6,554 research outputs found
Josephson Oscillation and Transition to Self-Trapping for Bose-Einstein-Condensates in a Triple-Well Trap
We investigate the tunnelling dynamics of Bose-Einstein-Condensates(BECs) in
a symmetric as well as in a tilted triple-well trap within the framework of
mean-field treatment. The eigenenergies as the functions of the zero-point
energy difference between the tilted wells show a striking entangled star
structure when the atomic interaction is large. We then achieve insight into
the oscillation solutions around the corresponding eigenstates and observe
several new types of Josephson oscillations. With increasing the atomic
interaction, the Josephson-type oscillation is blocked and the self-trapping
solution emerges. The condensates are self-trapped either in one well or in two
wells but no scaling-law is observed near transition points. In particular, we
find that the transition from the Josephson-type oscillation to the
self-trapping is accompanied with some irregular regime where tunnelling
dynamics is dominated by chaos. The above analysis is facilitated with the help
of the Poicar\'{e} section method that visualizes the motions of BECs in a
reduced phase plane.Comment: 10 pages, 11 figure
Heat transport of electron-doped Cobaltates
Within the t-J model, the heat transport of electron-doped cobaltates is
studied based on the fermion-spin theory. It is shown that the temperature
dependent thermal conductivity is characterized by the low temperature peak
located at a finite temperature. The thermal conductivity increases
monotonously with increasing temperature at low temperatures T 0.1, and
then decreases with increasing temperature for higher temperatures T
0.1, in qualitative agreement with experimental result observed from
NaCoO .Comment: 4 pages, 1 fig, corrected typos, accepted for publication in Commun.
Theor. Phy
Involvement of NADH Oxidase in Biofilm Formation in Streptococcus sanguinis
Biofilms play important roles in microbial communities and are related to infectious diseases. Here, we report direct evidence that a bacterial nox gene encoding NADH oxidase is involved in biofilm formation. A dramatic reduction in biofilm formation was observed in a Streptococcus sanguinis nox mutant under anaerobic conditions without any decrease in growth. The membrane fluidity of the mutant bacterial cells was found to be decreased and the fatty acid composition altered, with increased palmitic acid and decreased stearic acid and vaccenic acid. Extracellular DNA of the mutant was reduced in abundance and bacterial competence was suppressed. Gene expression analysis in the mutant identified two genes with altered expression, gtfP and Idh, which were found to be related to biofilm formation through examination of their deletion mutants. NADH oxidase-related metabolic pathways were analyzed, further clarifying the function of this enzyme in biofilm formation
Bifurcation from a degenerate simple eigenvalue
It is proved that a symmetry-breaking bifurcation occurs at a simple eigenvalue despite the usual transversality condition fails, and this bifurcation from a degenerate simple eigenvalue result complements the classical one with the transversality condition. The new result is applied to an imperfect pitchfork bifurcation, in which a forward transcritical bifurcation changes to a backward one when the perturbation parameter changes. Several applications in ecological and genetics models are shown. (C) 2013 Elsevier Inc. All rights reserved
A Double Saddle-Node Bifurcation Theorem
In this paper, we consider an abstract equation F(lambda, u) = 0 with one parameter lambda, where F epsilon C-P(R x X, Y), p \u3e= 2, is a nonlinear differentiable mapping, and X, Y are Banach spaces. We apply Lyapunov-Schmidt procedure and Morse Lemma to obtain a double saddle-node bifurcation theorem with a two-dimensional kernel. Applications include a perturbed problem and a semilinear elliptic equation
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