From clay- to organoclay-film modified electrodes: tuning charge selectivity in ion exchange voltammetry

The surface of two natural smectite-type clay samples was chemically modified by covalent grafting of amine groups, by reaction with γ-aminopropyltriethoxysilane, which were easily protonated in HCl medium. Multisweep cyclic voltammograms of clay-film modified glassy carbon electrodes made of either the raw clays or the propylammonium-functionalized samples exposed to Ru(NH₃)₆³⁺ or Fe(CN)₆³⁻ electroactive probes were obtained. The results indicated a permselective behavior of these clay and organoclay-films based on either favorable or unfavorable electrostatic interactions. The cation-exchanging raw clay film modified electrodes exhibited accumulation properties for Ru(NH₃)₆³⁺ species while rejecting Fe(CN)₆³⁻, whereas the anion-exchanging organoclay coatings acted as a barrier against Ru(NH₃)₆³⁺ while increasing dramatically the concentration of Fe(CN)₆³⁻ species at the electrode surface. Strong binding of the probe to the organoclays resulted in a potential shift of ca. 0.1 V of the voltammetric signals characteristic of the Fe(CN)₆^3−/4− couple in the anodic direction. Their good preconcentration efficiency at low analyte concentration highlighted their interest for electroanalytical applications.     

Collaborative and Cognitive Network Platforms: Vision and Research Challenges

In this paper, we present a visionary concept referred to as Collaborative and Cognitive Network Platforms (CCNPs) as a future-proof solution for creating a dependable, self-organizing and self-managing communication substrate for effective ICT solutions to societal problems. CCNP creates a cooperative communication platform to support critical services across a range of business sectors. CCNP is based on the personal network (PN) technology which is an inherently cooperative environment prototyped in the Dutch Freeband PNP2008 and the European Union IST MAGNET projects. In CCNP, the cognitive control plane strives to exploit the resources to better satisfy the requirements of networked applications. CCNP facilitates collaboration inherently. Through cognition in the cognitive control plane, CCNP becomes a self-managed substrate. The self-managed substrate, in this paper, is defined as cognitive and collaborative middleware on which future applications run without user intervention. Endemic sensor networks may be incorporated into the CCNP concept to feed its cognitive control plane. In this paper, we present the CCNP concept and discuss the research challenges related to collaboration and cognition.     

Cooperative Communications in Future Home Networks

The basic idea behind cooperative communications is that mobile terminals collaborate to send data to each other. This effectively adds diversity in the system and improves the overall performance. In this paper, we investigate the potential gains of cooperative communication in future home networks. We derive analytical expressions for the error probability of binary phase shift keying (BPSK) signals over Nakagami-m fading channels in a multi relay communication network. Following to the analytical study, we analyze the contribution of cooperative relaying to the 60GHz network connectivity through simulations using a realistic indoor environment model. We compare the performance of different relay configurations under variable obstacle densities. We show that a typical 60GHz indoor network should employ either a multi-relay configuration or a single-relay configuration with a smart relay selection mechanism to achieve acceptable outage rates. In the use of multiple-relay configuration, both analytical and simulation studies indicate that increasing the number of cooperative relays does not improve the system performance significantly after a certain threshold.     

A Novel Approach for the Link Layer in Impulse-based UWB Ad Hoc Networks

Ultra Wide Band (UWB) impulse radio, promises to be suitable for short-range, low-power, low cost and high data rate applications. While most UWB research is concentrating on the physical layer, little research has been published on the link layer. The fundamental operations in the link layer need to take into account the specifics of impulse radio and also the particular features of ad hoc networks. A novel self-organizing link layer protocol based on time hopping impulse radio, called SDD, was proposed by the authors. This protocol is a collision-free mechanism that enables the devices to discover neighboring nodes and arrange the access to communication resources shared among the nodes. In this paper, some issues related to the self-organizing link layer based on UWB impulse radio are investigated and addressed. The SDD protocol is further developed and specified in detail. The simulations are carried out using GloMoSim simulation environment. An SDD module has been developed and embedded in the simulator. Results show that the SDD protocol can work properly and efficiently in a single-hop ad hoc network.     

Preconcentration and voltammetric analysis of mercury(II) at a carbon paste electrode modified with natural smectite-type clays grafted with organic chelating groups

This study is devoted to the evaluation of a carbon paste electrode modified by a natural 2:1 phyllosilicate clay functionalized with either amine or thiol groups as a sensor for mercury(II). Functionalization was achieved by grafting the pristine clay via its reaction with 3-aminopropyltriethoxysilane (APTES) or 3-mercaptopropyltrimethoxysilane (MPTMS), respectively. The electroanalytical procedure comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using differential pulse anodic stripping voltammetry. The different parameters that govern the two steps (accumulation time, concentration of the analyte, composition of the detection medium, potential and duration of electrolysis) were studied in detail. After optimization, a linear response was obtained in the concentration range from 0.1 to 0.7 μM Hg(II). In these conditions, the detection limits of the method were found to be 8.7 × 10⁻⁸ and 6.8 × 10⁻⁸ M, respectively, for the amine- and thiol-functionalized clays, on the basis of a signal-to-noise ratio of 3. The effect of potential interference on the determination of Hg(II) by the carbon paste electrode modified with the thiol-functionalized clay was also studied and the applicability of the method to real sample analysis was evaluated.     

XRD studies of nickel hydride formation in alkaline solutions containing a promotor

An effect of cathodic charging conditions on the amount of the β-NiH_x phase formed in nickel electrode in alkaline solutions was studied by means of X-ray diffraction technique. Electrolytic nickel coatings on copper substrate were hydrogenated in KOH, NaOH, LiOH and NH₄OH solutions containing promoters such as As₂O₃, Sb and GeO₂. Dependences of the β-NiH_x phase volume fraction on the promotor concentration, charging current density and charging duration were studied. Optimal values of these charging conditions parameters were determined. The volume fraction of the β-NiH_x phase amounted up to ∼56% of 10 μm thick nickel coating. The quantity of nickel hydride did not depend on the alkali and its concentration. Promoters were arranged in the following order of effectiveness in causing nickel hydride formation: S>As>Sb>Ge. It was suggested that NiAs type compounds could take part in the nickel hydride formation.     

Touch tracking with a particle filter

We report on a system for multi-touch tracking from linescan cameras using particle filters. We show that a particle filter incorporating a local search element is almost as accurate as an exhaustive search algorithm and is significantly faster as the number of touches increases. The system achieves over 95 % correct tracking with an error tolerance of 1 mm for up to eight touches.