bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reliability and Validity of the Visual Analog Mood Scales in Non‐English‐Speaking Pain Patients
Authors: House Erica D. , Arruda James E. , Andrasik Frank , Grazzi Licia
Published: March 2012

Objectives:  This study assessed the validity and reliability of the Visual Analog Mood Scales (VAMS) when administered to a non‐English‐speaking, headache population.

Methods:  The VAMS and another frequently administered measure of mood, the Profile of Mood States (POMS), were administered to sixty patients at a headache clinic in Milan, Italy. The VAMS and POMS were both administered before and after a regularly scheduled appointment at the clinic. Multitrait–multimethod analyses were conducted to assess the validity of each subscale comprising the VAMS.

Results:  All subscales comprising the VAMS possessed high test–retest reliability, and the “confused,”“sad,”“angry,”“energetic,” and “tired” subscales of the VAMS were shown to be valid when administered to a non‐English‐speaking pain population. Further, compared to age‐matched controls (from available normative data), pain patients reported being significantly more confused, sad, and tense on the VAMS and significantly more tired, confused, depressed, and tense on the POMS.

Discussion:  Given the evidence of strong reliability and validity, the VAMS may be useful as a clinical diagnostic tool when administered to non‐English‐speaking pain populations.
Are People Willing to Buy Natural Disaster Insurance in China? Risk Awareness, Insurance Acceptance, and Willingness to Pay
Authors: Wang Ming , Liao Chuan , Yang Saini , Zhao Weiting , Liu Min , Shi Peijun
Published: March 2012

After the Wenchuan earthquake (magnitude 7.9, May 12, 2008), intensive debates on how China should establish a natural disaster insurance system were initiated among researchers, policymakers, and insurance professionals. Our focus was the social aspects of disaster insurance, explored in China through a nationwide survey. Our questionnaires investigated people's risk awareness, insurance acceptance, their opinions on governmental measures for disaster management, and their willingness to pay for disaster house insurance. We analyzed the results at both regional and individual scales. We found that the integrated hazard index and respondents’ experience of insurance (considered objective factors), and their opinions on the importance of insurance and government responsibility (considered subjective factors) showed strong correlation with the regional overall acceptance of disaster insurance. An individual's decision to participate highly depended on his/her experience of both insurance and disaster and his/her opinion on the importance of insurance as a coping mechanism. Respondents from poverty‐stricken or less‐developed counties were not necessarily more reluctant to accept natural disaster insurance, though they exhibited relatively lower ability to afford insurance. In general, respondents had correct perceptions of natural disasters in their areas; however, people from regions with a greater multihazard threat showed less willingness to accept disaster insurance because they tended to expect the government to undertake to cover losses and considered insurance to be less important. People's willingness to pay for an assumed disaster house insurance was also investigated and analyzed. We consequently discuss the policy implications for developing a disaster insurance system in China.
Toxicology and Characteristics of Deaths Involving Zolpidem in New South Wales, Australia 2001–2010*
Authors: Darke Shane , Deady Mark , Duflou Johan
Published: March 2012

Abstract:  All cases presenting to the New South Wales Department of Forensic Medicine between January 1, 2001 and September 31, 2010 in which zolpidem was detected, were retrieved. A total of 91 cases were identified. The mean age was 49.4 years, 65.9% were male, and 61.5% were suicides. Zolpidem was a factor contributing to death in 35 (37.3%) cases, of which 31 (34.1%) involved zolpidem toxicity. The median blood zolpidem concentration was 0.20 mg/L (range 0.05–3.50 mg/L), with no significant gender difference. Drug toxicity cases involving zolpidem had significantly higher median blood zolpidem concentrations than other cases (0.50 vs. 0.10 mg/L). In 83.5% of cases, psychoactive substances other than zolpidem were detected, most commonly antidepressants (46.2%), benzodiazepines (35.2%), opioids (26.4%), and alcohol (39.6%). In summary, zolpidem was a factor contributing to death in a large proportion of cases, predominately involving drug toxicity and suicide.
Management of postmenopausal women with vaginal bleeding when the endometrium can not be visualized
Authors: BURBOS NIKOLAOS , MUSONDA PATRICK , CROCKER SIMON G. , MORRIS EDWARD P. , NIETO JOAQUIN J. , DUNCAN TIMOTHY J.
Published: March 2012

Objective. To determine the risk of endometrial cancer when endometrial thickness is not visualized using ultrasonography. Design. Cross‐sectional study. Setting. Gynecological oncology center in the United Kingdom. Population. All postmenopausal women referred with vaginal bleeding. Methods. All women were investigated using gray‐scale transvaginal ultrasonography. Women were arbitrarily stratified into four groups according to the endometrial thickness measurement. Women with endometrial thickness that was not adequately visualized on ultrasonography were included in a separate group. Main outcome measures. Endometrial cancer diagnosis. Results. Over a 50‐month period, 4454 women were investigated for postmenopausal vaginal bleeding. A total of 259 (6%) of women were diagnosed with endometrial carcinoma. Endometrial thickness measured 5–9.9mm in 1201 (27%), 10–14.9mm in 468 (11%), 15–19.9mm in 209 (5%), and equal to or greater than 20mm in 197 (4%) of women. In 174 (4%) of women, the endometrial thickness was not visualized on transvaginal ultrasonography. For women where the endometrial thickness was not adequately visualized, the final histology included benign endometrium (124), endometrial cancer (26), endometrial polyps (11), endometritis (7), and other pathology (7). The odds of endometrial cancer in women where the endometrial thickness was not visualized were found to be significantly higher than the odds of cancer for women with an endometrial thickness of 5–9.9mm (OR = 5.23, 95%CI 3.10–8.85, p‐value <0.0001). Conclusions. For women presenting with postmenopausal bleeding and where the endometrial thickness cannot be adequately visualized on ultrasonography, hysteroscopic evaluation is recommended.
Multi‐scale patterns of moss and lichen richness on the Antarctic Peninsula
Authors: Casanovas Paula , Lynch Heather J. , Fagan William F.
Published: March 2012

Mosses and lichens are the dominant macrophytes of the Antarctic terrestrial ecosystem. Using occurrence data from existing databases and additional published records, we analyzed patterns of moss and lichen species diversity on the Antarctic Peninsula at both a regional scale (1°latitudinal bands) and a local scale (52 and 56 individual snow‐ and ice‐free coastal areas for mosses and lichens, respectively) to test hypothesized relationships between species diversity and environmental factors, and to identify locations whose diversity may be particularly poorly represented by existing collections and online databases. We found significant heterogeneity in sampling frequency, number of records collected, and number of species found among analysis units at the two spatial scales, and estimated species richness using projected species accumulation curves to account for potential biases stemming from sample heterogeneity. Our estimates of moss and lichen richness for the entire Antarctic Peninsula region were within 20% of the total number of known species. Area, latitude, spatial isolation, mean summer temperature, and penguin colony size were considered as potential covariates of estimated species richness. Moss richness was correlated with isolation and latitude at the local scale, while lichen richness was correlated with summer mean temperature and, for 17 sites where penguins where present with <20 000 breeding pairs, penguin colony size. At the regional scale, moss richness was correlated with temperature and latitude. Lichen richness, by contrast, was not significantly correlated with any of the variables considered at the regional scale. With the exception of temperature, which explained 91% of the variation in regional moss diversity, explained variance was very low. Our results show that patterns of moss and lichen biodiversity are highly scale‐dependent and largely unexplained by the biogeographic variables found important in other systems.
SPONDYLOSIS DEFORMANS AND DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS (DISH) RESULTING IN ADJACENT SEGMENT DISEASE
Authors: Ortega Maria , Gonçalves Rita , Haley Allison , Wessmann Annette , Penderis Jacques
Published: March 2012

Spondylosis deformans and diffuse idiopathic skeletal hyperostosis (DISH) are usually incidental findings and in most dogs are either asymptomatic or associated with mild clinical signs. Severe spondylosis deformans andDISHcan result in complete bony fusion of consecutive vertebral segments. One of the recognised complications following vertebral fusion in human patients is the development of adjacent segment disease, which is defined as degenerative changes, most commonly degenerative intervertebral disc disease, in the mobile vertebral segment neighboring a region of complete vertebral fusion. A similar syndrome following cervical fusion in dogs has been termed the domino effect. The purpose of this retrospective study was to investigate the hypothesis that vertebral fusion occurring secondary to spondylosis deformans orDISHin dogs would protect fused intervertebral disc spaces from undergoing degeneration, but result in adjacent segment disease at neighbouring unfused intervertebral disc spaces. Eight dogs with clinical signs of thoracolumbar myelopathy, magnetic resonance imaging of the thoracolumbar vertebral column, and spondylosis deformans orDISHproducing fusion of ≥2 consecutive intervertebral disc spaces were evaluated. Vertebral fusion of ≥2 consecutive intervertebral disc spaces was correlated (P= 0.0017) with adjacent segment disease at the neighbouring unfused intervertebral disc space. Vertebral fusion appeared to protect fused intervertebral disc spaces from undergoing degeneration (P< 0.0001). Adjacent segment disease should be considered in dogs with severe spondylosis deformans orDISHoccurring in conjunction with a thoracolumbar myelopathy.
USEFULNESS OF A HALF‐FOURIER ACQUISITION SINGLE‐SHOT TURBO SPIN‐ECHO PULSE SEQUENCE IN IDENTIFYING ARACHNOID DIVERTICULA IN DOGS
Authors: Seiler Gabriela S. , Robertson Ian D. , Mai Wilfried , Widmer William R. , Suran Jantra , Nemanic Sarah , Lamb Christopher R. , Lang Johann , Johnson Jeffrey L. , Thrall Donald E.
Published: March 2012

Single‐shot turbo spin‐echo sequences are heavily T2‐weighted sequences that are exceptionally well suited to evaluate the subarachnoid space. In the T2‐weighted fast spin‐echo sequences that are used routinely in spinal magnetic resonance (MR) imaging, the subarachnoid space is not well differentiated from the surrounding epidural fat, which could lead to decreased detection of lesions of the subarachnoid space such as arachnoid diverticula. Our purpose was to determine the added value of a single‐shot turbo spin‐echo sequence in identifying cystic lesions of the subarachnoid space in dogs. MR images of six dogs with a confirmed arachnoid diverticulum and 24 dogs with other spinal disease were included. Six observers were asked to interpret only T2‐weighted images initially, and in a second session, T2‐weighted and half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) sequences. The MR images were anonymized, and no signalment, history, or clinical information was provided. Without the HASTE sequences, 25% of arachnoid diverticula were identified. Adding the HASTE sequence increased the diagnosis of arachnoid diverticulum to 52.8%. The resulting difference, after adding the HASTE sequence, of 27.8% was statistically significant (P = 0.002). No false‐positive diagnoses of arachnoid diverticulum were made with either sequence. Although sensitivity in this study was likely artificially low, the significantly increased detection rate of arachnoid diverticula when using HASTE imaging indicates that this sequence is a valuable addition to MR imaging protocols for the canine spine.
A model of dirigent proteins derived from structural and functional similarities with allene oxide cyclase and lipocalins
Authors: Pickel Benjamin , Pfannstiel Jens , Steudle Alexander , Lehmann Axel , Gerken Uwe , Pleiss Jürgen , Schaller Andreas
Published: March 2012

Dirigent proteins impart stereoselectivity on the phenoxy radical‐coupling reaction, yielding optically active lignans from two molecules of coniferyl alcohol. By an unknown mechanism, they direct the coupling of two phenoxy radicals toward the formation of optically active (+)‐ or (−)‐pinoresinol. We show here that the dirigent protein AtDIR6 from Arabidopsis thaliana is a homodimeric all‐beta protein in the superfamily of calycins. Based on its homology with calycins, the structure of AtDIR6 was modeled using allene oxide cyclase as template. The structural model of AtDIR6 was supported experimentally by confirmation of a predicted disulfide bridge and by the characterization of two N‐linked glycans at the solvent‐exposed protein surface. The model shows AtDIR6 as an eight‐stranded antiparallel β‐barrel with a central hydrophobic cavity for substrate binding, suggesting that dirigent proteins evolved from hydrophobic ligand‐binding proteins. The data are fully consistent with the current view of the dirigent protein mode of action, according to which each subunit of the homodimer captures one of the substrate radicals and orients them in a way that precludes undesired reaction channels, thus favoring the formation of the optically pure coupling product.

Structured digital abstract 

 AtDIR6 and AtDIR6 bind by cross‐linking study (View interaction)

 AtDIR6 and AtDIR6 bind by molecular sieving (View interaction)
Modeling of Oxygen Transport and Cell Killing in Type‐II Photodynamic Therapy
Authors: Gkigkitzis Ioannis , Feng Yuanming , Yang Chunmei , Lu Jun Q. , Hu Xin‐Hua
Published: March 2012

Photodynamic therapy (PDT) provides an effective option for treatment of tumors and other diseases in superficial tissues and attracts attention for in vitro study with cells. In this study, we present a significantly improved model of in vitro cell killing through Type‐II PDT for simulation of the molecular interactions and cell killing in time domain in the presence of oxygen transport within a spherical cell. The self‐consistency of the approach is examined by determination of conditions for obtaining positive definitive solutions of molecular concentrations. Decay constants of photosensitizers and unoxidized receptors are extracted as the key indices of molecular kinetics with different oxygen diffusion constants and permeability at the cell membrane. By coupling the molecular kinetics to cell killing, we develop a modeling method of PDT cytotoxicity caused by singlet oxygen and obtain the cell survival ratio as a function of light fluence or initial photosensitizer concentration with different photon density or irradiance of incident light and other parameters of oxygen transport. The results show that the present model of Type‐II PDT yields a powerful tool to quantitate various events underlying PDT at the molecular and cellular levels and to interpret experimental results of in vitro cell studies.
Concomitant activation of functionally opposing prostacyclin and thromboxane prostanoid receptors by cyclo‐oxygenase‐1‐mediated prostacyclin synthesis in mouse arteries
Authors: Liu Bin , Luo Wenhong , Zhang Yingzhan , Li Hui , Zhang Jiling , Tan Xue‐Rui , Zhou Yingbi
Published: March 2012

This study aimed to determine whether cyclo‐oxygenase‐1 (COX‐1) mediates dilatation of mouse arteries via synthesis of prostacyclin (PGI2) and, if so, how PGI2 (IP) receptors contribute and whether thromboxane prostanoid (TP) receptors are implicated in the process. Mesenteric arteries were isolated from wild‐type mice or mice with COX‐1 deficiency (COX‐1−/−). The vasomotor reaction to the COX substrate arachidonic acid (AA) was determined with isometric force measurement, while the in vitro production or the plasma level of the PGI2 metabolite 6‐keto‐PGF1α was analysed with high‐performance liquid chromatography–mass spectroscopy or enzyme immunoassay, respectively. Results showed that AA, which evoked endothelium‐dependent 6‐keto‐PGF1α production, elicited relaxation that was inhibited or enhanced by antagonizing IP or TP receptors, respectively. Also, IP receptor blockade resulted in contraction in response to AA (following NO synthase inhibition), which was prevented by a concomitant TP receptor antagonism. Meanwhile, COX‐1−/− or COX‐1 inhibition abolished the in vitro 6‐keto‐PGF1α production and reduced the relaxation or contraction observed with AA. Real‐time PCR showed that whereas TP receptor mRNAs were detected at similar levels, IP receptor mRNAs were present at higher levels in the branches than in the main stem of the mesenteric artery. In addition, antagonizing the IP receptors enhanced the contraction evoked by PGI2 in the carotid artery. Also, we noted that COX‐1−/− mice had a reduced basal plasma 6‐keto‐PGF1α level. These results demonstrate an explicit vasodilator role for COX‐1‐mediated endothelial PGI2 synthesis and suggest that the functionally opposing IP and TP receptors concomitantly mediate the vasomotor reaction to PGI2, with the dilator activity of IP receptors being compromised by the vasoconstrictor effect of TP receptors and vice versa.
Development of an Optical Sensor for Temperature Measurement and Water Droplet Detection in PEMFC Gas Channels
Authors: Inman Kristopher , Wang Xia , Sangerozan Brian
Published: March 2012

Thermal and water management in Proton Exchange Membrane (PEM) fuel cells provide a significant challenge for engineers and fuel cell designers as both have a direct effect on performance and durability. Internal temperature is very difficult to measure due to component geometry and the internal environment possessed by PEM fuel cells along with a lack of sufficient temperature measurement methods which are often highly invasive. This research presents initial developments for creating a non-intrusive temperature measurement system, based on the principles of phosphor thermometry, which also has the ability to optically detect liquid water formation and movement in PEMFC gas channels. The sensor was designed, calibrated and then installed in a 25 cm2 PEM fuel cell for in-situ testing. The experimental data show that a relationship exists between temperature variation and water droplet movement in gas channels of a PEM fuel cell.
Synthesis of Mixed Oxide-Ion and Carbonate-Ion Conductors Supported by a Prefabricated Porous Solid Oxide Matrix
Authors: Zhang Lingling , Li Xue , Wang Siwei , Romito Kevin Gregory , Huang Kevin
Published: March 2012

A novel two-step approach is used to fabricate a two-phase mixed oxide-ion and carbonate-ion conductor (MOCC) that has been recently developed for intermediate temperature solid oxide fuel cells (IT-SOFCs) and CO2 separation membranes. In this study, a samarium doped ceria (SDC) is selected as an example to demonstrate the prefabrication of porous matrix by the “sacrificial template” methodology with NiO as the template material. NiO has been reduced into elemental Ni in the composite, and then removed by dissolving into a nitric acid. It was demonstrated by XRD, EDS and weight changes. The microstructure of the SDC matrix characterized with an SEM imaging reveals a uniform distribution of homogeneous micro-pores across the solid-oxide matrix. The strong porous solid-oxide matrix is prefabricated at high temperature, into which a molten carbonate phase is subsequently infiltrated. A Li-Na-carbonate-impregnated MOCC supported by a 41.8% porous SDC matrix shows an effective ionic conductivity of 0.43 S/cm at 650 °C.
Status of Solid State Hydrogen Storage Technology for Fuel Cells in Korea
Authors: Chung Moon-Sun , Kim Jong-Won
Published: March 2012

There are four R&D programs on hydrogen and fuel cell in Korea. Two of them are supported by MEST (Ministry of Education, Science and Technology) and others are funded by MKE (Ministry of Knowledge Economy). The hydrogen production technologies examined in Korea cover 3 main bases, fossil fuel, renewable energy including photo-catalytic, bio-hydrogen technology, and high temperature gas-cooled reactor. In October 2003, Korean government launched Hydrogen Energy R&D Center (HERC) as a member of the 21st Century Frontier R&D programs supported by the Ministry of Education, Science and Technology (MEST). The HERC has conducted research on the key technologies for the production, storage, and utilization of hydrogen energy for expediting realization of hydrogen economy based on renewable energy sources. The main purposes of this paper are to overview the current status of research programs for hydrogen storage technologies conducted by Hydrogen Energy R&D Center based on the patent applications as well as research topics and to introduce specific achievements in each research program.
Response Surfaces for Key Controlled Variables in a Hybrid Solid Oxide Fuel Cell/Gas Turbine System
Authors: Rosen William G. , Banta Larry , Gorrell Megan , Restrepo Bernardo , Tucker David
Published: March 2012

Hybrid generation systems have been extensively modeled as a first step toward the development of automatic controls for the system. In most cases, it is impossible to validate mathematical models against real hardware because only a handful of hardware systems exist in the world. Data taken from the existing hardware has demonstrated significant nonlinearity, complex coupling between controlled variables, and sometimes non-intuitive behavior. This work exploits the capability of the HyPer hardware test bed at the National Energy Technology Laboratory (NETL) to generate data from a real recuperated gas turbine coupled with hardware simulations of a fuel cell cathode and appropriate ancillary equipment. Prior work has characterized the system only over a limited range of its operating envelope, due to the inability to manipulate multiple control inputs simultaneously. The work presented here fills the gaps using data from a 34 factorial experiment to generate quasi-continuous response surfaces describing the operating state space of the HyPer system. Polynomial correlation functions have been fitted to the data with excellent agreement. Relationships between the control inputs and critical state variables such as cathode mass flow, cathode temperature, turbine inlet and exhaust temperatures and other key system parameters are presented.
Characterization of a Solid Oxide Fuel Cell Gas Turbine Hybrid System Based on a Factorial Design of Experiments Using Hardware Simulation
Authors: Restrepo Bernardo , Banta Larry E. , Tucker David
Published: March 2012

A full factorial experimental design and a replicated fractional factorial design were carried out using the Hybrid Performance (HyPer) project facility installed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to simulate gasifer/fuel cell/turbine hybrid power systems. The HyPer facility uses hardware in the loop (HIL) technology that couples a modified recuperated gas turbine cycle with hardware driven by a solid oxide fuel cell model. A 34 full factorial design (FFD) was selected to study the effects of four factors: cold-air, hot-air, bleed-air bypass valves, and the electric load on different parameters such as cathode and turbine inlet temperatures, pressure and mass flow. The results obtained, compared with former results where the experiments were made using one-factor-at-a-time (OFAT), show that no strong interactions between the factors are present in the different parameters of the system. This work also presents a fractional factorial design (ffd) 34-2 in order to analyze replication of the experiments. In addition, a new envelope is described based on the results of the design of experiments (DoE), compared with OFAT experiments, and analyzed in an off-design integrated fuel cell/gas turbine framework. This paper describes the methodology, strategy, and results of these experiments that bring new knowledge concerning the operating state space for this kind of power generation system.
Trace Level Sulfur Sensor for Fuel Cells
Authors: Yasar Murat , Ede Rama K. , Kalkan A. Kaan
Published: March 2012

The primary objective of this work is to develop a trace level sulfur sensor for high sensitivity detection of impurities before they reach hydrogen fuel cell membranes. A novel sensing mechanism, “hybrid plasmon damping”, was explored to detect and quantify the sulfur traces in hydrogen fuels using the spectral shifts that is generated by the interaction of silver nanoparticles and sulfur compounds. We have investigated the sensor technology for detection of sulfur compounds to the part per billion (ppb) trace levels that are typically present in hydrogen fuels, and demonstrated this unique sensing mechanism through bench top experimental set ups and analysis methods.
Methane-Based Flame Fuel Cell Using Anode Supported Solid Oxide Fuel Cells
Authors: Wang Kang , Zeng Pingying , Ahn Jeongmin
Published: March 2012

This work presents the performance of the flame fuel cell based on the anode-supported solid oxide fuel cell (AS-SOFC) with a methane flame, which serves not only as a fuel reformer but also as a heat source to sustain the fuel cell operation. The anode-supported SOFC showed an extraordinary fuel cell performance of 475 mW/cm2 by using a methane flame. The fuel cell performance was determined by fuel cell temperature and fuel concentration which varied with the equivalent ratio and methane flow rate.
Effect of Inlet Flow Conditions on Flow Uniformity in a PEM Fuel Cell
Authors: Grega Lisa M. , Voinier Steven
Published: March 2012

The use of fuel cells as an alternative to traditional small scale power producing devices such as internal combustion engines or disposable batteries has continued to gain widespread acceptance. Flow maldistribution within cells in a stack continues to be an issue in fuel cell design and can adversely affect performance and longevity. Current research in this field has focused on effects of inlet configurations (plug flow versus circular inlet, for example) on the flow in a rectangular manifold and the resulting distribution into individual cells in the stack. In a typical small scale application, the piping which transports the reactant will contain bends in it. As these bends can introduce Dean vortices and flow asymmetries within the pipe flow, such conditions should be examined to determine whether they will affect the manifold flow and further impact cell maldistribution. A simplified scaled up model of a PEM fuel cell was fitted with different inlet flow configurations, including straight piping and piping containing a 90 degree bend prior to entering the manifold. Particle Image Velocimetry (PIV) was used to obtain mean and fluctuating velocity statistics within the manifold and in individual cells. These distributions will be compared with previous results obtained from this apparatus corresponding to a partially developed square inlet profile, as well as available experimental and computational data in the literature.
Through-Plane Gas Permeability of Proton Exchange Membrane Fuel Cell Gas Diffusion Layers
Authors: Tamayol A. , McGregor F. , Bahrami M.
Published: March 2012

Effects of mechanical compression and PTFE content on the through-plane gas permeability of gas diffusion layers (GDLs) of PEM fuel cells are investigated both experimentally and theoretically. A new test bed is designed and built which allows pressure drop and air flow rate measurement for various fibrous samples. The measured values are used to calculate the through-plane permeability. Various GDLs are obtained and tested over a wide range of PTFE content and compression ratio. The experimental data shows a reverse relationship between the through-plane permeability and both PTFE content and mechanical compression. An existing model for through-plane permeability of planar structures is revisited to develop a model that accommodates effects of PTFE content and GDL compression. The proposed model captures the trends of the experimental data for through-plane permeability, measured in the present study or reported by others.
Development of Production Technology for Membrane-Electrode Assemblies With Radical Capturing Layer
Authors: Kobayashi T. , Hirai E. , Itoh H. , Moriga T.
Published: March 2012

This paper describes the development of mass-production technology for membrane-electrode assemblies (MEA) with a radical capturing layer and verifies its performance. Some of the authors of this paper previously developed an MEA with a radical capturing layer along the boundaries between the electrode catalyst layer and the polymer membrane to realize an endurance time of 20,000 h in accelerated daily start and daily stop (DSS) deterioration tests. Commercialization of these MEAs requires a production technology that suits mass production lines and provides reasonable cost performance. After developing a water-based slurry and selecting a gas diffusion layer (GDL), a catalyst layer forming technology uses a rotary screen method for electrode formation. Studies confirmed continuous formation of the catalyst layer, obtaining an anode/cathode thickness of 55 μm (+10/−20)/50 μm (+10/−20) by optimizing the opening ratio and thickness of the screen plate. A layer-forming technology developed for the radical capturing layer uses a two-fluid spraying method. Continuous formation of an 8-μm-thick (±3 μm) radical capturing layer proved feasible by determining the appropriate slurry viscosity, spray head selection, and optimization of spraying conditions.
Multiple Degradation Phenomena in Polymer Electrolyte Fuel Cell Operation With Dead-Ended Anode
Authors: Matsuura Toyoaki , Siegel Jason B. , Chen Jixin , Stefanopoulou Anna G.
Published: March 2012

Dead-ended anode (DEA) operation of Polymer Electrolyte Fuel Cell (PEFC) can simplify the fuel cell auxiliary and reduce system cost, however durability and lifetime in this operating mode requires further study. In this work, we investigate the electrode and membrane degradations of one 50 cm2 active area fuel cell under DEA operation using a combination of post-mortem evaluation and in-situ performance evaluation protocol. We experimentally identify multiple degradation patterns using a cell which we have previously modeled and experimentally verified the spatio-temporal patterns associated with the anode water flooding and nitrogen blanketing. The change in cell voltage and internal resistance during operation and ex situ Scanning Electron Microscope (SEM) images of aged electrode/membrane are analysed to determine and characterize the degradation of the membrane electrode assembly (MEA). Chemical degradations including carbon corrosion in the catalyst layer and membrane decomposition are found after operating the cell with a DEA. Mechanical degradations including membrane delamination are also observed. Unique features of DEA operation including fuel starvation/nitrogen blanketing in the anode and uneven local water/current distribution, are considered as culprits for degradation.
Direct Spraying of Catalyst Inks for PEMFC Electrode Manufacturing
Authors: Hoffman Casey J. , Walczyk Daniel F.
Published: March 2012

Automated manufacturing techniques are needed to reduce production costs for polymer electrolyte membrane (PEM) fuel cell electrodes. The work presented in this paper focuses on the use of a low pressure, low volume direct spray valve that uses air pressure to atomize fluids and transfer them to a gas diffusion layer (GDL) to produce a gas diffusion electrode (GDE). Two of these electrodes would then be joined with a polymer electrolyte membrane to produce a fuel cell membrane electrode assembly (MEA). Accurate and reproducible deposition methods such as this will result in less wasted materials, especially platinum, and increased throughput compared to common laboratory-scale techniques such as paint brushing and Mayer-rod coating. In this study, the production of inks will be discussed including a catalyst ink containing platinum nano-particles supported on carbon (20% loading by weight) and a similar analog ink which is identical except for that it does not contain the platinum. Two different substrates, mylar transparency film and actual carbon paper GDL substrate will be used and presented in this study. Ink rheology (viscosity, solids content, etc.) will also be discussed as it pertains to optimizing spray pattern uniformity and process efficiency. Initial results of thickness measurements which are used for determining uniformity and the required overlapping of multiple coats will be presented. In addition, a comparison of scanning electron microscopy (SEM) images of electrode surface structures prepared by mayer-rod and spraying will be shown. A brief discussion of the future work planned by the authors in order to study the effects of processing variables on actual fuel cell performance will also be given.
Semi-Empirical Flow and Pressure Distribution Modeling of a Flowing Electrolyte Direct Methanol Fuel Cell Stack
Authors: Kablou Yashar , Cruickshank Cynthia A. , Ouellette David , Matida Edgar
Published: March 2012

The pressure distribution across a flowing electrolyte - direct methanol fuel cell (FE-DMFC) stack was numerically evaluated using semi-empirical equations for friction and loss coefficients. The stack is considered to have “U” shape manifold design with parallel serpentine fuel channels. The flow is assumed to be laminar and the flow rate in each cell of the stack is determined using the Hardy-Cross method. The results show that, the mass flow rate of methanol is greater at the inlet and declines as the fuel travels further within the stack manifolds. It was further discovered that pressure drop inside the inlet manifolds increases with stack length while the pressure drop inside the individual cell channels tend to decrease with stack length. Finally, the stack power output is estimated by assuming single cell power outputs at various operating current densities and methanol inlet flow rates based on experimental data obtained from the literature.
Network Model for the Analysis and Diagnosis of Large SOFC Stacks
Authors: Verda Vittorio , Sciacovelli Adriano , Colella Francesco
Published: March 2012

In this paper a detailed model for the simulation of large tubular solid oxide fuel cell stacks is presented. The model solves heat transfer, current transfer and fluid flow in the stack. The effect of mass transfer is accounted by means of the information provided by a CFD model of a single cell. The approach used to build the model allows one to simulate large stacks, predicting the temperature, current and mass flow rate profiles, which is particularly suitable for diagnosis purpose. Here the analysis is mainly focused on the thermal model. The model is first applied to a single cell in order to compare the results with a full CFD model. Then the analysis of a large stack is proposed and the results are compared with some available measurements.
IGFC Response to Initial Fuel Cell Load for Various Syngas Compositions
Authors: Tucker David , Hughes Dimitri O. , Haynes Comas L.
Published: March 2012

The system response to an initial electric load of the fuel cell during the startup of a direct-fired fuel cell turbine power system was studied using the Hybrid Performance (Hyper) project hardware-based simulation facility at the U.S. Department of Energy, National Energy Technology Laboratory for a range of input fuel compositions. The facility was brought to a steady condition at a temperature deemed adequate to minimize stress on the fuel cell during the initial load transient. A 1D distributed fuel cell model operating in real-time was used to produce individual cell transient temperature profiles during the course of the load change. The process was conducted with humidified hydrogen, and then repeated with various syngas compositions representative of different gasifier technologies. The results provide insight into control strategy requirements for mitigation of expected fuel cell failure modes relevant to available gasifier technology.
Characterizing Performance of a PEM Fuel Cell for a CMET Balloon
Authors: McKahn Denise A. , McMackin Whitney
Published: March 2012

We present the design of a multi-cell, low temperature PEM fuel cell for controlled meteorological balloons. Critical system design parameters that distinguish this application are the lack of reactant humidification and cooling due to the low power production, high required power mass-density and relatively short flight durations. The cell is supplied with a pressure regulated and dead ended anode, and flow controlled cathode at variable air stoichiometry. The cell is not heated and allowed to operate with unregulated temperature. Our prototype cell was capable of achieving power densities of 43 mW/cm2/cell or 5.4 mW/g. The cell polarization performance of large format PEM fuel cell stacks is an order of magnitude greater than for miniature PEM fuel cells. These performance discrepancies are a result of cell design, system architecture, and reactant and thermal management, indicating that there are significant gains to be made in these domains. We then present design modifications intended to enable the miniature PEM fuel cell to achieve power densities of 13 mW/g, indicating that additional performance gains must be made with improvements in operating conditions targeting achievable power densities of standard PEM fuel cells.
Design of Air, Water, Temperature and Hydrogen Controls for a PEM Fuel Cell System
Authors: Ahn Jong-Woo , He Jinglin , Choe Song-Yul
Published: March 2012

Polymer electrolyte membrane (PEM) fuel cell is the potential power source for vehicle applications, where supply of fuels and rejection of heat play significant roles in ensuring performance and durability. Operations of the fuel cells require four subsystems, air supply system, water and thermal management and hydrogen delivery system. Air supply system consists of a blower and a gas-to-gas humidifier. The air is supplied to the stack by the blower and humidified by a gas-to-gas humidifier using stack exhaust gas. Controls for the air supply system are designed based on a static feed-forward control and a state feedback control with integrator to maintain the oxygen excess ratio at a desired level regardless of any load applied. Flow rates of air controlled by a voltage of an electric motor driving a blower should be able to supply oxygen to dynamically follow changes of loads, whereby oxygen excess rate should be kept at a level that prevents oxygen starvation. At the same time, water in the stack should be maintained optimally to keep from low proton conductivity and water flooding in porous materials. Therefore, supplying air is humidified with a humidifier that captures moistures exiting the stack. In order to manipulate the amount of humidity, we propose to use an extra bypass valve, which opening is controlled to optimally maintain humidification of the membrane and avoid water flooding. Thermal management system consists of two thermal circuits because of cooling effectiveness, where the inner thermal circuit is made of a bypass valve, a heat exchanger, a water reservoir and a water pump, while the outer thermal circuit is made of a radiator along with a fan, a coolant reservoir and a pump. In order to maintain the stack working temperature at a desired temperature and reduce parasitic powers, a state feedback controller with integrator is employed. Fuel delivery system is a hybridized one that consists of two recirculation lines with an ejector and a blow in order to increase efficiency of fuel usage. The supply line is made of a hydrogen tank, a flow control valve and a low pressure regulator. Controls are designed to track a flow rate where pressure is kept at constant and purging operations are allowed. In this paper, controls for four subsystems of fuel cell system were proposed and examined on a dynamic one dimensional model for a stack that considers non isothermal and two-phase effects. Optimized state feedback controllers with integrator and observers are used to improve control performances and results are presented.
Experimental Study of Electrical Switching Characteristics of Vanadium Oxide Thin Films on Bipolar Plates for Improving Thaw-at-Start
Authors: Jung Hye-Mi , Noh Jung-Hun , Um Sukkee
Published: March 2012

The ultimate goal of cold start of hydrogen-powered polymer electrolyte fuel cell vehicles is to minimize the significant system thaw energy requirement and to achieve the short time period desired for freeze start (e.g. less than 30 seconds) in a subfreezing environment. As part of an effort to improve cold start capability for fuel cell vehicles, this work presents a new thaw-at-start strategy using electrical characteristics of vanadium oxide thin films as self-heating source at sub-zero temperature. Vanadium-based thin film coated on the surface of flat bipolar plates (e.g. carbon-based graphite and metallic bipolar plates) have been synthesized by a dip-coating method via aqueous sol-gel chemistry. Subsequently, the detailed in-/ex-situ analyses of the thin films have been carried out using diverse diagnostic techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to investigate the chemical composition, crystallinity, and microstructure. In addition, electrical switching characteristics of the thin films on bipolar plates was cautiously observed over a temperature range from −20°C to 80°C by means of 4-point probes installed in a thermo -hygrostat. By doing so, it has been possible to correctly infer the relationship between a tendency of the thermally-induced electrical switching hysteresis and bipolar plate materials. Also, comprehensive theoretical study on the basis of the experimental results have been performed to estimate the heat dissipation rate by Joule heating from the solid thin films on bipolar plates for the rapid cold-start operation of fuel cell vehicles.
A Degradation Model for Degradation of Solid Oxide Fuel Cell Anodes due to Impurities in Coal Syngas
Authors: Cayan Fatma N. , Pakalapati Suryanarayana R. , Celik Ismail
Published: March 2012

A new phenomenological one-dimensional model is formulated to simulate the typical degradation patterns observed in Solid Oxide Fuel Cell (SOFC) anodes due to coal syngas contaminants such as arsenic (As) and phosphorous (P). The model includes gas phase diffusion and surface diffusion within the anode and the adsorption reactions on the surface of the Ni-YSZ-based anode. Model parameters such as reaction rate constants for the adsorption reactions are obtained through indirect calibration to match the degradation rates reported in the literature for arsine (AsH3), phosphine (PH3) and hydrogen sulfide (H2S) under accelerated testing conditions. Results from the model demonstrate that the deposition of the impurity on the Ni catalyst starts near the fuel channel/anode interface and slowly moves toward the active anode/electrolyte interface as observed in the experiments. Parametric studies performed at different impurity concentrations and operating temperatures show that the coverage rate increases with increasing temperature and impurity concentration, as expected. The calibrated model was then used for prediction of the performance curves at different impurity concentrations and operating temperatures. Good agreement is obtained between the predicted results and the experimental data reported in the literature.
Parametric Analysis of the Cathode Catalyst Layer of Proton Exchange Membrane Fuel Cells Using Artificial Neural Network
Authors: Khajeh-Hosseini-Dalasm N. , Ahadian S. , Fushinobu K. , Okazaki K.
Published: March 2012

A mathematical model was developed to study the cathode catalyst layer (CL) performance of a proton exchange membrane fuel cell (PEMFC). A number of CL parameters affecting its performance are implemented into the CL agglomerate model. These parameters are: saturation and eight structural parameters, i.e., ionomer film thickness covering the agglomerate, agglomerate radius, platinum and carbon loading, membrane content, gas diffusion layer penetration content and CL thickness. An artificial neural network (ANN) approach along with statistical methods was used for modeling, prediction, and analysis of the CL performance, which is determined by activation over-potential. The ANN was constructed to develop a relationship between the named (input) parameters and activation overpotential. An statistical analysis, namely, analysis of means (ANOM) was performed on the data obtained by the trained ANN and resulted in the main effect of each input parameter, sensitivity factors of structural parameters and their mutual combination.
Performance of PEM Fuel Cells at Sub-Freezing Temperatures
Authors: Mishler Jeffrey , Wang Yun , Lujan Roger , Borup Rodney L. , Mukundan Rangachary
Published: March 2012

The ability of the polymer electrolyte fuel cell to start up at sub-freezing temperatures, also called cold start, is paramount for its transportation application. The ability to cold start is governed by whether the fuel cell is able to overcome 0 °C before the produced ice terminates the electrochemical reaction. Therefore, fundamental understanding of the fuel cell performance at sub-freezing temperatures is highly needed to improve its cold start characteristics. In this work, we investigated the fuel cell sub-freezing operation through experimental investigation. PEFCs using various membranes and catalyst layer configurations were constructed. In particular, various catalyst layer thickness, ionomer-catalyst ratios, RHs, and membrane thicknesses were considered, and their influence on fuel cell cold start performance was investigated. The voltage, current, high-frequency resistance, and the coulombs passed before failure were recorded and presented to reveal the fuel cell cold start operation. Further, a simplified analysis of cold start was performed based on an electrode model. The cell voltage evolution and solid water build up were predicted and compared with the experimental data.
Graphene Reinforced Composite Bipolar Plate for Polymer Electrolyte Membrane Fuel Cell
Authors: Kakati Biraj Kumar , Ghosh Avijit , Verma Anil
Published: March 2012

Composite bipolar plates for polymer electrolyte membrane fuel cell (PEMFC) were developed by compression molding technique using vinyl ester resin as a binder and natural graphite, carbon black, and carbon fiber as conductive reinforcements. The developed bipolar plates were characterized for electrical conductivity, flexural strength, deflection at mid-span, hydrogen permeability, and morphology. The in-plane and through-plane electrical conductivities of the composite bipolar plate (VER:25%;CB:5%;CF:5%;NG:65%) were 355.05 and 95.96 S·cm−1, respectively. The flexural strength of the same bipolar plate was 53.50 MPa with a deflection of 5.37%. The hydrogen permeability of the bipolar plate was in the order of 10−9 cm3·cm−1·s−1 at 50°C. The overall properties of the composite bipolar plate were found to achieve the benchmark set by USA-Department of Energy. However, the through-plane electrical conductivity of the above composite was edge below the target value. Therefore, graphene, being one of the most electrical conductive materials, has been reinforced into the composite bipolar plate. The results were very encouraging as 1% graphene reinforcement increased the in-plane and through-plane electrical conductivities of the bipolar plate by around 6 and 35%, respectively. The performance of a PEMFC was evaluated using the developed bipolar plate in in-situ condition.