Design and performance of air flow-assisted ionization imaging mass spectrometry system

The imaging mass spectrometry（IMS） technology has experienced a rapid development in recent years.A new IMS technology which is based on air flow assisted ionization（AFAI） was reported.It allows for the convenient pretreatment of the samples and can image a large area of sample in a single measurement with high sensitivity.The AFAI in DESI mode was used as the ion source in this paper.The new IMS method is named AFADESI-IMS.The adoption of assisted air flow makes the sample pretreatment easy and convenient.An optimization of the distance between the ion transport tube and MS orifice increases the sensitivity of the system.For data processing,a program based on MATLAB with the function of numerical analysis was developed.A theoretical imaging resolution of a few hundred microns can be achieved.The composite AFAI-IMS images of different target analytes were imaged with high sensitivity.A typical AFAI-IMS image of the whole-body section of a rat was obtained in a single analytical measurement.The ability to image a large area for relevant samples in a single measurement with high sensitivity and repeatability is a significant advantage.The method has enormous potentials in the MS imaging of large and complicated samples.

GHz bursts in MHz burst(BiBurst) enabling high-speed femtosecond laser ablation of silicon due to prevention of air ionization

For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts(2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses(2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation(single-pulse mode). As a result, ablation speed can be enhanced by a factor of23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided.

Development of a portable cold air plasma jet device and observation of its photo ionization process

Photo ionization plays a critical role in the formation and propagation of atmospheric pressure plasma jet plumes.But in experiments,it is very difficult to observe the photo ionization due to its relative lower density of photo electrons.In the present study,we develop a portable cold air plasma jet device and observe the ionization wave in adc spark air plasma jet.The discharge images acquired by an ICCD camera show that the ionization wave front performs as a quickly moving bright ball.Breakdown could take place at another side of the quartz plate or pork tissue layer(6 mm thick),which suggests that the ionization should be attributed to photo ionization.The laser schlieren images indicate there is propagation of a shock wave along with the plasma bullet.Based on the photo ionization theory and the photo-electric measurement,the direct photo ionization and multistage photo ionization are the main factors in charge of generating the cold air plasma jet.In addition,the plasma jet outside of the cathode nozzle is colder than 320 K and can be touched safely by a human.In view of the plasma jet including a large amount of active particles,such as NO,O,OH,emitted photons,etc,the proposed portable cold air plasma jet device could be qualified for plasma bio-medicine applications.

Determination of Xenon in Air by a Pulse-discharge Helium Ionization Detector

A pulse-discharge helium ionization detector（Valco, PD-D3-I） was used to measure xenon concentration in air. The dependences of the detector relative response on various gas chromatograph parameters were investigated. Based on the well prepared gas connections for the detector system and optimized gas chromatography（GC） working conditions, the atmospheric xenon concentration could be measured by the cheap GC method with a detection level of 0.7×10-9（parts by volume）. Moreover, the xenon concentration in the ground level air around our laboratory was measured with the result of 0.085×10-6（parts by volume） and RSD of 0.91%.

Effect of a commercial air ionizer on dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae(Acari:Pyroglyphidae) in the laboratory

Objective:To investigate the short and long tenn efficacy of a commercial air ionizer in killing Dermatophagoides pteronyssinus(D.pteronyssinus)and Dermalophagoides farinae(D.farinae)mites.Methods:The effect of a commercial ionizer on D.pteronyssinus and D.farinae was evaluated in the laboratory,using a specially designed test.Mortality was assessed after 6,16and 24 hours for direct exposure and after 24,36,48,60 and 72 hours for exposure in simulated mattress.New batches of mites were used for each exposure time.Results:LT_(50)for direct exposure of ionizer was 10 hours for D.pteronyssinus and 18 hours for D.farinae.The LT_(50)for exposure in simulated mattress was 132 hours or 5.5 days for D.pteronyssinus and 72 hours or 3days for D.farinae.LT_(95)for direct exposure of ionizer was 36 hours for D.pteronyssinus and D.farinae.Meanwhile,the LT_(95)for exposure in simulated mattress was 956 hours or 39.8 days for D.pteronyssinus and 403 hours or 16.8 days for D.farinae.Conclusions:This study demonstrates the increasing mite mortalities with increasing exposure time of a commercial ionizer and suggests that negative ions produced by an ionizer kill dust mites and can be used to reduce natural mile populations on exposed surfaces such as floors,clothes,curtains,etc.However,there is reduced efficacy on mites inside stuffed materials as in mattresses and furniture.

A high-performance bio-tissue imaging method using air flow-assisted desorption electrospray ionization coupled with a high-resolution mass spectrometer

Mass spectrometry imaging (MSI) technology can simultaneously obtain the spatial distribution of thousands of chemical compounds and has unique advantages compared to other techniques that allow mapping the surface of bio-tissue. Here, we combined an air flow-assisted desorption electrospray ionization (AFADESI) MSI device with a high-resolution mass spectrometer to optimize the system parameters and achieve more accurate spatial distribution characteristics for compounds of interest while investigating bio-tissue sections. The platform set-up, required instrumentation, sample pretreatment, parameter optimization and bio-tissue characterization are described and discussed.Finally, the parameter conditions that can provide optimal ionic intensity and enhanced resolution were confirmed. The reasonable resolution and sensitivity improvements of AFADESI-MSI have been achieved through tandem a high-resolution mass spectrometer system, therefore, it would be a promising technique for the bio-tissue imaging analysis.

Dependence of plasma structure and propagation on microwave amplitude and frequency during breakdown of atmospheric pressure air

The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell’s equations coupled with plasma fluid equations.In this model,we adopt the effective electron diffusion coefficient,which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma.The filamentary plasma arrays observed in experiments are well reproduced in the simulations.The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data.The size of plasma filament parallel to the electric field decreases with increasing frequency,and it increases with the electric field amplitude.The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes.The plasma propagation speed shows little change with the frequency,and it increases with the amplitude.The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.

Influence on the Ground and Air and Mathematical Description of the High-Voltage Discharge

According to trends of the development the high-voltage devices’ usage and unpredictable weather causes,we find it very important to research electrical discharge from different sources.In our opinion,the most important is to analyze an influence of the atmospheric electricity on the air and ground, create an exact mathematical model of the physical processes,and describe the ecological influence.

Working Voltage of Double Grid Air Counter

Based on analysis of the discharging course in double grid air counter (DGAC),the dischargin model is built up by applying the conception of average ionizing free path. An effective algorithm is presented for the working voltage of DGAC using this model. The working voltage is nearly related to the geometric parameters of DGAC, the sensitivity of the circuitry and the number of discharges. Computing results confirm that the working voltage increases with the ratio of the radius of the anode to that of the cathode. The number of discharges follows the similar rule.

Novel Air Purification System for Installation in Air Handling Units： Development, Assembly and Experimental Analysis

Nowadays, people pass 90% of their time in closed spaces, therefore, an increasing care in the creation and upkeep of healthier environments as a personal and as professional level become a major issue. The present project has as goal the verification and optimization of the implicit need of an OCRAMclima~ AHU （air handling units） in IAQ （indoor air quality） and its effectiveness in treatment and/or air purification, having as basis the legal national and European requirements for IAQ. This work was based on the study of the state of the art of the techniques in air purification and in the evaluation of their performance, culminating in the production of the prototype OCRAMclima~ NPS （nano purifying system）. The purifying phenomena involved are UVGI （ultraviolet germicidal irradiation） and catalytic ionization of air. The performance test was accomplished in a closed loop circuit, which results, obtained by an independent IAQ analyst, were satisfactory, indicating the viability of application of this system to indoor air disinfection. The outcome revealed that the conjugating of both phenomena, the air sterilizing by UV and catalytic ionization, is efficient when used for air purification, mainly for volatile organic compounds and bioaerosols.

环境自动监测站固定式辐射监测仪性能测试与评价

参考计量技术规范《固定式环境γ辐射空气比释动能(率)仪现场校准规范》(JJF 1733—2018),对辐射环境空气自动监测站78台高气压电离室开展辐射特性测试。现场校准方面,仅88%的电离室满足1±0.2的响应范围要求;78台电离室的重复性均不超过1%,响应的非线性均不超过6.5%,符合规范要求。针对电离室开展辐射性能测试,发现电离室在9.0×10^(-2)~1.0×10^(9)μGy/h范围内的响应均不超过1±0.2;电离室对164 keV以上的光子的能量响应趋于1.0,对60 keV以下的光子无响应能力,而当光子能量在60~164 keV范围内时,响应曲线会因γ光子与电离室内部惰性气体的光电效应出现“鼓包”;电离室不具备对核临界事故脉冲辐射的监测与警示能力;电离室能够在2 s内给出测量范围内的准确示值,但在分段电压的交界处,响应时间会延长至180~360 s;电离室的响应受环境温度、湿度变化的影响大小不足±0.01,表明电离室的环境适应性优良。

Competition between multiphoton/tunnel ionization and filamentation induced by powerful femtosecond laser pulses in air

In this work we present experiments by focusing 42 femtosecond laser pulses in air using three differentfocal length lenses: f=100, 30 and 5 cm. For the longest focal length, only the filament, which is aweak plasma column,is observed. When the shorter focal length lens is used, a high density plasma isgenerated near the geometrical focus and coexists with a weak plasma channel of the filamemt. Under thetightest focusing condition, filamentation is prevented and only a strong plasma volume appears at tehgeometrical focus.

含铜危固废冶炼烟气中电收尘的设计及操作要点

江西兴南环保科技有限公司10万t/a含铜二次资源综合利用项目,于2021年6月生产试运行。试运行期间,针对底吹吹炼系统电收尘工艺、设备、操作和磨合的过程中的问题,在数据支撑下,进行设计、操作方面的探索,从根本上降低吨铜加工成本。

辐射环境空气自动监测站故障及处理的研究

随着核电事业的快速发展和核技术应用的不断扩大,辐射环境安全问题日益受到社会关注。辐射环境空气自动监测站作为监测环境辐射水平的重要设施,在保障公众健康、维护社会稳定方面发挥着不可替代的作用。然而,由于自动监测站长期在野外运行,设备老化、供电系统不稳定、网络通信故障等问题频发,严重影响了监测数据的准确性和时效性。因此,开展辐射环境空气自动监测站故障与处理的研究,对提高监测站运行效率、保障监测数据质量具有重要意义。

重复频率高功率微波脉冲的大气击穿

理论研究了重复频率高功率微波脉冲在大气中的传输特性,推导了n个高功率微波脉冲之后空间某点的电子密度,数值模拟并给出了在不同微波频率、大气压强、脉冲宽度以及脉冲间隔的条件下,大气击穿时,透射过去的脉冲个数与微波功率的关系。模拟结果表明:当微波脉冲参数一定时,压强越小,透射过去的脉冲个数越少,大气越容易发生击穿;当压强一定时,脉宽越宽,微波频率越小,透射过去的脉冲个数越少,大气越容易发生击穿。

激光击穿大气等离子体的光谱实验研究

对一个大气压的N2 ,O2 和纯净空气 ,用YAG脉冲激光的 1 .0 6μm光束产生激光等离子体 ,对该等离子体在大约 40 0— 80 0nm谱段的发射光谱进行了实验研究 .实验表明 ,空气及其主要组分的激光等离子体光谱均由较强的连续光谱背景和迭加在其上的若干线状光谱组成 .随着光谱采样的延时 ,激光等离子体中各光谱组分的强度有很不相同的相对变化 .而且 ,处于等离子体不同空间部位发出的光谱 ,也有很大的不同 .

EFFECT OF COOLING/LUBRICATION MEDIUM ON MACHINABILITY OF Ti6Al4V

To better understand and know the roles of cooling/lubrication medium in the cutting process and expand their applicability,uncoated cemented carbide tools are used in high-speed turning Ti6Al4V.Dry,cold air,minimal quantity lubrication（MQL）,cryogenic MQL,and ionized air as the cooling/lubrication conditions are studied.Experimental results show that at speed 120 m/min turning Ti6Al4V,the cutting force under ionized air is smallest under all lubricant conditions,and tool life is best,next is cryogenic MQL.MQL and cold air almost have the same effect,a little better than dry.Meanwhile the smallest surface roughness is also obtained under ionized air condition.Flank wear and crater wear are the dominant failure modes when high-speed turning Ti6Al4V by SEM analysis.Finally the conclusion is drawn that ionized air and cryogenic MQL have better cooling/lubrication effects and can effectively improve the tool life.

常压敞开式离子化质谱技术研究进展

近年来,无需复杂样品前处理、且在开放环境下实现离子化的常压敞开式离子化质谱技术(Ambientionization mass spectrometry,AI-MS)的研制与应用成为质谱学领域的前沿及备受关注的研究方向。该文综述了AI离子源的基本原理、特征与应用进展,并结合笔者研制的空气动力辅助离子化(Air flow assisted ioniza-tion,AFAI)技术,介绍了气流辅助常压敞开式离子化技术的基本特点及其应用。展望了常压敞开式离子化技术的发展趋势。

高功率微波大气击穿阈值分析及实验

对高功率微波脉冲的大气击穿进行了理论分析和数值模拟,推导了单脉冲和重复频率脉冲两种情况下电子数密度的变化表达式通过计算给出了在不同大气压强、脉冲宽度以及重复频率的条件下,高功率微波脉冲大气击穿阈值的变化规律。设计了高功率微波大气击穿实验系统,并开展了实验研究,实验的结果与数值模拟结果基本一致。

因子分析法在质谱成像数据分析中的应用

对因子分析法在质谱成像数据分析中的应用进行了研究。本方法分析的质谱成像数据来源于空气动力辅助离子源质谱成像技术,所用样品为含有3种不同颜料(红色、蓝色、黑色)的笔迹样品。对该样品的成像数据进行因子分析后,将成像数据分为了背景、黑色、蓝色和红色因子。分析结果显示,m/z 443.2,478.4,322.2(344.2)分别在红色、蓝色、黑色因子中的贡献值远大于其它质荷比,因此是3种颜料的特征质荷比。此结果与实际情况相符,证明使用因子分析方法对质谱成像数据进行分析和特征提取是可行的。对因子分析与主成分分析的成像数据处理结果进行了比较,结果显示,因子分析可以更简单和定量地对特征质荷比进行取舍,在生物标志物提取、疾病诊断、药理分析等方面有较大的应用潜力。