Resonant non-linear waves—III. Elastic continuum with quadratic non-linearity

The paper derives the relevant non-linear integro-differential evolution equation by the method due to Collins expanding on a procedure by Keller. The quadratically non-linear case is not a trivial variation over the cubically non-linear case that was presented in preceding papers. As expected a different scaling and ordering of terms is needed and the first order perturbation solution provides no information on resonance. Nevertheless, although obtained by much longer calculations, the final equation for the present case is of identical form, with differences only in numerical coefficients, with the cubic case that was presented and solved earlier.     

Possible cooling of electrons in solids in the presence of an electric field

A possible cooling of electrons at low temperatures is predicted from a newly-developed approach to steady-state nonlinear transport in the presence of an electric field. The lowering of the electron temperature below the lattice temperature occurs in low-impurity samples and at such a current density for which the average drift velocity of the carriers is near the sound speed.     

HgCdTe材料应用与制备的进展

HgCdTe是一种有广泛应用前景的Ⅱ-Ⅵ族化合物半导体光电材料。从投资上看,它已为仅次于Si和GaAs的第三种最重要的半导体。HgCdTe是制作红外探测器的最佳材料。本文简要地介绍了HsCdTe材料的性质以及它的应用和制备进展,着重描述了在红外探测器上的应用。对制备HgCdTe单晶的各种工艺方法作了比较说明,较详细地介绍了滑动液相外延(LPE)制备HgCdTe单晶薄膜技术。     

反射型磁光多层膜隔离器工作稳定性的研究

与单纯的磁光晶体相比,由磁光介质与电介质周期性或准周期性排列构成的一维磁光光子晶 体能够显著增强磁光效应,可以用于实现小尺度的磁光隔离器,从而大大减小器件的尺寸. 给出更为一般的可用于求解斜入射情况下偏振光在各向异性介质中传播时的传输矩阵方法, 并用这种方法在波长为1053μm处,针对两种“三明治”型的反射磁光多层膜隔离器的 结构,具体讨论了器件应用时入射角度及工艺制作时膜层制备厚度对它们工作稳定性的影响 .发现中心磁光介质夹层较厚的结构具有膜层数目少、工作稳定性好的优点. 关键词： 光隔离器 磁光效应 一维光子晶体     

Synthesis of the non-classical acetogenin mucocin: a modular approach based on olefinic coupling reactions

A three component modular synthesis of the potent antitumor agent mucocin, based on olefinic coupling reactions, is described. A cross-metathesis on tetrahydropyran and tetrahydrofuran alkene components was used to assemble a stereochemically complex, non-adjacently-linked bicyclic ether. The latter was elaborated to a sulfone and partnered with a butenolide aldehyde component in a Julia-Kocienski olefination to provide the mucocin framework, which was converted to the natural product after hydrogenation and alcohol deprotection.     

Fusion of conventional ultrasound imaging and acousto-optic sensing by use of a standard pulsed-ultrasound scanner

Acousto-optic sensing (AOS) is a dual-wave sensing technique based on the ultrasound modulation of diffuse light in a turbid medium. We experimentally demonstrate the feasibility of combining AOS and conventional ultrasound imaging by use of a commercially available pulsed-ultrasound scanner coupled with a photorefractive crystal-based optical interferometry system. Optically absorbing targets embedded in highly diffusive phantoms (mus'= 10 cm(-1)) are imaged through a thickness of 27 mm with millimeter resolution. The acousto-optic images are intrinsically coregistered with the ultrasound images.     

Analysis of guanosine-5′-monophosphate at nM level based on the co-luminescence effect of Tb-Gd-GMP system

This paper first found the co-luminescence effect of guanosine-5′-monophosphate (GMP) system. Experiment showed that La³⁺, Gd³⁺, Sc³⁺ and Y³⁺ all could enhance the luminescence of Tb-GMP system, among which Gd³⁺ has the greatest enhancement. Under the optimum conditions, the enhanced intensity of the system is in proportion to the concentration of GMP in the range from 3×10⁻⁸ to 3×10⁻⁵ mol/l. The detection limit is 3.9×10⁻⁹ mol/l. In the study of mechanism, we propose that both Tb and Gd complexes can form bigger netlike compound by the link of the oxygen bridge, through which the energy absorbed by Gd complex may transfer to Tb³⁺ in Tb complex.     

Influence of the atomic structure on the Raman spectra of graphite edges

A study of step edges in graphite with different atomic structures combining Raman spectroscopy and scanning probe microscopy is presented. The orientation of the carbon hexagons with respect to the edge axis, in the so-called armchair or zigzag arrangements, is distinguished spectroscopically by the intensity of a disorder-induced Raman peak. This effect is explained by applying the double resonance theory to a semi-infinite graphite crystal and by considering the one-dimensional character of the defect.