Role of Interstitial and Interstitial-Impurity Interaction on Irradiation-Induced Segregation in Austenitic Steels

ABSTRACTSegregation under irradiation in austenitic steels is due to a permanent flux of vacancies and interstitials produced by irradiation towards sinks like surfaces and interfaces. A model based on a mean field lattice rate theory is proposed where kinetics and thermodynamics are treated in a mutually consistent way. For a Fe-Ni-Cr ternary alloy, the 15 parameters defining the jump frequencies of vacancies were fitted on equilibrium properties including ordering energies and tracer diffusion experiments with no use of segregation data. Measurements of RIS by Auger Electron Spectroscopy (AES) were used in the last step of the fitting procedure in order to choose the best set of the 27 interstitial jump frequencies. This fitting procedure strongly supports the idea that the interstitials are contributing to RIS in Fe-Cr-Ni alloys. We also simulate the trapping of interstitials by an impurity model and reproduce the total inhibition of RIS by this impurity as observed experimentally [1].</jats:p

Noninferiority trials: a specific design with a particular methodology

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Is passive leg raising clinically useful in predicting intradialytic hypotension?

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Mean arterial pressure is a major determinant of hypotension prediction index

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Fluid removal tolerance during the de-escalation phase: is preload unresponsiveness the best guiding candidate?

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Relationship between point-of-care ultrasound venous congestion assessment parameters, intravenous pressure, and venous return: a post-hoc analysis of a prospective cohort study

Abstract Background A recent study suggested that point-of-care ultrasound (POCUS) venous congestion assessment poorly describes the changes in venous return during a fluid challenge. The aim of the present study was to explore the relationship between POCUS venous congestion assessment parameters and the determinants of venous return in steady state and during a fluid challenge. Methods This study is a post-hoc analysis of a single-centre prospective cohort study of patients presenting acute circulatory failure and venous congestion. The protocol consisted in a fluid administration of 4mL/kg over five minutes, just preceded and followed by the acquisition of haemodynamic data and POCUS venous congestion assessment parameters (VExUS score and portal pulsatility index, PPi). Venous return (dVR) was defined as the difference between mean systemic filling pressure analogue estimated by the mathematical approach of Parkin and Leaning (Pmsa) and central venous pressure (CVP). Relationships between Pmsa, CVP, dVR, and VExUS score and PPi were analysed using linear regression and Jonckheere-Terpstra test for trend. Results Thirty-two patients were included in the analysis. Fluid challenge induced a significant increase in CVP, Pmsa, dVR, and VExUS score. In steady state, there was a significant association of VExUS score and PPi with CVP (P-value = 0.006 and 0.002, respectively) and Pmsa (P-value = 0.004 and 0.003, respectively) but not with dVR (P-value = 0.943 and 0.408, respectively). The variations induced by fluid challenge in CVP, Pmsa and dVR were not associated with variations in PPi (P-value = 0.844, 0.912 and 0.716, respectively). Patients without VExUS score increase during the fluid challenge presented a higher increase in Pmsa than patients with an increase in VExUS score. Conclusion In steady state, POCUS venous congestion assessment parameters are associated with CVP and Pmsa but not with dVR. After fluid administration, changes in POCUS venous congestion assessment parameters were not associated with changes in CVP, Pmsa, and dVR

Prevention and Treatment of New-Onset Postoperative Atrial Fibrillation in the Acute Care Setting: A Narrative Review

New-onset postoperative atrial fibrillation (POAF) is common after cardiac and major noncardiac surgery and significantly associated with short- and long-term adverse events. Multiple management strategies have been described but the lack of evidence from large randomized controlled trials and the lack of consensus regarding best practices has led to major variations in practice patterns. Considering on the one hand its serious adverse effects and complex drug interactions, and on the other hand discrepancies among recent international guidelines, the indications of amiodarone to both prevent and treat POAF should be reserved to patients at high risk of POAF only, or patients with hemodynamic instability and/or severely reduced left ventricular ejection fraction. Perioperative optimization of oral and intravenous cardio-selective beta-blockers to prevent POAF, and control heart rate when POAF occurs with a rapid ventricular response is the recommended first-line strategy, simultaneously with the treatment of associated factors. Given their efficient and safe profile, ultra-short-acting intravenous beta-blockers like esmolol or landiolol could be preferentially used in acute care patients. Besides waiting for the results of ongoing RCTs in cardiac and noncardiac surgery, the use of oral anticoagulation in patients with POAF should take into account the individualized thromboembolic/hemorrhagic risk ratio