A large number of studies demonstrated that major depressive disorder (MDD) is characterized by the alterations in brain functional connections which is also identifiable during the brain's "resting-state." But, in the present study, the approach of constructing functional connectivity is often biased by the choice of the threshold. Besides, more attention was paid to the number and length of links in brain networks, and the clustering partitioning of nodes was unclear. Therefore, minimum spanning tree (MST) analysis and the hierarchical clustering were first used for the depression disease in this study. Resting-state electroencephalogram (EEG) sources were assessed from 15 healthy and 23 major depressive subjects. Then the coherence, MST, and the hierarchical clustering were obtained. In the theta band, coherence analysis showed that the EEG coherence of the MDD patients was significantly higher than that of the healthy controls especially in the left temporal region. The MST results indicated the higher leaf fraction in the depressed group. Compared with the normal group, the major depressive patients lost clustering in frontal regions. Our findings suggested that there was a stronger brain interaction in the MDD group and a left-right functional imbalance in the frontal regions for MDD controls.
Dendritic flux avalanches and the accompanying thermal stress and strain in type-II superconducting thin films under transverse magnetic fields are numerically simulated in this paper. The influence of the magnetic field ramp rate, edge defects, and the temperature of the surrounding coolant are considered. Maxwell's equations and the highly nonlinear E-J powerlaw characteristics of superconductors, coupled with the heat diffusion equation, are adopted to formulate these phenomena. The fast Fourier transform-based iteration scheme is used to track the evolution of the magnetic flux and the temperature in the superconducting film. The finite element method is used to analyze the thermal stress and strain induced in the superconducting film. It is found that the ramp rate has a significant effect on the flux avalanche process. The avalanches nucleate more easily for a film under a large magnetic field ramp rate than for a film under a small one. In addition, the avalanches always initiate from edge defects or areas that experience larger magnetic fields. The superconducting films experience large thermal strain induced by the large temperature gradient during the avalanche process, which may even lead to the failure of the sample.
In this paper, the anisotropic flux avalanche processes in thin square-shaped type-II superconducting films are numerically investigated by solving the coupled nonlinear Maxwell’s equations and the thermal diffusion equations. Influences of the non-uniformities and intrinsic critical current density anisotropies originate from the manufacturing process are considered in the simulation. In addition, we also studied the effect of the extrinsic anisotropy induced by the in-plane magnetic field. The results demonstrate that the non-uniformities and anisotropies of the critical current density play significant roles in the flux avalanche process of the thin film superconductors. Slight anisotropy (either intrinsic or extrinsic) can dramatically change the propagation direction of avalanches in the superconducting film, which is consistent with the experimental results. Simulations on the thin square-shaped isotropic superconducting films show that the threshold magnetic field for the flux avalanches increases with the angle between the applied field and the superconducting film-plane. In addition, the flux avalanche patterns change with the angular variation of the in-plane component of external magnetic field. When the in-plane magnetic field component is along the diagonal lines of the superconducting square, symmetric flux avalanche penetration patterns occur to the film.
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