-dimensional NMR (gCOSY, gHSQC, gHMBC, NOESY) and one-dimensional nuclear Overhauser effect (NOE) experiments. 相似文献
72.
The one matrix model is known to reproduce in the continuum limit the (2,2p+1) minimal Liouville gravity. Recently, two of the authors have shown how to construct arbitrary critical boundary conditions within this matrix model. So far, between two such boundary conditions only one boundary operator was constructed. In this Letter, we explain how to construct all the set of boundary operators that can be inserted. As a consistency check, we reproduce the corresponding Liouville boundary 2pt function from the matrix model correlator. In addition, we remark a connection between a matrix model relation and the boundary ground ring operator insertion in the continuum theory. 相似文献
73.
74.
Characterization of stimulated Brillouin scattering in small core microstructured chalcogenide fiber
We report a full modal characterization of the stimulated Brillouin scattering (SBS) properties in small core As2Se3-based chalcogenide photonic crystal fibers (PCFs). Our results include the calculation of Brillouin gain spectrum (BGS), Brillouin gain coefficient (gB), Brillouin frequency shift (BFS) by taking into account the contribution of the higher-order acoustic modes. We show that for a highly nonlinear PCF having a 2-μm hole-to-hole pitch and a 0.5-μm hole diameter, a Brillouin gain coefficient gB = 5.91 10? 9 m.W? 1 is obtained around the acoustic frequency of 8.19 GHz, which is more than 340 times larger than that of the same PCF made with silica glass. We demonstrate that the BGS of small core PCF structures show strong SBS and multipeaked behavior, with a presence of a second peak, when decreasing the core diameter which is to be attributed to the higher-order acoustic modes. We designed small core PCFs with tailored Brillouin response for a wide range of applications. 相似文献
75.
We have investigated the temperature- and frequency-dependent ionic conductivity in (Li0.67 ? xNa0.33 Rbx)2B4O7 (LNRBO) glasses with x = 0, 0.07, 0.2, 0.33, 0.47, and 0.6. The mixed alkali effect of the ternary mixed alkali system LNRBO is compared with that of the binary mixed alkali systems (Li1 ? xNax)2B4O7 (LNBO), (Li1 ? xRbx)2B4O7 (LRBO) and the single alkali glass Rb2B4O7 (RBO). From the results of the dc conductivity and dc activation energy, we observe that the LNRBO system exhibits the combined characteristic of binary mixed alkali systems LNBO and LRBO. It is found that the power-law exponent n for binary alkali glass is the same as that for ternary alkali glass but it is lower than that for single alkali glass. This indicates that the dimensionality of conducting pathway in the mixed alkali glasses of LNBO, LRBO and LNRBO is lower than that in the single alkali RBO. We discuss the concentration dependence of the dc conductivity and dc activation energy in the framework of the bond valence technique to reverse Monte Carlo produced structural model [Phys. Rev. Lett. 90, 155507 (2003)]. 相似文献
76.
We study four-dimensional κ -Minkowski spacetime constructed by the twist deformation of U(igl(4,R)). We demonstrate that the differential structure of such twist-deformed κ-Minkowski spacetime is closed in four dimensions contrary to the construction of κ-Poincaré bicovariant calculus which needs an extra fifth dimension. Our construction holds in arbitrary dimensional spacetimes. 相似文献
77.
We present a numerical study of stimulated Brillouin scattering in optical fibers based on a full modal analysis of the acoustic and optical properties. The computation of each acoustic mode supported by the fiber structure allows us an accurate and detailed investigation of the characteristics of the Brillouin gain spectrum. We focus our attention on the contribution of the higher-order acoustic modes which are sometimes ignored because of computational issues in particular on optical fibers that act as acoustic antiwaveguides. Our analysis clearly highlights their role and their dependence on the physical and geometrical structure of the fiber. 相似文献
78.
Boo Rim Choe Hyungwoon Koo Michael Stessin 《Integral Equations and Operator Theory》2009,63(4):501-520
We obtain new characterizations of Carleson measures via uniform boundedness of BMO norms of certain mass functions associated
with the given measure in a natural way.
This research was performed during M. Stessin’s visit to Korea University. He thanks the Mathematics Department of Korea University
and the “Brain Pool” program for their hospitality and support. The first two authors were supported by the Korea Research
Foundation Grant funded by the Korean Government (KRF-2008-314-C00012). 相似文献
79.
A large mode area photonic crystal fiber (LMA PCF) with an effective area of 180 μm2 is used to generate a high energy, micro-joule range, flat, octave spanning supercontinuum (SC) extending from ~ 600 nm to ~ 1720 nm. A train of femtosecond pulses from a widely-tunable parametric amplifier pumped by a Ti:Sapphire regenerative amplifier system are coupled into a 20 cm length of LMA PCF generating a SC of 1.4 μJ energy. We present an experimental study of the high energy SC as a function of the input power and the pumping wavelength. The spectrum obtained at a pump wavelength of 1260 nm presents spectral flatness variation less than 12 dB over more than 1.1 octave bandwidth. The physical processes behind the SC formation are described in the normal and the anomalous dispersion regions. Our experimental results are successfully compared with the numerical solution of the nonlinear Schrödinger equation. 相似文献
80.
A novel phase‐matching scheme which is based on the dispersion compensation in the nonlinear optical composite materials containing metal nanoparticles is proposed. Anomalous dispersion originating from the plasmon resonance in metal nanoparticles compensates the dispersion of the host nonlinear material, leading to the perfect phase‐matching and high efficiency of nonlinear optical wavelength conversion. The effectiveness of this approach is theoretically demonstrated, taking third‐order nonlinear processes such as the direct third‐harmonic generation and four‐wave mixing in ZnO composites containing silica‐core–silver‐shell nanoparticles as examples. The results show that with the proposed phase‐matching scheme, unprecedentedly high conversion efficiency can be obtained compared with preceding results in third‐order nonlinear optical solid‐state materials. 相似文献