467 research outputs found
Intense slow beams of bosonic potassium isotopes
We report on an experimental realization of a two-dimensional magneto-optical
trap (2D-MOT) that allows the generation of cold atomic beams of 39K and 41K
bosonic potassium isotopes. The high measured fluxes up to 1.0x10^11 atoms/s
and low atomic velocities around 33 m/s are well suited for a fast and reliable
3D-MOT loading, a basilar feature for new generation experiments on
Bose-Einstein condensation of dilute atomic samples. We also present a simple
multilevel theoretical model for the calculation of the light-induced force
acting on an atom moving in a MOT. The model gives a good agreement between
predicted and measured flux and velocity values for our 2D-MOT.Comment: Updated references, 1 figure added, 10 pages, 9 figure
Collisional properties of sympathetically cooled K
We report the experimental evidence of the sympathetic cooling of K
with Rb down to 1 K, obtained in a novel tight confining magnetic
trap. This allowed us to perform the first direct measurement of the elastic
cross section of K below 50 K. The result obtained for the triplet
scattering length, Bohr radii, agrees with previous results
derived from photoassociation spectra and from Feshbach spectroscopy of
K.Comment: 7 pages, 4 figures, submitted to Phys. Rev.
Double species condensate with tunable interspecies interactions
We produce Bose-Einstein condensates of two different species, Rb and
K, in an optical dipole trap in proximity of interspecies Feshbach
resonances. We discover and characterize two Feshbach resonances, located
around 35 and 79 G, by observing the three-body losses and the elastic
cross-section. The narrower resonance is exploited to create a double species
condensate with tunable interactions. Our system opens the way to the
exploration of double species Mott insulators and, more in general, of the
quantum phase diagram of the two species Bose-Hubbard model.Comment: 4 pages, 4 figure
Metrics and peer review agreement at the institutional level
In the past decades, many countries have started to fund academic
institutions based on the evaluation of their scientific performance. In this
context, peer review is often used to assess scientific performance.
Bibliometric indicators have been suggested as an alternative. A recurrent
question in this context is whether peer review and metrics tend to yield
similar outcomes. In this paper, we study the agreement between bibliometric
indicators and peer review at the institutional level. Additionally, we also
quantify the internal agreement of peer review at the institutional level. We
find that the level of agreement is generally higher at the institutional level
than at the publication level. Overall, the agreement between metrics and peer
review is on par with the internal agreement among two reviewers for certain
fields of science. This suggests that for some fields, bibliometric indicators
may possibly be considered as an alternative to peer review for national
research assessment exercises
Observation of dynamical instability for a Bose-Einstein condensate in a moving 1D optical lattice
We have experimentally studied the unstable dynamics of a harmonically
trapped Bose-Einstein condensate loaded into a 1D moving optical lattice. The
lifetime of the condensate in such a potential exhibits a dramatic dependence
on the quasimomentum state. This is unambiguously attributed to the onset of
dynamical instability, after a comparison with the predictions of the
Gross-Pitaevskii theory. Deeply in the unstable region we observe the rapid
appearance of complex structures in the atomic density profile, as a
consequence of the condensate phase uniformity breakdown
Unstable regimes for a Bose-Einstein condensate in an optical lattice
We report on the experimental characterization of energetic and dynamical
instability, two mechanisms responsible for the breakdown of Bloch waves in a
Bose-Einstein condensate interacting with a 1D optical lattice. A clear
separation of these two regimes is obtained performing measurements at
different temperatures of the atomic sample. The timescales of the two
processes have been determined by measuring the losses induced in the
condensate. A simple phenomenological model is introduced for energetic
instability while a full comparison is made between the experiment and the 3D
Gross-Pitaevskii theory that accounts for dynamical instability
Framing the ultimatum game: the contribution of simulation
It has now become widely accepted that economic decisions are influenced by cognitive and emotional processes. In the present study, we aimed at disentangling the neural mechanisms associated with the way in which the information is formulated, i.e., framing effect, in terms of gain or loss, which influences people\u2019s decisions. Participants played a fMRI version of the Ultimatum Game (UG) where we manipulated bids through two different frames: the expression \u201cI give you\u201d (gain) focusing on money the respondent would receive if she/he agreed with the proponent, and the expression \u201cI take\u201d (loss) focusing on the money that would be removed from the respondent in the event that she/he accepted the offer. Neuroimaging data revealed a frame by response interaction, showing an increase of neural activity in the right rolandic operculum/insular cortex, the anterior cingulate, among other regions, for accepting the frame \u201cI take\u201d vs. rejecting, as compared to accepting the frame \u201cI give you\u201d vs. rejecting. In addition, the left occipito-temporal junction was activated for \u201cI take\u201d vs. \u201cI give you\u201d for offer 5, corresponding to the equal offer made unpleasant by the presence of the frame \u201cI take,\u201d where is the proposer that takes the money. Our data extend the current understanding of the neural substrates of social decision making, by disentangling the structures sensitive to the way in which the information is formulated (i.e., framing effect), in terms of gain or loss
Atomic fountains and optical clocks at SYRTE: status and perspectives
In this article, we report on the work done with the LNE-SYRTE atomic clock
ensemble during the last 10 years. We cover progress made in atomic fountains
and in their application to timekeeping. We also cover the development of
optical lattice clocks based on strontium and on mercury. We report on tests of
fundamental physical laws made with these highly accurate atomic clocks. We
also report on work relevant to a future possible redefinition of the SI
second
Impact of IFN lambda 3/4 single nucleotide polymorphisms on the cytomegalovirus reactivation in autologous stem cell transplant patients
Cytomegalovirus (CMV) infection represents one of the main cause mortality after Stem Cell Transplantation. Recently, a protective effect of the T allele of rs12979860 IL28B Single Nucleotide Polymorphisms (SNPs) against CMV infection in the allogenic stem cell transplantation was suggested. We investigate whether the rs12979860 IL28B SNP and the relative rs368234815 (IFNλ4) genotype may affect the incidence of active CMV infection in Autologous stem cell transplantation (Auto-SCT) setting. The study included 99 patients who underwent to Auto-SCT. IL28 and IFNÎ4 SNPs were correlated with CMV reactivation along with other clinical and treatment parameters. CMV reactivation by CMV DNAemia was evaluated once a week until day 100 from Auto-SCT. CMV reactivation was documented in 50% (TT-ÎG/ÎG), 35% (CC-TT/TT) and 29.2% (CT-TT/ÎG) of the patients respectively. No differences in CMV copies number were recorded at reactivation between different IL28/IFNλ4 genotypes. The analysis of patients older than 60 years showed a significantly higher incidence of active CMV infection in the TT-ÎG/ÎG (83%) population with respect to CC-TT/TT (21%) and CT-TT/ÎG (40%) patients. Our data suggest a negative role of TT-ÎG/ÎG genotype in the CMV reactivation in Auto-SCT. The exposure to rituximab and the pre-infusion presence of anti CMV IgG also significantly influenced CMV reactivation
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