106 research outputs found
Enhanced thermoelectric properties by Ir doping of PtSb2 with pyrite structure
The effects of Ir doping on the thermoelectric properties of Pt1-xIrxSb2 (x =
0, 0.01, 0.03, and 0.1) with pyrite structure were studied. Measurements of
electrical resistivity rho, Seebeck coefficient S, and thermal conductivity
kappa were conducted. The results showed an abrupt change from semiconducting
behavior without Ir (x = 0) to metallic behavior at x = 0.01. The sample with x
= 0.01 exhibited large S and low rho, resulting in a maximum power factor
(S^2/rho) of 43 muW/cmK^2 at 400 K. The peculiar "pudding mold"-type electronic
band dispersion could explain the enhanced thermoelectric properties in the
metallic state.Comment: 3 pages, 2 figure
Superconductivity at 38 K in Iron-Based Compound with Platinum-Arsenide Layers Ca10(Pt4As8)(Fe2-xPtxAs2)5
We report superconductivity in novel iron-based compounds
Ca10(PtnAs8)(Fe2-xPtxAs2)5 with n = 3 and 4. Both compounds crystallize in
triclinic structures (space group P-1), in which Fe2As2 layers alternate with
PtnAs8 spacer layers. Superconductivity with a transition temperature of 38 K
is observed in the n = 4 compound with a Pt content of x ~ 0.36 in the Fe2As2
layers. The compound with n = 3 exhibits superconductivity at 13 K.Comment: OPEN SELECT article, 11 pages, 5 figures, 2 table
Giant Negative Thermal Expansion Induced by the Synergistic Effects of Ferroelectrostriction and Spin-Crossover in PbTiO3-Based Perovskites
The discovery of unusual negative thermal expansion (NTE) provides the
opportunity to control the common but much desired property of thermal
expansion, which is valuable not only in scientific interests but also in
practical applications. However, most of the available NTE materials are
limited to a narrow temperature range, and the NTE effect is generally weakened
by means of various modifications. Here, we report an enhanced NTE effect that
occurs over a wide temperature range (\alpha V = -5.24 * 10-5 {\deg}C^-1,
25-575 {\deg} C), and this NTE effect is accompanied by an abnormal enhanced
tetragonality, a large spontaneous polarization, and a G-type antiferromagnetic
ordering in the present perovskite-type ferroelectric of (1-x)PbTiO3-xBiCoO3.
Specifically, for the composition of 0.5PbTiO3-0.5BiCoO3, an extensive
volumetric contraction of ~4.8 % has been observed near the Curie temperature
of 700 {\deg}C, which represents the highest level in PbTiO3-based
ferroelectrics. According to our experimental and theoretical results, the
giant NTE originates from a synergistic effect of the ferroelectrostriction and
spin-crossover of cobalt on the crystal lattice. The actual NTE mechanism is
contrasted with previous functional NTE materials, in which the NTE is simply
coupled with one ordering such as electronic, magnetic, or ferroelectric
ordering. The present study sheds light on the understanding of NTE mechanisms
and it attests that NTE could be simultaneouslycoupled with different
orderings, which will pave a new way toward the design of large NTE materials.Comment: 30 page
Full Relativistic Electronic Structure and Fermi Surface Sheets of the First Honeycomb-Lattice Pnictide Superconductor SrPtAs
We report full-potential density functional theory (DFT)-based {\it ab
initio} band structure calculations to investigate electronic structure
properties of the first pnictide superconductor with a honeycomb-lattice
structure: SrPtAs. As a result, electronic bands, density of states, Fermi
velocities and the topology of the Fermi surface for SrPtAs are obtained. These
quantities are discussed in comparison to the first available experimental
data. Predictions for future measurements are provided
Superconductivity at 5.4 K in -BiPd
We investigate bulk superconductivity in a high-quality single crystal of
BiPd (-BiPd, space group; I4/mmm) at temperatures less than 5.4
K by exploring its electrical resistivity, magnetic susceptibility, and
specific heat. The temperature dependence of the electrical resistivity shows
convex-upward behaviors at temperatures greater than 40-50 K, which can be
explained by a parallel-resistor model. In addition, we demonstrate that this
material is a multiple-band/multiple-gap superconductor based on the
temperature dependences of the specific heat and the upper critical field.Comment: 4 pages, 3 figure
Arsenic trioxide, a potent inhibitor of NF-κB, abrogates allergen-induced airway hyperresponsiveness and inflammation
BACKGROUND: Overactivation of nuclear factor κB (NF-κB) orchestrates airway eosinophilia, but does not dampen airway hyperresponsiveness in asthma. NF-κB repression by arsenic trioxide (As(2)O(3)) contributes to apoptosis of eosinophils (EOS) in airways. Here we provide evidence that As(2)O(3 )abrogates allergen (OVA)-induced airway eosinophilia by modulating the expression of IκBα, an NF-κB inhibitory protein, and decreases the airway hyperresponsiveness. METHODS: Using a murine model of asthma, the airway hyperresponsiveness was conducted by barometric whole-body plethysmography. Airway eosinophilia, OVA-specific IgE in serum, and chemokine eotaxin and RANTES (regulated upon activation, normal T cell expressed and secreted) in bronchoalveolar lavage fluid were measured by lung histology, Diff-Quick staining, and ELISA. Chemokine-induced EOS chemotactic activity was evaluated using EOS chemotaxis assay. Electrophoretic mobility shift assay and Western blot analysis were performed to assess pulmonary NF-κB activation and IκBα expression, respectively. RESULTS: As(2)O(3 )attenuated the allergen-induced serum IgE, chemokine expression of eotaxin and RANTES, and the EOS recruitment in bronchoalveolar lavage fluid, which is associated with an increased IκBα expression as well as a decreased NF-κB activation. Also, As(2)O(3 )suppressed the chemotaxis of EOS dose-dependently in vitro. Additionally, As(2)O(3 )significantly ameliorated the allergen-driven airway hyperresponsiveness, the cardinal feature underlying asthma. CONCLUSION: These findings demonstrate an essential role of NF-κB in airway eosinophilia, and illustrate a potential dissociation between airway inflammation and hyperresponsiveness. As(2)O(3 )likely exerts its broad anti-inflammatory effects by suppression of NF-κB activation through augmentation of IκBα expression in asthma
Deep Annotation of Populus trichocarpa microRNAs from Diverse Tissue Sets
Populus trichocarpa is an important woody model organism whose entire genome has been sequenced. This resource has facilitated the annotation of microRNAs (miRNAs), which are short non-coding RNAs with critical regulatory functions. However, despite their developmental importance, P. trichocarpa miRNAs have yet to be annotated from numerous important tissues. Here we significantly expand the breadth of tissue sampling and sequencing depth for miRNA annotation in P. trichocarpa using high-throughput smallRNA (sRNA) sequencing. miRNA annotation was performed using three individual next-generation sRNA sequencing runs from separate leaves, xylem, and mechanically treated xylem, as well as a fourth run using a pooled sample containing vegetative apices, male flowers, female flowers, female apical buds, and male apical and lateral buds. A total of 276 miRNAs were identified from these datasets, including 155 previously unannotated miRNAs, most of which are P. trichocarpa specific. Importantly, we identified several xylem-enriched miRNAs predicted to target genes known to be important in secondary growth, including the critical reaction wood enzyme xyloglucan endo-transglycosylase/hydrolase and vascular-related transcription factors. This study provides a thorough genome-wide annotation of miRNAs in P. trichocarpa through deep sRNA sequencing from diverse tissue sets. Our data significantly expands the P. trichocarpa miRNA repertoire, which will facilitate a broad range of research in this major model system
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