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OBJECTIVES: The first confirmed case of coronavirus disease 2019 (COVID-19) in South Korea was reported in January 2020, with 28 confirmed cases reported as of February 14th, 2020. The epidemiological and clinical characteristics of all 28 cases were analyzed in response to this disease. METHODS: The epidemiological characteristics and early clinical features of the 28 patients from Korea with confirmed COVID-19 were analyzed using COVID-19 reporting and surveillance data and the epidemiological investigation reports prepared by the rapid response team. RESULTS: There were 16 patients that entered Korea from foreign countries: Wuhan, China (11 patients), Zhuhai, China, (1 patient), Singapore (2 patients), Japan (1 patient), and Thailand (1 patient). The early symptoms were fever, sore throat, cough or sputum production, chills, and muscle ache. Three patients were asymptomatic, however, 18 developed pneumonia. Of the 28 cases, 16 were index cases imported from abroad, with 10 cases of secondary infection originating in Korea, and the route of transmission still under investigation for 2 patients. The 10 patients with secondary infection were infected from contact with family members or acquaintances of primary patients, and the suspected sites of transmission were mostly at home. CONCLUSION: COVID-19 in Korea was spread by 16 infected individuals traveling from other countries, leading to second-generation cases. The initial symptoms were mostly minor, but the disease was infectious at this stage, resulting from close contact, particularly at home. Establishing an early detection strategy for COVID-19 is crucial for managing the transmission of the disease.

Background Despite the extraordinary speed of mass vaccination efforts, an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant in a vaccinee with coronavirus disease 2019 (COVID-19) mRNA vaccine was identified in an adult day service center (ADSC) of Jeju, South Korea. The primary objective of this study was to investigate the epidemiologic features in infection-vulnerable facilities with a high vaccination rate of BNT162b2 mRNA COVID-19 vaccine. The second was to estimate the secondary transmission prevention effect of the vaccine in the household members by vaccination status. Methods We included all ADSC participants, staff and their household members. All COVID-19 infected cases were confirmed by reverse transcriptase polymerase chain reaction. We calculated attack rate in ADSC and the secondary attack rate (SAR) in household members by vaccination status. Results Among a total of 42 participants and 16 staff, of which 96.6% were fully vaccinated with BNT162b2 mRNA COVID-19 vaccine, 12 symptomatic cases and 13 asymptomatic confirmed cases of COVID-19 were found. The attack rate was 43.1%, with 13 isolates identified as SARS-CoV-2 virus, delta variant. The SAR in unvaccinated and partially vaccinated household members were 27.8% (5/18) and 25.0% (5/20), respectively, while the SAR in fully vaccinated household members was 12.5% (1/8). Conclusion We describe a SARS-CoV-2 delta variant outbreak in ADSC with high vaccine coverage rate, characterized by high infection rate, high transmissibility, and low clinical severity. The outbreak proceeded to unvaccinated or partially vaccinated household members, emphasizing the need for immunizing close contacts of high-risk groups., Graphical Abstract

In an electrochemical system, ion transport near ion exchange membranes or electrodes induces inevitable concentration polarization ( i.e. , formation of diffusion boundaries), which impedes the mass transport and worsens the energy efficiency. To mitigate the effect of concentration polarization (CP), various efforts towards mass transport enhancement employed structures, often called spacers, which promote mixing and modify the flow velocity distribution in the channel. In this work, we employed an electrodialysis (ED) system as a model to investigate the mass transport effects of embedded microstructures, which can redistribute the local flow velocity. We placed a row of cylindrical posts inside the diluate channel and varied the distance from the posts to the membranes. We studied the effect of this post-to-membrane distance on the mass transport by measuring the current-voltage responses and visualizing ion concentration and flow velocity profiles. The study was done through microfluidic ED model experiments and direct numerical simulation based on the coupled Navier-Stokes and Poisson-Nernst-Planck equations. Our results indicate that when the posts are positioned near the center of the channel, the mass transport is enhanced due to the increase in local convection near the concentration boundary layers. More importantly, we discovered that the mass transport is maximized when the location of the posts is slightly off-centered, due to the asymmetry of the cation/anion diffusivity (D Na+ Cl- ). Compared to a system without any structures, the embedded posts can improve both the electrical energy efficiency and the salt removal.

Background In February 2020, a coronavirus disease 2019 (COVID-19) outbreak was reported in fitness centers in Cheonan, Korea. Methods From February 24 to March 13, an epidemiological investigation was conducted on the fitness center outbreak. All those who were screened were tested for severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) using real-time reverse transcriptase polymerase chain reaction. Contacts were traced and self-isolated for 14 days. We determined the epidemiological characteristics of confirmed cases of SARS-CoV-2 infection, and estimated the time-dependent reproduction number to assess the transmission dynamics of the infection. Results A total of 116 cases were confirmed, and 1,687 contacts were traced. The source cases were 8 Zumba instructors who led aerobics classes in 10 fitness centers, and had the largest average number of contacts. A total of 57 Zumba class participants, 37 of their family members, and 14 other contacts were confirmed as cases. The attack rate was 7.3%. The contacts at Zumba classes and homes had a higher attack rate than other contacts. The mean serial interval (± standard deviation) were estimated to be 5.2 (± 3.8) days. The time-dependent reproduction number was estimated to be 6.1 at the beginning of the outbreak, but it dropped to less than 1, 2 days after the epidemiological investigation was launched. Conclusion The results suggest that the COVID-19 outbreak was effectively contained with rigorous contact tracing, isolating, and testing in combination with social distancing without a lock-down., Graphical Abstract

A techno-economic analysis is used to evaluate the economic feasibility of ion concentration polarization (ICP) desalination for seawater desalination and brine management. An empirical optimization model based on a limited set of experimental data, which was obtained from a lab-scale ICP desalination prototype, was established to calculate the required energy and membrane area for a given set of operating parameters. By calculating operating and capital expenses in various feed and product cases, the optimal levelized cost of water is determined over a range of feed salinities, mostly above seawater salinity (35 g/kg). Through these analyses, we study the economic feasibility of three applications: 1) partial desalination of brine discharge by ICP (feed varied from 35 to 75 g/kg) to common seawater RO feed level (35 g/kg) in a hybrid ICP-RO system; 2) the concentration of seawater desalination brine for salt production, and 3) partial desalination of oilfield wastewater. The economic feasibility of ICP desalination processes has been evaluated and the rough cost of treatment has been generated for several relevant applications. The approach taken in this work could be employed for other new and existing desalination processes, where a priori process modeling and optimization is scientifically and/or numerically challenging. Keywords: Electromembrane desalination; High salinity desalination; Brine management; Economic analysis; Ion concentration polarization

A “lotus-like” effect is applied to demonstrate the ability of the Leidenfrost water droplets to recover Cu particles on a heated Al substrate. Cu particles on the heated surface adhere to the rim of the Leidenfrost droplets and eventually coat the droplets' surface to form an aggregation. When Fe filings are added to the Cu particles, the aggregated mixture can then be collected using a strong rare earth magnet (NdFeB) upon evaporation of the water. We also show that the Leidenfrost effect can be effectively utilized to recover both hydrophobic (dust and activated carbon) and hydrophilic (SiO2 and MgO) particles from heated Al surfaces without any topographical modification or surfactant addition. Our results show that hydrophobic and hydrophilic materials can be collected with >92% and >96% effectiveness on grooved and smooth Al surfaces, respectively. Furthermore, we observed no significant differences in the amount of material collected above the Leidenfrost point within the tested temperature range (240 °C vs. 340 °C) as well as when the Al sheet was replaced with a Cu sheet as the substrate. However, we did observe that the Leidenfrost droplets were able to collect a greater amount of material when the working liquid was water than when it was ethanol. Our findings show promise in the development of an effective precious coinage metal filings recovery technology for application in the mint industry, as well as the self-cleaning of metallic and semiconductor surfaces where manual cleaning is not amenable.

Two different lots of cation-exchange membranes (CMX-SB-1 and -2) were compared in terms of physico-chemical and electrochemical properties. Further, electrodialysis with both membrane lots was carried out under pulsed electric field (PEF) on model solution containing Ca 2 + and Mg 2 + ions. It was found that CMX-SB-1 was more scaled with prevalence of Ca compounds on both membrane sides. CMX-SB-2 contained less scaling with prevalence of Ca compounds on diluate side and Mg compounds on concentrate side. The different behavior of membranes was hypothesized to be due to the differences in their intrinsic structure and surface properties. The CMX-SB-2 has higher concentration of fixed charges and water content, which cause larger size of inner channels and easier transport of Mg 2 + ; the structural organization of CMX-SB-1 with presumably narrower nanochannels leads to the slower Mg 2 + migration and their low quantity on CMX-SB-1 concentrate side. Additionally, the surface hydrophobicity and heterogeneity of CMX-SB-2 is higher than that of CMX-SB-1 what allow easier water slip on CMX-SB-2 surface facilitating electroconvection. Thus, more scaled CMX-SB-1 membrane with less developed electroconvection yielded lower values of demineralization (59.0% and 57.2% for 2 s/0.5 s and 2 s/0.67 s PEF respectively) than the less scaled CMX-SB-2 with better developed electroconvection (77.3% and 75.2% respectively).

Computational image analysis is used in many areas of biological and medical research, but advanced techniques including machine learning remain underutilized. Here, we used automated segmentation and shape analyses, with pre-defined features and with computer generated components, to compare nuclei from various premature aging disorders caused by alterations in nuclear proteins. We considered cells from patients with Hutchinson-Gilford progeria syndrome (HGPS) with an altered nucleoskeletal protein; a mouse model of XFE progeroid syndrome caused by a deficiency of ERCC1-XPF DNA repair nuclease; and patients with Werner syndrome (WS) lacking a functional WRN exonuclease and helicase protein. Using feature space analysis, including circularity, eccentricity, and solidity, we found that XFE nuclei were larger and significantly more elongated than control nuclei. HGPS nuclei were smaller and rounder than the control nuclei with features suggesting small bumps. WS nuclei did not show any significant shape changes from control. We also performed principle component analysis (PCA) and a geometric, contour based metric. PCA allowed direct visualization of morphological changes in diseased nuclei, whereas standard, feature-based approaches required pre-defined parameters and indirect interpretation of multiple parameters. Both methods yielded similar results, but PCA proves to be a powerful pre-analysis methodology for unknown systems.

Problems related to string inclusion and non-inclusion have been vigorously studied in diverse fields such as data compression, molecular biology and computer security. Given a finite set of positive strings and a finite set of negative strings , a string α is a consistent superstring if every positive string is a substring of α and no negative string is a substring of α . The shortest (resp. longest) consistent superstring problem is to find a string α that is the shortest (resp. longest) among all the consistent superstrings for the given sets of strings. In this paper, we first propose a new graph model for consistent superstrings for given and . In our graph model, the set of strings represented by paths satisfying some conditions is the same as the set of consistent superstrings for and . We also present algorithms for the shortest and the longest consistent superstring problems. Our algorithms solve the consistent superstring problems for all cases, including cases that are not considered in previous work. Moreover, our algorithms solve in polynomial time the consistent superstring problems for more cases than the previous algorithms. For the polynomially solvable cases, our algorithms are more efficient than the previous ones.

We report the use of a simple yet highly effective magnetite-waste tea composite to remove lead(II) (Pb[superscript 2+]) ions from water. Magnetite-waste tea composites were dispersed in four different types of water–deionized (DI), artificial rainwater, artificial groundwater and artificial freshwater–that mimic actual environmental conditions. The water samples had varying initial concentrations (0.16–5.55 ppm) of Pb[superscript 2+] ions and were mixed with the magnetite-waste tea composite for at least 24 hours to allow adsorption of the Pb[superscript 2+] ions to reach equilibrium. The magnetite-waste tea composites were stable in all the water samples for at least 3 months and could be easily removed from the aqueous media via the use of permanent magnets. We detected no significant leaching of iron (Fe) ions into the water from the magnetite-waste tea composites. The percentage of Pb adsorbed onto the magnetite-waste tea composite ranged from ~70% to 100%; the composites were as effective as activated carbon (AC) in removing the Pb[superscript 2+] ions from water, depending on the initial Pb concentration. Our prepared magnetite-waste tea composites show promise as a green, inexpensive and highly effective sorbent for removal of Pb in water under environmentally realistic conditions., SUTD-MIT International Design Center (Research Grant IDG11200105/IDD11200109), Singapore-MIT Alliance