The regulation of mycorrhiza formation— carbohydrate and hormone theories reviewed

Two “classical” theories, both originating in Elias Melin's laboratory in Uppsala, have tried to explain the regulation of ectomycorrhiza formation. The carbohydrate theory, formulated by E. Björkman in 1942, identifies root carbohydrate concentrations as regulatory, while these are in turn considered to be strongly influenced by plant mineral nutrition and light conditions. The hormone theory, expounded by V. Slankis in the 1960s, claims auxin of fungal origin to be the key regulator, influencing root carbohydrate status, while the fungus itself may, to some extent, be affected by mineral nutrition. Both theories have been subject to much discussion and have led to further work, without ever having been conclusively proven experimentally. Recent results in Uppsala and elsewhere have shed new light on several of the key issues. The development of research in this field since 1942 is critically reviewed in light of later data, and a unifying theory is sketched on the basis of E. Hacskaylo's proposal from 1969 to reconcile contradictory results.     

Non-industrial Private Forest Owners' Risk Preferences

A set of hypotheses was formulated on the basis of available knowledge about non-industrial private forest (NIPF) owners' risk preferences. The empirical material used for testing the hypotheses was gathered in telephone interviews with 130 randomly selected NIPF owners. The results confirm that direct economic risks such as price and cost changes are seen by this group as much more important than indirect economic risks such as biological damage. The forest owners regarded forest holdings as a safer investment than stocks or bank savings. The results on risk attitudes were ambiguous. However, when larger amounts of money were at stake, the forest owners could be considered risk averters and a decrease in absolute and relative risk aversion could be confirmed.     

豚草化学防除效果研究

采取目前湖北市场上常见的几种除草剂对豚草进行防除,其结果表明:20%克芜踪的灭杀效果最好,第7 d可达100%;而加少许中性洗衣粉的10%草甘膦对豚草的灭杀效果比不加洗衣粉的效果更为明显,但总体防效均较克芜踪缓慢。     

间接ELISA法对禽霍乱抗体的动态监测

将40只50日龄健康禽霍乱非免疫鸡随机分为四组，每组10只。用禽霍乱蜂胶佐剂灭活疫苗对各组鸡进行不同水平的免疫，同时设非免疫对照组。各组鸡间隔5-7天采血，以间接ELISA法测定血清P／N值，并确定临界值。将P／N值在2.1-4.7的13只试验鸡以一个最小致死量（相当于10个菌／ml）进行攻毒试验，同时设攻毒对照，在1周内3只对照鸡均表现感染发病并死亡，而试验鸡均健活，从而初步证明所确定的临界值是合理的。     

Duration of load effects of solid wood: A review of methods and models

Abstract

Test methods for studying the effect of long-term loading on the load-carrying capacity of structural wood are discussed. The impact of sampling procedures on test results is investigated and is exemplified. It is concluded from this investigation that the sampling method has a significant impact on the test results. A number of mathematical models for estimation of the effect of load duration are also presented and brief outlines of the theoretical background for five categories of models are given. No attempt is made to compare the models in order to nominate the best model. Effort is, however, made to illustrate the futility of calibrating models against one type of test when the model is redundant to the test type.     

Growth-independent effects of a fluctuating thermal regime on the life-history traits of the Japanese medaka (Oryzias latipes)

Abstract –  Temperature fluctuation has been shown to affect somatic growth rates and metabolic functions of fish, but little is known about the effects of fluctuating temperatures on life-history traits. We examined these effects on female Japanese medaka ( Oryzias latipes ) reared from hatch to maturity at two mean temperatures (27 and 30 °C) with diel temperatures either held constant or allowed to fluctuate ±5 °C. Feeding regimes were manipulated to equilibrate medaka growth rates in all treatments. Age and length at maturity decreased as a result of thermal fluctuation, whereas there was no effect of temperature fluctuation on the proportion of fish attaining maturity or on the number of eggs produced by a mature female. We hypothesise that short-term high temperatures associated with temperature fluctuation decreases development time, whereas reduced energy conversion efficiency at higher temperatures does not allow for increased egg production.     

汽车变速箱嵌入式诊断系统设计与实现

根据大跨度中承式拱桥的三维空间结构形式及主拱风荷载相互干扰的特点,提出了抖振响应的非线性时域分析方法.通过节段模型风洞试验,确定了前后拱在相互干扰下的静力三分力系数.结合试验得出的两榀拱的抖振力时程数据,求出前后拱在相互干扰下的脉动风速功率谱.采用谐波合成法模拟大跨度中承式拱桥的三维风场,通过FFT变换、功率谱插值等技术提高了模拟效率.以重庆菜园坝长江大桥为工程实例,进行了考虑几何非线性的时域抖振分析,计算结果与风洞试验结果吻合较好.     

论中国电影的书法审美

书法是中国最为独特的艺术形式之一,在中国电影尤其是古装影片中是必不可少的组成部分。书法在电影中一般有两种审美表现形式:一种是作为背景镜头,另一种是作为特写镜头。书法作品不仅是一种道具,它还是时代、文化、修养、人格的标志。     

竞争种群最优开发与管理的生态经济模型

建立了具有竞争关系的2资源种群开发与管理的生态经济模型,给出了开发多种资源种群时应遵循的基本原则,详细地说明了该模型所隐含的生态经济意义.认为要使相互竞争的多个种群能够共存,就必须以适当的力度开发资源种群,且这种开发力度要取决于种群的生态学特征.     

化学除草剂对改培型生物防火林带土壤理化性质及防火效果的影响

以试点中的黑龙江省改培型生物防火林带阻隔系统工程为依托,以可燃物载量为指标,探讨了除草剂对改培型生物防火林带土壤理化性质及防火效果的影响。结果表明:施用除草剂(森草净)后,改培型生物防火林带阻隔体系可燃物载量大幅减少,可有效地阻隔地表火的蔓延,减缓高强度林火的蔓延速度,且3 a后该建带方法未对土壤物理性质产生显著影响。