The dark matter distribution in z~0.5 clusters of galaxies. I : Determining scaling relations with weak lensing masses

The total mass of clusters of galaxies is a key parameter to study massive halos. It relates to numerous gravitational and baryonic processes at play in the framework of large scale structure formation, thus rendering its determination important but challenging. From a sample of the 11 X-ray bright clusters selected from the excpres sample, we investigate the optical and X-ray properties of clusters with respect to their total mass derived from weak gravitational lensing. From multi-color wide field imaging obtained with MegaCam at CFHT, we derive the shear profile of each individual cluster of galaxies. We perform a careful investigation of all systematic sources related to the weak lensing mass determination. The weak lensing masses are then compared to the X-ray masses obtained from the analysis of XMM observations and assuming hydrostatic equilibrium. We find a good agreement between the two mass proxies although a few outliers with either perturbed morphology or poor quality data prevent to derive robust mass estimates. The weak lensing mass is also correlated with the optical richness and the total optical luminosity, as well as with the X-ray luminosity, to provide scaling relations within the redshift range 0.4<z<0.6. These relations are in good agreement with previous works at lower redshifts. For the L_X-M relation we combine our sample with two other cluster and group samples from the literature, thus covering two decades in mass and X-ray luminosity, with a regular and coherent correlation between the two physical quantities

Fault-Tolerant Extension of Hypercube Algorithm for Efficient, Robust Group Communications in MANETs

Securing multicast communications in Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless networking and security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security on the other hand, is becoming an indispensable requirement of our modern life for all these applications. However, the limitations of the dynamic, infrastructure-less nature of MANETs impose major difficulties in establishing a secure framework suitable for group communications. The design of efficient key management (KM) schemes for MANET is of paramount importance, since the performance of the KM functions (key generation, entity authentication, key distribution/agreement) imposes an upper limit on the efficiency and scalability of the whole secure group communication system. In this work, we contribute towards efficient, robust and scalable, secure group communications for MANETs, by extending an existing key agreement (KA) scheme (where all parties contribute equally to group key generation) ypercube - to tolerate multiple member failures with low cost, through its integration with a novel adaptively proactive algorithm. We assume that the participating users have already been authenticated via some underlying mechanism and we focus on the design and analysis of a fault-tolerant Hypercube, with the aim to contribute to the robustness and efficiency of Octopus-based schemes (an efficient group of KA protocols for MANETs using Hypercube as backbone). We compare our algorithm with the existing approach, and we evaluate the results of our analysis. Through our analysis and simulation results we demonstrate how the new Hypercube algorithm enhances the robustness of the Octopus schemes maintaining their feasibility in MANETs at the same time. Key terms: Key Management, Key Agreement, Hypercube Protocol, Fault-Tolerance, Octopus Schemes, Elliptic Curves Cryptograph

Staying on Track from Paris: Advancing the Key Elements of the Paris Agreement

The Paris Agreement adopted in December 2015 provides essential building blocks for universal action to address climate change. Now, much work is needed to breathe life into the provisions and commitments of the Agreement in order to realize the globally agreed vision to limit temperature rise, build the ability to adapt to climate impacts, and align financial flows toward zerocarbon and climate-resilient development. The Parties to the United Nations Framework Convention on Climate Change (UNFCCC) must continue to cooperate effectively to unpack and clarify the key tasks and activities outlined in the Agreement in order to provide a well-defined pathway to implementation. This paper takes an in-depth look at the Paris Agreement, highlighting important outcomes and the tasks and activities that now need to be undertaken to elaborate and develop the critical rules and processes under the Agreement. Ensuring that these rules and processes are strong and effective will be essential to promoting ambitious climate action and accelerating it in the coming years

Robust Modeling of Epistemic Mental States

This work identifies and advances some research challenges in the analysis of facial features and their temporal dynamics with epistemic mental states in dyadic conversations. Epistemic states are: Agreement, Concentration, Thoughtful, Certain, and Interest. In this paper, we perform a number of statistical analyses and simulations to identify the relationship between facial features and epistemic states. Non-linear relations are found to be more prevalent, while temporal features derived from original facial features have demonstrated a strong correlation with intensity changes. Then, we propose a novel prediction framework that takes facial features and their nonlinear relation scores as input and predict different epistemic states in videos. The prediction of epistemic states is boosted when the classification of emotion changing regions such as rising, falling, or steady-state are incorporated with the temporal features. The proposed predictive models can predict the epistemic states with significantly improved accuracy: correlation coefficient (CoERR) for Agreement is 0.827, for Concentration 0.901, for Thoughtful 0.794, for Certain 0.854, and for Interest 0.913.Comment: Accepted for Publication in Multimedia Tools and Application, Special Issue: Socio-Affective Technologie