848 research outputs found
Cold Atom Clock Test of Lorentz Invariance in the Matter Sector
We report on a new experiment that tests for a violation of Lorentz
invariance (LI), by searching for a dependence of atomic transition frequencies
on the orientation of the spin of the involved states (Hughes-Drever type
experiment). The atomic frequencies are measured using a laser cooled
Cs atomic fountain clock, operating on a particular combination of
Zeeman substates. We analyze the results within the framework of the Lorentz
violating standard model extension (SME), where our experiment is sensitive to
a largely unexplored region of the SME parameter space, corresponding to first
measurements of four proton parameters and improvements by 11 and 13 orders of
magnitude on the determination of four others. In spite of the attained
uncertainties, and of having extended the search into a new region of the SME,
we still find no indication of LI violation.Comment: 4 pages, accepted for Physical Review Letter
Feshbach resonances in Cesium at Ultra-low Static Magnetic Fields
We have observed Feshbach resonances for 133Cs atoms in two different
hyperfine states at ultra-low static magnetic fields by using an atomic
fountain clock. The extreme sensitivity of our setup allows for high
signal-to-noise-ratio observations at densities of only 2*10^7 cm^{-3}. We have
reproduced these resonances using coupled-channels calculations which are in
excellent agreement with our measurements. We justify that these are s-wave
resonances involving weakly-bound states of the triplet molecular Hamiltonian,
identify the resonant closed channels, and explain the observed multi-peak
structure. We also describe a model which precisely accounts for the
collisional processes in the fountain and which explains the asymmetric shape
of the observed Feshbach resonances in the regime where the kinetic energy
dominates over the coupling strength.Comment: 5 pages, 4 figures, 1 tabl
An Experimental Test of a Causal Link between Problem-Solving Performance and Reproductive Success in Wild Great Tits
This work was supported by a NSERC grant to A.B., a PICS grant from the CNRS (INEE, n° 31520) to B.D., a PhD writing up grant from the FESP (UdM) and a scholarship from the Biological Sciences Department (UdM) to LC and a mobility grant ERASMUS to M.L. We are also grateful to the ABS, the BOU, the BES, the Frank M. Chapman from AMNH and the Fred Cooke from the SCO for awards and research grants attributed to L.C.Peer reviewedPublisher PD
Evaluation de la mise en oeuvre du plan canicule dans le canton de Vaud en 2015
Le SSP a mis en place depuis 2009 un plan cantonal de prévention et d'intervention sanitaire en cas de canicule qui a depuis évolué et s'est affiné pour aboutir au plan canicule actuel, daté de mars 2014. Ce plan a pour objectifs principaux « de prévenir et d'atténuer les atteintes à la santé de la population dues à la chaleur accablante et d'éviter la surcharge du système sanitaire ». Ce plan décrit les procédures à suivre et le rôle des différent-e-s acteurs/actrices concerné-e-s en cas de canicule. Ces personnes sont réunies au sein d'un groupe appelé « Groupe alerte canicule » (GA) formé de représentant-e-s de divers services de l'administration cantonale et des professionnel-le-s du domaine socio-sanitaire. Si toute la population est visée par les messages de prévention et les recommandations de ce plan, les cibles principales en sont les personnes âgées de 70 ans et plus, à travers notamment le système des visites communautaires.
Le niveau « canicule persistante » de ce plan a été activé pour la première lors des deux épisodes caniculaires de l'été 2015, suite à quoi le SSP a mandaté l'IUMSP pour mener une évaluation de processus portant sur la mise en oeuvre de ce plan
Promotion de l'activité physique au cabinet médical: manuel de référence à l'intention des médecins
[Table des matières] 1. Introduction: que vais-je apprendre? - quelques définitions - recommandations pour une activité physique favorable à la santé - comment mesure-t-on l'activité physique? - déterminants de l'activité physique. - 2. Épidémiologie de la sédentarité: prévalence de la sédentarité - coûts imputables à la sédentarité. - 3. Bénéfices pour la santé: un effet dose-réponse non linéaire - estimation des bénéfices de l'activité physique. - 4. Rôle du médecin de premier recours. - 5. Prise en charge: description générale d'un modèle de prise en charge - comment s'y prendre dans les détails - appréciation des risques liés à l'activité physique. - 6. Exemples d'outils: brochure pour les patients - podomètre: 10000 pas quotidiens pour sa santé! - 7. Autres ressources à disposition: site internet: www.paprica.ch. - Glossaire
[Introduction (extrait)] Ce manuel décrit la perspective et le rôle du médecin de premier recours dans la promotion d'une activité physique bénéfique pour la santé. Il s'inscrit, avec la brochure d'accompagnement destinée aux patients, dans un concept global de promotion de l'activité physique au cabinet médical. Développé pour être le plus concis possible, ce manuel fait la synthèse des connaissances et des savoir-faire utiles à la pratique du conseil en activité physique au cabinet médical
An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock
We have developed an ultra-stable source in the deep ultraviolet, suitable to
fulfill the interrogation requirements of a future fully-operational lattice
clock based on neutral mercury. At the core of the system is a Fabry-P\'erot
cavity which is highly impervious to temperature and vibrational perturbations.
The mirror substrate is made of fused silica in order to exploit the
comparatively low thermal noise limits associated with this material. By
stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity,
and including an additional link to LNE-SYRTE's fountain primary frequency
standards via an optical frequency comb, we produce a signal which is both
stable at the 1E-15 level in fractional terms and referenced to primary
frequency standards. The signal is subsequently amplified and frequency-doubled
twice to produce several milliwatts of interrogation signal at 265.6 nm in the
deep ultraviolet.Comment: 7 pages, 6 figure
A Search for Variations of Fundamental Constants using Atomic Fountain Clocks
Over five years we have compared the hyperfine frequencies of 133Cs and 87Rb
atoms in their electronic ground state using several laser cooled 133Cs and
87Rb atomic fountains with an accuracy of ~10^{-15}. These measurements set a
stringent upper bound to a possible fractional time variation of the ratio
between the two frequencies : (d/dt)ln(nu_Rb/nu_Cs)=(0.2 +/- 7.0)*10^{-16}
yr^{-1} (1 sigma uncertainty). The same limit applies to a possible variation
of the quantity (mu_Rb/mu_Cs)*alpha^{-0.44}, which involves the ratio of
nuclear magnetic moments and the fine structure constant.Comment: 4 pages, 3 figures, 1 table submitted to Phys. Rev. Let
Progress in Atomic Fountains at LNE-SYRTE
We give an overview of the work done with the Laboratoire National de
M\'etrologie et d'Essais-Syst\`emes de R\'ef\'erence Temps-Espace (LNE-SYRTE)
fountain ensemble during the last five years. After a description of the clock
ensemble, comprising three fountains, FO1, FO2, and FOM, and the newest
developments, we review recent studies of several systematic frequency shifts.
This includes the distributed cavity phase shift, which we evaluate for the FO1
and FOM fountains, applying the techniques of our recent work on FO2. We also
report calculations of the microwave lensing frequency shift for the three
fountains, review the status of the blackbody radiation shift, and summarize
recent experimental work to control microwave leakage and spurious phase
perturbations. We give current accuracy budgets. We also describe several
applications in time and frequency metrology: fountain comparisons,
calibrations of the international atomic time, secondary representation of the
SI second based on the 87Rb hyperfine frequency, absolute measurements of
optical frequencies, tests of the T2L2 satellite laser link, and review
fundamental physics applications of the LNE-SYRTE fountain ensemble. Finally,
we give a summary of the tests of the PHARAO cold atom space clock performed
using the FOM transportable fountain.Comment: 19 pages, 12 figures, 5 tables, 126 reference
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