5 resultados para collective excitations in multilayers

em Duke University


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The Million Mom March (favoring gun control) and Code Pink: Women for Peace (focusing on foreign policy, especially the war in Iraq) are organizations that have mobilized women as women in an era when other women's groups struggled to maintain critical mass and turned away from non-gender-specific public issues. This article addresses how these organizations fostered collective consciousness among women, a large and diverse group, while confronting the echoes of backlash against previous mobilization efforts by women. We argue that the March and Code Pink achieved mobilization success by creating hybrid organizations that blended elements of three major collective action frames: maternalism, egalitarianism, and feminine expression. These innovative organizations invented hybrid forms that cut across movements, constituencies, and political institutions. Using surveys, interviews, and content analysis of organizational documents, this article explains how the March and Code Pink met the contemporary challenges facing women's collective action in similar yet distinct ways. It highlights the role of feminine expression and concerns about the intersectional marginalization of women in resolving the historic tensions between maternalism and egalitarianism. It demonstrates hybridity as a useful analytical lens to understand gendered organizing and other forms of grassroots collective action. © 2010 American Political Science Association.

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Due to their informality, the favelas of Rio de Janeiro are in a precarious position. Though the informal neighborhoods have long served as sites of affordable housing for Rio’s poorest residents, changes within in the city related to public security, mega-events, real estate speculation, and urban revitalization jeopardize their permanence. As one possible solution, this study, conducted for the client Catalytic Communities, investigated collective titling in favelas modeled after quilombos, territories recognized and titled by Brazilian federal law as patrimonies of black cultural traditions.

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The goal of this paper is to improve our understanding of the role of institutional arrangements and ecological factors that facilitate the emergence and sustainability of successful collective action in small-scale fishing social-ecological systems. Using a modified logistic growth function, we simulate how ecological factors (i.e. carrying capacity) affect small-scale fishing communities with varying degrees of institutional development (i.e. timeliness to adopt new institutions and the degree to which harvesting effort is reduced), in their ability to avoid overexploitation. Our results show that strong and timely institutions are necessary but not sufficient to maintain sustainable harvests over time. The sooner communities adopt institutions, and the stronger the institutions they adopt, the more likely they are to sustain the resource stock. Exactly how timely the institutions must be adopted, and by what amount harvesting effort must be diminished, depends on the ecological carrying capacity of the species at the particular location. Small differences in the carrying capacity between fishing sites, even under scenarios of similar institutional development, greatly affects the likelihood of effective collective action. © 2009 Elsevier B.V. All rights reserved.

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“War Worlds” reads twentieth-century British and Anglophone literature to examine the social practices of marginal groups (pacifists, strangers, traitors, anticolonial rebels, queer soldiers) during the world wars. This dissertation shows that these diverse “enemies within” England and its colonies—those often deemed expendable for, but nonetheless threatening to, British state and imperial projects—provided writers with alternative visions of collective life in periods of escalated violence and social control. By focusing on the social and political activities of those who were not loyal citizens or productive laborers within the British Empire, “War Worlds” foregrounds the small group, a form of collectivity frequently portrayed in the literature of the war years but typically overlooked in literary critical studies. I argue that this shift of focus from grand politics to small groups not only illuminates surprising social fissures within England and its colonies but provides a new vantage from which to view twentieth-century experiments in literary form.

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Dynamic processes such as morphogenesis and tissue patterning require the precise control of many cellular processes, especially cell migration. Historically, these processes are thought to be mediated by genetic and biochemical signaling pathways. However, recent advances have unraveled a previously unappreciated role of mechanical forces in regulating these homeostatic processes in of multicellular systems. In multicellular systems cells adhere to both deformable extracellular matrix (ECM) and other cells, which are sources of applied forces and means of mechanical support. Cells detect and respond to these mechanical signals through a poorly understood process called mechanotransduction, which can have profound effects on processes such as cell migration. These effects are largely mediated by the sub cellular structures that link cells to the ECM, called focal adhesions (FAs), or cells to other cells, termed adherens junctions (AJs).

Overall this thesis is comprised of my work on identifying a novel force dependent function of vinculin, a protein which resides in both FAs and AJs - in dynamic process of collective migration. Using a collective migration assay as a model for collective cell behavior and a fluorescence resonance energy transfer (FRET) based molecular tension sensor for vinculin I demonstrated a spatial gradient of tension across vinculin in the direction of migration. To define this novel force-dependent role of vinculin in collective migration I took advantage of previously established shRNA based vinculin knock down Marin-Darby Canine Kidney (MDCK) epithelial cells.

The first part of my thesis comprises of my work demonstrating the mechanosensitive role of vinculin at AJ’s in collectively migrating cells. Using vinculin knockdown cells and vinculin mutants, which specifically disrupt vinculin’s ability to bind actin (VinI997A) or disrupt its ability to localize to AJs without affecting its localization at FAs (VinY822F), I establish a role of force across vinculin in E-cadherin internalization and clipping. Furthermore by measuring E-cadherin dynamics using fluorescence recovery after bleaching (FRAP) analysis I show that vinculin inhibition affects the turnover of E-cadherin at AJs. Together these data reveal a novel mechanosensitive role of vinculin in E-cadherin internalization and turnover in a migrating cell layer, which is contrary to the previously identified role of vinculin in potentiating E-cadherin junctions in a static monolayer.

For the last part of my thesis I designed a novel tension sensor to probe tension across N-cadherin (NTS). N-cadherin plays a critical role in cardiomyocytes, vascular smooth muscle cells, neurons and neural crest cells. Similar to E-cadherin, N-cadherin is also believed to bear tension and play a role in mechanotransduction pathways. To identify the role of tension across N-cadherin I designed a novel FRET-based molecular tension sensor for N-cadherin. I tested the ability of NTS to sense molecular tension in vascular smooth muscle cells, cardiomyocytes and cancer cells. Finally in collaboration with the Horwitz lab we have been able to show a role of tension across N-cadherin in synaptogenesis of neurons.