5,000 research outputs found
Dynamics of Order Parameter in Photoexcited Peierls Chain
The photoexcited dynamics of order parameter in Peierls chain is investigated
by using a microscopic quantum theory in the limit where the hot electrons may
establish themselves into a quasi-equilibrium state described by an effective
temperature. The optical phonon mode responsible for the Peierls instability is
coupled to the electron subsystem, and its dynamic equation is derived in terms
of the density matrix technique. Recovery dynamics of the order parameter is
obtained, which reveals a number of interesting features including the change
of oscillation frequency and amplitude at phase transition temperature and the
photo-induced switching of order parameter.Comment: 5 pages, 3 figure
Layer Antiferromagnetic State in Bilayer Graphene : A First-Principle Investigation
The ground state of bilayer graphene is investigated by the density
functional calculations with local spin density approximation. We find a ground
state with layer antiferromagnetic ordering, which has been suggested by former
studies based on simplified model. The calculations prove that the layer
antiferromagnetic state (LAF) is stable even if the remote hopping and nonlocal
Coulomb interaction are included. The gap of the LAF state is about 1.8 meV,
comparable to the experimental value. The surface magnetism in BLG is of the
order of
Magnetic Coupling of a Rotating Black Hole with Advection-Dominated Accretion Flows
A model of magnetic coupling (MC) of a rotating black hole (BH) with
advection- dominated accretion flow (MCADAF) is proposed. It turns out that
MCADAF providers a natural explanation for the transition radius between ADAF
and SSD, and could be used to interpret the highest luminosity of GX 339-4 in
hard-state. A very steep emissivity index can be produced in the innermost part
of the MCADAF,which is consistent with the recent XMM-Newton observations of
the nearby bright Seyfert 1 galaxy MCG-6-30-15 and with two X-ray binaries
(XRBs): XTE J1655-500 and GX 339-4. In addition, we estimate the BH spins in
Seyfert 1 galaxy MCG-6-30-15 and in the two XRBs based on this model.Comment: 18 pages, 9 figures,acceptted by New Astronom
Exploration of Multi-State Conformational Dynamics and Underlying Global Functional Landscape of Maltose Binding Protein
An increasing number of biological machines have been revealed to have more than two macroscopic states. Quantifying the underlying multiple-basin functional landscape is essential for understanding their functions. However, the present models seem to be insufficient to describe such multiple-state systems. To meet this challenge, we have developed a coarse grained triple-basin structure-based model with implicit ligand. Based on our model, the constructed functional landscape is sufficiently sampled by the brute-force molecular dynamics simulation. We explored maltose-binding protein (MBP) which undergoes large-scale domain motion between open, apo-closed (partially closed) and holo-closed (fully closed) states responding to ligand binding. We revealed an underlying mechanism whereby major induced fit and minor population shift pathways co-exist by quantitative flux analysis. We found that the hinge regions play an important role in the functional dynamics as well as that increases in its flexibility promote population shifts. This finding provides a theoretical explanation of the mechanistic discrepancies in PBP protein family. We also found a functional “backtracking” behavior that favors conformational change. We further explored the underlying folding landscape in response to ligand binding. Consistent with earlier experimental findings, the presence of ligand increases the cooperativity and stability of MBP. This work provides the first study to explore the folding dynamics and functional dynamics under the same theoretical framework using our triple-basin functional model
Modeling and analysis of a high-static-low-dynamic stiffness vibration isolator with experimental investigation
In order to attenuate low-frequency vibration, a novel nonlinear vibration isolator with high-static-low-dynamic stiffness (HSLDS) is developed in this paper by combining the negative stiffness corrector in parallel with a vertical linear spring. The force and stiffness characteristics are first derived by the static analysis. Then, the displacement transmissibility of the HSLDS system is obtained to evaluate the isolation performance using the harmonic balance method. The parametric analysis shows that the proposed HSLDS system can outperform the equivalent linear one in some aspects. Besides, the initial isolation frequency is defined and further investigated with the purpose of providing some useful guidelines for choosing parameter combinations conveniently. Finally, a prototype is developed and the experimental test is conducted to verify the isolation performance of the proposed HSLDS system
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