8,108 research outputs found
Efficient sorting of Bessel beams
We demonstrate the efficient sorter of Bessel beams separating both the azimuthal and radial components. This is based upon the recently reported transformation of angular to transverse momentum states. We separately identify over forty azimuthal and radial components, with a radial spacing of 1588 m<sup>−1</sup>, and outline how the device could be used to identify the two spatial dimensions simultaneously
National Autism Indicators Report: Vocational Rehabilitation 2016
Employment is about more than simply earning a paycheck - it influences quality of life, independence, and wellness. Historically, employment outcomes for adults with autism are poor. The U.S. Vocational Rehabilitation system (VR) is designed to provide support to states for implementation of services to assist people with disabilities to prepare for, find, and keep employment. VR data allow us to examine some outcomes for those with autism compared to their peers.To make a difference, research must reach those who need it. The National Autism Indicators Report series presents our research findings in a clearly communicated, open-access, online format to speed the delivery of information to decision-makers while maintaining very high standards of scientific credibility
National Autism Indicators Report: Transition into Young Adulthood
There is very little research published concerning how people with autism do in the adult portion of their lifespans. We analyzed data from "The National Longitudinal Transition Study-2" and "The Survey of Pathways to Diagnosis and Services" to examine the service needs and life outcomes of adolescents and young adults on the autism spectrum. This report describes the prevalence of a wide variety of indicators related to transition planning, services access, unmet needs, employment, postsecondary education, living arrangements, social participation, and safety and risk
Realization of a superconducting atom chip
We have trapped rubidium atoms in the magnetic field produced by a
superconducting atom chip operated at liquid Helium temperatures. Up to
atoms are held in a Ioffe-Pritchard trap at a distance of 440
m from the chip surface, with a temperature of 40 K. The trap
lifetime reaches 115 s at low atomic densities. These results open the way to
the exploration of atom--surface interactions and coherent atomic transport in
a superconducting environment, whose properties are radically different from
normal metals at room temperature.Comment: Submitted to Phys. Rev. Let
Multimer formation in 1D two-component gases and trimer phase in the asymmetric attractive Hubbard model
We consider two-component one-dimensional quantum gases at special imbalanced
commensurabilities which lead to the formation of multimer (multi-particle
bound-states) as the dominant order parameter. Luttinger liquid theory supports
a mode-locking mechanism in which mass (or velocity) asymmetry is identified as
the key ingredient to stabilize such states. While the scenario is valid both
in the continuum and on a lattice, the effects of umklapp terms relevant for
densities commensurate with the lattice spacing are also mentioned. These ideas
are illustrated and confronted with the physics of the asymmetric
(mass-imbalanced) fermionic Hubbard model with attractive interactions and
densities such that a trimer phase can be stabilized. Phase diagrams are
computed using density-matrix renormalization group techniques, showing the
important role of the total density in achieving the novel phase. The effective
physics of the trimer gas is as well studied. Lastly, the effect of a parabolic
confinement and the emergence of a crystal phase of trimers are briefly
addressed. This model has connections with the physics of imbalanced
two-component fermionic gases and Bose-Fermi mixtures as the latter gives a
good phenomenological description of the numerics in the strong-coupling
regime.Comment: 17 pages, 15 figure
Scattering by a toroidal coil
In this paper we consider the Schr\"odinger operator in with
a long-range magnetic potential associated to a magnetic field supported inside
a torus . Using the scheme of smooth perturbations we construct
stationary modified wave operators and the corresponding scattering matrix
. We prove that the essential spectrum of is an
interval of the unit circle depending only on the magnetic flux across
the section of . Additionally we show that, in contrast to the
Aharonov-Bohm potential in , the total scattering cross-section
is always finite. We also conjecture that the case treated here is a typical
example in dimension 3.Comment: LaTeX2e 17 pages, 1 figur
Scaling Laws of Stress and Strain in Brittle Fracture
A numerical realization of an elastic beam lattice is used to obtain scaling
exponents relevant to the extent of damage within the controlled, catastrophic
and total regimes of mode-I brittle fracture. The relative fraction of damage
at the onset of catastrophic rupture approaches a fixed value in the continuum
limit. This enables disorder in a real material to be quantified through its
relationship with random samples generated on the computer.Comment: 4 pages and 6 figure
Towards a guided atom interferometer based on a superconducting atom chip
We evaluate the realization of a novel geometry of a guided atom
interferometer based on a high temperature superconducting microstructure. The
interferometer type structure is obtained with a guiding potential realized by
two current carrying superconducting wires in combination with a closed
superconducting loop sustaining a persistent current. We present the layout and
realization of our superconducting atom chip. By employing simulations we
discuss the critical parameters of the interferometer guide in particular near
the splitting regions of the matter waves. Based on measurements of the
relevant chip properties we discuss the application of a compact and reliable
on-chip atom interferometer.Comment: 14 pages, 7 figures, accepted for New Journal of Physic
From ballistic to Brownian vortex motion in complex oscillatory media
We show that the breaking of the rotation symmetry of spiral waves in
two-dimensional complex (period-doubled or chaotic) oscillatory media by
synchronization defect lines (SDL) is accompanied by an intrinsic drift of the
pattern. Single vortex motion changes from ballistic flights at a well-defined
angle from the SDL to Brownian-like diffusion when the turbulent character of
the medium increases. It gives rise, in non-turbulent multi-spiral regimes, to
a novel ``vortex liquid''.Comment: 5 pages, 4 figure
Mobile particles in an immobile environment: Molecular Dynamics simulation of a binary Yukawa mixture
Molecular dynamics computer simulations are used to investigate thedynamics
of a binary mixture of charged (Yukawa) particles with a size-ratio of 1:5. We
find that the system undergoes a phase transition where the large particles
crystallize while the small particles remain in a fluid-like (delocalized)
phase. Upon decreasing temperature below the transition, the small particles
become increasingly localized on intermediate time scales. This is reflected in
the incoherent intermediate scattering functions by the appearance of a plateau
with a growing height. At long times, the small particles show a diffusive
hopping motion. We find that these transport properties are related to
structural correlations and the single-particle potential energy distribution
of the small particles.Comment: 7 pages, 5 figure
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