The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates virus entry by binding to the host cell receptor, human angiotensin converting enzyme 2 (hACE2), and catalyzing virus–host membrane fusion. The S protein also mediates cell–cell fusion, potentially allowing the virus to spread virion-independently. Here, we compared the fusogenicity of SARS-CoV-2 variant S proteins using a cell–cell fusion assay. In cells overexpressing hACE2, cell–cell fusion ability of all tested SARS-CoV-2 variants was similar to that of the Wuhan-Hu-1 strain. However, in cells with endogenous hACE2, SARS-CoV-2 variants, especially the Delta variant, stimulated significantly greater cell–cell fusion than the original strain. Our results showed that the Delta variant S protein is highly fusogenic and can spread rapidly by utilizing small amounts of hACE2.

We investigated the distribution of asbestos in Seoul for 16 school buildings built before and after 1990, includingkindergartens, elementary schools, middle schools and high schools. The risk assessment standards of AHERA,HSE and ASTM were reviewed and a comparative analysis of assessment standards was conducted in schoolbuildings. For the risk assessment of 16 schools, 170 samples were selected, each of which was assessed usingstandards of AHERA, HSE and ASTM. The school buildings included the ACM (asbestos containing materials)ranged 3-4% of chrysotile and 1-3% of amosite in classroom ceilings and has 7-8% chrysotile in partitions of studenttoilets. The airborne concentrations of fiber materials were ranged with 0.002-0.022 fiber/cc in school buildingsby PCM. In this study, a simplified rating scale was used three categories of Good, Damaged and SignificantlyDamaged. In the result of comparative analysis for the risk assessment criteria, it was found that 113 samples, 132samples and 82 samples were classified as Good when assessed by AHERA, HSE and ASTM, respectively; and46 samples, 29 samples and 53 samples as Damaged, respectively; and 12 samples, 8 samples and 34 samples asSignificantly Damaged, respectively. From the distribution of asbestos and the comparative analysis for the riskassessment criteria, the management plan and new risk assessment were made based on the Korea backgroundshould be established to control asbestos exposure to students from damaged ACM and will be revealed that theassessment for the current condition and potential for disturbance on asbestos in school buildings.

The current interest in atmospheric particulate matter (PM) is mainly due to its effect on human health.Exposure to outdoor PM is associated with a wide range of adverse health effects. Indoor air contains a complexmixture of bioaerosols such as bacteria, fungi and allergens. Children are known to be more susceptible tothe exposures of PM and bioaerosols which are represented by airborne bacteria, fungi, and allergens. Thisstudy is to assess concentrations of the atmospheric PM and bioaerosols indoors and outdoors at 15 daycarecenters for children located in Seoul. Particles were measured indoors and outdoors with automatic particlemonitoring using beta radiation absorption. Airborne bacteria and fungi were sampled by Anderson sampler.Analysis shows that average indoor PM10 was 95.7µg/m³ (SD 26.6µg/m³) and average level of airbornebacteria and fungi were 575.0CFU/m³ (SD 431.6CFU/m³) and 77.9CFU/m³ (SD 45.6CFU/m³), respectively.Finally, efficient ventilation and effective air cleaning strategies are necessary to reduce indoor concentrationsof particles and bioaerosols.

This study investigated the effect of various buried depth(0.8m, 1.0m, 1.2m) on the stress distribution of gas pipe. Numerical analysis and field tests were carried out with API 5L steel gas pipes. From the results, it can be suggested that field test results including compaction energy can represent the stress distribution of gas pipe more precisely.