10,841 research outputs found
Two-body anticorrelation in a harmonically trapped ideal Bose gas
We predict the existence of a dip below unity in the second-order coherence
function of a partially condensed ideal Bose gas in harmonic confinement,
signaling the anticorrelation of density fluctuations in the sample. The dip in
the second-order coherence function is revealed in a canonical-ensemble
calculation, corresponding to a system with fixed total number of particles. In
a grand-canonical ensemble description, this dip is obscured by the
occupation-number fluctuation catastrophe of the ideal Bose gas. The
anticorrelation is most pronounced in highly anisotropic trap geometries
containing small particle numbers. We explain the fundamental physical
mechanism which underlies this phenomenon, and its relevance to experiments on
interacting Bose gases.Comment: 10 pages, 5 figures. v2: Minor changes and corrections to figures and
text. To appear in PR
Resolving asymmetries along the pulsation cycle of the Mira star X Hya
The mass-loss process in Mira stars probably occurs in an asymmetric way
where dust can form in inhomogeneous circumstellar molecular clumps. Following
asymmetries along the pulsation cycle can give us clues about these mass-loss
processes. We imaged the Mira star X Hya and its environnement at different
epochs to follow the evolution of the morphology in the continuum and in the
molecular bands. We observed X Hya with AMBER in J-H-K at low resolution at two
epochs. We modelled squared visibilities with geometrical and physical models.
We also present imaging reconstruction results obtained with MiRA and based on
the physical a priori images. We report on the angular scale change of X Hya
between the two epochs. 1D CODEX profiles allowed us to understand and model
the spectral variation of squared visibilities and constrain the stellar
parameters. Reconstructed model-dependent images enabled us to reproduce
closure phase signals and the azimuthal dependence of squared visibilities.
They show evidence for material inhomogeneities located in the immediate
environment of the star.Comment: Accepted for publication in A&A, 17 pages, 16 figure
The reliability of toe systolic pressure and the toe brachial index in patients with diabetes
<p>Abstract</p> <p>Background</p> <p>The Ankle Brachial Index is a useful clinical test for establishing blood supply to the foot. However, there are limitations to this method when conducted on people with diabetes. As an alternative to the Ankle Brachial Index, measuring Toe Systolic Pressures and the Toe Brachial Index have been recommended to assess the arterial blood supply to the foot. This study aimed to determine the intra and inter-rater reliability of the measurement of Toe Systolic Pressure and the Toe Brachial Index in patients with diabetes using a manual measurement system.</p> <p>Methods</p> <p>This was a repeated measures, reliability study. Three raters measured Toe Systolic Pressure and the Toe Brachial Index in thirty participants with diabetes. Measurement sessions occurred on two occasions, one week apart, using a manual photoplethysmography unit (Hadeco Smartdop 45) and a standardised measurement protocol.</p> <p>Results</p> <p>The mean intra-class correlation for intra-rater reliability for toe systolic pressures was 0.87 (95% LOA: -25.97 to 26.06 mmHg) and the mean intra-class correlation for Toe Brachial Indices was 0.75 (95% LOA: -0.22 to 0.28). The intra-class correlation for inter-rater reliability was 0.88 for toe systolic pressures (95% LOA: -22.91 to 29.17.mmHg) and 0.77 for Toe Brachial Indices (95% LOA: -0.21 to 0.22).</p> <p>Conclusion</p> <p>Despite the reasonable intra-class correlation results, the range of error (95% LOA) was broad. This raises questions regarding the reliability of using a manual sphygmomanometer and PPG for the Toe Systolic Pressure and Toe Brachial Indice.</p
Interferometer-Type Structures for Guided Atoms
We experimentally demonstrate interferometer-type guiding structures for
neutral atoms based on dipole potentials created by micro-fabricated optical
systems. As a central element we use an array of atom waveguides being formed
by focusing a red-detuned laser beam with an array of cylindrical microlenses.
Combining two of these arrays, we realize X-shaped beam splitters and more
complex systems like the geometries for Mach-Zehnder and Michelson-type
interferometers for atoms.Comment: 4 pages, 6 figure
An optical study of interdiffusion in ZnSe/ZnCdSe
Copyright 1996 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 69, 1579 (1996) and may be found at
The sediment of mixtures of charged colloids: segregation and inhomogeneous electric fields
We theoretically study sedimentation-diffusion equilibrium of dilute binary,
ternary, and polydisperse mixtures of colloidal particles with different
buoyant masses and/or charges. We focus on the low-salt regime, where the
entropy of the screening ions drives spontaneous charge separation and the
formation of an inhomogeneous macroscopic electric field. The resulting
electric force lifts the colloids against gravity, yielding highly
nonbarometric and even nonmonotonic colloidal density profiles. The most
profound effect is the phenomenon of segregation into layers of colloids with
equal mass-per-charge, including the possibility that heavy colloidal species
float onto lighter ones
Performance of a deterministic source of entangled photonic qubits
We study the possible limitations and sources of decoherence in the scheme
for the deterministic generation of polarization-entangled photons, recently
proposed by Gheri et al. [K. M. Gheri et al., Phys. Rev. A 58, R2627 (1998)],
based on an appropriately driven single atom trapped within an optical cavity.
We consider in particular the effects of laser intensity fluctuations, photon
losses, and atomic motion.Comment: 10 pages, 6 figure
Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror
We present experimental results showing the diffuse reflection of a
Bose-Einstein condensate from a rough mirror, consisting of a dielectric
substrate supporting a blue-detuned evanescent wave. The scattering is
anisotropic, more pronounced in the direction of the surface propagation of the
evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure
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