Effect of disorder close to the superfluid transition in a two-dimensional Bose gas

We experimentally study the effect of disorder on trapped quasi two-dimensional (2D) 87Rb clouds in the vicinity of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. The disorder correlation length is of the order of the Bose gas characteristic length scales (thermal de Broglie wavelength, healing length) and disorder thus modifies the physics at a microscopic level. We analyze the coherence properties of the cloud through measurements of the momentum distributions, for two disorder strengths, as a function of its degeneracy. For moderate disorder, the emergence of coherence remains steep but is shifted to a lower entropy. In contrast, for strong disorder, the growth of coherence is hindered. Our study is an experimental realization of the dirty boson problem in a well controlled atomic system suitable for quantitative analysis

A multi-photon magneto-optical trap

We demonstrate a Magneto-Optical Trap (MOT) configuration which employs optical forces due to light scattering between electronically excited states of the atom. With the standard MOT laser beams propagating along the {\it x}- and {\it y}- directions, the laser beams along the {\it z}-direction are at a different wavelength that couples two sets of {\it excited} states. We demonstrate efficient cooling and trapping of cesium atoms in a vapor cell and sub-Doppler cooling on both the red and blue sides of the two-photon resonance. The technique demonstrated in this work may have applications in background-free detection of trapped atoms, and in assisting laser-cooling and trapping of certain atomic species that require cooling lasers at inconvenient wavelengths.Comment: 10 pages, 5 figure

Le Bois Pargas, à Pageas (Haute-Vienne) : un nouveau témoin du Néolithique final en Limousin.

International audienceNear to the village of Pageas, in Haute-Vienne (Limousin, France), the archaeological site of the "Bois Pargas" was discovered after the violent storms of the end of the year 1999, by the finding of artefacts into the stump of a reversed chestnut tree. A small excavation bring to the fore that the tree grew on a Neolithic pit. Although no organic remains are preserved, the archaeological artefacts let us interpret the structure as a pseudo megalithic monument. The funerary pit contained six Pressignian flint daggers, along with arrowheads, "scies à coches", ceramics and some ornaments. All theses artefacts are typical of the IIIrd millennium BC and the technological analysis of the daggers discriminates two times of production which brings to discuss the duration of use of the burial.Le gisement du Bois Pargas, situé sur la commune de Pageas en Haute-Vienne, fut identifié à la suite des violentes tempêtes de la fin de l'année 1999, par la découverte de matériel archéologique pris dans une souche de châtaigner renversé. La réalisation d'un sondage permit de montrer que cet arbre s'était enraciné sur une fosse préhistorique. Bien qu'aucun vestige organique n'ait été conservé, le type de matériel archéologique découvert permet d'interpréter cette structure comme le témoin d'un monument funéraire pseudo-mégalithique. La fosse sépulcrale contenait en effet un ensemble de six poignards en silex du Grand-Pressigny, associés à des pointes de flèches, des scies à coches, de la céramique et des éléments de parure. Ce matériel permet de situer le gisement au IIIe millénaire avant notre ère, et l'analyse technologique des poignards met en évidence deux époques de production qui conduisent à s'interroger sur la durée de fonctionnement de la structure funéraire

Comparison of phosphodiesterase 10A and dopamine transporter levels as markers of disease burden in early Parkinson's disease

BACKGROUND: Recent work has shown loss of phosphodiesterase 10A levels in middle-stage and advanced treated patients with PD, which was associated with motor symptom severity. OBJECTIVES: To assess phosphodiesterase 10A levels in early PD and compare with loss of dopamine transporter as markers of disease burden. METHODS: Seventy-eight subjects were included in this study (17 early de novo, 15 early l-dopa-treated, 24 moderate-advanced l-dopa-treated patients with PD, and 22 healthy controls). All participants underwent [11 C]IMA107 PET, [11 C]PE2I PET, and 3-Tesla MRI scan. RESULTS: Early de novo PD patients showed loss of [11 C]IMA107 and of [11 C]PE2I binding in caudate and putamen (P < 0.001); early l-dopa-treated PD patients showed additional loss of [11 C]IMA107 in the caudate (P < 0.001; annual decline 3.6%) and putamen (P < 0.001; annual decline 2.8%), but loss of [11 C]PE2I only in the putamen (P < 0.001; annual decline 6.8%). Lower [11 C]IMA107 correlated with lower [11 C]PE2I in the caudate (rho = 0.51; P < 0.01) and putamen (rho = 0.53; P < 0.01). Longer disease duration correlated with lower [11 C]IMA107 in the caudate (rho = -0.72; P < 0.001) and putamen (rho = -0.48; P < 0.01), and with lower [11 C]PE2I only in the putamen (rho = -0.65; P < 0.001). Higher burden of motor symptoms correlated with lower [11 C]IMA107 in the caudate (rho = -0.42; P < 0.05) and putamen (rho = -0.41; P < 0.05), and with lower [11 C]PE2I only in the putamen (rho = -0.69; P < 0.001). CONCLUSION: Our findings demonstrate loss of phosphodiesterase 10A levels very early in the course of PD and is associated with the gradual and progressive increase of motor symptoms. Phosphodiesterase 10A imaging shows similar potential with dopamine transporter imaging to follow disease progression. © 2019 International Parkinson and Movement Disorder Society

Old stones' song: Use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya)

Evidence of Oldowan tools by w2.6 million years ago (Ma) may signal a major adaptive shift in hominin evolution. While tool-dependent butchery of large mammals was important by at least 2.0 Ma, the use of artifacts for tasks other than faunal processing has been difficult to diagnose. Here we report on use-wear analysis ofw2.0 Ma quartz and quartzite artifacts from Kanjera South, Kenya. A use-wear framework that links processing of specific materials and tool motions to their resultant use-wear patterns was developed. A blind test was then carried out to assess and improve the efficacy of this experimental use-wear framework, which was then applied to the analysis of 62 Oldowan artifacts from Kanjera South. Usewear on a total of 23 artifact edges was attributed to the processing of specific materials. Use-wear on seven edges (30%) was attributed to animal tissue processing,corroborating zooarchaeological evidence for butchery at the site. Use-wear on 16 edges (70%)was attributed to the processing of plant tissues, including wood, grit-covered plant tissues that we interpret asunderground storage organs (USOs), and stems of grass or sedges. These results expand our knowledge of the suite of behaviours carried out in the vicinity of Kanjera South to include the processing of materials that would be ‘invisible’ using standard archaeological methods. Wood cutting and scraping may represent the production and/or maintenance of wooden tools. Use-wear related to USO processing extends the archaeological evidence for hominin acquisition and consumption of this resource by over 1.5 Ma. Cutting of grasses, sedges or reeds may be related to a subsistence task (e.g., grass seed harvesting, cutting out papyrus culm for consumption) and/or a non-subsistence related task (e.g., production of ‘twine,’ simple carrying devices, or bedding). These results highlight the adaptive significance of lithic technology for hominins at Kanjera

Drying colloidal systems: laboratory models for a wide range of applications

The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art

Propriétés d'équilibre et de transport de gaz de Bose bidimensionnels en présence de désordre

In this thesis, we study the influence of disorder on the transport and equilibrium properties of two-dimensional (2D) Bose gases in the regime of quantum degeneracy. The systems we study are ultra-cold clouds of Rubidium 87, cooled and trapped by optical means, confined in 2D between two light sheets. The disordered potential is generated by laser speckles. The first experiment we describe studies the coherence properties of an interacting gas in the vicinity of the superfluid transition, called Berezinskii-Kosterlitz-Thouless transition. We quantitatively study the behavior of the momentum distribution of the gas through time-of-flight measurements. Our results are in agreement with Quantum Monte-Carlo simulation. In the presence of disorder, we observe that the growth of coherence is shifted to lower entropies. This result is a first step to the detailed study of the combined effects of interactions and disorder for 2D Bose gases. Our second experiment is a study of the transport properties of a 2D gas expanding in disorder. We first analyse in details the classical diffusion regime. We observe the characteristic decay of the central density with time and measure the diffusion coefficients depending on energy. The experimental results are in agreement with a specially developed classical numerical simulation. We then describe the experimental progress to reach the regime of quantum diffusion and Anderson localisation, together with a numerical simulation, with which we investigate experimental signatures of weak and strong localisation.Dans cette thèse, nous étudions l'influence du désordre sur les propriétés d'équilibre et de transport de gaz de Bose bidimensionnels dans le régime de dégénérescence quantique. Les échantillons étudiés sont des nuages de Rubidium 87 ultra-froids, refroidis et piégés par des méthodes optiques, confinés à deux dimensions entre deux nappes de lumières. Le potentiel désordonné est un potentiel optique de speckle. La première expérience que nous décrivons est une étude des propriétés de cohérence du gaz en interaction au voisinage de la transition superfluide, appelée transition Berezinskii-Kosterlitz-Thouless. Nous étudions quantitativement le comportement de la distribution d'impulsion du gaz par mesure de temps de vol. Nos résultats sont en accord avec une simulation Monte-Carlo Quantique. En présence de désordre, nous observons que l'augmentation de la cohérence est décalée vers les plus basses entropies. Ce résultat constitue une première étape dans l'étude détaillée des effets combinés des interactions et du désordre pour des gaz de Bose 2D. Notre deuxième expérience est une étude des propriétés de transport d'un gaz 2D en expansion dans le désordre. Nous étudions d'abord le régime de diffusion classique. Nous observons la décroissance caractéristique de la densité centrale en fonction du temps et nous mesurons les coefficients de diffusion dépendant de l'énergie. Les résultats expérimentaux sont en accord avec une simulation numérique classique. Nous décrivons les améliorations expérimentales mises en place pour atteindre le régime de diffusion quantique et la localisation d'Anderson, ainsi qu'une simulation numérique avec laquelle nous explorons des signatures expérimentales de la localisation faible et forte.

Prise en charge à domicile de la maladie d'Alzheimer

POITIERS-BU Médecine pharmacie (861942103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Propriétés d'équilibre et de transport de gaz de Bose bidimensionnels en présence de désordre

Dans cette thèse, nous étudions l'influence du désordre sur les propriétés d'équilibre et de transport de gaz de Bose bidimensionnels dans le régime de dégénérescence quantique. Les échantillons étudiés sont des nuages de Rubidium 87 ultra-froids, refroidis et piégés par des méthodes optiques, confinés à deux dimensions entre deux nappes de lumières. Le potentiel désordonné est un potentiel optique de speckle. La première expérience que nous décrivons est une étude des propriétés de cohérence du gaz en interaction au voisinage de la transition superfluide, appelée transition Berezinskii-Kosterlitz-Thouless. Nous étudions quantitativement le comportement de la distribution d'impulsion du gaz par mesure de temps de vol. Nos résultats sont en accord avec une simulation Monte-Carlo Quantique. En présence de désordre, nous observons que l'augmentation de la cohérence est décalée vers les plus basses entropies. Ce résultat constitue une première étape dans l'étude détaillée des effets combinés des interactions et du désordre pour des gaz de Bose 2D. Notre deuxième expérience est une étude des propriétés de transport d'un gaz 2D en expansion dans le désordre. Nous étudions d'abord le régime de diffusion classique. Nous observons la décroissance caractéristique de la densité centrale en fonction du temps et nous mesurons les coefficients de diffusion dépendant de l'énergie. Les résultats expérimentaux sont en accord avec une simulation numérique classique. Nous décrivons les améliorations expérimentales mises en place pour atteindre le régime de diffusion quantique et la localisation d'Anderson, ainsi qu'une simulation numérique avec laquelle nous explorons des signatures expérimentales de la localisation faible et forteIn this thesis, we study the influence of disorder on the transport and equilibrium properties of two-dimensional (2D) Bose gases in the regime of quantum degeneracy. The systems we study are ultra-cold clouds of Rubidium 87, cooled and trapped by optical means, confined in 2D between two light sheets. The disordered potential is generated by laser speckles. The first experiment we describe studies the coherence properties of an interacting gas in the vicinity of the superfluid transition, called Berezinskii-Kosterlitz-Thouless transition. We quantitatively study the behavior of the momentum distribution of the gas through time-of-flight measurements. Our results are in agreement with Quantum Monte-Carlo simulation. In the presence of disorder, we observe that the growth of coherence is shifted to lower entropies. This result is a first step to the detailed study of the combined effects of interactions and disorder for 2D Bose gases. Our second experiment is a study of the transport properties of a 2D gas expanding in disorder. We first analyse in details the classical diffusion regime. We observe the characteristic decay of the central density with time and measure the diffusion coefficients depending on energy. The experimental results are in agreement with a specially developed classical numerical simulation. We then describe the experimental progress to reach the regime of quantum diffusion and Anderson localisation, together with a numerical simulation, with which we investigate experimental signatures of weak and strong localisationPALAISEAU-Polytechnique (914772301) / SudocSudocFranceF