226 research outputs found
A ring trap for ultracold atoms
We propose a new kind of toroidal trap, designed for ultracold atoms. It
relies on a combination of a magnetic trap for rf-dressed atoms, which creates
a bubble-like trap, and a standing wave of light. This new trap is well suited
for investigating questions of low dimensionality in a ring potential. We study
the trap characteristics for a set of experimentally accessible parameters. A
loading procedure from a conventional magnetic trap is also proposed. The
flexible nature of this new ring trap, including an adjustable radius and
adjustable transverse oscillation frequencies, will allow the study of
superfluidity in variable geometries and dimensionalities.Comment: 4 figures, 10 pages ; the order of the sections has been changed ; to
appear in Phys. Rev.
Evaporative cooling in a radio-frequency trap
A theoretical investigation for implementing a scheme of forced evaporative
cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing
the atoms to be trapped by a rf field RF1, the cooling procedure is facilitated
using a second rf source RF2. This second rf field produces a controlled
coupling between the spin states dressed by RF1. The evaporation is then
possible in a pulsed or continuous mode. In the pulsed case, atoms with a given
energy are transferred into untrapped dressed states by abruptly switching off
the interaction. In the continuous case, it is possible for energetic atoms to
adiabatically follow the doubly-dressed states and escape out of the trap. Our
results also show that when the frequencies of the fields RF1 and RF2 are
separated by at least the Rabi frequency associated with RF1, additional
evaporation zones appear which can make this process more efficient.Comment: 12 pages, 11 figure
RF spectroscopy in a resonant RF-dressed trap
We study the spectroscopy of atoms dressed by a resonant radiofrequency (RF)
field inside an inhomogeneous magnetic field and confined in the resulting
adiabatic potential. The spectroscopic probe is a second, weak, RF field. The
observed line shape is related to the temperature of the trapped cloud. We
demonstrate evaporative cooling of the RF-dressed atoms by sweeping the
frequency of the second RF field around the Rabi frequency of the dressing
field.Comment: 7 figures, 8 pages; to appear in J. Phys.
A micromanipulation setup for comparative tests of microgrippers
A micromanipulation setup allowing comparative tests of manipulation micro tools has been developed. Repeatability measurements of positioning as well as optimization of manipulation conditions can be run with parts of typically 5 to 50ÎŒm over a large set of parameters including environment conditions, substrate and tip specifications, and different strategies (robot trajectories at picking and releasing time). The workstation consists of a high precise parallel robot, the Delta3, to position the gripper, linear stages to place the parts in the field of view and two microscopes for the visual feedback and position measurement. The setup is placed in a chamber for controlling relative humidity and temperature. An interface was developed to integrate every kind of tool on the robot. Automated operations and measurement have been carried out based on localization and tracking of micro objects and gripper. Integration of micro tools was successfully accomplished and comparative tests were executed with micro tweezers. Sub micrometer position repeatability was achieved with a success rate of pick and pick operations of 95%
Automatic system for the renal and cancer segmentation in CT images
This article presents the concept of a complex system for automatic detection of kidneys and kidney tumors in computed tomography images. An effective treatment of cancer depends on a quick and effective diagnosis. Computer support for medical diagnostics is crucial in effective specialistsâ analysis. Automatic and accurate location, together with precise detection of the kidney and/or tumor contour is a demanding task. In this article, authors present a complex system for automatic detection of kidneys and kidney tumors, based on machine learning techniques, using the U-Net network. Convolutional neural network recognition results are then processed in multiple stages, using morphological processing, 3D model analysis, geometric coefficients analysis and region-growth implementation. The results of the system detection were compared to the reference images marked by an expert. The system presented in the article is characterized by a very high efficiency of recognition and segmentation of kidney and tumor areas
Characterization of an inertial micro gripper based on adhesion forces
Adhesive forces become predominant in the micro world comparing to the gravity effect implying the development of new micro manipulation strategies. This paper presents the design and conception of a gripper that use the inertial principle for the release (applying a high acceleration, in the order of 10â000g) and the adhesion for catching a micro part of 50ÎŒm with the goal of precisely control the position after release. Experiments were conducted and showed a positioning repeatability of 2ÎŒm to 6ÎŒm depending on the relative humidity with a success rate of more than 90%
Micro-gripper Ă haute dynamique
Dans le monde microscopique, la force de gravitĂ© devient nĂ©gligeable par rapport aux forces dâadhĂ©sion (capillaritĂ©, Van der Waals). Ce projet vise Ă utiliser ces forces pour la prise de bille dâune taille caractĂ©ristique de 50[ÎŒm]. La dĂ©pose quand Ă elle sâeffectue de maniĂšre dynamique, en utilisant lâinertie de la bille soumise Ă une forte accĂ©lĂ©ration. Le but de ce projet est de caractĂ©riser la prise (taux de succĂšs) et la dĂ©pose (seuil dâaccĂ©lĂ©ration, taux de succĂšs, prĂ©cision et rĂ©pĂ©tabilitĂ©). La prise dĂ©pend essentiellement du type de matĂ©riaux utilisĂ©s ; sa caractĂ©risation a Ă©tĂ© faite pour un gripper en silicium et un gripper en verre dans lâair ambiant (20% humiditĂ© relative) et lâazote (3%). Pour fournir une accĂ©lĂ©ration, un piĂ©zoĂ©lectrique est utilisĂ© (cristal qui se dĂ©forme lorsquâune tension est appliquĂ©e Ă ses bornes). Lâavantage principal est que la dĂ©formation est bien contrĂŽlable en intensitĂ© et direction. La dĂ©pose quand Ă elle a Ă©tĂ© caractĂ©risĂ©e dans les mĂȘmes conditions que la prise et en excitant le piĂ©zoĂ©lectrique avec des sinus continus ou en crĂ©ant une seule impulsion Au final, il a Ă©tĂ© montrĂ© que cette technique est viable pour la micromanipulation. Toutefois des points clĂ©s nĂ©cessaires Ă un bon contrĂŽle des opĂ©rations ont Ă©tĂ© identifiĂ©s, notamment au niveau de la rigiditĂ© du substrat pour Ă©viter lâĂ©crasement des objets et au niveau de la qualitĂ© des surfaces de contact
Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror
We present experimental results showing the diffuse reflection of a
Bose-Einstein condensate from a rough mirror, consisting of a dielectric
substrate supporting a blue-detuned evanescent wave. The scattering is
anisotropic, more pronounced in the direction of the surface propagation of the
evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure
The EKiTE network (epidemiology in kidney transplantation - a European validated database): an initiative epidemiological and translational European collaborative research
Background: Kidney transplantation is considered to be the treatment of choice for people with end-stage renal disease (ESRD). However, due to the shortage of available organs and the increase in the ESRD prevalence in Europe, it is essential to improve transplantation outcomes by studying the related prognostic factors. Today, there is no European registry collecting data to perform such clinical epidemiology studies. Main body: Entitled EKiTE, for European cohort for Kidney Transplantation Epidemiology, this prospective and multicentric cohort includes patients from Spanish (Barcelona), Belgian (Leuven), Norwegian (Oslo) and French (Paris Necker, Lyon, Nantes, Nancy, Montpellier, Nice and Paris Saint Louis) transplantation centers and currently contains 13, 394 adult recipients of kidney (only) transplantation from 2005 and updated annually. A large set of parameters collected from transplantation until graft failure or death with numbers of post-transplantation outcomes. The long-term follow-up and the collected data enable a wide range of possible survival and longitudinal analyses. Conclusion: EKiTE is a multicentric cohort aiming to better assess the natural history of the ESRD in European kidney transplant recipients and perform benchmarking of clinical practices. The data are available for clinical epidemiology studies and open for external investigators upon request to the scientific council. Short-term perspectives are to extend EKITE network to other European countries and collect additional parameters in respect of the common thesaurus
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