Dynamics of explosion venting in a compartment with methane-air mixtures

A series of experiments on explosion venting of methane-air mixtures are performed to scrutinize the pressure evolution as well as the flame dynamics and morphology at various vent conditions. Specifically, a premixed flame is ignited at the center of a polycarbonate cylindrical compartment, with three various vent areas considered (with negligible vent relief pressure). As expected, the highest maximum pressure is observed in the case of the smallest vent area. For all three cases, the pressure evolution experiences two major peaks, associated with the instants (i) when the maximum flame front surface area in the chamber is reached and (ii) when an external explosion occurs due to venting of unburned gases, respectively. For the fuel-rich mixtures, a flashback is observed subsequent to the external explosion, constituting the key outcome of the present work. The flame tip velocities show two general trends, namely, exponential acceleration towards the vent, while a flame propagates towards the blocked side of the compartment with no acceleration, which is important to know in the fire/explosion safety applications.     

有害结局路径(AOP)框架在水体复合污染监测研究中的应用

水体复合污染包含低浓度、种类复杂的毒害化学污染物,威胁人类健康和生态安全。监测并识别水体关键毒害污染因子是进行水质管理的前提,也是复合污染研究的难点。目前国内外在水复合污染毒性监测研究上主要基于动物活体试验或者生物体外测试。由于受限于毒理学测试方法,常见的应用通常仅关注于某方面的毒性效应或者少数的分子指标,因而受到质疑和挑战。有害结局路径(Adverse outcome pathway,AOP)的概念将化学污染物的结构、致毒的分子启动事件和生物毒性的有害结局建立关联,为污染物的毒性测试、预测和评估提供了新的模式。本文旨在论述有害结局路径在复合污染毒性评估和关键毒害物质鉴别中的指导性价值和意义。在有害结局路径的指导框架下,借助于生物体外高通量测试技术、化学分析的靶向和非靶向分析技术和生物信息学技术,可以系统地分析化学混合物在分子、细胞水平上健康相关指标的响应水平,评估水体中复杂结构污染物,与不同生态和健康有害结局之间的关联,为水环境评价和优先污染物的筛选管理提供有效支撑。本文通过综述AOP框架在复合水体中毒害物质风险研究的现状和优势,对AOP在水环境环境管理上的应用前景提出展望。     

Selective and sensitive extractive spectrophotometric determination of micro amounts of palladium(II) in spiked samples: using a new reagent N-ethyl-3-carbazolecarbaxaledehydethiosemicarbazone

N-Ethyl-3-cabazolecarboxaldehydethiosemicarbazone (ECCT) is proposed as a new, sensitive and selective complexing reagent for the separation and extractive spectrophotometric determination of palladium(II) at pH: 4.0 to form a yellowish orange colored 1:1 chelate complex, which is very well extracted in to n-butanol. The absorbance was measured at a maximum wavelength, 410 nm. This method obeys Beer’s law in the concentration range 0.0–6.6 μg mL⁻¹ and the correlation coefficient of Pd(II)-ECCT complex is 0.998, which indicates an excellent linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 1.647 × 10⁴ l mol⁻¹cm⁻¹, 6.49 × 10⁻³ μg cm⁻², respectively. The instability constant of complex calculated from Edmond’s method, 2.724 × 10⁻⁵ was in good agreement with the value calculated from Asmus’ method 2.624 × 10⁻⁵, at room temperature. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.839. Edmond’s method was observed to be a more selective method in the presence of EDTA, oxalate and phosphate ions. The method was successfully applied for the determination of Pd(II) in water samples, synthetic mixtures and hydrogenation catalysts, employing an atomic absorption spectrometer for comparing these results.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

“鸡尾酒”式混合抗生素对细菌耐药性的影响

选择四环素、磺胺、磺胺增效剂3类常用抗生素, 以其对大肠杆菌(E. coli)的单一兴奋效应(hormesis)最大促进效应对应浓度(HC_max)配制等HC_max比的二元及三元混合体系, 探究混合体系对细菌生长和耐药性(突变、质粒接合转移)的联合效应.结果表明, 二元混合抗生素对E. coli生长和接合转移频率起到协同抑制, 对E. coli的突变频率起协同刺激; 三元混合抗菌剂对这三种效应均协同抑制.因此, 推测二元混合体系会导致毒性和耐药性风险同时增加; 三元混合体系会导致毒性风险增加、耐药性风险降低.     

高温红外吸收法测定水煤浆中可燃硫方法研究

研究采用高温红外吸收法直接测定水煤浆中可燃硫方法,确定了用浆状水煤浆试样或粉末固体试样的样品制备和红外测硫仪的炉温设定范围(900℃～950℃),通过与间接差减法测定结果对比分析,表明此法可行.     

生理药代动力学模型及其在健康风险评价中的应用研究进展

生理药代动力学(Physiologically Based Pharmacokinetic,PBPK)模型在健康风险评估中的应用逐渐成为研究的焦点.简要阐述了PBPK模型的定义及发展历程,在此基础上详细介绍了PBPK模型建立的过程及其在致癌风险评估、混合物健康风险评估中的应用.最后,总结了该模型在健康风险评估应用中的受限因素,提出跨学科合作有利于解决这些受限因素,从而进一步推进该模型在混合物健康风险评价中的应用.     

Validation of a new formula for predicting the lower flammability limit of hybrid mixtures

A correlation of the lower flammability limit for hybrid mixtures was recently proposed by us. The experimental conditions including ignition energy and turbulence which play a primary role in a gas or dust explosion were at fixed values. The sensitivity of such experimental conditions to the accuracy of the proposed formula was not thoroughly discussed in the previous work. Therefore, this work studied the effect of varying the ignition energy and turbulence intensity to the formula proposed in our previous paper. For ignition energy effect, results from methane/niacin mixture demonstrated that the MEC and LFL will not be affected by changing ignition energy. There is no distinguishable difference among gas explosion index (K_G) and dust explosion index (K_St) derived from tests with every ignition energy (2.5 kJ, 5 kJ and 10 kJ) in a 36 L vessel. The proposed formula is independent of ignition energy. For turbulence effect, the proposed formula can have a good prediction of the explosion and non-explosion zone if the ignition delay time is within a certain range. The formula prediction is good as the ignition delay time increases up to 100 ms in this work. Propane/niacin and propane/cornstarch mixtures are also tested to validate the proposed formula. It has been confirmed that the proposed formula predicts the explosion and non-explosion zone boundary of such mixtures.     

Study of the explosion parameters of vapor–liquid diethyl ether/air mixtures

The knowledge of the vapor–liquid two-phase diethyl ether (DEE)/air mixtures (mist) on the explosion parameters was an important basis of accident prevention. Two sets of vapor–liquid two-phase DEE/air mixtures of various concentrations were obtained with Sauter mean diameters of 12.89 and 22.90 μm. Experiments were conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at an ignition energy of 40.32 J and at an initial room temperature and pressure of 21 °C and 0.10 MPa, respectively. The effects of the concentration and particle size of DEE on the explosion pressure, the explosion temperature, and the lower and upper flammability limits were analyzed. Finally, a series of experiments was conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at various ignition energies. The minimum ignition energies were determined, and the results were discussed. The results were also compared against our previous work on the explosion characteristics of vapor–liquid two-phase n-hexane/air mixtures.     

On the explosion and flammability behavior of mixtures of combustible dusts

In the work presented in this paper, the explosion and flammability behavior of combustible dust mixtures was studied. Lycopodium, Nicotinic acid and Ascorbic acid were used as sample dusts.In the case of mixtures of two dusts, the minimum explosive concentration is reproduced well by a Le Chatelier's rule-like formula, whereas the minimum ignition energy is a linear combination of the ignition energies of the pure dusts.An unexpected behavior has been found in relation to the explosion behavior and the reactivity. When mixing Lycopodium and Nicotinic acid or Ascorbic acid, the rate of pressure rise of the mixture is much higher than the rate of pressure rise obtained by linearly averaging the values of the pure dusts (according to their weight proportions), thus suggesting that strong synergistic effects arise; but it is comparable to that of the most reactive dust in the mixture.The observed behavior seems to be linked to the presence of minerals in the Lycopodium particles which catalyze oxidation reactions of Nicotinic acid and Ascorbic acid, as suggested by TG analysis.In the case of mixtures of three dusts, a similar behavior is observed when the concentration of Lycopodium is twice that of the other two dusts.