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551.
磁铁矿纳米颗粒(magnetite nanoparticles, MNPs)是一种环境友好型吸附剂,广泛应用于废水中Pb~(2+)的处理。目前,有不少关于MNPs毒性的研究,但对MNPs处理Pb~(2+)形成的复合物的毒性却鲜有报道,其复合毒性亟待深入研究。本文以大鼠肾细胞(NRK)作为细胞模型,系统研究不同Pb含量的MNPs-Pb复合物,以及相应浓度的MNPs和Pb~(2+),对大鼠肾细胞活性、细胞形态和密度的影响,考察细胞对纳米颗粒的摄取以及细胞凋亡的作用机制,评估MNPs-Pb的毒性效应。结果表明,在本实验浓度和暴露时间(12 h)条件下,Pb~(2+)能够显著抑制细胞活性,改变细胞形态,促进细胞凋亡,对细胞有显著的毒性效应,并且呈现剂量相关性;利用MNPs吸附水环境中Pb~(2+)形成的复合物MNPs-Pb对大鼠肾细胞没有显著的毒性作用(P<0.05),MNPs对Pb~(2+)的吸附可能是Pb~(2+)的细胞毒性降低的原因。 相似文献
552.
Zeyuan Qiu 《Journal of the American Water Resources Association》2010,46(5):944-956
Qiu, Zeyuan, 2010. Prioritizing Agricultural Lands for Conservation Buffer Placement Using Multiple Criteria. Journal of the American Water Resources Association (JAWRA) 1-13. DOI: 10.1111/j.1752-1688.2010.00466.x Abstract: Although conservation buffers are multifunctional, the current conservation buffer planning strategies tend to use a single criterion, most frequently a hydrological or soil condition indicator, to guide conservation buffer placement. This study presents a watershed planning approach that prioritizes agricultural lands for conservation buffers based on multiple selection criteria and applies the approach to Raritan Basin in central New Jersey. The multiple selection criteria include soil erodibility, hydrological sensitivity, wildlife habitat, and impervious surface rate. These criteria capture the conservation buffers’ benefits in reducing soil erosion, controlling runoff generation, enhancing wildlife habitat, and mitigating stormwater impacts, respectively. An expert panel was used to identify and define the section criteria, review the measured values of those criteria, and develop the classification scales that assign the class score to each criterion. The prioritization is based on the summation of the criteria class scores. About one-third of agricultural lands are prioritized for conservation buffers in Raritan Basin. The total program cost of converting those prioritized agricultural lands to conservation buffers in Raritan Basin is estimated to be between $54.8 and 102.9 million depending on the composition of installed conservation buffer practices. 相似文献
553.
554.
目的基于航天器结构自由度数大且结构复杂,直接对有限元模型修正计算效率低的问题,利用二级近似方法来提高有限元模型修正的计算效率。方法根据特征向量建立Ritz空间推导出频率响应及其敏度的一级近似计算公式,利用近似函数二级近似计算结构参数变化后的动刚度矩阵,通过多重优化流程消除近似计算引入的误差。结果通过两个数值算例进行验证,该方法提高了结构模型修正的计算效率。结论该方法适用于航天器结构的模型修正。 相似文献
555.
在没有密度分层的容泄水体条件下,对某污水排海工程多孔喷头的射流特性进行了实验研究。文中介绍了不同排污流量和环境流速条件下,多孔喷头附近的流速场和污水场特性;并对出流平均稀释度作了分析。最后,还对该喷头周围的冲淤形态进行了探讨.文中所得的结果对实际排污系统的设计和进一步研究有一定的参考价值。 相似文献
556.
Khaparde VV 《Environmental monitoring and assessment》2006,116(1-3):217-231
A workshop on analytical quality control (AQC) of ambient air quality measurement methods for nitrogen dioxide (NO2) and sulphur dioxide (SO2) was conducted by Central Pollution Control Board (CPCB) for officials involved in National Ambient Air Quality Monitoring
(NAAQM) in India. Concentrations of NO2 and SO2 were generated by dynamic dilution system under laboratory conditions at low and high levels and measured using static dilution
system and wet chemical methods laid down by CPCB under section 16(2)(h) of the air act 1981. CPCB provided the measured values
as reference values for comparing the means obtained by the officials participated from thirteen organizations. A tolerance
limit of ±15% of the reference values was specified to accept the results. Generated concentrations, which were unknown to
the participants, were measured using gaseous sampling assembly (Envirotech APM 411, New Delhi, India), and wet chemical methods
laid down by CPCB i.e. the same methodology which is used by the organizations to generate the data of NO2 and SO2 in ambient air. Simultaneously, concentrations were checked by CPCB using automatic analyzers as a check on reference concentration.
It is observed that results of automatic analyzers for NO2 and SO2 were within a tolerance of ±5% with %RSD below 3. On the other hand, results of most of the participants showed variability
in the measurements with %RSD ranging between ±0.8 and ±88.6 and exceedences of means from the tolerance limit with bias ranging
between 1.4 and −59%. To check the cause of high variability in the measurements obtained under identical conditions, duplicate
sampling was performed by one of the participants for SO2 at low concentration level. In this study, results of wet chemical methods, automatic analyzers and results of duplicate
sampling are analysed statistically to assess the cause of high variability in the measurements. Analysis of t-test and analysis of variance (ANOVA) showed highly significant results for NO2 and SO2 at high concentration levels (α 0.05) and for SO2 at both the levels (α 0.01) respectively indicating some bias is existing either in the sampling or in analytical technique.
Duplicate sampling performed to check precision in parallel measurements showed high %RSD indicating the presence of systematic
error in sampling technique as the same calibration factor (CF) was used to measure the concentration of duplicate samples.
Statistical analysis of flow rates of duplicate sampling showed that the sampling assembly could not maintain the constant
flow rate within the ±10% with that measured at the start of the sampling. This resulted in high %RSD and deviation from the
reference values for the results of most of the participants, even after accepting ±15% tolerance limit. There is a need to
improve and evaluate this gaseous sample collection device under laboratory conditions to generate reliable database of NO2 and SO2 in ambient air. 相似文献
557.
分析了2起因能量的意外释放导致的伤害事故,提出了具备多能源设备的锁定和挂牌的安全流程,并附有能源隔离安全检查表和流程图. 相似文献
558.
鉴于PM2.5对人体的危害,为了提前预测PM2.5浓度值并及时通过降雨方法降低其浓度,开展了PM2.5浓度综合预测研究。通过对西安市一个空气质量监测点收集到观测数据分析与PM2.5浓度强相关的因素,随后综合考虑天气、温度、风力风向对PM2.5浓度观测值的影响,通过添加虚拟变量及因子分析提取因子的方法,将强相关因素、提取的天气、温度、风力风向因子与PM2.5浓度观测值进行回归预测,最终得到较好预测效果。 相似文献
559.
Ellen T. Chang Elizabeth Delzell 《Journal of environmental science and health. Part. B》2016,51(6):402-434
This systematic review and meta-analysis rigorously examines the relationship between glyphosate exposure and risk of lymphohematopoietic cancer (LHC) including NHL, Hodgkin lymphoma (HL), multiple myeloma (MM), and leukemia. Meta-relative risks (meta-RRs) were positive and marginally statistically significant for the association between any versus no use of glyphosate and risk of NHL (meta-RR = 1.3, 95% confidence interval (CI) = 1.0–1.6, based on six studies) and MM (meta-RR = 1.4, 95% CI = 1.0–1.9; four studies). Associations were statistically null for HL (meta-RR = 1.1, 95% CI = 0.7–1.6; two studies), leukemia (meta-RR = 1.0, 95% CI = 0.6–1.5; three studies), and NHL subtypes except B-cell lymphoma (two studies each). Bias and confounding may account for observed associations. Meta-analysis is constrained by few studies and a crude exposure metric, while the overall body of literature is methodologically limited and findings are not strong or consistent. Thus, a causal relationship has not been established between glyphosate exposure and risk of any type of LHC. 相似文献
560.
Pranav Chanchani Barry R. Noon Larissa L. Bailey Rekha A. Warrier 《Conservation biology》2016,30(3):649-660
Tiger (Panthera tigris) conservation efforts in Asia are focused on protected areas embedded in human‐dominated landscapes. A system of protected areas is an effective conservation strategy for many endangered species if the network is large enough to support stable metapopulations. The long‐term conservation of tigers requires that the species be able to meet some of its life‐history needs beyond the boundaries of small protected areas and within the working landscape, including multiple‐use forests with logging and high human use. However, understanding of factors that promote or limit the occurrence of tigers in working landscapes is incomplete. We assessed the relative influence of protection status, prey occurrence, extent of grasslands, intensity of human use, and patch connectivity on tiger occurrence in the 5400 km2 Central Terai Landscape of India, adjacent to Nepal. Two observer teams independently surveyed 1009 km of forest trails and water courses distributed across 60 166‐km2 cells. In each cell, the teams recorded detection of tiger signs along evenly spaced trail segments. We used occupancy models that permitted multiscale analysis of spatially correlated data to estimate cell‐scale occupancy and segment‐scale habitat use by tigers as a function of management and environmental covariates. Prey availability and habitat quality, rather than protected‐area designation, influenced tiger occupancy. Tiger occupancy was low in some protected areas in India that were connected to extensive areas of tiger habitat in Nepal, which brings into question the efficacy of current protection and management strategies in both India and Nepal. At a finer spatial scale, tiger habitat use was high in trail segments associated with abundant prey and large grasslands, but it declined as human and livestock use increased. We speculate that riparian grasslands may provide tigers with critical refugia from human activity in the daytime and thereby promote tiger occurrence in some multiple‐use forests. Restrictions on human‐use in high‐quality tiger habitat in multiple‐use forests may complement existing protected areas and collectively promote the persistence of tiger populations in working landscapes. 相似文献