3,455 research outputs found
Experimental Studies of Low-field Landau Quantization in Two-dimensional Electron Systems in GaAs/AlGaAs Heterostructures
By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional
electron systems, we study the low-field Landau quantization when the thermal
damping is reduced with decreasing the temperature. Magneto-oscillations
following Shubnikov-de Haas (SdH) formula are observed even when their
amplitudes are so large that the deviation to such a formula is expected. Our
experimental results show the importance of the positive magneto-resistance to
the extension of SdH formula under the damping induced by the disorder.Comment: 9 pages, 3 figure
From insulator to quantum Hall liquid at low magnetic fields
We have performed low-temperature transport measurements on a GaAs
two-dimensional electron system at low magnetic fields. Multiple
temperature-independent points and accompanying oscillations are observed in
the longitudinal resistivity between the low-field insulator and the quantum
Hall (QH) liquid. Our results support the existence of an intermediate regime,
where the amplitudes of magneto-oscillations can be well described by
conventional Shubnikov-de Haas theory, between the low-field insulator and QH
liquid.Comment: Magneto-oscillations governed by Shubnikov-de Haas theory are
observed between the low-field insulator and quantum Hall liqui
KxFe2-ySe2 single crystals: Floating-zone growth, Transport and Structural properties
Single crystals of superconducting KxFe2-ySe2 have been grown with the
optical floating-zone technique under application of 8 bar of argon pressure.
We found that large and high quality single crystals with dimensions of
~\varnothing6 \times 10 mm could be obtained at the termination of the grown
ingot through quenching, while the remaining part of the ingot decomposed.
As-grown single crystals commonly represent an intergrowth of two sets of the
c-axis characterized by slightly different lattice constants. Single crystal of
K0.80Fe1.81Se2 shows a superconducting transition at Tc = 31.6 K, leading to a
near 100% expulsion of the external magnetic field in magnetization
measurements. On the other hand, neutron-diffraction data indicate that
superconductivity in the sample coexists with a iron-vacancy superstructure and
static antiferromagnetic order. The anisotropic ratio of the upper critical
field Hc2 for both H//c and H//ab configurations is \sim3.46
Prevalence, incidence and mortality of hypertrophic cardiomyopathy based on a population cohort of 21.9 million in China
There are limited studies on the prevalence and incidence of clinically diagnosed hypertrophic myocardiopathy (HCM) and its mortality in the Chinese population, and the projected population burden of HCM over the next decades. We collected data on HCM and its mortality from the Beijing Municipal Health Commission Information Center (BMHCIC) database and estimated the prevalence and incidence based on the whole Beijing population. Calculation of population trends was performed using annual percentage change (APC) and average annual percentage change (AAPC). Finally, future HCM incidence was built by modelling projection of HCM to the next decades using Poisson regression analysis and Gray Model 1,1(GM [1,1]). The prevalence of HCM was 0.0069% (95%CI, 0.0065–0.0072%; N = 1343) in 2010, rising to 0.076% (95% CI, 0.074–0.077%; N = 16,616) in 2019, and the incidence of HCM was 6.85 per 100 000 person-year in 2010, rising to 11.76 per 100 000 person-year in 2019. Males had higher prevalence and incidence of HCM than females. The APPC for the rising incidence of HCM was 5.8% and the expected numbers will double increase in 2029 by assuming the same increase trend as the last decades. HCM had increased annual incidence of HF (APPC: 8.4, 4.4–12.6, p 0.05) during the studied period. Males had lower mortality (2.70% vs. 4.20%, p < 0.001) than females. The calculated HCM prevalence was much lower compared to prior screening studies from 2004, although the predicted HCM incidence would double over the next decades. HCM was associated with a stable risk of mortality during the studied period
Evaluation of the selfitis behavior scale across two Persian-speaking countries, Iran and Afghanistan: advanced psychometric testing in a large-scale sample
Selfitis—which started off as a hoax but has now been investigated empirically—has been defined as the obsessive–compulsive desire to take photos of oneself and post them on social media. Furthermore, a scale to assess selfitis, the Selfitis Behavior Scale (SBS), has been developed. This study applied advanced psychometric testing methods, including confirmatory factor analysis (utilizing classical test theory) and the Rasch model (utilizing modern test theory), to examine the psychometric properties among Persian speakers (in Iran and Afghanistan). The participants (3163 Iranians and 1100 Afghanistani) completed an online survey posted on Instagram pages. The SBS showed promising properties, including satisfactory reliability (e.g., internal consistency and test–retest reliability), excellent construct validity (e.g., good fit in the CFA and Rasch models), and acceptable measurement invariance across Iranian and Afghan samples. Consequently, the SBS is a valid and reliable instrument for assessing selfitis among Persian-speaking samples
Observation of B+ -> p pbar pi+, B0 -> p pbar K0, and B+ -> p pbar K*+
We report the first observation of a b -> u type charmless baryonic B decay,
B+ -> p pbar pi+, as well as b -> s type B0 -> p pbar K0 and B+ -> p pbar K*+
decays. The analysis is based on a 78fb^{-1} data sample recorded on the
Upsilon(4S) resonance with the Belle detector at KEKB. We find BF(B+ -> p pbar
pi+) = (3.06^{+0.73}_{-0.62} \pm 0.37)*10^{-6}, BF(B0 -> p pbar K0)
=(1.88^{+0.77}_{-0.60} \pm 0.23)*10^{-6}, and BF(B+ -> p pbar K*+) =
(10.3^{+3.6 + 1.3}_{-2.8 -1.7})*10^{-6}. We also update BF(B+ -> p pbar K+) =
(5.66^{+0.67}_{-0.57} \pm 0.62)* 10^{-6}, and present an upper limit on BF(B0
-> p pbar K*0) at the 90% confidence level. A common feature of the observed
decay modes is threshold peaking in baryon pair invariant mass.Comment: 10 pages, 12 figure file
Transverse thermal depinning and nonlinear sliding friction of an adsorbed monolayer
We study the response of an adsorbed monolayer under a driving force as a
model of sliding friction phenomena between two crystalline surfaces with a
boundary lubrication layer. Using Langevin-dynamics simulation, we determine
the nonlinear response in the direction transverse to a high symmetry direction
along which the layer is already sliding. We find that below a finite
transition temperature, there exist a critical depinning force and hysteresis
effects in the transverse response in the dynamical state when the adlayer is
sliding smoothly along the longitudinal direction.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
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