3,007 research outputs found
Spectral and optical properties in the antiphase stripe phase of the cuprate superconductors
We investigate the superconducting order parameter, the spectral and optical
properties in a stripe model with spin (charge) domain-derived scattering
potential (). We show that the charge domain-derived scattering
is less effective than the spin scattering on the suppression of
superconductivity. For , the spectral weight concentrates on
the () antinodal region, and a finite energy peak appears in the optical
conductivity with the disappearance of the Drude peak. But for , the spectral weight concentrates on the () nodal region,
and a residual Drude peak exists in the optical conductivity without the finite
energy peak. These results consistently account for the divergent observations
in the ARPES and optical conductivity experiments in several high-
cuprates, and suggest that the "insulating" and "metallic" properties are
intrinsic to the stripe state, depending on the relative strength of the spin
and charge domain-derived scattering potentials.Comment: 7 pages, 4 figure
Coexistence of the antiferromagnetic and superconducting order and its effect on spin dynamics in electron-doped high- cuprates
In the framework of the slave-boson approach to the model, it is
found that for electron-doped high- cuprates, the staggered
antiferromagnetic (AF) order coexists with superconducting (SC) order in a wide
doping level ranged from underdoped to nearly optimal doping at the mean-field
level. In the coexisting phase, it is revealed that the spin response is
commensurate in a substantial frequency range below a crossover frequency
for all dopings considered, and it switches to the incommensurate
structure when the frequency is higher than . This result is in
agreement with the experimental measurements. Comparison of the spin response
between the coexisting phase and the pure SC phase with a
-wave pairing plus a higher harmonics term (DP+HH) suggests
that the inclusion of the two-band effect is important to consistently account
for both the dispersion of the spin response and the non-monotonic gap behavior
in the electron-doped cuprates.Comment: 6 pages, 5 figure
Morphological Variation in Pachytriton labiatus and a Re-Assessment of the Taxonomic Status of P. granulosus (Amphibia: Urodela: Salamandridae)
Variation in relation to age and sex in a population of Pachytriton labiatus from Mt. Huangshan, Anhui Province, China was examined. There appeared to be distinct morphological variation among age/sex groups. We suggest that some of this variation is associated with ecology and behavior. Examination of the newt species from the type locality and nearby localities of Pachytriton granulosus (=Pingia granulosa), a taxonomically problematic species, revealed that this taxon was almost indistinguishable from juvenile P. labiatus. We therefore conclude that P. granulosus is a junior synonym of P. labiatus
Performance stability and degradation mechanism of La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes under solid oxide fuel cells operation conditions
The performance stability and degradation mechanism of La0.6Sr0.4Co0.2Fe0.8O3d (LSCF)cathodes and LSCF impregnated Gd0.1Ce0.9O2d (LSCF-GDC) cathodes are investigated undersolid oxide fuel cell operation conditions. LSCF and LSCF-GDC cathodes show initiallyperformance improvement but degrade under cathodic polarization treatment at 750 C for120 h. The results confirm the grain growth and agglomeration of LSCF and in particularGDC-LSCF cathodes as well as the formation of SrCoOx particles on the surface of LSCFunder cathodic polarization conditions. The direct observation of SrCoOx formation hasbeen made possible on the surface of dense LSCF electrode plate on GDC electrolyte. Theformation of SrCoOx is most likely due to the interaction between the segregated Sr and Cofrom LSCF lattice under polarization conditions. The formation of SrCoOx would contributeto the deterioration of the electrocatalytic activity of the LSCF-based electrodes for the O2reduction in addition to the agglomeration and microstructure coarsenin
Chromium and Sulfur Contaminants on La0.6Sr0.4Co0.2Fe0.8O3-δ Cathodes of Solid Oxide Fuel Cells
The presence of both chromium and sulfur (Cr/S) contaminants on the microstructure and electrocatalytic activity properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) electrodes of solid oxide fuel cells (SOFCs) is studied, using Confocal laser Raman spectroscopy, XRD, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and electrical conductivity relaxation (ECR) methods. LSCF dense bar samples were heat treated in the presence of Cr2O3 and 20 ppm SO2 and in the temperature range of 600–900°C. The deposition and reaction products between LSCF and Cr/S depend on the temperature: SrCrO4 only forms on LSCF samples at 900°C and 800°C, while formation of SrSO4 phase occurs at all temperatures studied. The results indicate that sulfur shows a higher activity with LSCF, as compared to gaseous Cr species. Segregated SrO is more likely to react with gaseous Cr species at higher temperatures, however, reaction with SO2 is more pronounced at lower temperatures, forming SrSO4. ECR results indicate that co-deposition of Cr and sulfur significantly deteriorates the surface exchange and diffusion processes for the O2 reduction reaction on LSCF electrodes
Two variants on T2DM susceptible gene HHEX are associated with CRC risk in a Chinese population
Increasing amounts of evidence has demonstrated that T2DM (Type 2 Diabetes Mellitus) patients have increased susceptibility to CRC (colorectal cancer). As HHEX is a recognized susceptibility gene in T2DM, this work was focused on two SNPs in HHEX, rs1111875 and rs7923837, to study their association with CRC. T2DM patients without CRC (T2DM-only, n=300), T2DM with CRC (T2DM/CRC, n=135), cancer-free controls (Control, n=570), and CRC without T2DM (CRC-only, n=642) cases were enrolled. DNA samples were extracted from the peripheral blood leukocytes of the patients and sequenced by direct sequencing. The χ(2) test was used to compare categorical data. We found that in T2DM patients, rs1111875 but not the rs7923837 in HHEX gene was associated with the occurrence of CRC (p= 0.006). for rs1111875, TC/CC patients had an increased risk of CRC (p=0.019, OR=1.592, 95%CI=1.046-2.423). Moreover, our results also indicated that the two variants of HEEX gene could be risk factors for CRC in general population, independent on T2DM (p< 0.001 for rs1111875, p=0.001 for rs7923837). For rs1111875, increased risk of CRC was observed in TC or TC/CC than CC individuals (p<0.001, OR= 1.780, 95%CI= 1.385-2.287; p<0.001, OR= 1.695, 95%CI= 1.335-2.152). For rs7923837, increased CRC risk was observed in AG, GG, and AG/GG than AA individuals (p< 0.001, OR= 1.520, 95%CI= 1.200-1.924; p=0.036, OR= 1.739, 95%CI= 0.989-3.058; p< 0.001, OR= 1.540, 95%CI= 1.225-1.936). This finding highlights the potentially functional alteration with HHEX rs1111875 and rs7923837 polymorphisms may increase CRC susceptibility. Risk effects and the functional impact of these polymorphisms need further validation
Observation of prolonged coherence time of the collective spin wave of atomic ensemble in a paraffin coated Rb vapor cell
We report a prolonged coherence time of the collective spin wave of a thermal
87Rb atomic ensemble in a paraffin coated cell. The spin wave is prepared
through a stimulated Raman Process. The long coherence time time is achieved by
prolonging the lifetime of the spins with paraffin coating and minimize
dephasing with optimal experimental configuration. The observation of the long
time delayed-stimulated Stokes signal in the writing process suggests the
prolonged lifetime of the prepared spins; a direct measurement of the decay of
anti-Stokes signal in the reading process shows the coherence time is up to 300
us after minimizing dephasing. This is one hundred times longer than the
reported coherence time in the similar experiments in thermal atomic ensembles
based on the Duan-Lukin-Cirac-Zoller (DLCZ) and its improved protocols. This
prolonged coherence time sets the upper limit of the memory time in quantum
repeaters based on such protocols, which is crucial for the realization of
long-distance quantum communication. The previous reported fluorescence
background in the writing process due to collision in a sample cell with buffer
gas is also reduced in a cell without buffer gas.Comment: 4 pages, 4 figure
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