A place-focused model for social networks in cities

The focused organization theory of social ties proposes that the structure of human social networks can be arranged around extra-network foci, which can include shared physical spaces such as homes, workplaces, restaurants, and so on. Until now, this has been difficult to investigate on a large scale, but the huge volume of data available from online location-based social services now makes it possible to examine the friendships and mobility of many thousands of people, and to investigate the relationship between meetings at places and the structure of the social network. In this paper, we analyze a large dataset from Foursquare, the most popular online location-based social network. We examine the properties of city-based social networks, finding that they have common structural properties, and that the category of place where two people meet has very strong influence on the likelihood of their being friends. Inspired by these observations in combination with the focused organization theory, we then present a model to generate city-level social networks, and show that it produces networks with the structural properties seen in empirical data.Comment: 13 pages, 7 figures. IEEE/ASE SocialCom 201

Group colocation behavior in technological social networks.

We analyze two large datasets from technological networks with location and social data: user location records from an online location-based social networking service, and anonymized telecommunications data from a European cellphone operator, in order to investigate the differences between individual and group behavior with respect to physical location. We discover agreements between the two datasets: firstly, that individuals are more likely to meet with one friend at a place they have not visited before, but tend to meet at familiar locations when with a larger group. We also find that groups of individuals are more likely to meet at places that their other friends have visited, and that the type of a place strongly affects the propensity for groups to meet there. These differences between group and solo mobility has potential technological applications, for example, in venue recommendation in location-based social networks.This is the final manuscript published by PLOS One. It was originally published here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0105816

Caractérisation du comportement au feu des matériaux de l'habitat : Influence de l'effet d'échelle.

The origin of home fires can be as diverse as poor wiring, a smoldering cigarette, poor maintenance of a fireplace... This manuscript deals with the flammability of various household materials exposed to a radiative source. Several parameters such as dimension, orientation and nature of materials were investigated in similar operating conditions. These studies led to the development of new experimental device enabling working at different scales: RAPACES (RAdiant PAnel Concentrator Experimental Setup). The results obtained on PMMA showed that geometric factors play a major role (i) on ignition (variation of thermal radiative properties) and (ii) on combustion dynamics through structural phenomena (destabilization, collapsing and polymer melting). This approach was also applied to complex materials (plywood, tapestry, carpet). A numerical model was used to validate some hypothesis regarding the fire behavior of PMMA. Finally, original configurations including material assemblies were performed and clearly evidenced the effect of fuel interactions on ignition and flame propagation.L’origine des incendies domestiques peut être aussi diverse qu’une mauvaise installation électrique, une cigarette mal éteinte, un mauvais entretien d’une cheminée… Ce mémoire traite de l’inflammabilité de différents matériaux de l’habitat face à une source radiative. Plusieurs paramètres tels que la dimension, l’orientation et la nature des matériaux ont été étudiés dans des conditions opératoires similaires. Ces travaux ont conduit au développement d’un nouveau dispositif expérimental permettant de travailler à différentes échelles : le RAPACES (RAdiant PAnel Concentrator Experimental Setup). Les résultats obtenus sur le PMMA ont permis de mettre en évidence que les facteurs géométriques jouent un rôle prépondérant; d’une part sur l’ignition (variation des propriétés thermo-radiatives) et d’autre part sur la dynamique de combustion à travers des phénomènes structuraux (déstabilisation structurelle, affaissement et écoulement du matériau). Cette démarche a également été appliquée à des matériaux plus complexes (contreplaqué, tapisserie, moquette). L’utilisation d’un modèle numérique a permis de valider certaines hypothèses concernant le comportement au feu du PMMA. Enfin, des configurations originales constituées d’assemblages de matériaux ont été testées et ont permis de mettre en évidence les interactions entre combustibles en termes d’ignition et de propagation de flamme

Immobilization of Metal Hexacyanoferrate Ion-Exchangers for the Synthesis of Metal Ion Sorbents—A Mini-Review

Metal hexacyanoferrates are very efficient sorbents for the recovery of alkali and base metal ions (including radionuclides such as Cs). Generally produced by the direct reaction of metal salts with potassium hexacyanoferrate (the precursors), they are characterized by ion-exchange and structural properties that make then particularly selective for Cs(I), Rb(I) and Tl(I) recovery (based on their hydrated ionic radius consistent with the size of the ion-exchanger cage), though they can bind also base metals. The major drawback of these materials is associated to their nanometer or micrometer size that makes them difficult to recover in large-size continuous systems. For this reason many techniques have been designed for immobilizing these ion-exchangers in suitable matrices that can be organic (mainly polymers and biopolymers) or inorganic (mineral supports), carbon-based matrices. This immobilization may proceed by in situ synthesis or by entrapment/encapsulation. This mini-review reports some examples of hybrid materials synthesized for the immobilization of metal hexacyanoferrate, the different conditionings of these composite materials and, briefly, the parameters to take into account for their optimal design and facilitated use

Les nouveaux entrants de l'information locale: un journalisme de rupture?

International audienc

Les nouveaux entrants de l'information locale: un journalisme de rupture?

International audienc

Contester l’hégémonie médiatique locale: Entre engagement journalistique et repolitisation des territoires

International audienceThis article examines the ability of the new players of local news to renew the process of democratic debate in their zone of distribution, in the face of hegemonic regional daily press. We thus hypothesize that local journalism, built in opposition to or alongside dominant players, could catalyze the transformations at work in the journalistic field by championing the introduction of dissenting voices (Benson & Neveu, 2005; Smyrnaios & Thiong-Kay, 2023) in territories characterized until now by the media’s construction of consensus. Based on the "multi-referential" conception of territory put forward by Boure and Lefebvre (2000), we consider it to be structured by the opposition between, on the one hand, the exercise of institutional power and the crystallization of collective social time and, on the other, asymmetrical social relationships and plural or competing enactments of meaning. Ultimately, our aim was to understand the "territorial work" of the media (Noyer & Raoul 2011). Our study focused on 11 media located in the Auvergne Rhône-Alpes region, each of which had at least one professional journalist on its editorial staff. Through semi-structured interviews, combined with a focus on the media's meta-discourse, we examined the media's relationship with its territory from three perspectives (market, field and local public space). Our results confirm, among the actors studied, the structuring dynamics of professionalization previously observed in alternative media (Ferron 2006). They also reveal a form of polarization between two journalistic ideal-types, which we characterize in the light of Nielsen's work (2015). Indeed, while some media aim to reduce disparities in access to knowledge of public affairs among citizens (reduction of the "knowledge gap"), others seem above all committed to fostering civic and political engagement among citizens in the local space (reduction of the "engagement gap").Este artículo se propone examinar la capacidad de los nuevos operadores de la información local para renovar el proceso de alimentación del debate democrático en sus territorios de difusión, frente a una Prensa Diaria Regional hegemónica. De este modo, nuestra hipótesis es que un periodismo local, construido en contra o al lado del actor hegemónico, sería capaz de catalizar las transformaciones en marcha en el campo periodístico, defendiendo la introducción de voces disidentes (Benson y Neveu, 2005; Smyrnaios y Thiong-Kay, 2023) en territorios hasta ahora marcados por la construcción mediática del consenso. Partiendo de la concepción "multirreferencial" del territorio propuesta por Boure y Lefebvre (2000), consideramos que este está estructurado por la oposición entre el ejercicio de un poder institucional y la cristalización de un tiempo social compartido, por un lado, y las relaciones sociales asimétricas y las significaciones plurales o concurrentes, por el otro. En definitiva, lo que hemos tratado de comprender es el "trabajo territorial" de los medios de comunicación (Noyer y Raoul, 2011). Nuestro estudio se ha centrado en 11 medios de comunicación situados en la región de Auvernia-Ródano-Alpes y que cuentan con al menos un periodista profesional en su redacción. Mediante entrevistas semiestructuradas, complementadas con una atención al metadiscurso de los medios de comunicación, consideramos su relación con el territorio en una dimensión triple (mercado, terreno y espacio público local). Nuestros resultados confirman en primer lugar, entre los actores estudiados, una dinámica estructurante de profesionalización previamente observada en los medios alternativos (Ferron, 2006). Pero también revelan una forma de polarización entre dos ideales-tipos periodísticos, que caracterizamos a la luz de los trabajos de Nielsen (2015). En efecto, mientras que algunos medios de comunicación pretenden reducir las disparidades en el acceso al conocimiento de los asuntos públicos entre los ciudadanos (reducción de la brecha del conocimiento o knowledge gap), otros parecen sobre todo comprometidos con el fomento del compromiso cívico y político de los ciudadanos a nivel local (reducción de la brecha del compromiso o engagement gap).FR. Cet article propose de questionner la capacité des nouveaux entrants de l’information locale à renouveler le processus d’alimentation du débat démocratique dans leur territoire de diffusion, face à une Presse Quotidienne Régionale en situation hégémonique. Nous faisons ainsi l’hypothèse qu’un journalisme local, construit contre ou à côté de l’acteur hégémonique, serait en mesure de catalyser les transformations à l’œuvre dans le champ journalistique en défendant l’introduction de voix dissidentes (Benson & Neveu, 2005 ; Smyrnaios & Thiong-Kay, 2023) dans des territoires jusqu’ici marqués par la construction médiatique du consensus. À partir de la conception « multiréférentielle » du territoire avancée par Boure et Lefebvre (2000), nous envisageons en effet celui-ci comme structuré par l’opposition entre, d’un côté, l’exercice d’un pouvoir institutionnel et la cristallisation d’un temps social partagé et, de l’autre, des rapports sociaux dissymétriques et des mises en sens plurielles ou concurrentes. Au final, c’est donc le « travail territorial » des médias (Noyer & Raoul 2011) que nous avons cherché à appréhender. Notre étude a porté sur 11 médias situés en région Auvergne Rhône-Alpes et comportant dans leur rédaction au moins un journaliste professionnel. Par le biais d’entretiens semi-directifs, complétés d’une attention au méta-discours des médias, nous envisageons leur rapport au territoire dans une triple dimension (marché, terrain et espace public local). Nos résultats confirment d’abord, chez les acteurs étudiés, une dynamique structurante de professionnalisation précédemment observée dans les médias alternatifs (Ferron 2006). Mais ils révèlent également une forme de polarisation entre deux idéaux-types journalistiques, que nous caractérisons à la lumière des travaux de Nielsen (2015). En effet, si certains médias ambitionnent de réduire les disparités d’accès à la connaissance des affaires publiques parmi les citoyens (réduction du « knowledge gap »), d’autres semblent avant tout attachés à susciter l’engagement civique et politique des citoyens dans l’espace local (réduction de l’« engagement gap »).O objeto deste artigo é discutir como os novos atores do noticiário local podem renovar o processo de documentação do debate democrático em suas áreas de transmissão, frente à posição hegemônica da Imprensa Diária Regional. Levanta-se a hipótese de que um jornalismo local, construído contra ou ao lado do ator hegemônico, seja capaz de catalisar as transformações em curso no campo jornalístico ao defender a introdução de vozes dissidentes (Benson & Neveu, 2005; Smyrnaios & Thiong-Kay, 2023) em territórios até então marcados pela construção midiática do consenso. De fato, com base na concepção “multirreferencial” do território apresentada por Boure e Lefebvre (2000), considera-se que o território é estruturado pela oposição entre, de um lado, o exercício do poder institucional e a cristalização de um tempo social compartilhado e, de outro, as relações sociais assimétricas e as atribuições de sentidos plurais ou concorrentes. Dessa forma, em última análise, o que procuramos compreender é o “trabalho territorial” da mídia (Noyer & Raoul 2011). O estudo considerou 11 meios de comunicação localizados na região de Auvergne Rhône-Alpes, com pelo menos um jornalista profissional em sua equipe editorial. Por meio de entrevistas semiestruturadas, complementadas por um foco no metadiscurso da mídia, analisou-se a relação desses veículos com o território sob uma tripla perspectiva (de mercado, em campo e no espaço público local). Os resultados confirmam, em primeiro lugar, que há, entre os atores estudados, a mesma dinâmica estruturante de profissionalização já observada na mídia alternativa (Ferron, 2006). Mas evidencia-se também uma forma de polarização entre dois tipos de ideais jornalísticos, caracterizados aqui à luz do trabalho de Nielsen (2015). Com efeito, enquanto alguns meios de comunicação objetivam reduzir as disparidades no acesso ao conhecimento dos assuntos públicos entre os cidadãos (redução do “knowledge gap”), outros parecem estar comprometidos principalmente com a promoção do engajamento cívico e político dos cidadãos no espaço local (redução do “engagement gap”)

Characterization of the flammability of household materials subjected to high radiative flux

International audienc

Characterization of the flammability of household materials subjected to high radiative flux

International audienc