Analysis of dipolar relaxation in polyurethane/polyaniline blend

Thin films of blend made up of castor oil-based polyurethane (PU) and polyaniline (PANI) were obtained by casting. The molecular mobility was studied using dielectric spectroscopy and thermally stimulated depolarization current (TSDC) for blends with two different compositions (90/10, 80/20) and the results were compared with PU pure. The peak located around -60 degrees C in TSDC thermograms of PU/PANI blend has dipolar behavior and might be attributed to the change in the molecular chain due to the interaction between isocyanate and the solvent. Vogel-Fulcher Tammann fits was performed on the observed relaxation and the result shows a alpha-relaxation-like. (c) 2005 Springer Science + Business Media, Inc.

Anisotropic sound and shock waves in dipolar Bose-Einstein condensate

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Two-dimensional dipolar Bose-Einstein condensate bright and vortex solitons on a one-dimensional optical lattice

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Numerical and variational solutions of the dipolar Gross-Pitaevskii equation in reduced dimensions

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Dynamics of quasi-one-dimensional bright and vortex solitons of a dipolar Bose-Einstein condensate with repulsive atomic interaction

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Gap solitons in a dipolar Bose-Einstein condensate on a three-dimensional optical lattice

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Localization of a dipolar Bose-Einstein condensate in a bichromatic optical lattice

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Dipolar Bose-Einstein condensate soliton on a two-dimensional optical lattice

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Study of a degenerate dipolar Fermi gas of Dy-161 atoms

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Dipolar Bose-Einstein condensates with large scattering length

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Dipolar Bose-Einstein condensate in a ring or in a shell

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Mixing, demixing, and structure formation in a binary dipolar Bose-Einstein condensate

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Dipolar droplet bound in a trapped Bose-Einstein condensate

We study the statics and dynamics of a dipolar Bose-Einstein condensate (BEC) droplet bound by interspecies contact interaction in a trapped nondipolar BEC. Our findings are demonstrated in terms of stability plots of a dipolar 164Dy droplet bound in a trapped nondipolar 87Rb BEC with a variable number of 164Dy atoms and interspecies scattering length. A trapped nondipolar BEC of a fixed number of atoms can bind only a dipolar droplet containing fewer atoms than a critical number for the interspecies scattering length between two critical values. The shape and size (statics) as well as the small breathing oscillation (dynamics) of the dipolar BEC droplet are studied using numerical and variational solutions of a mean-field model. We also suggest an experimental procedure for achieving such a 164Dy droplet by relaxing the trap on the 164Dy BEC in a trapped binary 87Rb-164Dy mixture. © 2013 American Physical Society.

Stability of trapped degenerate dipolar Bose and Fermi gases

Trapped degenerate dipolar Bose and Fermi gases of the cylindrical symmetry with the polarization vector along the symmetry axis are only stable for the strength of dipolar interaction below a critical value. In the case of bosons, the stability of such a dipolar Bose-Einstein condensate (BEC) is investigated for different strengths of contact and dipolar interactions using a variational approximation and a numerical solution of a mean-field model. In the disc shape, with the polarization vector perpendicular to the plane of the disc, the atoms experience an overall dipolar repulsion and this fact should contribute to the stability. However, a complete numerical solution of the dynamics leads to the collapse of a strongly disc-shaped dipolar BEC due to the long-range anisotropic dipolar interaction. In the case of fermions, the stability of a trapped single-component degenerate dipolar Fermi gas is studied including the Hartree-Fock exchange and Brueckner-Goldstone correlation energies in the local-density approximation valid for a large number of atoms. Estimates for the maximum allowed number of polar Bose and Fermi molecules in the BEC and degenerate Fermi gas are given. © 2013 IOP Publishing Ltd.

Bright solitons in quasi-one-dimensional dipolar condensates with spatially modulated interactions

We introduce a model for the condensate of dipolar atoms or molecules, in which the dipole-dipole interaction (DDI) is periodically modulated in space due to a periodic change of the local orientation of the permanent dipoles, imposed by the corresponding structure of an external field (the necessary field can be created, in particular, by means of magnetic lattices, which are available to the experiment). The system represents a realization of a nonlocal nonlinear lattice, which has a potential to support various spatial modes. By means of numerical methods and variational approximation (VA), we construct bright one-dimensional solitons in this system and study their stability. In most cases, the VA provides good accuracy and correctly predicts the stability by means of the Vakhitov-Kolokolov criterion. It is found that the periodic modulation may destroy some solitons, which exist in the usual setting with unmodulated DDI and can create stable solitons in other cases, not verified in the absence of modulations. Unstable solitons typically transform into persistent localized breathers. The solitons are often mobile, with inelastic collisions between them leading to oscillating localized modes. © 2013 American Physical Society.