不同热辐射强度下秸秆燃烧特性实验研究

为了探讨秸秆在不同规模火灾中的燃烧特性,采用锥形量热仪测得秸秆点燃时间、热释放速率、一氧化碳产生率等参数进行模拟实验,结合热重分析法研究秸秆的热解过程。结果表明:随着辐射强度的升高,秸秆由阴燃向明火转化,热释放速率、烟释放速率随之加快,缩短了点燃时间并降低了CO等有毒气体排放速率。热重分析得到秸秆在各个温度段下的反应情况,解释了在不同辐射强度下秸秆点燃性能实验现象及其反应机理,为防止火灾事故发生提供了可靠的理论依据。     

Reactive chemical hazards of diazonium salts

Many diazonium salts are thermally unstable and sensitive to friction and shock. Most diazonium salts are known for their violent decomposition hazard in the solid state. There are many industrial and laboratory incidents caused by this group of chemicals. For safety purposes, the hazards related to the preparation and the handling of diazonium salts are discussed. Twelve cardinal rules are provided:1. Use only a stoichiometric amount of sodium nitrite when generating diazonium salts, avoiding excess sodium nitrite.2. Check for the excess of nitrous acid by starch–potassium iodide papers and neutralize it.3. Minimize the presence of nitrous acid by combining amine and acid first, then subsequently adding the sodium nitrite.4. Keep the temperature below 5 °C.5. Always vent the gases generated.6. Determine the thermal stability of diazonium compounds in your system.7. Understand the explosive properties of diazonium salts. If unknown, always assume they are explosive.8. Never allow the undesired precipitation of diazonium salts out of solution.9. Analyze the residual diazo compounds in the final product, especially for new process conditions.10. Quench the remaining diazonium salts before any further treatments.11. Isolate no more than 0.75 mmol of explosive diazonium salts at one time; also consider the addition of an inert material to stabilize the diazonium salts.12. Use a plastic spatula when handling the solid. The dried powder should not be “scratched” with a metal spatula or ground finely.An example of a testing strategy and data interpretation is provided for a process which has multiple steps and two diazonium compounds. Differential Scanning Calorimetry (DSC) and Heat of Mixing calorimetry (HOM) successfully serve as efficient tests to screen thermal stability and gas generation, identifying the candidates for advanced tests.     

聚类GO术语在基因表达差异研究中的应用

针对基因功能分类体系基因本体(Gene Ontology,GO)特殊的有向无环图特点,改进传统的用单个GO术语检测基因差异表达信号的缺陷,设计出"聚类GO术语提升差异表达检测(ScaGO)"算法.通过简单的输入对照和实验组表达谱上的全部基因表达信号,来研究一些比较新的差异表达功能组,有助于进一步解释基因差异表达的生物学意义,如疾病发病机制、药物作用机理等.将ScaGO和基于单GO术语差异分析法应用到急性淋巴细胞性白血病数据集和酵母Rap1 DNA绑定突变体差异表达数据集上,结果显示,ScaGO能比基于单GO术语差异分析法发现一些新的与差异表达相关联的功能类基因,对于指导实验具有积极意义.图1表3参21     

堆肥制作中微生物侵染秸秆的环境扫描电镜(ESEM)观察

为了探索堆肥制作中木质纤维素类物质的生物降解过程,在堆肥进程中取不同分解阶段的秸秆样品,利用环境扫描电镜(ESEM)观察微生物的分布情况,并从机械作用的角度探讨了微生物在秸秆分解过程中的作用。结果表明,堆肥制作前新鲜秸秆表面未发现微生物分布,堆肥制作前期微生物开始附着在秸秆表面,随着堆肥进程,秸秆表面微生物密度有所增加,秸秆分解时产生的裂缝中发现也有微生物分布。堆肥制作中,参与秸秆分解的微生物以群落形式分布,从个体形态来看,这些微生物主要由球菌和丝状菌组成,但不同形态微生物个体大小差异较大。分析认为大型丝状菌通过秸秆分解产生的裂缝侵入秸秆内部时所产生的机械作用可促进秸秆的崩解。     

Mapping eucalypt forest susceptible to dieback associated with bell miners (Manorina melanophys) using laser scanning, SPOT 5 and ancillary topographical data

Mapping the location and extent of forest at risk from damaging agents or processes assists forest managers in prioritizing their planning and operational mitigation activities. In Australia, Bell Miner Associated Dieback (BMAD) refers to a form of canopy decline observed in eucalypt crowns occupied by colonies of bell miners (Manorina melanophrys). High densities of bell miners are associated with decreased avian abundance and diversity and an increase in psyllid abundance on crown foliage. BMAD has recently been nominated as a key threatening process in New South Wales (NSW). Consequently, a modelling system for predicting bell miner distribution in coastal eucalypt forests of NSW has been developed. The presence or absence of bell miners was recorded in 130 plots located within a 12,800 ha catchment study area containing a range of eucalypt forest types. The modelling system was produced by integrating a machine learning software suite (WEKA), and the statistical software R within the geographic resources analysis support system (GRASS) geographical information system (GIS). The variable modelled was the binary variable: presence or absence of bell minors. Six modelling techniques (Logistic regression; generalised additive models; two tree-based ensemble classification algorithms, random forest and Adaboost and Neural Networks) were integrated with airborne laser scanning; SPOT 5 and topographic derived variables. Model evaluation and parameter selection were measured by three threshold dependent measures (sensitivity, specificity and kappa) and the threshold independent Receiver Operator Curve (ROC) analysis. The final presence and absence maps were obtained through maximisation of the kappa statistic and applied at a resolution of 10 m across the entire catchment study area. For this data set, the most accurate algorithm for predicting the distribution of bell miner colonies was random forest (kappa = 0.84; ROC area under curve = 0.97). Variables most commonly selected in the six models were the laser scanning metrics; coefficient of variation, skewness, and the 10th and 90th percentiles derived from the shape of the height frequency distribution which, in turn, is directly influenced by vertical structure of the forest. An image textural statistic based on the shortwave infrared (SWIR) band of SPOT 5 was also commonly selected by the models. The SWIR band is sensitive to vegetation and soil moisture content. These models predicted that forest stands with a sparse eucalypt canopy over a moist, dense understorey were susceptible to being colonised by bell miners and hence BMAD.     

过氧化氢异丙苯热稳定性与热安全性研究

为研究过氧化氢异丙苯(CHP)的热稳定性和热安全性,利用C80微量量热仪对CHP在空气中的热分解进行试验研究。利用热分析技术研究CHP的热分解,得到了升温速率对CHP热分解的影响,CHP热分解的活化能,绝热条件下最大反应速率到达时间Tmrad和不同包装下的自加速分解温度。结果表明:随着升温速率的增加,CHP的起始放热温度和最大放热温度随之升高;CHP热分解的活化能范围为52～91 kJ/mol;Tmrad为1,8,24,50和100 h时对应的起始温度分别为118.08,75.41,55.83,44.83和34.52℃;CHP的储罐内径越大,其对应的自加速分解温度越低。     

碳质大气颗粒物的扫描质子微探针分析

碳质颗粒物是大气颗粒物的重要组成部分,对全球气候变化、环境质量、人类健康等有重要影响.本研究使用扫描质子微探针对上海两个典型环境监测点的大气颗粒物及7类污染排放源的单颗粒进行了分析.利用微束非卢瑟福弹性背散射谱micro-EBS(non-Rutherford elastic backscattering,EBS)分析了单颗粒中的C含量,发现燃煤烟尘、燃油烟尘、汽车尾气、柴油公交车尾气等污染源中碳质颗粒物占优,而水泥尘、钢铁工业尘、土壤尘中无机颗粒物占优;中心城区的碳质颗粒物占优,而工业区的无机颗粒物占优,单颗粒物的元素分布可以反映颗粒物发生大气化学反应的重要信息,利用微束质子激发X射线荧谱micro-PIXE(particle induced X-ray emission,PIXE)分析得到了大气颗粒物的S、Ca、Fe等元素分布,发现含Ca的碳质颗粒在大气中发生了硫化反应.     

广州市交通主干道空气中苯系物的测量

为了研究广州市道边空气中苯系物的污染状况,利用差分吸收光谱(DOAS)系统于2010年11～12月广州亚运会期间对广州市荔湾区黄沙大道道边空气中的苯系物(苯、甲苯、二甲苯等)及常规污染物NO2、O3等进行了监测.结果表明,在整个测量期间,苯系物在夜间显示了较高的浓度值,苯的平均浓度为15.9μg·m-3、甲苯为61.3μg·m-3、对-二甲苯为6.5μg·m-3、间-二甲苯为16.9μg·m-3、苯酚为0.88μg·m-3.甲苯与苯的平均浓度与国内其他城市的平均水平较为接近,两者的比值变化范围在1.2～6.16.通过比对甲苯与苯的相关性,在整个测量期间内其相关系数为0.86,在浓度值较高时段,其相关系数达到0.985,表明在该区域苯与甲苯存在同源性;以甲苯为例,分析其与CO的相关性,相关系数为0.78,表明交通排放是苯、甲苯的一个主要来源.结合风速风向等气象数据的分析得出气象条件是影响苯系物污染物浓度水平的一个重要因子,并给出了可能的点污染源.