883 research outputs found
Paediatric interventional cardiology in Costa Rica: diagnostic reference levels and estimation of population dose
No full textThe current work was carried out under the framework of the International Atomic Energy Agency regional project RLA/9/075, Strengthening National Infrastructure for End-Users to Comply with Regulations and Radiological Protection Requirements. C Ubeda acknowledges the support of the Research Directorate at Tarapaca University through senior research project no. 7710-14.El presente trabajo se llevó a cabo en el marco del proyecto regional RLA/9/075 del Organismo Internacional de Energía Atómica, Fortalecimiento de la Infraestructura Nacional para el Cumplimiento de la Regulación y los Requisitos de Protección Radiológica por parte de los Usuarios Finales. C. Ubeda agradece el apoyo de la Dirección de Investigación de la Universidad de Tarapacá a través del proyecto de investigación sénior n.º 7710-14
Is Prevention Better than Cure? Framing Effects in Public Good Provision
No full textThis paper studies, both theoretically and experimentally, frame effects in the context of a strategic situation in which players have to make a costly contribution either i) to achieve or ii) not to loose a non excludable monetary prize (i.e. a public good). By contrast with related works on framing in public good situations, our experimental protocol lead to public good provision (not deterioration) only if a certain contribution level is achieved. In this respect, we find that a) subjects' behavior is highly sensitive to framing effects and that ii) which frame leads to higher contribution schedule crucially depends on the contribution schedule. We apply Prospect Theory to intepret our experimental findings, calibrating the equilibria to the parameter models which better suit our experimental evidence
Water diffusion modulates the cest effect on Tb(III)-mesoporous silica probes
No full textThe anchoring of lanthanide(III) chelates on the surface of mesoporous silica nanoparticles (MSNs) allowed their investigation as magnetic resonance imaging (MRI) and chemical exchange saturation transfer (CEST) contrast agents. Since their efficiency is strongly related to the interaction occurring between Ln-chelates and “bulk” water, an estimation of the water diffusion inside MSNs channels is very relevant. Herein, a method based on the exploitation of the CEST properties of TbDO3A-MSNs was applied to evaluate the effect of water diffusion inside MSN channels. Two MSNs, namely MCM-41 and SBA-15, with different pores size distributions were functionalized with TbDO3A-like chelates and polyethylene glycol (PEG) molecules and characterized by HR-TEM microscopy, IR spectroscopy, N2 physisorption, and thermogravimetric analysis (TGA). The different distribution of Tb-complexes in the two systems, mainly on the external surface in case of MCM-41 or inside the internal pores for SBA-15, resulted in variable CEST efficiency. Since water molecules diffuse slowly inside silica channels, the CEST effect of the LnDO3A-SBA-15 system was found to be one order of magnitude lower than in the case of TbDO3A-MCM-41. The latter system reaches an excellent sensitivity of ca. 55 ± 5 μM, which is useful for future theranostic or imaging applications
The Consistency of Fairness Rules: An Experimental Study
No full textIn the last two decades, experimental papers on distributive justice have abounded. Two main results have been replicated Firstly, there is a multiplicity of fairness rules. Secondly, fairness decisions differ depending on the context. This paper studies individual consistency in the use of fairness rules, as well as the structural factors that lead people to be inconsistent. We use a within-subject design, which allows us to compare individual behavior when the context changes. In line with the literature, we find a multiplicity of fairness rules. However, when we control for consistency, the set of fairness rules is considerably smaller. Only selfishness and strict egalitarianism seem to survive the stricter requirement of consistency. We observe that this result is mainly explained by a self-serving bias. Participants select the rule that is individually optimal in each situation.Justice, Fairness, Laboratory Experiments, Self-serving bias, Consistency
Capacity precommitment and price competition yield the Cournot outcome
No full textWe introduce a simple model of oligopolistic competition where firms first build capacity, and then, after observing the capacity decisions, choose a reservation price at which they are willing to supply their capacities. This model describes many markets more realistically than the model of Kreps and Scheinkman [Kreps, D., Scheinkman, J., 1983. Quantity precommitment and Bertrand competition yield Cournot outcomes. Bell J. Econ. 14, 326–337]. We show that in this new model every pure strategy equilibrium yields the Cournot outcome, and that the Cournot outcome can be sustained by a pure strategy subgame perfect equilibrium.Publicad
Auto-organisation efficace en énergie pour réseaux de capteurs
No full textDans un réseau de capteurs, les nuds communiquent en mode multi-sauts. Les principaux enjeux de ces réseaux sont d\u27économiser l\u27énergie (ressource limitée car embarquée dans le capteur) et l\u27auto-organisation (afin de s\u27adapter aux changements de topologie). Les contributions majeures de cette thèse sont: - Nous proposons un protocole d\u27accès au médium qui évite le maintien des tables de voisinage pour chaque nud. Notre protocole ne construit cette table qu\u27à la demande, ce qui permet d\u27être robuste aux changements de topologies. - Nous utilisons des coordonnées virtuelles comme base pour l\u27auto-organisation du réseau de capteurs. Ces coordonnées sont utilisées par un protocole de routage pour découvrir des chemins multi-sauts. Chaque capteur met continuellement à jour ses coordonnées pour augmenter la robustesse. - Nous combinons ces propositions pour former une architecture de communication transcouches. Des résultats expérimentaux montrent l\u27efficacité de nos propositions
Transgene expression in mice of the Opa1 mitochondrial transmembrane protein through bicontinuous cubic lipoplexes containing gemini imidazolium surfactants
No full textBackground: Lipoplexes are non-viral vectors based on cationic lipids used to deliver DNA into cells, also known as lipofection. The positively charge of the hydrophilic head-group provides the cationic lipids the ability to condensate the negatively charged DNA into structured complexes. The polar head can carry a large variety of chemical groups including amines as well as guanidino or imidazole groups. In particular, gemini cationic lipids consist of two positive polar heads linked by a spacer with different length. As for the hydrophobic aliphatic chains, they can be unsaturated or saturated and are connected to the polar head-groups. Many other chemical components can be included in the formulation of lipoplexes to improve their transfection efficiency, which often relies on their structural features. Varying these components can drastically change the arrangement of DNA molecules within the lamellar, hexagonal or cubic phases that are provided by the lipid matrix. Lipofection is widely used to deliver genetic material in cell culture experiments but the simpler formulations exhibit major drawbacks related to low transfection, low specificity, low circulation half-life and toxicity when scaled up to in vivo experiments. Results: So far, we have explored in cell cultures the transfection ability of lipoplexes based on gemini cationic lipids that consist of two C16 alkyl chains and two imidazolium polar head-groups linked with a polyoxyethylene spacer, (C16Im)2(C4O). Here, PEGylated lipids have been introduced to the lipoplex formulation and the transgene expression of the Opa1 mitochondrial transmembrane protein in mice was assessed. The addition of PEG on the surface of the lipid mixed resulted in the formation of Ia3d bicontinuous cubic phases as determined by small angle X-ray scattering. After a single intramuscular administration, the cubic lipoplexes were accumulated in tissues with tight endothelial barriers such as brain, heart, and lungs for at least 48 h. The transgene expression of Opa1 in those organs was identified by western blotting or RNA expression analysis through quantitative polymerase chain reaction. Conclusions: The expression reported here is sufficient in magnitude, duration and toxicity to consolidate the bicontinuous cubic structures formed by (C16Im)2(C4O)-based lipoplexes as valuable therapeutic agents in the field of gene delivery. Graphical Abstract: [Figure not available: see fulltext.]
Détection d\u27anomalies comportementales appliquée à la vision globale
No full textFace à l\u27évolution et la croissance de nouvelles attaques, les systèmes de protection classiques (farewalls, IDS) sont devenus rapidement insuffisants pour contrôler ces menaces. Des scénarios d\u27attaques complexes tentent d\u27être assimilés à des comportements d\u27usage normaux du SI afin de contourner les défenses locales. Nous proposons dans nos travaux une méthode de détection d\u27anomalies comportementale portant sur la vision globale des SI. En intégrant les contraintes liées à l\u27observation de l\u27ensemble d\u27un SI (hétérogénéité, volume de données), nous avons bâtis des profils statistiques d\u27usage du système et mis en place une méthode de détection d\u27anomalies. La mise à jour continuelle de ces profils nous permet de suivre l\u27évolution des comportements légitimes des utilisateurs et de limiter le nombre de fausses alertes. Outre la détection d\u27anomalies comportementales, nos travaux ont délimité le périmètre d\u27observation des comportements en se focalisant sur les démarches des attaquants
Ecology drives intragenomic conflict over menopause
No full textMenopause is the transition from reproductive to non-reproductive life well before natural death. Rather than involving a smooth, rapid change, it is normally preceded by a long period of erratic hormonal fluctuation that is accompanied by a plethora of unpleasant symptoms. Here, we (1) suggest that this turbulent period owes to conflict, between a woman's maternally inherited (MI) and paternally inherited (PI) genes, over the trade-off between reproduction and communal care; (2) perform a theoretical analysis to show that this conflict is resolved either through silencing or fluctuating expression of one of the genes; (3) highlight which of the symptoms preceding menopause may result from antagonistic co-evolution of MI and PI genes; (4) argue that ecological differences between ancestral human populations may explain the variability in menopause among different ethnic groups; (5) discuss how these insights may be used to inform family planning and cancer risk assessment based on a woman's ancestral background.Peer reviewe
Modèle dynamique de sécurité pour réseaux spontanés
No full textLes objets communicants sont devenus pratiquement incontournables dans notre quotidien. La multiplication des normes de communication sans fil permet à ces appareils dont la nature peut-être très hétérogène, de se connecter rapidement entre eux. Cependant, de nombreux obstacles se dressent à l\u27avènement de réseaux interconnectables à volonté. En particulier, l\u27absence de modèle de sécurité aisément réalisable et socialement acceptable est un frein important à leur utilisation. Afin de surmonter ces obstacles, une architecture de gestion de la confiance doit être préalablement développée dès lors qu\u27il s\u27agit de considérer des interactions spontanées entre des objets divers n\u27ayant pas forcément une autorité de confiance commune. Le modèle de gestion de la confiance que nous présentons ici est inspiré des résultats obtenus par l\u27analyse des relations humaines. Dans ce modèle, la confiance est vue comme une relation pseudo-transitive entre les différentes entités. Le niveau de confiance à accorder aux différentes parties est évalué à partir de données cryptographiquement prouvables stockées dans un historique. Pour des raisons de sécurité, le non-transfert des données de l\u27historique à un tiers non-autorisé est également assuré. Les simulations numériques présentées montrent que le modèle peut facilement s\u27instancier dans des réseaux sans fil de grande échelle. La modélisation permet également de fixer certains paramètres libres du modèle afin d\u27en optimiser l\u27usage dans la pratique. Son implémentation détaillée est également présentée
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