295 research outputs found
All optical cooling of K to Bose Einstein condensation
We report the all-optical production of Bose Einstein condensates (BEC) of
K atoms. We directly load atoms in a large volume
optical dipole trap from gray molasses on the D1 transition. We then apply a
small magnetic quadrupole field to polarize the sample before transferring the
atoms in a tightly confining optical trap. Evaporative cooling is finally
performed close to a Feshbach resonance to enhance the scattering length. Our
setup allows to cross the BEC threshold with atoms every 7s. As
an illustration of the interest of the tunability of the interactions we study
the expansion of Bose-Einstein condensates in the 1D to 3D crossover
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
Microscopic Observation of Pauli Blocking in Degenerate Fermionic Lattice Gases
The Pauli exclusion principle is one of the most fundamental manifestations
of quantum statistics. Here, we report on its local observation in a
spin-polarized degenerate gas of fermions in an optical lattice. We probe the
gas with single-site resolution using a new generation quantum gas microscope
avoiding the common problem of light induced losses. In the band insulating
regime, we measure a strong local suppression of particle number fluctuations
and a low local entropy per atom. Our work opens a new avenue for studying
quantum correlations in fermionic quantum matter both in and out of
equilibrium.Comment: 8 pages, 6 figure
Imaging magnetic polarons in the doped Fermi-Hubbard model
Polarons are among the most fundamental quasiparticles emerging in
interacting many-body systems, forming already at the level of a single mobile
dopant. In the context of the two-dimensional Fermi-Hubbard model, such
polarons are predicted to form around charged dopants in an antiferromagnetic
background in the low doping regime close to the Mott insulating state.
Macroscopic transport and spectroscopy measurements related to high
materials have yielded strong evidence for the existence of such quasiparticles
in these systems. Here we report the first microscopic observation of magnetic
polarons in a doped Fermi-Hubbard system, harnessing the full single-site spin
and density resolution of our ultracold-atom quantum simulator. We reveal the
dressing of mobile doublons by a local reduction and even sign reversal of
magnetic correlations, originating from the competition between kinetic and
magnetic energy in the system. The experimentally observed polaron signatures
are found to be consistent with an effective string model at finite
temperature. We demonstrate that delocalization of the doublon is a necessary
condition for polaron formation by contrasting this mobile setting to a
scenario where the doublon is pinned to a lattice site. Our work paves the way
towards probing interactions between polarons, which may lead to stripe
formation, as well as microscopically exploring the fate of polarons in the
pseudogap and bad metal phase
Continuous Activation of Autoreactive CD4+ CD25+ Regulatory T Cells in the Steady State
Despite a growing interest in CD4+ CD25+ regulatory T cells (Treg) that play a major role in self-tolerance and immunoregulation, fundamental parameters of the biology and homeostasis of these cells are poorly known. Here, we show that this population is composed of two Treg subsets that have distinct phenotypes and homeostasis in normal unmanipulated mice. In the steady state, some Treg remain quiescent and have a long lifespan, in the order of months, whereas the other Treg are dividing extensively and express multiple activation markers. After adoptive transfer, tissue-specific Treg rapidly divide and expand preferentially in lymph nodes draining their target self-antigens. These results reveal the existence of a cycling Treg subset composed of autoreactive Treg that are continuously activated by tissue self-antigens
Impact of post-procedural glycemic variability on cardiovascular morbidity and mortality after transcatheter aortic valve implantation : a post hoc cohort analysis
International audienceBackground : Glycemic variability is associated with worse outcomes after cardiac surgery, but the prognosis value of early glycemic variability after transcatheter aortic valve implantation is not known. This study was therefore designed to analyze the prognosis significance of post-procedural glycemic variability within 30 days after transcatheter aortic valve implantation.Methods : A post hoc analysis of patients from our center included in the FRANCE and FRANCE-2 registries was conducted. Post-procedural glycemic variability was assessed by calculating the mean daily δ blood glucose during the first 2 days after transcatheter aortic valve implantation. Major complications within 30 days were death, stroke, myocardial infarction, acute heart failure, and life-threatening cardiac arrhythmias.Results : We analyzed 160 patients (age (median [interquartile] = 84 [80–88] years; diabetes mellitus (n) = 41 (26%) patients; logistic Euroscore = 20 [12–32]). The median value of mean daily δ blood glucose was 4.3 mmol l−1. The rate of major complications within 30 days after procedure among patients with the lowest quartile of glycemic variability was 12%, increasing from 12 to 26%, and 39% in the second, third, and fourth quartiles, respectively. In multivariate analysis, glycemic variability was independently associated with an increased risk of major complications within 30 days after the procedure (odds ratio [95% CI] = 1.83 [1.19–2.83]; p = 0.006).Conclusions : This study showed that post-procedural glycemic variability was associated with an increased risk of major complications within 30 days after transcatheter aortic valve implantation
Microscopic evolution of doped Mott insulators from polaronic metal to Fermi liquid
The competition between antiferromagnetism and hole motion in two-dimensional
Mott insulators lies at the heart of a doping-dependent transition from an
anomalous metal to a conventional Fermi liquid. Condensed matter experiments
suggest charge carriers change their nature within this crossover, but a
complete understanding remains elusive. We observe such a crossover in
Fermi-Hubbard systems on a cold-atom quantum simulator and reveal the
transformation of multi-point correlations between spins and holes upon
increasing doping at temperatures around the superexchange energy. Conventional
observables, such as spin susceptibility, are furthermore computed from the
microscopic snapshots of the system. Starting from a magnetic polaron regime,
we find the system evolves into a Fermi liquid featuring incommensurate
magnetic fluctuations and fundamentally altered correlations. The crossover is
completed for hole dopings around . Our work benchmarks theoretical
approaches and discusses possible connections to lower temperature phenomena
Robust Bilayer Charge-Pumping for Spin- and Density-Resolved Quantum Gas Microscopy
Quantum gas microscopy has emerged as a powerful new way to probe quantum
many-body systems at the microscopic level. However, layered or efficient
spin-resolved readout methods have remained scarce as they impose strong
demands on the specific atomic species and constrain the simulated lattice
geometry and size. Here we present a novel high-fidelity bilayer readout, which
can be used for full spin- and density-resolved quantum gas microscopy of
two-dimensional systems with arbitrary geometry. Our technique makes use of an
initial Stern-Gerlach splitting into adjacent layers of a highly-stable
vertical superlattice and subsequent charge pumping to separate the layers by
m. This separation enables independent high-resolution images of each
layer. We benchmark our method by spin- and density-resolving two-dimensional
Fermi-Hubbard systems. Our technique furthermore enables the access to advanced
entropy engineering schemes, spectroscopic methods or the realization of
tunable bilayer systems
Deregulation and Targeting of TP53 Pathway in Multiple Myeloma
Multiple Myeloma (MM) is an incurable disease characterized by a clonal evolution across the course of the diseases and multiple lines of treatment. Among genomic drivers of the disease, alterations of the tumor suppressor TP53 are associated with poor outcomes. In physiological situation, once activated by oncogenic stress or DNA damage, p53 induces either cell-cycle arrest or apoptosis depending on the cellular context. Its inactivation participates to drug resistance in MM. The frequency of TP53 alterations increases along with the progression of the disease, from 5 at diagnosis to 75% at late relapses. Multiple mechanisms of regulation lead to decreased expression of p53, such as deletion 17p, TP53 mutations, specific microRNAs overexpression, TP53 promoter methylations, and MDM2 overexpression. Several therapeutic approaches aim to target the p53 pathway, either by blocking its interaction with MDM2 or by restoring the function of the altered protein. In this review, we describe the mechanism of deregulation of TP53 in MM, its role in MM progression, and the therapeutic options to interact with the TP53 pathway
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