Correlations between regional characteristics of counties and the ratio of intracounty to extracounty sources of COVID-19 in Gangwon Province, Republic of Korea.

BACKGROUND: This study aimed to examine the correlations between the regional characteristics of counties in Gangwon Province, Republic of Korea and the ratio of intracounty to extracounty sources of coronavirus disease 2019 (COVID-19) infection. METHODS: The region of the infectious contact was analysed for each COVID-19 case reported in Gangwon Province between February 22, 2020 and February 7, 2022. The population, population density, area, the proportion of urban residents, the proportion of older adults (>65 years), financial independence, and the number of adjacent counties were assessed for each of the 18 counties in Gangwon Province. Correlation coefficients between regional characteristics and the ratio of intracounty to extracounty infections were calculated. RESULTS: In total, 19,645 cases were included in this study. The population, population density, proportion of older adults, and proportion of urban residents were significantly correlated with the ratio of intracounty to extracounty infections. A stratified analysis with an age cut-point of 65 years showed that the proportion of older adults had a significant negative correlation with the ratio of intracounty to extracounty infections. In other words, the proportions of extracounty infections were higher in countries with higher proportions of older adults. CONCLUSION: Regions with ageing populations should carefully observe trends in infectious disease outbreaks in other regions to prevent possible transmission.

Reducing Moisture Absorption in Polypropylene Nanocomposites for Automotive Headlamps Using Hydrophobicity-Modified Graphene/Montmorillonite.

Polypropylene (PP) is used as a housing material in automotive headlamps but can cause fogging as a result of absorbed moisture and temperature differences between the exterior and interior of the housing. In this study, PP was combined with a graphene/montmorillonite hybrid (MMT-G) to yield a nanocomposite with reduced moisture absorption. Crucially, the modified nanofiller had low hydrophilicity and good compatibility with the PP matrix. Notably, the water contact angle of the MMT-G improved by 676%. Furthermore, the maximum moisture absorption of the PP/MMT-G nanocomposites was reduced by up to 11.22% compared to that of commercial PP composites, and the weight of the headlamp housing was decreased by 3.6%. Therefore, the designed nanocomposites are expected to help mitigate headlamp fogging while slightly reducing the housing weight.

Hygroscopic Behavior of Polypropylene Nanocomposites Filled with Graphene Functionalized by Alkylated Chains.

Owing to stringent international environmental and fuel efficiency requirements for lightweight automotive systems, polymer composites have attracted widespread attention. Polypropylene (PP) is a widely employed commercial polymer because of its lightweight and low cost. In this study, PP nanocomposites were fabricated to reduce the moisture absorption of PP composites in automotive headlamp housings. Alkylated chemically modified graphene (CMG-R) was synthesized to reduce the surface hydrophilicity of graphene and increase compatibility with the PP matrix. Fourier transform-infrared spectroscopy and scanning electron microscopy were performed to analyze the nanofillers. X-ray diffraction was performed to determine the interlayer spacing of the nanofiller resulting from surface treatment. Differential scanning calorimetry was used to analyze the crystallinity of the nanocomposites. The results indicated that the improved hydrophobicity of the nanofiller due to alkylation reduced the maximum moisture absorption of the PP nanocomposites by 15% compared to PP composites. The findings of this study are useful for reducing fogging in automotive headlamps.

Tribological Properties of Polyamide 46/Graphene Nanocomposites.

Polyamide 46 (PA46) is used in various automotive parts because of its excellent heat resistance and mechanical properties. This study aims to improve the frictional properties of PA46 using the lubricating ability of graphene. Nanocomposites are prepared via two mixing methods: Graphene powder is compounded directly with PA46 pellets through a twin-screw extruder, or PA46 powder is added to graphene dispersion for self-adsorption, and subsequently, it is dried and compounded with PA46 through the twin-screw extruder. Application of the nanocomposite in the friction field is evaluated via the pin-on-disk method. The coefficient of friction of the nanocomposite prepared by self-adsorption is lower than that of the nanocomposite prepared by direct compounding. The mechanical properties of the nanocomposite fabricated by self-adsorption are superior to those of other materials. This can be attributed to the uniform dispersion of graphene and the strong attractive force between the PA46 matrix and graphene.

Characteristics of transmission routes of COVID-19 cluster infections in Gangwon Province, Korea.

This study investigated the characteristics of transmission routes of COVID-19 cluster infections (⩾10 linked cases within a short period) in Gangwon Province between 22 February 2020 and 31 May 2021. Transmission routes were divided into five major categories and 35 sub-categories according to the relationship between the infector and the infectee and the location of transmission. A total of 61 clusters occurred during the study period, including 1741 confirmed cases (55.7% of all confirmed cases (n = 3125)). The the five major routes of transmission were as follows: 'using (staying in) the same facility (50.7%), 'cohabiting family members' (23.3%), 'social gatherings with acquaintances' (10.8%), 'other transmission routes' (7.0%), and 'social gatherings with non-cohabiting family members/relatives' (5.5%). For transmission caused by using (staying in) the same facility, the highest number of confirmed cases was associated with churches, followed by medical institutions (inpatient), sports facilities, military bases, offices, nightlife businesses, schools, restaurants, day-care centres and kindergarten, and service businesses. Our analysis highlights specific locations with frequent transmission of infections, and transmission routes that should be targeted in situations where adherence to disease control rules is difficult.

Electromagnetic interference (EMI) transparent shielding of reduced graphene oxide (RGO) interleaved structure fabricated by electrophoretic deposition.

Here we introduce the electromagnetic shielding effectiveness (SE) of reduced graphene oxide (RGO) sheets interleaved between polyetherimide (PEI) films fabricated by electrophoretic deposition (EPD). Incorporating only 0.66 vol % of RGO, the developed PEI/RGO composite films exhibited an electromagnetic interference shielding effectiveness (EMI SE) at 6.37 dB corresponding to ∼50% shielding of incident waves. Excellent flexibility and optical transparency up to 62% of visible light was demonstrated. It was achieved by placing the RGO sheets in the localized area as a thin film (ca. 20 nm in thickness) between the PEI films (ca. 2 µm) to be an interleaved and alternating structure. This unique interleaved structure without any delamination areas was fabricated by a successive application of cathodic and anodic EPD of both RGO and PEI layers. The EPD fabrication process was ensured by an alternating deposition of the quarternized-PEI drops and RGO, each taking positive and negative charges, respectively, in the water medium. We believe that the developed facile fabrication method of RGO interleaved structure with such low volume fraction has great potential to be used as a transparent EMI shielding material.