45 research outputs found
The correspondence between shadows and test fields in four-dimensional charged Einstein-Gauss-Bonnet black holes
In this paper, we investigate the photon sphere, shadow radius and
quasinormal modes of a four-dimensional charged Einstein-Gauss-Bonnet black
hole. The perturbation of a massless scalar field in the background of the
black hole is adopted. The quasinormal modes are gotten by the order WKB
approximation approach and shadow radius, respectively. The degree of
coincidence of the quasinormal modes derived by the two approaches increases
with the increase of the values of the Gauss-Bonnet coupling constant and
multiple number. It shows the correspondence between the shadow and test field
in the four-dimensional Einstein-Gauss-Bonnet-Maxwell gravity. The radii of the
photon sphere and shadow increase with the decrease of the Gauss-Bonnet
coupling constant.Comment: 16 page
Atomistic Control in Molecular Beam Epitaxy Growth of Intrinsic Magnetic Topological Insulator MnBi2Te4
Intrinsic magnetic topological insulators have emerged as a promising
platform to study the interplay between topological surface states and
ferromagnetism. This unique interplay can give rise to a variety of exotic
quantum phenomena, including the quantum anomalous Hall effect and axion
insulating states. Here, utilizing molecular beam epitaxy (MBE), we present a
comprehensive study of the growth of high-quality MnBi2Te4 thin films on Si
(111), epitaxial graphene, and highly ordered pyrolytic graphite substrates. By
combining a suite of in-situ characterization techniques, we obtain critical
insights into the atomic-level control of MnBi2Te4 epitaxial growth. First, we
extract the free energy landscape for the epitaxial relationship as a function
of the in-plane angular distribution. Then, by employing an optimized
layer-by-layer growth, we determine the chemical potential and Dirac point of
the thin film at different thicknesses. Overall, these results establish a
foundation for understanding the growth dynamics of MnBi2Te4 and pave the way
for the future applications of MBE in emerging topological quantum materials.Comment: 20 pages, 4 figure
Association between actual weight status, perceived weight and depressive, anxious symptoms in Chinese adolescents: a cross-sectional study
<p>Abstract</p> <p>Backgroud</p> <p>The purpose of this study was to describe actual measured weight and perceived weight and to explore associations with depressive, anxiety symptoms in school adolescents in China.</p> <p>Methods</p> <p>A sample of 1144 Chinese adolescents was randomly selected from four schools in Wuhan, China, including 665 boys and 479 girls with ages ranging between 10 and 17 years. Actual measured weight and height and perceived weight status were compared to anxiety and depressive symptoms measured using the revised Self-Rating Anxiety Scale and Children's Depression Inventory. A general linear model was used to compare differences in psychological symptoms among the teenagers with different measured and perceived weights.</p> <p>Results</p> <p>When compared with standardized weight tables (WHO age- and gender-specific body mass index (BMI) cutoffs (2007 reference)), girls were more likely to misperceive themselves as overweight, whereas more boys misclassified their weight status as underweight. The adolescents who perceived themselves as overweight were more likely to experience depressive and anxiety symptoms (except girls) than those who perceived themselves as normal and/or underweight. However, no significant association was found between depressive and anxiety symptoms actual measured weight status.</p> <p>Conclusions</p> <p>Perceived weight status, but not the actual weight status, was associated with psychological symptoms.</p
Mudskipper genomes provide insights into the terrestrial adaptation of amphibious fishes
Mudskippers are amphibious fishes that have developed morphological and physiological adaptations to match their unique lifestyles. Here we perform whole-genome sequencing of four representative mudskippers to elucidate the molecular mechanisms underlying these adaptations. We discover an expansion of innate immune system genes in the mudskippers that may provide defence against terrestrial pathogens. Several genes of the ammonia excretion pathway in the gills have experienced positive selection, suggesting their important roles in mudskippersâ tolerance to environmental ammonia. Some vision-related genes are differentially lost or mutated, illustrating genomic changes associated with aerial vision. Transcriptomic analyses of mudskippers exposed to air highlight regulatory pathways that are up- or down-regulated in response to hypoxia. The present study provides a valuable resource for understanding the molecular mechanisms underlying water-to-land transition of vertebrates
The bound of Lyapunov exponent in Einstein-Maxwell-Dilaton-Axion black holes
In this paper, we investigate the influence of the angular momentum of a
charged particle on the bound of the Lyapunov exponent in non-extremal and
extremal Einstein-Maxwell-Dilaton-Axion black holes. The derivation of the
exponent relies on the effective potential of the particle. We find that when
the angular momentum takes specific values, the bound is violated at the
certain distances from the event horizons. This violation always exists when
the rotation parameter of the black holes is large enough and the rotation
direction of the particle is opposite to that of the black holes. In the
near-horizon regions, the violation of the bound depends on the rotation
directions of the extremal black hole and particle, and does not depend on the
value of the angular momentum of the particle in the non-extremal black hole.Comment: 16 page
The correspondence between shadow and test field in a four-dimensional charged EinsteinâGaussâBonnet black hole
In this paper, we investigate the photon sphere, shadow radius and quasinormal modes of a four-dimensional charged EinsteinâGaussâBonnet black hole. The perturbation of a massless scalar field in the black holeâs background is adopted. The quasinormal modes are gotten by the 6th order WKB approximation approach and shadow radius, respectively. When the value of the GaussâBonnet coupling constant increase, the values of the real parts of the quasinormal modes increase and those of the imaginary parts decrease. The coincidence degrees of quasinormal modes derived by the two approaches increases with the increase of the values of the GaussâBonnet coupling constant and multipole number. It shows the correspondence between the shadow and test field in the four-dimensional EinsteinâGaussâBonnetâMaxwell gravity. The radii of the photon sphere and shadow increase with the decrease of the GaussâBonnet coupling constant