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551.
The photocatalytic disinfection of Escherichia coli K-12 is investigated by the natural sphalerite (NS) under different spectra, wavelengths and intensities of visible light (VL) emitted by light-emitting-diode lamp (LED). The spectrum effect of VL on disinfection efficiency is studied by using white LED, fluorescent tube (FT) and xenon lamp (XE), which indicates that the “discreted peak spectrum” of FT is more effective to inactivate bacteria than “continuous spectrum” of LED and XE. Besides, the photocatalytic disinfection of bacteria is compared under different single spectrum (blue, green, yellow and red color) LEDs. The results show that the most effective wavelength ranges of VL for photocatalytic disinfection with the NS are 440-490 and 570-620 nm. Furthermore, a positive relationship is obtained between the disinfection efficiency and the VL intensity. The experiment shows that NS can completely inactivate 107 cfu mL−1E. coli K-12 within 8 h irradiation by white LED with the intensity of 200 mW cm−2 at pH 8. Moreover, the destruction process of the cell wall and the cell membrane are directly observed by TEM. Finally, no bacterial colony can be detected within a 96 h regrowth test of inactivated bacteria, which reveals that the VL-photocatalytic disinfection leads to an irreversible damage to the bacterial cells. 相似文献
552.
There is no place like England to witness the role of pubs as a social networking hotspot. Social networks lie at the foundations of most of the social and economic interactions of individuals. The aim of this paper is to assess the importance of pubs as natural locations for the development of social networks and how their presence affects the socio-economic activity of a given area or region. The econometric analysis conducted on rural parishes in Cumbria, a peripheral county in Northern England, reveals that village pubs have a positive influence on the socio-economic activity of local communities. 相似文献
553.
土壤微生物是表征土壤质量最有潜力的敏感性指标,高质量的土壤应具有稳定的微生物群落组成和结构、高微生物生物量及良好的微生物活性。本文从微生物的群落组成与多样性、微生物生物量和微生物活性3个方面进行了综述。微生物指标研究目前任务是确定一套评价土壤质量的微生物学指标最小参数集。建议今后加强土壤样品收集、储存、预处理及分析方法规范化,深层土壤微生物对土壤质量的作用及建立本底土壤微生物属性数据库等方面的研究。 相似文献
554.
555.
采用微乳法制备铁掺杂TiO2纳米晶(Fe-TiO2)复合体,通过热重-差热(TG-DTA)、X射线衍射(XRD)、扫描电镜(SEM)和紫外漫反射光谱(DRS)等对其结构和形态进行表征;以亚甲基蓝溶液(MB)为标准模拟降解物,对Fe-TiO2,纯TiO2和P25光催化降解性能进行评价。结果表明,Fe-TiO2的光催化活性明显〉P25,原因是Fe掺杂不仅能抑制TiO2晶粒生长,提高TiO2的热稳定性和比表面积,而且能够拓展TiO2的吸收波长范围至可见光区,提高了Ti3+离子浓度,降低了光生载流子的复合几率。 相似文献
556.
以多壁碳纳米管(MWNTs)为载体,在煅烧温度200~900℃、煅烧时间1~7 h、溶胶体系pH值为2~10的工艺条件下,采用溶胶-凝胶法制备复合光催化剂(MWNTs/TiO2)。通过其对甲基橙的光催化降解效果对比,评价各种复合光催化剂催化活性之间的差异,结果表明,随着煅烧温度的升高,复合光催化剂中纳米TiO2的晶型由锐钛型逐渐向金红石型转变,500℃时为2种晶型的混合相;pH值为2的强酸性条件有利于形成金红石晶型,pH值为5的中性及弱酸性条件则有利于形成锐钛型,而pH值为3时为2种晶型的混合相;在煅烧温度500℃、煅烧时间3 h、溶胶凝胶体系pH值为3的最佳制备工艺条件下,复合光催化剂催化活性最高,借助扫描电镜发现其TiO2均匀地包覆在多壁碳纳米管管壁上。 相似文献
557.
Outdoor school environments are sites for play and physical activity for many children, and shortcomings within these environments are considered significant factors that contribute to children's inactive lifestyles and high levels of childhood obesity. This study explores the associations between the physical characteristics of schoolyards and the physical activity of third and fourth year students in five Turkish primary schools. Data were collected through multiple methods, including behavior mapping of student activities during recess, physical assessments of schoolyards, and interviews with students, teachers and administrations. The findings show similarities in the landscape features and physical qualities of schoolyards, particularly in the types of play and activities in which students engage. Results indicated that active students who walk to and from schools have lower body mass index (BMI) values than passive students, and students in schools with larger yards have lower BMI values. Most of the students prefer spacious and vegetated yards. A major concern is the crowdedness of the yards during recess that limit children's activity. Schoolyards with advanced landscape features are preferred more, and this in turn affects students’ positive satisfaction. Outdoor school environments have a correlation to health outcomes and should be designed to promote more activity. Improving the physical and landscape qualities of the public schoolyards should be the primary concern of the designers in order to increase awareness of natural environment and more important, increase the health of children. 相似文献
558.
以十六烷基三甲基溴化胺为模板剂,用溶胶-凝胶法制备了介孔TiO2,用x射线衍射、透射电子显微镜、热重/差热分析及氮气吸附等方法对其进行了分析表征,并用偶氮染料阳离子红X-GRL为目标污染物分析了它的光催化活性.实验结果表明,450℃热处理后的介孔TiO2是锐钛矿型的,平均孔径为18 nm.氮气吸附曲线呈典型的介孔材料Ⅳ型吸附等温线特征.由于介孔TiO2具有较大的比表面积,因此表现出比非介孔TiO2高的光催化活性. 相似文献
559.
560.
为探索絮体老化与pH值调节对回流进水颗粒组成及混凝的影响,采用激光粒度仪进行了絮体粒径分析并通过Al(OH)3胶体(Al-gel)的老化实验探究了老化与pH值调节对絮体形态及性质的内在影响机制.结果表明,原水颗粒物粒径呈现单峰分布,絮体回流进水颗粒物粒径呈现双峰分布,并且回流进水颗粒d50随着絮体老化时间的增加而减小;由于絮体回流提高了颗粒物与混凝剂接触机率和碰撞效率,因此加快了絮体的生长;絮体在pH=5的环境下老化12h后进行回流混凝的絮体粒径生长速率最高(1.16μm/s)并且生成的絮体具有较大的分形维数(2.35).Al-gel的老化实验结果表明,絮体老化过程会涉及羟桥反应和结晶反应并导致絮体的表面活性基团数量减少,从而不利于与原水颗粒物的相互作用.pH值调节对絮体产生不同的影响,p H=5的条件下进行老化会加速絮体的羟桥反应和结晶反应,而p H=9的条件下进行老化则会涉及溶解-沉淀-结晶反应. 相似文献