Impact of propagation effects on intersubband Rabi flopping in semiconductor quantum wells

We investigate intersubband Rabi flopping in modulation-doped semiconductor quantum wells with and without the propagation effects, respectively. It is shown that propagation effects have a larger impact on Rabi flopping than the nonlinearities rooted from electron-electron interactions in multiple quantum wells. By using ultrashort π pulses, an almost complete population inversion exists if the propagation effects are not considered; while no complete population inversion occurs in the presence of propagation effects. Furthermore, the magnitude of the impact of propagation effects may be controlled by varying the carrier density.     

直流辉光放电光谱分析铜合金的基本特性研究

用自行组装的直流辉光放电原子发射光谱（ｄｃ Ｇ Ｄ Ａ Ｅ Ｓ）仪器对分析铜合金的某些基本特性进行了研究 探讨了光源放电室结构、放电气体压力、放电电压等操作参数以及试样尺寸大小对放电性能及元素谱线强度的影响,并进行了优化 考察了在不同放电气压条件下样品的溅射率和优化条件下辉光放电的稳定性最后,分析了铜合金标准样品中的 Ａｌ和 Ｍｎ,结果较满意     

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Optimal switching from recording to fixing for high diffraction from a LiNbO3:Ce:Cu photorefractive nonvolatile hologram

An oscillatory characteristic of diffraction is observed as a result of strong beam coupling in a weakly oxidized LiNbO3:Ce:Cu crystal during the recording step in the production of nonvolatile photorefractive holograms. On this basis the optimal switching time from the recording step to the fixing step for high diffraction of a fixed hologram is studied. It is shown that switching after the first diffraction maximum leads theoretically to fixed diffraction of as much as 100% with a suitable switching time. Both an experimental demonstration and a theoretical simulation are presented.     

Photoluminescence and optical absorption properties of polymer modified carbon nanotubes

Polymethyl methacrylate modified carbon nanotubes were prepared using γ radiation, and the modified carbon nanotubes exhibited strong luminescence (∼ ∼568 nm) at room temperature and an absorption peak at ∼ ∼247 nm can be observed in the polymer modified samples.     

Recent Development in the Synthesis of Natural Saponins and Their Derivatives

Naturally occurring saponins are attractive candidates or lead compounds for new drug design and development and thus have become important synthetic targets. This short account reviews the recent progress in the chemical synthesis and structure-activity relationship (SAR) studies of naturally occurring saponins and their derivatives.     

Synthesis and Structure of E-2-(2,4,6-tri tert butylphenylphosphinyl)-2-〔N-(tert-butyldimethylsilyl)-N-(p-chrolophenyl)〕amino-1-(2,4,6-tri tert-butyl-phenyl)phosphacthylene

1　INTRODUCTIONItwaswellknown thatelementsofthesecondary and higherrow are in generaldifficulty to form multiplebondsin which apπ hybridized stateisinvolved〔1〕.Thus,simple compounds containing multiple phosphorus carbon bonds,such as methyl dynephosphine( HC≡P) 〔2 - 3〕 and methylenephosphine( H2 C=PH〔4〕,are notstableat room temperature.Three methods to stabilize compounds containing double ormultiple bond involving phosphorusatom in the pπ hybridized state are often used.The f…     

Energy Estimate for the Type-Ⅱ Superconducting Film

We study the minimizers of the Ginzburg-Landau model for variable thickness, superconducting, thin films with high k, placed in an applied magnetic field hex, when hex is of the order of the ＂first critical field＂, i.e. of the order of ｜lnε｜. We obtain the asymptotic estimates of minimal energy and describe the possible locations of the vortices.     

3D visualization of the microstructure of Quedius beesoni Cameron using micro-CT

The investigation of the internal morphology of insects is usually performed using classical microtomy yielding optical micrographs of stained thin sections. The achievement of high-quality cross sections for microtomy is time-consuming and the risk of damaging sections is unavoidable. Moreover, the approach is impractical, in particular when quick acquisition of 3D structural information is required. Recently, X-ray computed microtomography (micro-CT) with a high spatial resolution was considered as a potential tool for the morphological classification of insects. We used micro-CT to investigate Quedius beesoni Cameron at the cellular length scale. This method provides a new powerful and nondestructive approach to obtain 3D structural information on the biological organization of insects. The preliminary images presented in this contribution clearly reveal the endoskeleton and the muscles of the head and the thorax with a full 3D structure. We also reconstructed the 3D structure of the brain of Quedius beesoni Cameron, and this is the first reconstruction in Staphylinidae, which will be a great advancement for morphological and phylogenic research. We claim that both the spatial resolution and the contrast characteristic of micro-CT imaging may fulfill the requirements necessary for zoological insect morphology and phylogeny, in particular, when a classification of a rare and unique insect specimen is required.     

Determination of Fatty Acid Methyl Esters in Biodiesel Produced from Yellow Horn Oil by LC

A simple and accurate HPLC method with refractive index detection was developed to determine the main fatty acid methyl esters in biodiesel produced from yellow horn oil. Methyl linoleate, methyl linolenate, methyl arachidate, methyl stearate, methyl palmitate and methyl oleate were separated on a HIQ SIL C18W column using methanol as mobile phase. The method has good repeatability and precision, the intraday and interday RSD for both retention time and peak area was less than 3.2%. The LOD (S/N = 3) and LOQ (S/N = 9) were less than 0.004 and 0.015 mg mL⁻¹, respectively.