Electromagnetic 3-D model for active linear devices: application to pHEMTs in the linear regime

In this paper, we describe a three-dimensional (3D) electromagnetic (EM) approach to the modeling of active devices in their linear regime. The technique basically relies on the self-consistent introduction of distributed controlled current sources in the 3D EM simulation of passive components. The approach is validated by comparing measured and calculated results for a pseudomorphic high electron-mobility transistor in the millimeter-wave range. However, it may also be applied to a larger class of field-effect transistors, including MESFETs.     

Diffusional control in the intergranular corrosion of some hcp metals in iodine alcoholic solutions

Some hexagonal closed-packed metals (titanium, zirconium and one of its alloys, Zircaloy-4) were found to undergo intergranular attack in solutions of iodine in different alcohols at room temperature. It was determined that the rate-controlling step of the intergranular corrosion was the diffusion of iodine-alcoholic complexes to the front of the attack. The diffusion coefficients of the different iodine-alcohol complexes in the respective solutions of iodine in alcohol were measured. These measurements agree with the calculated values of the diffusion coefficients obtained by means of the Einstein-Stokes equation where molecular modelling was used to estimate the size of the species involved. In addition, the value obtained in iodine-methanol solution is in agreement with that found in literature measured by means of a rotating disk electrode.     

Polyhedral reachable set with positive controls

Given a reachable discrete-time linear system (A,b), the reachable set is a cone when a positive constraint is imposed on the input. The problem to be studied is the geometrical structure of the reachable set = cone(b, Ab, A²b,...) in terms of the spectrum ofA. In particular, conditions which ensure , or its closureR, is a polyhedral proper cone are derived. The impact of the given results on finite-time reachability and positive realizability is also discussed.     

Novel Synthetic Approach to Tune the Surface Properties of Polymeric Films: Ionic Exchange Reaction between Sulfonated Polyarylethersulfones and Ionic Liquids

Currently, no studies dealing with the role played by ionic liquids on tailoring surface features of polymer films are available. In this work, ionic liquids influence on the surface of sulfonated polyarylethersulfones was investigated. Sulfonated polyarylethersulfones with different degrees of sulfonation were synthesized; their surface properties were modulated through an ionic exchange reaction between the K⁺ cation of sulfonated polyarylethersulfones and ionic liquids, synthesized changing the length of cation of apolar groups. Hydrophobic properties of sulfonated polyarylethersulfones–ionic liquids films improve with both an increase in degrees of sulfonation and the length of ionic liquids alkyl chains due to higher surface roughness, as shown by scanning electron microscopy and atomic force microscopy.     

Distribution and dynamics of birds in a rural sub-Mediterranean landscape

The richness and abundance of birds in a sub-Mediterranean rural landscape (north Italy, Massa Carrara Province) were investigated across two spatial scales (10 km × 10 km and 5 km × 5 km), two functional scales (land use mosaic and ecotope) and two temporal scales (annual and seasonal).Information on birds collected using the line transect method was compared with some landscape attributes (altitude, orientation, patch size, distance from cultivations).Distribution, abundance and seasonal turnover of birds were described efficiently by land use cover and ecotopes, but altitude, orientation, patch size and neighboring patch types were also important.Pure crop areas and crops mixed within woodlands and farming villages were the areas preferred by birds especially out of the breeding period, although woodlands supported more stable birds assemblages over the year. The multiscalar approach proposed was an efficient strategy to investigate these bird assemblages living in a patchy rural mosaic in which resources were made seasonally available by agricultural practices.The recent landscape change due to abandonment of agriculture in most of the sub-Mediterranean mountainous rural areas and the consequent woodland encroachment were expected to produce impoverishment of both diversity and abundance of resident and migratory birds.     

Peripheral electrical stimulation triggered by self-paced detection of motor intention enhances motor evoked potentials

This paper proposes the development and experimental tests of a self-paced asynchronous brain-computer interfacing (BCI) system that detects movement related cortical potentials (MRCPs) produced during motor imagination of ankle dorsiflexion and triggers peripheral electrical stimulations timed with the occurrence of MRCPs to induce corticospinal plasticity. MRCPs were detected online from EEG signals in eight healthy subjects with a true positive rate (TPR) of 67.15 ± 7.87% and false positive rate (FPR) of 22.05 ±9.07%. The excitability of the cortical projection to the target muscle (tibialis anterior) was assessed before and after the intervention through motor evoked potentials (MEP) using transcranial magnetic stimulation (TMS). The peak of the evoked potential significantly (P=0.02) increased after the BCI intervention by 53 ± 43% (relative to preintervention measure), although the spinal excitability (tested by stretch reflexes) did not change. These results demonstrate for the first time that it is possible to alter the corticospinal projections to the tibialis anterior muscle by using an asynchronous BCI system based on online motor imagination that triggered peripheral stimulation. This type of repetitive proprioceptive feedback training based on self-generated brain signal decoding may be a requirement for purposeful skill acquisition in intact humans and in the rehabilitation of persons with brain damage.