bluuebunny/crossref_metadata_2025 huggingface dataset:
Constructing Multi‐Country Rational Expectations Models
Authors: Dees Stephane , Hashem Pesaran M. , Vanessa Smith L. , Smith Ron P.
Published: October 2014

This article considers some of the technical issues involved in using the global vector autoregression (GVAR) approach to construct a multi‐country rational expectations (RE) model and illustrates them with a new Keynesian model for 33 countries estimated with quarterly data over the period 1980–2011. The issues considered are: the measurement of steady states; the determination of exchange rates and the specification of the short‐run country‐specific models; the identification and estimation of the model subject to the theoretical constraints required for a determinate rational expectations solution; the solution of a large RE model; the structure and estimation of the covariance matrix and the simulation of shocks. The model used as an illustration shows that global demand and supply shocks are the most important drivers of output, inflation and interest rates in the long run. By contrast, monetary or exchange rate shocks have only a short‐run impact in the evolution of the world economy. The article also shows the importance of international connections, directly as well as indirectly through spillover effects. Overall, ignoring global inter‐connections as country‐specific models do, could give rise to misleading conclusions.
Heat stress in crop plants: its nature, impacts and integrated breeding strategies to improve heat tolerance
Authors: Jha Uday Chand , Bohra Abhishek , Singh Narendra Pratap
Published: October 2014

Increasing severity of high temperature worldwide presents an alarming threat to the humankind. As evident by massive yield losses in various food crops, the escalating adverse impacts of heat stress (HS) are putting the global food as well as nutritional security at great risk. Intrinsically, plants respond to high temperature stress by triggering a cascade of events and adapt by switching on numerous stress‐responsive genes. However, the complex and poorly understood mechanism of heat tolerance (HT), limited access to the precise phenotyping techniques, and above all, the substantial G × E effects offer major bottlenecks to the progress of breeding for improving HT. Therefore, focus should be given to assess the crop diversity, and targeting the adaptive/morpho‐physiological traits while making selections. Equally important is the rapid and precise introgression of the HT‐related gene(s)/QTLs to the heat‐susceptible cultivars to recover the genotypes with enhanced HT. Therefore, the progressive tailoring of the heat‐tolerant genotypes demands a rational integration of molecular breeding, functional genomics and transgenic technologies reinforced with the next‐generation phenomics facilities.
o‐Amino Analogs of Green Fluorescence Protein Chromophore: Photoisomerization, Photodimerization and Aggregation‐induced Emission
Authors: Huang Guan‐Jhih , Lin Che‐Jen , Liu Yi‐Hung , Peng Shie‐Ming , Yang Jye‐Shane
Published: October 2014

The photochemical properties of three o‐amino analogs of the green fluorescence protein chromophore O0, O1 and O8 (o‐ABDIs) have been investigated and compared with those of the m‐ and p‐amino isomers (m‐ABDIs and p‐ABDIs) in solutions, aggregates, and the solid state. In aprotic solvents, the fluorescence competes with the Z → E photoisomerization for all cases, and the o‐ABDIs display a fluorescence quantum efficiency of 1–6%, lying between the m‐ABDIs of 5–48% and the p‐ABDIs of < 0.1%. The fluorescence of both the o‐ and m‐ABDIs is nearly quenched in protic solvents, attributable to the solvent–solute hydrogen bonding (SSHB) interactions. The phenomenon of aggregation‐induced emission observed for O8 in poor solvents resembles the behavior of M8 as a consequence of exclusion of the SSHB interactions and restriction of internal rotation for molecules located inside the aggregates. The occurrence of [2 + 2] photodimerization for O0 in the solid state is unique among the ABDIs, and the X‐ray crystal structures of O0 and the photodimer OD reveal the head‐to‐tail syn‐oriented stereochemistry. Analysis on the X‐ray crystal structures of O0, O1, M0, M1 and P0 shows that not only the pairwise topochemical geometry but also the columnar packing mode is important in determining the photodimerization reactivity.
A landscape of hairy and twisted: hunting for new trichome mutants in the Saskatoon Arabidopsis T‐DNA population
Authors: Taheri A. , Gao P. , Yu M. , Cui D. , Regan S. , Parkin I. , Gruber M.
Published: October 2014

A total of 88 new Arabidopsis lines with trichome variation were recovered by screening 49,200 single‐seed descent T3 lines from the SK activation‐tagged population and from a new 20,000‐line T‐DNA insertion population (called pAG). Trichome variant lines were classified into 12 distinct phenotype categories. Single or multiple T‐DNA insertion sites were identified for 89% of these mutant lines. Alleles of the well‐known trichome genes TRY, GL2 and TTG1 were recovered with atypical phenotype variation not reported previously. Moreover, atypical gene expression profiles were documented for two additional mutants specifying TRY and GL2 disruptions. In remaining mutants, ten lines were disrupted in genes coding for proteins not implicated in trichome development, five were disrupted in hypothetical proteins and 11 were disrupted in proteins with unknown function. The collection represents new opportunities for the plant biology community to define trichome development more precisely and to refine the function of individual trichome genes.
Playing Politics with Sex Offender Laws: An Event History Analysis of the Initial Community Notification Laws acrossAmerican States
Authors: Easterly Bianca
Published: October 2014

Despite a decline in crime rates, the 1990s witnessed extensive media coverage of several high‐profile stranger abductions and murders of children. State legislators' swift response to the public's growing fear of sex offenders with the adoption of sex offender registration and notification (SORN) laws raises questions about the role of politics. Punctuated equilibrium theory and the diffusion of innovation jointly provide a context to conduct an event history analysis to assess the extent to which politics enhanced legislative responsiveness to public opinion inSORNpolicymaking. Contrary to the commonly held belief that attributes legislative interest inSORNto salient crimes against children, the results suggest that factors such as the percentage of a conservative population, district‐level competition, and state innovativeness accelerated the diffusion of innovation of the laws.
Herbert Hoover, Occupation Withdrawal, and the Good Neighbor Policy
Authors: McPherson Alan
Published: October 2014

Historians still associate the Good Neighbor Policy inLatinAmerica almost exclusively withFranklinRoosevelt while admitting that Republican administrations before his set some precedents. This article argues more forcefully for recognizing the work ofHerbertHoover in establishing the major pillar of the policy—the withdrawal ofU.S.troops fromLatinAmerica. More attuned than previous presidents to dissenting voices throughout theAmericas, Hoover abandoned the rhetoric of paternalism towardCentralAmerica and the Caribbean and understood the moral and economic damage that occupation was doing to theUnitedStates. His diplomatic footprint was most visible in withdrawals fromNicaragua andHaiti.
The Historical Presidency “Contested Legacies and Disputed Reputations:” The Presidencies of Theodore Roosevelt and Woodrow Wilson
Authors: Bogle Lori L.
Published: October 2014

Review of: A Companion to Theodore Roosevelt – Edited by Serge Ricard

A Companion to Woodrow Wilson – Edited by Ross A. Kennedy
Euvolemia in Hemodialysis Patients: A Potentially Dangerous Goal?
Authors: Huang Shih‐Han S. , Filler Guido , Lindsay Robert , McIntyre Chris W.
Published: October 2014

Dialysis patients have high mortality rate and the leading cause of death is cardiovascular disease. Uremic cardiomyopathy differs from that due to conventional atherosclerosis, where cardiovascular changes result in ineffective circulation and lead to tissue ischemia. Modern dialysis has significant limitations with fluid management probably the most challenging. Current evidence suggests that both volume overload and aggressive fluid removal can induce circulatory stress and multi‐organ injury. Furthermore, we do not have accurate volume assessment tools. As a result, targeting euvolemia might result in more harm than benefit with conventional hemodialysis therapy. Therefore, it might be time to consider a degree of permissive over‐hydration until we have better tools to both determine ideal weight and improve current renal replacement therapy so that the process of achieving it is not so fraught with the current dangers.
The Impact of the Electoral System on Political Campaigning: Are Candidates for the Council of States More Moderate than their Fellow Candidates for the National Council?
Authors: Ladner Andreas
Published: October 2014

It is commonly believed that majority voting enhances parties to cluster around the centre of the political space, whereas proportional systems (PR) foster great ideological divergence. The theoretical arguments for these expectations go back to the work of Downs (1957) and Duverger (1954). More recent studies, however, produced quite contradictory empirical findings. In this paper I will test whether similar arguments hold true for the positioning of candidates campaigning in different electoral systems. The elections for the two chambers of the Swiss Parliament and the data from the Swiss Electoral Studies (SELECTS) and the Swiss Voting Advice Application (VAA) smartvote offer an excellent – almost laboratory like – opportunity to do so empirically. The analyses show clearly, the theoretical claims that majority voting necessarily fosters more moderate positions find no support. The candidates for the Council of States, elected in a majority system, are not more moderate than their fellow party candidates for the National Council which are elected in a PR system.
Identification of a novel HLA‐A*02 allele, A*02:428, by sequence‐based typing
Authors: Han S.‐H. , Heo Y.‐A. , Kwon O.‐J. , Kim Y.‐J. , Lee K.‐R.
Published: October 2014

HLA‐A*02:428 differs from A*02:06:01 by a non‐synonymous mutation at codon 260 (CAT to GAT) in exon 4.
HLA‐A*02:510, a variant of HLA‐A*02, discovered in a Taiwanese unrelated hematopoietic stem cell donor
Authors: Yang K. L. , Lee S. K. , Hung J. H. , Lin P. Y.
Published: October 2014

Two nucleotide changes in codon 116 (TAC → TTA) of HLA‐A*02:01:01:01 result in a novel allele, HLA‐A*02:510.
A novel KIR2DL3 allele, KIR2DL3*026, found in an individual from a southern Chinese Han population
Authors: Zhen J.‐X. , Wang D.‐M. , Deng Z.‐H.
Published: October 2014

KIR2DL3*026 differs from the closest allele KIR2DL3*00101 by a nonsynonymous mutation in exon 4.
Identification of a new HLA‐B*57 allele, HLA‐B*57:71, by next‐generation sequencing
Authors: Kuranov A. B. , Steiert I. , Goodridge D. , Müller C. A.
Published: October 2014

The sequence of a novel allele, HLA‐B*57:71, differs from HLA‐B*57:01:01 by three‐nucleotide exchanges in exon 2.
Measuring the north–south coseismic displacement component with high‐resolution multi‐aperture InSAR
Authors: Merryman Boncori John Peter , Pezzo Giuseppe
Published: October 2014

Earthquake source inversions based on space‐borne Synthetic Aperture Radar interferometry (InSAR) are used extensively. Typically, however, only the line‐of‐sight (LoS) surface displacement component is measured, which is mainly sensitive to the vertical and E–W deformations, although well‐established methods also exist to estimate the flight‐path component, which is highly sensitive to the N–S displacement. With high‐resolution sensors, these techniques are particularly appealing, because accuracies in the order of 3 cm can be achieved, while retaining spatial resolutions between 45 m and a few km, depending on the required level of filtering. We discuss the application to COSMO‐SkyMed SAR imagery of the Spectral Diversity or Multi Aperture Interferometry technique, presenting the first SAR flight‐path displacement field associated with the Mw 6.3, 2009 L'Aquila event (central Apennines). Finally, we observe and characterize a previously unknown misregistration pattern.
Nonlinear Dynamics of a Rotating Flexible Link
Authors: Sandeep Reddy B. , Ghosal Ashitava
Published: October 2014

This paper deals with the study of the nonlinear dynamics of a rotating flexible link modeled as a one dimensional beam, undergoing large deformation and with geometric nonlinearities. The partial differential equation of motion is discretized using a finite element approach to yield four nonlinear, nonautonomous and coupled ordinary differential equations (ODEs). The equations are nondimensionalized using two characteristic velocities—the speed of sound in the material and a velocity associated with the transverse bending vibration of the beam. The method of multiple scales is used to perform a detailed study of the system. A set of four autonomous equations of the first-order are derived considering primary resonances of the external excitation and one-to-one internal resonances between the natural frequencies of the equations. Numerical simulations show that for certain ranges of values of these characteristic velocities, the slow flow equations can exhibit chaotic motions. The numerical simulations and the results are related to a rotating wind turbine blade and the approach can be used for the study of the nonlinear dynamics of a single link flexible manipulator.
A Compliance-Based Parameterization Approach for Type Synthesis of Flexure Mechanisms
Authors: Jia M. , Jia R. P. , Yu J. J.
Published: October 2014

This paper presents an approach based on parameterized compliance for type synthesis of flexure mechanisms with serial, parallel, or hybrid topologies. The parameterized compliance matrices have been derived for commonly used flexure elements, which are significantly influenced by flexure parameters including material and geometric properties. Different parameters of flexure elements generate different degree of freedom (DOF) characteristic of types. Enlightened by the compliance analysis of flexure elements, a parameterization approach with detailed processes and steps is introduced in this paper to help analyze and synthesize flexure mechanisms with the case study as serial chains, parallel chains, and combination hybrid chains. For a hybrid flexure, the results of finite element (FE) modeling simulations are compared to analytical compliance elements characteristic. Under linear deformations, the maximum compliance errors of analytical models are less than 6% compared with the FE models. The final goal of this work is to provide a parameterized approach for type synthesis of flexure mechanisms, which is used to configure and change the parameters of flexure mechanisms to achieve the desired DOF requirements of types initially.
Pentapods With Mobility 2
Authors: Nawratil Georg , Schicho Josef
Published: October 2014

In this paper, we give a full classification of all pentapods with mobility 2, where neither all platform anchor points nor all base anchor points are located on a line. Therefore, this paper solves the famous Borel–Bricard problem for two-dimensional motions beside the excluded case of five collinear points with spherical trajectories. But even for this special case, we present three new types as a side-result. Based on our study of pentapods, we also give a complete list of all nonarchitecturally singular hexapods with two-dimensional self-motions.
Kinematics Modeling of a Notched Continuum Manipulator
Authors: Du Zhijiang , Yang Wenlong , Dong Wei
Published: October 2014

In this paper, the kinematics modeling of a notched continuum manipulator is presented, which includes the mechanics-based forward kinematics and the curve-fitting-based inverse kinematics. In order to establish the forward kinematics model by using Denavit–Hartenberg (D–H) procedure, the compliant continuum manipulator featuring the hyper-redundant degrees of freedom (DOF) is simplified into finite discrete joints. Based on that hypothesis, the mapping from the discrete joints to the distal position of the continuum manipulator is built up via the mechanics model. On the other hand, to reduce the effect of the hyper-redundancy for the continuum manipulator's inverse kinematic model, the “curve-fitting” approach is utilized to map the end position to the deformation angle of the continuum manipulator. By the proposed strategy, the inverse kinematics of the hyper-redundant continuum manipulator can be solved by using the traditional geometric method. Finally, the proposed methodologies are validated experimentally on a triangular notched continuum manipulator which illustrates the capability and the effectiveness of our proposed kinematics for continuum manipulators and also can be used as a generic method for such notched continuum manipulators.
Investigation Into Mechanical Behavior of the Current Collector for the Molten Carbonate Fuel Cell Through Finite Element Analysis Using Hexahedral Mesh Coarsening
Authors: Lee Chang-Whan , Yang Dong-Yol , Park Jong-seung , Kim Yun-sung , Lee Tae-Won
Published: October 2014

The current collector for the molten carbonate fuel cell (MCFC), which is a repeated structure of sheared protrusions, is manufactured from the three-stage forming process. For the precise and efficient simulation of the mechanical behavior of the current collector, the results of the forming process such as the deformed geometry and the distribution of plastic strain should be considered properly. In this work, an efficient method to construct the simulation model of the current collector considering the results of the forming process was introduced. First, hexahedral mesh coarsening was first conducted using the simulation results of the three-stage forming process of a sheared protrusion. Then, the equivalent plastic strain was mapped from the old mesh to the newly generated mesh. Finally, the simulation model for the current collector was constructed by duplicating and reflecting the newly generated mesh. For the verification of the proposed method, various numerical examples were investigated. The simulation results using the proposed method were compared with the experimental results of the three-point bending at 20 °C (room temperature) and 650 °C (operating temperature of the MCFC). From the examples for verification, it was found that the proposed simulation for the current collector was found to be efficient and applicable to the simulation of the mechanical behavior of the current collector for practical application.
Comparing the Permeability Calculation Between Different System Size of the Computational Gas Diffusion Layer Sample in PEMFC
Authors: Gao Yuan
Published: October 2014

The gas diffusion layers (GDLs) are key components in proton exchange membrane fuel cells and understanding fluid flow through them plays a significant role in improving fuel cell performance. We used a combination of multiple-relaxation time (MRT) lattice Boltzmann method (LBM) and X-ray micro tomography imaging technology to compare results on dependence of the permeability calculation on the different system size of the computational gas diffusion layer sample. The micro-structures of the carbon paper (HP_1.76) and carbon cloth (HP_1.733) GDL were all digitizing 3D images acquired by X-ray computed micro-tomography at a resolution of 1.76 and 1.733 microns meter respectively, and the fluid flow was simulated by applying pressure gradient in both the through-plane and in-plane direction respectively. The lattice Boltzmann method for permeability calculation has already been tested in our previous work. In this work, we will focus on the permeability calculation of the realistic gas diffusion layer samples depend on the different size samples. The results show the permeability increases with fluctuations as the porosity rises. All the permeability and porosity converge to the value of large size sample that can be regarding a representative volume element. As the porosity and permeability of these Porous samples differs significantly for each other, the anisotropic permeability is nearly same for each one. We can choose part of the sample to calculate the characters if the sample is too big to calculate. We systematically study the effect of system size and periodic boundary condition and validate Darcy’s law from the linear dependence of the flux on the body force exerted.
Dynamic Analysis of a Self-Sustainable Renewable Hydrogen Fueling Station
Authors: Zhao Li , Brouwer Jacob , Samuelsen Scott
Published: October 2014

To evaluate the dynamic operation and feasibility of designing and operating a self-sustainable hydrogen fueling station using renewable energy sources, system models for a hydrogen fueling station using a proton exchange membrane (PEM) electrolyzer and fuel cell have been developed to simulate the renewable sources and fueling dynamics together with hydrogen production and station operation. Theoretical models have been integrated to simulate station performance when subjected to measured power and fueling demand dynamics from a public fueling station and measured renewable energy supply dynamics. The theoretical models that are integrated into various self-sustainable station design configurations include a Proton Exchange Membrane (PEM) electrolyzer and PEM fuel cell, hydrogen compressor, and storage tank. The fueling dynamics and power consumption dynamics were obtained from an operating public hydrogen fueling station and implemented in the system model. Various control strategies are simulated and the station performance is determined to depend upon the way renewable power is utilized in the station. Due to the round trip efficiency penalty associated with converting electricity to hydrogen (in an electrolyzer) and vice versa (in a fuel cell), the results suggest that the station operation power should be supplied by the renewable sources directly whenever possible, and that the hydrogen fuel cell should provide power only when there is no renewable power available (the third control strategy tested in this paper). The simulated hydrogen fueling station powered by 200 kW wind turbines or 360 kW solar PV were determined to successfully operate in a self-sustainable manner while dispensing ∼25 kg of hydrogen per day. This study provides insights regarding the sizing of the station components such as renewable energy conversion devices, electrolyzer and fuel cell, and storage tank. The cost of the hydrogen was determined to be $8.01 per kg when the station is powered by 200 kW of wind turbines and operated using control strategy 3, while it increased to $20.22 per kg when the station is powered by 360 kW of PV array and operated using control strategy 3. This study provides a basis for achieving self-sustainable renewable hydrogen fueling stations. With further optimization and development, these self-sustainable renewable hydrogen fueling stations could provide valuable interconnections (especially in remote locations) throughout the hydrogen infrastructure network and further support the integration of renewable sources for vehicle fuels.
Performance Degradation Tests of Phosphoric Acid Doped PBI Membrane Based High Temperature PEM Fuel Cells
Authors: Zhou Fan , Araya Samuel Simon , Grigoras Ionela Florentina , Andreasen Søren Juhl , Kær Søren Knudsen
Published: October 2014

Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation. Continuous tests with H2 and simulated reformate which was composed of H2, water steam and methanol as the fuel were performed on both single cells. 12-h-startup/12-h-shutdown dynamic tests were performed on the first single cell with pure dry H2 as the fuel and on the second single cell with simulated reformate as the fuel. Along with the tests electrochemical techniques such as polarization curves and electrochemical impedance spectroscopy (EIS) were employed to study the degradation mechanisms of the fuel cells. Both single cells showed an increase in the performance in the H2 continuous tests, because of a decrease in the ORR kinetic resistance probably due to the redistribution of PA between the membrane and electrodes. EIS measurement of first fuel cell during the start/stop test showed that the mass transfer resistance and ohmic resistance increased which can be attributed to the corrosion of carbon support in the catalyst layer and degradation of the PBI membrane. During the continuous test with simulated reformate as the fuel the ORR kinetic resistance and mass transfer resistance of both single cells increased. The performance of the second single cell experienced a slight decrease during the start/stop test with simulated reformate as the fuel.
Parametric Sensitivity Tests — European PEM Fuel Cell Stack Test Procedures
Authors: Araya Samuel Simon , Andreasen Søren Juhl , Kær Søren Knudsen
Published: October 2014

As fuel cells are increasingly commercialized for various applications, harmonized and industry-relevant test procedures are necessary to benchmark tests and to ensure comparability of stack performance results from different parties. This paper reports the results of parametric sensitivity tests performed based on test procedures proposed by a European project, Stack-Test. The sensitivity of a Nafion-based low temperature PEMFC stack’s performance to parametric changes was the main objective of the tests. Four crucial parameters for fuel cell operation were chosen; relative humidity, temperature, pressure, and stoichiometry at varying current density. Furthermore, procedures for polarization curve recording were also tested both in ascending and descending current directions.
Towards the Development of a Fuel Cell System for Residential Applications: Propane Reforming via Catalytic Partial Oxidation
Authors: Waller Michael G. , Walluk Mark R. , Trabold Thomas A.
Published: October 2014

The Environmental Protection Agency (EPA) has estimated that 5% of air pollutants originate from small internal combustion engines (ICE) used in non-automotive applications. While there have been significant advances towards developing more sustainable systems to replace large ICEs, few designs have been implemented with the capability to replace small ICEs such as those used in the residential sector for lawn and garden equipment. Replacing these small residential internal combustion engines presents a unique opportunity for early market penetration of fuel cell technologies. This paper describes the initial efforts to build an innovative residential-scale fuel cell system using propane as its fuel source, and the deployment of this technology in a commonly used device found throughout the U.S. There are three main components to this program, including the development of the propane reforming system, fuel cell operation, and the overall system integration. This paper presents the reforming results of propane catalytic partial oxidation (cPOx). The primary parameters used to evaluate the reformer in this experiment were reformate composition, carbon concentration in the effluent, and reforming efficiency as a function of catalyst temperature and O2/C ratio. When including the lower heating value (LHV) for product hydrogen and carbon monoxide, maximum efficiencies of 84% were achieved at an O2/C ratio of 0.53 and a temperature of 940°C. Significant solid carbon formation was observed at catalyst temperatures below 750°C.
Design, Construction, and Testing of a Hydrogen Fuel Cell Powered Vehicle
Authors: Verhasselt Eric , Macfarland Cornelius , Abel Imoleayo , Quevedo Raundi , Macken Nelson
Published: October 2014

We have designed, built and tested a hydrogen fuel cell powered vehicle. The vehicle was constructed to specifications set forth for an international competition, which challenges high schools and universities to build and test energy efficient vehicles. We use a commercially available polymer exchange membrane (PEM) fuel cell system with a maximum output of 1.2 kW (1.6HP). The three-wheeled vehicle has a welded frame design utilizing aluminum square tubular components, an Ackermann steering system and an aerodynamically efficient hand-molded fiberglass body. A hub motor/controller powers the single rear wheel. Vehicle performance was determined in the laboratory. Performance curves for fuel consumption, torque and efficiency are presented. The vehicle successfully competed in the hydrogen fuel cell division of the competition.
A Ceramic-Membrane-Based Methane Combustion Reactor With Tailored Function of Simultaneous Separation of Carbon Dioxide From Nitrogen
Authors: Zeng Pingying , Wang Kang , Falkenstein-Smith Ryan , Ahn Jeongmin
Published: October 2014

Today, industry has become more dependent on natural gases and combustion processes, creating a tremendous pressure to reduce their emissions. Although the current methods such as chemical looping combustion (CLC) and pure oxygen combustion have several advantages, there are still many limitations. A ceramic membrane based methane combustion reactor is an environmentally friendly technique for heat and power generation. This work investigates the performance of a perovskite-type SrSc0.1Co0.9O3−δ (SSC) membrane reactor for the catalytic combustion of methane. For this purpose, the mixed ionic and electronic conducting SSC oxygen-permeable planar membrane was prepared by a dry-pressing technique, and the SSC powder catalyst was spray coated on the permeation side of the membrane. Then, the prepared SSC membrane with the catalyst was used to perform the catalytic combustion of methane. The oxygen permeability of the membrane reactor was studied. Also, the methane conversion rates and CO2 selectivity at various test conditions were reported.
Lattice Boltzmann Modeling of Water Cumulation at the Gas Channel-Gas Diffusion Layer Interface in PEM Fuel Cells
Authors: Maggiolo Dario , Marion Andrea , Guarnieri Massimo
Published: October 2014

Several experiments have proved that water in liquid phase can be present at the anode of a PEM fuel cell due to vapor condensation resulting in mass transport losses. Nevertheless, it is not yet well understood where exactly water tends to cumulate and how the design of the gas channel (GC) and gas diffusion layer (GDL) could be improved to limit water cumulation. In the present work a three-dimensional lattice Boltzmann based model is implemented in order to simulate the water cumulation at the GC-GDL interface at the anode of a PEM fuel cell. The numerical model incorporates the H2-H2O mixture equation of state and spontaneously simulates phase separation phenomena. Different simulations are carried out varying pressure gradient, pore size and relative height of the GDL. Results reveal that, once saturation conditions are reached, water tends to cumulate in two main regions: the upper and side walls of the GC and the GC-GDL interface, resulting in a limitation of the reactant diffusion from the GC to the GDL. Interestingly, the cumulation of liquid water at the interface is found to diminish as the relative height of the GDL increases.
Electricity Generation From Fuel Cell Waste Heat Using an Organic Rankine Cycle
Authors: Bronicki Lucien , Nett Carl N. , Nordquist Josh
Published: October 2014

Fuel cells produce exhaust waste heat that can be harnessed to either meet local heating needs or produce additional electricity via an appropriately chosen bottoming cycle. Power production can often be more economically attractive than heating due to the much higher value of electricity than heat on an equivalent energy basis, especially given fuel cell incentives and subsidies that are based on the net electrical output of the (combined cycle) fuel cell power plant. In this paper we review the application of the Organic Rankin Cycle (ORC) for power production from fuel cell waste heat, with emphasis on the resulting improvements in overall power plant power output, efficiency, economics (e.g., cents/kWh maintenance costs), and emissions levels (e.g., lb/MWh emissions). We also highlight a much less obvious advantage of ORC bottoming of fuel cells; namely, its ability to partially compensate for fuel cell stack degradation over time, and corresponding potential to extend the time required between fuel cell stack overhauls. We will also review the relative difficulty of several well established commercial applications of the ORC for power production from waste heat — such as power production from gas turbine exhaust, etc. — in comparison to fuel cell applications. We conclude that not only is the ORC ideal for fuel cell bottoming, but also that fuel cells are a nearly ideal commercial application area for the ORC. In closing, we summarize a recently completed project believed to be the world’s first commercial application of ORC technology to a fuel cell power plant. This project was completed in less than a year after its initiation, and utilizes a single ORC in conjunction with five fuel cells, all located within a fuel cell park that produces nearly 15 MW of electricity.
Advances in Electrochemical Compression of Hydrogen
Authors: Moton Jennie M. , James Brian D. , Colella Whitney G.
Published: October 2014

This paper evaluates the potential for electrochemical hydrogen compression systems (EHCs) regarding their engineering performance, manufacturability, and capital costs. EHCs could enhance or replace mechanical hydrogen compressors. The physical embodiment of EHCs is similar to that of low temperature (LT) proton exchange membrane (PEM) fuel cell systems (FCSs). They also share common operating principles with LT PEM FCS and with PEM electrolysis systems. Design for Manufacturing and Assembly (DFMA™) analysis is applied to EHCs to identify manufactured designs, manufacturing methods, projected capital costs under mass-production, and cost drivers for both the EHC stack and the balance of plant (BOP). DFMA™ analysis reveals that EHC stack costs are expected to be roughly equal to EHC BOP costs, under a variety of scenarios. (Total EHC system costs are the sum of stack and BOP costs.) Within the BOP, the primary cost driver is the electrical power supply. Within the stack, the primary cost drivers include the membrane electrode assembly (MEA), the stamped bipolar plates, and the expanded titanium (Ti) cell supports, particularly at lower hydrogen outlet pressures. As outlet pressure rises, capital costs escalate nonlinearly for several reasons. Higher pressure EHCs experience higher mechanical loads, which necessitate using a greater number of smaller diameter cells and a greater tie rod mass. Higher pressure EHCs also exhibit a higher degree of back-diffusion, which necessitates using more cells per system.
Saint-Gobain’s All Ceramic SOFC Stack: Architecture and Performance
Authors: Barabasz Robin , Dutton Emma , Feldman Brian , Lin Guangyong , Mohanram Aravind , Narendar Yeshwanth , Pietras John , Qi Frank Chunming , Patterson Zachary , Poizeau Sophie , Sarikaya Ayhan , Zandi Morteza
Published: October 2014

Saint-Gobain has developed a unique all ceramic SOFC stack with performance characteristics that make it an attractive solution to the cost and durability challenges of commercializing conventional SOFCs. Saint-Gobain’s all ceramic stacks achieve power density higher than 200 mW/cm2 when operating at 800 °C and 0.75 V/cell. Power degradation is low at <0.2% per kilohour over more than 12,000 hours of testing. Ceramic interconnect stability is verified for >16,000 hours using accelerated testing. Good performance under thermal cycling, power cycling and unplanned transients such as fuel or air loss has also been confirmed. With reliable R&D scale manufacturing and targeted testing platforms, Saint-Gobain has increased sub-scale stack power density by 61% and decreased interconnect cell resistance by 65% with further improvements in development.
Dosimetric feasibility of real‐time MRI‐guided proton therapy
Authors: Moteabbed M. , Schuemann J. , Paganetti H.
Published: October 2014

Purpose:

Magnetic resonance imaging (MRI) is a prime candidate for image‐guided radiotherapy. This study was designed to assess the feasibility of real‐time MRI‐guided proton therapy by quantifying the dosimetric effects induced by the magnetic field in patients’ plans and identifying the associated clinical consequences.

Methods:

Monte Carlo dose calculation was performed for nine patients of various treatment sites (lung, liver, prostate, brain, skull‐base, and spine) and tissue homogeneities, in the presence of 0.5 and 1.5 T magnetic fields. Dose volume histogram (DVH) parameters such as D95, D5, and V20 as well as equivalent uniform dose were compared for the target and organs at risk, before and after applying the magnetic field. The authors further assessed whether the plans affected by clinically relevant dose distortions could be corrected independent of the planning system.

Results:

By comparing the resulting dose distributions and analyzing the respective DVHs, it was determined that despite the observed lateral beam deflection, for magnetic fields of up to 0.5 T, neither was the target coverage jeopardized nor was the dose to the nearby organs increased in all cases except for prostate. However, for a 1.5 T magnetic field, the dose distortions were more pronounced and of clinical concern in all cases except for spine. In such circumstances, the target was severely underdosed, as indicated by a decrease in D95 of up to 41% of the prescribed dose compared to the nominal situation (no magnetic field). Sites such as liver and spine were less affected due to higher tissue homogeneity, typically smaller beam range, and the choice of beam directions. Simulations revealed that small modifications to certain plan parameters such as beam isocenter (up to 19 mm) and gantry angle (up to 10°) are sufficient to compensate for the magnetic field‐induced dose disturbances. The authors’ observations indicate that the degree of required corrections strongly depends on the beam range and direction relative to the magnetic field. This method was also applicable to more heterogeneous scenarios such as skull‐base tumors.

Conclusions:

This study confirmed the dosimetric feasibility of real‐time MRI‐guided proton therapy and delivering a clinically acceptable dose to patients with various tumor locations within magnetic fields of up to 1.5 T. This work could serve as a guide and encouragement for further efforts toward clinical implementation of hybrid MRI–proton gantry systems.
Transforming Science, Service, and Society
Authors: Coleman C. Norman , Love Richard R.
Published: October 2014

Battling cancer in developing countries requires partnerships between cancer-care mentors from high-income countries and local community health workers.
Targeting latent TGFβ release in muscular dystrophy
Authors: Ceco Ermelinda , Bogdanovich Sasha , Gardner Brandon , Miller Tamari , DeJesus Adam , Earley Judy U. , Hadhazy Michele , Smith Lucas R. , Barton Elisabeth R. , Molkentin Jeffery D. , McNally Elizabeth M.
Published: October 2014

Blocking cleavage of latent TGFβ binding protein 4, a modifier of muscular dystrophy in humans and mice, inhibits release of latent TGFβ and decreases pathology in muscular dystrophy.
Salivary Mucins Protect Surfaces from Colonization by Cariogenic Bacteria
Authors: Frenkel Erica Shapiro , Ribbeck Katharina
Published: October 2014

Understanding how the body's natural defenses function to protect the oral cavity from the myriad of bacteria that colonize its surfaces is an ongoing topic of research that can lead to breakthroughs in treatment and prevention. One key defense mechanism on all moist epithelial linings, such as the mouth, gastrointestinal tract, and lungs, is a layer of thick, well-hydrated mucus. The main gel-forming components of mucus are mucins, large glycoproteins that play a key role in host defense. This study focuses on elucidating the connection between MUC5B salivary mucins and dental caries, one of the most common oral diseases. Dental caries is predominantly caused by
Streptococcus mutans
attachment and biofilm formation on the tooth surface. Once
S. mutans
attaches to the tooth, it produces organic acids as metabolic by-products that dissolve tooth enamel, leading to cavity formation. We utilize CFU counts and fluorescence microscopy to quantitatively show that
S. mutans
attachment and biofilm formation are most robust in the presence of sucrose and that aqueous solutions of purified human MUC5B protect surfaces by acting as an antibiofouling agent in the presence of sucrose. In addition, we find that MUC5B does not alter
S. mutans
growth and decreases surface attachment and biofilm formation by maintaining
S. mutans
in the planktonic form. These insights point to the importance of salivary mucins in oral health and lead to a better understanding of how MUC5B could play a role in cavity prevention or diagnosis.
Bioengineering of Bacteria To Assemble Custom-Made Polyester Affinity Resins
Authors: Hay Iain D. , Du Jinping , Burr Natalie , Rehm Bernd H. A.
Published: October 2014

Proof of concept for the
in vivo
bacterial production of a polyester resin displaying various customizable affinity protein binding domains is provided. This was achieved by engineering various protein binding domains into a bacterial polyester-synthesizing enzyme. Affinity binding domains based on various structural folds and derived from molecular libraries were used to demonstrate the potential of this technique. Designed ankyrin repeat proteins (DARPins), engineered OB-fold domains (OBodies), and V
HH
domains from camelid antibodies (nanobodies) were employed. The respective resins were produced in a single bacterial fermentation step, and a simple purification protocol was developed. Purified resins were suitable for most lab-scale affinity chromatography purposes. All of the affinity domains tested produced polyester beads with specific affinity for the target protein. The binding capacity of these affinity resins ranged from 90 to 600 nmol of protein per wet gram of polyester affinity resin, enabling purification of a recombinant protein target from a complex bacterial cell lysate up to a purity level of 96% in one step. The polyester resin was efficiently produced by conventional lab-scale shake flask fermentation, resulting in bacteria accumulating up to 55% of their cellular dry weight as polyester. A further proof of concept demonstrating the practicality of this technique was obtained through the intracellular coproduction of a specific affinity resin and its target. This enables
in vivo
binding and purification of the coproduced “target protein.” Overall, this study provides evidence for the use of molecular engineering of polyester synthases toward the microbial production of specific bioseparation resins implementing previously selected binding domains.
Selection for Growth on 3-Nitrotoluene by 2-Nitrotoluene-Utilizing Acidovorax sp. Strain JS42 Identifies Nitroarene Dioxygenases with Altered Specificities
Authors: Mahan Kristina M. , Penrod Joseph T. , Ju Kou-San , Al Kass Natascia , Tan Watumesa A. , Truong Richard , Parales Juanito V. , Parales Rebecca E.
Published: October 2014

Acidovorax
sp. strain JS42 uses 2-nitrotoluene as a sole source of carbon and energy. The first enzyme of the degradation pathway, 2-nitrotoluene 2,3-dioxygenase, adds both atoms of molecular oxygen to 2-nitrotoluene, forming nitrite and 3-methylcatechol. All three mononitrotoluene isomers serve as substrates for 2-nitrotoluene dioxygenase, but strain JS42 is unable to grow on 3- or 4-nitrotoluene. Using both long- and short-term selections, we obtained spontaneous mutants of strain JS42 that grew on 3-nitrotoluene. All of the strains obtained by short-term selection had mutations in the gene encoding the α subunit of 2-nitrotoluene dioxygenase that changed isoleucine 204 at the active site to valine. Those strains obtained by long-term selections had mutations that changed the same residue to valine, alanine, or threonine or changed the alanine at position 405, which is just outside the active site, to glycine. All of these changes altered the regiospecificity of the enzymes with 3-nitrotoluene such that 4-methylcatechol was the primary product rather than 3-methylcatechol. Kinetic analyses indicated that the evolved enzymes had enhanced affinities for 3-nitrotoluene and were more catalytically efficient with 3-nitrotoluene than the wild-type enzyme. In contrast, the corresponding amino acid substitutions in the closely related enzyme nitrobenzene 1,2-dioxygenase were detrimental to enzyme activity. When cloned genes encoding the evolved dioxygenases were introduced into a JS42 mutant lacking a functional dioxygenase, the strains acquired the ability to grow on 3-nitrotoluene but with significantly longer doubling times than the evolved strains, suggesting that additional beneficial mutations occurred elsewhere in the genome.
The Aerobic and Anaerobic Respiratory Chain of
Escherichia coli
and
Salmonella enterica
: Enzymes and Energetics
Authors: Unden Gottfried , Steinmetz Philipp Aloysius , Degreif-Dünnwald Pia
Published: October 2014

Escherichia coli
contains a versatile respiratory chain that oxidizes 10 different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors.
Salmonella
is able to use two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. A large number of respiratory pathways can be established by combining different electron donors and acceptors. The respiratory dehydrogenases use quinones as the electron acceptors that are oxidized by the terminal reductase and oxidases. The enzymes vary largely with respect to their composition, architecture, membrane topology, and the mode of energy conservation. Most of the energy-conserving dehydrogenases (FdnGHI, HyaABC, HybCOAB, and others) and the terminal reductases (CydAB, NarGHI, and others) form a proton potential (Δ
p
) by a redox-loop mechanism. Two enzymes (NuoA-N and CyoABCD) couple the redox energy to proton translocation by proton pumping. A large number of dehydrogenases and terminal reductases do not conserve the redox energy in a proton potential. For most of the respiratory enzymes, the mechanism of proton potential generation is known or can be predicted. The H
+
/2e
−
ratios for most respiratory chains are in the range from 2 to 6 H
+
/2e
−
. The energetics of the individual redox reactions and the respiratory chains is described and related to the H
+
/2e
−
ratios.