177 research outputs found

    Magnetization Oscillation of a Spinor Condensate Induced by Magnetic Field Gradient

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    We study the spin mixing dynamics of ultracold spin-1 atoms in a weak non-uniform magnetic field with field gradient GG, which can flip the spin from +1 to -1 so that the magnetization m=ρ+ρm=\rho_{+}-\rho_{-} is not any more a constant. The dynamics of mF=0m_F=0 Zeeman component ρ0\rho_{0}, as well as the system magnetization mm, are illustrated for both ferromagnetic and polar interaction cases in the mean-field theory. We find that the dynamics of system magnetization can be tuned between the Josephson-like oscillation similar to the case of double well, and the interesting self-trapping regimes, i.e. the spin mixing dynamics sustains a spontaneous magnetization. Meanwhile the dynamics of ρ0\rho_0 may be sufficiently suppressed for initially imbalanced number distribution in the case of polar interaction. A "beat-frequency" oscillation of the magnetization emerges in the case of balanced initial distribution for polar interaction, which vanishes for ferromagnetic interaction.Comment: 6 pages, 5 figures, Phys. Rev. A accepte

    Density Operator Description of Atomic Ordered Spatial Modes in Cavity QED

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    We present a quantum Monte-Carlo simulation for a pumped atom in a strong coupling cavity with dissipation, where two ordered spatial modes are formed for the atomic probability density, with the peaks distributed either only in the odd sites or only in the even ones of the lattice formed by the cavity field. A mixed state density operator model, which describes the coupling between different atomic spatial modes and the corresponding cavity field components, is proposed, which goes beyond the pure state interpretation. We develop a new decomposition treatment to derive the atomic spatial modes as well as the cavity field statistics from the simulation results for the steady state. With this treatment, we also investigate the dynamical process for the probabilities of the atomic spatial modes in the adiabatic limit. According to the analysis of the fitting error between the simulation results and the density operator model, the latter is a good description for the system

    Stabilization of Cr(III) wastes by C3S and C3S hydrated matrix : comparison of two incorporation methods

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    In the present study, the influence of Cr(III) on the properties of C3S and its stabilization in C3S hydrates was investigated by either direct incorporation as Cr2O3 during C3S preparation or introduced as nitrate salt during hydration. Levels of Cr used were from 0.1 to 3.0 wt% of C3S. The effect of Cr on the polymorph and hydration of C3S and its immobilization in the hydrates was detected by means of DTA/TG, XRD, isothermal calorimeter and ICP-AES, etc. When doped during sintering process, Cr caused a C3S polymorph transformation from T1 to T2 and led a decomposition of C3S into C2S and CaO resulting in high f-CaO content. Cr doping showed an obvious promotion effect on the hydration properties. The promotion effect decreased when the Cr addition increased to 3.0 wt%. When Cr was added as nitrate salt, Cr showed a retardation effect on the hydration of C3S due to the formation of Ca2Cr(OH)7 center dot 3H(2)O, which resulted in a high degree of Cr stabilization

    Oscillation of Certain Emden-Fowler Dynamic Equations on Time Scales

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    The theory of time scales has attracted a great deal of attention since it was first introduced by Hilger [1] in order to unify continuous and discrete analysis. For completeness, we recall the following concepts related to the notion of time scales; see [2, 3] for more details. A time scale T is an arbitrary nonempty closed subset of the real numbers R. In this paper, since we shall be concerned with the oscillatory behavior of solutions, we shall also assume that sup T = ∞.We define the time scale interval [0,∞)T by [0,∞)T := [0,∞)∩T.The forward and backward jump operators are defined b

    Long-time nonlinear dynamical evolution for P-band ultracold atoms in an optical lattice

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    We report the long-time nonlinear dynamical evolution of ultracold atomic gases in the P-band of an optical lattice. A Bose-Einstein condensate (BEC) is fast and efficiently loaded into the Pband at zero quasi-momentum with a non-adiabatic shortcut method. For the first one and half milliseconds, these momentum states undergo oscillations due to coherent superposition of different bands, which are followed by oscillations up to 60ms of a much longer period. Our analysis shows the dephasing from the nonlinear interaction is very conducive to the long-period oscillations induced by the variable force due to the harmonic confinement.Comment: 8 pages, 7 figure

    Electrochemical Sensors for Food Safety

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    Food safety poses an increasing threat to human health worldwide. The development of analytical methods and techniques to ensure food safety is therefore of great importance. Electrochemical sensors provide unique opportunity to realize sensitive, accurate, rapid, and portable detection for food safety. They have the potential to overcome the restrictions and limitations of traditional methods. In this chapter, we review the progress of electrochemical sensors for the detection of food contaminants including heavy metals, illegal additives, pesticide residues, veterinary drug residues, biological toxins, and foodborne pathogen. Future perspectives and challenges are also discussed
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