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  • 11
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    Ferrimagnetic and spin-glass transition in the Aurivillius compound SrBi5Ti4Cr0.5Co0.5O18 (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-06-20
    Description: Single-phase polycrystalline SrBi 5 Ti 4 CrO 18 and SrBi 5 Ti 4 Cr 0.5 Co 0.5 O 18 were synthesized by a modified Pechini method. Both samples have an orthorhombic structure with the space group B 2 cb . The valence state of Cr is suggested to be +3 and the Co ions exist in the form of Co 2+ and Co 3+ based on the results of x-ray photoelectron spectroscopy. The sample SrBi 5 Ti 4 CrO 18 exhibits the paramagnetic state, whereas SrBi 5 Ti 4 Cr 0.5 Co 0.5 O 18 undergoes a ferrimagnetic transition at 89 K originating from the antiferromagnetic coupling of Cr-based and Co-based sublattices. In addition, SrBi 5 Ti 4 Cr 0.5 Co 0.5 O 18 shows a typical spin-glass behavior below 89 K with zν  = 6.02 and τ 0  = (1.75 ± 0.33) × 10 −14 s as evidenced by the results of the frequency dependence of ac susceptibility and magnetic relaxation measurements. In particular, both the dielectric constant and dielectric loss of SrBi 5 Ti 4 Cr 0.5 Co 0.5 O 18 exhibit the characteristics of dielectric relaxation around 89 K with the activation energy of (0.14 ± 0.02) eV, which can be ascribed to the electron hopping of Co 2+ - V O -Co 3+ through the bridging oxygen vacancies.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 12
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    Bayesian integration of genetics and epigenetics detects causal regulatory SNPs underlying expression variability (2015)
    Springer Nature
    Details
    Publication Date: 2015-10-14
    Description: Article Das et al . present a novel Bayesian approach called expression Quantitative Trait enhancer Loci (eQTeL), which effectively integrates genetic and epigenetic information to identify combination of regulatory genomic variants underlying expression variance. Using various functional data, the authors show the variants identified by eQTeL are likely to be causal. Nature Communications doi: 10.1038/ncomms9555 Authors: Avinash Das, Michael Morley, Christine S. Moravec, W. H. W. Tang, Hakon Hakonarson, Kenneth B. Margulies, Thomas P. Cappola, Shane Jensen, Sridhar Hannenhalli
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 13
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    Canonical hedgehog signaling augments tumor angiogenesis by induction of VEGF-A in stromal perivascular cells [Medical Sciences] (2011)
    National Academy of Sciences
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    Publication Date: 2011-06-08
    Description: Hedgehog (Hh) signaling is critical to the patterning and development of a variety of organ systems, and both ligand-dependent and ligand-independent Hh pathway activation are known to promote tumorigenesis. Recent studies have shown that in tumors promoted by Hh ligands, activation occurs within the stromal microenvironment. Testing whether ligand-driven Hh signaling promotes tumor angiogenesis, we found that Hh antagonism reduced the vascular density of Hh-producing LS180 and SW480 xenografts. In addition, ectopic expression of sonic hedgehog in low-Hh–expressing DLD-1 xenografts increased tumor vascular density, augmented angiogenesis, and was associated with canonical Hh signaling within perivascular tumor stromal cells. To better understand the molecular mechanisms underlying Hh-mediated tumor angiogenesis, we established an Hh-sensitive angiogenesis coculture assay and found that fibroblast cell lines derived from a variety of human tissues were Hh responsive and promoted angiogenesis in vitro through a secreted paracrine signal(s). Affymetrix array analyses of cultured fibroblasts identified VEGF-A, hepatocyte growth factor, and PDGF-C as candidate secreted proangiogenic factors induced by Hh stimulation. Expression studies of xenografts and angiogenesis assays using combinations of Hh and VEGF-A inhibitors showed that it is primarily Hh-induced VEGF-A that promotes angiogenesis in vitro and augments tumor-derived VEGF to promote angiogenesis in vivo.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 14
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    Novel pre-alloyed powder processing of modified alnico 8: Correlation of microstructure and magnetic properties (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-04-14
    Description: Progress is reviewed on development of an improved near-final bulk magnet fabrication process for alnico 8, as a non-rare earth permanent magnet with promise for sufficient energy density and coercivity for electric drive motors. This study showed that alnico bulk magnets in near-final shape can be made by simple compression molding from spherical high purity gas atomized pre-alloyed powder. Dwell time at peak sintering temperature (1250 °C) greatly affected grain size of the resulting magnet alloys. This microstructure transformation was demonstrated to be useful for gaining partially aligned magnetic properties and boosting energy product. While a route to increased coercivity was not identified by these experiments, manufacturability of bulk alnico magnet alloys in near-final shapes was demonstrated, permitting further processing and alloy modification experiments that can target higher coercivity and better control of grain anisotropy during grain growth.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 15
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    Cyclooctatetraenophanes: A Computational Study (2015)
    American Chemical Society (ACS)
    Details
    Publication Date: 2015-06-23
    Description: The Journal of Organic Chemistry DOI: 10.1021/acs.joc.5b00842
    Print ISSN: 0022-3263
    Electronic ISSN: 1520-6904
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society (ACS)
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  • 16
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    Improved ferroelectric polarization of V-doped Bi6Fe2Ti3O18 thin films prepared by a chemical solution deposition (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-06-25
    Description: We prepared V-doped Bi 6 Fe 2 Ti 3 O 18 thin films on Pt/Ti/SiO 2 /Si (100) substrates by using a chemical solution deposition route and investigated the doping effect on the microstructure, dielectric, leakage, and ferroelectric properties of Bi 6 Fe 2 Ti 3 O 18 thin films. The Bi 5.97 Fe 2 Ti 2.91 V 0.09 O 18 thin film exhibits improved dielectric properties, leakage current, and ferroelectric properties. The incorporation of vanadium resulted in a substantially enhanced remnant polarization (2 P r ) over 30  μ C/cm 2 in Bi 5.97 Fe 2 Ti 2.91 V 0.09 O 18 thin film compared with 10  μ C/cm 2 in Bi 6 Fe 2 Ti 3 O 18 thin film. It is demonstrated that the improved properties may stem from the improvement of crystallinity of the films with the contribution of suppressed oxygen vacancies and decreased mobility of oxygen vacancies caused by the V-doping. The results will provide a guidance to optimize the ferroelectric properties in Bi 6 Fe 2 Ti 3 O 18 thin films by chemical solution deposition, which is important to further explore single-phase multiferroics in the n  = 5 Aurivillius thin films.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 17
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    Structural, magnetic, and dielectric studies of the Aurivillius compounds SrBi5Ti4MnO18 and SrBi5Ti4Mn0.5Co0.5O18 (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-01-14
    Description: We have successfully synthesized the Aurivillius compounds SrBi 5 Ti 4 MnO 18 and SrBi 5 Ti 4 Mn 0.5 Co 0.5 O 18 using a modified Pechini method. Both samples have an orthorhombic structure with the space group B2cb . The valence state of Mn is suggested to be +3 and the doped Co ions exist in the form of Co 2+ and Co 3+ based on the results of x-ray photoelectron spectroscopy. The sample SrBi 5 Ti 4 MnO 18 exhibits a dominant paramagnetic state with the existence of superparamagnetic state as evidenced by the electron paramagnetic resonance results, whereas SrBi 5 Ti 4 Mn 0.5 Co 0.5 O 18 undergoes a ferrimagnetic transition at 161 K originating from the antiferromagnetic coupling of Co-based and Mn-based sublattices, and a ferromagnetic transition at 45 K arising from the Mn 3+ -O-Co 3+ (low spin) interaction. The sample SrBi 5 Ti 4 Mn 0.5 Co 0.5 O 18 exhibits two dielectric anomalies. One corresponds to a relaxor-like dielectric relaxation which follows the Vogel-Fulcher function and the other dielectric relaxation obeys the Arrhenius law arising from the collective motion of oxygen vacancies. In addition, the sample SrBi 5 Ti 4 Mn 0.5 Co 0.5 O 18 exhibits a magnetodielectric effect caused by the Maxwell-Wagner effect because of the conductivity of the sample. This is demonstrated by the fact that the activation energy in dielectric loss process is close to that for dc conductivity and the magnetodielectric effect is sensitive to the measured frequency.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 18
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    MetaDiff: differential isoform expression analysis using random-effects meta-regression (2015)
    BioMed Central
    Details
    Publication Date: 2015-07-03
    Description: Background: RNA sequencing (RNA-Seq) allows an unbiased survey of the entire transcriptome in a high-throughput manner. A major application of RNA-Seq is to detect differential isoform expression across experimental conditions, which is of great biological interest due to its direct relevance to protein function and disease pathogenesis. Detection of differential isoform expression is challenging because of uncertainty in isoform expression estimation owing to ambiguous reads and variability in precision of the estimates across samples. It is desirable to have a method that can account for these issues and is flexible enough to allow adjustment for covariates. Results: In this paper, we present MetaDiff, a random-effects meta-regression model that naturally fits for the above purposes. Through extensive simulations and analysis of an RNA-Seq dataset on human heart failure, we show that the random-effects meta-regression approach is computationally fast, reliable, and can improve the power of differential expression analysis while controlling for false positives due to the effect of covariates or confounding variables. In contrast, several existing methods either fail to control false discovery rate or have reduced power in the presence of covariates or confounding variables. The source code, compiled JAR package and documentation of MetaDiff are freely available at https://github.com/jiach/MetaDiff. Conclusion: Our results indicate that random-effects meta-regression offers a flexible framework for differential expression analysis of isoforms, particularly when gene expression is influenced by other variables.
    Electronic ISSN: 1471-2105
    Topics: Biology , Computer Science
    Published by BioMed Central
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  • 19
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    Microbial methane production in oxygenated water column of an oligotrophic lake [Environmental Sciences] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-12-07
    Description: The prevailing paradigm in aquatic science is that microbial methanogenesis happens primarily in anoxic environments. Here, we used multiple complementary approaches to show that microbial methane production could and did occur in the well-oxygenated water column of an oligotrophic lake (Lake Stechlin, Germany). Oversaturation of methane was repeatedly recorded in the well-oxygenated upper 10 m of the water column, and the methane maxima coincided with oxygen oversaturation at 6 m. Laboratory incubations of unamended epilimnetic lake water and inoculations of photoautotrophs with a lake-enrichment culture both led to methane production even in the presence of oxygen, and the production was not affected by the addition of inorganic phosphate or methylated compounds. Methane production was also detected by in-lake incubations of lake water, and the highest production rate was 1.8–2.4 nM⋅h−1 at 6 m, which could explain 33–44% of the observed ambient methane accumulation in the same month. Temporal and spatial uncoupling between methanogenesis and methanotrophy was supported by field and laboratory measurements, which also helped explain the oversaturation of methane in the upper water column. Potentially methanogenic Archaea were detected in situ in the oxygenated, methane-rich epilimnion, and their attachment to photoautotrophs might allow for anaerobic growth and direct transfer of substrates for methane production. Specific PCR on mRNA of the methyl coenzyme M reductase A gene revealed active methanogenesis. Microbial methane production in oxygenated water represents a hitherto overlooked source of methane and can be important for carbon cycling in the aquatic environments and water to air methane flux.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 20
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    Lower Thermospheric Enhanced Sodium Layers Observed at Low Latitude and Possible Formation: Case Studies (2013)
    Wiley
    Details
    Publication Date: 2013-02-28
    Description: [1]  We report two lower thermospheric enhanced sodium layer (TeSL) cases observed at a low latitude station, Lijiang, China (26.7°N, 100.0°E), on March 10 and April 10, 2012, respectively. The TeSLs in the two cases were located at altitudes near 122 and 112 km, respectively. In addition, strong sporadic sodium layers (SSLs) near 100 km accompanied the TeSL observed on March 10, 2012. Both the TeSLs and SSLs exhibited tidal-induced downward motion. The adjacent ground-based and space-borne ionospheric radio observations showed strong Es layers before the appearance of the TeSLs, suggesting an " Es – TeSLs (SSLs)" chain formed through the tidal wind shear mechanism. Assuming that the vertical tidal wavelengths remain unchanged, it is found that in different regions caused by the tidal wind shear, different TeSLs evolution processes are expected: (1) in a tidal-convergence region, a TeSL/SSL with a downward propagation phase is enhanced due to a rapid decrease in the Na + lifetime at the lower altitude; (2) in an ion convergence-divergence interface region, a TeSL/SSL will still follow the tidal downward phase progression, but sodium density does not exhibit evident enhancement; and (3) when a TeSL/SSL enters into a tidal wind-divergence zone, the layer density tends to decrease.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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