294 research outputs found
Dispersion control for matter waves and gap solitons in optical superlattices
We present a numerical study of dispersion manipulation and formation of
matter-wave gap solitons in a Bose-Einstein condensate trapped in an optical
superlattice. We demonstrate a method for controlled generation of matter-wave
gap solitons in a stationary lattice by using an interference pattern of two
condensate wavepackets, which mimics the structure of the gap soliton near the
edge of a spectral band. The efficiency of this method is compared with that of
gap soliton generation in a moving lattice recently demonstrated experimentally
by Eiermann et al. [Phys. Rev. Lett. 92, 230401 (2004)]. We show that, by
changing the relative depths of the superlattice wells, one can fine-tune the
effective dispersion of the matter waves at the edges of the mini-gaps of the
superlattice Bloch-wave spectrum and therefore effectively control both the
peak density and the spatial width of the emerging gap solitons.Comment: 8 pages, 9 figures; modified references in Section 2; minor content
changes in Sections 1 and 2 and Fig. 9 captio
Vestibular Function and Beta-Amyloid Deposition in the Baltimore Longitudinal Study of Aging
Beta-amyloid (Aβ) plaque deposition is a key feature of Alzheimer’s disease (AD), and occurs years before the onset of symptoms. Aβ plaque deposition has been shown to be present in ~30% of cognitively normal older adults using amyloid C-11 labeled Pittsburgh Compound B (11C-PiB) Positron Emission Tomography (PET) imaging. Prior studies have reported a link between reduced vestibular function and poorer cognition in healthy older adults. It is unknown whether vestibular impairment occurs in association with AD pathology among individuals in the preclinical phase of AD, which could contribute to the observed association between vestibular and cognitive function in healthy older adults. Using the Baltimore Longitudinal Study of Aging (BLSA), we analyzed the association between a comprehensive set of vestibular function measures and PiB status in 98 healthy participants with a mean age of 77.3 (±8.26). We did not observe a significant relationship between any vestibular function measure and PiB status in cognitively-intact older adults in the BLSA. This finding suggests that Aβ deposition does not explain the observed association between reduced vestibular function and poorer cognition in healthy older adults
Nonlinear Bloch-wave interaction and Bragg scattering in optically-induced lattices
We study, both theoretically and experimentally, the Bragg scattering of
light in optically-induced photonic lattices and reveal the key physical
mechanisms which govern nonlinear self-action of narrow beams under the
combined effects of Bragg scattering and wave diffraction, allowing for
selecting bands with different effective dispersion.Comment: 4 pages, 6 figure
Slow-light optical bullets in arrays of nonlinear Bragg-grating waveguides
We demonstrate how to control independently both spatial and temporal
dynamics of slow light. We reveal that specially designed nonlinear waveguide
arrays with phase-shifted Bragg gratings demonstrate the frequency-independent
spatial diffraction near the edge of the photonic bandgap, where the group
velocity of light can be strongly reduced. We show in numerical simulations
that such structures allow a great flexibility in designing and controlling
dispersion characteristics, and open a way for efficient spatiotemporal
self-trapping and the formation of slow-light optical bullets.Comment: 4 pages, 4 figures; available from
http://link.aps.org/abstract/PRL/v97/e23390
Modulational instability of spinor condensates
We demonstrate, analytically and numerically, that the ferromagnetic phase of
the spinor Bose-Einstein condenstate may experience modulational instability of
the ground state leading to a fragmentation of the spin domains. Together with
other nonlinear effects in the atomic optics of ultra-cold gases (such as
coherent photoassociation and four-wave mixing) this effect provides one more
analogy between coherent matter waves and light waves in nonlinear optics.Comment: 4 pages, 4 figures. Accepted for Phys. Rev. A Rapid Communication
Multi-component optical solitary waves
We discuss several novel types of multi-component (temporal and spatial)
envelope solitary waves that appear in fiber and waveguide nonlinear optics. In
particular, we describe multi-channel solitary waves in bit-parallel-wavelength
fiber transmission systems for high performance computer networks, multi-colour
parametric spatial solitary waves due to cascaded nonlinearities of quadratic
materials, and quasiperiodic envelope solitons due to quasi-phase-matching in
Fibonacci optical superlattices.Comment: 12 pages, 11 figures; To be published in: Proceedings of the Dynamics
Days Asia-Pacific: First International Conference on Nonlinear Science
(Hong-Kong, 13-16 July, 1999), Editor: Bambi Hu (Elsevier Publishers, 2000
Does Sensory Function Decline Independently or Concomitantly with Age? Data from the Baltimore Longitudinal Study of Aging
Objectives. To investigate whether sensory function declines independently or in parallel with age within a single individual. Methods. Cross-sectional analysis of Baltimore Longitudinal Study of Aging (BLSA) participants who underwent vision (visual acuity threshold), proprioception (ankle joint proprioceptive threshold), vestibular function (cervical vestibular-evoked myogenic potential), hearing (pure-tone average audiometric threshold), and Health ABC physical performance battery testing. Results. A total of 276 participants (mean age 70 years, range 26–93) underwent all four sensory tests. The function of all four systems declined with age. After age adjustment, there were no significant associations between sensory systems. Among 70–79-year-olds, dual or triple sensory impairment was associated with poorer physical performance. Discussion. Our findings suggest that beyond the common mechanism of aging, other distinct (nonshared) etiologic mechanisms may contribute to decline in each sensory system. Multiple sensory impairments influence physical performance among individuals in middle old-age (age 70–79)
Collapse of solitary excitations in the nonlinear Schrödinger equation with nonlinear damping and white noise
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