Quantum tunneling of magnetization in dipolar spin-1 condensates under external fields

We study the macroscopic quantum tunneling of magnetization of the F=1 spinor condensate interacting through dipole-dipole interaction with an external magnetic field applied along the longitudinal or transverse direction. We show that the ground state energy and the effective magnetic moment of the system exhibit an interesting macroscopic quantum oscillation phenomenon originating from the oscillating dependence of thermodynamic properties of the system on the vacuum angle. Tunneling between two degenerate minima are analyzed by means of an effective potential method and the periodic instanton method.Comment: 2 figures, accepted PR

Effects of Low Intensity Focused Ultrasound on Liposomes Containing Channel proteins.

The ability to reversibly and non-invasively modulate region-specific brain activity in vivo suggests Low Intensity Focused Ultrasound (LIFU) as potential therapeutics for neurological dysfunctions such as epilepsy and Parkinson's disease. While in vivo studies provide evidence of the bioeffects of LIFU on neuronal activity, they merely hint at potential mechanisms but do not fully explain how this technology achieves these effects. One potential hypothesis is that LIFU produces local membrane depolarization by mechanically perturbing the neuronal cell membrane, or activating channels or other proteins embedded in the membrane. Proteins that sense mechanical perturbations of the membrane, such as those gated by membrane tension, are prime candidates for activating in response to LIFU and thus leading to the neurological responses that have been measured. Here we use the bacterial mechanosensitive channel MscL, which has been purified and reconstituted in liposomes, to determine how LIFU may affect the activation of this membrane-tension gated channel. Two bacterial voltage-gated channels, KvAP and NaK2K F92A channels were also studied. Surprisingly, the results suggest that ultrasound modulation and membrane perturbation does not induce channel gating, but rather induces pore formation at the membrane protein-lipid interface. However, in vesicles with high MscL mechanosensitive channel concentrations, apparent decreases in pore formation are observed, suggesting that this membrane-tension-sensitive protein may serve to increase the elasticity of the membrane, presumably because of expansion of the channel in the plane of the membrane independent of channel gating

Fault Diagnosis of Train Axle Box Bearing Based on Multifeature Parameters

Failure of the train axle box bearing will cause great loss. Now, condition-based maintenance of train axle box bearing has been a research hotspot around the world. Vibration signals generated by train axle box bearing have nonlinear and nonstationary characteristics. The methods used in traditional bearing fault diagnosis do not work well with the train axle box. To solve this problem, an effective method of axle box bearing fault diagnosis based on multifeature parameters is presented in this paper. This method can be divided into three parts, namely, weak fault signal extraction, feature extraction, and fault recognition. In the first part, a db4 wavelet is employed for denoising the original signals from the vibration sensors. In the second part, five time-domain parameters, five IMF energy-torque features, and two amplitude-ratio features are extracted. The latter seven frequency domain features are calculated based on the empirical mode decomposition and envelope spectrum analysis. In the third part, a fault classifier based on BP neural network is designed for automatic fault pattern recognition. A series of tests are carried out to verify the proposed method, which show that the accuracy is above 90%

Event-triggered output consensus for linear multi-agent systems via adaptive distributed observer

summary:This paper investigates the distributed event-triggered cooperative output regulation problem for heterogeneous linear continuous-time multi-agent systems (MASs). To eliminate the requirement of continuous communication among interacting following agents, an event-triggered adaptive distributed observer is skillfully devised. Furthermore, a class of closed-loop estimators is constructed and implemented on each agent such that the triggering times on each agent can be significantly reduced while at the same time the desired control performance can be preserved. Compared with the existing open-loop estimators, the proposed estimators can provide more accurate state estimates during each triggering period. It is further shown that the concerned cooperative output regulation problem can be effectively resolved under the proposed control scheme and the undesirable Zeno behavior can be excluded. Finally, the effectiveness of the proposed results is verified by numerical simulations

Pulsed Large Volume Injection Gas Chromatography Coupled with Electron-Capture Negative Ionization Quadrupole Mass Spectrometry for Simultaneous Determination of Typical Halogenated Persistent Organic Pollutants

A pulsed large-volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry (pLVI-GC/ECNI-qMS) was developed for the simultaneous determination of typical halogenated persistent organic pollutants (H-POPs). By monitoring the characteristic ions of large mass-to-charge ratio (m/z) for each of the H-POPs rather than the chlorine and/or bromine ions, this method avoided the possible interferences arising from the H-POPs themselves and from complex matrices encountered frequently in current GC/qMS methods; and allowed, on the other hand, the use of 13C-labeled and perdeuterated analogues as internal standards for reliable quantification. pLVI up to 120 μL improved the instrumental detection limits down to pg–fg mL−1, comparable to or lower than those obtained by the recognized GC/high-resolution MS methods reported so far. The H-POPs including 12 polybrominated diphenyl ethers, 1 polybrominated biphenyl, 10 polychlorinated biphenyls (PCBs), 4 hexachlorocyclohexane isomers, and hexachlorobenzene were involved in this study. The method developed demonstrated good linearity (r2 = 0.9904–0.9999) within 0.5 to 50,000 pg mL−1 for PCBs and 0.05 to 5000 pg mL−1 for other H-POPs, and was satisfactory in terms of both repeatability (0.07%–2.2%) and reproducibility (2.1%–8.4%). It was validated by analyzing a NIST standard reference material SRM-1946 of Lake Superior fish tissue with low 0.01 to 63 pg g−1 method detection limits, and successfully applied to the determination of the H-POPs in five reference materials of different matrices