810 research outputs found
Higher-order Topological Phases of Magnons in van der Waals Honeycomb Ferromagnets
We theoretically propose a second-order topological magnon insulator by
stacking the van der Waals honeycomb ferromagnets with antiferromagnetic
interlayer coupling. The system exhibits Z topological phase, protected
by pseudo-time-reversal symmetry (PTRS). An easy-plane anisotropy term breaks
PTRS and destroys the topological phase. Nevertheless, it respects a magnetic
two-fold rotational symmetry which protects a second-order topological phase
with corner modes in bilayer and hinge modes along stacking direction.
Moreover, an introduced staggered interlayer coupling establishes a
ZZ topology, giving rise to gapped topological surface modes
carrying non-zero Chern numbers. Consequently, chiral hinge modes propagate
along the horizontal hinges in a cuboid geometry and are robust against
disorders. Our work bridges the higher-order topology and magnons in van der
Waals platforms, and could be used for constructing topological magnonic
devices
Discovery potential for the LHCb fully-charm tetraquark state via annihilation reaction
Inspired by the observation of the fully-charm tetraquark state at
LHCb, the production of in
reaction is studied within an effective Lagrangian approach and Breit-Wigner
formula. The numerical results show that the cross section of at the
c.m. energy of 6.9 GeV is much larger than that from the background
contribution. Moreover, we estimate dozens of signal events can be detected by
D0 experiment, which indicates that searching for the via
antiproton-proton scattering may be a very important and promising way.
Therefore, related experiments are suggested to be carried out.Comment: 4 pages, 2 figure
Surf and turf: predation by egg-eating snakes has led to the evolution of parental care in a terrestrial lizard
Animals display a great diversity of parental care tactics that ultimately enhance offspring survival, but how such behaviors evolve remains unknown for most systems. Here, we studied the evolution of maternal care, in the form of nest guarding, in a single population of long-tailed sun skink (Eutropis longicaudata) living on Orchid Island (Taiwan). This species typically does not provide protection to its offspring. Using a common garden experiment, we show that maternal care is genetically determined in this population. Through field manipulations, we demonstrate that care provides a significant increase in egg survival on Orchid Island by reducing predation from egg-eating snakes (Oligodon formosanus); this predator is not abundant in other populations of the lizard, which do not display parental care. Finally, using extensive field surveys, we show that the seasonal availability of green sea turtle (Chelonia mydas) nests is the cause for the high abundance of snake predators on Orchid Island, with the snakes consuming lizard eggs when green turtle eggs are not available. Together, these lines of evidence provide the first full demonstration of how predation can trigger the evolution of parental care in a species derived from a non-caring ancestor
Surface Metallization of Polyimide as a Photoanode Substratefor Rear-Illuminated Dye-Sensitized Solar Cells
Plastic film is promising as a photoanode substrate of dye-sensitized solar cell (DSSC) for flexible applications, while a lowtemperaturesintering process is generally adopted for the TiO2 mesoporous film due to unstable thermal property of general plastics.This study demonstrates that typical high-temperature TiO2 sintering can be adopted for preparing the photoanode when using asurface-metallized polyimide (PI) film. A Sn/Ni bi-layer is formed on a PI film via a chemical process as the conductive layer. TheSn/Ni-coated PI photoanode can withstand high-temperature TiO2 sintering at a peak temperature of 430◦C for 30 min withoutsignificant visual deformation due to high thermal stability of PI and strength reinforcement caused by surface metallization. TheDSSC employing the Sn/Ni-coated PI film as the photoanode substrate reaches an energy conversion efficiency of 3.44% under1 sun rear-side illumination
Dendrobium officinale
Background. Dendrobium officinale (DO) Kimura et Migo is a precious Chinese herb that is considered beneficial for health due to its antioxidant and antidiabetes properties, and so on. In this research, we try to determine the preventive effect of DO on the early complications of STZ-induced diabetic rats. Methods. Type 1 diabetic rats were produced with a single intraperitoneal injection of STZ (50 mg/kg). DO (1 g/kg/day) was then orally administered for 5 weeks. Blood glucose, TC, TG, BUN, CREA, and GSH-PX levels were determined, and electroretinographic activity and hypoalgesia were investigated. Pathological sections of the eyes, hearts, aortas, kidneys, and livers were analyzed. Results. Treatment with DO significantly attenuated the serum levels of TC, TG, BUN, and CREA, markedly increased the amplitudes of ERG a- and b-waves and Ops, and reduced the hypoalgesia and histopathological changes of vital organs induced by hyperglycemia. The protective effect of DO in diabetic rats may be associated with its antioxidant activity, as evidenced by the marked increase in the serum level of glutathione peroxidase. However, DO had no significant effect on blood glucose levels and bodyweight of diabetic rats. Conclusions. DO supplementation is an effective treatment to prevent STZ-induced diabetic complications
Differential vascular cell adhesion molecule-1 expression and superoxide production in simulated microgravity rat vasculature
Exposure to microgravity leads to orthostatic intolerance in astronauts and differential vascular structural and functional adaptations have been implicated in its occurrence. The present study tended to clarify the characteristics of vascular inflammation and oxidative stress in
hindlimb unweighting (HU) rat vasculature. Male Sprague-Dawley rats were randomly divided into control (CON) and hindlimb unweighting (HU) groups. Three weeks later, immunohistochemistry was used to localize the expression of vascular cell adhesion molecule-1 (VCAM-1) and laser scanning confocal microscope were used to detect superoxide production. Immunohistochemical results revealed positive staining of VCAM-1 on endothelial cells in HU rat basilar and carotid arteries compared with CON, but not in abdominal aorta and femoral arteries. Meanwhile, HU increased O2·- levels in all the layers of basilar and carotid
arteries from HU rat but not in abdominal aorta and femoral arteries from HU rat. These data suggested that differential expression of VCAM-1 and O2- production were concomitant with the vascular adaptations to simulated microgravity and whether they participate in vascular structure and function remodeling merits further investigation
Transport evidence for the surface state and spin-phonon interaction in FeTeSe
The iron chalcogenides have been proved to be intrinsic topological
superconductors to implement quantum computation because of their unique
electronic structures. The topologically nontrivial surface states of
FeTeSe have been predicted by several calculations and then
confirmed by high-resolution photoemission and scanning tunneling experiments.
However, so far, the shreds of the electrical transport evidence for
topological surface states are still in absence. By carrying out electrical
transport experiments, we observe a topological transition with a nonlinear
Hall conductivity and simultaneous linear magnetoresistance near the
superconducting transition temperature. Furthermore, we observe a sign reversal
of the Hall coefficient accompanied by a concurrently softening of the
phonon mode at about 40 K, indicating a nematic transition. The
synchronized phonon softening with nematicity manifests an enhanced fluctuation
state through spin-phonon interaction. Our results solidly corroborate the
topological surface states of FeTeSe and provide an
understanding of the mechanism of the superconductivity in iron chalcogenides.Comment: 10 pages, 8 figure
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