飞行时间方法测量电荷态分布

我们已经研制出了飞行时间 ＴＯＦ（Ｔｉｍｅ ｏｆ Ｆｌｉｇｈｔ）方法电荷态分布测量系统，并用该系统测定了ＭＥＶＶＡ（ＭｅｔａｌＶ ｐｏｒ Ｖａｃｕｕｍ Ａｒｃ）源产生离子的电荷态分布。在实验中，把ＭＥＶＶＡ源作为产生离子的手段；ＭＥＶＶＡ源是一种新型的离子源，该源阴极材料及运行条件较宽，能够产生强流的多电荷态离子。电荷态谱是用ＴＯＦ方法获得的，同时也测量了弧流及弧压降。在本文中，将介绍 ＴＯＦ方法测量电荷态的原理、结构和一些初步的实验结果，对 ＭＥＶＶＡ源也作了必要的介绍。     

SIMOX材料的SIMS分析

对ＳＩＭＯＸ材料进行了ＳＩＭＳ深度剖析，研究了电荷积累效应、二次离子传输效率等实验因素对测试结果的影响，氧检测的动态范围达三个量级。对国内、外的ＳＩＭＯＸ材料做了对比研究。     

GaAs二次离子发射的氧和铯效应

在二次离子质谱学中，氧和铯效应是影响二次离子发射最重要和复杂的现象。概括地总结了自９０年代以来对ＧａＡｓ二次离子发射氧和铯效应基础研究的主要成果。在准静态条件下，解决了用惰性气体Ａｒ＾＋源注氧研究复杂ＧａＡｓ基体上二次离子发射氧效应的主要困难，得到了表面注氧和覆铯使ＧａＡｓ二次离子产额和能量分布变化的实验规律，用ＴＯＦ－ＳＩＭＳ研究了砷化镓中ＭＣｓ＾＋ ＭＣｓ２＾＋等原子团离子的发射特性，对其发射     

SiO2中Na及Si中B的SIMS分析

ＳＩＭＳ对二氧化硅中钠离子有相当高的检测灵敏度，但其定量分析较为困难。在二氧化硅的ＳＩＭＳ图谱中，由一二氧化硅中的Ｎａ离子的计数和与“ＳｉＯ２”计数和之比正比于二氧化硅中的Ｎａ离子的平均体密度，因此中采用做过ＢＴ（温度偏压）实验的ＭＯＳ电容作为“标定”。因此用ＭＯＳ电容的ＢＴ实验也仅能求出可动钠离子的面密度，因此该方法仅能半定量地对二氧化硅中的Ｎａ离子进行估算。     

TRAITR晶体管S类功率放大器例作刘高赋——电子管音频放大器制作(二)

尽管ＵＨＣＭＯＳＦＥＴ管（超大电流ＭＯＳＦＥＴ）和ＩＧＢＴ管（绝缘栅双极型晶体管）功放如火如荼，使得Ｒｏｗｌａｎｄ、Ｔｈｒｅｓｈｏｌｄ等名牌功放被称至顶。便毕竟ＵＨＣＭＯＳＦＥＴ管、ＩＧＢＴ管的价格在国内达百多元一对，多管并联时是要经济能力的。因...     

一种低压差稳压器

如图１所示,ＭＡＸ８８６０是一种低噪声、低压差线性稳压器,其特点在于当输出电压脱离稳定电压范围时可给出一个ＦＡＵＬＴ输出信号,它工作于２－５Ｖ至６－５Ｖ的输入范围,输出电流最大可达３００ｍＡ。ＭＡＸ８８６０采用电阻很低的ＰＭＯＳ作为调整元件,使静态电源电流在满负载下仅有１１０μＡ,同时使压差降低至５５ｍＶ（于１００ｍＡ）。输出电容采用２μＦ的小电容,降低了整个系统的尺寸和成本,并缩短了启动时间。ＭＡＸ８８６０还具有Ｄｕａｌ－ＭｏｄｅＴＭ工作的特点：输出电压可采用预定值（ＭＡＸ８８６０Ａ为２－７７…     

新式小型便携飞行时间质谱计系统

开发了基于新式小型飞行时间质谱计（Ｍｉｎｉ－ＴＯＦＭＳ）的便携式分析系统。整个仪器包括小型飞行管、配套电源和小型分子泵——薄膜机组等，体积仅为４５ｃｍ×６０ｃｍ×２５ｃｍ。实测质量分辨体领（Ｍ／ΔＭ）５０％Ｈ可达３００，质量范围达到５００ａｍｕ。仪器小巧轻便，具有较高的性能价格比，在大气污染监测和工业气体成分在线分析等领域有应用前景。     

HF催化快速制备SiO2气凝胶

ＳｉＯ２气凝胶晃一种新型轻质纳米多孔泡沫材料,本文以正硅酸乙酯（ＴＥＯＳ）为原料,以乙醇为溶剂,以ＨＦ为催化溶胶－凝胶法快速制备出了ＳｉＯ２气凝胶。ＨＦ的加入大大加速了溶胶－凝胶反应速度,使凝胶时间减少至几分钟甚至更短;同时使凝胶温度降低至室温。ＢＥＴ及ＴＥＭ测试结果表明所制备的ＳｉＯ２气凝胶具有大比表面积（６７３．８ｍ＾２ｇ＾－１）、纳米多孔结构（骨架颗粒为几纳米,孔洞尺寸为５～３０ｎｍ）。     

出租车计价器计算机管理系统的开发

我所自１９９５年来开始对全市近千台出租车实行打表计时计程 ,直到１９９７年才全部安装上计价器。期间还因厂家计价器质量不稳定进行过免费更换 ,还有出租车易主等 ,造成出租车初装日期不一 ,使计价器的管理较为混乱 ,而人工查找一台出租车的相关数据更是费时费力。为此 ,开发出租车管理系统（ＴａｘｉＭａｎａｇｅｍｅｎｔＳｙｓｔｅｍ简称ＴＭＳ）势在必行。一、ＴＭＳ的开发运行平台开发ＴＭＳ主要采用汉字ＦｏｘＢＡＳＥ +２ １数据库语言 ,操作系统为ＤＯＳ６ ２２ ,中文平台为ＵＣＤＯＳ５ ０版本 ,本系统在Ｐｅｎｔｉｕｍ１６６型…     

薄膜全耗尽CMOS／SIMOX的高温特性分析

在室温－２００℃的不同温度睛测量了薄膜全耗尽ＣＭＯＳ／ＳＩＭＯＸ的Ｐ沟，Ｎ沟ＭＯＳＦＥＴ的亚阈特性曲线，分析了阈值电压和泄漏电流随温度的变化关系，并同相应的体硅器件作了比较。     

Arrayed time-of-flight mass spectrometry for time-critical detection of hazardous agents

The design and operation of an arrayed time-of-flight (TOF) mass spectrometer for simultaneous data acquisition from multiple samples is described. Versions of the instrument employ sets of two or four linear or reflectron mass analyzers. They are housed in the same vacuum chamber and utilize the same laser for ion desorption. Instrument performance is illustrated in the example of a two-linear-mass-analyzer array using MALDI-MS for mixtures of commercially available proteins as well as intact microorganisms. We also describe the properties of a novel short delay time (<170 ns) pulsed extraction method for linear TOF analyzers. This configuration allows uniform resolution improvements to be achieved in a wide m/z range. In addition, we present multiplexed sample preparation methods, using different reagents prior to mass analysis in the arrayed system, to increase the overall sensitivity of the MS method and to allow wider and more efficient detection across the entire range of potentially hazardous agents. In addition to the multifold increase in data collection rates, arrayed TOF-MS configurations provide a high degree of redundancy, critical for rapid, high confidence agent identification as well as for reduction in false alarm rates.     

Effects of bombardment on optical properties during the deposition of silicon nitride by reactive ion-beam sputtering

Thin silicon nitride (Si(1_x)N(x)) films were synthesized without substrate heating by means of reactive argon-ion sputtering of either silicon or a silicon nitride target in the 1000-1500-eV energy range at a nitrogen partial pressure of 1.3 × 10(-2) Pa and with simultaneous nitrogen ion-assisted bombardment in the 300-500-eV low energy range. The extinction coefficient and refractive index of the films were directly dependent on the N(+) ion-to-atom arrival ratio, assisted ion energy, film growth rate, and indicated a correlation with film stoichiometry and disorder. Si(3)N(4) films were obtained for N(+) ion/Si atom arrival ratios from 0.6 to 1.7 and for different Si:N atom arrival rates and had a refractive index as high as 2.04 (633 nm) and a low hydrogen content as indicated by IR spectra.     

The determination of the minimum safe dead time in 4π β−γ coincidence counting

Allowance for the dead time loss is one of the major correction factors required in 4πβ ? γ coincidence counting. A simple method is described for obtaining the optimum β channel dead time, which involves determining a dead time curve, relating the observed total system dead time as a function of an additional dead time inserted in the β channel.     

Optimized algorithm for the spatial nonuniformity correction of an imaging system based on a charge-coupled device color camera

We present an optimized linear algorithm for the spatial nonuniformity correction of a CCD color camera's imaging system and the experimental methodology developed for its implementation. We assess the influence of the algorithm's variables on the quality of the correction, that is, the dark image, the base correction image, and the reference level, and the range of application of the correction using a uniform radiance field provided by an integrator cube. The best spatial nonuniformity correction is achieved by having a nonzero dark image, by using an image with a mean digital level placed in the linear response range of the camera as the base correction image and taking the mean digital level of the image as the reference digital level. The response of the CCD color camera's imaging system to the uniform radiance field shows a high level of spatial uniformity after the optimized algorithm has been applied, which also allows us to achieve a high-quality spatial nonuniformity correction of captured images under different exposure conditions.     

Unambiguous identification of volatile organic compounds by proton-transfer reaction mass spectrometry coupled with GC/MS

Interest in on-line measurements of volatile organic compounds (VOCs) is increasing, as sensitive, compact, and affordable direct inlet mass spectrometers are becoming available. Proton-transfer reaction mass spectrometry (PTR-MS) distinguishes itself by its high sensitivity (low ppt range), high time resolution (200 ms), little ionization-induced fragmentation, and ionization efficiency independent of the compound to be analyzed. Yet, PTR-MS has a shortcoming. It is a one-dimensional technique that characterizes compounds only via their mass, which is not sufficient for positive identification. Here, we introduce a technical and analytical extension of PTR-MS, which removes this shortcoming, while preserving its salient and unique features. Combining separation of VOCs by gas chromatography (GC) with simultaneous and parallel detection of the GC effluent by PTR-MS and electron impact MS, an unambiguous interpretation of complex PTR-MS spectra becomes feasible. This novel development is discussed on the basis of characteristic performance parameters, such as resolution, linear range, and detection limit. The recently developed drift tube with a reduced reaction volume is crucial to exploit the full potential of the setup. We illustrate the performance of the novel setup by analyzing a complex food system.     

Capillary electrophoresis with lamp-based wavelength-resolved fluorescence detection for the probing of protein conformational changes

Native protein fluorescence spectra encompass information on protein conformation. In this study, capillary electrophoresis (CE) combined with lamp-based wavelength-resolved fluorescence detection (wrFlu) is presented as a novel tool for the analysis of protein mixtures and the monitoring of protein unfolding. The CE-wrFlu system provides three-dimensional data (time, emission wavelength, intensity) from which electropherograms and accurate emission spectra of separated proteins can be extracted. For model proteins, linear detector responses (peak height vs concentration) were obtained (R(2) > 0.96) with detection limits (LODs) in the 6-32 nM range. The minimum protein concentration required for precise determination of the maximum emission wavelength by CE-wrFlu was about 15 times the LOD. Unfolding of various model proteins was induced by protein incubation and analysis in background electrolyte (BGE) containing 7.0 M urea. CE-wrFlu of the unfolded species revealed peaks with clear red-shifted spectra, which adequately corresponded to reference spectra obtained on a standard spectrophotometer. Moreover, unfolded proteins showed a significant decrease in effective electrophoretic mobility (after correction for BGE viscosity) due to the increase of their molecular hydrodynamic radii. It is concluded that the CE-wrFlu system provides two independent indicators for changes in protein folding and will allow the simultaneous assessment of protein purity and conformation.     

Corrections from extending dead times with activity measurements on radionuclides decaying via metastable states

The dead-time corrections for an extending dead time are analyzed for measurements on radionuclides decaying via metastable states and correction formulas are developed. It is shown that for large dead times with λ ? 1(λ = decay constant, τ = dead time) the dead-time correction approximates the usual case of a prompt decay besides a term that enlarges the dead-time correction.     

Versatile immunosensor using CdTe quantum dots as electrochemical and fluorescent labels

A versatile immunosensor using CdTe quantum dots as electrochemical and fluorescent labels has been developed for sensitive protein detection. This sandwich-type sensor is fabricated on an indium tin oxide chip covered with a well-ordered gold nanoparticle monolayer. Gel imaging systems were successfully introduced to develop a novel high-efficient optical immunoassay, which could perform simultaneous detection for the samples with a series of different concentrations of a target analyte. The linear range of this assay was between 0.1 and 500 ng/mL, and the assay sensitivity could be further increased to 0.005 ng/mL with the linear range from 0.005 to 100 ng/mL by stripping voltammetric analysis. The immunosensor showed good precision, high sensitivity, acceptable stability, and reproducibility and could be used for the detection of real sample with consistent results in comparison with those obtained by the ELISA method.     

Integrated microfluidic device for mass spectrometry-based proteomics and its application to biomarker discovery programs

The present investigation describes the analytical performances of a microfluidic device comprising an enrichment column, a reversed-phase separation channel, and a nanoelectrospray emitter embedded altogether in polyimide layers. This configuration minimizes transfer lines and connections and reduces postcolumn peak broadening and dead volumes. This compact and versatile modular nanoLC-chip system was interfaced to both ion trap and time-of-flight mass spectrometers, and its analytical potentials were evaluated in the context of proteomics applications. The figures of merit of this system in terms of peak capacity, reproducibility, sensitivity, and linear dynamic range of peptide detection were determined using tryptic digests of complex protein extracts including albumin- and immunoglobulin-depleted rat plasma samples. The analysis of peak profiles for more than 600 peptide ions reproducibly detected across replicate nanoLC-chip-MS runs (n = 10) indicated that this system provided good reproducibility of retention time and peak intensity with RSD values of less than 0.5 and 9.1%, respectively. Variation in peptide abundance as low as 2-fold changes was identified for spiked tryptic digests present at levels of 2-5 fmol in plasma samples. Sensitivity measurements were performed on dilution series of protein digests spiked into rat plasma samples and provided a detection limit of 1-5 fmol. The modular concept of the microfluidic systems also facilitated the integration of two-dimensional chromatography (strong cation exchange/C18) thereby increasing the sample loading and selectivity of the nanoLC-chip-MS system. The application of this integrated device was evaluated for complex rat plasma samples to compare the number of protein identifications obtained using one- and two-dimensional nanoLC-chip-MS/MS.     

Performance evaluation of a hybrid linear ion trap/orbitrap mass spectrometer

Design and performance of a novel hybrid mass spectrometer is described. It couples a linear ion trap mass spectrometer to an orbitrap mass analyzer via an rf-only trapping quadrupole with a curved axis. The latter injects pulsed ion beams into a rapidly changing electric field in the orbitrap wherein they are trapped at high kinetic energies around an inner electrode. Image current detection is subsequently performed after a stable electrostatic field is achieved. Fourier transformation of the acquired transient allows wide mass range detection with high resolving power, mass accuracy, and dynamic range. The entire instrument operates in LC/MS mode (1 spectrum/s) with nominal mass resolving power of 60,000 and uses automatic gain control to provide high-accuracy mass measurements, within 2 ppm using internal standards and within 5 ppm with external calibration. The maximum resolving power exceeds 100,000 (fwhm). Rapid, automated data-dependent capabilities enable real-time acquisition of up to three high-mass accuracy MS/MS spectra per second.