Ab initio molecular dynamics (AIMD) calculations were performed on the atomic configuration of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass. The local structures were characterized in terms of ...structure factors (SF), pair correlation functions (PCF), coordinate numbers, bond pairs and Voronoi polyhedra. The glass transition temperature, generalized PCF and SF predicated by AIMD are in good agreement with the experimental data. Icosahedral short-range orders (ISRO) are found to be the most dominant, in view of the presence of the majority of bond pairs with 1551, 1541 and 1431, and Voronoi polyhedra with < 0,3,6,1 > , < 0,2,8,1 > , < 0,0,12,0 > and < 0,2,8,4 > . Icosahedral medium range orders (IMROs) are formed from icosahedra via the linkage of vertex-, edge-, face- and intercross-shared atoms. The glass structure on the nanometer scale is accumulated by polyhedra through an efficient packing mode. It is suggested that the extraordinary glass-forming ability of this alloy is essentially attributable to the formation of ISRO and IMRO, and the dense packing of atoms.
•We propose a vacancy mechanism to describe diffusivity of oxygen in bcc Fe.•Oxygen in octahedral interstice of bcc Fe is always energetically favorable.•Vacancy possesses an extremely high affinity ...for oxygen in bcc Fe.•First-principles diffusivity of oxygen in bcc Fe agrees well with measurements.
Diffusivity of interstitial oxygen (O) in bcc iron (Fe) with and without the effect of vacancy has been investigated in terms of first-principles calculations within the framework of transition state theory. Examination of migration pathway and phonon results indicates that O in octahedral interstice is always energetically favorable (minimum energy) with and without vacancy. It is found that vacancy possesses an extremely high affinity for O in bcc Fe, increasing dramatically the energy barrier (∼80%) for O migration, and in turn, making the predicted diffusion coefficient of O in bcc Fe in favorable accord with experiments.
Abstract
The radio radiation mechanism is one of the open questions for pulsars. Multiband observations are very helpful to constrain pulsar radiation models. We observed PSR J1848-0123 at the 5 GHz ...band with the Shanghai Tianma 65 m radio telescope (TMRT). The 5 GHz observation together with the European Pulsar Network (EPN) and CSIRO ATNF Data Archives databases provides a broadband evolution property of the pulse profiles for this pulsar. We reprocessed these data sets to obtain the multiband pulse profiles. It was found that the pulse profile of PSR J1848-0123 narrows with increasing emission frequency. We separated the emission components of each pulse profile with a multi-Gaussian fitting method, and then calculated the beaming angle and emission radius of each component with the basic radiation geometry of pulsar. With the calculated beam angles and radiation radii, we simulated the radius-frequency mapping of this pulsar with an inverse Compton scatting model (ICS). It was found that the observed radio radiation could be generated in the core gap region above the polar cap of the pulsar. The beaming angle and emission radius versus frequency for PSR J1848-0123 can be explained well with the ICS model.
To investigate the role of proline 4-hydroxylase Ⅱ (P4HA2) in the occurrence and progression of liver cancer.
GEPIA and Human Protein Atlas database were used to predict the expression of P4HA2 in ...hepatocellular carcinoma (HCC), and K-M plotter online database was used to analyze the relationship between P4HA2 expression and the prognosis of HCC. We also examined the expressions of P4HA2 in HCC cells and normal hepatocytes using qRT-PCR and Western blotting. With lentivirus-mediated RNA interference, P4HA2 expression was knocked down in hepatoma SNU-449 and Hep-3B cells, and the changes in cell proliferation, migration and invasion were assessed using cell counting kit-8 (CCK-8) assay, colony formation test, scratch test and Transwell assay. The changes in the expressions of epithelial-mesenchymal transition (EMT) and PI3K/Akt/mTOR signal pathway-related proteins were detected using Western blotting.
Online database analysis showed that the expression of P4HA2 was significantly higher in HCC tissues than in n
Abstract
The radio radiation mechanism is one of the open questions in pulsar physics. Multiband observations are very important for constraining the pulsar radiation mechanism. In this paper, we ...investigate the pulse profiles of PSR B1737+13 and its evolution with the frequency. The integrated pulse profiles are obtained from the European Pulsar Network and the Australia Telescope National Facility data, together with recent observations from the largest dish Five-hundred-meter Aperture Spherical radio Telescope. The radiation components are separated with the squared hyperbolic secant functions, and the radiation altitudes of each radiation component at different frequencies are calculated. It is found that the radio radiation at different frequencies comes from different altitudes. The frequency evolutions of separations for the inner and outer cone components are studied. It is found that the separations of the inner and outer cone components have opposite frequency dependence. We simulate the RFM of PSR B1737+13 with the inverse Compton scattering (ICS) model and find that the RFM can be naturally described by the ICS model. Through the simulation, the radio radiation region of PSR B1737+13 is determined, and the result shows that the radio radiation of this pulsar may be generated in the annular gap region.
► The lattice dynamics in the DFT framework is used to investigate elastic constants, thermal expansions, bulk moduli and heat capacities for the La–Mg compounds. ► Phase stability analyses show that ...LaMg2 and La5Mg41 are metastable at low temperatures. ► The elastic anisotropy is presented with color contour maps.
Thermodynamic and mechanical properties of the six known phases in the La–Mg phase diagram, viz. LaMg, LaMg2, LaMg3, La5Mg41, La2Mg17, and LaMg12, and their elemental antecedents, Mg and La, are computed with density functional theory (DFT) using the PBE and PBEsol exchange-correlation functionals. Phase stability analyses show that both LaMg2 and La5Mg41 are metastable at low temperatures which is consistent with experiments and vibrational spectra. We generalize an existing approach for computing the crystallographic dependence of Young's modulus and Poisson's ratio, which is presently limited to cubic systems, to address any space group symmetry using 0K elasticity tensor components (Cij) from DFT. Isothermal and isentropic Cij(T) are computed with the quasiharmonic approximation (QHA) as are the linear thermal expansion of the cubic compounds, the average linear thermal expansion for the non-cubic compounds, the bulk modulus, and the constant pressure heat capacity. A critical comparison of theoretical results from the PBE and PBEsol functionals is made with available experimental data.
Objective
To assess the current status of caesarean delivery (CD) in China, propose reference CD rates for China overall, and by regions, investigate the main indications for CDs and identify ...possible areas for safe reduction.
Design
A multicentre cross‐sectional study.
Setting
A total of 94 hospitals across 23 provinces in China.
Population
A total of 73 977 randomly selected deliveries.
Methods
We used a modified Robson classification to characterise CDs in subgroups and by regions, and the World Health Organization (WHO) C‐Model to calculate reference CD rates.
Main outcome measures
CD rates in China.
Results
In 2015–2016, the overall CD rate in China was 38.9% (95% CI 38.6–39.3%). Considering the obstetric characteristics of the population, the multivariable model‐based reference CD rate was estimated at 28.5% (95% CI 28.3–28.8%). Accordingly, an absolute reduction of 10.4% (or 26.7% relative reduction) may be considered. The CD rate varied substantially by region. Previous CD was the most common indication in all regions, accounting for 38.2% of all CDs, followed by maternal request (9.8%), labour dystocia (8.3%), fetal distress (7.7%) and malpresentation (7.6%). Overall, 12.7% of women had prelabour CDs, contributing to 32.8% of the total CDs.
Conclusions
Nearly 39% of births were delivered by caesarean in China but a reduction of this rate by a quarter may be considered attainable. Repeat CD contributed more than one‐third of the total CDs. Given the large variation in maternal characteristics, region‐specific or even hospital‐specific reference CD rates are needed for precision management of CD.
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The caesarean rate in 2015–2016 in China was 38.9%, whereas the reference rate was 28.5%.
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The caesarean rate in 2015–2016 in China was 38.9%, whereas the reference rate was 28.5%.
Linked article This article is commented on by M Varner, p. 148 in this issue. To view this mini commentary visit https://doi.org/10.1111/1471-0528.16953.
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