Nosocomial transmission of COVID-19 among immunocompromised hosts can have a serious impact on COVID-19 severity, underlying disease progression and SARS-CoV-2 transmission to other patients and healthcare workers within hospitals. We experienced a nosocomial outbreak of COVID-19 in the setting of a daycare unit for paediatric and young adult cancer patients. Between 9 and 18 November 2020, 473 individuals (181 patients, 247 caregivers/siblings and 45 staff members) were exposed to the index case, who was a nursing staff. Among them, three patients and four caregivers were infected. Two 5-year-old cancer patients with COVID-19 were not severely ill, but a 25-year-old cancer patient showed prolonged shedding of SARS-CoV-2 RNA for at least 12 weeks, which probably infected his mother at home approximately 7–8 weeks after the initial diagnosis. Except for this case, no secondary transmission was observed from the confirmed cases in either the hospital or the community. To conclude, in the day care setting of immunocompromised children and young adults, the rate of in-hospital transmission of SARS-CoV-2 was 1.6% when applying the stringent policy of infection prevention and control, including universal mask application and rapid and extensive contact investigation. Severely immunocompromised children/young adults with COVID-19 would have to be carefully managed after the mandatory isolation period while keeping the possibility of prolonged shedding of live virus in mind.

In spite of significant concerns about Hg contamination and its toxic impacts in the environment, limited studies have been carried out in Korea. The objectives of this study are to investigate the extent and degree of Hg contamination in soil, sediment, dust and sludge from various anthropogenic sources in Korea, and to understand the distribution patterns of Hg in the study areas. The anthropogenic sources of Hg contamination were divided into four major sources: (1) by-product from abandoned Au-Ag mines; (2) coal combustion; (3) cement production; and (4) industrial and domestic discharges. A calculation of enrichment factor and index of geoaccumulation for Hg in soils and sediments indicated that some samples from mining sites were enriched in Hg. In addition, Hg concentrations in marine sediments from industrial sites were above the Effects Range Median (ERM) criteria suggested by the National Oceanic and Atmospheric Administration of the United States (NOAA). Therefore, it can be concluded that samples from various sites were directly influenced by anthropogenic sources of Hg in the surface environment.

A total of 27 accessions from ten Vicia species were investigated for flavonoid contents, total polyphenol contents, and DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2′-azinobis(3-ethylbenzothiazoline 6-sulfonic acid)] free radical-scavenging activities. The results revealed that NAC17 (V. monantha) and NAC14 (V. hyrcanica) had the highest total flavonoid content (1.42 ± 0.09 mg/g) and total polyphenol content [124.2 ± 0.5 μg/gallic acid equivalents (GAE) mg], respectively. Among four flavonoids, naringenin was detected at high concentrations in Vicia species. The DPPH and ABTS assays showed values in the range of 57.2 (IC50) (NAC13, V. faba) to 6530.0 (IC50) (NAC24, V. sativa subsp. nigra) and 19.1 μg/Trolox mg (NAC7, V. cracca) to 253.4 μg/Trolox mg (NAC13, V. faba), respectively. Among ten Vicia species, V. monantha and V. hyrcanica had the highest flavonoid content (1.31 ± 0.09 mg/g) and total polyphenol content (116.5 ± 2.0 μg/GAE mg), respectively. The highest antioxidant activity was detected in V. faba. These results will expand the flavonoid database and provide valuable information on Vicia species for the development of functional foods or feed-additive resources.

Effects of Ag content on microstructure, mechanical properties, and electrical conductivity in long time aged Cu-Ti-Ag alloys were investigated. In short time ageing condition, both electrical conductivity and mechanical properties were enhanced by Ag addition. On the other hand, in long time ageing condition, Ag addition showed a faster deterioration of mechanical properties than Ag free CuTi alloys.

Ferromagnetic Cu-doped GaN film was grown on a GaN-buffered sapphire (0001) substrate by a hybrid physical-chemical-vapor-deposition method (HPCVD). The GaCuN film (Cu: 3.6 at.%) has a highly c-axis-oriented hexagonal wurtzite crystal structure, which is similar to GaN buffer but without any secondary phases such as metallic Cu, CuxNy, and CuxGay compounds. Two weak near-band edge (NBE) emissions at 3.38 eV and donor-acceptor-pair (DAP) transition at 3.2 eV with a typical strong broad yellow emission were observed in photoluminescence spectra for GaN buffer. In contrast, the yellow emission was completely quenched in GaCuN film because Ga vacancies causing the observed yellow emission in undoped GaN were substituted by Cu atoms. In addition, GaCuN film exhibits a blue shift of NBE emission, which could be explained with the +2 oxidation state of Cu ions, replacing +3 Ga ions resulting in band gap increment. The valance sate of Cu in GaCuN film was also confirmed by x-ray photoelectron spectroscopy (XPS) analysis. The GaCuN film shows ferromagnetic ordering and possesses a residual magnetization of 0.12 emu/cm3 and a coercive field of 264 Oe at room temperature. The unpaired spins in Cu2+ ions (d9) are most likely to be responsible for the observed ferromagnetism in GaCuN.

Rapid thermal annealing (RTA) processing under N2 and O2 ambient is suggested and characterized in this work for improvement of SiCOH ultra-low-k (k = 2.4) film properties. Low-k film was deposited by plasma-enhanced chemical vapor deposition (PECVD) with decamethylcyclopentasiloxane and cyclohexane precursors. The PECVD films were treated by RTA processing in N2 and O2 environments at 550 °C for 5 min, and k values of 1.85 and 2.15 were achieved in N2 and O2 environments, respectively. Changes in the k value were correlated with the chemical composition of C–Hx and Si–O related groups determined from the Fourier transform infrared (FTIR) analysis. As the treatment temperature was increased from 300 to 550 °C, the signal intensities of both the CHx and Si–CH3 peaks were markedly decreased. The hardness and modulus of the film processed by RTA have been determined as 0.44 and 3.95 GPa, respectively. Hardness and modulus of RTA-treated films were correlated with D-group [O2Si–(CH3)2] and T-group [O3Si–(CH3)] fractions determined from the FTIR Si–CH3 bending peak. The hardness and modulus improvement in this work is attributed to the increase of oxygen content in (O)x–Si–(CH3)y by rearrangement.

We have conducted low-temperature flip-chip bonding for both optical interconnect and microwave applications. Flip-chip bonding of vertical-cavity surface-emitting laser (VCSEL) arrays was performed on a fused silica substrate that provides propagation paths of laser beams and also supports a polymeric waveguide. To avoid thermal damage of the polymeric waveguide during the flip-chip bonding, indium bumps were used and the bonding condition of the flip-chip was determined as a heating temperature of 150 °C and a pressure of 500 gf. Experimentally, a thin silver (Ag) layer coated on the indium bump was very effective to enhance the adhesion strength between the indium bump and the VCSEL chip pads. In addition, the microwave characteristic of coplanar waveguide (CPW) package was slightly improved by the Ag coating.

The strain relaxation mechanism via the homogeneous nucleation of misfit dislocations from interface during interdiffusion in lattice-matched semiconductor heterostructures has been investigated. Transmission electron microscopy studies in intermixed GaInAsP/InP heterostructures revealed that the critical interdiffusion depth for the nucleation of 90° 1/6<112> partial dislocations from a tensile interface is much shallower than that of 60° 1/2<110> perfect dislocations from a compressive interface. A critical thickness model for the interface nucleation of these dislocations is developed as a modification of the classical surface nucleation'model.