汞对土壤酶活性的影响

利用室内模拟方法,研究了重金属Hg对不同土样脲酶、转化酶和中性磷酸酶活性的影响.结果表明,Hg可显著地抑制土壤脲酶和转化酶的活性,但不同土样Hg对两种酶活性的抑制程度有很大差别.HgCl2浓度与两种酶活性之间的关系均可用对数方程很好地描述(P<0.05).4个土样的脲酶ED50(生态剂量)分别为87.99、5.47、24.05和19.88mg.kg-1;转化酶的ED50分别为76.68、727.49、236.52和316.59mg.kg-1.脲酶对Hg污染比转化酶敏感;有机质对土壤酶活性有一定的保护作用.除连续2年施用大量有机肥的草甸棕壤土样中Hg对中性磷酸酶有显著的激活作用外(P<0.05),其它土样无显著变化,表明中性磷酸酶活性对Hg污染反应不敏感.

汞和两种农药复合污染对土壤转化酶活性的影响

通过模拟方法研究了豆磺隆,呋喃丹2种农药与重金属汞(Hg)单一及复合污染对草甸棕壤和黑土4个土壤转化酶活性的影响.结果显示,在试验浓度范围内,土壤添加豆磺隆和呋喃丹后,转化酶变化幅度分别为-12%~7%和-6%~7%,表明2种农药对土壤转化酶的毒性较小;Hg对转化酶最大抑制率为22%~35%,二者之间呈显著的对数负相关关系,表明Hg对转化酶的毒性较大,转化酶在一定程度上可作为Hg污染的监测指标,通过对数方程计算出4个土样的生态剂量(ED50)分别为76.68,727.49,236.52,316.59mg/kg;Hg和2种农药之间普遍存在交互作用,豆磺隆与Hg复合污染引起土壤转化酶最大净变化量(?I)为对照的-12%~15%,呋喃丹和Hg为-25%~-6%,有机质对复合污染产生的毒性有明显的缓冲作用.

辽河三角洲滨海湿地景观规划预案设计及其实施措施的确定

系统介绍了景观规划“预案”研究的有关概念及预案设计的原则和方法。以辽河三角洲滨海湿地为实例 ,对其协调区域开发与湿地保护的景观规划进行了多预案设计 ,运用景观生态决策与评价支持系统 ( LEDESS)确定实现各预案所需措施并对其涉及的空间范围进行了模拟和定位。模拟结果以空间直观的形式显示实现各预案景观规划目标所需采取的措施和涉及的空间范围 ,可为区域开发的方法和模式选择、湿地保护的生态工程设计提供具体的参考依据。

杉木连栽土壤对其幼树生长的影响

在会同林区采用３种不同连栽杉木次数的土壤，进行杉木幼树盆栽试验．结果表明，杉木连栽不利其幼树生长．连裁使幼树高生长下降３７—４０％，基径下降１９—２８％，冠幅下降２１—２９％，总生物量减少４５—５０％．杉木连栽还造成土壤养分递减，即腐殖质减少７—２８％，速效养分下降２３—２８％，土壤微生物数量和活性也大大降低．因此，杉木纯林连栽经营方式应尽快改变．

中国木腐菌两新记录种

粗孢林氏孔菌Lindtneria trachyspora(Bourdot&Galzin)P ilát和乳白粗糙革孔菌Trechispora nivea(Pers.)K.H.Larss.首次报道于我国的青海省和陕西省,为中国新记录种。这两种木材腐朽菌均生长在阔叶树腐朽木上,造成木材白色腐朽。本文根据中国采集的标本材料对它们进行了详细的描述。

白光有机发光二极管的最新进展

有机发光二极管(Organic Light-Emitting Diodes,OLEDs)以其制备工艺简单、成本低、发光颜色可在可见光区内任意调节以及易于大面积制作和柔韧弯曲等优点,被认为是未来重要的显示技术之一,在未来照明光源领域也显示了诱人的应用前景.一般认为,如果OLED的发光效率超过100 lm/W,就有可能取代一般照明.本文综述了实现白光OLED的方法及其最新进展,并对白光OLED存在的问题及其发展趋势进行了讨论.

Effects of molecular weight, solvent and substrate on the dewetting morphology of polystyrene films

Surface morphology of polystyrene (PS) films on different substrates by spin-coating before and after annealing was observed using atomic force microscopy (AFM). The effects of polymer molecular weight, substrates, solvents, and annealing conditions on the morphology of the films were investigated. Before annealing, the grain height decreases, and simultaneously the grain diameter increases with molecular weight (M-w) within the measured molecular weight. After annealing. the situation is opposite, i.e., the grain height increases while the grain diameter decreases with M-w. Furthermore, after annealing the smaller surface roughness (Ra) was obtained. It was also found that film surface roughness (Ra) depends on the vapor pressure and dipole moment of different used solvents as well as the substrates. The experimental results show that when the used solvents have similar dipole moment but different vapor pressure, the Ra of PS film decreased with the decreasing vapor pressure of solvents whether on silicon or on mica. And when the used solvents have close vapor pressure but different dipole moment, the Ra decreased with the increasing of solvent dipole moments on both substrates.

Direct patterning of rhodamine 6G molecules on mica by dip-pen nanolithography

Dip-pen nanolithography (DPN) has been developed to pattern monolayer film of various molecules on suitable substrate through the controlled movement of ink-coated atomic force microscopy (AFM) tip, which makes DPN a potentially powerful tool for making the functional nanoscale devices. In this paper, the direct patterning of rhodamine 6G on mica by dip-pen nanolithography was demonstrated. R6G features patterned on the mica was successfully achieved with different tip movement which can be programmed by Nanoscript(TM) language. From the AFM image of R6G patterns, we know that R6G molecule is flatly binding to the mica surface through electrostatic interaction, thus stable R6G nanostructures could be formed on mica. The influence of translation speed and contact time on DPN was discussed. The method can be extended to direct patterning of many other organic molecules, and should open many opportunities for miniaturized optical device and site-specific biological staining.

Determination of ranitidine in urine by capillary electrophoresis-electrochemiluminescent detection

The fast analysis of ranitidine is of clinical importance in understanding its efficiency and a patient's treatment history. In this paper, a novel determination method for ranitidine based on capillary electrophoresis-electrochemiluminescence detection is described. The conditions affecting separation and detection were investigated in detail. End-column detection of ranitidine in 5 mM Ru(bpy)(3)(2+) solution at applied voltage of 1.20 V was performed. Favorable ECL intensity with higher column efficiency was achieved by electrokinetic injection for 10 s at 10 kV. The R.S.D. values of ECL intensity and migration time were 6.38 and 1.84% for 10(-4) M and 6.01 and 0.60% for 10(-5) M, respectively. A detection limit of 7 x 10(-8) M (S/N = 3) was achieved. The proposed method was applied satisfactorily to the determination of ranitidine in urine in 6 min.

The structure and electrochemical characteristics of La0.67Mg0.33 (Ni0.8Co0.1Mn0.1)(x) (x=2.5-5.0) multiphase alloys for nickel-metal hydride batteries

This paper presents results concerning structure and electrochemical characteristics of the La0.67Mg0.33 (Ni0.8Co0.1Mn0.1) (x) (x=2.5-5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5-3.5 is LaMg2Ni9 phase with a PuNi3-type rhombohedral structure, but the main phase of the alloys with x=4.0-5.0 is LaNi(5)phase with a CaCu5-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg2Ni9 phase and the LaNi5 phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g (x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I-0) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability of the alloy electrodes.