Effects of Self-Compatibility on the Distribution Range of Invasive European Plants in North America

Abstract:  Many plant species have been introduced to new continents, but only a small subset of these have become invasive. It has been predicted that self-compatible species, particularly those that do not need the services of pollinators, are more likely to establish and spread after long-distance dispersal. We tested whether this hypothesis, commonly called Baker's law, applies to 361 species that have invaded the United States from Europe. Species capable of autonomous seed production occurred in significantly more states than species requiring a pollen vector. Moreover, of the species that are not capable of autonomous seed production, self-compatible species occurred in significantly more states than those that are not self-compatible. The positive effect of autonomous seed production on the range of invasion was larger for abiotically pollinated species than for biotically pollinated species and for monocarpic species than for polycarpic species. These results support Baker's law, and we recommend that screening protocols for predicting invasiveness of species considered for introduction should include assessment of their breeding system.     

金属离子污染砂土复电阻率的时变特征及形成机制

为研究不同污染情况下土壤复电阻率的时间变异特征及控制机制,设计了人工砂土和水2种不同的介质作对照,以NaCl、MnCl₂和模拟海水作为污染物分别模拟海水入侵和金属离子污染场景,测量10⁰~10³Hz范围内的相位变化并观测其时变特性.结果显示,无论在纯液相介质中还是在土壤介质中,相位值都随着污染物浓度的增大而减小,随频率的增大而增大.随着污染物浓度的变化,土壤介质中的相位比水相介质中更加敏感.在土壤和水的背景环境下,通入1g/L的NaCl溶液,在1Hz条件下测量,土壤相位下降了约42%,而水相介质几乎看不出相位变化.针对固定频率进行多次测量的结果表明,水相介质中的相位值稳定而土壤介质中的相位值在中高频段（>16Hz）表现出了明显的时变特征,这种时变性也随着污染物浓度的增大而减小.在10²Hz时,测得沙柱背景值的相位浮动范围在-4.05~-11.67mrad,方差达到4.8,而在水相溶液中方差仅为0.09.复电阻率法对金属离子污染土壤的反应很灵敏,有较好的指示意义,其参数变化主要与孔隙水中金属离子含量有关.但由于多相介质的相界面特征以及孔隙结构的复杂性,使得交变电流下电荷载流子在介质中的迁移极化规律混乱,造成相位波动.     

大气等离子喷涂SrZrO3热障涂层工艺与性能的研究

目的探究大气等离子喷涂制备Sr ZrO_3涂层的融化状态最好、沉积效率最高的最优工艺,研究SrZrO_3热障涂层的热物理性能及其热循环寿命。方法采用大气等离子喷涂技术制备SrZrO_3热障涂层,通过设计田口实验研究不同的喷涂工艺对粉末融化状况和沉积效率的影响,采用扫描电镜观察涂层融化状况等。采用优化后的工艺制备厚涂层,使用高温热膨胀仪和激光导热仪测试涂层的热膨胀系数、抗烧结性能以及热扩散系数。结果当喷涂距离为90 mm时,SrZrO_3涂层沉积效率最高,最大单遍喷涂厚度达到15.3μm;当喷涂距离为100 mm时,涂层的熔化状态最好。制备态SrZrO_3涂层中出现第二相t-Zr O_2,1600℃热处理条件下,随着热处理时间的延长,t-Zr O_2逐渐消失,热处理360 h后,m-ZrO_2的质量分数逐渐增加至27%。SrZrO_3涂层热膨胀系数为(8～10)×10~(-6) K~(-1)(200～1400℃),随着热处理时间的延长,涂层的热膨胀系数逐渐降低。SrZrO_3涂层的热导率随着热处理时间的延长先增加后减小,热处理360h后SrZrO_3涂层的热导率为1.82W/(m·K)(1000℃)。SrZrO_3/YSZ双层涂层炉内循环548次后,涂层整体脱落。结论 SrZrO_3涂层最优喷涂工艺为电流550 A、氩气流量40 L/min、氢气流量10 L/min、喷涂距离100 mm、功率35.8 kW。随着热处理时间的延长,涂层中的第二相m-ZrO_2能够降低涂层的热膨胀系数和热导率。SrZrO_3/YSZ双层涂层的循环次数远高于SrZrO_3单层涂层。     

不敏感装药高温相变影响机制研究进展与思考

综述了HMX、CL-20以FOX-7等未来不敏感装药主要候选组分的相变研究进展,归纳了高温相变对安全性带来影响的几个原因,主要包括炸药本身的稳定性下降、炸药密度改变及炸药内部缺陷增加的原因。针对如何降低高温相变对不敏感装药安全性的影响进行了初步思考,认为目前为了降低高温相变对炸药安全性的影响,主要手段仍是对相变进行一定程度的抑制,而共晶技术、包覆技术、晶型控制剂抑制技术和配方抑制相变技术是未来相变抑制技术的主要研究方向。     

新型固相微萃取头测定胶粘剂中苯及其同系物

结合分子印迹技术与溶胶-凝胶技术,自制新型联苯分子印迹溶胶-凝胶聚合物涂层固相微萃取头,结合顶空固相微萃取-气相色谱法(HS-SPME-GC),测定水溶液中的苯及其同系物。结果表明,该方法精密度良好(RSD<5%),线性范围超过2个数量级,最低检出限达到10ng/mL。运用该法对市售胶粘剂中苯及其同系物进行检测,结果令人满意。     

Sample Preparation Followed by High Performance Liquid Chromatographic (HPLC) Analysis for Monitoring Muconic Acid as a Biomarker of Occupational Exposure to Benzene

Factors affecting solid phase extraction (SPE) of trans,trans-muconic acid (ttMA), as a benzene biomarker, including sample pH, sample concentration, sample volume, sample flow rate, washing solvent, elution solvent, and type of sorbent were evaluated. Extracted samples were determined by HPLC-UV(highperformance liquid chromatography-ultraviolet). The analytical column was C18, UV wave length was 259 nm, and the mobile phase was H2O/methanol/acetic acid run at flow rate of 1 ml/min. A strong anion exchange silica cartridge was found successful in simplifying SPE. There was a significant difference between recoveries of ttMA when different factors were used (p < .001). An optimum recovery was obtained when sample pH was adjusted at 7. There was no significant difference when different sample concentrations were used (p > .05). The optimized method was then validated with 3 different pools of samples showing good reproducibility over 6 consecutive days and 6 within-day experiments.     

Natural remobilization of multicomponent DNAPL pools due to dissolution

Mixtures of dense nonaqueous phase liquids (DNAPLs) trapped in the subsurface can act as long-term sources of contamination by dissolving into flowing groundwater. If the components have different solubilities then dissolution will alter the composition of the remaining DNAPL. We theorized that a multicomponent DNAPL pool may become mobile due to the natural dissolution process. In this study, we focused on two scenarios: (1) a DNAPL losing light component(s), with the potential for downward migration; and (2) a DNAPL losing dense component(s), with the potential for upward migration following transformation into a less dense than water nonaqueous phase liquid (LNAPL). We considered three binary mixtures of common groundwater contaminants: benzene and tetrachloroethylene (PCE), PCE and dichloromethane (DCM), and DCM and toluene. A number of physical properties that control the retention and transport of DNAPL in porous media were measured for the mixtures, namely: density, interfacial tension, effective solubility, and viscosity. All properties except density exhibited nonlinear relationships with changing molar ratio of the DNAPL. To illustrate the potential for natural remobilization, we modelled the following two primary mechanisms: the reduction in pool height as mass is lost by dissolution, and the changes in fluid properties with changing molar ratio of the DNAPL. The first mechanism always reduces the capillary pressure in the pool, while the second mechanism may increase the capillary pressure or alter the direction of the driving force. The difference between the rate of change of each determines whether the potential for remobilization increases or decreases. Static conditions and horizontal layering were assumed along with a one-dimensional, compositional modelling approach. Our results indicated that for initial benzene/PCE ratios greater than 25:75, the change in density was sufficiently faster than the decline in pool height to promote DNAPL breakthrough into the adjacent porous medium. In contrast, there was no potential for natural remobilization of a PCE-DCM mixture, primarily because the densities of the components are not sufficiently different. Dissolution of a DCM-toluene mixture decreased the density, reducing the tendency for downward displacement. However, the ultimate transformation from a DNAPL to an LNAPL may induce upward displacement. These results suggest that at sites with DNAPL pools containing a mix of components of sufficiently different densities and relative solubilities, natural remobilization may be an active mechanism, with implications for site evaluation and remediation.     

玉米对土壤中重金属铅的吸收特性及污染防治

通过山东五莲玉米盆栽试验,研究作物对土壤中铅的吸收效应,探讨环境土壤重金属元素对作物和人类健康的影响.玉米盆栽试验表明,当土壤中加入不同比例的铅时(0～4 000 mg/kg),基本没有观察到铅对玉米的毒害病症,铅对作物的生长发育没有明显的宏观影响.但微区调查揭示,玉米对土壤中的铅具有强烈的吸收性,并可残留在作物的各个部位,且吸收量随土壤中铅添加量的增加而提高;其中根系的吸收性最强,是秸杆、籽实的几十至几千倍,表明作物根系为秸杆、籽实对铅的吸收提供了良好的屏障.不同铅化合物对作物吸收铅的影响不尽相同,用Pb(NO3)2处理的铅吸收量比用PbCl2处理的明显偏高,特别是当土壤中铅添加量较高时,该特征更为显著;而用PbCl2处理的作物,当铅添加量达到一定程度后,除根系外,作物对铅的吸收趋于饱和.运用根系对土壤中铅的特殊吸收性,可以在铅污染的土壤区通过自然作物栽培,并将作物根系从土壤中清除,来逐渐达到环境土壤修复的目的.     

固相微萃取技术的应用及其进展

固相微萃取技术（SPME）是一种新型的样品前处理方法，它可一步完成取样，萃取和浓缩，简化了传统前处理方法的繁琐步骤，而且不会造成二次污染。因此，SPME技术在短短几年内已广泛运用于各个研究领域。本文对SPME技术的原理作了简要介绍，对目前的应用研究情况作了初步的总结，并对今后的发展趋势作了预测。     

矿井通风系统与耗散结构理论

把通风系统看成一个开放系统 ,利用耗散结构理论 ,对通风系统的耗散条件和耗散行为进行研究 ,得到了通风系统稳定工作的条件以及通风参量与非平衡相变的关系 ,为矿井通风系统优化和日常通风管理工作提供指导 ,同时为通风系统数值模拟的参数选定提供理论依据。通过对耗散参量的研究 ,认识通风系统中参数作用方式 ,了解系统有序相变临界耗散趋势 ,理解整个通风系统的演化规律。