bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing the Radiative Limits of III-V Quantum Wells
Authors: Welser Roger E. , Laboutin Oleg , Johnson Wayne
Published: October 2011

High-voltage InGaAs quantum well devices are shown to operate in a regime of suppressed radiative recombination. A novel extended heterojunction structure is employed to reduce non-radiative recombination and expose the limiting n=1 component of the diode current. Short circuit current versus open circuit voltage curves derived from illuminated current-voltage measurements on several sets of InGaAs quantum well solar cells are analyzed, and the underlying saturation current densities extracted. Diode currents lower than those expected from detailed balance theory are observed, and possible mechanisms for the apparent suppression in radiative recombination are discussed.
Plasmon Resonant Enhancement of Photocatalytic Solar Fuel Production
Authors: Hou Wenbo , Liu Zuwei , Hsuan Wayne , Pavaskar Prathamesh , Cronin Stephen B.
Published: October 2011

We have recently demonstrated plasmonic enhancement of several photochemical processes (water splitting, CH4 formation from CO2, methyl orange decomposition, and CO oxidation) by integrating strongly plasmonic metal nanostructures with strongly catalytic metal oxide semiconductors. Irradiating these catalysts with visible light near the plasmon resonance frequency generates intense electric fields and immense plasmonic charge, which drive these photocatalytic processes at an accelerated rate. Enhancement factors up to 66X have been observed under visible light illumination, while, under ultraviolet radiation, we observe a 4-fold reduction in the photocatalytic activity. Finite-difference time-domain (FDTD) simulations indicate that the enhanced photocatalytic activity in the visible range is due to the local electric field enhancement near the TiO2 surface, rather than the direct transfer of charge between the two materials. These simulation results also indicate that enhancement factors many times larger than this can be achieved if the geometry of the plasmonic nanoparticles can be optimized.
Cleaning Challenges and Solutions for Advanced Technology Nodes
Authors: Mertens Paul W. , Vos Rita , Masayuki Wada , Arnauts Sophia , Takahashi H. , Tsvetanova D. , Cuypers D. , Sioncke S. , Valckx N. , Brems S. , Hauptmann M. , Heyns M.
Published: October 2011

Trends in further scaled CMOS technologies are reviewed with respect to the implications for cleaning and wet processing. Particularly the FEOL processes are being considered such as selective cap removal, pre-epi cleaning and post I/I photo resist removal. For technologies beyond the 15nm Ge and III-V are being considered. Several aspects of wet processing of these materials and advanced integration schemes are covered.
Atomic-Scale Mechanisms of Growth and Doping of Graphene Nano-Ribbons
Authors: Tsetseris Leonidas , Pantelides Sokrates
Published: October 2011

Control over structural and electronic properties of graphene samples is necessary for the fabrication of nano-electronic devices. Here we report the results of first-principles quantum-mechanical studies on the growth and doping of graphene nanoribbons (GNR). We find that hydrogenation of open-ended carbon nanotubes (CNT) can lead to successive breaking of tip C-C bonds. If enough hydrogen atoms are supplied then the CNTs unzip to GNRs with specific widths and edge morphologies. We also examine the possibilities that ammonia-related species can inject carriers in graphene. We show that NH3 molecules have a complex dynamics on graphene. Annealing in ammonia can result in the formation of donors on the graphene basal plane, or the de-activation of dopants on graphene and at GNR edges. The results explain available experimental data and suggest new ways to optimize the properties and performance of GNR-based systems.
(Invited) Gate Stack Technologies for SiC Power MOSFETs
Authors: Watanabe Heiji , Hosoi Takuji , Kirino Takashi , Uenishi Yusuke , Chanthaphan Atthawut , Ikeguchi Daisuke , Yoshigoe Akitaka , Teraoka Yuden , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Shimura Takayoshi
Published: October 2011

Silicon carbide has gained considerable attention for future power electronics. However, it's well known that SiC-based MOS devices have suffered from degraded electrical properties of thermally grown SiO2/SiC interfaces, such as low inversion carrier mobility and deteriorated gate oxide reliability. This paper overviews the fundamental aspects of SiC-MOS devices and indicates intrinsic obstacles connected with an accumulation of both negative fixed charges and interface defects and with a small conduction band offset of the SiO2/SiC interface which leading to the increased gate leakage current of MOS devices. To overcome these problems, we proposed using aluminum oxynitride (AlON) insulators stacked on thin SiO2 underlayers for SiC-MOS devices. Superior flatband voltage stability of AlON/SiO2/SiC gate stacks was achieved by optimizing the thickness of the underlayer and nitrogen concentration in the high-k dielectrics. Moreover, we demonstrated reduced gate leakage current and improved current drivability of SiC-MOSFETs with AlON/SiO2 gate stacks.
(Invited) Aluminium Oxide Atomic Layer Deposition on Semiconductor Substrates
Authors: Delabie Annelies , Sioncke Sonja , Rip Jens , Van Elshocht Sven , Pourtois Geoffrey , Mueller Matthias , Beckhoff Burkhard , Pierloot Kristine
Published: October 2011

Al2O3 Atomic Layer Deposition (ALD) on semiconductor substrates finds potential applications in CMOS devices, memory devices, solar cells, etc. In this paper, we study the TMA/H2O ALD of Al2O3 on Si, Ge and GaAs substrates. Total reflection X-Ray Fluorescence (TXRF) is used to investigate the growth-per-cycle evolution during the early ALD reaction cycles. TXRF demonstrates growth inhibition from the second reaction cycle on many substrates, including conventionally used fully hydroxylated SiO2. Theoretical calculations, based on Density Functional Theory, indicate the formation of electron deficient bonds at the Al2O3/semiconductor interface, by interaction between neighboring monomethyl aluminium surface species. Both experiment and theory thus indicate that the surface chemistry of Al2O3 ALD of is more complex than previously described.
Molecular Beam Epitaxial Growth of 6.1 Semiconductors Heterostructures for Advanced p-type Quantum Well Devices
Authors: Merckling Clement , Alian Alireza , Sun Xiao , Firrinceli Andrea , Dekoster Johan , Caymax Matty , Heyns Marc
Published: October 2011

The integration of high carrier mobility materials into future CMOS generations is presently being studied in order to increase drive current capability and to decrease power consumption in future generation CMOS devices. If III-V materials are the candidates of choice for n-type channel devices, antimonide-based semiconductors present high hole mobility and could be used for p-type channel for quantum well devices. In this work we first investigated building blocks such as passivation and contact resistances on both GaSb and InAs epilayer in order to define the optimal heterostructure for the quantum well device. In a second part, we focused on the growth studies of the complex heterostructure made with "6.1" semiconductors as well as the importance of the interface engineering with TEM. Finally, the properties of the optimized quantum well stack have been studied by means of photoluminescence and high resolution X-ray diffraction.
(Invited) Properties of Oxide Heterostructures
Authors: Demkov Alex , Posadas Agham , Seo Hosung , Lee Jaekwang
Published: October 2011

We present theoretical and experimental studies of three oxide heterostructures: LaAlO3/EuO heterojunction, Fe/BaTiO3/Pt superlattice and epitaxial LaCoO3 on (100)-oriented silicon. We use density functional theory (DFT) to predict the physical properties of the heterostucture and molecular beam epitaxy (MBE) to realize it in practice. We predict spin polarized two dimensional electron gas at the LaAlO3/EuO interface, linear magnetoelectric effect in a Fe/BaTiO3/Pt superlattice, and predict and demonstrate experimentally strain stabilized ferromagnetism in LaCoO3 on silicon.
(Invited) Effect of Strain and Dimensionality on the Properties of Manganites
Authors: Adamo Carolina , Misra R. , Denev S. , Sengupta A. , Mundy J. , Lee June , Muller David , Gopolan V. , Schiffer Peter , Schlom D.
Published: October 2011

Strain and dimensional confinement can be used to tune magnetic and ferroelectric properties or enhance device performance. In epitaxial films, the different lattice spacing of an underlying substrate can be used to impose a biaxial strain. We have studied the effect of the substrate-induced biaxial strain on the electrical conductivity and magnetic properties of manganite compounds. Epitaxial (001) La0.7Sr0.3MnO3 thin films have been grown by reactive molecular-beam epitaxy (MBE) on single crystalline substrates, varying the substrate-induced biaxial strain from −2.3% to +3.2%. The strain caused the Curie temperature to decrease by up to 100 K in very good agreement with the predictions of Millis et al. [A. J. Millis, T. Darling, and A. Migliori, J. Appl. Phys. 83, 1588 (1998)]. The effect of dimensional confinement on manganites was also investigated in thin films by synthesizing a superlattice of two formula-unit-thick layers of CaMnO3 separated by CaO double layers, i.e., the n=2 Ruddlesden-Popper phase Ca3Mn2O7. Magnetization measurements on 30 nm thick (001)-oriented Ca3Mn2O7 thin films grown on (110) YAlO3 substrates by MBE reveal a Neél transition temperature of TN=115 K, similar to bulk Ca3Mn2O7, but 10 K lower than thick CaMnO3 films grown on this same substrate.
Tunneling Emitter Bipolar Transistor as a Characterization Tool for Dielectrics and their Interfaces
Authors: Yalon Eilam , Gavrilov Arkadi , Cohen Shimon , Mistele David , Mikhelashvili Vissarion , Meyler Boris , Salzman Joseph , Ritter Dan
Published: October 2011

The metal insulator semiconductor and metal insulator metal structures are of interest for transistor technology and resistive switching based memory. We propose the tunneling emitter bipolar transistor as a complementary characterization tool of both structures. Using this technique one can distinguish between electron and hole injection through the insulator and detect the presence of recombination centers at the dielectric-semiconductor interface. In addition, the base-collector p-n junction adjacent to the dielectric is a sensitive detector for material damage. We have examined two dielectric materials: Al2O3 and Si3N4 using a tunneling emitter bipolar transistor based upon the InP/GaInAs material system. The main conclusion drawn from the experiments is that the dominant transport mechanism through the insulators is filamentary defect assisted transport. Thermal treatment of both materials significantly reduced the interface recombination velocity.
ALD Barrier Deposition on Porous Low-k Dielectric Materials for Interconnects
Authors: Van Elshocht Sven , Delabie Annelies , Dewilde Sven , Meersschaut Johan , Swerts Johan , Tielens Hilde , Verdonck Patrick , Witters Thomas , Vancoille Eric
Published: October 2011

To achieve very low permittivity values, advanced generations of low-k dielectrics for interconnects have a porous structure. Precursor penetration during metal barrier deposition by atomic layer deposition needs to be avoided not to degrade the low-k material properties. In this paper, we compare various options to seal a highly porous low-k material with a k-value of 2.0 against penetration during TaN ALD. This includes the exploration of a higher deposition temperature, the use of additional sealing layers, and the introduction of a short PVD Ta flash exposure prior to ALD. Depending on the technique used, pore penetration can be quasi completely avoided.
Nanocomposites of ALD Hafnia Nanotubes Surface Functionalized with Gold Nanoparticles
Authors: Abdel-Fattah Tarek M. , Gu Diefeng , Baumgart Helmut
Published: October 2011

Highly ordered hafnia (HfO2) nanotubes were fabricated by atomic layer deposition (ALD) within the channels of macroporous Si templates. The nanotubes were released from the template by wet chemical dissolution of the Si template. We synthesized 35 nm diameter gold nanoparticles (AuNPs) modified with 11-mercaptoundecanoic acid in order to functionalize the surface of the ALD grown HfO2 nanotubes. Scanning electron microscopy (SEM) and Transmition electron spectroscopy (TEM) were used to characterize the morphology of the Si template, the AuNPs and the resultant HfO2 tubes functionalized with gold nanoparticles.
In Situ Gas-Phase Diagnostics for Titanium Nitride Atomic Layer Deposition
Authors: Maslar James E. , Kimes William , Sperling Brent
Published: October 2011

This report describes the performance of a technique for the simultaneous, rapid measurement of major gas phase species present during titanium nitride thermal atomic layer deposition involving tetrakis(dimethylamido) titanium (TDMAT) and ammonia. In this chemical system, the three primary gas phase species are the two reactants, TDMAT and ammonia, and the reaction product, dimethyl amine. For the measurement of these three species, a direct absorption method based on a broadband infrared source with two different mid-infrared bandpass filters and utilizing amplitude modulation and synchronous detection was developed. By splitting the optical beam exiting the deposition chamber and selecting appropriate filters, all three species could be monitored simultaneously. It is also demonstrated that the high time resolution of this technique permits the observation of differences in the delivery into and removal from the deposition chamber of both TDMAT and ammonia with different carrier gases.
(Invited) High Throughput Atomic Layer Deposition for Encapsulation of Large Area Electronics
Authors: Kools Jacques
Published: October 2011

Fundamental aspects of the deployment of ALD deposited barriers in high volume manufacturing are reviewed. Based on an analysis of the limiting factors of in conventional cross-flow reactors, a parallel precursor wave technology system has been developed.
Atomic Layer Deposited Oxides for Passivation of Silicon Photoelectrodes for Solar Photoelectrochemical Cells
Authors: Kalanyan Berc , Parsons Gregory
Published: October 2011

Although crystalline silicon is an industrially significant device substrate, its use in photoelectrochemical cells is complicated by the thin oxide film that forms at the electrode surface. We applied thin coatings of atomic layer deposited films on n- and p-type Si substrates to block the growth of SiO2 during solar light-driven water splitting reactions. Voltammetry accompanied by ellipsometric measurements show us that metal oxide coatings as thin as 1.6 nm are effective at stopping electrode oxidation during dark and photoelectrochemistry. We observed similar passivating behavior among TiO2, ZnO, and Al2O3 thin films. Titania and zinc oxide films enhanced photocurrent due to their absorption in the UV wavelengths. We also applied a common water oxidation catalyst, cobalt, to show the feasibility of catalyst integration on top of ALD passivating films.
Morphological Factors Affecting the Behavior of Water in Proton Exchange Membrane Materials
Authors: Divoux Gilles M. , Finlay Katherine A. , Park Jong K. , Song Ju-Myung , Yan Bing , Zhang Mingqiang , Dillard David A. , Moore Robert B.
Published: October 2011

Perfluorosulfonic acid ionomers (PFSAs), such as Nafion®, have become the benchmark membrane material for proton exchange membrane fuel cells (PEMFCs). Despite their commercial success, little is known about the complex morphology-property relationships governing the chemical and physical properties. For example, the detailed structure of PFSA crystallites within the amorphous phase and the spatial arrangement of the crystallites around the ionic aggregates of PFSA materials are virtually unknown. In addition, the effect of processing on the membrane performance and durability in PEMFC applications is not yet fully understood. The first part of this work focuses on the significance of the crystalline component with respect to polymer-water interactions. The second part of this work addresses the impact on changes in morphology that could occur during long-term operation in a fuel cell including the effects of heat and humidity.
Modeling the Effects of MPL on the Transient Response of Proton-Exchange Membrane Using Experimentally Measured Capillary Pressure
Authors: Olapade Peter O. , Meyers Jeremy P.
Published: October 2011

A model to investigate the effect the effects of MPL on the transient response of proton-exchange membrane to load change is developed. The model shows that the use of cathode MPL slows down the transient process, especially within the first few hundred seconds, when the voltage is increased. However, the use of cathode MPL does not have a significant effect on the transient process when the cell voltage is decreased. Decreasing the MPL absolute permeability is observed to prolong the transient process in the membrane when the cell voltage is increased. We also observed that making the MPL more hydrophobic increasing the time for the transport in the cathode catalyst layer to reach the steady state when the cell voltage is increased.
The Influence of Micro Structure of the GDL and MPL on the Mass Transport in PEFC
Authors: Kotaka Toshikazu , Aoki Osamu , Shiomi Takeshi , Fukuyama Yosuke , Kubo Norio , Tabuchi Yuichiro
Published: October 2011

The relationship between micro structures of the GDL/MPL and mass transport property was investigated through coupled visualization and numerical analyses. The electron transport resistance of the GDL was high with the increase in compression pressure, while the oxygen transport resistance was almost unchanged. The GDL structure obtained by micro X-ray computed tomography showed the decrease in large pores as well as porosity under compression. The random walk simulation based on the obtained GDL image suggested that the increase in the number of contact points between carbon fibers contributed to the reduction of electron transport resistance. In addition to GDL, the MPL structure was reconstructed by nano X-ray computed tomography. The porosity distribution was similar in all directions, indicating that the MPL had isotropic structure. These analyses revealed that the understanding of the transport properties based on more realistic structure is essential to provide the refined insights for improving cell performance.
Effect of Temperature on In-Plane Permeability of the Gas Diffusion Layer of PEM Fuel Cell
Authors: Banerjee Rupak , Kandlikar Satish G.
Published: October 2011

The in-plane permeability is an important property of the gas diffusion layer (GDL) in a Proton Exchange Membrane Fuel Cell. It governs the transport of reactants and water vapor from the channel to the GDL regions under the land of the bipolar plate, and the bulk mass transport in the case of interdigitated flow fields. The current focus in literature has been on studying the effect of porosity on this property. These studies have traditionally been conducted at room temperature. However, typical PEMFCs operate most efficiently between 65 and 90°C. In this study, an ex-situ test setup has been developed to investigate the effect of temperature on the in-plane permeability of the GDL. The in-plane permeability of moist air is measured for system temperatures of 25, 40, 60 and 80°C for samples from Toray Inc., SGL Corp. and Mitsubishi Rayon Corp.
Identification of Gas Diffusion Layer PTFE Content Local Anomalies Using a Segmented Cell System
Authors: Reshetenko Tatyana V. , St-Pierre Jean , Bethune Keith , Rocheleau Richard
Published: October 2011

A segmented cell system was employed to investigate the impact of localized gas diffusion layer (GDL) PTFE content variations on fuel cell performance. An artificial defect was created by exchanging the standard cathode GDL with 13 wt. % PTFE located at segment 4 with a similar GDL (8, 17, 26, or 35 wt. % PTFE loading). An increase in PTFE loading caused a local performance decrease at high current density. For the 8 wt. % PTFE case, the local performance variation was relatively small. Other segments and the whole cell performance were not significantly affected by the defect. Spatially distributed data analysis with polarization and electrochemical impedance spectroscopy (EIS) revealed that such performance decreases are attributed to an increase in mass transfer overpotential ascribe to a decrease in porosity, average pore size and gas permeability with an increase in GDL defect PTFE loading.
Microstructure Analysis Tools for Quantification of Key Structural Properties of Fuel Cell Materials
Authors: Cecen Ahmet , Wargo Eric A. , Hanna Anne C. , Turner David M. , Kalidindi Surya R. , Kumbur Emin C.
Published: October 2011

The objective of this work is to develop advanced microstructure analysis tools for direct quantification of the key structural properties of complex fuel cell materials. Computationally efficient algorithms have been developed to extract the key structural parameters from measured microstructure datasets of these materials. In addition to determination of the traditional structural measures (e.g., porosity, surface area, phase connectivity), two novel microstructure analysis techniques are introduced for the quantification of pore size and tortuosity distributions. For initial demonstration purposes, the methods developed are applied to a digitally reconstructed sample of the micro-porous layer (MPL) of a polymer electrolyte fuel cell (PEFC). The results produced from these analyses are compared to previously reported experimental and model-derived values where applicable.
Determination of Aging Markers and their Use as a Tool to Characterize Pt/C Nanoparticles Degradation Mechanism in Model PEMFC Cathode Environment
Authors: Vion-Dury Benoit , Chatenet Marian , Guétaz Laure , Maillard Frédéric
Published: October 2011

Identical Location transmission electron microscopy (IL-TEM) was coupled to CO-stripping voltammetry to characterize the morphology of a benchmark Pt/C 50 wt% electrocatalyst (TEC10 - E50E, by Tanaka TKK). From the thorough analysis of the experimental data, 19 relevant structural markers were determined. These were subsequently used to quantify the structural degradations occurring during a simple electrochemical aging procedure (square-wave voltammetry from 0.1 to 0.9 V vs. RHE) performed in model PEMFC cathode environment (1 M H2SO4). Thanks to these markers, the mechanisms at stake during the Pt/C degradation were determined: Pt crystallite migration and coalescence, carbon corrosion and platinum dissolution/re-precipitation are at stake, the latter mechanism not being predominant.
Proton Conduction on Ionomer-Free Pt Surfaces
Authors: Thompson Eric L. , Baker Daniel
Published: October 2011

AC impedance was measured for PTFE-bound, unbound, and ionomer-bound Pt-black electrodes, as well as for a conventional Pt/Vulcan electrode. Adsorbed water contributes to the proton conduction on ionomer-free Pt black surfaces, which display a strong dependence on relative humidity. The conductivity was 1-2 orders of magnitude lower than that of ionomer-containing electrodes. While non-dimensional scaling of the impedance data indicates a single conduction mechanism occurring in each electrode type, activation energies suggest that the mechanisms were different between ionomer-free and ionomer-bound electrodes. Ionomer-bound electrodes show an activation energy that strongly depends upon RH, while that of ionomer-free Pt black does not. Remarkably, conductivity on Pt black is 2-3 orders of magnitude greater than that of bulk water, suggesting an enhanced conduction mechanism occurring at the Pt surface.
Pore Structure and Cell Performance Analysis of PEMFC Catalyst Layers Fabricated by Decal Transfer Method with Variation of Hot Pressing Pressure
Authors: Suzuki Takahiro , Tsushima Shohji , Hirai Shuichiro
Published: October 2011

In proton exchange membrane fuel cells (PEMFCs), catalyst layers (CLs) are one of the most important components to achieve both high performance and cost reduction. Synthesizing CLs and catalyst coated membranes (CCMs) has been gathering much attention for optimization to satisfy these demands. In this study, we focused on hot pressing process and investigated effects of its pressure on the structure of the CLs. Performance evaluation, cross-sectional visualization and N2 physisorption experiment of CCMs were performed. According to increasing the pressure up to 2 MPa, the cell performance was improved because of the enhancement of ionomer and carbon network in low humidification condition. On the other hand, drastic voltage drop appeared when the hot pressing pressure was over 2 MPa, because of decrease of the porosity and the pore size in the catalyst layer.
On Electrospinning of PFSA: A Comparison between Long and Short-Side Chain Ionomers
Authors: Subianto Surya , Cavalière Sara , Jones Deborah , Rozière Jacques
Published: October 2011

Long- and short-side chain perfluorosulfonic acid polymers have been electrospun into nonwoven nanofibre membranes. The membranes show homogeneous nanofibrous morphology, with the short-side chain showing narrower fibre size distribution and thinner fibre dimension due to lower threshold concentration of carrier polymer for fibre formation. The electrospun membranes show comparable proton conductivity to cast membranes.
Borohydride Oxidation on Platinum Electrodes - Is Platinum Really a Faradaic Inefficient BOR Electrocatalyst
Authors: Molina Concha M. Belen , Freitas KÊnia , Martini Pasqualeti Aniélli , Chatenet Marian , Lima Fabio H. B. , Ticianelli Edson A.
Published: October 2011

Sodium borohydride electrooxidation was studied on platinum electrodes, using in situ physical techniques coupled to electrochemistry. The results from Fourier transform infrared spectroscopy put forward the formation/depletion of BH3 and BH2 containing moieties upon potential increase. In addition, mass-spectrometry data reveal that the generation of hydrogen, although consequent at low potential, fast levels off upon positive polarization. The corresponding reaction pathway consists of BH3OH- + H2 generation at low potential, followed by their fast electrooxidation into BH2-containing intermediates + H2O. Such BH2 intermediates are rather stable at the Pt surface, but quantitatively electrooxidize in the Pt-oxide region, producing the final product of the BOR: BO2-. The formation of stable BOR intermediates at Pt emphasizes the effect of the time of residence of the reactant/intermediates on the overall completion of the BOR. In consequence, the concept of BOR faradaic (in)efficient electrocatalyst must be revisited for Pt electrodes.
Hydrodynamics and Current Distribution Analysis of Bipolar Plates for Direct Ethanol Fuel Cells
Authors: Orozco Diana C. , Sánchez Carlos , Lobato Justo , Úbeda Diego
Published: October 2011

The aim of this paper is obtaining a 3D model for designing bipolar plates by simulating fuel cell behavior with different flow field configuration and thus improving the performance of a direct ethanol fuel cell by modeling different flow fields using a 3D representation. Experimental results presented here were obtaining with hydrogen fuel cells as a first approach of modeling. Results show that activation zone is not well simulated. Flow fields better performance is obtaining with a width ratio of .Current and flow distribution shows that deeper channels had better performance in serpentine flow field.
Development of an Alkaline Anion Exchange Membrane Direct Ethylene Glycol Fuel Cell Stack
Authors: Cremers Carsten , Niedergesäß André , Jung Florina , Müller Dominik , Tübke Jens
Published: October 2011

KOH-doped PBI and quaternary amine alkaline anion exchange membranes were tested with commercial and homemade gas diffusion electrodes employing a non-noble metal catalyst. Tests were performed using either ethanol or ethylene glycol as fuel. The highest initial performance values were achieved with a quaternary amine anion exchange membrane fuel cell using ethylene glycol as fuel. A high conversion to CO2 was also achieved using ethylene glycol. Some important differences were found in the performance degradation between cells using quaternary amine and KOH doped PBI membranes. A short stack with 5 cells was built using quaternary-amine-membrane-based membrane electrode assemblies. Initial stack performance measurements are reported.
Electrode Compositions for High-Temperature Polymer Electrolyte Fuel Cell (HT-PEFC)
Authors: Kaz Till , Xia Jiabing , Chromik Andreas , Atanasov Vladimir , Häring Thomas , Kerres Jochen A.
Published: October 2011

One theoretical advantage of High Temperature Polymer-Electrolyte Fuel Cells (HT-PEFC) is the higher kinetic of the anode and cathode reaction. Whereas on the anode side the higher kinetic can be achieved practically, the kinetic on the cathode side is in practice lower than in low temperature PEFCs. In this paper different kind of electrode compositions for anode and cathode are prepared to improve the interface between an acid-base blend membrane (Polybenzimidazol-sulfonated Polysulfon) in respect to the cathode kinetic and the ohmic resistance of the Membrane-Electrode-Assembly (MEA).
Preparation and Characterization of Oxygen Reduction Activity and Durability of Non-Pt Carbon-alloy Catalysts for PEMFC MEAs
Authors: Wu Libin , Nabae Yuta , Kuroki Shigeki , Kakimoto Masa-aki , Miyata Seizo
Published: October 2011

A series of Pt-free carbon alloy cathode catalysts (CACs) with high ORR activities and durability were prepared by pyrolyzing mixtures of Fe phthalocyanine (FePc) and phenolic resin (PhRs) in single and multi-step protocols. By comparing their electrocatalytic activities and MEA performance, the effects of pyrolysis protocols on these electrocatalytic properties were studied, and an optimized protocol being capable to overcome the trade-off between catalytic activity and durability was found. At last, the changes of MEA performance before and after durability tests were analyzed by electrochemical impedance spectroscopy (EIS). The results indicate that the performance dropping during initial 100 hours was predominantly caused by the decomposition of ionomer in catalyst layers, especially for the catalyst prepared by optimized protocol.
Older men exhibit reduced efficacy of and heightened potency downregulation by intravenous pulses of recombinant human LH: a study in 92 healthy men
Authors: Veldhuis Johannes D. , Liu Peter Y. , Keenan Daniel M. , Takahashi Paul Y.
Published: October 2011

Direct sampling of the human spermatic veins has disclosed concomitant LH and testosterone (T) pulses, suggesting pulsatile LH concentration-dependent stimulation of T secretion. However, studies to date have examined this hypothesis using only pharmacological stimulation with hCG. The present study tests the hypothesis that age is marked by decreased T secretory responses to repeated near-physiological iv pulses of recombinant human LH administered in a Clinical Translational Science Center. Participants included 92 healthy men aged 18–75 yr with BMI 18–34 kg/m2. The contribution of endogenous LH pulses was minimized by combined injection of a selective GnRH receptor antagonist sc and successive pulses of biosynthetic LH iv. A new analytical dose response model was applied to estimate the properties of exogenous LH's drive of T secretion. Regression of LH-T dose response potency estimates on age showed that the efficacy of pulses of biosynthetic LH progressively decreased with age ( P = 0.014, r = 0.26). Testis sensitivity to exogenous LH pulses also declined with age ( P = 0.011, r = 0.27). Moreover, estimated Leydig cell downregulation by LH pulses rose significantly with age ( P = 0.039, r = 0.22). These outcomes were selective, since the recovery potency of infused LH was not affected by age but was reduced by increasing BMI ( P = 0.011, r = 0.27). Assuming stable bioactivity of infused recombinant human LH, these novel data indicate that factors associated with age and BMI attenuate LH efficacy and testis sensitivity and augment Leydig cell downregulation in healthy men.
Inverse Problem with Respect to Domain and Artificial Neural Network Algorithm for the Solution
Authors: Majidzadeh Kambiz
Published: October 2011

We consider the inverse problem with respect to domain. We suggested a new approach for reducing the inverse problem for a domain to an equivalent problem in a variational setting and gave an effective solution algorithm for solving such problems. In order to solve boundary problem, the artificial neural network is used in each step of the iteration.
Using DEA Factor Efficiency Scores to Eliminate Subjectivity in Goal Programming
Authors: Lewis Herbert F.
Published: October 2011

Many real-world problems require decision makers to consider multiple criteria when performing an analysis. One popular method used to analyze multicriteria decision problems is goal programming. When applying goal programming, it is often difficult if not impossible to determine the target values and unit penalty weights with any level of confidence. Thus, in many situations, managers and decision makers may be forced to specify these parameters subjectively. In this paper, we present a model framework designed to eliminate the arbitrary assignment of target values and unit penalty weights when applying goal programming to solve multicriteria decision problems. In particular, when neither of these parameters is available, we show how to integrate factor efficiency scores determined from data envelopment analysis into the model. We discuss an application of the methodology to ambulatory surgery centers and demonstrate the model framework via a product mix example.
Quantitative Evaluation of Bacteria Adherent and in Biofilm on Single-Wall Carbon Nanotube-Coated Surfaces
Authors: Pantanella Fabrizio , Berlutti Francesca , Passeri Daniele , Sordi Daniela , Frioni Alessandra , Natalizi Tiziana , Terranova Maria Letizia , Rossi Marco , Valenti Piera
Published: October 2011

Biofilm is a common bacterial lifestyle, and it plays a crucial role in human health, causing biofilm-mediated infections. Recently, to counteract biofilm development, new nano-structured biomaterials have been proposed. However, data about the antibacterial properties of nano-structured surfaces are fragmentary and controversial, and, in particular, the susceptibility of nano-structured materials to colonization and biofilm formation by bacterial pathogens has not been yet thoroughly considered. Here, the ability of the pathogenicStreptococcus mutansandPseudomonas aeruginosato adhere and form biofilm on surfaces coated with single-wall carbon nanotubes (SWCNTs) was analyzed. Our results showed that the surfaces of SWCNTs-coated glass beads (SWCNTs-GBs) were colonized at the same extent of uncoated GBs both byS. mutansandP. aeruginosa. In conclusion, our results demonstrate that single wall SWCNTs-coated surfaces are not suitable to counteract bacterial adhesion and biofilm development.
Cancers in Togo from 1984 to 2008: Epidemiological and Pathological Aspects of 5251 Cases
Authors: Amégbor Koffi , Darre Tchin , Ayéna Koffi Didier , Padaro Essohana , Tengué Kodjo , Abalo Anani , Napo-Koura Gado
Published: October 2011

Objective. To describe the epidemiological and histological aspects of cancers in Togo.Materials and Methods. We made a retrospective review of the epidemiological and pathological features of cancers observed from 1984 to 2008 at the laboratory of pathology of CHU-TOKOIN in Lomé, Togo.Results. During our study period, we found 5251 cases of cancers with an annual average frequency of 210 cases. The sex ratio, male/female, was 0.9 and the average age of occurring was 45.3 years. This average age was 46.9 years for men and 43.8 years for women. The most frequent cancers for men were prostate cancer (12.9%), nonmelanoma skin cancer (10.4%), and gastric cancer (10.3%). For women it was breast cancer (27.1%), cervix cancer (11.2%) and non-Hodgkin lymphoma (6.3%). Histologically, it was carcinomas in 68.1% of the cases, sarcomas in 11% of the cases and non-Hodgkin lymphomas in 12.6% of the cases. Children cancers were primarily Burkitt lymphoma (27.9% of cases) and retinoblastoma (8.5% of cases).Conclusion. This study shows that cancers are frequent in Togo and emphasizes on the necessity of having a cancer register for the prevention and the control of this disease in Togo.
Partial Ureteropelvic Junction Disruption after Blunt Trauma: Case Report
Authors: El Ammari Jalal Eddine , Ahallal Youness , El Fassi Mohammed Jamal , Farih M. Hassan
Published: October 2011

Partial ureteropelvic junction disruption as a result of blunt trauma is rare and frequently missed by the initial trauma evaluation. Delays in diagnosis have also been associated with significant morbidity. A high index of suspicion should lead to appropriate investigations, and the management will be determined by the severity of the disruption. We present herein a 24-year-old man who was admitted to the Emergency Room with multiple organ injuries caused by a severe blunt trauma. Emergency celiotomy was performed for massive hemoperitoneum and shattered spleen which led to splenectomy. The diagnosis of partial UPJ disruption was missed preoperatively and suspected in CT scan after appearance of flank tender mass. Confirmation was obtained in retrograde ureteropyelography and treated conservatively with indwelling ureteral stent. We present herein an extensive review of the literature to examine the current status of this entity and to determine if improvements could be made in the diagnosis and treatment.
Dynamic Analysis of Cracked Octagonal Quasicrystals
Authors: Li Wu , Fan Tian You
Published: October 2011

We focus on the dynamic fracture problem of octagonal quasicrystals by applying a rectangular sample with a Griffith crack which is often used in classical elastic media based on the method of finite difference. This paper mainly is to investigate the variation of phonon, phason fields, and stress singularity around the crack tip including the stress intensity factor. In addition, the moving boundary due to the crack propagation has also been treated by introducing an additional condition for determining solution. The influence of wave propagation and diffusion in the dynamic process is also discussed in detail. Through comparing the results of octagonal quasicrystals with the results of crystal, this paper proclaims the influence of phonon‐phason coupling in dynamic fracture problem of octagonal quasicrystals which should not be neglected.
Evaluating Grayware Characteristics and Risks
Authors: Chen Zhongqiang , Liang Zhanyan , Zhang Yuan , Chen Zhongrong
Published: October 2011

Grayware encyclopedias collect known species to provide information for incident analysis, however, the lack of categorization and generalization capability renders them ineffective in the development of defense strategies against clustered strains. A grayware categorization framework is therefore proposed here to not only classify grayware according to diverse taxonomic features but also facilitate evaluations on grayware risk to cyberspace. Armed with Support Vector Machines, the framework builds learning models based on training data extracted automatically from grayware encyclopedias and visualizes categorization results with Self-Organizing Maps. The features used in learning models are selected with information gain and the high dimensionality of feature space is reduced by word stemming and stopword removal process. The grayware categorizations on diversified features reveal that grayware typically attempts to improve its penetration rate by resorting to multiple installation mechanisms and reduced code footprints. The framework also shows that grayware evades detection by attacking victims' security applications and resists being removed by enhancing its clotting capability with infected hosts. Our analysis further points out that species in categoriesSpywareandAdwarecontinue to dominate the grayware landscape and impose extremely critical threats to the Internet ecosystem.
Validation of a Biofeedback System for Wheelchair Propulsion Training
Authors: Guo Liyun , Kwarciak Andrew M. , Rodriguez Russell , Sarkar Nilanjan , Richter W. Mark
Published: October 2011

This paper describes the design and validation of the OptiPush Biofeedback System, a commercially available, instrumented wheel system that records handrim biomechanics and provides stroke-by-stroke biofeedback and targeting for 11 propulsion variables. Testing of the system revealed accurate measurement of wheel angle (0.02% error), wheel speed (0.06% error), and handrim loads. The maximum errors in static force and torque measurements were 3.80% and 2.05%, respectively. Measured forces were also found to be highly linear (0.985 < slope < 1.011) and highly correlated to the reference forces (r2> .998). Dynamic measurements of planar forces ( and ) and axle torque also had low error (−0.96 N to 0.83 N for force and 0.10 Nm to 0.14 Nm for torque) and were highly correlated (r> .986) with expected force and torque values. Overall, the OptiPush Biofeedback System provides accurate measurement of wheel dynamics and handrim biomechanics and may be a useful tool for improving manual wheelchair propulsion.
Statistics of Conditional Fluid Velocity in the Corrugated Flamelets Regime of Turbulent Premixed Combustion: A Direct Numerical Simulation Study
Authors: Chakraborty Nilanjan , Lipatnikov Andrei N.
Published: October 2011

The statistics of mean fluid velocity components conditional in unburned reactants and fully burned products in the context of Reynolds Averaged Navier Stokes (RANS) simulations have been studied using a Direct Numerical Simulation database of statistically planar turbulent premixed flame representing the corrugated flamelets regime combustion. Expressions for conditional mean velocity and conditional velocity correlations which are derived based on a presumed bimodal probability density function of reaction progress variable for unity Lewis number flames are assessed in this study with respect to the corresponding quantities extracted from DNS data. In particular, conditional surface averaged velocities and the velocity correlations in the unburned reactants are demonstrated to be effectively modelled by the unconditional velocities and velocity correlations , respectively, for the major part of turbulent flame brush with the exception of the leading edge. By contrast, conditional surface averaged velocities and the velocity correlations in fully burned products are shown to be markedly different from the unconditional velocities and velocity correlations , respectively.
Comparison of Perioperative Outcomes of Total Laparoscopic and Robotically Assisted Hysterectomy for Benign Pathology during Introduction of a Robotic Program
Authors: Kilic Gokhan Sami , Moore Gradie , Elbatanony Ayman , Radecki Carmen , Phelps John Y. , Borahay Mostafa A.
Published: October 2011

Study Objective. Prospectively compare outcomes of robotically assisted and laparoscopic hysterectomy in the process of implementing a new robotic program.Design. Prospectively comparative observational nonrandomized study.Design Classification. II-1.Setting. Tertiary caregiver university hospital.Patients. Data collected consecutively 24 months, 34 patients underwent laparoscopic hysterectomy, 25 patients underwent robotic hysterectomy, and 11 patients underwent vaginal hysterectomy at our institution.Interventions. Outcomes of robotically assisted, laparoscopic, and vaginal complex hysterectomies performed by a single surgeon for noncancerous indications.Measurements and Main Results. Operative times were minutes for laparoscopic, minutes for robotic, and minutes for vaginal (). Estimated blood loss for patients undergoing laparoscopic surgery was  cc,  cc for robotic surgery, and  cc for vaginal surgery (). The mean length of stay ranged from 1.8 to 2.3 days for the 3 methods. Association was significant for uterine weight () among surgery methods.Conclusion. Robotically assisted hysterectomy is feasible with low morbidity, a shorter hospital stay, and less blood loss. This suggests that robotic assistance facilitates a minimally invasive approach for patients with larger uterine size even during implementing a new robotic program.
Skull Repair after Major Crush Injury
Authors: Sudhoff H. , Hoff H. J. , Lehmann M.
Published: October 2011

Reconstructive surgery after trauma of the head and neck is a wide field in ENT surgery. The repair of bony defects often requires implantation of engineered prostheses. We present the case of a 48-year-old male patient who had suffered a major crush injury to his head resulting in a complex bony defect. A computer-assisted designed (CAD/CAM) Titanium implant was used for reconstruction. Direct prefabrication of the individually designed implant led to an excellent coverage of the bony defect and easy adaptation to the defect margins.Results. Treatment plan and surgery as well as implant design and manufacturing were performed in a multidisciplinary team. Skin expander implantation prior to reconstructive surgery ensured a tension-free closure. This team approach led to a satisfactory outcome for this patient. This case illustrates the necessity of a multidisciplinary approach for the optimum management of complex head and neck injuries.
Prophylactic Ligation of the Innominate Artery and Creation of Tracheostomy in a Neurologically Impaired Girl: A Case Report
Authors: Obatake Masayuki , Tokunaga Takayuki , Hashizume Koji , Mochizuki Kyoko , Nagayasu Takeshi
Published: October 2011

Tracheoinnominate artery fistula is known as a potentially fatal complication for patients who depend on tracheostomy or tracheoesophageal diversion. Since the bleeding from a TIF is often difficult to control, preventative procedures are recommended to avoid this complication. An 11-year-old girl with hypoxic-ischemic encephalopathy and scoliosis developed tracheal stenosis caused by compression from the innominate artery. Respiratory control with intubation through the tracheal stenosis was needed, and the patient was at high risk for developing a TIF. She underwent ligation of the innominate artery at tracheostomy. Subsequent tracheostomy revealed a widened tracheal lumen and no further complications. Prophylactic ligation of the innominate artery and creation of tracheostomy might be considered as a valid option for patients at high risk of developing TIF.
Study on the Electrospun CNTs/Polyacrylonitrile-Based Nanofiber Composites
Authors: Qiao Bo , Ding Xuejia , Hou Xiaoxiao , Wu Sizhu
Published: October 2011

CNTs/PAN nanofibers were electrospun from PAN-based solution for the preparation of carbon nanofiber composites. The as-spun polyacrylonitrile-based nanofibers were hot-stretched by weighing metal in a temperature controlled oven. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology of the nanofibers, which indicated that carbon nanotubes were dispersed well in the composites and were completely wrapped by PAN matrix. Because of the strong interfacial interaction between CNTs and PAN, the CNTs/PAN application performance will be enhanced correspondingly, such as the mechanical properties and the electrical conductivity. It was concluded that the hot-stretched CNTs/PAN nanofibers can be used as a potential precursor to produce high-performance carbon composites.