~(60)Coγ射线对甘薯黑斑病(Ceratocystis fimbriata)的抑制效果

用60~(Co)γ射线25—400krad的不同剂量辐照甘著黑斑病菌及带病甘薯(Ipomoeabatatas Lam.)薯块,发现200及400krad剂量的辐照对菌丝体和子囊孢子有一定的抑制作用,对分生孢子、厚垣孢子抑制作用甚微;200krad在20天内基本抑制薯块上病斑的发生和发展,薯块外观良好,接种发病率比对照低75％,病斑平均直径不及对照的五分之一;400krad的抑茵效果更高,但尚不能完全杀死病菌孢子,并对薯块外表有伤害,使其色泽变暗,贮藏后期易产生干腐。本试验表明,200krad剂量的辐照处理对甘著贮藏有实践意义。     

Composition,distribution and sources of polycyclic aromatic hydrocarbons in sediments of the western harbour of alexandria,egypt

Aim and Background  Little data are available on the levels of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Mediterranean Sea Coast of Egypt in general and the Alexandria coastal zone in particular. It was therefore deemed necessary to set up a monitoring programme to determine the current concentrations of PAHs in bottom sediments, and to identify any area where high concentrations of these potential hazardous contaminants were present in the Western Harbour of Alexandria. Methods  The composition, distribution and the source of PAHs in surficial sediments of the harbour were investigated. To document the spatial PAH input, surficial sediment samples from 23 locations throughout the harbour were analysed. as]Results and Discussion The total PAH load determined in the surficial sediment samples ranged from 8 to 131150 ng g¹ dry wt, generally with most of the samples having total concentrations of PAHs greater than 5000 ng g¹ dry weight. The highest concentration of total PAHs was recorded in sediments of the inner harbour. Ratio values of specific compounds such as phenanthrene to anthracene, fluoranthrene to pyrene, methyl-phen-anthrene to phenanthrene, methyl-dibenzothiophenes to dibenzothiophenes, alkylated to non-alkylated and high molecular weight to low molecular weight PAH, were calculated to evaluate the possible source of PAH contamination in the harbour sediments. Conclusions  Two main sources of PAH in the study area have been found: pyrolytic and petrogenic. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed for most samples. The dominant sources of PAH appear to be the combustion processes through run-off, industrial and sewage discharges, and atmospheric input. The concentrations of PAHs were generally above levels expected to cause adverse biological effects. Recommendations and outlook  Information from this study and any other relevant studies should be useful in designing future strategies for environmental protection and management of the harbour.     

A non-ACC pathway for ethylene biosynthesis in Botrytis cinerea

Premature softening and tissue senescence occur in kiwifruit infected with Botrytis cinerea. While ethylene production is enhanced in infected fruit and B. cinerea produces ethylene on defined media in vitro the source of ethylene in this pathosystem is unclear. Ethylene production by B. cinerea was enhanced when methionine or ∝-keto-methylthiobutyric acid (KMBA) was added to a defined (modified Pratts) medium. Although 1-aminocyclopropane-1-carboxylic acid (ACC) did not stimulate ethylene production, ∝-aminooxyacetic acid (AOA) was inhibitory suggesting a role for a pyridoxal phosphate mediated enzyme reaction down stream from the methionine/KMBA stimulated ethylene biosynthetic pathway. Cobalt chloride (Co²⁺) was inhibitory, but after a 4-d lag period ethylene production from B. cinerea cultures containing methionine and Co²⁺ reached the same level as those without Co²⁺. [U ¹⁴C] methionine was converted to ¹⁴C-ethylene with high efficiency indicating that it is a direct precursor, while [2,3 ¹⁴C]-ACC did not yield radioactively labelled ethylene. These results suggest that the ethylene biosynthetic pathway in B. cinerea does not involve ACC as a precursor and that the enzyme responsible for synthesising ethylene is similar to, but different from, ACC oxidase from higher plants. The ethylene biosynthetic pathway in B. cinerea is yet to be determined.     

一个新的水稻窄叶突变体的遗传分析和基因定位

水稻叶片形态相关突变体是水稻功能基因组学研究和株型改良的重要材料.本研究以新的窄叶突变体MR11为研究材料,发现该突变体在整个生育期表现为窄叶、叶长变短和植株矮化.叶片组织结构观察发现由于叶脉数减少和叶脉问宽度减小,导致突变体倒二叶叶片宽度不及野牛型的1/2.F2和BC1F1两个群体分离结果表明该窄叶突变体表型受一对隐...     

Image denoising using HMT in PDTDFB domain

Based on the dependency of the PDTDFB coefficients across the interscale and interdirection and the statistical properties of HMT for the correlation properties, a new HMT in PDTDFB domain was put forward. Compared with the other typical denoising methods, the experimental results demonstrate that the proposed method shows better performance in image denoising, especially in edge maintenance.     

Comparative study of low voltage ride-through techniques for doubly-fed induction generator wind turbines under asymmetrical grid faults

Asymmetrical grid faults occur more frequently and have more adverse effects on the doubly fed induction generator (DFIG) than symmetrical grid faults in the transmission system. The transient response of DFIG under asymmetrical grid faults is analyzed firstly. Meanwhile, operation behaviors of several low voltage ride-through (LVRT) techniques under severe asymmetrical grid faults are given by simulation with the Matlab/Simulink software. Then the characteristics of these LVRT techniques are further researched and analyzed based on the simulation results. Finally, the economies of these LVRT techniques are discussed. The conclusion lays a certain foundation for engineering development of these LVRT techniques.     

Enhancing the Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET: Validation with the METRIC model

Evapotranspiration (ET) can be derived from satellite data using surface energy balance principles. METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is one of the most widely used models available in the literature to estimate ET from satellite imagery. The Simplified Surface Energy Balance (SSEB) model is much easier and less expensive to implement. The main purpose of this research was to present an enhanced version of the Simplified Surface Energy Balance (SSEB) model and to evaluate its performance using the established METRIC model. In this study, SSEB and METRIC ET fractions were compared using 7 Landsat images acquired for south central Idaho during the 2003 growing season. The enhanced SSEB model compared well with the METRIC model output exhibiting an r² improvement from 0.83 to 0.90 in less complex topography (elevation less than 2000 m) and with an improvement of r² from 0.27 to 0.38 in more complex (mountain) areas with elevation greater than 2000 m. Independent evaluation showed that both models exhibited higher variation in complex topographic regions, although more with SSEB than with METRIC. The higher ET fraction variation in the complex mountainous regions highlighted the difficulty of capturing the radiation and heat transfer physics on steep slopes having variable aspect with the simple index model, and the need to conduct more research. However, the temporal consistency of the results suggests that the SSEB model can be used on a wide range of elevation (more successfully up 2000 m) to detect anomalies in space and time for water resources management and monitoring such as for drought early warning systems in data scarce regions. SSEB has a potential for operational agro-hydrologic applications to estimate ET with inputs of surface temperature, NDVI, DEM and reference ET.     

施肥对苜蓿开花期叶面积及比叶重的影响

【研究目的】研究了不同施肥处理对3年生紫花苜蓿开花期叶面积、叶干重及比叶重的影响。【方法】用叶面积扫描仪测定苜蓿叶面积,在105℃下杀青,65℃下烘干24h,称取苜蓿叶干重,计算比叶重(SLW)。【结果】①氮、磷、钾单施或不同方式的配施均能增加苜蓿开花期叶面积和叶干重。其中以K40P60配施最有利于扩大苜蓿光合叶面积。以K40P40N10配施最有利于提高苜蓿开花期叶干重。②施氮,尤其是氮与磷配施能明显提高苜蓿开花期的比叶重,以P20N10配施效果最好。而单施磷(P20、P40、P60)、单施钾(K20、K40)或K20P20配施均不利于增加苜蓿开花期比叶重。【结论】①苜蓿施K40P60最有利于扩大开花期光合叶面积,增强光合作用。②施K40P40N10最有利于提高苜蓿开花期叶干重,从而有利于晒制干草。③施P20N10能明显提高苜蓿开花期比叶重,有助于苜蓿提高其光合速率,积累更多的光合产物。     

表面活性剂与纳米SiO2作用下聚合铝的絮凝特性

在6NTU高岭土原水中,溶入低浓度溶解性有机物-阴离子表面活性剂(十二烷基硫酸钠,SDS),投加聚合铝PAC与新型水处理剂-纳米SiO2稳定分散液进行动态混凝实验与静止沉降实验.借助图像分析技术与分形理论,对SDS与纳米SiO2作用下PAC的絮凝特性与絮体分形结构的形态学特征进行研究.结果表明:存在SDS时,高岭土颗粒表面ζ电位增加.SDS在颗粒表面的吸附等温曲线符合Langmiur方程;PAC对无机颗粒的去除效果明显,但对SDS的表观去除率较低.SDS阻碍絮凝初絮体的形成.纳米SiO2使颗粒表面ζ电位增加,对无机颗粒处理效果较差,但对去除有机物有利.絮凝机理主要是吸附架桥;助凝剂纳米SiO2能促进PAC对无机颗粒与SDS絮凝,处理效果显著.悬浊液中絮体粒径大,有效质量密度增加,沉速加快,分维值下降.