Laser lineshape effects on cavity-enhanced absorption spectroscopy signals

The quantitative effects of laser lineshape on signals from cavity-enhanced absorption spectroscopy (CEAS) and integrated cavity output spectroscopy (ICOS) experiments are examined. The governing equations for CEAS signals including the laser lineshape are derived. Approximations under which the laser lineshape may be neglected or replaced with an effective lineshape are presented. It is shown that the laser lineshape effects may be parameterized with two dimensionless variables: the laser linewidth normalized by the absorption linewidth, and the peak sample absorbance normalized by the mirror loss. In terms of the dimensionless variables, we simulate CEAS and ICOS signals and the absorbances inferred from them. The simulation results provide a useful tool for CEAS and ICOS practitioners to gauge the importance of laser lineshape effects in specific experiments. Simulations are performed for the four combinations of Gaussian and Lorentzian lineshapes for the laser and the absorption. PACS 42.62.Fi; 78.40.-q; 32.70.Jz     

Determination of 17 kinds of banned organochlorine pesticides in water by activated carbon fiber-solid phase microextraction coupled with GC-MS.

Activated carbon fiber (ACF) as extraction fiber for solid-phase microextraction (SPME) and its application for the analysis of banned organochlorine pesticides (OCPs) were investigated. Firstly, ACF was activated by different concentration of zinc chloride, which indicated that ACF activated by 60% zinc chloride had a reasonable specific surface area, pore volume and pore distribution. Secondly, the parameters for the ACF-SPME procedure, the adsorption and desorption conditions, were also optimized when coupled with gas chromatography-mass spectrometry (GC-MS). Thirdly, the ACF-SPME was used to analyze 17 kinds of OCPs in water. The linearity of most pesticides was found to be between 0.2 and 50 microg/l with GC-MS under the selected ion monitoring (SIM) acquisition mode. The limits of detection (LOD) at the sub microg/l were obtained. The work demonstrated here shows that ACF is a promising alternative for the SPME procedure.     

Morphological characterization of the mouthparts of the vector leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae)

The leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae), is one of the most significant economic pests of wheat in Western China. This insect vectors a phytoplasma that causes wheat blue dwarf (WBD), a severe disease limiting wheat production in the Western China. A microscopic analysis of the ultrastructure of the mouthparts of the adult was conducted using scanning electron microscopy and the putative functions of the mouthparts were determined. The piercing-sucking mouthparts of P. striatus are of the conventional type comprising a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and an uppermost small cone-shaped labrum. The mandibular stylets, located laterad of the maxillary stylets, have sculpture on their tips, which may function in tearing plant tissue, cutting channels into the plant tissues, and attaching the body to the host plant during molting. The maxillary stylets are interlocked to form two separate compartments, a larger food canal and a smaller salivary canal. Two dendritic canals are also found in each maxilla and one in each mandible. Four kinds of sensilla were found on the labium: s. trichodea I, s. trichodea II, s. basiconic I, s. basiconic II. These may be involved in host recognition and are likely chemo- or mechanosensory, or both.     

空间光束实时捕获、跟踪实验与分析

提出一种空间光束捕获、跟踪设计方案,在实验室条件下实现其主要功能,并对其定位精度和实时性进行了分析,结果表明：信标光定位处理的时间为25 ms,角度测量的相对误差为1.3％,显示出良好性能.同时,为由理论分析到实际星载PAT系统提供试验依据.     

力矩教学剖析

力矩在物理课教学中占有举足轻重的地位．力矩的概念并不难理解，但应用起来却涉及到很多知识点，且能翻出不少新花样．让我们来看下面的问题：放在地面上的板条箱(如图)，受到R=120N力的作用．试求该力对点A的力矩：(1)根据力臂计算；(2)根据该力在作用点B处的分力计算；(3)根据该力在作用线上其它某一适当点处的分力计算．     

On the Formation of Nanostructures from Stilbazolium-like Dyes

Nanostructures with well-defined shape and highly monodisperse size were fabricated from model stilbazolium-like dyes with specific molecular structural and conformational characteristics. With the help of absorption and fluorescence optical spectroscopy, the correlated spectroscopy (COSY) and two- dimensional nuclear Overhauser effect spectroscopy (2D NOESY) techniques, along with X-ray diffraction (XRD) measurement, distinctively different aggregation processes of the model molecules are demonstrated. For model dye molecule with linear donor–π system–acceptor (D–π–A) structure, strong D–A pair, and planar conformation, specific intermolecular interaction was identified and special crystal structures as well as spectral properties were observed. For model dye molecules bearing nonlinear D–π–A–π–D structure, weak D–A pair but actual amphiphilic characteristics, a special aggregation process was confirmed and a focused size distribution of the produced nanostructures was obtained.     

{Bis­[2‐(2‐oxido‐1‐naphthylmethylidene­amino)­phenyl] disulfide}chloroiron(III)

The crystal structure of the title compound, {bis­[2‐(2‐oxido‐2‐naphthyl­idene­amino)­phenyl] di­sulfide‐κ⁵O,N,S,N′,O′}chloroiron(III), [FeCl(C₃₄H₂₂N₂O₂S₂)], has been determined. The structure consists of monomeric iron(III) complexes with distorted octahedral coordination. The di­sulfide functions as a pentadentate ligand and the Fe^III atom is coordinated through two N, two O and one S atom, and one chloride ion. The distance between the second S atom and the Fe^III atom is a non‐bonding 3.8473 (14) Å.