117 research outputs found
Hybridizing matter-wave and classical accelerometers
We demonstrate a hybrid accelerometer that benefits from the advantages of
both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and
long term stability. First, the use of a real time correction of the atom
interferometer phase by the signal from the classical accelerometer enables to
run it at best performances without any isolation platform. Second, a
servo-lock of the DC component of the conventional sensor output signal by the
atomic one realizes a hybrid sensor. This method paves the way for applications
in geophysics and in inertial navigation as it overcomes the main limitation of
atomic accelerometers, namely the dead times between consecutive measurements
Metrology with Atom Interferometry: Inertial Sensors from Laboratory to Field Applications
Developments in atom interferometry have led to atomic inertial sensors with
extremely high sensitivity. Their performances are for the moment limited by
the ground vibrations, the impact of which is exacerbated by the sequential
operation, resulting in aliasing and dead time. We discuss several experiments
performed at LNE-SYRTE in order to reduce these problems and achieve the
intrinsic limit of atomic inertial sensors. These techniques have resulted in
transportable and high-performance instruments that participate in gravity
measurements, and pave the way to applications in inertial navigation.Comment: 7 pages, 5 figure
Lessons from the analysis of nonhuman primates for understanding human aging and neurodegenerative diseases
Animal models are necessary tools for solving the most serious challenges facing medical research. In aging and neurodegenerative disease studies, rodents occupy a place of choice. However, the most challenging questions about longevity, the complexity and functioning of brain networks or social intelligence can almost only be investigated in nonhuman primates. Beside the fact that their brain structure is much closer to that of humans, they develop highly complex cognitive strategies and they are visually-oriented like humans. For these reasons, they deserve consideration, although their management and care are more complicated and the related costs much higher. Despite these caveats, considerable scientific advances have been possible using nonhuman primates. This review concisely summarizes their role in the study of aging and of the mechanisms involved in neurodegenerative disorders associated mainly with cognitive dysfunctions (Alzheimerâs and prion diseases) or motor deficits (Parkinsonâs and related diseases)
Station préhistorique de Gouyronne (Hérault)
Lautier J. Station préhistorique de Gouyronne (Hérault). In: Bulletin de la Société préhistorique de France, tome 47, n°5, 1950. pp. 258-263
DĂ©veloppement dâun accĂ©lĂ©romĂštre atomique compact pour la gravimĂ©trie de terrain et la navigation inertielle
We present the development of a compact atomic gravimeter, relying on atom interferometry using stimulated Raman transitions. We demonstrate a significant improvement in terms of compactness and simplicity for each element of the device (sensor head, laser source, micro-wave frequency reference, vibration rejection system). This work relies on the use of a hollow-pyramid in place of the usual retro-reflecting mirror. This component allows realizing each step of measurement (trapping and cooling of the atoms, interferometer, detection) with a single laser beam. We developed a very compact sensor head, for which we have simplified every key element. The laser source features only one single laser diode, emitting at 1560 nm to interrogate Rubidium 87 atoms. It benefits from the use of fibered optical telecom components, which have already demonstrated to be performing and robust to environmental conditions. All the elements of the accelerometer prototype are now gathered to allow for the operation of the interferometer. On-field gravimetry will greatly benefit from such compact absolute gravimeter. In parallel, we have developed a novel vibration rejection method, based on digital electronics. The atomic phase shift induced by vibrations is pre-compensated before the recombination of the wave-packets, directly on the optical phase on the Raman lasers. This ensures that each measurement point stays at maximum sensitivity, even in the presence of great acceleration noise. As a result, for a gravimeter operating directly on the ground in an urban environment, we have reached sensitivity to acceleration at a level of at 1 s, which improves down to after 300 s. Finally, our method lead us to fully hybridize the atom gravimeter with a classical accelerometer, which results in an accurate very large-band accelerometer [DC , 430 Hz]. This demonstration is very promising for applications in inertial navigation.Nous prĂ©sentons le dĂ©veloppement d'un prototype de gravimĂštre atomique compact reposant sur l'interfĂ©romĂ©trie atomique avec des transitions Raman stimulĂ©es. Nous dĂ©montrons une amĂ©lioration importante de la compacitĂ© et de la simplicitĂ© de chaque Ă©lĂ©ment du dispositif expĂ©rimental (tĂȘte de senseur, source laser, rĂ©fĂ©rence de frĂ©quence micro-onde, systĂšme de filtrage des vibrations). Ce travail s'appuie sur l'utilisation d'une pyramide creuse comme miroir de rĂ©tro-rĂ©flexion, ce qui permet de rĂ©aliser toutes les fonctions d'un interfĂ©romĂštre atomique (piĂ©geage et refroidissement des atomes, interfĂ©romĂštre, dĂ©tection) avec un unique faisceau laser. Nous avons donc dĂ©veloppĂ© une tĂȘte de senseur trĂšs compacte, dont les fonctions clĂ©s ont toutes Ă©tĂ© simplifiĂ©es. La source laser met en jeu un unique laser Ă©mettant Ă 1560 nm pour interroger des atomes de Rubidium 87. Elle bĂ©nĂ©ficie de l'utilisation de composants optiques tĂ©lĂ©coms fibrĂ©s, qui ont dĂ©jĂ dĂ©montrĂ© leur performance et leur robustesse aux conditions environnementales. Tous les Ă©lĂ©ments du prototype sont assemblĂ©s pour permettre la mise en place de l'interfĂ©romĂštre. Ce type de gravimĂštre compact est trĂšs intĂ©ressant pour la gravimĂ©trie de terrain. En parallĂšle, nous avons dĂ©veloppĂ© un systĂšme de rĂ©jection du bruit de vibration, basĂ© sur l'Ă©lectronique numĂ©rique. La contribution des vibrations sur la phase atomique est prĂ©-compensĂ©e avant la fermeture de l'interfĂ©romĂštre, directement sur la phase optique des lasers. Ceci garantit que chaque point de mesure a une sensibilitĂ© maximum, malgrĂ© un bruit de d'accĂ©lĂ©ration important. Ainsi, pour un gravimĂštre posĂ© au sol en environnement urbain, nous avons dĂ©montrĂ© une sensibilitĂ© Ă lâaccĂ©lĂ©ration de lâordre de Ă 1 seconde, qui atteint aprĂšs 300 secondes dâintĂ©gration. Notre dispositif nous a finalement conduit Ă lâhybridation complĂšte du gravimĂštre atomique avec un accĂ©lĂ©romĂštre classique, conduisant Ă un accĂ©lĂ©romĂštre exact trĂšs large bande [DC , 430 Hz]. Ce rĂ©sultat est trĂšs prometteur, notamment pour la navigation inertielle
Development of a compact atomic accelerometer for on-field gravimetry and inertial navigation
Nous prĂ©sentons le dĂ©veloppement d'un prototype de gravimĂštre atomique compact reposant sur l'interfĂ©romĂ©trie atomique avec des transitions Raman stimulĂ©es. Nous dĂ©montrons une amĂ©lioration importante de la compacitĂ© et de la simplicitĂ© de chaque Ă©lĂ©ment du dispositif expĂ©rimental (tĂȘte de senseur, source laser, rĂ©fĂ©rence de frĂ©quence micro-onde, systĂšme de filtrage des vibrations). Ce travail s'appuie sur l'utilisation d'une pyramide creuse comme miroir de rĂ©tro-rĂ©flexion, ce qui permet de rĂ©aliser toutes les fonctions d'un interfĂ©romĂštre atomique (piĂ©geage et refroidissement des atomes, interfĂ©romĂštre, dĂ©tection) avec un unique faisceau laser. Nous avons donc dĂ©veloppĂ© une tĂȘte de senseur trĂšs compacte, dont les fonctions clĂ©s ont toutes Ă©tĂ© simplifiĂ©es. La source laser met en jeu un unique laser Ă©mettant Ă 1560 nm pour interroger des atomes de Rubidium 87. Elle bĂ©nĂ©ficie de l'utilisation de composants optiques tĂ©lĂ©coms fibrĂ©s, qui ont dĂ©jĂ dĂ©montrĂ© leur performance et leur robustesse aux conditions environnementales. Tous les Ă©lĂ©ments du prototype sont assemblĂ©s pour permettre la mise en place de l'interfĂ©romĂštre. Ce type de gravimĂštre compact est trĂšs intĂ©ressant pour la gravimĂ©trie de terrain. En parallĂšle, nous avons dĂ©veloppĂ© un systĂšme de rĂ©jection du bruit de vibration, basĂ© sur l'Ă©lectronique numĂ©rique. La contribution des vibrations sur la phase atomique est prĂ©-compensĂ©e avant la fermeture de l'interfĂ©romĂštre, directement sur la phase optique des lasers. Ceci garantit que chaque point de mesure a une sensibilitĂ© maximum, malgrĂ© un bruit de d'accĂ©lĂ©ration important. Ainsi, pour un gravimĂštre posĂ© au sol en environnement urbain, nous avons dĂ©montrĂ© une sensibilitĂ© Ă lâaccĂ©lĂ©ration de lâordre de Ă 1 seconde, qui atteint aprĂšs 300 secondes dâintĂ©gration. Notre dispositif nous a finalement conduit Ă lâhybridation complĂšte du gravimĂštre atomique avec un accĂ©lĂ©romĂštre classique, conduisant Ă un accĂ©lĂ©romĂštre exact trĂšs large bande [DC , 430 Hz]. Ce rĂ©sultat est trĂšs prometteur, notamment pour la navigation inertielle.We present the development of a compact atomic gravimeter, relying on atom interferometry using stimulated Raman transitions. We demonstrate a significant improvement in terms of compactness and simplicity for each element of the device (sensor head, laser source, micro-wave frequency reference, vibration rejection system). This work relies on the use of a hollow-pyramid in place of the usual retro-reflecting mirror. This component allows realizing each step of measurement (trapping and cooling of the atoms, interferometer, detection) with a single laser beam. We developed a very compact sensor head, for which we have simplified every key element. The laser source features only one single laser diode, emitting at 1560 nm to interrogate Rubidium 87 atoms. It benefits from the use of fibered optical telecom components, which have already demonstrated to be performing and robust to environmental conditions. All the elements of the accelerometer prototype are now gathered to allow for the operation of the interferometer. On-field gravimetry will greatly benefit from such compact absolute gravimeter. In parallel, we have developed a novel vibration rejection method, based on digital electronics. The atomic phase shift induced by vibrations is pre-compensated before the recombination of the wave-packets, directly on the optical phase on the Raman lasers. This ensures that each measurement point stays at maximum sensitivity, even in the presence of great acceleration noise. As a result, for a gravimeter operating directly on the ground in an urban environment, we have reached sensitivity to acceleration at a level of at 1 s, which improves down to after 300 s. Finally, our method lead us to fully hybridize the atom gravimeter with a classical accelerometer, which results in an accurate very large-band accelerometer [DC , 430 Hz]. This demonstration is very promising for applications in inertial navigation
Sépultures du type des Champs d'Urnes de la Ravailhé (Commune de Castelnau-de-Lévis, Tarn)
Lautier J., Soutou André. Sépultures du type des Champs d'Urnes de la Ravailhé (Commune de Castelnau-de-Lévis, Tarn). In: Bulletin de la Société préhistorique de France, tome 54, n°7-8, 1957. Travaux en retard. pp. 387-396
La nécropole de la Maladrerie à Albi (Tarn)
A rescue excavation carried out in the south-western outskirts of the town of Albi in 1978 brought to light twelve graves that represent almost an entire necropolis. These graves, cremation pits, yielded various objects characteristic of the transition Bronze/Iron in a context Moulin/Grand Bassin I. Among the pottery are elements comparable to those of the Garonne valley, the Languedoc coastal area and particularly the necropolises formerly discovered in the Tarn (LavÚne-Monsalvi, Saint Sulpice-la-Pointe, etc.). The metal objects show affinity with series from the Tarn, the Languedoc and the Pyrenees. All this information leads to questions concerning the movements of men , objects and ideas in the middle Garonne basin.Une fouille de sauvetage menée en 1978 dans la banlieue sud-ouest de la ville d'Albi a mis au jour douze sépultures qui représentent la presque totalité d'une nécropole. Ces tombes à incinération en fosse ont fourni un mobilier diversifié, caractéristique de la transition Bronze/Fer dans un contexte Moulin/Grand Bassin I. La céramique fournit des éléments comparatifs pertinents avec la vallée de la Garonne, le littoral du Languedoc et surtout les nécropoles découvertes anciennement dans le Tarn (LavÚne-Monsalvi, Saint-Sulpice-la-Pointe...). Le mobilier métallique présente des affinités avec des séries du Tarn, du Languedoc et des Pyrénées. Toutes ces informations permettent de poser pour la moyenne Garonne des questions liées à la circulation des hommes, des objets et des idées.Muller André, Lautier Jean. La nécropole de la Maladrerie à Albi (Tarn). In: Documents d'Archéologie Méridionale, vol. 18, 1995. pp. 7-24
La nécropole de la Maladrerie à Albi (Tarn) - Documents CD-ROM
Muller André, Lautier Jean. La nécropole de la Maladrerie à Albi (Tarn) - Documents CD-ROM. In: Documents d'Archéologie Méridionale, vol. 18, 1995. pp. 1-110
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