A new fuel cell using aqueous ammonia-borane as the fuel

Ammonia-borane (NH₃BH₃), as a source of protide (H⁻), is initially proposed to release its energy through a fuel cell (direct ammonia-borane fuel cell, DABFC). Cell performance has been elucidated in a 25 cm² laboratory cell constructed with an oxygen cathode and an ammonia-borane solution fed anode, where the catalyst layers are made of Vulcan XC-72 with 30 wt.% Pt. The potential is 0.6 V at the current density of 24 mA cm⁻², corresponding to power density >14 mW cm⁻² at room temperature. The direct electron transfer from protide (H⁻) in NH₃BH₃ to proton (H⁺) has been further proved by the open circuit potential and the cyclic voltammetry results, which show the possibility of improvement in the performance of DABFC by, for example, exploring new electrode materials.     

Chemical synthesis and low temperature electrical transport in polypyrrole doped with sodium bis(2-ethylhexyl) sulfosuccinate

Polypyrrole (PPy) is polymerized by chemical oxidative polymerization in presence of anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (DEHS) as the dopant. The electrical conductivity was optimized in terms of oxidant to monomer molar ratio and polymerization yield was measured for these reactions. We have used ammonium persulphate (APS) as the oxidant for polymerization in this series of experiments. The effect of concentration of oxidant on the electrical conductivity is examined. Chemical synthesis of polypyrrole is supported by FTIR spectrum. The electrical conductivity of doped and undoped polypyrrole has been measured in the temperature range of 10–300 K and is found to increase with rise in temperature. Electrical conductivity of PPy was analyzed in the light of various charge transport models. Analysis of the electrical conductivity data reveals that in the temperature range 60–300 K electrical transport is predominantly governed by power law behaviour given by Kivelson model. However in the low temperature range 10–60 K electrical transport is dominated by the fluctuation assisted mechanism.     

Novel route for rapid biosynthesis of lead nanoparticles using aqueous extract of Jatropha curcas L. latex

We are reporting a novel, low-cost and eco-friendly route for rapid synthesis of lead nanoparticles by using 0.5% aqueous extract of Jatropha curcas L. latex. Lead nanoparticles were characterized initially by UV–vis spectroscopy and shown distinct peak at 218 nm. This peak was highly specific for lead nanoparticles. Formation of Pb (0) was confirmed by X-ray diffraction technique (XRD).Transmission electron microscopy (TEM) was performed for estimating the size and shape of nanoparticles. The average size of lead nanoparticles was found to be in the range of 10 to 12.5 nm. Energy dispersive analysis of X-rays (EDAX) showed distinct peaks of lead. Fourier Transform Infrared Spectroscopy (FTIR) were performed to find the role of cyclic peptides namely curcacycline A (an octapeptide) and curcacycline B (a nonapeptide) as a possible reducing and capping agents present in the latex of Jatropha curcas L. Lead nanoparticles formed by the above method were monodisperse.     

Processing of Dense ζ‐Ta4C3−x by Reaction Sintering of Ta and TaC Powder Mixture

Tantalum carbides are commonly processed by hot pressing, canned hot‐isostatic‐pressing, or spark plasma sintering because of their high melting temperatures and low diffusivities. This paper reports processing of dense ζ‐Ta₄C_3?x by reaction sintering of a Ta and TaC powder mixture (C/Ta atomic ratio = 0.66). ζ‐Ta₄C_3?x is of interest due to its rhombohedral (trigonal) crystal structure that may be characterized as a polytype with both face‐centered‐cubic and hexagonal‐close‐packed Ta stacking sequences interrupted by stacking faults and missing carbon layers. This structure leads to easy cleaving on the basal planes and high fracture toughness. A key step in processing is the hydrogenation of the Ta powder to produce β‐TaH_x, a hard and brittle phase that enables efficient comminution during milling and production of small, equiaxed Ta particles that can be packed to high green density with the TaC powder. Studies of phase evolution by quantitative X‐ray diffraction during sintering revealed several intermediate reactions: (1) decomposition of β‐TaH_x to Ta; (2) diffusion of C from γ‐TaC to Ta leading to the formation of α‐Ta₂C_y' with the kinetics described by the Avrami equation with an exponent, n = 0.5, and an activation energy of 219 kJ/mole; (3) equilibration of α‐Ta₂C_y' and γ‐TaC_0.78 phases; and (4) formation of ζ‐Ta₄C_2.56 from the equilibrated α‐Ta₂C and γ‐TaC_0.78 phases with the kinetics characterized by a higher Avrami exponent (n ≈ 3) and higher activation energy (1007 kJ/mole). The sintered material contained ~0.86 weight fraction ζ‐Ta₄C_2.56 and ~0.14 weight fraction γ‐TaC_0.78 phases. The microstructure showed evidence of nucleation and growth of the ζ‐Ta₄C_2.56 phase in both the α‐Ta₂C and γ‐TaC_0.78 parent phases with distinct difference in the morphology due to the different number of variants of the habit plane.     

Rheology of concentrated sulfonated poly(ether ether ketone) solutions

Sulfonated polyether ether ketone (SPEEK), an ionic polymer, has been shown to be a potential candidate for fuel cell electrolyte as a proton exchange membrane. Rheological behavior of SPEEK solutions is of great interest to understand the molecular associations as well as due to implications in membrane processing. In this work, SPEEK of various degrees of sulfonation (58–80) was prepared and rheology of concentrated solutions of SPEEK was studied. The rheological properties were evaluated using steady and oscillatory shear. It was found that steady shear viscosity and storage modulus at any given concentration, is the highest for the lowest degree of sulfonation SPEEK solutions in N‐methyl‐2‐pyrrolidone. The low frequency plateau in storage modulus was observed at some combinations of degrees of sulfonation and concentrations, indicating gel‐like behavior in these SPEEK solutions. No significant change in rheological behavior was observed with different polar solvents. Increase of several orders of magnitude in viscosity, storage and loss moduli were observed with increasing concentrations. The role of hydrophobic aggregation and inter‐chain associations in determining rheology of SPEEK solutions is argued based on comparisons with other material systems. The rheological behavior of SPEEK solutions with 70 as the degree of sulfonation, suggests crossover from hydrophobic‐hydrophilic balance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40044.     

Health benefits of soy isoflavonoids and strategies for enhancement: a review

Soybean consumption has been linked to a reduced risk for certain cancers and diseases of old age. The health benefits associated with soybean consumption have been linked to the action of isoflavonoids, the major phenolic phytochemicals found in soybean. Isoflavonoids possess numerous biological activities that may support chemoprevention through the promotion of apoptosis in diseased cells. In this study, we discuss the current state of knowledge concerning soybean isoflavonoids, their chemopreventive actions against postmenopausal health problems, cancer, and cardiovascular disease, and also biotechnology approaches toward the enrichment of soybean for isoflavonoid content.     

XpressSpace: a programming framework for coupling partitioned global address space simulation codes

Complex coupled multiphysics simulations are playing increasingly important roles in scientific and engineering applications such as fusion, combustion, and climate modeling. At the same time, extreme scales, increased levels of concurrency, and the advent of multicores are making programming of high‐end parallel computing systems on which these simulations run challenging. Although partitioned global address space (PGAS) languages attempt to address the problem by providing a shared memory abstraction for parallel processes within a single program, the PGAS model does not easily support data coupling across multiple heterogeneous programs, which is necessary for coupled multiphysics simulations. This paper explores how multiphysics‐coupled simulations can be supported by the PGAS programming model. Specifically, in this paper, we present the design and implementation of the XpressSpace programming system, which extends existing PGAS data sharing and data access models with a semantically specialized shared data space abstraction to enable data coupling across multiple independent PGAS executables. XpressSpace supports a global‐view style programming interface that is consistent with the PGAS memory model, and provides an efficient runtime system that can dynamically capture the data decomposition of global‐view data‐structures such as arrays, and enable fast exchange of these distributed data‐structures between coupled applications. In this paper, we also evaluate the performance and scalability of a prototype implementation of XpressSpace by using different coupling patterns extracted from real world multiphysics simulation scenarios, on the Jaguar Cray XT5 system at Oak Ridge National Laboratory. Copyright © 2013 John Wiley & Sons, Ltd.     

Hello ADIOS: the challenges and lessons of developing leadership class I/O frameworks

Applications running on leadership platforms are more and more bottlenecked by storage input/output (I/O). In an effort to combat the increasing disparity between I/O throughput and compute capability, we created Adaptable IO System (ADIOS) in 2005. Focusing on putting users first with a service oriented architecture, we combined cutting edge research into new I/O techniques with a design effort to create near optimal I/O methods. As a result, ADIOS provides the highest level of synchronous I/O performance for a number of mission critical applications at various Department of Energy Leadership Computing Facilities. Meanwhile ADIOS is leading the push for next generation techniques including staging and data processing pipelines. In this paper, we describe the startling observations we have made in the last half decade of I/O research and development, and elaborate the lessons we have learned along this journey. We also detail some of the challenges that remain as we look toward the coming Exascale era. Copyright © 2013 John Wiley & Sons, Ltd.     

Design criteria for transparent single-wall carbon nanotube thin-film transistors

A study based on two-dimensional percolation theory yielding quantitative parameters for optimum connectivity of transparent single-wall carbon nanotube (SWNT) thin films is reported. Optimum SWNT concentration in the filtrated solution was found to be 0.1 mg/L with a volume of 30 mL. Such parameters lead to SWNT fractions in the films of approximately Phi = 1.8 x 10(-3), much below the metallic percolation threshold, which is found to be approximately PhiC = 5.5 x 10(-3). Therefore, the performance of transparent carbon nanotube thin-film transistors is limited by the metallic SWNTs, even below their percolation threshold. We show how this effect is related to hopping or tunneling between neighboring metallic tubes.