SrB_6O_(10)中铕和铽的发光

大部分稀土离子都有变价行为,稀土的功能特性与其价态密切相关。铕和铽都有变价行为,Eu~(3+)和Tb~(3+)为电子组态共轭的一对稀土离子,是发光材料的重要激活离子。本文首次在空气中合成了SrB_6O_(10):xEu,yTb荧光粉,研究了它们的光谱特征,发现该体系中Eu~(3+),Tb~(3+)和Eu~(2+)离子共存,并随其掺入Tb~(3+)离子浓度的增加,Eu~(2+)的荧光相对发射强度增强。我们用已提出的关于稀土离子对之间电子组态共轭性与价态变化相关性的结论对此现象进行了解释。这一现象的发现有助于了解固相反应中共轭稀土离子对间的电子转移过程,为新型异常价态稀土化合物的预测与合成,为新材料的设计与制备提供了重要依据。

Studies on structure-property relationship between color reagents and contrast of their color reactions with cerium by topological indices

In this paper, three topological indices A(m1), A(m2) and A(m3) have been applied to multivariate analysis in structure property relationship studies. The topological indices oi fourty-three asymmetrical phosphono bisazo derivatives of chromotropic acid have been calculated, The structure-property relationship between color reagents and contrast of color reactions with cerium has been studied by A, indices and structure selective factors, Good results have been obtained.

拓扑指数法研究稀土显色剂结构与铈显色反应对比度的关系

计算了４３种不对称变色酸双偶氮膦酸型显色剂的Ａ_ｍ拓扑指数，并将其与结构选择性因子相结合，用于偶氮类显色剂结构与铈显色反应对比度的相关性研究，讨论了显色剂结构对拓扑指数及对比度的影响。

铕和铽与3,4-呋喃二甲酸双核配合物的合成、表征及其晶体结构

本文首次合成了铕(Ⅲ)和铽(Ⅲ)与3,4-呋喃二甲酸配合物,研究了它们的IR、DTA、TG、DTG和荧光光谱等性质,并完成了单晶的晶体分析。结果表明,配合物为〔Ln·HL_2(H_2O)_2〕_2·2H_2O(Ln=Eu(Ⅲ),Tb(Ⅲ);H_2L=3,4-呋喃二甲酸),属单斜晶系,P2/c空间群,Z=2,晶胞参数对铕和铽配合物分别为α=10.842(1),10.801(4);b=8.725(2),8.664(2);c=16.366(4),16.308(6)A;β=93.50(1),93.67(3)°;V=1545.3(5),1523.0(8)A~3。

A nitrogen budget of the Changjiang river catchment

Based on 1997-1998 field investigations in the Changjiang river mouth, rain sampling from the river's upper reaches to the mouth, historical data, and relevant literature, the various sources of Total Nitrogen (TN) and Dissolved Inorganic Nitrogen (DIN) in the Changjiang river catchment and N transport in the Changjiang river mouth were estimated. The export fluxes of various form of were mainly controlled by the river runoff, and the export fluxes of NO3-N, DIN and TN in 1998 (an especially heavy flood year) were 1438 103 tonnes (t) yr(-1) or 795.1 kg km(-2) yr(-1) 1746 10(3) t yr(-1) or 965.4 kg km(-2) yr(-1) and 2849 10(3) t yr(-1) or 1575.3 kg km(-2) yr(-1), respectively. The TN and DIN in the Changjiang river came mainly from precipitation, agricultural nonpoint sources, N lost from fertilizer and soil, and point sources of industrial waste and residential sewage discharge, which were about 56.2% and 62.3%, 15.4% and 18.5%, 17.1% and 14.4%, respectively, of the N outflow at the Changjiang river mouth; maximum transport being in the middle reaches.

Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

有限元结构动力分析的广义特征值的神经计算

广义特征值问题是结构动力分析计算的关键之一.应用Reyle igh极小值原理,将神经网络的能量函数的极小点对应于广义特征值问题的最小特征值所对应的特征向量,在神经网络朝着能量函数极小点运动的同时得到了最小特征值所对应的特征向量的精确解答.从特征值的变分特性出发,给出了基于罚函数法的其他特征值的神经网络求解方案,从而在理论上给出了广义特征值问题的所有特征值的神经网络求解方法.仿真计算表明,该方法正确、有效可行.

客户／服务器环境下的OS／22·1操作系统

ＯＳ／２２·１是当今客户／服务器计算模式的首选操作系统之一。本文对ＩＢＭＯＳ／２２·１操作系统所具备的，对客户／服务器计算模式的各种支持功能作了详细的介绍。

三维荧光光谱研究溶解有机质与汞的相互作用

随着荧光光谱技术的进展 ,三维荧光光谱被广泛应用于研究各种天然水体中溶解有机质 (包括腐殖质 )的各种环境行为 .本文利用三维荧光光谱和荧光猝灭滴定技术研究河流溶解有机质与Hg(Ⅱ )的相互作用 .结果表明 ,溶解有机质中含有的3种类型荧光基团都能够不同程度地被Hg(Ⅱ )猝灭 ,并采用非线性回归分析拟合出Hg(Ⅱ )与 3种荧光基团之间的条件稳定常数 .pH值对Hg(Ⅱ ) DOM体系具有显著影响 .Cl-对Hg(Ⅱ ) DOM体系具有强烈的竞争作用 .Ca(Ⅱ )能够 使Hg(Ⅱ ) DOM体系荧光增强 ,而Mg(Ⅱ )对之影响很小 .此外 ,Cu(Ⅱ )与Hg(Ⅱ ) 都是DOM的荧光猝灭剂 ,但是其猝灭机理存在差异

季节性缺氧水库甲基汞的产生及其对下游水体的影响

本文采用蒸馏-乙基化结合GC-CVAFS法对贵州红枫湖水库及其各人库和出库河流中的甲基求日寸空分布和控制因素进行研究在春、秋、冬季节总甲基汞浓度和分布无明显时空变化, 在0.053-0.333ng/L之间，春季河流是水库甲基汞一个重要的输入源夏季水库下层甲基汞显著升高, 缺氧层最高值达0.923ng/L，同时发现, 缺氧层升高的甲纂未主要来自于水体自己产生或上层水体甲基汞的沉降, 而不是来自于沉积物的释放各季节湖水和河流样异, 的总甲基未和溶解氧存在显著的负相关关系,Personal相关系数r为-0.81(78)。在春、秋、冬季节溶解态甲基汞比例略低于颗粒态甲基汞, 但在夏季, 特别是缺氧层甲基汞主要以溶解态存在夏季河流入水经水库蓄水后到再流出时已经富含甲基未出库河流中总甲基汞浓度已达到各人湖河流总甲基汞平均值的5.5倍, 很明显在夏季红枫湖已成为下游水体甲基未的输人源, 必将会对下游生态系统产牛一定影响

A Computational Model for the Acquisition and Use of Phonological Knowledge

Does knowledge of language consist of symbolic rules? How do children learn and use their linguistic knowledge? To elucidate these questions, we present a computational model that acquires phonological knowledge from a corpus of common English nouns and verbs. In our model the phonological knowledge is encapsulated as boolean constraints operating on classical linguistic representations of speech sounds in term of distinctive features. The learning algorithm compiles a corpus of words into increasingly sophisticated constraints. The algorithm is incremental, greedy, and fast. It yields one-shot learning of phonological constraints from a few examples. Our system exhibits behavior similar to that of young children learning phonological knowledge. As a bonus the constraints can be interpreted as classical linguistic rules. The computational model can be implemented by a surprisingly simple hardware mechanism. Our mechanism also sheds light on a fundamental AI question: How are signals related to symbols?

Exploring perspectives on Human Resource Development: an introduction.

The problem and the solution. This issue overview presents a brief justification for adopting a multiperspectival approach to theory and practice in human resource development (HRD). It is argued that such an approach has the potential to add theoretical depth and breadth to HRD discourse as well as contributing to reflective HRD practice.The contributions are then briefly introduced.

Shh/Boc signaling is required for sustained generation of ipsilateral projecting ganglion cells in the mouse retina

Sonic Hedgehog (Shh) signaling is an important determinant of vertebrate retinal ganglion cell (RGC) development. In mice, there are two major RGC populations: (1) the Islet2-expressing contralateral projecting (c)RGCs, which both produce and respond to Shh; and (2) the Zic2-expressing ipsilateral projecting RGCs (iRGCs), which lack Shh expression. In contrast to cRGCs, iRGCs, which are generated in the ventrotemporal crescent (VTC) of the retina, specifically express Boc, a cell adhesion molecule that acts as a high-affinity receptor for Shh. In Boc −/− mutant mice, the ipsilateral projection is significantly decreased. Here, we demonstrate that this phenotype results, at least in part, from the misspecification of a proportion of iRGCs. In Boc−/− VTC, the number of Zic2-positive RGCs is reduced, whereas more Islet2/Shh-positive RGCs are observed, a phenotype also detected in Zic2 and Foxd1 null embryos.