Dielectric features of two grades of bi‐oriented isotactic polypropylene

The dielectric properties of two grades of bi‐oriented isotactic polypropylene were studied with a variety of techniques: breakdown field measurements, dielectric spectroscopy, thermally stimulated depolarization currents (Is), and direct‐current (dc) conduction I values. Standard polypropylene (STPP) and high‐crystallinity polypropylene (HCPP) films were investigated. Measurements were carried out over a wide temperature range (?150°C/+125°C). The breakdown fields in both materials showed a very small difference. On the other hand, the dielectric losses and dc conduction I values were significantly lower in HCPP. Both materials showed a decrease in the dielectric loss versus temperature in the range 20–90°C; this is favorable for application in alternating‐current power capacitors. The analysis of the dc I value allowed us to find evidence of two main conduction mechanisms: (1) below 80°C in both materials, a hopping mechanism due to the motion of electrons occurred in the amorphous phase, and (2) above 80°C, ionic conduction occurred in HCPP, and hopping conduction occurred in STPP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42224.     

Effects of equal‐channel,multiple‐angular extrusion on the physical and mechanical properties of glassy polymers

Through the examples of polycarbonate and poly(methyl acrylate), the evolution of the structure and properties of glassy polymers processed by equal‐channel multiple‐angular extrusion (ECMAE) were studied. It was demonstrated that ECMAE allowed the substantial improvement of the set of strain–strength characteristics of these materials, regardless of the direction of loading applied. With the use of the data from scanning electron microscopy, differential scanning calorimetry, and dilatometry, we found that the simultaneous growth in the strength, plasticity, and impact resistance was related to the formation of a net of biaxially oriented polymeric chains, the decrease in the free volume, and the reinforcement of intermolecular interaction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42180.     

Polypropylene/silica micro‐ and nanocomposites modified with poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)

The effects of different silica loadings and elastomeric content on interfacial properties, morphology and mechanical properties of polypropylene/silica 96/4 composites modified with 5, 10, 15, and 20 vol % of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) SEBS added to total composite volume were investigated. Four silica fillers differing in size (nano‐ vs. micro‐) and in surface properties (untreated vs. treated) were chosen as fillers. Elastomer SEBS was added as impact modifier and compatibilizer at the same time. The morphology of ternary polymer composites revealed by light and scanning electron microscopies was compared with morphology predicted models based on interfacial properties. The results indicated that general morphology of composite systems was determined primarily by interfacial properties, whereas the spherulitic morphology of polypropylene matrix was a result of two competitive effects: nucleation effect of filler and solidification effect of elastomer. Tensile and impact strength properties were mainly influenced by combined competetive effects of stiff filler and tough SEBS elastomer. Spherulitic morphology of polypropylene matrix might affect some mechanical properties additionally. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41486.     

IPO遴选管制下审计师地缘关系与IPO机会

以我国2007—2009年IPO申请公司为样本,研究IPO遴选管制背景下的审计师地缘关系对IPO机会的影响。研究发现,由于IPO遴选管制,在金融危机背景下,聘请当地事务所的IPO申请公司其IPO申请通过发审委审核的可能性显著大于聘请异地事务所的IPO公司,审计师地缘关系对企业IPO机会产生重要影响。     

"Age differences in psychosocial predictors of positive and negative affect: A longitudinal investigation of young, midlife, and older adults": Correction to Windsor and Anstey (2010).

Reports an error in "Age differences in psychosocial predictors of positive and negative affect: A longitudinal investigation of young, midlife, and older adults" by Tim D. Windsor and Kaarin J. Anstey (Psychology and Aging, 2010[Sep], Vol 25[3], 641-652). Contains an error in Figure 3, on page 649. The correction discusses where to find the correct data. (The following abstract of the original article appeared in record 2010-18944-009.) Research has consistently shown that despite aging-related losses, older adults have high levels of emotional well-being relative to those in young and midlife adults. We aimed to contribute to knowledge around the factors that predict emotional well-being over the life course by examining age group differences in associations of positive and negative social exchanges and mastery beliefs with positive and negative affect in a sample of 7,472 young, midlife, and older adults assessed on 2 measurement occasions, 4 years apart. Results from structural equation models indicated lower levels of negative affect with advancing age. Mastery was consistently related to higher well-being, with the strongest associations evident for young adults. Older adults reported the most frequent positive and least frequent negative social exchanges; however, associations of social relations with affect tended to be stronger among young and midlife adults relative to older adults. Results are discussed in the context of life course perspectives on goal orientations and self-regulatory processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The influence of macromolecular architecture on the critical aggregation concentration of large amphiphilic starch derivatives

A range of hyperbranched emulsifiers were prepared by reaction between starch and 2-octen-1-yl succinic anhydride (OSA, commonly used in the food industry), under slightly basic conditions in water, leading to starches bearing hydrophobic OSA groups randomly distributed along the chains. By using different starch backbones and varying the amount of OSA during the synthesis, amphiphilic OSA-modified starches were obtained that formed aggregates in water and having controlled structural parameters. These parameters were characterized using ¹H NMR, multiple-angle laser light scattering and size-exclusion chromatography. The critical aggregation concentration (CAC) was measured for samples with different levels of OSA modification, of macromolecular size and degree of starch branching. Increasing the dispersity in macromolecular size and/or degree of OSA substitution noticeably decreased the CAC. The results are interpreted in terms of the branching structure and conformation of the modified starches: all findings can be understood in terms of the various influences of molecular size, composition and flexibility. The structural factors affecting the CAC of large hyperbranched surfactants are found to be similar to those seen with smaller and simpler branched synthetic surfactants.     

Forum A historical context for theories underpinning the production of the built environment

The quest for ‘theory’ in the Building Research & Information special issue ‘Developing Theories of the Built Environment’ (36(3) 2008) needs to be understood within a larger historical and political context. It would benefit from engaging with a rich vein of work on the production of the built environment over the last 30 years. Theory inherently develops in the political context in which it exists; if it fails to do so, it may be dangerous. This commentary traces the intellectual underpinning concerned with understanding the process of change in the built environment, particularly the result of changes in social relations and the social labour process. The production of the built environment is seen as encompassing all the social processes concerned with producing the built environment, built products, buildings and infrastructure, and out of natural resources, whilst consumption is applied to all the processes involved in consuming these, including the well-being of tenants. And between these are situated the processes of exchange, distribution, and circulation, involving complex webs of relations between developers, builders, and landlords and landowners. The challenge is not only to engage and learn from past work, but also to state explicitly what is currently driving the need for a theory (or set of theories).

La quête de la « théorie » dans ce numéro spécial de Building Research & Information consacré aux théories du développement du milieu bâti (volume 36(3), 2008) doit être comprise dans un contexte historique et politique plus large. Elle aurait intérêt à s'appuyer sur les nombreux travaux concernant la production du cadre bâti publiés au cours de ces 30 dernières années. La théorie se développe, de manière inhérente, dans le contexte politique dans lequel elle existe; dans le cas contraire, la situation pourrait devenir dangereuse. Cet article analyse le raisonnement intellectuel sous-jacent concernant la compréhension du processus de changement dans le milieu bâti, notamment les conséquences des changements dans les relations sociales et dans le processus social du travail. La production du cadre bâti est considérée comme englobant tous les processus sociaux liés à la production du cadre bâti, des produits de construction, des bâtiments et des infrastructures et aux ressources naturelles alors que la consommation s'applique à tous les processus qui entrent en jeu dans la consommation de ceux-ci, y compris le bien-être des occupants. Entre ces deux notions, on trouve les processus d'échange, de distribution et de circulation qui font intervenir des réseaux de relations entre promoteurs, constructeurs, bailleurs et propriétaires fonciers. La difficulté ne vient pas seulement du fait qu'il faut tirer profit des travaux et de l'expérience passés mais qu'il faut également expliquer ce qui motive aujourd'hui la nécessité d'une théorie (ou d'un ensemble de théories).

Mots clés: cadre bâti, cadres conceptuels, consommation, processus de travail, cadre politique, production, relations sociales     

乡村关系研究的视野与路径——以甘肃省若干乡镇为例

村民自治语境下的乡村关系应该赋予新的时代内涵,如何处理好乡村关系是个理论问题,要具体分析政策法规的规定,还要调查多年来乡村关系形成的历史痕迹对乡村关系的影响。在调查研究的基础上,分析了不同类型的乡村关系,提出了新时期定位乡村关系必须处理好的几个问题,并在方法上予以指导。     

UNIQUENESS CONDITIONS OF CL-STRUCTURES IN GL-STRUCTURE EQUIVALENCE CLASSES OF SYSTEM RECONSTRUCTABILITY ANALYSIS

This paper first introduces the basic notions of overall systems with logical relations, their subsystems, structure representation graphs, sets of H-structures and G-structures with logical relations S _H ^L and S _G ^L, immediate refinement and aggregate with logical relations, structure-graph mappings r_V ^L, r_G ^L, etc., and the notions of inclusiveness with logical relations, upper bounding and lower bounding with logical relations. Then it proves the sufficient conditions under which representation graphs R ^L form a lattice. By defining the least upper bound and largest lower bound of (R^L, ) and recommending a lemma on distributivity, this paper proves the sufficient conditions under which G-structures with logical relations form Boolean lattices. Finally after defining the M-structures and C-structures with logical relations, i.e. M-structures and C-structures, this paper proposes the sufficient conditions for the uniqueness of C-structures in G-structure equivalence classes, and proves that the C ^L-structure is the least refined GL-structure in equivalence class S _G ^L/r _G ^L.