A New Generation of Catalytic Poly(vinylidene fluoride) Membranes: Coupling Plasma Treatment with Chemical Immobilization of Tungsten‐Based Catalysts

A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low‐temperature plasma‐modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH₃ radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten‐based heterogeneous catalysts. Particular attention has been focused on tungstate, WO₄^2–, and decatungstate, W₁₀O₃₂^4–, which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma‐modified membranes surface‐tailored with WO₄^2– have been used in catalytic membrane reactors to activate hydrogen peroxide for oxidizing secondary amines to nitrones; membranes modified with W₁₀O₃₂^4– have been used for the complete degradation of phenol. The obtained results, in terms of amine–nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W‐based catalysts on plasma‐treated membranes.     

Integration of non-repudiation services in mobile DRM scenarios

In any kind of electronic transaction, it is extremely important to assure that any of the parties involved can not deny their participation in the information exchange. This security property, which is called non-repudiation, becomes more important in Digital Rights Management (DRM) scenarios, where a consumer can freely access to certain contents but needs to obtain the proper Right Object (RO) from a vendor in order to process it. Any breach in this process could result on financial loss for any peer, thus it is necessary to provide a service that allows the creation of trusted evidence. Unfortunately, non-repudiation services has not been included so far in DRM specifications due to practical issues and the type of content distributed. In this paper we analyze how to allow the integration of non-repudiation services to a DRM framework, providing a set of protocols that allows the right objects acquisition to be undeniable, alongside with a proof-of-concept implementation and a validation process.     

Antenna Designer's Notebook

In his classic 1948 paper, Lan J. Chu presented the equivalent circuit for an electrically small antenna. This circuit quantified the relationship between the lower bound for the radiation Q of an electrically small antenna and its physical size relative to the wavelength. A recent article has highlighted the fact that Chu defined a lower bound for a hypothetical antenna. A key issue is how close can the Chu limit be approached, in practice? Chu's lower bound assumes that there is no stored energy inside a sphere that circumscribes the largest antenna dimension. Another recent article has extended Chu's work to include the internal stored energy, and provides new lower bounds for electrically small antennas. This paper presents a summary of the recent findings regarding this issue.     

Power System Frequency Measurement Under Nonstationary Situations

A new method for the measurement of the instantaneous power-system frequency is proposed. It is based on the frequency estimation of the voltage signal using three equidistant samples. An algorithm is developed that diminishes the variance of the estimation. The procedure is applied to the case of single- and three-phase networks, and uncertainty in the frequency estimation is obtained with simulated signal and severe conditions of signal quality. A frequency variation has been assumed as plusmn2 Hz around the nominal value, with a maximum rate of change of 1 Hz/s. The uncertainty of 25 mHz and 3.5 mHz has been obtained for single- and three-phase signals, respectively. A low-cost virtual instrument has been developed to make frequency measurements over the actual voltage signal.     

A randomized controlled trial of a parent-centered intervention in preventing substance use and HIV risk behaviors in Hispanic adolescents.

The present study evaluated the efficacy of Familias Unidas + Parent-Preadolescent Training for HIV Prevention (PATH), a Hispanic-specific, parent-centered intervention, in preventing adolescent substance use and unsafe sexual behavior. Two hundred sixty-six 8th-grade Hispanic adolescents and their primary caregivers were randomly assigned to 1 of 3 conditions: Familias Unidas + PATH, English for Speakers of Other Languages (ESOL) + PATH, and ESOL + HeartPower! for Hispanics (HEART). Participants were assessed at baseline and at 6, 12, 24, and 36 months postbaseline. Results showed that (a) Familias Unidas + PATH was efficacious in preventing and reducing cigarette use relative to both control conditions; (b) Familias Unidas + PATH was efficacious, relative to ESOL + HEART, in reducing illicit drug use; and (c) Familias Unidas + PATH was efficacious, relative to ESOL + PATH, in reducing unsafe sexual behavior. The effects of Familias Unidas + PATH on these distal outcomes were partially mediated by improvements in family functioning. These findings suggest that strengthening the family system, rather than targeting specific health behaviors, may be most efficacious in preventing and/or reducing cigarette smoking, illicit drug use, and unsafe sex in Hispanic adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-sidelobe patterns from linear and planar arrays with uniformexcitations except for phases of a small number of elements

The use of genetic algorithms allows synthesis of linear and planar arrays with excitations of uniform amplitude that generate radiation patterns with sidelobe levels closely approaching the recognised minima for phase-only control, in spite of only a small number of elements having non-zero phase     

Plastic straining effects on the microstructure of a Ti-rich NiTi shape memory alloy

A Ni-52 at. pct Ti shape memory alloy, cold drawn to 30 pct, was annealed at 1173 K for 1 hour, water quenched, and then subjected to differential scanning calorimetry (DSC). No evidence of the premartensiticR transformation was found during either the forward or the reverse transformation. Microstructurally, it was found that the alloy possessed a relatively large volume fraction (∼0.05) of coarse second-phase brittle particles. These precipitates acted as preferential sites for martensite plate nucleation and gave rise to a “starlike” morphology. The tensile and compressive properties of the alloy in the as-received condition were also investigated. The alloy exhibited relatively good ductility (fracture strain=0.28), which was attributed to its inherent ability to relieve or delay the development of plastic instabilities through rapid strain hardening. In addition, X-ray diffraction (XRD) of deformed specimens indicated the presence of an extraintensity peak corresponding to the B2 phase (110)_B2 when the alloy was plastically deformed in compression. Accordingly, it is suggested that plastic deformation induces the reverse transformation to the B2 phase in highly stressed local regions. Transmission electron microscopy (TEM) of deformed martensite structures showed slip lines probably due to dislocation slip, as well as variant interpenetration. Besides, optical and scanning microscopy of regions adjacent to the fractured surfaces indicated that fine martensite plates and/or “apparent” new grains develop at regions of prior stress intensification (former crack-tip regions) during crack propagation.