Correlation length of hydrophobic polyelectrolyte solutions

The combination of two techniques (Small Angle X-ray Scattering and Atomic Force Microscopy) has allowed us to measure in reciprocal and real space the correlation length $\xi$ of salt-free aqueous solutions of highly charged hydrophobic polyelectrolyte as a function of the polymer concentration $C_p$, charge fraction $f$ and chain length $N$. Contrary to the classical behaviour of hydrophilic polyelectrolytes in the strong coupling limit, $\xi$ is strongly dependent on $f$. In particular a continuous transition has been observed from $\xi \sim C_p^{-1/2}$ to $\xi\sim C_p^{-1/3}$ when $f$ decreased from 100% to 35%. We interpret this unusual behaviour as the consequence of the two features characterising the hydrophobic polyelectrolytes: the pearl necklace conformation of the chains and the anomalously strong reduction of the effective charge fraction.Comment: 7 pages, 5 figures, submitted to Europhysics Letter

Nonperturbative renormalization group approach to Lifshitz critical behaviour

The behaviour of a d-dimensional vectorial N=3 model at a m-axial Lifshitz critical point is investigated by means of a nonperturbative renormalization group approach that is free of the huge technical difficulties that plague the perturbative approaches and limit their computations to the lowest orders. In particular being systematically improvable, our approach allows us to control the convergence of successive approximations and thus to get reliable physical quantities in d=3.Comment: 6 pages, 3 figure

Joint Learning of Pre-Trained and Random Units for Domain Adaptation in Part-of-Speech Tagging

Fine-tuning neural networks is widely used to transfer valuable knowledge from high-resource to low-resource domains. In a standard fine-tuning scheme, source and target problems are trained using the same architecture. Although capable of adapting to new domains, pre-trained units struggle with learning uncommon target-specific patterns. In this paper, we propose to augment the target-network with normalised, weighted and randomly initialised units that beget a better adaptation while maintaining the valuable source knowledge. Our experiments on POS tagging of social media texts (Tweets domain) demonstrate that our method achieves state-of-the-art performances on 3 commonly used datasets

A glassy phase in quenched disordered graphene and crystalline membranes

We investigate the flat phase of $D$-dimensional crystalline membranes embedded in a $d$-dimensional space and submitted to both metric and curvature quenched disorders using a nonperturbative renormalization group approach. We identify a second order phase transition controlled by a finite-temperature, finite-disorder fixed point unreachable within the leading order of $\epsilon=4-D$ and $1/d$ expansions. This critical point divides the flow diagram into two basins of attraction: that associated to the finite-temperature fixed point controlling the long distance behaviour of disorder-free membranes and that associated to the zero-temperature, finite-disorder fixed point. Our work thus strongly suggests the existence of a whole low-temperature glassy phase for quenched disordered graphene, graphene-like compounds and, more generally, crystalline membranes.Comment: 6 pages, 1 figur

Hydrophobic Polyelectrolytes in Better Polar Solvent. Structure and Chain Conformation as seen by Saxs and Sans

We demonstrate in this paper the influence of solvent quality on the structure of the semi-dilute solution of a hydrophobic polyelectrolyte, partially sulfonated Poly-Styrene Sulfonate. Two solvents are used: (i) one mixture of water and an organic solvent: THF, which is also slightly polar; (ii) DMSO, a polar organic solvent. In case (i), it is shown by SAXS study that the structure - namely the scattering from all chains, characterised by a maximum ("polyelectrolyte peak"), of the aqueous hydrophobic polyelectrolyte solutions (PSS) depends on the solvent quality through the added amount of organic solvent THF. This dependence is more pronounced when the sulfonation rate is low (more hydrophobic polyelectrolyte). It is proposed that when THF is added, the chain conformation evolves from the pearl necklace shape already reported in pure water, towards the conformation in pure water for fully sulfonated PSS, which is string-like as also reported previously. On the contrary, for a hydrophilic polyelectrolyte, AMAMPS, no evolution occurs with added THF in the aqueous solution. In case (ii), it is shown directly by SANS study that PSS can behave as a classical solvophilic polyelectrolyte when dissolved in an organic polar solvent such as DMSO: the structure (total scattering) as well as the form factor (single chain scattering measured by SANS using the Zero Average Contrast method) of the PSS chains is independent of the charge content in agreement with Manning condensation, and identical to the one of a fully charged PSS chain in pure water, which has a classical polyelectrolyte behaviour in the semi-dilute regime

Adaptive parameters adjustment in WBAN to mitigate Wi-Fi interferences

Wireless Body Area Network (WBAN), called also Wireless Body Sensor Network (WBSN), is composed of a set of tiny wireless devices (sensors) attached, implanted or ingested into the body. It offers real time and ubiquitous applications thanks to the small form, the lightness, and the wireless interface of sensors. WBAN performance is expected to be considerably degraded in the presence of Wi-Fi networks. Their operating channels overlap in the 2.4 GHz Industrial Scientific and Medical (ISM) band which produces interference when they transmit data, accompanied by data losses and quick battery exhaustion. Therefore, it is crucial to mitigate the interference between WBAN and Wi-Fi networks in order to maintain the efficiency and the reliability of the WBAN system. Proposals in the literature use an added complex hardware in WBAN system, or perform the exchange of additional information, or establish expensive communications, or affect the quality of service of the WBAN. Unlike previous researches, we proposed simple, low cost and dynamic method that adaptively adjusts specific parameters in the Medium Access Control (MAC) layer. We have proved the effectiveness of our approach based on theoretical analysis and simulation using MiXiM framework of OMNet++ simulato

Biotic and abiotic interactions between the superficial and interstitial water of a river to the Middle Atlas (Oued Tizguit)

Biotic and abiotic interactions between the superficial and interstitial waters have been analysed on the level of the interfacing zone between a river (Tizguit oued) and its underflow. The interactions were the results of water, mineral nutrients, organic matter and live beings transfers. Biotic interactions estimated by the taxonomic richness of invertebrate interstitial and superficial communities permitted to describe a zone of interfacing characterized by a dominance of epigean taxa and the scarcity of hypogean individus, represented here by the only stygobionte species Pseudoniphargus sp. The physico-chemistry of water permits to determines its quality and detect a certain natural or artificial pollution. It allows to determine its origin and explain the variations of the biological function. The interstitial waters of the Oued are relatively cold, slightly alkalised, mineralised, and relatively similar to the superficial waters from which they originate. The dynamic of exchanges at the level of interfacing zone between the river and its underflow is a direct vertical type. Exchanges take place from the surface to interstitial middle. They drag in depth epigean fauna, washed P.O.M (Particulate organic matter) and the physico-chemical features of the superficial water.Biotic and abiotic interactions between the superficial and interstitial waters have been analysed on the level of the interfacing zone between a river (Tizguit oued) and its underflow. The interactions were the results of water, mineral nutrients, organic matter and live beings transfers. Biotic interactions estimated by the taxonomic richness of invertebrate interstitial and superficial communities permitted to describe a zone of interfacing characterized by a dominance of epigean taxa and the scarcity of hypogean individus, represented here by the only stygobionte species Pseudoniphargus sp. The physico-chemistry of water permits to determines its quality and detect a certain natural or artificial pollution. It allows to determine its origin and explain the variations of the biological function. The interstitial waters of the Oued are relatively cold, slightly alkalised, mineralised, and relatively similar to the superficial waters from which they originate. The dynamic of exchanges at the level of interfacing zone between the river and its underflow is a direct vertical type. Exchanges take place from the surface to interstitial middle. They drag in depth epigean fauna, washed P.O.M (Particulate organic matter) and the physico-chemical features of the superficial water

A Proactive Approach for Coping with Uncertain Resource Availabilities on Desktop Grids

International audienceUncertainties stemming from multiple sources affect distributed systems and jeopardize their efficient utilization. Desktop grids are especially concerned by this issue as volunteers lending their resources may have irregular and unpredictable behaviors. Efficiently exploiting the power of such systems raises theoretical issues that received little attention in the literature. In this paper, we assume that there exist predictions on the intervals during which machines are available. When these predictions have a limited error, it is possible to schedule a set of jobs such that the effective total execution time will not be higher than the predicted one. We formally prove it is the case when scheduling jobs only in large intervals and when provisioning sufficient slacks to absorb uncertainties. We present multiple heuristics with various efficiencies and costs that are empirically assessed through simulations