bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat acclimation increases arterial elasticity in young men
Authors: Kaldur Triin , Kals Jaak , Ööpik Vahur , Burk Andres , Kampus Priit , Zagura Maksim , Zilmer Mihkel , Unt Eve
Published: March 2013

The major physiological adaptations that occur during heat acclimation (HA) are well documented. However, no studies have provided compelling evidence about the effect of HA on arterial elastic properties. The aim of this study was to examine the changes in large artery elasticity (LAE) and small artery elasticity (SAE) concomitant with HA and to determine the potential relationships among changes in arterial elasticity, baseline aerobic fitness level, and improvement in endurance capacity (EC). During 10-day HA, the subjects (n = 21) exercised daily on a treadmill for 110 min at an intensity of 55%–60% of peak oxygen uptake in a climatic chamber preset to 42 °C and 18% relative humidity. EC was tested in the heat before and after HA. Arterial elasticity was assessed by diastolic pulse wave analysis (HDI/Pulse Wave CR-2000) at baseline and after HA. Blood samples were drawn at baseline. After HA, there was a 17% increase in LAE (from 21.19 ± 4.72 mL·mm Hg−1 × 10 to 24.77 ± 5.91 mL·mm Hg−1 × 10, p < 0.05) and an 18% increase in SAE (from 9.32 ± 1.76 mL·mm Hg−1 × 100 to 10.98 ± 1.75 mL·mm Hg−1 × 100, p < 0.01). EC increased by 86% (from 88.62 ± 27.51 min to 161.95 ± 47.80 min, p < 0.001) as a result of HA. No significant associations were revealed between changes in arterial elasticity parameters and improvement in EC or baseline aerobic fitness level. We demonstrated, for the first time, that HA has a positive impact on the parameters of arterial elasticity. Further investigations are needed to determine the mechanisms underlying these changes and the potential relationships among arterial elasticity, aerobic fitness level, and EC.
A study on the modified holographic Ricci dark energy in logarithmic f(T) gravity
Authors: Pasqua Antonio , Chattopadhyay Surajit
Published: March 2013

In this paper, we have studied and investigated the behavior of a modified holographic Ricci dark energy (DE) model interacting with pressureless dark matter (DM) under the theory of modified gravity, dubbed logarithmic f(T) gravity. We have chosen the interaction term between DE and DM in the form Q = 3γHρm and investigated the behavior of the torsion, T, the Hubble parameter, H, the equation of state parameter, ωDE, the energy density of DE, ρDE, and the energy density contribution due to torsion, ρT, as functions of the redshift, z. We have found that T increases with the redshift, z, H increases with the evolution of the universe, ωDE has a quintessence-like behavior, and both energy densities increase going from higher to lower redshifts.
A SIMULATED ANNEALING FOR INTRA-CELL LAYOUT DESIGN OF DYNAMIC CELLULAR MANUFACTURING SYSTEMS WITH ROUTE SELECTION, PURCHASING MACHINES AND CELL RECONFIGURATION
Authors: KIA REZA , JAVADIAN NIKBAKHSH , PAYDAR MOHAMMAD MAHDI , SAIDI-MEHRABAD MOHAMMAD
Published: March 2013

This paper develops a novel mixed integer nonlinear programming model for the intra-cell layout design of dynamic cellular manufacturing systems. In dynamic environment, the product mix and part demand are varying during a multi-period planning horizon. As a result, the cell configuration for one period may not be efficient for successive periods and thus necessitates reconfigurations. The proposed model incorporates several design features including intra-cell layout, operation sequence, operation time, alternative process routings, duplicate machines, purchase machine, machine capacity, route selection, production volume of parts, part movements in batch and cell reconfiguration. By considering intra-cell layout and operation sequence, the material handling volume and related cost is calculated more exactly. The objective is to minimize the total costs of inter-cell material handling, forward and backward intra-cell material handling, setting up route, machine relocation, purchasing new machines, machine overhead and machine processing. The main constraints are route selection among flexible routings, machine availability, cell size, machine time-capacity and machine location. The proposed model cannot be solved for large-sized problems optimally within a reasonable amount of computational time. Therefore, an efficient simulated annealing algorithm is developed to overcome NP-hardness of the proposed model.
VOROS PRODUCT AND NONCOMMUTATIVE INSPIRED BLACK HOLES
Authors: GANGOPADHYAY SUNANDAN
Published: March 2013

We emphasize the importance of the Voros product in defining the noncommutative (NC) inspired black holes. The computation of entropy for both the noncommutative inspired Schwarzschild and Reissner–Nordström (RN) black holes show that the area law holds up to order [Formula: see text]. The leading correction to the entropy (computed in the tunneling formalism) is shown to be logarithmic. The Komar energy E for these black holes is then obtained and a deviation from the standard identity E = 2STH is found at the order [Formula: see text]. This deviation leads to a nonvanishing Komar energy at the extremal point TH = 0 of these black holes. The Smarr formula is finally worked out for the NC Schwarzschild black hole. Similar features also exist for a de Sitter–Schwarzschild geometry.
COSMOLOGICAL EVOLUTION OF EQUATION OF STATE FOR DARK ENERGY IN G-ESSENCE MODELS
Authors: BAMBA KAZUHARU , RAZINA OLGA , YERZHANOV KOBLANDY , MYRZAKULOV RATBAY
Published: March 2013

We explore the cosmological evolution of equation of state (EoS) for dark energy in g-essence models, the action of which is described by a function of both the canonical kinetic term of both the scalar and fermionic fields. We examine g-essence models with realizing the crossing of the phantom divide line of w DE = -1 as well as the models in which the universe always stays in the nonphantom (quintessence) phase (w DE > -1). In particular, we find an explicit g-essence model with the crossing from the nonphantom phase to the phantom one (w DE < -1). This transition behavior is consistent with the recent observational data analyses.
NUMERICAL ANALYSIS OF CIRCULAR CONCRETE-FILLED STEEL TUBULAR SLENDER BEAM-COLUMNS WITH PRELOAD EFFECTS
Authors: PATEL VIPULKUMAR ISHVARBHAI , LIANG QING QUAN , HADI MUHAMMAD N. S.
Published: March 2013

This paper presents a new numerical model for the nonlinear analysis of circular concrete-filled steel tubular (CFST) slender beam-columns with preload effects, in which the initial geometric imperfections, deflections caused by preloads, concrete confinement and second order effects are incorporated. Computational algorithms are developed to solve the nonlinear equilibrium equations. Comparative studies are undertaken to validate the accuracy of computational algorithms developed. Also included is a parametric study for examining the effects of the preloads, column slenderness, diameter-to-thickness ratio, loading eccentricity, steel yield stress and concrete confinement on the behavior of circular CFST slender beam-columns under eccentric loadings. The numerical model is demonstrated to be capable of predicting accurately the behavior of circular CFST slender beam-columns with preloads. The preloads on the steel tubes can affect significantly the behavior of CFST slender beam-columns and must be taken into account in the design.
COLUMN BUCKLING TESTS OF 420 MPA HIGH STRENGTH STEEL SINGLE EQUAL ANGLES
Authors: BAN H. Y. , SHI G. , SHI Y. J. , WANG Y. Q.
Published: March 2013

This paper presents the results of the experimental studies conducted on the buckling behavior of 420 MPa high strength steel, hot-rolled, equal angle columns, numbering a total of 66 specimens with a wide range of column slenderness and section sizes. Based on the test results, the buckling modes and capacities were analyzed and the nondimensional buckling strengths were obtained and compared with the design strength predicted from Eurocode 3, ANSI/AISC 360-10 and Chinese standards GB50017-2003. The experimental results in previous studies were also employed in the comparison. The effect of width to thickness ratio of legs of an angle on buckling modes and strengths were investigated. It was found that the buckling strengths from test results were much higher than the corresponding design values and current design approaches were too conservative. Based on present and previous experimental results, a new design approach is suggested for the design of angle columns with 420 MPa high strength steel.
BAYESIAN ESTIMATION IN RANDOM CENSORSHIP MODEL FOR WEIBULL DISTRIBUTION UNDER DIFFERENT LOSS FUNCTIONS
Authors: DANISH MUHAMMAD YAMEEN , ASLAM MUHAMMAD
Published: March 2013

This paper deals with Bayesian estimation of parameters in the proportional hazards model of random censorship for the Weibull distribution under different loss functions. We consider both the informative and noninformative priors on the model parameters to obtain the Bayes estimates using Gibbs sampling scheme. Maximum likelihood estimates are also obtained for comparison purposes. A simulation study is carried out to observe the behavior of the proposed estimators for different sample sizes and for different censoring parameters. One real data analysis is performed for illustration.
From Developmental Origins of Adult Disease to Life Course Research on Adult Disease and Aging: Insights from Birth Cohort Studies
Authors: Power Chris , Kuh Diana , Morton Susan
Published: March 2013

Maturation of long-running birth cohort studies has fostered a life course approach to adult health, function, and disease and related to conceptual frameworks. Using broad concepts of human development including physical, cognitive, and emotional function, birth cohorts provide insights into the processes across the life course and between generations that link to adult outcomes. We discuss findings on the determinants and health consequences of lifetime trajectories of body size, cognitive and emotional function, and socioeconomic position. Findings from the studies suggest that, for some adult health outcomes, explanations will be incomplete unless exposures and processes from across the life course are taken into account. New birth cohort studies are poised to delineate further the nature and timing of life course relationships in contemporary generations of children.
Hyundai's FCEVs: A Pathway to New Possibilities
Authors: Lim Taewon , Ahn Byung-Ki
Published: March 2013

Due to the energy and environment issues, polymer electrolyte membrane fuel cells (PEMFCs) are actively being studied for use in passenger cars and fleet vehicles. PEMFCs are known to possess high current density, and the stack structure is rather simple. PEMFC has other advantages such as rapid start-up and response and long endurance. Recently, fleet of fuel cell electric vehicles (FCEVs) of the major automakers is seen in numbers in USA, in cities throughout Europe, and in Japan. Hyundai-Kia Motors Co. (HKMC) started fuel cell researches with the aid of government funded programs since 1999. HKMC has been developing several kinds of fuel cell sports utility vehicles and buses, and so far has been operating over 200 vehicles worldwide. The total mileage has exceeded 4 million km. In this paper, overall aspects of Hyundai-Kia Motors' fuel cell researches are presented along with the development history and the future roadmap.
Detailed Numerical Modeling of a Hybrid Polymer Electrolyte Fuel Cell
Authors: McNealy Benjamin E. , Hertz Joshua L.
Published: March 2013

Numerical modeling has been used to investigate the resistive behavior of a novel hybrid polymer electrolyte fuel cell design that utilizes a porous wicking layer to eliminate flooding. The resistance of the porous layer is shown to depend upon current and to increase nonlinearly with layer thickness. The relationship between conductivity and thickness was found to be related to the physical size of the reaction zone in the porous layer, and the scaling of the reaction zone with current was investigated. The porous layer resistance was also found to increase with temperature in most cases due to a decrease in charge carrier concentration at elevated temperatures.
Study on Protocols for Evaluating Reactant Gas Transport in Cathode Catalyst Layers of PEFC
Authors: Yasuda Hiroshi , Kobayashi Kengi , Daimaru Akimasa , Hori Michio
Published: March 2013

Some in-situ techniques measuring limiting current in order to analyze the reactant gas transport structure have been proposed. By these methods, it has been found that the reactant gas transport resistance (Rother) in catalyst layers (CLs) was separated into two parts, Knudsen diffusion resistance (Rk) and the local transport resistance around Pt surface (RPt). And it was also found that RPt became significantly large when Pt load on CLs was reduced. However, the causes and contents of RPt is not clear enough today. And also some measurement methods of RPt are proposed. In order to better understanding and measurement of RPt, we tried to evaluate it by mean of these methods.
Visualizing Liquid Water Evolution in a PEM Fuel Cell Using Synchrotron Radiography
Authors: Hinebaugh James , Lee Jongmin , Bazylak Aimy
Published: March 2013

Synchrotron X-ray radiography was utilized to study the time evolution of liquid water in an operating polymer electrolyte membrane (PEM) fuel cell. A high aspect ratio fuel cell, designed with offset anode and cathode flow field channels, was operated at conditions that produced critical water management issues. The X-ray beam was directed into the plane of the fuel cell, and was therefore employed to elucidate the through-plane distribution of liquid water in the porous materials. Due to the offset between the anode/cathode gas channels, the membrane electrode assembly exhibited sinusoidal warping, and liquid water accumulated in possible areas of delamination. Liquid water first appeared near the cathode catalyst layer, and then travelled laterally within the porous gas diffusion layer. Finally, future design considerations are presented, including membrane thickness and attenuation estimates.
Microstructure-Driven Analysis of Two-Phase Transport in Diffusion Media of PEFCs
Authors: Wargo Eric A. , Schulz Volker P. , Cecen Ahmet , Kalidindi Surya R. , Kumbur Emin Caglan
Published: March 2013

The objective of this work is to evaluate the multiphase transport characteristics of diffusion media (DM) of polymer electrolyte fuel cells (PEFCs) using advanced microstructure quantification and pore-scale modeling techniques. The microstructure of a gas diffusion layer (GDL) sample is characterized using micro x-ray computed tomography. The microstructure dataset is analyzed using in-house structural analysis tools and a full pore morphology model to determine the water imbibition characteristics and key measures of structure, including the porosity, pore (void) connectivity, tortuosity, and capillary pressure-saturation curves.
Improvement of PEFC Performance by Removing GDLs
Authors: Takeuchi Kazuya , Kato Ikuyasu , Shiozawa Masahiro , Hamada Shigetaka , Goto Sogo , Kondo Masaaki , Sano Seiji
Published: March 2013

To reduce the cost and size of a polymer electrolyte fuel cell (PEFC), we propose removing the gas diffusion layers (GDLs) from the cell. Removing the GDLs improves the gas supply to the catalyst layer. On the other hand, it is possible that removing the GDLs will lower the performance of the PEFC via flooding or dry-out. This paper verifies the effect of removing GDLs on the cell performance, and discusses a method of improving the performance of PEFCs without GDLs
Understanding the effects of Contaminants from Balance of Plant Assembly Aids Materials on PEMFCs -In Situ Studies
Authors: Opu Md Safaruddin , Ohashi Masato , Cho Hyun-Seok , Macomber Clay S. , Dinh Huyen N. , Van Zee John W.
Published: March 2013

The main challenges for commercialization of fuel cells are cost and durability. Using off-the-shelf materials for system components in Proton Exchange Membrane Fuel Cells (PEMFCs) may lower the cost provided they do not compromise function, fuel cell performance, or life. The purpose of this paper is to increase the understanding of contamination effects of these materials and the contaminants that leach from them. This paper in-situ screening data for six families of materials (i.e., urethane, silicone, epoxy, acrylic, methacrylate, and perfluoroalkylether) broadly classified as assembly aids that may be used as adhesive and lubricants in PEMFC systems.
The Impact of Operating Conditions on the Performance effect of Selected Airborne PEMFC Contaminants
Authors: Zhai Yunfeng , St-Pierre Jean , Angelo Michael S.
Published: March 2013

The effects of the airborne contaminants naphthalene, acetonitrile, and propene on the performance of a single PEMFC were investigated at different operating conditions. The results indicated that higher contaminant concentrations resulted in higher performance losses and faster degradations, while the rate of performance recovery was more rapid. Lower temperatures caused increased performance losses, more rapid degradations, slower recoveries, and irrecoverable losses. Higher contaminant concentrations and lower temperatures caused voltage oscillations when the PEMFC was contaminated with naphthalene. The exposure of the PEMFC to propene at higher temperatures resulted in performance recovery to a level that was temporarily greater than its performance prior to propene exposure. The PEMFC performance loss at different current densities was dependent on specific contaminants. At higher current densities, naphthalene and propene caused greater performance losses as well as faster degradation and recovery. Acetonitrile caused similar performance losses at all current densities. The performance degradation caused by naphthalene and acetonitrile may be dependent on the cathode potential. EIS analysis indicated that contaminant exposure affected catalytic and mass transport processes for all the impurities tested and that acetonitrile increased the membrane resistance.
Effect of Cationic Contaminants on Polymer Electrolyte Fuel Cell Performance
Authors: Qi Jing , Wang Xiaofeng , Pasaogullari Ugur , Bonville Leonard J. , Molter Trent
Published: March 2013

To correlate the cationic contaminant uptake of the membrane electrode assembly (MEA) with the polymer electrolyte fuel cell (PEFC) performance, MEAs were contaminated by saturating in varying concentrations of H2SO4 and Al2(SO4)3 solution to establish ex situ equilibrium cation uptake. The MEAs were then assembled and tested in a single cell hardware to determine the performance as a function of cationic contamination level. Smaller MEA coupons were also saturated at the same time as full-size MEA and were characterized to determine the cationic occupation fraction by acid site titration. It is found that the acid site occupation in the MEA increased and the cell performance decreased with increased Al ion concentration in the solution. With less than 10% occupation, the cell performance dropped from 1000 mA/cm2 to 100 mA/cm2 at 0.6 V. Upon re protonation of the MEA with H2SO4, it is found the cell performance was fully recovered.
MEA Design for Improved Cathode Durability under Startup Shutdown Automotive Conditions
Authors: Roberts Joy , Berretta Francine , Haas Herwig , Yang Amy , Ronasi Sima , Kundu Sumit , Leow Andrew , Lew Brian , Elvidge Chris , Bellosillo Irwin , Orha Georgeta , Hsieh Yvonne , Barsan Nicolae
Published: March 2013

A novel MEA design solution - an "intelligent switch" to provide protection of the cathode catalyst layer from degradation caused by startup/shutdown events is proposed (1). This unique approach adapts gas sensor-type materials (2) that exhibit several orders of magnitude change in resistance depending on its gas environment (1) in PEM fuel cell anodes. The high resistance of the new layer in air environments prevents corrosion loop currents. In hydrogen environments, the layer becomes conductive and fuel cell performance is minimally hindered. In-situ fuel cell test results demonstrate a successful reduction in cathode peak potentials during startup events leading to reduced performance degradation in startup/shutdown stress tests. This strategy of preventing corrosion loop currents is compatible with various catalyst types and with different catalyst loadings. The approach enables MEA design to minimize air/air start/stop degradation and provides a pathway for the use of alternative catalyst options.
Fabrication of Bipolar Plates Based on Graphite Sheet via Stamping Method
Authors: Park Taehyun , Chang Ikwhang , Lee Yoon Ho , Cha Suk Won
Published: March 2013

In this paper, graphite sheet (or exfoliated/expanded graphite) was used as material for bipolar plates in DMFC. These were substituted to graphite bipolar plates adopted in commercialized DMFC and their performances were characterized in order to identify its feasibility of commercialization. The results showed that there is little difference of performances between graphite and graphite sheet bipolar plates, while this difference became larger with increasing number of cells in stack. It is speculated that higher ohmic resistance of graphite sheet than that of graphite and its flexibility which affected ribs of flow channels to compress GDL excessively accounted for worse performances of DMFC with a number of cells. Finally, this bipolar plate can reduce 22 % of weight compared to graphite and cost under $ 2 per a sheet, which makes it attractive to bipolar plates for DMFC.
Immobilized Viologen Polymers for Carbohydrate Fuel Cells
Authors: Pan Yining , Stockton James , Urie Russell , Pitt William , Wheeler Dean R
Published: March 2013

Viologen, organic catalyst, must be immobilized on the anode of a direct-carbohydrate fuel cell to achieve a recyclable and efficient fuel cell. Novel viologen monomers, called 1-(3-acrylamidopropyl)-(4, 4'-bipyridin)-1-ium (AAPB), are synthesized and immobilized on a gold electrode surface by electroreductive polymerizaiton. The polymeric viologen film is examined and visibly seen under SEM. Cyclic voltammograms of these monomers have been run and the results are reported here.
Nanoscale Transport Phenomena in PEM of PEFC by Large Scale Molecular Dynamics Simulations
Authors: Tokumasu Takashi
Published: March 2013

In this paper, we analyzed the nanoscale transport phenomena in membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) by large scale molecular dynamics (MD) simulations. Especially, (1) transport phenomena of proton and water in polymer electrolyte membrane (PEM), (2) oxygen permeability of ionomer in catalyst layer (CL), and (3) transport phenomena of water droplet in a nano pore were simulated, and the nanoscale transport characteristics were analyzed in detail. In the analysis of proton transfer in PEM, the simulation results were compared with some experimental results to evaluate the validity of our simulation. With regards to the oxygen permeability of ionomer, the dependence of water content on the permeability was estimated and the difference of characteristics between ionomer and bulk membrane was discussed. In the analysis of transport phenomena of a water droplet in a nano pore, we compared the results of our simulation with macroscopic governing equation.
Investigation of PEM Degradation Kinetics and Degradation Mitigation Using In Situ Fluorescence Spectroscopy and Real-Time Monitoring of Fluoride-Ion Release
Authors: Prabhakaran Venkateshkumar , Arges Christopher G , Ramani Vijay K.
Published: March 2013

In-situ fluorescence experiments were performed with 6-carboxy fluorescein (6CFL) as the fluorescent molecular probe for monitoring reactive oxygen species (ROS) formation in an operating fuel cell. Modified rhodamine 6G (R6G) was used to prevent platinum-6CFL interactions (metal-dye interactions) during these measurements. ROS generated during fuel cell operation degrade the Nafion® membrane resulting in the release of fluoride ions. The concentration of fluoride was measured ex-situ in the effluent stream at regular time intervals and the trend of the ex-situ fluoride-ion concentration data mirrored the trend of the in-situ fluorescence data. The effect of relative humidity on ROS induced degradation was examined with the in-situ and ex-situ techniques. Lower relative humidities resulted in greater ROS induced degradation. Additionally, we report the modification of cerium (IV) oxide with doped nitrogen resulted in a sustained efficacy for free radical scavenging.
Synthesis and Proton Exchange Membrane Application of Aromatic Diblock Copolymer Electrolytes
Authors: Oshima Tatsuya , Umezawa Kensuke , Yoshizawa-Fujita Masahiro , Ohira Akihiro , Takeoka Yuko , Rikukawa Masahiro
Published: March 2013

A poly(p-phenylene)-based diblock copolymer P2-P1 was synthesized with a hydrophilic monomer, 2,5-dibromo-1,4-di [4-(2,2-dimetylpropoxysulfonyl)phenyl]butoxybenzene, and a hydrophobic monomer, 2,5-dibromo-1,4-dihexyloxybenzene, via a catalyst transfer polycondensation. Deprotection of the neopentyl groups using diethylamine hydrobromide and subsequent acidic hydrolysis provided a sulfonated diblock copolymer SP2-P1. The diblcok copolymer SP2-P1 showed similar hydration numbers to the random copolymer SP2-ran-P1 in the rage of 30-90% RH at 80 ºC. The proton conductivity of the SP2-P1 was higher than that of SP2-ran-P1 membranes at 80 ºC despite of the lower IEC and the comparable hydration numbers.
Polyvinyl Alcohol Based Nanocomposite Membranes Containing Aluminum Hydroxide Gel
Authors: Radionova Olga I. , Prokhorov Igor Yu. , Akimov Gennady Ya.
Published: March 2013

Cross-linked PVA/Al(OH)3 nanocomposite polymer membranes with a very small thickness were produced by diluted acidic solution casting. Dry and wet membranes were characterized by impedance spectroscopy and densitometry. Wet membranes had shown pure ionic conductivity of the order of 10-3 S/cm at 90 deg C and optimal filler content between 3 and 7 wt. % corresponding to pre-coagulation condition as revealed by hydrostatic densitometry. Temperature dependence of conductivity was in good accordance with VTF model. Considering very small thickness of cross-linked films, such membranes are promising for use in DMFC due to high expected specific power.
Cross-Linked Poly(Arylene Ether Ketone) Membranes Containing Pendant Sulfonic Acid Groups for Fuel Cell Applications
Authors: Dang Hai-Son , Kim Dukjoon
Published: March 2013

A new class of cross-linkable poly(arylene ether ketone)s (cPAEKs) with sulfonic acid groups on both the backbone and pedant positions were synthesized. The chemical structures of the synthesized polymers were confirmed by 1H-nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy. The thermal and mechanical properties were investigated by TGA analysis and stress-strain testing. The major advantage of synthesized membranes is their exceptionally high proton conductivities. All the csPAEK membranes exhibited higher proton conductivity than Nafion® 117 over the temperature range from 40 - 90oC. In most cases, the cross-linked sPAEK membranes with 15% cross-linking density exhibited low methanol permeability, good thermal stability, and showed very high strain at break. The effects of sulfonation degree (SD) on proton conductivity, methanol permeability, water uptake, thermal and tensile properties of csPAEK membranes were investigated.
Theoretical Study of Particle Size effect on Oxygen Reduction Reaction on Pt Catalyst
Authors: Kawamura Yoshiumi , Jinnouchi Ryosuke
Published: March 2013

Particle size effect on the oxygen reduction reaction on Pt catalysts was studied by a first principles-based mean-field model. Elementary redox potentials were approximately described by Kelvin equations and were used to estimate elementary reaction rates on nano-particles. Results indicated that the specific activity decreases with the decrease in the particle size because increased Pt-O surface coverage hinders the ORR. The mass activity becomes maximal at a diameter of 2 nm as reported in experimental studies.
The effect of Platinum Oxide Growth on Platinum Stability in PEMFCs
Authors: Redmond Erin L , Trogadas Panagiotis , Alamgir Faisal M. , Fuller Thomas F.
Published: March 2013

In this study electrochemical and XAS techniques are combined to monitor in situ oxide growth at long potential holds. The value of the potential has a greater effect than the length of the potential hold for large time scales. Evidence suggests that PtO2 is the dominant oxide phase under the experimental conditions.
Application of Electrospinning Technique in the Fabrication of Catalyst Layer of Membrane Electrode Assemblies
Authors: Sightler Joshua Jerome , McPherson Eli , Rigdon William A , Huang Xinyu
Published: March 2013

Inspired by the original work published by Pintauro's group, the authors investigated the application of an electrospinning (E-spin) method for the fabrication of the catalyst layer of proton exchange membrane fuel cell electrode. Electrochemical performance of the membrane electrode assemblies (MEA) produced by E-spin was characterized can compared with MEA produced with an ultrasonic spraying technique. A simple polarization curve analysis was conducted to help resolve the sources of over-potential. The platinum loading, electrode morphology were characterized by X-ray fluorescence and scanning electron microscopy. The electrospinning technique was found to yield high performance electrode with low platinum loading. The E-spin method resulted in an electrode with high electrochemical area and platinum utilization.
Investigation of Solvent Effects on the Dispersion of Carbon Agglomerates and Nafion Ionomer Particles in Catalyst Inks Using Ultra Small Angle X-ray Scattering and Cryo-TEM
Authors: Sun Lili , Zhang Hangyu , Ilavsky Jan , Li Zhefei , Xie Jian
Published: March 2013

In a catalyst ink, the solvent plays a critical role for the dispersion of both Nafion ionomer and Pt/C catalyst particles. In this work, different solvents were used to study the solvent effects on the dispersion of catalyst inks. The size and micro-geometry of ionomer particles and carbon black particles in different solvents were derived from the USAXS data and directly observed using cryo-TEM. It was found that the particle size of XC-72 carbon black decreased when dispersed with Nafion ionomer in ethanol and glycerol solvents. The particle size of the XC-72 dispersed in the ethanol + Nafion solvent was larger than that in the glycerol + Nafion solvent.
A Study of Electrochemical Ostwald Ripening in Pt and Ag Catalysts Supported on Carbon
Authors: Parthasarathy Preethy , Virkar Anil V.
Published: March 2013

Electrochemical Ostwald ripening in Pt/Ag commercial catalysts supported on high surface area carbon was studied by an electrochemical method. The effect of electrolyte composition on nano particle coarsening was investigated. The procedure consisted of immersing two graphite rods in an electrolyte solution: one with nano Pt/Ag painted on it and the other with bulk Pt/Ag wire wrapped around it. It was observed that nano Pt/Ag became electrically negative, consistent with higher chemical potential due to the Gibbs-Thompson effect. The voltage measured decreased with time as the nano particles coarsened and the difference in chemical potentials between the two electrodes decreased. The measured voltage difference is in good agreement with theory. The process involves coupled transport of Pt/Ag ions through the electrolyte and of electrons through the carbon/graphite support. Despite high Pt4+ concentration in PtCl4+DMSO, coarsening of Pt was slower due to low Pt2+ concentration in the electrolyte.
Development of Highly Active Pt2Ni/CCC Catalyst for PEM Fuel Cell
Authors: Xie Tianyuan , Jung Won Suk , Kim Taekeun , Akos Kriston , Ganesan Prabhu , Popov Branko N.
Published: March 2013

A non-platinum carbon based composite catalyst (CCC) with active catalytic sites for the oxygen reduction reaction (ORR) is used as a catalyst support to synthesize a hybrid cathode catalyst (HCC), thus combining the contributions of active sites from the CCC support and Pt-alloy catalyst. The performance in rotating ring disc electrode (RRDE) and fuel cell showed significant improvement for the HCC when compared to a pure Pt/C catalyst. The Pt2Ni/CCC catalyst exhibited a current density of 1.5 mA cm-2 and mass activity of 0.441 A mgPt-1 at 0.9 ViR-free in RRDE and fuel cell, respectively. Under H2-air fuel cell conditions when using cathodic stoic flow of 2.0, a current of 1.4 A cm-2 was observed at 0.58 ViR-free.
Highly Active Titanium Oxide-based Catalyst for Oxygen Reduction Reaction for PEFC
Authors: Suito Kazuaki , Ishihara Akimitsu , Arao Masazumi , Matsumoto Masashi , Imai Hideto , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro
Published: March 2013

Platinum, which is used as cathode electrocatalysts for polymer electrolyte fuel cell, have many problems such as its high cost, small amount of resource, insufficient activity for oxygen reduction reaction (ORR) and stability. In this study, we focused on titanium, which had large amount of resources, and tried to prepare higher active catalysts by pyrolysis or combination of pyrolysis and partial oxidation of oxytitanium phthalocyanine which had both C and N. It was revealed that the partial oxidation of catalyst during heat treatment was efficient to obtain high activity of ORR. The maximum current density at 0.8V vs. RHE was about 108 mA g-cat./C-1. This result indicated that the titanium oxide-based compounds had great potential as alternative cathodes for platinum.
Oxygen Reduction on TiO2-Coated Carbon Nanofibers Decorated with Graphene Platelets
Authors: McClure Joshua P. , Devine Christina , Loebl Andrew , Jiang Rongzhong , Chu Deryn , Cuomo Jerome , Parsons Gregory , Fedkiw Peter S.
Published: March 2013

The oxygen reduction reaction (ORR) was studied on heat-treated electrospun polyacrylonitrile (PAN) nanofibers with and without iron (II) phthalocyanine using rotating ring disk electrode voltammetry. In an effort to mitigate loss of the active sites and increase durability, atomic layer deposition was used to coat the nanofibers with TiO2 thin films. The results show that Fe-containing heat-treated nanofibers and TiO2-coated Fe-containing nanofibers exhibit a ~4-electron reduction of O2 with low % H2O2 yields (~1-1.5 %).
Electrospun Iron/Polyacrylonitrile Derived Nanofibrous Catalysts for Oxygen Reduction Reaction
Authors: Wu Jason , Higgins Drew Christopher , Chen Zhongwei
Published: March 2013

Current proton exchange membrane fuel cells (PEMFCs) suffers from high material costs due to the use of platinum based catalysts necessary for the catalysis of the notoriously slow oxygen reduction reaction (ORR) occurring at the cathode of the cell. The use of significantly cheaper non-precious metal catalysts over expensive platinum catalysts can significantly reduce the material cost of PEMFCs. In the current work, non-precious nanofibrous catalysts were prepared by electrospinning a solution of iron acetate and polyacrylonitrile and subjecting the electrospun fibers to high temperature pyrolysis. The resulting nanofibrous catalysts were evaluated for their ORR activity and characterized via SEM, BET surface area analysis, and XPS. The nanofibrous catalysts were also acid leached and exposed to a second high temperature pyrolysis treatment, showing improved ORR activity. Physical characterization of the twice pyrolyzed catalyst suggests that the catalyst exhibits higher ORR activity due to increased surface area and micropore volume.
Development of Hybrid Cathode Catalyst for PEM Fuel Cells
Authors: Kim Taekeun , Jung Won Suk , Xie Tianyuan , Kriston Akos , Ganesan Prabhu , Gamliel David , Murphy Brian , Popov Branko N.
Published: March 2013

Hybrid cathode catalyst (HCC) was investigated as a cathode catalyst for polymer electrolyte membrane (PEM) fuel cell applications. Cobalt containing carbon composite catalyst (CCC) was synthesized and used as a catalyst support. Transmission electron microscope (TEM) images revealed a uniform distribution of Pt nanoparticles (dPt = 2-3 nm) on the CCC support. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis indicated the formation of Pt1.3Co1 HCC after controlled heat treatment. HCC shows much better fuel cell performance than the as deposited Pt/CCC catalyst. The HCC mass activity is 2.7 times higher than that of 30 wt.% Pt/CCC.
Ammonia Electrooxidation on NiPd Nanoparticles in Alkaline Media: Effect of pH and Concentration
Authors: Allagui Anis , Sarfraz Saad , Middleton Blair , Almomani Fares , Baranova Elena A.
Published: March 2013

Ammonia electrooxidation on NiPd nanoparticles with 99:1 nominal atomic composition is investigated in NaNO3 at different pH and NH4NO3 concentrations. As-prepared NiPd has very low to no activity towards this reaction, whereas the catalytic activity of NiPd can be significantly improved by building up a layer of Ni(OH)2 by continuous cycling in NaNO3 at pH 9 in -0.95 to +1.35 V vs. HgO/Hg. Cyclic voltammetry shows that ammonia oxidation on Ni(OH)2/NiPd occurs around 1.28 V vs. HgO/Hg and is highly pH-dependent. Direct and indirect electron transfer mechanisms are discussed: at low ammonia concentration (< 100 mM) the direct electron transfer takes place, whereas indirect electron transfer mechanism is believed to occur at higher concentrations. The stability of the electrooxidation reaction is evaluated by chronoamperometry. 12-hours electrolysis at 10 mA.cm-2 showed 22 % of initial ammonia is mainly transformed into nitrogen, with traces of NO2 (1.6 %) and NO3 (0.9 %).
Reaction Mechanism of Ethanol Oxidation over Gold Catalyst under Alkaline Environment
Authors: Koyama Michihisa , Amano Yuki , Liu Shixue , Ishimoto Takayoshi
Published: March 2013

Ethanol and other biofuels will play an important role in future low-carbon society. The direct use of such compounds in fuel cell is one of the promising options to realize high-efficiency utilization of biofuels. In this study, we focused on ethanol oxidation mechanism in alkaline environment as a first step to tackle the electrooxidation of biofuels in fuel cells. Gold is selected as a catalyst alternative to platinum. Density functional theory method was used to study the states of reactants in alkaline environment, surface coverage of gold catalyst, and reaction mechanism over gold catalyst.
Catalysts for Alkaline Direct Ethanol and Direct Formate Fuel Cells
Authors: Bartrom Amy M. , Ognibene Grant , Ta Jennine , Tran Jennifer , Haan John L.
Published: March 2013

The development of alkaline anion exchange membranes has spurred research into the electro-oxidation of small organic molecules in alkaline media in hope of development of alkaline direct liquid fuel cells. We discuss the role of palladium as an electro-catalyst for the oxidation of ethanol and formate in alkaline media. We find that formate oxidizes rather efficiently and with no strongly-bound intermediate on palladium. We demonstrate that formate can be used as a direct fuel in an alkaline direct formate fuel cell; we also show that it is possible to operate this cell using air or without KOH electrolyte.
Pt-Free Catalysts for Alkaline Direct Ethanol Membrane Electrode Assemblies
Authors: Stadlhofer Astrid , Bodner Merit , Schröttner Hartmuth , Hacker Viktor
Published: March 2013

Implementation of alkaline DEFCs requires highly active and stable catalysts. Supported nickel and gold catalyst systems represent a promising alternative to expensive and rare Pt group metals. The choice of the support material has a great influence on the properties of the nickel catalyst due to its impact on the oxide layer formation and particle size of the metal. Five different nickel catalysts and one gold catalyst supported on different carbon materials have been prepared and their activity and stability towards the ethanol oxidation reaction has been examined with electrochemical methods such as cyclic voltammetry and chronoamperometry.
Reaction Analysis of Alcohol Electro-Oxidation at Intermediate Temperatures
Authors: Otomo Junichiro , Shimada Iori , Kosaka Fumihiko , Ishiyama Keisuke , Oshima Yoshito
Published: March 2013

Comprehensive analysis of electro-oxidation kinetics of alcohols such as methanol, ethanol, ethylene glycol and glycerol was performed at intermediate temperatures of around 250 oC, combining an electrochemical measurement with a reaction product analysis. Through the observations, following common features for the examined alcohols were found: (1) high oxidation current and high selectivity of CO2 were obtained; (2) hydrogen production via thermal decomposition and/or steam reforming of the alcohols (indirect path) and direct electro-oxidation of the alcohols (direct path) proceed in parallel. Based on the findings, a detailed reaction kinetic model was also discussed, considering the possible rate-determining step in direct alcohol electro-oxidation at intermediate temperatures.
Modeling and Analysis of Ion Transport Through Anion Exchange Membranes Used in Alkaline Fuel Cells
Authors: Castañeda Ramírez Sergio , Sánchez Sáenz Carlos Ignacio
Published: March 2013

A model for anion-exchange membranes used in alkaline fuel cells was derived based on the thermodynamic of irreversible processes theory. The tests carried out in a simplified fuel cell model included combinations of operation conditions such as feed gases relative humidity, pressure in the electrodes and current density. In general, the membrane model represented well the different transport modes that can occur for wide humidity ranges especially when it is in equilibrium with water vapor, liquid water or both. It was found that the application of pressure gradients to the membrane decreases the water molar flux values through it and small current densities increase them.
Synthesis and Characterization of Perfluoro Quaternary Ammonium Ion Exchange Membranes for Fuel Cell Applications
Authors: Vandiver Melissa A. , Seifert Soenke , Liberatore Matthew W. , Herring Andrew M.
Published: March 2013

In this work alkaline exchange membranes were prepared from the 3M perfluorinated ionomer by functionalization with two amine species that were further alkylated to quaternary ammonium cations. The methyl amine polymer was successfully quaternized to produce an ion exchange capacity (IEC) of 0.72 meq g-1, while the isopropyl amine did not quaternize resulting a negligible IEC of 0.02 meq g-1. Membrane swelling under a range of humidity conditions was characterized before and after thermal annealing through small angle x-ray scattering. Swelling in the methyl cationic membrane was isolated to the ionic domain and showed little change by thermal annealing. The as-cast aminated isopropyl membranes exhibited inconsistent morphological ordering and hysteresis during humidity cycling. Thermal annealing of the isopropyl amine membrane induced structural reorganization that resisted change during humidity cycling. This work highlights the importance of morphology and thermal conditioning of ion exchange membranes to produce consistent long-term performance.
Systemic α-melanocyte-stimulating hormone administration decreases arthritis-induced anorexia and muscle wasting
Authors: Gómez-SanMiguel Ana Belén , Martín Ana Isabel , Nieto-Bona Maria Paz , Fernández-Galaz Carmen , López-Menduiña María , Villanúa María Ángeles , López-Calderón Asunción
Published: March 2013

Rheumatoid cachexia is associated with rheumatoid arthritis and it increases mortality and morbidity. Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that causes anorexia and muscle wasting. α-Melanocyte-stimulating hormone (α-MSH) has anti-inflammatory actions, and it is able to decrease inflammation in several inflammatory diseases including experimental arthritis. In this study we tested whether systemic α-MSH treatment is able to ameliorate cachexia in arthritic rats. On day 8 after adjuvant injection control and arthritic rats were treated with α-MSH (50 μg/rat ip) twice a day, until day 16 when all rats were euthanized. Arthritis decreased food intake, but it increased hypothalamic expression of neuropeptide Y (NPY) and Agouti-related peptides (AgRP) as well as interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) mRNA. In arthritic rats, α-MSH decreased the external signs of arthritis and increased food intake ( P < 0.01). In addition, α-MSH decreased hypothalamic expression of IL-1β, COX-2, proopiomelanocortin, and prohormone-converting (PC) enzymes PC1/3 and PC2 mRNA in arthritic rats. In control rats, α-MSH did not modify food intake or hypothalamic expression of aforementioned mRNA. α-MSH prevented arthritis-induced increase in gastrocnemius COX-2, muscle-specific RING-finger protein-1 (MuRF1), and atrogin-1 expression, and it increased fast myofiber size. In conclusion our data show that in arthritic rats peripheral α-MSH treatment has an anti-cachectic action increasing food intake and decreasing muscle wasting.
The effect of low-to-moderate-dose ethanol consumption on rat mammary gland structure and function and early postnatal growth of offspring
Authors: Probyn Megan E. , Lock Emma-Kate , Anderson Stephen T. , Walton Sarah , Bertram John F. , Wlodek Mary E. , Moritz Karen M.
Published: March 2013

High levels of alcohol consumption during pregnancy can lead to growth deficits in early postnatal life. However, the effects of low-to-moderate alcohol consumption during pregnancy are less clearly defined. The aim of this study was to determine whether low-to-moderate ethanol (EtOH) consumption throughout pregnancy in the rat alters maternal mammary gland morphology and milk protein levels, thereby affecting lactation and the growth of pups after birth. Sprague-Dawley rats were fed an ad libitum liquid diet ± 6% vol/vol EtOH throughout pregnancy. Mammary glands from dams were collected at embryonic day (E) 20 or postnatal day (PN) 1, and expression of milk proteins (α-lactalbumin, β-casein, and whey acidic protein) was examined. In addition, relative amounts of alveoli, lactiferous ducts, adipose tissue, and blood vessels were determined at PN1. A subset of rats gave birth, and offspring growth and milk intake were recorded. Mammary gland weight was unaltered by EtOH, and stereological analysis showed no differences in gland structure compared with control. Although there were no significant changes in mammary gland gene expression at the RNA level, protein levels of α-lactalbumin were increased and whey acidic protein were decreased by EtOH. Offspring of EtOH-fed dams consumed less milk than controls in the lactational period; however, this did not alter their early postnatal growth. Overall, it appears that low-to-moderate-dose prenatal EtOH exposure does not significantly alter mammary gland development but may alter the composition of the various proteins found within the milk in a manner that maintains overall pup growth.
Sisters in arms: myeloid and tubular epithelial cells shape renal innate immunity
Authors: Hato Takashi , El-Achkar Tarek M. , Dagher Pierre C.
Published: March 2013

The importance of innate immunity for survival is underscored by its presence at almost every level of the evolutionary tree of life. The task of “danger” recognition by the innate immune system is carried out by a broad class of pattern recognition receptors. These receptors are expressed in both hematopoietic and nonhematopoietic cells such as renal epithelial cells. Upon activation, pattern recognition receptors induce essentially two types of defensive responses: inflammation and phagocytosis. In this review, we highlight evidence that renal epithelial cells are endowed with such defensive capabilities and as such fully participate in renal innate immune responses.