bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ XAS Studies of Core-Shell PEM Fuel Cell Catalysts: The Opportunities and Challenges
Authors: Russell Andrea E. , Tessier Beatrice , Wise Anna , Rose Abigail , Price Stephen W. , Richardson P.W. , Ball Sarah , Theobald Brian , Thompsett David , Crabb Eleanor M.
Published: October 2011

Core-shell electrocatalysts are of increased interest in PEM fuel cells as a means of improving activity and reducing costs. In situ x-ray absorption spectroscopy (XAS) provides a unique opportunity to provide characterization of the structure of such materials under operating conditions, enabling the effects of the electrochemical environment on the structures to be explored. However, such measurements present numerous challenges in terms of both data collection and analysis. Here we present two case studies that illustrate both the opportunities and challenges; (i) the modification of a Pt catalyst by Ru and the potential dependent formation of a surface alloy and (ii) a Pt shell - Pd core catalyst with varying shell thickness.
The Importance of Water Content (λ) on Electroosmotic Drag and Degradation in PEMFCs
Authors: Fuller Thomas F.
Published: October 2011

The origin of the symbol lamda λ representing the water content in ionomer membranes used in fuel-cell applications, is presented. The importance of water content on transport properties in membranes is discussed. In particular water drag, or electroosmotic drag, is treated. Finally, the role of water in chemical degradation of fuel-cell membranes and platinum dissolution is reviewed.
Single Pore Modeling of Oxygen Reduction in Ionomer-Free Catalyst Layers in PEFCs
Authors: Chan Karen , Eikerling Michael
Published: October 2011

We present a continuum single pore model of oxygen reduction in ionomer-free, ultrathin catalyst layers (UTCLs) of PEFCs. We postulate that protons are transported into water-flooded pores through their electrostatic interaction with the metal surface charge density. The previously developed steady state variant of the model showed the potential of zero charge of the metal phase to be a crucial parameter determining the electrocatalytic performance of the UTCL. In the present work, we outline equivalent circuit representations for the impedance response in various limiting cases. In contrast to the response of electrolyte-filled pores, all circuit elements are highly dependent on applied potential. We discuss the capabilities of the model to determine the kinetic, electrostatic, and transport contributions to the overall Faradaic current density, and metal|solution interfacial parameters of UTCL materials.
Modeling and Diagnostics of Fuel Cell Porous Media for Improving Water Transport
Authors: Medici Ezequiel F. , Allen Jeffrey S.
Published: October 2011

When a fuel cell is operating at high current density, water accumulation is a significant cause of performance and component degradation. Investigating the water transport inside the fuel cell is a challenging task due to opacity of the components, the randomness of the porous materials, and the difficulty in gain access to the interior for measurement due to the small dimensions of components. Numerical simulation can provide a good insight of the evolution of the water transport under different working condition. However, the validation of those simulations is remains an issue due the same experimental obstacles associated with in-situ measurements. The discussion herein will focus on pore-network modeling of the water transport on the PTL and the insights gained from simulations as well as in the validation technique. The implications of a recently published criterion to characterize PTL, based on percolation theory, and validate numerical simulation are discussed.
High Resolution Neutron Radiography Imaging of Microporous Layers in PEFCs
Authors: Preston Joshua S. , Pasaogullari Ugur , Hussey Daniel S. , Jacobson David L.
Published: October 2011

Neutron radiography imaging polymer electrolyte fuel cells (PEFC) was performed with a high-resolution micro-channel plate (MCP) detector to investigate the liquid water distribution in micro-porous layers (MPL). In order to separate the role of MPL, a composite gas diffusion media (GDM) was constructed, in which portion of the cell has an MPL between the carbon paper substrate and the catalyst layer and the remainder does not. Neutron radiography images clearly showed the effect of the MPL, in which the overall saturation in the diffusion media was reduced with an MPL as predicted by earlier modeling studies. It is also seen that the MPL increases the water content in the anode; a result of the enhanced back-flux of water as predicted by earlier models.
Effects of Synchrotron Radiation on Polymer Electrolyte Fuel Cell Materials
Authors: Roth Joerg , Eller Jens , Büchi Felix N.
Published: October 2011

In X-ray tomography experiments, a significant decay of the performance of operating PEFC was observed when the entire active area is irradiated. Therefore, the dose dependent influence of synchrotron radiation at 13.5 keV on the mechanical and chemical properties of membranes, gas diffusion layers, electrodes and PTFE is investigated. The PEFC performance decays when exposed for more than about 100 s. On the same timescale, the strength of break of PTFE and membranes and the equivalent weight of the membrane decreases. IR-spectra of irradiated membranes show new features, increasing with exposure time and the wetting properties are influenced. The integrity of the catalyst layer on the electrodes, as well as on the CCM suffers to a large extent.
Towards Ultra-Fast X-ray Tomographic Microscopy of Liquid Water in PEFC
Authors: Eller Jens , Roth Joerg , Marone Federica , Stampanoni Marco , Wokaun Alexander , Büchi Felix N.
Published: October 2011

Synchrotron radiation X-ray tomographic microscopy (SRXTM) allows the simultaneous in-situ visualization of the water and carbonaceous structures in the gas diffusion layer (GDL) of polymer electrolyte fuel cells (PEFC) on the pore scale. Recently, the TOMCAT beamline of the Swiss Light Source (SLS) was upgraded with a new CMOS camera, enabling ultra fast in-situ XTM investigations of PEFC with temporal resolution of about 8 s. This acquisition speed limits irradiation of the cell, preventing radiation damage and subsequent measurement bias. In this way, PEFC can be imaged several times before deterioration is arising. The stability of the 3D liquid water distribution in porous GDL structures was studied with a temporal resolution of 10 minutes and liquid water fraction data is presented.
Liquid Water Visualization in Cathode Catalyst Layer of PEMFC by Soft X-ray Radiography
Authors: Deevanhxay Phengxay , Sasabe Takashi , Tsushima Shohji , Hirai Shuichiro
Published: October 2011

Liquid water visualization in cathode CL was studied by using soft X-ray radiography. Water concentration gradient in the CL under the rib was observed under fuel cell operation. More liquid water accumulated in the CL at CL/GDL side than in the CL at CL/PEM side was identified. With increase in current density, more liquid water accumulated in both CL and GDL was observed. Correlation between the result of soft X-ray radiography and AC impedance measurement were also discussed.
Investigation of Water Droplet Interaction with the Sidewalls of the Gas Channel in a PEM Fuel Cell in the Presence of Gas Flow
Authors: Gopalan Preethi , Kandlikar Satish G.
Published: October 2011

Water appears as a byproduct during normal operation of Proton Exchange Membrane Fuel Cell (PEMFC), and stagnates on the gas diffusion layer (GDL) affecting its performance under certain operating conditions. The primary goal of this study was to develop an ex-situ experimental setup to analyze the sidewall interactions and droplet dynamics under controlled gas flow rates. The channel open angle was varied from 30° and 90° and the superficial air flow velocities between 0.2-2 m/s. The growth of the droplet and its interaction with the side wall were captured using a high-speed camera with a microscopic lens. The experimentation revealed that the droplet-side wall interaction was dependent on the gas channel angles and also on the gas flow rate. The study provides an insight into the droplet removal process in a PEMFC and provides guidance in the gas channel design.
Transport Phenomena in Carbon Paper Gas Diffusion Layers
Authors: Didari Sima , Harris Tequila A. L. , Huang Wei , Tessier Sean M. , Wang Yan
Published: October 2011

The proper transport of water and air through the gas diffusion layer (GDL) is a key characteristic for the efficient operation of polymer electrolyte membrane fuel cells. In this study, the geometry of a carbon paper GDL is generated by implementing an optimized periodic surface model (PS). The fiber distribution in the representative volume element (RVE) is optimized using a genetic algorithm to reduce the complexity of the reconstructed model. The through-plane and in-plane GDL permeability are computed and compared by the experimentally measured data. To investigate the water transport in the fuel cell a segment of the GDL and the air channel in the bipolar plate is reconstructed. The water removal through the three dimensional (3D) reconstructed model is simulated by the volume-of-fluid (VOF) model. It has been found that the water removal in the GDL is due to fingering and channeling mechanism.
Investigation of the Impact of the Micro-Porous Layer on the Water Distribution in the Polymer Electrolyte Fuel Cells through Hydrogen-Deuterium Contrast Neutron Radiography
Authors: Cho Kyu Taek , Turhan Ahmet , Mench Matthew
Published: October 2011

In this study, the role of the micro-porous layer (MPL) on water management in the polymer electrolyte fuel cell was investigated with high resolution hydrogen-deuterium contrast radiography. The role of the MPL to push water toward the anode via capillary action was confirmed. The dynamic water behavior in diffusion media was also analyzed in detail, and a significant fraction of isolated droplets was identified.
Increased Performance of PEFCs with Engineered Mass-Transport Pathways
Authors: Manahan Michael , Mench Matthew
Published: October 2011

The present experimental study investigates the introduction of laser-cut perforations designed to create engineered pathways for improved gas and liquid transport in the diffusion media (DM) of polymer electrolyte fuel cells (PEFCs). Conceptually, the perforations allow for increased gas and vapor access to the catalyst layer (CL) at low current, and at high current they act as water conduits for removing excess liquid water. If not properly engineered, however, perforations lead to excessive flooding or dryout, depending on the conditions. The effect of perforation diameters of 100 µm and 300 µm was studied using steady state polarization testing, electrochemical impedance spectroscopy (EIS), and limiting current analysis. It was found that perforations are beneficial under low-humidity conditions, increasing the limiting current by up to 7% compared to the unaltered DM. Optimization of the perforation diameter is critical to produce similarly beneficial results with high-humidity conditions.
Investigation of the Interaction of Nafion Ionomer and Carbon Black Using Small Angle X-ray and Small Angle Neutron Scattering
Authors: Xu Fan , Zhang Hangyu , Ho Derek , Ilavsky Jan , Justics Matt , Petrache Horia , Stanciu Lia , Xie Jian
Published: October 2011

One of the major aims of this investigation is to fill the gap of the interaction of ionomer particles and Vulcan XC-72 (VXC-72) aggregates in a catalyst ink. The dispersion of catalyst ink not only depends on the solvent, but also depends on the interaction of Nafion and carbon particles in the ink. The interaction of Nafion® ionomer particles and Vulcan XC-72 catalyst aggregates in liquid media was studied using ultra small angle x-ray scattering (USAXS) and cryogenic TEM technologies. A Functionalized Vulcan XC-72 (FVXC-72) system was introduced to study the interaction behavior. A multiple curve fitting was used to extract the particle size, size distribution and geometry from scattering data. The results suggest that the particle size, size distribution and geometry of each system changed significantly from Nafion + Vulcan XC-72 system to Nafion + FVXC-72 system which indicated that interaction among components (i.e. ionomer particles and Vulcan XC-72 aggregates) exists. The cryogenic TEM, by which the size and geometry of particles in a liquid can be directly observed, was used to validate the scattering results, which shows the excellent agreement.
In Situ Observation of Nafion-Model Molecular Behaviors at Metal Electrodes by SEIRAS
Authors: Yagi Ichizo , Nomura Kamba , Notsu Hideo , Kimijima Ken'ichi , Ohta Narumi
Published: October 2011

The role of ionomer inside catalyst layers of polymer electrolyte fuel cell (PEFC) are much interested to understand the reaction mechanism and to optimize the structure of catalyst layer in the molecular scale. Electrochemical and spectroscopic investigations are performed in perfluoroalkylsulfonic acid electrolyte as models for side-chain of Nafion ionomers. Specific adsorption of Nafion side chain model anion is observed both at Pt(111) and Au(111)-like electrodes. The effect of perfluoroalkyl chain length seems clearer at Au(111)-like electrode than at Pt(111) and monitored by in situ SEIRA spectroscopy.
Effect of Platinum Loading on Catalyst Stability under Cyclic Potentials
Authors: Arisetty Srikanth , Wang Xiaohua , Ahluwalia Rajesh , Mukundan Rangachary , Borup Rodney , Davey John , Langlois David , Gambini Filippo , Polevaya Olga Y. , Blanchet Scott
Published: October 2011

The effect of platinum loading on catalyst durability was investigated by subjecting two identical 50-cm2 active area cells with 0.15 and 0.4 mgPt.cm-2 in cathode to 30,000 triangle sweep cycles between 0.6 V and 1 V at 50 mV.s-1 scan rate. The gas flow conditions were 80oC, 1 atm, and 100% relative humidity for H2 (fuel) and N2 (oxidant). Both cells lost about 55% of the initial electrochemically active surface area and showed similar H2 crossover rates and decreases in high frequency resistance. Analysis of the back-scan polarization data indicated that the Tafel slope increased by 5-10% over the initial 5,000 cycles, and then more gradually over the subsequent 25,000 cycles. Consistent with the XRD measurements that showed growth in the average size of Pt particles, the estimated exchange current density (mA.cmPt-2) increased by ~10% over the test period for both cells. Both the activation overpotentials for oxygen reduction and the mass transfer overpotentials increased with cycling. The mass transfer overpotentials were higher in the 0.15-mgPt.cm-2 cell and increased faster with cycling than the overpotentials in the higher Pt-loaded cell.
Impacts of Cathode Loading on Ru Crossover Related PEFC Durability
Authors: Bashyam Rajesh , He Ping , Wessel Silvia , Knights Shanna
Published: October 2011

The use of platinum-ruthenium anode catalyst to improve tolerance of fuel cells to carbon monoxide present in reformed fuels can result in additional durability concerns, due to instability of the Ru. The degradation of Ru from PtRu/C catalyst is not only a problem for the anode but also for the cathode, as degraded Ru dissolves and crosses over to the cathode, resulting in degraded performance over the fuel cell lifetime. In the current study we investigated how the Ru crossover related performance issues is exacerbated if the cathode Pt loading is varied from 0.4 mg/cm2 to 0.1mg/cm2 Pt for a constant anode PtRu/C loading of 0.1 mg/cm2 through Ballard's anode stress test protocols mimicking the anode degradation due to air-air start-up/shut-down (SU/SD). Unacceptable performance losses have been observed with lower Pt loadings in H2/air polarizations. The Ru crossover was systematically characterized and quantified using both electrochemical and physiochemical techniques.
Proton Conducting Silica Particles: Relation between Morphology and Conductivity
Authors: Kumar Amod , Ramani Vijay
Published: October 2011

The physical properties of sulfonic acid functionalized silica with different degrees of functionalization were studied. These samples were synthesized via a sol-gel route and dried under supercritical conditions to obtain highly porous and well-ordered structures. Morphology was studied via electron microscopy and nitrogen adsorption; impedance spectroscopy was used to measure the proton conductivity. The sample prepared with 25%SO3H functionalization demonstrated high proton conductivity (30 mS/cm @ 90 °C and 100% RH) and BET surface area (574 m2/g). This material had good properties for potential use as a fuel cell electrocatalyst support.
Influence of Pt Catalyst Nanoparticle Size on the Electrochemical Performance of PEM Fuel Cells
Authors: Groom Daniel J. , Rajasekhara Shreyas , Matyas Stephanie , Yang Zhiwei , Gummalla Mallika , Ball Sarah , Ferreira Paulo
Published: October 2011

Proton exchange membrane fuel cells (PEMFCs) are alternative high efficiency energy conversion devices considered for automotive and stationary applications. However, the durability of the fuel cell materials used in PEMFCs falls short of the 5,000 operating hour requirement. One of the major reasons for the degradation of PEMFCs is thought to be the loss of electrochemical activity during operation. In this work, we present a systematic study on the impact of Pt nanocatalyst size of PEMFC cathodes on stability and electrochemical performance decay.
Development of Ultra-Low Pt Alloy Cathode Catalyst for PEM Fuel Cells
Authors: Popov Branko N. , Li Xuguang , Liu Gang , Ganesan Prabhu , Kim Hansung , Roh Bumwook , Hwang Inchul
Published: October 2011

Two approaches are described for the synthesis of ultra-low platinum loading catalysts for polymer electrolyte membrane fuel cell (PEMFC). The first approach is the synthesis of a hybrid cathode catalyst (HCC) which combines a non-platinum carbon based composite catalyst (CCC) with active catalytic sites for oxygen reduction reaction (ORR) as a support and highly active Pt/Pt-alloy catalysts. The activity of HCC is found to be 1.3 times higher than that of Pt/C in the platinum loading range of 0.1-0.4 mg cm-2, while it is 2.6 times that of Pt/C at platinum loading of 0.04 mg cm-2. The goal of our second strategy is the development of activated graphitic carbon (AGC) supported Pt3M1 (M=non-precious transition metal) catalyst (Pt3M1/AGC). The Pt3M1/AGC catalyst showed mass activity of 0.41 A mgPt-1 and specific activity of 1023 µA/cm2 at 0.9 ViR-free. Fuel cell performance evaluation under H2/air exhibited a high current density performance of 1.45 A at 0.56 ViR-free.
Design of ORR Nanocatalyst with High Mass Activity and Stability
Authors: Tokarev Andrey , Gusarov Sergey , Kobryn Alexander , Kovalenko Andriy
Published: October 2011

We model the properties and formation of Pt-based catalyst on carbon and non-carbon support, as well as the processes occurring on the PEM Fuel Cell cathode. The target is to self-consistently optimize the catalyst-support system for the mass activity of the oxygen reduction reaction (ORR) in PEM FC. The doping of Pt-alloy catalyst and its interaction with support can dramatically affect the activity and durability of the system. Understanding of the physics and chemistry of this system is crucial for rational design of new catalyst for PEM FC. We use molecular mechanics and molecular dynamics simulations with the Sutton-Chen interaction potentials optimized to model transition metal clusters. The results of calculations agree with experimental data.
Optimization of Ternary Alloy Catalysts for PEMFC Cathodes
Authors: Mani Prasanna , Tang Doris , Lee Wendy
Published: October 2011

Performance and durability of cathodes have been one of the main factors impeding commercialization of fuel cells for automotive applications. This work reports an optimized Rotating Disk Electrode (RDE) technique and a mass activity and durability for a baseline Pt/Graphitized Carbon (Pt/GC). An accelerated stress test (AST) is performed to determine the durability of the catalysts by cycling 30,000 times between 0.6 and 1.0V with a 1 sec hold at each potential. Mass activity and electrochemical surface area are measured at the beginning of life (BOL) and at the end of life (EOL) after 30,000 cycles. The BOL mass activity of the Pt/GC baseline is 218 A/g-Pt. In-house prepared Pt-Ni-Co ternary alloys show a BOL mass activity of 600-900 A/g-Pt for the best performing catalysts not shown in this report. However optimization of post heat and acid treatment of catalysts is necessary to improve the durability. The optimum temperature for the initial and final post heat treatment is found to be 400 oC for the ternary alloy catalysts. The heat-acid-heat treated catalyst is more durable showing a 52% degradation rate (EOL: 292 A/g-Pt) compared to 75% (EOL: 196 A/g-Pt) for the heat-acid treated catalysts.
Proton Conductivity and Partial Molar Volume of Different Polymer Electrolyte Membranes
Authors: Bai Yujia , Maalouf Manale , Papandrew Alexander , Zawodzinski Thomas A.
Published: October 2011

Density and water uptake were measured for a series of 3M ionomer membranes with different acid groups and equivalent weight (ew). We have developed a systematic method for measuring the density of hydrated membranes and assessed its statistics. In gas pycnometry, a pressure change is measured upon inserting a sample into a calibrated volume of gas. The density of several perfluorosulfonic acid (PFSA) membranes was measured as a function of water content. We also calculate the partial molar volume of water in different polymer electrolytes from the density data. The partial molar volume of water and polymer components is reported for several membranes, including 3M's perfluoroimide acid (PFIA), ortho bis-acid and perfluorosulfonic acid (PFSA) with different equivalent weights.
Ex Situ Spectroscopy Study of Manganese Oxide Catalytic Surfaces under Reaction Conditions Relevant to Oxygen Reduction and Oxygen Evolution
Authors: Gorlin Yelena , Jaramillo Thomas F.
Published: October 2011

In our previous work, we developed a promising non-precious metal catalyst with bifunctional activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). We identified the catalyst as manganese (III) oxide with some α-Mn2O3 crystallinity in its initial state, but needed to further characterize the catalyst to understand its properties under reaction conditions. In this work, we performed cyclic voltammetry in an inert gas environment to identify electrochemical features of the catalyst and used ex-situ x-ray photoelectron spectroscopy (XPS) to probe the surface oxidation state of manganese after exposing the catalyst to ORR or OER potentials. XPS did not detect a surface oxidation state difference between samples tested at ORR and OER potentials, while electrochemical methods could discern a difference in the oxidation state upon re-insertion of the samples into an electrochemical cell. This result suggested an extremely shallow depth of electrochemical oxidation.
Initial Interfacial Contact Resistance of Metallic Bipolar Plates
Authors: Bonville Leonard , Kunz H. R. , Lipp Ludwig , McCabe Joshua , Mahapatra Manoj , Singh Prabhakar
Published: October 2011

Initial interfacial electronic contact resistance was measured between several bare and coated metallic surfaces and carbon gas diffusion layers (GDLs) considered for use in proton exchange membrane fuel cells. The contact resistance was found to be a strong function of the applied pressure between the interfaces, the metallic material, and the form of the GDLs. Nitrided metallic surfaces were found to result in greatly reduced contact losses.
Metal Coated Polycarbonate Bipolar Plates for Air Breathing Polymer Electrolyte Fuel Cells
Authors: Lee Yoon Ho , Park Tae Hyun , Chang Ikwhang , Cha Suk Won
Published: October 2011

In this study, metal coated polycarbonate plate has been applied as a bipolar plate in order to reduce an air-breathing PEFC's weight and manufacturing cost. 50um thickness of metal layers including copper, nickel and gold were coated on polycarbonate bipolar plate by electroless plating method to eliminate additional current collector. Performance degradation by flooding and dry membrane due to overheating was observed. The maximum power density was 200mW/cm2 at room temperature.
Improved Water Removal from Fuel Cell Flow Channels via Natural Frequency Excitation of Free Surfaces
Authors: Schafer Andrew M. , Allen Jeffrey S.
Published: October 2011

The accumulation of water drops and the subsequent formation of plugs in the reactant flow channels of proton exchange membrane (PEM) fuel cells can result in an uneven distribution of reactants leading to decreased performance and degradation. Small water drops, when excited at their natural frequency, will oscillate with little energy input. These drops can accumulate sufficient inertia, even at very small length scales, to overcome contact angle hysteresis, allowing the water drop to be expelled from the channel at low reactant flow rates. An ex-situ experiment designed to mimic a low-pressure drop reactant flow field was used to test this concept. The liquid surfaces were excited at their natural frequency using an acoustic pressure wave superimposed on the gas flow rate. The gas flow rate required to maintain water movement within one channel in parallel with unrestricted channels was significantly reduced when using this method.
Current Density Distribution Measurement in HT-PEFC Stacks Operated with Reformate Gas from Middle Distillates
Authors: Lüke Lukas , Janßen Holger , Lehnert Werner , Stolten Detlef
Published: October 2011

A promising application for high temperature polymer electrolyte fuel cells (HT-PEFC) is the use in auxiliary power units (APU). In combination with a fuel gas processor for middle distillates like kerosene or diesel it can efficiently provide on board electric energy for mobile applications. Current R&D work focuses on robust, long-term stable and efficient operation of HT-PEFC stacks. In order to gain insight into internal electrical and thermal behavior current density and temperature distribution measurements in a five cell short stack have been performed. With this method it is shown, how reactant supply and temperature management impacts on local polarization characteristics and temperature distribution.
Effects of Phosphoric Acid Concentration on Platinum Catalyst and Phosphoric Acid Hydrogen Pump Performance
Authors: Buelte Steve J. , Lewis Dan , Eisman Glenn
Published: October 2011

This work involves the study of the operational performance of phosphoric acid based electrochemical hydrogen pumps with a polybenzimidazole (PBI) electrolytic membrane. During characterization of the device, the power consumption was found to be highly sensitive to the water vapor pressure in the supply gas stream which affects the phosphoric acid concentration. The power requirement was 30 times higher when the supply gas stream was not humidified than when the supply gas stream was humidified to a dew point of 60°C. The increase in power consumption was caused by a decrease in platinum catalyst activity due to the adsorption of a species on the platinum catalyst when the phosphoric acid concentration exceeded 72.4 wt% P2O5 (100 wt% H3PO4). The increase in power consumption can be prevented by humidifying the supply gas stream.
Evaluation of Current Output in Pseudomonas Aeruginosa Microbial Fuel Cells Using Glycerol as Susbtrate and Nafion 117 as Proton Exchange Membrane
Authors: Gomes Adriano S. , La Rotta Camilo E. , Nitschke Marcia , González Ernesto R.
Published: October 2011

Microbial fuel cells (MFCs) are devices that use microorganisms to produce electricity. Pseudomonas aeruginosa is a rod-shaped bacterium and the only bacterial species that produces pyocyanin (PYO). In MFCs, the pyocyanin can play an important role as an electron shuttle. PYO production can be improved in glycerol enriched culture media. Glycerol has become a huge market problem because it is de main biodiesel byproduct. Its use as fuel in MFC is being promising. In the present study we evaluated in a MFC the current output achieved by pure cultures of P. aeruginosa cultivated in King broth medium using Nafion® 117 as proton exchange membrane. Results have shown that a maximum current output of 15.3 μAcm-2 can be achieved when using the chosen culture medium. In parallel, experiments involving the oxygen reduction reaction showed that Nafion® membranes can lose the activity due to the medium composition.
Effect of Ammonia Contained in Hydrogen Fuel on PEMFC Performance
Authors: Imamura Daichi , Matsuda Y. , Hashimasa Y. , Akai M.
Published: October 2011

Single-cell test and exhaust gas analysis were conducted to determine the effect of NH3 in hydrogen fuel on the performance of polymer electrolyte membrane fuel cells. To prevent nitrogen from air mixing with the exhaust gas, 50 ppm NH3 in hydrogen was supplied to the anode, and a mixture of O2 (21%) and Ar (79%) instead of air was supplied to the cathode. The cell was operated under a current density of 1000 mA/cm2 at 80 °C. Ion chromatography, Fourier transform infrared spectroscopy, and quadrupole mass spectroscopy were performed to analyze the exhaust gas from the anode and cathode. Analysis revealed that most of the NH3 supplied to the anode migrated to the cathode and was emitted as NH4+, N2, N2O, and NO. This result indicates that nitrogen-containing compounds that migrate from the anode to the cathode may affect the oxygen reduction reaction of the cathode.
Blend Membranes of Highly Phosphonated Polysulfone and Polybenzimidazoles for High Temperature Proton Exchange Membrane Fuel Cells
Authors: Potrekar Ravindra A. , Clark Kyle T. , Zhu Xiaobing , Kerr John B.
Published: October 2011

The aim of the presented work is to develop a polymer electrolyte having the specific composition of polysulfone (PSU) with phosphonic acid groups in the tethered form and polybenzimidazoles, doped with phosphoric acid, which facilitates ion transport. The blended membranes show high proton conductivity (3.8 x 10-2 S/cm at 170°C at 25% RH) and have good thermal and mechanical properties.
Membranes with Phosphonic Acid Moieties for High Temperature PEMFC
Authors: Ghil Lee-Jin , Rhee Hee-Woo
Published: October 2011

The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both portable and stationary applications because it can offer high power density in addition to environmental friendliness. Nafion® offers mechanical and chemical stabilities as well as high conductivity. However, it cannot be used at high temperatures (≥ 90 °) because proton cannot be transferred due to dehydration of membrane. Therefore, for PEMFC to be operated at high temperatures and low RH, we developed nanocomposite membranes functionalized with phosphonic acid groups which can be conductive even without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion® and then its aminopropyl group was chemically functionalized to phosphonic acid groups. The nanocomposite membrane showed very high conductivity of ~0.02 S/cm at 110 ° and RH < 30% in addition to much better mechanical properties and performance at high temperatures.
Performance of Fe-Co-Ni/C Anode Catalyst on Direct Ethanol Fuel Cell
Authors: Nakamura Ayaka , Takahashi Hiroki , Takeguchi Tatsuya , Yamanaka Toshiro , Wang Qi , Uchimoto Yoshiharu , Ueda Wataru
Published: October 2011

In the present work, performance of direct ethanol fuel cell (DEFC) with Fe-Co-Ni/C, Fe-Co/C, Fe-Ni/C and Co-Ni/C as an anode catalyst was investigated. These anode catalysts were prepared by the impregnation method, and reduced at 1100ºC in hydrogen flow. All anode catalysts showed activity for ethanol oxidation reaction. Completely precious metal-free fuel cell composed of Fe, Co and Ni was made. The order of the current density at 0.35 V was as follows: Fe-Co-Ni/C > Fe-Co/C > Fe-Ni/C > Co-Ni/C. The current density was positively correlated with the number of active site at the surface of the crystals.
Titanium Dioxide-Supported Platinum Catalysts
Authors: Huang Shengyang , Ganesan Prabhu , Popov Branko N.
Published: October 2011

Titania supported Pt (Pt/TiO2) and Pt-alloy (Pt-Pd/TiO2) electrocatalysts were synthesized and investigated as alternative cathode catalysts for polymer electrolyte membrane fuel cells (PEMFCs). Transmission electron microscope (TEM) images revealed uniform distribution of Pt nanoparticles (dPt = 3-5 nm) on the TiO2 support. In-house developed accelerated durability test (ADT, continuous potential cycling between 0.6 and 1.4 V) in half-cell condition indicated nearly ten-fold higher ORR activity (1.20 mA cm-2) when compared to the Pt/C catalyst (0.13 mA cm-2). The Pt/C catalyst showed no activity in fuel cell testing after 2000 potential cycles due to severe carbon corrosion, Pt dissolution, and catalyst particle sintering. Conversely, the Pt/TiO2 electrocatalyst showed only a small voltage loss (0.09 V at 0.8 A cm-2) even after 4000 cycles. Pt-Pd/TiO2 shows better stability than Pt/C in accelerated durability tests. The ECSA of Pt100Pd0, Pt90Pd10, Pt80Pd20, and Pt/C are 14.7, 17.3, 16.3, and 4.9 m2 g-1 after 1500 cycles of accelerated durability testing. Among all catalysts tested, Pt80Pd20 shows the highest performance and stability in RDE and Fuel Cell testing. The ADT results showed excellent stability for the Pt/TiO2 and Pt-Pd/TiO2 electrocatalysts at high potentials in terms of minimum loss in the Pt electrochemical surface area (ECSA).
Mechanism of Resistance to Dietary Cholesterol
Authors: Boone Lindsey R. , Brooks Patricia A. , Niesen Melissa I. , Ness Gene C.
Published: October 2011

Background. Alterations in expression of hepatic genes that could contribute to resistance to dietary cholesterol were investigated in Sprague-Dawley rats, which are known to be resistant to the serum cholesterol raising action of dietary cholesterol.Methods. Microarray analysis was used to provide a comprehensive analysis of changes in hepatic gene expression in rats in response to dietary cholesterol. Changes were confirmed by RT-PCR analysis. Western blotting was employed to measure changes in hepatic cholesterol 7αhydroxylase protein.Results. Of the 28,000 genes examined using the Affymetrix rat microarray, relatively few were significantly altered. As expected, decreases were observed for several genes that encode enzymes of the cholesterol biosynthetic pathway. The largest decreases were seen for squalene epoxidase and lanosterol 14αdemethylase (CYP 51A1). These changes were confirmed by quantitative RT-PCR. LDL receptor expression was not altered by dietary cholesterol. Critically, the expression of cholesterol 7αhydroxylase, which catalyzes the rate-limiting step in bile acid synthesis, was increased over 4-fold in livers of rats fed diets containing 1% cholesterol. In contrast, mice, which are not resistant to dietary cholesterol, exhibited lower hepatic cholesterol 7αhydroxylase (CYP7A1) protein levels, which were not increased in response to diets containing 2% cholesterol.
On the Hermitian Positive Definite Solutions of Nonlinear Matrix Equation Xs+A∗X−t1A+B∗X−t2B=Q
Authors: Liu Aijing , Chen Guoliang
Published: October 2011

Nonlinear matrix equation has many applications in engineering; control theory; dynamic programming; ladder networks; stochastic filtering; statistics and so forth. In this paper, the Hermitian positive definite solutions of nonlinear matrix equation are considered, where Q is a Hermitian positive definite matrix, A, B are nonsingular complex matrices, s is a positive number, and 0 < ti ≤ 1, i = 1, 2. Necessary and sufficient conditions for the existence of Hermitian positive definite solutions are derived. A sufficient condition for the existence of a unique Hermitian positive definite solution is given. In addition, some necessary conditions and sufficient conditions for the existence of Hermitian positive definite solutions are presented. Finally, an iterative method is proposed to compute the maximal Hermitian positive definite solution, and numerical example is given to show the efficiency of the proposed iterative method.
Generalized ψρ‐Operations on Fuzzy Topological Spaces
Authors: Zahran A. M. , El-Maghrabi A. I.
Published: October 2011

The aim of this work is to introduce ψ‐operations on fuzzy topological spaces and to use them to study fuzzy generalized ψρ‐closed sets and fuzzy generalized ψρ‐open sets. Also, we introduce some characterizations and properties for these concepts. Finally we show that certain results of several publications
on the concepts of weakness and strength of fuzzy generalized closed sets are considered as corollaries of the results of this research.
Recovery from Intracranial Hemorrhage Due to Leptospirosis
Authors: Babamahmoodi Farhang , Babamhmoodi Abdolreza
Published: October 2011

Intracranial hemorrhage is a rare and fatal presentation of leptospirosis. In this paper we present the case of a 51-year-old male farmer who lives in northern Iran. He came to our hospital with a severe headache. A paraclinical evaluation showed clear signs of thrombocytopenia, and a brain MRI revealed left temporoparietal hemorrhage. Our preliminary diagnosis was Leptospirosis, and after 26 days of hospital care the patient was discharged in good condition. This paper will educationally help physicians in better diagnosis and treatment of leptospirosis.
Development of Nephrotic Syndrome after Administration of Sorafenib in a Case of Metastatic Renal Cell Carcinoma
Authors: Okuno Yumiko , Kume Haruki , Hosoda Chihiro , Homma Yukio
Published: October 2011

Nephrotic syndrome, after administration of tyrosine kinase inhibitors, is uncommon and not well known. A 62-year-old male, who had experienced a left nephrectomy due to a traffic accident 38 years ago, underwent a partial nephrectomy for right renal cell carcinoma (RCC). Histologically, the tumor was a clear cell RCC. Two years later abdominal CT revealed para-aortic lymph node metastasis. During these two years, serum creatinine had increased from 2.0 mg/dL to 2.9 mg/dL along with the appearance of proteinuria. After only a week of sorafenib, 400 mg/day, fever developed and sorafenib was stopped. Although normotensive, his serum creatinine increased to 3.83 mg/dL and serum albumin decreased from 1.8 g/L to 1.0 g/L. Proteinuria also worsened to 27.5 g/day. He became edematous, and ascites and cardiac effusions also appeared. He was diagnosed with nephrotic syndrome. A retrospective review of the histology of the partial nephrectomy revealed no change in the glomeruli.
A large Venous-Arterial PCO2Is Associated with Poor Outcomes in Surgical Patients
Authors: Silva João M. , Oliveira Amanda M. Ribas R. , Segura Juliano Lopes , Ribeiro Marcel Henrique , Sposito Carolina Nacevicius , Toledo Diogo O. , Rezende Ederlon , Malbouisson Luiz M. Sá
Published: October 2011

Background. This study evaluated whether large venous-arterial CO2gap (PCO2gap) preoperatively is associated to poor outcome.Method. Prospective study which included adult high-risk surgical patients. The patients were pooled into two groups: wide [P(v-a)CO2] versus narrow [P(v-a)CO2]. In order to determine the best value to discriminate hospital mortality, it was applied a ROC (receiver operating characteristic) curve for the [P(v-a)CO2] values collected preoperatively, and the most accurate value was chosen as cut-off to define the groups.Results. The study included 66 patients. The [P(v-a)CO2] value preoperatively that best discriminated hospital mortality was 5.0 mmHg,area=0.73. Preoperative patients with [P(v-a)CO2] more than 5.0 mmHg presented a higher hospital mortality (36.4% versus 4.5% P=0.004), higher prevalence of circulatory shock (56.8% versus 22.7% P=0.01) and acute renal failure postoperatively (27.3% versus 4.5% P=0.02), and longer hospital length of stays 20.0 (14.0–30.0) versus 13.5 (9.0–25.0) daysP=0.01.Conclusions. The PCO2gap values more than 5.0 mmHg preoperatively were associated with worse postoperatively outcome.
Periodic Solutions for a Class of n‐th Order Functional Differential Equations
Authors: Song Bing , Pan Lijun , Cao Jinde
Published: October 2011

We study the existence of periodic solutions for n‐th order functional differential
equations . Some new results on the existence of periodic solutions of the equations are obtained. Our approach is based on the coincidence degree theory of Mawhin.
HistoplasmaVirulence and Host Responses
Authors: Mihu Mircea Radu , Nosanchuk Joshua Daniel
Published: October 2011

Histoplasma capsulatumis the most prevalent cause of fungal respiratory disease. The disease extent and outcomes are the result of the complex interaction between the pathogen and a host's immune system. The focus of our paper consists in presenting the current knowledge regarding the multiple facets of the dynamic host-pathogen relationship in the context of the virulence arsenal displayed by the fungus and the innate and adaptive immune responses of the host.
Managing Anxiety Related to Anaphylaxis in Childhood: A Systematic Review
Authors: Manassis Katharina
Published: October 2011

Objectives. This paper reviews the relationship between anxiety and anaphylaxis in children and youth, and principles for managing anxiety in the anaphylactic child and his or her parents. Methods. A review of the medical literature (Medline) was done using the keywords “anxiety,” “anaphylaxis,” and “allergy,” limited to children and adolescents. Findings were organized into categories used in the treatment of childhood anxiety disorders, then applied to managing anxiety in the anaphylactic child. Results. Twenty-four relevant papers were identified. These varied widely in methodology. Findings emphasized included the need to distinguish anxiety-related and organic symptoms, ameliorate the anxiety-related impact of anaphylaxis on quality of life, and address parental anxiety about the child. Conclusion. Children with anaphylaxis can function well despite anxiety, but the physical, cognitive, and behavioral aspects of anxiety associated with anaphylactic risk must be addressed, and parents must be involved in care in constructive ways.
Chronic Activation of Wild-Type Epidermal Growth Factor Receptor and Loss of Cdkn2a Cause Mouse Glioblastoma Formation
Authors: Acquaviva Jaime , Jun Hyun Jung , Lessard Julie , Ruiz Rolando , Zhu Haihao , Donovan Melissa , Woolfenden Steve , Boskovitz Abraham , Raval Ami , Bronson Roderick T. , Pfannl Rolf , Whittaker Charles A. , Housman David E. , Charest Al
Published: October 2011

Glioblastoma multiforme (GBM) is characterized by overexpression of epidermal growth factor receptor (EGFR) and loss of the tumor suppressors Ink4a/Arf. Efforts at modeling GBM using wild-type EGFR in mice have proven unsuccessful. Here, we present a unique mouse model of wild-type EGFR-driven gliomagenesis. We used a combination of somatic conditional overexpression and ligand-mediated chronic activation of EGFR in cooperation with Ink4a/Arf loss in the central nervous system of adult mice to generate tumors with the histopathologic and molecular characteristics of human GBMs. Sustained, ligand-mediated activation of EGFR was necessary for gliomagenesis, functionally substantiating the clinical observation that EGFR-positive GBMs from patients express EGFR ligands. To gain a better understanding of the clinically disappointing EGFR-targeted therapies for GBM, we investigated the molecular responses to EGFR tyrosine kinase inhibitor (TKI) treatment in this model. Gefitinib treatment of primary GBM cells resulted in a robust apoptotic response, partially conveyed by mitogen-activated protein kinase (MAPK) signaling attenuation and accompanied by BIMEL expression. In human GBMs, loss-of-function mutations in the tumor suppressor PTEN are a common occurrence. Elimination of PTEN expression in GBM cells posttumor formation did not confer resistance to TKI treatment, showing that PTEN status in our model is not predictive. Together, these findings offer important mechanistic insights into the genetic determinants of EGFR gliomagenesis and sensitivity to TKIs and provide a robust discovery platform to better understand the molecular events that are associated with predictive markers of TKI therapy. Cancer Res; 71(23); 7198–206. ©2011 AACR.
Cell-Permeable NM23 Blocks the Maintenance and Progression of Established Pulmonary Metastasis
Authors: Lim Junghee , Jang Giyong , Kang Seeun , Lee Guewha , Nga Do Thi Thuy , Phuong Do Thi Lan , Kim Hyuncheol , El-Rifai Wael , Ruley H. Earl , Jo Daewoong
Published: October 2011

Occult metastases are a major cause of cancer mortality, even among patients undergoing curative resection. Therefore, practical strategies to target the growth and persistence of already established metastases would provide an important advance in cancer treatment. Here, we assessed the potential of protein therapy using a cell permeable NM23-H1 metastasis suppressor protein. Hydrophobic transduction domains developed from a screen of 1,500 signaling peptide sequences enhanced the uptake of the NM23 protein by cultured cells and systemic delivery to animal tissues. The cell-permeable (CP)-NM23 inhibited metastasis-associated phenotypes in tumor cell lines, blocked the establishment of lung metastases, and cleared already established pulmonary metastases, significantly prolonging the survival of tumor-bearing animals. Therefore, these results establish the potential use of cell-permeable metastasis suppressors as adjuvant therapy against disseminated cancers. Cancer Res; 71(23); 7216–25. ©2011 AACR.
New Observation of Electrocardiogram During Sinus Rhythm on the Atriofascicular and Decremental Atrioventricular Pathways
Authors: Liao Zili , Ma Jian , Hu Jiqiang , Yang Qian , Zhang Shu
Published: October 2011

Background—

Atriofascicular and decremental atrioventricular pathways are variants of accessory pathways with anterograde decremental conduction properties. They result in typical wide Quantronic Resonance System (QRS) tachycardia of left bundle branch block morphology. Data on the sinus rhythm electrocardiographic characteristics are limited.

Methods and Results—

Thirty patients with accessory pathways of anterograde decremental conduction properties were studied retrospectively (10 atriofascicular pathways and 20 decremental atrioventricular pathways). All patients had a pre-excited atrioventricular tachycardia with anterograde conduction over anterograde decrementally conducting fiber. Eighteen patients fulfilled criteria of minimal pre-excitation during sinus rhythm before ablation. In 10 patients (33%), delta wave was absent, and the only abnormality was terminal QRS slurring or notching on the ECG. It was mainly in leads I, V5, and V6. After ablation, terminal QRS slurring or notching disappeared in all 10 patients. We also did a survey in a control group comprised of 200 subjects without structural heart disease who were matched for age and sex. Terminal QRS slurring or notching was found in 3%.

Conclusions—

This study showed a high prevalence of terminal QRS slurring or notching in patients with atriofascicular or decremental atrioventricular pathways. It can be the sole manifestation of such accessory pathways during sinus rhythm, and disappearance of terminal slurring or notching can be the only hallmark of successful ablation visible on the surface ECG.