Flame Propagation Across Gelled Alkane-In-Water Emulsions

Flame propagation rates were measured for flames spreading across surfaces of gel-like alkane-in-water emulsions. A long, slender, water-cooled trough was used to contain the mixtures. Abrupt changes in the flame propagation velocities - of nearly two orders of magnitude - were observed to occur near ‘critical’ concentrations of certain alkane/water mixtures. Four alkanes were used - pentane, hexane, heptane, and octane - and fuel rich emulsions (in which water was the continuous phase) were employed. The ability of the aqueous phase of the emulsion to inhibit the release of fuel into the vapor phase plays an important role in the observed behavior. That is, the rate at which fuel can diffuse through both the emulsion and the thin liquid layers that reside on it, is an essential kinetic aspect of the phenomena which determine the flame propagation rate across gelled alkane-in-water emulsions.     

MINIMIZING THE IMPACT OF URBANIZATION ON LONG TERM RUNOFF1

Increasing concern about the problems caused by urban sprawl has encouraged development and implementation of smart growth approaches to land use management. One of the goals of smart growth is water resources protection, in particular minimizing the runoff impact of urbanization. To investigate the magnitude of the potential benefits of land use planning for water resources protection, possible runoff impacts of historical and projected urbanization were estimated for two watersheds in Indiana and Michigan using a long term hydrological impact analysis model. An optimization component allowed selection of land use change placements that minimize runoff increase. Optimizing land use change placement would have reduced runoff increase by as much as 4.9 percent from 1973 to 1997 in the Indiana study watershed. For nonsprawl and sprawl scenarios in the Michigan watershed for 1978 to 2040, optimizing land use change placement would have reduced runoff increase by 12.3 percent and 20.5 percent, respectively. The work presented here illustrates both an approach to assessing the magnitude of the impact of smart growth and the significant potential scale of smart growth in moderating runoff changes that result from urbanization. The results of this study have significant implications for urban planning.     

Aerosol structure and vertical distribution in a multi-source dust region

The vertical distribution of aerosols was directly observed under various atmospheric conditions in the free troposphere using surface micro-pulse lidar (MPL4) at the Zhangye Station (39.08°N, 100.27°E) in western China in the spring of 2008. The study shows that the aerosol distribution over Zhangye can be vertically classified into upper, middle and lower layers with altitudes of 4.5 to 9 km, 2.5 to 4.5 km, and less than 2.5 km, respectively. The aerosol in the upper layer originated from the external sources at higher altitude regions, from far desert regions upwind of Zhangye or transported from higher atmospheric layers by free convection, and the altitude of this aerosol layer decreased with time; the aerosols in the middle and lower layers originated from both external and local sources. The aerosol extinction coefficients in the upper and lower layers decreased with altitude, whereas the coefficient in the middle layer changed only slightly, which suggests that aerosol mixing occurs in the middle layer. The distribution of aerosols with altitude has three features: a single peak that forms under stable atmospheric conditions, an exponential decrease with altitude that occurs under unstable atmospheric conditions, and slight change in the mixed layer. Due to the impact of the top of the atmospheric boundary layer, the diurnal variation in the aerosol extinction coefficient has a single peak, which is higher in the afternoon and lower in the morning.     

节能型虹吸式滗水器的设计与应用

详细介绍了虹吸式滗水器的构成、特点及工作原理,结合理论和实践经验给出了虹吸式滗水器的设计、计算方法及关键设计参数,提出了常规使用方法,整套设备的设计全面而简单明了。     

某涡轮风扇发动机试车台的声环境研究

涡轮风扇发动机试车台空气流量大,试车噪声呈宽带强噪声,其中突出的低频域噪声可远距离传播,易造成大范围的环境污染。为掌握某型涡轮风扇发动机在室内试车时的噪声特性,并检验试车台建筑物和各项降噪设备的效果,我们对新建试车台的声环境进行了测量。通过对该试车台内、外环境噪声数据的分析,表明新建试车台的声环境满足了我国有关规范的要求。本次研究工作对今后试车台的声学设计具有重要的借鉴意义。     

From waste hot-pot oil as carbon precursor to development of recyclable attapulgite/carbon composites for wastewater treatment

The utilization of waste products as valuable materials was a technical imperative for waste management. In this study, the cost-effective attapulgite/carbon(APT/C) composite was developed for wastewater treatment using waste hot-pot oil as a carbon precursor through a facile one-step calcination process. The APT/C composite prepared at 300°C exhibited the excellent adsorption capacity and rapid equilibrium rate over a broad p H range for the removal of various pollutants. More importantly, the removal ratios of the composites toward Methyl Violet and tetracycline still remained 77.6% and 60.2% of the initial adsorption capacity after ten adsorption–regeneration cycles via a facile thermal regeneration strategy, respectively.Beyond all doubt, this research provided a feasible and economical way for the sustainable utilization of waste hot-pot oil in wastewater treatment, achieving the concept of disposal waste with waste and recycling.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin promotes migration ability of primary cultured rat astrocytes via aryl hydrocarbon receptor

Emerging evidence showed that 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) could induce expression of certain reactivation-associated genes in astrocytes, however, the consequent cellular effects and molecular mechanisms are still unclear. During the process of astrocyte reactivation, migration is a critical cellular event. In the present study, we employed wound-healing assay and Transwell® motility assay to explore the effects of TCDD on cell migration in primary cultured rat cortical astrocytes. We found that upon TCDD treatments at relative low concentrations (10^? 10 and/or 10^? 9?mol/L), the ability of primary astrocytes to migrate horizontally and vertically was promoted. In line with this cellular effect, the mRNA expression of two pro-migratory genes, including cell division cycle 42 (CDC42) and matrix metalloproteinase 2 (MMP2) was induced by TCDD treatment. Dioxin exerts its toxic effects mainly through aryl hydrocarbon receptor (AhR) pathway. So the role of AhR pathway in the pro-migratory effects of TCDD was examined using an AhR antagonist, CH223191. We found that application of CH223191 significantly reversed the pro-migratory effects of TCDD. Interestingly, the basal ability of horizontal migration as well as basal levels of CDC42 and MMP2 expression were dramatically reduced suggesting a possible physiological role of AhR in maintaining the endogenous migration ability of the primary astrocytes. These findings support the notion that dioxin promotes astrocyte reactivation at molecular and cellular levels.     

Enzyme-electrolytic degradation of dichloromethane: Efficiency, kinetics and mechanism

Enzymatic electrolysis cell(EEC) has advantages over microbial electrolysis cell(MEC) due to the needless of microbe inoculation and high-efficiency of enzymatic reaction. In this study, an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane(CH_2Cl_2) was utilized as a model pollutant. The results indicate that the degradation efficiency of CH_2Cl_2 after 2 hr reaction in the EEC was almost100%, which was significantly higher than that with enzyme(51.1%) or current(19.0%). The current induced the continuous regeneration of reduced glutathione(GSH), thus CH_2Cl_2 was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination, and successively formed monochloromethane(CH_3Cl) and methane(CH_4). The kinetic result shows that with a current of 15 mA, the maximum specific degradation rate of CH_2Cl_2(3.77 × 10~(-3) hr~(-1)) was increased by 5.7 times. The optimum condition for CH_2Cl_2 dechlorination was also obtained with pH, current and temperature of 7.0, 15 mA and 35°C,respectively. Importantly, this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC, providing a possible treatment technology for halogenated organic pollutants.     

First trimester maternal serum placenta growth factor (PIGF)concentrations in pregnancies with fetal trisomy 21 or trisomy 18

Placenta growth factor (PIGF), an angiogenic factor belonging to the vascular endothelial growth factor family, pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotrophin (β-hCG) were measured in maternal serum from 45 pregnancies with trisomy 21, 45 with trisomy 18 and 493 normal controls at 10–13 completed weeks of gestation. In the normal pregnancies maternal serum PIGF levels increased exponentially with gestation. The median multiple of the median (MoM) PIGF concentration in the trisomy 21 group (1.26 MoM) was significantly higher (p<0.0001) than in the control group (1.00 MoM). In the trisomy 18 group the median PIGF was lower (0.889 MoM) but this did not quite reach significance (p=0.064). The corresponding median MoM values for PAPP-A were 1.00 MoM for the controls, 0.49 MoM for trisomy 21 and 0.16 MoM for trisomy 18. The median MoM values for free β-hCG were 1.00 MoM for the controls, 2.05 MoM for trisomy 21 and 0.38 MoM for trisomy 18. In the control group there was a small but significant correlation of PIGF with free β-hCG (r=+0.1024) and PAPP-A (r=+0.2288). In the trisomy 18 group there was a significant association between PIGF and free β-hCG (r=+0.2629) but not with PAPP-A (r=+0.0038). In the trisomy 21 group there was a small but significant association with PAPP-A (r=+0.1028) but not with free β-hCG (r=+0.0339). The separation of affected and unaffected pregnancies in maternal serum PIGF is small, and therefore it is unlikely that measurement of PIGF would improve screening for these abnormalities provided by the combination of fetal nuchal translucency and maternal serum PAPP-A and free β-hCG. Copyright © 2001 John Wiley & Sons, Ltd.