1,300 research outputs found
Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
Following the discovery of superconductivity in an iron-based arsenide
LaO1-xFxFeAs with a superconducting transition temperature (Tc) of 26 K[1], Tc
was pushed up surprisingly to above 40 K by either applying pressure[2] or
replacing La with Sm[3], Ce[4], Nd[5] and Pr[6]. The maximum Tc has climbed to
55 K, observed in SmO1-xFxFeAs[7, 8] and SmFeAsO1-x[9]. The value of Tc was
found to increase with decreasing lattice parameters in LnFeAsO1-xFx (Ln stands
for the lanthanide elements) at an apparently optimal doping level. However,
the F- doping in GdFeAsO is particularly difficult[10,11] due to the lattice
mismatch between the Gd2O2 layers and Fe2As2 layers. Here we report observation
of superconductivity with Tc as high as 56 K by the Th4+ substitution for Gd3+
in GdFeAsO. The incorporation of relatively large Th4+ ions relaxes the lattice
mismatch, hence induces the high temperature superconductivity.Comment: 4 pages, 3 figure
Alkaloids, Diarylheptanoid and Naphthalene Carboxylic Acid Ester from Rhoiptelea chiliantha
Two pyrrolidine alkaloids (1, 2) were isolated from the fruits of Rhoiptelea chiliantha DIEL et HAND.-MAZZ. (Rhoipteleaceae). A diphenyl ether-type diarylheptanoid (3), and a naphthalene carboxylic acid methyl ester (4) which is biogenetically-related to juglone were isolated from the branches of the same plant. Their chemical structures were elucidated on the basis of spectroscopic analysis and chemical evidence
Superconductivity in LaFeAsPO: effect of chemical pressures and bond covalency
We report the realization of superconductivity by an isovalent doping with
phosphorus in LaFeAsO. X-ray diffraction shows that, with the partial
substitution of P for As, the FeAs layers are squeezed while the
LaO layers are stretched along the c-axis. Electrical resistance and
magnetization measurements show emergence of bulk superconductivity at 10
K for the optimally-doped LaFeAsPO (). The upper
critical fields at zero temperature is estimated to be 27 T, much higher than
that of the LaFePO superconductor. The occurrence of superconductivity is
discussed in terms of chemical pressures and bond covalency.Comment: 5 pages, 6 figures, more data presente
New Insights into Traffic Dynamics: A Weighted Probabilistic Cellular Automaton Model
From the macroscopic viewpoint for describing the acceleration behavior of
drivers, this letter presents a weighted probabilistic cellular automaton model
(the WP model, for short) by introducing a kind of random acceleration
probabilistic distribution function. The fundamental diagrams, the
spatio-temporal pattern are analyzed in detail. It is shown that the presented
model leads to the results consistent with the empirical data rather well,
nonlinear velocity-density relationship exists in lower density region, and a
new kind of traffic phenomenon called neo-synchronized flow is resulted.
Furthermore, we give the criterion for distinguishing the high-speed and
low-speed neo-synchronized flows and clarify the mechanism of this kind of
traffic phenomena. In addition, the result that the time evolution of
distribution of headways is displayed as a normal distribution further
validates the reasonability of the neo-synchronized flow. These findings
suggest that the diversity and randomicity of drivers and vehicles has indeed
remarkable effect on traffic dynamics.Comment: 12 pages, 5 figures, submitted to Europhysics Letter
Overexpression of transglutaminase 4 and prostate cancer progression: a potential predictor of less favourable outcomes
Synthesis of Mesoporous Silica@Co–Al Layered Double Hydroxide Spheres: Layer-by-Layer Method and Their Effects on the Flame Retardancy of Epoxy Resins
Hierarchical mesoporous silica@Co–Al layered double hydroxide (m-SiO2@Co–Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co–Al LDH, the synthetic m-SiO2@Co–Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co–Al LDH nanosheets. Subsequently, the m-SiO2@Co–Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co–Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co–Al LDH play pivotal roles in the flame retardance enhancement
The comparison of grey-scale ultrasonic and clinical features of hepatoblastoma and hepatocellular carcinoma in children: a retrospective study for ten years
<p>Abstract</p> <p>Background</p> <p>Hepatoblastoma (HBL) and hepatocellular carcinoma (HCC) are respectively the first and the second most common pediatric malignant liver tumors. The purpose of this study was to evaluate the combined use of the ultrasound examination and the assessment of the patients' clinical features for differentiating HBL from HCC in children.</p> <p>Methods</p> <p>Thirty cases of the confirmed HBL and 12 cases of the confirmed HCC in children under the age of 15 years were enrolled into our study. They were divided into the HBL group and the HCC group according to the histological types of the tumors. The ultrasonic features and the clinical manifestations of the two groups were retrospectively analyzed, with an emphasis on the following parameters: onset age, gender (male/female) ratio, positive epatitis-B-surface-antigen (HBV), alpha-fetoprotein increase, and echo features including septa, calcification and liquefaction within the tumors.</p> <p>Results</p> <p>Compared with the children with HCC, the children with HBL had a significantly younger onset age (8.2 years vs. 3.9 years, P < 0.001) and a significantly smaller frequency of positive HBV (66.7% vs. 13.3%, P < 0.001). The septa and liquefaction were more frequently found in HBL than in HCC (25/30, 83.3% vs. 2/12, 16.7%, P < 0.001; 17/30, 56.7% vs. 3/12, 25%, P = 0.02). When a combination of the liquefaction, septa, negative HBV and onset age smaller than 5 years was used in the evaluation, the sensitivity was raised to 90%, the accuracy was raised to 88%, and the negative predictive value was raised to 73%.</p> <p>Conclusion</p> <p>Ultrasonic features combined with clinical manifestations are valuable for differentiating HBL from HCC in children.</p
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