5,465 research outputs found
Nonlinear Hall Effects in Strained Twisted Bilayer WSe
Recently, it has been pointed out that the twisting of bilayer WSe would
generate topologically non-trivial flat bands near the Fermi energy. In this
work, we show that twisted bilayer WSe (tWSe) with uniaxial strain
exhibits a large nonlinear Hall (NLH) response due to the non-trivial Berry
curvatures of the flat bands. Moreover, the NLH effect is greatly enhanced near
the topological phase transition point which can be tuned by a vertical
displacement field. Importantly, the nonlinear Hall signal changes sign across
the topological phase transition point and provides a way to identify the
topological phase transition and probe the topological properties of the flat
bands. The strong enhancement and high tunability of the NLH effect near the
topological phase transition point renders tWSe and related moire materials
new platforms for rectification and second harmonic generations.Comment: 5 pages, 3 figures. Comments are welcom
Chronic Heat Stress Weakened the Innate Immunity and Increased the Virulence of Highly Pathogenic Avian Influenza Virus H5N1 in Mice
Chronic heat stress (CHS) can negatively affect immune response in animals. In this study we assessed the effects of CHS on host innate immunity and avian influenza virus H5N1 infection in mice. Mice were divided into two groups: CHS and thermally neutral (TN). The CHS treatment group exhibited reduced local immunity in the respiratory tract, including the number of pulmonary alveolar macrophages and lesions in the nasal mucosa, trachea, and lungs. Meanwhile, CHS retarded dendritic cells (DCs) maturation and reduced the mRNA levels of IL-6 and IFN-β significantly (P < .05). After the CHS treatment, mice were infected with H5N1 virus. The mortality rate and viral load in the lungs of CHS group were higher than those of TN group. The results suggest that the CHS treatment could suppress local immunity in the respiratory tract and innate host immunity in mice significantly and moderately increased the virulence in H5N1-infected mice
A New Approach to Constrain Black Hole Spins in Active Galaxies Using Optical Reverberation Mapping
A tight relation between the size of the broad-line region (BLR) and optical
luminosity has been established in about 50 active galactic nuclei studied
through reverberation mapping of the broad Hbeta emission line. The R_blr-L
relation arises from simple photoionization considerations. Using a general
relativistic model of an optically thick, geometrically thin accretion disk, we
show that the ionizing luminosity jointly depends on black hole mass, accretion
rate, and spin. The non-monotonic relation between the ionizing and optical
luminosity gives rise to a complicated relation between the BLR size and the
optical luminosity. We show that the reverberation lag of Hbeta to the varying
continuum depends very sensitively to black hole spin. For retrograde spins,
the disk is so cold that there is a deficit of ionizing photons in the BLR,
resulting in shrinkage of the hydrogen ionization front with increasing optical
luminosity, and hence shortened Hbeta lags. This effect is specially striking
for luminous quasars undergoing retrograde accretion, manifesting in strong
deviations from the canonical R_blr-L relation. This could lead to a method to
estimate black hole spins of quasars and to study their cosmic evolution. At
the same time, the small scatter of the observed R_blr-L relation for the
current sample of reverberation-mapped active galaxies implies that the
majority of these sources have rapidly spinning black holes.Comment: 6 pages, 5 figures, to appear in ApJ
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