210 research outputs found
Observation of Ferromagnetic Clusters in Bi0.125Ca0.875MnO3
The electron doped manganite system, Bi0.125Ca0.875MnO3, exhibits large bulk
magnetization of unknown origin. To select amongst possible magnetic ordering
models, we have conducted temperature and magnetic field dependent small-angle
neutron scattering measurements. Nontrivial spin structure has been revealed.
Ferromagnetic spin clusters form in the antiferromagnetic background when
temperature is decreased to Tc~108K. With a further reduction in temperature or
the application of external magnetic field, the clusters begin to form in
larger numbers, which gives an overall enhancement of magnetization below Tc.Comment: 14 pages, 6 figue
Probing clustering features around Cl 0024+17
I present a spatial analysis of the galaxy distribution around the cluster Cl
0024+17. The basic aim is to find the scales where galaxies present a
significant deviation from an inhomogeneous Poisson statistical process. Using
the generalization of the Ripley, Besag, and the pair correlation functions for
non-stationary point patterns, I estimate these transition scales for a set of
1,000 Monte Carlo realizations of the Cl 0024+17 field, corrected for
completeness up to the outskirts. The results point out the presence of at
least two physical scales in this field at 31.4 and 112.9 arcseconds. The
second one is statistically consistent with the dark matter ring radius (about
75 arcseconds) previously identified by Jee et al. (2007). However, morphology
and anisotropy tests point out that a clump at about 120 arcseconds NW from the
cluster center could be the responsible for the second transition scale. These
results do not indicate the existence of a galaxy counterpart of the dark
matter ring, but the methodology developed to study the galaxy field as a
spatial point pattern provides a good statistical evaluation of the physical
scales around the cluster. I briefly discuss the usefulness of this approach to
probe features in galaxy distribution and N-body dark matter simulation data.Comment: Accepted for publication in New Astronomy. 14 pages. 8 figure
Tracing the Peculiar Dark Matter Structure in the Galaxy Cluster CL 0024+17 with Intracluster Stars and Gas
ICL is believed to originate from the stars stripped from cluster galaxies.
They are no longer gravitationally bound to individual galaxies, but to the
cluster, and their smooth distribution potentially makes them serve as much
denser tracers of the cluster dark matter than the sparsely distributed cluster
galaxies. We present our study of the ICL in Cl 0024+17 using both ACS and
Subaru data, where we previously reported discovery of a ringlike dark matter
structure with gravitational lensing. The ACS images provide much lower sky
levels than ground data, and enable us to measure relative variation of surface
brightness reliably. This analysis is repeated with the Subaru images to
examine if consistent features are recovered despite different reduction scheme
and instrumental characteristics. We find that the ICL profile clearly
resembles the peculiar mass profile, which stops decreasing at r~50" (~265 kpc)
and slowly increases until it turns over at r~75" (~397 kpc). This feature is
seen in both ACS and Subaru images for nearly all available passband images
while the features are stronger in red filters. The consistency across
different filters and instruments strongly rules out the possibility that the
feature might come from any residual, uncorrected calibration errors. In
addition, our re-analysis of the cluster X-ray data shows that the peculiar
mass structure is also indicated by a non-negligible bump in the intracluster
gas profile when the geometric center of the dark matter ring, not the peak of
the X-ray emission, is chosen as the center of the radial bin. The location of
the gas ring is closer to the center by ~15" (~80 kpc), raising an interesting
possibility that the ring-like structure is expanding and the gas ring is
lagging behind perhaps because of the ram pressure if both features in mass and
gas share the same dynamical origin.Comment: Accepted to ApJ for publicatio
Promotion of water-mediated carbon removal by nanostructured barium oxide/nickel interfaces in solid oxide fuel cells
The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C3H8, CO and gasified carbon fuels at 750°C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity
Directed Culturing of Microorganisms Using Metatranscriptomics
The vast majority of bacterial species remain uncultured, and this severely limits the investigation of their physiology, metabolic capabilities, and role in the environment. High-throughput sequencing of RNA transcripts (RNA-seq) allows the investigation of the diverse physiologies from uncultured microorganisms in their natural habitat. Here, we report the use of RNA-seq for characterizing the metatranscriptome of the simple gut microbiome from the medicinal leech Hirudo verbana and for utilizing this information to design a medium for cultivating members of the microbiome. Expression data suggested that a Rikenella-like bacterium, the most abundant but uncultured symbiont, forages on sulfated- and sialated-mucin glycans that are fermented, leading to the secretion of acetate. Histological stains were consistent with the presence of sulfated and sialated mucins along the crop epithelium. The second dominant symbiont, Aeromonas veronii, grows in two different microenvironments and is predicted to utilize either acetate or carbohydrates. Based on the metatranscriptome, a medium containing mucin was designed, which enabled the cultivation of the Rikenella-like bacterium. Metatranscriptomes shed light on microbial metabolism in situ and provide critical clues for directing the culturing of uncultured microorganisms. By choosing a condition under which the desired organism is rapidly proliferating and focusing on highly expressed genes encoding hydrolytic enzymes, binding proteins, and transporters, one can identify an organismâs nutritional preferences and design a culture medium
Interactive metagenomic visualization in a Web browser
<p>Abstract</p> <p>Background</p> <p>A critical output of metagenomic studies is the estimation of abundances of taxonomical or functional groups. The inherent uncertainty in assignments to these groups makes it important to consider both their hierarchical contexts and their prediction confidence. The current tools for visualizing metagenomic data, however, omit or distort quantitative hierarchical relationships and lack the facility for displaying secondary variables.</p> <p>Results</p> <p>Here we present Krona, a new visualization tool that allows intuitive exploration of relative abundances and confidences within the complex hierarchies of metagenomic classifications. Krona combines a variant of radial, space-filling displays with parametric coloring and interactive polar-coordinate zooming. The HTML5 and JavaScript implementation enables fully interactive charts that can be explored with any modern Web browser, without the need for installed software or plug-ins. This Web-based architecture also allows each chart to be an independent document, making them easy to share via e-mail or post to a standard Web server. To illustrate Krona's utility, we describe its application to various metagenomic data sets and its compatibility with popular metagenomic analysis tools.</p> <p>Conclusions</p> <p>Krona is both a powerful metagenomic visualization tool and a demonstration of the potential of HTML5 for highly accessible bioinformatic visualizations. Its rich and interactive displays facilitate more informed interpretations of metagenomic analyses, while its implementation as a browser-based application makes it extremely portable and easily adopted into existing analysis packages. Both the Krona rendering code and conversion tools are freely available under a BSD open-source license, and available from: <url>http://krona.sourceforge.net</url>.</p
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