The effects of the last glacial paleo-aeolian sands on desertification in northern China

IEECAS SKLLQG

双奇核~(140)Pr的高自旋态能级纲图

通过130 Te(14 N ,4n)反应首次对双奇核14 0 Pr进行了在束γ谱学研究 .在实验中进行了γ射线的激发函数、γ射线单谱和γ γ t符合测量 .建立了激发能达 4 717.3keV的14 0 Pr的能级纲图 ,其中包括新发现的 4 2条γ射线和新建立的 2 7个能级 .基于实验测量的γ跃迁各向异性度 ,建议了14 0 Pr部分能级的自旋值 .根据14 0 Pr附近同位素核结构的系统性 ,对部分能级的准粒子组态作了定性的讨论 .

不同有机酸对铅胁迫小麦幼苗的缓解作用

研究了在铅胁迫条件下,加入外源有机酸对小麦铅毒害的缓解效应。结果表明,低浓度的草酸和乙酸能增加铅胁迫小麦叶绿素含量,不同程度地提高SOD、CAT、POD活性,降低MDA含量,而高浓度草酸和乙酸及柠檬酸对此则无明显的缓解作用;乙酸处理减少根系活跃吸收面积,柠檬酸能明显提高根系活力。草酸对铅胁迫的缓解效果最明显。

长白落叶松三种等位酶遗传型初步分析

长白落叶松三种等位酶遗传型初步分析张军丽（中国科学院沈阳应用生态研究所，沈阳１１００１５）本文采用淀粉凝胶电泳法，在酶水平上，利用“水平切片染色法”分析了长白落叶松（Ｌａｒｉｘｏｌｇｅｎｓｉｓ）自然群体单株采集种子胚乳的三种等位酶的遗化变化情况。对苹...

Boundary Characterization Experiment Series Overview

Ocean acoustic propagation and reverberation in continental shelf regions is often controlled by the seabed and sea surface boundaries. A series of three multi-national and multi-disciplinary experiments was conducted between 2000-2002 to identify and measure key ocean boundary characteristics. The frequency range of interest was nominally 500-5000 Hz with the main focus on the seabed, which is generally considered as the boundary of greatest importance and least understood. Two of the experiments were conducted in the Mediterranean in the Strait of Sicily and one experiment in the North Atlantic with sites on the outer New Jersey Shelf (STRATAFORM area) and on the Scotian Shelf. Measurements included seabed reflection, seabed, surface, and biologic scattering, propagation, reverberation, and ambient noise along with supporting oceanographic, geologic, and geophysical data. This paper is primarily intended to provide an overview of the experiments and the strategies that linked the various measurements together, with detailed experiment results contained in various papers in this volume and other sources

黄土丘陵区纸坊沟流域农业生态安全预警分析

为黄土丘陵区生态安全预警及其建设提供科学依据。【方法】以纸坊沟流域近70年代表年份生态安全态势及影响因子的分析为基础,参考压力-状态-响应(PSR)模型建立农业生态安全预警指标体系。运用层次分析法(AHP)和德尔菲法(Delphi)确定指标权重,采用综合指数法计算生态安全质量值,用演化轴解释生态安全预警模式,定量评价该流域1938~2005年的农业生态安全状况,并预测2015年的发展趋势。【结果】纸坊沟流域1938年处于蓝灯区,无需预警;1958年为黑灯区,需作生态安全恶化速度预警;1975和1985年处于红灯区,需作生态安全较差状态预警;1995年处于黄灯区,2005和2015年继续向良好方向演化,均不需预警,但从发展趋势来看,预计人口密度于2020年左右进入警戒状态。【结论】研究结果与该流域的实际情况相符,该指标体系和生态安全预警模型可以应用于黄土丘陵区。

半湿润地区农田夏玉米氮肥利用率及土壤硝态氮动态变化

以土垫旱耕人为土为供试土壤,通过田间试验,研究了不同施氮量下(0、45、90、135和180 kg.hm-2)夏玉米生育期土壤剖面NO3--N的变化特征、氮素利用率及施氮量与土壤NO3--N残留的关系.结果表明:在整个生育期内,土壤NO3--N含量均以0~20 cm土层最高,且施氮量越高,NO3--N含量也越高;0~60 cm土层NO3--N含量变化显著,60~100 cm土层NO3--N含量变化不大.夏玉米整个生育期,受玉米对氮素的需求和降雨的影响,0~100cm土层NO3--N累积量呈波动式降低趋势;当施氮量小于135 kg.hm-2时,作物氮肥利用率随施氮量的增加而显著提高,但当施氮量超过135 kg.hm-2时呈下降趋势.氮肥农学利用率随施氮量的增加而减小,氮肥生理利用率随施氮量的增加而递增.土壤中残留NO3--N与施氮量呈极显著正线性相关关系(R2=0.957**,n=5);施氮处理籽粒产量显著高于不施氮处理(P<0.05);施氮量与籽粒产量呈极显著正线性相关关系(R2=0.934**,n=5).在本试验条件下,夏玉米生长季适宜施氮量为135 kg.hm-2.该施氮水平可保证效益和环境的双赢.

Vulcanization of polybutadiene latex induced by Co-60 gamma radiation

Polybutadiene latex (PBL) vulcanization induced by Co-60 radiation and the influence of dose on crosslinking were investigated. Morphology and particle size distribution were examined by AFM and a particle size analyzer. The casting films were characterized for their swelling and mechanical properties as a function of dose.