3种小跌水景观空气负离子浓度分布特征

本研究以阳江银滩滨海旅游区3种景观小跌水为研究对象,进行微尺度下空气负离子浓度的分布观测。研究周期约为一年,按季度随机选择检测时间,2012年12月至2013年10月期间共检测12次,结果表明：在风速范围为1.1～2.3 m·s-1的情况下,滨海景观小跌水环境空气负离子浓度明显高于旅游区无水体的内路段,且高浓度尺度为以水体为中心半径0～1.5 m 处,1.5 m 之外随距离增加而浓度急剧下降,渐趋底线后缓和持平;小跌水负离子浓度与距离和湿度呈正相关关系,与温度相关性不大。小跌水是园林景观水体中最常用的形式,建议设计应缩短活动场地与水体间距离,增大两者接触面;适当种植遮阴乔木,通过合理的空间流向设计形成有利的风导向,从而最大程度地实现空气负离子对人体的保健效用。     

Hyper-susceptibility to deltamethrin in para DDT resistant Drosophila melanogaster

The extensively studied para gene encodes a α-subunit of the voltage-activated sodium channel in Drosophila melanogaster, which is the documented target site of DDT and pyrethroid insecticides. The para^ts-1 fruit fly line carries a recessive sex-linked insecticide-resistance trait (para^ts-1 allele) that has been defined on the basis of the behavioral phenotype of temperature-sensitive paralysis. We have determined that para^ts-1 confers hyper-susceptibility to deltamethrin in addition to the previously annotated resistance to DDT, revealing the presence of negative cross-resistance. We investigated the potential use of negative cross-resistance shifting para^ts-1 gene frequencies in D. melanogaster populations. After five generations of selection, the para^ts-1 allele, respectively, became more or less frequent whether Drosophila populations were selected with DDT or deltamethrin.