bluuebunny/crossref_metadata_2025 huggingface dataset:
Melatonin Counteracts Alterations in Oxidative Metabolism and Cell Viability Induced by Intracellular Calcium Overload in Human Leucocytes: Changes with Age
Authors: Espino Javier , Bejarano Ignacio , Paredes Sergio D. , González David , Barriga Carmen , Reiter Russel J. , Pariente José A. , Rodríguez Ana B.
Published: February 2010

Abstract:  Ageing is associated with an increased production of free radicals and alterations in the mechanisms of adaptation to oxidative stress. In fact, the free radical theory of ageing proposes that deleterious actions of free radicals are responsible for the functional deterioration associated with ageing. Moreover, a close relationship exists between calcium homeostasis and oxidative stress. The current work was aimed at proving that intracellular calcium overload induced by N‐formyl‐methionyl‐leucyl‐phenylalanine (FMLP) and/or thapsigargin leads to oxidative stress. We additionally examined the effect of melatonin on the levels of reactive oxygen species (ROS) and cell viability in human leucocytes collected from young (20–30‐year‐old) and elderly (65–75‐year‐old) individuals under both basal and oxidative stress‐induced conditions. Treatments with 10 nM FMLP and/or 1 μM thapsigargin induced a transient increase in cytosolic free‐calcium concentration ([Ca2 + ]c) in human leucocytes due to calcium release from internal stores, and led in turn to oxidative stress, as assessed by intracellular ROS measurement. Non‐treated leucocytes from aged individuals exhibited higher ROS levels and lower rates of cell survival when compared to leucocytes from young individuals. Similar results were obtained in FMLP and/or thapsigargin‐treated leucocytes from elderly individuals when compared to those from the young individuals. Melatonin treatment significantly reduced both hydrogen peroxide (H2O2) and superoxide anion levels, likely due to its free‐radical scavenging properties, and enhanced leucocyte viability in both age groups. Therefore, melatonin may be a useful tool for the treatment of disease states and processes where an excessive production of oxidative damage occurs.
L‐type calcium channel as a cardiac oxygen sensor
Authors: Movafagh Shahrzad , Morad Martin
Published: February 2010

Acute oxygen sensing in the heart is thought to occur through redox regulation and phosphorylation of membrane channels. Here we report a novel O2‐sensing mechanism involving the C‐terminus of the L‐type Ca2+ channel and regulated by PKA phosphorylation. In patch‐clamped myocytes, oxygen deprivation decreased ICa within 40 s. The suppressive effect of anoxia was relieved by PKA‐mediated phosphorylation only when Ca2+ was the charge carrier, whereas phosphorylated IBa remained sensitive to O2 withdrawal. Suppression of Ca2+ release by thapsigargin did not alter the response of ICa to anoxia, suggesting a mandatory role for Ca2+ influx and not Ca2+‐induced Ca2+ release (CICR) in O2 regulation of the channel. Consistent with this idea, mutation of 80 amino acids in the Ca2+/CaM‐binding domain of the recombinant α1C subunit that removes Ca2+ dependent inactivation (CDI) abolished O2 sensitivity of the channel. Our findings suggest that the Ca2+/CaM binding domain of the L‐type Ca2+ may represent a molecular site for O2 sensing of the heart.
Application of Chlorite Geothermometry to Hydrothermal Alteration in Toyoha Geothermal System, Southwestern Hokkaido, Japan
Authors: Inoue Atsuyuki , Kurokawa Kyohei , Hatta Tamao
Published: February 2010

In this study, we applied chemical geothermometers to the estimation of formation temperatures of chlorites from various types of hydrothermally altered rocks in the Toyoha geothermal field, using core samples from six drill holes (TH‐2 to TH‐7) together with wasted ore samples from Toyoha vein‐type ore deposit. Based on the preliminary examination of mineral assemblages by X‐ray powder diffraction and optical microscopy, hydrothermal alteration observed through the drill holes was classified into four types of alteration zones: propylitic, mixed‐layer minerals, kaolin minerals, and ore mineralized zones. The mineral assemblage of the ore mineralized zone observed through TH‐2, TH‐4, and TH‐6 is similar to those of Toyoha ore veins reported previously. The Fe3+/ΣFe ratios of chlorites were determined by X‐ray photoelectron spectroscopy (XPS), in addition to the usual microprobe analyses. The ratios ranged from 0.20–0.26 for chlorites from the propylitic alteration zone and from 0.13 to 0.17 for those from the ore mineralized zone associated with sulfide minerals. After correcting the Fe3+ contents in the octahedral sites of chlorite structures, we obtained acceptable temperatures of the chlorite formation by application of geothermometers, for instance, a similar range of 150–300°C for chlorites from either the propylitic zone or the ore mineralized zone developed through TH‐2, TH‐4, and TH‐6. Chlorites from the ore mineralized zone proximal to the Toyoha deposit are characterized by high Fe and Mn contents compared to the propylitic chlorites, which is similar to the Toyoha vein‐filling chlorites; the formation temperatures were close to both the homogenization temperatures of fluid inclusions and the present subsurface temperatures measured through drill holes. Chlorites from the Toyoha ore veins, however, gave slightly higher formation temperatures (180–350°C) than those of chlorites from the ore mineralized zone in the drill cores. This suggests that several types of hydrothermal alteration occurred at different stages in the Toyoha geothermal field and the composition of product chlorite was controlled not only by the temperature but also the composition of fluid related to the formation. Reliable estimation of temperature for the chlorite formation provides basic information on evaluating correctly other physicochemical conditions prevalent at the formation.
Adjunctive antidepressant use and its clinical correlates in patients with schizophrenia: an East Asia multicenter comparative prescribing audit
Authors: Sim Kang , Fujii Senta , Yang Shu‐yu , Chong Mian‐Yoon , Ungvari Gabor S , Si Tianmei , He Yan Ling , Chung Eun Kee , Shinfuku Naotaka , Kua Ee Heok , Tan Chay Hoon
Published: February 2010

Aims: Previous pharmacoepidemiological studies have highlighted considerable rates of adjunctive psychotropic medication prescriptions in patients with schizophrenia, including the use of adjunctive antidepressants, but this has not previously been studied in East Asia. This study examined the frequency of adjunctive antidepressant prescriptions in patients with schizophrenia and their clinical correlates in six East Asian countries and territories.

Methods: Co‐prescription of antidepressants for a sample of 2,136 patients with schizophrenia from six countries and territories (China, Hong Kong, Korea, Japan, Taiwan, Singapore) were evaluated in 2004 using a standardized protocol.

Results: Adjunctive antidepressant prescriptions were found in 6.5% (n=139) of the patients with some intercountry differences. Co‐prescription of antidepressants was significantly associated with younger age, shorter duration of index admission, electroconvulsive therapy in the past month, less likelihood of manifesting disorganized speech, and prescription of first generation antipsychotic drugs. Concomitant antidepressant prescription was associated with greater weight and increased number of adverse events including constipation, sedation and sexual dysfunction. On multivariate analysis, it was found that country, younger age and history of electroconvulsive therapy for the past month were significantly associated with adjunctive antidepressant use.

Discussion: Adjunctive antidepressant use for schizophrenia in East Asia was associated with a number of demographic, clinical, and treatment variables. The association with greater weight and more adverse events reinforces the notion that prescription of adjunctive psychotropic medication is not without its costs. The challenge for the clinician is to constantly reevaluate the risk benefit ratio in the process of understanding the patient in a holistic context and to optimize the treatment regimes for patients with schizophrenia.
Duration of untreated psychosis, ethnicity, educational level, and gender in a multiethnic South‐East Asian country: report from Malaysia schizophrenia registry
Authors: Chee K.Y. , Muhammad Dain N.A. , Abdul Aziz S. , Abdullah A.A.
Published: February 2010

Introduction: Duration of untreated psychosis (DUP) determines the outcome of schizophrenia. Previously, there was no information about the DUP among patients in Malaysia with schizophrenia. The aim of the present study was to investigate the association between DUP and patients' demographic, social cultural background and clinical features.

Method: This is a cross‐sectional study on patients who presented with first episode schizophrenia. Data from 74 primary care centers and hospitals between 1 January 2003 and 31 December 2007 were included in the analysis. All patients with first‐episode schizophrenia were enrolled in the study.

Results: The mean DUP was 37.6 months. The indigenous community appeared to have the shortest DUP compared to the Malay, Chinese and Indian communities. Female, people with lower educational level, and comorbidity with medical illness during contact had longer DUP.

Discussion: DUP in this multiethnicity country was found to be significantly short among the indigenous people, which may sugest that traditional values and strong family and community ties shorten the DUP. Educational level may need to be further investigated, because as upgrading the general educational level could lead to shorter DUP among the patients as well.
A hypoxia complement differentiates the muscle response to endurance exercise
Authors: Schmutz Silvia , Däpp Christoph , Wittwer Matthias , Durieux Anne‐Cécile , Mueller Matthias , Weinstein Felix , Vogt Michael , Hoppeler Hans , Flück Martin
Published: February 2010

Metabolic stress is believed to constitute an important signal for training‐induced adjustments of gene expression and oxidative capacity in skeletal muscle. We hypothesized that the effects of endurance training on expression of muscle‐relevant transcripts and ultrastructure would be specifically modified by a hypoxia complement during exercise due to enhanced glycolytic strain. Endurance training of untrained male subjects in conditions of hypoxia increased subsarcolemmal mitochondrial density in the recruited vastus lateralis muscle and power output in hypoxia more than training in normoxia, i.e. 169 versus 91% and 10 versus 6%, respectively, and tended to differentially elevate sarcoplasmic volume density (42 versus 20%, P= 0.07). The hypoxia‐specific ultrastructural adjustments with training corresponded to differential regulation of the muscle transcriptome by single and repeated exercise between both oxygenation conditions. Fine‐tuning by exercise in hypoxia comprised gene ontologies connected to energy provision by glycolysis and fat metabolism in mitochondria, remodelling of capillaries and the extracellular matrix, and cell cycle regulation, but not fibre structure. In the untrained state, the transcriptome response during the first 24 h of recovery from a single exercise bout correlated positively with changes in arterial oxygen saturation during exercise and negatively with blood lactate. This correspondence was inverted in the trained state. The observations highlight that the expression response of myocellular energy pathways to endurance work is graded with regard to metabolic stress and the training state. The exposed mechanistic relationship implies that the altitude specificity of improvements in aerobic performance with a ‘living low–training high’ regime has a myocellular basis.
Heat Transfer in Microchannels With Suspended Solid Particles: Lattice-Boltzmann Based Computations
Authors: Khiabani Reza H. , Joshi Yogendra , Aidun Cyrus K.
Published: February 2010

This paper presents computational results on the effect of fixed or suspended cylindrical solid particles on heat transfer in a channel flow. The computational method is based on the solution of the lattice-Boltzmann equation for the fluid flow, coupled with the energy equation for thermal transport and the Newtonian dynamic equations for direct simulation of suspended particle transport. The effects of Reynolds number, particle-to-channel size ratio, and the eccentricity of the particle on heat transfer from the channel walls for single and multi-particles are presented. The multi-particle flow condition represents a case with solid particles suspended in the cooling medium, such as in micro/nanofluids, to augment heat transfer. The results provide insight into the mechanism by which suspended particles can change the rate of heat transfer in a microchannel.
Segmental Stiffness Achieved by Three Types of Instrumented Fixation for Unstable Lumbar Spondylolytic Motion Segments
Authors: Pfeiffer Ferris M. , Choma Theodore J. , Vallurupalli Santaram , Mannering Irene H.
Published: February 2010

Spondylolysis is a defect in the vertebral pars interarticularis. Its cause may be developmental or due to mechanical etiologies such as trauma. Most childhood and adolescent spondylolisthesis (defined as a slip of one vertebrae relative to another) is associated with spondylolysis of the pars interarticularis at the L5–S1 motion segment.
Pulmonary Delivery of Isoproterenol Aerosol Generated With Silicon-Based MHz Ultrasonic Nozzles
Authors: Tsai S. C. , Mao R. W. , Mukai D. , Lin S. K. , Yang J. Y. , Wang N. , Wilson A. F. , Brenner M. , George S. C. , Wang P. , Tsai C. S.
Published: February 2010

Monodisperse micron-sized aerosol is ideal for pulmonary drug delivery. This paper reports delivery of monodisperse aerosol of medicinal droplets generated by MHz ultrasonic nozzles using an anatomically realistic upper airway model. The MHz ultrasonic nozzle is fabricated using MEMS technology, and comprised of a piezoelectric drive section and a silicon resonator of multiple Fourier horns (see Fig. 1) [1]. The dissolved medication is pumped into a central channel (200×200 μm2) inside the nozzle and exits at the nozzle tip that vibrates longitudinally at the nozzle resonant frequency. The novel design of multiple horns facilitates generation of a column of monodisperse droplets at electric drive power as low as 15mW [1]. Monodisperse ethanol droplets 2.4 μm and water droplets 4.5 μm in diameter have been produced, respectively, using 1.5 MHz and 1.0 MHz nozzles. We used an aqueous solution of 25mg/ml (2.5wt%) β2-agonist (isoproterenol) for generation of monodisperse droplets using the 1.0 MHz ultrasonic nozzles. A yield of >54% (to the lower airways on total amount of inhaled isoproterenol basis), significantly higher than the reported highest lower airways deposition (32%) using metered-dose-inhalers (MDIs) [2], has been accomplished.
Arthroscopic Challenges in Treating Rotator Cuff Tears of the Shoulder
Authors: Park Maxwell C.
Published: February 2010

Rotator cuff tears can be the source of significant morbidity. Impingement syndrome involving repetitive and prolonged mechanical irritation of the rotator cuff against the roof of the shoulder creates a progression of disease. Chronic tendon inflammation can lead to structural loss of integrity, leading to partial tears, and if left unchecked, full-thickness tears. Currently, the surgeon has the ability to repair full-thickness tears using minimally invasive techniques. However, the persistent tear rate after repair is remarkably high, more than 50% in some studies. One surgical goal is to alter progression of disease, and repair partial-thickness tears, for example. Another goal is to optimize the healing environment with the repair construct itself, accounting for biomechanical considerations. When using an arthroscopic approach, the challenges for treating partial- versus full-thickness tears varies significantly given anatomic restrictions—particularly, during repair of partial-thickness tears, the surgeon is “blind” for portions of the procedure as the arthroscope is typically placed intra-articularly, while instruments are passed from above the tendon, extra-articularly. Ideally, new technologies can be developed to optimize rotator cuff repair and healing in this setting.
Soft Tissue Fixation and Implant Development: Regulatory
Authors: Kolber Michael
Published: February 2010

OVERVIEW: a. The Art of Regulatory Science. What engineers should know about the regulatory process. Getting your class 1 or 2 device market cleared in the US. b. What about Europe. CE mark, Notified Bodies, Competent Authorities and other interesting facts. c. Regulatory pitfalls.
Soft Tissue Fixation and Implant Development: Development
Authors: Miller Todd
Published: February 2010

Development: This presentation will discuss approaches to vetting new ideas for soft tissue fixation, establishing a concept to pursue, and moving a concept into new product development.
Spinal Surgery and Implants
Authors: Bhatia Nitin N.
Published: February 2010

Provide an introduction and overview of the major aspects and challenges of bringing a new spinal implant or product from concept to market.
Development of a Novel Micro-Manipulation Device and Its Simulation Using COMSOL
Authors: Chen Hsiu-hung , Gao Dayong
Published: February 2010

The manipulation of particles in fluids using microfluidic devices is a fundamental task in Lab-on-a-Chip applications. Grooved structures have been widely studied in particle handling and fluid mixing in microfluidic channel systems. In this study, we report use of patterning flows produced by a series of grooved surfaces with different geometrical setups integrated into a microfluidic device, to continuously manipulate the flowing particles, ranging from 6 to 20 μm in diameters, of comparable sizes to the depth of the channel. COMSOL, a multiphysics modeling software that can help predict engineering trends, is used to systematically quantify the following parameters: 1) channel depth, 2) groove width, 3) groove depth, 4) groove angle, and 5) flow speed, which may affect the performance of separation for flowing particles inside the channel. The device is fabricated using softlithographic techniques and is composed of inlets, microfluidic channels, and outlets for loading, manipulating and retrieving cell suspensions, respectively. Experimental results indicated that the particles were evenly distributed in the entrance of the microchannel and illustrate patterns of enriching, focusing, or size-selective profiles after passing through the grooved area. The preliminary simulation results also demonstrated that particles tend to bias towards the sidewall after flowing through the grooves.
Evolution of Technology in Rotator Cuff Repair
Authors: Schlegel Theodore F.
Published: February 2010

Key Questions — Learning Objectives: A. What has lead to the historical progress with rotator cuff repairs? B. Is there basic science supporting an “all-arthroscopic” rotator cuff repair? C. What are the future technologies that are promising to enhance rotator cuff healing?
Development of Polymer-Based Materials for Proton Exchange Membrane Fuel Cell Bipolar Plates: Ways to Increase Through-Plane Electrical Conductivity and to Decrease Gas Permeability
Authors: Mighri Frej , Nguyen Luc
Published: February 2010

This research work aimed at developing, by twinscrew extrusion process, electrically conductive sheets for proton exchange membrane fuel cell (PEMFC) bipolar plates. For this, a series of highly conductive blends were carefully formulated from a co-continuous mixture of polythylene terephthalate (PET)/polyvinylidene fluoride (PVDF) and high specific surface area carbon black (CB) and graphite (GR) conductive additives. Several major factors, such as CB/GR content, PVDF/PET composition and morphology, and also PET crystallinity were shown to have remarkable effects on these three main properties.
Reliability Model of SOFC Anode Material Under Thermo-Mechanical and Fuel Gas Contaminants Effects
Authors: Iqbal Gulfam , Guo Huang , Kang Bruce S.
Published: February 2010

Solid Oxide Fuel Cells (SOFCs) work under severe environment which deteriorate anode material properties and reduce its serviceable life. Besides electrochemical performance, structural integrity of SOFC anode is essential for successful long-term operation. SOFC anode material is subjected to stresses at high temperature, thermal and redox cycles and fuel gas contaminants effects on its structure during long-term operation. These mechanisms can degrade anode microstructure and decrease electrochemical performance and structural properties. In this research an anode material degradation model is developed and implemented in finite element analysis. The model incorporates thermo-mechanical and fuel gas contaminants degradation effects and predicts long-term structural integrity of SOFC anode. An analytical solution is also developed for button cell deformation under uniform pressure to establish correlation between the degradation model and experimental measurements. Preliminary results of the model application on the planar co-flow SOFC are also presented.
Rapid Startup of a PEM Fuel Cell From Subzero Temperature
Authors: Jiang Fangming , Wang Chao-Yang , Chen Ken S.
Published: February 2010

Current-ramping strategy can be used for rapid startup of PEM fuel cells (PEMFC) from subzero temperatures. Via numerical modeling a series of parametric studies are performed in this work to explore the optimum parameter set for current-ramping cold-start. A PEMFC with standard cell thermal mass, 0.4 J/cm2/K, starting from −30°C is of primary interest in this work. It is found that either a small initial current density (100mA/cm2) combined with an intermediate ramping rate, or a relatively large initial current density (200 mA/cm2) in combination with a small ramping rate, can lead to successful self-starts if the membrane electrode assembly (MEA) is sufficiently dry prior to startups. However, the current-ramping cold-start with a too small initial current density (≤50mA/cm2) is found to shut down with whatever the current-ramping rate. More rapid self-start can be achieved by increasing the initial current density, which is limited mainly by the initial water content in the MEA. Hence, keeping the MEA mildly hydrated prior to cold start can be favorable to the rapid current-ramping startup. This is particularly important for the rapid startup of next-generation PEMFCs with reduced thermal mass. Results show that a PEMFC with 0.2 J/cm2/K thermal mass and a relatively wetted MEA can be successfully started up from −30°C in a few seconds if it is possible to draw the current density as high as 1 A/cm2 right from the beginning.
Influence of Ammonia on Membrane-Electrode Assemblies in Polymer Electrolyte Fuel Cells
Authors: Zhang Xiaoyu , Preston Joshua , Pasaogullari Ugur , Molter Trent
Published: February 2010

An experimental investigation of contamination of polymer electrolyte fuel cell (PEFC) membranes and catalyst layers with ammonia (NH3) is reported. Cyclic voltammetry (CV) scans and electrochemical impedance spectroscopy (EIS) analyses show that trace amounts of ammonia can significantly contaminate both the polymer electrolyte membrane (PEM) and the catalyst layers. The results show that the catalyst layer contamination can be reversed under certain conditions, while the membrane recovery tends to be much slower, and permanent effects of ammonia contamination is observed. Mechanisms of contamination of the polymer electrolyte and catalyst layers, and performance degradation of the PEFC are also postulated.
LTNE Approach and Simulation for Anode-Supported SOFCs
Authors: Andersson Martin , Yuan Jinliang , Sunde´n Bengt , Wang Wei Guo
Published: February 2010

Fuel cells are promising for future energy systems, since they are energy efficient and, when hydrogen is used as fuel, there are no emissions of greenhouse gases. Fuel cells have during recent years various improvements, however the technology is still in the early phases of development, this can be noted by the lack of dominant design both for singe fuel cells, stacks and for entire fuel cell systems. In this study a CFD approach (COMSOL Multiphysics) is employed to investigate the effect on temperature distribution from inlet temperature, oxygen surplus, ionic conductivity and current density for an anode-supported intermediate temperature solid oxide fuel cell (IT-SOFC). The developed model is based on the governing equations of heat-, mass- and momentum transport. A local temperature non equilibrium (LTNE) approach is introduced to calculate the temperature distribution in the gas- and solid phase separately. The results show that the temperature increasing along the flow direction is controlled by the degree of surplus air. It is also found that the ohmic polarization in the electrolyte and the activation polarization in the anode and cathode have major influence on the performance. If a count flow approach is employed the inlet temperature for the fuel stream should be close to the outlet temperature for the air flow to avoid a too high temperature gradient.
Diurnal Temperature and Pressure Effects on Axial Turbo-Machinery Stability in Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems
Authors: Maclay James D. , Brouwer Jacob , Samuelsen G. Scott
Published: February 2010

A dynamic model of a 100 MW solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system has been developed and subjected to perturbations in diurnal ambient temperature and pressure as well as load sheds. The dynamic system responses monitored were the fuel cell electrolyte temperature, gas turbine shaft speed, turbine inlet temperature and compressor surge. Using a control strategy that primarily focuses on holding fuel cell electrolyte temperature constant and secondarily on maintaining gas turbine shaft speed, safe operation was found to occur for expected ambient pressure variation ranges and for ambient temperature variations up to 28 K, when tested non-simultaneously. When ambient temperature and pressure were varied simultaneously, stable operation was found to occur when the two are in phase but not when the two are out of phase. The latter case leads to shaft over-speed. Compressor surge was found to be more likely when the system is subjected to a load shed initiated at minimum ambient temperature rather than at maximum ambient temperature. Fuel cell electrolyte temperature was found to be well-controlled except in the case of shaft over-speeds. Turbine inlet temperature remained in safe bounds for all cases.
Numerical Analysis of the Effects of Processing Conditions on the Casting of High Temperature PEMFC Membrane Solutions
Authors: Bhamidipati Kanthi Latha , Harris Tequila A. L.
Published: February 2010

Polymer Electrolyte Membranes have numerous failure modes resulting from chemical, mechanical and thermal influences. The conventional state–of–the–art low temperature Nafion® membrane is susceptible to such failures due to its sensitivity to high temperatures and the presence of carbon monoxide (CO) in the reactant streams, which poisons the platinum catalyst at low temperatures. To circumvent these problems, novel, cost-effective membranes that operate at high temperatures (>120°C) and low humidity levels, such as phosphoric acid doped polybenzimidazole (PBI/PA) membranes, have been developed. However, an optimized manufacturing process for the PBI membranes is required to negate failure mechanisms that are mechanically and thermally induced; e.g., gas cross-over due to pinholes. This paper focuses on understanding defects arising in the fluid state during manufacturing, using Computational Fluid Dynamics (CFD) techniques. Simulations are performed to understand the effects of processing conditions (substrate velocity, inlet velocity and temperature) on the quality of the cast and pressure drop through the system. It is found that processing speeds affected both the cast quality and pressure drop, while temperature only affected the pressure drop.
Cathode Supported Honeycomb SOFCs for Intermediate Temperature Operation
Authors: Shimizu Sota , Yamaguchi Toshiaki , Fujishiro Yoshinobu , Awano Masanobu
Published: February 2010

A novel cathode supported honeycomb SOFC for intermediate temperature operation has been developed for application as a compact power module with quick start-up and shut-down functions. In this study, effects of resistances of glass sealant and anode current collector formed on the edge face of the honeycomb on the SOFC performance was investigated using an electrical simulation and a practical electrochemical evaluation method. Open circuit voltage (OCV) for a honeycomb SOFC unit was improved with an increase in the resistance glass sealant or a decrease in anode current collector. The fabricated honeycomb SOFC showed the OCV values above 1.05 V in a temperature range of 500 to 600 °C.
Performance Behavior for Solid Oxide Electrolysis Cells
Authors: Park Kwangjin , Kim Yu-Mi , Bae Joongmyeon
Published: February 2010

The performance behavior of solid oxide electrolysis cell (SOEC) was investigated. Initial performance of the cell as solid oxide fuel cell (SOFC) mode at 800°C was measured as 0.15 W/cm2. The SOEC showed the stable performance during 5 hours operation at −0.15A/cm2. The power for electrolysis was increased during the first 30 minutes operation due to the increase of internal resistance of the cell. After 5 hours operation, the degradation rate of SOEC performance was about 3% due to redox reaction of hydrogen electrode.
Using Staged Compression and Expansion to Enhance the Performance of a Gas Turbine Fuel Cell Hybrid System
Authors: VanOsdol John , Parsons Edward L.
Published: February 2010

It has long been recognized that the heat generated from a solid oxide fuel cell (SOFC) is adequate to drive an external heat engine. The combination of the fuel cell plus the heat engine is called a gas turbine fuel cell hybrid power generation system. In most hybrid systems the heat engine consists of a single compressor and single turbine, arranged in either a Brayton cycle or a recuperated Brayton cycle. One characteristic of hybrid power cycles is that the compression costs are substantial. When this cycle is used in a coal fired hybrid system that is configured with an isolated anode stream to isolate and compress CO2, the work to compress the cathode air can greatly exceed the work to compress the CO2. It has also been shown for this same system that using intercooled compression for the cathode air reduces this compression cost. Since there have been no exhaustive studies performed which quantify these effects it is not clear exactly how much reduction in compression cost is possible. In this work we compare three hybrid systems. The first systems has a single compressor and turbine, run at a low pressure ratio as a recuperated Brayton cycle and at high pressure ratio as a simple Brayton cycle (see Figure 1). We then alter the recuperated Brayton cycle using both staged compression and staged expansion. The second system is thus configured with two compressors and two turbines. For this system an intercooler is placed between the compressors and the fuel cell stack is divided into two stacks each followed by a turbine (see Figure 3). Similarly the third system divides the compression and expansion legs of the cycle again into three compressors with intercoolers, and three fuel cell stacks each followed by its own turbine (see Figure 5). As the system configuration is altered by successive divisions of both the compression and expansion legs of the thermal heat engine cycle, the system configuration is transformed from a simple Brayton cycle to a staged approximation to an Ericsson cycle. We show that this new configuration for the gas turbine fuel cell hybrid system not only reduces the high cost of compression, but it makes more heat available for auxiliary system operations. In coal fired systems these auxiliary operations would include pre heating coal for the gasification system, reheating the syngas after cooling or even heating steam for a bottoming cycle.
Development and Fabrication of Passive DMFCs
Authors: Li Peiwen , Dhar Nikesh , Dumay Anthony
Published: February 2010

The present work developed direct methanol fuel cells (DMFC) which have passive methanol feeding designs integrated. The design eliminated any mechanical parts in the DMFC and both methanol feeding and carbon dioxide exclusion on the anode side are accomplished through the special designs of the fluidic channels on current collecting plate on anode side. The anode of this DMFC is not submerged into liquid methanol. Therefore, the crossover of methanol and water from anode side to cathode side is significantly reduced, which relieves cathode water flooding dramatically. The cathode is designed to have air-breathing function that draws air by natural convection mass transfer method. A stable and lasting power output of 1.5 (mW/cm2) at 0.35 (V) was obtained for a single cell which operates at room temperature and completely eliminated with parasitic parts. It is expected that the methanol delivery and control in a passive mode through the presently developed special design of flow channels will greatly promote the development of cost-effective DMFCs with easy maintenance and high reliability.
Three Dimensional Non-Isothermal Model of a High Temperature PEM Fuel Cell
Authors: Shi Zhongying , Wang Xia
Published: February 2010

The proton exchange membrane (PEM) fuel cell using a polybenzimidazole (PBI) membrane operates between 120 °C and 180 °C, higher than the PEM fuel cell with a Nafion based membrane (lower than 80°C). Few studies have been conducted in the theoretical modeling of the PEM fuel cell with a PBI membrane. Experimental results have shown that the conductivity of a PBI membrane is affected by the phosphoric acid doping level, the cell operating temperature and the relative humidity. The fuel cell performance is thus affected by these parameters as well. The objective of this paper is to develop a three dimensional non-isothermal model to investigate the performance of the fuel cell with a PBI membrane. This new model considers influences of the relative humidity of the inlet air, the phosphoric acid doping level, and the operating temperature on the performance of fuel cells. The model is validated using the experimental data. A high oxygen concentration is found under the flow channel, as well as a high temperature region. The performance of fuel cells increases with the increase of the phosphoric doping level, temperature or relative humidity. The fuel cell performance is found to be more sensitive to the doping level and temperature changes, and less sensitive to the change of relative humidity.
High Temperature Mechanical Properties of a Crystallized BaO-B2O3-Al2O3-SiO2 Glass Ceramic for SOFC
Authors: Chang Hsiu-Tao , Lin Chih-Kuang , Liu Chien-Kuo
Published: February 2010

The high temperature mechanical properties in a glass-ceramic sealant of BaO-B2O3-Al2O3-SiO2 system was studied by four-point bending test at room temperature, 550°C, 600°C, 650°C, and 700°C, to investigate the variation of Young’s modulus, flexural strength, and stress relaxation. Weibull statistic analysis was applied to describe the fracture strength of the given glass ceramic. The crystalline phase was produced by controlled heat treatment and analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the flexural strength was enhanced at high temperatures when the testing temperature was below the glass transition temperature (Tg). This was presumably due to a crack healing effect taking place at high temperature. Significant stress relaxation for the given glass ceramic was observed to generate extremely large deformation without breaking the specimens when the testing temperature was set at 700°C.
Numerical Study of Different Anode and Cathode Channel Design on the Performance of Piezoelectric Proton Exchange Membrane Fuel Cells (PZT-PEMFCs)
Authors: Ma Hsiao-Kang , Wang Jyun-Sheng , Huang Shih-Han , Huang Yu-Jen , Kuo Yao-Zong
Published: February 2010

Previous studies [18, 19] have indicated that a novel ribbed PZT-PEMFC design has been developed, and that a three-dimensional, transitional model has been successfully built to study its major characteristics and fuel cell performance. A ribbed cathode channel can reduce internal resistance and double current density. At a higher PZT vibration frequency (f = 64 Hz), an air-breathing PZT-PEMFCs device compresses more oxygen into the catalyst layer and thus enhances the electrochemical reaction, resulting in a higher current output. On the other hand, the accumulated water vapor may be pumped out from the cathode channel during the compression process. Previous studies [11, 12] also demonstrated that serpentine and interdigitated flow fields could induce better performance than other flow fields in traditional PEMFCs, such as parallel and pin-type. In this study, the 3-D theoretical model of PZT-PEMFCs has been successfully developed in order to investigate the effects of anode and cathode channel designs on the performance of PZT-PEMFCs. Different cathode open area ratios, which are 80.5%, 63.2%, 47.9%, and 34.7%, were chosen for consideration of current density, PZT vibration frequency, and species concentrations. The results show that the cathode open area ratio of 47.9% is a better choice than 80.5%, 63.2%, or 34.7%. The results also establish that a lower vibration frequency may draw less air into the cathode channel, cause water vapor accumulation in the space of the electrochemical reaction area, and ultimately cause a drop in current over time. On the other hand, the designs of the anode flow field are found to have a big influence on the current density and water vapor profiles. The simulation results prove that the interdigitated flow field in the anode side, which is different from the traditional PEMFCs, performs much better than the serpentine and parallel flow fields.
Transparent PEM Fuel Cells for Direct Visualisation Experiments
Authors: Rosli M. I. , Pourkashanian M. , Ingham D. B. , Ma L. , Borman D. , Ismail M. S.
Published: February 2010

This paper reviews some of the previous research works on direct visualisation inside PEM fuel cells via a transparent single cell for the water behaviour investigation. Several papers which have employed the method have been selected and summarised and a comparison between the design of the cell, materials, methods and visual results are presented. The important aspects, advantages of the method and a summary on the previous work are discussed. Some initial work on transparent PEM fuel cell design using a single serpentine flow-field pattern is described. The results show that the direct visualisation via transparent PEM fuel cells could be one potential technique for investigating the water behavior inside the channels and a very promising way forward to provide useful data for validation in PEM fuel cell modelling and simulation.
Dynamics and Control of a Portable DMFC System
Authors: Zenith Federico , Krewer Ulrike
Published: February 2010

The current state of research on direct methanol fuel cells focuses heavily on the cell itself, with only a small minority of published articles about the management of the complete DMFC system. It is of particular importance to learn about the dynamics and control of such systems in order to provide autonomous and robust operation in spite of changing environmental conditions. We simulate and analyse a reference DMFC system consisting of, besides a model of the fuel cell, a mixer, coolers, separators, pumps and a fuel tank. A control analysis of a DMFC system is presented, to understand which variables are to be controlled by what means, and what constraints the system sets on the control loops. Some apparently negative phenomena can be beneficial to control performance: methanol cross-over stabilises the concentration dynamics and allows the usage of simple feedforward controllers. A portable DMFC system may be used in various environments, with very different environmental conditions. It is therefore explored how these conditions influence the system’s operation and control strategy, especially in regard to environmental temperature and humidity. The current implementation of the model has been designed to study the long-term transients, such as overall anode-loop water and energy holdups, assuming pseudo-steady state for most units.
Curvature and Strength of Ni-YSZ Solid Oxide Half-Cells After RedOx Treatments
Authors: Faes Antonin , Lund-Frandsen Henrik , Pihlatie Mikko , Kaiser Andreas , Goldstein Darlene R.
Published: February 2010

One of the main drawbacks of anode-supported solid oxide fuel cell technology is the limited capability to withstand reduction and oxidation (“RedOx”) of the Ni phase. This study compares the effect of RedOx cycles on curvature and strength of half-cells, composed of a Ni-YSZ support, a Ni-YSZ anode and an 8YSZ electrolyte. Five different treatments were studied: (i) reduction at 600°C, (ii) reduction at 1000°C, (iii) 1 RedOx cycle at 750°C, (iv) 5 RedOx cycles at 750°C and (v) 5 RedOx cycles at 600°C. The strength was measured by the ball-on-ring method, where it is calculated analytically from the force. In this calculation the thermal stresses have been estimated from the curvature of the half-cell. For each treatment, more than 30 samples were tested. About 20 ball-on-ring samples were laser cut from one original 12×12 cm2 half-cell. Curvature and porosity were measured for each sample before and after RedOx treatments. The first observations show that increasing the reduction temperature enhance strength but does not influence the curvature, whereas 1 RedOx cycle at 750°C increases the curvature without changing the strength. Consecutive RedOx cycles seem to decrease anode-supported cell strength, but this is coupled to lower porosity of the sample.
Through-Plane Permeability for Untreated and PTFE-Treated Gas Diffusion Layers in Proton Exchange Membrane Fuel Cells
Authors: Ismail Mohammed , Hughes Kevin , Ingham Derek , Ma Lin , Pourkashanian Mohamed , Rosli Masli
Published: February 2010

The through-plane permeability has been experimentally measured for untreated and PTFE-treated gas diffusion layers (GDLs), as used in proton exchange membrane fuel cells. Contrary to what the literature has previously shown, the results suggest that there exists an optimum value for the wet-proofing agent, PTFE, at which the though-plane permeability of the GDL is a maximum. The analysis that is undertaken to investigate the effect of the air compressibility shows that there is an underestimation in the through-plane permeability of the tested GDLs by of the order of 9% if the density of the air is assumed to be constant. Also, a non-dimensionlisation analysis shows that ignoring the non-Darcy effects at the maximum reported flow rates results in negligible errors for the untreated and treated GDLs.
Evaluation of the Performance Characteristics and Modeling of an Alkaline Fuel Cell
Authors: Mohan Sujith , Bade Shrestha S. O.
Published: February 2010

Alkaline fuel cells are one of the low cost types of fuel cells. In this contribution, the performance of an alkaline fuel cell was investigated by varying different operational parameters. The cell was tested under four different electrolyte concentrations and three different levels of anode flow rates. The results of the test revealed that the efficiency of the cell increases with the increase in electrolyte concentration. Anode flow rate was not found to have a considerable impact on the cell performance. Impedance spectroscopy has been conducted to validate the mathematical model and further investigate ohmic resistance, anode and cathode activation losses and mass transport losses. The optimal level of electrolyte concentration and anode flow rate for an alkaline fuel cell has been deduced through modeling & statistical analysis.
Evaluation of the Performance Characteristics of a Direct Methanol Fuel Cell With Multi Fuels
Authors: Mohan Sujith , Bade Shrestha S. O.
Published: February 2010

Direct methanol fuel cells are one of the alternate power sources for the field of power electronics because of their high energy density. The benefits of a fuel cell towards the environment can be greatly improved if the fuel used for its application comes from renewable sources. In this study, the performance of a direct methanol fuel cell was investigated under five different methanol concentrations. The effect of methanol concentration on the cell operating temperature is studied. Impedance spectroscopy was conducted to measure the ohmic, activation and mass transport losses for all concentrations. The cell performance was evaluated using methane and ethanol fuels and this was compared with methanol operation.
Dynamic Modeling of a Solid Oxide Fuel Cell Combined Heat and Power System With Thermal Storage for Commercial Building Applications
Authors: Nanaeda Kimihiro , Mueller Fabian , Brouwer Jacob , Samuelsen Scott
Published: February 2010

A dynamic model of an integrated solid oxide fuel cell (SOFC) combined heat and power (CHP) system has been developed. The model was developed by modifying a previously developed generic 5 kW simple-cycle SOFC system. Fuel cell model modifications include changes in methods and constants for estimating over-potentials to better simulate a modern anode-supported planar SOFC. In addition to scaling up and modifying the fuel cell model, a thermal energy storage (TES) tank, exhaust gas duct burner and hot water exhaust gas recuperator model were integrated into the system model. The fully integrated system model can effectively simulate an SOFC-CHP system and evaluate the system performance and efficiency in meeting building electricity and heating demand profiles. For the present effort, dynamic building electricity and heating data from a hotel operated in Orange County, southern California during the months of July and August 2008 were analyzed. Specifically, tradeoffs between SOFC performance and thermal energy storage have been investigated. The simulation results show that the SOFC-CHP system has the ability to follow the dynamic electrical load with appropriate system design and controls. Due to thermal power mismatch during electricity load-following operation, supplementary exhaust gas duct burner heat and/or a TES is required to independently dispatch the fuel cell power and meet the hotel heating demand. However, if the fuel cell is sufficiently sized, the system can achieve greater than 70% efficiency with only a small TES tank and without the need to fire the duct burner. The dynamic model and integrated SOFC-TES concept are shown to be useful for developing integrated CHP systems and to evaluate performance.