bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors limiting the low temperature operation of
SOFCs
Authors: Carter J. David , Cruse T. A. , Ingram B. J. , Krumpelt M.
Published: December 2010

Over the history of solid oxide fuel cell (SOFC) development, many investigators have sought to reduce the operating temperature. In this article, we present and discuss factors that lead to a lower limit on the effective operating temperature of these fuel cells. Among these factors, the cathode polarization resistance and fuel oxidation on the anode show the greatest effects on limiting low‐temperature operation. The strontium‐doped lanthanum manganite cathode is limited to ≥800 °C for 0.6 W cm
−2
at 0.85 V. Mixed‐ionic and electronic conducting materials are more active and can operate at ∼750 °C, but they are more prone to interact with the yttria‐stabilized zirconia (YSZ) electrolyte. Modified Ni‐based/YSZ anodes operating on carbonaceous fuels have a thermodynamic temperature limit of 500 °C because of carbon formation in the absence of steam, but also need to have their power densities improved to operate below 650 °C. The electrolyte resistance is not a significant factor for 8 mol% YSZ being able to operate as low as 530 °C, and for other electrolytes at even lower temperatures. Also, the electrical resistance of the interconnect, including that of the protective scale on metallic interconnects, becomes significant at temperatures below 600 °C. Cell geometry is another factor that limits low‐temperature operation, favoring planar over other stack designs.
Heat and water transport models for polymer electrolyte fuel cells
Authors: Pasaogullari U.
Published: December 2010

Owing to conflicting requirements of membrane hydration and avoiding flooding by liquid water, water management is very critical for polymer electrolyte fuel cells (PEFC). Water saturation pressure is strongly dependent on temperature around the PEFC operating temperatures. Therefore water transport and water management are strongly dependent on temperature distribution and thermal transport within the fuel cell. In this article, heat and water management in PEFCs is explored with a focus on modeling of the coupled heat and water transport. Effect of membrane hydration on fuel cell operation and performance is investigated in detail. Heat generation in PEFCs is described and breakdown of heat sources is given, and models describing the thermal transport and temperature distribution are reviewed. Coupled two‐phase heat and mass transport is elucidated along with the results from the computational models describing the phenomena.
Proton exchange membrane fuel cell (PEMFC) down‐the‐channel performance model
Authors: Gu W. , Baker D. R. , Liu Y. , Gasteiger H. A.
Published: December 2010

This article presents a down‐the‐channel model for proton exchange membrane fuel cell (PEMFC) performance prediction needed in system modeling and in fuel cell component selection for automotive application. With focus on the quantification of voltage loss terms, we have reviewed the required input physical‐chemical parameters for the model and the methods to obtain those kinetic and transport parameter values. Constructed based on multiple one‐dimensional cell models coupled with down‐the‐channel gas flow, the model is formulated to meet the high computational efficiency required by the system modeling aiming at improving fuel cell performance without incurring significant cost increase. With no free fitting parameters, the model is validated with reasonably good agreement against the experimental data, including cell performance, current distribution, and water balance, obtained from the short stacks with large active area and straight‐channel flow fields under subsaturated operating conditions desired for automotive application. Therefore, while further fundamental understanding and improvement of measurement techniques to obtain fundamental materials properties are needed, the down‐the‐channel model that quantifies the various voltage loss terms is a valuable tool for predicting stack performance with new materials under various new sets of operating conditions.
Performance during start‐up of proton exchange membrane (PEM) fuel cells at subfreezing conditions
Authors: Thompson E. L. , Gu W. , Gasteiger H. A.
Published: December 2010

This article discusses recent performance studies of PEM (proton exchange membrane) fuel cells operating at subfreezing temperatures. The major sources of voltage loss (kinetic, ohmic, and transport) are experimentally isolated to quantify their contribution to the total voltage loss. Thus, the oxygen reduction reaction (ORR) kinetics and membrane proton conduction resistances are quantified at subfreezing temperatures. To provide a mechanistic explanation for the observed temperature and water‐content dependency of proton conductivity, phase transitions and state of absorbed water in Nafion®was measured using differential scanning calorimetry.

While it is reasonably well known that a successful PEM fuel cell cold start strongly depends upon the effective use of membrane and electrode to store product water (ice) until the cell temperature reaches 0 °C, the exact water (or charge) storage capacity of the membrane and the cathode electrode as well as the estimated water partitioning into these two locations as a function of operating conditions has not been discussed in detail and is presented here. In addition, cryo‐SEM is used to examine ice formation in the electrode and confirm the above estimates. The electron proton conduction resistance was used to predict the ORR current distribution within the cathode electrode, which provides insight into how ice filling proceeds in the electrode, and is supported by cryo‐SEM findings. Finally, the measured and estimated voltage losses are summarized to highlight the contribution of the various voltage loss terms on the overall initial voltage loss during operation at −20 °C, for a wide range of membrane water contents and current densities.
Use of neutron imaging for proton exchange membrane fuel cell (PEMFC) performance analysis and design
Authors: Trabold T. A. , Owejan J. P. , Gagliardo J. J. , Jacobson D. L. , Hussey D. S. , Arif M.
Published: December 2010

Efficient water management is one of the key design objectives for proton exchange membrane fuel cells (PEMFCs) due to the influence of water on material selection, bipolar plate design, and operating conditions. Neutron imaging has proven to be one of the most important diagnostic methods available for PEMFC research, as the technique affords the ability to observe,in situ, water transport and accumulation phenomena. In this article, we provide an overview of the neutron imaging method, in terms of both the imaging technique itself, as well as special considerations for fuel cell test article design. Descriptions of specific applications areas are provided, including water gradients normal to the membrane‐electrode assembly, diffusion media and flow field channel water management, multicell and transient phenomena, and low temperature and freeze performance. Finally, we offer perspectives on future developments in the application of neutron imaging to fuel cells.
Modeling the impact of cation contamination in a polymer electrolyte membrane fuel cell
Authors: Greszler T. A. , Moylan T. E. , Gasteiger H. A.
Published: December 2010

Starting from fundamental principles, we have developed an isothermal, one‐dimensional model for cation contamination of a proton exchange membrane (PEM) fuel cell. When current is drawn, the foreign cations migrate toward the cathode under the influence of the potential gradient while diffusion acts to balance this migration. The model provides the electrolyte potential along with the concentration of water, cation, and proton across the membrane electrode assembly (MEA) at steady‐state condition. The voltage loss associated with cation contamination is largely thermodynamic in nature owing to the proton concentration (pH) difference that develops between the anode and cathode. This potential loss is proportional to current density and inversely proportional to water content. If the cation fraction in the cathode approaches unity, the cell current becomes limited because of proton starvation. The model is validated with experimental hydrogen pump performance data using lithium‐doped MEAs. Hydrogen/oxygen operation is presented experimentally and discussed, but not explicitly modeled because of the added complications introduced by the sluggish oxygen reduction reaction kinetics. Experimental data for cobalt‐doped MEAs, which can react in the cathode when the local pH increases above five, is presented and explained with the aid of cobalt's Pourbaix diagram. Finally, the effect of cobalt ion contamination (e.g., from PtCo cathode catalysts degradation) on H
2
/air PEMFC performance under automotive conditions is shown.
Electrochemical impedance spectroscopy as diagnostic tool
Authors: Jensen S. H. , Hjelm J. , Hagen A. , Mogensen M.
Published: December 2010

The aim of electrochemical impedance spectroscopy (EIS) is to gain knowledge about those processes that contribute to the impedance of an electrochemical system such as a fuel cell or just a single electrode. Usually several processes contribute, and they typically overlap in impedance spectra. This sets a limit to the amount of knowledge that can be derived about the individual processes. First, a brief review of the literature is given. Next, a method to separate individual contributions by systematic variation of operating parameters is described. Only processes depending on the variation contribute to the difference in the impedance. This makes it easier to analyze the difference than the impedance itself. The derivative with respect to ln(frequency) of the real part of the difference of the impedance spectra is easy to obtain and provides a good resolution of the contributions.
Electron microscopy to study membrane electrode assembly (
MEA
) materials and structure degradation
Authors: Chatenet M. , Guetaz L. , Maillard F.
Published: December 2010

The mass production of proton exchange membrane fuel cell (PEMFC) for stationary or mobile applications requires long‐term durability and minimization of the voltage loss observed upon operation. The extent of PEMFC performance degradation depends on the type of materials composing the membrane electrode assembly (MEA), their manufacturing technique, their structure, and the operating conditions of the cell. Recently, electron microscopy (EM) has become a technique of choice to achieve a better understanding of the physical/chemical origin of the MEA degradation as a function of operation time. Unlike most other physical, chemical, and electrochemical
in situ
or
ex situ
techniques (global techniques), EM enables the identification of local changes to the various components of the MEA. For example, defect formation at the micrometer scale in the proton exchange membrane (PEM) and the active layer (observed by scanning electron microscopy), change of porosity and redistribution of the electrocatalyst at the nanometer scale (observed by field‐emission gun scanning electron microscopy (FEG‐SEM) and transmission electron microscopy (TEM)), or structure/composition degradation of electrocatalyst nanoparticles at the atomic scale (observed by high‐resolution transmission electron microscopy (HRTEM)) can be derived from EM. A combination of the conclusions derived from local EM observations with those derived from other global characterization techniques yields the determination of MEA degradation mechanisms and provides some important routes to improve the PEM fuel cell performance and durability.
Proton exchange membrane fuel cell degradation: mechanisms and recent progress
Authors: Madden T. , Perry M. , Protsailo L. , Gummalla M. , Burlatsky S. , Cipollini N. , Motupally S. , Jarvi T.
Published: December 2010

We report a selective review of the literature on proton exchange membrane (PEM) fuel cell degradation. The review begins with an overview of the essential driving forces that influence degradation rates. Thereafter, we summarize key mechanisms of and progress toward mitigating carbon corrosion, platinum dissolution, and membrane degradation. Finally, we summarize useful research directions, and also identify those that deserve less attention.
Cold‐start durability of membrane‐electrode assemblies
Authors: Wang C. Y. , Yang X. G. , Tabuchi Y. , Kagami F.
Published: December 2010

Durability of membrane‐electrode assemblies (MEAs) cycled under cold‐start conditions is reviewed. It is shown that MEAs cycled under 100 mA cm
−2
from −30 °C show no degradation after 100 cycles, but exhibit mild degradation after 150 cycles under 300 mA cm
−2
from −30 °C, and furthermore suffer severe degradation after 110 cycles under 500 mA cm
−2
from −20 °C. Transmission electron microscopy (TEM) and X‐ray diffraction using cross‐sectional samples of the aged MEAs further revealed three primary degradation mechanisms: (i) interfacial delamination between the cathode catalyst layer (CL) and membrane, (ii) cathode CL pore collapse and densification upon melting of a fully ice‐filled CL, and (iii) Pt particle coarsening and Pt dissolution in the perfluorosulfonic acid (PFSA) ionomer. The interfacial delamination and CL densification appear to be closely related to each other, and the key parameter to affect both is the ice volume fraction in the cathode CL after each cold‐start step. Eliminating or minimizing these two degradation processes could improve the MEA cold‐start durability by 280%. Mitigation strategies include improved gas purge prior to cold start, good MEA design, small start‐up current density, and low cell thermal mass.
Membranes and catalyst performance targets for automotive fuel cells
Authors: Iiyama A. , Shinohara K. , Iguchi S. , Daimaru A.
Published: December 2010

Membrane and catalyst performance targets for automotive fuel cells are presented. The Fuel Cell Commercialization Conference of Japan (FCCJ) has worked with three automobile manufacturers in Japan to define the target performance, durability, and cost of fuel cells for transportation application, and in January 2007 produced a booklet describing them. This article provides an overview of these target values and highlights the durability parameters specifically required in the automotive application in relation to the current knowledge of degradation mechanisms of fuel cells. On the basis of this information, FCCJ has proposed a methodology for testing membrane‐electrode assemblies (MEAs) as an approach to the evaluation of materials for the two most important components: electrolyte membranes and electrode catalysts. This is intended to assist the development of materials that achieve the target durability, which is described below.
Field experience with portable
DMFC
products
Authors: Müller J.
Published: December 2010

Direct methanol fuel cell (DMFC) systems and their user acceptance have a critical pioneering role in the developing fuel cell markets. This article focuses on commercial aspects of early markets for DMFC products, selection criteria why these markets were chosen, and customer benefits. Then, the process of matching customer requirements with technical capabilities of state‐of‐the‐art DMFC systems is described. The frequently discussed technical challenges of DMFC technology (e.g., methanol crossover) are reviewed and discussed in light of real‐world experience on thousands of DMFC systems globally. An important result is that the focus of many scientific research projects is quite different from realties in the marketplace. It is concluded that better alignment of academic research with industrial needs is required in order to advance fuel cell technology further. Next, degradation mechanisms in real‐world applications are reviewed and compared with known degradation mechanisms under laboratory conditions. Again, significant discrepancies occur, which must be addressed by any company attempting to sell fuel cell systems commercially.
Design concepts and durability challenges for mini fuel cells
Authors: Gottesfeld S.
Published: December 2010

Recent developments in direct methanol fuel cell (DMFC) technology are described. Starting in 2006, early commercialization of DMFC power sources of 20–100 W for recreational vehicles and boats and, most recently, 1 kW level DMFC systems for forklift power source applications has taken place. This development clearly suggests a significant degree of maturity of mainstream DMFC technology. Further, very recent technology advancements have opened the door to DMFC power sources of high system simplicity, which is of special significance to micro‐fuel cell applications. They include a DMFC platform with direct supply of 100% methanol into the DMFC anode, based on spontaneous supply of water from the cathode to the anode within the cell, thereby eliminating any need for water pumping around the cell. Fuel utilization of the order of 90% is achievable even with methanol‐leaky poly(perfluorosulfonic acid) (poly(PFSA)) membranes under such direct supply of 100% methanol to the DMFC anode, by adjusting the feed of neat methanol to a stoichiometric flow rate near 1.1. Quantitative analysis is provided for the requirements to embed a DMFC power system into small spaces defined by sizes of consumer electronics devices. The results show that, while implementation of DMFC power sources for hand‐held or laptop power applications is feasible with present technology through the use of external chargers, embedding such power units inside hand‐held devices is awaiting increase of the DMFC power density achievable under the operation conditions relevant for hand‐held applications, from the present level of 50–100 to over 300 mW cm
−3
.
Overview of solid oxide fuel cell degradation
Authors: Yokokawa H.
Published: December 2010

This article summarizes the general features of the degradation behavior of those solid oxide fuel cells stacks/systems that have to meet the requirements for chemical as well as mechanical compatibilities in addition to normal requirements concerning respective cell components. Sealless tubular stacks developed for large stationary applications and exhibiting excellent durability are first analyzed (0.3%/1000 h for more than 70 000 h as cells and 0.1%/1000 h for more than 30 000 as systems). Degradation of stacks that have been designed for application in small residential cogeneration or in transportation, however, exhibits different features mainly because of differences in materials used and stack design of such new applications. This article describes the characteristic features of degradation from cell to stack levels. Finally, to obtain full understanding of degradation and to establish a well‐designed solid oxide fuel cells (SOFC) control system, there is a discussion on what is to be realized and what is to be overcome.
Impact of impurities on reliability of materials in solid oxide fuel cell (SOFC) stack/modules
Authors: Yokokawa H. , Sakai N. , Horita T. , Yamaji K.
Published: December 2010

The impurity behavior in solid oxide fuel cells is discussed in terms of the thermodynamic characteristic properties in particular on the basis of acid–base concept in theoretical consideration and in terms of actually observed quantities of impurities with SIMS techniques. The thermochemical stability of cathodes can be represented in the chemical potential diagrams where the thermodynamic activity of basic oxides (SrO, La2O3) are used. By adopting the same axes, this makes it possible to compare thermodynamic properties for different elements in the La–Sr–M–O system (M = elements). By using this diagram, the acidity of respective impurity elements are defined and compared with the main transition metal element in cathode materials. The impurity behavior inside SOFC stacks is also examined by using the diagram with temperature and oxygen potential axes. This makes it possible to see the interaction of the cell component with impurities as functions of temperature and oxygen potentials. Examples are given for Ni–S–O–H system. Finally, the impurity behavior in actual stacks detected by SIMS was examined and compared with thermodynamic prediction with the emphasis on the interaction between impurities and the main component as functions of fuel utilization and other fuel cell conditions.
Nishorting in relation to acid‐base equilibrium of molten carbonate for molten cabonate fuel cell (MCFC) application
Authors: Mitsushima S.
Published: December 2010

One of the important methods to improve the endurance of the molten carbonate fuel cell is to reduce the nickel precipitate that forms the shorting. The nickel precipitate shorting consists of three processes: the dissolution of the NiO cathode, the flux of the nickel ion to the anode side, and the reduction to metal by hydrogen from the anode side. The NiO solubility affects all processes of the shorting.

The dissolution of the NiO in the molten carbonate is an acidic dissolution mechanism in the range of the practical operating conditions of the molten carbonate fuel cells. Therefore, to reduce the solubility of NiO, a basic molten carbonate must be selected. These behaviors are explained by the fact that the solubility of the NiO in the molten carbonate is a function of the Coulomb force parameter that indicates charge density of the molten salts.

The time function of the nickel shorting can be described by experimental equations. On the basis of an interpretation of the experimental equations and the simple model of the nickel shorting based on the diffusion of the nickel ion, it is seen that the reduction in the solubility improves the durability of the molten carbonate fuel cells.
Porous Single Crystals of Calcite from Colloidal Crystal Templates: ACC Is Not Required for Nanoscale Templating
Authors: Hetherington Nicola B. J. , Kulak Alex N. , Kim Yi‐Yeoun , Noel Elizabeth H. , Snoswell David , Butler Michael , Meldrum Fiona C.
Published: December 2010

This article investigates the formation of nanostructured single crystals of calcite using direct, ion‐by‐ion precipitation methods and shows that single crystals with complex morphologies and curved surfaces can readily be formed using this technique. Calcite crystals with inverse opal and direct opal structures are prepared using templates of colloidal crystals and polystyrene reverse opals, respectively, and excellent replication of the template structures are achieved, including the formation of 200‐nm spheres of calcite in the direct opal structure. These highly porous crystals also display extremely regular, crystalline gross morphologies. The methodology is extremely versatile and challenges the preconception that nanostructured crystals cannot be prepared by simple diffusion of reagents into the template due to blocking of the channels. The results are also discussed in light of alternative templating methods using amorphous calcium carbonate (ACC) as a precursor phase and provide insight into the role of ACC in biological calcification processes.
Hoffman syndrome: New patients, new insights
Authors: Hügle Boris , Hoffman Hal , Bird Lynne M. , Gebauer Corinna , Suchowerskyj Philipp , Sack Ulrich , Kohlhase Jürgen , Schuster Volker
Published: December 2010

Hypogammaglobulinemia or agammaglobulinemia are major features of specific syndromes, including X‐linked agammaglobulinemia and common variable immunodeficiency. However, the combination of hypogammaglobulinemia with specific dysmorphic features is less common, with only a few reported cases. One such report was a sporadic case of humoral immunodeficiency, facial dysmorphism, and limb anomalies in a young girl, later referred to as Hoffman syndrome. We report on a 7‐year‐old girl with almost complete loss of B cells, facial dysmorphism, and malformation of the limbs and genitalia, whose mother shows similar dysmorphic features with an attenuated version of the B‐cell deficiency. We believe that all three cases described above represent the same condition. The features of the three affected individuals with Hoffman syndrome are reviewed. Further investigations in this recently recognized B‐cell immunodeficiency syndrome are warranted. © 2010 Wiley‐Liss, Inc.
Cranial neural crest cells on the move: Their roles in craniofacial development
Authors: Cordero Dwight R. , Brugmann Samantha , Chu Yvonne , Bajpai Ruchi , Jame Maryam , Helms Jill A.
Published: December 2010

The craniofacial region is assembled through the active migration of cells and the rearrangement and sculpting of facial prominences and pharyngeal arches, which consequently make it particularly susceptible to a large number of birth defects. Genetic, molecular, and cellular processes must be temporally and spatially regulated to culminate in the three‐dimension structures of the face. The starting constituent for the majority of skeletal and connective tissues in the face is a pluripotent population of cells, the cranial neural crest cells (NCCs). In this review we discuss the newest scientific findings in the development of the craniofacial complex as related to NCCs. Furthermore, we present recent findings on NCC diseases called neurocristopathies and, in doing so, provide clinicians with new tools for understanding a growing number of craniofacial genetic disorders. © 2010 Wiley‐Liss, Inc.
Clinical manifestations of the deletion of Down syndrome critical region including DYRK1A and KCNJ6
Authors: Yamamoto Toshiyuki , Shimojima Keiko , Nishizawa Tsutomu , Matsuo Mari , Ito Masahiro , Imai Katsumi
Published: December 2010

A relatively small region of human chromosome 21 (Hsa21) is considered to play a major role in Down syndrome (DS) phenotypes, and the concept of a Down syndrome critical region (DSCR) has been proposed. The goal of the phenotype–genotype correlation study is to discover which genes are responsible for each DS phenotype. Loss of the genomic copy numbers of Hsa21 can give us important suggestion to understand the functions of the involved genes. Genomic copy number aberrations were analyzed by micro‐array‐based comparative genomic hybridization (aCGH) in 300 patients with developmental delay. Partial deletions of Hsa21 were identified in three patients with developmental delay, epilepsy, microcephaly, and distinctive manifestations. Two of the patients had mosaic deletions of 21q22‐qter including a part of DSCR; one of whom whose mosaic ratio was higher than the other showed more severe brain morphogenic abnormality with colpocephaly, which was similar to the previously reported patients having pure deletions of 21q22‐qter, indicating the critical region for cortical dysplasia at this region. The remaining patient had the smallest microdeletion with 480 kb in DSCR including DYRK1A and KCNJ6. Although we could not identify any nucleotide alteration in DYRK1A and KCNJ6 in our cohort study for 150 patients with mental retardation with/without epilepsy, this study underscores the clinical importance of DSCR not only for DS but also for developmental disorders. © 2010 Wiley‐Liss, Inc.
A complex 6p25 rearrangement in a child with multiple epiphyseal dysplasia
Authors: Bedoyan Jirair K. , Lesperance Marci M. , Ackley Todd , Iyer Ramaswamy K. , Innis Jeffrey W. , Misra Vinod K.
Published: December 2010

Genomic rearrangements are increasingly recognized as important contributors to human disease. Here we report on an 11½‐year‐old child with myopia, Duane retraction syndrome, bilateral mixed hearing loss, skeletal anomalies including multiple epiphyseal dysplasia, and global developmental delay, and a complex 6p25 genomic rearrangement. We have employed oligonucleotide‐based comparative genomic hybridization arrays (aCGH) of different resolutions (44 and 244K) as well as a 1 M single nucleotide polymorphism (SNP) array to analyze this complex rearrangement. Our analyses reveal a complex rearrangement involving a ∼2.21 Mb interstitial deletion, a ∼240 kb terminal deletion, and a 70–80 kb region in between these two deletions that shows maintenance of genomic copy number. The interstitial deletion contains eight known genes, including three Forkhead box containing (FOX) transcription factors (FOXQ1, FOXF2, and FOXC1). The region maintaining genomic copy number partly overlaps the dual specificity protein phosphatase 22 (DUSP22) gene. Array analyses suggest a homozygous loss of genomic material at the 5′ end of DUSP22, which was corroborated using TaqMan® copy number analysis. It is possible that this homozygous genomic loss may render both copies of DUSP22 or its products non‐functional. Our analysis suggests a rearrangement mechanism distinct from a previously reported replication‐based error‐prone mechanism without template switching for a specific 6p25 rearrangement with a 1.22 Mb interstitial deletion. Our study demonstrates the utility and limitations of using oligonucleotide‐based aCGH and SNP array technologies of increasing resolutions in order to identify complex DNA rearrangements and gene disruptions. © 2010 Wiley‐Liss, Inc.
Evaluation of 64 candidate single nucleotide polymorphisms as risk factors for neural tube defects in a large Irish study population
Authors: Carter Tonia C. , Pangilinan Faith , Troendle James F. , Molloy Anne M. , VanderMeer Julia , Mitchell Adam , Kirke Peadar N. , Conley Mary R. , Shane Barry , Scott John M. , Brody Lawrence C. , Mills James L.
Published: December 2010

Individual studies of the genetics of neural tube defects (NTDs) contain results on a small number of genes in each report. To identify genetic risk factors for NTDs, we evaluated potentially functional single nucleotide polymorphisms (SNPs) that are biologically plausible risk factors for NTDs but that have never been investigated for an association with NTDs, examined SNPs that previously showed no association with NTDs in published studies, and tried to confirm previously reported associations in folate‐related and non‐folate‐related genes. We investigated 64 SNPs in 34 genes for association with spina bifida in up to 558 case families (520 cases, 507 mothers, 457 fathers) and 994 controls in Ireland. Case‐control and mother‐control comparisons of genotype frequencies, tests of transmission disequilibrium, and log‐linear regression models were used to calculate effect estimates. Spina bifida was associated with over‐transmission of the LEPR (leptin receptor) rs1805134 minor C allele [genotype relative risk (GRR): 1.5; 95% confidence interval (CI): 1.0–2.1; P = 0.0264] and the COMT (catechol‐O‐methyltransferase) rs737865 major T allele (GRR: 1.4; 95% CI: 1.1–2.0; P = 0.0206). After correcting for multiple comparisons, these individual test P‐values exceeded 0.05. Consistent with previous reports, spina bifida was associated with MTHFR 677C>T, T (Brachyury) rs3127334, LEPR K109R, and PDGFRA promoter haplotype combinations. The associations between LEPR SNPs and spina bifida suggest a possible mechanism for the finding that obesity is a NTD risk factor. The association between a variant in COMT and spina bifida implicates methylation and epigenetics in NTDs. © 2010 Wiley‐Liss, Inc.
Evolutionary perspectives on mother–infant sleep proximity and breastfeeding in a laboratory setting
Authors: Gettler Lee T. , McKenna James J.
Published: December 2010

Human maternal and infant biology likely coevolved in a context of close physical contact and some approximation of frequent, “infant‐initiated” breastfeeding. Still, mothers and infants commonly sleep apart from one another in many western societies, indicating a possible “mismatch” between cultural norms and infant biology. Here we present data from a 3‐night laboratory‐based study that examines differences in mother–infant sleep physiology and behavior when mothers and infants sleep together on the same surface (bedsharing) and apart in separate rooms (solitary). We analyze breastfeeding frequency and interval data from the first laboratory night (FN) for 52 complementary breastfeeding mothers and infants (26 total mother–infant pairs), of which 12 pairs were routine bedsharers (RB) and 14 were routine solitary sleepers (RS). RB infants were 12.0 ± 2.7 (SD) weeks old; RS infants were 13.0 ± 2.4 weeks old. On the FN, RB mother–infant pairs (while bedsharing) engaged in a greater number of feeds per night compared to RS (while sleeping alone) (P < 0.001). RB also showed lower intervals (min) between feeds relative to RS (P < 0.05). When we evaluated data from all three laboratory nights (n = 36), post hoc, RB breastfed significantly more often (P < 0.01) and showed a trend towards lower intervals between feeds (P < 0.10). Given the widely known risks associated with little or no breastfeeding, the demonstrated mutually regulatory relationship between bedsharing and breastfeeding should be considered in future studies evaluating determinants of breastfeeding outcomes. Am J Phys Anthropol, 2011. © 2010 Wiley‐Liss, Inc
Miscibility studies of sodium carboxymethylcellulose/poly(vinyl alcohol) blend membranes for pervaporation dehydration of isopropyl alcohol
Authors: Prasad C. Venkata , Sudhakar H. , Yerri Swamy B. , Reddy G. Venkata , Reddy C. L. N. , Suryanarayana C. , Prabhakar M. N. , Subha M. C. S. , Rao K. Chowdoji
Published: December 2010

Miscibility studies of sodium carboxymethylcellulose/poly(vinyl alcohol) (NaCMC/PVA) blends of different compositions (100/0, 80 : 20, 60 : 40, 50 : 50, 40 : 60, 20 : 80, and 0 : 100) were investigated using viscometric method. NaCMC, PVA, and their blend membranes were prepared by solution‐casting technique and were then crosslinked with glutaraldehyde (GA). The effect of blend composition on mechanical, swelling, and pervaporation results (flux and selectivity) was also investigated in this study. Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) results showed that the blends are miscible over the entire studied composition range and further confirmed the crosslinking reaction with GA. FTIR studies reveal that the blends containing 50 : 50 (NaCMC/PVA) are an optimum miscible blend. Thermogravimetric analysis confirms that the thermal stability increased with increase in NaCMC content in NaCMC/PVA blend membrane. XRD and DSC showed a corresponding decrease in crystallinity and increase in melting point with increase in NACMC content, respectively. NaCMC/PVA blends of all the composition under study were used for dehydration of isopropyl alcohol at different compositions of IPA/water mixture (90 : 10, 87.5 : 12.5, 85 : 15, and 82.5 : 17.5) at 35°C. Swelling studies and PV results reveal that increase in NaCMC content in the blend leads to an increase in flux of water, whereas selectivity decreases. The optimum flux and selectivity were observed for the blend containing 50 : 50 NaCMC/PVA content at a feed ratio of 87.5 : 12.5 IPA/water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Yttrium barium copper oxide‐filled polystyrene as a dielectric material
Authors: Abraham Rosalin , Kuryan Soosy , Isac Jayakumari , Zacharia Ajesh K. , Thomas Sabu
Published: December 2010

Electrical impedance measurements are carried out on high temperature superconducting ceramic Yttrium Barium Copper Oxide (YBCO)–Polystyrene (PS) composite materials, in which superconducting particles are embedded in polystyrene matrix. The results of impedance versus frequency (100 Hz–13 MHz), phase angle versus temperature for volume percentage of superconductor (0–40%) are presented. No marked transition in phase angle is observed when the material goes through the superconducting transition temperature of the filler. The dielectric constant and losses increase with increasing YBCO content. However the increase in losses is modest and the excellent dielectric properties of the composites are not adversely affected. The system conforms to Clausius‐Mossotti equation. Dipole moment of YBCO particles and polarizability of the composites are calculated using the Clausius‐Mossotti approaches. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Electrospinning fabrication and characterization of poly(vinyl alcohol)/waterborne polyurethane nanofiber membranes in aqueous solution
Authors: Yang Jeong Han , Yoon Nam Sik , Park Jae Hyeung , Kim In Kyo , Cheong In Woo , Deng Yulin , Oh Weontae , Yeum Jeong Hyun
Published: December 2010

Poly(vinyl alcohol) (PVA)/waterborne polyurethane (WBPU) nanofiber mats were prepared using electrospinning method with aqueous solutions. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermal gravimetric analyzer (TGA), and tensile strength testing machine (ZWICK) were used to characterize the morphology and properties of the PVA/WBPU nanofiber mats. The results showed that the morphologies of PVA/WBPU nanofiber mats changed with the total solid concentration and the mass ratio of PVA/WBPU in the spinning solution. The tensile strength and thermal stability of the fibers could be significantly affected by the WBPU contents. The electrospun PVA/WBPU membranes showed higher water uptake, which would have potential applications in wound dressings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effect of hydrophobic comonomer content on assembling of poly (N‐isopropylacrylamide) and thermal properties
Authors: Yang Xia , Lee Hyeon Yong , Kim Jin‐Chul
Published: December 2010

Copolymers of N‐isopropylacrylamide and octadecyl acrylate (PNO), of which the content of octadecyl acrylate (ODA) was 1.3% (PNO 1.5), 1.7% (PNO 2.0), and 3.0% (PNO 4.0), were prepared using a free radical reaction. Various assemblies were obtained depending on the concentration of PNOs and the contents of ODA. Hydrophobic interaction between ODA residues is likely to act as crosslinker. PNO 1.5 formed hydrogel at the concentration of 7%. With PNO 2.0, hydrogels were formed when the concentration was 5 and 7%. With PNO 4.0, the opaque gel was obtained when the concentration was 7%. Upon heating across the lower critical solution temperature, the hydrogels shrank but the opaque gel was broken down into a suspension. At 40°C, the release degrees of fluorescein isothiocyanate‐dextran were much smaller than those of release at 23°C. The temperature‐sensitive release is due to temperature‐sensitive swelling ratio. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Dynamics of in situ synthetized silver‐epoxy nanocomposites as studied by dielectric relaxation spectroscopy
Authors: Kortaberria G. , Arruti P. , Mondragon I. , Vescovo L. , Sangermano M.
Published: December 2010

In situ synthetized silver‐photocurable epoxy resin nanocomposites were analyzed by dielectric spectroscopy to study the local dynamics at temperatures well below the glass‐transition temperature and the effect of silver nanoparticles on them. Two secondary processes, β and γ, were detected both for the neat matrix and nanocomposites. Relaxation times of the β secondary relaxation, obtained by fitting to Havriliak‐Negami equation, were lower in the nanocomposites, as well as the activation energies calculated from the Arrhenius temperature dependence of relaxation times, due to the plasticization effect of the trapped solvent. The electric modulus formalism was used to detect the interfacial or MWS polarization, present both in the neat matrix and in the nanocomposites due to heterogeneities and interfaces. The activation energy of this relaxation increased with nanoparticle content, thus indicating an increase of the heterogeneities due to the nanoparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effects of compatibility between tackifier and polymer on adhesion property and phase structure: Tackifier‐added polystyrene‐based triblock/diblock copolymer blend system
Authors: Nakamura Yoshinobu , Adachi Manabu , Ito Keiko , Kato Yosuke , Fujii Syuji , Sasaki Mariko , Urahama Yoshiaki , Sakurai Shinichi
Published: December 2010

The effects of compatibility of tackifier with polymer matrix and mixing weight ratio of triblock/diblock copolymers as the matrix on the adhesion property and phase structure of tackifier‐added polystryrene triblock/diblock copolymer blends were investigated. For this purpose, polystyrene‐block‐polyisoprene‐block‐polystyrene triblock and polystyrene‐block‐polyisoprene diblock copolymers were used and the diblock weight ratio in the blend was varied from 0 to 1. Spherical polystyrene domains with a mean size of about 20 nm were dispersed in the polyisoprene (PI) continuous phase. In the case of the hydrogenated cycloaliphatic resin as tackifier having a good compatibility with PI and a poor compatibility with polystyrene, the peel strength increased with an increase of the tackifier content, and the degree of increase became significant above 40 wt % of tackifier. It was found that the nanometer‐sized agglomerates of tackifier in the PI matrix were formed and the distance between the nearest neighbors of agglomerates was about 15 nm from SAXS measurement. The peel strength increased with an increase of the nanometer‐sized agglomerates of tackifier from TEM observation. On the other hand, in the case of the rosin phenolic resin as tackifier having a good compatibility with both polystyrene and PI, the peel strength increased effectively at the lower tackifier content, while no significant increase at higher tackifier content was observed. The agglomerates of tackifier were never confirmed in this system. The higher peel strength was obtained at the diblock weight ratio in the blend of 0.5–0.7 for both tackifier‐added systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermoplastic corn starch reinforced with cotton cellulose nanofibers
Authors: Teixeira Eliangela de M. , Lotti Cybele , Corrêa Ana C. , Teodoro Kelcilene B. R. , Marconcini José M. , Mattoso Luiz H. C.
Published: December 2010

This work evaluates the use of cotton cellulose nanofibers (CCN) as a reinforcing agent to prepare thermoplastic corn starch (TPS) matrix plasticized with 30 wt % of glycerol. The nanocomposites were filled with 0.5–5.0 wt % of CCN on a dry‐starch basis. The dried nanofibers were resuspended through the use of an ultrasonicator and then introduced in the fixed water formulation for obtaining TPS. The nanocomposites were compounded in a corotating twin‐screw extruder. Scanning transmission electron microscopy (STEM), field emission gun (FEG), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA), in air atmosphere, were used to characterize nanofibers, neat TPS, and nanocomposites. The results showed that the nanofibers had needlelike structure with an average length of about 135 ± 50 nm and an average diameter of about 14 ± 4 nm. The addition of CCN was effective to enhance the mechanical properties of neat TPS in compositions above 2.5 wt %, although some agglomeration could be observed. The resulting nanocomposites showed good structural stability, because the amylopectin transcrystallization phenomena on the surface of nanofibers had not occurred. Only a slight decrease in the crystallinity index and a minor increase in the water absorption in relation to neat TPS were observed. An increase in the thermal stability of TPS nanocomposites with respect to neat TPS was verified, but it was independent of the CCN content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Morphological and thermal evaluation of soy protein concentrate on graft copolymerization with ethylmethacrylate
Authors: Kaith Balbir Singh , Jindal Rajeev , Bhatia Jaspreet Kaur
Published: December 2010

Soy protein concentrate was grafted with ethylmethacrylate using ascorbic acid/potassium persulphate as a redox initiator. Different reaction parameters, such as reaction time, reaction temperature, solvent amount, initiator ratio, and pH, and monomer concentration were optimized to get maximum graft yield (134.12%). The graft copolymer formed was characterized by Fourier transform infrared spectrophotometer, X‐ray diffraction, and scanning electron microscope techniques. Thermogravimetric analysis, differential thermal analysis, and differential thermogravimetric analysis studies showed that graft copolymer was thermally more stable than the backbone. Thermal decomposition studies indicated that the rate of weight loss per minute was found more in case of backbone when compared with that of graft copolymer. Further, graft copolymer was also found more resistant toward acid–base attack and was found to be more water repellent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermal and dynamic mechanical properties of vitamin E infused and blended ultra‐high molecular weight polyethylenes
Authors: Puértolas J. A. , Martínez‐Morlanes M. J. , Mariscal M. D. , Medel F. J.
Published: December 2010

Vitamin E (or α‐tocopherol) is an alternative via to thermal treatments to achieve oxidative stability of gamma or electron beam irradiated ultra‐high molecular weight polyethylenes (UHMWPE) used in total joint replacements. Our aim was to study the effects of vitamin E on the molecular dynamics and microstructural properties of UHMWPE. We hypothesized that the antioxidant would plasticize UHMWPE. Vitamin E was incorporated into UHMWPE at different concentrations by diffusion and blending and detected by ultraviolet and infrared spectroscopies from 500 ppm and 4000 ppm, respectively. Dynamic mechanical thermal analysis was used to characterize the influence of this antioxidant in the relaxations of the raw material. Differential scanning calorimetry and transmission electron microscopy served to characterize thermal and microstructure properties, respectively. Vitamin E concentrations above 3% by weight significantly reduced the degree of crystallinity and increased the melting transition temperature of raw UHMWPE. The presence of increasing concentrations of α‐tocopherol introduced and/or strengthened the beta relaxation, which was also shifted toward gradually lower temperatures and had rising activation energies up to 188 kJ/mol. In addition, the gamma relaxation remained unaltered on vitamin E addition. Therefore, no plasticizing effects of vitamin E on the molecular dynamics of UHMWPE could be confirmed from mechanical spectroscopy data. However, the α relaxation was modified in intensity and location due to the changes in the degree of crystallinity introduced by the incorporation of vitamin E. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
A Lattice‐Engineering Route to Heterostructured Functional Nanohybrids
Authors: Paek Seung‐Min , Oh Jae‐Min , Choy Jin‐Ho
Published: December 2010

The fabrication of layered nanomaterials, such as inorganic–inorganic, organic–inorganic, and bioinorganic nanohybrids has been demonstrated through controlled lattice engineering techniques including intercalation, exfoliation–reassembling, and pillaring reactions. Such a lattice engineering method gives rise to an almost unlimited set of new hybrid compounds with a large spectrum of desirable properties. Due to the unique two‐dimensional structures and properties, various kinds of functional nanohybrid materials can be utilized as photocatalysts, electrode materials, superconducting thin films, gas separation membranes, drug‐delivery systems, and biomolecule reservoirs.
An improved delay‐dependent bounded real lemma (BRL) and H∞ controller synthesis for linear neutral systems
Authors: Parlakçi Mehmet Nur Alpaslan
Published: December 2010

In this paper, a novel delay‐dependent bounded real criterion and an improved sufficient condition are derived for the design of an H∞ state‐feedback controller for linear neutral time‐delay systems. On the basis of an augmented Lyapunov‐Krasovskii functional, a new bounded real lemma is introduced in terms of a convex linear matrix inequality (LMI) condition that can be solved using interior point algorithms. The bounded real lemma is extended to obtain a sufficient condition for the existence of a delay‐dependent H∞ memoryless state‐feedback controller. Neither any model transformation nor bounding of any of the cross terms are utilized while deriving the bounded real lemma. Moreover, the use of any free slack matrix variable approach is avoided to a certain extent in order not to increase the complexity of the synthesis problem. A cone complementary nonlinear minimization algorithm is employed to achieve a feasible solution set for the synthesis conditions. Finally, seven numerical examples are given to illustrate the effectiveness of the proposed method.

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