La Ceinture verte d’Île-de-France à l’épreuve du Grand Paris : effacement ou renouveau ? Reconfigurations spatiales, territoriales et paysagères dans les marges de l’aire urbaine métropolitaine

Référence de la thèseFlégeau M. (2018). La Ceinture verte d’Île-de-France à l’épreuve du Grand Paris : effacement ou renouveau ? Reconfigurations spatiales, territoriales et paysagères dans les marges de l’aire urbaine métropolitaine. Géographie. Université Paris 13 - Sorbonne Paris Cité. Aux lisières de la métropole parisienne, les paysages, marqués par un enchevêtrement d’espaces agricoles, de lotissements, de zones d’activités, de zones boisées, de délaissés ou encore de centres-villes anc..

Populations reléguées et projets paysagers dans les marges de l’agglomération parisienne. Le cas de la plaine de Pierrelaye

L’intérêt récent pour les délaissés urbains de la part des acteurs publics de l’aménagement se manifeste dans l’aire urbaine centrale de la métropole parisienne mais aussi dans ses marges. On se propose ici d’étudier un projet d’aménagement en plaine de Pierrelaye, cherchant à transformer cette plaine agricole polluée en une forêt aménagée. Cet espace est aujourd’hui pour partie occupée par des familles de Gens du voyage et de Roms. Bien que l’abandon des activités soit lié à l’interdiction de consommer les produits agricoles issus de la plaine, la présence de ces populations est à la fois jugée comme une des raisons de la situation de déshérence que connait la plaine et comme un frein à la réalisation du projet. L’article aborde la difficile prise en compte des populations marginalisées et la part d’instrumentalisation dont fait l’objet le projet pour se défaire des occupations illégales, appuyé par un argumentaire paysager et social.The recent interest of public stakeholders towards wastelands in the central part of the Paris region appears also clearly in its margins. We would like to study a landscape project in the Pierrelaye’s plain. The project aims to transform this wasteland, that is today a polluted area, into a forest. Mainly composed by unexploited agricultural lands, this space is also occupied by families from the Travelling Community and Roma population. The travelers are altogether accused of being responsible for the decline of this space and of being an issue for the implementation of the project. We will focus on how the project realization is leaving them out and how the land regulation is established for the sake of the project and not according to the law

Cyclic and fatigue behaviour of an industrial high pressure die cast brass

Ces travaux de thèse portent sur le comportement élastoplastique et la durée de vie sous chargement cyclique d'un alliage cuivre-zinc injecté sous pression. L'apport essentiel de ces travaux de thèse est la mise en évidence d'un écrouissage isotrope qui s'estompe très rapidement dès la première décharge en plasticité. Une analyse qualitative montre que l'évolution de l'amplitude de contrainte est liée à celle de la contrainte interne. Cette étude est multi-échelles, en effet des observations en microscopie électronique à transmission ont permis d'émettre des hypothèses sur l'origine des phénomènes observés lors des essais mécaniques. Les essais de fatigue ont également montré que la durée de vie du matériau dépend fortement des défauts inhérents au procédé de fabrication. L'utilisation d'un modèle multimécanismes simplifié a permis de modéliser le comportement cyclique du matériau étudié, et de prendre en compte l'évolution quasi instantanée de l'écrouissage isotrope.These research works deal with the investigation of the cyclique and fatigue behaviour of an industrial high-pressure die cast brass. Mechanical tests highlight relatively important changes of elasticity domain during monotonic loading, mainly due to changes of the internal stress. This study was conducted under different scales of observation. TEM observations enabled hypothesis to explain the "original" cyclic behaviour of the alloy. Fatigue tests showed that fatigue life of the material is quite dependent of the presence of defects that may be due to manufacture process. A simplified version of a multi-mechanism model was used to simulate the cyclic behaviour of the study alloy

Comportement cyclique et en fatigue d'un alliage cuivreux injecté sous pression

These research works deal with the investigation of the cyclique and fatigue behaviour of an industrial high-pressure die cast brass. Mechanical tests highlight relatively important changes of elasticity domain during monotonic loading, mainly due to changes of the internal stress. This study was conducted under different scales of observation. TEM observations enabled hypothesis to explain the "original" cyclic behaviour of the alloy. Fatigue tests showed that fatigue life of the material is quite dependent of the presence of defects that may be due to manufacture process. A simplified version of a multi-mechanism model was used to simulate the cyclic behaviour of the study alloy.Ces travaux de thèse portent sur le comportement élastoplastique et la durée de vie sous chargement cyclique d'un alliage cuivre-zinc injecté sous pression. L'apport essentiel de ces travaux de thèse est la mise en évidence d'un écrouissage isotrope qui s'estompe très rapidement dès la première décharge en plasticité. Une analyse qualitative montre que l'évolution de l'amplitude de contrainte est liée à celle de la contrainte interne. Cette étude est multi-échelles, en effet des observations en microscopie électronique à transmission ont permis d'émettre des hypothèses sur l'origine des phénomènes observés lors des essais mécaniques. Les essais de fatigue ont également montré que la durée de vie du matériau dépend fortement des défauts inhérents au procédé de fabrication. L'utilisation d'un modèle multimécanismes simplifié a permis de modéliser le comportement cyclique du matériau étudié, et de prendre en compte l'évolution quasi instantanée de l'écrouissage isotrope

La Ceinture verte d’Île-de-France à l’épreuve du Grand Paris : effacement ou renouveau ? Reconfigurations spatiales, territoriales et paysagères dans les marges de l’aire urbaine métropolitaine

The concept of green belt is a manner of thinking the margins of the surroundings of Paris. This urban planning tool has been used by the Île-de-France regional Council in the early 1980’s. The implementation of a green belt aimed to give a global vision of the woodland, cropland and wasteland in that area. Due to a lack of law support and political changes, the Green belt policy never really came to an existence. However, the area of the Green belt is filled with several expectations in terms of recreation, landscapes, quality of life and environment from the city dwellers and public players. Meanwhile, the Grand Paris project tends, in the same time, to put under pressure these spaces by its urban planning projects, and to consider the idea of a green belt for the Paris region.We have chosen in this thesis to highlight the features of the Green belt by a social and spatial approach of the dynamics through a multiscalar approach. It reveals the fragmentation and the heterogeneity of this space on several levels: spatial organization, landscapes and social distribution. The study of the dynamics concerning the territories shows the discrepancy of the urban planning logics in the Île-de-France region. In the Green belt space, a large number of territory projects occurs around open spaces. It aims, in most of the case, to preserve the qualities of the landscapes (in the vallée de Chevreuse for example) or to attain a certain type of landscape (the forest project in Plaine de Pierrelaye shows that). But this type of territorialities leaves out marginalized population, living in the Green belt space. Finally, this study enlightens the mixed relationship and the tensions between local and metropolitan authorities in a decentralized context.Cette thèse se propose de porter un regard géographique sur les espaces végétalisés – boisés, agricoles ou délaissés – situés aux marges de l’aire urbaine métropolitaine de Paris, au travers de la notion de ceinture verte. Ce dispositif d’aménagement, élaboré au début du XXe siècle, a été utilisé par le Conseil régional d’Île-de-France à partir du début des années 1980. Placée à cheval entre l’urbain et le rural, la Ceinture verte francilienne devait permettre de proposer une vision cohérente de ces marges, en leur donnant une consistance et une identité. Faute notamment de moyens réglementaires au Conseil régional, le projet de Ceinture verte n’a finalement jamais eu de véritable existence. Pourtant, les espaces végétalisés de l’agglomération font aujourd’hui l’objet d’attentes renouvelées de la part des acteurs de l’aménagement et des habitants, en particulier en termes récréatifs, paysagers, de qualité de vie, et désormais environnementaux. En outre, dans le projet du Grand Paris est évoquée l’idée d’une ceinture verte, alors même que ses projets d’aménagement remettent sous pression les espaces végétalisés des franges de la métropole.Nous avons d’abord cherché à qualifier cet espace sous un angle socio-spatial en adoptant une démarche multiscalaire. Il ressort de ce travail la grande hétérogénéité et l’importante fragmentation de la Ceinture verte sur les plans de son organisation spatiale, socio-spatiale ainsi que du paysage. Par ailleurs, l’étude des dynamiques territoriales en Ceinture verte fait ressortir les contradictions de l’aménagement francilien. Cette thèse souligne la multiplicité des initiatives locales de projets de territoire, formulées autour des espaces végétalisés. Leur mise en valeur est surtout centrée sur les critères paysagers, comme en vallée de Chevreuse comme à Marne-et-Gondoire, où l’on souhaite maintenir un cadre de vie préservé, ou comme en plaine de Pierrelaye, où un projet de forêt doit permettre d’accéder à un paysage, inversant ainsi la trajectoire de déclin du site. Dans le même temps, ces projets paysagers excluent les populations marginalisées ayant trouvé refuge dans certaines parties de la Ceinture verte, comme dans le cas de la Butte Pinson. Enfin, cette thèse met en lumière les jeux de résistance et d’opposition locale au projet du Grand Paris, ce dernier pouvant être à l’inverse un levier pour des projets de territoire, dans un contexte décentralisé. Cet espace apparait donc en tension entre une vue métropolitaine d’ensemble des marges parisienne et des visées locales pour un paysage préservé ou en voie de l’être

Comportement cyclique et en fatigue d'un alliage cuivreux injecté sous pression

These research works deal with the investigation of the cyclique and fatigue behaviour of an industrial high-pressure die cast brass. Mechanical tests highlight relatively important changes of elasticity domain during monotonic loading, mainly due to changes of the internal stress. This study was conducted under different scales of observation. TEM observations enabled hypothesis to explain the "original" cyclic behaviour of the alloy. Fatigue tests showed that fatigue life of the material is quite dependent of the presence of defects that may be due to manufacture process. A simplified version of a multi-mechanism model was used to simulate the cyclic behaviour of the study alloy.Ces travaux de thèse portent sur le comportement élastoplastique et la durée de vie sous chargement cyclique d'un alliage cuivre-zinc injecté sous pression. L'apport essentiel de ces travaux de thèse est la mise en évidence d'un écrouissage isotrope qui s'estompe très rapidement dès la première décharge en plasticité. Une analyse qualitative montre que l'évolution de l'amplitude de contrainte est liée à celle de la contrainte interne. Cette étude est multi-échelles, en effet des observations en microscopie électronique à transmission ont permis d'émettre des hypothèses sur l'origine des phénomènes observés lors des essais mécaniques. Les essais de fatigue ont également montré que la durée de vie du matériau dépend fortement des défauts inhérents au procédé de fabrication. L'utilisation d'un modèle multimécanismes simplifié a permis de modéliser le comportement cyclique du matériau étudié, et de prendre en compte l'évolution quasi instantanée de l'écrouissage isotrope

Cartilage tissue engineering by extrusion bioprinting utilizing porous hyaluronic acid microgel bioinks

3D bioprinting offers an excellent opportunity to provide tissue-engineered cartilage to microtia patients. However, hydrogel-based bioinks are hindered by their dense and cell-restrictive environment, impairing tissue development and ultimately leading to mechanical failure of large scaffolds in vivo. Granular hydrogels, made of annealed microgels, offer a superior alternative to conventional bioinks, with their improved porosity and modularity. We have evaluated the ability of enzymatically crosslinked hyaluronic acid (HA) microgel bioinks to form mature cartilage in vivo. Microgel bioinks were formed by mechanically sizing bulk HA-tyramine hydrogels through meshes with aperture diameters of 40, 100 or 500 mu m. Annealing of the microgels was achieved by crosslinking residual tyramines. Secondary crosslinked scaffolds were stable in solution and showed tunable porosity from 9% to 21%. Bioinks showed excellent rheological properties and were used to print different objects. Printing precision was found to be directly correlated to microgel size. As a proof of concept, freeform reversible embedding of suspended hydrogels printing with gelation triggered directly in the bath was performed to demonstrate the versatility of the method. The granular hydrogels support the homogeneous development of mature cartilage-like tissues in vitro with mechanical stiffening up to 200 kPa after 63 d. After 6 weeks of in vivo implantation, small-diameter microgels formed stable constructs with low immunogenicity and continuous tissue maturation. Conversely, increasing the microgel size resulted in increased inflammatory response, with limited stability in vivo. This study reports the development of new microgel bioinks for cartilage tissue biofabrication and offers insights into the foreign body reaction towards porous scaffolds implantation.ISSN:1758-5082ISSN:1758-509

What evidence exists on the possible effects of urban forms on terrestrial biodiversity in western cities? A systematic map protocol

International audienceBackground: As urban areas expand, scientists now agree that the city is an important space for biodiversity conservation. Yet, still relatively little is known about how urban forms could have a differential impact on terrestrial species and ecosystems. If some reviews have been conducted to examine the link between biodiversity and urban characteristics at an infra-city scale, none have explored the relationship between urban organization and biodiversity and tried to assess the capacity of various urban forms to maintain and possibly favour flora and fauna in the city. The resulting map will present the state of knowledge regarding possible relationships between urban forms and its features on the establishment and settlement of terrestrial and temperate biodiversity at infra-city scale in western cities. Methods: The systematic map will follow the Collaboration for Environmental Evidence (CEE) Guidelines. We will collect the relevant peer-reviewed and grey literature in French and English language. The scientific literature will be retrieved with the use of a search string in two publication databases, one environmental and one social science database (Web Of Science Core Collection, and Cairn.info). We will also perform supplementary searches (search engines, call for literature, search for relevant reviews). All references will be screened for relevance using a three-stage process, according to a predefined set of eligibility criteria. Our study will concentrate on urban areas at the infra-city scale in cities of the temperate biogeographical zone. The subject population will include terrestrial species and ecosystems, except for archaea and bacteria. The exposure will consider all types of urban forms described by any urban descriptors or measures including heterogeneity, fragmentation, housing density, organisation of urban matrix, urban fabric) and all types of urban features (e.g. size, age of the buildings, materials, urban artefacts). All relevant outcomes will be considered (e.g. species richness, abundance, behaviour). We will provide an open-access database of the studies included in the map. Our results will also be presented narratively, together with tables and graphs summarising the key information coded from the retained articles (e.g. study characteristics, types and areas of research that has been undertaken, types of exposure, population concerned, etc.)

Toward the development of biomimetic injectable and macroporous biohydrogels for regenerative medicine

International audienceRepairing or replacing damaged human tissues has been the ambitious goal of regenerative medicine for over 25 years. One promising approach is the use of hydrated three-dimensional scaffolds, known as hydrogels, which have had good results repairing tissues in pre-clinical trials. Benefiting from breakthrough advances in the field of biology, and more particularly regarding cell/matrix interactions, these hydrogels are now designed to re-capitulate some of the fundamental cues of native environments to drive the local tissue regeneration. We highlight the key parameters that are required for the development of smart and biomimetic hydrogels. We also review the wide variety of polymers, crosslinking methods, and manufacturing processes that have been developed over the years. Of particular interest is the emergence of supramolecular chemistries, allowing for the development of highly functional and reversible biohydrogels. Moreover, advances in computer assisted design and three-dimensional printing have revolutionized the production of macroporous hydrogels and allowed for more complex designs than ever before with the opportunity to develop fully reconstituted organs. Today, the field of biohydrogels for regenerative medicine is a prolific area of research with applications for most bodily tissues. On top of these applications, injectable hydrogels and macroporous hydrogels (foams) were found to be the most successful. While commonly associated with cells or biologics as drug delivery systems to increase therapeutic outcomes, they are steadily being used in the emerging fields of organs-on-chip and hydrogel-assisted cell therapy. To highlight these advances, we review some of the recent developments that have been achieved for the regeneration of tissues, focusing on the articular cartilage, bone, cardiac, and neural tissues. These biohydrogels are associated with improved cartilage and bone defects regeneration, reduced left ven-tricular dilation upon myocardial infarction and display promising results repairing neural lesions. Combining the benefits from each of these areas reviewed above, we envision that an injectable biohydrogel foam loaded with either stem cells or their secretome is the most promising hydrogel solution to trigger tissue regeneration. A paradigm shift is occurring where the combined efforts of fundamental and applied sciences head toward the development of hydrogels restoring tissue functions, serving as drug screening platforms or recreating complex organs

Multidose Hyaluronidase Administration as an Optimal Procedure to Degrade Resilient Hyaluronic Acid Soft Tissue Fillers

Minimally invasive hyaluronan (HA) tissue fillers are routinely employed to provide tissue projection and correct age-related skin depressions. HA fillers can advantageously be degraded by hyaluronidase (HAase) administration in case of adverse events. However, clear guidelines regarding the optimal dosage and mode of administration of HAase are missing, leaving a scientific gap for practitioners in their daily practice. In this study, we implemented a novel rheological procedure to rationally evaluate soft tissue filler degradability and optimize their degradation kinetics. TEOSYAL RHA® filler degradation kinetics in contact with HAase was monitored in real-time by rheological time sweeps. Gels were shown to degrade as a function of enzymatic activity, HA concentration, and BDDE content, with a concomitant loss of their viscoelastic properties. We further demonstrated that repeated administration of small HAase doses improved HA degradation kinetics over large single doses. Mathematical analyses were developed to evaluate the degradation potential of an enzyme. Finally, we tuned the optimal time between injections and number of enzymatic units, maximizing degradation kinetics. In this study, we have established a scientific rationale for the degradation of HA fillers by multidose HAase administration that could serve as a basis for future clinical management of adverse events