CL-20/HTPB热分解机理的ReaxFF/lg反应分子动力学模拟

目的 揭示CL-20和HTPB复合体系的热分解机理,同时为CL-20/HTPB复合推进剂配方设计与应用提供理论依据。方法 采用反应分子动力学方法(ReaxFF/lg),研究CL-20/HTPB混合体系在2 500~3 500 K中5个温度下的热分解机理。结果 混合体系中的CL-20分子间反应路径仍为脱硝基和开环等反应。HTPB为混合体系引入大量的H原子与OH基团,这些自由基会与CL-20及CL-20的分解产物发生反应,例如与HNO2的大量化学反应促进了CL-20的热分解。相比CL-20单质体系,混合体系下,HNO2生成反应数量均有不同程度的增加。通过与单组分产物数量的比较可以发现,H2O的含量大大增加,且曲线到达峰值的时间更短,体系分解反应速率更快,同时CO2的含量也大幅度地减少。除此之外,所计算的混合体系的活化能(Ea)与指前因子的自然对数lnA分别为114.684 kJ/mol与25.896。对比CL-20单质体系,混合体系的活化能较小。结论 HTPB会对CL-20的热分解起到促进的作用,降低了系统对热刺激的不敏感程度。     

Using a common commensal bacterium in endangered Takahe as a model to explore pathogen dynamics in isolated wildlife populations

Predicting and preventing outbreaks of infectious disease in endangered wildlife is problematic without an understanding of the biotic and abiotic factors that influence pathogen transmission and the genetic variation of microorganisms within and between these highly modified host communities. We used a common commensal bacterium, Campylobacter spp., in endangered Takahe (Porphyrio hochstetteri) populations to develop a model with which to study pathogen dynamics in isolated wildlife populations connected through ongoing translocations. Takahe are endemic to New Zealand, where their total population is approximately 230 individuals. Takahe were translocated from a single remnant wild population to multiple offshore and mainland reserves. Several fragmented subpopulations are maintained and connected through regular translocations. We tested 118 Takahe from 8 locations for fecal Campylobacter spp. via culture and DNA extraction and used PCR for species assignment. Factors relating to population connectivity and host life history were explored using multivariate analytical methods to determine associations between host variables and bacterial prevalence. The apparent prevalence of Campylobacter spp. in Takahe was 99%, one of the highest reported in avian populations. Variation in prevalence was evident among Campylobacter species identified. C. sp. nova 1 (90%) colonized the majority of Takahe tested. Prevalence of C. jejuni (38%) and C. coli (24%) was different between Takahe subpopulations, and this difference was associated with factors related to population management, captivity, rearing environment, and the presence of agricultural practices in the location in which birds were sampled. Modeling results of Campylobacter spp. in Takahe metapopulations suggest that anthropogenic management of endangered species within altered environments may have unforeseen effects on microbial exposure, carriage, and disease risk. Translocation of wildlife between locations could have unpredictable consequences including the spread of novel microbes between isolated populations.     

Transforming submerged-arc welding slags into magnetic glass-ceramics

Submerged-arc welding slag (SAWS) and rice husk (RH) wastes represent two particularly abundant metallurgical and agricultural wastes. This work focusses on the feasibility of SAWS, together with glass cullet and RHs, to develop lightweight porous glass–ceramics that could be useful for technical purposes. Effects of temperatures and amounts of RHs on the porosity and water absorption of porous glass–ceramics were discussed at various dosages of husks up to 20 wt%. Depending on the sintering temperature, XRD measurements confirmed the presence of more than two crystalline phases: diopside, jacobsite, MgAl₂O₄, Ca_1.82Al_3.64Si_0.36O₈ and pyrope. These samples exhibited magnetic properties which were related to the presence of jacobsite phase. Magnetization curve is a characteristic of soft ferromagnetic materials with magnetization saturating at ~0.82 emu/g. The present results show a promising way to treat submerged-arc welding slags, transforming it into useful porous and functional glass–ceramic products via a simple powder technology and sintering approach.     

Agro-waste biosorbents: Effect of physico-chemical properties on atrazine and imidacloprid sorption

Low cost agro-waste biosorbents namely eucalyptus bark (EB), corn cob (CC), bamboo chips (BC), rice straw (RS) and rice husk (RH) were characterized and used to study atrazine and imidacloprid sorption. Adsorption studies suggested that biosorbents greatly varied in their pesticide sorption behaviour. The EB was the best biosorbent to sorb both atrazine and imidacloprid with K_F values of 169.9 and 85.71, respectively. The adsorption isotherm were nonlinear in nature with slope (1/n) values <1. The Freundlich constant Correlating atrazine/imidacloprid sorption parameter [K_F.(1/n)] with the physicochemical properties of the biosorbents suggested that atrazine adsorption correlated significantly to the aromaticity, polarity, surface area, fractal dimension, lacunarity and relative C-O band intensity parameters of biosorbents. Probably, both physisorption and electrostatic interactions were responsible for the pesticide sorption. The eucalyptus bark can be exploited as low cost adsorbent for the removal of these pesticides as well as a component of on-farm biopurification systems.     

厌氧膜生物反应器处理含盐废水运行效能及膜污染特性

采用厌氧膜生物反应器(anaerobic membrane bioreactor,An MBR)处理模拟含盐有机废水,研究盐度变化对反应器运行效能及膜污染特性的影响.结果表明,当进水盐度逐渐增加但低于9. 1 g·L~(-1)时,反应器运行稳定,出水效果良好;当盐度增加至10 g·L~(-1),反应器COD去除率、产气量及甲烷含量都明显下降;污泥浓度、污泥体积指数(SVI)、溶解性微生物产物(SMP)和胞外聚合物(EPS)均随盐度增加而先升后降,污泥絮体紧密,沉降性良好.中空纤维膜组件在118 d内运行了3个周期,随着盐度增加膜运行周期由31 d延长为48 d,膜污染有所减缓.用SEM-EDX分析发现膜面污染物中有类似结晶状物质,Na、Mg、Al、Si、Cl、K、Ca和Fe为主要无机元素.三维荧光光谱(EEM)分析表明,蛋白质与腐殖酸是膜面有机污染物的主要成分.     

紫云英还田与化肥减量配施对稻田土壤细菌群落组成和功能的影响

紫云英是豫南稻区土壤培肥的重要有机肥资源,探究紫云英还田与化肥减量配施对稻田土壤理化性质和细菌群落特性的影响,旨在为该区域的土壤培肥和化肥减量提供依据.开展连续12 a田间定位试验,设置了6个施肥处理(空白对照,CK;单施化肥,F100;80%化肥和22.5t·hm^-2紫云英还田量配施,MV1F80;80%化肥和45 t·hm^-2紫云英还田量配施,MV2F80;60%化肥和22.5 t·hm^-2紫云英还田量配施,MV1F60;60%化肥和45 t·hm^-2紫云英还田量配施,MV2F60).通过采用高通量测序方法比较不同施肥处理对土壤细菌群落多样性、组成和结构特性的影响;采用FAPROTAX功能预测的方法分析不同施肥处理间功能类群的丰度差异,并结合土壤理化性质,探究改变土壤细菌群落结构与功能特性的关键土壤环境因子.结果表明,紫云英还田与化肥减量配施降低了土壤容重,提高了土壤有机碳(SOC)、全氮(TN)、全磷(TP)和全钾(TK)含量,较CK提高的范围分别为12.7%～35.5%、38.2%～65.7...     

黄河三角洲盐碱土根际微环境的微生物多样性及理化性质分析

土壤盐碱化是限制全世界农业发展的主要问题.在盐碱土壤上种植盐生植物和耐盐植物可以对盐碱土壤进行脱盐,而盐碱土壤中的微生物对盐生植物和耐盐植物的生长起着重要作用.本研究在盐碱地上选取玉米、棉花、盐地芦苇和盐地碱蓬这4种有代表性的植物,采集土壤样品,探究植物根系与非根系主要细菌群落与土壤理化性质和盐碱土壤微生物多样性的关系.结果表明,盐地碱蓬的根系微生物在一定程度上影响了土壤的pH,土壤中的盐度与土壤营养物质呈明显的负相关关系.所有土壤样品中相对丰度较高的前5个细菌门均为变形菌门、放线菌门、拟杆菌门、绿弯菌门和酸杆菌门.其中,棉花、芦苇和盐地碱蓬中根系土壤与非根系土壤耐盐菌门存在较大差异,分析高通量测序结果可以得出3种植物根系与非根系土壤中差异较大的耐盐细菌属,如棉花土壤中差异较大的Actinophytocola和Lechevalieria,芦苇土壤中差异较大的Bacillus和Filobacillus,以及盐地碱蓬土壤中的Echinicola.本研究可为盐碱地中接种促进植物生长的微生物提供理论依据.     

城市雨水径流中溶解性有机物的分子化学多样性

雨水径流中溶解性有机物(dissolved organic matter,DOM)是影响城市水生态环境安全的重要因素.为了揭示城市不透水路面雨水径流(pavement runoff,PR)和绿地雨水径流(greenland runoff,GR)中DOM组分特征及其来源上的区别,应用具有超高分辨率的傅里叶变换离子回旋共振质谱(fourier transform ion cyclotron resonance mass spectrometer,FT-ICR-MS)对两者的DOM分子化学多样性进行表征,并从DOM分子化学多样性与环境因子之间的斯皮尔曼(Spearman)相关性的角度进行分析.结果表明:①在分子累计到达饱和状态下,PR-DOM的分子累计数量(12498种)远大于GR-DOM(7015种),其分子分布(150～750)比GR-DOM(150～850)更为集中,且相对分子质量普遍小于GR-DOM;②根据分子组成及其相关性分析,PR-DOM和GR-DOM的组分及来源存在明显差异.PR-DOM组成受人为活动影响较大,其主要成分(CHOS)中含有大量可能来源于人为使用的表面活性剂的磺酸类物质,且显著存在的脂肪族成分的主要来源应为交通污染.而GR-DOM组成受人为活动影响较小,其主要成分(CHO)以NOM为主,且大部分高度不饱和酚类化合物主要来源于降雨对土壤表层植物残体降解所形成的腐殖质的冲刷.     

甲醇和有机混合溶剂提取棕碳气溶胶光学性质的差异及原因探讨

棕碳(吸光性有机物)气溶胶对地表太阳辐射平衡有重要影响,溶剂萃取法是测量其光学性质的主要手段之一,但是该方法的结果很大程度上取决于所采用的溶剂.本研究分别采用甲醇和有机混合溶剂(乙腈:二氯甲烷:正己烷=2:2:1)提取大气总悬浮颗粒物样品(TSP)中的棕碳组分,并通过长光程(0.94 m)液芯波导毛细管流通池/紫外 —?可见分光光度计测量了两种溶剂所提取棕碳的吸收光谱(250—?600 nm).结果表明:300—?600 nm甲醇提取棕碳的吸收系数均值是混合溶剂的(1.8±0.1)倍.而对于质量吸收效率,在280—?600 nm甲醇提取的棕碳稍高于混合溶剂((1.2±0.1)倍),在250—?280 nm混合溶剂提取的棕碳则明显高于甲醇((1.4±0.5))倍.为了研究这两种溶剂萃取棕碳光学性质的差异,本研究对比了两种溶剂对有机化合物的提取效率以及主要发色团组分(硝基芳香族化合物和多环芳烃类物质)在两种溶剂中的吸收光谱.实验结果表明:甲醇和混合溶剂所萃取棕碳的吸收光谱出现差异的主要原因包括以下三个方面:(1)与混合溶剂相比,甲醇对有机物提取效率更高.甲醇的提取效率为63.1％ ±3.4％,混合溶剂为42.9％ ±3.6％;(2)甲醇和混合溶剂所萃取棕碳的化学组成存在差异;(3)部分棕碳类物质(如硝基芳香族化合物)在两种溶剂中的吸收光谱存在差异.     

北洛河流域植物多样性地理格局与环境关系

通过野外调查和历史文献及标本统计分析,确定并分析北洛河流域种子植物信息数据.结果表明：该区共有种子植物123科581属1671种,占黄土高原种子植物的83.67%、67.24%、51.83%,集中分布于大型科（>50种）、较大科（21~50种）和单种属（1种）、小型属（2~5种）内.11个干流流经的地理单元植物相似性聚类分为5组,较早分离的是黄龙县,最大类因子午岭山脉连接而包含4个地理单元（富县、合水县、宜君县、黄陵县）.富县、合水县和黄龙县植物丰富度SD值最高,洛川县、华池县和甘泉县SD值最低.该区地理成分在属级水平上有15个分布区类型16个变型,以温带分布及其变型为主（287属,占49.40%）,并与热带分布及其变型联系紧密（115属,占19.79%）,植物丰富度SD值与温带成分显著正相关;黄陵县、洛川县、黄龙县R/T值最高,热带性质最强,华池县、定边县R/T值最低,热带性质最弱.R/T值受海拔影响,随温度和降水从东南向西北递减.该区植物起源古老,分化程度高,物种多样性丰富,地理成分复杂,是重要的植物种质资源库.植物物种多样性地带性格局过渡性明显,体现出这些类群的生态位需求.需加强保护该区原生环境和植物,合理开发利用,可选择6大优势科（菊科、禾本科、蔷薇科、豆科、唇形科和毛茛科）中适地适树适草的物种（温带性质）,进行植被恢复和水土流失治理.