Polymer Brushes: From Self-Consistent Field Theory to Classical Theory

We consider planar brushes formed by end-grafted polymers with moderate to strong excluded-volume interactions. We first rederive the mean-field theory and solve the resulting self-consistent equations numerically. In the continuum limit, the results depend sensitively on a single parameter, beta, whose square is the ratio of the scaling prediction for the brush height to the unperturbed polymer radius of gyration, and which measures therefore the degree to which the polymers are stretched. For large values of beta, the density profile is close to parabolic, as predicted by the infinite-stretching theory of Zhulina et al. and of Milner et al. As beta decreases, the profile deviates strongly from a parabolic one. By calculating the most probable paths and comparing their contribution to various properties with those obtained from the full self-consistent theory, we determine the effect of the fluctuations about such paths. At large values of beta, these effects are very small everywhere. As beta decreases, fluctuation effects on the density profile become increasingly important near the grafting surface, but remain small far from it. For all values of beta, we find that polymer paths which begin far from the grafting surface are strongly, and almost uniformly, stretched throughout their length, including their free end points. Paths which begin close to the grafting surface are also stretched, but they initially move away from the grafting surface before reaching a maximum height and then returning to it. The classical theory is then derived from the self-consistent field equations by retaining, for each end point location, only that single trajectory which minimizes the free energy of the system. This free energy contains an entropy, of relative weight beta-1, which arises from the distribution of end points. Even for brushes which are only moderately stretched, the results of the classical theory for the brush profile and polymer end point distribution agree well with those of the full self-consistent theory except near the grafting surface itself. There the density profile as calculated in the self-consistent theory shows a characteristic decrease which is not captured by the classical theory. However it does capture the fact that the individual polymer paths are stretched in general throughout their length, including the end points, and yields nonmonotonic paths for polymers whose end points are close to the grafting surface. In addition, it reproduces extremely well the form of the density distribution far from the grafting surface, which is essentially Gaussian. This results from the fact that the stretching energy dominates the interaction energy of those polymers which extend far from the grafting surface, so that their behavior is nearly ideal. In the limit of infinite stretching, beta --> infinity, the theory reduces to that of Zhulina et al. and of Milner et al.     

中国古代"赵氏孤儿"型故事简述

"赵氏孤儿"型故事从唐代以来就以各种形式在小说及戏曲中出现,明清两代是"赵氏孤儿"型故事的繁荣阶段.当代金庸先生是最擅长利用此类模式的大家.     

从量子谱到经典轨道:圆形腔中的弹子球

用半经典的方法来研究粒子经典运动已成为处理某些量子问题必不可少的工具.周期轨道理论已经成为人们研究定态体系的量子谱和所对应粒子经典运动的关系的主要工具.本文应用周期轨道理论,运用量子谱函数,这种量子谱函数的傅利叶变换包含了体系内许多经典轨道的信息.以二维无限深圆环势阱为例,利用它们的能量本征值和本征函数,用态密度公式计算周期轨道的情况下,量子能态密度的傅立叶变换p(L).在|p(L)|2随L变化的函数图像中得到了一系列的峰,量子峰的位置与用经典方法得到的轨道长度符合得很好,这不但证明经典行为和量子行为具有很好的对应,同时也显示这种半经典的方法是连接经典与量子的一座很好的桥梁.     

中国古典园林对精神文化的形式表达

从中国古典园林与文化有着千丝万缕的联系入手,强调中国古典园林所追求的精神特征是其形式表达的必然性所在,它与中国的哲学文化、社会体制以及其他一些文化现象是密不可分的,分析了中国古典园林在心态层面的特征,认为其在精神表达与诉求方面具有独特的文化内涵,即"天人合一"的自然观、"以礼和天"的礼制文化以及归隐、求安的隐逸观.探讨了中国古典园林形式对精神文化的具体表达,指出其在自然观的形式表达方面崇尚自然、万物有道,因地制宜、巧于因借,摹写自然、仿造山水;在分析对隐逸观的形式表达方面,着重于园林题名匾额对隐逸文化的表达、园林中含蓄的形体表达方式对"隐"的体现;从宅园的布局与宅的营造上探讨了中国古典园林的礼制与秩序:在此基础上细致并深入地感悟古人的精神世界,认为中国人的精神模式是古典园林造型的源泉,山水、植物、建筑及其组合形态所表达的正是人的精神追求境界.     

Universal Features of Personality Traits From the Observer's Perspective: Data From 50 Cultures.

To test hypotheses about the universality of personality traits, college students in 50 cultures identified an adult or college-aged man or woman whom they knew well and rated the 11,985 targets using the 3rd-person version of the Revised NEO Personality Inventory. Factor analyses within cultures showed that the normative American self-report structure was clearly replicated in most cultures and was recognizable in all. Sex differences replicated earlier self-report results, with the most pronounced differences in Western cultures. Cross-sectional age differences for 3 factors followed the pattern identified in self-reports, with moderate rates of change during college age and slower changes after age 40. With a few exceptions, these data support the hypothesis that features of personality traits are common to all human groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Between-Individual Comparisons in Performance Evaluation: A Perspective From Prospect Theory.

This article examines how between-individual comparisons influence performance evaluations in rating tasks. The authors demonstrated a systematic change in the perceived difference across ratees as a result of changing the way performance information is expressed. Study 1 found that perceived performance difference between 2 individuals was greater when their objective performance levels were presented with small numbers (e.g., absence rates of 2% vs. 5%) than when they were presented with large numbers (e.g., attendance rates of 98% vs. 95%). Extending this finding to situations involving trade-offs between multiple performance attributes across ratees, Study 2 showed that the relative preference for 1 ratee over another actually reversed when the presentation format of the performance information changed. The authors draw upon prospect theory (D. Kahneman & A. Tversky, 1979; A. Tversky & D. Kahneman, 1981) to offer a theoretical framework describing the between-individual comparison aspect of performance evaluation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

作品异本与作品集异本——以郭沫若后期作品为例

郭沫若后期(1949-1978年)的许多诗作呈现了不同的文本形态,有的是具体作品多次修改,但没有注明;还有的是作品集就有差异很大的版本,尤其是单行本<沫若诗词选>和<郭沫若全集>中的<沫若诗词选>异本现象最为突出.     

Critical Success Factors for PPPs in Infrastructure Developments: Chinese Perspective

With the rapid growth of the Chinese economy, the desperate demand for infrastructure developments has created bottlenecks in the country’s sustainable development. Infrastructure investment could not be funded completely by the government alone. Taking Beijing as an example, there will be about 2,400 infrastructure projects to be developed during 2006–2010 with a total investment of over RMB 470 billion, which may impose budgetary pressure on the government. As a result, public-private partnership (PPP) could be considered as a favorable option to help provide these rapidly demanded public works and services. In order to investigate the potential for adopting PPPs in the People’s Republic of China, this paper aims to explore the critical success factors (CSFs) necessary to conduct PPP projects. The views from Chinese experts were collected via an empirical questionnaire survey. The respondents were invited to rate a total of 18 CSFs that contribute to the success of PPP projects as gleaned from the contemporary literature. The results of this survey were analyzed by the factor analysis technique. The findings showed that the 18 CSFs could be grouped into five underlying factors including: Factor 1—stable macroeconomic environment; Factor 2—shared responsibility between public and private sectors; Factor 3—transparent and efficient procurement process; Factor 4—stable political and social environment; and Factor 5—judicious government control.     

Professional Burnout in the Mirror: A Qualitative Study From a Lacanian Perspective.

This article reports on a qualitative interview study that examined the job experiences of a group of burned-out professionals (n = 15). The authors studied the meanings these professionals associate with incidents in their intersubjective relations, as well as how they relate these incidents to their identity. The interpretation of the data starts from Lacanian psychoanalytic theory on identity (Lacan's "schema of the 2 mirrors"). The authors show how the concepts under discussion enable one to trace burnout dynamics in the relation between subject and other. A tripartite conceptual model that accounts for dynamic processes is presented. Each process is formulated conceptually on the basis of Lacan's schema of the 2 mirrors and is discussed with narrative data drawn from interview research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CSP板卷及冷轧镀锌板表面缺陷分析

为研究CSP及其后续产品的表面质量,对马钢CSP、冷轧和镀锌生产线投产以来出现的主要表面缺陷进行分析,研究结果表明:夹杂类缺陷、边裂和氧化铁皮压入是热轧板卷的主要缺陷,这些缺陷将不同程度地遗传到后续产品.产生表面缺陷的主要原因有钢水质量、连铸和轧制工艺、除鳞工艺和后续设备自身状况等,分析认为提高钢水和连铸坯质量是消除热轧板卷和后续产品表面缺陷的关键.