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Search Results: 1 - 10 of 119770 matches for " Wang Yujun "
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Quantum interference in a four-level system of a $^{87}\mathrm{Rb}$ atom: Effects of spontaneously generated coherence
Dongsheng Wang,Yujun Zheng
Physics , 2010, DOI: 10.1103/PhysRevA.83.013810
Abstract: In this work, the effects of quantum interference and spontaneously generated coherence (SGC) are theoretically analyzed in a four level system of a $^{87}\mathrm{Rb}$ atom. For the effects of SGC, we find that a new kind of EIT channel can be induced due to destructive interference, and the nonlinear Kerr absorption can be coherently narrowed or eliminated under different strengths of the coupling and switching fields.
Center Specification Property and Entropy for Partially Hyperbolic Diffeomorphisms
Lin Wang,Yujun Zhu
Mathematics , 2015,
Abstract: Let $f$ be a partially hyperbolic diffeomorphism on a closed (i.e., compact and boundaryless) Riemannian manifold $M$ with a uniformly compact center foliation $\mathcal{W}^{c}$. The relationship among topological entropy $h(f)$, entropy of the restriction of $f$ on the center foliation $h(f, \mathcal{W}^{c})$ and the growth rate of periodic center leaves $p^{c}(f)$ is investigated. It is first shown that if a compact locally maximal invariant center set $\Lambda$ is center topologically mixing then $f|_{\Lambda}$ has the center specification property, i.e., any specification with a large spacing can be center shadowed by a periodic center leaf with a fine precision. Applying the center spectral decomposition and the center specification property, we show that $ h(f)\leq h(f,\mathcal{W}^{c})+p^{c}(f)$. Moreover, if the center foliation $\mathcal{W}^{c}$ is of dimension one, we obtain an equality $h(f)= p^{c}(f)$.
Efimov Trimer Formation via Ultracold Four-body Recombination
Yujun Wang,B. D. Esry
Physics , 2008, DOI: 10.1103/PhysRevLett.102.133201
Abstract: We discuss the collisional formation of Efimov trimers via ultracold four-body recombination. In particular, we consider the reaction A+A+A+B->A3+B with A and B ultracold atoms. We obtain expressions for the four-body recombination rate and show that it reflects the three-body Efimov physics either as a function of collision energy or as a function of the two-body s-wave scattering length between A atoms. In addition, we briefly discuss issues important for experimentally observing this interesting and relatively unexplored process.
Universal three-body physics at finite energy near Feshbach resonances
Yujun Wang,B. D. Esry
Physics , 2010, DOI: 10.1088/1367-2630/13/3/035025
Abstract: We find that universal three-body physics extends beyond the threshold regime to non-zero energies. For ultracold atomic gases with a negative two-body $s$-wave scattering length near a Feshbach resonance, we show the resonant peaks characteristic of Efimov physics persist in three-body recombination to higher collision energies. For this and other inelastic processes, we use the adiabatic hyperspherical representation to derive universal analytical expressions for their dependence on the scattering length, the collision energy, and --- for narrow resonances --- the effective range. These expressions are supported by full numerical solutions of the Schr\"odinger equation and display log-periodic dependence on energy characteristic of Efimov physics. This dependence is robust and might be used to experimentally observe several Efimov features.
Universal bound and scattering properties for two dipoles
Yujun Wang,Chris H. Greene
Physics , 2011, DOI: 10.1103/PhysRevA.85.022704
Abstract: The bound state and low-energy scattering properties of two oriented dipoles are investigated for both bosonic and fermionic symmetries. Interestingly, a universal scaling emerges for the expectation value of the angular momentum for deeply-bound two-dipole states. This scaling traces to the pendulum motion of two dipoles in strong dipole regime. The low-energy scattering phase shifts of two dipoles also show universal behavior. These universal observations make connections to the scaling laws reported in Refs. [1, 2] for three dipoles. Atomic units are used throughout this work.
Universal van der Waals Physics for Three Ultracold Atoms
Yujun Wang,Paul S. Julienne
Physics , 2014, DOI: 10.1038/nphys3071
Abstract: Experimental studies with ultracold atoms have enabled major breakthroughs in understanding three-body physics, historically a fundamental yet challenging problem. This is because the interactions among ultracold atoms can be precisely varied using magnetically tunable scattering resonances known as Feshbach resonances. The collisions of ultracold atoms have been discovered to have many universal aspects near the unitarity limit. Away from this limit, many quantum states are expected to be active during a three-body collision, making the collisional observables practically unpredictable. Here we report a major development in predicting three-body ultracold scattering rates by properly building in the pairwise van der Waals interactions plus the multi-spin properties of a tunable Feshbach resonance state characterized by two known dimensionless two-body parameters. Numerical solution of the Schr{\"o}dinger equation then predicts the three-atom collisional rates without adjustable fitting parameters needed to fit data. Our calculations show quantitative agreement in magnitude and feature position and shape across the full range of tuning of measured rate coefficients for three-body recombination and atom-dimer collisions involving ultracold Cs atoms.
Alternative Complement Activity in the Egg Cytosol of Amphioxus Branchiostoma belcheri: Evidence for the Defense Role of Maternal Complement Components
Yujun Liang, Shicui Zhang, Zhiping Wang
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004234
Abstract: Background The eggs in most invertebrates are fertilized externally, and therefore their resulting embryos are exposed to an environment full of microbes, many of which are pathogens capable of killing other organisms. How the developing embryos of invertebrates defend themselves against pathogenic attacks is an intriguing question to biologists, and remains largely unknown. Methodology/Principal Findings Here we clearly demonstrated that the egg cytosol prepared from the newly fertilized eggs of amphioxus Branchiostoma belcheri, an invertebrate chordate, was able to inhibit the growth of both the Gram-negative bacterium Vibrio anguillarum and the Gram-positive bacterium Staphylococcus aureus. All findings point to that it is the complement system operating via the alternative pathway that is attributable to the bacteriostatic activity. Conclusions/Significance This appears to be the first report providing the evidence for the functional role of the maternal complement components in the eggs of invertebrate species, paving the way for the study of maternal immunity in other invertebrate organisms whose eggs are fertilized in vitro. It also supports the notion that the early developing embryos share some defense mechanisms common with the adult species.
Existence and nonexistence results for second-order Neumann boundary value problem
Feng Wang,Yujun Cui,Fang Zhang
Surveys in Mathematics and its Applications , 2009,
Abstract: In this paper some existence and nonexistence results for positive solutions are obtained for second-order boundary value problem -u"+Mu=f(t,u), t∈(0,1) with Neumann boundary conditions u'(0)=u'(1)=0, where M>0, f∈C([0,1]×R+, R+). By making use of fixed point index theory in cones, some new results are obtained.
Studies on Extracting Microcystin-Lr from Microcystis Aeruginosa by Water Bath  [PDF]
Li Fang, Wenqing Liu, Nanjing Zhao, Jingbo Duan, Zhigang Wang, Yujun Zhang, Xue Xiao, Jing Liu, Gaofang Yin, Chaoyi Shi
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.41B013
Abstract: Different temperatures of water bath was used to extract the intracellular microcystin-LR(MC-LR) of Microcystis aeruginosa. Researching the extraction efficiency under the suitable temperature, so that it could find out the best temperature and time for extracting MC-LR from Microcystis aeruginosa cells. Five equal Microcystis aeruginosa was used to find out the best temperature, extracting at 60℃, 70℃, 80℃, 90℃ and 100℃ for 15 minutes, respectively. Results showed that the content of MC-LR extracted with the water under 100℃ was the highest. But meanwhile, the type and the content of impurities was the highest, too. In addition, another six equal Microcystis aeruginosa was extract with the water under 100℃ for 5min, 10 min, 15 min, 20 min, 25 min and 30 min respectively. It was proved that 20 minutes was enough for extracting MC-LR from Microcystis aeruginosa, no long time was needed.
Simulation of Monopole and Multipole Seismoelectric Logging
Zhiwen Cui,Jinxia Liu,Yujun Zhang,Kexie Wang,Hengshan Hu
Advances in Acoustics and Vibration , 2011, DOI: 10.1155/2011/107827
Abstract: In a fluid-saturated porous formation, acoustics and electromagnetic waves are coupled based on Pride seismoelectric theory. An exact treatment of the nonaxisymmetric seismoelectric field excited by acoustic multipole sources is presented. The frequency wavenumber domain representations of the acoustic field and associated seismoelectric field due to acoustic multipole sources are formulated. The full waveforms of acoustic waves and electric and magnetic fields in the time domain propagation in borehole are simulated by using discrete wave number integration, and frequency versus axial-wave number responses are presented and analyzed. 1. Introduction The study of wave propagation in a fluid-saturated porous medium is of considerable interest in acoustics and geophysics due to its important applications in various technical and engineering processes. The investigation of wave propagation in fluid-saturated porous media was early developed by Biot [1, 2]. One of the major findings of Biot’s theory was that there is a compressional slow wave in a fluid-saturated porous medium. The first clear experimental observation of this slow wave was reported by Plona [3]. Biot predicted the slow waves should have an important bearing on electrokinetic effect [4]. This predication has been quantitatively confirmed by Pride [5] and Hu [6]. Elastic waves propagating in fluid-saturated porous media generate a movement of the ions in the pore fluid. Such movement induces an electromagnetic (EM) field. Thompson and Gist [7] have made field measurement clearly demonstrating that seismic waves can induce electromagnetic disturbances in saturated sediments. Pride [8] derived the governing equations for the coupled acoustics and electromagnetic waves in fluid-saturated porous media. Pride and Haartsen [9] analyzed the basic properties of seismoelectric waves. The electric field induced by elastic waves is weak and attenuates in propagation. In order to detect the seismoelectric signal effectively, Haartsen and Pride [10] suggested measuring vertical electroseismic profile. Mikhailov et al. [11] measured the electric field converted from low frequency Stoneley waves in a borehole and made theoretical analysis. Seismoelectric logging method has been proposed to detect deep target formation. The advantage of seismoelectric logging is the distance both from transmitter to target formation and from the transmitter to the receiver is small, and signals can be received with relative high amplitude. Zhu et al. [12–14] made laboratory experiments and observed the seismoelectric
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