Pressure-induced polymorphism in enstatite (MgSiO3) at room temperature: clinoenstatite and orthoenstatite

The phase transition of a synthetic clinoenstatite in a diamond-anvil cell has been studied by using Raman spectroscopy at various pressures and room temperature. The phenomena observed in clinoenstatite have been compared with that observed in orthoenstatite. It is found that the pressure-induced phase transitions in the two enstatites are reversible, but with different transition pressures and transition behavior. An analysis of Raman spectra has revealed that the two enstatites have different high-pressure polymorphs. This result suggests that the space group of the high-pressure polymorph of orthoenstatite is not of C2/c, and that orthoenstatite and orthoferrosilite have different transition routes at room temperature and high pressure. The compressional behavior of the high-PC2/c enstatite is also discussed according to the pressure dependences of Raman frequencies.     

静压下半导体微腔内激子与光子行为的研究

由于腔模与激子对压力的依赖关系不同,所以可以选择不同的压力使激子和光场处于不同的耦合状态,从而实现对耦合的调谐。利用这种办法,我们观测到了代表激子与光场强耦合作用的Rabi分裂。由于在我们现有样品结构中压力对激子本征行为的影响很小,与以前报道的温度、电场等调谐方式相比,这种调谐方法不仅可以有效地调谐半导体微腔内激子与腔模的耦合程度,而且能够保持激子的本征性质在整个调谐过程中基本不变。这有助于研究在强耦合过程中激子极化激元的本征性质。将实验结果与压力下激子与腔模耦合理论进行拟合,得出了正确的Rabi分裂值。     

Proper Efficiency in Vector Optimization on Real Linear Spaces

In this paper, we use an algebraic type of closure, which is called vector closure, and through it we introduce some adaptations to the proper efficiency in the sense of Hurwicz, Benson, and Borwein in real linear spaces without any particular topology. Scalarization, multiplier rules, and saddle-point theorems are obtained in order to characterize the proper efficiency in vector optimization with and without constraints. The usual convexlikeness concepts used in such theorems are weakened through the vector closure.     

Apparatus for High-Resolution Solid Hydrogen Matrix Isolation Spectroscopy and Its Application

Apparatus integrating a Fourier transform-infrared (FT-IR) spectrometer and a mid-infrared difference frequency generation (DFG) laser spectrometer was built for the study of the matrix isolation spectrum in solid molecular hydrogen. A 3-cm-long molecular hydrogen crystal was grown in a liquid-helium Dewar, and its infrared absorption spectrum in the 1-5 μm region was recorded to test the system. The W₀(0) (ν=0←0, J=6←0) line around 2410 cm⁻¹ of solid hydrogen was investigated with the DFG laser spectroscopy. High-resolution matrix isolation spectrum of CO² co-deposited with hydrogen on a BaF₂ cold plate at liquid-helium temperature was studied.     

热线法测定气体导热系数实验的探讨与改进

在准静态低气压下测量气体的热传导系数时，理论上在低压强范围内应得到Q^-1低-p^-1线性关系图象，但实验数据所绘出的图象出现明显的非线性．本文着重分析出现非线性的原因，并提出实验改进的方法。     

A novel capacitive pressure sensor structure with high sensitivity and quasi-linear responseUne nouvelle structure de capteur de pression capacitif avec haute sensibilitée et réponse quasi-linéaire

This paper describes a new capacitive structure of pressure sensor to increase simultaneously the sensitivity and the linearity of the transducer. This structure contains two capacitors which change in response to pressure, but in opposite senses. To increase even more the sensitivity of each capacitor, the pressure sensitive diaphragm carries a central boss. The optimal position and the length of the boss are also calculated. To cite this article: A. Ettouhami et al., C. R. Mecanique 332 (2004).     

Simultaneous Determination of Carbamate and Organophosphorus Pesticides in Honeybees by Liquid Chromatography-Mass Spectrometry

Summary The potential of liquid chromatography-mass spectrometry (LC-MS) has been studied for the simultaneous determination of sixteen carbamate and organophosphorus pesticides in honeybees using a traditional sample preparation protocol based on acetone extraction and dichloromethane partitioning. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ES) interfaces were compared. APCI offered better sensitivity and specificity for a higher range of pesticides. Limits of quantification were from 0.01 to 0.17 mg kg^–1, at which recoveries obtained were between 64 and 93%, except for pirimicarb that was at 13%, with relative standard deviations ranging from 7 to 20%. Fenitrothion, fenoxycarb, methiocarb and phoxim were found in bees from Valencian Community beehives at concentrations between 0.03 and 3.75 mg kg^–1.     

CsBr高压X光研究

 采用同步辐射X光源和能散法，对CsBr粉末样品进行高压原位X光衍射实验。由金刚石对顶压砧高压装置（DAC）产生高压，用已知状态方程的Pt粉末作内标，由Pt的衍射数据确定样品压力，最高压力达64.4 GPa。实验结果表明：室温常压下原始CsBr样品是具有简单立方结构的晶体，其晶格常数α＝0.428 5 nm。高压下CsBr的结构有所变化，在51.3~58.4 GPa的压力范围内，(110)线和(211)线发生劈裂，从而形成了四方相。     

Minimum Disparity Estimation in Linear Regression Models: Distribution and Efficiency

This paper deals with the minimum disparity estimation in linear regression models. The estimators are defined as statistical quantities which minimize the blended weight Hellinger distance between a weighted kernel density estimator of errors and a smoothed model density of errors. It is shown that the estimators of the regression parameters are asymptotic normally distributed and efficient at the model if the weights of the density estimators are appropriately chosen.