698 research outputs found
Disorder-induced linear magnetoresistance in AlO/SrTiO heterostructures
The unsaturated linear magnetoresistance (LMR) has attracted widely attention
because of potential applications and fundamental interest. By controlling the
growth temperature, we realized the metal-to-insulator transition in
AlO/SrTiO heterostructures. The LMR is observed in metallic samples
with the electron mobility varying over three orders of magnitude. The observed
LMR cannot be explained by the guiding center diffusion model even in samples
with very high mobility. The slope of the observed LMR is proportional to the
Hall mobility, and the crossover field, indicating a transition from quadratic
(at low fields) to linear (at high fields) field dependence, is proportional to
the inverse Hall mobility. This signifies that the classical model is valid to
explain the observed LMR. More importantly, we develop an analytical expression
according to the effective-medium theory that is equivalent to the classical
model. And the analytical expression describes the LMR data very well,
confirming the validity of the classical model.Comment: 22 Pages, 4 figures, 1 tabl
A structure-preserving doubling algorithm for quadratic eigenvalue problems arising from time-delay systems
AbstractWe propose a structure-preserving doubling algorithm for a quadratic eigenvalue problem arising from the stability analysis of time-delay systems. We are particularly interested in the eigenvalues on the unit circle, which are difficult to estimate. The convergence and backward error of the algorithm are analyzed and three numerical examples are presented. Our experience shows that our algorithm is efficient in comparison to the few existing approaches for small to medium size problems
Cordycepin reverses cisplatin resistance in human bladder cancer cells via the PTEN/PI3K/AKt pathway
Purpose: To study the influence of cordycepin (Cor) on cisplatin insensitivity in bladder carcinoma, and its underlying mechanism of action.Methods: The effects of cisplatin and Cor treatments on the viability of T24-sensitive and T24/DDPinsensitive bladder carcinoma cells were investigated by using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) method to assess selectivity index. Flow cytometry was employed to evaluate the apoptosis of T24/DDP-resistant bladder cancer cells treated with cisplatin and Cor. The concentrations of PTEN, p-AKt and Akt in T24/DDP-resistant bladder cancer cells treated with cisplatin and Cor were determined by western blot assay.Results: Compared with T24-sensitive cells, the sensitivity of T24/DDP-resistant bladder cancer cells to cisplatin was significantly decreased, along with significant increase in half-inhibitory concentration (IC50) value, resulting in 10.56-fold increase in resistance (p < 0.05). The median effective concentration (EC50) value of Cor for DDP reversal was 1.03 ± 0.15 μM, and it had a high selectivity index for normal cells (> 48.5). The results from flow cytometry showed that Cor significantly enhanced the apoptosisinducing capacity of DDP in T24/DDP-resistant cells (p < 0.05), while Western blot data indicate that PTEN protein expression increased and phosphorylated Akt protein expression decreased in T24/DDPresistantcells after Cor treatment when compared with control group (p < 0.05).Conclusion: Cordycepin significantly improves the sensitivity of T24/ DDP-resistant bladder cancer cells to cisplatin via a mechanism related to the activation of PTEN/AKt signaling pathway, thus indicating that it is a potential candidate reversing DDP-resistance in bladder cancer.
Keywords: Bladder cancer, Cordycepin, Cisplatin resistance, PTEN/Akt signaling pathwa
Compensation effect in carbon nanotube quantum dots coupled to polarized electrodes in the presence of spin-orbit coupling
We study theoretically the Kondo effect in carbon nanotube quantum dot
attached to polarized electrodes. Since both spin and orbit degrees of freedom
are involved in such a system, the electrode polarization contains the spin-
and orbit-polarizations as well as the Kramers polarization in the presence of
the spin-orbit coupling. In this paper we focus on the compensation effect of
the effective fields induced by different polarizations by applying magnetic
field. The main results are i) while the effective fields induced by the spin-
and orbit-polarizations remove the degeneracy in the Kondo effect, the
effective field induced by the Kramers polarization enhances the degeneracy
through suppressing the spin-orbit coupling; ii) while the effective field
induced by the spin-polarization can not be compensated by applying magnetic
field, the effective field induced by the orbit-polarization can be
compensated; and iii) the presence of the spin-orbit coupling does not change
the compensation behavior observed in the case without the spin-orbit coupling.
These results are observable in an ultraclean carbon-nanotube quantum dot
attached to ferromagnetic contacts under a parallel applied magnetic field
along the tube axis and it would deepen our understanding on the Kondo physics
of the carbon nanotube quantum dot.Comment: 8 pages, 6 figure
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