Improved thermoelectric properties in ceramic composites based on Ca3Co4O9 and Na2Ca2Nb4O13

The oxide materials Ca3Co4O9 and Na2Ca2Nb4O13 were combined in a new ceramic composite with promising synergistic thermoelectric properties. Both compounds show a plate-like crystal shape and similar aspect ratios but the matrix material Ca3Co4O9 with lateral sizes of less than 500 nm is about two orders of magnitude smaller. Uniaxial pressing of the mixed compound powders was used to produce porous ceramics after conventional sintering. Reactions between both compounds and their compositions were thoroughly investigated. In comparison to pure Ca3Co4O9, mixing with low amounts of Na2Ca2Nb4O13 proved to be beneficial for the overall thermoelectric properties. A maximum figure-of-merit of zT = 0.32 at 1073 K and therefore an improvement of about 19% was achieved by the ceramic composites

HAEC-SIM: A Simulation Framework for Highly Adaptive Energy-Efficient Computing Platforms

This work presents a new trace-based parallel discrete event simulation framework designed for predicting the behavior of a novel computing platform running energy-aware parallel applications. Discrete event traces capture the runtime be- havior of parallel applications on existing systems and form the basis for the simulation. The simulation framework pro- cesses the events of the input trace by applying simulation models that modify event properties. Thus, the output are again event traces that describe the predicted application behavior on the simulated target platform. Both input and simulated traces can be visualized and analyzed with estab- lished tools. The modular design of the framework enables the simulation of different aspects such as temporal perfor- mance and energy efficiency by applying distinct simulation models e.g.: (i) A performance model for communication that allows to evaluate the target communication topology and link properties. (ii) An energy model for computations that is based on measurements of current hardware. We showcase the potential of this simulation by simulating the execution of benchmark applications to explore design al- ternatives of highly adaptive and energy-efficient computing applications and platforms

Species Variation in a Pheromone Complex is Maintained at the Population Level in the Eastern Red-Backed Salamander

Protein pheromones in salamanders of the genus Plethodon have experienced rapid and pervasive directional selection. Variation in mate recognition components, such as the sex-specific pheromones used by plethodontid salamanders, may influence sexual incompatibility and therefore provide a biochemical mechanism for the maintenance of discrete, isolated populations. Recent studies suggest that multiple, genetically distinct lineages of Eastern Red-Backed Salamanders (Plethodon cinereus) are present throughout their broad range. Representative populations from two of these lineages (the Ohio [OH] and Pennsylvania [PA] clades) span the southern shore of Lake Erie in northern Ohio. This distribution pattern creates a unique opportunity to study how phenotypic differences may reinforce population boundaries and possibly lead to speciation. The objectives of this study were to 1) characterize the pheromone profiles of male P. cinereus and 2) determine pheromone variation among populations and between the OH and PA clades. The composition of proteins associated with two known courtship pheromones, Plethodontid Modulating Factor (PMF) and Plethodontid Receptivity Factor (PRF), were compared among eight populations in northern Ohio. Analyses of Similarity (ANOSIM) suggest that both PMF and PRF profiles differ among populations but not between clades. These data suggest that the sex-specific pheromones of P. cinereus in the two clades are not yet different enough to allow reproductive isolation between the two genetic lineages. Although the relative roles of selection and genetic drift are unknown in our populations, specific pheromone isoforms and their effects on mate compatibility should be the focus of future studies aiming to determine mechanisms involved in maintaining population differences

Verification of Resilient Communication Models for the Simulation of a Highly Adaptive Energy-Efficient Computer

Delivering high performance in an energy-efficient manner is of great importance in conducting research in computational sciences and in daily use of technology. From a computing perspective, a novel concept (the HAEC Box) has been proposed that utilizes innovative ideas of optical and wireless chip-to-chip communication to allow a new level of runtime adaptivity for future computers, which is required to achieve high performance and energy efficiency. HAEC-SIM is an integrated simulation environment designed for the study of the performance and energy costs of the HAEC Box running communication-intensive applications. In this work, we conduct a verification of the implementation of three resilient communication models in HAEC-SIM. The verification involves two NAS Parallel Benchmarks and their simulated execution on a 3D torus system with 16x16x16 nodes with Infiniband links. The simulation results are consistent with those of an independent implementation. Thus, the HAEC-SIM based simulations are accurate in this regard. Delivering high performance in an energy-efficient manner is of great importance in conducting research in computational sciences and in daily use of technology. From a computing perspective, a novel concept (the HAEC Box) has been proposed that utilizes innovative ideas of optical and wireless chip-to-chip communication to allow a new level of runtime adaptivity for future computers, which is required to achieve high performance and energy efficiency. HAEC-SIM is an integrated simulation environment designed for the study of the performance and energy costs of the HAEC Box running communication-intensive applications.In this work, we conduct a verification of the implementation of three resilient communication models in HAEC-SIM. The verification involves two NAS Parallel Benchmarks and their simulated execution on a 3D torus system with 16x16x16 nodes with Infiniband links. The simulation results are consistent with those of an independent implementation.Thus, the HAEC-SIM based simulations are accurate in this regard

Mechanochemical synthesis of nanocrystalline lead selenide

Mechanochemical synthesis of lead selenide PbSe nanoparticles has been performed by high-energy milling of lead and selenium powder in a planetary ball mill Pulverisette 6 (Fritsch, Germany) and in an industrial eccentric vibratory mill ESM 654 (Siebtechnik GmbH, Germany). Structural properties of the synthesized lead selenide were characterized by X-ray diffraction, which confirms crystalline nature of PbSe nanoparticles (JCPDS 6-354). The average size of PbSe crystallites of 37 nm was calculated from XRD data by Williamson-Hall method. The methods of particle size distribution analysis, specific surface area measurement, scanning electron microscopy and transmission electron microscopy were used for characterization of surface, mean particle size, and morphology of PbSe. An application of industrial mill verified a possibility of the synthesis of a narrowband-gap semiconductor PbSe at ambient temperature and in a relatively short reaction time

Tuning the Thermoelectric Performance of CaMnO3-Based Ceramics by Controlled Exsolution and Microstructuring

The thermoelectric properties of CaMnO3-δ/CaMn2O4 composites were tuned via microstructuring and compositional adjustment. Single-phase rock-salt-structured CaO-MnO materials with Ca:Mn ratios larger than unity were produced in reducing atmosphere and subsequently densified by spark plasma sintering in vacuum. Annealing in air at 1340 °C between 1 and 24 h activated redox-driven exsolution and resulted in a variation in microstructure and CaMnO3-δ materials with 10 and 15 vol % CaMn2O4, respectively. The nature of the CaMnO3-δ/CaMn2O4 grain boundary was analyzed by transmission electron microscopy on short- and long-term annealed samples, and a sharp interface with no secondary phase formation was indicated in both cases. This was further complemented by density functional theory (DFT) calculations, which confirmed that the CaMnO3-δ indeed is a line compound. DFT calculations predict segregation of oxygen vacancies from the bulk of CaMnO3-δ to the interface between CaMnO3-δ and CaMn2O4, resulting in an enhanced electronic conductivity of the CaMnO3-δ phase. Samples with 15 vol % CaMn2O4 annealed for 24 h reached the highest electrical conductivity of 73 S·cm-1 at 900 °C. The lowest thermal conductivity was obtained for composites with 10 vol % CaMn2O4 annealed for 8 h, reaching 0.56 W·m-1K-1 at 700 °C. However, the highest thermoelectric figure-of-merit, zT, was obtained for samples with 15 vol % CaMn2O4 reaching 0.11 at temperatures between 800 and 900 °C, due to the enhanced power factor above 700 °C. This work represents an approach to boost the thermoelectric performance of CaMnO3-δ based composites

Nonequilibrium structure of Zn 2SnO 4 spinel nanoparticles

Zinc stannate (Zn 2SnO 4) nanoparticles with an average size of about 26 nm are synthesized via single-step mechanochemical processing of binary oxide precursors (ZnO and SnO 2) at ambient temperature, without the need for the subsequent calcination, thus making the synthesis route very simple and cost-effective. The mechanically induced phase evolution of the 2ZnO + SnO 2 mixture is followed by XRD and by a variety of spectroscopic techniques including 119Sn MAS NMR, Raman spectroscopy, 119Sn Mössbauer spectroscopy, and XPS. High-resolution TEM studies reveal a non-uniform structure of mechanosynthesized Zn 2SnO 4 nanoparticles consisting of a crystalline core surrounded by a structurally disordered surface shell. Due to the ability of the applied solid-state spectroscopies to probe the local environment of Sn cations, valuable complementary insight into the nature of the local structural disorder of mechanosynthesized Zn 2SnO 4 is obtained. The findings hint at a highly nonequilibrium state of the as-prepared stannate characterized by its partly inverse spinel structure and the presence of deformed polyhedra in the surface shell of nanoparticles. © 2012 The Royal Society of Chemistry

A comprehensive score reflecting memory-related fMRI activations and deactivations as potential biomarker for neurocognitive aging

Older adults and particularly those at risk for developing dementia typically show a decline in episodic memory performance, which has been associated with altered memory network activity detectable via functional magnetic resonance imaging (fMRI). To quantify the degree of these alterations, a score has been developed as a putative imaging biomarker for successful aging in memory for older adults (Functional Activity Deviations during Encoding, FADE; Düzel et al., Hippocampus, 2011; 21: 803–814). Here, we introduce and validate a more comprehensive version of the FADE score, termed FADE-SAME (Similarity of Activations during Memory Encoding), which differs from the original FADE score by considering not only activations but also deactivations in fMRI contrasts of stimulus novelty and successful encoding, and by taking into account the variance of young adults' activations. We computed both scores for novelty and subsequent memory contrasts in a cohort of 217 healthy adults, including 106 young and 111 older participants, as well as a replication cohort of 117 young subjects. We further tested the stability and generalizability of both scores by controlling for different MR scanners and gender, as well as by using different data sets of young adults as reference samples. Both scores showed robust agegroup-related differences for the subsequent memory contrast, and the FADE-SAME score additionally exhibited age-group-related differences for the novelty contrast. Furthermore, both scores correlate with behavioral measures of cognitive aging, namely memory performance. Taken together, our results suggest that single-value scores of memory-related fMRI responses may constitute promising biomarkers for quantifying neurocognitive aging

Complex networks for climate model evaluation with application to statistical versus dynamical modeling of South American climate

Acknowledgments: This paper was developed within the scope of the IRTG 1740/TRP 2011/50151-0, funded by the DFG/FAPESP. Furthermore, this work has been financially supported by the Leibniz Society (project ECONS), and the Stordalen Foundation (JFD). For certain calculations, the software packages pyunicorn (Donges et al. 2013a) and igraph (Csa´rdi and Nepusz 2006) were used. The authors would like to thank Manoel F. Cardoso, Niklas Boers, and the reviewers for helpful comments on the manuscript. Open Access: This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.Peer reviewedPostprin