170 research outputs found

    A compact high-flux source of cold sodium atoms

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    We present a compact source of cold sodium atoms suitable for the production of quantum degenerate gases and versatile for a multi-species experiment. The magnetic field produced by permanent magnets allows to simultaneously realize a Zeeman slower and a two-dimensional MOT within an order of magnitude smaller length than standard sodium sources. We achieve an atomic flux exceeding 4x10^9 atoms/s loaded in a MOT, with a most probable longitudinal velocity of 20 m/s, and a brightness larger than 2.5x10^(12) atoms/s/sr. This atomic source allowed us to produce a pure BEC with more than 10^7 atoms and a background pressure limited lifetime of 5 minutes.Comment: 8 pages, 6 figures, submitted to Phys. Rev.

    Dynamical Equilibration Across a Quenched Phase Transition in a Trapped Quantum Gas

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    The formation of an equilibrium quantum state from an uncorrelated thermal one through the dynamical crossing of a phase transition is a central question of non-equilibrium many-body physics. During such crossing, the system breaks its symmetry by establishing numerous uncorrelated regions separated by spontaneously-generated defects, whose emergence obeys a universal scaling law with the quench duration. Much less is known about the ensuing re-equilibrating or "coarse-graining" stage, which is governed by the evolution and interactions of such defects under system-specific and external constraints. In this work we perform a detailed numerical characterization of the entire non-equilibrium process, addressing subtle issues in condensate growth dynamics and demonstrating the quench-induced decoupling of number and coherence growth during the re-equilibration process. Our unique visualizations not only reproduce experimental measurements in the relevant regimes, but also provide valuable information in currently experimentally-inaccessible regimes.Comment: Supplementary Movie Previes: SM-Movie-1: https://youtu.be/3q7-CvuBylg SM-Movie-2: https://youtu.be/-Gymaiv9rC0 SM-Movie-3: https://youtu.be/w-O2SPiw3nE SM-Movie-4: https://youtu.be/P4xGyr4dwK

    Logic tensor networks for semantic image interpretation

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    Semantic Image Interpretation (SII) is the task of extracting structured semantic descriptions from images. It is widely agreed that the combined use of visual data and background knowledge is of great importance for SII. Recently, Statistical Relational Learning (SRL) approaches have been developed for reasoning under uncertainty and learning in the presence of data and rich knowledge. Logic Tensor Networks (LTNs) are a SRL framework which integrates neural networks with first-order fuzzy logic to allow (i) efficient learning from noisy data in the presence of logical constraints, and (ii) reasoning with logical formulas describing general properties of the data. In this paper, we develop and apply LTNs to two of the main tasks of SII, namely, the classification of an image's bounding boxes and the detection of the relevant part-of relations between objects. To the best of our knowledge, this is the first successful application of SRL to such SII tasks. The proposed approach is evaluated on a standard image processing benchmark. Experiments show that background knowledge in the form of logical constraints can improve the performance of purely data-driven approaches, including the state-of-theart Fast Region-based Convolutional Neural Networks (Fast R-CNN). Moreover, we show that the use of logical background knowledge adds robustness to the learning system when errors are present in the labels of the training data

    Echocardiography and pulse contour analysis to assess cardiac output in trauma patients.

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    Echocardiography is a valuable technique to assess cardiac output (CO) in trauma patients, but it does not allow a continuous bedside monitoring. Beat-to-beat CO assessment can be obtained by other techniques, including the pulse contour method MostCare. The aim of our study was to compare CO obtained with MostCare (MC-CO) with CO estimated by transthoracic echocardiography (TTE-CO) in trauma patients. METHODS: Forty-nine patients with blunt trauma admitted to an intensive care unit and requiring hemodynamic optimization within 24 hours from admission were studied. TTE-CO and MC-CO were estimated simultaneously at baseline, after a fluid challenge and after the start of vasoactive drug therapy. RESULTS: One hundred sixteen paired CO values were obtained. TTE-CO values ranged from 2.9 to 7.6 L·min-1, and MC-CO ranged from 2.8 to 8.2 L·min-1. The correlation between the two methods was 0.94 (95% confidence interval [CI] = 0.89 to 0.97; p<0.001). The mean bias was -0.06 L·min-1 with limits of agreements (LoA) of -0.94 to 0.82 L·min-1 (lower 95% CI, -1.16 to -0.72; upper 95% CI, 0.60 to 1.04) and a percentage error of 18%. Changes in CO showed a correlation of 0.91 (95% CI = 0.87 to 0.95; p<0.001), a mean bias of - 0.01 L·min-1 with LoA of -0.67 to 0.65 L·min-1 (lower 95% CI, -0.83 to -0.51; upper 95% CI, 0.48 to 0.81). CONCLUSION: CO measured by MostCare showed good agreement with CO obtained by transthoracic echocardiography. Pulse contour analysis can complement echocardiography in evaluating hemodynamics in trauma patients

    Effects of changes in arterial pressure on organ perfusion during septic shock

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    Septic shock is characterized by altered tissue perfusion associated with persistent arterial hypotension. Vasopressor therapy is generally required to restore organ perfusion but the optimal mean arterial pressure (MAP) that should be targeted is uncertain. The aim of this study was to assess the effects of increasing MAP using norepinephrine (NE) on hemodynamic and metabolic variables and on microvascular reactivity in patients with septic shock.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

    The boundary Riemann solver coming from the real vanishing viscosity approximation

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    We study a family of initial boundary value problems associated to mixed hyperbolic-parabolic systems: v^{\epsilon} _t + A (v^{\epsilon}, \epsilon v^{\epsilon}_x ) v^{\epsilon}_x = \epsilon B (v^{\epsilon} ) v^{\epsilon}_{xx} The conservative case is, in particular, included in the previous formulation. We suppose that the solutions vϵv^{\epsilon} to these problems converge to a unique limit. Also, it is assumed smallness of the total variation and other technical hypotheses and it is provided a complete characterization of the limit. The most interesting points are the following two. First, the boundary characteristic case is considered, i.e. one eigenvalue of AA can be 00. Second, we take into account the possibility that BB is not invertible. To deal with this case, we take as hypotheses conditions that were introduced by Kawashima and Shizuta relying on physically meaningful examples. We also introduce a new condition of block linear degeneracy. We prove that, if it is not satisfied, then pathological behaviours may occur.Comment: 84 pages, 6 figures. Text changes in Sections 1 and 3.2.3. Added Section 3.1.2. Minor changes in other section

    Spontaneous creation of Kibble-Zurek solitons in a Bose-Einstein condensate

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    When a system crosses a second-order phase transition on a finite timescale, spontaneous symmetry breaking can cause the development of domains with independent order parameters, which then grow and approach each other creating boundary defects. This is known as Kibble-Zurek mechanism. Originally introduced in cosmology, it applies both to classical and quantum phase transitions, in a wide variety of physical systems. Here we report on the spontaneous creation of solitons in Bose-Einstein condensates via the Kibble-Zurek mechanism. We measure the power-law dependence of defects number with the quench time, and provide a check of the Kibble-Zurek scaling with the sonic horizon. These results provide a promising test bed for the determination of critical exponents in Bose-Einstein condensates.Comment: 7 pages, 4 figure

    Atypical hemolytic uremic syndrome: Unique clinical presentation linked to rare CFHR5 mutation.

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    In adults, the diagnosis and the clinical management of atypical hemolytic uremic syndrome is still a challenge for hematologists [1–3]. Here, we report a case of a 40-year-old previously healthy man presented to the emergency department with fever (39.6◦C) and bilateral persistent foot pain

    Fatal cytokine release syndrome by an aberrant FLIP/STAT3 axis

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    Inflammatory responses rapidly detect pathogen invasion and mount a regulated reaction. However, dysregulated anti-pathogen immune responses can provoke life-threatening inflammatory pathologies collectively known as cytokine release syndrome (CRS), exemplified by key clinical phenotypes unearthed during the SARS-CoV-2 pandemic. The underlying pathophysiology of CRS remains elusive. We found that FLIP, a protein that controls caspase-8 death pathways, was highly expressed in myeloid cells of COVID-19 lungs. FLIP controlled CRS by fueling a STAT3-dependent inflammatory program. Indeed, constitutive expression of a viral FLIP homolog in myeloid cells triggered a STAT3-linked, progressive, and fatal inflammatory syndrome in mice, characterized by elevated cytokine output, lymphopenia, lung injury, and multiple organ dysfunctions that mimicked human CRS. As STAT3-targeting approaches relieved inflammation, immune disorders, and organ failures in these mice, targeted intervention towards this pathway could suppress the lethal CRS inflammatory state

    suPAR as a prognostic biomarker in sepsis

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    Sepsis is the clinical syndrome derived from the host response to an infection and severe sepsis is the leading cause of death in critically ill patients. Several biomarkers have been tested for use in diagnosis and prognostication in patients with sepsis. Soluble urokinase-type plasminogen activator receptor (suPAR) levels are increased in various infectious diseases, in the blood and also in other tissues. However, the diagnostic value of suPAR in sepsis has not been well defined, especially compared to other more established biomarkers, such as C-reactive protein (CRP) and procalcitonin (PCT). On the other hand, suPAR levels have been shown to predict outcome in various kinds of bacteremia and recent data suggest they may have predictive value, similar to that of severity scores, in critically ill patients. This narrative review provides a descriptive overview of the clinical value of this biomarker in the diagnosis, prognosis and therapeutic guidance of sepsis
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