Assessment of Bioaerosol Sampling Techniques for Viable Legionella pneumophila by Ethidium Monoazide Quantitative PCR

Legionella pneumophila causes severe pneumonia and Pontiac fever in humans. Rapid and sensitive bioaerosol monitoring techniques for viable L. pneumophila are unavailable. Coupled with a newly developed viable assay called ethidium monoazide with quantitative PCR (EMA-qPCR), this study applies EMA-qPCR to aerobiology for the first time to evaluate the effects of the method of sampling (all-glass impinger (AGI-30), BioSampler, and MAS-100 sampler) and sampling time (3, 30, 60 min) on the collection of viable L. pneumophila. The effects of the collection fluid (deionized water (DW) and Tween mixture) and the replenishment of DW every 15 min during 60-min sampling were also assessed. Escherichia coli, as a model microorganism in bioaerosol research, was also tested. Using the Tween mixture (DW containing 1% peptone, 0.01% Tween 80, and 0.005% antifoam), the AGI-30 and BioSampler performed significantly better than the MAS-100 sampler for collecting viable L. pneumophila and viable E. coli (P < 0.05). An increase in sampling time adversely affected the quantification of both bacterial species (P < 0.05). The collection with DW yielded greater recovery of viable L. pneumophila than the Tween mixture in both AGI-30 and BioSampler, regardless of sampling time, by a factor of 1.4–6.9 (P < 0.05). The replenishment of DW every 15 min further improved the collection of viable L. pneumophila. This study demonstrates that viable L. pneumophila can be efficiently sampled by the AGI-30 and BioSampler and successfully quantified by EMA-qPCR.     

Numerical Performance Simulation of a Wetted Wall Bioaerosol Sampling Cyclone

Computational fluid dynamics techniques are used to study the performance of an axial flow bioaerosol sampling cyclone that continuously collects particles onto a flowing liquid film. A special shell-volume concept was developed to study formation and development of the liquid film on the inner wall of the cyclone. For a previous version of the cyclone, simulations demonstrated the presence of a ring of liquid in the region just upstream of the liquid skimmer that was suspected of causing liquid carryover into the exhaust air stream and degradation in aerosol collection efficiency. This ring was eliminated by re-design of the cyclone. For the upgraded version of the cyclone, CFD was used to successfully predict aerosol collection efficiency and cyclone pressure drop. The simulations reveal a complex flow evolution inside the cyclone. Stream-tubes are used to describe a significant narrowing of the width of the airflow as it enters the cyclone and an inward displacement of the flow as it travels in the axial direction. The particle deposition occurs primarily in a region that is subtended approximately by the length of the rectangular entrance slot and the first half turn of the flow in the cyclone. Cutpoint Stokes number is about 0.05 and the cutpoint particle size is about 1 μm aerodynamic diameter. At a flow rate of 1250 L/min, the pressure drop across the cyclone is 5.6 kPa (22 inches of water).     

Liquid Consumption of Wetted Wall Bioaerosol Sampling Cyclones: Characterization and Control

Advances in microfluidic, lab on chip, and other near-real-time biological identification technologies have driven the desire to concentrate bioaerosols into hydrosol sample volumes on the order of tens of microliters (μL). However, typical wet biological aerosol collector outputs are an order or two of magnitude above this goal. The ultimate success of bioaerosol collectors and biological identifiers requires an effective coupling at the macro-to-micro interface. Liquid collection performance was studied experimentally for a family of dynamically scaled wetted wall bioaerosol sampling cyclones (WWC's). Steady-state liquid collection rates and system response times were measured for a range of environmental conditions (temperatures from 10°C to 50°C and relative humidities from 10% to 90%), liquid input rates, and WWC airflow configurations. A critical liquid input rate parameter was discovered that collapsed all experimental data to self-similar empirical performance correlations. A system algorithm was then developed from empirical correlations to provide control over the liquid output rate and resulting concentration factor for a cyclone with an airflow rate of 100 L/min. Desired liquid output rates of 25 to 50 μL/min were maintained while sampling outdoor air over diurnal ranges of environmental conditions. These flow rates are associated with concentration factors on the order of 1,000,000 to 2,000,000 and liquid outputs that are a steady stream of 10 to 30 drops/min of 7 to 10 μL droplets. These developments should allow wetted wall cyclones to be effectively coupled to advanced biological identification systems.     

Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. II: Sampling Efficiency and Half-Life Time

Using uranine as a physical tracer, this study assessed the sampling efficiencies of four bioaerosol samplers (Andersen 6-stage impactor, all glass impinger “AGI-30,” OMNI-3000, and Airport MD8 with gelatin filter) for collecting Gram-positive bacteria (Enterococcus faecalis), Gram-negative bacteria (Escherichia coli and Campylobacter jejuni), and bacteria without cell wall (Mycoplasma synoviae) which were aerosolized in a HEPA isolator. In addition, the half-life times of these bacteria in aerosols were estimated. The uranine concentrations collected by the samplers were used for calculating the physical efficiencies, and the bacteria/uranine ratios were used for calculating the biological efficiencies. The results show the Airport MD8 had the highest physical efficiency. Compared with the Airport MD8, the physical efficiencies of the AGI-30 and the OMNI-3000 were 74% and 49%, respectively. A low physical efficiency of the Andersen impactor (18%) was obtained, but it was mainly caused by the incomplete recovery of uranine when handling the air samples, so could not be ascribed to the sampler efficiency. Both the Andersen impactor and the AGI-30 showed high biological efficiencies for all four bacterial species. The biological efficiencies of the OMNI-3000 for C. jejuni (1%) and of the Airport MD8 for E. coli (38%) and C. jejuni (2%) were significantly lower than 100%, indicating that their sampling stresses inactivated the bacterial culturability. The half-life times at 21–23°C temperature and 80–85% relative humidity were 43.3 min for E. faecalis, 26.7 min for M. synoviae, 21.2 min for E. coli, and 4.0 min for C. jejuni in the air.     

Design and Collection Efficiency of a New Electrostatic Precipitator for Bioaerosol Collection

We have developed and tested a new bioaerosol sampler in which airborne microorganisms are collected by electrostatic means. In this sampler, 2 ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection. The organisms are then subjected to a precipitating electric field and are collected onto 2 square agar plates positioned along the flow axis. Tests with nonbiological NaCl particles versus B. subtilis var. niger (BG) spores and vegetative cells have shown that airborne microorganisms are collected more efficiently than nonbiological particles, even when the microorganisms have first passed through an electric charge neutralizer with no additional charging applied. The difference was attributed to the natural charges contained in cell membranes or spore coats of the microorganisms. Charge-neutralized BG spores and vegetative cells were collected at 4 L/min with efficiencies close to 80%, depending on the precipitation voltage, versus 50-60% for NaCl test particles. When incoming BG spores were charged with positive ions and then collected by a precipitating voltage of + 1,300 V, about 80% of the incoming spores were collected and more than 70% of incoming spores formed colonies. These experiments with BG spores have also indicated that there were no significant particle losses inside the sampler. The collection efficiency of biological and nonbiological particles increased to 90-100% when the particles were externally charged and the precipitating voltage was increased to more than - 4,000 V. It has also been shown that the aerosolized BG spores (used as anthrax simulants for bioaerosol sensors) carry a net negative electric charge. Thus the collection efficiency depends on the polarity of the electric field applied across the agar plates. These findings indicate that the collection of airborne microorganisms is possible by electrostatic precipitation without prior electric charging if the microorganisms already carry electric charges. These are usually high immediately after their release into the air.     

Comparative Testing and Evaluation of Nine Different Air Samplers: End-to-End Sampling Efficiencies as Specific Performance Measurements for Bioaerosol Applications

Accurate exposure assessments are needed to evaluate health hazards caused by airborne microorganisms and require air samplers that efficiently capture representative samples. This highlights the need for samplers with well-defined performance characteristics. While generic aerosol performance measurements are fundamental to evaluate/compare samplers, the added complexity caused by the diversity of microorganisms, especially in combination with cultivation-based analysis methods, may render such measurements inadequate to assess suitability for bioaerosols. Specific performance measurements that take into account the end-to-end sampling process, targeted bioaerosol and analysis method could help guide selection of air samplers.

Nine different samplers (impactors/impingers/cyclones/ electrostatic precipitators/filtration samplers) were subjected to comparative performance testing in this work. Their end-to-end cultivation-based biological sampling efficiencies (BSEs) and PCR-/microscopy-based physical sampling efficiencies (PSEs) relative to a reference sampler (BioSampler) were determined for gram-negative and gram-positive vegetative bacteria, bacterial spores, and viruses.

Significant differences were revealed among the samplers and shown to depend on the bioaerosol's stress–sensitivity and particle size. Samplers employing dry collection had lower BSEs for stress-sensitive bioaerosols than wet collection methods, while nonfilter-based samplers showed reduced PSEs for 1 μm compared to 4 μm bioaerosols. Several samplers were shown to underestimate bioaerosol concentration levels relative to the BioSampler due to having lower sampling efficiencies, although they generally obtained samples that were more concentrated due to having higher concentration factors.

Our work may help increase user awareness about important performance criteria for bioaerosol sampling, which could contribute to methodological harmonization/standardization and result in more reliable exposure assessments for airborne pathogens and other bioaerosols of interest.

Copyright 2014 American Association for Aerosol Research     

窑尾余热发电热效率及发电效率提高途径

本文以迁安市永固油井水泥有限公司的生产工艺线及生产实际参数为例,从热力学的观点,对水泥企业窑尾带余热锅炉发电系统的能量分布进行分析,谈谈提高发电效率和热利用率的几个关键问题。迁安市永固油井水泥有限公司工艺流程为一条龙生产线,主机七磨一窑:生料磨机两台(!2.2m×6.     

基于极点配置下的采样周期分析

从实际控制系统应用出发,研究了基于极点配置下采样周期变化对系统性能的影响。采用Delta算子理论将闭环系统离散化,通过对满足要求的矩阵不等式的分析,给出了一种求解最大采样周期的算法,并针对一实际系统进行了仿真研究,得到了最大采样周期,并给出了采样周期从零到最大变化时控制律和特征根的变化情况,结果表明衰减率和控制量存在矛盾,在实际的控制系统设计中必须加以权衡。     

Biomass Thermogravimetric Analysis: Uncertainty Determination Methodology and Sampling Maps Generation

The objective of this study was to develop a methodology for the determination of the maximum sampling error and confidence intervals of thermal properties obtained from thermogravimetric analysis (TG), including moisture, volatile matter, fixed carbon and ash content. The sampling procedure of the TG analysis was of particular interest and was conducted with care. The results of the present study were compared to those of a prompt analysis, and a correlation between the mean values and maximum sampling errors of the methods were not observed. In general, low and acceptable levels of uncertainty and error were obtained, demonstrating that the properties evaluated by TG analysis were representative of the overall fuel composition. The accurate determination of the thermal properties of biomass with precise confidence intervals is of particular interest in energetic biomass applications.     

Effect of Agar Plate Volume on Accuracy of Culturable Bioaerosol Impactors

Agar plate volume in bioaerosol impactors affects collection efficiency, but it is often overlooked in practice. This study investigated the effect of agar volume (20, 35, and 50 mL) and, consequently, jet-to-plate distance on accuracy of culturable impactors. Laboratory experiments investigated sensitive Escherichia coli and hardy Bacillus atrophaeus bacteria with a BioStage impactor. Outdoors bacterial and fungal sampling assessed effects of varying agar volume in BioStage, Sampl’air Lite, and SAS Super 180 multinozzle impactors relative to a reference BioStage with 35 mL agar. The results demonstrate that agar plate volume affects not only overall collection efficiency, but also species selection and colony masking. Culturable concentrations of E. coli in laboratory were underestimated by 35% when using 20 versus 35 mL agar volume (p < 0.001). However, data indicate selection of healthier bacteria, as E. coli colonies were significantly larger on 50 versus 20 mL agar plates (p < 0.001). For outdoors, lower agar volume significantly improved accuracy of Sampl’air relative to the reference BioStage for bacterial (p < 0.001) and fungal (p = 0.03) aerosols. Changes for other samplers were not statistically significant, likely due to wide variability in microbial profiles. Outdoors data indicate that culturable concentrations may be positively correlated with increasing dimensionless jet-to-plate distance, especially for bacteria (p = 0.04). This effect may be attributable to sampler jet dissipation with lower nozzle number impactors (i.e., the Sampl’air) being more sensitive. This study demonstrates that bioaerosol impactor agar plate volume should be considered prior to sampling.

Copyright 2013 American Association for Aerosol Research     

BP网络在加热炉效率评定中的应用

以工艺管式炉有关数据为例,将BP网络有效应用于数据的压缩存储和快速计算,为加热炉效率评定软件提供了BP网络模型。利用MATLAB软件实现了BP网络的训练及仿真分析,并讨论了应用过程中参数的选择以及训练数据的特点对网络训练产生的影响。     

Generation of Chiral Olefins Based on L-Aspartic Acid

A new chiral olefin 4 was synthesized starting from L -aspartic acid. The structures of the intermediate oxazolidinones 6 and 7 were proven by X-ray analysis to be diastereomers. It was shown that 4 is unreactive in Diels-Alder reactions with cyclopentadiene and 1,3-diphenyliso-benzofuran because of its steric overloading (M.M. calculations) rather than by electronic effects (FMO by AM1 calculations).     

基于DSP的ADC采样校正与显示系统

为了实现传统DSP的ADC采集校正与显示功能,设计了DSPF2812开发板和参考电压电路,通过为ADC采样通道提供两路精准的参考电压,消除了DSP采样时系统本身存在的误差和漂移。对温度和湿度采样信号进行限幅数字滤波,通过OCMJ8×15D液晶进行温湿度显示,实现人机交互。实验调试结果表明:校正后采样值与实际值的误差不超过0.3%,而且系统运行稳定,弥补了传统单纯采用DSP在ADC采集方面的不足。     

基于聚砜膜的透析进样毛细管电泳系统与性能评价

通过在毛细管进样端口原位相转化法制备透析膜,实现了膜预处理与毛细管电泳分离的在柱耦合的毛细管电泳方法.以多巴胺和牛血清白蛋白(BSA)为研究体系,该系统能成功拦截大分子BSA,有效避免蛋白质的干扰.膜在毛细管端口原位生成,与毛细管电泳之间几乎无死体积;与常规毛细管电泳相比,加膜后柱效和重现性损失小,出峰时间和电泳电流有...     

一种基于等效采样技术的高速数据采集系统

介绍一种采用可编程逻辑器件（Comp lex Programm ab le Logic Device,CPLD）,以单片机为核心的高速数据采集系统。给出了电路组成原理及实现过程,该系统实现了低速单片机完成高速数据采集的功能,节约了硬件成本。本系统能完成单次触发存储显示功能及对被测信号进行采集、存储和显示功能。该电路可应用在数字示波器等电子设备的输入通道,具有较高的性价比。     

Injection Molding Warpage Optimization Based on a Mode-Pursuing Sampling Method

This paper presents a new optimization approach for minimizing the warpage defect of injection-molded plastic parts. Existing methods in warpage optimization are either computationally expensive or, when inexpensive surrogate models are employed with fixed set of sample points, the accuracy of the surrogate model will only be ensured by a large number of sample points, which in turn will increase the amount of required computation. To address this problem, this paper applies a mode-pursuing sampling (MPS) method for warpage optimization, by integrating injection molding simulation with MPS, and by proposing a reinforced convergence criterion for the optimization process, in an attempt to search for the optimal process parameters of injection molding for minimizing warpage defect both effectively and efficiently. The MPS method can systematically generate more sample points in the neighborhood of the current optimal solution while statistically covering the entire search space. A case study of a scanner frame, where injection time, melt temperature and mold temperature are selected as the design variables, demonstrates that the proposed optimization method can effectively decrease the warpage deflection of an injection-molded part with significantly less computation required. Based on the optimization results, the paper also studied the influences of different process parameters on the severity of the warpage defect, providing a guideline for the setting of the proper process parameters.     

镇江地区环境变量对光伏发电效率的影响研究

为了研究镇江地区光伏发电量与环境变量之间的影响关系,以镇江建科院示范楼屋顶自行设计建造的43 kWp分布式光伏电站为研究对象,分别研究太阳能辐射强度、温度与发电量之间的关系,同时对光伏阵列效率、逆变器转换效率等进行了计算.可知日均发电量为109.46kW.h,平均发电效率值为10.78％,逆变器转换效率的平均值为83.78％,东、西、南三个坡面单位面积日均发电量分别为1.92、2.53及2.84kWh.     

基于能量吸收效率的泡沫塑料缓冲材料选择

讨论了几种不同密度EPS泡沫、EPE泡沫的单项压缩性能，并绘制了材料的能量吸收效率一应力关系图及能量吸收效率一密度关系图。图线显示材料吸收的能量随应变量的增加而增加；不同密度的同类材料的能量吸收效率随应力增大有相同的变化趋势；在一定应力下材料能量吸收效率随着材料密度增大呈近似抛物线趋势变化并有惟一极值点。阐述了在缓冲包装设计中利用材料的能量吸收效率一应力图线合理选择材料密度的方法。     

注塑模CAE用实体模型的表面网格模型生成方法

为了实现注塑模CAE软件与商用CAD软件之间的数据交换,给出了基于STL文件的三维实体模型的表面有限元网格划分方法。该算法利用STL文件传递薄壁注塑件的实体模型信息,在对该模型的表面区域进行合并的基础上,重新进行网格划分,可生成质量较好的表面三角形网格,从而得到满足成型模拟需要的有限元网格模型。     

基于统计分析的固废产生量预测方法初探

文章利用全国30个主要城市一般工业固废产生量数据,探讨GM(1,1)模型在固体废物产生量预测中的适用性.将统计学中的聚类分析与GM(1,1)结合,可有效筛选适用数据,降低了GM(1,1)运用于固废产生量预测中的相对误差。