Studies on design of heterogeneous catalysts for biodiesel production

The production of biodiesel is gaining momentum with the ever increasing demand of the fuel. Presently, limited literature is available with respect to well designed solid heterogeneous catalyst for biodiesel production considering all the characteristics, process and operation parameters. Hence, a study was conducted to design effective heterogeneous catalyst for biodiesel production. Further, the significant impact of different catalysts, different feed stock, various reaction conditions such as temperature, methanol oil molar ratio, catalyst concentrations and stability/inactivation of the catalysts, are detailed out for transesterification process of biodiesel production. Based on the studies it can be concluded that well designed heterogeneous catalyst can yield high throughput of biodiesel.     

Effects of heterogeneities on capillary pressure-saturation-relative permeability relationships

In theories of multiphase flow through porous media, capillary pressure-saturation and relative permeability-saturation curves are assumed to be intrinsic properties of the medium. Moreover, relative permeability is assumed to be a scalar property. However, numerous theoretical and experimental works have shown that these basic assumptions may not be valid. For example, relative permeability is known to be affected by the flow velocity (or pressure gradient) at which the measurements are carried out. In this article, it is suggested that the nonuniqueness of capillary pressure-relative permeability-saturation relationships is due to the presence of microheterogeneities within a laboratory sample. In order to investigate this hypothesis, a large number of "numerical experiments" are carried out. A numerical multiphase flow model is used to simulate the procedures that are commonly used in the laboratory for the measurement of capillary pressure and relative permeability curves. The dimensions of the simulation domain are similar to those of a typical laboratory sample (a few centimeters in each direction). Various combinations of boundary conditions and soil heterogeneity are simulated and average capillary pressure, saturation, and relative permeability for the "soil sample" are obtained. It is found that the irreducible water saturation is a function of the capillary number; the smaller the capillary number, the larger the irreducible water saturation. Both drainage and imbibition capillary pressure curves are found to be strongly affected by heterogeneities and boundary conditions. Relative permeability is also found to be affected by the boundary conditions; this is especially true about the nonaqueous phase permeability. Our results reveal that there is much need for laboratory experiments aimed at investigating the interplay of boundary conditions and microheterogeneities and their effect on capillary pressure and relative permeability.     

Reproductive impairment of sea urchins upon chronic exposure to cadmium. Part I: Effects on gamete quality

Successful reproduction is a determining factor for species survival. Pollution may impair reproductive success of adults through effects on gamete quality. Reproductive impairment of the sea urchin Anthocidaris crassispina upon chronic (4 weeks) exposure to 0.01 and 0.1 mg l-1 Cd2+ was investigated. Criteria used for assessing gamete quality included sperm motility, egg morphology, fertilization rate and dynamics of first cleavage. A dose-response relationship was found between Cd2+ levels and changes in sperm motility, and percentage fertilization. Sperm motility, measured by computer-assisted sperm analysis, indicated that percent motile sperm, velocities, and percent sperm with normal trajectory were significantly affected by chronic exposure to > or = 0.1 mg l-1 Cd2+. A decline in sperm motility was also accompanied by a decrease in fertilization success of sea urchin sperm. Width/height ratio of sea urchin eggs was not affected by cadmium, but larger egg sizes were found when sea urchins were exposed to 0.1 mg l-1 Cd2+. Male sea urchins exposed to Cd2+ produced poorer quality sperm, as indicated by a lower percent fertilization and lower cleavage rate, implying that male sea urchins were more sensitive than females to chronic Cd2+ exposure. Results of the present study provide an explanation of reproductive impairment in marine invertebrates upon chronic exposure to Cd2+.     

Diesel particulate extracts in bacterial test systems

The Ames bacterial mutagenicity test system was used to evaluate parameters which may affect the mutagenic activity of diesel particulate extracts. The optimal extraction conditions, extractability of mutagens by simulated biological fluids and the effect of collection method were investigated. The role of solvent was examined by extracting diesel particles with methanol, acetone, cyclohexane, ethyl acetate, n-hexane, dichloromethane, benzene and a benzene-ethanol mixture. Of these, the dichloromethane extract exhibited the highest activity in the Ames test, although methanol yielded the largest extractable mass. Diesel particles were also extracted by dimethyl sulfoxide (DMSO) and four other simulated biological fluids for 48 h at 25, 37, and 45°C to study the effects of temperature. The mutagenic activity of the DMSO extract began to decline at temperatures higher than 37°C after 8 h of incubation. Fetal calf serum was the only simulated biological fluid which eluted mutagenic activity from the particles. No activity was detected in the 0.5% bovine serum albumin, simulated lung surfactant and saline extracts. Diesel particles collected by electrostatic precipitation (ESP) and filtration were studied. The mutagenic activities of both extracts were comparable when expressed as revertants per mg of particle. After the extracts were separated into nine fractions by a solvent partitioning scheme, the majority of the activity was found in the neutral-nonpolar II, neutral polar, strong acid and weak acid fractions. The acid salt fraction from the ESP sample was inactive. These results demonstrate that differences in the extraction conditions can result in differences in the mutagenic activity of diesel particulate extract. Since the mutagens in the extracts are not readily extractable by simulated biological fluids, the question of bioavailability of mutagens in diesel particles must be considered in the final assessment of their potential effects in biological systems and organisms.     

Minimum propagation diameter and thickness of high explosives

The critical diameter and critical thickness of two heterogeneous explosives were measured experimentally. By comparing these experimentally determined values of critical diameter and critical thickness, the role of front curvature in the failure of the detonation can be investigated. Current theories of detonation based on front curvature would predict the critical diameter should be twice the critical thickness. Experimentally, the expected two-to-one ratio was only validated for the case of a heterogeneous explosive with very fine scale heterogeneities. The ratios of critical diameter to critical thickness (for the two selected explosives) are also compared to previously measured values for homogeneous (liquid) explosives in order to contrast the dominant failure mechanism in these different explosives.     

Mass media and environmental knowledge of secondary school students in Hong Kong

A postal survey on a random cluster sample of 1032 secondary school students in Hong Kong was conducted to investigate what and how much students know about the environment and how their knowledge is related to use of mass media. Results indicated that students were very knowledgeable on general and local environmental issues. The average score for environmental knowledge was 60.7 on a 100-point scale. There was some indications that students' environmental knowledge was shaped and limited by the reporting of environmental news in Hong Kong. Television news viewership had positive correlation with students' environmental knowledge while Chinese newspaper readership had a positive but weak correlation. Male students and students in higher forms were more knowledgeable about the environment. The study established a comprehensive measure for both general and local environmental knowledge with an acceptable level of internal consistency for subsequent studies.     

Prenatal sonographic detection of intra-abdominal extralobar pulmonary sequestration: Report of three cases and literature review

Three cases of intra-abdominal extralobar pulmonary sequestration detected antenatally by ultrasound are reported. One case was associated with a large left diaphragmatic hernia. Sonographically, all the cases were found in the left supra-renal region presenting as a well-defined echogenic mass with cystic hypoechoic areas. The condition should be considered in the differential diagnosis of all antenatally detected upper abdominal echogenic masses, particularly when associated with a diaphragmatic hernia. Postnatal ultrasound-guided fine needle aspiration biopsy in one case yielded respiratory type epithelium and this procedure could provide a reasonably confident diagnosis of the lesion.     

城市污水快速渗滤处理技术与常用污水处理技术的对比分析

快速渗滤技术与传统氧化塘技术比较，单位处理负荷大幅度提高，占地面积明显减少；与传统污水处理厂比较，设计施工简便、建设费用低、运行费用小，管理方便。     

陕西省冬春季PM2.5时空分布特征研究

根据陕西省2016年12月至2017年5月PM_2.5质量浓度逐小时数据，利用ArcGIS分析陕西省PM_2.5污染时空变化格局，并分析造成南北差异的原因，再利用小波分析手段探讨各市PM_2.5污染时间序列周期和突变特性。结果表明：（1）陕西省冬季PM_2.5污染重，春季污染轻，并表现出"关中高，南北低"的特征，秦岭南北经济发展差异和供暖差异是控制陕西省PM_2.5污染空间格局的主要原因；（2）冬季和春季单日PM_2.5浓度变化趋势基本一致，为"双峰双谷型"，日最低值出现在16∶00~18∶00；（3）Morlet小波分析结果显示，陕西省PM_2.5日均变化序列存在多时间尺度特征。陕北城市PM_2.5污染第1主周期为40 d，关中城市和陕南商洛市有40 d和65 d两个共同周期，安康市和汉中市共同周期为20 d和80 d；（4）陕西省PM_2.5突变事件冬季频繁而春季较少，多发生在1月和2月，春季1次大范围的沙尘天气，造成了陕西省5月5日8个城市PM_2.5污染浓度剧增。