1,829 research outputs found
A magnetic lens for cold atoms controlled by a rf field
We report on a new type of magnetic lens that focuses atomic clouds using a
static inhomogeneous magnetic field in combination with a radio-frequency
field. The experimental study is performed with a cloud of cold cesium atoms.
The rf field adiabatically deforms the magnetic potential of a coil and
therefore changes its focusing properties. The focal length can be tuned
precisely by changing the rf frequency value. Depending on the rf antenna
position relative to the DC magnetic profile, the focal length of the atomic
lens can be either decreased or increased by the rf field
Resonant demagnetization of a dipolar BEC in a 3D optical lattice
We study dipolar relaxation of a chromium BEC loaded into a 3D optical
lattice. We observe dipolar relaxation resonances when the magnetic energy
released during the inelastic collision matches an excitation towards higher
energy bands. A spectroscopy of these resonances for two orientations of the
magnetic field provides a 3D band spectroscopy of the lattice. The narrowest
resonance is registered for the lowest excitation energy. Its line-shape is
sensitive to the on-site interaction energy. We use such sensitivity to probe
number squeezing in a Mott insulator, and we reveal the production of
three-body states with entangled spin and orbital degrees of freedom.Comment: 5 pages, 3 Figures, Supplemental Materia
All-Optical Production of Chromium Bose-Einstein Condensates
We report on the production of ^52Cr Bose Einstein Condensates (BEC) with an
all-optical method. We first load 5.10^6 metastable chromium atoms in a 1D
far-off-resonance optical trap (FORT) from a Magneto Optical Trap (MOT), by
combining the use of Radio Frequency (RF) frequency sweeps and depumping
towards the ^5S_2 state. The atoms are then pumped to the absolute ground
state, and transferred into a crossed FORT in which they are evaporated. The
fast loading of the 1D FORT (35 ms 1/e time), and the use of relatively fast
evaporative ramps allow us to obtain in 20 s about 15000 atoms in an almost
pure condensate.Comment: 4 pages, 4 figure
Development of probabilistic models for quantitative pathway analysis of plant pest introduction for the EU territory
This report demonstrates a probabilistic quantitative pathway analysis model that can be used in risk assessment for plant pest introduction into EU territory on a range of edible commodities (apples, oranges, stone fruits and wheat). Two types of model were developed: a general commodity model that simulates distribution of an imported infested/infected commodity to and within the EU from source countries by month; and a consignment model that simulates the movement and distribution of individual consignments from source countries to destinations in the EU. The general pathway model has two modules. Module 1 is a trade pathway model, with a Eurostat database of five years of monthly trade volumes for each specific commodity into the EU28 from all source countries and territories. Infestation levels based on interception records, commercial quality standards or other information determine volume of infested commodity entering and transhipped within the EU. Module 2 allocates commodity volumes to processing, retail use and waste streams and overlays the distribution onto EU NUTS2 regions based on population densities and processing unit locations. Transfer potential to domestic host crops is a function of distribution of imported infested product and area of domestic production in NUTS2 regions, pest dispersal potential, and phenology of susceptibility in domestic crops. The consignment model covers the several routes on supply chains for processing and retail use. The output of the general pathway model is a distribution of estimated volumes of infested produce by NUTS2 region across the EU28, by month or annually; this is then related to the accessible susceptible domestic crop. Risk is expressed as a potential volume of infested fruit in potential contact with an area of susceptible domestic host crop. The output of the consignment model is a volume of infested produce retained at each stage along the specific consignment trade chain
Dipolar atomic spin ensembles in a double-well potential
We experimentally study the spin dynamics of mesoscopic ensembles of
ultracold magnetic spin-3 atoms located in two separated wells of an optical
dipole trap. We use a radio-frequency sweep to selectively flip the spin of the
atoms in one of the wells, which produces two separated spin domains of
opposite polarization. We observe that these engineered spin domains are
metastable with respect to the long-range magnetic dipolar interactions between
the two ensembles. The absence of inter-cloud dipolar spin-exchange processes
reveals a classical behavior, in contrast to previous results with atoms loaded
in an optical lattice. When we merge the two subsystems, we observe
spin-exchange dynamics due to contact interactions which enable the first
determination of the s-wave scattering length of 52Cr atoms in the S=0
molecular channel a_0=13.5^{+11}_{-10.5}a_B (where a_B is the Bohr radius).Comment: 9 pages, 7 figure
Accumulation and thermalization of cold atoms in a finite-depth magnetic trap
We experimentally and theoretically study the continuous accumulation of cold
atoms from a magneto-optical trap (MOT) into a finite depth trap, consisting in
a magnetic quadrupole trap dressed by a radiofrequency (RF) field. Chromium
atoms (52 isotope) in a MOT are continuously optically pumped by the MOT lasers
to metastable dark states. In presence of a RF field, the temperature of the
metastable atoms that remain magnetically trapped can be as low as 25 microK,
with a density of 10^17 atoms.m-3, resulting in an increase of the phase-space
density, still limited to 7.10^-6 by inelastic collisions. To investigate the
thermalization issues in the truncated trap, we measure the free evaporation
rate in the RF-truncated magnetic trap, and deduce the average elastic cross
section for atoms in the 5D4 metastable states, equal to 7.0 10^-16m2.Comment: 9 pages, 10 Figure
Crossing fishery statistics with marine turtle bycatch data and habitat mapping in Martinique, FW
Toward a Common Framework and Database of Materials for Soft Robotics
To advance the field of soft robotics, a unified database of material constitutive models and experimental characterizations is of paramount importance. This will facilitate the use of finite element analysis to simulate their behavior and optimize the design of soft-bodied robots. Samples from seventeen elastomers, namely Body Double™ SILK, Dragon Skin™ 10 MEDIUM, Dragon Skin 20, Dragon Skin 30, Dragon Skin FX-Pro, Dragon Skin FX-Pro + Slacker, Ecoflex™ 00–10, Ecoflex 00–30, Ecoflex 00–50, Rebound™ 25, Mold Star™ 16 FAST, Mold Star 20T, SORTA-Clear™ 40, RTV615, PlatSil® Gel-10, Psycho Paint®, and SOLOPLAST 150318, were subjected to uniaxial tensile tests according to the ASTM D412 standard. Sample preparation and tensile test parameters are described in detail. The tensile test data are used to derive parameters for hyperelastic material models using nonlinear least-squares methods, which are provided to the reader. This article presents the mechanical characterization and the resulting material properties for a wide set of commercially available hyperelastic materials, many of which are recognized and commonly applied in the field of soft robotics, together with some that have never been characterized. The experimental raw data and the algorithms used to determine material parameters are shared on the Soft Robotics Materials Database GitHub repository to enable accessibility, as well as future contributions from the soft robotics community. The presented database is aimed at aiding soft roboticists in designing and modeling soft robots while providing a starting point for future material characterizations related to soft robotics research
Spatio-temporal variability of otolith shape of the red band parrotfish (Sparisoma aurofrenatum) in Martinique
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