903 resultados para Connaissance collective


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The report ‘Sustainability of Open Access Services - Phase 3: The Collective Provision of Open Access Resources’ discusses the economic and institutional issues faced by those sustaining free infrastructure services. It also identifies strategies to coordinate the collective provision of infrastructure services. These considerations are valuable input for the phases 4 and 5 of the project ‘Sustainability of Open Access Services’. This body of work will lead to practical recommendations for funders and project planners to consider when initiating an infrastructure service. The report was written by Raym Crow and funded by SPARC. Several key messages from the report are of interest. Providing infrastructure services as a public good imposes specific requirements on the design of the sustainability model. The challenge is to get enough institutions to reveal their demand for the service and support this. Arguments for an institution to support can be altruism or reciprocity or there being sufficient benefit to the institution for supporting a service. Institutions can also work together on a service through collective action (collecting voluntary contributions) and cross subsidies (funding collected by offering exclusive benefits to contributors).

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Cooperative director fluctuations in lipid bilayers have been postulated for many years. ^2H-NMR T_1^(-1), T_(1P)^(-1) , and T_2^(-1); measurements have been used identify these motions and to determine the origin of increased slow bilayer motion upon addition of unlike lipids or proteins to a pure lipid bilayer.

The contribution of cooperative director fluctuations to NMR relaxation in lipid bilayers has been expressed mathematically using the approach of Doane et al.^1 and Pace and Chan.^2 The T_2^(-1)’s of pure dimyristoyllecithin (DML) bilayers deuterated at the 2, 9 and 10, and all positions on both lipid hydrocarbon chains have been measured. Several characteristics of these measurements indicate the presence of cooperative director fluctuations. First of all, T_2^(-1) exhibits a linear dependence on S2/CD. Secondly, T_2^(-1) varies across the ^2H-NMR powder pattern as sin^2 (2, β), where , β is the angle between the average bilayer director and the external magnetic field. Furthermore, these fluctuations are restricted near the lecithin head group suggesting that the head group does not participate in these motions but, rather, anchors the hydrocarbon chains in the bilayer.

T_2^(-1)has been measured for selectively deuterated liquid crystalline DML hilayers to which a host of other lipids and proteins have been added. The T_2^(-1) of the DML bilayer is found to increase drastically when chlorophyll a (chl a) and Gramicidin A' (GA') are added to the bilayer. Both these molecules interfere with the lecithin head group spacing in the bilayer. Molecules such as myristic acid, distearoyllecithin (DSL), phytol, and cholesterol, whose hydrocarbon regions are quite different from DML but which have small,neutral polar head groups, leave cooperative fluctuations in the DML bilayer unchanged.

The effect of chl a on cooperative fluctuations in the DML bilayer has been examined in detail using ^2H-NMR T_1^(-1), T_(1P)^(-1) , and T_2^(-1); measurements. Cooperative fluctuations have been modelled using the continuum theory of the nematic state of liquid crystals. Chl a is found to decrease both the correlation length and the elastic constants in the DML bilayer.

A mismatch between the hydrophobic length of a lipid bilayer and that of an added protein has also been found to change the cooperative properties of the lecithin bilayer. Hydrophobic mismatch has been studied in a series GA' / lecithin bilayers. The dependence of 2H-NMR order parameters and relaxation rates on GA' concentration has been measured in selectively deuterated DML, dipalmitoyllecithin (DPL), and DSL systems. Order parameters, cooperative lengths, and elastic constants of the DML bilayer are most disrupted by GA', while the DSL bilayer is the least perturbed by GA'. Thus, it is concluded that the hydrophobic length of GA' best matches that of the DSL bilayer. Preliminary Raman spectroscopy and Differential Scanning Calorimetry experiments of GA' /lecithin systems support this conclusion. Accommodation of hydrophobic mismatch is used to rationalize the absence of H_(II) phase formation in GA' /DML systems and the observation of H_(II) phase in GA' /DPL and GA' /DSL systems.

1. J. W. Doane and D. L. Johnson, Chem. Phy3. Lett., 6, 291-295 (1970). 2. R. J. Pace and S. I. Chan, J. Chem. Phy3., 16, 4217-4227 (1982).

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Understanding friction and adhesion in static and sliding contact of surfaces is important in numerous physical phenomena and technological applications. Most surfaces are rough at the microscale, and thus the real area of contact is only a fraction of the nominal area. The macroscopic frictional and adhesive response is determined by the collective behavior of the population of evolving and interacting microscopic contacts. This collective behavior can be very different from the behavior of individual contacts. It is thus important to understand how the macroscopic response emerges from the microscopic one. In this thesis, we develop a theoretical and computational framework to study the collective behavior. Our philosophy is to assume a simple behavior of a single asperity and study the collective response of an ensemble. Our work bridges the existing well-developed studies of single asperities with phenomenological laws that describe macroscopic rate-and-state behavior of frictional interfaces. We find that many aspects of the macroscopic behavior are robust with respect to the microscopic response. This explains why qualitatively similar frictional features are seen for a diverse range of materials. We first show that the collective response of an ensemble of one-dimensional independent viscoelastic elements interacting through a mean field reproduces many qualitative features of static and sliding friction evolution. The resulting macroscopic behavior is different from the microscopic one: for example, even if each contact is velocity-strengthening, the macroscopic behavior can be velocity-weakening. The framework is then extended to incorporate three-dimensional rough surfaces, long- range elastic interactions between contacts, and time-dependent material behaviors such as viscoelasticity and viscoplasticity. Interestingly, the mean field behavior dominates and the elastic interactions, though important from a quantitative perspective, do not change the qualitative macroscopic response. Finally, we examine the effect of adhesion on the frictional response as well as develop a force threshold model for adhesion and mode I interfacial cracks.

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Three ponds were chosen for this study. The two lower ones were of 2 - 4 hectares in area, the depth of the littoral zone was 2.5 - 3 metres at the time of maximum flooding and the mud which covered the floor of the ponds was homogeneous and autochthonous in nature with very few vegetable remnants. The ponds which were originally set up in 1950. were intended for water supply and populated with Crucian Carp (for human consumption). A survey was done in the ponds in order to establish number and biomass of Tendipes semireductus. The author concludes that in these ponds T.semireductus has 2-3 generations per year.

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Nesta tese, considerando as críticas e as queixas ao distanciamento entre as políticas públicas, a formação docente e a prática profissional, problematizamos a produção / circulação de expectativas sobre o trabalho do professor. Investimos numa dupla perspectiva teórica: a da psicologia social e a da linguística. A partir de uma compreensão da subjetividade como produção, recorremos a noções como as de governamentalização neoliberal (FOUCAULT, 2008a; FOUCAULT, 2008b) para encaminhar uma análise das formas de controle (DELEUZE, 2006a) e o desafio de constituir a experiência (BENJAMIN, 1996) como um plano (DELEUZE; GUATTARI, 2005). Do ponto de vista dos estudos da linguagem, priorizam-se os debates em torno interdiscurso (BAKHTIN, 2004; MAINGUENEAU, 2005), conceito que é responsável por descartar aportes baseados estritamente no conteudismo e ressignifica os planos da enunciação e da pragmática. Em nossas análises, colocamos em confronto textos de prescrição à atividade docente e discussão de professores e estagiários apontando o que ganha consistência ou não em seu cotidiano profissional. As análises desdobram-se em três momentos. No primeiro deles, discutimos o Decreto do PDE como gênero do discurso (BAKHTIN, 2000), analisando as tarefas atribuídas ao professor nas metas e as estratégias de poder instauradas pelo IDEB. No segundo momento, observamos as dicas ao professor divulgadas no portal eletrônico Todos pela Educação, considerando como marca linguística os pressupostos (DUCROT, 1987; MAINGUENEAU, 2005). A análise dos pressupostos nos conduziu a ocorrências de enunciados em afirmação polêmica. No terceiro momento, constituímos uma discussão em grupo com professores e com estagiários, colocando em análise temas como trabalho, formação, práticas de si e relação com a pesquisa. Os resultados das análises apontam para uma desqualificação da análise coletiva das demandas do cotidiano, gerando a redução do trabalho do professor como execução de tarefas e transmissão de saberes. As políticas públicas agem por mecanismos de competição e recompensa, colocando a ênfase sobre a performance. Fortalece-se a figura de um professor empreendedor, como alguém que pretende apenas atingir as metas, sem discutir sua eficácia e seus efeitos. Ao lado disso, o vetor precarização indica lutas por melhores condições e reconhecimento de trabalho. Para além das metas propostas, o percurso com o conhecimento surge como possibilidade de experiência singular, compartilhada entre professores e alunos.

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Qens/wins 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers / editado por:Frick, B; Koza, MM; Boehm, M; Mutka, H

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[EUS] Laurogeita hamarreko hamarkadan, Eusko Jaurlaritzako Berriztapen Pedagogikoaren Zuzendaritzak eta Bartzelonako Unibertsitateko CREA (Gizarte eta Heziketarako Ikerkuntza Zentroa) ikerkuntza-taldeak Ikas Komunitateen proiektua jarri zuten martxan, elkarlanean, Euskal Autonomia Erkidegoko lau zentrotan. Zentro horiek hezkuntza-proiektu berri bat abiatzeko bidea ematen dute; izan ere, porrot akademiko handia izatearren hautatu dira, ikasle-taldeen aniztasunaren egoerari heltzeko arazo ugari dituztelako edota dauden lekuetan gizarte-bazterkeriarekin loturiko arazo anitz daudelako. Aldi berean, proiektuak eraldaketa proposatzen du, bai eskolarena, baita inguruarena ere, eta, horretarako, eskolako partaide guztiak hartzen ditu kontuan. Emaitza onak ikusi ostean, eta, hezkuntza-berriztapenaren alorrean lehentasuna izanik, ekimena zabaltzen hasi zen hastapeneko zentroez bestelako ezaugarri sozioedukatiboak dituzten eskoletara ere. Esperientzia berritzaile horiek aurrera eramateko gogo handiz agertu ziren, baita ere, «praktika on»en paradigma ez zirenak, eta, emaitzei begiratzen badiegu, dirudienez, etekin onak lortzen ari dira zentroetan. Ikas Komunitateen proiektuak berekin daraman gaitasun eraldatzaileak egokitzeko berezko ahala erakusten du. Egokitzapen horretan, eskolaren —inguruarekin batera— eta proiektuaren arteko sinbiosia lortzen da, hezkuntzako arrakasta- ekintzak sustatuz.

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A first treatment of the statistical data of 1978 and 1979 on the collective fishing showed a decrease of total catches in the Ebrié Lagoon. The same diminution was found in the amount of smoked-fish collected in two different places of the lagoon. This fall is due to a smaller effort in the lagoon of the purse-seines in the Abidjan area and a decrease of the catches per unit of effort.

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Where natural resources are a key component of the rural economy, the ability of the poor to realize their visions for the future depends significantly on institutional structures that govern resource access and management. This case study reports on an initiative on the shores of Lake Kariba in Zambia, where lakeshore residents face competition over fishing, tourism, and commercial aquaculture. Multistakeholder dialogue produced agreements with investors and increased accountability of state agencies and traditional leaders, enabling communities to have greater influence over their futures through improvements in aquatic resource governance. The report documents the rationale for the approach followed and steps in the capacity-building process, discusses obstacles encountered, and identifies lessons for policymakers and practitioners seeking to implement a similar approach.

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A number of biological processes, such as embryo development, cancer metastasis or wound healing, rely on cells moving in concert. The mechanisms leading to the emergence of coordinated motion remain however largely unexplored. Although biomolecular signalling is known to be involved in most occurrences of collective migration, the role of physical and mechanical interactions has only been recently investigated. In this paper, a versatile framework for cell motility is implemented in-silico in order to study the minimal requirements for the coordination of a group of epithelial cells. We find that cell motility and cell-cell mechanical interactions are sufficient to generate a broad array of behaviours commonly observed in vitro and in vivo. Cell streaming, sheet migration and susceptibility to leader cells are examples of behaviours spontaneously emerging from these simple assumptions, which might explain why collective effects are so ubiquitous in nature. This analysis provides also new insights into cancer metastasis and cell sorting, suggesting in particular that collective invasion might result from an emerging coordination in a system where single cells are mechanically unable to invade.

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The role of geometrical confinement on collective cell migration has been recognized but has not been elucidated yet. Here, we show that the geometrical properties of the environment regulate the formation of collective cell migration patterns through cell-cell interactions. Using microfabrication techniques to allow epithelial cell sheets to migrate into strips whose width was varied from one up to several cell diameters, we identified the modes of collective migration in response to geometrical constraints. We observed that a decrease in the width of the strips is accompanied by an overall increase in the speed of the migrating cell sheet. Moreover, large-scale vortices over tens of cell lengths appeared in the wide strips whereas a contraction-elongation type of motion is observed in the narrow strips. Velocity fields and traction force signatures within the cellular population revealed migration modes with alternative pulling and/or pushing mechanisms that depend on extrinsic constraints. Force transmission through intercellular contacts plays a key role in this process because the disruption of cell-cell junctions abolishes directed collective migration and passive cell-cell adhesions tend to move the cells uniformly together independent of the geometry. Altogether, these findings not only demonstrate the existence of patterns of collective cell migration depending on external constraints but also provide a mechanical explanation for how large-scale interactions through cell-cell junctions can feed back to regulate the organization of migrating tissues.