An altruistic cross‐layer recovering mechanism for ad hoc wireless networks

Video streaming services have restrictive delay and bandwidth constraints. Ad hoc networks represent a hostile environment for this kind of real‐time data transmission. Emerging mesh networks, where a backbone provides more topological stability, do not even assure a high quality of experience. In such scenario, mobility of terminal nodes causes link breakages until a new route is calculated. In the meanwhile, lost packets cause annoying video interruptions to the receiver. This paper proposes a new mechanism of recovering lost packets by means of caching overheard packets in neighbor nodes and retransmit them to destination. Moreover, an optimization is shown, which involves a video‐aware cache in order to recover full frames and prioritize more significant frames. Results show the improvement in reception, increasing the throughput as well as video quality, whereas larger video interruptions are considerably reduced. Copyright © 2014 John Wiley & Sons, Ltd.     

Samarium as a Schottky barrier on p-type-silicon

The electrical and structural characteristics of the samarium-silicon contact have been investigated after thermal treatments up to 300°C for 30 min in vacuum. Good Schottky barriers have been realized for treatments up to 200°C obtaining a barrier height of 0.70 eV. The electrical barrier properties degrade at temperatures above 250°C, where a continuous Layer of SmSi_1.7 is formed.     

Visualisation of extensive water ribbons and networks in a DNA minor-groove drug complex

The crystal structure is reported of a complex between an ethyl derivative of the minor-groove drug furamidine and the dodecanucleotide duplex d(CGCGAATTCGCG)2, which has been refined to 1.85 A resolution and an R factor of 16.6% for data collected at -173 degreesC. An exceptionally large number (220) of water molecules have been located. The majority of these occur in the first coordination shell of solvation. There are extensive networks of connected waters, both in the major and minor grooves. In particular, there are 21 water molecules associated with the minor-groove drug, via hydrogen bonds from the four charged nitrogen atoms. One cluster of four waters is situated in the groove itself; the majority are on the outer edge of the groove, and serve to bridge between the outward-directed drug nitrogen atoms and backbone phosphate oxygen atoms. These bridges are both intra- and inter-strand, with the net effect that the outer edge of the drug molecule is covered by ribbons of water molecules.     

Resistivity of phosphorus-doped sputter-deposited polycrystalline silicon films

The resistivity of phosphorus-doped sputter-deposited polycrystalline silicon films has been extensively investigated as a function of many technological parameters with the aim of establishing whether these films can be doped to the desired resistivity values for MOS applications. An empirical expression has been determined for a standard doping process which relates the final sheet resistance of the film to the deposition rate and to the temperature of an annealing treatment carried out before predeposition. Once specified the desired sheet resistance, the two above parameters can be chosen in such a way as to minimize the annealing temperature, if high-temperature processing is to be prevented.     

Structural Changes in the BODIPY Dye PM567 Enhancing the Laser Action in Liquid and Solid Media

In the search for more efficient and photostable solid‐state dye lasers, newly synthesized analogs of the borondipyrromethene (BODIPY) dye PM567, bearing the polymerizable methacryloyloxypropyl group at position 2 (PMoMA) or at positions 2 and 6 (PDiMA), have been studied in the form of solid copolymers with methyl methacrylate (MMA). The parent dye PM567, as well as the model analogs bearing the acetoxypropyl group in the same positions, PMoAc and PDiAc, respectively, have been also studied both in liquid solvents and in solid poly(MMA) (PMMA) solution. Although in liquid solution PMoAc and PDiAc have the same photophysical properties as PM567, PDiAc exhibited a photostability up to 10 times higher than that of PM567 in ethanol under 310 nm‐irradiation. The possible stabilization factors of PDiAc have been analyzed and discussed on the basis of the redox potentials, the ability for singlet molecular oxygen [O₂(¹Δ_g)] generation, the reactivity with O₂(¹Δ_g), and quantum mechanical calculations. Both PMoAc and PDiAc, pumped transversally at 532 nm, lased in liquid solution with a high (up to 58 %), near solvent‐independent efficiency. This enhanced photostabilization has been also observed in solid polymeric and copolymeric media. While the solid solution of the model dye PDiAc in PMMA showed a lasing efficiency of 33 %, with a decrease in the laser output of ca. 50 % after 60 000 pump pulses (10 Hz repetition rate) in the same position of the sample, the solid copolymer with the double bonded chromophore, COP(PDiMA‐MMA), showed lasing efficiencies of up to 37 %, and no sign of degradation in the laser output after 100 000 similar pump pulses. Even under the more demanding repetition rate of 30 Hz, the laser emission from this material remained at 67 % of its initial laser output after 400 000 pump pulses, which is the highest laser photostability achieved to date for solid‐state lasers based on organic polymeric materials doped with laser dyes. This result indicates that the double covalent linkage of the BODIPY chromophore to a PMMA polymeric matrix is even more efficient than the simple linkage, for its photostabilization under laser operation.     

Performance Evaluation of Video Streaming Over Ad Hoc Networks Using Flat and Hierarchical Routing Protocols

A performance evaluation of real time services (such as video streaming) over mobile ad-hoc networks using both hierarchical and flat routing protocols is shown in this paper. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network have been simulated using NS-2. We use OLSR (Optimized Link State Protocol) as the flat routing protocol and our own implementation of HOLSR (Hierarchical OLSR)—which uses HNA (Host and Network Association) messages—as the hierarchical one, modifying other previous HOLSR version and maintaining the maximum compatibility with the flat OLSR. We carry out a complete comparison between these protocols focused on video evaluation. The simulation lets us compare the quality of service (QoS) of the video streaming paying attention to objective parameters (PSNR, packet delivery ratio, packet delay and interruptions). Some drawbacks of the hierarchical environment are also analyzed, as the link load between cluster heads and the lack of QoS-state-aware in HOLSR design. Quantitative results indicate that the protocol overhead is reduced (more than 40% in larger networks) and the video quality is improved (from 1 to 6 dB in certain cases) using hierarchical protocols.     

Finite element approximation of regularized solutions of the inverse potential problem of electrocardiography and applications to experimental data

Summary This paper investigates the problem of estimating the electric potential distribution in proximity of the heart from potential data given on the body and is here reformulated as a control problem in terms of a ?transfer? operator and stabilized by means of a suitable regularization operator. The numerical approximation by means of the finite element method of the regularized problem is investigated; convergence results and error estimates are established. The numerical procedures for the computation of the approximate ?transfer? operator and for the solution of the least square problem approximating the regularized control problem are described. The performance of several criteria for the best choice of the regularization parameter is analyzed. Finally the numerical inverse procedure, extensively tested using test functions and data fromin vitro experiments, is applied to human data. Dedicated to Professor S. Faedo on his 70th birthday This work was supported through grants by MPI 40%, the Special Program on Bioengineering of CNR and IAN of CNR.