工艺尾气氚测量装置的研制

通过选择装置材料、优化结构及参数,设计制作了有效体积为11.0 mL的测氚电离室,用于工艺尾气中氚含量的测量。用质谱法标定绘制了工作曲线,工作曲线线性范围为0.013 4%～0.168%(体积)。测试表明:装置泄漏率为5.5×10^-7 Pa·m³/s,密封性良好;本底电流为2.98×10^-14A;装置探测下限值为1.35×10^-4 %(体积);变异系数≤1.50%;仪器响应时间≤10 s,响应速度快,测量周期短,满足工艺样品的检测需求。     

MALDI Q-TOF CID MS for Diagnostic Ion Screening of Human Milk Oligosaccharide Samples

Human milk oligosaccharides (HMO) represent the bioactive components of human milk, influencing the infant’s gastrointestinal microflora and immune system. Structurally, they represent a highly complex class of analyte, where the main core oligosaccharide structures are built from galactose and N-acetylglucosamine, linked by 1–3 or 1–4 glycosidic linkages and potentially modified with fucose and sialic acid residues. The core structures can be linear or branched. Additional structural complexity in samples can be induced by endogenous exoglycosidase activity or chemical procedures during the sample preparation. Here, we show that using matrix-assisted laser desorption/ionization (MALDI) quadrupole-time-of-flight (Q-TOF) collision-induced dissociation (CID) as a fast screening method, diagnostic structural information about single oligosaccharide components present in a complex mixture can be obtained. According to sequencing data on 14 out of 22 parent ions detected in a single high molecular weight oligosaccharide chromatographic fraction, 20 different oligosaccharide structure types, corresponding to over 30 isomeric oligosaccharide structures and over 100 possible HMO isomers when biosynthetic linkage variations were taken into account, were postulated. For MS/MS data analysis, we used the de novo sequencing approach using diagnostic ion analysis on reduced oligosaccharides by following known biosynthetic rules. Using this approach, de novo characterization has been achieved also for the structures, which could not have been predicted.     

Investigation of the ionization of atom driven by a few-cycle laser pulse in phase space

We perform a comprehensive study of the ionization of hydrogen atom by a few-cycle laser pulse with a fixed carrier-envelop in phase space through calculating the Wigner functions. The results show that the electrons always locate around the nucleus before the laser electric field force reaches a certain intensity. While as the force of the laser electric field increases, the electrons are gradually deviated away from the nucleus. The ionized electrons are driven back to the core region and make a wiggling motion because of the variation of the laser electric field force with time. Moreover Wigner functions enable us to clearly show the classical and quantum behaviours during ionization process are presented in phase space, and explicitly attribute the arc fringes to the interference effect between the electronic wavepackets born at different ionization times.     

Characterization by Stm and Electrical Conductivity of Single-Walled Carbon Nanotubes

Abstract

Single-walled carbon nanotubes (SWCNT) prepared by a DC-Arc-Discharge and purified by a hydrothermal treatment followed by several steps of procedures including heating, burning, extracting and acid-washing are investigated by a conventional STM technique morphologically and spectroscopically. The electical resistivities of compacted pellets (mats) of SWCNT are measured as a function of temperature in the range from the room-temperature to 1.5K. The behaviors seems to be essentially originated in the metallic nature of individual SWCNT.     

Aerosol laser time-of-flight mass spectrometer for the on-line measurement of secondary organic aerosol in smog chamber

An aerosol laser time of flight mass spectrometer (ALTOFMS) that can be used for real-time measurement of the size and composition of individual aerosol particles has been designed and utilized to provide on-line measurement of secondary organic aerosol (SOA) particles resulted from Cl-initiated oxidation of toluene in smog chamber. Both the size and chemical compositions of individual aerosol particles were obtained in real-time. According to a large number of single aerosol diameters and mass spectra, the size distribution and chemical composition of aerosol were determined statistically. Experimental results indicate that aerosol particles produced from Cl-initiated oxidation of toluene were predominantly in the form of PM 2.5 particles, and nine positive laser desorption/ionization mass spectra peaks: m/z 18, 29, 30, 44, 46, 52, 65, 77, and 94 may come from the fragment ions of the products of the SOA: aromatic aldehydes, aromatic acids, phenolic compounds, and nitrogenated organic compounds. These results were in good agreement with those ones from previous Cl-initiated oxidation of toluene. These were demonstrated that ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chamber.     

水基气雾剂中右旋炔丙菊酯、右旋苯醚菊酯、氯菊酯气相色谱法测定

目的:建立水基气雾剂中右旋炔丙菊酯、右旋苯醚菊酯、氯菊酯的气相检测方法。方法:采用邻苯二甲酸二戊酯和邻苯二甲酸二丁酯两种物质作内标进行对比,丙酮作为溶剂,用HP-5的毛细管柱为分离柱,采用程序升温的方法进行分离,FID检测器,进样口温度300℃,检测器温度300℃,柱温初始180℃以20℃/min升温至280℃,保留5 min。结果:3种物质在标样与内标质量比1∶5~5∶1范围内呈良好线性关系,相关系数大于0.999,回收率为92.34%~105.12%,RSD为0.182%~0.649%。结论:此方法准确可靠,并且检测快速、高效,对原有方法进行补充。     

剂量电离室数字滤波器设计

为满足上海先进质子治疗装置治疗头中剂量电离室电子学A/D转换后的数据率和降噪要求,提出一种多级级联的数字滤波器结构。本文中设计LMS自适应滤波器来滤除50 Hz的工频噪音,相比于传统数字陷波器,不会对有用信号造成损失。通过MATLAB软件仿真对信号处理结果表明,电子学延时减少到170μs,数据率50 kHz,基本符合量化后的剂量数据处理要求。     

Development of Laser Ionization Techniques for Evaluation of the Effect of Cancer Drugs Using Imaging Mass Spectrometry

Recently, combined therapy using chemotherapy and photodynamic therapy (PDT) has been proposed as a means of improving treatment outcomes. In order to evaluate the efficacy of combined therapy, it is necessary to determine the distribution of the anticancer drug and the photosensitizer. We investigated the use of imaging mass spectrometry (IMS) to simultaneously observe the distributions of an anticancer drug and photosensitizer administered to cancer cells. In particular, we sought to increase the sensitivity of detection of the anticancer drug docetaxel and the photosensitizer protoporphyrin IX (PpIX) by optimizing the ionization-assisting reagents. When we used a matrix consisting of equal weights of a zeolite (NaY5.6) and a conventional organic matrix (6-aza-2-thiothymine) in matrix-assisted laser desorption/ionization, the signal intensity of the sodium-adducted ion of docetaxel (administered at 100 μM) increased about 13-fold. Moreover, we detected docetaxel with the zeolite matrix using the droplet method, and detected PpIX by fluorescence and IMS with α-cyano-4-hydroxycinnamic acid (CHCA) using the spray method.     

Plasma Behavior in a High‐Temperature Noble Gas Plasma Disk‐Shaped MHD Power Generator

R‐θ two‐dimensional numerical simulations have been carried out to clarify the plasma behavior in a high‐temperature noble gas plasma disk‐shaped magnetohydrodynamic (MHD) generator. At low inlet total temperature and high load resistance, the plasma has spiral structure which is similar to the nonuniform structure under the weak noble gas ionization condition in a seed‐plasma MHD generator. As seen in a linear‐shaped Faraday‐type MHD generator, the plasma becomes stable with increase in the inlet total temperature because the coulomb collision of electrons becomes dominant. Even at low inlet total temperature, the ionization instability can be suppressed for low load resistance, because the relatively low electron temperature due to less Joule heating makes the ionization relaxation time longer than plasma residential time.     

Simulation study of the influence of leak electrons on the discharge characteristics of a cusped field thruster

Previous studies have shown that leak electrons in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the exit. In this paper, a one- dimensional fluid model is built along two typical electron paths to study the influence of leak electrons on the discharge characteristics of a cusped field thruster, considering the electron temperature equation. It is found that the frequencies of low-frequency oscillations increase with a decrease in the proportion of leak electrons, which is related to an increase in the ion speed in the channel. Simulation results show that the position of the peak electron temperature is near the magnetic cusp on the exit and the position of the peak electron density is located downstream from the middle magnetic tip. With a decrease in the proportion of the leak electrons, the peak electron temperature and peak electron density decrease and the position of the peak electron density moves away from the exit, which is related to a decrease in the potential fall on the exit and an increase in confinement of electrons to the middle magnetic cusp.