Éditeur(s) : HAL CCSD
Résumé : International audience
While the impact of network properties on information spread- ing is now widely studied, in uence of network dynamics is very little known. In this paper, we study how evolution mechanisms tradition- ally observed within social networks can a ect information di usion. We present an approach that merges two models: model of informa- tion di usion through social networks and model of network evolution. Since epidemics provide a reference in application domains of information spreading, we measure the impact of basic network structure changes on epidemic peak value and timing. Then we investigate observed trends in terms of changes appearing in the network structure. Our results provide promising results on how and why network dynamics is a strong param- eter to integrate in requirements for information spreading modelling.
World Summit on the Knowledge Society
Mykonos, Greece

hal-00768405
https://hal.archives-ouvertes.fr/hal-00768405

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
A hallmark of living systems is the management and the storage of information through genetic and epigenetic mechanisms. Although the notion of epigenetics was originally given to any regulation beyond DNA sequence, it has often been restricted to chromatin modifications, supposed to behave as cis-markers, specifying the sets of genes to be expressed or repressed. This definition does not take into account the initial view of epigenetics, based on nonlinear interaction networks whose "attractors" can remain stable without need for any chromatin mark. In addition, most chromatin modifications are the steady state resultants of highly dynamic modification and de-modification activities and, as such, seem poorly appropriate to work as long-term memory keepers. Instead, the basic support of epigenetic memory could remain the attractors, to which chromatin modifications belong as do many other components. The influence of chromatin modifications in memory is highly questionable when envisioned as static structural marks, but can be recovered under the dynamic circuitry perspective, thanks to their self-templating properties. Beside their standard repressive or permissive functions, chromatin modifications can also influence transcription in multiple ways such as: (1) by randomizing or inversely stabilizing gene expression, (2) by mediating cooperativity between pioneer and secondary transcription factors, and (3) in the hysteresis and the ultrasensitivity of gene expression switches, allowing the cells to take unambiguous transcriptional decisions.
ISSN: 1420-682X

hal-01063617
https://hal.archives-ouvertes.fr/hal-01063617
DOI : 10.1007/s00018-012-0923-7
PUBMED : 22331281

Éditeur(s) : HAL CCSD Geological Society of America
Résumé : International audience
Fluid-rock interactions can control earthquake nucleation and the evolution of earthquake sequences. Experimental studies of fault frictional properties in the presence of fluid can provide unique insights into these interactions. We report the first results from experiments performed on cohesive silicate-bearing rocks (microgabbro) in the presence of pressurized pore fluids (H2O, drained conditions) at realistic seismic deformation conditions. The experimental data are compared with those recently obtained from carbonate-bearing rocks (Carrara marble). Contrary to theoretical arguments, and consistent with the interpretation of some field observations, we show that frictional melting of a microgabbro develops in the presence of water. In microgabbro, the initial weakening mechanism (flash melting of the asperities) is delayed in the presence of water; conversely, in calcite marble the weakening mechanism (brittle failure of the asperities) is favored. This opposite behavior highlights the importance of host-rock composition in controlling dynamic (frictional) weakening in the presence of water: cohesive carbonate-bearing rocks are more prone to slip in the presence of water, whereas the presence of water might delay or inhibit the rupture nucleation and propagation in cohesive silicate-bearing rocks.
ISSN: 0091-7613

hal-01054327
https://hal.archives-ouvertes.fr/hal-01054327
DOI : 10.1130/G34916.1

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
Traditional network generation models aim to replicate global structural properties observed on various real-world networks through synthetic link formation mechanisms such as triadic closure or preferential attachment. Nowadays, the large amount of data available allow to study more precisely the link formation processes and to compare models with real situations. In this work, we analyze the network formed by the communication activities of the users of a telephony operator for studying the link formation process. Our goal is to identify the underlying formation mechanisms and checking if they match those proposed in traditional models. Indeed, the communications emitted and received by users are strong indicators for understanding the underlying patterns of the link formation process and highlighting how some individual properties induce the formation process in such a network. In a first study conducted at a global level, we show that the traditional mechanisms commonly used in network generation models cannot reproduce alone the link formation in this network. In a second study, we adopt a new point of view and analyze locally the link formation process by searching for correlations between some user attributes and the formation of the new links. The results obtained show that a very strong percentage of new links are formed between individuals with strong similarity.
ISSN: 1869-5450

hal-01312310
https://hal.univ-antilles.fr/hal-01312310
DOI : 10.1007/s13278-015-0304-y

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Seventy percent of breast tumors express the estrogen receptor (ER), which is generally considered to predict a better outcome relative to ER-negative tumors, as they often respond to antiestrogen therapies. During cancer progression, mammary tumors can escape from estrogen control, resulting in the acquisition of invasive properties and resistance to treatment. ER expression is a dynamic phenomenon and is finely regulated at numerous levels, including the gene, mRNA, and protein levels. As a consequence, many molecular mechanisms have been implicated in modulating ER activity and estrogen signaling in mammary cancer. In fact, one-third of ER-positive breast cancer cells do not respond to first-line endocrine therapies, and a large subset of relapsing tumors retain ER expression. Increased knowledge of these mechanisms has led to the development of better prognostic methods and targeted therapies for patients; however, additional research is still needed to improve patient survival. In this chapter, we focus on the signaling pathways leading to changes in or loss of ER activity in breast cancer progression.
ISSN: 0083-6729

hal-00874313
https://hal.archives-ouvertes.fr/hal-00874313
DOI : 10.1016/B978-0-12-416673-8.00004-6
PUBMED : 23810005

Résumé : L'objectif de cette thèse est de s'intéresser à la chimie des substances naturelles (extraction et caractérisation des molécules issues des forêts de Guyane) et d'étudier des extraits ou familles de molécules naturelles ayant des propriétés inhibitrices de la corrosion du zinc. Dans la première partie du document, un screening de plantes a été effectué. Celles dont les extraits ont présenté les propriétés inhibitrices les plus intéressantes - la Mansoa alliaceae et la Bagassa guianensis -ont été sélectionnées parmi les Il plantes étudiées. Dans la seconde partie du document, différentes techniques électrochimiques ont été utilisées- la spectroscopie d'impédance électrochimique (SEI) et la polarisationlinéaire (PL)- afin de calculer les taux d'inhibition et de remonter aux mécanismes réactionnels caractérisant l'inhibition. Ainsi, le rôle des paramètres tels que le mode d'extraction et le milieu corrosif (ASTM et NaCI3%) sur le taux d'inhibition ont été étudiés. Ces travaux ont débouché sur de nombreux résultats expérimentaux nouveaux et notamment un modèle dynamique prenant en compte l'efficacité de l'inhibiteur en fonction de sa concentration dans le milieu
The objective of this thesis is to focus on the chemistry of na tura! substances (extraction and characterization of molecules from forests of French Guiana) and to study extracts or families ofnatural molecules with inhibiting properties of zinc corrosion. In the first part of the document, a screening of plants was made. Those whose extracts have shown the most interesting potential inhibitors - the Mansoa alliaceae and Bagassa guianensis - were selected among the Il plants studied. In the second part of the paper, different electrochemical techniques were used - the electrochemical impedance spectroscopy (EIS) and linear polarization (LP) - to calculate the inhibition rate and to understand the reaction mechanisms characterizing the inhibition. Thus, the role of parameters such as the method of extraction and the corrosive medium (ASTM and NaCI3%) on the inhibition rate were studied. This work bas led to many new experimental results including a dynamic mode! taking into account the effectiveness of the inhibitor according to its concentration in the medium

http://www.theses.fr/2014AGUY0745/document

Résumé : L’ingénierie agroécologique vise à produire des savoirs actionnables, pour concevoir des systèmes de cultures économiquement et écologiquement performants, par la valorisation de régulations naturelles. Notre problématique est centrée sur la santé des cultures, et plus particulièrement sur la bactérie phytopathogène Ralstonia solanacearum, agent du flétrissement bactérien alors qu’une souche extrêmement agressive menace la production de tomates en plein champ en Martinique. La nécessité d’explorer et de développer des alternatives aux méthodes conventionnelles de protection des plantes (variétés résistantes, pesticides), actuellement inefficaces, invite à la mise en œuvre d’une démarche de conception innovante. Nos travaux montrent que la mobilisation d’une barrière rhizosphérique est une stratégie de régulation biologique alternative. Différents processus y contribuent, telle que la mycorhization, symbiose entre racines et champignons mycorhiziens à arbuscules, présents dans la plupart des sols. Nous montrons que la mobilisation de réseaux de mycorhizes indigènes à partir d’un sol agricole permet une mycorhization précoce de la tomate. De plus, l’association de plantes aux propriétés mycorhizotrophes et assainissantes en conditions contrôlées montre des effets bioprotecteurs partiels et ouvre de nouvelles perspectives de combinaisons entre processus. Ces combinaisons sont mobilisables par des leviers d’actions multi-scalaires. Nous avons produit une grille d’analyse générique de ces leviers d’action pour la conception, par des trajectoires d’innovation multidirectionnelles, de « systèmes de culture bioprotégés ». Dans le contexte agricole martiniquais, une démarche d’apprentissage permet en effet l’émergence d’une dynamique de co-conception de systèmes de cultures recourant aux plantes mycorhizotrophes. Nos travaux proposent des outils pour une exploration collective de nouvelles stratégies de gestion durable de la santé des cultures.
Agroecological engineering aims to produce actionable knowledge to design economically and environmentally efficient cropping systems, based on the exploitation of natural regulation mechanisms. Our issue is centered on crop health, especially on the plant pathogenic bacterium Ralstonia solanacearum (bacterial wilt agent), of which an extremely aggressive strain threatens field tomato production in Martinique. The need to explore and develop alternatives to conventional methods of plant protection (resistant varieties, pesticides), ineffective in our case, calls for the implementation of an innovative design approach. Our work shows that the protection of the roots via the formation of a self-sustaining rhizospheric barrier may be an alternative biological control strategy. Different processes contribute, such as mycorrhizal symbiosis between roots and arbuscular mycorrhizal fungi, which are present in most soils. We show that the mobilization of indigenous mycorrhizal networks from an agricultural soil allows early mycorrhization of tomatoes. In addition, the association of plants with mycorrhizal and sanitizing properties in controlled conditions showed partial bioprotective effects and opens up new prospects for combinations between processes. These combinations may be exploited in various ways. We produced a generic analysis grid of key levers to design "healthy cropping systems " through multi-directional innovation trajectories. In Martinique's agricultural context, a learning process allows the emergence of a dynamic co-design of cropping systems using mycorrhizal plants. Our work thus provides tools for collective exploration of new sustainable management strategies for crop health.

http://www.theses.fr/2015AGUY0828/document