Theoretical investigation of LaC3n+ (n = 0, 1, 2) clusters by density functional theory

LaC3n+ (n = 0, 1, 2) clusters have been studied using B3LYP (Becke 3-parameter-Lee-Yang-Parr) density functional method. The basis set is Dunning/ Huzinaga valence double zeta for carbon and [2s2p2d] for lanthanum, denoted LANL1DZ. Four isomers are presented for each cluster; two of them are edge binding isomers with C-2 upsilon symmetry, the other two are Linear chains with C-infinity upsilon symmetry. Meanwhile, two spin states for each isomer, that is, singlet and triplet for LaC3+, doublet and quartet for LaC3 and LaC32+, respectively, are also considered. Geometries, vibrational frequencies, infrared intensities, and other quantities are reported and discussed. The results indicate that at some spin states; the C-2 upsilon symmetry isomers are the dominant structures, while for the other spin states, linear isomers are energetically favored. (C) 1998 John Wiley & Sons, Inc.

新型无机高分子混凝剂聚硅酸铝铁的应用及动态模拟实验研究

目前在废水处理领域，其处理方法有生物化学法、离子交换法、化学氧化法、电渗析法和混凝沉淀法等，而应用最普遍、并且成本较低的处理方法仍然是混凝沉淀法。它几乎可以用于各种工业废水和城市污水的预处理、中间处理和最终处理，以及污泥处理当中。混凝剂性能是影响混凝沉淀处理效果的关键因素。因此，研制和开发高效能、低毒无公害、低能耗、低成本的新型混凝剂就显得非常重要。我们自行研制成功的聚硅酸铝铁类系列混凝剂(PSAFC、PSAFS、PSAFCS)，作为新型的无机高分子复合型混凝剂，属于水溶性无机高分子物质。其实质为铝、铁盐类水解过程的中间产物与硅酸根阴离子等基团的结合体。本文在前人工作的基础上，主要研究了复合型聚硅酸铝铁类混凝剂(PSAFCS)的配制、各类不同配比混凝剂的粘度、ζ电位与混凝效果的关系、以及对印染废水、垃圾渗滤液和造纸废水的静态和动态混凝处理效果等，得到了以下相应的认识和结论。1．在聚硅酸铝铁类混凝剂配制阶段，由于SiO_2的引入将影响混凝剂的聚合度、Zeta电位、存放时间和混凝处理效果等，本论文测定出水玻璃模数K，其值为2.86。而且，硅的存在使混凝剂形态发生了改变，吸附架桥能力增强，增加了混凝剂聚合度，但在某种程度上降低了混凝剂的电中和能力。2．考虑到铝和铁在聚合反应中速度的差异，铁具有极强的亲OH~-能力，能极快地与OH~-形成多羟基聚合物；而铝的亲OH~-能力相对较弱，聚合反应速度缓慢。为了能够使铝盐与铁盐交叉共聚，在配制混凝剂时需采取先加含铝原料，稳定后再加含铁原料的方式。碱化度B是在制备混凝剂时的一个重要操作指标，寻求最佳的碱化度值有利于制备出高效的混凝剂。3. 在PSAFCS中，硫酸根的引入在某种程度上可以增加混凝剂的聚合度和稳定性，增强絮凝能力。并且不同SO_4~(2-)/CI~-比的混凝剂在混凝效果上存在差异。另外，目前市场上工业硫酸与工业盐酸价格相差不大，而工业硫酸的当量数是工业盐酸的1.94倍，故用硫酸代替部分盐酸可降低酸耗成本。4．Ferron逐时络合比色法被广泛应用于铝盐、铁盐溶液的形态分析，并且可得出较好的分析结果。但是在铝铁共存的溶液中进行形态分析，尚有一定困难。5．混凝剂的表观分子量与粘度之间存在着正比关系，通过测定，聚硅酸铝铁类混凝剂的增比粘度随着存放时间有一定的上升趋势，其中硫酸盐型混凝剂(PSAFS)的趋势最明显，存放时间相对较短。盐酸盐型混凝剂(PSAFC)的增比粘度与PSAFS和PSAFCS相比最小。说明其聚合度最小，硫酸根的介入可使聚硅酸铝铁类混凝剂的聚合度增大。比浓粘度与质量浓度之间存在着一定的正相关关系。6. 混凝剂的ζ电位值由于硅的引入而变得有正有负，这与不同类型混凝剂中硅、铝、铁的相对含量有关。一般SiO_2:(Al+Fe)比值大于1:2时，ζ电位为负值。7．系统阐述了PSAFC和PSAFS在印染废水处理中的应用，经过混凝处理的印染废水出水中，残留硅的含量在0.16mg／L～1.68mg／L之间；残留铁的含量在22.4 μg／L～0.52mg／L之间；残留铝的含量在0.1lmg／L～2.60mg／L之间，而且残留铝含量与碱化度B值之间有着很好的负相关关系，即随着混凝剂碱化度值的增大，残留铝含量降低。系列聚硅酸铝铁类混凝剂对印染废水的色度、浊度、COD等都有较好的去除效果。8．第一次把聚硅酸铝铁类混凝剂应用于垃圾填埋场渗滤液的处理上，通过混凝一臭氧氧化处理后，垃圾渗滤液的BOD_去除率达75.4％、COD去除率达70．6％、色度去除率达94％，其出水水质基本接近我国生活垃圾填埋场污染控制标准(GBl6889--1997)二级标准。9．首次在实验室内进行动态模拟实验，我们用自行设计的动态处理装置，选用13号PSAFCS型混凝剂对造纸废水进行试验，混凝剂SiO_2:Al:Fe比值为1:0.75:0.75，ζ电位为10.8毫伏。在最佳水力条件和最佳混凝剂投量的情况下，对造纸废水的COD去除率达92.5％、色度去除率达96.9％，达到国家造纸工业污染物排放一级标准，说明复合型聚硅酸铝铁类混凝剂(PSAFCS)对造纸废水有着优异的去除效果。

注意在视觉刺激位置编码中的作用

There is extensive agreement that attention may play a role in spatial stimmlus coding (Lu & Proctor, 1995). Some authors investigated the effects of spatial attention on the spatial coding by using spatial cueing procedure and spatial Stroop task. The finding was that the stroop effects were modulated by spatial cueing. Three hypotheses including attentional shift account, referential coding account, and event integration account were used to explain the modulation of spatial cueing over the spatial Stroop effects. In these previous studies, on validly cued trials, cue and target not only appeared at the same location, but also in the same object, which resulted in both location and object cued. Consequently, the modulation of spatial attentional cueing over spatial Stroop effects was confounded with the role of object-based attention. In the third chapter of this dissertation, using a modification of double rectangles cueing procedure developed by Egly, Driver and Rafal (1994) and spatial Stroop task employed by Lupiáñez and Funes (2005), separate effects of spatial attention and object-based attention on the location code of visual stimuli were investigated. Across four experiments, the combined results showed that spatial Stroop effects were modulate by object-based attention, but not by location-based attention. This pattern of results could be well explained by event integration account, but not by attentional shift account and referential coding account. In the fourth chapter, on the basis of the prior chapter, whether the modulation of attentional cueing on location code occurred at the stage of perceptual identification or response choice was investigated. The findings were that object-based attention modulated spatial Stroop effects and did not modulate the Simon effects, whereas spatial attention did not modulate Stroop and Simon effects. This pattern of results partially replicated the outcome of the previous chapter. The previous studies generally argued that the conflicts of spatial Stroop task and Simon task respectively occurred at at the stage of perceptual identification and response choice. Therefore, it is likely to conclude that the modulation of attention over spatial Stroop effect was mediated by object-based attention, and this modulation occurred at the stage perceptual identification. Considering that the previous studies mostly investigated the effects of attention captured by abrupt onset on the spatial Stroop effects, few studies investigated the effects of attention captured by offset cue on the spatial Stroop effects. The aim of the fifth chapter was to investigate the role of attention induced by offset and abrupt onset cue in the spatial Stroop task. These results showed that attention elicited by offset cue or abrupt onset cue modulated the spatial Stroop effects, which reconciled with event integration account.