Arrival timing and seasonal reproductive performance in a long-distance migratory landbird

The date when a landbird migrant arrives on its breeding grounds may have reproductive consequences. Generally, early arriving individuals begin breeding earlier and consequently experience greater seasonal reproductive performance. Here, we describe relationships between arrival timing and seasonal reproductive performance in the American redstart (Setophaga ruticilla), a long-distance passerine migrant, arriving at northerly breeding grounds in Michigans eastern Upper Peninsula. Evidence suggests that both males and females benefited from early arrival at the breeding grounds. Early males appeared to settle on higher quality territories and hatched nestlings sooner than later arrivals. Early females began their clutches early, produced heavier nestlings and possibly laid more eggs than later arrivals. Larger clutches and heavier offspring increase the likelihood of offspring recruiting into the breeding population. The findings of this study point to fitness consequences arising from when a bird arrives at its breeding grounds. These results also have implications for understanding how events occurring during spring migration influence reproductive performance as migratory delays likely influence arrival timing.Communicated by: W. Wiltschko     

农村畜禽养殖污染的综合防治

畜禽养殖污染已成为农村环境污染的突出问题。本文通过调查分析广安市辖区内畜禽养殖业的发展和污染现状,在实地研究广安市两个畜禽养殖示范工程的基础上,借鉴现有的畜禽养殖污染防治技术成果,提出了一套以"养殖—沼气—农灌"和"养殖—堆肥—沼气—农灌"两种模式为技术基础,结合政策和法律措施,系统防治畜禽养殖污染的方案,有助于指导农村畜禽养殖的科学、绿色发展。     

单元板式轨道扣件刚度突变对行车安全性的影响分析

为研究单元板式无砟轨道扣件刚度整体及局部突变对行车安全的影响,指导扣件系统的养护维修,利用有限元方法和轮轨耦合系统动力学原理,建立车辆-轨道-路基系统垂向耦合动力学模型。研究扣件系统整体刚度突变和局部刚度突变对列车的振动特性和轮轨垂向作用力的影响规律。结果表明:扣件刚度从20 kN/mm增加到80 kN/mm时,轮对和转向架的振动加速度分别增加40.1%和28.2%,轮轨垂向力增加28.4%,车体变化不大;当局部扣件刚度突变时,车体、轮对、转向架的振动加速度和轮轨垂向力均较基本刚度(50 kN/mm)有所增大。扣件刚度整体突变以及局部突变均会对列车振动特性和轮轨垂向作用力产生不利的影响,建议及时对扣件系统进行养护检修,以保证行车的平稳性和安全性。     

沿空留巷直接顶稳定性突变分析及其控制

保持直接顶稳定,降低其突变所引起的危害是沿空留巷顶板控制的关键。基于沿空留巷直接顶力学模型,采用能量平衡分析法,建立直接顶突变的燕尾突变模型。结合某工程实例,阐述沿空留巷直接顶稳定性突变机理,分析巷帮煤体支撑力、巷内支护阻力、充填体支撑力对直接顶稳定性突变的影响。实践表明,增加工作面超前加固范围,巷内支护采用高预应力强力锚杆与锚索等主动支护,巷旁采用膏体充填,能够提高充填体早期强度,延缓直接顶稳定性突变的发生和减轻突变发生的烈度。     

丘陵地区农牧渔生态系统的研究

经四年研究，本文提出了适宜丘陵地区的作物－猪－鱼复合生态系统模型。在该系统中，淡水鱼的养殖以半精养方式最佳。本文还讨论了半精养方式的混养结构、水质管理和饵料组合等配套技术。     

三价钇对紫露草的遗传毒性研究

用紫露草四分体微核试验法和紫露草雄蕊毛细胞突变法研究了稀土元素三价钇的遗传毒性．结果表明：Y3＋能引起紫露草四分体微核率显著升高，提示Y3＋是诱变剂或纺锤丝毒剂；Y3＋能引起雄蕊毛细胞突变率显著升高，进一步明确Y3＋是诱变剂．     

王锦蛇的无冬眠饲养试验

2004年11月～2005年4月，进行了王锦蛇的冬眠期饲养试验．结果表明：在王锦蛇的冬眠期内，人工保持其环境温度为25～30℃，相对湿度为60％～85％，并提供其所需要的食物条件，就能够使王锦蛇在冬眠期内正常地生长发育，不仅能缩短其饲养时间，而且能提高其成活率，从而达到高效饲养王锦蛇的目的．