5,817 research outputs found
An Effective EMTR-Based High-Impedance Fault Location Method for Transmission Lines
This paper summarizes the electromagnetic time reversal (EMTR) technique for
fault location, and further numerically validates its effectiveness when the
fault impedance is negligible. In addition, a specific EMTR model considering
the fault impedance is derived, and the correctness of the model derivation is
verified by various calculation methods. Based on this, we found that when the
fault impedance is large, the existing EMTR methods might fail to accurately
locate the fault. We propose an EMTR method that improves the location effect
of high-impedance faults by injecting double-ended signals simultaneously.
Theoretical calculations show that this method can achieve accurate location
for high-impedance faults. To further illustrate the effectiveness, the
proposed method is compared with the existing EMTR methods and the most
commonly used traveling wave-based method using wavelet transform. The
simulation results show that the proposed double-ended EMTR method can
effectively locate high-impedance faults, and it is more robust against
synchronization errors compared to the traveling wave method. In addition, the
proposed method does not require the knowledge or the a priori guess of the
unknown fault impedance
In vitro Anti-Gastric Tumor Activities and Possible Mechanisms of Action of Paederosidic Acid from Paederia scandens (Lour) Merrill
Purpose: To evaluate the anti-tumor activity and explore the possible mechanisms of action of paederosidic acid isolated from Paederia scandens (Lour.) Merrill.Methods: Paederosidic acid (PA) was isolated from P. scandens and identified by spectroscopic methods. The cytotoxic effects of PA in gastric cancer cell lines (MGC-803, BGC-823, and SGC-7901 cells) were assayed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). Apoptosis of PA in SGC-7901 cells was evaluated by DAPI staining. To investigate the possible mechanisms of apoptosis, the effect of PA on C-caspase-3, C-caspase-9, Bcl-2 and Bax expressions in SGC-7901 cells were assayed by Western blot analysis.Results: PA exerted significant inhibitory effects on MGC-803, BGC-823, and SGC-7901 cells with 50 % inhibitory concentration (IC50) values of 42.2, 43.7, and 30.5 μM, respectively, and in a concentration-dependent manner. Subsequently, SGC-7901 cells were selected for further studies. After treatment with PA, obvious condensation of the nucleus was observed in fluorescence photomicrographs, which is a characteristic of apoptosis. In addition, caspase-3, caspase-9 proteins and Bax were significantly up-regulated (p < 0.05), whereas Bcl-2 was significantly down-regulated (p < 0.05) by PA in a concentration-dependent manner.Conclusion: PA has significant anti-tumor activity on SGC-7901 cells in vitro, and the possible mechanism of action may be related to PA-induced apoptosis via mitochondria-mediated apoptosis pathway.Keywords: Paederosidic acid, Paederia scandens, Anti-tumor activity, Apoptosis, Gastric cance
Green's Function Zeros in Fermi Surface Symmetric Mass Generation
The Fermi surface symmetric mass generation (SMG) is an intrinsically
interaction-driven mechanism that opens an excitation gap on the Fermi surface
without invoking symmetry-breaking or topological order. We explore this
phenomenon within a bilayer square lattice model of spin-1/2 fermions, where
the system can be tuned from a metallic Fermi liquid phase to a
strongly-interacting SMG insulator phase by an inter-layer spin-spin
interaction. The SMG insulator preserves all symmetries and has no mean-field
interpretation at the single-particle level. It is characterized by zeros in
the fermion Green's function, which encapsulate the same Fermi volume in
momentum space as the original Fermi surface, a feature mandated by the
Luttinger theorem. Utilizing both numerical and field-theoretical methods, we
provide compelling evidence for these Green's function zeros across both strong
and weak coupling regimes of the SMG phase. Our findings highlight the
robustness of the zero Fermi surface, which offers promising avenues for
experimental identification of SMG insulators through spectroscopy experiments
despite potential spectral broadening from noise or dissipation.Comment: 12 pages, 7 figures. 1 appendi
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