Individual variation in early life-history traits in brown trout

Abstract – We studied the variability of early life history traits in individually raised progeny of brown trout Salmo trutta L. Eggs from two dams were each fertilized with sperm from 10 sires, producing 20 full-sib families. Each individual progeny was followed from fertilization until death without exogenous food. Egg size was positively correlated with a number of life-history traits, especially length and yolk sac volume at hatching and length at death, and these traits were strongly influenced by maternal effects. We found significant additive genetic variance for growth rate, length at death and life span without external food. Thus these early life-history traits may be modulated by natural selection. We found positive phenotypic and genetic correlations between most early life-history traits. However, life span without external food was negatively correlated with growth rate, indicating a genetic trade-off. ^Note     

不同pH条件下接种菌根真菌对柑橘砧木苗生长及光合效应的影响

本文以枳橙（Citrus sinensis (L.) Osbeck譸oncirus trifoliate (L.)）为试验材料，利用盆栽试验，研究不同pH条件下接种丛枝菌根(Arbuscular mycorrhiza)真菌摩西球囊霉(Glomus mosseae)对柑橘砧木枳橙苗的生长及植株光合效应的影响。试验选定3个pH范围（pH 5.5~6.5, 6.5~7.5, 7.5~8.5）和接种摩西球囊霉为试验因子，共设6个处理组合，以不同pH条件下未接种摩西球囊霉为对照。采用单株小区，随机区组排列，重复10次。结果表明，接种摩西球囊霉能有效地侵染枳橙植株，菌根侵染率65%以上。试验还发现，处理植株的菌根侵染率和株高、生物量干重均显著高于对照植株，同时，接种AM真菌显著增加了植株叶片叶绿素含量，并显著提高处理植株光合作用速率和蒸腾速率。研究结果表明，接种AM真菌增强了宿主植物对土壤酸碱度的适应性，在酸性和碱性土壤上均能显著提高柑橘的光合效应。     

汇率预测的理论与方法及其最新进展

总结了众多国内外学者在汇率预测方面的理论及其研究方法。通过对传统的统计方法与非参数方法的比较分析,得出结论:大多数传统的时间序列模型是线性的,不能抓住非线性时间序列数据的内在特征。而相对于传统的预测模型而言,非参数方法能发现观察结果和输入数据的关系,不需要事先确定模型,其拟合结果能更好的捕捉汇率的动态特征与走势。     

浅析淮北地区麦茬直播稻栽培的安全性

探讨了响水县直播稻的安全齐穗与高产栽培的关系,通过对气象资料进行分析,明确了9月中旬初可作为安全齐穗的时间节点,并提出了水稻特性与品种利用的关系。     

Effect of Gypsum Application on Long Term Changes in Soil Properties and Crop Growth in Sodic Soils under Field Conditions

In a field study, conducted on farmer's waste sodic soils, Aquic Natrustalf, 12.5 t/ha gypsum was surface mixed. Effect of gypsum application on soil properties and crop yields of rice and wheat grown in succession was evaluated after one to five years of gypsum application. The results showed that soil pH, electrical conductivity, calcium carbonate and soil dispersion decreased, whereas organic carbon, hydraulic conductivity, water infiltration and storage increased considerably after five years of gypsum application. In the initial years the improvement in soil properties was more in the surface layers and extended to lower layers slowly in the following years. Average grain yields of rice and wheat in the first year were 4.2 and 1.8 t/ha, respectively. The yields further increased to 6.1 and 2.5 t/ha in the 5th year, but the yields were lower than the yields obtained in research experiment. Relationships between wheat grain yield and pH of 0–15 and 15–30 cm layers were established. Wheat yield reduced by 45 percent when pH of 0–15 cm layer increased from 9.0 to 9.5. The sodicity of sub soil was still too high to permit the cultivation of deep rooted crops even after five years of gypsum application. Normal crop production is possible in these sodic soils, given sufficient time to reduce the sub soil sodicity.     

无线网络的一种动态多门限呼叫接入控制方案

针对无线网络的多类业务提出了一种呼叫接入控制方案．该方案基于动态保护信道机制，根据优先级为各类业务设置相应的服务门限，服务门限能根据系统负荷的变化动态地调整．仿真结果显示：与已有静态方案相比，该方案不仅能够保证业务的优先性，而且能够跟随业务量的实时变化，保持良好性能．     

立式捏合机混合釜内流场遍历性研究

流场遍历是流场混合的必要条件.根据立式捏合机混合釜内螺旋桨刃尖的运动特征,定义了穿越、遍历率和遍历时间等基本概念;提出了用遍历率和遍历时间来评价流场遍历性能;分析了螺旋桨的自转公转转速比对流场遍历率和遍历时间的影响.研究结果表明:螺旋桨的自转公转转速比对流场遍历性能具有极大影响,并可以通过比较不同转速比所对应的遍历率大小得到较优的螺旋桨的自转公转转速比;采用双螺旋桨能明显提高系统遍历率,降低遍历时间.     

控制性隔沟交替灌溉条件下土壤蒸发的预测研究

棵间土壤蒸发是控制性交替灌溉条件下农田土壤耗水的重要组成部分,为了了解沈阳地区潮棕壤土条件下大豆田不同控制性交替灌溉制度下的土壤蒸发变化规律,对土壤蒸发进行预报,采用Micro-lysimeters(MLS)对不同灌溉处理下的土壤蒸发量进行了测定,并建立了以气象因子、土壤含水率和叶面积指数为自变量的土壤蒸发的预报模型.结果表明,在本试验的条件下,各处理的相对土壤蒸发率(E/ET0)与表层土壤含水率(θ)的关系均呈指数函数形式,决定系数在0.71以上.各处理的E/ET0与LAI之间亦呈很好的指数函数关系,决定系数均在0.78以上.     

一种用于香蕉叶斑病防治的新型施药技术

试验一种将内吸性农药稀释后灌注于香蕉叶柄基部防治香蕉叶斑病的新型精确定量施药技术。结果表明，这种施药技术与常规施药技术相比，防效相当，且对香蕉的生长无不良影响，而农药成本仅为常规防治的18%，农药利用率提高4倍，值得推广应用。     

Relationship between zooplankton abundance and the early marine life history of juvenile chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> in eastern Hokkaido,Japan

Interannual variations in abundance, timing of outmigration from rivers, growth rate and condition of juvenile chum salmon (Oncorhynchus keta) were studied in the Nemuro Strait (eastern Hokkaido, Japan) during 1999–2002 to establish a possible relationship to zooplankton abundance. The otolith microstructure of juveniles was examined each year in late June to determine their time and size at sea entry (i.e., outmigration), and to estimate the early marine growth rates. Salmon outmigration peaked in mid- or late May, which coincided, in three of the four study years, with the peak release of juveniles into rivers within the study area. Abundance, growth rate and condition of fish were higher in 2001, when—compared to other years—smaller fish experienced higher growth rates, coinciding with greater zooplankton abundance for that year. Our results suggest that high zooplankton abundance positively influenced juvenile chum salmon growth and the condition of the fish during their early marine life despite their small size at sea entry.