129 research outputs found

    Cosmological constraints on neutrino self-interactions with a light mediator

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    If active neutrinos undergo non-standard (`secret') interactions (NSÎœ\nuI) the cosmological evolution of the neutrino fluid might be altered, leaving an imprint in cosmological observables. We use the latest publicly available CMB data from Planck to constrain NSÎœ\nuI inducing Μ−Μ\nu-\nu scattering, under the assumption that the mediator ϕ\phi of the secret interaction is very light. We find that the effective coupling constant of the interaction, geff4â‰ĄâŸšÏƒv⟩TÎœ2g_\mathrm{eff}^4 \equiv \langle \sigma v\rangle T_\nu^2, is constrained at <2.35×10−27< 2.35\times10^{-27} (95\% credible interval), which stregthens to geff4<1.64×10−27g_\mathrm{eff}^4 < 1.64\times10^{-27} when Planck non-baseline small-scale polarization is considered. Our findings imply that after decoupling at T≃1T\simeq 1 MeV, cosmic neutrinos are free streaming at redshifts z>3800z>3800, or z>2300z>2300 if small-scale polarization is included. These bounds are only marginally improved when data from geometrical expansion probes are included in the analysis to complement Planck. We also find that the tensions between CMB and low-redshift measurements of the expansion rate H0H_0 and the amplitude of matter fluctuations σ8\sigma_8 are not significantly reduced. Our results are independent on the underlying particle physics model as long as ϕ\phi is very light. Considering a model with Majorana neutrinos and a pseudoscalar mediator we find that the coupling constant gg of the secret interaction is constrained at â‰Č7×10−7\lesssim 7\times 10^{-7}. By further assuming that the pseudoscalar interaction comes from a dynamical realization of the see-saw mechanism, as in Majoron models, we can bound the scale of lepton number breaking vσv_\sigma as ≳(1.4×106)mÎœ\gtrsim (1.4\times 10^{6})m_\nu.Comment: V2. Replaced to match version accepted for publication in PRD. Added more detailed discussion about parameter degeneracies. 14 pages, 6 figures, 3 table

    Preclinical and clinical evidence on the approach-avoidance conflict evaluation as an integrative tool for psychopathology

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    The approach-avoidance conflict (AAC), i.e. the competing tendencies to undertake goal-directed actions or to withdraw from everyday life challenges, stands at the basis of humans' existence defining behavioural and personality domains. Gray's Reinforcement Sensitivity Theory posits that a stable bias toward approach or avoidance represents a psychopathological trait associated with excessive sensitivity to reward or punishment. Optogenetic studies in rodents and imaging studies in humans associated with cross-species AAC paradigms granted new emphasis to the hippocampus as a hub of behavioural inhibition. For instance, recent functional neuroimaging studies show that functional brain activity in the human hippocampus correlates with threat perception and seems to underlie passive avoidance. Therefore, our commentary aims to (i) discuss the inhibitory role of the hippocampus in approach-related behaviours and (ii) promote the integration of functional neuroimaging with cross-species AAC paradigms as a means of diagnostic, therapeutic, follow up and prognosis refinement in psychiatric populations

    Thermalisation of sterile neutrinos in the early universe in the 3+1 scheme with full mixing matrix

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    In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full 4×4 mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, Neff, and its dependence on the three additional mixing angles (ξ_14, ξ_24, ξ_34) and on the squared mass difference Δm^2_41 is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised (Neff≃4)

    Hospital-Acquired Infections in Critically Ill Patients With COVID-19

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    Background: Few small studies have described hospital-acquired infections (HAIs) occurring in patients with COVID-19. Research Question: What characteristics in critically ill patients with COVID-19 are associated with HAIs and how are HAIs associated with outcomes in these patients? Study Design and Methods: Multicenter retrospective analysis of prospectively collected data including adult patients with severe COVID-19 admitted to eight Italian hub hospitals from February 20, 2020, through May 20, 2020. Descriptive statistics and univariate and multivariate Weibull regression models were used to assess incidence, microbial cause, resistance patterns, risk factors (ie, demographics, comorbidities, exposure to medication), and impact on outcomes (ie, ICU discharge, length of ICU and hospital stays, and duration of mechanical ventilation) of microbiologically confirmed HAIs. Results: Of the 774 included patients, 359 patients (46%) demonstrated 759 HAIs (44.7 infections/1,000 ICU patient-days; 35% multidrug-resistant [MDR] bacteria). Ventilator-associated pneumonia (VAP; n = 389 [50%]), bloodstream infections (BSIs; n = 183 [34%]), and catheter-related BSIs (n = 74 [10%]) were the most frequent HAIs, with 26.0 (95% CI, 23.6-28.8) VAPs per 1,000 intubation-days, 11.7 (95% CI, 10.1-13.5) BSIs per 1,000 ICU patient-days, and 4.7 (95% CI, 3.8-5.9) catheter-related BSIs per 1,000 ICU patient-days. Gram-negative bacteria (especially Enterobacterales) and Staphylococcus aureus caused 64% and 28% of cases of VAP, respectively. Variables independently associated with infection were age, positive end expiratory pressure, and treatment with broad-spectrum antibiotics at admission. Two hundred thirty-four patients (30%) died in the ICU (15.3 deaths/1,000 ICU patient-days). Patients with HAIs complicated by septic shock showed an almost doubled mortality rate (52% vs 29%), whereas noncomplicated infections did not affect mortality. HAIs prolonged mechanical ventilation (median, 24 days [interquartile range (IQR), 14-39 days] vs 9 days [IQR, 5-13 days]; P &lt; .001), ICU stay (24 days [IQR, 16-41 days] vs 9 days [IQR, 6-14 days]; P = .003), and hospital stay (42 days [IQR, 25-59 days] vs 23 days [IQR, 13-34 days]; P &lt; .001). Interpretation: Critically ill patients with COVID-19 are at high risk for HAIs, especially VAPs and BSIs resulting from MDR organisms. HAIs prolong mechanical ventilation and hospitalization, and HAIs complicated by septic shock almost double mortality. Trial Registry: ClinicalTrials.gov; No.: NCT04388670; URL: www.clinicaltrials.go

    Planck intermediate results. XLIX. Parity-violation constraints from polarization data

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    Parity-violating extensions of the standard electromagnetic theory cause in vacuo rotation of the plane of polarization of propagating photons. This effect, also known as cosmic birefringence, has an impact on the cosmic microwave background (CMB) anisotropy angular power spectra, producing non-vanishing T–B and E–B correlations that are otherwise null when parity is a symmetry. Here we present new constraints on an isotropic rotation, parametrized by the angle α, derived from Planck 2015 CMB polarization data. To increase the robustness of our analyses, we employ two complementary approaches, in harmonic space and in map space, the latter based on a peak stacking technique. The two approaches provide estimates for α that are in agreement within statistical uncertainties and are very stable against several consistency tests.Considering the T–B and E–B information jointly, we find from the harmonic analysis and from the stacking approach. These constraints are compatible with no parity violation and are dominated by the systematic uncertainty in the orientation of Planck’s polarization-sensitive bolometers

    Planck 2018 results. VIII. Gravitational lensing

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    We present measurements of the cosmic microwave background (CMB) lensing potential using the final Planck 2018 temperature and polarization data. We increase the significance of the detection of lensing in the polarization maps from 5σ to 9σ. Combined with temperature, lensing is detected at 40σ4. We present an extensive set of tests of the robustness of the lensing-potential power spectrum, and construct a minimum-variance estimator likelihood over lensing multipoles 8≀L≀400. We find good consistency between lensing constraints and the results from the Planck CMB power spectra within the ΛCDMΛCDM model. Combined with baryon density and other weak priors, the lensing analysis alone constrains σ8Ω0.25m=0.589±0.020 (1σ errors). Also combining with baryon acoustic oscillation (BAO) data, we find tight individual parameter constraints, σ8=0.811±0.019, H0=67.9+1.2−1.3kms−1Mpc−1, and Ωm=0.303+0.016−0.018. Combining with Planck CMB power spectrum data, we measure σ8 to better than 1% precision, finding σ8=0.811±0.006. We find consistency with the lensing results from the Dark Energy Survey, and give combined lensing-only parameter constraints that are tighter than joint results using galaxy clustering. Using Planck cosmic infrared background (CIB) maps we make a combined estimate of the lensing potential over 60% of the sky with considerably more small-scale signal. We demonstrate delensing of the Planck power spectra, detecting a maximum removal of 40% of the lensing-induced power in all spectra. The improvement in the sharpening of the acoustic peaks by including both CIB and the quadratic lensing reconstruction is detected at high significance (abridged)

    Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth

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    This paper describes the identification, modelling, and removal of previously unexplained systematic effects in the polarization data of the Planck High Frequency Instrument (HFI) on large angular scales, including new mapmaking and calibration procedures, new and more complete end-to-end simulations, and a set of robust internal consistency checks on the resulting maps. These maps, at 100, 143, 217, and 353 GHz, are early versions of those that will be released in final form later in 2016. The improvements allow us to determine the cosmic reionization optical depth τ using, for the first time, the low-multipole EE data from HFI, reducing significantly the central value and uncertainty, and hence the upper limit. Two different likelihood procedures are used to constrain τ from two estimators of the CMB E- and B-mode angular power spectra at 100 and 143 GHz, after debiasing the spectra from a small remaining systematic contamination. These all give fully consistent results. A further consistency test is performed using cross-correlations derived from the Low Frequency Instrument maps of the Planck 2015 data release and the new HFI data. For this purpose, end-to-end analyses of systematic effects from the two instruments are used to demonstrate the near independence of their dominant systematic error residuals. The tightest result comes from the HFI-based τ posterior distribution using the maximum likelihood power spectrum estimator from EE data only, giving a value 0.055 ± 0.009. In a companion paper these results are discussed in the context of the best-fit PlanckΛCDM cosmological model and recent models of reionization
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