The Peer’s Dilemma: A general framework to examine cooperation in pure peer-to-peer systems

The exploration of social dilemmas is being considered a major foundation for encountering the enforced necessities of cooperation in self-organizing environments. Such environments are characterized by self-interested parties and the absence of trusted third parties. Recent approaches apply evolutionary socio-inspired games to formally prove the existence and further prolongation of cooperation patterns within communities. For instance, the Prisoner’s Dilemma game has thus provided a rich opportunity to examine self-interested behaviors in pure peer-to-peer networks. However, assuming a total absence of coalitions, incentives and punishment mechanisms, several works argue against a durable maintenance of cooperation neither at single-shot nor repeated-scenarios. In this article, we formally and experimentally demonstrate a counterexample for the latter by applying evolutionary game theory and a particular instance of the Rock–Scissors–Paper game. Our framework proves that the cyclic dominance of certain type of nodes within a P2P system has an impact and introduces a strategic aspect to the evolution of the overall community.     

A supplemental computer-assisted intervention programme to prevent early reading difficulties in Spanish learners: A stratified random control trial

Difficulties in implementing effective instruction for at-risk students arise from two challenges: the transfer of evidence-based knowledge and the lack of economic resources. Computer-assisted programmes offer a suitable solution, providing quality instruction using low-cost resources. Thirty-two first-grade students with early learning difficulties were identified and paired based on at least three of the pre-intervention reading measures (reading efficiency of monosyllabic and disyllabic items, words, pseudowords and text reading speed). Each pair was assigned to one of two different intervention programmes: a computer-assisted intervention programme (CAIP) focused on syllables or the programme provided by the Spanish State School Assistance Services (SSAS). Every week, the CAIP participants received in pairs four 15-min training sessions on syllable decoding plus one 30-min group comprehension session. The CAIP was delivered by trainee students. The SSAS programme typically consisted of a 1-hr individual or in small groups sessions per week delivered by trained practitioners. Both programmes were administered for 11 weeks. The CAIP intervention showed better results than the SSAS intervention for both decoding and comprehension, with moderate to large effect sizes.     

Properties and Printability of Inkjet and Screen-Printed Silver Patterns for RFID Antennas

We report the modeling, and geometrical and electrical characterization, of inkjet and screen-printed patterns on different polymeric substrates for use as antennas in radio-frequency identification (RFID) applications. We compared the physical and electrical characteristics of two silver nanoparticle-based commercial inkjet-printable inks and one screen-printable silver paste, when deposited on polyimide (PI), polyethylene terephthalate (PET), and polyetherimide (PEI) substrates. First, the thickness of the inkjet-printed patterns was predicted by use of an analytical model based on printing conditions and ink composition. The predicted thickness was confirmed experimentally, and geometrical characterization of the lines was completed by measuring the root-mean-square roughness of the patterns. Second, direct-current electrical characterization was performed to identify the printing conditions yielding the lowest resistivity and sheet resistance. The minimum resistivity for the inkjet-printing method was 8.6 ± 0.8 μΩ cm, obtained by printing four stacked layers of one of the commercial inks on PEI, whereas minimum resistivity of 44 ± 7 μΩ cm and 39 ± 4 μΩ cm were obtained for a single layer of screen-printed ink on polyimide (PI) with 140 threads/cm mesh and 90 threads/cm mesh, respectively. In every case, these minimum values of resistivity were obtained for the largest tested thickness. Coplanar waveguide transmission lines were then designed and characterized to analyze the radio-frequency (RF) performance of the printed patterns; minimum transmission losses of 0.0022 ± 0.0012 dB/mm and 0.0016 ± 0.0012 dB/mm measured at 13.56 MHz, in the high-frequency (HF) band, were achieved by inkjet printing on PEI and screen printing on PI, respectively. At 868 MHz, in the ultra-high-frequency band, the minimum values of transmission loss were 0.0130 ± 0.0014 dB/mm for inkjet printing on PEI and 0.0100 ± 0.0014 dB/mm for screen printing on PI. Although the resistivity achieved is lower for inkjet printing than for screen printing, RF losses for inkjetted patterns were larger than for screen-printed patterns, because thicker layers were obtained by screen printing. Finally, several coil inductors for the HF band were also fabricated by use of both printing techniques, and were used as antennas for semi-passive smart RFID tags on plastic foil capable of measuring temperature and humidity.     

A Markov-Based Channel Model Algorithm for Wireless Networks

Techniques for modeling and simulating channel conditions play an essential role in understanding network protocol and application behavior. In [11], we demonstrated that inaccurate modeling using a traditional analytical model yielded suboptimal error control protocol parameters choices. In this paper, we demonstrate that time-varying effects on wireless channels result in wireless traces which exhibit non-stationary behavior over small window sizes. We then present an algorithm that extracts stationary components from a collected trace in order to provide analytical channel models that, relative to traditional approaches, more accurately represent characteristics such as burstiness, statistical distribution of errors, and packet loss processes. Our algorithm also generates artificial traces with the same statistical characteristics as actual collected network traces. For validation, we develop a channel model for the circuit-switched data service in GSM and show that it: (1) more closely approximates GSM channel characteristics than traditional Markov models and (2) generates artificial traces that closely match collected traces' statistics. Using these traces in a simulator environment enables future protocol and application testing under different controlled and repeatable conditions.     

Mechanism and kinetics of sulfamethoxazole photocatalytic ozonation in water

The photocatalytic ozonation of sulfamethoxazole (SMT) has been studied in water under different experimental conditions. The effect of gas flow rate, initial concentration of ozone, SMT and TiO₂ has been investigated to establish the importance of mass transfer and chemical reaction. Under the conditions investigated the process is chemically controlled. Both, SMT and TOC kinetics have been considered. Fast and slow kinetic regime of ozone reactions have been observed for SMT and TOC oxidation, respectively. Application of different inhibitors allows for the establishment of reaction mechanism involving direct ozonation, direct photolysis, hydroxyl radical reactions and photocatalytic reactions. Rate constants of the direct reaction between ozone and protonated, non-protonated and anionic SMT species have been determined to be 1.71 × 10⁵, 3.24 × 10⁵ and 4.18 × 10⁵ M⁻¹ s⁻¹, respectively. SMT quantum yield at 313 nm was found to be 0.012 moles per Einstein at pH 5 and 0.003 moles per Einstein at pHs 7 and 9. Main contributions to SMT removal were direct ozone reaction, positive hole oxidation and hydroxyl radical reactions. For TOC removal, main contributions were due to positive hole oxidation and hydroxyl radical reactions.     

Effect of frozen storage of hake,sardine and mixed minces on natural actomyosin extracted in salt solutions

Natural actomyosin extracted in salt solutions from mixtures of hake and sardine minces (3:1; 1:1 and 1:3 w/w) stored frozen for up to 1 year differed in the amount extracted and in the characteristics of the extracts. In the mixed minces the amount of natural actomyosin extracted decreased during frozen storage at a higher rate than that theoretically corresponding to the amount of hake in the mixes. With increasing storage time and proportion of sardine a lower percentage of myosin heavy chain and actin was observed by electrophoresis. An increased size of aggregates was also observed by electrophoresis and transmission electron microscopy. The stability of emulsions was enhanced when aggregates appeared in the extracts. The decrease in the amount of natural actomyosin extracted does not explain the changes observed in the texture of the minces during frozen storage. This may indicate that the size of the aggregates unextractable in salt solutions, independently of the type of bonds that bind the proteins in the aggregates, plays an important role in the textural changes observed. Copyright © 2003 Society of Chemical Industry     

The inhibition of the viability of myeloma cells and the production of cytokine by two strains of Lactobacillus sakei from meat

Ten strains of lactic acid bacteria were isolated from a dry fermented sausage and tested for stimulation or inhibition of the viability of Vero and myeloma cells. They did not significantly affect the viability of Vero cells but two isolates (CBL/H and CBL/K) showed a strong and moderate inhibition of the myeloma cell viability (at 10⁸ CFU mL^?1, 17.6 and 33.2%, respectively, survival of myeloma cells). The isolates were identified as Lactobacillus sakei by DNA sequencing of the 16S rRNA products of a polymerase chain reaction. No protective effect was found, at the concentrations used, against cytotoxicity of N‐nitrosamines. To test the effect of L. sakei CBL/H and CBL/K on cytokine production [tumour necrosis factor alpha (TNF‐α), interleukin‐1β (IL‐1β) and interleukin‐8 (IL‐8)], the human macrophage cell line (THP‐1) was cultured in the presence and absence of lipopolysaccharide (LPS). Lactobacillus sakei CBL/H and CBL/K induced IL‐1β and IL‐8 release when cells were stimulated with and without LPS. However there was TNF‐α release only in the presence of the LPS.     

Updating the carbon footprint of the Galician fishing activity (NW Spain)

Recent life cycle assessment studies have revealed the relevance of cooling agent leakage when assessing the greenhouse gas (GHG) emissions generated by fishing vessel operations. The goal of this communication is to update the carbon footprinting of the Galician fishing activity (NW Spain) by including the GHG emissions from cooling agent leakage. Results proved the relevant role played by refrigerants regarding their contribution to the carbon footprint of fishing activities. Thus, an overall increase of 13% was found when comparing the final global carbon footprint for the Galician fishing activity with previous calculations that did not include these emissions. Nevertheless, further efforts should be made in order to provide robust data in this respect.     

Application of the envelope‐transient method to the analysis and design of autonomous circuits

The envelope transient enables a very efficient simulation of circuits with two different time scales, such as those that contain modulated signals (for example, amplifier or mixers), where an accurate prediction of intermodulation distortion is needed. The method has also been extended to oscillator analysis, where it requires additional techniques in order to avoid convergence to degenerate mathematical solutions, for which the circuit is not actually oscillating. It allows an efficient analysis of transients in these circuits and an accurate prediction of the phase‐noise spectrum. This article presents an overview of the envelope‐transient method and its most recent applications to the simulation of autonomous circuits, such as free and forced oscillators, frequency dividers, and phase‐locked loops. Using this method, the operation bands of these circuits (which are delimited by qualitative stability changes or bifurcations) can be determined in a straightforward manner. This technique can also be applied to predict intermodulation distortion in self‐oscillating mixers and to simulate the response of synchronized oscillators containing modulated signals. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

On the development of colloidal nanoparticles towards multifunctional structures and their possible use for biological applications

In this Review, we describe the synthesis of high-quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.