2,016 research outputs found
Terahertz Atmospheric Windows for High Angular Resolution Terahertz Astronomy from Dome A
Atmospheric transmission from Dome A, Antarctica, presents new possibilities
in the field of terahertz astronomy, where space telescopes have been the only
observational tools until now. Using atmospheric transmission measurements from
Dome A with a Fourier transform spectrometer, transmission spectra and
long-term stabilities have been analyzed at 1.461 THz, 3.393 THz, 5.786 THz and
7.1 THz, which show that important atmospheric windows for terahertz astronomy
open for a reasonable length of time in the winter season. With large aperture
terahertz telescopes and interferometers at Dome A, high angular resolution
terahertz observations are foreseen of atomic fine-structure lines from ionized
gas and a water ice feature from protoplanetary disks.Comment: 6 pages, 3 figures, to appear in Advances in Polar Scienc
Observation of Landau level-like quantizations at 77 K along a strained-induced graphene ridge
Recent studies show that the electronic structures of graphene can be
modified by strain and it was predicted that strain in graphene can induce
peaks in the local density of states (LDOS) mimicking Landau levels (LLs)
generated in the presence of a large magnetic field. Here we report scanning
tunnelling spectroscopy (STS) observation of nine strain-induced peaks in LDOS
at 77 K along a graphene ridge created when the graphene layer was cleaved from
a sample of highly oriented pyrolytic graphite (HOPG). The energies of these
peaks follow the progression of LLs of massless 'Dirac fermions' (DFs) in a
magnetic field of 230 T. The results presented here suggest a possible route to
realize zero-field quantum Hall-like effects at 77 K
Theoretical understanding of correlation between magnetic phase transition and the superconducting dome in high-Tc cuprates
Many issues concerning the origin of high-temperature superconductivity (HTS)
are still under debate. For example, how the magnetic ordering varies with
doping and its relationship with the superconducting temperature; and why the
maximal Tc always occurs near the quantum critical point. In this paper, taking
hole-doped La2CuO4 as a classical example, we employ the first-principles band
structure and total energy calculations and Monte Carlo simulations to explore
how the symmetry-breaking magnetic ground state evolves with hole doping and
the origin of a dome-shaped superconductivity region in the phase diagram. We
demonstrate that the local antiferromagnetic ordering and doping play key roles
in determining the electron-phonon coupling, thus Tc. Initially, the La2CuO4
possesses a checkerboard local antiferromagnetic ground state. As the hole
doping increases, Tc increases with the increase of the density of states at
the Fermi surface. But as the doping increases further, the strength of the
antiferromagnetic interaction weakens. At the critical doping level, a magnetic
phase transition occurs that reduces the local antiferromagnetism-assisted
electron-phonon coupling, thus diminishing the Tc. The superconductivity
disappears in the heavily overdoped region when the antiferromagnetic ordering
disappears. These observations could account for why cuprates have a
dome-shaped superconductivity region in the phase diagram. Our study, thus,
contributes to a fundamental understanding of the correlation between doping,
local magnetic ordering, and superconductivity of HTS.Comment: 14 pages, 3 figures in the main text; 11 pages, 7 figures in the
supplementary material
Non-Muscle Myosin IIA Facilitates Vesicle Trafficking for MG53-Mediated Cell Membrane Repair
The Mechanism of Intragranular Acicular Ferrite Nucleation Induced by Mg-Al-O Inclusions
The features of inclusion and microstructure for carbon structural steel containing Mg-Al-O inclusions were studied through the scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). It can be seen that, in Mg-Al-O inclusions, the elements of Mn, Si, and S coexist, and their central mole ratio of Mg/Al varies in a wide range. This value for most inclusions is larger than 0.5, which suggests the formation of solid solution between MgAl2O4 and MgO. After etching, the typical microstructure of intragranular acicular ferrites is observed, which is due to the nucleation effect induced by Mg-Al-O inclusions. From the SEM-EDS mapping images, it is found that the element of sulfur accumulates on the periphery of nucleation inclusion. Moreover, line EDS analysis hints that Mn-depletion zone (MDZ) exists in steel matrix, which is adjacent to the complex inclusion. Combined with the theoretical analysis, this phenomenon can be explained by the absorption of Mn due to the magnesium vacancy in MgAl2O4, and this MDZ promotes the nucleation of intragranular acicular ferrite. Through statistical analysis of SEM images for microstructure, the probabilistic nature of inducing nucleation effect is revealed. These results may be helpful to clarify the nature of oxide metallurgy
Diverse Profiles of AI-1 Type Quorum Sensing Molecules in Cultivable Bacteria from the Mangrove (Kandelia obovata) Rhizosphere Environment
Factors related to children’s caries: a structural equation modeling approach
BACKGROUND: Dental caries among preschool children is highly prevalent in many less-developed countries. METHODS: A model which explored the factors related to children’s dental caries was tested in this study using structural equation modeling. Caregivers of children aged 5 years were surveyed on their socioeconomic status, and their oral health knowledge, attitudes and practices. In addition, information on their children’s oral health practices, dental insurance and dental service utilization were collected. Examination of caries was conducted on all children who returned fully completed questionnaires. RESULTS: The results showed that socioeconomic factors influenced children’s oral health practices through the impact of caregivers’ oral health knowledge and practices; that caregivers’ oral health knowledge affected children’s oral health practices through the influence of caregivers’ oral health attitudes and practices; and finally, that children’s oral health practices were linked directly to their caries. CONCLUSION: The findings have important applications for promoting policies aimed at advancing children’s oral health
The impact of ability-, motivation- and opportunity-enhancing HR sub-bundles on employee wellbeing: An examination of nonlinearities and occupational differences in skill levels
Existing research examines the impact of human resource (HR) practices on employee wellbeing by considering each practice in isolation or multiple practices as a bundle, focusing on linear associations. Drawing on the too-much-of-a-good-thing (TMGT) meta-theory, we examine possible nonlinear effects of Ability Motivation-Opportunity (AMO) sub-bundles on job satisfaction and job stress. We, also, examine boundary conditions on whether and how the nature of the identified curvilinear associations varies across employees in high-, medium-, and low-skilled occupations. Using data from the Workplace Employment Relations Study (WERS2011), we uncover an inverse U-shaped association between motivation-enhancing (ME) practices and job satisfaction and a U-shaped association between opportunity-enhancing (OE) practices and job stress. No evidence of a curvilinear ability-enhancing (AE) practices-wellbeing association emerges. Additionally, occupational differences in skills levels moderate the curvilinear ME practices-stress association. Likewise, occupational skills differences moderate the associations between OE practices and job satisfaction, and work stress. There is no suggestion that occupational differences moderate the AE practices-wellbeing association. These findings underline the contingent nature of the TMGT effect and call for a more nuanced investigation of the HR-wellbeing association
Strain Induced One-Dimensional Landau-Level Quantization in Corrugated Graphene
Theoretical research has predicted that ripples of graphene generates
effective gauge field on its low energy electronic structure and could lead to
zero-energy flat bands, which are the analog of Landau levels in real magnetic
fields. Here we demonstrate, using a combination of scanning tunneling
microscopy and tight-binding approximation, that the zero-energy Landau levels
with vanishing Fermi velocities will form when the effective pseudomagnetic
flux per ripple is larger than the flux quantum. Our analysis indicates that
the effective gauge field of the ripples results in zero-energy flat bands in
one direction but not in another. The Fermi velocities in the perpendicular
direction of the ripples are not renormalized at all. The condition to generate
the ripples is also discussed according to classical thin-film elasticity
theory.Comment: 4 figures, Phys. Rev.
Electronic Structures of Graphene Layers on Metal Foil: Effect of Point Defects
Here we report a facile method to generate a high density of point defects in
graphene on metal foil and show how the point defects affect the electronic
structures of graphene layers. Our scanning tunneling microscopy (STM)
measurements, complemented by first principle calculations, reveal that the
point defects result in both the intervalley and intravalley scattering of
graphene. The Fermi velocity is reduced in the vicinity area of the defect due
to the enhanced scattering. Additionally, our analysis further points out that
periodic point defects can tailor the electronic properties of graphene by
introducing a significant bandgap, which opens an avenue towards all-graphene
electronics.Comment: 4 figure
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