218 research outputs found
Sub-Doppler resonances in the back-scattered light from random porous media infused with Rb vapor
We report on the observation of sub-Doppler resonances on the back-scattered
light from a random porous glass medium with rubidium vapor filling its
interstices. The sub-Doppler spectral lines are the consequence of saturated
absorption where the incident laser beam saturates the atomic medium and the
back-scattered light probes it. Some specificities of the observed spectra
reflect the transient atomic evolution under confinement inside the pores.
Simplicity, robustness and potential miniaturization are appealing features of
this system as a spectroscopic reference.Comment: 6 pages, 4 figure
Magnetometer suitable for Earth field measurement based on transient atomic response
We describe the development of a simple atomic magnetometer using Rb
vapor suitable for Earth magnetic field monitoring. The magnetometer is based
on time-domain determination of the transient precession frequency of the
atomic alignment around the measured field. A sensitivity of 1.5 nT/
is demonstrated on the measurement of the Earth magnetic field in the
laboratory. We discuss the different parameters determining the magnetometer
precision and accuracy and predict a sensitivity of 30 pT/Comment: 6 pages, 5 figure
Theoretical Prediction of Experimental Jump and Pull-In Dynamics in a MEMS Sensor
The present research study deals with an electrically actuated MEMS device. An experimental investigation is performed, via frequency sweeps in a neighbourhood of the first natural frequency. Resonant behavior is explored, with special attention devoted to jump and pull-in dynamics. A theoretical single degree-of-freedom spring-mass model is derived. Classical numerical simulations are observed to properly predict the main nonlinear features. Nevertheless, some discrepancies arise, which are particularly visible in the resonant branch. They mainly concern the practical range of existence of each attractor and the final outcome after its disappearance. These differences are likely due to disturbances, which are unavoidable in practice, but have not been included in the model. To take disturbances into account, in addition to the classical local investigations, we consider the global dynamics and explore the robustness of the obtained results by performing a dynamical integrity analysis. Our aim is that of developing an applicable confident estimate of the system response. Integrity profiles and integrity charts are built to detect the parameter range where reliability is practically strong and where it becomes weak. Integrity curves exactly follow the experimental data. They inform about the practical range of actuality. We discuss the combined use of integrity charts in the engineering design. Although we refer to a particular case-study, the approach is very general
Nonlinear atomic spectroscopy inside a random porous medium
International audienceWe studied a novel spectroscopy setup where alkali atoms are infused in random micro-porous glass and the light probing the atoms have a diffuse nature after the propagation in this strong scattering medium
Theoretical study of dark resonances in micro-metric thin cells
We investigate theoretically dark resonance spectroscopy for a dilute atomic
vapor confined in a thin (micro-metric) cell. We identify the physical
parameters characterizing the spectra and study their influence. We focus on a
Hanle-type situation, with an optical irradiation under normal incidence and
resonant with the atomic transition. The dark resonance spectrum is predicted
to combine broad wings with a sharp maximum at line-center, that can be singled
out when detecting a derivative of the dark resonance spectrum. This narrow
signal derivative, shown to broaden only sub-linearly with the cell length, is
a signature of the contribution of atoms slow enough to fly between the cell
windows in a time as long as the characteristic ground state optical pumping
time. We suggest that this dark resonance spectroscopy in micro-metric thin
cells could be a suitable tool for probing the effective velocity distribution
in the thin cell arising from the atomic desorption processes, and notably to
identify the limiting factors affecting desorption under a grazing incidence.Comment: 12 pages, 11 figures theoretical articl
Microsurgical neurovascular anastomosis: The example of superficial temporal artery to middle cerebral artery bypass. Technical principles
AbstractThe superficial temporal artery to the middle cerebral artery (STA-MCA) bypass is a good example of cerebrovascular anastomosis. In this article, we describe the different stages of the procedure: patient installation, superficial temporal artery harvesting, recipient artery exposure, microsurgical anastomosis, and closure of the craniotomy. When meticulously performed, with the observance of important details at each stage, this technique offers a high rate of technical success (patency>90%) with a very low morbi-mortality (respectively 3% and 1%). Some anesthetic parameters have to be considered to insure perioperative technical and clinical success. STA-MCA bypass is a very useful technique for the management of complex or giant aneurysms where surgical treatment sometimes requires the sacrifice and revascularization of a main arterial trunk. It is also a valuable option for the treatment of chronic and symptomatic hemispheric hypoperfusion (Moyamoya disease, carotid or middle cerebral artery occlusion)
Escape orbits and Ergodicity in Infinite Step Billiards
In a previous paper we defined a class of non-compact polygonal billiards,
the infinite step billiards: to a given decreasing sequence of non-negative
numbers , there corresponds a table \Bi := \bigcup_{n\in\N} [n,n+1]
\times [0,p_{n}].
In this article, first we generalize the main result of the previous paper to
a wider class of examples. That is, a.s. there is a unique escape orbit which
belongs to the alpha and omega-limit of every other trajectory. Then, following
a recent work of Troubetzkoy, we prove that generically these systems are
ergodic for almost all initial velocities, and the entropy with respect to a
wide class of ergodic measures is zero.Comment: 27 pages, 8 figure
Typical support and Sanov large deviations of correlated states
Discrete stationary classical processes as well as quantum lattice states are
asymptotically confined to their respective typical support, the exponential
growth rate of which is given by the (maximal ergodic) entropy. In the iid case
the distinguishability of typical supports can be asymptotically specified by
means of the relative entropy, according to Sanov's theorem. We give an
extension to the correlated case, referring to the newly introduced class of
HP-states.Comment: 29 pages, no figures, references adde
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