41 research outputs found

    Experimental status of 7Be production and destruction at astrophysical relevant energies

    No full text
    The production and destruction of 7Be plays a significant role in the Big Bang Nucleosynthesis as well as in the framework of the solar neutrino. The 3He(α, γ)7Be reaction cross sections has been measured several times in the last decades, but the precision achieved on reaction rate determinations at the relevant astrophysical energies is not yet satisfactory. The experimental status of this reaction will be critically reviewed, and the theoretical descriptions available will be discussed

    Recent Achievements of the ERNA Collaboration

    Get PDF
    For more than two decades, the ERNA collaboration has investigated nuclear processes of astrophysical interest through the direct measurement of cross sections or the identification of the nucleosynthesis effects. Measurements of cross-section, reported in this publication, of radiative capture reactions have been mainly conducted using the ERNA Recoil Mass Separator, and more recently with an array of charged particle detector telescopes designed for nuclear astrophysics measurements. Some results achieved with ERNA will be reviewed, with a focus on the results most relevant for nucleosynthesis in AGB and advanced burning phases

    Improved astrophysical rate for the 18O(p,α)15N reaction by underground measurements

    Get PDF
    The 18O(p,\u3b1)15N reaction affects the synthesis of 15N, 18O and 19F isotopes, whose abundances can be used to probe the nucleosynthesis and mixing processes occurring deep inside asymptotic giant branch (AGB) stars. We performed a low-background direct measurement of the 18O(p,\u3b1)15N reaction cross-section at the Laboratory for Underground Nuclear Astrophysics (LUNA) from center of mass energy Ec.m.=340keV down to Ec.m.=55keV, the lowest energy measured to date corresponding to a cross-section of less than 1 picobarn/sr. The strength of a key resonance at center of mass energy Er=90keV was found to be a factor of 10 higher than previously reported. A multi-channel R-matrix analysis of our and other data available in the literature was performed. Over a wide temperature range, T=0.01\u20131.00GK, our new astrophysical rate is both more accurate and precise than recent evaluations. Stronger constraints can now be placed on the physical processes controlling nucleosynthesis in AGB stars with interesting consequences on the abundance of 18O in these stars and in stardust grains, specifically on the production sites of oxygen-rich Group II grains

    Elective surgery cancellations due to the COVID-19 pandemic: global predictive modelling to inform surgical recovery plans.

    Get PDF
    BACKGROUND: The COVID-19 pandemic has disrupted routine hospital services globally. This study estimated the total number of adult elective operations that would be cancelled worldwide during the 12 weeks of peak disruption due to COVID-19. METHODS: A global expert response study was conducted to elicit projections for the proportion of elective surgery that would be cancelled or postponed during the 12 weeks of peak disruption. A Bayesian β-regression model was used to estimate 12-week cancellation rates for 190 countries. Elective surgical case-mix data, stratified by specialty and indication (surgery for cancer versus benign disease), were determined. This case mix was applied to country-level surgical volumes. The 12-week cancellation rates were then applied to these figures to calculate the total number of cancelled operations. RESULTS: The best estimate was that 28 404 603 operations would be cancelled or postponed during the peak 12 weeks of disruption due to COVID-19 (2 367 050 operations per week). Most would be operations for benign disease (90·2 per cent, 25 638 922 of 28 404 603). The overall 12-week cancellation rate would be 72·3 per cent. Globally, 81·7 per cent of operations for benign conditions (25 638 922 of 31 378 062), 37·7 per cent of cancer operations (2 324 070 of 6 162 311) and 25·4 per cent of elective caesarean sections (441 611 of 1 735 483) would be cancelled or postponed. If countries increased their normal surgical volume by 20 per cent after the pandemic, it would take a median of 45 weeks to clear the backlog of operations resulting from COVID-19 disruption. CONCLUSION: A very large number of operations will be cancelled or postponed owing to disruption caused by COVID-19. Governments should mitigate against this major burden on patients by developing recovery plans and implementing strategies to restore surgical activity safely

    Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study

    Get PDF
    BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223

    Measurement of 3^{3}He(α\alpha, γ\gamma)7^{7}Be cross section with the recoil mass separator ERNA

    No full text
    Die Arbeit beschreibt die Durchführung einer Messung des absoluten Wirkungsquerschnitts der Reaktion 3^{3}He(α\alpha, γ\gamma)7^{7}Be im Energiebereich von Ecm_{cm}=0.65 - 3.15 MeV. Die Messung fand in inverser Kinematik am Europäischen Rückstoß-Separator für Nukleare Astrophysik ERNA statt. Mit diesem Gerät werden die Beryllium-Rückstoßkerne direkt nachgewiesen. Das fensterloses, doppelseitig differentiell gepumpte, rezirkulierende 3^{3}He-Gastarget wurde charakterisiert. In weiteren Messungen wurde dann zusätzlich die direkte γ\gamma-Strahlung gemessen, sowie in einem weiteren Abschnitt des Experiments eine Aktivierungsmessung vorgenommen. Die Übereinstimmungen der zur Extrapolation verwendeten Theorien mit den experimentellen Wirkungsquerschnitts-Daten wurden untersucht.This work reports on the results of a new experimental approach, where the absolute cross section of the nuclear reaction 3^{3}He(α\alpha, γ\gamma)7^{7}Be is determined by the direct detection of the 7^{7}Be recoils using the European Recoil mass separator for Nuclear Astrophysics (ERNA) at the Dynamitron Tandem Laboratorium of the Ruhr-Universität Bochum. The modifications to the experimental setup to match the requirements of this reaction, including the characterization of the windowless differentially pumped recirculating 3^{3}He gas-target are presented. Determinations of the cross section through the detection of the γ\gamma-rays in coincidence with the recoils at selected energies as well with the activation\it {activation} method are made. The extrapolation of the S-factor to solar energies with the available theories is discussed in detail

    The SHADES neutron detection array

    No full text
    The detection of neutrons in low energy astrophysics poses two main problems: low cross section measurement requires high detection efficiency and ideally, beam-induced and external neutron backgrounds should be identified through an energy sensitive detector. In recent years, capture-gated neutron spectroscopy has found new opportunities to grow through new materials and better availability of modern data acquisition systems. In this work we will present the design, expected capabilities and preliminary characterization of the hybrid neutron detector array SHADES. Its purpose is the first direct measurement of the reaction 22Ne(α, n)25Mg in the Gamow window for s-process nucleosynthesis with LUNA-MV in the deep underground environment of the LNGS

    evaluation of the aquatic toxicity of two veterinary sulfonamides using five test organisms

    No full text
    The aquatic toxicity of sulfaquinoxaline (SQO) and sulfaguanidine (SGD) was evaluated on the following test organisms: Daphnia magna (reproduction test), Pseudokirchneriella subcapitata, Scenedesmus dimorphus, Synecococcus leopoliensis (algal growth inhibition test) and Lemna gibba (duckweed growth inhibition test). Furthermore, the additivity of the two compounds was measured on D. magna (acute immobilisation test) and P. subcapitata (algal growth inhibition test) using the isobologram method. Results show that SQO and SGD are more toxic to green algae and daphnids, respectively, than other veterinary sulfonamides (SAs) and that their mixtures have a less then additive interaction. Taking into account the highest concentrations detected so far in surface waters for SQO (0.112 lg L_1) and for SGD (0.145 lg L_1) and the lowest NOECs obtained with the five test organisms, divided by an assessment factor of 10, the following PNECs and risk quotients (RQs) were calculated. SQO: PNEC 2 lg L_1; RQ 0.056. SGD: PNEC 39.5 lg L_1; RQ 0.004. Consequently, at the concentrations actually detected in the aquatic environment, the two SAs alone should not harm the freshwater organisms. However, it seems advisable, for veterinary mass treatments, the use of other SAs that have a lesser impact on the aquatic environment. Furthermore, considering the high probability of having complex mixtures of different SAs residues in water, each individual contamination should be evaluated by applying to the SAs mixtures the conservative criteria of additivity
    corecore