4,722 research outputs found
Stability of small amplitude normal modes of a Bose-Einstein condensate with a singly quantized vortex confined in an optical lattice
We study the dynamics of a BEC with a singly quantized vortex, placed in the
combined potential of a 1-D (2-D) optical lattice and an axi-symmetric harmonic
trap. A time-dependent variational Lagrangian analysis shows that an optical
lattice helps to stabilize the vortex which in absence of the optical lattice
is unstable. We find that the normal modes are stable only if the depth of the
optical potential is more than a certain critical value. This critical value of
the optical potential depends on the interaction parameter.In general higher
the interaction parameter,lower the value of the optical potential required to
stabilize the vortex. The BEC with the singly quantized vortex is found to be
relatively more unstable in a 2-D optical lattice compared to a 1-D optical
lattice.Comment: Revised version with 11 pages including 1 figur
Effect of ripening temperature on the chemical composition of lingonberries (Vaccinium vitis-idaea L.) of northern and southern origin
Lingonberries (Vaccinium vitis-idaea L.) from two locations, northern (69â—¦N, 18â—¦E) and southern (59â—¦N, 10â—¦E)
Norway, were grown under controlled conditions in a phytotron at two temperatures (9 and 15 â—¦C) to study the
effects of the ripening temperature and origin on the chemical composition of the berries. The concentrations of
phenolic compounds, sugars, and organic acids as well as the profile of volatile organic compounds (VOCs) were
determined using chromatographic and mass spectrometric methods. Five anthocyanins, eleven flavonols, eight
cinnamic acid derivatives, three flavan-3-ols, three sugars, three organic acids, and 77 VOCs were identified, of
which 40 VOCs had not previously been reported in lingonberries. Berries from both locations, were found to
have higher contents of anthocyanins and cinnamic acid derivatives when ripened at lower temperature (9 â—¦C),
compared to the higher temperature (15 â—¦C). Lingonberries of northern origin had a different VOC profile and
higher contents of anthocyanins and organic acids than berries originating from the south. Lingonberries from
the northern location also had higher proportions of cyanidin-3-O-glucoside and cyanidin-3-O-arabinoside than
lingonberries from the southern location. The results show that the composition of lingonberries is influenced by
both the environment and the origin of the plants, with phenolic compounds mainly influenced by the growth
temperature and VOCs mainly influenced by plant origin
Exploring the association of Brownfield remediation status with socioeconomic conditions in Wayne County, MI
Urban neighborhoods with locations of environmental contamination, known as brownfields, impact entire neighborhoods, but corrective environmental remedial action on brownfields is often tracked on an individual property basis, neglecting the larger neighborhood-level impact. This study addresses this impact by examining spatial differences between brownfields with unmitigated environmental concerns (open site) and sites that are considered fully mitigated or closed in urban neighborhoods (closed site) on the US census tract scale in Wayne County, MI. Michigan’s Department of Environment, Great Lakes, and Energy’s leaking underground storage tank (LUST) database provided brownfield information for Wayne County. Local indicators of spatial association (LISA) produced maps of spatial clustering and outliers. A McNemar’s test demonstrated significant discordances in LISA categories between LUST open and closed sites (p\u3c0.001). Geographically weighted regressions (GWR) evaluated the association between open and closed site spatial density (open-closed) with socioeconomic variables (population density, proportion of White or Black residents, proportion of college educated populations, the percentage of owner-occupied units, vacant units, rented units, and median household value). Final multivariate GWR showed that population density, being Black, college education, vacant units, and renter occupied units were significantly associated (p\u3c0.05) with open-closed, and that those associations varied across Wayne County. Increases in Black population was associated with increased open-closed. Increases in vacant units, renter-occupied units, and college education were associated with decreased open-closed. These results provide input for environmental justice research to identify inequalities and discover the distribution of environmental hazards among urban neighborhoods
Dynamics of a Vortex in a Trapped Bose-Einstein Condensate
We consider a large condensate in a rotating anisotropic harmonic trap. Using
the method of matched asymptotic expansions, we derive the velocity of an
element of vortex line as a function of the local gradient of the trap
potential, the line curvature and the angular velocity of the trap rotation.
This velocity yields small-amplitude normal modes of the vortex for 2D and 3D
condensates. For an axisymmetric trap, the motion of the vortex line is a
superposition of plane-polarized standing-wave modes. In a 2D condensate, the
planar normal modes are degenerate, and their superposition can result in
helical traveling waves, which differs from a 3D condensate. Including the
effects of trap rotation allows us to find the angular velocity that makes the
vortex locally stable. For a cigar-shape condensate, the vortex curvature makes
a significant contribution to the frequency of the lowest unstable normal mode;
furthermore, additional modes with negative frequencies appear. As a result, it
is considerably more difficult to stabilize a central vortex in a cigar-shape
condensate than in a disc-shape one. Normal modes with imaginary frequencies
can occur for a nonaxisymmetric condensate (in both 2D and 3D). In connection
with recent JILA experiments, we consider the motion of a straight vortex line
in a slightly nonspherical condensate. The vortex line changes its orientation
in space at the rate proportional to the degree of trap anisotropy and can
exhibit periodic recurrences.Comment: 19 pages, 6 eps figures, REVTE
Vortex stabilization in a small rotating asymmetric Bose-Einstein condensate
We use a variational method to investigate the ground-state phase diagram of
a small, asymmetric Bose-Einstein condensate with respect to the dimensionless
interparticle interaction strength and the applied external rotation
speed . For a given , the transition lines between no-vortex
and vortex states are shifted toward higher relative to those for the
symmetric case. We also find a re-entrant behavior, where the number of vortex
cores can decrease for large . In addition, stabilizing a vortex in a
rotating asymmetric trap requires a minimum interaction strength. For a given
asymmetry, the evolution of the variational parameters with increasing
shows two different types of transitions (sharp or continuous), depending on
the strength of the interaction. We also investigate transitions to states with
higher vorticity; the corresponding angular momentum increases continuously as
a function of
Is a Trapped One-Dimensional Bose Gas a Luttinger Liquid?
The low-energy fluctuations of a trapped, interacting quasi one-dimensional
Bose gas are studied. Our considerations apply to experiments with highly
anisotropic traps. We show that under suitable experimental conditions the
system can be described as a Luttinger liquid. This implies that the
correlation function of the bosons decays algebraically preventing
Bose-Einstein condensation. At significantly lower temperatures a finite size
gap destroys the Luttinger liquid picture and Bose-Einstein condensation is
again possible.Comment: 4 pages (revtex), 1 figure (eps file
Anomalous modes drive vortex dynamics in confined Bose-Einstein condensates
The dynamics of vortices in trapped Bose-Einstein condensates are
investigated both analytically and numerically. In axially symmetric traps, the
critical rotation frequency for the metastability of an isolated vortex
coincides with the largest vortex precession frequency (or anomalous mode) in
the Bogoliubov excitation spectrum. As the condensate becomes more elongated,
the number of anomalous modes increases. The largest frequency of these modes
exceeds both the thermodynamic critical frequency and the nucleation frequency
at which vortices are created dynamically. Thus, anomalous modes describe not
only the critical rotation frequency for creation of the first vortex in an
elongated condensate but also the vortex precession in a single-component
spherical condensate.Comment: 4 pages revtex, 3 embedded figure
In-situ characterization of the Hamamatsu R5912-HQE photomultiplier tubes used in the DEAP-3600 experiment
The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum
efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and
is of significant interest for future dark matter and neutrino experiments
where high signal yields are needed.
We report on the methods developed for in-situ characterization and
monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of
typical measured single-photoelectron charge distributions, correlated noise
(afterpulsing), dark noise, double, and late pulsing characteristics. The
characterization is performed during the detector commissioning phase using
laser light injected through a light diffusing sphere and during normal
detector operation using LED light injected through optical fibres
Immune Function in Alcoholism: A Controlled Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66331/1/j.1530-0277.1993.tb00763.x.pd
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