Investigation into the effect of Si doping on the performance of SrFeO3-δ SOFC electrode materials

In this paper we report the successful incorporation of silicon into SrFeO3-δ perovskite materials for potential applications as electrode materials for solid oxide fuel cells. It is observed that Si doping leads to a change from a tetragonal cell (with partial ordering of oxygen vacancies) to a cubic one (with the oxygen vacancies disordered). Annealing experiments in 5% H2/95% N2 (up to 800 °C) also showed the stabilization of the cubic form for the Si-doped samples under reducing conditions, suggesting that they may be suitable for both cathode and anode applications. In contrast to the cubic cell of the reduced Si doped system, reduction of undoped SrFeO3-δ leads to the formation of a brownmillerite structure with ordered oxide ion vacancies. SrFe 0.90Si0.10O3-δ and SrFe 0.85Si0.15O3-δ were analysed by neutron powder diffraction, and the data confirmed the cubic cell, with no long range oxygen vacancy ordering. Mössbauer spectroscopy data were also recorded for SrFe0.90Si0.10O3-δ, and indicated the presence of only Fe3+ and Fe5+ (i.e. disproportionation of Fe4+ to Fe3+ and Fe5+) for such doped samples. Conductivity measurements showed an improvement in the conductivity on Si doping. Composite electrodes with 50% Ce0.9Gd0.1O 1.95 were therefore examined on dense Ce0.9Gd 0.1O1.95 pellets in two different atmospheres: air and 5% H2/95% N2. In both atmospheres an improvement in the area specific resistance (ASR) values is observed for the Si-doped samples. Thus the results show that silicon can be incorporated into SrFeO3-δ- based materials and can have a beneficial effect on the performance, making them potentially suitable for use as cathode and anode materials in symmetrical SOFCs. © 2013 The Royal Society of Chemistry.Peer Reviewe

A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

The genetic architecture of the human cerebral cortex

INTRODUCTION The cerebral cortex underlies our complex cognitive capabilities. Variations in human cortical surface area and thickness are associated with neurological, psychological, and behavioral traits and can be measured in vivo by magnetic resonance imaging (MRI). Studies in model organisms have identified genes that influence cortical structure, but little is known about common genetic variants that affect human cortical structure. RATIONALE To identify genetic variants associated with human cortical structure at both global and regional levels, we conducted a genome-wide association meta-analysis of brain MRI data from 51,665 individuals across 60 cohorts. We analyzed the surface area and average thickness of the whole cortex and 34 cortical regions with known functional specializations. RESULTS We identified 306 nominally genome-wide significant loci (P < 5 × 10−8) associated with cortical structure in a discovery sample of 33,992 participants of European ancestry. Of the 299 loci for which replication data were available, 241 loci influencing surface area and 14 influencing thickness remained significant after replication, with 199 loci passing multiple testing correction (P < 8.3 × 10−10; 187 influencing surface area and 12 influencing thickness). Common genetic variants explained 34% (SE = 3%) of the variation in total surface area and 26% (SE = 2%) in average thickness; surface area and thickness showed a negative genetic correlation (rG = −0.32, SE = 0.05, P = 6.5 × 10−12), which suggests that genetic influences have opposing effects on surface area and thickness. Bioinformatic analyses showed that total surface area is influenced by genetic variants that alter gene regulatory activity in neural progenitor cells during fetal development. By contrast, average thickness is influenced by active regulatory elements in adult brain samples, which may reflect processes that occur after mid-fetal development, such as myelination, branching, or pruning. When considered together, these results support the radial unit hypothesis that different developmental mechanisms promote surface area expansion and increases in thickness. To identify specific genetic influences on individual cortical regions, we controlled for global measures (total surface area or average thickness) in the regional analyses. After multiple testing correction, we identified 175 loci that influence regional surface area and 10 that influence regional thickness. Loci that affect regional surface area cluster near genes involved in the Wnt signaling pathway, which is known to influence areal identity. We observed significant positive genetic correlations and evidence of bidirectional causation of total surface area with both general cognitive functioning and educational attainment. We found additional positive genetic correlations between total surface area and Parkinson’s disease but did not find evidence of causation. Negative genetic correlations were evident between total surface area and insomnia, attention deficit hyperactivity disorder, depressive symptoms, major depressive disorder, and neuroticism. CONCLUSION This large-scale collaborative work enhances our understanding of the genetic architecture of the human cerebral cortex and its regional patterning. The highly polygenic architecture of the cortex suggests that distinct genes are involved in the development of specific cortical areas. Moreover, we find evidence that brain structure is a key phenotype along the causal pathway that leads from genetic variation to differences in general cognitive function

Small Whale Co-management in the Eastern Canadian Arctic: A Case History and Analysis

This paper explores the problems and challenges of co-management of beluga and narwhal populations in the Eastern Arctic region of the Northwest Territories. The political and regulatory context of co-management has changed in the last 14 years. Regulations were amended in 1980 and 1990 to limit harvest and the conditions of harvest. The Nunavut Land Claim Settlement Agreement-in-Principle of 1990 created a new framework for wildlife management. The 1990 Supreme Court decision in the Sparrow case was a strong admonition for native involvement in management of their fisheries resources. Canada and Greenland formed a joint commission for conservation and management of shared stocks of narwhals and belugas. The history of Southeast Baffin beluga co-management, our case study, is one of informal and incomplete co-management, because the hunters did not have full participation in the research pertaining to the evaluation of stock status, nor did they have the power to decide on the management of the stock. The decision of Fisheries and Oceans to severely limit beluga hunting created a crisis, which eventually led to the creation of a formal complete beluga co-management committee. We conclude that complete co-management, with full participation of Inuit hunters, is necessary for effective conservation and management of eastern Canadian small whales. Nevertheless, the vast area through which narwhal and beluga populations range, the large number of people and communities that would be involved in such a co-management process and the difficulty in determining stock status are important challenges to co-managers.Key words: Southeast Baffin, Baffin Bay, High Arctic, Greenland, hunters, harvesting, conservation, protection, Nunavut, SparrowDans cet article, nous discutons des probl&egrave;mes et d&eacute;fits de la co-gestion des populations de b&eacute;lugas et de narvals de la r&eacute;gion est arctique des Territoires du Nord-Ouest. Le contexte politique et juridique de la co-gestion a chang&eacute; durant les quatorze derni&egrave;res ann&eacute;es. Les r&eacute;glements ont &eacute;t&eacute; amend&eacute; en 1980 et 1990 pour limiter le niveau ou les conditions de chasse. L'accord de principe de 1990 sur la revendication territoriale du Nunavut a cr&eacute;&eacute; un nouveau cadre pour la gestion de la faune. La d&eacute;cision de la Cour Supr&egrave;me sur le cas Sparrow a &eacute;t&eacute; une forte exhortation en faveur de la participation des aborig&egrave;nes dans la gestion de leurs ressources halieutiques. L'historique de la co-gestion du b&eacute;luga du sud-est de la Terre de Baffin, notre sujet d'&eacute;tude, en est un de co-gestion informelle et incompl&egrave;te, parce que les chasseurs n'avaient pas pleine participation dans les recherches visant &agrave; l'&eacute;valuation du statut de ce stock ou le pouvoir de prendre des d&eacute;cisions de gestion. La d&eacute;cision de P&ecirc;ches et Oc&eacute;ans de s&eacute;v&egrave;rement limiter la chasse aux b&eacute;lugas a cr&eacute;&eacute; une crise qui a &eacute;ventuellement men&eacute;e &agrave; la cr&eacute;ation d'un comit&eacute; officiel de compl&egrave;te co-gestion du b&eacute;luga. Nous concluons qu'un syst&egrave;me de compl&egrave;te co-gestion est n&eacute;cessaire pour la conservation et la gestion des petites baleines de l'est de l'Arctique canadien. Cependant, l'immensit&eacute; de la r&eacute;partition des b&eacute;lugas et des narvals, le grand nombre de gens et de communaut&eacute;s impliqu&eacute;s dans un tel processus de co-gestion et la difficult&eacute; d'&eacute;valuer l'&eacute;tat des populations sont d'importants d&eacute;fits pour les co-gestionnaires.Mot cl&eacute;s: sud-est de Baffin, baie de Baffin, haut Arctique, Gro&euml;nland, chasseurs, r&eacute;colte , conservation, protection, Nunavut, Sparro

Strength, thermal defects, and solid solution hardening in nickel-containing B2 iron aluminides

Nickel-containing ternary iron aluminides with an aluminum concentration of 45 at.% were investigated with respect to room temperature strength, equilibrium vacancy concentration, and the kinetics of vacancy removal. As compared to binary iron aluminides with the same Al concentration, nickel additions reduce the thermal equilibrium vacancy concentration at 1,273 K, whereas they increase this concentration at 973 K. Furthermore, at low temperatures such as 673 K, nickel additions increase dramatically the time needed to reach vacancy equilibrium. During prolonged annealing at 673 K, the density of dislocations in Fe-45Al-3Ni (at.%) increased by an order of magnitude. This suggests that dislocations act as sinks for vacancies. At the same time, the number density of small (20--50 nm) voids decreased, indicating that they were not stable in the absence of substantial vacancy supersaturations. The findings show also that the solid solution strengthening of iron aluminides due to Ni is much weaker than previously thought