接触辉光放电等离子体降解水体中的邻氯苯酚

接触辉光放电电解是一种新型的产生等离子体的电化学方法。本文测定了催化剂、pH 值对接触辉光放电等离子体降解水体中邻氯苯酚降解效率的影响;并利用高效液相色谱检测了中间产物和邻氯苯酚降解浓度随时间的变化。实验表明:碱性条件下降解有利,Fe2+催化作用下降解效率明显提高。     

高含水率非离子型水凝胶角膜接触镜材料的合成及性能研究

以丙烯酰胺(AM)和甲基丙烯酸β-羟乙酯(HEMA)为主要原料,采用适宜的制备工艺,得到一种高含水率、非离子型交联共聚水凝胶角膜接触镜材料,对影响其平衡溶胀率的各种因素、透光率、饱和含水率、力学强度等进行了研究.结果表明,所得膜材料的透光率、饱和含水率、力学强度均能很好满足水凝胶角膜接触镜的要求.     

Insecticidal compounds from the essential oil of Chinese medicinal herb Atractylodes chinensis

BACKGROUND: In a screening programme for new agrochemicals from Chinese medicinal herbs, the essential oil of Atractylodes chinensis (DC.) Koidz was found to possess strong insecticidal activity against the common vinegar fly, Drosophila melanogaster L. The essential oil was extracted via hydrodistillation, and its constituents were determined by GC‐MS analysis. RESULTS: The main components of A. chinensis essential oil were β‐eudesmol (21.05%), β‐selinene (11.75%), γ‐elemene (7.16%) and isopetasam (5.36%). Bioactivity‐directed chromatographic separation on repeated silica gel columns led to the isolation of five compounds, namely atractylon, α‐elemol, β‐eudesmol, hinesol and β‐selinene. β‐Selinene, α‐elemol and hinesol showed pronounced contact toxicity against D. melanogaster adults, with LD₅₀ values of 0.55, 0.65 and 0.71 µg adult^?1 respectively. Atractylon and β‐eudesmol were also toxic to the fruit flies (LD₅₀ = 1.63 and 2.65 µg adult^?1 respectively), while the crude oil had an LD₅₀ value of 2.44 µg adult^?1. CONCLUSION: The findings suggested that the essential oil of Atractylodes chinensis and its active constituents may be explored as natural potential insecticides. Copyright © 2011 Society of Chemical Industry     

田间有效软路面谱形成过程分析

田间有效软路面谱形成过程包括轮胎—软路面动压实和接地印迹包络平滑的两个过程,该文分别建立了两个过程的力学模型,并进行了理论计算。通过大量试验,其结果与理论计算一致,表明所建的模型是正确的。并提出当其他条件相同情况下,驱动轮下的有效谱低于从动轮下的有效谱。     

Effect of soil macroporosity and aggregate size on seed-soil contact

The influence of soil structure on the degree of seed-soil contact within a seedbed is poorly understood. This paper presents a simple analogue of seed-soil contact which allows the examination of the influence of macroporosity and relative aggregate size on the degree of contact within a bed of deformable spheres. A method is described in which a rigid disc or sphere representing a seed is placed within a bed of deformable spheres of uniform size representing soil aggregates. The structure is then compressed uniaxially to a given macroporosity. Contact areas were measured by a technique involving the use of paint, dismantling of the sample, and image analysis. Results show that degree of contact increases as macroporosity decreases. Greatest levels of contact are achieved where rigid and deformable spheres are of similar size. This result appears to be a consequence of maximum stress concentration occurring at this size ratio. Contact points were unevenly distributed over the surface of the rigid sphere. The applicability of these findings is considered.     

A Novel Particle Contact Assay with the Yeast Saccharomyces cerevisiae (8 pp)

Goal, Scope and Background   Numerous xenobiotics released into surface waters are transferred to suspended particulate matter and finally attached to sediments. Aquatic organisms may be exposed to them by direct particle feeding, by physical contact with contaminated surfaces as an exposure route, and by the uptake of dissolved contaminants after equilibration via the free water phase. In order to assess potential sediment toxicity, each of these exposure routes has to be addressed. This paper presents a newly developed particle contact assay that uses the fermentation performance of a specific Saccharomyces cerevisiae strain for the assessment of toxic effects in sediments. The test procedure is based on the characteristic feature of growing yeast cells to attach to sediment particles, which are also relevant for the accumulation of contaminants. The physical contact with lipophilic contaminants mirrors an exposition pathway for the direct uptake into the cells. In order to quantitatively characterize the toxic effects of particle attached pollutants on the fermentation performance, unpolluted native reference sediment was spiked with representatives for widely distributed anthropogenic contaminants. Methods   Saccharomyces cerevisiae was established as sensitive eukaryotic microorganism for the ecotoxicological assessment of particle attached anthropogenic contaminants in freshwater sediments. For this purpose, yeast cells were cultivated in sediment samples and the resulting fermentation performance was continuously measured. Sediments artifically spiked with HCB, PCB, g-HCH, DDT, and benzo(a)pyrene and solutions of each contaminant were comparatively investigated by means of their adverse effects on yeast fermentation performance. Additionally, four native river sediments characterized by increasing levels of pollution were assessed by the yeast particle contact assay, and simultaneously by standard aquatic tests with algae, daphniae, and luminescent bacteria using pore water and elutriates. Results of the bioassays were related to specific sediment contamination with respect to metals and organic priority pollutants. Results and Discussion   In sediments spiked with PCB and benzo(a)pyrene fermentation, performance was affected extensively below concentrations inhibiting fermentation in contaminant solutions. This suggests a high efficiency of the exposure route by physical contact. The fermentation performance was only slightly affected by single lipophilic pollutants, whereas mixtures of individually spiked sediments caused critically reduced fermentation performance suggesting additive synergistic effects. Native river sediments modestly to critically polluted by hazardous organic compounds lead to a slightly to dangerously reduced fermentation performance in the yeast contact assay. These inhibitory effects were much less pronounced in the standard bioassays conducted with algae, daphniae and luminescent bacteria, applying pore waters and elutriates as sample matrices. Using pore water, inhibition was measured only in the most polluted sediment, elutriates lead to a slight inhibition of the algal growth in the undiluted sample only. These results indicate an improved sensitivity of the yeast particle contact assay compared to the standard assays, due to uptake and physical cell contact as additional routes of exposure. Conclusion   The yeast particle contact assay is a valuable tool for the assessment of ecotoxicological potential in freshwater sediments. Since the assay addresses physical contact as an exposure route, it indicates bioavailability of lipophilic compounds in sediments. Outlook   The sensitive indication of bioavailable contaminants associated to sediment particles by the newly developed yeast particle contact assay recommends it as a complementary microbial bioassay in a test battery for assessing major pathways of contaminants in whole sediments.     

土荆芥果实挥发油的抑菌活性及其组分分析

为了比较土荆芥果实挥发油的熏蒸和触杀抑菌活性,测定了其对植物病原真菌菌丝生长和孢子萌发的熏蒸与触杀抑制作用,初步研究了其抑菌机制。结果表明,土荆芥果实挥发油对植物病原真菌具有强烈的抑制作用,熏蒸和触杀抑制作用均随着挥发油剂量增加而增强,随处理时间延长多呈减弱趋势。其对白菜黑斑病菌、小麦赤霉病菌、水稻胡麻斑病菌3种真菌菌丝生长的熏蒸和触杀抑制作用半数有效浓度(EC50)分别为17.4~22.1μL/L、103.9~241.7μL/L,对水稻胡麻斑病菌孢子萌发的熏蒸和触杀抑制作用EC50分别为28.8μL/L、789.3μL/L。土荆芥果实挥发油通过熏蒸方式作用于水稻胡麻斑病菌菌丝,使其细胞内含物渗漏;通过触杀方式作用于水稻胡麻斑病菌菌丝,随挥发油浓度升高和处理时间延长,相对电导率增加。GC-MS分析结果显示,土荆芥果实挥发油主要成分为2-蒈烯和驱蛔素。综合分析土荆芥果实挥发油的抑菌活性,熏蒸作用的效果优于触杀作用。     

Effect of soil drying on mucilage exudation and its water repellency: a new method to collect mucilage

Despite the importance of mucilage for soil–plant relations, little is known about the effect of soil drying on mucilage exudation. We introduce a method to collect mucilage from maize growing in wet and dry soils. Mucilage was collected from brace roots. The amount of mucilage exuded did not change with soil water content and transpiration rate. Mucilage exuded in dry soils had a higher degree of hydrophobicity, suggesting that the wetting properties of mucilage change in response to soil drying.     

Ovicidal and nymphicidal effects of some fungicides on the greenhouse whitefly<Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis>

Eggs and L1 nymphs of the greenhouse whiteflyTrialeurodes vaporariorum (Westwood) (Hem.: Aleyrodidae) on bean leaves were directly sprayed with the fungicides maneb and mancozeb at recommended rates for practical use. Strong ovicidal and nymphicidal effects were observed. These fungicides may prove to have practical use for integration in IPM programs for whitefly control, as they also exert low or no toxicity to the whitefly parasitoidEncarsia formosa. http://www.phytoparasitica.org posting April, 30, 2004.     

组合式污水处理设备在湖滨带中的应用探讨

指出了组合式污水处理设备是针对我国目前的分散型生活污水的收集和处理的实际进行开发和设计的,采用2级厌氧和2级好氧的完全混流曝气技术。从处理效率高、抗冲击负荷强、占地面积小等方面分析了组合式污水处理设备的优势,探讨了其在洱海湖滨带污水治理中的应用。