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231.
运用实时定量即时聚合链式反应RT-PCR方法,研究了双酚A对斑马鱼成鱼肝脏的功能基因转录水平的影响。结果显示,28 d半静水暴露以后,FGF8A和STAU 2 表现出传统的正剂量—效应关系,CLDN 1和CALCA的表达为倒剂量—抑制效应关系,SP 4基因在15 μg·L-1 双酚A时表现为显著抑制效应,但是在150 和1 500 μg·L-1却表现为显著的诱导效应。 试验进一步探讨了这些表达异常的基因在双酚A干扰去除后能否自我调节和修复。结果显示,CLDN 1能恢复到正常表达水平,而其他4个基因在低剂量组却维持原来的高毒性作用水平甚至表现出更高的毒性作用。研究证明双酚A对斑马鱼成鱼肝脏的基因转录调控具有一定的非单调剂量—效应作用。 相似文献
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Modeling changes in the coastal ecosystem of the Pearl River Estuary from 1981 to 1998 总被引:2,自引:0,他引:2
The coastal ecosystem of the Pearl River Estuary (PRE) has been overfished and received a high level of combined pollution since the 1980s. Ecopath with Ecosim was used to construct two ecosystem models (for 1981 and 1998) to characterize the food web structure and functioning of the ecosystem. Pedigree work and simple sensitivity analysis were carried out to evaluate the quality of data and the uncertainty of the models. The two models seem reliable with regards to input data of good quality. Comparing the variations of outputs of these two models aimed to facilitate assessment of changes of the ecosystem during the past two decades.The trophic structure of the ecosystem has changed with an increase in the biomass proportion of lower trophic level (TL) organisms and a decrease in top predator biomass proportion. All the indices of ecosystem maturity examined show that the system was in a more mature condition in 1981 than in 1998, although the system has been in a condition of stress due to anthropogenic disturbances, such as environmental pollution and habitat destruction since 1981. The ecosystem was aggregated into six and seven integral TLs in 1981 and 1998, respectively, using the trophic aggregation routine of Ecopath. Most of the total system biomass and catch took place at TL II and III in both years. But the distribution of the total system biomass and catch at different TLs changed with decreasing proportions in higher TLs in 1998. The mean transfer efficiency was 9.1% and 10.2% in 1981 and 1998, respectively.Comparative network analysis allowed quantification of the importance of direct and indirect trophic interactions among functional groups. Moreover, a method derived from the mixed trophic impact (MTI) analysis allowed estimating importance of groups in terms of “keystoneness” and identifying the keystone species in the two models over the past two decades. The results indicate that there were no clear keystone species in 1998 but two keystone species at medium trophic levels were identified in 1981. Moreover, organisms located at low trophic levels such as phytoplankton, zooplankton and benthic invertebrates were identified to have relatively high keystoneness in the ecosystem. 相似文献
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1概述 随着城市建设的不断发展,建设规模不断扩大、人口增加、机动车辆增加,一种过去常常被人们忽视的城市环境污染已经凸现了出来,这就是城市环境噪声的污染. 相似文献
237.
Lian Yang Qinxue Wen Zhiqiang Chen Ran Duan Pan Yang 《Frontiers of Environmental Science & Engineering》2019,13(3):32
238.
Biochar, is a low-cost material that can be used as an alternative adsorbent for the removal of heavy metals. In this study, a low-cost and efficient adsorbent synthesised from Jatropha curcas seeds was used for the uptake of Cu2+ from aqueous solutions. The as-prepared adsorbent was characterised by scanning electron microscopy and Brunauer–Emmett–Teller analysis post calcination at 500 °C, its BET surface area and total pore volume were 39.62?m2?g?1 and 0.049?m3?g?1, respectively. Subsequently, the effects of initial pH of the solution, contact time, and adsorbent material dosage on the adsorption of Cu2+ by the prepared adsorbent were investigated. The as-prepared adsorbent exhibited a high performance, with a maximum adsorption amount of 32.895?mg?g?1 for Cu2+ at pH 5.0 and 25 °C, owing to the presence of ?OH, C=O, C–O, Si-O-Si, and O-Si-O on its surface. The predominant Cu2+ adsorption mechanism was assumed to be ion exchange. Notably, the Cu2+ adsorption could attain equilibrium within 90?min. In addition, the fact that the Langmuir model was a better fit than the Freundlich model for the isotherm data of Cu2+ adsorption by the as-prepared adsorbent suggested that the adsorption of Cu2+ was a monolayer adsorption process. 相似文献
239.
岩土体中的渗流是引发各种地质灾害的重要因素。针对现有渗流监测技术的不足,提出了一种基于光纤布拉格光栅FBG的准分布式内加热刚玉管FBG渗流监测方法;介绍了该方法的原理;发明了一种新型内加热刚玉管渗流传感器;推导出了温度特征值与渗流速率之间的关系,并通过砂性土室内模型试验对此关系进行了率定。试验结果表明:(1)本方法对砂性土中渗流速率进行监测是可行的;(2)利用刚玉管封装的新型传感器具有很好的监测性能;(3)在给定加热功率条件下,一定渗流速率范围内,温度特征值与渗流速率间存在线性关系,渗流速率越大,温度特征值越小;(4)一定加热功率条件下的渗流速率监测存在相应的测试量程,提高给定加热功率可提高监测量程。 相似文献
240.
进行了3根预应力CFRP筋混凝土梁的抗火性能试验,考虑了荷载比对试验梁抗火性能的影响,分析了梁截面温度场、跨中挠度变形和CFRP应力随时间的变化规律。试验结果表明:(1)当保护层厚度为90 mm时,CFRP筋的温度不超过200 ℃,可有效降低CFRP筋的受火温度;(2)受火初期试验梁的挠度变形增长较快,随后增长速度趋于平缓;(3)随着荷载比的增加,试验梁的抗火性能不断降低;(4)与传统预应力钢筋相比,预应力 CFRP筋更易受到温度的影响,最终试验梁由于CFRP筋的断裂而破坏。因此,对于预应力CFRP筋混凝土构件,应采取有效的防火措施。 相似文献