1,239 research outputs found
SoniControl - A Mobile Ultrasonic Firewall
The exchange of data between mobile devices in the near-ultrasonic frequency
band is a new promising technology for near field communication (NFC) but also
raises a number of privacy concerns. We present the first ultrasonic firewall
that reliably detects ultrasonic communication and provides the user with
effective means to prevent hidden data exchange. This demonstration showcases a
new media-based communication technology ("data over audio") together with its
related privacy concerns. It enables users to (i) interactively test out and
experience ultrasonic information exchange and (ii) shows how to protect
oneself against unwanted tracking.Comment: To appear in proceedings of 2018 ACM Multimedia Conference October
22--26, 2018, Seoul, Republic of Kore
Improving Raman velocimetry of laser-cooled cesium atoms by spin-polarization
We study the peformances of Raman velocimetry applied to laser-cooled,
spin-polarized, cesium atoms. Atoms are optically pumped into the F=4, m=0
ground-state Zeeman sublevel, which is insensitive to magnetic perturbations.
High resolution Raman stimulated spectroscopy is shown to produce
Fourier-limited lines, allowing, in realistic experimental conditions, atomic
velocity selection to one-fiftieth of a recoil velocity.Comment: 12 pages, 6 figures, Elsevier style, to appear in Opt. Commu
Quantum Ratchets for Quantum Communication with Optical Superlattices
We propose to use a quantum ratchet to transport quantum information in a
chain of atoms trapped in an optical superlattice. The quantum ratchet is
created by a continuous modulation of the optical superlattice which is
periodic in time and in space. Though there is zero average force acting on the
atoms, we show that indeed the ratchet effect permits atoms on even and odd
sites to move along opposite directions. By loading the optical lattice with
two-level bosonic atoms, this scheme permits to perfectly transport a qubit or
entangled state imprinted in one or more atoms to any desired position in the
lattice. From the quantum computation point of view, the transport is achieved
by a smooth concatenation of perfect swap gates. We analyze setups with
noninteracting and interacting particles and in the latter case we use the
tools of optimal control to design optimal modulations. We also discuss the
feasibility of this method in current experiments.Comment: Published version, 9 pages, 5 figure
Theoretical analysis of quantum dynamics in 1D lattices: Wannier-Stark description
This papers presents a formalism describing the dynamics of a quantum
particle in a one-dimensional tilted time-dependent lattice. The description
uses the Wannier-Stark states, which are localized in each site of the lattice
and provides a simple framework leading to fully-analytical developments.
Particular attention is devoted to the case of a time-dependent potential,
which results in a rich variety of quantum coherent dynamics is found.Comment: 8 pages, 6 figures, submitted to PR
Actively stabilized wavelength-insensitive carrier elimination from an electro-optically modulated laser beam
We demonstrate a simple and robust technique for removal of the carrier wave
from a phase-modulated laser beam, using a non-interferometric method that is
insensitive to the modulation frequency and instead exploits the
polarization-dependence of electro-optic modulation. An actively stabilized
system using feedback via a liquid crystal cell yields long-term carrier
suppression in excess of 28 dB at the expense of a 6.5 dB reduction in sideband
power.Comment: 9 pages, 5 figure
Visceral fat mass determination in rodent: validation of dual-energy x-ray absorptiometry and anthropometric techniques in fat and lean rats
<p>Abstract</p> <p>Background</p> <p>Because abdominal obesity is predisposed to various metabolic disorders, it is of major importance to assess and track the changes with time of this specific fat mass. The main issue for clinicians or researchers is to use techniques for assessing abdominal fat deposition and its accumulation or changes over time, without sacrificing of experimental subjects. In the rat, techniques to investigate in-vivo visceral fat mass are lacking. The purpose of the study was to validate indirect Dual-energy X-ray Absorptiometry technique and abdominal circumference measurement as tools to predict visceral adipose tissue in rats.</p> <p>Forty-three Wistar male rats from different body weight, fat mass and ages were included in the study. Visceral fat mass was assessed by weighing the total perirenal and peri-epididymal adipose tissues after dissection. Statistical methods were used to discriminate the best region of interest allowing the in-vivo measure of Central Fat Mass by DXA. Abdominal circumference was measured at the same time as the DXA scan.</p> <p>Results</p> <p>A region of interest including Central Fat Mass from the whole body DXA scan (extending from L2 to L5 vertebrae), correlated strongly with <it>ex-vivo </it>Fat Mass (r = 0.94, p < 0.001). Abdominal circumference correlated significantly with <it>ex-vivo </it>Fat Mass (r = 0.82, p < 0.001) and Central Fat Mass (0.90, p < 0.001) in the whole group of rats. When dividing the whole group into lean and fat rats, correlations remained significant between Central Fat Mass and <it>ex-vivo </it>Fat Mass but disappeared for the lean group between abdominal circumference and <it>ex-vivo </it>Fat Mass.</p> <p>Conclusions</p> <p>This study validates the Central Fat Mass determined by DXA as a non-sacrificial technique to assess visceral fat for in-vivo investigations in rats. The abdominal circumference measure appears useful in studying overweight or obese rats. These two techniques could be convenient tools in follow-up and longitudinal studies.</p
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