Duration and Risk Factors of Post-COVID Symptoms Following Recovery Among the Medical Doctors in Bangladesh

A large number of coronavirus disease 2019 (COVID-19) recovered patients are suffering from related symptoms. We conducted telephone interviews with 186 COVID-19 recovered medical doctors to determine the post-COVID symptoms, duration, and associated risk factors. About 70% of participants had at least one acute post-COVID symptom, including fatigue (43.0%), sleep disturbance (13.4%), lack of concentration (11.8%), breathing difficulty (10.2%), headache (6.5%), and muscle pain (6.5%). However, about 24% of participants reported having long post-COVID symptoms. Logistic regression analysis showed that female sex (odds ratio {OR}, 2.79; 95% CI, 1.28-6.06; p-value: 0.010) and comorbid conditions (OR, 2.28; 95% CI, 1.08-4.79; p: value, 0.030) are risk factors for the long post-COVID symptoms.

Optimization of bio-cement production from cement kiln dust using microalgae

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CKD with microalgae sp. Chlorella kessleri is investigated for maximum bio-cement yields.

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A predictive quadratic model was developed for CaCO₃ yield with R² value of c.a. 92%.

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Low temperature and high pH were found to be important parameters in RSM study.

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Under optimal set, a maximum of 96% Ca was extracted experimentally from CKD.

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FTIR, XRD and EDS analysis confirmed the produced bio-cement compound.

The main aim of this study was to maximize bio-cement (CaCO₃) production through a waste feedstock of cement kiln dust (CKD) as a source of calcium by deployment of microalgae sp. Chlorella kessleri. The effect of process parameters such as temperature, pH and time-intervals of microalgae cultivation, were set as criteria that ultimately subscribe to a process of optimization. In this regard, a single factor experiments integrated with response surface methodology (RSM) via central composite design (CCD) was considered. A quadratic model was developed to predict the maximum CaCO₃ yield. A ceiling of 25.18 g CaCO₃ yield was obtained at an optimal set of 23 °C, pH of 10.63 and day-9 of microalgae culture. Under these optimized conditions, maximum 96% calcium was extracted from CKD. FTIR, XRD and EDS analyses were conducted to characterize the CaCO₃ precipitates. Compressive modes of mechanical testing seemed to hold conventional cement complimented by CaCO₃ co-presence markedly superior to mere cement performance as far as compressive strength is concerned. The latter criterion exhibited further increase in correspondence with rise in cement to bio-cement ratio. This investigative endeavour at hand offers a simple pivotal platform on the basis of which a scale-up of microalgae-infested bio-cement production might be facilitated in conjunction with the added benefit of alleviation in environmental pollution through cement waste utilization.