65 research outputs found
Belly, Doc, KUDZU
Belly, Doc, KUDZU is a magical-realist adventure novel whose setting alternates between the contemporary United States and the realms of Heaven and Hell. The novel's protagonist is Dr. Belvin Turner, a terminally ill molecular biologist tasked by the United States government to discover a means by which human mortality may be extended indefinitely. The novel's title refers to the three different versions of Belvin created over the course of the novel: "Belly" (his liberated soul), "Doc" (his reanimated body), and "KUDZU" (a digitized approximation of his intellect). These various incarnations of Belvin allow the novel to address anxieties such as death and regret from multiple perspectives. The novel employs a humorous satirical lens to explore its subject matter. By highlighting the fallibility of religious figures and institutions, the novel continues a grand literary tradition of religious critique as enjoyed by the authors of its primary influences, specifically Mark Twain, Mikhail Bulgakov, Antoine de Saint-Exupéry, and, more recently, Garth Ennis
Mobile spin impurity in an optical lattice
We investigate the Fermi polaron problem in a spin-1/2 Fermi gas in an
optical lattice for the limit of both strong repulsive contact interactions and
one dimension. In this limit, a polaronic-like behaviour is not expected, and
the physics is that of a magnon or impurity. While the charge degrees of
freedom of the system are frozen, the resulting tight-binding Hamiltonian for
the impurity's spin exhibits an intriguing structure that strongly depends on
the filling factor of the lattice potential. This filling dependency also
transfers to the nature of the interactions for the case of two magnons and the
important spin balanced case. At low filling, and up until near unit filling,
the single impurity Hamiltonian faithfully reproduces a single-band,
quasi-homogeneous tight-binding problem. As the filling is increased and the
second band of the single particle spectrum of the periodic potential is
progressively filled, the impurity Hamiltonian, at low energies, describes a
single particle trapped in a multi-well potential. Interestingly, once the
first two bands are fully filled, the impurity Hamiltonian is a near-perfect
realisation of the Su-Schrieffer-Heeger model. Our studies, which go well
beyond the single-band approximation, that is, the Hubbard model, pave the way
for the realisation of interacting one-dimensional models of condensed matter
physics.Comment: 13 pages, 12 figures, accepted in New Journal of Physic
Bragg spectroscopy of a cigar shaped Bose condensate in optical lattices
We study properties of excited states of an array of weakly coupled
quasi-two-dimensional Bose condensates by using the hydrodynamic theory. We
calculate multibranch Bogoliubov-Bloch spectrums and its corresponding
eigenfunctions. The spectrum of the axial excited states and its eigenfunctions
strongly depends on the coupling among various discrete radial modes within a
given symmetry. This mode coupling is due to the presence of radial trapping
potential. The multibranch nature of the Bogoliubov-Bloch spectrum and its
dependence on the mode-coupling can be realized by analyzing dynamic structure
factor and momentum transferred to the system in Bragg spectroscopy
experiments. We also study dynamic structure factor and momentum transferred to
the condensate due to the Bragg spectroscopy experiment.Comment: 7 pages, 5 figures, to appear in Journal of Physics B: Atomic,
Molecular & Optical Physic
Excitation of a Dipole Topological Mode in a Strongly Coupled Two-Component Bose-Einstein Condensate
Two internal hyperfine states of a Bose-Einstein condensate in a dilute
magnetically trapped gas of Rb atoms are strongly coupled by an
external field that drives Rabi oscillations between the internal states. Due
to their different magnetic moments and the force of gravity, the trapping
potentials for the two states are offset along the vertical axis, so that the
dynamics of the internal and external degrees of freedom are inseparable. The
rapid cycling between internal atomic states in the displaced traps results in
an adiabatic transfer of population from the condensate ground state to its
first antisymmetric topological mode. This has a pronounced effect on the
internal Rabi oscillations, modulating the fringe visibility in a manner
reminiscent of collapses and revivals. We present a detailed theoretical
description based on zero-temperature mean-field theory.Comment: 10 pages, 8 eps figures included; submitted to PR
Collective ferromagnetism in two-component Fermi-degenerate gas trapped in finite potential
Spin asymmetry of the ground states is studied for the trapped
spin-degenerate (two-component) gases of the fermionic atoms with the repulsive
interaction between different components, and, for large particle number, the
asymmetric (collective ferromagnetic) states are shown to be stable because it
can be energetically favorable to increase the fermi energy of one component
rather than the increase of the interaction energy between up-down components.
We formulate the Thomas-Fermi equations and show the algebraic methods to solve
them. From the Thomas-Fermi solutions, we find three kinds of ground states in
finite system: 1) paramagnetic (spin-symmetric), 2) ferromagnetic (equilibrium)
and 3) ferromagnetic (nonequilibrium) states. We show the density profiles and
the critical atom numbers for these states obtained analytically, and, in
ferromagnetic states, the spin-asymmetries are shown to occur in the central
regions of the trapped gas, and grows up with increasing particle number. Based
on the obtained results, we discuss the experimental conditions and current
difficulties to realize the ferromagnetic states of the trapped atom gas, which
should be overcome.Comment: submit to PR
Phase separation and vortex states in binary mixture of Bose-Einstein condensates in the trapping potentials with displaced centers
The system of two simultaneously trapped codensates consisting of
atoms in two different hyperfine states is investigated theoretically in the
case when the minima of the trapping potentials are displaced with respect to
each other. It is shown that the small shift of the minima of the trapping
potentials leads to the considerable displacement of the centers of mass of the
condensates, in agreement with the experiment. It is also shown that the
critical angular velocities of the vortex states of the system drastically
depend on the shift and the relative number of particles in the condensates,
and there is a possibility to exchange the vortex states between condensates by
shifting the centers of the trapping potentials.Comment: 4 pages, 2 figure
Does inter-vertebral range of motion increase after spinal manipulation? A prospective cohort study.
Background: Spinal manipulation for nonspecific neck pain is thought to work in part by improving inter-vertebral range of motion (IV-RoM), but it is difficult to measure this or determine whether it is related to clinical outcomes.
Objectives: This study undertook to determine whether cervical spine flexion and extension IV-RoM increases after a course of spinal manipulation, to explore relationships between any IV-RoM increases and clinical outcomes and to compare palpation with objective measurement in the detection of hypo-mobile segments.
Method: Thirty patients with nonspecific neck pain and 30 healthy controls matched for age and gender received quantitative fluoroscopy (QF) screenings to measure flexion and extension IV-RoM (C1-C6) at baseline and 4-week follow-up between September 2012-13. Patients received up to 12 neck manipulations and completed NRS, NDI
and Euroqol 5D-5L at baseline, plus PGIC and satisfaction questionnaires at follow-up. IV-RoM accuracy, repeatability and hypo-mobility cut-offs were determined. Minimal detectable changes (MDC) over 4 weeks were calculated
from controls. Patients and control IV-RoMs were compared at baseline as well as changes in patients over 4 weeks. Correlations between outcomes and the number of manipulations received and the agreement (Kappa) between palpated and QF-detected of hypo-mobile segments were calculated.
Results: QF had high accuracy (worst RMS error 0.5o) and repeatability (highest SEM 1.1o, lowest ICC 0.90) for
IV-RoM measurement. Hypo-mobility cut offs ranged from 0.8o to 3.5o. No outcome was significantly correlated with increased IV-RoM above MDC and there was no significant difference between the number of hypo-mobile segments in patients and controls at baseline or significant increases in IV-RoMs in patients. However, there was a modest and significant correlation between the number of manipulations received and the number of levels and directions whose IV-RoM increased beyond MDC (Rho=0.39, p=0.043). There was also no agreement between palpation and QF in identifying hypo-mobile segments (Kappa 0.04-0.06).
Conclusions: This study found no differences in cervical sagittal IV-RoM between patients with non-specific neck pain and matched controls. There was a modest dose-response relationship between the number of manipulations given and number of levels increasing IV-RoM - providing evidence that neck manipulation has a mechanical effect at segmental levels. However, patient-reported outcomes were not related to this
Resonant Generation of Topological Modes in Trapped Bose Gases
Trapped Bose atoms cooled down to temperatures below the Bose-Einstein
condensation temperature are considered. Stationary solutions to the
Gross-Pitaevskii equation (GPE) define the topological coherent modes,
representing nonground-state Bose-Einstein condensates. These modes can be
generated by means of alternating fields whose frequencies are in resonance
with the transition frequencies between two collective energy levels
corresponding to two different topological modes. The theory of resonant
generation of these modes is generalized in several aspects: Multiple-mode
formation is described; a shape-conservation criterion is derived, imposing
restrictions on the admissible spatial dependence of resonant fields; evolution
equations for the case of three coherent modes are investigated; the complete
stability analysis is accomplished; the effects of harmonic generation and
parametric conversion for the topological coherent modes are predicted. All
considerations are realized both by employing approximate analytical methods as
well as by numerically solving the GPE. Numerical solutions confirm all
conclusions following from analytical methods.Comment: One reference modifie
Nonlinear Coherent Modes of Trapped Bose-Einstein Condensates
Nonlinear coherent modes are the collective states of trapped Bose atoms,
corresponding to different energy levels. These modes can be created starting
from the ground state condensate that can be excited by means of a resonant
alternating field. A thorough theory for the resonant excitation of the
coherent modes is presented. The necessary and sufficient conditions for the
feasibility of this process are found. Temporal behaviour of fractional
populations and of relative phases exhibits dynamic critical phenomena on a
critical line of the parametric manifold. The origin of these critical
phenomena is elucidated by analyzing the structure of the phase space. An
atomic cloud, containing the coherent modes, possesses several interesting
features, such as interference patterns, interference current, spin squeezing,
and massive entanglement. The developed theory suggests a generalization of
resonant effects in optics to nonlinear systems of Bose-condensed atoms.Comment: 26 pages, Revtex, no figure
Ground state and elementary excitations of single and binary Bose-Einstein condensates of trapped dipolar gases
We analyze the ground-state properties and the excitation spectrum of
Bose-Einstein condensates of trapped dipolar particles. First, we consider the
case of a single-component polarized dipolar gas. For this case we discuss the
influence of the trapping geometry on the stability of the condensate as well
as the effects of the dipole-dipole interaction on the excitation spectrum. We
discuss also the ground state and excitations of a gas composed of two
antiparallel dipolar components.Comment: 12 pages, 9 eps figures, final versio
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