bluuebunny/crossref_metadata_2025 huggingface dataset:
Power-Cost Efficiency of Eight Macrobenthic Sampling Schemes in Puget Sound, Washington, USA
Authors: Ferraro Steven P. , Cole Faith A. , DeBen Waldemar A. , Swartz Richard C.
Published: May 2010

Power-cost efficiency (PCEi = (n × c)min/(ni × ci), where i = sampling scheme, n = minimum number of replicate samples needed to detect a difference between locations with an acceptable probability of Type I (α) and Type II (β) error (e.g. α = β = 0.05), c = mean "cost," in time or money, per replicate sample, and (n × c)min= minimum value of (n × c) among the i sampling schemes) is the appropriate expression for comparing the cost efficiency of alternative sampling schemes having equivalent statistical rigor when the statistical model is a redistribution for comparisons of two means. PCEs were determined for eight macrobenthic sampling schemes (four sample unit sizes and two sieve mesh sizes) in a comparison of a reference site versus a putative polluted site in Puget Sound, Washington. Laboratory processing times were, on average, about 2.5 times greater for the [Formula: see text]- than the [Formula: see text] samples. The 0.06-m2, 0- to 8-cm-deep sample unit size and 1.0-mm sieve mesh size was the overall optimum sampling scheme in this study; it ranked first in PCE on 8 and second on 3 of 11 measures of community structure. Rank order by statistical power of the 11 measures for this scheme was Infaunal Index > log10(mollusc biomass + 1) > number of species > log10(numerical abundance) > log10(polychaete biomass + 1) > log10(total biomass + 1) > log10(crustacean biomass + 1) > McIntosh's index > 1 – Simpson's Index > Shannon's Index > Dominance Index.
Primary Production in a Tidally Energetic Fjord: Environmental Forcing of Vertical Phytoplankton Distribution
Authors: Kessler T. A. , Parsons T. R.
Published: May 2010

Time dependent changes in the vertical phytoplankton distribution, during two short-term intensive studies in a tidally energetic sill-fjord, were examined with the objective of identifying processes responsible for a seasonal dependence between biomass and stability in a 7-yr environmental data set for the region. Reconciling an apparent divergence between calculated chlorophyl a (Chla) and NO3− mass balances identified diapycnal mixing to be an important term in the NO3− budget, but not in the Chla budget. The balancing mixing rate required was consistent with a wind stress origin and inconsistent with a tidal origin. This calculation, combined with evidence that mixing events in the surface layer were generally more closely correlated with the wind than the tide was used to support a hypothesis relating the seasonal biomass–stability relationship to seasonally dependent tidal mixing in the surface layer.
Water Column Methylmercury in the Wabigoon/English River–Lake System: Factors Controlling Concentrations, Speciation, and Net Production
Authors: Parks J. W. , Lutz A. , Sutton J. A.
Published: May 2010

Ten years after major releases of inorganic mercury from a chloralkalai plant were sharply reduced, methylmercury (MeHg) levels remain markedly elevated in waters in most of the Wabigoon River system downstream of Dryden, Ontario, Canada. The water column appears to be a very important site for methylation and demethylation. In water, MeHg and inorganic Hg appear to be in quasi equilibrium, as the MeHg: total mercury ratio is independent of contact time with sediments, the atmosphere, and the theoretical residence time of waters. The MeHg: total Hg ratio increased with distance downstream of Dryden, but MeHg always averaged less than 10% of the total Hg concentration. MeHg was mostly soluble, as defined by field centrifugation. Net production of MeHg appeared to be directly related to the amount of MeHg required to establish and maintain equilibrium conditions with inorganic Hg. A model is developed which adequately describes water column MeHg concentrations. Considerations of the model suggests different restoration strategies for different parts of the Wabigoon/English River–Lake system.
ON D3-BRANE DYNAMICS AT STRONG WARPING
Authors: CHEN HENG-YU , NAKAYAMA YU , SHIU GARY
Published: May 2010

We study the dynamics of a D3 brane in generic IIB warped compactifications, using the Hamiltonian formulation discussed in arXiv:0805.3700. Taking into account of both closed and open string fluctuations, we derive the warped Kähler potential governing the motion of a probe D3 brane. By including the backreaction of D3, we also comment on how the problem of defining a holomorphic gauge coupling on wrapped D7 branes in warped background can be resolved.
COUPLING gϕa0γ AND gϕσγ IN LIGHT-CONE SUM-RULES
Authors: DU CHANG-QIAO , ZHOU MING-ZHEN
Published: May 2010

In this paper, we calculate the coupling constants gϕa0γ and gϕσγ by utilizing ω–ϕ mixing scheme and taking into account the contributions of the three-particle twist-4 distribution amplitudes of the photon in the light-cone sum-rule approach. Our results: (1) 0.130 ≤ gϕa0γ ≤ 0.194 is in agreement with the previous estimations of these coupling constants which obtained from phenomenological considerations but less than the experimental value gϕa0γ = 1.64±0.05; (2) 0.055 ≤ gϕσγ ≤ 0.076 is consistent with the phenomenological value and the experimental value gϕσγ = 0.060±0.008.
ENERGY ESTIMATION OF ULTRA-HIGH ENERGY COSMIC RAY HADRONS BY MONTE CARLO SIMULATIONS OF EXTENSIVE AIR SHOWERS
Authors: GERANIOS A. , KOUTSOKOSTA D. , MASTICHIADIS A. , MALANDRAKI O. , ROSAKI-MAVROULI H. , MALTEZOS S.
Published: May 2010

Ultra-High Energy Cosmic Rays (E ≥ 5 ×1019 eV ) are detected through Extensive Air Showers that are created when a primary cosmic ray particle interacts with the atmosphere of the Earth. The energy of the primary particle can be estimated experimentally based on simulations. In this paper we attempt to estimate the energy of UHECR hadrons ( He, Li, C, Fe ) by applying a Monte Carlo simulation code and we compare the results with the ones derived in our previous paper for proton initiated showers. The scenario of simulations is adapted to the P. Auger Observatory site.
INFLUENCE OF COATING SOLUTION COMPOSITION ON REBa2Cu3Oy (RE=Gd AND Sm, Eu, Gd) FILMS FABRICATED BY FLUORINE-FREE METAL–ORGANIC DEPOSITION
Authors: NAKAMURA T. , KITA R. , KAWABATA S. , MIURA O. , ICHINOSE A. , MATSUMOTO K. , YOSHIDA Y. , MUKAIDA M. , HORII S.
Published: May 2010

GdBa 2 Cu 3 O y ( GdBCO ) and Sm 0.33 Eu 0.33 Gd 0.33 Ba 2 Cu 3 O y ( SEG ) films were prepared by metal–organic deposition (MOD) using two fluorine-free solutions: a metal 2-ethylhexanate (2-EH) and a complex solution (CS) consisting of metal 2-EH and metal-naphthenate. We investigated the effects of these new fluorine-free solutions, and their potential use in the fabrication of several REBCO ( RE : rare earth) materials. The crystal growth, surface morphology, and superconducting properties of films prepared on single-crystal LaAlO 3 substrates at low oxygen partial pressure strongly depended upon the coating solution used. Films prepared using 2-EH exhibited improved thermal stability of the superconducting phase during heat treatment. On the other hand, films prepared by CS had a flat superconducting matrix, with a roughness of several tens of nm and large precipitates 2–3 μm in diameter. In addition, the CS films had a higher critical temperature (91.2 K) than the 2-EH film. The zero-field critical current density at 77.3 K was 0.19 MA/cm2 for 2-EH films, and 0.61 MA/cm2 for CS films.
THEORETICAL ANALYSIS OF GAIN SATURATION CHARACTERISTICS OF WIDE-BAND FIBER RAMAN AMPLIFIERS
Authors: HAN QUN , NING JIPING , SHENG ZHAOXIA
Published: May 2010

The gain saturation characteristics of wide-band fiber Raman amplifiers (FRAs) are analyzed by numerical solution of the FRA equations. The results show that the stimulated Raman scattering induced gain-tilt in saturated FRAs is not only related to the signal power, but also depends on the pumping geometry of the amplifier. The saturated gain spectrum tilts towards the longer wavelength for counter-pumped FRAs while it tilts towards the shorter wavelength for co-pumped ones. These results indicate that gain-flatness-preserving FRAs with the changing of the signal power can be designed.
EFFECT OF PROCESSING CONDITIONS ON ELECTRICAL PROPERTIES OF CaCu3Ti4O12 CERAMICS
Authors: KASHYAP RAMAN , DHAWAN TANUJ , GAUTAM PRIKSHIT , THAKUR O. P. , MEHRA N. C. , TANDON R. P.
Published: May 2010

CaCu 3 Ti 4 O 12 ( CCTO ) ceramics were prepared by the solid-state reaction route. Effect of sintering time was studied on the polarization (P) versus electric field (E) behavior. Unlike conventional ferroelectric hysteresis loop, PE hysteresis behavior in CCTO ceramics was observed to exhibit ferroelectric-like loop where polarization does not saturate but gives a maximum value. Remnant polarization and maximum polarization was observed to increase with sintering time. Current (I)–voltage (V) characteristics shows a nonlinear behavior making them useful for varistor applications. Coefficient of non-linearity (α) is also found to depend on sintering duration.
THE ROLE OF 'PROFESSIONAL ADVISORS ON FINANCIAL MATTERS' IN ENTREPRENEURIAL NETWORKS
Authors: KLYVER KIM , HINDLE KEVIN
Published: May 2010

This study investigated the influence that 'professional advisors on financial matters' have in comparison with other people with whom entrepreneurs discuss their venture. Based on follow-up surveys completed in relation to the Danish participation in the Global Entrepreneurship Monitor (GEM) survey, it was found that professional advisors on financial matters only play a minor role in the two early phases of the entrepreneurial process before the venture is actually started. It was further revealed that the ties between professional advisors on financial matters and entrepreneurs often are weaker than the ties entrepreneurs have with others in their discussion network. Two practical implications for professional advisors on financial matters emerged from the study.
INTEGRATING THEORY AND PRACTICE FOR STUDENT ENTREPRENEURS: AN APPLIED LEARNING MODEL
Authors: GILBERT DAVID
Published: May 2010

This paper reports on an innovative pilot project embedded in a capstone unit of Australia's leading undergraduate degree program in Entrepreneurship. The project was developed as part of an industry linkage pilot agreement between the Entrepreneurship program and one of the 'Big Four' consultancy companies, Deloitte Touche Tohmatsu. A pedagogically innovative model of applied learning is proposed that enabled Higher Education students enrolled in a Bachelor of Business (Entrepreneurship) degree to apply in a dynamic (and sometimes chaotic) environment skill and capabilities they already possessed (as opposed to work-based learning about a particular job). Results presented in this paper indicate that educating young entrepreneurs in a Higher Educational setting needs to be like the practice itself; creative, risky, exciting and above all highly satisfying.
THE ROLE OF CREATIVITY IN ENTREPRENEURSHIP
Authors: FILLIS IAN , RENTSCHLER RUTH
Published: May 2010

This paper evaluates the contribution of creativity to entrepreneurship theory and practice in terms of building an holistic and transdisciplinary understanding of its impact. Acknowledgement is made of the subjectivist theory of entrepreneurship which embraces randomness, uncertainty and ambiguity but these factors should then be embedded in wider business and social contexts. The analysis is synthesised into a number of themes, from consideration of its definition, its link with personality and cognitive style, creativity as a process and the use of biography in uncovering data on creative entrepreneurial behaviour. Other relevant areas of discussion include creativity's link with motivation, actualisation and innovation, as well as the interrogation of entrepreneurial artists as owner/managers. These factors are embedded in a critical evaluation of how creativity contributes to successful entrepreneurship practice. Modelling, measuring and testing entrepreneurial creativity are also considered and the paper includes detailed consideration of several models of creativity in entrepreneurship. Recommendations for future theory and practice are also made.
MANAGEMENT OF CANDIDAL VERTEBRAL OSTEOMYELITIS – REPORT OF SIX CASES
Authors: Chen Po-Quang , Yang Shu-Hua , Wu Chun-Ting
Published: May 2010

From September 1994 to April 2001, we treated six cases of Candida spondylitis (five patients by surgery, and one by conservative approach). The age ranged from 16 to 60 years old. Four were men, and two women. The patients were associated with the following underlying diseases: one with renal failure, one with rheumatic heart with valve replacement, one with drug addiction, one apparently healthy patient, and two patients with leukemia. Because five patients had suffered from severe and persistent low back pain and had neurological deficits, anterior approach to debride the infected vertebral focus and strut bone grafting was performed. Additional posterior implant placement was performed in two cases, and anterior instrumentation in one case for further stabilization. Fluconazole was supplementary to amphotericin B in three patients. The other three patients received fluconazole. One patient had double spinal lesions — one in the lumbar, while the other in the thoracic T9–10 level caused paraplegia. Staged operation was performed, starting from lumbar and followed by operating over the thoracic lesion. Infection was under control, but the patient had partial neurological recovery (Frankel D). He died 54 months later due to poor general conditions, recurrent bacterial sepsis and pneumonia. In other five patients, infection was well under control and without neurological sequel.

The treatment principles of Candida spinal infection are similar to those of pyogenic spondylitis. Anterior debridement of the infective focus and bone grafting are beneficial in controlling infection and achieving stable healing. Posterior instrumentation can be applied for further stabilization without compromising the control of Candida infection. Fluconazole was effective in treating Candida spondylitis, and it must be prescribed after surgery.
ESTIMATION OF EXTERNAL AND INTERNAL HUMAN BODY DIMENSIONS FROM FEW EXTERNAL MEASUREMENTS
Authors: Bertrand Samuel , Kojadinovic Ivan , Skalli Wafa , Mitton David
Published: May 2010

Purpose. The primary objective of the study was to determine a way to obtain subject-specific body dimensions. The aim was then to develop linear statistical models for estimating human body geometry from a small number of body measurements. Methods. Internal (bone dimensions) and external (body) measurements were collected on 64 healthy adults representative of three morphotypes. Simple and multiple linear regression models between external and internal body dimensions were then obtained and assessed. Results. The statistical analysis provided 184 anthropometrical models which allow estimation of subject-specific external and internal data from 10 external dimensions that can be easily measured on any subject. Among them, 62 models had a 2SEE (i.e. twice the Standard Error of Estimate) lower than 10%. Conclusion. This study proposes a non-invasive approach to estimate both external and internal body dimensions.
ASSIGNMENT QUERY AND ITS IMPLEMENTATION IN MOVING OBJECT DATABASES
Authors: KONAN ALİ R. , GÜNDEM TAFLAN İ. , KAYA MURAT E.
Published: May 2010

Moving object databases (MOD) are being used in a wide range of location-based services that are of growing interest in many application areas. In the literature, several query types such as nearest neighbor, reverse nearest neighbor, k-nearest neighbor, and proximity queries have been considered in MOD. In this paper, we propose a novel operator called the assignment operator as a query type for MOD. The assignment operator is an operator used in a query to solve the assignment problem (also known as the weighted bipartite graph-matching problem). Assignment operator finds a perfect match between two sets of objects in a manner that minimizes a total cost. For instance, a set of moving objects such as taxi cabs are assigned to a set of customers in a manner that minimizes the total cost of traveling for the taxis. A possible implementation of the assignment operator in MOD and its performance evaluation are given.
A LAGRANGIAN-BASED SOLUTION ALGORITHM FOR STRATEGIC SUPPLY CHAIN DISTRIBUTION DESIGN IN UNCERTAIN ENVIRONMENT
Authors: NASIRI G. REZA , DAVOUDPOUR HAMID , KARIMI BEHROOZ
Published: May 2010

In this paper a multi-product, multi-echelon location–allocation model for the optimization of a supply chain design is proposed. This model integrated inventory decisions into distribution network design with stochastic market demands. The goal is to select the optimum numbers, locations, and capacities of the opening warehouses so that all customer demands to be satisfied at minimum total costs of the distribution network. We develop a nonlinear mixed-integer model and propose an efficient heuristic solution procedure for the problem. The solution approach is based on Lagrangian relaxation, improved with efficient heuristic to solve complex sub-problems. Computational results indicate that the proposed method yields good solutions with high quality within a reasonable computational time for various real-size problems.
ANALYSIS OF THE ALIGNMENT OF COMPANY GOALS TO WEB CONTENT USING ANP
Authors: CABALLERO-LUQUE ANTONIO , ARAGONÉS-BELTRÁN PABLO , GARCÍA-MELÓN MÓNICA , DEMA-PÉREZ CARLOS
Published: May 2010

Today, most institutions use their website as one of the major means of consolidating communications channels within their organization and among their customers and users. Nevertheless, many of these organizations either have not clearly formulated the goals they want to achieve through their website or do not know to what extent their website contributes to satisfying these goals. This paper presents a model based on Analytic Network Process (ANP) aimed at helping organization managers to verify if their website contents are appropriate for satisfying the goals they have established. This analysis is achieved by studying the relationships among the goals established for the website, website contents, and potential users grouped into segments. The model was applied to a study case, analyzing the website of a foundation pertaining to a major banking institution in Spain.
Optimization of the PEM Fuel Cell Catalyst Layer: An Analytical Approach
Authors: Foli Kwasi
Published: May 2010

A procedure aimed at optimizing the design of catalyst layers for high temperature polymer electrolyte membrane (PEM) fuel cells is presented. In developing the methodology the concept of catalyst effectiveness expressed as a function of the Thiele modulus is applied in determining the optimum thickness of a catalyst layer. Three variables that control the catalyst layer performance are the catalyst loading, specific surface area of catalyst particles and the layer thickness. Given any two of the above variables it is possible to determine the third for optimum catalyst performance. The approach is very simple and only accurate for small size fuel cells systems because of the underlying assumptions in the analysis. For large size systems the method offers, at best, qualitative results that are good enough to guide the design of such systems and serve as a good first-step approach to more complex three-dimensional analyses.
Fluid Flow and Electrochemical Performance in Miniaturized HT-PEMFCs
Authors: Bandlamudi George C. , Siegel C. , Van der Schoot N. , Heinzel A.
Published: May 2010

In the current work, three types of flow field structures were analysed: i) Fluid flow patterns such as uniformity in gas distribution in various channels of these flow fields were studied using particle image velocimetry (PIV) technique, ii) Pressure drop across each flow field structure was measured using standard anemometers, iii) Impedance of 3 single cells built with these three types of flow fields, each with a commercially available Celtec-P 1000 based membrane electrode assembly (MEA) was examined, to ensure, adequate contact between various cell components using electrochemical impedance spectroscopy (EIS) technique, iv) 3Dcomputational fluid dynamics (CFD) simulations were performed using a commercially available software to ascertain oxidant distribution in these flow fields. Finally, v) Experiments were performed in a test stand with these three types of single cells, (with hydrogen and air as reactant gases) to gauge each cell's overall performance. The active area of each cell was 27.6 cm². High temperature stable graphite compound based bipolar plates (FU 4369) from Schunk Kohlenstofftechnik GmbH, Germany were used in each cell.
A Compact High Efficiency PEFC System for Underwater Platforms
Authors: Yoshida Hiroshi , Hyakudome Tadahiro , Ishibashi Shojiro , Sawa Takao , Tsukioka Satoshi , Aoki Taro , Tani Toshihiro , Iwata Mitsuyoshi , Moriga Takuya
Published: May 2010

Long endurance underwater platforms are needed for wide area surveys such as the research into the global change, ocean-trench earthquake, and biodiversity and the explorations of ocean resources. We have succeeded in developing a new concept PEFC system prototype for the underwater platforms. This high efficiency PEFC developed by MHI runs with 60 % of efficiency at an operation point. This closed-cycle fuel cell is not equipped with humidifiers and blowers, being downsized and power saving. Function tests and a 1000-hour endurance test were successfully completed in last November.
Effect of Surface Modification for the Growth of Multi-Walled Carbon Nanotubes on Carbon Paper for Proton Exchange Membrane Fuel Cells
Authors: Aparna Ramasimha , Munukutla Lakshmi , Madakannan Arunachala
Published: May 2010

Gas Diffusion Layers (GDL) were fabricated with carbon paper substrate and multi-walled carbon nanotubes (MWCNTs) grown in situ as microporous layer by chemical vapor deposition (CVD) process. In order to nucleate, various nano-oxides viz., aerosil-380, hydrophilic silica, hydrophobic silica, Al2O3 and a mixed oxide (Al2O3 and SiO2) and TiO2 were evaluated for optimum growth of MWCNTs. The GDL samples with the MWCNTs were characterized by surface morphology, and wetting characteristics using a scanning electron microscope and goniometer, respectively. Pt nanocatalyst was deposited on the MWCNTs both for anode and cathode. The fuel cell performance of the Pt/MWCNTs/carbon paper cathodes was evaluated by using PEMFC with H2/O2 and H2/air, at 80 oC and at different RH conditions using Nafion-212 electrolyte. Al2O3 led to homogenous growth of MWCNTs and the GDL exhibited the maximum performance. The in-situ Pt/CNT/carbon paper electrodes showed 1 and 0.5 W.cm-2 with H2/O2 and H2/air, respectively.
Evaluation of a High Performance Separator for Practical PEFC
Authors: Yamauchi Makoto , Ueda Tatsuro , Shimatani Shota , Sugiura Kimihiko
Published: May 2010

PEFC has water management issues, such as flooding, where condensate blocks the pores of the gas-diffusion-layer, and plugging, where condensate blocks the gas channels. We confirmed that the flooding/plugging phenomena, in the anode gas channel, occur in low humidity when water is transported from the cathode to the anode through the membrane. Moreover, we have been developing a high performance separator. The high performance separator is composed of two channels of gas and drainage, and a water-absorption-layer (WAL) between GDL and the current collector. The WAL is a porous material made of stainless steel that absorbs the condensate from the GDL and the gas channel. The water absorbed by the WAL is supplied to the electrolyte membrane. The water supersaturated in the WAL is exhausted outside the cell through the drainage channel. We implemented a WAL in a fuel cell made of stainless steel and evaluated its effectiveness
Comparison Between Voltage and Current Boundary Conditions in PEMFC Model
Authors: Nguyen Dinh An , Kaewmanee Wattana , Hinaje Melika , Fontchastagner Julien , Netter Denis , Rael Stephane , Davat Bernard
Published: May 2010

With an aim of optimizing the points of operation of the proton exchange membrane fuel cell (PEMFC), it is better to understand the working procedure with the physical effects and to seek a prediction of the behaviour of this type of fuel cell. This work presents a comparison of the numerical results obtained using two different boundary conditions (current density and voltage boundaries) for the charge transport equation by using a 2D static model of a single cell .
PEM Fuel Cell Water Transport - Simulation and Neutron Imaging Experiment
Authors: Quan Peng , Lai Ming-Chia D.
Published: May 2010

Using Volume of Fluid (VOF) technique in FLUENT, it is shown that hydrophilic surfaces could facilitate water transport along channel edges or walls, although at the cost of increased pressure drop for serpentine flow channels. For interdigitated air flow channel design, it is observed that liquid water exists only in the outlet channel and that water distribution inside the GDL becomes uneven due to the pressure distribution. The neutron imaging results of an operational PEM fuel cell shows that water content peak is closer to catalyst layer for the low stoic case. The peak value increases with increasing current density and reaches its maximum at certain moderate current density and then decreases due to heating effect at higher current density. Minimum water content can be observed inside GDLs, which is caused by the barriers from the hydrophobic nature of GDL pores. PEMFC model improvement in FLUENT and a more consistent two-phase water model treatment across the membrane into flow channel are required to achieve better model predictabilities.
Microstructure of Electrospray Deposited Catalyst Layers for PEMFC Electrodes
Authors: Chaparro Antonio M. , Folgado M.A. , Aparicio Paloma F. , Martín Antonio J. , Daza Loreto
Published: May 2010

Catalyst layers composed of Pt/C catalyst and NafionR ionomer have been prepared by electrospray deposition and characterized. It is shown that electrospray deposition gives rise to particular properties of the layers, regarding porosity and morphology. A dendritic morphology growth gives rise to enhanced porosity in the meso and macroporous range. The porosity study by means of N2 adsorption isotherm and mercury porosimetry reflects that the ionomer film is better accommodated within the microporous structure of the Pt/C catalyst on electrospray deposited layers, compared with layers deposited by airbrushing. Supporting analysis by thermogravimetry coupled with mass spectrometry appears to show a specific interaction between the ionomer film and the Pt/C catalyst surface. These properties may be responsible for the lower resistivity and enhanced platinum utilization that we have encountered in catalyst layers working in the cathode of PEMFC.
Effect of Hydrophilic Properties of Gas Channel on Freezing Properties of PEM Fuel Cells
Authors: Tomimura Tetsuya , Shoyama Masashi , Mizutani Seiji , Marubayashi Ryoji
Published: May 2010

Effect of hydrophilic and hydrophobic properties of gas channel including bipolar plates on cell performances at freezing temperature was developed. Cell starting performance was improved as hydrophilic properties of bipolar plates increased at freezing temperature, such as -20ºC.
Investigation of Locally Resolved Current Density Distribution of Segmented PEM Fuel Cells to Detect Malfunctions
Authors: Lin Rui , Sander Heinz , Gülzow Erich , Friedrich Andreas
Published: May 2010

With the aid of PCB technology, current density distribution could be achieved by measuring the local current density inside the fuel cell, which would be more precisely reflecting the local electrochemical reaction. An important application of segmented cell technology was used for in-situ error detection of the evolution of membrane leakage. From the evolution of current density distributions, starting locations of membrane leakages and their spreading could be detected. The effect of operation conditions could be found: the steeply decreased pressure and the fast cooling of the local membrane was the main reason for the degradation of the membrane. It caused large temperature gradient in different local membranes, which resulted in inhomogeneous current density distribution and mechanical strain and stress. With the aid of segmented cell, malfunction could be detected at an early stage and thereby catastrophic failure of the whole stack may be avoided.
Anode Degradation Effects in PEMFC Stacks by Localized Fuel Starvation
Authors: Ferreira-Aparicio Paloma , Chaparro Antonio M. , Gallardo Blanca , Folgado M.A. , Daza Loreto
Published: May 2010

A study is presented of the anode degradation in a proton exchange membrane fuel cell (PEMFC), due to fuel starvation. First the basic principles of fuel starvation are discussed. We find that fuel starvation may be attained either below a limiting flow rate or below a limiting partial pressure, giving rise to two different processes in the cell, that we name starvation-by-current and starvation-by-voltage, respectively. Then, experimental results are presented and analyzed for anodes working under different conditions in a PEMFC stack. Severe degradation occurs in the anodes of PEMFCs affected by fuel starvation. Degraded anodes become visibly thinner, cracked, and appear firmly adhered to the bipolar plates when disassembling the stack. Thermogravimetric analysis coupled with mass spectrometry shows degradation occurring in the microporous gas diffusion layer and the hydrophobic agent (PTFE), as well as the carbon fibres of the macroporous support (carbon cloth). The initial oxidation of the gas diffusion substrate in the anodes provokes massive flooding of the affected cells and exacerbates their progressive degradation.
High Temperature Ceramic Proton Exchange Membranes for Direct Methanol Fuel Cells
Authors: Lu Shanfu , Wang Deli , Xiang Yan , Jiang San Ping
Published: May 2010

A novel inorganic proton exchange membrane based on H3PW12O40 (HPW)/MCM-41 mesoporous silica nanocomposites was successfully prepared by a simple vacuum-assisted impregnation method (VIM). The VIM-assembled HPW/MCM-41 electrolyte has a high proton conductivity of 0.018 and 0.045 Scm-1 at 25 and 150oC, respectively. Single fuel cells based on VIM-30wt%HPW/MCM-41 composite membranes produced a peak power density of 95 mWcm-2 at 100oC and 100% RH in H2/O2 and 90 mWcm-2 at 150oC and a low relative humidy of 0.67%. The results demonstrate for the first time that the VIM-assembled HPW/MCM-41 mesoporous silica can be used as effective proton exchange membrane for elevated high temperature PEMFCs and DMFCs.
Design Rules and Failure Modes of DMFC Stack Development
Authors: Na Youngseung , Yoon Seong Kee , Park Jungkurn , Suh Jun Won , Song Inseob , Choi Kyoung Hwan , Cho Hyejung
Published: May 2010

Fuel cell is regarded as a next generation power source for portable electronics as well as military applications due to significantly higher energy density compared to that of a battery. The key issues in developing DMFC systems for portable applications are volume and weight. In this paper, we describe three design rules to optimize the stack design, such as a flow field design, in consideration of volume, weight, robustness, and efficiency. In addition, the stack development history and two fatal failure modes are reported to aid in designing robust and reliable DMFC stacks.
Analysis of Air Supply in Multi-Cells Connecting Bellows Type DMFC by Three-Dimensional Simulation
Authors: Imai Tatsunori , Yachi Toshiaki
Published: May 2010

Bellows type DMFC was previously proposed as a structure of a new fuel cell to be able to expect high efficiency and a high output. Bellows type DMFC attempts increasing in the amount of fuel supply and making of the density uniform by soaking the cell material directly in the fuel container filled with the methanol-water solution. In the previous report, the airflow path in the cathode for a single cell was examined by using three dimensional simulations. As a result, it was shown that the air diffusion material to diffuse air uniformly was very effective. Moreover, one particular solution was shown as the best shape of the air diffusion material. In this paper, the dependence of the air supply speed, the cell output power when two or more cells were connected has been examined by the simulation. In addition, the airflow path has been analyzed.
Possibility of SOFC using Biomass-fuel and Distributed Carbon Capture and Storage (DCCS)
Authors: Tokoro Tatsuki , Tanaka Yohei , Kato Tohru , Kato Ken , Negishi Akira , Nozaki Ken
Published: May 2010

Bio-Energy with Carbon Storage (BECS), which is the system to combine the power generation system using biomass-fuels and Carbon Capture and Storage (CCS), is one of the most efficient systems to realize negative CO2 emission, which allows atmospheric CO2 recovery with power generation. In this study, the BECS system with a SOFC system using biomass-fuels and a newly proposed Distributed CCS (DCCS) technique is described. The case study in a model island clarifies that the BECS system can supply the 4600 MWh of electric energy and recover 5,200-t atmospheric CO2 per year.
Influence of the Segmented Electrode use on Electrolyte Leakage in Molten Carbonate Fuel Cell
Authors: Sugiura Kimihiko , Niwata Akitoshi , Yamauchi Makoto , Tanimoto Kazumi
Published: May 2010

We study the causal relation between the segmented electrode and electrolyte leakage and gas crossover using a visualization technique for which the cost of Molten Carbonate Fuel Cells systems would decrease. If the segmented electrode was applied to MCFC, there are three kinds of combination of the division parts about the electrode-electrode, the electrode-cell frame, and the electrode-cell frame-electrode. The electrolyte leakage of these division parts and the effectiveness of the segmented electrode are examined by the visualization technique and the cell test. As a result, in either case of an anode and cathode, the electrolyte leakage from the division part of electrode-electrode and the gas crossover could not be ob-served by the visualization technique. Though the electrolyte leakage is observed from the division part of electrode-cell frame, it disappears within one week. Therefore, the application of the segmented electrode to MCFC is effective.
Operation Results of the External Reforming Type 75kW Class MCFC Stack
Authors: Kim Seung-Goo , Kuk Seung Taek , Choi Young-Jae , Jun Joonghwan , Kim Do-Hyung , Kim Beomjoo , Lim Hee-Chun
Published: May 2010

A 75kW class pilot scale MCFC stack composed of 128 unit cells was assembled and operated. 10,000cm2 class MCFC stack components are also developed to fabricate the MCFC stack. The separators with the effective area of 10,000 cm2 were adopted new design concepts such as 3-piece architecture, simple channel structure, and flat mask plate to improve the gas flow behavior and wet seal performance. The electrolyte impregnated anode and cathode with the effective area of 10,000 cm2 were fabricated by the ex-situ process to enhance the reliability of the stack during the heat-treatment. Finally, the gas distribution manifold embedded light-weight stack structure was employed. The stack showed the average open circuit voltage of 1.065V that near meet theoretical one and 78.5kW DC in power output. A 125kW class MCFC stack using the same components will be assembled and started to operate by the end of 2009.
Development of New-type Matrix for Internal-manifold MCFC
Authors: Kuk Seung Taek , Kim Young Woo , Kim Seung-Goo , Choi Young-Jae , Lim Hee-Chun , Jun Joonghwan
Published: May 2010

The MCFC matrix has a unique structure in order to maintain homogeneous distribution of molten carbonate melt. It is composed of an electronically insulation material which is stable in molten carbonate melt. Specially, in case of internal-manifold MCFC stack, the sealing on wet-seal side is the most important role and the matrix in internal-manifold stack should be completely flooded by the melt. In this study, we prepared the matrix using nano-sized LiAlO2 powder obtained by ultrasonic spraying heating method. The pore size distribution of the matrix was narrower than that of commercial matrix made of micro-sized powder and the pore size is also smaller than it. The performance of single cell showed that the mean voltage was 0.85 V at 150 mA/cm2 for 600 hours.
High Efficiency Hydrogen and Oxygen Storage System Development for Underwater Platforms Powered by Fuel Cell
Authors: Hyakudome Tadahiro , Yoshida Hiroshi , Tsukioka Satoshi , Sawa Takao , Ishibashi Shojiro , Aoki Taro , Iwamoto Takashi , Kawaharazaki Yoshinori , Muto Atsutoshi , Oda Tomomasa , Fujita Yasuhiro
Published: May 2010

In 2007, we started research and development of a demonstration long-range vehicle to cruise 3000 kilometers. It is important to improve a system performance of a fuel cell system and to improve storage methods of the pure hydrogen and the pure oxygen to achieve this aim. It is necessary to install an oxygen tank on the vehicle because the oxygen is not taken from environment in the sea. A large quantity of hydrogen and oxygen need to let the fuel cell system generate electricity for a long time to cruise at 3,000 kilometers. Because energy efficiency becomes worse if the body of the vehicle becomes big, the gases must storage compactly. We are developing a pressure vessel for the hydrogen storage, metal hydrides and an oxygen storage system.
Optimization of Hydrogen Production by Ammonia Electrolysis
Authors: Sugiura Kimihiko , Yamamoto Yudai , Tsumura Mika
Published: May 2010

The fundamental characteristics of hydrogen production by ammonia electrolysis are elucidated by an H type electrolyzer. As a result, the amount of hydrogen product increases with an increase of the ammonia concentration. It is clear that the electrical potential for ammonia electrolysis is lower than that of water electrolysis as more nitrogen is generated than oxygen while ammonia is present. Moreover, ammonia electrolysis and water electrolysis are promoted by adding alkaline solution. However, because the electrolysis voltage of ammonia is larger than theory electrolysis voltage, we optimize the ammonia electrolyzer by changing an interelectrode distance and a feed rate of ammonia solution. If the interelectrode distance is shorter and the electrolyte solution is circulated by pomp, the electrolysis voltage of ammonia has approached the theory electrolysis voltage. Therefore, this electrolysis method shows great promise as a hydrogen production mechanism if the operating conditions are further optimized.
On the substrate recognition and negative regulation of SPAK, a kinase modulating Na+-K+-2Cl− cotransport activity
Authors: Gagnon Kenneth B. , Delpire Eric
Published: May 2010

Threonines targeted by Ste20-related proline-alanine-rich kinase (SPAK) for phosphorylation have been identified in Na+-K+-2Cl− cotransporter type 1 (NKCC1), NKCC2, and Na+-Cl− cotransporter (NCC). However, what constitutes the substrate recognition of the kinase is still unknown. Using site-directed mutagenesis and functional measurement of NKCC1 activity in Xenopus laevis oocytes, we determined that SPAK recognizes two threonine residues separated by four amino acids. Addition or removal of a single residue abrogated SPAK activation of NKCC1. Although both threonines are followed by hydrophobic residues, in vivo experiments have determined that SPAK activation of the cotransporter only requires a hydrophobic residue after the first threonine. Interestingly, downstream of the second threonine residue, we have identified a conserved aspartic acid residue which is critical for NKCC1 function. Mouse SPAK activity requires phosphorylation of two specific residues by WNK [with no lysine (K)] kinases: a threonine (T243) in the catalytic domain and a serine (S383) in the regulatory domain. We found that mutating the threonine residue into a glutamic acid (T243E) combined with mutation of the serine into an aspartic acid (S383D) rendered SPAK constitutively active. Surprisingly, alanine substitution of S383 or mutation of residues surrounding this residue also resulted in a constitutively active kinase. Interestingly, deletion of amino acids 356–398 identified another serine residue in the catalytic domain (S321) as another putative target of WNK phosphorylation. We found that WNK4 is capable of stimulating the deletion mutant when S321 is present, but not when S321 is mutated into an alanine.
Neonatal intermittent hypoxia impairs neuronal nicotinic receptor expression and function in adrenal chromaffin cells
Authors: Souvannakitti Dangjai , Kuri Barbara , Yuan Guoxiang , Pawar Anita , Kumar Ganesh K. , Smith Corey , Fox Aaron P. , Prabhakar Nanduri R.
Published: May 2010

We recently reported that adrenomedullary chromaffin cells (AMC) from neonatal rats treated with intermittent hypoxia (IH) exhibit enhanced catecholamine secretion by hypoxia (Souvannakitti D, Kumar GK, Fox A, Prabhakar NR. J Neurophysiol 101: 2837–2846, 2009). In the present study, we examined whether neonatal IH also facilitate AMC responses to nicotine, a potent stimulus to chromaffin cells. Experiments were performed on rats exposed to either IH (15-s hypoxia-5-min normoxia; 8 h/day) or to room air (normoxia; controls) from ages postnatal day 0 (P0) to P5. Quantitative RT-PCR analysis revealed expression of mRNAs encoding α3-, α5-, α7-, and β2- and β4-nicotinic acetylcholine receptor (nAChR) subunits in adrenal medullae from control P5 rats. Nicotine-elevated intracellular Ca2+ concentration ([Ca2+]i) in AMC and nAChR antagonists prevented this response, suggesting that nAChRs are functional in neonatal AMC. In IH-treated rats, nAChR mRNAs were downregulated in AMC, which resulted in a markedly attenuated nicotine-evoked elevation in [Ca2+]i and subsequent catecholamine secretion. Systemic administration of antioxidant prevented IH-evoked downregulation of nAChR expression and function. P35 rats treated with neonatal IH exhibited reduced nAChR mRNA expression in adrenal medullae, attenuated AMC responses to nicotine, and impaired neurogenic catecholamine secretion. Thus the response to neonatal IH lasts for at least 30 days. These observations demonstrate that neonatal IH downregulates nAChR expression and function in AMC via reactive oxygen species signaling, and the effects of neonatal IH persist at least into juvenile life, leading to impaired neurogenic catecholamine secretion from AMC.
Involvement of cAMP in nerve growth factor-triggered p35/Cdk5 activation and differentiation in PC12 cells
Authors: Chen Mei-Chih , Lin Ho , Hsu Fu-Ning , Huang Pao-Hsuan , Lee Guan-Shun , Wang Paulus S.
Published: May 2010

The signaling mechanisms underlying cell differentiation have been extensively studied with the use of rat PC12 cells as a model system. Nerve growth factor (NGF) is a trophic factor inducing PC12 cell differentiation through the activation of the p35/cyclin-dependent kinase 5 (Cdk5) complex. It has been reported that adenylyl cyclase activation and cAMP production may be involved in NGF-dependent actions. Our previous results indicate that cAMP activates the p35/Cdk5 complex in reproductive cells. Therefore, the role of cAMP in NGF-triggered p35/Cdk5 activation and PC12 differentiation was interesting to explore. Our results indicate that roscovitine, a molecular inhibitor of Cdk5, blocks cAMP-triggered PC12 differentiation, which was evaluated by neurite initiation, a decrease in proliferation, and cell cycle G1 arrest. The following data show that cAMP treatment increased Cdk5 activity through p35 upregulation. cAMP downstream components, protein kinase A (PKA) and phosphorylated cAMP response element binding protein (CREB), are involved in this regulation. The immunocytochemical results indicate that PKA inhibition disrupted cAMP-triggered p35/Cdk5 localization in PC12 cells. In addition, adenylyl cyclase inhibition was found to diminish NGF-induced intracellular cAMP production, CREB phosphorylation, and p35 expression. The cAMP antagonist and the PKA inhibitors reduced NGF-induced p35 expression. Finally, NGF-triggered PC12 differentiation was partially decreased by adenylyl cyclase or PKA inhibitors. In conclusion, these results demonstrate that cAMP may play a role in NGF-p35/Cdk5-dependent PC12 differentiation.
The anemia of the newborn induces erythropoietin expression in the developing mouse retina
Authors: Scheerer N. , Dünker N. , Imagawa S. , Yamamoto M. , Suzuki N. , Fandrey J.
Published: May 2010

The hematopoietic hormone erythropoietin (Epo), regularly produced by the kidneys and the liver, is also expressed in neuronal tissue, where it has been found to mediate paracrine neuroprotective effects. In most studies exploring the rescue effects of Epo, apoptosis was exogenously induced by different cell death stimuli. Herein, we set out to study the expression and function of Epo in physiologically occurring apoptosis in a model of retinal development. We made use of an organotypic retinal wholemount culture system that resembles the physiological in vivo situation with cell connections still retained. Epo mRNA expression in the retina, liver, and kidney showed a significant increase during early development, coinciding with the anemia of the newborn. In the retina of Epo-green fluorescent protein transgenic mice, Epo-expressing cells were identified and found to be distributed in the retinal ganglion cell layer. Treatment of retinal wholemount cultures with recombinant Epo resulted in a significant decrease of apoptotic ganglion cells as well as photoreceptor cells throughout retinal development. Moreover, transforming growth factor-β-induced apoptosis was completely antagonized by Epo when both factors were simultaneously applied. Investigations on the signaling pathway revealed a decrease in Bax mRNA levels in Epo-treated retinal cells. We conclude that Epo exerts wide and prolonged neuroprotective activity in physiologically occurring apoptosis and thus contributes to proper retinal development.
Chronic stimulation of the hypothalamic vasoactive intestinal peptide receptor lengthens circadian period in mice and hamsters
Authors: Pantazopoulos Harry , Dolatshad Hamid , Davis Fred C.
Published: May 2010

Evidence suggests that circadian rhythms are regulated through diffusible signals generated by the suprachiasmatic nucleus (SCN). Vasoactive intestinal peptide (VIP) is located in SCN neurons positioned to receive photic input from the retinohypothalamic tract and transmit information to other SCN cells and adjacent hypothalamic areas. Studies using knockout mice indicate that VIP is essential for synchrony among SCN cells and for the expression of normal circadian rhythms. To test the hypothesis that VIP is also an SCN output signal, we recorded wheel-running activity rhythms in hamsters and continuously infused the VIP receptor agonist BAY 55-9837 in the third ventricle for 28 days. Unlike other candidate output signals, infusion of BAY 55-9837 did not affect activity levels. Instead, BAY 55-9837 lengthened the circadian period by 0.69 ± 0.04 h ( P < 0.0002 compared with controls). Period returned to baseline after infusions. We analyzed the effect of BAY 55-9837 on cultured SCN from PER2::LUC mice to determine if lengthening of the period by BAY 55-9837 is a direct effect on the SCN. Application of 10 μM BAY 55-9837 to SCN in culture lengthened the period of PER2 luciferase expression (24.73 ± 0.24 h) compared with control SCN (23.57 ± 0.26, P = 0.01). In addition, rhythm amplitude was significantly increased, consistent with increased synchronization of SCN neurons. The effect of BAY 55-9837 in vivo on period is similar to the effect of constant light. The present results suggest that VIP-VPAC2 signaling in the SCN may play two roles, synchronizing SCN neurons and setting the period of the SCN as a whole.