bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-Dose Vaccination of a Recombinant Parainfluenza Virus 5 Expressing NP from H5N1 Virus Provides Broad Immunity against Influenza A Viruses
Authors: Li Zhuo , Gabbard Jon D. , Mooney Alaina , Gao Xiudan , Chen Zhenhai , Place Ryan J. , Tompkins S. Mark , He Biao
Published: March 2013

Influenza viruses often evade host immunity via antigenic drift and shift despite previous influenza virus infection and/or vaccination. Vaccines that match circulating virus strains are needed for optimal protection. Development of a universal influenza virus vaccine providing broadly cross-protective immunity will be of great importance. The nucleoprotein (NP) of influenza A virus is highly conserved among all strains of influenza A viruses and has been explored as an antigen for developing a universal influenza virus vaccine. In this work, we generated a recombinant parainfluenza virus 5 (PIV5) containing NP from H5N1 (A/Vietnam/1203/2004), a highly pathogenic avian influenza (HPAI) virus, between HN and L (PIV5-NP-HN/L) and tested its efficacy. PIV5-NP-HN/L induced humoral and T cell responses in mice. A single inoculation of PIV5-NP-HN/L provided complete protection against lethal heterosubtypic H1N1 challenge and 50% protection against lethal H5N1 HPAI virus challenge. To improve efficacy, NP was inserted into different locations within the PIV5 genome. Recombinant PIV5 containing NP between F and SH (PIV5-NP-F/SH) or between SH and HN (PIV5-NP-SH/HN) provided better protection against H5N1 HPAI virus challenge than did PIV5-NP-HN/L. These results suggest that PIV5 expressing NP from H5N1 has the potential to be utilized as a universal influenza virus vaccine.
Influence of Antigen Insertion Site and Vector Dose on Immunogenicity and Protective Capacity in Sendai Virus-Based Human Parainfluenza Virus Type 3 Vaccines
Authors: Mason John N. , Elbahesh Husni , Russell Charles J.
Published: March 2013

Recombinant Sendai virus (rSeV) was used as a live, attenuated vaccine vector for intranasal inoculation and mucosal expression of the hemagglutinin-neuraminidase (HN) surface glycoprotein of human parainfluenza virus type 3 (HPIV3). Two vaccine candidates rSeV-HPIV3HN(P-M) and rSeV-HPIV3(F-HN) were constructed in which the HPIV3 HN open reading frame and an additional gene junction was inserted in the P-M and F-HN gene junctions of rSeV, respectively. The rSeV-HPIV3HN(P-M) virus was attenuated compared to rSeV-HPIV3(F-HN) in LLC-MK2 cells, and yet both vaccine candidates grew to similar extents in NHBE cells and in the respiratory tracts of cotton rats. These results suggest that
in vitro
vector growth in NHBE cells more accurately predicts virus yield in cotton rats than does growth in LLC-MK2 cells. Both vaccine vectors elicited high levels of serum neutralizing antibodies and conferred protection from HPIV3 challenge in cotton rats. Compared to vaccination with a high dose (2,000,000 PFU), intranasal inoculation with a low dose (200 PFU) resulted in a 10-fold decrease in vector growth in the nasal cavity and trachea and a 50-fold decrease in the lungs. However, low-dose vaccination resulted in only modest decreases in anti-HPIV3 antibodies in sera and was sufficient to confer complete protection from HPIV3 challenge. Varying the HPIV3 antigen insertion site and vector dose allowed fine-tuning of the
in vivo
growth and immunogenicity of rSeV-based vaccines, but all four vaccination strategies tested resulted in complete protection from HPIV3 challenge. These results highlight the versatility of the rSeV platform for developing intranasally administered respiratory virus vaccines.
Different Mechanisms Regulate Productive Herpes Simplex Virus 1 (HSV-1) and HSV-2 Infections in Adult Trigeminal Neurons
Authors: Bertke Andrea S. , Ma AyeAye , Margolis Mathew S. , Margolis Todd P.
Published: March 2013

Herpes simplex virus 1 (HSV-1) and HSV-2 establish latency in different neuronal subtypes (A5+ and KH10+) in murine trigeminal ganglia, results which correlate with restricted productive infection in these neurons
in vitro
. HSV-2 latency-associated transcript (LAT) contains a
cis
-acting regulatory element near the transcription start site that promotes productive infection in A5+ neurons and a second element in exon 1 that inhibits productive infection in KH10+ neurons. HSV-1 contains no such regulatory sequences, demonstrating different mechanisms for regulating productive HSV infection in neurons.
The Transmembrane Domain of the Adenovirus E3/19K Protein Acts as an Endoplasmic Reticulum Retention Signal and Contributes to Intracellular Sequestration of Major Histocompatibility Complex Class I Molecules
Authors: Sester Martina , Ruszics Zsolt , Mackley Emma , Burgert Hans-Gerhard
Published: March 2013

The human adenovirus E3/19K protein is a type I transmembrane glycoprotein of the endoplasmic reticulum (ER) that abrogates cell surface transport of major histocompatibility complex class I (MHC-I) and MHC-I-related chain A and B (MICA/B) molecules. Previous data suggested that E3/19K comprises two functional modules: a luminal domain for interaction with MHC-I and MICA/B molecules and a dilysine motif in the cytoplasmic tail that confers retrieval from the Golgi apparatus back to the ER. This study was prompted by the unexpected phenotype of an E3/19K molecule that was largely retained intracellularly despite having a mutated ER retrieval motif. To identify additional structural determinants responsible for ER localization, chimeric molecules were generated containing the luminal E3/19K domain and the cytoplasmic and/or transmembrane domain (TMD) of the cell surface protein MHC-I Kd. These chimeras were analyzed for transport, cell surface expression, and impact on MHC-I and MICA/B downregulation. As with the retrieval mutant, replacement of the cytoplasmic tail of E3/19K allowed only limited transport of the chimera to the cell surface. Efficient cell surface expression was achieved only by additionally replacing the TMD of E3/19K with that of MHC-I, suggesting that the E3/19K TMD may confer static ER retention. This was verified by ER retention of an MHC-I Kdmolecule with the TMD replaced by that of E3/19K. Thus, we have identified the E3/19K TMD as a novel functional element that mediates static ER retention, thereby increasing the concentration of E3/19K in the ER. Remarkably, the ER retrieval signal alone, without the E3/19K TMD, did not mediate efficient HLA downregulation, even in the context of infection. This suggests that the TMD is required together with the ER retrieval function to ensure efficient ER localization and transport inhibition of MHC-I and MICA/B molecules.
Polyprotein Context Regulates the Activity of Poliovirus 2C
ATPase
Bound to Bilayer Nanodiscs
Authors: Springer Courtney L. , Huntoon Harrison P. , Peersen Olve B.
Published: March 2013

Positive-strand RNA viruses generally replicate in large membrane-associated complexes. For poliovirus, these replication complexes are anchored to the membrane via the viral 2B, 2C, and 3A proteins. 2C is an AAA+ family ATPase that plays a key role in host cell membrane rearrangement, is a putative helicase, and is implicated in virion assembly and packaging. However, the membrane-binding characteristics of all of these viral proteins have made it difficult to elucidate their exact roles in virus replication. We show here that small lipid bilayers known as nanodiscs can be used to chaperone the
in vitro
expression of soluble poliovirus 2C, 2BC, and 2BC3AB polyproteins in a membrane-bound form. ATPase assays on these proteins show that the activity of the core 2C domain is stimulated ∼60-fold compared to the larger 2BC3AB polyprotein, with most of this stimulation occurring upon removal of 2B. The proteins are active over a wide range of salt concentrations, exhibit slight lipid headgroup dependence, and show significant stimulation by acetate. Our data lead to a model wherein the replication complex can be assembled with a minimally active form of 2C that then becomes fully activated by proteolytic cleavage from the adjacent 2B viroporin domain.
Piso-hamate hiatus syndrome in a patient with Riche-Cannieu anastomosis
Authors: Rovers Jörgen M P , Brekelmans Geert J F , Visser Leo H
Published: March 2013

Various nerve anastomoses and anatomic variants in the nervous system have been described. It is important to be familiar with these anastomoses because they can mimic several clinical conditions, possibly leading to misdiagnosis. We report the case of a patient who experienced progressive loss of strength in his left hand without sensory complaints. On neurological examination atrophy was seen in the thenar and first dorsal interosseous muscles of the left hand. Serial electrophysiological studies ruled out motor neuron disease. Electromyography and nerve conduction studies revealed a Riche-Cannieu anastomosis in the left hand. In combination with piso-hamate hiatus syndrome, this anastomosis explained the clinical condition of the patient. It is important to be aware of this anastomosis and this syndrome because it can mimic motor neuron disease.
Familial hypercholesterolaemia presenting with coronary artery disease in a young patient
Authors: Subramani K S , Kolhari Vikram B , Manjunath C N , Bhairappa Shivkumar
Published: March 2013

A man in his early 20s presented with an angina on exertion and postprandial angina. Upon examination, the patient had carotid artery bruit and multiple tendon xanthomas. His lipid profile showed a very high total and low-density lipoprotein cholesterol; treadmill test was strongly positive. Subsequent coronary angiogram revealed triple vessel disease. The patient underwent revascularisation and is on lipid lowering therapy.
Small is challenging; distal femur fracture management in an elderly lady with achondroplastic dwarfism
Authors: Murphy Colin G , Chrea Bopha , Molloy Alan P , Nicholson Paul
Published: March 2013

Achondroplasia is an autosomal dominant dwarfing condition that represents the most common form of skeletal dysplasia. The disease is caused by a mutation in the gene encoding fibroblast growth factor receptor 3 (FGFR3) found at the p16.3 locus on chromosome 4 which results in severe inhibition of subchondral bone growth. Anatomic variations, including articular and periarticular deformities classically seen with this condition, amplify the complexity of fracture fixation. Blood volume loss, age-related bone fragility, component selection and positioning pose serious orthopaedic challenges. Concomitant cardiovascular, respiratory and neurological comorbidities pose additional high-risk perioperative considerations. Despite an estimated prevalence of 1:25 000 in the general population, there is little literature concerning the operative and postoperative treatment challenges faced by orthopaedic surgeons dealing with fracture management on a patient with this condition. We present a case of an intercondylar femoral fracture in an elderly achondroplastic lady successfully treated with percutaneous screw fixation.
Inventing the medical portrait: photography at the ‘Benevolent Asylum’ of Holloway, c. 1885–1889
Authors: Sidlauskas Susan
Published: March 2013

In 1885, Holloway Sanatorium, an asylum for the ‘mentally afflicted of the middle classes’ opened in Egham, Surrey, 20 miles outside London. Until 1910, photographs of about a third of the patients—both those ‘Certified Lunatic by Inquisition’ and the ‘Voluntary Boarders’ who admitted themselves—were pasted into the asylum's case books. This paper analyses the photographs that were included in the very first of these, when there was a great uncertainty as to how to represent these patients, or whether to represent them at all. The photographs are unlike any other institutional images of the period, and raise critical questions about the imagined incompatibility between documentary photography and personal agency.
Fictional father?: Oliver Sacks and the revalidation of pathography
Authors: Hull Andrew John
Published: March 2013

This paper is a revalidation of Oliver Sacks's role in the development of medicine's narrative turn and, as such, a reinterpretation of the history of narrative in medicine. It suggests that, from the late 1960s, Sacks pioneered in his ‘Romantic Science’ a new medical mode that reunited the seemingly incommensurable art and science of medicine while also offering a way for medical humanities to shape clinical reasoning more effectively.
Relascope sampling for crown ratio estimation
Authors: Schnell Sebastian , Wikman Jonas , Ståhl Göran
Published: March 2013

In this study, we apply vertical angle count sampling to estimate the crown ratio of trees in unthinned forest stands. The rationale is to be able to quickly assess the relative crown size of forest stands to support thinning decisions by simply counting trees. We provide estimators and discuss their precision based on pilot studies in Scots pine (Pinus sylvestris L.) plantations in northern Sweden. A separate study was conducted to investigate the amount of measurement errors, i.e., how many trees are wrongly selected or overlooked when using the method. Sampling errors for estimating crown ratio were found to be remarkably low, partly due to high correlation between crown length and tree height and partly due to low variability in the study sites. Measurement errors were in the range of what is commonly obtained with horizontal angle count sampling for basal area estimation.
OUT FLOW IN A VIRTUAL MTR STATION USING A LOCAL VIEW FLOOR FIELD MODEL
Authors: LENG BIAO , WANG JIANYUAN , ZHAO XIAOXI , FANG JUN , XIONG ZHANG
Published: March 2013

The floor field (FF) model, up until now, has been the most widely used simulation in pedestrian flow dynamics for simple based scenarios. This paper presents an improvement on and upon the local view FF model by simulating pedestrian flow in more complex scenarios with typical goals and obstacles that may block or assist the sight of the pedestrian. In addition this model will also provide a detailed analysis entailing the simulation of multi-goal selections. This involves the visibility information on each cell being set, and a dynamic priority list of goals for every pedestrian being updated as he/she moves. The pedestrians select the convenient goal according to the priority of goals, the distances to the candidate goals and the degree of congestion. To aid in the theory of this and to make a better understanding of reality, a simulation scenario is conducted on a virtual MTR station, where parameter settings are discussed and some regular phenomena helpful to the designers of stations is put forward.
MONOJET EVENTS: FROM DARK MATTER TO EXTRA DIMENSIONS, A SEARCH FOR THE EXOTICS USING THE STANDARD MODEL
Authors: BEAUCHEMIN PIERRE-HUGUES , REZVANI REYHANEH
Published: March 2013

Monojet events consist in event topologies with a high transverse momentum jet and a large amount of missing transverse energy. They constitute a promising final state that could lead to phenomena beyond the Standard Model. The theoretical models giving rise to such a signature include the pair production of Weakly Interacting Massive Particles, as dark matter candidates, and models of large extra dimensions. Monojet events can even be used to measure the Standard Model properties of Z boson decays, provided that the precision of the analysis is high enough. Such precision can be achieved by using data-driven determinations of the Standard Model contributions to monojet events. Exotics searches for new physics in such a final state have been performed at all high energy hadronic collider experiments since SPS. The ATLAS and CMS analyses with 7 TeV LHC data provide the latest and most useful information obtained from monojet studies. Their results are presented and discussed in this review paper.
GAUGED LIFSHITZ MODEL WITH CHERN–SIMONS TERM
Authors: LOZANO GUSTAVO S. , SCHAPOSNIK FIDEL A. , TALLARITA GIANNI
Published: March 2013

We present a gauged Lifshitz Lagrangian including second- and fourth-order spatial derivatives of the scalar field and a Chern–Simons term, and study nontrivial solutions of the classical equations of motion. While the coefficient β of the fourth-order term should be positive in order to guarantee positivity of the energy, the coefficient α of the quadratic one need not be. We investigate the parameter domains and find significant differences in the field behaviors. Apart from the usual vortex field behavior of the ordinary relativistic Chern–Simons–Higgs model, we find in certain parameter domains oscillatory solutions reminiscent of the modulated phases of Lifshitz systems.
RECENT DEVELOPMENTS IN ASTROPHYSICAL AND COSMOLOGICAL EXPLOITATION OF MICROWAVE SURVEYS
Authors: BURIGANA CARLO , DAVIES RODNEY D. , DE BERNARDIS PAOLO , DELABROUILLE JACQUES , DE PAOLIS FRANCESCO , DOUSPIS MARIAN , KHATRI RISHI , LIU GUO CHIN , MARIS MICHELE , MASI SILVIA , MENNELLA ANIELLO , NATOLI PAOLO , NORGAARD-NIELSEN HANS ULRIK , POINTECOUTEAU ETIENNE , REPHAELI YOEL , TOFFOLATTI LUIGI
Published: March 2013

In this paper, we focus on the astrophysical results and the related cosmological implications derived from recent microwave surveys, with emphasis to those coming from the Planck mission. We critically discuss the impact of systematic effects and the role of methods to separate the cosmic microwave background (CMB) signal from the astrophysical emissions and each different astrophysical component from the others. We then review the state-of-the-art diffuse emissions, extragalactic sources, cosmic infrared background and galaxy clusters, addressing the information they provide to our global view of the cosmic structure evolution and for some crucial physical parameters, as the neutrino mass. Finally, we present three different kinds of scientific perspectives for fundamental physics and cosmology offered by the analysis of on-going and future CMB projects at different angular scales dedicated to anisotropies in total intensity and polarization and to absolute temperature.
NEW FABRICATION METHOD OF THREE-ELECTRODE SYSTEM ON CYLINDRICAL CAPILLARY SURFACE AS A FLEXIBLE IMPLANTABLE MICRONEEDLE
Authors: YANG ZHUOQING , ZHANG YI , ITOH TOSHIHIRO , MAEDA RYUTARO
Published: March 2013

In this present paper, a three-electrode system has been fabricated and integrated on the cylindrical polymer capillary surface by micromachining technology, which could be used as a flexible and implantable microneedle for glucose sensor application in future. A UV lithography system is successfully developed for high resolution alignment on cylindrical substrates. The multilayer alignment exposure for cylindrical polymer capillary substrate is for the first time realized utilizing the lithography system. The ±1 μm alignment precision has been realized on the 330 μm-outer diameter polymer capillary surface, on which the three-electrode structure consisting of two platinum electrodes and one Ag/AgCl reference electrode has been fabricated. The fabricated whole device as microneedle for glucose sensor application has been also characterized in 1 mol/L KCl and 0.02 mol/L K3Fe ( CN )6mix solution. The measured cyclic voltammetry curve shows that the prepared three-electrode system has a good redox property.
BEHAVIOR OF STEEL PORTAL FRAMES IN FIRE: COMPARISON OF IMPLICIT AND EXPLICIT DYNAMIC FINITE ELEMENT METHODS
Authors: RAHMAN MAHBUBUR , XU YIXIANG , LIM JAMES B. P. , SWITZER CHRISTINE , HAMILTON ROBERT , COMLEKCI TUGRUL , PRITCHARD DAVID
Published: March 2013

The use of finite element methods to determine the collapse behavior of steel portal frames in fire requires temperature, large deformation, complex geometry, boundary conditions and degradation of material stiffness to be taken into account. For such analyses, the cost of computation is important as well as the accuracy, robustness and stability of the analyses. The implicit dynamic method is a rigorous technique that considers the equilibrium of every time step. However, convergence may become an issue, particularly if the frame undergoes structural instability while using a direct time incrementation scheme. In contrast, the explicit dynamic method does not require the equilibrium criteria to be met in every time step, and thus convergence problems are not encountered, although the cost of computation may be tremendous if the natural time scale is used. This paper presents a comparison between the efficiency, stability and accuracy of computations using the implicit and explicit dynamic methods, in determining the collapse behavior of portal frames at elevated temperatures; the models are quasi-static since inertia forces are ignored. It is found that similar results can be obtained using both the implicit and explicit dynamic methods, although the analysis times differ significantly. It is shown that, if the applied artificial inertia forces, in terms of residual forces, are magnified and an automatic time incrementation scheme is activated in the implicit dynamic method, then this method shows significant superiority over the explicit dynamic method both in terms of the cost of computation and the accuracy of results obtained for such structures.
EFFECT OF TRUCK COLLISION ON DYNAMIC RESPONSE OF TRAIN–BRIDGE SYSTEMS AND RUNNING SAFETY OF HIGH-SPEED TRAINS
Authors: XIA CHAOYI , XIA HE , ZHANG NAN , GUO WEIWEI
Published: March 2013

A dynamic analysis model is established for a coupled high-speed train and bridge system subjected to collision loads. A 5 × 32 m continuous high-speed railway bridge with PC box girders is considered in the illustrative case study. Entire histories of a CRH2 high-speed EMU train running on the bridge are simulated when the truck collision load acts on the bridge pier, from which the dynamic responses such as displacements and accelerations of the bridge, and the running safety indices such as derailment factors, offload factors and lateral wheel/rail forces of the train are computed. For the case study, the running safety indices of the train at different speeds on the bridge when its pier is subjected to a truck collision with different intensities are compared with the corresponding allowances of the Chinese Codes. The results show that the dynamic response of the bridge subjected to truck collision loads is much greater than the one without collision, which can drastically influence the running safety of high-speed trains.
STRUCTURAL PARAMETER IDENTIFICATION USING DAMPED TRANSFER MATRIX AND STATE VECTORS
Authors: NANDAKUMAR P. , SHANKAR K.
Published: March 2013

A new method for identification of structural parameters is proposed using Damped Transfer Matrices (DTM) and state vectors. A new transfer matrix is derived for continuous mass systems including the damping parameters. The state vector at a location is the sum of the internal and external contributions of displacements, forces, and moments at that point, when it is multiplied with the transfer matrix, state vector at the adjacent location is obtained. The structural identification algorithm proposed here involves prediction of displacement responses at selected locations of the structure using DTM and compares them with the measured responses at the respective locations. The mean square deviations between the measured and predicted responses at all locations are minimized using a nonclassical optimization algorithm, and the optimization variables are the unknown stiffness and damping parameters in the DTM. A nonclassical heuristic Particle Swarm Optimization algorithm (PSO) is used, since it is especially suited for global search. This DTM algorithm with successive identification strategy is applied on one element or sub-structure of a structure at a time and identifies all the parameters of adjacent elements successively. The algorithm is applied on numerically simulated experiments of two structures such as ten degrees of freedom lumped mass system and a cantilever with seven finite elements and one sub-structure of a nine member frame structure. Also this algorithm is verified experimentally on a sub-structure of a fixed beam. The main advantage of this algorithm is that it can be used for the local identification in a zone in a structure without modeling the entire global structure.
SOME REMARKS ON THE DOZIER–SILVERSTEIN THEOREM FOR RANDOM MATRICES WITH DEPENDENT ENTRIES
Authors: ADAMCZAK RADOSŁAW
Published: March 2013

The Dozier–Silverstein theorem asserts the almost sure convergence of the empirical spectral distribution of information plus noise matrices, i.e. perturbations of deterministic matrices whose spectral distribution converges (information matrices) by random matrices with i.i.d. entries (noise matrices). We show that a modification of the original proof given by Dozier and Silverstein allows to extend this result to more general noise matrices, in particular matrices with independent columns satisfying a natural concentration inequality for quadratic forms, matrices with independent entries, satisfying a Lindeberg-type condition (recovering a recent result by Xie), matrices with heavy-tailed entries in the domain of attraction of the Gaussian distribution and certain classes of matrices with dependencies among columns (generalizing those investigated recently by O'Rourke and containing matrices with exchangeable entries). As a corollary we obtain the circular law for random matrices with independent log-concave isotropic rows.
Current Perspective on the Global and United States Cancer Burden Attributable to Lifestyle and Environmental Risk Factors
Authors: Schottenfeld David , Beebe-Dimmer Jennifer L. , Buffler Patricia A. , Omenn Gilbert S.
Published: March 2013

Our objective is to provide a current perspective on the avoidable causes of global and US cancer incidence and mortality. Cancer registry–based incidence patterns, population behavioral risk-factor survey data, and systematic reviews of epidemiologic studies are the basis for estimates of relative risk, the prevalence of exposures to various lifestyle and environmental risk factors, and their impact expressed as population attributable fractions (PAFs). Of the total 59 million global deaths in 2008, 12–13% were attributed to cancer. The increasing burden of cancers in low- and middle-income countries (LMICs) is attributable in part to increasing urbanization, expansion of the adult population at risk, and increasing or persistent exposures to infectious agents, tobacco, and dietary deficiencies. Attributable fractions for lifestyle and environmental risk factors are summarized for the United States, the United Kingdom, and France. Assuming minimal overlap in the distribution of risk factors in the population and discounting the potential for interaction in their combined effects, we estimate that a maximum of 60% of cancer deaths in the United States may be attributed to eight risk factors: tobacco, alcohol, ionizing and solar radiations, occupations, infectious agents, obesity, and physical inactivity.
The Epidemiology of Depression Across Cultures
Authors: Kessler Ronald C. , Bromet Evelyn J.
Published: March 2013

Epidemiological data are reviewed on the prevalence, course, socio-demographic correlates, and societal costs of major depression throughout the world. Major depression is estimated in these surveys to be a commonly occurring disorder. Although estimates of lifetime prevalence and course vary substantially across countries for reasons that could involve both substantive and methodological processes, the cross-national data are clear in documenting meaningful lifetime prevalence with wide variation in age-of-onset and high risk of lifelong chronic-recurrent persistence. A number of sociodemographic correlates of major depression are found consistently across countries, and cross-national data also document associations with numerous adverse outcomes, including difficulties in role transitions (e.g., low education, high teen childbearing, marital disruption, unstable employment), reduced role functioning (e.g., low marital quality, low work performance, low earnings), elevated risk of onset, persistence and severity of a wide range of secondary disorders, and increased risk of early mortality due to physical disorders and suicide.
Development of Advanced Materials and Devices for Cost Reduction of PEFC CHP System
Authors: Ohara Hideo , Omura Toshiya
Published: March 2013

Significant cost reduction is required for the full-fledged commercialization of residential PEFC co-generation systems. This paper reports the current status of present research project which aims to develop the reliable and robust MEA components and sub-systems, which contribute to simplify the whole system with reduced cost.
Limiting Current as a Tool to Study Oxygen Transport in PEM Fuel Cells
Authors: Baker Daniel R. , Caulk David A.
Published: March 2013

This survey article reviews the results of three of our papers, which develop limiting current as a tool for studying oxygen transport resistance in PEM fuel cells. Experimental methods are discussed, which allow one to separate the total oxygen transport resistance into its component contributions, as well as to distinguish between resistance due to intermolecular gas diffusion and other diffusion sources, such as Knudsen diffusion or diffusion through liquid water and ionomer. One can also clearly distinguish conditions in which water starts to condense in the cell and measure the impact of this condensation on transport resistance. Special emphasis is given to the question of how to determine when apparent limiting currents are due to transport limitations and when they are caused by other non-related effects. The problem of modeling these processes is also discussed.
Ionomer in the Catalyst Layer
Authors: Holdcroft Steven
Published: March 2013

The role of the ionomer in catalyst layers is critical to the performance of PEM fuel cells. Close attention should be paid not only to the inherent properties of the ionomer but also to the choice of dispersing solvent(s) and carbon support, as these control and influence, in conjunction with the ionomer, the porosity and proton conductivity of the catalyst layer. The ionomer also determines electrochemical FC kinetics through its influence on surface adsorption and gas permeability. The replacement of PFSA ionomer in the catalyst layer with hydrocarbon ionomers is particularly challenging as this is often results in a decrease in electrochemical fuel cell kinetics and mass transport.
Modeling Oxygen Concentration Oscillation in the Gas Channel of Polymer Electrolyte Fuel Cells: A Comparison between Numerical and Analytical Approaches
Authors: Guillemet Philippe , Maranzana Gaël , Mainka Julia , Lamibrac Adrien , Dillet Jérôme , Lottin Olivier
Published: March 2013

Considering the complexity of the electrical behavior (polarization curve and impedance spectrum) of PEFC and the lack of relevant models that could be used to identify the main transport parameters in Membrane Electrode Assemblies (MEA), a semi-analytical pseudo-bidimensionnal model is currently developed. Its main characteristics are first recalled. Then the results of a full numerical two-dimensional model are compared to those of the pseudo-bidimensionnal approach and analyzed. It is shown that oxygen diffusion inside the GDL can be considered as a 1D diffusion without any appreciable discrepancy and that the electrode can be modeled as a plane without major error either on impedance spectrum or polarization curve. Oxygen diffusion through the gas channel reveals an important discrepancy between volumetric and plane descriptions, leading to the necessity of a more complex model of the fluid flow in the gas channel.
Diffusive - Kinetic Evaporation Models for Fuel Cells
Authors: Médici Ezequiel F. , Fritz David L. , Alllen Jeffrey S.
Published: March 2013

Modeling evaporation within a fuel cell porous transport layer (PTL) is a complex, conjugate phenomenon that is highly dependent upon the local morphology, wetting, and operating conditions. Two very distinct evaporation models, one diffusive and one kinetic have been used to study evaporation in fuel cell porous media. Both evaporation models are implemented into a pore network model of a PTL. Simulation using both models are compared under the same morphological, wetting, and operation condition. The mass of evaporated water and liquid water distribution inside the PTL compared for the two models.
A Map to Start PEFC under Freezing Temperature -Theoretical Analysis of Super-Cooled State in Cell-
Authors: Ishikawa Yuji , Shiozawa Masahiro , Kondo Masaaki , Ito Kohei
Published: March 2013

Efficient cold start of PEFC under freezing point can be realized by keeping the super-cooled state of generated water. If a condition is satisfied, the cell can start under a freezing point with generated heat, and the cell reaches a steady state without the gas-supply block caused by the ice from the generated water. Moreover, difficult task, such as a shorter cold-start at a lower temperature, is possible by adequate choice of component material used in the cell, and by active heat generation with a suppressed air supply. Against such a background, this paper discussed which characteristic of the component in cell leads to the success of cold start, namely of keeping super-cooled state during cold start. This analysis was performed on the basis of heterogeneous nucleation theory which considers the wettability of surface of the component material.
Statistical Simulation of the Performance and Degradation of a PEMFC Membrane Electrode Assembly
Authors: Harvey David A. , Bellemare-Davis Alexander , Karan Kunal , Jayansankar Barath , Pharoah Jon G. , Colbow Vesna , Young Alan , Wessel Silvia
Published: March 2013

A 1-D MEA Performance model was developed that considered transport of liquid water, agglomerate catalyst structure, and the statistical variation of the MEA characteristic parameters. The model was validated against a low surface area carbon supported catalyst across various platinum loadings and operational conditions. The statistical variation was found to play a significant role in creating noise in the validation data and that there was a coupling effect between movement in material properties with liquid water transport. Further, in studying the low platinum loaded catalyst layers it was found that liquid water played a significant role in the increasing the overall transport losses. The model was then further applied to study platinum dissolution via potential cycling accelerated stress tests, in which the platinum was found to dissolve nearest the membrane effectively resulting in reaction distribution shifts within the layer.
Multi-Scale First-Principles Modeling of Three-Phase System of Polymer Electrolyte Membrane Fuel Cell
Authors: Brunello Giuseppe F. , Choi Ji Il , Harvey David A. , Jang Seung Soon
Published: March 2013

The three-phase system consisting of Nafion, graphite and platinum in the presence of water is studied using molecule dynamics simulation. The force fields describing the molecular interaction between the components in the system are developed to reproduce the energies calculated from density functional theory modeling. The configuration of such complicated three-phase system is predicted through MD simulations. The nanophase-segregation and transport properties are investigated from the equilibrium state. The coverage of the electrolyte on the platinum surface and the dissolution of oxygen are analyzed.
Variational Models of Pore Networks in Ionomer Membranes: The Role of Electrostatics
Authors: Promislow Keith , Jones Jaylan , Xu Zhengfu , Gavish Nir , Christlieb Andrew
Published: March 2013

We present a self-consistent, dynamic model for the morphology of the pore networks which form in Nafion and other ionomer membranes when they imbibe solvent. The model incorporates the interactions of the tethered ionic groups with the solvent and the entropic energy of the counter ions. Numerical simulations are presented which display hysteresis, and the development of pearled pore structures. A framework for extensions of the model that couple the electrostatic double layer at the interface of the pore wall and the transport equations for the counter-ions is presented. The framework derives the ionic transport and generalized Poisson equation from an action whose gradient flows dissipate a related free energy, in agreement with the second law of thermodynamics.
Molecular Simulation of Proton and Water Transport in Hydrated Nafion Membrane
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: March 2013

We have proposed a model of Nafion membrane based on DREIDING force field validated by comparing the density, water diffusivity, and Nafion morphology with experimental data. The simulated final density agrees with experiment within 1.3 % for various water contents. In addition to determination of diffusion coefficients of liquid molecules as a function of hydration level for dynamical validation, we have also calculated static structure factors among liquid molecules for mesoscopic structural validation. The diffusion coefficient of water molecules is found to be in good agreement with experimental data. The diffusion coefficient of hydronium ions has showed that general trends in the experimental data are reproduced although the classical models have the limitation of hydronium dynamics. The static structure factors of liquid molecules at low wave length provide insights into the periodic structure of the inter-clusters which are consistent with the experimental data based on small-angle X-ray and neutron scattering.
Numerical Simulation of the Interfacial Oxygen Transport Resistance for a PEMFC Cathode Incorporating Water Droplet Coverage
Authors: Koz Mustafa , Kandlikar Satish G
Published: March 2013

The transport resistance of oxygen in a PEMFC flow field and gas diffusion layer interface was numerically investigated in a 3D model. This model solved for the convection of air and the diffusion of oxygen in the air in a single flow field channel. The interfacial oxygen transport resistance was expressed with the Sherwood number. For a dry channel, the numerically obtained Sherwood number was validated by the relationship between Nusselt and Sherwood numbers through the Lewis number. Following the validation, the model simulated conditions of a single water droplet that remained adhered on the flow field and gas diffusion layer interface. The effects of droplet size, flow velocity, and variations in vapor content in air due to changes in temperature were analyzed and discussed. For the selected range of droplet sizes and flow velocities, numerically obtained drag forces were compared against experimentally obtained adhesion forces.
3D Modeling of One and Two Component Gas Flow in Fibrous Microstructures in Fuel Cells by Using the Lattice-Boltzmann Method
Authors: Brinkmann Jan Philipp , Froning Dieter , Reimer Uwe , Schmidt Volker , Lehnert Werner , Stolten Detlef
Published: March 2013

In fuel cells, a homogeneous distribution of gas flow is desirable for optimal performance. The gas diffusion layer (GDL) often used in PEM-like fuel cells is one of the key elements responsible for a uniform distribution under channels and ribs. To assess this ability of GDL-materials, characteristic numbers, e.g. the permeability, are often introduced. In this paper, we simulate one and two component gas flow through a virtual GDL material under operating conditions of a HT-PEFC. We observe the influence of discretization and viscosity choice on the macroscopic output of the Lattice-Boltzmann algorithm we apply. To achieve this, we first study their effects on empty square channels and finally transfer our interpretation to the output of a GDL simulation.
Maximum Efficiency Point Tracking Type Power Control System for a Fuel Cell Power Generation System
Authors: Itako Kazutaka , Takahashi Hiroshi
Published: March 2013

In this paper, from the viewpoint of practical use of a fuel cell, we propose a new control system that suppresses fuel consumption to the fullest extent in a given environment for a required output power in a fuel cell power generation system. The new maximum efficiency point tracking (MEPT) control method reduces the maximum efficiency point detecting time. we carry out tests to compare the fuel consumption suppression effect to that for conventional MPPT control.
Application of Impedance Spectroscopy to Characterize Polymer-Electrolyte-Membrane (PEM) Fuel Cells
Authors: Orazem Mark E.
Published: March 2013

Impedance spectroscopy provides a powerful tool for in-situ identification and quantification of physical phenomena which influence cell performance, but interpretation of data is difficult. This paper summarizes issues associated with application of impedance spectroscopy to characterize PEM fuel cells. These include error analysis, development of models based on proposed reaction mechanisms, and simplified asymptotic analysis in terms of effective capacitance, and integration with other measurements.
An Oxygen Flux Interrupt Method and In Situ Micro-Sensor for Characterizing Oxygen Transport in PEFCs
Authors: Epting William K , Litster Shawn
Published: March 2013

We present a thin-film amperometric sensor capable of sensing in-situ the oxygen concentration at the interface between the diffusion medium (DM) and cathode of a polymer electrolyte fuel cell. Because changes in relative humidity due to water production in the fuel cell operation confound pre-calibrated amperometic oxygen measurements, we also develop a novel method to instantaneously calibrate the sensor each time a measurement is made. Using the oxygen flux interrupt method, we measure the oxygen concentration at several points across polarization curves with 21% and 10% oxygen in air.
In-Plane Liquid Water Distribution at the Interface between the Gas Diffusion Layer and Catalyst Layer in the Cathode of a Polymer Electrolyte Fuel Cell with a Hybrid Pattern Flow Field
Authors: Nakajima Hironori , Kitahara Tatsumi , Takazono Yasutaka , Miyahara Satoshi , Shimizu Akira
Published: March 2013

We have investigated the effect of flow field patterns without cathode humidification in a polymer electrolyte fuel cell (PEFC) using electrochemical impedance spectroscopy (EIS) with triple-parallel-serpentine, interdigitated, and serpentine-interdigitated hybrid flow fields. The hybrid flow fields exhibit better performance than the others. The EIS results indicate that dehydration of the membrane and catalyst layer (CL) is significant for the triple-parallel-serpentine flow fields whereas that for the hybrid flow fields is not so severe. Thus the serpentine-interdigitated hybrid flow field has advantage in cell operation without cathode humidification, possibly because it provides a relatively uniform current distribution due to the interdigitated flow channel, and in addition, the serpentine flow channel involved in the hybrid flow field supplies water vapor along the channel. This water distribution behavior is also indicated by ex-situ tracer distribution observation using gas diffusion layers sprayed with water soluble metal salt tracer at the CL side.
Calculating Hydrogen Mass Transport Coefficients in a PEMFC at Different Operating Conditions Using a Hydrogen Pump Configuration
Authors: Angelo Michael S. , Bethune Keith P. , Rocheleau Rick E.
Published: March 2013

A proton exchange membrane fuel cell system (PEMFCS) operated electroytically at its limiting current was proposed previously as a technology to separate the H2 and He through the electrochemical oxidation of H2. In this work the fraction of H2 remaining in the effluent of two different sized PEMFCs with different flow field designs was studied at several operating conditions which included different: system temperatures, inlet relative humidity (R.H.), and system pressures to determine the most efficient operating condition. Experiments were performed at a fixed dry gas flow rate with an inlet H2 dry gas fraction of 10 %. System performance was found to depend significantly on operating conditions with optimum performance attained at 60 ºC and 100 % R.H. for both system sizes. To assist in the performance modeling of each system a differential chemical reactor model was used to determine H2 mass transport coefficients at each operating condition.
In Situ Water Distribution Visualization in MEA by Soft X-ray Radiography
Authors: Tsushima Shohji , Deevanhxay Phengxay , Sasabe Takashi , Hirai Shuichiro
Published: March 2013

Development of in situ water distribution visualization in membrane electrode assembly (MEA) in proton exchange membrane fuel cell (PEMFC) by laboratory-based soft X-ray radiography is described. Advantage and/or limitation of the technique are briefly presented with future perspectives. Spatial and temporal variation of liquid water distribution in catalyst layer (CL), microporous layer (MPL) and gas diffusion layer (GDL) revealed inhomogeneous and intermittent evolution of liquid water drainage and accumulation behaviors in porous media, which gives detailed insights on water transport process and its management.
Visualization of Liquid Water Accumulation in PEMFCs Operating at Different Temperatures by Soft X-ray Radiography
Authors: Deevanhxay Phengxay , Sasabe Takashi , Tsushima Shohji , Hirai Shuichiro
Published: March 2013

In situ observation of liquid water accumulation in PEMFCs operating at 30ºC, 50ºC, and 70ºC was performed by using high-resolution soft X-ray radiography. A less amount of liquid water in the MPL and GDL was observed in the elevated operating temperature. It is suggested that water generated in the electrode is mainly transported as vapor at higher temperature conditions investigated. The liquid water accumulation was significantly smaller in the MPL than in the GDL, independently observed in all operating temperature.
Electron Tomography Based 3D Reconstruction of Fuel Cell Catalysts
Authors: Jankovic Jasna , Susac Darija , Soboleva Tatyana , Stumper Jürgen
Published: March 2013

Fuel cell catalyst powders consisting of Pt metal catalyst deposited on three types of carbon supports were imaged using the electron tomography TEM technique. Electron tomograms were used to reconstruct 3D models of the carbon supports and catalyst particles. The 3D models served to visualize the catalyst powders and to calculate total surface areas, the interaction surface areas between the support and the catalyst, as well as catalyst particle size distribution. Results showed good agreement with other available experimental data.
3D Chemical Mapping of PEM Fuel Cell Cathodes by Scanning Transmission Soft X-ray SpectroTomography
Authors: Berejnov Viatcheslav , Susac Darija , Stumper Jürgen , Hitchcock Adam P.
Published: March 2013

Soft X-ray spectrotomography was applied for 3D chemical analysis of fuel cell cathodes at the nano scale. The goal was to obtain 3D maps of the components constituting the catalyst layer, and, in particular, to differentiate 3D networks of carbon support and ionomer. Using scanning transmission soft X-ray microscopy (STXM) with a rotating sample holder we produced a series of images at selected photon energies and different rotational angles of the sample. The rotational image stacks were tomographically reconstructed, while the X-ray absorption fingerprints at the C1s and F1s edges were used to generate 3D maps of the networks of carbon-support/catalyst and the fluorine-rich ionomer.
Effects of Channel Structure and Wettability on Liquid Water Transport in Cathode of PEFC
Authors: Ishizaki Yugo , Taniguchi Ryo , Nishida Kosuke , Tsushima Shohji , Hirai Shuichiro
Published: March 2013

Water plugging in cathode channel of polymer electrolyte fuel cells (PEFCs) is one of the critical issues for high performance operation. In this study, the optical visualization of liquid water behavior and the differential pressure measurement in the cathode channel of an operating PEFC were simultaneously performed using the transparent separators with different wettabilities, and the effects of channel structures (serpentine and parallel) and wettability on the liquid water transport were investigated. It was found that the hydrophobic or hydrophilic treatment reduce the pressure drop in the serpentine flow field. On the other hand, in the case of parallel flow field, the cell voltage of the hydrophilic channel is more stable than that of the untreated channel, but the hydrophobic treatment decreases the cell performance.