275,476 research outputs found

    Looking into DNA breathing dynamics via quantum physics

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    We study generic aspects of bubble dynamics in DNA under time dependent perturbations, for example temperature change, by mapping the associated Fokker-Planck equation to a quantum time-dependent Schroedinger equation with imaginary time. In the static case we show that the eigenequation is exactly the same as that of the β\beta-deformed nuclear liquid drop model, without the issue of non-integer angular momentum. A universal breathing dynamics is demonstrated by using an approximate method in quantum mechanics. The calculated bubble autocorrelation function qualitatively agrees with experimental data. Under time dependent modulations, utilizing the adiabatic approximation, bubble properties reveal memory effects.Comment: 5 pages, 1 figur

    An ALMA Dynamical Mass Estimate of the Proposed Planetary-mass Companion FW Tau C

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    Dynamical mass estimates down to the planet-mass regime can help to understand planet formation. We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations of FW Tau C, a proposed ~10 MJupM_{\rm Jup} planet-mass companion at ~330 au from the host binary FW Tau AB. We spatially and spectrally resolve the accretion disk of FW Tau C in 12{}^{12}CO (2-1). By modeling the Keplerian rotation of gas, we derive a dynamical mass of ~0.1 MM_\odot. Therefore, FW Tau C is unlikely a planet, but rather a low-mass star with a highly inclined disk. This also suggests that FW Tau is a triple system consisting of three ~0.1 MM_\odot stars.Comment: Accepted for publication in ApJ

    Orbital ordering in the ferromagnetic insulator Cs2_2AgF4_4 from first principles

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    We found, using density-functional theory calculations within the generalized gradient approximation, that Cs2_2AgF4_4 is stabilized in the insulating orthorhombic phase rather than in the metallic tetragonal phase. The lattice distortion present in the orthorhombic phase corresponds to the x2z2x^2-z^2/y2z2y^2-z^2 hole-orbital ordering of the Ag2+^{2+} 4d94d^9 ions, and this orbital ordering leads to the observed ferromagnetism, as confirmed by the present total-energy calculations. This picture holds in the presence of moderate 4d-electron correlation. The results are compared with the picture of ferromagnetism based on the metallic tetragonal phase.Comment: 5 pages, 4 figures, 1 table; a few energy/moment entries in Table I are corrected due to a proper treatment of the Ag 4s semicore stat

    Comment on "Quantitative Condition is Necessary in Guaranteeing the Validity of the Adiabatic Approximation" [arXiv:1004.3100]

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    Recently, the authors of Ref.1[arXiv:1004.3100] claimed that they have proven the traditional adiabatic condition is a necessary condition. Here, it is claimed that there are some mistakes and an artificial over-strong constraint in [1], making its result inconvincible.Comment: 1 pag
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