Experimental study on the monotonic mechanical behavior of completely decomposed granite soil reinforced by disposable face-mask chips.

In response to the global outbreak of the coronavirus pandemic (COVID-19), a staggering amount of personal protective equipment, such as disposable face masks, has been used, leading to the urgent environmental issue. This study evaluates the feasibility of mask chips for the soil reinforcement, through triaxial tests on samples mixed with complete decomposed granite (CDG) and mask chips (0%, 0.3%, 0.5%, 1%, 5% by volume). The experimental results show that adding a moderate volumetric amount of mask chips (0.3%-1%) improves the soil strength, especially under high confining pressure. The optimum volumetric content of mask chips obtained by this study is 0.5%, raising the peak shear strength up to 22.3% under the confining stress of 120 kPa. When the volumetric content of mask chips exceeds the optimum value, the peak shear strength decreases accordingly. A limited amount of mask chips also increases the elastic modulus and makes the volumetric response more dilative. By contrast, excessive mask chips create additional voids and shift the strong soil-mask contacts to weak mask-mask contacts. The laser scanning microscope (LSM) and scanning electron microscope (SEM) images on the typical samples demonstrate the microstructure of mask fibers interlocking with soil particles, highly supporting the macro-scale mechanical behavior.

Static and dynamic behaviors of granular soil reinforced by disposable face-mask chips

The stock of disposable face masks has climbed steadily due to COVID-19, which results in an urgent worldwide environmental problem. This investigation aims to assess the potential of using waste mask chips (MC) as reinforcement in granular soil. To evaluate the mechanical properties of the mask chips - granular soil mixture (MSM), a series of monotonic and cyclic triaxial tests with different confining pressures and MC contents are conducted. Then, the shear behavior of MSM is quantified from both static (strength, stiffness, dilatancy) and dynamic (energy absorption capacity, resilient modulus, deformation) perspectives. Furthermore, based on the static and dynamic indexes, the effects of adding MC into granular soil are comprehensively analyzed. All experimental results indicate that the MSMs exbibit an increase of shear strength and a reduction of shear-induced volumetric dilation, but a decrease in stiffness. The addition of MC also leads to an increase in energy absorption but will not affect the cumulative strain of MSMs. Thus, MC has great potential to be used in the embankment construction of road and railway, backfill or reclamation construction, and so on. In addition, the influence of mask chip content on mechanical behaviors of MSM can be considered in current constitutive models for further engineering calculation and design relating to of MSMs. This experimental study provides a new perspective and thought on the recycling of waste face masks in civil engineering.

Association of liver abnormalities with in-hospital mortality in patients with COVID-19.

BACKGROUND & AIMS: The evolution and clinical significance of abnormal liver chemistries and the impact of hepatitis B infection on outcome in patients with COVID-19 is not well characterized. This study aimed to explore these issues. METHODS: This large retrospective cohort study included 2,073 patients with coronavirus disease 2019 (COVID-19) and definite outcomes in Wuhan, China. Longitudinal liver function tests were conducted, with associated factors and risk of death determined by multivariate regression analyses. A prognostic nomogram was formulated to predict the survival of patients with COVID-19. The characteristics of liver abnormalities and outcomes of patients with COVID-19, with and without hepatitis B, were compared after 1:3 propensity score matching. RESULTS: Of the 2,073 patients, 1,282 (61.8%) had abnormal liver chemistries during hospitalization, and 297 (14.3%) had a liver injury. The mean levels of aspartate aminotransferase (AST) and direct bilirubin (D-Bil) increased early after symptom onset in deceased patients and showed disparity compared to levels in discharged patients throughout the clinical course of the disease. Abnormal AST (adjusted hazard ratio [HR] 1.39; 95% CI 1.04-1.86, p = 0.027) and D-Bil (adjusted HR 1.66; 95% CI 1.22-2.26; p = 0.001) levels at admission were independent risk factors for mortality due to COVID-19. A nomogram was established based on the results of multivariate analysis and showed sufficient discriminatory power and good consistency between the prediction and the observation. HBV infection in patients did not increase the risk of poor COVID-19-associated outcomes. CONCLUSIONS: Abnormal AST and D-Bil levels at admission were independent predictors of COVID-19-related mortality. Therefore, monitoring liver chemistries, especially AST and D-Bil levels, is necessary in hospitalized patients with COVID-19. LAY SUMMARY: Liver test abnormalities (in particular elevations in the levels of aspartate aminotransferase [AST] and direct bilirubin [D-Bil]) were observed after symptom onset in patients who went on to die of coronavirus disease 2019 (COVID-19). Abnormal levels of AST and D-Bil at admission were independent predictors of COVID-19-related mortality. HBV infection in patients did not increase the risk of poor COVID-19-associated outcomes.