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Local Forces (local + force)
Selected AbstractsFluorophores as Optical Sensors for Local Forces,CHEMPHYSCHEM, Issue 12 2009Stefan Marawske Abstract The main aim of this study is to investigate correlations between the impact of an external mechanical force on the molecular framework of fluorophores and the resultant changes in their fluorescence properties. Taking into account previous theoretical studies, we designed a suitable custom-tailored oligoparaphenylenevinylene derivative (OPV5) with a twisted molecular backbone. Thin foils made of PVC doped with 100 nM OPV were prepared. By applying uniaxial force, the foils were stretched and three major optical effects were observed simultaneously. First, the fluorescence anisotropy increased, which indicates a reorientation of the fluorophores within the matrix. Second, the fluorescence lifetime decreased by approximately 2.5,% (25 ps). Finally, we observed an increase in the emission energy of about 0.2,% (corresponding to a blue-shift of 1.2 nm). In addition, analogous measurements with Rhodamine 123 as an inert reference dye showed only minor effects, which can be attributed to matrix effects due to refractive index changes. To relate the observed spectroscopic changes to the underlying changes in molecular properties, quantum-chemical calculations were also performed. Semiempirical methods had to be used because of the size of the OPV5 chromophore. Two conformers of OPV5 (C2 and Cisymmetry) were considered and both gave very similar results. Both the observed blue-shift of fluorescence and the reduced lifetime of OPV5 under tensile stress are consistent with the results of the semiempirical calculations. Our study proves the feasibility of fluorescence-based local force probes for polymers under tension. Improved optical sensors of this type should in principle be able to monitor local mechanical stress in transparent samples down to the single-molecule level, which harbors promising applications in polymer science and nanotechnology. [source] Politics of Scale and the Globalization of the South Korean Automobile IndustryECONOMIC GEOGRAPHY, Issue 2 2003Bae-Gyoon Park Abstract: This article explains the liberalization and globalization of the South Korean automobile industry, with an emphasis on the multiscalar processes of globalization. In particular, it explores the processes by which the South Korean government shifted its policy for the automobile industry, from a nationalist and protectionist orientation toward liberalization in the late 1990s, which, in turn, attracted inward investments from foreign automakers and facilitated the globalization of the nation's automobile market. While exploring the roles of diverse actors and forces,operating at various geographic scales,in these processes, I placed more analytical weight on examining the ways in which contestation between national and local forces contributed to the government's liberalization policy. I argue that the globalization of the South Korean automobile industry in recent years was not only an outcome of the globalizing strategies of foreign automakers, but also was facilitated by an institutional fix by the nation-state (particularly the liberalization of policy) to a regulatory deficit, which stemmed from the national-local tension with respect to a state-led economic restructuring project. [source] Finite element analysis of land subsidence above depleted reservoirs with pore pressure gradient and total stress formulationsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2001Giuseppe Gambolati Abstract The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three-dimensional axisymmetric porous medium if the FE integration is performed using the average element-wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary. Copyright © 2001 John Wiley & Sons, Ltd. [source] The Urban Question as Cargo Cult: Opportunities for a New Urban PedagogyINTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 3 2008ROB SHIELDS Abstract Urban research is unreflexive toward its object of study, the city, compromising its methodologies and theoretical capacity. This polemic draws on examples such as ,creative cities', which have been profiled and analysed for their local recipes for economic success. ,Global cities' have become stereotypes of a neoliberal form of the ,good life' to which much recent urban research is a handmaiden, a hegemonic knowledge project. These ,metro-poles' of value are a form of urban pedagogy that presents lesser local elites with lessons to be followed. A form of cargo cult theory suggests, build it and wealth will come , hence the symmetry of urban scholarship with the fad for city rankings in pop journalism. In contrast to neo-structural analyses of the global city, other research focuses too closely on regional geographies, local forces and urban affordances. A synthetic level of theory is proposed to bridge the divide which marks urban and regional studies. The ,urban' needs to be rediscovered as a central question. The urban is an object of theory and the city is a truth spot. The urban is more than infrastructure and bodies but an intangible good or ,virtuality' that requires an appropriate methodological toolkit. Résumé La recherche urbaine manque de réflexivitéà l'égard de son objet d'étude, la ville, ce qui compromet ses méthodologies et sa capacité théorique. Cette critique part d'exemples tels que les "villes créatives" dont on a établi le profil et l'analyse pour en déterminer les recettes locales de réussite économique. Les "villes planétaires" sont devenues des stéréotypes d'une forme néolibérale de la "bonne vie" au service de laquelle se met généralement la recherche urbaine, un projet de savoir hégémonique. Ces métro-pôles de valeur constituent une sorte de pédagogie urbaine qui expose aux moindres élites locales des leçons à suivre. Un genre de théorie du culte du cargo suggère qu'il suffit de construire pour voir la richesse arriver, d'où la symétrie entre les travaux de recherche urbaine et la mode pour les palmarès de villes dans le journalisme populaire. Contrairement aux analyses néo-structuralistes de la ville planétaire, d'autres études se consacrent de trop près aux géographies régionales, aux forces locales et aux affordances urbaines. Un niveau de théorie synthétique est proposé pour franchir la ligne de démarcation des études urbaines et régionales. Il faut redécouvrir "l'urbain" en tant que question centrale. L'urbain est un objet de théorie, la ville est un lieu de vérité. L'urbain est plus qu'une infrastructure et des entités, c'est un bien intangible, une "virtualité", qui nécessite un jeu d'outils méthodologiques approprié. [source] Dendritic network structure constrains metacommunity properties in riverine ecosystemsJOURNAL OF ANIMAL ECOLOGY, Issue 3 2010B. L. Brown Summary 1.,Increasingly, ecologists conceptualize local communities as connected to a regional species pool rather than as isolated entities. By this paradigm, community structure is determined through the relative strengths of dispersal-driven regional effects and local environmental factors. However, despite explicit incorporation of dispersal, metacommunity models and frameworks often fail to capture the realities of natural systems by not accounting for the configuration of space within which organisms disperse. This shortcoming may be of particular consequence in riverine networks which consist of linearly -arranged, hierarchical, branching habitat elements. Our goal was to understand how constraints of network connectivity in riverine systems change the relative importance of local vs. regional factors in structuring communities. 2.,We hypothesized that communities in more isolated headwaters of riverine networks would be structured by local forces, while mainstem sections would be structured by both local and regional processes. We examined these hypotheses using a spatially explicit regional analysis of riverine macroinvertebrate communities, focusing on change in community similarity with distance between local communities [i.e., distance-decay relationships; (DDRs)], and the change in environmental similarity with distance. Strong DDRs frequently indicate dispersal-driven dynamics. 3.,There was no evidence of a DDR in headwater communities, supporting our hypothesis that dispersal is a weak structuring force. Furthermore, a positive relationship between community similarity and environmental similarity supported dynamics driven by local environmental factors (i.e., species sorting). In mainstem habitats, significant DDRs and community × environment similarity relationships suggested both dispersal-driven and environmental constraints on local community structure (i.e., mass effects). 4.,We used species traits to compare communities characterized by low vs. high dispersal taxa. In headwaters, neither strength nor mode (in-network vs. out of network) of dispersal changed our results. However, outcomes in mainstems changed substantially with both dispersal mode and strength, further supporting the hypothesis that regional forces drive community dynamics in mainstems. 5.,Our findings demonstrate that the balance of local and regional effects changes depending on location within riverine network with local (environmental) factors dictating community structure in headwaters, and regional (dispersal driven) forces dominating in mainstems. [source] Mitochondrial displacements in response to nanomechanical forcesJOURNAL OF MOLECULAR RECOGNITION, Issue 1 2008Yaron R. Silberberg Abstract Mechanical stress affects and regulates many aspects of the cell, including morphology, growth, differentiation, gene expression and apoptosis. In this study we show how mechanical stress perturbs the intracellular structures of the cell and induces mechanical responses. In order to correlate mechanical perturbations to cellular responses, we used a combined fluorescence-atomic force microscope (AFM) to produce well defined nanomechanical perturbations of 10,nN while simultaneously tracking the real-time motion of fluorescently labelled mitochondria in live cells. The spatial displacement of the organelles in response to applied loads demonstrates the highly dynamic mechanical response of mitochondria in fibroblast cells. The average displacement of all mitochondrial structures analysed showed an increase of ,40%, post-perturbation (,160,nm in comparison to basal displacements of ,110,nm). These results show that local forces can produce organelle displacements at locations far from the initial point of contact (up to ,40,µm). In order to examine the role of the cytoskeleton in force transmission and its effect on mitochondrial displacements, both the actin and microtubule cytoskeleton were disrupted using Cytochalasin D and Nocodazole, respectively. Our results show that there is no significant change in mitochondrial displacement following indentation after such treatments. These results demonstrate the role of the cytoskeleton in force transmission through the cell and on mitochondrial displacements. In addition, it is suggested that care must be taken when performing mechanical experiments on living cells with the AFM, as these local mechanical perturbations may have significant structural and even biochemical effects on the cell. Copyright © 2008 John Wiley & Sons, Ltd. [source] Building knowledge city in transformation era: Knowledge-based urban development in Beijing in the context of globalisation and decentralisationASIA PACIFIC VIEWPOINT, Issue 1 2010Pengjun Zhao Abstract This study examines knowledge-based urban development in Beijing with the objective of revealing the impact of the ,synergetic' forces of globalisation and local government intervention on knowledge-based urban development in the context of the coexisting processes of globalisation and decentralisation. The findings in this paper show that due to the rapid growth of the cultural industry sector, knowledge-based urban development has created various kinds of ,cultural industry clustered areas', which were recently promoted by the 2008 Olympic Games. ,Synergetic' global and local forces are leading knowledge-based urban development, with the emergence of a local coalition regime in which local government manages local development, considered as ,enterprises' in the decentralisation process, while the State retains a significant influence on knowledge-based urban development. The central and municipal governments tend to emphasise strategies to ,facilitate the climate for growth' rather than the centrally planned control they exerted prior to the 1980s. [source] 3411: Update on physiopathology of cystoid macular edemaACTA OPHTHALMOLOGICA, Issue 2010P MORA Purpose To offer an overview on the historical and most recent acquisitions about the mechanisms that have been proposed to explain how cystoid macular edema (CME) develops. Methods Review of the literature and presentation of personal evidences and imagines. Results CME represents an excessive presence of fluid within the layers of the retina. A breakdown in the blood-retinal barrier normally is the causative event for fluid to accumulate in cystoid spaces within the retina. Several mechanisms have been proposed to explain the blood-retinal barrier alteration and consequent CME formation. The intraocular diffusion of inflammatory mediators (eg, prostaglandins), following mechanical or biological insults, remains the most proven evidence. Another mechanism refers to the role of tractional forces on the macula from disruption of the normal vitreoretinal interface. According to this theory, a release of mediators that lead to a breakdown of the blood-retinal barrier, would have triggered mainly by local forces. Photic injury, finally, has been implicated in the development of pseudophakic or post-vitrectomy CME. Conclusion A full comprehension of the pathogenesis of CME will significantly help in focussing and developing an effective treatment even for the chronic form of CME. [source] | |||||||||||||