Compact Dual-Linear Polarized Wideband Antenna for VHF/UHF band.

International audienceA new compact dual-linearly polarized ultrawideband (UWB) antenna for VHF/UHF applications is proposed on this letter. The antenna is miniaturized thanks to inductive loading and lumped resistances. In addition, to reduce back radiation and to optimize the impedance matching at low frequencies, a ferrite layer is placed close to the radiating element. This antenna provides broadband characteristics and unidirectional radiation patterns over the whole bandwidth with a length and a height respectively limited to 6 LF l and 13 LF l , where LF l is the wavelength at the lowest frequency of the operating band. Simulations and measurements are found to be in good agreements

Catalyst-free soft-template synthesis of ordered mesoporous carbon tailored using phloroglucinol/ glyoxylic acid environmentally friendly precursors

International audienceCarbon porous materials with a periodically ordered pore structure, controlled pore size and geometry and high thermal stability are synthesized using self-assembly of environmentally friendly phloroglucinol/ glyoxylic acid precursors with an amphiphilic triblock copolymer template. Glyoxylic acid, a plant-derived compound, is used for the first time as a substituent of carcinogen formaldehyde usually employed in such a synthesis. Thanks to the double functionality, i.e., aldehyde and carboxylic acid, glyoxylic acid plays not only the role of a cross-linker for the formation of the resin but also the role of a catalyst by creation of H-bonding or specific reactions between the precursors. Hence, no extra catalyst such as strong acids (HCl) or bases (NaOH) is any longer required. Carbon films and powders were successfully prepared with high surface areas (up to 800 m2 g−1), high porous volume (up to 1 cm3 g−1), tunable pore size (0.6 nm to 7 nm) and various pore architectures (hexagonal, cubic, and ink-bottle) by tuning the precursor ratio and by applying different manufacturing engineering strategies. Insights on the synthesis mechanism of the phenolic resin and carbon mesostructures were obtained using several analysis techniques, i.e., nuclear magnetic resonance (13C NMR) and FTIR spectroscopy, temperature programmed desorption coupled with mass spectrometry (TPD-MS) and thermo-gravimetric analysis (TGA)

Hybrid Polymer/Lipid Vesicles: Influence of polymer architecture and molar mass on line tension

Hybrid polymer/lipid vesicles are self-assembled structures that have been the subject of an increasing number of studies in recent years. They are particularly promising tools in the development of cell membrane models as they offer the possibility to fine-tune their membrane structure by adjusting the distribution of components (presence or absence of “raft like” lipid domains) which is of prime importance to control their membrane properties. Line tension in multiphase membranes is known to be a key parameter on membrane structuration but remains unexplored, either experimentally or by computer modelling for hybrid polymer /lipid vesicles. In this study we were able to measure the line tension on different budded hybrid vesicles, using micropipette aspiration technique, and show the influence of the molar mass and the architecture of block copolymers on line tension and its consequences for membrane structuration

Organogels from trehalose difatty esters amphiphiles

International audienceSaccharide diesters have been recently shown to be excellent gelators of vegetable oils. In this paper, different fatty acid trehalose diesters were synthesized by a selective enzymatic transesterification performed only on the primary hydroxyl group of the trehalose. The resulting trehalose diesters demonstrated their ability to self-assemble in a large variety of edible vegetable oils with a minimum gelation concentration of 0.25 wt%/v. Microscopic analysis and X-ray scattering studies indicate that the gels are obtained by the self-assembly of trehalose diesters in crystalline fibers constituting the tridimensional network. The rheological study revealed that the properties of the gels depend on the kind of fatty acid grafted on the trehalose but are also influenced by the vegetable oil composition

Are restricted and repetitive behaviours in two‐ and six‐year‐olds associated with emotional and behavioural difficulties?

Background: Restricted and repetitive patterns of behaviour (RRBs) serve an adaptive role in development. Elevated levels of RRBs beyond the early years, however, are associated with poorer outcome in language, cognition, and wellbeing, and are seen across a range of neurodevelopmental conditions. This study aimed to characterize the association of distinct RRB subtypes at two and six years of age, with internalising and externalising difficulties in a community sample of children. Methods: 485 parents reported on their child's insistence on sameness (IS) and repetitive sensory and motor (RSM) RRBs at two and six years of age using the Repetitive Behaviour Questionnaire (RBQ‐2). Emotional and behavioural difficulties were measured using the Strengths and Difficulties Questionnaire (SDQ) at age six. Results: Consistent with previous research, RRBs later in development better predicted emotional and behavioural difficulties at age six than RRBs earlier in development. Moreover, IS RRBs were selectively associated with internalising behaviours and RSM RRBs with externalising behaviours. Importantly, these selective associations depended on when RRBs were measured. Only IS RRBs at age six were significantly associated with internalising behaviour. By contrast, while more RSM RRBs at age six were associated with higher rates of externalising behaviours, higher rates of RSM RRBs at age two were associated with fewer externalising behaviours, adding further support to the previously reported adaptive role of RRBs in early behaviour regulation. Conclusion: Although there is a need for further research to provide a detailed profile of the adaptive periods for IS and RSM RRBs, the present findings support the potential utility of elevated RRBs as a signal for emotional and behavioural difficulties at age six

Bio-Based Polyricinoleate and Polyhydroxystearate: Properties and Evaluation as Viscosity Modifiers for Lubricants

This paper aims to design bio-based polyester as a viscosity modifier for lubricant properties. Bio-based polyricinoleate (PRic) and its saturated homologous polyhydroxystearate (PHS) have been synthesized from fatty acid methyl esters. The polycondensation performed in bulk in a one-step reaction without any purification leads to two series of polyesters within a large range of molecular weights, with Mw between 3 and 130 kg·mol–1. Their thermal properties were investigated. Good thermal stability was observed with degradation temperatures above 300 °C. As expected, PRic appeared to be amorphous with a particularly low glass-transition temperature, while PHS is semicrystalline. A rheological study determined that polyricinoleate entangled when its molecular weight was above 25 kg·mol–1. These two bio-based and biodegradable polymers were then evaluated as viscosity modifiers in both organic and mineral oils. PHS with high molecular weights appeared to be an excellent thickener as well as a good viscosity index improver with a viscosity index (VI) increase above +50 in organic lubricant oil and +64 in mineral oil

The frequency of restricted and repetitive behaviours in a community sample of 15 month-old infants

Objective: To investigate the frequency and pattern of a wide range of restricted and repetitive behaviors (RRBs) in the second year of life. Method: Parents of 139 15-month-old typically developing infants from a community sample completed the Repetitive Behaviour Questionnaire-2 (RBQ-2), giving information on RRBs (e.g. stereotyped motor movements, sensory interests, routines and rituals and preoccupations with restricted interests) seen in their children. Results: The RBQ-2 was found to be a reliable measure of these behaviors at this age and revealed a high frequency of particular types of repetitive motor movements in 15-month-olds. Conclusion: These findings have implications for the early detection of disorders characterized by high levels of restricted and repetitive behaviors, such as Autism Spectrum Disorder (ASD)

Application de la borne de Cramer-Rao dans le cas de systèmes antennaires complexes de goniométrie

Généralement, la borne de Cramer-Rao des directions d'arrivée de signaux sur un réseau de capteurs est calculée de façon théorique [1] [2] [3]. Or dès que l'on désire effectuer une application numérique de la borne de Cramer-Rao pour un système donné, on est souvent amené à effectuer des suppositions et/ou des simplifications. En effet, il est souvent très difficile de tenir compte et de modéliser l'environnement et les différents phénomènes pouvant perturber le réseau de capteurs, comme le couplage entre antennes, l'influence d'un porteur (mat ou véhicule) en termes de diffraction, de réflexion ou même la présence d'un sol. Dans ce travail, nous utilisons un logiciel de simulation électromagnétique pour estimer l'impact de l'environnement réel sur le vecteur direction d'un système antennaire complexe de goniométrie. La borne de Cramer-Rao déterministe des directions d'arrivée de signaux est ensuite déterminée pour le réseau de capteurs de goniométrie soumis à des perturbations. Les résultats montrent que la précision dépend fortement de la prise en compte des couplages et perturbations du système antennaire. On montre ainsi que l'environnement a un impact non négligeable et que l'on peut calculer une borne de Cramer Rao des directions d'arrivée plus réaliste et ainsi optimiser dans certains cas le système antennaire de goniométrie en fonction de son environnement

Eco-friendly synthesis of SiO2 nanoparticles confined in hard carbon: A promising material with unexpected mechanism for Li-ion batteries

Times Cited: 3Nita, Cristina Fullenwarth, Julien Monconduit, Laure Le Meins, Jean-Marc Fioux, Philippe Parmentier, Julien Ghimbeu, Camelia MateiGhimbeu, Camelia/N-7855-2015Ghimbeu, Camelia/0000-0003-3600-587731873-3891A fast, simple and environmentally friendly one-pot route to obtain carbon/SiO2 hybrid materials is reported in this work. This consists in simple mixture of carbon and silica precursors, followed by thermal annealing at different temperatures. An interpenetrating hybrid network composed of hard carbon and amorphous SiO2 nanoparticles (2–5 nm) homogeneously distributed was achieved. Increasing the annealing temperature from 600 °C up to 1200 °C, the material porosity and oxygen functional groups are gradually removed, while the amorphous nature of SiO2 is conserved. This allows to diminish the irreversible capacity during the first charge-discharge cycle and to increase the reversible capacity. An excellent cycling capability, with a reversible capacity up to 535 mA h/g at C/5 constant current rate was obtained for C/SiO2 materials used as anodes for Li-ion batteries. An atypical increase of the capacity during the first 50 cycles followed by a stable plateau up to 250 cycles was observed and related to electrolyte wettability limitation through the materials, particularly for those annealed at high temperatures which are more hydrophobic, less porous and the SiO2 nanoparticles less accessible. The SiO2 lithiation mechanism was evaluated by XRD, TEM and XPS post-mortem analyses and revealed the formation of reversible lithium silicate phases