Crosslinking effects on hybrid organic–inorganic proton conducting membranes based on sulfonated polystyrene and polysiloxane

New hybrid semi‐interpenetrating proton‐conducting membranes were obtained using sulfonated polystyrene (SPS) and inorganic–organic polysiloxane phases with the aim of improving the mechanical and thermal characteristics of the pristine polymer and to study the effects of crosslinking in the latter phase in several of their properties, mainly proton conductivity. Siloxane phases were prepared using poly(dimethylsiloxane) (PDMS) and PDMS with tetraethoxysilane (TEOS) or phenyltrimethoxysilane (PTMS) as crosslinking agents. To study the crosslinking effect, membranes were prepared with different TEOS:PDMS and PTMS:PDMS mole ratios. The films obtained were characterized by FTIR, ²⁹Si‐HPDEC MAS‐NMR, ¹³C‐CP‐MAS NMR, elemental and thermal analyses. Certain properties, such as water uptake (WU), ion exchange capacity (IEC) and the state of the water, were determined. The proton conductivity was measured at different temperatures (30°C and 80°C) and relative humidities (50–95%). The water content of the hybrid membranes declined significantly, compared with the SPS membranes, depending on the nature and amount of siloxane phase added. Nonetheless, the conductivity values remained relatively high (>100 mS cm^?1 at 80°C and 95% RH) when compared to Nafion®117 presumably because of the formation of well developed proton channels, which makes them potentially promising as proton exchange membranes for fuel cells. These membranes proved to be thermally stable up to 350°C. Scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) were used to characterize the hybrid membranes microstructures; the latter provided contrast for the conductive domains. Copyright © 2015 John Wiley & Sons, Ltd.     

Dissipative curvature fluctuations in bilayer vesicles: Coexistence of pure-bending and hybrid curvature-compression modes

We have studied the relaxation dynamics of shape fluctuations in unilamellar lipid vesicles by neutron spin echo (NSE). The presence of a hybrid curvature-compression mode coexisting with the usual bending one has been revealed in the experimental relaxation functions at high q . Differently to the conventional relaxation ∼ q ³ typical for bending modes, the hybrid mode was found to relax as ∼ q ² , which is compatible with a dissipation mechanism arising from intermonolayer friction. Complementary data obtained from flickering spectroscopy (FS) in giant unilamellar vesicles confirm the existence of both modes coexisting together. By combining NSE and FS data we have depicted the experimental bimodal dispersion diagram, which is found compatible with theoretical predictions for reliable values of the material parameters. From the present data two conventional dynamical methods (NSE and FS) have been shown to be suitable for measuring intermonolayer friction coefficients in bilayer vesicles.     

Increment of lateral resolution in digital holography by speckle noise removal

Experimental features such as wavelength, camera specifications and reconstruction distance determine the theoretical limit for lateral resolution in digital holography. However, the actual experimental resolution limit is about 50% below such theoretical limit due to the high-contrast speckle noise presented in the reconstructed holograms. Recently, a technique has been introduced to reduce the contrast of speckle noise that is based on the superposition of uncorrelated hologram reconstructions of the same static object [5] (Garcia-Sucerquia et al., 2006). By this approach of reducing the contrast of the speckle noise, it is experimentally shown that an improvement of the order of 50% can be reached when 100 reconstructed images are superimposed.     

Fiber transmission and generation of ultrawideband pulses by direct current modulation of semiconductor lasers and chirp-to-intensity conversion

Optical pulses generated by current modulation of semiconductor lasers are strongly frequency chirped. This effect has been considered pernicious for optical communications. We take advantage of this effect for the generation of ultrawideband microwave signals by using an optical filter to achieve chirp-to-intensity conversion. We also experimentally achieve propagation through a 20 km nonzero dispersion shifted fiber with no degradation of the signal at the receiver. Our method constitutes a prospective low-cost solution and offers integration capabilities with fiber-to-the-customer-premise systems.     

Design of Multi-core Fiber Patch Panel for Space Division Multiplexing Implementations

A multi-core fiber (MCF) patch panel was designed, allowing easy coupling of individual signals to and from a 7-core MCF. The device was characterized, measuring insertion loss and cross talk, finding highest insertion loss and lowest crosstalk at 1300 nm with values of 9.7 dB and -36.5 dB respectively, while at 1600 nm insertion loss drops to 4.8 dB and crosstalk increases to -24.1 dB. Two MCF splices between the fan-in module, the MCF, and the fan-out module are included in the characterization, and splicing parameters are discussed.     

Influence of deposition conditions on nanocrystalline InN layers synthesized on Si(1 1 1) and GaN templates by RF sputtering

We present a detailed investigation on the influence of deposition conditions on morphological, structural and optical properties of InN films deposited on Si(1 1 1) and GaN-on-sapphire templates by reactive radio-frequency (RF) sputtering. The deposition parameters under study are nitrogen content in the sputtering gas, substrate–target distance, substrate temperature and RF power. X-ray diffraction measurements confirm the (0 0 0 1) preferred growth orientation and the wurtzite crystallographic structure of the material. For optimized deposition conditions, InN on Si(1 1 1) substrates presents smooth surface with root-mean-square roughness ∼1 nm. Surface quality of the InN films can be further improved by deposition on GaN-on-sapphire templates, achieving root-mean-square roughness as low as ∼0.4 nm, comparable to that of the underlying substrate. The room-temperature absorption edge is located at 1.70 eV. Intense low-temperature photoluminescence peaking at 1.60 eV is observed.     

Banzhaf index for multiple voting systems. An application to the European Union

Multi-criteria simple games constitute an extension of the basic framework of voting systems and collective decision-making. The study of power index plays an important role in the theory of multi-criteria simple games. Thus, in this paper, we propose the extended Banzhaf index for these games, as the natural generalization of this index in conventional simple games. This approach allows us to compare various criteria simultaneously. An axiomatic characterization of this power index is established. The Banzhaf index is computed by taking into account the minimal winning coalitions of each class. Since this index depends on the number of ways in which each player can effect a swing, one of the main difficulties for finding this index is that it involves a large number of computations. We propose a combinatorial procedure, based on generating functions, to obtain the Banzhaf index more efficiently for weighted multi-criteria simple games. As an application, the distribution of voting power in the European Union is calculated.     

Optical properties of hydrogenated amorphous silicon films doped with fluorinated gases

Doped amorphous silicon films were prepared by plasma-enhanced chemical vapour deposition of silane and hydrogen mixtures, using phosphorus pentafluoride (PF₅) and boron trifluoride (BF₃) as dopant precursors. The films were studied by UV-vis spectroscopy and their photo and dark conductivity were measured, the latter as a function of temperature. The optical gap of the n-type samples, doped with PF₅, diminished as the concentration of this gas in the plasma was increased. However, the optical gap of p-type samples, doped with BF₃, did not show any appreciable optical gap decrease as the concentration of BF₃ was varied from 0.04% to 4.7%. The dark conductivity of the p-type films at these extremes of the doping range were 7.6 × 10⁻¹⁰ and 3.5 × 10⁻¹ Ω⁻¹ cm⁻¹, respectively.     

Acetamide degradation by a continuous-fed batch culture ofBacillus sphaericus

Applied Biochemistry and Biotechnology - The methanogenesis of acetamide occurs through a two-step reaction in methanogenic sludges. First, acetamide is hydrolyzed to acetate and ammonia by a...