2,803 research outputs found
Measurement of the Entropy and Critical Temperature of a Strongly Interacting Fermi Gas
We report a model-independent measurement of the entropy, energy, and
critical temperature of a degenerate, strongly interacting Fermi gas of atoms.
The total energy is determined from the mean square cloud size in the strongly
interacting regime, where the gas exhibits universal behavior. The entropy is
measured by sweeping a bias magnetic field to adiabatically tune the gas from
the strongly interacting regime to a weakly interacting regime, where the
entropy is known from the cloud size after the sweep. The dependence of the
entropy on the total energy quantitatively tests predictions of the
finite-temperature thermodynamics.Comment: 16 pages, 3 figure
Excess mortality during heat waves in Ireland
Ireland is not known for having extreme high temperatures, with values above 30C uncommon. Ireland has significant excess winter mortality compared to summer. The objective of this study is to estimate the impact of nation-wide heat waves on the total, cardiovascular and respiratory relationship, for the period 1981–2003, to determine if there are any periods of excess summer mortality
Probe-based Rapid Hybrid Hyperspectral and Tissue Surface Imaging Aided by Fully Convolutional Networks
Tissue surface shape and reflectance spectra provide rich intra-operative
information useful in surgical guidance. We propose a hybrid system which
displays an endoscopic image with a fast joint inspection of tissue surface
shape using structured light (SL) and hyperspectral imaging (HSI). For SL a
miniature fibre probe is used to project a coloured spot pattern onto the
tissue surface. In HSI mode standard endoscopic illumination is used, with the
fibre probe collecting reflected light and encoding the spatial information
into a linear format that can be imaged onto the slit of a spectrograph.
Correspondence between the arrangement of fibres at the distal and proximal
ends of the bundle was found using spectral encoding. Then during pattern
decoding, a fully convolutional network (FCN) was used for spot detection,
followed by a matching propagation algorithm for spot identification. This
method enabled fast reconstruction (12 frames per second) using a GPU. The
hyperspectral image was combined with the white light image and the
reconstructed surface, showing the spectral information of different areas.
Validation of this system using phantom and ex vivo experiments has been
demonstrated.Comment: This paper has been submitted to MICCAI2016 on 17 March, 2016, and
conditionally accepted on 2 June, 201
Observation of Anomalous Spin Segregation in a Trapped Fermi Gas
We report the observation of spin segregation, i.e., separation of spin
density profiles, in a trapped ultracold Fermi gas of Li with a
magnetically tunable scattering length close to zero. The roles of the spin
components are inverted when the sign of the scattering length is reversed. The
observed density profiles are in qualitative agreement with the spin-wave
theory applied previously to explain spin segregation in a Bose gas, but
disagree in amplitude by two orders of magnitude. The observed atomic density
profiles are far from equilibrium, yet they persist for 5 seconds in a
trap with an axial frequency of 150 Hz. We attribute this long
lifetime to Fermi statistics: The scattering amplitude is nonzero only for
atoms in opposite states, and vanishes for atoms in the same state. By
measuring the magnetic field at which spin segregation ceases, we precisely
determine the zero crossing in the scattering length of Li as
G.Comment: 4 pages, 3 figure
An integrated information retrieval and document management system
This paper describes the requirements and prototype development for an intelligent document management and information retrieval system that will be capable of handling millions of pages of text or other data. Technologies for scanning, Optical Character Recognition (OCR), magneto-optical storage, and multiplatform retrieval using a Standard Query Language (SQL) will be discussed. The semantic ambiguity inherent in the English language is somewhat compensated-for through the use of coefficients or weighting factors for partial synonyms. Such coefficients are used both for defining structured query trees for routine queries and for establishing long-term interest profiles that can be used on a regular basis to alert individual users to the presence of relevant documents that may have just arrived from an external source, such as a news wire service. Although this attempt at evidential reasoning is limited in comparison with the latest developments in AI Expert Systems technology, it has the advantage of being commercially available
Structural Fluctuations in the Spin Liquid State of Tb2Ti2O7
High resolution X-ray scattering measurements on single crystal Tb2Ti2O7
reveal finite structural correlations at low temperatures. This geometrically
frustrated pyrochlore is known to exhibit a spin liquid, or cooperative
paramagnetic state, at temperatures below ~ 20 K. Parametric studies of
structural Bragg peaks appropriate to the Fdm space group of Tb2Ti2O7
reveal substantial broadening and peak intensity reduction in the temperature
regime 20 K to 300 mK. We also observe a small, anomalous lattice expansion on
cooling below a density maximum at ~ 18 K. These measurements are consistent
with the development of fluctuations above a cooperative Jahn-Teller,
cubic-tetragonal phase transition at very low temperatures.Comment: 5 pages, 4 figures, submitted for publicatio
Revisiting Static and Dynamic Spin Ice Correlations in Ho2Ti2O7
Elastic and inelastic neutron scattering studies have been carried out on the
pyrochlore magnet Ho2Ti2O7. Measurements in zero applied magnetic field show
that the disordered spin ice ground state of Ho2Ti2O7 is characterized by a
pattern of rectangular diffuse elastic scattering within the [HHL] plane of
reciprocal space, which closely resembles the zone boundary scattering seen in
its sister compound Dy2Ti2O7. Well-defined peaks in the zone boundary
scattering develop only within the spin ice ground state below ~ 2 K. In
contrast, the overall diffuse scattering pattern evolves on a much higher
temperature scale of ~ 17 K. The diffuse scattering at small wavevectors below
[001] is found to vanish on going to Q=0, an explicit signature of expectations
for dipolar spin ice. Very high energy-resolution inelastic measurements reveal
that the spin ice ground state below ~ 2 K is also characterized by a
transition from dynamic to static spin correlations on the time scale of
10^{-9} seconds. Measurements in a magnetic field applied along the
[10] direction in zero-field cooled conditions show that the system
can be broken up into orthogonal sets of polarized alpha chains along
[10] and quasi-one-dimensional beta chains along [110]. Three
dimensional correlations between beta chains are shown to be very sensitive to
the precise alignment of the [10] externally applied magnetic field.Comment: 11 pages, 10 figures. Submitted for publicatio
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