执行国际协定的限制因素:博茨瓦纳执行《蒙特利尔议定书》的情况

本文分析了在博茨瓦纳有效执行<蒙特利尔议定书>中遇到的困难;并就在发展中国家执行国际协定问题时如何向决策者提出建议提供了一个总的认识.对臭氧耗损物质(ODSs)的正式和非正式用户进行的问卷调查表明:所散发的有关ODSs的信息,对于用户们选择制冷气体几乎没有什么影响,而且这个信息偏向有利于ODSs的正式用户.因此,ODS使用数量的年统计资料可能估计偏低.困难在于,要在短期内从老技术转向新技术,成本较高.回收废气和处理废旧硬件设备的基础设施缺乏或不足.这些问题的解决需要一个全面的政策,它能满足所有ODSs用户的要求;还需要把经济发展与环境保护结合起来进行考虑.     

Synthesis and structure-activity relationship of diene modified analogs of<Emphasis Type="Italic"> Matsucoccus</Emphasis> sex pheromones

The biological activity of the Matsucoccus spp. sex pheromones and diene modified analogs has been tested in forests of Israel and Portugal in order to explore the structure-activity relationship of the pine bast scale pheromone/kairomone system. The response of the adult predatory bugs, Elatophilus hebraicus and E. crassicornis and of the brown lacewing, Hemerobius stigma is more selective than that of the conspecific Matsucoccus males. The removal of the terminal methyl group from the diene terminus of both pheromones 1 and 2 eliminates all kairomonal activity but retains moderate pheromonal activity. Addition of a methyl group to the diene terminus of pheromones 1 and 2 sustains full pheromonal and kairomonal activities of the Elatophilus spp. but eliminates entirely the kairomonal activity of H. stigma. Subtle designed alterations in the structure of the diene group, typical of all Matsucoccus pheromones, change the mode of the kairomonal activity markedly.     

Rapid prediction of disinfection by-product formation potential by fluorescence

Recent drinking water regulations have lowered the disinfection by-product standards as well as added new disinfection by-products for regulation. Natural organic matter (NOM) plays a major role in the formation of undesirable organic by-products following disinfection/oxidation of drinking water. It is suspected that most precursors to disinfection by-products are humic, although nonhumic substances are also suspected of contributing to these by-products. Many of the disinfection by-products have adverse health effects in humans (i.e., carcinogenic or mutagenic effects). The primary chlorinated disinfection by-products of concern include trihalomethanes, haloacetic acids, and haloacetonitrile. Fluorescence spectroscopy was used to study humic and fulvic acids. The two fractions of humic substances, humic and fulvic acids, were characterized by a double-peak phenomena in an overlapping fluorescing region. Disinfection by-product formation potentials of humic and fulvic acids have been correlated with total organic carbon, UV absorbance at 254 nm, specific absorbance and fluorescence. River humic and fulvic acid was found to have the highest reactivity to disinfection by-product formation as compared to soil and peat humic and fulvic acid. Fluorescence spectroscopy has shown to be a rapid and predictive tool for disinfection by-products formation potential of humic and fulvic acids.     

Triploid fetus: An important consideration in the evaluation of very high maternal serum alpha-fetoprotein

Two patients referred for evaluation of very high maternal serum alpha-fetoprotein (10–20 multiples of the median) were carrying triploid fetuses with placentas showing features of partial hydatidiform mole. The diagnosis of fetal triploidy should be considered when there is a very high maternal serum alpha-fetoprotein and no ultrasound evidence of open neural tube defect, ventral wall defect, or any other explanation. Therefore, chromosomal analysis of amniotic fluid cells in such cases is essential.