Cross-layer Perceptual ARQ for Video Communications over 802.11e Wireless Networks

This work presents an application-level perceptual ARQ algorithm for video streaming over 802.11e wireless networks. A simple and effective formula is proposed to combine the perceptual and temporal importance of each packet into a single priority value, which is then used to drive the packet-selection process at each retransmission opportunity. Compared to the standard 802.11 MAC-layer ARQ scheme, the proposed technique delivers higher perceptual quality because it can retransmit only the most perceptually important packets reducing retransmission bandwidth waste. Video streaming of H.264 test sequences has been simulated with ns in a realistic 802.11e home scenario, in which the various kinds of traffic flows have been assigned to different 802.11e access categories according to the Wi-Fi alliance WMM specification. Extensive simulations show that the proposed method consistently outperforms the standard link-layer 802.11 retransmission scheme, delivering PSNR gains up to 12 dB while achieving low transmission delay and limited impact on concurrent traffic. Moreover, comparisons with a MAC-level ARQ scheme which adapts the retry limit to the type of frame contained in packets and with an application-level deadline-based priority retransmission scheme show that the PSNR gain offered by the proposed algorithm is significant, up to 5 dB. Additional results obtained in a scenario in which the transmission relies on an intermediate node (i.e., the access point) further confirms the consistency of the perceptual ARQ performance. Finally, results obtained by varying network conditions such as congestion and channel noise levels show the consistency of the improvements achieved by the proposed algorithm

An Exact Renormalization Group analysis of 3-d Well Developed turbulence

We take advantage of peculiar properties of three dimensional incompressible turbulence to introduce a nonstandard Exact Renormalization Group method. A Galilean invariance preserving regularizing procedure is utilized and a field truncation is adopted to test the method. Results are encouraging: the energy spectrum E(k) in the inertial range scales with exponent -1.666+/- 0.001 and the Kolmogorov constant C_K, computed for several (realistic) shapes of the stirring force correlator, agrees with experimental data.Comment: 12 pg, 2figures, LaTex, To be published on Physics Letters

Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque

Spin-orbit effects [1-4] have the potential of radically changing the field of spintronics by allowing transfer of spin angular momentum to a whole new class of materials. In a seminal letter to Nature [5], Kajiwara et al. showed that by depositing Platinum (Pt, a normal metal) on top of a 1.3 $\mu$m thick Yttrium Iron Garnet (YIG, a magnetic insulator), one could effectively transfer spin angular momentum through the interface between these two different materials. The outstanding feature was the detection of auto-oscillation of the YIG when enough dc current was passed in the Pt. This finding has created a great excitement in the community for two reasons: first, one could control electronically the damping of insulators, which can offer improved properties compared to metals, and here YIG has the lowest damping known in nature; second, the damping compensation could be achieved on very large objects, a particularly relevant point for the field of magnonics [6,7] whose aim is to use spin-waves as carriers of information. However, the degree of coherence of the observed auto-oscillations has not been addressed in ref. [5]. In this work, we emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current. This requires to reduce both the thickness and lateral size in order to reach full damping compensation [8] , and we show clear evidence of coherent spin-orbit torque induced auto-oscillation in micron-sized YIG discs of thickness 20 nm

Collider signals of brane fluctuations

Assuming that we live on a non rigid brane with TeV-scale tension, the scalar fields that control the coordinates of our brane in the extra dimensions give rise to missing energy signals at high-energy colliders with a characteristic angular and energy spectrum, identical to the one due to graviton emission in 6 extra dimensions. LEP bounds and LHC capabilities are analyzed.Comment: 8 pages. v2: ref.s added, misprints fixed. v3: footnote about string "predictions" for branon/graviton rates added at pag.

Network reduction towards a scale-free structure preserving physical properties

International audienc

Subgraph detection for average detectability of LTI systems

International audienceObservation and detection of networked systems aim to reconstruct the evolution of the system based on the measurement of few nodes. In large-scale networks, reconstructing the exact state of each node becomes more complex and in practice it is often superfluous. Reconstructing an aggregated version of the system is often sufficient. In the light of this observation, we consider the notion of average detectability: A system is said to be average detectable if it is possible to reconstruct the average of the subset of its unmeasured nodes. We show here that for a particular type of system, that is negative uniform networks, the average detectability property is reached when the subgraph induced by the unmeasured nodes is regular. Thus, we study the detection of such regular induced subgraph and we propose an algorithm to complete this task. We introduce also the relaxed notion of quasi-regularity ensuring an approximate reconstruction of the average. This paper presents algorithms to detect regular induced subgraphs (RIS) and quasi-regular induced subgraph (q-RIS). We propose an extension to detect multiple quasi-regular induced subgraphs (mq-RIS) in order to reconstruct the average of several subgraphs of the system. Finally we apply our method to the evolution of an epidemic spreading over a simulated contact network over the largest cities in France based on a SIS model

MergeToCure: a New Strategy to Allocate Cure in an Epidemic over a Grid-like network Using a Scale-Free Abstraction

International audienceIn the context of epidemic spreading over a network the problem of allocating a limited number of cure to curb the spreading is often discussed. While strategies exist for heterogeneous networks as scale-free networks (networks with a power-law degree distribution), we introduce here a new strategy for homogeneous networks as grid-like networks. To do so we use a scale-free abstraction of the network allowing to identify the most interesting zones to cure. Moreover we present a theoretical result linking the scale-free coefficient and the efficiency of the strategy of allocation in scale-free networks

Mesoporous titania coating: determination of its physicochemical properties and yeast behavior

We have synthesized titania mesoporous films using titanium (IV) chloride as sol-gel precursor and surfactants from Pluronics® (Pluronic F-127, POE-POP-POE) and Brij ? series (B96 y B58, alquil-POE) that act like molds for pore size and distribution. Nanotopography is known to be key for adhesion and cellular growth. In this experiment, we demonstrate that nanotopography is also determinant for proliferation of eukaryotic microorganisms such as Candida albicans (ATCC 10231). We cultivated the microorganism in the presence of the films, the films derivatized with APTES ((3-Aminopropyl)triethoxysilane) and the films derivatized with APTES and then doped with CuCl2 (a known fungicide). Results show that mesoporous films prepared with Brij-96 presented the best outcome in regards of controlling cellular proliferation (up to a 75% inhibition of development in the Brij-96 derivatized with APTES-CuCl2). We also characterized the mesoporous films by performing a scratch essay, which determines damage resistance of the material, and a contact angle assay. Results showed that every film tested can resist up to 40N without tearing and the contact angle, that determines superficial hydrophilicity, allowed us to establish that the coating made with Brij-96 is the least hydrophilic coating of all. This is in accordance with minor cellular proliferation results using this surface. We observed our films through scanning electron microscopy (SEM) and demonstrate that films derivatized with APTES or with APTES-CuCl2 did not change the original nanotopography of the coating. Lastly, we did an EDS (Energy-dispersive X-ray spectroscopy) essay to ratify the presence of Ti in all of the films, C and N in the ones derivatized with APTES, and C, N and Cu in the ones derivatized with APTES-CuCl2.Fil: Morcillo, Marina Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Tuttolomondo, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Catalano, Paolo Nicolás. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Bellino, Martin Gonzalo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaXX Jornadas Anuales de la Sociedad Argentina de Biología y XVII Jornadas de la Sociedad Uruguaya de Biociencias. “NANOBIOTECNOLOGÍA: Pequeñas soluciones para grandes problemasBuenos AiresArgentinaSociedad Argentina de Biologí