2,815 research outputs found
Dynamical Realization of Macroscopic Superposition States of Cold Bosons in a Tilted Double Well
We present exact expressions for the quantum sloshing of Bose-Einstein
condensates in a tilted two-well potential. Tunneling is suppressed by a small
potential difference between wells, or tilt. However, tunneling resonances
occur for critical values of the tilt when the barrier is high. At resonance,
tunneling times on the order of 10-100 ms are possible. Furthermore, such
tilted resonances lead to a dynamical scheme for creating few-body NOON-like
macroscopic superposition states which are protected by the many body
wavefunction against potential fluctuations.Comment: 6 pages, 5 figures, final version, only minor changes from previous
arXiv versio
Nutrient Limitation of Periphyton in a Spring-Fed, Coastal Stream in Florida, USA.
There is strong evidence to suggest that ground-water
nitrate concentrations have increased in recent years and
further increases are expected along portions of the central
Gulf coast of Florida. Much of the nitrate enriched groundwater
is discharged into surface waters through numerous
freshwater springs that are characteristic of the area and the
potential for eutrophication of their receiving waters is a
legitimate concern. To test the potential effects of elevated
nutrient concentrations on the periphyton community an
in
situ
nutrient addition experiment was conducted in the
spring-fed Chassahowitzka River, FL, USA, during the summer
of 1999. Plastic tubes housing arrays of glass microscope
slides were suspended in the stream. Periphyton colonizing
the microscope slides was subjected to artificial increases in
nitrogen, phosphorus or a combination of both. Slides from
each tube were collected at 3- to 4- day intervals and the
periphyton communities were measured for chlorophyll concentration.
The addition of approximately 10 μg/L of phosphate
above ambient concentrations significantly increased
the amount of periphyton on artificial substrates relative to
controls; the addition of approximately 100 μg/L of nitrate
above ambient concentrations did not. The findings from
this experiment implicated phosphorus, rather than
nitrogen, as the nutrient that potentially limits periphyton
growth in this system.(PDF contains 4 pages.
A Deep Radio Survey of Abell 2125 III: The Cluster Core - Merging and Stripping
We use radio, near-IR, optical, and X-ray observations to examine dynamic
processes in the central region of Abell 2125. In addition to the central
triple, including members of both major dynamical subsystems identified from a
redshift survey, this region features a galaxy showing strong evidence for
ongoing gas stripping during a high-velocity passage through the gas in the
cluster core. The disk galaxy C153 exhibits a plume stretching toward the
cluster center seen in soft X-rays by Chandra, parts of which are also seen in
[O II] emission and near-UV continuum light. HST imaging shows a distorted
disk, with star-forming knots asymmetrically distributed and remnant spiral
structure possibly defined by dust lanes. The stars and ionized gas in its disk
are kinematically decoupled, demonstrating that pressure stripping must be
important, and that tidal disruption is not the only mechanism at work.
Comparison of the gas properties seen in the X-ray and optical data on the
plume highlight significant features of the history of stripped gas in the
intracluster medium. The nucleus of C153 also hosts an AGN, shown by the weak
and distorted extended radio emission and a radio compact core. The unusual
strength of the stripping signatures in this instance is likely related to the
high relative velocity of the galaxy with respect to the intracluster medium,
during a cluster/cluster merger, and its passage very near the core of the
cluster. Another sign of recent dynamical events is diffuse starlight
asymmetrically placed about the central triple in a cD envelope. Transient and
extreme dynamical events as seen in Abell 2125 may be important drivers of
galaxy evolution in the cores of rich clusters.Comment: 36 pages, 16 figures, accepted AJ, paper with full resolution figures
is available at http:www.aoc.nrao.edu/~fowen/papers/a2125/a2125paper3.ps.g
Measurement of dynamic Stark polarizabilities by analyzing spectral lineshapes of forbidden transitions
We present a measurement of the dynamic scalar and tensor polarizabilities of
the excited state 3D1 in atomic ytterbium. The polarizabilities were measured
by analyzing the spectral lineshape of the 408-nm 1S0->3D1 transition driven by
a standing wave of resonant light in the presence of static electric and
magnetic fields. Due to the interaction of atoms with the standing wave, the
lineshape has a characteristic polarizability-dependent distortion. A
theoretical model was used to simulate the lineshape and determine a
combination of the polarizabilities of the ground and excited states by fitting
the model to experimental data. This combination was measured with a 13%
uncertainty, only 3% of which is due to uncertainty in the simulation and
fitting procedure. The scalar and tensor polarizabilities of the state 3D1 were
measured for the first time by comparing two different combinations of
polarizabilities. We show that this technique can be applied to similar atomic
systems.Comment: 13 pages, 7 figures, submitted to PR
Feasibility study on the design of a probe for rectal cancer detection
Rectal examination techniques are considered in terms of detection capability, patient acceptance, and cost reduction. A review of existing clinical techniques are considered in terms of detection capability, patient acceptance, and cost reduction. A review of existing clinical techniques and of relevant aerospace technology included evaluation of the applicability of visual, thermal, ultrasound, and radioisotope modalities of examination. The desired improvements can be obtained by redesigning the proctosigmoidoscope to have reduced size, additional visibility, and the capability of readily providing a color photograph of the entire rectosigmoid mucosa in a single composite view
Observation of a Large Atomic Parity Violation Effect in Ytterbium
Atomic parity violation has been observed in the 6s^2 1S0 - 5d6s 3D1 408-nm
forbidden transition of ytterbium. The parity-violating amplitude is found to
be two orders of magnitude larger than in cesium, where the most precise
experiments to date have been performed. This is in accordance with theoretical
predictions and constitutes the largest atomic parity-violating amplitude yet
observed. This also opens the way to future measurements of neutron skins and
anapole moments by comparing parity-violating amplitudes for various isotopes
and hyperfine components of the transition
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