Effect of Na₂CO₃ Replacement Quantity and Activator Modulus on Static Mechanical and Environmental Behaviours of Alkali-Activated-Strain-Hardening-Ultra-High-Performance Concrete

The application of alkali-activated concrete (AAC) shows promise in reducing carbon emissions within the construction industry. However, the pursuit of enhanced performance of AAC has led to a notable increase in carbon emissions, with alkali activators identified as the primary contributors. In an effort to mitigate carbon emissions, this study introduces Na2CO3 as a supplementary activator, partially replacing sodium silicate. The objective is to develop a low-carbon alkali-activated-strain-hardening-ultra-high-performance concrete (ASUHPC). The experimental investigation explores the impact of varying levels of Na2CO3 replacement quantity (0, 0.75 Na2O%, and 1.5 Na2O%) and activator modulus (1.35, 1.5, and 1.65) on the fresh and hardened properties of ASUHPC. The augmentation of Na2CO3 replacement quantity and activator modulus are observed to extend the setting time of the paste, indicating an increase in the modulus of the activator and Na2CO3 replacement quantity would delay the setting time. While the use of Na2CO3 intensifies clustering in the fresh paste, it optimizes particle grading, resulting in higher compressive strength of ASUHPC. The tensile crack width of ASUHPC conforms to the Weibull distribution. ASUHPC with a Na2CO3 replacement quantity of 0.75 Na2O% exhibits superior crack control capabilities, maintaining a mean crack width during tension below 65.78 μm. The tensile properties of ASUHPC exhibit improvement with increasing Na2CO3 replacement quantity and activator modulus, achieving a tensile strength exceeding 9 MPa; otherwise, increasing the activator modulus to 1.5 improves the deformation capacity, reaching 8.58%. Moreover, it is observed that incorporating Na2CO3 as a supplementary activator reduces the carbon emissions of ASUHPC. After considering the tensile performance indicators, increasing the activator modulus can significantly improve environmental performance. The outcomes of this study establish a theoretical foundation for the design of low-carbon, high-performance-alkali-activated-strain-hardening-ultra—high-performance concrete

Implementation of Recommendations on the Use of Corticosteroids in Severe COVID-19

Importance: Research diversity and representativeness are paramount in building trust, generating valid biomedical knowledge, and possibly in implementing clinical guidelines. Objectives: To compare variations over time and across World Health Organization (WHO) geographic regions of corticosteroid use for treatment of severe COVID-19; secondary objectives were to evaluate the association between the timing of publication of the RECOVERY (Randomised Evaluation of COVID-19 Therapy) trial (June 2020) and the WHO guidelines for corticosteroids (September 2020) and the temporal trends observed in corticosteroid use by region and to describe the geographic distribution of the recruitment in clinical trials that informed the WHO recommendation. Design, setting, and participants: This prospective cohort study of 434 851 patients was conducted between January 31, 2020, and September 2, 2022, in 63 countries worldwide. The data were collected under the auspices of the International Severe Acute Respiratory and Emerging Infections Consortium (ISARIC)-WHO Clinical Characterisation Protocol for Severe Emerging Infections. Analyses were restricted to patients hospitalized for severe COVID-19 (a subset of the ISARIC data set). Exposure: Corticosteroid use as reported to the ISARIC-WHO Clinical Characterisation Protocol for Severe Emerging Infections. Main outcomes and measures: Number and percentage of patients hospitalized with severe COVID-19 who received corticosteroids by time period and by WHO geographic region. Results: Among 434 851 patients with confirmed severe or critical COVID-19 for whom receipt of corticosteroids could be ascertained (median [IQR] age, 61.0 [48.0-74.0] years; 53.0% male), 174 307 (40.1%) received corticosteroids during the study period. Of the participants in clinical trials that informed the guideline, 91.6% were recruited from the United Kingdom. In all regions, corticosteroid use for severe COVID-19 increased, but this increase corresponded to the timing of the RECOVERY trial (time-interruption coefficient 1.0 [95% CI, 0.9-1.2]) and WHO guideline (time-interruption coefficient 1.9 [95% CI, 1.7-2.0]) publications only in Europe. At the end of the study period, corticosteroid use for treatment of severe COVID-19 was highest in the Americas (5421 of 6095 [88.9%]; 95% CI, 87.7-90.2) and lowest in Africa (31 588 of 185 191 [17.1%]; 95% CI, 16.8-17.3). Conclusions and relevance: The results of this cohort study showed that implementation of the guidelines for use of corticosteroids in the treatment of severe COVID-19 varied geographically. Uptake of corticosteroid treatment was lower in regions with limited clinical trial involvement. Improving research diversity and representativeness may facilitate timely knowledge uptake and guideline implementation

The value of open-source clinical science in pandemic response: lessons from ISARIC

International audienc

Characteristics and outcomes of COVID-19 patients admitted to hospital with and without respiratory symptoms

Background: COVID-19 is primarily known as a respiratory illness; however, many patients present to hospital without respiratory symptoms. The association between non-respiratory presentations of COVID-19 and outcomes remains unclear. We investigated risk factors and clinical outcomes in patients with no respiratory symptoms (NRS) and respiratory symptoms (RS) at hospital admission. Methods: This study describes clinical features, physiological parameters, and outcomes of hospitalised COVID-19 patients, stratified by the presence or absence of respiratory symptoms at hospital admission. RS patients had one or more of: cough, shortness of breath, sore throat, runny nose or wheezing; while NRS patients did not. Results: Of 178,640 patients in the study, 86.4 % presented with RS, while 13.6 % had NRS. NRS patients were older (median age: NRS: 74 vs RS: 65) and less likely to be admitted to the ICU (NRS: 36.7 % vs RS: 37.5 %). NRS patients had a higher crude in-hospital case-fatality ratio (NRS 41.1 % vs. RS 32.0 %), but a lower risk of death after adjusting for confounders (HR 0.88 [0.83-0.93]). Conclusion: Approximately one in seven COVID-19 patients presented at hospital admission without respiratory symptoms. These patients were older, had lower ICU admission rates, and had a lower risk of in-hospital mortality after adjusting for confounders