抗生素与LED209对大肠杆菌的联合毒性机制

抗生素是一把双刃剑,在提高医疗水平的同时会促进抗性基因的发展。群体感应抑制剂(quorum sensing inhibitors,QSIs)可有效地避免这一缺陷,有望成为抗生素的替代品而与抗生素有环境共存的可能,但目前尚缺乏它们的联合毒性机制及其相关的环境风险评价研究。本文以大肠杆菌为受试生物,测定了群体感应抑制剂N-苯基-4-(3-苯基硫代脲基)苯磺酰胺(LED209)与5种抗生素的单一和二元联合毒性。结果表明,LED209与5种抗生素的联合毒性作用均表现为拮抗,推测是LED209通过影响鞭毛合成,减弱了抗生素对大肠杆菌的生物有效性;同时通过拆分分子式,发现了拮抗作用可能源于LED209分子式中的含苯基和硫代脲基的L1分子,因此建议未来在LED209药物优化时,应尽可能的保留L1部分的基团,从而保证混合体系的最小环境风险。本研究不仅为联合用药提供依据,而且从环境风险评价角度为抗生素替代品LED209的结构优化提供理论指导。     

四氨基酞菁钯/γ-Al_2O_3可见光催化降解罗丹明B

采用浸渍法制备了四氨基酞菁钯(PdTAPc)/γ-Al_2O_3负载型光催化剂,采用UV-Vis,FTIR,XRD,SEM技术对其进行了表征,并将其用于罗丹明B的可见光催化降解,考察了光催化剂加入量、溶液pH、H_2O_2加入量、反应温度对罗丹明B降解效果的影响,并对光催化剂的稳定性进行了测试。表征结果显示,PdTAPc以圆片状负载于γ-Al_2O_3上,二者的结构均未发生明显变化。实验结果表明:在光催化剂加入量1.6 g/L、溶液pH 7.0、H_2O_2加入量12 mmol/L、反应温度20℃的优化条件下反应120 min,罗丹明B(质量浓度0.05 g/L)的降解率高达95%;光催化剂具有较高的稳定性,使用4次后罗丹明B的降解率仍高于85%。     

航天器局部载荷模态分析方法研究

文章在介绍了模态试验基本方法和基本原理的基础上,着重探讨了锤击法测量航天器局部载荷结构的模态试验方法。通过对该载荷不同方向的激励,得到了其各个方向的模态频率、模态阻尼和模态振型,为航天器有效载荷设计及修改提供参考意见。     

Comparison of metabolome profiles in zebrafish (Danio rerio) intestine induced by polystyrene microplastics with different sizes

Environmental Science and Pollution Research - Microplastics (MPs) are widespread in aquatic environments. They could induce intestinal toxicity in the fish. However, research on the metabolic...     

Diversity of crude oil-degrading bacteria and alkane hydroxylase (<Emphasis Type="Italic">alkB</Emphasis>) genes from the Qinghai-Tibet Plateau

The aim of this study was to survey the response of the microbial community to crude oil and the diversity of alkane hydroxylase (alkB) genes in soil samples from the Qinghai-Tibet Plateau (QTP). The enrichment cultures and clone libraries were used. Finally, 53 isolates and 94 alkB sequences were obtained from 10 pristine soil samples after enrichment at 10 °C with crude oil as sole carbon source. The isolates fell into the phyla Proteobacteria, Actinobacteria, and Bacteroidetes, with the dominance of Pseudomonas and Acinetobacter. The composition of degraders was different from polar habitats where Acinetobacter sp. is not a predominant responder of alkane degradative microbial communities. Phylogenetic analysis showed that the alkB genes from isolates and enrichment communities formed eight clusters and mainly related with alkB genes of Pseudomonas, Rhodococcus, and Acinetobacter. The alkB gene diversity in the QTP was lower than marine environments and polar soil samples. In particular, a total of 10 isolates exhibiting vigorous growth with crude oil could detect no crude oil degradation-related gene sequences, such as alkB, P450, almA, ndoB, and xylE genes. The Shannon-Wiener index of the alkB clone libraries from the QTP ranged from 1.00 to 2.24 which is similar with polar pristine soil samples but lower than that of contaminated soils. These results indicated that the Pseudomonas, Acinetobacter, and Rhodococcus genera are the candidate for in situ bioremediation, and the environment of QTP may be still relatively uncontaminated by crude oil.     

自然资源资产及其负债表编制与审计

自然资源资产仍然是一个新概念,还需要在理论和方法层面进行系统的研究。就当今及今后一个时期看,自然资源资产负债表的编制和自然资源资产审计,是亟需研究的理论和现实问题。在此,重点对自然资源资产的概念、属性、分类进行探讨,并就自然资源资产负债表及编制的重点与基础,自然资源资产审计及其重点与方式等,进行系统讨论。     

基于对应分析法的废弃金属尾矿库重金属污染原位监测点优化研究

重金属污染物原位监测是对废弃金属尾矿库重金属污染治理的基础,由于缺乏基础监测数据,基础数据采集工作量巨大.采用对应分析法建立某尾矿库的土壤样本和污染物之间的联系,以达到优化监测点和监测因子的目的.将监测点和监测因子反映到同一因子轴的图形上,能清晰直观地表述监测点和污染物间的内在联系和分布特征;确定主监测点和主监测指标,...     

有机膨润土的制备及其在6-硝废水处理中的应用

以CTMAB为改性剂制备有机膨润土,并用改性后的膨润土吸附6-硝废水.膨润土改性条件为:液固体积(mL)质量(g)比6∶1,pH值为1,反应温度为60℃,反应时间为1 h进行酸活化;将上述酸活化的膨润土按膨润土阳离子交换容量的100%加人CTMAB,反应时间为80 min得到有机膨润土;6-硝废水吸附条件为:取上述有机...     

等离子体固态可燃物液化反应动力学分析

本文利用介质阻挡放电等离子体技术,对以煤和生物质为代表的固态可燃物液化反应机理进行研究,以期探索能源利用新途径.借助碰撞理论和Boltzman方程,对高能电子碰撞引发多种离解反应的速率常数进行数值模拟,计算结果和实验曲线对比,证明模型具有一定的适用性和可靠性.在一定的电子温度下,通过不同离解反应速率常数的对比,可以判断...     

Variation of low molecular weight organic acids in precipitation and cloudwater at high elevation in South China

To investigate the sources and chemical behaviors of carboxylic acids in Southern China, precipitation and corresponding cloudwater samples were collected in an acid rain-prone area of Mount Heng. The carboxylic acid levels in the samples were measured, and the concentration patterns were evaluated with respect to temporal and seasonal variations. Formic and acetic acids were predominant among the carboxylic acids identified for both precipitation and cloudwater. Most of the organic acids in the precipitation had a clear seasonal pattern, reaching higher levels during the warm season; these higher levels were attributed to the stronger source strength of biogenic emissions during this season. The cloud–fog samples did not display a similar trend. A distinctive diurnal pattern in carboxylic acids was only observed in the precipitation samples during the warm season. In cloud–fog, the ratio of formic to acetic acid differed considerably with time, with these values varying little in the precipitation samples. This result indicates that the organic acids in precipitation originate consistently from primary sources throughout the entire period, while those in cloud are mainly associated with direct emissions in the earlier stage and with secondary sources in the later period.