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571.
Parabensare are widely used as preservatives in cosmetics, foods and pharmaceutical products. Although parabens have generally been considered safe, several studies have cautioned that parabens have estrogenic or endocrine-disrupting properties. With the present study, the effects of four concentrations of propylparabens (200, 500, 1000, and 2000 mg L?1) on fecundity, development and the lifespan of Drosophila melanogaster have been investigated. Decreased daily mean egg production was found in all exposure groups. In addition, the 100 mg L?1 treatment significantly shortened egg-to-prepupa time and extended flies lifespan, consistent with a significant reduction in malonyldialdehyde (MDA) level and an increase in superoxide dismutase (SOD) activities. The 200 mg L?1 treatment prolonged egg-to-prepupa time and decreased flies lifespan significantly, being consistent with a significant increase in MDA level and reduction in SOD activities. 相似文献
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HCHs and DDTs in salt marsh plants taken from intertidal flats in the Yangtze estuary and coastal area in April and July 2002 were determined by GC-ECD. A significant seasonal effect was observed for HCHs and DDTs in sources and concentration levels in different sample types including above-ground tissues and roots as well as the whole plants and rhizospheric sediments. The results indicated that the concentration of t-HCH was higher in the above-ground tissues than in their roots in April; however, the partitioning of DDTs between contaminated sediments and the roots showed the higher concentrations of t-DDT in their roots. HCHs and DDTs concentration levels were higher in above-ground tissues than in roots in July. BCFs of HCHs and DDTs exhibited lower values with higher levels of contaminants in sediments, and higher values with lower levels in sediments. 相似文献
574.
Sorption of small metabolites of nonylphenol polyethoxylates in single and complex systems on aquatic suspended particulate matter 总被引:1,自引:0,他引:1
Sorption of nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) as well as their binary and ternary mixtures were studied and compared on three simulated suspended particulate matters (SPMs). Sorption dynamics of NP on the three SPMs could be divided into two phases, the rapid sorption phase and the slow sorption phase. A third phase, 'apparent desorption' occurred before the slow sorption phase for NP1EO and NP2EO as well as for all mixtures. Initial sorption rate increased with the OC% content of the SPMs. At low concentration, the sorption of NP, NP1EO and NP2EO (only at low concentration for 3# SPM) followed linear isotherm on the three SPMs. The linear Kd value of NP or NP1EO increased with the OC% content of SPM. In mixtures, sorption of NP, NP1EO and NP2EO increased significantly, and a 'critical point', after which sorption increased significantly, was observed in certain sorption isotherms. 相似文献
575.
Abstract This study explained the importance of environmental protection in tourism development and illustrated the relationship between recreational resource valuation and environmental consideration. We compare different models of travel cost method and reiterates long-time existing problems of multi-destination and treats of time opportunity cost (TOC). Taking Jiayuguan’s cultural sights as an example, we establish an updated method called multidestination zonal tourism cost method to evaluate the recreational values (RVs) of selected three cultural sights. We divide trip packages of Jiayuguan’s tourists into 11 portfolios. Each portfolio can be seen as a separate commodity, and each commodity has its own demand curve. According to demand curves we can calculate consumer surplus (CS) of different portfolios of tourist destinations and later we sum up the total travel costs (including travel expenditure and TOC) and CS to come to the RVs of each portfolio. We then apply suitable proportions to calculate the RVs between different destinations in the portfolio. In the end, we add up all the RVs calculated for the objective destination. Using this method, we draw conclusions that Jiayuguan’s RV in 2006 includes national and international values, summing up to 738.4762 million yuan. The tourist expenditure, CS and TOC of Jiayuguan is proportionating 62.96, 32.28 and 4.76%, respectively. This study is also an example of non-market valuation of cultural tourism resources. 相似文献
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577.
Hung-Yi Hou Chung-Hwei SuChi-Min Shu 《Journal of Loss Prevention in the Process Industries》2012,25(1):176-180
Many studies have been performed to clarify the basic thermal runaway hazards and kinetics of cumene hydroperoxide (CHP) decomposition. However, materials that are incompatible with CHP have not been clearly identified. Alkaline solutions have been used as a catalyst to form dimethylphenyl carbinol (DMPC) and dicumyl peroxide (DCPO); however, these solutions also affect the reaction and storage temperature of CHP. In this study, thermal calorimeters, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), were used to compare the effects of various bases on the decomposition of CHP in cumene. Specifically, the exothermic onset temperature, change in pressure over time, self-heating rate and heat of decomposition were evaluated. Moreover, to appraise the degree of hazard associated with the use of CHP, the compatibility of CHP with various substances was analyzed, and a risk matrix for thermal runaway reactions was obtained. The results of the present study could be used to design safety procedures for the production of CHP and its derivatives. 相似文献
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