Small substitutions of BaZrO, into Ba[(Zn,Ni),Ta,]O, are utilized in the commercial preparation of low-loss perovskite microwave dielectrics. The structures of a series of these phases with substitution levels ranging from 1% to 5% BaZrO, were examined using high-resolution TEM.For I2.15% BaZrO, the solid solutions retain the ordered "1:2" structure of the Ba[(Zn,Ni),,Ta,]O, end-member but are comprised of small ordered domains whose size decreases as the Zr content is raised. The decrease in the size of the domains parallels a decrease in the processing time required to access a low-loss state. Although for pure Ba[(Zn,Ni),,Ta,]O, reductions in the degree of cation order produce a large increase in the dielectric loss, the Zrsubstituted ceramics retain a very low loss. We believe the low losses of the 1:2 ceramics are derived from the stabilization of the ordering-induced domain boundaries via the partial segregation of the Zr cations. For substitutions between 3% and 5 % BaZrO, the size of the ordered domains continues to decrease but the system undergoes an abrupt transformation to a cubic "1:l" ordered structure with a doubled perovskite repeat. The structures of these phases have been interpreted using a "random layer" model in which one site is occupied by Ta and the other by a random distribution of Zn, Zr, and the remaining Ta cations, i.e., ing is confined to nano-sized domains, these ceramics also exhibit low losses, again reflecting the relative stability of the domain boundaries. In this case we believe the low losses reflect the effectiveness of the random layer in stabilizing the anti-phase boundaries.
ImportanceSARS-CoV-2 infection is associated with persistent, relapsing, or new symptoms or other health effects occurring after acute infection, termed postacute sequelae of SARS-CoV-2 infection (PASC), also known as long COVID. Characterizing PASC requires analysis of prospectively and uniformly collected data from diverse uninfected and infected individuals.ObjectiveTo develop a definition of PASC using self-reported symptoms and describe PASC frequencies across cohorts, vaccination status, and number of infections.Design, Setting, and ParticipantsProspective observational cohort study of adults with and without SARS-CoV-2 infection at 85 enrolling sites (hospitals, health centers, community organizations) located in 33 states plus Washington, DC, and Puerto Rico. Participants who were enrolled in the RECOVER adult cohort before April 10, 2023, completed a symptom survey 6 months or more after acute symptom onset or test date. Selection included population-based, volunteer, and convenience sampling.ExposureSARS-CoV-2 infection.Main Outcomes and MeasuresPASC and 44 participant-reported symptoms (with severity thresholds).ResultsA total of 9764 participants (89% SARS-CoV-2 infected; 71% female; 16% Hispanic/Latino; 15% non-Hispanic Black; median age, 47 years [IQR, 35-60]) met selection criteria. Adjusted odds ratios were 1.5 or greater (infected vs uninfected participants) for 37 symptoms. Symptoms contributing to PASC score included postexertional malaise, fatigue, brain fog, dizziness, gastrointestinal symptoms, palpitations, changes in sexual desire or capacity, loss of or change in smell or taste, thirst, chronic cough, chest pain, and abnormal movements. Among 2231 participants first infected on or after December 1, 2021, and enrolled within 30 days of infection, 224 (10% [95% CI, 8.8%-11%]) were PASC positive at 6 months.Conclusions and RelevanceA definition of PASC was developed based on symptoms in a prospective cohort study. As a first step to providing a framework for other investigations, iterative refinement that further incorporates other clinical features is needed to support actionable definitions of PASC.
BackgroundInherited thrombophilias are well‐established predisposing factors for venous thromboembolism, but their role in arterial thrombosis, such as arterial ischemic stroke, remains uncertain. We aimed to evaluate the association between inherited thrombophilia (factor V Leiden, prothrombin G20210A mutation, protein C deficiency, protein S deficiency, and antithrombin deficiency) and risk of arterial ischemic stroke in adults.Methods and ResultsWe searched PubMed, EMBASE, and Cochrane Library Databases from inception to December 31, 2018. We included case‐control or cohort studies of adults reporting the prevalence of inherited thrombophilias in those with arterial ischemic stroke and subjects without arterial ischemic stroke. Two reviewers (T.C., E.D.) independently searched the literature and extracted data. Pooled odds ratios (ORs) and 95% CIs were calculated using random‐effects model. We identified 68 eligible studies, which collectively enrolled 11 916 stroke patients and 96 057 controls. The number of studies reporting factor V Leiden, prothrombin G20210A mutation, protein C deficiency, protein S deficiency, and antithrombin deficiency were 56, 45, 15, 17, and 12, respectively. Compared with controls, patients with arterial ischemic stroke were significantly more likely to have the following inherited thrombophilias: factor V Leiden (OR, 1.25; 95% CI, 1.08–1.44; I2=0%), prothrombin G20210A mutation (OR, 1.48; 95% CI, 1.22–1.80; I2=0%), protein C deficiency (OR, 2.13; 95% CI, 1.16–3.90; I2=0%), and protein S deficiency (OR, 2.26; 95% CI, 1.34–3.80; I2=8.8%). Statistical significance was not reached for antithrombin deficiency (OR, 1.25; 95% CI, 0.58–2.67; I2=8.8%).ConclusionsInherited thrombophilias (factor V Leiden, prothrombin G20210A mutation, protein C deficiency, and protein S deficiency) are associated with an increased risk of arterial ischemic stroke in adults. The implications of these findings with respect to clinical management of patients with ischemic stroke require further investigation.
Background The PLASMIC score was developed to identify patients with thrombotic microangiopathy who are most likely to have immune thrombotic thrombocytopenic purpura (TTP) and benefit from therapeutic plasma exchange (TPE). PLASMIC scores of 0‐4, 5, and 6‐7 are said to correspond to low, intermediate, and high probability of TTP, respectively. Study Design and Methods We conducted a systematic review and meta‐analysis on the diagnostic accuracy of the PLASMIC score in adults with suspected TTP. We evaluated the sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of PLASMIC score thresholds of ≥5 and ≥6. Study quality was appraised using the QUADAS‐2 tool. Results We identified 13 eligible studies, which collectively enrolled 970 patients. The median prevalence of TTP among eligible studies was 35%. The sensitivity and specificity of a PLASMIC score ≥5 was 0.99 (95% confidence interval [CI], 0.91‐1.00) and 0.57 (95% CI, 0.41‐0.72), respectively. At a prevalence of 35%, the NPV of a PLASMIC score ≥5 was 0.99 (95% CI, 0.92‐1.00). A PLASMIC score ≥6 was associated with a sensitivity and specificity of 0.85 (95% CI, 0.67‐0.94) and 0.89 (95% CI, 0.81‐0.94), respectively. The NPV of a PLASMIC score ≥6 at a prevalence of 35% was 0.92 (95% CI, 0.82‐0.97). Conclusion A PLASMIC score threshold of ≥5 is associated with high sensitivity and NPV and may be a useful screening tool for identifying patients who are unlikely to have TTP and do not require TPE, though prospective assessment is required. A PLASMIC score <6 appears to have insufficient sensitivity to rule out TTP and the need for TPE.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.