Dislocation Driven Chromium Precipitation in Fe-9Cr Binary Alloy: A Positron Lifetime Study

The influence of initial heat treatment on anomalous Cr precipitation within high temperature solubility region in Fe-9Cr alloy has been investigated using positron lifetime studies. Air-quenched samples with pre-existing dislocations exhibited a distinct annealing stage in positron lifetime between 800 and 1100 K corresponding to Cr-precipitation. During this stage, Transmission Electron Microscopy showed fine precipitates of average size 4 nm, dispersed throughout the sample and from EDS analysis they are found to be Cr-enriched. The existence of dislocations is found to be responsible for Cr precipitation.Comment: Revised version Submitted to Phys. Rev.

Rivaroxaban or aspirin for patent foramen ovale and embolic stroke of undetermined source: a prespecified subgroup analysis from the NAVIGATE ESUS trial

Background: Patent foramen ovale (PFO) is a contributor to embolic stroke of undetermined source (ESUS). Subgroup analyses from previous studies suggest that anticoagulation could reduce recurrent stroke compared with antiplatelet therapy. We hypothesised that anticoagulant treatment with rivaroxaban, an oral factor Xa inhibitor, would reduce the risk of recurrent ischaemic stroke compared with aspirin among patients with PFO enrolled in the NAVIGATE ESUS trial. Methods: NAVIGATE ESUS was a double-blinded, randomised, phase 3 trial done at 459 centres in 31 countries that assessed the efficacy and safety of rivaroxaban versus aspirin for secondary stroke prevention in patients with ESUS. For this prespecified subgroup analysis, cohorts with and without PFO were defined on the basis of transthoracic echocardiography (TTE) and transoesophageal echocardiography (TOE). The primary efficacy outcome was time to recurrent ischaemic stroke between treatment groups. The primary safety outcome was major bleeding, according to the criteria of the International Society of Thrombosis and Haemostasis. The primary analyses were based on the intention-to-treat population. Additionally, we did a systematic review and random-effects meta-analysis of studies in which patients with cryptogenic stroke and PFO were randomly assigned to receive anticoagulant or antiplatelet therapy. Findings: Between Dec 23, 2014, and Sept 20, 2017, 7213 participants were enrolled and assigned to receive rivaroxaban (n=3609) or aspirin (n=3604). Patients were followed up for a mean of 11 months because of early trial termination. PFO was reported as present in 534 (7·4%) patients on the basis of either TTE or TOE. Patients with PFO assigned to receive aspirin had a recurrent ischaemic stroke rate of 4·8 events per 100 person-years compared with 2·6 events per 100 person-years in those treated with rivaroxaban. Among patients with known PFO, there was insufficient evidence to support a difference in risk of recurrent ischaemic stroke between rivaroxaban and aspirin (hazard ratio [HR] 0·54; 95% CI 0·22-1·36), and the risk was similar for those without known PFO (1·06; 0·84-1·33; pinteraction=0·18). The risks of major bleeding with rivaroxaban versus aspirin were similar in patients with PFO detected (HR 2·05; 95% CI 0·51-8·18) and in those without PFO detected (HR 2·82; 95% CI 1·69-4·70; pinteraction=0·68). The random-effects meta-analysis combined data from NAVIGATE ESUS with data from two previous trials (PICSS and CLOSE) and yielded a summary odds ratio of 0·48 (95% CI 0·24-0·96; p=0·04) for ischaemic stroke in favour of anticoagulation, without evidence of heterogeneity. Interpretation: Among patients with ESUS who have PFO, anticoagulation might reduce the risk of recurrent stroke by about half, although substantial imprecision remains. Dedicated trials of anticoagulation versus antiplatelet therapy or PFO closure, or both, are warranted

1013 Preoperative Nasopharyngeal Swab Testing and Postoperative Pulmonary Complications in Patients Undergoing Elective Surgery During The SARS-Cov-2 Pandemic

Abstract Introduction This study aimed to evaluate the association between preoperative SARS-CoV-2 testing and postoperative pulmonary complications in patients undergoing elective cancer surgery. Method International cohort study including adult patients undergoing elective surgery for cancer in areas affected by SARS-CoV-2 up to 19 April 2020 (NCT04384926). Patients suspected preoperatively of SARS-CoV-2 infection were excluded. The primary outcome measure was postoperative pulmonary complications at 30 days after surgery. Results Of 8784 patients (432 hospitals, 53 countries), 2303 patients (26.2%) underwent preoperative testing: 1458 (16.6%) had a swab test, 521 (5.9%) CT only, and 324 (3.7%) swab and CT. The overall pulmonary complication rate was 3.9% and SARS-CoV-2 infection rate was 2.6%. After risk adjustment, only a nasopharyngeal swab test (adjusted odds ratio 0.68, 95% confidence interval 0.68-0.98, p = 0.040) was associated with lower rates of pulmonary complications. Swab testing remained beneficial before major surgery and in high SARS-CoV-2 population risk areas but not before minor surgery in low incidence areas. Conclusions Preoperative nasopharyngeal swab testing was beneficial before major surgery and in high SARS-CoV-2 incidence areas. There was no proven benefit of swab testing before minor surgery in low incidence areas. </jats:sec