329 research outputs found
Taoufik Souami, Ecoquartiers et urbanisme durable, Paris, ProblÚmes politiques et sociaux, Paris, La Documentation Française, N°981, 111 pages, 2011.
Dans la lignĂ©e de son ouvrage publiĂ© rĂ©cemment aux carnets de lâinfo, Taoufik Souami nous livre ici une compilation briĂšvement introduite de textes sur ce vĂ©ritable phĂ©nomĂšne que reprĂ©sentent aujourdâhui les Ă©coquartiers sur la scĂšne urbanistique française. Il sâagit dâun regard salutaire posant plus de questions que nâoffrant de rĂ©ponses, sur cette âfabriqueâ des Ă©coquartiers et de leur place dans les enjeux urbains contemporains. Donnons tout de suite les limites de lâexercice, liĂ©es au for..
Dynamical effects induced by long range activation in a nonequilibrium reaction-diffusion system
We both show experimentally and numerically that the time scales separation
introduced by long range activation can induce oscillations and excitability in
nonequilibrium reaction-diffusion systems that would otherwise only exhibit
bistability. Namely, we show that the Chlorite-Tetrathionate reaction, where
autocatalytic species diffuses faster than the substrates, the spatial
bistability domain in the nonequilibrium phase diagram is extended with
oscillatory and excitability domains. A simple model and a more realistic model
qualitatively account for the observed behavior. The latter model provides
quantitative agreement with the experiments.Comment: 19 pages + 9 figure
ĂlĂ©ments pour une critique de la ville durable
International audienceLa âville durableâ est prĂ©sentĂ©e comme Ă©tant la rĂ©ponse la plus appropriĂ©e aux problĂšmes environnementaux que nous connaissons aujourdâhui. Le succĂšs de cette notion et de celle de dĂ©veloppement durable dont elle est issue, sâexplique selon nous par le fait que les temporalitĂ©s des milieux habitĂ©s y sont reprĂ©sentĂ©es Ă la fois comme promesse (âles gĂ©nĂ©rations futuresâ) et comme catĂ©gorie dâaction (âpenser global, agir localâ). Pour rĂ©pondre aux problĂšmes environnementaux, cette promesse de durabilitĂ© urbaine associe de maniĂšre systĂ©mique dĂ©veloppement Ă©conomique et bien-ĂȘtre humain et environnemental et cette catĂ©gorie dâaction, permet Ă lâensemble des entitĂ©s participant Ă lâurbain de travailler ensemble ici et maintenant (âles petits gestesâ). Si la ville durable nâest pas seulement une promesse, mais aussi un instrument, il nous semble que lorsque nous portons la ville durable, en installant un rĂ©seau intelligent ou en triant nos dĂ©chets, nous nâagissons pas en suivant dâautres logiques dâaction âsous couvert de durabilitĂ©â, mais nous participons activement dâune vĂ©ritable transformation urbaine et anthropologique âpar le durableâ. Quel sens donner alors Ă lâĂ©volution des projets urbains qui sont censĂ©s incarner une rĂ©ponse aux problĂšmes environnementaux ? Que signifie âtransformerâ par le durable et quelles en sont les consĂ©quences ? Dans quelle mesure une transformation urbaine par le durable rĂ©sulte-t-elle des conflits et controverses qui les traversent
Pour qui ? Pourquoi ? Comment ? Les âvilles intelligentesâ doivent-elles rendre les politiques urbaines âacceptablesâ ou âdiscutablesâ ?
International audienc
Direct contact measurement of the dielectric properties of glass ionomer cements for MEMs design
This investigation was aimed at measuring the changes in dielectric properties of glass ionomer cements during their setting reaction in order to observe if there is a correlation between these properties and the cement curing. Commercial glass ionomer cements were prepared and their setting process was monitored over a 24 hour period using FT-IR and direct contact impedance measurement. An impedance bridge with a dielectric test assembly, based on previous work by Braden et al, was used to measure the dielectric properties of a number of different glass ionomer cements using a simple design. Using the dielectric properties of the glass ionomer cements, it could be possible to develop a micro-electro-mechanical sensor (MEMS) based on this design, which could be implanted into a dental restoration and interrogated remotely. During the curing of the cements examined, the dielectric data collected from the co-planar assembly showed a change in impedance over the course of the setting of the cement, which when compared to FT-IR spectra over the same period, showed a correlation between the dielectric properties and the chemical changes within the cement
Cultures territoriales et sociabilités dans le mouvement
Contrat de recherche "Cultures, villes et dynamiques sociales"Cette recherche tente de comprendre le rĂŽle du mouvement dans la composition de cultures et de territoires, constamment redĂ©finis par les coordinations entre reprĂ©sentations et pratiques ; Ă diffĂ©rentes Ă©chelles, interactionnelle, structurale, temporelle, ou spatiale. Afin de surmonter les Ă©preuves qu'entrainent les contradictions Ă©ventuelles entre ces Ă©chelles, les institutions jouent un rĂŽle majeur dans la rationalisation de ces cultures et de ces territoires. Elles tentent ainsi de repousser les frottements, les incertitudes et les troubles que provoquent les rĂ©actualisations de la dimension territoriale des cultures et de la dimension culturelle des territoires. Or, nos quatre terrains d'enquĂȘte (un village touristique, les 'seuils' entre une salle d'Ă©change RATP et un Centre Commercial, une performance publique de hackers et des rassemblement de jeunes), montrent que les tensions participent de maniĂšre essentielle Ă l'hybridation de ces "cultures territoriales". En faisant appel Ă des compĂ©tences distribuĂ©es parmi les acteurs et les espaces, les mises en mouvement nous permettent en effet d'expĂ©rimenter la vulnĂ©rabilitĂ© de ces "cultures territoriales", mais aussi leur capacitĂ© mobilisatrice
La nature contre la culture ?
Les entrepreneurs et les autoritĂ©s portuaires dâAnvers ont Ă©tĂ© contraints de suspendre en 2005 un projet dâextension du port. Ceux-ci ont alors intĂ©grĂ© dans le processus de gouvernance lâassociation Ă©cologiste Natuurpunt qui en Ă©tait la cause. Le ComitĂ© dâaction Doel 2020 revendique lui, une approche culturelle des polders et des villages menacĂ©s. Alors que cette vision plus en prise avec les problĂ©matiques socioĂ©conomiques aurait dĂ» lui rĂ©server les faveurs des autoritĂ©s portuaires, câest Natuurpunt qui a Ă©tĂ© retenue comme interlocutrice unique. Sâappuyant sur une modĂ©lisation systĂ©mique de la nature, cette derniĂšre a participĂ© activement Ă lâĂ©laboration dâun compromis politique. Cependant, ce rĂ©ductionnisme lui interdisait de discuter du bien-fondĂ© des objectifs poursuivis en termes dâintĂ©rĂȘt gĂ©nĂ©ral et a participĂ© Ă la « mise en ordre » des hommes en Ă©vacuant la dimension culturelle et, Ă travers elle, la question sociale.In 2005, the entrepreneurs and authorities of the Port of Antwerp were forced to postpone a project to extend the port. The ecological association Natuurpunt responsible for this postponement was subsequently asked to join the governance process. For its part, the Doel 2020 Action Committee adopted a cultural approach to the polders and villages under threat. Whereas this vision â more in line with current socioeconomic issues â should have curried favour in the eyes of the port authorities, it was Natuurpunt which was instead designated as the unique contact partner. Relying on the systemic modelling of nature, the latter played an active role in establishing a political compromise. This reductionism nevertheless prevented it from discussing the validity of the objectives pursued in terms of their general interest and contributed to the âorderingâ of people by eliminating the cultural and, consequently, the social dimension
Establishment and neural differentiation of neural crest-derived stem cells (NCSCs) from human dental pulp in serum-free conditions
The potential of obtaining cell cultures with neural crest resemblance (neural crest-derived stem cells; NCSCs) from dental-related tissues, including human dental pulp cells (hDPCs) has been discussed in the literature. However, most reports include the use of serum-rich conditions and do not describe the potential for neural differentiation, slowing translation to the clinic. Therefore, we aimed to culture and characterize NCSCs from the human dental pulp in vitro and evaluate their ability to differentiate into neurons; we also investigated the effectiveness of the addition of BMP4 to enhance this potential. Cultures were established from a varied cohort of patient samples and grown, as monolayers, in serum, serum-free and also under sphere-aggregation conditions to induce and identify a NCSC phenotype. hDPC cultures were characterized by immunocytochemistry and reverse transcription quantitative polymerase chain reaction. Monolayer cultures expressed stem cell, neural progenitor and neural crest-related markers. Culturing hDPCs as neurospheres (hDPCNCSCs) resulted in an increased expression of neural crest-related genes, while the addition of BMP4 appeared to produce better NCSC characteristics and neural differentiation. The neural-like phenotype was evidenced by the expression of TUJ1, peripherin, NFH, TAU, SYN1 and GAP43. Our results describe the establishment of hDPC cultures from a large variety of patients in serum-free medium, as NCSC that differentiate into neural-like cells, as well as an important effect of BMP4 in enhancing the neural crest phenotype and differentiation of hDPCs
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