bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, Characterization and Physiochemical Properties of Platinum Supported on Mesoporous Carbon
Authors: Titinchi Salam J. J. , Saban Waheed , Petrik Leslie , Abbo Hanna S.
Published: March 2012

Ordered mesoporous carbon (OMC) has been prepared by impregnating the pores of the silica template (SBA-15) with liquid petroleum gas (LPG) or sucrose. The desired support (OMC) was obtained after dissolution with NaOH. Platinum nanoparticles were dispersed on ordered mesoporous carbons using Chemical Vapour Deposition (CVD) method and Pt(acac)2 as metal source. The resulting ordered mesoporous carbon possess a large surface area with high microporosity, and a controlled pore size distribution, High-quality carbon replicas of SBA-15 show an X-ray diffraction peak at low angle, which indicates that the structural periodicity of the (111) planes has been maintained. Their pore volume and specific surface area are high and the pore volume is almost entirely microporous. The synthesized Pt/OMC was characterized by powder X-Ray diffraction, HR-TEM, HR-SEM, EDS, thermogravimetric analysis, and nitrogen adsorption. The performance of Pt catalyst supported OMC was evaluated by electrochemical studies, which shows almost similar activity to the commercial catalyst.
Water Crossover Experiments in an Open-Cathode Direct Methanol Fuel Cell
Authors: Kuo C. C. , Neal L. M. , Crisalle O. D. , Lear W. E. , Fletcher J. H.
Published: March 2012

A direct methanol fuel cell (DMFC) that does not require an external water feed or a powered water-recovery system has potential for wide application in portable electronic devices. This paper provides experimental data for the water recovery rate in a novel DMFC design featuring a hydrophobic cathode gas-diffusion layer that allows for passive water recovery. Water and methanol crossover rates were experimentally characterized by measuring the water vapor and carbon dioxide concentration at the cathode exit with an infrared sensor. The result showed that the mass-transport parameter of water vapor, increases linearly with increasing cell temperature and remains invariant with respect to the cell current density. Water neutrality of the DMFC stack was achieved while the cell operated close to 50 °C and 150 mA/cm2 with a 1M methanol solution. A comprehensive empirical equation based on the experimental results is presented, along with system-level insights into the controllability of water management in designing an open cathode DMFC system.
Experimental Investigation of Gas Purge and Voltage Undershoot for an Air-Breathing PEMFC
Authors: Zhai Shuang , Zhou Su , Sun Pengtao , Chen Fengxiang , Niu Jigao , Ding Mingchao
Published: March 2012

The effect of anode gas purge on the air-breathing PEMFC performance is experimentally investigated by measuring and analyzing the recovery of output stack voltage in this paper. The amount of hydrogen exhaust during each gas purge is obtained by a drainage method. Secondly, the utilization efficiency of hydrogen which flows from the hydrogen tank to the anode side and then is drained away during purge events is verified according to the consumed hydrogen in the stack and hydrogen exhaust. This verification program can also be used for our next work on air-breathing PEMFC modeling and simulation. Different gas purge schedule on the anode side, such as the interval time and duration time under various loads, are investigated as well. The experimental results show that a slight reduction of stack voltage is observed under a low current. However, a large voltage recovery is found under a high current which may be due to the severe flooding effect. In addition, the degree of voltage undershoot under different load change is investigated as well, which can provide a guidance for the safety operation design of air-breathing PEMFC.
Experimental Performance Evaluation of a High Temperature PEM Fuel Cell Prototype Under Various Operating Conditions
Authors: Das Susanta K.
Published: March 2012

In this study, we experimentally evaluated our newly designed high temperature PEM fuel cell (HTPEMFC) prototype performance at different operating conditions. In particular, we investigated the effects of operating temperature, pressure, air stoichiometry and CO poisoning in the anode fuel stream on the current-voltage characteristics of the HTPEMFC prototype. Experimental results obtained from the single HTPEM fuel cell show that the performance is quite steady with high CO-level reformate at high operating temperature which makes it possible to feed the reformate gas directly from the reformer to the stack without further CO removal. In order to develop design parameters for fuel reformer, experimental data of this type would be very useful. The results obtained from this study showed significant variations in current-voltage characteristics of HTPEMFC at different temperatures with different CO poisoning rates. The results are promising to understand the overall system performance development strategy of HTPEMFC in terms of current-voltage characteristics while fed with reformate with different CO ratios in the anode fuel stream.
Heterogeneous Electrode Designs for Planar SOFC Optimizations
Authors: Shi Junxiang , Xue Xingjian
Published: March 2012

Suitable porous electrode design may play a significant role in the performance enhancement of solid oxide fuel cells (SOFCs). In this paper, a genetic algorithm optimization method is employed to design electrodes based on a 2-D planar SOFC model development. The objective is to find out suitable porosity and particle size distributions for both anode and cathode electrodes so that the cell performance can be maximized. The results indicate that the optimized heterogeneous electrode may better improve SOFC performance than the homogeneous count-part, particularly under relatively high current density conditions. The optimization results are dependent on the operating conditions. The effects of pressure losses along the anode/cathode channels and inlet fuel compositions are investigated. The proposed approach provides a systematical method for electrode microstructure designs of high performance SOFCs.
Experimental Comparison and Performance Evaluation of Planar Solid Oxide Single Cell
Authors: Cinti Giovanni , Desideri Umberto , Discepoli Gabriele , Sisani Elena , Penchini Daniele
Published: March 2012

Nowadays, in a world characterized by the need to reduce the production of pollutants, by global climate changes, by the progressive lack of availability of cheap fossil fuels, one of the most important goals of scientific research is to design systems that can provide energy with low environmental impact. Planar Solid Oxide Fuel Cells (SOFC) are considered to be power generators with high efficiency independent on size and low emissions. Fuel cell laboratory (FCLab) of University of Perugia has focused his studies on SOFC operating at high temperature (800–1000°C), characterized by greater flexibility in the choice of fuel. This study focuses on definition and realization of experimental test able to define the quality of a SOFC single cell and on the effect of test condition parameter. The performance of the cell is evaluated via polarization curves realized in different external conditions. Area Specific Resistance (ASR) is used as main test output. Results analysis confirm that ASR gives important information on fuel cell performance and can be used to compare an qualify SOFC single cell.
Computational Analysis of Heat Transfer in Air-Cooled Fuel Cells
Authors: Shahsavari S. , Bahrami M. , Kjeang E.
Published: March 2012

Temperature distribution in a fuel cell significantly affects the performance and efficiency of the fuel cell system. Particularly, in low temperature fuel cells, improvement of the system requires addressing the heat management issues, which reveals the importance of developing thermal models. In this study, a 3D numerical thermal model is presented to analyze heat transfer and predict the temperature distribution in air-cooled proton exchange membrane fuel cells (PEMFC). In the modeled fuel cell stack, forced air flow supplies oxidant as well as cooling. Conservation equations of mass, momentum, and energy are solved in the oxidant channel, whereas energy equation is solved in the entire domain, including the gas diffusion layers (GDLs) and separator plates, which play a significant role in heat transfer. A parametric study is done to investigate the effect of various operating conditions on maximum cell temperature. The results are further validated with experiment. This model provides a theoretical foundation for thermal analysis of air-cooled stacks, where temperature non-uniformity is high and thermal management and stack cooling is a significant engineering challenge.
Effect of Geometry and Operating Parameters on Simulated SOFC Stack Temperature Uniformity
Authors: Koeppel Brian J. , Lai Kevin , Khaleel Moe A.
Published: March 2012

A uniform temperature field is desirable in the solid oxide fuel cell stack to avoid local hot regions that contribute to material degradation, thermal stresses, or very high current densities. Various geometric and operational design changes were simulated by numerical modeling of co-flow and counter-flow multi-cell stacks, and the effects on stack maximum temperature, stack temperature difference, and maximum cell temperature difference were characterized. The results showed that 11–17% methane fuel composition for on-cell steam reforming and a reduced reforming rate of 25–50% of the nominal rate was beneficial for a more uniform temperature field. Fuel exhaust recycling up to 30% was shown to provide lower temperature differences for reforming fuel in the co-flow stack, but counter-flow stacks with hydrogen fuel showed higher temperature differences. Cells with large aspect ratios showed a more uniform temperature response due to either the strong influence of the inlet gas temperatures or the greater thermal exchange with the furnace boundary condition. Improved lateral heat spreading with thicker interconnects was demonstrated, but greater improvements towards a uniform thermal field for the same amount of interconnect mass could be achieved using thicker heat spreader plates appropriately distributed along the stack height.
Stress-Lifetime Characterization of Proton Exchange Membrane Using 3-D Digital Image Correlation and Pressure-Loaded Blister Tests
Authors: Siuta Chase M. , Case Scott W. , Dillard David A. , Moore Robert B. , Ellis Michael W. , Li Yongqiang , Lai Yeh-Hung , Gittleman Craig S.
Published: March 2012

The strength of the proton exchange membrane (PEM) and its ability to withstand cyclic, environmentally induced stresses plays an important role in membrane integrity and consequently, fuel cell durability. In this study, pressure loaded blister tests are used to characterize the biaxial strength of a model commercially available membrane, Gore-Select® series 57, at the 90°C dry condition under ramped, constant and cyclic pressure loading. Gas leakage is used as the failure criterion, making it analogous to the stresses and failures seen during fuel cell operation. Three-dimensional digital image correlation is used to measure the deformation of the bulging membrane. A quasi-static, spherical pressure vessel approximation of the central portion of the blister then allows the biaxial stress state at this location of the PEM to be tracked through time. A damage accumulation model is applied to the data taken during constant pressure loading to determine the damage parameters. The model is then used to predict the failure of blisters from ramped and cyclic fatigue test modes. The successful lifetime prediction suggests an understanding of the stress state in the blister test and the model’s ability to relate different mechanical loadings and predict failure.
On Modeling Development of Microscopic Spatial Structure for the Catalyst Layer in a Proton Exchange Membrane Fuel Cell
Authors: Xiao Yu , Yuan Jinliang , Sunde´n Bengt
Published: March 2012

The typical catalyst layers (CLs) in proton exchange membrane fuel cells (PEMFCs) are fabricated as random heterogeneous composites to meet the multifunctional requirements of transport phenomena and electrochemical activity. The employment of Pt nano-particles, carbonaceous substrates and Nafion ionomers in CLs allows effective diffusion of hydrogen and oxygen, transport and phase change of water, migration and diffusion of protons, migration of electrons to and from the catalytic sites, which is accompanied by the oxidation of hydrogen in anodes and the generation of water and heat in cathodes. Based on the coarse-grained (CG) molecular dynamics method, a systematic technique is developed to provide insight into the self-organization phenomena and the microscopic spatial structure of the CLs. The formation of a CL is simulated by considering the interactions of the Pt clusters, carbon slabs, Nafion ionomers, hydronium ions and water. Meanwhile, the morphologies of Pt clusters are presented and compared with three cases. Moreover, the pair correlation functions (PCFs) are employed to predict the distributions and hydrophilic properties of the components. Finally, the TPB features are shown at the nano-scale level, which provides deeper view to understand the Pt utilization in the CLs.
Simulation of Turbulent Combustion in Porous Ceramic Materials
Authors: deLemos Marcelo J. S. , Coutinho Jose´ E. A.
Published: March 2012

This paper presents two-dimensional numerical simulations of combustion of an air/methane mixture in a radial porous combustor using a model that explicitly considers the intra-pore levels of turbulent kinetic energy. Transport equations are written in their time-and-volume averaged form and a volume-based statistical turbulence model is applied to simulate turbulence generation due to the porous matrix. A cylindrical porous combustor is analyzed, in which the mixture flows inside it in the axial direction, being the flue gases ejected through the lateral surface. Combustion is modeled via a unique simple closure. For high excess air, the flame front moves towards the lateral exit of the burner. Also, increasing the inlet flow rate for stoichiometric mixture pushes the flame out of the porous material.
5 KWe + 5 KWt PEM-FC Generator From Bioethanol: Fuel Processor and Development of New Reforming Catalysts
Authors: Rossetti Ilenia , Biffi Cesare , Forni Lucio , Tantardini Gian Franco , Faita Giuseppe , Raimondi Mario , Vitto Edoardo , Salogni Andrea
Published: March 2012

A power unit constituted by a reformer, a H2 purification section and a fuel cell is being tested c/o the Dept. of Physical Chemistry and Electrochemistry of Universita` degli Studi di Milano, on the basis of a collaboration with Helbio S.A. Hydrogen and Energy Production Systems (supplier of the unit) and some sponsors (Linea Energia S.p.A., Parco Tecnologico Padano and Provincia di Lodi). The system size allows to cogenerate 5 kWe (a.c.) + 5 kWt (hot water at 65°C) as peak output. Bioethanol, obtainable by different non-food competitive biomass is transformed into syngas by a prereforming and a reforming stage and the reformate is purified from CO to a concentration below 20 ppmv, suitable to feed the proton exchange membrane fuel cells (PEMFC) stack integrated in the fuel processor. This result is achieved by feeding the reformate to two water gas shift reactors, connected in series and operating at high and low temperature, respectively. CO concentration in the outcoming gas is ca. 0.7 vol% and the final CO removal to meet the specifications is accomplished by two methanation stages in series. The second methanation step acts as a guard since ca. 15 ppmv of CO are obtained even after the first reactor. The purified H2 is suitable for feeding a 5 kWe PEMFC stack, which should have an expected overall efficiency higher than 80% (including thermal output). The main goal of the present project is to check system performance under different operating conditions, to verify the effectiveness of the proposed technology and to suggest adequate improvements. In particular, the system will be tested under different load, to check for the readyness of response. Another point will be the effect of bioethanol origin, purity and concentration, so to open the way to separation processes different from distillation. Due to the demonstrative character of the project the main part of the experimentation focuses on the accumulation of a suitable amount of hours-on-stream to validate the system feasibility. A parallel investigation is active on the development of alternative nanostructured catalysts for the present application. In particular, Ni, Co and Cu-based catalysts, supported over La2O3, TiO2 and SiO2 were tested at 500, 625 and 750°C. At the moment no perfect candidate has been found to operate the steam reforming at the lowest temperature, due to unsatisfactory material balances and by-products formation at 500°C with most catalysts. Good H2 productivity, with 100% C balance has been achieved at higher temperature (≥ 625°C).
Electrical Properties of Sr0.86Y0.08TiO3 Under Redox and Full Cell Fabrication Conditions
Authors: Zhao Li , Brouwer Jacob
Published: March 2012

The effects of manufacturing and preparation conditions on the structural and electrical properties of Sr0.86Y0.08TiO3 (SYT) reduced in 5% NH3 (95% N2) are discussed. The realization of an SYT-based SOFC anode is challenging because the conductivity of SYT is highly dependent upon the thermal history combined with heat treatment atmosphere used in manufacturing. To obtain highly conductive SYT as a candidate for an SOFC anode material, all samples in this study were prereduced to 1400°C under reducing conditions (ammonia) for 8 hours. After pre-reduction, 3 samples were oxidized in air at 850°C, 950°C and 1050°C, respectively, for 4 hours to evaluate the impact of oxidizing conditions in practical cell fabrication processes on the SYT conductivity. XRD analyses showed that the lattice parameter of SYT sintered in ammonia was slightly different than the sample sintered in air. Measured at 800°C in reducing atmosphere (dry N2/4%H2), the maximum electrical conductivity of 36.3 S/cm was observed in SYT reduced in ammonia at 1400°C. However, the observed conductivities were not preserved after oxidation-reduction cycles. Various SYT samples pre-reduced in ammonia at 1400°C and then oxidized in air at 850°C, 950°C and 1050°C showed an irreversible drop on conductivity measured in a reducing atmosphere, and the higher the oxidation temperature, the lower the conductivity became. The conductivity results indicate a strong dependence upon the SYT manufacturing and processing conditions. Despite the irreversible drop due to the oxidation cycle, the conductivity of SYT sintered in ammonia at 1400°C is still reasonable as a candidate for SOFC anodes, with careful management of cell fabrication conditions to avoid any oxidation processes at temperatures above 1050°C.
Solid Oxide Fuel Cell System Development for Stationary Power Applications
Authors: Ghezel-Ayagh Hossein , Jolly Stephen , Davis Keith E. , Walzak James , Patel Dilip , Way Rich , Stauffer David
Published: March 2012

Integrated Gasification Fuel Cell (IGFC) power plants incorporating solid oxide fuel cells (SOFCs) are attractive alternatives to traditional pulverized coal-fired and Integrated Gasification Combined Cycle (IGCC) power plants. IGFC systems are projected to achieve electrical generation efficiencies greater than 50% based on high heating value of coal, while separating at least 90% of the carbon dioxide emissions for capture and environmentally secure storage. A comprehensive IGFC system design and optimization study is presented based on recent SOFC performance testing and technology advancements. Details of the system power island cost break-down are also presented, indicating the cost-competitiveness of IGFC systems relative to other coal-fueled power generation technologies. Comparisons of the projected IGFC system efficiency and water consumption are made to pulverized coal-fired and IGCC power plants.
The Effect of Inhomogeneous Compression on Water Transport in the Cathode of a PEM Fuel Cell
Authors: Olesen Anders C. , Berning Torsten , Kær So̸ren Knudsen
Published: March 2012

A three-dimensional, multi-component, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS inc.), is used to investigate the effect of porous media compression on transport phenomenon of a PEM Fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas diffusion layer, micro-porous layer and catalyst layer, excluding the membrane and anode. In the porous media liquid water transport is described by the capillary pressure gradient, momentum loss via the Darcy-Forchheimer equation and mass transfer between phases by a non-equilibrium phase change model. Furthermore, the presence of irreducible liquid water is taken into account. In order to account for compression, porous media morphology variations are specified based on the GDL throughplane strain and intrusion which are stated as a function of compression. These morphology variations affect gas and liquid water transport, and hence liquid water distribution and the risk of blocking active sites. Hence, water transport is studied under GDL compression, in order to investigate the qualitative effects. Two simulation cases are compared; one with and one without compression.
Logistics for Designing a Recharging Grid for the Hybrid Vehicle System: Part II
Authors: Ubong Etim U. , Caufield Cameron , Lathers Steven , Gonzalez Ricky , Perzyk Robert , Li Tianao , Manning Tom , Zaharopoulos George
Published: March 2012

As the number of hybrid vehicles on the road increases, there is an imminent need for an infrastructural support to make these new acquisitions practicable. This project details the infrastructural design using fuel cell energy from the Technology Park of Kettering University for setting up 10 pilot recharging outlets at the parking lot for the experimental fleet all year round. The Technology Park houses a hydrogen refueling station for a fleet of five buses, fuel cell and solar energy laboratories and various incubators for various alternative energy companies. The current resources at the Center include a 2 kW high temperature HT-PEM produced by GEI, LLC and a GREENLIGHT Test station. The use of solar energy-electrolyzer and fuel cell during the day is also considered for a public parking lot with a capacity of 30 vehicles. The applicable codes and standards regarding such installations are reviewed.
HeteroFoaMs: Electrode Modeling in Nano-Structured Heterogeneous Materials for Energy Systems
Authors: Chiu W. K. S. , Virkar A. V. , Reifsnider K. L. , Rabbi F. , Liu Q.
Published: March 2012

Heterogeneous Functional Materials, e.g., “HeteroFoaMs” are at the heart of countless energy systems, including (from left to right below) heat storage materials (a), batteries (b), solid oxide fuel cells (c), and polymer electrolyte fuel cells (d). HeteroFoaMs are generally nano-structured and porous to accommodate transport of gasses or fluids, and must be multi-functional (i.e., active operators on mass, momentum, energy or charge, in combinations). This paper will discuss several aspects of modeling the relationships between the constituents and microstructure of these material systems and their device functionalities. Technical advances based on these relationships will also be identified and discussed. Three major elements of the general problem of how to model HeteroFoaM electrodes will be addressed. Modeling approaches for ionic charge transfer with electrochemistry in the nano-structured porosity of the electrode will be discussed. Second, the effect of morphology and space charge on conduction through porous doped ceria particle assemblies, and their role in electrode processes will be modeled and described. And third, the effect of local heterogeneity and morphology on charge distributions and polarization in porous dielectric electrode materials will be analyzed using multi-physics field equations set on the details of local morphology. Several new analysis methods and results, as well as experimental data relating to these approaches will be presented. The value, capabilities, and limitations of the approaches will be evaluated.
Proton Transfer in Polymer Electrolyte Membrane by Molecular Dynamics Method
Authors: Tokumasu Takashi
Published: March 2012

This paper describes characteristics of proton transfer in polymer electrolyte membrane by Molecular Dynamics (MD) simulation. Nafion was used as a membrane. Grotthus mechanism as well as Vehicle mechanism was considered in the simulation. To treat Grotthus mechanism, Empirical Valence Bond (EVB) method was used. The parameters or functions of the interaction potential of EVB method were determined so that potential energy barrier of proton hopping obtained by EVB method is consistent with that obtained by Density Functional Theory (DFT) and adjusted so that the diffusion coefficient of hydronium ion in water obtained by MD simulation is consistent with that of experimental results. After annealing the system, radial distribution function or mean square displacements of hydronium ion and water, which correspond to diffusivity of each compound, was obtained. These results show the nanoscale characteristics of proton transfer in polymer electrolyte membrane.
The thermodynamic efficiency of heat engines with friction
Authors: Bizarro João P. S.
Published: March 2012

The presence of the work done against friction is incorporated into the analysis of the efficiency of heat engines based on the first and second laws of thermodynamics. We obtain the efficiencies of Stirling and Brayton engines with friction and recover results known from finite-time thermodynamics. We show that ηfric/η ≈ (1 − Wfric/W), where ηfric/η is the ratio of the efficiencies with and without friction and Wfric/W is the fraction of the work W performed by the working fluid which is spent against friction forces.
Persistence of Nasal Colonization with Livestock-Associated Methicillin-Resistant Staphylococcus aureus in Pig Farmers after Holidays from Pig Exposure
Authors: Köck Robin , Loth Bea , Köksal Mahir , Schulte-Wülwer Josef , Harlizius Jürgen , Friedrich Alexander W.
Published: March 2012

Livestock-associated methicillin-resistant
Staphylococcus aureus
(LA-MRSA) is frequently transmitted from pigs to farmers. This study analyzed whether an absence from direct contact with pigs during holidays had an impact on nasal MRSA colonization rates of pig farmers. Overall, 59% of the farmers did not clear MRSA colonization during their leave.
Real-Time PCR Detection of Phaeomoniella chlamydospora and Phaeoacremonium aleophilum
Authors: Martín Maria Teresa , Cobos Rebeca , Martín Laura , López-Enríquez Lorena
Published: March 2012

Phaeomoniella chlamydospora
and
Phaeoacremonium aleophilum
are the two main fungal causal agents of Petri disease and esca. Both diseases cause significant economic losses to viticulturalists. Since no curative control measures are known, proactive defensive measures must be taken. An important aspect of current research is the development of sensitive and time-saving protocols for the detection and identification of these pathogens. Real-time PCR based on the amplification of specific sequences is now being used for the identification and quantification of many infective agents. The present work reports real-time PCR protocols for identification of
P. chlamydospora
and
P. aleophilum
. Specificity was demonstrated against purified DNA from 60
P. chlamydospora
isolates or 61
P. aleophilum
isolates, and no amplification was obtained with 54 nontarget DNAs. The limits of detection (i.e., DNA detectable in 95% of reactions) were around 100 fg for
P. chlamydospora
and 50 fg for
P. aleophilum
. Detection was specific and sensitive for
P. chlamydospora
and
P. aleophilum
. Spores of
P. chlamydospora
and
P. aleophilum
were detected without the need for DNA purification. The established protocols detected these fungi in wood samples after DNA purification.
P. chlamydospora
was detectable without DNA purification and isolation in 67% of reactions. The detection of these pathogens in wood samples has great potential for use in pathogen-free certification schemes.
Specific Binding of Radiolabeled Cry1Fa Insecticidal Protein from Bacillus thuringiensis to Midgut Sites in Lepidopteran Species
Authors: Hernández-Rodríguez Carmen Sara , Hernández-Martínez Patricia , Van Rie Jeroen , Escriche Baltasar , Ferré Juan
Published: March 2012

Cry1Fa insecticidal protein was successfully radiolabeled with
125
I-Na. Specific binding to brush border membrane vesicles was shown for the lepidopteran species
Ostrinia nubilalis
,
Spodoptera frugiperda
,
Spodoptera exigua
,
Helicoverpa armigera
,
Heliothis virescens
, and
Plutella xylostella
. Homologous competition assays were performed to obtain equilibrium binding parameters (

K
d

[dissociation constant] and

R
t

[concentration of binding sites]) for these six insect species.
Polymorphisms in
rpoS
and Stress Tolerance Heterogeneity in Natural Isolates of Cronobacter sakazakii
Authors: Álvarez-Ordóñez Avelino , Begley Máire , Hill Colin
Published: March 2012

Significant phenotypic diversity was observed when we examined the abilities of a number of
Cronobacter sakazakii
natural isolates to cope with various sublethal stress conditions (acid, alkaline, osmotic, oxidative, or heat stress). Levels of catalase activity and use of acetate as a carbon source, phenotypes commonly used as indirect assays to predict RpoS function, revealed a high correlation between predicted RpoS activity and tolerance to acid, alkaline, osmotic, and oxidative treatments. The
rpoS
genes were sequenced and analyzed for polymorphisms. Loss-of-function mutations were found in two strains;
C. sakazakii
DPC 6523 and the genome-sequenced strain
C. sakazakii
ATCC BAA-894. The complementation of these strains with a functional
rpoS
gene resulted in an increase in bacterial tolerance to acid, osmotic, and oxidative stresses. The pigmentation status of strains was also assessed, and a high variability in carotenoid content was observed, with a functional
rpoS
gene being essential for the production of the characteristic yellow pigment. In conclusion, the evidence presented in this study demonstrates that
rpoS
is a highly polymorphic gene in
C. sakazakii
, and it supports the importance of RpoS for the tolerance under stress conditions that
C. sakazakii
may encounter in the food chain and in the host during infection.
Indole-3-Glycerol-Phosphate Synthase Is Recognized by a Cold-Inducible Group II Chaperonin in Thermococcus kodakarensis
Authors: Gao Le , Danno Atsushi , Fujii Sayaka , Fukuda Wakao , Imanaka Tadayuki , Fujiwara Shinsuke
Published: March 2012

Thermococcus kodakarensis
optimally grows at 85°C and possesses two chaperonins, cold-inducible CpkA and heat-inducible CpkB. Gene disruptants DA1 (Δ
cpkA
) and DB1 (Δ
cpkB
) showed decreased cell growth at 60°C and 93°C, respectively. The DB2 mutant (Δ
cpkA
∷
cpkB
Δ
cpkB
), whose
cpkB
gene was expressed under the control of the
cpkA
promoter, did not grow at 60°C, and the DB3 mutant [Δ
cpkA
(1–524)∷
cpkB
(1–524) Δ
cpkB
], whose CpkA amino acid residues 1 to 524 were replaced with corresponding CpkB residues that maintained the C-terminal region intact, grew at 60°C, implying that the CpkA C-terminal region plays a key role in cell growth at 60°C. To screen for specific CpkA target proteins, comparative pulldown studies with anti-Cpk were performed using cytoplasmic fractions from DA1 cells cultivated at 93°C and DB1 cells cultivated at 60°C. Among the proteins coprecipitated with anti-Cpk, TK0252, encoding indole-3-glycerol-phosphate synthase (TrpC), showed the highest Mascot score. Counter-pulldown experiments were also performed on DA1 and DB1 extracts using anti-TrpC. CpkA coimmunoprecipitated with anti-TrpC while CpkB did not. The results obtained indicate that TrpC is a specific target for CpkA. The effects of Cpks on denatured TrpC were then examined. The refolding of partially denatured TrpC was accelerated by the addition of CpkA but not by adding CpkB. DA1 cells grew optimally in minimal medium only in the presence of tryptophan but hardly grew in the absence of tryptophan at 60°C. It has been suggested that a lesion of functional TrpC is caused by
cpkA
disruption, resulting in tryptophan auxotrophy.
What gets published: the characteristics of quality improvement research articles from low- and middle-income countries
Authors: Sifrim Zoë K , Barker Pierre M , Mate Kedar S
Published: March 2012

Objectives

Reports of quality improvement (QI) research from low- and middle-income countries (LMICs) remain sparse in the scientific literature. The authors reviewed the published literature to describe the characteristics of such reports.

Methods

The authors conducted a systematic search for QI research articles from LMICs catalogued in the PubMed databases prior to December 2011, complemented by recommendations from experts in the field. Articles were categorised based on bibliometric and research characteristics. Twenty papers were randomly selected for narrative analysis regarding strategies used to present the methods and results of interventions.

Results

Seventy-six articles met the inclusion criteria. Publication rate accelerated over time, particularly among observational studies. Most studies did not use a concurrent control group; pre-/post-study designs were most common overall. Four papers were published in top-tier journals, 17 in journals at the top of their specialty and 20 in quality-specific journals. Among the papers selected for narrative analysis, four distinct components were observed in most: a description of the problem state, a description of the improvement processes and tools, a separate description of the interventions tested and a description of the evaluation methods.

Discussion

The small number of articles identified by this review suggests that publication of QI research from LMICs remains challenging. However, recent increases in publication rates, especially among observational studies, may attest to greater interest in the topic among scientific audiences. Though the authors are not able to compare this sample with unpublished papers, the four components observed by them in the narrative analysis seem to strengthen QI research reports.
Observer agreement comparing the use of virtual slides with glass slides in the pathology review component of the POSH breast cancer cohort study
Authors: Shaw Emily Clare , Hanby Andrew M , Wheeler Kevin , Shaaban Abeer M , Poller David , Barton Sheila , Treanor Darren , Fulford Laura , Walker Rosemary A , Ryan Deirdre , Lakhani Sunil R , Wells Clive A , Roche Heather , Theaker Jeffrey M , Ellis Ian O , Jones J Louise , Eccles Diana M
Published: March 2012

Aims

(1) To compare the use of scanned virtual slide images (virtual microscopy) with glass slides (conventional microscopy) in the assessment of morphological characteristics of breast cancers within the setting of the Prospective study of Outcomes in Sporadic versus Hereditary breast cancer (POSH), involving a cohort of women under 40 years of age, presenting with breast cancer. (2) To assess the acceptability to histopathologists of the use of virtual slide images.

Methods

13 histopathologists from the UK and Australia participated in the POSH pathology review. The observers were asked to assess multiple morphological features such as tumour grade and type. Comparisons were made for a single observer using both virtual images and glass slides. Intra- and inter-observer variability was calculated using the κ statistic and a comparison was made between the use of each image modality.

Results

Diagnostic performance with virtual slides was comparable to conventional microscopic assessment, with the measurement of agreement best for vascular invasion, necrosis and the presence of a central scar (κ=0.37–0.78), and poor for more subjective parameters such as pleomorphism, stroma, the nature of the tumour border and the degree of lymphocytic infiltrate (κ=0.1).

Conclusion

Virtual slides represent an acceptable methodology for central review of breast cancer histopathology and can circumvent the need for either travel to view material, or the potential problems of sending it by post.
Mre11-Dependent Degradation of Stalled DNA Replication Forks Is Prevented by BRCA2 and PARP1
Authors: Ying Songmin , Hamdy Freddie C. , Helleday Thomas
Published: March 2012

PARP inhibitors are currently being used in clinical trials to treat BRCA1- or BRCA2-defective tumors, based on the synthetic lethal interaction between PARP1 and BRCA1/2-mediated homologous recombination (HR). However, the molecular mechanisms that drive this synthetic lethality remain unclear. Here, we show increased levels of Mre11, a key component of MRN (Mre11-Rad50-Nbs1) complex that plays a role in the restart of stalled replication forks and enhanced resection at stalled replication forks in BRCA2-deficient cells. BRCA2-deficient cells also showed hypersensitivity to the Mre11 inhibitor mirin. Interestingly, PARP1 activity was required to protect stalled forks from Mre11-dependent degradation. Resistance to PARP inhibition in BRCA2-mutant cells led to reduced levels of Mre11 foci and also rescued their sensitivity to mirin. Taken together, our findings not only show that Mre11 activity is required for the survival of BRCA2 mutant cells but also elucidate roles for both the BRCA2 and PARP1 proteins in protecting stalled replication forks, which offers insight into the molecular mechanisms of the synthetic lethality between BRCA2 and PARP1. Cancer Res; 72(11); 2814–21. ©2012 AACR.
Computed Tomography Myocardial Perfusion Imaging With 320-Row Detector Computed Tomography Accurately Detects Myocardial Ischemia in Patients With Obstructive Coronary Artery Disease
Authors: George Richard T. , Arbab-Zadeh Armin , Miller Julie M. , Vavere Andrea L. , Bengel Frank M. , Lardo Albert C. , Lima João A.C.
Published: March 2012

Background—

Computed tomography coronary angiography (CTA) has been shown to be accurate in detecting anatomic coronary arterial obstruction, but is limited for the detection of myocardial ischemia. The primary aim of this study was to assess the accuracy of 320-row computed tomography perfusion imaging (CTP) to detect atherosclerosis causing myocardial ischemia.

Methods and Results—

Fifty symptomatic patients with recent single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) underwent a comprehensive cardiac computed tomography (CT) protocol that included 320-CTA, followed by adenosine stress CTP. CTP images were analyzed quantitatively for the presence of subendocardial perfusion deficits. All analyses were blinded to imaging and clinical results. CTA alone was a limited predictor of myocardial ischemia compared with SPECT, with a sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of 56%, 75%, 56%, and 75%, and the area under the receiver operator characteristic curve (AUC) was 0.65 (95% CI, 0.51–0.78,
P
=0.07). CTP was a better predictor of myocardial ischemia, with a sensitivity, specificity, PPV, and NPV of 72%, 91%, 81%, and 85%, with an AUC of 0.81 (95% CI, 0.68–0.91,
P
<0.001), and was an excellent predictor of myocardial ischemia on SPECT-MPI in the presence of stenosis (≥50% on CTA), with a sensitivity, specificity, PPV, and NPV of 100%, 81%, 50%, and 100%, with an AUC of 0.92 (95% CI, 0.80–0.97,
P
<0.001). The radiation dose for the comprehensive cardiac CT protocol and SPECT were 13.8±2.9 and 13.1±1.7; respectively (
P
=0.15).

Conclusions—

Computed tomography perfusion imaging with rest and adenosine stress 320-row CT is accurate in detecting obstructive atherosclerosis causing myocardial ischemia.
Planning estimates for the mental health community support sector
Authors: Siskind Dan , Harris Meredith , Buckingham Bill , Pirkis Jane , Whiteford Harvey
Published: March 2012

Objective: To describe the approach undertaken to derive planning estimates for the mental health community support sector in Queensland, Australia.

Methods: We quantified the needs for services by calculating the prevalence of mental illness in Queensland and by stratifying mental illness by severity. A taxonomy of services in the mental health community support sector was developed and target groups for services identified. Resource targets were set based on a review of the academic and grey literature, expert opinion and consultation with the funding body.

Results: To provide adequate supported accommodation, 88 beds per 100,000 population are required, with 33.6 full-time equivalents (FTEs) per 100,000 population of attached personalised support. An additional 12.7 FTEs per 100,000 population of personalised support is required for individuals living independently in the community. We estimated that 6.9 FTEs per 100,000 population would be required for the provision of group support services. We estimated that a target of 1.6% of total mental health community support sector budget should be allocated to mutual support and self-help and 5% to community development.

Conclusions: The mental health community support sector is now a major provider of services for people with mental illness, and is likely to continue to grow. When compared to public sector clinical mental health services, the mental health community support sector has lacked clarity surrounding what services are provided, and the quantity of resources required to provide these services. In the absence of other planning information for the community mental health support sector, the estimates described here provide a first step to guide governments and policymakers. Further research and testing in the real world by mental health community support sector practitioners is required to increase the evidence base and refine resource targets.
Ethnomethodology reconsidered: The practical logic of social systems theory
Authors: Liu Yu Cheng
Published: March 2012

This article compares ethnomethodology to social systems theory and attempts to clarify their theoretical concerns, differences and similarities when synthetically considering the former as a practical logic of the latter. As two poles on a continuum of research methods, ethnomethodology is a microanalysis of social order and human agency, whereas systems theory assumes a macro and theoretical abstraction of system formation and social evolution. When attempts are made to solve the problems of the micro/macro, part/whole, or individual/society relation, this comparison is conducive to elucidating how the practical logic is implied on both micro and macro sides, and to enhance our understanding of the human social world. Three points are suggested. First, systems theory and ethnomethodology do not contradict each other; they are complementary in an intricately dialectical process. Second, ethnomethodology can be observed through indexical rather than objective expressions. Third, due to a higher level of abstraction of systems theory, this article argues that ethnomethodology can possibly be utilized to explicate and also be regarded as the practical logic of systems theory. This comparison may contribute to reformulating systems theory, and also to some philosophical puzzles.
Item Discrimination and Type I Error in the Detection of Differential Item Functioning
Authors: Li Yanju , Brooks Gordon P. , Johanson George A.
Published: March 2012

In 2009, DeMars stated that when impact exists there will be Type I error inflation, especially with larger sample sizes and larger discrimination parameters for items. One purpose of this study is to present the patterns of Type I error rates using Mantel–Haenszel (MH) and logistic regression (LR) procedures when the mean ability between the focal and reference groups varies from zero to one standard deviation. The findings can be used as guides for alpha adjustment when using MH or LR methods when impact exists. A second purpose is to better understand the conditions that cause Type I error rates to inflate. The results indicate that inflation can be controlled even in the presence of large ability differences and with large samples.
Bayesian Comparison of Alternative Graded Response Models for Performance Assessment Applications
Authors: Zhu Xiaowen , Stone Clement A.
Published: March 2012

This study examined the relative effectiveness of Bayesian model comparison methods in selecting an appropriate graded response (GR) model for performance assessment applications. Three popular methods were considered: deviance information criterion (DIC), conditional predictive ordinate (CPO), and posterior predictive model checking (PPMC). Using these methods, several alternative GR models were compared with Samejima’s unidimensional GR model, including the one-parameter GR model, the rating scale model, simple- and complex-structure two-dimensional GR models, and the GR model for testlets. Results from a simulation study indicated that these methods appeared to be equally accurate in selecting the preferred model. However, CPO and PPMC can be used to compare models at the item level, and PPMC can also be used to compare both the relative and absolute fit of different models.
Good Neighbours in Bad Neighbourhoods: Narratives of Dissociation and Practices of Neighbouring in a ‘Problem’ Place
Authors: van Eijk Gwen
Published: March 2012

This paper challenges the idea that living in a ‘problem’ neighbourhood strains neighbour relations, by examining the relation between narratives of dissociation and practices of neighbouring. Several studies have suggested that confrontations with ethnoracial diversity, disorder and stigma would cause residents to withdraw from interacting with their fellow-residents. Based on a mixed-method study in a ‘problem’ and a ‘problem-free’ neighbourhood, the paper shows that, while narratives of dissociation may suggest withdrawal, such talk does not necessarily reflect in practices of neighbouring. First, negative neighbourhood talk can go together with efforts to connect with fellow-residents. Secondly, perceptions of diversity or disorder do not matter much when neighbour relations evolve around chance encounters and norms of good neighbouring. Inferring practices from narratives risks reproducing images of deprived neighbourhoods as dysfunctional and applying a double standard in explaining distant neighbour relations, while misrecognising the ways in which residents do maintain neighbourly relations.
Effect of granulocyte colony-stimulating factor administration on tissue regeneration due to carbon tetrachloride–induced liver damage in experimental model
Authors: Qujeq Durdi , Abassi Roya , Faeizi Farideh , Parsian Hadi , Faraji Alieh Sohan , Taheri Hassan , Tatar Mohsen , Elmi Marym M , Halalkhor Sohhrab
Published: March 2012

The mechanism by which granulocyte colony-stimulating factor (G-CSF) could lead to the protection from liver injury is not well known. Therefore, the resolution of this role needs further basic and clinical experimental investigation. Acute liver injury was induced in rats by single intraperitoneal injection of a 0.50-mL/kg dose of carbon tetrachloride (CCl4 ). Granulocyte colony-stimulating factor or vehicle of 150 µg/kg was given immediately after intoxicating the liver by CCl4 . The animals were divided into four groups of twelve each. Administration of G-CSF caused a decrease in the activity of liver enzymes,  aminotransferases, compared with the untreated group.
Accessing Escalators
Authors: Archer Hilary A. , Faldon Mary E. , Davies Rosalyn , Bronstein Adolfo
Published: March 2012

About 20% of childhood tumors originate within the central nervous system. Progress in assessment and treatment of these lesions has led to improved survival rates. We describe a patient with a posterior fossa ependymoma who despite a remarkable recovery following treatment has been frustrated by difficulty in using escalators. Such symptom selectivity is explained by specific vertical visuomotor and high-frequency vestibular deficits disrupting the execution of this complex motor act.