269 research outputs found
Gravitational Effects of Rotating Bodies
We study two type effects of gravitational field on mechanical gyroscopes
(i.e. rotating extended bodies). The first depends on special relativity and
equivalence principle. The second is related to the coupling (i.e. a new force)
between the spins of mechanical gyroscopes, which would violate the equivalent
principle. In order to give a theoretical prediction to the second we suggest a
spin-spin coupling model for two mechanical gyroscopes. An upper limit on the
coupling strength is then determined by using the observed perihelion
precession of the planet's orbits in solar system. We also give predictions
violating the equivalence principle for free-fall gyroscopes .Comment: LaTex, 6 page
A spin-rotation mechanism of Einstein-de Haas effect based on a ferromagnetic disk
Spin-rotation coupling (SRC) is a fundamental phenomenon that connects
electronic spins with the rotational motion of a medium. We elucidate the
Einstein-de Haas (EdH) effect and its inverse with SRC as the microscopic
mechanism using the dynamic spin-lattice equations derived by elasticity theory
and Lagrangian formalism. By applying the coupling equations to an iron disk in
a magnetic field, we exhibit the transfer of angular momentum and energy
between spins and lattice, with or without damping. The timescale of the
angular momentum transfer from spins to the entire lattice is estimated by our
theory to be on the order of 0.01 ns, for the disk with a radius of 100 nm.
Moreover, we discover a linear relationship between the magnetic field strength
and the rotation frequency, which is also enhanced by a higher ratio of Young's
modulus to Poisson's coefficient. In the presence of damping, we notice that
the spin-lattice relaxation time is nearly inversely proportional to the
magnetic field. Our explorations will contribute to a better understanding of
the EdH effect and provide valuable insights for magneto-mechanical
manufacturing
Delisheng, a Chinese medicinal compound, exerts anti-proliferative and pro-apoptotic effects on HepG2 cells through extrinsic and intrinsic pathways
The anti-proliferative, cytotoxic and apoptogenic activities of delisheng, a Chinese medicinal compound, has been investigated. In this study, the hepatocarcinoma cell line (HepG2) and the liver cell line (L-02) were exposed to delisheng (6.25, 50 and 100 μl/ml). Delisheng suppressed the proliferation and viability of normal liver L-02 cells slightly, but strongly inhibited the proliferation and viability of hepatocarcinoma HepG2 cells. The flow cytometric analysis of HepG2 cells demonstrated that delisheng primarily arrested the HepG2 cells at the G1 phase of the cell cycle. Annexin V-FITC/PI staining corroborates the apoptogenic nature of delisheng on HepG2 cells. The anti-proliferative and pro-apoptotic effect of delisheng in HepG2 cells was associated with changes in the Bcl-2/Bax ratio and the induction of caspase-mediated apoptosis. Upregulation of DR5 expression was observed in HepG2 cells after treatment with delisheng. The findings from the present study suggest that delisheng has selective cytotoxic activities against HepG2 cells. Delisheng triggered time- and dose-dependent apoptosis in HepG2 cells by activating the mitochondria-mediated and death receptor-mediated apoptotic pathways
Practical Quantum Simulation of Non-Hermitian Dynamics
Non-Hermitian quantum systems have recently attracted considerable attentions
due to their exotic properties. Though many experimental realizations of
non-Hermitian systems have been reported, the non-Hermiticity usually resorts
to the hard-to-control environments. An alternative approach is to use quantum
simulation with the closed system, whereas how to simulate general
non-Hermitian Hamiltonian dynamics remains a great challenge. To tackle this
problem, we propose a protocol by combining a dilation method with the
variational quantum algorithm. The dilation method is used to transform a
non-Hermitian Hamiltonian into a Hermitian one through an exquisite quantum
circuit, while the variational quantum algorithm is for efficiently
approximating the complex entangled gates in this circuit. As a demonstration,
we apply our protocol to simulate the dynamics of an Ising chain with nonlocal
non-Hermitian perturbations, which is an important model to study quantum phase
transition at nonzero temperatures. The numerical simulation results are highly
consistent with the theoretical predictions, revealing the effectiveness of our
protocol. The presented protocol paves the way for practically simulating
general non-Hermitian dynamics in the multi-qubit case.Comment: 9 pages, 5 figure
Control-enhanced quantum metrology under Markovian noise
Quantum metrology is supposed to significantly improve the precision of
parameter estimation by utilizing suitable quantum resources. However, the
predicted precision can be severely distorted by realistic noises. Here, we
propose a control-enhanced quantum metrology scheme to defend against these
noises for improving the metrology performance. Our scheme can automatically
alter the parameter encoding dynamics with adjustable controls, thus leading to
optimal resultant states that are less sensitive to the noises under
consideration. As a demonstration, we numerically apply it to the problem of
frequency estimation under several typical Markovian noise channels. Through
comparing our control-enhanced scheme with the standard scheme and the
ancilla-assisted scheme, we show that our scheme performs better and can
improve the estimation precision up to around one order of magnitude.
Furthermore, we conduct a proof-of-principle experiment in nuclear magnetic
resonance system to verify the effectiveness of the proposed scheme. The
research here is helpful for current quantum platforms to harness the power of
quantum metrology in realistic noise environments.Comment: 9 pages, 5 figure
Measuring Quantum Entanglement from Local Information by Machine Learning
Entanglement is a key property in the development of quantum technologies and
in the study of quantum many-body simulations. However, entanglement
measurement typically requires quantum full-state tomography (FST). Here we
present a neural network-assisted protocol for measuring entanglement in
equilibrium and non-equilibrium states of local Hamiltonians. Instead of FST,
it can learn comprehensive entanglement quantities from single-qubit or
two-qubit Pauli measurements, such as R\'enyi entropy, partially-transposed
(PT) moments, and coherence. It is also exciting that our neural network is
able to learn the future entanglement dynamics using only single-qubit traces
from the previous time. In addition, we perform experiments using a nuclear
spin quantum processor and train an adoptive neural network to study
entanglement in the ground and dynamical states of a one-dimensional spin
chain. Quantum phase transitions (QPT) are revealed by measuring static
entanglement in ground states, and the entanglement dynamics beyond measurement
time is accurately estimated in dynamical states. These precise results
validate our neural network. Our work will have a wide range of applications in
quantum many-body systems, from quantum phase transitions to intriguing
non-equilibrium phenomena such as quantum thermalization.Comment: 5 pages, 4 figures. All comments are welcom
A Novel Lipopolysaccharide Recognition Mechanism Mediated by Internalization in Teleost Macrophages
Macrophages in teleosts are less sensitive to lipopolysaccharide (LPS) compared to mammals. The functional equivalent of the mammalian LPS surface receptor in teleost macrophages for the pro-inflammatory response is either non-existent or replaced by negative regulation. LPS signaling in teleost macrophages remains unclear. Here, we found a scavenger receptor class B 2a (PaSRB2a) that played a crucial role in LPS signaling in teleost macrophages. The internalization of LPS and subsequent pro-inflammatory responses in macrophages were mediated by PaSRB2a, which is a novel isoform of the mammalian SRB2 gene. LPS internalization by PaSRB2a is dependent on its C-terminal intracellular domain. Following LPS internalization, it interacts with the ayu intracellular receptors nucleotide-binding oligomerization domain protein 1 (PaNOD1) and PaNOD2. Moreover, LPS pre-stimulation with sub-threshold concentrations reduced the effect of secondary LPS treatment on pro-inflammatory responses that were mediated by PaSRB2a. The pro-inflammatory responses in LPS-treated ayu were down-regulated upon PaSRB2a knockdown by lentivirus siRNA delivery. In grass carp and spotted green pufferfish, SRB2a also mediated LPS internalization and pro-inflammatory responses. Our work identifies a novel LPS signaling pathway in teleosts that differs from those in mammals, and contributes to our understanding of the evolution of pathogen recognition in vertebrates
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