RESUMEN
With excellent mechanical properties and distinct solidification, the AZ31B series magnesium alloy has great potential for targeting engineering applications and synthesized via die casting process found a drawback on oxidation results porosity and reduced mechanical properties. Here, the magnesium alloy AZ31B series nanocomposite was synthesized with varied weight percentages of zirconium dioxide nanoparticles through a liquid metallurgy route with an applied stir speed of 200 rpm under an argon nature. With the help of a scanning electron microscope, the distribution of particles in the composite surface was found to be homogenous and void-free surface, which output results in less percentage of porosity (<1 %), and the composite contained 6 wt% ZrO2 offers superior yield strength (212 ± 3 MPa), tensile strength (278 ± 2 MPa), and impact strength of 16.4 ± 0.4 J/mm2. In addition, 8 wt% ZrO2 blended composite showed the maximum microhardness value (78.3 ± 1 HV). The best-enhanced result of NC3 (AZ31B/6 wt% ZrO2) is suggested for lightweight to high-strength structural applications.
RESUMEN
OBJECTIVE: To describe COVID-19 in children and the differences between the two waves. METHODS: The electronic medical records of children younger than 16 y of age with laboratory-confirmed COVID-19 infection between June 1st 2020 and May 31st 2021 at Christian Medical College, Vellore were retrospectively reviewed. Demographic, clinical, and laboratory data were collected on a predesigned case record form and analyzed. RESULTS: A total of 988 children were diagnosed with confirmed COVID-19 during the study period. Of these, there were 585 children diagnosed during the 1st wave (June 2020-Feb 2021) and 403 children during the 2nd wave (March 2021-May 2021). It was found that loose stools and rash were significantly more frequent during the 1st wave and fever, cough, coryza, heart rate and temperature were significantly more during the 2nd wave. There was no significant difference between the two groups in terms of requirement of oxygen therapy, need for ICU admission, duration of ICU stay or hospital stay, or severity of illness. Mortality was significantly higher during the 2nd wave (0.3% vs. 2%). CONCLUSION: The COVID-19 pandemic among children during the 1st and 2nd waves were similar in severity, though there was a higher mortality during the 2nd wave.