A comparative study of Ag/Al2O3 and Cu/Al2O3 catalysts for the selective catalytic reduction of NO by C3H6

The selective catalytic reduction (SCR) of NO by C₃H₆ in excess oxygen was evaluated and compared over Ag/Al₂O₃ and Cu/Al₂O₃ catalysts. Ag/Al₂O₃ showed a high activity for NO reduction. However, Cu/Al₂O₃ showed a high activity for C₃H₆ oxidation. The partial oxidation of C₃H₆ gave surface enolic species and acetate species on the Ag/Al₂O₃, but only an acetate species was clearly observed on the Cu/Al₂O₃. The enolic species is a more active intermediate towards NO + O₂ to yield—NCO species than the acetate species on the Ag/Al₂O₃ catalyst. The Ag and Cu metal loadings and phase changes on Al₂O₃ support can affect the activity and selectivity of Ag/Al₂O₃ and Cu/Al₂O₃ catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al₂O₃ catalyst for NO reduction is higher than that of the Cu/Al₂O₃ catalyst.     

全球牙膏市场与产品的最新进展

全球牙膏市场被划分为美国、日本、两欧、东欧、亚太、拉美和中东7个区域市场，介绍了各区域市场的牙膏销售最和产品特点。全球牙膏产品通常被划分为儿童、抗龋、抗过敏、牙龈保护、除牙斑、抗菌、美自、多效、新感觉和天然10个类别，同时，介绍了2003／2004年度各类别上市新品的最新进展。最后，文章对中外牙膏在市场、产品及管理方面的差异进行了分析，并提出相关的对策建议。     

Habitat Suitability and Landscape Structure: A Maximum Entropy Approach in a Mediterranean Area

Species distribution models have recently become important tools in ecological research. Prediction of suitable habitats for threatened and endangered species is essential for the conservation and management of their native habitats. A landscape scale approach is relevant for biodiversity conservation since landscape planning and management are generally conducted at wide spatial scales, focusing on areas with complex landscape configuration as a consequence of human activities. The aims of this study were to test a maximum entropy approach (Maxent) to the development of a niche-based model for species of conservation interest and to relate this model to landscape structure metrics. The results obtained here showed a good predictive power of Maxent for the three target species and highlighted the importance of landscape structure analysis for the detection of patterns of habitat suitability. Moreover, this work stressed that combining classical environmental information with landscape structure in analysing habitat suitability for species of conservation interest may be used to guide conservation efforts and landscape management practices.     

国外城市树种选择指导及其借鉴

城市园林树种选择关系到城市绿化建设的成败,如何正确选择城市园林树种值得深入探讨.国外没有类似我国城市树种规划类型的文件,他们通过制定城市树种选择指导手册或树种特性表等实现对城市树种选择和应用的指导.研究分析了国外城市树种选择指导的原则、选择指标和指导方式,并与我国城市树种选择相关内容进行比较,认为我国树种选择中存在2个主要问题:1)“适地适树”原则过于宏观,设计师在具体环境中应用时难以贯彻;2)城市园林植物的基础研究不够,研究成果分散,因此对城市树种选择支撑力度不强.我国可从国外城市树种选择指导中2点借鉴:1)适地适树原则针对小环境具体化,根据不同环境制定树种选择指标;2)推荐使用的城市树种名录包含每种树的全部信息,方便从业人员掌握.最后建议我国应该在现行树种规划层面下研制各城市树种选择指导手册或城市树种信息库,以提高在城市具体环境下树种选择的科学性,保证城市树种规划的贯彻执行.     

盐碱地区混凝土的腐蚀破坏与防护

介绍了混凝土的腐蚀类型及作用机理，分析了秦皇岛盐碱地区钢筋混凝土结构物产生腐蚀破坏的状况，总结出盐碱地区混凝土防腐破坏的方法，提出了防护建议。     

Nitrogen transformations and retention in planted and artificially aerated constructed wetlands

Nitrogen (N) processing in constructed wetlands (CWs) is often variable, and the contribution to N loss and retention by various pathways (nitrification/denitrification, plant uptake and sediment storage) remains unclear. We studied the seasonal variation of the effects of artificial aeration and three different macrophyte species (Phragmites australis, Typha angustifolia and Phalaris arundinacea) on N processing (removal rates, transformations and export) using experimental CW mesocosms. Removal of total nitrogen (TN) was higher in summer and in planted and aerated units, with the highest mean removal in units planted with T. angustifolia. Export of ammonium (NH₄⁺), a proxy for nitrification limitation, was higher in winter, and in unplanted and non-aerated units. Planted and aerated units had the highest export of oxidized nitrogen (NO_y), a proxy for reduced denitrification. Redox potential, evapotranspiration (ETP) rates and hydraulic retention times (HRT) were all predictors of TN, NH₄⁺ and NO_y export, and significantly affected by plants. Denitrification was the main N sink in most treatments accounting for 47-62% of TN removal, while sediment storage was dominant in unplanted non-aerated units and units planted with P. arundinacea. Plant uptake accounted for less than 20% of the removal. Uncertainties about the long-term fate of the N stored in sediments suggest that the fraction attributed to denitrification losses could be underestimated in this study.     

The distribution, abundance and diversity of birds in Manila's last greenspaces

Urban environments are not considered areas with conservation importance. However greenspaces in cities have been previously identified as areas with significant avian biodiversity. We investigated the distribution and diversity of birds in what are increasingly considered as Metropolitan Manila's last greenspaces; the University of the Philippines campus, military cemeteries and two government operated parks. Using species–area analysis, abundance and diversity indices, TWINSPAN ordination and logistic regression to determine important landscape features for species presence, we describe the distribution of bird communities and diversity in Metropolitan Manila. Two major bird community groupings were observed. These are the urban exploiters and the urban adaptable with the former occurring in high abundances and the latter in low abundances in greenspaces. The number of built and natural spatial entities determines abundances. Species area analysis suggests that the greenspaces are distinct habitats that preserve faunal uniqueness whereas urbanization tends to decrease diversity. These observations suggest that greenspaces harbor significant avian biodiversity as well as the presence of endemic and threatened species. As the greenspaces possess remnant wetland and wooded habitat we recommend that they be preserved and maintained by ensuring that these habitats are incorporated in any urban development plan.     

保护大熊猫遗传多样性——拯救人工饲养下的 大熊猫种群的历史回顾

对1984—1995年中国拯救大熊猫物种工作进行历史回顾:创建了中国动物园协会;成都大熊猫繁育研究基地落成;促成建设部和林业部2个部门的合作;与多国政府及非政府组织磋商,达成多项国际合作;推行"动物园是野生动物移地保护基地"的理念;启动了为大熊猫种群开辟新栖息地——"大熊猫进,人类退"的前期工程。该时期开创了拯救人工饲养下的大熊猫种群工作的系统工程,成功拯救了动物园濒临灭绝的大熊猫种群,在国际上被誉为中国的奇迹。     

莫桑比克前寒武纪地质与成矿特征

莫桑比克作为全球重要的前寒武纪变质单元之一,是冈瓦纳古陆重要的组成部分。对其基础地质研究过程从19世纪初至今主要经历了4个阶段,本世纪初至今新理论和新方法的应用使得其基础地质研究得到飞跃发展。莫桑比克的前寒武纪地质单元可划分为津巴布韦-马尼卡克拉通基底、莫桑比克构造带及伊鲁米德构造带3个部分,其每部分又可进一步细分不同的构造单元(细化)。结合地质特征及矿产分布情况明确了莫桑比克的优势矿产资源为天然气、煤、钛、金、钽及石墨等矿种。莫桑比克可划分为北赞比西河成矿省、津巴布韦克拉通边界-巴鲁埃杂岩成矿省、乌南戈-利欣加成矿省、莫桑比克带-鲁伍马-赞比西成矿带省等四大成矿省和21个具有找矿前景的多金属成矿远景区。本文详细地划分了莫桑比克前寒武纪重要成矿区带并分析其成矿地质条件,结合近年来的矿产勘查工作认识,系统梳理了莫桑比克前寒武纪重要成矿区带的成矿条件和规律,重点总结了优势矿种的成矿特征,为莫桑比克矿业投资提供参考,并针对开展莫桑比克重要战略矿产的投资提供依据。     

单压下有序多裂隙脆性材料破坏机制及其简化模型

采用试件养护前期拔出预埋插片形成预制裂隙的方法制作多裂隙脆性材料试件,并在伺服控制单轴加载系统上对其进行加载试验。基于单压下脆性材料局部破损的应变软化机理建立裂隙体数值模型,对比试验与数值计算结果分析有序多裂隙脆性材料破坏机制及其影响因素。结果表明:除裂隙倾角及其几何排布外,裂隙在试件中的相对分布位置也影响裂隙体的破坏特征,且影响程度与裂隙面上有效剪切力大小有关,有效剪切力越大,则影响越显著。试验与数值计算结果显示:多裂隙试件中存在一组优势破坏面,与和裂隙走向相一致的试件斜对角线重合,裂隙分布在优势破坏面上或附近时,其尖端发育微裂纹的机率大于远离优势破坏面位置裂隙。结合有序多裂隙试件破坏特征及数值模型单元屈服状态,提出2种近置裂隙尖端裂纹发育简化模型,并结合本试验结果验证了简化模型的可行性。